Cooling device

Abstract

To provide a cooling device which is capable of efficiently cooling an oil even in a case where a heating amount of a motor increases and of which the installation space is small.SOLUTION: A cooling device is installed in a housing of a transaxle and cools an oil lubricating a motor that the transaxle involves. The cooling device comprises: a partition part which divides the inside of the housing into a first space and a second space; a communication part communicating the first space and the second space which are divided by the partition part; an oil channel which is installed in the second space and moves the oil flowing in from the first space and passing through the communication part inside the second space; a plurality of tubular cooling water paths installed in the second space so as to include a region in contact with the oil channel and circulating cooling water for cooling the oil flowing in the oil channel; and an oil pump which circulates the oil between the first space and the second space.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cooling device.

Background Art

[0002] Recently, the electrification of vehicles has been promoted, and electrified vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles that use an electric motor as a power source have been put into practical use. In such electrified vehicles, with the increase in the output of the electric motor, improvement of the cooling performance of the electric motor is desired.

[0003] For example, Patent Document 1 discloses a motor unit provided with an oil cooler outside a housing that houses a motor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the motor unit disclosed in Patent Document 1, the oil heated by the motor was cooled by installing an oil cooler outside the housing that houses the motor and the gear. Recently, with the increase in the current and output of the motor, the amount of heat generated by the motor has increased. If an oil cooler corresponding to this is prepared, it is necessary to increase the number of stacked stages, so the oil cooler may become large and compress the vehicle body space.

[0006] An object of the present invention is to provide a cooling device that can efficiently cool oil even when the amount of heat generated by the motor increases and that has a small installation space.

Means for Solving the Problems

[0007] To achieve the above objective, the cooling device according to the present invention is a cooling device installed inside the housing of a transaxle for cooling the oil that lubricates the electric motor contained within the transaxle, comprising: a partition that divides the inside of the housing into a first space and a second space; a connecting part that connects the first space and the second space separated by the partition; an oil passage installed in the second space for moving the oil that has flowed in from the first space through the connecting part within the second space; and a plurality of tubular cooling water passages installed in the second space so as to include a region in contact with the oil passage, for circulating cooling water that cools the oil flowing through the oil passage. Downstream of the cooling water channel in the oil passage, there is an oil outflow space from which oil flows out of the oil passage, and the oil outflow space It includes an oil pump that circulates oil between a first space and a second space.

[0008] This configuration allows for efficient cooling of the oil even when the motor generates more heat, by forming an oil passage in contact with the cooling water passage. Furthermore, it provides a cooling device that requires minimal installation space.

[0009] Furthermore, in the cooling device of the present invention, the cooling water channel comprises a first group of cooling pipes having an elongated cross-sectional shape and extending in parallel, and a second group of cooling pipes having gaps between each cooling pipe constituting the adjacent first group of cooling pipes, and extending in a staggered pattern such that a portion of the first group of cooling pipes and the adjacent cooling pipes overlap.

[0010] This configuration allows for an increased contact area between the oil passage and the cooling water passage, thereby increasing the heat flow rate from the oil to the cooling water. This improves the cooling efficiency of the oil.

[0011] Furthermore, the cooling device according to the present invention is formed at the bottom of the transaxle.

[0012] With this configuration, the inside of the cooling device is filled with oil, making it difficult for air pockets to form, thus improving the cooling efficiency of the oil.

[0013] Furthermore, in the cooling device according to the present invention, the oil that has passed through the cooling device is drawn up to the oil pump across a space formed inside the second space.

[0014] With this configuration, the oil, cooled by coolant at different temperatures flowing through the cooling water passages, mixes together before reaching the oil pump, thus ensuring a uniform temperature for the cooled oil. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a cooling device that can efficiently cool the oil even when the amount of heat generated by the motor increases, and that also requires a small installation space. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is an external view showing an example of a transaxle equipped with a cooling device according to an embodiment. [Figure 2] Figure 2 is an XZ cross-sectional view showing an example of the cross-sectional structure of a transaxle equipped with a cooling device according to the embodiment. [Figure 3] Figure 3 is an external perspective view showing an example of the detailed structure of the cooling device according to the embodiment. [Figure 4] Figure 4 is a top view showing an example of the detailed structure of the cooling device according to the embodiment. [Figure 5] Figure 5 illustrates a method for calculating the heat flow rate between ATF and water in contact across a cooling water pipe. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0018] (Embodiment) Using FIG. 1, the cooling device according to an embodiment of the present invention will be described. FIG. 1 is an external view showing an example of a transaxle provided with the cooling device according to the embodiment.

[0019] (Schematic Configuration of Transaxle) The transaxle 10 houses a motor 14 that drives a vehicle inside a housing 13. Note that the number of motors 14 housed in the transaxle 10 is not limited to one. For example, in a hybrid vehicle equipped with both an engine and a motor, a power generation motor that generates electricity by rotating with the driving force of the engine and a driving motor that drives the vehicle using the electric power generated by the power generation motor are housed.

[0020] Since the motor 14 generates heat when it rotates, it is cooled by spraying ATF (Automatic Transmission Fluid). Note that ATF is an example of the oil in the present disclosure.

[0021] The ATF warmed by the heat of the motor 14 is cooled by a cooling device 12 installed at the bottom of the housing 13, sucked up by an oil pump, and cools the motor 14 again. The cooling device 12 cools the ATF warmed by the heat of the motor 14 with the cooling water supplied by a water pump 22 (see FIG. 4) from the outside of the transaxle 10. The structure of the cooling device 12 will be described in detail later (see FIGS. 2, 3, and 4).

[0022] (Structure of Cooling Device) Using FIGS. 2, 3, and 4, the structure of the cooling device 20 will be described. FIG. 2 is an XZ cross-sectional view showing an example of the cross-sectional structure of a transaxle provided with the cooling device according to the embodiment. FIG. 3 is an external perspective view showing an example of the detailed structure of the cooling device according to the embodiment. FIG. 4 is a top view showing an example of the detailed structure of the cooling device according to the embodiment.

[0023] A partition plate 15 is installed inside the transaxle 10, dividing the inside of the housing 13 into a first space 16a and a second space 16b. The first space 16a is the space containing the motor 14. The second space 16b is the space containing the cooling device 12. In the example in Figure 2, the partition plate 15 is installed horizontally (in the XY plane in Figure 2) and separates the first space 16a formed above from the second space 16b formed below. Note that the partition plate 15 is an example of a partition in this disclosure.

[0024] A communication hole 17 is formed in a part of the partition plate 15. The communication hole 17 introduces the ATF, which has been heated by the heat generated by the motor 14, into the cooling device 12. Note that the communication hole 17 is an example of a communication part in this disclosure.

[0025] The ATF introduced into the second space 16b from the communication hole 17 flows along the oil passage 29 shown in Figure 2, following arrow A. That is, the ATF is cooled as it moves along the X-axis by coming into contact with the first group of cooling pipes 19a and 20a and the second group of cooling pipes 19b and 20b, which will be described later.

[0026] The ATF cooled by the cooling device 12 is drawn out from the oil outlet 26 by the oil pump 28. The drawn-out ATF is returned to the first space 16a and used to cool the motor 14.

[0027] The cooling device 12 has a cooling water channel 18 through which cooling water flows. The cooling water channel 18 comprises a first group of cooling pipes 19a and 20a, a second group of cooling pipes 19b and 20b, and cooling water channels 21a and 21b. The first group of cooling pipes 19a and 20a and the second group of cooling pipes 19b and 20b are made of a material with high thermal conductivity, such as aluminum.

[0028] The first group of cooling pipes 19a are pipes that form a cooling water channel that directs cooling water flowing in from outside the transaxle 10 toward the negative side of the Y-axis. The first group of cooling pipes 19a is a bundle of multiple cooling pipes along the Y-axis. All cooling pipes constituting the first group of cooling pipes 19a have the same oval cross-sectional shape and are arranged parallel to each other. Furthermore, the ends of the first group of cooling pipes 19a on the positive side of the Z-axis are arranged to abut against the partition plate 15.

[0029] The second group of cooling pipes 19b is a pipe that forms a cooling water channel that directs cooling water flowing in from outside the transaxle 10 toward the negative side of the Y-axis. The second group of cooling pipes 19b is a bundle of multiple cooling pipes along the Y-axis. All cooling pipes forming the second group of cooling pipes 19b have the same cross-sectional shape as the cooling pipes that make up the first group of cooling pipes 19a and are arranged parallel to each other. In addition, the end of the second group of cooling pipes 19b on the negative side of the Z-axis is positioned to abut against the bottom of the housing 13.

[0030] Thus, the second group of cooling pipes 19b are arranged in a staggered pattern, parallel to the first group of cooling pipes 19a, with gaps between adjacent cooling pipes of the first group of cooling pipes 19a, and overlapping with a portion of the adjacent first group of cooling pipes 19a.

[0031] The first group of cooling pipes 20a is a pipe that forms a cooling water channel that allows the cooling water that has flowed through the first group of cooling pipes 19a to flow out of the housing 13. The first group of cooling pipes 20a is a bundle of multiple cooling pipes along the Y axis. All cooling pipes constituting the first group of cooling pipes 20a have the same oval cross-sectional shape and are arranged parallel to each other. Furthermore, the end of the first group of cooling pipes 20a on the positive Z axis side is arranged to abut against the partition plate 15. Each cooling pipe constituting the first group of cooling pipes 20a is thicker and longer than each cooling pipe constituting the first group of cooling pipes 19a. Also, the number of cooling pipes constituting the first group of cooling pipes 20a is less than the number of cooling pipes constituting the first group of cooling pipes 19a. This configuration allows the flow of cooling water flowing in from the first group of cooling pipes 19a to flow out of the first group of cooling pipes 20a without stagnation.

[0032] The second group of cooling pipes 20b is a pipe that forms a cooling water channel that allows the cooling water that has flowed through the second group of cooling pipes 19b to flow out of the housing 13. The second group of cooling pipes 20b is a bundle of multiple cooling pipes along the Y axis. All cooling pipes constituting the second group of cooling pipes 20b have the same oval cross-sectional shape and are arranged parallel to each other. Furthermore, the end of the second group of cooling pipes 20b on the negative Z axis is positioned to abut against the bottom of the housing 13. Each cooling pipe constituting the second group of cooling pipes 20b is thicker and longer than each cooling pipe constituting the second group of cooling pipes 19b. Also, the number of cooling pipes constituting the second group of cooling pipes 20b is less than the number of cooling pipes constituting the second group of cooling pipes 19b. This configuration allows the cooling water flowing in from the second group of cooling pipes 19b to flow out of the second group of cooling pipes 20b without stagnation. Furthermore, if the number of cooling pipes 19a in the first group and cooling pipes 19b in the second group is set to be equal to the number of cooling pipes 20a in the first group and cooling pipes 20b in the second group, that is, if the number of cooling pipes connected to the water distribution section 24a (see Figure 3) is set to be equal to the number of cooling pipes connected to the water collection section 24b (see Figure 3), then it is not necessary to make the cooling pipes 20a in the first group and cooling pipes 20b in the second group thicker and longer.

[0033] The cooling water channel 21a is installed on the negative Y-axis side of the first group of cooling pipes 19a and connects each cooling pipe constituting the first group of cooling pipes 19a to the first group of cooling pipes 20a. As a result, the cooling water flowing into the first group of cooling pipes 19a reaches the first group of cooling pipes 20a.

[0034] The cooling water channel 21b is installed on the negative Y-axis side of the second group of cooling pipes 19b and connects each cooling pipe constituting the second group of cooling pipes 19b to the second group of cooling pipes 20b. As a result, the cooling water flowing into the second group of cooling pipes 19b reaches the second group of cooling pipes 20b.

[0035] Thus, the cooling water passage 18 includes a first group of cooling pipes 19a and 20a that are in contact with the oil passage 29, and a second group of cooling pipes 19b and 20b.

[0036] The structure of the cooling water channel 18 will be explained in more detail using Figure 3. Figure 3 is an external perspective view showing only the portion of the cooling water channel 18 formed in the cooling device 12 shown in Figure 2.

[0037] Cooling water flows into the water distribution section 24a through the inlet pipe 23a. The water distribution section 24a is connected to the first group of cooling pipes 19a and the second group of cooling pipes 19b. The cooling water that flows into the water distribution section 24a is divided into the first group of cooling pipes 19a and the second group of cooling pipes 19b, and flows downstream, that is, towards the negative side of the Y axis in Figure 3.

[0038] The cooling water that has passed through the multiple cooling pipes constituting the first group of cooling pipes 19a flows into the cooling water channel 21a and merges. The merged cooling water then flows downstream, that is, towards the positive X-axis in Figure 3.

[0039] The cooling water that has passed through the multiple cooling pipes constituting the first group of cooling pipes 19a flows into and merges with the cooling water channel 21b (not shown in Figure 3, see Figure 2). The merged cooling water then flows downstream, that is, towards the positive X-axis in Figure 3.

[0040] The cooling water flowing through the cooling water channel 21a flows into the first group of cooling pipes 20a. The cooling water then flows downstream, that is, towards the positive Y-axis in Figure 3, through the multiple cooling pipes that make up the first group of cooling pipes 20a.

[0041] Similarly, the cooling water that has flowed through the cooling water channel 21b flows into the second group of cooling pipes 20b. The cooling water then flows downstream, that is, towards the positive Y-axis in Figure 3, through the cooling pipes that make up the second group of cooling pipes 20b.

[0042] The cooling water flowing through the first group of cooling pipes 20a and the second group of cooling pipes 20b merge at the water collection section 24b. The cooling water is then discharged from the cooling device 12 through the outlet pipe 23b.

[0043] Specifically, the cooling water flows into the cooling device 12 in the direction of arrow B shown in Figure 3. The cooling water then passes through the aforementioned cooling water channel 18 formed inside the cooling device 12 and flows out in the direction of arrow E shown in Figure 3.

[0044] The structure of the cooling device 12 will be explained in more detail using Figure 4. Figure 4 is a top view of the cooling device 12 as seen from above the transaxle 10. Note that the partition plate 15 installed above the cooling device 12 (positive Z-axis side) has been removed, and only the communication holes 17 formed in the partition plate 15 are shown.

[0045] As shown in Figure 4, the first group of cooling pipes 19a, the second group of cooling pipes 19b, the first group of cooling pipes 20a, and the second group of cooling pipes 20b are installed parallel to the Y-axis. Gaps are provided between adjacent first group of cooling pipes 19a and second group of cooling pipes 19b, and between adjacent first group of cooling pipes 20a and second group of cooling pipes 20b.

[0046] The ATF, heated by the motor 14, enters the cooling device 12 through the communication hole 17. The ATF then moves along the positive X-axis, passing through the gaps between adjacent first-group cooling pipes 19a and second-group cooling pipes 19b, and between adjacent first-group cooling pipes 20a and second-group cooling pipes 20b. That is, the ATF moves along the oil passage 29 in the direction of arrow A. At this time, the ATF is cooled by the cooling water flowing in the direction of arrow C through the first-group cooling pipes 19a and second-group cooling pipes 19b, and by the cooling water flowing in the direction of arrow D through the first-group cooling pipes 20a and second-group cooling pipes 20b. Since the direction in which the cooling water flows is perpendicular to the direction in which the ATF flows, the ATF is cooled efficiently. In order to efficiently allow the ATF to flow into the cooling device 12, the shape of the communication hole 17 is, for example, an elongated hole shape that is aligned with the extension direction of the cooling pipes, as shown in Figure 4.

[0047] The ATF that has passed between the first group of cooling pipes 19a, 20a and the second group of cooling pipes 19b, 20b flows out into the oil outlet space 25 formed inside the second space 16b. An oil outlet 26 is formed in a part of the oil outlet space 25. This oil outlet 26 is connected to an oil pump 28. Therefore, the ATF that has flowed out into the oil outlet space 25 is sucked out from the oil outlet 26 by the suction force of the oil pump 28. As a result, the ATF that has flowed out into the oil outlet space 25 changes direction towards the oil outlet 26. At this time, the ATF that has passed between the first group of cooling pipes 19a, 20a and the second group of cooling pipes 19b, 20b mixes as it passes inside the oil outlet space 25, so the temperature of the ATF becomes uniform.

[0048] Since an oil outlet space 25 is formed between the first group of cooling pipes 20a and the second group of cooling pipes 20b and the oil outlet 26, even if there is a temperature variation in the ATF that has passed through the first group of cooling pipes 20a and the second group of cooling pipes 20b, the ATF is agitated between the oil outlet space 25 and the oil outlet 26, thus reducing the temperature variation of the ATF.

[0049] The location of the oil outlet 26 is not limited to the example in Figure 4. As long as an oil outflow space 25 is formed after the oil has passed through the first group of cooling pipes 20a and the second group of cooling pipes 20b, the oil outlet 26 may be formed, for example, on the wall on the positive X-axis side of the housing 13.

[0050] The number of cooling pipes constituting the first group of cooling pipes 19a and the number of cooling pipes constituting the second group of cooling pipes 19b are set according to the cooling performance of the ATF. In other words, increasing the number of cooling pipes constituting the first group of cooling pipes 19a and the second group of cooling pipes 19b increases the contact area between the ATF and the cooling pipes, thereby improving the cooling performance of the ATF. See Figure 5 for details.

[0051] Furthermore, the number of cooling pipes constituting the first group of cooling pipes 20a is set to a number that prevents stagnation of the cooling water flow, in accordance with the number of cooling pipes constituting the first group of cooling pipes 19a. Similarly, the number of cooling pipes constituting the second group of cooling pipes 20b is set to a number that prevents stagnation of the cooling water flow, in accordance with the number of cooling pipes constituting the second group of cooling pipes 19b.

[0052] Furthermore, the lengths of the cooling pipes constituting the first group of cooling pipes 19a and 20a, and the lengths of the cooling pipes constituting the second group of cooling pipes 19b and 20b, are set according to the bottom shape of the housing 13 of the transaxle 10. The longer the length of the cooling pipes, the greater the contact area between the ATF and the cooling pipes, thereby improving the cooling performance of the ATF.

[0053] In this description, the cooling device 12 is installed at the bottom of the housing 13 of the transaxle 10. However, the installation location of the cooling device 12 is not limited to the bottom of the housing 13. For example, the cooling device 12 may be installed above the motor 14 (on the positive Z-axis side) with a partition plate 15 in between. Alternatively, the motor 14 and the cooling device 12 may be installed with a partition plate 15 that aligns with the XZ plane in between. In other words, the motor 14 and the cooling device 12 only need to be installed in adjacent positions with a partition plate 15 in between.

[0054] (Heat flow rate between ATF and coolant) The heat flow rate Q between ATF 32 and cooling water 30 will be explained using Figure 5. Figure 5 is a diagram illustrating the method for calculating the heat flow rate between ATF and water in contact across a cooling water pipe.

[0055] Assume that the cooling water 30 and ATF 32 are in contact with either the first group of cooling pipes 19a or the second group of cooling pipes 19b (hereinafter simply referred to as cooling pipe 19). Assume that the cooling water 30 and the cooling pipe 19 are in contact with a contact area S, and that the ATF 32 and the cooling pipe 19 are in contact with a contact area S. Assume that the cooling pipe 19 has a length L2 in the direction of contact between the cooling water 30 and the ATF 32, and that the cooling water 30 and the ATF 32 each have a length L1 in the direction of contact.

[0056] At this time, the ATF 32 is at temperature T1 and the cooling water 30 is at temperature T2, and a heat flow rate Q flows from the ATF 32 to the cooling water 30. Assuming that the path from the ATF 32 to the cooling water 30 via the cooling pipe 19 has a thermal resistance R, the heat flow rate Q can be calculated using equation (1).

[0057] Q = (T1 - T2) / R ... (1)

[0058] Assuming that the cooling water 30 has a thermal resistance R1, the cooling pipe 19 has a thermal resistance R2, and the ATF 32 has a thermal resistance R3, the thermal resistances R1, R2, and R3 are calculated using equations (2), (3), and (4), respectively. It should also be assumed that the cooling water 30 has a heat transfer coefficient h1, the cooling pipe 19 has a thermal conductivity k, and the ATF 32 has a heat transfer coefficient h2.

[0059] R1 = L1 / h1S ... (2)

[0060] R² = L² / kS ... (3)

[0061] R3 = L1 / h2S ... (4)

[0062] Therefore, the thermal resistance R is expressed by equation (5).

[0063] R=L1 / h1S+L2 / kS+L1 / h2S...(5)

[0064] To efficiently cool the ATF32, that is, to increase the heat flow rate Q, the thermal resistance R in equation (5) should be minimized. Here, the heat transfer coefficient h1 of the cooling water 30, the thermal conductivity k of the cooling pipe 19, and the heat transfer coefficient h2 of the ATF32 are fixed values, so in order to minimize the thermal resistance R, the contact area S should be increased. In particular, since the heat transfer coefficient h2 of the ATF32 is greater than the heat transfer coefficient h1 of the cooling water 30, it can be seen that, given that lengths L1 and L2 are constant, it is effective to maximize the contact area S between the ATF32 and the cooling pipe 19 in order to minimize the thermal resistance R.

[0065] Based on this concept, the cooling device 12 of the aforementioned embodiment increases the contact area S between the ATF 32, the cooling water 30, and the cooling pipes 19 by increasing the number of cooling pipes constituting the first group of cooling pipes 19a and 20a, and the number of cooling pipes constituting the second group of cooling pipes 19b and 20b.

[0066] (Effects of the embodiment) As described above, the cooling device 12 of the embodiment is a cooling device installed inside the housing 13 of the transaxle 10 to cool the ATF (oil) that lubricates the motor 14 (electric motor) enclosed within the transaxle 10, and comprises a partition plate 15 (partition) that divides the inside of the housing 13 into a first space 16a and a second space 16b, and a communication hole 17 (communication hole) that connects the first space 16a and the second space 16b separated by the partition plate 15. The device comprises: an oil passage 29 installed in the second space 16b to move the ATF that has flowed in from the first space 16a through the communication hole 17 within the second space 16b; a plurality of tubular cooling water passages 18 installed in the second space 16b, including a region in contact with the oil passage 29, to circulate cooling water to cool the ATF flowing through the oil passage 29; and an oil pump 28 that circulates the ATF between the first space 16a and the second space 16b. Therefore, by forming an oil passage in contact with the cooling water passage, the ATF can be efficiently cooled even when the amount of heat generated by the motor 14 increases. Furthermore, a cooling device that requires less installation space can be provided.

[0067] Furthermore, in the cooling device 12 of this embodiment, the cooling water channel 18 comprises a first group of cooling pipes 19a, 20a having an oval cross-sectional shape and extending in parallel, and a second group of cooling pipes 19b, 20b that extend in a staggered pattern with gaps between each cooling pipe constituting the adjacent first group of cooling pipes 19a, 20a, so that a portion of the first group of cooling pipes 19a, 20a and the adjacent cooling pipes overlap. Therefore, the contact area between the oil channel 29 and the cooling water channel 18 can be increased, thereby increasing the heat flow rate from the oil to the cooling water. This improves the cooling efficiency of the oil.

[0068] Furthermore, in the cooling device 12 of this embodiment, the cooling water passage 18 and the oil passage 29 are perpendicular to each other. Therefore, the contact area between the oil passage 29 and the cooling water passage 18 can be further increased. This makes it possible to further improve the cooling efficiency of the oil.

[0069] Furthermore, the cooling device 12 in this embodiment is formed at the bottom of the transaxle 10. Therefore, the inside of the cooling device 12 is filled with ATF, making it difficult for air pockets to form, thus improving the cooling efficiency of the ATF.

[0070] Furthermore, in the cooling device 12 of this embodiment, the ATF (oil) that has passed between the first group of cooling pipes 19a, 20a and the second group of cooling pipes 19b, 20b is drawn up to the oil pump 28 across the oil outlet space 25 formed inside the second space 16b. Therefore, the ATF cooled by the cooling water of different temperatures flowing through the cooling water passage mixes inside the oil outlet space 25 before reaching the oil pump 28, thus making the temperature of the ATF returning to the oil pump 28 uniform.

[0071] Although embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Moreover, this embodiment is included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0072] 10 transaxles 12 Cooling device 13 Housing 14 motors 15. Partition plate (partition section) 16a The first space 16b The second space 17 Communication hole (communication part) 18 Cooling Channel 19 Cooling piping 19a, 20a Cooling piping of the first group 19b, 20b Cooling piping for group 2 21a,21b Cooling channel 22 Water pump 23a Water inlet pipe 23b Outlet pipe 24a Watershed 24b Water collection section 25 Oil spill space 26 Oil outlet 28 Oil pump 29 Oil passage 30 Cooling water 32 ATF (oil) h1, h2 heat transfer coefficient k thermal conductivity L1, L2 Length Q heat flow R,R1,R2,R3 Thermal resistance S Contact area T1,T2 temperature

Claims

1. A cooling device installed inside the housing of a transaxle, which cools the oil that lubricates the electric motor contained within the transaxle, The interior of the housing is divided into a first space and a second space by a partition, A connecting portion that connects the first space and the second space, which are divided by the partition portion, An oil passage is installed in the second space and moves the oil that has flowed in from the first space through the communication section within the second space, The second space includes a plurality of tubular cooling water channels, which are installed to include a region in contact with the oil passage and circulate cooling water to cool the oil flowing through the oil passage, Downstream of the cooling water channel in the oil passage, there is an oil outflow space from which oil flows out of the oil passage, The system includes an oil pump that circulates the oil in the oil outlet space between the first space and the second space. Cooling device.

2. The aforementioned cooling water channel is The system comprises a first group of cooling pipes having an oval cross-sectional shape and extending in parallel, and a second group of cooling pipes extending in a staggered pattern with gaps between each adjacent cooling pipe constituting the first group of cooling pipes, such that a portion of the first group of cooling pipes and the adjacent cooling pipes overlap. The cooling device according to claim 1.

3. The cooling device is formed at the bottom of the transaxle. A cooling device according to claim 1 or claim 2.

4. The oil that has passed between the first group of cooling pipes and the second group of cooling pipes is drawn up to the oil pump through a space formed inside the second space. The cooling device according to claim 2.

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