Differential device for vehicle

Abstract

[Problem]: To provide a small and lightweight differential device that can suppress freewheeling of a differential gear mechanism. [Solution]: A differential device 22 has: a planetary gear mechanism 81, which has a plurality of planet gears 4 and a carrier 5; and a differential gear mechanism 82, which has a pair of side gears 71, 72 and a plurality of pinion sets 6. Each planet gear 4 has a large-diameter gear part 41 and a small-diameter gear part 42. Each pinion set 6 is formed by the engagement of a first pinion 61, which engages with one side gear 71, and a second pinion 62, which engages with the other side gear 72. The first pinion 61 and the second pinion 62 are held in a retaining hole 510 formed in the carrier 5. The positions of the plurality of pinion sets 6 in a radial direction perpendicular to an axis of rotation O of the carrier 5 are closer to the side of the axis of rotation O than the positions in the radial direction of the small-diameter gear parts 42 of the plurality of planet gears 4.

Description

Technical field

[0001] The present invention relates to a vehicle differential device mounted on a vehicle having an electric motor as a drive source, which distributes the drive force input by the electric motor to a pair of side wheels and outputs the drive force. Technical background

[0002] In recent years, electrified vehicles, which use an electric motor as a drive source, have become more widespread. As described, for example, in patent literature 1 and 2, some of these electrified vehicles are equipped with a differential device that includes a planetary gear mechanism for reducing the output speed of the electric motor and a differential gear mechanism for distributing the drive force, amplified by the planetary gear mechanism, to a right and a left wheel. The differential gear mechanism has a pair consisting of a right and a left output gear, and a right and a left axle are correspondingly connected to these output gears.

[0003] The applicant has proposed the differential device described in patent literature 3 as a differential device for distributing the driving force from a drive source, such as a machine, to drive shafts which are accordingly connected to a right and a left wheel, while allowing differential movement. List of patent literature Patent Literature 1: JP 2021-110374 A Patent Literature 2: JP 2016-95034 A Patent Literature 3: JP 2019-007505 A Summary of the invention: Technical problem

[0004] It is highly desirable that a differential device fitted to an electrified vehicle be small and lightweight, while ensuring a desired level of strength to provide space for installing components such as a battery and to improve energy efficiency.

[0005] Compared to vehicles that use a motor as a power source, electrified vehicles are able to rapidly increase the driving force during, for example, rapid acceleration or a sudden start. However, in the differential gear mechanism designs described in patent literature 1 and 2, if one of the right and left wheels slips due to an increase in driving force, the differential pinion or gear rotates freely, and as a consequence, the driving force is not transmitted to the other wheel. It is therefore desirable to reduce such free rotation.

[0006] Therefore, it is an object of the present invention to provide a small and lightweight vehicle differential device that is able to reduce free rotation of a differential gear mechanism. Solution to the problem

[0007] To achieve the above objective, the present invention provides a vehicle differential device having a pair of side wheels arranged coaxially and rotatably relative to each other, and designed to distribute a driving force input by an electric motor to the pair of side wheels and to output the driving force.The vehicle drive device comprises: a planetary gear mechanism, including a sun gear to which the driving force is input; a plurality of planet gears, each having a large-diameter gear section and a small-diameter gear section arranged coaxially and having different pitch circle diameters; a carrier rotatably supporting the plurality of planet gears; and a ring gear arranged around the outer circumference of the carrier; and a plurality of pinion sets, each having a first pinion meshing with one side gear of the pair of side gears and a second pinion meshing with the other side gear of the pair of side gears, the first and second pinions meshing with each other. Each of the plurality of planet gears is configured such that the large-diameter gear section meshes with the sun gear and the small-diameter gear section meshes with the ring gear.The first and second pinions are housed in a retaining hole provided in the carrier, such that each of the first and second pinions is rotatable about an axis of rotation parallel to an axis of rotation of the carrier. When the pair of side gears rotates differentially, the tooth faces of the first and second pinions slide against an inner surface of the retaining hole, generating a frictional resistance force. Positions of the multiple pinion sets in a radial direction perpendicular to the axis of rotation are closer to the axis of rotation than positions of the small-diameter gear sections of the multiple planetary gears in the radial direction. Advantageous effects of the invention

[0008] The present invention can provide a small and lightweight differential device that is capable of reducing free rotation of a differential gear mechanism. Brief description of the drawings Fig. Figure 1 is a design diagram that schematically shows an example of the general design of a four-wheel-drive vehicle according to an embodiment of the present invention. Fig. Figure 2 is a schematic diagram showing the design of a front-wheel-drive vehicle. Fig. Figure 3 is a perspective view of a multitude of planetary gears and a carrier. Fig. Figure 4 is a perspective exploded view of a differential device. Fig. 5 is a sectional view along a line AA in Fig. 3. Fig. Figure 6 is a perspective view showing a gear set. Fig. Figure 7 is a side view showing the first sprocket. Fig. Figure 8 is a perspective sectional view of a support body. Fig. Figure 9 is a cross-sectional view along a line BB in Fig. 5. Fig. 10 is a cross-sectional view along a line CC in Fig. 5. Fig. Figure 11 is an external view showing one end of the support body. Fig. Figure 12 is a cross-sectional view of the support body perpendicular to an axial direction. Fig. Figure 13 is a cross-sectional view of a differential device according to a modification. Fig. Figure 14 is a schematic diagram showing a modification of a drive device. Description of embodiment examples (emphasis example)

[0009] An embodiment of the present invention is described with reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11 to Fig. 12. The embodiment described below is shown as a suitable specific example for carrying out the present invention, and part of the embodiment specifically represents various technically preferred features. However, the technical scope of the present invention is not limited to such specific aspects.

[0010] Fig. Figure 1 is a design diagram that schematically shows an example of the general design of a four-wheel-drive vehicle 1 according to the embodiment of the present invention. The four-wheel-drive vehicle 1 has: a front-wheel drive device 2 that drives a left front wheel 11 and a right front wheel 12; a rear-wheel drive device 3 that drives a left rear wheel 13 and a right rear wheel 14; and a control device 10 that controls the front-wheel drive device 2 and the rear-wheel drive device 3.

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

[0012] The rear-wheel drive device 3 has an electric motor 31, a differential device 32, and left and right axles 33, 34. The differential device 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 has an intermediate shaft 171 and constant velocity joints 172, 173, which are attached to both ends of the intermediate shaft 171. The right drive shaft 18 has an intermediate shaft 181 and constant velocity joints 182, 183, which are attached to both ends of the intermediate shaft 181.

[0013] The control device 10 is designed to obtain information about the results of measurements from various sensors located in the vehicle, which are mounted on the four-wheel-drive vehicle 1, via a network located in the vehicle, such as a CAN (Control Area Network). The sensors located in the vehicle include wheel speed sensors that measure the wheel speeds, specifically the rotational speeds of the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the right rear wheel 14; a steering angle sensor that measures the steering angle of a steering wheel operated by the driver; and an accelerator pedal sensor that measures the amount of pressure applied to an accelerator pedal.Based on the above information, the control device 10 controls the electric motor 21 of the four-wheel-drive vehicle 2 by supplying a motor current to the electric motor 21 and also controls the electric motor 31 of the rear-wheel drive device 3 by supplying a motor current to the electric motor 31.

[0014] Fig. Figure 2 is a schematic diagram showing the design of the front-wheel drive device 2. The rear-wheel drive device 3 is designed in the same way as the front-wheel drive device 2.

[0015] The electric motor 21 has a motor housing 210, a stator 211 fixed to the motor housing 210, a rotor 212 rotating relative to the stator 211, and a tubular motor shaft 213 rotating with the rotor 212. The stator 211 generates a magnetic field through a motor current supplied by the control device 10, and a permanent magnet in the rotor 212 generates a torque due to this magnetic field. The torque generated in the rotor 212 is transmitted by the motor shaft 213 to the differential device 22 as a driving force to power the left front wheel 11 and the right front wheel 12.

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

[0017] The plurality of planetary gears 4, the carrier 5, and the ring gear 221 form a planetary gear mechanism 81, which functions as a speed reduction device to decrease the output speed of the electric motor 21. The plurality of pinion sets 6 and the first and second side gears 71, 72 form a differential gear mechanism 82, which distributes the driving force of the electric motor 21, which has been amplified by the planetary gear mechanism 81, to the left and right axles 23, 24, while allowing differential movement. That is, the differential device 22 of the present embodiment is a differential device with a speed reduction device that incorporates the planetary gear mechanism 81 as a speed reduction device for decreasing the output speed of the electric motor 21.

[0018] The housing 220 contains the plurality of planet gears 4 and the carrier 5. Lubricating oil for lubricating components of the differential device 22 is tightly enclosed in the housing 220. The planet gear 4 has a plurality of supported sections provided at axially spaced positions, and the plurality of supported sections is supported by the carrier 5. The carrier 5 has a plurality of support sections that support the plurality of supported sections of each planet gear 4.

[0019] The motor shaft 213 of the electric motor 21, the support 5, and the side wheels 71, 72 are arranged side by side in the width direction of the four-wheel-drive vehicle 1 and coaxially to be rotatable relative to each other. The ring gear 221 is arranged around the outer circumference of the support 5. The left axle 23 is inserted through the center of the motor shaft 213 of the electric motor 21. The left axle 23 is longer than the right axle 24 by the length of the motor shaft 213.

[0020] The left axle 23 is connected to the left side wheel 71 so that it is not rotatable relative to the left side wheel 71. The right axle 24 is connected to the right side wheel 72 so that it is not rotatable relative to the right side wheel 72. Hereinafter, of the side wheels 71 and 72, the left side wheel 71 is referred to as the first side wheel 71, and the right side wheel 72 is referred to as the second side wheel 72. The first side wheel 71 is designed to have a larger diameter than the second side wheel 72.

[0021] Fig. Figure 3 is a perspective view showing the multitude of planetary gears 4 and the carrier 5. Fig. Figure 4 is a perspective exploded view of the differential device 22, showing the plurality of planet gears 4, the carrier 5, the plurality of pinion sets 6, the first and second side gear 71, 72, etc. Fig. 5 is a sectional view along a line AA in Fig. 3. In Fig. 3 and Fig. In Figure 5, the axis of rotation O of the carrier 5 and the central axis C of each of the plurality of planetary gears 4 are indicated by lines with a long and a short stroke. The axis of rotation O of the carrier 5 and the central axis C of each of the plurality of planetary gears 4 are parallel to each other.

[0022] The planetary gear mechanism 81 has three planet gears 4 arranged at equal intervals along the circumferential direction of the carrier 5. Each planet gear 4 has a large-diameter gear section 41 and a small-diameter gear section 42, which are arranged coaxially and have different pitch circle diameters. The large-diameter gear section 41 meshes with the sun gear 40, and the small-diameter gear section 42 meshes with the ring gear 221 at the outer circumference of the carrier 5. The pitch circle diameter of the large-diameter gear section 41 is, for example, at least twice the pitch circle diameter of the small-diameter gear section 42.

[0023] When the sun gear 40 rotates with the motor shaft 213, the large-diameter gear section 41 and the small-diameter gear section 42 of each of the plurality of planet gears 4 rotate together about the central axis C. The large-diameter gear section 41 and the small-diameter gear section 42 are helical gears, each having, on its outer circumferential surface, a plurality of helical teeth whose tooth lines are inclined with respect to the axial direction. Fig. 3, Fig. 4 to Fig. Figure 5 omits a representation of the inclined teeth, and the large-diameter gear section 41 and the small-diameter gear section 42 are shown in a simplified manner.

[0024] The planet gear 4, as the plurality of supported sections supported by the carrier 5, has a supported section 43 located on one side and a supported section 44 located on the other side, which are coaxial with the large-diameter gear section 41 and the small-diameter gear section 42. The supported section 43 located on one side is supported by the carrier 5 on an axial side of the small-diameter gear section 42, which is the side that is closer to the large-diameter gear section 41. The supported section 44 located on the other side is supported by the carrier 5 on the other axial side of the small-diameter gear section 42. In the present embodiment, the supported section 43 located on one side is provided between the large-diameter gear section 41 and the small-diameter gear section 42.The supported section 44, located on another side, is provided at the end of the planet gear 4 opposite the large-diameter gear section 41.

[0025] The carrier 5 has a carrier body 50 and a carrier cover 500, and the carrier cover 500 is fixed to the carrier body 50 by a plurality of bolts 501. The carrier body 50 is provided with a support section that supports at least one of the plurality of supported sections (the supported section 43 located on one side and the supported section 44 located on another side) of the planet gear 4. In the present embodiment, the carrier body 50 has in one piece the following: a cylindrical pinion retaining section 51; a plurality of support sections 52 located on one side, each supporting the supported section 43 located on one side of a corresponding planet gear 4; and a plurality of support sections 53 located on another side, each supporting the supported section 44 located on another side of a corresponding planet gear 4.

[0026] The plurality of support sections 52 located on one side are provided on the outer circumference of the end of the pinion retaining section 51 on the side of the large-diameter gear sections 41 of the planet gears 4, in order to project radially perpendicular to the axis of rotation O. The plurality of support sections 53 located on the other side are provided on the outer circumference of the end of the pinion retaining section 51 opposite the large-diameter gear sections 41 of the planet gears 4, in order to project radially perpendicular to the axis of rotation O.

[0027] The plurality of support sections 52 located on one side each support the corresponding supported section 43 of a corresponding planet gear 4 via a corresponding first bearing 91. The first bearing 91 is a ball bearing in which a plurality of rolling elements (balls) 913 are arranged between an outer ring 911 and an inner ring 912, and is housed in a casing bore 520 formed in the support section 52 located on one side. Axial movement of the outer ring 911 is restricted by a retaining ring 901 that fits into the support section 52 located on one side. Axial movement of the inner ring 912 relative to the planet gear 4 is restricted by a retaining ring 902 that fits onto the planet gear 4.

[0028] The plurality of support sections 53 located on opposite sides each support the supported section 44 of a corresponding planet gear 4 located on opposite sides via a corresponding second bearing 92. The second bearing 92 is a needle roller bearing in which a plurality of needle rollers 922 are arranged inside a cylindrical outer ring 921 and is housed in a casing bore 530 formed in the support section 53 located on opposite sides. The plurality of needle rollers 922 are retained by a cage 923 and roll on an outer circumferential surface 44a of the supported section 44 located on opposite sides.

[0029] The support cover 500 is arranged axially along the support body 500 and is fixed at one of two ends of the support body 50 on the side where the plurality of support sections 53 located on the opposite side is provided. The first side gear 71 is positioned closer to the large-diameter gear sections 41 of the planet gears 4 than the second side gear 72. The second side gear 72 is positioned on the opposite side closer to the plurality of support sections 53 located on the opposite side than to the plurality of support sections 52 located on one side. In the present embodiment, an axial section of the second side gear 72 is arranged radially inward from the plurality of support sections 53 located on the opposite side in a direction perpendicular to the axis of rotation O.

[0030] A section of the pinion retaining section 51 is aligned axially with the first side gear 71, and a first side spacer 93 is arranged between the first side gear 71 and the pinion retaining section 51. A center spacer 94 is arranged between the first side gear 71 and the second side gear 72. A second side spacer 95 is arranged between the second side gear 72 and the carrier cover 500.

[0031] The first pinion 61 meshes with the first side gear 71. The second pinion 62 is arranged on the outer circumference of the second side gear 72 and meshes with both the first pinion 61 and the second side gear 72. In the present embodiment, each of the plurality of pinion sets 6 has a first pinion 61 and two second pinions 62, and the first pinion 61 is arranged between the two second pinions 62. The number of pinion sets 6 in the differential device 22 is the same as the number of planet gears 4. In the present embodiment, three pinion sets 6 are held by the pinion retaining section 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, each having, on its outer circumferential surface, a plurality of inclined teeth whose tooth lines are inclined with respect to the axial direction. Fig. 3, Fig. 4 to Fig. Figure 5 omits a representation of the inclined teeth, and each gear is shown in a simplified manner. A plurality of retaining holes 510, each serving to hold the first pinion 61 and the two second pinions 62 of a corresponding pinion set 6, are formed in the pinion retaining section 51 of the carrier body 50.

[0033] The plurality of retaining holes 510 is formed in the axial direction parallel to the axis of rotation O between the plurality of support sections 52 located on one side and the plurality of support sections 53 located on the other side. An axial section of each of the plurality of retaining holes 510 is formed inwards from a corresponding plurality of support sections 53 located on the other side in a radial direction perpendicular to the axis of rotation O.

[0034] Fig. Figure 6 is a perspective view showing a pinion set 6. Fig. Figure 7 is a side view showing the first pinion 61. In the example shown in Fig. 6 and Fig. As shown in Figure 7, six inclined teeth 610 are formed on the first pinion 61, and the same number of inclined teeth 620 are formed on every second pinion 62. The tooth end faces 610a, 620a of the inclined teeth 610, 620 are formed with a predetermined width in a direction perpendicular to the tooth line. The gear axis G1 of the first pinion 61 and the gear axes G2 of the second pinions 62 are parallel to the axis of rotation O of the carrier 5.

[0035] The second pinions 62 are axially shorter than the first pinion 61 and mesh with the first pinion 61 on the outer circumferential side of the second side gear 72. The axial length of the first pinion 61 corresponds to the combined axial widths of the first side gear 71 and the second side gear 72. The axial length of each second pinion 62 corresponds to the axial width of the second side gear 72.

[0036] In the first pinion 61, a large-diameter section 611 and a small-diameter section 612, having different pitch circle diameters, are formed side by side in the axial direction. The large-diameter section 611 meshes with the first side gear 71. The small-diameter section 612 meshes with the two second pinions 62. As shown in Fig. As shown in Figure 5, the entire large-diameter section 611 is arranged in the axial direction parallel to the axis of rotation O of the beam 5 between the plurality of support sections 52 located on one side and the plurality of support sections 53 located on the other side. An axial section of the small-diameter section 612 is arranged inwards from the plurality of support sections 53 located on the other side in a radial direction perpendicular to the axis of rotation O.

[0037] If P1 represents the pitch circle diameter of the large-diameter section 611 and P2 represents the pitch circle diameter of the small-diameter section 612, then the ratio of P1 to P2 (P1 / P2) is, for example, from 1.05 to 1.15. If θ1 represents the helix angle of a tooth line 611a in the large-diameter section 611 and θ2 represents the helix angle of a tooth line 612 in the small-diameter section 612, then θ1 is greater than θ2, and the ratio (θ1 / θ2) is, for example, the same as the ratio of the pitch circle diameters of the large-diameter section 611 and the small-diameter section 612.

[0038] Fig. Figure 8 is a perspective sectional view of the carrier body 50 and shows the interior of the pinion holding section 51. Fig. Figure 9 is a cross-sectional view of the differential gear mechanism 82 and the planetary gear mechanism 81 along a line BB in Fig. 5. Fig. Figure 10 is a cross-sectional view of the differential gear mechanism 82 and the planetary gear mechanism 81 along a line CC in Fig. 5. Fig. Figure 11 is an external view of the end of the support body 50 on the side where the support sections 53 located on another side are situated, from a view in one direction along the axis of rotation O. Fig. Figure 12 is a sectional view of the support body 50 along a line CC in Fig. 5.

[0039] Three retaining holes 510 are formed at equal intervals in the circumferential direction in the pinion retaining section 51 of the carrier body 50. Each retaining hole 510 has a first hole section 511 for retaining the first pinion 61 and two second hole sections 512, each for retaining one of the two second pinions 62. The first hole section 511 and the two second hole sections 512 are interconnected. The first pinion 61 and the two second pinions 62 are accommodated in the retaining hole 510 such that each of the first and second pinions 61, 62 rotates (rotates rapidly) about its axis parallel to the axis of rotation O of the carrier 5.

[0040] The first hole section 511 and the second hole sections 512 open to an inner circumferential surface 51a of the pinion retaining section 51. A circumferential section of the first pinion 61 projects from the first hole section 511 to the interior of the pinion retaining section 51 and meshes with the first side gear 71. A circumferential section of the second pinion 62 projects from the second hole section 512 to the interior of the pinion retaining section 51 and meshes with the second side gear 72.

[0041] The first hole section 511 and the second hole sections 512 open to an axial end surface 51b of the support body 50 in the pinion retaining section 51. The support cover 500 rests against the axial end surface 51b of the pinion retaining section 51 by axial forces of the plurality of bolts 501 and closes an axial end of each of the plurality of retaining holes 510.

[0042] The driving force of the electric motor 21, which is applied to the carrier 5, is transmitted to the first pinion 61 and the second pinions 62 by contact of the tooth end surfaces 610a, 620a with an inner surface 511a of the first hole section 511 and inner surfaces 512a of the second hole sections 512, specifically the inner surface of the retaining hole 510. The driving force transmitted to the large-diameter section 611 and the small-diameter section 612 of the first pinion 61 is transmitted from the large-diameter section 611 to the first side gear 71. The driving force transmitted to the two second pinions 62 is transmitted to the second side gear 72.

[0043] When a wheel speed difference occurs between the left front wheel 11 and the right front wheel 12, and the first side wheel 71 and the second side wheel 72 rotate differentially, the tooth head surfaces 610a of the plurality of inclined teeth 610 of the first pinion 61 slide on the inner surface 511a of the first hole section 511, and the tooth head surfaces 620a of the plurality of inclined teeth 620 of the second pinion 62 slide on the inner surface 512a of the second hole section 512, thereby generating a frictional resistance force.

[0044] Due to this frictional resistance force, it becomes less likely that, if the driving force can no longer be transmitted to one of the left front wheels 11 and the right front wheel 12 due to slippage, etc., the differential gear mechanism 82 will rotate freely and the driving force can no longer be transmitted to the other wheel. That is, the frictional resistance force generated between the inner surface of the retaining hole 510 and the tooth end faces 610a, 620a of the first pinion 61 and the second pinion 62 serves as a differential limiting force to restrict differential movement between the left front wheel 11 and the right front wheel 12.

[0045] The first hole section 511 has a large-diameter hole section 511b, which holds the large-diameter section 611 of the first pinion 61, and a small-diameter hole section 511c, which holds the small-diameter section 612 of the second pinion 62. The large-diameter hole section 511b is configured to have a larger diameter than the small-diameter hole section 511c. Fig. 11 is a part of each large diameter hole section 511b marked with a dashed line.

[0046] As in Fig. 5, Fig. 9 and Fig. As shown in Figure 10, the positions of the plurality of pinion sets 6 in a radial direction perpendicular to the axis of rotation O of the carrier 5 are closer to the axis of rotation O than the positions of the small-diameter gear sections 42 of the plurality of planet gears 4 in the radial direction.

[0047] The plurality of retaining holes 510 is formed inwards of the plurality of planet gears 4 in a radial direction perpendicular to the axis of rotation O. The entire axial extent of each first hole section 511 is located radially inwards of the small-diameter gear sections 42 and the supported sections 44 of the plurality of planet gears 4 located on another side.

[0048] As in Fig. 9 is shown, in a cross-section perpendicular to the axis of rotation O, when a pair of half-lines extending from the axis of rotation O, one half-line being tangent to one end of the retaining hole 510 in the circumferential direction around the axis of rotation O and the other half-line being tangent to the other end of the retaining hole 510, as L 11 , L 12 The central axis C of each of the plurality of planetary gears 4 is defined as being between the corresponding half-lines L. 11 , L 12located. If a pair of half-lines, each extending from the axis of rotation O, wherein one half-line is tangent to one end of the small-diameter section 612 of the first pinion 61 in the circumferential direction around the axis of rotation O and wherein the other half-line is tangent to the other end of the small-diameter section 612 of the first pinion 61, as L 21 , L 22 The central axis C of each of the plurality of planetary gears 4 is defined as being between the corresponding half-lines L. 21 , L 22 located.

[0049] As in Fig. Figure 10 shows a cross-section perpendicular to the axis of rotation O when a pair of half-lines, wherein one half-line is tangent to one end of the large-diameter section 611 of the first pinion 61 in the circumferential direction around the axis of rotation O and wherein the other half-line is tangent to the other end of the large-diameter section 611 of the first pinion 61, is L 31 , L 32 The central axis C of each of the plurality of planetary gears 4 is defined as being between the corresponding half-lines L. 31 , L 32 In the present embodiment, the gear axis G1 of the first pinion 61 of each of the plurality of pinion sets 6 is aligned with the central axis C of a corresponding plurality of planet gears 4 in a radial direction perpendicular to the axis of rotation O.

[0050] As in Fig. 5, Fig. 8 and Fig. As shown in Figure 11, a plurality of bolt insertion holes 513, each for inserting a corresponding plurality of bolts 501 that fix the support cover 500 to the support body 50, are formed in the pinion retaining section 51 of the support body 50 to be parallel to the axis of rotation O. The pinion retaining section 51 also has a plurality of recesses 514 extending from its outer circumferential surface 51c to its inner circumferential surface 51a, with the deepest portion of each recess 514 opening to the inner circumferential surface 51a. The recesses 514 function as oil holes, allowing lubricating oil to flow between the interior and exterior of the pinion retaining section 51. Forming the plurality of recesses 514 reduces the weight of the pinion retaining section 51.

[0051] The bolt 501 has a shank 501a, which is inserted through the bolt insertion hole 513, and a head 501b, which has a larger diameter than the shank 501a. The head 501b is located within the recess 514. Screw holes 500a, into which the distal ends of the shanks 501a, which have been passed through the bolt insertion holes 513, are screwed, are formed in the support cover 500 to extend through it in the axial direction.

[0052] When the support 5 is viewed along the axis of rotation O from the side of the support cover 500, the plurality of bolts 501 is arranged between the plurality of retaining holes 510 in the circumferential direction around the axis of rotation O. Fig. 9 is an imaginary circle VC having a center on the axis of rotation O and passing through the centers 501c of the plurality of bolts 501, indicated by a line with one long and two short dashes. The imaginary circle VC intersects a section of each of the plurality of retaining holes 510.

[0053] In the differential device 22, which is designed as described above, when the sun gear 40 is driven by the electric motor 21, the plurality of planet gears 4 rotate around the axis of rotation O. This causes the carrier 5 to rotate relative to the housing 220 due to the engagement between the small-diameter gear section 42 of each planet gear 4 and the ring gear 221. If a wheel speed difference occurs between the left front wheel 11 and the right front wheel 12, for example, during cornering of the four-wheel-drive vehicle 1, the first and second pinions 61, 62 rotate in the retaining holes 510, thereby distributing the driving force from the first and second side gears 71, 72 to the left and right axles 23, 24, while allowing differential movement.Furthermore, if one of the left front wheel 11 and the right front wheel 12 slips, differential movement between the left and right axles 23, 24 is limited by the frictional resistance force generated between the tooth head surfaces 610a, 620a of the first and second pinion 61, 62 and the inner surfaces of the retaining holes 510. (Effects of the exemplary implementation)

[0054] According to the embodiment described above, due to the design in which the plurality of pinion sets 6 are arranged inwards from the plurality of planet gears 4 in a radial direction perpendicular to the axis of rotation O of the carrier 5, and the design in which the first and second pinions 61, 62 rotate within the plurality of retaining holes 510 formed in the carrier 5, it is possible to reduce the free rotation of the differential gear mechanism 82 and to reduce the size and weight of the differential device 22.

[0055] Furthermore, in the present embodiment, the number of planet gears 4 is the same as the number of pinion sets 6, and the plurality of retaining holes 510 are formed inwards from the planet gears 4 in a radial direction perpendicular to the axis of rotation O of the carrier 5. Consequently, it is more likely that the force absorbed by each planet gear 4 through engagement with the ring gear 221 will be transmitted directly to the first and second pinions 61, 62 of the pinion set 6, which makes it possible to reduce the size and weight of the carrier 5 while ensuring its strength.

[0056] In the present embodiment, since the retaining holes 510 are formed in the axial direction of the carrier body 50 between the plurality of support sections 52 located on one side and the plurality of support sections 53 located on the other side, the space inside the plurality of planet gears 4 can be effectively used as a space for accommodating the differential gear mechanism 82. Furthermore, the driving force can be transmitted in a well-balanced manner from the carrier body 50 over the entire lengths of the first and second pinions 61, 62 in the direction of the gear axes G1, G2.

[0057] In the present embodiment, a section of each retaining hole 510 extends inwards from a corresponding support section 53 located on a different side of the carrier 5 in a radial direction perpendicular to the axis of rotation O of the carrier 5, and the corresponding first and second pinions 61, 62 are located in this section of each retaining hole 510. Consequently, the drive force transmission path between each of the support sections 53 located on a different side and the corresponding first and second pinions 61, 62 is shortened. This makes it possible to reduce elastic deformation of the carrier 5 and to transmit the drive force efficiently.

[0058] In the present embodiment, due to the positional relationship between the planet gears 4, the pinion sets 6 and the retaining holes 5, as with reference to Fig. 9 and Fig. As described in section 10, the driving force is efficiently and in a well-balanced manner transmitted from each planet gear 4 to a corresponding pinion set 6. This makes it possible to reduce the size and weight of the carrier 5 while ensuring its strength. (First modification)

[0059] Next, a first modification, in which the design of the differential device 22 is modified, is described with reference to Fig. 13 described. In the first modification, the relative positional relationship between the planet gears 4, the plurality of pinion sets 6 and the retaining holes 510 in the circumferential direction around the axis of rotation O of the carrier 5 differs from that in the preceding embodiment.

[0060] Fig. Figure 13 is a cross-sectional view of the differential device 22 according to the first modification. Fig. Figure 13 shows a cross-section at a position corresponding to that of Fig. 9 of the preceding embodiment. Fig. Figure 13 also shows a line segment L4 that connects the axis of rotation O of the carrier 5 and the central axis C of the planet gear 4.

[0061] In the cross-section that is in Fig. As shown in Figure 13, the differential device 22 according to the first modification is designed such that the central position of each of the plurality of pinion sets 6 is located circumferentially around the axis of rotation O forward with respect to the line segment L4 in the main direction of rotation of the carrier 5 relative to the ring gear 221. The central position of the pinion set 6 in the circumferential direction corresponds to the position of the gear axis G1 of the first pinion 61. The main direction of rotation of the carrier 5 is the direction in which the carrier 5 rotates when the four-wheel-drive vehicle 1 is moving forward. Fig. 13 is a direction in which the carrier 5 moves when the four-wheel-drive vehicle 1 moves forward, indicated by an arrow D.

[0062] According to the first modification, particularly when the four-wheel-drive vehicle 1 is moving forward, the power received by each planetary gear 4 through engagement with the ring gear 221 is more easily transmitted directly to the first and second pinions 61, 62 of a corresponding pinion set 6. As a result, it becomes easier to reduce bending deformation of the support 5 when the four-wheel-drive vehicle 1 is moving forward, and it is possible to reduce the size and weight of the support 5 while ensuring its strength. (Second modification)

[0063] Fig. Figure 14 is a schematic diagram showing a second modification in which the positional relationship between the electric motor 21 and the differential device 22 in the drive device 2 is modified. The preceding embodiment represents the case in which the electric motor 21 and the support 5 are arranged coaxially. In the second modification, which is shown in Fig. As shown in Figure 14, the electric motor 21 and the support 5 are arranged side by side in the radial direction and parallel to each other. A speed reduction mechanism 25 is also provided between the electric motor 21 and the planetary gear mechanism 81.

[0064] The speed reduction mechanism 25 has a small-diameter gear 251 fixed to the motor shaft 213 of the electric motor 21, a large-diameter gear 252 meshing with the small-diameter gear 251, and a hollow shaft section 253 rotating with the large-diameter gear 252, with a sun gear 40 fixed to one end of the shaft section 253. The left axle 23 passes through the shaft section 253. The output speed of the electric motor 21 is reduced primarily by the speed reduction mechanism 25, then secondarily by the planetary gear mechanism 81, and transmitted to the support 5.

[0065] According to the second modification, the output speed of the electric motor 21 is reduced by a larger reduction ratio compared to the preceding embodiment. Therefore, even an electric motor 21 with a small maximum output torque can drive the right and left wheels of the vehicle. Furthermore, the length of the drive device 2 can be reduced in the direction of the vehicle's width. (Additional notes)

[0066] Although the present invention has been described above based on the exemplary embodiment and modifications, it is not intended that the exemplary embodiment and modifications limit the invention according to the claims. It should be noted that not all combinations of features described in the exemplary embodiment and modifications are essential means of solving the problem in the invention. The present invention can be modified as appropriate by omitting some components or adding or substituting components without departing from the core and scope of the present invention. For example, the present invention can be modified as described below.

[0067] The foregoing embodiment represents the case in which the differential device of the present invention is applied to the four-wheel-drive vehicle 1. However, the present invention is not limited thereto, and the differential device of the present invention can be applied to a two-wheel-drive vehicle that drives only the right and left front wheels or the right and left rear wheels.

[0068] The preceding embodiment describes the case in which the support section 52 of the carrier 5, located on one side, supports the planet gear 4 at a position between the large-diameter gear section 41 and the small-diameter gear section 42. However, the present invention is not limited to this, and the support section 52 located on one side can support the planet gear 4 at an end of the planet gear 4 that is located on the side opposite the support section 53 located on another side. Furthermore, the planet gear 4 can be formed in a hollow shape with a cavity formed at its center, and the carrier 5 can be provided with a support shaft that is inserted through the center of the planet gear 4.Bearings supporting the planet gear 4 relative to the support shaft on one axial side and the other axial side of the small-diameter gear section 42 of the planet gear 4 can be arranged between the outer circumferential surface of the support shaft and the inner circumferential surface of the cavity of the planet gear 4. In this case, a section of the support shaft on one axial side of the small-diameter gear section 42 serves as the one-side support section of the present invention, and a section of the support shaft on the other axial side of the small-diameter gear section 42 serves as the other-side support section of the present invention. Reference symbol list 21 electric motor 22 Differential device 4 planetary gear 41 large diameter gear section 42 small diameter gear section 43 Supported section located on one side 44 supported section located on another side 5 carriers 50 carrier bodies 500 carrier cover 501 bolts 501c Center 51 Pinion holding section 510 retaining hole 52 Support section located on one side 53 support section located on another side 6 sprocket set 61 first sprocket 610a Tooth head surface 611 large diameter section 612 small diameter section 62 second sprocket 620a Tooth head surface 71 first side wheel 72 second side wheel 81 Planetary gear mechanism C Central axis L 11 , L 12 , L 21 , L 22 , L 31 , L 32 Half-bar L4 line segment O axis of rotation VC imaginary circle QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2021-110374 A

[0003] JP 2016-95034 A

[0003] JP 2019-007505 A

[0003]

Claims

[1] Vehicle differential device with a pair of side wheels arranged coaxially and rotatably relative to each other, wherein the vehicle differential device is designed to distribute a driving force input by an electric motor to the pair of side wheels and to output the driving force, wherein the vehicle differential device comprises: a planetary gear mechanism comprising a sun gear to which the driving force is input, a plurality of planet gears, each having a large-diameter gear section and a small-diameter gear section arranged coaxially and having different pitch circle diameters, a carrier rotatably supporting the plurality of planet gears, and a ring gear arranged around an outer circumference of the carrier; a plurality of pinion sets, each having a first pinion that meshes with one side gear of the pair of side gears, and a second pinion that meshes with the other side gear of the pair of side gears, wherein the first pinion and the second pinion mesh with each other, wherein: Each of the many planetary gears is designed such that the large-diameter gear section meshes with the sun gear and the small-diameter gear section meshes with the ring gear; the first pinion and the second pinion are housed in a retaining hole provided in the carrier, such that each of the first pinion and the second pinion is rotatable about an axis of rotation parallel to an axis of rotation of the carrier, and, when the pair of side gears rotates differentially, tooth head surfaces of the first pinion and the second pinion slide on an inner surface of the retaining hole and generate a frictional resistance force; and Positions of the multitude of pinion sets in a radial direction perpendicular to the axis of rotation are closer to the axis of rotation than positions of the small-diameter gear sections of the multitude of planet gears in the radial direction. [2] Vehicle differential device according to claim 1, wherein the number of planetary gears is the same as the number of multiple pinion sets; and the carrier has a plurality of retaining holes, each of which holds a corresponding plurality of pinion sets, each plurality of retaining holes being provided inwards by a corresponding plurality of planet gears in the radial direction. [3] Vehicle differential device according to claim 1, wherein: Each of the multiple planetary gears has a supported section located on one side, which is supported by the carrier on an axial side of the small-diameter gear section that is closer to the large-diameter gear section, and a supported section located on another side that is supported by the carrier on the other axial side of the small-diameter gear section; the carrier has a plurality of support sections located on one side, each of which supports the supported section located on one side of a corresponding plurality of planetary gears, and a plurality of support sections located on another side, each of which supports the supported section located on another side of a corresponding plurality of planetary gears; and The retaining hole is provided between the support sections located on one side and the support sections located on the other side in an axial direction parallel to the axis of rotation. [4] Vehicle differential device according to claim 3, wherein a section of the retaining hole is provided inwards in the radial direction from the support section located on another side. [5] Vehicle differential device according to claim 4, wherein: Each of the multiple sets of pinions has one of the first pinions and two of the second pinions, the first pinion being arranged between the two second pinions, and the first pinion and the two second pinions meshing with each other on an outer circumferential side of the other side gear; and in a cross-section perpendicular to the axis of rotation, a central axis of each of the plurality of planetary gears is located between a pair of half-lines extending from the axis of rotation, one of the half-lines being tangent to one end of the first pinion in a circumferential direction around the axis of rotation and the other half-line being tangent to the other end of the first pinion. [6] Vehicle differential device according to claim 5, wherein In the first pinion, a large-diameter section and a small-diameter section, having different pitch circle diameters, are arranged side by side in the axial direction, the large-diameter section meshing with one side gear and the small-diameter section meshing with the second pinion; and in the cross-section perpendicular to the axis of rotation, the central axis of each of the plurality of planetary gears is located between a pair of half-lines extending from the axis of rotation, one of the half-lines being tangent to one end of the large-diameter section of the first pinion in the circumferential direction around the axis of rotation, and the other half-line being tangent to the other end of the large-diameter section of the first pinion. [7] Vehicle differential device according to claim 6, wherein a central axis of the first pinion of each of the plurality of pinion sets is aligned with the central axis of a corresponding plurality of planetary gears in the radial direction. [8] Vehicle differential device according to one of claims 5 to 7, wherein, in the cross-section, a central position of each of the plurality of pinion sets is located in the circumferential direction forward with respect to a line segment in a main direction of rotation of the carrier relative to the ring gear, wherein the line segment is a line segment connecting the axis of rotation and the central axis of a corresponding plurality of planet gears.

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