JPH037268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an automobile engine, and in particular, a flat solid electrolyte oxygen sensor and a solid electrolyte oxygen pump are arranged opposite to each other with a small space between them.
During this time, the exhaust gas of the engine is introduced into the engine, and an output signal corresponding to the pump current of the oxygen pump necessary to maintain the electromotive force generated by the oxygen sensor at a predetermined value is used to The apparatus is equipped with an air-fuel ratio sensor configured to detect a fuel ratio and a means for changing the electromotive force of the oxygen sensor maintained at the predetermined value according to the operating state of the engine, so as to feedback the operating air-fuel ratio of the engine to an arbitrary value. The present invention provides an air-fuel ratio control device for an engine that can control the air-fuel ratio of an engine.

Conventionally, an oxygen sensor composed of an ion-conducting solid electrolyte (e.g. stabilized zirconia) has been used, and the theory is based on the change in electromotive force caused by the difference between the oxygen partial pressure of exhaust gas and the oxygen partial pressure of air. It is well known that, for example, an automobile engine can be controlled to operate at a stoichiometric air-fuel ratio by detecting a combustion state at an air-fuel ratio. By the way, the oxygen sensor mentioned above has an air-fuel ratio (A/
When F) is the stoichiometric air-fuel ratio of 14.7, a large change in output can be obtained, but there is almost no change in other air-fuel ratio ranges, and when the engine is operated at an air-fuel ratio other than the stoichiometric air-fuel ratio, the output of the oxygen sensor mentioned above There was a problem with not being able to use . The present invention provides an air-fuel ratio control device for an engine that is capable of performing feedback control using an air-fuel ratio sensor even when operating at an air-fuel ratio other than the stoichiometric air-fuel ratio.

An embodiment of the present invention shown in the drawings will be described below. FIG. 1 is a configuration diagram showing an embodiment of the present invention, in which 1 is an engine, 2 is an intake pipe of the engine 1,
3 is a throttle valve; 4 is an intake air amount detection device for detecting the amount of intake air taken into the engine 1; 5 is a fuel supply valve provided upstream of the throttle valve 3; and 6 is the intake air detection device. 4 is an air cleaner disposed upstream of the engine 1; 7 is an exhaust pipe of the engine 1; 8 is an air-fuel ratio sensor attached to the exhaust pipe 7; 9 is an air-fuel ratio detection electronic device; 10 is the engine 1;
The rotational speed detector 11 inputs the output signals of the rotational speed detector 10, the intake air amount detection device 4, and the air-fuel ratio detection electronic device 9, and operates the fuel supply valve 5 in accordance with these input information. This is an electronic control device that drives the engine 1 and controls the amount of fuel supplied to the engine 1.
This electronic control device 11 also has a function of changing the reference voltage V _R of the air-fuel ratio detection electronic device 9 according to the input information. FIG. 2 is a detailed configuration diagram of the air-fuel ratio sensor 8 and the air-fuel ratio detection electronic device 9, and FIG. 3 is a sectional view taken along the - line in FIG. 2. In the figure, the air-fuel ratio sensor 8 is a solid electrolyte oxygen pump 16 constructed by providing platinum electrodes 14 and 15 on both sides of a flat ion-conductive solid electrolyte (stabilized zirconia) 13 with a thickness of approximately 0.5 mm. , a solid electrolyte oxygen sensor 20 configured by providing platinum electrodes 18 and 19 on both sides of a flat ion-conducting solid electrolyte 17 like the oxygen pump 16, and the oxygen pump 16 and the oxygen sensor. It is composed of a support stand 21 for arranging the two members 20 facing each other with a minute distance d of about 0.1 mm interposed therebetween. Further, the air-fuel ratio detection electronic device 9 applies the electromotive force e generated between the electrodes 18 and 19 by the oxygen sensor 20 to the inverting input terminal of the operational amplifier A through the resistor _R1 , and The output of the operational amplifier A is proportional to the difference between the reference voltage V _R applied to the input terminal and the electromotive force e.
The above oxygen pump 16 is driven by the transistor _TR.
It has a function of controlling the pump current _P flowing between the electrodes 14 and 15. That is, the electromotive force e
The above pump current _P required to maintain V _R at a constant value
It acts to supply. In addition, the above reference voltage V _R
is changed to a predetermined value by the electronic control device 11 according to the operating state of the engine 1. A resistor R _O is provided for obtaining an output signal corresponding to the pump current _P supplied from the DC power supply B.
This resistor R _O corresponds to the DC power source B, and a desired resistance value is selected so that the pump current _P does not flow excessively. C is a capacitor. Fourth
The figure is a characteristic diagram obtained by testing the air-fuel ratio sensor 8 shown in FIG. 2 above by installing it in a 2000 c.c. gasoline engine for a domestic passenger car. If an excessive pump current _P flows, the oxygen pump 16 will be destroyed, so the pump current _P is limited by the DC power supply B so that it does not flow more than 100 mA. Above reference voltage V _R
Change the above electromotive force e to 200mV, 100mV,
This figure shows the change in the pump current _P when the air-fuel ratio (A/F) of the engine is varied while maintaining the voltage at 80 mV and 60 mV, respectively. When the electromotive force e is maintained at 200 mV, the pump current _P changes rapidly at a stoichiometric air-fuel ratio of 14.7. When the electromotive force e is reduced, the pump current _P changes in proportion to the air-fuel ratio in an air-fuel ratio range smaller than the stoichiometric air-fuel ratio. This invention utilizes the characteristics shown in FIG. 4 obtained through the above test, and the operation of this invention device will be described below.

When the engine 1 is started, the intake air taken into the engine 1 is introduced from the atmosphere into the air cleaner 6, and the intake air amount is detected by the intake air amount detection device 4.
The air is introduced into the engine 1 through the intake pipe 2. The electronic control unit 11 inputting the output signal of the intake air amount detection device 4 drives the fuel supply valve 5 to inject and supply fuel corresponding to the intake air amount to the engine 1. When the engine 1 is operated at the stoichiometric air-fuel ratio by the output signal of the air-fuel ratio detection electronic device 9 based on the reaction of the air-fuel ratio sensor 8 attached to the exhaust pipe 7, the electronic control device 11 controls the air-fuel ratio The reference voltage V _R of the detection electronic device 9 is controlled to maintain the electromotive force e generated by the oxygen sensor 20 at 200 mV.
As a result, as shown in the characteristics shown in Fig. 4, the output signal (pump current) from the air-fuel ratio sensor 8 changes rapidly at the stoichiometric air-fuel ratio of 14.7, so this change signal can be used to generate a signal similar to the conventional device. The engine 1 is feedback-controlled at the stoichiometric air-fuel ratio. next,
The engine 1 is determined by the output signal of the intake air amount detection device 4 and the output signal of the rotation speed detector 10.
In the operating state, when the operating air-fuel ratio is set to 12, for example, the electromotive force e is maintained at 60 mV, and the electronic control unit 11 controls the fuel supply valve 5 so that the pump current _P of the air-fuel ratio sensor 8 becomes, for example, 80 mA. It controls the amount of fuel injected from the engine. If the operating air-fuel ratio is desired to be 14, the electromotive force e may be changed to 100 mV.

As described above, in this invention, a solid electrolyte oxygen sensor, which is constructed by providing electrodes on both sides of a flat solid electrolyte, and a solid electrolyte oxygen pump are placed opposite each other through a small space between them, and engine exhaust gas is supplied between them. the air-fuel ratio of the engine is detected by an output signal corresponding to the pump current of the oxygen pump necessary to maintain the electromotive force generated by the oxygen sensor at a predetermined value; means for changing the electromotive force of the oxygen sensor maintained at the predetermined value according to the operating state of the engine;
Since a means for controlling the amount of fuel supplied to the engine is provided so that the output signal corresponding to the pump current becomes a desired value, feedback control using the air-fuel ratio sensor can be performed even when operating at an air-fuel ratio other than the stoichiometric air-fuel ratio. An engine air-fuel ratio control device capable of
It has become possible to control the air-fuel ratio with greater precision than conventional oven control.

In addition, in the above explanation, the amount of fuel supplied to the engine is controlled so that the output signal corresponding to the pump current becomes the desired value, but the same effect can be achieved even if the amount of air is controlled instead of the amount of fuel. The effect of this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the air-fuel ratio sensor used in the device of the present invention, and FIG.
A sectional view taken along the line, FIG. 4 is a characteristic diagram of the air-fuel ratio sensor of FIG. 2. In the figure, 1 is the engine, 4 is the intake air amount detection device, 5 is the fuel supply valve, 7 is the exhaust pipe, 8 is the air-fuel ratio sensor, 11 is the electronic control device, 16 is the solid electrolyte oxygen pump, and 20 is the solid electrolyte oxygen It is a sensor.

Claims (1)

[Claims] 1. A solid electrolyte oxygen sensor and a solid electrolyte oxygen pump are configured by providing electrodes on both sides of a flat solid electrolyte. In addition to being configured to introduce exhaust gas, the air-fuel ratio sensor of the engine is provided with an output signal corresponding to the pump current of the oxygen pump necessary to maintain the electromotive force generated by the oxygen sensor at a predetermined value. When the output signal corresponding to the pump current is set to a predetermined constant value, the relationship between a predetermined air-fuel ratio and the electromotive force of the corresponding oxygen sensor is determined, and the oxygen sensor is maintained at a predetermined value so as to satisfy the relationship. The electromotive force of the pump is changed according to a predetermined operating state of the engine, and the amount of fuel or air supplied to the engine is controlled so that the output signal corresponding to the pump current becomes a predetermined constant value. Characteristic engine air-fuel ratio control device.