CN115199377A - Laminar scavenged engine muffler - Google Patents

Abstract

The present invention provides a muffler for a laminar scavenging type engine, without major modification and size change of the existing muffler main body and cylindrical catalyst, minimizing the number of cells in the cylindrical catalyst where the exhaust gas does not flow, and enabling the exhaust gas to flow uniformly. The cylindrical catalyst can obtain a desired exhaust gas purification rate, can effectively suppress the THC emission amount, and is excellent in cost performance. The distance (A) from the inlet (16) to the partition plate (13), the distance (D) from the front wall surface (11a) of the front chamber (R1) to the front end surface (20a) of the cylindrical catalyst (20), and the At least one of the distances (T) (the protruding length of the catalyst (20) into the front chamber (R1)) from the partition plate (13) to the front end surface (20a) of the cylindrical catalyst (20) is set within a predetermined range, The airflow introduced into the front chamber (R1) from the introduction port (16), collides with the partition plate (13), and reverses as much as possible so as not to jump over the cell located at the upper end of the cylindrical catalyst (20).

Description

Laminar scavenged engine muffler

technical field

The present invention relates to a muffler having a built-in catalyst for exhaust gas purification, which is suitable for a layered scavenging type engine of portable power working machines such as lawn mowers, electric saws, and power blowers.

Background technique

Conventionally, during scavenging, scavenging air (also referred to as pilot air, etc.) is blown out to scavenge the combustion gas before supplying the mixed gas to the combustion chamber. scavenging engines) are well known. In such a stratified scavenging type engine, the blow-by amount of the unburned air-fuel mixture is reduced compared to a conventional general two-stroke engine, and harmful effects such as THC (total discharge amount of HC components, also referred to as total hydrocarbons) can be suppressed. Discharge of substances (refer to Patent Documents 1, 2, and 3).

In the above-mentioned laminar scavenging type engine, in order to further improve the exhaust gas purification performance, there is a laminar scavenging type engine in which a monolithic cylindrical catalyst for exhaust gas purification is built in a muffler arranged in the exhaust system (refer to Patent Documents 2 and 3). ).

An example of a layered scavenging type engine muffler incorporating the monolithic cylindrical catalyst will be briefly described with reference to the schematic configuration diagram of FIG. 6 .

The muffler 4 of the illustrated example includes a box-shaped container-shaped muffler body 10 including a square-disk-shaped front chamber panel 11 that defines a front chamber R1 and is open on one side, and a front chamber panel 11 that defines a rear chamber R2 and is open on one side A square disc-shaped rear chamber panel 12 . In the muffler main body 10 , the partition plate 13 that airtightly partitions the interior of the muffler main body 10 into the front chamber R1 and the rear chamber R2 is disposed so as to be sandwiched between the front chamber panel 11 and the rear chamber panel 12 .

An introduction port 16 for introducing exhaust gas from an exhaust port 9 provided in the cylinder 8 of the laminar scavenging engine is provided in the upper half of the front wall surface 11a of the front chamber R1. The partition plate 13 is arranged perpendicular to the introduction direction of the exhaust gas.

In substantially the lower half of the partition plate 13, the monolithic column-shaped catalyst 20 for exhaust gas purification is attached so that its axis is perpendicular to the partition plate 13 and spans the front chamber R1 and the rear chamber R2.

The column-shaped catalyst 20 is an oxidation catalyst capable of oxidizing and combusting THC such as unburned fuel components contained in the exhaust gas, and has a metal or ceramic carrier 22, and a plurality of carriers 22 having communication is provided in a lattice shape. In the cells 24 of the linear passage portions 24 a of the front chamber R1 and the rear chamber R2 , the inside of the carrier 22 (each cell 24 ) is coated with a platinum group oxidation catalyst material such as platinum and rhodium, and the outer periphery of the carrier 22 is coated A metal cylindrical case 23 is externally fitted and fixed.

prior art literature

Patent Document 1: Specification of US Patent No. 6591606

Patent Document 2: Specification of US Patent No. 6647713

Patent Document 3: Japanese Patent Laid-Open Publication No. 2020-63700

The cylindrical catalyst built into the muffler is easier to manufacture than the prismatic catalyst, but when the vertical and horizontal dimensions are the same, the cross-sectional area becomes small, and therefore, there is a disadvantage that the exhaust gas purification rate decreases.

To compensate for this, it is important that the exhaust gas flows uniformly over the cylindrical catalyst.

In addition, in the above-mentioned laminar scavenging type engine, since the scavenging air, the unburned mixed gas, and the combustion gas are sequentially introduced into the muffler, the above-mentioned gases are uniformly mixed and then flowed to the catalyst, so that oxygen in the air can be removed. effectively used in catalysts.

However, when preparing a plurality of mufflers with different positions in the front-rear direction (exhaust gas introduction direction) of the partition plate 13 and the column-shaped catalyst 20, the mufflers were compared for each muffler by computer simulation, a high-speed camera, and PIV (Particle Image Velocity Measurement). When visualizing the gas flow and flow velocity in the inner and cylindrical catalysts, there are obviously the following problems that should be solved.

That is, in the muffler 4 shown in FIG. 6 , the exhaust gas containing the blow-by gas of the combustion gas, the scavenging air, and the unburned air-fuel mixture from the exhaust port 9 provided in the cylinder 8 of the laminar scavenging engine passes through the The introduction port 16 is straightly introduced into the front chamber R1, collides with the partition wall plate 13 violently, and is reversed, diffused, and mixed. However, depending on the size of each part of the muffler 4 , in the reversed gas flow, the gas flow above the cylindrical catalyst 20 may skip a large amount of the cylindrical catalyst 20 at the upper end as indicated by the hollow arrows in FIG. 6 . The cell part of the column (shortcut).

Specifically, in the analysis model 4M shown in FIG. 7 , which simulates the muffler 4 shown in FIG. 6 , the gas flow and flow velocity in the muffler (A) and the cylindrical catalyst (B) are visualized by density, The airflow above the cylindrical catalyst 20 in the reversed airflow skips the part of the multi-column unit 24 located at the upper end of the cylindrical catalyst 20, and the part of the multi-column unit 24 (white part) skipped by the airflow Almost no gas flows, and therefore, the exhaust gas is not purified by oxidative combustion in this part of the unit 24 . Therefore, a desired exhaust gas purification rate cannot be obtained by the catalyst 20, and there is a problem that the THC emission amount cannot be sufficiently suppressed.

Here, as a measure to improve the exhaust gas purification rate of the catalyst, it is most common to increase the volume of the catalyst to reduce the flow velocity of the gas in the muffler and to fill the whole with the gas. However, if the volume of the catalyst is increased, the weight and cost will also increase, and furthermore, the muffler itself with the built-in catalyst may be remodeled and enlarged, which is not a good solution in terms of cost performance. On the other hand, if the catalyst is only reduced in size, as described with reference to FIG. 6 , the airflow that violently collides with the partition plate reaches only a part of the catalyst and forms a local flow.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a layered scavenging type engine muffler, which can reduce the number of cylindrical catalysts as much as possible without significantly remodeling or changing the size of the existing muffler main body and cylindrical catalyst. The number of units in which the exhaust gas does not flow, the exhaust gas can be uniformly flowed to the column-shaped catalyst, the desired exhaust gas purification rate can be obtained, the THC emission amount can be effectively suppressed, and the cost performance is excellent.

In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies, and as a result obtained the following findings.

That is, it was found that, as described with reference to FIGS. 6 and 7 , the airflow above the column-shaped catalyst 20 in the airflow that collided with the partition wall plate 13 and was reversed violently skipped over many of the column-shaped catalysts 20 located at the upper end. The phenomenon of the row unit 24 is determined by the distance A from the inlet 16 to the partition wall plate 13, the distance D from the front wall surface 11a of the front chamber R1 to the front end surface 20a of the columnar catalyst 20, and the distance from the partition wall plate 13 to the columnar catalyst. When at least one of the distances T (the protruding length of the catalyst 20 into the front chamber R1 ) of the front end surface 20a of the 20 is set within a predetermined range, the above phenomenon does not occur.

The muffler for a laminar scavenging type engine of the present invention was completed based on the above-mentioned knowledge and the examination based on the above-mentioned knowledge, and basically includes a muffler main body for introducing exhaust gas from a laminar scavenging type engine and extracting the purified exhaust gas. A partition plate, which airtightly divides the muffler body into a front chamber and a rear chamber on the downstream side of the front chamber, and is arranged perpendicular to the introduction direction of the exhaust gas, in the upper half of the front chamber A portion is provided with an introduction port for introducing the exhaust gas; and a cylindrical catalyst for exhaust gas purification is attached to the partition plate so that its axis is orthogonal to the partition plate and spans the front chamber and the rear chamber The cylindrical catalyst is a monolithic catalyst in which a plurality of cells having linear passages connecting the front chamber and the rear chamber are arranged in a lattice shape, and the column-shaped catalyst extends from the inlet to the At least one of the distance A of the partition wall plate, the distance D from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst, and the distance T from the partition wall plate to the front end surface of the cylindrical catalyst is set. It is set within a predetermined range so that the airflow which is introduced into the front chamber from the introduction port, collides with the partition wall plate, and is reversed does not skip the cell located at the upper end of the cylindrical catalyst as much as possible.

In a preferred aspect, a part of the reversed airflow flows into the cell located at the upper end of the cylindrical catalyst while being guided by the outer peripheral surface of the cylindrical shell provided on the outer periphery of the cylindrical catalyst.

In another preferred embodiment, the cylindrical catalyst is composed of an oxidation catalyst, a redox catalyst, or a three-way catalyst capable of oxidatively combusting at least an unburned fuel component contained in the exhaust gas.

In another preferred aspect, a catalyst mounting portion having an arbitrary position capable of fixing the columnar catalyst in a direction perpendicular to the partition plate is provided in substantially the lower half of the partition plate. circular through hole.

In another preferred embodiment, the cylindrical catalyst is airtightly mounted to the catalyst mounting portion by welding.

In another preferred embodiment, the volume of the front chamber is set at 4 to 6 times the displacement of the laminar scavenging engine.

In another preferred embodiment, the distance A from the introduction port to the partition plate is set to be 21.5 mm or more, and the distance D from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst is set 5 mm or more, the distance T from the partition plate to the front end surface of the cylindrical catalyst is set to 7 mm or more, and the distance H from the lower end of the introduction port to the upper end of the cylindrical catalyst is set to 9 mm or more. .

In another preferred embodiment, the distance A from the introduction port to the partition plate is set within a range of 25 mm to 30 mm, and the distance from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst D is set in the range of 5 mm to 20 mm, the distance T from the partition plate to the front end surface of the cylindrical catalyst is set in the range of 7 mm to 16 mm, and the distance from the lower end of the introduction port to the cylindrical catalyst The distance H from the upper end of the catalyst is set in the range of 9 mm to 20 mm.

In another preferred mode, the exhaust gas volume of the layered scavenging engine is in the range of 20cc to 40cc, the diameter C of the cylindrical catalyst is in the range of 25mm to 50mm, and the diameter of the cylindrical catalyst is in the range of 25mm to 50mm. The length L is in the range of 15 mm to 35 mm.

The layered scavenging type engine muffler of the present invention does not change the external dimensions of the muffler main body, the position of the introduction port, the diameter and length of the cylindrical catalyst, and the height direction of the cylindrical catalyst in the muffler main body in the existing muffler. In the case of the position, the distance A from the inlet to the partition plate, the distance D from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst, and the distance T from the partition plate to the front end surface of the cylindrical catalyst (the catalyst direction At least one of the protruding lengths in the front chamber) is set within a predetermined range so that the exhaust gas introduced into the front chamber from the inlet and colliding with the partition plate and reversed does not skip the cells located at the upper end of the cylindrical catalyst as much as possible.

Therefore, a part of the airflow that has collided with the partition plate and is reversed flows into the cell located at the upper end of the cylindrical catalyst while being guided by the outer peripheral surface of the cylindrical shell provided on the outer periphery of the cylindrical catalyst. By reducing the number of cells in the cylindrical catalyst through which the exhaust gas does not flow, the exhaust gas can be made to flow uniformly through the cylindrical catalyst. As a result, a desired exhaust gas purification rate can be obtained, and the THC emission amount can be effectively suppressed.

Furthermore, the layered scavenging type engine muffler of the present invention uses the existing muffler member including the cylindrical catalyst as it is, and only adjusts the distance from the partition plate to the cylindrical catalyst based on the results of an analysis experiment using a computer performed in advance, for example. The distance T from the front end surface of the catalyst, in other words, the protruding length of the catalyst in the front chamber (the axial position of the catalyst relative to the partition plate) can obtain the above-mentioned effects, so the cost performance is excellent.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing an embodiment (Example 1) of a laminar scavenging type engine muffler of the present invention.

FIG. 2 is a diagram showing the gas flow and flow velocity in the muffler (A) and in the cylindrical catalyst (B), which are visualized in shades in an analysis model simulating the muffler shown in FIG. 1 .

3 is a schematic cross-sectional view showing one embodiment (Example 2) of the laminar scavenging type engine muffler of the present invention.

FIG. 4 is a diagram showing the gas flow and flow velocity in the muffler (A) and the cylindrical catalyst (B) in a visual representation of density in an analysis model simulating the muffler shown in FIG. 3 .

5 is a schematic cross-sectional view showing one embodiment (Example 3) of the laminar scavenging type engine muffler of the present invention.

6 is a schematic cross-sectional view showing a muffler that is a conventional comparative product (comparative example) to the muffler shown in FIG. 1 and the like.

FIG. 7 is a diagram showing the gas flow and flow velocity in the muffler (A) and the cylindrical catalyst (B) by visualizing the density and lightness in the analysis model simulating the muffler shown in FIG. 6 .

8 is a graph showing the ratio of gas that does not pass through the catalyst when the positions of the partition plate and the columnar catalyst are changed with the vertical axis taking the ratio of the gas that does not pass through the catalyst and the horizontal axis taking the distance from the reference position of the partition plate.

9 is a table showing the ratio of the gas that does not pass through the catalyst when the distance A from the inlet to the partition plate and the distance D from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst are changed as muffler size parameters, respectively.

Fig. 10 shows the region in which the protruding length T(A-D) of the catalyst in the front chamber is taken on the vertical axis, and the distance A from the inlet to the partition plate is taken on the horizontal axis, and the ratio of the gas that does not pass through the catalyst is divided into three steps. picture.

Description of reference numbers:

1, 2, 3, 4 laminar scavenged engine mufflers

8 cylinders

9 Exhaust port

10 Muffler body

11 Front panel

11a Front wall

12 rear panel

13 Partition board

14 Catalyst Installation Department

14a round through hole

16 inlet

17 Export port

20 Cylindrical catalyst

20a Front face

22 carriers

23 Cylindrical shell

24 units

24a Linear passage part

R1 Front Room

R2 back room

A Distance from the inlet to the partition plate

D Distance from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst

T Distance from the partition plate to the front end face of the cylindrical catalyst

H Distance from the lower end of the introduction port to the upper end of the cylindrical catalyst

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 , 3 , and 5 are schematic cross-sectional views showing one embodiment (Examples 1, 2, and 3) of laminar scavenging engine mufflers 1 , 2 , and 3 of the present invention, and FIG. 6 shows a conventional A schematic cross-sectional view of a muffler 4 of a comparative product (comparative example).

In addition, FIGS. 2 , 4 , and 7 respectively show the inside of the muffler (A) and the inside of the cylindrical catalyst (B) in shades in the analysis models 1M, 2M, and 4M for simulating the mufflers 1, 2, and 4, respectively. Diagram of gas flow, velocity. In FIG. 2 , FIG. 4 , and FIG. 7 , the denser part indicates that the flow velocity of the gas is fast, and the lighter part indicates that the flow velocity of the gas is slow (the gas does not flow).

The basic structures of the muffler 1 of the first embodiment shown in FIG. 1 , the muffler 2 of the second embodiment shown in FIG. 3 , and the muffler 3 of the third embodiment shown in FIG. 5 and the muffler of the comparative example shown in FIG. 6 described above 4 is the same, so the parts of the mufflers 1 , 2 , and 3 corresponding to the parts of the muffler 4 are denoted by common reference numerals.

The mufflers 1 , 2 , 3 , and 4 are provided with a muffler body 10 in the form of a box-shaped container that introduces exhaust gas from a laminar scavenging type engine and leads out the purified exhaust gas. In the muffler body 10 , partition walls 13 are provided in the front and rear of the muffler body to be airtight. Ground separated front chamber R1 and rear chamber R2.

An introduction port 16 for introducing exhaust gas from an exhaust port 9 provided in the cylinder 8 of the laminar scavenging engine is provided in the upper half of the front chamber R1. The partition plate 13 is arranged perpendicular to the introduction direction of the exhaust gas. A lead-out port 17 for leading out the exhaust gas purified by the cylindrical catalyst 20 is provided in the lower portion of the rear chamber R2 on the downstream side of the front chamber R1.

The monolithic cylindrical catalyst 20 for exhaust gas purification is attached to substantially the lower half of the partition plate 13 so that its axis is perpendicular to the partition plate 13 and spans the front chamber R1 and the rear chamber R2.

The column-shaped catalyst 20 is an oxidation catalyst capable of oxidizing and combusting THC such as unburned fuel components contained in the exhaust gas, and has a metal or ceramic carrier 22, and a plurality of carriers 22 having communication is provided in a lattice shape. In the cells 24 of the linear passage portions 24 a of the front chamber R1 and the rear chamber R2 , the inside of the carrier 22 (each cell 24 ) is coated with a platinum group oxidation catalyst material such as platinum and rhodium. A metal cylindrical case 23 is fitted and fixed. In addition, the cylindrical catalyst 20 is composed of a redox catalyst, a three-way catalyst, or the like.

A catalyst mounting portion 14 is provided in substantially the lower half of the partition plate 13 , and the catalyst mounting portion 14 has a circular insertion hole 14 a that can fix the cylindrical catalyst 20 at right angles to the partition plate 13 . Any position in the direction of the catalyst 20 (the axial direction of the catalyst 20 ). The cylindrical catalyst 20 is airtightly mounted on the catalyst mounting portion 14 by methods such as welding, bonding, brazing, and the like.

The exhaust volume of the laminar scavenging engine using mufflers 1, 2, 3, and 4 is about 30cc (for example, 20cc to 40cc, especially about 28cc to 32cc). The front chamber R1 in the mufflers 1, 2, 3, and 4 The volume is 4 to 6 times the exhaust volume (if it is necessary to explain this in detail, refer to Patent Document 3).

Here, as described above, the inventors of the present invention found that the airflow above the column-shaped catalyst 20 jumps in the airflow that has collided with the partition plate 13 and is reversed as described with reference to FIGS. 6 and 7 . The phenomenon of passing through the portion of the plurality of rows of cells 24 located at the upper end (outer peripheral portion) of the cylindrical catalyst 20 is caused by the distance A from the inlet 16 to the partition plate 13 , the distance A from the front wall surface 11 a of the front chamber R1 to the cylindrical catalyst 20 . At least one of the distance D of the front end surface 20a and the distance T from the partition wall plate 13 to the front end surface 20a of the cylindrical catalyst 20 (the protruding length of the catalyst 20 into the front chamber R1) is set within a predetermined range, so that no occurrence of the above phenomenon.

In detail, in FIG. 8 , the vertical axis is the ratio of the gas that does not pass through the catalyst 20 , and the horizontal axis is the distance from the reference position of the partition wall plate 13 , indicating that the front-rear direction positions of the partition wall plate 13 and the column-shaped catalyst 20 are changed. Changes in the ratio of gases that do not pass through the catalyst.

The reference position of the partition plate 13 is the position in the front-rear direction of the partition plate 13 in the muffler 2 ( FIG. 3 ) of Example 2, that is, the center position in the front-rear direction of the columnar catalyst 20 . In the muffler 4 of the comparative example shown in FIG. 6 , the partition plate 13 is moved by 7 mm from the reference position to the inlet 16 side (front or windward side). In the muffler 3 of the third embodiment shown in FIG. 5 , the partition plate 13 is moved by 3.5 mm toward the inlet 16 side (front or windward side) from the reference position. In addition, in the muffler 1 of Example 1 shown in FIG. 1, the partition plate 13 moved 5 mm to the rear or the leeward side from the said reference position.

The cylindrical catalyst 20 used in the mufflers 1, 2, 3, and 4 is the above-mentioned monolithic catalyst having a diameter C of about 30 mm and a length L of about 21 mm.

The ratio of the gas that does not pass through the catalyst 20 is the ratio of the part of the catalyst 20 where no gas flows, and here is the ratio calculated by dividing the number of cells through which no gas flows by the total number of cells when viewed in a central cross section.

In the mufflers 1, 2, 3, and 4, the position of the column-shaped catalyst 20 with respect to the entire muffler body is the same (fixed at D=14.5 mm), and only the position of the partition plate 13 in the front-rear direction is different. In addition, in FIG. 8, the point drawn on the line is the ratio of the gas that does not pass through the column-shaped catalyst 20 when the position of the column-shaped catalyst 20 is fixed and only the front-rear direction position of the partition wall plate 13 is changed. In addition, in FIG. 8 , the dots marked with numbers next to the plotted dots change the position of the columnar catalyst 20 in the front-rear direction in addition to the position of the partition plate 13 in the front-rear direction. The numbers in FIG. 8 basically correspond to the numbers in FIG. 9 .

In the muffler 4 of the comparative example shown in FIG. 6 in which the partition plate 13 is moved from the reference position to the inlet 16 side (front or windward side) by 7 mm (ie, T=3.5 mm), as shown in FIG. In the analysis model 4M, the gas flow and flow velocity in the muffler (A) and in the cylindrical catalyst (B) are visualized by density, and the airflow above the cylindrical catalyst 20 in the reversed airflow skips the cylindrical catalyst. 20 at the upper end of the multi-column cell 24 part, the multi-column cell 24, 24, . . . part (white part) skipped by the gas flow hardly flows through the gas. Therefore, the ratio of the gas that does not pass through the catalyst 20 is about 20%, and further, the flow velocity difference in the catalyst 20 is large, so the muffler 4 is a defective product.

In addition, in the muffler 3 of Example 3 shown in FIG. 5 in which the partition plate 13 is moved from the reference position to the inlet 16 side (front or windward side) by 3.5 mm (ie, T=7.0 mm), although not shown In the model for analysis, although the airflow above the column-shaped catalyst 20 in the reversed gas flow skips the unit 24 part of the column-shaped catalyst 20 located about one row at the upper end of the column-shaped catalyst 20, the gas that does not pass through the catalyst 20 is The ratio is about 14%, which is within the allowable range (pass).

In addition, in the muffler 2 of Example 2 shown in FIG. 3 in which the partition plate 13 is located at the reference position (ie, T=10.5 mm), as in the analysis model 2M shown in FIG. 4 that simulates the muffler 2 with The density visualization shows the gas flow and flow velocity in the muffler (A) and the cylindrical catalyst (B), although the airflow above the cylindrical catalyst 20 in the reversed airflow skips the upper end of the cylindrical catalyst 20. This muffler 2 is an acceptable product, but the ratio of the gas that does not pass through the catalyst 20 is slightly higher than 6%.

In addition, in the muffler 1 of Example 1 shown in FIG. 1 in which the partition wall plate 13 is moved from the reference position to the rear or leeward side by 5 mm (ie, T=15.5 mm), as shown in FIG. 2 that simulates the muffler 1 In the analysis model 1M, the gas flow and flow velocity in the muffler (A) and in the cylindrical catalyst (B) are visualized in shades, and a part of the gas flow that has collided with the partition plate 13 and is reversed is surrounded by the circle of the cylindrical catalyst 20. The outer peripheral surface of the cylindrical case 23 (on the front chamber R1 side or the introduction port 16 side) guides the cell 24 located at the upper end of the columnar catalyst 20 while flowing. Therefore, the ratio of the gas that does not pass through the catalyst 20 is almost 0%, and further, the flow velocity difference in the catalyst 20 is also small, so the muffler 1 is an excellent product.

In addition, the ratio of the gas that does not pass through the catalyst 20 is preferably 7% or less (Examples 1 and 2), but if it is in the range of 7 to 14% (Example 3), it is an allowable range (pass), and if it exceeds 14% is not eligible.

In addition, it was found that the distance H from the lower end of the introduction port 16 to the upper end of the columnar catalyst 20 is preferably 9 mm or more.

FIG. 9 is a diagram showing a case where the distance A from the introduction port 16 to the partition plate 13 and the distance D from the front wall surface 11a of the front chamber R1 to the front end surface 20a of the catalyst 20 are changed respectively as muffler size parameters without passing the catalyst 20 . A table of ratios of gases. As described above, the numbers in FIG. 9 correspond to those in FIG. 8 .

In FIG. 9 , the sample No. 17 (A=18.0mm, D=2.0mm) is a defective product because the distance D from the front wall surface 11a of the front chamber R1 to the front end surface 20a of the catalyst 20 is extremely narrow, and it is difficult for the gas to flow to the catalyst In the vicinity of the outer periphery of the catalyst 20, the flow of the gas is concentrated in the center of the catalyst 20, and the flow of the gas in the catalyst 20 becomes uneven as a whole. Therefore, it can be seen that the distance D from the front wall surface 11a of the front chamber R1 to the front end surface 20a of the catalyst 20 needs to be ensured to be 5 mm or more (see also samples No. 13 and 18 which are qualified products).

10 shows the protruding length T (A-D) of the catalyst 20 in the front chamber R1 on the vertical axis and the distance A from the introduction port 16 to the partition plate 13 on the horizontal axis, and divides the ratio of the gas that does not pass through the catalyst 20 The figure for the 3-stage region representation.

According to the above description, since the protruding length T(AD) of the catalyst 20 into the front chamber R1 needs to be ensured to be 7 mm or more, the range of the distance A from the introduction port 16 to the partition plate 13 is preferably 25 mm or more under this condition. . However, if the protruding length T(A-D) of the catalyst 20 into the front chamber R1 can be ensured to some extent, even if the distance A from the introduction port 16 to the partition plate 13 is 25 mm or less (for example, 21.5 mm or more in Example 3) ), the ratio of the gas that does not pass through the catalyst 20 can also satisfy the allowable range of 7 to 14% (acceptable).

According to the results of the analysis experiments shown in FIGS. 8 , 9 , and 10 described above, when the displacement of the engine is about 30cc (for example, about 20cc to 40cc, especially about 28cc to 32cc), the cylindrical catalyst 20 has a diameter C of In the case of the above-mentioned monolithic conventional product having a length L of 25 mm to 50 mm and a length L of 15 mm to 35 mm, it is preferable to set the distance A from the introduction port 16 to the partition wall plate 13 to 21.5 mm or more, from the front wall surface 11a of the front chamber R1. The distance D to the front end surface 20a of the cylindrical catalyst 20 is set to be 5 mm or more, the distance T from the partition plate 13 to the front end surface 20a of the cylindrical catalyst 20 is set to be 7 mm or more, from the lower end of the introduction port 16 to the cylindrical catalyst The distance H of the upper end of 20 is set in the range of 9 mm or more. In addition, considering the overall size of the muffler, etc., it is preferable to set the distance A from the inlet 16 to the partition plate 13 to 25 mm to 30 mm, and the distance A from the front wall surface 11 a of the front chamber R1 to the front end surface 20 a of the columnar catalyst 20 is preferably set to 25 mm to 30 mm. The distance D is set at 5 mm to 20 mm, the distance T from the partition plate 13 to the front end surface 20a of the cylindrical catalyst 20 is set at 7 mm to 16 mm, and the distance H from the lower end of the introduction port 16 to the upper end of the cylindrical catalyst 20 is set in the range of 9mm to 20mm. In this way, it is possible to avoid a phenomenon in which the airflow above the columnar catalyst 20 in the reversed airflow that strongly collides with the partition plate 13 skips over a plurality of rows of cells located at the upper end (outer peripheral portion) of the columnar catalyst 20 , The ratio of the gas that does not pass through the catalyst 20 can be made about 14% or less.

As can be understood from the above description, the layered scavenging engine muffler 1 of the present embodiment does not change the external dimensions of the muffler main body, the position of the introduction port, the diameter and length of the column-shaped catalyst, And in the case of the position of the columnar catalyst in the height direction in the muffler body, the distance A from the inlet 16 to the partition plate 13 and the distance D from the front wall surface 11a of the front chamber R1 to the front end surface 20a of the columnar catalyst 20 and at least one of the distance T from the partition plate 13 to the front end surface 20a of the cylindrical catalyst 20 (the protruding length of the catalyst 20 into the front chamber R1) is set within a predetermined range, and the introduction port 16 is introduced into the front chamber R1 The exhaust gas collided with the partition plate 13 and reversed does not skip over the cell 24 located at the upper end of the column-shaped catalyst 20 as much as possible. In this way, by defining only the structure around the cylindrical catalyst, it is possible to increase the efficiency of the catalyst reaction without increasing the size of the muffler, and it is possible to contribute to the compactness of the entire working machine including the layered scavenging engine.

Therefore, a part of the airflow that has collided with the partition wall plate 13 and has been reversed flows into the cell 24 at the upper end of the cylindrical catalyst 20 while being guided by the outer peripheral surface of the cylindrical shell 23 provided on the outer periphery of the cylindrical catalyst 20 , In this way, the number of cells in the columnar catalyst 20 through which the exhaust gas does not flow can be reduced as much as possible, and the exhaust gas can be uniformly flowed through the columnar catalyst 20 .

In addition, the layered scavenging type engine muffler 1 of the present embodiment uses the existing muffler member including the columnar catalyst 20 as it is, and based on the results of an analysis experiment using a computer performed in advance, for example, only adjustment from the partition plate 13 is performed. The distance T to the front end surface 20a of the cylindrical catalyst 20, in other words, the protruding length of the catalyst 20 into the front chamber R1 (the axial position of the catalyst 20 with respect to the partition plate 13), can obtain the above-mentioned effects, so the cost performance is excellent. .

In addition, in the above-mentioned embodiment, the muffler used in the laminar scavenging type engine with a displacement of about 30 cc has been described, but the muffler of the present invention can of course be applied to a laminar scavenging engine with a displacement other than about 30 cc. type engine.

Claims (9)

1. a laminar scavenging type engine muffler, is characterized in that, has: The muffler main body, which introduces the exhaust gas from the laminar scavenging engine and exports the purified exhaust gas; A partition plate for airtightly dividing the inside of the muffler body into a front chamber and a rear chamber on the downstream side of the front chamber, and is disposed perpendicularly to the introduction direction of the exhaust gas, in the upper half of the front chamber an introduction port for introducing the exhaust gas is provided; and A cylindrical catalyst for exhaust gas purification is attached to substantially the lower half of the partition plate so that its axis is perpendicular to the partition plate and spans the front chamber and the rear chamber, The cylindrical catalyst is a monolithic catalyst in which a plurality of cells having linear passages connecting the front chamber and the rear chamber are arranged in a lattice shape, The distance (A) from the inlet to the partition plate, the distance (D) from the front wall surface of the front chamber to the front end surface of the columnar catalyst, and the distance from the partition plate to the columnar At least one of the distances (T) of the front end surfaces of the catalysts is set within a predetermined range so that the airflow introduced into the antechamber from the introduction port and collided with the partition wall plate and reversed does not skip the passage as much as possible. The unit at the upper end in a cylindrical catalyst. 2. The muffler for a laminar scavenged air engine according to claim 1, characterized in that, A part of the reversed airflow flows into the cell located at the upper end of the cylindrical catalyst while being guided by the outer peripheral surface of the cylindrical shell provided on the outer periphery of the cylindrical catalyst. 3. The muffler for a laminar scavenging type engine according to claim 1 or 2, characterized in that, The cylindrical catalyst is composed of an oxidation catalyst, a redox catalyst, or a three-way catalyst capable of oxidatively combusting at least an unburned fuel component contained in the exhaust gas. 4. The muffler for a laminar scavenged air engine according to claim 1 or 2, characterized in that, A catalyst mounting portion having a circular insertion hole capable of fixing the columnar catalyst at an arbitrary position in a direction perpendicular to the partition plate is provided in substantially the lower half of the partition plate. 5. The muffler for a laminar scavenged air engine according to claim 4, characterized in that, The cylindrical catalyst is airtightly mounted to the catalyst mounting portion by welding. 6. The muffler for a laminar scavenging type engine according to claim 1 or 2, characterized in that, The volume of the front chamber is set to be 4 to 6 times the displacement of the laminar scavenging engine. 7. The muffler for a laminar scavenged air engine according to claim 1 or 2, characterized in that, The distance (A) from the inlet to the partition plate is set to be 21.5 mm or more, and the distance (D) from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst is set to be 5 mm or more, The distance (T) from the partition plate to the front end surface of the cylindrical catalyst is set to be 7 mm or more, and the distance (H) from the lower end of the introduction port to the upper end of the cylindrical catalyst is set to be 9 mm or more. . 8. The muffler for a laminar scavenged air engine according to claim 7, characterized in that, The distance (A) from the introduction port to the partition plate is set in the range of 25 mm to 30 mm, and the distance (D) from the front wall surface of the front chamber to the front end surface of the cylindrical catalyst is set in the range of 25 mm to 30 mm. Within the range of 5 mm to 20 mm, the distance (T) from the partition plate to the front end surface of the cylindrical catalyst is set in the range of 7 mm to 16 mm, and the distance from the lower end of the introduction port to the front end of the cylindrical catalyst is set in the range of 7 mm to 16 mm. The distance (H) of the upper end is set in the range of 9 mm - 20 mm. 9. The muffler for a laminar scavenged air engine according to claim 1 or 2, characterized in that, The exhaust volume of the layered scavenging engine is in the range of 20cc to 40cc, the diameter (C) of the cylindrical catalyst is in the range of 25 mm to 50 mm, and the length (L) of the cylindrical catalyst is 15 mm ~35mm range.

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