JPS6240947A - Pinion cold forging method for rack pinion type steering gear - Google Patents

Abstract

PURPOSE:To manufacture at a low cost pinion having high accuracy by forming a stepped outside peripheral wall and a stepped hole by an extrusion molding of a columnar base material, executing its annealing and lubricating treatment, and thereafter, forming plural grooves and a serration by punch molding to the inside peripheral wall of the stepped hole. CONSTITUTION:A columnar base material 4 whose volume is roughly equal to the total volume of a pinion at the time of completion is brought to an extrusion molding from the axial direction, and a stepped outside peripheral wall consisting of a large diameter part 4a and a small diameter part 4b is formed, and also a center hole 5 and a stepped hole 6 are formed the tip face of the small diameter part 4b side and the tip face of the large diameter part 4a side, respectively. A molding material which has been obtained in this way is annealed, and thereafter, its lubricating treatment is performed. Subsequently, to the inside peripheral wall of a large diameter hole 6a of the stepped hole 6 of said molding material, a spline groove 7 alternately disposed of a groove 7a having a stepped part and a groove 7b having no stepped part is formed by punch molding. Next, to the inside peripheral wall of a small diameter hole 6b, a serration 8 extending in the axial direction is formed by punch molding. Thereafter, a pinion is obtained by forming a tooth part (omitted in the figure) in the small diameter part 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to a method for manufacturing a pinion for a rack-pinin type steering gear, and more particularly, to a method for cold forging a pinion using a cold forging method.

(Prior Art) As shown in FIG. 3, the structure of a rack and pinion steering gear is as follows: A toothed portion 1a formed on a pinion 1 connected to a shaft that transmits rotation of the steering wheel, and a toothed portion 1a formed on a side wall of a rack 2. The formed teeth 2a mesh with each other, and as the steering wheel is turned, the rack 2 is rotated in the axial direction (
It is driven in the left-right direction in the drawing to pull both wheels of the vehicle in a predetermined direction.

The structure of the pinion of such a rack and pinion type steering gear is as shown in the cross-sectional view of FIG. 4(a) and the side view of FIG. A substantially cylindrical hole 3 is formed in the axial direction from the end of the large diameter portion 1C, and a hole 3 is formed for spline-fitting the shaft from the steering wheel. Spline grooves 3a and serrations 3b are formed on the inner circumferential wall of 3.

(Problem that the invention attempts to solve) However, conventionally, manufacturing of such pinions requires
Since machining such as cutting and electrical discharge machining are performed, the number of machining steps is large, resulting in a high cost of 1~, and there is also a drawback that the machining accuracy of spline grooves, serrations, etc. varies from product to product.

(Means for solving the problem) The present invention was made in view of the above problems, and the purpose is to provide a pinion manufacturing method that can reduce the number of machining steps and improve the machining accuracy. In order to achieve this objective, the present invention forms a cylindrical material with a volume approximately equal to the total volume of the pinion when completed in the first step, and in the second step, the cylindrical material is oriented in the axial direction. Extrusion molding is performed from both ends to form a stepped outer circumferential wall having a large diameter portion and a small diameter portion, and a center hole is formed on the tip surface of the small diameter portion side, and a stepped hole extending in the axial direction is formed on the tip surface of the large diameter hole side. In the third step, the molded material formed in the second step is annealed and then subjected to lubrication treatment, and in the fourth step, the large diameter side of the stepped hole of the molded material is annealed. Punch forming a plurality of grooves or stepped grooves extending in the axial direction on the inner circumferential wall, and in a fifth step, punch forming a plurality of serrations extending in the axial direction on the inner circumferential wall on the small diameter side of the stepped hole of the molded material. The technical point is to use the cold forging method described above.

(Example) Figure 1 is an explanatory diagram showing an example of the present invention.
The manufacturing process is shown sequentially from a) to (e), and (b) to (d) are cross-sectional views.
) side.

First, in FIG. 4A showing the first step, a cylindrical material 4 having a volume approximately equal to the total volume of the completed pinion is formed.

In the next second step, a die (di
Using e), the cylindrical material 4 is extruded from both ends in the axial direction to form a stepped outer peripheral wall having a large diameter portion 4a and a small diameter portion 4b. At the same time, by this extrusion molding, a center hole 5 is formed in the center of the tip surface on the small diameter part 4b side, and a center hole 5 is formed in the center of the tip surface on the small diameter part 4b side.
A stepped hole 6 is formed in the axial direction from the center of the side tip surface.

Although the third step is not shown, the molded material molded in FIG. 3(b) is annealed and then subjected to a lubrication treatment.

Next, in the same figure (C) showing the fourth step, a spline groove 7 extending in the axial direction is punch-formed on the inner circumferential wall of the large diameter hole 6a of the stepped hole 6. Incidentally, the spline groove 7 is formed by alternately arranging grooves 78 having stepped portions and grooves 7b having no stepped portions.

In the same figure (d) showing the fifth step, a selection 8 extending in the axial direction is punch-formed on the inner circumferential wall of the small diameter hole 6b of the stepped hole 6. Then, a tooth portion (not shown) is formed in the small diameter portion 4b.

FIG. 4(e) is a side view of the large diameter portion 4a as seen from the end surface side, and the shaft from the steering wheel is fitted into the spline groove 7 and the serrations 8.

Next, another embodiment will be described based on FIG. 2(a) to FIG. 2[f]. Note that Figures (a) to (d) show cross sections, and Figures (e) and (f) show side views.

First, in the first step, as shown in FIG. 1(a),
A cylindrical material having a volume approximately equal to the total volume of the pinion when completed is formed.

In the next second step, first, as shown in Figure 2(a),
The cylindrical material is extruded from both ends in the axial direction using a die having a predetermined mold hole to form a stepped outer circumferential wall having a large diameter portion 9a and a small diameter portion 9b. At the same time, by this extrusion molding, a center hole 10 is formed at the center of the tip surface on the small diameter portion 9b side, and a cylindrical hole 11 is formed in the axial direction from the center of the tip surface on the large diameter portion 9a side. - Further, as shown in (1) of the same figure and (e) of the same figure, which is a side view of (b), a small diameter hole 12 is formed in the axial direction of the hole 11.
A groove 13 for end face correction is formed at the open end by extrusion molding.

This embodiment differs from the previous embodiment in that the large diameter hole 11 and the small diameter hole 12 are formed in separate steps.

Although the third step is not shown, after annealing the molded material shown in FIGS.

Next, in the same figure (C) showing the fourth step, the large diameter hole 1
A spline groove 14 extending in the axial direction is punch-formed on the inner circumferential wall of No. 1. Incidentally, the spline groove 14 is formed by alternately arranging a groove 148 having a stepped portion and a groove 14b having no stepped portion.

In the same figure (d) showing the fifth step, serrations 15 extending in the axial direction are punch-formed on the inner circumferential wall of the small diameter hole 12. Then, a tooth portion (not shown) is formed in the small diameter portion 9b.

FIG. 6(f) is a side view of the large-diameter portion 9a as seen from the end surface, in which the shaft from the steering wheel is connected to the spline groove 14.
It is designed to fit into the serrations 15.

If the manufacturing method described in the above two embodiments is used, the number of man-hours is significantly reduced compared to conventional mechanical processing, so manufacturing costs can be lowered, and the processing accuracy can be increased to produce uniform products. It becomes possible to manufacture

(Effects of the invention) As explained above, according to this invention, it is possible to reduce the number of processing steps and significantly reduce the manufacturing cost.
It is possible to manufacture pinions with high precision without variations from product to product.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are explanatory diagrams showing the manufacturing process of one embodiment of the present invention, and FIGS. 2(a) to 2(f) are illustrations of another embodiment of the present invention. FIG. 3 is a schematic diagram showing the structure of a rack and pinion steering gear, and FIGS. 4(a) and 4(b) are explanatory diagrams illustrating a conventional manufacturing method. 4: Cylindrical material 4a, 9a: Large diameter portion 4b, 9b: Small diameter portion 5.10: Center hole 6: Stepped hole 6a, 11: Large diameter hole 6b, 12: Small diameter hole 7.14 Varnish spline groove 8.15 : Serration 13: Groove Utility Model Registration Applicant Rhythm Auto Parts Manufacturing Co., Ltd.

Claims (2)

[Claims] (1) A method for cold forging a pinion of a rack and pinion type steering gear, which includes a first step of forming a cylindrical material with a volume approximately equal to the total volume of the pinion when completed, and extruding the cylindrical material from both ends in the axial direction. Molding is performed to form a stepped outer peripheral wall having a large diameter portion and a small diameter portion, and a center hole is formed in the tip surface on the small diameter portion side, and a stepped hole extending in the axial direction is formed in the tip surface on the large diameter portion side. a second step; a third step of annealing the molded material formed in the second step and then subjecting it to a lubrication treatment; a fourth step of punch-forming a plurality of grooves or stepped grooves extending in the direction; and a fifth step of punch-forming serrations extending in the axial direction on the inner circumferential wall on the small diameter side of the stepped hole of the molded material. A pinion cold forging method for a rack and pinion steering gear, which is characterized by: (2) In the second step, the stepped hole is molded in two steps: a large-diameter hole and a small-diameter hole, and the end surface on the large-diameter hole side is subjected to end face correction. A pinion cold forging method for a rack and pinion steering gear as described in .