Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1998-11-12
2001-01-16
Lo, Wellun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090310
Reexamination Certificate
active
06173687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic apparatus for adjusting the timing of the opening and closing of one or both engine valves, the intake valve and/or the exhaust valves of an engine using an actuator, according to the operating state of the engine.
2. Description of the Prior Art
Such hydraulic apparatuses for adjusting the timing of opening and closing of an engine valve are disclosed, as prior art, in JP7-139319A, JP7-139320A, JP8-28219A, JP8-121122A, JP9-60507A, JP9-60508A in which cam shafts are driven using a timing pulley synchronized with the engine crank shaft and a chain sprocket. A vane type valve timing mechanism which is arranged between the timing pulley and the cam shaft is driven by an actuator using a working oil provided from an oil pump through an oil control valve (hereinafter to be called “OCV”), so as to rotate the cam shaft relative to the crank shaft for advancing or retracting the cam shaft rotation relative to the crank shaft rotation. Thus, the timing of the opening or closing of the engine valve relative to the engine shaft rotation is shifted for the purpose of reducing exhaust gases and improving fuel efficiency.
A plunger in the actuator employed in such hydraulic apparatuses of the prior art is formed as a tapered pin, having an acute cone angle. Such a plunger is disclosed as a stopper pin, for example, in JP9-60508A.
In the hydraulic apparatuses having such a structure for adjusting the timing of the opening and closing of an engine valve in the prior art, a relatively large clearance is required between the tapered surface of the plunger and its engaging hole.
When the engine begins running from a state in which the engine is stopped with the plunger engaged with the hole, humming results in the engine. In turn this causes unpleasant noises. Additionally, when the tapered surface of the plunger is engaging with the hole, the engaging surface is inclined with respect to the rotation axis, and this causes a partial force urging the plunger in a direction of detachment. Thus, there is a tendency for the plunger to fall off.
SUMMARY OF THE INVENTION
An object of the present invention is to avoid the aforementioned problems, and to propose a hydraulic apparatus for adjusting the timing of the opening and closing of an engine valve having a plunger structure, by which humming is not caused by the rotor of the engine, due to the clearance between the plunger and the hole, when the engine starts running from a state in which the engine is in a stopped state.
A hydraulic apparatus for adjusting the, timing of opening and closing of an engine valve according to the present invention contains:
a cam shaft driven to rotate in synchronization with the engine rotation;
an actuator installed on the cam shaft for changing the timing of the opening and closing of a valve using a control of a working oil supply so as to change the timing of opening and closing of the intake valve and/or the exhaust valve;
a slidable plunger disposed in the actuator;
a rotor disposed in the actuator, to engage with the plunger by an engaging hole;
and a spring to urge the plunger to move into the engaging hole to make an engagement therebetween, when the engine is stopped,
and when the engine begins to run, working oil is supplied into the engaging hole to push out the plunger from the engaging hole, to release the engagement between the housing and the rotor;
wherein
the engaging hole and the plunger having a surface parallel with the slide direction of the plunger, and the clearance therebetween is smaller than 0.17 mm when they are engaging with each other.
In an embodiment of the present invention, the slide direction of the plunger is parallel with the direction of the cam shaft.
In an embodiment of the present invention, the plunger is installed in the housing, and the engaging hole is disposed in the rotor.
In an embodiment of the present invention, the plunger is installed in the rotor, and the engaging hole is disposed in the housing.
In an embodiment of the present invention, the whole engaging portion is parallel with the slide direction of the plunger.
In an embodiment of the present invention, the plunger has a recess at its tip portion. The recess functions as a reservoir of debrit in the working oil to prevent the entering of small particles into the clearance space between the plunger and the engaging hole.
In an embodiment of the present invention, the clearance between the plunger and its engaging hole is less than 0.17 mm, when they are engaging with each other.
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Fukuhara Katsuyuki
Sugawara Masafumi
Ueno Chikara
Yamauchi Makoto
Lo Wellun
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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