Electric motor

Abstract

An electric motor comprising a housing that is provided with a cooling water path, a stator and rotor that are disposed inside the housing, a cylindrical sleeve that is disposed between an inner peripheral surface of the stator and an outer peripheral surface of the rotor, a first cover that is disposed at one end surface of the housing in the axial direction of the rotor, and a second cover that is disposed at the other end surface of the housing in the axial direction of the rotor, said electric motor comprising a coolant circulation path through which a coolant other than coolant water flows, and which includes: an upper coolant tank that is provided to an upper surface of the housing; a first coolant chamber that is formed by an end surface of the stator, an outer peripheral surface of the sleeve, and the housing; a second coolant chamber that is formed by the end surface of the stator, the outer peripheral surface of the sleeve, the housing, and the second cover; a first coolant path that passes through the first cover 8; a second coolant path that communicates between the first coolant path and the first coolant chamber; a third coolant path that communicates between the first coolant chamber and the second coolant chamber; and a fourth coolant path that communicates between the second coolant chamber and the upper coolant tank.

Description

electric motor

[0001] The present invention relates to an electric motor.

[0002] When an electric motor is driven, the coils wound around the stator generate heat due to copper loss, iron loss, and the like, causing the motor temperature to rise. For this reason, it is necessary to cool the stator. JP 2013-225976A discloses a cooling structure for cooling coil end portions that protrude axially outward from the axial ends of a stator core with a coolant as a refrigerant. The cooling structure in the above document includes a coil end cover for flowing coolant through the coil end portions, and is configured so that the flow direction of the coolant flowing through the coil end on one end and the flow direction of the coolant flowing through the coil end on the other end are countercurrent to each other.

[0003] However, the cooling structure of the above document does not include a device (e.g., a heat exchanger) for lowering the temperature of the coolant that has risen in temperature due to heat received from the coil ends, so there is room for improvement in the cooling efficiency of the stator. Furthermore, even if a heat exchanger were to be added to the cooling structure of the above document, it would inevitably increase the size and cost of the device due to the additional space and piping required to accommodate the heat exchanger.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an electric motor that is capable of efficiently cooling the stator without adding a heat exchanger.

[0005] According to one aspect of the present invention, there is provided an electric motor comprising: a housing having a cooling water passage through which cooling water flows; a stator arranged inside the housing; a rotor arranged inside the stator; a cylindrical sleeve arranged between the inner surface of the stator and the outer surface of the rotor; a first cover arranged on one end face of the housing in the rotor axial direction; and a second cover arranged on the other end face of the housing in the rotor axial direction. This electric motor is equipped with a refrigerant circulation path through which a refrigerant different from cooling water flows, the path including: an upper refrigerant tank provided on the upper surface of the housing; a first refrigerant chamber formed by one axial end face of the stator, the outer peripheral surface of the sleeve, and the housing; a second refrigerant chamber formed by the other axial end face of the stator, the outer peripheral surface of the sleeve, the housing, and a second cover; a first refrigerant passage provided in the first cover, penetrating the first cover and having one end opening at a mating surface with the housing; a second refrigerant passage provided in the housing, connecting the first refrigerant passage and the first refrigerant chamber; a third refrigerant passage formed by a slot in the stator and the sleeve, connecting the first refrigerant chamber and the second refrigerant chamber; and a fourth refrigerant passage provided in the housing, connecting the second refrigerant chamber and the upper refrigerant tank.

[0006] Fig. 1 is a cross-sectional view of a portion above the rotor rotation shaft of an electric motor. Fig. 2 is an enlarged view of region II in Fig. 1. Fig. 3 is an enlarged view of region III in Fig. 1. Fig. 4 is a cross-sectional view of a portion of a stator as viewed in the rotor axial direction. Fig. 5 is a cross-sectional view of an electric motor as viewed in the rotor axial direction.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] Fig. 1 is a cross-sectional view of a portion above the rotor rotation shaft of an electric motor 100 according to this embodiment. Fig. 2 is an enlarged view of region II in Fig. 1. Fig. 3 is an enlarged view of region III in Fig. 1. Fig. 4 is a cross-sectional view of a portion of a stator 4 as viewed in the rotor axial direction.

[0009] The electric motor 100 includes a housing 1 having a cooling water passage 11 through which cooling water flows, a stator 4 disposed inside the housing 1 , and a rotor 6 disposed inside the stator 4 .

[0010] The housing 1 has a double-pipe structure including an outer housing 2 and an inner housing 3. The cooling water passage 11 is formed between the outer peripheral surface of the inner housing 3 and the inner peripheral surface of the outer housing 2 so as to spirally surround the stator 4. For example, the cooling water passage 11 is formed by fixing the inner housing 3, which has a groove on its outer peripheral surface, to the outer housing 2 by shrink fitting or the like. In other words, at least a portion of the cooling water passage is provided along the circumferential direction on the outer periphery of the stator when viewed in the rotor axial direction.

[0011] In this embodiment, the housing 1 has a double-tube structure, but the present invention is not limited to this and may be an integrally molded structure.

[0012] A first cover 8 is disposed on one end face of the housing 1 in the rotor axial direction, and a second cover 9 is disposed on the other end face. In this embodiment, the end face on the left side in the drawing is referred to as the "one end face" and the end face on the right side is referred to as the "other end face."

[0013] An upper refrigerant tank 26 is provided on the upper surface of the housing 1 .

[0014] Inside the housing 1, a terminal block 13 is provided to which a plurality of motor side bus bars 12 and a plurality of inverter side bus bars 14 are connected by bolts 15, respectively.

[0015] The stator 4 includes a so-called open-slot stator core 4A and coils 4C housed in slots 4B of the stator core 4A. Both ends of the coil 4C protrude from the stator core 4A in the rotor axial direction to form coil ends 10A, 10B.

[0016] The rotor 6 is fixedly supported on a rotor shaft 5 which is rotatably supported by the housing 1 .

[0017] Furthermore, a cylindrical sleeve 7 is disposed between the inner peripheral surface of the stator 4 and the outer peripheral surface of the rotor 6. The sleeve 7 has a thick portion on one end side, and a tapered portion 30 is provided at the end of the thick portion. An adhesive is disposed in the space formed by this tapered portion 30 and the inner housing 3, and one end of the sleeve 7 is fixed in a watertight manner to the inner housing 3. The other end of the sleeve 7 is fixed in a watertight manner by an O-ring 17 disposed in a groove 16 provided in the second cover 9.

[0018] Next, the cooling structure of the electric motor 100 will be described.

[0019] The electric motor 100 is cooled by cooling water supplied to a cooling water passage 11 by a cooling water pump (not shown) and by a refrigerant supplied to a refrigerant circulation path (described below). The refrigerant is different from the cooling water and is, for example, oil.

[0020] The refrigerant circulation path includes four refrigerant paths, namely, a first refrigerant path 20, a second refrigerant path 21, a third refrigerant path 23, and a fourth refrigerant path 25, two refrigerant chambers, namely, a first refrigerant chamber 22 and a second refrigerant chamber 24, and an upper refrigerant tank 26.

[0021] The first refrigerant chamber 22 is defined by one axial end surface of the stator 4 , the outer circumferential surface of the sleeve 7 , and the inner housing 3 .

[0022] The second refrigerant chamber 24 is formed by the other axial end face of the stator 4, the outer peripheral surface of the sleeve 7, the outer housing 2, the inner housing 3, and the second cover.

[0023] The first refrigerant passage 20 is provided in the first cover 8 , and one end thereof opens facing the upper refrigerant tank 26 , and the other end thereof opens at the mating surface with the inner housing 3 .

[0024] The second refrigerant passage 21 is provided in the inner housing 3 and connects the first refrigerant passage 20 and the first refrigerant chamber 22 .

[0025] The third refrigerant passage 23 is a flow passage that passes through the stator 4 and connects the first refrigerant chamber 22 and the second refrigerant chamber 24. Specifically, the third refrigerant passage 23 is a space formed by the sleeve 7 and the opening of the slot 4B provided in the stator core 4A.

[0026] The fourth refrigerant passage 25 is provided in the outer housing 2 and connects the second refrigerant chamber 24 with the upper refrigerant tank 26 .

[0027] In the refrigerant circulation path, the refrigerant is supplied from a refrigerant pump 46 (described later) to the first refrigerant passage 20, and then flows from there into the first refrigerant chamber 22 via the second refrigerant passage 21. The refrigerant accumulates in the first refrigerant chamber 22 and flows into the second refrigerant chamber 24 via the third refrigerant passage 23. When the liquid level in the second refrigerant chamber 24 rises, the refrigerant flows into the upper refrigerant tank 26 via the fourth refrigerant passage 25.

[0028] As a result, the coil end 10A is cooled in the first coolant chamber 22, the stator 4 is cooled by passing through the third coolant passage 23, and the coil end 10B is cooled in the second coolant chamber 24.

[0029] In the upper refrigerant tank 26, the refrigerant is cooled by heat exchange with the cooling water flowing through the cooling water passage 11. To further increase the cooling efficiency here, it is desirable to adjust the flow rate of the refrigerant, etc. so that the liquid level of the refrigerant in the upper refrigerant tank 26 is higher than the apex of the arc portion of the outer housing 2 that fits with the stator 4.

[0030] Generally, when oil or the like is used as a refrigerant, a heat exchanger is often provided to cool the refrigerant whose temperature has risen due to heat exchange with the object to be cooled. In this case, a heat exchanger and piping connecting to the heat exchanger are required, which inevitably increases the size and cost of the device. In this regard, in the configuration of this embodiment, as described above, the refrigerant after heat exchange with the coil ends 10A, 10B and the stator 4 is cooled by cooling water, so there is no need to provide a heat exchanger.

[0031] In order to cool the entire coil end, it is desirable that the opening of the second coolant passage 21 on the side of the first coolant chamber 22 be located higher than the coil end 10A.

[0032] Next, the path of the refrigerant that has flowed into the upper refrigerant tank 26 until it is supplied again to the first refrigerant passage 20 will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view of the electric motor 100 as viewed in the rotor axial direction.

[0033] The inner housing 3, which forms part of the upper refrigerant tank 26, has an arc shape that follows the outer peripheral surface of the stator 4. That is, at least a part of the upper refrigerant tank 26 has an arc shape that is concentric with the cooling water passage 11 when viewed in the rotor axial direction.

[0034] The portion of the inner housing 3 that fits with the lower half of the stator 4 and the portion of the outer housing 2 that fits with the corresponding portion have an arc shape concentric with the outer peripheral surface of the stator 4. An oil pan 40 is disposed below the arc-shaped portion 2B of the outer housing 2, and the outer housing 2 and the oil pan 40 form a lower refrigerant tank 45. The arc-shaped portion 2B and the side wall portion 2A of the outer housing 2 are connected via a pair of connecting portions 47.

[0035] A middle cover 41 having an arc-shaped configuration concentric with the arc-shaped portion of the outer housing 2 is disposed radially outward of the arc-shaped portion of the outer housing 2. An arc-shaped sixth refrigerant passage 43 is formed between the middle cover 41 and the outer housing 2. The distance between the arc-shaped portion of the outer housing 2 and the arc-shaped portion of the middle cover 41 is preferably such that the refrigerant comes into contact with both due to surface tension. The middle cover 41 is fixedly supported by the side wall portion 2A of the outer housing 2.

[0036] The upper refrigerant tank 26 and the lower refrigerant tank 45 are separated by a pair of connecting portions 47. The connecting portions 47 are provided with one or more fifth refrigerant passages 42 that connect the upper refrigerant tank 26 and the sixth refrigerant passage 43. The outer housing 2 is a cast product, and the fifth refrigerant passage 42 is formed using a core during the casting process. Therefore, in consideration of the ease of removing the core, it is desirable that the pair of connecting portions 47 be provided at the same height as the rotor shaft 5, and that the fifth refrigerant passage 42 vertically pass through the connecting portions 47.

[0037] At the lowest point of the middle cover 41 , one or more seventh refrigerant passages 44 are provided, which connect the sixth refrigerant passage 43 with the lower refrigerant tank 45 .

[0038] The refrigerant flows from the upper refrigerant tank 26 through the fifth refrigerant path 42 to the sixth refrigerant path 43, flows from the sixth refrigerant path 43 through the seventh refrigerant path 44 to the lower refrigerant tank 45, and is supplied from the lower refrigerant tank 45 to the first refrigerant path 20 by the refrigerant pump 46.

[0039] Without the middle cover 41, the refrigerant that has passed through the fifth refrigerant passage 42 would simply fall into the lower refrigerant tank 45. However, in this embodiment, the middle cover 41 is provided to form the sixth refrigerant passage 43. As a result, the refrigerant is cooled in the sixth refrigerant passage 43 by heat exchange with the coolant.

[0040] The refrigerant circulation path of the electric motor 100 can be summarized as follows: lower refrigerant tank 45 → refrigerant pump 46 → first refrigerant path 20 → second refrigerant path 21 → first refrigerant chamber 22 → third refrigerant path 23 → second refrigerant chamber 24 → fourth refrigerant path 25 → upper refrigerant tank 26 → fifth refrigerant path 42 → sixth refrigerant path 43 → seventh refrigerant path 44 → lower refrigerant tank 45.

[0041] Here, the flow of the refrigerant in the sixth refrigerant passage 43 will be described.

[0042] As described above, the refrigerant exchanges heat with the coolant in the sixth refrigerant passage 43. From the viewpoint of cooling efficiency, it is desirable that the sixth refrigerant passage 43 be filled with refrigerant. Therefore, when the total flow path cross-sectional area of ​​the fifth refrigerant passage 42 is cross-sectional area A and the total flow path cross-sectional area of ​​the seventh refrigerant passage 44 is cross-sectional area B, cross-sectional area A is larger than cross-sectional area B. That is, the amount of refrigerant flowing in from the fifth refrigerant passage 42 is greater than the amount of refrigerant flowing out from the seventh refrigerant passage 44. However, if too much refrigerant passes through the fifth refrigerant passage 42, the liquid level of the refrigerant in the upper refrigerant tank 26 drops, reducing the cooling efficiency of the refrigerant in the upper refrigerant tank 26. Furthermore, since the viscosity of the refrigerant decreases with increasing temperature, the fluidity increases as the temperature increases, requiring cooling, and the amount of refrigerant passing through the fifth refrigerant passage 42 increases. Therefore, the cross-sectional area A is sized so that the liquid level of the refrigerant is higher than the upper end of the portion of the outer housing 1 that fits with the upper half of the stator 4, even when the refrigerant reaches the viscosity specified for the maximum temperature.

[0043] Furthermore, from the viewpoint of cooling efficiency, it is desirable for the refrigerant to flow at an appropriate flow rate in the sixth refrigerant path 43. The refrigerant in the sixth refrigerant path 43 is subjected to pressure generated by the weight of the refrigerant in the upper refrigerant tank 26. The flow rate of the refrigerant in the sixth refrigerant path 43 is determined by the relationship between this pressure and the flow path resistance of the fifth refrigerant path 42 and the flow path resistance of the seventh refrigerant path 44.

[0044] Therefore, the flow resistance of the fifth refrigerant passage 42 is set low enough to allow the refrigerant to pass through. Specifically, the flow resistance of each fifth refrigerant passage 42 is set so that both the flow resistance and the cross-sectional area A are satisfied. Note that "sufficiently low" here means that the cross-sectional area is negligibly low. The flow resistance of the seventh refrigerant passage 44 is set to a value that balances the pressure generated by the refrigerant's own weight in the upper refrigerant tank. Specifically, the flow resistance of each seventh refrigerant passage 44 is set so that both the flow resistance and the cross-sectional area B are satisfied. Because refrigerant cooling becomes an issue at high temperatures, the flow resistance is set based on the viscosity of the refrigerant at its specified maximum temperature. Note that "balanced" here does not only refer to a case where the two are strictly equal, but also includes a case where there is a difference within the bounds of common technical knowledge.

[0045] As described above, in this embodiment, an electric motor 100 is provided which includes a housing 1 having a cooling water passage 11 through which cooling water flows, a stator 4 arranged inside the housing 1, a rotor 6 arranged inside the stator 4, a cylindrical sleeve 7 arranged between the inner surface of the stator 4 and the outer surface of the rotor 6, a first cover 8 arranged on one end face of the housing 1 in the rotor axial direction, and a second cover 9 arranged on the other end face of the housing 1 in the rotor axial direction. This electric motor 100 is provided with a refrigerant circulation path through which a refrigerant different from cooling water flows, the refrigerant circulation path including: an upper refrigerant tank 26 provided on the upper surface of the housing 1; a first refrigerant chamber 22 formed by one rotor axial end face of the stator 4, the outer peripheral surface of the sleeve 7, and the housing 1; a second refrigerant chamber 24 formed by the other rotor axial end face of the stator 4, the outer peripheral surface of the sleeve 7, the housing 1, and the second cover 9; a first refrigerant passage 20 penetrating the first cover 8 and one end opening at a mating surface with the housing 1; a second refrigerant passage 21 provided in the housing 1 and connecting the first refrigerant passage 20 and the first refrigerant chamber 22; a third refrigerant passage 23 formed by the slot 4B of the stator 4 and the sleeve 7 and connecting the first refrigerant chamber 22 and the second refrigerant chamber 24; and a fourth refrigerant passage 25 provided in the housing 1 and connecting the second refrigerant chamber 24 and the upper refrigerant tank 26. This allows the stator 4 and coil ends 10A, 10B to be cooled by the refrigerant, and the refrigerant whose temperature has risen due to heat absorption can be cooled by the cooling water. In other words, the electric motor 100 can be efficiently cooled without providing a heat exchanger or the like for cooling the refrigerant, which prevents the motor system from becoming larger and more expensive.

[0046] In this embodiment, at least a portion of the cooling water passage 11 is provided circumferentially on the outer periphery of the stator 4 as viewed in the rotor axial direction. At least a portion of the upper refrigerant tank 26 has an arc-shaped configuration coaxial with the cooling water passage 11 as viewed in the rotor axial direction. A circular arc-shaped middle cover 41 is disposed radially outward of a portion of the housing 1 that engages with the lower half of the stator, and an arc-shaped sixth refrigerant passage 43 is formed between the middle cover 41 and the housing 1. A lower refrigerant tank 345 is formed below the middle cover 41. The electric motor 100 also includes one or more fifth refrigerant passages 42 that communicate the upper refrigerant tank 26 and the sixth refrigerant passage 43, one or more seventh refrigerant passages 44 that are provided at the lowest point of the middle cover 41 and that communicate the sixth refrigerant passage 43 and a lower refrigerant tank 45, and a refrigerant pump 46 that supplies refrigerant from the lower refrigerant tank 45 to the first refrigerant passage 20. This allows the refrigerant to be cooled even in the portion of the cooling water passage 11 that covers the lower half of the stator 4, thereby allowing the refrigerant to be cooled efficiently.

[0047] In this embodiment, the cross-sectional area A, which is the total flow path cross-sectional area of ​​the fifth refrigerant path 42, is larger than the cross-sectional area B, which is the total flow path cross-sectional area of ​​the seventh refrigerant path 44, and is sized so that even when the refrigerant reaches the viscosity at the maximum temperature specified, the liquid level of the refrigerant will be higher than the upper end of the portion of the housing 1 that fits with the upper half of the stator 4. This allows the sixth refrigerant path 43 to be filled with refrigerant without reducing the cooling efficiency of the upper refrigerant tank 26.

[0048] In this embodiment, the flow resistance of the fifth refrigerant path 42 is low enough for the refrigerant to pass through, and the flow resistance of the seventh refrigerant path 44 is balanced with the pressure generated by the weight of the refrigerant in the upper refrigerant tank 26. This allows the refrigerant to flow through the sixth refrigerant path 43 at an appropriate flow rate, thereby enabling the refrigerant to be cooled efficiently.

[0049] In this embodiment, the housing 1 has a double-pipe structure consisting of an outer housing 2 and an inner housing 3, and the cooling water passage 11 is formed by the inner peripheral surface of the outer housing 2 and a spiral groove surrounding the inner housing 3 on the outer peripheral surface of the inner housing 3. This makes it easier to manufacture the housing 1 with the cooling water passage 11 inside than if it were integrally molded.

[0050] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. An electric motor comprising: a housing having a cooling water passage through which cooling water flows; a stator arranged inside the housing; a rotor arranged inside the stator; a cylindrical sleeve arranged between an inner peripheral surface of the stator and an outer peripheral surface of the rotor; a first cover arranged on one end face of the housing in the rotor axial direction; and a second cover arranged on the other end face of the housing in the rotor axial direction, wherein the electric motor comprises: an upper refrigerant tank provided on an upper surface of the housing; a first refrigerant chamber formed by one of the rotor axial end faces of the stator, the outer peripheral surface of the sleeve, and the housing; a second refrigerant chamber formed by the other rotor axial end face of the stator, the outer peripheral surface of the sleeve, the housing, and the second cover; a first refrigerant passage that penetrates first cover 8 and has one end opening at a mating surface with housing 1; a second refrigerant passage provided in the housing that connects the first refrigerant passage with the first refrigerant chamber; and a third refrigerant passage formed by a slot in the stator and the sleeve that connects the first refrigerant chamber with the second refrigerant chamber. a fourth refrigerant passage provided in the housing and communicating between the second refrigerant chamber and the upper refrigerant tank, the fourth refrigerant passage including the fourth refrigerant passage and through which a refrigerant different from the cooling water flows.

2. An electric motor as claimed in claim 1, wherein at least a portion of the cooling water passage is provided circumferentially on the outer periphery of the stator when viewed in the rotor axial direction, at least a portion of the upper refrigerant tank has an arc-shaped configuration coaxial with the cooling water passage when viewed in the rotor axial direction, an arc-shaped middle cover is arranged radially outward of a portion of the housing that fits with the lower half of the stator, and an arc-shaped sixth refrigerant passage is formed between the middle cover and the housing, and a lower refrigerant tank is formed below the middle cover, one or more fifth refrigerant passages connecting the upper refrigerant tank and the sixth refrigerant passage, one or more seventh refrigerant passages provided at the lowest point of the middle cover and connecting the sixth refrigerant passage with the lower refrigerant tank, and a refrigerant pump that supplies refrigerant from the lower refrigerant tank to the first refrigerant passage.

3. An electric motor as claimed in claim 2, wherein cross-sectional area A, which is the total flow cross-sectional area of ​​the fifth refrigerant path, is larger than cross-sectional area B, which is the total flow cross-sectional area of ​​the seventh refrigerant path, and is so sized that even when the refrigerant reaches its viscosity at the maximum temperature specified, the liquid level of the refrigerant will be higher than the upper end of the part of the housing that fits into the upper half of the stator.

4. An electric motor according to claim 3, wherein the flow resistance of the fifth refrigerant path is low enough to allow the refrigerant to pass through, and the flow resistance of the seventh refrigerant path is balanced with the pressure generated by the weight of the refrigerant in the upper refrigerant tank.

5. An electric motor according to claim 1, wherein the housing has a double-pipe structure consisting of an outer housing and an inner housing, and the cooling water passage is formed by the inner peripheral surface of the outer housing and a spiral groove provided on the outer peripheral surface of the inner housing that surrounds the inner housing.

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