Universal joint

Abstract

To provide a universal joint that is excellent in durability without deteriorating strength of a shaft even when an outer diameter of the shaft decreases to insert a ring.SOLUTION: A universal joint 41 comprises a cylindrical ring 42 inserted into each shaft 45 constituting a cross shaft 2 and abutting against an outer peripheral surface 45b of the shaft 45, a plurality of rollers 43 arranged in multiple stages in an axial direction of each shaft 45 and abutting against an outer peripheral surface 42a of the ring 42, and an outer ring 44 supporting the rollers 43, where an inner diameter 42b of the ring 42 is gradually increased from a position B, which is a predetermined distance L away from a position A located on a contact surface between the roller 43 arranged in the stage farthest from an open end 45a of the shaft 45 and the outer peripheral surface 42a of the ring 42 and being farthest from an open end 45a of the shaft 45, toward the open end 45a of the shaft 45, as it moves away from the open end 45a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a universal joint, and more particularly to a universal joint having high durability. [Background technology]

[0002] A universal joint used to connect a drive shaft and a driven shaft with different axis centers, for example, as shown in Figures 2 and 3, is configured by having two sets of a cross shaft 2, bearings 3 supporting each shaft of the cross shaft 2, a pair of yokes 4, 5 rotatably connected to each other via the cross shaft 2 and the bearings 3, and bearing caps 6 fixed to the yokes 4, 5 with bolts 7 so as to cover each of the bearings 3, connected by tubes 8 (see Patent Document 1).

[0003] As shown in FIG. 4, the universal joint 1 described above has a problem in that if a crack 10 occurs due to the oscillation of each shaft 21 of the cross shaft 2 supported by bearings 3 and the load applied to the surface 21a of the shaft 21, the entire cross shaft 2 must be replaced, resulting in huge maintenance costs.

[0004] Therefore, as shown in Figure 5, a ring (inner race) 31 is shrink-fitted onto the shaft 21, and if flaking occurs in the ring 31, the ring 31 is removed and replaced with a new one, allowing the cross shaft 2 to continue being used as is and reducing maintenance costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-038600 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the structure using the above-mentioned ring 31 requires the outer diameter of shaft 21 to be reduced in order to attach ring 31, and if the rotational outer diameter of shaft 21 is not changed, there is a problem that the strength of shaft 21 is reduced by the amount of ring 31.

[0007] Therefore, the present invention has been made in consideration of the above-mentioned conventional technology, and has an object to provide a universal joint which has excellent durability and in which the strength of shaft 21 is not reduced even if the outer diameter of shaft 21 is reduced to accommodate ring 31. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a universal joint comprising a cylindrical ring which is inserted into each of the shafts constituting a cross shaft and which abuts against the outer peripheral surface of the shaft, a plurality of rollers which are arranged in multiple stages in the axial direction of each of the shafts and which abut against the outer peripheral surface of the ring, and an outer ring which supports the plurality of rollers, the inner diameter of the ring being located on the abutment surface between the outer peripheral surface of the ring and the rollers arranged in the stage furthest from the open end of the shaft, and which gradually increases from a position which is furthest from the open end of the shaft and a predetermined distance away towards the open end of the shaft as it moves away from the open end.

[0009] According to the present invention, the diameter of the inner surface of the ring is gradually increased from a predetermined position away from the open end of the shaft as it moves away from the open end, thereby making it possible to avoid stress concentration at the contact surface between the shaft and the ring, and providing a universal joint with excellent durability without reducing the strength of the shaft even if the outer diameter of the shaft is reduced. Effect of the Invention

[0010] As described above, according to the present invention, even if the outer diameter of the shaft is reduced to accommodate a ring, the strength of the shaft does not decrease, and it is possible to provide a universal joint that is excellent in durability. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an embodiment of a universal joint according to the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing an example of the overall structure of a conventional universal joint. [Diagram 3] FIG. 3 is an exploded perspective view of the universal joint of FIG. 2. [Figure 4] 3 is a cross-sectional view showing bearings supporting each shaft of the cross shaft in the universal joint of FIG. 2 and their vicinity. FIG. [Diagram 5] 3 is a cross-sectional view showing a state in which rings are attached to each shaft of the cross shaft in the universal joint of FIG. 2. FIG. [Figure 6] FIG. 1 is a cross-sectional view showing the cross shafts of three universal joints that were the subject of FEM analysis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, an embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 shows one embodiment of a universal joint according to the present invention. This universal joint 41 comprises each shaft 45 of a cross shaft 2, a ring 42 inserted into the shaft 45 and attached to the outer peripheral surface 45b of the shaft 45, rollers 43 as multiple rolling elements arranged in multiple stages (four stages in this embodiment) in the axial direction of the shaft 45 and in contact with the outer peripheral surface 42a of the ring 42, and an outer ring 44 supporting the multiple rollers 43.

[0014] The shaft 45 has an open end 45a, a cross section of which is circular, and the outer diameter of the shaft 45 gradually increases with increasing distance from the open end 45a.

[0015] The ring 42 is made of the same steel material as the shaft 45 and has the same outer diameter over its entire length. The ring 42 is located on the contact surface between the outer peripheral surface 42a of the ring 42 and the roller 43a arranged in the stage farthest from the open end 45a of the shaft 45. The inner diameter of the ring 42 gradually increases from the position A farthest from the open end 45a of the shaft 45 to the position B at a predetermined distance L toward the open end 45a of the shaft 45 (toward the bottom in FIG. 1) as it moves away from the open end 45a. This is a characteristic feature of the present invention. The outer peripheral surface 45b of the shaft 45 also gradually increases along the inner peripheral surface 42b of the ring 42. The ring 42 is attached to the shaft 45 by shrink fitting, press fitting, or cold fitting the shaft 45. The predetermined distance L and the degree of gradual increase in the inner diameter (R-shape) are appropriately adjusted according to the dimensions of the shaft 45.

[0016] Next, the results of a strength evaluation of the universal joint according to the present invention by FEM (finite element method) analysis will be described.

[0017] FIG. 6 shows the cross shafts 2 of three universal joints that were the subject of the FEM analysis. FIG. 6(a) shows a conventional one in which no ring is present (corresponding to FIG. 4, Comparative Example 1). FIG. 6(b) shows a one in which a ring 32 with uniform outer and inner diameters is used (corresponding to FIG. 5, Comparative Example 2). FIG. 6(c) shows a one according to the present invention having a ring 42 whose inner diameter gradually increases toward one open end (lower end) (corresponding to FIG. 1, Example).

[0018] The outer diameter D of shaft 21 of Comparative Example 1 in Fig. 6(a), the outer diameter D of ring 32 of Comparative Example 2 in Fig. 6(b), and the outer diameter D of ring 42 of the embodiment in Fig. 6(c) are all equal, and other dimensions are expressed as ratios relative to D = 1. The thickness of ring 32 of Comparative Example 2 and the thickness of the portion of ring 42 of the embodiment where the inner diameter is not gradually increased were 0.02 to 0.06.

[0019] When the same magnitude of force was applied in a direction perpendicular to the outer peripheral surface of each shaft of these cross shafts 2 and a stress analysis was performed on each shaft, the strength of Comparative Example 2 was lower than that of Comparative Example 1, and the strength of the embodiment was equivalent to that of Comparative Example 2.

[0020] The illustrated embodiments are merely examples and are not intended to limit the technical scope of the present invention. [Explanation of symbols]

[0021] 41 Universal joint 42 Ring 43 Around 44 Outer Ring 45 Axis

Claims

[Claim 1] a cylindrical ring inserted into each of the shafts constituting the cross shaft and abutting against the outer circumferential surface of the shaft; a plurality of rollers arranged in a plurality of stages in the axial direction of each of the shafts and in contact with an outer circumferential surface of the ring; an outer ring supporting the rollers; A universal joint characterized in that the inner diameter of the ring is gradually increased from a position located a predetermined distance away from the open end of the shaft toward the open end of the shaft, on the abutment surface between the outer peripheral surface of the ring and a roller arranged in a step farthest from the open end of the shaft.

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