Motor cooling structure and motor

The present invention relates to a motor cooling structure that cools a motor by oil, and a motor.

A motor is used in various applications, but generates heat by Joule heating of a coil included in a stator, an eddy current loss and a hysteresis loss generated in a rotor core, or the like. In particular, when the power output of a motor increases, the current supplied to the motor also increases accordingly, so that the heat generation of the motor also increases. When the heat generation amount of the motor increases, since the performance of the motor degrades, the motor needs to be cooled. For example, Patent Literature 1 discloses a technology for cooling a motor by using a cooling medium such as oil.

Patent Literature

Patent Literature 1: Japanese Patent Application Laid-open No. 9-182375

Technical Problem

A motor cooling circuit disclosed in Patent Literature 1 flows oil as a cooling medium from an axial oil passage of a rotor shaft to a plurality of radial oil passages and a plurality of axial oil passages of a core. In the motor cooling circuit disclosed in Patent Literature 1, since the distances from an inlet of the axial oil passage of the rotor shaft to inlets of the respective radial oil passages are different, the flow rates of oil flowing through the respective radial oil passages and the rotor axial oil passage may become non-uniform and thus the cooling variation of a cooling target such as a rotor, a stator coil, and the like may increase. An object of the present invention is to suppress a cooling variation of a cooling target when cooling a motor by a cooling medium.

Solution to Problem

To achieve the object mentioned above, according to the present invention, a motor cooling structure for cooling a motor, which includes a shaft transmitting power and a rotor core attached to an outside of the shaft, by a cooling medium, comprises: a cooling medium supply passage that extends to an inside of the shaft in an axial direction of the shaft and passes the cooling medium through the cooling medium supply passage; and a plurality of cooling medium passages that are branched from the cooling medium supply passage to cool the rotor core while flowing the cooling medium without branching the cooling medium in the axial direction and then eject the cooling medium from a plurality of ejection holes opened to a surface of the rotor core, wherein distances from a cooling medium inlet, through which the cooling medium flows into the cooling medium supply passage, to the respective ejection holes are equal between the plurality of cooling medium passages.

As a preferred aspect of the present invention, it is preferable that the ejection holes are opened to both end portions of the rotor core.

As a preferred aspect of the present invention, it is preferable that an even number of the cooling medium passages are branched from the cooling medium supply passage.

As a preferred aspect of the present invention, it is preferable that a position at which each of the plurality of cooling medium passages is branched from the cooling medium supply passage is a central portion of the rotor core in the axial direction.

As a preferred aspect of the present invention, it is preferable that the plurality of cooling medium passages have an equal dimension and shape in a case where the cooling medium passages are cut along a plane that is parallel to a flow direction of the cooling medium.

As a preferred aspect of the present invention, it is preferable that the shaft includes a surface including a groove that extends in the axial direction, and a part of the cooling medium passage is formed between the groove and the rotor core.

As a preferred aspect of the present invention, it is preferable that the rotor core includes a through hole that passes through in the axial direction, and the groove and the through hole are connected at an end portion of the rotor core.

As a preferred aspect of the present invention, it is preferable that the rotor core includes a magnet holding hole that passes through in the axial direction and holds a magnet.

As a preferred aspect of the present invention, it is preferable that the balance plate, which is provided at an end portion of the rotor core includes a connection portion that connects the groove and the through hole.

As a preferred aspect of the present invention, it is preferable that each of the plurality of cooling medium passages includes: a first cooling medium passage that is branched from the cooling medium supply passage to an outer side of the shaft in a radial direction; a second cooling medium passage that is connected to the first cooling medium passage and extends in the axial direction; and the connection portion that is connected to the second cooling medium passage.

As a preferred aspect of the present invention, it is preferable that a housing that stores the shaft, to which the rotor core is attached, and a stator disposed at an outside of the rotor core includes a coil end cooling passage at a portion facing a coil end of a coil included in the stator.

As a preferred aspect of the present invention, it is preferable that the shaft includes two bearings that rotatably support the shaft, and the cooling medium passage includes: a first cooling medium ejection passage that is opened to a side of one end of the shaft than one of the bearings of a surface of the shaft; and a second cooling medium ejection passage that is opened to a side of the other end of the shaft than the other of the bearing of the surface of the shaft.

According to the present invention, a motor cooling structure for cooling a motor, which includes a shaft transmitting power and a rotor core attached to an outside of the shaft, by a cooling medium, comprises: a cooling medium supply passage that extends to an inside of the shaft in an axial direction of the shaft; and a plurality of cooling medium passages, wherein each of the cooling medium passages includes: a first cooling medium passage that extends from the cooling medium supply passage to an outer side of the shaft in a radial direction at a position corresponding to a central portion of the rotor core in the axial direction, and is perpendicular to the cooling medium supply passage; a second cooling medium passage that is formed by a space surrounded by the rotor core and a groove formed at a surface of the shaft and extending in the axial direction, wherein the space is connected to the first cooling medium passage; a third cooling medium passage that is provided in a balance plate installed at an end portion of the rotor core and is connected to the second cooling medium passage; a fourth cooling medium passage that passes through the rotor core in the axial direction and is connected to the third cooling medium passage; and an ejection hole to which the fourth cooling medium passage is opened at an end portion of the rotor core, wherein a distance from a cooling medium inlet, through which the cooling medium flows into the cooling medium supply passage, to the ejection hole of the cooling medium passage opened to one end portion of the rotor core is equal to a distance from the cooling medium inlet, through which the cooling medium flows into the cooling medium supply passage, to the ejection hole of the cooling medium passage opened to the other end portion of the rotor core.

According to the present invention, a motor comprising the motor cooling structure.

Advantageous Effects of Invention

The present invention can suppress a cooling variation of a cooling target when cooling a motor by a cooling medium.

FIG. 1 is an explanatory diagram illustrating a wheel loader.

FIG. 2 is a pattern diagram illustrating a drive system of the wheel loader.

FIG. 3 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to the present embodiment.

FIG. 4 is a front view of a shaft and a rotor core included in the motor according to the present embodiment, when viewed from an input/output side of the shaft.

FIG. 5 is a side view of the shaft and the rotor core included in the motor according to the present embodiment.

FIG. 6 is an A-A arrow view of FIG. 4 .

FIG. 7 is an enlarged view of a groove illustrated in FIG. 6 .

FIG. 8 is a B-B arrow view of FIG. 4 .

FIG. 9 is an enlarged view of a groove illustrated in FIG. 8 .

FIG. 10 is a C-C arrow view of FIG. 5 .

FIG. 11 is a D-D arrow view of FIG. 5 .

FIG. 12 is an E-E arrow view of FIG. 5 .

FIG. 13 is an enlarged view of the rotor core included in the motor according to the present embodiment.

FIG. 14 is a view illustrating a cooling structure and a cooling medium passage according to the present embodiment.

FIG. 15 is a view illustrating a cooling structure and a cooling medium passage according to the present embodiment.

FIG. 16 is a perspective view illustrating a cooling medium supply passage and a cooling medium passage.

FIG. 17 is a pattern diagram illustrating an arrangement of the cooling medium supply passage and the cooling medium passage.

FIG. 18 is a pattern diagram illustrating a modified example of the cooling medium passage included in the cooling structure according to the present embodiment.

FIG. 19 is a pattern diagram illustrating a modified example of the cooling medium passage included in the cooling structure according to the present embodiment.

FIG. 20 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to a first modified example of the present embodiment.

FIG. 21 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to a second modified example of the present embodiment.

Modes (embodiments) for implementing the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. Also, the components described below include substantially equivalent ones that can be easily conceived by those skilled in the art. In addition, the components described below can be combined appropriately.

A motor generates heat by Joule heating of a coil included in a stator, an eddy current loss and a hysteresis loss of a rotor core, or the like. A motor cooling structure according to the present embodiment (hereinafter referred to as a cooling structure if necessary) is configured such that the pressure losses of a plurality of cooling medium passages, which are branched from a cooling medium supply passage provided in a shaft of a motor to flow a cooling medium therethrough and eject the cooling medium from a surface of a rotor core with a plurality of stacked steel plates, are equalized (including a tolerance and a manufacturing error), taking into account a centrifugal force caused by the rotation of the shaft and the rotor core. By this configuration, the cooling structure according to the present embodiment cools the rotor core, a magnet, and a coil (specifically, a coil end) by using the cooling medium. Next, a configuration of a motor including the cooling structure according to the present embodiment will be described. The motor according to the present embodiment includes the above cooling structure. The cooling structure and the motor according to the present embodiment are suitable for a construction vehicle. First, a wheel loader will be described as an example of the construction vehicle that uses the motor according to the present embodiment.

<Wheel Loader>

FIG. 1 is an explanatory diagram illustrating a wheel loader. A wheel loader 100 includes a vehicle body 101 , a lift arm (operation machine) 102 installed at a front portion of the vehicle body 101 , a bucket (operation machine) 103 installed at a front end of the lift arm 102 , two front wheels 104 F and two rear wheels 104 R driving the vehicle body 101 by rotating while supporting the vehicle body 101 , and a cab 105 mounted on top of the vehicle body 101 .

FIG. 2 is a pattern diagram illustrating a drive system of the wheel loader. In the present embodiment, the wheel loader 100 includes, as a power source, an internal combustion engine 106 such as a gasoline engine or a diesel engine, and a motor 1 . In this manner, a drive mode of the wheel loader 100 is a so-called hybrid mode. In the present embodiment, the wheel loader 100 includes the internal combustion engine 106 and the motor 1 . The power outputs of the internal combustion engine 106 and the motor 1 are input to a transmission 107 . The transmission 107 combines the power outputs of the internal combustion engine 106 and the motor 1 and outputs the result to a front wheel propeller shaft 108 F and a rear wheel propeller shaft 108 R. The output of the front wheel propeller shaft 108 F is transmitted to the two front wheels 104 F through a front wheel differential gear 109 F and a front wheel drive shaft 110 F. Also, the output of the rear wheel propeller shaft 108 R is transmitted to the two rear wheels 104 R through a rear wheel differential gear 109 R and a rear wheel drive shaft 110 R. In this manner, the power outputs of the internal combustion engine 106 and the motor 1 are transmitted to the front wheels 104 F and the rear wheels 104 R to drive the wheel loader 100 . There is also a case where only the power output of the motor 1 or only the power output of the internal combustion engine 106 is transmitted to the transmission 107 during the operation of the wheel loader 100 . That is, during the operation of the wheel loader 100 , the power output of the motor 1 and the power output of the internal combustion engine 106 are not always transmitted to the transmission 107 . Also, the wheel loader 100 may include one or more motors 1 . In addition, the wheel loader 100 includes an inverter that controls an operation (powering or regeneration) of the motor 1 , and an electric storage device such as a capacitor or a secondary battery that stores energy (power) obtained by the regeneration of the motor 1 . Also, in the present embodiment, the wheel loader 100 may be an electric vehicle (construction vehicle) that drives the motor 1 by the power of an electric storage device without using an internal combustion engine. That is, the cooling structure according to the present embodiment can be applied to either a hybrid vehicle or an electric vehicle.

In the present embodiment, the motor 1 and the internal combustion engine 106 are disposed transversely. That is, the power transmission shafts of the motor 1 and the internal combustion engine 106 are disposed to be perpendicular to the traveling direction of the wheel loader 100 in a straight-ahead mode. More specifically, the power transmission shafts of the motor 1 and the internal combustion engine 106 are disposed to be perpendicular to the front wheel propeller shaft 108 F and the rear wheel propeller shaft 108 R. In addition, the motor 1 and the internal combustion engine 106 are not limited to being disposed transversely, but may be disposed longitudinally. That is, the power transmission shafts of the motor 1 and the internal combustion engine 106 may be disposed in parallel to the front wheel propeller shaft 108 F and the rear wheel propeller shaft 108 R. Next, the cooling structure and the motor according to the present embodiment will be described.

<Cooling Structure and Motor>

FIG. 3 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to the present embodiment. The motor 1 includes a cooling structure 2 , a housing 3 , a shaft 10 as a power transmission shaft, a rotor core 20 , and a stator 6 . The shaft 10 outputs the power generated by the motor 1 to the outside of the motor 1 , and inputs power to the motor 1 when the motor 1 is used as a generator. The rotor core 20 is attached to the outer periphery of the shaft 10 . The rotor core 20 is a cylindrical structure that includes stacked disk-shaped steel plates (electromagnetic steel plates) 21 . At the outside of the rotor core 20 , the stator 6 is disposed. The stator 6 is disposed at the outside of the rotor core 20 . In the present embodiment, the rotor core 20 includes a plurality of embedded permanent magnets, which will be described below. In this manner, in the present embodiment, the motor 1 includes an IPM (Interior Permanent Magnet), but may include an SPM (Surface Permanent Magnet). The stator 6 is a structure including a stator core 6 Y and a coil 6 C, and the coil 6 C is wound around the stator core 6 Y. A portion protruding from the stator core 6 Y of the coil 6 C is a coil end 6 CE. The stator core 6 Y is a structure that includes a plurality of stacked steel plates (electromagnetic steel plates). Also, the motor 1 may be a motor without a permanent magnet, for example, an induction motor or the like. That is, the cooling structure 2 can be applied regardless of whether the motor 1 includes a magnet.

The housing 3 stores the shaft 10 and the stator 6 to which the rotor core 20 is attached. The housing 3 includes a shaft extraction side member 3 T, a cylindrical side portion 3 S, and a cylindrical opposite shaft extraction side member 3 R. The space surrounded by the shaft extraction side member 3 T, the cylindrical side portion 3 S, and the opposite shaft extraction side member 3 R is the inside of the housing 3 . The shaft extraction side member 3 T includes a through hole 3 HA for extracting the shaft 10 to the outside of the housing 3 . The shaft 10 stored in the housing 3 is extracted through the through hole 3 HA. In the present embodiment, the shaft extraction side member 3 T and the side portion 3 S may be integratedly formed by, for example, casting or the like, but may be separately formed and connected by a fastening member such as screws. The opposite shaft extraction side member 3 R is attached to the side portion 3 S in the opposite side to the shaft extraction side member 3 T. The opposite shaft extraction side member 3 R is attached to the side portion 3 S by a fastening member such as screws.

The stator 6 is attached to the inner periphery of the side portion 3 S of the housing 3 . The stator 6 is an annular structure, and is attached around the entire inner periphery of the side portion 3 S. The rotor core 20 to which the shaft 10 is attached is disposed at the inner periphery side of the stator 6 . Bearings 4 A and 4 B are attached to both sides of the shaft 10 . The two bearings 4 A and 4 B are attached to the housing 3 , and rotatably support the shaft 10 . More specifically, the bearing 4 A is attached to the shaft extraction side member 3 T, and the bearing 4 B is attached to the opposite shaft extraction side member 3 R. By this configuration, the housing 3 rotatably supports the shaft 10 by the bearings 4 A and 4 B. The shaft 10 rotates around a central rotation axis Zr.

One end portion 10 C of the shaft 10 protrudes from the through hole 3 HA of the shaft extraction side member 3 T. For example, a gear, a joint, or the like is attached to the one end portion 10 C side of the shaft 10 . By this configuration, the power of the motor 1 is extracted from the shaft 10 through the gear, the joint, or the like, or power is input to the motor 1 to generate power from the motor 1 . The one end portion 10 C of the shaft 10 is an input/output side of the shaft 10 .

Sealing members 5 A and 5 B are provided between the shaft 10 and the housing 3 . Also, a rotation number sensor 51 detecting the rotation number of the shaft 10 is provided between the shaft 10 and the housing 3 . Also, the rotation number sensor 51 is disposed between the bearing 4 B and the sealing member 5 B. The sealing member 5 A is located in the through hole 3 HA of the shaft extraction side member 3 T, and is attached between the bearing 4 A and the one end portion 10 C of the shaft 10 . A sealing member 4 b is disposed at the other end portion 10 R side of the shaft 10 than the bearing 4 B, and is attached to the opposite shaft extraction side member 3 R. In the present embodiment, the inside of the motor 1 is cooled by a cooling medium (for example, oil) and simultaneously the bearings 4 A and 4 B are lubricated. Therefore, in order to suppress the cooling medium from leaking from the shaft 10 to the outside of the housing 3 , the sealing members 5 A and 5 B are provided between the housing 3 and the shaft 10 . Also, an oil seal 5 C as a sealing member is provided between the bearing 4 B and the sealing member 5 B.

The rotor core 20 is a structure including a plurality of steel plates 21 that are stacked and attached to the shaft 10 . When the plurality of steel plates 21 is in a state of being attached to the shaft 10 , the stacking direction of the plurality of steel plates 21 is parallel to the axial direction of the shaft 10 , that is, the central rotation axis Zr. Balance plates 30 A and 30 B are provided at both end portions of the rotor core 20 in the stacking direction. Also, the balance plates 30 A and 30 B are annular members, and are attached to the outer periphery of the shaft 10 . The rotor core 20 including the plurality of stacked steel plates 21 is sandwiched between the two balance plates 30 A and 30 B. In one side of the balance plate 30 A, the shaft 10 includes a rotor core fixing portion 14 that has an outer diameter larger than the inner diameter of the balance plate 30 A. Therefore, the balance plate 30 A attached to the shaft 10 from the other end portion 10 R side of the shaft 10 is restricted from being further moved when contacting the rotor core fixing portion 14 . The balance plate 30 A, the rotor core 20 , and the balance plate 30 B are attached to the shaft 10 in the order named, and a rotor core fixing nut 13 is screwed into the shaft 10 , so that the rotor core 20 is attached to the shaft 10 . In this state, the balance plates 30 A and 30 B applies a compressive force to the rotor core 20 , that is, the plurality of stacked steel plates 21 . The diameter of the balance plates 30 A and 30 B is equal to or smaller than the diameter of the steel plates 21 .

The shaft 10 includes a cooling medium supply passage 11 for passing a cooling medium for cooling the inside of the motor 1 . In the present embodiment, the cooling medium supply passage 11 is provided along the central rotation axis Zr. It is preferable that the cooling medium supply passage 11 is provided on the central rotation axis Zr. Also, the shaft 10 may be a hollow shaft, and an additional shaft may be provided to pass through the shaft 10 . In this case, the space formed between the shaft 10 and the additional shaft 10 passing through the shaft 10 may be the cooling medium supply passage 11 . The cooling medium supply passage 11 is located inside the shaft 10 , and extends from the other end portion 10 R in the axial direction of the shaft 10 , that is, the central rotation axis Zr direction. Therefore, the other end portion 10 R of the shaft 10 is provided with a cooling medium inlet 11 I through which a cooling medium flows into the cooling medium supply passage 11 . In this manner, the other end portion 10 R of the shaft 10 is the cooling medium inlet side.

In the present embodiment, the cooling medium supply passage 11 is provided partway toward the axial direction of the shaft 10 . The cooling medium supply passage 11 includes cooling medium ejection passages 12 A and 12 B that extend toward the radial outside of the shaft 10 . The cooling medium ejection passages 12 A and 12 B are opened to the cooling medium supply passage 11 . The cooling medium ejection passage (first cooling medium ejection passage) 12 A is located at a surface 10 S of the shaft 10 , and is opened to the one end portion 10 C side of the shaft 10 than the one side bearing 4 A. The cooling medium ejection passage (second cooling medium ejection passage) 12 B is located at the surface 10 S of the shaft 10 , and is opened to the other end portion 10 R side of the shaft 10 than the other side bearing 4 B. By this configuration, the cooling medium ejection passages 12 A and 12 B communicate with the cooling medium supply passage 11 and the surface 10 S of the shaft 10 . The cooling medium supplied to the cooling medium supply passage 11 is ejected from the cooling medium ejection passages 12 A and 12 B, and cools and lubricates the bearings 4 A and 4 B while flowing through a cooling medium recovery passage 7 B to be described below. Also, the motor 1 may not necessarily include the cooling medium ejection passages 12 A and 12 B.

A plurality of cooling medium passages 40 A and 40 B are branched from the cooling medium supply passage 11 . Also, FIG. 3 illustrates a cross-sectional surface in the case where the shaft 10 is cut along a plane that is parallel to the central rotation axis Zr of the shaft 10 and includes the central rotation axis Zr. However, for the convenience of description, the plurality of cooling medium passages 40 A and 40 B are shown on the same cross-sectional surface. However, in actuality, as will be described below, the cooling medium passages 40 A are shown on the respective cross-sectional surfaces in the case where the shaft 10 is cut along planes that have 90 degrees different center angles around the central rotation axis Zr.

The plurality of cooling medium passages 40 A and 40 B, which are branched from the cooling medium supply passage 11 , cools the rotor core 20 while flowing a cooling medium in one direction without branching the cooling medium with respect to the axial direction of the shaft 10 , and then ejects the cooling medium from ejection holes 40 AH and 40 BH that are opened to the surface of the rotor core 20 . The plurality of cooling medium passages 40 A and 40 B have the same distance (passage distance) from the cooling medium inlet 11 I, through which the cooling medium flows into the cooling medium supply passage 11 , to the ejection holes 40 AH and 40 BH. The cooling medium passages 40 A and 40 B will be described later in detail. The cooling medium ejected from the ejection holes 40 AH and 40 BH flows into the inside of the housing 3 from cooling medium outlets 31 B and 31 A included in the balance plates 30 B and 30 A. When the rotor core 20 is rotated, the cooling medium flowed from the cooling medium outlets 31 B and 31 A is blown to the radial outside of the rotor core 20 by a centrifugal force caused by the rotation. The cooling medium blown to the radial outside of the rotor core 20 cools the coil end 6 CE.

The cooling medium recovery passage 7 B is provided at the side portion 3 S of the housing 3 . When the motor 1 is in use, the cooling medium recovery passage 7 B is provided at a downward side (which is a gravity direction side and is a direction side indicated by an arrow G in FIG. 3 ). For example, when the motor 1 is mounted on the wheel loader 100 illustrated in FIG. 1 , the state of the wheel loader 100 being grounded to a horizontal plane is referred to as the state of the motor 1 being used. In this state, the cooling medium recovery passage 7 B is provided at a position in the downward side.

In the present embodiment, the housing 3 includes a coil end cooling passage 7 T at a portion that faces the coil end 6 CE and is out of the cooling medium recovery passage 7 B. A cooling medium is also supplied from the coil end cooling passage 7 T to the coil end 6 CE to cool the coil end 6 CE. Also, the coil end cooling passage 7 T need not necessarily be provided. For example, whether to provide the coil end cooling passage 7 T in the housing 3 is determined according to the specifications of the motor 1 , a mounting target of the motor 1 , or the like, or according to the operation conditions. When the motor 1 is disposed such that the central rotation axis Zr of the shaft 10 is perpendicular to the vertical direction (the gravity direction), it is preferable that the coil end cooling passage 7 T is disposed at the upward side (the opposite side to the vertical direction). In this case, it is more preferable that the coil end cooling passage 7 T is disposed at the uppermost side (that is, the top side).

In the present embodiment, the cooling medium is supplied to the motor 1 by a pump 8 as a cooling medium circulation means, and is suctioned by the pump 8 after cooling the motor 1 . A suction port of the pump 8 is connected to the cooling medium recovery passage 7 B by a first cooling medium pipe CL 1 . Also, a discharge port of the pump 8 is connected to the motor 1 by a second cooling medium pipe CL 2 . In the present embodiment, the second cooling medium pipe CL 2 is branched into a shaft side supply pipe CLA and a coil end side supply pipe CLB. The former is connected to the cooling medium inlet 11 I of the cooling medium supply passage 11 , and the latter is connected to the coil end cooling passage 7 T, so that the cooling medium discharged from the pump 8 is supplied to the respective connection targets.

In the present embodiment, the cooling structure 2 includes the cooling medium supply passage 11 and the plurality of cooling medium passages 40 A and 40 B. A portion of the cooling medium discharged from the pump 8 flows through the second cooling medium pipe CL 2 into the shaft side supply pipe CLA, and the other flows into the coil end side supply pipe CLB. The cooling medium flowing into the shaft side supply pipe CLA flows through the cooling medium inlet 11 I, and then a portion thereof flows into the respective cooling medium passages 40 A and 40 B. The cooling medium cools the rotor core 20 while passing through the cooling medium passages 40 A and 40 B, and is ejected from the ejection holes 40 AH and 40 BH into the housing 3 . The cooling medium ejected into the housing 3 reaches the coil end 6 CE by the centrifugal force of the rotor core 20 and cools the coil end 6 CE. The cooling medium not flowing into the cooling medium passages 40 A and 40 B is ejected from the cooling medium ejection passages 12 A and 12 B to cool and lubricate the bearings 4 A and 4 B. The cooling medium flowing through the coil end side supply pipe CLB flows into the coil end cooling passage 7 T and then is supplied to the coil end 6 CE to cool the coil end 6 CE. Even when the motor 1 is operated under the condition that the coil end 6 CE is apt to be insufficiently cooled by the cooling medium flowed from the cooling medium outlets 31 B and 31 A, the coil end 6 CE can be cooled by the coil end cooling passage 7 T. Therefore, the coil end cooling passage 7 T can stably operate the motor 1 in various operation conditions.

The cooling medium having cooled the coil end 6 CE and the cooling medium having cooled and lubricated the bearings 4 A and 4 B flow downward of the housing 3 by the action of gravity. This cooling medium is discharged through the cooling medium recovery passage 7 B to the outside of the housing 3 . The cooling medium discharged to the outside of the housing 3 is suctioned though the pump 8 into the first cooling medium pipe CL 1 . The pump 8 discharges the suctioned cooling medium to the second cooling medium pipe CL 2 . In this manner, in the cooling structure 2 , the pump 8 is used to circulate the cooling medium between the motor 1 , the first cooling medium pipe CL 1 , the second cooling medium pipe CL 2 , the shaft side supply pipe CLA, and the coil end side supply pipe CLB. The cooling structure 2 repeats the cooling of the rotor core 20 and the coil end 6 CE and the lubricating and cooling of the bearings 4 A and 4 B, which have been described above. Also, the first cooling medium pipe CL 1 and the second cooling medium pipe CL 2 may be provided with a filter for removing foreign substances from the cooling medium, and a cooler for cooling the heated-up cooling medium by cooling the rotor core 20 and the coil end 6 CE. Also, as means for supplying the cooling medium to the coil end cooling passage 7 T, in addition to the above-described cooling medium circulation structure, an additional cooling medium supply pump different from the pump 8 may be provided to supply the cooling medium to the coil end cooling passage 7 T. That is, the motor 1 may include a cooling circuit dedicated to the coil end cooling passage 7 T. Next, the components of the motor 1 will be described in more detail.

<Shaft and Rotor Core>

FIG. 4 is a front view of the shaft and the rotor core included in the motor according to the present embodiment, when viewed from the input/output side of the shaft. FIG. 5 is a side view of the shaft and the rotor core included in the motor according to the present embodiment. FIGS. 4 and 5 are to illustrate the cross-sectional surface illustrated in FIG. 12 from FIGS. 6, 8 and 10 . FIG. 6 is an A-A arrow view of FIG. 4 , and FIG. 7 is an enlarged view of the groove illustrated in FIG. 6 . FIG. 8 is a B-B arrow view of FIG. 4 , and FIG. 9 is an enlarged view of the groove illustrated in FIG. 8 . FIG. 10 is a C-C arrow view of FIG. 5 , and FIG. 11 is a D-D arrow view of FIG. 5 . FIG. 12 is an E-E arrow view of FIG. 5 . FIG. 13 is an enlarged view of the rotor core included in the motor according to the present embodiment.

As illustrated in FIG. 6 , two first cooling medium passages 41 A and 41 A extending to the radial outside are branched from the cooling medium supply passage 11 . In the present embodiment, each of first cooling medium passages 41 A and 41 B has a central axis perpendicular to the central rotation axis Zr. Therefore, the first cooling medium passages 41 A and 41 B are branched in a direction that is inclined by 90 degrees with respect to the cooling medium supply passage 11 included in the shaft 10 . By this configuration, the two first cooling medium passages 41 A and 41 A extend toward the radial outside of the shaft 10 . Also, the angle between the central rotation axis Zr and the central axis of the first cooling medium passages 41 A and 41 B may be other than 90 degrees.

Two grooves 15 A and 15 A extending in the axial direction of the shaft 10 are formed at the surface 10 S of the shaft 10 . That is, the shaft 10 includes the grooves 15 A and 15 A extending in the axial direction. As illustrated in FIGS. 6 and 7 , the first cooling medium passages 41 A and 41 A are opened in the respective grooves 15 A and 15 A. Also, the grooves 15 A and 15 A extend toward the one end portion 10 C of the shaft 10 . The first cooling medium passage 41 A is a portion of the cooling medium passage 40 A illustrated in FIG. 3 . Also, when the rotor core 20 is attached to the shaft 10 , the space surrounded by the groove 15 A and the rotor core 20 becomes a second cooling medium passage 42 A. That is, the second cooling medium passage 42 A extends in the axial direction of the shaft 10 . The second cooling medium passage 42 A is also a portion of the cooling medium passage 40 A illustrated in FIG. 3 .

FIG. 8 illustrates a cross-sectional surface in the case where the shaft 10 is cut along a plane that is different by 90 degrees from that of FIG. 6 in terms of the center angle around the central rotation axis Zr. As illustrated in FIG. 8 , two first cooling medium passages 41 B and 41 B extending to the radial outside are branched from the cooling medium supply passage 11 . Two grooves 15 B and 15 B extending in the axial direction of the shaft 10 are formed at the surface 10 S of the shaft 10 . That is, the shaft 10 includes the grooves 15 B and 15 B extending in the axial direction. As illustrated in FIGS. 8 and 9 , the first cooling medium passages 41 B and 41 B are opened in the respective grooves 15 B and 15 B. Also, unlike the above-described grooves 15 A and 15 A, the grooves 15 B and 15 B extend toward the other end portion 10 R of the shaft 10 . The first cooling medium passage 41 B is a portion of the cooling medium passage 40 B illustrated in FIG. 3 . Also, when the rotor core 20 is attached to the shaft 10 , the space surrounded by the groove 15 B and the rotor core 20 becomes a second cooling medium passage 42 B. That is, the second cooling medium passage 42 B extends in the axial direction of the shaft 10 . The second cooling medium passage 42 B is also a portion of the cooling medium passage 40 B illustrated in FIG. 3 .

The cooling medium flowing from the cooling medium inlet 11 I into the cooling medium supply passage 11 flows into the first cooling medium passage 41 A illustrated in FIG. 6 and the first cooling medium passage 41 B illustrated in FIG. 8 , and then changes the direction by 90 degrees and flows into the second cooling medium passage 42 A illustrated in FIG. 6 and the second cooling medium passage 42 B illustrated in FIG. 8 . In the present embodiment, the cooling medium flowing into the cooling medium supply passage 11 is branched into four passages. When the grooves 15 A and 15 B provided at the surface 10 S of the shaft 10 are used as the second cooling medium passages 42 A and 42 B, it is not necessary to process the rotor core 20 in order to form the second cooling medium passages 42 A and 42 B. Therefore, in the present embodiment, since the degradation of the magnetic characteristics of the rotor core 20 caused by the providing of the second cooling medium passages 42 A and 42 B hardly occurs, the performance degradation of the motor 1 by the second cooling medium passages 42 A and 42 B hardly occurs. Also, since the processing of the rotor core 20 is unnecessary, the manufacturing cost of the rotor core 20 can be reduced. In addition, since the grooves 15 A and 15 B can prevent slippage when holding the shaft 10 , and can serve as a landmark when attaching the rotor core 20 or the balance plates 30 A and 30 B to the shaft 10 , the manufacturing efficiency of the motor 1 can be improved.

<Balance Plate>

As illustrated in FIG. 10 , the balance plate 30 A includes a plurality of cooling medium outlets 31 A (four cooling medium outlets 31 A in the present embodiment) and two connection portions 32 A and 32 A. As illustrated in FIG. 3 , the cooling medium outlet 31 A is connected to the ejection hole 40 BH where the cooling medium passage 40 B is opened to the surface of the rotor core 20 . The connection portion 32 A is a concave portion that is concaved toward the thickness direction of the balance plate 30 A (the direction parallel to the central rotation axis Zr). The connection portion 32 A is a third cooling medium passage 43 A, and is a portion of the cooling medium passage 40 A illustrated in FIG. 3 . The connection portion 32 A connects the groove 15 A (second cooling medium passage 42 A) and a through hole of the rotor core 20 (fourth cooling medium passage) at the end portion of the rotor core 20 . In the present embodiment, the connection portion 32 A is connected to two through holes toward the circumferential direction of the rotor core 20 , but may be connected to at least one through hole. The through hole (fourth cooling medium passage) will be described below. The two connection portions 32 A and 32 A are disposed to be point-symmetrical with respect to the central rotation axis Zr. Also, the plurality of cooling medium outlets 31 A are disposed to be line-symmetrical with respect to a line that passes through the two grooves 15 A and 15 A and the central rotation axis Zr. The shaft 10 is provided with a key groove 16 , and the balance plate 30 A is also provided with a key groove 33 A. A key 34 A is interposed between a key groove 16 A and the key groove 33 A, so that the position of the balance plate 30 A attached to the shaft 10 is determined and the rotation thereof is restricted. Also, the cooling medium supply passage 11 is represented at the shaft 10 .

As illustrated in FIG. 11 , the balance plate 30 B includes a plurality of cooling medium outlets 31 B (four cooling medium outlets 31 B in the present embodiment) and two connection portions 32 B and 32 B. As illustrated in FIG. 3 , the cooling medium outlet 31 B is connected to the ejection hole 40 AH where the cooling medium passage 40 A is opened to the surface of the rotor core 20 . Like the above-described connection portion 32 A, the connection portion 32 B is a concave portion that is concaved toward the thickness direction of the balance plate 30 B (the direction parallel to the central rotation axis Zr). The connection portion 32 B is a third cooling medium passage 43 B, and is a portion of the cooling medium passage 40 B illustrated in FIG. 3 . The connection portion 32 B connects the groove 15 B (second cooling medium passage 42 B) and a through hole 24 of the rotor core 20 (fourth cooling medium passage 44 B). In the present embodiment, the connection portion 32 B is also connected to two through holes toward the circumferential direction of the rotor core 20 , but may be connected to at least one through hole. The through hole 24 passes through the rotor core 20 toward the stacking direction of the plurality of steel plates 21 (the direction parallel to the central rotation axis Zr). Therefore, the through hole 24 is connected to the balance plates 30 A and 30 B.

The two connection portions 32 B and 32 B are disposed to be point-symmetrical with respect to the central rotation axis Zr. The plurality of cooling medium outlets 31 B are disposed to be line-symmetrical with respect to a line that passes through the two grooves 15 B and 15 B and the central rotation axis Zr. In FIG. 11 , the through hole 24 of the rotor core 20 (fourth cooling medium passage 44 A) is represented at each of the cooling medium outlets 31 B.

The shaft 10 is provided with the key groove 16 , and the balance plate 30 B is also provided with a key groove 33 B. Also, the cooling medium supply passage 11 is represented at the shaft 10 . A key 34 B is interposed between a key groove 16 B and the key groove 33 B, so that the position of the balance plate 30 B attached to the shaft 10 is determined and the rotation thereof is restricted. The key groove 16 provided in the shaft 10 is common at any position in the balance plates 30 A and 30 B. With respect to the key groove 16 , the connection portions 32 B and 32 B of the balance plate 30 B are disposed at positions that are determined by rotating the connection portions 32 A and 32 A of the balance plate 30 A by 90 degrees around the central rotation axis Zr. Also, the plurality of cooling medium outlets 31 B of the balance plate 30 B are disposed at positions that are determined by rotating the plurality of cooling medium outlets 31 A of the balance plate 30 A by 90 degrees around the central rotation axis Zr. By this configuration, while the balance plates 30 A and 30 B are in a state of being attached to the shaft 10 , when the connection portion 32 A of the balance plate 30 A is projected on the balance plate 30 B, the cooling medium outlet 31 B of the balance plate 30 B and the connection portion 32 A overlap with each other. Likewise, in the same state, when the connection portion 32 B of the balance plate 30 B is projected on the balance plate 30 A, the cooling medium outlet 31 A of the balance plate 30 A and the connection portion 32 B overlap with each other.

The through hole 24 of the rotor core 20 (fourth cooling medium passage 44 A) is represented at the connection portion 32 B of the balance plate 30 B, and the through hole 24 (fourth cooling medium passage 44 B) is represented at each of the plurality of cooling medium outlets 31 B. As described above, the through hole 24 passes through the rotor core 20 toward the stacking direction of the plurality of steel plates 21 and is connected to the balance plates 30 A and 30 B. In the present embodiment, the rotor core 20 includes a plurality of through holes (eight through holes in this example), and the plurality of through holes 24 are provided on concentric circles around the central rotation axis Zr.

Since the cooling medium outlet 31 B of the balance plate 30 B and the connection portion 32 A of the balance plate 30 A overlap with each other, both are connected by the through hole 24 that is the fourth cooling medium passage 44 B. Also, since the connection portion 32 B of the balance plate 30 B and the cooling medium outlet 31 B of the balance plate 30 A overlap with each other, both are connected by the through hole 24 that is the fourth cooling medium passage 44 A. As will be described below, the fourth cooling medium passage 44 A is a portion of the cooling medium passage 40 A illustrated in FIG. 3 , and the fourth cooling medium passage 44 B is a portion of the cooling medium passage 40 B illustrated in FIG. 3 .

<Rotor Core>

As illustrated in FIG. 12 , a protrusion 25 is provided at each of the steel plates 21 included in the rotor core 20 . The protrusion 25 is fitted into the key groove 16 of the shaft 10 to determine the position of the steel plate 21 and restrict the rotation thereof. Since the key groove 16 of the shaft 10 is common toward the axial direction of the shaft 10 , the positional relation between the plurality of steel plates 21 and the balance plates 30 A and 30 B are determined with respect to the key groove 16 .

As illustrated in FIGS. 12 and 13 , the rotor core 20 includes the through hole 24 and a magnet holding hole 22 . The through hole 24 passes through toward the axial direction of the shaft 10 (the stacking direction of the stacked steel plates). The through hole 24 is opened to both end portions of the rotor core 20 , and is also opened to the magnet holding hole 22 . The magnet holding hole 22 passes through toward the axial direction of the shaft 10 (the stacking direction of the stacked steel plates), and holds a magnet (permanent magnet) 23 . Also, the through hole 24 may not be opened to the magnet holding hole 22 . Also, in the present embodiment, a plurality of magnet holding holes 22 ( 16 magnet holding holes 22 in this example) are formed along the circumferential direction of the rotor core 20 , but the number of magnet holding holes 22 is not limited thereto.

In the present embodiment, the through holes 24 are provided at portions adjacent to two magnet holding holes 22 in the radial inside of the rotor core 20 , and are opened respectively. Therefore, in the present embodiment, the through hole 24 connects two adjacent magnet holding holes 22 . In the present embodiment, the through holes 24 are provided at a plurality of positions (eight positions in the present embodiment) along the circumferential direction of the rotor core 20 . The through holes 24 of the rotor core 20 are used to cool the rotor core 20 . In this embodiment, eight through holes 24 are provided, but at least one through hole 24 may be provided and the number of through holes 24 is not limited thereto. Also, the through holes 24 are not limited to those of the present embodiment. For example, two through holes 24 may be separately opened to two adjacent magnet holding holes 22 .

As illustrated in FIG. 13 , the through holes 24 overlap with the cooling medium outlets 31 A and 31 B and the connection portions 32 A and 32 B (third cooling medium passages 43 A and 43 B). As described above, the through holes 24 are the fourth cooling medium passages 44 A and 44 B that are the portions of the cooling medium passages 40 A and 40 B. The cooling medium passes through the through hole 24 toward the cooling medium outlet 31 A from the cooling medium outlet 31 B or the connection portion 32 B. While the cooling medium passes through the through hole 24 , the rotor core 20 is cooled. Also, since the through hole 24 is opened to the magnet holding hole 22 , a portion of the magnet 23 is exposed to the through hole 24 . Therefore, the cooling medium flows through the through hole 24 , so that the magnet 23 is also cooled. Also, the through hole 24 need not necessarily be opened to the magnet holding hole 22 .

<Cooling Structure and Cooling Medium Passage>

FIGS. 14 and 15 are views illustrating the cooling structure and the cooling medium passage according to the present embodiment. FIG. 16 is a perspective view illustrating the cooling medium supply passage and the cooling medium passage. FIG. 17 is a pattern diagram illustrating an arrangement of the cooling medium supply passage and the cooling medium passage. As described above, the cooling medium passage 40 A represented at the A-A cross-sectional surface includes a first cooling medium passage 41 A, a second cooling medium passage 42 A (groove 15 A), a third cooling medium passage 43 A (connection portion 32 A), a fourth cooling medium passage 44 A (through hole 24 ), and an ejection hole 40 AH. Also, the cooling medium passage 40 B represented at the B-B cross-sectional surface includes a first cooling medium passage 41 B, a second cooling medium passage 42 B (groove 15 A), a third cooling medium passage 43 B (connection portion 32 B), a fourth cooling medium passage 44 B (through hole 24 ), and an ejection hole 40 BH. The cooling structure 2 includes a cooling medium supply passage 11 and a plurality of cooling medium passages 40 A and 40 B.

The cooling medium flowing through the cooling medium supply passage 11 are branched from the first cooling medium passages 41 A and 41 B of the respective cooling medium passages 40 A and 40 B and flows to the radial outside of the shaft 10 . Thereafter, the cooling medium changes the flow direction by 90 degrees, flows into the second cooling medium passages 42 A and 42 B, and flows toward the radial direction of the shaft 10 . While passing through the second cooling medium passages 42 A and 42 B, the cooling medium cools the rotor core 20 from the inner periphery side. Therefore, since the rotor core 20 can be directly cooled and the magnet 23 of the rotor can be indirectly cooled, the heating-up of the magnet 23 can be suppressed and the degradation of the magnetic characteristics can be suppressed.

The cooling medium having passed through the second cooling medium passages 42 A and 42 B flows out from end portions 20 TA and 20 TB of the rotor core 20 . Thereafter, the cooling medium changes the flow direction by 180 degrees at the third cooling medium passages 43 A and 43 B disposed at the end portion of the rotor core 20 , and flows into the fourth cooling medium passages 44 A and 44 B. Thereafter, in the process of passing through the fourth cooling medium passages 44 A and 44 B, the cooling medium flows toward the ejection holes 40 AH and 40 BH while cooling the rotor core 20 and the magnet 23 of the rotor core 20 .

The ejection hole 40 AH of the cooling medium passage 40 A is opened to the end portion 20 TB of the rotor core 20 , and the ejection hole 40 BH of the cooling medium passage 40 B is opened to the end portion 20 TA of the rotor core 20 . In this manner, the election holes 40 AH and 40 BH are opened to the surface of the rotor core 20 . The cooling medium ejected from the ejection hole 40 AH flows out to the cooling medium outlet 31 B of the balance plate 30 B, and the cooling medium ejected from the ejection hole 40 BH flows out to the cooling medium outlet 31 A of the balance plate 30 A. When the rotor core 20 rotates together with the shaft 10 , the cooling medium is blown by the centrifugal force of the rotor core 20 from the cooling medium outlets 31 A and 31 B to the coil end 6 CE illustrated in FIG. 3 , so that the cooling medium collides against the coil end 6 CE and cools the coil end 6 CE.

In this manner, the respective ejection holes 40 AH and 40 BH of the cooling medium passages 40 A and 40 B are respectively opened to both end portions 20 TB and 20 TA of the rotor core 20 . By this configuration, the cooling medium can be supplied to the coil end 6 CE on both sides of the shaft 10 in the axial direction to cool the coil end 6 CE. Also, in the present embodiment, the cooling medium passages 40 A and 40 B have the same distance (passage distance) L from the cooling medium inlet 11 I to the ejection holes 40 AH and 40 BH. In the present embodiment, the equality not only includes complete equality, but also includes those that are different in tolerance or manufacturing error.

As illustrated in FIG. 17 , the passage distance L is equal to the sum (the length of the cooling medium passages 40 A and 40 B) of the distance (supply passage distance) L 1 from the cooling medium inlet 11 I to the inlets of the first cooling medium passages 41 A and 41 B, the length L 1 of the first cooling medium passages 41 A and 41 B, the length L 2 of the second cooling medium passages 42 A and 42 B, the length L 3 of the third cooling medium passages 43 A and 43 B, and the length L 4 of the fourth cooling medium passages 44 A and 44 B. In this embodiment, the passage distance is measured according to the central axis of the cooling medium supply passage 11 and the first cooling medium passages 41 A and 41 B (the axis obtained by connecting the centroids of the respective cross-sectional views).

As illustrated in FIGS. 16 and 17 , in the present embodiment, the third cooling medium passage 43 A branches the second cooling medium passage 42 A into two fourth cooling medium passages 44 A 1 and 44 A 2 . Also, the third cooling medium passage 43 B branches the second cooling medium passage 42 B into two fourth cooling medium passages 44 B 1 and 44 B 2 . Therefore, the length L 3 of the third cooling medium passage 43 A is equal to the distance from the inlet I 3 of the third cooling medium passage 43 A to the inlet I 4 of the fourth cooling medium passage 44 A 1 or 44 A 2 (the same is true for the third cooling medium passage 43 B). Also, the distance from the inlet I 3 of the third cooling medium passage 43 A to the inlet I 4 of the one-side fourth cooling medium passage 44 A 1 is equal to the distance from the inlet I 3 of the third cooling medium passage 43 A to the inlet I 4 of the other-side fourth cooling medium passage 44 A 2 .

When the length L 3 from the inlet I 3 of the third cooling medium passage 43 A to the one-side fourth cooling medium passage 44 A 1 is used as the length L 3 of the third cooling medium passage 43 A, the length of the fourth cooling medium passage 44 A 1 is used as the length L 4 of the fourth cooling medium passage 44 A. When the length L 3 from the inlet I 3 of the third cooling medium passage 43 A to the other-side fourth cooling medium passage 44 A 2 is used as the length L 3 of the third cooling medium passage 43 A, the length of the fourth cooling medium passage 44 A 2 is used as the length L 4 of the fourth cooling medium passage 44 A.

In the present embodiment, the positions of the plurality of cooling medium passages 40 A and 40 B branched from the cooling medium supply passage 11 are the same in the axial direction of the shaft 10 . Therefore, in the cooling medium passages 40 A and 40 B for ejecting the cooling mediums to the different end portions of the rotor core 20 , the respective supply passage distances L 1 are equal to each other.

In the present embodiment, the cooling medium supply passage 11 in the shaft 10 having a circular cross-sectional surface has a circular cross-section surface and has the central axis identical to the central rotation axis Zr (the cross-sectional surface is a cross-sectional surface taken along a plane perpendicular to the central rotation axis Zr). Therefore, in the portion where the cooling medium supply passage 11 , the thicknesses of the shaft 10 are equal, and the lengths L 1 of the first cooling medium passages 41 A and 41 B of the cooling medium passages 40 A and 40 B are equal.

The position at which each of the first cooling medium passages 41 A and 41 B is opened to the surface of the shaft 10 is the central portion of the rotor core 20 in the axial direction of the shaft 10 . Therefore, the lengths L 2 of the second cooling medium passages 42 A and 42 B connected respectively to the first cooling medium passages 41 A and 41 B are equal to each other.

The two connection portions 32 A and 32 B have the same dimension and shape. Also, the fourth cooling medium passages 44 A and 44 B, that is, the plurality of through holes 24 are provided on the same concentric circle around the central rotation axis Zr. Therefore, the lengths L 3 of the third cooling medium passages 43 A and 43 B are equal to each other. Since all of the fourth cooling medium passages 44 A and 44 B pass through the rotor core 20 in parallel to the central rotation axis Zr, the lengths L 4 of the fourth cooling medium passages 44 A and 44 B are equal to each other.

Therefore, as described above, in the cooling medium passages 40 A and 40 B for ejecting the cooling mediums to the different end portions of the rotor core 20 , the respective passage distances L (=L 1 +L 1 +L 2 +L 3 +L 4 ) are equal to each other.

In this way, the cooling medium passages 40 A and 40 B for ejecting the cooling mediums to the different end portions of the rotor core 20 have substantially the same pressure loss from the cooling medium inlet 11 I to ejection holes 40 AH 1 , 40 AH 2 , 40 BH 1 and 40 BH 2 . Therefore, the cooling structure 2 can substantially equalize the flow rates of the cooling mediums flowing through the respective cooling medium passages 40 A and 40 B, and can suppress a variation in the flow rates of the cooling mediums ejected from the respective ejection holes 40 AH 1 , 40 AH 2 , 40 BH 1 and 40 BH 2 . As a result, the cooling variation of the rotor core 20 by the cooling mediums flowing through the cooling medium passages 40 A and 40 B and the cooling variation of both coil ends 6 CE can be reduced. Therefore, the cooling structure 2 can suppress the local heating-up of the rotor core 20 and the coil end 6 CE, and thus can suppress the performance degradation of the motor 1 caused by the heating-up of the coil 6 C, the magnet 23 , and the rotor core 20 .

In the cooling structure 2 , when there is a variation in the flow rates of the cooling mediums ejected from the respective ejection holes 40 AH 1 , 40 AH 2 , 40 BH 1 and 40 BH 2 , it is necessary for the ejection hole with the lowest flow rate to achieve a required cooling performance. Then, the ejection hole with a high flow rate provides an excessive flow rate of cooling medium in comparison with the required cooling performance. This causes the supply of an excessive cooling medium to the cooling medium passage, thus leading to an increase in the energy required to eject the excessive cooling medium. Also, since an excessive amount of cooling medium is supplied from the ejection hole with a high flow rate, a large amount of cooling medium is supplied to the inside of the housing 3 . As a result, since the rotor core 20 agitates a large amount of cooling medium present in the housing 3 during rotation, the energy loss by the agitation of the cooling medium increases.

The cooling structure 2 of the present embodiment can substantially equalize the passage distances L of the respective cooling medium passages 40 A and 40 B, and thus can suppress a variation in the flow rates of the cooling mediums ejected from the respective ejection holes 40 AH 1 , 40 AH 2 , 40 BH 1 and 40 BH 2 . Therefore, since the excess of a cooling medium flow rate over the required cooling performance can be suppressed, the power consumption required for the supply of the cooling medium can be suppressed. Also, the cooling structure 2 can appropriately control the amount of the cooling medium present in the housing 3 , and thus can suppress the energy loss caused by the agitation of a large amount of cooling medium by the rotor core 20 .

Also, in the present embodiment, the cooling medium passage 40 A includes two fourth cooling medium passages 44 A 1 and 44 A 2 , and the cooling medium passage 40 B includes the two fourth cooling medium passages 44 B 1 and 44 B 2 . Accordingly, the cooling medium passage 40 A includes two ejection holes 40 AH 1 and 40 AH 2 as an ejection hole 40 AH, and the cooling medium passage 40 B includes two ejection holes 40 BH 1 and 40 BH 2 as an ejection hole 40 BH.

In the case of this configuration, it can be considered that the cooling medium passage 40 A includes two passages that are a passage including the fourth cooling medium passage 44 A 1 and a passage including the fourth cooling medium passage 44 A 2 . Herein, the length of the fourth cooling medium passage 44 A 1 is denoted by L 4 a , and the length of the fourth cooling medium passage 44 A 2 is denoted by L 4 b . Since all of the fourth cooling medium passages 44 A 1 and 44 A 2 pass through the rotor core 20 in parallel to the central rotation axis Zr, the lengths L 4 of the fourth cooling medium passages 44 A 1 and 44 A 2 are equal to each other (L 4 a =L 4 b ). Then, in the cooling medium passage 40 A, the passage distance L 1 (=L 1 +L 1 +L 2 +L 3 +L 4 a ) of a passage including the fourth cooling medium passage 44 A 1 is equal to the passage distance L 2 (=L 1 +L 1 +L 2 +L 3 +L 4 b ) of a passage including the fourth cooling medium passage 44 A 2 . Therefore, in the cooling medium passage 40 A, since the pressure loss of the passage including the fourth cooling medium passage 44 A 1 and the pressure loss of the passage including the fourth cooling medium passage 44 A 2 can be substantially equalized, the flow rate variation of the cooling mediums ejected from the fourth cooling medium passages 44 A 1 and 44 A 2 can be suppressed. When the cooling structure 2 includes two cooling medium passages 40 A, the respective passage distances L in four passages in the two cooling medium passages 40 A are equalized. As a result, since the pressure losses of the four passages in the two cooling medium passages 40 A can be substantially equalized, the flow rate variation of the cooling mediums ejected from the four passages can be suppressed.

The above-described relation is the same as for the respective cooling medium passages 40 B included in the cooling structure 2 . Therefore, in the entire cooling structure 2 , the passage distances L of eight passages in two cooling medium passages 40 A and two cooling medium passages 40 B are equalized. As a result, since the pressure losses of the eight passages can be substantially equalized, the flow rate variation of the cooling mediums ejected from openings, at which the eight passages are opened to both end portions of the rotor core 20 , can be suppressed.

After branching from the cooling medium supply passage 11 , each of the cooling medium passages 40 A and 40 B flows a cooling medium without branching the cooling medium in the axial direction of the shaft 10 . In the present embodiment, the cooling medium passages 40 A and 40 B include the second cooling medium passages 42 A and 42 B and the fourth cooling medium passages 44 A and 44 B that are parallel to the axial direction of the shaft 10 . The cooling medium passages 40 A and 40 B are connected to the second cooling medium passages 42 A and 42 B after branching from the cooling medium supply passage 11 in the first cooling medium passages 41 A and 41 B that are oriented to the radial outside of the shaft 10 (and rotor core 20 ). The second cooling medium passages 42 A and 42 B are connected to the third cooling medium passages 43 A and 43 B. Also, the fourth cooling medium passages 44 A and 44 B are connected to the third cooling medium passages 43 A and 43 B on the same side as the second cooling medium passages 42 A and 42 B. Therefore, the cooling medium passages 40 A and 40 B are returned by 180 degrees at the third cooling medium passages 43 A and 43 B.

The second cooling medium passages 42 A and 42 B connect the outlets of the first cooling medium passages 41 A and 41 B and the inlets of the third cooling medium passages 43 A and 43 B, and are not branched therebetween. Likewise, the fourth cooling medium passages 44 A and 44 B connect the outlets of the third cooling medium passages 43 A and the ejection holes 40 AH and 40 BH, and are not branched therebetween. In this configuration, for example, when the second cooling medium passages 42 A and 42 B parallel to the axial direction of the shaft 10 are branched in the axial direction, the cooling medium flows more to the side that is branched in the acting direction of a force of a component parallel to the axial direction of the shaft 10 . As a result, since the cooling medium is ejected more from the end portion of the rotor core 20 in the acting direction of the force, the cooling variation of the coil end 6 CE in the axial direction occurs.

The cooling medium passages 40 A and 40 B flows a cooling medium without branching the cooling medium in the axial direction of the shaft 10 . In this manner, since the cooling medium passages 40 A and 40 B do not include a passage branched in the axial direction, even when the cooling medium having flowed therethrough receives the force of the component parallel to the axial direction of the shaft 10 , the flow rate unbalance between the branched passages does not occur. As a result, the cooling structure 2 can suppress a flow rate change of the cooling mediums passing through the cooling medium passages 40 A and 40 B, which is caused by the force. Therefore, the cooling structure 2 can suppress the flow rate unbalance of the cooling mediums ejected from both end portions 20 TA and 20 TB of the rotor core 20 , and thus can reduce the cooling variation of the coil end 6 CE in the axial direction and the cooling variation of the rotor core 20 in the axial direction.

Particularly, in the present embodiment, the cooling medium passages 40 A and 40 B are opposite to the direction of the cooling medium passing through the second cooling medium passages 42 A and 42 B extending in parallel to the axial direction of the shaft 10 , and the direction of the cooling medium passing through the fourth cooling medium passages 44 A and 44 B extending in parallel to the axial direction of the shaft 10 . By this configuration, when a force of a component parallel to the axial direction of the shaft 10 accelerates the cooling medium passing through the second cooling medium passages 42 A and 42 B, the force decelerates the cooling medium passing through the fourth cooling medium passages 44 A and 44 B. Therefore, even when the cooling medium receives a force of a component parallel to the axial direction of the shaft 10 , the cooling structure 2 can nearly cancel the force between the second cooling medium passages 42 A and 42 B and the fourth cooling medium passages 44 A and 44 B. As a result, even when the cooling medium receives a force of a component parallel to the axial direction of the shaft 10 , the cooling structure 2 can suppress the flow rate variation of the cooling mediums between the plurality of cooling medium passages 40 A and 40 B, and thus can more securely reduce the cooling variation of the core end 6 CE in the axial direction and the cooling variation of the rotor core 20 in the axial direction.

A construction vehicle such as the wheel loader 100 illustrated in FIG. 1 usually performs an operation in an inclined area. In an inclined area, the cooling medium flowing through the cooling medium passages 40 A and 40 B is subject to receive a force of a component parallel to the axial direction of the shaft 10 . Also, the wheel loader rapidly enters earth and sand, skims the earth and sand into the bucket 103 , rapidly retreats, turns while accelerating rapidly in the forward direction, abruptly stops at the position of a dump or the like to be loaded with the earth and sand, and loads the earth and sand on the dump. In this manner, the wheel loader 100 may perform an operation that requires repeated rapid acceleration in the longitudinal direction and the lateral direction (perpendicular to the longitudinal direction). In this case, the cooling medium flowing through the cooling medium passages 40 A and 40 B may also be subject to receive a force of a component parallel to the axial direction of the shaft 10 . As described above, the cooling structure 2 and the motor 1 according to the present embodiment can suppress the cooling variation of the coil end 6 CE and the rotor core 20 in the axial direction even when the cooling medium receives a force of a component parallel to the axial direction of the shaft 10 . Therefore, the cooling structure 2 and the motor 1 are suitable for an operation requiring repeated rapid acceleration in the longitudinal direction and the lateral direction, such as in the wheel loader 100 .

Also, in the present embodiment, the third cooling medium passage 43 A of the cooling medium passage 40 A branches the cooling medium flowed in from the second cooling medium passage 42 A into two fourth cooling medium passages 44 A 1 and 44 A 2 (the same is true for the third cooling medium passage 43 B). That is, since the cooling medium is branched into two fourth cooling medium passages 44 A 1 and 44 A 2 toward the circumferential direction of the shaft 10 and the rotor core 20 , it satisfies the condition that the cooling medium is flowed without being branched in the axial direction of the shaft 10 .

It is preferable that each of the positions of the cooling medium passages 40 A and 40 B branched from the cooling medium supply passage 11 is the central portion of the rotor core 20 in the axial direction of the shaft 10 . In the example illustrated in FIGS. 14 and 15 , when the length of the rotor core 20 in the axial direction is Lr, each of the distances from the end portions 20 TA and 20 TB of the rotor core 20 to the positions of the first cooling medium passages 41 A and 41 B, that is, the distance to the branching position, is Lr/2. In this way, since the distribution of the cooling medium can be easily balanced on both axial sides of the shaft 10 , the cooling variation of the coil end 6 CE and the rotor core 20 in the axial direction can be easily suppressed. Also, the passage distances L can be easily equalized between the plurality of cooling medium passages 40 A and 40 B.

It is preferable that an even number of cooling medium passages 40 A and 40 B are branched from the cooling medium supply passage 11 . In the present embodiment, the respective two cooling medium passages 40 A and 40 B, that is, four cooling medium passages 40 A and 40 B are branched from the cooling medium supply passage 11 . In this way, since the same number of ejection holes can be provided at both end portions 20 TA and 20 TB of the rotor core 20 , the cooling medium can be ejected from both end portions 20 TA and 20 TB of the rotor core 20 at substantially equal flow rates. As a result, the cooling variation of the coil end 6 CE and the rotor core 20 in the axial direction can be easily suppressed.

It is preferable that the passage distances L of the plurality of cooling medium passages 40 A and 40 B are equalized and also the dimensions (cross-sectional passage dimensions) and shapes (cross-sectional passage shapes) in the case where the cooling medium passages 40 A and 40 B are cut along the plane perpendicular to the flow direction of the cooling medium are equalized. The passage distances L are dominant in the pressure losses of the cooling medium passages 40 A and 40 B. However, by equalizing the cross-sectional passage dimensions and cross-sectional passage shapes between the plurality of cooling medium passages 40 A and 40 B, the pressure losses between the plurality of cooling medium passages 40 A and 40 B can be further equalized. As a result, the flow rate variation of the cooling medium between the plurality of cooling medium passages 40 A and 40 B can be further suppressed, and the cooling variation of the coil end 6 CE and the rotor core 20 in the axial direction can be reduced. Also, when the cross-sectional passage dimensions and the cross-sectional passage shapes are equalized, the tolerance and the manufacturing error may be different.

As described above, in the cooling structure 2 , the pressure losses of the plurality of cooling medium passages 40 A and 40 B may be equalized in consideration of a centrifugal force caused by the rotation of the shaft 10 and the rotor core 20 . Therefore, in the plurality of cooling medium passages 40 A and 40 B, when the pressure losses considering the centrifugal force are equal, the cross-sectional passage dimensions and the cross-sectional passage shapes may be different. However, when the passage distances L, the cross-sectional passage dimensions, and the cross-sectional passage shapes are different, the pressure losses between the plurality of cooling medium passages 40 A and 40 B can be equalized under a specific condition, but it is difficult to equalize the pressure losses under other conditions. Therefore, in the plurality of cooling medium passages 40 A and 40 B, at least the passage distances L are equalized, and preferably, the cross-sectional passage dimensions and the cross-sectional passage shapes are also equalized. In this way, since the pressure losses between the plurality of cooling medium passages 40 A and 40 B can be simply equalized in different conditions, the stability and reliability of the cooling structure 2 can be improved. In particular, when the motor 1 is used in a construction vehicle, since the operation condition varies greatly, in order to accommodate this, it is preferable that the passage distances L or the like are equalized.

In order to equalize the pressure losses considering the centrifugal force, it is more preferable that the three-dimensional shapes of the plurality of cooling medium passages 40 A and 40 B are equalized. That is, it is preferable that the dimensions and shapes of the first cooling medium passages 41 A and 41 B, the dimensions and shapes of the second cooling medium passages 42 A and 42 B, the dimensions and shapes of the third cooling medium passages 43 A and 43 B, and the dimensions and shapes of the fourth cooling medium passages 44 A and 44 B are equalized. The shape equalization not only includes the equalization of the above-described cross-sectional passage shapes, but also includes the equalization of the angles between the passages and the equalization of the bent states of the portions connecting the passages. Also, the equality includes a difference in the tolerance or the manufacturing error. In this way, the pressure losses considering the centrifugal force can be substantially equalized between the plurality of cooling medium passages 40 A and 40 B. As a result, the flow rate variation of the cooling medium between the plurality of cooling medium passages 40 A and 40 B can be further suppressed, and the cooling variation of the coil end 6 CE and the rotor core 20 in the axial direction can be further reduced.

<Modified Example of Cooling Medium Passage>

FIGS. 18 and 19 are pattern diagrams illustrating modified examples of the cooling medium passage included in the cooling structure according to the present embodiment. A cooling structure 2 a of FIG. 18 includes first cooling medium passages 41 Aa and 41 Ba branched from the cooling medium supply passage 11 toward the radial outside of the shaft 10 , second cooling medium passages 42 Aa and 42 Ba extending in the axial direction of the shaft 10 , and ejection holes 40 AHa and 40 BHb opened to both end portions 20 TA and 20 TB of the rotor core 20 illustrated in FIGS. 15 and 16 . The cooling structure 2 a is configured such that the cooling medium passages 40 A and 40 B are not returned at both end portions 20 TA and 20 TB of the rotor core 20 .

In the cooling structure 2 a , the passage distance of cooling medium passages 40 Aa and 40 Ba is equal to the sum of the distance (supply passage distance) from the cooling medium inlet 11 I to the inlet of the first cooling medium passages 41 Aa and 41 Ba, the length of the first cooling medium passages 41 Aa and 41 Ba, and the length of the second cooling medium passages 42 Aa and 42 Ba. Like the cooling structure 2 , the cooling structure 2 a is configured such that the passage distances of the cooling medium passages 40 Aa and 40 Ba opened respectively both end portions of the rotor core 20 (the distances from the cooling medium inlet 11 I to the respective ejection holes 40 AHa and 40 BHa) are equal. As a result, the cooling structure 2 a can also suppress the cooling variation of the rotor core 20 and the coil end 6 CE.

A cooling structure 2 b of FIG. 19 includes first cooling medium passages 41 Ab and 41 Bb branched from the cooling medium supply passage 11 toward the radial outside of the shaft 10 , second cooling medium passages 42 Ab and 42 Bb extending in the axial direction of the shaft 10 , third cooling medium passages 43 Ab and 43 Bb extending toward the radial outside of the shaft 10 , fourth cooling medium passages 44 Ab and 44 Bb extending in the axial direction of the shaft 10 , and ejection holes 40 AHb and 40 BHb opened to both end portions 20 TA and 20 TB of the rotor core 20 illustrated in FIGS. 15 and 16 . The cooling structure 2 b is configured such that the third cooling medium passage 43 A or the like is connected to one of the fourth cooling medium passages 44 A 1 and 44 A 2 in the cooling structure 2 illustrated in FIGS. 16 and 17 .

In the cooling structure 2 b , the passage distance of cooling medium passages 40 Ab and 40 Bb is equal to the sum of the distance (supply passage distance) from the cooling medium inlet 11 I to the inlet of the first cooling medium passages 41 Ab and 41 Bb, the length of the first cooling medium passages 41 Ab and 41 Bb the length of the second cooling medium passages 42 Ab and 42 Bb, the length of the third cooling medium passages 43 Ab and 43 Bb, and the length of the fourth cooling medium passages 44 Ab and 44 Bb. Like the above-described cooling structures 2 and 2 a , the cooling structure 2 b is configured such that the passage distances of the cooling medium passages 40 Ab and 40 Bb opened respectively both end portions of the rotor core 20 (the distances from the cooling medium inlet 11 I to the respective ejection holes 40 AHb and 40 BHb) are equal. As a result, the cooling structure 2 a can also suppress the cooling variation of the rotor core 20 and the coil end 6 CE.

<First Modified Example of Cooling Structure>

FIG. 20 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to a first modified example of the present embodiment. A cooling structure 2 c and a motor 1 c of the first modified example are substantially the same as the above-described cooling structure 2 and the motor 1 . However, the cooling structure 2 c and the motor 1 c are different from the cooling structure 2 and the motor 1 in terms of the configuration of cooling medium passages 40 Ac and 40 Bc branched from the cooling medium supply passage 11 . The other configurations are the same as those of the above-described cooling structure 2 and the motor 1 , and thus a description thereof will be omitted.

The cooling medium passages 40 Ac and 40 Bc include branch passages 46 A and 46 B that are branched from the cooling medium supply passage 11 and are connected to the third cooling medium passages 43 A and 43 B (connection portions 32 A and 32 B). The branch passage 46 A extends slantly toward the radial outside of the shaft 10 and the one end portion 10 C, and the branch passage 46 B extends slantly toward the radial outside of the shaft 10 and the other end portion 10 R. This structure can also suppress the cooling variation of the rotor core 20 and the coil end 6 CE.

<Second Modified Example of Cooling Structure>

FIG. 21 is a cross-sectional view illustrating a motor cooling structure and a motor including the motor cooling structure according to a second modified example of the present embodiment. A cooling structure 2 d and a motor 1 d of the second modified example are substantially the same as the above-described cooling structure 2 and the motor 1 . However, the cooling structure 2 d and the motor 1 d are different from the cooling structure 2 and the motor 1 in that second cooling medium passages 42 Ad and 42 Bd included in cooling medium passages 40 Ad and 40 Bd are provided in a rotor core 20 d . The other configurations are the same as those of the above-described cooling structure 2 and the motor 1 , and thus a description thereof will be omitted.

A portion of the inner periphery of the rotor core 20 d is removed from a portion at which the first cooling medium passages 41 A and 41 B are opened to the shaft 10 , to the inlets of the third cooling medium passages 43 A and 43 B (connection portions 32 A and 32 B), toward the radial outside, thereby forming concave portions 26 A and 26 B. This portion becomes the second cooling medium passages 42 Ad and 42 Bd. Also, the second cooling medium passages 42 Ad and 42 Bd or the like may be formed in the rotor core 20 d . The cooling structure 2 d does not need to form grooves at the surface of the shaft 10 in order to form the second cooling medium passages 42 Ad and 42 Bd. This structure can also suppress the cooling variation of the rotor core 20 and the coil end 6 CE.

As described above, when cooling the motor by the cooling medium, the present embodiment and the modified examples equalize the passage distances L of the plurality of cooling medium passages and do not branch the cooling medium into the cooling medium passage that is parallel to the shaft of the motor. Accordingly, the pressure losses of the respective cooling medium passages can be maintained to be substantially constant, and the flow rates of the cooling mediums passing through the respective cooling passages can be maintained to be substantially constant. As a result, the present embodiment and the modified examples can suppress the cooling variation of the rotor core and the coil (specifically, the coil end), and thus can suppress the performance of the motor. Also, the present embodiment and the modified examples can stably operate the motor. In addition, since the cooling medium is not branched into the cooling medium passage parallel to the shaft of the motor, even when the cooling medium receives a force in the direction parallel to the shaft, the flow rate variation of the cooling medium caused by the force can be reduced. As a result, even in the case of the motor that is subject to receive a force in the direction parallel to the shaft, the flow rate variation of the cooling mediums passing through the respective cooling passages can be reduced, so that the cooling variation of the rotor core and the coil (specifically, the coil end) can be suppressed.

1 , 1 c , 1 d motor

2 , 2 a , 2 b , 2 c , 2 d motor cooling structure (cooling structure)

3 housing

3 R opposite shaft extraction side member

3 S side portion

3 T shaft extraction side member

4 A, 4 B bearing

6 stator

6 C coil

6 CE coil end

6 Y stator core

7 B cooling medium recovery passage

7 T coil end cooling passage

8 pump

10 shaft

10 C one end portion

10 R other end portion

11 cooling medium supply passage

11 I cooling medium inlet

15 A, 15 B groove

20 , 20 d rotor core

20 TA, 20 TB end portion

21 steel plate

22 magnet holding hole

23 magnet

24 through hole

30 A, 30 B balance plate

31 A, 31 B cooling medium outlet

32 A, 32 B connection portion

40 AH, 40 BH, 40 AH 1 , 40 BH 1 , 40 AHa, 40 AHb ejection hole

40 A, 40 Ac, 40 Ad, 40 B, 40 Bc, 40 Bd cooling medium passage

41 A, 41 Aa, 41 Ab, 41 B, 41 Ba, 41 Bb first cooling medium passage

42 A, 42 Aa, 42 Ab, 42 Ad, 42 B, 42 Ba, 42 Bb, 42 Bd second cooling medium passage

43 A, 43 Ab, 43 B, 43 Bb third cooling medium passage

44 A, 44 A 1 , 44 A 2 , 44 Ab, 44 B, 44 B 1 , 44 B 2 , 44 Bb fourth cooling medium passage

46 A, 46 B branch passage

100 wheel loader