Method of manufacturing cross shaft joint

Abstract

To provide a method of manufacturing a cross shaft joint capable of suppressing damage of a cup.SOLUTION: In the manufacturing method of a cross shaft joint, the cross shaft joint (first joint 100) includes a cross shaft 130 and a bearing 140 attached to a shaft part. The bearing includes a bottomed cylindrical cup 141 covering a shaft part of the cross shaft, and a rolling element 142 arranged around the shaft part. The cup has a bottom portion 143 facing the distal end surface of the shaft part. The inner bottom surface 146 of the bottom portion includes a convex surface 1461 protruding toward the distal end surface. In the bottom portion, an outer bottom surface 147 opposite to the inner bottom surface includes a concave surface 1471 recessed toward the distal end surface by a predetermined recess amount. The manufacturing method includes a press-fitting step of press-fitting a bearing to a shaft portion. In the press-fitting step, a jig 532 including a main body part 533 and a deformation relaxation part 534 protruding from the main body part by an amount smaller than a predetermined recessed amount is arranged so that the recessed surface of the cup and the deformation relaxation part face each other, and the cup is pushed into the shaft part by the main body part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a cross joint. [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] Patent Publication No. 2021-60090 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the manufacturing process of a cross joint includes a step of pressing the bottom of the cup toward the shaft to close the axial gap, but this pressing can damage the cup.

[0005] An object of the present invention is to provide a method for manufacturing a cross joint that can suppress damage to the cups. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, one aspect of the present invention provides a method for manufacturing a cross joint, the cross joint comprising: a cross shaft having four shaft portions arranged in a cross shape; and bearings attached to the shaft portions; the bearings comprising a cylindrical cup with a bottom that covers the shaft portions; and rolling elements housed in the cup and arranged around the shaft portions; the cup has a bottom facing a tip surface of the shank; an inner bottom surface of the bottom facing the tip surface includes a convex surface that protrudes toward the tip surface; and an outer bottom surface of the bottom opposite the inner bottom surface includes a concave surface that is recessed by a predetermined amount toward the tip surface; the manufacturing method includes a press-fitting step of press-fitting the bearing into the shank, the press-fitting step including a jig including a main body and a deformation mitigating portion that protrudes from the main body by less than the predetermined amount, wherein the jig is positioned so that the concave surface of the cup faces the deformation mitigating portion, and the cup is pressed into the shank by the main body. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for manufacturing a cross joint that can suppress damage to the cup. [Brief explanation of the drawings]

[0008] [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] 1 is an explanatory diagram showing the configuration of a main part of a cross joint manufacturing device according to an embodiment. FIG. [Figure 6] FIG. 2 is an explanatory view showing the cross joint manufacturing device according to the embodiment in a press-fit state. [Figure 7] 10A to 10C are cross-sectional views showing changes in the state of the cup during a press-fitting process according to the embodiment. [Figure 8] 10A to 10C are cross-sectional views showing changes in the state of the cup during a press-fitting process according to the embodiment. [Figure 9] 10A to 10C are cross-sectional views showing changes in the state of the cup during a press-fitting process according to the embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a cup according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Each bearing 140 includes an iron cup 141 and rolling elements 142 (see FIG. 7). 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.

[0023] 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.

[0024] Next, a method for manufacturing a cross joint according to an embodiment will be described. In the following explanation, a method for manufacturing the first joint 100 will be exemplified. The second joint 200 is also manufactured in a similar manner, so its description will be omitted. Also, although the example shown here illustrates the assembly of the cross shaft 130 and bearing 140 to the first yoke 110 of the first joint 100, the same applies when assembling the cross shaft 130 and bearing 140 to the second yoke 120.

[0025] First, a manufacturing apparatus 500 used in the method for manufacturing a cross joint will be described. Fig. 5 is an explanatory diagram showing the configuration of the main parts of the manufacturing apparatus 500 for a cross joint according to an embodiment. In Fig. 5, members other than the cross shaft 130 are shown in cross section.

[0026] The manufacturing apparatus 500 includes a yoke holder (not shown), a cross shaft holder 510, a bearing holder 520, and a press-fit portion 530.

[0027] The yoke holding portion is a portion that holds the first yoke 110 in a predetermined position during assembly. The yoke holding portion maintains the first yoke 110 in a predetermined position even if pressure acts on the first yoke 110 from the press-fit portion 530 during assembly.

[0028] The cross shaft holding portion 510 is a portion that holds the cross shaft 130 relative to the first yoke 110, which is held by the yoke holding portion. Specifically, the cross shaft holding portion 510 is equipped with a pin member 511, the tip of which fits into the through hole 112 of the first yoke 110. A recess 512 is formed in the tip surface of the pin member 511, and the shaft portion 132 of the cross shaft 130 fits into this recess 512. This fixes the relative positional relationship between the cross shaft 130 and the first yoke 110. In this state, the shaft portion 132 on the opposite side to the shaft portion 132 fitted into the recess 512 is positioned within the other through hole 112 of the first yoke 110. This positioning makes it possible to assemble the bearing 140 to the shaft portion 132 on the opposite side to the shaft portion 132 fitted into the recess 512 and the other through hole 112 of the first yoke 110. Hereinafter, the shaft portion 132 and the through hole 112 to which the bearing 140 is to be assembled will be referred to as the "shaft portion 132a" and the "through hole 112a." The shaft portion 132a and the through hole 112a are coaxially arranged by positioning the cross shaft holding portion 510.

[0029] The bearing holder 520 is a portion that holds the bearing 140 before assembly. By supporting the bearing 140, the bearing holder 520 positions the bearing 140 with respect to the shaft portion 132a and the through-hole 112a. By positioning the bearing holder 520, the bearing 140 is arranged coaxially with the shaft portion 132a and the through-hole 112a.

[0030] The press-fit portion 530 is a portion where the bearing 140 is press-fitted into the through-hole 112a of the first yoke 110 and the shaft portion 132a of the cross shaft 130. Specifically, the press-fit portion 530 includes a seat portion 531 and a jig 532.

[0031] Pedestal portion 531 is a portion that moves while holding jig 532. Specifically, pedestal portion 531 moves back and forth in the axial direction of shaft portion 132a by power from a drive source (not shown). Examples of the drive source include a motor such as a servo motor.

[0032] The jig 532 is a part that presses the bearing 140 into the through-hole 112a of the first yoke 110. The jig 532 is a cylindrical part that is long in the axial direction of the shaft portion 132a, and has a base end portion fixed to the pedestal portion 531. The jig 532 will be described in detail later.

[0033] Fig. 6 is an explanatory diagram showing the state during press-fitting of the cross joint manufacturing apparatus 500 according to the embodiment. From the state shown in Fig. 5, when the jig 532 approaches the cross shaft 130 in the press-fitting direction due to movement of the base portion 531, the tip of the jig 532 comes into contact with the bearing 140, and the bearing 140 is press-fitted all the way into the through hole 112a, as shown in Fig. 6. As a result, the bearing 140 is press-fitted into the through hole 112a and the shank 132a of the cross shaft 130. In other words, the steps shown in Figs. 5 and 6 are the press-fitting step of press-fitting the bearing 140 into the shank 132a.

[0034] 7 to 9 are cross-sectional views showing changes in state of the cup 141 during the press-fitting process according to the embodiment.

[0035] First, the cup 141 will be described in detail. As described above, the cup 141 is cylindrical with a bottom and houses a plurality of rolling elements 142 therein. After press-fitting, the shaft portion 132a is rotatably fitted by the plurality of rolling elements 142. The cup 141 includes a bottom portion 143 and a cylindrical wall portion 144, which are integrally formed. Here, the surface of the bottom portion 143 that faces the tip end surface of the shaft portion 132a is referred to as an inner bottom surface 146, and the opposite surface is referred to as an outer bottom surface 147.

[0036] The inner bottom surface 146 includes a convex surface 1461 that protrudes toward the tip surface of the shaft portion 132a. The convex surface 1461 is located in the center of the bottom portion 143. The convex surface 1461 is formed in a truncated cone shape. A top surface 1462 of the convex surface 1461 faces the tip surface of the shaft portion 132a and contacts the tip surface of the shaft portion 132a after press-fitting.

[0037] 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 132a. 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. A bottom surface 1472 of the concave surface 1471 is located in a position opposite the top surface 1462.

[0038] Next, a detailed description will be given of the jig 532. As shown in Fig. 7, the jig 532 has a cylindrical main body 533 and a deformation mitigating portion 534 provided at the tip of the main body 533.

[0039] The deformation mitigating portion 534 is a portion for mitigating deformation of the cup 141 during press-fitting. The deformation mitigating portion 534 is a portion that protrudes in the axial direction from the tip end of the main body portion 533. The deformation mitigating portion 534 is disposed in the center of the tip surface of the main body portion 533 and may have any shape as long as it fits within the concave surface 1471. Specifically, the deformation mitigating portion 534 is formed in a truncated cone shape, and its top surface 5341 faces the bottom surface 1472 of the concave surface 1471. Furthermore, the protrusion amount d of the deformation mitigating portion 534 is smaller than the recess amount D of the concave surface 1471. Due to this relationship, the deformation mitigating portion 534 is disposed within the concave surface 1471 but is disposed with a gap between it and the bottom surface 1472 from the start of press-fitting to just before the completion of press-fitting as shown in FIG. 7 . At this time, the outer periphery of the tip surface of main body 533 abuts against the outer periphery of outer bottom surface 147 of cup 141, applying the pressure required for press-fitting bearing 140.

[0040] Thereafter, jig 532 further advances in the press-fitting direction, pushing in bottom portion 143 and deflecting it by a predetermined amount. As a result, top surface 1462 of inner bottom surface 146 comes into contact with the tip surface of shaft portion 132a, as shown in FIG. 8. As jig 532 further advances in the press-fitting direction, top surface 5341 of deformation mitigating portion 534 comes into contact with bottom surface 1472 of concave surface 1471 while pushing in bottom portion 143, as shown in FIG. 9. This contact prevents deformation mitigating portion 534 from advancing further, thereby mitigating further deformation of bottom portion 143. Note that even after jig 532 retreats from bottom portion 143, top surface 1462 of inner bottom surface 146 remains in contact with the tip surface of shaft portion 132a.

[0041] FIG. 10 is a cross-sectional view showing a jig 532z according to a comparative example. FIG. 10 is a view corresponding to FIG. 9. The jig 532z shown in FIG. 10 differs from the present embodiment in that it does not include a deformation mitigation portion and the tip surface of the main body portion 533z is entirely flat. As shown in FIG. 10, the jig 532z without a deformation mitigation portion advances in the press-fitting direction, pushing in the bottom portion 143 and bending it by a predetermined amount. As a result, the top surface 1462 of the inner bottom surface 146 contacts the tip surface of the shaft portion 132a. In this state, a gap exists between the tip surface of the jig 532z and the bottom surface 1472 of the concave surface 1471, allowing further advancement of the jig 532z. If the jig 532z advances further, the bottom portion 143 will be pushed in excessively. This pushing may deform the bottom portion 143, potentially causing the outer periphery of the bottom surface 1472 (within the dashed circle in FIG. 10) to crack and become damaged. In this embodiment, this damage is suppressed.

[0042] As described above, in the press-fitting step, deformation mitigating portion 534, which protrudes from main body portion 533 by less than predetermined recess amount D, is arranged to face concave surface 1471 of cup 141, and main body portion 533 presses cup 141 into shaft portion 132a. As a result, when bottom portion 143 of cup 141 is bent by a predetermined amount, deformation mitigating portion 534 comes into contact with concave surface 1471 of bottom portion 143. This contact prevents deformation mitigating portion 534 from moving forward, thereby mitigating further deformation of bottom portion 143. This makes it possible to prevent damage to bottom portion 143 of cup 141.

[0043] Furthermore, in the press-fitting step, when bottom 143 of cup 141 is bent, deformation mitigating portion 534 comes into contact with bottom surface 1472 of concave surface 1471, thereby more reliably blocking the progress of deformation mitigating portion 534. Therefore, further deformation of bottom 143 can be more reliably mitigated.

[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 shaft portion 132a of the cross shaft 130 and the bearing 140 are assembled to one of the pair of arms 111 of the first yoke 110. However, the shaft portions 132a of the cross shaft 130 and the bearings 140 may be assembled to both of the pair of arms 111 at the same time.

[0046] In the above embodiment, the deformation mitigating portion 534 contacts the bottom surface 1472 of the concave surface 1471. However, the deformation mitigating portion may contact the tapered surface of the concave surface. In this case, too, it is possible to block the progress of the deformation mitigating portion.

[0047] Furthermore, in the above embodiment, the first joint 100 provided in the steering device 10 of an automobile has been described 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.

[0048] 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]

[0049] The present invention is applicable to a method of manufacturing a cross joint having a cross shaft and a bearing. [Explanation of symbols]

[0050] 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, 112a...Through hole, 120...Second yoke, 121...Arm, 122...Through hole, 130...Cross shaft, 131...Body portion, 132...Shaft portion, 132a...Shaft portion, 140...Bearing, 141...Cup, 142...Rolling element, 143 ...Bottom, 144...Cylindrical wall, 146...Inner bottom surface, 147...Outer bottom surface, 200...Second joint (cross joint), 210...First yoke, 220...Second yoke, 230...Cross, 240...Bearing, 500...Manufacturing apparatus, 510...Cross holder, 511...Pin member, 512...Recess, 520...Bearing holder, 530...Press-fit portion, 531...Pedestal, 532...Jig, 532z...Jig, 533...Main body, 533z...Main body, 534...Deformation mitigation portion, 1461...Convex surface, 1462...Top surface, 1471...Concave surface, 1472...Bottom surface, 5341...Top surface, d...Protrusion amount, D...Recess amount

Claims

1. 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 press-fitting step of press-fitting the bearing into the shaft portion, The press-fitting step includes: a jig including a main body and a deformation mitigating portion protruding from the main body by a distance smaller than the predetermined recession amount, arranged so that the concave surface of the cup faces the deformation mitigating portion, and the cup is pressed against the stem portion by the main body; Manufacturing method of cross joint.

2. In the press-fitting step, when the bottom portion of the cup is bent, the deformation mitigation portion comes into contact with a bottom surface of the concave surface. A method for manufacturing a cross joint according to claim 1.

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