Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-10-08
2001-02-13
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090310
Reexamination Certificate
active
06186104
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to an internal combustion engine in which a variable valve timing controlling apparatus is installed which varies open and closure timings of one or both of an intake valve or intake valves and an exhaust valve or exhaust valves according to an engine driving condition.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 9-280017 published on Oct. 28, 1997 exemplifies a first previously proposed variable valve timing controlling apparatus of a vane type.
The first previously proposed variable valve timing controlling apparatus of the vane type disclosed in the above-identified Japanese Patent Application First Publication includes a timing pulley having a cylindrical housing in which a vane fixed to an end of a camshaft is rotatably housed and an advance-angle hydraulic pressure chamber and a retardation-angle hydraulic pressure chamber defined between two approximately trapezoid shaped partitioning wall sections and two blade portions. The cylindrical housing of the timing pulley has an opening enclosed by a front cover and a rear cover. The trapezoid shaped partitioning wall sections are located on an inner peripheral surface of the housing and mutually projected toward their inner directions from a radial direction thereof.
Then, a hydraulic pressure (working oil pressure) is supplied or exhausted (drained) through a hydraulic pressure circuit into or from each of the advance-angle hydraulic pressure chamber and the retardation-angle hydraulic pressure chamber according to an engine driving condition so that the related hydraulic pressure causes the vane to rotate in either the normal direction or reverse direction. As the result, a relative rotational phase between the timing pulley and the camshaft is varied to enable the variation of open-and-closure timings of an intake valve of the engine.
However, in the first previously proposed variable valve timing controlling apparatus described above, each hydraulic passage in a hydraulic circuit to supply the hydraulic pressure into either the advance angle hydraulic pressure chamber or the retardation angle hydraulic pressure chamber is communicated with a main gallery which supplies a lubricating oil into each slide portion of the engine, viz, in an open circuit configuration. A positive or negative revolution variation torque is, hence, developed so that a rotation of the vane becomes unstable. That is to say, it is well known that a rotation variation (fluctuating) torque (in a form of an alternating torque) in a normal direction or reverse direction due to a presence in a spring force of a valve spring disposed along a stem of each engine valve is developed during an engine operation.
If a large rotation variation torque is acted upon the camshaft during a rotational drive of the vane in an advance or retardation angle side, the vane is rotated in the advance angle side progressively repeating the normal rotation and the reverse rotation toward the advance angle side or the retardation angle side (as denoted by a broken line of
FIG. 8B
) since the hydraulic pressure supplied to the advance angle hydraulic chamber is pressed against a reaction force exerted by the normal directional variation torque and which is acted upon in an opposite direction to the rotation direction. Hence, since the camshaft also carries out the relative rotation to the timing pulley repeating the normal rotation and the reverse rotation, a control response characteristic of the valve open-and-closure timing control for the intake valve is reduced.
Especially, when the vane is rotated in the advance-angle direction, a quick switching action is demanded since the vane advance-angle direction rotation means generally the switching from an engine idling state to a normal driving state. However, during a transition from a low-engine-speed region to a middle-engine-speed region, it becomes easy for the vane to be reversed due to a reaction force of the rotation variation torque.
A Japanese Patent Application First Publication No. Heisei 8-121123 published on May 14, 1996 exemplifies a second previously proposed variable valve timing controlling apparatus of the vane type.
In the second previously proposed variable valve timing controlling apparatus, a pilot-type check valve is installed which includes a check valve and a pilot valve, both valves being extended in an inside portion of the vane and being operated to limit a reverse flow of the drive hydraulic pressure supplied to either the advance-angle or the retardation-angle hydraulic chamber within the hydraulic passage so as to prevent the reverse rotation of the vane due to the rotation variation torque.
SUMMARY OF THE INVENTION
However, since the pilot-type check valve described in the BACKGROUND OF THE INVENTION is operated directly utilizing the internal hydraulic pressure supplied to each hydraulic pressure chamber without exception, i.e., according to the variation in the internal hydraulic pressure.
Hence, a slight delay in time easily (a slight time lag) occurs until a check ball constituting the check valve is moved due to a pressure developed from a maximum rotation variation torque and this causes a reduction in a response characteristic of the check valve. In addition, when the reaction force of the variation torque is released, the check ball is, in turn, moved in the opposite direction to a valve body portion of the check valve to open the hydraulic passage. Hence, a time lag due to a forward-and-rearward movement of the check ball causes a reduction of the response characteristic to open and close the hydraulic passage.
Furthermore, the check ball itself provides a resistance of the oil flow within the hydraulic passage and may provide an obstruction against a quick boosting of the hydraulic pressure supplied to either the advance angle or retardation angle hydraulic pressure chamber.
It is, therefore, an object of the present invention to provide an improved variable valve timing controlling apparatus which prevents the reverse rotation of the vane due to the rotation variation torque and which provides the high control response characteristic of the valve open-and-closure timing control.
The above-described object can be achieved by providing a variable valve timing controlling apparatus for an internal combustion engine having an engine valve, comprising: a rotational body rotated in synchronization with an engine crankshaft; a camshaft, one end thereof being inserted into the rotational body and the camshaft including a cam located on an outer periphery of the camshaft to open the engine valve against a spring force exerted by a valve spring of the engine valve; a phase changing device interposed between the rotational body and the one end of the camshaft to hydraulically vary a relative rotational phase between the rotational body and the camshaft; a hydraulic pressure circuit to relatively supply and drain a hydraulic pressure to and from at least one retardation angle hydraulic pressure chamber and at least one advance angle hydraulic pressure chamber, each hydraulic pressure chamber being formed within the rotational body to drive the cam phase changing device; and an interrupting mechanism to interrupt: a hydraulic pressure passage of the hydraulic pressure circuit to supply the hydraulic pressure to at least one of the advance angle and retardation angle hydraulic pressure chambers for a time duration which corresponds to a torque peak region of a rotation variation torque developed on the camshaft.
REFERENCES:
patent: 5184578 (1993-02-01), Quinn, Jr. et al.
patent: 5289805 (1994-03-01), Quinn, Jr. et al.
patent: 5722356 (1998-03-01), Hara
patent: 5816204 (1998-10-01), Moriya et al.
patent: 6129060 (2000-10-01), Koda
patent: 6129062 (2000-10-01), Koda
patent: 1-92504 (1989-04-01), None
patent: 8-121123 (1996-05-01), None
patent: 9-280017 (1997-10-01), None
Ichinosawa Yoshinori
Torii Akira
Foley & Lardner
Lo Weilun
Unisia Jecs Corporation
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