Differential speed reduction device and electric drive device

Abstract

[Problem] To provide a differential speed reduction device and an electric drive device capable of suppressing increases in size and weight of a device while using a helical gear to form a speed reduction mechanism. [Solution] A differential speed reduction device 4 includes: a differential mechanism 5 for distributing driving force to a first shaft part 611 and a second shaft part 711; a first speed reduction mechanism 6; and a second speed reduction mechanism 7. The differential mechanism 5 has a first output gear 51 and a second output gear 52. The first speed reduction mechanism 6 has a first input gear 612, and the second speed reduction mechanism 7 has a second input gear 712. The first shaft part 611 is helical-spline-fitted to the first output gear 51, and the second shaft part 711 is helical-spline-fitted to the second output gear 52. The twist direction of the helical spline of the first shaft part 611 is the same as the twist direction of a helical tooth 612a of the first input gear 612, and the twist direction of the helical spline of the second shaft part 711 is the same as the twist direction of a helical tooth 712a of the second input gear 712.

Description

Differential reduction gear and electric drive device

[0001] The present invention relates to a differential reduction gear device having a differential mechanism and a reduction mechanism, and an electric drive device equipped with the differential reduction gear device.

[0002] Conventionally, drive devices described in Patent Documents 1 and 2 are known as electric drive devices for driving the left and right wheels on the front or rear side of a vehicle. The drive devices described in Patent Documents 1 and 2 include a motor consisting of a stator and a rotor that generates torque when supplied with current, a differential mechanism that distributes the motor torque to a pair of output shafts while allowing differential rotation, and a pair of planetary gear mechanisms that decelerate the rotation of the pair of output shafts to amplify the torque. The planetary gear mechanism includes a plurality of planetary gears arranged around the output shaft, a ring gear that meshes with the plurality of planetary gears, and a carrier that rotatably supports the plurality of planetary gears.

[0003] Japanese Patent Application Laid-Open No. 7-75285 Japanese Patent Application Laid-Open No. 2020-67183

[0004] It is desirable to use helical gears for planetary gears, which have higher meshing efficiency than spur gears. However, if the planetary gears are made up of helical gears, thrust forces in the axial direction are generated due to meshing reaction forces. This necessitates increased strength of the bearings that support the components of the planetary gear mechanism and the support members that support the bearings. This leads to an increase in the size and weight of the device.

[0005] Therefore, an object of the present invention is to provide a differential reduction gear and an electric drive device that can suppress increases in size and weight of the device even when the reduction mechanism is configured using helical gears.

[0006] In order to achieve the above object, the present invention provides a differential mechanism that outputs an input driving force of a vehicle while allowing differential motion from a first shaft portion and a second shaft portion, a first reduction mechanism that reduces the rotation speed of the first shaft portion, and a second reduction mechanism that reduces the rotation speed of the second shaft portion, wherein the differential mechanism has a first output gear that rotates integrally with the first shaft portion and a second output gear that rotates integrally with the second shaft portion, the first reduction mechanism has a first input gear having helical teeth on its outer periphery whose tooth trace is inclined with respect to the axial direction, the second reduction mechanism has a second input gear having helical teeth on its outer periphery whose tooth trace is inclined with respect to the axial direction, and the first shaft portion has a first output gear. the second shaft portion has a first fitting portion that helically spline-fits with one of the first output gear and the first input gear and is integrated with the other of the first output gear and the first input gear, the second shaft portion has a second fitting portion that helically spline-fits with one of the second output gear and the second input gear and is integrated with the other of the second output gear and the second input gear, the twist direction of the helical spline at the first fitting portion is the same as the twist direction of the helical teeth of the first input gear, and the twist direction of the helical spline at the second fitting portion is the same as the twist direction of the helical teeth of the second input gear.

[0007] In addition, in order to achieve the above-mentioned object, the present invention provides an electric drive device comprising the above-mentioned differential reduction gear, a device case that houses the differential mechanism, the first reduction mechanism, and the second reduction mechanism, and a motor that generates a driving force that is input to the differential mechanism.

[0008] According to the differential reduction gear device and electric drive device of the present invention, it is possible to suppress an increase in the size and weight of the device even though the reduction mechanism is configured using helical gears.

[0009] FIG. 1 is a cross-sectional view showing an electric drive unit according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing a first input shaft, a second input shaft, a plurality of first planetary gears, and a plurality of second planetary gears, together with a portion of each of a first output gear and a second output gear. FIG. 3 is a schematic diagram showing the relationship between the axial thrust force acting on the first fitting portion of the first input shaft and the axial thrust force acting on the first input gear when a vehicle accelerates forward. FIG. 4 is a cross-sectional view showing an electric drive unit according to a second embodiment. FIG. 5 is a cross-sectional view showing an electric drive unit according to a third embodiment. FIG. 6 is a cross-sectional view of the differential mechanism taken along line A-A in FIG. 5. FIG. 7 is a perspective cross-sectional view showing a portion of the differential mechanism.

[0010] [First embodiment] A first embodiment of the present invention will be described with reference to Figures 1 to 3. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technically preferable technical matters, the technical scope of the present invention is not limited to this specific embodiment.

[0011] FIG. 1 is a cross-sectional view showing an electric drive unit 1 according to a first embodiment of the present invention. The electric drive unit 1 includes a device case 2, and a motor 3 and a differential reduction gear 4 housed in the device case 2. The electric drive unit 1 is mounted on a vehicle and drives left and right wheels on the front or rear wheels side. The device case 2 is fixed to the vehicle body so as not to rotate. The motor 3 is a drive source for running the vehicle. The torque generated by the motor 3 becomes the drive force that drives the left and right wheels.

[0012] 1, as an example, the left side of the drawing corresponds to the left side in the vehicle width direction when the electric drive unit 1 is mounted on the vehicle, and the right side of the drawing corresponds to the right side in the vehicle width direction when the electric drive unit 1 is mounted on the vehicle. Hereinafter, for convenience of explanation, the terms "left" and "right" may be used, but these "left" and "right" do not limit the left and right directions when the electric drive unit 1 is mounted on the vehicle.

[0013] The device case 2 has first to fourth case members 21 to 24. The first to fourth case members 21 to 24 are fastened to one another by a plurality of bolts 25. The first case member 21 is disposed in the center of the device case 2 in the left-right direction and opens toward the right. The second case member 22 is disposed to the right of the first case member 21 so as to cover the opening of the first case member 21. The third case member 23 is disposed to the left of the first case member 21. The fourth case member 24 is disposed to the right of the second case member 22.

[0014] The interior of the device case 2 is partitioned into first to third storage spaces 201 to 203 by a first partition wall 211 provided in the first case member 21 and a second partition wall 221 provided in the second case member 22. The first storage space 201 is the space on the left side of the first partition wall 211. The second storage space 202 is the space on the right side of the second partition wall 221. The third storage space 203 is the space between the first partition wall 211 and the second partition wall 221.

[0015] The motor 3 has a stator 31 fixed to the device case 2 and a rotor 32 arranged inside the stator 31. The stator 31 has a stator core 311 and a winding 312. The stator core 311 is a laminated body formed by stacking a plurality of electromagnetic steel sheets. The winding 312 is wound around the stator core 311 and generates a rotating magnetic field in the stator core 311 by current supplied from an inverter (not shown). The stator 31 is housed in the third housing space 203 and fixed to the inner surface of the first case member 21.

[0016] The rotor 32 has a rotor core 321 and a plurality of magnets 322. The rotor core 321 is a laminated body formed by stacking a plurality of electromagnetic steel plates. The magnets 322 are held in holding holes 321a formed in the rotor core 321. When a current is supplied to the windings 312 of the stator 31, the rotor 32 rotates relative to the stator 31 with a torque corresponding to the magnitude of the current.

[0017] The differential reduction gear device 4 includes a differential mechanism 5, a first reduction mechanism 6, a second reduction mechanism 7, and bearings 80 to 89 that smooth the rotation of each part of the differential reduction gear device 4. The first reduction mechanism 6 is housed in a first housing space 201. The second reduction mechanism 7 is housed in a second housing space 202. The differential mechanism 5 is housed in a third housing space 203.

[0018] Bearings 80 to 89 are rolling bearings with multiple rolling elements disposed between an inner ring and an outer ring. In Fig. 1, bearings 80 to 89 are shown as ball bearings with spherical rolling elements. However, bearings 80 to 89 are not limited to ball bearings and may be, for example, tapered roller bearings or needle roller bearings.

[0019] The differential mechanism 5 outputs the driving force input from the motor 3 while allowing differential rotation between the first shaft 611 and the second shaft 711. The first reduction gear mechanism 6 reduces the rotation of the first shaft 611 and outputs it. The second reduction gear mechanism 7 reduces the rotation of the second shaft 711 and outputs it. The first partition wall 211 has an insertion hole 210 through which the first shaft 611 is inserted. The second partition wall 221 has an insertion hole 220 through which the second shaft 711 is inserted. In the present embodiment, the first shaft 611 is a part of the first input shaft 61 that constitutes the first reduction gear mechanism 6, and the second shaft 711 is a part of the second input shaft 71 that constitutes the second reduction gear mechanism 7.

[0020] The differential mechanism 5 includes a first output gear 51 that rotates integrally with the first shaft portion 611, a second output gear 52 that rotates integrally with the second shaft portion 711, a pair of pinion gears 53 that mesh with the first output gear 51 and the second output gear 52, a pinion shaft 54 ​​that rotatably supports the pair of pinion gears 53, and a rotating case 55. The device case 2 houses and rotatably supports the rotating case 55. The first output gear 51, the second output gear 52, and the pair of pinion gears 53 are bevel gears that are housed in the rotating case 55. That is, in this embodiment, the differential mechanism 5 is of a bevel gear type. The pinion shaft 54 ​​has both ends held by the rotating case 55 and is disposed perpendicular to the rotation axis O of the rotating case 55. Hereinafter, the direction parallel to the rotation axis O will be referred to as the axial direction.

[0021] The rotating case 55 has a first wall portion 551 on the left side, a second wall portion 552 on the right side, and a cylindrical peripheral wall portion 553 provided between the first wall portion 551 and the second wall portion 552. The first wall portion 551 is aligned with the first output gear 51 in the axial direction on the left side of the pinion shaft 54, and the second wall portion 552 is aligned with the second output gear 52 in the axial direction on the right side of the pinion shaft 54.

[0022] The first output gear 51 and the second output gear 52 are housed between a first wall portion 551 and a second wall portion 552, and are capable of relative rotation coaxially around the rotation axis O of the rotating case 55. Movement of the first output gear 51 in the rotating case 55 in a direction away from the second output gear 52, and movement of the second output gear 52 in the rotating case 55 in a direction away from the first output gear 51, are restricted by the rotating case 55.

[0023] A first side washer 56 is disposed between the first output gear 51 and the first wall portion 551. A second side washer 57 is disposed between the second output gear 52 and the second wall portion 552. A pinion washer 58 is disposed between each of the pair of pinion gears 53 and the peripheral wall portion 553.

[0024] The first output gear 51 has a fitting hole 510 into which a first fitting portion 610, which is a part of the first shaft portion 611, is helical spline fitted. The second output gear 52 has a fitting hole 520 into which a second fitting portion 710, which is a part of the second shaft portion 711, is helical spline fitted. Details of the configurations of the first fitting portion 610, the second fitting portion 710, and the fitting holes 510 and 520 will be described later.

[0025] The rotating case 55 is accommodated in the third accommodation space 203 of the device case 2. The rotor 32 is fixed to the outer periphery of a peripheral wall portion 553 of the rotating case 55, and the rotating case 55 rotates integrally with the rotor 32. Torque generated by the motor 3 is input to the rotating case 55 from the rotor 32. The rotating case 55 is rotatably supported relative to the device case 2 by a bearing 80 held by the first partition wall 211 and a bearing 81 held by the second partition wall 221. The motor 3 generates torque that rotates the rotating case 55 relative to the device case 2, as driving force for driving the wheels.

[0026] In this embodiment, the first reduction mechanism 6 and the second reduction mechanism 7 are planetary gear type reduction mechanisms. The first reduction mechanism 6 includes a first input shaft 61, a plurality of first planetary gears 62 arranged on the outer periphery of the first input shaft 61, a first ring gear 63 having an internal tooth portion 631 that meshes with the plurality of first planetary gears 62, a first carrier 64 that rotatably supports the plurality of first planetary gears 62, and a plurality of bearings 65 that rotatably support the plurality of first planetary gears 62 relative to the first carrier 64.

[0027] Similarly, the second reduction mechanism 7 has a second input shaft 71, a plurality of second planetary gears 72 arranged on the outer periphery of the second input shaft 71, a second ring gear 73 having an internal tooth portion 731 that meshes with the plurality of second planetary gears 72, a second carrier 74 that rotatably supports the plurality of second planetary gears 72, and a plurality of bearings 75 that rotatably support the plurality of second planetary gears 72 relative to the second carrier 74.

[0028] The first input shaft 61 has a first shaft portion 611 having a first fitting portion 610 at an end in the axial direction, and a first input gear 612 that meshes with the multiple first planetary gears 62, and the first shaft portion 611 is integrated with the first input gear 612. Here, being integrated means that relative axial movement and relative rotation between the first shaft portion 611 and the first input gear 612 are restricted. In this embodiment, the first shaft portion 611 and the first input gear 612 are integrated. However, this is not a limitation, and the first shaft portion 611 and the first input gear 612 may be integrated by, for example, crimping, bolting, or welding.

[0029] Similarly, the second input shaft 71 has a second shaft portion 711 having a second fitting portion 710 at an end in the axial direction, and a second input gear 712 that meshes with the plurality of second planetary gears 72, and the second shaft portion 711 is integrated with the second input gear 712. In this embodiment, the second shaft portion 711 and the second input gear 712 are integrated.

[0030] The first input shaft 61 is supported rotatably about the rotation axis O relative to the device case 2 by a bearing 82 held by the first partition wall 211 and a bearing 83 held by the first carrier 64. The bearing 82 supports a first shaft portion 611 of the first input shaft 61, and the bearing 83 supports an axial end of the first input shaft 61 opposite to the first fitting portion 610. The first input gear 612 is provided at a position between the bearing 82 and the bearing 83 in the axial direction of the first input shaft 61.

[0031] Similarly, the second input shaft 71 is supported rotatably about the rotation axis O relative to the device case 2 by a bearing 84 held by the second partition wall 221 and a bearing 85 held by the second carrier 74. The bearing 84 supports a second shaft portion 711 of the second input shaft 71, and the bearing 85 supports an axial end of the second input shaft 71 opposite to the second fitting portion 710. The second input gear 712 is provided at a position between the bearing 84 and the bearing 85 in the axial direction of the second input shaft 71.

[0032] The first carrier 64 includes a first carrier body 641, a first carrier cover 642 disposed on the left side of the first carrier body 641, a plurality of support shafts 643 supported between the first carrier body 641 and the first carrier cover 642, and a plurality of bolts 644 fastening the first carrier body 641 and the first carrier cover 642 together. In this embodiment, the first reduction mechanism 6 has three first planetary gears 62, and the first carrier 64 has the same number of support shafts 643 and bolts 644 as the first planetary gears 62. The first planetary gear 62 is hollow cylindrical, and the support shaft 643 is inserted through its center. The bearing 65 is disposed between the first planetary gear 62 and the support shaft 643. In this embodiment, the bearing 65 is a needle roller bearing.

[0033] The second carrier 74 has a configuration similar to that of the first carrier 64, and includes a second carrier body 741, a second carrier cover body 742 arranged on the right side of the second carrier body 741, a plurality of support shafts 743 supported between the second carrier body 741 and the second carrier cover body 742, and a plurality of bolts 744 that fasten the second carrier body 741 and the second carrier cover body 742. The second reduction mechanism 7 has three second planetary gears 72 formed in a hollow cylindrical shape, and the second carrier 74 has the same number of support shafts 743 and bolts 744 as the second planetary gears 72. A bearing 75 made of a needle roller bearing is arranged between the second planetary gears 72 and the support shaft 743.

[0034] The first carrier 64 is rotatably supported with respect to the device case 2 by a bearing 86 and a bearing 87. The bearing 86 supports the first carrier body 641, and the bearing 87 supports the first carrier lid body 642. The first carrier lid body 642 has an output shaft portion 642a at the left end opposite the first carrier body 641 side, and the output shaft portion 642a protrudes to the outside of the device case 2. The first ring gear 63 is disposed inside the third case member 23 and is fixed to the third case member 23 so as not to be rotatable relative to it.

[0035] Similarly, the second carrier 74 has a second carrier body 741 supported by a bearing 88 and a second carrier cover 742 supported by a bearing 89. The second carrier cover 742 has an output shaft 742a at its right end, which protrudes to the outside of the device case 2. The second ring gear 73 is disposed inside the third case member 23 and is fixed to the third case member 23 so as not to be rotatable relative to the third case member 23.

[0036] When the first input shaft 61 rotates together with the first output gear 51, the multiple first planetary gears 62 rotate about the support shaft 643 and revolve about the rotation axis O. The first carrier 64 rotates at a speed reduced from the rotation of the first input shaft 61 by a reduction ratio corresponding to the ratio between the number of teeth of the first input gear 612 and the number of teeth of the first ring gear 63. Furthermore, when the second input shaft 71 rotates together with the second output gear 52, the multiple second planetary gears 72 rotate about the support shaft 743 and revolve about the rotation axis O. The second carrier 74 rotates at a speed reduced from the rotation of the second input shaft 71 by a reduction ratio corresponding to the ratio between the number of teeth of the second input gear 712 and the number of teeth of the second ring gear 73.

[0037] Figure 2 is an explanatory diagram showing the first input shaft 61, the second input shaft 71, the plurality of first planetary gears 62, and the plurality of second planetary gears 72, along with a portion of each of the first output gear 51 and the second output gear 52.

[0038] The first input gear 612 is a helical gear having a plurality of helical teeth 612 a on its outer periphery, the tooth trace of which is inclined with respect to the axial direction. The first planetary gear 62 is a helical gear having a plurality of helical teeth 62 a on its outer periphery that mesh with the plurality of helical teeth 612 a of the first input gear 612. Similarly, the second input gear 712 is a helical gear having a plurality of helical teeth 712 a on its outer periphery, the tooth trace of which is inclined with respect to the axial direction, and the second planetary gear 72 is a helical gear having a plurality of helical teeth 72 a on its outer periphery that mesh with the plurality of helical teeth 712 a of the second input gear 712.

[0039] The first fitting portion 610 of the first shaft portion 611 is formed with a plurality of outer peripheral spline projections 610a extending in a direction inclined with respect to the axial direction. The inner surface of the fitting hole 510 of the first output gear 51 is formed with a plurality of inner peripheral spline projections 510a extending in a direction inclined with respect to the axial direction. The second fitting portion 710 of the second shaft portion 711 is formed with a plurality of outer peripheral spline projections 710a extending in a direction inclined with respect to the axial direction. The inner surface of the fitting hole 520 of the second output gear 52 is formed with a plurality of inner peripheral spline projections 520a extending in a direction inclined with respect to the axial direction.

[0040] In FIG. 2, the twist direction of the plurality of helical teeth 612a of the first input gear 612 when viewed from left to right is indicated by arrow A. １１ The twist direction of the plurality of helical teeth 712a of the second input gear 712 is indicated by arrow A ２１ The twisting direction of the helical spline in the first fitting portion 610, which is the twisting direction of the outer circumferential spline projection 610a, is indicated by an arrow A １２ The twisting direction of the helical spline in the second fitting portion 710, which is the twisting direction of the outer peripheral spline projection 710a, is indicated by arrow A ２２ is shown.

[0041] Arrow A １２ The twisting direction of the helical spline in the first fitting portion 610 indicated by arrow A １１ This is the same as the twist direction of the helical teeth 612a of the first input gear 612 indicated by arrow A. ２２ The twisting direction of the helical spline in the second fitting portion 710 indicated by arrow A ２１ The twist direction of the helical teeth 712a of the second input gear 712 is the same as the twist direction of the helical teeth 712a of the second input gear 712 shown by arrow A. １２ The twisting direction of the helical spline in the first fitting portion 610 indicated by arrow A ２２ The twist direction of the helical spline in the second fitting portion 620 is opposite to that indicated by .

[0042] The twisting direction of the helical spline at the first mating portion 610 and the twisting direction of the helical spline at the second mating portion 710 are the directions in which the first output gear 51 is pressed against the first wall portion 551 and the second output gear 52 is pressed against the second wall portion 552 by the driving force input to the differential mechanism 5 when the vehicle accelerates forward.

[0043] In FIG. 1, the direction of the axial thrust force acting on the first output gear 51 and the first fitting portion 610 due to the helical spline engagement between the first output gear 51 and the first fitting portion 610 when the vehicle accelerates forward is indicated by arrow F. １１ and arrow F １２ The direction of the axial thrust force acting on the second output gear 52 and the second fitting portion 710 due to the helical spline fitting between the second output gear 52 and the second fitting portion 710 is indicated by arrow F. ２１ and arrow F ２２ The arrows F １１ , F １２ , F ２１ , F ２２ The length of represents the magnitude of the thrust force.

[0044] In addition, in FIG. 1, the direction of the axial thrust force acting on the first input gear 612 due to the meshing of the first planetary gears 62 with the first input gear 612 when the vehicle accelerates forward is indicated by arrow F. １３ The direction of the axial thrust force acting on the second input gear 712 due to the meshing of the second planetary gears 72 with the second input gear 712 is indicated by arrow F ２３ is shown.

[0045] 1, in the first input shaft 61, the axial thrust force acting on the first fitting portion 610 and the axial thrust force acting on the first input gear 612 are directed in opposite directions, so these thrust forces cancel each other out. This reduces the load on the bearings 82 and 83 that support the first input shaft 61. In addition, the strength burden on the first partition wall 211 that supports the bearing 82 is also reduced.

[0046] Similarly, in the second input shaft 71, the axial thrust force acting on the second fitting portion 710 and the axial thrust force acting on the second input gear 712 are in opposite directions, so these thrust forces cancel each other out, reducing the load on the bearings 84, 85 that support the second input shaft 71 and also reducing the strength burden on the second partition wall 221 that supports the bearing 84.

[0047] Furthermore, when the vehicle accelerates forward, the first output gear 51 is pressed against the first wall portion 551, and the second output gear 52 is pressed against the second wall portion 552, so that the pressing force received from the first output gear 51 and the pressing force received from the second output gear 52 are balanced in the rotating case 55. This prevents the rotating case 55 from being pressed strongly in one axial direction, reducing the load on the bearings 80 and 81 that support the rotating case 55. Furthermore, the strength burden on the first partition wall 211 that supports the bearing 80 and the strength burden on the second partition wall 221 that supports the bearing 81 are also reduced.

[0048] When the vehicle is decelerating while traveling forward or accelerating while traveling backward, axial thrust forces are generated in each member in the direction opposite to the direction shown in Fig. 1, and the axial thrust force acting on the first fitting portion 610 of the first input shaft 61 and the axial thrust force acting on the first input gear 612 cancel each other out, and the axial thrust force acting on the second fitting portion 710 of the second input shaft 71 cancels out the axial thrust force acting on the second input gear 712. This reduces the load on the bearings 82 to 85 and also reduces the strength burden on the first partition wall 211 and the second partition wall 221.

[0049] Furthermore, when the vehicle is decelerating while traveling forward or accelerating while traveling backward, an axial thrust force acts on the first output gear 51 and the second output gear 52 in a direction toward the pair of pinion gears 53. Therefore, the twist angle, etc. of the inner spline protrusions 510a, 520a is adjusted so that the thrust force acting on the first output gear 51 does not exceed the axial thrust generated in the first output gear 51 due to the meshing between the first output gear 51 and the pair of pinion gears 53, and the thrust force acting on the second output gear 52 does not exceed the axial thrust generated in the second output gear 52 due to the meshing between the second output gear 52 and the pair of pinion gears 53.

[0050] FIG. 3 is a schematic diagram showing the relationship between the axial thrust force acting on the first fitting portion 610 of the first input shaft 61 and the axial thrust force acting on the first input gear 612 when the vehicle accelerates forward.

[0051] FIG. 3 shows one outer peripheral spline projection 610a in the first fitting portion 610, and the twist angle, which is the angle of inclination of this outer peripheral spline projection 610a with respect to the axial direction, is defined as θ １ 3 shows one helical tooth 612a of the first input gear 612, and the helix angle, which is the angle of inclination of this helical tooth 612a with respect to the axial direction, is represented by θ ２ Furthermore, in FIG. 3, the direction and magnitude of the rotational force that the outer peripheral spline projection 610a receives are indicated by arrow R １ The direction and magnitude of the rotational force that the helical tooth 612a receives are indicated by arrow R ２ is shown.

[0052] In the first input shaft 61, the first input gear 612 has a larger diameter than the first fitting portion 610, and the twist angle θ of the helical teeth 612a is set according to this difference in diameter. ２ is the twist angle θ of the outer peripheral spline projection 610a １ This twist angle θ １ and twist angle θ ２ The magnitude relationship between these forces is determined so that the difference between the axial thrust force acting on the first fitting portion 610 and the axial thrust force acting on the first input gear 612 is small.

[0053] In other words, since torque is generally expressed as force x radius of rotation, a larger force acts on the multiple outer peripheral spline protrusions 610a of the first fitting portion 610, which has a relatively small diameter, than on the multiple helical teeth 612a of the first input gear 612, which has a relatively large diameter. １ and twist angle θ ２ When these are equal, the axial thrust force acting on the first fitting portion 610 becomes larger than the axial thrust force acting on the first input gear 612, and the first input shaft 61 as a whole is pressed in the direction of the thrust force acting on the first fitting portion 610.

[0054] In contrast, in this embodiment, the helix angle θ of the helical teeth 612a is ２ is the twist angle θ of the outer peripheral spline projection 610a １ Since the difference between the axial thrust force acting on the first fitting portion 610 and the axial thrust force acting on the first input gear 612 is smaller than the torsion angle θ １ and twist angle θ ２ The load on the bearings 82 to 85 is further reduced than when the loads are equal to each other, and the strength burden on the first partition wall 211 and the second partition wall 221 is also reduced.

[0055] Similarly, for the second input shaft 71, the second input gear 712 has a larger diameter than the second mating portion 710, and the twist angle of the helical teeth 712a in the second input gear 712 is larger than the twist angle of the outer spline protrusions 710a in the second mating portion 710.

[0056] According to the first embodiment described above, even though the first reduction mechanism 6 and the second reduction mechanism 7 are constructed using helical gears, it is possible to prevent the electric drive unit 1 and the differential reduction device 4 from becoming larger and heavier.

[0057] Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. 4. FIG. 4 is a cross-sectional view showing an electric drive unit 1A according to the second embodiment. The electric drive unit 1A includes a device case 2, a motor 3, and a differential reduction gear unit 4A. The differential reduction gear unit 4A includes a differential mechanism 5A, a first reduction gear unit 6A, a second reduction gear unit 7A, and bearings 80-82, 831, 832, 84, 851, 852, and 86-89. In FIG. 4, components and the like that are common to those described in the first embodiment are designated by the same reference numerals as those in FIG. 1, and redundant description will be omitted.

[0058] In the first embodiment, a case has been described in which the first shaft portion 611, which is a part of the first input shaft 61 constituting the first reduction mechanism 6, is helical spline-fitted into the fitting hole 510 of the first output gear 51, and the second shaft portion 711, which is a part of the second input shaft 71 constituting the second reduction mechanism 7, is helical spline-fitted into the fitting hole 520 of the second output gear 52. In the second embodiment, the first shaft portion 511 that transmits driving force from the differential mechanism 5A to the first reduction mechanism 6A is integrated with the first output gear 51, and a first fitting portion 512 provided at an axial end of the first shaft portion 511 is helical spline-fitted into the fitting hole 613 formed in the center of the first input gear 612 that is formed in a cylindrical shape. In addition, in the second embodiment, the second shaft portion 521 that transmits driving force from the differential mechanism 5A to the second reduction mechanism 7A is integrated with the second output gear 52, and the second fitting portion 522 provided at the axial end of the second shaft portion 521 is helically spline fitted into a fitting hole 713 formed in the center of the cylindrically formed second input gear 712.

[0059] In the first reduction gear mechanism 6A, the first input gear 612 is rotatably supported by a pair of bearings 831 and 832 held by the first carrier 64. One bearing 831 is held by the first carrier body 641, and the other bearing 832 is held by the first carrier cover 642. In the second reduction gear mechanism 7A, the second input gear 712 is rotatably supported by a pair of bearings 851 and 852 held by the second carrier 74. One bearing 851 is held by the second carrier body 741, and the other bearing 852 is held by the second carrier cover 742.

[0060] The twist direction of the helical spline in the first fitting portion 512 is the same as the twist direction of the helical teeth 612 a of the first input gear 612. The twist direction of the helical spline in the second fitting portion 522 is the same as the twist direction of the helical teeth 712 a of the second input gear 712. Furthermore, the twist direction of the helical spline in the first fitting portion 512 is opposite to the twist direction of the helical spline in the second fitting portion 522. When the vehicle accelerates forward, the first output gear 51 is pressed against the first wall portion 551, and the second output gear 52 is pressed against the second wall portion 552.

[0061] The second embodiment also provides the same effects as the first embodiment.

[0062] Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 5 to 7. In the first and second embodiments, the differential reduction gear 4, 4A includes a bevel gear-type differential mechanism 5, 5A. In the third embodiment, the differential reduction gear 4B includes a parallel shaft gear-type differential mechanism 9. The differential mechanism 9 has a differential limiting function that limits the differential rotation between the left and right wheels when, for example, one of the left and right wheels slips, thereby preventing the driving force from being lost to the other wheel. The first reduction mechanism 6 and the second reduction mechanism 7, the device case 2, and the motor 3 combined with the differential mechanism 9 are configured in the same manner as in the first embodiment.

[0063] Fig. 5 is a cross-sectional view showing an electric drive unit 1B according to a third embodiment. Fig. 6 is a cross-sectional view of the differential mechanism 9 taken along line A-A in Fig. 5. Fig. 7 is a perspective cross-sectional view showing a portion of the differential mechanism 9. In Fig. 5, components that are the same as those described in the first embodiment are designated by the same reference numerals as those in Fig. 1, and redundant description will be omitted.

[0064] The differential mechanism 9 has a first output gear 91 that rotates integrally with the first shaft portion 611 of the first input shaft 61, a second output gear 92 that rotates integrally with the second shaft portion 711 of the second input shaft 71, a plurality of first pinion gears 93 that mesh with the first output gear 91, a plurality of second pinion gears 94 that mesh with the second output gear 92, a center washer 95 arranged between the first output gear 91 and the second output gear 92, a first side washer 96 arranged on the left side of the first output gear 91, a second side washer 97 arranged on the right side of the second output gear 92, and a rotating case 98 that houses these. The first output gear 91 and the second output gear 92 are rotatable relative to each other on the same axis around the rotation axis O of the rotating case 98, and are connected to rotate differentially by a plurality of first pinion gears 93 and a plurality of second pinion gears 94.

[0065] The rotating case 98 has a case body 98A and a case lid 98B, which are fastened together with a plurality of bolts 99. The rotating case 98 has a first wall 981 on the left side, a second wall 982 on the right side, and a cylindrical peripheral wall 983 provided between the first wall 981 and the second wall 982. The first wall 981 is aligned with the first output gear 91 in the axial direction to the left of the center washer 95, and the second wall 982 is aligned with the second output gear 92 in the axial direction to the right of the center washer 95. The rotor 32 of the motor 3 is fixed to the outer periphery of the peripheral wall 983, so that the rotating case 98 rotates integrally with the rotor 32.

[0066] The first output gear 91 and the second output gear 92 are housed between a first wall portion 981 and a second wall portion 982, and are capable of relative rotation coaxially around the rotation axis O of the rotating case 98. Movement of the first output gear 91 in the rotating case 98 in a direction away from the second output gear 92, and movement of the second output gear 92 in the rotating case 98 in a direction away from the first output gear 91, are restricted by the rotating case 98.

[0067] The first output gear 91 has a fitting hole 910 into which a first fitting portion 610, which is a part of the first shaft portion 611, is helical spline fitted. The second output gear 92 has a fitting hole 920 into which a second fitting portion 710, which is a part of the second shaft portion 711, is helical spline fitted.

[0068] When the vehicle accelerates forward, the direction of the axial thrust force acting on the first output gear 91 and the first fitting portion 610 due to the helical spline engagement between the first output gear 91 and the first fitting portion 610, and the direction of the axial thrust force acting on the second output gear 92 and the second fitting portion 710 due to the helical spline engagement between the second output gear 92 and the second fitting portion 710 are the same as in the first embodiment. In Figure 5, the directions of these thrust forces are indicated by arrows F in the same way as in Figure 1. １１ , F １２ , F ２１ , F ２２ It is expressed as:

[0069] As shown in Figure 7, the first output gear 91 has a plurality of helical teeth 911 formed on its outer periphery, with the tooth traces inclined relative to the axial direction. The second output gear 92 has a plurality of helical teeth 921 formed on its outer periphery, with the tooth traces inclined relative to the axial direction. The twist direction of the helical teeth 911 of the first output gear 91 is opposite to the twist direction of the helical teeth 921 of the second output gear 92. Furthermore, the twist direction of the helical teeth 911 of the first output gear 91 is the same as the twist direction of the helical spline in the fitting hole 910, and the twist direction of the helical teeth 921 of the second output gear 92 is the same as the twist direction of the helical spline in the fitting hole 920.

[0070] The first pinion gear 93 and the second pinion gear 94 are axially shaped, and have helical helical teeth 931, 941 formed on the outer periphery thereof. The helical teeth 931 of the first pinion gear 93 mesh with the helical teeth 911 of the first output gear 91. The helical teeth 941 of the second pinion gear 94 mesh with the helical teeth 921 of the second output gear 92. The rotation axis O of the first pinion gear 93 ９３ and the rotation axis O of the second pinion gear 94 ９４ is parallel to the rotation axis O of the rotating case 98.

[0071] In this embodiment, two first pinion gears 93 mesh with one second pinion gear 94 to form one pinion gear set 90. The differential mechanism 9 has three pinion gear sets 90. The second pinion gear 94 is axially longer than the first pinion gears 93, and meshes with the two first pinion gears 93 to the left of the center washer 95, and meshes with the second output gear 92 to the right of the center washer 95. The first output gear 91 has a smaller diameter than the second output gear 92, and does not mesh with the second pinion gear 94.

[0072] The torque generated in the motor 3 is transmitted from the rotor 32 to a plurality of first pinion gears 93 and second pinion gears 94 held in the rotating case 98, and is further distributed and transmitted from the plurality of first pinion gears 93 to the first output gear 91, and from the plurality of second pinion gears 94 to the second output gear 92.

[0073] The case body 98A is formed with three bores 900, each accommodating one of the three pinion gear sets 90. The bore 900 is a hollow cavity that accommodates two first pinion gear accommodating portions 901, each accommodating two first pinion gears 93, and one second pinion gear accommodating portion 902, accommodating one second pinion gear 94. The left opening of the bore 60 is closed by a case cover 98B.

[0074] Tooth tip surfaces 931 a of the helical teeth 931 of the first pinion gear 93 are pressed against an inner surface 901 a of the first pinion gear accommodating portion 901 by a meshing reaction force between the first pinion gear 93 and the first output gear 91. Tooth tip surfaces 941 a of the helical teeth 941 of the second pinion gear 94 are pressed against an inner surface 902 a of the second pinion gear accommodating portion 902 by a meshing reaction force between the second pinion gear 94 and the second output gear 92 and the two first pinion gears 93.

[0075] When differential rotation occurs between the first output gear 91 and the second output gear 92 inside the rotating case 98, the tooth tip surfaces 931 a of the helical teeth 931 of the first pinion gear 93 slide against the inner surface 901 a of the first pinion gear accommodating portion 901, and the tooth tip surfaces 941 a of the helical teeth 941 of the second pinion gear 94 slide against the inner surface 902 a of the second pinion gear accommodating portion 902. The frictional force generated by this sliding acts as a differential limiting force that suppresses differential rotation between the left and right wheels.

[0076] A thrust force in the axial direction is generated in the first output gear 91 by meshing with the plurality of first pinion gears 93. In Fig. 5, the direction of the thrust force generated in the first output gear 91 by meshing with the first pinion gears 93 when the vehicle accelerates forward is indicated by an arrow F. １３ The direction of this thrust force is indicated by arrow F in FIG. １１ This is opposite in direction to the thrust force, indicated by , generated in the first output gear 91 by the helical spline engagement with the first engagement portion 610.

[0077] A thrust force in the axial direction is generated in the second output gear 92 by meshing with the plurality of second pinion gears 94. In FIG. 5, the direction of the thrust force generated in the second output gear 92 by meshing with the second pinion gears 94 when the vehicle accelerates forward is indicated by an arrow F. ２３ The direction of this thrust force is indicated by arrow F in FIG. ２１ This is opposite in direction to the thrust force, indicated by , generated in the second output gear 92 by the helical spline engagement with the second engagement portion 710.

[0078] In this way, in this embodiment, the arrow F １１ The direction of the thrust force indicated by arrow F１３ Since the direction of the thrust force indicated by the arrow F is opposite to that of the thrust force indicated by the arrow F, these thrust forces cancel each other out. ２１ The direction of the thrust force indicated by arrow F ２３ Since the direction of the thrust force indicated by is opposite to that of the thrust force indicated by the arrows (a), these thrust forces cancel each other out. As a result, the rotating case 98 is not pressed strongly in one axial direction, and the load on the bearings 80 and 81 that support the rotating case 98 is reduced, and the strength burden on the first partition wall 211 that supports the bearing 80 and the strength burden on the second partition wall 221 that supports the bearing 81 are also reduced. The strength burden on the rotating case 98 is also reduced. In other words, this embodiment also provides the same effects as the first embodiment.

[0079] The twist direction of the helical teeth 911 of the first output gear 91 and the twist direction of the helical spline in the fitting hole 910 may be reversed, and the twist direction of the helical teeth 921 of the second output gear 92 and the twist direction of the helical spline in the fitting hole 920 may be reversed. In this case, the direction of the thrust force generated in the first output gear 91 by meshing with the first pinion gear 93 is the same as the direction of the thrust force generated in the first output gear 91 by helical spline engagement with the first fitting portion 610. Furthermore, the direction of the thrust force generated in the second output gear 92 by meshing with the second pinion gear 94 is the same as the direction of the thrust force generated in the second output gear 92 by helical spline engagement with the second fitting portion 710.

[0080] As a result, when the vehicle accelerates forward, the first side washer 96 is strongly pressed toward the first wall portion 981 by the resultant force of the thrust forces acting on the first output gear 91, and the second side washer 97 is strongly pressed toward the second wall portion 982 by the resultant force of the thrust forces acting on the second output gear 92. Then, the frictional forces generated in the first side washer 96 and the second side washer 97 suppress differential rotation between the first output gear 91 and the second output gear 92. Furthermore, when the vehicle decelerates, the resultant force of the thrust forces acting on the first output gear 91 and the second output gear 92 presses the center washer 95 from both sides in the axial direction, and the frictional force generated in the center washer 95 suppresses differential rotation between the first output gear 91 and the second output gear 92.

[0081] In other words, the differential limiting force can be increased by reversing the twist direction of the helical teeth 911 of the first output gear 91 and the twist direction of the helical spline in the fitting hole 910, and by reversing the twist direction of the helical teeth 921 of the second output gear 92 and the twist direction of the helical spline in the fitting hole 920. Also in this case, the load on the bearings 80, 81 that support the rotating case 98 is reduced, and the strength burden on the first partition wall 211 and the second partition wall 221 is also reduced.

[0082] (Note) While the present invention has been described above based on the first to third embodiments, these embodiments do not limit the scope of the claimed invention. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be appropriately modified and implemented by omitting some components or adding or substituting components within the scope of the spirit of the invention. Furthermore, some components of the above-described embodiments can be combined with each other, and modifications such as those described below are also possible.

[0083] In the first to third embodiments, the stator 31 of the motor 3 is fixed to the device case 2 and the rotor 32 is fixed to the rotating cases 55, 98. However, this is not limited to this, and for example, the torque of a motor arranged outside the device case 2 may be transmitted to the rotating cases 55, 98 via multiple gears.

[0084] Furthermore, in the first to third embodiments, the first reduction mechanism 6, 6A and the second reduction mechanism 7, 7A are described as planetary gear mechanisms. However, the first reduction mechanism 6, 6A and the second reduction mechanism 7, 7A are not limited to planetary gear mechanisms, and various configurations can be used.

[0085] DESCRIPTION OF SYMBOLS 1, 1A, 1B... Electric drive unit 2... Unit case 3... Motor 31... Stator 32... Rotor 4, 4A, 4B... Differential reduction device 5, 5A, 9... Differential mechanism 51, 91... First output gear 52, 92... Second output gear 55, 98... Rotating case 6, 6A... First reduction mechanism 61... First input shaft 610, 512... First fitting portion 611, 511... First shaft portion 612... First input gear 62... First planetary gear 63... First ring gear 631... Internal tooth portion 64... First carrier 7, 7A... Second reduction mechanism 71... Second input shaft 710, 522... Second fitting portion 711, 521... Second shaft portion 712... Second input gear 712a... helical teeth 72... second planetary gear 73... second ring gear 731... internal teeth portion 74... second carrier

Claims

1. The system comprises a differential mechanism that outputs the vehicle's driving force from a first shaft and a second shaft with differential action, a first reduction mechanism that reduces the rotation of the first shaft, and a second reduction mechanism that reduces the rotation of the second shaft. The differential mechanism comprises a first output gear that rotates integrally with the first shaft, a second output gear that rotates integrally with the second shaft, and a rotating case that houses and rotates the first output gear and the second output gear, wherein the first output gear and the second output gear are arranged in the rotating case so as to be able to rotate relative to each other on the same axis. The first reduction mechanism has a first input gear having oblique teeth on its outer circumference whose tooth traces are inclined with respect to the axial direction, The second reduction mechanism has a second input gear having oblique teeth on its outer circumference whose tooth traces are inclined with respect to the axial direction, The first shaft portion has a first fitting portion that helically spline-fits with one of the first output gear and the first input gear, and is integrated with the other of the first output gear and the first input gear. The second shaft portion has a second fitting portion that helically spline-fits with one of the second output gear and the second input gear, and is integrated with the other of the second output gear and the second input gear. The twisting direction of the helical spline in the first fitting portion is the same as the twisting direction of the helical teeth of the first input gear, The twisting direction of the helical spline in the second fitting portion is the same as the twisting direction of the helical teeth of the second input gear, The movement of the first output gear in the direction away from the second output gear, and the movement of the second output gear in the direction away from the first output gear, within the rotating case are restricted by the rotating case. Differential reduction gear.

2. (delete)

3. The twisting direction of the helical spline in the first fitting portion and the twisting direction of the helical spline in the second fitting portion are opposite. The differential reduction gear according to claim 1.

4. The rotating case has a first wall portion aligned axially with the first output gear and a second wall portion aligned axially with the second output gear, and the first output gear and the second output gear are housed between the first wall portion and the second wall portion. The twisting direction of the helical spline in the first fitting portion and the twisting direction of the helical spline in the second fitting portion are such that the first output gear is pressed toward the first wall and the second output gear is pressed toward the second wall by the driving force input to the differential mechanism when the vehicle accelerates forward. The differential reduction gear according to claim 3.

5. The first reduction mechanism includes a plurality of first planetary gears that mesh with the first input gear, a first ring gear having internal teeth that mesh with the plurality of first planetary gears, and a first carrier that rotatably supports the plurality of first planetary gears. The second reduction mechanism includes a plurality of second planetary gears that mesh with the second input gear, a second ring gear having internal teeth that mesh with the plurality of second planetary gears, and a second carrier that rotatably supports the plurality of second planetary gears. A differential reduction gear according to any one of claims 1, 3, or 4.

6. A differential reduction device according to any one of claims 1, 3, or 4, comprising: a device case housing the differential mechanism, the first reduction mechanism, and the second reduction mechanism; and a motor that generates the driving force input to the differential mechanism, Electric drive system.

7. The first input gear has a larger diameter than the helical spline in the first fitting portion, and the twist angle of the helical teeth of the first input gear is formed to be larger than the twist angle of the helical spline in the first fitting portion, such that the difference between the axial thrust force acting on the first input gear and the axial thrust force acting on the helical spline in the first fitting portion becomes small in proportion to the diameter difference between the first input gear and the helical spline in the first fitting portion. The second input gear has a larger diameter than the helical spline in the second fitting portion, and the twist angle of the helical teeth of the second input gear is formed to be larger than the twist angle of the helical spline in the second fitting portion, such that the difference between the axial thrust force acting on the second input gear and the axial thrust force acting on the helical spline in the second fitting portion becomes small in proportion to the diameter difference between the second input gear and the helical spline in the second fitting portion. The differential reduction gear according to claim 1.