Motor

The technique disclosed herein relates to a structure of coils in a motor.

Industry motors and on-vehicle motors have been highly demanded in recent years. In particular, a low cost but highly efficient motor has been demanded.

As a method for improving efficiency of a motor, increasing a space factor of coils respectively disposed within slots of a stator has been known. Increasing a space factor of coils can suppress a loss due to a current flowing into the coils when a motor is driven.

As a method for increasing a space factor of coils, such a configuration has been proposed that molded coils made of a copper material are respectively disposed within slots (e.g., see PTL 1).

When coils are produced through molding or forming, for example, the coils have been each made uniform in cross-sectional area to achieve uniform resistance. On the other hand, heat is a factor of lowering efficiency of a motor. When Joule heat is generated, heat easily accumulates in coils. A path of radiation of heat generated in each of the coils differs depending on arrangement of members respectively lying adjacent to the coils or a flow path of refrigerant, for example. Heat distribution in the coils is therefore not uniform. However, in coils each having a cross-sectional area made uniform, heat radiation effects due to the coils are concentrated within the cross-sectional areas.

Patent Literature

PTL 1: Unexamined German Patent Publication No. 102012212637

In view of the problems described above, the technique disclosed herein has an object of further increasing heat radiation effects due to coils to achieve a highly efficient motor.

To achieve the object described above, a motor according to the technique disclosed herein includes a stator including a stator core and teeth respectively protruding from the stator core in predetermined directions of protrusion, and coils respectively wound onto the teeth n (n is an integer of 2 or greater) turns including first to n-th turns. Within each of ranges respectively wound with the coils onto the teeth in the predetermined directions of protrusion of the teeth, the first turn of each of the coils lies adjacent to a center of the motor. A k-th (k is an integer, 1<k≤n) turn of each of the coils lies opposite to the center of the motor. The first turn when each of the coils is cut in a corresponding one of the predetermined directions of protrusion of the teeth is greater in cross-sectional area than each of the k-th turn and the n-th turn.

With the configuration, the cross-sectional area of a part lying adjacent to the center of the motor is greater in each of the coils, further increasing heat radiation effects due to the coils with respect to the refrigerant flowing adjacent to the center of the motor or a space lying adjacent to the center of the motor, for example. Therefore, a highly efficient motor can be achieved.

The motor may be configured such that n is an integer of 3 or greater, k is an integer smaller than n, and the k-th turn of each of the coils is greater in cross-sectional area than the n-th turn.

The motor may be configured such that the first turn of each of the coils is largest in cross-sectional area among the first to n-th turns, and each of the coils gradually reduces in cross-sectional area from the first turn to the n-th turn.

According to the present disclosure, heat radiation effects due to the coils can be further increased, achieving a highly efficient motor.

FIG. 1A is a top view illustrating a motor according to an exemplary embodiment.

FIG. 1B is a side view illustrating the motor according to the exemplary embodiment.

FIG. 1C is a cross-sectional view taken along line 1 C- 1 C in FIG. 1B .

FIG. 2 is a partial enlarged view of FIG. 1C .

FIG. 3 is a cross-sectional view illustrating another configuration of one of teeth and one of coils.

An exemplary embodiment will be described herein in detail with reference to the accompanying drawings. The preferable exemplary embodiment described below is a substantially mere example, and does not intend to limit the present invention, applications, and purposes.

Exemplary Embodiment

Motor Structure

FIG. 1A is a top view illustrating motor 1 according to an exemplary embodiment. FIG. 1B is a side view illustrating motor 1 according to the exemplary embodiment. FIG. 1C is a cross-sectional view taken along line 1 C- 1 C in FIG. 1B . However, the views do not illustrate a cover case, for example. In FIG. 1C , only a main part is illustrated as a hatched cross section. Inside of the cover case (not illustrated), motor 1 includes shaft 2 , rotor 3 , stator 4 , coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 , and bus bars 51 to 54 .

In here, a longer direction (a direction vertical to a paper plane of FIG. 1A ) of shaft 2 is referred to as a Z-axis direction. Directions orthogonal to the Z-axis direction (directions parallel to the paper plane of FIG. 1A ) are respectively referred to as an X-axis direction and a Y-axis direction. The X-axis direction and the Y-axis direction are orthogonal to each other.

A term “integrated” or “integrally” denotes a state of an object where not only a plurality of constituent parts are mechanically coupled with each other with bolts or through caulking, for example, but also a plurality of constituent parts are electrically coupled with each other through material coupling such as covalent coupling, ion coupling, or metal coupling, for example, or a plurality of constituent parts are electrically coupled with each other through material coupling after all of the constituent parts are melted.

Shaft 2 internally includes hollow part 2 a extending in the Z-axis direction. A plurality of through holes 2 b are provided on a side surface of shaft 2 . Hollow part 2 a serves as a passage for refrigerant C used to cool inside of motor 1 . Refrigerant C flows inside of hollow part 2 a in the Z-axis direction. With an externally provided pump, for example (not illustrated), refrigerant C circulates and flows inside of motor 1 . Some of refrigerant C flowing inside of hollow part 2 a flows from the plurality of through holes 2 b outward from around a center of motor 1 , i.e., flows from rotor 3 toward stator 4 , to cool rotor 3 and stator 4 .

Rotor 3 is provided to abut an outer circumference of shaft 2 . Rotor 3 includes magnets 31 each facing stator 4 . Magnets 31 respectively have N-poles and S-poles alternately disposed in an outer circumference direction of shaft 2 . In the exemplary embodiment, neodymium magnets are used as magnets 31 used in rotor 3 . However, a material and a shape of each of magnets 31 can be appropriately changed in accordance with an output of a motor, for example.

Stator 4 includes stator core 41 having a substantially annular shape, a plurality of teeth 42 provided on an inner circumference of stator core 41 at equal intervals, and slots 43 respectively provided between teeth 42 . When viewed in the Z-axis direction, stator 4 is disposed outside of rotor 3 to be away from rotor 3 at a certain gap.

Stator core 41 is die-cut and formed from electromagnetic steel sheets containing silicon, for example, and laminated to each other, for example.

In the exemplary embodiment, rotor 3 includes a total of ten magnetic poles, including five N-poles and five S-poles facing stator 4 . A number of slots 43 is 12. However, a number of magnetic poles of rotor 3 and a number of slots 43 are not limited to the numbers described above. A combination of another number of magnetic poles and another number of slots is also applicable.

Stator 4 includes 12 coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 . Each of coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 is attached to a corresponding one of teeth 42 , and disposed in a corresponding one of slots 43 when viewed in the Z-axis direction. That is, coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 are respectively wound in a concentrated manner with respect to teeth 42 . Furthermore, coils U 11 to U 41 are integrally disposed to bus bar 51 , coils V 12 to V 42 are integrally disposed to bus bar 52 , and coils W 11 to W 41 are integrally disposed to bus bar 53 .

In each of symbols UPQ, VPQ, and WPQ representing the coils, a first letter represents one of phases of motor 1 (one of U-phase, V-phase, and W-phase in the exemplary embodiment). A second letter represents an order of arrangement of a corresponding one of the coils in the one of the phases. A third letter represents a direction of winding of the corresponding one of the coils. In the exemplary embodiment, 1 represents a clockwise direction, and 2 represents a counter-clockwise direction. Therefore, coil U 11 represents a first coil in an order of arrangement in the U-phase, and a direction of winding is the clockwise direction. Coil V 42 represents a fourth coil in an order of arrangement in the V-phase, and a direction of winding is the counter clockwise direction. A term “clockwise” denotes right-handed rotation when viewed from the center of motor 1 . A term “counter-clockwise” denotes left-handed rotation when viewed from the center of motor 1 .

Specifically, coils U 11 , U 41 are U-phase coils, whereas coils U 22 , U 32 are U-bar-phase (a direction of a magnetic field is opposite to a direction of a magnetic field generated from a U-phase coil) coils. However, the coils will be collectively referred to as U-phase coils unless otherwise specified. Similarly, coils V 12 to V 42 and coils W 11 to W 41 will be respectively collectively referred to as V-phase coils and W-phase coils.

(Features of Coil Cross Section)

FIG. 2 is a partial enlarged view of FIG. 1C . FIG. 2 illustrates one of teeth 42 respectively protruding from stator core 41 , and coil 5 A wound onto the one of teeth 42 . Stator core 41 lies on an outer side of motor 1 . Teeth 42 lie adjacent to the center of motor 1 . Coil 5 A corresponds to one of coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 illustrated in FIG. 1C . Coil 5 A is mainly made of one of materials including copper, aluminum, zinc, magnesium, brass, iron, and steel use stainless (SUS), for example.

Each of the directions of protrusion of teeth 42 from stator core 41 is herein referred to as an R direction. FIG. 2 illustrates a cross section in the R direction. In FIG. 2 , coil 5 A is wound onto the one of teeth 42 six turns. A 1 to A 6 respectively represent cross sections at a first turn to a sixth turn of coil 5 A. Symbols A 1 to A 6 may respectively represent cross-sectional areas at turns A 1 to A 6 .

In the exemplary embodiment, the turns of coil 5 A are not made uniform, but vary in cross-sectional area. A range wound with coil 5 A onto the one of teeth 42 in the R direction is referred to as range W. In here, first turn A 1 of coil 5 A lies adjacent to the center of motor 1 within range W.

In the configuration in FIG. 2 , first turn A 1 of coil 5 A is largest in cross-sectional area among first to sixth turns A 1 to A 6 . Coil 5 A gradually reduces in cross-sectional area from the first turn to the sixth turn (A 1 >A 2 >A 3 >A 4 >A 5 >A 6 ). In other words, coil 5 A gradually reduces in cross-sectional area outward from around the center of motor 1 within range W.

As described above, with the part that is expanded greater in cross-sectional area and that lies adjacent to the center of motor 1 in coil 5 A, a heat-radiation amount can be increased with respect to refrigerant C, preventing heat from accumulating in coil 5 A.

In the configuration in FIG. 2 , only first turn A 1 of coil 5 A may be expanded greater in cross-sectional area than each of the other turns (A 1 >A 2 =A 3 =A 4 =A 5 =A 6 ). Otherwise, the first turn to the sixth turn may be reduced in order in cross-sectional area in a stepwise manner (e.g., A 1 >A 2 =A 3 >A 4 =A 5 >A 6 ).

In the exemplary embodiment, the number of turns of each of the coils is specified to, but not limited to, six. The number of turns of each of the coils can be however appropriately changed in accordance with a size or capability, for example, of motor 1 .

FIG. 3 is a cross-sectional view illustrating another configuration of one of teeth and one of coils. A number of turns of coil 5 B is two. Similar to FIG. 2 , FIG. 3 illustrates one of teeth 42 respectively protruding from stator core 41 , and coil 5 B wound onto the one of teeth 42 . Similar to coil 5 A, coil 5 B corresponds to one of coils U 11 to U 41 , V 12 to V 42 , and W 11 to W 41 illustrated in FIG. 1C . Coil 5 B is mainly made of one of materials including copper, aluminum, zinc, magnesium, brass, iron, and SUS, for example.

Even in the configuration in FIG. 3 , with first turn B 1 being expanded greater in cross-sectional area than second turn B 2 (B 1 >B 2 ), a heat-radiation amount can be increased with respect to refrigerant C, preventing heat from accumulating in coil 5 B.

Even when a number of turns of a coil is other than two and six, the configuration described in here may be similarly applied. A number of turns may be an odd number. In other words, the first turn of coil 5 A or coil 5 B lies adjacent to the center of motor 1 within a range wound with coil 5 A or coil 5 B onto one of teeth 42 n (n is an integer of 2 or greater) turns. On the other hand, when the k-th (k is an integer, 1<k≤n) turn of coil 5 A or coil 5 B lies opposite to the center of motor 1 , the first turn when coil 5 A or coil 5 B is cut in each of the directions of protrusion of teeth 42 from stator core 41 may be made greater in cross-sectional area than each of the k-th turn and the n-th turn.

In the exemplary embodiment, the coils each have, without limitation, a substantially trapezoidal cross-sectional shape. However, the coils may each have a rectangular cross-sectional shape. Otherwise, the cross-sectional shapes of the coils may each be a circular shape, a polygonal shape, or a shape combined with a circular shape and a polygonal shape.

The exemplary embodiment has illustrated the example where coils U 11 to U 41 are integrated with bus bar 51 , coils V 12 to V 42 are integrated with bus bar 52 , and coils W 11 to W 41 are integrated with bus bar 53 . However, the coils may be respectively attached to the bus bars through fusing or welding, for example, to correspond to coil shapes.

In the configuration of the exemplary embodiment, refrigerant C flows in hollow part 2 a of shaft 2 . However, refrigerant C may circulate and flow in a space between rotor 3 and stator 4 , for example. Refrigerant C to be used can be liquid, such as oil, or gas, such as air, for example. Depending on specifications of motor 1 , for example, motor 1 may be configured to be internally naturally air-cooled. Even in this case, heat radiates from the first turn of coil 5 A, 5 B in the space between rotor 3 and stator 4 . Therefore, with the part having a cross-sectional area being expanded greater, heat radiation effects due to coil 5 A, 5 B can be increased.

As described above, motor 1 according to the exemplary embodiment includes stator 4 including stator core 41 and teeth 42 respectively protruding from stator core 41 , and coils 5 A respectively wound onto teeth 42 n (n is an integer of 2 or greater) turns including first to n-th turns. Within each of ranges respectively wound with coils 5 A onto teeth 42 in the directions of protrusion of teeth 42 from stator core 41 , the first turn of each of coils 5 A lies adjacent to the center of motor 1 . The k-th (k is an integer, 1<k≤n) turn of each of coils 5 A lies opposite to the center of motor 1 . The first turn when each of coils 5 A is cut in a corresponding one of the directions of protrusion of teeth 42 from stator core 41 is greater in cross-sectional area than each of the k-th turn and the n-th turn.

In this configuration, the cross-sectional area of the part lying adjacent to the center of motor 1 is greater in each of coils 5 A, further increasing heat radiation effects due to coils 5 A with respect to the refrigerant flowing adjacent to the center of motor 1 or the space lying adjacent to the center of motor 1 , for example. Therefore, motor 1 that is highly efficient can be achieved.

Motor 1 may be configured such that n is an integer of 3 or greater, k is an integer smaller than n, and the k-th turn of each of coils 5 A is greater in cross-sectional area than the n-th turn.

Motor 1 may be configured such that the first turn of each of coils 5 A is the largest in cross-sectional area among the first to n-th turns, and each of coils 5 A gradually reduces in cross-sectional area from the first turn to the n-th turn.

The present disclosure effectively further increases heat radiation effects due to the coils in the motor, achieving a low cost but highly efficient motor.

1 : motor

2 : shaft

2 a : hollow part

2 b : through hole

3 : rotor

4 : stator

5 A, 5 B: coil

31 : magnet

41 : stator core

42 : teeth

43 : slot

51 to 54 : bus bar

A 1 to A 6 : cross section at turn of coil 5 A

B 1 , B 2 : cross section at turn of coil 5 B

C: refrigerant

U 11 , U 22 , U 32 , U 41 , V 12 , V 21 , V 31 , V 42 , W 11 , W 22 , W 32 , W 41 : coil