Vehicle cooling structure

Abstract

To simplify a vehicular cooling structure.SOLUTION: A vehicular cooling structure 2 includes: a gear case 13 which houses a gear mechanism (for example, a rear differential gear 12) and an oil therein; an inverter 15 which is installed on an outer surface (for example, an outer surface 42a) of the gear case 13 and electrically connected to a motor 14; a step-down converter 16 which is installed on the outer surface (for example, the outer surface 42a) of the gear case 13 and electrically connected with the inverter 15; and a cooling passage 61 which is formed between an inner surface (for example, an inner surface 42b) of the gear case 13 and the inverter 15 and the step-down converter 16 and in which a refrigerant circulates.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cooling structure for a vehicle. [Background technology]

[0002] In a vehicle, a power conversion device such as an inverter is used to supply power to a motor. In order to maintain the performance of the power conversion device, it is necessary to cool the power conversion device. For example, Patent Document 1 discloses a technology for cooling an inverter by circulating a refrigerant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-105645 A Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, a vehicle is provided with a gear mechanism such as a rear differential gear. The gear mechanism is air-cooled, for example, by fins provided on a gear case that houses the gear mechanism. In conventional vehicles, a cooling structure for a power conversion device such as an inverter and a cooling structure for the gear mechanism are provided separately (i.e., for each object to be cooled). For this reason, the space occupied by the cooling structure becomes large, and as a result, it is difficult to improve the degree of freedom in vehicle design.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a simplified cooling structure for a vehicle. [Means for solving the problem]

[0006] In order to solve the above problems, a vehicle cooling structure according to one embodiment of the present invention includes a gear case that accommodates a gear mechanism and oil therein, an inverter that is installed on an outer surface of the gear case and electrically connected to a motor, a step-down converter that is installed on the outer surface of the gear case and electrically connected to the inverter, and a cooling flow path that is formed between an inner surface of the gear case and the inverter and the step-down converter and through which a refrigerant flows. The oil in the gear case and both the inverter and the step-down converter are cooled by a common refrigerant that flows through a cooling passage. . Effect of the Invention

[0007] According to the present invention, it is possible to simplify the vehicle cooling structure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a part of a vehicle according to this embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a power supply system for a vehicle according to this embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the cover portion according to the present embodiment. [Figure 4] FIG. 4 is a perspective plan view of the cover according to this embodiment as viewed from the rear. [Diagram 5] FIG. 5 is a diagram showing an example of the output characteristics of the motor according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0010] Fig. 1 is a schematic diagram showing a part of a vehicle 1 according to this embodiment. A vehicle cooling structure 2 is applied to the vehicle 1. In Fig. 1, the front, rear, left and right directions of the vehicle 1 are indicated by solid arrows. Fig. 2 is a schematic diagram showing a power supply system of the vehicle 1 according to this embodiment.

[0011] The vehicle 1 is, for example, an engine vehicle provided with an engine as a drive source for running. Note that the vehicle 1 may be an electric vehicle provided with a motor as a drive source for running, or may be a hybrid vehicle provided with an engine and a motor as drive sources.

[0012] As shown in Fig. 1, the vehicle 1 includes a propeller shaft 11, a rear differential gear 12, a gear case 13, a motor 14, an inverter 15, and a step-down converter 16. One end of the propeller shaft 11 is connected to a drive source for traveling (e.g., an engine) through a transmission. The rear differential gear 12 corresponds to an example of a gear mechanism according to the present invention. Furthermore, as shown in Fig. 2, the power supply system of the vehicle 1 includes a battery 17 in addition to the motor 14, the inverter 15, and the step-down converter 16.

[0013] The rear differential gear 12 includes an input shaft 21, a ring gear 22, a frame 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 gear 30, and a second pinion gear 31.

[0014] The input shaft 21 is specifically a drive pinion shaft. The other end of the propeller 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 tip of the input shaft 21. The bevel gear 21a is meshed with a ring gear 22. The frame body 23 protrudes from one side surface of the ring gear 22. The frame body 23 is formed hollow. The frame body 23 rotates integrally with the ring gear 22.

[0015] The first side gear 24, the second side gear 25, the first pinion gear 30 and the second pinion gear 31 are housed in the frame 23. The first side gear 24 and the second side gear 25 are arranged parallel to the ring gear 22 and opposed to each other with a gap therebetween. The first side gear 24 is connected to a first output shaft 26. The first output shaft 26 passes through the ring gear 22 and extends leftward, and is connected to the left rear wheel. The second side gear 25 is connected to a second output shaft 27. The second output shaft 27 passes through the frame 23 and extends rightward, and is connected to the right rear wheel.

[0016] The first pinion shaft 28 and the second pinion shaft 29 each protrude from the inner surface of the frame body 23. The first pinion gear 30 is rotatably supported by the frame body 23 via the first pinion shaft 28. The second pinion gear 31 is rotatably supported by the frame body 23 via the second pinion shaft 29. The first pinion gear 30 and the second pinion gear 31 are meshed with the first side gear 24 and the second side gear 25, respectively.

[0017] The gear case 13 is composed of a case main body 41 and a cover portion 42. A space 41a is formed inside the case main body 41. An opening 41b is provided on the rear side of the case main body 41. The cover portion 42 closes the opening 41b of the case main body 41 from the rear side. When the cover portion 42 is attached to the case main body 41, the gear case 13 is sealed. The gear case 13 is sealed with the rear differential gear 12 and oil contained therein. The oil lubricates each part of the rear differential gear 12.

[0018] In the rear differential gear 12, frictional heat is generated between the gears in response to the rotation of each gear. For example, a relatively large amount of frictional heat is generated between the bevel gear 21a of the input shaft 21 and the ring gear 22. The oil in the gear case 13 is heated by such frictional heat.

[0019] The motor 14 outputs power to assist the rotation of the rear wheels. The motor 14 is, for example, a three-phase AC motor. The motor 14 is arranged in parallel with the gear case 13 and connected to the rear differential gear 12. Although not shown, the motor 14 is connected to, for example, a ring gear 22 or a frame body 23.

[0020] The inverter 15 is disposed on an outer surface 42a of the cover portion 42 of the gear case 13. As shown in FIG. 2, the inverter 15 is electrically connected to the motor 14 through a power line. The step-down converter 16 is disposed on an outer surface 42a of the cover portion 42 of the gear case 13. As shown in FIG. 2, the step-down converter 16 is electrically connected to the inverter 15 through a power line. 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 step-down converter 16 through the power line. Note that, although FIG. 2 is simplified for ease of understanding, various devices (e.g., various inverters for devices other than the motor 14) not shown may be further connected to the battery 17.

[0021] The step-down converter 16 steps down (i.e., lowers the voltage) 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. In this way, the motor 14 is supplied with power from the battery 17 via a power conversion device including the inverter 15 and the step-down converter 16. The motor 14 is driven by the power supplied from the battery 17. The inverter 15 and the step-down converter 16 generate heat in response to the supply of current to the motor 14.

[0022] The vehicle cooling structure 2 includes a cooling passage 61 formed inside the cover portion 42 of the gear case 13. The cooling passage 61 is formed between the inner surface 42b of the cover portion 42 of the gear case 13 (i.e., the inner surface of the gear case 13) and the inverter 15 and the step-down converter 16. That is, the cooling passage 61 is formed in a portion of the gear case 13 where the inverter 15 and the step-down converter 16 are installed. A refrigerant flows through the cooling passage 61. As will be described in detail later, the refrigerant flowing through the cooling passage 61 cools both the oil in the gear case 13, which is the object to be cooled by the vehicle cooling structure 2, and the power conversion device (i.e., the inverter 15 and the step-down converter 16).

[0023] The vehicle 1 is provided with a heat exchanger 62 and a cooling pump 63. The positions of the heat exchanger 62 and the cooling pump 63 are not limited to the rear of the gear case 13, and may be in front of the gear case 13. As shown by the dashed arrows in Fig. 1, the cooling passage 61, the heat exchanger 62, and the cooling pump 63 form a cooling circuit in which the refrigerant circulates. The heat exchanger 62 cools the refrigerant discharged from the cooling passage 61 of the gear case 13. The cooling pump 63 discharges the refrigerant cooled by the heat exchanger 62 to the cooling passage 61 of the gear case 13.

[0024] Fig. 3 is a schematic cross-sectional view of the cover portion 42. In Fig. 3, the top, bottom, front and rear directions of the vehicle 1 are indicated by solid arrows. Also, the dashed arrows in Fig. 3 indicate that the cooling channels 61 are connected. As shown in Fig. 3, the cover portion 42 is attached to the case main body portion 41 by fastening members 71 such as bolts.

[0025] The inverter 15 includes a capacitor 15a and a power module 15b. The power module 15b is composed of a plurality of semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors). For example, in the power module 15b, six semiconductor switching elements are connected in a three-phase bridge between DC terminals connected to the step-down converter 16. The capacitor 15a is, for example, an electrolytic capacitor. The capacitor 15a is, for example, connected in parallel between DC terminals of the power module 15b. The capacitor 15a and the power module 15b generate heat when supplying a current to the motor 14.

[0026] The step-down converter 16 includes a reactor 16a and a power module 16b. The step-down converter 16 includes, for example, a chopper circuit. The reactor 16a is connected in series with a DC terminal of the chopper circuit that is connected to the battery 17. The power module 16b is a part of the chopper circuit that includes a semiconductor switching element such as an IGBT. The reactor 16a and the power module 16b generate heat when supplying a current to the motor 14.

[0027] The inverter 15 (specifically, the capacitor 15a and the power module 15b) and the step-down converter 16 (specifically, the reactor 16a and the power module 16b) are fixed to the outer surface 42a of the cover portion 42. The inverter 15 and the step-down converter 16 are fixed so that their heat dissipation surfaces are in contact with the cover portion 42. The electrical terminals of the inverter 15 and the step-down converter 16 are arranged on a surface other than the surface in contact with the cover portion 42, such as each side surface. The inverter 15 and the step-down converter 16 are also surrounded and covered by the protective portion 72. The inverter 15 and the step-down converter 16 are sealed by the cover portion 42 and the protective portion 72.

[0028] An inlet 61a and an outlet 61b that open to the rear are formed on the outer surface 42a of the cover portion 42. The cooling flow passage 61 communicates from the inlet 61a to the outlet 61b. The inlet 61a is connected to a cooling pump 63 via a pipe or the like. The outlet 61b is connected to a heat exchanger 62 via a pipe or the like.

[0029] As described above, the cooling flow passage 61 is formed between the inner surface 42b of the cover part 42 and the inverter 15 and the step-down converter 16. Specifically, the cooling flow passage 61 is formed so as to pass between the inner surface 42b of the cover part 42 and the capacitor 15a, between the inner surface 42b of the cover part 42 and the power module 15b, between the inner surface 42b of the cover part 42 and the power module 16b, and between the inner surface 42b of the cover part 42 and the reactor 16a.

[0030] The oil in the gear case 13 comes into contact with the inner surface 42b of the cover portion 42. Therefore, the oil in the gear case 13 is cooled by heat exchange with the refrigerant in the cooling flow passage 61 through the inner surface 42b of the cover portion 42. In addition, the condenser 15a and the power module 15b come into contact with the outer surface 42a of the cover portion 42. Therefore, the condenser 15a and the power module 15b are cooled by heat exchange with the refrigerant in the cooling flow passage 61 through the outer surface 42a of the cover portion 42. In addition, the reactor 16a and the power module 16b come into contact with the outer surface 42a of the cover portion 42. Therefore, the reactor 16a and the power module 16b are cooled by heat exchange with the refrigerant in the cooling flow passage 61 through the outer surface 42a of the cover portion 42.

[0031] In this way, in the vehicle cooling structure 2, both the oil in the gear case 13 and the power conversion device (i.e., the inverter 15 and the step-down converter 16) can be cooled by a common refrigerant flowing through the cooling flow path 61. This makes it possible, for example, to omit fins for air-cooling the gear case 13 in the vehicle cooling structure 2. As a result, in the vehicle cooling structure 2, it is possible to suppress an increase in the space occupied by the cooling structure.

[0032] Therefore, according to the vehicle cooling structure 2 of the present embodiment, the cooling structure can be simplified, and the degree of freedom in vehicle design can be improved.

[0033] The heat-resistant temperature of the oil in the gear case 13 exceeds, for example, 100° C. In contrast, the heat-resistant temperatures of the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b are less than 100° C., for example, about 80° C. In some cases, the temperature of the oil in the gear case 13 may become higher than the heat-resistant temperatures of the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b.

[0034] However, in the vehicle cooling structure 2, the refrigerant flows between the condenser 15a, the power module 15b, the reactor 16a, and the power module 16b, and the oil in the gear case 13. As a result, in the vehicle cooling structure 2, the refrigerant prevents the heat of the oil in the gear case 13 from being transferred to the condenser 15a, the power module 15b, the reactor 16a, and the power module 16b.

[0035] Therefore, in the vehicle cooling structure 2, even if the temperature of the oil in the gear case 13 becomes equal to or higher than the heat resistance temperatures of the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b, it is possible to make the temperatures of the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b lower than their own heat resistance temperatures. As a result, in the vehicle cooling structure 2, even if the inverter 15 and the step-down converter 16 are installed on the outer surface 42a of the gear case 13, damage to the inverter 15 and the step-down converter 16 can be prevented.

[0036] Moreover, the cooling flow passages 61 are formed to communicate in the vertical direction near the inverter 15 and the step-down converter 16. As a result, even if a small amount of air is mixed into the refrigerant, the air is moved upward. Therefore, in the vehicle cooling structure 2, it is possible to prevent the air in the refrigerant from accumulating near the inverter 15 and the step-down converter 16, and it is possible to prevent a decrease in the cooling effect of the inverter 15 and the step-down converter 16.

[0037] 3, the gear case 13 is formed with a plurality of fins 81 protruding from the inner surface of the cooling flow passage 61 into the cooling flow passage 61. The fins 81 are formed in an area of ​​the inner surface of the cooling flow passage 61 opposite to an area where the inverter 15 and the step-down converter 16 contact the gear case 13. In other words, the fins 81 are provided in positions of the cooling flow passage 61 corresponding to the installation positions of the inverter 15 and the step-down converter 16 (specifically, positions facing the inverter 15 and the step-down converter 16).

[0038] Specifically, the fins 81 are formed in a region of the inner surface of the cooling flow passage 61 opposite to a region where the condenser 15a contacts the gear case 13. The fins 81 are formed in a region of the inner surface of the cooling flow passage 61 opposite to a region where the power module 15b contacts the gear case 13. The fins 81 are formed in a region of the inner surface of the cooling flow passage 61 opposite to a region where the reactor 16a contacts the gear case 13. The fins 81 are formed in a region of the inner surface of the cooling flow passage 61 opposite to a region where the power module 16b contacts the gear case 13. The fins 81 are formed, for example, in a prismatic shape extending from the inner surface of the cooling flow passage 61. The shape of the fins 81 is not limited to a prismatic shape, and may be appropriately designed, such as a pyramidal shape.

[0039] In the vehicle cooling structure 2, the fins 81 are formed in positions close to the inverter 15 and the step-down converter 16, so that the area for heat exchange between the refrigerant flowing through the cooling passage 61 and the inverter 15 and the step-down converter 16 is increased. Therefore, in the vehicle cooling structure 2, the cooling effect of the inverter 15 and the step-down converter 16 can be improved.

[0040] The vehicle 1 can also be mechanically four-wheel-driven using a propeller shaft 11. In such a mechanical four-wheel-drive vehicle, the rear differential gear 12 may vibrate due to a phase difference in the power transmission between the front and rear wheels. Therefore, in a mechanical four-wheel-drive vehicle, an inertial mass, i.e., ballast, is provided at a rear position in the gear case 13 of the rear differential gear 12.

[0041] In the vehicle 1, as described above, the inverter 15 and the step-down converter 16 are located on the rear side of the vehicle 1 in the gear case 13. The inverter 15 and the step-down converter 16 have a certain amount of mass. This allows the inverter 15 and the step-down converter 16 to function as at least a part of the inertial mass described above. Therefore, in the vehicle 1, the mass of the inertial mass to be added can be reduced by the mass of the inverter 15 and the step-down converter 16. As a result, in the vehicle 1 to which the vehicle cooling structure 2 is applied, an increase in the total weight of the vehicle 1 can be suppressed.

[0042] Fig. 4 is a perspective plan view of the cover portion 42 as seen from the rear. In Fig. 4, solid arrows indicate the up, down, left and right directions of the vehicle 1. Also, the white arrows in Fig. 4 exemplify the direction in which the refrigerant flows.

[0043] The capacitor 15a and the power module 15b of the inverter 15 and the reactor 16a and the power module 16b of the step-down converter 16 are disposed near the center of the outer surface 42a of the cover part 42. The inlet 61a is located above the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b. The outlet 61b is located below the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b.

[0044] 4, cooling flow passage 61 is formed so as to expand in a spiral shape from an inner portion close to the center of outer surface 42a to an outer portion far from the center. Inlet 61a is located at the inner end of the spiral of cooling flow passage 61. Outlet 61b is located at the outer end of the spiral of cooling flow passage 61. Condenser 15a, power module 15b, reactor 16a, and power module 16b are located in the path of cooling flow passage 61 near inlet 61a.

[0045] The capacitor 15a is disposed above the power module 15b. That is, the capacitor 15a is disposed upstream of the power module 15b in the cooling flow path 61. The reactor 16a is disposed below the power module 16b. That is, the reactor 16a is disposed downstream of the power module 16b in the cooling flow path 61. The power module 15b of the inverter 15 and the power module 16b of the step-down converter 16 are aligned in the left-right direction. That is, the vertical position of the power module 15b and the vertical position of the power module 16b are approximately the same.

[0046] The refrigerant sent from the inlet 61a passes through the vicinity of the condenser 15a, the vicinity of the power module 15b and the power module 16b, and the vicinity of the reactor 16a, in that order. The condenser 15a, the power module 15b, the reactor 16a, and the power module 16b are cooled by the refrigerant with a sufficiently high cooling capacity, in other words, a refrigerant with a sufficiently low temperature. Therefore, in the vehicle cooling structure 2, the inverter 15 and the step-down converter 16 can be effectively cooled.

[0047] Here, in the inverter 15, the heat resistance of the capacitor 15a is lower than that of the power module 15b. Therefore, by arranging the capacitor 15a upstream of the power module 15b in the cooling flow path 61, the capacitor 15a can be cooled preferentially over the power module 15b. Also, in the step-down converter 16, the heat resistance of the power module 16b is lower than that of the reactor 16a. Therefore, by arranging the reactor 16a downstream of the power module 16b in the cooling flow path 61, the power module 16b can be cooled preferentially over the reactor 16a.

[0048] The refrigerant that has passed near the reactor 16a circulates around the periphery of the cover portion 42 and reaches the outlet 61b. As a result, the refrigerant cools a wide range of the inner surface 42b and the outer surface 42a of the cover portion 42. Therefore, the oil in contact with the inner surface 42b of the cover portion 42 can be effectively cooled. Also, as described above, the condenser 15a, the power module 15b, the reactor 16a, and the power module 16b may have a lower temperature than the oil. Therefore, the refrigerant that has exchanged heat with the condenser 15a, the power module 15b, the reactor 16a, and the power module 16b can sufficiently cool the oil.

[0049] Although an example of the positional relationship between the components of the capacitor 15a, the power module 15b, the reactor 16a, and the power module 16b has been described above with reference to Fig. 4, the positional relationship between the components is not limited to the example of Fig. 4. For example, the vertical positional relationship between the components may be different from that of the example of Fig. 4.

[0050] Fig. 5 is a diagram showing an example of the output characteristics of the motor 14. As shown in Fig. 5, the torque of the motor 14 increases as the rotation speed decreases, and decreases as the rotation speed increases.

[0051] The current supplied from inverter 15 to motor 14 increases as the torque of motor 14 increases. Therefore, as shown by dashed line A1 in Fig. 4, the amount of heat generated by inverter 15 and step-down converter 16 increases as the torque of motor 14 increases.

[0052] In contrast, the rotation speed of each gear of the rear differential gear 12 increases as the rotation speed of the motor 14 increases. When the rotation speed of each gear increases, the amount of heat generated by friction between the gears increases. In other words, as shown by the dashed line A2 in Figure 4, the amount of heat generated by the rear differential gear 12 increases as the rotation speed of the motor 14 increases.

[0053] In this way, inverter 15 supplies current to motor 14 so that the timing at which the amount of heat generated by inverter 15 and step-down converter 16 increases differs from the timing at which the amount of heat generated by rear differential gear 12 increases.

[0054] As a result, in the vehicle cooling structure 2, when the oil in the gear case 13 needs to be cooled significantly, the inverter 15 and the step-down converter 16 need not be cooled as much, and when the inverter 15 and the step-down converter 16 need to be cooled significantly, the oil in the gear case 13 need not be cooled as much. Therefore, in the vehicle cooling structure 2, it is possible to cool the oil in the gear case 13 and the power conversion device (i.e., the inverter 15 and the step-down converter 16) while suppressing an increase in the size of the heat exchanger 62 or the cooling pump 63.

[0055] Here, in the vehicle cooling structure 2, the step-down converter 16 is provided in addition to the inverter 15 as a power conversion device, and the following various effects are achieved.

[0056] For example, since the voltage of the inverter 15 can be stepped down by the step-down converter 16, it is possible to reduce switching loss in the inverter 15. As a result, an increase in the size of the inverter 15 can be suppressed.

[0057] In addition, for example, the voltage of battery 17 can be lowered by step-down converter 16 to supply power to motor 14, so that when the voltage of battery 17 is changed during the design of vehicle 1, it is possible to flexibly respond without reselecting each component. In other words, the flexibility to respond to system changes is increased.

[0058] Furthermore, since the voltage of motor 14 can be adjusted by step-down converter 16, for example, even if the induced voltage generated in motor 14 increases with an increase in the rotation speed of motor 14, the induced voltage can be prevented from exceeding the voltage of battery 17. This eliminates the need to set the voltage of inverter 15 excessively high in advance so that the induced voltage does not exceed the voltage of battery 17 regardless of the rotation speed of motor 14. Therefore, it is possible to suppress an increase in switching loss associated with an increase in the voltage in inverter 15, and to suppress an increase in the size of inverter 15.

[0059] Furthermore, for example, by providing the step-down converter 16, as described above, it is possible to reduce the switching loss in the inverter 15 without lowering the carrier frequency. Therefore, it is possible to suppress deterioration in the control response of the motor 14 that is caused by a decrease in the carrier frequency, and it is possible to suppress deterioration in the torque response.

[0060] As described above, according to the vehicle cooling structure 2 of the present embodiment, the cooling structure can be simplified while obtaining the various effects described above that are attributable to the provision of the step-down converter 16.

[0061] Although the embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that such examples also naturally belong to the technical scope of the present invention.

[0062] For example, in the above embodiment, the inverter 15 and the step-down converter 16 are disposed on the outer surface 42a of the cover portion 42. However, the inverter 15 and the step-down converter 16 may be disposed on the outer surface of the case main body portion 41, not limited to the cover portion 42.

[0063] Also, in the above embodiment, the inverter 15 and the step-down converter 16 are disposed on the rear side of the gear case 13. However, the positions of the inverter 15 and the step-down converter 16 are not limited to the rear side of the gear case 13, and the inverter 15 and the step-down converter 16 may be disposed at any position in the gear case 13. However, when the inverter 15 and the step-down converter 16 are made to function as part of the inertial mass, the inverter 15 and the step-down converter 16 are disposed on the rear side of the gear case 13.

[0064] In the vehicle cooling structure 2 of the above embodiment, the fins 81 are provided in the cooling passage 61. However, the fins 81 may be omitted. However, the cooling effect of the inverter 15 and the step-down converter 16 can be improved by providing the fins 81.

[0065] In the above embodiment, the inverter 15, the step-down converter 16, and the cooling passage 61 are provided in the gear case 13 that houses the rear differential gear 12. However, the gear case 13 in which the inverter 15, the step-down converter 16, and the cooling passage 61 are provided is not limited to the one that houses the rear differential gear 12. The gear case 13 may house various gear mechanisms such as a front differential gear, a transmission, or a reduction gear. In addition, the gear case 13 that houses these gear mechanisms also houses oil that lubricates the operation of the gear mechanisms. In the vehicle cooling structure 2 of this aspect, as in the above embodiment, the oil in the gear case 13 and the power conversion device (i.e., the inverter 15 and the step-down converter 16) can be cooled by a common refrigerant. [Explanation of symbols]

[0066] 1 vehicle 2. Vehicle cooling structure 11 Propeller shaft 12 Rear differential gear (gear mechanism) 13 Gear case 14 Motor 15 Inverter 15a capacitor 15b Power Module 16 Buck Converter 16a reactor 16b Power Module 17 Battery 61 Cooling Channel 81 Finn

Claims

1. a gear case that accommodates a gear mechanism and oil therein; An inverter that is installed on an outer surface of the gear case and electrically connected to a motor; a step-down converter that is installed on an outer surface of the gear case and is electrically connected to the inverter; a cooling passage formed between an inner surface of the gear case and the inverter and the step-down converter, through which a refrigerant flows; Equipped with The oil in the gear case, and both the inverter and the step-down converter are cooled by the common refrigerant flowing through the cooling flow path. Cooling structure for vehicles.

2. the gear mechanism is a rear differential gear connected to a propeller shaft, The inverter and the step-down converter are located on the rear side of the gear case toward the vehicle. The vehicle cooling structure according to claim 1 .

3. The cooling passage further includes a fin protruding from the inner surface of the cooling passage into the cooling passage in a region of the inner surface of the cooling passage opposite to a region where the inverter and the step-down converter contact the gear case. The vehicle cooling structure according to claim 1 or 2.

4. The inverter includes a capacitor and a power module. The capacitor is disposed upstream of the cooling flow path relative to a power module of the inverter. The vehicle cooling structure according to any one of claims 1 to 3.

5. The step-down converter includes a reactor and a power module, The reactor is disposed downstream of the cooling flow path with respect to a power module of the step-down converter. The vehicle cooling structure according to any one of claims 1 to 4.

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