JPS5934468A - Exhaust gas purifier for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain high output power, by detecting the high-load operation of an engine to close a solenoid valve in an air bleed passage during said operation to supply a too thick mixture into the cylinder of the engine. CONSTITUTION:When a throttle valve 11 is almost fully opened, namely, high- load operation such as full-load operation is performed, a throttle switch 54 is turned off so that an analogue switch 52 is also turned off. Consequently, an electrical current to a solenoid 43 is cut off to close a valve port 37 in an air bleed passage 35 to feed a too thick mixture into an engine cylinder so that high output power is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) A^r The present invention relates to an exhaust gas purification device for an internal combustion engine.

Three harmful components HC, CO and NOx in exhaust gas 7f
A three-way catalyst is known as a catalyst that can reduce the amount of water at the same time. The purification efficiency R of this three-way catalyst is the first (a)
As shown in the figure, the air-fuel ratio A/F is highest when it is the buried stoichiometric air-fuel ratio.
．． It has a narrow width of about 0.06 mm.

Usually, the air-fuel ratio range in which a purification efficiency of 80 percent or more can be obtained is called a window. Therefore, in order to reduce the three harmful components in the exhaust gas during opening using a three-way catalyst, the air-fuel ratio must be maintained within this narrow window W at all times. For this reason, in conventional exhaust gas purification devices, the air-fuel ratio is higher than the stoichiometric air-fuel ratio.
An oxygen concentration detector capable of determining 4% or more is installed in the engine exhaust passage, and the air-fuel ratio is controlled to be within the window W based on the output signal of this oxygen concentration detector. However, this type of exhaust gas purification system using oxygen concentration detector sound requires an expensive oxygen concentration detector (2) and an expensive electronic control unit for fuel ratio control. There is a problem of rising manufacturing costs.However, recently, 5AEpaperNo.

As described in No. 7, No. 60201 and Japanese Patent Publication No. 56-4741, the function of the three-way catalyst was gradually elucidated, and it was found that the three-way catalyst had all the oxygen retention functions. In other words, when the air-fuel ratio is on the lean side with respect to the stoichiometric air-fuel ratio, the three-way catalyst takes oxygen from NOx and
It completely reduces Ox and retains this stolen oxygen.
When the air-fuel ratio becomes closer to the stoichiometric air-fuel ratio, the retained oxygen is released to oxidize CO,i (C. Even if the reference air-fuel ratio deviates from the normal air-fuel ratio, the above-mentioned oxygen retention function promotes the reduction of NOx and the oxidation of Co and HC, resulting in high purification efficiency. Figure (b) shows the (3) window W of the reference air-fuel ratio A/F when the air-fuel ratio is varied by ±1.0 with respect to the reference air-fuel ratio at a frequency of I Hz. ) and Figure 1(b), it can be seen that when the fuel-fuel ratio is varied at a constant frequency, the window Wo becomes wider.In addition, if the fuel-fuel ratio is varied at a constant frequency, the reference air-fuel ratio is This means that high purification efficiency can be obtained even if there is a slight deviation from the air-fuel ratio. - If the frequency of fluctuation of the air-fuel ratio is lowered, that is, the period of fluctuation of the air-fuel ratio is lengthened, the oxygen retention capacity of the three-way catalyst will increase. saturation, the redox ability based on the oxygen retention function decreases, and the purification efficiency of the three-way catalyst decreases.

Figure 1(C) clearly shows this. 1st (C
) In the figure, the vertical axis R shows the total purification efficiency, and the horizontal axis F shows the fluctuation mantissa of the air-fuel ratio. show. If the air-fuel ratio is made smaller, the air-fuel ratio cannot be varied alternately between the rich side and the lean side, so the width of the window becomes narrower. Therefore, it can be seen that there are optimal air-fuel ratio fluctuation periods and fluctuation periods in order to widen the window.

As mentioned above, if the air-fuel ratio fluctuates relative to the standard air-fuel ratio and all the fluctuating frequencies are appropriately selected, the window (4) can be widened, and therefore high purification efficiency can be achieved even if the standard air-fuel ratio slightly fluctuates from the stoichiometric air-fuel ratio. Obtainable. Of course, this means that by using a narrow fuel supply system during fluctuations in the reference air-fuel ratio, high purification efficiency can be obtained without using feedback control based on the output signal of the r-cumulative concentration detector. , if the fuel injection valve sound is used as the fuel supply system, the reference 'g! Although the variable width of the combustion chamber can be narrowed, the fuel injection system is expensive, which increases the manufacturing cost of the engine.Therefore, in order to keep the engine installation cost low, a carburetor is used. Is required. However, in conventional fixed venturi type carburetors, the reference air-fuel ratio fluctuates widely, and in conventional variable bench and IJ type carburetors, the reference air-fuel ratio varies greatly during acceleration or depending on engine temperature. It is difficult to obtain high purification efficiency even when using a vaporizer or a variable venturi type vaporizer.

An object of the present invention is to provide an exhaust gas purification device that can ensure high exhaust gas purification efficiency using an inexpensive carburetor without using an oxygen concentration detector.

The present invention will be described in detail below with reference to the attached drawings. Referring to FIG. 2, a 1μ intake manifold, 2 a variable venturi carburetor mounted on the intake manifold l,
3 shows the exhaust manifold, 4 shows the catalytic converter,
A three-way monolith catalyst 5 is arranged inside the catalytic converter 4 . The variable bench type carburetor 2 has a carburetor housing 6 and an intake passage 7 extending in the nozzle 6 in a rectangular direction.
, a suction piston 8 that moves laterally within the intake passage 7, a needle 9 attached to the tip surface of the suction piston 8, and a needle 9 fixed on the inner wall surface of the intake passage w17 opposite to the tip surface of the suction piston 3. The spacer 10 is provided with a spacer 10, a throttle valve 11 provided in the intake passage 7 downstream of the suction piston 8, and a 70-tooth chamber 12. 3 is formed. A hollow cylindrical casing 14 is fixed to the carburetor housing 6 , and a casing 1 is attached to the inside of the casing 14
A four axially extending guide sleeve 15 is mounted. A bearing 17 with a number of balls 16 is inserted into the guide sleeve 15, and the outer end of the guide sleeve 15 is closed by a blind cover 18. - 10,000, a mineral guide rod 9 is fixed to the suction piston 8, and this guide rod 19
is inserted into the bearing 17 so as to be movable in the axial direction of the guide rod 19.

Since the suction piston 8 is thus supported by the casing 14 via the bearing 17, the suction piston 8 can move smoothly in its axial direction. The interior of the casing 14 is divided into a negative pressure chamber 20 and an atmospheric pressure chamber 21 by the suction piston 8, and a compression spring 22 is inserted into the negative chamber 20 to constantly press the suction piston 8 toward the venturi portion 13. The negative rotor 20 is vented through two suction holes formed in the suction piston 8! 7 B'li 13, and the atmospheric pressure chamber 21 is connected to the intake passage 7 upstream of the suction piston 8 through the air (γ) hole 24 formed in the carburetor housing 6.
connected within.

A fuel passage 25 extending in the axial direction of the needle 9 is formed in the carburetor housing 6 so that the needle 9 can enter therein, and a metering jet 26 is provided in the fuel passage 25. The fuel passage 25 upstream of the metering jet 26 is connected to the float chamber 12 via a fuel pipe 27 extending downward, and the fuel in the float chamber 12 is connected to the fuel pipe 27.
It is sent into the fuel passage 25 through the communication. Further, a nozzle 28 having a cylindrical inner wall and arranged coaxially with the fuel passage 25 is fixed to the spacer 10 . This nozzle 28 protrudes into the venturi portion 13 from the inner wall surface of the spacer 10, and the lower half of the tip of the nozzle 28 further protrudes from the lower half toward the suction piston 8. The needle 9 extends through the nozzle 28 and the metering jet 26 and the fuel is metered by the annular gap formed between the needle 9 and the metering jet 26 before being fed from the nozzle 28 into the intake passage 7 .

(8) As shown in FIG. 2, a raised wall 29 is formed at the upper end of the spacer 10 and projects horizontally into the intake passage 7, and between this raised wall 29 and the tip of the suction piston 8. Flow rate control is performed. When engine operation is started, air flows toward the inner wall of the intake passage 7 and downward. At this time, since the air flow is constricted between the suction piston 8 and the raised wall 29, negative pressure is generated in the vent IJ ff1l 13, and this negative pressure is guided into the negative pressure M2O through the suction hole 23'f. The zero suction piston 8 is designed so that the pressure difference between the negative pressure chamber 20 and the atmospheric pressure chamber 21 becomes a substantially constant pressure determined by the spring force of the compression spring 22, that is, so that the negative pressure inside the ventili portion 13 becomes substantially constant. 0 Referring to FIGS. 3 and 4, the entire tip surface of the suction piston located upstream of the needle 9 is raised from the mounting end surface 30 of the needle 9 toward the tip of the needle 9. A recess #ll31 extending in the axial direction of the intake passage 7 is formed on the tip end surface of the SAXICON piston.The upstream end 31a of the recess groove 31 has a U-shaped cross section and is connected to the needle mounting end surface 30. The remaining concave #4 portion 31b extends from the upstream end 31a to the needle mounting end surface 30.
It extends almost straight up to. Furthermore, the cross-sectional shape of the tip tube of the suction piston located on the upper N side of the needle 9 is a V-shape that expands from the concave groove 31 toward the ventilator portion 13, so that the suction piston tip ims A pair of inclined wall surface portions 32a are inclined toward the groove 31.

32b.

As can be seen from FIG. 3, when the amount of intake air is small, the raised wall 29 and the inclined wall portions 32a and 32b.

A substantially isosceles triangular intake air control throttle 8K is formed by the upstream end portion 31a of the concave groove.

By forming 'lk in the intake air control throttle part in this way, the lift seam of the suction piston 8 becomes proportional to the opening area of the intake air control throttle part, and therefore the lift of the suction piston 8) - [tU intake air It will increase smoothly as the amount increases. Furthermore, since the suction piston 8 is supported by the bearing 17, it moves with good response to changes in the amount of intake air, and thus the suction piston 8 responds to increases in the amount of intake air when the amount of intake air increases. Move gracefully and cleanly. As a result, even when the amount of intake air changes rapidly, such as during high-speed operation, the amount of suction piston 8 increases in proportion to the increase in the amount of intake air, so that it is supplied from the nozzle 28. The amount of fuel will always be proportional to the intake air cap. Furthermore, as can be seen from FIG. 3, when the amount of intake air is small, the μ intake air is made to flow through the entire center of the intake passage 7, and as a result, the fuel supplied from the nozzle 28 immediately flows into the engine cylinder together with the intake air flow. Therefore, even when the amount of intake air is small, the fuel supplied from the nozzle 28 is immediately supplied into the engine cylinder. Therefore, even if the intake air cap increases rapidly during acceleration, the amount of fuel supplied from the nozzle 28 is proportional to the amount of intake air as described above, and moreover, the fuel supplied from the nozzle 28 is immediately Since the air-fuel mixture is supplied into the engine cylinder, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is maintained substantially constant even if the amount of intake air changes rapidly. Furthermore, since the suction piston 8 is supported by the bearing 17, the engine temperature does not affect the movement of the suction piston 8.
In this way, the suction piston 8 can move with good responsiveness to changes in the amount of intake air, regardless of the engine temperature.

In this way, when the variable venturi type carburetor 2 shown in FIG. 2 is used, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders can be kept at approximately the same value, for example, approximately at the stoichiometric value, regardless of the engine temperature and engine operating conditions. fuel ratio can be maintained.

Referring to FIG. 2, an annular air chamber 33 is formed around the metering jet 26, and a plurality of air bleed holes 34 communicating with the annular air chamber 33 are formed on the inner peripheral wall surface of the metering jet 26. The annular air chamber 33 is connected to the raised wall 2 through the air bleed passage 35 and the air bleed jet 36.
A valve boat 37 is connected to the intake passage 7 upstream of the air bleed passage 35 and has an opening area controlled by a solenoid valve 40 formed within the air bleed passage 35 .

The linear solenoid box 40 is fully equipped with a valve body 41 that controls the opening area of the valve boat 37, a movable plunger 42 connected to the valve body 41, and a solenoid 43 that sucks the movable plunger 42'fc. is connected to the solenoid drive circuit 50. This linear solenoid cell 40 moves the movable plunger r42 by a distance proportional to the current flowing through the μ solenoid 43, and as the current flowing through the solenoid 43 increases, the valve body 41 moves to the right.

Therefore, the opening area of the valve boat 37 changes in proportion to the current flowing through the solenoid 43.

The solenoid drive direction @SO is as shown in Figure 5(a).
A sawtooth generator 51 that generates a sawtooth voltage with a frequency of Hz to 2Hz, an analog switch 52 connected to the output terminal of the sawtooth generator 51, and a voltage-current converter s3 connected to the output terminal of the analog switch 52. The output terminal of the voltage-current converter 53 is connected to the solenoid 43.

- 10,000, a throttle switch 54 is attached to the throttle valve 11 and responds to opening/closing operations of the throttle switch 54. This throttle switch 54 is turned off when the throttle valve is almost fully opened, that is, during high load operation such as almost full load operation, and turned on during other @ load operation. It is controlled by the analog switch 52 and the output voltage of the throttle switch 54, and becomes conductive when the throttle switch 54 is on.

As mentioned above, during partial load operation, analog switch 5
2 becomes conductive, the output voltage of the sawtooth generator 51 is sent to the voltage-current converter 53, where it is converted into a corresponding current and supplied to the solenoid 43.

As mentioned above, the opening area of the valve boat 37 is larger than that of the solenoid 4.
It can be seen that the opening area of the boat 37 changes in a sawtooth pattern because the solenoid 43 is supplied with a current as shown in FIG. 5(a).

As a result, when the opening area of the valve boat 37 changes in a sawtooth pattern, the amount of air supplied from the air bleed hole 34 into the fuel passage 25 also changes in a sawtooth pattern, so that the air-fuel ratio A of the air-fuel mixture supplied into the engine cylinder /F changes smoothly in a wave-like manner as shown in FIG. 5(b). Dimensions of air bleed jet 36 and valve boat 37 When the valve body 41 of the linear solenoid valve 40 repeatedly increases and decreases the flow area of the valve boat 37, the average value of the air-fuel ratio of the mixture supplied into the engine cylinder is As shown in Figure 5(b), the air-fuel ratio is approximately stoichiometric, and the air-fuel ratio is approximately ±0.2 to ±1.0 with respect to the stoichiometric air-fuel ratio during fluctuations. Regardless of the operating condition, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders is within ±0.0% of the stoichiometric air-fuel ratio at frequencies from IHz to 2Hz.
2 to ±1.0, and the average value of this air-fuel ratio is window W in FIG. 1(b). Since the same is maintained, high purification efficiency can be obtained by utilizing the oxygen retention function of the three-way monolith catalyst 5. Furthermore, Section 5(b)
As shown in the figure, since the air-fuel ratio fluctuates clearly, the combustion state does not change suddenly, and thus stable combustion can be ensured at all times regardless of the operating state of the engine.

- When the engine is operated under high load, the throttle switch 54 is turned off as described above, so the analog switch 52 becomes non-conductive. As a result, the supply of current to the solenoid 43 is stopped, and the valve body 41 completely closes the boat 37. In this way, a rich air-fuel mixture is supplied into the engine cylinders, so that a full high output can be obtained.

As described above, according to the present invention, exhaust gas can be thoroughly purified using an inexpensive carburetor without using an expensive oxygen concentration detector or an expensive electronic control unit for air-fuel ratio control. Furthermore, the structure is extremely simple since only a solenoid valve is provided in the air bleed passage, and therefore the reliability of the exhaust gas purification device can be completely improved. Also,
During high-load engine operation, excess air-fuel mixture is supplied into the engine cylinders, making it possible to obtain high output.

[Brief explanation of drawings]

Figure 1 is a diagram showing exhaust gas purification efficiency, Figure 2 is a cross-sectional view of the engine intake and exhaust system, Figure 3 is a plan view taken along the arrow ■ in Figure 2, and Figure 4 is a suction piston. FIG. 5 is a diagram showing all the fluctuations in the air-fuel ratio. 2... Carburetor, 8... Suction piston, 9... Needle, 25... Fuel passage,
28... Nozzle, 35... Air bleed passage, 40... Linear solenoid valve. Patent Applicant: Toyota Motor Corporation Patent Attorney: Akira Aomi, Patent Attorney, Kazuyuki Nishidate, Patent Attorney, Kyosuke Nakayama, Patent Attorney, Akiyuki Yamaguchi (゛)-42!

Claims (1)

[Claims] A carburetor was installed in the engine intake passage, and a three-way catalytic converter was installed in the engine exhaust passage, and the air bleed passage was fully connected to the fuel passage of the carburetor, so that exhaust gas was supplied from the air bleed passage into the fuel passage. In internal combustion engines,
A solenoid valve that changes the flow cross-sectional area of the air bleed passage at a constant frequency of approximately IH2 to 2 Hz is disposed in the air bleed passage, and when the flow cross-sectional area of the air bleed passage is changed, the air-fuel ratio is adjusted to the average. Approximately ±0.
The flow path surface of the air bleed passage is fully set so that the air-fuel ratio fluctuates periodically between 2 and ±1.0 and the average value of the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio. An exhaust gas purification device for an internal combustion engine, which is equipped with all of the above detectors and closes the solenoid valve when the engine is operated under high load.