Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1448—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure
  • F02D41/145—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure with determination means using an estimation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1448—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/04—Engine intake system parameters
  • F02D2200/0411—Volumetric efficiency
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/70—Input parameters for engine control said parameters being related to the vehicle exterior
  • F02D2200/703—Atmospheric pressure

Definitions

• This invention relates to methods for controlling the supply of fuel to an internal combustion engine.
• the fuel control system employs a digital computer to calculate the amount of fuel required by the engine. The calculation is done respectively to permit the fuel supply to be adjusted sufficiently often so that adequately precise control of fuel is achieved on a real-time basis.
• the computer preferably controls fuel in an interactive manner, that is, fuel supply, ignition timing and exhaust gas recirculation all are controlled simultaneously as interdependent output variables.
• US-A-3,969,614 describes an interactive engine control system.
• an output variable such as ignition timing
• another output variable such as the time and duration of injection in an intermittent-type fuel injection system.
• the speed-density fuel injection system described in US-A--4,086,884 requires that the volumetric efficiency of the engine to be used, directly or indirectly, in the calculation of the quantity of fuel to be supplied to the engine.
• the volumetric efficiency is a function of several parameters including engine speed and engine load. This means that these changing factors have had to be taken into account in the calculation of the quantity of fuel to be metered to the engine to satisfy the oxygen content of the intake mixture that actually enters the engine's combustion chambers.
• the desired fuel amount at any given time may, of course, be selected to provide a rich, a stoichiometric or a lean air/fuel mixture as may be required for engine operation in an open or closed-loop mode of engine operation.
• a method for controlling the supply of fuel to an internal combustion engine having an intake conduit and an exhaust conduit characterised by the steps of:
• the method of the invention improves fuel control in an internal combustion engine by providing for the computer calculation of an engine's current volumetric efficiency.
• the volumetric efficiency varies as a function of engine operating parameters, such as engine load, engine speed and other less significant variables.
• the method of the invention comprises the steps of determining the ratio of the absolute pressure in an engine's intake manifold to the absolute pressure of the products of combustion in a passage through which the products of combustion pass after leaving the engine's combustion chamber or chambers.
• This ratio of intake mixture and exhaust gas absolute pressures is combined mathematically with a second factor, which may be related to the engine speed, representative of forces acting upon the intake mixture as it flows toward the combustion chambers.
• the combined ratio and second factor are used to determine the volumetric efficiency of the engine with respect to the flow of gases into at least one combustion chamber thereof. This real-time volumetric efficiency may then be used to determine the amount of fuel metered to the engine.
• the method of the invention is of value as compared to the prior art because of the simplicity and accuracy with which an engine's current volumetric efficiency can be determined.
• the ratio of the intake mixture and exhaust gas absolute pressures is easily determined with the use of sensors typically found on engines having speed-density fuel control systems.
• the engine speed is a variable that is readily available on a continuous basis in electronic engine control systems.
• the prior art speed-density systems in contrast, have required the use of many time- consuming calculations, either digital or analog or both, based upon approximations of engine characteristics and design features.
• the system described US-A-4,086,884 mentioned above avoided this.
• the volumetric efficiency was treated as a function of temperature and pressure conditions in the intake manifold at the time the quantity of fuel to be delivered to the engine, i.e., the injector pulse width, was being calculated.
• a very significant advantage of the invention is that the real-time determination of volumetric efficiency takes into account the effects of changes in altitude on the characteristics of an engine's operation.
• the system disclosed in US-A-4,086,884 was intended to improve the speed density fuel control system by taking into account the effect of exhaust gas recirculation on the amount of fuel required by an engine.
• This much improved system also was designed to allow the slowly varying parameters of engine operation, such as volumetric efficiency, to be updated less frequently than the more rapidly varying parameters, such as intake manifold pressure and the quantity of recirculated exhaust gas.
• the method of the present invention carries the development of electronic fuel metering an additional step by providing an effective way to allow an engine's volumetric efficiency to be monitored on a real time basis.
• the volumetric efficiency of the engine can be of great significance where precise control of the air/fuel ratio of the mixture supplied to an engine is required. If fuel economy, engine performance and exhaust emissions are of concern, air/fuel mixtures must be precisely controlled over a range of rich, stoichiometric and lean air/fuel ratios.
• the volumetric efficiency of an engine is the volume gaseous material that enters the combustion chamber or chambers of the engine divided by the displacement volume of such combustion chamber or chambers of the engine; the volume of gaseous material entering the engine is reference to a selected temperature and pressure and in effect is a mass flow. This definition is useful here in that it indicates that volumetric efficiency, for an engine of fixed displacement, is dependent only upon the volume of gaseous material that enters the combustion chamber or chambers of the engine. Necessarily, this volume is not the same as the volume exhausted because additional gases are formed during combustion.
• volumetric efficiency of an engine in the past has been determined primarily from the intake manifold absolute pressure and the engine speed based upon accumulated engine dynamometer data for a given engine and exhaust system design. Every variation in intake manifold pressure changes the volumetric efficiency; intake manifold pressure is a function of both engine speed and engine load, as well as the density of the gaseous mixture in the manifold.
• the present invention is based on the appreciation that the volumetric efficiency, regardless of engine operation in geographical locations of widely varying altitudes, is related to the ratio of the intake manifold absolute pressure and the engine exhaust system absolute pressure immediately downstream of the combustion chamber. The relationship is almost hyperbolic. If the ratio is inverted, it is almost linear. Otherwise stated, the ratio of intake manifold absolute pressure to the absolute pressure in the engine's exhaust conduit, when combined with a second factor, can be used to determine volumetric efficiency.
• the second factor represents the frictional and inertial forces that are resisting the flow of the gaseous intake mixture entering the combustion chamber or chambers of the engine.
• volumetric efficiency of an engine is a measure cf the quantity of gaseous material inducted into a combustion chamber or chambers. Accurate determination of the volumetric efficiency makes possible delivery of exactly the right amount of fuel to the combustion chambers to satisfy the requirements of the air or oxygen in the combustion chambers. In other words, exact knowledge of an engine's volumetric efficiency throughout the operation of the engine allows the proper amount of fuel for the oxygen entering the combustion chamber or chambers during each cycle of the engine to be calculated and delivered.
• the pressure ratio of the engine can be expressed by a mnemonic suitable for use in computer programming. Thus, it may be represented as PIOPE, which means intake conduit absolute pressure, over or divided by exhaust conduit absolute pressure.
• the pressure ratio also can be represented mnemonically in other ways.
• the pressure ratio may be written as PEOPI, meaning exhaust pressure over or divided by intake pressure; the PEOPI is a pressure ratio, as is PIOPE.
• Volumetric efficiency VEFF preferably is related to PEOPI as follows:
• K 1 and K 2 are constants.
• the second factor represents the frictional and inertial forces acting on the air, or air and exhaust gas, or air, exhaust gas and fuel mixture moving within the intake conduit toward the intake valves and combustion chambers.
• the significant factor is the use of the PIOPE or PEOPI ratio of absolute pressures. These pressures in ratio and when combined with a second factor provide direct and accurate indications of current or real-time engine volumetric efficiency, i.e., volumetric efficiency as of the time the absolute pressures are determined. (This of course, assumes the intake and exhaust conduit pressures are measured or determined at the same or insignificantly different times).
• the second factor mentioned above is representative of the dynamic forces of friction and inertia that act upon, and tend to retard the flow of, the gaseous mixture in the engine's intake conduit; these forces are proportional to engine speed and other engine operating parameters of lesser significance.
• the second factor, and also the constants K, and K 2 above, can be determined by multiple regression analysis of data obtained by testing a particular engine design on an engine dynamometer. This method for determining the second factor typically results in the second factor being defined by a quadratic equation, having known constants K 3 , K 4 and K 5 , as follows:-
• a particularly suitable method for determining volumetric efficiency on a real-time basis is with the aid of values placed in computer memory in tabular form as a function of PIOPE and engine speed.
• the PIOPE and engine speed may be represented as binary numbers used to obtain access to a value or values of volumetric efficiency retained in computer memory.
• Well known techniques preferably are employed to interpolate between volumetric efficiency values stored in the memory; four-point interpolation is most accurate.
• the accessed volumetric efficiency value then can be used in a computer program for determining required fuel delivery.
• An example of a suitable equation for use in calculating fuel injection pulse width using the engine's volumetric efficiency, in a speed-density system, is given in US-A-4,086,884.
• Engine period and PEOPI, or some other suitable combination of pressure ratio with a second factor that together reflect the engine's current operational volumetric efficiency can be used to obtain the fuel delivery required for such current volumetric efficiency.
• the intake manifold absolute pressure is a quantity that is routinely used and available in known speed-density fuel injection systems for spark-ignition internal combustion engines.
• the ambient or barometric pressure also is available in such systems.
• the engine's combustion chamber displacement is a constant equal to the current mass flow of gases into the engine divided by the volumetric efficiency of the engine as calculated on the last cycle of the engine. (It should be noted that the exhaust conduit back pressure also is very much related to the mass flow of gases into the engine's combustion chamber or chambers immediately before it is exhausted to produce the exhaust pressure. This is a factor in determining the volumetric efficiency for the next succeeding engine cycle).
• the mass gas flow into the engine or volumetric efficiency for a preceding cycle may, therefore, be used to determine the volumetric efficiency for succeeding cycle.
• the displacement of the engine's combustion chambers may be divided by the volumetric efficiency last determined to yield a number approximately equal to the actual gas flow through the engine per complete engine cycle. If then this number is multiplied by the number of engine cycles per unit time (usually RPM/2), the gas flow rate through the engine is found. This flow rate may include recirculated exhaust gas and the amount of its contribution to the gas flow rate may be substracted as taught in the US-A-4,086,884.
• the exhaust conduit gage pressure is a simple quadratic function of engine air mass flow rate, that is, exhaust conduit gage pressure is equal to a constant times the sqaure of the air mass flow rate.
• the absolute value of the exhaust pressure is the gage pressure plus the known or sensed barometric pressure.
• the ratio PIOPE or PEOPI can be obtained with the use of the most recently available intake manifold absolute pressure and the calculated exhaust conduit absolute pressure. The ratio then is used, in combination with the aforementioned second factor representing frictional and inertial forces, to produce a new engine volumetric efficiency value. The calculation is repeated continually during engine operation.
• the exhaust system gage pressure may be regarded as a term that is equal to the sum of a constant and two or more other terms each having air mass flow as a factor with a coefficient that is selected for the particular engine or vehicle system in question.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Applications Claiming Priority (2)

Publications (3)

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• 1980
  • 1980-07-24 CA CA000357122A patent/CA1172731A/en not_active Expired
  • 1980-08-20 JP JP11460880A patent/JPS5647637A/ja active Granted
  • 1980-09-26 EP EP19800303375 patent/EP0026642B1/en not_active Expired
  • 1980-09-26 DE DE8080303375T patent/DE3070883D1/de not_active Expired

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