JPS604883B2 - Gear finishing method and its tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the fatigue strength of a tooth root portion of a gear by applying plastic working to the root portion of a gear that has been subjected to cutting or heat treatment, and a tool used therefor.

Conventionally, as a method of improving the fatigue strength of various mechanical parts, etc., it has been common practice to apply plastic working to the parts of these mechanical parts that are subjected to stress concentration after cutting or heat treatment. Roller processing in which a hard roller is pressed against a rotating workpiece and the rolling action is used, and the final two or three blades of a finishing broach are passed through while applying a compressive action to the workpiece without applying any cutting action at all. Burnishing processing or shot peening processing in which fine particles are accelerated by some method and collide with a workpiece are known. If such processing is carried out properly, compressive residual stress will be generated on the processed surface of the workpiece, giving work hardening to the surface layer, and the parts subject to repeated bending stress and sinking stress will be It is possible to significantly improve the fatigue strength of By the way, if the gear is made symmetrical, it is relatively practical for processing simple shapes such as gears that require a large pressure force in normal roll processing, but it is relatively practical for processing complex gears such as helical gears. For shaped gears, the required rigidity of each part of the processing device, such as the feed mechanism, must be increased, making it difficult to construct a practical machine.

Furthermore, since it is impossible to apply burnishing, which is a secondary processing means to broaching, to gears, shot peening is currently only used in some parts. As shown in FIG. 1, which shows the finished state of a gear by this shot peening process, a gear 1, which is a workpiece, is housed in a cylindrical drum 2, and a conveyor 3 pressed against this drum 2 is operated to produce a drum. 2 rotates to roll gear 1 within drum 2.

A shot 5 is blown into the drum 2 in an accelerated state by a shot injection device 4 installed above the drum 2.
After colliding violently with the gear 1 and plastically deforming the surface of the gear 1, the particles are deposited on the tray 6 fixedly provided below the conveyor 3 through a gap (not shown) formed in the conveyor 3. A bucket elevator 7 is provided connected to this tray section 6 to convey the shots 5 accumulated on this tray section 6 toward the shot injection device 4.
A hopper 8 feeds the shot 5 lifted by the bucket elevator 7 to the shot injection device 4 from the upper end of the bucket elevator 7.
is connected to the bucket elevator 7 and installed at its upper end. When the gear 1 is subjected to shot peening, the shot 5 scatters or generates noise, which worsens the working environment.In addition, the shot 5 collides with the entire gear of the gear 1, resulting in damage to the tooth surface. There is a drawback that accuracy and quality are reduced. Furthermore, in the case of mass-produced gears, processing must be carried out in batches, which causes problems such as finishing the gears by shot peening being removed from the production line. The present invention solves the drawbacks that occur when finishing gears by shot peening, and provides a method and a tool for use in which plastic working can be easily applied only to the tooth roots of gears that have been subjected to cutting or heat treatment. The purpose is to provide.

The configuration of the first invention that achieves this object is to apply the tip surface of a gear finishing tool, which is formed into a rough surface shape having a large number of minute protrusions, to the dedendum of the gear to be machined that has finished cutting or heat treatment. This method is characterized in that the fatigue strength of the dedendum is improved by applying plastic deformation to the surface layer of the dedendum.
The tip surface that is pushed into the tooth groove of the to-be-processed gear and contacts only the dedendum of the to-be-processed gear to press the dedendum is formed into a rough surface having a large number of minute protrusions. That is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of a gear finishing method and a tool thereof according to the present invention will be described in detail below with reference to FIGS. 2 to 7.

Fig. 2a shows the appearance of the tool tip in the first embodiment, Fig. 2b shows the state during machining of the gear to be machined using this, and Fig. 3 shows the machining system according to the present embodiment. As shown in the figure, the table top 11, which is rotatable around a vertical axis by a table rotation mechanism and can also be reciprocated in the horizontal direction by a horizontal movement mechanism, has a cover that is coaxial with the table 11. A fixing pick 13 for fixing the processed gear 12 is attached.

On the other hand, a rod-shaped tool 16 is provided with a distal end surface 15 having a shape corresponding to the root part 14 of the gear to be machined 12 fixed on the fixing jig 13, and which contacts only the root part 14 of the gear to be machined 12. is in a state where its rear end is fixed to the tool holder 17, and the rotating plate 1 that supports this tool holder 17
8 is rotatable around an axis horizontal to the head 19 by a rotating mechanism.

Furthermore, the head 19 that supports the rotating plate 18 is capable of vertical movement and horizontal movement with respect to the table 11 by a vertical movement mechanism and a horizontal movement mechanism, and is also capable of reciprocating in the horizontal direction perpendicular to the horizontal movement direction of the table 11. . The tip surface 15 of the tool 16 is formed into a rough surface covered with a large number of hemispherical or conical minute protrusions. It is necessary to select an appropriate size in consideration of the effect of improving fatigue strength.

For example, in the case of hemispherical microprotrusions, the practical value is 0.5 to 2
．． A diameter of about 0 mm is suitable. The microprotrusions may be formed on the tip surface 15 of the tool 16 by cutting, pressing, etc. in addition to welding, adhesion, etc. The gear 12 to be machined that has been cut or heat treated is fixed on the fixing tool 13, and the tool 16 is attached to the gear 12 to be machined.
In order to set the gear to a predetermined position in advance, the vertical movement mechanism and horizontal movement mechanism of the head 19 and the horizontal movement mechanism of the table 11 are operated, and if the gear 12 to be processed is a helical gear, the tip of the tool 16 The tool 16 is rotated by the rotating mechanism to rotate the rotating plate 18 at a certain angle so that the arrangement direction of the minute protrusions formed on the surface 15 is parallel to the tooth trace of the gear to be machined 12.
Tilt around. When the head 19 is vibrated horizontally in the opposite direction of the gear to be machined 12 by a vibration device attached to the horizontal movement mechanism of the head 19, the minute protrusions formed on the tip surface 15 of the tool 16 vibrate at the dedendum of the gear to be machined 12. 14 and plastically deforms the surface layer of this root part 14, the fatigue strength of this part is improved.At the same time, the vertical movement mechanism of the head 19 moves the head 19 up and down. The tool 16 is fed and moved in the face width direction of the gear 12 to be machined.

In addition, when the gear 12 to be processed is a helical gear, the table rotation mechanism and the vertical movement mechanism of the head 19 are operated synchronously by a synchronization control device in accordance with the helical angle of the helical gear, and the vertical movement of the head 19 is accompanied by the vertical movement of the head 19. Feed movement of tool 16 and table 1
It is necessary to synchronize the rotation of the gear 12 to be machined which rotates with the gear 1 . When machining of one tooth base 14 is completed, the head 19 is returned to the original machining start position by the vertical movement mechanism and horizontal movement mechanism, and the table 11 is rotated by a certain angle by the table rotation mechanism, and then the next After the dedendum portion 14 to be machined is directly opposed to the tool 16, the dedendum portion 14 is sequentially machined according to the procedure described above. Fourth
Figure a shows the tip surface 15 of the tool 16, in which the tool 21 is formed into a disk shape in order to extend the life of the tool 21, and its outer peripheral surface (tip surface) 22 that contacts the dedendum of the gear to be machined is the tip surface 15 of the tool 16.
FIG. 4b is a perspective view showing the external appearance of a tool 21 according to a second embodiment, which is formed into a rough surface having a similar number of microprotrusions and is used while being rolled. 5 is a cross-sectional view of the tool 21 showing a state in which the gear to be machined 23 is being machined using the tool 21. As shown in FIG.
1 is rotatably supported by a tool holder 24, and has the same structure as the first embodiment except that a vibration device is not attached to the horizontal movement mechanism of the head 26.

The horizontal movement mechanism of this head 25 presses the tool 21 against the gear to be machined 23, and the vertical movement mechanism presses the tool 21 against the gear 23 to be machined.
1 is moved up and down together with the head 25 to give a feed movement.
Since the tool 21 rolls on the root portion 26 of the gear to be machined 23 and plastically deforms the surface layer of the tooth root portion 26, the fatigue strength of this portion is improved. If the gear to be machined 2-3 is a helical gear, the tool 21 is made parallel to the tooth trace of the gear to be machined 23 by the turning mechanism in accordance with the helical angle, and then the head is moved by the synchronous control device. The table rotation mechanism is operated in synchronization with the vertical movement of the tool 25, and the to-be-processed gear 23 is rotated at a constant speed in conjunction with the vertical movement of the tool 21. Figure 6 is 31
FIG. 7 is an external view showing the machining state in a third embodiment in which the material is formed into a hob shape to enable continuous machining and to improve the work efficiency, and the machining system is as shown in FIG. Furthermore, in this embodiment, a tool rotation mechanism for rotating the tool 31 is additionally required compared to the second embodiment described above.

A spiral pressing crest 32 is formed on the outer peripheral surface of the tool 31, and the outer peripheral surface (tip surface) 35 of the pressing ridge 32, which contacts only the dedendum 34 of the gear to be machined 33, is as described above. The tip end surface 15 of the tool 16 is formed into a rough surface having a large number of minute protrusions. According to this, it is necessary to rotate the rotating shaft of the tool 31 by the turning mechanism in accordance with the helix angle of the gear to be processed 33 and the advance angle of the pressing crest 32 formed on the tool 31.

That is, the rotation axis of the tool 31 is rested so that the direction of the tooth trace of the gear to be machined 33 and the direction of the pressing crest 32 coincide with each other, and the axis of rotation of the tool 31 is placed in the direction of movement of the pressing ridge 32 that is moved by the vertical movement mechanism of the head 36. The processing gear 33 must be rotated by a table rotation mechanism. Processing is done using head 3.
When the tool 31 is pressed against the root part 34 of the gear to be machined 33 by the horizontal movement mechanism 6 and the vertical movement speed of the tool 31 and the rotational speed of the gear to be machined 33 are synchronized, the pressing ridge part 3
The outer circumferential surface 35 of No. 2 rolls on the dedendum 34 of the gear to be machined 33, plastically deforms the surface layer of the dedendum 34 and work-hardens it, improving its fatigue strength. Note that the conditions for synchronizing the vertical movement speed of the head 36 and the rotation speed of the table 37 are as follows:
The amount of vertical movement of the tool 31 per one revolution of the gear to be machined 33 is t, the number of rotations of the tool 31 per one revolution of the gear to be machined 33 is n, the number of openings (number of threads) of the pressing ridges 32 of the tool 31 is g, and the number of threads to be machined is g. If the helix angle of the gear 33 is 8, the tooth normal module of the gear 33 to be machined is m, and the number of teeth of the gear 33 to be machined is z, then the number of teeth of the gear 33 to be machined is n.

Here, the sign of ± in the above equation is between the tool 31 and the gear to be machined 33.
When there is a relative feed relationship in which the tool 31 is moved in the same direction as the rotating direction of the tool 31 on the mating surface, if the torsional directions of the tool 31 and the gear to be machined 33 are the same, it will be -, and it will be different. In this case, it will be ten. Moreover, when there is a reverse feed relationship, the sign is reversed. As described above, according to the gear finishing method and tool thereof according to the present invention, the tip surface of the tool that contacts only the dedendum of the gear to be machined is formed into a rough surface consisting of a large number of minute protrusions, and this is By pressing the tooth root and plastically working the tooth root surface layer, residual stress is generated here and the fatigue strength is improved, so unlike shot peening, there is no damage to the tooth surface of the processed gear. Moreover, since machining is performed in a concentrated manner, machining time is significantly shortened.
In addition, there are no problems with the working environment, and it is excellent in mass production, and it has fatigue strength equal to or higher than conventional products without using high-quality materials or making special design changes. It is possible to finish the gears. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the state of finish machining of a gear by shot peening, FIG. b
is a sectional view showing the processing state, and FIG. 3 is a processing system diagram.

Further, FIG. 4a is a perspective view showing the external appearance of a tool according to another embodiment of the present invention, FIG. 4b is a sectional view showing the machining state thereof, and FIG. 5 is a machining system diagram thereof. Furthermore, the sixth
The figure is an external view showing a processing state according to another embodiment of the present invention, and FIG. 7 is a processing system diagram thereof. In the drawing, 12, 23, and 33 are gears to be machined; 14, 26, and 34 are root parts of the gears to be machined; 15 are tip surfaces of the tool; 16, 21
, 31 are tools, and 22 and 35 are outer peripheral surfaces (tip surfaces) of the tools.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. Pressing the tip end surface of a gear finishing tool, which is formed into a rough surface shape having a large number of minute protrusions, only on the dedendum of a gear to be machined that has finished cutting or heat treatment, A gear finishing method characterized in that plastic deformation is applied to the surface layer of the gear to improve the fatigue strength of the tooth root. 2. The tip surface, which is pushed into the tooth groove of the gear to be machined and contacts only the dedendum of the gear to press the dedendum, is formed into a rough surface having a large number of minute protrusions. A gear finishing tool featuring: