JPH0158250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method in which only the bottom of a groove can be easily work-hardened with a small force.

It is known that in order to improve the fatigue strength of a material, it is sufficient to work harden the portion of the material that receives stress concentration. Conventionally, we have used roller machining, which uses a compaction effect by pressing a hard roller against the material, or in which the last few blades of a finishing broach do not perform any cutting action at all, but instead apply a compression action to the material as it passes through. Work hardening is applied to the material by burnishing or shot peening, in which small particles are accelerated in some way and collide with the material. According to these methods of work hardening by plastic working, if the amount of pressing pressure is appropriate, compressive residual stress is generated on the processed surface and the surface layer can be work hardened, and is subjected to deformation such as repeated bending and torsion. It becomes possible to significantly improve the fatigue strength of the part.

By the way, many mechanical parts such as power transmission shafts, rotating shafts, and reinforcement beams have oil grooves, key grooves, fastening grooves, etc., and when repeated loads are applied, large stress concentrations occur in these grooves. This may lead to fatigue failure. The aforementioned roller machining and shot peening methods can be considered as work hardening methods for symmetrical grooves, but in the latter case, they are not suitable for grooves with localized and complex shapes, and conventionally roller machining has been used exclusively. has been adopted.
As shown in FIG. 1, which shows the working principle of this roller machining, the width of the disc-shaped or rod-shaped tool 1 is wider than the width of the groove 3 formed in the workpiece 2.
The tool 1 is made larger by the desired amount of compressive deformation, and after pushing the tool 1 into the groove 3 so that the tip of the tool 1 reaches the bottom 4 of the groove 3, the tool 1 and the workpiece 2 are inserted into the groove 3. The entire groove 3 is machined by relatively moving along the groove 3. In the case of the groove 3, the part where stress is concentrated is the bottom part 4 other than the side wall part 5, so it is sufficient to work harden only this bottom part 4, but in the conventional groove, the side wall part 5 is also work hardened. Generally, the side wall portion 5 is often a portion to which only a small amount of stress is applied and does not need to be work hardened. Therefore, conventional roller machining requires a processing machine with a large number of contact surfaces and a large output capacity, which usually necessitates the use of high quality materials.

From this point of view, it is an object of the present invention to provide a method for easily work-hardening grooves without using a processing machine with a large output capacity and without using high-quality materials.

The structure according to the groove work hardening method of the present invention that achieves this object has a cross-sectional shape that almost corresponds to the bottom of the groove formed in the workpiece, and a width that is slightly smaller than or about the same as the width of the groove. A pressing tool having a width and forming a fluid chamber into which fluid can be supplied is inserted into the groove, and pressurized fluid is supplied to the fluid chamber so that the tip of the pressing tool presses the bottom of the groove. The tip of the pressing tool is deformed in this manner, and in this state, the workpiece and the pressing tool are relatively moved along the groove to work harden the bottom of the groove. It is something.

Hereinafter, reference will be made to FIG. 2, which shows the working principle, and FIG. 3, which shows the external appearance of the pressing tool, for an example in which the groove work hardening method according to the present invention is applied to an annular groove formed on a rotating shaft. This will be explained in detail. An annular groove 12 carved in the rotating shaft 11
The bottom part 1 is composed of a bottom part 13 and a pair of side wall parts 14, and has an arcuate shape that tends to cause stress concentration.
The tip of a pressing tool 15 having a shape substantially corresponding to the width of the groove 12 and having a width that is slightly smaller than or approximately the same as the width of the groove 12 is inserted into the groove 12. The tip of this pressing tool 15 is pressed by pressure oil from the pressure oil supply/discharge port 17 which communicates with the pressure oil supply/discharge port 17 via the oil passage 16 and is connected to a pressure oil supply source (not shown). A pressure oil chamber 18 is formed for expanding and compressing the bottom 13 of the groove 12, and this pressing tool 15 is therefore manufactured by known means such as casting. The tip of the pressing tool 15 is curved in an arc shape along the groove 12 as shown in FIG. 3, but it can also be formed into a spherical shape as shown in FIG. The shape may be any shape as long as it can compress the bottom 13 of the groove 12 when expanded. The width of the pressing tool 15 is the groove 1
2, the pressing tool 15 can be easily inserted into the groove 12 without damaging the side wall portion 14 when pressure oil is not being supplied to the pressure oil chamber 18. By feeding the pressure into the pressure oil chamber 18, the tip of the pressing tool 15 is expanded and the bottom 13 of the groove 12 is compressed. By rotating the rotating shaft 11 in this state, the bottom part 13 of the groove 12 is rolled and hardened.
1 is fixed and the pressing tool 15 is rotated around the rotating shaft 11 along the groove 12, the same effect can be obtained.

In this embodiment, the groove 12 is formed on the rotating shaft 11, but in the case where the groove is carved on a flat plate, the pressing tool is moved parallel to the flat plate along the groove, or vice versa. Since the flat plate must be moved, the tip of the pressing tool 15 is made straight as shown in FIG. Since the cross-sectional shape of the tip of the pressing tool 15 in this embodiment is a semicircular arc shape, it is particularly suitable for work-hardening the part of the bottom that connects to the side wall of the groove.

As described above, according to the groove work hardening method of the present invention, a pressurized fluid is supplied to the tip of the pressing tool having a width equal to or less than the width of the groove to expand it, and only the bottom of the groove is compressed to harden the workpiece. Since the pressing tool and the pressing tool are moved relative to each other along the groove, the groove can be easily work-hardened using a small-capacity processing machine because there are fewer contact areas. There is no longer a need to use materials.

[Brief explanation of drawings]

Fig. 1 is a working principle diagram showing a conventional groove work hardening method by roller processing, Fig. 2 is a working principle diagram showing a groove work hardening method according to an embodiment of the present invention, and Fig. 3 is a diagram of the pressing tool. 4 and 5 are respectively perspective views showing the appearance of another embodiment of the pressing tool according to the present invention. In the figures, 11 is a rotation shaft, 12 is a groove, 13
14 is the bottom of the groove, 14 is the side wall of the groove, 15 is a pressing tool, and 18 is a pressure oil chamber.

Claims (1)

[Claims] 1. A press having a cross-sectional shape substantially corresponding to the bottom of a groove formed in a workpiece, having a width slightly smaller than or approximately the same as the width of the groove, and forming a fluid chamber into which fluid can be supplied. A tool is inserted into the groove, and pressurized fluid is supplied to the fluid chamber to deform the tip of the pressing tool so that the tip presses the bottom of the groove, and in this state, pressurized fluid is supplied to the fluid chamber. A method for work hardening a groove, comprising moving a workpiece and the pressing tool relative to each other along the groove to work harden the bottom of the groove.