Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2001-09-18
2002-07-09
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090450
Reexamination Certificate
active
06415754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rocker arm support mechanism for an internal-combustion engine.
2. Description of the Related Art
Rocker arms are classified into those formed by forging and those formed by platework.
FIGS. 8 and 9
show a forged rocker arm
100
. As shown in
FIG. 9
, the rocker arm
100
has a boss
101
formed integrally with its middle part. The rocker arm
100
is mounted for a rocking motion on a rocker-arm shaft
103
fixedly held on a holder
102
with the rocker-arm shaft
103
fitted in a bore formed in the boss
101
. The rocker arm
100
has one end provided with a valve clearance adjusting mechanism including an adjusting screw
105
and a nut
106
and the other end provided with a recess
109
as shown in FIG.
8
. The lower end of the adjusting screw
105
is in contact with the end of a valve stem
108
and the upperend of a push rod
110
is received in the recess
109
as shown in FIG.
8
.
FIGS. 10 and 11
show a plate rocker arm
119
formed by plate work. As shown in
FIG. 11
, the rocker arm
119
has an upward concave spherical part
121
provided with a slot
120
in its middle part. A support bolt
123
set upright on a cylinder head penetrates the spherical part
121
. A holding member
125
having a spherical end part
125
a
is put on the support bolt
123
so that the spherical end part
125
a
is received in a spherical recess defined by the spherical part
121
. A nut
126
is screwed on the support bolt
123
to hold the holding member
125
in place. The rocker arm
119
has one end provided with a spherical protrusion
128
protruding downward so as to be inn contact with the end of a valve stem
127
and the other end provided with a spherical protrusion
132
protruding upward as shown in FIG.
10
and the head of a push rod is received in the spherical protrusion
132
. Valve clearance is adjusted by turning the nut
126
. The rocker arm formed by plate work is disclosed in JP-U No. Sho 61-145804.
The forged rocker arm
100
shown in
FIGS. 8 and 9
is costly and needs the adjusting screw
105
and the nut
106
additionally for valve clearance adjustment, which increases the cost and weight of the rocker arm.
The machining accuracy of press working for forming the spherical part
121
of the plate rocker arm
119
shown in
FIGS. 10 and 11
is not very high and the spherical part
121
is subject to deformation. Therefore it is possible that the accuracy of engagement of the spherical part
121
and the spherical end
125
a
of the holding member
125
is unsatisfactory. The rocker arm
119
is apt to shake in the directions of the arrows shown in FIG.
10
. Consequently, the adjustment of valve clearance is liable to take much time and to be unsatisfactory. Since the rocker arm
119
shakes, the operation of the rocker arm
119
is liable to be unstable. When the push rod
131
moves along an oblique line, the shaky motion of the rocker arm
119
varies valve clearance greatly. Usually, the push rod
131
is guided by a guide plate
140
provided with a guide hole
141
as shown in
FIG. 10
to suppress shaking.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a low-cost rocker arm support mechanism capable of suppressing the shaking of a rocker arm, of facility valve clearance adjustment and of ensuring correct valve clearance adjustment.
According to the present invention, a rocker arm support mechanism comprises: a holding member having a base wall fastened to an end surface of a cylinder head, and a pair of support walls each provided with a hole; a rocker arm shaft including an eccentric sleeve having a bore and a circumference eccentric to the bore and disposed between the support walls of the holding member, and a support shaft passed through the hole of one of the side walls of the holding member, the bore of the eccentric sleeve and the hole of the otherside wall of the holding member, wherein a rocker arm is put on the eccentric sleeve for turning on the eccentric sleeve, the eccentric sleeve is turned about the axis of the support shaft relative to the holding member to adjust the height of the rocker arm from the end surface of the cylinder head.
The rocker arm support mechanism does not need an adjusting screw an a nut specially for valve clearance adjustment. The valve clearance can be easily adjusted simply by turning the eccentric sleeve on the support shaft. The rocker arm support mechanism is capable of supporting the rocker arm so that the rocker arm may not shake.
In the rocker arm support mechanism according to the present invention, it is preferable that the rocker arm and the holding member are formed by plate work, the support shaft and the eccentric sleeve are manufactured separately, the support shaft has a head in one end part thereof and a threaded part in the other end part thereof, the eccentric sleeve has a cylindrical shape, the eccentric sleeve is restrained from turning relative to the support shaft, and a nut is screwed on the threaded part of the support shaft to clamp the eccentric sleeve firmly between the support walls of the holding member. Thus valve clearance can be accurately and easily adjusted even through the inexpensive rocker arm formed by plate work is employed.
In the rocker arm support mechanism according to the present invention, it is preferable that the rocker arm and the holding member are formed by plate work, the support shaft and the eccentric sleeve are manufactured separately, the support shaft has a head in one end part thereof and a threaded part in the other end part thereof, the eccentric sleeve has a cylindrical shape, the eccentric sleeve is mounted on a part between the support walls of the holding member of the support shaft for turning relative to the support shaft, and a nut is screwed on the threaded part of the support shaft to clamp the eccentric sleeve firmly between the support walls of the holding member. Thus valve clearance can be accurately and easily adjusting even through the inexpensive rocker arm formed by plate work is employed.
REFERENCES:
patent: 1948063 (1934-02-01), Burkhardt
patent: 4643141 (1987-02-01), Bledsoe
patent: U 61-145804 (1986-09-01), None
Hirano Michio
Shirai Tetsuaki
Kawasaki Jukogyo Kabushiki Kaisha
Lo Weilun
Oliff & Berridg,e PLC
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