Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
2000-03-20
2001-08-21
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
Reexamination Certificate
active
06276317
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 11-98127 filed on Apr. 5, 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 invention relates to an electromagnetically driven valve control apparatus and, more particularly, to a control apparatus for electromagnetically driven valves that are used as intake valves and exhaust valves of an internal combustion engine.
2. Description of the Related Art
An electromagnetically driven valve is disclosed in, for example, Japanese Patent Application Laid-Open No. HEI 10-252426. The electromagnetically driven valve has a valve body that functions as an intake or exhaust valve of an internal combustion engine, and an armature fixed to the valve body. The valve body and the armature are displaceable in the directions of an axis of the valve body.
A first electromagnetic coil and an upper spring are disposed above the armature. A second electromagnetic coil and a lower spring are disposed below the armature. During a stop of the internal combustion engine, the armature is held at a neutral position, that is, an intermediate position between the first electromagnetic coil and the second electromagnetic coil, by the urging force from the upper and lower springs. The first electromagnetic coil and the second electromagnetic coil separately produce electromagnetic forces to attract the armature, upon receiving exciting current.
The armature and the valve body of the electromagnetically driven valve described above can be displaced in a valve opening direction by supplying exciting current to the first electromagnetic coil. The armature and the valve body can be displaced in the valve opening direction by supplying exciting current to the second electromagnetic coil. Therefore, according to the conventional electromagnetically driven valve, the exhaust or intake valve can be repeatedly opened and closed at arbitrary timing by supplying exciting current to the first electromagnetic coil and the second electromagnetic coil at suitable timing.
In an internal combustion engine equipped with electromagnetically driven valves as described above, the supply of exciting current to the first and second electromagnetic coils of each electromagnetically driven valve is stopped immediately upon turning off an ignition switch to stop the engine operation. As a result, an attraction force acting on the armature of each electromagnetically driven valve discontinues, so that each armature is held at a neutral position, that is, an intermediate position between the first electromagnetic coil and the second electromagnetic coil, due to urging force from the upper and lower springs. When the armatures of the electromagnetically driven valves are at the neutral position, the exhaust valves and the intake valves are held in a half-open state. Thus, according to the conventional electromagnetically driven valves, the exhaust valves and the intake valves are held in the half-open state after the ignition switch is turned off.
Normally, during an operation of an internal combustion engine and immediately after the engine operation stops, the pressure in the intake pipe becomes negative and lower than the pressure in the exhaust pipe. Therefore, with the above-described electromagnetically driven valves, since the exhaust valves and the intake valves are held at the half-open position upon the turning-off of the ignition switch, exhaust gas having a low oxygen concentration flows into the intake pipe via the exhaust and intake valves immediately after the internal combustion engine stops. If exhaust gas having a low oxygen concentration exists in the intake pipe, there is a possibility that when the internal combustion engine is to be started again, degraded engine starting characteristics may result from insufficient oxygen.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a control apparatus that prevents exhaust gas from flowing into an intake passage of an internal combustion engine when the internal combustion engine stops.
In accordance with one aspect of the invention, a control apparatus includes electromagnetically driven actuators that respectively drive an intake valve and an exhaust valve of an internal combustion engine, at least the intake valve assuming an open state when its actuator is not electrified, and a controller coupled to the electromagnetically driven actuators that determines whether an ignition switch is turned off, and prevents an exhaust gas from flowing into an intake passage that communicates with the intake value by driving the electromagnetically driven actuators when the ignition switch is determined to have been turned off.
This control apparatus prevents exhaust gas having a low oxygen concentration from flowing into the intake passage by driving the electromagnetically driven actuators when the ignition switch is turned off to stop the internal combustion engine. Therefore, when the internal combustion engine is to be restarted, fresh air containing a sufficient amount of oxygen is supplied from the intake passage side into the combustion chamber, so that the degradation of the starting characteristic of the internal combustion engine is prevented.
In the control apparatus, the controller may hold the intake valve in a closed state during a predetermined length of time after the ignition switch is determined to have been turned off.
Therefore, during the predetermined time following the turning-off of the ignition switch, the intake valve is held in the closed state, thereby preventing exhaust gas from flowing into the intake pipe.
Furthermore, until a predetermined length of time elapses after the ignition switch is turned off, the controller may drive each of the valves at an opening-closing timing that is unchanged from an opening-closing timing that is used while the ignition switch is turned on during a normal operation of the internal combustion engine.
Therefore, until the predetermined length of time elapses after the ignition switch is turned off, each valve is driven (opened and closed) at the timing unchanged from the timing used during normal operation of the internal combustion engine. As a result, during the exhaust stroke, exhaust gas is discharged from the exhaust passage side and, during the intake stroke, fresh air is supplied from the intake passage side into the combustion chamber to fill the combustion chamber.
Still further, until a predetermined length of time elapses after the ignition switch is determined to have been turned off, the controller, during a process of displacement of a piston toward a top dead center, may set the intake valve to a closed state and may set an exhaust valve to the open state and, during a process of displacement of the piston toward a bottom dead center, may set the intake valve to the open state and may set the exhaust valve to the closed state.
Therefore, until the predetermined length of time elapses following the turning-off of the ignition switch, the intake valve is set to the closed state and the exhaust valve is set to the open state during the process of displacement of the piston toward the top dead center, so that exhaust gas is discharged. During the process of displacement of the piston toward the bottom dead center, the intake valve is set to the open state and the exhaust valve is set to the closed state, so that air is taken into the combustion chamber. Thus, after the ignition switch is turned off, the exhaustion and intake operation is performed in a two-stroke pumping manner as described above, so that exhaust gas is efficiently discharged out of the internal combustion engine and fresh air is drawn into the internal combustion engine from outside. The closed state of a valve means a completely closed state in which the corresponding intake or exhaust valve is seated on the valve seat. The open state of a valve means a state in which the corresponding intake or exhaust valve is a
Katsumata Shouji
Matsumoto Isao
Tanaka Masaaki
Yoeda Keiji
Oliff & Berridg,e PLC
Patel Vinod D
Toyota Jidosha & Kabushiki Kaisha
Walberg Teresa
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