JP2576909B2 - Exhaust purification system for two-cycle engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for a two-cycle engine that purifies exhaust gas by a catalytic converter provided in an exhaust pipe.

2. Description of the Related Art In an engine (internal combustion engine), a catalytic converter is provided in an exhaust pipe in order to purify exhaust gas by the action of a catalytic substance. For example, JP-A-1-24
In the publication No. 9915, a cross catalyst body in which a noble metal catalyst is supported on a ceramic cloth woven of ceramic fibers is provided in an upstream portion of an exhaust pipe, and a ceramic catalyst body made of a monolithic ceramic system is provided in a downstream portion. The catalyst body is intended to purify exhaust gas efficiently without lowering the engine output. Japanese Patent Application Laid-Open No. 1-236949 discloses a catalyst carrier for the above-mentioned monolithic catalyst body, in which a band-shaped flat plate and a corrugated plate are overlapped, and this is rolled up in a cylindrical shape to form a plurality of honeycomb-shaped passages in the axial direction. Are disclosed.

Problems to be Solved By the way, in the two-stroke engine, since the intake stroke and the exhaust stroke are not completely separated, unburned hydrocarbons and the like are apt to exist in the exhaust gas.
A simple exhaust gas purifying effect cannot be obtained by merely arranging the cross catalyst and the ceramic catalyst in the exhaust pipe as in -249915.

In addition, since the ceramic catalyst body becomes large in size due to its ceramic material, it is necessary to provide a strong stay or to increase the strength of the tail pipe itself in order to attach it to the tail pipe end of a two-cycle engine. there were.

Means and Effects for Solving the Problems The present invention relates to an improvement of a waste purification device for a two-cycle engine in response to such a demand, and a secondary air introduction port is provided at a position immediately after the engine exhaust port of an exhaust pipe, A cross catalyzer is disposed immediately downstream of the secondary air inlet, and a cylindrical metal catalyzer is provided at an end of a tail pipe protruding into an expansion chamber on the downstream side of the cross catalyzer. An outer tube surrounding the outer periphery of the cylindrical metal catalyst body is supported by a tube wall of the expansion chamber via a support member, and the cylindrical metal catalyst body is interposed between the outer tube and the cylindrical metal catalyst body. An exhaust emission control device for a two-cycle engine, which is supported elastically and movably in the axial direction via a heat-resistant elastic body.

Since the present invention is configured as described above, the unburned matter present in the exhaust gas discharged from the two-stroke engine is mixed with the air supplied from the secondary air inlet located immediately after the exhaust port, and Immediately after that, the exhaust gas purifying and oxidizing reaction is appropriately performed by touching the cross catalyst body in the downstream portion without lowering the temperature.

Then, the exhaust gas heated to a high temperature by touching the cross catalyst body uniformly contacts the metal catalyst body on the downstream side, and the exhaust gas purification reaction is sufficiently performed, so that the entire exhaust gas is reliably purified at a high level. sell.

Further, in the present invention, the cylindrical metal catalyst body laid at the end of the tail pipe in the expansion chamber is elastically and axially moved to the outer pipe surrounding the outer periphery of the cylindrical metal catalyst body via the heat-resistant elastic body. Since the outer tube is freely supported and the outer tube is supported by the tube wall of the expansion chamber via a support member, the outer tube is heated by the exhaust gas and the temperature change accompanying the purification reaction of the metal catalyst body. And even if the tailpipe supporting it expands or contracts, the expansion and contraction of the metal catalyst body and the tailpipe are absorbed, and the metal catalyst body is stably supported, and is also subject to engine vibration and exhaust pulsation. The accompanying vibration is suppressed from acting strongly on the metal catalyst body, and the durability of the metal catalyst is greatly improved.

Furthermore, in the present invention, since the outer periphery of the cylindrical metal catalyst body is stably supported without difficulty on the tube wall of the expansion chamber as described above, the cylindrical metal catalyst body extends into the expansion chamber and is cantilevered at the tip. A large bending load is prevented from acting on the tail pipe on which the metal catalyst is laid.

FIG. 1 is a side view of a main part of a motorcycle equipped with a two-stroke engine having an exhaust emission control device according to the present invention, and FIG. 2 is a plan view of the main part. Reference numeral 1 denotes a head pipe, and 2 denotes a pair of left and right main frames extending rearward from the head pipe 1 obliquely downward. A rear fork 3 extends rearward from the rear head of the main frame 2 so as to be tiltable up and down, and a rear wheel 4 is supported at the rear end of the rear fork 3. A seat 6 is mounted on 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 6. 60 is a front wheel, 61 is a radiator, 62 is a back stay, 63 is a rear cushion, and the vehicle body is covered with cover members such as a cowl 64 and a seat cowl 65.

An engine 9 is mounted between a stay member 8 hanging from a front portion of the main frame 2 and a lower end of a rear portion of the main frame 2. The rear wheel 4 is driven by the engine 9 via a drive chain 66. The engine 9 is a two-cycle engine. An air-fuel mixture to which lubricating oil is added is supplied to an intake port 10 communicating with a crank chamber via an intake pipe 11 and a carburetor 12.
The upstream side of the intake pipe 11 is connected to the air cleaner 13,
The air purified by the air cleaner 13 is guided to the intake pipe 11. An exhaust port 14 is provided in a cylinder 15 of the engine 9, and a front end of an exhaust pipe 16 is connected to the exhaust port 14.

After the exhaust pipe 16 extends downward from the exhaust port 14 forward,
It curves backward and passes under the engine 9, exits to the right of the rear wheel 4 at the rear, and connects to the muffler 17. Exhaust pipe
A first catalytic converter 18 is provided at the curved portion 16 at the front. The catalytic converter 18 itself is a conventionally known one having a cross catalytic body, and is shown in FIGS.
An example is shown in the figure. Numeral 19 denotes an outer pipe of the exhaust pipe 16, which is formed by abutting two divided halves as shown in FIG. Cross catalyst body along the inner wall surface of this outer tube 19
20 are provided. The cross catalyst body 20 is formed by spirally wrapping a cloth (cloth) carrying a catalyst substance around the outer periphery of a cylindrical body composed of a punching plate 22 having a number of holes 21 formed therein. The outer tube 19 bulges
The punching plate 22 is attached to 19a such that the inner diameter of the punching plate 22 is the same as the inner diameter of the exhaust pipe 16. In the present embodiment, the cross catalyst body 20 is an auxiliary catalyst, and a metal catalyst body 26 provided downstream thereof serves as a main catalyst. The cross catalyst body 20 reacts with exhaust gas upstream of the metal catalyst body 26 to react with the exhaust gas. It has the role of raising the temperature of the exhaust gas in 26.

The exhaust pipe 16 expands in diameter at the lower rear portion of the engine 9 to form an expansion chamber 23. The rear end 23 of the expansion chamber 23 whose diameter is reduced
A tail pipe 24 enters the room from a and extends forward along the axis, and a second catalytic converter 25 is provided at the front end thereof. FIG. 3 is a vertical sectional view of the catalytic converter 25 and the tail pipe 24, and FIG.
FIG. The catalytic converter 25 includes a metal catalyst 26. The support of the metal catalyst body 26 is constituted by a honeycomb-shaped multi-channel member made of ferritic stainless steel having a plurality of honeycomb-shaped passages formed in the axial direction, and the strip-shaped flat plate and the corrugated plate are stacked as described above. It may be formed by winding together in a column shape. On the surface of the support, after surface treatment for improving the adhesion of Al ₂ O ₃ (the whisker process), Al ₂ O ₃ and the coating (washcoat), platinum, rhodium, rare earth metals, cesium Noble metal catalyst is supported.
A two-piece outer tube 27 is fitted around the outer periphery of the metal catalyst 26, and the outer tube 27 and the metal catalyst 26 are connected to each other by a heat-resistant elastic material 28 on the outer surface of the metal catalyst 26. Can slide on each other in the axial direction. The heat-resistant elastic material 28 is made of a so-called SUS corrugated mesh obtained by solidifying a thin corrugated stainless steel wire 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 is also a fourth wall.
As shown in the figure, a semi-cylindrical attachment plate 30 is attached along the inner wall surface of each of the upper and lower tube wall portions which abut each other. A heat-resistant elastic material 31 similar to the heat-resistant elastic material 28 is provided between the attachment plate 30 and the pipe wall 29.
Is inserted. A stay piece 32 projecting radially inward is welded to the inner surface of the lower attachment plate 30, and an outer tube 27 of the catalytic converter 25 is welded to the inner end of the stay piece 32. Therefore, the metal catalyst 26 is made of the heat-resistant elastic material 28 and the outer tube 2.
7, the support member made of the stay piece 32, the attachment plate 30, and the heat-resistant elastic material 31 is elastically supported on the pipe wall 29 of the expansion chamber 23, and the vibration of the exhaust pipe 16 is transmitted to the metal catalyst body 26. Has been prevented.

In the present embodiment, the tail tube 24 is continuous and integral from the catalytic converter 25 to the rear end 23a of the expansion chamber 23,
As shown in FIG. 5, this tail tube 24 is divided into a front tail tube 24a and a rear tail tube 24b, and the rear tail tube 24b is lightly slidably inserted into the front tail tube 24a so that the heat of both ends is reduced. The expansion and contraction movements may be made free to prevent the occurrence of thermal stress. FIG. 6 is a drawing showing the structure of the sliding portion A of the two portions 24a and 24b in more detail. As shown in FIG. 6, a gasket 33 is inserted between the front tail tube 24a and the rear tail tube 24b. The gasket 33 is positioned by an L-shaped member 34 provided on the rear tail tube 24b.

As shown in FIGS. 1 and 2, the front end of the exhaust pipe 16 has a secondary air introduction port immediately after the engine exhaust port 14 (about 100 mm from the exhaust port) and immediately before the catalytic converter 18.
The secondary air introduction port 35 communicates with the clean side of the air cleaner 13 via a secondary air supply pipe 36. Reed valve as one-way valve for secondary air supply pipe 36
37 are provided. The reed valve 37 is mounted on the inner surface of the main frame 2 via a stay 37a as shown in FIG. When the 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 in the exhaust pipe 16, and the catalytic converters 18 and 2 are opened.
5 enhances the exhaust purification effect. Basically, the secondary air is for promoting the oxidizing action of the main catalytic converter 25, and a certain distance is required for the introduced secondary air and the exhaust gas to mix well. Therefore, the secondary air inlet is desirably provided upstream of the main catalytic converter 25 by 300 mm or more. In this embodiment, the secondary air inlet
35, the effect is further enhanced because it is provided upstream of the auxiliary catalytic converter 18.

The details of the secondary air introduction system will be described below with reference to the schematic diagram of FIG. 38 is a crankcase of the engine 9, 39 is a piston, and a scavenging opening 40 and an exhaust opening 41 are opened in the cylinder hole 15a. The upper edge of the exhaust opening 41 is a shaft
The exhaust valve 43 pivots around 42 and is partially opened and closed.When the engine speed is high and the output is high, the exhaust valve 43 is raised as shown by the dotted line in the figure and the exhaust opening 41 is fully opened. In this state, the opening timing of the exhaust opening 41 by the piston 39 is advanced and the closing timing is delayed. Exhaust valve 43
Is controlled by an exhaust valve operation motor 44. That is, the pulley 45 fixed to the shaft 42 and the exhaust valve operating motor
Two cables 47 are connected between the output shaft 44 and a pulley 46 fixed to the output shaft.
The exhaust valve 43 rotates through the pulley 47, the pulley 45, and the shaft 42.
The exhaust valve operation motor 44 rotates according to the rotation 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 opened and closed by the reed. When the exhaust pipe 16 becomes a negative pressure, the reed 37a is pulled to the exhaust pipe 16 side. Then, the valve port 37b is opened. However, valve 37 with lead 37a
Since the closing of b is not always complete, at the time of high output operation in which the exhaust pressure increases, the exhaust may flow back to the air cleaner 13 through the reed valve 37 when the exhaust pressure increases.

Therefore, a secondary air control valve 48 is further provided on the secondary air supply pipe 36 upstream of the reed valve 37. The secondary air control valve 48 has a valve body 51 urged in a direction to open a valve port 50 by a spring 49, and the valve body 51 is connected to a pulley 46 of the exhaust valve operation motor 44 by a cable 52. I have. Therefore, when the exhaust valve operating motor 44 raises the exhaust valve 43 to the fully open position of the exhaust opening 41 via the cable 47 during the high-power operation, the valve body 51 simultaneously lifts up against the spring 49 via the cable 52. The valve port 50 is completely closed. In this way, backflow of exhaust gas into the secondary air supply pipe 36 during high-power operation is prevented. In addition, the drive and control of the secondary air control valve 48 are performed using the exhaust valve operation motor 44, and no special drive or control device is required.
Costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view of a main part 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 part, FIG. FIG. 4 is a longitudinal sectional view of the tail pipe taken along the line III-III of FIG. 4, FIG. 4 is a cross-sectional view of the tail pipe taken along the line IV-IV of FIG. 1, and FIG. FIG. 6 is a longitudinal sectional view similar to FIG. 3 showing an embodiment, FIG. 6 is a detailed view of a part thereof, FIG. 7 is a longitudinal sectional view of a cross catalyst body, FIG. It is a schematic diagram for explaining a 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 ... Stay member, 9 ...
Engine, 10 intake port, 11 intake pipe, 12 carburetor, 13 air cleaner, 14 exhaust port, 15 cylinder, 16 exhaust pipe, 17 muffler, 18 Catalytic converter, 19 ... outer tube, 20 ... cross-catalyst, 21 ... hole, 22 ...
... Punching plate, 23 ... Expansion chamber, 24 ... Tail tube, 25
…… Catalyst converter, 26 …… Metal catalyst body, 27 …… Outer tube, 28 …… Heat-resistant elastic material, 29 …… Tube wall, 30 …… Attached plate, 31
... heat-resistant elastic material, 32 ... stay piece, 33 ... gasket, 34 ... L-shaped member, 35 ... secondary air inlet, 36 ...
Secondary air supply pipe, 37 Reed valve, 38 Crankcase, 39 Piston, 40 Scavenging opening, 41 Exhaust opening, 42 Shaft, 43 Exhaust valve, 44 Exhaust Valve operation 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 ... Backstay, 63 ... Rear cushion, 64 ... Cowl, 65 ... Seat cowl, 66 ... Drive chain.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-81223 (JP, A) JP-A-2-61312 (JP, A) JP-A-1-136618 (JP, U) JP-A 64-136 11316 (JP, U) Japanese Utility Model 1-162017 (JP, U)

Claims (1)

(57) [Claims] A secondary air inlet is provided at a position immediately after an engine exhaust port of an exhaust pipe, a cross catalyst body is disposed immediately downstream of the secondary air inlet, and a downstream side of the cross catalyst body is provided. A cylindrical metal catalyst body is attached to the end of the tail pipe projecting into the expansion chamber on the side, and an outer pipe surrounding the outer periphery of the cylindrical metal catalyst body is supported by a pipe wall of the expansion chamber via a support member, and A two-stroke engine, wherein the cylindrical metal catalyst body is supported elastically and freely in the axial direction via a heat-resistant elastic body interposed between the outer tube and the cylindrical metal catalyst body. Exhaust purification equipment.