JPH0259013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a kick starter arm for starting engines used in motorcycles, lawn mowers, buggies, scooters, etc.

(Prior Art) Conventionally, as shown in FIG. 7, in a kickstarter arm for a motorcycle, lawn mower, buggy, scooter, etc., the shape of the pedal stopper portion 51 at the base end and the crankshaft mounting portion 52 at the tip corresponds to the diameter of the arm main body 50. It is manufactured by hot die forging or cutting using die forging dies because cold swaging forging cannot release the mold and there is a greater degree of freedom in design. Ta.

(Problems to be solved by the invention) However, in hot die forging and cutting, 30 to 50% of the material is discarded as burrs and cutting waste, resulting in poor yields. Afterwards, that part must be manually finished using a grinder, or shot peened must be applied to remove scale from hot working.
There is a problem in that many processing steps are required, resulting in high costs. Furthermore, hot die forging dies suffer from greater wear than cold swaging forging dies and have a shorter lifespan, resulting in various problems such as inaccurate product shapes.

(Means for Solving the Problems) The present invention was completed in order to solve the conventional problems as described above. A swaging forging die is provided with a pair of mold recesses having a fan-shaped cross section with a maximum diameter equal to or less than the inner diameter of the circular hole main mold part, and a flat enlarged mold recess at the other end of the circular hole main mold part. A rod-shaped material is cold-swaged forged from one side to form a linear arm material that has a pedal stopper section with a fan-shaped cross section that is slightly smaller in diameter than the arm main body at the narrow diameter part of the base end, and a crankshaft attachment part at the tip. Next, the arm material is knocked out without dividing the swaging forging die, and then cold bent by a die forging die having a bent mating surface.

(Embodiments) Next, the present invention will be described in detail with reference to illustrated embodiments. In FIGS. 1 and 2, 5 is a die for swaging forging, in which a small diameter mold hole 3 having a smaller diameter than the diameter of the circular hole main mold part 1 is connected to one end of the circular hole main mold part 1. A pair of mold recesses 2 having a fan-shaped cross section with a maximum diameter equal to or less than the inner diameter of the circular hole main mold part 1 are formed in the small diameter mold hole part 3 at axially symmetrical positions, and a flat shaped mold recess 2 is formed at the other end of the circular hole main mold part 1. An enlarged recess 4 is formed therein. A rod-shaped material 6 is charged into the swaging forging die 5 as shown by the dashed line, and cold swaging forging is performed using the punch 7 to form the proximal end as shown in FIG. Narrow diameter part 1
A straight arm material 14 is obtained, which is provided with a pair of pedal stopper parts 12 having a slightly smaller diameter than the arm main body 11 at the end thereof, and has a crankshaft attachment part 13 formed at its tip.
At this time, since the maximum diameter of the pedal stopper portion 12 is smaller than the outer diameter of the arm main body 11, the cold swaging forging process is performed smoothly. Next, the dowel pin 8 is inserted without dividing the swaging forging die 5.
The arm blank 14 is released from the swaging forging die 5, and a cold forging die 21 having a mold recess 20 having the final finished shape of the arm blank 14 is formed as shown in FIGS. 4 and 5. arm material 1 in the lower die 22 of
Upper die 2 of the cold forging die 21 on which the upper die 2 is placed.
When the arm material 14 is lowered, the arm material 14 is cold-forged and bent into the final finished shape with almost no burrs, and the product 30 shown in FIG. 6 is obtained.

(Effects of the Invention) As is clear from the above description, the present invention performs cold swaging forging on a rod-shaped material using a swaging forging die to obtain an arm material, and then using a swaging forging die to obtain an arm material. Because the final finished product is obtained by cold bending the arm material, there are almost no burrs, and there is no waste of material due to burr trimming or cutting as in the past, which greatly improves yield. be done. Moreover, there is no need for special surface treatment, except when there is no scale and the surface has a beautiful mirror finish, as in the case of hot working, so there are fewer processing steps, and it is also easier to use than hot forging dies. It has many advantages, such as a long mold life and accurate mold shape, and is of great value to the industry.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing forging by cold swage forging, Figure 3 is a perspective view of the cold swage forged arm material, and Figures 4 and 5 are cold die forging. 6 is a perspective view of the final finished product, and FIG. 7 is a perspective view of a conventional kick starter arm. 1: circular hole main mold part, 2: mold recessed part, 3: small diameter mold hole part, 4: enlarged mold recessed part, 5: die for swaging forging,
6: Bar material, 14: Arm material, 21: Die forging.

Claims (1)

[Claims] 1 A pair of mold recesses 2 having a fan-shaped cross section with a maximum diameter equal to or less than the inner diameter of the circular hole main mold part 1 are provided in the small diameter mold hole 3 connected to one end of the circular hole main mold part 1, and the circular hole main mold part 1 At the other end of the mold part 1, a rod-shaped material 6 is cold swaged forged from one side using a swage forging die 5 having a flattened enlarged recess 4, and an arm main body 11 is formed at the narrow diameter portion at the base end. Forming a linear arm material 14 having a pedal stopper portion 12 with a fan-shaped cross section with a slightly smaller diameter and a crankshaft attachment portion 13 at the tip, and then swaging the arm material 14 and dividing the forging die 5. This method of manufacturing a kick starter arm is characterized by knocking out the arm without any problem and then cold bending it using a die forging die 21 with a bent mating surface.