JP2000170518A - Muffler for small sized engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized engine muffler, wherein by guiding an exhaust gas flow path in the muffler from a position far from an engine in an approaching direction and bringing it into contact with a catalyst during this time, low temperature exhaust gas not contacted with the catalyst is introduced to the outside of the muffler likely to be contacted by an operator to prevent the overheating of a muffler wall surface, and then exhaust gas overheated by its contact with the catalyst is passed through a vertical flow path going from the lower side to the upper side, and exhausted from the upper end of the muffler. SOLUTION: The inside of a muffler 3 is partitioned into an outer guiding room 5 away from the engine side and an inner guiding room 6 near the engine side by a vertical partition plate 4, an introduction tube 8 is provided between a cylinder exhaust port 2 and the partition plate 4 to introduce exhaust gas into the outer guiding room, a cylindrical catalyst 13 is provided in the partition plate below the introduction tube to introduce the exhaust gas of the outer guiding room to the inner guiding room 6, and an exhaust discharge port 17 is provided in the upper end of the inner guiding room 6 separated from the catalyst 13 by a long flow path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a muffler of a small two-stroke engine used as a power unit of various hand-held small work machines such as a brush cutter and a chain saw.

[0002]

2. Description of the Related Art Conventionally, as a muffler of this kind of small two-stroke engine, HC, C contained in exhaust gas has been used.
For the purpose of reducing O, etc., a catalyst is arranged in a muffler, and the unburned gas in the exhaust gas is brought into contact with the catalyst and recombusted by an oxidation reaction, thereby purifying the exhaust gas. For example, Japanese Patent Application Laid-Open No. 9-11225
8, JP-A-10-8942, JP-A-10-2129
No. 37 and the like.

[0003] Since the mufflers of these conventional small engines aim at causing unburned gas in the exhaust gas to come into contact with a catalyst to cause re-combustion by an oxidation reaction, all mufflers have a cylinder structure. The exhaust gas introduced from the exhaust port of the exhaust gas is discharged to the outside after being brought into contact with the catalyst in a flow path that guides the exhaust gas from a position close to the engine in the muffler to a direction far away from the engine.

[0004]

As described above, the purpose of providing the catalyst in the muffler is to bring unburned gas in the exhaust gas into contact with the catalyst and re-burn it by an oxidation reaction.
The catalyst is heated by the exhaust gas coming into contact with the catalyst, and as a result, the temperature of the exhaust gas on the downstream side passing through the catalyst is the temperature of the exhaust gas not yet in contact with the catalyst immediately after being introduced from the exhaust port of the cylinder. Will rise more.

As described above, since the temperature of the exhaust gas after contact with the catalyst is higher than that of the exhaust gas immediately after being introduced from the exhaust port of the cylinder, the exhaust gas in the muffler is different from the exhaust gas in the conventional muffler. If the flow path is set so that it is guided from a position close to the engine in the muffler to a position far away from the engine, the exhaust gas heated in contact with the catalyst may be exposed to the outside of the muffler where there is a danger of operator contact If the temperature of the cover that covers the outside of the muffler partially rises above the regulation value to prevent danger, or if the cover is made of synthetic resin, There was a problem that the cover would melt unless the gap between the muffler and the muffler was increased.

If the exhaust outlet of the muffler is provided at a position close to a catalyst provided in the muffler, the temperature of the exhaust discharged from the exhaust outlet becomes abnormally high and a fire may occur. There is a risk that it will occur.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the conventional muffler for a small engine.
By setting the exhaust gas flow path inside the muffler so that it comes in contact with the catalyst while guiding the exhaust gas flow path from a position farther from the engine in the muffler to a direction closer to the engine, it is possible to prevent the worker from touching the outside of the engine. In addition to preventing overheating of the muffler wall located, the exhaust gas that has been heated by contacting the catalyst in the flow passes through a relatively long vertical vertical flow path from the bottom to the top inside the muffler, An object of the present invention is to provide a muffler for a small engine capable of reducing the heat of exhaust gas heated by contact with a catalyst by discharging the exhaust gas from the upper end.

The muffler for a small engine according to the present invention includes, as a specific means, a muffler case having an outer guide chamber separated from the engine side by a vertical partition plate oriented in a direction perpendicular to the axial direction of the cylinder exhaust port. An introduction pipe partitioned into an inner guide chamber close to the engine side, and an introduction pipe for introducing exhaust gas from the exhaust port into the outer guide chamber between the inflow port connected to the cylinder exhaust port in the inner guide chamber and the partition plate. And a cylindrical catalyst that guides exhaust gas from the outer guide chamber to the inner guide chamber is provided on the partition plate below the inlet pipe, and an exhaust outlet is provided at an upper end of the inner guide chamber. .

It is preferable to provide a heat-resistant buffer plate inside the outer guide chamber wall surface facing the introduction pipe opening provided in the partition plate.

The introduction pipe for introducing the exhaust gas from the cylinder into the outer guide chamber may be constituted by a member formed by projecting a part of the partition plate toward an inflow port connected to the cylinder exhaust port by extrusion.

It is preferable that the exhaust discharge port is configured to be opened by a guide cover provided at the upper end of the inner guide chamber so that the exhaust gas flows in a lateral direction parallel to the crankshaft.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a muffler for a small engine according to the present invention will be described with reference to a first embodiment. This muffler is connected to an exhaust port 2 of a cylinder 1 as shown in FIG. The case 3 is provided with a vertical partition plate 4 in a direction orthogonal to the axial direction of the exhaust port 2 inside, so that the outer guide chamber 5 remote from the engine side and the inner guide chamber 6 close to the engine side are provided. It is partitioned.

The partition plate 4 is made of a stainless steel plate. The partition plate 4 is provided slightly outward from the center of the muffler case 3 when viewed from the engine side, so that the volume of the inner guide chamber 6 is larger than that of the outer guide chamber 5. Is also set to be somewhat larger.

An inflow port 7 connected to the exhaust port 2 of the cylinder 1 is provided above the wall surface 6a of the inner guide chamber 6, and the partition plate 4 has, as shown in FIG. A connection hole 9 corresponding to the inflow port 7 is opened, and between the inflow port 7 and the connection hole 9 of the partition plate 4, the exhaust gas introduced from the exhaust port 2 of the cylinder 1 is guided to the outside guide. An introduction pipe 8 for introduction into the chamber 5 is connected.

As shown in FIGS. 2 and 3, the introduction pipe 8 is set to have a length from the inflow port 7 to the connection hole 9 of the partition plate 4. A bolt insertion hole 10 corresponding to the length between the wall surface 6a of the inner guide chamber 6 and the wall surface 5a of the outer guide chamber 5 is provided. The bolt 12 is inserted into the bolt insertion hole 10 from the outside of the outer guide chamber wall surface 5 a so that the heat-resistant buffer plate 11 is sandwiched between the inside and the inside, and the tip of the bolt is screwed into the flange 2 a of the cylinder exhaust port 2. By attaching, the muffler case 3 is integrally connected to the cylinder exhaust port 2.

The heat-resistant buffer plate 11 is made of an iron plate, and connects the muffler case 3 to the cylinder exhaust port flange 2a by passing bolts 12 from outside the outer guide chamber wall 5a into bolt insertion holes 10 on both sides of the introduction pipe 8. While acting as a reinforcing plate for the tightening force when
The heat of the exhaust gas introduced from the exhaust port 2 of the cylinder 1 into the outer guide chamber 5 through the inlet pipe 8 prevents the outer guide chamber wall 5a facing the opening 8a of the inlet pipe 8 from being locally heated. Will be.

An outer periphery of a cylindrical catalyst 13 is fitted and fixed below the opening 8a of the introduction pipe 8 in the partition plate 4, and exhaust gas from the outer guide chamber 5 is exhausted from the cylindrical catalyst 13 The inside is guided into the inside guide room 6.

On the other hand, the upper end of the inner guide chamber 6 has an exhaust hole 1
4, a guide cover 15 provided with an exhaust discharge port 16 for discharging discharged exhaust gas laterally along the crankshaft direction of the engine is mounted on the outer upper surface of the exhaust hole 14. I have.

When the muffler case 3 is mounted on an engine, a heat insulating material 18 is provided between the inner guide chamber 6, the cylinder 1 and the crankcase 17, and
A muffler cover 19 is attached to the outside of the muffler case 3.

FIGS. 6 and 7 show a second embodiment. In the muffler according to the second embodiment, the space between the inlet 7 of the inner guide chamber wall 6a connected to the cylinder exhaust port 2 and the partition plate 4 is shown. Is formed by extruding a part of the upper part of the partition plate 4 in the oblong shape in the direction of the inflow port 7 so that the diameter of the partition plate 4 is smaller than that of the inflow port 7 side in the inner guide chamber wall surface 6a. Partition plate 4 expanded larger than the caliber
And a protruding portion integral with the protruding portion.

At the end of the introduction pipe 28, a hole 29 communicating with the inlet 7 of the inner guide chamber wall 6a and a pair of pipe insertion holes 30 on both sides of the hole 29 are formed. Inner guide room wall 6a and outer guide room wall 5
a between the inner and outer guide chamber wall surfaces 5a, 6a is supported at both ends of the pipe 31, and the pipe 3 is inserted from outside the outer guide chamber wall surface 5a.
The muffler case 3 is fixed to the cylinder 1 by inserting a bolt 32 into the cylinder 1 and screwing the tip of the bolt 32 to the cylinder exhaust port flange 2a outside the inner guide chamber wall surface 6a. .

In the muffler case 3 of the second embodiment, a cylindrical catalyst 13 is provided below the inlet pipe opening 28a of the partition plate 4, and exhaust gas is discharged laterally to the upper end of the inner guide chamber 6. The configuration including the exhaust outlet 16 is the same as that of the first embodiment.

In the muffler of the present invention having the above structure, the exhaust gas discharged from the exhaust port 2 of the cylinder 1 is first introduced into the outer guide chamber 5 through the introduction pipes 8 and 28 as shown by arrows. After that, the gas is introduced into the inner guide chamber 6 through the catalyst 13, then rises in the inner guide chamber 6, and is discharged from the upper exhaust discharge port 16 at a large distance from the catalyst 13. Released to the outside.

[0024]

According to the muffler of the present invention, the inside of the muffler case 3 is divided into an outer guide chamber 5 far from the engine and an inner guide chamber 6 close to the engine by the partition plate 4, and is discharged from the exhaust port 2 of the cylinder 1. The exhaust gas is first introduced into the outer guide chamber 5 distant from the engine through the introduction pipes 8 and 28, and is not brought into contact with the catalyst 13 in the outer guide chamber 5; 5
By guiding the exhaust gas at a relatively low temperature before coming into contact with the catalyst, the outer guide chamber 5 can be maintained at a temperature close to that of a muffler not using a catalyst.

On the other hand, the exhaust gas introduced into the outer guide chamber 5 comes into contact with the catalyst 13 in the process of being introduced into the inner guide chamber 6, so that the temperature in the inner guide chamber 6 is lower than that in the outer guide chamber 5. Although the height is increased, the inside guide chamber 6 has a low risk of touching by an operator, and a cooling air for the engine is introduced between the inside guide chamber 6 and the cylinder 1 and the crankcase 17, and a heat insulating material 18 is provided. By doing so, it is possible to provide a configuration that does not hinder the operation of the engine.

The exhaust gas, which has become hot due to contact with the catalyst 13, is introduced into the lower part of the inner guide chamber 6, and then rises in the inner guide chamber 6 toward the exhaust outlet 16 at the upper end. Since the catalyst 13 is located below the inner guide chamber 6, the exhaust discharge port 16 is located at the upper end of the inner guide chamber 6 and the distance between the exhaust outlet 16 and the exhaust gas outlet 16 is significantly large. In the process of flowing to the upper exhaust outlet 16, it is cooled to a temperature at which no danger of fire occurs.

The exhaust gas rising in the inner guide chamber 6 is discharged sideways from the exhaust discharge port 16 to be mixed with the air outside the muffler case 3, further cooled and discharged outside the muffler cover 19. .

Further, the exhaust gas at a relatively low temperature before coming into contact with the catalyst 13 is introduced into the outer guide chamber 5, and the temperature can be maintained at a temperature close to that of a muffler not using a catalyst, so that the volume can be reduced. In addition, even if a synthetic resin is used as the cover 19 that covers the outside of the muffler, the cover is not melted by heat, and the gap between the cover 19 and the muffler case 3 does not need to be particularly wide. Can be designed to be small and portable.

Further, in the configuration of the embodiment shown in FIGS. 6 and 7, since the introduction pipe 28 is formed integrally with a part of the partition plate 4 in advance, as in the first embodiment, the muffler case 3 is provided. When assembling, the work for attaching the introduction pipe 8 to the partition plate 4 can be simplified, and the assembling work can be performed more efficiently than in the case of the first embodiment. Reduction can be expected.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a first embodiment of a muffler according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a perspective view showing a configuration of an introduction pipe.

FIG. 4 is a perspective view showing the shape of a partition plate.

FIG. 5 is a perspective view showing the shape of an exhaust outlet.

FIG. 6 is a longitudinal sectional view showing a configuration of a muffler as a second embodiment.

FIG. 7 is a perspective view showing a shape of a partition plate in a second embodiment.

[Explanation of symbols]

 1: Cylinder 2: Exhaust port 2a: Exhaust port flange 3: Muffler case 4: Partition plate 5: Outside guide room 5a: Outside guide room wall 6: Inside guide room 6a: Inside guide room wall 7: Inlet 8, 28: Inlet 8a, 28a: Inlet opening 9: Connection port 10: Bolt insertion hole 11: Heat resistant buffer plate 12: Bolt 13: Catalyst 14: Exhaust hole 15: Guide cover 16: Exhaust outlet 17: Crank case 18: Heat insulation Material 19: Muffler cover 29: Hole 30: Pipe insertion hole 31: Pipe 32: Bolt

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuhiro Izumi 2373 Minamidaicho, Shiroko-cho, Nagao-gun, Chiba Pref.

Claims (4)

[Claims] The inside of a muffler case is divided into an outer guide chamber separated from an engine side and an inner guide chamber near an engine side by a vertical partition plate oriented in a direction perpendicular to an axial direction of a cylinder exhaust port, An introduction pipe for introducing the exhaust gas from the exhaust port into the outer guide chamber is provided between the inflow port connected to the cylinder exhaust port in the guide chamber and the partition plate, and the partition plate below the introduction pipe is provided in the partition plate. A muffler for a small engine, comprising: a cylindrical catalyst for guiding exhaust gas from an outer guide chamber to the inner guide chamber; and an exhaust outlet at an upper end of the inner guide chamber. 2. A muffler for a small engine according to claim 1, wherein a heat-resistant buffer plate is provided inside a wall surface of the outer guide chamber facing the opening of the introduction pipe provided in the partition plate. 3. An introduction pipe for introducing exhaust gas from a cylinder into an outer guide chamber is formed of a member formed by extruding a part of a partition plate toward an inflow port connected to a cylinder exhaust port. 1 Small engine muffler. 4. A muffler for a small engine according to claim 1, wherein the exhaust discharge port is opened by a guide cover provided at an upper end of the inner guide chamber so as to allow exhaust gas to flow in a lateral direction parallel to the crankshaft.