Differential device for a vehicle

Abstract

(Problem) To provide a differential device for a vehicle capable of preventing an increase in a differential restricting force due to thermal expansion of a wheel in a differential case while suppressing a decrease in the responsiveness of a differential restricting force.(Solution) A differential device 1 for a vehicle includes: a plurality of pinion gear pairs 2, a first side gear pair 3 formed by helically spline-fitting a first outer gear member 31 and a first inner gear member 32; a second side gear pair 4 formed by helically spline-fitting a second outer gear member 41 and a second inner gear member 42; a differential case 10 having a cylindrical portion 110 and first and second side wall portions 111, 121, which supports the plurality of pinion gear pairs 2; a first end plate 51 and a first disc spring 61 disposed between the first side gear pair 3 and the first side wall portion 111; and a second end plate 52 and a second disc spring 62 disposed between the second side gear pair 4 and the second side wall portion 121.

Description

Technical field

[0001] The present invention relates to a differential device for a vehicle having a differential limiting function. State of the art

[0002] Some differential devices that distribute driving force from a vehicle's power source to a right wheel and a left wheel while allowing differential movement have a differential restriction function that restricts differential rotation between the right wheel and the left wheel. For example, if one of the right wheel and the left wheel slips, such a differential device can transmit driving force to the other wheel and improve driving stability.

[0003] A differential device described in PTL 1 includes a plurality of planetary gear pairs, each formed by a pair of meshing planetary gears, a first sun gear meshing with one planetary gear of the pair of planetary gears, a second sun gear meshing with the other planetary gear of the pair of planetary gears, and a differential case (housing) that houses them. The differential case has a cylindrical portion having holding holes formed therein for holding the plurality of planetary gear pairs, and first and second side wall portions formed to close both end portions of the cylindrical portion. The first and second sun gears are arranged in series in an axial direction between a first side wall portion and a second side wall portion.Discs are arranged between the first sun gear and the first side wall section, between the second sun gear and the second side wall section 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 a substantially central portion thereof in a radial direction, and a spline portion formed on an outer periphery of the inner portion is spline-fitted with a spline hole formed on an inner periphery of the outer portion. Due to this spline fit, when torque is transmitted to the right gear and the left gear, thrust forces in opposite directions are generated between the outer portion and the inner portion, and axial-direction end surfaces of both the outer portion and the inner portion are pressed against the disk. A frictional force between the axial-direction end surfaces and the disk increases a differential restricting force. Citation listPatent literature

[0005] PTL 1: JP 2009-174577 A Brief description of the inventionTechnical problem

[0006] When driving under conditions where a large differential limiting force is frequently generated, such as when driving uphill on muddy roads or gravel roads, for example, the wheels in the differential case may expand due to frictional heat, causing their axial lengths to increase in the axial direction. In such a case, if thermal expansion of one of the wheels in the differential case causes both axial direction end surfaces of the wheel to be pressed against the disks, the differential limiting force may become larger than a force generated by the thrust force in the axial direction.Also, increasing a clearance (a backlash) between the wheels and the disks in the axial direction in the differential case to prevent a thrust force due to such thermal expansion of the wheels from increasing can reduce a responsiveness of the differential restricting force when wheel slippage or the like occurs.

[0007] Accordingly, it is an object of the present invention to provide a vehicle differential device that can suppress an increase in a differential restricting force due to thermal expansion of wheels in a differential case while suppressing a decrease in responsiveness of the differential restricting force. Solution to the problem

[0008] To achieve the above object, the present invention provides a vehicle differential device comprising a pinion gear pair including a first pinion gear and a second pinion gear having helical teeth whose flank lines are inclined with respect to an axial direction and which mesh with each other, a first side gear pair including a first outer gear member having a cylindrical shape and meshing with the first pinion gear, and a first inner gear member arranged on an inner side of the first outer gear member, wherein the first outer gear member and the first inner gear member are helically spline-fitted with each other, a second side gear pair including a second outer gear member having a cylindrical shape and meshing with the second pinion gear, and a second inner gear member arranged on an inner side of the second outer gear member,wherein the second outer gear member and the second inner gear member are helically splined to each other, a differential case comprising a cylindrical portion in which a retaining hole for rotatably accommodating the first pinion gear and the second pinion gear is formed, and first and second side wall portions, a first sliding member disposed between the first side gear pair and the first side wall portion, a second sliding member disposed between the second side gear pair and the second side wall portion, a third sliding member disposed between the first side gear pair and the second side gear pair, and an elastic member disposed in series with any one of the first to third sliding members, between the first side wall portion and the second side wall portion within the differential case in a rotational axis direction of the differential case,and which is elastically deformable in the direction of the rotation axis., Advantageous effects of the invention

[0009] According to the vehicle differential device of the present invention, an increase in the differential restricting force due to thermal expansion of the wheels in the differential case can be suppressed, while a decrease in the responsiveness of the differential restricting force is suppressed. Short descriptions of drawings ( Fig. 1) Fig. 1 is a cross-sectional view illustrating an example of a configuration of a vehicle differential device according to a first embodiment of the present invention. ( Fig. 2) Fig. 2 is a cross-sectional view taken along a line AA of Fig. 1. ( Fig. 3) Fig. 3 is a disassembled perspective view of the vehicle differential device. ( Fig. 4A) Fig. 4A is a cross-sectional view of a portion of the vehicle differential device during normal temperature driving. ( Fig. 4B) Fig. 4B is a cross-sectional view of a portion of the vehicle differential device during high temperature driving. ( Fig. 5A) Fig. 5A is a cross-sectional view of a portion of the vehicle differential device during coasting operation at normal temperature. ( Fig. 5B) Fig. 5B is a cross-sectional view of a portion of the vehicle differential device during high temperature coasting operation. ( Fig. 6A) Fig. 6A is a cross-sectional view of a portion of a vehicle differential device according to a comparative example during normal temperature driving. ( Fig. 6B) Fig. 6B is a cross-sectional view of a portion of the vehicle differential device according to the comparative example during high-temperature driving. ( Fig. 7) Fig. 7 is a cross-sectional view of a vehicle differential device according to a second embodiment. ( Fig. 8A) Fig. 8A is a cross-sectional view of a part of the vehicle differential device according to the second embodiment during normal temperature driving. ( Fig. 8B) Fig. 8B is a cross-sectional view of a portion of the vehicle differential device according to the second embodiment during high-temperature driving. Description of Embodiments (First Embodiment)

[0010] A first embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is presented as a suitable concrete example for carrying out the present invention, and although there are sections explaining various technically preferable technical matters in detail, the technical scope of the present invention is not limited to such concrete aspects.

[0011] Fig. 1 is a cross-sectional view illustrating an example of a configuration of a vehicle differential device 1 according to the first embodiment of the present invention. Fig. 2 is a cross-sectional view taken along a line AA of Fig. 1. Fig. 3 is a disassembled perspective view of the vehicle differential device 1. Fig. 1 represents a cross section along a line BB in Fig. 2, on a rotational axis of the vehicle differential device 1.

[0012] This vehicle differential device 1 is used to distribute the driving force of a vehicle's drive source to a pair of output shafts while enabling differential movement. An engine or an electric motor can be used as the drive source. The vehicle differential device 1 according to the present embodiment is used as a differential device that distributes the driving force of the drive source to right and left drive wheels, and distributes the driving force input thereto to right and left drive shafts serving as the pair of output shafts.

[0013] The vehicle differential device 1 includes a differential case 10 to which a driving force of the drive source is input, a plurality of pinion gear pairs 2 held in the differential case 10, first and second side gear pairs 3 and 4 arranged on an inner side of the plurality of pinion gear pairs 2 within the differential case 10, a first end plate 51 serving as a first sliding member, a second end plate 52 serving as a second sliding member, a center plate 53 serving as a third sliding member, and first and second disc springs 61 and 62 serving as elastic members.

[0014] The differential case 10 includes a differential case body 11 having a cylindrical shape with a bottom, and a differential case cover 12 arranged to cover an opening of the differential case body 11. The differential case body 11 integrally includes a cylindrical portion 110 having a cylindrical shape, a first side wall portion 111 formed to cover an end portion on one side of the cylindrical portion 110 in the axial direction thereof, an extension portion 112 having a cylindrical shape and extending outward from a center portion of the first side wall portion 111, and a flange portion 113 formed to widen outward from an outer peripheral surface of the cylindrical portion 110. A ring gear, which is omitted from the illustration, is fixed to the flange portion 113, and the driving force of the drive source is transmitted from this ring gear to the differential case 10.The differential case 10 rotates around a rotation axis line O under the driving force input thereto. Hereinafter, a direction parallel to the rotation axis line O is referred to as a rotation axis direction.

[0015] The differential case cover 12 integrally includes a second side wall portion 121 having a disc-like shape and an extension portion 122 having a cylindrical shape extending outward from a center portion of the second side wall portion 121. An end portion on an outer peripheral side 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 body 11 opposite to the first side wall portion 111.

[0016] In Fig. 1, the first and second bearings 71 and 72 supporting the differential case 10 are indicated with a hidden outline (long-dash double-dash lines). The differential case 10 is rotatably supported relative to a differential carrier, which is omitted from the illustration, by the first bearing 71 fitted to the extension portion 112 of the differential case body 11 and the second bearing 72 fitted to the extension portion 122 of the differential case cover 12. The first bearing 71 and the second bearing 72 are angular contact roller bearings to which a preload is applied in the axial direction.

[0017] In this embodiment, as shown in Fig. 2, four pinion gear pairs 2 are held in respective holding holes 100 formed in the cylindrical portion 110 of the differential case 10. Each pinion gear pair 2 includes 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. Each 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 communicate with each other. The first hole portion 101 and the second hole portion 102 open inwardly into the cylindrical portion 110.

[0018] The first pinion gear 21 integrally includes a long gear portion 211 and a short gear portion 212 having mutually different lengths in the axial direction, and a link portion 213 connecting the long gear portion 211 and the short gear portion 212 in the axial direction. A plurality of helical teeth 211a, 212a, whose flank lines are inclined with respect to the axial direction, are formed on 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 mutually different lengths in the axial direction, and a link portion 223 connecting the long gear portion 221 and the short gear portion 222 in the axial direction. A plurality of helical teeth 221a and 222a, the flank lines of which are inclined with respect to the axial direction, are formed on the outer peripheries of the long gear section 221 and the short gear section 222, respectively.

[0019] The short wheel section 212 of the first pinion wheel 21 meshes with a section of the long wheel section 221 of the second pinion wheel 22. The short wheel section 222 of the second pinion wheel 22 also meshes with a section of the long wheel section 211 of the first pinion wheel 21.

[0020] The first side gear pair 3 includes a first outer gear member 31 having a cylindrical shape and meshing with the first pinion gear 21, and a first inner gear member 32 disposed on an inner side of 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. The first outer gear member 31 has a plurality of helical teeth 31a formed on its outer periphery, the helical teeth 31a being inclined with respect to the axial direction, and these helical teeth 31a meshing with the helical teeth 211a of the long gear portion 211 of the first pinion gear 21. In other words, the long gear portion 211 of the first pinion gear 21 meshes at one portion thereof with the short gear portion 222 of the second pinion gear 22 and meshes at another portion thereof with the first outer gear element 31.

[0021] The first outer gear member 31 and the first inner gear member 32 are helically splined. Helical spline teeth 31b inclined with respect to the axial direction are formed on an inner periphery of the first outer gear member 31, and these helical spline teeth 31b mesh with helical spline teeth 32a formed on an outer periphery of the first inner gear member 32. A straight spline fitting portion 320 formed of a plurality of spline teeth 32b extending parallel to the rotation axis line O is formed on an inner periphery of the first inner gear member 32. An end portion of a drive shaft that transmits driving force to, for example, a left front wheel of the vehicle is connected to this straight spline fitting portion 320, so that it is incapable of relative rotation.

[0022] The second side gear pair 4 has a second outer gear member 41 having a cylindrical shape and meshing with the second pinion gear 22, and a second inner gear member 42 disposed on an inner side of 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. The second outer gear member 41 has a plurality of helical teeth 41a formed on its outer diameter, the helical teeth 41a being inclined with respect to the axial direction, 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, the long gear portion 221 of the second pinion gear 22 meshes with the short gear portion 212 of the first pinion gear 21 at one portion thereof and meshes with the second outer gear member 41 at another portion thereof.

[0023] The second outer gear member 41 and the second inner gear member 42 are helically splined. Helical spline teeth 41b inclined with respect to the axial direction are formed on an inner periphery of the second outer gear member 41, and these helical spline teeth 41b mesh with helical spline teeth 42a formed on an outer periphery of the second inner gear member 42. A straight spline fitting portion 420 formed of a plurality of spline teeth 42b extending parallel to the rotation axis line O is formed on an inner periphery of the second inner gear member 42. An end portion of the drive shaft, which transmits driving force to, for example, a right front wheel of the vehicle, is connected to this straight spline fitting portion 420, so that it is incapable of relative rotation.

[0024] The first end plate 51, the second end plate 52, and the center plate 53 are metal members that have a flat plate shape and a predetermined thickness in the rotational axis direction of the differential case 10. The first end plate 51 is arranged between the first side gear pair 3 and the first side wall portion 111 of the differential case 10. The second end plate 52 is arranged between the second side gear pair 4 and the second side wall portion 121 of the differential case 10. The center plate 53 is arranged between the first side gear pair 3 and the second side gear pair 4.

[0025] The first end plate 51 is housed in a recess 111a formed in the first side wall portion 111 of the differential case 10 and is movable relative to the differential case 10 in the rotation axis direction within the recess 111a. The first end plate 51 integrally includes a body portion 510 having an annular shape and a plurality of projections 511 formed outwardly from the body portion 510. Portions of the recess 111a protrude toward an outer peripheral side to form rotation stoppers 111b, and the projections 511 fit with these rotation stoppers 111b, thereby limiting the relative rotation of the first end plate 51 with respect to the differential case 10.

[0026] The second end plate 52 is housed in a recess 121a formed in the second side wall portion 121 of the differential case 10 and is movable relative to the differential case 10 in the rotational axis direction within the recess 121a. The second end plate 52 integrally includes a body portion 520 having an annular shape and a plurality of projections 521 formed outwardly from the body portion 520. Portions of the recess 121a protrude toward an outer peripheral side to form rotation stoppers 121b, and the projections 521 fit with these rotation stoppers 121b, thereby limiting the relative rotation of the second end plate 52 with respect to the differential case 10.

[0027] The center plate 53 has a body portion 530 having an annular shape and a plurality of projections 531 formed outwardly from the body portion 530. The plurality of projections 531 of the center plate 53 are respectively engaged between the linkage portions 213 and 223 of the first and second pinion gears 21 and 22, thereby limiting relative rotation with respect to the differential case 10, and also the center plate 53 is movable relative to the differential case 10 in the rotation axis direction.

[0028] Fig. 4A and Fig. 4B are cross-sectional views illustrating the first side wall portion 111 and the second side wall portion 121 and the first and second side gear pairs 3 and 4, the first and second end disks 51 and 52 and the center disk 53, and the first and second disk springs 61 and 62 disposed between the first side wall portion 111 and the second side wall portion 121 when torque in a vehicle forward direction is input to the differential case 10 of the vehicle differential device 1 (during traveling).

[0029] Fig. 4A illustrates the first outer gear member 31 and the first inner gear member 32 of the first side gear pair 3 and the first outer gear member 41 and the second inner gear member 42 of the second side gear pair 4 in a state of normal temperature. Fig. Fig. 4B illustrates a state in which the first outer gear member 31 and the first inner gear member 32 of the first side gear pair 3 and the second outer gear member 43 and the second inner gear member 42 of the second side gear pair 4 have thermally expanded and their lengths in the axial direction have become longer than at a normal temperature. It should be noted that in Fig. 4A and Fig. 4B, as well as in Fig. 5A and Fig. 5B, Fig. 6A and Fig. 6B and Fig. 8A and Fig. 8B described below, the amount of thermal expansion of each wheel element is shown in an exaggerated manner for clear description.

[0030] One surface of the first end plate 51 in the rotational axis direction of the differential case 10 is a sliding surface 51a that frictionally slides against an axial direction end surface 31c on the first side wall portion 111 side of the first outer gear member 31 and an axial direction end surface 32c on the first side wall portion 111 side of the first inner gear member 32. The other surface of the first end plate 51 in the rotational axis direction of the differential case 10, which is the rear surface from the sliding surface 51a, is an abutment surface 51b that abuts with the first disk spring 61. The first disk spring 61 is disposed between the abutment surface 51b of the first end plate 51 and the first side wall portion 111.

[0031] The first disc spring 61 is housed in the recess 111a of the first side wall portion 111 together with the first end plate 51 and is arrayed adjacent to the first end plate 51 in the rotational axis direction of the differential case 10. The first disc spring 61 is elastically deformable in the rotational axis direction of the differential case 10, with one end portion 611 thereof in the rotational axis direction abutting against the abutment surface 51b of the first end plate 51, and another end portion 612 thereof in the rotational axis direction abutting against a bottom surface 111c of the recess 111a. The first end plate 51 is pressed toward the first side gear pair 3 by a restoring force of the first disc spring 61 in the rotational axis direction of the differential case 10.

[0032] One surface of the second end plate 52 in the rotational axis direction of the differential case 10 is a sliding surface 52a that frictionally slides against an axial direction end surface 41c on the first side wall portion 111 side of the second outer gear member 41 and an axial direction end surface 42c on the second side wall portion 121 side of the second inner gear member 42. The other surface of the second end plate 52 in the rotational axis direction of the differential case 10, which is the rear surface of the sliding surface 52a, is an abutment surface 52b that abuts with the second disc spring 62. The second disc spring 62 is disposed between the abutment surface 52b of the second end plate 52 and the second side wall portion 121.

[0033] The second disc spring 62 is housed in the recess 121a of the second side wall portion 121 together with the second end plate 52 and is arranged adjacent to the second end plate 52 in the rotational axis direction of the differential case 10. The second disc spring 62 is elastically deformable in the rotational axis direction of the differential case 10, with one end portion 621 thereof in the rotational axis direction abutting against the abutment surface 52b of the second end plate 52, and another end portion 622 thereof in the rotational axis direction abutting against a bottom surface 121c of the recess 121a. The second end plate 52 is pressed toward the second side gear pair 4 by a restoring force of the second disc spring 62 in the rotational axis direction of the differential case 10.

[0034] In Fig. 4A and Fig. 4B, thrust forces in the rotational axis direction of the differential case 10 received by 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 through the vehicle differential device 1 are indicated by arrows F11, F12, F13, F21, F22, and F23. The direction of each arrow indicates the direction of the thrust force.

[0035] F11 is a thrust force that the first outer gear member 31 receives by meshing with the first pinion gear 21. F12 is a thrust force that the first outer gear member 31 receives from the helical spline fit with the first inner gear member 32. F13 is a thrust force that the first inner gear member 32 receives from the helical spline fit with the first outer gear member 31 as a reaction force to F12.

[0036] F21 is a thrust force that the second outer gear member 41 receives by meshing with the second pinion gear 22. F22 is a thrust force that the second outer gear member 41 receives from the helical spline fit with the second inner gear member 42. F23 is a thrust force that the second inner gear member 42 receives from the helical spline fit with the second outer gear member 41, as a reaction force to F22.

[0037] An axial direction end surface 31d on the center plate 53 side of the first outer gear member 31 is pressed against a first sliding surface 53a of the center plate 53 by the thrust forces F11 and F12 and receives a frictional resistance force from the center plate 53. The axial direction end surface 32c on the first side wall portion 111 side of the first inner gear member 32 is pressed against the sliding surface 51a of the first end plate 51 by the thrust force F13 and receives a frictional resistance force from the first end plate 51.

[0038] An axial direction end surface 41d on the center plate 53 side of the second outer gear member 41 is pressed against a second sliding surface 53b of the center plate 53 by the thrust forces F21 and F22 and receives a frictional resistance force from the center plate 53. An axial direction end surface 42c on the second side wall portion 121 side of the second inner gear member 42 is pressed against the sliding surface 52a of the second end plate 52 by the thrust force F23 and receives a frictional resistance force from the second end plate 52.

[0039] The frictional resistance force that the first outer wheel member 31 and the second outer wheel member 41 receive from the center disk 53, the frictional resistance force that the first inner wheel member 32 receives from the first end disk 51, and the frictional resistance force that the second inner wheel member 42 receives from the second end disk 52 act as differential restricting forces that restrict the differential rotation of the right and left wheels during traveling.

[0040] Fig. 5A and Fig. 5B are cross-sectional views illustrating the first side wall portion 111, the second side wall portion 121, the first and second side gear pairs 3 and 4, the first and second end disks 51 and 52 and the center disk 53, and the first and second disk springs 61 and 62 when torque is transmitted from the right and left wheel sides to the differential case 10 when the vehicle is traveling forward under inertia (during coasting). Fig. 5A shows the wheel elements at normal temperature and Fig. 5B shows the wheel elements in a state where their lengths in the axial direction have become longer than at a normal temperature due to thermal expansion.

[0041] During coasting, thrust forces act on the first outer wheel element 31, the first inner wheel element 32, the second outer wheel element 41, and the second inner wheel element 42 in directions opposite to those during driving. Fig. 5A and Fig. 5B these thrust forces are indicated by arrows -F11, -F12, -F13, -F21, -F22 and -F23.

[0042] Due to these thrust forces, the axial direction end surface 31c on the first side wall portion 111 side of the first outer gear member 31 is pressed against the sliding surface 51a of the first end plate 51, and an axial direction end surface 32d on the center plate 53 side of the first inner gear member 32 is pressed against the first sliding surface 53a of the center plate 53. Likewise, the axial direction end surface 41c on the second wall portion 121 side of the second outer gear member 41 is pressed against the sliding surface 52a of the second end plate 52, and an axial direction end surface 42d on the center plate 53 side of the second inner gear member 42 is pressed against the second sliding surface 53b of the center plate 53. The frictional resistance force thereby generated acts as a differential restricting force that limits the differential rotation of the right and left wheels during coasting.

[0043] The first disc spring 61 is compressed by the thrust force F13 during travel in the axial direction and also by the thrust forces -F11 and -F12 during coasting. In conjunction with the compression of the first disc spring 61, the first end plate 51 is displaced toward the side of the bottom surface 111c in the recess 111a of the first side wall portion 111. Accordingly, during travel, either at normal temperature, as shown in Fig. 4A, or at high temperature, as in Fig. 4B, the axial direction end surface 31c of the first outer gear member 31 does not come into contact with the sliding surface 51a of the first end disk 51 and the axial direction end surface 32d of the first inner gear member 32 does not come into contact with the first sliding surface 53a of the center disk 53. Even during a coasting operation, either at normal temperature, as in Fig. 5A, or at high temperature, as in Fig. 5B, the axial direction end surface 31d of the first outer gear member 31 does not come into contact with the first sliding surface 53a of the center disk 53, and the axial direction end surface 32c of the first inner gear member 32 does not come into contact with the sliding surface 51a of the first end disk 51.

[0044] The second disc spring 62 is compressed in the axial direction by the thrust force F23 during driving and also by the thrust forces -F21 and -F22 during coasting. In conjunction with the compression of the second disc spring 62, the second end plate 52 is displaced toward the side of the bottom surface 121c in the recess 121a of the second side wall portion 121. Accordingly, both at normal temperature and in Fig. 4A, or at high temperature, as in Fig. 4B, the axial direction end surface 41c of the second outer gear member 41 does not come into contact with the sliding surface 52a of the second end disk 52 and the axial direction end surface 42d of the second inner gear member 42 does not come into contact with the second sliding surface 53b of the center disk 53. Even during overrun operation, both at normal temperature and in Fig. 5A, or at high temperature, as in Fig. 5B, the axial direction end surface 41d of the second outer gear member 41 does not come into contact with the second sliding surface 53b of the center disk 53, and the axial direction end surface 42c of the second inner gear member 42 does not come into contact with the sliding surface 52a of the second end disk 52.

[0045] Thus, 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 thereof, and both end surfaces of these gear members in the axial direction do not come into contact with the center plate 53 and the first end plate 51 or the second end plate 52 at the same time. Thus, an increase in the differential restricting force due to thermal expansion of these gear members can be suppressed.

[0046] Likewise, even if the depths of the recesses 111a and 121a in the axial direction are increased to absorb this thermal expansion and increase a stroke distance over which the first end plate 51 and the second end plate 52 can move in an axial line direction, the first end plate 51 and the second end plate 52 are biased in the rotational axis line direction of the differential case 10 by the first disc spring 61 and the second disc spring 62, respectively, and accordingly, a decrease in the responsiveness of the differential restricting force can be suppressed. In other words, according to the present embodiment, an increase in the differential restricting force due to thermal expansion of the wheels in the differential case can be suppressed while a decrease in the responsiveness of the differential restricting force is suppressed. (Comparison example)

[0047] Fig. 6A and Fig. 6B are cross-sectional views illustrating, as a comparative example, a configuration of a vehicle differential device that does not have the first disc spring 61 and the second disc spring 62. Fig. 6A represents a condition during driving at normal temperature and Fig. 6B shows a state during high temperature driving.

[0048] In this comparative example, when the first outer gear member 31 and the second outer gear member 41 become hot and exhibit thermal expansion and the lengths thereof in the axial direction increase, both end surfaces 31c and 31d of the first outer gear member 31 in the axial direction come into contact with the first end plate 51 and the center plate 53, respectively, and both end surfaces 41c and 41d of the second outer gear member 41 in the axial direction come into contact with the second end plate 52 and the center plate 53, respectively, as shown in Fig. 6B. When clearances between the first outer gear member 31 and the second outer gear member 41 and the disks 51 to 53 between the first side wall portion 111 and the second side wall portion 121 become narrow in this way, a frictional force therebetween increases and the differential restricting force increases rapidly.

[0049] Likewise, when the first inner wheel member 32 and the second inner wheel member 42 exhibit thermal expansion and the axial lengths thereof increase, as in Fig. 6B, both end surfaces 32c and 32d of the first inner gear member 32 in the axial direction respectively abut with the first end plate 51 and the center plate 53, and both end surfaces 42c and 42d of the second inner gear member 42 in the axial direction respectively abut with the second end plate 52 and the center plate 53. When clearances between the first inner gear member 32 and the second inner gear member 42 and the plates 51 to 53 between the first side wall portion 111 and the second side wall portion 121 become narrow in this way, a frictional force therebetween increases, and the differential restricting force rapidly increases.

[0050] Also, in a case of increasing the clearances between the wheel members and the disks 51 to 53 so that the clearances are not closed even if the wheel members are thermally expanded in this way, the amount of movement of the wheel members in the axial direction before a friction force is generated becomes longer, causing a reduction in the responsiveness of the differential restricting force.

[0051] In contrast, according to the above first embodiment, clearances are formed in the rotational axis direction of the differential case 10, among at least one of the first disc spring 61, the first end plate 51, the first outer gear member 31 and the first inner gear member 32, the center plate 53, the second outer gear member 41 and the second inner gear member 42, the second end plate 52 and the second disc spring 62, 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.In other words, the amount of 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 a situation where all the clearances between the first side wall portion 111 and the second side wall portion 121 are closed does not occur, and accordingly, an increase in the differential restricting force due to thermal expansion of the wheels in the differential case can be suppressed while a decrease in the responsiveness of the differential restricting force is suppressed.

[0052] It should be noted that even in a case where, for example, the axial direction end surfaces 31c and 31d of the first outer gear member 31 respectively come into contact with both the first end plate 51 and the center plate 53, or in a case where the axial direction end surfaces 32c and 32d of the first inner gear member 32 respectively come into contact with both the first end plate 51 and the center plate 53, the above-described effect can be obtained as long as a clearance having a length in the rotation axis direction not smaller than that resulting in a thickness T of the first disc spring 61 (refer to Fig. 4A), is formed between the bottom surface 111c of the recess 111a of the first side wall portion 111 and the first end plate 51. The same also applies to the side of the second side gear 4. (Second embodiment)

[0053] Next, a second embodiment of the present invention will be described with reference to Fig. 7, Fig. 8A and Fig. 8B.

[0054] Fig. 7 is a cross-sectional view of a vehicle differential device 1A according to the second embodiment. Fig. 8A is a cross-sectional view of a portion of the vehicle differential device 1A at normal temperature. Fig. 8B is a cross-sectional view of a portion of the vehicle differential device 1A at high temperature.

[0055] In the first embodiment, a case was described in which the first disc spring 61 is arranged between the first end plate 51 and the first side wall part 111, the second disc spring 62 is arranged between the second end plate 52 and the second side wall part 121, and a center plate 53 is arranged between the first side gear pair 3 and the second side gear pair 4.In the vehicle differential device 1A according to the second embodiment, an elastic member such as a disc spring or the like is not disposed between the first end plate 51 and the first side wall portion 111, nor between the second end plate 52 and the second side wall portion 121, and instead of the center plate 53, two center plates 54 and 55 serving as third sliding members are disposed between the first side gear pair 3 and the second side gear pair 4, and a disc spring 63 serving as an elastic member is disposed between these center plates 54 and 55. Other configurations of the vehicle differential device 1A are the same as those of the vehicle differential device 1 according to the first embodiment.

[0056] Hereinafter, of the two center disks 54 and 55, the center disk 54 on the first side gear pair 3 side is referred to as a first center disk 54, and the center disk 55 on the second side gear pair 4 side is referred to as a second center disk 55. The first center disk 54 has a body portion 540 having an annular shape and a plurality of projections formed to project outward from the body portion 540. The second center disk 55 has a body portion 550 having an annular shape and a plurality of projections 551 formed to project outward from the body portion 550.The plurality of projections 541 and 551 of the first and second center plates 54 and 55 are respectively engaged with the linkage portions 213 and 223 of the first and second pinion gears 21 and 22, thereby restricting relative rotation to the differential case 10, and also the center plates 54 and 55 are movable relative to the differential case 10 in the rotation axis direction.

[0057] A surface of the first center disk 54 facing the first side gear pair 3 side is a first sliding surface 54a, which slides against the axial direction end surface 31d of the first outer gear member 31 during traveling and slides against the axial direction end surface 32d of the first inner gear member 32 during coasting. A surface of the second center disk 55 facing the second side gear pair 4 side is a second sliding surface 55a, which slides against the axial direction end surface 41d of the second outer gear member 41 during traveling and slides against the axial direction end surface 42d of the second inner gear member 42 during coasting.

[0058] The disc spring 63 is aligned with the first center plate 54 and the second center plate 55 in the rotational axis direction of the differential case 10, and is interposed between a first abutment surface 54b of the first center plate 54, which is a rear side of the first sliding surface 54a, and a second abutment surface 55b of the second center plate 55, which is a rear side of the second sliding surface 55a. One end portion 631 of the disc spring 63 in the rotational axis direction of the differential case 10 abuts the first abutment surface 54b of the first center plate 54, and another end portion 632 of the disc spring 63 abuts the second abutment surface 55b of the second center plate 55.

[0059] The disc spring 63 biases the first center disc 54 toward the first side gear pair 3 side and also biases the second center disc 55 toward the second side gear pair 4 side. Likewise, the disc spring 63 is compressed in the axial direction by thrust forces acting on the first outer gear member 31 and the second outer gear member 41 during traveling, and is compressed in the axial direction by thrust forces acting on the first inner gear member 32 and the second inner gear member 42 during coasting.

[0060] As with the first embodiment, with the vehicle differential device 1A according to this second embodiment, as well, an amount of 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 disc spring 63, and the distance between the first center disk 54 and the second center disk 55 is maintained at a distance longer than the thickness of the disc spring 63. This makes it possible to suppress an increase in the differential restricting force due to thermal expansion of the gears in the differential case, while suppressing a decrease in the responsiveness of the differential restricting force. (Additional Notes)

[0061] Although the present invention has been described above based on the first and second embodiments, the invention according to the claims is not limited to these embodiments. It should also be noted that not all combinations of features described in the embodiment are essential to means for solving the problem in the invention. Also, the present invention can be carried out as appropriately modified by omitting part of the configurations or adding or replacing configurations without departing from the spirit and scope thereof. Furthermore, part of the configurations of the above-described plurality of embodiments can be combined with each other and can also be modified, for example, as described below.

[0062] In the above first embodiment, a case was described where the first disc spring 61 is disposed between the first end plate 51 and the first side wall portion 111, and the second disc spring 62 is disposed between the second end plate 52 and the second side wall portion 121, but one of the first disc spring 61 and the second disc spring 62 may be omitted. For example, in a case where the first disc spring 61 is omitted, the first end plate 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 amount of 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.Likewise, in a case where the second disc spring 62 is omitted, the second end plate 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 amount of 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 of 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 is provided as an elastic member. Note that the elastic member is not limited to a disc spring, and a wave washer, a coil spring, or the like can be used, for example.

[0063] Also, in the first and second embodiments, a case is described where each pinion gear pair 2 is formed from a combination of two pinion gears (the first pinion gear 21 and the second pinion gear 22) having the same length in the axial direction, but this is not limitative, and a pinion gear pair may be formed by combining one pinion gear with two pinion gears having a shorter length than the one pinion gear, as proposed by the present applicant in JP 2020-94681 A, for example. In this case, a single pinion gear is used that has two gear portions, a large one and a small one, with different pitch diameters on one side and the other side of a longitudinal center portion, and the two short pinion gears mesh with the small-diameter gear portion thereof. List of reference symbols 1, 1A Vehicle differential device 10 Differential box 100 retaining hole 110 cylindrical section 111 first side wall section 2 pairs of pinions 21 first pinion wheel 22 second pinion wheel 3 first pair of side wheels 31 first outer wheel element 32 first inner wheel element 4 second pair of side wheels 41 second outer wheel element 42 second inner wheel element 51 first end plate (first sliding element) 52 second end plate (second sliding element) 53 Center disc (third sliding element) 54 first center disc (third sliding element) 55 second center disc (third sliding element) 61 first disc spring (elastic element) 62 first disc spring (elastic element) 63 first disc spring (elastic element) QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] JP 2009-174577 A

[0005] JP 2020-94681 A

[0063]

Claims

[1] Vehicle differential device comprising: a pinion gear pair comprising a first pinion gear and a second pinion gear having helical teeth whose flank lines are inclined with respect to an axial direction and which mesh with each other; a first side gear pair comprising a first outer gear member having a cylindrical shape and meshing with the first pinion gear, and a first inner gear member disposed on an inner side of the first outer gear member, the first outer gear member and the first inner gear member being helically spline-fitted to each other; a second side gear pair comprising a second outer gear member having a cylindrical shape and meshing with the second pinion gear, and a second inner gear member disposed on an inner side of the second outer gear member, the second outer gear member and the second inner gear member being helically spline-fitted to each other; a differential case including a cylindrical portion in which a holding hole for rotatably accommodating the first pinion gear and the second pinion gear is formed, and first and second side wall portions; a first sliding member disposed between the first side gear pair and the first side wall portion; a second sliding member disposed between the second side gear pair and the second side wall portion; a third sliding member disposed between the first side gear pair and the second side gear pair; and an elastic member arranged in series with any one of the first to third sliding members between the first side wall portion and the second side wall portion within the differential case in a rotational axis direction of the differential case, and elastically deformable in the rotational axis direction. [2] The vehicle differential device according to claim 1, wherein a surface of the first sliding member in the rotational axis direction is a sliding surface that frictionally slides against axial direction end surfaces of both the first outer gear member and the first inner gear member, and the elastic member is arranged between another surface of the first sliding member in the rotational axis direction and the first side wall portion. [3] The vehicle differential device according to claim 2, wherein a surface of the second sliding member in the rotational axis direction is a sliding surface that frictionally slides against axial direction end surfaces of both the second outer gear member and the second inner gear member, and the elastic member is arranged between another surface of the second sliding member in the rotational axis direction and the second side wall portion. [4] A vehicle differential device according to claim 3, wherein rotation of the first sliding member and the second sliding member relative to the differential case is limited and they are also movable relative to the differential case in the rotation axis direction. [5] The vehicle differential device according to any one of claims 1 to 4, wherein the vehicle differential device comprises two of the third sliding members, and the elastic member is arranged between the two third sliding members.

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