Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2000-06-29
2001-05-22
Koczo, Michael (Department: 3746)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
Reexamination Certificate
active
06233934
ABSTRACT:
TECHNICAL FIELD
The present invention relates to systems and methods for controlling a vehicle having an internal combustion engine including a variable geometry turbocharger.
BACKGROUND ART
In the control of internal combustion engines, the conventional practice utilizes electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor capable of executing a stored instruction set, to control the various functions of the engine and its associated systems. A particular electronic control unit communicates with numerous sensors, actuators, and other electronic control units to control various functions, which may include various aspects of fuel delivery, transmission control, turbocharger control, or many others.
A turbocharger consists of a turbine and a compressor. The pressure of the engine exhaust gases causes the turbine to spin. The turbine drives the compressor, which is typically mounted on the same shaft. The spinning compressor creates turbo boost pressure which develops increased power during combustion.
A variable geometry turbocharger has movable components in addition to the rotor group. These movable components can change the turbocharger geometry by changing the area or areas in the turbine stage through which exhaust gases from the engine flow, and/or changing the angle at which the exhaust gases enter or leave the turbine. Depending upon the turbocharger geometry, the turbocharger supplies varying amounts of turbo boost pressure to the engine. The variable geometry turbocharger may be electronically controlled to vary the amount of turbo boost pressure based on various operating conditions.
In a variable geometry turbocharger, the turbine housing is oversized for an engine, and the exhaust gas flow is choked down to the desired level. There are several designs for the variable geometry turbocharger. In one design, a variable inlet nozzle has a cascade of movable vanes which are pivotable to change the area and angle at which the exhaust gas flow enters the turbine wheel. In another design, the turbocharger has a movable side wall which varies the effective cross-sectional area of the turbine housing.
A conventional variable geometry turbocharger control system utilizes an electronic controller having a boost map stored therein. The boost map contains the optimum boost for an engine as a function of engine operating conditions. The controller monitors the engine operating conditions using sensors, and determines the desired boost from the boost map. Turbocharger geometry is incrementally adjusted based on the desired boost pressure obtained from the boost map.
A primary disadvantage associated with existing variable geometry turbocharger control systems is the fact that turbo boost pressure has a slow response time to incremental changes in turbocharger geometry. Because the optimum boost from the boost map varies continuously with varying engine operating conditions, the slow response time of the turbo boost pressure to the incremental changes in turbocharger geometry make is difficult to obtain precise control of the turbocharger. This slow response time renders many of the emissions and driveability benefits of the variable geometry turbocharger unachievable.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved system and method for controlling a vehicle having an internal combustion engine including a variable geometry turbocharger.
It is another object of the present invention to provide a system and method for controlling a vehicle having an internal combustion engine including a variable geometry turbocharger which allows precise turbo boost pressure control over a wide range of engine operating conditions.
In carrying out the above objects and other objects and features of the present invention, a system and method for controlling a vehicle having an internal combustion engine, a plurality of engine sensors having outputs indicative of current engine conditions, and a variable geometry turbocharger, is provided. Turbocharger geometry is varied by a controllable actuator. The system comprises a turbocharger sensor having an output indicative of turbocharger geometry, control logic for determining a desired turbocharger geometry based on the current engine conditions, and control logic for determining an error signal by comparing the current turbocharger geometry to the desired turbocharger geometry. Control logic controls the actuator based on the error signal to change the current turbocharger geometry so as to track the desired turbocharger geometry.
Preferably, the system further comprises control logic for determining an action signal based on the error signal, when error signal magnitude exceeds an action threshold value. Control logic determines at least one control term, and a modulated signal based on the at least one control term and the action signal. The modulated signal is applied to an input of the actuator.
Further, in a preferred embodiment, the system includes control logic for selecting an engine operating mode from the group consisting of a normal mode and at least one special mode based on the current engine conditions, and control logic for determining desired turbocharger geometry in each of the engine operating modes. In the normal mode, the control logic determines a filtered rate of change of a first engine parameter based on the current engine conditions. Desired turbocharger geometry is determined for steady state conditions of the first engine parameter; and, desired turbocharger geometry is determined for transient conditions of the first engine parameter.
The desired turbocharger geometry is based on the desired turbocharger geometry for steady state conditions of the first engine parameter, the desired turbocharger geometry for transient conditions of the first engine parameter, and the filtered rate of change the first engine parameter. Preferably, the desired turbocharger geometry is further based on a geometry offset. The geometry offset is based on a filtered rate of change of a second engine parameter.
Still further, in a preferred embodiment, control logic determines desired turbocharger geometry based on an engine speed parameter indicative of engine speed, and an engine torque parameter indicative of engine torque demand. Additionally, desired turbocharger geometry may be further based on a filtered rate of change of the engine speed parameter and a filtered rate of change of the engine torque parameter.
Further, in accordance with the present invention, an article of manufacture including a computer readable storage medium having information stored thereon representing instructions executable by a computer to control a vehicle having an internal combustion engine including a variable geometry turbocharger is provided. A computer readable storage medium further comprises instructions for determining a current turbocharger geometry based on a turbocharger sensor output, instructions for determining a desired turbocharger geometry, instructions for determining an error signal, and instructions for controlling the actuator.
Still further, in accordance with the present invention, a method for controlling a vehicle having an internal combustion engine including a variable geometry turbocharger is provided. The method comprises determining a current turbocharger geometry based on a turbocharger sensor output, determining a desired turbocharger geometry based on current engine conditions, determining an error signal, and controlling the actuator.
The advantages accruing to the present invention are numerous. For example, systems and methods of the present invention are capable of controlling a variable geometry turbocharger with such precision, that turbo boost pressure is accurately controllable over a wide range of engine speeds, loads, and operating modes.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for c
Church Peter D.
Rieflin Christopher M.
Brooks & Kushman P.C.
Detroit Diesel Corporation
Koczo Michael
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