Electric axle cooling structure

Abstract

To provide a cooling system of an electric axle which dispenses with a mounting structure for mounting a filtration filter at the outside of a casing of the electric axle by integrating the filtration filter with a pump and suppresses an increase in weight of the casing of the electric axle and an increase in manufacturing cost.SOLUTION: A cooling structure of an electric axle cools the electric axle by circulating oil to each section of the electric axle. The cooling structure includes: a pump 21 which is mounted in a casing 13 of the electric axle and circulates oil to a circulation path within the electric axle; and a filtration filter 31 which filters foreign matter such as dust included in the oil. The pump 21 is integrally provided with a filter case 25 forming a part of the circulation path. The filter case 25 is configured to be communicated with a pump discharge port 24b of the pump 21. The filtration filter 31 is provided to cross an oil passage within the filter case 25.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In an oil-cooled cooling system for an electric axle, oil is supplied from a pump to the motor and transaxle that make up the electric axle, and circulated to each heat-generating part. A filter is installed in the oil circulation path to filter out foreign matter such as dust in the oil. The oil also functions as a lubricant for the sliding parts within the electric axle (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2020-525708 Summary of the Invention [Problem to be solved by the invention]

[0004] In electric axles, the filtration filter is typically provided so as to protrude from the exterior of the electric axle housing. This requires the creation of a mounting structure for the filtration filter on the exterior of the electric axle housing, which inevitably increases the weight and manufacturing costs of the electric axle housing.

[0005] The objective of the technology disclosed in this specification is to integrate a filter with a pump in an electric axle cooling system, thereby eliminating the need for a mounting structure for attaching the filter to the outside of the electric axle housing, thereby suppressing increases in the weight and manufacturing costs of the electric axle housing. [Means for solving the problem]

[0006] In order to solve the above problems, the cooling structure for an electric axle disclosed in this specification takes the following measures.

[0007] The first means is a cooling structure for an electric axle that cools the electric axle by circulating a heat medium through each part of the electric axle, and includes a pump that is attached to the housing of the electric axle and circulates the heat medium through a circulation path within the electric axle, and a filtration filter that filters out foreign matter such as dust contained in the heat medium, the pump having an integral heat medium passage that forms part of the circulation path, the heat medium passage being configured to communicate with the heat medium inlet or heat medium outlet of the pump, and the filtration filter being arranged across the heat medium passage.

[0008] According to the first aspect, the pump is integrally provided with a heat medium passage that forms part of the heat medium circulation path, and a filter is provided across the heat medium passage. Therefore, there is no need to form a mounting structure for attaching a filter on the outside of the electric axle housing, and increases in the weight and manufacturing costs of the electric axle housing can be suppressed.

[0009] The second means is the first means described above, further comprising a cover member arranged to close an opening formed in the housing, the pump being a motor-driven electric pump fixed to the cover member together with the heat medium passage inside the housing, and a controller arranged on the cover member outside the housing for driving and controlling the electric pump, and the cover member is arranged so that the heat medium passage is between the controller and the pump.

[0010] According to the second aspect, a heat medium passage is interposed between the electric pump and the controller, and a heat medium is present in the heat medium passage. Therefore, although both the electric pump and the controller generate heat during operation, the heat of both is cooled by the heat medium, and it is possible to prevent the heat of the high-heat side from heating the low-heat side beyond its heat-resistant temperature.

[0011] A third means is the first or second means described above, wherein the filter is cylindrical, and the pump is disposed inside the cylindrical filter.

[0012] According to the third aspect, the pump is disposed inside the cylindrical filter, which provides better space efficiency than when the filter and pump are provided separately, and allows the filter to be seamlessly integrated with the pump.

[0013] A fourth means is the first means described above, wherein the pump is a motor-driven electric pump, and the electric pump has a pump case that houses the motor and the pump, and the pump case has the heat medium suction port formed on one end side of a rotating shaft of the motor and the pump, and the heat medium discharge port formed on the other end side.

[0014] According to the fourth aspect, the electric pump has a heat medium inlet at one end of its rotary shaft and a heat medium outlet at the other end. Therefore, as the electric pump operates, the heat medium flows through the inside of the electric pump from the heat medium inlet to the heat medium outlet. As a result, the inside of the electric pump also becomes a circulation path for the heat medium, allowing the motor and the pump to be cooled.

[0015] A fifth aspect is the second aspect, wherein a part of the heat medium passage is formed by the cover member.

[0016] According to the fifth aspect, the cover member constitutes a part of the heat medium passage, which simplifies the structure of the heat medium passage. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing an electric axle to which a first embodiment is applied. [Figure 2] FIG. 2 is an enlarged cross-sectional explanatory view of a main part of the first embodiment. [Figure 3] FIG. 3 is an enlarged cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 3 is an explanatory cross-sectional view corresponding to FIG. 2 and showing a second embodiment. [Figure 5] FIG. 10 is an explanatory cross-sectional view corresponding to FIG. 2 and showing a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Configuration of the first embodiment> Fig. 1 shows an overview of an electric axle 10 to which the first embodiment is applied. In Fig. 1, when the electric axle 10 is mounted on a vehicle, the direction of travel of the vehicle is the X-axis direction indicated by the arrows X1 and X2, and the width direction of the vehicle, which is perpendicular to the direction of travel, is the Y-axis direction indicated by the arrows Y1 and Y2. These directions are the same in other figures described later, and the up-down direction of the vehicle is the Z-axis direction indicated by the arrows Z1 and Z2 in Fig. 3.

[0019] As is well known, the electric axle 10 includes a drive motor 11 and a transaxle 12, which is a speed reducer. The electric axle 10 also includes an inverter, which is not shown here. The rotational torque generated by the drive motor 11 is controlled by the inverter, reduced by the transaxle 12, and transmitted to wheels 51 via a drive shaft 52 of the vehicle.

[0020] To cool and lubricate each part within the electric axle 10, oil, which is a heat medium, is circulated through each part within the electric axle 10. For this purpose, an electric pump assembly 20 is provided inside the housing 13 of the electric axle 10. Additionally, an oil cooler 40 is provided adjacent to the electric pump assembly 20 on the outside of the housing 13. The oil discharged from the electric pump assembly 20 is circulated to each part within the electric axle 10 via a circulation path as shown by the arrows in FIG. 1. Along the way through this circulation path, the oil is cooled by the oil cooler 40. The oil cooler 40 is a heat exchanger, and the dashed arrows indicate the flow of the refrigerant that cools the oil flowing within the oil cooler 40.

[0021] FIG. 2 shows an enlarged view of the detailed structure of the electric pump assembly 20. The electric pump assembly 20 is centered around an electric pump (also referred to as a pump) 21 housed in a generally cylindrical resin pump case 24. The pump 21 includes a motor 22 and an internal gear pump 23. The internal gear pump 23, which serves as a pump function for pumping oil into the pump case 24, is fixed to the Y2-side end of a rotating shaft 22a of the motor 22. A pump suction port 24a and a pump discharge port 24b are formed at both ends of the pump case 24 in the Y-axis direction, at positions radially offset from the fixed position of the rotating shaft 22a. The pump suction port 24a is provided on the Y2 side of the pump case 24 and protrudes in the Y2 direction. The pump discharge port 24b is provided on the Y1 side of the pump case 24 and protrudes in the Y1 direction. The pump suction port 24a serves as a heat medium suction port, and the pump discharge port 24b serves as a heat medium discharge port. When the pump 21 is operated, oil is sucked into the pump case 24 through the pump suction port 24a and discharged from the pump discharge port 24b.

[0022] The outer periphery of the pump case 24 is covered, with a predetermined gap therebetween, by a resin filter case 25 having a generally cylindrical shape. The filter case 25 has a double-pipe structure. The Y2-side ends of the outer and inner pipes of the double-pipe structure are closed by a ring-shaped closing wall 25c, closing the gap between the outer and inner pipes. The Y1-side end of the inner pipe of the double-pipe structure is also closed by a disk-shaped closing wall 25d. Meanwhile, the Y1-side end of the outer pipe of the double-pipe structure is open, forming an opening 25b. A cylindrical main filter element 31 serving as a filtration filter is inserted and disposed in the gap between the outer and inner pipes of the double-pipe structure. The Y2-side end of the main filter element 31 is in close contact with the closing wall 25c, and the Y1-side end of the main filter element 31 is in close contact with a cover member 26, which will be described later. A case discharge port 25a for discharging oil from the filter case 25 is formed in the closing wall 25c at a location on the outer periphery of the cylindrical shape of the main filter element 31. The filter case 25 forms a heat medium passage (oil passage) 29 together with the pump case 24. Oil discharged from the pump discharge port 24b flows along the closing wall 25d from the inner pipe to the outer pipe of the filter case 25. The main filter element 31 is disposed across the oil passage formed between the inner pipe and the outer pipe. Therefore, the oil flowing through the oil passage is filtered by the main filter element 31.

[0023] The Y1-side end of the pump discharge port 24b of the pump case 24 penetrates the closing wall 25d of the filter case 25 and is exposed on the Y1 side of the closing wall 25d. Therefore, the pump discharge port 24b is connected to the oil passage of the filter case 25. The Y1-side end of the pump discharge port 24b is heat-welded to an opening of the closing wall 25d, thereby integrating the filter case 25 with the pump case 24. Furthermore, the Y2-side end of the pump suction port 24a of the pump case 24 abuts against the Y1 side of a plate-shaped suction filter 32, which serves as another filtration filter. The Y2 side of the suction filter 32 is supported by a resin holder 28. A holder suction port 28a is formed in the holder 28 at a position opposite the pump suction port 24a. The holder 28, which includes the holder suction port 28a, forms a heat medium passage (oil passage) 29. The holder 28 is fitted into the filter case 25 from the Y2 side so as to close the entire Y2 side of the filter case 25. A holder discharge port 28b is formed in the holder 28 at a position corresponding to the case discharge port 25a, for discharging the oil that has passed through the case discharge port 25a to the Y2 side of the holder 28. A pipe 41 for guiding the oil to the oil cooler 40 is connected to the holder discharge port 28b.

[0024] The Y1 side of the opening 25b of the filter case 25 is fixed to the Y2 side surface of a resin plate-shaped cover member 26 and closed by the cover member 26. Therefore, in this case, the cover member 26 forms part of the heat medium passage (oil passage) 29. A controller 27 for controlling the rotation of the motor 22 is fixed to the Y1 side surface (outside the housing 13) of the cover member 26. The controller 27 is connected to the motor 22 via a wiring 27a. The cover member 26 is fixed to the outer surface of the housing 13 with bolts 26b while closing the opening 13a. An O-ring 26c is sandwiched between the cover member 26 and the outer surface of the housing 13, surrounding the opening 13a and ensuring a seal for the opening 13a. A cylindrical flange portion 13b is formed at the opening 13a of the housing 13 and extends toward the inside of the housing 13. The flange portion 13b covers the outer periphery of the electric pump assembly 20 with a predetermined gap between them. Therefore, the portion of the housing 13 where the opening 13a is formed is reinforced by a flange portion 13b. The flange portion 13b also protects the electric pump assembly 20 from being damaged by an external force.

[0025] <Actions and Effects of the First Embodiment> When motor 22 rotates in response to a control signal from controller 27, internal gear pump 23 is rotated via rotary shaft 22a. As a result, oil in housing 13 is sucked through holder suction port 28a and pump suction port 24a into pump case 24, as shown by the arrow. At this time, the oil passes through suction filter 32, which filters and removes foreign matter such as dust in the oil. When pump case 24 is eventually filled with oil, the oil flows from pump discharge port 24b through a passage formed by closing wall 25d and cover member 26, as shown by the arrow, into the gap between the inner and outer tubes of filter case 25. Because main filter element 31 is inserted in the gap between the inner and outer tubes of filter case 25, dust and other foreign matter in the oil are further filtered and removed by main filter element 31. The oil passes through the suction filter 32 and is purified as it passes from the inner periphery to the outer periphery of the main filter element 31, as shown by the arrows, and is then supplied to the oil cooler 40 from the pipe 41 through the case discharge port 25a and the holder discharge port 28b. The oil cooled in the oil cooler 40 is circulated within the electric axle 10 as shown by the arrows in FIG. 1.

[0026] 3, the arrows indicate the flow of oil when viewed from the Y1 side to the Y2 side along the Y axis. The oil discharged from the pump discharge port 24b flows along the Y1 side surface of the closing wall 25d to the entire inner circumferential side of the main filter element 31, passes through the main filter element 31 from the inner circumferential side to the outer circumferential side, and flows toward the case discharge port 25a. Therefore, the entire area of ​​the main filter element 31 is effectively used to filter the oil.

[0027] Maintenance of the motor 22, internal gear pump 23, etc., as well as maintenance of the suction filter 32 and main filter element 31, can be performed by removing the cover member 26 from the housing 13 and pulling the electric pump assembly 20 outside the housing 13.

[0028] According to the first embodiment described above, the following actions and effects are achieved.

[0029] (1) The filter case 25 is provided together with the motor 22 and the internal gear pump 23 inside the electric pump assembly 20. The main filter element 31 for oil filtration is provided inside the filter case 25. Therefore, unlike the prior art, there is no need to form a mounting structure for attaching an oil filter outside the housing 13, and increases in the weight and manufacturing costs of the housing 13 can be suppressed.

[0030] (2) The main filter element 31 has a cylindrical shape, and the electric pump 21 is disposed on the inner circumferential side of the cylindrical shape. Therefore, space efficiency is improved compared to when the main filter element 31 and the electric pump 21 are provided separately, and the main filter element 31 can be smoothly integrated into the electric pump assembly 20.

[0031] (3) An oil passage is formed between the lid member 26 that covers the opening 25b of the filter case 25 and the closing wall 25d. As a result, it is not necessary to form a wall facing the closing wall 25d using the filter case 25 in order to form the oil passage, and the configuration of the electric pump assembly 20 can be simplified.

[0032] (4) The controller 27 is provided outside the cover member 26. Therefore, the controller 27 and the motor 22, which are heat sources in the electric pump assembly 20, are disposed opposite each other across the oil passage formed by the cover member 26 and the closing wall 25d. Therefore, the heat generated by the controller 27 and the motor 22 is cooled by the oil flowing through the oil passage, and it is possible to prevent the heat from the higher-heat side of the controller 27 or the motor 22 from heating the lower-heat side of the controller 27 or the motor 22 beyond its heat-resistant temperature.

[0033] (5) Before the oil in the housing 13 is guided to the oil cooler 40, the oil flows through the pump case 24. Therefore, the oil circulated in the electric axle 10 is also used, which suppresses heat generation in the motor 22 and the internal gear pump 23.

[0034] Second Embodiment 4 shows a second embodiment. The second embodiment is characterized by the fact that the filtration filter is composed of only a suction filter 32, and the main filter element 31 provided in the first embodiment is omitted. The other configurations of the second embodiment are the same as those of the first embodiment, and therefore a repeated description of the same parts will be omitted.

[0035] In the second embodiment, the main filter element 31 is omitted, but the flow of oil within the electric pump assembly 20 is the same as in the first embodiment. As a result, the second embodiment also achieves the same functions and effects as the first embodiment, including (1) and (3) to (5) above.

[0036] Third Embodiment 5 shows a third embodiment. The third embodiment is characterized by the fact that, whereas in the first embodiment, the oil discharge port in the electric pump assembly 20 is formed by a case discharge port 25a and a holder discharge port 28b, in the first embodiment, the oil discharge port in the electric pump assembly 20 is an oil discharge port 26a formed in the cover member 26. The oil discharge port 26a is formed integrally with the cover member 26 and protrudes outward. In the third embodiment, the case discharge port 25a and the holder discharge port 28b are not formed. The other configurations of the third embodiment are the same as those of the first embodiment, and a repeated description of the same parts will be omitted.

[0037] In the third embodiment, oil flows through the pump case 24 and is discharged from the pump discharge port 24b, as in the first embodiment. The oil then flows into the gap between the inner and outer tubes of the filter case 25. The oil is purified as it passes from the inner periphery to the outer periphery of the main filter element 31 and is then supplied to the oil cooler 40 through the oil discharge port 26a, as indicated by the arrow. In FIG. 5, the oil discharge port 26a is shown adjacent to the pump discharge port 24b. However, in reality, the oil discharge port 26a and the pump discharge port 24b are spaced apart, similar to the positional relationship between the pump discharge port 24b and the case discharge port 25a shown in FIG. 3 in the first embodiment. As a result, the oil discharged from the pump discharge port 24b flows along the Y1 side surface of the closing wall 25d to the entire inner periphery of the main filter element 31, passes through the main filter element 31, and flows toward the oil discharge port 26a. Therefore, the entire area of ​​the main filter element 31 is effectively used for oil filtration.

[0038] In the third embodiment, the oil discharge port of the electric pump assembly 20 is the oil discharge port 26a, but the flow of oil within the electric pump assembly 20 is substantially the same as in the first embodiment. Therefore, the third embodiment also achieves the same functions and effects as the first embodiment described above in (1) to (5). Moreover, in the third embodiment, the oil discharge port 26a, which is the oil discharge port of the electric pump assembly 20, is disposed outside the housing 13. On the other hand, in the first and second embodiments, the case discharge port 25a and the holder discharge port 28b, which are the oil discharge ports of the electric pump assembly 20, are disposed inside the housing 13. Therefore, the third embodiment or the first and second embodiments can be selected depending on the structure of the oil intake port of the oil cooler 40.

[0039] <Other embodiments> Although the technology disclosed in this specification has been described above in relation to specific embodiments, it may be embodied in various other forms. For example, although the electric pump assembly 20 is provided inside the housing of the electric axle in the above embodiments, it may be provided outside the housing. Furthermore, although oil is used as the heat medium in the above embodiments, a material other than oil may be used. Furthermore, although the above embodiments are configured such that the lid member 26 closes the opening 25b of the filter case 25, thereby forming part of the heat medium passage (oil passage) 29, the heat medium passage 29 may be formed solely by the filter case 25. In this case, the lid member 26 is fixed integrally to the heat medium passage 29 formed by the filter case 25. Furthermore, although the above embodiments are configured such that the filter case 25 is provided at the pump discharge port 24b, the filter case 25 may also be provided at the pump suction port 24a. In this case, the suction filter 32 may be provided between the pump suction port 24a and the filter case 25, or the suction filter 32 may be omitted. [Explanation of symbols]

[0040] 10 Electric Axle 11 Drive motor 12 Transaxle 13. Cabinet 13a aperture 13b Flange 20 Electric pump assembly 21 Electric pump (pump) 22 Motor 22a Rotation axis 23 Internal gear pump (pump function part) 24 Pump case 24a Pump suction port (heat medium suction port) 24b Pump outlet (heat medium outlet) 25 Filter case 25a Case outlet 25b opening 25c, 25d closing wall 26 Lid member 26a Oil outlet 26b Bolt 26c O-ring 27 Controller 27a Wiring 28 Holder 28a Holder suction port 28b Holder outlet 29 Heat medium passage 31 Main filter element (filtration filter) 32 Suction filter (filtration filter) 40 Oil cooler 41 Pipe 51 Wheels 52 Drive shaft

Claims

1. A cooling structure for an electric axle that cools an electric axle by circulating a heat medium through each part of the electric axle, a pump attached to the housing of the electric axle and circulating the heat medium through a circulation path within the electric axle; a filtration filter that filters out foreign matter such as dust contained in the heat medium, the pump is integrally provided with a heat medium passage that forms part of the circulation path, the heat medium passage is configured to communicate with a heat medium suction port or a heat medium discharge port of the pump, the filtration filter is provided across the flow of the heat medium passing through the heat medium passage, a cover member provided to close an opening formed in the housing, The pump is fixed to the cover member together with the heat medium passage inside the housing. Cooling structure for electric axles.

2. In claim 1, the pump is a motor-driven electric pump, a controller provided on the cover member outside the housing and configured to control rotation of the electric pump; The cover member is disposed so that the heat medium passage is interposed between the controller and the pump. Cooling structure for electric axles.

3. In claim 1 or 2, The filter has a cylindrical shape, The pump is disposed inside the cylindrical filter. Cooling structure for electric axles.

4. In claim 1, the pump is a motor-driven electric pump, The electric pump includes a pump case that houses a motor and a pump function unit, and the pump case has the heat medium suction port formed on one end side of a rotary shaft of the motor and the pump function unit, and the heat medium discharge port formed on the other end side. Cooling structure for electric axles.

5. In claim 1, A part of the heat medium passage is formed by the cover member. Cooling structure for electric axles.

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