JPS61135950A - Air-fuel ratio feedback control method for electronically controlled engine - Google Patents

Abstract

PURPOSE:To enable to control the air-fuel ratio such that it is always kept at the theoretical air-fuel ratio, by correcting a reference value used for switching the mode of controlling the air-fuel ratio to 'lean' air-fuel ratio control or to 'rich' air-fuel ratio control when the minimum value of the output of an O2-sensor becomes out of a predetermined range in executing feedback control of the air-fuel ratio. CONSTITUTION:In operation of an engine, a control circuit 50 at first corrects a base fuel quantity calculated from the outputs of an air-flow meater 15 and an engine- speed sensor 29 according to the temperature of intake air and the air-fuel ratio detected by an O2-sensor 60, and then controls a fuel jinjection valve 20 according to the corrected injection quantity of fuel. Further, the output value of the O2-sensor 60 is compared with a reference value, and the mode of air-fuel ratio control is changed to 'lean' control or to 'rich' control according to the result of judgement whether the output value of the O2-sensor 60 is greater than said reference vlaue or not. With such an arrangement, the minimum value of the output signal of the sensor 60 is compared with a predetermined value range to correct said reference value in case that the minimum value becomes out of said value range. Thus, it is enabled to control the air-fuel ratio to keep it at the theoretical air-fuel ratio in spite of deterioration or other troubles of the O2-sensor 60.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an air-fuel ratio feedback control method for an electronically controlled engine, and in particular to an accurate air-fuel ratio control method by compensating for deviations in detection signals due to deterioration or variations in oxygen concentration sensors. The present invention relates to an air-fuel ratio feedback control method for an electronically controlled engine that can control the fuel ratio.

[Prior art]

The conventional air-fuel ratio feedback control method for this type of electronically controlled engine compares the detection signal from the oxygen concentration (0,) sensor installed in the engine's exhaust manifold with a reference value, and detects when the comparison result exceeds the reference value. Depending on whether there is
The system switches to lean control or rich control, thereby controlling the air-fuel ratio to the stoichiometric air-fuel ratio. Accordingly, the above reference value has been empirically adopted as a value of approximately o, 4s (:V').

By the way, O! The output characteristics of the seventh sensor are normal 0.0 as shown in Figure 4 (m). Richness may occur due to changes in sensor output characteristics due to exhaust gas heat or aging, or due to manufacturing variations (see figure n).
Or, it is known that the angle shifts to the lean side (see 0 in the same figure).

Since the output characteristics of the O sensor change in this way, a fixed reference value is used to set the output characteristic to 0. When compared with the detection signal from the sensor, the control air-fuel ratio would change, causing a problem in that the release rates of Ha, Co, and Hox would vary.

Therefore, in the conventional feedback control method, first, 0
．． We have solved the above problem by conducting durability tests on the sensor, investigating how the Ot sensor changes, and empirically determining the reference value based on this, thereby reducing the variation in manufacturing quality. .

[Problem that the invention seeks to solve]

However, recent engines have become four-valve and supercharged, and as a result, the range of use of the engine has expanded significantly compared to conventional engines, so the way the O sensor changes has changed depending on the driving pattern. It is starting to change significantly.

Therefore, with the conventional method of switching between lean control and rich control using a fixed reference value, a problem has arisen in that it is difficult to maintain the stoichiometric air-fuel ratio.

The present invention has been made in view of the above-mentioned problems, and
Its purpose is 0. It is an object of the present invention to provide an air-fuel ratio feedback control method for an electronically controlled engine that can control the controlled air-fuel ratio to the stoichiometric air-fuel ratio despite variations in sensor changes and manufacturing quality.

[Means for solving problems]

In order to achieve the above object, the present invention compares the detection signal from the Ot sensor installed in the exhaust manifold of the engine with a reference value, and adjusts the air-fuel ratio to lean depending on whether the comparison result exceeds the reference value. Alternatively, in an air-fuel ratio feedback control method for an electronic fullla engine that switches to rich control and controls the stoichiometric air-fuel ratio, the minimum value of the detection signal of the 0° sensor during feedback control is compared with a predetermined setting range, and the range is determined. The above reference value is corrected when the value exceeds the reference value.

[Effect]

According to the present invention thus constructed, the following effects are achieved.

0. The minimum value of the detection signal from the sensor is constantly monitored during feedback control. When the minimum value exceeds a predetermined setting range, it is assumed that a large change or variation has occurred in the 01 sensor, and the reference value for air-fuel ratio control is corrected to an optimal value. In this way, 0. When the output characteristics of the sensor change, the reference value is also changed accordingly, so the air-fuel ratio can always be controlled to the stoichiometric air-fuel ratio.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments. First, the drawings will be explained, and then the embodiments will be explained.

10) and (1) are flowcharts showing an overview of the air-fuel ratio feedback control method for an electronically controlled engine according to the present invention, FIG. 2 is an overall configuration diagram of an electronically controlled engine to which this embodiment is applied, and FIG. This figure is a block diagram showing the detailed configuration of a control device used in the engine of FIG. 2. In FIG. 2, 1 indicates an engine, and the engine 1 has a cylinder block 2 and a cylinder head 3. The cylinder block 2 receives a piston 4 in a cylinder bore formed inside the cylinder block 2. A combustion chamber 5 is defined above the piston 4 in cooperation with the cylinder head.

An intake boat 6 and an exhaust boat 7 are formed in the cylinder head 3, and these boats are opened and closed by an intake valve 8 and an exhaust valve 9, respectively. Also,
A spark plug 19 is attached to the cylinder head 3. The spark plug 19 is supplied with current generated by the ignition coil 26 via a distributor 27, and generates sparks by discharge within the combustion chamber 5.

An intake manifold 11, a surge tank 12, a throttle body 13, an intake tube 14, an air flow meter 15, and an air cleaner 16 are connected to the intake boat 6.

Further, an exhaust manifold 17 and an exhaust pipe 18 are connected to the exhaust boat 7 in this order.

A fuel injection valve 20 is attached near the connection end of the intake manifold 11 to each intake boat. A liquid fuel such as gasoline stored in a fuel tank 21 is supplied to the fuel injection valve 20 via a fuel supply pipe 23 by a pump 22 .

The throttle body 13 is provided with a throttle valve 24 for controlling the amount of intake air, and the throttle valve 24 is driven in response to depression of an accelerator pedal 25.

The air flow meter 15 detects the flow rate of air flowing through the engine intake system, and outputs a signal corresponding to the flow rate to the control device 50.

The distributor 27 has a built-in rotation speed sensor 29 that detects its rotation speed and rotation phase, in other words, the engine speed and crank angle, and this detection signal is input to the control device 50. There is. The control device 50 also includes an intake temperature sensor 58 and a water temperature sensor 59.
．． 0. Signals from a sensor 60 and an accelerator sensor 70 are supplied.

The control device 50 may be a microcomputer, an example of which is shown in FIG. This microcomputer includes a central processing unit (CPT7) 51, a read-only memory (ROM) 52, a random access memory (RAM) 53, and another nonvolatile random access memory that retains memory even after power is turned off. (c-RAM
)! 54+! : has an A/D converter 55 having a multiplexer and a device 56 having a buffer, which are connected to each other by a common path 57.

Here, the C-RAM 154 stores data from various sensors used for air-fuel ratio feedback control, which will be described later.

The A/D converter 55 receives an air flow rate signal detected by the air flow meter 15, an intake air temperature signal detected by the intake air temperature sensor 5B, a water temperature signal detected by the water temperature sensor 59, and an O sensor 60. The output oxygen concentration detection signal and the throttle valve opening signal detected by the throttle sensor 70 are input, and the A/D converter 55 A/D converts these data and converts the data into a predetermined signal according to instructions from the CPU 51. The data is output to the CPU 51 and random access memory 53 or 54 at the appropriate time. Also, engineering 1
The engine rotation speed signal and crank angle signal output from the rotation speed sensor 29 are input to the I1
0 device 56 stores those data in cpσ 51 and random access memory 5 at a predetermined time according to instructions from CPU 51.
It starts outputting to 3 or 54 and makes a noise.

CPtT! 51 calculates the fuel injection amount based on the data detected by each sensor and processes the signal based on it.
0 device 56 and is output to the fuel injection valve 20. In this case, the fuel supply amount is controlled by using the basic fuel amount determined from the air flow rate detected by the air flow meter 15 and the engine rotation speed detected by the rotation speed sensor 29, and the intake air temperature detected by the intake air temperature sensor 58. , the water temperature detected by the water temperature sensor 59, and o! sensor 6o
the air-fuel ratio detected by the sensor, and the accelerator sensor 70.
This is done by correcting the throttle valve opening according to the detected throttle valve opening.

Further, the CPU 51 reads an optimum ignition timing signal based on the basic fuel amount calculated by the CPU 151, the engine speed and crank angle detected by the rotation speed sensor 29, and the intake air temperature detected by the intake air temperature sensor 58.
2 and read this from the I10 device 56 to the ignition coil 2.
It is designed to output to 6.

Next, FIG. 1 shows the outline of the air-fuel ratio feedback control program executed by the control device 50.

Figure Wc1 (D shows a routine for learning the minimum value of the Ot sensor output signal of the present invention, and (U) of the same figure shows a learning routine for the comparison voltage used in the present invention.

In Figure (D), when the routine is started at step 100, the process moves to step 101.
Load with 5. In step 102, it is determined whether feedback control is in progress (determined by whether the flag is set). If it is determined that feedback control is in progress, the process proceeds to step 103, but if it is determined that feedback control is not in progress. ends this routine. Step 10
3 Teha, engine operating range is 0. It is determined whether the learning area has the minimum value of the output signal Vo of the sensor 6o. This determination is made based on the engine rotation NE, the injection amount 'rp, etc. If it is a learning area, the process advances to step 104, and if it is not a learning area, this routine ends. Step 1
0.4, 0. The output of the sensor 60 is o, 45 [v:
If it is small, proceed to step 105; if it is large, proceed to step 1071C. In step 105, it is determined whether the output signal vO from the t sensor 60 is smaller than the learned value of the minimum value V'o-, and if it is smaller, the process proceeds to step 106, and if it is larger, this routine is ended. In step 106, 0.
The learned value of the minimum value V'o- of the output of the sensor 60 is rewritten.

On the other hand, in step 107, the learned value V'o- is 0.45
It is determined whether or not it is smaller than [:V], and if it is smaller, the process proceeds to step 10g, and if it is larger, the process proceeds to step 109. In step 108, the learning value Va- is rewritten to V'o-, and then the process proceeds to step 109. In step 109, a series reset is performed by setting the learned value V'o- to o, 45 (V), and this routine ends.

In FIG. 1 (■), in step 111, the minimum learned value vO- of the output signal Vo of the zero sensor 60 is set to the first
If it is determined to be larger than the set value Vo8+, it is determined that the O sensor 60 is out of lean and the process proceeds to step 112, and if it is determined to be small, the process proceeds to step 113.

In step 112, the lean deviation correction outside α of the zero-level sensor 60 is added to the comparison reference voltage value Vt. Step 11
3 is 0. It is determined whether the minimum learned value vO- of the output signal vo from the sensor 60 is smaller than the second set value Vo8t, and if it is determined to be smaller, the value is set to 0. It is determined that the sensor 60 is out of rich, and the process proceeds to step 114. If it is determined that the rich deviation is large, this routine ends. In step 114, the comparison voltage VL is changed to 0. sensor 6
Subtract the rich deviation outside correction β of 0.

By learning the minimum value VO- of the output of the sensor 60 using the method described above, it is possible to learn the optimum comparison reference voltage value VL, and it is possible to learn the optimum comparison reference voltage value VL, regardless of how the 01 sensor 60 deteriorates or variations. , the control air-fuel ratio can be controlled to the stoichiometric air-fuel ratio, and variations in emissions can be suppressed.

In short, the above-mentioned embodiments can be summarized as follows: O during feedback control,
The minimum value VO- of the output signal vO of the sensor 60 falls within a predetermined range Vast~vos t ('VO8I >VO
11! ), the 1 comparison reference voltage value VL is reset to the optimum value according to the direction of the deviation.

〔Effect of the invention〕

As described above, according to the present invention, 0.0% during feedback control. When the minimum value of the output signal of the sensor exceeds a predetermined range, the comparison reference voltage value is reset according to the exceeded range. This has the effect of being able to control the air-fuel ratio to the stoichiometric ratio without being affected by sensor changes or variations.

[Brief explanation of the drawing]

Figures 1 (1) and (II) are flowcharts showing embodiments of the present invention, Figure 2 is an overall configuration diagram of an electronically controlled engine to which the present invention is applied, and Figure 3 shows a control device used in the engine. The block diagram shown in FIG. 4 is a waveform diagram showing the output signal of the 0° sensor. 1...Engine 50...Control device, 60...0. sensor.

Claims (1)

[Claims] (1) The detection signal from the oxygen concentration sensor installed in the engine's exhaust manifold, etc. is compared with the standard value, and depending on whether the comparison result exceeds the standard value, the air-fuel ratio is switched to lean or rich control. In an air-fuel ratio feedback control method for an electronically controlled engine that controls the fuel ratio, the minimum value of the detection signal of the oxygen concentration sensor during feedback control is compared with a predetermined setting range, and when the value exceeds the range, the above reference value is set. An air-fuel ratio feedback control method for an electronically controlled engine, the method comprising: correcting the air-fuel ratio of an electronically controlled engine.