Solenoid-operated valve for internal combustion engine

Details Solenoid-operated valve for internal combustion engine Solenoid-operated valve for internal combustion engine

1999-11-16

2001-05-15

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

Electrical system

C123S090650, C251S129150, C251S129160

Reexamination Certificate

active

06230673

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solenoid-operated valve for use in internal combustion engines which can be opened and closed under electromagnetic forces generated by solenoids or electromagnets.
2. Description of the Related Art
There have heretofore been known solenoid-operated valves for opening and closing exhaust passages in the cylinders of internal combustion engines under electromagnetic forces. The known solenoid-operated valves have a pair of solenoids or electromagnets confronting and spaced from each other, and a disk-shaped movable plate of magnetic metal disposed movably between the solenoids. The disk-shaped movable plate is fixed to the upper end of a valve stem which has a valve body on its lower end. The valve stem is slidably supported by and extends through an upper wall of an exhaust passage from an engine cylinder, with the valve body being positioned to selectively open and close the exhaust passage.
The disk-shaped movable plate is normally urged downwardly to open the exhaust passage by a spring positioned above the disk-shaped movable plate, and is also normally urged upwardly via the valve stem to close the exhaust passage by another spring positioned beneath the disk-shaped movable plate. The springs have equal resilient forces exerted to bias the disk-shaped movable plate in mutually confronting directions for thereby holding the disk-shaped movable plate intermediate between the solenoids.
When the exhaust stroke of the engine cylinder is completed, the upper solenoid is energized to magnetically attract the disk-shaped movable plate upwardly, so that the sum of the upward magnetic attractive force of the upper solenoid and the repelling force of the lower spring overcomes the biasing force of the upper spring thereby to displace the valve stem upwardly to cause the valve body to close the exhaust passage. When the exhaust stroke of the engine cylinder is started, the lower solenoid is energized to magnetically attract the disk-shaped movable plate downwardly, so that the sum of the downward magnetic attractive force of the lower solenoid and the biasing force of the upper spring overcomes the repelling force of the lower spring thereby to displace the valve stem downwardly to cause the valve body to open the exhaust passage.
At the start of the exhaust stroke of the engine cylinder, the internal pressure of the engine cylinder is relatively high and acts on the valve body in a direction to close the exhaust passage. Therefore, the valve body suffers a delay in its movement to open the exhaust passage, resulting in a failure to meet demands for higher rotational speeds and output power of the internal combustion engine.
One solution would be to increase the magnetic forces of the lower solenoid by supplying an increased current to the lower solenoid for thereby attract the diskshaped movable plate downwardly at an increased speed. However, the increased current supplied to the lower solenoid would be disadvantageous in that the solenoid-operated valve needs to have an increased power requirement.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a solenoid-operated valve for use in internal combustion engines which is less susceptible to the internal pressure of an engine cylinder that is applied to a valve body when the exhaust passage thereof is opened, and which is prevented from suffering a delay in its movement to open the exhaust passage without an increase in the power requirement of a solenoid.
To achieve the above object, there is provided a solenoid-operated valve for use in an internal combustion engine, comprising a valve body movable upwardly for closing an exhaust passage and movable downwardly for opening the exhaust passage, a valve stem extending upwardly from the valve body, a pair of upper and lower solenoids spaced from each other in an axial direction of the valve stem and confronting each other vertically, the valve stem extending through the upper and lower solenoids, a movable plate mounted on the valve stem and disposed between the solenoids, the movable plate being movable between the solenoids to cause the valve stem to open and close the valve body in response to being magnetically attracted by the solenoids, a first spring for normally biasing the valve body to open the exhaust passage, and a second spring for normally biasing the valve body to close the exhaust passage against the first spring, the first spring having a resilient force greater than a resilient force of the second spring, the arrangement being such that the movable plate is positioned between an intermediate position between the upper and lower solenoids and the lower solenoid when the valve body biased by the first and second springs is in equilibrium.
In the following description, the resilient force represents a preset strength of each of the first and second springs, and the repelling force represents a biasing strength as it varies when each of the first and second springs is extended and compressed.
The solenoid-operated valve opens and closes the exhaust passage by enabling the solenoids to generate magnetic attractive forces in timed relation to the exhaust stroke of the internal combustion engine. Specifically, when the movable plate is attracted by the upper solenoid, the valve stem causes the valve body to close the exhaust passage, and when the movable plate is attracted by the lower solenoid, the valve stem causes the valve body to open the exhaust passage.
The valve body is vertically biased by the first spring and the second spring. When the solenoids are not energized, the valve body and the movable plate are held in a position in which the biasing forces from the first and second springs are in equilibrium. Since the resilient force of the first spring is greater than the resilient force of the second spring, when the biasing forces from the first and second springs are in equilibrium (when the solenoids are not energized), the movable plate is positioned below the intermediate position between the upper and lower solenoids, thus positioning the valve body below a central position between a closed position and an open position thereof (closer to the open position).
When the internal combustion engine discharges exhaust gases in its operation, the internal pressure of the cylinder acts in a direction to prevent the valve body in the closed position from being opened. While the valve body is closing the exhaust passage, i.e., while the movable plate is being attracted by the upper solenoid, the first spring is compressed a large distance and the second spring is compressed a small distance as it has nearly been fully extended, the repelling force of the first spring is large. When the movable plate stops being attracted by the upper solenoid and starts being attracted by the lower solenoid, the attractive force of the lower solenoid and the repelling force of the first spring move the movable plate smoothly to a position in which the biasing forces of the springs are in equilibrium, against the internal pressure of the cylinder acting on the valve body, thus moving the valve body to open the exhaust passage. When the movable plate moves past the position in which the biasing forces of the springs are in equilibrium, the repelling force of the second spring becomes progressively greater than the repelling force of the first spring. Inasmuch as the position in which the biasing forces of the springs are in equilibrium is below the central position between the solenoids (closer to the open position of the valve body), the valve body moves smoothly to the open position sufficiently against the internal pressure of the cylinder applied to the valve body.
According to the present invention, as described above, by simply using the first spring whose resilient force is greater than the resilient force of the second spring, the solenoid-operated valve is less susceptible to the internal pressure of the cylinder that is applied to the valve body when th

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