DE19549633C2 - Air=fuel ratio controller for catalyser engine vehicle - Google Patents

Abstract

A controller for the air/fuel ratio of an opposed-cylinder (boxer) type engine and V-6, V-8 or V-12 engines with separate inlet manifolds for the two cylinder banks, joined below the throttle flap, and separate exhaust pipes (5, 7) from each exhaust manifold passing through primary catalysers (21, 22), before being linked by a collector pipe (8) attached to a secondary catalyser (23). Oxygen sensors (25, 26) are provided in the exhaust pipes between manifold and primary catalyser. One feeds a signals to a discriminator circuit (31) to establish a weak or rich condition and both feed signals to a phase difference detector (33). The discriminator outputs to a circuit (32) setting a correction factor for the air/fuel ratio. The phase difference detector outputs to a balancing circuit (34) for the injectors (11, 12).

Description

The invention relates to a method for regulating the force Material-air ratio of an engine with the characteristics of claim 1.

In a known control method of this type (JP 5- 272 382 A) are measuring devices for measuring the fat and lean times separately for each bank and a cor rectification device provided, which on the Regeleinrich treatment in the sense of an adjustment of the fat and lean times acts for both banks.

In the example of a boxer engine with horizontal ge opposite, right and left cylinder banks with the suction system is also in several cylinders right and left inlet pipes downstream of the Dros selventil divided, and the two inlet or intake pipes are with the cylinders over an intake manifold connected. The cylinders are also in the exhaust tract right and left bank with right and left respectively Connect the exhaust pipes via the corresponding exhaust manifold and the right and left exhaust pipes are also closed summarized in a single manifold, one of which End is connected to a muffler.

As an exhaust gas purification system for the one described above A catalyst system is known in the engine, in each case a catalyst in the left exhaust pipe and in the right exhaust gas tube, as well as an additional catalyst in the header hen are. It also has a fuel-air ratio re Gel system of the proposed type an oxygen sensor sor in the right and left exhaust pipe, the Air-fuel ratio based on each cylinder bank from the signals of the right and left oxygen sensors sors is determined to be the appropriate fuel to determine the injection quantity accordingly. With this system the exhaust gas from the catalysts in the right and left exhaust pipes cleaned, whereupon the exhaust gases, which coming from the right and left cylinder banks, further by means of the additional catalyst downstream of the main catalysts are cleaned.

With a fuel-air ratio control method according to the prior art described above will be the force Substance-air ratio separately for each cylinder bank If there are differences in the air-fuel ratio ses or in the sensor output or in the sensor character between the right and the left cylinder bank both fuel-air ratios can be present Values approach the stoichiometric value. The main catalyst cleaning conditions can can be optimized with this method. However, if one Difference between the outputs of the two oxygen sensors, the following difficulty arises. There the exhaust gases flow from the right and left exhaust pipes who summarized upwards of the additional catalyst the, the cleaning condition or the cleaning area tends condition of the additional catalyst, a phase difference between the two oxygen sensor outputs conclude with the result that it is often impossible to find one to achieve sufficient cleaning effect.

As shown in curves (a) and (b) of Fig. 6, who the exhaust gases from the right and left exhaust pipes in the event of an existing phase difference between the outputs of the oxygen sensors of the right and the left bank of the additional catalyst under the Condition that the phases of the fat-lean states differ from one another. As a result, the rich / lean conditions interfere with each other, so that, as shown in curve (c) of FIG. 6 for the additional catalyst, no definite periodic rich / lean changes can be obtained, which leads to deterioration of the cleaning function leads. Accordingly, in the catalyst system with a main catalyst for each cylinder bank and an additional catalyst for both cylinder banks (after collection), the fuel-air ratio of each of the three catalysts must be regulated to an optimal periodic rich / lean state.

An example of the state of the art of a fuel Air ratio control system for one engine with several Cylinder banks are disclosed in JP-POS 64-8332, in which the The air-fuel ratio of each cylinder group is independent from each other on the basis of the oxygen sensor signal Repatriation is regulated. To avoid the difficult speed with regard to the phase difference in the fuel-air ratio ratio between the corresponding cylinder groups an additional auxiliary oxygen sensor downstream of the Collection section of the exhaust pipes arranged, and each The feedback correction coefficient is based on the auxiliary Corrected oxygen sensor output so that the force material-air ratios of the corresponding cylinder groups can be compared.

As a second example of a known fuel-air supply Ratio control system of an engine with several cylinders JP-POS 3-26845 discloses that three fuel Air ratio sensors as in the first example are seen, and that the air-fuel ratio of the two cylinder banks based independently of each other on each outlet of the three air-fuel ratio sen sensors are regulated. Furthermore, one of the benches is on the Auxiliary fuel-air ratio sensor output on poses while the other bank based on the difference the air-fuel ratio between the two banks ken is set so that the said difference between between the two cylinder banks can be eliminated.

Also disclosed as a third example of a known one Air-fuel ratio control system for an engine with several cylinder banks the JP-GM-OS 63-79449 that a Main air-fuel ratio sensor in one of the exhaust gases pipes is housed that an auxiliary fuel-air ratio nissensor is provided in the manifold and that the force air / material ratios of the two banks to the same Ni veau based on the main air-fuel ratio Sorsignal are regulated and also based on the Auxiliary fuel-air ratio sensor signal corrected who the.

With the three control devices described last according to the prior art is an additional oxygen sensor provided in the manifold so that the number of Sauer fabric sensors is increased. Furthermore, in the first and the second example the air-fuel ratio of the two cylinder banks independently and so on corrected the base of the auxiliary oxygen sensor output, that the difference in air-fuel ratio between the cylinder banks can be eliminated. So that's it Control system quite complicated. Furthermore, the third example the two fuel-air ratios of the two cylinder banks based on the same controlled variable regulated when the distribution of the air-fuel ratio it is not uniform. This leads to the difficulty that the fuel / air ratio of the other bank is not specified measure can be regulated.

To remedy these difficulties, the task of Invention, a method with the features of To design the preamble of claim 1 so that even with a difference in the outputs of the right and the left oxygen sensor the use of an auxiliary acid substance sensor or measuring devices for fat / lean time ten of the two banks avoided and the cleaning effect  of the catalyst provided in the header pipe ver be improved.

To achieve this object, the invention provides a ver drive according to claim 1.

It is preferred if the method is also the Features of claim 2.

The invention is schematic below Drawings on an embodiment with others Details explained in more detail. Show it:

Fig. 1 is a block diagram of an entire fuel air system of the invention;

Fig. 2 vibration diagram, which compares the outputs of right and left oxygen sensors.

Fig. 3 is a flowchart for a control procedure for detecting a difference between two oxygen sensors;

Fig. 4 is a flow chart of a control procedure for a correction coefficient set based on the zen Diffe ence between the two oxygen sensors;

Fig. 5 is a block diagram with a modification of the air-fuel ratio control system according to the inven tion, wherein a learning device is additionally provided, and

Fig. 6 is a vibration diagram showing the output signals from oxygen sensors, which are representative of rich-lean conditions of an additional catalyst in a fuel-air ratio control method according to the prior art.

With reference to FIG. 1, a system is for controlling a fuel-air ratio of a Boxer-engine described. The boxer engine 1 is in a right cylinder bank 2 with three cylinders (e.g. # 1, # 3 and # 5) and a left cylinder bank 3 with three cylinders (e.g. # 2, # 4 and # 6) divided. In the gas system, the corresponding cylinders from the right bank 2 communicate with a right exhaust pipe 5 via an exhaust manifold 4 and, in the same way, correspond to the cylinders of the left bank 3 with a left exhaust pipe 7 via an exhaust manifold 6 . Furthermore, the right and left exhaust pipes 5 and 7 are connected to each other via a manifold 8 . Injectors 11 and 12 are arranged in inlet manifolds 9 and 10 of the right and left banks 2 , 3 for fuel injection.

The boxer engine has a triple catalytic converter system 20 . The catalytic system 20 comprises two main catalysts 21 and 22 , which are arranged in the right and left exhaust pipes 5 and 7, respectively, upstream of the manifold 8 , and also a catalytic converter 23 in the manifold 8 in its downstream section to one to form two-stage catalytic system. Correspondingly, toxic components in the exhaust gas of the six cylinders of the right and left cylinder banks 2 and 3 can be cleaned by means of the three catalysts 21 to 23 .

In the air-fuel ratio control system, two oxygen sensors 25 and 26 are provided upstream of the main catalysts 21 and 22 of the right and left exhaust pipes 5 and 7 , respectively, to measure the air-fuel ratio (rich or lean) of the exhaust gas based on the oxygen concentration , The corresponding outputs of the two oxygen sensors 25 and 26 form inputs of a control unit 30 for feedback control of the air-fuel ratios of the right and left cylinder banks 2 and 3 .

The principle of the fuel-air ratio feedback control is described below. When the air-fuel ratios of the right and left banks 2 and 3 are controlled multan based on the output of only the right oxygen sensor 25, the rich / lean change periods of the exhaust gases in the right and left exhaust pipes 5 and 7 synchronize with each other, and the same che periodic fat / lean variation is repeated significantly Lich in the exhaust gas collected in the manifold 8 , so that the cleaning condition for the additional catalyst 23 is optimized. In this case, the air-fuel ratio of the right bank 2 in the vicinity of the stoichiometric fuel-air ratio value can be regulated by means of the right oxygen sensor 25 , so that the cleaning condition of the main catalytic converter 21 is also optimized.

When the output of the left oxygen sensor 26 is detected under the condition that the right oxygen sensor 25 detects the oxygen concentration at the stoichiometric air-fuel ratio, a difference in air-fuel ratio between the two cylinders 2 and 3 can be based on a difference between the output signals of the two oxygen sensors 25 and 26 are discriminated. Therefore, if the fuel-air ratio of the left bank 3 is controlled based on the phase difference between the outputs of the two oxygen sensors 25 and 26 , it is also possible to roughly regulate the fuel-air ratio of the left bank 3 to the stoichiometric air-fuel ratio that the cleaning condition of the main catalyst 22 can be optimized.

Referring to FIG. 1, a control unit 30 determines the fuel injection amount, the ignition timing, etc. The control unit 30 includes a fuel-air ratio discriminating device 31 , a correction coefficient setting device 32 , a difference detecting device 33 , a correcting device 34 , one Basic computing device 35 for calculating a basic injection pulse width, a computing device 36 for calculating the fuel injection pulse width for the right bank 2 and a computing device 37 for the fuel injection pulse width for the left bank 3 .

The output of the oxygen sensor 25 of the right bank 2 is input into the discriminating device 31 . After starting and warming up the engine 1 , the exhaust gas can be cleaned by means of the catalysts. Therefore, the discriminating device 31 discriminates the rich / lean state of the exhaust gas based on the output signal of the oxygen sensor 25 of the right bank 2 . The discrimination result is input to the correction coefficient setting device 32 . The correction coefficient setting device 32 sets an appropriate feedback correction coefficient LAMBDA for the air-fuel ratio according to the discrimination result. The outputs of the two oxygen sensors 25 and 26 of the right and left banks 2 , 3 are entered into the difference detection device 33 . This device 33 detects a difference e between the two output signals of the two oxygen sensors 25 and 26 , ie a difference in the fat / lean state between the two banks 2 and 3 based on the outputs of the two oxygen sensors 25 and 26 . The detected difference signal is input into the correction device 34 . This correction device 34 determines a suitable correction coefficient Ke according to the detected difference between the two sensor signals, ie the difference in the fuel-air ratio between the two banks 2 and 3 .

Various engine operating conditions, such as the air intake amount detected by an air flow meter, the engine speed detected by a crank angle sensor, etc., are input to the arithmetic device 35 for calculating the basic injection pulse width. The computing device 35 calculates a basic injection pulse width Tp based on the detected engine operating conditions. The calculated basic injection pulse width Tp and the feedback correction coefficient LAMBDA are input into the computing device 36 for calculating the fuel injection pulse width of the right bank. The computing device 36 calculates a corresponding fuel injection pulse width TiR using another correction coefficient COEF as follows:

TiR = Tp × LAMBDA × COEF.

An injection signal of the calculated fuel injection pulse width TiR is output to the injector 11 of the right bank 2 .

Furthermore, the basic injection pulse width Tp, the feedback correction coefficient LAMBDA and the correction coefficient Ke are input to the arithmetic device 37 for calculating the fuel injection pulse width of the left bank. The computing device 37 calculates a suitable fuel injection pulse width TiL using a further correction coefficient COEF as follows:

TiL = Tp × LAMBDA × Ke × COEF.

An injection signal with the calculated pulse width TiL is output to the injector 12 of the right bank 3 .

The operation of the air-fuel ratio control system according to the invention is described below. When the engine is running, the exhaust gases of the right and left banks 2 and 3 flow through the right and left exhaust pipes 5 and 7 and thus through the main catalysts 21 and 22 of the catalyst system. Then the exhaust gases from the right and left exhaust pipes are collected in the collecting pipe 8 . The collected gas mixture flows through the additional catalyst 23 . The oxygen concentrations in the gas pipes 5 and 7 are separately detected by the two oxygen sensors 25 and 26 in order to obtain the fuel-air ratios in the right and left cylinder banks, respectively.

Now the output of the oxygen sensor 25 of the right bank is entered into the discrimination device 31 of the control unit 30 . After the engine has warmed up, the exhaust gases can be cleaned by the catalytic converters, with the discriminating device 31 discriminating the rich / lean state of the fuel based on the sensor outputs. Based on the discriminated rich / lean conditions, the correction coefficient setting device 32 sets a feedback correction coefficient LAMBDA of the air-fuel ratio. Starting from the basic injection pulse width Tp, which was obtained from the computing device 35 , and the feedback correction coefficient LAMBDA, which was set by the correction coefficient setting device 32 , the computing device 36 calculates the fuel injection for the fuel injection pulse width of the right bank Pulse widths TiR = Tp × LAMBDA × COEF. Based on the basic injection pulse width Tp determined by the computing device 35 , the feedback correction coefficient LAMBDA obtained from the correction coefficient setting device 32 , and the correction coefficient Ke obtained from the correction device 34 , the computing device calculates 37 for the fuel injection pulse width of the left bank, the fuel injection pulse width TiL = Tp × LAMBDA × Ke × COEF.

Both, the calculated fuel injection pulse width re presenting injection signals are output to the injectors 11 and 12 , so that the fuel injection ge according to the engine operating conditions and the fuel-air ratio conditions of both banks 2 and 3 can be controlled.

Thus, the fuel-air ratio of the right bank 2 , as shown by the solid curve R in Fig. 2 ge, can be feedback-controlled, with a rich / lean variation repeating the stoichiometric fuel-air ratio. Therefore, when the exhaust gas of the right bank 2 is passed through the main catalyst 21 , toxic components can be effectively removed from the exhaust gas.

Under these circumstances, the fuel-air ratio of the left bank 3 is simultaneously controlled on the basis of the output signal from the oxygen sensor 25 of the right bank 2 so that the rich / lean variation of the left bank 3 with the corresponding variation of the right bank 2 syn chronized, as shown by the solid curve L in Fig. 2. Consequently, the exhaust gas collected in the manifold 8 is passed through the additional catalyst 23 during a stable rich / lean period without being disturbed by the rich / lean states of the two banks. Under these conditions, a sufficient catalytic effect can be obtained in the additional catalytic converter 23 , so that it is possible to effectively remove toxic components from the exhaust gases for exhaust gas purification.

In the system described above, the difference detection device 33 detects the difference in air-fuel ratios of the two cylinder banks 2 and 3 based on the outputs of the two oxygen sensors 25 and 26 of the right and left banks 2 and 3 by the fuel-air ratio the left bank 3 to correct. This correction control is described in detail below with reference to the flow diagrams of FIGS . 3 and 4.

The control unit 30 (hereinafter simply referred to as controller) discriminates according to step S1 in FIG. 3 whether the output of the oxygen sensor 25 of the right bank 2 is inverted or not. If the sensor signal from the lean condition to a rich state according to point a or from a rich state to a lean state according to point b in Fig. 2 inverts or transitions, the controller discriminates that the sensor output is inverted. The inverting criterion shown (stoichiometric value) of this inverting level can be replaced by a level at each intermediate point between the maximum fat state and the minimum lean state.

After discriminating the invert state in step S1, the controller activates a timer (in step S2) and checks whether a predetermined time has passed after the sensor output has been inverted in step S3. If "YES", the following steps are taken to prevent fluctuations which could be caused by immediately correcting the air-fuel ratio after inverting the sensor outputs. The controller detects the outputs of the two oxygen sensors 25 and 26 of both cylinder banks 2 and 3 in step S4. Based on the detected output signals, the controller discriminates the difference in air-fuel ratios of the right and left banks 2 and 3 in step S5.

If the fuel-air ratio of the left bank 3 now deviates from that of the right bank 2 to the lean side, as shown by the solid curve L in FIG. 2, the output of the oxygen sensor 26 is lean at both points a and b. If the sensor characteristic of the left bank 3 is the same as that of the right bank 2 , the air-fuel ratio of both banks 2 and 3 may be the same. If the sensor outputs have a difference in spite of the fact that both banks are controlled simultaneously only on the basis of the output of the oxygen sensor 25 of the right bank 2 (eg in the case of "lean" at point a, but "rich" at point b) , this indicates an abnormality of the fuel system, so that it is also possible to use the differential detection as a diagnosis for the fuel system.

In step S5, in which the difference of the air-fuel ratio of the left bank 3 with respect to that of the right bank 2 is detected when the air-fuel ratio of the left bank is the same as that of the right bank 2 (that is, the output values of the two oxygen sensors 25 and 26 are the same on the rich or lean side), the controller resets the timer in step S7 and ends the control procedure. If, on the other hand, the fuel-air ratio of the left bank 3 differs from that of the right bank 2 (ie if the output value of one of the two oxygen sensors 25 , 26 is on the rich side and that of the other oxygen sensor is on the lean side), the controller forms correction coefficient Ke in step S6 and then resets the timer in step S7. If the fuel-air ratio deviates toward the lean side as shown in the solid curve L in FIG. 2, the correction coefficient Ke is set to Ke <1.

Thus, when the correction coefficient Ke is set to Ke <1, the fuel injection pulse width TiL of the left bank 3 is calculated based on this correction coefficient Ke, and the injection signal is output with a fuel-air ratio value thus corrected.

In detail, as shown in FIG. 4 discriminates the controller after setting the correction coefficient Ke Ke <1 (in step S11) whether this correction animals, the first correction after the Inver the output of the oxygen sensor 25 of the right bank 2 in step S12. In the case of "YES", the control increases the correction coefficient Ke with a large proportional increase rate (+ PR) to sharply correct the air-fuel ratio in step S13. In the case of "NO" in a second or more frequent correction, the controller increases the correction coefficient Ke with a small integral growth rate (+ I) in order to correct the air-fuel ratio weakly or "smoothly" according to step S14.

In contrast, when the air-fuel ratio is shifted in phase to the rich side, and thus the correction coefficient is set to Ke <1, the control proceeds from step S11 to step S15 and further to steps S16 or S17. Thus, the controller discriminates whether this correction is the first correction after inverting the output of the oxygen sensor 26 of the left bank 3 according to step S15. In the case of "YES", the controller lowers the correction coefficient Ke with a large proportional decrease rate (-PR) to correct the air-fuel ratio significantly or sharply in step S16. In the case of "NO" after two or more corrections, the controller lowers the correction coefficient Ke at a small integral rate (-I) to weakly or gently correct the air-fuel ratio in step S17.

Under these conditions, the fuel-air ratio of the left bank 3 , as shown by the dash-dotted curve L 'as shown in Fig. 2, is increasingly corrected to bring the fuel-air ratio of the bank 2 closer. Accordingly, when the exhaust gas of the left bank 3 is passed through the main catalyst 22 , the toxic components of the exhaust gas 12 can be effectively removed. As described above, in the catalyst system, the air-fuel ratios in the two main catalysts 21 and 22 for the right and left banks 2 and 3 , as well as for the additional catalyst 23 in the manifold 8, can be optimized so that toxic inventory parts in the exhaust gases can be removed most effectively by means of the two-stage cleaning with the result that the overall efficiency of the cleaning is improved.

Fig. 5 shows a modification of the invention in which the air-fuel ratio is controlled by means of learning effects. This modification is based on the system of FIG. 1 with the exception that a fuel-air ratio learning device 40 is connected upstream of the correction coefficient setting device 32 and that a correction learning device 41 is connected upstream of the correction device 34 . The air-fuel ratio learning device 40 stores a learning map or table with values representative of the return correction coefficient LAMBDA for the air-fuel ratio in accordance with the various engine operating conditions (speed, load, etc.) in an updatable form. Thus, the feedback correction coefficient LAMBDA can be output based on a difference between the previous value and the current Wen, thereby further improving the responsiveness of the air-fuel ratio control.

The correction learning device 41 stores the difference correction coefficients Ke in the learning table, and the correction value is updated whenever the phase difference is corrected. During the correction, a learning process is carried out such that an ongoing correction is made by multiplying the previous value by the updated value. It is therefore possible to minimize the fluctuations in the air-fuel ratio.

As described above, the fuel air ratio control system and the procedure according to the Er invention for an engine with right and left cylinders benches with a two-stage catalyst system Main catalysts and an additional catalyst and egg nem in each exhaust pipe upstream of the main catalytic converter arranged oxygen sensor the fuel air ver Ratios of both banks simultaneously starting from the end output signal controlled only one oxygen sensor, and that Air-fuel ratio of the other cylinder bank corresponding to the difference between the outputs of the corrected both oxygen sensors. So it is possible light, based on the fuel-air ratio of both banks on the difference between the two oxygen sensor Regulate outputs appropriately. As a result, the Rei cleaning capacity of the additional catalyst in the manifold be better used.

Furthermore, the air-fuel ratios of both Banks simultaneously based on the output of one of the the oxygen sensors are controlled so that the rain is simplified. Since only two oxygen sensors turned on the number of oxygen sensors is reduced changed. Furthermore, based on the difference between the two oxygen sensors back to their causes close so that it is possible to light the fuel system to diagnose.

In addition, the air-fuel ratio rule is carried out using learning effects, can the fuel-air ratio of the corrected bank ba based on a currently learned correction coefficient Getting corrected. This enables minimizing the Fluctuations in the air-fuel ratio.

Claims (2)

1. A method for regulating the fuel / air ratio of an engine with a first cylinder bank ( 2 ) on one side of the engine, a second cylinder bank ( 3 ) on the other side of the engine, a first inlet pipe ( 9 ), a second inlet pipe ( 10 ) connected to the second cylinder bank, a first exhaust pipe ( 5 ) connected to the first cylinder bank for discharging gases from the first cylinder bank, a second exhaust pipe ( 7 ) connected to the second cylinder bank for discharging gases from the second cylinder bank, a manifold ( 8 ) connected to the first and the second exhaust pipe for collecting the gases coming from these exhaust pipes, a first catalytic converter ( 21 ) in the first exhaust pipe (S) for cleaning those from the first Cylinder bank ( 2 ) coming exhaust gases, egg nem a second catalyst ( 22 ) in the second exhaust pipe ( 7 ) for cleaning the gases coming from the two th bank ( 3 ), one Additional catalyst ( 23 ) in the manifold ( 8 ) for further cleaning of the exhaust gases coming from the first and second exhaust pipes, egg nem first oxygen sensor ( 25 ) in the first exhaust pipe ( 5 ) between the first cylinder bank and the first catalyst for detecting a first oxygen concentration in the first exhaust pipe and for emitting a first oxygen concentration signal, egg nem a second oxygen sensor ( 26 ) in the second exhaust pipe ( 7 ) between the second cylinder bank and the second catalyst for detecting a second oxygen concentration in the second exhaust pipe and for emitting one second oxygen concentration signal, a discrimination device ( 31 ) for the fuel / air ratio, which discriminates a rich / lean state in the first exhaust pipe ( 5 ) and emits a discrimination signal on the first oxygen concentration signal, a correction coefficient setting device ( 32 ) which, based on the discrimination signal, has a feedback hr correction coefficient for the air / fuel ratio (LAMBDA) is based on the discriminated rich / lean state and outputs a correction signal, a first computing device ( 36 ) which, based on the correction signal, has a first fuel injection pulse width (TiR ) for the first cylinder bank ( 2 ) based on a basic injection pulse width (Tp) and the set feedback correction coefficient (LAMBDA) for the air-fuel ratio, and a second computing device ( 37 ) which has a second fuel injection pulse width (TiL) for calculates the second cylinder bank, characterized in that
that a difference (e) between the fuel / air ratios of the first and the second cylinder bank is detected based on the two measured oxygen concentrations and a difference signal is output;
starting from the difference signal, a correction coefficient (Ke) corresponding to the difference (e) it detects and a corrected difference signal is output and
depending on the correction signal and the corrected difference signal in the second computing device ( 37 ), the second fuel injection pulse width (TiL) is calculated based on a basic injection width signal (Tp) from a basic injection pulse width calculation device ( 35 ) by the fuel / air ratio to be adjusted to an optimal value in all engine operating conditions. 2. The method according to claim 1, characterized in that
stored and updated in a fuel / air ratio learning device ( 40 ) which forms part of the correction coefficient setting device ( 32 ), feedback correction coefficients (LAMBDA) for the fuel / air ratio, which are determined according to various operating conditions, and that a differential correction coefficient between a previous value and a current value is given, and
that various correction coefficients (Ke) defined in accordance with the various operating conditions of the engine are stored and updated in a correction learning device ( 41 ) which is part of the correction device, and that a correction coefficient (Ke) is output based on the previous value becomes.