JP3350250B2 - Exhaust gas purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin catalyst having an air gap along an inner peripheral surface of an exhaust pipe connected to an exhaust port of an internal combustion engine. The present invention relates to an exhaust gas purifying apparatus which makes good contact and has a high purification rate.

[0002]

2. Description of the Related Art An exhaust pipe having a large number of ventilation holes provided along an inner peripheral surface of an exhaust pipe connected to an exhaust port of an internal combustion engine and having a plurality of ventilation holes provided thereon and carrying a catalyst on the punching pipe. There was a purifying device (see JP-A-3-85318).

[0003] In the exhaust gas purifying apparatus, a heat point is provided upstream of the catalyst to burn unburned gas in the exhaust gas and sufficiently contact the exhaust gas with the catalyst. Contact the combustion gas,
After ignition and reburn, the catalyst was led to the catalyst (see Japanese Utility Model Application Laid-Open No. 56-169412).

[0004]

In the exhaust gas purifying apparatus described in Japanese Patent Application Laid-Open No. 3-85318, the flow velocity of the exhaust gas greatly decreases from the center of the exhaust pipe to the inner peripheral surface due to the resistance of the inner peripheral surface of the exhaust pipe. Most of the exhaust gas flowing at high speed through the center of the exhaust pipe has a large tendency to be discharged out of the exhaust pipe without coming into contact with the catalyst on the punching pipe adjacent to the inner peripheral surface of the exhaust pipe. It was difficult to obtain the effect.

In the exhaust gas purifying apparatus described in Japanese Utility Model Laid-Open Publication No. Sho 56-169412, unburned gas is burned at a heat point and exhaust gas flowing near the rod-shaped heat point causes turbulence. Does not spread over a wide area,
Even if the rod-shaped heat point is provided in the exhaust gas purifying apparatus described in Japanese Patent Application Laid-Open No. 3-85318, it is not possible to guide the turbulent exhaust gas over the entire surface of the catalyst on the punching tube, thereby greatly improving the purification efficiency. I couldn't do that.

[0006]

Means and Effects for Solving the Problems The present invention provides:
In connection with the improvement of exhaust gas purification devices that overcome these difficulties,
According to a first aspect of the present invention, in the exhaust system in which the thin catalyst is disposed along the inner peripheral surface of the exhaust pipe with a gap in the exhaust pipe with respect to the inner surface of the exhaust pipe, the thin catalyst has a large number of holes. The catalyst is carried on the surface of the thin steel plate provided, and there is a gap on the upstream side from the exhaust flow upstream end of the thin catalyst, over the entire circumference from the exhaust pipe inner surface, toward the center of the exhaust pipe,
A baffle plate protrudes, a butterfly valve type exhaust control valve is provided on the exhaust flow upstream side of the baffle plate, an inner diameter D of an exhaust pipe upstream end adjacent to the baffle plate, and the thin catalyst adjacent to the baffle plate. And the inner diameter d of the baffle plate is d ≦ d
δ <D, and the inner diameter d of the baffle plate
Is characterized in that d / D = 0.7 to 0.9 with respect to the inner diameter D of the exhaust pipe.

According to the first aspect of the present invention, as described above, there is a gap in the exhaust pipe with respect to the inner surface of the exhaust pipe, and the upstream side of the exhaust flow upstream end of the thin catalyst disposed along the inner peripheral surface of the exhaust pipe. Since there is a gap on the side, the baffle plate is protruded toward the center of the exhaust pipe over the entire circumference from the inner surface of the exhaust pipe,
When the exhaust gas flowing near the upstream inner peripheral surface of the exhaust pipe passes through the baffle plate, a turbulent flow occurs near the exhaust pipe inner peripheral surface downstream of the baffle plate over the entire circumference of the exhaust pipe, and the baffle plate The catalyst is sufficiently contacted with the thin-walled catalyst, which is adjacent to the inner peripheral surface of the exhaust pipe on the downstream side and has a gap on the downstream side from the baffle plate and has an upstream end disposed therein, so that the purification reaction by oxidation and reduction is reliably performed. Can wake up.

According to the first aspect of the present invention, since a thin catalyst is formed by carrying a catalyst on the surface of a large number of thin steel plates with holes, the space between the exhaust pipe and the thin catalyst and the space between the thin catalyst are reduced. The enclosed space communicates with the thin catalyst through a hole, and the exhaust gas in one of the two spaces can flow into the other space, and the exhaust gas in the other space is As a result of flowing into one space and being sufficiently contacted with the catalyst to be purified, a high-level exhaust purification performance can be obtained despite the fact that the exhaust purification device is produced at low cost.

Further, in the first aspect of the present invention, since the butterfly valve type exhaust control valve is provided on the upstream side of the exhaust flow of the baffle plate, the butterfly valve type exhaust control valve is fully opened or almost fully opened. When released, the exhaust flow at the center of the exhaust flow passes through the center of the baffle at a high speed without being affected by the baffle plate to the left, and the exhaust flow around the exhaust flow collides with the baffle plate. The turbulent exhaust flow causes the exhaust flow that has caused the turbulent flow to sufficiently contact the thin catalyst, and the exhaust flow at the center of the exhaust flow is agitated by the turbulence of the exhaust flow around the exhaust flow. As a result of contact with the thin catalyst, the exhaust resistance is low, and the engine output and purification performance are maintained at a high level. Still further, in the invention described in claim 1, when the butterfly valve type exhaust control valve is significantly throttled, most of the exhaust flow which collides with the baffle plate and causes turbulence is more than a gap from the baffle plate. Reaching the upstream end of the thin-walled catalyst arranged in the presence of the thin-walled catalyst, and distributed to the inner peripheral surface and the outer peripheral surface of the thin-walled catalyst,
Further, a high level of purification performance is obtained, and the exhaust pressure wave is appropriately reflected by the butterfly valve type exhaust valve and the baffle plate to increase the charging efficiency, and the internal combustion engine is replaced with a two-stroke cycle internal combustion engine. In this case, the intake and exhaust of fresh air and the unstable combustion at low load are prevented, and also in this aspect, the amount of unburned HC in exhaust gas is suppressed.

Further, according to the present invention, the inside diameter D of the upstream end of the exhaust pipe adjacent to the baffle plate, the inside diameter δ of the upstream end of the thin catalyst adjacent to the baffle plate, and the inside diameter of the baffle plate Since d is set to satisfy the relationship d ≦ δ <D, the exhaust flow that has generated a turbulent flow over the baffle plate is surrounded by the space between the exhaust pipe and the thin catalyst and the thin catalyst. The thin catalyst can sufficiently exhibit an exhaust gas purifying function.

Further, according to the first aspect of the present invention, the inner diameter d of the baffle plate is d / D = the inner diameter D of the exhaust pipe.
Since it is set in the range of 0.7 to 0.9, while the output of the internal combustion engine is maintained at a high level, the turbulence is large enough that the exhaust gas exceeding the baffle plate can sufficiently contact the thin catalyst. In addition, the amount of unburned HC discharged HC can be sufficiently reduced.

According to the second aspect of the present invention, the volume of the exhaust pipe from the inlet of the exhaust pipe to the baffle plate is set within a range of V / v = 2 to 4 with respect to the displacement V of the internal combustion engine. As a result, the unburned HC in the exhaust gas can come into contact with the thin catalyst at a state suitable for causing an oxidation reaction, particularly at a required temperature, and the emission of unburned HC is maintained at a low level.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in FIGS. 1 to 4 will be described below.

A two-cycle internal combustion engine 2 provided with an exhaust gas purifying apparatus 1 according to one embodiment of the present invention is mounted on a motorcycle (not shown), and an intake system 5 is provided in a crank chamber in a crankcase 3 of the two-cycle internal combustion engine 2. And a carburetor 6 is interposed in the intake system 5.

An exhaust pipe 8 of an exhaust system 7 is connected to an exhaust port (not shown) of the cylinder 4, and an exhaust control valve 10 is interposed between the exhaust pipe 8 and the exhaust pipe 9.
Accordingly, in the low load operation region, the two-cycle internal combustion engine 2 can self-ignite fresh air in the combustion chamber at an ignition timing preferable for operation of the two-cycle internal combustion engine 2 without causing abnormal combustion. ing.

Further, a valve case 11 of the exhaust control valve 10 is integrally fixed to the downstream end of the exhaust pipe 8 and
A flange 12 is formed at the downstream end of the valve case 11, and the valve case 11 has
A disc-shaped valve element 14 is integrally fixed to a valve shaft 13 that penetrates in the diameter direction, and a communication hole 14a is formed in the valve element 14 (the communication hole 14a is not necessarily required).

Furthermore, a thin catalyst 15 is concentrically fitted in the exhaust pipe 9 via an elastic holding member 17.
In 15, a thin steel plate (punching plate) having a large number of holes 16 is formed into a semi-cylindrical shape by bending, and both side edges are superimposed on each other to form a cylindrical carrier, and the surface of the carrier ( A water-soluble silica undercoat layer is formed on the undercoat layer (including the surface of the hole 16), and a washcoat layer obtained by mixing an activated alumina base material, a ceria-based additive, and a silica-based binder is formed on the undercoat layer; A noble metal catalyst in which platinum and rhodium are mixed at a weight ratio of 20: 1 is supported on the washcoat layer.

Further, at the upstream end of the exhaust pipe 9, a baffle plate 18 for bringing exhaust gas into good contact with the thin catalyst 15 is integrally fixed, and the baffle plate 18 serving as a flange and the flange 12 of the valve case 11 are connected to each other. Are bolts 19 passing therethrough and bolts 19
Are integrally joined together with a nut 20 screwed to the tip of the.

The inner diameter d of the baffle plate 18 is equal to the inner diameter D of the valve case 11 of the exhaust control valve 10 and the exhaust pipe 9 in the vicinity thereof.
Is set to 0.8, and the inner diameter δ of the thin catalyst 15 is set to be larger than the inner diameter d of the baffle plate 18. The baffle plate 18 may be formed not only in the direction perpendicular to the center line of the exhaust pipe 9 but also in the shape of a truncated cone inclined toward downstream.

The volume V of the exhaust pipe 8 is set to be three times as large as the displacement v of the two-cycle internal combustion engine 2.

Further, a pulley 21 is integrally fixed to the valve shaft 13 outside the valve case 11 of the exhaust control valve 10,
A cable 23 is bridged between the bracket 22 and the carburetor 6 integrated with the fin 11, and one end of a wire 24 in the cable 23 is connected to a throttle valve (not shown) of the carburetor 6 and
The other end of 24 is wound and connected to a pulley 21 (the exhaust control valve 10 is controlled by a computer that sets an optimum opening according to the operating state of the two-cycle internal combustion engine 2 without interlocking with the throttle valve. May be connected to a control motor.

Further, at the downstream end of the exhaust pipe 9, an expansion pipe 25,
The connection pipe 26 and the silencer 27 are sequentially connected in series, a catalytic converter is provided in the expansion pipe 25 as needed, and a secondary air supply pipe 29 is connected to the upstream side of the exhaust system 7 via a flange 28. A reed valve 30 is provided at the upstream end of the secondary air supply pipe 29. When the pressure in the exhaust pipe 8 becomes negative, the reed valve 30 is opened and external air is released from the secondary air. As a result, the air is introduced into the exhaust pipe 8 via the secondary air supply pipe 29.

Since the embodiment shown in FIGS. 1 to 4 is configured as described above, even in a low load operation range where a relatively abnormal combustion state is likely to occur, the exhaust control valve 10 allows the engine to operate in a normal combustion state. The cycle internal combustion engine 2 can be operated, and the emission of unburned HC is suppressed.

Further, not only in the low load operation range where the opening of the exhaust control valve 10 is narrowed, but also in the high load operation range where the exhaust control valve 10 is opened, the exhaust pipe 8 Of the exhaust gas that has passed through the exhaust control valve 10, the exhaust gas that has flowed near the inner peripheral surface of the valve case 11 is turbulent and turbulent when passing over the inner edge of the baffle plate 18. Not only can it penetrate into the gap 31 between the exhaust pipe 9 and the thin catalyst 15 from the end, but also from the center of the exhaust pipe 9 through the hole 16 to the gap 31 or from the gap 31 to the hole 16 Exhaust pipe 9
As a result, exhaust gas can contact the entire surface of the thin catalyst 15 as much as possible, and harmful components in the exhaust gas, particularly unburned HC, cause a purification reaction to remove harmful components as much as possible.

Further, when the capacity V of the exhaust pipe 8 is changed with respect to the displacement v of the two-cycle internal combustion engine 2 as shown in FIG. In this embodiment (V / v = 3), the unburned HC is discharged in a state in which the unburned HC in the exhaust gas flowing into the exhaust pipe 9 can effectively cause an oxidation reaction, particularly at a temperature. The amount is low.

Further, the inner diameter d of the baffle plate 18 is set to an exhaust control valve.
When the inner diameters D of the exhaust pipes 8 and 9 in the vicinity of 10 are changed as shown in FIG. 7, when the d / D is in the range of 0.7 to 0.9, the exhaust exceeding the baffle plate 18 is sufficient for the thin catalyst 15. The turbulence is such that the exhaust gas can be brought into contact with the exhaust pipe, and the amount of unburned HC discharged is at a low level, and the exhaust pressure of the exhaust pipes 8 and 9 is at a level that does not cause a large decrease in the output of the two-cycle internal combustion engine 2. In the embodiment (d / D = 0.8), unburned H
The output of the two-stroke internal combustion engine 2 can be maintained at a high level while the amount of C discharged is significantly reduced.

[0027]

Further, the inner peripheral edge of the baffle plate 18 is formed in a circular shape coinciding with the center of the inner peripheral surface of the exhaust pipe 9, but a baffle plate 32 may be formed as shown in FIG.

Furthermore, the catalyst supported on the thin catalyst 15 is a mixture of platinum and rhodium which easily causes an oxidation reaction, but may be a three-way catalyst using a combination of platinum, rhodium and palladium.

Further, the present invention is applicable not only to a two-cycle internal combustion engine but also to an exhaust system of a four-cycle internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a two-stroke internal combustion engine provided with an exhaust purification device according to one embodiment of the present invention.

FIG. 2 is an enlarged partial longitudinal sectional side view of a main part of FIG. 1;

FIG. 3 is a longitudinal sectional side view in which a main part of FIG. 2 is further enlarged.

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3;

FIG. 5 is a front view of a baffle according to another embodiment.

FIG. 6 shows an unburned HC in a case where the ratio of the exhaust pipe capacity V on the upstream side of the thin catalyst to the displacement v of the two-cycle internal combustion engine is changed.
FIG. 4 is a characteristic diagram illustrating a state of a change in an amount of discharge.

FIG. 7 is a characteristic diagram illustrating a state of a change in an unburned HC emission amount and a maximum output of the internal combustion engine when the ratio of the inner diameter d of the thin catalyst to the inner diameter D of the exhaust pipe is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification apparatus, 2 ... 2-cycle internal combustion engine, 3 ... Crankcase, 4 ... Cylinder, 5 ... Intake system, 6 ... Carburetor,
7 ... exhaust system, 8, 9 ... exhaust pipe, 10 ... exhaust control valve, 11 ... valve case, 12 ... flange, 13 ... valve shaft, 14 ... valve body, 15 ... thin catalyst, 16 ... hole, 17 ... elastic retention Member, 18 ... Baffle, 19 ... Bolt, 20 ... Nut, 21 ... Pulley, 22 ... Bracket, 23 ...
Cable, 24… Wire, 25… Expansion tube, 26… Connection tube, 27…
Silencer, 28 ... Flange, 29 ... Secondary air supply pipe, 30 ...
Reed valve, 31 ... void, 32 ... baffle plate.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-44455 (JP, A) JP-A-52-7377 (JP, A) JP-A-3-85316 (JP, A) Japanese Utility Model Showa 61- 108820 (JP, U) Japanese Utility Model Hei 6-4313 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) F01N 3/24-3/28 F01N 7/08

Claims (2)

(57) [Claims] In an exhaust system in which a thin catalyst is disposed along an inner peripheral surface of an exhaust pipe with a gap between the thin catalyst and the inner surface of the exhaust pipe in the exhaust pipe, the thin catalyst has a thin wall having a plurality of holes. Touch the surface of steel plate
And a gap upstream of an exhaust flow upstream end of the thin catalyst.
A baffle plate protrudes from the inner surface of the exhaust pipe to the entire circumference of the exhaust pipe toward the center of the exhaust pipe, and a butterfly valve type exhaust control valve is provided on the exhaust flow upstream side of the baffle plate.
Provided, the inner diameter D of the exhaust pipe upstream end adjacent to the baffle plate, said baffle
The upstream end inner diameter δ of the thin catalyst adjacent to the plate,
The inner diameter d of the baffle is set so as to satisfy d ≦ δ <D , and the inner diameter d of the baffle is
With respect to the inner diameter D of the exhaust pipe, d / D = 0.7 to 0.9.
An exhaust gas purification device characterized by being set . 2. The exhaust pipe volume V from the inlet of the exhaust pipe to the baffle plate is V / v = 2 with respect to the displacement v of the internal combustion engine.
2. The exhaust gas purifying apparatus according to claim 1, wherein the exhaust gas purifying apparatus is set within a range of?