Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Patent
1983-09-19
1984-08-21
Burns, Wendell E.
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
123568, F02M 2506
Patent
active
044664150
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to exhaust gas recirculation (EGR) and more particularly relates to EGR control systems for use with automotive diesel engines.
2. Background Art
Systems for controlling EGR in spark ignition engines have been in use for many years.
EGR in spark ignition engines reduces the emission of oxides of nitrogen (NO.sub.x) from the engines, thus minimizing harm to the environment from these gases. Typical EGR control systems constructed for use with spark ignition engines utilize engine intake manifold vacuum, in one way or another, for providing actuating power for controlling positioning of the EGR valve itself. Because intake manifold vacuum levels are indicative of operating conditions of the engine, the intake manifold vacuum level was also sometimes used by prior art systems as a control parameter tending to indicate the degree of opening of the carburetor throttle valve at a given load. Examples of such EGR control systems are disclosed by U.S. Pat. Nos. 3,884,200; 3,739,797; and 3,970,061, among others.
Diesel engines have not been considered to emit significant amounts of NO.sub.x ; however, in recent times the amounts of NO.sub.x entering the atmosphere from the exhaust of diesel engines has increased, at least in relative terms, and therefore the use of EGR control valves in diesel engines to reduce NO.sub.x emissions has become desirable.
Diesel engines differ from spark ignition engines in a number of important ways, one being that the diesel engine does not include a valved, or throttled, intake manifold into which the combustion air is induced through a throttle and valve. Diesel engines induce combustion air through manifold-like ducts; but the amount of gas induced is substantially constant in all operating conditions of the engine. Accordingly the vacuum pressure existing in a diesel engine intake duct, is slight at most. The source of vacuum pressure provided by the intake manifold of a spark ignition engine is therefore not available in a diesel engine.
Diesel engines utilized in automotive vehicles are often constructed and arranged to drive small vacuum pumps which form a source of operating vacuum pressure for various pneumatically operated components of the vehicle. The auxiliary vacuum pumps produce vacuum pressure levels adequately great to operate EGR valves for controlling recirculation of engine exhaust gas to the engine intake ducts.
In a diesel engine the engine speed under a given load is controlled by the quantity of fuel injected into the engine combustion chambers and accordingly the "throttle" of the diesel engine is considered to be a manually operated foot pedal connected by a linkage to a fuel pump for supplying the engine fuel injectors. The foot operated pedal is actuated to govern the quantity of fuel delivered by the fuel pump to the combustion chambers of the engine and thus controls the engine speed under a given load.
Since the gas induced into the combustion chamber remains constant while the quantity of fuel introduced into the combustion chamber varies, the production of NO.sub.x varies as a function of throttle setting. This being the case, EGR valves associated with diesel engines can be controlled in relation to operation of the engine throttle.
DISCLOSURE OF THE INVENTION
The present invention provides a new and improved EGR control system for diesel engines wherein the EGR valve is provided with operating pressure varying as a predetermined function of the engine throttle position setting and thus enables close control over the recirculation of exhaust gas in the engine.
In a preferred embodiment of the invention an EGR system for an automotive vehicle diesel engine is provided wherein an EGR valve assembly is operable to recirculate exhaust gas to the engine air intake in relation to the degree of operating vacuum pressure communicated to the EGR valve by an EGR valve controller responsive to the engine throttle position. The EGR valve controller comprises a regulator and a throttle position resp
REFERENCES:
patent: 4237837 (1980-12-01), Toda et al.
patent: 4295456 (1981-10-01), Nomura et al.
patent: 4300515 (1981-11-01), Straubel et al.
patent: 4416243 (1983-11-01), Naito et al.
Burns Wendell E.
Ranco Incorporated
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