JPS64588B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation device for reducing engine NOx emissions, and more particularly to a device for electrically controlling the amount of exhaust gas recirculation.

Exhaust gas recirculation devices that recirculate part of the exhaust gas to the engine intake system are known as a means of reducing engine NOx emissions, but as the amount of exhaust gas recirculation increases, the NOx reduction effect decreases. On the other hand, if this becomes excessive, the fuel efficiency of the engine will decrease,
Since the exhaust gas recirculation amount or recirculation rate has an adverse effect on the operating performance, it is necessary to control the exhaust gas recirculation amount or recirculation rate with high precision and quick response at all times under all operating conditions.

However, conventional exhaust gas recirculation systems operate the diaphragm of the exhaust control valve directly using the negative pressure of the carburetor's vent or the throttle valve near the throttle valve, resulting in poor control accuracy and Control according to operating conditions was not possible. This has led to problems such as increased NOx emissions and poor engine fuel efficiency, resulting in poor drivability.

The present invention has been made in view of the above points.
It consists of two solenoid valves and a control circuit, specifically one solenoid valve that controls intake pipe negative pressure, one solenoid valve that controls atmospheric pressure, and a solenoid valve that drives each solenoid valve at a constant cycle. It is composed of a control circuit that sets the driving time of the solenoid valve taking into consideration the body movement speed and the invalid energization time of the solenoid valve, and has quick response, and also maintains the control value accurately and at a constant value. An object of the present invention is to provide an exhaust gas recirculation device that can control the amount of exhaust gas recirculation (EGR) accurately and without fluctuation.

Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings. In Figure 1 showing the overall configuration, engine 1
is a known four-cylinder spark ignition engine installed in a car, and the air-fuel mixture produced by the carburetor 2 is
It is supplied to the combustion chamber via the throttle valve 3 and intake pipe 4. Further, the exhaust gas after combustion is discharged from the combustion chamber into the exhaust pipe 5, and is discharged into the atmosphere through a catalytic converter and a muffler (not shown).

In the exhaust gas recirculation system, a part of the exhaust gas is passed through a recirculation conduit 6 connected to an exhaust pipe 5, and an exhaust control valve 10 that opens and closes this conduit 6 according to a control pressure.
and via a recirculation conduit 7 connected to the intake pipe 4;
It is recirculated to the intake system of the engine 1.

The exhaust control valve 10 is of a diaphragm type, and has a valve body 1 operated by a diaphragm 11.
2 and a valve seat 13 provided in the exhaust gas passage constitute a variable throttle. Here, the diaphragm 11 is actuated by the pressure difference between the pressure chamber 14 formed by the housing and into which the control pressure is introduced and the atmospheric chamber 15 opened to the atmosphere, and by the spring force of the compression coil spring 16. When the pressure in the pressure chamber 14 increases, the opening degree of the valve body 12 is decreased, and when the pressure in the pressure chamber 14 decreases, the opening degree of the valve body 12 is increased. Further, an opening sensor 25 for detecting the opening of the valve body 12 is provided in the housing.

The pressure correction device 30 adjusts the correction pressure applied to the pressure chamber 14 of the exhaust control valve 10 in accordance with an electric signal. In this embodiment, the pressure correction device 30 adjusts the correction pressure applied to the pressure chamber 14 of the exhaust control valve 10. The first solenoid valve 21 provided in the conduit 31 that guides the pressure chamber 1
and a second electromagnetic valve 22 provided in a conduit 33 that guides atmospheric pressure to the second electromagnetic valve 22.

Here, when the first electromagnetic valve 21 is energized, it opens and connects the conduits 31 and 32 to apply negative pressure in the intake pipe to the pressure chamber 14, and conversely, when the energization is cut off, it closes and the intake pipe Cut off the application of negative pressure. When the electromagnetic valve 22 is energized, it opens and applies atmospheric pressure from the atmosphere A directly to the conduit 32, and conversely, when the energization is interrupted, it closes and cuts off the application of atmospheric pressure.

The control circuit 28 determines the optimum exhaust gas recirculation flow rate (hereinafter referred to as EGR amount) according to the engine operating condition.
calculates a target value for the exhaust control valve opening corresponding to , and compares this target value with the output of the opening sensor 25 to adjust the correction pressure applied to the exhaust control valve 10;
The first solenoid valve 21 and the second solenoid valve 2 of the pressure correction device 30 are adjusted so that the output of the opening sensor 25 becomes the target value.
The intake pipe negative pressure sensor 24 detects the intake pipe pressure of the intake pipe 4, and the engine 1.
A ring gear 26 rotationally driven by the output shaft of
an electromagnetic pickup 27 that detects the rotation of the valve, and an opening sensor 25 that directly detects the opening of the exhaust control valve 10.
detection signal is input. Pressure sensor 24
is a semiconductor type using a silicon diaphragm, and although a detailed explanation is omitted, it uses a device whose electric resistance value changes depending on pressure due to a piezoresistance effect.

The electromagnetic pickup 27 detects the rotation reference position of the ring gear 26 of the engine 1, for example, the position of a reference tooth 23 provided at a crank angle of 60 degrees before the top dead center of the first cylinder, thereby adjusting the output of the engine 1. One pulse signal is output for one revolution of the shaft, and a signal corresponding to the rotational speed of the engine 1 is sent to the control circuit 28.
give to Here, the intake pipe negative pressure sensor 24 and the electromagnetic pickup 27 constitute an engine sensor.

Next, the control circuit 28 will be explained with reference to FIG. The pulse generation circuit 28a generates a timing pulse signal based on the output signal of the electromagnetic pickup 27.The output signal of this pulse generation circuit 28a becomes a pulse signal having a period corresponding to the engine rotation speed, and the output signal of the pulse generation circuit 28a is a pulse signal having a period corresponding to the engine rotation speed. is input. The rotational speed detection circuit 28b detects the period of the timing pulse of the pulse generation circuit 28a as a reciprocal of the engine rotational speed, converts this detection signal into a binary code, and sends the signal to the microcomputer 2.
Output to 8c. A clock pulse signal C1 of a constant frequency supplied from a clock circuit 28d constituted by a known crystal oscillation circuit is used for the operation of the rotational speed detection circuit 28b. The A-D conversion circuit 28e converts an analog signal into a digital signal, and converts the analog intake pressure signal outputted from the intake pipe negative pressure sensor 24 and the analog opening degree signal outputted from the opening degree sensor 25 into a digital signal. and outputs it to the microcomputer 28c.

The microcomputer 28c performs predetermined calculations according to the engine rotation speed and the intake pipe negative pressure,
EGR according to the required exhaust gas recirculation rate (EGR rate)
The valve opening degree is determined, and the opening times of the first electromagnetic valve 21 and the second electromagnetic valve 22 are calculated in order to control the EGR valve opening degree to the required EGR valve opening degree. This microcomputer 28
For example, TLCS-12A manufactured by Toshiba may be used as c, and the detailed configuration and operation thereof are well known, and therefore a description thereof will be omitted.

The microcomputer 28c is configured to include a read-only memory (ROM), and is configured to control the valve body of the exhaust control valve 10 to recirculate the optimum amount of exhaust gas according to the engine speed and intake pressure. 12 opening setting value data in ROM
is stored in advance.

The duty generation circuit 28f converts the binary coded solenoid valve opening time signal output from the microcomputer 28c into a pulse width, and outputs this pulse signal to the drive circuit 28g. Drive circuit 28g
controls the energization of the solenoid valves 21 and 22 by the pulse signal from the duty generating circuit 28f, and controls the pressure in the pressure chamber 14 of the exhaust control valve 10, that is, the opening degree of the exhaust control valve 10, to generate the optimum amount of exhaust gas. Recirculate.

Next, detailed electric circuits of each block constituting the control circuit 28 will be explained. FIG. 3 shows the pulse generation circuit 28a and rotational speed detection circuit 28b. In FIG. 3, the pulse generating circuit 28a includes a low-pass filter consisting of a resistor 101, a capacitor 102, and a voltage clamping Zener diode 103, and resistors 104, 105, 10.
6, 107, 108 and a comparison circuit consisting of a comparator 109. Here, comparator 1
A bias DC voltage V _B is applied to the inverting input terminal (-) of 09 through the resistor 105, and the voltage is almost equal to the inverting input terminal side divided by the resistors 106 and 107 to the non-inverting input terminal (+). A bias voltage of value is applied. Further, the comparator 109 is configured so that the rising and falling edges of the output pulse signal are sharp due to the positive feedback resistor 108. Then, the electromagnetic pick-up 27 and the reference tooth 23
When the electromagnetic pickup 27 outputs a pulsating signal as shown in FIG. 4a, the comparator 10
9 outputs a timing pulse signal having a waveform as shown in FIG. 4b.

Next, the rotation speed detection circuit 28b will be explained. The binary counter 111 counts and frequency-divides the clock pulse signal C1 inputted to the clock terminal CL, and uses, for example, a CD4024 manufactured by RCA. This counter 111 divides the frequency of the clock pulse signal C1 of about 128 KHz as shown in FIG. 4c and outputs a frequency-divided pulse signal of about 32 KHz as shown in FIG. 4d from the output terminal Q2. . The counter with divider 112 basically counts the clock pulse signal C1 inputted to the clock terminal CL, and when the output signal of one of the output terminals Q2 to Q4 is at the "1" level, it starts counting. When a “1” level signal is input to the stop terminal EN, the counting operation is stopped.

Therefore, in this embodiment, the output terminal Q4 and the stop terminal EN are connected, and when the output of the output terminal Q4 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 timing pulse signal shown in FIG. 4b is input from the pulse generating circuit 28a to the reset terminal R, the counter 112 is reset and the output of the output terminal Q4 becomes "0" as shown in FIG. 4g.
level. Then, when time T has elapsed and the signal input to the reset terminal R reaches the "0" level, the counter 112 starts counting,
From output terminals Q2 and Q3, outputs e and f are shown in Figure 4, respectively.
Pulse signals are sequentially output as shown in FIG. Thereafter, when the output of the output terminal Q4 reaches the "1" level, the counter 112 stops counting again. The output signals of the counters 111, 112 and the pulse generation circuit 28a are respectively output from the NOR gate 11.
3,114 to the clock terminal CL of the 12-bit counter 115.
The Q3 output of 2 is the reset terminal R of the counter 115.
has been entered.

In other words, the pulse generating circuit 28a shown in FIG. 4b
The output signal of the counter 112 shown in FIG.
By using the three-output NOR logic, the NOR gate 113 outputs a pulse signal as shown in FIG. By taking NOR logic, NOR gate 1
14 outputs a pulse signal as shown in FIG. 4i, and this pulse signal is input to the counter 115.

Here, as the timing pulse signal shown in FIG. 4b falls to the "0" level, the timing pulse signal shown in FIG.
At time t1 when the output of the NOR gate 114 reaches the "1" level, the counter 115 stops counting. Thereafter, the outputs of the output terminals Q1 to Q12 of the counter 115 are transferred to shift registers 116 to 118 (for example, CD4035 manufactured by RCA) by the rise of the Q2 output of the counter 112 at time t2.
is temporarily retained and memorized. Next, when the Q3 output of the counter 112 reaches the "1" level at time t3, the counter 115 is reset and the counter 115 is reset to the "1" level.
When the Q4 output of the counter 112 reaches the "1" level at 4, the counter 115 starts counting again.

The operation of the counter 115 is repeatedly performed in synchronization with the timing pulse signal output when the electromagnetic pickup 27 detects the reference tooth 23, so that the engine rotation is output from each output terminal Q1 to Q4 of the shift registers 116 to 118. A binary signal proportional to the reciprocal 1/N of the speed N is output. The 3-state buffer 119 has a high impedance output while a "1" level signal is applied to the control terminal 119a, and the output terminal group 119
b is connected to the microcomputer 2 via the bus line.
Connected to 8c.

The output signal of the NAND gate 120 is input to the control terminal 119a, and the input/output control signal (hereinafter referred to as 1/0 signal) from the device control unit (DCU) built in the microcomputer 28c and the device are input to the NAND gate 120. A select signal (hereinafter referred to as SEL signal) is input. Then, when the output signal of the NAND gate 120 becomes "0" level, the shift register 116~
A binary signal proportional to 1/N of 118 is input to the microcomputer 28c.

Next, the AD conversion circuit 28e will be explained with reference to FIG. The resistors 121 and 122 form a bridge with the two resistors 24a and 24b of the intake pipe negative pressure sensor 24.
A DC bias voltage V _B is applied to 4a,
One ends of the resistor 122 and the resistor 24b are grounded. Note that the resistor 24 of the intake pipe negative pressure sensor 24
The resistance values of a and 24b change complementary to each other in proportion to the intake pressure value. The connection point between the resistors 24a and 24b and the connection point between the resistors 121 and 122 are connected to the OP amplifier 123 via input resistors 124 and 125, respectively.
It is connected to the. This OP amplifier 123 has
A grounding resistor 126 and a negative feedback resistor 127 are connected, and the OP amplifier 123 operates as a differential amplifier. Therefore, the output voltage of the OP amplifier 123 is
It is proportional to the intake pressure inside the intake pipe 4.
The output voltage of the OP amplifier 123 is determined by the analog multiplexer 140 (e.g. Deitel MX-808).
is input to the first input 1IN of. Opening sensor 25
The output voltage of is input to the second input 2IN of the analog multiplexer 140. NAND gate 14
2, the I/0 signal from the device control unit DCU of the microcomputer 28c is inputted via the inverter 143, and the SEL2 signal is also directly inputted. The output of NAND gate 142 is input to clock terminal CL of shift register 141. The shift register 141 is the same as that used in the rotational speed detection circuit, and D ₁
The inputs of ~ _D3 are connected to the bus line of the microcomputer 28c, and the outputs of _Q1 ~ _Q3 are connected to channel terminals CA1, 2, and 4 of the multiplexer 140.

The 1/O signal shown in FIG. 6a and the SEL signal shown in FIG. 6b are inputted to the NAND gate 129 and the AND gate 130 from the device control unit DCU of the microcomputer 28c. Also,
Inverter 131, resistor 132 and capacitor 1
33 constitutes a delay circuit, and the SEL signal is input to the AND gate 130 via this delay circuit. However, the AND gate 130 is
As shown in FIG. 6c, a pulse signal with a width of about 100 microseconds is output. This pulse signal is the A-D conversion command terminal of the successive approximation type A-D converter 128.
Entered into CNV.

The successive approximation type A-D converter 128 starts the conversion operation at the rise of the pulse signal applied to the A-D conversion command terminal CNV, and at the same time, the output signal of the conversion end terminal EOC rises to the "1" level. climb.
Here, the conversion end terminal EOC is connected to the busy terminal BUSY of the device control unit DCU of the microcomputer 28c, and the completion of the analog voltage reading command is indicated by the fall of the output signal of the conversion end terminal EOC to the "0" level. Until then, both the I/0 signal and SEL signal are “1”.
held at the level. And successive approximation type A-D
The converter 128 has an output signal of “1” at the EOC terminal.
Performs conversion operation between levels and output terminals B1 to B
12 outputs a digitized binary data signal. The 3-state buffer 134 is the same as that used in the rotational speed detection circuit 28b, and when a "0" level signal is applied to the control terminal 134a as shown in FIG. During the non-hatched period of FIG. 6f, a binary data signal is input to the computer 28c via the bus line.

When the A-D conversion operation of the A-D converter 128 is completed, the value on the bus line to the microcomputer 28c becomes stable, and the output signal of the conversion end terminal EOC shown in FIG. 6d becomes "0" level.
The standby state of the read command of the microcomputer 28c is released, and the intake pressure data on the bus line is read into the microcomputer 28c. Next, the microcomputer 28c receives the I/O signal and
3-state buffer 13 by setting the SEL signal to “0”
The output of No. 4 is set to high impedance and the analog voltage data read command operation is completed.

Here, the analog voltage input to the A-D converter 128 is selected by the analog multiplexer 140, and when the channel terminal is set to "000" in binary code, the intake pressure sensor 2
If "001" is set, it is the analog voltage of the opening sensor 25. In this way, the two analog voltages are read into the microcomputer 28c at any time.

Next, the operation of the microcomputer 28c will be explained. The microcomputer 28c determines an appropriate setting value Ld for the valve body 12 of the exhaust control valve 10 from a data signal indicating the intake pressure Pv and a data signal indicating the engine rotation speed N obtained by performing reciprocal calculation on 1/N. calculate.

Assuming that the set value Ld is expressed by the function shown in equation (1), Ld=f(Pv, N)...(1) A fixed interval of intake pressure Pv and rotational speed N corresponding to a predetermined EGR rate. Set value Ld for each △Pv, △N in ROM
be memorized in advance.

Therefore, using l and m shown in equations (2) and (3), l・△Pv≦Pv(l+1)・△Pv …(2) m・△N≦N(m+1)△N …( 3) (However, l and m are integers) Calculate the setting value Ld using equations (4), (5), and (6).

Ld1=((l+1)・△Pv−Pv)・f(l△Pv
, m△n)/△Pv + (Pv-l・△Pv)・f((l+1)△Pv,
m△n)/△Pv…(4) Ld2=((l+1)△Pv−Pv)・f(l・△Pv
, (m+1)△N)/△Pv + (Pv-l・△Pv)・f((l+1)△Pv,
(m+1)△N)/△Pv…(5) Ld2=((m+1)・△N−N)・Ld1+(N−
m△n)・Ld2/△N (6) When the above calculation is completed, the opening degree setting value Ld of the valve body 12 is calculated. The opening set value Ld thus obtained, the current opening value Ln of the valve body 12, and the diaphragm chamber pressure Pd of the pressure chamber 14 calculated therefrom.
, intake pipe pressure Pv, diaphragm chamber volume M,
Based on the opening area A of the solenoid valve, the valve body 1 when the solenoid valve is opened
The moving speed V of 2 is calculated. Furthermore, the energization time T of the solenoid valve for controlling Ln=Ld is calculated from the moving speed V, the opening degree setting value Ld, the opening value Ln, and the invalid energization time To of the solenoid valve. This process can be expressed as a calculation formula: T=To+K×｜Ld−Ln｜…(7) (Here, K is the value of Kαl/V) Solenoid valve to control Ln=Ld by the above equation (7) Since the energization time T is determined, T can be calculated if K, that is, the moving speed V of the valve body 12 is determined. To find it below, △W=α・A・√2・・(−)…(8
) Pd=Fl(M,W)...(9) Ln=F2(Pd)...(10) V=dLn/dt...(11) Here, △W: Weight flow rate per unit time a: Flow coefficient g: Dynamic acceleration rp: Air density W: Diaphragm Indoor air weight (Equation (8) is about intake pipe negative pressure, and for the atmosphere, Pv→Pa: atmospheric pressure) Above (8), (9), (10) ), the moving speed V of the valve body 12 can be calculated from the equation (11), and the energization time T of the solenoid valve for controlling Ln=Ld can be calculated from the equation (7) as described above. The T thus obtained is output to the duty generation circuit 28f as a parallel binary number. Then, the drive circuit 28g drives the first solenoid valve or the second solenoid valve during the energization time T converted into a pulse by the duty generation circuit 28f, so that Ln=Ld
The amount of exhaust gas recirculation (EGR) is controlled so that Here, whether to drive the first solenoid valve or the second solenoid valve depends on the relationship between the opening value Ln and the EGR valve opening area as shown in Figure 7.
When <Ld, the first solenoid valve 21 is driven to introduce negative pressure, and when Ln>Ld, the second solenoid valve 22 is driven to introduce atmospheric air.

Next, the duty generating circuit 28f will be explained with reference to FIG. The duty generating circuit 28f is composed of a duty generating circuit 170 for the first solenoid valve and a duty generating circuit 180 for the second solenoid valve. Duty generation circuit 170 for the first solenoid valve
is a presettable up-down counter 151,
152,153 (e.g. ICCD4029 manufactured by RCA)
and OR gates 155 to 158, NAND gate 16
0, buffer 159. The I/O signal of the microcomputer 28c is inverted by the inverter 163, and the NAND gate 161,
162, and the SEL4 and SEL5 signals are input to other inputs of NAND gates 161 and 162, respectively. A 64 microsecond clock _C2 from clock circuit 28d is input to NAND gate 160, and the output of OR gate 158 is input to the other input terminal. Here, when the energization time T of the first solenoid valve is set in the presettable down counters 151 to 153 by the SEL4 signal in FIG. 9c, the counter counts down by the 64 microsecond clock _C2. . and the output of each counter
When Q ₁ to _{Q 4} all become 0, the output of OR gate 158 goes low and NAND gate 160 inhibits clock C ₂ . In this way, terminal 16
4 outputs a pulse having a pulse width of energization time T ₂ as shown in FIG. Duty generation circuit 1 for second solenoid valve
80 has the same configuration and operation as the first electromagnetic valve duty generation circuit 170, so the explanation thereof will be omitted.

Next, the drive circuit 28g will be explained with reference to FIG. The drive circuit 28g includes a drive circuit 210 for the first solenoid valve and a drive circuit 220 for the second solenoid valve. The drive circuit 210 for the first solenoid valve has a resistor 1
91, 192, an NPN transistor 195, a resistor 194 for absorbing surge voltage generated by a solenoid valve, and a capacitor 193.
Drives the solenoid valve. Drive circuit 22 for the second solenoid valve
0 has the same configuration as the drive circuit 210 for the first solenoid valve, and drives the second solenoid valve by the pulse signal VSV2 from the duty generation circuit 28f.

In the above configuration, the microcomputer 28c of the control circuit 28 is configured to preset the voltage of the opening sensor 25 with respect to the set position of the valve body 12 of the exhaust control valve 10 so as to correspond to the rotational speed N of the engine 1 and the intake pressure of the intake pipe 4. Since the set value data is stored as
It is also controlled by the EGR rate. In addition, since the data-based control is performed by detecting the opening degree of the exhaust control valve 10 with the opening sensor 25 and comparing it with this, the EGR amount is accurately and precisely controlled to the set value.

The entire operation will be explained using the time chart shown in FIG. FIG. 9a shows an interrupt signal to the microcomputer 28c for calculating the EGR valve opening setting value Ld and the energization time of the solenoid valve using pulses with a period of 50 ms. Figure 9b is SEL4 in Figure 8.
The signal is a trigger signal for outputting and driving the energization time of the first solenoid valve. FIG. 9c shows the drive signal for the first solenoid valve output from the terminal 164 of the duty generating circuit 28f in FIG. 8. At HIGH level, the coil of the solenoid valve is energized, the valve opens, and negative pressure is introduced. . FIG. 9d is the SEL5 signal of FIG. 8, which is the output of the energization time of the second solenoid valve and the trigger signal for driving.
Figure 9e shows the drive signal for the second solenoid valve output from the terminal 165 of the duty generation circuit 28f in Figure 8. At HIGH level, the coil of the solenoid valve is energized, the valve opens, and atmospheric pressure is introduced. . Fig. 9f shows the opening setting value Ld of the valve body 12 obtained from the interrupt calculation every 50ms by the microcomputer 28c.
It is. FIG. 9g shows the current opening degree value of the valve body 12 controlled by the first and second solenoid valves.

Explaining each of the above signals over time,
The operation of this system will be explained. Time t1 in Figure 9
If the engine conditions (in the present invention, the intake pipe negative pressure or the engine rotational speed) change in , the interrupt signal to the microcomputer 28c in FIG. 9a at time t2 causes the valve body 12 to change under the current engine conditions. The opening degree setting value Ld is calculated as Ld ₂ . At this time
Since Ld ₂ > Ld ₁ with respect to the opening setting value Ld ₁ before t ₂ , in order to control Ln = Ld ₂ , the first solenoid valve must be
The microcomputer 28c calculates that the valve is opened by driving for the time T2, and at time t3, the duty generating circuit 1 for the first solenoid valve of the duty generating circuit 28f shown in FIG.
Binary data of the energization time T2 of the first solenoid valve is set at 70, and the pulse signal shown in FIG. 9c is generated.
The first solenoid valve is activated by the pulse signal shown in Figure 9c.
During T2, the coil is energized and the valve opens, and the pressure chamber 14
Negative pressure is introduced into the valve, and the valve opening value Ln changes from time t3 to t4, and is controlled to Ln=Ld2 at time t4.

Next, at time t5, the engine condition changes again, and at time t6, the opening degree setting value Ld of the valve body 12 under the current engine condition is changed by the interrupt signal shown in FIG. 9a.
It is calculated that Ld ₃ (Ld ₃ <Ld ₂ ), and in order to control Ln=Ld ₃ , it is calculated that the second electromagnetic valve is driven and opened for the time T3. At time t7, the duty generating circuit 180 for the second solenoid valve of the duty generating circuit 28f in FIG.
The binary data of 3 is set and the pulse of FIG. 9e is created. The second
The solenoid valve is opened by energizing the coil during time T3, atmospheric pressure is introduced into the pressure chamber 14, the valve opening value Ln changes from time t7 to t8, and is controlled to Ln=Ld ₃ at time t8. . It goes without saying that roughness in control such as hunting can be prevented by providing some dead zones above and below the opening setting value Ld.

By performing the above control, the exhaust control valve 1
Since the opening degree of 0 can be controlled to the value set in the control circuit 28, the EGR amount can always be accurately controlled to the set value.

FIG. 11 shows another embodiment of the present invention. 11th
As shown in the figure, if a system is used that includes a pressure control valve 60 and a pressure control valve 40 that controls the pressure of the pressure chamber 8 formed between the exhaust control valve 10 and the pressure control valve 60 at a constant level. , control accuracy is further improved. The following pressure adjustment valve 40, pressure control valve 60
I will explain about it.

The pressure control valve 60 is of a diaphragm type, and has a valve body 6 operated by a diaphragm 61.
2 and the valve seat 63 constitute a variable throttle. The diaphragm 61 is actuated by the pressure difference between the pressure chamber 64 and the atmospheric chamber 65 formed by the housing, and by the spring force of the compression coil spring 66. When the pressure in the pressure chamber 64 becomes low, the valve body 62 is activated. It operates to increase the opening degree.

The pressure regulating valve 40 controls the opening degree of the pressure control valve 60 according to the pressure in the passage 8 between the valve seats 13 and 63 of the exhaust control valves 10 and 60, and basically consists of a pressure conduit 51, a fixed The degree of opening is controlled by appropriately adding atmospheric pressure to the intake pressure (negative pressure) of the intake pipe 4 guided to the pressure chamber 64 via the throttle 52 and the pressure conduit 53. This pressure regulating valve 40 is also of a diaphragm type, with an atmospheric chamber 43 and a conduit 54 communicating with the atmosphere via a diaphragm 41 and an air filter 42.
The diaphragm 41 is provided with an exhaust pressure chamber 44 through which the exhaust pressure of the passage 8 is guided, and the diaphragm 41 connects the atmospheric chamber 43 and the exhaust pressure chamber 4.
4 and the spring force of the compression coil spring 45, the valve element 46 fixed to the diaphragm 41 is actuated to open and close the tip of the pipe 47. When the pressure in the exhaust pressure chamber 44 becomes lower than a predetermined value, the valve body 46 opens and atmospheric pressure is applied to the conduit 53, increasing the pressure in the pressure chamber 24. Conversely, when the pressure in the exhaust pressure chamber 44 becomes higher than a predetermined value, the valve body 46 closes to cut off the application of atmospheric pressure and lower the pressure in the pressure chamber 64. By controlling as described above, the exhaust pressure in the exhaust pressure chamber 44, that is, the passage 8 is controlled to be always constant.

In the above configuration, air, which is determined by the opening degree of the throttle valve 3 and taken into the engine 1, is mixed with fuel in the carburetor 2 and supplied to the combustion chamber via the intake pipe 4. The air-fuel mixture is combusted in the combustion chamber of the engine 1 and is discharged into the exhaust pipe 5 as exhaust gas.

At this time, an exhaust pressure Pe related to the amount of exhaust gas (approximately proportional to the amount of intake air) is generated in the exhaust pipe 5. This exhaust pressure Pe is determined by the recirculation conduit 6,
It is led to the exhaust pressure chamber 44 of the pressure regulating valve 40 via the passage 8 and the conduit 54. Therefore, this exhaust pressure
Due to Pe, the diaphragm 41 is displaced upward in FIG. 11, and the valve body 46 closes the tip of the pipe 47. Therefore, the intake pipe negative pressure (negative pressure) in the intake pipe 4 is guided to the pressure chamber 64 of the pressure control valve 60 without applying atmospheric pressure.

Therefore, the opening degree of the valve body 62 of the pressure control valve 60 increases, increasing the amount of exhaust gas recirculation. Therefore, the pressure in the passage 8 becomes small, and the pressure regulating valve 40
The diaphragm 41 is displaced downward in FIG. 11 by the force of the spring 45.

As a result, atmospheric pressure is applied to the intake pressure guided to the pressure chamber 64, and the pressure in the pressure chamber 64 increases. Therefore, the opening degree of the valve body 62 of the pressure control valve 60 becomes smaller, and the pressure in the passage 8 becomes higher.

The pressure in the passage 8 is thus kept at a certain value Ps. In this way, the EGR amount QEGR is QEGR=CA√− …(7) (where C is the flow coefficient and A is the orifice area), and if Ps is controlled to a value close to atmospheric pressure,
QEGR is approximately proportional to the amount of intake air.

However, the control by this pressure control valve 60 essentially controls only the exhaust pressure,
In order to more effectively reduce NOx or improve fuel efficiency, it is necessary to change the EGR rate according to various engine operating conditions and precisely control the EGR amount, which is not sufficient. Regarding control at that time, the opening degree of the exhaust control valve 10 may be controlled as described in the first embodiment of the present invention.

Further, FIG. 12 shows another embodiment of the present invention.
In the embodiment shown in FIG. 12, the technique of the present invention is applied to an engine equipped with a fuel injection device instead of a carburetor system. In the figure, 8 is an air flow meter that measures the amount of intake air flowing through the intake pipe, and 9 is a fuel injection solenoid valve, which opens in response to a command from the control circuit 28. The other parts are almost the same as the embodiment shown in FIG. 1, so the explanation will be omitted. In this embodiment as well, the valve body 12 of the exhaust control valve 10 is controlled using the pressure correction device 30 in the same manner as in the case of FIG.

In the present invention, the opening degree of the exhaust control valve 10 is directly detected by the opening degree sensor 25 and is controlled so that the opening degree of the exhaust control valve 10 becomes the target (opening degree) set value.
The EGR amount can be arbitrarily and precisely controlled according to the operating state of the engine, regardless of engine conditions.

Further, in the present invention, in order to control the opening value Ln of the exhaust control valve 10 to the opening setting value Ld, the coils of the first solenoid valve 21 and the second solenoid valve 22 are energized at a constant cycle, and the energization time is is calculated by taking into account the moving speed of the valve body and the invalid energization time of the solenoid valve, so the opening value Ln can be quickly controlled to the opening setting value Ld without hunting.

Further, in the present invention, when the opening value Ln of the opening sensor 25 reaches the opening setting value Ld, the two solenoid valves 21,
Because of the configuration in which all 22 valves can be closed, the control value can always be held at a constant value, and therefore
The opening degree of the EGR valve does not change, and fluctuations in the amount of EGR can also be eliminated. Further, in the present invention, by holding the valve as described above (all solenoid valves are turned off), the number of times the solenoid valve is driven can be reduced, and the life of the solenoid valve can be extended.

As described above, the present invention can always recirculate an accurate amount of exhaust gas based on the set value depending on the engine operating condition with quick response.
It has the excellent effect of constantly reducing NOx emissions without impairing engine drivability.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Fig. 2 is a block diagram showing the control circuit shown in Fig. 1, Fig. 3 is an electric circuit diagram showing the pulse generation circuit and rotation speed detection circuit shown in Fig. 2, and Fig. 4 is an electric circuit shown in Fig. 3. A time chart showing the operation of the figure,
Figure 5 is an electric circuit diagram showing the A-D conversion circuit shown in Figure 2, Figure 6 is a time chart showing the operation of the electric circuit diagram shown in Figure 5, and Figure 7 is an opening sensor for the exhaust control valve. A graph showing the relationship between opening value and valve opening area, Figure 8 is an electric circuit diagram of the duty generation circuit shown in Figure 2, and Figure 9 is an electric circuit diagram of the duty generating circuit shown in Figure 8 and the control system shown in Figure 1. 10 is an electric circuit diagram showing the drive circuit shown in FIG. 2, FIG. 11 is an overall configuration diagram showing the second embodiment of the present invention, and FIG. FIG. 3 is an overall configuration diagram showing a third embodiment. 1... Engine, 2... Carburetor, 3... Throttle valve, 4... Intake pipe, 5... Exhaust pipe, 6, 7...
... Recirculation conduit, 10 ... Exhaust control valve, 14 ... Pressure chamber, 15 ... Atmospheric chamber, 21 ... Solenoid valve, 22 ...
... Solenoid valve, 23 ... Reference tooth, 24 ... Intake pipe negative pressure sensor, 26 ... Ring gear, 27 ... Solenoid pickup, 28 ... Control circuit, 31, 32, 33
……conduit.

Claims (1)

[Claims] 1. A recirculation conduit that recirculates exhaust gas from the exhaust pipe of the engine to the intake pipe, and a valve body that moves in response to a pressure signal guided to a pressure chamber to change the degree of opening, and the exhaust gas flows through the recirculation conduit. an exhaust control valve that controls the recirculation amount of the exhaust control valve; a first electromagnetic valve that controls the intake pipe negative pressure that acts on the pressure chamber so as to increase the opening of the exhaust control valve; a second electromagnetic valve that controls the atmospheric pressure acting on the pressure chamber so as to reduce the pressure, an opening sensor that detects the opening of the exhaust control valve, and an engine sensor that detects the operating state of the engine. In the exhaust gas recirculation device, an opening setting value of the exhaust control valve is calculated based on a detection signal of the engine sensor, and this setting value is compared with a detection value of the opening sensor, and the opening setting value of the exhaust control valve is calculated based on the detection signal of the engine sensor. when the detected value is larger than the set value, controlling the energization of the second solenoid valve;
Further, when the detected value of the opening sensor is smaller than the set value, the energization of the first solenoid valve is controlled, and when the detected value is the set value, the energization of the first and second solenoid valves is controlled. The pressure in the pressure chamber is maintained at a constant value, and the first and second solenoid valves are energized at a predetermined period, and the energization time is determined by the difference between the detection value of the opening sensor and the set value. An exhaust gas recirculation device for an internal combustion engine, comprising: a control circuit that is set according to an ineffective energization time of the electromagnetic valve and a moving speed of the valve body.