Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2000-05-17
2001-07-24
Wolfe, Willis R. (Department: 3747)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S602000, C123S568110
Reexamination Certificate
active
06263672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust gas recirculation system for an engine with a turbocharger.
Recirculation of exhaust gas into the intake gas of an internal combustion engine is widely recognized as a significant method for reducing the production of nitrous oxides (NO
x
) during the combustion process. The recirculated exhaust gas partially quenches the combustion process and lowers the peak temperature produced during combustion. Since NO
x
formation is related to peak temperature, recirculation of exhaust gas reduces the amount of NO
x
formed.
In order to recirculate exhaust gas into the intake manifold, the exhaust gas must be at a pressure that is greater than the pressure of the intake gas. However, in a turbocharged engine, the intake gas is typically at a pressure higher than that of the exhaust gas. This is because the compressor of the turbocharger purposefully increases the pressure of the intake gas while producing only a signal increase in the pressure of the exhaust gas. Therefore, the pressure differential from exhaust gas, to intake gas for a turbocharged engine, is often in the wrong direction to have flow from the exhaust system to the intake system. This is especially true at peak torque operation, where the inlet system is significantly boosted in pressure, and the combustion temperatures are relatively high.
Various systems have been proposed to provide recirculated exhaust gas for an engine with a turbocharger. In one design, a butterfly-type valve is placed at the exhaust of the turbine so as to backpressure the exhaust system. However, this backpressuring of the turbine results in a thrust load on the turbocharger rotor system which increases wear of the turbocharger bearings. Furthermore, exhaust gas under pressure may leak past the seals and bearings of the turbocharger and flow with the returned lubricating oil into the crankcase of the engine, undesirably increasing engine crankcase pressure.
In yet another design, a combination backpressure/EGR valve is provided at the turbine inlet. In this valve, the actuation of the backpressure valve is mechanically locked to the actuation of the EGR valve. This valve does not include flexibility to change the backpressuring of the exhaust system independently of the recirculation of exhaust gas. This lack of flexibility means that the amount of exhaust gas recirculated may be optimized for a single or narrow range of conditions, and would be non-optimum for most conditions. Also, such a combination valve does not permit backpressuring of the exhaust system during cold start up of the engine without also permitting a high degree of recirculated exhaust gas flow. Such a combination valve would be less than optimum for reduction of white smoke from a diesel engine during cold starting and warm-up.
What is needed is an exhaust gas recirculation system that provides improvements to current systems. The present invention provides a novel and unobvious EGR system that provides those improvements.
SUMMARY OF THE INVENTION
One aspect of the present invention is an exhaust gas recirculation system for an internal combustion engine producing exhaust gas and accepting intake gas. The system includes a turbocharger for increasing the pressure of the intake gas to the engine, the turbocharger having a turbine. There is also a restrictor valve for accepting the exhaust gas from the engine which is adjustable to increase the pressure of the exhaust gas. The restrictor valve has an outlet in fluid communication with the turbine. There is also an exhaust gas recirculation valve (EGR) with an inlet for receiving exhaust gas from the engine and settable for providing exhaust gas to the intake gas of the engine. The restrictor valve is adjustable independently of the setting of the exhaust gas recirculation valve.
In another aspect, the present invention includes a turbocharger, a restrictor valve, and an exhaust gas recirculation valve. The turbocharger has a turbine and an inlet passage, the inlet passage having a first flow resistance. The restrictor valve is located proximate to the inlet passage, the restrictor valve having a variable flow resistance selectively variable between a maximum and a minimum. The maximum flow resistance is greater than the first flow resistance. The restrictor valve has a first inlet and a first outlet, the first outlet being in fluid communication with the turbine. The exhaust gas recirculation valve has a second inlet and a second outlet, and a valve member selectively movable between opened and closed positions. The second inlet is in fluid communication with the first inlet of the restrictor valve. The second inlet and second outlet are in fluid communication in the opened position. The second outlet is substantially sealed from the second inlet in the closed position. The restrictor valve is selectively variable independent of the movement of the valve member of the EGR valve.
In another aspect of the present invention, there is an apparatus that includes an internal combustion engine, a restrictor valve, and a turbocharger. The internal combustion engine accepts intake gas and produces exhaust gas. The restrictor valve has an inlet for accepting exhaust gas from the internal combustion engine, a first outlet, a second outlet, and a flow-restricting device movable between first and second positions. The first position substantially restricts fluid communication from the inlet to the first outlet, and from the inlet to the second outlet. The second position substantially restricts fluid communication from the inlet to the first outlet. The turbocharger has a turbine inlet in fluid communication with the first outlet of said restrictor valve. Exhaust gas from the second outlet is mixed with intake gas.
In another aspect of the present invention, there is a system which includes an internal combustion engine, a restrictor valve, a turbocharger, an EGR valve, a first sensor, a second sensor, and a controller. The engine produces exhaust gas and accepts intake gas, the exhaust gas being at a first pressure and the intake gas being at a second pressure. The engine also has an intake manifold. The restrictor valve receives exhaust gas from the engine and has a variable flow resistance and an actuatable flow restricting device for varying the flow resistance of the restrictor valve. The restrictor valve has a first outlet. The turbocharger has a turbine with a first inlet, the first inlet being in fluid communication with the first outlet of the restrictor valve. The EGR valve has a second inlet accepting the exhaust gas and a second outlet in fluid communication with the intake manifold. The first sensor provides a first signal corresponding to the first pressure. The second sensor provides a second signal corresponding to the second pressure. The controller is responsive to the first signal and the second signal, the controller actuating the flow-restricting device to increase the first pressure so that the first pressure is greater than the second pressure.
In another aspect of the present invention, there is a turbocharger for an internal combustion engine that produces exhaust gas. The turbocharger includes a turbine, a compressor, a restrictor valve, a poppet valve, and a support housing assembly. The turbine has a first inlet, and the compressor has a first outlet. The restrictor valve restricts the flow of exhaust gas into the first inlet of the turbine. The poppet valve has a second inlet and a second outlet. The second inlet is in fluid communication with the first inlet of the turbine, and the second outlet is in fluid communication with the first outlet of the compressor. The poppet valve has an opened position in which the second outlet is in fluid communication with the second inlet and a closed position in which the second outlet is substantially sealed from the first inlet. The support housing assembly supports the turbine, compressor, restrictor valve, and poppet valve.
The present invention also includes a method for
McKinley Steven R.
Roby Stephen I.
Borg-Warner Inc.
Dziegielewski Greg
Wolfe Willis R.
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