Cooling structure for rotating electrical machines

Abstract

To address a problem of achieving a state of being ready to immediately circulate a refrigerant for cooling a rotary electric machine when the rotary electric machine placed in a cold environment is restarted.SOLUTION: A cooling structure for a rotary electric machine, includes an annular stator, a rotor that is disposed to face the stator and is rotatable about a rotation axis, and a coil end that is formed on an axial side portion of the stator. The cooling structure includes a coil end cover that covers the coil end, and that includes a refrigerant introduction hole which can store a refrigerant therein and through which the refrigerant is introduced, and a refrigerant discharge hole which causes an overflow of the stored refrigerant so as to discharge the refrigerant to the outside therethrough, a refrigerant supply part that is connected to the refrigerant introduction hole and that supplies the refrigerant into the coil end cover, and a refrigerant discharge part that is connected to the refrigerant discharge hole and that discharges the refrigerant from the coil end cover.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling structure for a rotating electrical machine. [Background technology]

[0002] Rotating electric machines used as power sources for hybrid and electric vehicles generate heat when current is applied to their windings (coils). For this reason, various structures for cooling the windings have been proposed (see, for example, Patent Document 1). The rotating electric machine proposed in Patent Document 1 includes a winding cover that covers the coil ends, which are part of the windings, and a refrigerant supply unit located above the winding cover and supplying refrigerant to the windings. The outer peripheral surface of the winding cover is provided with a refrigerant inlet hole for introducing refrigerant into the coil ends. Furthermore, a refrigerant outlet hole is provided below the winding cover. This outlet hole is located vertically below the output shaft (rotating shaft member) and below the air gap between the stator core and the rotor. Therefore, the rotating electric machine proposed in Patent Document 1 is cooled by refrigerant supplied from above the windings and flowing downward. The refrigerant that flows down is temporarily stored in a storage unit such as an oil pan and then introduced back into the coil ends via the refrigerant supply unit. In other words, the refrigerant cools the windings while circulating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-161948 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, oil such as ATF (Automatic Transmission Fluid) is sometimes used as a coolant to cool the windings. The viscosity of such coolants changes depending on the temperature, and the fluidity decreases as the temperature decreases. When such a coolant is used and a vehicle equipped with a rotating electric machine is parked in a cold environment and the supply of coolant is stopped, the coolant that flows down may become more viscous in the reservoir and its fluidity may decrease. If the fluidity of the coolant decreases, it may take a long time for the pump to pump the coolant when the rotating electric machine is restarted, and the coolant may not be able to circulate immediately. The windings will not be cooled unless the coolant is circulated.

[0005] Therefore, the object of the invention disclosed in this specification is to make it possible to immediately circulate the refrigerant that cools the rotating electric machine when the rotating electric machine that has been placed in a cold environment is restarted. [Means for solving the problem]

[0006] The above-mentioned object can be achieved by a cooling structure for a rotating electric machine including a ring-shaped stator, a rotor arranged opposite the stator and rotatable about a rotation axis, and coil ends formed on axial sides of the stator, the cooling structure including a coil end cover that covers the coil ends and is capable of storing a refrigerant therein and is provided with a refrigerant inlet hole for introducing the refrigerant and a refrigerant discharge hole for causing the refrigerant stored therein to overflow and be discharged to the outside, and a refrigerant supply unit that is connected to the refrigerant inlet hole and supplies the refrigerant into the coil end cover.

[0007] The coolant discharge hole of the above configuration may be provided above the lowest position of the rotor when the rotating electric machine is installed with the radial direction of the stator aligned vertically.

[0008] Furthermore, the coolant discharge hole of the above configuration may be provided above the rotation axis when the rotating electric machine is installed with the radial direction of the stator aligned vertically.

[0009] Furthermore, the coolant discharge holes of the above configuration may be provided at a plurality of different positions in the vertical direction when the rotating electric machine is installed with the radial direction of the stator as the vertical direction.

[0010] Furthermore, the refrigerant inlet hole of the above configuration may be located below the refrigerant discharge hole, the refrigerant supply unit may include a refrigerant inlet path connected to the refrigerant inlet hole and introducing the refrigerant into the coil end cover by a refrigerant pump, and a portion of the refrigerant inlet path may be located above the refrigerant inlet hole.

[0011] Furthermore, the refrigerant introduction path of the above configuration may include a refrigerant tank in which the refrigerant is stored, a refrigerant introduction pipe connecting the refrigerant introduction hole and the refrigerant tank, and a refrigerant transfer piping connecting the refrigerant tank and the refrigerant pump, and a portion of the refrigerant transfer piping may be arranged above the refrigerant introduction hole.

[0012] The coolant supply unit may include a shower nozzle that introduces the coolant into the coil end cover through the coolant introduction hole.

[0013] Furthermore, the shower nozzle portion having the above configuration may be configured to spray the refrigerant at an angle with respect to the refrigerant introduction hole so that the sprayed refrigerant flows within the coil end cover in the circumferential direction of the stator.

[0014] Furthermore, the cooling structure of the rotating electric machine having the above configuration may further include a refrigerant straightening section at a position where the flow of the refrigerant along the circumferential direction of the stator exceeds the refrigerant discharge hole, which reverses the flow of the refrigerant that has passed the refrigerant discharge hole.

[0015] The cooling structure for a rotating electric machine having the above-described configuration may further include a coolant discharge portion connected to the coolant discharge hole and configured to discharge the coolant from inside the coil end cover. [Effects of the Invention]

[0016] The invention disclosed in this specification makes it possible to immediately bring the coolant that cools the rotating electrical machine into a state where it can be circulated when the rotating electrical machine that has been in a cold environment is restarted. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a front view that schematically illustrates a cooling structure for a rotating electrical machine according to a first embodiment. [Figure 2] FIG. 2 is a plan view schematically illustrating the cooling structure of the rotating electrical machine according to the first embodiment. [Figure 3] FIG. 3 is a side view that schematically illustrates the cooling structure of the rotating electrical machine according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along line X1-X1 in FIG. [Figure 5] FIG. 5 is an exploded cross-sectional view illustrating a state in which a coil end cover is removed from the stator in the rotating electric machine according to the first embodiment. [Figure 6] FIG. 6 is a front view schematically illustrating the cooling structure of the rotating electrical machine according to the second embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a rotating electrical machine according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing a schematic view of the refrigerant being sprayed from the shower nozzle in the second embodiment. [Figure 9] FIG. 9 is a diagram showing a modified example of the rotating electric machine. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions and proportions of the various parts in the drawings may not be exactly the same as those in reality. In addition, some details may be omitted in the drawings.

[0019] (First embodiment) [Configuration of the cooling structure of a rotating electrical machine] First, a schematic configuration of a cooling structure 100 for a rotating electric machine 1 according to a first embodiment (hereinafter simply referred to as "cooling structure") will be described with reference to Fig. 1 to Fig. 3. The cooling structure 100 cools the rotating electric machine 1. The rotating electric machine 1 is a three-phase AC motor having a U phase, a V phase, and a W phase, and is used, for example, as a traction motor for electrically powered vehicles such as hybrid vehicles equipped with an engine and a traction motor as a driving source for the vehicle, electric vehicles, and fuel cell vehicles. The rotating electric machine 1 not only generates driving force for the vehicle in response to power supply from a battery (not shown), but can also function as a motor generator that generates power through power transmission from the drive wheels of the vehicle and charges the battery.

[0020] The cooling structure 100 includes an oil pan 20 that stores oil as a refrigerant, and a coil end cover 10 that covers the coil ends 3b (see FIGS. 4 and 5) of the rotating electrical machine 1. The cooling structure 100 also includes an oil supply unit 21 that serves as a refrigerant supply unit.

[0021] The oil pan 20 is provided below the rotating electric machine 1. The oil pan 20 can store oil that is supplied to the rotating electric machine 1 to cool the rotating electric machine 1. The oil not only cools the rotating electric machine 1, but also contributes to the smooth rotation of the rotating electric machine 1.

[0022] 4 and 5, the schematic configuration of the rotating electric machine 1 will be described. The rotating electric machine 1 includes a case 2. The case 2 includes a cylindrical case body 2a with a bottom and a lid 2b attached to the opening of the case body 2a. A stator 3 and a rotor 4 are housed inside the case 2.

[0023] The stator 3 includes a stator core 3a, which is a generally cylindrical magnetic component. The stator core 3a is formed, for example, by stacking magnetic plates such as electromagnetic steel plates in the axial direction. A coil is formed by arranging a plurality of segment conductors in the stator core 3a, and coil ends 3b exposed from the stator core 3a are formed on both axial sides of the stator core 3a. The coil includes a three-phase coil, i.e., a U-phase coil, a V-phase coil, and a W-phase coil. Note that the coil may be wound around the teeth of the stator core 3a using concentrated winding.

[0024] The rotor 4 is disposed radially inside the stator 3, concentric with the stator 3, and facing the stator 3. A rotating shaft member 5 is provided in the center of the rotor 4. The rotating shaft member 5 is supported by bearings 6 provided in the case main body 2a and the lid portion 2b. This allows the rotor 4 to be supported by the case 2 in a state where it can rotate around the rotation axis AX. Note that an oil passage for circulating oil may be formed in the rotor 4 and the rotating shaft member 5 to cool the rotor 4.

[0025] <Coil end cover configuration> Next, the coil end cover 10 will be described. The coil end cover 10 is attached to the stator 3 so as to cover the coil ends 3b, store oil inside, and keep at least a portion of the coil ends 3b submerged in oil. As illustrated in FIGS. 4 and 5, a coil end cover 10 is provided for each of the two coil ends 3b of the stator 3. The coil end cover 10 is formed in an annular shape corresponding to the shape of the coil ends 3b. The coil end cover 10 has an inner flange 11a provided on the inner circumferential side and an outer flange 11b provided on the outer circumferential side. As shown in an enlarged view of portion X2 in FIG. 4, the coil end cover 10 is disposed so that the inner flange 11a and the outer flange 11b are in close contact with the stator 3, and is fixed to the stator 3 using bolts 12. Gaskets may be provided between the inner flange 11a and the stator 3 and between the outer flange 11b and the stator 3.

[0026] The coil end cover 10 is provided with an oil inlet hole 13 as a refrigerant inlet hole and an oil discharge hole 14 as a refrigerant discharge hole. The oil inlet hole 13 is provided at the lowest position when the rotating electric machine 1 is installed on a vehicle with its radial direction aligned vertically. An oil inlet pipe 25 is connected to the oil inlet hole 13. This oil inlet pipe 25 will be described in detail later. An oil discharge pipe 30 as a refrigerant discharge section is connected to the oil discharge hole 14. The oil discharge pipe 30 discharges oil that overflows from the oil discharge hole 14 into the oil pan 20.

[0027] Here, the vertical installation position of the oil discharge hole 14 will be explained. The coil end cover 10 stores oil inside, causing a portion of the coil end 3b to be submerged in oil. For this reason, when the rotating electric machine 1 is installed in a state in which the radial direction of the stator 3 is the vertical direction, the oil discharge hole 14 is provided above the lowest position of the stator 3, preferably above the lowest position BPr of the rotor 4 (see FIG. 1). This allows at least a portion of the coil end 3b to be submerged in oil. In this embodiment, the oil discharge hole 14 is provided above the highest position of the rotor 4. In other words, the coil discharge hole 14 is provided above the vertical height Hax of the rotation axis AX. This allows a larger portion of the coil end 3b to be submerged in oil.

[0028] Here, we will explain why oil is stored inside the coil end cover 10 and the coil ends 3b are submerged in oil. First, we will explain the state when the oil viscosity is low and the oil can circulate. When the oil viscosity is low, the cooling structure 100 uses the oil supply unit 21 to introduce oil into the coil end cover 10 through the oil inlet hole 13 provided at the bottom of the coil end cover 10. The oil that is continuously introduced into the coil end cover 10 is sequentially discharged through the oil discharge hole 14. The discharged oil is discharged into the oil pan 20 through the oil discharge pipe 30. The discharged oil is then supplied again into the coil end cover 10 through the oil supply unit 21.

[0029] In this way, the stator 3 including the coil ends 3b is cooled by the circulating oil.

[0030] Here, for example, assume that a vehicle equipped with the rotating electric machine 1 and the cooling structure 100 is parked in a cold environment. When the vehicle is parked, oil is stored in the coil end cover 10, and a portion of the coil end 3b is submerged in oil. When the rotating electric machine 1 in this state is placed in a cold environment, the viscosity of the oil in the coil end cover 10 gradually increases. In other words, when the vehicle is parked, oil with reduced fluidity is stored in the coil end cover 10. Note that when the vehicle is placed in a cold environment, the viscosity of oil in locations other than the coil end cover 10, for example, in the oil pan 20, also increases. For this reason, it is difficult for the oil to circulate through the oil supply unit 21.

[0031] When such a rotating electric machine 1 operates, current is applied to the coils provided in the stator 3. As a result, the coils, including the coil ends 3b, generate heat. As a result, the temperature of the oil stored around the coil ends 3b gradually rises, and the viscosity of the oil decreases.

[0032] In this way, by storing oil inside the coil end cover 10 and submerging the coil ends 3b in oil, heat generated by the coil can be effectively used to increase the temperature of the oil. As a result, when the rotating electric machine 1 that has been in a cold environment is restarted, the oil that cools the rotating electric machine 1 can be immediately circulated. Furthermore, because oil is present around the coil ends 3b when the rotating electric machine 1 is restarted, an excessive rise in the temperature of the coil ends 3b, and therefore an excessive rise in the temperature of the rotating electric machine 1, can be suppressed.

[0033] <Oil supply unit configuration> Next, the configuration of oil supply unit 21 will be described. Referring to Fig. 1, oil supply unit 21 includes a refrigerant introduction path 22 and an oil tank 26. Refrigerant introduction path 22 includes a first pipe 23, a second pipe 24, an oil introduction pipe 25, and an oil tank 26. Furthermore, refrigerant introduction path 22 is provided with an oil pump 27 as a refrigerant pump and an oil cooler 28 as a refrigerant cooler.

[0034] The lower end of the first pipe 23 is disposed within the oil pan 20, and the first pipe 23 extends upward from the oil pan 20. The upper end of the first pipe 23 is connected to the inlet side of the oil cooler 28. The oil cooler 28 is an air-cooled cooling device equipped with cooling fins (not shown), but may also be a water-cooled type that cools the oil by heat exchange with another refrigerant, for example, cooling water. An oil pump 27 is provided between the lower and upper ends of the first pipe 23. In this embodiment, the oil pump 27 is an electric pump, but may also be a mechanical pump. The oil pump 27 draws up oil from the oil pan 20 and delivers it to the oil cooler 28.

[0035] The upper end of the second pipe 24 is connected to the outlet side of the oil cooler 28, and the second pipe 24 extends toward the inside of the oil pan 20. An oil tank 26 is installed inside the oil pan 20. The lower end of the second pipe 24 is connected to the inlet side of the oil tank 26. The oil tank 26 has a top plate portion 26a.

[0036] The lower end of the oil introduction pipe 25 is connected to the outlet side of the oil tank 26. The upper end of the oil introduction pipe 25 is connected to an oil introduction hole 13 provided in the coil end cover 10.

[0037] The oil supplied into the coil end cover 10 by the oil supply unit 21 is sucked up from inside the oil pan 20 and pushed up to the position of the oil cooler 28. After passing through the oil cooler 28, the oil falls down to the oil tank 26. As oil is continuously supplied into the oil tank 26 through the second piping 24, the oil in the oil tank 26 is pushed out towards the oil inlet pipe 25. The oil pushed out towards the oil inlet pipe 25 is introduced into the coil end cover 10.

[0038] Here, the height position Hc of the oil cooler 28 will be described. The oil cooler 28 is disposed at a height Hc that is higher than the oil inlet hole 13 provided in the coil end cover 10. As a result, a portion of the second piping 24 connected to the oil cooler 28 is disposed higher than the oil inlet hole 13. The reason why a portion of the second piping 24 included in the refrigerant introduction path 22 is disposed higher than the oil inlet hole 13 is as follows: This is to prevent the oil stored in the coil end cover 10 from falling out due to its own weight, even when the vehicle is parked and the oil pump 27 is stopped. Preventing the oil from falling out due to its own weight allows the oil to be maintained in the coil end cover 10.

[0039] In this embodiment, when the oil pump 27 is stopped, the oil in the first pipe 23 falls into the oil pan 20 due to its own weight. On the other hand, the second pipe 24, the oil introduction pipe 25, and the coil end cover 10 are interconnected via the oil tank 26. Therefore, the oil stored in these pipes does not fall out and remains in this state.

[0040] In this embodiment, the oil tank 26 includes the top plate 26a, which allows oil to be easily stored in the oil tank 26. However, the top plate 26a may be removed. In this case, the oil tank 26 can be formed by installing a partition inside the oil pan 20.

[0041] In this embodiment, oil is introduced into the coil end cover 10 through an oil inlet hole 13 provided at the bottom of the coil end cover 10. This prevents oil from stagnating inside the coil end cover 10, allowing for smooth oil replacement.

[0042] When the oil pump 27 is restarted together with the rotating electric machine 1, the viscosity of the oil around the oil pump is high, causing a time delay before the oil is discharged from the oil pump 27. However, because oil is stored within the coil end cover 10, an excessive rise in temperature of the coil ends 3b is suppressed. Furthermore, even a small amount of oil is discharged from the oil pump 27, and the oil that has been warmed within the coil end cover 10 is discharged into the oil pan 20 through the oil discharge hole 14 and the oil discharge pipe 30. This also promotes a rise in the temperature of the oil stored in the oil pan 20.

[0043] According to this embodiment, even when the vehicle is parked and the oil pump 27 is stopped, oil is stored in the coil end cover 10. As a result, when the rotating electric machine 1 that has been in a cold environment is restarted, the heat generated by the coil ends 3b raises the temperature of the oil, enabling the refrigerant that cools the rotating electric machine 1 to immediately begin circulating.

[0044] (Second embodiment) Next, a cooling structure 200 of a second embodiment will be described with reference to Figs. 6 to 8. The cooling structure 200 of the second embodiment includes an oil supply unit 51 instead of the oil supply unit 21 included in the cooling structure 100 of the first embodiment. In addition, in accordance with the change in the oil supply unit, the coil end cover 10 has been changed to a coil end cover 40. In addition, the length of the oil discharge pipe 30 has been changed. As other configurations are generally the same between the first and second embodiments, the same reference numbers are used in the drawings for common components, and detailed description thereof will be omitted. The following description will focus on the differences from the first embodiment.

[0045] The oil supply unit 51 includes a first pipe 52, a second pipe 53, a shower pipe 54, and a shower nozzle unit 55. The lower end of the first pipe 52 is disposed within the oil pan 20 and extends upward from the oil pan 20. The upper end of the first pipe 52 is connected to the inlet side of the oil cooler 28. The oil pump 27 is disposed in the first pipe 52. One end of the second pipe 53 is connected to the outlet side of the oil cooler 28. The other end of the second pipe 53 is connected to the shower pipe 54. A shower nozzle unit 55 extends from the shower pipe 54. The shower nozzle unit 55 is disposed so as to spray oil toward an oil introduction hole 43 disposed in the upper edge of the coil end cover 40. The shower nozzle unit 55 is disposed so that the spray angle with respect to the normal direction of the coil end cover 40 is θ. By setting the injection angle θ, the injected oil is injected into the coil end cover 40 so as to flow along the circumferential direction of the coil end cover 40, i.e., the circumferential direction of the stator 3, as shown by arrow 8a in Figure 8.

[0046] The oil discharge hole 44 is located at a position where the oil introduced from the oil inlet hole 43 has traveled approximately one full circle in the circumferential direction inside the coil end cover 40. As a result, the oil travels approximately one full circle inside the coil end cover 40 and is discharged to the outside of the coil end cover 40, as shown by arrow 8b in Figure 8.

[0047] A rectifying section 45 is provided inside the coil end cover 40 at a position where the oil flow in the circumferential direction of the stator 3, i.e., the circumferential direction of the coil end cover 40, passes the oil discharge hole 44. The rectifying section 45 reverses the flow of oil that has passed the oil discharge hole 44. As a result, the oil flows backward as shown by arrow 8c and is discharged to the outside of the coil end cover 40 as shown by arrow 8b. If oil circulates multiple times inside the coil end cover 40, the cooling efficiency decreases. Therefore, the rectifying section 45 is provided to efficiently discharge the oil that has circulated once.

[0048] The coil end cover 40 of the second embodiment can be kept in a state in which oil is constantly stored, similar to the coil end cover 10 of the first embodiment. Therefore, even when the vehicle is parked and the oil pump 27 is stopped, oil is stored inside the coil end cover 40. As a result, when the rotating electric machine 1 that has been in a cold environment is restarted, the heat generated by the coil ends 3b raises the temperature of the oil, making it possible to immediately circulate the coolant that cools the rotating electric machine 1.

[0049] If oil circulates inside the coil end cover 40, the cooling efficiency of the coil end 3b will decrease. Therefore, as shown in FIG. 9, multiple oil discharge holes 44a, 44b may be provided. In this case, by providing oil discharge holes at multiple locations in different vertical positions, like the oil discharge holes 44a, 44b, the total area of ​​the openings can be increased, and the amount of oil discharged can be increased. The provision of additional oil discharge holes can also be applied to the first embodiment.

[0050] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention. Furthermore, it is obvious from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0051] 1. Rotating electric machine 2. Case 2a Case body 2b Lid 3 Stator 3a Stator core 3b Coil end 4 Rotor 5 Rotating shaft member 6 Bearing portion 10, 40 Coil end cover 13, 43 Oil inlet hole 14, 44 Oil drain hole 20 Oil pan 21, 51 Oil supply section 22 Refrigerant introduction path 23 1st pipe 24 2nd pipe 25 Oil inlet pipe 26 Oil tank 27 Oil pump 28 Oil cooler 30 Oil drain pipe 54 Shower piping 55 Shower nozzle part 100, 200 Cooling structure

Claims

1. A cooling structure for a rotating electric machine including: an annular stator; a rotor disposed opposite the stator and rotatable about a rotation axis; and a coil end formed on an axial side of the stator, a coil end cover that covers the coil ends and is capable of storing a coolant therein, and is provided with a coolant inlet hole through which the coolant is introduced, and a coolant discharge hole that is provided at a position approximately one full turn around the circumferential direction of the stator from the coolant inlet hole and through which the coolant stored therein overflows and is discharged to the outside; a shower nozzle portion that is provided to inject the refrigerant toward the refrigerant inlet hole and that injects the refrigerant at an angle with respect to a normal direction to the stator so that the refrigerant introduced from the refrigerant inlet hole flows in one direction along the circumferential direction of the stator within the coil end cover; a refrigerant flow straightening portion that protrudes toward the inside of the coil end cover that houses the coil ends at a position where the refrigerant flow along the circumferential direction of the stator has passed the refrigerant discharge hole, and reverses a portion of the refrigerant flow that has passed the refrigerant discharge hole; A cooling structure for a rotating electrical machine comprising:

2. The cooling structure for a rotating electric machine according to claim 1 , further comprising a coolant discharge portion connected to the coolant discharge hole for discharging the coolant from inside the coil end cover.

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