Patent ID: 6374792
Filing Date: 2002-04-23
Classification: F01L,F02B

Abstract:
An internal combustion engine comprising a cylinder block defining at least one cylinder bore therein, a crankshaft journaled for rotation relative to said cylinder block at one end of said cylinder bore and driven by a piston reciprocating in said cylinder bore, a cylinder head closing an opposite end of said cylinder bore and defining a combustion chamber with said piston and said cylinder bore, an intake passage communicating with said combustion chamber through an intake valve port, an intake valve configured to open and close said intake valve port, an exhaust passage extending from an exhaust port in said combustion chamber to discharge exhaust products from said combustion chamber, an exhaust valve configured to open and close said exhaust port, a camshaft rotating about a camshaft axis and being driven in timed relationship with said crankshaft to actuate at least one of said intake valve and said exhaust valve, and a decompression device to at least partially open one of said intake valve and said exhaust valve at least during a portion of a compression stroke to reduce a compression ratio of said combustion chamber to ease starting of said engine, said decompression device comprising an actuator mounted on said camshaft for pivotal movement about an actuator pivot axis extending generally normal to said camshaft axis, said actuator having a first section and a second section disposed opposite said first section relative to said actuator pivot axis, said actuator being made of a thin material, said second section comprising a pair of side portions, said first section comprising a bridge portion coupling together said side portions, said bridge portion comprising a cam lobe configured to hold said intake valve or said exhaust valve at least partially open when said actuator is placed at an initial position, said bridge portion having a surface, said cam lobe extending generally flush with said surface, said actuator being configured such that its center of gravity is located a distance d from said actuator pivot axis such that a rotational moment of said actuator is greater than a minimum moment that returns said actuator to said initial position under said actuator's own weight, and said center of gravity when said actuator is in said initial position also is located relative to said actuator pivot axis such that a displacement angle &thgr;g is generally less than a marginal angle &thgr;m, wherein said displacement angle &thgr;g is defined between a line that extends through said actuator pivot axis and said center of gravity and a datum line that extends through said actuator pivot axis and lies generally parallel to said camshaft axis, an arc being defined by said distance d from said actuator pivot axis, and said marginal angle &thgr;m corresponds to a maximum angle at which said center of gravity can be moved away from said datum line along said arc and still have said actuator release from said initial position at a predetermined minimum rotational speed of said camshaft.