Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
2000-05-17
2001-08-14
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
Reexamination Certificate
active
06273034
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 with a variable speed fan wherein a hydraulic pump drives a hydraulic fan motor via a closed loop control system based on a hydraulic oil pressure error signal for the fan motor.
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 hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor. 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 engine speed range between an idle speed and a full speed. The method comprises determining the applied fan request signal value based on at least one engine operating condition, determining a reference hydraulic oil pressure for the fan motor based on the applied fan request signal, and monitoring an actual hydraulic oil pressure for the fan motor. The method further comprises determining an error signal by comparing the reference pressure to the actual pressure, and driving the fan motor based on the error signal such that the actual pressure tracks the reference pressure.
In a preferred embodiment, determining the actual fan request signal further comprises determining a plurality of 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. Further, the applied fan request signal is determined as the preliminary fan request signal having the greatest value. In a preferred embodiment, driving the fan motor further comprises driving the fan motor based on the error signal, a proportional term, and an integral term such that the actual fan motor pressure tracks to the reference fan pressure.
Still further, in a preferred embodiment, the method further comprises determining a steady state error based on the error signal, establishing an acceptable error range, and generating a diagnostic signal indicative of a fan failure mode when the steady state error falls outside of the acceptable error range. The acceptable error range represents acceptable steady state error for the fan motor pressure during normal fan operation.
Even further, 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, and a fan under speed failure mode occurs when the steady state error exceeds the positive error limit. Preferably, an alert signal is generated to alert a vehicle operator of the fan failure mode, when present.
Further, in carrying out the present invention, 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 hydraulically driven variable speed fan wherein hydraulic oil is pumped by a pump to drive a hydraulic fan motor. 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 medium further comprises instructions for determining the applied fan request signal value based on at least one engine operating condition, instructions for determining a reference hydraulic oil pressure for the fan motor based on the applied fan request signal, and instructions for monitoring an actual hydraulic oil pressure for the fan motor. The medium further comprises instructions for determining an error signal by comparing the reference pressure to the actual pressure, and instructions for driving the fan motor based on the error signal such that the actual pressure tracks the reference pressure.
The advantages associated with embodiments of the present invention are numerous. For example, embodiments of the present invention, for the very first time, control a variable speed hydraulically driven engine fan with a closed loop system, wherein the closed loop control is based on hydraulic oil pressure present at the input to the fan motor. Further, preferred embodiments of the invention provide enhanced diagnostic capabilities.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
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Hawkins Jeffery Scott
Weisman Steve Miller
Argenbright Tony M.
Brooks & Kushman P.C.
Detroit Diesel Corporation
Harris Katrina B.
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