Spline connection structure of differential

Abstract

To provide a spline connection structure of a differential capable of eliminating looseness caused by spline fitness and having high durability.SOLUTION: A missing tooth is provided to a spline tooth of a spline fitting part 30a of a drive shaft 30, and a stick-like elastic body SM and a stick-like elastic body SMW having spring characteristics in a diameter direction or a circumferential direction in a longitudinal gap caused by the missing tooth. Thus, looseness in spline fitness between a spline tooth of an inner peripheral surface 28c1 of a side gear 28c and the spline tooth of the spline fitting part 30a of the drive shaft 30 is eliminated by the spring characteristics in a diameter direction or a peripheral direction of the stick-like elastic body SM and the stick-like elastic body SMW. Accordingly, the spline connection structure of the differential 28 eliminating the looseness caused by the spline fitting and having high durability can be obtained.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a connection structure between a differential mounted on a vehicle and a drive shaft connected to a wheel.

Background Art

[0002] In a differential mounted on a vehicle, the side gear of the differential and the drive shaft are connected by spline fitting. There is a gap between the spline teeth provided on the inner peripheral surface of the side gear and the spline teeth provided on the outer peripheral surface of the drive shaft. Therefore, for example, when the torque input from the engine to the differential and transmitted to the drive shaft changes, shock and time lag occur during acceleration or deceleration due to the play caused by the spline fitting between the side gear and the drive shaft. As a countermeasure, Patent Document 1 discloses a technique in which, after spline connection, the outer diameter of the inner end side of the drive shaft is expanded by tightening a wedge screw inserted into the drive shaft from a working opening provided in the differential, and a just-fit (zero interference fit) or tight-fit (interference fit) state is achieved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the countermeasure described in Patent Document 1 expands the outer diameter of the inner end side of the drive shaft, the inner end side portions of the tooth surfaces of the spline teeth come into local contact with each other. And since the inner end side portions of the tooth surfaces are likely to wear, there is a problem that the play of the fitting is likely to increase even in the just-fit or tight-fit state.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a spline connection structure for a differential that can eliminate backlash caused by spline fitting and has high durability.

Means for Solving the Problems

[0006] The gist of the first invention is a spline connection structure for a differential that (a) spline-fits and connects a side gear and a drive shaft, and (b) provides missing teeth on the spline teeth of the drive shaft, and disposes a rod-shaped elastic body having spring characteristics in the radial direction or the circumferential direction in the longitudinal gap generated by the missing teeth.

Effects of the Invention

[0007] According to the first invention, in the spline connection structure of the differential, missing teeth are provided on the spline teeth of the drive shaft, and a rod-shaped elastic body having spring characteristics in the radial direction or the circumferential direction is disposed in the longitudinal gap generated by the missing teeth. Thereby, the backlash of the spline fitting between the spline teeth of the side gear and the spline teeth of the drive shaft is eliminated by the elastic force due to the spring characteristics of the rod-shaped elastic body in the radial direction or the circumferential direction. Therefore, a spline connection structure for a differential that can eliminate backlash caused by the spline fitting and has high durability can be obtained.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

Embodiment

[0010] FIG. 1 is a diagram for explaining a schematic configuration of a vehicle 10 to which the present invention is applied. In FIG. 1, the vehicle 10 includes an engine 12 as a power source, drive wheels 14, a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14, and the like.

[0011] The engine 12 is a known internal combustion engine, and the engine torque Te, which is the torque of the engine 12, is controlled by control from an engine control device 50 including a fuel injection device and the like provided in the vehicle 10.

[0012] The power transmission device 16 is housed in a non-rotatable case 18 attached to the vehicle body. The power transmission device 16 includes a transmission unit 20, a driven gear 22, a driven shaft 24, a final gear 26, a differential (hereinafter referred to as a "diff") 28, and the like. The diff 28 is a differential gear device having a differential ring gear 28a, a differential case 28b, side gears 28c, a differential pinion 28d, and a pinion shaft 28e. A pair of left and right drive shafts 30 are connected to the diff 28. The above "left and right" refers to the left and right with respect to the forward direction of the vehicle 10.

[0013] The transmission unit 20 is connected to the engine 12. The driven gear 22 meshes with the drive gear 20a which is the output rotating member of the transmission unit 20. The driven shaft 24 has the driven gear 22 and the final gear 26 provided thereon in a non-rotatable relative manner. The final gear 26 has a smaller diameter than the driven gear 22 and meshes with the differential ring gear 28a. The differential ring gear 28a is the input rotating member of the differential 28. The differential 28 distributes the power from the engine 12 to the left and right drive wheels 14.

[0014] The power transmission device 16 transmits the power output from the engine 12 to the driven gear 22 via the transmission unit 20. The power transmission device 16 transmits the power transmitted to the driven gear 22 to the left and right drive wheels 14 sequentially via the driven shaft 24, the final gear 26, the differential 28, the left and right drive shafts 30, etc.

[0015] FIG. 2 is a diagram for explaining an example of the configuration of the differential 28. Further, FIG. 2 is a diagram showing an example of the state before the differential 28 and the drive shaft 30 are assembled. In FIG. 2, the differential 28 includes a differential case 28b. Inside the differential case 28b, a pair of side gears 28c, a pair of differential pinions 28d, and a pinion shaft 28e are accommodated. The differential ring gear 28a is integrally connected to the outside of the differential case 28b. The drive shaft 30 includes a spline fitting portion 30a, a bore fitting portion 30b, etc.

[0016] The differential case 28b is rotatably supported by the case 18 via a bearing about the rotation axis CL1 (hereinafter referred to as the axis CL1). The differential case 28b is formed with a bore portion 28b1 which is a through hole into which the drive shaft 30 is fitted in a relatively rotatable manner. The differential case 28b is formed with a shaft hole 28b2 which is a through hole into which the pinion shaft 28e is fitted in a non-rotatable relative manner. The differential case 28b is the carrier of the differential 28 which houses the side gears 28c, the differential pinions 28d, etc. and into which the drive shaft 30 is fitted in a relatively rotatable manner.

[0017] The side gear 28c and the differential pinion 28d are internal gears 28b in the differential 28. The side gear 28c has an inner peripheral surface 28c1 of a through hole into which the drive shaft 30 is fitted in a non-rotatable manner. Spline teeth are formed on the inner peripheral surface 28c1. The differential pinion 28d meshes with the side gear 28c. The differential pinion 28d is supported on the pinion shaft 28e in a relatively rotatable manner. The pinion shaft 28e is fitted into the shaft hole 28b2 and fixed to the differential case 28b.

[0018] The spline fitting portion 30a is formed at the end of the drive shaft 30 on the differential 28 side. Spline teeth are formed on the outer peripheral surface of the spline fitting portion 30a. When the spline fitting portion 30a of the drive shaft 30 is fitted into the side gear 28c, the drive shaft 30 and the side gear 28c are spline-fitted in a non-rotatable manner. That is, the side gear 28c and the drive shaft 30 rotate integrally around the axis CL1. The bore fitting portion 30b is formed adjacent to the drive wheel 14 side of the spline fitting portion 30a. The bore fitting portion 30b is fitted into the bore portion 28b1 of the differential case 28b in a relatively rotatable manner.

[0019] FIG. 3 is a diagram for explaining an example of the spline connection structure of the present invention. FIG. 3 is a cross-sectional view of the connection state between the side gear 28c and the drive shaft 30 as seen from the rotational direction about the axis CL1. In FIG. 3, the inner peripheral surface 28c1 of the side gear 28c and the spline fitting portion 30a of the drive shaft 30 are spline-fitted. Further, in FIG. 3, the right side of the drawing shows an enlarged view of the spline fitting state of the portion surrounded by the broken line. The lower stage of the enlarged view shows the spline fitting state in the conventional example. In the spline fitting state in the conventional example, the spline teeth without missing teeth of the spline fitting portion 30a of the drive shaft 30 are shown, and the teeth D1, D2, and D3 are the spline teeth of the spline fitting portion 30a. The tooth S1, which is the spline tooth of the inner peripheral surface 28c1 of the side gear 28c, is located between the teeth D1 and D2, and the tooth S2 is located between the teeth D2 and D3. In contrast to such a conventional example, in the case of the present embodiment, as shown in the upper stage on the right side of the drawing in FIG. 3, the tooth D2 is a missing tooth, and a rod-shaped elastic body SM having spring characteristics is preferably disposed in a pressure-applied state in the longitudinal gap generated by the missing tooth of the tooth D2. The elastic force due to the spring characteristics of the disposed rod-shaped elastic body SM, which will be described later, eliminates the play in the spline fitting due to the gaps between the spline teeth S1 and S2 of the inner peripheral surface 28c1 of the side gear 28c and the spline teeth D1 and D3 of the spline fitting portion 30a of the drive shaft 30.

[0020] FIG. 4 is a diagram for explaining the spring characteristics of the rod-shaped elastic body SM. FIG. 4(a) shows the case where the spring characteristics are set in the radial direction. The left side of the paper surface of FIG. 4(a) shows a perspective view of the drive shaft 30 in FIG. 3. As shown in the upper right blowout of the paper surface of FIG. 4(a), the rod-shaped elastic body SM, for example, in a natural state, the central portion of the axial length L has a displacement width H in the outer side in the radial direction, and has a spring characteristic of returning from the accommodation posture in the longitudinal gap to the natural state. Therefore, the elastic force (spring load) of the rod-shaped elastic body SM is, as shown in the lower right blowout of the paper surface of FIG. 4(a), the tooth surfaces FS1, FS2 exposed in the gaps between the spline teeth S1, S2 of the inner peripheral surface 28c1 of the side gear 28c and the outer peripheral surface of the spline fitting portion 30a of the drive shaft 30, and is applied in the radial direction (the direction of the white arrow), and the backlash of the spline engagement is eliminated. The rod-shaped elastic body SM is formed in a triangular prism shape having a substantially triangular cross-sectional shape similar to the longitudinal gap generated by the missing tooth of the tooth D2. The rod-shaped elastic body SM is formed with a pair of inclined surfaces F1, F2 that are in surface contact with each other along the inclinations of the tooth surface FS1 of the spline tooth S1 and the tooth surface FS2 of the spline tooth S2, respectively. By this surface contact, the surface pressure applied to the rod-shaped elastic body SM is reduced, thereby suppressing wear and improving the durability of the spline connection structure. The rod-shaped elastic body SM is preferably formed from a metal spring material such as spring steel or a rubber-based material. Also, the displacement width H and the spring characteristics (spring constant) are predetermined values set in advance and are preferably obtained design-wise or experimentally.

[0021] Figure 4(b) shows the case where the spring characteristics are set in the circumferential direction (rotation direction). The left side of the paper of Figure 4(b) shows a perspective view of the drive shaft 30 in Figure 3, similar to (a). As shown in the upper right blowout of the paper of Figure 4(b), for example, in the natural state, the rod-shaped elastic body SM has a spring characteristic that the central part of the axial length L shown in (b1) has a displacement width W in the circumferential direction and returns from the accommodation posture in the longitudinal gap to the natural state. Further, for example, in the natural state, the rod-shaped elastic body SM has a spring characteristic that the end part of the axial length L shown in (b2) has a displacement width W in the circumferential direction and returns from the accommodation posture in the longitudinal gap to the natural state. Thus, when the spring characteristics are set in the circumferential direction (rotation direction), as shown in the lower right blowout of the paper of Figure 4(b), the elastic force (spring load) of the rod-shaped elastic body SM is applied in the circumferential direction (rotation direction) between the tooth surfaces FS1, FS2 exposed in the gaps of the spline teeth S1, S2 on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth D1, D3 of the spline fitting portion 30a of the drive shaft 30, and the backlash of the spline engagement is eliminated (see the white arrow). Regarding the material and shape (including the displacement width W) of the rod-shaped elastic body SM, it is preferably formed in the same manner as in the case of Figure 4(a).

[0022] Figure 5 is a diagram for explaining an arrangement example of the rod-shaped elastic body SM (and the missing teeth). The locations (indicated by arrows) where the rod-shaped elastic body SM (and the missing teeth) are arranged are, in order, (a) one location (rod-shaped elastic body SM1), (b) two locations (rod-shaped elastic bodies SM1, SM2), (c) three locations (rod-shaped elastic bodies SM1, SM2, SM3), and (d) four locations (rod-shaped elastic bodies SM1, SM2, SM3, SM4). As shown in Figures 5(b) to (d), in the case of arranging a plurality of rod-shaped elastic bodies SM (and the missing teeth), the rod-shaped elastic bodies SM (and the missing teeth) are arranged so that the intervals on each circumference are equal. Thereby, by balancing the elastic forces (spring loads) of the respective rod-shaped elastic bodies SM, the centering of the rotation axes of the side gear 28c and the drive shaft 30 to the axis CL1 is performed, and the backlash of the spline engagement is eliminated more efficiently.

Embodiment

[0023] FIG. 6 is a view for explaining another embodiment of the spline connection structure to which the present invention is applied. FIG. 6 is a cross-sectional view of the connection state between the side gear 28c and the drive shaft 30 as seen from the rotational direction about the axis CL1. In FIG. 6, the inner peripheral surface 28c1 of the side gear 28c and the spline fitting portion 30a of the drive shaft 30 are spline-fitted. Further, in FIG. 6, the right side of the drawing shows an enlarged view of the spline fitting state of the portion surrounded by the broken line. The lower stage of the enlarged view shows the spline fitting state in the conventional example (the same as FIG. 3 of the first embodiment), and the description thereof is omitted. In the present embodiment, as shown in the upper stage on the right side of the drawing of FIG. 6, in addition to the missing teeth of the spline teeth D2, the adjacent spline teeth S2 are also made missing teeth, and a bar-shaped elastic body SMW having spring characteristics is preferably disposed in the longitudinal gap generated by the missing teeth of the spline teeth D2 and the spline teeth S2 in a pressure-applied state. The disposed bar-shaped elastic body SMW is formed in a quadrangular prism shape having a substantially parallelogram cross-sectional shape similar to the longitudinal gap generated by the missing teeth of the teeth D2 and the teeth S2, and is also formed to have spring characteristics in the radial direction or the circumferential direction (rotational direction) in the same manner as in the case of FIG. 4 of the first embodiment. Further, regarding other materials and shapes, they are preferably formed in the same manner as in the case of the first embodiment. When the bar-shaped elastic body SMW has spring characteristics in the radial direction, the elastic force (spring load) of the bar-shaped elastic body SMW is applied in the radial direction between the missing tooth portion S2r of the inner peripheral surface 28c1 of the side gear 28c and the missing tooth portion D2r of the spline fitting portion 30a of the drive shaft 30. When it has spring characteristics in the circumferential direction (rotational direction), the elastic force (spring load) of the bar-shaped elastic body SMW is applied in the circumferential direction (rotational direction) between the tooth surface FS1 exposed in the gap of the tooth S1 of the inner peripheral surface 28c1 of the side gear 28c and the tooth surface FD3 exposed in the gap of the tooth D3 of the spline fitting portion 30a of the drive shaft 30 (see the white arrow).As shown by the arrows in the figure, the elastic force (spring load) of the rod-shaped elastic body SMW acts directly between the toothless portion S2r and the toothless portion D2r, or between the tooth surface FS1 of the spline tooth S1 and the tooth surface FD3 of the spline tooth D3, that is, between the inner peripheral surface 28c1 of the side gear 28c and the spline fitting portion 30a of the drive shaft 30. Therefore, the backlash due to the clearance between the spline teeth on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth on the spline fitting portion 30a of the drive shaft 30 in the spline fitting is eliminated more efficiently. A pair of inclined surfaces F1 and F3 are formed on the rod-shaped elastic body SMW in contact with each other along the inclinations of the tooth surface FS1 of the spline tooth S1 and the tooth surface FD3 of the spline tooth D3, respectively. By this surface contact, the surface pressure applied to the rod-shaped elastic body SMW is reduced, thereby suppressing wear and improving the durability of the spline connection structure.

[0024] Also, in the case of arranging a plurality of rod-shaped elastic bodies SMW (and adjacent toothless portions), similar to the case of the first embodiment (Fig. 5), the rod-shaped elastic bodies SMW (and adjacent toothless portions) are arranged so that the intervals on each circumference are equal. As a result, the elastic forces (spring loads) of the respective rod-shaped elastic bodies SMW are balanced, thereby centering the axis of rotation of the side gear 28c and the drive shaft 30 on the axis CL1, and the backlash of the spline fitting is eliminated more efficiently.

[0025] As described above, according to the spline connection structures of the first and second embodiments, toothless portions are provided on the spline teeth of the spline fitting portion 30a of the drive shaft 30, and rod-shaped elastic bodies SM and SMW having spring characteristics in the radial direction or the circumferential direction are arranged in the longitudinal gaps generated by the toothless portions. Thereby, due to the spring characteristics in the radial direction or the circumferential direction of the rod-shaped elastic bodies SM and SMW, the backlash of the spline fitting between the spline teeth on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth on the spline fitting portion 30a of the drive shaft 30 is eliminated. Therefore, a spline connection structure of the differential 28 that can eliminate the backlash caused by the spline fitting and has high durability can be obtained.

[0026] Further, according to the spline connection structures of Example 1 and Example 2, a plurality of rod-shaped elastic bodies SM, rod-shaped elastic bodies SMW (and toothless portions) are arranged such that the intervals on the circumference are equal. Thereby, by balancing the elastic forces (spring loads) of the respective rod-shaped elastic bodies SM, the centering of the rotation axes of the side gear 28c and the drive shaft 30 with respect to the axis CL1 is performed, and the play in the spline fitting is eliminated more efficiently.

[0027] Further, according to the spline connection structure of Example 2, a second toothless portion is provided on the spline teeth of the inner peripheral surface 28c1 of the side gear 28c adjacent to the toothless portion provided on the spline teeth of the spline fitting portion 30a of the drive shaft 30, and the rod-shaped elastic body SMW is arranged in the gap formed by the toothless portion and the second toothless portion. Thereby, since the elastic force (spring load) of the rod-shaped elastic body SMW acts directly between the inner peripheral surface 28c1 that abuts against the rod-shaped elastic body SMW and the spline fitting portion 30a, the play in the spline fitting between the spline teeth of the inner peripheral surface 28c1 of the side gear 28c and the spline teeth of the spline fitting portion 30a of the drive shaft 30 is eliminated more efficiently.

[0028] Further, according to the spline structures of Example 1 and Example 2, a pair of inclined surfaces F1, F2 that are in surface contact with the tooth surfaces FS1, FS2 of the spline teeth S1, S2 of the inner peripheral surface 28c1 of the side gear 28c that are exposed in the gap are formed on the rod-shaped elastic body SM. Also, a pair of inclined surfaces F1, F3 that are in surface contact with the tooth surface FS1 of the spline tooth S1 of the inner peripheral surface 28c1 of the side gear 28c and the tooth surface FD3 of the spline tooth D3 of the spline fitting portion 30a, respectively, that are exposed in the gap are formed on the rod-shaped elastic body SMW. By this surface contact, the surface pressure applied to the rod-shaped elastic body SM and the rod-shaped elastic body SMW is reduced, thereby obtaining wear suppression and durability of the spline connection structure. Therefore, a differential spline connection structure that can eliminate the play caused by spline fitting and has high durability is obtained.

[0029] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0030] 28: Differential, 28c: Side Gear, 28c1: Inner Peripheral Surface, 30: Drive Shaft, 30a: Spline Fitting Portion, F1: Inclined Surface, F2: Inclined Surface, F3: Inclined Surface, FD3: Tooth Surface, FS1: Tooth Surface, FS2: Tooth Surface, SM: Rod-shaped Elastic Body, SMW: Rod-shaped Elastic Body

Claims

1. A spline connection structure of a differential that spline-fits and connects a side gear and a drive shaft, wherein missing teeth are provided on the spline teeth of the drive shaft, and a rod-shaped elastic body having spring characteristics in the radial direction or the circumferential direction is disposed in the longitudinal gap formed by the missing teeth. A spline connection structure of a differential, characterized in that.

2. A plurality of the missing teeth and the rod-shaped elastic bodies are arranged at equal intervals on the circumference. The spline connection structure of the differential according to claim 1, characterized in that.

3. Second missing teeth are provided on the spline teeth of the side gear adjacent to the missing teeth of the drive shaft, and the rod-shaped elastic body is disposed in the longitudinal gap formed by the missing teeth and the second missing teeth. The spline connection structure of the differential according to claim 1, characterized in that.

4. The rod-shaped elastic body includes a pair of inclined surfaces that are in surface contact with the tooth surfaces of the spline teeth exposed in the longitudinal gap, respectively. The spline structure of the differential according to any one of claims 1 to 3, characterized in that.

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