Spline connection structure of differential mechanism

Abstract

The invention provides a spline connection structure of a differential mechanism, which can eliminate loosening caused by spline embedding and is high in durability. Spline teeth of a spline fitting part (30a) of a drive shaft (30) are provided with missing teeth, and rod-shaped elastic bodies (SM) and (SMW) having spring characteristics in the radial direction or the circumferential direction are arranged in long gaps generated by the missing teeth. Thus, by means of the spring characteristics of the rod-shaped elastic body (SM) and the rod-shaped elastic body (SMW) in the radial direction or the circumferential direction, looseness of spline fitting between spline teeth of the inner circumferential surface (28c1) of the side gear (28c) and spline teeth of a spline fitting part (30a) of the drive shaft (30) is eliminated. Therefore, the spline connection structure of the differential (28) can eliminate loosening caused by spline fitting and is high in durability.

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, a side gear of the differential is connected to a drive shaft 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, due to the looseness caused by the spline fitting between the side gear and the drive shaft, shocks or delays occur during acceleration or deceleration. As a countermeasure, the following technique is disclosed in Patent Document 1: After spline connection, by further tightening a wedge-shaped screw inserted into the drive shaft through an operation opening provided in the differential, the outer diameter of the inner end side of the drive shaft is expanded to achieve an accurate fit (zero interference fit) or a tight fit (interference fit) state.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-292121 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in the countermeasure described in Patent Document 1, the outer diameter of the inner end side of the drive shaft is expanded. Therefore, the inner end side portions of the tooth surfaces of the spline teeth are locally in contact with each other. Moreover, since the inner end side portions of the tooth surfaces are easily worn, there is a problem that even if an accurate fit or a tight fit state is achieved, the looseness of the fit easily increases.

[0008] The present invention has been made against the above background, and an object thereof is to provide a spline connection structure for a differential that can eliminate looseness caused by spline fitting and has high durability.

[0009] Means for Solving the Problems

[0010] The gist of the first invention is as follows: (a) A spline connection structure for a differential that connects a side gear and a drive shaft by spline fitting, wherein (b) missing teeth are provided on the spline teeth of the drive shaft, and a rod-shaped elastic body having spring characteristics in the radial or circumferential direction is disposed in a long gap generated by the missing teeth.

[0011] Advantages of the Invention

[0012] According to the first invention described above, 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 arranged in the long strip-shaped gap generated by the missing teeth. Thus, the looseness of the spline engagement between the spline teeth of the side gear and the spline teeth of the drive shaft is eliminated by the elastic force generated by the spring characteristics in the radial direction or the circumferential direction of the rod-shaped elastic body. Therefore, a spline connection structure of a differential that can eliminate looseness caused by the spline engagement and has high durability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. is a diagram illustrating an example of the schematic structure of a vehicle to which the present invention is applied.

[0014] Figure 2 FIG. is a diagram illustrating an example of the structure of a differential, and is also a diagram illustrating an example of the state before assembly of the differential and the drive shaft.

[0015] Figure 3 FIG. is a diagram illustrating an example of a spline connection structure to which the present invention is applied.

[0016] Figure 4 FIG. is a diagram illustrating an example of the spring characteristics of a rod-shaped elastic body.

[0017] Figure 5 FIG. is a diagram illustrating an example of the arrangement of a rod-shaped elastic body.

[0018] Figure 6 FIG. is a diagram illustrating another embodiment of a spline connection structure to which the present invention is applied.

[0019] REFERENCE SIGNS LIST

[0020] 28: Differential (differential gear device), 28c: Side gear, 28c1: Inner peripheral surface, 30: Drive shaft, 30a: Spline engagement 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. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that in the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of each part are not necessarily accurately depicted.

[0022] [Embodiment 1]

[0023] Figure 1 FIG. is a diagram illustrating the schematic structure of a vehicle 10 to which the present invention is applied. In Figure 1In this case, 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 so on.

[0024] 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.

[0025] The power transmission device 16 is housed in a non-rotatable housing 18 mounted on the vehicle body. The power transmission device 16 includes a speed change section 20, a driven gear 22, a driven shaft 24, a final drive gear 26, a differential (differential gear device) 28, and so on. The differential 28 is a differential gear device having a differential ring gear 28a, a differential housing 28b, side gears 28c, differential pinions 28d, and a pinion shaft 28e. A pair of left and right drive shafts 30 are connected to the differential 28. The above-mentioned "left and right" refers to the left and right with respect to the forward direction of the vehicle 10.

[0026] The speed change section 20 is connected to the engine 12. The driven gear 22 meshes with a drive gear 20a that is an output rotating member of the speed change section 20. The driven shaft 24 is provided such that the driven gear 22 and the final drive gear 26 cannot rotate relative to each other. The diameter of the final drive gear 26 is smaller than that of the driven gear 22, and the final drive gear 26 meshes with the differential ring gear 28a. The differential ring gear 28a is an 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.

[0027] The power transmission device 16 transmits the power output from the engine 12 to the driven gear 22 via the speed change section 20. The power transmission device 16 transmits the power transmitted to the driven gear 22 to the left and right drive wheels 14 via the driven shaft 24, the final drive gear 26, the differential 28, the left and right drive shafts 30, and so on.

[0028] Figure 2 is a diagram showing an example of the structure of the differential 28. In addition, Figure 2 is a diagram showing an example of the state before the differential 28 and the drive shaft 30 are assembled. In Figure 2 the differential 28 includes a differential housing 28b. A pair of side gears 28c, a pair of differential pinions 28d, and a pinion shaft 28e are housed in the differential housing 28b. The differential ring gear 28a is integrally connected to the outside of the differential housing 28b. The drive shaft 30 includes a spline fitting portion 30a, a hole fitting portion 30b, and so on.

[0029] The differential case 28b is supported by the housing 18 via bearings so as to be rotatable about the rotation axis CL1 (hereinafter referred to as the axis CL1). The differential case 28b is formed with a through hole, i.e., a hole portion 28b1, into which the drive shaft 30 is relatively rotatably fitted. The differential case 28b is formed with a through hole, i.e., a shaft hole 28b2, into which the pinion shaft 28e is non-rotatably fitted. The differential case 28b is a bracket of the differential 28 that houses the side gear 28c, the differential pinion 28d, etc. and into which the drive shaft 30 is relatively rotatably fitted.

[0030] The side gear 28c and the differential pinion 28d are internal gears 28bing of the differential 28. The side gear 28c has an inner peripheral surface 28c1 of a through hole into which the drive shaft 30 is non-rotatably fitted. Spline teeth are formed on the inner peripheral surface 28c1. The teeth of the differential pinion 28d mesh with the side gear 28c. The differential pinion 28d is rotatably supported by the pinion shaft 28e. The pinion shaft 28e is fitted into the shaft hole 28b2 and fixedly provided on the differential case 28b.

[0031] A 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 non-rotatably spline-fitted. That is, the side gear 28c and the drive shaft 30 rotate integrally about the axis CL1. A hole fitting portion 30b is formed adjacent to the drive wheel 14 side of the spline fitting portion 30a. The hole fitting portion 30b is relatively rotatably fitted into the hole portion 28b1 of the differential case 28b.

[0032] Figure 3 It is a diagram showing an example of the spline connection structure of the present invention. Figure 3 It is a cross-sectional view showing the connection state of the side gear 28c and the drive shaft 30 as viewed from the rotation direction with the axis CL1 as the center. In Figure 3 it, the inner peripheral surface 28c1 of the side gear 28c and the spline fitting portion 30a of the drive shaft 30 are spline-fitted. In addition, in Figure 3 it, the right side of the drawing shows an enlarged view of the spline fitting state of the portion surrounded by the dashed line. The lower part of this enlarged view shows the spline fitting state in the prior art example. In the spline fitting state in the prior art example, the spline teeth of the spline fitting portion 30a of the drive shaft 30 without missing teeth are shown. The teeth D1, D2, and D3 are the spline teeth of the spline fitting portion 30a. The tooth S1 of the spline teeth 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. Compared with such a prior art example, in the case of the present embodiment, as in Figure 3As shown in the upper part on the right side of the paper surface, taking the tooth D2 as a missing tooth, a rod-shaped elastic body SM with spring characteristics is preferably arranged in a pressurized state within the long strip-shaped gap generated by the missing tooth of the tooth D2. By using the elastic force generated by the spring characteristics of the arranged rod-shaped elastic body SM described later, the looseness of the spline engagement caused by the gap between the spline teeth S1 and S2 on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth D1 and D3 of the spline engagement portion 30a of the drive shaft 30 is eliminated.

[0033] Figure 4 It is a diagram for explaining the spring characteristics of the rod-shaped elastic body SM. Figure 4 (a) shows the case where the spring characteristics are set in the radial direction. Figure 4 The left side of the paper surface of (a) shows Figure 3 a perspective view of the drive shaft 30 in. As Figure 4 shown in the lead-out frame in the upper right part of the paper surface of (a), for example, in the natural state, the central part of the axial length L of the rod-shaped elastic body SM has a displacement amplitude H on the outer side in the radial direction, and has spring characteristics of returning from the housed posture within the long strip-shaped gap to the natural state. Therefore, the elastic force (spring load) of the rod-shaped elastic body SM is as Figure 4 shown in the lead-out frame in the lower right part of the paper surface of (a), and is applied in the radial direction (hollow arrow direction) between the outer peripheral surface of the spline engagement portion 30a of the drive shaft 30 and the tooth surfaces FS1 and FS2 exposed in the gap between the spline teeth S1 and S2 on the inner peripheral surface 28c1 of the side gear 28c, eliminating the looseness of the spline engagement. The rod-shaped elastic body SM is formed into a triangular prism shape with a cross-sectional shape substantially the same as the long strip-shaped gap generated by the missing tooth of the tooth D2. A pair of inclined surfaces F1 and F2 are formed on the rod-shaped elastic body SM, and the pair of inclined surfaces F1 and F2 are in surface contact with the tooth surface FS1 of the spline tooth S1 and the tooth surface FS2 of the spline tooth S2 respectively along the inclination of the tooth surface FS1 of the spline tooth S1 and the tooth surface FS2 of the spline tooth S2. Through this surface contact, the surface pressure applied to the rod-shaped elastic body SM is reduced, thereby enabling wear suppression and durability of the spline connection structure. The rod-shaped elastic body SM is preferably formed of a metal spring component such as spring steel or a rubber-based material, for example. In addition, the displacement amplitude H and the spring characteristics (spring coefficient) are preset specified values, and are appropriately obtained through design or experiments.

[0034] Figure 4 (b) shows the case where the spring characteristics are set in the circumferential direction (rotation direction). Figure 4 The left side of the paper surface of (b) shows the same as (a) Figure 3 a perspective view of the drive shaft 30 in. As Figure 4As shown in the lead-out frame in the upper right part of the paper surface of (b), in the natural state of the rod-shaped elastic body SM, for example, the central part of the axial length L shown in (b1) has a displacement amplitude W in the circumferential direction and has a spring characteristic of returning from the housed posture in the long and narrow gap to the natural state. In addition, in the natural state of the rod-shaped elastic body SM, for example, the end part of the axial length L shown in (b2) has a displacement amplitude W in the circumferential direction and has a spring characteristic of returning from the housed posture in the long and narrow gap to the natural state. Thus, when the spring characteristic is set in the circumferential direction (rotation direction), as Figure 4 As shown in the lead-out frame in the lower right part of the paper surface of (b), the elastic force (spring load) of the rod-shaped elastic body SM is applied in the circumferential direction (rotation direction) between the spline teeth D1, D3 of the spline fitting part 30a of the drive shaft 30 and the tooth surfaces FS1, FS2 exposed in the gaps between the spline teeth S1, S2 on the inner circumferential surface 28c1 of the side gear 28c, eliminating the looseness of the spline fitting (see the hollow arrow). Regarding the material and shape (including the displacement amplitude W) of the rod-shaped elastic body SM, it is appropriately formed in the same manner as Figure 4 the case of (a).

[0035] Figure 5 FIG. is a diagram for explaining an arrangement example of the rod-shaped elastic body SM (and the missing teeth), and the parts (indicated by arrows) where the rod-shaped elastic body SM (and the missing teeth) are arranged are sequentially set as (a) one part (rod-shaped elastic body SM1), (b) two parts (rod-shaped elastic body SM1, SM2), (c) three parts (rod-shaped elastic body SM1, SM2, SM3), (d) four parts (rod-shaped elastic body SM1, SM2, SM3, SM4) as examples. As Figure 5 shown in (b) to (d), in the arrangement of a plurality of rod-shaped elastic bodies SM (and the missing teeth), the rod-shaped elastic bodies SM (and the missing teeth) are arranged at equal intervals on their respective circumferences. Thereby, the elastic forces (spring loads) of the respective rod-shaped elastic bodies SM are balanced, centering the rotation axes of the side gear 28c and the drive shaft 30 with respect to the axis CL1, and more efficiently eliminating the looseness of the spline fitting.

[0036] [Embodiment 2]

[0037] Figure 6 FIG. is a diagram for explaining another embodiment of the spline connection structure to which the present invention is applied. Figure 6 FIG. is a cross-sectional view showing the connection state of the side gear 28c and the drive shaft 30 as viewed from the rotation direction with the axis CL1 as the center. In Figure 6 this, the inner circumferential surface 28c1 of the side gear 28c is spline-fitted with the spline fitting part 30a of the drive shaft 30. In addition, in Figure 6In the figure, the enlarged view on the right side of the paper surface shows the spline fitting state of the part surrounded by the dashed line. The lower part of this enlarged view shows the spline fitting state in the existing example (the same as that of Embodiment 1 Figure 3 ), and the description thereof is omitted. In this embodiment, as shown in the upper part on the right side of the paper surface in Figure 6 , in addition to the missing teeth of the spline tooth D2, the adjacent spline tooth S2 is also provided with missing teeth. In the long gap generated by the missing teeth of the spline tooth D2 and the spline tooth S2, the rod-shaped elastic body SMW having spring characteristics is preferably arranged in a pressurized state. The arranged rod-shaped elastic body SMW is formed into a prismatic shape with a cross-sectional shape of a substantially parallelogram that is the same as the long gap generated by the missing teeth of the teeth D2 and the teeth S2. In addition, similar to the case of Figure 4 of Embodiment 1, it is formed to have spring characteristics in the radial direction or the circumferential direction (rotation direction). In addition, regarding other materials and shapes, they are appropriately formed in the same manner as in the case of Embodiment 1. When the rod-shaped elastic body SMW has spring characteristics in the radial direction, the elastic force (spring load) of the rod-shaped elastic body SMW is applied in the radial direction between the missing tooth part S2r of the inner peripheral surface 28c1 of the side gear 28c and the missing tooth part D2r of the spline fitting part 30a of the drive shaft 30. When it has spring characteristics in the circumferential direction (rotation direction), the elastic force (spring load) of the rod-shaped elastic body SMW is applied in the circumferential direction (rotation direction) between the tooth surface FS1 exposed in the gap of the tooth S1 on the inner peripheral surface 28c1 of the side gear 28c and the tooth surface FD3 exposed in the gap of the tooth D3 on the spline fitting part 30a of the drive shaft 30 (refer to the hollow 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 missing tooth part S2r and the missing tooth part 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 part 30a of the drive shaft 30. Therefore, the looseness based on the spline fitting caused by the gap between the spline teeth on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth on the spline fitting part 30a of the drive shaft 30 is more efficiently eliminated. A pair of inclined surfaces F1 and F3 are formed on the rod-shaped elastic body SMW, and the pair of inclined surfaces F1 and F3 are in surface contact with the tooth surface FS1 of the spline tooth S1 and the tooth surface FD3 of the spline tooth D3 respectively along the inclination of each of them. Through this surface contact, the surface pressure applied to the rod-shaped elastic body SMW is reduced, thereby enabling wear suppression and durability of the spline connection structure.

[0038] In addition, in the arrangement of a plurality of rod-shaped elastic bodies SMW (and adjacent missing teeth), similar to Embodiment 1 ( Figure 5Similarly, the rod-shaped elastic bodies SMW (and the adjacent tooth gaps) are arranged at equal intervals on their respective circumferences. Thus, by balancing the elastic forces (spring loads) of the respective rod-shaped elastic bodies SMW, centering of the rotational axes of the side gear 28c and the drive shaft 30 with respect to the axis CL1 is performed, and looseness of the spline engagement is eliminated more efficiently.

[0039] As described above, according to the spline connection structures of Embodiment 1 and Embodiment 2, tooth gaps are provided in the spline teeth of the spline engagement portion 30a of the drive shaft 30, and rod-shaped elastic bodies SM and rod-shaped elastic bodies SMW having spring characteristics in the radial direction or the circumferential direction are arranged in the elongated gaps generated by the tooth gaps. Thus, by the spring characteristics in the radial direction or the circumferential direction of the rod-shaped elastic bodies SM and the rod-shaped elastic bodies SMW, looseness of the spline engagement between the spline teeth on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth of the spline engagement portion 30a of the drive shaft 30 is eliminated. Therefore, a spline connection structure of the differential 28 that can eliminate looseness caused by spline engagement and has high durability can be obtained.

[0040] In addition, according to the spline connection structures of Embodiment 1 and Embodiment 2, a plurality of rod-shaped elastic bodies SM and rod-shaped elastic bodies SMW (and tooth gaps) are arranged at equal intervals on the circumference. Thus, by balancing the elastic forces (spring loads) of the respective rod-shaped elastic bodies SM, centering of the rotational axes of the side gear 28c and the drive shaft 30 with respect to the axis CL1 is performed, and looseness of the spline engagement is eliminated more efficiently.

[0041] In addition, according to the spline connection structure of Embodiment 2, second tooth gaps are provided in the spline teeth on the inner peripheral surface 28c1 of the side gear 28c adjacent to the tooth gaps in the spline teeth of the spline engagement portion 30a provided on the drive shaft 30, and rod-shaped elastic bodies SMW are arranged in the gaps generated by the tooth gaps and the second tooth gaps. Thus, the elastic force (spring load) of the rod-shaped elastic body SMW acts directly between the inner peripheral surface 28c1 in contact with the rod-shaped elastic body SMW and the spline engagement portion 30a, and therefore, looseness of the spline engagement between the spline teeth on the inner peripheral surface 28c1 of the side gear 28c and the spline teeth of the spline engagement portion 30a of the drive shaft 30 is eliminated more efficiently.

[0042] In addition, according to the spline structures of Embodiment 1 and Embodiment 2, a pair of inclined surfaces F1 and F2 are formed on the rod-shaped elastic body SM that are in surface contact with the tooth surfaces FS1 and FS2 of the spline teeth S1 and S2 of the inner peripheral surface 28c1 of the side gear 28c exposed in the gap. In addition, a pair of inclined surfaces F1 and F3 are formed on the rod-shaped elastic body SMW 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 exposed in the gap and the tooth surface FD3 of the spline tooth D3 of the spline fitting portion 30a exposed in the gap, respectively. Through this surface contact, the surface pressure applied to the rod-shaped elastic body SM and the rod-shaped elastic body SMW is reduced, thereby enabling wear suppression and durability of the spline connection structure. Therefore, a spline connection structure of a differential that can eliminate looseness caused by spline fitting and has high durability can be obtained.

[0043] As described above, the embodiments of the present invention have been described in detail based on the drawings. However, the above content is only one embodiment, and the present invention can be implemented in various modified and improved ways based on the knowledge of those skilled in the art.

Claims

1. A spline connection structure of a differential, which connects a side gear and a drive shaft by spline fitting, is characterized in that missing teeth are provided on the spline teeth of the drive shaft, and a rod-shaped elastic body having spring characteristics in the radial or circumferential direction is arranged in the long strip-shaped gap generated by the missing teeth.

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

3. The spline connection structure of a differential according to claim 1, characterized in that 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 arranged in the long strip-shaped gap generated by the missing teeth and the second missing teeth.

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

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