Drive device

Abstract

This drive device comprises a motor that is accommodated in a motor compartment and a gear mechanism that is accommodated in a gear compartment, and is configured so that the motor and the gear mechanism are cooled by a circulating coolant. The drive device comprises a connecting path that allows the coolant to flow between the bottom of the motor compartment and the bottom of the gear compartment. The drive device comprises a backflow prevention mechanism that is provided in the connecting path, restricts the flow of the coolant from the gear compartment to the motor compartment, and permits the flow of the coolant from the gear compartment to the motor compartment in cases when the pressure applied by the coolant on the gear compartment side is greater than the pressure applied by the coolant on the motor compartment side by at least a prescribed value.

Description

Drive unit

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

[0002] JP2021-136834A discloses a drive device that includes a motor chamber on the motor side, a gear chamber having a gear, and a through hole connecting the motor chamber and the gear chamber.

[0003] When the drive unit is accelerated from the gear chamber to the motor chamber during left or right turns, the oil in the gear chamber can flow back into the motor chamber through the through-hole. This reduces the amount of oil in the gear chamber, and there is a risk that air will be sucked in through the strainer that sucks up the oil.

[0004] Furthermore, if the oil level in the gear chamber rises locally due to the acceleration described above, and if there is a communication hole that connects to the motor case at the point where the oil level rises, the oil in the gear chamber may seep into the motor. In particular, if oil seeps into the air gap between the rotor and stator of the motor, the viscosity of the oil can cause a significant loss of driving force in the motor.

[0005] The present invention has been made in consideration of such problems, and aims to provide a drive device that can suppress backflow of refrigerant from the gear chamber to the motor chamber while suppressing local rise of refrigerant within the gear chamber.

[0006] According to one aspect of the present invention, a drive device includes a motor housed in a motor chamber and a gear mechanism housed in a gear chamber, and is configured to cool the motor and the gear mechanism with a circulating refrigerant. The drive device includes a communication passage that allows refrigerant to flow between a lower portion of the motor chamber and a lower portion of the gear chamber. The drive device also includes a backflow prevention mechanism that is provided in the communication passage and restricts refrigerant flow from the gear chamber to the motor chamber, while allowing refrigerant flow from the gear chamber to the motor chamber when the pressure of the refrigerant on the gear chamber side exceeds the pressure of the refrigerant on the motor chamber side by at least a predetermined value.

[0007] FIG. 1 is a perspective view showing a cross section of a main part of a drive unit equipped with a cooling device according to this embodiment. FIG. 2 is a cross section showing a main part of the drive unit. FIG. 3 is a cross section showing a backflow prevention mechanism in an open state. FIG. 4 is a cross section showing a backflow prevention mechanism in a closed state. FIG. 5 is a cross section showing a backflow prevention mechanism in a connected state. FIG. 6 is a cross section showing the vicinity of the backflow prevention mechanism. FIG. 7 is a perspective view showing a magnet. FIG. 8 is a perspective view showing a magnet according to a first modified example. FIG. 9 is a perspective view showing a magnet according to a second modified example. FIG. 10 is a perspective view showing a magnet according to a third modified example. FIG. 11 is a perspective view showing a backflow prevention mechanism according to a fourth modified example. FIG. 12 is a cross section taken along line XII-XII in FIG. 11. FIG. 13 is a perspective view showing the backflow prevention mechanism in an open state.

[0008] <Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0009] Fig. 1 is a perspective view showing a cross section of a main part of a drive unit 12 equipped with a cooling device 10 according to this embodiment. Fig. 2 is a cross section showing a main part of the drive unit 12.

[0010] 1 and 2, the drive unit 12 is mounted on, for example, an electric vehicle, and drives drive wheels (not shown) with a motor 20. A motor chamber 24 that houses the motor 20 and a gear chamber 28 (see FIG. 2) that houses a gear mechanism (not shown) are arranged adjacent to each other in a casing 22 of the drive unit 12.

[0011] The cooling device 10 in the drive unit 12 cools the motor 20 and the gear mechanism (not shown) with a circulating refrigerant 30. The parts of the motor 20 cooled by the refrigerant 30 include bearings 34 that support axes such as the shaft 32, the motor coil 36, bearings of the gear mechanism (not shown), and meshing portions of the gears that make up the gear mechanism (not shown).

[0012] An example of the refrigerant 30 is oil. The oil constituting the refrigerant 30 functions as a cooling oil that cools the cooling parts of the motor 20 and the gear mechanism of the gear chamber 28, and also functions as a lubricating oil that lubricates the rotating parts of the motor 20 and the gear mechanism of the gear chamber 28.

[0013] The drive unit 12 includes a communication passage 40 that allows the refrigerant 30 to flow between the lower part of the motor chamber 24 and the lower part of the gear chamber 28. The drive unit 12 includes a backflow prevention mechanism 42 that is provided in the communication passage 40 and that restricts the flow of the refrigerant 30 from the gear chamber 28 toward the motor chamber 24. The backflow prevention mechanism 42 is configured to allow the refrigerant 30 to flow from the gear chamber 28 toward the motor chamber 24 when the pressure received from the refrigerant 30 on the gear chamber 28 side becomes higher than the pressure received from the refrigerant 30 on the motor chamber 24 side by a predetermined value or more.

[0014] 2, the drive device 12 includes a motor housing 50 and a cover 52 that closes one end of the motor housing 50, and has a motor chamber 24 inside the motor housing 50. The motor 20 in the motor chamber 24 has a stator 56 fixed to a motor case portion 54 of the motor housing 50, a rotor 58 rotatably held inside the stator 56, and a shaft 32 that rotates together with the rotor 58.

[0015] (Shaft) The base end of the shaft 32 is supported by the cover 52 via the bearing 34. The tip end of the shaft 32 is supported by the motor case portion 54 of the motor housing 50 via the bearing 34. The tip end of the shaft 32 extends into the gear chamber 28.

[0016] The gap between the base end of the shaft 32 and the cover 52 is sealed by a seal member 60. The gap between the cover 52 and a rotor base end member 62 provided on the base end side of the rotor 58 is sealed by the seal member 60.

[0017] (Rotor) The rotor 58 has, for example, a permanent magnet (not shown) on its outer peripheral surface. Inside the rotor 58, a cooling path 70 is formed along the inner peripheral surface 58A of the rotor 58. The above-mentioned refrigerant 30 flows through the cooling path 70. The rotor 58 is cooled by the flowing refrigerant 30. The cooling path 70 extends from the base end side of the rotor 58 to the tip end.

[0018] The base end of the cooling path 70 opens into the inner circumferential surface 58A of the rotor 58. The tip end of the cooling path 70 opens into the tip end surface 58B of the rotor 58. A refrigerant guide 72 is provided on the tip end surface 58B of the rotor 58. The refrigerant guide 72 is inclined in a direction away from the shaft 32 as it extends toward the gear chamber 28. An outflow hole 76 is formed in the wall surface 54A of the motor case 54 located on the tip side of the refrigerant guide 72, for allowing the refrigerant 30 guided by the refrigerant guide 72 to flow into the gear chamber 28.

[0019] This prevents the coolant 30 that has cooled the rotor 58 from flowing into the air gap 80 formed between the rotor 58 and the stator 56 .

[0020] (Stator) The motor coil 36 is wound around the stator 56. The stator 56 is excited when the motor coil 36 is energized. The air gap 80 described above is secured between the stator 56 and the rotor 58. When the motor coil 36 is energized to control the excited state of the stator 56, the rotor 58 rotates in response to the magnetic force of the stator 56. This causes the shaft 32 to rotate together with the rotor 58, and the rotation of the shaft 32 is transmitted to the gear mechanism in the gear chamber 28.

[0021] The stator 56 is provided with a frame 84 that covers the motor coil 36. The coolant 30 that cools the motor coil 36 and the stator 56 flows through the frame 84. The frame 84 is configured so that the coolant 30 flowing inside does not flow into the air gap 80.

[0022] (Gear Chamber) The gear chamber 28 is provided in a gear housing 86 that, together with the motor housing 50 , constitutes the casing 22 .

[0023] A gear mechanism (not shown) is provided in the gear chamber 28. The gear mechanism constitutes a reducer that reduces the rotation transmitted by the shaft 32 of the motor 20 and outputs it from an output shaft (not shown). An oil pan 90 is formed at the bottom of the gear chamber 28. The oil pan 90 temporarily stores the refrigerant 30 that has cooled the gear mechanism.

[0024] A strainer 92 is provided in the oil pan 90. The strainer 92 is connected to a suction port of a pump 94. An oil cooler 96 is connected to a delivery port of the pump 94. A pipe 100 is connected to the oil cooler 96.

[0025] As a result, the refrigerant 30 stored in the oil pan 90 is sucked up by the pump 94 through the strainer 92. The refrigerant 30 sent out from the pump 94 is cooled by the oil cooler 96 and then sent to the pipe 100.

[0026] The piping 100 supplies the refrigerant 30 to, for example, the bearings 34 of the motor 20, the cooling passages 70 of the rotor 58, and the inside of the frame 84. The refrigerant 30 supplied to the cooling passages 70 of the rotor 58 flows into the gear chamber 28 via the outlet holes 76 of the motor case 54. The refrigerant 30 supplied to the bearings 34 of the motor 20 and the inside of the frame 84 collects at the bottom of the motor housing 50.

[0027] (Communicating Passage) The communicating passage 40 described above is formed in the lower part of the motor housing 50, between the outer peripheral wall 50A of the motor housing 50 and the motor case portion 54. The communicating passage 40 has a circular cross section. The communicating passage 40 extends linearly from the cover 52 side toward the gear chamber 28. As an example, the communicating passage 40 is provided in two locations in the lower part of the casing 22 (see FIG. 1). Each communicating passage 40 is provided with a backflow prevention mechanism 42.

[0028] (Backflow Prevention Mechanism) The backflow prevention mechanism 42 and the surrounding structure of the backflow prevention mechanism 42 will be described with reference to FIGS. 3 to 7. FIG.

[0029] Fig. 3 is a cross-sectional view showing the backflow prevention mechanism 42 in the open state 150. Fig. 4 is a cross-sectional view showing the backflow prevention mechanism 42 in the closed state 152. Fig. 5 is a cross-sectional view showing the backflow prevention mechanism 42 in the communicating state 154. Fig. 6 is a cross-sectional view of the vicinity of the backflow prevention mechanism 42. Fig. 7 is a perspective view showing the magnet 166.

[0030] As shown in Figure 3, the backflow prevention mechanism 42 is formed at the outlet portion of each communication passage 40. The communication passages 40 are formed in the motor housing 50. The communication passages 40 extend to the lower part of the motor chamber 24 (see Figure 2). The communication passages 40 are composed of a portion formed in the housing main body 110 of the motor housing 50 and a portion formed in a dividing portion 112 connected to the end of the housing main body 110.

[0031] The backflow prevention mechanism 42 includes a first snap ring 120 fixed to a passage wall surface 40A of the communication passage 40 in the housing main body 110. The first snap ring 120 is formed in a ring shape with a portion cut out. The first snap ring 120 is fixed to the passage wall surface 40A with its outer periphery inserted into a first locking groove 122 in the passage wall surface 40A.

[0032] The backflow prevention mechanism 42 is provided in the communicating passage 40 and includes a first ring plate 124 that is positioned closer to the gear chamber GR than the first snap ring 120. The first ring plate 124 is made of a circular ring-shaped metal plate. The outer diameter of the first ring plate 124 is slightly smaller than the inner diameter of the communicating passage 40.

[0033] A circular first plate opening 124A is formed in the center of the first ring plate 124. The first ring plate 124 is sized so that its outer peripheral edge comes into contact with the first snap ring 120. When the outer peripheral edge of the first ring plate 124 abuts against the first snap ring 120, axial movement of the first ring plate 124 toward the motor chamber MR is restricted.

[0034] The backflow prevention mechanism 42 includes a spring 126, one end of which is supported by the first ring plate 124. The spring 126 is configured as a coil spring. The diameter of the spring 126 is larger than the inner diameter of the first plate opening 124A of the first ring plate 124. The spring 126 is disposed so that the other end faces the gear chamber side GR.

[0035] The backflow prevention mechanism 42 includes a second ring plate 128 that is supported on the passage wall surface 40A and that holds the spring 126 together with the first ring plate 124. The second ring plate 128 is made of a circular ring-shaped metal plate. A circular second plate opening 128A is formed in the center of the second ring plate 128.

[0036] The outer diameter of the second ring plate 128 is larger than the outer diameter of the first ring plate 124. The inner diameter of the second plate opening 128A of the second ring plate 128 and the inner diameter of the first plate opening 124A of the first ring plate 124 are approximately the same size. As a result, the other end of the spring 126 contacts the second ring plate 128, and the spring 126 is held in a compressed state between the first ring plate 124 and the second ring plate 128.

[0037] The backflow prevention mechanism 42 includes a support groove 130 that extends in the circumferential direction and is formed in the passage wall surface 40A. The support groove 130 is formed by a countersunk hole 131 that is formed in the outer periphery of the communicating passage 40 in the end face of the dividing portion 112, and a housing main body end face 110A of the housing main body 110 that abuts against the end face of the dividing portion 112. This allows the second ring plate 128 to be set in the support groove 130.

[0038] The support groove 130 accommodates the plate outer peripheral edge 128B of the second ring plate 128. The support groove 130 has a depth that allows a first gap 132 to be formed between the plate outer peripheral edge 128B and a groove bottom 130B of the support groove 130. The support groove 130 has a groove width that allows the plate outer peripheral edge 128B to move along the communication passage 40. A groove side surface 130C on the gear chamber side GR of the support groove 130 forms a seating surface on which the plate outer peripheral edge 128B sits and leaves.

[0039] The backflow prevention mechanism 42 includes a piston 134 that is disposed closer to the gear chamber GR than the second ring plate 128. The piston 134 is configured as a disk-shaped member. The outer diameter of the piston 134 is smaller than the inner diameter of the communicating passage 40. A second gap 136 is formed between a peripheral edge 134A of the piston 134 and the passage wall surface 40A. The piston 134 is movable along the communicating passage 40.

[0040] The outer diameter of the piston 134 is larger than the inner diameter of the second plate opening 128A of the second ring plate 128. A ring-shaped seal ring 138 is provided on the surface of the piston 134 on the motor chamber side MR. The seal ring 138 is sized to be in contact with the second ring plate 128 over its entire periphery.

[0041] The backflow prevention mechanism 42 includes a second snap ring 140 that is fixed to the passage wall surface 40A and restricts movement of the piston 134 toward the gear chamber side GR. The second snap ring 140 is formed in a ring shape with a portion cut out. The second snap ring 140 is fixed to the passage wall surface 40A with its peripheral edge inserted into a second locking groove 142 in the passage wall surface 40A. The inner diameter of the second snap ring 140 is smaller than the outer diameter of the piston 134. This allows the second snap ring 140 to prevent the piston 134 from disengaging toward the gear chamber side GR.

[0042] The piston 134 is capable of forming an open state 150 (see FIG. 3), a closed state 152 (see FIG. 4), and a communicating state 154 (see FIG. 5).

[0043] 3, when a motor chamber pressure P1 representing the pressure of the refrigerant 30 on the motor chamber side MR is higher than a gear chamber pressure P2 representing the pressure of the refrigerant 30 on the gear chamber side GR, the piston 134 receives the motor chamber pressure P1 and moves to the gear chamber side GR. This causes the piston 134 to open the second plate opening 128A of the second ring plate 128. Then, the refrigerant 30 on the motor chamber side MR flows to the gear chamber side GR through the second plate opening 128A, the second gap 136 between the piston 134 and the passage wall surface 40A, and the notch portion of the second snap ring 140.

[0044] As a result, the piston 134 receives the motor chamber pressure P1, which is the pressure of the refrigerant 30 on the motor chamber side MR, and moves away from the second ring plate 128, forming an open state 150 that connects the second plate opening 128A of the second ring plate 128 to the gear chamber side GR.

[0045] 4, when the gear chamber pressure P2 becomes higher than the motor chamber pressure P1, the piston 134 moves toward the motor chamber MR. As a result, the seal ring 138 of the piston 134 comes into contact with the second ring plate 128 over the entire circumference, and the second plate opening 128A of the second ring plate 128 is closed by the piston 134.

[0046] As a result, the piston 134 receives the gear chamber pressure P2 of the refrigerant 30 on the gear chamber side GR and comes into contact with the second ring plate 128, forming a closed state 152 that closes the second plate opening 128A.

[0047] 5, when the gear chamber pressure P2 becomes even higher than the motor chamber pressure P1 and the gear chamber pressure P2 becomes higher than the motor chamber pressure P1 by a predetermined value or more, the piston 134 moves the second ring plate 128 toward the motor chamber side MR against the biasing force of the spring 126. As a result, a gap is formed between the plate outer peripheral edge 128B of the second ring plate 128 and the groove side surface 130C that forms the seating surface. Then, the refrigerant 30 on the gear chamber side GR flows to the motor chamber side MR via the second gap 136 on the outer periphery of the piston 134, the gap between the plate outer peripheral edge 128B and the groove side surface 130C, the first gap 132 on the outer periphery of the second ring plate 128, and the first plate opening 124A.

[0048] As a result, the piston 134 forms a gap between the plate outer edge 128B and the groove side surface 130C that forms the seat surface, creating a communication state 154 that connects the motor chamber side MR, which is closer to the second ring plate 128, to the gear chamber side GR, which is closer to the piston 134.

[0049] The magnitude of the pressure difference between the motor chamber pressure P1 and the gear chamber pressure P2 at which the refrigerant 30 starts to flow from the gear chamber side GR to the motor chamber side MR is determined by the spring constant of the spring 126. Therefore, the spring constant of the spring 126 is determined based on the target value of the pressure difference at the time when the refrigerant 30 starts to flow from the gear chamber side GR to the motor chamber side MR.

[0050] More specifically, when the vehicle on which the drive unit 12 is mounted turns left or right, acceleration may occur from the gear chamber 28 toward the motor chamber 24. At this time, a pressure difference occurs between the motor chamber pressure P1 and the gear chamber pressure P2, and this pressure difference is applied to the backflow prevention mechanism 42. Furthermore, when the vehicle travels on an inclined surface or slope, or when the vehicle is parked on an inclined surface or slope, a pressure difference occurs between the motor chamber pressure P1 and the gear chamber pressure P2, and this pressure difference is applied to the backflow prevention mechanism 42.

[0051] In these cases, the liquid level 160 (see FIG. 2) of the refrigerant 30 in the gear chamber 28 may tilt as shown by the dashed line in FIG. 2 and may reach the outflow hole 76 formed in the motor case 54. If the liquid level 160 reaches the outflow hole 76, the refrigerant 30 in the gear chamber 28 may flow back from the outflow hole 76 toward the motor 20.

[0052] For this reason, the spring constant of the spring 126 of the backflow prevention mechanism 42 is set so that the communication state 154 (see FIG. 5) is achieved before the pressure difference that occurs when the liquid level 160 of the refrigerant 30 in the gear chamber 28 reaches the outflow hole 76 occurs.

[0053] 6, the drive unit 12 includes a magnet 166 on a bottom 164 located near the outlet of the communication passage 40 and closer to the gear chamber side GR than the backflow prevention mechanism 42. The magnet 166 is provided on a dividing portion 112 connected to the housing main body 110. The magnet 166 uses magnetic force to collect conductive contaminants generated by wear of the gear mechanism (not shown) and hold them in a magnetically attracted state.

[0054] 7, the magnet 166 is a permanent magnet formed with an arc-shaped cross section. The arc-shaped magnet 166 is disposed along the passage wall surface 40A of the communication passage 40, which has a circular cross section.

[0055] In this embodiment, the magnet 166 has an arc-shaped cross section, but the shape of the magnet 166 is not limited to this. The magnet 166 may have the shapes shown in the following modifications. Each of the modifications showing the shape of the magnet 166 will be described with reference to the drawings.

[0056] Fig. 8 is a perspective view showing a magnet 166 according to a first modified example, Fig. 9 is a perspective view showing a magnet 166 according to a second modified example, and Fig. 10 is a perspective view showing a magnet 166 according to a third modified example.

[0057] 8, the magnet 166 according to the first modification is a flat permanent magnet. As in the embodiment, the magnet 166 is provided on the bottom 164 of the dividing portion 112, which is located closer to the gear chamber GR than the backflow prevention mechanism 42 (see FIG. 6).

[0058] 9, the magnet 166 according to the second modification is a cylindrical permanent magnet. As in the embodiment, the magnet 166 is provided on the bottom 164 of the dividing portion 112, which is located closer to the gear chamber GR than the backflow prevention mechanism 42 (see FIG. 6).

[0059] The magnet 166 can collect conductive contaminants generated by wear of the gear mechanism (not shown) and the like by magnetic force and hold them in the inner circular space 170 .

[0060] 10, the magnet 166 according to the third modification is a disk-shaped permanent magnet. As in the embodiment, the magnet 166 is provided on the bottom 164 of the dividing portion 112, which is located closer to the gear chamber GR than the backflow prevention mechanism 42 (see FIG. 6).

[0061] In addition, in the present embodiment, the backflow prevention mechanism 42 is configured using the spring 126, the piston 134, and the like, but the backflow prevention mechanism 42 is not limited to this configuration. The backflow prevention mechanism 42 may also be configured as shown in the following modified example.

[0062] <Fourth Modification> Fig. 11 is a perspective view showing a backflow prevention mechanism 200 according to a fourth modification. Fig. 12 is a cross-sectional view taken along line XII-XII in Fig. 11. Fig. 13 is a perspective view showing the backflow prevention mechanism 200 in the open state 220.

[0063] 11 to 13, a backflow prevention mechanism 200 according to the fourth modification includes a door 202 that closes the communicating passage 40 (see FIGS. 11 and 12) when subjected to the pressure of the refrigerant 30 on the gear chamber side GR. The door 202 is displaced by the pressure of the refrigerant 30 on the motor chamber side MR to open the communicating passage 40 (see FIG. 13). The door 202 is made of a porous material that allows the refrigerant 30 to pass through the interior of the door 202 in accordance with the pressure difference between the refrigerant 30 on the motor chamber side MR and the refrigerant 30 on the gear chamber side GR.

[0064] It should be noted that the components other than the backflow prevention mechanism 200 are configured in the same manner as in the above-described embodiment.

[0065] More specifically, a rectangular fixing plate 212 is provided on the end face of the motor housing 50 connected to the gear housing 86 (see FIG. 2) so as to cover an end opening 210 (see FIG. 12) of the communication passage 40. A vertically long rectangular communication hole 214 is formed in the fixing plate 212.

[0066] A rectangular door 202 is disposed along a surface 212A on the gear chamber side GR of the fixed plate 212. The door 202 is fastened together with the fixed plate 212 to the end surface of the motor housing 50 by screws 216 that pass through the door 202 and the fixed plate 212.

[0067] The door 202 is made of a porous material. The porous material has many small holes through which the refrigerant 30 can pass. The porous material can be made of a thin porous plate or a porous film. The door 202 of this modified example is made of a flexible porous film.

[0068] 13 , when the motor chamber pressure P1 received from the refrigerant 30 on the motor chamber side MR is higher than the gear chamber pressure P2 received from the refrigerant 30 on the gear chamber side GR, the door 202 deforms so that the free end is displaced toward the gear chamber side GR. As a result, the door 202 forms an open state 220 in which the communication hole 214 of the fixed plate 212 is open. In the open state 220, the refrigerant 30 on the motor chamber side MR flows to the gear chamber side GR through the communication hole 214 of the fixed plate 212.

[0069] In addition, in a configuration in which the door 202 is a porous plate, the upper edge of the porous plate can be supported on the end surface of the motor housing 50 by a hinge, making it possible to displace the free end of the door 202 toward the gear chamber side GR.

[0070] 11 and 12 , when the gear chamber pressure P2 received from the refrigerant 30 on the gear chamber side GR is higher than the motor chamber pressure P1 received from the refrigerant 30 on the motor chamber side MR, the door 202 comes into close contact with the surface 212A of the fixed plate 212. This causes the door 202 to form a closed state 230 in which the communication hole 214 of the fixed plate 212 is closed. In the closed state 230, the flow of refrigerant 30 from the motor chamber side MR to the gear chamber side GR is restricted.

[0071] When the gear chamber pressure P2 received from the refrigerant 30 on the gear chamber side GR in the closed state 230 becomes higher than a predetermined value or more than the motor chamber pressure P1 received from the refrigerant 30 on the motor chamber side MR, the refrigerant 30 on the gear chamber side GR flows to the motor chamber side MR through small holes in the porous material that constitutes the door 202.

[0072] The pressure difference between the motor chamber pressure P1 and the gear chamber pressure P2 at which the refrigerant 30 starts to flow from the gear chamber side GR to the motor chamber side MR is determined by the thickness, average size, and density of the small holes of the porous material that constitutes the door 202. The flow rate that changes in response to the pressure difference is also determined by the thickness, average size, and density of the small holes of the porous material that constitutes the door 202.

[0073] Therefore, the porous material that constitutes the door 202 is selected in accordance with the pressure difference at the start of flow and the target value of the flow rate that changes depending on the pressure difference.

[0074] The backflow prevention mechanism 200 is configured such that the refrigerant 30 on the gear chamber side GR flows through the interior of the porous member that constitutes the door 202 to the motor chamber side MR before a pressure difference occurs that would allow the liquid level 160 (see Figure 2) of the refrigerant 30 in the gear chamber 28 to reach the outflow hole 76.

[0075] As an example, if the amount of refrigerant 30 flowing from the motor chamber side MR to the gear chamber side GR in the open state 220 is set to "1", the porous member is selected so that the amount of refrigerant 30 flowing from the gear chamber side GR to the motor chamber side MR through the door 202 in the closed state 230 is "0.2".

[0076] This makes it possible to moderate the temporal change in the liquid level 160 of the refrigerant 30 in the gear chamber side GR.

[0077] (Operation and Effect) As described above, the drive unit 12 of this embodiment is a drive configured to include the motor 20 housed in the motor chamber 24 and the gear mechanism (not shown) housed in the gear chamber 28, and to cool the motor 20 and the gear mechanism with circulated refrigerant 30. The drive unit 12 includes a communication passage 40 that allows the refrigerant 30 to flow between the lower part of the motor chamber 24 and the lower part of the gear chamber 28. The drive unit 12 also includes a backflow prevention mechanism 42, 200 that is provided in the communication passage 40 and restricts the flow of the refrigerant 30 from the gear chamber 28 toward the motor chamber 24, while allowing the refrigerant 30 to flow from the gear chamber 28 toward the motor chamber 24 when the gear chamber pressure P2, which represents the pressure received from the refrigerant 30 on the gear chamber side GR, is higher than the motor chamber pressure P1, which represents the pressure received from the refrigerant 30 on the motor chamber side MR, by a predetermined value or more.

[0078] In the drive unit 12 configured as described above, the backflow prevention mechanisms 42 and 200 provided in the communication passage 40 regulate the flow of the refrigerant 30 from the gear chamber 28 to the motor chamber 24 .

[0079] Therefore, even if acceleration occurs from the gear chamber 28 toward the motor chamber 24 when the vehicle on which the drive unit 12 is installed turns left or right, the drive unit 12 can suppress backflow of the refrigerant 30 from the gear chamber 28 to the motor chamber 24 via the communication passage 40. This makes it possible for the drive unit 12 to suppress the phenomenon in which the refrigerant 30 in the gear chamber 28 decreases and air is sucked through the strainer 92 that sucks up the refrigerant 30.

[0080] Furthermore, if the liquid level 160 of the refrigerant 30 in the gear chamber 28 rises locally due to the acceleration described above, and if the outflow hole 76 communicating with the motor case 54 is present at the location of the rise, there is a risk that the refrigerant 30 in the gear chamber 28 will seep into the motor 20. However, the backflow prevention mechanism 42 of the communicating passage 40 allows the refrigerant 30 to flow from the gear chamber 28 toward the motor chamber 24 when the gear chamber pressure P2 received from the refrigerant 30 on the gear chamber side GR is higher than the motor chamber pressure P1 received from the refrigerant 30 on the motor chamber side MR by a predetermined value or more.

[0081] Therefore, the drive device 12 can suppress a local rise in the refrigerant 30 in the gear chamber 28, and can suppress infiltration of the refrigerant 30 into the motor 20 through the outlet holes 76 for the refrigerant 30 in the gear chamber 28. This suppresses infiltration of the refrigerant 30 into the air gap 80 between the rotor 58 and the stator 56 of the motor 20, and can suppress loss of driving force due to the viscosity of the refrigerant 30.

[0082] Furthermore, the refrigerant 30 on the gear chamber side GR may contain conductive contaminants. However, since the refrigerant 30 containing conductive contaminants can be prevented from entering the motor 20, it is possible to prevent the contaminants from entering the electrically conducting parts of the motor 20.

[0083] In this embodiment, the backflow prevention mechanism 42, 200 includes a first snap ring 120 fixed to the passage wall surface 40A of the communicating passage 40. The backflow prevention mechanism 42, 200 includes a first ring plate 124 that is provided in the communicating passage 40 and positioned closer to the gear chamber side GR than the first snap ring 120. The backflow prevention mechanism 42, 200 includes a spring 126 that has one end supported by the first ring plate 124 and the other end facing the gear chamber side GR. The backflow prevention mechanism 42, 200 includes a second ring plate 128 that is supported by the passage wall surface 40A and that holds the spring 126 together with the first ring plate 124. The backflow prevention mechanism 42, 200 is configured to include a support groove 130 formed in the passage wall surface 40A and extending in the circumferential direction, which accommodates the plate outer peripheral edge 128B of the second ring plate 128 movably along the communication passage 40 in a state in which a first gap 132 can be formed between a plate outer peripheral edge 128B of the second ring plate 128 and a groove bottom 130B of the support groove 130, and a seat surface where the plate outer peripheral edge 128B contacts a groove side surface 130C of the support groove 130 located on the gear chamber side GR is set. The backflow prevention mechanism 42, 200 is configured to include a piston 134 movably provided on the gear chamber side GR relative to the second ring plate 128 in a state in which a second gap 136 can be formed between the passage wall surface 40A and the circumferential edge 134A. The backflow prevention mechanism 42, 200 is fixed to the passage wall surface 40A and includes a second snap ring 140 that restricts movement of the piston 134 toward the gear chamber side GR. When the piston 134 receives motor chamber pressure P1, which is the pressure of the refrigerant 30 on the motor chamber side MR, it moves away from the second ring plate 128 and can establish an open state 150 in which a second plate opening 128A, which is a plate opening of the second ring plate 128, is connected to the gear chamber side GR. When the piston 134 receives gear chamber pressure P2, which is the pressure of the refrigerant 30 on the gear chamber side GR, it comes into contact with the second ring plate 128 and can establish a closed state 152 in which the second plate opening 128A is closed.The piston 134 moves the second ring plate 128 toward the motor chamber side MR under further pressure from the refrigerant 30 on the gear chamber side GR, forming a gap between the plate outer peripheral edge 128B and the groove side surface 130C that forms the seat surface, thereby forming a communication state 154 that connects the motor chamber side MR closer to the second ring plate 128 and the gear chamber side GR closer to the piston 134.

[0084] In the drive device 12 configured as described above, the piston 134 of the backflow prevention mechanism 42 is in an open state 150 under normal circumstances when the motor chamber pressure P1 is higher than the gear chamber pressure P2, and the refrigerant 30 flows from the motor chamber side MR to the gear chamber side GR.

[0085] On the other hand, when the gear chamber pressure P2 becomes higher than the motor chamber pressure P1, the piston 134 of the backflow prevention mechanism 42 is brought into a closed state 152, and the refrigerant 30 does not flow.

[0086] However, when the pressure difference increases due to the acceleration described above and the pressure received from the refrigerant 30 on the gear chamber side GR exceeds the pressure received from the refrigerant 30 on the motor chamber side MR by a predetermined value or more, the piston 134 of the backflow prevention mechanism 42 compresses the spring 126 to enter the communicating state 154. This allows the refrigerant 30 to flow from the gear chamber side GR to the motor chamber side MR.

[0087] In this way, when the pressure difference between the gear chamber pressure P2 and the motor chamber pressure P1 becomes equal to or greater than a predetermined value, the piston 134 of the backflow prevention mechanism 42 enters the communicating state 154. This makes it possible to suppress problems that may occur when the liquid level 160 of the refrigerant 30 in the gear chamber 28 becomes locally high.

[0088] In this embodiment, the backflow prevention mechanism 200 includes a door 202 that closes the communication passage 40 when subjected to gear chamber pressure P2, which is the pressure of the refrigerant 30 on the gear chamber side GR, and that displaces when subjected to motor chamber pressure P1, which is the pressure of the refrigerant 30 on the motor chamber side MR, to open the communication passage 40. The door 202 is made of a porous member that allows the refrigerant 30 to pass through inside the door 202 depending on the pressure difference between the refrigerant 30 on the motor chamber side MR and the refrigerant 30 on the gear chamber side GR.

[0089] In the drive unit 12 configured as described above, the door 202 of the backflow prevention mechanism 200 is normally in an open state 220 when the motor chamber pressure P1 is higher than the gear chamber pressure P2, and the refrigerant 30 flows from the motor chamber side MR to the gear chamber side GR. On the other hand, when the gear chamber pressure P2 becomes higher than the motor chamber pressure P1, the door 202 of the backflow prevention mechanism 200 is in a closed state 230, and the refrigerant 30 does not flow.

[0090] However, when the pressure difference increases due to the acceleration described above and the pressure received from the refrigerant 30 on the gear chamber side GR exceeds the pressure received from the refrigerant 30 on the motor chamber side MR by a predetermined value or more, the refrigerant 30 begins to flow through the small holes in the porous member that makes up the door 202. This allows the refrigerant 30 to flow from the gear chamber side GR to the motor chamber side MR.

[0091] In this way, when the pressure difference between the gear chamber pressure P2 and the motor chamber pressure P1 exceeds a predetermined value, the refrigerant 30 flows through the small holes in the porous member that constitutes the door 202 in the closed state 230. This makes it possible to suppress problems that may occur when the liquid level 160 of the refrigerant 30 in the gear chamber 28 becomes locally high.

[0092] Furthermore, the porous member that constitutes the door 202 functions as a filter when the refrigerant 30 in the gear chamber 28 flows into the motor chamber 24. Therefore, the door 202 can prevent contaminants contained in the refrigerant 30 from entering the motor chamber 24.

[0093] In addition, in this embodiment, the drive device 12 includes a magnet 166 on the bottom portion 164 located near the outlet of the communication passage 40 and on the gear chamber side GR relative to the backflow prevention mechanisms 42 and 200 .

[0094] In the drive unit 12 configured as described above, conductive contaminants contained in the refrigerant 30 flowing from the gear chamber side GR to the motor chamber side MR via the backflow prevention mechanisms 42, 200 are attracted to the magnet 166 provided near the outlet of the communication passage 40. This reduces the contaminants contained in the refrigerant 30, making it possible to prevent problems caused by the intrusion of contaminants compared to when the contaminants contained in the refrigerant 30 are sent to the motor chamber side MR without being reduced.

[0095] The above describes the embodiments and modifications of the present invention, but the above embodiments and modifications merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments and modifications.

[0096] The above-described embodiment and each of the modified examples have been described by taking as an example a case where the cooling device 10 is applied to a drive device 12 for an electric vehicle, but the cooling device 10 may also be applied to other drive devices 12 .

Claims

1. A drive device comprising a motor housed in a motor chamber and a gear mechanism housed in a gear chamber, and configured to cool the motor and the gear mechanism with a circulating refrigerant, the drive device comprising: a communication passage that allows the refrigerant to flow between the lower part of the motor chamber and the lower part of the gear chamber; and a backflow prevention mechanism that is provided in the communication passage and restricts the flow of the refrigerant from the gear chamber toward the motor chamber, while allowing the refrigerant to flow from the gear chamber toward the motor chamber when the pressure received from the refrigerant on the gear chamber side becomes higher than the pressure received from the refrigerant on the motor chamber side by a predetermined value or more.

2. A drive unit according to claim 1, wherein the backflow prevention mechanism comprises: a first snap ring fixed to a passage wall surface of the communicating passage; a first ring plate provided within the communicating passage and positioned closer to the gear chamber than the first snap ring; a spring having one end supported by the first ring plate and the other end facing the gear chamber; a second ring plate supported on the passage wall surface and holding the spring together with the first ring plate; a support groove formed in the passage wall surface and extending in the circumferential direction, the support groove accommodating the outer circumferential edge of the second ring plate movably along the communicating passage in a state where a gap can be formed between the outer circumferential edge of the second ring plate and the groove bottom of the support groove, and a seat surface with which the outer circumferential edge comes into contact is set on the groove side surface of the support groove located on the gear chamber side; a piston provided movably on the gear chamber side of the second ring plate in a state where a gap can be formed between the passage wall surface and its periphery; and a second snap ring fixed to the passage wall surface and restricting movement of the piston towards the gear chamber side, a closed state in which the second ring plate is in contact with the second ring plate under pressure of the refrigerant on the gear chamber side and closes the plate opening; and a communicating state in which the second ring plate is moved toward the motor chamber under further pressure of the refrigerant on the gear chamber side and forms a gap between the plate outer circumferential edge and the seat surface, thereby communicating between the motor chamber side of the second ring plate and the gear chamber side of the piston.

3. A drive device as claimed in claim 1, wherein the backflow prevention mechanism includes a door that closes the communication passage when subjected to the pressure of the refrigerant on the gear chamber side, and that displaces to open the communication passage when subjected to the pressure of the refrigerant on the motor chamber side, and the door is made of a porous material that allows the refrigerant to pass through inside the door depending on the pressure difference between the refrigerant on the motor chamber side and the refrigerant on the gear chamber side.

4. A drive device according to any one of claims 1 to 3, comprising a magnet at the bottom located near the outlet of the communication passage and closer to the gear chamber than the backflow prevention mechanism.

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