WO2006109543A1 - Method for fuel injection amount optimization and fuel injection control apparatus for internal combustion engine - Google Patents

Method for fuel injection amount optimization and fuel injection control apparatus for internal combustion engine Download PDF

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Publication number
WO2006109543A1
WO2006109543A1 PCT/JP2006/306054 JP2006306054W WO2006109543A1 WO 2006109543 A1 WO2006109543 A1 WO 2006109543A1 JP 2006306054 W JP2006306054 W JP 2006306054W WO 2006109543 A1 WO2006109543 A1 WO 2006109543A1
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Prior art keywords
fuel injection
injection amount
angular acceleration
amount
fuel
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PCT/JP2006/306054
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French (fr)
Inventor
Koichi Ueda
Kota Sata
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Toyota Jidosha Kabushiki Kaisha
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Publication of WO2006109543A1 publication Critical patent/WO2006109543A1/en

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    • 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
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • 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
    • F02D41/1497—With detection of the mechanical response of the engine
    • F02D41/1498—With detection of the mechanical response of the engine measuring engine roughness

Definitions

  • the present invention relates to a method for determining an optimum injection amount for internal combustion engine startup.
  • the operating performance characteristics of an internal combustion engine greatly vary with the values of control parameters such as the fuel injection amount and ignition timing. Therefore, when an internal combustion engine is to be developed, the control parameter values are optimized to obtain optimum operating performance characteristics, for instance, by testing a real machine.
  • the information concerning fuel injection amount setup for startup is set forth in Japanese Patent Laid-open No. 2004-68621.
  • the fuel injection amount for startup is an important control parameter that determines, for instance, startability and exhaust emission equality.
  • 2004-68621 performs setup for the first cycle at the time of startup so that the fuel injection amount sequentially increases for the first to subsequent cylinders, and performs setup for the second and subsequent cycles so that the fuel injection amount sequentially decreases for the first to subsequent cylinders. Setup is also performed so that the fuel injection amount for each cylinder sequentially decreases for a predetermined number of cycles beginning with the first cycle.
  • Japanese Patent Laid-open No. 2004- 68621 describes the tendency concerning the fuel injection amount of each injection or cycle, it does not describe a quantitative index for fuel injection amount determination. Therefore, when a particular fuel injection amount is to be determined, it is necessary to use a conventional method of empirically finding an optimum value for each injection or cycle. However, empirical optimization would not clearly determine the fuel injection amount, and ideal startability cannot always be obtained depending on the empirically optimized fuel injection amount.
  • the present invention has been made to solve the above problem. It is an object of the present invention to provide a fuel injection amount optimization method for the purpose of accurately determining the fuel injection amount for obtaining ideal startability .
  • the above object is achieved by a method according to a first aspect of the present invention.
  • the method includes following steps for optimizing a fuel injection amount at internal combustion engine startup.
  • a target angular acceleration is preset for each predefined injection unit.
  • the angular acceleration for each predefined injection unit is determined when fuel is actually injected.
  • the injection amount for obtaining the target angular acceleration is then determined for each predefined injection unit in accordance with the relationship between the injection amount and angular acceleration.
  • the fuel injection amount for obtaining ideal startability can be accurately determined when the fuel injection amount is optimized for each predefined injection unit (e.g., for each injection or cycle) in accordance with angular acceleration, which is used as a quantitative index.
  • the method according to the first aspect of the present invention may further include following steps. As a third step of the method, a reference fuel injection amount so as to obtain a predefined reference angular acceleration of not lower than zero is determined for each injection. As a fourth step of the method, the reference fuel injection amount is multiplied by a coefficient according to the target angular acceleration. The resulting value is then set as an optimum injection amount.
  • the optimum injection amount is determined by multiplying the reference injection amount by the coefficient according to the target angular acceleration. Therefore, even when the target angular acceleration is changed, the optimum value appropriate for the changed target angular acceleration can easily be determined.
  • the angular acceleration may be the average angular acceleration for a region between the compression top dead center of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders.
  • the fuel injection amount for obtaining ideal startability can be accurately determined when the fuel injection amount is optimized by using the average angular acceleration as an index.
  • the above object is also achieved by a fuel injection control apparatus according to a fourth aspect of the present invention.
  • the apparatus includes a storage unit for storing the fuel injection amount optimized by the method according to any one of the first to third aspects of the present invention as an optimum injection amount for startup.
  • the apparatus also includes a startup fuel injection control unit for exercising fuel injection control in accordance with the optimum injection amount memorized by the storage unit .
  • the apparatus also includes a normal fuel injection control unit for exercising fuel injection control in accordance with a fuel injection amount that is calculated from an intake air amount .
  • a fuel injection control switching unit is provided for switching from fuel injection control by the startup fuel injection control unit to fuel injection control by the normal fuel injection control unit with predefined timing after internal combustion engine startup. Further, a fuel injection amount correction unit is provided.
  • the fuel injection amount correction unit when a fuel injection control mode is changed by the fuel injection control switching unit, corrects the fuel injection amount in accordance with the difference between the optimum injection amount and the fuel injection amount calculated from the intake air amount so that the fuel injection amount gradually changes from the optimum injection amount to the fuel injection amount calculated from the intake air amount.
  • the fourth aspect of the present invention corrects the fuel injection amount in accordance with the difference. Therefore, the fuel injection control mode can be smoothly switched from startup fuel injection control, which is based on the optimum injection amount, to normal fuel injection control, which is based on the intake air amount.
  • the fuel injection amount correction unit may determine a correction amount for the fuel injection amount in accordance with fuel properties .
  • the fuel injection control mode can be smoothly switched from startup fuel injection control, which is based on the optimum injection amount, to normal fuel injection control, which is based on the intake air amount, without being affected by fuel properties .
  • Fig. 1 is a flowchart for describing the fuel injection amount optimization method according to an embodiment of the present invention
  • Fig. 2 is a graph illustrating the relationship between the average angular acceleration and the engine rotation speed change
  • Fig. 3 is a graph illustrating the relationship between the average angular acceleration and the fuel injection amount
  • Fig. 4 is a graph illustrating the relationship among the fuel injection amount, angular acceleration, startability , and exhaust emission quality
  • Fig. 5 is a graph for illustrating typical target angular acceleration settings
  • Fig. 6 is a graph illustrating rotation behaviors that are obtained at the typical target angular acceleration settings
  • Fig. 7 is a flowchart illustrating a fuel injection control routine that is executed by an embodiment of the present invention.
  • Fig. 8 is a graph illustrating fuel injection amount changes that occur before and after fuel injection control mode switching due to the execution of the fuel injection control routine
  • Fig. 9 is a graph illustrating fuel injection amount changes that occur before and after fuel injection control mode switching according to a modification of the preferred embodiment of the present invention.
  • Fig. 10 is a graph illustrating settings of the coefficient "C" for fuel properties according to a modification of the preferred embodiment of the present invention
  • Fig. 11 is a graph illustrating settings of the attenuation rate " ⁇ " for fuel properties according to a modification of the preferred embodiment of the present invention .
  • Figs. 1 to 6 illustrate a method for optimizing the fuel injection amount at internal combustion engine startup in accordance with an embodiment of the present invention .
  • the fuel injection amount optimization method according to the present embodiment is characterized by the fact that it optimizes the fuel injection amount by using the angular acceleration of an internal combustion engine as a quantitative index. More specifically, the average angular acceleration for a region between the compression TDC of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders (a region between the compression TDC and BDC in the case of a four- cylinder engine) is used as an index for fuel injection amount optimization. It is assumed that the present embodiment optimizes the fuel injection amount for four-cylinder engine startup. The following advantage is provided when the average angular acceleration for the above-mentioned region is used as an index for fuel injection amount optimization. When a motion equation is used, the indicated torque "Ti" , which is generated on a crankshaft when combustion occurs in the internal combustion engine, can be calculated from Equations (1) and (2) below:
  • Equation (2) represents torque that generates the indicated torque "Ti".
  • Equation (1) represents torque that consumes the indicated torque "Ti” .
  • Equation (1) "J” denotes the inertia moment of a drive member that is driven due to air-fuel mixture combustion; "d ⁇ /dt”, crankshaft angular acceleration, and “Tf”, drive section friction torque.
  • J x (d ⁇ /dt) represents dynamic loss torque that results from the angular acceleration of the internal combustion engine.
  • the friction torque “Tf” is torque that is generated due to mechanical friction between various mating parts such as friction between a piston and cylinder inner wall. It includes torque that is generated due to mechanical friction caused by auxiliaries.
  • Tgas denotes torque that is generated by in-cylinder gas pressure
  • Teinertia denotes inertial torque that is generated by the reciprocating inertial mass of the piston and the like.
  • the torque "Tgas” that is generated by the in-cylinder gas pressure is torque that is generated due to the combustion of injected fuel .
  • the angular acceleration change after each injection determines the post-startup rotation behavior of the internal combustion engine (the curve of the rotation speed with respect to time). Therefore, when the angular acceleration is used as an index for fuel injection amount optimization, it is conceivable that the fuel injection amount for obtaining ideal startability can be determined.
  • the internal combustion engine's angular acceleration "d ⁇ /dt” includes the influence of inertial torque "Tinertia” that is based on reciprocating inertial mass.
  • the inertial torque "Tinertia” based on reciprocating inertial mass is irrelevant to the fuel injection amount and generated by the inertial mass of a piston or other reciprocating member. To accurately determine the fuel injection amount for obtaining ideal startability, therefore, it is necessary to eliminate the influence of inertial torque "Tinertia” based on reciprocating inertial mass from the angular acceleration "d ⁇ /dt", which is used as the index.
  • the fuel injection amount can be optimized by using the measured in-cylinder gas pressure as a quantitative index.
  • the reason is that the internal combustion engine's angular acceleration "d ⁇ /dt" is determined by the torque "Tgas” based on the in- cylinder gas pressure as is obvious from Equations (1) and (2). For a reason indicated below, however, it is difficult to optimize the fuel injection amount by using a measured in-cylinder gas pressure value.
  • the in-cylinder gas pressure can be measured with an in-cylinder pressure sensor.
  • mass- produced internal combustion engines are not always provided with in-cylinder pressure sensors. Even if they are provided with in-cylinder pressure sensors, each cylinder is not always provided with an in- cylinder pressure sensor. Due to cost and reliability considerations, it is practically difficult to provide every cylinder in mass-produced engines with an in- cylinder pressure sensor. It is therefore necessary to prepare a development engine whose cylinders are all provided with an in-cylinder pressure sensor.
  • the mass- produced engines and the development engine will differ in the ignition plug position.
  • the air-fuel mixture combustion state prevailing within a cylinder varies with the ignition plug position. Therefore, even when the fuel injection amount is optimized by using the development engine, the resulting optimum value does not always enable the mass-produced engines to exhibit ideal startability .
  • the average angular acceleration which is used by the fuel injection amount optimization method according to the present embodiment, can be measured with a crank angle sensor that is always mounted in each mass-produced engine. Therefore, the optimum value obtained by performing an optimization procedure on the development engine can be applied as is to the mass-produced engines.
  • the fuel injection amount optimization method according to the present embodiment will now be described in detail with reference to a flowchart in Fig. 1. Individual steps described below may be performed one after another by a human or performed automatically by an apparatus.
  • the first step (step 100) is performed to determine a target angular acceleration for each of the first to Nth injections.
  • the symbol "N" represents the final injection count for using the optimum value as the fuel injection amount.
  • an ECU calculates the fuel injection amount in accordance with the intake air amount.
  • the graph in Fig. 4 illustrates the relationship among the fuel injection amount, angular acceleration, startability, and exhaust emission quality. As indicated in the graph, the fuel injection amount for maintaining excellent exhaust emission quality is within a certain range (enclosed by a broken line in the figure) .
  • the target angular acceleration is set within this fuel injection amount setting range. Conversely, the target angular acceleration can be freely set as far as the fuel injection amount is within the fuel injection amount setting range.
  • the target angular acceleration can be set in accordance with desired rotation behavior.
  • Fig. 5 shows typical target angular acceleration settings.
  • Fig. 6 shows rotation behaviors that are obtained at the typical target angular acceleration settings.
  • the target angular acceleration settings for the second and subsequent cycles should be relatively high as indicated by a broken line in Fig. 5.
  • the rotation speed increase is to be suppressed as indicated by a solid line in Fig. 6, the target angular acceleration settings for the second and subsequent cycles should be low as indicated by a solid line in Fig. 5.
  • Fig. 5 indicates that the target angular acceleration is set for each cycle, such setup is merely an example. Alternatively, the target angular acceleration may be set for each injection as mentioned earlier.
  • the settings indicated in Fig. 5 are determined in relation to rotation speed buildup, the settings may be varied so as to place emphasis on startability for a cold start or on exhaust emission quality for an ordinary- temperature start.
  • step 102 the target angular acceleration for each of the first to Nth injections, which was set in step 100, is substituted by an angular acceleration coefficient.
  • the angular acceleration coefficient is set in accordance with the relationship between a fuel injection amount increase/decrease and angular acceleration increase/decrease.
  • the angular acceleration coefficient setting is 1.
  • the angular acceleration coefficient setting increases with an increase in the target angular acceleration. In the present embodiment, it is assumed that the reference angular acceleration is zero.
  • Steps 100 and 102 are the processing steps that should be completed before an optimization procedure is performed on a real machine.
  • the optimization procedure is performed on the real machine.
  • step 104 is performed for the first time
  • the fuel injection amount for the first injection is set provisionally.
  • step 106 the real machine is operated to inject fuel for the first injection and ignite the fuel with predefined ignition timing. As a result, the fuel burns in a cylinder to generate torque so that an angular acceleration is applied to the crankshaft.
  • Step 108 is performed to measure the average angular acceleration of an expansion stroke subsequent to the first injection, that is, the region between the TDC and BDC (which is equivalent to a crank angle of 180°).
  • Step 110 is performed to judge whether the average angular acceleration measured in step 108 is zero. If the average angular acceleration is greater than zero or smaller than zero, step 112 is performed to correct the fuel injection amount for the first injection, which was provisionally set in step 104. The first injection is then performed by using the corrected fuel injection amount (step 108). Next, step 110 is performed to remeasure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
  • the average angular acceleration is measured while correcting the fuel injection amount for the first injection as indicated in Fig. 3.
  • that fuel injection amount (the fuel injection amount that was provisionally set in step 104 or 112) is set as a minimum required injection amount (reference injection amount) for the first injection.
  • the minimum required injection amount is a fuel injection amount for obtaining an average angular acceleration of zero.
  • the minimum required injection amount is multiplied by the angular acceleration coefficient, which was set in step 102.
  • the resulting fuel injection amount is then determined as the optimum injection amount for the first injection (step 116).
  • the fuel injection amount optimization procedure for the first injection is now completed.
  • step 104 is performed to provisionally set the fuel injection amount for the nth injection.
  • step 106 the real machine is operated to inject fuel sequentially for the first to nth injections. It goes without saying that ignition occurs for each injection with predefined ignition timing.
  • the fuel injection amounts for the first to n-lth injections are the optimum injection amounts that are obtained by performing the optimization procedure.
  • the fuel injection amount for the nth injection is a fuel injection amount that is provisionally set.
  • Step 108 is performed after the nth injection to measure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
  • Fig. 2 shows engine rotation speed changes that are encountered when the first and second injections are performed by using the optimum injection amount and the third injection is performed by using the provisionally set fuel injection amount.
  • the rotation speed behavior varies with the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
  • Step 110 is performed to judge whether the average angular acceleration measured in step 108 is zero. If the average angular acceleration is greater than zero or smaller than zero, step 112 is performed to correct the fuel injection amount for the nth injection, which was provisionally set in step 104. Step 108 is then performed to sequentially inject fuel for the first to nth injections by using the corrected fuel injection amount.
  • step 110 is performed after the nth injection to remeasure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
  • fuel is sequentially injected for the first to nth injections while correcting the fuel injection amount for the nth injection. Further, the average angular acceleration is measured after the nth injection. When the average angular acceleration for a certain fuel injection amount is zero, that fuel injection amount (the fuel injection amount that was provisionally set in step 104 or 112) is set as a minimum required injection amount for the nth injection The minimum required injection amount is multiplied by the angular acceleration coefficient, which was set in step 102. The resulting fuel injection amount is then determined as the optimum injection amount for the nth injection (step 116).
  • Step 118 is performed to judge whether the injection count "n" reached when the optimization procedure is completed by performing steps 104 to 116 coincides with the final injection count "N” . If the final injection count "N" is not reached by performing the optimization procedure, step 120 is performed to update the injection count "n” , and steps 104 to 116 are followed to perform the optimization procedure for the next injection count. When a series of processing steps is repeatedly performed until the optimum injection amount for the Nth injection is determined, the optimization process terminates.
  • the fuel injection amount for obtaining ideal startability can be accurately determined by optimizing the fuel injection amount for each injection in accordance with the angular acceleration, which is used as a quantitative index. Further, the optimum injection amount (optimum value) is determined by multiplying the minimum required injection amount by the angular acceleration coefficient according to the target angular acceleration. Therefore, even when the target angular acceleration is changed, the optimum value appropriate for the changed target angular acceleration can easily be determined.
  • the optimum injection amount for each injection which is determined by the optimization method according to the present embodiment, is stored in a ROM of the ECU that controls the internal combustion engine
  • the ECU functions as a fuel injection control device for the internal combustion engine in accordance with an embodiment of the present invention.
  • the fuel injection control function of the ECU will now be described with reference to Figs . 7 and 8.
  • the ECU accesses its ROM to read the optimum injection amount for each of the first to Nth injections, and exercises fuel injection control in accordance with the read optimum injection amount.
  • Startup fuel injection control is exercised for the first to Nth injections in the internal combustion engine.
  • normal fuel injection control is exercised in accordance with the intake air amount.
  • the ECU calculates the fuel injection amount appropriate for the intake air amount in accordance with a target air-fuel ratio.
  • the ECU multiplies the calculated value by a predetermined amount increase coefficient, and sets the resulting value as the final fuel injection amount.
  • the amount increase coefficient increases the fuel injection amount to ensure that switching from startup fuel injection control to normal fuel injection control smoothly takes place.
  • the amount increase coefficient is set so that it decreases after each injection or cycle until it is equal to the value 1.
  • the fuel injection amount set by startup fuel injection control may greatly differ from the fuel injection amount set by normal fuel injection control depending on the operating conditions.
  • a significant torque change occurs when the fuel injection control mode switches from startup fuel injection control to normal fuel injection control, thereby varying the engine rotation speed.
  • the ECU exercises fuel injection control in accordance with a flowchart in Fig. 7 to ensure smooth switching from startup fuel injection control to normal fuel injection control.
  • the flowchart in Fig. 7 illustrates a fuel injection control routine that the ECU executes as an internal combustion engine fuel injection control device according to the present embodiment .
  • the fuel injection control routine shown in Fig. 7 is executed when an ignition switch is turned ON to start the ECU.
  • the first step (step 200) is performed to judge whether the current injection count "k" is greater than a predetermined count "N" .
  • the predetermined count “N” is the final injection count for startup fuel injection control. If the injection count "k” is not greater than the final injection count "N” , step 202 is followed to exercise startup fuel injection control.
  • step 202 the optimum injection amount "fi(k)" for the kth injection is read from the ROM.
  • the ROM stores the optimum injection amount for each of the first to Nth injections.
  • step 204 the read optimum injection amount "fi(k)” is stored as a pre-switching injection amount "fit”. The pre- switching injection amount "fit” is updated each time the optimum injection amount "fi(k)” is newly read.
  • a switching completion flag remains OFF (step 206).
  • step 220 the optimum injection amount "fi(k)” read in step 202 is set as a final injection amount "fif (k) " .
  • step 208 is followed to exercise normal fuel injection control.
  • the fuel injection control mode switches from startup fuel injection control to normal fuel injection control.
  • Step 208 is performed to judge whether the switching completion flag is OFF.
  • the switching completion flag remains OFF until steps 210 to 214 are performed to complete a switching process, which will be described subsequently. Therefore, the first judgment result obtained in step 208 indicates that the switching completion flag is OFF.
  • the process to be performed in step 210 is selected.
  • a basic injection amount "fib(k)” is calculated in accordance with the intake air amount.
  • the basic injection amount “fib(k)” is a fuel injection amount that is used when normal fuel injection control is exercised. As mentioned earlier, the basic injection amount “fib(k)” is obtained by multiplying the fuel injection amount calculated according to the intake air amount by the predetermined amount increase coefficient.
  • the basic injection amount "fib(k)” calculated in step 210 and the stored pre-switching injection amount “fit” are used to calculate a correction amount " ⁇ fi(k)” from Equation (3), which is shown below.
  • the pre-switching injection amount "fit” is the optimum injection amount "fi(N)" for the Nth injection.
  • Equation (3) the coefficient 11 C" is a constant between 0 and 1.
  • step 212 The correction amount " ⁇ fi(k)" calculated in step 212 is added to the basic injection amount "fib(k)", which was calculated in step 210.
  • the resulting sum "fib(k) + ⁇ fi(k)” is calculated as the injection amount "fi(k)" for switching.
  • step 214 the switching completion flag turns ON (step 216).
  • step 216 the flow proceeds to step 220.
  • step 220 the injection amount "fi(k)” calculated in step 214 is set as the final injection amount "fif(k)".
  • step 2118 a post-switching injection amount n fi(k)" is calculated in accordance with the intake air amount .
  • the post-switching injection amount n fi(k)" is a fuel injection amount that is used when normal fuel injection control is exercised. It is obtained by multiplying the fuel injection amount calculated according to the intake air amount by the predetermined amount increase coefficient.
  • step 220 the post-switching injection amount "fi(k)" calculated in step 218 is set as the final injection amount "fif(k)". Fig.
  • the optimum value obtained during startup fuel injection control is set as the injection amount for the Nth injection.
  • the post-switching injection amount obtained during normal fuel injection control is set as the injection amount.
  • the value obtained by adding the correction amount " ⁇ fi" to the post-switching injection amount is set as the injection amount.
  • the injection amount difference between the Nth injection and N+lth injection then decreases by the correction amount " ⁇ fi” . This reduces the torque change that may occur when the fuel injection control mode switches from startup fuel injection control to normal fuel injection control.
  • correction amount " ⁇ fi" is set so that it is proportional to the injection amount difference as indicated in Equation (3). Therefore, an increase in the degree of the torque change occurring upon switching is avoided even when the injection amount difference between startup fuel injection control and normal fuel injection control increases depending on the operating conditions.
  • the "startup fuel injection control unit" according to the present invention is implemented when the ECU follows steps 202 to 220 to perform a series of processes
  • the "normal fuel injection control unit” according to the present invention is implemented when the ECU follows steps 218 to 220 to perform a series of processes.
  • the "fuel injection control switching unit” according to the present invention is implemented when the ECU follows steps 200 and 208 to perform a series of processes
  • the "fuel injection amount correction unit” according to the present invention is implemented when the ECU follows steps 210 to 220 to perform a series of processes.
  • the optimization method according to the embodiment described above uses the average angular acceleration as an index.
  • the energy that is generated by the internal combustion engine and used for rotation may be used as the index.
  • This energy is proportional to the average angular acceleration. Therefore, using this energy as the index is substantially the same as using the average angular acceleration as the index.
  • the optimization method according to the embodiment described above optimizes the fuel injection amount for each injection.
  • the fuel injection amount may alternatively be optimized for each cycle.
  • Another alternative is to optimize the fuel injection amount for some other predefined injection unit.
  • the optimization method according to the embodiment described above searches for the minimum required injection amount that obtains an average angular acceleration of zero (reference angular acceleration), multiplies the minimum required injection amount by the angular acceleration coefficient, and uses the resulting value as the optimum injection amount.
  • an alternative is to directly search for an injection amount that provides the average angular acceleration equal to the target angular acceleration and uses such an injection amount as the optimum injection amount.
  • the fuel injection control device adds the correction amount ⁇ fi to the post-switching injection amount for only the N+lth injection, which occurs immediately after fuel injection control mode switching from startup fuel injection control to normal fuel injection control.
  • the correction amount may also be added to the post-switching injection amounts for the N+2th and subsequent injections as indicated in Fig. 9.
  • the correction amounts for the N+2th and subsequent injections be decreased at a predetermined attenuation rate ⁇ with the correction amount " ⁇ fi" for the N+lth injection used as an initial value.
  • the relationship between the correction amount " ⁇ fi(k)" for the kth injection and the correction amount " ⁇ fi(k- 1)" for the k-lth injection is as indicated in Equation (4) below:
  • the above equation indicates that the fuel injection control mode can be smoothly switched from startup fuel injection control to normal fuel injection control.
  • the attenuation rate " ⁇ " may be varied in accordance with the magnitude of the initial value for the correction amount " ⁇ fi" .
  • the fuel injection control device assumes that the coefficient "C" in Equation (3) is a fixed value. Alternatively, however, the value of the coefficient "C” may be varied in accordance with fuel properties as indicated in Fig. 10. In such an instance, it is preferred that the above-mentioned attenuation rate " ⁇ " also vary with fuel properties as indicated in Fig. 11. This ensures that the fuel injection control mode can smoothly switch from startup fuel injection control to normal fuel injection control without being affected by the fuel properties.
  • the fuel properties affect the combustion state. The heavier the fuel, the unstabler the combustion state and the more likely the combustion state will vary. In this instance, there is a negative correlation among a plurality of past values of the average angular acceleration or the torque. Therefore, the fuel properties can be judged by noting the correlation among a plurality of past values of them.
  • the injection amount to be provided at the time of fuel injection control mode switching from startup fuel injection control to normal fuel injection control may be corrected for each cylinder. More specifically, in the case of a four-cylinder engine, the correction amount to be added to the post-switching injection amount for the N+lth injection is determined in accordance with the difference from the injection amount for the N-3th injection.
  • the correction amount to be added to the post-switching injection amount for the N+2th injection is determined in accordance with the difference from the injection amount for the N- 2th injection. Further, the correction amount to be added to the post-switching injection amount for the N+3th injection is determined in accordance with the difference from the injection amount for the N-lth injection. Finally, the correction amount to be added to the post-switching injection amount for the N+4th injection is determined in accordance with the difference from the injection amount for the Nth injection.

Abstract

A target angular acceleration is preset for each predefined injection unit. The angular acceleration for each predefined injection unit is determined when fuel is actually injected. The injection amount for obtaining the target angular acceleration is determined for each predefined injection unit in accordance with the relationship between the injection amount and angular acceleration.

Description

DESCRIPTION
Method for Fuel Injection Amount Optimization and Fuel Injection Control Apparatus for Internal Combustion Engine
Technical Field
The present invention relates to a method for determining an optimum injection amount for internal combustion engine startup.
Background Art
The operating performance characteristics of an internal combustion engine, such as the torque, fuel efficiency, and exhaust emission quality, greatly vary with the values of control parameters such as the fuel injection amount and ignition timing. Therefore, when an internal combustion engine is to be developed, the control parameter values are optimized to obtain optimum operating performance characteristics, for instance, by testing a real machine. The information concerning fuel injection amount setup for startup is set forth in Japanese Patent Laid-open No. 2004-68621. The fuel injection amount for startup is an important control parameter that determines, for instance, startability and exhaust emission equality. The technology described in Japanese Patent Laid-open No. 2004-68621 performs setup for the first cycle at the time of startup so that the fuel injection amount sequentially increases for the first to subsequent cylinders, and performs setup for the second and subsequent cycles so that the fuel injection amount sequentially decreases for the first to subsequent cylinders. Setup is also performed so that the fuel injection amount for each cylinder sequentially decreases for a predetermined number of cycles beginning with the first cycle.
Although Japanese Patent Laid-open No. 2004- 68621 describes the tendency concerning the fuel injection amount of each injection or cycle, it does not describe a quantitative index for fuel injection amount determination. Therefore, when a particular fuel injection amount is to be determined, it is necessary to use a conventional method of empirically finding an optimum value for each injection or cycle. However, empirical optimization would not clearly determine the fuel injection amount, and ideal startability cannot always be obtained depending on the empirically optimized fuel injection amount.
Disclosure of the Invention The present invention has been made to solve the above problem. It is an object of the present invention to provide a fuel injection amount optimization method for the purpose of accurately determining the fuel injection amount for obtaining ideal startability .
The above object is achieved by a method according to a first aspect of the present invention. The method includes following steps for optimizing a fuel injection amount at internal combustion engine startup. As a first step of the method, a target angular acceleration is preset for each predefined injection unit. As a second step of the method, the angular acceleration for each predefined injection unit is determined when fuel is actually injected. The injection amount for obtaining the target angular acceleration is then determined for each predefined injection unit in accordance with the relationship between the injection amount and angular acceleration. According to the first aspect of the present invention, the fuel injection amount for obtaining ideal startability can be accurately determined when the fuel injection amount is optimized for each predefined injection unit (e.g., for each injection or cycle) in accordance with angular acceleration, which is used as a quantitative index. According to a second aspect of the present invention, the method according to the first aspect of the present invention may further include following steps. As a third step of the method, a reference fuel injection amount so as to obtain a predefined reference angular acceleration of not lower than zero is determined for each injection. As a fourth step of the method, the reference fuel injection amount is multiplied by a coefficient according to the target angular acceleration. The resulting value is then set as an optimum injection amount.
According to the second aspect of the present invention, the optimum injection amount is determined by multiplying the reference injection amount by the coefficient according to the target angular acceleration. Therefore, even when the target angular acceleration is changed, the optimum value appropriate for the changed target angular acceleration can easily be determined. According to a third aspect of the present invention, In the method according to the first or second aspect of the present invention, the angular acceleration may be the average angular acceleration for a region between the compression top dead center of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders. When the angular acceleration for a region between the compression top dead center of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders is averaged, the influence of inertial torque, which is based on reciprocating inertial mass, can be eliminated from the angular acceleration. According to the third aspect of the present invention, therefore, the fuel injection amount for obtaining ideal startability can be accurately determined when the fuel injection amount is optimized by using the average angular acceleration as an index.
The above object is also achieved by a fuel injection control apparatus according to a fourth aspect of the present invention. The apparatus includes a storage unit for storing the fuel injection amount optimized by the method according to any one of the first to third aspects of the present invention as an optimum injection amount for startup. The apparatus also includes a startup fuel injection control unit for exercising fuel injection control in accordance with the optimum injection amount memorized by the storage unit . The apparatus also includes a normal fuel injection control unit for exercising fuel injection control in accordance with a fuel injection amount that is calculated from an intake air amount . A fuel injection control switching unit is provided for switching from fuel injection control by the startup fuel injection control unit to fuel injection control by the normal fuel injection control unit with predefined timing after internal combustion engine startup. Further, a fuel injection amount correction unit is provided. The fuel injection amount correction unit, when a fuel injection control mode is changed by the fuel injection control switching unit, corrects the fuel injection amount in accordance with the difference between the optimum injection amount and the fuel injection amount calculated from the intake air amount so that the fuel injection amount gradually changes from the optimum injection amount to the fuel injection amount calculated from the intake air amount.
When there is a difference between the optimum injection amount and the fuel injection amount calculated from the intake air amount, the fourth aspect of the present invention corrects the fuel injection amount in accordance with the difference. Therefore, the fuel injection control mode can be smoothly switched from startup fuel injection control, which is based on the optimum injection amount, to normal fuel injection control, which is based on the intake air amount. According to a fifth aspect of the present invention, in the apparatus according to the fourth aspect of the present invention, the fuel injection amount correction unit may determine a correction amount for the fuel injection amount in accordance with fuel properties .
According to the fifth aspect of the present invention, the fuel injection control mode can be smoothly switched from startup fuel injection control, which is based on the optimum injection amount, to normal fuel injection control, which is based on the intake air amount, without being affected by fuel properties .
Brief Description of Drawings
Fig. 1 is a flowchart for describing the fuel injection amount optimization method according to an embodiment of the present invention;
Fig. 2 is a graph illustrating the relationship between the average angular acceleration and the engine rotation speed change;
Fig. 3 is a graph illustrating the relationship between the average angular acceleration and the fuel injection amount; Fig. 4 is a graph illustrating the relationship among the fuel injection amount, angular acceleration, startability , and exhaust emission quality;
Fig. 5 is a graph for illustrating typical target angular acceleration settings;
Fig. 6 is a graph illustrating rotation behaviors that are obtained at the typical target angular acceleration settings;
Fig. 7 is a flowchart illustrating a fuel injection control routine that is executed by an embodiment of the present invention;
Fig. 8 is a graph illustrating fuel injection amount changes that occur before and after fuel injection control mode switching due to the execution of the fuel injection control routine;
Fig. 9 is a graph illustrating fuel injection amount changes that occur before and after fuel injection control mode switching according to a modification of the preferred embodiment of the present invention;
Fig. 10 is a graph illustrating settings of the coefficient "C" for fuel properties according to a modification of the preferred embodiment of the present invention; and Fig. 11 is a graph illustrating settings of the attenuation rate "α" for fuel properties according to a modification of the preferred embodiment of the present invention .
Best Mode for Carrying out the Invention An embodiment of the present invention will now be described with reference to the accompanying drawings .
Figs. 1 to 6 illustrate a method for optimizing the fuel injection amount at internal combustion engine startup in accordance with an embodiment of the present invention .
First of all, the fuel injection amount optimization method according to the present embodiment will be described. The fuel injection amount optimization method according to the present embodiment is characterized by the fact that it optimizes the fuel injection amount by using the angular acceleration of an internal combustion engine as a quantitative index. More specifically, the average angular acceleration for a region between the compression TDC of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders (a region between the compression TDC and BDC in the case of a four- cylinder engine) is used as an index for fuel injection amount optimization. It is assumed that the present embodiment optimizes the fuel injection amount for four-cylinder engine startup. The following advantage is provided when the average angular acceleration for the above-mentioned region is used as an index for fuel injection amount optimization. When a motion equation is used, the indicated torque "Ti" , which is generated on a crankshaft when combustion occurs in the internal combustion engine, can be calculated from Equations (1) and (2) below:
Ti = J x (dω/dt) + Tf (1)
Ti = Tgas + Tinertia (2)
The right side of Equation (2) represents torque that generates the indicated torque "Ti". The right side of Equation (1) represents torque that consumes the indicated torque "Ti" .
On the right side of Equation (1), "J" denotes the inertia moment of a drive member that is driven due to air-fuel mixture combustion; "dω/dt", crankshaft angular acceleration, and "Tf", drive section friction torque. "J x (dω/dt)" represents dynamic loss torque that results from the angular acceleration of the internal combustion engine. The friction torque "Tf" is torque that is generated due to mechanical friction between various mating parts such as friction between a piston and cylinder inner wall. It includes torque that is generated due to mechanical friction caused by auxiliaries. On the right side of Equation (2), "Tgas" denotes torque that is generated by in-cylinder gas pressure; and "Tinertia" denotes inertial torque that is generated by the reciprocating inertial mass of the piston and the like. The torque "Tgas" that is generated by the in-cylinder gas pressure is torque that is generated due to the combustion of injected fuel . When fuel is injected from an injector and burned in a cylinder, torque is generated to vary the angular acceleration of the internal combustion engine. The angular acceleration change after each injection determines the post-startup rotation behavior of the internal combustion engine (the curve of the rotation speed with respect to time). Therefore, when the angular acceleration is used as an index for fuel injection amount optimization, it is conceivable that the fuel injection amount for obtaining ideal startability can be determined.
However, as is obvious from Equations (1) and (2), the internal combustion engine's angular acceleration "dω/dt" includes the influence of inertial torque "Tinertia" that is based on reciprocating inertial mass. The inertial torque "Tinertia" based on reciprocating inertial mass is irrelevant to the fuel injection amount and generated by the inertial mass of a piston or other reciprocating member. To accurately determine the fuel injection amount for obtaining ideal startability, therefore, it is necessary to eliminate the influence of inertial torque "Tinertia" based on reciprocating inertial mass from the angular acceleration "dω/dt", which is used as the index.
When attention is focused on a region between the TDC and BDC in a four-cylinder engine, which is equivalent to a crank angle of 180°, the average inertial torque "Tinertia" based on the reciprocating inertial mass within the region is zero. Therefore, when the torque values in Equations (1) and (2) are calculated as the average value of the region between the TDC and BDC, the inertial torque "Tinertia" based on the reciprocating inertial mass can be regarded as zero. The influence of inertial torque "Tinertia", which is based on the reciprocating inertial mass, on the indicated torque "Ti" can then be eliminated. Further, the influence on the angular acceleration
"dω/dt" can also be eliminated. In other words, when the average angular acceleration for the region between the TDC and BDC is used as an index for fuel injection amount optimization, it is possible to eliminate the influence of inertial torque based on the reciprocating inertial mass and accurately determine the fuel injection amount for obtaining ideal startability .
When the in-cylinder gas pressure can be measured, the fuel injection amount can be optimized by using the measured in-cylinder gas pressure as a quantitative index. The reason is that the internal combustion engine's angular acceleration "dω/dt" is determined by the torque "Tgas" based on the in- cylinder gas pressure as is obvious from Equations (1) and (2). For a reason indicated below, however, it is difficult to optimize the fuel injection amount by using a measured in-cylinder gas pressure value.
The in-cylinder gas pressure can be measured with an in-cylinder pressure sensor. However, mass- produced internal combustion engines are not always provided with in-cylinder pressure sensors. Even if they are provided with in-cylinder pressure sensors, each cylinder is not always provided with an in- cylinder pressure sensor. Due to cost and reliability considerations, it is practically difficult to provide every cylinder in mass-produced engines with an in- cylinder pressure sensor. It is therefore necessary to prepare a development engine whose cylinders are all provided with an in-cylinder pressure sensor. However, when the cylinders are provided with in-cylinder pressure sensors, it is highly likely that the mass- produced engines and the development engine will differ in the ignition plug position. The air-fuel mixture combustion state prevailing within a cylinder varies with the ignition plug position. Therefore, even when the fuel injection amount is optimized by using the development engine, the resulting optimum value does not always enable the mass-produced engines to exhibit ideal startability .
As described above, it is theoretically possible but practically difficult to optimize the fuel injection amount by using the in-cylinder gas pressure as an index. On the other hand, the average angular acceleration, which is used by the fuel injection amount optimization method according to the present embodiment, can be measured with a crank angle sensor that is always mounted in each mass-produced engine. Therefore, the optimum value obtained by performing an optimization procedure on the development engine can be applied as is to the mass-produced engines. The fuel injection amount optimization method according to the present embodiment will now be described in detail with reference to a flowchart in Fig. 1. Individual steps described below may be performed one after another by a human or performed automatically by an apparatus. The first step (step 100) is performed to determine a target angular acceleration for each of the first to Nth injections. The symbol "N" represents the final injection count for using the optimum value as the fuel injection amount. After the Nth injection, an ECU calculates the fuel injection amount in accordance with the intake air amount.
When the target angular acceleration is to be determined, the exhaust emission equality is also considered. The graph in Fig. 4 illustrates the relationship among the fuel injection amount, angular acceleration, startability, and exhaust emission quality. As indicated in the graph, the fuel injection amount for maintaining excellent exhaust emission quality is within a certain range (enclosed by a broken line in the figure) . The target angular acceleration is set within this fuel injection amount setting range. Conversely, the target angular acceleration can be freely set as far as the fuel injection amount is within the fuel injection amount setting range.
Therefore, the target angular acceleration can be set in accordance with desired rotation behavior.
Fig. 5 shows typical target angular acceleration settings. Fig. 6 shows rotation behaviors that are obtained at the typical target angular acceleration settings. When, for instance, the rotation speed is to be increased as indicated by a broken line in Fig. 6, the target angular acceleration settings for the second and subsequent cycles should be relatively high as indicated by a broken line in Fig. 5. When, on the other hand, the rotation speed increase is to be suppressed as indicated by a solid line in Fig. 6, the target angular acceleration settings for the second and subsequent cycles should be low as indicated by a solid line in Fig. 5. Although Fig. 5 indicates that the target angular acceleration is set for each cycle, such setup is merely an example. Alternatively, the target angular acceleration may be set for each injection as mentioned earlier. Although the settings indicated in Fig. 5 are determined in relation to rotation speed buildup, the settings may be varied so as to place emphasis on startability for a cold start or on exhaust emission quality for an ordinary- temperature start.
In the next step (step 102), the target angular acceleration for each of the first to Nth injections, which was set in step 100, is substituted by an angular acceleration coefficient. The angular acceleration coefficient is set in accordance with the relationship between a fuel injection amount increase/decrease and angular acceleration increase/decrease. When the target angular acceleration is equal to the reference angular acceleration, the angular acceleration coefficient setting is 1. The angular acceleration coefficient setting increases with an increase in the target angular acceleration. In the present embodiment, it is assumed that the reference angular acceleration is zero.
Steps 100 and 102 are the processing steps that should be completed before an optimization procedure is performed on a real machine. In the next step (step 104) and subsequent steps, the optimization procedure is performed on the real machine. When step 104 is performed for the first time, the fuel injection amount for the first injection is set provisionally. In the next step (step 106), the real machine is operated to inject fuel for the first injection and ignite the fuel with predefined ignition timing. As a result, the fuel burns in a cylinder to generate torque so that an angular acceleration is applied to the crankshaft. Step 108 is performed to measure the average angular acceleration of an expansion stroke subsequent to the first injection, that is, the region between the TDC and BDC (which is equivalent to a crank angle of 180°).
Step 110 is performed to judge whether the average angular acceleration measured in step 108 is zero. If the average angular acceleration is greater than zero or smaller than zero, step 112 is performed to correct the fuel injection amount for the first injection, which was provisionally set in step 104. The first injection is then performed by using the corrected fuel injection amount (step 108). Next, step 110 is performed to remeasure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
Subsequently, the average angular acceleration is measured while correcting the fuel injection amount for the first injection as indicated in Fig. 3. When the average angular acceleration for a certain fuel injection amount is zero, that fuel injection amount (the fuel injection amount that was provisionally set in step 104 or 112) is set as a minimum required injection amount (reference injection amount) for the first injection. The minimum required injection amount is a fuel injection amount for obtaining an average angular acceleration of zero. The minimum required injection amount is multiplied by the angular acceleration coefficient, which was set in step 102. The resulting fuel injection amount is then determined as the optimum injection amount for the first injection (step 116). The fuel injection amount optimization procedure for the first injection is now completed. When steps 104 to 116 are performed for each injection, the fuel injection amounts for all injections are sequentially determined. When the optimum injection amounts are already determined for the first to n-lth injections, step 104 is performed to provisionally set the fuel injection amount for the nth injection. In step 106, the real machine is operated to inject fuel sequentially for the first to nth injections. It goes without saying that ignition occurs for each injection with predefined ignition timing. In this instance, the fuel injection amounts for the first to n-lth injections are the optimum injection amounts that are obtained by performing the optimization procedure. The fuel injection amount for the nth injection is a fuel injection amount that is provisionally set. Step 108 is performed after the nth injection to measure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
Fig. 2 shows engine rotation speed changes that are encountered when the first and second injections are performed by using the optimum injection amount and the third injection is performed by using the provisionally set fuel injection amount. As indicated in this figure, the rotation speed behavior varies with the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°. Step 110 is performed to judge whether the average angular acceleration measured in step 108 is zero. If the average angular acceleration is greater than zero or smaller than zero, step 112 is performed to correct the fuel injection amount for the nth injection, which was provisionally set in step 104. Step 108 is then performed to sequentially inject fuel for the first to nth injections by using the corrected fuel injection amount. Next, step 110 is performed after the nth injection to remeasure the average angular acceleration of the region between the TDC and BDC, which is equivalent to a crank angle of 180°.
Subsequently, fuel is sequentially injected for the first to nth injections while correcting the fuel injection amount for the nth injection. Further, the average angular acceleration is measured after the nth injection. When the average angular acceleration for a certain fuel injection amount is zero, that fuel injection amount (the fuel injection amount that was provisionally set in step 104 or 112) is set as a minimum required injection amount for the nth injection The minimum required injection amount is multiplied by the angular acceleration coefficient, which was set in step 102. The resulting fuel injection amount is then determined as the optimum injection amount for the nth injection (step 116). Step 118 is performed to judge whether the injection count "n" reached when the optimization procedure is completed by performing steps 104 to 116 coincides with the final injection count "N" . If the final injection count "N" is not reached by performing the optimization procedure, step 120 is performed to update the injection count "n" , and steps 104 to 116 are followed to perform the optimization procedure for the next injection count. When a series of processing steps is repeatedly performed until the optimum injection amount for the Nth injection is determined, the optimization process terminates.
When the optimization method according to the present embodiment, which has been described above, is used, the fuel injection amount for obtaining ideal startability can be accurately determined by optimizing the fuel injection amount for each injection in accordance with the angular acceleration, which is used as a quantitative index. Further, the optimum injection amount (optimum value) is determined by multiplying the minimum required injection amount by the angular acceleration coefficient according to the target angular acceleration. Therefore, even when the target angular acceleration is changed, the optimum value appropriate for the changed target angular acceleration can easily be determined. The optimum injection amount for each injection, which is determined by the optimization method according to the present embodiment, is stored in a ROM of the ECU that controls the internal combustion engine The ECU functions as a fuel injection control device for the internal combustion engine in accordance with an embodiment of the present invention. The fuel injection control function of the ECU will now be described with reference to Figs . 7 and 8.
When the internal combustion engine starts up, the ECU accesses its ROM to read the optimum injection amount for each of the first to Nth injections, and exercises fuel injection control in accordance with the read optimum injection amount. Startup fuel injection control is exercised for the first to Nth injections in the internal combustion engine. For injections subsequent to the Nth injection, normal fuel injection control is exercised in accordance with the intake air amount. After switching to normal fuel injection control, the ECU calculates the fuel injection amount appropriate for the intake air amount in accordance with a target air-fuel ratio. The ECU then multiplies the calculated value by a predetermined amount increase coefficient, and sets the resulting value as the final fuel injection amount. The amount increase coefficient increases the fuel injection amount to ensure that switching from startup fuel injection control to normal fuel injection control smoothly takes place. The amount increase coefficient is set so that it decreases after each injection or cycle until it is equal to the value 1.
However, even when the amount of fuel is increased by the amount increase coefficient, the fuel injection amount set by startup fuel injection control may greatly differ from the fuel injection amount set by normal fuel injection control depending on the operating conditions. In such an instance, a significant torque change occurs when the fuel injection control mode switches from startup fuel injection control to normal fuel injection control, thereby varying the engine rotation speed.
Under the above circumstances, the ECU exercises fuel injection control in accordance with a flowchart in Fig. 7 to ensure smooth switching from startup fuel injection control to normal fuel injection control. The flowchart in Fig. 7 illustrates a fuel injection control routine that the ECU executes as an internal combustion engine fuel injection control device according to the present embodiment . The fuel injection control routine shown in Fig. 7 is executed when an ignition switch is turned ON to start the ECU. The first step (step 200) is performed to judge whether the current injection count "k" is greater than a predetermined count "N" . The predetermined count "N" is the final injection count for startup fuel injection control. If the injection count "k" is not greater than the final injection count "N" , step 202 is followed to exercise startup fuel injection control. In step 202, the optimum injection amount "fi(k)" for the kth injection is read from the ROM. As mentioned earlier, the ROM stores the optimum injection amount for each of the first to Nth injections. In step 204, the read optimum injection amount "fi(k)" is stored as a pre-switching injection amount "fit". The pre- switching injection amount "fit" is updated each time the optimum injection amount "fi(k)" is newly read. While startup fuel injection control is exercised, a switching completion flag remains OFF (step 206). After completion of step 206, the flow proceeds to step 220. In step 220, the optimum injection amount "fi(k)" read in step 202 is set as a final injection amount "fif (k) " .
If, on the other hand, the judgment result obtained in step 200 indicates that the current injection count "k" is greater than the final injection count "N" for startup fuel injection control, step 208 is followed to exercise normal fuel injection control. In other words, the fuel injection control mode switches from startup fuel injection control to normal fuel injection control. Step 208 is performed to judge whether the switching completion flag is OFF. The switching completion flag remains OFF until steps 210 to 214 are performed to complete a switching process, which will be described subsequently. Therefore, the first judgment result obtained in step 208 indicates that the switching completion flag is OFF. Thus, the process to be performed in step 210 is selected.
In step 210, a basic injection amount "fib(k)" is calculated in accordance with the intake air amount. The basic injection amount "fib(k)" is a fuel injection amount that is used when normal fuel injection control is exercised. As mentioned earlier, the basic injection amount "fib(k)" is obtained by multiplying the fuel injection amount calculated according to the intake air amount by the predetermined amount increase coefficient. In the next step (step 212), the basic injection amount "fib(k)" calculated in step 210 and the stored pre-switching injection amount "fit" are used to calculate a correction amount "Δfi(k)" from Equation (3), which is shown below. The pre-switching injection amount "fit" is the optimum injection amount "fi(N)" for the Nth injection.
Δfi(k) = C x (fit - fib(k)) --- (3) In Equation (3) above, the coefficient 11C" is a constant between 0 and 1.
The correction amount "Δfi(k)" calculated in step 212 is added to the basic injection amount "fib(k)", which was calculated in step 210. The resulting sum "fib(k) + Δfi(k)" is calculated as the injection amount "fi(k)" for switching. After completion of step 214, the switching completion flag turns ON (step 216). Upon completion of step 216, the flow proceeds to step 220. In step 220, the injection amount "fi(k)" calculated in step 214 is set as the final injection amount "fif(k)".
Since the switching completion flag is turned ON, the process to be performed in step 218 is selected after the next judgment result is obtained in step 208. In step 218, a post-switching injection amount nfi(k)" is calculated in accordance with the intake air amount . The post-switching injection amount nfi(k)" is a fuel injection amount that is used when normal fuel injection control is exercised. It is obtained by multiplying the fuel injection amount calculated according to the intake air amount by the predetermined amount increase coefficient. After completion of step 218, the flow proceeds to step 220. In step 220, the post-switching injection amount "fi(k)" calculated in step 218 is set as the final injection amount "fif(k)". Fig. 8 shows fuel injection amount changes that occur before and after fuel injection control mode switching due to the execution of the fuel injection control routine described above. More specifically, the optimum value obtained during startup fuel injection control is set as the injection amount for the Nth injection. For the N+2th and subsequent injections, the post-switching injection amount obtained during normal fuel injection control is set as the injection amount. For the N+lth injection, which occurs immediately after mode switching from startup fuel injection control to normal fuel injection control, the value obtained by adding the correction amount "Δfi" to the post-switching injection amount is set as the injection amount. The injection amount difference between the Nth injection and N+lth injection then decreases by the correction amount "Δfi" . This reduces the torque change that may occur when the fuel injection control mode switches from startup fuel injection control to normal fuel injection control.
Further, the correction amount "Δfi" is set so that it is proportional to the injection amount difference as indicated in Equation (3). Therefore, an increase in the degree of the torque change occurring upon switching is avoided even when the injection amount difference between startup fuel injection control and normal fuel injection control increases depending on the operating conditions.
In the present embodiment, the "startup fuel injection control unit" according to the present invention is implemented when the ECU follows steps 202 to 220 to perform a series of processes, and the "normal fuel injection control unit" according to the present invention is implemented when the ECU follows steps 218 to 220 to perform a series of processes. Further, the "fuel injection control switching unit" according to the present invention is implemented when the ECU follows steps 200 and 208 to perform a series of processes, and the "fuel injection amount correction unit" according to the present invention is implemented when the ECU follows steps 210 to 220 to perform a series of processes.
While the present invention has been described in terms of a preferred embodiment, it should be understood that the invention is not limited to the preferred embodiment, and that variations may be made without departure from the scope and spirit of the invention. For example, the following modifications may be made to the preferred embodiment of the present invention . The foregoing embodiment description deals with the fuel injection amount optimization method for a four-cylinder engine. However, the method according to the present invention can also be applied to six- cylinder engines, eight-cylinder engines, and other multi-cylinder internal combustion engines. In such an instance, the average angular acceleration of a region between the compression TDC of each cylinder and an angle obtained by dividing a crank angle of 720° by the number of cylinders should be used as an index for fuel injection amount optimization. For a six-cylinder engine, the above-mentioned region is equivalent to a crank angle of 120°. For an eight-cylinder engine, the above-mentioned region is equivalent to a crank angle of 90°.
The optimization method according to the embodiment described above uses the average angular acceleration as an index. Alternatively, however, the energy that is generated by the internal combustion engine and used for rotation may be used as the index.
This energy is proportional to the average angular acceleration. Therefore, using this energy as the index is substantially the same as using the average angular acceleration as the index.
The optimization method according to the embodiment described above optimizes the fuel injection amount for each injection. However, the fuel injection amount may alternatively be optimized for each cycle. Another alternative is to optimize the fuel injection amount for some other predefined injection unit.
The optimization method according to the embodiment described above searches for the minimum required injection amount that obtains an average angular acceleration of zero (reference angular acceleration), multiplies the minimum required injection amount by the angular acceleration coefficient, and uses the resulting value as the optimum injection amount. However, an alternative is to directly search for an injection amount that provides the average angular acceleration equal to the target angular acceleration and uses such an injection amount as the optimum injection amount. The fuel injection control device according to the embodiment described above adds the correction amount Δfi to the post-switching injection amount for only the N+lth injection, which occurs immediately after fuel injection control mode switching from startup fuel injection control to normal fuel injection control. However, the correction amount may also be added to the post-switching injection amounts for the N+2th and subsequent injections as indicated in Fig. 9. In such an instance, it is preferred that the correction amounts for the N+2th and subsequent injections be decreased at a predetermined attenuation rate α with the correction amount "Δfi" for the N+lth injection used as an initial value. In this instance, the relationship between the correction amount "Δfi(k)" for the kth injection and the correction amount "Δfi(k- 1)" for the k-lth injection is as indicated in Equation (4) below:
Δfi(k) = α x Δfi(k-l) --- (4)
The above equation indicates that the fuel injection control mode can be smoothly switched from startup fuel injection control to normal fuel injection control. The attenuation rate "α" may be varied in accordance with the magnitude of the initial value for the correction amount "Δfi" .
The fuel injection control device according to the embodiment described above assumes that the coefficient "C" in Equation (3) is a fixed value. Alternatively, however, the value of the coefficient "C" may be varied in accordance with fuel properties as indicated in Fig. 10. In such an instance, it is preferred that the above-mentioned attenuation rate "α" also vary with fuel properties as indicated in Fig. 11. This ensures that the fuel injection control mode can smoothly switch from startup fuel injection control to normal fuel injection control without being affected by the fuel properties.
The fuel properties affect the combustion state. The heavier the fuel, the unstabler the combustion state and the more likely the combustion state will vary. In this instance, there is a negative correlation among a plurality of past values of the average angular acceleration or the torque. Therefore, the fuel properties can be judged by noting the correlation among a plurality of past values of them. The injection amount to be provided at the time of fuel injection control mode switching from startup fuel injection control to normal fuel injection control may be corrected for each cylinder. More specifically, in the case of a four-cylinder engine, the correction amount to be added to the post-switching injection amount for the N+lth injection is determined in accordance with the difference from the injection amount for the N-3th injection. Similarly, the correction amount to be added to the post-switching injection amount for the N+2th injection is determined in accordance with the difference from the injection amount for the N- 2th injection. Further, the correction amount to be added to the post-switching injection amount for the N+3th injection is determined in accordance with the difference from the injection amount for the N-lth injection. Finally, the correction amount to be added to the post-switching injection amount for the N+4th injection is determined in accordance with the difference from the injection amount for the Nth injection. When the injection amount to be provided at the time of switching is corrected on an individual cylinder basis as described above, it is conceivable that switching from startup fuel injection control to normal fuel injection control can be made with increased smoothness.

Claims

l.A method for optimizing a fuel injection amount at internal combustion engine startup, the method comprising the steps of: presetting a target angular acceleration for each predefined injection unit; and determining the angular acceleration of each injection unit when fuel is actually injected, and determining the fuel injection amount for attaining the target angular acceleration for each injection unit in accordance with the relationship between the fuel injection amount and angular acceleration.
2. The method according to claim 1, further comprising the steps of: determining a reference fuel injection amount for each injection unit so as to obtain a predefined reference angular acceleration of not lower than zero; and multiplying the reference fuel injection amount by a coefficient according to the target angular acceleration and setting the resulting value as an optimum injection amount.
3. The method according to claim 1 or 2 , wherein the angular acceleration is the average angular acceleration for a region between the compression top dead center of each cylinder and an angle obtained by dividing an angle of 720 degrees by the number of cylinders .
4.A fuel injection control apparatus for an internal combustion engine, the apparatus comprising: storage means for storing an optimum injection amount for startup; startup fuel injection control means for exercising fuel injection control in accordance with the optimum injection amount memorized by the storage means ; normal fuel injection control means for exercising fuel injection control in accordance with a fuel injection amount that is calculated from an intake air amount ; fuel injection control switching means for switching from fuel injection control by the startup fuel injection control means to fuel injection control by the normal fuel injection control means with predefined timing after internal combustion engine startup; and fuel injection amount correction means, which, when a fuel injection control mode is changed by the fuel injection control switching means, corrects the fuel injection amount in accordance with the difference between the optimum injection amount and the fuel injection amount calculated from the intake air amount so that the fuel injection amount gradually changes from the optimum injection amount to the fuel injection amount calculated from the intake air amount; wherein the optimum injection amount is optimized by the method comprising the steps of: presetting a target angular acceleration for each predefined injection unit; and determining the angular acceleration of each injection unit when fuel is actually injected, and determining the fuel injection amount for attaining the target angular acceleration for each injection unit in accordance with the relationship between the fuel injection amount and angular acceleration.
5. The fuel injection control apparatus according to claim 4, wherein the fuel injection amount correction means determines a correction amount for the fuel injection amount in accordance with fuel properties .
PCT/JP2006/306054 2005-03-30 2006-03-20 Method for fuel injection amount optimization and fuel injection control apparatus for internal combustion engine WO2006109543A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009007605A2 (en) * 2007-07-09 2009-01-15 Peugeot Citroën Automobiles SA Method for starting an internal combustion engine
FR2980529A1 (en) * 2011-09-26 2013-03-29 Renault Sa FUEL INJECTION CONTROL WHEN STARTING A THERMAL ENGINE
DE102010061015B4 (en) 2009-12-04 2019-01-31 Denso Corporation Control unit for an internal combustion engine

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4640654B2 (en) * 2006-12-15 2011-03-02 トヨタ自動車株式会社 Fuel supply abnormality determination method and apparatus
JP6646367B2 (en) * 2015-06-24 2020-02-14 ダイハツ工業株式会社 Control device for internal combustion engine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4329448A1 (en) * 1993-09-01 1995-03-02 Bosch Gmbh Robert Method and device for the metering of fuel in the starting of an internal combustion engine
US5447138A (en) * 1994-07-29 1995-09-05 Caterpillar, Inc. Method for controlling a hydraulically-actuated fuel injections system to start an engine
EP0889224A2 (en) * 1997-07-04 1999-01-07 Bayerische Motoren Werke Aktiengesellschaft, Patentabteilung AJ-3 Method for supplying a given fuel quantity to a combustion engine during the starting phase
JPH11173188A (en) * 1997-12-10 1999-06-29 Denso Corp Fuel injection control device of internal combustion engine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4329448A1 (en) * 1993-09-01 1995-03-02 Bosch Gmbh Robert Method and device for the metering of fuel in the starting of an internal combustion engine
US5447138A (en) * 1994-07-29 1995-09-05 Caterpillar, Inc. Method for controlling a hydraulically-actuated fuel injections system to start an engine
EP0889224A2 (en) * 1997-07-04 1999-01-07 Bayerische Motoren Werke Aktiengesellschaft, Patentabteilung AJ-3 Method for supplying a given fuel quantity to a combustion engine during the starting phase
JPH11173188A (en) * 1997-12-10 1999-06-29 Denso Corp Fuel injection control device of internal combustion engine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 1999, no. 11 30 September 1999 (1999-09-30) *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009007605A2 (en) * 2007-07-09 2009-01-15 Peugeot Citroën Automobiles SA Method for starting an internal combustion engine
FR2918712A1 (en) * 2007-07-09 2009-01-16 Peugeot Citroen Automobiles Sa METHOD FOR STARTING AN INTERNAL COMBUSTION ENGINE
WO2009007605A3 (en) * 2007-07-09 2009-03-26 Peugeot Citroen Automobiles Sa Method for starting an internal combustion engine
US8600649B2 (en) 2007-07-09 2013-12-03 Peugeot Citroen Automobiles Sa Method for starting an internal combustion engine
DE102010061015B4 (en) 2009-12-04 2019-01-31 Denso Corporation Control unit for an internal combustion engine
FR2980529A1 (en) * 2011-09-26 2013-03-29 Renault Sa FUEL INJECTION CONTROL WHEN STARTING A THERMAL ENGINE
WO2013045805A1 (en) * 2011-09-26 2013-04-04 Renault S.A.S. Control of the injection of fuel upon combustion engine start-up

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