Differential device for vehicle

Abstract

[Problem] To provide a small and lightweight differential device for a vehicle.　[Solution] A differential device 22 includes: a planetary gear mechanism 81 including a plurality of planetary gears 4 and a carrier 5; and a differential gear mechanism 82 including a pair of side gears 71, 72 and a plurality of pinion gear sets 6. In each planetary gear 4, a one-side supported part 43 and an another-side supported part 44 are supported by the carrier 5. In each pinion gear set 6, a first pinion gear 61 that engages with one side gear 71 and a second pinion gear 62 that engages with the another side gear 72 are engaged in a holding hole 510 of the carrier 5. The carrier 5 includes a carrier main body 50 in which a plurality of the holding holes 510 are formed, and a carrier lid body 500 that closes one end in an axial direction of the plurality of holding holes 510. The carrier main body 50 includes: a plurality of one-side support parts 52 that support the one-side supported parts 43 of the plurality of planetary gears 4; and a plurality of another-side support parts 53 that support the another-side supported parts 44.

Description

Vehicle differential

[0001] The present invention relates to a vehicle differential that is mounted on a vehicle having an electric motor as a drive source, and that distributes and outputs input driving force from the electric motor to a pair of side gears.

[0002] In recent years, electric vehicles using electric motors as drive sources have become increasingly popular. Some of these electric vehicles are equipped with a differential gear including a planetary gear mechanism that reduces the output rotation of the electric motor and a differential gear mechanism that distributes the drive force amplified by the planetary gear mechanism to left and right wheels, as described in Patent Documents 1 and 2, for example. The differential gear mechanism includes a pair of left and right output gears, and left and right wheel axles are connected to these output gears, respectively.

[0003] The present applicant has proposed a differential device described in Patent Document 3 for distributing the driving force of a driving source such as an engine to drive shafts connected to the left and right wheels while allowing differential movement.

[0004] JP 2021-110374 A JP 2016-95034 A JP 2019-007505 A

[0005] There is a strong demand for differentials mounted on electric vehicles that are small and lightweight while maintaining the necessary strength in order to ensure space for batteries and other components and to improve power efficiency. An object of the present invention is to provide a small and lightweight vehicle differential.

[0006] In order to achieve the above object, the present invention provides a differential for a vehicle having a pair of side gears that are rotatable relative to one another on the same axis, and which distributes and outputs the driving force of an input electric motor to the pair of side gears, the differential comprising: a planetary gear mechanism having a sun gear to which the driving force is input, a plurality of planetary gears meshing with the sun gear, a carrier that rotatably supports the plurality of planetary gears, and a ring gear that meshes with the plurality of planetary gears on the outer periphery of the carrier; a first pinion gear that meshes with one of the pair of side gears, and a second pinion gear that meshes with the other of the pair of side gears, and a front gear that is connected to the first pinion gear; and a plurality of pinion gear sets meshing with the second pinion gear, each of the plurality of planetary gears having a plurality of supported portions provided at positions spaced apart in the axial direction supported by the carrier, the carrier having a carrier body having retaining holes formed therein that rotatably hold the first pinion gear and the second pinion gear about a rotation axis parallel to the rotation axis of the carrier, and a carrier cover body that is aligned with the carrier body in the axial direction and closes one axial end of the retaining hole, and a support portion that supports at least any of the plurality of supported portions of the plurality of planetary gears is provided on the carrier body.

[0007] According to the present invention, a small and lightweight differential can be provided.

[0008] FIG. 1 is a schematic diagram showing an example of the general configuration of a four-wheel drive vehicle according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of a front-wheel drive unit. FIG. 3 is a perspective view of a plurality of planetary gears and a carrier. FIG. 4 is an exploded perspective view of a differential unit. FIG. 5 is a cross-sectional view taken along line A-A in FIG. 3. FIG. 6 is a perspective view showing a set of pinion gears. FIG. 7 is a side view showing a first pinion gear. FIG. 8 is a perspective cross-sectional view of a carrier body. FIG. 9 is a cross-sectional view taken along line B-B in FIG. 5. FIG. 10 is a cross-sectional view taken along line C-C in FIG. 5. FIG. 11 is an external view showing the end of the carrier body. FIG. 12 is a cross-sectional view of the carrier body perpendicular to the axial direction.

[0009] [Embodiments] Embodiments of the present invention will be described with reference to Figures 1 to 12. Note that the embodiments described below are shown as preferred specific examples for carrying out the present invention, and while some of the embodiments specifically exemplify various technically preferred aspects, the technical scope of the present invention is not limited to these specific embodiments.

[0010] 1 is a schematic diagram showing an example of the general configuration of a four-wheel drive vehicle 1 according to an embodiment of the present invention. The four-wheel drive vehicle 1 has a front-wheel drive unit 2 that drives a left front wheel 11 and a right front wheel 12, a rear-wheel drive unit 3 that drives a left rear wheel 13 and a right rear wheel 14, and a control device 10 that controls the front and rear wheel drive units 2, 3.

[0011] The front-wheel drive unit 2 includes an electric motor 21, a differential 22, and left and right axles 23, 24. The differential 22 distributes the driving force of the electric motor 21 to the left and right axles 23, 24. The left axle 23 and the left front wheel 11 are connected by a left drive shaft 15, and the right axle 24 and the right front wheel 12 are connected by a right drive shaft 16. The left drive shaft 15 includes an intermediate shaft 151 and constant velocity joints 152, 153 attached to both ends of the intermediate shaft 151. The right drive shaft 16 includes an intermediate shaft 161 and constant velocity joints 162, 163 attached to both ends of the intermediate shaft 161.

[0012] The rear-wheel drive unit 3 includes an electric motor 31, a differential 32, and left and right axles 33, 34. The differential 32 distributes the driving force of the electric motor 31 to the left and right axles 33, 34. The left axle 33 and the left rear wheel 13 are connected by a left drive shaft 17, and the right axle 34 and the right rear wheel 14 are connected by a right drive shaft 18. The left drive shaft 17 includes an intermediate shaft 171 and constant velocity joints 172, 173 attached to both ends of the intermediate shaft 171. The right drive shaft 18 includes an intermediate shaft 181 and constant velocity joints 182, 183 attached to both ends of the intermediate shaft 181.

[0013] The control device 10 can acquire information on the detection results of various on-board sensors mounted on the four-wheel drive vehicle 1 via an on-board network such as a CAN (Control Area Network). These on-board sensors include wheel speed sensors that detect the wheel speeds, which are the rotational speeds of the left front wheel 11, the right front wheel 12, and the left rear wheel 13, and the right rear wheel 14, a steering angle sensor that detects the steering angle of the steering wheel operated by the driver, and an accelerator pedal sensor that detects the amount of depression of the accelerator pedal. Based on this information, the control device 10 supplies a motor current to the electric motor 21 of the front-wheel drive unit 2 to control the electric motor 21, and supplies a motor current to the electric motor 31 of the rear-wheel drive unit 3 to control the electric motor 31.

[0014] 2 is a schematic diagram showing the configuration of the front-wheel drive unit 2. The rear-wheel drive unit 3 is configured in the same manner as the front-wheel drive unit 2.

[0015] The electric motor 21 has a motor case 210, a stator 211 fixed to the motor case 210, a rotor 212 that rotates relative to the stator 211, and a cylindrical motor shaft 213 that rotates integrally with the rotor 212. The stator 211 generates a magnetic field by a motor current supplied from the control device 10, and the permanent magnet of the rotor 212 generates torque by this magnetic field. The torque generated in the rotor 212 is output from the motor shaft 213 to the differential device 22 as a driving force that drives the left front wheel 11 and the right front wheel 12.

[0016] The differential device 22 has a housing 220 fixed to the motor case 210, a sun gear 40 fixed to the motor shaft 213, a plurality of planetary gears 4, a carrier 5 that rotatably supports the plurality of planetary gears 4, a ring gear 221 fixed to the housing 220, a plurality of pinion gear sets 6 formed by meshing a first pinion gear 61 with a second pinion gear 62, and a pair of left and right side gears 71, 72.

[0017] The multiple planetary gears 4, the carrier 5, and the ring gear 221 constitute a planetary gear mechanism 81 that functions as a reducer that reduces the output rotation of the electric motor 21. The multiple pinion gear sets 6 and the first and second side gears 71, 72 constitute a differential gear mechanism 82 that distributes the driving force of the electric motor 21, amplified by the planetary gear mechanism 81, to the left and right axles 23, 24 while allowing differentials. In other words, the differential device 22 of this embodiment is a differential device with a reducer that has the planetary gear mechanism 81 as a reducer that reduces the output rotation of the electric motor 21.

[0018] The housing 220 houses the plurality of planetary gears 4 and the carrier 5. The housing 220 is filled with lubricating oil that lubricates each part of the differential device 22. The planetary gear 4 has a plurality of supported parts provided at positions spaced apart in the axial direction, and the plurality of supported parts are supported by the carrier 5. The carrier 5 has a plurality of supporting parts that support the plurality of supported parts of each planetary gear 4.

[0019] The motor shaft 213 of the electric motor 21, the carrier 5, and the side gears 71, 72 are aligned in the vehicle width direction of the four-wheel drive vehicle 1 and are arranged coaxially so as to be rotatable relative to one another. The ring gear 221 is arranged on the outer periphery of the carrier 5. The left axle 23 is inserted through the center of the motor shaft 213 of the electric motor 21. The length of the left axle 23 is longer than the right axle 24 by the length of the motor shaft 213.

[0020] The left axle shaft 23 is connected to the left side gear 71 so as to be non-rotatable relative to the right axle shaft 24. The right side gear 72 is connected to the right side gear 72 so as not to be rotatable relative to the left axle shaft 23. Hereinafter, of the side gears 71 and 72, the left side gear 71 will be referred to as the first side gear 71, and the right side gear 72 will be referred to as the second side gear 72. The first side gear 71 has a larger diameter than the second side gear 72.

[0021] Fig. 3 is a perspective view showing the multiple planetary gears 4 and the carrier 5. Fig. 4 is an exploded perspective view of the differential device 22 showing the multiple planetary gears 4, the carrier 5, the multiple pinion gear sets 6, and the first and second side gears 71, 72. Fig. 5 is a cross-sectional view taken along line A-A in Fig. 3. In Figs. 3 and 5, the rotation axis O of the carrier 5 and the central axis C of each of the multiple planetary gears 4 are indicated by dashed lines. The rotation axis O of the carrier 5 and the central axis C of each of the multiple planetary gears 4 are parallel to each other.

[0022] The planetary gear mechanism 81 has three planetary gears 4 arranged at equal intervals around the circumferential direction of the carrier 5. Each planetary gear 4 has a large-diameter gear portion 41 and a small-diameter gear portion 42, each having a different pitch circle diameter, arranged coaxially. The large-diameter gear portion 41 meshes with the sun gear 40, and the small-diameter gear portion 42 meshes with the ring gear 221 on the outer periphery of the carrier 5. The pitch circle diameter of the large-diameter gear portion 41 is, for example, at least twice the pitch circle diameter of the small-diameter gear portion 42.

[0023] When the sun gear 40 rotates together with the motor shaft 213, the large-diameter gear portion 41 and the small-diameter gear portion 42 of each of the plurality of planetary gears 4 rotate integrally about the central axis C. The large-diameter gear portion 41 and the small-diameter gear portion 42 are helical gears having a plurality of helical teeth on their outer circumferential surfaces, the tooth trace of which is inclined with respect to the axial direction. In Figures 3 to 5, the helical teeth are not shown, and the large-diameter gear portion 41 and the small-diameter gear portion 42 are shown in a simplified manner.

[0024] The planetary gear 4 has a plurality of supported portions supported by the carrier 5, namely, a one-side supported portion 43 and an other-side supported portion 44, which are coaxial with the large-diameter gear portion 41 and the small-diameter gear portion 42. The one-side supported portion 43 is supported by the carrier 5 on one axial side of the small-diameter gear portion 42, closer to the large-diameter gear portion 41. The other-side supported portion 44 is supported by the carrier 5 on the other axial side of the small-diameter gear portion 42. In this embodiment, the one-side supported portion 43 is provided between the large-diameter gear portion 41 and the small-diameter gear portion 42. The other-side supported portion 44 is provided at the end of the planetary gear 4 opposite to the large-diameter gear portion 41 side.

[0025] The carrier 5 has a carrier body 50 and a carrier lid body 500, and the carrier lid body 500 is fixed to the carrier body 50 with a plurality of bolts 501. The carrier body 50 is provided with support portions that support at least one of a plurality of supported portions (one-side supported portions 43 and the other-side supported portions 44) of the planetary gear 4. In this embodiment, the carrier body 50 integrally includes a cylindrical pinion gear holding portion 51, a plurality of one-side support portions 52 that support the one-side supported portions 43 of each planetary gear 4, and a plurality of other-side support portions 53 that support the other-side supported portions 44 of each planetary gear 4.

[0026] The plurality of one-side support portions 52 are provided on the outer periphery of the end portion of the pinion gear holding portion 51 on the large-diameter gear portion 41 side of the planetary gear 4, protruding in a radial direction perpendicular to the rotation axis O. The plurality of other-side support portions 53 are provided on the outer periphery of the end portion of the pinion gear holding portion 51 opposite to the large-diameter gear portion 41 side of the planetary gear 4, protruding in a radial direction perpendicular to the rotation axis O.

[0027] The plurality of one-side support portions 52 each support the one-side supported portion 43 of the planetary gear 4 via a first bearing 91. The first bearing 91 is a ball bearing in which a plurality of spherical rolling elements 913 are arranged between an outer ring 911 and an inner ring 912, and is housed in a housing hole 520 formed in the one-side support portion 52. The outer ring 911 is restricted from moving in the axial direction by a snap ring 901 fitted to the one-side support portion 52. The inner ring 912 is restricted from moving in the axial direction relative to the planetary gear 4 by a snap ring 902 fitted to the planetary gear 4.

[0028] The multiple other-side support portions 53 support the other-side supported portion 44 of the planetary gear 4 via second bearings 92. The second bearings 92 are needle roller bearings in which multiple needle rollers 922 are arranged inside a cylindrical outer ring 921, and are housed in housing holes 530 formed in the other-side support portions 53. The multiple needle rollers 922 are held in a cage 923 and roll on the outer peripheral surface 44a of the other-side supported portion 44.

[0029] The carrier cover 500 is aligned with the carrier body 50 in the axial direction and is fixed to one of both end portions of the carrier body 50 on the side where the multiple other-side support portions 53 are provided. The first side gear 71 is disposed closer to the large-diameter gear portion 41 of the planetary gear 4 than the second side gear 72. The second side gear 72 is disposed closer to the multiple other-side support portions 53 than the multiple one-side support portions 52. In this embodiment, in the radial direction perpendicular to the rotation axis O, a portion of the axial direction of the second side gear 72 is disposed inside the multiple other-side support portions 53.

[0030] A portion of the pinion gear holding portion 51 is aligned with the first side gear 71 in the axial direction, and a first side washer 93 is disposed between the first side gear 71 and the pinion gear holding portion 51. A center washer 94 is disposed between the first side gear 71 and the second side gear 72. A second side washer 95 is disposed between the second side gear 72 and the carrier lid 500.

[0031] The first pinion gear 61 meshes with the first side gear 71. The second pinion gear 62 is disposed on the outer periphery of the second side gear 72 and meshes with the first pinion gear 61 and the second side gear 72. In the present embodiment, each of the multiple pinion gear sets 6 has one first pinion gear 61 and two second pinion gears 62, and the first pinion gear 61 is disposed between the two second pinion gears 62. The number of pinion gear sets 6 in the differential device 22 is the same as the number of planetary gears 4, and in the present embodiment, three pinion gear sets 6 are held by the pinion gear holding portion 51 of the carrier 5.

[0032] The first and second pinion gears 61, 62 and the first and second side gears 71, 72 are helical gears having a plurality of helical teeth on their outer circumferential surfaces, with the tooth traces inclined relative to the axial direction. In Figures 3 to 5, the helical teeth are not shown, and each gear is shown in a simplified manner. The pinion gear holding portion 51 of the carrier body 50 is formed with a plurality of holding holes 510 that hold the first pinion gear 61 and the two second pinion gears 62 of each pinion gear set 6.

[0033] The plurality of retaining holes 510 are formed between the plurality of one-side support portions 52 and the plurality of other-side support portions 53 in the axial direction parallel to the rotation axis O. In addition, the plurality of retaining holes 510 are formed inside the plurality of other-side support portions 53 in the radial direction, with part of the axial direction perpendicular to the rotation axis O.

[0034] Fig. 6 is a perspective view showing one pinion gear set 6. Fig. 7 is a side view showing a first pinion gear 61. In the example shown in Figs. 6 and 7, six helical teeth 610 are formed on the first pinion gear 61, and the same number of helical teeth 620 are formed on the second pinion gear 62. The tooth tip surfaces 610a, 620a of the helical teeth 610, 620 are formed with a predetermined width in a direction perpendicular to the tooth trace. The gear axis G of the first pinion gear 61 １ and the gear axis G of the second pinion gear 62 ２ is parallel to the rotation axis O of the carrier 5.

[0035] The second pinion gear 62 is formed so that its axial length is shorter than that of the first pinion gear 61, and is meshed with the first pinion gear 61 on the outer circumferential side of the second side gear 72. The axial length of the first pinion gear 61 is equivalent to the combined axial width of the first side gear 71 and the axial width of the second side gear 72. The axial length of the second pinion gear 62 is equivalent to the axial width of the second side gear 72.

[0036] The first pinion gear 61 has a large diameter portion 611 and a small diameter portion 612, which have different pitch circle diameters, arranged side by side in the axial direction. The large diameter portion 611 meshes with the first side gear 71. The small diameter portion 612 meshes with the two second pinion gears 62. As shown in FIG. 5 , the large diameter portion 611 is entirely disposed between the multiple one-side support portions 52 and the multiple other-side support portions 53 in the axial direction parallel to the rotation axis O of the carrier 5. A portion of the small diameter portion 612 in the axial direction is disposed inside the multiple other-side support portions 53 in the radial direction perpendicular to the rotation axis O.

[0037] The pitch circle diameter of the large diameter portion 611 is P １ and the pitch circle diameter of the small diameter portion 612 is P２ Then, P ２ P for １ The ratio (P １ / P ２ ) is, for example, 1.05 to 1.15. In addition, the twist angle of the tooth trace 611a in the large diameter portion 611 is θ １ and the twist angle of the tooth trace 612a in the small diameter portion 612 is θ ２ Then, θ １ is θ ２ is larger than the ratio (θ １ / θ ２ ) is the same as the ratio of the pitch circle diameters of the large diameter portion 611 and the small diameter portion 612, for example.

[0038] Fig. 8 is a perspective cross-sectional view of the carrier body 50 showing the inside of the pinion gear holding portion 51. Fig. 9 is a cross-sectional view of the differential gear mechanism 82 and the planetary gear mechanism 81 taken along line B-B in Fig. 5. Fig. 10 is a cross-sectional view of the differential gear mechanism 82 and the planetary gear mechanism 81 taken along line CC in Fig. 5. Fig. 11 is an external view of the end of the carrier body 50 on the other-side support portion 53 side, as viewed from the direction along the rotation axis O. Fig. 12 is a cross-sectional view of the carrier body 50 taken along line CC in Fig. 5.

[0039] Three retaining holes 510 are formed at equal intervals in the circumferential direction in the pinion gear retaining portion 51 of the carrier body 50. Each retaining hole 510 includes a first hole portion 511 that retains the first pinion gear 61 and two second hole portions 512 that retain two second pinion gears 62, respectively, and the first hole portion 511 and the two second hole portions 512 are in communication with each other. The first pinion gear 61 and the two second pinion gears 62 are housed in the retaining holes 510 so as to rotate (spin) about rotation axes that are parallel to the rotation axis O of the carrier 5.

[0040] The first hole portion 511 and the second hole portion 512 open to the inner circumferential surface 51 a of the pinion gear holding portion 51. A circumferential portion of the first pinion gear 61 protrudes inward from the first hole portion 511 into the pinion gear holding portion 51 and meshes with the first side gear 71. A circumferential portion of the second pinion gear 62 protrudes inward from the second hole portion 512 into the pinion gear holding portion 51 and meshes with the second side gear 72.

[0041] The first hole 511 and the second hole 512 open to an axial end surface 51 b of the carrier body 50 in the pinion gear holding portion 51. The carrier lid 500 abuts against the axial end surface 51 b of the pinion gear holding portion 51 by the axial forces of the plurality of bolts 501, and closes one axial end of each of the plurality of holding holes 510.

[0042] The driving force of the electric motor 21 input to the carrier 5 is transmitted to the first pinion gear 61 and the second pinion gear 62 by contact between the tooth tip surfaces 610a, 620a and the inner surface 511a of the first hole portion 511 and the inner surface 512a of the second hole portion 512, which are the inner surfaces of the retaining hole 510. The driving force transmitted to the large diameter portion 611 and the small diameter portion 612 of the first pinion gear 61 is transmitted from the large diameter portion 611 to the first side gear 71. The driving force transmitted to the two second pinion gears 62 is transmitted to the second side gear 72.

[0043] When a difference occurs in the wheel speeds of the left front wheel 11 and the right front wheel 12, causing the first side gear 71 and the second side gear 72 to rotate differentially, the tooth tip surfaces 610a of the multiple twist teeth 610 of the first pinion gear 61 slide against the inner surface 511a of the first hole portion 511, and the tooth tip surfaces 620a of the multiple twist teeth 620 of the second pinion gear 62 slide against the inner surface 512a of the second hole portion 512, generating frictional resistance.

[0044] This frictional resistance force prevents the differential gear mechanism 82 from spinning freely and being unable to transmit driving force to the other wheel when it becomes impossible to transmit driving force to one of the left front wheel 11 and the right front wheel 12 due to slippage or the like. In other words, the frictional resistance force between the tooth tips 610 a, 620 a of the first pinion gear 61 and the second pinion gear 62 and the inner surface of the retaining hole 510 serves as a differential limiting force that limits the differential movement of the left front wheel 11 and the right front wheel 12.

[0045] The first hole portion 511 includes a large diameter hole portion 511b that holds the large diameter portion 611 of the first pinion gear 61, and a small diameter hole portion 511c that holds the small diameter portion 612 of the second pinion gear 62. The large diameter hole portion 511b is formed to have a larger diameter than the small diameter hole portion 511c. In Figure 11, a portion of the large diameter hole portion 511b is indicated by a dashed line.

[0046] 5 , 9 , and 10 , the positions of the multiple pinion gear sets 6 in the radial direction perpendicular to the rotation axis O of the carrier 5 are closer to the rotation axis O than the radial positions of the small diameter gear portions 42 of the multiple planetary gears 4. The multiple retaining holes 510 are formed inside the multiple planetary gears 4 in the radial direction perpendicular to the rotation axis O. The entire axial length of the first hole portion 511 is located radially inside the small diameter gear portions 42 and the other-side supported portions 44 of the multiple planetary gears 4.

[0047] As shown in FIG. 9 , in a cross section perpendicular to the rotation axis O, a pair of half lines that respectively circumscribe one end and the other end of the retaining hole 510 in the circumferential direction centered on the rotation axis O are defined as L. １１ , L １２ Then, these half lines L １１ , L １２ The central axes C of the planetary gears 4 are located between the axes L and L. Furthermore, a pair of semi-lines that respectively circumscribe one end and the other end of the small diameter portion 612 of the first pinion gear 61 in the circumferential direction centered on the rotation axis O and the rotation axis O is defined as L. ２１ , L ２２ Then, these half lines L ２１ , L ２２ The central axes C of the planetary gears 4 are located between the two.

[0048] As shown in FIG. 10, in a cross section perpendicular to the rotation axis O, a pair of half lines circumscribing one end and the other end of the large diameter portion 611 of the first pinion gear 61 in the circumferential direction centered on the rotation axis O are defined as L. ３１ , L ３２ Then, these half lines L ３１ , L ３２ In this embodiment, the gear axis G of each of the first pinion gears 61 of the pinion gear sets 6 is located between the center axis C of each of the planetary gears 4 and the center axis G of each of the first pinion gears 61 of the pinion gear sets 6. １ and the central axes C of the planetary gears 4 are aligned in a radial direction perpendicular to the rotation axis O.

[0049] As shown in Figures 5, 8, and 11, the pinion gear holding portion 51 of the carrier body 50 has a plurality of bolt insertion holes 513 formed parallel to the rotation axis O, through which a plurality of bolts 501 for fixing the carrier lid body 500 to the carrier body 50 are inserted, respectively. The pinion gear holding portion 51 also has a plurality of recesses 514 formed therein, recessed from the outer peripheral surface 51c toward the inner peripheral surface 51a, with the deepest portions of the recesses 514 opening to the inner peripheral surface 51a. The recesses 514 function as oil holes that allow lubricating oil to circulate between the inside and outside of the pinion gear holding portion 51. The formation of the plurality of recesses 514 also contributes to a reduction in the weight of the pinion gear holding portion 51.

[0050] The bolt 501 has a shaft portion 501a inserted into the bolt insertion hole 513 and a head portion 501b having a larger diameter than the shaft portion 501a. The head portion 501b is disposed in the recess 514. A threaded hole 500a is formed in the carrier lid 500 so as to penetrate in the axial direction and into which the tip end of the shaft portion 501a passing through the bolt insertion hole 513 is threadedly engaged.

[0051] When the carrier 5 is viewed from the carrier lid 500 side along the rotation axis O, the multiple bolts 501 are arranged between the multiple retaining holes 510 in the circumferential direction centered on the rotation axis O. In Fig. 9, an imaginary circle VC that is centered on the rotation axis O and passes through center points 501c of the multiple bolts 501 is shown by a two-dot chain line. The imaginary circle VC intersects with a portion of each of the multiple retaining holes 510.

[0052] In the differential device 22 configured as described above, the sun gear 40 is rotationally driven by the electric motor 21, causing the plurality of planetary gears 4 to revolve around the rotation axis O, and the engagement of the small-diameter gear portion 42 of each planetary gear 4 with the ring gear 221 causes the carrier 5 to rotate relative to the housing 220. When a difference in wheel speed occurs between the left front wheel 11 and the right front wheel 12, such as when the four-wheel drive vehicle 1 is turning, the first and second pinion gears 61, 62 rotate within the retaining hole 510, and driving force is distributed from the first and second side gears 71, 72 to the left and right axles 23, 24 while allowing differential rotation, and frictional resistance between the tooth tips 610 a, 620 a of the first and second pinion gears 61, 62 and the inner surface of the retaining hole 510 limits differential rotation between the left and right axles 23, 24.

[0053] Effect of the embodiment According to the embodiment of the present invention described above, the carrier 5 is configured by the carrier main body 50 in which the plurality of retaining holes 510 are formed and the carrier cover body 500 that closes the plurality of retaining holes 510, and the plurality of one-side support portions 52 and the other-side support portions 53 are provided on the carrier main body 50. Therefore, compared to a case in which the pinion gear retaining portion 51 and the plurality of one-side support portions 52 and the other-side support portions 53 are separate, the driving force input from the plurality of planetary gears 4 to the plurality of one-side support portions 52 and the other-side support portions 53 can be directly transmitted to the plurality of pinion gear sets 6, and the differential device 22 can be made smaller and lighter while ensuring the strength of the carrier 5. Note that, if at least one of the plurality of one-side support portions 52 and the plurality of other-side support portions 53 is provided on the carrier main body 50, the effect of making the differential device 22 smaller and lighter while ensuring the strength of the carrier 5 can be obtained.

[0054] Furthermore, in this embodiment, since the carrier lid 500 is fixed to one of both end portions of the carrier main body 50 on the side where the multiple other-side support portions 53 are provided, the carrier lid 500 can be attached to and detached from the carrier main body 50 without the large-diameter gear portion 41 becoming an obstacle, even when multiple planetary gears 4 are attached to the carrier 5, making assembly easy. Furthermore, since the carrier lid 500 is attached to the axial end surface 51 b of the carrier main body 50 where both the first hole portion 511 and the second hole portion 512 are open, one first pinion gear 61 and two second pinion gears 62 of each pinion gear set 6 can be easily assembled to the pinion gear holding portion 51 of the carrier main body 50.

[0055] In addition, in this embodiment, the carrier body 50 has a plurality of one-side support portions 52 and other-side support portions 53 that protrude radially perpendicular to the rotation axis O from the outer periphery of the cylindrical pinion gear holding portion 51, so that spaces are formed between the plurality of one-side support portions 52 and other-side support portions 53, making the carrier body 50 lighter.

[0056] In addition, in this embodiment, in a cross section of the carrier body 50 perpendicular to the rotation axis O, the multiple bolts 501 are arranged so that an imaginary circle VC passing through the center points 501c of the multiple bolts 501 intersects with the multiple retaining holes 510, so that the carrier cover body 500 can be fixed to the carrier body 50 by the multiple bolts 501 while preventing the pinion gear retaining portion 51 from becoming larger in diameter.

[0057] (Note) While the present invention has been described above based on the embodiments, the invention according to the claims is not limited to these embodiments. 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 implemented by omitting some components, or by adding or substituting components, as appropriate, without departing from the spirit of the invention. For example, the following modifications are possible.

[0058] In the above embodiment, the differential gear of the present invention has been described as being applied to a four-wheel drive vehicle 1, but this is not limiting, and the differential gear of the present invention can also be applied to a two-wheel drive vehicle that drives only the left and right front wheels or the left and right rear wheels.

[0059] In addition, in the above embodiment, the first side gear 71 is connected to the left axle 23 and the second side gear 72 is connected to the right axle 24, but this left-right relationship may be reversed.

[0060] In the above embodiment, the one-side support portion 52 of the carrier 5 supports the planetary gear 4 at a position between the large-diameter gear portion 41 and the small-diameter gear portion 42. However, this is not limiting, and the one-side support portion 52 may support the planetary gear 4 at one end of the planetary gear 4 opposite the other-side support portion 53. Furthermore, the planetary gear 4 may be formed hollow with a cavity formed in the center, and a support shaft inserted into the center of the planetary gear 4 may be provided on the carrier 5. Bearings that support the planetary gear 4 relative to the support shaft on one axial side and the other axial side of the small-diameter gear portion 42 of the planetary gear 4 may be disposed between the outer circumferential surface of the support shaft and the inner circumferential surface of the cavity in the planetary gear 4. In this case, a portion of the support shaft on one axial side of the small-diameter gear portion 42 corresponds to the one-side support portion of the present invention, and a portion of the support shaft on the other axial side of the small-diameter gear portion 42 corresponds to the other-side support portion of the present invention.

[0061] DESCRIPTION OF SYMBOLS 21... Electric motor 22... Differential device 4... Planetary gear 41... Large diameter gear portion 42... Small diameter gear portion 43... One side supported portion 44... Other side supported portion 5... Carrier 50... Carrier main body 500... Carrier cover body 51... Pinion gear holding portion 510... Holding hole 52... One side support portion 53... Other side support portion 6... Pinion gear set 61... First pinion gear 62... Second pinion gear 71... First side gear 72... Second side gear 81... Planetary gear mechanism O... Rotation axis VC... Virtual circle

Claims

1. A vehicle differential device having a pair of side gears that are coaxially rotatable relative to one another, and that distributes and outputs an input driving force of an electric motor to the pair of side gears, a planetary gear mechanism including a sun gear to which the driving force is input, a plurality of planetary gears meshing with the sun gear, a carrier rotatably supporting the plurality of planetary gears, and a ring gear meshing with the plurality of planetary gears on an outer periphery of the carrier; a first pinion gear meshing with one of the pair of side gears and a second pinion gear meshing with the other of the pair of side gears, and a plurality of pinion gear sets formed by meshing the first pinion gear with the second pinion gear, Each of the plurality of planetary gears has a plurality of supported portions provided at positions spaced apart in the axial direction and supported by the carrier, the carrier includes a carrier body having a holding hole formed therein, the holding hole holding the first pinion gear and the second pinion gear rotatably about a rotation axis parallel to the rotation axis of the carrier, and a carrier cover body that is aligned with the carrier body in the axial direction and closes one axial end of the holding hole, a support portion that supports at least one of the plurality of supported portions of the plurality of planetary gears is provided on the carrier body, the retaining hole has a first hole portion that retains the first pinion gear and a second hole portion that retains the second pinion gear, the first hole portion and the second hole portion being in communication with each other; a driving force is transmitted from the carrier to the first pinion gear by a tooth tip surface of the first pinion gear contacting an inner surface of the first hole portion; a driving force is transmitted from the carrier to the second pinion gear by a tooth tip surface of the second pinion gear contacting an inner surface of the second hole portion; Vehicle differential.

2. Each of the plurality of planetary gears has a large diameter gear portion and a small diameter gear portion having different pitch circle diameters, and the plurality of supported portions, which are arranged coaxially, and the large diameter gear portion meshes with the sun gear and the small diameter gear portion meshes with the ring gear, the plurality of supported portions include a one-side supported portion supported by the carrier on one axial side closer to the large-diameter gear portion than the small-diameter gear portion, and an other-side supported portion supported by the carrier on the other axial side closer to the small-diameter gear portion, the carrier body has a plurality of other-side supporting portions that support the other-side supported portions of the plurality of planetary gears, 2. The vehicle differential according to claim 1.

3. the carrier body has a plurality of one-side supporting portions that support the one-side supported portions of the plurality of planetary gears, 3. The vehicle differential according to claim 2.

4. the carrier body has a cylindrical pinion gear holding portion having a plurality of holding holes formed therein, and the plurality of other-side support portions are provided on an outer periphery of the pinion gear holding portion so as to protrude in a radial direction perpendicular to the rotation axis; 3. The vehicle differential according to claim 2.

5. the carrier lid is fixed to one of both end portions of the carrier body on the side where the plurality of other-side support portions are provided; 5. A vehicle differential according to claim 2.

6. the carrier cover is fixed to the carrier body by a plurality of bolts, In a cross section perpendicular to the rotation axis, an imaginary circle centered on the rotation axis and passing through center points of the plurality of bolts intersects with the retaining holes.

2. The vehicle differential according to claim 1.