JPH0740839A - Steering shaft and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a steering shaft, in particular an upper shaft in the form of a solid round bar in an uncut chip (chipless) manner. CONSTITUTION:An upper shaft 1 is formed by a cold-forging process for cold- forging the raw material of a solid round bar to form a shaft thin part, a forming process for forming a peripheral groove 4 and a low diameter part 12 swollen in the right and left of the peripheral groove 4 on the shaft thin part by roller forming, and a rolling process for forming a serration 3 on the peripheral surface of the lower diameter part 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering shaft for an automobile steering system and a method for manufacturing the steering shaft.

[0002]

2. Description of the Related Art A steering apparatus for a vehicle transmits rotation input to a steering wheel to a steering gear box via a steering shaft mounted on the steering wheel, and the steering gear box steers left and right front wheels. Is.

This steering shaft uses a metal rod or a metal hollow rod having a predetermined strength to transmit a torsion torque. However, in order to ensure the safety of an occupant in a collision accident, the steering shaft is axially moved. A contracting structure is adopted. That is, the steering shaft is composed of an upper shaft having a steering wheel mounted on the upper end thereof and a lower shaft fitted with the lower end of the upper shaft, and these fitting portions are engaged with serrations.

Regarding the serration engagement, as shown in FIG. 6, a serration portion 21 is engraved in a circumferential direction at a lower end portion of an upper shaft 20 made of a solid round bar in a circumferential direction.
The peripheral groove 23 is machined into the serration portion 21, and the upper portion of the serration portion 21 is machined into a fine axial shape. The lower shaft 24 is engraved with a serration portion 25 that fits with the serration portion 21 on the inner peripheral surface of the entire length, or is engraved with a predetermined length on the inner peripheral surface of the upper end portion and the lower end portion is engraved. It is composed of a hollow round bar with a thick shaft. Then, the resin is injected into the circumferential groove 23 through the through hole 26 formed in the lower shaft 24 and molded, and when the axial load is applied to the upper shaft 20, the resin is broken and shrinks into the lower shaft 24. It has become.

In such a steering shaft, a solid round bar is cut for the upper shaft 20, and a serration process is performed on the inner peripheral surface of the hollow round bar for the lower shaft. In particular, regarding the manufacture of the upper shaft 20, a solid round bar is cut into a predetermined length, the upper end is made thick and the shaft is formed thin from the center to the lower end, and the steering wheel is attached to the upper end. After forming a threaded portion to form a serration at the lower end, the outer diameter is cut to a rolling lower diameter tolerance for forming serrations, and a groove is cut for forming the circumferential groove, and then a predetermined serration is formed.

[0006]

However, cutting a solid round bar causes a large amount of cutting chips (chips), resulting in a poor material yield, which requires a long time for processing, resulting in cost increase. Deteriorates strength due to cutting. Furthermore, the chips may deteriorate the environment at the work site, and the chips may be distressed due to pollution and environmental problems, and transportation costs and labor costs for transporting them to the processing plant are required. .

Therefore, the present invention is intended to manufacture a steering shaft, particularly an upper shaft, with a solid round rod without cutting chips (chipless).

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 is to form a shaft portion formed by cold forging on a solid round rod body, and roller forming the shaft portion. And a serration portion formed on the peripheral surface of the lower diameter portion raised to the left and right of the peripheral groove by the roller molding.

According to the second aspect of the invention, a cold forging step of cold forging the material of the solid round bar to form a shaft detail,
It is characterized by comprising a forming step of forming a peripheral groove and a lower diameter portion raised to the left and right of the peripheral groove on the shaft details by roller forming, and a rolling step of forming serrations on the peripheral surface of the lower diameter portion. And

[0010]

According to the invention as set forth in claim 1, although the diameter of the cold-forged shaft details is small, the composition flow of the solid round bar is not interrupted, so that there is no great difference from the strength of the thick shaft part. The roller-formed peripheral groove may be resin-molded to be connected to the lower shaft, or a bolt may be inserted to connect the yoke portion of the universal joint.

According to the second aspect of the present invention, since the cutting process is not performed at all, the steering shaft can be manufactured without a chip. Therefore, the material yield can be improved, the cost can be reduced, and the strength can be improved. Improve.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the upper shaft 1 has a threaded portion 2 for pivotally attaching a steering wheel to an upper end portion of a thick shaft portion 1a, and a shaft detail 1 from a central portion to a lower end portion.
A pair of serration parts A and B formed in b and having a diameter slightly larger than the shaft diameter of the lower end thereof are formed at a predetermined distance. A peripheral groove 4 is formed between the serration portions 3 and 3, and the peripheral groove 4 is fitted to the lower shaft,
It is a portion where resin is injected through a hole formed in the lower shaft and molded. Shaft detail 1 of upper shaft 1
b is formed by cold forging the thick shaft portion 1a, and the pair A and B of the serration portion 3 is formed by roller forming and rolling.

Therefore, the method of manufacturing the upper shaft 1 will be described. First, as shown in FIG. 2 (A), a material 10 appropriately cut into a length as an upper shaft.
As shown in FIG. 2 (B), the material 10 is cold forged to form the thick shaft portion 1a and the small shaft portion 1b. Cold forging is by forging at room temperature without heating the material,
This is a process in which the meat of the outer peripheral portion of the material 10 is pressed into the axial center portion and crushed.
Therefore, although the diameter of the shaft details 1b is contracted, the composition flow is not interrupted by cutting, the internal composition becomes dense, the hardness increases, and the strength improves.

Then, as shown in FIG. 2 (C), the rollers 11 and 11 are applied to the shaft details 1b and rotated to form the serrated portion 3, so that the lower diameter portions 12 and 1 are formed.
Mold 2. As shown in FIG. 3, the roller 11 is provided with circumferential protrusions 13 having a substantially circular cross section for forming the circumferential groove 4, and arranged on both sides of the circumferential protrusion 13 so as to form the lower diameter portion 12. It comprises grooves 14 and 14 and abutting portions 15 and 15 which are in pressure contact with the shaft details 1b outside the circumferential grooves 14 and 14, respectively.

Therefore, when the circumferential protrusion 13 is pressed against the shaft details 1b, the meat of the pressed portion flows to the circumferential groove 14 side, and the side wall portion 14a of the circumferential groove 14 stops the flow and rises in the radial direction. The diameter portion 12 is formed. If the lower diameter portion 12 is not sufficiently formed by only the circumferential groove 14, the both ends of the material 10 are fixed to suppress the elongation in the axial direction.

Then, as shown in FIG. 2 (D), the rolling roller 16 is applied to the peripheral surfaces of the lower diameter portions 12, 12 to form the serration portion 3. In the pair of serrations 3 A and B, the peaks and the troughs must be aligned on the same line. Therefore, the rolling roller 16 is formed of one serration integrally formed.

The upper shaft 1 thus formed
4, is engaged with the serration portion 6 engraved on the inner peripheral surface of the axial detail 5b of the lower shaft 5 through the serration portion 3 so as to be contractible in the axial direction. A resin is injected into the circumferential groove 4 through a through hole 7 formed in the shaft detail 5b and molded. The shaft details 5b are formed by drawing from the shaft thick portion 5a.

Although the present invention has been described only with respect to the upper shaft 1 in the above embodiment, it can be applied to the lower shaft and the intermediate shaft. That is, when the upper shaft is made of a hollow round bar and the lower shaft fitted to this is made of a solid round bar, the upper shaft is connected to the upper shaft at the upper end and the universal joint is connected to the lower end. A serration unit is required to do this. Also,
An intermediate shaft is connected to the universal joint via a serration portion.

As shown in FIG. 5, in the universal joint 9, a serrated portion 9b is engraved on the inner peripheral surface of a tubular tightening portion 9a. Therefore, the serration portion 8c engaging with the serration portion 9b is provided on the lower shaft 8 or the intermediate shaft,
It is formed by the above method. That is, the lower shaft 8
Is cold-forged using a solid round bar as a material, and after forming the lower diameter portion 8a and the circumferential groove 8b by the roller 11 at the lower end,
The serrated portion 8c may be formed on the lower diameter portion 8a by the rolling roller 16.

[0020]

According to the present invention described above, since no cutting is performed by cold forging, roller forming and rolling, the material yield is improved, and the cutting cost,
The problem of cutting chips can be solved. Since the shaft details are formed by cold forging, the diameter of the shaft details is smaller than that of the thick shaft part, but since the flow of the composition flow is not interrupted in the material, the rigidity between the thick shaft part and the shaft detail part is reduced. It does not cause deterioration or strength reduction. Moreover, since the rolling process can be applied only to the necessary parts, the rolling pressure is small, and therefore the rolling facility is small and the tact is quick.

[Brief description of drawings]

FIG. 1 is a front view of an upper shaft showing an embodiment of the present invention.

FIG. 2 is a process drawing showing the manufacturing method of the present invention.

FIG. 3 is a schematic diagram of a part of the manufacturing process.

FIG. 4 is a sectional front view in which the upper shaft manufactured according to the present invention is fitted to the lower shaft.

FIG. 5 is a partial cross-sectional front view showing an example in which the present invention is applied to a lower shaft that is connected to a universal joint.

FIG. 6 is a cross-sectional front view of an upper shaft of a conventional example.

[Explanation of symbols]

 1 ... Upper shaft 1a, 5a ... Shaft thick part 1b, 5b ... Shaft detail 3,6, 8c, 9b ... Serration part 4 ... Circumferential groove 5 ... Lower shaft 8a, 12 ... Lower diameter part 10 ... Material 11 ... Roller 13 ... Circumferential projection 14 ... Circumferential groove 15 ... Contact portion 16 ... Rolling roller

Claims (2)

[Claims] 1. A solid round bar body, a shaft detail formed by cold forging, a circumferential groove formed by roller-molding the shaft detail, and raised to the left and right of the circumferential groove by the roller molding. A steering shaft, comprising: a serration portion formed on a peripheral surface of a lower diameter portion. 2. A cold forging step of forming a shaft detail by cold forging a material of a solid round bar, and forming a circumferential groove and a lower diameter portion raised to the left and right thereof by roller forming on the shaft detail. And a rolling step of forming serrations on the peripheral surface of the lower diameter portion.