JPH03238134A - Dedendum reinforcing tool - Google Patents

Abstract

PURPOSE:To uniformly generate residual compressive stresses in bottom and dedendum parts and to make improvement in the fatigue strength of dedendum parts by forming the parts of the dedendum reinforcing tool which come into contact with the dedendum as a projecting shape. CONSTITUTION:The load W predetermined according to the material, size, etc., of a gear 3 which is a part to be treated is applied between the tool 1 and a guide gear 5 which backs up the gear 3 to press the bottom part 3a of the gear 3 by the tooth-shaped projections 2 of the dedendum reinforcing tool 1. A guide gear 5 is simultaneously driven rotationally in an arrow direction. The tool 1 and the gear 3 are respectively rotated in arrow directions by this rotation and the respective tooth-shaped projections 2 of the tool 1 come into contact successively with the respective bottom parts 3a, thereby pressing these parts and generating the residual compressive stresses from the bottom parts 3a to the dedendum parts 3b of the gear 3. The tooth-shaped projections 2 press the bottom parts 3a of the gear 3 with the projecting parts 2a at the front ends thereof at this time and, therefore, even if ruggedness is generated in the bottom parts 3a, the generation of the residual stresses even in the recesses parts thereof is obtained.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a tool for reinforcing the dedendum of a part having teeth, such as a gear, which is used to press the bottom of the tooth of a gear to strengthen the dedendum of the part. (Prior Art) In order to improve the strength of the root part of a part having teeth, such as a gear, which has the weakest fatigue strength, shot peening has been conventionally performed after heat treatment. Shot peening is a method of projecting metal particles onto the surface of a workpiece at high speed to harden the surface and generate compressive residual stress in the surface layer, which is a means of improving fatigue strength. In addition to the gears mentioned above, it is widely used for springs, shafts, etc. However, when shot peening is applied to parts to improve tooth root strength, it is difficult to narrow down the shot peening treatment range due to restrictions on shot peening equipment such as nozzle diameter, so metal particles are Tips of teeth other than the original. As a result of being projected onto areas where shot peening is not necessary, such as the tooth surface, there is a problem in that rough skin and bulges occur on the tooth root and tooth surface. To solve this problem, the inventor of the present invention pressed the bottom of a toothed part with a tool that presses the bottom of the tooth to generate compressive residual stress from the bottom to the root of the tooth. We have discovered a method for strengthening the root of the tooth that can improve the fatigue strength of the tooth root without causing unevenness such as roughness or bulges, and we are currently making a separate proposal. (Problem to be solved by the invention) However, undulations tend to occur on the tooth bottom and tooth surface during machining, such as hobbing, and parts with such unevenness on the tooth bottom have a tendency to have undulations. When the tooth base strengthening method is applied, the tool comes into contact only with the curved part of the tooth bottom, so it is not possible to press all four parts, resulting in uneven generation of compressive residual stress and insufficient improvement of fatigue strength. This has been a problem with the dentinal strengthening method described above. (Object of the Invention) The present invention has been made in order to solve the above-mentioned problems in a tooth base strengthening method, and is intended to solve the problems described above in a tooth base strengthening method. It is an object of the present invention to provide a tool for strengthening the dedendum, which can uniformly generate compressive residual stress in the tooth root and dedendum, thereby maximizing the fatigue strength of the dedendum.

[Structure of the invention]

(Means for Solving the Problems) A dedendum strengthening tool according to the present invention is a dedendum strengthening tool that presses the bottom of a component having teeth to strengthen the dedendum of the component, the tool The part that abuts on the root of the tooth is configured to have a convex shape, and is characterized in that the above-mentioned configuration of the tooth base strengthening tool is used as a means for solving the above-mentioned problems. (Function) In the dedendum strengthening tool according to the present invention, the portion that comes into contact with and presses the tooth bottom of a component having teeth has a convex shape. Therefore, even if the tooth bottom of the component has irregularities due to hobbing or the like, the convex portion of the tool can come into contact with all four parts of the tooth bottom to generate compressive residual stress. As a result, the fatigue strength of the root portion of the component is improved. (Example) Hereinafter, the present invention will be specifically explained with reference to Examples. FIG. 1 shows an example of a tooth root strengthening tool according to the present invention, and as shown in the figure, the tooth root strengthening tool 1 includes:
In this embodiment, it is gear-shaped with a total of 18 tooth-like protrusions 2 that protrude radially, and the tip of each tooth-like protrusion 2 has a center portion in the tooth width direction that further protrudes in the tooth tip direction. It is formed into a mountain shape and has a convex portion 2a, and this convex portion 2a comes into contact with the root of the tooth of the part to be treated to undergo root strengthening treatment. In addition, the pitch of the tooth-like protrusions 2 of the tooth base strengthening tool 1 is as follows:
The pitch is made to match the pitch of the part to be processed so as to mesh with the teeth of the part to be processed. The tooth base strengthening tool 1 having such a shape is shown in Fig. 2(a) (
It is arranged as shown in b) and applied to strengthen the root of a component having teeth. That is, in FIGS. 2(a) and 2(b), a gear 3, which is a part to be processed, is rotatably supported by a workpiece holder 4 in the center of the figure, and the gear 3 on the left side of the figure is A tooth-shaped kite gear 5 is installed to mesh with the gear 3, and is designed to back up the load W applied to the gear 3 during dedendum strengthening treatment. On the other hand, on the right side of the gear 3 in the figure, the root strengthening tool 1 having the shape described above is disposed, and the convex portion 2 of the tooth-like projection 2
The gears 3a and 3a are joined together so that they abut against the tooth bottom portion 3a of the gear 3. Further, the shaft 5a of the guide gear 5 and the shaft 1a of the root strengthening tool 1 are connected via a synchronization mechanism (not shown), so that the rotation of the guide gear 5 is transmitted to the root strengthening tool 4 in synchronization. It has become. In this state, a predetermined load W is applied between the tool 1 and the guide gear 5 that backs up the gear 3, depending on the material, size, etc. of the gear 3, which is the part to be processed,
At the same time that the tooth bottom portion 3a of the gear 3 is pressed by the tooth-like protrusion 2 of the tool 1 for reinforcing the tooth base, the guide gear 5 is driven to rotate, for example, in the direction of the arrow in the figure. As a result of this rotation, the tool 1 and the gear 3 rotate in the directions of the arrows, and each tooth-like protrusion 2 of the tool 1 comes into n-th contact with each tooth bottom 3a of the gear 3, and presses the tooth bottom 3a of the gear 3. 3a
A compressive residual stress is generated in the dedendum portion 3b. At this time, the tooth-shaped protrusion 2 presses the tooth bottom part 3a of the gear 3 with the convex part 2a at the tip thereof, so even if the tooth bottom part 3a has irregularities, the four parts are Residual stress can be generated. Further, at this time, since the contact area between the tool 1 and the gear 3 becomes smaller, the load W can be reduced, and the load burden on the root strengthening treatment device can be reduced. Simultaneously with this rotation, as shown in FIG. By relatively moving the gear by a distance corresponding to the tooth width, compressive residual stress can be uniformly generated from the tooth bottom to the tooth root of the gear 3, and the tooth root strength of the gear 3 can be improved. It becomes possible. FIG. 3 shows another embodiment of the tooth root strengthening tool according to the present invention. As shown in the figure, the tooth root strengthening tool 10 in this embodiment has a shape roughly similar to that of the tooth root strengthening tool 1 according to the previous example, except that the tooth root strengthening tool 10 has convex tooth-shaped protrusions 11 provided radially. The position of the shaped portion 11a is sequentially shifted in the tooth width direction for each tooth-like projection 11. The tooth root strengthening tool 10 having such a shape has the same effect as the tooth root strengthening tool 1, and has the effect that the relative movement distance between the tool 10 and the processed part can be reduced. It also has That is, in the tooth root strengthening tool 10, since the tooth-like protrusions 11 having the convex portions 11a at different positions generate compressive residual stress at respective positions on the tooth bottom of the processed part, the tool 10 and the tooth root strengthening tool 10 have different positions. The relative moving distance with respect to the processed part is determined by the convex portions 11a, l of the adjacent tooth-like protrusions ti, ii.
Only the height difference d (see Fig. 3) of la is sufficient.

【Effect of the invention】

As explained above, the dedendum strengthening tool according to the present invention is a dedendum strengthening tool that presses the bottom of a part having teeth to strengthen the dedendum of the part. Since the part that comes into contact with the bottom is configured to have a convex shape, even if the part has unevenness on the tooth bottom, compressive residual stress is generated uniformly at the tooth bottom and tooth root. This has the excellent effect of maximally improving the fatigue strength of the tooth root.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the tooth root strengthening tool according to the present invention, and FIG. 2 (a) is an illustration of a situation in which root strengthening treatment is performed using the tooth root strengthening tool. 2(b) is an enlarged top view of FIG. 2(a), and FIG. 3 is a perspective view showing another embodiment of the tooth base strengthening tool according to the present invention. 1.10... Tool for strengthening the tooth base, 2a, lla... Convex portion, 3... Gear (parts having teeth).

Claims (1)

[Claims] (1) A tooth base strengthening tool for strengthening the tooth base of a part having teeth by pressing the tooth base, characterized in that a portion of the tool that comes into contact with the tooth base has a convex shape. A tool for strengthening the tooth root.