Crankcase for a multiple cylinder engine

Details Crankcase for a multiple cylinder engine Crankcase for a multiple cylinder engine

1999-10-29

2001-06-12

Yuen, Henry C. (Department: 3747)

Internal-combustion engines

Frame construction

Horizontal cylinder

C123S1950HC, C123S1960CP

Reexamination Certificate

active

06244238

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a crankcase for a multiple cylinder engine, and more particularly, to a structure for providing breathing holes having a sufficient hole diameter in journal walls of the crankcase.
2. Description of Related Art
In a multiple cylinder engine, due to reciprocal movement of the pistons there are large variations in the internal pressure of the crank chamber during high-speed rotation of the crankshaft. As a result, friction loss becomes large. In order to solve this problem, breathing holes are formed which open into the journal walls. These breathing holes for each journal wall are formed by machine processing in a direction parallel to a central axis of the crankshaft with respect to a cast cylinder block; this results in each breathing hole being arranged coaxially (see, for example, Japanese patent laid-open No. Hei. 10-77905).
Oilways and bolt fastening sections are also provided in the journal walls. These oilways and bolt fastening sections are integrally formed when the cylinder block is casted. Therefore, the breathing hole diameter must be made small enough to avoid the oilways and bolt fastening sections. However, this makes it difficult to provide breathing hole diameters large enough to reduce friction loss.
SUMMARY OF THE INVENTION
In order to solve the above problem of the conventional art, it is an object of the present invention to provide a multiple cylinder engine having crank chambers for each cylinder of the multiple cylinder engine arranged along the axial direction of a crankshaft, with breathing holes communicating between the crank chambers and respective journal walls supporting the crankshaft and constituting wall sections of each crank chamber, wherein the breathing holes are lined up along the crankshaft, and at least one of the breathing holes has a center different from centers of the other breathing holes.
A further object is to provide a multiple cylinder engine where the breathing holes are provided for each journal wall, and the number of breathing holes is the same as the number of journal walls. Various combinations of breathing holes may be implemented, from a combination where only the center position of one breathing hole is different, to a combination where the center positions of all the breathing holes are different.
Another object of the present invention is to provide a multiple cylinder engine where the journal wall, in which the breathing hole having a different center is provided, has an oilway and the breathing hole is formed at a position avoiding this oilway.
Yet another object of the present invention is to provide a multiple cylinder engine, where the journal wall with the breathing hole having a different center has a bolt fastening section and the breathing hole is formed at a position avoiding this bolt fastening section.
These and other objects of the present invention are accomplished by way of a plurality of breathing holes provided in each journal wall, each of breathing holes having a center different from all the others. Therefore, it is possible to vary the position of the breathing holes according to the structure of the journal wall, with the result that the diameter of the breathing holes can be made sufficiently large to ensure an opening area sufficient to reduce friction loss.
In the case where an oilway is provided in the journal wall, since the breathing hole is formed avoiding the oilway, it is possible to form the breathing hole having a sufficiently large diameter without interfering with the oilway. Therefore, the oilway may be formed in an uncomplicated manner.
In the case where a bolt fastening section is provided in the journal wall, and the breathing hole is formed avoiding the bolt fastening sections, it is possible to form the breathing hole having a sufficiently large diameter; therefore, preventing having to shorten the length of the bolts.
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: 4630579 (1986-12-01), Atkin
patent: 4876998 (1989-10-01), Wunsche
patent: 5501189 (1996-03-01), Bezeij
patent: 5829406 (1998-11-01), Mazzola et al.
patent: 5852992 (1998-12-01), Boggs et al.
patent: 5868110 (1999-02-01), Betsch
patent: 5931135 (1999-08-01), Yamada
patent: 6076495 (2000-06-01), Takahashi et al.
patent: 3727670A (1989-03-01), None
patent: 2099075A (1982-12-01), None
patent: 10-77905 (1998-03-01), None
Patent Abstracts of Japan, vol. 013, No. 181 (E-750), 27 Apr. 1989 (Apr. 4, 1989) & JP 01-007790A (FUJI PHOTO FILM CO. LTD), Jan. 11, 1989 (Jan. 1, 1989) *abstract*.

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