JPS6030456Y2 - Air bypass type air fuel ratio control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine, and particularly to an air-pulse type air-fuel ratio control device for an automobile engine.

There are various types of conventional air bypass type air-fuel ratio control devices, such as those disclosed in Japanese Patent Application Laid-Open No. 51-07983 and Japanese Patent Application Laid-open No. 51-07%31, but this invention is the object of the present invention. This is a device that controls the air-fuel ratio by changing the opening area of the intake passage using negative pressure downstream of the throttle valve.

In this type of device, the amount of air taken in from the bypass is affected by the engine's intake negative pressure, so it is necessary to adjust the opening area of the bypass passage in accordance with the amount of intake air of the engine.

Further, since the displacement of the actuator that changes the opening area of the bypass path depends on the control negative pressure acting on the actuator, it is necessary to increase the control negative pressure in accordance with the engine intake air amount.

This controlled negative pressure is usually obtained using an electro-pneumatic converter, etc.
During acceleration, etc., when it is necessary to greatly change the control negative pressure, a delay in the signal to the electro-pneumatic converter, a delay in the operation of the electro-pneumatic converter, a delay in the actuator, etc. are added, resulting in a delay in the operation of the actuator.

Therefore, there has been a drawback that the control device is delayed, particularly during acceleration, and the content of pollutants in the exhaust gas is increased.

The present invention aims to provide an air-fuel ratio control device with good followability, and includes a bypass passage that bypasses the air cleaner upstream of the venturi portion of the carburetor and the intake passage downstream of the throttle valve, and The air valve has an air valve that controls the amount of intake air passing through the bypass passage by changing the cross-sectional area of the flow passage, and the air valve detects a signal generated by the engine rotation speed and negative pressure downstream of the throttle valve, and the exhaust components of the engine. In the air bypass type air-fuel ratio control device, the air valve is formed between a first diaphragm and a second diaphragm having a larger area than the first diaphragm. The control negative pressure chamber has a control negative pressure chamber, an atmospheric pressure chamber provided on the first diaphragm side, and a pressure chamber provided on the second diaphragm side, and the control negative pressure chamber communicates with the intake pipe. and has a communication hole with the atmosphere whose opening and closing are regulated by the operation of a solenoid whose duty ratio is determined by the output generated for a certain period of time every cycle of the engine's rotational speed, and the pressure chamber is connected to the second diamond. A compression spring that holds the plum, a communication path that communicates with the intake pipe via a ball valve and leads to a reserve tank maintained at a constant negative pressure, and an exhaust path between the engine outlet and the three-way catalyst pipe. The atmospheric pressure chamber is connected to the bypass passage via a needle valve fixedly supported on the first and second diaphragms. It is characterized by being connected.

FIG. 1 is an explanatory diagram of an air bypass type air-fuel ratio control device which is an embodiment of the present invention.

Air entering from the air cleaner 1 sucks fuel into the venturi portion of the carburetor 2, passes through a gap around the throttle valve 3, and is supplied to the engine 5 through the intake pipe 4.

The exhaust gas after combustion in the engine 5 is detected by the 02 sensor 14.
The amount is detected, purified by the three-way catalyst pipe 19, and released to the outside air.

The exhaust gas purification rate by the three-way catalyst is best at the three-way point, which is the theoretical air-fuel ratio of the air-fuel mixture taken into the engine, so it is desirable to control the air-fuel mixture to the three-way point.

Such air-fuel mixture control is closely related to the following means which detects the amount of O2 in the exhaust gas using the O2 sensor 14 and performs closed loop control to control the air-fuel ratio.

A bypass passage 13 is provided that directly communicates the air cleaner 1 and the intake pipe 4, and this bypass passage 13 has an air valve 6.
is installed.

Air valve 6 has diaphragm B8 and diaphragm AIO
A pressure chamber 7 containing a compression spring from above,
It is partitioned into three chambers: a control negative pressure chamber 9 and an atmospheric pressure chamber 11.

The pressure chamber 7 communicates with a reserve tank 15 maintained at a constant negative pressure via a solenoid B17.
communicates with the intake pipe 4 via a ball valve.

The control negative pressure chamber 9 introduces the negative pressure of the intake pipe 4, and its duty ratio is adjusted by opening and closing a communication hole with the atmosphere by operating the solenoid A16.

Further, the atmospheric pressure chamber 11 communicates with the bypass passage 13, and the opening of the bypass passage 13 is connected to the diaphragm B8.
and is limitedly adjusted by a needle valve 12 fixedly supported on the diaphragm AIO.

Note that the diaphragm AIO has a smaller area than the diaphragm B8.

Solenoid A16 is connected to amplifier A21, and amplifier A2
1 is connected to a rotation sensor 18, and the rotation sensor 18 detects the rotation speed of the engine 5.

The amplifier A21 generates an output that opens the solenoid A16 for a certain period of time at a period T corresponding to the engine speed.

FIG. 2 is a diagram illustrating the operation of the amplifier A21 in FIG. 1, and the horizontal axis is time.

When a trigger signal 23 corresponding to the engine rotational speed is generated, the output signal 22 of the amplifier A21 generates an output for time t0 every period T to open the solenoid A16.

Therefore, the negative pressure in the control negative pressure chamber 9 of the air valve 6 in FIG. 1 decreases over time, and the needle valve 12 is strongly pulled up to open the bypass passage 13 and increase the bypass intake air amount.

As the amplifier rotational speed increases, the period T decreases and t□ remains unchanged, so the duty ratio increases and the bypass intake air amount further increases.

Figure 3 is a diagram showing the relationship between the engine speed and the actual opening area of the solenoid A16. The actual opening area varies in proportion to the engine speed.

Figure 4 shows the engine speed controlled by the negative pressure chamber 9 of the air valve 6.
This is a diagram showing the relationship between the negative pressure of

Lines 24, 25, and 26 indicate that the negative pressure in the intake pipe is -400, respectively.
, -300, -200m*Hg, and when the engine speed is high, the control negative pressure chamber 9
negative pressure decreases.

Further, when the negative pressure in the intake pipe 4 is large, the negative pressure in the control negative pressure chamber 9 becomes large.

FIG. 5 is a diagram showing the relationship between the engine speed and the cross-sectional area of the bypass passage.

When the engine speed increases, as shown in FIG. 4, the negative pressure in the control negative pressure chamber 9 decreases, so that the upward distance of the needle valve 12 increases, increasing the cross-sectional area of the bypass passage.

Also, the engine intake pressure of the intake pipe 4 is 27°28.29
, 30, the negative pressure in the control negative pressure chamber 9 increases and the cross-sectional area of the bypass passage decreases.

The reason why such a change occurs is that when the negative pressure in the control negative pressure chamber 9 of the air valve 6 in FIG. This is because the amount of movement of the valve 12 becomes smaller.

FIG. 5 shows that the opening degree of the bypass passage can be controlled as a function of the engine speed and the negative pressure of the intake pipe 4 in this way.

That is, this shows that the opening degree of the bypass passage is controlled by the operating state of the engine.

Therefore, if the operating conditions of the engine are adjusted to the three-way point where the three-way catalyst filled in the three-way catalyst tube 19 is most effective, engine exhaust gas can be purified most effectively.

However, in practice, it is difficult to operate the engine with the air-fuel ratio of the gas-liquid mixture supplied to the engine always matching the ternary point because various disturbance conditions are added, but the following describes what makes this possible. It is a closed loop.

In FIG. 1, the 0□ sensor 14 detects the amount of 02 in the exhaust gas of the engine 5, and it is detected whether the air-fuel ratio of the gas-liquid mixture supplied to the engine is appropriate.

The output of the 02 sensor 14 is input to the amplifier B20 and compared with a ternary point to determine whether the air-fuel ratio is rich or lean.

Based on this determination, the amplifier 20 outputs an on/off signal that generates an output and controls the opening time of the solenoid B17.

That is, when the air-fuel ratio is rich, the actual or apparent upper opening area of the solenoid B17 is increased.

Therefore, the reserve tank 15 is maintained at a constant pressure.
, the negative pressure in the pressure chamber 7 increases.

A force is generated to pull up the diaphragm B8, which increases the negative pressure in the pressure chamber 7, pulls up the needle valve 12, enlarges the opening of the bypass passage 13, and leans the air-fuel ratio.

Contrary to the above, when the amplifier B20 receives a lean signal from the 02 sensor 14, the passage area is reduced by the solenoid B17, the negative pressure in the pressure chamber 7 is reduced, and the degree of rise of the needle valve 12 is reduced. This reduces the amount of bypass air and enriches the air-fuel ratio supplied to the engine.

By alternately repeating such closed-loop control, the air-fuel ratio of the gas-liquid mixed flow supplied to the engine can be converged to a ternary point.

FIG. 6 is a diagram showing the relationship between the air-fuel ratio and the exhaust gas purification rate, in which the line 31 shows the CO and HC purification rates, and the line 32 shows the NOx purification rate.

The three-way point often used in the above explanation refers to the narrow air-fuel ratio range where lines 31 and 32 intersect, and when a three-way catalyst is used, this air-fuel ratio (14,7±0. In 2), the content of substances that cause pollution in the exhaust gas is minimized.

The device of this embodiment can automatically control the air-fuel ratio in a closed loop using the 0° sensor 14 so as to reach this ternary point 33.

As described above, the air valve type air-fuel ratio control device of this embodiment changes the supply air amount through the bypass passage depending on the engine operating condition, and also adjusts the air-fuel ratio to the three-way point in a closed loop, thereby achieving a quick response. It is possible to perform air-fuel ratio control with good followability.

As a result, the combustion state of the engine is automatically maintained at an optimal state, and the exhaust gas is passed through the three-way catalyst layer to be well purified.

FIG. 7 is a front view of a needle valve that is a modification of the one shown in FIG. 1. The needle valve 12 in FIG. 1 has a conical shape. There is.

Therefore, as the needle valve 12 moves up and down, the opening of the bypass passage 13 changes in a quadratic curve.

FIG. 8 is a diagram showing the relationship between the amount of movement of the needle valve, the cross-sectional area of the bypass passage, and the negative pressure of the air valve control negative pressure chamber when the needle valve of FIG. 7 is used. The amount of movement increases as it goes to the right.

The curve 34 shows the change in the cross-sectional area of the bypass passage, which changes in a quadratic curve as described above.

On the other hand, a straight line 35 indicates a change in the negative pressure in the air valve control negative pressure chamber 9, which changes in inverse proportion to the amount of movement of the needle valve.

FIG. 9 is a diagram showing the relationship between the negative pressure in the air valve control negative pressure chamber and the cross-sectional area of the bypass passage, and as the negative pressure in the control negative pressure chamber 9 decreases, the hatched area surrounded by line 36 and line 37 is shown. This indicates that the width of the bypass passage 13 becomes larger, and the range of change in the cross-sectional area of the bypass passage 13 becomes wider.

Therefore, when the negative pressure in the control negative pressure chamber 9 of the air valve 6 is small, that is, when the engine intake amount is large, the opening area of the bypass passage 13 can be changed greatly using the needle valve 12 shown in FIG. This shows that the ratio of the amount of bypass air to the amount of air passing through the device can be kept constant and controlled.

By using the needle valve of this modification, it is possible to maintain a constant ratio between the amount of air passing through the carburetor and the amount of air passing through the bypass passage, and more precisely control the amount of air supplied to the engine to adjust the air-fuel ratio. It has the effect of being able to

As described above, the air bypass type air-fuel ratio control device of the present invention has the advantage that it has good followability and can control the air-fuel ratio with high precision.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an Air Viper type air-fuel ratio control device which is an embodiment of the present invention, Fig. 2 is a diagram illustrating the operation of the amplifier 21 shown in Fig. 1, and Fig. 3 is a diagram showing the engine speed and solenoid. A diagram showing the relationship between the actual opening area product of A21, FIG. 4 is a diagram showing the relationship between the engine speed and the negative pressure in the control negative pressure chamber 9 of the air valve 6, and FIG. 5 is a diagram showing the relationship between the engine speed and the bypass A diagram showing the relationship between the flow passage cross-sectional area of the passage, FIG. 6 a diagram showing the relationship between the air-fuel ratio and the exhaust purification rate, and FIG. 7 a front view of a needle valve that is a modification of FIG. Figure 8 is a diagram showing the relationship between the needle valve movement amount, the cross-sectional area of the bypass passage, and the negative pressure in the air valve control negative pressure chamber when the needle valve shown in Figure 7 is used, and Figure 9 is a diagram showing the relationship between the needle valve movement amount, the flow path cross-sectional area of the bypass passage, and the negative pressure of the air valve control negative pressure chamber, and Figure 9 is the air valve FIG. 6 is a diagram showing the relationship between the negative pressure of the control negative pressure chamber and the flow path cross-sectional area of the bypass passage. 2... Carburizer, 3... Throttle valve, 4...
...Intake pipe, 5...Engine, 6...
...Air valve, 8...Diaphragm B, 9.
...Diaphragm, 12...Needle valve, 13...Bypass passage, 14...0
2 sensors, 19...Three-way catalyst tube.

Claims (1)

[Scope of utility model registration request] It has a bypass passage that provides bypass communication between the air cleaner upstream of the venturi portion of the carburetor and the intake passage downstream of the throttle valve, and an air valve that changes the cross-sectional area of the bypass passage and controls the intake passage passing through the bypass passage. In the air valve type air-fuel ratio control device, the air valve is operated by a signal generated by the rotational speed of the carburetor and a negative pressure downstream of the throttle valve, and a signal from a detector that detects exhaust components of the carburetor. The air valve includes a control negative pressure chamber formed between a first diaphragm and a second diaphragm having a larger area than the first diaphragm, and an atmospheric pressure chamber provided on the first diaphragm side. and a pressure chamber provided on the second diaphragm side. The pressure chamber has a communication hole with the atmosphere whose opening and closing are regulated by the operation of the Tsuremade, which determines the duty ratio, and the pressure chamber is in constant communication with the compression spring that holds the second diaphragm and the intake pipe through a ball valve. It has a solenoid that opens and closes the communication passage in response to a signal generated by an oxygen detector installed in a communication passage leading to a reserve tank maintained at negative pressure and an exhaust passage between the outlet of the engine and the three-way catalyst pipe. The air bypass air-fuel ratio control device is characterized in that the atmospheric pressure chamber communicates with the bypass passage via a needle valve fixedly supported by the first and second diaphragms.