CA1172731A - Method for improving fuel control in an internal combustion engine - Google Patents
Method for improving fuel control in an internal combustion engineInfo
- Publication number
- CA1172731A CA1172731A CA000357122A CA357122A CA1172731A CA 1172731 A CA1172731 A CA 1172731A CA 000357122 A CA000357122 A CA 000357122A CA 357122 A CA357122 A CA 357122A CA 1172731 A CA1172731 A CA 1172731A
- Authority
- CA
- Canada
- Prior art keywords
- engine
- volumetric efficiency
- pressure
- ratio
- fuel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
Abstract
ABSTRACT
A method for improving fuel control in an inter-nal combustion engine employs a pressure ratio to deter-mine the engine's actual volumetric efficiency continuously as the engine is operating. The air/fuel ratio of the engine's combustible mixture is affected by the volumetric efficiency. The volumetric efficiency varies during engine operation. Determination of the actual volumetric efficiency on a real-time basis allows greater accuracy in fuel metering. The pressure ratio used in the determination of the volumetric efficiency is the ratio of the intake and exhaust pressures or the inverse of this ratio. The ratio of pressures is combined with a second factor representative of the forces acting upon the air or air/fuel mixture inducted into the engine. The pressure ratio may be ob-tained without actual measurement of the pressure in the engine's exhaust conduit.
A method for improving fuel control in an inter-nal combustion engine employs a pressure ratio to deter-mine the engine's actual volumetric efficiency continuously as the engine is operating. The air/fuel ratio of the engine's combustible mixture is affected by the volumetric efficiency. The volumetric efficiency varies during engine operation. Determination of the actual volumetric efficiency on a real-time basis allows greater accuracy in fuel metering. The pressure ratio used in the determination of the volumetric efficiency is the ratio of the intake and exhaust pressures or the inverse of this ratio. The ratio of pressures is combined with a second factor representative of the forces acting upon the air or air/fuel mixture inducted into the engine. The pressure ratio may be ob-tained without actual measurement of the pressure in the engine's exhaust conduit.
Description
1 7~73 ~
A METHOD FOR IMPROVING FUEL CONTROL IN AN
INTERNAL COMBUSTION ENGINE
This invention is related to U.S. Patent 3,969,614 to Moyer et al issued July 13, 1976 and entitled "Method 5 and Apparatus for Engine Control" and to U.S. Patent 4,086,884 to Moon et al issued May 2, 1978 and entitled `'Method and Apparatus for Controlling the Amount of Fuel Metered into an Internal Combustion Engine", both issued to Ford Motor Company.
This invention relates to a method for improving fuel control in an internal combustion engine. More particularly, it relates to a method for improving the manner in which fuel is metered in an internal combustion engine fuel control system of the speed-density type.
There are two types of systems for controlling electrically the amount of fuel metered to an internal combustion engine. One of these is the mass air flow system, in which the volume or mass of air flowing into an engine is actually measured and the fuel is metered accordingly. The other system, speed-density, uses engine speed and the engine intake manifold absolute pressure to determine indirectly the amount of air entering an engine. In both types of electronic fuel control systems, the appropriate quantity of fuel is metered with a suitable fuel control apparatus. This apparatus typically has been a plurality o~ electromagnetic fuel injectors intermittently operated to deliver fuel into - the intake manifold upstream of the usually provided intake valves.
In the speed-density fuel control system described in the aforementioned U.S. patent 4,086,8~4, the fuel control system employs a digital computer to calculate the amount of fuel required by the engine, The calculation is done -'', '~
, .
repetitively 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.
The aforementioned U.S. patent 3,969,614 describes an interactive engine control system. In such a digital computer engine control system, an output variable, such as ignition timing, is taken into account in the determination of another output variable, such as the time and duration of injection in an intermittent-type fuel injection system. (If the injection is continuous, of course, determination of the usual points in the engine cycle at which injection is to be initiated is unnecessary.) The speed-density fuel injection syste,n described in U.S. patent 4,08~,884 requires that the volumetric efficiency of the engine be used, directly or indirectly, in the calculation of the quantity of fuel to be supplied to the engine. Unfortunately, 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.
The improved method of the present invention permits the volumetric efficiency of an engine having a speed-density electronic fuel control system to be determined much more accurately, under varying engine operating conditions, than is the case in the prior art systems. As a result, much more accurate fuel control is made possible and desired fuel economy and emission control benefits may be realized under certain circumstances.
- 3 - ~1 72~31 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.
Specifically, in accordance with the present invention there is provided a method for improving the fuel control of an internal combustion engine having an intake conduit 10 and an exhaust conduit, the method comprising the steps of: (a) measuring the intake conduit pressure; (b) establishing an exhaust conduit pressure; (c) determining the ratio between the engine's intake conduit pressure and its exhaust conduit pressure; td) using the 15 determined ratio to determine the volumetric efficiency value of the engine, the volumetric efficiency being determined with respect to the flow of gases into at least one combustion chamber of the engine; (e) calculating the air mass flow into the engine based upon 20 such determined volumetric efficiency value; (f) metering fuel to the engine in a quantity based upon such calculated air mass flow, and when a value for air mass flow is available, the step of establishing an exhaust conduit pressure includes calculating the exhaust conduit pressure using the latest available air mass flow.
The method of the inven~ion 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 30 mixture and exhaust gas pressures is easily determined with the use of sensors typically found on engines having speed-density fuel control systems. Also, the engine speed i5 a variable that is readily available on a continuous basis in electronic engine control systems.
3~ 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 in Moon et al patent - 3a- ~ 172~31 4,086,884 mentioned above avoided this. The volumetric efficiency was treated as a /
35 ~ .
. ..~
.
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 feature 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 prior art calculation of the quantity of fuel to be supplied to an engine employing a speed-density fuel control system, wbether accomplished with analog electronic circuitry or with a digital computer and associated software or a combination of these, has been based primarily on the speed of the engine and the intake manifold pressure at the 15 time the calculation is made. In these prior art control systems for spark-ignition internal combustion engines, the other parameters of engine operation have been regarded as being of substantially lesser significance. The other parameters are less variable, generally speaking, and consequently can be treated as environmental conditions that should be taken into account for purposes of accuracy and calibration. The more extreme modes of engine operation, such as occur during engine c~anking at start, cold-engine warm-up and wide-open throttle, usually have been treated as situations requiring separate co~ltrol provisions. Because catalysts of the three-way type now are used extensively in automotive engines and because exhaust gas recirculation makes the oxygen content of the intake mixture less predictable under all conditions of engine operation, the use of engine speed and intake manifold pressure alone to determine the quantity of fuel to be supplied to an engine no longer is satisfactory, whether or not the density of the intake mixture is taken into account.
The system disclosed in Moon et al patent 4,086,884 was intended to improve the speed-density fuel control system by taking into account the effect of exhaust gas recirculation _ 5 _ i~72~3~
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 s 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 of gaseous material that enters the combustion chamber or chambers of an engine divided by the displacement volume of such combustion chamber or chambers of the engine; the volume of gaseous material entering the engine is referenced 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 fixecl 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.
:
- 6 _ il7273~
The inventors have ound that 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 o 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.
All of the gaseous mixture entering the engine's intake system and flowing toward the engine's combustion chamber or chambers travels through the engine's intake conduit or manifold before passing through the respective intake valves and into the corresponding combustion chambers.
There is resistance to this flow in the form of frictional and inertial forces. The frictional forces are the result of the interaction of the fluids entering the combustion chambers with the intake conduit and the intake valves.
Volumetric efficiency of an engine is a measure of 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 tlle 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.
.. ,q _ 7 _ t17273~
The pressure ratio of the engine can be expressed by a pnemonic 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 pnemonically in other ways. For example, the pressure ratio may be written as PEOPI, meaning exhaust pressure over or divided by intake pressure; the PEOPI is a pressure ratio, as 10 is PIOPE. Volumetric efficiency VEFF preferably is related to PEOPI as follows:
VEFF = [(PEOPI) (Kl) + K2] (second factor).
In this equation, Kl and K2 are constants. The second factor represents the frictional and inertial forces acting on tne 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.
Whatever the pnemonic representation in the digital computer computation of volumetric efficiency or its equivalents, 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 factGr 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 r and also the constants Kl and K2 above, can be determined by multiple regression analysis of data obtained by testing a particular engine design on an engine dynamometer 7~731 This method for determining the second factor typically results in the second factor being defined by a quadratic equation, having known constants K3, K4 and K5, as follows:
second factor = K3 + (K4)(engine RPM) + (K5)(engine RP~2).
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 o PIOPE and engine speed. ThR 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 ~oon et al patent 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 ef~iciency, can be used to obtain the fuel delivery required for such current voll~netric: efficiency.
In the determination of the absolute pressure ratio, it is not necessary to actually measure the absolute pressure in the exhaust conduit of the engine. 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. tIt 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 , ` 9 ~ ~2~3I
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 a succeeding cycle. To do this, 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 tusually 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 subtracted as taught in the Moon et al patent 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 square of the air mass flow rate. The absolute value of the exhaust pressure is the gage pressure plus the known or sensed barometric pressure. Following this, the ratio PIOPE or P~OPI 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.
If it is desired to use the digital computer program and memory for more than one engine or vehicle system without changing the volumetric efficiency table that is selected, this can be accomplished by the use of scaling factors and terms in the basic equation that rela-tes mass air flow into the engine's combustion chambers to the exhaust system gage pressure. For this purpose, 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.
-lo- ~ 1 72~31 The calculations, which are effected in the present invention and their sequence, are clarified by the accompanying drawings, wherein:
Figures lA and lB are a logic flow block diagram in accordance with an embodiment of the invention; and Figure 2 is a table of values suitable for use in accordance with an embodiment of the invention.
A METHOD FOR IMPROVING FUEL CONTROL IN AN
INTERNAL COMBUSTION ENGINE
This invention is related to U.S. Patent 3,969,614 to Moyer et al issued July 13, 1976 and entitled "Method 5 and Apparatus for Engine Control" and to U.S. Patent 4,086,884 to Moon et al issued May 2, 1978 and entitled `'Method and Apparatus for Controlling the Amount of Fuel Metered into an Internal Combustion Engine", both issued to Ford Motor Company.
This invention relates to a method for improving fuel control in an internal combustion engine. More particularly, it relates to a method for improving the manner in which fuel is metered in an internal combustion engine fuel control system of the speed-density type.
There are two types of systems for controlling electrically the amount of fuel metered to an internal combustion engine. One of these is the mass air flow system, in which the volume or mass of air flowing into an engine is actually measured and the fuel is metered accordingly. The other system, speed-density, uses engine speed and the engine intake manifold absolute pressure to determine indirectly the amount of air entering an engine. In both types of electronic fuel control systems, the appropriate quantity of fuel is metered with a suitable fuel control apparatus. This apparatus typically has been a plurality o~ electromagnetic fuel injectors intermittently operated to deliver fuel into - the intake manifold upstream of the usually provided intake valves.
In the speed-density fuel control system described in the aforementioned U.S. patent 4,086,8~4, the fuel control system employs a digital computer to calculate the amount of fuel required by the engine, The calculation is done -'', '~
, .
repetitively 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.
The aforementioned U.S. patent 3,969,614 describes an interactive engine control system. In such a digital computer engine control system, an output variable, such as ignition timing, is taken into account in the determination of another output variable, such as the time and duration of injection in an intermittent-type fuel injection system. (If the injection is continuous, of course, determination of the usual points in the engine cycle at which injection is to be initiated is unnecessary.) The speed-density fuel injection syste,n described in U.S. patent 4,08~,884 requires that the volumetric efficiency of the engine be used, directly or indirectly, in the calculation of the quantity of fuel to be supplied to the engine. Unfortunately, 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.
The improved method of the present invention permits the volumetric efficiency of an engine having a speed-density electronic fuel control system to be determined much more accurately, under varying engine operating conditions, than is the case in the prior art systems. As a result, much more accurate fuel control is made possible and desired fuel economy and emission control benefits may be realized under certain circumstances.
- 3 - ~1 72~31 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.
Specifically, in accordance with the present invention there is provided a method for improving the fuel control of an internal combustion engine having an intake conduit 10 and an exhaust conduit, the method comprising the steps of: (a) measuring the intake conduit pressure; (b) establishing an exhaust conduit pressure; (c) determining the ratio between the engine's intake conduit pressure and its exhaust conduit pressure; td) using the 15 determined ratio to determine the volumetric efficiency value of the engine, the volumetric efficiency being determined with respect to the flow of gases into at least one combustion chamber of the engine; (e) calculating the air mass flow into the engine based upon 20 such determined volumetric efficiency value; (f) metering fuel to the engine in a quantity based upon such calculated air mass flow, and when a value for air mass flow is available, the step of establishing an exhaust conduit pressure includes calculating the exhaust conduit pressure using the latest available air mass flow.
The method of the inven~ion 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 30 mixture and exhaust gas pressures is easily determined with the use of sensors typically found on engines having speed-density fuel control systems. Also, the engine speed i5 a variable that is readily available on a continuous basis in electronic engine control systems.
3~ 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 in Moon et al patent - 3a- ~ 172~31 4,086,884 mentioned above avoided this. The volumetric efficiency was treated as a /
35 ~ .
. ..~
.
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 feature 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 prior art calculation of the quantity of fuel to be supplied to an engine employing a speed-density fuel control system, wbether accomplished with analog electronic circuitry or with a digital computer and associated software or a combination of these, has been based primarily on the speed of the engine and the intake manifold pressure at the 15 time the calculation is made. In these prior art control systems for spark-ignition internal combustion engines, the other parameters of engine operation have been regarded as being of substantially lesser significance. The other parameters are less variable, generally speaking, and consequently can be treated as environmental conditions that should be taken into account for purposes of accuracy and calibration. The more extreme modes of engine operation, such as occur during engine c~anking at start, cold-engine warm-up and wide-open throttle, usually have been treated as situations requiring separate co~ltrol provisions. Because catalysts of the three-way type now are used extensively in automotive engines and because exhaust gas recirculation makes the oxygen content of the intake mixture less predictable under all conditions of engine operation, the use of engine speed and intake manifold pressure alone to determine the quantity of fuel to be supplied to an engine no longer is satisfactory, whether or not the density of the intake mixture is taken into account.
The system disclosed in Moon et al patent 4,086,884 was intended to improve the speed-density fuel control system by taking into account the effect of exhaust gas recirculation _ 5 _ i~72~3~
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 s 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 of gaseous material that enters the combustion chamber or chambers of an engine divided by the displacement volume of such combustion chamber or chambers of the engine; the volume of gaseous material entering the engine is referenced 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 fixecl 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.
:
- 6 _ il7273~
The inventors have ound that 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 o 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.
All of the gaseous mixture entering the engine's intake system and flowing toward the engine's combustion chamber or chambers travels through the engine's intake conduit or manifold before passing through the respective intake valves and into the corresponding combustion chambers.
There is resistance to this flow in the form of frictional and inertial forces. The frictional forces are the result of the interaction of the fluids entering the combustion chambers with the intake conduit and the intake valves.
Volumetric efficiency of an engine is a measure of 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 tlle 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.
.. ,q _ 7 _ t17273~
The pressure ratio of the engine can be expressed by a pnemonic 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 pnemonically in other ways. For example, the pressure ratio may be written as PEOPI, meaning exhaust pressure over or divided by intake pressure; the PEOPI is a pressure ratio, as 10 is PIOPE. Volumetric efficiency VEFF preferably is related to PEOPI as follows:
VEFF = [(PEOPI) (Kl) + K2] (second factor).
In this equation, Kl and K2 are constants. The second factor represents the frictional and inertial forces acting on tne 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.
Whatever the pnemonic representation in the digital computer computation of volumetric efficiency or its equivalents, 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 factGr 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 r and also the constants Kl and K2 above, can be determined by multiple regression analysis of data obtained by testing a particular engine design on an engine dynamometer 7~731 This method for determining the second factor typically results in the second factor being defined by a quadratic equation, having known constants K3, K4 and K5, as follows:
second factor = K3 + (K4)(engine RPM) + (K5)(engine RP~2).
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 o PIOPE and engine speed. ThR 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 ~oon et al patent 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 ef~iciency, can be used to obtain the fuel delivery required for such current voll~netric: efficiency.
In the determination of the absolute pressure ratio, it is not necessary to actually measure the absolute pressure in the exhaust conduit of the engine. 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. tIt 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 , ` 9 ~ ~2~3I
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 a succeeding cycle. To do this, 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 tusually 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 subtracted as taught in the Moon et al patent 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 square of the air mass flow rate. The absolute value of the exhaust pressure is the gage pressure plus the known or sensed barometric pressure. Following this, the ratio PIOPE or P~OPI 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.
If it is desired to use the digital computer program and memory for more than one engine or vehicle system without changing the volumetric efficiency table that is selected, this can be accomplished by the use of scaling factors and terms in the basic equation that rela-tes mass air flow into the engine's combustion chambers to the exhaust system gage pressure. For this purpose, 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.
-lo- ~ 1 72~31 The calculations, which are effected in the present invention and their sequence, are clarified by the accompanying drawings, wherein:
Figures lA and lB are a logic flow block diagram in accordance with an embodiment of the invention; and Figure 2 is a table of values suitable for use in accordance with an embodiment of the invention.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for improving the fuel control of an internal combustion engine having an intake conduit and an exhaust conduit, the method comprising the steps of:
(a) measuring the intake conduit pressure;
(b) establishing an exhaust conduit pressure;
(c) determining the ratio between the engine's intake conduit pressure and its exhaust conduit pressure;
(d) using the determined ratio to determine the volumetric efficiency value of the engine, the volumetric efficiency being determined with respect to the flow of gases into at least one combustion chamber of the engine;
(e) calculating the air mass flow into the engine based upon such determined volumetric efficiency value;
(f) metering fuel to the engine in a quantity based upon such calculated air mass flow, and when a value for air mass flow is available, said step of establishing an exhaust conduit pressure includes calculating the exhaust conduit pressure using the latest available air mass flow.
(a) measuring the intake conduit pressure;
(b) establishing an exhaust conduit pressure;
(c) determining the ratio between the engine's intake conduit pressure and its exhaust conduit pressure;
(d) using the determined ratio to determine the volumetric efficiency value of the engine, the volumetric efficiency being determined with respect to the flow of gases into at least one combustion chamber of the engine;
(e) calculating the air mass flow into the engine based upon such determined volumetric efficiency value;
(f) metering fuel to the engine in a quantity based upon such calculated air mass flow, and when a value for air mass flow is available, said step of establishing an exhaust conduit pressure includes calculating the exhaust conduit pressure using the latest available air mass flow.
2. A method according to claim 1 wherein the sequence of steps recited therein is repeated and said step of establishing an exhaust conduit pressure includes:
calculating the exhaust conduit pressure a first time assuming a value of zero for air mass flow, and calculating the exhaust conduit pressure subsequent to the first time using the most recently available air mass flow determined in step (e) of claim 1.
calculating the exhaust conduit pressure a first time assuming a value of zero for air mass flow, and calculating the exhaust conduit pressure subsequent to the first time using the most recently available air mass flow determined in step (e) of claim 1.
3. A method according to claim 1 wherein the volumetric efficiency value is established from data contained in a table stored in the memory of a digital computer as a function of the ratio between the engine's intake conduit pressure value and the engine exhaust conduit pressure value, and as a function of engine speed.
4. A method according to claim 1 wherein the pressure ratio and a second factor are combined to obtain the volumetric efficiency determined in accordance with step (d) in claim 1.
5. A method according to claim 4 wherein the pressure ratio together with said second factor representing the frictional and inertial forces acting upon the mixture of gases flowing through the engine's intake conduit are used to obtain the volumetric efficiency determined in accordance with step (d) in claim 1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7929379A | 1979-09-27 | 1979-09-27 | |
| US79,293 | 1979-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1172731A true CA1172731A (en) | 1984-08-14 |
Family
ID=22149613
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000357122A Expired CA1172731A (en) | 1979-09-27 | 1980-07-24 | Method for improving fuel control in an internal combustion engine |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0026642B1 (en) |
| JP (1) | JPS5647637A (en) |
| CA (1) | CA1172731A (en) |
| DE (1) | DE3070883D1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1179959B (en) * | 1984-02-08 | 1987-09-23 | Fiat Auto Spa | METHOD AND DEVICE FOR THE AUTOMATIC CORRECTION OF THE FUEL RATIO IN AN ALTERNATIVE ENDOTHERMAL ENGINE |
| JPS61149535A (en) * | 1984-12-25 | 1986-07-08 | Honda Motor Co Ltd | Fuel feed control method for internal-combustion engine with supercharger |
| DE19618691A1 (en) * | 1996-05-09 | 1997-11-13 | Bosch Gmbh Robert | Method and device for controlling an internal combustion engine |
| US6560526B1 (en) * | 2000-03-03 | 2003-05-06 | General Motors Corporation | Onboard misfire, partial-burn detection and spark-retard control using cylinder pressure sensing |
| CN110312564B (en) | 2017-02-13 | 2021-11-16 | 卡尔冈碳素公司 | Chloramine and chlorine removal material and preparation method thereof |
| MX2023002244A (en) | 2020-08-31 | 2023-03-17 | Calgon Carbon Corp | Copper and nitrogen treated sorbent and method for making same. |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1304262A (en) * | 1969-01-31 | 1973-01-24 | ||
| US3688750A (en) * | 1970-04-30 | 1972-09-05 | Physics Int Co | Mass flow metered fuel injection system |
| US3888458A (en) * | 1972-08-09 | 1975-06-10 | Gen Motors Corp | Mass flow air meter |
| DE2507917C2 (en) * | 1975-02-24 | 1986-01-02 | Robert Bosch Gmbh, 7000 Stuttgart | Device for regulating the optimal operating behavior of an internal combustion engine |
| US4086884A (en) * | 1976-06-14 | 1978-05-02 | Ford Motor Company | Method and apparatus for controlling the amount of fuel metered into an internal combustion engine |
| FR2406727A1 (en) * | 1977-10-21 | 1979-05-18 | Herbault Patrick | Electronic fuel injection system for IC engine - has air flow detector responding to pressure upstream of throttle, with signal fed to circuit which also receives tachometer output |
| JPS5491622A (en) * | 1977-12-28 | 1979-07-20 | Nissan Motor Co Ltd | Electronic control exhaust recirculation apparatus |
-
1980
- 1980-07-24 CA CA000357122A patent/CA1172731A/en not_active Expired
- 1980-08-20 JP JP11460880A patent/JPS5647637A/en active Granted
- 1980-09-26 DE DE8080303375T patent/DE3070883D1/en not_active Expired
- 1980-09-26 EP EP19800303375 patent/EP0026642B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0026642A2 (en) | 1981-04-08 |
| EP0026642B1 (en) | 1985-07-17 |
| JPS5647637A (en) | 1981-04-30 |
| DE3070883D1 (en) | 1985-08-22 |
| EP0026642A3 (en) | 1982-02-03 |
| JPH0158331B2 (en) | 1989-12-11 |
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