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. In particular, heat easily accumulates in a center portion of each of the coils. 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 an aspect of 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 3 or greater) turns including first to n-th turns. A k-th (k is an integer, 1<k<n) turn of each of the coils lies at a center of a range wound with each of the coils onto the teeth in a corresponding one of the predetermined directions of protrusion of the teeth from the stator core. Each of the first turn and the n-th 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 the k-th turn.

With the configuration, each of ends of each of the coils is greater in cross-sectional area than a center portion of each of the coils. Therefore, heat can easily radiate from the center portion, at where heat easily accumulates, of each of the coils toward both of the ends of each of the coils. The coils can therefore average thermal efficiency. Heat radiation effects due to the coils can thus further be increased, achieving a highly efficient motor.

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

A motor according to another aspect of the technique disclosed herein includes a stator including a stator core and teeth respectively protruding from the stator core, and coils respectively wound onto the teeth n (n is an even number of 4 or greater) turns including first to n-th turns. In each of predetermined directions of protrusion of the teeth from the stator core, j-th and (j+1)-th turns (j is an integer, 1<j<n−1) of each of the coils are two turns both lying closest to a center of a range wound with each of the coils onto the teeth. Each of a (j−1)-th turn and a (j+2)-th turn when each of the coils is cut in a corresponding one of the predetermined directions of protrusion of the teeth from the stator core is greater in cross-sectional area than each of the j-th turn and the (j+1)-th turn.

With the configuration, heat can easily radiate from a center portion, at where heat easily accumulates, of each of the coils toward both of the ends. The coils can therefore average thermal efficiency. Heat radiation effects due to the coils can thus further be increased, achieving a highly efficient motor.

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 another partial enlarged view of FIG. 1C .

FIG. 4 is still another partial enlarged view of FIG. 1C .

FIG. 5 is a different partial enlarged view of FIG. 1C .

FIG. 6 is another different partial enlarged view of FIG. 1C .

FIG. 7 is a cross-sectional view illustrating a configuration where a number of turns of each of coils of the motor according to the exemplary embodiment is six.

FIG. 8 is another cross-sectional view of FIG. 7 .

FIG. 9 is still another cross-sectional view of FIG. 7 .

FIG. 10 is a different cross-sectional view of FIG. 7 .

FIG. 11 is another different cross-sectional view of FIG. 7 .

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.

(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 to circulate and flow 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 the cross-sectional 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 five turns. A 1 to A 5 respectively represent cross sections at a first turn to a fifth turn of coil 5 A. Symbols A 1 to A 5 may respectively represent cross-sectional areas at turns A 1 to A 5 .

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, third turn A 3 of coil 5 A lies at a center of range W. Third turn A 3 of coil 5 A is smaller in cross-sectional area than each of first turn A 1 and fifth turn A 5 respectively lying at both of ends of range W.

In the configuration in FIG. 2 , third turn A 3 of coil 5 A is smallest in cross-sectional area among first turn A 1 to fifth turn A 5 . Coil 5 A gradually expands in cross-sectional area from the third turn to the first turn (A 3 <A 2 <A 1 ). Coil 5 A gradually expands in cross-sectional area from the third turn to the fifth turn (A 3 <A 4 <A 5 ). In other words, coil 5 A gradually expands in cross-sectional area from the center toward both of the ends of range W.

With the configuration described above, heat easily radiates from an outside turn of coil 5 A, i.e., from the fifth turn, to stator core 41 . Heat also easily radiates from an inside turn of coil 5 A, i.e., from the first turn, via refrigerant C flowing inside of shaft 2 lying adjacent to the center of motor 1 . Heat in a center portion of coil 5 A, where heat of each of teeth 42 easily accumulates, i.e., in this case, heat in the third turn, radiates via the turns lying at both sides of the center portion, i.e., via the first and second turns, toward the center of motor 1 , as well as radiates, via the fourth and fifth turns, to stator core 41 . As described above, parts lying at both of the ends in coil 5 A are made greater in cross-sectional area than the center portion, at where heat easily accumulates. Coil 5 A can thus average thermal efficiency.

Even when a number of turns of a coil is an odd number other than five, the configuration described herein may be similarly applied. In other words, a k-th (k is an integer, 1<k<n) turn of coil 5 A lies at a center of a range wound with coil 5 A onto each of teeth 42 n (n is an integer of 3 or greater) turns. Each of the first turn and the n-th turn when coil 5 A is cut in a corresponding one of the directions of protrusion of teeth 42 from stator core 41 may be greater in cross-sectional area than the k-th turn.

Turn A 1 has a quadrangular cross section having opposite sides that are not parallel to each other. This can increase a space factor of coil 5 A.

FIG. 3 is another partial enlarged view of FIG. 1C . FIG. 4 is still another partial enlarged view of FIG. 1C . In FIG. 3 , coil 5 A has a trapezoidal cross section. With coil 5 A having a trapezoidal cross section, a space factor of coil 5 A can be increased. A side surface of coil 5 A lies opposite to each of teeth 42 , and extends straight. As illustrated in FIG. 4 , with coil 5 A having the side surface that lies opposite to a corresponding one of teeth 42 and that extends and aligns straight, a gap between coils 5 A wound onto two adjacent ones of teeth 42 can be kept uniform, suppressing coating from being damaged due to contact.

FIG. 5 is a different partial enlarged view of FIG. 1C . In FIG. 5 , coil 5 A has a parallelogram cross section. With the parallelogram coil cross section, which is a shape, a space factor of coil 5 A can be increased. As well as, as illustrated in FIG. 4 , a gap between coils 5 A wound onto adjacent ones of teeth 42 can be kept uniform, suppressing coating from being damaged due to contact. As a result, refrigerant C can easily flow into the gap formed between each of teeth 42 and each of coils 5 .

FIG. 6 is another different partial enlarged view of FIG. 1C . In FIG. 6 , turn A 0 of coil 5 A lies at a most distant position from stator core 41 in a corresponding one of the directions of protrusion of teeth 42 and has a triangular cross section. Therefore, a part having a slanted cross section of each of teeth 42 can be embedded in coil 5 A, increasing a space factor of coil 5 A.

A number of turns may be an even number. FIG. 7 is a cross-sectional view illustrating a configuration where a number of turns of each of coils of the motor according to the exemplary embodiment is six. Similar to FIG. 2 , FIG. 7 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.

In here, coil 5 B is wound onto the one of teeth 42 six turns. B 1 to B 6 respectively represent cross sections at a first turn to a sixth turn of coil 5 B. Symbols B 1 to B 6 may respectively represent cross-sectional areas at B 1 to B 6 .

In the configuration in FIG. 7 , two turns of coil 5 B lie closest to a center of range W, and are the third and fourth turns. Third and fourth turns B 3 , B 4 lie adjacent to the center of range W. Each of third and fourth turns B 3 , B 4 is smaller in cross-sectional area than each of second turn B 2 and fifth turn B 5 both lying outsides of third and fourth turns B 3 , B 4 . In this case, the cross-sectional areas at B 3 , B 4 may be identical to each other. Otherwise, one of the cross-sectional areas at B 3 , B 4 may be greater than another one of the cross-sectional areas at B 3 , B 4 .

As described above, with parts that lie on both sides of a center portion of coil 5 B and that are each greater in cross-sectional area than the center portion of coil 5 B, heat can securely radiate outward of coil 5 B from the center portion, at where heat of teeth 42 easily accumulates, of coil 5 B.

Even when a number of turns of a coil is an even number other than six, the configuration described herein may be similarly applied. In other words, in each of the directions of protrusion of teeth 42 from stator core 41 , j-th and (j+1)-th turns (j is an integer, 1<j<n−1) of coil 5 B are two turns both lying closest to the center of the range wound with coil 5 B onto each of teeth 42 . Each of a (j−1)-th turn and a (j+2)-th turn when coil 5 B is cut in a corresponding one of the directions of protrusion of teeth 42 from stator core 41 may be greater in cross-sectional area than each of the j-th turn and the (j+1)-th turn.

Turn B 1 has a quadrangular cross section having opposite sides that are not parallel to each other. This can increase a space factor of coil 5 B.

FIG. 8 is another partial enlarged view of FIG. 7 . FIG. 9 is still another partial enlarged view of FIG. 7 . In FIG. 8 , coil 5 B has a trapezoidal cross section. With coil 5 B having a trapezoidal cross section, a space factor of coil 5 B can be increased. A side surface of coil 5 B lies opposite to each of teeth 42 , and extends straight. As illustrated in FIG. 9 , with coil 5 B having the side surface that lies opposite to a corresponding one of teeth 42 and that extends straight, a gap between coils 5 B wound onto two adjacent ones of teeth 42 can be kept uniform, suppressing coating from being damaged due to contact.

FIG. 10 is a different cross-sectional view of FIG. 7 . In FIG. 10 , coil 5 B has a parallelogram cross section. With the parallelogram coil cross section, which is a shape, a space factor of coil 5 B can be increased. As well as, as illustrated in FIG. 9 , a gap between coils 5 B wound onto adjacent ones of teeth 42 can be kept uniform, suppressing coating from being damaged due to contact. As a result, refrigerant C can easily flow into the gap formed between each of teeth 42 and each of coils 5 B.

FIG. 11 is another different cross-sectional view of FIG. 7 . In FIG. 11 , turn B 0 of coil 5 B lies at a most distant position from stator core 41 in a corresponding one of the directions of protrusion of teeth 42 and has a triangular cross section. Therefore, a part having a slanted cross section of each of teeth 42 can be embedded in coil 5 B, increasing a space factor of coil 5 B.

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 gap 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 toward a space between rotor 3 and stator 4 . Coil 5 A, 5 B can thus average thermal efficiency.

As described above, an example of motor 1 according to the exemplary embodiment includes stator 4 including stator core 41 and teeth 42 respectively protruding from stator core 41 in the predetermined directions of protrusion, and coils 5 A respectively wound onto teeth 42 n (n is an integer of 3 or greater) turns including first to n-th turns. The k-th (k is an integer, 1<k<n) turn of coil 5 A lies at the center of the range wound with coil 5 A onto each of teeth 42 in a corresponding one of the directions of protrusion of teeth 42 from stator core 41 . Each of the first turn and the n-th turn when coil 5 A is cut in the corresponding one of the directions of protrusion of teeth 42 is greater in cross-sectional area than the k-th turn.

With the configuration, each of the ends of coil 5 A is greater in cross-sectional area than the center portion of coil 5 A. Therefore, heat can easily radiate from the center portion, at where heat easily accumulates, of coil 5 A toward both of the ends of coil 5 A. Coil 5 A can therefore average thermal efficiency. Heat radiation effects due to coil 5 A can thus further be increased, achieving a highly efficient motor 1 .

Motor 1 may be configured such that the k-th turn of coil 5 A is smallest in cross-sectional area among the first to n-th turns. Coil 5 A may gradually expand in cross-sectional area from the k-th turn to the first turn, and from the k-th turn to the n-th turn.

Another example of motor 1 according to the exemplary embodiment includes stator 4 including stator core 41 and teeth 42 respectively protruding from stator core 41 in the predetermined directions of protrusion, and coils 5 B respectively wound onto teeth 42 n (n is an even number of 4 or greater) turns including first to n-th turns. In each of the directions of protrusion of teeth 42 from stator core 41 , the j-th and (j+1)-th turns (j is an integer, 1<j<n−1) of coil 5 B are two turns both lying closest to the center of the range wound with coil 5 B onto each of teeth 42 . Each of the (j−1)-th turn and the (j+2)-th turn when coil 5 B is cut in a corresponding one of the directions of protrusion of teeth 42 is greater in cross-sectional area than each of the j-th turn and the (j+1)-th turn.

With the configuration, heat can easily radiate from the center portion, at where heat easily accumulates, of coil 5 B toward both of the ends. Coil 5 B can therefore average thermal efficiency. Heat radiation effects due to coil 5 B can thus further be increased, achieving a highly efficient motor.

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 5 : cross section at turn of coil 5 A

B 1 to B 6 : 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