Electric axle cooling system

Abstract

To reduce the number of component parts and simplify the configuration by integrating an electric pump that circulates oil into an electric axle with a heat exchanger in a cooling system that uses a heat exchanger to cool the oil that cools the inside of the electric axle.SOLUTION: An electric axle cooling system includes an electric pump 30 that circulates oil within the electric axle to cool an electric axle, and an oil cooler 40 that forms a heat exchanger. The electric pump 30 includes a motor 31, an internal gear pump 32, and a motor case 33 that houses them. In the motor case 33, an oil suction port 33b is formed at one end of a rotating shaft 31a of the motor 31, and an oil discharge port 33c is formed at the other end, such that oil flows into the motor 31. The oil cooler 40 includes a cooler case 42 that covers the motor case 33 from the outside. Cooling water flows through the gap between the motor case 33 and the cooler case 42. The motor case 33 includes fins 33a on the outer wall surface.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed in this specification relates to a cooling device for an electric axle, which is a drive source of an electric vehicle.

Background Art

[0002] In an oil-cooled cooling system of an electric axle, oil from an electric pump is supplied to a motor and a transaxle constituting the electric axle, and circulated through each heat-generating part. A heat exchanger is provided in the oil circulation path to cool the oil (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional cooling system, the electric pump and the heat exchanger are provided separately. As a result, there is a problem that the number of component parts increases and the configuration around the electric axle becomes complicated.

[0005] The problem of the technology disclosed in this specification is that in a cooling device that cools a heat medium for cooling inside an electric axle with a heat exchanger, by integrating an electric pump that circulates the heat medium inside the electric axle with the heat exchanger, the number of component parts of the cooling device is suppressed and the configuration around the electric axle is simplified.

Means for Solving the Problems

[0006] To solve the above problems, the cooling device for an electric axle disclosed in this specification takes the following means.

[0007] The first means comprises an electric pump that cools an electric axle by circulating a main heat transfer medium such as oil within the electric axle, and a heat exchanger that cools the main heat transfer medium with an exchange heat transfer medium such as cooling water, wherein the electric pump comprises a motor, a pump function unit that is rotationally driven by a rotating shaft concentric with the rotating shaft of the motor, and a motor case that houses the motor and the pump function unit, wherein the motor case has an intake port for the main heat transfer medium formed on one end of the pump function unit and the rotating shaft of the motor, and an outlet port for the main heat transfer medium formed on the other end, and the main heat transfer medium flows through the motor, the heat exchanger comprises a heat exchanger case that covers the motor case from the outside, the exchange heat transfer medium flows through the gap between the motor case and the heat exchanger case, the portion of the motor case covered by the heat exchanger case is made of a heat conductor and has protrusions or recesses on its outer wall surface that increase the surface area of ​​the outer wall surface.

[0008] According to the first method described above, the main heat transfer medium, whose temperature rises due to the cooling of the electric axle, is cooled by the exchange heat transfer medium flowing on the outside of the motor case as it passes through the electric pump. Therefore, the heat exchanger is integrated with the electric pump, eliminating the need to provide a separate heat exchanger. As a result, the number of components in the electric axle cooling device can be reduced, simplifying the configuration around the electric axle. In the electric pump, the rotation axes of the motor and the pump function unit are concentric. Therefore, the size of the motor case in the rotation axis direction, which houses the motor and the pump function unit, increases, and the surface area of ​​the motor case increases. Consequently, the heat exchange efficiency as a heat exchanger can be increased. In addition, the outer wall surface of the motor case is provided with protrusions or recesses to further enhance the heat exchange efficiency as a heat exchanger. Moreover, since the outside of the motor case is covered by the heat exchanger case, a heat dissipation structure prioritizing heat dissipation performance can be provided on the outer wall surface. Furthermore, since the outside of the motor case is covered by the heat exchanger case, the strength of the motor case can be reduced compared to the case where it is not covered by the heat exchanger case, thus enabling weight reduction. Furthermore, since the main heat transfer fluid flows through the motor of the electric pump, the motor can also be cooled by the main heat transfer fluid.

[0009] The second means is that, in the first means described above, a closed space is formed on the outer wall surface of the motor case inside the heat exchanger case, independent of the heat exchanger case and the motor case, and the controller board for the electric pump is housed in this closed space.

[0010] According to the second method described above, the controller board can be cooled by the heat exchange medium. Moreover, since the controller board is housed in a closed space, it is not exposed to the heat exchange medium, thus eliminating the need for waterproofing and other measures that would be required if it were exposed.

[0011] The third means is that, in the second means described above, the controller board is fixed to the wall surface on the side away from the motor case within the enclosed space.

[0012] According to the third method described above, since the controller board is fixed to the wall away from the motor case, heating from the main heat transfer medium, which is relatively hot, is suppressed, and since the controller board is fixed near the exchange heat transfer medium, it is efficiently cooled by the exchange heat transfer medium.

[0013] The fourth means is that, in any of the first to third means described above, an exchange heat transfer medium pump for circulating the exchange heat transfer medium is provided inside the heat exchanger case, and the exchange heat transfer medium pump is rotationally driven by a rotating shaft concentric with the rotating shaft of the motor.

[0014] According to the fourth method described above, the motor of the electric pump also rotates the heat exchange fluid pump. Therefore, there is no need to provide a separate drive source for the heat exchange fluid pump, and the configuration of the heat exchanger system can be simplified.

[0015] The fifth means is that, in any of the first to third means described above, the protrusion of the motor case is a fin formed on the outer wall surface of the motor case, projecting toward the inner wall surface of the heat exchanger case.

[0016] According to the fifth means described above, the heat transfer efficiency of the motor case with respect to the heat exchange medium can be enhanced by the fins.

[0017] The sixth means is as follows: in the fifth means described above, the motor case forms a cylindrical shape concentric with the rotation axis of the motor, and the fins are formed in a spiral shape concentric with the rotation axis of the motor on the outer peripheral surface of the cylindrical body of the motor case.

[0018] According to the sixth means described above, since the heat exchange medium flows along the spiral fins, the time during which the heat exchange medium touches the outer wall surface of the motor case becomes longer, and the heat exchange efficiency as a heat exchanger can be enhanced.

Brief Description of the Drawings

[0019] [Figure 1] It is an explanatory diagram showing an electric axle to which the first embodiment is applied. [Figure 2] It is an enlarged cross-sectional explanatory diagram of the main part showing the first embodiment. [Figure 3] It is an explanatory diagram showing the flow of cooling water in the first embodiment. [Figure 4] It is an enlarged cross-sectional explanatory diagram of the main part showing the second embodiment. [Figure 5] It is an enlarged cross-sectional explanatory diagram of the main part showing the third embodiment.

Modes for Carrying Out the Invention

[0020] <Configuration of an Electric Axle to which the First Embodiment is Applied> FIG. 1 shows an overview of an electric axle 10 to which the first embodiment is applied. In FIG. 1, with the electric axle 10 mounted on a vehicle, the traveling direction of the vehicle is the X-axis direction indicated by the arrows X1 and X2, and the width direction of the vehicle orthogonal to the traveling direction is the Y-axis direction indicated by the arrows Y1 and Y2. These directions are the same in other figures described later, and regarding the vertical direction of the vehicle, it is the Z-axis direction indicated by the arrows Z1 and Z2 in FIG. 3.

[0021] As is well known, the electric axle 10 includes a drive motor 11, a transfer axle 12 as a speed reducer, and an inverter 13. The rotational torque generated by the drive motor 11 is controlled by the inverter 13, reduced by the transfer axle 12, and transmitted to the wheels 51 via the drive shaft 52 of the vehicle.

[0022] To cool and lubricate the drive motor 11 and the transfer axle 12 within the electric axle 10, oil as the main heat medium is circulated as indicated by the arrows to each part within the housing 11a of the drive motor 11 and within the housing 12a of the transfer axle 12. The oil is circulated by an electric pump unit 20 provided inside the housing 12a of the transfer axle 12. Also, to cool the inside of the inverter 13, cooling water is circulated as indicated by the arrows within the inverter 13.

[0023] The electric pump unit 20 has an electric pump 30 and an oil cooler 40 as a heat exchanger integrated as described later. Cooling water that cools the inside of the inverter 13 flows through the oil cooler 40 of the electric pump unit 20, and the cooling water also cools the oil circulated by the electric pump 30. Therefore, the cooling water serves as the heat exchange medium of the heat exchanger. The cooling water is passed through a radiator 44 provided outside the electric axle 10 and heat is dissipated by the radiator 44.

[0024] <Configuration of the electric pump unit 20> Figure 2 shows an enlarged view of the detailed structure of the electric pump unit 20. The electric pump unit 20 is constructed by covering the outside of the electric pump 30 with a cooler case (corresponding to the heat exchanger case) 42 of an oil cooler 40 which acts as a heat exchanger. The electric pump 30 includes a motor 31 and an internal gear pump 32. The internal gear pump 32, which is the pump function part that draws oil into the motor case 33 of the electric pump 30, is fixed to the Y2 side end of the rotating shaft 31a of the motor 31. The motor case 33 and the cooler case 42 have a cylindrical shape that is concentric with the rotating shaft 31a of the motor 31. Here, the cylindrical shape is defined as having closed ends. The motor case 33 is made of metal such as aluminum, copper, iron, or alloys of these metals, and is constructed of a heat conductor.

[0025] The motor case 33 has an inlet 33b and a discharge port 33c formed on its outer circumference. The inlet 33b is located on the Y2 side of the motor case 33 and protrudes in the X1 direction. The discharge port 33c is located on the Y1 side of the motor case 33 and protrudes in the X1 direction. When the electric pump 30 is operated, oil is drawn into the motor case 33 from the inlet 33b and discharged from the discharge port 33c, as indicated by the arrows.

[0026] On the Y1 side of the motor case 33, a closed space 34 is provided integrally with the motor case 33, independent of the space inside the motor case 33 and the space inside the cooler case 42. The controller board 31b is housed in the closed space 34 and is fixed to the wall on the side away from the motor case 33, that is, the wall on the opposite side of the motor case 33. The controller board 31b is a circuit board for controlling the rotation of the motor 31 and is connected to the stator coil 31d of the motor 31, the power supply circuit (not shown), etc. via wiring 31c. The wiring 31c is led out to the outside of the closed space 34 through pipe 34a.

[0027] Within the cooler case 42, a centrifugal pump 41, which forms a heat exchange fluid pump, is provided on the Y1 side of the enclosed space 34. The centrifugal pump 41 is coupled to the motor 31 so as to be rotated by the rotating shaft 31a. In addition, a suction port 42a for the cooling water, which is the heat exchange fluid, is provided at the Y1 end of the cooler case 42, and a discharge port 42b for the cooling water is provided at the Y2 end of the cooler case 42. Therefore, when the centrifugal pump 41 rotates, cooling water is drawn in from the suction port 42a as indicated by the arrow. The cooling water flows through the gap between the motor case 33 and the cooler case 42 and is discharged from the discharge port 42b.

[0028] On the outer circumferential surface of the motor case 33, fins 33a are formed to protrude toward the inner wall surface of the cooler case 42, acting as protrusions that increase the surface area of ​​the outer wall. The fins 33a are formed integrally with the motor case 33 and are formed in a spiral shape concentric with the rotation axis 31a on the outer wall of the motor case 33. Therefore, the cooling water flowing through the gap between the motor case 33 and the cooler case 42 is guided by the spiral fins 33a and flows in a spiral pattern, as indicated by the direction symbols in Figure 2. Figure 3 shows how the cooling water flows in a spiral pattern on the outer wall of the motor case 33, as indicated by the arrows. In Figure 3, the tip of the arrow (cooling water) appears to be broken, but on the Z2 side of the motor case 33, the tip of the arrow (cooling water) is connected to the adjacent arrow (cooling water) on the Y2 side.

[0029] <Operation and Effects of the First Embodiment> The oil drawn in through the suction port 33b and discharged from the discharge port 33c by the operation of the electric pump 30 cools and lubricates the drive motor 11 and transaxle 12 of the electric axle 10. At the same time, it also cools the inside of the motor 31. When the electric pump 30 is operated, the centrifugal pump 41 draws in cooling water through the suction port 42a and discharges it from the discharge port 42b. The cooling water cools the inverter 13 of the electric axle 10. At the same time, as the cooling water passes through the gap between the cooler case 42 and the motor case 33, it cools the motor case 33 and cools the oil flowing inside the motor case 33. Thus, the electric pump unit 20 functions as a heat exchanger. The cooling water, whose temperature has risen due to the cooling of the inverter 13 and the oil flowing inside the motor case 33, is cooled again by the radiator 44.

[0030] According to the first embodiment, the heat exchanger is integrated with the electric pump 30 by the electric pump unit 20, eliminating the need to provide a separate heat exchanger. Therefore, the number of components as a cooling device for the electric axle 10 can be reduced, simplifying the configuration around the electric axle 10. The electric pump 30 has the same rotating shaft 31a for both the motor 31 and the internal gear pump 32. Therefore, the size of the motor case 33 that houses the motor 31 and the internal gear pump 32 in the direction of the rotating shaft 31a is increased, and the surface area of ​​the motor case 33 is increased. Consequently, the heat exchange efficiency as a heat exchanger can be increased. Furthermore, fins 33a are provided as protrusions on the outer wall surface of the motor case 33 to increase the heat exchange efficiency as a heat exchanger. Moreover, since the outside of the motor case 33 is covered by the cooler case 42, a heat dissipation structure prioritizing heat dissipation performance can be provided on the outer wall surface. Furthermore, since the outside of the motor case 33 is covered by the cooler case 42, the strength of the motor case 33 can be reduced compared to a case where it is not covered by the cooler case 42, thereby reducing its weight. In addition, since the oil flows through the motor 31 of the electric pump 30, the motor 31 can also be cooled by the oil.

[0031] The cooling water drawn in through the suction port 42a also cools the controller board 31b fixed to the wall of the enclosed space 34. Therefore, a heat dissipation configuration for the controller board 31b can be eliminated. Moreover, the controller board 31b is fixed to the wall away from the motor case 33 of the electric pump 30, thus preventing it from being heated by the high-temperature oil flowing inside the electric pump 30. Furthermore, since the controller board 31b is housed within the enclosed space 34, it is not exposed to the cooling water, eliminating the need for waterproofing. In addition, the centrifugal pump 41 is rotationally driven by the rotating shaft 31a of the motor 31 of the electric pump 30, eliminating the need for a separate drive means to rotate the centrifugal pump 41 and simplifying the system configuration as a heat exchanger.

[0032] The motor case 33 is provided with fins 33a, and the fins 33a are formed in a spiral shape. As a result, the cooling water flowing through the gap between the motor case 33 and the cooler case 42 flows along the spirally formed fins 33a, increasing the time the cooling water is in contact with the outer surface of the motor case 33, and efficiently cooling the oil flowing inside the motor case 33. In other words, the heat exchange efficiency as a heat exchanger can be increased.

[0033] <Second Embodiment> Figure 4 shows the second embodiment. The distinguishing feature of the second embodiment compared to the first embodiment is that the centrifugal pump 41, as in the first embodiment, is not placed inside the electric pump unit 20, but is provided outside the electric pump unit 20. The other configurations are the same in the second embodiment as in the first embodiment, and a further explanation is omitted.

[0034] In the second embodiment, the centrifugal pump 41 is provided independently at any location in the cooling water circulation path shown in Figure 1. For example, the centrifugal pump 41 can be provided in the cooling water circulation path within the inverter 13. Alternatively, the centrifugal pump 41 can be provided independently at any location in the cooling water circulation path outside the electric axle 10 that connects to the radiator 44.

[0035] In the second embodiment, the electric pump unit 20 does not include a centrifugal pump 41, thus simplifying the configuration of the electric pump unit 20. Furthermore, since the rotating shaft 31a does not penetrate the controller board 31b as in the first embodiment, the design flexibility of the controller board 31b can be increased.

[0036] <Third Embodiment> Figure 5 shows the third embodiment. The distinguishing feature of the third embodiment compared to the first embodiment is that air is used as the heat exchange medium instead of cooling water as in the first embodiment. Because air is used as the heat exchange medium, the electric pump unit 20 is preferably located outside the housing 12a of the transaxle 12, rather than inside the housing 12a as in the first embodiment. On the other hand, the piping for the cooling water that cools the inverter 13 is configured not to pass through the electric pump unit 20. The other configurations are the same in the third embodiment as in the first embodiment, and a further explanation is omitted.

[0037] In the third embodiment, similar to the cooling water in the first embodiment, the operation of the air-cooling fan 43 causes air to flow through the gap between the motor case 33 and the cooler case 42, and this air cools the oil in the electric pump 30 via the motor case 33. In the third embodiment, the piping for the cooling water that cools the inverter 13 does not pass through the electric pump unit 20, thus simplifying the cooling water piping route.

[0038] <Other Embodiments> Although the technology disclosed herein has been described in specific embodiments, it can be implemented in various other forms. For example, in the above embodiments, the main heat transfer medium is oil and the exchange heat transfer medium is water or air, but various other heat transfer mediums can be used. In the above embodiments, the cooling of the inverter 13 of the electric axle 10 is performed by cooling water as the exchange heat transfer medium, but it may also be configured to be performed together with the drive motor 11 and transaxle 12 by oil as the main heat transfer medium. In the above embodiments, the rotating shaft 31a of the motor 31 of the electric pump 30 and the rotating shaft of the internal gear pump 32 as the pump function part, and the rotating shaft 31a of the motor 31 of the electric pump 30 and the rotating shaft of the centrifugal pump 41 are the same rotating shaft, but they may each be separate rotating shafts that are concentrically coupled. In the above embodiments, fins 33a are provided as protrusions on the outer wall surface of the motor case 33, but recesses with recessed walls may be provided on the outer wall surface of the motor case 33. In each of the above embodiments, the internal gear pump 32, which constitutes the pump function unit, is provided on the suction port side of the motor case 33, but it may also be provided on the discharge port side of the motor case 33. In the first and third embodiments above, the centrifugal pump 41 and the cooling fan 43, which constitute the exchange heat transfer medium pump, are provided on the suction port 42a side of the cooler case 42, but they may also be provided on the discharge port 42b side of the cooler case 42. [Explanation of Symbols]

[0039] 10 Electric Axle 11 Drive motor 12 transaxles 11a, 12a enclosure 13 Inverter 20 Electric pump units 30 Electric pumps 31 Motor 31a Rotation axis 31b Controller board 31c wiring 31d Stator Coil 32. Internal gear pump (pump function unit) 33 Motor Case 33a Fin (convex part) 33b Inlet 33c outlet 34 Closed space 34a pipe 40. Oil cooler (heat exchanger) 41. Centrifugal pump (exchange heat transfer pump) 42 Cooler Case (Heat Exchanger Case) 42a Inlet 42b Discharge port 43. Air-cooling fan (exchange heat transfer fluid pump) 44 Radiator 51 wheels 52 Drive shaft

Claims

1. An electric pump circulates oil, which is the main heat transfer medium, within the electric axle to cool it, The system comprises a heat exchanger that cools the main heat transfer medium with cooling water or air, which is an exchange heat transfer medium, The aforementioned electric pump is Motor and, A pump function unit that is rotationally driven by a rotating shaft concentric with the rotating shaft of the motor, The system comprises a motor case housing the motor and the pump function unit, The motor case has an intake port for the main heat transfer medium formed on one end of the pump function unit and the motor's rotating shaft, and an outlet port for the main heat transfer medium formed on the other end, so that the main heat transfer medium flows through the motor. The heat exchanger comprises a heat exchanger case that covers the motor case from the outside, and the heat exchange medium is passed through the gap between the motor case and the heat exchanger case. The portion of the motor case covered by the heat exchanger case is made of a heat conductor and has protrusions or recesses on its outer wall surface that increase the surface area of ​​the outer wall surface. Cooling system for electric axle.

2. In claim 1, Inside the heat exchanger case, on the outer wall surface of the motor case, a closed space independent of the heat exchanger case and the motor case is formed, and the circuit board for the electric pump controller is housed within this closed space. Cooling system for electric axle.

3. In claim 2, The controller board is fixed to the wall surface on the side away from the motor case within the enclosed space. Cooling system for electric axle.

4. In any of claims 1 to 3, A heat exchange pump for circulating the heat exchange medium is provided within the heat exchanger case, and the heat exchange pump is rotationally driven by a rotating shaft concentric with the rotating shaft of the motor. Cooling system for electric axle.

5. In any of claims 1 to 3, The protrusions on the motor case are fins formed on the outer wall surface of the motor case, projecting toward the inner wall surface of the heat exchanger case. Cooling system for electric axle.

6. In claim 5, The motor case has a cylindrical shape that is concentric with the rotation axis of the motor. The fins are formed spirally on the outer surface of the cylindrical body of the motor case, concentric with the rotation axis of the motor. Cooling system for electric axle.

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