JPS5832944A - Air-fuel ratio control method - Google Patents

Abstract

PURPOSE:To make it possible to prevent engine failure due to the extreme control of air fuel ratio, by limiting the control of air-fuel ratio in a predetermined range around the mean value of the integration value of air-fuel ratio feedback. CONSTITUTION:A comparator CP delivers a signal L or H in accordance with a lean or ritch signal from an air fuel ratio sensor 35, a counter CT1 carries out adding operating each time when the signal L or H is reversed, and the mean value C1 thereof is delivered from a register REG. A data selector DS normally changes the output period of a frequency divider DIV in accordance with the output of the comparator CP, for performing the feedback control of the valve opening time of a fuel supply valve in accordance with an intake air amount. However, the valve opening time is cripped on a limiter LM1 or LM2 to its lowermost or uppermost value even if the output of the comparator CP is held at H or L level due to any reason so that the control of valve opening time is limited thereabove. Accordingly, the engine failure due to the extreme control of air-fuel ratio is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an air-fuel ratio control system that detects an air-fuel ratio based on the exhaust gas components of an internal combustion engine, and uses this detection signal to feedback control the air-fuel ratio of a mixture supplied to the internal combustion engine to a predetermined value. The present invention relates to a fuel ratio control method.

An oxygen sensor is usually used as a means of detecting the air-fuel ratio by exhaust gas components of an internal combustion engine, and the output of the oxygen sensor is compared with a predetermined voltage level, and the direction of integration of the integrator is reversed based on the comparison result. A common method is to control the air-fuel ratio by varying the amount of fuel supplied to the internal combustion engine in proportion to the output of the integrator. If the oxygen sensor malfunctions or is disconnected, the output of the oxygen sensor will no longer respond to changes in the air-fuel ratio, and the integrator will continue to integrate in one direction, resulting in an extremely lean or rich air-fuel ratio. There is a risk of stopping the internal combustion engine. To prevent this, it may be possible to limit the variation range of the integrator (feedback control width), but in this case, the air-fuel ratio set by open loop based on various parameters of the internal combustion engine will vary from engine to engine, and if If the air-fuel ratio at this time were to shift to the lean side, the width of the foot-noic control to the rich side would be too narrow, resulting in poor controllability. In order to improve this, the output of the integrator is averaged, the output of the integrator is averaged in a predetermined width around this averaged value, and the air-fuel ratio due to the output of the integrator is determined by this averaged value. When controlling the control width, it is necessary to make the averaging interval sufficiently long in order to stabilize the averaged value. However, when the averaging interval is made long, the feedback control range is narrow and the controllability is poor after the internal combustion engine is started until the feedback control is performed and the averaged value is obtained.

The wood invention was made to solve the above-mentioned problems. Immediately after starting the internal combustion engine, the averaging interval is shortened, and once the internal combustion engine has been averaged, it is averaged at a sufficiently long interval. This is intended to improve feedback controllability from the initial stage after startup.

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

FIG. 1 is a block diagram of the invention, in which (1) is a Karman vortex type air flow sensor through which intake air from an internal combustion engine (3) passes. A vortex is generated downstream of the vortex generator 0 installed in the air flow sensor (1), and the ultrasonic waves generated from the ultrasonic transmitter undergo frequency modulation every time obesity occurs. and reaches the ultrasonic receiver (2).

The vortex detection device (2) outputs a signal that generates the ultrasonic wave to the ultrasonic transmitter (2), and also demodulates the signal detected by the pharyngeal receiver (incorporated) using a built-in FM signal demodulator (not shown). fit outputs a pulse train of a frequency corresponding to the frequency of the Karman vortex generated downstream of the vortex generator α force.

The frequency of this pulse train is proportional to the amount of air passing through the air flow sensor (1), that is, the amount of air taken into the internal combustion engine (3). (3) is an internal combustion engine used in a car, for example, in which air is taken in through an intake pipe (to) and a fuel supply valve (b) is installed upstream of a throttle valve (to).
It operates by inhaling a mixture of fuel and fuel supplied by the engine. (
2) is a throttle valve that adjusts the amount of air taken into the internal combustion engine (3). A fuel pump and a fuel pressure regulator (not shown) are connected to the fuel supply valve (b), and the differential pressure between the pressure of the suction pipe (to) and the fuel pressure supplied to the fuel supply valve G0 is kept constant. (b) is an internal combustion engine,
A water temperature sensor that detects the temperature of cooling water, such as a thermistor whose resistance increases as the temperature decreases. ■
detects the air-fuel ratio in the exhaust gas from the exhaust pipe (b), and when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio (rich),
This is an oxygen sensor that outputs a voltage of about 0.01v when the air-fuel ratio is higher than the stoichiometric air-fuel ratio (lean). , (4) is the vortex detection device i! (2), the internal combustion This is a control device that controls the amount of fuel supplied to the engine (3).

FIG. 2 is a diagram showing the configuration of the control device (4).

2) calculates the time for the fuel supply valve to open at zero power based on the signals from the vortex detection device (2), the cooling water temperature sensor (to), etc. using a time width calculation device, and calculates the digital value corresponding to this time as a timer. Output to (TM). (O8CI) is an oscillator, and the output of the oscillation terminal is frequency-divided by a divider (DIV) and input to a timer (TM). The division ratio of the division device (DIM) is controlled by the feedback control device (2) according to the output of the oxygen sensor (to). In addition, the vortex detection device M f2
1-(7) Output is divided into 1/2 by a flip 70 tube (FF) and outputs a trigger signal to a timer (TM). When the trigger signal is input, the timer (TM) sets the output to rHJ, loads the value output from the time width calculation device (), and starts counting the output pulses of the frequency divider (DIV). , after counting the above value, the driver (DR) sets the output to rLJ, and the output of the timer (TM) becomes r.
The period fuel supply valve e1) of HJ is driven. Here, since the output frequency of the vortex detection device (2) is proportional to the intake air amount of the internal combustion engine (3), when this intake air amount increases, the timer (
The number of times the trigger signal is input to the fuel supply valve (TM) increases, and therefore the number of times the fuel supply valve (b) is opened increases. If the output pulse width of the timer (TM) is constant, a substantially constant amount of fuel is always supplied to the internal combustion engine (3) with respect to the amount of intake air. In addition, the time width calculation device detects the temperature of the cooling water with a cooling water temperature thermistor, for example, and changes the digital value output to the timer (TM). When the output t<7 of the TM) is lengthened, the internal combustion engine (3
) increases the amount of fuel supplied to the The feedback control device θ is the internal combustion engine (detected by the oxygen sensor (2)).
3) The air-fuel ratio of the engine is determined from the oxygen concentration in the exhaust gas, and the set value to the division device (DIV) is changed, thereby changing the cycle of the basic clock supplied to the timer (TM). In this step, the output pulse period of the oscillation M (O3CI) is set to T, and the value set in the divider (DIV) by the feedback control device is set in the timer (TM) by the M1 time width calculation device. If the numerical value is N, the output pulse width of the timer (TM) when the above trigger signal is input to the timer is TXMXN, which is controlled in accordance with the calculated value @) and the output of the oxygen sensor (to). .

In addition, the division device (DIV) is composed of a down counter, which counts the output of the oscillator (O8CI) and presets the output value of the feedback control device @power into the down counter at 11 o'clock when the count value becomes zero. It's like starting a down count again.

FIG. 8 is a diagram illustrating the configuration of the phytovac system @ship θ force. The oscillator [)SC2) outputs pulses with a constant period to the counter (CTI). A comparator (CP) compares the output m sweat of the oxygen sensor enzyme with a set voltage, and outputs an rHJ signal if it is higher than 0.6v, and an rLJ signal if it is lower, for example. The counter (CTI) is an 8-bit up/down counter that is preset to a value of 128 when the internal combustion engine (3) is stopped. After the engine has started, it counts down if the output of the comparator (CP) is "H".
If it is "L", count up. Here, internal combustion m
[A13) Stop detection is performed by, for example, detecting the ignition cycle of the internal combustion engine (3), and if the ignition cycle of the internal combustion engine (3) is equal to or less than a predetermined cycle, it is determined that the engine has stopped. Completion of starting is also determined based on the ignition cycle. (ADD
) adds the count value of the counter (CTI) at this time every time the output of the comparator (CP) is inverted.
It is a bit adder. (C70) counts the number of inversions of the comparator (CP) with a 4-bit counter,
It becomes zero every time the comparator (CP) inverts 166 times.

However, when the power of the control device (4) is turned on, the value is preset to 4, and only after the start, the filter plate (CP) is inverted four times and becomes zero. (TDI) is a delay that delays the output of the comparator (CP) and triggers the monostable multivibrator (O8).

The monostable multivibrator (O5) outputs a pulse of a predetermined width with delay output changes (changes from "H" to rLJ and from "■," to rHJ). The gate (G) has a period r when the counter (C70) is zero and the above pulse is input.
It outputs the HJ signal and is "L" in other cases. (
REG) is an 8-bit register, and the output of the gate (G) changes from rLJ to rHJ and flips 70 bits (DF).
When rHJ, the upper 8 bits of the addition result of the adder (ADD) are stored. Here, storing the upper 8 bits of the 12-bit addition result of the adder (ADD) in the register (REG) means that the above addition result becomes 1716. In addition, the above register is such that the output of the gate (G) is r
When changing from LJ to rHJ, flip-flop (DF
) is rLJ, the 8 bits from the 8th bit (from the least significant bit of the addition result of the adder (ADD))
If the output of ADD) is 001101010010, data 11010100) is stored. This means that the above addition result is reduced to 1/4. The flip-flop (DF) is rLJ when the IF power of the control device (4) is turned on.
be made into

In addition, the output of the gate (G) is delayed by a delay (TD2) and input to the clear terminal of the adder (ADD).
After the adder (REG) stores the result of the adder (ADD), it sets the result of the adder to zero and makes the flip-flop (DF) rHJ.

Therefore, the control 80 device f(4
), the average value of the four count values of the counter (CTI) is stored every time the comparator (CP) is inverted, and thereafter, the average value of the count values of 16 times is stored. Ru. The storage result of the register (REG) is input to the limiter (LMI) (CLM2). The limiter (LMI) adds a predetermined value to the result of the register (REG), and outputs the resulting upper limit value to the digital converter 1 (MC1).
2) subtracts a predetermined numerical value from the result of the register (REG) and outputs the lower limit value to the digital comparator (MCI). Digital comparator (M
CI)1. t, compare the output of the counter (C'TI) with the above upper limit value, and if the output of the counter (CTI) is larger, set rHJ to the data selector (
DS). Digital comparator (MC2)
compares the output of the counter (CTI) with the lower limit value, and if the output of the counter (CTI) is smaller, outputs "H"; otherwise, outputs the rLJ signal to the data selector (DS). The data selector (DS) is a counter (
CTI ), limiter (LMI), (Ll2) output values are input, and digital comparator (MCI), (
One of the above three output values is selected and output based on the output of MC2). In other words, a digital comparator (M
When the digital comparator (MC2) is rHJ, the output of the limiter (Ll2) is output. When both the digital comparator (MCI) and (MC2) are rLJ, the output of the limiter (Ll2) is output. selects the output of the counter (CTI) and outputs it to the divider (DIV).

Therefore, the output of the oscillator (O8CI) is divided by 11 (DIV) according to the output value of the data selector (DS), and the period of this output becomes larger as the output value of the data selector (DS) becomes larger. become longer.

Figure 4 is a timing chart showing the operation of the control device (4). In the same figure, (a) is Combare-2
(.,),)lj1kaa, white engine (3) (7) If the air-fuel ratio is 2, it will be rLJ, and if it is rich, it will be rHJ.

(C1) is the initial value of the counter (CTI) when the internal combustion engine (3) is stopped, and (C2) is the register (・REG)
, that is, the average value of the values added every time the comparator (CP) of the counter (CTI) is inverted. (
Ll) is the upper limit value, which is W greater than the average value (Cm), and (L2) is the lower limit value, which is the average value, and is W larger than the average value (Cm).
W smaller than C2). The setting value of the divider (DIV) is determined by the data selector (
DS) output, (2) varies according to this output (2)
The period of the output of the divider (DIV) changes depending on the time. Therefore, the output pulse width of the timer (TM) is the output (2)
If the output of the fuel comparator CCP> is "L", that is, the air-fuel ratio of the internal combustion engine (3) is lean, the opening time of the fuel supply valve (b) is gradually lengthened, and the comparator (CP) is If the output of rHJ is low or low, and the air-fuel ratio is low or low, the air-fuel ratio of the internal combustion engine (3) is feedback-controlled by shortening the opening time of the gradual fuel supply valve (2), and its average Make sure that the value is the stoichiometric air-fuel ratio. if,
For some reason, the comparator (CP) output is "H"
Even if it remains the same, the value of the output (2) will be clipped at the lower limit value (L2), that is, the lower limit of the setting for the divider (DIV) will be clipped, and the value of the fuel supply valve C1p will be clipped.
Avoid shortening the valve opening time. Therefore, the air-fuel ratio control of the internal combustion engine is prevented from becoming abnormally lean. Further, even when the output of the comparator (CP) becomes "L", it is similarly clipped at the upper limit value (Ll) to prevent the air-fuel ratio from becoming extremely rich. If here, the divider (D
If the upper limit of the set value for IV) is set to a fixed value, for example, the upper limit value (L8) will be larger than the initial value (C1) by W, and the opening time of the fuel supply valve (2) will be set to To (L8
), the control range of the air-fuel ratio becomes narrower and controllability deteriorates.

Here, the air-fuel ratio was feedback-controlled by controlling the amount of fuel supplied, but the fuel supply was set to be richer than the stoichiometric air-fuel ratio, and the throttle valve (
2) The amount of air supplied downstream without passing through the near flow sensor (1) is gradually increased when the output of the comparator (CP) is rHJ, and gradually decreased when the output is rLJ. You can also strain it.

Moreover, if the number of times of averaging is 4 and 16 times, other times may be used. Alternatively, other methods may be used for the t-1 averaging, for example, the values averaged 4 or 16 times by the counter (CTI) and the values previously stored in the register (REG) are further averaged, and the values stored in the register (REG) are averaged. It is also possible to store the information in the following manner.

As is clear from the above explanation, according to the present invention, the control of the air-fuel ratio is limited within a predetermined range centered on the average of the integral value of the feedback of the air-fuel ratio of the internal combustion engine, so that the controllability is not impaired and the controllability is improved. It is possible to perform air-fuel ratio control, and even if the integral control goes too far in one direction for some reason, it will be clipped midway, so it is possible to prevent the air-fuel ratio from being controlled too much and causing the internal combustion engine to malfunction. .

Furthermore, since the number of times of initial averaging is shortened, the responsiveness of averaging is improved, and the period during which the control width is narrowed at the beginning of feedback control is shortened. can be converted into

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the antibacterial device shown in FIG. 1, FIG. 8 is a block diagram of the feedback control device shown in FIG. 2, and FIG. FIG. 2 is a timing chart of the control device. (1) Air flow sensor, (2) Vortex detection device, (3)
Internal combustion engine, (4) control device, (b) fuel supply valve, operating throttle half, (to) oxygen sensor, feedback control device, hourly range calculation device, (O8CI), (O5C2)
) oscillator, (DIV) frequency divider, (TM) timer, (D
R) Driver, (CP) Comparator, (CTI
), (CT2) counter, (TDI), (TD2) delay, (ADD) register, (LMI), (LM
2) Limiter 1 (MCI), (MC2) Digital comparator, (DS) Data selector Note that the same symbols in each figure indicate the same parts 6 Figure 1 Figure 3 Figure 4 - M4 Minus

Claims (1)

[Claims] Integrating the output signal of the exhaust sensor that detects the air-fuel ratio of the engine's intake air-fuel mixture based on engine exhaust gas components, controlling the air-fuel ratio of the engine's intake air-fuel mixture according to the result of this integration, and further integrating the The processed results are averaged, and a control limit value that determines the control width of the air-fuel ratio control based on the integral result is controlled according to the averaged value, and the averaging interval is changed depending on the operating state of the engine. Air-fuel ratio control method.