JPS5910725A - Exhaust gas purifying device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To make the efficiency of exhaust gas control securable even using an inexpensive carburetor, by enlarging the suction pressure to be imposed on an air feed part by degrees in proportion to the increase of a suction air quantity. CONSTITUTION:In proportion to enlargement in the opening of a throttle valve 11, that is, in proportion to the increase of a suction air quantity, the suction pressure to be imposed on an air port 40 grows larger so that an air quantity to be fed from the air feed port 40 becomes increased. The variation range of an air-fuel ratio on the basis of the action of air feeding from the air feed port 40 comes constant irrespective of the suction air quantity. In opening or closing a solenoid valve 50, the opening area of the solenoid valve 50 is set so as to cause the variation range of the air-fuel ratio to be fed inside an engine cylinder to be periodically varied between somewhere around + or -0.2-+ or -1.0 to a theoretical air- fuel ratio.

Description

[Detailed description of the invention] The present invention relates to an exhaust gas purification device for an internal combustion engine.

A three-way catalyst is known as a catalyst that can simultaneously reduce the three harmful components HC, Co, and NOx in exhaust gas. The purification efficiency R of this three-way catalyst is highest when the air-fuel ratio A/F is approximately the stoichiometric air-fuel ratio, as shown in Figure 1(a). The air-fuel ratio range that can be obtained is when the air-fuel ratio is 0.0.
It has a narrow width of about 6 mm.

Usually, the air-fuel ratio region in which a purification efficiency of 80·P-cent or more can be obtained is called a window W.

Therefore, in order to simultaneously reduce the three harmful components in exhaust gas using a three-way catalyst, the air-fuel ratio must be constantly maintained within this narrow window W. For this purpose, a conventional exhaust gas purification system (Niji uses an oxygen concentration detector in the engine exhaust passage that can determine whether the air-fuel ratio is greater or less than the stoichiometric air-fuel ratio, and the output signal of this oxygen concentration detector is The air-fuel ratio is controlled to be within the window W based on There is a problem in that the manufacturing cost of the exhaust gas purification device increases because the exhaust gas purification device requires an electronic control unit.

However, recently, 5AEpaper No. 7
As described in No. 60201 or Japanese Patent Publication No. 56-4741, the function of the three-way catalyst was gradually elucidated.
It was discovered that the three-way catalyst has an oxygen retention function. 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
At the same time, this stolen oxygen is retained, and when the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, the retained oxygen is released to oxidize Co and HC. Therefore, if the air-fuel ratio is alternately varied between the lean side and the rich side with respect to the standard air-fuel ratio, even if the standard air-fuel ratio deviates from the stoichiometric air-fuel ratio, the double oxygen retention function will reduce NOx and Co, HC. The oxidation effect of the gas is promoted and high purification efficiency can be obtained. FIG. 1(b) shows the window Wo of the standard air-fuel ratio A/F when the air-fuel ratio is varied by ±1.0 with respect to the standard air-fuel ratio at a frequency of 1 Hy. It can be seen from FIGS. 1(a) and 1(b) that when the air-fuel ratio is varied at a constant frequency, the window Wo becomes wider. This means that if the air-fuel ratio is varied at regular intervals, a high purification efficiency can be obtained even if the reference air-fuel ratio deviates somewhat from the stoichiometric air-fuel ratio. On the other hand, if the fluctuation frequency of the air-fuel ratio is increased, that is, if the fluctuation period of the air-fuel ratio is lengthened, the oxygen retention capacity of the three-way catalyst will become saturated, and the oxidation stability based on the oxygen retention function will decrease.
The purification efficiency of the three-way catalyst decreases. Figure 1(C) clearly shows this. In FIG. 1(C), the vertical axis R shows the purification efficiency, and the horizontal axis F shows the fluctuation frequency of the air-fuel ratio.

Furthermore, if the air-fuel ratio fluctuation 1] is made smaller, the air-fuel ratio cannot be alternately varied from rich to rich, so the width of win 1' becomes narrower. Therefore, it can be seen that there is an optimal air-fuel ratio fluctuation cycle and fluctuation [1] in order to widen the +lJ window.

As mentioned above, if the air-fuel ratio is fluctuating relative to the standard air-fuel ratio and the fluctuation frequency is appropriately selected, the window will become wider.
Therefore, high purification efficiency can be obtained even if the reference air-fuel ratio varies somewhat with respect to the stoichiometric air-fuel ratio. 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 oxygen concentration detector.

In theory, if a fuel injection valve is used as a fuel supply system, it is possible to narrow the fluctuation period of the reference air-fuel ratio, but since the fuel injection device is expensive, the manufacturing cost of the engine increases.

Therefore, in order to keep the manufacturing cost of the engine low, it is necessary to use a carburetor. However, in the conventional fixed venturi type carburetor, the reference air-fuel ratio fluctuates widely, whereas in the conventional variable venturi type carburetor, the reference air-fuel ratio fluctuates greatly during acceleration or depending on the engine temperature, so these fixed venturi type carburetors Alternatively, it is difficult to obtain high purification efficiency even if a variable venturi type vaporizer is used.

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 while also using an oxygen concentration detector.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawing 1111.
I will clarify.

Referring to FIG. 2, 1 is an intake manifold, 2 is a variable venturi carburetor installed on the intake manifold 1,
3 indicates an exhaust manifold, 4 indicates a catalytic converter,
A three-way monolith catalyst 5 is arranged inside the catalyst converter 4. The variable venturi type carburetor 2 includes a carburetor nozzle 6, an intake passage 7 extending vertically inside the nozzle 6, a suction piston 8 that moves laterally within the intake passage 7, and a suction piston 8. A needle 9 attached to the tip surface, a spacer 10 fixed to the inner wall surface of the intake passage 7 facing the tip surface of the suction piston 3, and a spacer 10 provided in the intake passage 7 downstream of the suction piston 8. It is equipped with a throttle valve 11 and a float chamber 12, and a venturi portion 13 is formed between the front end surface of the suction piston 8 and the spacer 10. Carburetor housing 6
A hollow cylindrical casing 14 is fixed to the casing 14.
A guide sleeve 15 is mounted which extends in the axial direction.

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 . On the other hand, Zakujon Piston 8
A guide rod 19 is fixed to the guide rod 19, and the 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 by the suction piston 8 into a negative pressure chamber 20 and an atmospheric pressure chamber 21, and a compression spring 22 is inserted into the negative pressure chamber 20 to constantly press the suction piston 8 toward the venturi section 13. . The negative pressure chamber 20 is connected to the venturi section 13 through a suction hole 23 formed in the suction piston 8, and the atmospheric pressure chamber 21 is connected to the suction piston 8 upstream through an air hole 24 formed in the carburetor housing 6. It is connected to the intake passage 7.

On the other hand, a fuel passage 25 is formed in the carburetor housing 6 and extends in the axial direction of the needle 9 so that the needle 9 can enter therein.
will be provided. The fuel passage 25 of the metering jet 26 is connected to the float chamber 12 via a fuel tube 2 extending downward.
The fuel in the float chamber 12 is sent into the fuel passage 25 via the fuel pipe 27. Furthermore, a hollow cylindrical nozzle 28 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,
Moreover, the upper half of the tip of the nozzle 2B protrudes toward the suction piston 8 from the lower half. needle 9
extends through the nozzle 28 and the cutting nozzle 26, the fuel being metered into the annular gap formed between the needle 9 and the metering jet 26 from the nozzle 28 into the intake passage 7.

As shown in FIG. 2, a raised wall 29 is formed at the upper end of the suction piston 10 and projects horizontally into the intake passage 7. Flow rate control is performed. When engine operation is started, air flows downward in the intake passage 7. At this time, the airflow is restricted between the suction piston 8 and the raised wall 29, so negative pressure is generated in the venturi section 13.
, are introduced into the negative pressure chamber 20 through the suction hole 23. The suction piston 8 is arranged 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 venturi section 13 becomes constant. Moving.

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 groove 31 extending in the axial direction of the intake passage 7 is formed on the tip end surface of the piston. The upstream end 31 of the concave groove 31 has a U-shaped cross section and is closer to the needle 9 than the needle mounting end surface 30.
The remaining concave groove portion 31
b extends almost straight from the upstream end 31a to the needle extra edition end face 30. Furthermore, the cross-sectional shape of the tip of the suction piston located on the upstream side of the needle 9 and υ is V-shaped, expanding from the concave groove 31 toward the venturi portion 13. Therefore, the tip of the suction piston is A pair of inclined wall surface portions 32a that are inclined toward the groove 31.

32b.

As shown in Fig. 3, when the amount of intake air is small, the raised wall 29. Slanted wall section 3211.32b.

The upstream end portion 31a of the concave groove forms an intake air control throttle portion K having a substantially isosceles triangular shape.

By forming the intake air control throttle part K in this way, the lift opening of the suction piston 8 becomes proportional to the opening area of the intake air control throttle part. It will increase smoothly as it 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 when the amount of intake air starts to increase, the suction piston 8 moves with good response to changes in the amount of intake air. Moves smoothly and responsively. the result,
Even when the amount of intake air changes rapidly, such as during acceleration, the amount of fuel supplied from the nozzle 28 remains constant, so that the lift of the suction piston 8 is proportional to the increase in the amount of intake air. It will always be proportional to the amount of air. Furthermore, as can be seen from FIG. 3, when the amount of intake air is small, the intake air is made to flow through the 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 amount of intake air increases rapidly as 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 amount of fuel supplied from the nozzle 28 is immediately increased. 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 <a even if the amount of intake air changes rapidly. Furthermore, since the Zakujo piston 8 is supported by the bearing 17, the engine temperature does not affect the movement of the Zakujo piston 8, and thus the Zakujo piston 8 can control the amount of intake air regardless of the engine temperature. Able to move responsively to changes. Thus, when the edible venturi type carburetor 2 shown in FIG. The air-fuel ratio can be maintained at the same level.

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 intake passage 7 upstream of the raised wall 29 via an air bleed passage 34, into which an air bleed jet 35 is inserted. Further, an auxiliary air bleed passage 36 branches off from the air bleed passage 34, and this auxiliary air bleed passage 36 opens into the fuel passage 25 downstream of the consumption jet 26. When the engine starts operating, air bleeds through these air bleed holes 34 and the auxiliary air bleed passage 3.
6 into the fuel passage 25.

On the other hand, as shown in FIG. 2, on the inner wall surface of the intake passage 7 facing the peripheral edge of the throttle valve 11, there is an elongated air supply line extending in the axial direction of the intake passage 7. -) 40 is formed. The air supply port 40 can be formed to have a substantially uniform width over its entire length, as shown in FIG. 5(a), or may have a substantially uniform width as shown in FIG. It can also be formed so that the width increases as it goes upstream. As shown by the broken line in FIG. 2, when the throttle valve 11 is in the idling position, the lower end of the air supply port 40 slightly opens into the intake passage 7 downstream of the throttle valve 11, and the air supply port 40 slightly opens into the intake passage 7 downstream of the throttle valve 11. The opening area of the air supply port 40 that opens inward gradually increases as the throttle valve 11 opens. Therefore, it can be seen that as the throttle valve 11 opens, the negative pressure applied to the air supply 19-to-4o gradually increases. This air supply port 40 extends through the walls of the carburetor housing 6 and the intake Manbold 1 and is connected to a solenoid valve 50 via a cold air supply passage 41 .

The solenoid valve 50 has a valve chamber 52 that communicates with the atmosphere via an air filter 51 and an air supply passage 41 that opens into the valve chamber 52.
a valve port 53 connected to the valve port 53, a valve body 54 for controlling the valve +19-tosa, a flexible l1iIJ7'' ginger 55 connected to the valve body 54, and a movable blanker 55.
The solenoid 56 is connected to a solenoid drive circuit 60. The solenoid drive circuit 60 operates at lHz as shown in FIG.
The output terminal of the power multiplier 62 is connected to the output terminal of the solenoid 56. connected to. The valve element 54 normally closes the valve port 53, but when the pulse generator 61 generates a noise, the solenoid 56 is energized and the valve element 54 opens the valve port 53. Therefore, the valve body 54 is l T-1
Is there a valve with 16 frequencies from z to 2Hz? - The port 53 will be opened. When the valve body 54 opens the valve port 53, air flows through the air filter 51. Air supply 7 via valve chamber 52, valve port 53 and air supply passage 41]? -) Since the air-fuel mixture is supplied into the intake passage 7 from 40, the air-fuel mixture supplied into the engine cylinder becomes lean. On the other hand, the valve body 52
3, the air supply to the air supply port 40 is stopped, so that the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder becomes richer. As mentioned above, as the opening degree of the throttle valve 11 increases, that is, as the amount of intake air increases, the negative pressure applied to the air supply port 40 increases. The amount of air supplied from the air supply port 40 increases, and thus, during the fluctuation of the air-fuel ratio based on the air supply action from the air supply port 40, the amount of air supplied from the air supply port 40 becomes almost constant regardless of the amount of intake air.

The dimensions of the valve boat 53 and the air supply port 40 and the carburetor 2 are determined by the air-fuel ratio A/F of the mixture supplied into the engine cylinder when the valve element 54 of the solenoid valve 50 repeatedly opens and closes the valve port 53. The average value of is determined to be approximately the stoichiometric air-fuel ratio as shown in FIG. 6(b), and the air-fuel ratio is determined to be approximately ±02 to ±10 with respect to the stoichiometric air-fuel ratio during fluctuation. Therefore, regardless of engine temperature and engine operating conditions, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders will be approximately ± with respect to the stoichiometric air-fuel ratio at frequencies from lHz to 21'f.
Since the average value of the air-fuel ratio is maintained within the window Wo shown in FIG. Purification efficiency can be obtained.

As described above, according to the present invention, exhaust gas can be effectively purified using an inexpensive carburetor without using an expensive oxygen concentration detector or an expensive electronic control unit for air-fuel ratio control. It is possible to significantly reduce the manufacturing cost. Furthermore, since only a solenoid valve is provided in the air supply passage, the structure is extremely simple, and therefore the reliability of the exhaust gas purification device can be improved.

[Brief explanation of drawings]

Figure 1 is a diagram showing exhaust gas purification efficiency, Figure 2 is a side sectional view of the engine intake and exhaust system, Figure 3 is a plan view taken along arrow 1■ in Figure 2, and Figure 4 is the suction piston. FIG. 5 is a front view of the air supply port, and FIG. 6 is a diagram showing fluctuations in the air-fuel ratio. 2...fi conversion 5.8...suction piston, 9.
... Needle, 25... Fuel passage 28... Nozzle, 40... Air supply date, 41... Air supply passage, 50... Solenoid valve. Patent Applicant Toyota Motor Corporation Patent Attorney Akira Aoki Kazuyuki Nishidate Patent Attorney Yasushi Nakayama Patent Attorney Akiyuki Yamaguchi Figure 3 Figure 4 8 Figure 5 (Q) , ( b) Figure 6 ((1)

Claims (1)

[Claims] In an internal combustion engine with a carburetor installed in the engine intake passage and a three-way catalytic converter installed in the engine exhaust passage, an opening that opens into the carburetor intake passage downstream of the carburetor throttle valve as the carburetor throttle valve opening increases. An elongated air supply port with an increasing area is formed on the inner wall surface of the carburetor intake passage facing the peripheral edge of the throttle valve, and the air supply port is connected to the atmosphere through a solenoid valve that opens and closes at a constant frequency of approximately IHz to 2Hz. The opening area of the solenoid valve is determined so that when the solenoid valve is opened and closed, the air-fuel ratio periodically fluctuates within approximately ±0.2 to ±10 with respect to the average value, and the air-fuel ratio An exhaust gas purification device for an internal combustion engine in which the carburetor is set so that the average value of t is the stoichiometric air-fuel ratio.