Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2000-02-17
2001-06-19
Nguyen, Hoang (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S605200, C060S614000
Reexamination Certificate
active
06247311
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to control of a diesel engine equipped with a variable capacity turbocharger and an exhaust recirculation device.
BACKGROUND OF THE INVENTION
Tokkai Hei 7-139413 published by the Japanese Patent Office in 1995 discloses a control method of a diesel engine equipped with a turbocharger and an exhaust gas recirculation (EGR) device. The EGR device comprises an EGR valve which regulates an EGR flowrate. The control method determines a turbocharging region and an EGR region according to a load and rotation speed of the engine.
“Simulation of a variable geometry turbocharged-diesel engine for control algorithm development”, C524/127/97 published by the United Kingdom Institution of Mechanical Engineers (IMechE) in 1997 discloses a control method for controlling the EGR valve and a variable nozzle of the turbocharger in a transient state of the diesel engine.
“EGR System in a Turbocharged Diesel Engine”, pp. 193-196, Technical Preprints, published by the Japan Institute of Automobile Technology in October, 1996, discloses control of the EGR flowrate of the EGR device by varying the opening area of the variable nozzle of the turbocharger.
SUMMARY OF THE INVENTION
In some of the prior art techniques, when the EGR flowrate is varied, the supercharging pressure of the turbocharger is maintained constant, and when the variation of turbocharging pressure is performed, the EGR amount is maintained constant.
However, when the EGR flowrate is varied, the turbocharging pressure will vary, and when the turbocharging pressure is varied, the EGR flowrate will also vary because the exhaust pressure varies. That is, the turbocharging pressure and the EGR flowrate affect each other. Therefore, if it is attempted to keep the turbocharging pressure constant when varying the EGR flowrate the opening of the variable nozzle of the turbocharger must be readjusted. Moreover, if it is attempted to keep the EGR flowrate constant when the turbocharging pressure is varied, the opening of the EGR valve must be readjusted.
This control works effectively when the engine is operated in a steady state, but it does not work well in the transient state when running conditions of the engine vary. Further, if the opening of the variable nozzle and the opening of the EGR valve are changed simultaneously, the change in one of the turbocharging pressure and EGR flowrate may result in a disturbance in the control of the other.
In a diesel engine, the turbocharging pressure and the EGR flowrate affect the amount of noxious substances in the exhaust gas, so both the turbocharging pressure and the EGR flowrate must be controlled to optimum values in order to reduce the amount of noxious substances. However, it is difficult to control the EGR flowrate and the turbocharging pressure to optimum values for the above-mentioned reason, especially in the transient state of the engine.
It is therefore an object of this invention to actively vary a turbocharging pressure and EGR flowrate based on identical parameters, and control both the turbocharging pressure and EGR flowrate to optimum values.
In order to achieve the above object, this invention provides a control device for controlling an opening of an exhaust recirculation valve which is provided in an exhaust gas recirculation passage of an diesel engine and an opening of a turbine nozzle which is provided in a turbine of a turbocharger of the diesel engine. The diesel engine is provided with an intake passage and an exhaust passage which is connected by the exhaust gas recirculation passage. The turbine is disposed in the exhaust passage and drives a compressor disposed in the intake passage.
The control device comprises a sensor which detects an engine rotation speed, and a microprocessor. The microprocessor is programmed to calculate a target exhaust gas recirculation flowrate based on a target exhaust gas recirculation rate, calculate a target exhaust gas recirculation valve opening surface area based on the target exhaust gas recirculation flowrate, control the opening of the exhaust gas recirculation valve to the target exhaust gas recirculation valve opening surface area, calculate a target turbocharging pressure, calculate an exhaust system total opening surface area from the target turbocharging pressure and the engine rotation speed, calculate an opening surface area of the turbine nozzle when the same flowrate of exhaust gas as the target exhaust gas recirculation flowrate flows through the turbine, as an exhaust gas recirculation valve opening surface area equivalent value, calculate a nozzle opening surface area equivalent value by deducting the exhaust gas recirculation valve opening surface area equivalent value from the exhaust system total opening surface area, calculate a target nozzle opening surface area based on the nozzle opening surface area equivalent value, and control the opening of the turbine nozzle to the target nozzle opening surface area.
This invention also provides a control method for controlling an opening of an exhaust recirculation valve which is provided in an exhaust gas recirculation passage of an diesel engine and an opening of a turbine nozzle which is provided in a turbine of a turbocharger of the diesel engine. The diesel engine is provided with an intake passage and an exhaust passage which are connected by the exhaust gas recirculation passage. The turbine is disposed in the exhaust passage and drives a compressor disposed in the intake passage. The control method comprises detecting an engine rotation speed, calculating a target exhaust gas recirculation flowrate based on a target exhaust gas recirculation rate, calculating a target exhaust gas recirculation valve opening surface area based on the target exhaust gas recirculation flowrate, controlling the opening of the exhaust gas recirculation valve to the target exhaust gas recirculation valve opening surface area, calculating a target turbocharging pressure, calculating an exhaust system total opening surface area from the target turbocharging pressure and the engine rotation speed, calculating an opening surface area of the turbine nozzle when the same flowrate of exhaust gas as the target exhaust gas recirculation flowrate flows through the turbine, as an exhaust gas recirculation valve opening surface area equivalent value, calculating a nozzle opening surface area equivalent value by deducting the exhaust gas recirculation valve opening surface area equivalent value from the exhaust system total opening surface area, calculating a target nozzle opening surface area based on the nozzle opening surface area equivalent value, and controlling the opening of the turbine nozzle to the target nozzle opening surface area.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
REFERENCES:
patent: 4235076 (1980-11-01), Meloche et al.
patent: 5996347 (1999-12-01), Nagae et al.
patent: 6067798 (2000-05-01), Okada et al.
patent: 6128902 (2000-10-01), Kolmanovsky et al.
patent: 7-139413 (1995-05-01), None
A J Truscott,“Simulation of a variable geometry turbocharged-diesel engine for control algorithm development,”IMechE, pp. 69-77, (1997).
Susumu Kohketsu et al,“EGR System in a Turbocharged Diesel Engine,”Japan Institute of Automobile Technology, pp. 193-196, (Oct. 1996).
Itoyama Hiroyuki
Miura Manabu
Shirakawa Takashi
Foley & Lardner
Nguyen Hoang
Nissan Motor Co,. Ltd.
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