Machine element or mechanism – Elements – Cranks and wrist pins
Reexamination Certificate
2000-01-04
2001-12-04
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Elements
Cranks and wrist pins
C123S192200
Reexamination Certificate
active
06324942
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a forged crankshaft for an internal combustion engine, and more particularly to such a crankshaft having larger counter weights but not causing interference between the counter weights and neighboring parts of the engine.
2. Description of the Related Art
Making of crankshafts for internal combustion engines by forging is known in the art. In general, a crankshaft has a plurality of counter weights to improve dynamic balance of the crankshaft. The improved dynamic balance will reduce vibrations of the engine.
In order to improve the balancing of the crankshaft, larger counter weights may be attached to the crankshaft so that a weight of the crankshaft with the counter weights increases. However, other parts such as pistons, connecting rods and cylinder block exist near the counter weights, so that use of larger counter weights is generally difficult. In order to place the larger counter weights in a limited space, the counter weights may be machined to complicated shapes so that the counter weights extend in gaps between the neighboring parts and do not contact the neighboring parts. This approach, however, raises a manufacturing cost of the crankshaft because of the machining process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a crankshaft for an internal combustion engine, on which larger counter weights can be mounted without increasing the manufacturing process step and cost.
Another object of the present invention is to provide an engine crankshaft having larger counter weights that do not interfere with neighboring parts.
Still another object of the present invention is to provide a forged crankshaft having larger counter weights that can be fabricated by simply changing forging dies while employing a conventional manufacturing method in other aspects.
Yet another object of the present invention is to provide a method of manufacturing an engine crankshaft by forging, which can realize both easy removal of forging dies from a product (crankshaft) and formation of large counter weights.
According to one aspect of the present invention, there is provided an engine crankshaft having at least one counter weight and made by forging, the forging being performed by pressing two dies with each other, characterized in that the counter weight has a plurality of inclinations to facilitate removal of the dies from the crankshaft after the forging process is completed, and degree of inclination of the plurality of inclinations is reduced as the plurality of inclinations are apart from a die mating surface.
Conventionally, each counter weight has a single inclination to facilitate removal of the forging dies from the crankshaft. In the invention, there are provided a plurality of inclinations to effectively enlarge the size of each counter weight. The inclinations are determined such that the maximum thickness of each counter weight is not enlarged, but the total volume of the counter weights is enlarged. Since the maximum thickness is the same as a conventional crankshaft, interference between the crankshaft and neighboring parts is avoided. No machining is required after the fording process, in order to have counter weights having a desired enlarged shape.
REFERENCES:
patent: 1660171 (1928-02-01), Larcher
patent: 1661341 (1928-03-01), Oldson
patent: 1705165 (1929-03-01), Twyman et al.
patent: 1705187 (1929-03-01), Keeports
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patent: 2815682 (1957-12-01), Kolbe et al.
patent: 4730512 (1988-03-01), Ito et al.
patent: 4867007 (1989-09-01), Krotky
patent: 5305656 (1994-04-01), Kamiya et al.
patent: 6-79406 (1994-03-01), None
patent: 08105431 (1996-04-01), None
patent: 10029032 (1998-02-01), None
Koike Takayuki
Matsui Toshihiro
Green Mary Ann
Isuzu Motors Limited
McCormick Paulding & Huber LLP
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