JP2004257370A - Exhaust muffler of small engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust muffler of a simple and small structure, in which exhaust gas is purified in better ways, compared with conventional mufflers. <P>SOLUTION: In the exhaust muffler of a small engine in which an exhaust reactor member 1 is connected to the exhaust gas inlet of the muffler through which exhaust gas from the engine enters, the structure of the exhaust reactor includes the inlet 5 for exhaust gas from the engine formed along the tangent line of the external circumference of a round cavity 2, an exhaust gas outlet 4 formed on the side face 3 of the round cavity 2, the exhaust reactor member 1 surrounded by muffler cases 6, 6', and an exhaust gas outlet 7 for the discharge of exhaust gas from the muffler cases to the atmosphere formed in some portions of these muffler cases 6, 6'. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust muffler for a small engine capable of reducing harmful gas components in exhaust gas.
[0002]
[Prior art]
Conventionally, in an engine in which a small amount of oil is mixed with fuel and burned, an oil separation chamber is provided upstream of a muffler main body, and an exhaust nozzle is disposed in the oil separation chamber in a state of being directed in a circumferential direction. A diffuser section communicating with the outer periphery of the nozzle is provided to form an ejector section for introducing secondary air, and a reaction chamber is provided via a stay at the center of the muffler body on the downstream side of the oil separation chamber. In addition, an exhaust device for an engine, wherein a gas mixing ejector portion is formed by facing an oil guide portion that converges and extends from a circumferential direction of the oil separation chamber to a gas discharge port of the reaction chamber. It is provided (for example, see Patent Document 1).
[0003]
Further, conventionally, a joining portion of two box-shaped exhaust muffler pieces formed by press-forming a steel plate is integrally formed by brazing or welding, and an exhaust gas introduction pipe and an exhaust pipe are disposed therein. The muffler is vertically divided into two parts and can be integrated with an exhaust muffler piece fixed to the main body of the engine and an outer exhaust muffler piece fitted to the exhaust muffler piece. A holding portion for the sound absorbing / purifying material communicating with the exhaust gas introduction pipe is formed in the facing portion, and a stopper is provided across the mating surface of the two exhaust muffler pieces, and the outer side is provided with a stopper. There is provided an exhaust muffler for an internal combustion engine for a small working machine, in which only an exhaust muffler piece is made detachable (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-6-207512 (Claims)
[Patent Document 2]
Japanese Utility Model Publication No. 5-7456 (claim for utility model registration)
[0005]
[Problems to be solved by the invention]
In the exhaust system of an engine as disclosed in Patent Document 1, the stay supporting the reactor equipped with the catalyst is interposed in the swirl passage of the exhaust gas, so that the swirl of the exhaust gas is smooth. Is not performed at the same time.
Further, in the exhaust muffler of the internal combustion engine for a small working machine as disclosed in Patent Document 2, there is a problem that there is no function of turning exhaust gas.
[0006]
As is well known, a two-cycle engine has a large amount of blow-by gas at the time of exhaust and a small expansion stroke, so that incomplete combustion gas is easily discharged. For this reason, the exhaust gas contains a large amount of O ₂ and HC.
The most frequently used exhaust gas after-treatment is purification of exhaust gas by a catalyst. However, if the amount of the harmful gas component in the exhaust gas is too large, the amount of the exhaust gas to be treated by the catalyst increases, the temperature of the catalyst rises too much, and the catalyst dissolves and is damaged by heat, which greatly impairs reliability and commercial value.
In contrast, lean reactors (reactors that may be used to purify harmful gases from the combustion of a lean mixture with an air-fuel ratio of 15 or more) have an air-fuel ratio of 15 or more when used in a four-stroke engine. lean (lean) air-fuel ratio range, there excess O ₂ is sufficiently, there is the exhaust temperature is utilized in a high place.
However, in the case of a two-cycle engine, even when the air-fuel ratio is in a rich region, 4 to 7% of residual O ₂ in the exhaust gas is exhausted, which is effective as O ₂ for purifying the exhaust gas. . In addition, since a large amount of HC is blown out, the conditions for purifying exhaust gas are prepared.
[0007]
According to the present invention, the exhaust gas is swirled in the exhaust reactor, so that the unburned gas and the burned gas or the residual O ₂ can easily contact and mix with each other, and the purification reaction of the exhaust gas can be performed more efficiently. In addition, when the engine is small, the exhaust temperature is difficult to rise, but in that case, the catalyst is coated on the inner wall surface of the circular cavity of the exhaust reactor to promote the activation of unburned gas and enhance the purification of exhaust gas. It is an object of the present invention to provide an exhaust muffler for a small engine that can be used.
[0008]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, the invention according to claim 1 is directed to an exhaust gas of a small engine in which an exhaust reactor member 1 is connected to an exhaust gas inlet portion of an exhaust muffler into which exhaust gas from the engine enters. In the exhaust muffler, the structure of the exhaust reactor member 1 is such that an exhaust gas inlet 5 from an engine is formed in a tangential direction of an outer periphery of the circular cavity 2, and an exhaust gas outlet 4 is formed in a side surface 3 of the circular cavity 2. A structure in which the exhaust reactor member 1 is surrounded by muffler cases 6, 6 ', and an exhaust gas outlet 7 through which exhaust gas in the muffler case is released to the atmosphere is formed in a part of the muffler cases 6, 6'. And an exhaust muffler for a small engine.
[0009]
According to a second aspect of the present invention, there is provided an exhaust muffler for a small engine according to the first aspect, wherein a catalyst 2a is coated on an inner wall surface of the circular cavity 2 of the exhaust reactor member 1.
[0010]
With such an exhaust muffler, the exhaust gas smoothly swirls and flows in the circular cavity 2 of the exhaust reactor member 1, so that the exhaust gas circulation distance in the exhaust muffler is equal to that of the exhaust muffler. The swirling of the exhaust gas within the exhaust gas 2 prolongs the passage time of the exhaust gas, and the contact and mixing of the high-temperature exhaust gas and the low-temperature exhaust gas proceed, and the harmful gas in the exhaust gas is reduced in temperature. The combustion gas is reduced by the high gas, and the exhaust gas is purified.
[0011]
Further, the gas swirling in the circular cavity 2 of the exhaust reactor member 1 has a low temperature and is heavier, so that the gas swirls along the inner wall surface of the circular cavity 2 by centrifugal force due to the centrifugal force, and the oxidized gas has a higher temperature and is lighter. The lost gas collects in the center of the circular cavity. Since the lightened gas sequentially gathers at the center of the circular cavity 2, the high-temperature gas, which has undergone the oxidation reaction, comes first through the exhaust gas outlet 4 formed in the side surface 3 of the exhaust reactor member 1. leak.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
First, exhaust gas purification will be described. In one cycle of the two-stroke engine (crank rotation angle: 360 degrees), about 1/3 exhaust gas is exhausted, and about 2/3 the exhaust port is closed. Therefore, the exhaust gas in the exhaust system is neither a constant exhaust gas composition nor an emission amount. Further, even during the period in which the exhaust port is open, the amount of gas discharged from the cylinder is high and the combustion gas pressure is high when the exhaust port starts to open. At this time, the exhaust gas composition in the early stage of the discharge includes a gas that has not been completely burned, and has a large amount of unburned gas components.
[0013]
Generally, by the end of blowdown, burned gas comes out, and the amount of unburned gas in the gas decreases. However, in a two-stroke engine, scavenging gas is pumped to the cylinder while the exhaust port is open.
Since this newly pumped scavenging gas is fed into the cylinder at a considerably high speed, the gas that has made one round while scavenging inside the cylinder blows out a considerable amount (15 to 20% by estimation) from the exhaust port. come. The exhaust gas that has blown out is fresh air and contains a very large amount of HC. Thus, the composition and amount of the gas that comes out of the exhaust vary greatly from moment to moment. Therefore, in a structure in which the exhaust gas is sequentially extruded in a tocoro type like an exhaust system of a general muffler, there is little opportunity for the unburned gas to come into contact with the residual O ₂ or the high-temperature gas, and the exhaust system has Purification of exhaust gas does not progress very much.
[0014]
An exhaust muffler for a small engine according to the present invention has been made in order to eliminate the above-mentioned problems, and an embodiment thereof will be described below in detail with reference to the drawings.
FIG. 1 is an exploded perspective view of an exhaust muffler of a small engine according to the present invention, FIG. 2 is a perspective view of an assembled state, FIG. 3 is a longitudinal sectional view, and FIG. 4 is a sectional view taken along line AA of FIG.
[0015]
An exhaust muffler for a small engine according to claim 1 of the present invention is an exhaust muffler for a small engine in which an exhaust reactor member 1 is connected to an exhaust gas inlet portion of an exhaust muffler into which exhaust gas from an engine (not shown) enters. In the structure of the exhaust reactor member 1, an inlet 5 for exhaust gas from an engine is formed in a tangential direction of an outer periphery of the circular cavity 2, and exhaust gas outlets 4, 4 are formed in both side surfaces 3 of the circular cavity 2. A structure in which the exhaust reactor member 1 is surrounded by muffler cases 6, 6 ', and a part of the muffler cases 6, 6' is formed with an exhaust gas outlet 7 through which exhaust gas in the muffler case is released to the atmosphere. It is characterized by including. In the embodiment shown in FIGS. 1 to 4, the exhaust reactor member 1 has a drum shape, and exhaust gas outlets 4, 4 are formed on both side surfaces 3, 3 corresponding to the drum belly. .
[0016]
An exhaust muffler for a small engine according to a second aspect of the present invention is characterized in that the inner wall surface of the circular cavity 2 of the exhaust reactor member 1 is coated with a catalyst 2a. The catalyst 2a is made of a material containing, for example, platinum or the like.
[0017]
As described above, the present invention includes, in the exhaust muffler, an exhaust reactor member 1 having a circular cavity 2 in which the exhaust gas smoothly swirls and flows so that the exhaust gas stays long in the exhaust muffler. Since the surroundings of the exhaust reactor member 1 are surrounded by the muffler cases 6 and 6 ′, the still hot exhaust gas coming out of the circular cavity 2 of the exhaust reactor member 1 wraps around the exhaust reactor member 1. Since the exhaust gas swirling in the circular cavity 2 of the exhaust reactor member 1 can be maintained at a high temperature, the exhaust gas can be purified well.
[0018]
More specifically, when the exhaust gas swirls in the circular cavity 2 of the exhaust reactor member 1, the gas flowing into the circular cavity 2 and the gas flowing in later come into contact with each other in the circular cavity 2. Mixing increases the chance that the unburned gas comes into contact with O ₂ , thereby further promoting the oxidation reaction by contacting the unburned gas with the oxidized hot gas. By circulating the exhaust gas having a large amount of unburned gas in the circular cavity 2 to contact and mix with the high-temperature gas, the oxidation reaction is promoted and the oxidation reaction rate can be increased.
[0019]
From the above description, the more the exhaust gas stays in the circular cavity 2 by rotating in the circular cavity 2 of the exhaust reactor member 1 (the longer the residence time), the more the hot gas of the oxidation reaction and As the contact / mixing with the low-temperature gas including the combustion gas progresses, the number of encounters between O ₂ and the unburned gas increases, and as the ambient temperature of the exhaust gas increases, the reaction rate of the exhaust gas increases.
[0020]
The present invention has a structure in which the chance of contact of unburned gas with O ₂ is increased, and the temperature of exhaust gas oxidized with O ₂ can be effectively utilized. That is, the gas discharged from the exhaust port of the engine flows into the circular cavity 2 of the exhaust reactor provided in the muffler. The exhaust gas flows from the tangential direction of the outer periphery of the circular cavity 2 along the wall surface having the largest diameter, and swirls in the circular cavity 2. The swirling of the exhaust gas increases the contact between the gas that has flowed in earlier and the gas that has flowed in later, thereby increasing the chance of combining the unburned gas with O ₂ . By increasing the chance of bonding with O ₂ , the temperature of the exhaust gas also increases, and the oxidation reaction of the unburned gas is promoted.
[0021]
In the case of a small engine, if the temperature is hard up, the catalyst 2a film (coat) Then oxidation reactions involving the inner wall surface of the circular cavities 2 such as platinum or the like is promoted, the O ₂ in the treatment of HC at about 700 ° C. effectively it works, O ₂ is reduced to be consumed in the processing of the CO. This is an effective means for efficiently treating HC even when the amount of residual O ₂ is limited.
[0022]
Further, the surroundings of the exhaust reactor member 1 having the circular cavity 2 are surrounded by muffler cases 6 and 6 ′, and the still high-temperature exhaust gas coming out of the circular cavity 2 wraps around the exhaust reactor member 1, so that the exhaust gas is exhausted. Since the exhaust gas swirling in the circular cavity 2 of the reactor member 1 can be maintained at a high temperature, the exhaust gas can be purified well.
[0023]
As shown in FIG. 2, the exhaust muffler is assembled by forming a flange portion 5a formed around an exhaust gas inlet 5 of the exhaust reactor member 1 in a muffler case 6 on the side to be attached to an engine. Abuts on the inner wall side of the inlet 6a. The bolt insertion sleeve 8 is interposed between the inner wall side of the bolt insertion hole 6b 'drilled in the outer muffler case 6' and the bolt insertion hole 5b drilled in the flange 5a. ′, And the joining periphery 6c of the muffler case 6 is caulked and joined to the joining periphery 6c ′ of the muffler case 6 ′ to assemble integrally. In addition, a stainless steel wire mesh 9 is provided outside the exhaust gas outlet 7 formed in the muffler case 6, and the wire mesh 9 is pressed by a push lid 10 having an exhaust gas outlet 10a. The muffler case 6 is fixed to the muffler case 6 with set screws 11 to complete the muffler case.
[0024]
To attach this exhaust muffler to the engine, an exhaust port of a cylinder (not shown) is joined to an exhaust gas inlet 6a drilled in a muffler case 6 on the attachment side to the engine, and the other muffler case 6 'is connected to the bolt insertion sleeve. The bolt 12 is inserted into the bolt 8, and the tip of the bolt 12 is fastened to an engine case (not shown).
[0025]
FIG. 5 is a cross-sectional view showing another embodiment of the exhaust muffler of the present invention. The exhaust reactor member 1 is formed in a spherical shape, and exhaust gas outlets 4 and 4 are formed in the opposite side surfaces 3 of the circular cavity 2. The other components are the same as those of the above embodiment.
[0026]
Since the exhaust muffler of the small engine according to the present invention is configured as described above, the exhaust gas from the engine is used as an exhaust reactor constituting a part of the exhaust muffler as shown by arrows in FIGS. When the exhaust gas enters the circular cavity 2 forming the member 1 from the tangential direction of the outer periphery, the exhaust gas swirls and flows in the circular cavity 2, and the swirled exhaust gas eventually flows to the side surface 3 of the circular cavity 2. The exhaust gas exits from the exhaust gas outlet 4 and passes between the exhaust reactor member 1 and the muffler cases 6 and 6 ′ surrounding the exhaust reactor member 1, and is exhausted to the atmosphere from an exhaust gas outlet 7 drilled in the muffler case 6. Is done.
[0027]
【The invention's effect】,
With the exhaust muffler of the small engine of the present invention configured as described above, the exhaust gas from the engine swirls and flows in the circular cavity forming the exhaust reactor member disposed in the muffler case, and this circular In the cavity, the opportunity for the unburned gas to come into contact with and mix with O ₂ or high-temperature gas increases, and eventually the gas comes out of the exhaust gas outlet drilled on the side of the circular cavity, and the exhaust reactor member and the muffler case communicate with each other. The exhaust gas that has flowed into the intervening room surrounds the exhaust reactor member, and is finally exhausted to the atmosphere from an exhaust gas outlet formed in a part of the muffler case. That is, the oxidation reaction of the exhaust gas is promoted in the exhaust reactor member in the exhaust muffler, and the exhaust reactor member is still surrounded by the high-temperature exhaust gas. , The amount of total hydrocarbons (THC) is reduced, and the purification is improved.
[0028]
Further, the exhaust muffler for a small engine according to the present invention can be made extremely simple and small in size, and is suitable as, for example, an exhaust muffler for a two-cycle engine used in a small brush cutter or the like. In addition, when the inner wall surface of the circular cavity of the exhaust reactor is coated with a catalyst, the oxidation reaction rate is higher than that of a conventional plate catalyst.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an exhaust muffler of a small engine according to the present invention.
FIG. 2 is a perspective view of the exhaust muffler of the small engine of the present invention in an assembled state.
FIG. 3 is a longitudinal sectional view of an exhaust muffler of the small engine of the present invention.
FIG. 4 is a sectional view taken along line AA of FIG. 3;
FIG. 5 is a longitudinal sectional view of another embodiment of the exhaust muffler of the small engine of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exhaust reactor member 2 Circular cavity 2a Catalyst 3 Side 4 Exhaust gas outlet 5 Exhaust gas inlet 5a Collar 5b Bolt insertion hole 6, 6 'Muffler case 6a Exhaust gas inlet 6b, 6b' Bolt insertion hole 6c, 6c 'Joined Peripheral 7 Exhaust gas outlet 8 Bolt insertion sleeve 9 Wire mesh 10 Push lid 10a Exhaust gas outlet 11 Set screw 12 Bolt

Claims (2)

An exhaust muffler for a small engine in which an exhaust reactor member (1) is connected to an exhaust gas inlet of an exhaust muffler into which exhaust gas from the engine enters,
In the structure of the exhaust reactor member (1), an inlet (5) for an exhaust gas from an engine is formed in a tangential direction on an outer periphery of the circular cavity (2), and an exhaust gas is formed on a side surface (3) of the circular cavity (2). Exit (4) is drilled,
The exhaust reactor member (1) is surrounded by a muffler case (6, 6 '), and a part of the muffler case (6, 6') is provided with an exhaust gas outlet (7 An exhaust muffler for a small engine, characterized by including a structure formed with a). The exhaust muffler of a small engine according to claim 1, wherein a catalyst (2a) is coated on an inner wall surface of the circular cavity (2) of the exhaust reactor member (1).

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