Vehicle differential

Abstract

[Problem] To provide a differential device for a vehicle with which it is possible to prevent an increase in differential limit force due to thermal expansion of a gear in a differential case while suppressing a reduction in the responsiveness of differential limit force. [Solution] A differential device 1 for a vehicle comprises: a plurality of pinion gear pairs 2, a first side gear pair 3 formed by helical spline fitting of a first outer gear member 31 and a first inner gear member 32; a second side gear pair 4 formed by helical spline fitting of a second outer gear member 41 and a second inner gear member 42; a differential case 10 having a cylindrical part 110 and first and second side wall parts 111, 121 holding the plurality of pinion gear pairs 2; a first end washer 51 and a first disc spring 61 disposed between the first side gear pair 3 and the first side wall part 111; and a second end washer 52 and a second disc spring 62 disposed between the second side gear pair 4 and the second side wall part 121.

Description

[Technical Field]

[0001] The present invention relates to a vehicle differential having a differential limiting function. [Background technology]

[0002] Conventionally, a differential that distributes driving force from a drive source of a vehicle to left and right wheels while allowing differential rotation between them includes a differential limiting function that limits the differential rotation between the left and right wheels. Such a differential can transmit driving force to the other wheel even when one of the left and right wheels slips, for example, thereby improving driving stability.

[0003] The differential device described in Patent Document 1 includes a plurality of planetary gear pairs, each of which is formed by meshing a pair of planetary gears, a first sun gear meshing with one of the pair of planetary gears, a second sun gear meshing with the other of the pair of planetary gears, and a differential case (housing) that houses these. The differential case has a cylindrical portion formed with retaining holes that hold the plurality of planetary gear pairs, and first and second sidewall portions formed to close both ends of the cylindrical portion. The first and second sun gears are arranged side by side in the axial direction between the first sidewall portion and the second sidewall portion. Washers are respectively arranged between the first sun gear and the first sidewall portion, between the second sun gear and the second sidewall portion, and between the first sun gear and the second sun gear.

[0004] The first and second sun gears are divided into an outer portion and an inner portion at approximately their radial centers, and a spline portion formed on the outer periphery of the inner portion is spline-fitted with a spline hole formed on the inner periphery of the outer portion. Due to this spline fitting, thrust forces in opposite directions are generated between the outer portion and the inner portion when torque is transmitted to the left and right wheels, and the axial end faces of the outer portion and the inner portion are pressed against the washers. The frictional force between these axial end faces and the washers increases the differential limiting force. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-174577 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when traveling on muddy or gravel roads, where a large differential limiting force is frequently generated, the gears in the differential case may expand due to frictional heat, increasing their axial length. In such a case, if the thermal expansion of one of the gears in the differential case causes both axial ends of that gear to be pressed against the washer, the differential limiting force may become greater than the magnitude generated by the axial thrust force. Furthermore, if the axial gap (backlash) between the gears and the washer in the differential case is increased to prevent the increase in thrust force due to the thermal expansion of the gears, the responsiveness of the differential limiting force when wheel slippage occurs may be reduced.

[0007] Therefore, an object of the present invention is to provide a vehicle differential device that can suppress an increase in the differential limiting force due to thermal expansion of the gears in the differential case while suppressing a decrease in the responsiveness of the differential limiting force. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a differential device for a vehicle that distributes the driving force of a driving source of the vehicle to a pair of output shafts while allowing differential movement, the differential device comprising: a pinion gear set formed by meshing a first pinion gear and a second pinion gear, each having helical teeth whose tooth trace is inclined with respect to the axial direction; a cylindrical first outer gear member that meshes with the first pinion gear; and a first inner gear member disposed inside the first outer gear member, the first outer gear member and the first inner gear member being helically splined. a second side gear set having a cylindrical second outer gear member meshing with the second pinion gear and a second inner gear member disposed inside the second outer gear member, the second outer gear member and the second inner gear member being helically spline-fitted; a differential case having a cylindrical portion formed with a retaining hole for rotatably accommodating the first pinion gear and the second pinion gear, and first and second side wall portions; a first sliding member disposed between the first outer gear member and the first inner gear member and the first side wall portion; a second sliding member disposed between the second outer gear member and the second inner gear member of the second side gear set and the second side wall portion; a third sliding member disposed between the first outer gear member and the first inner gear member of the first side gear set and the second outer gear member and the second inner gear member of the second side gear set; and a third sliding member disposed between the first side wall portion in the differential case and the first side wall portion in the differential case. and an elastic member that is arranged in line with any of the first to third sliding members in the rotational axis direction of the differential case between the first side wall portion and the second side wall portion, and is elastically deformable in the rotational axis direction, wherein the elastic member is compressed in the rotational axis direction by the first outer gear member and the second outer gear member, or the first inner gear member and the second inner gear member, both during driving, in which torque in the forward direction of the vehicle is input to the differential case, and during coasting, in which the vehicle is coasting forward. The first sliding member and the second sliding member are restricted in their relative rotation with respect to the differential case and are movable relative to the differential case in the direction of the rotation axis. A vehicle differential is provided. [Effects of the Invention]

[0009] According to the vehicle differential device of the present invention, it is possible to suppress an increase in the differential limiting force due to thermal expansion of the gears in the differential case while suppressing a decrease in the response of the differential limiting force. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an example of the configuration of a vehicle differential device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is an exploded perspective view of a vehicle differential. [Figure 4A] 1 is a cross-sectional view of a portion of a vehicle differential during driving at normal temperature. [Figure 4B] 1 is a cross-sectional view of a portion of a vehicle differential during high-temperature driving. [Figure 5A] 1 is a cross-sectional view of a portion of a vehicle differential during coasting at room temperature; [Figure 5B] FIG. 2 is a cross-sectional view of a portion of a vehicle differential during coasting at high temperatures. [Figure 6A] 10 is a partial cross-sectional view of a vehicle differential device according to a comparative example during driving at room temperature. FIG. [Figure 6B] FIG. 10 is a cross-sectional view of a portion of a vehicle differential device according to a comparative example during high-temperature driving. [Figure 7] FIG. 6 is a cross-sectional view of a vehicle differential according to a second embodiment. [Figure 8A] FIG. 10 is a partial cross-sectional view of a vehicle differential device according to a second embodiment when driven at room temperature. [Figure 8B] FIG. 10 is a partial cross-sectional view of a vehicle differential device according to a second embodiment during high-temperature driving. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] A first embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technically preferable technical matters, the technical scope of the present invention is not limited to this specific embodiment.

[0012] Fig. 1 is a cross-sectional view showing an example of the configuration of a vehicle differential 1 according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 3 is an exploded perspective view of the vehicle differential 1. Fig. 1 shows a cross-section taken along line BB in Fig. 2 along the rotation axis of the vehicle differential 1.

[0013] This vehicle differential 1 is used to distribute the driving force of a vehicle's drive source to a pair of output shafts while allowing differential movement. An engine or an electric motor can be used as the drive source. The vehicle differential 1 according to this embodiment is used as a differential device that distributes the driving force of the drive source to left and right drive wheels, and distributes the input driving force to left and right drive shafts as a pair of output shafts.

[0014] The vehicle differential device 1 includes a differential case 10 to which the driving force of the drive source is input, a plurality of pinion gear sets 2 held in the differential case 10, first and second side gear sets 3, 4 arranged inside the plurality of pinion gear sets 2 within the differential case 10, a first end washer 51 as a first sliding member, a second end washer 52 as a second sliding member, a center washer 53 as a third sliding member, and first and second disc springs 61, 62 as elastic members.

[0015] The differential case 10 has a cylindrical differential case body 11 with a bottom, and a differential case cover 12 arranged to close an opening of the differential case body 11. The differential case body 11 integrally includes a cylindrical portion 110, a first side wall portion 111 formed to close one axial end of the cylindrical portion 110, a cylindrical extension portion 112 extending outward from the center of the first side wall portion 111, and a flange portion 113 formed to protrude outward from the outer peripheral surface of the cylindrical portion 110. A ring gear (not shown) is fixed to the flange portion 113, and driving force from a driving source is transmitted from the ring gear to the differential case 10. The differential case 10 rotates about a rotation axis O due to the input driving force. Hereinafter, a direction parallel to the rotation axis O will be referred to as the rotation axis direction.

[0016] The differential case cover 12 integrally includes a disk-shaped second side wall portion 121 and a cylindrical extension portion 122 extending outward from the center of the second side wall portion 121. An outer peripheral end portion of the second side wall portion 121 is fixed, for example, by welding, to an end portion of the cylindrical portion 110 of the differential case main body 11 opposite to the first side wall portion 111.

[0017] 1, first and second bearings 71, 72 that support the differential case 10 are indicated by imaginary lines (two-dot chain lines). The differential case 10 is rotatably supported with respect to a differential carrier (not shown) by the first bearing 71 fitted onto the extension portion 112 of the differential case main body 11 and the second bearing 72 fitted onto the extension portion 122 of the differential case cover 12. The first bearing 71 and the second bearing 72 are tapered roller bearings to which axial preload is applied.

[0018] In this embodiment, as shown in FIG. 2 , four pinion gear sets 2 are respectively held in holding holes 100 formed in the cylindrical portion 110 of the differential case 10. Each pinion gear set 2 has a first pinion gear 21 and a second pinion gear 22, and the first pinion gear 21 and the second pinion gear 22 mesh with each other. The holding hole 100 has a first hole portion 101 that holds the first pinion gear 21 and a second hole portion 102 that holds the second pinion gear 22, and the first hole portion 101 and the second hole portion 102 are in communication with each other. The first hole portion 101 and the second hole portion 102 open toward the inside of the cylindrical portion 110.

[0019] The first pinion gear 21 integrally includes a long gear portion 211 and a short gear portion 212 having different axial lengths, and a connecting portion 213 that axially connects the long gear portion 211 and the short gear portion 212. A plurality of helical teeth 211a, 212a whose tooth traces are inclined with respect to the axial direction are formed on the outer peripheries of the long gear portion 211 and the short gear portion 212, respectively. Similarly, the second pinion gear 22 integrally includes a long gear portion 221 and a short gear portion 222 having different axial lengths, and a connecting portion 223 that axially connects the long gear portion 221 and the short gear portion 222, respectively. A plurality of helical teeth 221a, 222a whose tooth traces are inclined with respect to the axial direction are formed on the outer peripheries of the long gear portion 221 and the short gear portion 222, respectively.

[0020] The short gear portion 212 of the first pinion gear 21 meshes with a part of the long gear portion 221 of the second pinion gear 22. In addition, the short gear portion 222 of the second pinion gear 22 meshes with a part of the long gear portion 211 of the first pinion gear 21.

[0021] The first side gear set 3 has a cylindrical first outer gear member 31 that meshes with the first pinion gear 21, and a first inner gear member 32 that is disposed inside the first outer gear member 31. The first outer gear member 31 meshes with a portion of the long gear portion 211 of the first pinion gear 21. A plurality of helical teeth 31a that are inclined with respect to the axial direction are formed on the outer periphery of the first outer gear member 31, and these helical teeth 31a mesh with the helical teeth 211a of the long gear portion 211 of the first pinion gear 21. In other words, a portion of the long gear portion 211 of the first pinion gear 21 meshes with the short gear portion 222 of the second pinion gear 22, and another portion meshes with the first outer gear member 31.

[0022] The first outer gear member 31 and the first inner gear member 32 are helical spline-fitted. Helical spline teeth 31b inclined with respect to the axial direction are formed on the inner periphery of the first outer gear member 31, and these helical spline teeth 31b mesh with helical spline teeth 32a formed on the outer periphery of the first inner gear member 32. A straight spline-fitting portion 320 consisting of a plurality of spline teeth 32b extending parallel to the rotation axis O is formed on the inner periphery of the first inner gear member 32. One end of a drive shaft that transmits driving force to, for example, the left front wheel of a vehicle is connected to this straight spline-fitting portion 320 so as not to rotate relative to the first inner gear member 32.

[0023] The second side gear set 4 has a cylindrical second outer gear member 41 that meshes with the second pinion gear 22, and a second inner gear member 42 that is disposed inside the second outer gear member 41. The second outer gear member 41 meshes with a portion of the long gear portion 221 of the second pinion gear 22. A plurality of helical teeth 41a that are inclined with respect to the axial direction are formed on the outer periphery of the second outer gear member 41, and these helical teeth 41a mesh with the helical teeth 221a of the long gear portion 221 of the second pinion gear 22. In other words, a portion of the long gear portion 221 of the second pinion gear 22 meshes with the short gear portion 212 of the first pinion gear 21, and another portion meshes with the second outer gear member 41.

[0024] The second outer gear member 41 and the second inner gear member 42 are helical spline-fitted. Helical spline teeth 41b inclined with respect to the axial direction are formed on the inner periphery of the second outer gear member 41, and these helical spline teeth 41b mesh with helical spline teeth 42a formed on the outer periphery of the second inner gear member 42. A straight spline-fitting portion 420 made up of a plurality of spline teeth 42b extending parallel to the rotation axis O is formed on the inner periphery of the second inner gear member 42. One end of a drive shaft that transmits driving force to, for example, the right front wheel of the vehicle is connected to this straight spline-fitting portion 420 so as not to rotate relative to the second inner gear member 42.

[0025] The first end washer 51, the second end washer 52, and the center washer 53 are flat metal members having a predetermined thickness in the direction of the rotation axis of the differential case 10. The first end washer 51 is disposed between the first side gear set 3 and a first side wall portion 111 of the differential case 10. The second end washer 52 is disposed between the second side gear set 4 and a second side wall portion 121 of the differential case 10. The center washer 53 is disposed between the first side gear set 3 and the second side gear set 4.

[0026] The first end washer 51 is housed in a recess 111a formed in a first side wall portion 111 of the differential case 10, and is movable within the recess 111a in the direction of the rotation axis relative to the differential case 10. The first end washer 51 integrally has an annular main body portion 510 and a plurality of protrusions 511 formed to protrude outward from the main body portion 510. The recess 111a has a rotation prevention portion 111b formed to protrude outward from a portion thereof, and the protrusions 511 are fitted into the rotation prevention portion 111b, thereby restricting the rotation of the first end washer 51 relative to the differential case 10.

[0027] The second end washer 52 is housed in a recess 121a formed in the second side wall portion 121 of the differential case 10, and is movable within the recess 111a in the direction of the rotation axis relative to the differential case 10. The second end washer 52 integrally includes an annular main body portion 520 and a plurality of protrusions 521 formed to protrude outward from the main body portion 520. The recess 121a has a rotation prevention portion 121b formed to protrude outward from the main body portion 520. The rotation prevention portion 121b is fitted into the protrusions 521, thereby restricting the rotation of the second end washer 52 relative to the differential case 10.

[0028] The center washer 53 has an annular main body 530 and a plurality of protrusions 531 formed to protrude outward from the main body 530. The plurality of protrusions 531 engage with the connecting portions 213, 223 of the first and second pinion gears 21, 22, respectively, so that the center washer 53 is restricted from rotating relative to the differential case 10 and is movable relative to the differential case 10 in the direction of the rotation axis.

[0029] Figures 4A and 4B are cross-sectional views showing the first side wall portion 111 and the second side wall portion 121 when torque in the forward direction of the vehicle is input to the differential case 10 of the vehicle differential device 1 (when driving), and the first and second side gear sets 3, 4, first and second end washers 51, 52, center washer 53, and first and second disc springs 61, 62 arranged between the first side wall portion 111 and the second side wall portion 121.

[0030] Fig. 4A shows the first outer gear member 31 and the first inner gear member 32 of the first side gear set 3 and the second outer gear member 41 and the second inner gear member 42 of the second side gear set 4 at room temperature. Fig. 4B shows the first outer gear member 31 and the first inner gear member 32 of the first side gear set 3 and the second outer gear member 41 and the second inner gear member 42 of the second side gear set 4 in a state where they have thermally expanded and their axial lengths have become longer than at room temperature. Note that in Figs. 4A and 4B, as well as Figs. 5A and 5B, 6A and 6B, and 8A and 8B described below, the amount of thermal expansion of each gear member is exaggerated for clarity of explanation.

[0031] The first end washer 51 has one surface in the rotational axis direction of the differential case 10 as a sliding surface 51a that frictionally slides against an axial end surface 31c of the first outer gear member 31 on the first side wall portion 111 side and an axial end surface 32c of the first inner gear member 32 on the first side wall portion 111 side. The other surface of the first end washer 51 in the rotational axis direction of the differential case 10, which corresponds to the back side of the sliding surface 51a, is an abutting surface 51b that abuts against a first disc spring 61. The first disc spring 61 is disposed between the abutting surface 51b of the first end washer 51 and the first side wall portion 111.

[0032] The first disc spring 61 is housed in the recess 111a of the first side wall portion 111 together with the first end washer 51, and is arranged adjacent to the first end washer 51 in the direction of the rotational axis of the differential case 10. The first disc spring 61 is elastically deformable in the direction of the rotational axis of the differential case 10, with one end 611 in the direction of the rotational axis abutting against the abutment surface 51b of the first end washer 51 and the other end 612 in the direction of the rotational axis abutting against the bottom surface 111c of the recess 111a. The first end washer 51 is pressed against the first side gear set 3 in the direction of the rotational axis of the differential case 10 by the restoring force of the first disc spring 61.

[0033] The second end washer 52 has one surface in the rotational axis direction of the differential case 10 as a sliding surface 52a that frictionally slides against an axial end face 41c of the second outer gear member 41 on the first side wall portion 111 side and an axial end face 42c of the second inner gear member 42 on the second side wall portion 121 side. The other surface of the second end washer 52 in the rotational axis direction of the differential case 10, which corresponds to the back side of the sliding surface 52a, is an abutment surface 52b that abuts against the second disc spring 62. The second disc spring 62 is disposed between the abutment surface 52b of the second end washer 52 and the second side wall portion 121.

[0034] The second disc spring 62 is housed in the recess 121a of the second side wall portion 121 together with the second end washer 52, and is arranged adjacent to the second end washer 52 in the direction of the rotational axis of the differential case 10. The second disc spring 62 is elastically deformable in the direction of the rotational axis of the differential case 10, with one end 621 in the direction of the rotational axis abutting against the abutment surface 52b of the second end washer 52 and the other end 622 in the direction of the rotational axis abutting against the bottom surface 121c of the recess 121a. The second end washer 52 is pressed against the second side gear set 4 in the direction of the rotational axis of the differential case 10 by the restoring force of the second disc spring 62.

[0035] 4A and 4B, the thrust force in the rotational axis direction of the differential case 10 that is applied to the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42 when torque is transmitted by the vehicle differential device 1 is represented by F 11 ,F 12 ,F 13 ,F 21 ,F 22 ,F 23 The direction of each arrow indicates the direction of the thrust force.

[0036] F 11 is the thrust force that the first outer gear member 31 receives as a result of meshing with the first pinion gear 21. 12 is the thrust force that the first outer gear member 31 receives due to the helical spline engagement with the first inner gear member 32. 13 is F12 The reaction force is a thrust force that the first inner gear member 32 receives due to helical spline engagement with the first outer gear member 31.

[0037] F 21 is the thrust force that the second outer gear member 41 receives as a result of meshing with the second pinion gear 22. 22 is the thrust force that the second outer gear member 41 receives due to the helical spline engagement with the second inner gear member 42. 23 is F 22 The reaction force is a thrust force that the second inner gear member 42 receives due to helical spline engagement with the second outer gear member 41.

[0038] The first outer gear member 31 has an axial end surface 31d on the side of the center washer 53 that is resistant to the thrust force F 11 and F 12 The first inner gear member 32 is pressed against the first sliding surface 53a of the center washer 53 by the force of the first side wall portion 111, and receives a frictional resistance force from the center washer 53. The axial end surface 32c of the first inner gear member 32 on the first side wall portion 111 side is subjected to a thrust force F 13 , the bearing 51 is pressed against the sliding surface 51 a of the first end washer 51 and receives frictional resistance from the first end washer 51 .

[0039] The second outer gear member 41 has an axial end surface 41d on the side of the center washer 53 that is resistant to the thrust force F 21 and F 22 The second inner gear member 42 is pressed against the second sliding surface 53b of the center washer 53 by the force of the second side wall portion 121, and receives a frictional resistance force from the center washer 53. The axial end surface 42c of the second inner gear member 42 on the second side wall portion 121 side is subjected to a thrust force F 23 , and is pressed against the sliding surface 52 a of the second end washer 52 , and receives frictional resistance force from the second end washer 52 .

[0040] The frictional resistance force that the first outer gear member 31 and the second outer gear member 41 receive from the center washer 53, the frictional resistance force that the first inner gear member 32 receives from the first end washer 51, and the frictional resistance force that the second inner gear member 42 receives from the second end washer 52 act as differential limiting forces that limit the differential rotation of the left and right wheels when driving.

[0041] 5A and 5B are cross-sectional views showing the first side wall portion 111, the second side wall portion 121, the first and second side gear sets 3 and 4, the first and second end washers 51 and 52, the center washer 53, and the first and second disc springs 61 and 62 when torque is transmitted from the left and right wheels to the differential case 10 during forward coasting (coasting) of the vehicle. Fig. 5A shows the state in which each gear member is at room temperature, and Fig. 5B shows the state in which each gear member has thermally expanded and its axial length has become longer than at room temperature.

[0042] During coasting, thrust forces in the opposite direction to those during driving act on the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42. In Figures 5A and 5B, these thrust forces are represented as -F 11 ,-F 12 ,-F 13 ,-F 21 ,-F 22 ,-F 23 The arrows indicate the

[0043] Due to these thrust forces, the axial end face 31c of the first outer gear member 31 on the first side wall portion 111 side is pressed against the sliding surface 51a of the first end washer 51, and the axial end face 32d of the first inner gear member 32 on the center washer 53 side is pressed against the first sliding surface 53a of the center washer 53. Furthermore, the axial end face 41c of the second outer gear member 41 on the second side wall portion 121 side is pressed against the sliding surface 52a of the second end washer 52, and the axial end face 42d of the second inner gear member 42 on the center washer 53 side is pressed against the second sliding surface 53b of the center washer 53. The frictional resistance force generated thereby serves as a differential limiting force that limits the differential rotation of the left and right wheels during coasting.

[0044] The first disc spring 61 generates a thrust force F 13 and when coasting, thrust force -F 11 and -F 12 4B. As the first disc spring 61 is compressed, the first end washer 51 is displaced toward the bottom surface 111c of the recess 111a of the first side wall portion 111. As a result, during driving, the axial end surface 31c of the first outer gear member 31 does not contact the sliding surface 51a of the first end washer 51, and the axial end surface 32d of the first inner gear member 32 does not contact the first sliding surface 53a of the center washer 53, both at room temperature as shown in FIG. 4A and at high temperature as shown in FIG. 4B. Furthermore, during coasting, at room temperature as shown in FIG. 5A and at high temperature as shown in FIG. 5B, the axial end face 31d of the first outer gear member 31 does not contact the first sliding surface 53a of the center washer 53, and the axial end face 32c of the first inner gear member 32 does not contact the sliding surface 51a of the first end washer 51.

[0045] The second disc spring 62 generates a thrust force F 23 and when coasting, thrust force -F 21 and -F 22 4B. As the second disc spring 62 is compressed, the second end washer 52 is displaced toward the bottom surface 121c of the recess 121a of the second side wall portion 121. As a result, during driving, the axial end surface 41c of the second outer gear member 41 does not contact the sliding surface 52a of the second end washer 52, and the axial end surface 42d of the second inner gear member 42 does not contact the second sliding surface 53b of the center washer 53, both at room temperature as shown in FIG. 4A and at high temperature as shown in FIG. 4B. Furthermore, during coasting, at room temperature as shown in FIG. 5A and at high temperature as shown in FIG. 5B, the axial end face 41d of the second outer gear member 41 does not contact the second sliding surface 53b of the center washer 53, and the axial end face 42c of the second inner gear member 42 does not contact the sliding surface 52a of the second end washer 52.

[0046] As described above, in the present embodiment, even if the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42 thermally expand, the first disc spring 61 and the second disc spring 62 absorb the amount of thermal expansion, and the axial end faces of these gear members do not simultaneously come into contact with the center washer 53 and the first end washer 51 or the second end washer 52. Therefore, it is possible to suppress an increase in the differential limiting force due to thermal expansion of these gear members.

[0047] Furthermore, even if the axial depth of the recesses 111a, 121a is increased to increase the axially movable stroke distance of the first end washer 51 and the second end washer 52 in order to absorb this thermal expansion, the first end washer 51 and the second end washer 52 are biased in the direction of the rotation axis of the differential case 10 by the first disc spring 61 and the second disc spring 62, respectively, and therefore it is possible to prevent a decrease in the responsiveness of the differential limiting force. In other words, according to the present embodiment, it is possible to suppress an increase in the differential limiting force due to thermal expansion of the gears in the differential case while suppressing a decrease in the responsiveness of the differential limiting force.

[0048] [Comparative Example] 6A and 6B are cross-sectional views showing, as a comparative example, the configuration of a vehicle differential gear that does not have the first disc spring 61 and the second disc spring 62. Fig. 6A shows the state when driving at normal temperature, and Fig. 6B shows the state when driving at high temperature.

[0049] In this comparative example, when the first outer gear member 31 and the second outer gear member 41 reach a high temperature and thermally expand, increasing their axial length, as shown in Fig. 6B, both axial end faces 31c, 31d of the first outer gear member 31 come into contact with the first end washer 51 and the center washer 53, and both axial end faces 41c, 41d of the second outer gear member 41 come into contact with the second end washer 52 and the center washer 53. When the gaps between the first outer gear member 31 and the second outer gear member 41 and the washers 51 to 53 are narrowed between the first side wall portion 111 and the second side wall portion 121 in this way, the frictional force therebetween increases, and the differential limiting force increases sharply.

[0050] Furthermore, when the first inner gear member 32 and the second inner gear member 42 thermally expand and increase in axial length, as shown in Fig. 6B, both axial end faces 32c, 32d of the first inner gear member 32 come into contact with the first end washer 51 and the center washer 53, and both axial end faces 42c, 42d of the second inner gear member 42 come into contact with the second end washer 52 and the center washer 53. When the gaps between the first inner gear member 32 and the second inner gear member 42 and the washers 51 to 53 between the first side wall portion 111 and the second side wall portion 121 become narrow in this way, the frictional force therebetween increases, and the differential limiting force increases sharply.

[0051] Furthermore, if the gap between each gear member and each washer 51-53 is increased so that the gap does not become narrow even when each gear member thermally expands, the amount of axial movement of each gear member before a frictional force is generated becomes longer, resulting in a decrease in the responsiveness of the differential limiting force.

[0052] In contrast, according to the above-described first embodiment, a gap is formed in at least a portion of the differential case 10 in the direction of the rotational axis between the bottom surface 111c of the recess 111a of the first side wall portion 111 and the bottom surface 121c of the recess 121a of the second side wall portion 121, among the first disc spring 61, the first end washer 51, the first outer gear member 31 and the first inner gear member 32, the center washer 53, the second outer gear member 41 and the second inner gear member 42, the second end washer 52, and the second disc spring 62. In other words, the thermal expansion of the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42 can be absorbed by the first disc spring 61 and the second disc spring 62, and all gaps between the first side wall portion 111 and the second side wall portion 121 are not blocked, so that the increase in the differential limiting force due to the thermal expansion of the gears in the differential case can be suppressed while suppressing a decrease in the responsiveness of the differential limiting force.

[0053] Note that, for example, even when the axial end faces 31c, 31d of the first outer gear member 31 contact both the first end washer 51 and the center washer 53, or when the axial end faces 32c, 32d of the first inner gear member 32 contact both the first end washer 51 and the center washer 53, the above effect can be obtained as long as a gap having a length in the rotation axis direction equal to or greater than the thickness T (see FIG. 4A ) of the first disc spring 61 is formed between the bottom surface 111c of the recess 111a of the first side wall portion 111 and the first end washer 51. The same applies to the second side gear 4 side.

[0054] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. 7, 8A and 8B.

[0055] Fig. 7 is a cross-sectional view of a vehicle differential 1A according to a second embodiment. Fig. 8A is a cross-sectional view of a portion of the vehicle differential 1A at room temperature. Fig. 8B is a cross-sectional view of a portion of the vehicle differential 1A at a high temperature.

[0056] In the first embodiment, a case has been described in which the first disc spring 61 is disposed between the first end washer 51 and the first side wall portion 111, the second disc spring 62 is disposed between the second end washer 52 and the second side wall portion 121, and one center washer 53 is disposed between the first side gear set 3 and the second side gear set 4. In the vehicle differential 1A according to the second embodiment, no elastic members such as disc springs are disposed between the first end washer 51 and the first side wall portion 111 and between the second end washer 52 and the second side wall portion 121. Instead of the center washer 53, two center washers 54, 55 serving as third sliding members are disposed between the first side gear set 3 and the second side gear set 4, and the disc spring 63 is disposed between these center washers 54, 55 as an elastic member. Other configurations of the vehicle differential 1A are similar to those of the vehicle differential 1 according to the first embodiment.

[0057] Hereinafter, of the two center washers 54, 55, the center washer 54 on the first side gear set 3 side will be referred to as the first center washer 54, and the center washer 55 on the second side gear set 4 side will be referred to as the second center washer 55. The first center washer 54 has an annular main body 540 and a plurality of protrusions 541 formed protruding outward from the main body 540. The second center washer 55 has an annular main body 550 and a plurality of protrusions 551 formed protruding outward from the main body 550. The first and second center washers 54, 55 have the plurality of protrusions 541, 551 engage with the connecting portions 213, 223 of the first and second pinion gears 21, 22, respectively, so that relative rotation with respect to the differential case 10 is restricted and the first and second center washers 54, 55 are movable relative to the differential case 10 in the rotational axis direction.

[0058] The surface of the first center washer 54 facing the first side gear set 3 is a first sliding surface 54a that slides against the axial end face 31d of the first outer gear member 31 during driving and against the axial end face 32d of the first inner gear member 32 during coasting. The surface of the second center washer 55 facing the second side gear set 4 is a second sliding surface 55a that slides against the axial end face 41d of the second outer gear member 41 during driving and against the axial end face 42d of the second inner gear member 42 during coasting.

[0059] The disc spring 63 is aligned with the first center washer 54 and the second center washer 55 in the rotational axis direction of the differential case 10, and is disposed between a first contact surface 54b of the first center washer 54 that is located behind the first sliding surface 54a and a second contact surface 55b of the second center washer 55 that is located behind the second sliding surface 55a. One end 631 of the disc spring 63 in the rotational axis direction of the differential case 10 abuts against the first contact surface 54b of the first center washer 54, and the other end 632 of the disc spring 63 abuts against the second contact surface 55b of the second center washer 55.

[0060] The disc spring 63 biases the first center washer 54 toward the first side gear set 3, and biases the second center washer 55 toward the second side gear set 4. Furthermore, the disc spring 63 is compressed in the axial direction by the thrust force acting on the first outer gear member 31 and the second outer gear member 41 during driving, and is compressed in the axial direction by the thrust force acting on the first inner gear member 32 and the second inner gear member 42 during coasting.

[0061] As with the first embodiment, the vehicle differential 1A according to the second embodiment also allows the disc springs 63 to absorb the thermal expansion of the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42, and maintains the distance between the first center washer 54 and the second center washer 55 at a distance greater than the thickness of the disc springs 63. This makes it possible to suppress an increase in the differential limiting force due to thermal expansion of the gears in the differential case while suppressing a decrease in the responsiveness of the differential limiting force.

[0062] (Addendum) The present invention has been described above based on the first and second embodiments, but these embodiments do not limit the scope of the claimed invention. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be implemented by appropriately modifying it by omitting some components or adding or substituting some components, without departing from the spirit of the invention. Furthermore, some components of the above-described embodiments can be combined with each other, and modifications such as those described below are also possible.

[0063] In the above-described first embodiment, the first disc spring 61 is disposed between the first end washer 51 and the first side wall portion 111, and the second disc spring 62 is disposed between the second end washer 52 and the second side wall portion 121. However, one of the first disc spring 61 and the second disc spring 62 may be omitted. For example, when the first disc spring 61 is omitted, the first end washer 51 abuts against the bottom surface 111c of the recess 111a of the first side wall portion 111, and the second disc spring 62 absorbs the thermal expansion of the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42. Furthermore, if the second disc spring 62 is omitted, the second end washer 52 abuts against the bottom surface 121c of the recess 121a of the second side wall portion 121, and the first disc spring 61 absorbs the thermal expansion of the first outer gear member 31, the first inner gear member 32, the second outer gear member 41, and the second inner gear member 42. In other words, the effects of the present invention can be obtained as long as at least one disc spring is used as the elastic member among the first disc spring 61 and the second disc spring 62 according to the first embodiment and the disc spring 63 according to the second embodiment. Note that the elastic member is not limited to a disc spring, and for example, a wave washer, a coil spring, or the like can be used.

[0064] In the first and second embodiments, each pinion gear set 2 is described as being composed of two pinion gears (first pinion gear 21 and second pinion gear 22) having the same axial length. However, this is not limiting. For example, as proposed by the present applicant in Japanese Patent Application Laid-Open Publication No. 2020-94681, a pinion gear set may be configured by combining one pinion gear with two pinion gears that are shorter than the one pinion gear. In this case, a single pinion gear is used that has two gear portions, one large and one small, with different pitch circle diameters on one side and the other of the longitudinal center, and the two short pinion gears are meshed with the smaller diameter gear portion. [Explanation of symbols]

[0065] 1,1A...Vehicle differential 10...Differential case 100...Retaining hole 110...Cylindrical part 111...first side wall portion 2...Pinion gear set 21...First pinion gear 22...Second pinion gear 3...First side gear set 31...First outer gear member 32...First inner gear member 4...Second side gear set 41...Second outer gear member 42...Second inner gear member 51...First end washer (first sliding member) 52...Second end washer (second sliding member) 53...Center washer (third sliding member) 54...First center washer (third sliding member) 55...Second center washer (third sliding member) 61...First disc spring (elastic member) 62...First disc spring (elastic member) 63...First disc spring (elastic member)

Claims

1. A differential device for a vehicle that distributes driving force of a driving source of a vehicle to a pair of output shafts while allowing differential motion, a pinion gear set including a first pinion gear and a second pinion gear meshed with each other, the first pinion gear and the second pinion gear having helical teeth whose tooth traces are inclined with respect to the axial direction; a first side gear set including a cylindrical first outer gear member that meshes with the first pinion gear and a first inner gear member that is disposed inside the first outer gear member, the first outer gear member and the first inner gear member being helical spline-fitted; a second side gear set including a cylindrical second outer gear member that meshes with the second pinion gear and a second inner gear member that is disposed inside the second outer gear member, the second outer gear member and the second inner gear member being helical spline-fitted; a differential case having a cylindrical portion formed with a retaining hole that rotatably accommodates the first pinion gear and the second pinion gear, and first and second side wall portions; a first sliding member disposed between the first outer gear member and the first inner gear member of the first side gear set and the first side wall portion; a second sliding member disposed between the second outer gear member and the second inner gear member of the second side gear set and the second side wall portion; a third sliding member disposed between the first outer gear member and the first inner gear member of the first side gear set and the second outer gear member and the second inner gear member of the second side gear set; An elastic member that is arranged alongside any one of the first to third sliding members in the rotational axis direction of the differential case between the first side wall portion and the second side wall portion in the differential case and is elastically deformable in the rotational axis direction, The elastic member is compressed in the direction of the rotation axis by the first outer gear member and the second outer gear member, or the first inner gear member and the second inner gear member, both during driving when torque in the forward direction of the vehicle is input to the differential case and during coasting when the vehicle is coasting forward, The first sliding member and the second sliding member are restricted from rotating relative to the differential case and are movable relative to the differential case in the direction of the rotation axis. Vehicle differential.

2. one surface of the first sliding member in the rotational axis direction is a sliding surface that frictionally slides against axial end surfaces of the first outer gear member and the first inner gear member, and the elastic member is disposed between the other surface in the rotational axis direction and the first side wall portion.

2. The vehicle differential according to claim 1.

3. one surface of the second sliding member in the rotational axis direction is a sliding surface that frictionally slides against axial end surfaces of the second outer gear member and the second inner gear member, and the elastic member is disposed between the other surface in the rotational axis direction and the second side wall portion.

3. The vehicle differential according to claim 2.

4. two third sliding members are provided, and the elastic member is disposed between the two third sliding members; 4. A vehicle differential according to claim 1.

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