JPH0526251A - Manufacture of fork for universal coupling - Google Patents

Abstract

PURPOSE:To prevent the occurrence of breakage to a punched part owing to a processing hardening action during a bending work after punching of raw material and to enable firm bolt fastening through the increase of the thickness of the selvage piece for fastening a bolt in a cylindrical hub part, in press molding of a fork for an universal coupling. CONSTITUTION:A pair of tubs 4 are formed to the one side part of a rectangular sheet 2 and a metallic sheet material having selvage pieces 7 formed at two end parts is sheared. A series of processes through a bending work, a spline work, a boring work, and a tapped hole forming work includes a process wherein each of a pair of the selvage pieces 2 is folded in the middle to superpose the folded parts with each other, a process wherein a connecting part between the tub 4 and the rectangular sheet 2 is pressed, and a process wherein the tub 4 and the hub tubular part 11 are bent in an arcuate shape so that they are positioned approximately concentrically to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a universal joint for connecting a cylindrical hub having a fork and a shaft having an arm portion perpendicular to the axis, and a method for manufacturing a universal joint fork.

[0002]

2. Description of the Related Art A universal joint of this type is usually used for angular connection between a cross shaft having a cross arm and a rotary shaft such as an electric shaft, and a pair of forks formed at the tip of a cylindrical hub has a cross shaft. The arm is inserted through a cup with a needle. It is known in the prior art to manufacture a cylindrical hub with a fork from a flat metal plate by plastic working. For example, as shown in FIGS. 4 and 5, a metal plate material 1 is provided with a rectangular plate 2 on which a cylindrical hub is to be formed, and a rectangular plate 2 which is continuous with both ends of the rectangular plate and is bent into a cylindrical shape. Shaped hub 5 (Fig. 5)
Punched out as a blank having a pair of tabs 3 to form bolting protrusions 6 and a pair of tabs 4 to form a fork 8, the rectangular plate 2 is bent into a cylindrical shape, and the tabs are bent. As shown in FIG. 5, the part 3 is folded back inward from the middle part to form the insertion hole 14 and the screw hole 16 of the tightening bolt,
Further, the fork 8 is formed with a through hole 13 for inserting the cross-shaped arm portion 19, and the spline groove 1 is formed on the inner peripheral surface of the hub.
7 is performed to obtain a universal joint fork as shown in FIG.

[0003]

The conventional universal joint shown in FIG. 5 described above is work-hardened because the work-hardening action when the material is punched causes cracks in the punched portion during subsequent bending. An annealing process is required to remove the. In particular, there is a problem that cracks are likely to occur at the connecting portion between the tab 4 and the rectangular plate 2 and the yield is low.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks and problems, in which a tab serving as a pair of fork branch pieces on one side of a rectangular flat plate and both end portions of the flat plate are provided. Forming a hub tubular portion by cutting the thin metal plate material so as to have a pair of ears, and bending the rectangular flat plate into a cylindrical shape concentric with the tab so that the ears face each other. And a cutting step in which two aligned through holes are bored in the tab so that the cross arm of the cross shaft can be inserted, and the inner circumference of the cylindrical tubular hub portion is splined. And a cutting step in which a bolt insertion hole is formed in one of the ear pieces for passing a tightening screw and a screw hole is formed in the other side by aligning the screw hole with each other, and the tab and the rectangular flat plate are provided. And the process of pressing the connecting part with A step of superimposing by bending each of said pair of lugs, the one in which the tab is made and a step Komu bent to have a circular cross-sectional shape of the hub tubular portion substantially coaxial.

[0005]

In the present invention, since the fork branch piece is bent so as to be concave substantially inward with the cylindrical hub so as to be concave inward, it is possible to exhibit high rigidity against torsional stress, and also the base of the tab. By pressing the punching portion of the portion, the surface roughness is improved, and the annealing treatment is unnecessary. Further, since the protruding portion for tightening the bolt is formed by folding the metal plate ear piece in the middle, the wall thickness around the screw hole portion becomes large, and the strength of the bolt fastening portion is improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. 1 to 3 are views showing a manufacturing process of an embodiment of the present invention. First, a material 25 shown in FIG. 1A is punched out from a metal plate material or a coil material by press working, and a pair of tabs 4 is formed on one side (upper side) of the rectangular plate 2.
However, ear pieces 7 are formed on both ends thereof. In addition,
The portion of the rectangular plate 2 becomes a hub tubular portion described later, and the tab 4
Is a fork branch piece, and the ear piece 7 is a pair of parallel protrusions extending along the axial direction at the position of the cutting edge of the hub tubular portion for tightening the bolt. Following this first punching step, FIG.
In the second step shown in, the root parts 21 and 2 of the tabs 4 which are the fork branch pieces of the cut surface punched by the press.
The cut surface portions of 2a and 22b are pressed as shown by broken lines to give plastic deformation and improve the surface roughness. Next, in a third step shown in FIG. 1C, both ear pieces 7, 7 are bent and overlapped as indicated by reference numeral 9. In the fourth step of FIG. 1D,
Only the tab 4 is bent in an arc shape with a radius of curvature R centering on a point A slightly deviated from the center C of the rectangular plate 2 so that the tab 4 has a partially circular cross-sectional shape.

In the next step (fifth step), FIG.
As shown in FIG. 1, as a pre-stage of forming the rectangular plate 2 into a cylindrical shape, a primary bending is performed around the center C thereof in a substantially parabolic shape. In the sixth step shown in FIG. 1 (f), in order to form the parabolic rectangular plate 2 into a more complete cylindrical shape, secondary bending is performed to form the hub tubular portion 11, and
The pair of ear pieces 7 and 7 are arranged so as to face the hub tubular portion 11 substantially in the radial direction. At this time, the tab portion bent in the arc shape in the fourth step becomes a fork branch piece 12 which is bent substantially concentrically with the hub tubular portion 11. With the above, the cold forging process by the press is completed, and as shown in FIG.
A cold forged finished product as shown in (b) and (c) is obtained. As can be seen from FIG. 2, in this forged product, the pair of fork branch pieces 12 formed by bending from the tab 4 are
The hub tubular portions 11 formed from the rectangular plate 2 that face each other at a required distance d and that are connected with the fork branch pieces are
Both edge portions at the cut-off position are abutted at one place on the circumference, and the ear pieces 7 extending in the radial direction in parallel with each other by the bending process of the sixth step have a certain distance D following the both edge portions. Facing each other.

Thereafter, as a seventh step, cutting and spline processing steps are performed to obtain the universal joint fork 20 shown in FIGS. 3 (a) to 3 (c). That is, the fork branch pieces 12, 12 are aligned with the through-hole 13 into which the cross-shaped arm of the cross shaft and the cup with the needle are to be fitted, and the bolt insertion hole 14 and the seat 15 are provided on one of the ear pieces 7, 7. But,
On the other side, a screw hole 16 to be screwed with the threaded portion of the bolt is drilled, and on the inner peripheral surface of the hub tubular portion 11, a spline groove 17 for connecting with a spline shaft is provided to form one part of the universal joint. The fork 20 is completed.

[0009]

As described above, according to the present invention, the punching cut surface of the root portion of the fork branch piece is pressed to improve the surface roughness, so that the occurrence of cracks due to the bending can be prevented. The annealing step can be omitted, and the fork branch piece is bent so that the cross section perpendicular to the axial direction is concave inward, so it exhibits high rigidity against torsion stress during use, Further, by bending and overlapping the ear piece portion, the wall thickness of this portion is increased, and firm screw tightening becomes possible, and other practical advantages and effects are brought about.

[Brief description of drawings]

FIG. 1 is a diagram showing a step of press-forming a fork for a universal joint according to the present invention.

FIG. 2 is a cross-sectional view showing a press-molded finished product which is an intermediate product of a fork when the present invention is applied.

FIG. 3 is a cross-sectional view of the finished fork when cutting is completed according to the present invention.

FIG. 4 is a plan view of a conventional universal joint fork material.

FIG. 5 is a cross-sectional view of a conventional universal joint fork.

[Explanation of symbols]

 2 rectangular plate 4 tab 7 ear piece 9 protrusion 11 hub tubular portion 12 fork branch piece 13 through hole 14 bolt insertion hole 16 screw hole 17 spline groove 20 fork for universal joint 25 material

Claims (1)

Claim: What is claimed is: 1. A step of cutting a thin metal plate material so that a tab serving as a pair of fork branch pieces is provided on one side of a rectangular flat plate and a pair of ear pieces is provided at both ends of the flat plate. A step of bending the rectangular flat plate into a cylindrical shape concentric with the tab so that the ear pieces face each other to form a hub tubular portion; and the tab so that the cross arm of the cross shaft can be inserted. A cutting step in which two aligned through holes are drilled in and a spline process is performed on the inner circumference of the hub tubular portion bent into the cylindrical shape;
A bolt insertion hole is provided in one of the ear pieces for passing the tightening screw.
In a method for manufacturing a fork for a universal joint having a cutting step of aligning and drilling a screw hole on the other side, a step of pressing a connecting portion of the tab and the rectangular flat plate, and each of the pair of ear pieces. A method of manufacturing a fork for a universal joint, comprising: a step of bending and superimposing and a step of bending so that the tab has a circular cross-sectional shape substantially concentric with the hub tubular portion.