Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1998-05-27
2001-07-10
Kamen, Noah P. (Department: 3747)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S611000
Reexamination Certificate
active
06256992
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to engine control systems and, more particularly, to a system and method for controlling a turbocharger to maximize performance of an internal combustion engine.
BACKGROUND OF THE INVENTION
The use of turbochargers to increase the horsepower and torque of an internal combustion engine is well known in the art. With the addition of an exhaust-driven turbocharger, a relatively small, fuel-efficient engine can be used in a vehicle to provide economical operation during normal driving while providing additional horsepower and torque during acceleration and/or full-throttle operation.
A turbocharger includes a compressor and a turbine. The turbine drives the compressor with exhaust energy created by the internal combustion engine. The engine exhaust drives a turbine wheel in the turbine of the turbocharger and is discharged through an exhaust system. The turbine wheel drives a shaft connected to a compressor wheel in the compressor which pressurizes intake air, previously at atmospheric pressure, and forces it typically through an intercooler and over a throttle valve and into an engine intake manifold. Controlling the output of the turbocharger to obtain desired engine operation has been a long-standing problem. Too much output can create erratic engine performance and permanently damage engine components. Too little output causes engine hesitation, loss of power, and inefficient operation. Additionally, changes in atmospheric pressure, ambient temperature, and engine speed affect the overall efficiency of the turbocharger, which directly affects the performance, power output, and fuel economy of the engine.
In most, if not all, exhaust-driven turbocharger installations, a wastegate is employed to limit the maximum boost pressure developed by the turbocharger. Turbocharger speed regulation is achieved by diverting a portion of the exhaust gases through a wastegate instead of permitting all of the exhaust gases to pass through the turbine. Typically, the wastegate comprises a valve disposed in the exhaust flow path and an actuator for moving the valve. The actuator moves the valve between opened and closed positions in response to boost pressure. In the open position, the flow of the exhaust gases is diverted around the turbine housing whereas in the closed position, all of the exhaust gas travels through the turbine housing.
Prior art turbocharger systems are prone to certain failures. One of the principal sources of failure is overspeed of the turbine rotor assembly; that is, the turbine is rotated at revolutions per minute (RPM) higher than that for which the turbocharger is designed. Additionally, because the turbocharger is typically mounted near the exhaust manifold of the engine in order to efficiently receive exhaust gases for turning the turbine, the turbocharger is prone to overheating if its temperature is not regulated in some manner. If any of these conditions are left to exist for too long a period, the turbocharger will ultimately destroy itself
There is therefore a need for a system and method for controlling a turbocharger which allows the turbocharger to deliver the appropriate air mass flow to the engine to maximize engine performance and, at the same time, protects the turbocharger from excessive shaft speed and excessive turbine inlet temperature. The present invention is directed toward meeting these needs.
SUMMARY OF THE INVENTION
The present invention relates to a system and method for managing the operation of a turbocharger and is responsible for controlling the turbocharger to cause a desired air mass flow to be provided to the engine and for protecting the turbocharger from excessive shaft speed and excessive turbine inlet temperature. The protection modes have higher priority than the performance control. First, turbocharger shaft speed is checked against a programmable limit, and the turbocharger is adjusted to bring the speed under control if its speed exceeds this limit. If the speed is not above the limit, the turbine inlet temperature is checked against a second programmable limit. If the turbocharger inlet temperature is above the predetermined limit, the turbocharger is adjusted to bring the inlet temperature under control. If, after either of these adjustments are made, the predetermined limits are still exceeded by the turbocharger, then the system invokes a derating of the fueling to the engine in order to protect the turbocharger. If none of the limits have been exceeded, then the system operates the turbocharger to provide the desired air mass flow to the engine in order to maximize engine performance.
In one form of the invention, a system for controlling a turbocharger supplying air to an internal combustion engine is disclosed, the system comprising: a combustion manager operative to determine a desired air mass rate based upon a current operating point of the engine; an air system manager operative to determine an air mass rate error as a difference between the desired air mass rate and an actual air mass rate of the engine; and a turbo manager operative to control an operating state of the turbocharger so as to minimize the air mass rate error.
In another form of the invention, a system for controlling a turbocharger supplying air to an internal combustion engine is disclosed, the system comprising: a combustion manager operative to determine a desired air mass rate based upon a current operating point of the engine; an air system manager operative to determine an air mass rate error as a difference between the desired air mass rate and an actual air mass rate of the engine; and a turbo manager operative to control an operating state of the turbocharger so as to minimize the air mass rate error while preventing the turbocharger from maintaining a turbocharger shaft speed in excess of a first predetermined limit and while preventing the turbocharger from maintaining a turbocharger temperature in excess of a second predetermined limit.
In another form of the invention, a method for controlling a turbocharger supplying air to an internal combustion engine is disclosed, comprising the steps of: a) determining a current operating point of the engine; b) determining a desired air mass rate based upon the current operating point; c) determining an actual air mass rate of the engine; d) determining an air mass rate error as a difference between the desired air mass rate and the actual air mass rate; and e) controlling an operating state of the turbocharger so as to minimize the air mass rate error.
In another form of the invention, a method for controlling a turbocharger supplying air to an internal combustion engine is disclosed, comprising the steps of: a) determining a current operating point of the engine; b) determining a desired air mass rate based upon the current operating point; c) determining an actual air mass rate of the engine; d) determining an air mass rate error as a difference between the desired air mass rate and the actual air mass rate; and e) controlling an operating state of the turbocharger so as to minimize the air mass rate error while preventing the turbocharger from maintaining a turbocharger shaft speed in excess of a first predetermined limit and while preventing the turbocharger from maintaining a turbocharger temperature in excess of a second predetermined limit.
In another form of the invention, a method for controlling a turbocharger supplying air to an internal combustion engine, is disclosed, comprising the steps of: a) empirically determining a desired operating state of the turbocharger for any chosen engine speed and commanded fueling rate; b) storing the empirically determined operating states as a function of engine speed and commanded fueling rate in a lookup table; c) measuring a current engine speed and a current commanded fueling rate of the engine; d) retrieving a desired operating state of the turbocharger from the lookup table based upon the current engine speed and the current commanded fueling rate; and e) setting the turbo
Bryan W. Barry
Lewis, Jr. Spencer C.
Mohos Joseph F.
Pyclik Mark W.
Rauznitz Peter
Cummins Engine Company, Inc.
Kamen Noah P.
Woodard Emhardt Naughton Moriarty & McNett
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