JP2017145945A - Telescopic shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a structure capable of stably sliding an inner shaft and an outer tube even in applying a structure for reducing backlash of a male spline portion and a female spline portion, and further securing rigidity of a connecting portion between the male spline portion and a small diameter shaft portion of the inner shaft.SOLUTION: A large diameter hole portion 42, an intermediate diameter hole portion 43 having an inner diameter dimension smaller than an inner diameter dimension of the large diameter hole portion 42, and a small diameter hole portion 16a having an inner diameter dimension smaller than the inner diameter dimension of the intermediate diameter hole portion 43 are successively formed from an axial one side of an inner peripheral face of a part on which a male spline portion 8b is formed, of an inner shaft 9b. A second connection step portion 69 between the intermediate diameter hole portion 43 and the small diameter hole portion 16a is disposed at an axial one side with respect to an outer peripheral face of a connecting portion 21a. Thus an inward projecting portion 70 projecting radially inward is formed over the whole periphery at the axial other end portion of an inner peripheral face of the male spline portion 8b.SELECTED DRAWING: Figure 1

Description

  The telescopic shaft according to the present invention is used as, for example, an intermediate shaft that constitutes an automobile steering device.

  2. Description of the Related Art Conventionally, an automobile steering apparatus having a structure as shown in FIG. 6 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. 7 shows the structure of the telescopic intermediate shaft 4 described in Patent Document 1. The intermediate shaft 4 includes an inner shaft 9 in which a male spline portion 8 is formed on the outer peripheral surface of one axial end portion (the front end portion and the left end portion in FIG. 7; the end portion on the outer tube 10 side in the assembled state). And a circular outer tube 10 having a male spline portion 8 and a female spline portion 12 that can be spline-engaged with each other. 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. 7, 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.

  Like the intermediate shaft 4 having the above-described configuration, the telescopic shaft in which the inner shaft 9 and the outer tube 10 can transmit torque and can be expanded and contracted (slidable) in the axial direction has a rotational direction. It is required that the rattling is small and the sliding resistance during expansion and contraction is small. Therefore, conventionally, a coating layer made of a synthetic resin having a low friction coefficient such as polyamide resin is provided on the outer peripheral surface of the male spline portion 8 of the inner shaft 9, and the male spline portion 8 and the female spline portion 12 are provided. Are engaged with each other with a tightening margin. However, in the case of such a structure, if the rigidity in the radial direction of the inner shaft 9 where the coating layer is provided is high, the variation in sliding resistance (sliding load) with respect to the tightening margin becomes sensitive. Therefore, it may be difficult to stabilize the sliding of the inner shaft 9 with respect to the outer tube 10. Such a problem becomes more prominent as the tightening margin is increased in order to sufficiently suppress the rattling.

  FIG. 8 shows the structure of the intermediate shaft 4a described in Patent Document 2. In the case of this intermediate shaft 4a, a large-diameter hole portion 14, a medium-diameter hole portion 15, and a small-diameter hole portion 16 are formed on the inner peripheral surface of the hollow inner shaft 9a from the one end side in the axial direction. A portion corresponding to the large-diameter hole portion 14 in the inner shaft 9a is a thin-walled portion 17 having a small thickness dimension in the radial direction, and a portion corresponding to the medium-diameter hole portion 15 is also related to the radial direction. A thickness portion 18 having a thickness dimension larger than that of the thin-walled portion 17 is used, and a portion corresponding to the small-diameter hole portion 16 is also defined as a thick-walled portion 19 having a thickness dimension in the radial direction larger than that of the middle-walled portion 18. . In this way, the rigidity in the radial direction of the portion of the inner shaft 9a where the male spline portion 8a is formed is lowered. According to the invention described in Patent Document 2 as described above, it is possible to prevent a variation in sliding resistance (sliding load) of the inner shaft 9a with respect to the outer tube 10a from becoming sensitive, and thus the outer tube 10a with respect to the outer tube 10a. It is possible to stabilize the sliding of the inner shaft 9a. However, in the case of the invention described in Patent Document 2, the position of the other end edge in the axial direction (the right end edge in FIG. 8) of the inner wall part 18 (the inner diameter hole part 15) in the axial direction is the male spline part 8a. Is located on the other side in the axial direction with respect to the continuous portion 21 existing between the one end edge in the axial direction and the small-diameter shaft portion 20 on the other side in the axial direction with respect to the male spline portion 8a. Such a boundary portion between the continuous portion 21 and the small-diameter shaft portion 20 is a portion where stress is easily concentrated as compared with other portions, and there is room for improvement in terms of securing rigidity.

JP 2015-21596 A JP-A-2015-180837

  In view of the circumstances as described above, the present invention also adopts a structure that can suppress the backlash in the rotational direction of the engaging portion between the male spline portion of the inner shaft and the female spline portion of the outer tube. Realizes a structure that can stably slide the inner shaft and the outer tube, and can secure the rigidity of the continuous part that exists between the male spline part and the small-diameter shaft part of the inner shaft. To do.

The telescopic shaft of the present invention includes an inner shaft, an outer tube, and a coating layer.
Of these, the inner shaft is provided on a male spline portion formed on the outer peripheral surface of one end portion in the axial direction, and on the other side portion in the axial direction from the male spline portion, and the outer diameter dimension is a circumscribed circle of the male spline portion. This is a hollow member having a small-diameter shaft portion smaller than the diameter.
The outer tube has a female spline portion formed on the inner peripheral surface.
The said coating layer is provided in the state which covers the outer peripheral surface of the said male spline part.
Then, the inner shaft and the outer tube can transmit torque and can be extended and contracted by engaging the male spline portion and the female spline portion through the coating layer. It is combined.

In particular, in the telescopic shaft of the present invention, the portion of the inner shaft where the male spline portion is formed is provided on the other side in the axial direction with respect to the thin portion provided at one axial end portion. And a thick part having an inner diameter smaller than the inner diameter of the thin part.
Further, the inner peripheral surface of the inner shaft includes a large-diameter hole portion formed in the inner peripheral surface of the thin-walled portion, a medium-diameter hole portion formed on the other side in the axial direction from the large-diameter hole portion, And a small-diameter hole formed on the other side in the axial direction than the medium-diameter hole.
And the continuous step part which exists between the said medium diameter hole part and the said small diameter hole part is an axial direction one side rather than the outer peripheral surface of the continuous part which exists between the said male spline part and the said small diameter shaft part. By being positioned, an inwardly projecting portion projecting radially inward over the entire circumference is formed at the other axial end portion of the inner peripheral surface of the male spline portion.

  When the telescopic shaft of the present invention as described above is implemented, additionally, in the range of the telescopic stroke between the inner shaft and the outer tube in use, as in the invention described in claim 2. It is possible to adopt a configuration in which at least a part of the male spline portion formed on the outer peripheral surface of the thick portion and the female spline portion of the outer tube are always in spline engagement.

When the telescopic shaft of the present invention as described above is implemented, the cross-sectional area of the thick part and the cross-sectional area of the small-diameter shaft part are additionally provided as in the invention described in claim 3. The same configuration can be adopted.
When the telescopic shaft according to the present invention as described above is implemented, additionally, as in the invention described in claim 4, the yoke portion is outwardly provided at the other axial end portion of the inner shaft. A configuration in which the flange portion is coupled and fixed to the inner shaft can be employed.

  In the case of the telescopic shaft of the present invention having the above-described configuration, the coating layer is provided so as to cover the outer peripheral surface of the male spline portion of the inner shaft. Along with this, a thin portion and a thick portion are provided in order from one side in the axial direction in a portion corresponding to the male spline portion of the hollow inner shaft. For this reason, the rigidity in the radial direction of the entire portion where the male spline portion of the inner shaft is formed can be made smaller than in the case of a solid inner shaft. In particular, the rigidity in the radial direction of the portion corresponding to the thin portion of the portion where the male spline portion of the inner shaft is formed may be lower than the rigidity in the radial direction of the portion corresponding to the thick portion. it can. Therefore, in order to prevent rattling in the rotational direction of the engagement portion between the male spline portion of the inner shaft and the female spline portion of the outer tube, even if this engagement portion is provided with a tightening allowance, Variations in sliding resistance (sliding load) with respect to the margin can be made insensitive, and sliding of the inner shaft relative to the outer tube can be stabilized.

  In the case of the present invention, the continuous step portion existing between the medium-diameter hole portion and the small-diameter hole portion is more axial than the outer peripheral surface of the continuous portion existing between the male spline portion and the small-diameter shaft portion. By being positioned on one side, an inwardly projecting portion projecting radially inward over the entire circumference is formed at the other axial end portion of the inner peripheral surface of the male spline portion. For this reason, the thickness dimension in the radial direction of a portion where stress tends to concentrate, such as the boundary portion between the continuous portion of the inner shaft and the small-diameter shaft portion, is secured, and the rigidity of the portion is secured. I can do things. As a result, the durability of the inner shaft can be improved.

The partial cutaway side view which shows the intermediate shaft which attached the 10 axis | shaft universal joint to the both ends which shows the 1st example of embodiment of this invention. Similarly, sectional drawing which shows the inner shaft before fixing a yoke part. Similarly, the partial perspective view of an inner shaft. The figure similar to FIG. 1 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 1 which shows the 3rd example of embodiment of this invention. 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. The partial cross section figure regarding a spline engaging part which shows the structure of another example of the intermediate shaft of conventional structure.

[First example of embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. In this example, the present invention is applied to an intermediate shaft constituting a steering device. However, the present invention can be applied to a structure of a telescopic shaft used for various purposes other than such an intermediate shaft. Further, the structure of the steering apparatus incorporating the intermediate shaft 4b of this example has the same structure as the steering apparatus shown in FIG. However, the intermediate shaft 4b of this example is not limited to the structure of the steering apparatus shown in FIG. 6, but can be incorporated in various conventionally known steering apparatuses. Hereinafter, after briefly explaining the structure of the steering device, the structure of the intermediate shaft 4b of this example will be described.

  In the steering apparatus incorporating the intermediate shaft 4b of this example, the steering wheel 1 (see FIG. 6) 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 4b. . Furthermore, 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 4b has one axial end portion of the inner shaft 9b corresponding to one example of the inner shaft described in the claims (the right end portion in FIG. 1 and the outer tube 10b side in the assembled state). And the other axial end portion of the outer tube 10b corresponding to one example of the outer tube (the left end portion in FIG. 1 and the end portion on the inner shaft 9b 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 4b will be described.

The outer tube 10b includes a small-diameter cylindrical portion 22, a continuous portion 23, a large-diameter cylindrical portion 24, and a yoke portion 25 in order from the other axial side.
Of these, the small-diameter cylindrical portion 22 has a cylindrical shape, and is provided in a portion of the outer tube 10b extending from the other axial end portion to the axial intermediate portion. The outer peripheral surface of such a small diameter cylindrical portion 22 has a cylindrical surface shape whose outer diameter dimension does not change over the entire axial length. On the inner peripheral surface of the small-diameter cylindrical portion 22, a female spline portion 26 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. In the case of this example, the thickness dimension of the small diameter cylindrical portion 22 is the same over the entire length in the axial direction.

The continuous portion 23 has a partial conical cylindrical shape in which the outer diameter dimension and the inner diameter dimension increase toward one side in the axial direction (the right side in FIG. 1), and the other end edge in the axial direction is the axial direction of the small diameter cylindrical part 22. It is continuous to one edge.
The large-diameter cylindrical portion 24 has a cylindrical shape, and the other axial end edge is continuous with the one axial end edge of the continuous portion 23. The inner diameter dimension and the outer diameter dimension of such a large diameter cylindrical portion 24 are larger than the inner diameter dimension and the outer diameter dimension of the small diameter cylindrical portion 22.

  The yoke portion 25 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 24 on the opposite side in the diameter direction with respect to the large-diameter cylindrical portion 24. It consists of a pair of arm portions 27 and 27 provided in a state extending in one direction. A pair of circular holes 28 and 28 are formed in a portion near both ends in the axial direction of both the arm portions 27 and 27 in such a manner that the central axes of the arms 27 and 27 are coaxial. In the assembled state shown in FIG. 1, bottomed cylindrical bearing cups 29 and 29 are fitted and fixed inside the pair of circular holes 28 and 28, respectively. At the same time, a pair of shaft portions 32 of the four shaft portions 32, 32 constituting the cross shaft 31 are provided inside the bearing cups 29, 29 via a plurality of needles 30, 30 respectively. The end part of 32 is supported rotatably.

Of the four shaft portions 32, 32 constituting the cross shaft 31, a pair of shaft portions 32 other than the shaft portions 32, 32 supported in the circular holes 28, 28 of the yoke portion 25 ( The ends of one shaft portion 32 are not shown) and are formed on a pair of arm portions 34 (one arm portion 34 is not shown) constituting a yoke 33 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 25 is provided integrally with the outer tube 10b 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 9b is hollow and includes a spline forming portion 35, a continuous portion 21a, a small-diameter shaft portion 20a, and a yoke portion 36 in order from one axial side (the right side in FIGS. 1 and 2). ing.
Among these, the spline formation part 35 is provided in the part from the axial direction intermediate part of the said inner shaft 9b to a part near an axial direction one end. On the outer peripheral surface of such a spline forming portion 35, a male spline portion 8b comprising a plurality of concave portions 37, 37 and convex portions 38, 38 which are long in the axial direction and are alternately formed with respect to the circumferential direction, Is formed.

A large-diameter hole portion 42 is formed in the inner peripheral surface of the spline forming portion 35 from the axially intermediate portion to one axial end portion. The inner diameter of such a large-diameter hole portion 42 is constant over the entire length in the axial direction.
Further, in the inner peripheral surface of the spline forming portion 35, a portion from the axially intermediate portion to the other axial end portion has a medium diameter hole portion whose inner diameter dimension is smaller than the inner diameter dimension of the large diameter hole portion 42. 43 is formed. The inner diameter dimension of the medium diameter hole portion 43 is constant over the entire length in the axial direction.
Further, the other end portion in the axial direction of the inner peripheral surface of the spline forming portion 35 (the portion located on the other side in the axial direction with respect to the medium diameter hole portion 43) has an inner diameter dimension. A small-diameter hole 16a smaller than the size is formed.

The other end edge in the axial direction of the large-diameter hole portion 42 and the one end edge in the axial direction of the medium-diameter hole portion 43 are continuous by the first continuous step portion 44.
The other end in the axial direction of the medium diameter hole 43 and the one end in the axial direction of the small diameter hole 16a are formed by a second continuous step 69 corresponding to the continuous step described in the claims. It is continuous. In the case of this example, the second continuous step portion 69 is located on one side in the axial direction from the outer peripheral surface of the continuous portion 21a. Further, the first continuous step portion 44 and the second continuous step portion 69 are formed in a state of being inclined in a direction toward one axial direction as going outward in the radial direction. In addition, a 1st continuous step part or a 2nd continuous step part can also be provided on the virtual plane orthogonal to the central axis of the said inner shaft 9b. Further, the first continuous step portion 44 and the second continuous step portion 69 can be formed in a partial spherical shape. In other words, specifically, the cross-sectional shape of the first continuous step portion 44 and the second continuous step portion 69 with respect to a virtual plane including the central axis of the inner shaft 9b is an arc shape. To do. When such a configuration is adopted, the curvature radius R of the cross-sectional shape of the first continuous step portion 44 and the second continuous step portion 69 with respect to the virtual plane is 0.2 mm or more (preferably 0 0.5 mm or more). By adopting such a configuration, it is possible to prevent stress concentration from occurring in the first continuous step portion 44 and the second continuous step portion 69.

  Further, a portion corresponding to the large-diameter hole portion 42 in the spline forming portion 35 is a thin portion 45. On the other hand, in the spline forming portion 35, the portion corresponding to the medium diameter hole portion 43 and the small diameter hole portion 16a has a thickness dimension in the radial direction larger than a thickness dimension in the radial direction of the thin portion 45. The thick portion 46 is used. In the case of this example, on the inner peripheral surface of the other axial end portion of the thick portion 46 (spline forming portion 35), the inner periphery of the thick portion 46 is more radially inward than the intermediate portion in the axial direction. A projecting inward projecting portion 70 is formed. In this way, the thickness dimension in the radial direction of the portion where the inwardly projecting portion 70 is formed in the thick portion 46 is set to the other portion of the thick portion 46 (this inwardly projecting portion 70). It is made larger than the radial thickness dimension of the portion where no is formed.

Further, the cross-sectional area of the thin portion 45 with respect to the virtual plane perpendicular to the central axis of the inner shaft 9b is smaller than the cross-sectional area of the thick portion 46 with respect to the virtual plane.
Further, in the present example, the other axial end edge of the thin portion 45, the length in the axial direction of the spline forming section 35 (the male spline portion 8b) when the L _35, the spline forming section 35 (the male spline portion 8b) is disposed at a position of (0.6 to 0.9) · L ₃₅ from one end edge in the axial direction.

  In addition, the cross-sectional area of the portion of the thick portion 46 where the inwardly projecting portion 70 is formed is related to the virtual plane in the other portion of the thick portion 46 (this inwardly projecting portion 70 is formed). Larger than the cross-sectional area of the virtual plane).

  The continuous portion 21a is formed in a portion of the inner shaft 9b adjacent to the other side in the axial direction of the spline forming portion 35. On the outer peripheral surface of such a continuous portion 21a, a plurality of concave portions 39, 39 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 9b have a right triangle shape. The incomplete spline part 41 which consists of the convex parts 40 and 40 is formed. The outer peripheral surface of each convex part 40 which comprises such an incomplete spline part 41 inclines in the direction where an outer diameter dimension becomes small, so that it goes to the other axial direction. Further, one axial end edge of the outer peripheral surface of each convex portion 40, 40 of the incomplete spline portion 41 is continuous with the other axial end edge of the outer peripheral surface of each convex portion 40, 40 constituting the male spline portion 8b. doing. On the other hand, the other axial end edge of the outer peripheral surface of each convex portion 40, 40 of the incomplete spline portion 41 is continuous with one axial end edge of the outer peripheral surface of the small diameter shaft portion 20a. In the case of this example, the diameter of the circumscribed circle of the concave portions 37, 37 of the male spline portion 8b is equal to the diameter of the circumscribed circle of the concave portions 39, 39 of the incomplete spline portion 41.

  The inner peripheral surface of the continuous portion 21a is formed in a cylindrical surface shape whose inner diameter does not change in the axial direction. The inner diameter of the inner peripheral surface of such a continuous portion 21a is equal to the inner diameter of the small diameter hole portion 16a. Further, one axial end edge of the inner peripheral surface of the continuous portion 21a is continuous with the other axial end edge of the small diameter hole portion 16a. On the other hand, the other axial end edge of the inner peripheral surface of the continuous portion 21a is continuous with one axial end edge of the inner peripheral surface of the small diameter shaft portion 20a.

  The small-diameter shaft portion 20a is provided in a portion of the inner shaft 9b from a position adjacent to the other axial side of the continuous portion 21a to the other axial end portion. Such a small-diameter shaft portion 20 a has a large-diameter portion 47, a small-diameter portion 48, a step portion 49, and an outward flange portion (caulking portion) 50.

  Of these, the large-diameter portion 47 is formed in a portion of the small-diameter shaft portion 20a extending from one end in the axial direction to a portion closer to the other end in the axial direction. The outer peripheral surface of such a large diameter portion 47 is formed in a cylindrical surface shape whose outer diameter does not change in the axial direction. The inner diameter of the large-diameter portion 47 has a constant inner diameter over the entire length in the axial direction, and this inner diameter is equal to the inner diameter of the continuous portion 21a and the inner diameter of the small-diameter hole 16a. . One end edge in the axial direction of the inner peripheral surface of the large-diameter portion 47 is continuous with the other end edge in the axial direction of the continuous portion 21a. In the case of this example, the inwardly projecting portion 70 of the thick portion 46 is not formed in the cross-sectional area of the large diameter portion 47 with respect to a virtual plane orthogonal to the central axis of the inner shaft 9b. It is substantially equal to the cross-sectional area of the portion with respect to the imaginary plane (except for dimensional tolerance that is unavoidable in manufacturing). Further, the cross-sectional area of the large-diameter portion 47 with respect to the virtual plane is made smaller than the cross-sectional area of the thick portion 46 where the inwardly projecting portion 70 is formed with respect to the virtual plane.

  The small diameter portion 48 is formed in a portion near the other end in the axial direction of the small diameter shaft portion 20a. On the outer peripheral surface of such a small-diameter portion 48, male serrations 51, which are concave and convex portions formed by alternately arranging concave portions and convex portions in the circumferential direction, are formed. The diameter dimension of the circumscribed circle of the convex portion constituting the male serration 51 is smaller than the outer diameter dimension of the large diameter portion 47.

  The step portion 49 is formed in a state where the other axial end edge of the outer peripheral surface of the large diameter portion 47 and the one axial end edge of the outer peripheral surface of the small diameter portion 48 are continuous. Such a step 49 exists on a virtual plane orthogonal to the central axis of the inner shaft 9b.

  The outward flange 50 is formed on the other axial end of the small-diameter shaft portion 20a so as to protrude radially outward from the outer peripheral surface of the small-diameter portion 48 over the entire circumference. Such an outward flange 50 is formed by, for example, rolling caulking the other axial end of the inner shaft 9b in the state shown in FIG. 2 (the inner shaft 9b before the outward flange 50 is formed). Formed by spreading around the circumference. In the state shown in FIG. 2 (the state before the outward flange portion 50 is formed), the other axial end portion of the inner shaft 9b is more radial than the portion adjacent to one side in the axial direction of the outer portion. A second thin portion 68 having a small thickness is formed. In this way, the rigidity of the other axial end portion of the inner shaft 9b in the state before the outward flange portion 50 is formed is reduced to facilitate the formation of the outward flange portion 50.

  The yoke portion 36 is coupled and fixed to the other axial end portion of the small diameter shaft portion 20a. In the case of this example, the front side of the universal joints 3c and 3d (see FIG. 5) by the yoke portion 36, the cross shaft 52, and the yoke 53 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 36 is provided in a state of extending from the cylindrical base portion 54 and two positions opposite to the central axis of the base portion 54 to the other side in the axial direction on the outer peripheral surface of the base portion 54. And a pair of arm portions 55, 55.
Of these, the base 54 has a central hole 56 formed in the center. On the inner peripheral surface of the center hole 56, a female serration 57 is formed which is an uneven portion formed by alternately arranging concave portions and convex portions in the circumferential direction. Such a base portion 54 is inserted into the center hole 56 through the small diameter portion 48 and the female serration 57 and the male serration 51 are serrated and engaged with the stepped portion 49 and the outward flange. It is clamped between the parts 50.

In addition, a pair of circular holes 58 and 58 are formed in the arm portion 55 and 55 near the end opposite to the base portion 54 in the axial direction with the center axes of the arms 55 and 55 being coaxial. Yes.
Further, in the assembled state shown in FIG. 1, cylindrical bearing cups 59 and 59 having a bottom are respectively provided inside the pair of circular holes 58 and 58 of the pair of arm portions 55 and 55, respectively. It is fitted and fixed. At the same time, a pair of shaft portions 61 out of the four shaft portions 61, 61 constituting the cross shaft 52 are provided inside the bearing cups 59, 59 via a plurality of needles 60, 60, respectively. , 61 are rotatably supported.

  Of the four shaft portions 61, 61 constituting the cross shaft 52, a pair of shaft portions 61 other than the shaft portions 61, 61 supported in the circular holes 58, 58 of the yoke portion 36 ( The end of one shaft portion 61 is not shown in the figure, and a bearing is provided inside a circular hole (not shown) formed in a pair of arm portions 63 (one arm portion 63 is not shown) constituting the yoke 62. It is rotatably supported via a cup (not shown) and a needle (not shown).

  A coating layer 64 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 8b constituting the inner shaft 9b. Specifically, in this example, the coating layer 64 is a portion of the outer peripheral surface of the inner shaft 9b that is closer to one end in the axial direction of the small-diameter shaft portion 20a than the one end edge in the axial direction of the spline forming portion 35 (see above). It is a portion that is located on the other side in the axial direction from the other end edge in the axial direction of the continuous portion 21a, and is provided in a portion extending to a position indicated by a straight line X in FIG.

Hereinafter, a method for manufacturing the inner shaft 9b will be briefly described.
First, in the first step, a shaft of a hollow circular material (not shown) 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. A portion (a portion corresponding to the spline forming portion 35) from the direction intermediate portion to the one axial end portion is used as a first intermediate material by expanding the diameter of the portion. The work for expanding the diameter in this way is performed, for example, by inserting a mandrel inside the portion from the axially intermediate portion to one axial end portion of the material, and handling the inner peripheral surface of the material by the mandrel. To do. In such a diameter expansion operation, an outer mold having a cylindrical inner peripheral surface can be disposed on the outer diameter side of the portion to be expanded in the material.

  Next, in the second step, by cutting the outer peripheral surface of the enlarged portion of the first intermediate material, the outer diameter of the portion is changed to the rolling lower diameter (press lower diameter). Process. In this way, a second intermediate material is obtained.

  Next, in the third step, a concave portion and a convex portion are formed in the circumferential direction by rolling or press-molding a portion of the second intermediate material that has been processed into the rolling lower diameter (press lower diameter). And the male spline portion 8b, which is a concavo-convex portion that is alternately arranged. In this way, a third intermediate material is obtained. When forming the male spline portion 8b as described above, a support shaft is inserted into the inner diameter side of the portion of the second intermediate material that has been processed into the rolling lower diameter (press lower diameter). Perform in the state. In the above-described process, the incomplete spline portion 41 is also formed together with the male spline portion 8b.

  Next, in the fourth step, the other end portion in the axial direction of the outer peripheral surface of the third intermediate material is subjected to, for example, cutting, rolling, or press molding, so that the small diameter portion 48 (male serration portion). 51) and the stepped portion 49 are formed. In this way, a fourth intermediate material is obtained.

  Next, in the fifth step, in the fourth intermediate material, from one axial end portion to the axial intermediate portion (the portion located on the other side in the axial direction from the portion corresponding to the continuous portion 21a), for example, A rough coating layer is formed by a fluid dipping method, an electrostatic coating method, or the like. Then, the coating layer 64 is formed by shaving the rough coating layer. In this way, the fifth intermediate material is obtained.

  Next, in the sixth step, by cutting a portion of the fifth intermediate material corresponding to the male spline portion 8b from one end portion in the axial direction of the inner peripheral surface to the intermediate portion in the axial direction. The large diameter hole portion 42 (the thin portion 45) is formed. On the other hand, of the fifth intermediate material, the portion corresponding to the male spline portion 8b from the axially intermediate portion to the other axial end portion of the inner peripheral surface is the medium-diameter hole intermediate-diameter hole portion 43 as it is. And

Finally, in the seventh step, the yoke portion 36 is fixed to the other axial end portion of the sixth intermediate material (the inner shaft 9b shown in FIG. 2 before the yoke portion 36 is fixed). The inner shaft 9b is used. The operation of coupling and fixing the yoke portion 36 to the sixth intermediate material is performed by spreading the other end in the axial direction of the sixth intermediate material over the entire circumference and rolling it by rolling caulking.
In addition, it is possible to implement each process mentioned above as appropriate, as long as no contradiction occurs.

  The inner shaft 9b having the above-described configuration has the male spline portion 8b over the entire length, and is engaged with the female spline portion 26 of the outer tube 10b through the coating layer 64, so that the outer tube 9b is engaged. 10b. In this assembled state, a predetermined amount of tightening allowance is provided at the engaging portion between the male spline portion 8b and the female spline portion 26. In this way, the inner shaft 9b and the outer tube 10b are combined in a state where torque can be transmitted and the entire length can be expanded and contracted.

  In the case of this example, the thick portion 46 (medium-diameter hole portion 43) of the male spline portion 8b is within the range of the expansion / contraction stroke between the inner shaft 9b and the outer tube 10b in use. The portion corresponding to is always restricted to be spline engaged with the female spline portion 26.

According to the intermediate shaft 4b of the present example having the above-described configuration, the rotational direction of the engaging portion between the male spline portion 8b of the inner shaft 9b and the female spline portion 26 of the outer tube 10b is rattled. Even when a structure that can be kept small is employed, the sliding resistance between the inner shaft 9b and the outer tube 10b can be kept small.
That is, in the case of this example, the inner shaft 9b is made hollow, and the thin portion 45 and the thick portion 46 are provided in order from one side in the axial direction at the portion where the male spline portion 8b is formed. Yes. For this reason, compared with the case of a solid inner shaft, the rigidity in the radial direction of the portion where the male spline portion 8b is formed can be reduced. In particular, in the case of this example, the radial rigidity of the portion where the thin portion 45 is formed in the portion where the male spline portion 8b is formed is moderate compared with the portion where the thick portion 46 is also formed. Can be made smaller. Accordingly, in order to prevent rattling in the rotational direction of the engaging portion between the male spline portion 8b and the female spline portion 26, even when the engaging portion is provided with a tightening allowance, the sliding with respect to the tightening allowance is prevented. Variations in dynamic resistance (sliding load) can be made insensitive, and sliding of the inner shaft 9b with respect to the outer tube 10b can be stabilized.

  Further, as described above, since the radial rigidity of the male spline portion 8b can be appropriately reduced, the rotational direction of the engaging portion between the male spline portion 8b and the female spline portion 26 is unstable. In order to prevent this, even when a structure in which a tightening margin is provided at the engaging portion is employed, the sliding resistance (sliding load) with respect to the tightening margin can be reduced. Further, the fluctuation of the sliding resistance (sliding load) becomes insensitive, and the sliding of the inner shaft 9b with respect to the outer tube 10b can be stabilized. Furthermore, even when a large range (dimensional tolerance) in which the error of the inner shaft 9b can be tolerated is ensured, the sliding resistance can be prevented from increasing due to the influence of the dimensional tolerance. Therefore, the manufacturing cost of the inner shaft 9b and the outer tube 10b can be reduced.

  Further, in the case of this example, by positioning the second continuous step portion 69 on one side in the axial direction with respect to the outer peripheral surface of the continuous portion 21a, one end in the axial direction of the thick portion 46 (spline forming portion 35). An inwardly projecting portion 70 is formed on the inner circumferential surface of the thick portion 46 so as to project radially inward over the entire circumference from the other axial end of the thick portion 46. In this way, by securing a large thickness dimension in the radial direction of the continuous portion 21a, the rigidity of a portion where stress is likely to concentrate, such as a boundary portion between the continuous portion 21a and the small-diameter shaft portion 20a. The durability of the inner shaft 9b can be improved.

  Further, in the case of this example, the medium-diameter hole portion 43 (thick wall portion 46) of the male spline portion 8b within the range of the expansion / contraction stroke between the inner shaft 9b and the outer tube 10b in use. The portion corresponding to is always restricted to be spline engaged with the female spline portion 26. For this reason, torque transmission between the inner shaft 9b and the outer tube 10b is performed on the medium-diameter hole portion having relatively high radial rigidity in the portion of the inner shaft 9b where the male spline portion 8b is formed. It can be performed in a portion corresponding to 43 (thick portion 46). As a result, the durability of the inner shaft 9b can be improved while improving the slidability.

[Second Example of Embodiment]
A second example of the embodiment of the present invention will be described with reference to FIG.
The outer tube 10c constituting the intermediate shaft 4c of this example includes a small-diameter cylindrical portion 22a, a continuous portion 23, a large-diameter cylindrical portion 24, and a yoke portion 25.
Of these, the small-diameter cylindrical portion 22a has a stepped cylindrical shape, and is provided in a portion of the outer tube 10c extending from the other axial end portion to the axial intermediate portion. Specifically, the small-diameter cylindrical portion 22a is provided in a large-diameter portion 65 provided in one half of the axial direction and a half-portion in the other half in the axial direction, and the outer diameter dimension is the outer diameter of the large-diameter portion 65. A small-diameter portion 66 smaller than the size, and a stepped portion 67 in which the other axial end edge of the outer peripheral surface of the large-diameter portion 65 and one axial end edge of the outer peripheral surface of the small-diameter portion 66 are continuous. A female spline portion 26 is formed on the inner peripheral surface of the small diameter cylindrical portion 22a over the entire length. The structures of the continuous portion 23, the large diameter cylindrical portion 24, and the yoke portion 25 are the same as those in the first example of the embodiment described above. The structure of the inner shaft 9b is the same as that in the first example of the above-described embodiment.

  Also in this example having the above-described configuration, the male spline portion 8b of the inner shaft 9b and the female spline portion 26 of the outer tube 10c are spline-engaged via the coating layer 64, thereby The inner shaft 9b and the outer tube 10c are combined so that torque can be transmitted and the entire length can be expanded and contracted. In this state, a predetermined amount of tightening allowance is provided at the engaging portion between the male spline portion 8b and the female spline portion 26.

  In the case of this example, it corresponds to the large-diameter portion 65 of the female spline portion 26 of the outer tube 10c within the range of the expansion / contraction stroke between the inner shaft 9b and the outer tube 10c in use. The portion is always regulated so as to be in spline engagement with the male spline portion 8b. Other structures, operations and effects are the same as those of the first example of the embodiment described above.

[Third example of embodiment]
A third example of the embodiment of the present invention will be described with reference to FIG.
The outer tube 10d constituting the intermediate shaft 4d of this example includes a small-diameter cylindrical portion 22b, a continuous portion 23, a large-diameter cylindrical portion 24, and a yoke portion 25.
Of these, the small-diameter cylindrical portion 22b has a stepped cylindrical shape, and is provided in a portion of the outer tube 10d extending from the other axial end portion to the axial intermediate portion. Specifically, the small-diameter cylindrical portion 22b includes a large-diameter portion 65a provided in a portion from the portion near the other end in the axial direction to one end portion in the axial direction, and the other end portion in the axial direction. A stepped portion 67a in which a small-diameter portion 66a smaller than the outer diameter of the large-diameter portion 65a, the other axial end edge of the outer peripheral surface of the large-diameter portion 65a, and one axial end edge of the outer peripheral surface of the small-diameter portion 66a are continuous. It consists of. That is, in the case of this example, the position of the stepped portion 67a in the axial direction is positioned on the other side in the axial direction from the stepped portion 67 of the second example of the above-described embodiment. A female spline portion 26 is formed on the inner peripheral surface of the small diameter cylindrical portion 22b over the entire length. The structures of the continuous portion 23, the large diameter cylindrical portion 24, and the yoke portion 25 are the same as those in the first and second examples of the above-described embodiment.

  In the case of this example, the other end edge in the axial direction of the large diameter hole portion 42a and the one end edge in the axial direction of the medium diameter hole portion 43a are formed on the inner peripheral surface of the spline forming portion 35a constituting the inner shaft 9c. The axial direction position of the continuous stepped portion 44a is positioned on one side in the axial direction as compared with the first and second examples of the embodiment described above. In other words, in the case of this example, the length dimension in the axial direction of the large-diameter hole portion 42a is made shorter than in the case of the first example and the second example of the embodiment described above, and The length dimension in the axial direction of the diameter hole portion 43a is made longer than those in the first and second examples of the above-described embodiment.

  Also in the case of this example having the above-described configuration, the male spline portion 8b of the inner shaft 9c and the female spline portion 26 of the outer tube 10d are spline-engaged via the coating layer 64, thereby The inner shaft 9c and the outer tube 10d are combined so that torque can be transmitted and the entire length can be expanded and contracted. In this state, a predetermined amount of tightening allowance is provided at the engaging portion between the male spline portion 8b and the female spline portion 26.

  In the case of this example, it corresponds to the large-diameter portion 65a of the female spline portion 26 of the outer tube 10d within the range of the expansion / contraction stroke between the inner shaft 9c and the outer tube 10d in use. At least a part of the part and at least a part of the part corresponding to the thick part 46a (medium diameter hole part 43a) of the male spline part 8b of the inner shaft 9c are regulated so as to always be in spline engagement. ing. Other structures, operations, and effects are the same as those in the first and second examples of the above-described embodiment.

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.
Further, the order of the steps constituting the method for manufacturing the inner shaft for the telescopic shaft described in each example of the above-described embodiment can be changed within a range where no contradiction occurs. 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, 4b, 4c, 4d Intermediate shaft 5 Steering gear unit 6 Input shaft 7 Tie rod
8, 8a, 8b Male spline part 9, 9a, 9b, 9c Inner shaft
10, 10a, 10b, 10c, 10d Outer tube 11 First yoke 12 Female spline portion 13 Second yoke 14 Large diameter hole portion 15 Medium diameter hole portion 16 Small diameter hole portion 17 Thin portion 18 Medium thickness portion 19, 19a Thickness Meat part 20, 20a Small diameter shaft part 21, 21a Continuous part 22, 22a, 22b Small diameter cylindrical part 23 Continuous part 24 Large diameter cylindrical part 25 Yoke part 26 Female spline part 27 Arm part 28 Circular hole 29 Bearing cup 30 Needle 31 Cross shaft 32 Shaft part 33 Yoke 34 Arm part 35, 35a Spline forming part 36 Yoke part 37 Recessed part 38 Convex part 39 Concave part 40 Convex part 41 Incomplete spline part 42, 42a Large diameter hole part 43, 43a Medium diameter hole part 44, 44a First One continuous step portion 45 Thin portion 46, 46a Thick portion 47 Large diameter portion 48 Small diameter portion 49, 49a Step portion 50 Outward flange portion 51 Serrations 52 cross shaft 53 yoke 54 base 55 arms 56 central bore
57 female serration 58 circular hole 59 bearing cup 60 needle 61 shaft portion 62 yoke 63 arm portion 64 coating layer 65, 65a large diameter portion 66, 66a small diameter portion 67, 67a step portion 68 second thin portion 69 second continuous step Part 70 Inward overhang

Claims (4)

A male spline portion formed on the outer peripheral surface of one end portion in the axial direction, and a small-diameter shaft provided on the other axial side of the male spline portion and having an outer diameter smaller than the diameter of the circumscribed circle of the male spline portion A hollow inner shaft having a portion;
An outer tube having a female spline portion formed on the inner peripheral surface;
A coating layer provided in a state of covering the outer peripheral surface of the male spline part,
By engaging the male spline part and the female spline part through the coating layer, the inner shaft and the outer tube are combined in a state where torque can be transmitted and the total length can be expanded and contracted. A telescopic shaft,
A portion of the inner shaft where the male spline portion is formed is provided at a thin wall portion provided at one end in the axial direction, and is provided on the other side in the axial direction from the thin wall portion. Has a thicker portion that is larger than the thinned portion,
The inner peripheral surface of the inner shaft includes a large-diameter hole portion formed on the inner peripheral surface of the thin-walled portion, a medium-diameter hole portion formed on the other axial side of the large-diameter hole portion, and the medium-diameter portion. A small-diameter hole formed on the other side in the axial direction than the hole,
The continuous step portion that exists between the medium-diameter hole portion and the small-diameter hole portion is located on one axial side of the outer peripheral surface of the continuous portion that exists between the male spline portion and the small-diameter shaft portion. By this, an inwardly projecting portion projecting radially inward over the entire circumference is formed at the other axial end portion of the inner peripheral surface of the male spline portion.
Telescopic shaft.   At least a part of a portion formed on the outer peripheral surface of the thick portion of the male spline portion and a female spline of the outer tube within a range of expansion and contraction strokes of the inner shaft and the outer tube in use. The telescopic shaft according to claim 1, wherein the portion is always in spline engagement.   The telescopic shaft according to any one of claims 1 to 2, wherein a cross-sectional area of the thick portion and a cross-sectional area of the small-diameter shaft portion are the same.   The telescopic shaft according to any one of claims 1 to 3, wherein the yoke portion is coupled and fixed to the inner shaft by an outward flange provided at the other axial end portion of the inner shaft. .

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