JPS58200060A - Air-fuel ratio controlling device of internal-combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

Generally, an oxygen sensor is used as a means to detect the air-fuel ratio based on the exhaust gas components of an internal combustion engine.The output of this oxygen sensor is compared with a predetermined voltage level, and the direction of integration of the integrator is determined based on the result of this comparison. The air-fuel ratio is controlled by inverting the integrator and changing the amount of fuel supplied to the internal combustion engine in proportion to the output of the integrator. However, in the case of internal combustion engines for automobiles, an air-fuel ratio that is slightly richer than the stoichiometric air-fuel ratio is required under high-load operating conditions, and in this case, feedback control of the air-fuel ratio by the butterfly oxygen sensor is stopped. There must be. Further, since commonly used oxygen sensors start operating at temperatures above 350° C., feedback control cannot be performed when the internal combustion engine is cold. However, if feedback control is stopped, errors in the control system may cause the air-fuel ratio to deviate from the one to be controlled. Therefore, the output of the integrator during feedback control is averaged and stored in memory, and the data stored in this memory is retained even when the key switch of the internal combustion engine is turned off, as described above. If it is not possible to perform feedback control, it may be possible to compensate for errors in the control system that controls the air-fuel ratio based on data stored in memory.

However, in the case of internal combustion engines for automobiles, there are many transient states such as acceleration and deceleration, and it is difficult to control the air-fuel ratio to the stoichiometric ratio during these periods, so the output of the integrator may fluctuate more than in a steady state. Since the average value of the output of the integrator also includes errors other than static errors of the control system, the air-fuel ratio cannot be controlled satisfactorily.

The present invention has been made to eliminate the above-mentioned drawbacks.) The averaging means for averaging the output of the integrating means performs averaging when the rate of change of the output of the integrating means is within a predetermined range. Therefore, averaging is not performed in the transient state of the internal combustion engine, and when control according to the output of the integrator □ stage is inappropriate, such as during overload operation or cold conditions, the averaging is performed according to the output of the averaging means. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can always accurately control the air-fuel ratio (by controlling the air-fuel ratio control pipe).

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, %l is a Karman vortex type air flow sensor provided at the tip of the intake pipe 31 of the internal combustion engine 3, through which the intake air of the internal combustion engine 3 passes. Therefore, a vortex is generated downstream of the vortex generator 11 installed in the air flow sensor, and the ultrasonic wave generated by the ultrasonic oscillator 21 installed on the outer periphery of the air flow sensor generates the vortex. Each wave is frequency modulated and reaches the ultrasonic receiver 22, which is also provided on the outer periphery of the air flow sensor. The vortex detection device 2 outputs a signal for generating ultrasonic waves to the ultrasonic oscillator 21, and also demodulates the signal detected by the ultrasonic receiver 22 using a built-in FM signal demodulator (not shown) to convert the signal to the frequency of the Karman vortex. It outputs a pulse train of nine corresponding frequencies. The frequency of this pulse train is proportional to the amount of intake air of the internal combustion engine 3 that passes through the air flow sensor. 32 is the suction pipe 31
The internal combustion engine 3 operates by inhaling a mixture of air taken in through the intake pipe 31 and fuel supplied from the fuel supply valve 32. do. The throttle valve 33 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 32.

The pressure difference between the pressure inside the suction pipe 31 and the fuel pressure supplied to the fuel supply valve 32 is kept constant. A water temperature sensor 34 detects the temperature of the cooling water of the internal combustion engine 3, and is composed of, for example, a thermistor whose resistance increases as the temperature decreases. 35 detects the air-fuel ratio from the oxygen concentration in the exhaust gas discharged from the exhaust pipe 36 of the internal combustion engine 3, and when the air-fuel ratio is smaller (rich) than the stoichiometric air-fuel ratio, the air-fuel ratio is larger than the stoichiometric air-fuel ratio by IVV (
37 is the throttle valve 33 of the intake pipe 31.
This is a vacuum switch that is installed on the downstream side of the suction pipe 31 and is turned on when the negative pressure in the suction pipe 31 becomes higher than a predetermined value, and turned off in other cases. Further, 4 is a vortex detection device 2. Water temperature sensor 34. Oxygen sensor 35 and vacuum switch 3
7 output etc. are input.

The control device controls the amount of fuel supplied to the internal combustion engine 3 by controlling the opening time of the fuel supply valve 32 in accordance with the operating state of the internal combustion engine 3. The control device 4 controls the amount of fuel supplied to the internal combustion engine 3 when the vacuum switch 37 is on. In this case, it is determined that the internal combustion engine 3 is in a high-load operating state.

FIG. 2 shows the configuration of the control device 4, and 42 is the vortex detection device 2.
．． This is a time width calculation device that receives the outputs of the water temperature sensor 34 and the vacuum switch 37, calculates the opening time of the fuel supply valve 32, and outputs a digital value corresponding to this time to the timer TM.

Further, 08CI is an oscillator, the output of which is frequency-divided by a divider DIV and then input to the timer TM.

The frequency division ratio of the divider DIV is controlled by the feedback control device 41 according to the output of the oxygen sensor 35. The output of the vortex detection device 2 is frequency-divided by 1 in the free lag flop FF and then added to the timer TM as a trigger signal.

When this trigger signal is applied, the timer TM changes its output to rH.
The numerical value output from the time width calculation device 42 is loaded as J, and counting of the output pulses of the frequency divider DIV is started, and after counting the above numerical value, the output is set to rLJ.

The driver DR drives the fuel supply valve 32 to open it while the output of the timer TM is rHJ. Since the output frequency of the vortex detection device 2 is proportional to the intake air amount of the internal combustion engine 3, as this intake air amount increases, the number of trigger signals to the timer TM increases, and the number of times the fuel supply valve 32 is opened increases. Therefore,
If the output pulse width of the timer TM is constant, the amount of fuel in the internal combustion engine 3 is always at a substantially constant ratio to the amount of intake air.
supplied to On the other hand, the output of the time width calculation device 42 changes depending on the output change of the water temperature sensor 34, and for example,
When the unit is cold, the digital value of its output is large.
As a result, the output pulse width of the timer TM also increases, and the amount of fuel supplied to the internal combustion engine 3 increases. Further, the feedback control device 41 determines the air-fuel ratio based on the oxygen concentration in the exhaust gas of the internal combustion engine 3 detected by the oxygen controller 35, changes the set value of the divider DIV based on this, and sets the timer T.
Change the period of the basic clock supplied to M. Here, if the period of the output pulse of the oscillator O8CI is τ, the value set in the frequency divider DIV by the feedback control device 41 is M1, and the value set in the timer TM by the time width calculation device 42 is N, The output pulse width of the timer TM generated upon input of the trigger signal is τX M When the vacuum switch 37 of the time range calculation device 42 is off, that is, when the internal combustion engine 3 is not in a high-load operating state, a digital value corresponding to the stoichiometric air-fuel ratio is set in the timer TM, and a feedback control signal is sent to the feedback control device 41. Output to. Further, when the vacuum switch 37 is on, that is, when the internal combustion engine 3 is in a high-load operating state, the time width calculating device 42 sets a digital value that is more accurate than the stoichiometric air-fuel ratio in the timer TM, and also feeds back a feedback stop signal. Output to the control device 41. Similarly, the divider DIV is composed of a down counter, which counts the output of the oscillator O8CI, and when the count value reaches zero, presets the output value of the feedback control device 41 and starts down counting again. It has become.

FIG. 3 shows the configuration of the feedback control device 41, in which the oscillator 08C2 outputs pulses with a constant period to the counter CTI, and the output voltage of the comparator cpFi oxygen sensor 35 is compared with the set voltage, and the difference is, for example, o, sv. ,ib
If it is high, it outputs rHJ, and if it is lower than 0.5v, it outputs rLJ. The counter CTI is an 8-bit up/down counter, which is preset to a numerical value of 128 when the internal combustion engine 3 is stopped, and stops counting when the time span calculating device 42 outputs the aforementioned feedback stop signal.

After starting the internal combustion engine 3, the counter CTI is the comparator C.
If the output of P is "H", it counts down, and if it is "L", it counts up. The stoppage of the internal combustion engine 3 is detected by detecting, for example, the ignition cycle of the internal combustion engine 30, and if the cycle is equal to or greater than a predetermined cycle, it is determined that the internal combustion engine 3 has stopped. Each time the output of the comparator CP is inverted, the data selector DS selects registers REG4 to
It operates to sequentially store the value of counter CTI in REG7. As a result, each time the comparator CP is inverted, the registers RIG4, REG5, REG6 . R.E.
The values of the counter CTI are stored in the order of G7°REG4, REG5, . . . . Adder ADD2 adds registers REG4 and REG5, and adder ADD3 adds registers REG6 and REG7. Digital comparator CMP is connected to adder ADD2. The outputs of ADD3 are compared, and if the difference is less than a predetermined value, an rLJ signal is output, and if the difference is greater than a predetermined value, an IHJ signal is output. The program DDI is a 12-bit adder, and its output is zero when the time width arithmetic unit 42 outputs a feedback stop signal and when the output of the digital comparator CMP is rHJ; otherwise, the output of the comparator CP is zero. The count value of counter CTI is added each time it is inverted.

CT2d is a 4-bit counter, and its output is zero when the feedback stop signal is output from the time width arithmetic unit 42 and when the output signal from the digital comparator CMP is rHJ. Otherwise, it counts the number of inversions of the comparator cp, and It becomes zero every 16 rotations of CP. The f-V converter AD that converts the output frequency of the FVtiVt device 2 into a voltage is an AD converter that digitally converts the output of the f-V converter FV. Correction calculator 4
3, the counter CT I O1' is connected to the frequency divider DIV while the time width arithmetic unit 42 outputs the feedback control signal.
Set to . Therefore, the output of comparator CP is rLJ
In other words, if the air-fuel ratio of the internal combustion engine 3 is lean, the splitter DIV
The setting value for the fuel control valve 32 is gradually increased, and the valve opening time of the fuel control valve 32 is controlled to become longer. Conversely, if the output of the comparator CP is rHJ, that is, the air-fuel ratio of the internal combustion engine 3 is rich, the valve opening time is shortened. controlled so that Further, the correction calculator 43 is outputting the feedback control signal, and the output of the digital comparator CMP is rLJ, that is, the adder ADD2. ．． If the deviation of ADD3 is within the specified value, then 7. . 1°. Each time the value of the counter CTI when the comparator CP is inverted is added to the adder ADDl 16 times, the addition result is set as t-,46, and the internal combustion RIG,3 is Store it in either one. The intake air amount is determined based on the output of the A-D converter AD. Therefore, the correction calculator 43 selects and stores the average value of the 16 outputs of the counter CTI in one of the registers REGI to REG3 according to the output of the AD converter AD. Further, when the time width calculation device 42 outputs a feedback stop signal, the correction calculation device 43 selects one of the registers REGI-REG3 according to the output of the A-D converter AD and divides the stored data. Set to device DIV. Therefore, the average value of the counter CTI is set in the central branch divider DIV that outputs the feedback stop signal.

FIG. 4 is a timing chart showing the operation of the control device 4, and (a) shows the state of the vacuum switch 37.

(b) shows the output of the comparator CP, (C) shows the output of the correction calculator 43, and (1) shows the change in the output pulse width of the tie YTM.Assuming that the vacuum switch 37 was off until time t, the correction calculation is performed. The counter 43 is a counter CTI.
Outputs the count value. For this reason, the comparator CP
If the output is "L", that is, the air-fuel ratio is lean, the output numerical value of the correction calculator 43 gradually increases.

The output pulse width of the timer TM also gradually increases. Accordingly, the opening time of the fuel supply valve 32 becomes gradually longer, and the amount of fuel supplied to the internal combustion engine 3 increases.

If the output of the comparator CP is "H", that is, the air-fuel ratio is rich, the above will be reversed, and the amount of fuel supplied to the internal combustion engine 3 will decrease. Next, at time t, the vacuum switch 37
When turned on, the time width arithmetic unit 42 issues a feedback stop signal, and the correction arithmetic unit 43a register RE:G1
.about.REG3, that is, the average value of the 16 peak values of the counter CTI is output. Here, when the output value of the correction calculator 43 when the vacuum switch 37 is turned off is 128, that is, the air-fuel ratio correction coefficient by the feedback control device 41 is 1.0 (corresponding to C2), the air-fuel ratio of the internal combustion engine 3 is Assuming the fuel ratio is slightly lean, the empty/
The 16-time average value of the peak value of CTI is υ larger than 128, and the average value of the peak value of CTI is larger than 02, like l and CI. Therefore, when the vacuum switch 37 is on, the feedback control device 41 is adjusted so that the output pulse width of the timer TM is a value di that is slightly richer than the value d2 when the air-fuel ratio correction coefficient is 1.0. controlled. That is, even when the vacuum switch 37 is on, the air-fuel ratio is accurately controlled to a predetermined air-fuel ratio.

(Figure 5 is also a timing chart showing the operation of the control device 4)
(e) C: The output % of the comparator CP (f) indicates the output of the counter CTI, and (B) indicates the output of the digital comparator CMP. Assuming that the throttle valve 33 is suddenly opened at time t and the air-fuel ratio becomes lean, the count value of the count CTI controls up-counting until time t. Therefore, comparator CP is rLJ
The time t when it reverses from to rHJ.

The value stored in the V register REG4 is also larger than the value when the comparator CP was previously inverted from rLJ to rHJ, and therefore the value of the adder ADD2 is larger than the value stored in the V register REG4.
The value of D3) is also large, and the digital comparator C
The output of MP becomes rHJ.

The above-mentioned air-fuel ratio ratio is gradually controlled to a predetermined air-fuel ratio by the feedback control device 41, and if the air-fuel ratio returns to the state before the sudden opening of the throttle valve 33 at time t, then the comparator CP is adjusted three times. Adder ADD2 at inverted time t4.

When there is almost no difference between ADD3, the output of digital comparator CMP becomes rLJ. The output of the digital comparator CMP is r! (During J, counter CT
Since the outputs of the adder ADDI that adds the output of I and the counter CT2 that counts the number of inversions of the comparator CP are set to zero, averaging of the output of the counter CTI is stopped. In this way, when the air-fuel ratio of the internal combustion engine 3 changes significantly to lean or rich due to the sudden opening and closing of the throttle valve 33, the averaging process of the counter CTI is stopped,
To prevent registers REGI-REG3 from storing values affected by large changes in air-fuel ratio.

In the above embodiment, the added value of the counter CTI is compared every two times when the comparator CP is inverted, and if the deviation is large, the averaging process of the counter CTI is stopped, thereby controlling the transient state of the internal combustion engine. counter CTI without being affected by large changes in air-fuel ratio.
By averaging the output, it is possible to accurately control the air-fuel ratio even when normal feedback control is not possible.In the above embodiment, the average of the counter CTI Although the number of times was set to 16, any number of times other than this may be used. Alternatively, the averaging can be performed using other methods, such as further averaging the 16 average values of the counter CTI and the values previously stored in the registers REGI-REG3, and storing them in the registers REGI-REG3. Also good. Also, register REGI-REG3
Even if the power supply to the control device 4 is cut off, power is constantly supplied to the water temperature sensor 3 from the start of the internal combustion engine 3.
During the cooling state until the resistance value of 4 becomes less than a predetermined value, that is, until the temperature of the cooling water of the internal combustion engine 3 becomes more than a predetermined value, the air-fuel ratio control by the oxygen sensor 35 is stopped and the registers REGI-REG3 are The air-fuel ratio may be controlled based on a stored value. Furthermore, the air-fuel ratio may be controlled by the value of the register REGI-REG3 even in normal times other than overload or cold conditions.

As described above, the present invention includes an integrating means for integrating the output of the air-fuel ratio detecting means.

An averaging means is provided for averaging the output of the integrating means only when the rate of change is within a certain range.

Therefore, since the averaging means does not perform averaging in the transient state of the internal combustion engine where fluctuations are large, the output thereof has less error. Therefore, even when normal air-fuel ratio control cannot be performed according to the output of the integrating means, such as during overload, the air-fuel ratio can be accurately controlled using the output of the averaging means, and the internal combustion engine The air-fuel ratio can be accurately controlled in all operating ranges, resulting in better exhaust gas and drivability.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an air-fuel ratio control device for an internal combustion engine according to the present invention, FIG. 2 is a block diagram of a control device according to the present invention, and FIG. Fourth
5 is a timing chart of the control device according to the present invention. l...Air 70-sensor, 2°°° vortex detection device, 3
... Internal combustion engine %4 ... Control device, 32 ... Fuel supply valve. 34...Water temperature sensor, 35...Oxygen sensor, 37.
...] Kumu switch, 41-°° feedback control device, 42... Time width calculating device, 43... Correction calculating unit, 08C1-08C2... Oscillator, DIV...
・Branch unit, TM...timer, DR...driver, C
P...Comparator, CTI-CT2...Counter, ADDI~ADD3...Adder, REGI-REG
7...Register, CMP...Digital comparator. The same reference numerals in the figures indicate the same or equivalent parts. Agent Shin Kuzuno −

Claims (1)

[Claims] Q) Comprising an air-fuel ratio detection means for detecting the air-fuel ratio based on the exhaust gas components of the internal combustion engine and an integrating means for integrating the output of the air-fuel ratio detection means, and controlling the air-fuel ratio of the internal combustion engine according to the output of the integrating means. In an air-fuel ratio control device for an internal combustion engine, an averaging means is provided to average the output of the integrating means when the rate of change thereof is within a certain range, and the air-fuel ratio control according to at least the i-force of the integrating means is inappropriate. An air-fuel ratio control device for an internal combustion engine, wherein the air-fuel ratio is controlled in accordance with the output of the averaging means.