Short stroke solenoid actuated EGR valve

Details Short stroke solenoid actuated EGR valve Short stroke solenoid actuated EGR valve

1999-08-23

2001-02-20

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Charge forming device

Exhaust gas used with the combustible mixture

C251S129150, C123S568210

Reexamination Certificate

active

06189519

ABSTRACT:

TECHNICAL FIELD
This invention relates to exhaust gas recirculation (EGR) valves for automotive engines, and more particularly, to a short stroke solenoid actuated EGR valve designed to be controlled by variable frequency pulse width modulation by an open loop control.
BACKGROUND OF THE INVENTION
It is known in modern emissions controlled automotive engines to place the metering of exhaust gas recirculation (EGR) under the control of an engine management computer. This has often been accomplished in an analog manner using an axially movable pintle valve. A linear solenoid, energized by the computer, withdraws the valve from the seat while position feedback is provided by a resistive potentiometer. The flow of recirculated exhaust gas is a function of the position of the valve above its seat.
While these systems have performed well in numerous applications, they have a number of disadvantages which are inherent to the concept. One disadvantage is that a sensor must be provided to indicate the valve position to the electrical control module (ECM). Also, a sophisticated closed-loop control algorithm is required to maintain a desired valve position. Both of these introduce undesired cost and complexity into the system.
A second factor is that the valve utilized is generally a more or less conical pintle operating in a circular seat. To expose lateral area equivalent to that of the circular hole, the stroke of the valve must be about half the hole radius, as much as a few millimeters in an automotive EGR valve. Since the size and mass of the linear solenoid is a direct function of the required stroke, the solenoid for this type of EGR valve tends to be quite bulky and massive. If a particularly large amount of EGR flow is needed, the solenoid may become unacceptably large.
Other types of EGR valves which have been proposed also involve additional materials, complications or control problems that may add to their cost or operability.
SUMMARY OF THE INVENTION
The present invention provides a simplified EGR valve actuated by compact single or dual solenoids having a short stroke. The short stroke is made possible by one or more annular orifices in a preferably flat valve seat or valve plate. The orifices are fed from both radially inner and outer sides upon opening movement of the valve plate a short distance away from the valve seat.
The use of annular orifices allows a relatively large gas flow through the valve with a short stroke or movement of the valve plate. This also permits use of a solenoid or solenoids of relatively low power and mass. The valve may be operated by pulse width modulation (PWM) of an electrical signal controlled by the vehicle ECM to vary the percentage of open time of the valve in order the vary EGR flow in a known manner. Thus, the need for a valve position sensor and feedback control is avoided which, together with reduced actuator mass and volume, provides a substantially reduced cost and operating complexity for the system.
The valve assembly, including a valve plate, a pintle shaft and an attached solenoid armature, may be made very light so that response time to opening and closing commands is rapid and the use of relatively low power solenoid actuation is enhanced.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.


REFERENCES:
patent: 5460146 (1995-10-01), Frankenberg

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