JP2012117560A - Extensible shaft, method of manufacturing the same, and steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive extensible shaft which is easily assembled.SOLUTION: An inner shaft 35 inserted from a first end 361 side of a cylindrical outer shaft 36 can slide in the axial direction X1. A surface of a male spline 40 of the outer periphery of the inner shaft 35 is formed with a resin coating. A female spline of the inner periphery of the outer shaft 36 includes a long-size first female spline 51 and a second female spline 52. When the inner shaft 35 is shortened to the shortest state, an interference part of the second female spline 52 interferes the resin coating of the tip 351 of the inner shaft. With this interference, an intermediate shaft is temporarily held in the shortest state, restricting the tare.

Description

  The present invention relates to a telescopic shaft, a manufacturing method thereof, and a vehicle steering apparatus.

The steering shaft of the vehicle steering system is a column shaft supported by a steering column, a pinion shaft of a steering mechanism composed of a rack and pinion mechanism, and an intermediate that can be expanded and contracted in the axial direction by connecting the column shaft and the pinion shaft. And a shaft.
Usually, the intermediate shaft is configured by spline fitting a cylindrical outer shaft and an inner shaft. When assembling this kind of intermediate shaft to the vehicle, first, the upper end of the intermediate shaft is assembled to the instrument panel module (instrument panel module), and in that state, the instrument panel module is attached to the vehicle body. Next, after the suspension member is attached to the vehicle body, the lower end of the intermediate shaft is assembled to a pinion shaft (or an extension shaft connected to the pinion shaft) extending upward from the suspension member.

  However, it was difficult to assemble the lower end of the intermediate shaft. That is, the intermediate shaft having splines as described above tends to extend to the longest position under its own weight. For this reason, the assembling work of the lower end of the intermediate shaft becomes a work while supporting the intermediate shaft in the contracted state after returning the intermediate shaft to the contracted state, and the workability is poor.

Therefore, the following first, second and third techniques have been proposed.
In the first technique, the intermediate shaft is connected to the intermediate shaft by using a separation preventing tool having one end engaged with the universal joint yoke at the upper end of the intermediate shaft and the other end engaged with the universal joint yoke at the lower end of the intermediate shaft. Temporarily held in the shortest state (see, for example, Patent Document 1).

In the second technique, the intermediate shaft is temporarily held in the shortest state by elastically engaging the O-ring accommodated in the outer peripheral groove of the inner shaft with the female spline of the outer shaft.
Further, in the third technique, the inner shaft and the outer shaft are connected to the shortest state by using a wire band (binding line).

JP 2008-239110 A

The first and second techniques require separate parts that do not perform any function after assembly, such as a separation prevention tool or an O-ring. In the third technique, the wire band is disposable, and these techniques increase the manufacturing cost.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an extendable shaft that is inexpensive and easy to assemble, a method for manufacturing the same, and a vehicle steering apparatus.

  In order to achieve the above object, a first aspect of the present invention is a cylindrical outer shaft (36) having first and second ends (361, 362), and the first end portion side of the outer shaft. An inner shaft (35) that is slidable in the axial direction (X1), the inner periphery of the outer shaft includes female splines (51, 52), and the outer periphery of the inner shaft is the female shaft. A male spline (40) that fits into the spline is included, and a resin coating (41) is formed on the surface (40a) of the male spline. A retractable shaft (5) having an interference portion (53; 53A; 53B) that interferes with the resin coating at the tip portion (351) of the inner shaft as it is shortened.

  According to a second aspect of the present invention, the outer shaft includes a small-diameter portion (363) extending from the first end portion and having the female spline formed therein, and a large-diameter portion (364) extending from the second end portion. And a tapered portion (365) formed between the small diameter portion and the large diameter portion, and the female spline of the small diameter portion extends from the first end portion. ) And a second female spline (52) disposed between the first female spline and the tapered portion, and the interference portion may be provided on the second female spline. .

  Further, as in claim 3, the second radius is greater than the radius of curvature (R1) of the first corner R portion (51c) formed by the tooth surface (51a) and the tooth tip surface (51b) of the first female spline. By reducing the curvature radius (R2) of the second corner R portion (52c) formed by the tooth surface (52a) and the tooth tip surface (52b) of the female spline, the interference is caused by a part of the second corner R portion. May be configured.

Further, as in claim 4, the radius of curvature (R3) of the corner R portion (40c) of the tooth groove (40b) of the male spline may be equal to the radius of curvature of the first corner R portion. .
Further, the invention of claim 5 provides a vehicle steering apparatus (1) in which the telescopic shaft described above is used as an intermediate shaft.
According to a sixth aspect of the present invention, in the method for manufacturing a telescopic shaft according to the above aspect, the first end, the second end, the small diameter portion extending from the first end, and the second end Into the cylindrical manufacturing intermediate (360) including a large-diameter portion extending from and a tapered portion formed between the small-diameter portion and the large-diameter portion from the first end side to the tapered portion. A die insertion step of inserting the die (70) to a position immediately before the die, and a die removal step of extracting the die to the first end side. In the die insertion step, the die is inserted into the outer shaft. Accordingly, a female spline is processed in the small-diameter portion, and when the die is pulled out from the outer shaft, the outer shape of the female spline is caused to bulge out by a spring back, and immediately before the tapered portion. The bulging amount within a predetermined range (P1) from the position A method for manufacturing a telescopic shaft is formed by forming the second female spline within the predetermined range and forming the first female spline outside the predetermined range by making the amount larger than the bulging amount in .

Moreover, in the manufacturing method of the extendable shaft as in claim 7, the bulge amount is obtained by an orthodontic jig (71) inserted from the second end side as a subsequent step of the die removal step. In some cases, a bulge amount reducing step of reducing the swell is included.
Further, as in claim 8, in the method for manufacturing the telescopic shaft, as a step subsequent to the die removal step, the end surface (52d) of the second female spline is pushed in the axial direction to thereby reduce the bulge amount. There is a case in which a step of increasing the amount of swelling is included.

Further, in the method for manufacturing the telescopic shaft according to claim 9, the bulge is formed by pushing the tooth tip surface of the second female spline radially outward as a subsequent step of the die removal step. A bulge amount increasing step for increasing the amount may be included.
In the above description, the alphanumeric characters in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

According to the first aspect of the present invention, when the inner shaft is inserted into the outer shaft to the shortest state, the interference portion of the female spline on the outer shaft interferes with the resin coating on the male spline at the tip portion of the inner shaft. Thereby, since the shortest state of the inner shaft is temporarily held, the extendable shaft can be easily assembled to the vehicle, for example.
According to a second aspect of the present invention, the outer shaft includes a tapered portion between the small diameter portion extending from the first end portion and the large diameter portion extending from the second end portion, and the small diameter portion includes the first diameter portion. In the case where the second female spline having the interference portion is included between the first female spline extending from the end of the first taper and the tapered portion, there are the following advantages. That is, in order to form a female spline on the outer shaft, when a die as a tool is press-fitted in the axial direction and then the die is removed, a springback occurs in the tooth profile of the formed female spline. At this time, since the rigidity of the tapered portion is higher than that of the small-diameter portion, the region adjacent to the tapered portion (region adjacent to the tapered portion from the first end side) in the direction opposite to the die insertion direction. The amount of the spring back is increased. As a result, an interference part capable of interfering with the resin coating of the male spline can be easily formed.

According to the invention of claim 3, the second corner R can be obtained by making the radius of curvature of the second corner R portion of the second female spline larger than the radius of curvature of the first corner portion of the first female spline. The interference part can be easily formed by the part.
According to the invention of claim 4, since the radius of curvature of the corner R portion of the groove bottom portion of the tooth groove of the male spline is equal to the radius of curvature of the first corner R portion, the second female spline of the outer shaft The second corner R portion of the inner shaft can be temporarily held by causing it to reliably interfere with the corner R portion of the groove bottom portion at the tip portion of the inner shaft in the shortest state. In particular, the inner shaft manufacturing intermediate is reciprocally slid in the axial direction with respect to the first female spline in the outer shaft under a predetermined heating condition, and the surface of the resin film on the inner shaft is brought into contact with the male spline on the outer shaft. It can be suitably used when performing a process for fitting the tooth surface (so-called heat-fitting process). In this case, the shape of the corner R portion of the groove bottom of the tooth groove of the male spline follows the shape of the first corner R portion of the first female spline of the outer shaft.

  Further, according to a fifth aspect of the present invention, in the case of a vehicle steering apparatus using the extendable shaft as an intermediate shaft, the intermediate shaft is suspended when the intermediate shaft is suspended with the upper end of the intermediate shaft attached to the steering column. The shaft can be temporarily held in the shortest state. In this state, the work of attaching the lower end of the intermediate shaft to the pinion shaft or the extension shaft can be easily performed. Therefore, the assembly to a vehicle becomes easy.

  According to the method for manufacturing the telescopic shaft according to the sixth aspect, the die is pulled out after the female spline is processed in the small diameter portion with the insertion of the die into the outer shaft. When the die is pulled out, the outer shape of the female spline is bulged by a springback, but the bulging amount within a predetermined range from the position immediately before the tapered portion is larger than the bulging amount outside the predetermined range. This is because the rigidity of the taper portion is high, and it is difficult for meat to escape to the taper portion side, and therefore, the bulge amount by the springback is larger than the predetermined range within the predetermined range adjacent to the taper portion. Because it becomes. According to this principle, the second female spline can be formed within the predetermined range, and the first female spline can be formed outside the predetermined range. The shape change between each female spline can be obtained only by die processing, and the manufacturing cost can be reduced.

In addition, as described in claim 7, after the second female spline is formed, the amount of bulging is reduced by the tooth shape correcting jig inserted from the second end side, thereby accurately adjusting the interference amount of the interference portion. It becomes possible to do.
In addition, as described in claim 8, after the second female spline is formed, the end face of the second female spline is pushed in the axial direction to increase the bulge amount, thereby accurately adjusting the interference amount of the interference portion. It becomes possible.

  In addition, as described in claim 9, after the second female spline is formed, the tooth tip surface of the second female spline is pushed outward in the radial direction to increase the bulge amount. It becomes possible to adjust well.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a vehicle steering apparatus in which an extendable shaft according to an embodiment of the present invention is applied to an intermediate shaft. It is sectional drawing of the principal part of an intermediate shaft. It is sectional drawing which follows the III-III line of FIG. (A) is sectional drawing which follows an IVa-IVa line, (b) is sectional drawing which follows an IVb-IVb line. It is process drawing which shows the manufacturing method of the outer shaft of an intermediate shaft, (a) shows the intermediate body for manufacture of an outer shaft, (b)-(c) shows a die insertion process, (c)-(d ) Shows a die removal process. It is a schematic sectional drawing which shows the denture correction process which reduces a bulging amount using a denture orthodontic jig as a post process of a die extraction process. (A) is a schematic sectional drawing which shows the bulging amount increase process which increases a bulging amount using an axial direction pressing jig as a post process of a die extraction process, (b) is a sectional view of a tooth profile. . (A) is a schematic sectional drawing which shows the bulging amount increase process which reduces a bulging amount using a radial direction pressing jig as a post process of a die extraction process, (b) is a sectional view of a tooth profile. .

A preferred embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus 100 in which an extendable shaft according to an embodiment of the present invention is applied to an intermediate shaft 5 that is a part of a steering shaft 2. Referring to FIG. 1, a vehicle steering apparatus 100 includes a steering shaft 2 that transmits a steering force of a steering member 1 such as a steering wheel. The steering shaft 2 includes a column shaft 3 connected to the steering member 1, an intermediate shaft 5 as an extendable shaft connected to the column shaft 3 via a first universal joint 4, and an intermediate shaft 5 connected to the intermediate shaft 5. And a pinion shaft 7 connected through two universal joints 6.

  Further, the vehicle steering apparatus 100 includes a rack shaft 8 as a steered shaft having a rack 8 a that meshes with a pinion 7 a provided in the vicinity of the end of the pinion shaft 7. A steering mechanism A1 is configured by a rack and pinion mechanism including the pinion shaft 7 and the rack shaft 8. The rack shaft 8 is supported by a housing 10 fixed to the vehicle body side member 9 so as to be movable in an axial direction along the left-right direction of the vehicle (a direction perpendicular to the paper surface). Although not shown, each end of the rack shaft 8 is connected to a corresponding steered wheel via a corresponding tie rod and a corresponding knuckle arm.

The column shaft 3 includes a first column shaft 11 and a second column shaft 12 connected coaxially to the first column shaft 11. The first column shaft 11 has an upper shaft 13 and a lower shaft 14 that are fitted so as to be able to rotate together and to slide relative to each other in the axial direction using spline fitting.
Further, the second column shaft 12 can transmit torque to the first end 5a of the intermediate shaft 5 through the input shaft 15 connected to the lower shaft 14 so as to be able to rotate together with the lower shaft 14 and the first universal joint 4. It has the output shaft 16 connected, and the torsion bar 17 which connects the input shaft 15 and the output shaft 16 so that relative rotation is possible. On the other hand, the second end portion 5 b of the intermediate shaft 5 is connected to the pinion shaft 7 via the second universal joint 6 so that torque can be transmitted.

The column shaft 3 is rotatably supported by a steering column 20 fixed to the vehicle body side members 18 and 19 via a bearing (not shown).
The steering column 20 includes a cylindrical upper jacket 21 and a cylindrical lower jacket 22 that are fitted so as to be relatively movable in the axial direction, and a housing 23 connected to the lower end in the axial direction of the lower jacket 22. The housing 23 houses a speed reduction mechanism 25 that decelerates the power of the steering assisting electric motor 24 and transmits it to the output shaft 16.

The speed reduction mechanism 25 includes a drive gear 26 that is coupled to a rotation shaft (not shown) of the electric motor 24 so as to be able to rotate together with the drive gear 26 and a driven gear 27 that meshes with the drive gear 26 and rotates together with the output shaft 16. . The drive gear 26 is composed of, for example, a worm shaft, and the driven gear 27 is composed of, for example, a worm wheel.
The steering column 20 is fixed to the vehicle body side members 18 and 19 via an upper bracket 28 on the vehicle rear side and a lower bracket 29 on the vehicle front side. The upper bracket 28 can be fixed to the upper jacket 21 of the steering column 20 via a column bracket described later. The upper bracket 28 uses a fixing bolt (stud bolt) 30 that protrudes downward from the vehicle body side member 18, a nut 31 that is screwed to the fixing bolt 30, and a capsule 32 that is detachably held by the upper bracket 28. The vehicle body side member 18 is fixed.

The lower bracket 29 is fixed to the housing 23 of the steering column 20. Further, the lower bracket 29 is fixed to the vehicle body side member 19 using a fixing bolt (stud bolt) 33 protruding from the vehicle body side member 19 and a nut 34 screwed into the fixing bolt 33.
As shown in FIGS. 1 and 2, the intermediate shaft 5 includes an inner shaft 35 that is, for example, a lower shaft, and a cylindrical outer shaft 36 that is, for example, an upper shaft. The inner shaft 35 and the outer shaft 36 are spline-fitted so as to be relatively slidable in the axial direction X1 and to be able to rotate together. The upper end of the outer shaft 36 is connected to the corresponding yoke 4 a of the first universal joint 4, and the lower end of the inner shaft 35 is connected to the corresponding yoke 6 a of the second universal joint 6.

As shown in FIG. 2, the outer shaft 36 has a first end 361 that is an open end and a second end 362 that is a closed end. The second end 362 of the outer shaft 36 is connected to the end of the yoke 4a of the first universal joint 4 and is closed. The inner shaft 35 is inserted into the outer shaft 36 from the first end 361 side and is slidable in the axial direction X1.
Specifically, the inner shaft 35 and the outer shaft 36 are spline-fitted. That is, the outer periphery of the inner shaft 35 has a male spline 40. Further, the inner periphery of the outer shaft 36 has a first female spline 51 and a second female spline 52 as female splines fitted to the male spline 40.

As shown in FIG. 3, which is a cross-sectional view taken along the line III-III in FIG. 2, the surface 40 a of the male spline 40 is covered with a resin film 41.
As shown in FIG. 2, the outer shaft 36 extends from the first end 361 and extends from the second end 362 and a small diameter portion 363 in which the first female spline 51 and the second female spline 52 are formed. It has a large diameter portion 364 and a tapered portion 365 formed between the small diameter portion 363 and the large diameter portion 364. The inclination angle of the tapered portion 365 is appropriately adjusted, for example, in the range of 5 ° to 35 °.

The first female spline 51 extends from the first end 361 of the outer shaft 36 to be long. The second female spline 52 is disposed between the first female spline 51 and the tapered portion 365.
The feature of the present embodiment is that an interference portion 53 is provided on the tooth surface 52a of the second female spline 52, and the interference portion 53 reduces the inner shaft 35 to the shortest state. This is in that the shortest state of the inner shaft 35 is temporarily held by interfering with the resin film 41 of the tip portion 351 of the shaft.

FIG. 4A is a cross-sectional view taken along line IVa-IVa in FIG. 2 and shows a cross section of the first female spline 51. FIG. 4B is a cross-sectional view taken along line IVb-IVb in FIG. 2 and shows a cross section of the second female spline 52.
As shown in FIG. 4 (a), the first female spline 51 has a first corner R portion 51c formed by the tooth surface 51a and the tooth tip surface 51b, as shown in FIG. 4 (b). The second female spline 52 has a second corner R portion 52c formed by the tooth surface 52a and the tooth tip surface 52b.

On the other hand, as shown in FIG. 3, the curvature radius R3 of the corner R portion 40c of the tooth groove 40b of the male spline 40 of the inner shaft 35 is the curvature radius of the first corner R portion 51c of the first female spline 51 of the outer shaft 36. Equal to or approximately equal to R1 (R3≈R1)
The curvature radius R2 of the second corner R portion 52c is made smaller than the curvature radius R1 of the first corner R portion 51c (R2 <R1). Accordingly, the curvature radius R2 of the second corner R portion 52c of the second female spline 52 of the outer shaft 36 is smaller than the curvature radius R3 of the corner R portion 40c of the tooth groove 40b of the male spline 40 of the inner shaft 35. (R2 <R3).

  For this reason, as the inner shaft 35 is contracted into the outer shaft 36 and becomes the shortest state, a part of the second corner R portion 52c of the second female spline 52 of the outer shaft 36 becomes part of the inner shaft 35. It will interfere with the resin coating 41 at the corner R portion 40c of the male spline 40 of the tip portion 351. As a result, the shortest state of the inner shaft 35 can be temporarily held. That is, the part of the second corner R portion 52 c constitutes the interference portion 53.

  5A to 5D show a method for manufacturing the outer shaft 36 of the intermediate shaft 5 as an extendable shaft. First, a cylindrical material is drawn to prepare an intermediate 360 for manufacturing the outer shaft 36 as shown in FIG. The manufacturing intermediate 360 includes a first end 361, a second end 362, a small diameter portion 363 extending from the first end 361, a large diameter portion 364 extending from the second end 362, A tapered portion 365 formed between the small diameter portion 363 and the large diameter portion 364 is provided. However, the small diameter portion 363 of the manufacturing intermediate 360 is not yet formed with a female spline, and the yoke 4a of the first universal joint 4 is connected to the second end 362 of the manufacturing intermediate 360. This is different from the completed outer shaft 36.

In this manufacturing method, as shown in FIGS. 5B to 5C, the die 70 is moved from the first end 361 side in a state where the outer diameter of the small diameter portion 363 is constrained by a cylindrical restraining jig 55. It includes a die insertion step of inserting the die 70 to a position immediately before the taper portion 365, and a die removal step of pulling the die 70 toward the first end portion 361 as shown in FIGS. 5 (c) to 5 (d).
In the die insertion step, a female spline is processed on the inner periphery of the small diameter portion 363 as the die 70 is inserted. Next, in the die removal step, when the die 70 is pulled out, the outer shape of the female spline bulges due to the spring back.

  In the female spline on the inner periphery of the small-diameter portion 363, the bulge amount within the predetermined range P1 [see FIG. 5 (d)] from the position immediately before the taper portion 365 is larger than the bulge amount outside the predetermined range P1. That is, since the rigidity of the taper portion 365 is high, it is difficult for meat to escape to the taper portion 365 side. For this reason, the bulging amount due to the springback within the predetermined range P1 adjacent to the taper portion 365 is outside the predetermined range P1. It becomes larger than the bulging amount by the spring back.

According to this principle, the second female spline 52 can be formed within the predetermined range P1, and the first female spline 51 can be formed outside the predetermined range P1. Only by die processing, the difference in shape between the female splines 51 and 52 can be obtained, and the manufacturing cost can be reduced.
If the taper angle of the taper portion 365 is small, a sufficient bulge amount due to the spring back cannot be obtained. Therefore, the taper angle of the taper portion 365 is appropriately adjusted within a range of 5 ° to 35 °, for example.

  Further, after the first female spline 51 and the second female spline 52 are formed by the steps shown in FIGS. 5A to 5D, the bulge amount is reduced by the bulge amount reduction step shown in FIG. You may make it adjust so. In other words, the bulging amount is reduced by the shaft-like tooth orthodontic jig 71 inserted from the second end 362 side. The end portion of the orthodontic jig 71 has a correction tooth 71a that enters each tooth groove of the second female spline 52 along the axial direction X1. By correcting the tooth profile with each of the correction teeth 71a and reducing the bulge amount, the interference amount of the interference unit 53 can be adjusted with high accuracy.

  Further, after the first female spline 51 and the second female spline 52 are formed by the steps shown in FIGS. 5A to 5D, the bulge amount is increased by the bulge amount increasing step shown in FIG. You may make it adjust so that may be increased. That is, by pushing a part of the toothed direction of the end surface 52d of the second female spline 52 in the axial direction X1 by the convex portion 72b of the end surface 72a of the axial pressing jig 72 inserted from the second end 362 side. As shown in FIG. 7B, the bulging amount of the interference portion 53A is increased. By increasing the bulge amount, the interference amount of the interference unit 53 can be adjusted with high accuracy.

  Further, after the first female spline 51 and the second female spline 52 are formed by the steps shown in FIGS. 5A to 5D, the bulge amount is increased by the bulge amount increasing step shown in FIG. You may make it adjust so that may be increased. That is, by pressing the tooth tip surface 52b of the second female spline 52 radially outward by the radial pressing jig 73 inserted from the second end 362 side, as shown in FIG. The amount of swelling of the interference part 53B is increased. By increasing the bulge amount, the interference amount of the interference unit 53 can be adjusted with high accuracy.

The radial pressing jig 73 has a cam follower 73a as a plurality of diameter-expanding members arranged in the circumferential direction, and a conical tapered cam surface that matches the conical tapered surface of the inner periphery of the cam follower 73a, and moves in the axial direction. Cam 73b. The radial pressing jig 73 presses the tooth tip surface 52b of the second female spline 52 radially outward by the outer diameter portion of the cam follower 73a.
The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 ... Steering member, 2 ... Steering shaft, 3 ... Column shaft, 5 ... Intermediate shaft (expandable shaft), 7 ... Pinion shaft, 11 ... First column shaft, 20 ... Steering column, 35 ... Inner shaft, 351 ... Tip portion 36 ... outer shaft 360 ... intermediate for production 361 ... first end portion 362 ... second end portion 363 ... small diameter portion 364 ... large diameter portion 365 ... taper portion 40 ... male Spline, 40a ... surface, 40b ... tooth gap, 40c ... corner R portion, 41 ... resin coating, 51 ... first female spline, 51a ... tooth surface, 51b ... tooth tip surface, 51c ... first corner R portion, 52 ... Second female spline, 52a ... tooth surface, 52b ... tooth tip surface, 52c ... second corner R portion, 52d ... end surface, 53; 53A; 53B ... interference portion, 70 ... die, 71 ... tooth orthodontic jig, 72 ... Axial pressing jig, 3 ... radial pressing jig, A1 ... steering mechanism, P1 ... predetermined range, R1 ... radius of curvature (of the first corner R portion), R2 ... radius of curvature (of the second corner R portion), R3 ... (corner R) Radius of curvature, X1 ... axial direction

Claims (9)

A cylindrical outer shaft having first and second ends;
An inner shaft inserted into the outer shaft from the first end side and slidable in the axial direction,
The inner circumference of the outer shaft includes a female spline,
The outer periphery of the inner shaft includes a male spline that fits with the female spline,
A resin film is formed on the surface of the male spline,
A telescopic shaft in which a portion of the female spline in the axial direction has an interference portion that interferes with the resin coating at the tip of the inner shaft as the inner shaft is shortened to the shortest state. 2. The outer shaft according to claim 1, wherein the outer shaft extends from the first end portion, has a small diameter portion formed with the female spline, a large diameter portion extends from the second end portion, the small diameter portion, and the large diameter portion. A taper portion formed between and
The female spline of the small diameter portion includes a first female spline extending from the first end portion, and a second female spline disposed between the first female spline and the tapered portion,
A telescopic shaft in which the interference portion is provided on the second female spline.   The second angle R formed by the tooth surface and the tooth tip surface of the second female spline according to claim 2, wherein the radius of curvature of the first corner R portion formed by the tooth surface and the tooth tip surface of the first female spline is larger. A telescopic shaft in which the interference portion is configured by a part of the second corner R portion by reducing the curvature radius of the portion.   4. The extendable shaft according to claim 3, wherein a radius of curvature of a corner R portion of the tooth groove of the male spline is equal to a radius of curvature of the first corner R portion.   A vehicle steering apparatus using the extendable shaft according to any one of claims 1 to 4 as an intermediate shaft. In the manufacturing method of the telescopic shaft according to any one of claims 2 to 4,
A first end, a second end, a small diameter portion extending from the first end, a large diameter portion extending from the second end, and a portion between the small diameter portion and the large diameter portion. A die insertion step of inserting a die from the first end side to a position immediately before the tapered portion into a cylindrical manufacturing intermediate including a tapered portion;
A die removing step of drawing the die to the first end side,
In the die insertion step, with the insertion of the die into the outer shaft, a female spline is processed in the small diameter portion,
In the die pulling-out step, when the die is pulled out from the outer shaft, the outer shape of the female spline is caused to bulge by a spring back, and the bulging amount within the predetermined range from the position immediately before the tapered portion is outside the predetermined range. A method of manufacturing a telescopic shaft, wherein the second female spline is formed within the predetermined range and the first female spline is formed outside the predetermined range by making the amount larger than the bulging amount in the first step.   The method of manufacturing an extendable shaft according to claim 6, further comprising a bulge amount reducing step of reducing the bulge amount by a tooth orthodontic jig inserted from the second end side as a subsequent step of the die pulling out process. .   The method of manufacturing a telescopic shaft according to claim 6, further comprising a bulge amount increasing step of increasing the bulge amount by pushing an end face of the second female spline in the axial direction as a subsequent step of the die pulling out step.   7. The expandable / contractable step according to claim 6, further comprising a bulge amount increasing step of increasing the bulge amount by pushing the tooth tip surface of the second female spline radially outward as a subsequent step of the die pulling out step. Manufacturing method of shaft.

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