Vehicle drive shaft device

Abstract

To provide a vehicle drive shaft device that can suppress a decrease in durability even when excessive torque is applied to the drive shaft without increasing its diameter. [Solution] The connecting shaft portion 28 is connected to the cylindrical member 26 so as to be rotatable relative to it, and the first disc-shaped member 30 located inside the cylindrical member 26 is concentrically fixed to the connecting shaft portion 28. Inside the cylindrical member 26, there is a second disc-shaped member 32 that is not rotatable relative to the cylindrical member 26 and is movable in the axial direction, facing the first disc-shaped member 30, and a coil spring 34 that applies a load to the second disc-shaped member 32 on the first disc-shaped member 30, causing the two members 30 and 32 to slide against each other.

Description

[Technical Field]

[0001] The present invention relates to a vehicle drive shaft device that limits input of drive torque to a vehicle drive shaft. [Background Art]

[0002] A driving component provided in a power transmission path that transmits drive torque from a power source to drive wheels may be subjected to excessive input torque, which may reduce durability. To mitigate this problem, vehicle differential devices that limit the magnitude of input torque are known. For example, the differential device described in Patent Document 1 is one such device. Patent Document 1 discloses that a mechanical element having a torque limiter function provided between a ring gear and a differential case in the differential device limits the magnitude of drive torque transmitted from the ring gear to the differential case.

[0003] As a driving component provided in the power transmission path, a drive shaft having a pair of constant velocity joints and an intermediate shaft connecting the pair of constant velocity joints is known. Since this drive shaft has a large ratio of length to diameter, a torsion phenomenon is likely to occur, and a resonance phenomenon caused by the torsion phenomenon may generate input torque greater than expected, which may impair durability. To address this problem, when the torque limiter function is not used, it is conceivable to use a means for suppressing the magnitude of input torque through control or the like, but there have been cases where the input torque to the drive shaft cannot always be sufficiently suppressed transiently. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2014-52048 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Given these circumstances, it is conceivable to apply the torque limiter described in Patent Document 1 to the drive shaft. However, the radial size of the mechanical elements constituting the torque limiter described in Patent Document 1 is approximately the size of the inner circumferential surface of the differential case, which is large compared to the diameter of the drive shaft. Therefore, applying the torque limiter described in Patent Document 1 to the drive shaft would result in the drive shaft components becoming larger.

[0006] The present invention was made to solve the above-mentioned problems, and its objective is to provide a vehicle drive shaft device that can suppress a decrease in durability even when excessive torque is applied to the drive shaft due to resonance caused by torsional phenomena, without increasing the diameter of the drive shaft. [Means for solving the problem]

[0007] The gist of the present invention is a vehicle drive shaft device having (a) a pair of constant velocity couplings and an intermediate shaft connecting the constant velocity couplings, and having a drive shaft arranged in the power transmission path of a vehicle, wherein one of the pair of constant velocity couplings has an inner ring connected to the intermediate shaft and an outer ring housing the inner ring, and the outer ring has a cylindrical member and a connecting shaft portion, (b) the connecting shaft portion of the outer ring is connected to the cylindrical member so as to be rotatable relative to it, (c) a first disc-shaped member located inside the cylindrical member is fixed concentrically to the connecting shaft portion, and (d) inside the cylindrical member there is a second disc-shaped member that is not rotatable relative to the cylindrical member and is movable in the axial direction, facing the first disc-shaped member, and a biasing member that applies a load to the second disc-shaped member toward the first disc-shaped member to cause the first disc-shaped member and the second disc-shaped member to slide into contact. [Effects of the Invention]

[0008] According to the vehicle drive shaft device of the present invention, a torque limiter is configured by a first disc-shaped member, a second disc-shaped member, and a biasing member housed within a cylindrical member of the outer ring. This provides a vehicle drive shaft device that does not require an increase in the diameter of the drive shaft and can suppress a decrease in durability even when excessive torque is applied to the drive shaft. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view illustrating a vehicle drive shaft device according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing a portion of a torque limiter constituting a vehicle drive shaft device according to another embodiment 2 of the present invention. [Figure 3] This is a cross-sectional view showing a portion of a torque limiter constituting a vehicle drive shaft device according to another embodiment 3 of the present invention. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0011] Figure 1 is a cross-sectional view illustrating a vehicle drive shaft device 10 according to one embodiment of the present invention. The driving torque is transmitted from a vehicle power source (not shown), such as an engine, to the drive shaft 20 via a power transmission path (not shown), and further transmitted to the drive wheels (not shown). The drive shaft 20 consists of a first constant velocity coupling 14, a second constant velocity coupling 16, and an intermediate shaft 18 connected to both couplings 14 and 16. Here, the first constant velocity coupling 14 and the second constant velocity coupling 16 correspond to a pair of constant velocity couplings in the present invention, and the first constant velocity coupling 14 corresponds to one of the constant velocity couplings.

[0012] The first constant velocity coupling 14 has an inner ring 22 fitted and connected to an intermediate shaft 18 so as not to rotate relative to it, and an outer ring 24 that houses the inner ring 22. The outer ring 24 has a cylindrical member 26 and a connecting shaft portion 28. One end of the connecting shaft portion 28 is connected to the cylindrical member 26 so as to rotate relative to it. The other end of the connecting shaft portion 28 is connected to a side gear shaft of a differential device (not shown). A disc-shaped first disc-shaped member 30 is fixed concentrically to one end of the connecting shaft portion 28. The cylindrical member 26 has a bottomed circular hole 26b on the opposite side of the bottomed circular hole 26a that houses the inner ring 22 in the axial direction CL. A disc-shaped second disc-shaped member 32 and a coil spring 34 are located inside the bottomed circular hole 26b. The second disc-shaped member 32 is positioned opposite the first disc-shaped member 30 and is provided with respect to the cylindrical member 26 in a manner that prevents relative rotation around the axis CL and allows movement in the direction of the axis CL.

[0013] The cylindrical member 26 has a flange portion 26c projecting radially from the opening of the bottomed circular hole 26b. The cylindrical bearing member 36 has a bearing 38 fixed to its inner circumferential surface and an oil seal 40 fitted into it, and has a flange portion 36a projecting radially from the opening on the cylindrical member 26 side. The connecting shaft portion 28 is inserted into the inner circumference of the oil seal 40 and is supported by the bearing 38 so as to be rotatable relative to the cylindrical member 26, with both flange portions 26c and 36a fastened together by fastening bolts 42.

[0014] On the surface of the first disc-shaped member 30 facing the second disc-shaped member 32, a first tooth surface 30a is provided, which is formed radially around the axis CL, the rotation center of the first disc-shaped member 30, and has an isosceles trapezoidal cross-section in the circumferential direction. On the surface of the second disc-shaped member 32 facing the first disc-shaped member 30, a second tooth surface 32a is provided, similar to the first tooth surface 30a. Between the surface of the second disc-shaped member 32 opposite to the second tooth surface 32a and the bottom surface of the bottomed circular hole 26b, a plurality of coil springs 34 are disposed in a compressed state. The second disc-shaped member 32 is subjected to a load by the coil springs 34 on the first disc-shaped member 30, causing the first tooth surface 30a and the second tooth surface 32a to mesh and engage with each other. Here, the coil springs 34 correspond to the biasing members in the present invention.

[0015] With the above configuration, the drive torque input from the side gear shaft is transmitted from the first disc-shaped member 30 to the second disc-shaped member 32. When the drive torque is transmitted from the first disc-shaped member 30 to the second disc-shaped member 32, a force perpendicular to the tooth surface acts from the first tooth surface 30a to the second tooth surface 32a. Since the circumferential cross-sections of the first tooth surface 30a and the second tooth surface 32a are isosceles trapezoids, the component of the force perpendicular to the tooth surface in the axial direction CL acts to push the second disc-shaped member 32 in the axial direction CL. When the component of the force in the axial direction CL exceeds the load applied to the coil spring 34, the meshing between the first tooth surface 30a and the second tooth surface 32a disengages, and the meshing engagement between the first disc-shaped member 30 and the second disc-shaped member 32 is broken.

[0016] Once the meshing engagement is broken, the second disc-shaped member 32 is pushed by the load applied by the coil spring 34 and slides against the first disc-shaped member 30. Subsequently, the first tooth surface 30a and the second tooth surface 32a mesh again, and the first disc-shaped member 30 and the second disc-shaped member 32 engage. As this behavior is repeated, the driving torque transmitted from the first disc-shaped member 30 to the second disc-shaped member 32 is limited.

[0017] According to the vehicle drive shaft device 10 of the present embodiment, a torque limiter is constituted by a first disc-shaped member 30, a second disc-shaped member 32, and a coil spring 34 accommodated in a cylindrical member 26 of an outer ring 24. As a result, even when excessive torque is input to the drive shaft 20, the transmitted torque is limited, so that a decrease in durability of the drive shaft 20 can be suppressed. Further, the radial dimension of the torque limiter is smaller than the outer diameter of the outer ring 24 of the first constant velocity joint 14, and the diameter of the drive shaft is not increased.

[0018] Next, another embodiment of the present invention will be described. Note that the same reference numerals are given to portions common to the above-described Embodiment 1, and description thereof is omitted.

Example

[0019] Figure 2 is a cross-sectional view of a portion constituting a torque limiter, for explaining a vehicle drive shaft device 110 according to Embodiment 2. Only the first disk-shaped member 130 and the second disk-shaped member 132 differ from the first embodiment. By applying a load to the coil spring 34 to the second disk-shaped member 132, a second friction surface 132a, which is one side surface of the second disk-shaped member 132, is pressed against a first friction surface 130a, which is one side surface of the first disk-shaped member 130. The first friction surface 130a and the second friction surface 132a each have characteristics of a high friction coefficient and durability against slipping due to their surface treatments.

[0020] By the frictional force generated between the first friction surface 130a and the second friction surface 132a, driving torque is transmitted from the first disc-shaped member 130 to the second disc-shaped member 132. When the driving torque input to the first disc-shaped member 130 increases and the frictional force that transmits this torque exceeds the maximum static friction force between the first friction surface 130a and the second friction surface 132a, slippage occurs between the two surfaces, and the first friction surface 130a and the second friction surface 132a come into sliding contact. When slippage occurs, dynamic friction force smaller than the maximum static friction force acts from the first friction surface 130a to the second friction surface 132a, and torque of a corresponding magnitude is transmitted from the first disc-shaped member 130 to the second disc-shaped member 132. Accordingly, the driving torque transmitted from the first disc-shaped member 130 to the second disc-shaped member 132 is limited.

[0021] According to the vehicle drive shaft device 110 of the present embodiment, a torque limiter is configured by the first disc-shaped member 130, the second disc-shaped member 132, and the coil spring 34 accommodated in the cylindrical member 26 of the outer ring 24. Accordingly, even when excessive torque is input to the drive shaft 20, the transmitted torque is limited, thereby suppressing a decrease in durability. In addition, the radial dimension of the torque limiter is approximately equal to the outer diameter of the outer ring 24 of the first constant velocity joint 14, and the diameter of the drive shaft is not increased. Example

[0022] Figure 3 is a cross-sectional view of a portion constituting the torque limiter, for explaining the vehicle drive shaft device 210 according to the third embodiment. The only difference from the second embodiment is the disc spring 234, which is the biasing member. The disc spring 234 is an elastic body in which a disc is formed into a conical shape. The second friction surface 132a of the second disc-shaped member 132 is pressed against the first friction surface 130a of the first disc-shaped member 130 by applying a load to the coil spring 34 on the second disc-shaped member 132.

[0023] The function of the torque limiter in the present embodiment and the effect of the present embodiment are the same as those of the second embodiment, so the description is omitted here.

[0024] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0025] For example, in Examples 1, 2, and 3, a torque limiter is configured between the cylindrical member 26 and the connecting shaft portion 28 in the outer ring 24 constituting the first constant velocity coupling 14, but a torque limiter may also be configured in the outer ring constituting the second constant velocity coupling 16.

[0026] It should be noted that the above-described embodiment is merely one example, 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 Symbols]

[0027] 10: Vehicle drive shaft device, 14: First constant velocity coupling, 16: Second constant velocity coupling, 18: Intermediate shaft, 20: Drive shaft, 22: Inner ring, 24: Outer ring, 26: Cylindrical member, 28: Connecting shaft section, 30: First disc-shaped member, 32: Second disc-shaped member, 34: Coil spring (biasing member), 234: Disc spring (biasing member)

Claims

[Claim 1] A drive shaft device for a vehicle comprising a pair of constant velocity couplings and an intermediate shaft connecting the constant velocity couplings, wherein the drive shaft is arranged in the power transmission path of a vehicle, and one of the pair of constant velocity couplings has an inner ring connected to the intermediate shaft and an outer ring housing the inner ring, and the outer ring has a cylindrical member and a connecting shaft portion, The connecting shaft portion of the outer ring is connected to the cylindrical member so as to be rotatable relative to it. The first disc-shaped member, located within the cylindrical member, is concentrically fixed to the connecting shaft portion. Within the cylindrical member, there is a second disc-shaped member provided so as to be unable to rotate relative to the cylindrical member and movable in the axial direction, facing the first disc-shaped member, and a biasing member provided to apply a load to the second disc-shaped member toward the first disc-shaped member, thereby causing the first disc-shaped member and the second disc-shaped member to slide against each other. A vehicle drive shaft device characterized by the following features.

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