JP5890681B2 - Engine control system - Google Patents

Description

  The present invention relates to an engine control system.

  In recent years, vehicles using gaseous fuel have attracted attention in order to improve fuel efficiency while taking environmental measures. One typical example of such a vehicle is a bi-fuel engine system that selectively switches between liquid fuel such as gasoline and gaseous fuel such as compressed natural gas (CNG) and supplies it to a single engine. Vehicle equipped with.

  Many of the above-described bi-fuel engine systems have been developed so that gaseous fuel can be used in an engine system that uses liquid fuel. For this reason, the engine control system of the bi-fuel engine system has an additional control device suitable for engine control when gaseous fuel is selected, compared to a control device suitable for engine control when liquid fuel is selected. Often configured.

Patent Document 1 below discloses a technique for maintaining a good exhaust gas state with a simple configuration in a system in which a non-gasoline fuel control device is added to a gasoline engine system equipped with a gasoline control device. . Specifically, in Patent Document 1 below, the output signal from the O ₂ sensor provided in the exhaust pipe is shaped by the waveform shaping means and then input to the gasoline control device to maintain a good exhaust gas state. ing.

JP 2008-69637 A

By the way, in the technique disclosed in Patent Document 1 described above, the output signal from the O ₂ sensor is simply shaped by the waveform shaping means and then input to the gasoline control device. It is thought that there is nothing to do. However, the cited document 1 has a problem that high-precision air-fuel ratio feedback control cannot be realized because the output signal from the O ₂ sensor is simply waveform-shaped.

  Here, as is well known, air-fuel ratio feedback control refers to controlling the fuel injection amount so that the air-fuel ratio becomes a target value (theoretical air-fuel ratio) in engine operation control. In general air-fuel ratio feedback control, if the air-fuel ratio is “rich” with respect to the target value, the feedback correction amount is set so that the fuel injection amount decreases, and the air-fuel ratio is “lean” with respect to the target value. If so, the air-fuel ratio is converged to the target value by setting the feedback correction amount so that the fuel injection amount increases.

  If the accuracy of the above air-fuel ratio feedback control is poor, the state of the exhaust gas may deteriorate, affecting the environment and reducing the fuel efficiency. For this reason, in the bi-fuel engine system, in order to improve the fuel efficiency while taking environmental measures, it is highly accurate whether the liquid fuel is used or the gaseous fuel is used. It is necessary to perform fuel ratio feedback control.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine control system capable of realizing highly accurate air-fuel ratio feedback control according to the fuel used.

In order to solve the above problems, an engine control system of the present invention is an engine control system that selectively switches between first and second fuels to perform operation control of a single engine, and that exhausts exhausted from the engine. A sensor for detecting the amount of residual oxygen in the gas, and an input terminal to which a detection signal of the sensor can be input, and controls the operation of the engine by the first fuel and is a signal input from the input terminal A first control device that performs air-fuel ratio feedback control so that the air-fuel ratio becomes a target air-fuel ratio, an input unit to which a detection signal of the sensor is input, and the input when the second fuel is selected A second control device having a correction unit that corrects the detection signal input to the unit, and an output unit that outputs the detection signal corrected by the correction unit to the input end of the first control device. It is characterized.
Further, in the engine control system of the present invention, the correction unit has an air-fuel ratio when the second fuel is selected with respect to a relationship between the air-fuel ratio when the first fuel is selected and the output of the sensor. The detection signal input to the input unit is corrected according to the amount of deviation in the relationship with the output of the sensor.
In the engine control system of the present invention, when the first fuel is selected, the correction unit outputs the detection signal input to the input unit to the output unit without correcting the detection signal. It is said.
Further, in the engine control system of the present invention, when the second control device performs operation control of the engine with the second fuel, and the first control device selects the second fuel, A control amount related to air-fuel ratio feedback control is output to the second control device.

  According to the present invention, when the second fuel is selected, the detection signal from the sensor input to the input unit of the second control device is corrected by the correction unit, and the corrected detection signal is output from the output unit. Since the input is made to the input terminal of the first control device, the change in the sensor characteristic that occurs when the second fuel is selected is corrected, so that even when the second fuel is selected, high accuracy is achieved. The air / fuel ratio feedback control can be realized.

It is a block diagram which shows the principal part structure of the engine control system by one Embodiment of this invention. In one embodiment of the present invention, it is a diagram for explaining a characteristic change of the O ₂ sensor caused when the gaseous fuel is selected. It is a figure for demonstrating the effect in one Embodiment of this invention.

  Hereinafter, an engine control system according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, control of a bi-fuel engine system that selectively switches between liquid fuel (first fuel) such as gasoline and gaseous fuel (second fuel) such as compressed natural gas (CNG) and supplies the fuel to a single engine. An engine control system that performs the above will be described as an example.

  FIG. 1 is a block diagram showing a main configuration of an engine control system according to an embodiment of the present invention. As shown in FIG. 1, the engine control system 1 of the present embodiment includes a sensor group 10, a control target group 20, a fuel changeover switch 30, a first ECU (Electronic Control Unit) 40 (first control device), and a second ECU 50 (first 2 control device), liquid fuel or gaseous fuel is supplied to the engine to control the operation of the engine.

The sensor group 10 includes a crank angle sensor 11, an intake pressure sensor 12, an intake air temperature sensor 13, a throttle opening sensor 14, a coolant temperature sensor 15, an O ₂ sensor 16 (sensor), and the like for detecting the state of the engine. Provided. The crank angle sensor 11 is, for example, an electromagnetic pickup sensor, and outputs a pair of pulse signals having different polarities to the first ECU 40 and the second ECU 50 each time the crankshaft of the engine rotates by a certain angle.

  The intake pressure sensor 12 is installed in the intake pipe of the engine so that the sensitive part is exposed to the intake flow path, and outputs an intake pressure signal corresponding to the internal pressure (intake pressure) of the intake pipe to the first ECU 40. The intake air temperature sensor 13 is installed in the intake pipe of the engine so that the sensitive part is exposed to the intake flow path, and outputs an intake air temperature signal corresponding to the internal temperature (intake air temperature) of the intake pipe to the first ECU 40. The throttle opening sensor 14 outputs to the first ECU 40 a throttle opening signal corresponding to the opening of a throttle valve provided in the intake pipe of the engine.

The coolant temperature sensor 15 outputs a coolant temperature signal corresponding to the engine coolant temperature to the first ECU 40. The O ₂ sensor 16 is an oxygen sensor using, for example, zirconia as a gas detection substance, and is installed in the exhaust pipe of the engine so that the gas contact portion is exposed to the exhaust flow path. The oxygen concentration of the exhaust gas (residual oxygen) The oxygen concentration signal indicating the amount) is output to the second ECU 50.

  The control target group 20 includes an ignition coil 21, a liquid fuel injection valve 22, a fuel pump 23, a gas fuel injection valve 24, a cutoff valve 25, and the like, and is provided for operating the engine. The ignition coil 21 is a transformer composed of a primary winding and a secondary winding, boosts an ignition signal supplied from the first ECU 40 to the primary winding, and supplies the boosted signal from the secondary winding to the engine spark plug.

  The liquid fuel injection valve 22 is an electromagnetic valve installed in the intake pipe so that the injection port is exposed in the intake flow path, and is supplied from the liquid fuel tank according to the fuel injection valve drive signal supplied from the first ECU 40. Liquid fuel is injected from the injection port. The fuel pump 23 pumps out the liquid fuel in the liquid fuel tank according to the pump drive signal supplied from the first ECU 40 and pumps it to the fuel inlet of the liquid fuel injection valve 22.

  The gaseous fuel injection valve 24 is an electromagnetic valve installed in the intake pipe so that the injection port is exposed in the intake passage, and is supplied from the gaseous fuel tank in accordance with the fuel injection valve drive signal supplied from the second ECU 50. Gas fuel is injected from the injection port. The shutoff valve 25 is an electromagnetic valve inserted in a gaseous fuel supply path from the gaseous fuel tank to the regulator, and the gaseous fuel from the gaseous fuel tank is supplied to the gaseous fuel according to the cutoff valve drive signal supplied from the second ECU 50. Whether to supply to the injection valve 24 is switched.

  The fuel change-over switch 30 is a switch that allows the fuel to be changed by a manual operation. The state of the switch, that is, whether the liquid fuel is selected as the fuel used in the engine or the gaseous fuel is selected. A fuel designation signal is output to the second ECU 50.

  The first ECU 40 includes a waveform shaping circuit 41, a rotation speed counter 42, an A / D converter 43, an ignition circuit 44, a fuel injection valve drive circuit 45, a pump drive circuit 46, a ROM (Read Only Memory) 47a, and a RAM (Random Access Memory). ) 47b, a communication circuit 48, and a CPU (Central Processing Unit) 49. The first ECU 40 having such a configuration performs engine operation control and air-fuel ratio feedback control using liquid fuel.

  The waveform shaping circuit 41 shapes the pulse signal from the crank angle sensor 11 into a square wave pulse signal, and outputs it to the rotation speed counter 42 and the CPU 49. In other words, this square-wave pulse signal is a signal having one cycle as the time required for the crankshaft to rotate by a certain angle. Hereinafter, the square-wave pulse signal output from the waveform shaping circuit 41 is referred to as a crank pulse signal.

  The rotation speed counter 42 calculates the engine rotation speed based on the crank pulse signal from the waveform shaping circuit 41 and outputs the calculation result to the CPU 49. The A / D converter 43 includes an intake pressure signal from the intake pressure sensor 12, an intake air temperature signal from the intake air temperature sensor 13, a throttle opening signal from the throttle opening sensor 14, a cooling water temperature signal from the cooling water temperature sensor 15, And an oxygen concentration signal (details will be described later) input from the input terminal T1, and converts them into digital signals (intake pressure value, intake air temperature value, throttle opening value, cooling water temperature value, oxygen concentration value). To the CPU 49.

  The ignition circuit 44 includes a capacitor that stores electric power supplied from a battery (not shown), and ignites the primary winding of the ignition coil 21 by discharging the electric power stored in the capacitor in response to a request from the CPU 49. Output a signal. The fuel injection valve drive circuit 45 generates a fuel injection valve drive signal and outputs it to the liquid fuel injection valve 22 in response to a request from the CPU 49. The pump drive circuit 46 generates a pump drive signal in response to a request from the CPU 49 and outputs it to the fuel pump 23.

  The ROM 47a is a non-volatile memory that stores in advance an engine control program for realizing various functions of the CPU 49 and various setting data. The RAM 47b is a volatile memory used for temporarily storing various data used in the engine control program when the CPU 49 executes the engine control program and performs various operations. The communication circuit 48 is connected to the second ECU 50 via the communication cable C <b> 1 and performs data communication with the second ECU 50 under the control of the CPU 49.

  The CPU 49 performs engine operation control with liquid fuel according to the engine control program stored in the ROM 47a. Specifically, the crank pulse signal from the waveform shaping circuit 41, the engine speed from the speed counter 42, and the digital signal from the A / D converter 43 (intake pressure value, intake temperature value, throttle opening value, Based on various information from the second ECU 50 obtained through the communication circuit 48 and the coolant temperature value and the oxygen concentration value, engine operation control with liquid fuel is performed.

  More specifically, the CPU 49 monitors the rotation state of the crankshaft (in other words, the piston position in the cylinder) based on the crank pulse signal from the waveform shaping circuit 41. Then, when the piston reaches a position corresponding to the ignition timing, the ignition circuit 44 is requested to output an ignition signal, and the ignition coil 21 is ignited.

  When the fuel indicated by the fuel designation signal from the second ECU 50 received by the communication circuit 48 is liquid fuel, the CPU 49 performs liquid fuel injection control. That is, the CPU 49 requests the pump drive circuit 46 to generate a pump drive signal, and when the piston reaches a position corresponding to the fuel injection timing, the fuel injection valve drive circuit 45 sends a fuel injection valve drive signal. Liquid fuel injection by the liquid fuel injection valve 22 is performed.

  Further, the CPU 49 performs air-fuel ratio feedback control while referring to the oxygen concentration value from the A / D converter 43 in addition to the above-described engine operation control by the liquid fuel. Specifically, the CPU 49 calculates the air-fuel ratio based on the oxygen concentration value from the A / D converter 43, and if the air-fuel ratio is “rich” with respect to the target air-fuel ratio, the fuel injection amount decreases. Such a feedback correction amount is calculated, and if the air-fuel ratio is “lean” with respect to the target air-fuel ratio, a feedback correction amount that increases the fuel injection amount is calculated.

  When the fuel indicated by the fuel designation signal from the second ECU 50 received by the communication circuit 48 is a liquid fuel, the CPU 49 corrects the fuel injection amount using the feedback correction amount obtained by the calculation. Then, the liquid fuel injection valve 22 is controlled so that liquid fuel corresponding to the corrected fuel injection amount is injected into the engine. On the other hand, when the fuel indicated by the fuel designation signal is gaseous fuel, the CPU 49 sends the feedback correction amount (control amount related to the air-fuel ratio feedback control) obtained by the calculation via the communication circuit 48. To the second ECU 50.

  The second ECU 50 includes a waveform shaping circuit 51, a rotation speed counter 52, an A / D converter 53 (input unit), a D / A converter 54 (output unit), a fuel injection valve drive circuit 55, a shutoff valve drive circuit 56, and a ROM 57a. RAM 57b, communication circuit 58, and CPU 59 (correction unit). The second ECU 50 having such a configuration performs engine operation control using gaseous fuel.

  The waveform shaping circuit 51 shapes the pulse signal from the crank angle sensor 11 into a square wave pulse signal (crank pulse signal) and outputs it to the rotation number counter 52 and the CPU 59. The rotation speed counter 52 calculates the engine rotation speed based on the crank pulse signal from the waveform shaping circuit 51 and outputs the calculation result to the CPU 59.

The A / D converter 53 receives the oxygen concentration signal from the O ₂ sensor 16 as an input, converts this oxygen concentration signal into a digital signal (oxygen concentration value), and outputs it to the CPU 59. The D / A converter 54 converts the oxygen concentration value (details will be described later) corrected by the CPU 59 into an analog signal (oxygen concentration signal), and the converted analog signal is connected to the input terminal T1 of the first ECU 40. The signal is output to the first ECU 40 via the signal line C2.

  The fuel injection valve drive circuit 55 generates a fuel injection valve drive signal in response to a request from the CPU 59 and outputs it to the gaseous fuel injection valve 24. The shutoff valve drive circuit 56 generates a shutoff valve drive signal in response to a request from the CPU 59 and outputs it to the shutoff valve 25. The ROM 57a is a non-volatile memory that stores in advance an engine control program for realizing various functions of the CPU 59 and various setting data. The RAM 57b is a volatile memory used for temporarily storing various data used in the engine control program when the CPU 59 executes the engine control program and performs various operations. The communication circuit 58 is connected to the first ECU 40 via the communication cable C <b> 1 and performs data communication with the first ECU 40 under the control of the CPU 59.

  The CPU 59 performs engine operation control using gaseous fuel according to the engine control program stored in the ROM 57a. Specifically, the fuel designation signal input from the fuel changeover switch 30, the crank pulse signal input from the waveform shaping circuit 51, the engine speed obtained from the speed counter 52, and the first ECU 40 via the communication circuit 58. Based on the various information obtained from the above, engine operation control with gaseous fuel is performed.

  More specifically, the CPU 59 performs gaseous fuel injection control when the fuel indicated by the fuel designation signal from the fuel changeover switch 30 is gaseous fuel. That is, the CPU 59 requests the cutoff valve drive circuit 56 to generate a cutoff valve drive signal to open the cutoff valve 25, and at the time when the piston reaches a position corresponding to the fuel injection timing, By requesting the circuit 55 to generate a fuel injection valve drive signal, the gaseous fuel is injected by the gaseous fuel injection valve 24.

  In addition, when the fuel indicated by the fuel designation signal is gaseous fuel, the CPU 59 corrects the fuel injection amount using the feedback correction amount received from the first ECU 40 received by the communication circuit 58, and after the correction The gaseous fuel injection valve 24 is controlled so that the fuel for the fuel injection amount is injected into the engine. That is, the CPU 59 causes the air-fuel ratio feedback control performed by the first ECU 40 to be realized via the second ECU 50 when the gaseous fuel is selected.

Further, the CPU 59 corrects the oxygen concentration value from the A / D converter 53 and supplies the corrected oxygen concentration value to the D / A converter 54 when the fuel indicated by the fuel designation signal is gaseous fuel. Perform output processing. Specifically, the CPU 59 has a relationship between the air-fuel ratio when the gaseous fuel is selected and the output of the O ₂ sensor 16 with respect to the relationship between the air-fuel ratio when the liquid fuel is selected and the output of the O ₂ sensor 16. The oxygen concentration value from the A / D converter 53 is corrected according to the deviation amount.

Such correction is performed in order to realize highly accurate air-fuel ratio feedback control even when gaseous fuel is selected. FIG. 2 is a diagram for explaining the characteristic change of the O ₂ sensor that occurs when gaseous fuel is selected in one embodiment of the present invention. As shown in FIG. 2, the O ₂ sensor 16 has a configuration in which platinum-based electrodes are attached to both surfaces of zirconia as a gas detection substance. From the oxygen concentration side (sensor side) to the low side (exhaust flow channel side). The oxygen concentration is detected by an electromotive force generated by the movement of oxygen ions.

Here, when the gaseous fuel is selected, the concentration of hydrogen (H ₂ ) in the exhaust gas increases (for example, increases by about 2 times) compared to the case where the liquid fuel is selected, and FIG. As shown, the amount of hydrogen ions moving inside the zirconia from the exhaust flow path side to the sensor side increases. Then, a large electromotive force is generated by the increased amount of hydrogen ions, which increases the output of the O ₂ sensor 16. This means that the characteristic of the O ₂ sensor 16 has changed to a characteristic for detecting an oxygen concentration higher than the actual oxygen concentration.

Since the air-fuel ratio calculated using the oxygen concentration signal output from the O ₂ sensor 16 with such characteristics changed is “richer” than the actual air-fuel ratio, the accuracy of the air-fuel ratio feedback control decreases. . In the present embodiment, the gaseous fuel is selected by correcting the oxygen concentration signal (the oxygen concentration value from the A / D converter 53) output from the O ₂ sensor 16 whose characteristics have changed as described above. Even in such a case, highly accurate air-fuel ratio feedback control is realized.

Specifically, the CPU 59 uses, for example, a correction table stored in the ROM 57a (the characteristic change of the O ₂ sensor 16 described above (gas fuel with respect to the relationship between the air-fuel ratio when liquid fuel is selected and the output of the O ₂ sensor 16). The oxygen concentration value from the A / D converter 53 is corrected using a table that can correct the deviation amount of the relationship between the air-fuel ratio and the output of the O ₂ sensor 16). This correction table is a table in which the correction amount is defined for each value of the oxygen concentration signal output from the O ₂ sensor 16, and is created by conducting an experiment in advance.

  In order to realize highly accurate air-fuel ratio feedback control, it is desirable to correct the oxygen concentration value from the A / D converter 53 using the above correction table. However, if the hydrogen concentration in the exhaust gas does not change significantly during air-fuel ratio feedback control, correction is performed using a correction value that is fixed in advance without using a correction table. May be. When such a correction value is used, the processing amount of the CPU 59 can be reduced as compared with the case where a correction table is used.

When the fuel indicated by the fuel designation signal from the fuel changeover switch 30 is liquid fuel, the CPU 59 outputs the oxygen concentration value from the A / D converter 53 to the D / A converter 54 without correcting it. . This is because when the liquid fuel is selected, the characteristic change of the O ₂ sensor 16 that occurs when the gaseous fuel is selected does not occur, and thus correction is not necessary. Note that the CPU 59 also has a function of controlling the communication circuit 58 to transmit a fuel designation signal input from the fuel changeover switch 30 to the first ECU 40.

  Next, the operation of the engine control system having the above configuration will be described. In the following, for the sake of simplicity, only the operation related to the air-fuel ratio feedback control will be described. The operation when liquid fuel is selected by the fuel selector switch 30, the gaseous fuel is selected by the fuel selector switch 30. The operation in such a case will be described in order.

<Operation when liquid fuel is selected>
When liquid fuel is selected by manually operating the fuel switch 30, a fuel designation signal indicating that the liquid fuel has been selected is output from the fuel switch 30 to the CPU 59 of the second ECU 50. Then, the CPU 59 controls the communication circuit 58 to transmit a fuel designation signal to the first ECU 40 and outputs it to the D / A converter 54 without correcting the oxygen concentration value from the A / D converter 53. Thereby, the oxygen concentration signal output from the O ₂ sensor 16 is input to the input terminal T1 of the first ECU 40 without being corrected by the second ECU 50.

  When the communication circuit 48 receives the fuel designation signal from the second ECU 50, the CPU 49 of the first ECU 40 reads out the target air-fuel ratio from the ROM 47a and performs air-fuel ratio feedback control using the target air-fuel ratio. Specifically, the CPU 49 calculates the air-fuel ratio based on the oxygen concentration value output from the A / D converter 43 (the oxygen concentration value that has not been corrected by the second ECU), and this air-fuel ratio is the target air-fuel ratio. If “rich”, the feedback correction amount is calculated so that the fuel injection amount decreases. If the calculated air-fuel ratio is “lean” with respect to the target air-fuel ratio, the CPU 49 determines that the fuel injection amount is A feedback correction amount that increases is calculated.

  Then, the CPU 49 corrects the fuel injection amount using the feedback correction amount obtained by the calculation, and controls the liquid fuel injection valve 22 so that liquid fuel corresponding to the corrected fuel injection amount is injected into the engine. . The fuel injection amount before correction is a value calculated by the CPU 49 in advance based on information indicating the engine operating state such as the engine speed and the throttle opening value.

<Operation when gaseous fuel is selected>
When the gas is selected by manually operating the fuel switch 30, a fuel designation signal indicating that the gas fuel has been selected is output from the fuel switch 30 to the CPU 59 of the second ECU 50. Then, the CPU 59 controls the communication circuit 58 to transmit the fuel designation signal to the first ECU 40, reads the correction table from the ROM 57a, corrects the oxygen concentration value from the A / D converter 53, and corrects the corrected oxygen concentration value. Is output to the D / A converter 54. Thus, the oxygen concentration signal corrected by the second ECU 50 is input to the input terminal T1 of the first ECU 40.

  When the communication circuit 48 receives the fuel designation signal from the second ECU 50, the CPU 49 of the first ECU 40 reads out the target air-fuel ratio from the ROM 47a and performs air-fuel ratio feedback control using the target air-fuel ratio. Specifically, the CPU 49 calculates the air-fuel ratio based on the oxygen concentration value output from the A / D converter 43 (the oxygen concentration value corrected by the second ECU), and the relationship between the air-fuel ratio and the target air-fuel ratio. A feedback correction amount corresponding to (“rich” or “lean”) is calculated. Then, the CPU 49 controls the communication circuit 48 and transmits the feedback correction amount obtained by the calculation to the second ECU 50.

  When the feedback correction value transmitted from the first ECU 40 is received by the communication circuit 58, the CPU 59 of the second ECU 50 corrects the fuel injection amount using the feedback correction amount. Then, the gaseous fuel injection valve 24 is controlled so that gaseous fuel corresponding to the corrected fuel injection amount is injected into the engine.

FIG. 3 is a diagram for explaining an effect in one embodiment of the present invention. The graph shown in FIG. 3 is a graph showing the characteristics of the O ₂ sensor 16, where the horizontal axis represents the air-fuel ratio and the vertical axis represents the output voltage of the O ₂ sensor 16. As shown in FIG. 3, when the liquid fuel is selected, the target air-fuel ratio R1 is assumed when the output voltage of the O ₂ sensor 16 is V2.

When the gaseous fuel is selected, the characteristic change of the O ₂ sensor 16 occurs. For example, even if the actual air-fuel ratio is the target air-fuel ratio R1, the output voltage of the O ₂ sensor 16 is higher than V2. V1. Then, the air-fuel ratio calculated based on the output voltage of the O ₂ sensor 16 becomes “rich” with respect to the target air-fuel ratio R1 (the air-fuel ratio deviated by δ from the target air-fuel ratio R1). Air-fuel ratio feedback control is performed so that the air-fuel ratio deviates from the fuel ratio R1.

On the other hand, in this embodiment, since the CPU 59 of the _second ECU 50 corrects the output voltage of the O ₂ sensor 16 so that the voltage is changed from V1 to V2, it is calculated based on the output voltage of the O ₂ sensor 16. The air / fuel ratio becomes the original target air / fuel ratio R1. In this way, the amount of deviation of the air-fuel ratio due to the characteristic change of the O ₂ sensor 16 ([delta]) is being addressed by the output voltage of the O ₂ sensor 16 is corrected, realizing an air-fuel ratio feedback control with high precision can do.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be freely changed within the scope of the present invention. For example, in the above embodiment, the case where liquid fuel such as gasoline and gaseous fuel such as compressed natural gas (CNG) are used has been described as an example. However, the present invention uses a fuel other than gasoline and compressed natural gas. It is also applicable to.

1 ... engine control system, 16 ... _{O 2} sensor, 40 ... first 1ECU, 50 ... first 2ECU, 53 ... A / D converter, 54 ... D / A converter, 59 ... CPU, T1 ... input

Claims (4)

An engine control system for selectively operating a first engine and a second fuel to control operation of a single engine,
A sensor for detecting a residual oxygen amount of exhaust gas discharged from the engine;
It has an input end to which the detection signal of the sensor can be input, and controls the operation of the engine by the first fuel, and the air-fuel ratio becomes the target air-fuel ratio based on the signal input from the input end A first control device for performing air-fuel ratio feedback control,
An input unit to which the detection signal of the sensor is input, a correction unit for correcting the oxygen concentration value of the detection signal input to the input unit when the second fuel is selected, and the correction unit An engine control system comprising: a second control device having an output unit that outputs a detection signal to an input terminal of the first control device.   The correction unit is a deviation amount of a relationship between an air-fuel ratio when the second fuel is selected and an output of the sensor with respect to a relationship between the air-fuel ratio when the first fuel is selected and the output of the sensor. The engine control system according to claim 1, wherein the detection signal input to the input unit is corrected according to the operation.   The said correction | amendment part outputs to the said output part, without correcting the detection signal input into the said input part, when the said 1st fuel is selected. Engine control system. The second control device performs operation control of the engine with the second fuel,
The first control device according to any one of claims 1 to 3, wherein the first control device outputs a control amount related to the air-fuel ratio feedback control to the second control device when the second fuel is selected. The engine control system according to any one of the above.

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