JPS6054372B2 - Method for hardening the outer surface of the outer ring of a constant velocity universal joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating the outer surface of an outer ring of a constant velocity universal joint mainly used in a rotational force transmitting part of an automobile or the like by high-frequency induction heating.

In general, a constant velocity universal joint represented by Japanese Patent Publication No. 33-1305 has a stem portion 2 on which a running wheel (not shown) is fitted and held, and a bell mouth-shaped socket portion provided at one end of this stem 2, as shown in Fig. 3. 3, an inner ring 5 connected to a drive shaft 4, and a joint ball 6 inserted between the outer ring 1 and the inner ring 5 to transmit power. Then, the bearing between the outer ring 1 and the above-mentioned running wheel is fitted.
L' ・1,... ^"1" A part of the socket part 3 that the P part contacts (hereinafter mainly referred to as the socket part) has a first
An ideal hardening pattern indicated by reference numeral A in the figure is used to increase the hardness of the outer surface of the outer ring 1 by applying surface roughening by high-frequency induction heating. However, on the inner surface of the socket 3 which is to be heat-treated among the outer surfaces of this type of outer ring 1, grooves 7 for fitting the joint balls are carved with a cutter or the like.
Since the tip of the cutter hits the inner wall surface of the shoulder of the socket, a relatively deep pocket 8 as shown in FIGS. 1 and 3 is formed in the shoulder of the socket 9. Therefore, the wall thickness of the socket shoulder portion 9 is formed to be very thin. Therefore, when high-frequency induction heating is subsequently applied to the above-mentioned outer surface of the outer ring 1, the hardened layer a extends up to the pocket 8 as shown in FIG. It reaches the inner wall surface of the socket (causing so-called ``drop-out'' of the hardened layer), making it impossible to obtain the desired hardening pattern A as shown in FIG. Then, when this ``missing'' occurs, the fourth
A change in the structure of the material occurs between the hardened shoulder layer a in the figure and the stem side and socket side that sandwich it, resulting in a difference in strength, and the rotational force is transmitted from the drive shaft 4 to the outer ring 1. During the quenching process, there is a drawback that the torsional force generated between the socket part 3 and the stem part 2 induces localized fatigue failure due to the hardened shoulder layer a. Also, the socket part 3 deforms relative to the stem part 2 with the shoulder hardened layer a as the bending point,
There was a problem that the socket part 3 came into contact with the hardened coil body that heats the stem part 2. The present invention is intended to prevent such inconvenience, and as shown in FIG. 2, a surface-hardened coil body 10 is disposed on the outer periphery of the outer ring 1 for simultaneous high-frequency induction heating of the stem portion 2 and the socket portion 3. When applying current to the coil body 10 while rotating either the outer ring 1 or the surface-hardened coil body 10 to apply surface hardening to the outer surface of the stem 2 and the socket part 3 of the outer ring 1, the opening of the socket part 3 is With the part facing downward, cooling water 11 is applied directly from this opening in the socket part 3 to the inner wall surface of the socket, especially the pocket 8, and the thin part of the socket shoulder part 9 corresponding to this pocket 8 is cooled. , and the heating rate of the socket shoulder 9 is suppressed by applying water so that the heating rate of the socket shoulder 9 is relatively slower than that of other parts, for example, that of the stem part 2, and the heating rate of the socket shoulder This is to prevent the cured layer from coming off in the portion 9.

As detailed above, the present invention provides surface hardening of the outer ring of a constant velocity universal joint to a required depth by high-frequency induction heating. Since the cooling water is applied in parallel with the above-mentioned surface hardening operation and the surface heating rate is suppressed to a slow state, a pocket is provided in the socket as in the above embodiment. If the method of the present invention is applied to a socket portion having a thin local wall thickness, it is possible to prevent the hardened layer in the socket portion from slipping out over the inner and outer surfaces of the socket portion.
This is useful in obtaining the ideal curing pattern as shown in FIG.

In particular, in this type of joint shaft, the stem portion and the socket portion are hardened together by a single hardened coil body, so the heating rate of the socket portion must be suppressed to a slower state than the quenching speed of the stem portion. However, in the present invention, by applying water, the quenching rate of the socket part is locally suppressed to a slow state independently of the heating rate of the stem part. It is possible to reliably prevent the socket from coming off, which tends to occur in products where the mouth is hardened in one piece.Furthermore, the opening of the bellmouth-shaped socket is directed downward, and the outer periphery of the stem and socket is fixed. Since a heat generating coil body is arranged in the part and the cooling water is applied directly to the inner wall surface from the opening of the socket part, the cooling water does not scatter on the outer surface to be quenched. Concerns about product defects such as unevenness are significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the ideal hardening pattern during surface hardening of the response shaft (joint shaft) of a constant velocity universal joint, Figure 2 is a schematic diagram for explaining the method of the present invention, and Figure 3 is a constant velocity universal joint. A cross-sectional configuration diagram showing an example of a universal joint, and Fig. 4 is a schematic diagram showing the "° pull-out phenomenon" of a conventional hardened layer. 1... Outer ring, 2... Stem part , 3...
... Socket part, 10 ... Hardened coil body for high frequency induction heating, 11 ... Cooling water.

Claims (1)

[Claims] 1. A method for uniformly induction hardening the outer surface of the stem portion and bellmouth-shaped socket portion of the outer ring of a constant velocity universal joint to a desired depth using a heating hardening coil body disposed on the outer periphery thereof, The opening of the socket section is directed downward, a heating coil body is arranged around the outer periphery of the stem section and the socket section, and the opening is placed on the inner wall surface of the socket section corresponding to the surface to be hardened of the socket section. A constant velocity control device characterized by directly applying cooling water to cool the inner wall surface of the socket part in combination with the heating operation, and suppressing the surface heating rate to a relatively slow rate. Method for hardening the outer surface of the outer ring of the joint.