Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2000-12-26
2002-10-15
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090360, C123S090420, C123S090440, C074S559000
Reexamination Certificate
active
06463899
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve operating system in an internal combustion engine, including a swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam.
2. Description of the Related Art
Such a valve operating system is conventionally known, for example, from Japanese Patent Application Laid-open No. 6-185322.
In a valve operating system constructed such that a plurality of engine valves are driven by a single rocker arm, a difference in tappet clearance may be produced between the plurality of engine valves and a plurality of valve abutments provided on the rocker arm in individual correspondence to the engine valves due to the lapse of an operating time. If such a difference in tappet clearance is produced, a force causing the rocker arm to be inclined is applied to the rocker arm by a large load generated on a line interconnecting the cam abutment and one of the valve abutments at one end of an array of the valve abutments. For this reason, a large load is applied to opposite ends of the swinging support section in an axial direction of the rocker shaft, and if the swinging support section does not have a rigidity enough to withstand such load, there is a possibility that uneven wear may be produced in the swinging support section, resulting in a reduction in durability of the swinging support section. In the rocker arm of the above known valve operating system, however, the swinging support section is formed into a cylindrical shape at a wall thickness uniform over the entire length in the axial direction of the rocker shaft, and if the wall thickness of the swinging support section is increased in order to enhance the rigidity of the swinging support section, the weight of the rocker arm is increased.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a valve operating system in an internal combustion engine, wherein the durability of the rocker arm is enhanced, while avoiding an increase in weight of the rocker arm.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, including a cylindrical swinging support section provided at a base end of a rocker arm and swingably carried on a rocker shaft mounted in a cylinder head, a plurality of valve abutments provided at a tip end of the rocker arm and capable of being individually put into abutment against upper ends of a plurality of engine valves, and a cam abutment provided on the rocker arm in an intermediate portion between the swinging support section and each of the valve abutments to come into contact with a valve operating cam, wherein the swinging support section includes a thinner cylindrical portion surrounding the rocker shaft, and thicker cylindrical portions which are form ed at a thickness larger than that of the thinner cylindrical portion into a cylindrical shape to surround the rocker shaft and which are integrally and continuously provided at axially opposite ends of the thinner cylindrical portion, respectively.
With such arrangement of the first feature, a central portion of the swinging support section can be formed at a smaller thickness, thereby avoiding an increase in weight of the rocker arm, while the opposite end portions of the swinging support section, to which a large load may be possibly applied, can be formed at a larger thickness, thereby enhancing the rigidity of supporting of the rocker arm to enhance the durability of th e rocker arm.
According to a second aspect and feature of the present invention, in addition to the first feature, the swinging support section has grooves defined in its inner surface at opposite ends thereof along the axis of the rocker shaft and capable of accumulating an oil between the opposite ends and an outer surface of the rocker shaft, respectively.
With such arrangement of the second feature, the oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft, and even if the rocker arm is inclined, the generation of uneven wear can be prevented to the utmost, thereby enhancing the durability of the rocker arm. Moreover, the grooves are merely provided in the inner surface of the swinging support section at its opposite ends and hence, the weight of the rocker arm cannot be increased.
According to a third aspect and feature of the present invention, in addition to the second feature, first one of the valve abutments arranged in parallel to the axis of the rocker shaft, which is disposed on one side along the axis of the rocker shaft, is provided at a tip end of a first support wall provided to extend from one end of the swinging support section at a location corresponding to one of the grooves, and second one of the valve abutments, which is disposed on the other side along the axis of the rocker shaft, is provided at a tip end of a second support wall provided to extend from the other end of the swinging support section at a location corresponding to the other groove.
With such arrangement of the third feature, a reduction in rigidity of the opposite ends of the swinging support section due to the provision of the grooves can be made up for by the support walls.
According to a fourth aspect and feature of the present invention, in addition to the first feature, the swinging support section includes a thinner cylindrical portion surrounding the rocker shaft, and thicker cylindrical portions which are formed at a thickness larger than that of the thinner cylindrical portion into a cylindrical shape to surround the rocker shaft and which are integrally and continuously provided at axially opposite ends of the thinner cylindrical portion, the thicker cylindrical portions having grooves provided in their inner surfaces respectively and capable of accumulating an oil between the inner surfaces and an outer surface of the rocker shaft.
With such arrangement of the fourth feature, a central portion of the swinging support section can be formed at a smaller thickness, thereby avoiding an increase in weight of the rocker arm, while the opposite end portions of the swinging support section, to which a large load may be possibly applied, can be formed at a larger thickness, thereby enhancing the rigidity of supporting of the rocker arm. Further, the oil can be accumulated between the opposite ends of the swinging support section and the rocker shaft and hence, the generation of uneven wear can be prevented to the utmost. Moreover, since the grooves are provided in the inner surface of the thicker cylindrical portion, it is possible to avoid a reduction in rigidity of the swinging support section due to the provision of the grooves and to reliably enhance the durability.
According to a fifth aspect and feature of the present invention, in addition to the first feature, a pair of intersection points, at which the following straight lines and the axis of the rocker shaft intersect one another, are disposed at locations inner than the axially opposite ends of the swinging support section: a first straight line passing through (1) a center of first one of the valve abutments arranged in parallel to the axis of the rocker shaft, which is disposed at one end along the axis of the rocker shaft, and (2) an area of contact of the valve operating cam with the cam abutment; and a second straight line passing through (1) a center of second one of the valve abutments, which is disposed at the other end along the axis of the rocker shaft and (2) the area of contact of the valve operating cam with the c
Iwamoto Jun'ichi
Nakamura Hiromu
Tanaka Chikara
Yamada Noriyuki
Armstrong Westerman & Hattori, LLP
Honda Giken Kogyo Kabushiki Kaisha
Lo Weilun
LandOfFree
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