Valve timing control apparatus and method of internal...

Details Valve timing control apparatus and method of internal... Valve timing control apparatus and method of internal...

2001-02-20

2004-03-09

Vo, Hieu T. (Department: 3747)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

With indicator or control of power plant

C123S090150

Reexamination Certificate

active

06704642

ABSTRACT:

INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Applications No. 2000-055558 filed on Mar. 1, 2000 and No. 2001-001553 filed on Jan. 9, 2001 each including the specification, drawings and abstract are incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a valve timing control apparatus and method of an internal combustion engine.
2. Description of Related Art
Conventional internal combustion engines, such as engines installed on vehicles, are provided with a valve timing apparatus that controls the valve timing of the engine in an attempt to improve the output performance and enhance the emission quality, for example. Such a valve timing control apparatus includes a variable valve timing mechanism that is actuated by hydraulic pressure to change the valve timing of the engine. The variable valve timing mechanism includes, for example, a movable member connected to an intake camshaft of the engine, and timing advance-side hydraulic chambers and timing retard-side hydraulic chambers that are provided so as to sandwich the movable member therebetween. By selectively supplying hydraulic fluid to these hydraulic chambers so as to move the movable member by hydraulic pressure, the rotational phase (or angular position) of the camshaft relative to that of the crankshaft of the engine is changed. Thus, the relative rotation phase of the camshaft is changed in this manner, so that the valve timing of the intake valves of the engine is changed.
At the time of the start of the internal combustion engine, hydraulic fluid has been discharged from the hydraulic fluid chambers. Therefore, even if the hydraulic fluid begins to be supplied to the hydraulic chambers at the same time that the engine is started, a certain period of time is required before the movable member can be moved by hydraulic pressure. During this period, therefore, the valve timing of the intake valves cannot be controlled. Furthermore, since hydraulic pressure does not act on the movable member, the relative rotational phase of the camshaft (valve timing) is brought into the most retarded state due to reaction forces resulting from the opening and closing actions of the intake valves. In order to achieve good engine performance at the start of the engine, therefore, it may be desirable to set a (limited) control range of the valve timing of the intake valves so that valve timing suitable for the start of the engine (hereinafter, referred to as “engine start valve timing”) can be obtained when the valve timing is brought into the most retarded state.
However, if the control range of the valve timing is set so as to satisfy the aforementioned requirement, the control range is undesirably reduced, thus making it difficult to optimally control the valve timing over the entire operating region of the engine. In order to suppress the reduction in the control range of valve timing control while optimizing the valve timing at the time of the start of the engine, it has been proposed to fix the valve timing of the intake valves to a state in which the valve timing of the intake valves is advanced by a certain amount away from the most retarded state when the engine is started. An example of such a valve timing control apparatus that is adapted for fixing the valve timing as mentioned above is disclosed in Japanese Patent laid-open Publication (Kokai) No. 11-241608.
The apparatus disclosed in the aforementioned publication includes a spring that urges or biases a movable member so as to bring the valve timing of the intake valves to a predetermined state between the most retarded state and the most advanced state when the valve timing is currently on the retard side of the predetermined state. Then, the control range of the valve timing control is set so that the predetermined state of the valve timing becomes the engine start valve timing. Furthermore, the apparatus includes a stopper mechanism that fixes the valve timing of the intake valves when the valve timing is placed in the predetermined state (engine start valve timing) under the bias force of the spring.
In the valve timing control apparatus disclosed in the aforementioned publication, the valve timing of the intake valves is set to the engine start valve timing by the bias force of the spring at the time of the start of the engine, and the valve timing in this state is fixed by the stopper mechanism. Since the valve timing of the intake valves is fixed to the engine start valve timing upon the start of the engine in this manner, good engine performance can be achieved at the time of the start of the engine. Furthermore, when the hydraulic chambers of the variable valve timing mechanism become filled with hydraulic fluid after the engine is started, the hydraulic pressure thus developed operates to discontinue the fixed state of the valve timing established by the stopper mechanism. After the fixed state of the valve timing is discontinued, it becomes possible to optimally control the valve timing over the entire operating region of the engine by performing valve timing control over the entire control range of the valve timing control.
When the valve timing control apparatus disclosed in the aforementioned publication controls the valve timing to be the retard side of the engine start valve timing, the bias force of the spring acts on the camshaft (movable member) in the timing advancing direction. The bias force of the spring gradually increases as the relative rotational phase of the camshaft (valve timing) shifts toward the most retarded position. When the valve timing is controlled in a state in which the bias force of the spring is acting on the camshaft, the bias force, which changes with the relative rotational phase of the camshaft, adversely affects the valve timing control.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a valve timing control apparatus of an internal combustion engine that is capable of accurately controlling the valve timing irrespective of bias force applied by a biasing device, such as a spring, which biases the valve timing toward a predetermined state between the most retarded state and the most advanced state.
To accomplish the above and/or other objects, one aspect of the invention provides a valve timing control apparatus of an internal combustion engine that includes a biasing device that exerts a bias force so as to bring valve timing of the engine into a predetermined state when the valve timing is in a predetermined range, which control apparatus includes a controller that controls the valve timing while taking into account the bias force of the biasing device.
In the apparatus constructed as described above, even where the biasing device applies a bias force to, for example, a camshaft of intake valves, the valve timing is controlled while taking into account the bias force of the biasing device. Therefore, the valve timing can be accurately controlled irrespective of the bias force exerted by the biasing device.
In one preferred embodiment of the invention as described above, the predetermined state is between a most retarded state and a most advanced state, and the biasing device exerts the bias force so as to bring the valve timing of the engine into the predetermined state when the valve timing is on a retard side of the predetermined state. In this embodiment, the controller controls the valve timing while taking into account the bias force of the biasing device at least when the valve timing is on the retard side of the predetermined state.
With the above arrangement, while the bias force is applied by the biasing device when the valve timing is on the retard side of the predetermined state, the valve timing control is performed taking into account the biasing force, and the valve timing can be appropriately controlled regardless of the bias force.
In another preferred embodiment of the invention, the controller sets a target value of the valve timing in accordance with an operating state of the engine, and calc

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