Power transmission device

Abstract

Provided is a power transmission device that makes it possible to satisfactorily lubricate a bearing. One embodiment of the present disclosure is a power transmission device that is mounted to a vehicle and that comprises a case and a transmission mechanism which is provided with a shaft, first and second gears, first and second bearings, and an oil guide plate. The first gear sends oil toward the first bearing from the position where the first gear meshes with the second gear. The first bearing sends the oil via an inflow hole to an oil reservoir space between a plate-shaped portion and the case. A tubular portion sends the oil in the oil reservoir space to a hollow portion of the shaft through an outflow hole. The hollow portion supplies the oil to the second bearing through an opening on the second bearing side.

Description

power transmission device

[0001] The present disclosure relates to a power transmission.

[0002] A technology for supplying oil to parts to be lubricated in a power transmission device mounted on a vehicle is known. According to the technology disclosed in Patent Document 1, oil in the power transmission device is scooped up and splashed by a ring gear, then captured by a guide portion and falls into an oil reservoir located below the guide portion. The oil stored in the oil reservoir then flows into a hollow portion that axially penetrates the rotor shaft through an opening at one end of the rotor shaft and flows out from an opening at the other end. This allows the oil to be supplied to a bearing that supports the rotor shaft on the other side.

[0003] Japanese Patent Application Laid-Open No. 2021-105425

[0004] However, in the technology disclosed in Patent Document 1, oil scooped up by the ring gear and splashed is captured by a guide located above the oil reservoir and falls back into the oil reservoir. This slows down the speed at which the oil flows from the ring gear into the oil reservoir. This can result in a longer time for oil to be supplied to the other bearing, potentially resulting in insufficient lubrication of the other bearing.

[0005] One aspect of the present disclosure is the desire to provide good bearing lubrication.

[0006] One aspect of the present disclosure is a power transmission device mounted on a vehicle, comprising a transmission mechanism and a case. The case houses the transmission mechanism. The transmission mechanism comprises a shaft, a first gear, a second gear, a first bearing, a second bearing, and an oil guide plate. The first gear is mounted on the shaft and has the same rotational axis as the shaft. The second gear has a rotational axis parallel to the rotational axis of the first gear and meshes with the first gear. The first bearing rotatably supports the shaft at a first axial end of the shaft. The second bearing rotatably supports the shaft at a second end opposite the first end. The oil guide plate is disposed between the first end and the case in the axial direction of the shaft. The shaft has a hollow portion axially penetrating the shaft. The first gear is disposed between the first and second bearings and adjacent to the first bearing. The first bearing is a rolling bearing including an inner ring, an outer ring, and rolling elements arranged in the space between the inner ring and the outer ring, and the space between the inner ring and the outer ring is open to both axial sides of the first bearing. The oil guide plate includes a plate-like portion, an inlet hole, a cylindrical portion, and an outlet hole. The inlet hole penetrates the plate-like portion in the plate thickness direction. The cylindrical portion protrudes from the plate-like portion in the plate thickness direction. The outlet hole is a space surrounded by the cylindrical portion and penetrates the oil guide plate in the plate thickness direction. The inlet hole is connected to the space between the inner ring and outer ring of the first bearing. The cylindrical portion is arranged within an opening on the first end side of the hollow portion of the shaft. An oil storage space in which oil for the power transmission device is stored is formed between the plate-like portion and the case. The first gear is a helical gear configured to send oil toward the first bearing from a position where it meshes with the second gear when rotating in the first direction, with the direction in which the first gear rotates when the vehicle moves forward being defined as a first direction. The first bearing is configured to send oil sent from the first gear from a space between the inner ring and the outer ring through an inlet hole to an oil storage space. The cylindrical portion is configured to send oil stored in the oil storage space through an outlet hole and from an opening on a first end side of the hollow portion to the hollow portion. The hollow portion is configured to supply oil to the second bearing by allowing the oil sent to the hollow portion to flow out from an opening on a second end side.

[0007] According to the above configuration, oil is sent from the meshing position between the first gear and the second gear toward the first bearing. The oil sent to the first bearing then flows from the space between the inner and outer rings of the first bearing through the inlet hole into the oil storage space. This increases the speed at which the oil moves into the oil storage space. This shortens the time it takes for the oil to reach the second bearing. This allows the second bearing to be well lubricated.

[0008] In one aspect of the present disclosure, the shaft may be a motor shaft driven by a motor, and the motor shaft may receive driving force from the motor at a position between the first and second bearings and on the second end side relative to the first gear.

[0009] According to the above configuration, the second bearing that supports the motor shaft at a position away from the first gear can be well lubricated.

[0010] In one aspect of the present disclosure, the motor shaft may be molded integrally with the first gear. A first space in which the first and second gears are disposed may be connected to a second space in which the motor is disposed. The transmission mechanism may not include a bearing for supporting the motor shaft between the first space and the second space. Furthermore, the transmission mechanism may not include a seal for blocking the inflow of oil between the first space and the second space.

[0011] With this configuration, a bearing supporting the motor shaft and a seal blocking the inflow of oil are not disposed between the first space and the second space, which allows the axial dimension of the motor shaft to be shortened. This shortens the path for oil to be supplied from the oil storage space to the second bearing, thereby reducing the time it takes for oil to be supplied to the second bearing.

[0012] In one aspect of the present disclosure, the transmission mechanism may further include a countershaft having a second gear and the same rotational axis as the second gear, a third gear having an outer diameter smaller than that of the second gear, provided on the countershaft, and arranged concentrically with the second gear, and a fourth gear having an outer diameter larger than that of the third gear, having a rotational axis parallel to the rotational axis of the third gear, and meshing with the third gear. The countershaft may be arranged such that, when viewed axially of the motor shaft, the rotational axis of the countershaft is located below a line connecting the rotational axes of the motor shaft and the fourth gear in the up-down direction. The second gear may be immersed in oil accumulated at the bottom of the case.

[0013] With this configuration, the rotational speed of the second gear is faster than the rotational speed of the fourth gear, and the oil is scooped up by the second gear, which has a higher rotational speed, so the time it takes for the oil to be supplied to the second bearing can be shortened.

[0014] FIG. 4 is a cross-sectional view of the power transmission device taken along line II shown in FIGS. 2 and 3. FIG. 5 is a left side view of the power transmission device with the second case and some components removed. FIG. 6 is a right side view of the power transmission device with the first case and some components removed. FIG. 7 is a perspective view of the power transmission device with the second case and some components removed. FIG. 8 is a diagram showing the arrangement of an oil guide plate in the power transmission device. FIG. 9 is a diagram showing an oil guide plate.

[0015] 1...power transmission device, 2...transmission mechanism, 3...case, 21...motor shaft, 211...pinion gear, 212...first end, 213...second end, 214...hollow portion, 22...counter shaft, 221...first counter gear, 222...second counter gear, 23...ring gear, 24...differential case, 25...differential mechanism, 26...oil guide plate, 261...plate-shaped portion, 262...inlet hole, 263...cylindrical portion, 264...outlet hole, 265...periphery, 27...motor, 21A...first motor shaft bearing, 21B...second motor shaft bearing, K...oil storage space, L1, L2, L3...rotation axis, O...oil, S1...first space, S2...second space.

[0016] Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.

[0017] 1 is mounted on a vehicle and transmits power to the wheels. When the power transmission device 1 is mounted on a vehicle, a rotational axis L1 of a motor shaft 21 (described later) is parallel to the left-right direction of the vehicle. Furthermore, when the power transmission device 1 is mounted on a vehicle, the rotational axis L1 of the motor shaft 21 is located rearward of a rotational axis L3 of a ring gear 23 (described later).

[0018] The power transmission device 1 includes a transmission mechanism 2 and a case 3 .

[0019] <Transmission Mechanism> The transmission mechanism 2 includes a motor shaft 21 , a pinion gear 211 , a counter shaft 22 , a first counter gear 221 , a second counter gear 222 , a ring gear 23 , a differential case 24 , a differential mechanism 25 , an oil guide plate 26 , and a motor 27 .

[0020] Furthermore, the power transmission mechanism 2 includes first and second motor shaft bearings 21A, 21B, first and second counter shaft bearings 22A, 22B, and first and second differential case bearings 24A, 24B.

[0021] <Motor Shaft> The motor shaft 21 is drivingly coupled to the motor 27 and rotates by the driving force of the motor 27. The motor shaft 21 rotates in a first direction D1 when the vehicle moves forward. The first direction D1 is the clockwise direction when the transmission mechanism 2 is viewed from the right, as shown in FIG. 2 . Furthermore, when the vehicle moves backward, the motor shaft 21 rotates in a second direction D2 opposite to the first direction D1. The rotation axis L1 of the motor shaft 21 is parallel to the left-right direction. The motor shaft 21 has a first end 212 which is the left end, and a second end 213 which is the end opposite to the first end 212, i.e., the right end.

[0022] The motor shaft 21 has a hollow portion 214, which is a space that passes through the motor shaft 21 in the axial direction from the first end 212 to the second end 213 (see FIG. 1 ). The hollow portion 214 has a small diameter portion 214A, which is a portion of the motor shaft 21 on the first end 212 side, and a large diameter portion 214B, which is a portion of the motor shaft 21 on the second end 213 side, and has an inner diameter larger than that of the small diameter portion 214A. A step is formed at the boundary between the small diameter portion 214A and the large diameter portion 214B.

[0023] <Pinion Gear> The pinion gear 211 is an external gear that has the same rotation axis L1 as the motor shaft 21. The pinion gear 211 is molded integrally with the motor shaft 21. As an example, the pinion gear 211 according to this embodiment is formed by directly cutting teeth on the outer circumferential surface of the motor shaft 21. The pinion gear 211 is disposed between the first and second motor shaft bearings 21A, 21B, and, as an example, is adjacent to the first motor shaft bearing 21A.

[0024] The pinion gear 211 is a helical gear with left-handed teeth (see FIG. 4 ), in other words, the pinion gear 211 has teeth that are inclined in the first direction D1 as they extend to the right.

[0025] <First Counter Gear> The first counter gear 221 is an external gear having a rotation axis L2 that is parallel to the rotation axis L1 of the pinion gear 211. The rotation axis L2 of the first counter gear 221 is located forward and below the rotation axis L1 of the pinion gear 211. The first counter gear 221 is disposed between the first and second counter shaft bearings 22A, 22B.

[0026] 3 and 4, the first counter gear 221 meshes with the pinion gear 211 at an meshing position SS. That is, the first counter gear 221 rotates in the opposite direction to the pinion gear 211. The meshing position SS is located forward and below the rotation axis L1.

[0027] The first counter gear 221 is a helical gear with right-hand helical teeth (see FIG. 4). In other words, the first counter gear 221 has teeth that are inclined in the second direction D2 as they extend to the right.

[0028] The outer diameter of the first counter gear 221 is larger than the outer diameter of the pinion gear 211. The first counter gear 221 is fixed to the counter shaft 22, for example, by spline fitting. A lower portion of the first counter gear 221 is immersed in oil O collected at the bottom of the case 3 (see FIG. 2).

[0029] <Countershaft> The countershaft 22 is a hollow member having the same rotation axis L2 as the first counter gear 221.

[0030] <Second Counter Gear> The second counter gear 222 is an externally toothed gear that is formed integrally with the counter shaft 22 and is arranged concentrically with the first counter gear 221. In other words, the second counter gear 222 has the same rotation axis L2 as the first counter gear 221. The second counter gear 222 is a helical gear with right-hand helix teeth.

[0031] The outer diameter of the second counter gear 222 is smaller than the outer diameter of the first counter gear 221. The counter shaft 22 is formed integrally with the second counter gear 222. As an example, the second counter gear 222 according to this embodiment is formed by directly cutting teeth on the outer circumferential surface of the counter shaft 22. The second counter gear 222 is disposed between the first and second counter shaft bearings 22A, 22B and to the left of the first counter gear 221.

[0032] <Ring Gear> The ring gear 23 has a rotation axis L3 parallel to the rotation axis L1 of the pinion gear 211, and is an external gear that meshes with the second counter gear 222. That is, the ring gear 23 rotates in the opposite direction to the second counter gear 222 (i.e., the same direction as the pinion gear 211). The ring gear 23 is a helical gear with left-hand twisted teeth.

[0033] The rotation axis L3 of the ring gear 23 is located forward and above the rotation axis L2 of the countershaft 22 (see FIG. 2). The ring gear 23 is disposed between the first and second differential case bearings 24A, 24B. The ring gear 23 rotates the differential case 24 by the rotational force transmitted from the second counter gear 222. A lower portion of the ring gear 23 is immersed in oil O accumulated at the bottom of the case 3.

[0034] <Differential Case> The differential case 24 is fixed to the ring gear 23 and rotates together with the ring gear 23 about the rotation axis L3 of the ring gear 23 (see FIG. 2). The differential case 24 rotates in the opposite direction to the countershaft 22, i.e., in the same direction as the motor shaft 21.

[0035] The differential case 24 includes a differential mechanism housing portion 241, a flange portion 242, a first shaft portion 243, and a second shaft portion 244 (see FIGS. 1 and 4). The differential mechanism housing portion 241 houses the differential mechanism 25. The flange portion 242 protrudes radially outward from the differential mechanism housing portion 241. The ring gear 23 is fastened to the flange portion 242 by, for example, a plurality of bolts.

[0036] The first shaft portion 243 is disposed on the right side of the differential mechanism housing portion 241 and is a cylindrical portion through which the first output shaft ST1 connected to the differential mechanism 25 is inserted. The second shaft portion 244 is disposed on the left side of the differential mechanism housing portion 241 and is a cylindrical portion through which the second output shaft (not shown) connected to the differential mechanism 25 is inserted.

[0037] <Differential Mechanism> The differential mechanism 25 is a mechanism that distributes and transmits the rotation of the differential case 24 to the first output shaft ST1 and the second output shaft while causing the first output shaft ST1 and the second output shaft to rotate differentially. The differential mechanism 25 is disposed inside the differential mechanism accommodating portion 241.

[0038] The differential mechanism 25 has two side gears connected to the first output shaft ST1 and the second output shaft, respectively, and two pinion gears that transmit the rotation of the differential case 24 to the two side gears. The rotational axes of the first output shaft ST1 and the second output shaft coincide with the rotational axis L3 of the ring gear 23. The first output shaft ST1 and the second output shaft rotate differentially while rotating in the rotational direction of the differential case 24 (i.e., the rotational direction of the motor shaft 21).

[0039] <Oil Guide Plate> As shown in Fig. 1 , the oil guide plate 26 is disposed between the first end 212 and the case 3 in the axial direction of the motor shaft 21. As shown in Fig. 6 , the oil guide plate 26 includes a plate-shaped portion 261, at least one inlet hole 262 (for example, two), a cylindrical portion 263, an outlet hole 264, and a peripheral portion 265.

[0040] The plate-shaped portion 261 is a circular plate-shaped portion. An oil storage space K, which is a space for storing oil O of the power transmission device 1, is formed between the plate-shaped portion 261 and a first case 3A described later.

[0041] The two inlet holes 262 penetrate the plate-shaped portion 261. The two inlet holes 262 have a fan shape that widens circumferentially from near the center of the plate-shaped portion 261 toward the outer edge. The two inlet holes 262 are arranged so as to connect to the space between the inner ring and outer ring of the first motor shaft bearing 21A. The lowermost ends of the two inlet holes 262 in the vertical direction are arranged above the lowermost end of the outlet hole 264.

[0042] The tubular portion 263 is a cylindrical portion that protrudes in the thickness direction from the center of the plate-like portion 261. The tubular portion 263 is inserted into the hollow portion 214 of the motor shaft 21 from the opening on the first end 212 side of the hollow portion 214.

[0043] The outflow hole 264 is a space surrounded by the cylindrical portion 263 and penetrates the oil guide plate 26 in the thickness direction of the plate-shaped portion 261 .

[0044] The peripheral edge portion 265 is a plate-shaped portion provided to surround the plate-shaped portion 261. The peripheral edge portion 265 is disposed in the protruding direction of the cylindrical portion 263 relative to the plate-shaped portion 261, and a step is formed between the plate-shaped portion 261 and the peripheral edge portion 265. The oil guide plate 26 is fixed to the case 3 by sandwiching the peripheral edge portion 265 between the first case 3A and the outer ring of the first motor shaft bearing 21A.

[0045] <Motor> The motor 27 outputs driving force for running the vehicle. The motor 27 is an inner rotor brushless motor including a stator 271 and a rotor 272 located inside the stator 271 (see FIG. 1). The rotor 272 is disposed on the motor shaft 21 between the first and second motor shaft bearings 21A and 21B and adjacent to the second motor shaft bearing 21B. In other words, the motor shaft 21 receives driving force from the rotor 272, which is disposed between the first and second motor shaft bearings 21A and 21B and on the second end 213 side of the pinion gear 211.

[0046] <Motor shaft bearings> The first and second motor shaft bearings 21A, 21B are ball bearings that each include an inner ring, an outer ring, and a plurality of rolling elements arranged in the space between the inner and outer rings, and rotatably support the motor shaft 21 (see FIG. 1). The first and second motor shaft bearings 21A, 21B do not include a seal or shield to isolate the space between the inner and outer rings from the outside. In other words, the space between the inner and outer rings of the first and second motor shaft bearings 21A, 21B is open to both sides in the axial direction.

[0047] The first motor shaft bearing 21A supports a first end 212 of the motor shaft 21, and the second motor shaft bearing 21B supports a second end 213 of the motor shaft 21. The first motor shaft bearing 21A is attached to the first case 3A, and the second motor shaft bearing 21B is attached to the third case 3C.

[0048] <Countershaft Bearings> The first and second countershaft bearings 22A, 22B are ball bearings that each include an inner ring, an outer ring, and a plurality of rolling elements arranged in the space between the inner ring and the outer ring, and that rotatably support the countershaft 22 (see FIG. 1).

[0049] The first countershaft bearing 22A supports the left end of the countershaft 22, and the second countershaft bearing 22B supports the right end of the countershaft 22. The first countershaft bearing 22A is attached to the first case 3A, and the second countershaft bearing 22B is attached to the second case 3B.

[0050] <Differential case bearings> The first and second differential case bearings 24A, 24B are ball bearings that each include an inner ring, an outer ring, and a plurality of rolling elements arranged in the space between the inner ring and the outer ring, and rotatably support the differential case 24 (see FIG. 1).

[0051] The first differential case bearing 24A supports the second shaft portion 244 of the differential case 24, and the second differential case bearing 24B supports the first shaft portion 243 of the differential case 24. The first differential case bearing 24A is attached to the first case 3A, and the second differential case bearing 24B is attached to the second case 3B.

[0052] <Cases> The case 3 houses the power transmission mechanism 2. The case 3 includes a first case 3A, a second case 3B, and a third case 3C (see FIG. 1). The first case 3A is disposed on the left side of the power transmission mechanism 2, and the third case 3C is disposed on the right side of the power transmission mechanism 2. The second case 3B is disposed between the first case 3A and the third case 3C in the left-right direction.

[0053] The first case 3A and the second case 3B are connected to each other by a plurality of bolts, and a first space S1 is formed between the first case 3A and the second case 3B.

[0054] The first space S1 accommodates a portion of the motor shaft 21 on the first end 212 side, the pinion gear 211, the counter shaft 22, the first counter gear 221, and the second counter gear 222. The first space S1 also accommodates the ring gear 23, the differential case 24, the differential mechanism 25, and the oil guide plate 26. The first space S1 also accommodates the first motor shaft bearing 21A, the first and second counter shaft bearings 22A and 22B, and the first and second differential case bearings 24A and 24B.

[0055] The second case 3B and the third case 3C are connected to each other with a plurality of bolts, and a second space S2 is formed between the second case 3B and the third case 3C. The second space S2 accommodates the portion of the motor shaft 21 on the side of the second end 213, the motor 27, and the second motor shaft bearing 21B.

[0056] The case 3 includes a hole 31 , a catch tank 32 , and a communication groove 33 .

[0057] The hole 31 penetrates the second case 3B in the left-right direction. The first space S1 and the second space S2 are connected via the hole 31. The hole 31 is located at the position of the rotational axis L1 of the motor shaft 21. The motor shaft 21 is located between the first and second spaces S1 and S2 through the hole 31. The transmission mechanism 2 does not include a bearing for supporting the motor shaft 21 between the first space S1 and the second space S2. The transmission mechanism 2 also does not include a seal for blocking the inflow of oil O between the first space S1 and the second space S2.

[0058] <Catch Tank> The catch tank 32 is a portion where oil O of the power transmission device 1 is stored. The catch tank 32 includes a first rib 32A that protrudes from the inner surface of the first case 3A toward the second case 3B (i.e., toward the right) and a second rib 32B that protrudes from the inner surface of the second case 3B toward the first case 3A (i.e., toward the left) (see FIGS. 2 and 3). The right end face of the first rib 32A abuts against the left end face of the second rib 32B. The first and second ribs 32A, 32B extend along a curved path so as to protrude downward. The catch tank 32 stores oil O in downwardly recessed portions of the upper surfaces of the first and second ribs 32A, 32B.

[0059] The catch tank 32 is disposed above the countershaft 22. The catch tank 32 is disposed at a position overlapping the countershaft 22 when viewed from above.

[0060] The catch tank 32 also includes a flow path (not shown) for discharging the stored oil O. The oil O stored in the catch tank 32 passes through the flow path and is supplied to the first and second countershaft bearings 22A, 22B.

[0061] <Communication Groove> The communication groove 33 is a groove-shaped portion provided on the inner surface of the first case 3A, with its depth directed to the left (see FIG. 5). The communication groove 33 is located above and forward of the rotational axis L1 of the motor shaft 21, and extends forward and upward from the portion of the first case 3A that houses the first motor shaft bearing 21A. The communication groove 33 communicates between the oil storage space K and the space above the catch tank 32.

[0062] <Oil Behavior> When the vehicle moves forward, that is, when the motor shaft 21 and the pinion gear 211 rotate in the first direction D1, the oil O that has accumulated at the bottom of the case 3 is scooped up and scattered by the first counter gear 221 and the ring gear 23. At this time, the oil O adheres to the teeth of the first counter gear 221. In addition, some of the scattered oil O adheres to the teeth of the pinion gear 211.

[0063] The pinion gear 211 is a helical gear with left-hand helix teeth, and the first counter gear 221 is a helical gear with right-hand helix teeth. Therefore, when the pinion gear 211 rotates in the first direction D1 and meshes with the first counter gear 221 at the meshing position SS, the right ends of the teeth come into contact with each other. As the pinion gear 211 continues to rotate in the first direction D1, the position at which the teeth come into contact with each other shifts to the left. Therefore, the oil O adhering to the teeth of the pinion gear 211 and the first counter gear 221 is squeezed out from the meshing position SS toward the first motor shaft bearing 21A.

[0064] The oil O discharged from the meshing position SS toward the first motor shaft bearing 21A flows into the space between the inner and outer rings of the first motor shaft bearing 21A. The oil O in the space between the inner and outer rings of the first motor shaft bearing 21A is displaced upward as the rolling elements rotate in the first direction D1. The oil O displaced upward flows out of the space between the inner and outer rings of the first motor shaft bearing 21A to the left and flows into the oil storage space K through the two inlet holes 262.

[0065] In addition, some of the oil O that is scooped up and scattered by the ring gear 23 reaches the communication groove 33 and flows into the oil storage space K through the communication groove 33.

[0066] The oil O flows into the oil storage space K, thereby increasing the amount of oil O stored in the oil storage space K. When the liquid level of the oil O stored in the oil storage space K reaches a position higher than the lowermost end of the outflow hole 264 in the vertical direction, the oil O passes through the outflow hole 264 and flows into the hollow portion 214 from the opening on the first end 212 side of the hollow portion 214.

[0067] The oil O that has flowed into the hollow portion 214 flows out from the opening on the second end portion 213 side and flows into the space between the inner ring and outer ring of the second motor shaft bearing 21B. As a result, the second motor shaft bearing 21B is lubricated by the oil O.

[0068] Furthermore, some of the oil O that is scooped up and scattered by the first counter gear 221 and the ring gear 23 is stored in the catch tank 32. The oil O stored in the catch tank 32 is supplied to the first and second counter shaft bearings 22A, 22B through a flow path in the catch tank 32. As a result, the first and second counter shaft bearings 22A, 22B are lubricated by the oil O.

[0069] When the vehicle is reversed, that is, when the motor shaft 21 and the pinion gear 211 rotate in the second direction D2, the oil O accumulated at the bottom of the case 3 is scooped up by the first counter gear 221 and the ring gear 23 and splashed out.

[0070] When the pinion gear 211 rotates in the second direction D2 and meshes with the first counter gear 221 at the meshing position SS, the left ends of the teeth come into contact with each other. Subsequently, as the pinion gear 211 rotates in the second direction D2, the position where the teeth come into contact with each other shifts to the right. Therefore, when the pinion gear 211 rotates in the second direction D2, the amount of oil O discharged from the meshing position SS toward the first motor shaft bearing 21A decreases compared to when the pinion gear 211 rotates in the first direction D1.

[0071] On the other hand, when the pinion gear 211 rotates in the second direction D2, the ring gear 23 also rotates in the second direction D2. In this case, the teeth of the ring gear 23 are displaced from front to rear above the rotation axis L3, so that oil O adhering to the teeth of the ring gear 23 is scattered toward the communicating groove 33 located rearward of the ring gear 23. Therefore, when the pinion gear 211 rotates in the second direction D2, the amount of oil O flowing from the communicating groove 33 into the oil storage space K increases compared to when the pinion gear 211 rotates in the first direction D1. The oil O flowing into the oil storage space K is supplied to the second motor shaft bearing 21B, just as when the vehicle is moving forward. Therefore, the second motor shaft bearing 21B is lubricated by oil O even when the vehicle is moving backward.

[0072] When the vehicle is temporarily stopped, i.e., when the rotation of the motor shaft 21 is temporarily stopped, the flow of oil O into the oil storage space K is stopped. As a result, the supply of oil O to the second motor shaft bearing 21B is stopped.

[0073] At this time, the oil O stored before the vehicle was temporarily stopped remains in the oil storage space K. Therefore, when the vehicle starts moving again, the supply of oil O to the second motor shaft bearing 21B can be resumed more quickly.

[0074] When the vehicle is stopped for a long period of time, the oil O stored in the oil storage space K gradually leaks out from the gap between the plate-shaped portion 261 and the first case 3A and is returned to the bottom of the case 3.

[0075] [1-2. Effects] According to the embodiment described above in detail, the following effects can be obtained.

[0076] (1a) When the vehicle moves forward, oil O accumulated at the bottom of the case 3 adheres to the teeth of the first counter gear 221 and the pinion gear 211 and is discharged from the meshing position SS toward the first motor shaft bearing 21A. The oil O discharged toward the first motor shaft bearing 21A then flows from the space between the inner and outer rings of the first motor shaft bearing 21A through the two inlet holes 262 into the oil storage space K. This increases the speed at which the oil O moves from the bottom of the case 3 to the oil storage space K. This shortens the time it takes for the oil O to be supplied from the bottom of the case 3 to the second motor shaft bearing 21B. This allows the second motor shaft bearing 21B to be well lubricated.

[0077] (1b) Furthermore, the motor shaft 21 receives a driving force from the rotor 272, which is located between the first and second motor shaft bearings 21A and 21B and is located closer to the second end 213 of the pinion gear 211. Therefore, the second motor shaft bearing 21B, which supports the motor shaft 21 at a position away from the pinion gear 211, can be well lubricated.

[0078] (1c) Furthermore, because no bearing supporting the motor shaft 21 or a seal blocking the inflow of oil O is disposed between the first space S1 and the second space S2, the axial dimension of the motor shaft 21 can be shortened. This shortens the path along which the oil O is supplied from the oil storage space K to the second motor shaft bearing 21B. This shortens the time it takes for the oil O to be supplied from the bottom of the case 3 to the second motor shaft bearing 21B.

[0079] (1d) Furthermore, when viewing the power transmission device 1 from the right side, the rotational axis L2 of the countershaft 22 is located below the line connecting the rotational axis L1 of the motor shaft 21 and the rotational axis L3 of the ring gear 23. The lower portion of the first counter gear 221 is immersed in the oil O accumulated at the bottom of the case 3. Therefore, the first counter gear 221 can effectively scoop up the oil O accumulated at the bottom of the case 3. Furthermore, the first counter gear 221 and the second counter gear 222 have the same rotational speed, and because the outer diameter of the second counter gear 222 is smaller than the outer diameter of the ring gear 23, the rotational speed of the first counter gear 221 is faster than the rotational speed of the ring gear 23. Therefore, because the first counter gear 221, which has a higher rotational speed, scoops up the oil O, the time it takes for the oil O to be supplied from the bottom of the case 3 to the second motor shaft bearing 21B can be shortened.

[0080] In the above embodiment, the motor shaft 21 corresponds to an example of a shaft, the pinion gear 211 corresponds to an example of a first gear, the first counter gear 221 corresponds to an example of a second gear, the first and second motor shaft bearings 21A and 21B correspond to an example of a first and second bearing, the second counter gear 222 corresponds to an example of a third gear, and the ring gear 23 corresponds to an example of a fourth gear.

[0081] [2. Other Embodiments] Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take on various forms.

[0082] (2a) According to the above embodiment, the power transmission device 1 can effectively lubricate the second motor shaft bearing 21B. However, the present disclosure is not limited to this. As an example, the power transmission device 1 may be configured to effectively lubricate the second countershaft bearing 22B. Specifically, the oil guide plate 26 may be disposed between the left end of the countershaft 22 and the case 3. Furthermore, the second counter gear 222 may be configured to send oil O from the position where it meshes with the ring gear 23 toward the first countershaft bearing 22A. The first countershaft bearing 22A may be configured to send oil O from the space between the inner ring and the outer ring through the inlet hole 262 to the oil storage space K. The cylindrical portion 263 may be configured to send oil O stored in the oil storage space K through the outlet hole 264 and from the opening at the left end of the countershaft 22 to the hollow portion. The hollow portion of the countershaft 22 may be configured to supply oil O to the second countershaft bearing 22B by allowing oil O that flows in through an opening at the left end to flow out through an opening at the right end.

[0083] (2b) In the above embodiment, the motor shaft 21 is drivingly connected to the motor 27. However, the present disclosure is not limited to this. As an example, the motor shaft 21 may be drivingly connected to an internal combustion engine. Also, as another example, the motor shaft 21 may be rotated by receiving driving force from another shaft that receives driving force from a power source.

[0084] (2c) In the above embodiment, the pinion gear 211 is molded integrally with the motor shaft 21. However, the present disclosure is not limited to this. As an example, the pinion gear 211 may be a separate member from the motor shaft 21 and fixed to the motor shaft 21.

[0085] (2d) In the above embodiment, when viewed in the axial direction of the motor shaft 21, the rotational axis L2 of the countershaft 22 is located below the line connecting the rotational axis L1 of the motor shaft 21 and the rotational axis L3 of the ring gear 23 in the vertical direction. However, the present disclosure is not limited to this. As an example, when viewed in the axial direction of the motor shaft 21, the rotational axis L2 of the countershaft 22 may be located above the line connecting the rotational axis L1 of the motor shaft 21 and the rotational axis L3 of the ring gear 23 in the vertical direction.

[0086] (2e) In the above embodiment, the hollow portion 214 of the motor shaft 21 includes a small-diameter portion 214A and a large-diameter portion 214B. However, the present disclosure is not limited to this. As an example, the hollow portion 214 may have a tapered shape in which the inner diameter increases from the first end 212 toward the second end 213. With this configuration, oil O that flows into the hollow portion 214 from the opening on the first end 212 side is subjected to centrifugal force due to the rotation of the motor shaft 21 and is displaced toward the second end 213. This reduces the time it takes for the oil O to be supplied to the second motor shaft bearing 21B.

[0087] (2f) Multiple functions of one component in the above embodiments may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

Claims

1. A power transmission device mounted on a vehicle, comprising: a transmission mechanism; and a case that houses the transmission mechanism, wherein the transmission mechanism comprises: a shaft; a first gear that is provided on the shaft and has the same rotational axis as the shaft; a second gear that has a rotational axis parallel to the rotational axis of the first gear and meshes with the first gear; a first bearing that rotatably supports the shaft at a first end in the axial direction of the shaft; a second bearing that rotatably supports the shaft at a second end opposite to the first end; and an oil guide plate that is arranged between the first end and the case in the axial direction of the shaft, wherein the shaft has a hollow portion that axially passes through the shaft; and the first gear is arranged between the first and second bearings and adjacent to the first bearing, the first bearing is a rolling bearing including an inner ring, an outer ring, and rolling elements disposed in a space between the inner ring and the outer ring, and the space between the inner ring and the outer ring is open toward both sides in the axial direction of the first bearing; the oil guide plate includes a plate-like portion, an inlet hole penetrating the plate-like portion in a plate thickness direction, a cylindrical portion protruding from the plate-like portion in the plate thickness direction, and an outlet hole which is a space surrounded by the cylindrical portion and penetrates the oil guide plate in the plate thickness direction, the inlet hole being connected to the space between the inner ring and the outer ring of the first bearing; the cylindrical portion being disposed within an opening on the first end side of the hollow portion of the shaft; and an oil storage space which is a space for storing oil of the power transmission device being formed between the plate-like portion and the case, The first gear is a helical gear configured to send the oil toward the first bearing from a position where it meshes with the second gear when rotating in a first direction, the direction in which the first gear rotates when the vehicle moves forward; the first bearing is configured to send the oil sent from the first gear from a space between the inner ring and the outer ring to the oil storage space through the inlet hole; and the cylindrical portion is configured to send the oil stored in the oil storage space through the outlet hole and from an opening on the first end side of the hollow portion to the hollow portion.The hollow portion is configured to supply the oil to the second bearing by causing the oil sent into the hollow portion to flow out from an opening on the second end side.

2. A power transmission device according to claim 1, wherein the shaft is a motor shaft driven by a motor, and the motor shaft receives driving force from the motor at a position between the first and second bearings and on the second end side of the first gear.

3. A power transmission device as claimed in claim 2, wherein the motor shaft is integrally formed with the first gear, a first space in which the first and second gears are arranged is connected to a second space in which the motor is arranged, and the transmission mechanism does not include a bearing for supporting the motor shaft between the first space and the second space, and does not include a seal for blocking the inflow of oil between the first space and the second space.

4. A power transmission device as claimed in claim 2 or 3, wherein the transmission mechanism further comprises: a counter shaft on which the second gear is mounted and which has the same rotational axis as the second gear; a third gear having an outer diameter smaller than that of the second gear, mounted on the counter shaft and arranged concentrically with the second gear; and a fourth gear having an outer diameter larger than that of the third gear, having a rotational axis parallel to that of the third gear and meshing with the third gear; wherein the counter shaft is arranged such that, when viewed from the axial direction of the motor shaft, the rotational axis of the counter shaft is located below a line connecting the rotational axes of the motor shaft and the fourth gear in the vertical direction; and wherein the second gear is immersed in the oil accumulated in the bottom of the case.

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