Differential device

Abstract

To provide a differential device of a bevel gear type, capable of obtaining large differential limit force.SOLUTION: A differential device 1 has pinion gears 11, 12, which are bevel gears, and side gears 13, 14, where the side gears 13, 14 come into contact with a differential case 10 due to a gear reaction force against the pinion gears 11, 12 to obtain a differential limit force. The pinion gears 11, 12 are supported so as to be movable within a predetermined range along a rotation direction of the differential case 10 and to be movable perpendicularly to a rotation axis of the differential case 10, and cams 24, 25 are provided in the differential case 10, which press the pinion gears 11, 12 against the side gears 13, 14 in accordance with circumferential positions of the pinion gears 11, 12 in the differential case 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a differential device used in a drive system of a vehicle or the like. [Background technology]

[0002] A differential device is used in the drive system of an automobile or the like to transmit power while allowing differential motion between two drive shafts. A known type of differential is an LSD (limited slip differential), which limits the differential function when one drive shaft spins. For example, the differential device (LSD) described in Patent Document 1 includes a differential case rotatably supported on a vehicle body, a pinion gear rotatably supported in the differential case, and a pair of side gears supported relatively rotatably in the differential case and meshing with the pinion gear, the pinion gear and the side gear being bevel gears. Furthermore, the side gear is movable in the axial direction relative to the differential case, and when a driving torque is transmitted between the pinion gear and the side gear, the gear reaction force causes the side gear to move and come into contact with the differential case, generating a frictional force and obtaining a differential limiting force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-102772 A Summary of the Invention [Problem to be solved by the invention]

[0004] The differential device in Patent Document 1 is provided with a cone clutch in which the portion of the inner wall surface of the differential case that abuts against the side gear is cone-shaped, and is structured so that frictional force increases as the side gear moves outward. However, in a differential device with a structure in which the differential limiting force is obtained by the cone clutch, the differential limiting force depends on the taper angle of the cone surface, and therefore, it is necessary to set the taper angle to prevent the cone surface from sticking, which causes a problem that the differential limiting force cannot be obtained sufficiently.

[0005] The present invention has been made to solve such problems, and has an object to provide a bevel gear type differential device which can obtain a large differential limiting force. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a differential device having a rotationally driven differential case, a pinion gear rotatably supported within the differential case, and a pair of side gears rotatably supported within the differential case and meshing with the pinion gear, the pinion gear and the side gear being bevel gears, the side gear abutting against the differential case due to a gear reaction force with the pinion gear to obtain a differential limiting force, the pinion gear being supported so as to be movable within a predetermined range along the rotational direction of the differential case and so as to be movable in a direction perpendicular to the rotational axis of the differential case, and the differential device is provided with gear pressing means for pressing the pinion gear against the side gear in accordance with the rotational position of the pinion gear in the differential case. It is characterized by:

[0007] As a result, the orbital position of the pinion gear relative to the differential case (the rotational position on the differential case) moves due to the rotational difference between the differential case and the side gear, and the pinion gear is pressed toward the side gear by the gear pressing means, thereby increasing the gear reaction force between the pinion gear and the side gear. Preferably, the contact surfaces of the side gear and the differential case are provided perpendicular to the rotation axis of the differential case and parallel to each other.

[0008] This makes it possible to prevent the side gear from sticking to the differential case pinion gear when the pressing force between the side gear and the pinion gear is released after the side gear and the pinion gear are pressed against each other and the side gear abuts against the differential case due to the gear reaction force, thereby obtaining a differential limiting force. Preferably, the pinion gear is supported on the differential case via a shaft member extending perpendicular to the rotation axis of the differential case, both ends of the shaft member are supported on the peripheral wall of the differential case so as to be movable within a predetermined range along the rotation direction of the differential case, and the pinion gear is supported on the shaft member so as to be movable in the axial direction.

[0009] This makes it possible to simply and compactly configure the pinion gear that is supported by the differential case so as to be movable within a predetermined range along the rotational direction of the differential case and so as to be movable perpendicular to the rotational axis of the differential case. Preferably, a pair of long holes extending in the rotational direction of the differential case are formed in the peripheral wall of the differential case, into which both ends of the shaft member are inserted, and the gear pressing means is a cam provided on the inner wall surrounding the long holes of the differential case and formed so that its protruding height toward the side gear increases toward the longitudinal end of the long holes.

[0010] This makes it possible to easily configure the gear pressing means for pressing the pinion gear against the side gear in accordance with the orbital position of the pinion gear relative to the differential case. Preferably, the differential device is provided between the left and right drive wheels of the vehicle, the differential case is rotationally driven by a drive source mounted on the vehicle, one of the pair of side gears is connected to the right drive wheel of the vehicle via a right axle shaft, and the other of the pair of side gears is connected to the left drive wheel of the vehicle via a left axle shaft.

[0011] As a result, in a differential device mounted on a vehicle, the gear reaction force between the pinion gear and the side gear can be increased, thereby increasing the differential limiting force. Effect of the Invention

[0012] According to the differential device of the present invention, the gear pressing means can increase the gear reaction force between the pinion gear and the side gear due to the rotational difference between the differential case and the side gear, thereby increasing the pressing force between the side gear and the differential case, and thereby increasing the differential limiting force. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of an internal structure of a differential device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram of the internal structure of a differential device when differential limiting is not performed. [Diagram 3] FIG. 4 is an outer circumferential wall view showing the structure of a support portion for a pinion gear shaft in the differential device. [Figure 4] FIG. 4 is a cross-sectional view of a differential device showing the structure of a support portion of a pinion gear shaft. [Diagram 5] 10 is an explanatory diagram showing an operating state of a support portion of a pinion gear shaft when the vehicle is stationary. FIG. [Figure 6] 11 is an explanatory diagram showing an operating state of a support portion of a pinion gear shaft at the start of driving for traveling; FIG. [Figure 7] 5A to 5C are explanatory diagrams showing an operating state of a support portion of a pinion gear shaft when the vehicle is running. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the internal structure of a differential device according to one embodiment of the present invention. The differential device 1 of this embodiment is mounted, for example, between the left and right drive wheels of a vehicle, and transmits driving force from a drive source such as an engine or a motor to the drive shafts of the left and right drive wheels (right axle shaft 2, left axle shaft 3), respectively, and has a differential function that absorbs the rotation difference between the left and right drive wheels.

[0015] The differential device 1 is a limited slip differential (LSD) that has a function of limiting the differential between the left and right drive shafts. As shown in FIG. 1, the differential device 1 is disposed between a right axle shaft 2 and a left axle shaft 3, which are output shafts extending coaxially in the vehicle width direction, and has a pair of pinion gears (first pinion gear 11, second pinion gear 12) and a pair of side gears (right side gear 13, left side gear 14) built into a differential case 10.

[0016] The differential case 10 has a substantially cylindrical shape, is coaxial with the axle shafts 2, 3, and is rotatable about its axis relative to the vehicle body. A ring gear 15 is provided on the outer circumferential surface of the differential case 10 and extends in the circumferential direction around the axis of the axle shafts 2, 3. A rotational driving force is input from a drive source via an input shaft 16 and an input gear 17 to the ring gear 15, causing the differential case 10 to rotate.

[0017] The pinion gears 11, 12 and the side gears 13, 14 are bevel gears. A left end of the right axle shaft 2 and a right end of the left axle shaft 3 are inserted into the differential case 10 and are supported by the differential case 10 so as to be rotatable. A right side gear 13 is supported on the left end of the right axle shaft 2, and a left side gear 14 is supported on the right end of the left axle shaft 3. The right axle shaft 2 and the right side gear 13, and the left axle shaft 3 and the left side gear 14 are connected to each other by, for example, a spline connection so as to be capable of transmitting a rotational driving force. The right side gear 13 and the left side gear 14 are disposed at an interval in the axial direction (left-right direction). The teeth 13a of the right side gear 13 and the teeth 14a of the left side gear 14 are formed on the inner inclined surface.

[0018] Between the right side gear 13 and the left side gear 14, a pinion gear shaft 21 (shaft member) which is a support shaft extending perpendicularly to the axial direction of the right side gear 13 and the left side gear 14 is supported by the differential case 10. A pair of pinion gears (first pinion gear 11, second pinion gear 12) are arranged spaced apart from each other across an intersection O of the axis of the pinion gear shaft 21 and the axis of the side gear, and are supported on the pinion gear shaft 21 so as to be rotatable, i.e., rotatable about their own axes.

[0019] The first pinion gear 11 and the second pinion gear 12 have inner inclined surfaces formed with teeth 11a, 12a which mesh with teeth 13a of a right side gear 13 and teeth 14a of a left side gear 14, respectively. The back surfaces 13b, 14b (contact surfaces) of the teeth 13a, 14a of the side gears 13, 14 and the opposing inner wall surfaces 10a, 10b (contact surfaces) of the differential case 10 are parallel to each other and form friction surfaces that abut against each other to generate frictional force.

[0020] Fig. 2 is a diagram showing the internal structure of the differential device 1 when differential limiting is not performed. Fig. 3 is a diagram showing an outer peripheral wall surface showing the structure of a support portion of the pinion gear shaft 21 in the differential device 1. Fig. 4 is a cross-sectional view of the differential device 1 showing the structure of a support portion of the pinion gear shaft 21. Fig. 3 is a view seen from an arrow A in Fig. 2. Fig. 4 is a cross-sectional view of a portion BB in Fig. 2.

[0021] 1 to 4, in the differential device 1 of this embodiment, a first pinion gear 11 and a second pinion gear 12 are supported by one pinion gear shaft 21. The pinion gear shaft 21 is supported by the differential case 10 so as to be movable in the rotational direction of the differential case 10 about an intersection O between the axis of the pinion gear shaft 21 and the axis of the side gears 13 and 14. Furthermore, the first pinion gear 11 and the second pinion gear 12 are each supported by the pinion gear shaft 21 so as to be movable in the axial direction.

[0022] The pinion gear shaft 21 is supported by having both ends inserted into two support holes 22, 23 (long holes) provided in the differential case 10, and these two support holes 22, 23 are long holes extending in the rotation direction of the differential case 10. This allows the pinion gear shaft 21 to move within a predetermined range back and forth in the rotation direction of the differential case 10.

[0023] Cams 24, 25 (gear pressing means) are formed on the inner wall surface of the differential case 10, protruding inward along the support holes 22, 23. The cams 24, 25 are inclined in an arc shape so that the amount of inward protrusion is small near the circumferential center positions of the support holes 22, 23 and the amount of protrusion increases smoothly from the circumferential center positions of the support holes 22, 23 toward the front and rear in the circumferential direction (the longitudinal ends of the support holes 22, 23).

[0024] Fig. 5 is an explanatory diagram showing the operating state of the support portion of the pinion gear shaft 21 when the vehicle is stationary. Fig. 6 is an explanatory diagram showing the operating state of the support portion of the pinion gear shaft 21 when the vehicle starts to drive. Fig. 7 is an explanatory diagram showing the operating state of the support portion of the pinion gear shaft 21 when the vehicle is running. For example, as shown in Fig. 5, when the end of the pinion gear shaft 21 is located at the circumferential center of the support holes 22, 23, i.e., the longitudinal center of the cam 24, with respect to the differential case 10 in a stationary state of the vehicle, the pinion gear 11 can be located at the radially outermost position. Note that, although Figs. 5 to 7 show one end of the pinion gear shaft 21, the other end is also in a point-symmetric state with respect to the axis (intersection point O).

[0025] As shown in Fig. 6, when the vehicle starts moving from a stopped state and the differential case 10 rotates left by a driving source such as a motor, the pinion gear shaft 21 moves rightward along the long holes (support holes 22, 23) relative to the differential case 10, so that the pinion gears 11, 12 move radially inward by the cams 24, 25. Therefore, the side gears 13, 14 move radially inward by the two pinion gears 11, 12.

[0026] As shown in Figure 7, when the differential case 10 further rotates to the left, the circumferential movement of the pinion gear shaft 21 relative to the differential case 10 is restricted, and the pinion gear shaft 21 rotates together with the differential case 10, thereby driving the axle shafts 2 and 3 to rotate via the pinion gears 11 and 12 and the side gears 13 and 14. By employing the differential device 1 in a vehicle, if a difference in rotation occurs between the right axle shaft 2 and the left axle shaft 3, for example, when the vehicle is turning, the difference in rotation is absorbed by the rotation of the pinion gears 11, 12.

[0027] Furthermore, when the driving force of one of the left and right drive wheels decreases, the gear reaction force between the pinion gears 11, 12 and the side gears 13, 14 presses the back surfaces 13b, 14b of the side gears 13, 14 against the inner wall surfaces 10a, 10b of the differential case 10, and the frictional force suppresses the rotation of the side gears 13, 14 relative to the differential case 10. This suppresses the rotation of the pinion gears 11, 12 relative to the differential case 10, limiting the differential.

[0028] As described above, the differential device 1 of this embodiment is disposed between the left and right drive wheels of the vehicle, inputs rotational driving force from the ring gear 15 and outputs rotational driving force to the left and right axle shafts 2, 3, and absorbs the rotational speed difference between the left and right axle shafts 2, 3, i.e., the rotational speed difference between the left and right drive wheels. It is also a limited slip differential equipped with a differential limiting mechanism that limits the torque difference between the left and right drive wheels.

[0029] In the differential device 1, the pinion gears 11, 12 are supported so as to be movable within a predetermined range along the rotation direction of the differential case 10 and to be movable in a direction perpendicular to the rotation axis of the differential case 10. Furthermore, the differential device 1 is provided with cams (gear pressing means) that press the pinion gears 11, 12 against the side gears 13, 14 in accordance with the positions of the pinion gears 11, 12 relative to the differential case 10 (the circumferential positions of the differential case 10).

[0030] By pressing the pinion gears 11, 12 toward the side gears 13, 14 in this manner, it is possible to increase the gear reaction force between the pinion gears 11, 12 and the side gears 13, 14. Therefore, it is possible to increase the pressing force of the side gears 13, 14 against the differential case 10, and to increase the differential limiting force. The inner wall surfaces 10a, 10b of the differential case 10, which abut against the back surfaces 13b, 14b of the side gears 13, 14, are arranged perpendicular to the rotation axis of the differential case 10 and parallel to each other. Therefore, when the side gears 13, 14 and the pinion gears 11, 12 are pressed against each other and the side gears 13, 14 abut against the differential case 10 due to the gear reaction force to obtain a differential limiting force, and then the pressing force between the side gears 13, 14 and the pinion gears 11, 12 is released, sticking between the side gears 13, 14 and the pinion gears 11, 12 can be suppressed.

[0031] Further, the pair of pinion gears 11, 12 are supported by the differential case 10 via a pinion gear shaft 21 extending perpendicular to the rotation axis of the differential case 10, and both ends of the pinion gear shaft 21 are supported on the peripheral wall of the differential case 10 so as to be movable within a predetermined range along the rotation direction of the differential case 10, and the pinion gear 11 is supported by the pinion gear shaft 21 so as to be movable in the axial direction. Therefore, the pinion gears 11, 12 supported by the differential case 10 so as to be movable within a predetermined range along the rotation direction of the differential case 10 and so as to be movable perpendicular to the rotation axis of the differential case 10 can be configured simply and compactly.

[0032] Further, a pair of elongated support holes 22, 23 are formed in the peripheral wall of the differential case 10, extending in the rotational direction of the differential case 10 and into which both ends of the pinion gear shaft 21 are inserted, and cams 24, 25 are formed on the inner walls around the support holes 22, 23 of the differential case 10 so as to protrude higher inwardly of the differential case 10 toward the longitudinal ends of the support holes 22, 23. This makes it possible to easily configure gear pressing means that presses the pinion gears 11, 12 against the side gears 13, 14 in accordance with the orbital positions of the pinion gears 11, 12 relative to the differential case 10 (the rotational position in the differential case 10).

[0033] It should be noted that the present invention is not limited to the above embodiment, and the detailed shapes of the components of the differential device 1 may be modified as appropriate. For example, in the above embodiment, the inner wall surfaces 10a, 10b of the differential case 10 that come into contact with the back surfaces 13b, 14b of the side gears 13, 14 to obtain frictional force are installed perpendicular to the axial direction of the differential case 10, but may be slightly inclined from the perpendicular direction to the axial direction. Also, the back surfaces 13b, 14b of the side gears 13, 14 and the inner wall surfaces 10a, 10b of the differential case 10 are parallel to each other, but may be inclined at a slightly different angle.

[0034] Furthermore, the two pinion gears 11, 12 are supported by one pinion gear shaft 21, but they may be supported individually by two shafts. The differential device of the present invention can be widely applied to the driving systems of vehicles such as automobiles. [Explanation of symbols]

[0035] 1 Differential device 2 Right axle shaft 3 Left axle shaft 10 Differential case 10a, 10b Inner wall surface (contact surface) 11, 12 Pinion gear 13, 14 Side gear 13b, 14b Back side (contact surface) 21 Pinion gear shaft (shaft member) 22, 23 Support holes (slotted holes) 24, 25 Cam (gear pressing means)

Claims

1. A differential device having a rotationally driven differential case, a pinion gear rotatably supported in the differential case, and a pair of side gears rotatably supported in the differential case and meshing with the pinion gear, wherein the pinion gear and the side gear are bevel gears, and the side gears abut against the differential case due to a gear reaction force with the pinion gear to obtain a differential limiting force. The pinion gear is supported so as to be movable within a predetermined range along the rotation direction of the differential case and so as to be movable in a direction perpendicular to the rotation axis of the differential case, A gear pressing means is provided for pressing the pinion gear toward the side gear in accordance with a rotational position of the pinion gear in the differential case. A differential device characterized by:

2. The contact surfaces of the side gear and the differential case are provided perpendicular to the rotation axis of the differential case and parallel to each other.

2. The differential device according to claim 1,

3. The pinion gear is supported by the differential case via a shaft member extending perpendicular to a rotation axis of the differential case, Both ends of the shaft member are supported by a peripheral wall of the differential case so as to be movable within a predetermined range along the rotation direction of the differential case, The pinion gear is supported on the shaft member so as to be axially movable.

2. The differential device according to claim 1,

4. A pair of elongated holes extending in a rotational direction of the differential case and into which both ends of the shaft member are inserted are formed in a peripheral wall of the differential case, The gear pressing means is a cam provided on an inner wall around the long hole of the differential case, and formed so that the protruding height toward the side gear increases toward the longitudinal end of the long hole.

4. The differential device according to claim 3,

5. The differential device is provided between left and right drive wheels of a vehicle, The differential case is rotationally driven by a drive source mounted on the vehicle, One of the pair of side gears is connected to a right driving wheel of the vehicle via a right axle shaft, The other of the pair of side gears is connected to a left driving wheel of the vehicle via a left axle shaft.

2. The differential device according to claim 1,

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