EP0811758A2 - Méthode de commande de rapport air/carburant dans un moteur à combustion interne - Google Patents

Méthode de commande de rapport air/carburant dans un moteur à combustion interne Download PDF

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Publication number
EP0811758A2
EP0811758A2 EP97108963A EP97108963A EP0811758A2 EP 0811758 A2 EP0811758 A2 EP 0811758A2 EP 97108963 A EP97108963 A EP 97108963A EP 97108963 A EP97108963 A EP 97108963A EP 0811758 A2 EP0811758 A2 EP 0811758A2
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EP
European Patent Office
Prior art keywords
fluctuation
torque
amount
angular velocity
cylinder
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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.)
Granted
Application number
EP97108963A
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German (de)
English (en)
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EP0811758B1 (fr
EP0811758A3 (fr
Inventor
Nobuyuki Shibagaki
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Toyota Motor Corp
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Toyota Motor Corp
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Priority claimed from JP14188296A external-priority patent/JP3303669B2/ja
Priority claimed from JP14176396A external-priority patent/JP3156588B2/ja
Application filed by Toyota Motor Corp filed Critical Toyota Motor Corp
Publication of EP0811758A2 publication Critical patent/EP0811758A2/fr
Publication of EP0811758A3 publication Critical patent/EP0811758A3/fr
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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
    • F02D41/14—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
    • 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
    • F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
    • F02D2200/1015—Engines misfires
    • 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
    • F02D2200/702—Road conditions

Definitions

  • the present invention relates to a method of controlling an air-fuel ratio of an engine.
  • the combustion pressure causes the angular velocity of the crankshaft to rise from a first angular velocity ⁇ a to a second angular velocity ⁇ b.
  • the combustion pressure causes the kinetic energy to rise from (1 ⁇ 2) ⁇ I ⁇ a 2 to (1 ⁇ 2) ⁇ I ⁇ b 2 .
  • the amount of rise of the kinetic energy (1 ⁇ 2) ⁇ I ⁇ ( ⁇ b 2 - ⁇ a 2 ) causes a torque to be generated, so the generated torque becomes proportional to ( ⁇ b 2 - ⁇ a 2 ).
  • the generated torque is found from the difference between the square of the first angular velocity ⁇ a and the square of the second angular velocity ⁇ b and, therefore, in the above-mentioned internal combustion engine, the amount of fluctuation of the torque is calculated from the thus found generated torque.
  • An object of the present invention is to provide a method of control of an air-fuel ratio capable of preventing the air-fuel ratio from deviating from a target air-fuel ratio when a vehicle is driving over a rough road.
  • a method of control of an air-fuel ratio in an engine comprising the steps of setting a first crank angle range in a crank angle region from the end of a compression stroke to the beginning of an expansion stroke, setting a second crank angle range in a crank angle region in the middle of the expansion stroke a predetermined crank angle away from the first crank angle range, detecting a first angular velocity of the crankshaft in the first crank angle range, detecting a second angular velocity of the crankshaft in the second crank angle range, finding the amount of change of the drive power generated by each cylinder based on the first angular velocity and the second angular velocity, judging whether the vehicle is driving over a rough road, and prohibiting the correction of the air-fuel ratio based on the amount of change of the drive power when it is judged that the vehicle is driving over a rough road.
  • FIG. 1 shows an engine body provided with four cylinders consisting of the No. 1 cylinder #1, No. 2 cylinder #2, No. 3 cylinder #3, and No. 4 cylinder #4.
  • the cylinders #1, #2, #3, and #4 are respectively connected through the corresponding intake pipes 2 to a surge tank 3.
  • fuel injectors 4 for injecting fuel toward the corresponding intake ports.
  • the surge tank 3 is connected through an intake duct 5 to an air cleaner 6.
  • a throttle valve 7 is arranged.
  • the cylinders #1, #2, #3, and #4 are connected through an intake manifold 8 and an exhaust pipe 9 to a casing 11 accommodating an NOx absorbent 10.
  • This NOx absorbent 10 has the function of absorbing the NOx included in the exhaust gas when the air-fuel ratio is lean and releasing the absorbed NOx when the air-fuel ratio is the stoichiometric air-fuel ratio or rich.
  • the electronic control unit 20 is comprised of a digital computer and is provided with a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, a backup RAM 25 connected to a constant power supply, an input port 26, and an output port 27 connected with each other by a bidirectional bus 21.
  • the output shaft of the engine 12 has attached to it a rotor 13 with outer teeth.
  • a crank angle sensor 14 comprising an electromagnetic pickup is arranged facing the outer teeth of the rotor 13.
  • the rotor 13 has an outer tooth formed on its periphery at every 30° crank angle and, for example, has part of the outer teeth removed for detecting the top dead center of the compression stroke of the No. 1 cylinder. Therefore, except for the portion where the outer teeth are removed, that is, the non-tooth portion, the crank angle sensor 14 generates an output pulse every time the output shaft 12 turns by 30° crank angle. This output pulse is input to the input port 26.
  • the surge tank 3 has attached to it a pressure sensor 15 for generating an output voltage proportional to the absolute pressure in the surge tank 3.
  • the output voltage of this pressure sensor 15 is input through a corresponding AD converter 28 to the input port 26.
  • the throttle valve 7 has attached to it an idle switch 16 for detecting when the throttle valve 7 is at the idling opening position.
  • the output signal of this idle switch 16 is input to the input port 26.
  • the intake manifold 8 has disposed in it an air-fuel ratio sensor (O 2 sensor) 17 for detecting the air-fuel ratio.
  • the output signal of this air-fuel ratio sensor 17 is input through the corresponding AD converter 28 to the input port 26.
  • the output port 27 is connected through the corresponding drive circuit 29 to the fuel injectors 4.
  • TAU TP ⁇ FLEAN ⁇ FLLFB ⁇ FAF+TAUV
  • TP shows a basic fuel injection time
  • FLEAN a lean correction coefficient
  • FLLFB a lean limit feedback correction coefficient
  • FAF a stoichiometric air-fuel ratio feedback correction coefficient
  • TAUV an invalid injection time
  • the basic fuel injection time TP shows the injection time required for making the air-fuel ratio the stoichiometric air-fuel ratio. This basic fuel injection time TP is found from experiments. This basic fuel injection time TP is stored in the ROM 22 in advance in the form of a map shown in Fig. 2 as a function of the absolute pressure PM in the surge tank 3 and the engine speed N.
  • the lean correction coefficient FLEAN is a correction coefficient for making the air-fuel ratio a target lean air-fuel ratio.
  • This lean correction coefficient FLEAN is stored in advance in the ROM 22 in the form of the map shown in Fig. 4 as a function of the absolute pressure PM in the surge tank 3 and the engine speed N.
  • the lean limit feedback correction coefficient FLLFB is a correction coefficient for maintaining the air-fuel ratio at the lean limit.
  • the learning region for the lean air-fuel ratio feedback control for the absolute pressure PM in the surge tank 3 and the engine speed N is divided into nine regions as shown in Fig. 5 for example.
  • Lean limit feedback correction coefficients FLLFB11 to FLLFB33 are set for the learning regions.
  • the stoichiometric air-fuel ratio feedback correction coefficient FAF is a coefficient for maintaining the air-fuel ratio at the stoichiometric air-fuel ratio.
  • the stoichiometric air-fuel ratio feedback correction coefficient FAF is controlled based on the output signal of the air-fuel ratio sensor 17 so as to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. At this time, the stoichiometric air-fuel ratio feedback correction coefficient FAF varies substantially about 1.0.
  • the lean correction coefficient FLEAN is set in accordance with the operating state of the engine for the operating region enclosed by the broken lines in Fig. 4. In this operating region, the air-fuel ratio is maintained at the target lean air-fuel ratio. As opposed to this, in the operating region outside the region enclosed by the broken line in Fig. 4, the air-fuel ratio is maintained at the stoichiometric air-fuel ratio.
  • the lean correction coefficient FLEAN and the lean limit feedback correction coefficient FLLFB are fixed at 1.0 and the stoichiometric air-fuel ratio feedback correction coefficient FAF is controlled based on the output signal of the air-fuel ratio sensor 17.
  • the stoichiometric air-fuel ratio feedback correction coefficient FAF is fixed at 1.0, that is, the feedback control based on the output signal of the air-fuel ratio sensor 17 is stopped, and the lean correction coefficient FLEAN and the lean limit feedback correction coefficient FLLFB are used to control the air-fuel ratio to the target lean air-fuel ratio.
  • Fig. 3 shows the relationship between the amount of fluctuation of the torque of the engine output and the amount of generation of NOx and the air-fuel ratio.
  • the leaner the air-fuel ratio the smaller the fuel consumption rate. Further, the leaner the air-fuel ratio, the smaller the amount of generation of NOx. Therefore, viewed from these points, the air-fuel ratio should desirably be made as lean as possible. Note, however, that when the air-fuel ratio becomes leaner than a certain extent, the combustion becomes unstable and, as a result, as shown in Fig. 3, the amount of fluctuation of the torque becomes large. Therefore, in this embodiment according to the present invention, as shown in Fig. 3, the air-fuel ratio is maintained in the air-fuel ratio control region where the torque fluctuation starts to increase.
  • the lean correction coefficient FLEAN is determined so that the air-fuel ratio becomes the middle of the air-fuel ratio control region shown in Fig. 3 when the lean limit feedback correction coefficient FLLFB is made 1.0.
  • the lean limit feedback correction coefficient FLLFB is controlled to within the torque fluctuation control region shown in Fig. 3 in accordance with the amount of fluctuation of the torque.
  • the lean limit feedback correction coefficient FLLFB is increased, that is, the air-fuel ratio is made smaller
  • the lean limit feedback correction coefficient FLLFB is reduced, that is, the air-fuel ratio is made larger. In this way, the air-fuel ratio is controlled to within the air-fuel ratio control region shown in Fig. 3.
  • the lean limit feedback correction coefficient FLLFB is set to substantially the same region as the engine operating region where the lean correction coefficient FLEAN is set.
  • the amount of fluctuation of the torque is controlled to within the torque fluctuation control region shown in Fig. 3, an excellent drivability of the vehicle may be ensured while the fuel consumption rate and the amount of generation of NOx can be greatly reduced.
  • the amount of fluctuation of the torque must be detected. To detect the amount of fluctuation of the torque, the torque must be detected.
  • the angular velocities ⁇ a and ⁇ b can be calculated from the output signal of the crank angle sensor provided in the internal combustion engine in the past, so when calculating the output torque based on the angular velocities ⁇ a and ⁇ b, there is the advantage that there is no need to mount a new sensor.
  • the amount of fluctuation of the angular velocity of the crankshaft becomes larger due to the vehicle driving over a rough road, it is necessary to prohibit the correction of the air-fuel ratio.
  • the present invention calls for calculating the generated torque based on the angular velocity and prohibiting the correction of the air-fuel ratio when it is judged that the vehicle is driving over a rough road.
  • crank angle sensor 14 produces an output pulse each time the crankshaft rotates by 30° crank angle. Further, the crank angle sensor 14 is arranged to generate an output pulse at the top dead center TDC of the compression stroke of the cylinders #1, #2, #3, and #4. Therefore, the crank angle sensor 14 produces an output pulse for each 30° crank angle from the top dead center TDC of the compression stroke of the cylinders #1, #2, #3, and #4. Note that, the ignition sequence of the internal combustion engine used in the present invention is 1-3-4-2.
  • the vertical axis T30 shows the elapsed time of 30° crank angle from when the crank angle sensor 14 produces an output pulse to when it produces the next output pulse.
  • Ta(i) shows the elapsed time from the top dead center of the compression stroke (hereinafter referred to as TDC) to 30° after top dead center of the compression stroke (hereinafter referred to as ATDC) of the No. I cylinder
  • Tb(i) shows the elapsed time from ATDC 60° to ATDC 90° of the No. I cylinder. Therefore, for example, Ta(1) shows the elapsed time from TDC to ATDC 30° of the No.
  • the combustion pressure causes the kinetic energy to increase from (1 ⁇ 2) ⁇ I ⁇ a 2 to (1 ⁇ 2) ⁇ I ⁇ b 2 .
  • the amount of increase of the kinetic energy (1 ⁇ 2) ⁇ I ⁇ ( ⁇ b 2 - ⁇ a 2 ) expresses the torque generated by that cylinder, therefore it becomes possible to calculate the torque generated by a cylinder from the difference ( ⁇ b 2 - ⁇ a 2 ) between the square of the first angular velocity ⁇ a and the square of the second angular velocity ⁇ b.
  • crank angle range for detecting the first angular velocity ⁇ a and the crank angle range for detecting the second angular velocity ⁇ b are set in accordance with the engine so that ( ⁇ b- ⁇ a) best expresses the drive force generated by the engine or so that ( ⁇ b 2 - ⁇ a 2 ) best expresses the torque generated by the engine.
  • the crank angle range for detecting the first angular velocity ⁇ a may be from before top dead center of the compression stroke BTDC 30° to TDC, while the crank angle range for detecting the second angular velocity ⁇ b may be from ATDC 90° to ATDC 120°.
  • the first crank angle range is set in the crank angle region from the end of the compression stroke to the beginning of the expansion stroke
  • the second crank angle range is set in a crank angle region in the middle of the expansion stroke a predetermined crank angle away from the first crank angle range
  • the first angular velocity ⁇ a of the crankshaft in the first crank angle range is detected
  • the second angular velocity of the crankshaft ⁇ b in the second crank angle range is detected.
  • Fig. 7 shows the changes in the elapsed time Ta(i) successively calculated for each cylinder when the engine drive system experiences torsional vibration.
  • this torsional vibration causes the angular velocity of a crankshaft to be cyclically increased and decreased, so the elapsed time Ta(i) increases and decreases cyclically as shown in Fig. 7.
  • Fig. 8 shows the portion where the elapsed time Ta(i) is reduced in an enlarged manner.
  • the elapsed time Ta(i) falls by the time ho between Ta(1) and Ta(3).
  • This reduction of the time ho is believed to be due to an increase in the amount of torsion due to the torsional vibration.
  • the amount of decrease of the elapsed time due to the torsional vibration between Ta(1) and Ta(3) is believed to increase substantially linearly along with the elapse of time, therefore this amount of decrease of the elapsed time due to the torsional vibration is shown by the difference between the broken line connecting Ta(1) and Ta(3) and the horizontal line passing through Ta(1). Therefore, between Ta(1) and Tb(1), the torsional vibration causes the elapsed time to fall by exactly h.
  • Tb(1) is lower in elapsed time than Ta(1), but this lower elapsed time includes the amount of decrease f of the elapsed time due to the combustion pressure and the amount of decrease h of the elapsed time due to the torsional vibration. Therefore, to find just the elapsed time Tb'(1) decreased due to the combustion pressure, it becomes necessary to add h to Tb(1). That is, when the elapsed time Ta(i) decreases between cylinders (Ta(1) ⁇ Ta(3)), to find just the elapsed time Tb'(1) decreased due to the combustion pressure, the detected elapsed time Tb(1) must be corrected in the upward direction. In other words, when the first angular velocity ⁇ a increases between cylinders, the second angular velocity ⁇ b of the cylinder where the combustion was first performed must be corrected in the downward direction.
  • the elapsed time Tb(1) reduced from Ta(1) includes the amount of decrease of the elapsed time due to the combustion pressure and the amount of increase of the elapsed time due to the torsional vibration. Therefore, in this case, to find just the elapsed time Tb'(1) reduced due to the combustion pressure, the amount of increase of the elapsed time due to the torsional vibration must be subtracted from Tb(1). That is, when the elapsed time Ta(i) increases between cylinders, to find just the elapsed time Tb'(1) decreased due to the combustion pressure, the detected elapsed time Tb(1) must be corrected in the downward direction. In other words, when the first angular velocity ⁇ a decreases between cylinders, the second angular velocity ⁇ b of the cylinder where the combustion was first performed must be corrected in the upward direction.
  • correction of the second angular velocity ⁇ b enables the drive force generated by each cylinder to be accurately detected from the difference ( ⁇ b- ⁇ a) between the first angular velocity ⁇ a and the second angular velocity ⁇ b even when the engine drive system experiences torsional vibration and enables the torque generated by each cylinder to be accurately calculated from the difference ( ⁇ b 2 - ⁇ a 2 ) between the square of the first angular velocity ⁇ a and the square of the second angular velocity ⁇ b.
  • Fig. 9 shows the case where the space between the outer tooth of the rotor 13 showing the TDC of the No. 1 cylinder #1 and the outer tooth of the rotor 31 showing ATDC 30° is smaller than the space between other outer teeth.
  • the elapsed time Ta(1) will end up becoming smaller than the correct elapsed time for 30° crank angle. Further, at this time, as will be understood from a comparison of Fig. 8 and Fig.
  • the actually detected elapsed time Ta(i) for each cylinder is multiplied by the ratio KTa(i) so as to find the final elapsed time Ta(i) for each cylinder and the actually detected elapsed time Tb(i) for each cylinder is multiplied by the ratio KTb(i) so as to find the final elapsed time Tb(i) for each cylinder.
  • Fig. 10 shows the fluctuation in Ta(i) when the vehicle is traveling over a rough road.
  • AMP of Fig. 10 shows the difference between the minimum Ta(i) and maximum Ta(i), that is, the amplitude.
  • the amplitude AMP does not become that large and therefore at this time it is possible to calculate the h shown in Fig. 8 by the method explained previously so as to accurately detect the value of Tb'(i) showing just the elapsed time reduced due to the combustion pressure.
  • the drive force or the torque generated at a cylinder at which particularly Ta(i) becomes maximum or minimum can no longer be accurately detected. That is, in Fig. 10, when for example the cylinder first giving the maximum Ta(i) is the No. 1 cylinder, the amount of decrease h due to the torsional vibration for calculating the Tb'(1) of the No. 1 cylinder #1 is found from the inclination of the broken line connecting Ta(1) and Ta(3) in Fig. 10. However, near when the No. 1 cylinder #1 reaches TDC, the amount of increase or the amount of decrease of the elapsed time due to the torsional vibration changes by the smooth curve passing through Ta(2), Ta(1), and Ta(3).
  • the average value of the amplitude AMP of the fluctuation of the elapsed time Ta(i) is found and correction of the air-fuel ratio is prohibited when the average value of the amplitude AMP exceeds a predetermined value for over a certain time.
  • Fig. 21 shows the timing for calculation of the various values performed in each routine.
  • Fig. 11 shows an interruption routine performed at every 30° crank angle.
  • the routine for calculating the elapsed times Ta(i) and Tb(i) is proceeded to (step 100).
  • This routine is shown in Fig. 12.
  • the routine for calculating the amplitude of the fluctuation of the elapsed time Ta(i) is proceeded to (step 200).
  • This routine is shown in Fig. 13 to Fig. 15.
  • the routine for calculating the torque is proceeded to (step 300).
  • This routine is shown in Fig. 17.
  • the routine for calculating the ratios KTa(i) and KTb(i) is proceeded to (step 400).
  • This routine is shown in Fig. 18 and Fig. 19.
  • the routine for processing of the counter CDLNIX used for calculation of the torque fluctuation value is proceeded to (step 500).
  • This routine is shown in Fig. 20.
  • step 101 the time is made the TIME0.
  • the electronic control unit 20 is provided with a free run counter showing the time. The time is calculated from the count value of this free run counter.
  • step 102 the current time is fetched. Therefore, the TIME0 of step 101 expresses the time of 30° crank angle before.
  • step 103 whether the No. 1 cylinder is currently at ATDC 30° or not is judged.
  • step 106 is jumped to, where whether the No. 1 cylinder is currently at ATDC 90° or not is judged.
  • the routine for calculation of the elapsed times Ta(i) and Tb(i) is ended.
  • the final elapsed time Ta(1) from TDC to ATDC 30° of the No. 1 cylinder #1 is calculated from KTa(1) ⁇ (TIME-TIME0).
  • (TIME-TIME0) expresses the elapsed time Ta(1) actually measured from the crank angle sensor 14 and KTa(1) is a ratio for correction of the error due to the spaces of the outer teeth of the rotor 13, therefore the final elapsed time Ta(1) obtained by multiplying (TIME-TIME0) with KTa(1) comes to accurately express the elapsed time when the crankshaft rotates by 30° crank angle.
  • the flag XCAL(i-1) of the No. (i-1) cylinder where combustion had been performed one time before showing that the generated torque should be calculated is set (XCAL(i-1) ⁇ "1").
  • the flag XCAL(2) of the No. 2 cylinder #2 where the combustion had been performed one time before showing that the generated torque should be calculated is set.
  • the flag XCAL(1) is set, when the final elapsed time Ta(4) is to be calculated, the flag XCAL(3) is set, and when the final elapsed time Ta(2) is to be calculated, the flag XCAL(4) is set.
  • the final elapsed time Tb(1) from ATDC 60° to ATDC 90° of the No. 1 cylinder #1 is calculated from KTb(1) ⁇ (TIME-TIME0).
  • the ratio KTb(1) for correcting the error due to the spaces of the outer teeth of the rotor 13 is multiplied with (TIME-TIME0)
  • the final elapsed time Tb(1) accurately expresses the elapsed time in the period when the crankshaft rotates by 30° crank angle.
  • step 201 whether one of the cylinders is currently at ATDC 30° or not is judged. When none of the cylinders is currently at ATDC 30°, the processing cycle is ended, while when one of the cylinders is at ATDC 30°, step 202 is proceeded to.
  • step 202 to step 204 the maximum elapsed time T30max when the elapsed time Ta(i) increases and then decreases is calculated. That is, at step 202, whether the Ta(i) calculated at the routine shown in Fig. 12 is larger than the maximum elapsed time T30max or not is judged.
  • step 205 is jumped to, while when T30max ⁇ Ta(i), step 203 is proceeded to, where Ta(i) is made T30max.
  • the increase flag XMXREC showing that Ta(i) is increasing is set (XMXREC ⁇ "1"), then step 205 is proceeded to.
  • step 205 to step 207 the minimum elapsed time T30min when the elapsed time Ta(i) decreases and then increases is calculated. That is, at step 205, whether the Ta(i) calculated by the routine shown in Fig. 12 is smaller than the calculated minimum elapsed time T30min or not is judged.
  • step 208 is jumped to, while when T30min ⁇ Ta(i), step 206 is proceeded to, where Ta(i) is made T30min.
  • step 207 the decrease flag XMNREC showing that Ta(i) has decreased is set (XMNREC ⁇ "1"), then step 208 is proceeded to.
  • step 209 is proceeded to. That is, step 209 is proceeded to at the time t 2 when the elapsed time Ta(i) starts to decrease.
  • the maximum elapsed time T30max is made TMXREC.
  • the minimum elapsed time TMNREC (found at the later explained step 216) is subtracted from the maximum elapsed time TMXREC so as to calculate the amplitude AMP of the fluctuation of Ta(i).
  • the initial value of the minimum elapsed time T30min is made Ta(i).
  • the increase flag XMXREC is reset (XMXREC ⁇ "0").
  • step 213 is proceeded to.
  • step 205 to step 206 is proceeded to, where the Ta(1) is made T30min, then at step 207, the decrease flag XMNREC is set.
  • the interruption routine performed at the time t 4 of Fig. 16 jumps from step 205 to step 208.
  • step 214 is proceeded to. That is, step 214 is proceeded to at the time t 4 where the elapsed time Ta(i) starts to be increased.
  • the minimum elapsed time T30min is made TMNREC.
  • the minimum elapsed time TMNREC is subtracted from the maximum elapsed time TMXREC so as to calculate the amplitude AMP of the fluctuation of Ta(i).
  • the initial value of the maximum elapsed time T30max is made Ta(i).
  • the decrease flag XMNREC is reset (XMNREC ⁇ "0").
  • step 218 is proceeded to.
  • the amplitude AMP of Ta(i) is added to the cumulative value ⁇ AMP of the amplitude of Ta(i).
  • step 219 whether the amplitude AMP has been cumulatively added n number of times or not is judged.
  • ⁇ AMP is cleared.
  • step 301 whether the flag XCAL(i-1) showing that the generated torque of the No. (i-1) cylinder where combustion had been performed one time before should be calculated is set or not is judged.
  • the processing cycle is ended.
  • step 302 is proceeded to, where the flag XCAL(i-1) is reset, then step 303 is proceeded to.
  • Tb'(i-1) Tb(i-1)+h
  • This generated torque DN(i-1) expresses the torque after elimination of the effect due to the torsional vibration of the engine drive system and the effect due to the variation in spaces of the outer teeth of the rotor 13, therefore this generated torque DN(i-1) expresses the true torque generated due to the combustion pressure.
  • DN(i-1)j expresses the generated torque of the same cylinder one cycle (720° crank angle) before for DN(i-1).
  • step 307 whether the amount of fluctuation of the torque DLN(i-1) is positive or not is judged.
  • step 309 is jumped to, where the cumulative addition request flag XCDLN(i-1) showing that the amount of fluctuation of the torque DLN(i-1) of the cylinder at which the combustion was performed one time before should be cumulatively added is set (XCDLN(i-1) ⁇ "1").
  • step 308 is proceeded to, where DLN(i-1) is made zero.
  • step 309 is proceeded to.
  • step 401 whether the supply of fuel has been stopped during the deceleration operation or not, that is, whether the fuel has been cut or not. is judged.
  • step 415 is proceeded to, where the cumulative values ⁇ Ta(i) and ⁇ Tb(i) of the elapsed times Ta(i) and Tb(i) are cleared, then the processing cycle is completed.
  • step 402 is proceeded to, where whether the amplitude AMP of Ta(i) is larger than a set value B 0 or not is judged.
  • step 415 is proceeded to, while when AMP ⁇ B 0 , step 403 is proceeded to.
  • KTa(i) is calculated. That is, at step 403, the corresponding elapsed time Ta(i) for each cylinder is added to the cumulative value ⁇ Ta(i). For example, Ta(1) is added to ⁇ Ta(1) and Ta(2) is added to ⁇ Ta(2).
  • step 404 whether the Ta(i) for each cylinder has been cumulatively added n number of times each or not is judged. When not cumulatively added n number of times each, step 409 is jumped to, while when cumulatively added n number of times, step 405 is proceeded to.
  • the ratio KTa(i) is updated based on the following equation: KTa(i) ⁇ KTa(i)+ ⁇ (i)-KTa(i) ⁇ /4
  • the ratios KTa(1), KTa(2), KTa(3), and KTa(4) for the cylinders are calculated. For example, if ⁇ (1) has become larger than the KTa(1) used up to then, one-quarter of the difference between ⁇ (1) and KTa(1) ⁇ (1)-KTa(1) ⁇ is added to KTa(1), therefore KTa(1) gradually approaches ⁇ (1).
  • the KTa(i) for each cylinder is calculated, then step 408 is proceeded to, where the cumulative value ⁇ Ta(i) for each cylinder is cleared.
  • KTb(i) is calculated. That is, at step 409, the corresponding elapsed time Tb(i) for each cylinder is added to the cumulative value ⁇ Tb(i). For example, Tb(1) is added to ⁇ Tb(1) and Tb(2) is added to ⁇ Tb(2).
  • step 410 whether the Tb(i) for each cylinder has each been cumulatively added n number of times or not is judged. When not cumulatively added n number of times each, the processing cycle is ended, while when cumulatively added n number of times, step 411 is proceeded to.
  • the ratio KTb(i) is updated based on the following equation: KTb(i) ⁇ KTb(i)+ ⁇ (i)-KTb(i) ⁇ /4
  • the ratios KTb(1), KTb(2), KTb(3), and KTb(4) for the cylinders are calculated. For example, assuming that ⁇ (1) has become larger than the KTb(1) used up to then, one-quarter of the difference between ⁇ (1) and KTb(1) ⁇ (1)-KTb(1) ⁇ is added to KTb(1), therefore KTb(1) gradually approaches ⁇ (1).
  • step 414 is proceeded to, where the cumulative value ⁇ Tb(i) for each cylinder is cleared.
  • the count value of the counter CDLNIX is used for the later explained calculation of the torque fluctuation value.
  • step 502 is proceeded to. At step 502, whether the conditions for calculating the torque fluctuation value stand or not is judged.
  • step 508 is proceeded to, where the count value CDLNIX is incremented by exactly 1.
  • the increment action of this count value CDLNIX is performed every time the No. 3 cylinder #3 reaches ATDC 30°, that is, every 720° crank angle.
  • step 509 the average value of the engine speed N AVE and the average value PM AVE of the absolute pressure in the surge tank 3 in the period from when the increment action of the count value CDLNIX is started to when the count value CDLNIX is cleared are calculated.
  • step 503 is proceeded to, where the count value CDLNIX is cleared.
  • step 504 the cumulative value DLNI(i) of the torque fluctuation value DLN(i) for each cylinder (this cumulative value is calculated by the later explained routine) is cleared.
  • step 505 the cumulative count value CDLNI(i) for each cylinder (this cumulative count value is calculated by the later explained routine) is cleared.
  • the target torque fluctuation value LVLLFB is calculated.
  • the air-fuel ratio is feedback controlled so that the calculated torque fluctuation value becomes this target torque fluctuation value LVLLFB.
  • This target torque fluctuation value LVLLFB as shown by Fig. 22A showing the equivalent fluctuation value by the solid line, becomes larger the higher the absolute pressure PM in the surge tank 3 and becomes larger the higher the engine speed N.
  • This target torque fluctuation value LVLLFB is stored in the ROM 22 in advance in the form of a map shown in Fig. 22B as a function of the absolute pressure PM in the surge tank 3 and the engine speed N.
  • the torque fluctuation value DLNISM(i) of each cylinder is made the target torque fluctuation value LVLLFB calculated from the map of Fig. 22B.
  • Fig. 23 shows the repeatedly executed main routine.
  • the routine for calculation of the torque fluctuation value step 600
  • This routine is shown in Fig. 24 and Fig. 25.
  • the routine for calculation of the lean limit feedback correction coefficient FLLFB step 700
  • the routine for calculation of the injection time step 800
  • the routine for calculation of the injection time step 800
  • the other routines step 900
  • step 609 is jumped to, while when the cumulative addition request flag XCDLN(i)is set, step 602 is proceeded to.
  • step 602 the cumulative addition request flag XCDLN(i) is reset.
  • step 603 the amount of fluctuation of the torque DLN(i) is added to the cumulative value DLNI(i) of the amount of fluctuation of the torque.
  • the cumulative count value CDLNI(i) is incremented by exactly 1. That is, for example, at step 601, if the cumulative addition request flag XCDLN(1) is set for the No. 1 cylinder, this flag XCDLN(1) is reset at step 602, the cumulative value DLNI(1)of the amount of fluctuation of the torque is calculated at step 603, and the cumulative count value CDLNI(1) is incremented by exactly 1 at step 604.
  • step 605 whether the cumulative count value CDLNI(i) has become "8” or not is judged.
  • step 607 the cumulative value DLNI(i) of the amount of fluctuation of the torque for each cylinder is cleared, then at step 608, the cumulative count value CDLNI(i) is reset.
  • step 609 whether the count value CDLNIX calculated at the routine shown in Fig. 20 has become “8” or not is judged.
  • CDLNIX is not "8"
  • step 611 the count value CDLNIX is cleared. In this way, the value DLNISM expressing the amount of fluctuation of the torque of the engine is calculated.
  • step 701 whether the conditions for updating the lean limit feedback correction coefficient FLLFB stand or not is judged. For example, at the time of engine warmup or when the operating state of the engine is not in the learning region enclosed by the broken lines in Fig. 5, it is judged that the conditions for updating do not stand, while at other times it is judged that the conditions for updating stand.
  • the processing cycle is ended, while when the conditions for updating stand, step 702 is proceeded to.
  • step 702 whether the average value SINPAC of the amplitude AMP of the fluctuation of the elapsed time Ta(i) exceeds the standard value SINP 0 or not is judged.
  • step 703 is proceeded to, where the rough road counter CRR is cleared. That is, when SINPAV is smaller than the standard value SINP 0 as in the zone Z in Fig. 29, the rough road counter CRR is maintained at zero.
  • the target torque fluctuation value LVLLFB is calculated from the absolute pressure PM in the surge tank 3 and the engine speed N based on the map shown in Fig. 22B.
  • the fluctuation amount judgement values DH(n) and DL(n) are determined in advance as shown in Fig. 28A. That is, as will be understood from Fig. 28A, three positive values are set for DH(n) which are in the relationship of DH(3) > DH(2) > DH(1). Further, these DH(1), DH(2), and DH(3) gradually increase as the target torque fluctuation value LVLLFB becomes larger. On the other hand, three negative values are set for DL(n) which are in the relationship of DL(1) > DL(2) > DL(3). Further, the absolute values of these DL(1), DL(2), and DL(3) gradually increase as the target torque fluctuation value LVLLFB becomes larger.
  • the target torque fluctuation value LVLLFB calculated at step 704 is the value shown by the broken line.
  • the values of DH(1), DH(2), and DH(3) on the broken line plus the target torque fluctuation value LVLLFB are made the levels of torque fluctuation LVLH(1), LVLH(2), and LVLH(3) and, at step 706, the values of DL(1), DL(2), and DL(3) on the broken line plus the target torque fluctuation value LVLLFB are made the levels of torque fluctuation LVLL(1), LVLL(2), and LVLL(3).
  • the feedback correction values +a 1 , +a 2 , +a 3 , +a 4 , -b 1 , -b 2 , -b 3 , and -b 4 are determined in advance for the regions between the levels of torque fluctuation LVLH(n) and LVLL(n) as shown in Fig. 28B.
  • the feedback correction value becomes +a 2 for the region where the level of torque fluctuation is between LVLH(1) and LVLH(2).
  • These feedback correction values are +a 4 > +a 3 > +a 2 > +a 1 and -b 1 > -b 2 > -b 3 > -b 4 .
  • the feedback correction values +a 1 , +a 2 , +a 3 , +a 4 , -b 1 , - b 2 , -b 3 , and -b 4 shown in Fig. 28B are shown in the corresponding regions of Fig. 28A.
  • step 707 is proceeded to, where whether the mean torque fluctuation value DLNISM calculated in the routine for calculation of the torque fluctuation value shown in Fig. 24 and Fig. 25 is between the levels of torque fluctuation LVLH(n) and LVLL(n) shown in Fig. 28B or not is judged.
  • step 708 the corresponding feedback correction value DLFB is calculated. For example, when the target fluctuation level LVLLFB is the value shown by the broken line in Fig. 28A and the calculated mean value DLNISM of the torque fluctuation value is between LVLH(1) and LVLH(2) of Fig.
  • step 709 what lean limit feedback correction coefficient of which learning region shown in Fig. 5 the lean limit feedback correction coefficient FLLBFij to be updated based on the average value of the engine speed N AVE and the average value PM AVE of the absolute pressure in the surge tank 3 found at step 509 of the processing routine of CDLNIX shown in Fig. 20 is is determined.
  • step 710 the lean limit feedback correction coefficient FLLFBij determined at step 709 is increased by the feedback correction value DLFB.
  • the lean limit feedback correction coefficient FLLFBij is increased by +a 2 .
  • the air-fuel ratio becomes smaller, so the amount of fluctuation of the torque of each cylinder is reduced.
  • the lean limit feedback correction coefficient FLLFBij is increased by -b 2 .
  • the air-fuel ratio becomes large, so the amount of fluctuation of the torque of the cylinders is increased. In this way the air-fuel ratio at the time of lean operation is controlled so that the mean value DLNISM of the amount of fluctuation of the torque of all of the cylinders becomes the target torque fluctuation value LVLLFB.
  • the DLNISM(i) is made LVLLFB and therefore the mean value DLNISM of the torque fluctuation value is also made the target torque fluctuation value LVLLFB. Therefore, at this time, the lean limit feedback correction coefficient FLLFBij is not updated.
  • step 711 is proceeded to, where the learning count value CFLLFB is incremented by exactly 1.
  • step 712 whether the rough road count value CRR is zero and the learning count value CFLLFB has reached a constant value n or not is judged When CRR is not 0 or CFLLFB is not n, the processing cycle ends.
  • m is a positive integer.
  • the learning value KBUij is decided on for each learning region corresponding to each learning region of FLLFBij shown in Fig. 5 as shown in Fig. 30.
  • KBUij is added to the value of this difference multiplied by 1/m, therefore the learning value KBUij changes to gradually approach FLLFBij.
  • step 714 is proceeded to, where the learning counter CFLLFB is cleared. That is, as shown by the zone Z of Fig. 29, each time the learning count value CFLLB reaches n, the corresponding learning value KBUij is updated based on the lean limit feedback correction coefficient FLLBFij and then the learning counter CFLLFB is cleared.
  • step 715 is proceeded to, where the rough road count value CRR is incremented by exactly 1.
  • step 716 the learning counter CFLLFB is cleared.
  • step 717 whether a predetermined time TC has elapsed from the start of the countup action of the rough road counter CRR or not is judged.
  • step 704 is proceeded to, therefore the action for updating the lean limit feedback correction coefficient FLLBFij is performed.
  • the mean torque fluctuation value DLNISM becomes larger, so as shown in Fig. 29 FLLFBij increases. Note that the action for updating the learning value KBUij is stopped at this time.
  • step 718 is proceeded to, where whether the engine has operated for eight cycles is judged.
  • step 719 is proceeded to, where the lean limit feedback correction coefficient FLLFBij is decreased by exactly the predetermined value ⁇ .
  • step 720 whether FLFBiji has become smaller than the corresponding learning value KBUij or not is judged.
  • step 721 is proceeded to, where FLLFBij is made KBUij. That is, as shown in Fig. 29, when a predetermined time TC elapses from when SINPAV1 or SINPAV2 exceeds the standard SINP 0 , the lean limit feedback correction coefficient FLLFBij is gradually returned to the learning value KBUij.
  • the lean limit feedback correction coefficient FLLFBij becomes larger as shown in Fig. 29.
  • the air-fuel ratio moves to the rich side and therefore the amount of NOx generated increases.
  • torque fluctuation occurs at this time due to the driving over the rough road and not due to the fluctuation of the combustion pressure.
  • the optimal lean limit feedback correction coefficient FLLFBij at this time substantially matches with the learning value KBUij. Therefore, to suppress the generation of NOx and obtain a good combustion, FLLFBij is gradually returned to the learning value KBUij. Note that if FLLFBij is returned to KBUij when the vehicle is driving over a rough road in this way, there is the advantage that the lean limit feedback correction coefficient FLLFBij will not become disturbed when passing from the rough road to a smooth road.
  • step 801 the basic fuel injection time TP is calculated from the map shown in Fig. 2.
  • step 802 whether the operating state is one in which a lean operation should be performed or not is judged.
  • step 803 is proceeded to, where the value of the stoichiometric air-fuel ratio feedback correction coefficient FAF is fixed at 1.0.
  • step 804 the lean correction coefficient FLEAN is calculated from the map shown in Fig. 4, then, at step 805, the lean limit feedback correction coefficient FLLFB is read from the map shown in Fig. 5.
  • step 806 is proceeded to, where the lean correction coefficient FLEAN is fixed at 1.0, then, at step 807, the lean limit feedback correction coefficient FLLFB is fixed at 1.0.
  • step 808 the stoichiometric air-fuel ratio feedback correction coefficient FAF is controlled based on the output signal of the air-fuel ratio sensor 17 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio.
  • step 809 is proceeded to, where the fuel injection time TAU is calculated.
  • this standard value SINP 0 is preferably made a function of the amount of fluctuation of the torque, for example, the mean torque fluctuation value DLNISM. This will be explained next with reference to Fig. 32.
  • Fig. 32 shows the relationship between the average value SINPAV of the amplitude of fluctuation of Ta(i) and the mean torque fluctuation value DLNISM.
  • the region for judgement that the vehicle is driving over a rough road in Fig. 32 is shown by the hatching SS. That is, the state where the vehicle is currently driving over a smooth road and the mean torque fluctuation value DLNISM is maintained at the target torque fluctuation value LVLLFB is shown by the point P 1 in Fig. 32.
  • the mean torque fluctuation value DLNISM will move from the point P 1 to the point P 3 in Fig. 32. That is, if the degree of roughness of the road becomes larger under the same conditions of fluctuation of combustion, the mean torque fluctuation value DLNISM will change along the solid line Q 13 of Fig. 32. Note that in this case, the point P 3 becomes the standard value SINP 0 where it is judged that the vehicle is driving over a rough road.
  • the mean torque fluctuation value DLNISM will change along the solid line Q 24 parallel to the solid line Q 13 . Since the length of the solid line Q 24 and the length of the solid line Q 13 up until the road is judged to be rough should become equal, the point P 4 becomes positioned on the line passing through the point P3 and parallel to the broken line Q 12 .
  • the standard value SINP 0 serving as the standard fo rthe judgement that the vehicle is driving over a rough road is positioned on the line parallel to the broken line Q 12 and therefore the standard value SINP 0 becomes larger than greater the mean torque fluctuation value DLNISM. If the point determined by DLNISM and SINPAV passes the standard value SINP 0 , it is judged that the vehicle is driving over a rough road and therefore, as explained above, the hatching region SS of Fig. 32 shows the region where the vehicle is judged to be driving over a rough road.
  • Fig. 33 shows another embodiment of the fluctuation value judgement values DH(n) and DL(n) shown in Fig. 28A for moving the air-fuel ratio to the rich side when the vehicle is traveling over a rough road.
  • the fluctuation value judgement values DL(1), DH(2), and DH(3) at the side where the mean torque fluctuation value DLNISM becomes smaller than the target torque fluctuation value LVLLFB are maintained constant regardless of the target torque fluctuation value LVLLFB and the amplitude average value SINPAVC.
  • the fluctuation value judgement values DH(1), DH(2), and DH(3) at the side where the mean torque fluctuation value DLNISM becomes larger than the target torque fluctuation value LVLLFB are straight lines having the same inclination as the solid lines Q 13 and Q 24 shown in Fig. 32. That is, the fluctuation value judgement values DH(n) gradually increase as the amplitude average value SINPAV becomes larger.
  • the hatching region SS in Fig. 33 shows the region where the vehicle is judged to be driving over a rough road in the same way as Fig. 32.
  • the fluctuation value judgement values DH(n) form the same inclinations as the solid lines Q 13 and Q 24 of Fig. 32, therefore when the degree of roughness of the road increases in a state where the amount of fluctuation of the combustion pressure does not change, the mean torque fluctuation value DLNISM will change along with the fluctuation value judgement value DN(n), so the feedback correction values +a 1 , +a 2 , +a 3 , and +a 4 will not change. For example, assume the current feedback correction value is +a 2 .
  • the degree of roughness of the road increases from this state without a change in the amount of fluctuation of the combustion pressure, the amount of torque fluctuation will increase at this time, but the feedback correction value will be maintained as is at +a 2 without increasing to +a 3 . Therefore, even if the vehicle drives over a rough road, the air-fuel ratio will not move to the rich side and the air-fuel ratio will be maintained at the optimum air-fuel ratio determined from the fluctuation of the combustion pressure.
  • Fig. 34 and Fig. 35 show the routine for calculation of the lean limit feedback correction coefficient FLLFB in the case of use of the method of judgement of driving on a rough road shown in Fig 32 and the fluctuation value judgement values DH(n) shown in Fig. 33.
  • the routine for calculation of FLLFB differs from the routine shown in Fig. 26 and Fig. 27 only at step 702'. The rest of it is the same as the routine shown in Fig. 26 and Fig. 27. That is, in the routine shown in Fig. 34 and Fig. 35, at step 702', whether the point determined from the mean torque fluctuation value DLNISM and the amplitude average value SINPAV is within the region SS of Fig. 32 is judged.
  • the torque fluctuation levels LVLH(n) and LVLL(n) are calculated at step 705 and step 706 from the fluctuation value judgement values DH(n) and DL(n) shown in Fig. 33 and the target torque fluctuation value LVLLFB, then at steps 707 and 708, the feedback correction value DLFB is determined from the feedback correction values +a 1 , +a 2 , +a 3 , +a 4 , - b 1 , -b 2 , -b 3 , and -b 4 shown in Fig. 33.
  • Fig. 36 to Fig. 51 show the case of application of the present invention to an engine provided with a torque converter provided with a lockup mechanism.
  • the crankshaft 12 is connected to an automatic transmission 30.
  • the output shaft 31 of the automatic transmission 30 is connected to the drive wheels.
  • the automatic transmission 30 is provided with a torque converter 32.
  • a torque converter 32 In this torque converter 32 is provided a lockup mechanism 33. That is, the torque converter 32 is provided with a pump cover 34 which is connected to the crankshaft 12 and rotates together with the crankshaft 12, a pump impeller 35 which is supported by the pump cover 34, a turbine runner 37 which is attached to an input shaft 36 of the automatic transmission 30, and a stator 37a. The rotational motion of the crankshaft 12 is transmitted through the pump cover 34, pump impeller 35, and turbine runner 37 to the input shaft 36.
  • the lockup mechanism 33 is provided with a lockup clutch plate 38 which is attached to the input shaft 36 in a manner movable along its axial direction and rotates together with the input shaft 36.
  • a lockup clutch plate 38 which is attached to the input shaft 36 in a manner movable along its axial direction and rotates together with the input shaft 36.
  • pressurized oil is supplied in the chamber 39 between the lockup clutch plate 38 and the pump cover 34 through an oil passage in the input shaft 36, then the pressurized oil flowing out from this chamber 39 is fed into a chamber 40 around the pump impeller 35 and turbine runner 37, then is exhausted through the oil passage in the input shaft 36.
  • a rotational speed sensor 41 which generates an output pulse expressing the rotational speed of the input shaft 36, that is, the turbine runner 37, and a rotational speed sensor 42 which generates an output pulse expressing the rotational speed of the output shaft 31.
  • the output pulses of these rotational speed sensors 41 and 42 are input to an input port 26.
  • the lockup mechanism 33 when the lockup mechanism 33 is on, the average value of the amplitude AMP is found and when the average value of the amplitude AMP exceeds a certain value for more than a predetermined period, the correction of the air-fuel ratio is prohibited.
  • the amount of fluctuation of the rotational speed of the turbine runner 37 of the torque converter 32 is detected from the output pulse of the rotational speed sensor 41.
  • the lockup mechanism 33 is off, if the average value of the amount of fluctuation of the rotational speed of the turbine runner 32 exceeds a certain value for more than a predetermined period, it is judged that the vehicle is driving over a rough road and the correction of the air-fuel ratio is prohibited.
  • crankshaft 12 also fluctuates in rotational speed due to the fluctuation in the combustion pressure, therefore it is not known whether the fluctuation in the rotational speed of the crankshaft 12 is due to the vehicle driving over a rough road or the fluctuation in the combustion pressure.
  • the rotational speed of the turbine runner 37 fluctuates by a large degree only when the vehicle is driving on a rough road, therefore it is possible to judge that the vehicle is driving on a rough road when the fluctuation in the rotational speed of the turbine runner 37 becomes large. Accordingly, in this embodiment, when the lockup mechanism 22 is off, if the average value of the amount of fluctuation of the rotational speed of the turbine runner 32 exceeds a certain value for more than a predetermined time, it is judged that the vehicle is driving on a rough road and the correction of the air-fuel ratio is prohibited.
  • Fig. 37 shows an interruption routine performed at every 30° crank angle.
  • the routine for calculating the elapsed times Ta(i) and Tb(i) is proceeded to (step 1100). This routine is shown in the previously explained Fig. 12.
  • the routine for checking whether the calculation of the torque is permitted is proceeded to. This routine is shown in Fig. 41.
  • the routine for calculating the ratios KTa(i) and KTb(i) is proceeded to (step 1400).
  • This routine is shown in the previously explained Fig. 18 and Fig. 19.
  • the routine for processing of the counter CDLNIX used for calculation of the torque fluctuation value is proceeded to (step 1500). This routine is shown in the previously explained Fig. 20.
  • This routine is provided to prohibit the calculation of the torque for a specific cylinder when the amplitude (Fig. 10) of the fluctuation of Ta(i) becomes large due to the vehicle driving over a rough road and for finding the mean value of the amplitude AMP serving as the standard for judgement for prohibiting the correction of the air-fuel ratio.
  • step 1201 whether one of the cylinders is currently at ATDC 30° or not is judged. When none of the cylinders is currently at ATDC 30°, the processing cycle is ended, while when one of the cylinders is at ATDC 30°, step 1202 is proceeded to.
  • step 1202 to step 1204 the maximum elapsed time T30max when the elapsed time Ta(i) increases and then decreases is calculated. That is, at step 1202, whether the Ta(i) calculated at the routine shown in Fig. 12 is larger than the maximum elapsed time T30max or not is judged.
  • step 1205 is jumped to, while when T30max ⁇ Ta(i), step 1203 is proceeded to, where Ta(i) is made T30max.
  • the increase flag XMXREC showing that Ta(i) is increasing is set (XMXREC ⁇ "1"), then step 1205 is proceeded to.
  • step 1205 to step 1207 the minimum elapsed time T30min when the elapsed time Ta(i) decreases and then increases is calculated. That is, at step 1205, whether the Ta(i) calculated by the routine shown in Fig. 12 is smaller than the calculated minimum elapsed time T30min or not is judged.
  • step 1208 is jumped to, while when T30min ⁇ Ta(i), step 1206 is proceeded to, where Ta(i) is made T30min.
  • step 1207 the decrease flag XMNREC showing that Ta(i) has decreased is set (XMNREC ⁇ "1"), then step 1208 is proceeded to.
  • step 1202 to step 1203 is proceeded to, where the Ta(1) is made T30max, then, at step 1204, the increase flag XMXREC is set.
  • step 1202 to step 1205 is jumped to.
  • step 1209 is proceeded to. That is, step 1209 is proceeded to at the time t 2 when the elapsed time Ta(i) starts to decrease.
  • the maximum elapsed time T30max is made TMXREC.
  • the minimum elapsed time TMNREC (found at the later explained step 1216)is subtracted from the maximum elapsed time TMXREC so as to calculate the amplitude AMP of the fluctuation of Ta(i).
  • the initial value of the minimum elapsed time T30min is made Ta(i).
  • the increase flag XMXREC is reset (XMXREC ⁇ "0").
  • step 1213 whether the amplitude AMP is larger than the setting A 0 or not is judged. When AMP ⁇ A 0 , step 1215 is jumped to.
  • step 1214 is proceeded to, where the torque calculation prohibition flag XNOCAL is set (XNOCAL ⁇ 1"). That is, in the interruption routine performed at the time t 2 in Fig. 16, the torque generated at the No. 1 cylinder #1 is calculated as explained above Therefore, in this interruption routine, when AMP ⁇ A 0 and the torque calculation prohibition flag XNOCAL is set, the calculation of the torque generated at the No. 1 cylinder #1, that is, the calculation of the torque generated at the cylinder giving the maximum Ta(i) is prohibited.
  • step 1205 to step 1206 is proceeded to, where the Ta(1) is made T30min, then at step 1207, the decrease flag XMNREC is set.
  • the interruption routine performed at the time t 4 of Fig. 16 jumps from step 1205 to step 1208.
  • step 1216 is proceeded to. That is, step 1216 is proceeded to at the time t 4 where the elapsed time Ta(i) starts to be increased.
  • the minimum elapsed time T30min is made TMNREC.
  • the minimum elapsed time TMNREC is subtracted from the maximum elapsed time TMXREC so as to calculate the amplitude AMP of the fluctuation of Ta(i).
  • the initial value of the maximum elapsed time T30max is made Ta(i).
  • the decrease flag XMNREC is reset (XMNREC ⁇ "0").
  • step 1220 whether the amplitude AMP is larger than the setting A 0 or not is judged. When AMP ⁇ A 0 , step 1222 is jumped to.
  • step 1221 is proceeded to, where the torque calculation prohibition flag XNOCAL is set (XNOCAL ⁇ 1"). That is, in the interruption routine performed at the time t 4 in Fig. 16, the torque generated at the No. 1 cylinder #1 is calculated as explained above Therefore, in this interruption routine, when AMP ⁇ A 0 and the torque calculation prohibition flag XNOCAL is set, the calculation of the torque generated at the No. 1 cylinder #1, that is, the calculation of the torque generated at the cylinder giving the minimum Ta(i) is prohibited.
  • step 1222 to step 1223 calculation of the torque for cylinders where the elapsed time Ta(i) sharply changes is prohibited. That is, at step 1222, whether
  • K 0 is a value of 3.0 to 4.0 or so.
  • step 1224 is jumped to, while when [Ta(i-2)-Ta(i-1)
  • the amplitude AMP is added to cumulative value ⁇ AMP of the amplitude.
  • step 1225 whether the amplitude AMP has been cumulatively added n number of times or not is judged.
  • C 1 is a constant.
  • ⁇ AMP is cleared.
  • step 1301 whether the flag XCAL(i-1) of the No. (i-1) cylinder where the combustion was performed one time before showing that the generated torque should be calculated is set or not is judged.
  • the processing cycle is ended.
  • step 1302 is proceeded to, where the flag XCAL(i-1) is reset, then step 1303 is proceeded to.
  • step 1311 is proceeded to, where the prohibition flag XNOCAL is reset.
  • step 1304 is proceeded to. That is, only when the flag XCAL is set and prohibition flag XNOCAL is reset is step 1304 proceeded to.
  • Tb'(i-1) Tb(i-1)+h
  • This generated torque DN(i-1) expresses the torque after elimination of the effect of the torsional vibration of the engine drive system and the effect of the variation in spaces between the outer teeth of the rotor 13 and therefore expresses the true torque generated due to the combustion pressure.
  • DN(i-1)j expresses the generated torque of the same cylinder one cycle (720° crank angle) before for DN(i-1).
  • step 1308 whether the amount of fluctuation of the torque DLN(i-1) is positive or not is judged.
  • step 1310 is jumped to, where the cumulative addition request flag XCDLN(i-1) of the cylinder at which the combustion was performed one time before showing that the amount of fluctuation of the torque DLN(i-1) should be cumulatively added is set (XCDLN(i-1) ⁇ "1").
  • step 1309 is proceeded to, where the DLN(i-1) is made zero, then step 1310 is proceeded to.
  • a rotational speed sensor 41 is provided so as to be able to face these projections.
  • the rotational speed sensor 41 generates a pulse each time it faces a projection, therefore the rotational speed sensor 41 generates a pulse every time the input shaft 36, that is, the turbine runner 37, turns 22.5 degrees.
  • the engine drive system experiences torsional vibration of a certain period determined by the natural frequency of the engine drive system. It has been confirmed by experiments that at this time, to find the amount of fluctuation of the rotational speed caused by the torsional vibration, it is preferable to detect the rotational speed of the turbine runner 37 from the time interval of generation of the output pulses by the rotational speed sensor 41 about eight to 10 times during one period of the torsional vibration.
  • the turbine runner 37 fluctuates in speed constantly at a short period. This fluctuation in speed is superposed over the fluctuation in speed of the turbine runner 37 caused by driving on a rough road.
  • the frequency of sampling for calculation of the speed of the output pulse of the rotational speed sensor 41 is changed in accordance with the rotational speed of the turbine runner 17 so as to enable detection of the rotational speed of the turbine runner 17 from eight to 10 times during one period of the torsional vibration. That is, in Fig. 42A and Fig. 42B, P shows the time of generation of the output pulse of the rotational speed sensor 41, while S shows the timing of sampling of the output pulse for calculation of speed. Fig. 42A shows the time when the rotational speed of the turbine runner 37 is low, while Fig. 42B shows the time when the rotational speed of the turbine runner 37 is high. As shown in Fig.
  • step 1550 the average rotational speed NT AV of the turbine runner 37 is calculated from the output pulse of the rotational speed sensor 41.
  • step 1551 whether the average rotational speed NT AV of the turbine runner 37 is lower than a predetermined speed setting, for example, 1800 rpm, or not is judged.
  • a predetermined speed setting for example, 1800 rpm
  • step 1552 is proceeded to, where whether the output pulse of the rotational speed sensor 41 has been generated four times is judged.
  • step 1563 is jumped to, while when the output pulse has been generated four times, step 1553 is proceeded to.
  • NTj-2 is made NTj-3
  • NTj-1 is made NTj-2
  • NTj is made Ntj-1.
  • the previously calculated elapsed time NT360j-1 is subtracted from the currently calculated elapsed time NT360j to calculate the amount of fluctuation DLNT of the elapsed time.
  • NT360j-1 is made NT360j-1, then step 1563 is proceeded to.
  • step 1557 is proceeded to, where whether the output pulse of the rotational speed sensor 41 has been generated eight times or not is judged.
  • step 563 is jumped to, while when the output pulse has been generated eight times, step 1558 is proceeded to.
  • step 1558 the elapsed time Ntj fromj the generatoin of the output pulse eight times before to the currently generated output pulse is caculated.
  • Ntj is made Ntj-1.
  • step 1561 the result of subtraction of the previously calculated elapsed time NT360j-1 fromj the currently calculated elapsed time NT360j is halved so as to calculate the amount of fluctuation DLNT of the elapsed time. Note that the relationship between NT360j-1 and NT360j is shown in Fig. 42B.
  • step 1561 the difference in elapsed time (NT360j-NT360j-1) calculated at step 1561 becomes double the difference in elapsed time (NT360j-NT360j-1) calculated at step 1556, so at step 1561, one-half of (NT360j-NT360j-1) is made DLNT.
  • step 1562 NT360j is made NT360j-1, then step 1563 is proceeded to.
  • step 1563 to step 1582 processing similar to the routine performed from Fig. 13 to Fig. 15 is performed and the average value of the amplitude AMN of the amount of fluctuation DLNT in the elapsed time is calculated.
  • step 1563 the maximum value NTmax when DLNT increases and then decreases is calculated. That is, at step 1563, whether DLNT is larger than the maximum value NTmax or not is judged.
  • step 1566 is jumped to, while when NTmax ⁇ DLNT, step 1564 is proceeded to, where DLNT is made NTmax.
  • step 1565 the increase flag XNXREC showing that DLNT is increasing is set (XNXREC ⁇ 1"), then step 1566 is proceeded to.
  • step 1568 the minimum value NTmin when DLNT decreases, then increases is calculated. That is, at step 1566, whether DLNT is smaller than the minimum value NTmin or not is judged.
  • step 1569 is jumped to, while when NTmin ⁇ DLNT, step 1567 is proceeded to, where DLNT is made NTmin.
  • step 1568 the decrease flag XNNREC showing that DLNT is decreasing is set (XNNREC ⁇ 1"), then step 1569 is proceeded to.
  • step 1563 the routine proceeds from step 1563 to step 1564, where DLNT is made NTmax, then the increase flag XNXREC is set at step 1565.
  • the maximum value NTmax is made TNXREC.
  • the minimum value TNNREC (found by the later explained step 1575) is subtracted from the maximum value TNXREC to calculate the amplitude AMN of DLNT.
  • the initial value of the minimum value NTmin is made DLNT.
  • the increase flag XNXREC is reset (XNXREC ⁇ 0").
  • step 1575 is proceeded to. That is, step 1575 is proceeded to at the time t 4 when DLNT starts to increase.
  • the minimum value NTmin is made TNNREC.
  • the minimum value TNNREC is subtracted from the maximum value TNXREC so as to calculate the amplitude AMN of DLNT.
  • the initial value of the maximum value Ntmax is made DLNT.
  • the decrease flag XNNREC is reset (XNNREC ⁇ 0").
  • the amplitude AMN is added to the cumulative amplitude ⁇ AMN of the amplitude.
  • step 1580 whether the amplitude AMN has been cumulatively added n number of times or not is judged.
  • C 2 is a constant.
  • ⁇ AMN is cleared.
  • Fig. 48 shows the repeated executed main routine.
  • the routine for calculation of the amount of fluctuation of the torque step 1600
  • This routine is shown in the previously explained Fig. 24 and Fig. 25.
  • the routine for calculation of the lean limit feedback correction coefficient FLLFB step 1700
  • the routine for calculation of the injection time step 1800
  • the routine for calculation of the injection time step 1800
  • the other routines step 1900 are executed.
  • step 1701 whether the conditions for updating the lean limit feedback correction coefficient FLLFB stand or not is judged. For example, at the time of engine warmup or when the operating state of the engine is not in the learning region enclosed by the broken lines in Fig. 5, it is judged that the conditions for updating do not stand, while at other times it is judged that the conditions for updating stand.
  • the processing cycle is ended, while when the conditions for updating stand, step 1702 is proceeded to.
  • step 1702 whether either the average value SINPAV1 of the amplitude AMP of the fluctuation of the elapsed time Ta(i) or the average value SINPAV2 of the amplitude AMP of the fluctuation of the DLNT expressing the fluctuation of the rotational speed of the turbine runner 37 exceeds the standard value SINP 0 or not is judged.
  • SINPAV1 and SINPAV2 are both smaller than the standard value SINP 0
  • step 1703 is proceeded to, where the rough road counter CRR is cleared. That is, when SINPAV1 and SINPAV2 are both smaller than the standard value SINP 0 as in the zone Z in Fig. 51, the rough road counter CRR is maintained at zero.
  • the target torque fluctuation value LVLLFB is calculated from the absolute pressure PM in the surge tank 3 and the engine speed N based on the map shown in Fig. 22B.
  • the fluctuation amount judgement values DH(n) and DL(n) are determined in advance as shown in Fig. 28A and the feedback correction values +a 1 , +a 2 , +a 3 , +a 4 , -b 1 , -b 2 , -b 3 , and -b 4 are determined in advance for the regions between the levels of torque fluctuation LVLH(n) and LVLL(n) as shown in Fig. 28B.
  • step 1707 is proceeded to, where whether the mean torque fluctuation value DLNISM calculated in the routine for calculation of the torque fluctuation value shown in Fig. 24 and Fig. 25 is between the levels of torque fluctuation LVLH(n) and LVLL(n) shown in Fig. 28B or not is judged.
  • step 1708 the corresponding feedback correction value DLFB is calculated.
  • step 1709 what lean limit feedback correction coefficient of which learning region shown in Fig. 5 the lean limit feedback correction coefficient FLLBFij to be updated based on the average value of the engine speed N AVE and the average value PM AVE of the absolute pressure in the surge tank 3 found at step 509 of the processing routine of CDLNIX shown in Fig. 20 is is determined.
  • step 1710 the lean limit feedback correction coefficient FLLFBij determined at step 1709 is increased by the feedback correction value DLFB.
  • step 711 is proceeded to, where the learning count value CFLLFB is incremented by exactly 1.
  • step 1712 whether the rough road count value CRR is zero and the learning count value CFLLFB has reached a constant value n or not is judged
  • m is a positive integer.
  • the learning value KBUij is decided on for each learning region corresponding to each learning region of FLLFBij shown in Fig. 5 as shown in Fig. 30.
  • KBUij is added to the value of this difference multiplied by 1/m, therefore the learning value KBUij changes to gradually approach FLLFBij.
  • step 1714 is proceeded to, where the learning counter CFLLFB is cleared.
  • step 1715 is proceeded to, where the rough road counter value CRR is incremented by exactly 1.
  • step 1716 the learning counter CFLLFB is cleared.
  • step 1717 whether a predetermined time TC has elapsed from the start of the countup actionb of the rough road counter CRR or not is judged.
  • step 1704 is proceeded to, therefore the action for updating the lean limit feedback correction coefficient FLLBFij is performed. Since the mean torque fluctuation value DLNISM becomes larger at this time, the FLLFBij increases as shown in Fig. 51. Note that at this time, the action for updating the learning value KBUij is stopped.
  • step 1718 is proceeded to, where whether the engine has operated for eight cycles is judged.
  • step 1719 is proceeded to, where the lean limit feedback correction coefficient FLLFBij is decreased by exactly the predetermined value ⁇ .
  • step 1720 whether FLFBiji has become smaller than the corresponding learning value KBUij or not is judged.
  • step 1721 is proceeded to, where FLLFBij is made KBUij. That is, as shown in Fig. 51, when a predetermined time TC elapses from when SINPAV1 or SINPAV2 exceeds the standard SINP 0 , the lean limit feedback correction coefficient FLLFBij is gradually returned to the learning value KBUij.
  • the lean limit feedback correction coefficient FLLFBij becomes larger as shown in Fig. 51.
  • the air-fuel ratio moves to the rich side and therefore the amount of Nox generated increases.
  • torque fluctuation occurs at this time due to the driving over the rough road and not due to the fluctuation of the combustion pressure.
  • the optimal lean limit feedback correction coefficient FLLFBij at this time substantially matches with the learning value KBUij. Therefore, to suppress the generation of Nox and obtain a good combustion, FLLFBij is gradually returned to the learning value KBUij.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
EP97108963A 1996-06-04 1997-06-04 Méthode de commande de rapport air/carburant dans un moteur à combustion interne Expired - Lifetime EP0811758B1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP14188296A JP3303669B2 (ja) 1996-06-04 1996-06-04 内燃機関の空燃比制御方法
JP141882/96 1996-06-04
JP14176396A JP3156588B2 (ja) 1996-06-04 1996-06-04 内燃機関の空燃比制御方法
JP14188296 1996-06-04
JP14176396 1996-06-04
JP141763/96 1996-06-04

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EP0811758A2 true EP0811758A2 (fr) 1997-12-10
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0849456A2 (fr) * 1996-12-19 1998-06-24 Toyota Jidosha Kabushiki Kaisha Méthode de commande du rapport air-carburant d'un moteur à combusion
GB2329979A (en) * 1997-09-23 1999-04-07 Siemens Ag Controlling running smoothness of an internal combustion engine
EP2019196A1 (fr) * 2006-05-11 2009-01-28 Yanmar Co., Ltd. Moyen de détection du couple d'un moteur
WO2016204672A1 (fr) * 2015-06-15 2016-12-22 Scania Cv Ab Procédé et système pour la détection d'écarts de couple d'un moteur dans un véhicule

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11255282B2 (en) * 2019-02-15 2022-02-22 Toyota Jidosha Kabushiki Kaisha State detection system for internal combustion engine, data analysis device, and vehicle

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Publication number Priority date Publication date Assignee Title
US4691286A (en) * 1984-06-27 1987-09-01 Nippon Soken, Inc. Method and apparatus for detecting combustion variations in internal combustion engine
EP0424630A2 (fr) * 1989-08-25 1991-05-02 Hitachi, Ltd. Méthode et appareil de détection de l'état de combustion dans un moteur à combustion, et méthode et appareil de commande dudit moteur en utilisant lesdits méthode et appareil
EP0610508A1 (fr) * 1992-06-09 1994-08-17 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Methode de detection des rates d'allumage en utilisant les fluctuations de rotation du vilebrequin
JPH07279732A (ja) * 1994-04-08 1995-10-27 Mitsubishi Motors Corp 内燃機関の燃焼制御方法および燃焼制御装置

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WO1995017592A1 (fr) * 1993-12-21 1995-06-29 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Procede d'evaluation de l'etat de combustion d'un moteur a combustion interne et procede et appareil de regulation de l'etat de combustion d'un moteur a combustion interne

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4691286A (en) * 1984-06-27 1987-09-01 Nippon Soken, Inc. Method and apparatus for detecting combustion variations in internal combustion engine
EP0424630A2 (fr) * 1989-08-25 1991-05-02 Hitachi, Ltd. Méthode et appareil de détection de l'état de combustion dans un moteur à combustion, et méthode et appareil de commande dudit moteur en utilisant lesdits méthode et appareil
EP0610508A1 (fr) * 1992-06-09 1994-08-17 Mitsubishi Jidosha Kogyo Kabushiki Kaisha Methode de detection des rates d'allumage en utilisant les fluctuations de rotation du vilebrequin
JPH07279732A (ja) * 1994-04-08 1995-10-27 Mitsubishi Motors Corp 内燃機関の燃焼制御方法および燃焼制御装置

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0849456A2 (fr) * 1996-12-19 1998-06-24 Toyota Jidosha Kabushiki Kaisha Méthode de commande du rapport air-carburant d'un moteur à combusion
EP0849456A3 (fr) * 1996-12-19 1999-11-10 Toyota Jidosha Kabushiki Kaisha Méthode de commande du rapport air-carburant d'un moteur à combusion
US6135089A (en) * 1996-12-19 2000-10-24 Toyota Jidosha Kabushiki Kaisha Method of controlling an air-fuel ratio of an engine
US6155232A (en) * 1996-12-19 2000-12-05 Toyota Jidosha Kabushiki Kaisha Method of controlling an air-fuel ratio of an engine
GB2329979A (en) * 1997-09-23 1999-04-07 Siemens Ag Controlling running smoothness of an internal combustion engine
GB2329979B (en) * 1997-09-23 2001-10-10 Siemens Ag Method for controlling running smoothness
EP2019196A1 (fr) * 2006-05-11 2009-01-28 Yanmar Co., Ltd. Moyen de détection du couple d'un moteur
EP2019196A4 (fr) * 2006-05-11 2012-08-29 Yanmar Co Ltd Moyen de détection du couple d'un moteur
WO2016204672A1 (fr) * 2015-06-15 2016-12-22 Scania Cv Ab Procédé et système pour la détection d'écarts de couple d'un moteur dans un véhicule
US10247124B2 (en) 2015-06-15 2019-04-02 Scania Cv Ab Method and system for detection of torque deviations of an engine in a vehicle

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DE69725929D1 (de) 2003-12-11
DE69725929T2 (de) 2004-07-29
EP0811758B1 (fr) 2003-11-05
EP0811758A3 (fr) 1999-09-01

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