JP2017106566A - Manufacturing method of male shaft for telescopic shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a manufacturing method of a male shaft for a telescopic shaft which can reduce a manufacturing cost.SOLUTION: A first intermediate raw material 57 having a raw shaft part 58 is manufactured at a portion which is shifted to the other end in an axial direction from one end in the axial direction. Then, a raw center hole 61 is formed at one end of the first intermediate raw material 57 in the axial direction, and a second intermediate raw material 62 is manufactured. Then, a center hole 52 is formed by expanding an inside diameter of the raw center hole 61 by inserting a mandrel 65 to the inside of the raw center hole 61, a diameter-expanded part 67 is formed by expanding an outside diameter of a portion existing on an outside diameter side of the raw center hole 61 out of the second intermediate raw material 62, and a third intermediate raw material 66 is manufactured. A male spline part is formed at an external peripheral face of the diameter-expanded part 67 in a state that a support shaft is inserted to the inside of the center hole 52.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an improvement in a manufacturing method of a male shaft constituting a telescopic shaft used as an intermediate shaft constituting, for example, an automobile steering device.

  2. Description of the Related Art Conventionally, an automobile steering apparatus having a structure as shown in FIG. 8 is known. In the steering apparatus, a steering wheel 1 is fixed to a rear end portion of a steering shaft 2. At the same time, the front end portion of the steering shaft 2 is connected to the base end portion of the input shaft 6 constituting the steering gear unit 5 via a pair of universal joints 3 a and 3 b and the intermediate shaft 4. Further, a pair of left and right tie rods 7 and 7 are pushed and pulled by a rack and pinion mechanism built in the steering gear unit 5 so that the steering angle corresponding to the operation amount of the steering wheel 1 is given to the pair of left and right steering wheels. It is configured to grant.

  The intermediate shaft 4 incorporated in such a steering device is, for example, for preventing (absorbing) vibrations input from an automobile during traveling from being transmitted to the steering wheel 1 or, A telescopic type is used in order to incorporate it into the car body with its full length shortened.

  FIG. 9 shows the structure of the telescopic intermediate shaft 4 described in Patent Document 1. The intermediate shaft 4 includes an inner shaft 9 having a male spline portion 8 formed on the outer peripheral surface of one axial end portion (the front end portion and the left end portion in FIG. 9; the end portion on the outer tube 10 side in the assembled state). And a circular outer tube 10 in which a female spline portion 12 capable of spline engagement with the male spline portion 8 is formed on the inner peripheral surface. The male spline portion 8 and the female spline portion 12 are spline-engaged, so that the inner shaft 9 and the outer tube 10 are combined in a freely stretchable manner.

In the case of the structure shown in FIG. 9, the inner shaft 9 is disposed on the rear side (the front-rear direction refers to the front-rear direction of the vehicle body. The same applies throughout the present specification and claims), and The outer tube 10 is arranged on the front side. The first yoke 11 constituting the universal joint 3a disposed on the rear side of the universal joints 3a and 3b is externally fitted (fixed) to the other axial end of the inner shaft 9. ing. On the other hand, a second yoke 13 constituting the universal joint 3b disposed on the front side of the universal joints 3a and 3b is externally fitted and fixed (press-fitted) to one axial end portion of the outer tube 10. .
The coupling between the inner shaft 9 and the first yoke 11 or the coupling between the outer tube 10 and the second yoke 13 can be performed by welding. Further, a structure in which the inner shaft is disposed on the front side and the outer tube is disposed on the rear side can be employed as in the structure of the embodiment described later.

  By the way, conventionally, the small-diameter shaft portion 34 existing at the intermediate portion in the axial direction of the inner shaft 9 constituting the intermediate shaft 4 is formed by cutting. Specifically, in a state in which the outer diameter of the intermediate member that is the basis of the inner shaft 9 is processed to the rolling lower diameter over the entire length, or in the state where the male spline portion is formed over the entire length of the intermediate member, A portion corresponding to the small diameter shaft portion 34 is cut. Such cutting is troublesome and not only increases the processing time, but also the yield of the material is low by the amount of chips generated during the cutting, and the manufacturing cost may increase.

JP 2015-21596 A

  In view of the circumstances as described above, the present invention realizes a method for manufacturing a male shaft for a telescopic shaft that can reduce the manufacturing cost.

The male shaft for a telescopic shaft that is the object of the manufacturing method of the present invention has a male spline portion, a small diameter shaft portion, a yoke portion, and a center hole.
Among these, the male spline part is formed in the outer peripheral surface of the axial direction one end part of the said male shaft.
The small-diameter shaft portion is formed on the other side in the axial direction from the male spline portion, and the outer diameter is smaller than the diameter of the circumscribed circle of each convex portion of the male spline portion.
The yoke portion is provided integrally with the other axial end portion of the small diameter shaft portion.
The center hole has one axial end opening at one axial end surface of the male shaft.
Such a male shaft for a telescopic shaft is capable of transmitting torque to and from the female shaft by engaging the male spline portion with a female spline portion formed on the inner peripheral surface of the female shaft, and Combined in a stretchable state.

In particular, in the method for manufacturing a male shaft for a telescopic shaft according to the present invention, a cylindrical raw shaft portion whose outer diameter does not change over the entire length is provided in a portion from one axial end portion to the other axial end portion. It has the process of making an intermediate material.
In addition, by drilling the intermediate material, there is a step of forming an elementary center hole in which one end in the axial direction opens to one end surface in the axial direction of the intermediate material and the inner diameter is smaller than the inner diameter of the center hole. doing.
In addition, the method includes a step of expanding the inner diameter of the element center hole to form the center hole, and forming an enlarged diameter portion by expanding the outer diameter of the portion where the element center hole is formed. Yes.
Furthermore, it has the process of forming the said male spline part in the outer peripheral surface of the said enlarged diameter part.
And at least one part of the part except the said enlarged diameter part of the said raw shaft part is made into the said small diameter shaft part as it is.
Note that the order of the steps described above can be changed within a range where no contradiction occurs. Each of these steps can be performed simultaneously as far as possible.

  When carrying out the method for manufacturing a male shaft for a telescopic shaft according to the present invention as described above, specifically, a state in which a support shaft is inserted inside the center hole as in the invention described in claim 2 Thus, it is possible to adopt a configuration in which a male spline part is formed on the outer peripheral surface of the enlarged diameter part.

  When carrying out the above-described method for manufacturing a male shaft for a telescopic shaft according to the present invention, specifically, when the male spline portion is formed as in the invention described in claim 3, the male spline is formed. It is possible to adopt a configuration in which the diameter of the circumscribed circle of each concave portion of the portion is larger than the outer diameter of the bare shaft portion.

  When the manufacturing method of the male shaft for a telescopic shaft of the present invention as described above is carried out, in addition, as in the invention described in claim 4, with the opening of the center hole being closed, A coating layer is formed on the outer peripheral surface of the male spline portion.

  In the case of the manufacturing method of the male shaft for a telescopic shaft according to the present invention having the above-described configuration, the diameter-enlarged portion that is the portion that forms the male spline portion is the portion of the intermediate material in which the element center hole is formed. It is made by expanding the outer diameter. In other words, in the case of the present invention, it is possible to produce a portion having a different outer diameter, such as a portion corresponding to the small diameter shaft portion and a portion corresponding to the enlarged diameter portion, without performing cutting. Therefore, the cutting process for forming the small-diameter shaft portion employed in the above-described conventional manufacturing method is not required, and the manufacturing cost can be reduced.

The partial cutting side view which shows the intermediate shaft which attached the 10 axis | shaft type universal joint to the both ends which shows an example of embodiment of this invention. Similarly, the enlarged view which shows the part corresponded to (a) part of FIG. 1 among inner shafts. Similarly, the perspective view of an inner shaft. Similarly, sectional drawing for demonstrating the 1st-4th process among the manufacturing processes of an inner shaft. Similarly, sectional drawing for demonstrating the 5th-8th process among the manufacturing processes of an inner shaft. Similarly, the figure for demonstrating the specific example of the 7th, 8th process among the manufacturing processes of an inner shaft. Similarly, AA sectional view (A) of FIG. 6, BB sectional view (B), and CC sectional view (C). The partially cut side view which shows an example of the steering apparatus known conventionally. The partial cutting side view which takes out and shows an intermediate shaft.

[Example of Embodiment]
An example of an embodiment of the present invention will be described with reference to FIGS. In this example, a male shaft for a telescopic shaft, which is an object of the manufacturing method of the present invention, is combined with a female shaft and applied to an intermediate shaft constituting a steering device. However, the male shaft for a telescopic shaft that is the object of the production method of the present invention can be used for a telescopic shaft used in various applications other than such an intermediate shaft. In addition, the structure of the steering device incorporating the intermediate shaft of this example is substantially the same as the structure of the steering device shown in FIG. However, the intermediate shaft 4a of this example is not limited to the structure of the steering device shown in FIG. 8, but can be applied to the structures of various steering devices known in the art. Hereinafter, after briefly explaining the structure of the steering apparatus in which the intermediate shaft 4a of this example can be incorporated, the structure of the intermediate shaft 4a of this example and the manufacturing method of the intermediate shaft 4a will be explained.

  In the steering apparatus incorporating the intermediate shaft 4a of this example, the steering wheel 1 (see FIG. 8) is fixed to the rear end portion of the steering shaft 2. At the same time, the front end portion of the steering shaft 2 is connected to the base end portion of the input shaft 6 constituting the steering gear unit 5 through a pair of universal joints 3c and 3d and the intermediate shaft 4a. . Further, the rack and pinion mechanism built in the steering gear unit 5 pushes and pulls the pair of left and right tie rods 7 and 7 so that the steering angle corresponding to the operation amount of the steering wheel 1 is given to the pair of left and right steering wheels. It is configured to grant.

  The intermediate shaft 4a has one axial end portion of the inner shaft 9a corresponding to one example of the male shaft described in the claims (the right end portion in FIG. 1 and the outer tube 10a side in the assembled state). And the other axial end portion of the outer tube 10a corresponding to one example of the female shaft (the left end portion in FIG. 1 and the end portion on the inner shaft 9a side in the assembled state). Are combined so that torque can be transmitted and the entire length can be expanded and contracted. Hereinafter, a specific structure of the intermediate shaft 4a will be described.

The outer tube 10 a includes a small-diameter cylindrical portion 18, a continuous portion 19, a large-diameter cylindrical portion 20, and a yoke portion 21 in order from the other axial side.
Of these, the small-diameter cylindrical portion 18 has a cylindrical shape, and is provided in a portion of the outer tube 10a extending from the other axial end portion to the axial central portion. The outer peripheral surface of such a small diameter cylindrical portion 18 has a cylindrical surface shape whose outer diameter dimension does not change over the entire length in the axial direction. On the inner peripheral surface of the small-diameter cylindrical portion 18, a female spline portion 22 composed of a plurality of concave portions and convex portions that are long in the axial direction and are alternately formed in the circumferential direction is formed over the entire length. Yes.

The continuous portion 19 has a partial conical cylindrical shape in which the outer diameter dimension and the inner diameter dimension increase toward the one side in the axial direction (the right side in FIG. 1), and the other end in the axial direction is the axial direction of the small diameter cylindrical part 18. It is continuous to one edge.
The large-diameter cylindrical portion 20 has a cylindrical shape, and the other axial end edge is continuous with the one axial end edge of the continuous portion 19. The inner diameter dimension and the outer diameter dimension of such a large diameter cylindrical portion 20 are larger than the inner diameter dimension and the outer diameter dimension of the small diameter cylindrical portion 18.

  The yoke portion 21 constitutes the universal joint 3c, and is pivoted from two axial positions on one end edge in the axial direction of the large diameter cylindrical portion 20 on the opposite side in the diameter direction with respect to the large diameter cylindrical portion 20. It consists of a pair of arm parts 23 and 23 provided in a state extending in one direction. A pair of circular holes 24, 24 are formed in the vicinity of one end in the axial direction of both the arm portions 23, 23 in such a manner that the central axes are coaxial. In the assembled state shown in FIG. 1, bottomed cylindrical bearing cups 25 and 25 are fitted and fixed inside the circular holes 24 and 24, respectively. At the same time, a pair of shaft portions 28 of the four shaft portions 28, 28 constituting the cross shaft 27 are provided inside the bearing cups 25, 25 via a plurality of needles 26, 26, respectively. The end part of 28 is supported rotatably.

Of the four shaft portions 28, 28 constituting the cross shaft 27, a pair of shaft portions 28 other than the shaft portions 28, 28 supported in the circular holes 24, 24 of the yoke portion 21 ( The ends of one shaft portion 28 are not shown) and are formed on a pair of arm portions 30 (one arm portion 30 is not shown) constituting a yoke 29 supported and fixed to the front end portion of the steering shaft 2. A circular hole (not shown) is rotatably supported via a bearing cup and a needle (not shown).
In the case of this example, the structure in which the yoke portion 21 is provided integrally with the outer tube 10a is adopted. However, the outer tube and the yoke portion are provided separately and are joined and fixed by welding or fitting. Can also be adopted.

The inner shaft 9a includes a spare shaft portion 31, a spline forming portion 32, a continuous portion 33, a small diameter shaft portion 34a, and a yoke portion 35 in order from one axial side (the right side in FIGS. 1 to 3). Yes.
Of these, the spare shaft portion 31 is provided at one axial end portion of the inner shaft 9a. The outer peripheral surface of the preliminary shaft portion 31 is formed in a cylindrical surface shape that does not change over the entire length in the axial direction except for a chamfered portion formed at one end edge in the axial direction.

  The spline forming portion 32 is formed in a portion (an axially one side portion of the axially intermediate portion) from the axially intermediate portion of the inner shaft 9a to a portion closer to one end in the axial direction. One end edge in the axial direction of the spline forming portion 32 is continuous with the other end edge in the axial direction of the spare shaft portion 31 (left end edge in FIG. 1). On the outer peripheral surface of the spline forming portion 32, a male spline portion 37 composed of a plurality of concave portions 77 and convex portions 36, which are long in the axial direction and are alternately formed in the circumferential direction, is formed over the entire length. ing.

  The continuous portion 33 is formed in a portion of the inner shaft 9a adjacent to the other side in the axial direction of the spline forming portion 32. On the outer peripheral surface of such a continuous portion 33, a plurality of concave portions (not shown) alternately formed in the circumferential direction and a cross-sectional shape with respect to a virtual plane including the central axis of the inner shaft 9a is a right triangle shape. The incomplete spline part 39 which consists of this convex part 38 is formed. The outer peripheral surface of each convex portion 38 constituting such an incomplete spline portion 39 is inclined in a direction in which the outer diameter dimension becomes smaller toward the other axial direction. Further, one axial end edge of the outer peripheral surface of each convex portion 38 of the incomplete spline portion 39 is continuous with the other axial end edge of the outer peripheral surface of each convex portion 36 constituting the male spline portion 37. On the other hand, the other axial end edge of the outer peripheral surface of each convex portion 38 of the incomplete spline portion 39 is continuous with one axial end edge of the outer peripheral surface of the small diameter shaft portion 34a. In the case of this example, the diameter of the circumscribed circle of the concave portion 77 of the male spline portion 37 is equal to the diameter of the circumscribed circle of the concave portion of the incomplete spline portion 39.

  The small-diameter shaft portion 34a is formed from a position adjacent to the other axial side of the continuous portion 33 to a portion closer to the other axial end portion of the inner shaft 9a. One end edge in the axial direction of such a small diameter shaft portion 34 a is continuous with the other end edge in the axial direction of the continuous portion 33. The outer diameter dimension of the small-diameter shaft portion 34a is the diameter of the circumscribed circle of the concave portion 77 and the convex portion 36 constituting the male spline portion 37, and the concave portion and the convex portion 38 constituting the incomplete spline portion 39. It is smaller than the diameter of the circumscribed circle. Further, the outer peripheral surface of the small-diameter shaft portion 34a is constituted by the outer peripheral surface itself of a material to be described later (or a portion corresponding to the small-diameter shaft portion 34a in the first intermediate material 57). In other words, the outer peripheral surface of the small-diameter shaft portion 34a is not cut.

  The yoke portion 35 is provided integrally with the small diameter shaft portion 34a at the other axial end portion of the small diameter shaft portion 34a. In the case of this example, the front side of the universal joints 3c and 3d (see FIG. 5) is constituted by the yoke portion 35, the cross shaft 40, and the yoke 41 supported and fixed to the base end portion of the input shaft 6. The universal joint 3d arranged on the left side of 1 is configured.

Such a yoke portion 35 has a substantially rectangular plate-like base portion 42 and two axial positions on the outer peripheral surface of the base portion 42 which are opposite to the longitudinal direction of the base portion 42 (vertical direction in FIG. 3). It consists of a pair of arm parts 43 and 43 provided in the state extended to the side.
Of these, the base portion 42 is provided in a state where the central portion of one axial side surface is continuous with the other axial end surface of the small-diameter shaft portion 34a.

  In addition, a pair of circular holes 44, 44 are formed in a portion of the both arm portions 43, 43 near the end opposite to the base portion 42 with respect to the axial direction so that the central axes are coaxial. Yes. In addition, a pair of first relief recesses 45, 45 are formed at both ends of the arms 43, 43 on both side surfaces facing each other in the short direction (vertical direction in FIGS. 4 and 5), respectively. Yes. The first relief recesses 45, 45 are for securing a large joint angle. Further, a second relief recess 46 is formed at the tip of both arms 43, 43 facing each other (the end opposite to the base 42 and the left end in FIGS. 4 and 5). Is formed. Such a second relief recess 46 is for preventing interference between the cross shaft 40 and the arms 43, 43 when the cross shaft 40 is assembled to the circular holes 44, 44. is there.

  In the assembled state shown in FIG. 1, cylindrical cups 47 and 47 having bottoms are fitted and fixed inside the circular holes 44 and 44 of the arms 43 and 43, respectively. At the same time, a pair of shaft portions 49 of the four shaft portions 49, 49 constituting the cross shaft 40 are provided inside the bearing cups 47, 47 via a plurality of needles 48, 48, respectively. , 49 are rotatably supported.

  Of the four shaft portions 49, 49 constituting the cross shaft 40, a pair of shaft portions 49 other than the shaft portions 49, 49 supported in both the circular holes 44, 44 of the yoke portion 35 ( The end of one shaft portion 49 is not shown) inside a circular hole (not shown) formed in a pair of arm portions 51 (one arm portion 51 is not shown) constituting the yoke 50, It is rotatably supported via a bearing cup (not shown) and a needle (not shown).

In the case of this example, one end in the axial direction extends from one end edge in the axial direction of the inner shaft 9a to a position on the one side in the axial direction with respect to the other end edge in the axial direction of the male spline portion 37. A central hole 52 opened in one axial end surface of the shaft portion 31) is formed.
Specifically, the center hole 52 includes a cylindrical surface portion 53 and a conical surface portion 54.
Among these, the cylindrical surface portion 53 has a cylindrical surface shape whose inner diameter does not change over the entire length, and with respect to the axial direction, the shaft of the spline forming portion 32 extends from one axial end edge of the inner shaft 9a (the preliminary shaft portion 31). It is formed in a portion extending toward the other end in the direction. That is, the other end edge in the axial direction of the cylindrical surface portion 53 (the boundary between the cylindrical surface portion 53 and the conical surface portion 54) is one end edge in the axial direction of the continuous portion 33 (the male spline portion 37 and the continuous portion 33). It is a boundary and is located on one side in the axial direction from the position indicated by the straight line X in FIG. In addition, when the said center hole 52 is formed with the manufacturing method of this example mentioned later, the said conical surface part 54 may not be formed in perfect cone shape. Specifically, the radially outer end portion of the conical surface portion 54 may be formed in a spherical shape that follows the shape of the radially outer end portion of the other axial side surface of the mandrel 65 described later. In other words, the center hole is constituted by a cylindrical surface portion, a conical surface portion, and a spherical surface portion that is continuous with the other axial end edge of the cylindrical surface portion and the radially outer end edge of the conical surface portion. There is.

The conical surface portion 54 is formed such that one end edge in the axial direction is continuous with the other end edge in the axial direction of the cylindrical surface portion 53. Such a conical surface portion 54 is formed in a state in which the inner diameter dimension becomes smaller toward the other side in the axial direction. In the case of this example, the other end edge in the axial direction of the conical surface portion 54 is also one end edge in the axial direction of the continuous portion 33 (the boundary between the male spline portion 37 and the continuous portion 33; (Position indicated by X) is located on one side in the axial direction. Specifically, when the axial end edge of the conical surface portion 54, the length dimension in the axial direction of the spline forming section 32 (the male spline portion 37) was set to L _32, the spline forming section 32 ( from one axial end edge of the male spline section 37), disposed at a position which becomes (0.5~1.0) · _{L 32.} Preferably, the other axial end edge of the conical surface portion 54 is at a position where (0.7 to 0.9) · L ₃₂ from the axial one end edge of the spline forming portion 32 (the male spline portion 37). Deploy.
In the case of this example, portions of the inner shaft 9a other than the reference hole 55 formed in the central portion of the other side surface in the axial direction of the base hole 52 and the base portion 42 of the yoke portion 35 are formed in a solid shape. Has been.

  A coating layer 56 made of a synthetic resin that is slippery (having a low coefficient of friction) is provided on the outer peripheral surface of the male spline portion 37 constituting the inner shaft 9a. Specifically, in the case of this example, the coating layer 56 is a portion of the outer peripheral surface of the inner shaft 9a that is closer to one end in the axial direction of the small-diameter shaft portion 34a than one end edge in the axial direction of the auxiliary shaft portion 31 (see It is a portion located on the other side in the axial direction from the other end edge in the axial direction of the continuous portion 33, and is provided in a portion extending to a position indicated by a straight line Y in FIG. The coating layer 56 is not provided on one axial end surface of the inner shaft 9a (the preliminary shaft portion 31) and the inner peripheral surface of the center hole 52.

  The inner shaft 9a having the above-described configuration has the male spline portion 37 formed over the entire length, and is spline-engaged with the female spline portion 22 of the outer tube 10a via the coating layer 56. 10a. In this assembled state, a predetermined amount of tightening allowance is provided at the engaging portion between the male spline portion 37 and the female spline portion 22. In this manner, the inner shaft 9a and the outer tube 10a are combined in a state where torque can be transmitted and the entire length can be expanded and contracted.

Next, the manufacturing method of the inner shaft 9a which comprises the intermediate shaft 4a of this example is demonstrated, referring FIGS.
First, in the first step, a circular (cylindrical) material (illustrated) made of an iron-based alloy such as carbon steel (for example, S10C to S45C), or a light alloy such as an aluminum-based alloy or a magnesium alloy. The first intermediate material 57 as shown in FIG. 4A is manufactured by performing cold forging processing such as forward extrusion processing and backward extrusion processing, and press processing. In the case of this example, the material is constituted by a material obtained by cutting an extrusion molding material or a drawing material into a predetermined length.

The first intermediate material 57 as described above is a member corresponding to the intermediate material described in the claims, and is provided from one end portion in the axial direction (the right end portion in FIGS. 4 and 5) to a portion closer to the other end in the axial direction. And a raw yoke portion 59 provided at the other axial end portion.
Raw axis portion of this 58 is a solid cylindrical shape overall length over the outside diameter D ₅₈ in the axial direction does not change. Such a raw shaft portion 58 is formed by subjecting the portion corresponding to the raw shaft portion 58 of the material to the backward extrusion described above.

  The element yoke portion 59 is formed at the other axial end portion of the first intermediate material 57 by the above-described forward extrusion and pressing, and has a substantially disc-shaped base portion 42 and a pair. It comprises a bare arm portion 60 (one bare arm portion 60 is not shown). Both the bare arm portions 60 are provided so as to extend from two positions on the outer circumferential surface of the base portion 42 on the opposite side in the diameter direction of the base portion 42 to the other side in the axial direction. Further, a pair of first relief recesses 45, 45 are formed at the ends in the short direction (vertical direction in FIGS. 4 and 5) of the opposite side surfaces of the both arm portions 60, respectively. Further, a second relief recess 46 is formed at the front end portions of both the opposite side surfaces of the both arm portions 60 (the end portion opposite to the base portion 42 and the left end portion in FIGS. 4 and 5). Has been.

  Further, the reference hole 55 is formed in the central portion of the other side surface in the axial direction of the base portion 42. Such a reference hole 55 is formed by drilling after the first step, but the reference hole 55 may be omitted.

Next, in the second step, an elementary center hole (lower hole) 61 is formed by drilling one end surface of the first intermediate material 57 in the axial direction, as shown in FIG. Such a second intermediate material 62 is used. The element center hole 61 includes a cylindrical surface portion 63 and a conical surface portion 64.
Of these, the cylindrical surface portion 63 is formed in a state having a predetermined length from one end surface in the axial direction of the first intermediate material 57 with respect to the axial direction without changing the inner diameter dimension over the entire length.
The conical surface portion 64 is formed such that one end edge in the axial direction is continuous with the other end edge in the axial direction of the cylindrical surface portion 63. Such a conical surface portion 64 is formed in such a state that the inner diameter dimension becomes smaller toward the other side in the axial direction.

Next, in a third step, a mandrel 65 is inserted into the inner diameter side of the elementary center hole 61 of the second intermediate material 62, and the inner peripheral surface of the elementary center hole 61 is handled by the mandrel 65. Then, as the mandrel 65 is displaced toward the other side in the axial direction, the inner diameter of the element center hole 61 is expanded (expanded), and the center hole 52 is formed.
On the other hand, with the displacement of the mandrel 65 to the other side in the axial direction, the outer diameter of the portion of the outer peripheral surface of the second intermediate material 62 that aligns with the element center hole 61 in the axial direction increases (expands). ), An enlarged diameter portion 67 (spline forming portion 32) is formed.
In this way, the third intermediate material 66 as shown in FIG.

Outer diameter D ₆₇ of the enlarged diameter portion 67, wherein the element yoke portion 59 of the third portion from the axially intermediate portion toward the one axial end portion of the intermediate material 66 (the third intermediate material 66 is formed and excluding the portion) of the portion, larger than the outer diameter _{D 58} of the portions other than the enlarged diameter portion _{67 (D 67> D 58)} . Of the other axial end portion of the enlarged diameter portion 67, the portion where the incomplete spline portion 39 is formed (the other axial end portion of the enlarged diameter portion 67) is more outwardly directed toward the other axial side. It is formed in the shape of an inclined surface with a reduced diameter. Further, the other axial portion of the raw shaft portion 58 in the axial direction from the enlarged diameter portion 67 becomes the small diameter shaft portion 34a of the inner shaft 9a. In other words, in the case of this example, the other-diameter portion of the raw shaft portion 58 in the axial direction relative to the enlarged-diameter portion 67 is not subjected to cutting, so that the small-diameter shaft portion 34a is formed.

The mandrel 65 includes a handling part 68 and a shaft part 69.
Of these, the handling portion 68 is a substantially disk-shaped member whose both axial side surfaces are partially spherical and whose axial center portion of the outer peripheral surface is cylindrical.
The other end of the shaft portion 69 is coupled and fixed to one side surface of the handling portion 68 in the axial direction.
In such a mandrel 65, the handling portion 68 is inserted into one end opening in the axial direction of the element center hole 61, and a portion closer to the outer diameter side of the other axial side surface of the handling portion 68 and the outer periphery of the handling portion 68. With the surface, the handling portion 68 is inserted until it is located at the other axial end of the cylindrical surface portion 63 of the elementary center hole 61 while handling the inner peripheral surface of the elementary center hole 61.

In the third step as described above, when the inner peripheral surface of the element center hole 61 is handled by the handling portion 68, the other side surface in the axial direction of the handling portion 68 has a spherical shape. When the handling portion 68 is displaced in the other axial direction, the inner peripheral surface of the element center hole 61 is pressed radially outward and in the other axial direction. Therefore, when the handling portion 68 is displaced in the other axial direction, the diameter of the other axial side portion of the outer peripheral surface of the second intermediate material 62 is also larger than that of the handling portion 68. In particular, in the third step, an outer mold (not shown) whose inner peripheral surface is cylindrical is formed on the outer diameter side of the portion from the axial intermediate portion to the axial one end portion of the second intermediate material 62. When arranged, the metallic material constituting the portion existing around the element center hole 61 whose displacement (flow) to the outer diameter side is regulated by the inner peripheral surface of the outer mold is moved to the other side in the axial direction. And can easily flow. For this reason, it is possible to easily expand the diameter of the other axial side portion of the outer peripheral surface of the second intermediate material 62 rather than the handling portion 68.
In this way, when the handling portion 68 is displaced in the other axial direction, the diameter of the outer peripheral surface of the second intermediate material 62 is also enlarged by increasing the diameter of the other side in the axial direction relative to the handling portion 68. When the length dimension in the axial direction of the portion 67 is L ₆₇ (L ₆₇ = L ₃₂ ), the other axial end edge of the conical surface portion 54 of the center hole 52 is connected to the male portion of the enlarged diameter portion 67. From one end edge in the axial direction of the portion where the spline portion 37 is formed (the portion excluding the portion where the preliminary shaft portion 31 and the incomplete spline portion 39 are formed in the enlarged diameter portion 67) (from 0.5 to 1.0) · L ₃₂ {preferably (0.7 to 0.9) · L ₆₇ }.

  Next, in a fourth step, by cutting the outer peripheral surface of the enlarged diameter portion 67 of the third intermediate material 66, the outer diameter dimension of the enlarged diameter portion 67 is a rolling lower diameter (press lower diameter). ) Is a fourth intermediate material 71 as shown in FIG. 4D. However, the portion corresponding to the small diameter shaft portion 34a in the third intermediate material 66 is not cut. It is also possible to proceed to the next step without cutting the outer peripheral surface of the enlarged diameter portion 67 of the third intermediate material 66.

Next, in the fifth step, the outer peripheral surface of the final enlarged diameter portion 70 of the fourth intermediate material 71 is alternately arranged with concave and convex portions in the circumferential direction by rolling or press molding. The male spline portion 37, which is an uneven portion, is formed. In addition, when rolling or press-molding the final diameter-expanded portion 70, the support shaft 72 is inserted into the inner peripheral surface of the final diameter-expanded portion 70 (inside the center hole 52). By providing the support shaft 72, the rolling or pressing can be performed in a state where the rigidity in the radial direction of the final enlarged diameter portion 70 is constant (or substantially constant) over the entire length. As a result, the properties of the male spline portion 37 (the height of the convex portion, the depth of the concave portion, etc.) can be formed constant (or substantially constant) in the axial direction. In the fifth step, the incomplete spline portion 39 is formed together with the male spline portion 37.
Further, the outer peripheral surface of the fourth intermediate material 71 after the male spline portion 37 is formed is subjected to a cutting process to adjust the shape (outer diameter) of the outer peripheral surface. Thus, the preliminary shaft portion 31 is formed. Then, a fifth intermediate material 73 as shown in FIG.

  In the third step described above, a configuration in which a cylindrical outer mold (not shown) is disposed on the outer diameter side of the portion from the axial intermediate portion to one axial end portion of the second intermediate material 62 is adopted. In this case, the outer mold having a female spline portion having a shape along the shape of the male spline portion 37 on the inner peripheral surface may be employed. In the case of adopting such an outer mold, the mandrel 65 is inserted into the inner diameter side of the element center hole 61 of the second intermediate material 62 and at the same time the outer peripheral surface of the second intermediate material 62. The male spline portion 37 can be formed (rolled) by pressing the outer peripheral surface of the portion whose diameter is increased by insertion against the outer female spline portion. That is, when such a configuration is adopted, the process of making the fifth intermediate material 73 from the second intermediate material 62 shown in FIG. 4C can be performed in one process.

  Next, in a sixth step, the circular arm 44 is formed by drilling the bare arm portion 60 constituting the elementary yoke portion 59 to form the inner hole as shown in FIG. The shaft 9a. Note that the sixth step can be performed at any point in time from after the first step to before the fifth step.

Next, in a seventh step, a portion of the outer peripheral surface of the inner shaft 9a extending from one axial end edge of the inner shaft 9a (preliminary shaft portion 31) to the other axial side of the male spline portion 37. Then, a rough coating layer 74 is formed.
A method of forming the rough coating layer 74 will be described with reference to FIG.
First, as shown in FIG. 6A, a rectangular parallelepiped holding jig 75 made of, for example, a magnet is provided on the axial end end surface {the lower end surface of FIG. 6A) of the inner shaft 9a. It fixes so that the opening part of one axial direction may be closed. As the structure of the holding jig 75, various structures such as a cylindrical shape and a polygonal column shape can be adopted as long as the axial end opening of the center hole 52 can be closed.

Next, the inner shaft 9a to which the holding jig 75 is fixed as described above is immersed in a molten synthetic resin 76 as shown in FIG. 6B by a predetermined length from one side in the axial direction. By (dipping), a rough coating layer 74 as shown in FIG. 6C is formed. Specifically, in the case of this example, a portion of the inner shaft 9a extending from one end edge in the axial direction of the spare shaft portion 31 to the other side in the axial direction from the male spline portion 37 is placed in the synthetic resin. The rough coating layer 74 is formed in the portion by dipping.
The rough coating layer 74 formed in this way is formed in a continuous state in the axial direction and the circumferential direction.
As a method of forming the rough coating layer 74, for example, a fluid dipping method, an electrostatic coating method, or the like can be employed.

Finally, the coating layer 56 is formed by shaving the rough coating layer 74.
Such a shaving process is performed, for example, inside a cylindrical shaving mold (shaving cutter) having an inner peripheral surface shape along an outer peripheral surface of a portion covering the male spline portion 37 in the coating layer 56. By inserting a portion of the inner shaft 9a where the rough coating layer 74 is formed, a portion of the rough coating layer 74 near the outer end in the radial direction of the portion covering the male spline portion 37 is scraped off.
In the shaving process, the holding jig 75 may be removed and the center hole 52 may be used for centering (operation for aligning the center axes of the shaving cutter and the inner shaft 9a). it can.
In addition, each process which comprises the manufacturing method of the male shaft for telescopic shafts of this example as mentioned above can be implemented by changing the order in a range where no contradiction occurs. Each of these steps can be performed simultaneously as far as possible.

According to the intermediate shaft 4a of the present example having the above-described configuration, the rotation direction of the engaging portion between the male spline portion 37 of the inner shaft 9a and the female spline portion 22 of the outer tube 10a is rattled. Even when a structure that can be kept small is adopted, the sliding resistance between the inner shaft 9a and the outer tube 10a can be kept small.
That is, in the case of this example, the center hole 52 is formed in the inner shaft 9a.
Then, the position of the axial end edge of said central hole 52, the length in the axial direction of the spline forming section 32 (the male spline section 37) in the case of the L _32, the spline forming section 32 (the from one axial end edge of the male spline section _{37), (0.5~1.0) · L} 32 { preferably, (0.7~0.9) · _{L 32}} are arranged in positions to be. For this reason, the rigidity in the radial direction of the spline forming portion 32 (the male spline portion 37) can be appropriately reduced. As a result, in order to prevent rattling in the rotational direction of the engagement portion between the male spline portion 37 and the female spline portion 22 of the outer tube 10a, a structure in which the engagement portion has a tightening margin is employed. Even in this case, the sliding resistance (sliding load) with respect to the tightening allowance can be reduced. Further, the fluctuation of the sliding resistance (sliding load) becomes insensitive, and the sliding of the inner shaft 9a with respect to the outer tube 10a can be stabilized. Furthermore, even when a large range (dimensional tolerance) in which the error of the inner shaft 9a can be tolerated is ensured, it is possible to prevent the sliding resistance from increasing due to the influence of the dimensional tolerance. Therefore, the manufacturing cost of the inner shaft 9a and the outer tube 10a can be reduced.

  In the case of this example, the spare shaft portion 31 is provided at one axial end portion of the inner shaft 9a. For this reason, when the rough coating layer 74 is formed on the inner shaft 9a by the method as described above, the rough coating layer 74 is formed continuously over the entire circumference of the outer peripheral surface of the spare shaft portion 31. it can. For this reason, after the rough coating layer 74 is formed, when the restraining jig 75 is removed from one axial end surface of the inner shaft 9a, it is pulled by the restraining jig 75 and the axial direction of the rough coating layer 74 is reached. It is possible to prevent the male spline portion 37 from being exposed by turning one end edge. Furthermore, even when the inner shaft 9a and the outer tube 10a slide during use, it is possible to prevent the one end edge in the axial direction of the coating layer 56 from turning over.

  In the case of this example, the other axial end edge of the conical surface portion 54 of the center hole 52 is the same as the other axial end edge of the spline forming portion 32 (the male spline portion 37) or the spline forming portion 32. It arrange | positions in the axial direction one side rather than the axial direction other end edge of (the said male spline part 37). For this reason, it is possible to ensure the rigidity of a portion where stress is easily concentrated, such as a boundary portion between the continuous portion 33 and the small-diameter shaft portion 34a of the inner shaft 9a. As a result, the durability of the inner shaft 9a can be improved.

  In the case of this example, the inner shaft 9a employs a structure in which the yoke portion 35 is integrally provided at the other axial end of the small diameter shaft portion 34a. For this reason, it is possible to reduce the number of parts and prevent troublesome parts management and assembly work.

  Further, in the case of the manufacturing method of this example, the portion corresponding to the spline forming portion 32 (the male spline portion 37) is inserted into the mandrel in the elementary center hole 61 of the second intermediate material 62 as in the third step. It is formed by inserting 65 and expanding the diameter. That is, a portion having a different outer diameter, such as a portion corresponding to the small-diameter shaft portion 34a and a portion corresponding to the spline forming portion 32 (the male spline portion 37), is formed without cutting. Can do. As a result, it is possible to reduce the processing cost (shortening the processing time) and the material cost, thereby reducing the manufacturing cost.

Further, as described above, since the portion corresponding to the small diameter shaft portion 34 a is not formed by cutting, the outer peripheral surface of the small diameter shaft portion 34 a is used as the outer peripheral surface of the raw shaft portion 58 of the first intermediate material 57. It can be configured by itself. The outer peripheral surface of such a small-diameter shaft portion 34a has a sufficiently low surface roughness, and scratches generated on the surface are also long scratches in the axial direction that do not lead to breakage or the like. On the other hand, in the case of forming by cutting, there is a possibility that circumferential cutting traces having variations in depth may occur, and the deep cutting traces of the cutting traces are bent to the small diameter shaft portion 34a. When stress or the like acts, it tends to be a starting point of stress concentration. By performing a finishing process such as a grinding process, such a cutting mark can be erased, but the processing cost increases.
In this way, in the case of this example, since the small-diameter shaft portion 34a is formed without being subjected to cutting processing, the inner shaft 9a is less likely to be scratched as a starting point of stress concentration as described above. It is possible to ensure sufficient bending rigidity. As a result, it is possible to prevent the inner shaft 9a from being broken and losing its function as a steering device.

In one example of the above-described embodiment, the present invention has been described with respect to an example in which the present invention is applied to an inner shaft constituting an intermediate shaft constituting a steering device. However, the present invention can be applied to the structure of a telescopic shaft used for various purposes other than such an inner shaft.
Moreover, when implementing this invention, each process which comprises the manufacturing method of the male shaft for telescopic shafts can be changed order in the range which does not produce inconsistency. Each of these steps can be performed simultaneously as far as possible.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3a, 3b, 3c, 3d Universal joint 4, 4a Intermediate shaft 5 Steering gear unit 6 Input shaft 7 Tie rod
8 Male spline part 9, 9a Inner shaft
10, 10a Outer tube 11 First yoke 12 Female spline portion 13 Second yoke 14 Cross shaft 15 Yoke 16 Cross shaft 17 Yoke 18 Small diameter cylindrical portion 19 Continuous portion 20 Large diameter cylindrical portion 21 Yoke portion 22 Female spline portion 23 Arm Part 24 circular hole 25 bearing cup 26 needle 27 cross shaft 28 shaft part 29 yoke 30 arm part 31 spare shaft part 32 spline forming part 33 continuous part 34, 34a small diameter shaft part 35 yoke part 36 convex part 37 male spline part 38 convex part 39 Incomplete spline portion 40 Cross shaft 41 Yoke 42 Base portion 43 Arm portion 44 Circular hole 45 First relief recess 46 Second relief recess 47 Bearing cup 48 Needle 49 Shaft portion 50 Yoke 51 Arm portion 52 Center hole
53 cylindrical surface portion 54 conical surface portion 55 reference hole 56 coating layer 57 first intermediate material 58 bare shaft portion 59 elementary yoke portion 60 bare arm portion 61 elementary center hole 62 second intermediate material 63 cylindrical surface portion 64 conical surface portion 65 mandrel 66 third intermediate Material 67 Expanded portion 68 Handling portion 69 Shaft portion 70 Final expanded portion 71 Fourth intermediate material 72 Support shaft 73 Fifth intermediate material 74 Coarse coating layer 75 Holding jig 76 Synthetic resin 77 Concavity

Claims (4)

A male spline portion formed on the outer peripheral surface of one end portion in the axial direction, and formed on the other side in the axial direction from the male spline portion, the outer diameter being larger than the diameter of the circumscribed circle of each convex portion of the male spline portion A small-diameter shaft portion, a yoke portion integrally provided at the other axial end portion of the small-diameter shaft portion, and a central hole having one axial end opening at one axial end surface, By engaging the spline part with the female spline part formed on the inner peripheral surface of the female shaft, torque can be transmitted between the female shaft and the male for a telescopic shaft combined with the full length of the female shaft. A method of manufacturing a shaft,
A step of making an intermediate material having a cylindrical raw shaft portion whose outer diameter does not change over the entire length in a portion from one end portion in the axial direction to a portion closer to the other end in the axial direction;
By drilling the intermediate material, one end in the axial direction is opened on one end surface in the axial direction of the intermediate material, and the inner diameter is smaller than the inner diameter of the central hole, forming a center hole,
Forming the center hole by expanding the inner diameter of the element center hole, and forming the expanded portion by expanding the outer diameter of the portion where the element center hole is formed;
Forming the male spline part on the outer peripheral surface of the enlarged diameter part,
Of the raw shaft portion, at least a part of the portion excluding the enlarged diameter portion is directly used as the small diameter shaft portion.
Manufacturing method of male shaft for telescopic shaft.   The method for manufacturing a male shaft for a telescopic shaft according to claim 1, wherein a male spline portion is formed on an outer peripheral surface of the enlarged diameter portion in a state where a support shaft is inserted inside the center hole.   The said male spline part WHEREIN: The diameter of the circumscribed circle of each recessed part of the said male spline part is made larger than the outer diameter of the said bare shaft part, It described in any one of Claims 1-2 Manufacturing method of male shaft for telescopic shaft.   The male shaft for a telescopic shaft according to any one of claims 1 to 3, further comprising a step of forming a coating layer on an outer peripheral surface of the male spline portion in a state where the opening of the center hole is closed. Manufacturing method.

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