Internal-combustion engines – Poppet valve operating mechanism – Lubrication
Reexamination Certificate
2002-05-14
2004-01-20
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Lubrication
C123S090390, C123S090340
Reexamination Certificate
active
06679210
ABSTRACT:
This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in Japanese Patent Application No.
2001-148157
filed May 17, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rocker arm for an internal combustion engine, and more particularly to a roller-type rocker arm comprising a roller that is in contact with a camshaft in a slidable fashion.
2. Description of the Related Art
In a valve mechanism of an internal combustion engine, a rocker arm connecting to an intake valve or an exhaust valve to increase the lift of the cam of the camshaft is known. Further, there are various friction surfaces surrounding the rocker arm, and a lubrication mechanism described below is employed to lubricate these friction surfaces.
FIG. 3
shows a conventional rocker arm. In the rocker arm
51
, one end of the main body of the rocker arm
52
(hereinafter referred to as “main body”) is rotatably supported by a rocker shaft
53
, and the other end becomes an actuator that presses the shaft-end of the intake valve or exhaust valve (hereinafter referred to as “valve”)
54
downward. A roller
55
is rotatably supported through a roller pin
56
in the middle part of the main body
52
in a longitudinal direction. A cam
58
of a camshaft
57
slides in contact with the roller
55
from above. In this valve mechanism, the cam
58
applies downward force to the roller
55
, thereby depressing the main body
52
. The valve
54
resists a valve spring (not shown in the drawings) and is lifted up. Note that the actuator comprises an adjustment mechanism consisting of a cap
60
having a ball screw
59
and a spherical seat
60
a
, and a locking nut
61
.
In this construction, friction surfaces exist between a push
72
attached to the main body
52
and the rocker shaft
53
, between the roller
55
and the roller pin
56
, between the roller
55
and the cam
58
, between the ball screw
59
and the spherical seat
60
a
, and between the cap
60
and the shaft-end surface
54
a
. Accordingly, a lubrication mechanism is employed to lubricate these friction surfaces.
In other words, lubricating oil sent from the engine's oil pump flows through a shaft hole
62
inside the rocker shaft
53
, and this oil is supplied to the friction surfaces between the push
72
and the rocker shaft
53
by an oil hole
63
that branches off in a radial direction. Subsequently, the oil is guided from an oil hole
64
inside the main body
52
to an oil passage
65
inside the roller pin
56
. Since the exit of the oil passage
65
opens to the external circumference of the roller pin
56
, the area between the roller
55
and the roller pin
56
is lubricated. Additionally, the oil is transmitted to both surfaces of the roller
55
by a centrifugal force, and is sprayed in an external radial direction, thereby lubricating the area between the roller
55
and the cam
58
. Further, the oil sprayed from the cam
58
by the centrifugal force reaches between the ball screw
59
and the spherical seat
60
a
, and between the cap
60
and the shaft-end surface
54
a
, thereby lubricating the friction surfaces.
As shown in
FIG. 4
, the roller insertion part of the main body
52
is an opening
66
that runs above and below. Reference numerals
67
and
68
depict the push insertion hole and the roller pin insertion hole respectively. The roller pin
56
is constituted as shown in
FIGS. 5
a
-
5
c
and is fixed by pressure in the roller pin insertion hole
68
. The oil passage
65
consists of a first hole
69
connected to the oil hole
64
of the main body
52
, a second hole
70
extending downward from the first hole
69
axially at a slope, and a taper hole
71
formed to open into the middle part of the pin, which constitutes the exit of the second hole
70
and the oil passage
65
. The oil flowing out of the taper hole
71
lubricates the area between the roller
55
and the roller pin
56
.
However, when the engine stops, oil flows down from the moving valves, including the rocker arm, to the oil gallery. On the other hand, when the engine starts up, it takes time for the oil to flow up from the oil gallery to the shaft hole
62
in the rocker shaft
53
. Even more time is required until the oil reaches each sliding part described above. This is even more so if the oil temperature is low when the engine starts up. Accordingly, when the engine is started up under low temperature conditions after a long period of shutdown, sliding occurs without lubrication for a comparatively long period of time, and there is the possibility of causing abnormal wear, particularly of the roller pin
56
, the roller
55
, the cam
58
and the valve shaft-end surface
54
a.
Therefore, the present invention was designed with the foregoing problems in view, and it is an object of the present invention to prevent abnormal wear of the friction surfaces surrounding the rocker arm, while also improving reliability by preventing poor lubrication under conditions which are disadvantageous to lubrication, such as when an engine is started up at low temperature after a long period of shutdown.
SUMMARY OF THE INVENTION
A rocker arm for an internal combustion engine according to the present invention comprises a bag-shaped oil sump opening upward in the rocker arm main body, and an oil supply port and oil exhaust to conduct the supply and discharge of oil to and from the oil sump as well as control the oil level height of the oil sump. A roller is rotatably provided inside the oil sump and the bottom end of this roller is positioned lower than the oil level height so that at least the bottom end of the roller will be immersed in the oil in the oil sump.
Therefore, when the engine is stopped, the oil in the oil sump adheres to the roller, so that when the engine is started up again, until the time that the oil rises up, the oil adhering to the roller is used and the area between the roller and the cam can be lubricated. In addition, due to the rotation between the roller and the cam, oil can be sprayed onto other friction surfaces. Accordingly, poor lubrication can be prevented even when starting the engine up at low temperature after a long period of shutdown.
Here the roller is mounted to the rocker arm main body and is rotatably supported by a roller pin inserted into the centre of the roller, and it is desirable that the bottom end of this roller pin is positioned lower than the oil level height so that at least the bottom end of the roller pin will be immersed in the oil in the oil sump.
Therefore, when the engine is stopped, the oil in the oil sump is able to adhere to the sliding part between the roller and the roller pin as well, and the problem of poor lubrication can be further eliminated.
It is desirable that the oil supply port is formed so as to penetrate the rocker arm main body, and comprises an entry hole to guide the oil from the shaft passage inside the rocker shaft to the oil sump. It is desirable that the oil exhaust is formed so as to penetrate the rocker arm main body, and consists of an exit hole to supply oil from the oil sump by spraying it near the valve shaft-end.
Therefore, the oil supply port and oil exhaust can be drilled and the drilling process can be conducted with greater ease and at less cost. Further, abnormal wear of the valve shaft-end surface can be prevented, since oil from the oil sump is supplied by spraying near the valve shaft-end.
Further, the valve mechanism of an internal combustion engine according to the present invention is a valve mechanism of an internal combustion engine, which comprises a rocker arm main body, of which one end is rotatably supported by the engine's rocker shaft, and the other end forms an actuator to press the shaft-end of the intake valve or exhaust valve downward, and a roller rotatably supported by a roller pin in the middle part of the rocker arm main body, a camshaft being in contact with the roller from above in a slidable fashion,
wherein a shaft passage is formed insi
Denion Thomas
Isuzu Motors Limited
McCormick Paulding & Huber LLP
Riddle Kyle
LandOfFree
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