Crankshaft rotation structure for four cycle engine

Details Crankshaft rotation structure for four cycle engine Crankshaft rotation structure for four cycle engine

1999-09-10

2001-03-27

Kamen, Noah P. (Department: 3747)

Internal-combustion engines

Lubricators

Crankcase, pressure control

Reexamination Certificate

active

06205971

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement to a crankshaft rotation structure for a four cycle engine.
2. Description of Related Art
Referring to Japanese Patent Publication No. 2629936, FIG. 10 discloses, a cylinder a, a crankcase d, a sidewall e of the crankcase d, a crankshaft bearing i provided in the sidewall e, and an oil jet h provided in an upper part of the crankshaft bearing i of the side wall e for cooling a piston b.
The above described crank shaft bearing i is a single row bearing. Furthermore, the bearing has a large outer diameter. As a result, the attachment position of an oil jet h provided outside of the crankshaft bearing i becomes greatly separated from the crankshaft center. The piston b should be separated from the crankshaft center so that when the piston b is at a bottom dead center position, it does not interfere with the oil jet h. Accordingly, it is necessary to raise the piston to avoid the oil jet h. As a result, since the distance from the crankshaft center to a cylinder head attached to the cylinder a is increased, the size of the engine must be increased.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a crankshaft rotation structure for a four cycle engine, wherein even if an oil jet is present, it is possible to reduce the distance from the crankshaft center to an attachment position of the oil jet. Accordingly, the size of the engine can be reduced.
In order to achieve the above described object, the present invention includes a crankshaft rotation structure for a four cycle engine having a radial ball bearing fitted into a first main bearing section of a crankcase, a radial roller bearing fitted into a second main bearing section of the crankcase, a crankshaft being rotatably supported by the radial ball bearing and the radial roller bearing. Furthermore, an oil jet nozzle for cooling a piston of the four cycle engine is provided in the second main bearing section.
The load bearing ability of the radial roller bearing is higher than that of the radial ball bearing. Accordingly, when the diameters of the shafts on which the bearings are mounted are the same, the outer diameter of the radial roller bearing can be made smaller than the outer diameter of the radial ball bearing. Accordingly, even if an oil jet nozzle is provided in the second main bearing section where the radial roller bearing is fitted it is possible to reduce the distance from the crank shaft center to an attachment position of the oil jet on the second main bearing section. Therefore, the size of the engine can be reduced.
According to another aspect of the present invention, a main oil passage for supplying oil to the oil jet nozzle, and a secondary oil passage branching off from the main oil passage and leading to the radial roller bearing is provided in the second main bearing section.
It is possible to supply oil from the secondary oil passage to the radial roller bearing. Therefore, the durability of the radial roller bearing can be improved, and the lifespan of the bearing can be prolonged.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


REFERENCES:
patent: 5092292 (1992-03-01), Iguchi et al.
patent: 5533472 (1996-07-01), Sands et al.
patent: 5915350 (1999-06-01), Suzuki et al.
patent: 2-2629936 (1918-04-01), None

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