JPH03286122A - Exhaust purification device of two-cycle engine - Google Patents

Abstract

PURPOSE:To effectively purify exhaust gas without decreasing an engine output by arranging a cloth catalyst at the direct downstream part of a secondary air introduction port, and a metallic catalyst at an end part of a tail pipe. CONSTITUTION:In a two-cycle engine 9, a secondary air introduction port 35 is provided just at the rear position of an exhaust opening 41 of an exhaust pipe 16. At the direct downstream part of the secondary air introduction port 35, a catalyst converter 18 which has a cloth catalyst is arranged. At an end part of a tail pipe 24 which projects to the inside of a rear expansion chamber 23, a catalyst converter 25 which has a metal catalyst arranged. Since air is introduced via the secondary air introduction port 35 in the exhaust gas inside an exhaust pipe 16, even if much uncombusted components are present in the exhaust gas, effective purification is made possible by the cloth and metallic catalysts without decrease in the output of the engine 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device for a two-stroke engine that purifies exhaust gas using a catalytic converter provided in an exhaust pipe.

2. Description of the Related Art In conventional engines (internal combustion engines), a catalytic converter is provided in the middle of the exhaust pipe in order to purify the exhaust gas through the action of a catalytic substance.

For example, in Japanese Patent Application Laid-open No. 1-249915, a cloth catalyst body in which a noble metal catalyst is supported on a ceramic cloth made of woven ceramic fibers is provided in the upstream part of the exhaust pipe, and a ceramic catalyst body made of a monolithic ceramic system is provided in the downstream part. A vehicle is shown in which a medium is provided to efficiently purify exhaust gas using these catalyst bodies without reducing engine output. Furthermore, Japanese Patent Application Laid-Open No. 1-236949 discloses that, as a catalyst carrier for the monolithic catalyst body, a band-shaped flat plate and a corrugated plate are stacked and wound into a cylindrical shape to form a plurality of honeycomb-shaped passages in the axial direction. A honeycomb-like multi-channel member is disclosed.

By the way, in a two-stroke engine, the intake stroke and exhaust stroke are not completely separated, so unburned hydrocarbons, etc. are likely to be present in the exhaust gas.
Merely arranging the cloth catalyst body and the ceramic catalyst body in the exhaust pipe as in No. 24991.5 does not provide a sufficient exhaust gas purification effect.

In addition, because the ceramic catalyst carrier itself is large due to the ceramic material, it is necessary to install a strong stay or increase the strength of the tail pipe itself in order to attach it to the end of the tail pipe of a 2-stroke engine. there were.

The present invention was made in view of these circumstances.
In the exhaust gas purification device for a two-stroke engine according to the present invention, a secondary air inlet is provided in the exhaust pipe at a position immediately after the engine exhaust port, and a cross catalyst is disposed immediately downstream of the secondary air inlet, and A metal catalyst body is disposed at the end of the tail pipe that protrudes into the rear expansion chamber.

According to the present invention, air is introduced into the exhaust gas in the exhaust pipe through the secondary air inlet, so even if there is a large amount of unburned substances in the exhaust gas, the cross catalyst body does not reduce the output of the engine. The metal catalyst body efficiently purifies exhaust gas. Furthermore, there is no need to make the catalyst body particularly strong, and a simple and lightweight exhaust system can be provided.

FIG. 1 is a side view of a main part of a motorcycle equipped with a two-stroke engine having an exhaust gas purification device according to the present invention, and FIG. 2 is a plan view of the main part. Reference numeral 1 indicates a head pipe, and 2 indicates a pair of left and right main frames extending obliquely downward and rearward from the head vibrator 1. A rear fork 3 extends rearward from the rear end of the main frame 2 so as to be tiltable up and down, and a rear wheel 4 is pivotally supported at the rear end of the rear fork 3. A seat 6 is attached to a seat rail 5 extending rearward from an intermediate portion of the main frame 2, and a fuel tank 7 is mounted in front of the seat rail 5. 60 is a front wheel, 61 is a radiator, 62 is a backstay, 63 is a rear suspension, and the vehicle body is covered with cover members such as a cowl 64 and a seat cowl 65.

An engine 9 is attached between a stem member 8 hanging down from the front part of the main frame 2 and the rear lower end of the main frame 2. The rear wheels 4 are driven by the engine 9 via a tribe chain 66.

The engine 9 is a two-stroke engine, and an air-fuel mixture to which lubricating oil has been added is supplied to an intake port 10 leading to a crank chamber through an intake pipe 11 and a carburetor 12. The upstream side of the intake pipe 11 is connected to 13 air cleaners.
The air purified by 3 is guided to the intake pipe 11. 14
is an exhaust port provided in the cylinder 15 of the engine 9, and the front end of an exhaust pipe 16 is connected to the exhaust port 14.

The exhaust pipe 16 extends forward and downward from the exhaust port 14, curves backward, passes under the engine 9, exits to the right side of the rear wheel 4 at the rear, and connects to the muffler 17. A first catalytic converter 18 is provided in the curved portion at the front of the exhaust pipe 16. The catalytic converter 18 itself is a conventionally known type having a cross catalyst body, and an example thereof is shown in FIGS. 7 and 8. Reference numeral 19 denotes an outer pipe of the exhaust pipe 16, which is made up of two halves that are butted together as shown in FIG. A cross catalyst body 20 is provided along the inner wall surface of the outer tube 19. The cloth catalyst body 20 is constructed by winding a substance (cross) supporting a catalyst material in a spiral shape around the outer periphery of a cylindrical body consisting of a punched plate 22 with a large number of holes 21. The punching plate 22 is attached to the bulging portion 19a of the outer pipe 19 so that the inner diameter of the punching plate 22 is the same as the inner diameter of the exhaust pipe 16. In this embodiment, this cross catalyst body 20 is an auxiliary catalyst, and the metal catalyst body 26 provided downstream thereof is the main catalyst.The cloth catalyst body 20 reacts with exhaust gas upstream of the metal catalyst body 26, and the metal catalyst body 26
It has the role of increasing the temperature of the exhaust gas.

The exhaust pipe 16 has a diameter at the lower rear portion of the engine 9 and forms an expansion chamber 23 . A tail pipe 24 enters the chamber from the rear end 23a of the expansion chamber 23 and extends forward along the axis, and a second catalytic converter 25 is attached to the front end of the tail pipe 24.
is provided. 3 is a longitudinal cross-sectional view of the catalytic converter 25 and the tail pipe 24, and FIG. 4 is a cross-sectional view of the exhaust pipe 16 in the catalytic converter 25 portion. This catalytic converter 25 includes a metal catalyst body 26. The carrier of the metal catalyst body 26 is composed of a honeycomb-shaped multi-channel member made of ferritic stainless steel with a plurality of honeycomb-shaped passages formed in the axial direction, and as described above, it is made of a layered flat plate and a corrugated plate. They may be formed by winding them together into a cylindrical shape. After surface treatment (whisker treatment) to improve the adhesion of Alto3 to the surface of this carrier, Altos is coated (wash coated) to support noble metal catalysts such as platinum, rhodium, rare earth metals, and cesium. It is. An outer tube 27 divided into two is fitted around the outer periphery of the metal catalyst body 26 and supported on the outer surface of the metal catalyst body 26 via a heat-resistant elastic material 28 .

The heat-resistant elastic material 28 is made from a so-called SUS corrugated mesh made of thin corrugated stainless steel wires hardened into a mesh shape, and has good heat resistance and elasticity.

The tube wall 29 of the expansion chamber 23 surrounding the catalytic converter 25 also extends from two upper and lower tube wall portions that abut each other, as shown in FIG. A splint plate 30 is attached. A heat-resistant elastic material 31 similar to the heat-resistant elastic material 28 is inserted between the splint plate 30 and the tube wall 29. A stem piece 32 that projects radially inward is welded to the inner surface of the lower splint 30, and the outer tube 27 of the catalytic converter 25 is welded to the inner end of the stem piece 32. . Therefore, the metal catalyst body 26 is transferred to the tube wall 2 of the expansion chamber 23 via the heat-resistant elastic material 28, the outer tube 27, the stem piece 32, the splint plate 30, and the heat-resistant elastic material 31.
9 to prevent vibrations of the exhaust pipe 16 from being transmitted to the metal catalyst body 26.

In this embodiment, the tail pipe 24 is continuous and integral from the catalytic converter 25 to the rear end 23a of the expansion chamber 23, but as shown in FIG.
and a rear tail tube 24b, and the rear tail tube 24b is slidably and lightly press-fitted into the front tail tube 24a, thereby allowing thermal expansion and contraction movements of both to be free and preventing the generation of thermal stress. Good too. FIG. 6 shows the image portion 24a.

A drawing showing the structure of the sliding part A of 24b in more detail,
As shown in the figure, a gasket 33 is inserted between the front tail tube 24a and the rear tail tube 24b.
3 is positioned by an L-shaped member 34 provided on the rear tail tube 24b.

As shown in FIG. 1 and FIG.
mm), a secondary air inlet 35 is provided at a position immediately before the catalytic converter 18;
5 communicates with the clean side of the air cleaner 13 via a secondary air supply pipe 36. The secondary air supply pipe 36 is provided with a reed valve 37 as a one-way valve. As shown in FIG. 2, the reed valve 37 is attached to the inner surface of the main frame 2 via a stay 37a. When this reed valve 37 is opened by the negative pressure in the exhaust pipe 16, secondary air is introduced from the air cleaner 13 into the exhaust gas in the exhaust pipe 16, thereby enhancing the exhaust purification effect of the catalytic converters 1B and 25. Basically, the secondary air is for promoting the oxidation effect of the main catalytic converter 25, and a certain distance is required for the introduced secondary air and exhaust to mix well. It is desirable that the secondary air inlet is provided 300 mm or more upstream from the main catalytic converter 25. In this embodiment, the secondary air inlet 35 is provided further upstream of the auxiliary catalytic converter 18, so that the negative layer effect is large.

The details of the secondary air introduction system will be explained below with reference to the explanatory schematic diagram of FIG. 9. 38 is a crankcase of the engine 9, 39 is a piston, and a scavenging opening 40 is provided in the cylinder hole 15a.
And the exhaust opening 41 is open.

The upper edge of the exhaust opening 41 is partially opened and closed by an exhaust valve 43 that rotates around a shaft 42. At high engine speed and high output, the exhaust valve 43 is opened and closed as shown by the dotted line in the figure. The opening time of the exhaust opening 41 by the piston 39 is advanced, and the time of closing the exhaust opening 41 is delayed.

The operation of the exhaust valve 43 is controlled by an exhaust valve operating motor 44.
Wholesale. That is, the pulley 45 fixed to the shaft 42
and a pulley 4 fixed to the output shaft of the exhaust valve operating motor 44.
Two cables 47 are connected between the pulley 46 and the exhaust valve 43, and when the pulley 46 rotates, the exhaust valve 43 rotates via the cables 47, the boo IJ 45, and the shaft 42. The exhaust valve operating motor 44 rotates in accordance with the rotational speed of the engine 9 to operate the exhaust valve 43 as described above.

The reed valve 37 provided in the secondary air supply pipe 36 has a reed 37a and a valve port 37b that is opened and closed by the reed. is attracted to open the valve port 37b.

However, since the valve port 37b is not necessarily completely closed by the reed 37a, during high-output operation where the exhaust pressure increases, there is a risk that the exhaust gas may flow back through the reed valve 37 to the air cleaner 13 side when the exhaust pressure increases.

Therefore, a secondary air control valve 48 is further provided in the secondary air supply pipe 36 on the upstream side of the closed valve 37.

This secondary air control valve 48 has a valve body 51 biased by a spring 49 in a direction to open a valve port 50.
1 is connected to the pulley 46 of the exhaust valve operating motor 44 by a cable 52. Therefore, when the exhaust valve operating motor 44 pulls up the exhaust valve 43 via the cable 47 to the fully open position of the exhaust opening 41 during high output operation, the valve body 51 simultaneously moves via the cable 52 to the spring 49.
The valve port 50 is pulled up against the pressure and completely closes the valve port 50. In this way, backflow of exhaust gas into the secondary air supply pipe 36 during high output operation is prevented. Moreover, the secondary air control valve 4
8 is driven and controlled using the exhaust valve operating motor 44, and no other special drive or control device is required, so costs can be reduced.

The exhaust gas purification device for a two-stroke engine according to the present invention includes a secondary air inlet in the exhaust pipe immediately after the engine exhaust port, and a cross catalyst body immediately downstream of the secondary air inlet. At the same time, a metal catalyst body is arranged at the end of the tail pipe that protrudes into the rear expansion chamber, so that by introducing air through the secondary air inlet into the exhaust gas in the exhaust pipe, Unburnt! P! Even if there are many substances such as carbon dioxide in the exhaust, the cross catalyst body and metal catalyst body can efficiently purify the exhaust without reducing engine output, and the installation of the catalyst body is particularly strong. It is possible to obtain a simple and lightweight exhaust system without the need.

[Brief explanation of the drawing]

Fig. 1 is a side view of the main parts of a motorcycle equipped with a two-stroke engine having an exhaust purification device according to the present invention, Fig. 2 is a plan view of the main parts, and Fig. 3 is a metal catalyst body of the exhaust purification device and its main parts. FIG. 4 is a cross-sectional view taken along line IV-■ in FIG. 1, FIG. 5 is a longitudinal cross-sectional view similar to FIG. 3 showing another embodiment of the tail tube, FIG. 6 is a detailed view of a part thereof, FIG. 7 is a longitudinal sectional view of the cross catalyst body, FIG. 8 is a cross sectional view thereof, and FIG. 9 is a schematic diagram for explaining the secondary air introduction system. 1...Head pipe, 2...Main frame, 3.
...Rear fork, 4...Rear wheel, 5...Seat rail, 6...Seat, 7...Fuel tank, 8...Steel member, 9...Engine, 10... Intake port, 11
...Intake pipe, 12...Carburizer, 13...Air cleaner, 14...Exhaust port, 15...Cylinder, 16...
...Exhaust pipe, 17...Muffler, 18...Catalytic converter, 19...Outer pipe, 20...Cross catalyst body, 21
... Hole, 22 ... Punching plate, 23 ...
Expansion chamber, 24...tail pipe, 25...catalytic converter,
26...Metal catalyst body, 27...Outer tube, 28...
Heat-resistant elastic material, 29... Pipe wall, 30... Splinter plate, 31
... Heat-resistant elastic material, 32 ... Stee piece, 33 ...
Gasket, 34...L-shaped member, 35...Secondary air inlet, 36...Secondary air supply pipe, 37...Reed valve, 38...Crank case, 39...Piston , 40...Scavenging opening, 41...Exhaust opening, 42...
・Shaft, 43... Exhaust valve, 44... Exhaust valve operating motor, 45° 46... Pulley, 47... Cable, 48
...Secondary air control valve, 49.--Spring, 50.
... Valve port, 51... Valve body, 52... Cable, 60
...front wheel, 61...radiator, 62...hack stay, 63...reaction, 64...cowl, 65...seat cowl, 66...tribe chain.

Claims (1)

[Claims] A secondary air inlet is provided in the exhaust pipe immediately after the engine exhaust port, a cross catalyst is provided immediately downstream of the secondary air inlet, and a metal is installed at the end of the tail pipe that protrudes into the rear expansion chamber. An exhaust purification device for a two-stroke engine that is equipped with a catalyst.