JPS60565B2 - Structure of crankshaft for two-cylinder engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of an integrally molded product of cast iron or cast steel, and
This invention relates to the structure of a crankshaft for a two-cylinder engine with a crank angle of 180 degrees.

A balance weight is installed on the crank arm to offset the unbalanced force induced by the mass of the rotating part of the crankshaft, but as a result, the sand mold for molding the arm and balance weight becomes longer. ,
In addition, in the case of a structure in which the length of the crank pin is short, the sand mold part becomes thinner, and the sand mold part has less sand adhesion to the sand mold body, which tends to cause the mold to collapse.

In view of the above-mentioned circumstances, it is an object of the present invention to eliminate the above-mentioned drawbacks through extremely simple improvements.Next, embodiments of the present invention will be described in detail with reference to illustrative drawings.

To configure the crankshaft for a two-cylinder engine, two pairs of crank arms 2, 2 are installed at a crank angle of 180 degrees to each other on a journal concentric with the crankshaft. At the same time, the pair of arms 2, 2 are connected to each other by a crank pin 3, and the arm corner a on the opposite side from the pin connection part is cut and molded to reduce the weight due to this and the weight due to the attachment of the pin 3. Based on the increased weight difference, a balance weight 4 is installed on each of the arms 2 in order to balance the corner forces around the crankshaft center, and these are integrally molded by casting with ductile cast iron. When casting the above-mentioned crankshaft using a sand mold, one of the balance weights 4 connected to the crank arm 2, on both ends of the crankshaft, is made shorter than the one adjacent to it. , crank pin 3
, 3 is provided with a hollow part 5 for suppressing the collapse of the weight balance due to the shortening of the balance weight, and a sand mold part 6 for molding the crank arm 2 and the balance weight 4 in a state where the entire crankshaft is balanced. is made short to prevent the sand mold part 6 from losing its shape.

The material of the crankshaft can be selected from various materials such as regular cast iron, ordinary steel, special cast iron, and special twilled steel, and the hollow part 5 for weight balance may be machined after casting.

In summary, the present invention has the structure of the crankshaft for a two-cylinder engine as described above, in which the balance weights on both ends of the crankshaft are made shorter than the balance weights adjacent thereto, and The crank pin is characterized by being provided with a hollow part for suppressing the collapse of the weight balance due to the shortening of the balance weight.

In other words, there is sand in the sand mold part between the balance weights.
It's hard to do anything about this because it depends on the length of the crankpin, but by shortening the balance weight and shortening the length of the sand mold part in that area, the strength of the sand mold part itself can be increased. It is possible to prevent the crank pin from losing its shape, and to maintain good vehicle balance simply by providing a simple hollow part in the crank pin. In order to prevent the sand mold from losing its shape, all of the balance weights may be made shorter, but this increases the size of the hollow part for weight balance, which leads to a decrease in pin strength. Since it is only necessary to shorten one balance weight of the pair with respect to the crank pin, there is no significant decrease in strength, and in addition, one balance weight can be connected to the other pair of crank arms to make the sand mold part. Since the crankshaft is set at both ends of the crankshaft, which is different from the one that forms the narrow adjacent part, it is possible to effectively suppress the deformation of the sand mold part, and as a whole, the sand mold strength is increased without reducing the shaft strength. It is now possible to raise the

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is an overall vertical sectional side view illustrating an embodiment of the structure of a crankshaft for a two-cylinder engine according to the present invention.

2...Crank arm, 3...Crank pin, 4...
・Balance weight, 5...Hollow part.

Claims (1)

[Claims] 1. A crankshaft structure for a two-cylinder engine that is made of an integrally molded product of cast iron or cast steel and has a crank angle of 180 degrees, in which both ends of the crankshaft are connected to the balance weight 4 connected to the crank arm 2. The one on the side is configured to be shorter than the one next to it, and the crank pin 3
, 3, a structure of a crankshaft for a two-cylinder engine, characterized in that a hollow portion 5 is provided for suppressing the collapse of the weight balance due to the shortening of the balance weight.