JPS6231715A - Formation of crank shaft for single and plural cylinders - Google Patents

Abstract

PURPOSE:To prevent a semiprocessed product from deforming in a forging process by heating the semiprocessed product in order to be pressurized in the axial direction, and finishing pin axes and a crank shaft at the specified sizes. CONSTITUTION:A die 16 is provided with parts 17 for forming pin axes 13 in the state of being stretched long and thin, and other parts 18 used for forming crank arms 12 and having the same length of intervals as of the parts 17 for forming the pin axes 13. Hence, thickness, in the axial direction of a main shaft 11 of parting parts 19 between the mutually adjacent parts 18 enlarges. Therefore, even if the parting parts 19 are heated by a heated material in a process of forming a semiprocessed product, easy inclination or deformation can not take place during forging operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming crankshafts in single and double cylinders, and in response to a demand for thinning of the portion of a crankshaft forging mold corresponding to the cylinder shaft, the mold portion is heated during forging. The present invention aims to provide a method for forming a crankshaft that prevents forging from becoming impossible in a short period of time due to collapse or deformation.

Recently, in order to downsize engines, there has been a demand for downsizing of crankshafts for single-cylinder and multi-cylinder engines. Therefore, the crankshaft 1 shown in FIGS.
The length of the pin shaft 2 is shortened, that is, the connecting rod insertion portion 3 is made as narrow as possible, and the overall length of the crankshaft 1 is shortened.

Therefore, as shown in FIG. 4, the forging die 4 for this type of crankshaft was adapted to this, and the forming part 5 for the connecting rod part 3 was directly narrowed. However, such molds have the following drawbacks.

The useful life of the mold is very short, there are many defective products, and it is not cost-effective. The reason for this is that the width of the connecting rod insertion part 3 shown in Figure 1 is narrow, or in other words, the wall thickness of the mold part of the forming part 5 shown in Figure 4 is thin, so the heating temperature for forging is set to about 1,200°C. During forging, the mold 4 is heated and the temperature of the mold increases, especially the temperature of the upper end of the forming part 5, which causes collapse and deformation of this part as shown in Fig. 5 during forging. This is because the forging operation becomes impossible.The present invention forges the product so that the pin shaft has a length and final volume that ensure a partition of the required thickness between the crank arm forming parts of the forging die. Then, by heating this product and applying pressure from both sides, the pin shaft was molded into a predetermined length and volume. Therefore, the thickness of the mold was increased between the parts corresponding to the crank arm. Therefore, even if the portion corresponding to the bottle shaft is heated to a high temperature from the heated material during forging of the product, it will not collapse or deform during the forging operation. In this product, the distance between the crank arms is too large, and the volume of the pin shaft is insufficient for connecting the connecting rod, so it must be heated to a temperature below approximately 1,200℃).
Pressure is applied from the outside using a mechanical press, hydraulic press, etc. to finish the length and volume of the pin shaft to predetermined dimensions and volume. Since the length and volume of the pin shaft in the semi-finished product are determined to match that of the finished product, there is no excess material. Of course, the length of the semi-finished pin shaft may be longer than the final length by an extremely small dimension, for example, 1 mm.

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 6 shows the product. 11 is the main shaft, 12 is the crank arm, 13 is the eccentric pin shaft for connecting connecting rod, 14
is the reference plane. The length and volume of this pin shaft 13 are calculated and determined in advance so that when this pin shaft 13 is compressed and deformed into a finished product, it will have a predetermined length and volume. 20 Pressure is applied to the semi-finished product from the outside in the axial direction of the main shaft 11, compressing and deforming the pin shaft 13, so that the crank arm 12 comes to a predetermined position I, that is, the reference plane 14, and the axial length and diameter of the main shaft 11 are also adjusted to specified dimensions. Finish the finished product as shown in Figure 7.

A mold as shown in Figure 8 is used to forge the product. FIG. 9 is a sectional view taken along the line 9--9 in FIG. 8. That is, the mold 16 has a part 17 for molding the pin shaft 13 into a long and thinly extending state, and a part 18 for molding the crank arm 12, which is spaced by the same length as the molding part 17 of the pin shaft 13.
1°.Therefore, the thickness in the axial direction of the main shaft 11 of the partition 9 between the portions 18 becomes large. Therefore, even if the partition portion 19 is heated by the heated material during molding of the product, it will not easily tilt or deform during the forging operation.

According to the present invention, the pin shaft is forged to a length that has the required dimensions and volume when it is a finished product, and which ensures a partition of the required thickness between the crank arm forming parts of the mold when it is a semi-finished product. By heating this product and applying pressure in the axial direction, the pin shaft is finished to the specified dimensions and volume, and the axial length and diameter of the crankshaft are finished to the specified dimensions, so that the crank arm molding of the mold is possible. The size of the partition between the working parts can be increased, that is, it can be made thicker, and when the material is forged into a product, the core part is heated by the heat of the material and can be prevented from collapsing or deforming during forging. It has various features, such as allowing the mold to be used for a long time and in an accurate state, producing a finished product simply by heating and pressurizing the product in the axial direction, and of course reducing product costs.

[Brief explanation of the drawing]

1 to 3 are side, left and right side views showing an example of a crankshaft, respectively. FIG. 4 is a cross-sectional view of the lower mold for molding the crankshaft shown in FIG. 5
The figures are Fig. 4, which is a cross-sectional view explaining the phenomenon of the lower die falling down, Fig. 6, a side view of an example of the product produced by the present invention, Fig. 7, a side view of the finished product, and Fig. 8, the molded product. Top view of mold for use, No. 9
The figure is a sectional view taken along line 9-9 in FIG. 11...Main shaft, 12...Crank arm, 13...Pin shaft, 14...Reference surface, 16...Mold, 17...Part, 1
8...part, 19...partition part. Patent applicant: Omi Tozawa, Jitsukai
Kakuda Iron Works Co., Ltd. Procedure Amendment Form

Claims (1)

[Claims] A semi-finished product is forged so that the pin shaft has a length and final volume that can secure a partition of the required thickness between the crank arm forming parts of the forging die, and the semi-finished product is heated and pressurized from both sides. A method for forming crankshafts for single and double cylinders, characterized by forming the pin shaft to a predetermined length and volume.