Variable valve timing system

Details Variable valve timing system Variable valve timing system

2001-08-03

2002-06-25

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090150

Reexamination Certificate

active

06408807

ABSTRACT:

The present application is based on and claims under 35 U.S.C. § 119 with respect to Japanese Patent Application No. 2000-236010 filed on Aug. 3, 2000 and Japanese Patent Application No. 2001-157080 filed on May 25, 2001, the entire content of both of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to variable valve timing systems. More particularly, the present invention pertains to a variable valve timing system for controlling the opening and closing time of an intake valve and an exhaust valve of a vehicle-mounted internal combustion engine.
BACKGROUND OF THE INVENTION
A known variable valve timing system is described in Japanese Patent Laid-Open Publication No. Hei. 09(1997)-324613. The disclosed variable valve timing system includes a housing member disposed in the driving force transmitting system for transmitting the driving force from the crankshaft of the combustion engine to the camshaft for controlling the opening and closing of either one of the intake valve and the exhaust valve of the combustion engine. The housing member rotates as a unit with one of the crankshaft and the camshaft.
The variable valve timing system also includes a rotor member rotatably assembled on a shoe portion provided on the housing member. The rotor member forms an advanced angle chamber and a retarded angle chamber at a vane portion in the housing member and integrally rotates with one of the camshaft and the crankshaft.
The variable valve timing system further includes a relative rotation controlling mechanism. The relative rotation controlling mechanism allows the relative rotation of the housing member and the rotor member by an unlock operation by the supply of an operation fluid. The relative rotation controlling mechanism restricts the relative rotation of the housing member and the rotor member at an intermediate angle phase between a retarded angle phase and an advanced angle phase by a lock operation by the discharge of the operation fluid. The variable valve timing system still further includes a hydraulic pressure circuit for controlling the supply and discharge of the operation fluid to the relative rotation controlling mechanism as well as for controlling the supply and discharge of the operation fluid to the advanced angle chamber and the retarded angle chamber.
In the aforementioned variable valve timing system, to make the internal combustion engine start in a smooth manner, the open/close timing of one of the intake valve and the exhaust valve is set, under the condition that the relative rotation controlling mechanism restricts the relative rotation between the housing member and the rotor member at a lock phase position within an intermediate region which is located at a position other than the rotation limit ends corresponding to the advanced and retarded angle phase positions, respectively. Thus, at the initial stage of the internal combustion engine, if such the restriction at the lock phase position is not performed, the starting ability of the internal combustion engine may become worse.
With respect to the relative rotation controlling mechanism which restricts the relative rotation between the rotor member and the housing member at the lock phase position, the restriction may be inhibited due to the design of the hydraulic pressure circuit and/or the remaining operation fluid in at least one of the relative rotation controlling mechanism, the advanced angle chamber, and the retarded angle chamber. In addition, in the conventional hydraulic pressure circuit, no consideration has been made as to how to control a hydraulic control pressure valve, which is connected into the hydraulic pressure circuit, upon initiation of the internal combustion engine. This results in the relative rotation phase between the housing member and the rotor member becoming unstable temporally when the internal combustion engine is transferred from its initiation to steady operation condition.
Thus, a need exists for a variable valve timing system for overcoming the aforementioned drawbacks.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a variable valve timing system includes a housing member provided in a driving force transmitting system in which is transmitted a driving force from a crankshaft of an internal combustion engine to a camshaft for controlling opening/closing of one of an intake valve and an exhaust valve of the internal combustion engine, with the housing member rotating together with one of the crankshaft and the camshaft. A rotor member is relatively rotatably assembled on a shoe portion provided on the housing member and forms an advanced angle chamber and a retarded angle chamber at a vane portion in the housing member, with the rotor member rotating together with the other of the camshaft or the crankshaft. A relative rotation controlling mechanism, upon unlock operation thereof established by being supplied with an operation fluid, allows relative rotation between the housing member and the rotor member. The relative rotation controlling mechanism, upon lock operation thereof established by a discharge of the operation fluid therefrom, restricts the relative rotation between the housing member and the rotor member at a lock phase position in an intermediate region located at a position other than the rotation limit ends corresponding to the advanced and retarded angle phase positions, respectively. A hydraulic pressure circuit controls an operation fluid supply/discharge of the relative rotation controlling mechanism and controls an operation fluid supply/discharge of each of the advanced angle chamber and the retarded angle chamber. The hydraulic pressure circuit, upon initiation of the internal combustion engine, discharges the operation fluid from the relative rotation controlling mechanism and the advanced and retarded angle chambers until a pressure of the operation fluid reaches a controllable pressure value. The hydraulic pressure circuit, after the pressure of the operation fluid reaches the controllable pressure value, is adapted to make one of the advanced and retarded angle chambers which is at a superior side of the in phase transfer response characteristic operation fluid filled, is adapted to subsequently make the other of the advanced and retarded angle chambers operation fluid filled, and is adapted to supply the operation fluid to the relative rotation controlling mechanism.
The hydraulic pressure circuit includes a hydraulic pressure control valve in which a control value of the hydraulic pressure control valve is updated, when making one of the advanced and retarded angle chambers which is at the superior side of the in phase transfer response characteristic operation fluid filled, on the basis of a control value for retaining a phase of the relative rotation controlling mechanism while the internal combustion engine is in a steady operation stage before operation of the internal combustion engine is terminated. The control value of the hydraulic pressure control valve can be amended or changed on the basis of the temperature of the operation fluid.
After a time duration has elapsed as measured from the initiation of the internal combustion engine, a decision is made whether or not the pressure of the operation fluid has reached the controllable pressure. The elapse of the time duration is amended depending on one of the temperature of the operation fluid and the revolution number of the internal combustion engine.
A sixth aspect of the present invention is to provide a variable valve timing system whose gist is to modify the structure of the first aspect, wherein switching the supply of the operation fluid from one of the advanced and retarded angle chambers which is at a superior side of in phase transfer response characteristic to the other is established on the basis of a detected value derived from phase detection means. The relative rotation controlling mechanism is made up of a first control mechanism and a second control mechanism, with the first co

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