Vehicular drive apparatus

Abstract

A rear transaxle 1 is provided, in a casing, with: left and right output shafts that are respectively connected to drive shafts 7, 8 located on the left and right of a vehicle and that are arranged on the same axial line; a counter shaft 20 that is disposed radially apart from and in parallel to the output shafts; a differential device 4 interposed between the right and left output shafts; and a parking lock mechanism 51. The parking lock mechanism 51 has a parking gear 52 integrally formed with a counter driven gear 22 disposed on the counter shaft 20 in a first gear group, and a sprag 31 that restricts rotation of the output shafts by restricting rotation of the parking gear 52 through engagement with the parking gear 52.

Description

Vehicle drive unit

[0001] The present invention relates to a drive unit for driving a vehicle equipped with a differential gear.

[0002] As a drive unit for driving the left and right wheels of a vehicle, a drive source such as a motor, a reduction gear, and a differential gear have been developed as a unit. For example, in the drive unit described in Patent Document 1, an electric motor is built into the rear transaxle of a vehicle that has a differential gear. The output shaft of the electric motor is arranged coaxially with the output shaft of the rear transaxle.

[0003] The reducer has a countershaft (intermediate shaft) arranged parallel to the drive shaft within the casing, and a pair of gears between the motor output shaft and the countershaft, and between the countershaft and a differential case. In the drive unit of Patent Document 1, the motor output shaft is reduced in speed by two sets of gears via the countershaft to drive the differential case. This allows a single motor to transmit driving force while allowing differential movement between the left and right output shafts. Placing the motor coaxially with the output shaft allows for a compact configuration.

[0004] Also known is a transaxle equipped with a parking lock mechanism. The parking lock mechanism includes, for example, a parking gear in the power path within the transaxle and a lock mechanism that meshes with the parking gear to restrict rotation.

[0005] JP 2014-101959 A

[0006] However, as described above, a transaxle equipped with a parking lock mechanism has a problem in that the parking gear and lock mechanism are located inside the trunk axle casing, which makes the transaxle large and reduces its mountability in a vehicle. The present invention has been made in consideration of these problems, and its object is to provide a compact vehicle drive unit equipped with an electric motor and a parking lock mechanism.

[0007] In order to achieve the above object, the vehicle drive device of the present invention is a vehicle drive device including, within a casing, a motor, an output shaft including a first output shaft and a second output shaft each connected to a drive shaft that drives a wheel of the vehicle and arranged coaxially, an intermediate shaft arranged parallel to the output shaft and spaced apart in the radial direction, a differential device interposed between the first output shaft and the second output shaft, a reducer that reduces the output of the motor and inputs it to the differential device, and a parking lock mechanism that restricts rotation of the output shaft, wherein the motor output shaft that is the output shaft of the motor is formed hollow, and the second output shaft is disposed inside the motor. the motor is arranged rotatably with respect to the motor output shaft, the motor is arranged side by side with the differential device and the drive shaft in the axial direction with the reducer in between, the reducer has a pair of first gear groups provided on the motor output shaft and the intermediate shaft, and a pair of second gear groups provided between the intermediate shaft and the differential device, and the parking lock mechanism has a parking gear formed integrally with an intermediate shaft gear arranged on the intermediate shaft in the first gear group, and a locking member that locks with the parking gear to restrict rotation of the parking gear, thereby restricting rotation of the output shaft.

[0008] In the vehicle drive device of the present invention, the parking gear in the parking lock mechanism is configured integrally with the intermediate shaft gear arranged on the intermediate shaft of the reducer, so the vehicle drive device including the parking lock mechanism can be configured compactly in the axial direction.

[0009] FIG. 1 is a perspective view showing the outer shape of a rear transaxle according to this embodiment; FIG. 2 is a perspective view showing the internal structure of a rear transaxle according to this embodiment; FIG. 3 is a cross-sectional view showing the internal structure of a rear transaxle according to this embodiment; FIG. 4 is an explanatory diagram showing the structure of a parking lock mechanism; FIG. 5 is an explanatory diagram showing the structure of a support portion of a sprag in the parking lock mechanism; FIG. 6 is a structural diagram of sprags of the parking lock mechanism and their drive portion; FIG. 7 is a structural diagram of sprags of the parking lock mechanism and their drive portion.

[0010] An embodiment of a vehicle drive system embodying the present invention will now be described. FIG. 1 is a perspective view showing the exterior of a rear transaxle 1, which is a vehicle drive system according to one embodiment of the present invention. FIG. 2 is a perspective view showing the internal structure of the rear transaxle 1. FIG. 3 is a cross-sectional view showing the internal structure of the rear transaxle 1. Note that the rear transaxle 1 will be described below with reference to the vehicle direction when mounted on a vehicle.

[0011] 1 and 2, rear transaxle 1 is disposed between the left and right rear wheels of a vehicle and includes an electric motor 2, a reduction gear 3, and a differential 4. A right drive shaft 7 (drive shaft) that drives the right wheels of the vehicle and a left drive shaft 8 (drive shaft) that drives the left wheels of the vehicle are connected to rear transaxle 1. Rear transaxle 1 transmits driving force from electric motor 2 to the right and left rear wheels via right and left drive shafts 7 and 8, respectively, while allowing differential rotation between the right and left rear wheels.

[0012] The rear transaxle 1 is also provided with an inverter 10 that controls the drive of the electric motor 2. The inverter 10 is disposed adjacent to the electric motor 2. The rear transaxle 1 is configured in the shape of a rectangular box, with the electric motor 2, the reduction gear 3, the differential device 4, and the inverter 10 all assembled together.

[0013] The rear transaxle 1 includes output shafts including a right output shaft 12 (first output shaft) extending rightward from the differential 4 and a left output shaft 13 (second output shaft) extending leftward from the differential. The right output shaft 12 is formed integrally with the right drive shaft 7, and one end (left end) is connected to the differential 4. The left output shaft 13 has one end (right end) connected to the differential 4 and the other end (left end) connected to the left drive shaft 8. The right output shaft 12 and the left output shaft 13 are arranged coaxially side by side. The rear transaxle 1 also includes a countershaft 20 (intermediate shaft) parallel to the left output shaft 13 and spaced apart in the radial direction (hereinafter simply referred to as the "radial direction"). The countershaft 20 extends left-right so that its axial position overlaps with the right end of the left output shaft 13 and the differential 4.

[0014] The electric motor 2 is arranged on the left side of the differential device 4, aligned along the axial direction of the differential device 4 and the left output shaft 13 (hereinafter simply referred to as the "axial direction"). A rotor shaft 15 (motor output shaft), which is the output shaft of the electric motor 2, is formed hollow, and the left output shaft 13 is inserted inside so that they can rotate relative to each other. A motor drive gear unit 21 (first gear group, biasing means), which is a helical gear, is formed on the right end of the rotor shaft 15.

[0015] A counter driven gear 22 (first gear group, intermediate shaft gear, biasing means), which is a helical gear that meshes with the motor drive gear section 21, is fixed to the left end of the counter shaft 20. A final drive gear section 23 (second gear group), which is, for example, a helical gear, is formed at the right end of the counter shaft 20. The final drive gear section 23 is configured to mesh with a final driven gear 25 (second gear group) that is fixed to a differential case 24, which is a power input portion of the differential device 4. The counter shaft 20, the motor drive gear section 21, the counter driven gear 22, the final drive gear section 23, and the final driven gear 25 form the reducer 3. The output of the electric motor 2 is transmitted from the rotor shaft 15 to the motor drive gear section 21, the counter driven gear 22, the counter shaft 20, the final drive gear section 23, and the final driven gear 25 in that order, and is input to the differential device 4, and then output to the right output shaft 12 and the left output shaft 13.

[0016] The casing 11 of the rear transaxle 1 has a four-part structure, consisting of, lined up in the axial direction from the left side, a first casing 31, a second casing 32, a third casing 33, and a fourth casing 34. The first casing 31 is shaped like a lid that covers the left side of the electric motor 2, the second casing 32 houses the electric motor 2, the motor drive gear unit 21, and the counter driven gear 22, the third casing 33 houses the final drive gear unit 23 and the final driven gear 25, and the fourth casing 34 houses the differential device 4 and also serves as the right side wall of the casing 11.

[0017] The second casing 32 is provided with a first partition wall 37 that partitions the internal space of the casing 11 between the electric motor 2 and the motor drive gear unit 21 and between the inverter 10 and the counter driven gear 22. The third casing 33 is provided with a second partition wall 38 (center plate) that partitions the internal space of the casing 11 between the motor drive gear unit 21 and the counter driven gear 22 and between the final drive gear unit 23 and the final driven gear 25. The second partition wall 38 is provided with a through hole through which the left output shaft 13 passes.

[0018] A first bearing 41 (first bearing) that rotatably supports the left end portion of the left output shaft 13 and a second bearing 42 (second bearing) that rotatably supports the left end portion of the rotor shaft 15 are fixed to the first casing 31. The first bearing 41 and the second bearing 42 are arranged adjacent to each other in the axial direction. A third bearing 43 that rotatably supports the left end portion of the countershaft 20 is fixed to the first partition wall 37 of the second casing 32. A fourth bearing 44 (third bearing) that rotatably supports the right end portion of the rotor shaft 15 and a fifth bearing 45 that rotatably supports the left end portion of the differential case 24 are fixed to the second partition wall 38 of the third casing 33. The fourth bearing 44 is arranged on the left side of the second partition wall 38. The fifth bearing 45 is arranged on the right side of the second partition wall 38. A sixth bearing 46 that rotatably supports the right end of the countershaft 20 and a seventh bearing 47 that rotatably supports the right end of the differential case 24 are fixed to the fourth casing 34.

[0019] The counter driven gear 22 has a recessed rightward center (axial center) on its left side (one side), and a third bearing 43 that supports the left end of the counter shaft 20 is disposed in the recessed portion.

[0020] Figure 4 is an explanatory diagram showing the structure of the parking lock mechanism 51, and is a view of the rear transaxle 1 from the right side, excluding the third casing 33 and the fourth casing 34. Figure 5 is an explanatory diagram showing the structure of the support portion of the sprags 53 (locking members) in the parking lock mechanism 51, and is a cross-sectional view of the rear transaxle 1 taken along line A-A in Figure 4. Figures 6 and 7 are structural diagrams of the sprags 53 of the parking lock mechanism 51 and their drive portion.

[0021] The rear transaxle 1 is provided with a parking lock mechanism 51. The parking lock mechanism 51 is made up of a parking gear 52 formed integrally with the counter driven gear 22, claw-shaped sprags 53 that mesh with the parking gear 52 to prevent rotation of the parking gear 52, a spring (not shown) that biases the sprags 53 in a direction to disengage from the parking gear 52, a parking rod 55 that moves the sprags 53 toward the parking gear 52, and an actuator 56 that actuates the parking rod 55.

[0022] The sprags 53 are rod-shaped plates having one end with a claw 53a that meshes with the parking gear 52, and the other end is rotatably supported on the casing 11 by a pin 57. The pin 57 extends in the axial direction of the countershaft 20, and both ends are supported by a boss 58 provided on the first partition wall 37 of the second casing 32 and a boss 59 provided on the second partition wall 38 of the third casing 33.

[0023] The parking rod 55 extends downward in a tangential direction of the parking gear 52 and is provided with a roller 60 rotatably supported at its tip and abutting against the back surface 53 b of the claw portion 53 a of the sprag 53 .

[0024] A guide 61 that determines the movement direction of the roller 60 is fixed to the casing 11. The guide 61 is disposed radially outward of the position where the claws 53a of the sprags 53 engage with the parking gear 52. The guide 61 is sandwiched between a boss 62a provided on the first partition wall 37 of the second casing 32 and a boss 63a provided on the second partition wall 38 of the third casing, and between a boss 62b provided on the first partition wall 37 of the second casing 32 and a boss 63b provided on the second partition wall 38 of the third casing. The guide 61 is supported at two locations by a pin 64a whose opposite ends are supported by the bosses 62a and 63a, and a pin 64b whose opposite ends are supported by the bosses 62b and 63b. The pins 64a and 64b extend in the axial direction of the countershaft 20.

[0025] The guide 61 is formed, for example, by bending a plate member into a U-shape, and is arranged with its opening facing the parking gear 52, with the roller 60 disposed inside. The guide 61 is arranged to contact the side of the roller 60 opposite to the contact surface with the sprag 53, and is configured to contact the roller 60 so as to restrict movement of the roller 60 and the parking rod 55 other than axial movement of the parking rod 55 (movement in the up and down direction).

[0026] The inner wall surface of the guide 61 is inclined downward in the tangential direction of the parking gear 52 so as to approach the parking gear 52. Furthermore, the back surfaces 53b of the claw portions 53a of the sprags 53, which are the portions with which the rollers 60 come into contact, are inclined downward outward in the radial direction of the parking gear 52.

[0027] An actuator 56 installed in the casing 11 moves the parking rod 55 axially via a link 65, thereby switching between a locked state in which the roller 60 presses the sprag 53 to engage the claw portion 53a with the parking gear 52 and lock the parking gear 52, and an unlocked state in which the roller 60 reduces the pressure on the sprag 53 to release the engagement between the claw portion 53a and the parking gear 52.

[0028] The actuator 56 is disposed on the right side of the second partition wall 38. The operation of the actuator 56 is controlled by a control unit (not shown). The rear transaxle 1 is also provided with an oil passage for circulating oil for cooling the electric motor 2, and with an oil pump 85 for circulating oil through the oil passage.

[0029] The oil pump 85 is disposed to the right of the second partition wall 38, and is disposed next to the actuator 56 above the actuator 56. The actuator 56 and the oil pump 85 are disposed in front of the differential device 4 so as to overlap in the axial direction. With the second partition wall 38 in between, the parking lock mechanism 51 such as the sprags 53 is disposed on the left side, and the oil pump 85 is disposed next to the actuator 56 on the right side.

[0030] As described above, the rear transaxle 1 of this embodiment is configured by incorporating the inverter 10 , the electric motor 2 , the speed reducer 3 , the differential device, and the parking lock mechanism 51 into the casing 11 .

[0031] The rotor shaft 15, which is the output shaft of the electric motor 2, and the right output shaft 12 and left output shaft 13, which are output shafts of the rear transaxle 1, are arranged coaxially. The speed reducer 3 has a countershaft 20 that is parallel to the left output shaft 13 and separated radially (rearward) from them.

[0032] The reduction gear 3 protrudes rearward from the electric motor 2 on the right side thereof, so that the electric motor 2 and the reduction gear 3 are arranged in an L-shape when viewed from above, and the inverter 10 is arranged behind the electric motor 2. As a result, the rear transaxle 1 is configured in a rectangular shape when viewed from above.

[0033] The parking lock mechanism 51 has a parking gear 52, sprags 53, and a parking rod 55. The parking gear 52 is integral with the counter driven gear 22 disposed on the countershaft 20. The sprags 53 and the parking rod 55 are disposed at approximately the same axial position as the parking gear 52, adjacent to and rear of the parking gear 52, and to the right of the inverter 10.

[0034] Integrating the parking gear 52 and the counter driven gear 22 reduces the installation space for the parking gear 52 and the axial length of the countershaft 20. Furthermore, by locating the sprags 53 and the parking rod 55 behind the parking gear 52 and to the right of the inverter 10, the rear transaxle 1 including the parking lock mechanism 51 can be configured in a compact rectangular box shape, improving mountability in a vehicle.

[0035] Furthermore, the counter driven gear 22, which is integral with the parking gear 52, has a recess in the axial center portion of its left side surface, and a third bearing 43 that supports the left end of the counter shaft is disposed in this recess, with the third bearing 43 and the teeth of the counter driven gear 22 overlapping in the axial direction. This allows the counter driven gear 22 to be positioned further to the left than in a configuration in which, for example, the third bearing 43 and the counter driven gear 22 are arranged side by side in the axial direction. This therefore shortens the axial length of the counter shaft, and allows the final drive gear portion 23, the final driven gear 25, and the differential device 4 to be positioned further left (towards the inverter 10), thereby shortening the left-right length of the rear transaxle 1.

[0036] In addition, the second bearing 42, which is fixed to the first casing 31 and supports the left end of the rotor shaft 15, is a ball bearing with a snap ring and has a step on the rotor shaft 15, so that the rotor shaft 15 is restricted from moving leftward relative to the first casing 31 via the second bearing 42.

[0037] In addition, the counter driven gear 22 and the motor drive gear portion 21 are helical gears, and are configured so that when the vehicle is rotating forward, that is, when the vehicle is traveling forward, the motor drive gear portion 21 is urged leftward by a reaction force.

[0038] As a result, rotor shaft 15 is urged leftward during forward rotation, and leftward movement is restricted via second bearing 42, thereby positioning rotor shaft 15 in the axial direction relative to casing 11. This makes it possible to suppress axial wobble of rotor shaft 15. Furthermore, because a large thrust force is not applied to fourth bearing 44, which supports the right end of rotor shaft 15, fourth bearing 44 is a roller bearing.

[0039] The radial dimension can be reduced by using a roller bearing for the fourth bearing 44. The reduction in size of the fourth bearing 44 allows the parking gear 52, which is fixed to the countershaft 20, to be positioned coaxially with the fourth bearing 44.

[0040] If the fourth bearing 44 were a ball bearing capable of applying thrust force rather than a roller bearing, it would become larger in the radial direction. Therefore, in order to prevent interference with the parking gear 52, the fourth bearing 44 would have to be positioned to the left of the parking gear 52, which would mean that the differential device 4 would be positioned to the right, and the left-right length of the rear transaxle 1 would become longer.

[0041] In this embodiment, by positioning the parking gear 52 coaxially with the fourth bearing 44, the fourth bearing 44 and the second partition wall 38 can be positioned further to the left, and the differential device 4 can be positioned further to the left, thereby shortening the left-right length of the rear transaxle 1.

[0042] In addition, in the parking lock mechanism 51, when the sprag 53 is engaged with the parking gear 52, the guide 61 receives a reaction force via the roller 60, but the pins 64a and 64b that support the guide 61 and the pin 57 that rotatably supports the sprag 53 are structured so that both ends are supported by the first partition wall 37 and the second partition wall 38.

[0043] In this embodiment, as described above, by moving the second partition wall 38 to the left and shortening the distance between it and the first partition wall 37, the strength of the support structure for the sprags 53 and the guide 61 can be improved.

[0044] The rear transaxle 1 is also equipped with an oil pump 85 for circulating cooling oil. The oil pump 85 is positioned axially overlapping the differential device 4 in front of it, and is positioned on the right side of the second partition wall 38, thereby preventing the oil pump 85 from protruding outward, and allowing the rear transaxle 1 including the oil pump 85 to be configured in a compact rectangular box shape.

[0045] Furthermore, the sprags 53 in the parking lock mechanism 51 are configured to be pushed and moved by rollers 60 rotatably supported at the tip of the parking rod 60, and the rollers 60 and the sprags 53 are in rolling contact with each other, which reduces resistance when moving the sprags 53. This reduces the driving force required to drive the parking rod 55, and allows the actuator 56 for driving the parking rod 60 to be made smaller.

[0046] In addition, the back surfaces 53b of the sprags 53 with which the rollers 60 come into contact are inclined with respect to the tangent to the parking gear 52. This allows the parking rod 60 to be installed close to the parking gear 52 and to extend at an angle close to the tangent to the parking gear 52. In this embodiment, the sprags 53 are installed rearward of the parking gear 52, but the parking rod 60 can be installed in a longitudinal position close to the parking gear 52 and extending substantially in the vertical direction, allowing the rear transaxle 1 including the parking lock mechanism 51 to be made more compact in the longitudinal direction.

[0047] Since the roller 60 is designed to push the back surface 53b of the inclined sprag 53, the reaction force, i.e., the parking release operation force, received by the parking rod 60 varies depending on the direction and position of movement of the roller 60. However, by controlling the operation of the actuator 56, the impact on the driver's physical sensation can be reduced.

[0048] The present invention is not limited to the above embodiment, and can be modified within the scope of the invention. In this embodiment, the present invention is applied to a rear transaxle 1, but it can also be applied to a front transaxle that drives the front wheels of a vehicle.

[0049] 1. Rear transaxle (vehicle drive device) 2. Electric motor (motor) 3. Reducer 4. Differential 7. Right drive shaft (drive shaft) 8. Left drive shaft (drive shaft) 11. Casing 12. Right output shaft (first output shaft) 13. Left output shaft (second output shaft) 15. Rotor shaft (motor output shaft) 20. Counter shaft (intermediate shaft) 21. Motor drive gear section (first gear group, biasing means) ← Is this not the counter drive gear section? 22 Counter driven gear (first gear group, intermediate shaft gear, biasing means) 23 Final drive gear portion (second gear group) 25 Final driven gear (second gear group) 37 First partition wall 38 Second partition wall 42 Second bearing (second bearing) 43 Third bearing (first bearing) 44 Fourth bearing (third bearing) 51 Parking lock mechanism 52 Parking gear 53 Sprag (locking member) 57 Pin 55 Parking rod 60 Roller

Claims

1. A vehicle drive device comprising: a motor housed within a casing; an output shaft including a first output shaft and a second output shaft, each connected to a drive shaft that drives a vehicle wheel and arranged coaxially; an intermediate shaft arranged parallel to and spaced apart from the output shaft in the radial direction; a differential device interposed between the first output shaft and the second output shaft; a speed reducer that reduces the output of the motor and inputs it to the differential device; and a parking lock mechanism that restricts rotation of the output shaft, wherein the motor output shaft, which is the output shaft of the motor, is formed hollow, and the second output shaft is arranged inside so as to be rotatable relative to the motor output shaft, the motor is arranged side by side with the speed reducer in the axial direction of the differential device and the drive shaft, and the speed reducer has a pair of first gear groups provided on the motor output shaft and the intermediate shaft, and a pair of second gear groups provided between the intermediate shaft and the differential device, the parking lock mechanism includes: a parking gear integrally formed with an intermediate shaft gear arranged on the intermediate shaft in the first gear group; and a locking member that locks with the parking gear to restrict rotation of the parking gear and thereby restricts rotation of the output shaft.

2. The vehicle drive device according to claim 1, characterized in that one side of the axial center portion of the intermediate shaft gear is curved to form a recess, a first bearing that supports the intermediate shaft relative to the casing is disposed in the recess, and the teeth portion of the intermediate shaft gear and the first bearing are disposed so as to overlap in the axial direction.

3. A vehicle drive device as claimed in claim 1 or 2, characterized in that it comprises: a second bearing that rotatably supports one end of the motor output shaft relative to the casing and restricts axial movement of the motor output shaft; a third bearing that rotatably supports the other end of the motor output shaft on the differential device side relative to the casing; and biasing means that biases the motor output shaft towards the second bearing when the motor output shaft rotates.

4. A vehicle drive device according to claim 3, characterized in that the second bearing is a ball bearing with a snap ring, the third bearing is a roller bearing, and the biasing means is constituted by the first gear group which is a helical gear.

5. A vehicle drive device as described in any one of claims 1 to 4, characterized in that the casing has a first partition wall arranged between the motor and the first gear group, and a second partition wall arranged between the first gear group and the differential device, and the locking member is arranged between the first partition wall and the second partition wall and is rotatably supported by a pin whose both ends are supported by the first partition wall and the second partition wall.

6. A vehicle drive device according to any one of claims 1 to 4, characterized in that the parking lock mechanism has a parking rod that pushes the locking member and moves it towards the parking gear, and a roller that abuts against the locking member and pushes the locking member is rotatably supported at the end of the parking rod.

7. The vehicle drive device according to claim 6, wherein the contact surface of the locking member with the roller is inclined with respect to a tangent line of the parking gear.

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