Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
2000-07-07
2001-12-11
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
Reexamination Certificate
active
06328000
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of controlling an internal combustion engine including a variable speed fan.
BACKGROUND ART
In the control of heavy duty internal combustion engines, the conventional practice utilizes electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor that executes instructions to control the engine and its various systems and sub-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 field delivery, transmission control, and many others. When the engine includes a variable speed fan, the electronic control unit operates the fan in accordance with received fan request signals. Typically, although variable speed fans have been used with internal combustion engines, the control schemes utilized to control the variable speed fans have been simple and quite conservative to reduce the possibility of accidental overheating and engine component failure.
However, the heavy duty engine business is extremely competitive. Increased demands are being placed on engine manufacturers to design and build engines that provide better engine performance, improved reliability, and greater durability while meeting more stringent emission and noise requirements. Along with all of these, perhaps the greatest customer demand is to provide engines that are more fuel efficient. Demands for fuel efficiency are becoming so great, that all engine driven systems in the vehicle are being scrutinized in attempts to reduce power consumption when possible.
For the foregoing reasons, there is a need for an improved method of controlling an internal combustion engine including a variable speed fan in which the variable speed fan is aggressively controlled to improve vehicle fuel efficiency.
DISCLOSURE OF INVENTION
It is, therefore, an object of the present invention to provide a method of controlling an internal combustion engine using closed loop control based on fan speed, with a steady state speed error being used to generate a diagnostic signal indicative of a fan failure mode when the steady state error falls outside of an acceptable error range.
In carrying out the above object and other objects and features of the present invention, a method of controlling an internal combustion engine is provided. The engine includes a variable speed fan driven by a torque multiplying fan driver. The variable speed fan is driven in response to an applied fan request signal having a value between a predetermined maximum fan request value and a predetermined minimum fan request value. The engine is operable over an engine speed range between an idle speed and a full speed. The method comprises determining at least one preliminary initial fan request signals. Each request signal has a value based on at least one engine condition and between the minimum fan request value and the maximum fan request value. The method further comprises determining the applied fan request signal as the preliminary fan request signal having the greatest value, determining a reference fan speed based on the applied fan request signal, and monitoring the actual fan speed. An error signal is determined by comparing the reference fan speed to the actual fan speed. The fan is driven based on the error signal. In a preferred embodiment, the fan is driven based on the error signal, a proportional term, and an integral term such that actual fan speed tracks the reference fan speed.
In a preferred embodiment, the method further comprises determining a steady state error based on the error signal, and establishing an acceptable error range. The acceptable error range represents acceptable steady state error for the fan during normal fan operation. A diagnostic signal is generated, and indicates a fan failure mode when the steady state error falls outside of the acceptable range.
In a preferred embodiment, establishing the acceptable error range further comprises establishing a positive error limit and establishing a negative error limit. A fan over speed failure mode occurs when the steady state error falls below the negative error limit. A fan under speed failure mode occurs when the steady state error exceeds the positive error limit.
Preferably, the method further comprises generating an alert signal to alert a vehicle operator of the fan failure mode, when the mode is present. Further, embodiments of the present invention are suitable for a variable speed fan of the hydraulically driven type wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor.
Further, in carrying out the present invention, a computer readable storage medium having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine is provided. The engine includes a variable speed fan driven by a torque multiplying fan driver that is driven in response to an applied fan request signal having a value between a predetermined maximum fan request value and a predetermined minimum fan request value. The engine is operable over an engine speed range between an idle speed and a full speed. The medium further comprises instructions for determining at least one preliminary initial fan request signals, instructions for determining the applied fan request signal, instructions for determining a reference fan speed, instructions for monitoring the actual fan speed, and instructions for determining an error signal.
The medium further comprises instructions for driving the fan based on the error signal. In a preferred embodiment, the fan is driven based on the error signal, a proportional term, and an integral term, and instructions for determining a steady state error based on the error signal. The medium, in a preferred embodiment, further comprises instructions for establishing an acceptable error range, and instructions for generating a diagnostic signal indicative of a fan failure mode when the steady state error falls outside of the acceptable range.
In a preferred embodiment, the instructions for establishing the acceptable error range further comprise instructions for establishing a positive error limit and instructions for establishing a negative error limit. A fan over speed failure mode occurs when a steady state error falls below the negative error limit. A fan underspeed failure mode occurs when the steady state error exceeds the positive error limit. Further, preferably, the medium further comprises instructions for generating an alert signal to alert a vehicle operator of the fan failure mode, when present. Embodiments of the present invention are most suitable for a variable speed fan of the hydraulically driven type wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor, but may be suitable for other variable speed fan types.
The advantages associated with embodiments of the present invention are numerous. For example, methods of the present invention provide closed loop feedback using fan speed to enhance diagnostic capabilities. The following fan failure modes may be determined by comparing the desired or reference fan speed to the actual fan speed over a period of time. First, an over speed fan failure that results in the fan running continuously at higher speeds resulting in reduced fuel economy and reduced engine durability may be detected. This failure condition is determined if the actual fan speed remains at some value above the desired fan speed for a substantial period of time. A second fan failure mode that may be detected is a major fan failure wherein the fan stops or runs at reduced speeds for an extended period of time. When a major fan failure is detected, it may be desirable to stop the engine or reduce engine fueling to prevent engine overheating. The major fan failure is detected when there is a significant reduction in actual fan speed without a similar reduction in requested fan speed. Preferably, a digital output is pr
Hawkins Jeffery Scott
Weisman Steve Miller
Argenbright Tony M.
Brooks & Kushman P.C.
Detroit Diesel Corporation
Harris Katrina B.
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