Oil cooling device

Abstract

To provide an oil cooling device advantageous for miniaturization of an electric axle device.SOLUTION: An oil cooling device S is applied to an electric axle device 100 for a vehicle comprising: an axle housing 1 constituted to accommodate a differential device; a speed reducer 2 attached to the axle housing; and a motor 3 attached to the speed reducer. The oil cooling device comprises: an oil passage in a motor formed inside a motor housing 5 of the motor and to which cooling oil is distributed; and an oil cooler 9 attached to an outer peripheral part of the motor housing to cool the oil. The oil cooler is curved along a circumferential direction of the motor housing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an oil cooling device, and more particularly to an oil cooling device applied to a vehicle electric axle device.

Background Art

[0002] In a rigid axle suspension system employed in vehicles such as trucks, an axle housing containing a differential device is connected to the vehicle body via a spring such as a leaf spring. In recent years, an example has been seen in which a speed reducer and an electric motor are integrally attached to this axle housing to form a vehicle electric axle device. By using this vehicle electric axle device, an existing vehicle can be electrified relatively easily.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, it is conceivable to circulate cooling oil in the motor to cool the motor with the oil and cool the oil with a water-cooled oil cooler. And it is conceivable to attach the oil cooler to the outer peripheral portion of the motor housing of the motor.

[0005] However, if the oil cooler is attached to the outer peripheral portion of the motor housing, the outer dimensions will increase accordingly. This goes against the requirement for miniaturization and may deteriorate the mountability of the electric axle device on the vehicle.

[0006] Therefore, the present disclosure has been made in view of such circumstances, and an object thereof is to provide an oil cooling device that is advantageous for miniaturizing an electric axle device.

Means for Solving the Problems

[0007] According to one aspect of the present disclosure, an oil cooling device applied to a vehicle electric axle device including an axle housing configured to accommodate a differential device, a speed reducer attached to the axle housing, and a motor attached to the speed reducer, an oil passage inside the motor housing of the motor through which cooling oil flows, and an oil cooler attached to an outer peripheral portion of the motor housing for cooling the oil, is provided, wherein the oil cooler is curved along the circumferential direction of the motor housing. An oil cooling device characterized by this is provided.

[0008] Preferably, the oil cooler is formed by a plate-type heat exchanger, a plurality of plates of the plate-type heat exchanger are laminated along the radial direction of the motor housing, and the plurality of plates are curved along the circumferential direction of the motor housing.

[0009] Preferably, the oil cooler has a cooling water inlet and a cooling water outlet that protrude radially outward.

[0010] Preferably, a hollow rib protrudes from an outer peripheral portion of the motor housing, an oil passage inside the motor is defined inside the hollow rib, and the oil cooler is attached to an outer peripheral portion of the hollow rib and supplies and discharges oil to and from the oil passage inside the motor.

[0011] Preferably, an oil pump is attached to the outer peripheral portion of the motor housing.

[0012] Preferably, an inverter is attached to the outer peripheral portion of the motor housing, and cooling water is circulated through the oil cooler and the inverter.

[0013] Preferably, the oil cooling device includes a water pump for circulating cooling water through the oil cooler and a radiator for cooling the cooling water.

Advantages of the Invention

[0014] According to the present disclosure, an oil cooling device advantageous for miniaturization of an electric axle device can be provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that it should be noted that the present disclosure is not limited to the following embodiments.

[0017] FIG. 1 is a schematic perspective view showing an electric axle device according to a basic embodiment of the present disclosure. The electric axle device 100 is applied to a vehicle and is configured to be applied to a truck in this embodiment. However, the type of vehicle is arbitrary. The electric axle device 100 is configured to drive the left and right rear wheels (not shown) and constitutes a part of a rigid axle (or axle suspension type) suspension system for the rear wheels.

[0018] For convenience, the directions of front, rear, left, right, up, and down are defined as shown in the figure. These directions generally coincide with the directions of the vehicle.

[0019] The electric axle device 100 includes an axle housing 1 (only partially shown by a virtual line) configured to accommodate a differential device, a gearbox or a speed reducer 2 attached to the axle housing 1, and an electric motor, that is, a motor 3 attached to the speed reducer 2. The speed reducer 2 and the motor 3 each have a speed reducer housing 4 and a motor housing 5 for accommodating internal components.

[0020] The electric axle device 100 of this embodiment also includes an inverter 6 attached to the outer peripheral portion of the motor housing 5. The inverter 6 is an electrical component for controlling the rotation of the motor 3 and is electrically connected to the motor 3 via a relatively short cable.

[0021] In the figure, reference numeral C1 is the central axis of the left and right axle shafts housed in the axle housing 1. The central axis (referred to as the shaft axis) C1 of this axle shaft extends in the left - right direction, and the left and right drive wheels, that is, the rear wheels, are located at both ends thereof.

[0022] The rear end portion of the speed reducer 2 is attached to the axle housing 1. And the motor 3 is attached to the front end portion of the speed reducer 2. The central axis (referred to as the motor shaft) C2 of the motor 3 is positioned parallel to the shaft axis C1. Therefore, the speed reducer 2 is configured as a parallel multi-shaft type speed reducer. The output shaft (not shown) of the motor 3 protrudes from the motor housing 5 toward the right side and is positioned inside the speed reducer housing 4. The motor housing 5 is formed in a substantially cylindrical shape coaxial with the motor shaft C2.

[0023] Hereinafter, unless otherwise specified, the axial direction, circumferential direction, and radial direction (including the radius direction and diameter direction) with respect to the motor shaft C2 are simply referred to as the axial direction, circumferential direction, and radial direction.

[0024] A plurality of hollow ribs 7 protrude integrally from the outer peripheral portion of the motor housing 5. The hollow ribs 7 are basically provided to strengthen the rigidity of the motor housing 5 and improve the heat dissipation of the motor housing 5. On the other hand, although details will be described later, the hollow ribs 7 of the present embodiment are also characterized in that a motor internal oil passage 8 (see FIG. 5) for circulating cooling oil is defined inside thereof.

[0025] The hollow ribs 7 are formed in a ring shape extending over the entire circumference of the motor housing 5, and a plurality (four in the present embodiment) are formed at equal intervals in the axial direction. The cross-sectional shapes of the hollow ribs 7 and the motor internal oil passage 8 inside thereof are closed quadrilaterals. However, the cross-sectional shape, number, etc. of the hollow ribs 7 can be arbitrarily changed. The motor internal oil passage 8 is defined inside all the hollow ribs 7.

[0026] The motor 3 of the present embodiment is an oil-cooled type cooled by oil. In order to perform such oil cooling of the motor 3, an oil cooling device S is provided in the electric axle device 100 of the present embodiment.

[0027] FIG. 2 is a block diagram showing the configuration of the oil cooling device S. As shown in FIGS. 1 and 2, the oil cooling device S includes an in-motor oil passage 8 formed inside the motor housing 5 (particularly the hollow rib 7), and an oil cooler 9 for cooling the oil flowing through the in-motor oil passage 8. The oil cooling device S also includes an oil pump 10 for circulating the oil through the in-motor oil passage 8.

[0028] The oil cooling device S also includes a water pump 11 for circulating the cooling water for oil cooling through the oil cooler 9, and a radiator 12 for cooling the cooling water. Therefore, the oil cooler 9 is configured as a water-cooled oil cooler.

[0029] In the case of this embodiment, the inverter 6 is also cooled by the cooling water. Therefore, an in-inverter cooling water passage 13 for circulating the cooling water is provided inside the inverter 6, and the oil cooling device S includes the in-inverter cooling water passage 13.

[0030] In FIGS. 1 and 2, the flow of the oil O is indicated by a dashed arrow, and the flow of the cooling water W is indicated by a solid arrow. In FIG. 2, the elements shown within the frame a (the in-motor oil passage 8, the oil cooler 9, the oil pump 10, and the in-inverter cooling water passage 13) indicate the elements installed on the motor 3 side. On the other hand, the elements shown outside the frame a (the water pump 11 and the radiator 12) indicate the elements installed on the outer side of the motor 3. In this embodiment, the water pump 11 and the radiator 12 are installed on the vehicle side. In the case of a hybrid vehicle, the water pump 11 and the radiator 12 may be shared with the water pump and radiator for engine cooling.

[0031] In the case of this embodiment, the oil O discharged from the oil pump 10 is supplied to the oil cooler 9 via the in-motor oil passage 8, circulates through the oil cooler 9 and is cooled, and then circulates through the in-motor oil passage 8 to cool the motor 3. Then, it is returned to the oil pump 10.

[0032] Also, the cooling water W discharged from the water pump 11 flows through the radiator 12 and is cooled, and then flows through the inverter internal cooling water passage 13 to cool the inverter 6. Then, the cooling water W flows through the oil cooler 9 to cool the oil, and then is returned to the water pump 11.

[0033] As shown in FIG. 1, the oil cooler 9 is attached to the outer peripheral portion of the motor housing 5, particularly to the outer peripheral portion of the hollow rib 7, by bolts or the like (not shown), and directly supplies and discharges oil to and from the motor internal oil passage 8 in the hollow rib 7. The oil cooler 9 has a cooling water inlet 14 and a cooling water outlet 15 that project radially outward. The cooling water inlet 14 and the cooling water outlet 15 are each formed by an L-shaped pipe. The oil cooler 9 is attached at a position obliquely upward rearward on the outer peripheral portion of the motor housing 5. The cooling water inlet 14 and the cooling water outlet 15 project from the upper surface portion of the oil cooler 9 and are arranged at the same axial position with a circumferential interval therebetween. The inlet end of the cooling water inlet 14 is directed obliquely upward forward, and the outlet end of the cooling water outlet 15 is directed obliquely downward rearward. That is, the inlet end of the cooling water inlet 14 and the outlet end of the cooling water outlet 15 are directed in opposite directions so as to be separated from each other in the circumferential direction.

[0034] The oil pump 10 is attached to the outer peripheral portion of the motor housing 5, particularly to the outer peripheral portion of the hollow rib 7, by bolts or the like (not shown), and directly supplies and discharges oil to and from the motor internal oil passage 8 in the hollow rib 7. The oil pump 10 is formed in a cylindrical shape with its central axis extending in the left-right direction. The oil pump 10 is arranged at the position of the rear end portion on the outer peripheral portion of the motor housing 5 and at a position below the oil cooler 9.

[0035] The inverter 6 is horizontally disposed at the upper end position on the outer peripheral portion of the motor housing 5, particularly on the outer peripheral portion of the hollow rib 7, and above the oil cooler 9, and is attached by bolts or the like (not shown). The inverter 6 is formed in a flat rectangular box shape. The inverter 6 has a cooling water inlet 16 and a cooling water outlet 17 that project toward the rear side. The cooling water inlet 16 and the cooling water outlet 17 are each formed by a short linear pipe and are arranged in parallel in the left-right (axial direction). The cooling water inlet 16 is arranged on the right side and the cooling water outlet 17 is arranged on the left side, but these arrangements may be reversed.

[0036] The cooling water outlet 17 of the inverter 6 and the cooling water inlet 14 of the oil cooler 9 are connected by a pipe (not shown). To perform this connection easily and compactly, the cooling water outlet 17 and the cooling water inlet 14 are positioned at the same position in the axial direction and the radial direction, are positioned close to each other in the circumferential direction, and are arranged to face each other.

[0037] The cooling water outlet 15 of the oil cooler 9 and the cooling water inlet (not shown) of the water pump 11 are connected by a pipe (not shown). Also, the cooling water outlet (not shown) of the water pump 11 and the cooling water inlet (not shown) of the radiator 12 are connected by a pipe (not shown). Also, the cooling water outlet (not shown) of the radiator 12 and the cooling water inlet 16 of the inverter 6 are connected by a pipe (not shown).

[0038] In particular, the oil cooler 9 of the present embodiment is characterized in that it is curved in an arc shape along the circumferential direction of the motor housing 5, that is, along the circumferential direction with respect to the motor shaft C2.

[0039] FIG. 3 is an exploded perspective view schematically showing the configuration of the oil cooler 9. In the figure, the direction indicated by reference sign a is the radially inner side, and the direction indicated by reference sign b is the circumferential direction.

[0040] As shown in FIGS. 1 and 3, the oil cooler 9 is formed by a plate heat exchanger. Since the plate heat exchanger itself is already known, a detailed description thereof will be omitted (see, for example, Patent Document 2). What is different about the plate heat exchanger of the present embodiment from a normal plate heat exchanger is that a plurality of plates 18 of the plate heat exchanger are curved along the circumferential direction. That is, the plurality of plates 18 of the plate heat exchanger are stacked along the radial direction and curved along the circumferential direction.

[0041] The plurality of plates 18 are guided by guide bars (not shown) and stacked, and are tightened by fasteners (for example, bolts and nuts, not shown) so as to be in close contact with each other in the stacking direction. Between each plate 18, an oil flow path 19 through which the oil O flows and a cooling water flow path 20 through which the cooling water W flows are alternately formed in the stacking direction. The heat of the oil is transferred to the cooling water through the plate 18, thereby cooling the oil. A sealing material (not shown) for preventing leakage, leakage, and mixing of the oil O and the cooling water W is provided between each plate 18 or between each plate 18.

[0042] The plate 18 basically has four holes, that is, an oil supply hole 30, an oil discharge hole 21, a cooling water supply hole 22, and a cooling water discharge hole 23 at the four corners. The supply-side oil O supplied from an oil inlet (not shown) flows radially outward through the oil supply hole 30 of each plate 18. At this time, since the oil flow paths 19 communicating with the oil supply hole 30 appear alternately between each plate 18, when the oil flow path 19 communicates with the oil supply hole 30, the oil O branches and is introduced into the oil flow path 19.

[0043] On the other hand, the discharge-side oil O discharged from an oil outlet (not shown) flows radially inward through the oil discharge hole 21 of each plate 18 located on the circumferentially opposite side of the oil supply hole 30. In the oil flow path 19, the oil O flows in the circumferential direction from the oil supply hole 30 toward the oil discharge hole 21. Then, the oil O that has reached the oil discharge hole 21 merges into the flow through the oil discharge hole 21 of each plate 18.

[0044] The same applies to the cooling water W. The supply-side cooling water W supplied from the cooling water inlet 14 flows radially inward through the cooling water supply holes 22 of each plate 18. At this time, since the cooling water flow paths 20 communicating with the cooling water supply holes 22 alternately appear between the respective plates 18, when the cooling water flow path 20 communicates with the cooling water supply hole 22, the cooling water W branches and is introduced into the cooling water flow path 20.

[0045] On the other hand, the discharged-side cooling water W discharged from the cooling water outlet 15 flows radially outward through the cooling water discharge holes 23 of each plate 18 located on the opposite side in the circumferential direction of the cooling water supply holes 22. In the cooling water flow path 20, the cooling water W flows in the circumferential direction from the cooling water supply hole 22 toward the cooling water discharge hole 23. Then, the cooling water W that has reached the cooling water discharge hole 23 merges into the flow passing through the cooling water discharge holes 23 of each plate 18.

[0046] Thus, in this embodiment, the oil O is supplied and discharged to and from the oil cooler 9 from the radially inner side, and the cooling water W is supplied and discharged from the radially outer side. Also, the flow direction of the oil O in the oil flow path 19 and the flow direction of the cooling water W in the cooling water flow path 20 are opposite to each other in the circumferential direction. However, these flow directions may be the same.

[0047] The flow of the cooling water W toward the radially inner side through the cooling water supply holes 22 of each plate 18 turns back in the final cooling water flow path 20 (indicated by reference numeral 20A) located most radially inward, and becomes a flow of the cooling water W flowing radially outward through the cooling water discharge holes 23 of each plate 18. The plate 18 (referred to as the final cooling water supply-side plate and indicated by reference numeral 18A) forming the radially inner wall of this final cooling water flow path 20 (20A) is not provided with the cooling water supply hole 22 and the cooling water discharge hole 23.

[0048] Similarly, the flow of oil O directed radially outward through the oil supply holes 30 of each plate 18 turns back at the outermost final oil flow path 19 located radially outermost, and becomes a flow of oil O directed radially inward through the oil discharge holes 21 of each plate 18. The plate 18 (referred to as the outermost oil supply side plate and denoted by reference numeral 18B) that forms the radially outer inner wall of this final oil flow path 19 is not provided with the oil supply holes 30 and the oil discharge holes 21.

[0049] In the case of this embodiment, a curved outer peripheral plate 18C is laminated on the radially outer side of the outermost oil supply side plate 18B, and this outer peripheral plate 18C forms the outer peripheral surface of the oil cooler 9. The outer peripheral plate 18C is provided with a cooling water inlet 14 whose outlet end is positioned coaxially with the cooling water supply hole 22, and a cooling water outlet 15 whose inlet end is positioned coaxially with the cooling water discharge hole 23.

[0050] Similarly, a curved inner peripheral plate (not shown) is laminated on the radially inner side of the outermost cooling water supply side plate 18A, and this inner peripheral plate forms the inner peripheral surface of the oil cooler 9. The inner peripheral plate is formed with an oil inlet 24 (see FIG. 5) positioned coaxially with the oil supply hole 30 and an oil outlet 25 (see FIG. 5) positioned coaxially with the oil discharge hole 21.

[0051] FIG. 4 schematically shows the outer shape of the oil cooler 9 as viewed from the left side in the axial direction. As can also be seen from this figure, the oil cooler 9 has a substantially fan-shaped shape when viewed in the axial direction, and exhibits an appearance like a cut-out Baumkuhnen. Therefore, the oil cooler 9 and each of its plates 18 (including 18A to 18C) have their circumferential width or length (arc length) shortened as they go radially inward. The plurality of oil supply holes 30 provided in each plate 18 are positioned coaxially along the radial direction with respect to the motor shaft C2. The same applies to the other three holes, namely the oil discharge hole 21, the cooling water supply hole 22, and the cooling water discharge hole 23.

[0052] FIG. 5 is a schematic cross-sectional view showing a main part of the oil cooling device S, and is a schematic cross-sectional view when the motor housing 5, the oil cooler 9, and the oil pump 10 are viewed from the left side in the axial direction. Further, FIG. 5 shows a cross-section at an axial position where there is one hollow rib 7 through which the oil inlet 24 and the oil outlet 25 of the oil cooler 9 communicate with the oil passage 8 inside the motor.

[0053] As shown in the figure, a hollow rib 7 is provided so as to protrude radially outward on the outer peripheral portion of the motor housing 5, and an oil passage 8 inside the motor is defined along the longitudinal direction thereof inside the hollow rib 7. The oil cooler 9 is attached to the outer peripheral portion of the hollow rib 7 and supplies and discharges oil to and from the oil passage 8 inside the motor. The oil pump 10 is also attached to the outer peripheral portion of the hollow rib 7 and supplies and discharges oil to and from the oil passage 8 inside the motor.

[0054] Specifically, an oil inlet 24 and an oil outlet 25 are provided in the inner peripheral plate of the oil cooler 9 described above. Also, an oil outlet and an oil inlet for the oil passage 8 inside the motor are provided on the outer peripheral portion of the hollow rib 7. The oil cooler 9 is overlapped and attached to the hollow rib 7 such that the oil inlet 24 of the oil cooler 9 communicates with the oil outlet of the oil passage 8 inside the motor, and the oil outlet 25 of the oil cooler 9 communicates with the oil inlet of the oil passage 8 inside the motor. Note that the oil cooler 9 may not be fixed to the hollow rib 7 by bolt fastening or the like, and may be fixed to a portion of the motor housing 5 other than the hollow rib 7.

[0055] Similarly, the oil pump 10 is overlapped and attached to the hollow rib 7 such that the oil inlet 26 of the oil pump 10 communicates with the oil outlet of the oil passage 8 inside the motor, and the oil outlet 27 of the oil pump 10 communicates with the oil inlet of the oil passage 8 inside the motor. In the present embodiment, the oil inlet 24 and the oil outlet 25 of the oil cooler 9 and the oil inlet 26 and the oil outlet 27 of the oil pump 10 communicate with the oil passage 8 inside the motor within the same hollow rib 7. And the oil O discharged from the oil pump 10 is promptly supplied to the oil cooler 9.

[0056] In order to prevent the oil O from bypassing or short-circuiting the oil cooler 9 and the oil pump 10, a closing portion 28 for closing the oil passage 8 in the motor is provided integrally with the hollow rib 7.

[0057] The oil O discharged from the oil outlet 27 of the oil pump 10 travels through the oil passage 8 in the motor towards the oil cooler 9, and is then introduced into the oil cooler 9 from the oil inlet 24 of the oil cooler 9. Then, it flows through the oil flow path 19 in the oil cooler 9, is cooled by the cooling water W, and is then discharged from the oil outlet 25 of the oil cooler 9 into the oil passage 8 in the motor. In this way, the cooled oil can be circulated in the motor housing 5 to cool the motor 3.

[0058] As shown in FIG. 1, the oil passages 8 in the motor within all the hollow ribs 7 are in communication. Therefore, the cooled oil circulates within all the hollow ribs 7, enabling the motor 3 to be cooled evenly.

[0059] The oil passage 8 in the motor is also provided in locations other than the hollow ribs 7, enabling the motor 3 to be cooled at a wide range of positions.

[0060] FIG. 6 shows a cross-section at an axial position where there is another hollow rib 7 for reference. At this position, the oil inlet 24 and the oil outlet 25 of the oil cooler 9 do not exist, while the cooling water inlet 14 and the cooling water outlet 15 of the oil cooler 9 exist. The flow of the cooling water W can be easily understood from the figure. Note that the cooling water inlet 14 and the cooling water outlet 15 of the oil cooler 9 may be provided at an axial position where there is no hollow rib 7.

[0061] Next, the advantages of this embodiment will be described.

[0062] As described above, when an oil cooler is attached to the outer peripheral portion of the motor housing, the outer dimensions increase accordingly. This goes against the requirement for miniaturization and may deteriorate the mountability of the electric axle device on a vehicle.

[0063] In FIG. 4, a case where an oil cooler 9X of a comparative example composed of a plate type heat exchanger is attached to the outer peripheral portion of a motor housing 5 (particularly the hollow rib 7) is shown by a phantom line. In this comparative example, similar to a normal plate type heat exchanger, the shape of the oil cooler 9X when viewed from the axial direction is substantially square and not a curved shape. Each plate of the oil cooler 9X is also flat like a normal plate type heat exchanger and not curved. Therefore, the maximum radius RX at the circumferential position where the oil cooler 9X is attached becomes a relatively large value.

[0064] On the other hand, the oil cooler 9 of the present embodiment has a curved shape when viewed from the axial direction. Each plate 18 of the oil cooler 9 is also curved. Therefore, the maximum radius R at the circumferential position where the oil cooler 9X is attached can be made smaller than that of the comparative example.

[0065] Thereby, the outer dimensions (radius R) of the assembly of the motor housing 5 and the oil cooler 9 can be reduced, and an oil cooling device S advantageous for miniaturization of the electric axle device 100 can be provided.

[0066] Particularly in the present embodiment, the oil cooler 9 is formed by a plate type heat exchanger, a plurality of plates 18 of the plate type heat exchanger are stacked along the radial direction, and the plurality of plates 18 are curved along the circumferential direction. Thereby, a curved oil cooler 9 can be easily manufactured.

[0067] The oil cooler 9 of the present embodiment has a cooling water inlet 14 and a cooling water outlet 15 that protrude radially outward. Therefore, piping can be detached from the outside in the radial direction with respect to these cooling water inlet 14 and cooling water outlet 15, and workability can be improved. Also, the cooling water inlet 14 and the cooling water outlet 15 can be arranged at positions suitable for a curved plate type heat exchanger, which is advantageous for the adoption of the plate type heat exchanger.

[0068] In this embodiment, a hollow rib 7 protrudes from the outer peripheral portion of the motor housing 5, and a motor internal oil passage 8 is defined inside the hollow rib 7. The oil cooler 9 is attached to the outer peripheral portion of the hollow rib 7 and supplies and discharges oil to and from the motor internal oil passage 8. Therefore, oil can be efficiently supplied and discharged between the oil cooler 9 and the motor internal oil passage 8. Further, since a rib originally for reinforcement is made hollow and the motor internal oil passage 8 is defined inside, not only is the exchange of oil with the oil cooler 9 facilitated, but the motor housing 5 can be reduced in diameter by using the rib also as the oil passage.

[0069] Also in this embodiment, an oil pump 10 is attached to the outer peripheral portion of the motor housing 9. Therefore, it is advantageous for miniaturization of the assembly of the motor housing 9 and the oil pump 10. In particular, the oil pump 10 is attached to the outer peripheral portion of the hollow rib 7 and supplies and discharges oil to and from the motor internal oil passage 8 inside the hollow rib 7. Therefore, the exchange of oil between the oil pump 10 and the motor internal oil passage 8 can be performed easily and with high efficiency.

[0070] In this embodiment, an inverter 6 is attached to the outer peripheral portion of the motor housing 9. Usually, the inverter is attached to the vehicle body side and connected to the motor via a relatively long cable. However, in this case, the relatively long cable has to be routed along a predetermined route, which is difficult in terms of assemblability.

[0071] Also, when the vehicle is running, the axle housing moves up and down, and the motor follows and moves up and down accordingly. On the other hand, the inverter is fixed to the vehicle body side. Therefore, the cable has to be constantly deformed following the up and down movement of the motor with respect to the inverter, and there is a risk that the cable may be damaged or disconnected. Also, an unnecessary load is applied to the connectors connecting the cable to the inverter and the motor, and there is a risk that the connector connection portion may be damaged. All of these lead to a decrease in reliability.

[0072] However, in this embodiment, the inverter 6 is attached to the outer peripheral portion of the motor housing 9. By doing so, the cable connecting the inverter 6 and the motor 3 can be shortened, the routing of the cable becomes easy, and the assemblability can be improved.

[0073] Also, when the axle housing and the motor 3 move up and down during vehicle travel, the inverter 6 also moves up and down integrally following the motor 3. For this reason, relative movement does not occur between the inverter 6 and the motor 3, and deformation of the cable during up and down movement can be prevented. Therefore, it is possible to prevent the cable from being damaged or disconnected due to relative movement between the two. In addition, the connector connecting the cable to the inverter 6 and the motor 3 is not subjected to unnecessary load, and damage to the connector connection part can also be prevented. Thus, the reliability can be significantly improved.

[0074] In this embodiment, the same cooling water circulates through the oil cooler 9 and the inverter 6. For this reason, the inverter 6 can also be cooled using the cooling water that cools the oil. Further, since the inverter 6 is located upstream of the oil cooler 9 in the cooling water flow direction, the inverter 6, which is an electrical component vulnerable to heat, can be cooled by cooler cooling water and before the oil. Therefore, the inverter 6 can be protected from heat with priority over the motor 3, and failure of the inverter 6 can be prevented.

[0075] As described above, the embodiments of the present disclosure have been described in detail, but various other embodiments and modifications of the present disclosure are also conceivable.

[0076] For example, the oil inlet 24 and the oil outlet 25 of the oil cooler 9 and the oil inlet 26 and the oil outlet 27 of the oil pump 10 may communicate with the motor internal oil passages 8 of different hollow ribs 7. Further, the oil inlet 24 and the oil outlet 25 of the oil cooler 9 may communicate with the motor internal oil passages 8 of different hollow ribs 7. Similarly, the oil inlet 26 and the oil outlet 27 of the oil pump 10 may communicate with the motor internal oil passages 8 of different hollow ribs 7.

[0077] The oil cooler does not necessarily have to be formed by a plate heat exchanger, and its type is arbitrary. For example, it may be formed by a multi-tube (shell and tube type) heat exchanger.

[0078] The embodiments of the present disclosure are not limited to the foregoing embodiments only, and all modifications, application examples, and equivalents included in the idea of the present disclosure defined by the claims are included in the present disclosure. Therefore, the present disclosure should not be construed in a limited manner, and it is also applicable to any other technology belonging to the scope of the idea of the present disclosure.

Explanation of Reference Numerals

[0079] 1 Axle housing 2 Reducer 3 Motor 5 Motor housing 6 Inverter 7 Hollow rib 8 Oil passage inside the motor 9 Oil cooler 10 Oil pump 11 Water pump 12 Radiator 14 Cooling water inlet 15 Cooling water outlet 18 Plate 100 Electric axle device S Oil cooling device

Claims

1. An oil cooling device applied to an electric axle device for a vehicle, comprising an axle housing configured to accommodate a differential device, a speed reducer attached to the axle housing, and a motor attached to the speed reducer, an oil passage inside the motor housing of the motor through which cooling oil flows, and an oil cooler attached to the outer peripheral portion of the motor housing for cooling the oil. The oil cooler is curved along the circumferential direction of the motor housing. An oil cooling device characterized by this.

2. The oil cooler is formed by a plate type heat exchanger, a plurality of plates of the plate type heat exchanger are stacked along the radial direction of the motor housing, and the plurality of plates are curved along the circumferential direction of the motor housing. The oil cooling device according to Claim 1.

3. The oil cooler has a cooling water inlet and a cooling water outlet that protrude radially outward. The oil cooling device according to Claim 1.

4. A hollow rib protrudes from the outer peripheral portion of the motor housing, the oil passage inside the motor is defined inside the hollow rib, and the oil cooler is attached to the outer peripheral portion of the hollow rib and supplies and discharges oil to and from the oil passage inside the motor. The oil cooling device according to Claim 1.

5. An oil pump is attached to the outer peripheral portion of the motor housing. The oil cooling device according to Claim 1.

6. An inverter is attached to the outer peripheral portion of the motor housing, and cooling water circulates through the oil cooler and the inverter. The oil cooling device according to Claim 1.

7. The oil cooling device according to Claim 1, further comprising a water pump for circulating cooling water through the oil cooler and a radiator for cooling the cooling water. The oil cooling device according to Claim 1. ​

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