JP2015090205A - Method of assembling universal joint, and device for assembling universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of assembling a universal joint capable of suppressing the complication of a device, and shortening assembling time.SOLUTION: A universal joint 1 has a yoke 20 having a pair of arms 21; a cross shaft 10 having one shaft 12 inserted in a bearing hole 22 of one arm 21, and the other shaft 12 inserted in a bearing hole 22 of the other arm 21; and a bearing 30 having a plurality of needle rollers 32 and a bearing cup 31. In a method of assembling the universal joint 1, a center of the cross shaft 10 is disposed to be deviated to the other arm 21 side rather than a center position of the pair of the arms 21, so that, before the needle rollers 32 move to the inside in a diametrical direction of the bearing 30, a tip end portion of the other shaft 12 is inserted in the bearing 30 to fit the other shaft 12 and the plurality of needle rollers 32.

Description

  The present invention relates to a universal joint assembling method and a universal joint assembling apparatus.

  In an example of a conventional method for assembling a universal joint, when the bearing is press-fitted into the bearing hole, the bearing is displaced with respect to the cross shaft so that the center axis of the bearing and the center axis of the shaft coincide with each other. Thereby, it is suppressed that the axis | shaft of a cross shaft and the rolling element of a bearing are damaged. Patent Document 1 discloses an example of a conventional universal joint assembly method and universal joint assembly apparatus.

  The method of assembling the universal joint disclosed in Patent Document 1 discloses a method of displacing the bearing in a direction different from the press-fitting direction of the bearing as a displacement of the bearing with respect to the cross shaft, and a method of reciprocating in a direction along the press-fitting direction of the bearing. doing.

  The universal joint assembling apparatus of Patent Document 1 includes a cross shaft pressing jig that holds a cross shaft, a bearing pressing jig that holds a bearing, and a press-fitting punch that presses the bearing. In addition, the universal joint assembling apparatus of Patent Document 1 may have an actuator for moving the press-fitting punch in the press-fitting direction of the bearing.

JP 2008-39123 A

  By the way, the universal joint assembling device of Patent Document 1 is a moving device for displacing a bearing in a direction different from the press-fitting direction of the bearing when the direction in which the bearing is displaced with respect to the cross shaft is different from the press-fitting direction of the bearing. Is considered to be necessary. For this reason, the assembly apparatus of a universal joint becomes complicated. Further, in the method of assembling the universal joint of Patent Document 1, when the bearing is reciprocally displaced in the press-fitting direction so that the central axis of the bearing and the central axis of the bearing coincide with each other, press-fitting to the yoke of the bearing is completed after the press-fitting of the bearing into the yoke is completed. The time until is longer. For this reason, the assembly time of a universal joint becomes long.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a universal joint assembling method and a universal joint assembling apparatus capable of suppressing complication of the apparatus and shortening an assembling time.

  [1] An independent form of the method for assembling the universal joint has the following matters. That is, two yokes having a pair of arms and bearing holes formed in the arms, a cross shaft having four shafts inserted into the bearing holes, and an annularly arranged inner A universal joint assembling method comprising: a plurality of rolling elements that form a space; and a bearing that houses the plurality of rolling elements, has a bearing cup press-fitted into the bearing hole, and has the shaft inserted therein. Then, in a state where the yoke is held, the shaft is inserted into the bearing hole, the cross shaft is arranged so as to be biased to one of the pair of arms, and the cross shaft is set to any one of the pair of arms. When the bearing cup is press-fitted and the plurality of rolling elements move inward in the radial direction of the bearing, the bearing cup is inserted into the distal end portion of the shaft in a state where the bearing cup is disposed in a biased state. Part and the plurality of rolling elements are fitted together , Said bearing cup in a state where the top portion of the shaft has been fitted to the plurality of rolling elements is pressed into the bearing hole.

  According to the method for assembling the universal joint, the bearing cup is inserted into the tip end portion of the shaft before the rolling element moves inward in the radial direction of the bearing by press-fitting the bearing cup into the bearing hole. The rolling elements are fitted together. At this time, the fitting relationship between the shaft and the plurality of rolling elements is a clearance fit. For this reason, when the shaft and the bearing are not concentric, a plurality of rolling elements are likely to be fitted to the tip of the shaft. When the center axis of the shaft is tilted with respect to the center axis of the bearing, the plurality of rolling elements are fitted to the tip of the shaft, so that the plurality of rolling elements and the shaft come into contact with each other. At least one of the shaft and the bearing moves in a direction in which the shafts coincide with each other. The bearing cup is press-fitted in a state where the inclination of the central axis of the shaft relative to the central axis of the bearing is small. As the rolling element moves inward in the radial direction of the bearing due to the press-fitting of the bearing cup, the rolling element comes into contact with the shaft, so that the inclination of the central axis of the shaft with respect to the central axis of the bearing becomes small. For this reason, the period during which the bearing cup is press-fitted into the bearing hole as compared to the configuration in which the shaft and the plurality of rolling elements are fitted together after the rolling element has moved inward in the radial direction of the bearing by press-fitting the bearing cup In, the frictional force of the shaft and rolling elements tends to be small. For this reason, it is suppressed that a shaft and a rolling element are damaged.

  As described above, since the method for assembling the universal joint does not displace the bearing in a direction different from the press-fitting direction of the bearing, complication of the universal joint assembling apparatus is suppressed. Further, since the bearing is not reciprocated in the direction along the press-fitting direction, the time for press-fitting the bearing into the bearing hole is shortened. Therefore, the assembly time of the universal joint is shortened.

  [2] An independent form of the universal joint assembling apparatus has the following matters. That is, two yokes having a pair of arms and bearing holes formed in the arms, a cross shaft having four shafts inserted into the bearing holes, and an annularly arranged inner A universal joint assembling apparatus comprising: a plurality of rolling elements that form a space; and a bearing that houses the plurality of rolling elements, has a bearing cup press-fitted into the bearing hole, and has the shaft inserted therein. A hollow shaft inserted into the bearing hole of one arm of the pair of arms, a pin inserted into the recess, and an elastic member connected to the pin. A holding pin that biases the cross shaft toward the other arm side when the elastic member pushes the pin and the shaft is pushed toward the other arm of the pair of arms, and the other A cylinder disposed on the arm of the housing and containing the bearing cup, A press-fitting device having a piston for pushing the receiving cup toward the bearing hole of the other arm and press-fitting the bearing cup into the bearing hole; and an actuator for moving the piston toward the other arm; Is provided.

  According to this universal joint assembly device, since the cross shaft is pushed toward the other arm by the pin, the rolling element moves inward in the radial direction of the bearing by the press-fitting device press-fitting the bearing cup into the bearing hole. Before the bearing cup is inserted into the tip of the shaft, the shaft and a plurality of rolling elements are fitted together. At this time, the fitting relationship between the shaft and the plurality of rolling elements is a clearance fit. For this reason, when the center of the shaft and the center of the bearing are different from each other, a plurality of rolling elements are easily fitted to the tip of the shaft. When the center axis of the shaft is tilted with respect to the center axis of the bearing, the plurality of rolling elements are fitted to the tip of the shaft, so that the plurality of rolling elements and the shaft come into contact with each other. At least one of the shaft and the bearing moves in a direction in which the shafts coincide with each other. The bearing cup is press-fitted in a state where the inclination of the central axis of the shaft relative to the central axis of the bearing is small. As the rolling element moves inward in the radial direction of the bearing due to the press-fitting of the bearing cup, the rolling element comes into contact with the shaft, so that the inclination of the central axis of the shaft with respect to the central axis of the bearing becomes small. For this reason, the period during which the bearing cup is press-fitted into the bearing hole as compared to the configuration in which the shaft and the plurality of rolling elements are fitted together after the rolling element has moved inward in the radial direction of the bearing by press-fitting the bearing cup In, the frictional force of the shaft and rolling elements tends to be small. For this reason, it is suppressed that a shaft and a rolling element are damaged.

  Thus, since the assembly apparatus of this universal joint does not displace the bearing in a direction different from the press-fitting direction of the bearing, complication of the assembly apparatus of the universal joint is suppressed. Further, since the bearing is not reciprocated in the direction along the press-fitting direction, the time for press-fitting the bearing into the bearing hole is shortened. Therefore, the assembly time of the universal joint is shortened.

  The universal joint assembling method and the universal joint assembling apparatus can suppress the complication of the apparatus and can shorten the assembling time.

The fragmentary sectional view of the universal joint of an embodiment. Sectional drawing of the assembly apparatus of the universal joint of embodiment. The fragmentary sectional view which shows the cross-axis biasing process of the assembly method of the universal joint of embodiment. The fragmentary sectional view which shows the cross-axis biasing process of the assembly method of the universal joint of embodiment. The fragmentary sectional view which shows the bearing press injection process of the assembly method of the universal joint of embodiment. The fragmentary sectional view which shows the bearing press injection process of the assembly method of the universal joint of embodiment. The fragmentary sectional view which shows the bearing press injection process of the assembly method of the universal joint of embodiment. The fragmentary sectional view which shows the cross-axis arrangement | positioning process of the assembly method of the universal joint of a comparative example. The fragmentary sectional view which shows the bearing press-fit process of the assembly method of the universal joint of a comparative example. The fragmentary sectional view which shows the bearing press-fit process of the assembly method of the universal joint of a comparative example.

The configuration of the universal joint 1 will be described with reference to FIG.
The universal joint 1 is used, for example, for connecting an intermediate shaft and a pinion shaft (both not shown) of a steering device. The universal joint 1 has a cross shaft 10, two yokes 20, and four bearings 30.

  The cross shaft 10 is made of a magnetic material. The cross shaft 10 has a body portion 11 and four shafts 12. The four shafts 12 protrude from the body part 11. The four shafts 12 are equally spaced by 90 ° in the circumferential direction of the body portion 11. The tip of the shaft 12 is chamfered.

  The two yokes 20 are connected to each other by the cross shaft 10 and the four bearings 30. The yoke 20 has a pair of arms 21 and a fixing portion 23. A bearing hole 22 is formed in the arm 21. Two shafts 12 spaced apart by 180 ° are inserted into the bearing holes 22 of the arm 21 of one yoke 20. The remaining shaft 12 is inserted into the bearing hole 22 of the arm 21 of the other yoke 20.

  The four bearings 30 are one-end sealed shell needle roller bearings. The bearing 30, the shaft 12, and the bearing hole 22 have a coaxial relationship. The bearing 30 has a bearing cup 31 and a plurality of needle rollers 32 as a plurality of rolling elements.

The bearing cup 31 is press-fitted into the bearing hole 22. The bearing cup 31 accommodates a plurality of needle rollers 32.
The plurality of needle rollers 32 are arranged in an annular shape that is coaxial with the central axis of the bearing cup 31, thereby forming an internal space 33. The size of the internal space 33 in the radial direction is defined by the inscribed circle diameter of the plurality of needle rollers 32 (hereinafter, “inscribed circle diameter φFw”). The shaft 12 is inserted into the internal space 33. The relationship of the fitting of the plurality of needle rollers 32 and the shaft 12 is an interference fit. Grease (not shown) is applied to the surface of the needle roller 32.

With reference to FIG. 2, the structure of the assembly apparatus 100 of the universal joint 1 is demonstrated.
The assembling apparatus 100 includes a holding pin 110 and a press-fitting device 120. The holding pin 110 is inserted into a bearing hole 22 (hereinafter, “bearing hole 22 </ b> A”) of one arm 21 (hereinafter, “arm 21 </ b> A”) of the pair of arms 21 of the yoke 20. The press-fitting device 120 is disposed outside the other arm 21 (hereinafter referred to as “arm 21 </ b> B”) of the pair of arms 21.

  The holding pin 110 holds the cross shaft 10 (see FIG. 1). The holding pin 110 includes a hollow shaft 111, a lid 115, a coil spring 116 as an example of an elastic member, and a pin 117.

  An insertion portion 112 is formed at the distal end portion of the hollow shaft 111. The outer diameter of the insertion portion 112 is smaller than the outer diameter of the portion other than the insertion portion 112 of the hollow shaft 111. A recess 113 is formed in the insertion portion 112. The hole 114 of the hollow shaft 111 is continuous with the internal space of the recess 113. The lid 115 is fixed to the proximal end portion of the hollow shaft 111. The coil spring 116 is accommodated in the hole 114. One end of the coil spring 116 is fixed to the lid 115. The other end of the coil spring 116 is fixed to the pin 117. The pin 117 is formed of a permanent magnet. For example, the magnetic pole of the pin 117 has an N pole at the tip and an S pole at the base. The tip surface of the pin 117 is formed by a flat surface. The tip portion of the pin 117 protrudes from the insertion portion 112 when the coil spring 116 has a natural length.

  The press-fitting device 120 press-fits the bearing 30 into the bearing hole 22. The press-fitting device 120 includes a cylinder 121, a piston 122, an actuator 123, an operation unit (not shown), and a control device (not shown).

  The cylinder 121 accommodates the piston 122. The piston 122 is connected to the actuator 123. An example of the actuator 123 has an electric motor and a screw shaft connected to the output shaft of the electric motor. The screw shaft is screwed into a female screw (not shown) formed on the piston 122. The operation unit is electrically connected to the control device. The operation unit outputs a start signal for driving the actuator 123 to the control device. The control device is electrically connected to the actuator 123. The control device controls the operation of the actuator 123. The control device drives the actuator 123 based on the start signal from the operation unit.

A method for assembling the universal joint 1 will be described with reference to FIGS.
The method for assembling the universal joint 1 includes a bearing setting process, a yoke holding process, a holding pin insertion process, a cross shaft biasing process, and a bearing press-fitting process. The yoke holding step is a step of holding the yoke 20 by holding the fixing portion 23 of the yoke 20 in a jig (not shown). The holding pin insertion step is a step that is performed after the yoke holding step and attaches the holding pin 110 to the arm 21 </ b> A of the yoke 20. The cross shaft biasing step is performed after the holding pin insertion step, and one shaft 12 of the cross shaft 10 (hereinafter referred to as “shaft 12A”) is inserted into the recess 113 of the holding pin 110, and the bearing hole 22 ( Hereinafter, it is a step of inserting the other shaft 12 of the cross shaft 10 (hereinafter referred to as “shaft 12B”) into the “bearing hole 22B”). The bearing press-fitting step is performed after the cross shaft biasing step and press-fits the bearing 30 into the bearing hole 22B. The bearing setting process, the yoke holding process, the holding pin insertion process, and the cross shaft biasing process are performed manually.

The bearing setting process includes the following operations.
As shown in FIG. 2, the bearing 30 is inserted into the cylinder 121 of the press-fitting device 120. The bottom 31 </ b> B of the bearing cup 31 is in contact with the piston 122. The fitting relationship between the bearing cup 31 and the piston 122 is a clearance fit. At this time, the central axis of the bearing 30 and the central axis of the cylinder 121 substantially coincide. FIG. 2 shows an arrangement configuration in which the yoke 20 and the press-fitting device 120 are adjacent to each other. However, the yoke 20 is not disposed next to the press-fitting device 120 in the bearing setting process.

The yoke holding process includes the following operations.
The jig is disposed near the press-fitting device 120. The fixed portion 23 of the yoke 20 is sandwiched between jigs. The arm 21 </ b> B of the yoke 20 is adjacent to the cylinder 121 of the press-fitting device 120. At this time, the central axis of the bearing hole 22B of the arm 21B and the central axis of the cylinder 121 coincide. That is, the central axis of the bearing hole 22B and the central axis of the bearing 30 are coincident.

The holding pin insertion process includes the following operations.
As shown in FIG. 2, the insertion portion 112 of the hollow shaft 111 is inserted into the bearing hole 22 </ b> A of the yoke 20. The step portion 111A of the hollow shaft 111 is in contact with the peripheral portion of the bearing hole 22A.

The cross shaft biasing process includes the following operations.
First, the pin 117 is pushed to the lid 115 side. At this time, the coil spring 116 is compressed. Next, the cross shaft 10 is inserted between the pair of arms 21. Then, the pin 117 is attracted to the shaft 12A. Next, as shown in FIG. 3, the shaft 12 </ b> A is inserted into the recess 113. At this time, the central axis of the shaft 12A and the central axis of the bearing hole 22A substantially coincide. Further, the central axis of the shaft 12B and the central axis of the bearing hole 22B substantially coincide. At this time, in a state where the cross shaft 10 is held by the operator, the shaft 12A is pushed to the arm 21B side by the pin 117 based on the restoring force of the coil spring 116.

  Next, the cross shaft 10 moves toward the arm 21B. Then, as shown in FIG. 4, the body portion 11 contacts the arm 21 </ b> B. The tip surface of the shaft 12B protrudes from the arm 21B to the side opposite to the arm 21A. When the trunk portion 11 comes into contact with the arm 21B, the coil spring 116 is maintained in a compressed state. For this reason, the pin 117 pushes the shaft 12A toward the arm 21B by the restoring force of the coil spring 116. As a result, the cross shaft 10 is sandwiched between the pin 117 and the arm 21B.

The bearing press-fitting process includes the following operations.
The operator operates the operation unit (not shown) of the press-fitting device 120 to drive the actuator 123. Thereby, the piston 122 press-fits the bearing 30 into the bearing hole 22B. Note that, in a state before the bearing 30 is press-fitted into the bearing hole 22B, the fitting relationship between the plurality of needle rollers 32 and the shaft 12B is clearance fit.

Hereinafter, the relationship between the shaft 12B and the bearing 30 in the process of press-fitting the bearing 30 into the bearing hole 22B will be described.
As shown in FIG. 5, when the opening 31A of the bearing cup 31 is press-fitted into the bearing hole 22B, the bearing cup 31 is inserted into the distal end portion of the shaft 12B. Then, the shaft 12B and the plurality of needle rollers 32 are fitted together. At this time, a clearance fit is maintained in the fitting relationship between the shaft 12B and the plurality of needle rollers 32. Thereby, the tip of the shaft 12B is located in the internal space 33. Note that the drive current of the actuator 123 increases as the opening 31A of the bearing cup 31 is press-fitted into the bearing hole 22B.

  As shown in FIG. 6, as the press-fitting of the bearing cup 31 into the bearing hole 22B is further advanced, the bottom 31B of the bearing cup 31 approaches the tip of the shaft 12B. At this time, the end of the needle roller 32 on the opening 31A side and the side surface facing the shaft 12B are in contact with the shaft 12B. For this reason, the fitting relationship between the shaft 12B and the plurality of needle rollers 32 is such that the tip portion of the shaft 12B and the intermediate portion of the needle roller 32 are clearance fit, and the intermediate portion of the shaft 12B and the opening portion 31A side of the needle roller 32 are provided. The end of is an interference fit. Note that the drive current of the actuator 123 further increases as the bearing cup 31 is press-fitted into the bearing hole 22B.

  And the bottom part 31B of the bearing cup 31 contacts the front end surface of the shaft 12B. At this time, the fitting relationship between the shaft 12B and the plurality of needle rollers 32 is an interference fit. Then, the cross shaft 10 moves toward the arm 21 </ b> A together with the bearing 30. At this time, since the pin 117 is pushed to the lid 115 side by the shaft 12A, the coil spring 116 is compressed. For this reason, the drive current of the actuator 123 further increases.

  As shown in FIG. 7, when the tip surface of the shaft 12 </ b> A comes into contact with the bottom surface 113 </ b> A of the recess 113, the drive current of the actuator 123 increases rapidly and exceeds the threshold value. At this time, the control device of the press-fitting device 120 stops driving the actuator 123.

  After the press-fitting of the bearing 30 into the bearing hole 22B is completed, the holding pin 110 is removed from the arm 21A, and the press-fitting device 120 is removed from the arm 21B. Next, the press-fitting device 120 is set on the arm 21A. Then, the bearing 30 is press-fitted into the bearing hole 22 </ b> A by the press-fitting device 120. Thus, the shaft 12A is inserted into the bearing 30. The assembly of the remaining yoke 20, shaft 12, and bearing 30 is the same from the bearing setting process to the bearing press-fitting process of the above assembling method.

The operation of the method for assembling the universal joint 1 will be described with reference to FIGS. 4, 5, and 8 to 10.
The operation of the assembly method of the universal joint 1 can be described based on a comparison with the assembly method of the universal joint 1 of the comparative example shown in FIGS. 8 to 10 (hereinafter referred to as “comparative assembly method”). As shown in FIG. 8, in the comparative assembly method, the universal joint 1 is assembled using the comparative holding pin 200 and the press-fitting device 120. The comparison holding pin 200 has a configuration in which the coil spring 116 and the pin 117 are omitted from the holding pin 110.

  The comparative assembling method includes a bearing setting step, a yoke holding step, a comparative holding pin insertion step, a cross shaft placement step, and a bearing press-fitting step. The bearing setting process and the yoke holding process are the same as the bearing setting process and the yoke holding process of the present embodiment. The comparison holding pin insertion step is performed after the yoke holding step, and the comparison holding pin 200 is inserted into the bearing hole 22 </ b> A of the yoke 20. The comparison holding pin insertion step is the same as the holding pin insertion step of the present embodiment. The cross shaft placement step is performed after the comparison holding pin insertion step, and is a step of placing the cross shaft 10 between the pair of arms 21. The bearing press-fitting process is a process that is performed after the cross shaft arranging process and press-fits the bearing 30 into the bearing hole 22B. The bearing setting process, the yoke holding process, the comparison holding pin inserting process, and the cross shaft arranging process are performed manually.

The cross shaft arrangement process includes the following operations.
First, the shaft 12 </ b> A of the cross shaft 10 is inserted into the recess 202 of the comparison holding pin 200. The front end surface of the shaft 12A is in contact with the bottom surface 202A of the recess 202. At this time, the distance between the trunk portion 11 and the arm 21A and the distance between the trunk portion 11 and the arm 21B are equal to each other. The tip surface of the shaft 12A is located at the center position of the bearing hole 22A in the axial direction of the bearing hole 22A. The shaft 12B is inserted into the bearing hole 22B. The tip surface of the shaft 12B is located at the center position of the bearing hole 22B in the axial direction of the bearing hole 22B.

The bearing press-fitting process includes the same operation as the bearing press-fitting process of the present embodiment.
On the other hand, since the position of the shaft 12B with respect to the bearing hole 22B differs in the axial direction of the bearing hole 22B, the relationship between the press-fitting of the bearing cup 31 into the bearing hole 22B and the insertion of the shaft 12B into the internal space 33 is the present embodiment. Different from the bearing press-fitting process.

  As shown in FIG. 9, after the bearing cup 31 is press-fitted into the bearing hole 22B and the plurality of needle rollers 32 move inward in the radial direction of the bearing 30, that is, the inscribed circle diameter φFw of the plurality of needle rollers 32 is increased. After being reduced, the bearing cup 31 is inserted into the tip of the shaft 12B. For this reason, the fitting relationship between the needle roller 32 and the shaft 12B is an interference fit.

  By the way, since the insertion part 201 of the comparison holding pin 200 is smoothly inserted into the bearing hole 22A, the outer diameter of the insertion part 201 is slightly smaller than the inner diameter of the bearing hole 22A. Further, since the shaft 12A is smoothly inserted into the recess 202, the inner diameter of the recess 202 is slightly larger than the outer diameter of the shaft 12A.

  For this reason, the bearing hole 22A and the insertion portion 201 may not be concentric, and the recess 202 and the shaft 12A may not be concentric. Due to at least one of these, the shaft 12B and the bearing hole 22B may not be concentric. Further, the central axis of the insertion portion 201 may be inclined with respect to the central axis of the bearing hole 22A, and the central axis of the shaft 12A may be inclined with respect to the central axis of the recess 202. At least one of these may cause the cross shaft 10 to tilt with respect to the yoke 20.

  When the shaft 12B and the bearing hole 22B are not concentric, the end surface on the opening 31A side of the needle roller 32 contacts the shaft 12B before the needle roller 32 and the shaft 12B are fitted together. The bearing cup 31 is press-fitted into the bearing hole 22B with the end surface of the needle roller 32 on the opening 31A side in contact with the shaft 12B. For this reason, the needle roller 32 bites the shaft 12B.

  When the cross shaft 10 is inclined with respect to the yoke 20, the bearing 30 is press-fitted into the bearing hole 22B with the central axis of the shaft 12B inclined with respect to the central axis of the bearing hole 22B. For this reason, some needle rollers 32 contact the shaft 12B before the needle roller 32 and the shaft 12B are fitted together. Then, the bearing cup 31 is press-fitted into the bearing hole 22B in a state where some of the needle rollers 32 are in contact with the shaft 12B. Thus, since the bearing cup 31 is press-fitted into the bearing hole 22B in a state where the inscribed circle diameter φFw is small and the needle roller 32 is in contact with the shaft 12B, the frictional force between the needle roller 32 and the shaft 12B is large. Become. For this reason, the grease on the surface of the needle roller 32 is easily peeled off by the tip of the shaft 12B. When the shaft 12B and the bearing hole 22B are not concentric and the central axis of the shaft 12B is inclined with respect to the central axis of the bearing hole 22B, both of the above-described problems occur. In particular, after the universal joint 1 is assembled, when the fitting relationship between the shaft 12B and the needle roller 32 is an interference fit, the gap between the inscribed circle diameter φFw of the plurality of needle rollers 32 and the shaft 12B is reduced. Both of the above problems are likely to occur.

  Further, it is considered that the amount of the grease removed from the surface of the needle roller 32 increases as the speed at which the bearing 30 is press-fitted into the bearing hole 22B, that is, the speed at which the shaft 12B is inserted into the internal space 33 increases. Thereby, when the bearing 30 is press-fitted into the bearing hole 22B at a high speed, there may be a so-called grease breakage in which a necessary and sufficient amount of grease on the surface of the needle roller 32 cannot be secured. For this reason, the comparative assembly method requires that the bearing 30 be press-fitted into the bearing hole 22B at a low speed in order to make it difficult for the needle roller 32 to be broken. For this reason, in the comparative assembly method, the assembly time of the universal joint 1 becomes long.

  Further, in order to suppress the occurrence of the above-mentioned grease breakage and the occurrence of galling of the shaft 12B and the needle roller 32, it has been proposed that the shaft and the needle roller have the following structure. That is, a taper part is formed in the intermediate part of the axis | shaft continuous from the chamfering part of the front-end | tip part of an axis | shaft. The outer diameter of the tapered portion is smaller than the outer diameter of the portion other than the tip portion of the shaft. Further, a taper portion is formed on the needle roller. However, since the shaft needs to be tapered and the needle roller needs to be tapered (crowning), the processing cost of the shaft and the needle roller increases.

  In the method for assembling the universal joint 1 of the present embodiment, as shown in FIG. 4, the cross shaft 10 is biased toward the arm 21 </ b> B side of the yoke 20 in the cross shaft biasing step. For this reason, the shaft 12B protrudes from the arm 21B to the side opposite to the arm 21A. Therefore, as shown in FIG. 5, in the bearing press-fitting step, the shaft 12B and the plurality of needle rollers 32 are fitted together before the bearing cup 31 is press-fitted into the bearing hole 22B and the inscribed circle diameter φFw is reduced. For this reason, the fitting relationship between the needle roller 32 and the tip of the shaft 12B is a clearance fit. For this reason, even when the shaft 12B and the bearing hole 22B are not concentric, the shaft 12B and the plurality of needle rollers 32 are easily fitted. The needle roller 32 comes into contact with the shaft 12B as the needle roller 32 moves inward in the radial direction of the bearing 30 as the bearing cup 31 is pressed into the bearing hole 22B. At this time, when the central axis of the shaft 12B is inclined with respect to the central axis of the bearing 30, the needle roller 32 reduces the inclination of the central axis of the shaft 12B with respect to the central axis of the bearing 30. For this reason, compared with the structure assumed that the bearing cup 31 is inserted into the shaft 12B after the needle roller 32 moves inward in the radial direction of the bearing 30 by press-fitting the bearing cup 31 into the bearing hole 22B. During the period in which the bearing cup 31 is press-fitted into the bearing hole 22B, the frictional force between the shaft 12 and the needle roller 32 tends to be small. For this reason, the shaft 12B and the plurality of needle rollers 32 are damaged, and occurrence of grease breakage is suppressed. For this reason, even when the bearing 30 is press-fitted into the bearing hole 22B at a high speed, the occurrence of grease breakage of the needle roller 32 can be suppressed. Therefore, the assembly time of the universal joint 1 is shortened. Further, as described above, since the breakage of the grease and the occurrence of galling of the shaft 12B and the needle roller 32 are suppressed, the tapered portion of the shaft 12B and the crowning portion of the needle roller 32 become unnecessary. Therefore, the processing cost of the cross shaft 10 and the needle roller 32 is reduced.

The method for assembling the universal joint 1 of the present embodiment has the following effects.
(1) The bearing cup 31 is press-fitted into the bearing hole 22B in a state in which the fitting relationship between the tip end of the shaft 12B and the needle roller 32 is a clearance fit. For this reason, generation | occurrence | production of the grease piece of the needle roller 32 is suppressed. Therefore, since the press-fitting speed of the bearing 30 into the bearing hole 22B can be increased, the assembly time of the universal joint 1 is shortened.

  (2) The cross shaft 10 is made of a magnetic material, and the pin 117 is made of a permanent magnet. According to this configuration, the pin 117 sucks the shaft 12 </ b> A of the cross shaft 10. For this reason, the cross shaft 10 is restrained from being inclined with respect to the yoke 20 in the cross shaft biasing step and the bearing press-fitting step.

  In addition, the specific form which the assembly method of this universal joint and the assembly apparatus of this universal joint can take is not limited to the content shown by the said embodiment. The present universal joint assembling method and the present universal joint assembling apparatus can take the form of modifications of the embodiments described below, for example.

A seal is provided at the base end of each shaft 12. An example of the seal is an oil seal.
The assembly method of the universal joint having a seal is different in the following points. In the cross shaft biasing step, by adjusting at least one of the dimension of the coil spring 116 and the size of the pin 117, the cross shaft 10 moves the arm 21A more than the position of the cross shaft 10 with respect to the yoke 20 in the cross shaft biasing step of the above embodiment. Located on the side. At this time, the seal is not in contact with the arm 21B.

In the cross shaft biasing process, the tip end of the shaft 12B is located in the bearing hole 22B. In this case, the tip of the shaft 12B is positioned in the internal space 33 before the inscribed circle diameter φFw is reduced.
The material of the pin 117 may be an adsorption rubber instead of the permanent magnet. In this case, the cross shaft 10 is not limited to a magnetic body.

The elastic member may be a material other than the coil spring 116 such as a rubber member.
A bearing is provided on the inner peripheral portion of the hollow shaft 111 of the holding pin 110. An example of a bearing is a rolling bearing or a sliding bearing. The bearing supports the pin 117 in a state where the pin 117 can move with respect to the hollow shaft 111. According to this configuration, the central axis of the pin 117 is suppressed from being inclined with respect to the central axis of the hollow shaft 111. Further, the pin 117 can move smoothly with respect to the hollow shaft 111.

  In the holding pin insertion step, the holding pin 110 is inserted into the bearing hole 22A of the yoke 20 by a moving device (not shown) instead of manually. An example of the moving device includes a screw shaft that moves the hollow shaft 111 and an actuator that rotates the screw shaft. When the holding pin 110 is moved by the moving device, the hollow shaft 111 of the holding pin 110 is formed with a female screw into which the screw shaft is screwed.

  The universal joint 1 is used for a drive shaft instead of the steering shaft. Two universal joints 1 are used as a part of the outer joint of the drive shaft and a part of the inner joint.

The assembly apparatus for a universal joint includes means for solving the following problems.
(Additional remark 1) The said pin is a permanent magnet, The said cross shaft is an assembly apparatus of the universal joint of Claim 2 formed with a magnetic body.

  (Additional remark 2) The said holding pin is an assembly apparatus of the universal joint of Claim 2 which has a bearing attached to the inner peripheral part of the said hollow shaft, and supporting the movement of the said pin with respect to the said hollow shaft.

  DESCRIPTION OF SYMBOLS 1 ... Universal joint, 10 ... Cross axis, 12 ... Axis, 12A ... Axis (one axis), 12B ... Axis (the other axis), 20 ... Yoke, 21 ... Arm, 21A ... Arm (one arm), 21B ... arm (other arm), 22 ... bearing hole, 22A ... bearing hole (bearing hole for one arm), 22B ... bearing hole (bearing hole for the other arm), 30 ... bearing, 31 ... bearing cup, 31A ... Opening portion, 31B ... bottom, 32 ... needle roller (rolling element), 100 ... assembly device, 110 ... holding pin, 111 ... hollow shaft, 113 ... concave, 116 ... coil spring (elastic member), 117 ... pin, 120 ... Press-fitting device, 121 ... cylinder, 122 ... piston, 123 ... actuator.

Claims (2)

Two yokes having a pair of arms and bearing holes formed in the arms, a cross shaft having four shafts inserted into the bearing holes, and an annular space arranged in an annular shape A method of assembling a universal joint comprising: a plurality of rolling elements to be formed; and a bearing that houses the plurality of rolling elements, has a bearing cup press-fitted into the bearing hole, and has a bearing into which the shaft is inserted.
In a state where the yoke is held, the shaft is inserted into the bearing hole,
The cross shaft is biased to one of the pair of arms,
In a state where the cross shaft is biased to one of the pair of arms, the tip of the shaft is inserted before the bearing cup is press-fitted and the rolling elements move inward in the radial direction of the bearing. The bearing cup is inserted and the tip of the shaft and the plurality of rolling elements are fitted together,
A method for assembling a universal joint, wherein the bearing cup is press-fitted into the bearing hole in a state in which a tip portion of the shaft is fitted to the plurality of rolling elements. Two yokes having a pair of arms and bearing holes formed in the arms, a cross shaft having four shafts inserted into the bearing holes, and an annular space arranged in an annular shape A universal joint assembling apparatus comprising a plurality of rolling elements to be formed, and a bearing in which the plurality of rolling elements are accommodated, a bearing cup press-fitted into the bearing hole, and a bearing into which the shaft is inserted,
A hollow shaft to be inserted into the bearing hole of one arm of the pair of arms, a pin inserted into the recess, and an elastic member connected to the pin. A holding pin that biases the cross shaft toward the other arm side by pressing the pin against the other arm of the pair of arms when the elastic member pushes the pin;
A cylinder disposed on the other arm and containing the bearing cup; a piston for pressing the bearing cup toward the bearing hole of the other arm and press-fitting the bearing cup into the bearing hole; and And a press-fitting device having an actuator for moving the piston toward the other arm.