Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
2000-04-27
2001-10-23
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
C123S352000, C123S436000, C123S486000
Reexamination Certificate
active
06305351
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an engine control unit (ECU) and relates particularly to an engine control unit for a gas fuelled internal combustion engine.
BACKGROUND TO THE INVENTION
Commonly owned international application No. PCT/AU93/00649 (WO 94/13946) discloses an engine control unit (ECU) in which each of the following engine operating parameters are detected: engine speed, throttle position, manifold absolute pressure (MAP), gas pressure, gas temperature, battery voltage, manifold air temperature, engine phase and boost pressure control valve (BPCV) feedback position. Each of these parameters is provided as an input in the form of an electrical signal to the ECU controller, for controlling the operation of a gas fuelled internal combustion engine. The ECU controller typically employs the detected engine speed and throttle position to calculate a percentage full load (PFL) value for the engine. PFL is a non-dimensional measure of the load or torque produced by or required from the engine. The calculated PFL value can then be employed by the ECU controller to calculate the injector ON time (IOT) for each gas injector in a gas delivery system for the engine. Typically, the PFL value is employed together with the engine speed to calculate a required manifold absolute pressure (MAP) value. The calculated value of required MAP may then be employed, together with the PFL value, to calculate a percent allowable load (PAL) value. The PAL value is then employed by the ECU controller to calculate the IOT and spark advance for the engine. By employing gas injectors and accurately calculating the IOT, the ECU can control the correct amount of gaseous fuel to be injected into each cylinder to achieve optimum engine performance under the full range of engine speed and load conditions. The disclosure of WO 94/13946 is incorporated herein by reference.
The ECU of WO 94/13946 operates very satisfactorily and is still in use in some gas fuel vehicles. However, certain improvements to the ECU were perceived as desirable to provide better control over the delivery of air and gas to each cylinder of the engine. Compliance with the stringent exhaust emission standards now being introduced in many countries, which aim to reduce the level of NO
x
gases, carbon monoxide and hydrocarbons in engine exhaust fumes was also a factor. It was thought desirable to be able to provide a greater degree of control over the air:fuel ratio in each cylinder of the engine so that the engine can operate as lean as possible (to reduce NO
x
) without causing engine misfire to occur.
SUMMARY OF THE INVENTION
The present invention was developed with a view to providing an engine control unit capable of providing an improved level of control over the delivery of air and gaseous fuel to each cylinder of the engine in order to achieve optimum engine performance.
According to one aspect of the present invention there is provided a method of controlling the operation of a gas fuelled internal combustion engine, the engine having a gas injector for injecting gaseous fuel into each cylinder and an inlet manifold through which air flows into each cylinder of the engine, the inlet manifold having a manifold valve to control the flow of air into the inlet manifold, the method comprising the steps of:
detecting the current throttle position of the engine;
detecting a manifold air parameter representative of the mass of air flowing through the inlet manifold;
deriving a desired load value for the engine, based on said current throttle position; and,
calculating a manifold valve position based on said desired load value and manifold air parameter, wherein the correct amount of air is delivered to the engine cylinders responsive to current throttle position to achieve optimum engine performance.
Preferably the method further comprises detecting the current engine speed of the engine and employing the current engine speed in said step of deriving the desired load value.
Advantageously the method further comprises deriving a desired manifold air parameter and comparing it with the value of the detected manifold air parameter to obtain a manifold air parameter correction value, and employing said manifold air parameter correction value in said step of calculating the manifold valve position.
In a preferred embodiment said detected manifold air parameter is air density (AD) which is calculated from a detected manifold absolute pressure (MAP) and a detected manifold air temperature (MAT), said desired manifold air parameter is desired air density (DAD), and said manifold air parameter correction value is an air density error corresponding to the difference between the desired and detected air density.
Preferably the method further comprises deriving an allowed load value based on said desired load value reduced by the ratio of said detected manifold air parameter to desired manifold air parameter, and deriving an injector ON time for each cylinder based on said allowed load value.
Advantageously said step of deriving an injector on time (IOT) comprises calculating a base IOT and an individual injector offset for each cylinder of the engine wherein variances between cylinders due to dynamic air flow and resonance effects in the manifold can be taken into account to balance the cylinders of the engine. Preferably the individual IOT for each injector is also compensated for variations in gas pressure and gas temperature. Preferably the individual IOT for each injector is also compensated for variations in flow rate for each injector.
According to another aspect of the present invention there is provided an engine control unit for controlling the operation of a gas fuelled internal combustion engine, the engine having a gas injector for injecting gaseous fuel into each cylinder and an intake manifold through which air flows into each cylinder of the engine, a manifold valve being provided to control the flow of air into the intake manifold, the control unit comprising:
throttle position detecting means for detecting the current is throttle position of the engine;
manifold air detecting means for detecting a manifold air parameter representative of the mass of air flowing through the intake manifold; and,
processing means for deriving a desired load value for the engine based on said current throttle position, and for calculating a manifold valve position based on said desired load value and manifold air parameter, wherein the correct amount of air is delivered to the engine cylinders responsive to current throttle position to achieve optimum engine performance.
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Nelson Daniel
Neumann Barry R.
Wright William K.
Argenbright Tony M.
Nixon & Vanderhye
Orix Vehicle Technology Pty Ltd
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