JPS60546B2 - Air fuel ratio control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control device for controlling the air-fuel ratio of a carburetor for an internal combustion engine to a target air-fuel ratio.

In other words, the previously proposed air-fuel ratio control device had durability problems due to the large number of actuations of the actuator to adjust the amount of air bleed in the carburetor, and the control electric circuit was complicated. This is the purpose of this invention. Before giving a detailed explanation of the present invention, the previously proposed air-fuel ratio control device will first be described with reference to FIGS. 1, 2, and 3.

In FIG. 1, 100 is the engine body, 101 is the intake manifold, 102 is the exhaust manifold, 103 is the exhaust gas sensor, 20 is the main body of the carburetor, 201 is the float chamber,
202 is a small venturi, 203 is a large venturi, 2
04 is a throttle valve, 205 is a main system air lead introduction path, 2
06 is the low speed system air bleed introduction path, 207 is the main nozzle, 30 is the control circuit section. 306 is the battery, 400
4 is a solenoid valve installed in the main system air bleed introduction path 205.
01 is a solenoid valve provided in the low-speed system air bleed introduction path 206.

FIG. 2 is a circuit connection diagram of the control circuit 300, and shows RI to R17.
are resistors, C1 and C2 are capacitors, 301 to 304 are operational amplifiers, DI is a diode, TRI is a transistor, 305 is a duty ratio conversion circuit, and 308 is a triangular wave oscillator, which are connected as shown in the figure.

The signal from the exhaust gas sensor 103 is applied to the plus input terminal of the operational amplifier 301 through a filter made up of a resistor RI and a capacitor CI, divided by resistors R2 and R3, and compared with the voltage applied to the minus input terminal.

The voltage waveform at the output terminal point a of the operational amplifier 301 is shown on line a in FIG. C2, R5, R6 and operational amplifier 302
The outputs of these integrators and proportionalizers are RI1, R12, R13, R14,
The signal is applied to an adder including R15 and an operational amplifier 303 and added.

The voltage waveform of the output of this adder, that is, the proportional/integral signal, is shown by line b in FIG. The triangular wave oscillator generates a triangular wave with a relatively distant repetition frequency as shown by line c in Figure 3.
It is input to the duty ratio conversion circuit 305. The duty ratio conversion circuit 305 compares the magnitude of the proportional/integral signal b, which is the output of the adder, with the triangular wave c from the triangular wave oscillator, and outputs a high level output while the proportional/integral signal is larger than the triangular wave. It operates to produce a low level output while the proportional/integral signal is smaller than the triangular wave. This output is R
16, R17, and TRI to operate the solenoid valves 400 and 401. The input voltage waveform to the solenoid valve is shown on the d line in Figure 3. This voltage waveform is a rectangular wave in which the proportional/integral signal b is intermittent with the triangular wave c, the frequency of which is the same as that of the triangular wave, and the duty ratio is Since the waveform gradually changes, the solenoid valves 400 and 401 repeat opening and closing for each period of the triangular wave, and the average function thereof is determined by the duty ratio of the solenoid valve input voltage.

When the air-fuel ratio is rich, the output of the operational amplifier 301 becomes high level due to the signal from the exhaust gas sensor 103, and the proportional/integral signal output from the adder 303 gradually increases as shown by line b in FIG. Since the average opening degree of the solenoid valves gradually increases, the amount of stray bleed in the main system and low speed system gradually increases, and the system operates to suppress the air-fuel ratio to the target air-fuel ratio. In such an automatic control device, the solenoid valves 400 and 401 repeat opening and closing for each period of the triangular wave, so the operating frequency becomes more than 1 disc z, which poses a problem in the durability of the solenoid valves.

Another drawback is that the control electric circuit section 300 is complicated. In view of the above, this invention aims to propose a new air-fuel ratio control device that uses an air system instead of an electric circuit as the proportional/integral means, thereby simplifying the electric circuit and extending the life of the entire device. It is.

In other words, there is a diaphragm valve that has two diaphragms that operate independently and whose overall opening is determined by the positions of these two diaphragms, and a diaphragm valve that has one of the two diaphragms directly connected to the other and a throttle and tank connected to the other. A three-way solenoid valve that switches and supplies negative pressure or atmospheric pressure through an integrating means, a negative pressure regulator inserted between the engine intake manifold and the three-way solenoid valve, and an exhaust gas sensor that detects air/fuel pressure. and a control electric circuit unit that switches the three-way solenoid valve in response to a signal from the exhaust gas sensor, and the diaphragm valve is passed through an air bleed introduction path of the carburetor. A detailed description will be given below according to the embodiments shown in the drawings.

In FIG. 4, the elements indicated by symbols 1.00 to 206 are:
Elements with the same symbols in FIG. 1 correspond.

The control electric circuit section is indicated by the symbol 310, and receives an electric signal from the exhaust gas sensor 103 to control the solenoid of the three-way solenoid valve 700. 306 is a battery.

800 is a negative pressure regulator, and the intake manifold 10
1 and pipe 216, constant negative pressure is applied to pipe 215
A three-way solenoid valve 7001 is supplied through the three-way solenoid valve 7001.

The three-way solenoid valve 700 is connected to the diaphragm valve 5 by two pipes 211 and 212 branching from the pipe 214.
00 and the aperture 601 are threaded together. The aperture 601 is fitted at the inlet of the tank 600. The output of tank 600 is communicated to diaphragm valve 5001 via pipe 213. 210 is a pipe that connects the air intake port of the diaphragm valve 500 and the carburetor inlet; 209 is a pipe that connects the air intake port of the diaphragm valve 500 and the carburetor inlet
A pipe 208 connects the air outlet of the diaphragm valve 500 to the main air bleed introduction path 205, and a pipe 208 connects the air outlet of the diaphragm valve 500 to the low speed air bleed introduction path 206.

Diaphragm valve 500 is of horizontal construction as shown in FIGS. 501 and 502 are diaphragms forming diaphragm chambers 511 and 513, respectively; 503 and 504 are springs that bias the diaphragm 501; and 505 is a spring that includes a plunger 518 that can slide left and right inside the cylindrical case of the diaphragm valve. It is always biased to the left.

506 is a spring that urges the diaphragm 502 to the right; 507 and 508 are diaphragms 501 and 5, respectively;
Setting screws 509 and 51 for determining the limit position of 02
It is a ring that maintains airtightness.

512 and 514 are chambers that are connected to atmospheric pressure through the pipe 210; 515 is a connection port for communicating the diaphragm chamber 511 to the tank 600 through the pipe 213;
516 is a connection port for connecting the diaphragm chamber 513 to the pipe 211; 517 is a valve body; the right end of the rod portion is always connected to the diaphragm 50 by a spring 504;
It is forced to 1.

The left end of the valve body 517 has a piston-like shape that can slide left and right inside a plunger body 518 that is a cylindrical cylinder with a bottom, and this piston-like portion has two holes 517a that pass through it left and right. is dawning. The plunger body 518 has a protruding pin 518a extending further leftward from the center of the left bottom surface, and the left end of this pin is always pressed against the surface of the diaphragm 502. 519 is an air intake port connected to the pipe 210, and 520 and 521 are air outlets connected to the pipes 208 and 209, respectively.

Reference numeral 522 denotes a long groove-shaped ventilation hole formed in the cylindrical part of the plunger body at a position facing the air outlet 520, and the length of the hole is set to 1 with a hollow hollow as shown in FIG. There is.

Similarly, 522' is a cylindrical part of the plunger body, and is a vent hole of the same shape raised at a position where it can face the air outlet 521.

The diaphragm valve 500 in FIG.
1 and 513, and when there is no negative pressure, the valve body 517 is located to the left of the illustrated position due to the action of the spring 503, and the plunger body 518 is also located to the left due to the action of the spring 506.
The ventilation holes 522 and 522' are located to the right of the position opposite to the air outlets 520 and 521, respectively, so the air outlets 520 and 52' are
1 is essentially closed. The greater the negative pressure in the diaphragm chamber 511, the more the valve body moves to the right, and the greater the negative pressure in the diaphragm chamber 513, the more the plunger body 518 moves to the left.
The substantial opening area of 21 becomes larger. In other words, the diaphragm valve 500 operates to increase its function. 7th
The figure shows the configuration of a three-way solenoid valve 700, where 701 is a housing, 702 is a solenoid, 703 is a valve, 704 is a spring that always biases the valve 703 to the left, and 705
are vents to the atmosphere, and 706 and 707 are the fourth vents, respectively.
This is a connection port suitable for pipes 214 and 215 in the figure.

When the electromagnetic valve 700 is not energized, the valve 700 is
3 is pressed to the left, the space between 706 and 707 is closed, and the space between 705 and 706 is connected. solenoid 702
When energized, the valve 703 moves to the right against the spring 704, and the valve is switched so that the connection ports 706 and 707 are opened and the connection ports 706 and 705 are closed. FIG. 8 shows the structure of a negative pressure regulator 800, 801 is a case, 8
02 is a diaphragm, 803 and 804 are springs, 8
05 is a pressure setting screw, 806 is a diaphragm 802
807 is the valve seal part, 8
08 is a negative pressure outlet, and 809 is a negative pressure inlet. The negative pressure outlet 808 is connected to the pipe 215 shown in FIG. 4, and the negative pressure inlet 809 is connected to the pipe 216.

This negative pressure regulator 800 controls the negative pressure introduced from the intake manifold 101 of the engine to a constant negative pressure and supplies it to the electromagnetic valve. FIG. 9 shows details of the control electric circuit section 310, and the control circuit consists of a comparator having an operational amplifier 301 and a power amplifier having a transistor TRI.

The signal from the exhaust gas sensor 103 is applied to the positive input terminal of the operational amplifier 301 through a filter consisting of R1 and CI, divided by resistors R2 and R3, and compared with the voltage applied to the negative input terminal. The output of the operational amplifier 301 is amplified by a power amplifier composed of R16, R17, and TRI, and controls the solenoid of the electromagnetic valve 700 inserted in the collector circuit of the transistor TRI. In the embodiment shown in FIGS. 4 to 9 described above, when the air-fuel ratio becomes richer than the target value, the signal from the exhaust gas sensor 103 becomes larger, as shown in line a in FIG. 10. As shown in FIG. 508, and at the same time move the plunger body 518 to the left.
also moves to the left.

Furthermore, by energizing the solenoid valve 700, negative pressure is supplied to the integrating means consisting of the throttle 601 and the tank 600 through the pipe 512, and the time-integrated negative pressure is applied to the diaphragm chamber 511' of the diaphragm valve 500 through the pipe 213. Therefore, the diaphragm 501 is connected to the spring 50.
3, the valve body 517 moves to the right at tide.
moves to the right as the diaphragm 501 moves. The force that moves the diaphragm 501 to the right is the resultant force of the spring 504 and the negative pressure in the diaphragm chamber 511. Solenoid valve 700 opens as described above, actuates diaphragm 502, and plunger body 518 moves to the left.
When the air holes 522, 522' and the connection port 5 are moved
20, 521 and the valve body 517, the slit-shaped opening area of the diaphragm valve 500 is
o, and then as the negative pressure in the diaphragm chamber 511 increases with time, the valve body 517 gradually moves to the right, so the slit closing area increases with time as shown by line f in FIG. As a result, the entire system works to gradually increase the amount of vapor bleed in the carburetor and return the air-fuel ratio to the target air-fuel ratio. xo is the closing area that changes proportionally, x by adjusting the setting screw 508. can be changed, and the proportional sensitivity can be changed. Further, by changing the values of the aperture 601 and the tank 600, the integral constant can be changed. When the air-fuel ratio becomes leaner than the target value, the signal from the exhaust gas sensor 103 becomes smaller, and the operational amplifier 30
1 becomes a low level, the three-way solenoid valve 700 switches, atmospheric pressure is supplied from the three-way solenoid valve 700 to the diaphragm valve 500, and the opening degree (slit-shaped entrance area) of the diaphragm valve 500 decreases by 4. The entire system then operates to return the air/fuel ratio to the target value. As is clear from the above explanation, according to the present invention, the number of times the solenoid valve operates can be extremely reduced, thereby extending the life of the device.Furthermore, since the electric circuit is simplified, reliability can be improved. can contribute.

In fact, the operating speed of the three-way solenoid valve 700 can be reduced to several Hz or less.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view showing the entire conventional air-fuel ratio control device, FIG. 2 is an electric circuit, and FIG. 3 is an explanatory diagram of its operation. Figures 4 to 9 show examples of the present invention, with Figure 4 being a partial vertical cross-sectional view showing the whole, Figure 5 being a vertical cross-sectional view of the diaphragm valve, and Figure 6 being a perspective view of essential parts of the diaphragm valve. , FIG. 7 is a longitudinal sectional view of the three-way solenoid valve, FIG. 8 is a longitudinal sectional view of the negative pressure regulator, FIG. 9 is an electric circuit diagram, and FIG. 10 is an explanatory diagram of the operation of the embodiment. 100...Engine, 101...
...Intake manifold, 103...Exhaust gas sensor, 205...Main system air bleed introduction path, 206...
Low-speed system air bleed introduction path, 310...Control electric circuit section, 500...Diaphragm valve, 501
, 502... diaphragm, 511, 513... diaphragm chamber, 517... valve body, 518...
...Plunger body, 522, 522'...
Ventilation hole, 600...Tank, 601...Aperture, 700...
...-way solenoid valve, 800... Negative pressure regulator -
. spear 1 zu 2 zu spear 3 gum zu 5 ga 6 tusk 7 zu 8 square 9 10

Claims (1)

[Scope of Claims] 1. A diaphragm valve having two independently operating diaphragms, the overall opening of which is determined by the positions of these two diaphragms, and one of the diaphragm chambers formed by the two diaphragms. one directly, and the other a three-way solenoid valve that switches and supplies negative pressure or atmospheric pressure through an integral means consisting of a throttle and a tank, and a negative pressure regulator inserted between the engine intake manifold and the three-way solenoid valve. , an exhaust gas sensor that detects an air-fuel ratio, and a control electric circuit unit that switches the three-way solenoid valve according to a signal from the exhaust gas sensor, the diaphragm valve having two slit-shaped openings as a valve, An air-fuel ratio control device characterized in that one of the two is connected to a main system air bleed introduction passage of a carburetor, and the other is connected to a low speed system air bleed introduction passage. 2. The air-fuel ratio control device according to claim 1, wherein the opening area of both the slit-shaped openings increases and decreases simultaneously. 3. The air-fuel ratio control device according to claim 1 or 2, wherein negative pressure or atmospheric pressure is alternately applied to the diaphragm chamber based on a signal from an exhaust gas sensor.