JPS6277144A - Formation of engaging recessed part for lathe dog - Google Patents

Abstract

PURPOSE:To make a lathe dog contact with the inside peripheral wall of an engaging recessed part by a large contact area, and to form a recessed part by a small forging pressure, by forming a recessed part by forging on the end face of a shaft to be worked, and subsequently, forming a center hole by forging, and simultaneously, pressing the end face of the shaft to be worked, so as to become flat. CONSTITUTION:A recessed part 46 is formed on the upper end face of the first intermediate product 44 by inserting a rod material into a hole die 39 of a die 37, inserting a pair of the first push dies 41, 42 into both ends of the hole die 39, and executing the forging. A section of an opening edge of the recessed part 46 becomes a circular arc shape having a large radius of curvature. Subsequently, the first push dies 41, 42 are drawn out, the second push dies 48, 49 are inserted and the intermediate product is pressed and forged, and a turn center hole 26 and a stop center hole 28 are formed. In this case, a pressure surface 48a of the second push die 48 presses the end face of the second intermediate product 50 so as to become flat as a whole, therefore, a metal in the vicinity of the center hole 26 flows concentrically toward the opening edge side of the recessed part 46. In this way, a section of the opening edge of the recessed part 46 becomes a circular arc shape having a small radius of curvature, the inside peripheral wall of the recessed part 46 becomes roughly parallel to the shaft core of a rear axle, and it becomes an engaging recessed part 27.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a rotary engagement recess used in shaft machining on an end surface of a shaft to be machined.

(Prior art) When machining the outer circumferential surface of a shaft to be machined, if a part of the outer circumferential surface of the shaft to be machined is chunked to the rotating side of the machine tool,
This machine tool becomes an obstacle, making it impossible to machine the entire circumference of the shaft to be machined.

Therefore, when attempting to machine the entire circumference of the shaft to be machined,
Conventionally, the following measures have been taken.

That is, first, both centers of the machine tool are fitted into the center holes pre-formed on both end faces of the shaft to be machined to support the shaft to be machined, and then a center hole formed in advance on one end face of the shaft to be machined is supported. A rotary ring attached to the rotating side of the machine tool is engaged with the engaging recess, and a portion of the inner circumferential wall of the engaging recess is pushed by the rotary ring that rotates together with the rotating side. The processing shaft is rotated on the axis of the center. According to this, since there are no machine tool components on the outer peripheral surface of the shaft to be machined,
Enables machining of the entire circumference of the shaft to be machined.

(Problems to be Solved by the Invention) Incidentally, if a shaft to be machined as described above is to be produced by grinding, it is advantageous from the viewpoint of precision to form the engaging recessed portion by forging. However, when attempting to form the engaging recess by forging, the following problems arise.

That is, when the engaging recess is formed by forging, the cross section of the opening edge of the engaging recess becomes an arcuate shape with a large radius of curvature due to the metal flow during forging.

Therefore, when the rotary wheel pushes the inner circumferential wall of the engagement recess, the area where the rotor, which has an outer circumferential surface parallel to the axis of the workpiece shaft, and the inner circumferential wall of the engagement recess are in contact with each other is the circular arc mentioned above. It is reduced by the amount of the shape. Therefore, the load from the drive to the shaft to be machined is concentrated on a small area of the inner circumferential wall, and therefore, there is a possibility that such an engaging recess cannot cope with the driving force of the machine tool.

Therefore, it is conceivable to form an engagement recess with a large area and increase the area where the rotary ring and the inner circumferential wall of the engagement recess are in contact with each other. However, this requires a large forging pressure, and since the engaging recess is only for machining the shaft to be machined, it is preferable that it be as small as possible.

(Object of the Invention) This invention was made in view of the above-mentioned circumstances, and when forming an engaging recess on the end face of a shaft to be machined by forging, the inner circumferential wall of the engaging recess is The purpose of the present invention is to enable the two to be brought into contact with each other with a large contact area, and to form this engaging recessed portion with a small forging pressure.

(Structure of the Invention) A feature of the present invention for achieving the above object is that on the end face of the shaft to be machined, first, a recess is formed at each position where a retaining recess is to be formed, and then, A center hole into which the center of the machine tool is inserted is formed by forging on the end face of the shaft to be machined, and when the center hole is forged, the end face of the shaft to be machined is pressed flat.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, a rear axle S of a motorcycle will be explained as an example of a shaft to be machined.

First, with reference to FIG. 1, the power system of a motorcycle in which the rear axle S is used will be explained.

In FIG. 2, an engine 1 for driving the vehicle is a two-stroke engine, and the engine 1 drives rear wheels 2 via a transmission device 3. An arrow Fr in FIG.

The engine 1 has a cylinder 5, a piston 6, and a crankshaft 8 supported by a crankcase 7. A carburetor 9 is attached to the intake side of the engine 1, and an air cleaner 10 is attached to the intake port of the carburetor 9. The outside air passes through the air cleaner 10 to the carburetor 9.
(arrow A in the figure), where it is mixed with gasoline fuel and this air-fuel mixture is supplied to the engine 1 (arrow B in the figure). The combustion of this air-fuel mixture causes the engine 1 to operate, and power is output from the crankshaft 8.

The transmission device 3 has a transmission case 12 integrally attached to the rear part of the crankcase 7. The rear axle S is supported by a bearing 13 at the rear of the transmission case 12, and the rear wheel 2 is supported at the free end of the rear axle S that protrudes from the transmission case 12.

The rear wheel 2 has a hub 15 and a tire 16 supported by the hub 15, and the hub 15 is fitted onto the free end of the rear axle S by a spline 17, and the hub 15 is attached to the free end of the rear axle S. The rear axle S is fixed to the rear axle S by a nut 20 screwed into a threaded portion 18 formed in the rear axle S. From the crankshaft 8 to the rear axle S, a centrifugal clutch 21, a belt-type deceleration means 22, and a gear-type deceleration means 2 are connected.
Power is transmitted via 3. The rear axle S supports a driven gear 24 of a gear type speed reduction means 23.

Referring to FIGS. 2 and 3, the rear axle S will be explained in more detail. The rear axle S is constructed as follows.

That is, on the end face of the rear axle S on the opposite side to the threaded portion 18, a rotation center hole 26 is formed on the axis thereof into which the rotation center of the machine tool is inserted, and a rotation center hole 26 is formed on the end surface of the rear axle S on the opposite side to the threaded portion 18. Four engaging recesses 27 are formed at equal intervals in the circumferential direction. On the other hand, on the axial end surface on the threaded portion 18 side, a blind center hole 28 is formed on the axis at t±, into which the dead center of the same machine tool is inserted.

With reference to FIGS. 4 and 5, the engine oil in each center hole 26, 28 and the engagement recess 27 formed in the rear axle S will be explained.

In the figure, 29 is a rotating body of the machine tool, and this rotating body 29
is rotated around the rotation center 30. This rotating body 29
A rotation center 31 that rotates together with the rotation body 29 is provided on the rotation center 30 of the rotation body 29 . Also, this rotation center 3
0, there is a stop center 32 opposite to the rotation center 31.
This stop center 32 is supported by a tailstock (not shown) of the machine tool so as to be freely movable in the axial direction. and,
Position the rear axle S on the rotation center 30, rotate around the rotation center 31, and fit into the center hole 26, then stop at the center 3.
When the rear axle S is inserted into the center hole 28 with two axial movements, the rear axle S is supported on the machine tool.

The rotary body 29 is provided with a rotary ring 33 on an axis parallel to the bipedal rotation center 30. This rotating body 33 is the rotating body 29
A plurality of them are provided at equal intervals in the circumferential direction. The protruding end side of the rotary ring 33 is a cylindrical retaining shaft end 33a, and this engaging shaft end 33a is biased toward the rear axle S side by a spring 34. Each engagement shaft end 33a is fitted into the corresponding engagement recess 27 by the elastic force of the spring 34.

When the rotary body 29 rotates, the rotor 33 revolves around the rotation center 30, and the engagement shaft end 33a of the rotor 33 comes into contact with the inner circumferential wall 27a of the engagement recess 27. This causes the rear axle S to rotate on the rotation center 30 (arrow R in the figure), and processing such as cutting is performed on the outer peripheral surface of the rotating rear axle S.

Next, a method of forming the rear axle S will be explained with reference to FIGS. 6 to 10.

First, as a first step, a bar material 36 for forming the rear axle S by forging is inserted into a mold hole 39 of a mold 37, as shown in FIG. Then, a pair of first press molds 41 and 42 are inserted into both ends of the mold hole 39.

Next, as the second step, as shown in Figures 7 and @8,
By moving the pair of first pressing dies 41 and 42 in the directions indicated by the arrows in the figure, the bar 36 is pressurized and forged within the die hole 39, thereby forming the first intermediate product 44 of the rear axle S. to form.

In the above case, the pressing surface 41a of each first pressing die 41.42,
42 a has a flat surface perpendicular to the axis of the first intermediate product 44 . Furthermore, a recess molding die 43 is protruded from the suppressing surface 41a of the upper first pressing die 41 in correspondence with each position where the engaging recess 27 is to be formed. There are four recesses 46 on the upper end surface of the first intermediate product 44.
is formed. Note that when the recess 46 is formed in this way, the end face of the first intermediate product 44 and the recess 4 are formed as shown in FIG.
The cross section of the opening edge of the recess 46 has an arc shape with a large radius of curvature R.

Next, as a third step, as shown in FIGS. 9 and 10, after the first pressing mold 41.42 is extracted from the mold hole 39, a pair of second pressing molds 48.49 are inserted. . By moving this in the direction of arrow E in the figure, the first intermediate product 44 is pressurized and forged within the mold hole 39, thereby forming the second intermediate product 50 of the rear axle S.

In the above case, each second pressing die 4B, 49 suppression surface 48a,
49a is a flat surface perpendicular to the axis of the second intermediate product 50;
In addition, a center hole forming die 51 is provided protruding from each of the pressing surfaces 48a, 49a on the axis thereof. Then, the rotating center hole 26 and the blind center hole 28 are formed by each of the center hole forming molds 51.

When the circumferential center hole 26 is formed, the metal near the circumferential center hole 26 is removed from the concave portion 46 side or the second intermediate product 50.
tends to flow outward from the end face. However, at this time, since the suppressing surface 48a of the second pressing mold 48 presses the end surface of the second intermediate product 50 flatly as a whole, the metal flows intensively toward the opening edge side of the recess 46 ( 1st
0 (arrow F in figure). As a result, the cross section of the opening edge of the recess 46 has a small circular arc shape with a radius of curvature r, and the inner circumferential wall 46a of the recess 46 is formed to be approximately parallel to the axis of the rear axle S, which serves as the retaining recess 27. Ru. That is, the inner circumferential wall 27a of the engagement recess 27 is substantially parallel to the outer circumferential surface of the engagement shaft end 33a of the rotary ring 33 over almost the entire axial direction of the second intermediate product 50.

Next, the spline 17 and the threaded portion 18 are formed by machining on the second intermediate product 5°, which is formed like a biped, and the formation of the rear axle S is completed.

FIG. 11 shows a state in which the engaging shaft end 33a of the rotary ring 33 is in contact with the inner circumferential wall 27a' of the conventionally shaped engaging recess 27'. The cross section of the opening edge of this retaining recess 27' has a radius of curvature R
It has an arcuate shape with a large angle ', and therefore comes into contact with the outer circumferential surface of the engagement shaft end 33a over a small area as indicated by the parenthesis in the figure. Therefore, the load from the rotary ring 33 on the rear axle S is concentrated in this small area, and there is a possibility that such an engagement recess 27' cannot cope with the driving force of the machine tool.

On the other hand, FIG. 12 shows an engagement recess 27 formed according to an embodiment of the present invention, and the cross section of the opening edge of this engagement recess 27 has a circular arc shape with a small radius of curvature r. The inner circumferential wall 27a of the mating recess 27 is substantially parallel to the outer circumferential surface of the engagement shaft end 33a of the rotary ring 33 over almost the entire axial direction of the rear axle S. They will come into contact by area.

(Effect of the invention) According to the present invention, first, a recess is formed by forging on the end face of the shaft to be machined, and then a center hole into which the center of the machine tool is inserted is formed by forging into the end face of the shaft to be machined. In order to flatten the end face of the shaft to be machined when forging the center hole, even if the cross section of the opening edge of the recess becomes an arc with a large radius of curvature, By forging the center hole and pressing the end face of the shaft to be machined flat at this time, a part of the metal on the end face of the shaft to be machined is flowed toward the recess, thereby causing the cross section of the opening edge of the recess to is formed into a circular arc shape with a small radius of curvature. Then, an engagement recess is formed in which the inner circumferential wall has a surface parallel to the axis of the shaft to be processed over the entire axial direction. Therefore, when the rotary ring is engaged with the engagement recess, the rotary ring and the inner circumferential wall of the engagement recess come into contact with each other with a large contact area, and the load from the rotary ring can be sufficiently coped with.

Moreover, since the inner circumferential wall of the engagement recess is formed in a plane parallel to the axis of the shaft to be machined over the entire axial direction, the engagement recess has a sufficient contact area with the turner even if its area is small. It can be made large.

Therefore, it is sufficient that the retaining recess is small, and this recess can be formed with a small forging pressure.

[Brief explanation of drawings]

The figures show an embodiment of the invention, in which Fig. 1 is a plan sectional view of the transmission, Fig. 2 is a partially sectional side view of the rear axle, and Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2. Fig. 4 is a side cross-sectional view of how the rear axle is mounted on a machine tool when mechanically forming it, Fig. 5 is a cross-sectional view taken along the line v-V in Fig. 4, and Fig. 6 is a cross-sectional view of the machine for forging the rear axle. 1 process drawing, Fig. 7 is the same second process drawing, Fig. 8 is a partially enlarged sectional view of Fig. 7, Fig. 9 is the same third process drawing, Fig. 10 is a partially enlarged sectional view of Fig. 9, FIG. 11 is a conventional view showing a state in which the rotary ring and the engaging recess are engaged, and FIG. 12 is a view taken along the line ``--'' in FIG. 5. 26... Rotation center hole, 27... Engagement recess, 3-toe rotation center, 33 Fist/rotator, 46Φ/recess, 52... Engagement recess molding mold, S... Rear axle (processed shaft) .

Claims (1)

[Claims] 1. When forming a plurality of engagement recesses for engaging the rotary ring on the rotating side of the machine tool on the end face of the shaft to be machined at equal intervals in the circumferential direction, first, the above-mentioned engagement recesses are formed on the end face of the shaft to be machined. Then, a center hole into which the center of the machine tool is inserted is formed by forging on the end face of the shaft to be machined. A method for forming an engaging recess for a rotary turner, characterized by pressing the end face of a processing shaft flat.