JPH0225413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for hardening a rebro joint, and more particularly to a method for hardening the inner surface of an outer race constituting the rebro joint.

(Prior Art) A rebro joint, which is a telescopic constant velocity joint used in the automobile industry, is composed of a plurality of balls, usually six, a cage for holding the balls, an outer race, and an inner race. Ball grooves in the race and the inner race are arranged in a V-shape, that is, they are inclined symmetrically to each other by equal angles with respect to the rotation axis.

Since this ball groove rubs violently with the ball, it must have sufficient wear resistance. Conventionally, for the outer race, the inner race, and especially the outer race, the entire inner surface, including the groove where the ball contacts, is coated with a method such as high-frequency heating. Hardening was performed by

(Problems to be Solved by the Invention) However, the outer race is usually manufactured using steel. The structure of the steel material used in this case is a mixed structure of ferrite and pearlite, but when hardened by high-frequency heating, the structure changes to martensite, and at this time the volume expands. Since this volumetric expansion occurs only in the hardened portion, that is, the inner surface of the outer race, the inner surface is deformed and curved, and the inner diameter and grooves at both axial ends of the outer race are distorted and curved.
BBD (Between Ball Diameter) is larger than that at the center of the shaft. In particular, when the ball groove is in the V-shape described above, deformation due to strain becomes complicated, so it is very difficult to correct it by cutting, etc. after quenching.

For this reason, in the conventional outer race for rebro joints, the central part of the groove was raised compared to both ends, so there was a deviation from a true cylinder (height of the raised part), or cylindricity, of about 0.10 to 0.15 mm, and this hardening distortion caused The resulting noise and reduced durability have been problems.

The present invention is intended to solve the above-mentioned problems in the prior art, and its purpose is to provide a simple hardening method for obtaining a reversible joint with low cylindricity, low noise, and excellent durability. It is in.

(Means for Solving the Problems) That is, in the method of hardening a reversing joint of the present invention, when hardening the inner surface of the outer race constituting the reversing joint, the method hardens the inner surface of the outer race constituting the reversing joint at both axial ends of the inner surface and in the vicinity thereof, and at the balls of the reversing joint. It is characterized in that an unhardened part is provided in at least a part of the non-contact part.

As a means of hardening the inner surface of the outer race, for example, by inserting a ferrite core etc. into the inner surface and upper and lower surfaces of the coil, using a hardened coil whose magnetic flux is suddenly attenuated at the coil end surface, and using a frequency of 20 to 100 KHz. , on the wide side of the inner diameter part between the V grooves, there continues to be a small gap between the workpiece and the coil, which generates eddy current and induction heating up to the end face.
On the narrower side of the inner diameter between the grooves, the gap between the workpiece and the coil is short, so eddy currents are less likely to occur, and the area near the end faces is not subjected to induction heating. Therefore, when induction heating is performed for about 2.0 to 3.5 seconds at 150 to 200 KVA using the above coil and frequency, and then rapidly cooled, the inner diameter of the inner diameter of both end faces is heated at the narrow part of the inner diameter between the V grooves. An unhardened portion is formed.

Since the unhardened portion remains as a mixed structure of ferrite and pearlite, there is no change in volume due to transformation, and therefore the deformation of the hardened portion is suppressed from both ends, thereby reducing the amount of deformation of the hardened portion.

The size of the unhardened part varies depending on the size of the outer race and the diameter of the ball, but for vehicles, it should be 2 to 5 inches long in the axial direction from both axial ends.
It is preferable to have a continuous or interrupted band shape formed by a straight line or a curved line with a length of 15 to 30 mm in the inner circumferential direction. Also, it is preferable to provide them approximately equally on both ends.

When the unhardened portion is provided in the form of an interrupted band, if the interval between the interrupted portions is too wide, the effect of suppressing deformation will be lost, so it is preferable to set the interval to about 30 to 50 mm.

(Example) FIG. 1 shows an example of the present invention. Further, FIG. 2 is a sectional view taken along line A--A in FIG. 1. Insert a ferrite core etc. into the inner surface and upper and lower surfaces of the coil into the inner surface of the outer race 1 for the rebro joint, which has an outer diameter of 112 mm, an inner diameter of 74.6 mm, and a ball groove of 19 mm.
By using a hardened coil whose magnetic flux suddenly attenuates at the end face of the coil, and performing induction heating for 2.8 seconds at a frequency of 40KHz, and then rapid cooling, the inner periphery is applied to the hardened part 2 and the ball groove part 3 where the balls do not contact. Band-shaped unhardened portions 4 each having a direction length of 25 mm and an axial length of approximately 3 mm were provided at six locations, three locations each at the upper end and the lower end. This unhardened portion 4 does not undergo volumetric expansion due to martensitic transformation unlike the hardened portion 2, but on the contrary tends to contract due to thermal stress, so it serves the role of suppressing the expansion of both end surfaces of the outer race 1.

FIG. 3 is a schematic diagram showing the amount of deformation of each part of the outer race 1 after hardening. When the entire inner surface of the outer race 1 is subjected to induction hardening, the hardened portion 2 becomes a martensitic structure and expands in volume, so that the axial length of the inner surface of the outer race 1 becomes longer than the axial length of the outer surface. Therefore, the cylindricity of the central part 6 of the inner surface is the same as that of the front part 5 and rear part 7 near both end faces.
The cylindricity becomes larger than that of , and the inner surface is curved and the cross section becomes drum-shaped. The products using the conventional method had induction hardening applied to the entire inner surface, so the cylindricity was 0.1 to 0.15 mm as shown in the figure, but the product using the method of the present invention had a cylindricity of about 0.05 mm. This was reduced to 1/2 to 1/3 compared to the conventional method.

Durability comparison test: In an example, a rebro joint that had been hardened by the method of the present invention and a rebro joint that had been hardened by a conventional method were attached to a testing machine and their durability (durability time) was compared under the same conditions. The durability of the products using this method was improved by about 10 to 30% compared to those using the conventional method, and the noise during testing was also significantly reduced.

(Effects of the Invention) As described above, the method for hardening a rebro joint of the present invention suppresses deformation of the outer race by providing an unhardened portion on a part of the inner surface when hardening the inner surface of the outer race constituting the rebro joint. Therefore, the cylindricity after quenching, which was 0.1 to 0.15 mm when using the conventional method, is reduced to about 0.05 mm when using the method of the present invention, and the smoothness of the groove is greatly improved. did.

For this reason, the durability of the reversible joint is increased and the noise during use is significantly reduced, which has the effect of increasing the reliability and commercial value of products such as vehicles that use the reversible joint.

[Brief explanation of drawings]

Fig. 1 is a plan view of an outer race of a reversible joint showing an embodiment of the method of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is a plan view of an outer race after quenching. It is a schematic diagram showing the amount of deformation of each part. In the figure, 1... Outer race, 2... Hardened part, 3... Ball groove part, 4... Unhardened part, 5...
...front part, 6...center part, 7...rear part.

Claims (1)

[Claims] 1. A reversing joint characterized in that, when hardening the inner surface of an outer race constituting the reversing joint, unhardened portions are provided at both axial ends of the inner surface and in the vicinity thereof, and at least in part of the non-contact portions of the balls of the reversing joint. quenching method.