Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
2000-01-06
2001-08-14
Ponomarenko, Nicholas (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S041000, C290S04000F, C123S331000, C123S339100
Reexamination Certificate
active
06274944
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for controlling a vehicle including an internal combustion engine having an idle speed, and for controlling the idle speed.
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 circuitry, and a processor capable of executing an instruction set. The electronic control unit controls the various functions of the engine and associated systems. A particular electronic control unit communicates with numerous sensors, actuators, and sometimes with other electronic control units to control various functions and operating parameters of the engine. For example, an electronic control unit may control various aspects of fuel deliver, including the engine idle speed.
An existing method and apparatus for maintaining vehicle battery charge by controlling engine idle speed is described in U.S. Pat. No. 5,402,007, issued to Center et al. In this existing system, an alternator driven by the engine supplies power to drive electrical loads and to charge a vehicle battery. The system adaptively learns a system voltage set point. Thereafter, idle speed is controlled in response to the regulation state of the electrical system to preferably maintain the system in set point regulation, ensuring adequate battery charge or minimal battery discharge.
Because newer vehicles typically have greater system electrical loads than older vehicles, the details of the battery charging system are becoming more important. A higher engine idle speed may maintain battery charge during heavier electrical loads, but on the other hand, results in less fuel economy. Further, although existing battery charge maintenance systems are used in some applications that are commercially successful, the increasing electrical loads in vehicles and concerns about fuel economy create a need for an improved engine control method with more functionality in the charging subsystem than existing methods.
DISCLOSURE OF INVENTION
It is, therefore, an object of the present invention to provide a method for controlling a vehicle including an internal combustion engine having an idle speed, in which idle speed is increased when system voltage falls below a threshold and a vehicle speed status indicates that the vehicle is stationary.
In carrying out the above object and other objects and features of the present invention, a method for controlling a vehicle including an internal combustion engine is provided. The internal combustion engine has an idle speed, an alternator driven by the engine, a battery connected to the alternator, and a system voltage. The method comprises determining a threshold voltage, monitoring the system voltage, comparing the system voltage to the threshold voltage, and determining a vehicle speed status. The method further comprises controlling the idle speed based on the comparison. Controlling the idle speed includes increasing the idle speed when the system voltage falls below the threshold voltage and the speed status indicates that the vehicle is stationary.
In one suitable application, the threshold voltage is about 12.75 volts. In some embodiments, the method further comprises determining a voltage fluctuation that occurs when an injector fires, and determining the threshold voltage based in part on the voltage fluctuation.
For example, if the voltage fluctuation is 0.5 volts, and the desire is to have an average system voltage of at least 12.5 volts (meaning that a sample voltage when the injector fires would be 12.25 volts, while a sample voltage when the injector is not firing would be 12.75 volts), the voltage threshold could be set at, for example, about 12.75 volts. A voltage sample reading of 12.75 volts, if the sample was taken when an injector was not firing, means that the average system voltage is 12.5 volts. As such, system voltage may be sampled asynchronously to injector firing. Of course, in other embodiments, voltage sampling may be performed synchronously to the injector firing program such that sampling always occurs when an injector is not firing.
In some embodiments, controlling the idle speed further comprises increasing the idle speed from a normal speed to a raised speed for a limited period of time. Thereafter, the idle speed is decreased to the normal speed. In some embodiments, determining the vehicle speed status further comprises checking a parking brake status. The vehicle speed status is deemed as stationary when the parking brake status is engaged. In another implementation, a neutral switch status is checked. The vehicle speed status is deemed as stationary when the neutral switch status indicates that the vehicle is in neutral. In yet another embodiment, a vehicle speed sensor is checked. The vehicle speed status is deemed as stationary when the vehicle speed sensor indicates that the vehicle is stationary. Of course, a combination of items could be checked to determine the vehicle speed status.
Further, in carrying out the present invention, a method for controlling a vehicle including an internal combustion engine having a normal idle speed is provided. The method comprises determining a threshold voltage, monitoring the system voltage, comparing the system voltage to the threshold voltage, and determining a vehicle speed status. The method further comprises determining a raised idle speed that is greater than the normal idle speed. The idle speed is controlled based on the voltage comparison. The engine idle speed is increased when the system voltage falls below the threshold. The idle speed is increased from the normal idle speed to the raised idle speed when the speed status indicates that the vehicle is stationary.
In a preferred embodiment, the method further comprises determining a current engine speed. Controlling the idle speed based on a comparison includes increasing the engine idle speed when the system voltage falls below the threshold. The idle speed is increased to a lesser speed of the current engine speed and the raised idle speed when the speed status indicates that the vehicle is moving. This allows the idle speed to increase with the current engine speed up to the raised idle speed and then remain at the raised idle speed for a period of time, independent of the current engine speed. That is, when a vehicle is stationary, the idle speed may be immediately raised to the raised idle speed. On the other hand, when the vehicle is moving, the idle speed ramps up as the operator increases the current engine speed, and thereafter, when the engine returns to an idle state, the idle speed is the raised idle speed. As such, current engine speed may exceed idle, but upon the engine returning to an idle state, the engine idles at raised idle.
Still further, in carrying out the present invention, a computer readable storage medium is provided. The computer readable storage medium includes instruction stored on the medium. The instructions are executable by an engine controller to control a vehicle including an internal combustion engine having an idle speed. The storage medium further comprises instructions for establishing a threshold voltage, instructions for monitoring the system voltage, instructions for comparing the system voltage to the threshold voltage, and instructions for determining a vehicle speed status. The storage medium further comprises instructions for controlling the idle speed based on the comparison. The idle speed is increased when the system voltage falls below the threshold voltage and the speed status indicates that the vehicle is stationary.
The advantages associated with the present invention are numerous. For example, embodiments of the present invention reduce the potential for unintended vehicle acceleration. That is, because the increase in an engine idle speed may be a significant engine RPM increase, such as a few hundred RPM, embodiments of the present invention determine that the vehicle is stationary before increasing the idle speed. On the other hand,
Brooks & Kushman P.C.
Detroit Diesel Corporation
Ponomarenko Nicholas
LandOfFree
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