JPS587815B2 - kuunenpikikanshikinenriyoufunshiyaseigiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention determines the fuel injection amount of an electronic fuel injection control device by using a concentration detection signal from an oxygen concentration detector installed in the engine exhaust pipe. The present invention relates to an air-fuel ratio feedback type fuel injection control device that keeps the air-fuel ratio constant by feeding back the time width of an injection pulse.

In conventional electronic fuel injection devices, fuel injection is performed by calculating the amount of fuel commensurate with the intake air amount of the engine as determined by an intake air flow meter.

However, in order to keep the air-fuel ratio strictly constant, it is necessary to determine whether the air-fuel mixture is rich or lean based on the oxygen concentration value detected by the oxygen concentration detector installed in the exhaust pipe, and to adjust the time width of the fuel injection pulse. Feedback correction was applied, but the method was that the feedback correction output obtained from the output of the oxygen concentration detector shown in FIG. 5, 5B is an integral output as shown in FIG. At an excess air ratio λ=1, a limit cycle is generated around a value that is a stoichiometric air-fuel ratio at which the amount of fuel and oxygen in the air can be completely combusted.

This is because there is a time delay in the system from when fuel is injected until it reaches the exhaust pipe and when the oxygen concentration detector responds.

Therefore, the time width of the injection pulse of the electronic fuel injection control device is feedback-controlled by the feedback correction output of the integral waveform as shown in FIG. 5, 5A, using the output signal of the oxygen concentration detector shown in FIG. 5, 5B. , the time T1 from the point where the time width of the injection pulse of the limit cycle deviates from the target value (λ = 1) to the maximum until it returns to the target central value (λ = 1)
, T2 has the disadvantage that it becomes a completely wasted time, that is, a follow-up delay during feedback control.

In addition, when increasing or decreasing the injection amount using the integrator output as a conventional feedback correction output, there is a time delay in the feedback system, so it is better to change the integral constant depending on load fluctuations, changes in engine speed, air amount, etc. We were trying to obtain matching and transient response, so we had to set the integral constant to match the required value of the system according to the various detection signals mentioned above.

However, in a system that has been matched to some extent, there is not much need to change the integral constant, and in order to obtain steady matching and transient response, the feedback correction amount, that is, the injection amount, can be obtained by changing the integral constant over time. It is better to have a smaller change considering steady matching, and a larger change considering transient response.

In order to meet these conflicting demands, stability during steady state and matching during transient times can be achieved by setting the integral constant to be large at first and to become smaller over time.

The present invention has been made in view of the above points, and in a feedback system that has been matched to a certain extent, the integration constant of the output from the integrating means, which is the feedback correction output, is initially large and becomes smaller as time passes. The air-fuel ratio feedback type fuel injection control device is capable of improving steady-state stability and transient matching by changing the air-fuel ratio, as well as improving feedback followability and operating the engine at a constant air-fuel ratio. The purpose is to provide

An embodiment of the present invention shown in the drawings will be described below.

In the block diagram of the air-fuel ratio feedback type fuel injection control system shown in Fig. 1, 1 is the engine body which is an internal combustion engine, 2 is the intake pipe, 3 is the exhaust pipe, 4 is the throttle valve, and 5 is the front of the intake pipe 2. 6 is an oxygen concentration detector made of a solid electrolyte such as zirconium oxide, which is installed in the exhaust pipe 3 to measure the oxygen concentration in the exhaust gas. When the temperature of the exhaust gas exceeds an allowable temperature of 450° C. to 600° C., it operates normally in response to the oxygen concentration and generates a concentration detection signal.

Reference numeral 7 denotes an injection valve for injecting fuel into the intake pipe 2, which is opened by a fuel injection pulse signal output from a fuel injection control device to be described later.

Reference numeral 8 denotes an engine state detection means for detecting the engine state such as the engine speed, 9 an air cleaner, and 10 an electronic fuel injection control device, which corresponds to the output of the intake air flow meter 5 attached to the front part of the intake pipe 2. In order to supply the amount of fuel from the injection valve 7, a fuel injection pulse signal having a predetermined duration for opening the injection valve 7 is generated.

Reference numeral 11 denotes a feedback control circuit for feedback correcting the fuel injection amount by the electronic fuel injection control device 10 in accordance with a concentration detection signal output from the oxygen concentration detector 6 disposed in the exhaust pipe 3; has an output of a reference voltage VB/2 which is half of the power supply voltage VB, the reference voltage VB/2 is held, the correction amount of the feedback control system is set to zero, and the basic preset required fuel is injected. It's like this.

Therefore, the feedback control circuit 11 outputs the reference voltage VB/
The fuel injection amount is corrected by reducing the time width of the fuel injection pulse when the voltage is lower than 2, and by increasing the time width of the fuel injection pulse when the voltage is higher than the reference voltage VB/2. .

Next, the detailed configuration and operation of the feedback control circuit, which is the main part of the present invention, will be described with reference to FIGS. 2 to 4.

In Figure 2, VB is the power supply line of power supply voltage VB, G
ND is ground line, 201, 202, 203, 204
, 205 are resistors. In particular, the Zener voltage determined by the Zener diode 206 is divided by the resistors 202 and 203, and a reference voltage S at a predetermined level is set and input to the comparator Q1.

12 constitutes the main output correction means of the present invention;
07, 208 are voltage dividing resistors that provide a reference voltage at a predetermined level, 209, 210 are diodes, 211, 212,
213, 214, 215, 216, 217, 218 are resistors, 219, 220 are capacitors, and the resistor 215 and the capacitor 219, and the resistor 216 and the capacitor 220 constitute a discharge circuit having a predetermined time constant.

T1, T2, T3, T4 are transistors, comparator Q1
When the output is "0", the potential at point D in FIG. 2 becomes zero potential, transistors T2 and T3 become conductive, and transistors T1 and T4 are cut off.

On the other hand, when the output of comparator Q1 is "1", D
The point potential is close to the power supply voltage VB, and the transistors T1 and T4
becomes conductive, and transistors T2 and T3 are cut off.

221 and 222 are input resistances of the specifier Q2, 223 is an integration capacitor, and 224 is an output terminal.

To explain the operation of the above-mentioned configuration, the output waveform of the oxygen concentration detector 6 is as shown in FIG. This is determined by the output characteristics of

Therefore, if the reference voltage of the comparator Q1 is set to the voltage VS by the resistors 202 and 203, the output of the comparator Q1, that is, the output waveform at point D in the figure, will be as shown in FIG. 3, 3B.
This is an inverted waveform of the illustrated waveform.

Therefore, when the air-fuel mixture injected into the engine is rich, the oxygen concentration in the exhaust pipe 3 is low and the output voltage of the oxygen concentration detector 6 is high, and the output of the comparator Q1 is close to the ground potential. T4 is cut off and transistors T2 and T3 are turned on.

At this time, the voltage waveform at point A in the figure becomes a discharge waveform with a time constant determined by the resistor 215 and capacitor 219 as shown in FIG. Integrate.

On the other hand, when the air-fuel mixture injected into the engine is lean, the oxygen concentration in the exhaust pipe 3 becomes high and the oxygen concentration detector 6
The output of comparator Q1 becomes smaller, and the output of comparator Q1 becomes the power supply potential VB.
Therefore, transistors T, , T4 are conductive, and transistors T2 and T3 are in a cut-off state.

Therefore, the voltage waveform at point B in the figure at this time becomes a discharge waveform with a time constant determined by the resistor 216 and capacitor 220 as shown in FIG. 3D, and the integrator Q2 integrates the discharge waveform in the same manner as described above. Therefore, the output of integrator Q2, which inputs and integrates both the discharge waveform outputs of Fig. 3 3C and 3D, is shown in Fig. 3 3E.
The output shown in FIG. 3E, which has an output waveform as shown in FIG. This means that the amount of fuel injected from the injection valve 7 also changes in the same way.

Therefore, in a system where the air-fuel ratio has been matched to a certain extent, the rate of increase/decrease in the fuel injection amount is initially large, and the electronic fuel injection control device 10 is operated so that the rate of increase/decrease in the fuel injection amount becomes smaller as time passes. Become.

Therefore, the fuel injection amount can be controlled with good responsiveness without deviating from the target air-fuel ratio by more than a certain percentage.

As described above, in the device of the present invention, the signal waveform input to the integrating means is changed over time in accordance with the output from the comparing means, and the integral constant of the output from the integrating means is changed over time. Since it is equipped with a correction means, it is possible to achieve stability during steady state and matching during transient conditions, improve feedback correction response, improve feedback followability, and control air-fuel ratio variations within a certain range. This has an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an air-fuel ratio feedback type fuel injection control device according to the present invention, FIG. 2 is an electrical wiring diagram showing an embodiment of the feedback control circuit which is the main part of the present invention 3
4 is a characteristic diagram showing the output characteristics of the oxygen concentration detector, and FIG. 5 is an output waveform diagram illustrating the conventional device. 6...Oxygen concentration detector installed in the exhaust pipe, 10.
...Electronic fuel injection control device, 11...
Feedback control circuit, Q1... Comparator, Q2...
...Integrator, 12...Transistor T1, T2
, T3, T4, etc.

Claims (1)

[Claims] 1 The oxygen concentration in the exhaust gas of the internal combustion engine is detected by an oxygen concentration detector, and the detection output is compared with a preset value. In the air-fuel ratio feedback type fuel injection control device that controls the oxygen concentration to be constant by correcting the increase or decrease of the fuel injection amount using an integral output having an integrated increase/decrease characteristic, 1. An air-fuel ratio feedback type fuel injection control device comprising an output correction means for temporally changing the signal waveform of an input of the integrating means and temporally changing an integral constant of an output from the integrating means.