JP2010112506A - Method and structure for coupling universal joint with shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft-clamp coupling structure capable of being embodied in an axially compacted and simplified construction at low cost. <P>SOLUTION: The coupling structure is for coupling a clamp 10 with a shaft 20, wherein the clamp 10 is composed of a boss 12 having a serration hole 14 able to contract elastically in the diameter and a pair of arms 16a and 16b having holes 18a and 18b perpendicularly intersecting the axis of the boss 12, perpendicularly intersecting the axis of the boss 12, and parallel with each other within a plane including the axes of the holes 18a and 18b, while the shaft 20 has a serration shank part 22 and is furnished with a recess 24 at the periphery of the serration shank part 22 within its axially directed region, and in this coupling structure, the serration shank part 22 of the shaft 20 is inserted into the serration hole 14 in the clamp 10, and a sleeve 30 is inserted into the holes 18a and 18b in the arms 16a and 16b, followed by engagement with the recess 24 in the shaft 20, insertion of a bolt 40 through the sleeve 30, and fastening together of the two arms 16a and 16b, and thus the clamp-shaft coupling is established. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coupling structure and a coupling method of a universal joint and a shaft, and can be used for, for example, a coupling structure of a steering shaft and a universal joint in an automobile steering apparatus.

  In general, in a steering device that steers a front wheel of a vehicle, the movement of a steering shaft that is rotated by operation of a steering wheel is transmitted to an input shaft of a steering gear through a universal joint. For example, a universal joint is interposed between the upper shaft and the lower shaft of the steering shaft, and torque is transmitted at a predetermined bending angle. FIG. 8 shows an example of a steering apparatus having two universal joints J1 and J2. As shown in FIG. 9, when a cruciform universal joint (cross joint) 2 is adopted as a universal joint, a pair of yokes 4, 6 are coupled together via a cruciform shaft (spider) 8, thereby providing the yokes 4, 6. The rotational force can be transmitted between the yokes 4 and 6 even if the shaft centers are not located on the same straight line.

  Conventionally, in the joint structure of the universal joint 2 and the steering shaft 120, it has been common to provide a shaft clamp (hereinafter simply referred to as a clamp) 110 on the yoke 4 of the universal joint 2. That is, the clamp 110 includes a boss 112 having a serration hole 114 and a pair of arms 116a and 116b for reducing the diameter of the boss 112. The serration shaft portion 122 of the shaft 120 is inserted into the serration hole 114, and the bolt 110 By tightening 140 and pressing the pair of arms 116a and 116b toward each other, the serration hole 114 is reduced in diameter, and the clamp 110 and the shaft 120 are coupled so that torque can be transmitted without play.

  An annular groove 124 is formed on the outer peripheral surface of the shaft 120, and the shaft portion 142 of the bolt 140 is engaged with the annular groove 124 so that the shaft 120 does not come out of the clamp 110. Further, in order to prevent the bolt 140 from loosening, a washer 148 is interposed between the counterbore on the outer end surface of the arm 116 a and the seating surface 146 of the head portion 144 of the bolt 140.

  However, in such a conventional coupling structure, it is necessary to insert the bolt 140 while pressing both members so that the shaft 120 does not fall out of the clamp 110. Moreover, in order to smoothly insert and tighten the bolts 140, it is necessary to maintain a state in which the clamp 110 and the shaft 120 are pressed so as not to deviate from a predetermined axial position. Therefore, there is a problem that the work efficiency is lowered due to the labor and time required for the assembly work.

Patent Document 1 discloses a device for preventing the shaft from falling off from the yoke until the shaft and the yoke are bolted together when the vehicle is assembled. As shown in FIG. 10, a bottomed cylindrical engagement tube 304 formed of a thin metal plate is attached to the tip of the shaft 302, and the body of the engagement tube 304 is cut and raised to engage at a predetermined angle. The protrusion 306 is provided, and the tip 308 of the engagement protrusion 306 is locked to the engagement recess 314 formed in the clamp 312 of the yoke 310 to prevent the protrusion 306 from coming off. Further, when removing the shaft 302 from the clamp 312, a pressing jig 316 is inserted into the engagement recess 314 of the clamp 312 from the outside, and the engagement projection 306 is pushed down to engage the tip 308 with the engagement recess 314. Release the match.
JP 2007-292165 A

  In the coupling structure described in Patent Document 1, it is necessary to attach the engagement cylinder 304 to the shaft 302, and it is also necessary to provide the engagement recess 314 in the clamp 312. Moreover, since the engagement cylinder 304 is provided outside the region of the serration shaft portion of the shaft 302, it is necessary to provide the corresponding engagement recess 314 outside the region of the serration portion, and as a result, the processing cost of the clamp 312 is increased. In addition to the increase, there is a problem that the axial dimension of the clamp 312 becomes longer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost shaft displacement prevention mechanism that is compact in the axial direction and simplified.

  The present invention solves the problem by inserting a sleeve into a bolt hole. That is, the shaft-clamp coupling structure of the present invention has a boss portion having a serration hole that can be elastically reduced in diameter, a bolt hole perpendicular to the axis of the boss, and perpendicular to the axis of the boss. A clamp having a pair of arms parallel to each other in a plane including the axis of the bolt hole, a serration shaft portion, and a shaft having a recess formed in an outer periphery in an axial region of the serration shaft portion, Inserting the serration shaft portion of the shaft into the serration hole of the clamp, inserting a bolt into the bolt hole, fastening the pair of arms, and engaging the shaft portion of the bolt with the recess, The clamp is connected, and a sleeve is inserted between the bolt hole and the bolt.

  In connecting the shaft and the clamp, first, the serration shaft portion of the shaft is inserted into the serration hole of the clamp. And the phase of the recessed part of a shaft and the bolt hole of a clamp is matched. That is, the axial positions of the recess and the bolt hole are matched. In this state, the sleeve is inserted into the bolt hole. Then, the sleeve engages with the recess to prevent the shaft and clamp from coming off. Therefore, there is no fear that the shaft will come out of the clamp while the bolt is continuously inserted into the sleeve and the arm is fastened, and the fastening work can be easily performed (claim 10). The clamp member is formed of carbon steel.

  The sleeve includes a cylindrical portion inserted into the bolt hole and a flange portion formed at one end of the cylindrical portion. In this case, the flange serves as a washer that receives the bearing surface of the bolt. Therefore, it is not necessary to use a separate washer. In addition, since the flange part of a sleeve functions as a bolt washer, it is preferable to shape | mold with the material applied to a washer.

The bolt hole includes two holes formed in the pair of arms, and the holes penetrate through one arm, and the holes terminate in the middle of the other arm. The length L ₁ of the bolt hole is set to be longer than the length L ₂ of the cylindrical portion of the sleeve in a state where the arm is tightened (Claim 5). This is to prevent the sleeve from hitting the bottom of the bolt hole and hindering sufficient tightening when the bolt is tightened. Here, the length L ₁ of the bolt hole is the sum of the length of the hole of one arm, the length of the hole of the other arm, and the width of the slit between the pair of arms in a state where the arm is tightened. It shall be said.
In order to facilitate insertion of the sleeve, the inner diameter D _{1 of the} bolt hole is preferably slightly larger than the outer diameter D ₂ of the cylindrical portion of the sleeve.
A counterbore for receiving the flange portion is preferably formed in the arm on the side where the bolt hole is open on the surface.

  A slit may be provided in the sleeve and press-fitted into the bolt hole. Since the sleeve is easily reduced in diameter due to elastic deformation by providing the slit, the press-fitting in this case may be light press-fitting with a small press-fitting allowance so that the sleeve does not easily fall off. By providing a taper at the press-fitting start side end portion of the sleeve (Claim 4), the taper portion performs a guiding function at the start of press-fitting, and smooth press-fitting is possible.

A female screw is provided on one of the pair of arms. The one arm is specifically the arm on the side where the hole constituting the bolt hole is terminated halfway.
The female screw may be formed directly on the arm, or may be formed on a member other than the arm (claim 7). That is, a member other than the arm such as a nut may be used. Further, the member on which the female screw is formed may be integrated with the arm. For this purpose, press-fitting, caulking, welding, or other connecting means can be used.

  The present invention can be used for coupling a steering shaft and a universal joint in a steering device. In this case, the shaft is a steering shaft of a steering device (Claim 8), and the clamp is a part of a universal joint (Claim 9).

  The type of the universal joint is not particularly limited. Examples of the universal joint used in the steering device include a cardan joint (cross shaft joint), a double cardan universal joint, and a ball type fixed constant velocity joint. In the case of a ball type constant velocity joint, the ball track shape may be a track offset type having a single arc shape, or the ball track shape may be a track offset type without an undercut. Furthermore, what has a backpacking mechanism is also known.

  According to the present invention, by inserting the sleeve into the bolt hole, the shaft shape is maintained in the conventional shape, and the shaft and the clamp are removed during assembly without forming a new locking portion in the clamp. Misalignment can be prevented.

Embodiments of the present invention will be described below with reference to the drawings.
The embodiment shown in FIGS. 1, 2, and 3 is an example in which the yoke 4 of the cardan joint 2 and the shaft 20 are coupled. The cardan joint 2 is formed by connecting a pair of yokes 4 and 6 with a cross shaft (spider) 8 and is also called a cross joint.

  Regarding one yoke 4, a clamp 10 is provided at one end of the yoke 4. The clamp 10 includes a boss 12 and a pair of arms 16a and 16b. The boss 12 is integral with the yoke 4 and has a serration hole 14 formed therein. In the specification and claims, the term “serration” includes a spline. As can be seen from FIG. 3, there is a slit 15 between the boss 12 and the pair of arms 16a and 16b. Therefore, the pair of arms 16a and 16b face each other in parallel with the slit 15 in between. When the pair of arms 16a and 16b are tightened in the mutual direction, the boss 12 is elastically deformed and the serration hole 14 is reduced in diameter. Thus, the serration hole 14 can be elastically reduced in diameter.

  As shown in FIG. 3C, one arm 16a has a hole 18a, and the other arm 16b has a hole 18b and a female screw hole 18c. The axis of these holes 18a, the axis of the hole 18b, and the axis of the female screw hole 18c are all coaxial, and the axis of the boss 12 (the horizontal direction in FIGS. 1 and 2 and the direction perpendicular to the paper in FIG. 3). ) In a direction perpendicular to the paper surface in FIG. 1 (vertical direction in FIG. 2, vertical direction in FIG. 2, horizontal direction in FIG. 3A).

The hole 18a of the arm 16a passes through the arm 16a, and a counterbore 19 is provided on the outer end surface of the arm 16a.
The hole 18b of the arm 16b stops halfway, and the female screw hole 18c continues from there to the outer end surface of the arm 16b.

A sleeve 30 is inserted into the hole 18a of the arm 16a. As shown in FIG. 4A, the sleeve 30 includes a cylindrical portion 32 and a flange 34, and the cylindrical portion 32 fits into the hole 18 a, and the flange 34 is accommodated in the counterbore 19. The tip of the cylindrical portion 32 of the sleeve 30 enters the hole 18b of the arm 16b. As shown in FIG. 3B, a gap δ exists between the tip of the cylindrical portion 32 and the bottom of the hole 18b. In other words, the length L ₂ of the cylindrical portion 32 (FIG. 4A) is shorter than the sum L ₁ of the lengths of the holes 18a and 18b of the clamp 10 and the width dimension of the slit 15 in the natural state shown in FIG. (L ₁ > L ₂ ). More specifically, this dimensional relationship (L ₁ > L ₂ ) is such that the gap δ (FIG. 3B) is maintained with the pair of arms tightened until a desired clamping force is obtained. desirable.

If the outer diameter D ₂ (FIG. 4 (A)) of the cylindrical portion 32 of the sleeve 30 is equal to or slightly smaller than the inner diameter D ₁ (FIG. 3 (C)) of the holes 18a and 18b, the holes 18a and 18b can be easily formed. Can be inserted.
The inner diameter of the cylindrical portion 32 of the sleeve 30 is made smaller than the diameter of the shaft portion 42 of the bolt 40.

  Referring to FIG. 1, the shaft 20 has a serration shaft portion 22, and a recess 24 is formed on the outer periphery in the axial direction region of the serration shaft portion 22. The recess 24 is in the form of an annular groove over the entire circumference of the serration shaft 22 in the drawing, but can also be in the form of a cut-through groove formed in a part of the circumferential direction.

  In connecting the clamp 10 and the shaft 20, first, the serration shaft portion 22 of the shaft 20 is inserted into the serration hole 14 of the clamp 10. Then, the axial positions of the holes 18a and 18b of the clamp 10 and the concave portion 24 of the shaft 20 are substantially matched. In this state, the sleeve 30 is inserted into the holes 18a and 18b. Then, the cylindrical portion 32 of the sleeve 30 engages with the concave portion 24 of the shaft 20. Accordingly, the shaft 20 and the clamp 10 are temporarily fixed, and the two (10, 20) are not easily separated unless the sleeve 30 is removed.

  Next, the bolt 40 is inserted into the sleeve 30 to fasten the pair of arms 16a and 16b. In the case of this embodiment, the pair of arms 16a and 16b are tightened in a direction approaching each other by screwing the shaft portion 42 of the bolt 40 having the male thread cut into the female screw hole 18c of the arm 16b. At this time, since the flange 30 is formed at one end of the sleeve 30, the flange 34 is interposed between the seat surface 46 of the head portion 44 of the bolt 40 and the clamp 10 and serves as a washer. Therefore, a washer that has been incorporated as a bolt to prevent loosening of bolts is not necessary.

In order to securely tighten the bolt 40, the dimensional relationship between the sleeve 30 and the holes 18a and 18b is preferably set as follows.
Holes 18a, to reduce the outer diameter D ₂ of the cylindrical portion 32 of the sleeve 30 than the inner diameter D ₁ of the _{18b (D 1> D 2)} . This is to facilitate insertion of the cylindrical portion 32 of the sleeve 30 into the holes 18a and 18b.
The dimensional relationship between the shaft portion 42 of the bolt 40 and the cylindrical portion 32 of the sleeve 30 is a clearance fit. That is, the inner diameter of the cylindrical portion 32 of the sleeve 30 is made larger than the diameter of the shaft portion 42 of the bolt 40.

  Regarding the dimensional relationship between the concave portion 24 of the shaft 20 and the cylindrical portion 32 of the sleeve 30, when the cross section of the concave portion 24 as viewed in a cross section including the axis of the shaft 20 (see FIG. 1) is an arc shape, the sleeve 30 has a larger radius than the curvature radius. The outer diameter of the cylindrical portion 32 is preferably small.

Further, the length L ₂ of the cylindrical portion 32 of the sleeve 30 is made shorter than the sum L ₁ of the lengths of the holes 18 a and 18 b and the width of the slit 15 (L ₁ > L ₂ ). This is because if the cylindrical portion 32 of the sleeve 30 is longer, when the bolt 40 is tightened, the sleeve 30 interferes and a sufficient tightening amount cannot be secured. As can be understood from this, the sum L ₁ of the lengths of the holes 18a and 18b and the width of the slit 15 is the clearance δ shown in FIG. 3B with the bolt 40 tightened until a desired clamping force is obtained. Set to form.

  4B and 4C are examples in which a slit 36 is provided over the entire length of the sleeve 30. FIG. Since the slit 36 is easily elastically deformed, the sleeve 30 can be lightly press-fitted into the holes 18a and 18b to make it difficult to drop off. In this case, as shown in FIG. 4D, the press-fitting operation can be facilitated by providing a tapered surface 38 at the end of the sleeve 30 on the insertion start side. The size of the angle α is appropriately set in consideration of the material of the sleeve 30, the outer diameter D2 of the cylindrical portion 32, and the like.

  The female screw for receiving the male screw of the bolt 40 may be formed directly on the arm 16b as in the above-described embodiment, or a female screw member different from the arm 16b may be provided. FIG. 5A shows an example in which a nut 48 is employed as such a female screw member.

  The female screw member may be integrated with the arm 16b by press fitting, caulking, welding, or other appropriate means. FIG. 5B shows an example in which the female screw member 50 is press-fitted into a hole formed in the arm 16b and both are integrated. Instead of or in addition to press-fitting, an adhesive or welding may be employed.

  FIG. 6 shows an embodiment applied to a double cardan joint. As is well known, the cardan joint is an inconstant velocity joint, and therefore, when used in a steering device, the steering feeling may be adversely affected. Therefore, in order to eliminate this problem, a double cardan joint uses two cardan joints 2 as a set.

  FIG. 7 shows an embodiment applied to a fixed type constant velocity joint having a backpacking mechanism among ball type constant velocity joints. The fixed type constant velocity joint includes an outer ring 210 as an outer joint member, an inner ring 220 and a shaft 240 as inner joint members, a plurality of balls 230 as torque transmission members, and a cage 232 for holding the balls 230. Have.

  The outer ring 210 includes a mouse portion 212 and a stem portion 218, and the stem portion 218 is permanently connected to the clamp 10. The mouse portion 212 is bell-shaped, has a spherical inner peripheral surface 214, and has curved ball grooves 216 extending in parallel with the axis and formed at equal intervals in the circumferential direction.

  The inner ring 220 has a spherical outer peripheral surface 222, and curved ball grooves 224 extending in parallel with the axis are formed at equal intervals in the circumferential direction. The ball groove 216 of the outer ring 210 and the ball groove 224 of the inner ring 220 make a pair, and one ball 230 is incorporated in each pair of ball grooves 216 and 224. The number of balls 230 is arbitrary, but six or eight balls are known as specific examples. The cage 232 is interposed between the inner peripheral surface 214 of the outer ring 210 and the outer peripheral surface 222 of the inner ring 220, and pockets 234 are formed at predetermined intervals in the circumferential direction. The balls 230 are received in the pockets 234 of the cage 232, and all the balls 230 are held in the same plane by the cage 232.

  The inner ring 220 has a serration hole 226, and the serration hole 226 is connected to the serration shaft portion 242 of the shaft 240 so that torque can be transmitted. A retaining ring groove 244 is formed near the shaft end of the shaft 240, and the inner ring 220 is positioned on the shaft 240 by attaching a retaining ring 254 to the retaining ring groove 244. Here, the inner ring 220 and the shaft 240 are collectively referred to as an inner joint member.

  The center of the ball groove 216 of the outer ring 210 (outer ring track center) is the center of the inner peripheral surface 214 of the outer ring 210, and the center of the ball groove 224 of the inner ring 220 (inner ring track center) is the outer surface 222 of the inner ring 220. Each center is offset to the opposite side by an equal distance in the axial direction. The center of the outer peripheral surface of the cage 232 and the center of the inner peripheral surface 214 of the outer ring 210 both coincide with the joint center. Similarly, the center of the inner peripheral surface of the cage 232 and the center of the outer peripheral surface 222 of the inner ring 220 coincide with the joint center. Therefore, the offset amount of the outer ring track center is the distance between the outer ring track center and the joint center, and the offset amount of the inner ring track center is the axial distance between the inner ring track center and the joint center, and both are equal. The ball track formed by the pair of ball grooves 216 and 224 has a wedge shape that is reduced from the opening side of the mouth portion 212 of the outer ring 210 toward the back side.

When the axis of the outer ring 210 and the axis of the inner ring 220 form an angle, that is, when the joint has an operating angle, the ball 230 guided by the cage 232 is maintained within the bisector of the operating angle, Constant velocity is ensured.
The joint is filled with lubricating grease, and a boot 256 is attached to prevent leakage of the lubricating grease and to prevent foreign matter from entering from the outside. The boot 256 includes a cylindrical large-diameter portion, a cylindrical small-diameter portion, and an intermediate portion that connects the large-diameter portion and the small-diameter portion, and the intermediate portion has a bellows shape. The boot 256 has a large diameter portion attached to a boot groove or a boot fixing portion 215 formed on the outer ring 210, and a small diameter portion attached to a boot fixing portion formed on the shaft 240, and is fastened and fixed by a boot band 258, respectively.

The receiving member 238 attached to the cage 232 and the pressing member 250 attached to the shaft 240 constitute a backpacking mechanism for removing rotational backlash.
The pressing member 250 includes, for example, a substantially hemispherical head and a cylindrical body, and the body is slidably inserted into an axial hole formed at the shaft end of the shaft 240. The pressing member 250 is elastically pressed in a direction of protruding from the shaft end of the shaft 240 by an elastic member (not shown), typically a compression coil spring. For example, a compression coil spring is interposed between a portion projecting radially from the body portion of the substantially hemispherical head and the shaft end of the shaft 240.

  The receiving member 238 is attached to the cage 232. For example, the peripheral edge of the receiving member 238 is engaged with a recess formed on the inner periphery of the end of the outer ring mouth portion 212 of the cage 232, and is fixed by appropriate means such as press-fitting, caulking, or welding. As shown in the figure, the receiving member 238 has a partially spherical shape as a whole, and the inner surface of the receiving member 238, that is, the surface facing the end of the shaft 240 is a concave spherical shape, and the substantially hemispherical head of the pressing member 250 described above is formed. It functions as a receiving surface.

  In the above configuration, when the serration shaft portion of the shaft 240 is inserted into the serration hole of the inner ring 220 and positioned by the retaining ring 254, the pressing member 250 and the receiving member 238 come into contact with each other, and the elastic member is compressed. As a result, an axial elastic force acts between the inner ring 220 and the cage 232, and an axial relative movement occurs between the two. Due to this relative movement, the ball 230 is pushed through the cage 232 in the shrinking direction of the ball track (216, 224), so that the ball 230 and the ball grooves 216, 224 are always in contact with each other, thereby preventing rotational backlash. As described above, as a result of preventing the rotation backlash, the fixed type constant velocity joint can be suitably used for steering an automobile that does not like the rotation backlash.

  Although the fixed type constant velocity joint provided with the backpacking mechanism has been described, the present invention can be widely applied to those using other fixed type constant velocity joints. For example, in the track offset type in which the outer ring ball groove and the inner ring ball groove have an arc shape and the center is offset, the ball groove has a single arc and a straight part is formed in a part of the ball groove. There is an undercut free joint that eliminates the undercut.

It is the front view made into the partial cross section which shows the Example of this invention. It is the top view made into the partial cross section of the Example of FIG. 3A is a cross-sectional view taken along line III-III in FIG. 1, FIG. 3B is a partially enlarged view of FIG. 3A, and FIG. 3C is an enlarged view of the clamp in FIG. (A) is a sectional view of a sleeve, (B) is a sectional view of another sleeve, (C) is a side view of the sleeve of FIG. 4 (B), and (D) is a partially enlarged view of FIG. 4 (B). . (A) (B) is sectional drawing of the Example which made the internal thread provided in an arm a different body. It is the front view made into the partial cross section which shows the Example applied to the coupling | bonding of a double cardan joint and a shaft. It is the front view made into the partial cross section which shows the Example applied to the coupling | bonding of a fixed type constant velocity joint and a shaft. It is a side view of a steering device. (A) is the front view made into the partial cross section which shows the prior art, (B) is BB sectional drawing of FIG. 9 (A). It is a longitudinal cross-sectional view which shows another prior art.

Explanation of symbols

10 Clamp 12 Boss 14 Serration Hole 15 Slit 16a Arm 18a Hole 16b Arm 18b Hole 18c Female Thread Hole 19 Counterbore 20 Shaft 22 Serration Shaft 24 Recess 30 Sleeve 32 Cylindrical Part 34 Flange 36 Slot 38 Tapered Part 40 Bolt 42 Shaft Part 44 Head 46 Seating surface 48 Nut 50 Female thread member

Claims (10)

A boss portion having a serration hole that can be elastically reduced in diameter and a bolt hole perpendicular to the axis of the boss portion, and perpendicular to the axis of the boss portion and parallel to each other in a plane including the axis of the bolt hole A clamp consisting of a pair of arms;
A shaft having a serration shaft portion, having a recess formed in the outer periphery in the axial direction region of the serration shaft portion,
The shaft is inserted by inserting the serration shaft portion of the shaft into the serration hole of the clamp, inserting a bolt into the bolt hole, fastening the pair of arms, and engaging the shaft portion of the bolt with the recess. And a shaft-clamp coupling structure in which the clamp is coupled and a sleeve is inserted between the bolt hole and the bolt.   The coupling structure according to claim 1, wherein the sleeve includes a cylindrical portion inserted into the bolt hole and a flange portion formed at one end of the cylindrical portion.   The coupling structure according to claim 1, wherein the sleeve is slit and press-fitted into a bolt hole.   The coupling structure according to claim 3, wherein a taper is provided at a press-fitting start side end portion of the sleeve.   The coupling structure according to any one of claims 1 to 4, wherein a length of the sleeve is shorter than a length of a sleeve hole formed in the pair of arms.   The coupling structure according to any one of claims 1 to 5, wherein an internal thread is provided on one of the pair of arms.   The coupling structure according to claim 6, wherein the female screw is formed on a member different from the arm.   The coupling structure according to any one of claims 1 to 7, wherein the shaft is a steering shaft of a steering device.   The coupling structure according to claim 1, wherein the clamp is a part of a universal joint that is a part of a universal joint.   When the shaft and the clamp according to any one of claims 1 to 7 are coupled, the serration shaft portion of the shaft is inserted into the serration hole of the clamp, the phase of the concave portion of the shaft and the bolt hole of the clamp is matched, and the sleeve is aligned with the bolt hole. The shaft and clamp are connected by inserting a bolt and inserting a bolt into the sleeve to fasten the arm.

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