Differential device

Abstract

To provide a differential device having a side gear with a split structure, which increases strength while suppressing increase in size.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 side gears 13, 14 are divided in a rotation axis direction, and have first side gears 24, 26 having tooth parts 13a, 14a on one side surface that mesh with the pinion gears 11, 12, and second side gears 25, 27 having a friction surface 39 that comes into contact with the differential case 10. The other side surface of the first side gears 24, 26 is provided with a plurality of cam parts 31 that is aligned in a circumferential direction, is formed so as to protrude toward the second side gears 25, 27, and transmits rotational driving force to the second side gears 25, 27. The cam parts 31 are arranged at a circumferential position of a tooth bottom 40 of the tooth part 14a of the first side gears 24, 26.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 LSD described in Patent Document 1 is a differential device that includes a differential case rotatably supported on a vehicle body, a pinion gear rotatably supported within the differential case, and a pair of side gears that are supported relatively rotatably within the differential case and mesh with the pinion gear. Furthermore, when driving torque is transmitted between the pinion gear and the side gear, a gear reaction force causes the pinion gear to come into contact with the differential case, generating a frictional force and providing a differential limiting force.

[0003] Furthermore, the side gear in the differential device of Patent Document 1 is divided into a support member having teeth that mesh with the pinion gear, and an output member that rotates together with the output shaft (drive shaft). The support member and the output member transmit rotational driving force via a cam portion, and the output member is urged toward the friction surface of the differential case by the reaction force of the cam portion when the driving force is transmitted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6993242 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the side gear is divided as in Patent Document 1, there is a problem that when trying to store it in the limited space inside the differential case, the thickness of each part of the side gear becomes thin, reducing the strength of the side gear. The present invention has been made to solve such problems, and has an object to provide a differential device having side gears with a split structure that increases strength while suppressing an increase in size. [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 on the differential case, and a pair of side gears rotatably supported on the differential case and meshing with the pinion gear, the pinion gear and the side gear being 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, and the side gears are rotatably supported on the differential case and meshing with the pinion gear. The differential comprises a first side gear divided in the direction of the rotation axis and having a tooth portion on one side that meshes with the pinion gear, and a second side gear having an abutment surface that abuts against the differential case, and a cam portion formed on the other side of the first side gear so as to protrude toward the second side gear and transmit a rotational driving force to the second side gear, the cam portion being provided in multiple numbers in a line circumferentially on the other side of the first side gear and arranged at a circumferential position of the bottom of the tooth portion of the first side gear.

[0007] As a result, the cam portion is provided on the back surface of the tooth bottom of the first side gear, so that the thin portion of the first side gear is reinforced by the cam portion, thereby improving the strength of the first side gear. Preferably, the cam portion is disposed at a radially outer end portion of the other side surface of the first side gear.

[0008] This reduces the stress acting on the cam portion when transmitting a rotational driving force between the first side gear and the second side gear via the cam portion, and reduces the size of the cam portion, thereby reducing the overall thickness and weight of the side gear, for example, by reducing the protruding height of the cam portion. Preferably, the cam portions are provided corresponding to all tooth bottoms of the tooth portion.

[0009] As a result, all of the tooth bottom portions aligned in the circumferential direction are reinforced by the cam portion, thereby making it possible to further improve the strength of the first side gear. Preferably, the cam portion is formed such that an end face in a circumferential direction of the first side gear is inclined and a circumferential length on a protruding direction side is shorter. As a result, when a rotational driving force is transmitted between the first side gear and the second side gear via the cam portion, the second side gear receives a force in a direction moving axially away from the first side gear due to a reaction force of the cam portion, and therefore the second side gear is moved toward the differential case to increase the frictional force between the first side gear and the differential case, thereby increasing the differential limiting force.

[0010] 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 provided between the left and right drive wheels of a vehicle, the plate thickness can be reduced while ensuring the strength of the side gears, thereby enabling the differential device to be made smaller. Preferably, the differential device is provided between the front and rear drive shafts of a four-wheel drive vehicle, the differential case is rotated by a drive source mounted on the vehicle, one of the pair of side gears is connected to the front drive shaft via a front propeller shaft, and the other of the pair of side gears is connected to the rear drive shaft via a rear propeller shaft.

[0012] As a result, in a differential device provided between the front and rear drive shafts of a vehicle, it is possible to reduce the plate thickness while ensuring the strength of the side gears, thereby enabling the differential device to be made smaller. Effect of the Invention

[0013] According to the differential device of the present invention, the thin tooth bottom of the first side gear is reinforced by the cam portion, improving the strength of the first side gear, making it possible to reduce the thickness of the first side gear. This makes it possible to reduce the plate thickness while ensuring the strength of the first side gear, resulting in a differential device with a reduced size. [Brief description of the drawings]

[0014] [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. 4 is a rear view of a first side gear in the side gear of the differential device of the present embodiment. [Diagram 3] FIG. 2 is a side view of a first side gear according to the embodiment. [Figure 4] FIG. 2 is a front view of a first side gear according to the embodiment. [Diagram 5] FIG. 4 is a front view showing the shape of a second side gear in the side gear of the differential device of the present embodiment. [Figure 6] FIG. 4 is a side view showing the shape of a second side gear according to the embodiment. [Figure 7]FIG. 4 is a rear view showing the shape of the second side gear according to the embodiment. [Figure 8] FIG. 4 is a partially enlarged cross-sectional view of a first side gear. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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 1 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.

[0016] The differential device 1 is a limited slip differential (LSD) that has a function of limiting the differential motion between the left and right drive wheels. 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.

[0017] The differential case 10 is substantially cylindrical, and is installed coaxially with the axle shafts 2, 3 and rotatably about its axis relative to the vehicle body. A case 18 that houses the differential case 10 is provided around the differential case 10. The case 18 is fixed to the vehicle body and rotatably supports the differential case 10 via bearings 19. 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.

[0018] 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.

[0019] Between the right side gear 13 and the left side gear 14 , a pinion gear shaft 21 which is a support shaft extending perpendicularly to the axial direction of the right side gear 13 and the left side gear 14 is fixed to 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 the intersection O of the axis of the pinion gear shaft 21 and the axis of the side gears 13, 14, and are supported on the pinion gear shaft 21 so as to be rotatable, i.e., capable of rotating on their own axes.

[0020] 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 right side gear 13 is divided into a first side gear 24 having teeth 13a and a second side gear 25 having a friction surface 39 that comes into contact with the differential case 10. The left side gear 14 is divided axially (in the direction of the rotation axis Lc of the differential case 10) into a first side gear 26 having teeth 14a and a second side gear 27 having a friction surface 39 that comes into contact with the differential case 10.

[0021] Fig. 2 is a rear view of the first side gear 26. Fig. 3 is a side view of the first side gear 26. Fig. 4 is a front view of the first side gear 26. Fig. 5 is a front view of the second side gear 27. Fig. 6 is a side view of the second side gear 27. Fig. 7 is a rear view of the second side gear 27. Fig. 8 is a partially enlarged cross-sectional view of the first side gear 26, and is a cross-sectional view of the portion AA shown in Fig. 4.

[0022] The first side gear 24 has the same shape as the first side gear 26, and is disposed axially opposite the first side gear 26 within the differential case 10. The second side gear 25 has the same shape as the second side gear 27, and is disposed axially opposite the second side gear 27 within the differential case 10. 2 to 4, the first side gear 26 is an annular plate-shaped member having a hole 30 in the center into which the shaft portion 35 of the second side gear 27 is inserted, and one side surface is inclined to form the teeth portion 14a which is a bevel gear. In this embodiment, the teeth portion 14a has 10 teeth.

[0023] The other side surface of the first side gear 26, which is the back surface of the surface on which the tooth portion 14a is provided, is perpendicular to the axis and is provided with a cam portion 31. The cam portion 31 is a portion that protrudes axially outward. The cam portion 31 is provided near the radially outer end of the other side surface of the first side gear 26, and a plurality of cam portions 31 are provided lined up at equal intervals in the circumferential direction. The number of cam portions 31 in the first side gear 26 is 10, which is the same as the number of teeth of the tooth portion 14a. The circumferential side surface 31a of the cam portion 31 is inclined so that the protruding tip becomes narrower in the circumferential direction.

[0024] 5 to 7, the second side gear 27 has a cylindrical shaft portion 35 and a disk-shaped main body portion 36. The main body portion 36 has a larger diameter and a shorter axial length than the shaft portion 35, and the main body portion 36 and the shaft portion 35 are coaxially arranged and integrally configured. The shaft portion 35 is inserted into the hole 30 of the first side gear 26 so as to be axially movably. The shaft portion 35 has an axis that is formed with a spline hole 37 into which an end of an axle shaft (the right end of the left axle shaft 3) is inserted and through which a rotational driving force can be transmitted.

[0025] A recessed cam hole 38 into which the cam portion 31 is inserted is formed on one side surface of the main body portion 36. A plurality of cam holes 38 (the same number as the cam portions 31) are provided and arranged at equal intervals in the circumferential direction. The cam portion 31 of the first side gear 26 and the cam holes 38 of the second side gear are in the same radial position and are arranged at equal intervals in the circumferential direction. The other side of the main body 36, that is, the rear side of the surface on which the cam hole 38 is provided, is formed with a friction surface 39 (contact surface) that contacts the inner wall surfaces 10a, 10b of the differential case 10 to generate frictional force.

[0026] In this embodiment, the other side surface (friction surface 39) of the main body portion 36 and the inner wall surfaces 10a, 10b of the differential case 10 that abut against the friction surface 39 are parallel to each other and perpendicular to the axial direction (the direction of the rotation axis of the differential case 10). The friction surface 39 of the main body portion 36 and the inner wall surfaces 10a, 10b of the differential case 10 that abut against it may be inclined with respect to the direction perpendicular to the axial direction.

[0027] Furthermore, as shown in FIG. 8, the circumferential positions of the cam portions 31 of the first side gear 26 are aligned with all the tooth bottoms 40 of the teeth 14a on the back surface thereof, and are respectively disposed at the same circumferential positions. With the above-described configuration, in the differential device 1 of this embodiment, when a rotational driving force is input from a driving source such as a motor to the ring gear 15 via the input shaft 16 and the input gear 17, as the differential case 10 rotates, power is transmitted to the right axle shaft 2 and the left axle shaft 3 via the pinion gears 11, 12 and the side gears 13, 14.

[0028] For example, if a rotation difference occurs between the right axle shaft 2 and the left axle shaft 3 during cornering, the rotation of the pinion gears 11, 12 absorbs the rotation difference. In addition, 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 causes the first side gears 24, 26 and the second side gears 25, 27 of the side gears 13, 14 on the side where the driving force has decreased to move axially outward, causing the friction surfaces 39 of the second side gears 25, 27 to be pressed against the inner wall surfaces 10a, 10b of the differential case 10. The friction force suppresses the rotation of the side gears 13, 14 relative to the differential case 10, and the rotation of the pinion gears 11, 12 relative to the differential case 10, thereby limiting the differential.

[0029] In this embodiment, the side gears 13, 14 are divided into first side gears 24, 26 and second side gears 25, 27, and a structure is configured in which the rotational driving force is transmitted between the first side gears 24, 26 and the second side gears 25, 27 via a cam portion 31 and a cam hole 38. Bevel gear teeth 13a, 14a that mesh with the pinion gears 11, 12 are formed on one side of the first side gears 24, 26, and a cam portion 31 is formed on the back side of the teeth 13a, 14a. The circumferential position of the cam portion 31 is configured to coincide with the circumferential position of the tooth bottoms 40 of the teeth 13a, 14a. This allows the cam portion 31 to improve the strength of the first side gears 24, 26. This makes it possible to increase the rotational driving force and differential limiting force transmitted by the first side gears 24, 26 while suppressing the plate thickness of the first side gears 24, 26.

[0030] In particular, the cam portion 31 is disposed near the circumferential outer end of the first side gears 24, 26. This makes it possible to reduce the force acting on the cam portion 31, and to reduce the protruding height of the cam portion 31 and the depth of the cam holes 38 of the second side gears 25, 27, thereby ensuring the strength of the first side gears 24, 26 and the second side gears 25, 27, and thereby reducing the plate thickness of each, thereby reducing the axial length of the entire side gears 13, 14, and therefore the differential device 1, thereby making them more compact.

[0031] The first side gears 24, 26 are provided with the same number of cam portions 31 as the number of tooth bottoms 40 of the tooth portions 13a, 14a, and are provided on the back surfaces thereof in correspondence with all of the tooth bottoms 40. This allows the cam portions 31 to reinforce the locations of all of the tooth bottoms 40 lined up in the circumferential direction, thereby further improving the strength of the first side gears 24, 26. Furthermore, the circumferential end faces of the cam portion 31 and the cam hole 38 are inclined, and the circumferential length of the protruding direction side (second side gears 25, 27 side) of the cam portion 31 is shorter than the circumferential length of the base portion, so that a thrust force is generated that presses the second side gears 25, 27 axially outward when transmitting a rotational driving force between the first side gears 24, 26 and the second side gears 25, 27. As a result, the second side gears 25, 27 are pressed against the differential case 10, and the differential limiting force can be increased.

[0032] 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 and the friction surfaces 39 of the side gears 13, 14 are installed perpendicular to the rotational axis direction of the differential case 10, but they may be inclined from the perpendicular direction to the rotational axis direction.

[0033] Furthermore, the two pinion gears 11, 12 are supported by one shaft (pinion gear shaft 21), but a configuration in which they are supported by the differential case 10 individually by two shafts may also be used. The differential device 1 may also be used in a center differential that absorbs the difference in rotation between the front and rear wheels of a four-wheel drive vehicle. For example, the differential case 10 is rotated by a drive source such as an engine or a motor mounted on the four-wheel drive vehicle, and one of the pair of side gears 13, 14 is connected to the drive shaft of the front wheels including the differential devices for the left and right front wheels via a front propeller shaft, and the other of the pair of side gears 13, 14 is connected to the drive shaft of the rear wheels including the differential devices for the left and right rear wheels via a rear propeller shaft. This makes it possible to reduce the plate thickness while ensuring the strength of the built-in gears in the center differential of a four-wheel drive vehicle, thereby making the center differential smaller.

[0034] 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 11, 12 Pinion gear 13, 14 Side gear 14a Teeth 24, 26 1st side gear 25, 27 Second side gear 31 Cam section 39 Friction surface (contact surface) 40 Root

Claims

1. A differential device having a rotationally driven differential case, a pinion gear rotatably supported on the differential case, and a pair of side gears rotatably supported on 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 side gear is divided in the rotation axis direction and includes a first side gear having a tooth portion that meshes with the pinion gear on one side surface and a second side gear having an abutment surface that abuts against the differential case, a cam portion formed on the other side surface of the first side gear so as to protrude toward the second side gear and transmit a rotational driving force to the second side gear, The cam portion is provided in a plurality of pieces aligned in the circumferential direction on the other side surface of the first side gear, and is disposed at the circumferential position of the tooth bottom of the tooth portion of the first side gear. A differential device characterized by:

2. The cam portion is disposed at a radially outer end portion of the other side surface of the first side gear.

2. The differential device according to claim 1,

3. The cam portions are provided corresponding to all tooth bottoms of the tooth portion.

2. The differential device according to claim 1,

4. The cam portion is formed such that an end face in the circumferential direction of the first side gear is inclined and the circumferential length on the protruding direction side is short.

2. The differential device according to claim 1,

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,

6. The differential device is provided between a front drive shaft and a rear drive shaft of a four-wheel drive 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 drive shaft of the front wheels via a front propeller shaft, The other of the pair of side gears is connected to the drive shaft of the rear wheels via a rear propeller shaft.

2. The differential device according to claim 1,

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