Cross-axis joint and method for producing the same

Abstract

To more effectively reduce sliding resistance between a shaft part and a bearing.SOLUTION: A cross-axis joint (first joint 100) comprises a cross shaft 130 having four shaft parts 132 arranged in a cross shape, and a bearing 140 attached to the shaft parts. The bearing comprises a bottomed cylindrical cup 141 covering the shaft part, and rolling elements 142 accommodated in the cup and disposed around the shaft part. The cup has a bottom part 143 facing an end surface of the shaft part. In the bottom part, an inner bottom surface 146 facing the end surface includes a convex surface 1461 protruding toward the end surface. In the bottom part, an outer bottom surface 147 on the opposite side of the inner bottom surface includes a concave surface 1471 recessed toward the end surface at a position corresponding to the convex surface. An outer shape area of a top surface 1462 of the convex surface is smaller than an outer shape area of a bottom surface 1472 of the concave surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a cross joint and a method for manufacturing the same. [Background technology]

[0002] For example, in an automobile steering device, a cross joint is used to connect a steering shaft and a pinion shaft. The cross joint has a cross with four shaft portions protruding in all directions and a plurality of bearings that rotatably support each shaft portion (see, for example, Patent Document 1). A yoke with a pair of arms is provided at the end of each shaft, and the shaft portion of the cross is supported in a through hole formed in each arm via a bearing so that it can rotate freely around its axis. The bearing has rolling elements and a cylindrical cup with a bottom that houses the rolling elements. A protrusion is formed at the bottom of the cup that protrudes toward the shaft portion of the cross. This protrusion reduces sliding resistance between the shaft portion and the bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-90205 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for further suppression of the sliding resistance between the shaft portion and the bearing.

[0005] Therefore, an object of the present invention is to provide a cross joint that can further reduce the sliding resistance between the shaft portion and the bearing, and a method for manufacturing the same. [Means for solving the problem]

[0006] (Inventor's Knowledge) The convex portion formed on the bottom of the cup described above is convex when viewed from the surface facing the stem, but concave when viewed from the opposite surface. The outer area of ​​the convex portion is generally equal to or greater than the outer area of ​​the concave portion. The inventors have found that this structure makes it difficult to suppress friction between the convex portion and the stem.

[0007] In order to solve the above-mentioned problems, a cross joint according to one aspect of the present invention comprises a cross shaft having four shaft portions arranged in a cross shape, and bearings attached to the shaft portions, the bearing comprising a cylindrical cup with a bottom that covers the shaft portions, and rolling elements that are housed in the cup and arranged around the shaft portions, the cup having a bottom facing a tip surface of the shaft portions, the inner bottom surface of the bottom facing the tip surface including a convex surface that protrudes toward the tip surface, the outer bottom surface of the bottom opposite the inner bottom surface including a concave surface that is recessed toward the tip surface at a position corresponding to the convex surface, and the outer surface of the convex surface is smaller than the outer surface of the concave surface.

[0008] A method for manufacturing a cross joint according to another aspect of the present invention comprises a cross joint having four shaft portions arranged in a cross shape and bearings attached to the shaft portions, the bearing comprising a cylindrical cup with a bottom that covers the shaft portions and rolling elements that are housed in the cup and arranged around the shaft portions, the cup having a bottom facing a tip surface of the shaft portions, an inner bottom surface of the bottom facing the tip surface including a convex surface that protrudes toward the tip surface, and an outer bottom surface of the bottom opposite the inner bottom surface including a concave surface that is recessed by a predetermined amount toward the tip surface, and the manufacturing method includes a processing step of making the outer area of ​​the top surface of the convex surface smaller than the outer area of ​​the bottom surface of the concave surface. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a cross joint or the like that can further reduce the sliding resistance between the shaft portion and the bearing. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic diagram showing an example of a usage form of a cross joint according to an embodiment. FIG. [Figure 2] 1 is a perspective view showing a schematic configuration of an intermediate shaft according to an embodiment. FIG. [Figure 3] FIG. 2 is a perspective view showing a schematic configuration of a first joint according to the embodiment. [Figure 4] FIG. 2 is an exploded perspective view showing a portion of a first joint according to an embodiment. [Figure 5] FIG. 2 is an explanatory diagram showing a cup according to an embodiment. [Figure 6] 10A and 10B are explanatory views showing the final machining process for the cup according to the embodiment. [Figure 7] 10 is an explanatory view showing the final machining step for a cup according to the first modified example. FIG. [Figure 8] FIG. 10 is a cross-sectional view showing the bottom of a cup according to Modification 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement positions, and connection forms shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts will be described as optional components.

[0012] Furthermore, the drawings are schematic diagrams in which emphasis, omission, and proportions have been appropriately adjusted in order to illustrate the present invention, and may differ from the actual shapes, positional relationships, and proportions.

[0013] Fig. 1 is a schematic diagram showing an example of how a cross joint according to an embodiment is used. As shown in Fig. 1, the cross joint (first joint 100, second joint 200) is provided to an intermediate shaft 20 included in, for example, a steering device 10 of an automobile. Specifically, the steering device 10 includes a steering shaft 12 having a steering wheel 11 connected to one end thereof, a steering mechanism 16 consisting of a rack-and-pinion mechanism including a pinion shaft 13 and a rack shaft 14 for steering steered wheels 15, and an intermediate shaft 20 interposed between the steering shaft 12 and the pinion shaft 13 for transmitting steering torque.

[0014] One end of the intermediate shaft 20 is connected to the steering shaft 12 via a first joint 100. The other end of the intermediate shaft 20 is connected to the pinion shaft 13 via a second joint 200.

[0015] When the steering wheel 11 is operated to rotate the steering shaft 12, the rotation is transmitted to the pinion shaft 13 and the rack shaft 14 via the intermediate shaft 20. As a result, the steering mechanism 16 steers the steered wheels 15.

[0016] Fig. 2 is a perspective view showing a schematic configuration of the intermediate shaft 20 according to the embodiment. As shown in Fig. 2, the intermediate shaft 20 includes a telescopic intermediate shaft 21, a first joint 100 provided at one end of the intermediate shaft 21, and a second joint 200 provided at the other end of the intermediate shaft 21.

[0017] The first joint 100 includes a first yoke 110 connected to one end of the intermediate shaft 21, a second yoke 120 connected to the steering shaft 12, a cross shaft 130 connecting the first yoke 110 and the second yoke 120, and a plurality of bearings 140 that rotatably support each shaft portion 132 (see FIG. 4) of the cross shaft 130.

[0018] The second joint 200 includes a first yoke 210 connected to the other end of the intermediate shaft 21, a second yoke 220 connected to the pinion shaft 13, a cross shaft 230 connecting the first yoke 210 and the second yoke 220, and a plurality of bearings 240 that rotatably support each shaft portion (not shown) of the cross shaft 230.

[0019] The following describes in detail the first joint 100 (cross joint). Note that the first joint 100 and the second joint 200 have basically the same configuration, so details of the second joint 200 will be omitted.

[0020] Fig. 3 is a perspective view showing a schematic configuration of a first joint 100 according to an embodiment. Fig. 4 is an exploded perspective view showing a part of the first joint 100 according to an embodiment. Specifically, in Fig. 4, the second yoke 120 of the first joint 100 is omitted.

[0021] 3 and 4, the first yoke 110 is made of, for example, aluminum and includes a pair of arms 111 arranged to face each other. Each of the pair of arms 111 is formed with a through hole 112 to which a bearing 140 is fixed. The through holes 112 of the pair of arms 111 have the same axis. This axis is referred to as a first axis.

[0022] As shown in FIG. 3, the second yoke 120 is made of, for example, aluminum and includes a pair of arms 121 arranged to face each other. Each of the pair of arms 121 has a through hole 122 formed therein for fixing a bearing 140. The through holes 122 of the pair of arms 121 have the same axis. This axis is referred to as a second axis. The first axis and the second axis are perpendicular to each other. The first yoke 110 and the second yoke 120 may be made of, for example, an iron-based metal.

[0023] 4, the cross shaft 130 is made of iron and has a body portion 131 and four shaft portions 132 protruding in all directions from the side peripheral surface of the body portion 131. Of the four shaft portions 132, a pair of opposing shaft portions 132 are attached via bearings 140 to respective through holes 112 of a pair of arms 111 provided on the first yoke 110. Of the four shaft portions 132, the remaining pair of shaft portions 132 are attached via bearings 140 to respective through holes 122 of a pair of arms 121 provided on the second yoke 120.

[0024] Each bearing 140 includes an iron cup 141 and rolling elements 142 (see FIG. 5). The cup 141 is cylindrical with a bottom and houses the rolling elements 142 inside. The rolling elements 142 are cylindrical rollers (e.g., needle rollers), and a plurality of them are arranged along the cylindrical inner circumferential surface of the cup 141. Therefore, the inner circumferential surface of the cup 141 forms the raceway surface for the rolling elements 142. Details of the cup 141 will be described later.

[0025] Each bearing 140 is press-fitted into the through-hole 112 of the pair of arms 111 and the through-hole 122 of the pair of arms 121. Furthermore, each shaft portion 132 of the cross shaft 130 is press-fitted into each bearing 140. As a result, each shaft portion 132 of the cross shaft 130 is supported by each bearing 140 so as to be rotatable relative to each arm 111, 121. Therefore, the cross shaft 130 rotates about the first axis and also rotates about the second axis.

[0026] Next, the cup 141 will be described in detail. Fig. 5 is an explanatory diagram showing the cup 141 according to the embodiment. Specifically, Fig. 5(a) is a cross-sectional view of the bearing 140, and Fig. 5(b) is a plan view showing the top surface 1462 of the bottom part 143 of the cup 141.

[0027] Cup 141 is cylindrical with a bottom and accommodates a plurality of rolling elements 142 therein. After press-fitting, shaft portion 132 (shown by a two-dot chain line in FIG. 5 ) is rotatably fitted with the plurality of rolling elements 142. Cup 141 includes bottom portion 143 and cylindrical wall portion 144, which are integrally formed. Here, the surface of bottom portion 143 that faces the tip end surface of shaft portion 132 is referred to as inner bottom surface 146, and the opposite surface is referred to as outer bottom surface 147.

[0028] The inner bottom surface 146 includes a convex surface 1461 that protrudes toward the tip surface of the shaft portion 132. The convex surface 1461 is disposed in the center of the bottom portion 143. The convex surface 1461 is formed in a truncated cone shape. The outer circumferential surface of the convex surface 1461 is configured as a tapered surface with multiple steps (two steps in this embodiment). As a modified example, the outer circumferential surface of the convex surface 1461 may be a uniform tapered surface as a whole.

[0029] A top surface 1462 of the convex surface 1461 faces the tip surface of the shaft portion 132 and comes into contact with the tip surface of the shaft portion 132 after press-fitting. A plurality of concave lubricant reservoirs 1463 are formed on the top surface 1462. In the present embodiment, a case is illustrated in which nine quadrangular pyramidal lubricant reservoirs 1463 are arranged in a matrix, but the shape, number and layout of the lubricant reservoirs 1463 may be any. Note that the convex surface does not necessarily have to have a lubricant reservoir (see FIG. 8).

[0030] The outer bottom surface 147 includes a concave surface 1471 that is recessed by a predetermined amount toward the tip surface of the shaft portion 132. The concave surface 1471 is located in the center of the bottom portion 143. The concave surface 1471 is formed in a truncated cone shape. The outer peripheral surface of the concave surface 1471 is configured as a tapered surface with multiple steps (two steps in this embodiment). The outer peripheral surface of the concave surface 1471 may be a uniform tapered surface as a whole. Furthermore, the tapered surface may be linear or curved in cross section. A bottom surface 1472 of the concave surface 1471 is located in a position opposite the top surface 1462. The bottom surface 1472 is approximately parallel to the top surface 1462 and is flat as a whole.

[0031] In Fig. 5(b), the outline of the top surface 1462 is indicated by a solid line, and the outline of the bottom surface 1472 is indicated by a dashed line. As shown in Fig. 5(b), the outline area of ​​the top surface 1462 is smaller than the outline area of ​​the bottom surface 1472. This makes it possible to reduce the contact area between the top surface 1462 and the tip surface of the shaft portion 132 after press-fitting compared to conventional methods. Therefore, the sliding resistance between the shaft portion 132 and the bearing 140 can be further reduced.

[0032] Here, the volume formed by the convex surface 1461 is approximately the same as the volume formed by the concave surface 1471. Specifically, the volume formed by the convex surface 1461 is the volume of the portion protruding from the outer periphery of the convex surface 1461 (the volume of the region below the dashed line L1 in FIG. 5(a)). On the other hand, the volume formed by the concave surface 1471 is the volume of the space formed by the concave surface 1471 (the volume of the space below the dashed line L2 in FIG. 5(a)).

[0033] Next, a method for manufacturing a cross joint will be described, focusing on a method for manufacturing the cup 141. The cup 141 is manufactured by press working. Specifically, the cup 141 according to the embodiment is formed by pressing a metal plate a predetermined number of times. Here, the final processing step will be described as an example.

[0034] FIG. 6 is an explanatory diagram showing the final processing step for a cup 141 according to an embodiment. FIG. 6 illustrates a bottom 143 of the cup 141. As shown in FIG. 6(a), a concave surface 1471 and a convex surface 1461 are formed on the bottom 143 by press processing prior to the final processing step, but the bottom 143 has not been shaped to the designed shape. Therefore, in the final processing step, a first shaping mold 501 and a second shaping mold 502 are used to perform press processing, thereby shaping the concave surface 1471 and the convex surface 1461 (see FIG. 6(b)). As a result, the bottom 143 is shaped so that the outer area of ​​the top surface 1462 is smaller than the outer area of ​​the bottom surface 1472.

[0035] Next, a third mold 503 for forming the lubricant reservoirs 1463 is replaced with the second mold 502. Protrusions 5031 corresponding to the plurality of lubricant reservoirs 1463 are formed on the inner bottom surface of the third mold 503. By performing press working using this third mold 503 and the first mold 501, the plurality of lubricant reservoirs 1463 are formed on the top surface 1462 of the convex surface 1461.

[0036] As described above, at bottom 143 of cup 141, top surface 1462 of convex surface 1461 has a smaller outer surface area than bottom surface 1472 of concave surface 1471, so the contact area between top surface 1462 and the tip surface of shaft portion 132 after press-fitting can be reduced more than in the past. Therefore, the sliding resistance between shaft portion 132 and bearing 140 can be further suppressed.

[0037] Furthermore, since convex surface 1461 is provided with lubricant reservoir 1463, the lubricant stored in lubricant reservoir 1463 can further reduce friction between top surface 1462 and the tip surface of shaft portion 132. Therefore, the sliding resistance between shaft portion 132 and bearing 140 can be further reduced.

[0038] Furthermore, since the volume of the convex surface 1461 and the volume of the concave surface 1471 are substantially the same, it is possible to prevent excess material from being produced during press working, thereby improving workability.

[0039] [Variation 1] Next, a description will be given of the processing steps according to Modification 1. In the following description, the same parts as those in the above embodiment will be given the same reference numerals, and the description thereof may be omitted.

[0040] In the above embodiment, a case has been exemplified in which the shaping of the concave surface 1471 and the convex surface 1461 and the formation of the lubricant reservoir 1463 are performed in separate steps. In this Modification 1, a case will be described in which the shaping of the concave surface 1471 and the convex surface 1461 and the formation of the lubricant reservoir 1463 are performed in the same step.

[0041] FIG. 7 is an explanatory diagram showing the final processing step for the cup 141 according to the first modification. As shown in FIG. 7(a), a concave surface 1471 and a convex surface 1461 are formed on the bottom 143 by press processing prior to the final processing step, but the bottom 143 has not yet been shaped into the designed shape. Therefore, in the final processing step, press processing is performed using a first mold 501 and a fourth mold 504 for shaping. The fourth mold 504 has a recess corresponding to the convex surface 1461, and protrusions 5041 corresponding to the multiple lubricant reservoirs 1463 are formed on its inner bottom surface. By performing press processing using the fourth mold 504 and the first mold 501, the shapes of the concave surface 1471 and the convex surface 1461 are shaped, and multiple lubricant reservoirs 1463 are formed on the top surface 1462 of the convex surface 1461 (see FIG. 7(b)).

[0042] In this way, the shaping of the concave surface 1471 and the convex surface 1461 and the formation of the lubricant reservoir 1463 are carried out in the same process, so that it is possible to shorten the processing steps.

[0043] [Variation 2] Next, a processing step according to Modification 2 will be described. FIG. 8 is a cross-sectional view showing a bottom 143b of a cup 141b according to Modification 2. In FIG. 8, the bottom 143 according to the embodiment is indicated by a solid line, and portions different from the bottom 143 are indicated by dashed lines. In the bottom 143b according to Modification 2, a protruding relief portion 1465b is formed near the convex surface 1461b. In addition, in the bottom 143b, a protruding relief portion 1475b is formed inside the concave surface 1471b. The relief portion 1475b is disposed around the bottom surface 1472b of the concave surface 1471b. Both relief portions 1465b, 1475b are protruding portions compared to the bottom 143 according to the embodiment. In this modification, the relief portions 1465b, 1475b are formed in an annular shape when viewed in a plan view, but the shape when viewed in a plan view may be any shape. The relief portions 1465b and 1475b may be formed continuously or intermittently around the entire circumference. It is sufficient that at least one of the relief portions 1465b and 1475b is formed. In this way, the bottom portion 143b according to Modification 2 has the relief portions 1465b and 1475b protruding from at least one of the vicinity of the convex surface 1461b and the inner side of the concave surface 1471b. Therefore, when forming the cup 141b by press working, the relief portions 1465b and 1475b can be actively formed, thereby suppressing the occurrence of excess material (such as burrs). Note that if the relief portions are formed on the outer side of the concave surface 1471b, the jig used during press-fitting may interfere with the relief portions, adversely affecting the press-fitting, which is undesirable. On the other hand, if the relief portions are formed on the top surface of the convex surface 1461b, the stem portion 132 may interfere with the relief portions after press-fitting, which is undesirable. In other words, it is sufficient to form the relief portions within the allowable range shown in Fig. 8. In this modification, relief portions 1465b and 1475b are formed within the allowable range, which is preferable.

[0044] [others] Although the method for manufacturing a cross joint according to the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment.

[0045] For example, in the above embodiment, the first joint 100 provided in the steering device 10 of an automobile is given as an example of the cross joint according to the present invention. However, the manufacturing method according to the present invention can also be applied to cross joints provided in other devices.

[0046] In addition, the present invention also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions of the embodiments and modifications within the scope that does not deviate from the spirit of the present invention. [Industrial Applicability]

[0047] The present invention is applicable to a method of manufacturing a cross joint having a cross shaft and a bearing. [Explanation of symbols]

[0048] 10...Steering device, 11...Steering wheel, 12...Steering shaft, 13...Pinion shaft, 14...Rack shaft, 15...Steering wheel, 16...Steering mechanism, 20...Intermediate shaft, 21...Intermediate shaft, 100...First joint (cross joint), 110...First yoke, 111...Arm, 112...Through hole, 120...Second yoke, 121...Arm, 122...Through hole, 130...Cross shaft, 131...Body portion, 132...Shaft portion, 140...Bearing, 141...Cup, 141b...Cup, 142...Rolling element, 143...Bottom portion, 143b... Bottom portion, 144...cylindrical wall portion, 146...inner bottom surface, 147...outer bottom surface, 200...second joint (cross joint), 210...first yoke, 220...second yoke, 230...cross shaft, 240...bearing, 501...first mold, 502...second mold, 503...third mold, 504...fourth mold, 1461...convex surface, 1461b...convex surface, 1462...top surface, 1463...lubricant reservoir, 1465b...relief portion, 1471...concave surface, 1471b...concave surface, 1472...bottom surface, 1472b...bottom surface, 1475b...relief portion, 5031...protrusion, 5041...protrusion, L1...dashed line, L2...dashed line

Claims

1. a cross shaft having four shaft portions arranged in a cross shape; a bearing attached to the shaft portion, the bearing includes a cylindrical cup with a bottom that covers the shaft portion, and a rolling element that is housed in the cup and disposed around the shaft portion, the cup has a bottom portion facing the tip surface of the shaft portion, In the bottom portion, an inner bottom surface facing the tip surface includes a convex surface that protrudes toward the tip surface, In the bottom portion, an outer bottom surface opposite to the inner bottom surface includes a concave surface recessed toward the tip surface at a position corresponding to the convex surface, The outer area of ​​the top surface of the convex surface is smaller than the outer area of ​​the bottom surface of the concave surface. Cross shaft coupling.

2. The volume of the convex surface is substantially the same as the volume of the concave surface.

2. A cross joint according to claim 1.

3. The bottom portion has a protruding relief portion formed at least either near the convex surface or inside the concave surface.

2. A cross joint according to claim 1.

4. A method for manufacturing a cross joint, comprising: The cross joint is a cross shaft having four shaft portions arranged in a cross shape; a bearing attached to the shaft portion, the bearing includes a cylindrical cup with a bottom that covers the shaft portion, and a rolling element that is housed in the cup and disposed around the shaft portion, the cup has a bottom portion facing the tip surface of the shaft portion, In the bottom portion, an inner bottom surface facing the tip surface includes a convex surface that protrudes toward the tip surface, In the bottom portion, an outer bottom surface opposite to the inner bottom surface includes a concave surface that is concave by a predetermined concave amount toward the tip surface, The manufacturing method includes: a processing step of making the outer area of ​​the top surface of the convex surface smaller than the outer area of ​​the bottom surface of the concave surface, Manufacturing method of cross joint.

5. In the processing step, when the outer area of ​​the top surface of the convex surface is made smaller than the outer area of ​​the bottom surface of the concave surface, a concave lubricant reservoir is formed on the convex surface. A method for manufacturing a cross joint according to claim 4.

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