JPS6079133A - Air-fuel ratio controller - Google Patents

Abstract

PURPOSE:To avoid unsatisfactory operationability, in an air-fuel ratio controller having an air-fuel ratio sensor incorporating a heater, by storing the correction level based on the output from said sensor upon blown-off of heater then controlling the air-fuel ratio on the basis of a level corresponding to said stored level. CONSTITUTION:Under running of engine, a computer 13 in an air-fuel ratio control section 200 will calculate the basic injection on the basis of engine rotation N, suction air Q, etc. While on the basis of the difference between the current air-fuel ratio obtained from an output from O2 sensor control section 100 and the target air-fuel ratio, first correction level is calculated to correct the basic injection thus to determine total injection. Here, upon blown-off of heater 5 incorporated in the sensor 4, first correction level is calculated and stored then on the basis of first correction level stored immediately before blown-off, second correction level optimal to current engine operating condition is calculated. Then said basic injection is corrected by said second correction level to obtain total injection.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention detects the concentration of acid (1) contained in engine exhaust gas and feeds back the fuel supply amount to control the air-fuel ratio to a target value. The present invention relates to an air-fuel ratio control device.

[Prior art]

Conventionally used air-fuel ratio sensors that detect the oxygen concentration in exhaust gas have output values that change depending on the temperature of the sensor. can be detected. An air-fuel ratio control device using such an air-fuel ratio sensor was disclosed in Japanese Patent Application Laid-open No. 5
This method is known from, for example, Japanese Patent No. 7-140539. In this device, when the heater of the sensor is disconnected, the characteristics of the sensor are shifted, so the air-fuel ratio is controlled in the wrong direction, and after the monitor time T2 has elapsed, open-loop control is performed in which the air-fuel ratio is fixed at a constant value. The problem is that if the control is erroneously controlled to the lean side, engine operability may deteriorate, and in extreme cases, the engine may stop. When switching to open-loop control, the air-fuel ratio suddenly changes. Because it changes,
The engine's output torque may change suddenly, giving the driver an unpleasant shiver. In addition, if the air-fuel ratio is immediately set to a preset value when the heater burns out, the air-fuel ratio will change suddenly from the previous air-fuel ratio state, and if the previous air-fuel ratio was on the rich side, it will suddenly tend to become lean. This could lead to poor drivability.

(Object of the Invention) In view of the above-mentioned points, an object of the present invention is to improve the air-fuel ratio control immediately after a heater disconnection, thereby stabilizing the drivability of the engine.

Therefore, in the present invention, in a device that controls the air-fuel ratio of the air-fuel mixture supplied to the engine according to the correction value based on the output of the air-fuel ratio sensor, when the heater built in the air-fuel ratio sensor is disconnected, the correction value immediately before that is stored, and air-fuel ratio control is performed using a value corresponding to the stored correction value instead of the output of the air-fuel ratio sensor.

〔Example〕 Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of the invention. The air-fuel ratio control device in this embodiment is roughly divided into an oxygen sensor control (3) section 100 and an air-fuel ratio control section 200. The oxygen sensor control unit 100 has a determination circuit 1 that receives an operating state signal P as an input, determines whether the exhaust gas temperature is high or low, and outputs a determination signal Q thereof.

In this case, the operating state signal P is, for example, an engine rotational speed signal, a fuel injection pulse signal, a signal corresponding to the intake air amount or intake negative pressure, a throttle valve opening signal, or a combination of several of these signals. is used. 2 is a resistor 3 and a heater 5 of an oxygen sensor 4 as an air-fuel ratio sensor.
This is an analog switch connected between both ends of the power source (battery) 6 via the switch, and is closed only when a discrimination signal CI indicating that the exhaust temperature is low is sent from the discrimination circuit 1. Reference numeral 7 designates an analog switch connected between both ends of the switch 2 via a resistor 8, and is closed only when a discrimination signal C2 indicating that the exhaust gas temperature is high is sent from the discrimination circuit 1. Reference numeral 9 denotes an inflow current control circuit, which controls the inflow current to the sensor section of the oxygen sensor 4 in relation to the exhaust temperature discrimination signal supplied from the discrimination circuit 1.

(4) In the engine air-fuel ratio control device configured as described above, the sensor section 4 detects the oxygen concentration contained in the exhaust gas of the engine and supplies the oxygen concentration signal R to the air-fuel ratio control section 200. The air-fuel ratio control section 200 includes an A/D converter 12,
It consists of a computer 13, a comparator 14, a drive circuit 15, and an injector 16, and performs calculations to obtain the optimum air-fuel ratio based on an oxygen concentration signal R1 an engine rotation speed signal N1 an air flow meter output signal Q1, a cooling water temperature Tw, etc. The calculated output is used to control the fuel injection amount, thereby performing feedback control so as to obtain the optimum operating state. Further, when the heater 5 is disconnected, the potential at point a changes, so the output sh of the comparator 14 changes.

On the other hand, the determination circuit 1 inputs the operating state signal P and determines the exhaust temperature. For example, in operation in a low load range, the determination circuit 1 determines that the exhaust gas temperature is low and sends out a low temperature determination signal C1. When the low temperature discrimination signal C1 is sent out, only the switch 2 is closed, and the output of the power supply 6 is supplied to the heater 5 only through the resistor 3 (5), and a high voltage is applied to the heater 5. The amount of heat generated by the heated heater 5 is increased.

Next, when the engine is operated in a high load range, the special circuit 1 determines that the exhaust gas temperature is high and sends out a high temperature determination signal C2. When the high temperature determination signal C2 is sent,
Switch 7 is closed and the output of power supply 6 is supplied to heater 5 via resistor 8.3. As a result, the voltage applied to the heater 5 is lowered by the voltage drop across the resistor 8, and the amount of heat generated by the heater 5 is accordingly reduced. Therefore, the sensor section 4 is connected to (
Since the temperature is always maintained at a substantially constant temperature, the oxygen sensor can provide a stable output that is not affected by temperature changes due to exhaust gas temperature.

Further, 10 is an analog switch for stopping energization to each part of the sensor control unit 100 according to the engine state, and 11 is an energization control circuit that controls this switch 10. This energization control circuit 11 monitors the presence or absence of an activation signal STA of a starter switch (not shown), the terminal voltage of the vehicle battery, the output voltage of the power source (6), etc. when the starter is activated (that is, when the engine is started). When the predetermined voltage drops, the analog switch 10 is opened to stop energizing the heater 5, sensor section 4, etc. At other times, the analog switch 10 is always closed.

This causes a large amount of current (power) to be generated when starting the engine, etc.
When necessary, by cutting off the load such as the heater 5, it is possible to prevent a drop in the power supply voltage and improve the startability of the engine.

The air-fuel ratio sensor 4 is, for example, disclosed in Japanese Patent Application Laid-Open No. 57-4864.
8, Japanese Patent Application Laid-open No. 57-140539, and Japanese Patent Application Laid-Open No. 57-192852, etc., the structures are already known.

Next, the operation of the computer 13 will be explained. First, when the heater 5 is disconnected, the potential at point a changes, so the output S of the comparator 14 changes.

Therefore, the operation of the computer 13 will be explained using the flowchart in FIG. 2. When the heater is normal (7), the flag F=O remains, so step 1002
~1007.1010.1011 is executed. In other words,
In steps 1002 and 1003, the basic injection amount is calculated and stored using various parameters (N, Q, TW, etc.) indicating the engine status, and in step 1005, the current injection amount is calculated using the oxygen concentration signal R from the oxygen sensor 4. A first correction amount (so-called correction value) is calculated and stored based on the deviation between the air-fuel ratio and the target air-fuel ratio, and in step 1010, the total injection amount is calculated from the previously determined basic injection amount and the first correction amount. The amount is measured and output (step 1011).

On the other hand, when the heater 5 is disconnected, the detection signal S changes. Therefore, after calculating and storing the first correction amount in step 1005, a YES determination is made in step 1006, and the flag F
-1, and proceed to step 1009. This step 10
In step 09, a second correction amount optimal for the current engine operating condition is calculated based on the first correction amount stored immediately before. This second correction amount is the value of the first correction amount or its predetermined coefficient times as shown at time tI in FIG. 3 (bl) or time tl-t2 in FIG. 4 ('b) (8). , or a value that gradually decreases to a predetermined basic value with the elapsed time (or elapsed rotational speed) immediately after these values.

Then, in step 1010, the total injection amount is calculated from the basic injection amount and the second correction amount and output.

After that, when the heater is disconnected, the flag F=1, so step 10 is executed.
The process in step 05 is not performed, and the process in step 1009 is performed.

Therefore, the air-fuel ratio change when the heater is disconnected (time 1+) is reduced as shown in FIG. 3 1c) or FIG. 4 tc), eliminating unstable control periods and providing good drivability. Note that (a) in Figure 3.4 is the output of the oxygen sensor 4,
(bl is the feedback correction amount (that is, correction value) of the first correction amount and the second correction amount, and (C) is the air-fuel ratio of the engine.

〔Effect of the invention〕

As described above, in the present invention, when the heater in the air-fuel ratio sensor is disconnected, the feedback correction value at that time is stored, and a value corresponding to the stored correction value (9) is used instead of the output of the air-fuel ratio sensor. Since the air-fuel ratio is controlled using the heater, the air-fuel ratio can be effectively controlled immediately after a heater burnout, resulting in stable drivability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 and FIGS. 3 and 4 are flow charts and waveform diagrams for explaining the operation of the present invention. 4... Air-fuel ratio sensor (oxygen sensor), 5... Heater, 13... Computer, 14... Comparator, 16...
... Injector, 100 ... Oxygen sensor control section, 2
00...Air-fuel ratio control section. Representative patent attorney Takashi Okabe (10) Figure 3 1 Figure 4-11111→t

Claims (1)

[Claims] (11) A control means for disposing an air-fuel ratio sensor with a built-in heater in the exhaust system of the engine, and controlling the air-fuel ratio of the air-fuel mixture supplied to the engine in accordance with a correction value based on the output of the air-fuel ratio sensor. In the air-fuel ratio control device comprising:
When the heater is disconnected, the correction value at that time is stored;
An air-fuel ratio control device comprising means for setting a value corresponding to the stored correction value instead of the output of the air-fuel ratio sensor. (2) The value set by the setting means is configured to gradually decrease according to the elapsed time or the elapsed rotational speed of the engine immediately after the setting means. Fuel ratio control device.