JPS62118019A - Afterburner for engine - Google Patents

Abstract

PURPOSE:To accelerate burnt gas emission control at the time of engine high load, by installing a venturi part in and around a combustion chamber of an exhaust passage, and opening a secondary air passage which leads the atmosphere into this venturi part. CONSTITUTION:A venturi member 12 is installed in a spot proximate to a combustion chamber 5 of an exhaust passage 7, and a venturi part 122 is formed in this member 12. And, a secondary air passage 14, leading the atmosphere into this venturi part 122, is opened thereto. With this constitution, even when displacement is much and exhaust pipe internal pressure is high as in time of high load, a large quantity of the atmosphere is taken in, whereby the air quantity required for exhaust emission control is securable.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an exhaust reburning device for an engine mainly used in automobiles, and in particular, the present invention relates to an exhaust reburning device for an engine used mainly for automobiles. This invention relates to a device that oxidizes and removes carbon dioxide inside an exhaust pipe.

[Conventional technology and its problems]

Conventionally, in order to remove incomplete combustion components such as hydrocarbons and carbon oxides contained in engine exhaust, a secondary air passage that introduces the atmosphere is opened in the exhaust pipe, and when the inside of the exhaust pipe becomes negative pressure. A technique is known in which the atmosphere is introduced to oxidize and remove the incompletely burned components (for example, Utility Model Publication No. 52-3).
Publication No. 7696).

However, the pressure inside the exhaust pipe becomes negative only after a short period of time has passed after the exhaust valve is opened), and even if atmospheric air is introduced after that, it will be delayed compared to the time when burnt gas is discharged. Cannot mix sufficiently with burnt gas. Moreover, when the engine is operated under high load, a large amount of burnt gas is discharged, and the average pressure inside the exhaust pipe increases, making it even more difficult to introduce atmospheric air. Since the absolute amount of is large, its oxidation removal tends to be insufficient.

[Object of the invention, outline of the structure]

The object of this invention is to solve the above-mentioned problems and to provide a device with a simple structure that can introduce a large amount of secondary air that can purify a large amount of burnt gas generated even during high-load engine operation. The exhaust passage leading from the combustion chamber is provided with a venturi part close to the combustion chamber, and the venturi part is characterized by having an opening for introducing the atmosphere into the secondary air passage.

[For production]

As in the past, secondary air is sucked into the exhaust pipe when the exhaust pressure in the exhaust pipe becomes negative, and even when the exhaust pressure is positive during high-load operation with a large exhaust flow rate. When the exhaust gas discharged from the combustion chamber passes through the venturi section provided in the exhaust passage close to the combustion chamber, negative pressure is generated in the venturi, so the exhaust air is exhausted through the secondary air passage opened in the venturi section. Air is introduced into the pipe. As a result, unburned fuel components contained in the exhaust gas are oxidized and removed by the introduced atmosphere.

〔Example〕

Hereinafter, the present invention will be explained with reference to the illustrated embodiment. In the figure, 1 is a four-stroke engine. A cylinder 3 is fitted with a piston 2, and a cylinder end 4 closes the top surface of the piston 2. A Vζ combustion chamber 5 is formed. The cylinder head 4 is provided with an intake passage 6 and an exhaust passage 7 that open into the combustion chamber 5, and conventionally known intake valves 8 and exhaust valves 9 are provided in these openings, respectively, so as to be openable and closable. There is. 10 is an exhaust pipe connected to an exhaust passage T that opens on one side of the cylinder head 4; 12 is a bench member interposed between the cylinder head 4 and the exhaust pipe 10;

In order to facilitate molding by casting, the venturi member 12 consists of half parts 12g and 12b that can be separated in the axial direction, and a venturi part 122 that is inserted in the exhaust passage γ is formed by both halves 12g and 12b. A secondary air passage 14 introduces the atmosphere into the exhaust passage γ, and one end thereof opens to the venturi portion and the other end communicates with the atmosphere. In addition, the secondary air passage 14
includes an annular passageway 16 provided in venturi member 12. The annular passage 16 is formed so as to surround the venturi part 122 at the joint surface of the two halves 121L and 12b in order to improve the mixing of the atmosphere and the burnt gas, and the secondary air passage 14 is formed so as to surround the venturi part 122. It communicates with the exhaust passage γ through an opening 144 that is continuously open on the inner periphery of the portion 122 . 1
8 is an air filter provided at the upstream end of the secondary air passage 14, and 20 is a reverse valve that allows only airflow toward the exhaust passage γ, both of which have been used in conventional exhaust purification devices.

Next, the operation of this embodiment will be explained. When the engine starts running and the exhaust valve 9 opens at the end of the exhaust stroke, the burnt gas flows out into the exhaust passage 7 all at once, so the pressure inside the exhaust passage T increases as shown by the curve (,) in Fig. 2. It fluctuates. That is, the pressure increases temporarily when the valve is first opened, then becomes negative pressure all at once, and thereafter fluctuates in a wave motion and gradually decreases to atmospheric pressure. During this time, despite the pressure fluctuations in the exhaust pipe that change between positive and negative, the exhaust flow is
As shown by curve (b) in the figure, a large amount is discharged at once when the valve is opened, and once a slight backflow phenomenon occurs, the exhaust continues and the flow decreases in a relatively short time.

On the other hand, in this embodiment, since the venturi section 122 is installed in the exhaust passage T, the exhaust flow generates venturi negative pressure in the venturi section 122, and the check valve 20
is opened and atmospheric air is introduced into the exhaust passage T from the secondary air passage 14. Further, after a certain amount of time has passed, the exhaust pressure in the exhaust passage T fluctuates and becomes negative pressure, so regardless of the exhaust flow rate, this acts superimposed on the venturi negative pressure, and the check valve 20 continues to open, and a large amount of atmospheric air is introduced into the exhaust passage 7. This state is shown by curve (d) in the figure.

That is, in this embodiment, compared to the conventional one shown by curve (C) in the figure, the reverse valve 20 opens relatively early, and the atmosphere is mixed in from the beginning of the burnt gas discharge.

Furthermore, since the valve is open for a long time, the burnt gas and the atmosphere are exposed.

In addition, a large amount of atmospheric air can be introduced even during high-output operation with a large amount of burned gas discharged and high exhaust pipe pressure, ensuring the amount of air necessary to purify the exhaust gas.

〔Effect of the invention〕

As described above, in this invention, a venturi section is provided in the exhaust passage leading from the combustion chamber in the vicinity of the combustion chamber, and a secondary air passage for introducing the atmosphere into the venturi section is opened. Secondary air is introduced into the exhaust passage T from the time when the exhaust valve 9, which discharges a large amount of burnt gas into the passage 7, is opened, and the burnt gas and the atmosphere are mixed well, and as a result, This has the effect of ensuring that unburned fuel components in the exhaust gas are oxidized and removed.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a vertical cross-sectional view of the engine, and Fig. 2 shows pressure fluctuations in the exhaust pipe and exhaust flow. FIG. 4 is a characteristic diagram showing the opening timing of the check valve. γ...Exhaust passage, 9...Exhaust valve, 12...
Bench 1st member, 122...Venturi part, 14
...Secondary air passage, 2o...Check valve.

Claims (4)

[Claims] (1) An exhaust gas reburning device for an engine, in which a bench lily portion is provided in the exhaust passage led from the combustion chamber in close proximity to the combustion chamber, and a secondary air passage for introducing atmospheric air is opened in the bench lily portion. (2) The exhaust gas reburning device for an engine according to claim 1, wherein the bench lily portion is formed in a bench lily member, and the bench lily member is interposed between the cylinder head and the exhaust pipe of the engine. (3) The exhaust gas reburning device for an engine according to claim 2, wherein the bench lily member is provided with an annular passage surrounding the bench lily, and the annular passage is interposed in the secondary air passage. (4) The bench lily member is composed of two halves that can be separated in the axial direction, and a secondary air passage including an annular passage is formed at the joint surface of the two halves. Engine exhaust reburning device.