Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-10-14
2001-10-02
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C251S333000, C251S129150
Reexamination Certificate
active
06295975
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to exhaust gas recirculation (EGR) valves for internal combustion engines, and is particularly directed to a new and improved construction for improving the accuracy and response of the valve to electrical control signals. More particularly, it is directed to a double acting single valve EEGR.
BACKGROUND OF THE INVENTION
Controlled engine exhaust gas recirculation is a commonly-used technique for reducing oxides of nitrogen in products of combustion that are exhausted from an internal combustion engine to the atmosphere. A typical EGR system comprises an EGR valve connected either to the exhaust manifold or the intake manifold that is controlled in accordance with engine operating conditions to regulate the amount of engine exhaust gas that is recirculated to the induction air flow entering the engine for combustion so as to limit the combustion temperature and hence reduce the formation of oxides of nitrogen.
Since they are typically engine-mounted, EGR valves are subject to a harsh operating environment that includes wide temperature extremes and vibrations. Exhaust emission requirements impose more stringent demands for improved control of such valves. Use of an electric actuator is one means for obtaining improved control, but in order to be commercially successful, such an actuator must be able to operate properly in such extreme environments for an extended period of time. Moreover, in mass-production automobile vehicle applications, component cost-effectiveness is also essential. An EGR valve electric actuator that possesses more accurate and quicker response results in improved driveability and fuel economy for a vehicle having an internal combustion engine that is equipped with an EGR system. It also provides better control over tail pipe emissions.
One problem with the EGR valves is their ability to accurately control the amount of exhaust gas flow over a wide range of operating conditions. Many EGR valves have a substantially linear response over their entire range of opening. To provide accurate control, however, a higher degree of positioning accuracy is required at low flow rates than at high flow rates. Until now, this capability was limited due to the common construction of the EGR valves. As a result, it has been difficult to meter precise small amounts of exhaust gas through the EGR valve.
This is especially difficult for electrically operated EGR valves (EEGR valves) that depend upon linear electrically operated solenoids to open the valve. An example of such a valve is shown in U.S. Pat. No. 5,911,401, which is incorporated herein by reference for all that it teaches.
In the '401 patent, the EEGR valve comprises an elongate valve pintle having a tapered outer surface that is moved by an electrical solenoid towards and away from an annular valve seat. This operation provides a single valve opening with a flow area that varies proportional to the distance the valve pintle moves. As a result, the valve curve has a constant slope, and the valve error and lack of precision is substantially constant over the entire operating range of the valve.
What is needed, therefore, is an improved EGR valve having an improved valve response curve with lower error and higher resolution when the valve is almost closed. It is an object of this invention to provide such an EGR valve.
SUMMARY OF THE PRESENT INVENTION
One embodiment of the invention relates to an EGR valve having an EGR valve body, a valve pintle having a longitudinal axis and supported in the EGR valve body for axially sliding motion relative thereto and having an external substantially outwardly facing first valve sealing surface and a valve shaft extending axially away from the first valve sealing surface, a first valve ring having a substantially inwardly facing first valve seat configured to engage and seal against the first valve sealing surface and having a substantially outwardly facing second valve sealing surface, and a second valve ring fixedly mounted to the EGR valve body and having a substantially inwardly facing second valve seat configured to engage and seal against the second valve sealing surface.
The EGR valve may include an electric solenoid having an armature configured to engage and move the valve pintle in a first direction from a closed position in which the first valve sealing surface is sealed against the first valve seat and the second valve sealing surface is sealed against the second valve seat, to a second position in which the first valve sealing surface is unsealed from the first valve seat and the second valve sealing surface remains sealed against the second valve seat, to a third position in the first direction in which both the first and second valve sealing surfaces are unsealed from the first and second valve seats, respectively.
The average slope of the flow rate versus valve pintle displacement of the EGR valve measured from the closed position to the first position may be less than one-half of the average slope of the flow rate versus valve pintle displacement of the EGR valve measured from the first position to the second position. The diameter of the first valve sealing surface may be less than one-half of the diameter of the second valve sealing surface or less than one-third of the diameter of the second valve sealing surface. The first valve sealing surface and the first valve seat are frusto-conical surfaces may open outward in a direction of valve opening movement. The second valve sealing surface and the second valve seat may be frusto-conical surfaces opening outward in the direction of opening movement.
In accordance with a second embodiment of the invention, an EGR valve for an automotive internal combustion engine includes a valve body, an armature, an electric coil substantially surrounding the armature and configured to drive the armature in a first direction with respect to the valve body, a valve pintle having a longitudinal axis substantially parallel to the first direction, the valve pintle including a valve shaft with a first longitudinal end configured to engage and be driven by the armature, and a second longitudinal end having a frusto-conical first valve sealing surface, a valve ring having a frusto-conical first valve seat configured to sealingly engage the first valve sealing surface and having a frusto-conical second valve sealing surface on an outer surface thereof, anda second valve ring fixedly mounted to the valve body and having a frusto-conical second valve seat configured to sealingly engage the second valve sealing surface. The valve may include a valve ring support slidingly supported on and coaxial with the valve shaft and having a ring supporting surface abutting the valve ring, wherein the ring supporting surface and the frusto-conial first valve sealing surface cooperate to support the valve ring on the end of the pintle. It may also include a spring configured and disposed to press the valve ring support against the valve ring. The spring may be a coil spring surrounding the valve ring and coaxial with the valve shaft. The valve ring support may have a plurality of gas passageways adapted to transmit gas passing between the first valve sealing surface and the first valve seat, or a plurality of legs extending outward.
In accordance with a third embodiment of the invention, a method of operating an EGR valve having a first circular valve sealing surface engageable with a first circular valve seat and a second circular valve sealing surface engageable with a second circular valve seat, wherein the first sealing surface and first valve seat are concentric and have substantially the same first diameter and the second sealing surface and the second valve seat are concentric and have substantially the same second diameter larger than the first diameter, the method comprising the steps of spring tensioning the first valve sealing surface and the first valve seat together in a closed position, spring tensioning the second valve sealing surface and the second valve seat together in the closed
Cook John Edward
Yew Kwang
Castro Arnold
Dolinar Andrew M.
Siemens Canada Limited
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