Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
2000-05-03
2001-09-04
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C123S090280, C123S188800
Reexamination Certificate
active
06283073
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 11-131367 filed on May 12, 1999 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solenoid-operated valve control apparatus for an internal combustion engine, and in particular to such a solenoid-operated valve control apparatus that is adapted to open and close a valve body that functions as an intake or exhaust valve of the engine, using spring force and electromagnetic force, and a solenoid-operated valve control method.
2. Description of the Related Art
An example of a known solenoid-operated valve control apparatuses for an internal combustion engine is disclosed in Japanese Patent Laid-Open Publication No. HEI 9-250318. In the solenoid-operated valve control apparatus of the engine, each solenoid-operated valve includes a valve body that functions as an intake or exhaust valve of the engine, a pair of springs that biases the valve body in a valve opening direction and in a valve closing direction, and a pair of electromagnetic coils that generate electromagnetic forces that move the valve body in the valve opening direction and the valve closing direction. With this arrangement, the known solenoid-operated valve described above is able to drive the valve body to open and close the same by alternately energizing each of the electromagnetic coils at an appropriate timing.
When the engine is operated for a long period of time, carbon produced by oxidation or deterioration of engine oil or fuel, for example, may be deposited between the intake or exhaust valve and a valve seat against which the intake/exhaust valve is seated. If carbon is deposited in such a manner, the valve body is not appropriately seated on the valve seat upon closing of the valve body, and sealing between the valve body and the valve seat may deteriorate when the valve body is placed in the closed position.
In this apparatus, an exciting current supplied to the upper coil while the valve is held in the closed position is increased to a value larger than that during normal operations. In this method, an electromagnetic force applied in the valve closing direction is increased while the valve body is held in the closed position so that the above-described carbon deposits can be crushed between the valve body and the valve seat. With the apparatus of the related art, therefore, it is possible to prevent a reduction in the sealing between the valve body and the valve seat due to the presence of carbon when the valve body is in the closed position.
In the above-described apparatus, the electromagnetic force applied in the valve closing direction increases after the valve body has reached its closed position. Therefore, carbon deposited between the valve body and the valve seat will always be crushed by the same portion of the valve body. This may result in increased wear of a local area of the abutting face of the valve body on the valve seat.
SUMMARY OF THE INVENTION
The present invention was developed in the light of the above situation. It is therefore an object of the present invention to provide a solenoid-operated valve control apparatus for an internal combustion engine, which is able to remove carbon deposited between the valve body and the valve seat, without causing local wear of the valve body.
To accomplish the above object, the present invention provides a solenoid-operated valve control apparatus for an internal combustion engine, which includes at least one solenoid-operated valve including a valve body that functions as an intake or exhaust valve of the engine, a spring that biases the valve body in a valve closing direction, and an electromagnetic coil that generates an electromagnetic force that moves the valve body in the valve closing direction, and a current controller that controls current supplied to the electromagnetic coil so that a valve body speed at which the valve body moves toward a valve seat increases at certain points of time to a speed higher than a normal valve body speed.
According to the present invention, the waveform of current applied to the electromagnetic coil is controlled so that the valve body speed increases at certain points of time to a speed higher than a normal valve body speed. If the speed of seating the valve body is increased, carbon that has deposited between the valve body and the valve seat can be surely crushed therebetween. Furthermore, the valve body rotates about its axis due to the action of the spring while moving toward the valve seat Since the valve body displaces or moves at a certain speed in the valve closing direction while rotating about its axis, the carbon present between the valve body and the valve seat receives a force in the valve closing direction and a rotational force about the valve axis when the valve body is seated against the valve seat. Thus, the valve body is able to crush carbon while rotating about its axis, without always using the same portion thereof for crushing carbon. According to the present invention, therefore, it is possible to remove carbon that has deposited between the valve body and the valve seat, without causing local wear of the valve body.
In one preferred form of the invention, the current controller may increase the valve body speed when the engine operates with a large operating sound.
If the valve body speed at which the valve body moves toward the valve seat is increased according to the present invention, operating noise that occurs upon collision between the valve body and the valve seat is increased. In view of this problem, the current controller is adapted to control the waveform of current applied to the electromagnetic coil so that the valve body speed is increased when the engine is operating with a large operating sound. Thus, the present invention makes it possible to remove carbon that has deposited between the valve body and the valve seat, while preventing the operating noise that increases with an increase in the valve body speed from being offensive to the ear.
In another form of the invention, the current controller may increase the valve body speed each time a given period of time elapses.
In the above form of the invention, the current controller controls the waveform of current applied to the electromagnetic coil so that the valve body speed is increased each time a given period of time elapses or at given time intervals. Where the valve body speed is increased each time a given period of time elapses, the frequency of occurrence of an operating noise that increases with an increase in the valve body speed is limited or reduced as compared with the case where the valve body speed is increased each time the valve body is seated against the valve seat. Thus, the present invention makes it possible to remove carbon that has deposited between the valve body and the valve seat while suppressing an increase in the operating noise with an increase in the valve body speed.
In a further form of the invention, the engine may include a plurality of solenoid-operated valves, and the current controller may increase the valve body speed at different points of time with respect to the respective solenoid-operated valves or with respect to respective groups of the solenoid-operated valves.
In the above form of the invention, the engine has a plurality of solenoid-operated valves. The current controller controls the waveform of current applied to the electromagnetic coil so as to increase the valve body speed at different points of time with respect to the respective solenoid-operated valves or with respect to respective groups of the solenoid-operated valves. Thus, the present invention makes it possible to remove carbon while suppressing or restricting an increase in the operating noise resulting from an increase in the speed of seating the valve body.
According to another aspect of the present invention, a solenoid-operated valve control method of an internal combustion engi
Asano Masahiko
Hattori Hiroyuki
Iida Tatsuo
Izuo Takashi
Kenyon & Kenyon
Lo Weilun
Toyota Jidosha & Kabushiki Kaisha
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