JPS627376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device that corrects the air-fuel ratio of an air-fuel mixture supplied to an engine to an appropriate value. The present invention relates to a device capable of correcting to an appropriate value.

Conventionally, in engine fuel injection systems, an air flow meter measures the intake air flow rate, the fuel injection amount is determined based on this measured value, and the fuel injection amount is determined based on a signal from an air-fuel ratio sensor installed in the exhaust system. It is configured to correct the amount and keep the air-fuel ratio of the air-fuel mixture constant.

The closed-loop control using the air-fuel ratio sensor is advantageous in that the air-fuel ratio can be controlled to be constant even with changes in atmospheric pressure, intake air temperature, etc.
This type of air-fuel ratio sensor cannot detect the air-fuel ratio unless the operating temperature rises above a certain activation temperature, so in an inactive state below the activation temperature, the closed-loop control by the air-fuel ratio sensor is canceled and the air-fuel ratio sensor is activated. Performs loop control.

However, if the air flow meter is used for a long period of time,
Dust, dirt, etc. may adhere to the air passages, etc. If dust, dirt, etc. adhere, an error will occur in the measurement of the intake air flow rate, and if open-loop control is performed in such conditions, the air-fuel ratio will be A problem arises in that the air-fuel ratio deviates from the set air-fuel ratio (for example, the stoichiometric air-fuel ratio), and as a result, the exhaust gas emissions of the engine deteriorate.

This invention was made in view of the above points,
An object of the present invention is to provide a fuel injection device capable of controlling an air-fuel ratio to an initial setting value during open-loop control even if dirt, dust, etc. adhere to an air passage of an air flow meter.

In particular, the present invention provides a bypass passage that bypasses the air flow meter, an adjustment means that adjusts the opening area of the bypass passage, and an adjustment means that operates at a predetermined time according to an output signal of the processing means of the air-fuel ratio sensor. The air flow meter is characterized in that it is equipped with a correction means to correct the error of the air flow meter, and this configuration attempts to deal with the above problem.

The present invention will be explained below with reference to embodiments shown in the drawings. In Figure 1 showing the overall configuration, engine 1
is a spark ignition engine for driving automobiles, and its intake system includes an air cleaner 2, an air flow meter 3, an intake pipe 4,
A throttle valve 5, an electromagnetic fuel injection valve 6, and the like are provided, and the exhaust system is provided with an exhaust manifold 7, an exhaust pipe 8, an air-fuel ratio sensor 9, a three-way catalytic converter 10, and the like.

Here, the air flow meter 3 converts the rotational displacement of the measurement plate 11 into an electric signal using a potentiometer,
It outputs a signal according to the intake air flow rate, and also includes a bypass passage 12 through which air flows bypassing the measuring plate 11, and an adjustment screw 13 for adjusting the opening area of this bypass passage 12.

More specifically, this air flow meter 3 has a structure shown in FIG. A measuring plate 11 is rotatably installed around a shaft 15. Further, a damper plate 16 is integrally formed on the measuring plate 11, and the measuring plate 11 is further moved to a fully closed stopper 1 with a constant torque by a spiral spring (not shown).
It is biased to come into contact with 7.

An adjustment screw 13 is installed near the exit of the bypass passage 12, and a DC electric motor 19 is connected to this screw 13 via a gear mechanism 18.

Returning to FIG. 1, the throttle valve 5 is of a known butterfly type and is arbitrarily operated by an accelerator pedal (not shown). A throttle switch 20 is connected to the shaft of the throttle valve 5, and the throttle switch 20 is turned on when the throttle valve 5 is at or near the fully closed position.

The air-fuel ratio sensor 9 detects the oxygen concentration in the exhaust gas using zirconia (ZrO ₂ ) or titania (TiO ₂ ), and its output changes depending on the air-fuel ratio, which is closely related to this. When using the stoichiometric air-fuel ratio ST as shown in Figure 3,
The electromotive force V changes in steps with the boundary .

The output signal of this air-fuel ratio sensor 9 is transmitted to the processing circuit 3.
0 and undergoes signal processing. The processing circuit 30 is
An integrator 35 includes a comparator 31 that compares the output signal of the sensor 9 with a reference voltage Vref, an operational amplifier (hereinafter referred to as OP amplifier) 32, a capacitor 33, and an analog switch 34, and performs integration based on the integration reference voltage Vint. and an activation monitor circuit 36 that determines whether the air-fuel ratio sensor 9 is in an activated state.
It is composed of.

Among these, the activation monitor circuit 36 is a circuit that determines whether the air-fuel ratio sensor 9 is in an activated state based on the internal impedance of the air-fuel ratio sensor 9, and is turned on when the internal impedance of the air-fuel ratio sensor 9 is high and in an inactive state. The analog switch 34 of the integrator 35 is turned on by outputting a signal to cancel the closed loop control and establish open loop control. Then, when the air-fuel ratio sensor 9 becomes activated and the internal impedance becomes low, an off signal is output to turn off the analog switch 34 and start closed loop control. Note that the details of this circuit are well known and will not be described here.

The rotation sensor 21 detects the rotation speed of the engine 1. In this embodiment, an ignition circuit (igniter) is used as the sensor, and outputs a pulse signal with a frequency proportional to the engine rotation speed.

The water temperature sensor 22 detects the temperature of the cooling water of the engine 1, and is composed of, for example, a thermistor.

The fuel control unit 23 includes an electromagnetic fuel injection valve 6
It controls the valve opening time of the air flow meter 3, switch 20, sensors 21, 22, and processing circuit 30.
Basically, the valve opening time is determined based on the signal from the air flow meter 3, and the valve opening time is corrected based on the signal from the processing circuit 30, that is, the air-fuel ratio sensor 9. Note that this fuel control unit 2
Since the detailed circuit of No. 3 is well known, detailed explanation thereof will be omitted.

The correction unit 40 includes the switch 20 and the sensor 2.
1, 22 and a processing circuit 30 are inputted thereto, and a drive signal for the electric motor 19 is output based on these signals.

Next, the detailed circuit of this correction unit 40 will be explained with reference to FIG. This correction unit 40 is supplied with power by a battery 41, and a diode 42 prevents current from flowing when the battery 41 is reversely connected, thereby protecting each element.

Resistor 43, diode 44, capacitor 45 and resistor 46 are digital-analog (DA)
It constitutes a converter, and converts the pulse signal of the rotation sensor 21 input to the terminal a into a DC voltage.
Thus, a DC voltage corresponding to the engine rotational speed is output from the terminal e.

The input resistor 47, the divided resistors 48 and 49, the transistor 50, and the comparator 51 constitute a voltage comparison circuit, and when the transistor 50 is turned on, the comparator 51 detects the voltage determined by the voltage at the terminal e and the divided resistors 48 and 49. Comparison is made with the reference voltage.

The divided resistors 52 and 53 are connected to the throttle switch 2.
0 is turned on, the voltage input to terminal b is divided. Bias resistor 54, input resistor 55, dividing resistors 56, 57, comparator 58, and diode 59 constitute a voltage comparison circuit. Comparison is made with the reference voltage.

Dividing resistors 60, 61, 62, 63, 64, transistor 65, input resistor 66, comparators 67, 68
constitutes a correction amount comparison circuit, and a comparator 6 compares the correction amount signal VF of the processing circuit 30 inputted to the terminal d with the reference voltages V ₁ and V ₂ of the terminals f and g.
7,68.

Resistors 70-78 and transistors 79-82
constitutes a motor drive circuit, and comparator 6
The electric motor 19 is driven, stopped, and rotated in accordance with output signals 7 and 68.

The operation in the above configuration will be explained. The rotation angle θ of the measuring plate 11 of the air flow meter 3 changes depending on the intake air flow rate passing through the air passage 14, but when the air flow meter 3 is normal, the intake air amount is accurately measured. 1 is kept constant, and the output voltage VF of the processing circuit 30 also changes near the integral reference voltage Vint, as shown by period _T1 in FIG.

When the air flow meter 3 is used for a long period of time and dirt, dust, etc. adhere to it as shown by arrow D in FIG. 2, the opening area between the tip of the measuring plate 11 and the wall of the passage 14 becomes smaller. For this reason, the rotation angle θ of the measuring plate 11 becomes larger than before the dust adhered to it, causing an error in the flow measurement. Try to make it smaller.

However, the air-fuel ratio sensor 3 is in an activated state,
When the air-fuel ratio sensor 3 performs closed-loop control of the air-fuel ratio, the output voltage V _F of the processing circuit 30
As shown by the solid line during period _T2 in FIG. 5, the voltage decreases below the integral reference voltage Vint, and the fuel control unit 23 causes the fuel control unit 23 to reduce the fuel injection amount, so even if dust adheres to the air flow meter 3, the air-fuel ratio remains , the stoichiometric air-fuel ratio is maintained, and the three-way catalytic converter 10 has a high purification rate.
Purifies NOx, HC, and CO.

In this state, when the engine 1 is temporarily stopped and the air-fuel ratio sensor 9 becomes inactive as when the engine is started in a cold state, the activity monitor circuit 36 of the processing circuit 30 turns on the analog switch 34, and the processing circuit The output voltage V _F of 30 is fixed to the reference voltage Vint.

For this reason, in the past, the output voltage V _F was the reference voltage
Even though the air-fuel ratio is maintained at the stoichiometric air-fuel ratio in a state lower than Vint, the air-fuel ratio deviates from the stoichiometric air-fuel ratio toward the rich side because the output voltage V _F is set to Vint.

In contrast, in the present invention, the engine 1 is in a hot idle operating state (for example, the engine rotation speed is 900 rpm, the engine coolant temperature is 80°C, and the throttle switch is turned on), such as immediately before the engine 1 is stopped.
, the voltage at the C terminal in Fig. 4 is the resistance 56,5.
Comparator 5 becomes lower than the reference voltage determined by 7.
8 outputs a 1 level signal and the throttle switch 20 is turned on, so the transistor 50 is turned on.

At this time, the voltage at the e terminal, which is inversely proportional to the engine speed, becomes higher than the reference voltage determined by the resistors 48 and 49, so the comparator 51 outputs a 1-level signal.

As a result, the reference voltage V ₁ is generated at the f terminal, and since the transistor 65 is turned on, the reference voltage V ₂ is also generated at the g terminal. These reference voltages V ₁ , V ₂
are slightly different from each other around the integration reference voltage Vint applied to the integrator 35 of the processing circuit 30, and are set as shown in the following equation.

V ₁ <Vint<V ₂ The comparators 67 and 68 compare these reference voltages with the output voltage V _F of the processing circuit 30 inputted from the d terminal.

When dust, dirt, etc. adhere to the air flow meter 3, the output voltage of the processing circuit 30 decreases as described above and becomes lower than the reference voltage _V1 of the f terminal, so the comparator 67 outputs an O level signal and the other comparison The device 68 outputs a 1 level signal.

Therefore, transistors 81 and 82 are turned on, causing electric motor 19 to rotate counterclockwise and adjusting screw 13 to be retracted to increase the opening area of bypass passage 12. As a result, the amount of intake air from the engine 1 that passes through the bypass passage 12 increases and the amount that passes through the air passage 14 decreases, and the rotation angle θ of the measurement plate 11 returns to the rotation angle before dust was deposited. , errors in rotation angle are automatically corrected. Then, the output voltage V _F of the processing circuit 30 becomes larger than the reference voltage V ₁ and becomes approximately the integrated reference voltage Vint
When it becomes equal to , the comparators 67 and 68 both output 0 level signals to turn off the transistors 79 to 82 and stop the electric motor 19.

Therefore, the output voltage V _F of the processing circuit 30 changes again around the integral reference voltage Vint, as shown by the broken line in period T ₂ in FIG. 5, and in this state, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio.

If the engine 1 is stopped in such a state and then operated in a cold state, the air-fuel ratio sensor 9 is not activated and the activation monitor circuit 36 of the processing circuit 30 activates the analog switch 34. Even if it is turned on and the output voltage V _F of the integrator 35 is fixed at the integration reference voltage Vint, and the air-fuel ratio is controlled in an open loop, the error in the air flow meter 3 is corrected as described above, so dust and dirt are removed. The engine 1 is operated at the set air-fuel ratio regardless of the adhesion, and the exhaust gas emission is good.

Note that in the above case, correction was made when the rotation angle θ of the measurement plate 11 becomes larger than the initial setting, but if the rotation angle θ of the measurement plate 11 becomes smaller than the initial setting for some reason, the processing circuit 30 becomes larger than the reference voltage _{V 2} of the g terminal, the electric motor 19 rotates clockwise during hot idle to reduce the opening area of the bypass passage 12, and the rotation angle θ of the measuring plate 11 becomes This case is also well corrected.

In the above embodiment, the opening area of the bypass passage was changed by the adjusting screw 13, but other types of adjusting valves may be used, and the device driving the adjusting screw etc. is not limited to an electric motor. Other types such as an electromagnetic solenoid, a linear motor, or a diaphragm mechanism may also be used.

As described above, according to the present invention, the error of the air flow meter can be well corrected even if dust, dirt, etc. adhere to the air flow meter, and the air-fuel ratio can be controlled to the initial setting value even during open-loop control. This has the excellent effect of preventing deterioration of exhaust gas emissions.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is an enlarged sectional view showing the air flow meter shown in FIG. 1, and FIG. 3 is an output characteristic diagram of the air-fuel ratio sensor shown in FIG. 1. 4 is an electric circuit diagram showing the correction unit shown in FIG. 1, and FIG. 5 is a graph for explaining the operation. 1... Engine, 3... Air flow meter, 9... Air-fuel ratio sensor, 12... Bypass passage, 13, 19
. . . Adjustment screw constituting adjustment means, electric motor, 23 . . . Fuel control unit, 30 . . . Processing circuit, 40 . . . Correction unit.

Claims (1)

[Scope of Claims] 1. An air flow meter provided in the intake system of the engine, an air-fuel ratio sensor provided in the exhaust system of the engine, processing means for processing the output signal of the air-fuel ratio sensor, and In the fuel injection device, the air flow meter is bypassed, and the fuel injection device includes fuel control means for determining the fuel injection amount based on the output signal of the flow meter and correcting the fuel injection amount based on the output signal of the air-fuel ratio sensor. A bypass passage, an adjusting means for adjusting an opening area of the bypass passage, and a correcting means for operating the adjusting means at a predetermined time in accordance with an output signal of the processing means, and correcting the error of the air flow meter. A fuel injection device characterized by: 2. The fuel injection system according to claim 1, wherein the correction means is configured to operate the adjustment means when the engine is hot idling.