JP6413590B2 - Caulking punch - Google Patents

Description

  The present invention relates to a caulking punch. In particular, the present invention relates to a caulking punch that is suitably used for caulking the shaft shaft end of a hub unit and has improved strength by changing the shape.

  In assembling a hub unit for rotating and supporting a vehicle wheel, an inner ring member is integrally combined with a shaft end of the hub shaft, and then the shaft end is caulked to integrally assemble the hub shaft and the inner ring member. A swing caulking device is used to caulk the shaft end of the hub shaft. FIG. 9 shows a swing caulking device 100 disclosed in Patent Document 1.

The hub shaft 101 has a cylindrical workpiece 102 at the shaft end, and an inner ring member 103 is press-fitted into the workpiece 102. The workpiece 102 protrudes from the end surface of the inner ring member 103. In the swing caulking device 100, the punch 104 is pressed against the projecting portion 102 so as to be spread outward in the radial direction.
The punch 104 is attached to the tip of the main shaft 105 of the swing caulking device 100. The main shaft 105 is inclined by an angle θ with respect to the axis of the hub shaft 101 and precesses about the axis of the hub shaft 101. The punch 104 and the workpiece 102 are in contact at one point on the circumference. By lowering the punch 104 while turning around the axis of the hub shaft 101, the workpiece 102 is plastically deformed radially outward over the entire circumference, and the caulking portion 106 is formed. In FIG. 9, the shape of the workpiece 102 before plastic deformation is indicated by a two-dot chain line.

  The punch 104 is formed with a guide portion 107 protruding in the axial direction on the workpiece 102 side, and the guide surface 108 on the outer periphery of the guide portion 107 is connected to a caulking generation surface 109 for forming the caulking portion 106. . At the time of caulking, the workpiece 102 is deformed along the caulking generation surface 109 after being deformed outward in the radial direction by being pushed by the guide portion 107.

JP 2000-38005 A

  When the workpiece 102 is plastically deformed, a large load is generated at the contact portion between the punch 104 and the workpiece 102. In particular, at the end stage of the caulking process, in order to fix the inner ring member 103 to the hub shaft 101, it is necessary to press the caulking portion 106 strongly in the axial direction of the hub shaft 101 and press it against the inner ring member 103. For this reason, a large axial contact force acts on the caulking generation surface 109. Due to this load, a large stress is generated in the portion 111 where the guide surface 108 and the caulking generation surface 109 of the punch 104 are connected, and the punch 104 is damaged relatively early, so that the replacement frequency is high. For this reason, there is a problem that the production efficiency of the hub unit 110 is lowered.

  An object of the present invention is to avoid premature breakage of a caulking punch used in a process of caulking the shaft end of a hub shaft.

A caulking punch according to an embodiment of the present invention is pressed against a cylindrical work portion formed at the shaft end of a hub shaft that protrudes through an annular inner ring member, and the work portion is pressed against the hub shaft. It is used for the purpose of forming a caulking part by plastic deformation in the radial direction, and has a guide part protruding toward the processed part, and the outer periphery of the guide part is in contact with the inner periphery of the processed part A substantially cylindrical guide surface is formed, and a caulking generation surface is formed on the radially outer side of the guide surface to press the plastically deformed portion toward the inner ring member in the axial direction of the hub shaft. A caulking punch, wherein the guide surface and the caulking generation surface are connected to each other by a continuous portion, and a shape of an axial section of the continuous portion is a first arc connected to the caulking generation surface ; the guide surface And the second arc is in contact with each other, and the radius of curvature of the second arc is smaller than the radius of curvature of the first arc. .

  According to the present invention, premature breakage of the caulking punch used in the step of caulking the shaft end of the hub shaft can be avoided.

It is a principal part enlarged view of the caulking punch concerning embodiment of this invention. It is sectional drawing explaining the method of caulking to the axial end of a hub shaft using a rocking caulking apparatus. It is an axial sectional view of the caulking punch according to the embodiment of the present invention. It is a principal part enlarged view which shows the contact state of the crimping punch of an initial stage of a process, and a to-be-processed part. FIG. 5 is an enlarged view of main parts similar to FIG. 4 in a middle stage of processing. It is a principal part enlarged view similar to FIG. 4 of the completion | finish stage of a process. It is a stress distribution figure of the continuous part X of this embodiment in the process completion stage. It is a stress distribution figure of the continuous part Z of the comparative example in the process completion stage. It is a structural diagram explaining the structure of the conventional rocking caulking device.

An embodiment of a caulking punch (hereinafter simply referred to as “punch”) according to the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing a state in which the swing caulking device 40 is arranged above the hub unit 10 and caulking is performed on the shaft end of the hub shaft 11. In FIG. 2, the vertical direction is the vertical direction.
For easy understanding of the caulking process state, only the head portion 41 of the swing caulking device 40 is shown in FIG. Further, when actually processing, the lower end portion of the head portion 41 and the upper end portion of the hub shaft 11 are in contact with each other. However, since the drawing becomes complicated, the head portion 41 and the hub shaft 11 are separated vertically. It is displayed.

First, the structure of the hub unit 10 will be described.
When the hub unit 10 is attached to the vehicle, the lower side of FIG. 2 is the outer side of the vehicle. Therefore, in the following description, the lower side is described as the outer side and the upper side is described as the inner side. In the following description of the hub unit 10, the “axial direction” refers to the direction of the axis of the hub shaft 11, and the direction orthogonal thereto is referred to as the “radial direction”.

  The hub unit 10 includes an outer ring 12, a hub shaft 11, an inner ring member 13, balls 14 and 14, and cages 15 and 15.

  The outer ring 12 has a substantially cylindrical shape made of metal, and a flange portion 16 extending in the radial direction is integrally formed on the outer periphery thereof. Two rows of outer raceway surfaces 17 and 17 are formed on the inner circumference of the outer ring 12.

  The hub shaft 11 is made of carbon steel such as S55C, and the shaft portion 18 and the flange portion 19 are integrally formed.

An inner raceway surface 20 a is formed on the entire circumference of the outer periphery of the shaft portion 18. A cylindrical surface 21 is formed on the inner side of the inner raceway surface 20a. An inner ring coupling surface 22 is formed on the outer periphery of the inner side shaft end of the shaft portion 18. The inner ring mating surface 22 and the cylindrical surface 21 are connected by a side surface 23 extending in the radial direction. The inner ring mating surface 22 has a cylindrical shape coaxial with the cylindrical surface 21, and has an outer diameter smaller than that of the cylindrical surface 21.
An end surface 24 that extends in the radial direction is formed at the axial end of the shaft portion 18, and the outer edge thereof is connected to the inner ring mating surface 22. A hole having a predetermined depth is formed in the axial end portion in a direction perpendicular to the end surface 24, and the inner peripheral surface 25 of the hole has a cylindrical shape formed coaxially with the inner ring mating surface 22.

  The flange portion 19 has a disc shape and is formed on the outer side of the shaft portion 18. The flange portion 19 is provided with a plurality of bolts 26 penetrating in the axial direction in order to attach a wheel (not shown). A cylindrical wheel spigot 27 is coaxially provided on the outer side surface of the flange portion 19.

  The inner ring member 13 is made of bearing steel. On the outer periphery of the inner ring member 13, an inner raceway surface 20b is formed on the entire periphery. A small end surface 13 a and a large end surface 13 b are formed at both ends of the inner ring member 13 in the axial direction. Both the small end surface 13a and the large end surface 13b are flat surfaces extending in the radial direction and are parallel to each other.

  The hub shaft 11 is assembled by combining the outer ring 12 and the hub shaft 11 coaxially. At this time, a plurality of balls 14 are respectively incorporated between the outer raceway surfaces 17 and 17 and the inner raceway surfaces 20a and 20b that are opposed to each other in the radial direction. The balls 14 are held by the cage 15 at predetermined intervals along each track surface. The inner ring member 13 is fitted into the inner ring mating surface 22 and is press-fitted until the small end surface 13a and the side surface 23 come into contact with each other.

  The axial length of the inner ring mating surface 22 is longer than the axial length of the inner ring member 13. For this reason, when the inner ring member 13 is fitted to the inner ring engagement surface 22, a part of the inner ring engagement surface 22 protrudes from the large end surface 13 b of the inner ring member 13. Further, the axial length of the inner peripheral surface 25 is longer than the length from the end surface 24 to the large end surface 13 b of the inner ring member 13. In this way, the shaft end portion of the hub shaft 11 protrudes in the axial direction from the inner ring member 13 to form a cylindrical workpiece 28. The to-be-processed part 28 becomes a caulking part 29 by plastic deformation after caulking. In FIG. 2, the shape of the workpiece 28 before caulking is indicated by a two-dot chain line.

Similarly, referring to FIG. 2, the structure of the swing caulking device 40 will be described. In the swing caulking device 40, an axis 41 a (hereinafter referred to as “head axis”) of the head portion 41 is arranged coaxially with the hub shaft 11.
Although not shown, the head portion 41 is rotatably supported by a rolling bearing or the like, and can rotate around the head axis 41a. The rotational force is applied by an electric motor (not shown) or the like. The head portion 41 is supported by a linear motion bearing (not shown) and can move in the vertical direction. The vertical movement is performed by a ball screw or a hydraulic cylinder (not shown).

A main shaft 42 is incorporated in the head portion 41.
A cylindrical punch holder 43 is coaxially formed on the shaft end of the main shaft 42 on the side facing the hub unit 10. The punch holder 43 is formed with a punch attachment surface 43a to which the punch 30 is attached. A guide hole 44 for guiding the punch 30 coaxially with the axis of the main shaft 42 is formed in the punch mounting surface 43a.
The main shaft 42 is rotatably supported by two rows of needle roller bearings 45, 45, and rotates about its axis 42a (hereinafter referred to as “rotating axis”). The rotation axis 42a is inclined by a predetermined angle θ with respect to the head axis 41a. The rotation axis 42 a intersects the head axis 41 a at substantially the same position as the punch 30.
A thrust ball bearing 46 is incorporated at the shaft end of the main shaft 42 on the side opposite to the punch holder 43. The main shaft 42 is supported in the axial direction with respect to the housing 47.

  FIG. 3 is a cross-sectional view of the punch 30 in the axial direction. The shape of the punch 30 according to the embodiment of the present invention will be described with reference to FIG. The punch 30 is made of a metal material such as high-speed tool steel.

  The punch 30 has a substantially cylindrical shape. An attachment surface 51 that extends in the radial direction is formed on one side of the punch 30 in the axial direction. The inlay 52 protrudes from the mounting surface 51 in the axial direction. The inlay 52 has a cylindrical shape that is coaxial with the axis of the punch 30. The outer dimension of the inlay 52 is slightly smaller than the inner diameter dimension of the guide hole 44 of the punch holder 43. A screw hole 53 is coaxially formed from the end surface of the inlay 52 in the axial direction. The punch 30 is fixed coaxially with the main shaft 42 by tightening a bolt (not shown) penetrating the main shaft 42 into the screw hole 53.

  A guide portion 54 is formed on the other side in the axial direction of the punch 30. The guide portion 54 has a truncated cone shape and is formed coaxially with the axis of the punch 30. The end surface 54a of the guide part 54 is a plane formed in the radial direction. On the outer periphery of the guide portion 54, a guide surface 56 is formed, whose diameter increases from the outer peripheral end of the end surface 54a toward the axial direction.

  On the side surface of the punch 30 radially outward from the guide portion 54, a caulking generation surface 57 and a caulking end surface 58 are formed in an annular shape coaxial with the guide portion 54, respectively. In the shape of the axial cross section of the punch 30, the caulking generation surface 57 is slightly inclined toward the mounting surface 51 toward the outer side in the radial direction. The caulking end surface 58 is formed radially outward of the caulking generation surface 57, and is inclined in a direction away from the mounting surface 51 toward the radially outward direction. The outer peripheral edge of the caulking generation surface 57 and the inner peripheral edge of the caulking end surface 58 are smoothly connected to each other with a small arc.

FIG. 1 is an enlarged view of a main part of a portion where the caulking generation surface 57 and the guide surface 56 are connected to each other in the axial sectional view of the punch 30.
The caulking generation surface 57 has an inner peripheral edge connected to the guide surface 56. A portion where the caulking generation surface 57 and the guide surface 56 are connected to each other is hereinafter referred to as a “continuous portion”. In the punch 30 of this embodiment, the “continuous portion” is formed by a first arc 61 connected to the caulking generation surface 57 and a second arc 62 connected to the guide surface 56. The “continuous part” in this embodiment is defined as a continuous part X. In the following description of the punch 30, the upper side in FIG. 1 (on the side of the axial mounting surface 51) is referred to as “upper”, and the lower side (on the side of the axial guide portion 54) is “ "Down".

The first arc 61 has an arc shape that protrudes upward. The center of curvature C1 is below the caulking generation surface 57. The first arc 61 intersects or is in contact with the caulking generation surface 57. A point where the first arc 61 and the caulking generation surface 57 intersect is defined as P1. The first arc 61 intersects with the extension line of the guide surface 56 on the extension line.
The length L11 of the perpendicular line drawn from the center of curvature C1 to the caulking generation surface 57 is smaller than or equal to the curvature radius R1 of the first arc 61 (L11 ≦ R1), and the perpendicular line dropped from the center of curvature C1 to the guide surface 56. Is shorter than R1 (L12 <R1).

The second arc 62 has an arc shape that protrudes upward. The radius of curvature R2 of the second arc 62 is smaller than the radius of curvature R1 of the first arc 61. The second arc 62 intersects or is in contact with the guide surface 56. Further, the second arc 62 is in contact with the first arc 61. A point where the second arc 62 and the guide surface 56 intersect is T1, and a point where the first arc 61 and the second arc 62 are in contact is Q.
The center of curvature C2 of the second arc 62 is on a straight line connecting the center of curvature C1 of the first arc 61 and the point Q. The length L22 of the perpendicular line drawn from the center of curvature C2 to the guide surface 56 is smaller than or equal to R2 (L22 ≦ R2).

A change in the contact state between the punch 30 and the processed portion 28 when the processed portion 28 of the hub shaft 11 is caulked will be described with reference to FIGS. 2 and 4.
As shown in FIG. 2, the head portion 41 is coaxially disposed above the hub shaft 11 in the vertical direction. When caulking, the head portion 41 is lowered while rotating around the head axis 41a, and the punch 30 is pressed against the workpiece 28. In FIG. 2, the upper end of the main shaft 42 is inclined rightward with respect to the head axis 41a by an angle θ. For this reason, the punch 30 and the part 28 to be processed approach each other on the right side of FIG. 2 from the axis of the hub shaft 11.

4 to 6 are enlarged views of main parts for explaining the contact state between the punch 30 and the workpiece 28 during the caulking process, in which the main shaft 42 is shown in FIG. 2 (right side of the figure). The contact state when it is in a state of being inclined) is shown. FIG. 4 shows a contact state between the punch 30 and the workpiece 28 in the initial stage of machining. FIG. 5 shows a contact state in the middle of the process (mid-process stage) during which the deformation of the work part 28 proceeds and the caulking part 29 is formed. FIG. 6 shows a contact state when the formation of the caulking portion 29 is almost completed (processing end stage).
The hub shaft 11 is fixed to a base (not shown) and does not rotate.

When the head portion 41 is lowered, the guide surface 56 of the punch 30 and the inner peripheral surface 25 of the processed portion 28 come into contact (see FIG. 4). Thereafter, as the head portion 41 is lowered, the workpiece 28 is deformed radially outward along the guide surface 56. Since the main shaft 42 is pivoted, the workpiece 28 is pushed outward in the radial direction over the entire circumference. Furthermore, by displacing the head portion 41 downward in the vertical direction, the processed portion 28 is spread outward in the radial direction along the caulking generation surface 57 (see FIG. 5). Thereafter, the work portion 28 is strongly pressed toward the large end surface 13b of the inner ring member 13 to form a caulking portion 29 (see FIG. 6).
Thus, the caulking portion 29 is pressed against the large end surface 13 b of the inner ring member 13, so that the inner ring member 13 is prevented from coming out of the hub shaft 11.

When the main shaft 42 is turned 180 ° around the head axis 41a from the position shown in FIG. 2, the upper end of the main shaft 42 is inclined to the left in the figure by an angle θ with respect to the head axis 41a. Although not shown, in FIG. 2, the punch 30 and the workpiece 28 are in contact with each other on the left side of the drawing, and the punch 30 and the workpiece 28 are separated from each other on the right side of the drawing.
Although the main shaft 42 precesses as the head portion 41 rotates, the main shaft 42 is supported so as to be rotatable with respect to the head portion 41. The position hardly changes. Therefore, a caulking load acts on the punch 30 shown in FIG. 4 (the portion on the right side of the axis of the hub shaft 11 in FIG. 2) only when the main shaft 42 is inclined to the right. Thus, the caulking load is repeatedly applied to the punch 30 according to the turning of the main shaft 42.

The stress generated in the continuous part X will be described with reference to FIG.
4, the guide surface 56 of the punch 30 and the upper end of the workpiece 28 are in contact with each other. At this contact point, a load F acts on the guide surface 56 in a substantially vertical direction. In the initial stage of machining, the load F is relatively small because the deformation amount of the workpiece 28 is small. For this reason, the stress which arises in the continuous part X is small.
In the middle stage of machining in FIG. 5, the load F increases as the deformation amount increases. However, since the point at which the load F acts on the caulking generation surface 57 is close to the continuous portion X, the length of the arm of the moment is short, so the stress value generated in the continuous portion X is relatively small.
In the processing end stage of FIG. 6, the formation of the caulking portion 29 is almost completed. The workpiece 28 is pressed in the axial direction on the entire surface of the caulking generation surface 57 and the caulking end surface 58. For this reason, the load F acting on the punch 30 becomes the largest through the caulking process. Since the point at which the load F acts is away from the continuous part X in the radial direction, the length of the arm of the moment is long, so the stress value generated in the continuous part X is large. Thus, the largest bending moment M acts on the punch 30 at the end of processing.

FIG. 7 shows a stress distribution generated in the continuous portion X at the end of processing. The length of the line extending in the normal direction from each point on the line indicating the shape of the continuous portion X of the punch 30 represents the magnitude of stress at each point. The stress distribution shows the result calculated by the finite element method (FEM).
In calculating the stress value, the radius of curvature R1 of the first arc 61 was 10 mm, and the radius of curvature R2 of the second arc 62 was 4 mm. In addition, the dimension of each part used in the calculation of stress is as follows. The outer diameter dimension of the punch 30 is 80 mm, the axial thickness of the punch 30 is 20 mm, the outer diameter dimension of the workpiece 28 is 60 mm, and the inner diameter dimension of the workpiece 28 is 47 mm. Moreover, the Young's modulus of the main shaft 42 and the workpiece 28 is 208 GPa.

The stress generated in the first arc 61 will be described.
As shown in FIG. 6, a bending moment M acting counterclockwise is applied to the punch 30 by the load F. Due to this bending moment M, tensile stress is generated on the surface of the punch 30 from the caulking generation surface 57 to the continuous portion X. When the change in the surface shape from the caulking generation surface 57 to the continuous portion X is large in the cross-sectional shape in the axial direction of the punch 30, the tensile stress increases because the shape factor increases. The shape factor is a value obtained by dividing the maximum stress due to stress concentration by the nominal stress. The greater the value, the greater the degree of stress concentration.
In the present embodiment, since the radius of curvature (10 mm) of the first arc 61 is made larger than the conventional radius of curvature (4 mm), the surface shape changes gradually. For this reason, an increase in the surface stress generated in the first arc 61 can be suppressed.

Next, the stress generated in the second arc 62 will be described.
In the present embodiment, the radius of curvature R2 (4 mm) of the second arc 62 is smaller than the radius of curvature R1 (10 mm) of the first arc 61. Since the second arc 62 has a small radius of curvature, stress concentration occurs and a relatively large stress is generated. When a high stress is generated in the second arc 62, the stress generated in the first arc 61 is dispersed. As a result, the stress generated in the first arc 61 is reduced as a whole.

  Note that, in the portion of the second arc 62, the axial thickness of the punch 30 is increased, so that the section modulus with respect to the bending moment M is large. Therefore, even if the stress increases due to the dispersion of the stress in the first arc 61, the stress generated in the portion of the second arc 62 is not a problem that causes a problem with respect to the material strength.

  The stress generated at the point Q will be described. At the point Q, the first arc 61 and the second arc 62 are in contact with each other. Therefore, the surface shape of the continuous portion X gradually changes from the first arc 61 to the second arc 62. For this reason, an increase in stress can be suppressed at the point Q.

As described above, in the present embodiment, the stress generated in the portion of the first arc 61 can be dispersed by increasing the stress generated in the second arc 62. As a result, the tensile stress distribution generated in the continuous portion X is substantially uniform along the surface shape, and stress does not concentrate on a specific part. In this way, the maximum value of the stress generated in the continuous portion X can be reduced to a level that does not cause a problem as compared with the fatigue strength of the material, so that the early breakage of the punch 30 can be avoided.
In the present embodiment, the shape of the cross section in the axial direction of the caulking generation surface 57 has been described as a straight line. For example, the axial cross-sectional shape of the caulking generation surface 57 may be an arc.

  In order to explain the effect of the present invention, the stress distribution in the case of using “continuous part” of another shape (hereinafter referred to as “comparative example”) will be described. FIG. 8 shows the stress distribution of the “continuous part” (hereinafter referred to as the continuous part Z) in the comparative example. The shape of the punch 31 of the comparative example is the same as the shape of the punch 30 of the present embodiment except for the continuous portion Z. For this reason, in the following description, about the comparative example, the new number was provided only about the continuous part Z, and the same number as this embodiment was provided about the other site | part.

  In the comparative example, the continuous portion Z is formed by an arc 63 having a single radius of curvature R3. The arc 63 connects the caulking generation surface 57 and the guide surface 56. The radius of curvature R3 of the arc 63 is 4 mm. A point where the arc 63 and the guide surface 56 intersect is T2, and a point where the arc 63 and the caulking generation surface 57 intersect is P2.

  In the comparative example, since the radius of curvature (4 mm) of the arc 63 is smaller than the radius of curvature (10 mm) of the first arc 61 of the present embodiment, the surface shape changes greatly from the caulking generation surface 57 to the arc 63. . For this reason, the surface stress is increased at a portion of the arc 63 (the surface closer to the guide surface 56 than the point P2) (region G shown in FIG. 8). For this reason, there exists a possibility that the maximum value of the stress which generate | occur | produces in the continuous part Z may exceed the fatigue strength of material.

  In contrast to this comparative example, in this embodiment, the stress distribution generated in the continuous portion X is substantially uniform along the surface shape, and stress does not concentrate on a specific part. For this reason, in this embodiment, since the maximum value of the stress generated in the continuous portion X can be reduced to a level that does not cause a problem as compared with the fatigue strength of the material, early breakage of the punch 30 can be avoided. I can do it.

As described above, in the punch 30 using the present invention, by increasing the radius of curvature of the first arc 61 connected to the caulking generation surface 57, it is possible to suppress an increase in stress accompanying a change in surface shape. . Furthermore, by generating a high stress on the second arc 62, the stress generated on the first arc 61 can be dispersed. As a result, the maximum value of the stress generated in the “continuous portion” can be reduced to a level at which there is no problem in comparison with the fatigue strength of the material.
Thus, premature breakage of the punch used in the step of caulking the shaft end of the hub shaft can be avoided. Thereby, the replacement frequency of the punch used in the process of caulking the shaft end of the hub shaft can be lowered, and the production efficiency of the hub unit can be improved.

(Embodiment of the present invention) 10: Hub unit, 11: Hub shaft, 13: Inner ring member, 13b: Large end face, 22: Inner ring mating face, 24: End face, 25: Inner peripheral face, 28: Worked part, 29: Caulking portion, 30: Caulking punch, 31: Caulking punch (comparative example), 40: Oscillating caulking device, 41: Head portion, 41a: Head axis, 42: Main shaft, 42a: Rotating axis, 43: Punch Holder, 43a: Punch mounting surface, 44: Guide hole, 45: Needle roller bearing, 46: Thrust ball bearing, 47: Housing, 51: Mounting surface, 52: Inner, 54: Guide part, 54a: End surface, 56: Guide surface, 57: caulking generation surface, 58: caulking end surface, 61: first arc, 62: second arc, 63: arc (comparative example),
(Prior art) 100: Oscillating caulking device, 101: Hub shaft, 102: Processed part, 103: Inner ring member, 104: Caulking punch, 105: Main shaft, 106: Caulking part, 107: Guide part, 108: Guide Surface, 109: caulking generation surface, 110: hub unit

Claims (2)

A crimped portion is formed by being plastically deformed in the radial direction of the hub shaft by being pressed against a cylindrical processed portion formed at the shaft end of the hub shaft that protrudes through the annular inner ring member. Used for applications,
A guide portion protruding toward the workpiece,
On the outer periphery of the guide portion, a substantially cylindrical guide surface that is in contact with the inner periphery of the workpiece is formed,
A caulking punch in which a caulking generation surface is formed on a radially outer side of the guide surface to press the plastically deformed work portion toward the inner ring member in the axial direction of the hub shaft,
The guide surface and the caulking generation surface are connected to each other at a continuous portion,
The shape of the cross section in the axial direction of the continuous portion is formed by a first arc connected to the caulking generation surface and a second arc connected to the guide surface ,
The caulking punch, wherein the first arc and the second arc are in contact with each other, and the radius of curvature of the second arc is smaller than the radius of curvature of the first arc.   The first arc and the second arc are connected to each other at a point Q;
  2. The caulking punch according to claim 1, wherein the position of the center of curvature of the second arc is on a straight line connecting the center of curvature of the first arc and the point Q. 3.

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