JPS6231714A - Formation of crank shaft on single and plural cylinders - Google Patents

Abstract

PURPOSE:To prevent easily falling down of parts of a die for forging by inclining balancer weight parts outward against reference planes and placing said balancer weight parts onto the reference planes later. CONSTITUTION:Balancer weight parts 14 incline outward against their reference planes 15 at the stage of a semiprocessed product. The balancer weight parts 14 of the said semiprocessed product are pressurized by a press from outward so as to be placed onto the reference planes 15. Hence, in the case of a die 16, parts 17 which form the balancer weight parts 14 in relation to pin axes 13 face outward to incline toward the axis direction of main axes 11. Therefore, thickness of the parts 17 increase in outward direction, and even if the parts 17 are heated for forming a semiprocessed product, easily inclining or falling of said parts down do not occur during casting operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a crankshaft in a single or vented cylinder, and in response to a demand for thinning of a portion of a crankshaft forging mold corresponding to a pin shaft, the mold portion is heated during forging. The present invention aims to provide a method for forming a crankshaft that prevents the forging operation from being 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 l is shortened.

Therefore, as shown in FIG. 4, the forging die 4 for this type of crankshaft was adapted to this, and the part of the molding part 5 for the part 3 into which the connecting rod was to be inserted 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 conrod insertion part 3 shown in Fig. 1 is narrow, or in other words, the thickness of the mold part of the forming part 50 shown in Fig. 4 is thin. During the operation, 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, and the forging In the present invention, a semi-finished product is forged so that the balancer weight part is inclined outward with respect to the reference plane, and this semi-finished product is heated so that the inclined balancer weight part is pressed against the reference plane. I made it to be located at . Therefore, the mold also has a shape that is inclined outward, that is, in the axial direction of the crankshaft, at a portion corresponding to the balancer weight portion. Therefore, the part of the mold that corresponds to the balancer weight part is formed to be thick, so that it will not easily collapse or deform even if it is heated during forging of a semi-finished product. In this semi-finished product, the balancer weight part is still deformed, so heat it to about 1° to 200°C or less, pressurize this deformed part from the outside using a mechanical press, hydraulic press, etc., and position it on the reference plane. As a finished product.

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

Figure 6 shows a semi-finished product. 11 is the main shaft, 12 is the crank arm, 13 is the eccentric pin shaft for attaching the connecting rod, 14
is the balancer weight section. This balancer weight part 14 is inclined outward with respect to its reference plane 15 when it is a semi-finished product. This semi-finished product is pressed by pressing the balancer weight part 14 from the outside with a press, and is positioned on the reference surface 15 to form the finished product shown in FIG.

A mold like the one shown in Figure 8 is used to forge semi-finished products. FIG. 9 is a sectional view taken along the line 9--9 in FIG. 8. That is, the mold 16 is connected to the balancer weight portion 14 in relation to the pin shaft 13.
The portion 17 for forming the main shaft 11 faces outward and is inclined in the axial direction of the main shaft 11. Therefore, the wall thickness of the portion 17 gradually increases outwardly. Therefore, even if the portion 17 is heated by the heated material during molding of the semi-finished product, it will not easily tilt or deform during the forging operation.

According to the present invention, a semi-finished product is forged so that the balancer weight part is inclined outward with respect to the reference plane, and this semi-finished product is heated by a press to position the inclined balancer weight part on the reference plane. In the forging mold, the corresponding part of the balancer weight part does not needlessly become thinner, and therefore the mold does not easily fall over or deform during forging due to the heat received from the material, and the mold can be maintained in an accurate state for a long time. It has a variety of features, such as being able to read, reduce product costs, and guarantee product accuracy.

[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 forming the crankshaft shown in FIG. 5
The figures are Fig. 4, which is a cross-sectional view explaining the falling phenomenon of the lower mold, Fig. 6, a side view of an example of the semi-finished product according to the present invention, Fig. 7, a side view of the finished product, and Fig. 8, a mold for forming the semi-finished product. Top view of the mold, 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...Balancer weight part, 15...Reference surface Patent applicant Toyu Omi Mimuki Kakuda Iron Works Co., Ltd. Drawing 1! F (No change in nature) Figure 2 Figure 1 Figure 3 Procedural amendment November 22, 1985

Claims (1)

[Claims] Single and double cylinders characterized by forging a semi-finished product so that the balancer weight part is inclined outward with respect to a reference plane, heating this semi-finished product, and positioning the inclined balancer weight part on the reference plane by applying pressure. Crankshaft forming method.