Internal-combustion engines – Engine speed regulator – Idle speed control
Patent
1991-08-02
1993-10-12
Wolfe, Willis R.
Internal-combustion engines
Engine speed regulator
Idle speed control
123585, F02D 4108
Patent
active
052515974
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the controlling of the air supply to an internal combustion engine to enable the establishment of the correct air/fuel ratio in the engine cylinders for combustion of the fuel in an efficient and controlled manner.
There is currently a wide range of equipment available for the management of internal combustion engines, and in particular, the management of the combustion process in such engines. There is currently a trend towards such management systems, commonly referred to as drive-by-wire systems, wherein the driver has no direct mechanical control over either the fuel supply or air supply to the engine, both being managed by appropriate programs incorporated in an ECU. In such systems, the accelerator pedal or throttle control, operated by the driver, generates an electrical input signal to the ECU that indicates the power output required by the driver from the engine. From this input, and taking into account inputs from other engine parameters, such as temperature and speed, the ECU determines both the fuel and air requirements of the engine and operates appropriate apparatus to comply with these demands.
In such systems an electric motor is employed to control the air supply such as by varying the position of a throttle valve located in the engine air supply passage. This motor is activated by signals from the ECU to position the throttle valve in the appropriate position so the required rate of supply of air to the engine will be achieved. The electric motor must therefore be capable of providing a rapid response to changes in air supply requirements while also providing accuracy in positioning of the throttle valve. The rapid response and accuracy in positioning of the throttle valve must also be obtained with the throttle valve operating in a duct carrying the total air supply to the engine, and therefore subject to substantial forces that influence the energy required to move the throttle valve. Accordingly, such electric motors represent a significant cost in the overall engine management system and in many situations this cost can not be justified.
A lesser concern with engines having an electric motor driven throttle valve, or other air control devices as the sole air supply control, is the fact that a breakdown in the motor operation renders the engine unworkable. This can be a serious problem in engines installed in motor vehicles or boats as the vehicles or boat is immobilised and the occupants may be placed in danger or seriously inconvenienced. Accordingly, in engines for such uses, it is usually necessary to provide some alternate form of air control which would permit the engine to at least be kept operating and provide what is commonly referred to as a "limp home capacity".
The alternative to an electric motor driven air control device is to provide a mechanical coupling between the driver operated throttle or accelerator control and the air control device in the air intake system, and to then provide a sensor in the air intake system to indicate the rate of air supply to the engine. A signal from that sensor is fed to the ECU as an input to the determination of the required fuel supply of the engine. This system avoids the high cost of the motor as required in the drive-by-wire system, and inherently provides a limp home capacity, since it is normally possible to make temporary repairs to mechanical couplings between the throttle valve and the throttle or accelerator control. However, the employment of the mechanically coupled throttle valve reduces the level of accuracy that can be obtained in the control of the air flow to the engine.
Also under low to medium load conditions, it is frequently desirable to maintain a relatively steady rate of air supply to the engine, or at least small variations therein for relatively greater variations in fuel supply. This requirement presents difficulties in attainment in a practical engine where the driver required power output from the engine is initially determined from the change of air flow in the engine air intake sy
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Davis Robert M.
Smith Darren A.
Orbital Engine Company (Australia) Pty Limited
Wolfe Willis R.
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