JPS58222940A - Controller for air fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve fuel efficiency while meeting standards for the quantities of harmful emissions, by controlling the air fuel ratio depending on the output of a combustion fluctuation detector in operation with a thin mixture and on the output of an air fuel ratio sensor in operation at a theoretical air fuel ratio. CONSTITUTION:A fuel control unit CONT calculates the quantity of supplied fuel depending on the operating condition of an engine to drive an electromagnetic fuel injection valve 8. In the operation of the engine with a thin mixture, the air fuel ratio is controlled through a thin air fuel ratio compensation circuit 100 depending on the output of a torque detector 13. In the operation of the engine at a theoretical air fuel ratio, the ratio is controlled through a theoretical air fuel ratio compensation circuit 130 depending on the output of an air fuel ratio sensor 14. As a result, the fuel efficiency of the internal combustion engine is improved in its entire operation range as standards for the quantities of harmful emissions are met.

Description

[Detailed description of the invention] The present invention relates to an air-fuel ratio control device for an internal combustion engine.

Generally, as shown in Fig. 1, the exhaust gas components burned and discharged by the internal combustion engine and the fuel consumption rate FC of the internal combustion engine
is known to have a close relationship with the air-fuel ratio Ov'F) supplied to the internal combustion engine.

In addition to purifying exhaust gas, there is also a demand for reducing the fuel consumption rate of engines from the standpoint of resource conservation.

As shown in Figure 1, it is advantageous to operate an internal combustion engine in a lean mixture range to simultaneously achieve exhaust gas purification and fuel consumption reduction, but in a lean mixture range, problems such as misfires occur. Therefore, when considering the variation and deterioration of the engine and other accessories (carburizer, etc.), most engines cannot be operated in a lean mixture range close to the misfire limit, and the misfire limit is close to the misfire limit. Currently, the air-fuel ratio is used in a stable region of 2-rich. This poses a problem in purifying exhaust gas and achieving resource conservation.

The present inventor focused on the following small song. That is, as shown in FIG. 1, the minimum fuel consumption rate is achieved when the engine is operated at a lean air-fuel ratio just before the misfire region (MF REG).

Combustion fluctuations are related to A/11', and the closer to the misfire region, the sharper the combustion fluctuations become. In Fig. 1, Δτ represents the torque fluctuation range. Combustion fluctuations within the cylinders appear as vibrations in the engine body due to torque reaction forces generated in each cylinder, so combustion fluctuations in the engine body can be detected from the engine vibrations. Therefore, by determining the engine combustion fluctuation and controlling the air-fuel ratio supplied to the engine so that the engine combustion fluctuation remains at a certain value,
It is possible to achieve a significant improvement in fuel efficiency by always controlling the air-fuel ratio to be below the misfire range and at the best fuel efficiency point.

However, even if the actual combustion air-fuel mixture is controlled to the target value in the feedback control of the air-fuel ratio by the above operation, and the engine is operated at the best fuel efficiency, in some operating regions the unburned gas still emitted by the engine still remains. There are some places where the air-fuel ratio does not drop sufficiently. If the air-fuel ratio is made leaner, NOx will decrease, but misfires will occur and HC will increase. Therefore, it is practically difficult to further dilute the air-fuel ratio to reduce the amount of unburned gas in the exhaust gas, which poses a problem in terms of exhaust gas countermeasures.

An object of the present invention is to perform feedback control of the air-fuel ratio of the engine to the stoichiometric air-fuel ratio based on the output signal of an air-fuel ratio sensor provided in the exhaust passage in an operating range where unburned gas in the exhaust gas does not decrease sufficiently. The three-way catalyst simultaneously purifies HCSCo oxidation and NO reduction, and in the operating range where the unburned gas component in the engine exhaust gas is sufficiently low, the combustion fluctuation detector output signal Based on the concept of switching between two feedback controls, which feedback control the fuel ratio to the best fuel efficiency point in the lean air-fuel ratio range, based on a signal from an engine sensor that detects the operating state of the internal combustion engine, the system is designed to reduce exhaust emissions in all operating ranges of the internal combustion engine. The aim is to improve fuel efficiency by 1. while satisfying the emissions requirements for harmful components.

In the present invention, an intake air amount detection device, a rotation speed detection device, a combustion fluctuation detector that detects combustion fluctuations, an air-fuel ratio sensor provided in the exhaust passage, a three-way catalyst provided in the exhaust passage, and a skeleton intake air amount detection device , a fuel amount calculation circuit that controls the air-fuel ratio supplied to the internal combustion engine based on the detection signal of the rotation speed device and the combustion fluctuation detector; A lean air-fuel ratio correction circuit that corrects the air-fuel ratio, a stoichiometric air-fuel ratio correction circuit that corrects the air and fuel consumption supplied to the internal combustion engine according to the output signal of the air-fuel ratio sensor, and outputs of the lean air-fuel ratio correction circuit and the stoichiometric air-fuel ratio correction circuit. is selectively connected to the fuel amount calculation circuit, so that during lean air-fuel ratio operation, the output of the combustion fluctuation detector is determined, and during stoichiometric air-fuel ratio operation, the output of the air-fuel ratio sensor is An air-fuel ratio control device for an internal combustion engine is provided, in which air-fuel ratio control is performed in accordance with the air-fuel ratio.

An air-fuel ratio control device for an internal combustion engine as an embodiment of the present invention is shown in FIGS. 2 to 12. In FIG. 2, an internal combustion engine 1 is a spark ignition engine for driving a car, and combustion air is sucked into a combustion chamber 6 of the engine 1 through an air cleaner 2, an air flow meter 3, an intake conduit 4, and an intake valve 5. Ru.

The suction conduit 4 is provided with a throttle valve 7 that can be operated at will by the driver. Fuel is injected and supplied to the intake valve 5 from an electromagnetic fuel injection valve 8 installed in the intake conduit 4. The mixture of fuel and air is combusted in the combustion chamber 6 and is discharged into the atmosphere via an exhaust valve 9 and an exhaust conduit 10.

The fuel control unit (C0NT) calculates the amount of fuel to be supplied to the engine 1 according to the operating state of the engine 1, drives the electromagnetic fuel injection valve 8, and controls the amount of fuel to be supplied to the engine 1. The fuel control unit C0NT includes an air flow meter 3 that detects the intake air amount of the engine 1, an ignition coil 12, a torque detector 13 that detects torque fluctuations of the engine 1, and an oxygen concentration sensor for detecting the air-fuel ratio in the exhaust pipe. The detection signal of the device 14 is input.

In this example, the intake air amount to the engine 1 and the signal from the air flow meter 3 are used, but the air flow meter 3 also uses the intake pipe negative pressure generated downstream of the throttle valve 7 of the engine 1 and the engine speed. The amount of intake air may be determined from the engine, or the rotational speed may be determined by detecting a rotation signal from a cylinder gear, distributor, etc. that rotate in synchronization with the engine's 10 revolutions.

As shown in Fig. 2, the torque detector 13 is bolted to a mount 135 that supports the engine, and detects vibrations around the crankshaft in the lean band of the engine using a piezo element, etc. The purpose is to obtain an analog signal proportional to the target torque fluctuation, and in this embodiment, a total of two of them are arranged in one engine at symmetrical positions. Of course, a configuration may be adopted in which only one is disposed for one engine. Torque detector 1
3 consists of a pressure sensor 131, a rubber mount 133, and a rubber mount cover 134, and the pressure sensor 131, rubber mount cover 134, and rubber mount 133 are attached in this order from the arm 132 side. As the pressure sensor 131, for example, a commercially available pressure detector having piezo elements arranged in four directions and capable of detecting vibrations (mechanical torque fluctuations) in all directions is used.

The configuration of the fuel control unit (CONT) is shown in FIG. Amplifier 20 is a well-known type consisting of a buffer and an amplifier. The band pulse filter 30 extracts only the output with a frequency of IHz to several Hz from the analog signal from the amplifier 20, and for example, a model 852 manufactured by Rockland Systems is used. The clock circuit 40 is of a well-known type and includes an oscillation circuit using a crystal resonator and a counter that divides the frequency of this oscillation circuit.

The timing pulse generation circuit 50 is a circuit that generates a reset signal to the peak hold circuit 60 and an interrupt signal to the lean air-fuel ratio correction circuit 100 based on the clock from the clock circuit 40.

Its internal circuit is shown in FIG. In FIG. 4, signals of 02 Hz and 5 kHz are input from the clock circuit 40 to input terminals 510 and 511, respectively.

The input terminal 510 is connected to the reset terminal R of the counter with divider 501, and the input terminal 511 is connected to the clock terminal CLK of the counter with divider 501. The counter with divider 501 is an IC CD401 manufactured by RCA.
7 is used, and its output Q1 is used as a signal for interrupt calculation of the lean air-fuel ratio correction circuit 100 via the terminal 512. Outputs Q5 and Q8i1 are connected to the set terminal S and reset terminal R of the R-8 flip-flop 5020, respectively, and the output Q9 is connected to the clock enable terminal CEK. The R-S flip-flop 502 is, for example, R
CA company IC CD4013 is used. Its output Q is connected to peak hold circuit 60 via terminal 513.

The operation of timing pulse generation circuit 50 will now be described. The reset terminal of the counter with divider 501 has a first
The 2Hz pulse shown in Fig. 7 (1) is input, and when the pulse changes from "1" to rOJ, counting starts. A clock with a frequency of 5 kHz is input to the clock input of the counter 501. Therefore, when the first pulse comes, the output Q
1. Gurus is output. When the ninth 7,000 rus arrives, the output Q9 becomes "1" and the clock enable terminal becomes "1".
1, so the clock stops being input until the next reset.

Therefore, a pulse is outputted to the output Q1 as shown in FIG. 17(2). The output /4'rus is sent via a terminal 512 to a trigger 4 for starting the interrupt calculation of the lean air-fuel ratio correction circuit 1oo.
Becomes Luz. Outputs Q5 and Q8 set and reset R-87 flip-flop 502 and are the outputs of R-8 flip-flop 502. The No. 9 Rus in Figure 17 (3) is removed. The pulse is input to the peak hold circuit 60 via the terminal 513, has a pulse width of approximately 600 microseconds, and serves as a reset signal for the peak hold circuit.

FIG. 5 shows the configuration of the peak hold circuit 6o.

In FIG. 5, the positive and negative terminals of the diode 601 and the negative terminal of the diode 611 are connected to the output of the band Nori filter 3°, and the negative terminal of the diode 601 is connected to one end of the resistor 602. #The other end of the resistor 602 is connected to the positive terminal of the capacitor 603, the non-inverting input of the buffer amplifier 606, and the resistor 604. The negative electrode of capacitor 603 is grounded. The other end of the resistor 604 is connected to one end of an analog switch 605. The other end of the analog switch 605 is grounded, and the control terminal is connected to the signal (3) in FIG. 17 of the timing signal generating circuit 50. The inverting input of buffer amplifier 606 is connected to the output.

The positive terminal of the diode 611 is connected to one end of a resistor 612. The other end of the resistor 612 is connected to the negative terminal of a capacitor 613, the non-inverting input of a buffer amplifier 616, and a resistor 614. The positive terminal of capacitor 613 is grounded. The other end of the resistor 614 is connected to one end of an analog switch 615.

The other end of the analog switch 615 is grounded, and the control terminal is connected to the signal (3) in FIG. 17 of the timing pulse generating circuit 50.

The inverting input of buffer amplifier 616 is connected to the output. The output of the buffer amplifier 606 is connected to one end of the resistor 622, and the other end is connected to the non-inverting input of the buffer amplifier 625.
It is connected to the resistor 621. The other end of the resistor 621 is grounded. The output of buffer amplifier 616 is connected to one end of resistor 623, and the other end is connected to the inverting input of buffer amplifier 6250. The output of the buffer amplifier 625 is outputted to the AD conversion circuit 70 via an output terminal 633 and connected to one end of a resistor 624. The other end of resistor 624 is connected to the inverting input of buffer amplifier 625.

The operation of peak hold circuit 60 will be described below. When the pulse shown in FIG. 17(3) is applied from the timing pulse generation circuit 50 to the control inputs of the analog switches 605, 615, the analog switches 605, 615 are closed during the pulse width, so that the capacitors 603, 615 are closed.
The charge of 613 is discharged through resistors 604 and 614 of low resistance value, and the voltage of capacitors 603 and 613 is set to OV.

set. After that, the 17th of Pantone 9 filter 30
When the output waveform shown in FIG. 4 enters from the input terminal 632, the fun answer 603 is charged to a positive voltage through the diode 601 and the resistor 602. This capacitor 6
The positive peak value of the voltage 03 is held after being reset until the next reset. The capacitor 603
When the voltage is outputted through the next buffer amplifier 606 with high input impedance, the waveform becomes as shown in FIG. 17(5).

On the other hand, the output waveform shown in FIG. 17 (4) is shown at the input terminal 63.
2, the capacitor 613 is charged to a negative voltage through the diode 611 and the resistor 612. The voltage of this capacitor 613 is held at a negative peak value from the time it is reset until the next time it is reset. When the voltage of the capacitor 613 is outputted through the next buffer amplifier 616 with high input impedance, the voltage shown in FIG.
) waveform and longevity.

By taking the difference between the output of the buffer amplifier 606 and the output of the buffer amplifier 616 with the differential amplifier 625, the difference between the positive peak value and the negative peak value from one reset to the next reset is determined by the differential amplifier. 625, and its waveform is shown in FIG. 17 (7).

FIG. 6 shows the configuration of the AD conversion circuit 70.

In FIG. 6, the input/output control signal from the lean air-fuel ratio correction circuit 100 is directly input to the NAND dart 703, and input to the AND gate 06 after being inverted by the inverter 705. The device select signal (SEL signal) of the lean air-fuel ratio correction circuit 100 is directly input to the Nantes gate 703 and the ANDR-door 06. Also, inverter 707
, a resistor 708, and a capacitor 709 constitute a delay circuit, and the SEL signal is input to the AND gate 706 via this delay circuit. But And Dirt 7
06 outputs a pulse signal with a width of about 100 nanoseconds as shown in FIG. 17 (8). This pulse signal is input to the A-D conversion command terminal ○■ of the successive approximation type A-D converter 701. As the A-D converter 701, for example, ADC80AG-12 manufactured by Burr-Brown Corporation is used.

The conversion end terminal EOC of the AD converter 701 is connected to the busy terminal BSY of the correction calculation circuit 100, and the output terminals B1 to B12 are connected to the pass line of the lean air-fuel ratio correction circuit 100 via the 3-state buffer 702. . 3
The state buffer 702 is, for example, Toshiba IC TC50.
12 is used.

The operation of AD conversion circuit 70 will be explained below.

When the pulse shown in FIG. 17(2) is input from the timing pulse generation circuit 50 to the correction calculation circuit 100, the lean air-fuel ratio correction circuit 100 interrupts the program currently being executed and programs the AD conversion process. Execute. In the program, the AD conversion start command is executed as shown in Figure 17 (
8) is the AD conversion command terminal C of the AD converter 701.
It is applied to NV, and the conversion operation starts at the rising edge of this pulse.

At the same time, the conversion end terminal EOC shown in FIG. 17 (9)
The output signal rises to the "1" level.

Here, the conversion end terminal EOC is connected to the busy terminal BSY of the device control unit (DCU) of the correction calculation circuit 100, and the completion of the analog signal read command from the peak hold circuit 60 is determined by the output signal of the conversion end terminal EOC. "
The input/output control signal and the SEL signal are both held at the 11'' level until this time.

The successive approximation type A-D converter 701 performs a conversion operation while the output signal of the EOC terminal is at the "1" level, and outputs a digitized binary data signal from the output terminals B1 to B12. . When the A-D conversion operation is completed, the output signal at the conversion end terminal (■) goes to the "0" level, and the read command waiting state of the correction calculation circuit 100 is released, and the analog signal data of the peak hold circuit 60 is set to the lean air-fuel ratio. The data is read into the correction circuit 100.

FIG. 7 shows the configuration of the circuit speed detection circuit 80. The rotational speed detection circuit 80 includes a pulse shaping circuit 80m and a counting circuit 80b. The pulse shaping circuit SOa receives the pulse of the negative terminal of the ignition coil 12 through an input terminal 817, and the input terminal 817 is connected to a resistor 80.
It is connected to one end of 1.
The other end of resistor 801 is resistor 802
and a capacitor 803, and the other end of the capacitor 803 is grounded. The other end of the resistor 802 is the diode 8
04, and the cathode of the diode 804 is connected to a resistor 805, a capacitor 806, a Zener diode 807, and a resistor 808. resistance 805
, the other ends of the capacitor 806 and the Zener diode 807 are grounded, and the other end of the resistor 808 is connected to the transistor 8.
Connected to 18 paces. The transistor 818
The emitter of is grounded, and the collector is input to a resistor 809 and a Schmidt Nand r-) 810. A +5V power supply VC is input to one end of the resistor 809 and the other input of the shield 810.

The output of the Sea Mittenand Dart 810 is connected to the capacitor 8.
11 and a resistor 812 as a trigger pulse, and the output of the monostable multivibrator 813 is input as a trigger pulse to a monostable multivibrator 816 composed of a capacitor 814 and a resistor 815.
is input as a trigger pulse.

As the monostable multivibrators 813 and 816, for example, RCA IC CD4047 is used. In this way, from the output of the monostable multivibrator 816, the first
A timing pulse signal having a waveform as shown in FIG. 8 (2) is output.

Next, the counting circuit 80b will be described. The binary counter 851 counts and frequency-divides the clock pulse signal C1 input to the clock terminal CL, and uses, for example, a CD4024 manufactured by RCA. And the counter 85 with
1 is obtained by dividing the clock pulse signal C1 of approximately 128 kHz as shown in FIG. 18(3) to obtain the signal shown in FIG. 18(4).
A frequency-divided pulse signal of about 32 kHz as shown in FIG. 1 is output from the output terminal Q2. The counter with divider 852 basically counts the clock pulse signal C1 inputted to the clock terminal CL, and the counter 852 with a divider basically counts the clock pulse signal C1 inputted to the clock terminal CL.
When the output signal of one of the four output terminals is at the "1" level and the "1" level signal is input to the counting operation stop terminal EN, the set counting operation is stopped.

Therefore, in this embodiment, the output terminal Q4 and the stop terminal EN
is connected, and when the output of output terminal Q4 reaches the "1" level, a "1" level signal is input to the stop terminal EN,
Stop counting operation. In this state, the pulse shaping circuit is 80m
When the timing pulse signal shown in FIG. 18 (2) is input to the reset terminal R, the counter 852 is reset, and the output of the output terminal Q4 becomes "0" level as shown in FIG. 18 (7). . Then, when time T has elapsed and the signal input to the reset terminal R reaches the "0" level, the counter 852 starts the division operation and output terminal Q2
, Q3 sequentially output pulse signals as shown in FIG. 18 (5) and (6), respectively.

When the output of the extraction output terminal Q4 reaches the "1" level, the counter 852 stops counting again.

The output signals of the counters 851, 852 and the pulse shaping circuit 80m are inputted to the clock terminal CL of the 12-bit counter 855 via the no-go signals 853 and 854, respectively, and the Q3 output of the counter 852 is input to the clock terminal CL of the counter 855.
It is input to the reset terminal R of No. 5.

That is, the pulse shaping circuit 80m shown in FIG. 18(2)
The output signal of the counter 852 and the Q of the counter 852 shown in FIG.
By using the 3-output NOR logic, the Shino r-) 853 outputs the more Norse signal shown in FIG. By performing a NOR logic with the output signal of the counter 851 shown in FIG.
A pulse signal as shown in 9) is output, and this pulse signal is input to the counter 855.

The timing pulse signal shown in Fig. 18 (2) is
0'' level and the Noah r- shown in Figure 18 (8)
At time t1 when the output of counter 853 reaches the "1" level, counter 855 stops its division operation. Thereafter, the outputs of the output terminals Q1 to Q12 of the counter 855 are temporarily held and stored in the shift registers 856 to 858 (for example, a CD4035 manufactured by RCA is used) according to the rise of the Q2 output of the counter 852 at time t2.

Next, at time t3, the Q3 output of the counter 852 becomes 1.
1" level, the counter 855 is reset,
When the Q4 output of the counter 852 reaches the "1" level at time t4, the counter 855 starts counting again.

Since this operation of the counter 855 is repeated in synchronization with the ignition coil 12 outputting the ignition signal, the output terminals Q1 to Q4 of the shift registers 856 to 858 output the reciprocal number 1/N of the engine rotation speed N. Two proportional signals are output.

The 3-state buffer 860 outputs “1” to the control terminal 861.
While the level signal is applied, the output becomes high impedance, and the output terminal group 859 is connected to the lean air-fuel ratio correction circuit 100 via a pass line.

The output signal of the Nando Dart 862 is input to the control terminal 861, and the Lean air-fuel ratio correction circuit 1 is input to the Nando Dart 862.
00 built-in device control unit) (DCU
) input/output control signals and SEL signals are input. When the output signal of the Nant gate 862 reaches the 10'' level, the shift registers 856 to 858
Two communication signals proportional to //N are input to the correction calculation circuit 100.

Next, the intake air amount counting circuit 90 will be explained with reference to FIG. The input terminal 911 has a voltage of approximately 1 as shown in FIG. 19 (2).
A clock pulse of approximately 28 kHz is input to the Nant gate 902 and the clock terminal CL of the divider counter 901. The input terminal 912 is connected to the terminal shown in FIG.
) is input from the fuel amount calculation circuit 120, and the time T, which is proportional to the amount of intake air per revolution of the engine (hereinafter referred to as ), is input from the fuel amount calculation circuit 120. ! : Inputted to the reset terminal R of the counter with depider 901. The counter 901 with a divider is, for example, an IC manufactured by RCA.
CD4017 is used.

The counter with divider 901 basically has a clock terminal C.
The clock pulse signal C1 input to L is counted by 11, and the output signal of one of the output terminals Q2 to Q6 is at the "1" level, and the "1" level signal is at the counting operation stop terminal EN. When input, the counting operation is stopped.

However, in this embodiment, the output terminal Q6 and the stop terminal EN are connected, and when the output of the output terminal Q6 reaches the "1" level, a "1" level signal is input to the stop terminal EN, and the counting operation is stopped. In this state, when the pulse signal shown in FIG. 19 (1) is input from the fuel amount calculation circuit 120 to the reset terminal R, the counter 901 is reset, and when the input No. 16 reaches the "0" level, the counter 901
starts counting operation, and output terminal Q2. Pulse signals are sequentially outputted from Q4 as shown in FIG. 19 (4) and (5), respectively.

Thereafter, when the output of the output terminal Q6 reaches the 11'' level, the counter 901 stops counting again. Output Q2 of counter 901. Q4 is each shift register 90
4 to 906 (for example, RCA IC, CD403)
5 is used) clock terminal CL and counter 903
It is input to the reset terminal R of. Also Nando Dart 90
The output of 2 is input to the clock terminal CL of the counter 903.

Here, when a pulse of time T, which is proportional to the time shown in FIG. do. (i.e. time TP is counted). After that, at time to, the i'? When the pulse reaches the "0" level, the counter 903 stops counting. Next, at time t1, when the output Q2 of the counter 901 reaches the 11'' level, the outputs of the output terminals Q1 to Q12 of the counter 903 can be temporarily held in the shift registers 904 to 906. When the output Q4 of the counter 901 reaches the "1" level at time t2, the counter 903 is reset and enters a standby state for the next counting operation.

The operation of the counter 903 is repeated in synchronization with the pulse shown in FIG. 19 (1), so the shift register 903
Two signals proportional to YES are outputted from each of the output terminals Q1 to Q4 of 04 to 906 in synchronization with the engine rotation.

The three-state buffer 907 outputs a screen impedance while a "1" level signal is applied to the control terminal 909, and the output terminal group 908 is connected to the lean air-fuel ratio correction circuit 100 via a pass line. ing. The output signal of the NAND dart 910 is input to the control output terminal 9()9, and the input/output control signal and SEL signal from the DCU built in the lean air-fuel ratio correction circuit are input to the NAND r-)910. . When the output signal of the NAND dart 910 reaches the "0" level, two signals proportional to φ of the shift registers 904 to 906 are input to the lean air-fuel ratio correction circuit 100.

The configuration of the lean air-fuel ratio correction circuit is shown in FIG.

The lean air-fuel ratio correction circuit 100 is comprised of, for example, a Toshiba microcomputer TI, C8-12A, a random access memory (RAM), and a read-only memory (ROM).

The microcomputer TLC8-12A is composed of four large-scale integrated circuits (LSI). All 12-bit parallel processor (CPU) 1001 Ta205.8 level interrupt latch unit (INTU)
) 1002, T3219, memory control unit (
MCU) 1003 is Ta205, input/output control unit (DCU) 1004 is Ta205, four L
It is SI. Furthermore, 3 RAMs 1005 to 1007
For example, Toshiba J! ! ! TC5007 to 1008
．． For example, Fuji Renso MB85 is included in the two ROMs of 1009.
16 is used.

The LSI and memory described above are all connected by a 12-bit pass line 1010.

The operation is performed according to the program contents stored in advance in the ROMs 1008 and 1009.
performs all calculations.

Next, the DA conversion circuit 110 will be explained with reference to FIG. The DA conversion circuit 110 includes an inverter 1101, a NAND dart 1102, and shift registers 1103 to 11.
05 and a DA converter 1106 (for example, a DAC80 manufactured by Parr Brown is used). The input/output control signal of the CPU 100 is transmitted to the inverter 110.
After being inverted by 1, the SEL signal is input to the NAND gate 1102, and the SEL signal is directly input to the NAND gate 1102.

Therefore, the air-fuel ratio correction value F calculated by the CPU 100
d(7) When an output command is issued to the DA conversion circuit 110,
The input/output control signal is at “0” level, and the SEL signal is “1”.
level, and the Nant gate 1102 outputs a "°0" level signal. This "0" level signal is input to the clock terminals CL of the valley shift registers 1103 to 1105. The shift registers 1103 to 1105 are
This circuit is the same as the one used in the rotational speed detection circuit 80, and when a 10" level signal is input to the clock terminal CL, it takes in the signal applied to the data input terminals DI to D4, and outputs that signal from the output terminals Q1 to Q4. Output.

In this way, the binary data signal of the air-fuel ratio correction value Fd becomes D-
The voltage is input to the input terminals B1 to B12 of the A converter 1106, converted into an analog voltage, and then outputted from the output terminal OUT. In other words, an analog voltage proportional to the data signal indicating the air-fuel ratio correction value Fd is output from the output terminal OUT.

The configuration of switching circuit 120 is shown in FIG.

The switching circuit 120 is composed of inverters 1201 and 1204, a Nant gate 1202, a shift register 11o3, and analog switches 1105 and 1106. C.P.
The input/output control signal of U 100 is inverted by inverter 1201 and then input to NAND r-) 1202 . SEL
The two signals are directly input to the NAND signal 1202.

L, fcyb"-p"Cm H'l'aJ:JSM
IEEEj #u 1°OT't (I separate a lt
.

When a command is given to output the left signal to the switching circuit 120, the input/output control signal goes to "0" level and the SEL2 signal goes to "1".
According to the level, the Nando Dart 1202 outputs the rOJ level signal.

This “0” level signal is input to the clock terminal CL of the shift register 1203. “0” to clock terminal CL
When a level signal is input, it takes in the signal applied to the data input terminal and outputs that signal from the output terminal Q. When the output of the shift register 1203 is at the “1” level, the analog switch 1205 is closed and the DA converter 110
The analog output of is connected to the input of the fuel amount calculation circuit 140, and when the output is at the "0" level, the inverter 1204 outputs "
1'' level, the analog switch 1206 is closed, and the analog output of the stoichiometric air-fuel ratio correction circuit 130 is connected to the input of the fuel amount calculation circuit 140.

The configuration of the stoichiometric air-fuel ratio correction circuit 130 is shown in FIG. The stoichiometric air-fuel ratio correction circuit 130 includes a setting means 130a, an air-fuel ratio determination circuit 130b, and an integrator 130C, and outputs a correction value based on the signal from the 02 sensor 14 so that the ideal air-fuel ratio is achieved. Theoretical air-fuel ratio correction circuit 130
The zero circuit configuration is shown, for example, in Japanese Patent Application Laid-Open No. 50-54731 (Electronically Controlled Fuel Injection Device, Japan ■, Soko Co., Ltd.).

The fuel amount calculation circuit 140 is equivalent to a four-cylinder engine electronically controlled fuel injection system (hereinafter referred to as EFI) shown in Japanese Patent Application Laid-open No. 49-67016 (Electric fuel injection system equipped with a control device, Robert Bosch). This device has the following functions: an intake air amount signal from the air flow meter 3 and an ignition signal synchronized with engine crank rotation from the ignition coil 12 are input, and the basics of an electromagnetic fuel injection valve (hereinafter abbreviated as injection valve) are input. Calculate the valve opening time T (the time proportional to the amount of intake air per revolution of the engine mentioned above), and perform various correction calculations according to the engine operating condition to determine the valve opening time of the injection valve. Then, the injection valve 8 is driven to control the amount of fuel supplied to the engine 1 shown in FIG.

Here, the lean air-fuel ratio correction circuit 100 calculates DA
The lean air-fuel ratio correction value Fd or the 02 sensor output value converted into an analog voltage by the conversion circuit 110 is corrected by a method similar to the correction calculation for cooling water temperature and the like.

With the above configuration, the operation of the lean air-fuel ratio correction circuit 100 is
The explanation will be given according to the flowchart shown in the figure. When a key switch (not shown) is turned on, electricity is turned on and operation starts. In step S1, all memories are cleared to "O", and in step S2, the initial value of the air-fuel ratio correction value Fd is set to 2048 (1
2 bits), and flag C, which is used to determine the magnitude of torque fluctuation, is set to 1. In step S3, the master mask is set so that the CPU accepts interrupt calculations, and after that, Stella fs4 is in standby state for interrupt performance, and Stellar fs4 is always in standby state for interrupt performance except when waiting for interrupt calculation execution.
The state will be as follows.

After that, as time passes, the timing noise generation circuit 5
Interrupt calculation is started at the rising edge of the pulse shown in FIG. 17 (2) from 0 to 1. Once the interrupt operation is started, subsequent interrupts are prohibited in step 810. Stella:
At 7'S"'11, generate Fig. 17 (8) Gurus,
Using this signal as a trigger, the AD converter 701 starts ADi conversion and at the same time outputs the goc terminal as shown in FIG. 17 (9).
- When the signal becomes "1", the lean air-fuel ratio correction circuit 100 receives a BSY input of "11" and stops calculation. This is step 812.

When the AD conversion gain 701 ends the AD conversion, the output from the EOC terminal (9) in FIG. 17 becomes "0", and the lean air-fuel ratio correction circuit 100 restarts calculation. Once calculated, the torque fluctuation value Tn output from the AD converter 701 is read into the lean air-fuel ratio correction circuit 100 in step 813. As described above, the torque fluctuation value Tn is AD-converted and read at the step controllers 812 and 813.

In step S14, the value of Φ5 counted by the intake air amount counting circuit 90 is read. In step S15, a value 1/N which is inversely proportional to the engine/non engine speed counted by the engine speed detection circuit 80 is read, and by taking the reciprocal of this value, the engine speed N can be determined.

In step S16, the engine rotation speed N is the set rotation speed Ns.
(-280 Orpm) is determined.

If yes, go to step 818; if no, go to step 817. In step S17, it is determined whether or not the current value exceeds a set value K (=0.447 rev). If yes, go to step 818; if no, go to step 836.

Figure 14 shows N and i for engine operating conditions. This is a map showing, as a parameter, the peak value Ta of the torque fluctuation value when driving at the best fuel efficiency point under each condition. This is stored in advance in the bladder-removal memory (ROM). In step S18, the read 9 and N are the 14th
Search for ma and f in the diagram and extract Ta stored at the corresponding ROM address. Step 819
Then, the magnitude of Ta and Tn introduced in step 813 is determined, and it is determined whether the air-fuel ratio under the current engine operating state is richer RCH or leaner LN than the best fuel efficiency point.

That is, if Tn>Ta, it is determined that the torque fluctuation is large and the air-fuel ratio is close to 1, and in steps S20 to 826, the air-fuel ratio is richly corrected (COR, (RCH)) according to the difference between the output value of the torque fluctuation and the target value. Then, conversely, Tn<Ta
If so, the torque fluctuation is small and it is determined that the air-fuel ratio is rich.
In steps 827 to S33, lean correction COR is performed on the air-fuel ratio in multiple steps.

(LN) I will.

In step S20, the rich/lean discrimination flag C is set to 1, and the rich correction calculation is performed.Step 821 is the calculation of the rich correction value Fa and the current torque fluctuation value T. The air-fuel ratio is richly corrected in proportion to the difference between the target torque fluctuation value Ta and the target torque fluctuation value Ta. That is, if the difference in torque fluctuation values is large, the air-fuel ratio is corrected by a large amount, and if the difference is small, the air-fuel ratio is corrected by a small amount.

Steps 822 and 824 are the rich correction value F of the air-fuel ratio.
The maximum value of 1 is F"max.The maximum value Fm
ax was determined as an air-fuel ratio correction value that would change the engine from the air-fuel ratio at the boundary between the unstable combustion region and the stable combustion region to the air-fuel ratio in the stable combustion region. Step S24 calculates the current air-fuel ratio correction value Fd by adding the correction value F8 obtained in steps 821 to 823 to the air-fuel ratio correction f1αFd obtained in the previous calculation.

Stella fs25. S26 sets the air-fuel ratio correction value Fd to 12
The maximum value is regulated at the maximum bit value of 4095. In step 827, the flag C is checked to determine whether the interrupt calculation performed last time was a rich correction or a lean correction. If the previous calculation was a rich correction (when C=1), a lean correction value Fe is calculated in steps 828 to S30.

The Stella fS 28 reads out how many times the previously calculated rich correction value F& is to be divided into lean correction up to the target value from the table shown in FIG. 14, which is stored in the ROM in advance. The Stella fS 29 divides the rich correction value I/8 by the number of divisions of lean correction obtained in this way to calculate a lean correction value Fe per -CI time.

In step 830, the flag C is set to O, and when the next interrupt calculation is to continue the lean correction calculation, the lean correction value F0 is set to the same value as the previous one. Step S31 subtracts the lean correction value Fe from the previous air-fuel ratio correction value Fd to calculate the current air-fuel ratio correction value Fd.

In steps 832 and 833, the minimum value of Fd is set to 0 so that the air-fuel ratio correction value Fd does not become a negative number due to the calculation in step S31. Step 834 outputs the air-fuel ratio correction value Fd obtained by the above calculation to the DA conversion circuit 110.

Stella 7″35 (835) outputs “1” to the switching circuit 120. Step 36 (S36) outputs "10" to the switching circuit 120. Step 37 (S37) enables interrupts and returns to the program execution state before the interrupt occurred in step 37.

To summarize, among the engine conditions, engine speed is Nl
(However, in the following cases, the switching circuit 120 is set to "0".
The fuel calculation circuit 140 operates at the ideal air-fuel ratio. D if the engine conditions do not satisfy the above conditions.
A correction value is output to the fuel calculation circuit 140 via the A converter 110, and a signal of "1" is sent to the switching circuit 120 to cut off the correction value from the stoichiometric air-fuel ratio correction circuit 130, so that the fuel calculation circuit 140 performs the lean air operation. Operates on fuel ratio.

FIG. 15 shows a time chart of the air-fuel ratio correction calculation in the flowchart of FIG. 13. FIG. 15(1) shows the torque fluctuation signal after the filter circuit 30, and FIG. 15(2) shows the state of the rich/lean discrimination flag C.
Figure (3) shows an analog voltage obtained by AD converting the air-fuel ratio correction value Fd. When the torque fluctuation signal in FIG. 15 (1) becomes smaller than the torque fluctuation target value T & at the best fuel efficiency point, the rich correction COR, (RCH) l, becomes smaller according to steps 820 to S26 of the flowchart in FIG. 13. Lean correction COa according to steps 827 to 833
.

(LN) Yes In this example, the torque fluctuation value at the best fuel efficiency point is, for example, 2000 rpm under the engine operating conditions shown in Figure 1.
, 4 kg-m, there is 0.1 ky-m, and the relationship between the mater torque fluctuation value Δτ and the detection signal 5 (60) obtained from the peak bold circuit is as shown in Fig. 16.
Te, MfI Determination level T under engine operating conditions
a (step 517 in the flowchart of FIG. 13) is the output voltage from the peak hold circuit and was set to 1.5V.

The way to determine the rich correction value Fa when performing rich correction is to make corrections once (at 0.5 second intervals) from the air-fuel ratio at the boundary between the misfire region and the stable combustion region (air-fuel ratio 20.5 as shown in Figure 1). In order to correct the air-fuel ratio at the best fuel efficiency point and in the safe combustion range (air-fuel ratio 20 in Figure 1), the rich correction value Fa per time is 0.5 in terms of air-fuel ratio, and this is the maximum value. Value F'm
It was ay.

The proportionality constant was determined to be 1 so that a rich correction value of 0.5 per time could be obtained from the difference between the torque fluctuation values at the air-fuel ratios of 20.5 and 20.0. Here, when correcting to the rich side, it is important to quickly correct the air-fuel ratio to the stable combustion range in one correction in order to prevent engine misfires.

The correction value F8 per lean correction is obtained by equally dividing the previous rich correction value Fa into a number of divisions suitable for this value. The division number is set to D=4 so that the target value is reached in 20 seconds even when the air-fuel ratio changes by 0.5, which is the maximum air-fuel ratio change.
0, and as Fa became smaller, D was also made smaller.

When implementing the present invention, various modifications can be made in addition to the above-described embodiments. For example, lean air-fuel ratio correction circuit 100, switching circuit 120, stoichiometric air-fuel ratio correction circuit 1
30 and the fuel amount calculation circuit 140 can be integrated and controlled by one calculation device.

According to the present invention, it is possible to improve fuel efficiency while satisfying the emission amount conditions for harmful exhaust components in the entire operating range of an internal combustion engine.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing the relationship between air-fuel ratio, torque fluctuation, fuel consumption rate, and exhaust gas components, and Fig. 2 is a diagram showing the basic configuration of an air-fuel ratio control device for an internal combustion engine as an embodiment of the present invention. ,
3 is a block circuit diagram showing the configuration of the control unit in the device shown in FIG. 2, FIG. 4 is a circuit diagram showing the configuration of the timing pulse generation circuit in the control unit in FIG. 3, and FIG.
The figure is a circuit diagram showing the configuration of the peak hold circuit in the control unit of FIG. 3, FIG. 6 is a circuit diagram showing the configuration of the AD conversion circuit in the control unit of FIG. 3, and FIG.
FIG. 8 is a circuit diagram showing the configuration of the rotational speed detection circuit in the control unit shown in FIG. 3. FIG. 9 is a circuit diagram showing the configuration of the intake air amount counting circuit in the control unit shown in FIG. 3. 10 is a circuit diagram showing the configuration of the DA conversion circuit in the control unit of FIG. 3; FIG. 11 is a circuit diagram showing the switching circuit in the control unit of FIG. 3; FIG. 12 is a diagram showing the stoichiometric air-fuel ratio correction circuit in the control unit of FIG. 3;
Fig. 13 is a flowchart showing the calculation order of the calculation circuit in the control unit of Fig. 3, and Fig. 14 is a map showing the control target value map of torque fluctuation under each engine condition used for the calculation shown in Fig. 13. 15 is a waveform diagram showing the number of correction divisions in lean correction used in the calculation shown in FIG. 13, and FIG. 16 is a waveform diagram showing the number of correction divisions in the lean correction used in the calculation shown in FIG. 13. FIG. 16 is the engine torque fluctuation value and peak hold circuit output voltage in this embodiment. Figure 17 is a waveform diagram showing the waveforms of each part of the control unit in Figure 3, Figure 18 is a waveform diagram showing the waveforms of each part of the rotational speed detection circuit, and Figure 19 is a waveform diagram showing the waveforms of each part of the rotation speed detection circuit. FIG. 3 is a waveform diagram showing waveforms of each part of the quantity counting circuit. (Explanation of symbols) 1... Internal combustion engine, 2... Air cleaner, 3... Air flow meter, 4... Intake conduit, 5... Intake valve,
6... Combustion chamber, 7... Throttle valve, 8... Electromagnetic fuel injection valve, 9... Exhaust valve, 10... Exhaust pipe,
12... Ignition coil, 13... Torque detector, 14
...02 sensor, 20... amplifier, 30... band pass filter, 40... clock circuit, 50...
Timing pulse generation circuit, 60... Peak hold circuit, 70... AD conversion circuit, 80... Rotation speed detection circuit, 90... Intake air amount counting circuit, 100...
Lean air-fuel ratio correction circuit, 110...DA conversion circuit, 12
0...Switching circuit, 130...Theoretical air-fuel ratio correction circuit,
140...Fuel l: Arithmetic circuit, C0NT...Fuel control unit. Figure 1-U-AnoF Figure 5 60 Figure 6 0 Figure 8 Figure 9/100 1
−−−−−11 □□□□−−−−−−−−−−−−−−−1 Demand-1 1st
Figure 0, r Figure 11 20 Figure 12 Figure 14 Figure 15 - H> Δ Figure 18 t1t2t3t4 2 hours 1o
t+ t2 Continuation of the first shell 0 Inventor: Takashi Shigematsu, 1 Toyota-cho, Toyota-shi, Toyota Motor Corporation Applicant: Toyota Motor Corporation, 1-Toyota-cho, Toyota-shi

Claims (1)

[Claims] 1. Intake air amount detection device, rotation speed detection device, combustion fluctuation detector that detects combustion fluctuations, air-fuel ratio sensor provided in the exhaust passage, three-way catalyst provided in the exhaust passage, intake air amount detection device, rotation speed a fuel amount calculation circuit that controls the air-fuel ratio supplied to the internal combustion engine based on the detection signal of the combustion fluctuation detector; and a lean fuel amount calculation circuit that corrects the air-fuel ratio supplied to the internal combustion engine according to the detection signal of the combustion fluctuation detector an air-fuel ratio correction circuit; a stoichiometric air-fuel ratio correction circuit that corrects the air-fuel ratio supplied to the internal combustion engine according to an output signal of the air-fuel ratio sensor; and an output of the lean air-fuel ratio correction circuit and the stoichiometric air-fuel ratio correction circuit. is equipped with a switching circuit connected to the fuel amount calculation circuit, so that when operating at a lean air-fuel ratio, the switching circuit operates according to the output of the combustion fluctuation detector, and when operating at the stoichiometric air-fuel ratio, the switching circuit operates according to the output of the air-fuel ratio sensor. An air-fuel ratio control device for an internal combustion engine that performs air-fuel ratio control.