Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
1998-06-05
2001-01-23
Lo, Wellun (Department: 3747)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C251S129010, C251S129160
Reexamination Certificate
active
06176208
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims benefit of priority of Japanese Patent Applications No. Hei-9-194885 filed on Jul. 3, 1997, No. Hei-9-202502 filed on Jul. 10, 1997, and No. Hei-9-252892, filed on Sep. 1, 1997, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic valve driving apparatus, and more particularly to an electromagnetic apparatus for directly driving a valve used in an internal combustion engine, such as an intake valve, in which noises and vibration occurring when the valve is closed or opened are reduced.
2. Description of the Related Art
Electromagnetic apparatus for driving a valve used in an internal combustion engine have been known hitherto, and an example of this kind of apparatus is disclosed in JP-A-7-332044. The apparatus includes an armature fixed to a valve stem at its upper portion, a spring biasing the armature in a valve closing direction, another spring biasing the armature in a valve opening direction and an electromagnetic actuator. The valve is held at a neutral position by both springs when the electromagnetic actuator is not energized. The electromagnetic actuator includes an electromagnet for closing the valve (a closing solenoid) and another electromagnet for opening the valve (an opening solenoid), and it opens or closes the valve by attracting the armature. An example of relation between the valve positions and the valve speed in the conventional apparatus is shown in FIG.
18
. To bring the valve from an open position to a closed position, the valve opening solenoid is deenergized, and thereby the valve is moved toward the closed position by the spring biasing the valve toward the closed position. Then, the valve closing solenoid is energized, and thereby the armature is attached to the valve closing solenoid and the valve is brought to the closed position. As shown in the graph at the bottom, the valve speed increases just before the closed position because magnetic force attracting the armature increases as an air gap between the armature and the closing solenoid becomes smaller. Then, the valve sits on the valve seat abruptly at the closed position, thereby generating vibration and noises. The vibration of the valve is detrimental to durability of the valve.
The valve speed at a vicinity of the closed position cannot be controlled in the conventional apparatus, and therefore, the abrupt sitting cannot be avoided.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an electromagnetic apparatus for driving the valve such as an intake or exhaust valve used in an internal combustion engine, in which vibration and noises generated when the valve sits on a valve seat are alleviated or eliminated by reducing the sitting speed of the valve. Thereby, durability and reliability of the valve are improved.
A rod for moving the valve between its closed position and open position is connected to the valve which is disposed in a valve body. The rod is biased toward the closed position by a first spring and toward the open position by a second spring. An armature disc made of a magnetic material is fixed in the middle portion of the rod. A first solenoid for moving the valve to the closed position is disposed above the armature, and a second solenoid for moving the valve to the open position is disposed under the armature. Two chambers or spaces are formed above and under the armature. When both solenoids are not energized, the valve connected to the rod maintains an intermediate position between the open and closed positions because the biasing forces of both first and second springs are balanced. When the first solenoid is energized, the armature is attracted thereto and the valve moves to the closed position. When the second solenoid is energized, the armature is attracted thereto and the valve moves to the open position.
If the valve hits a valve seat at a high speed when it comes to the closed position, harmful vibration and noises are generated. The valve speed at the closed position is reduced to substantially zero according to the present invention. The valve speed may be controlled mechanically or electrically.
To control the valve speed mechanically, fluid may be filled in both chambers above and under the armature and is used as a cushion. Air may be used as a cushion fluid, and an one-way check valve is disposed on the armature so that the air in the upper chamber is compressed when the valve is moving toward the closed position while the air in the lower chamber is not compressed when the valve is moving toward the open position. Preferably, small orifices are formed on the armature so that the air pressure does not accumulate in the upper chamber during repeated operation. Alternatively, magnetic fluid comprising lubricant oil and small particles of a magnetic material dispersed in the oil may be used as a cushion fluid. In this case, small orifices are formed on the armature so that the magnetic fluid in both chambers can communicate with each other with a certain flow resistance. It is also possible to dispose closed spaces containing air therein which functions as an air cushion against the valve movement.
The first and second springs each having a non-linear spring modulus may be used so that the spring force becomes higher when the valve approaches the closed or open position. Such non-linear modulus spring may be realized by using two springs, one having a longer free length and the other having a shorter free length disposed in the former spring. Alternatively, a single spring having a barrel shape may be used.
Also, the valve speed can be electrically controlled. A valve position detector for generating an electrical signal representing the valve position is employed in the apparatus, and energization timing of the solenoids is controlled based on the electrical signal. More particularly, the first solenoid which is energized to move the valve to the closed position is temporarily deenergized to reduce the valve speed when the valve comes to a vicinity of the closed position. After the valve speed is sufficiently reduced, substantially to zero, the first solenoid is again energized to hold the valve on the valve seat. The timing of energization or deenergization of the solenoids is determined based on the electrical signal from the valve position detector.
As the valve position detector, an eddy current detector, a resistance detector or a spring load detector may be used. An eddy current detector of a known type may be additionally assembled with the apparatus, or components such as the armature and the solenoids may be utilized as elements of the eddy current detector. In this case, the armature may function as a target of the eddy current detector, the first solenoid as a primary coil, and the second solenoid as a secondary coil. Alternatively, a separate coil which functions as the secondary coil of the eddy current detector may be disposed on the armature or the first solenoid. In case the resistance detector is used as the valve position detector, the resistance detector measures a resistance between the armature and the valve body which represents the valve position. Further, a spring load detector which measures the spring load of the second spring biasing the valve toward the opening position may be used.
According to the present invention, the valve speed is sufficiently reduced, and the valve can sit softly on the valve seat without generating harmful vibration and noises. In addition, the armature does not hit the second solenoid hard when the valve comes to the open position.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.
REFERENCES:
patent: 4397180 (1983-08-01), Wolff et al.
patent: 4915072 (1990-04-01),
Arikawa Fumiaki
Tsuzuki Yoshihiro
Lo Wellun
Nippon Soken Inc.
Nixon & Vanderhye PC
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