Vehicle cooling structure

Abstract

The present application provides a simplified cooling structure for a vehicle. The cooling structure for a vehicle (2) includes: a gear box (13) that houses a gear mechanism (for example, a rear differential gear (12)) and oil inside; an inverter (15) that is provided on an outer surface (for example, an outer surface (42a)) of the gear box (13) and is electrically connected to a motor (14); a step-down converter (16) that is provided on the outer surface (for example, the outer surface (42a)) of the gear box (13) and is electrically connected to the inverter (15); and a cooling flow path (61) that is formed between the inverter (15) and the step-down converter (16) and an inner surface (for example, an inner surface (42b)) of the gear box (13) and allows a coolant to flow.

Description

Technical Field

[0001] This invention relates to a cooling structure for vehicles. Background Technology

[0002] In vehicles, power conversion devices such as inverters are used to supply electricity to the motor. To maintain the performance of these power conversion devices, cooling is required. For example, Patent Document 1 discloses a technique of circulating refrigerant to cool the inverter.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-105645 Summary of the Invention

[0004] However, vehicles are equipped with gear mechanisms such as rear differential gears. These gear mechanisms are air-cooled, for example, by heat sinks mounted on the gearbox that houses them. In conventional vehicles, cooling structures for power conversion devices such as inverters and cooling structures for gear mechanisms were separate (i.e., according to the object being cooled). Therefore, the cooling structures occupied a large space, resulting in limited design flexibility for the vehicle.

[0005] Therefore, the object of the present invention is to provide a simplified cooling structure for vehicles.

[0006] To address the aforementioned issues, a vehicle cooling structure according to one embodiment of the present invention comprises: a gearbox housing a gear mechanism and oil; an inverter disposed on the outer surface of the gearbox and electrically connected to a motor; a buck converter disposed on the outer surface of the gearbox and electrically connected to the inverter; and a cooling flow path formed between the inverter and the buck converter and the inner surface of the gearbox, for the flow of refrigerant.

[0007] According to the present invention, the cooling structure for vehicles can be simplified. Attached Figure Description

[0008] Figure 1 This is a partial schematic diagram showing the vehicle of this embodiment.

[0009] Figure 2 This is a schematic diagram illustrating the power supply system of the vehicle according to this embodiment.

[0010] Figure 3 This is a schematic cross-sectional view showing the cover portion of this embodiment.

[0011] Figure 4 This is a perspective top view of the cover of this embodiment as seen from the rear.

[0012] Figure 5 This is a diagram illustrating an example of the output characteristics of the motor according to this embodiment.

[0013] (Explanation of reference numerals in the attached diagram)

[0014] 1 vehicle

[0015] 2. Vehicle cooling structure

[0016] 11 Drive shaft

[0017] 12. Rear differential gear (gear mechanism)

[0018] 13 Gearbox

[0019] 14 motors

[0020] 15 Inverters

[0021] 15A capacitor

[0022] 15b power supply module

[0023] 16. Buck Converter

[0024] 16A reactor

[0025] 16b power supply module

[0026] 17 Storage batteries

[0027] 61 cooling flow path

[0028] 81 Heatsink Detailed Implementation

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in these embodiments are merely illustrative examples for ease of understanding of the invention and are not intended to limit the invention, except where specifically excluded. Furthermore, in this specification and the accompanying drawings, elements having substantially the same function or structure are labeled with the same reference numerals, thereby omitting repeated descriptions; additionally, elements not directly related to the present invention are omitted from the illustrations.

[0030] Figure 1 This is a partial schematic diagram showing the vehicle 1 according to this embodiment. A vehicle cooling structure 2 is applied to the vehicle 1. Figure 1 In the diagram, solid arrows indicate the front, back, left, and right directions of vehicle 1. Figure 2 This is a schematic diagram showing the power supply system of vehicle 1 according to this embodiment.

[0031] Vehicle 1 is, for example, an engine vehicle equipped with an engine as a driving source for travel. Alternatively, vehicle 1 may be an electric vehicle equipped with a motor as a driving source for travel, or a hybrid vehicle equipped with both an engine and a motor as driving sources.

[0032] like Figure 1 As shown, vehicle 1 includes a driveshaft 11, a rear differential gear 12, a gearbox 13, a motor 14, an inverter 15, and a buck converter 16. One end of the driveshaft 11 is connected to a driving source (e.g., an engine) via a transmission. The rear differential gear 12 corresponds to an example of the gear mechanism of the present invention. Additionally, as... Figure 2 As shown, the power supply system of vehicle 1 includes a motor 14, an inverter 15 and a step-down converter 16, and also includes a battery 17.

[0033] The rear differential gear 12 includes an input shaft 21, a gear ring 22, a housing 23, a first side gear 24, a second side gear 25, a first output shaft 26, a second output shaft 27, a first pinion shaft 28, a second pinion shaft 29, a first pinion 30, and a second pinion 31.

[0034] Specifically, the input shaft 21 is a drive pinion shaft. The other end of the transmission shaft 11 is connected to the input shaft 21. The input shaft 21 extends in the front-rear direction. A bevel gear 21a is formed at the front end of the input shaft 21. The bevel gear 21a meshes with the gear ring 22. The housing 23 protrudes from one side of the gear ring 22. The housing 23 is hollow. The housing 23 and the gear ring 22 rotate integrally.

[0035] A first side gear 24, a second side gear 25, a first pinion 30, and a second pinion 31 are housed in a housing 23. The first side gear 24 and the second side gear 25 are arranged parallel to each other on a gear ring 22 and face each other at a distance. The first side gear 24 is connected to a first output shaft 26. The first output shaft 26 extends to the left through the gear ring 22 and connects to the left rear wheel. The second side gear 25 is connected to a second output shaft 27. The second output shaft 27 extends to the right through the housing 23 and connects to the right rear wheel.

[0036] The first pinion shaft 28 and the second pinion shaft 29 protrude from the inner surface of the housing 23. The first pinion 30 is rotatably supported on the housing 23 by means of the first pinion shaft 28. The second pinion 31 is rotatably supported on the housing 23 by means of the second pinion shaft 29. The first pinion 30 and the second pinion 31 mesh with the first side gear 24 and the second side gear 25, respectively.

[0037] The gearbox 13 includes a main body 41 and a cover 42. A space 41a is formed inside the main body 41. An opening 41b is provided on the rear side of the main body 41. The cover 42 blocks the opening 41b of the main body 41 from the rear side. When the cover 42 is installed on the main body 41, the gearbox 13 is sealed. The gearbox 13 is sealed with the rear differential gear 12 and oil inside. The oil lubricates the various parts of the differential gear 12.

[0038] In the rear differential gear 12, frictional heat is generated between the gears as each gear rotates. For example, relatively large frictional heat is generated between the bevel gear 21a and the gear ring 22 on the input shaft 21. The oil in the gearbox 13 is heated by this frictional heat.

[0039] Motor 14 outputs power to assist the rotation of the rear wheels. Motor 14 is, for example, a three-phase AC motor. Motor 14 is arranged with gearbox 13 and connected to rear differential gear 12. Although not shown in the figure, motor 14 is connected to gear ring 22 or housing 23, for example.

[0040] The inverter 15 is disposed on the outer surface 42a of the cover 42 of the gearbox 13. For example... Figure 2 As shown, the inverter 15 is electrically connected to the motor 14 via wires. The buck converter 16 is disposed on the outer surface 42a of the cover 42 of the gearbox 13. Figure 2 As shown, the buck converter 16 is electrically connected to the inverter 15 via wires. A battery 17 (e.g., a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery) is electrically connected to the buck converter 16 via wires. Furthermore, in Figure 2 For ease of understanding, this is simplified, but various devices (e.g., various inverters for devices other than motor 14) may also be connected to the battery 17.

[0041] The buck converter 16 steps down the voltage of the power stored in the battery 17 and supplies it to the inverter 15. The inverter 15 converts the supplied DC power into AC power and supplies it to the motor 14. Thus, power is supplied from the battery 17 to the motor 14 via a power conversion device including the inverter 15 and the buck converter 16. The motor 14 is driven by the power supplied from the battery 17. The inverter 15 and the buck converter 16 generate heat as they supply current to the motor 14.

[0042] The vehicle cooling structure 2 includes a cooling flow path 61 formed inside the cover 42 of the gearbox 13. The cooling flow path 61 is formed between the inverter 15 and the buck converter 16 and the inner surface 42b of the cover 42 of the gearbox 13 (that is, the inner surface of the gearbox 13). In other words, the cooling flow path 61 is formed in the portion of the gearbox 13 where the inverter 15 and the buck converter 16 are located. Refrigerant flows through the cooling flow path 61. As will be detailed later, the refrigerant flowing through the cooling flow path 61 cools both the oil and the power conversion devices (that is, the inverter 15 and the buck converter 16) within the gearbox 13, which are the objects of cooling in the vehicle cooling structure 2.

[0043] A heat exchanger 62 and a cooling pump 63 are provided on vehicle 1. Furthermore, the location of the heat exchanger 62 and the cooling pump 63 is not limited to the rear of gearbox 13, but can also be in front of gearbox 13. Figure 1 As shown by the dashed arrow, the cooling path 61, heat exchanger 62, and cooling pump 63 form a cooling circuit for refrigerant circulation. The heat exchanger 62 cools the refrigerant delivered from the cooling path 61 of the gearbox 13. The cooling pump 63 delivers the refrigerant cooled in the heat exchanger 62 back to the cooling path 61 of the gearbox 13.

[0044] Figure 3 This is a schematic sectional view of the cover part 42. Figure 3 In the diagram, solid arrows indicate the vertical, horizontal, and longitudinal directions of vehicle 1. Additionally, Figure 3 The dashed arrow indicates that cooling flow path 61 is connected. For example... Figure 3 As shown, the cover 42 is installed on the main body 41 of the box by fastening components such as bolts.

[0045] Inverter 15 includes capacitor 15a and power module 15b. Power module 15b is composed of multiple semiconductor switching elements such as IGBT (Insulated Gate Bipolar Transistor). For example, in power module 15b, six semiconductor switching elements are bridged in three phases between the DC terminals connected to buck converter 16. Capacitor 15a is, for example, an electrolytic capacitor. Capacitor 15a is connected in parallel between the DC terminals of power module 15b, for example. Capacitor 15a and power module 15b generate heat when supplying current to motor 14.

[0046] The buck converter 16 includes a reactor 16a and a power module 16b. The buck converter 16 includes, for example, a chopper circuit. The reactor 16a is connected in series with the DC terminal of the battery 17 in the chopper circuit. The power module 16b is the portion of the chopper circuit that includes semiconductor switching elements such as IGBTs. The reactor 16a and the power module 16b generate heat when supplying current to the motor 14.

[0047] The inverter 15 (specifically, capacitor 15a and power module 15b) and buck converter 16 (specifically, reactor 16a and power module 16b) are fixed to the outer surface 42a of the cover 42. The inverter 15 and buck converter 16 are fixed such that their heat dissipation surfaces contact the cover 42. The electrical terminals of the inverter 15 and buck converter 16 are, for example, located on different surfaces of each side that contact the cover 42. Furthermore, the inverter 15 and buck converter 16 are surrounded and covered by a protective portion 72. The inverter 15 and buck converter 16 are sealed by the cover 42 and the protective portion 72.

[0048] A rearwardly opening inlet 61a and outlet 61b are formed on the outer surface 42a of the cover 42. A cooling flow path 61 connects from the inlet 61a to the outlet 61b. The inlet 61a is connected to the cooling pump 63 via a pipe or the like. The outlet 61b is connected to the heat exchanger 62 via a pipe or the like.

[0049] As described above, the cooling flow path 61 is formed between the inverter 15 and the buck converter 16 and the inner surface 42b of the cover 42. Specifically, the cooling flow path 61 is formed to pass between the inner surface 42b of the cover 42 and the capacitor 15a, between the inner surface 42b of the cover 42 and the power module 15b, between the inner surface 42b of the cover 42 and the power module 16b, and between the inner surface 42b of the cover 42 and the reactor 16a.

[0050] The oil inside the gearbox 13 comes into contact with the inner surface 42b of the cover 42. Therefore, the oil in the gearbox 13 passes through the inner surface 42b of the cover 42 and is cooled by heat exchange with the refrigerant in the cooling flow path 61. Additionally, the capacitor 15a and the power module 15b come into contact with the outer surface 42a of the cover 42. Therefore, the capacitor 15a and the power module 15b pass through the outer surface 42a of the cover 42 and are cooled by heat exchange with the refrigerant in the cooling flow path 61. Furthermore, the reactor 16a and the power module 16b come into contact with the outer surface 42a of the cover 42. Therefore, the reactor 16a and the power module 16b pass through the outer surface 42a of the cover 42 and are cooled by heat exchange with the refrigerant in the cooling flow path 61.

[0051] Thus, in the vehicle cooling structure 2, both the oil in the gearbox 13 and the power conversion devices (i.e., the inverter 15 and the buck converter 16) can be cooled by the common refrigerant flowing in the cooling flow path 61. Therefore, for example, the air-cooled heat sinks for the gearbox 13 can be omitted in the vehicle cooling structure 2. Consequently, the expansion of the space occupied by the cooling structure can be suppressed in the vehicle cooling structure 2.

[0052] Therefore, the vehicle cooling structure 2 according to this embodiment can simplify the cooling structure and increase the freedom of vehicle design.

[0053] Furthermore, the heat resistance temperature of the oil inside the gearbox 13 exceeds, for example, 100°C. In contrast, the heat resistance temperature of capacitor 15a, power module 15b, reactor 16a, and power module 16b is less than 100°C, for example, around 80°C. Moreover, depending on the circumstances, the temperature of the oil inside the gearbox 13 may sometimes be higher than the heat resistance temperatures of capacitor 15a, power module 15b, reactor 16a, and power module 16b.

[0054] However, in the vehicle cooling structure 2, refrigerant flows between capacitor 15a, power module 15b, reactor 16a and power module 16b and the oil in gearbox 13. Thus, in the vehicle cooling structure 2, the refrigerant prevents heat from the oil in gearbox 13 from being transferred to capacitor 15a, power module 15b, reactor 16a and power module 16b.

[0055] Therefore, in the vehicle cooling structure 2, even if the temperature of the oil inside the gearbox 13 exceeds the heat resistance temperature of the capacitor 15a, power module 15b, reactor 16a, and power module 16b, the temperatures of these components can be kept below their own heat resistance temperatures. As a result, in the vehicle cooling structure 2, even if the inverter 15 and buck converter 16 are located on the outer surface 42a of the gearbox 13, damage to the inverter 15 and buck converter 16 can be prevented.

[0056] Furthermore, the cooling flow path 61 is formed near the inverter 15 and the buck converter 16 in a vertically connected manner. Therefore, even if a small amount of air is mixed into the refrigerant, the air moves upwards. Thus, in the vehicle cooling structure 2, the retention of air in the refrigerant near the inverter 15 and the buck converter 16 can be prevented, and the cooling effect of the inverter 15 and the buck converter 16 can be prevented from decreasing.

[0057] like Figure 3 As shown, a plurality of heat sinks 81 are formed on the gearbox 13, protruding from the inner surface of the cooling flow path 61 into the cooling flow path 61. The heat sinks 81 are formed in the inner surface of the cooling flow path 61 in the region opposite to the region where the inverter 15 and the buck converter 16 contact the gearbox 13. That is, the heat sinks 81 are disposed in the cooling flow path 61 at a position corresponding to the placement position of the inverter 15 and the buck converter 16 (specifically, at a position facing the inverter 15 and the buck converter 16).

[0058] Specifically, heat sink 81 is formed in the inner surface of cooling flow path 61 on the opposite side of the region where capacitor 15a contacts gearbox 13. Additionally, heat sink 81 is formed in the inner surface of cooling flow path 61 on the opposite side of the region where power module 15b contacts gearbox 13. Furthermore, heat sink 81 is formed in the inner surface of cooling flow path 61 on the opposite side of the region where reactor 16a contacts gearbox 13. Additionally, heat sink 81 is formed in the inner surface of cooling flow path 61 on the opposite side of the region where power module 16b contacts gearbox 13. For example, heat sink 81 is formed as a prism extending from the inner surface of cooling flow path 61. Furthermore, the shape of heat sink 81 is not limited to a prism shape and can be appropriately designed, such as a pyramid shape.

[0059] In the vehicle cooling structure 2, since heat sinks 81 are formed near the inverter 15 and the buck converter 16, the area for heat exchange between the refrigerant flowing in the cooling flow path 61 and the inverter 15 and the buck converter 16 is increased. Therefore, the cooling effect of the inverter 15 and the buck converter 16 can be improved in the vehicle cooling structure 2.

[0060] Furthermore, vehicle 1 is capable of mechanical four-wheel drive using drive shaft 11. In such a mechanical four-wheel drive vehicle, the rear differential gear 12 sometimes vibrates due to the phase difference in power transmission between the front and rear wheels. Therefore, in a mechanical four-wheel drive vehicle, an inertial mass, i.e., a balancer, is provided at the rear side of the gearbox 13 of the rear differential gear 12.

[0061] In vehicle 1, as described above, the inverter 15 and the buck converter 16 are located at the rear of vehicle 1 within the gearbox 13. The inverter 15 and the buck converter 16 have a considerable mass. Therefore, the inverter 15 and the buck converter 16 can function as at least part of the aforementioned inertial mass. Thus, in vehicle 1, the mass of the inverter 15 and the buck converter 16 can be reduced by the added inertial mass. As a result, in vehicle 1 using the vehicle cooling structure 2, the increase in the overall weight of vehicle 1 can be suppressed.

[0062] Figure 4 This is a perspective top view of the cover 42 viewed from the rear. Figure 4 In the diagram, solid arrows indicate the up, down, left, and right directions of vehicle 1. Additionally, Figure 4 The hollow arrow indicates the direction of refrigerant flow.

[0063] The capacitor 15a and power module 15b of inverter 15 and the reactor 16a and power module 16b of buck converter 16 are disposed near the center of the outer surface 42a of cover 42. The feed inlet 61a is located above the capacitor 15a, power module 15b, reactor 16a, and power module 16b. The output outlet 61b is located below the capacitor 15a, power module 15b, reactor 16a, and power module 16b.

[0064] like Figure 4 As shown, the cooling flow path 61 is formed in a spiral shape, expanding from the inner portion near the center of the outer surface 42a towards the outer portion away from the center. The inlet 61a is located at the inner end of the spiral of the cooling flow path 61. The outlet 61b is located at the outer end of the spiral of the cooling flow path 61. The capacitor 15a, power module 15b, reactor 16a, and power module 16b are located near the inlet 61a in the path of the cooling flow path 61.

[0065] Capacitor 15a is positioned above power module 15b. That is, capacitor 15a is positioned upstream of power module 15b in the cooling flow path 61. Reactor 16a is positioned below power module 16b. That is, reactor 16a is positioned downstream of power module 16b in the cooling flow path 61. Power modules 15b of inverter 15 and buck converter 16 are arranged in a left-right direction. That is, the vertical position of power module 15b is approximately the same as the vertical position of power module 16b.

[0066] The refrigerant supplied through inlet 61a passes sequentially near capacitor 15a, power modules 15b and 16b, and reactor 16a. Capacitor 15a, power modules 15b, reactor 16a, and power modules 16b are cooled by refrigerant with sufficient cooling capacity, in other words, by refrigerant at a sufficiently low temperature. Therefore, in the vehicle cooling structure 2, inverter 15 and buck converter 16 can be effectively cooled.

[0067] Therefore, in inverter 15, the heat resistance of capacitor 15a is lower than that of power module 15b. Therefore, by configuring capacitor 15a upstream of power module 15b in the cooling flow path 61, capacitor 15a can be cooled preferentially relative to power module 15b. Furthermore, in buck converter 16, the heat resistance of power module 16b is lower than that of reactor 16a. Therefore, by configuring reactor 16a downstream of power module 16b in the cooling flow path 61, power module 16b can be cooled preferentially relative to reactor 16a.

[0068] The refrigerant that has passed near the reactor 16a travels around the periphery of the cover 42 and reaches the outlet 61b. Thus, the refrigerant cools a wide area of ​​both the inner surface 42b and the outer surface 42a of the cover 42. Therefore, the oil in contact with the inner surface 42b of the cover 42 can be effectively cooled. Furthermore, as described above, the temperatures of the capacitor 15a, power module 15b, reactor 16a, and power module 16b are lower than that of the oil. Therefore, the refrigerant, after heat exchange with the capacitor 15a, power module 15b, reactor 16a, and power module 16b, can adequately cool the oil.

[0069] In the above, refer to Figure 4 This illustrates an example of the positional relationship between the components of capacitor 15a, power module 15b, reactor 16a, and power module 16b, but the positional relationship between the components is not limited to this example. Figure 4 For example, the vertical positional relationship between the components can be compared to... Figure 4 The examples are different.

[0070] Figure 5This is a diagram illustrating an example of the output characteristics of motor 14. (See diagram for example.) Figure 5 As shown, for motor 14, the torque increases as the speed decreases, and the torque decreases as the speed increases.

[0071] The current supplied from inverter 15 to motor 14 increases as the torque of motor 14 increases. Therefore, as... Figure 5 As illustrated by the dashed line A1, the heat generated by the inverter 15 and the buck converter 16 increases as the torque of the motor 14 increases.

[0072] In contrast, the rotational speed of each gear in the rear differential gear 12 increases as the rotational speed of the motor 14 increases. If the rotational speed of each gear increases, the heat generated by friction between the gears increases. That is to say, if... Figure 5 As illustrated by the dashed line A2, the heat generated by the rear differential gear 12 increases as the speed of the motor 14 increases.

[0073] Thus, the inverter 15 supplies current to the motor 14 such that the timing of the heat generation of the inverter 15 and the buck converter 16 increases at a different time than the timing of the heat generation of the rear differential gear 12.

[0074] Therefore, in the vehicle cooling structure 2, the cooling of the inverter 15 and the buck converter 16 can be reduced when a significant amount of cooling of the oil in the gearbox 13 is required, and the cooling of the oil in the gearbox 13 can be reduced when a significant amount of cooling of the inverter 15 and the buck converter 16 is required. Thus, in the vehicle cooling structure 2, the oil in the gearbox 13 and the power conversion devices (i.e., the inverter 15 and the buck converter 16) can be cooled while preventing an increase in the size of the heat exchanger 62 or the cooling pump 63.

[0075] Here, in the vehicle cooling structure 2, an inverter 15 is provided as a power conversion device, and a step-down converter 16 is also provided, thereby achieving the following various effects.

[0076] For example, the voltage of the inverter 15 can be reduced by the buck converter 16, thus reducing the switching losses in the inverter 15. As a result, the size of the inverter 15 can be prevented from increasing.

[0077] Furthermore, for example, the voltage of the battery 17 can be reduced by the step-down converter 16 to supply power to the motor 14, so when the voltage of the battery 17 needs to be changed during the design of the vehicle 1, it can be flexibly addressed without reselecting individual components. In other words, the system has high flexibility.

[0078] Furthermore, for example, the voltage of the motor 14 can be adjusted by the buck converter 16, so even if the induced voltage generated in the motor 14 increases as the speed of the motor 14 increases, the induced voltage can be prevented from exceeding the voltage of the battery 17. Therefore, it is not necessary to pre-set the voltage of the inverter 15 too high so that the induced voltage will not exceed the voltage of the battery 17 regardless of the speed of the motor 14. Thus, the increase in switching losses in the inverter 15 due to the increase in voltage can be suppressed, and the size of the inverter 15 can be prevented from increasing.

[0079] Furthermore, by providing a buck converter 16, for example, the switching losses in the inverter 15 can be reduced without lowering the carrier frequency, as described above. Therefore, the deterioration of the control responsiveness of the motor 14 caused by the decrease in carrier frequency can be suppressed, and the deterioration of torque responsiveness can be suppressed.

[0080] As explained above, the vehicle cooling structure 2 according to this embodiment can simplify the structure while enjoying the various effects mentioned above due to the installation of the step-down converter 16.

[0081] The embodiments of the present invention have been described above with reference to the accompanying drawings; however, it is self-evident that the present invention is not limited to these embodiments. Obviously, those skilled in the art will be able to conceive of various modifications or alterations within the scope of the claims, and understand that these modifications or alterations also fall within the technical scope of the present invention.

[0082] For example, the inverter 15 and the buck converter 16 in the above embodiment can be provided on the outer surface 42a of the cover 42. However, the inverter 15 and the buck converter 16 are not limited to being provided on the cover 42, but can also be provided on the outer surface of the main body 41.

[0083] Furthermore, in the above embodiment, the inverter 15 and the buck converter 16 are disposed at the rear of the gearbox 13. However, the position of the inverter 15 and the buck converter 16 is not limited to the rear of the gearbox 13, and they can be disposed at any position within the gearbox 13. Specifically, the inverter 15 and the buck converter 16 are disposed at the rear of the gearbox 13 so that they function as part of the inertial mass.

[0084] Furthermore, in the vehicle cooling structure 2 of the above embodiment, a heat sink 81 is provided in the cooling flow path 61. However, the heat sink 81 can be omitted. However, providing the heat sink 81 can improve the cooling effect of the inverter 15 and the buck converter 16.

[0085] Furthermore, in the above embodiment, an inverter 15, a buck converter 16, and a cooling flow path 61 are provided in the gearbox 13 housing the rear differential gear 12. However, the gearbox 13 equipped with the inverter 15, buck converter 16, and cooling flow path 61 is not limited to the gearbox housing the rear differential gear 12. The gearbox 13 can be, for example, a gearbox housing various gear mechanisms such as a front differential gear, a transmission, or a reducer. In addition, the gearbox 13 housing these gear mechanisms also contains oil for lubricating the operation of the gear mechanisms. In this type of vehicle cooling structure 2, similarly to the above embodiment, the oil and power conversion devices (i.e., the inverter 15 and the buck converter 16) in the gearbox 13 can be cooled by a common refrigerant.

Claims

1. A vehicle cooling structure comprising: A gearbox contains a gear mechanism and oil. An inverter is disposed on the outer surface of the gearbox and is electrically connected to the motor; A step-down converter is disposed on the outer surface of the gearbox and electrically connected to the inverter; and A cooling flow path is formed between the inner surfaces of the inverter, the buck converter, and the gearbox, and provides a channel for refrigerant flow. The common refrigerant flowing in the cooling path cools both the oil, the inverter, and the buck converter, which are in contact with the inner surface of the gearbox.

2. The vehicle cooling structure according to claim 1, wherein, The gear mechanism is the rear differential gear connected to the drive shaft. The inverter and the buck converter are located on the rear side of the vehicle within the gearbox.

3. The vehicle cooling structure according to claim 1, wherein, The region on the opposite side of the area where the inverter and the buck converter contact the gearbox on the inner surface of the cooling flow path also has heat sinks protruding from the inner surface of the cooling flow path into the cooling flow path.

4. The vehicle cooling structure according to claim 2, wherein, The region on the opposite side of the area where the inverter and the buck converter contact the gearbox on the inner surface of the cooling flow path also has heat sinks protruding from the inner surface of the cooling flow path into the cooling flow path.

5. The vehicle cooling structure according to any one of claims 1 to 4, wherein, The inverter includes capacitors and a power supply module. The capacitor is configured to be positioned upstream of the power module of the inverter in the cooling path.

6. The vehicle cooling structure according to any one of claims 1 to 4, wherein, The step-down converter includes a reactor and a power supply module. The reactor is configured to be located downstream of the cooling path than the power module of the buck converter.

7. The vehicle cooling structure according to claim 5, wherein, The step-down converter includes a reactor and a power supply module. The reactor is configured to be located downstream of the cooling path than the power module of the buck converter.

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