Valves and valve actuation – Impact type actuator
Reexamination Certificate
1999-01-19
2001-04-10
Rivell, John (Department: 3753)
Valves and valve actuation
Impact type actuator
C251S129100, C251S129160, C123S568210
Reexamination Certificate
active
06213446
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an exhaust gas recirculation valve which controls flow of exhaust gas back to an internal combustion engine.
The invention relates in particular to such an exhaust gas recirculation valve in which the control of the flow of recirculated exhaust gas is obtained by moving a valve member off a valve seat by a regulated distance.
DESCRIPTION OF THE PRIOR ART
An exhaust gas recirculation valve is disclosed in DE 43 38 192 A 1 in which flow of engine exhaust gas back to a diesel engine is regulated as a function of operating conditions of the engine, in order to reduce NOx emissions and improve fuel consumption. For this purpose, the exhaust gas recirculation valve is arranged between the engine exhaust line and an air inlet line, preferably directly at the intake manifold. The exhaust gas recirculation valve can be actuated pneumatically or electrically. In the electrical actuator a magnetic field builds up when current is supplied to a coil to move an armature, which, in turn, acts on a valve rod to open the valve against a closing spring. In the pneumatically actuated exhaust gas recirculation valve, the valve is opened by applying suction pressure in a chamber to move a membrane connected to the valve rod. A reverse direction of operation is possible.
The valve which may be equipped with only one seat, preferably has two seats connected in series in the electrically actuated embodiment to reduce the required actuating force. For more precise flow control, which is dependent on the quantity of exhaust gas introduced into the inlet air of the engine, the valve is brought to a defined opening position by means of a potentiometer, of a positional regulation device, by an electromagnetic motor operator. In a pneumatic valve with positional feedback, the suction pressure is regulated appropriately in the operation chamber.
There occurs a deposition of carbon, lacquer and condensate in the exhaust gas recirculation valve due to the recirculation of exhaust gas, particularly when the recirculated exhaust gas is relatively cold, for example, under operating conditions in which the engine has not warmed up and in the case when the exhaust gas is cooled in heat exchangers for reduction of NOx emissions.
These residual deposits are applied to the sealing surfaces of the valve seat and the valve disk, and when the exhaust gas recirculation valve has been closed for a relatively long time, for example, during overnight parking of the vehicle, the valve disk becomes stuck to the valve seat. The adhesion of the disk to the seat exceeds by a multiple the maximum opening force of the electromagnetic or pneumatic actuator.
Thus, the valve can no longer open and its function is completely disrupted causing pollution of the environment and the need for repair.
SUMMARY OF THE INVENTION
An object of the invention is to provide means to avoid this costly and environmentally undesirable disruption of the exhaust gas recirculation system.
This object is achieved according to the invention by an exhaust gas recirculation valve comprising an inlet for recirculated exhaust gas, an outlet for supplying recirculated exhaust gas to an internal combustion engine, valve means for controlling communication between said inlet and said outlet, said valve means comprising a valve member, a seat for said valve member, a valve rod connected to said valve member and a head on said valve rod, means for moving said valve rod to control the valve member and regulate flow of the exhaust gas from said inlet to said outlet, and a device for developing kinetic energy to impact against said head and free the valve member when stuck to the valve seat.
In further accordance with the invention, a method is provided for operating the exhaust gas recirculation valve to free a valve member stuck to the valve set, by the steps comprising controlling flow of exhaust gas from an inlet of the exhaust gas recirculation valve to an engine-connected outlet thereof by regulated movement of a valve member off a seat therefor, and developing kinetic energy in a drive member when the valve member is on said seat to produce impact of the drive member on the valve member to free the valve member when stuck to the valve seat.
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Dismon Heinrich
Schurfeld Armin
Thonnessen Dieter
Ladas & Parry
Pierburg AG
Rivell John
Schoenfeld Meredith H.
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