JP3099733B2 - Exhaust gas purifier for small engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for a small engine used for a lawnmower, a small generator, a small power unit, and the like.

[0002]

2. Description of the Related Art Recently, in order to reduce air pollution as much as possible, exhaust gas purifying means is installed not only on large engines such as automobile engines but also on small engines used in general industrial machines and the like. HC and C contained in
There is a strong demand for purifying harmful components such as O and NOx. 2. Description of the Related Art Conventionally, as an exhaust gas purifying device for an automobile engine, various types of so-called catalytic converters, in which a pellet or monolithic carrier carries a catalytic substance such as platinum, palladium or rhodium, have been proposed and put into practical use. For example,
Japanese Patent Publication No. 59-26771 discloses a substantially cylindrical monolithic carrier having a plurality of communication holes formed in an axial direction, a casing surrounding the monolithic carrier, and a catalyst support fitting mounted between the monolithic carrier and the casing. A catalytic converter with is described.

[0003] The catalyst support fitting described in this publication has a knitted body folded into a flat plate with a rod-shaped sealing material attached to the center of a substantially cylindrical knitted body manufactured by knitting a thin metal wire. The knitted body is subjected to an attaching process, and furthermore, the knitted body is rolled into a cylindrical shape so that the sealing material becomes annular, and both ends thereof are joined to each other. The monolith carrier is elastically held through the catalyst supporting bracket to prevent the monolith carrier from being damaged due to vibration or the like, and to prevent the monolith carrier from being damaged from the gap between the casing and the monolith carrier by the sealing material provided in the catalyst supporting bracket. It is configured to prevent the outflow of the purified gas. on the other hand,
Due to the small displacement of small engines, there is no legal regulation on exhaust gas purification.
Although an expansion chamber may be provided in the middle of the exhaust passage in order to reduce the exhaust noise, the actual situation is that the exhaust gas is normally exhausted without purification.

[0004]

By the way, if the above-described catalytic converter for an automobile engine is interposed in the exhaust passage to purify the exhaust gas of a small engine, the exhaust system of the engine becomes large. There is a problem that it becomes heavy. In addition, if the expansion chamber and the catalytic converter are provided independently in the exhaust passage, the engine performance is greatly increased due to the increase in exhaust resistance due to the provision of the expansion chamber and the catalytic converter, and the increase in exhaust resistance due to the longer exhaust passage. descend. Furthermore, in order to obtain stable purification performance,
You need to keep the catalytic converter relatively hot,
In the case of a small engine, since the displacement is small, it is difficult to maintain the temperature in the initial state or at a light load, etc., and the purification performance may be significantly reduced. In addition, when the load is high, the temperature of the catalytic converter becomes extremely high, and the catalytic converter may be thermally degraded, or a fire may occur due to contact with other objects.

An object of the present invention is to provide an exhaust gas purifying apparatus for a small engine which is capable of purifying exhaust gas and reducing exhaust noise while minimizing deterioration of engine performance, and which is small, light and highly efficient. That is.

[0006]

Means for Solving the Problems An exhaust gas purification device for a small engine according to claim 1, interposed in the middle portion of the exhaust passage
Had an expansion chamber and an exhaust gas purification unit, a hollow box-shaped muffler
An expansion chamber is formed inside the case, and exhaust gas is exhausted into the expansion chamber.
An exhaust gas purifying apparatus for a small engine that houses the entire gas purifying means , wherein the exhaust gas purifying means has a cylindrical catalyst case having a gas inlet hole at an upstream end and a gas exhaust hole at a downstream end. A plurality of communication holes extending from the upstream side to the downstream side of the catalyst case, a monolithic carrier fixed and held in the catalyst case, and a downstream portion of the catalyst case.
A cylindrical buffer case that surrounds the upper end of the
Attach to the middle of the case in an airtight manner
A cylindrical buffer case which is fixed to the silencer case in an airtight manner and forms a buffer space connected to the external space in the expansion chamber, wherein the internal space of the catalyst case communicates with the expansion chamber through the gas introduction hole, This is connected to the buffer space via the discharge hole.

Here, the catalyst case is composed of a bottomed cylindrical case body and a lid member for closing the opening of the case body, and the outer peripheral portion of the bottom wall of the case body. And, at the outer peripheral portion of the lid member, an annular restricting portion for restricting the movement of the monolith carrier in the axial direction is formed respectively, and at the center of the bottom wall of the case body and the central portion of the lid member, a truncated cone is formed outward. 4. The method according to claim 3, wherein each of the protruding protrusions is formed, and a gas discharge hole is formed in a conical wall of the downstream protrusion, and a gas introduction hole is formed in a conical wall of the upstream protrusion. In addition, an annular seal / cushion material is attached to one between the annular regulating portion of the lid member and the monolith carrier or between the annular regulating portion of the bottom wall of the case body and the monolith carrier, and an annular cushion material is attached to the other. As described in claim 4, the peripheral wall of the catalyst case and the That the monolithic carrier between squirrel carrier mounting a cylindrical catalyst support fitting for elastically holding the catalyst case, it is the preferred embodiment and the like.

[0008]

In the exhaust gas purifying apparatus for a small engine according to the present invention, since the expansion chamber and the exhaust gas purifying means are provided at an intermediate portion of the exhaust passage, the exhaust noise is suppressed by the expansion chamber and the exhaust gas is exhausted. Is purified by exhaust gas purifying means. In addition, since the entire exhaust gas purifying means is housed in the silencing case , an exhaust pipe for communicating the exhaust gas purifying means with the expansion chamber is not required. The space can be effectively used as an expansion chamber.

The expansion chamber heats the exhaust gas purifying means immediately after the engine is started by the exhaust gas introduced into the expansion chamber, and keeps the exhaust gas purifying means warm under no load or light load. In addition, the temperature of the monolithic carrier is kept high to increase the purification efficiency of the exhaust gas, and during abnormal combustion such as high load and misfire, the heat from the high-temperature exhaust gas purification means is shielded, and the temperature of the outer wall of the exhaust gas purification device is reduced. Prevent the adverse effects of contact with other things.

[0010] Further, the entire catalyst case is disposed in the expansion chamber, and a downstream portion thereof is inserted into the buffer case.
The exhaust gas flows into the catalyst case from the expansion chamber through the gas introduction hole, is purified in the process of flowing through the plurality of communication holes of the monolithic carrier, passes through the buffer space from the gas exhaust hole, is silenced, and then is exhausted. Is discharged. Thus, since the whole catalyst case is disposed in the expansion chamber, it becomes unnecessary exhaust pipe for communicating the expansion chamber and the exhaust gas purification means, together with the exhaust passage becomes shorter, the dead space around the exhaust gas purification means It can be effectively used as an expansion chamber.
Further, it is possible to more efficiently heat and maintain the exhaust gas purifying means, and it is possible to surely prevent the high temperature exhaust gas purifying means from coming into contact with other objects.

In the device according to the second aspect, the axial movement of the monolith carrier in the catalyst case is regulated by the annular regulating portions formed on the bottom wall of the case body and the lid member, respectively. . Further, outwardly projecting portions are formed at the center of the bottom wall of the case body and at the center of the lid member, and a gas discharge hole and a gas introduction hole are respectively formed in the conical wall of the pair of protrusions. Since the catalyst case is formed, even if the catalyst case is arranged by bringing the bottom wall portion and the lid member of the case body into contact with the inner wall surface of the expansion chamber, the flow of exhaust gas into and out of the catalyst case is not hindered.

In the device according to the third aspect, both ends of the monolith carrier are elastically held by the catalyst case via the cushion material and the seal / cushion material, so that the movement of the monolith carrier in the catalyst case in the axial direction is restricted. In addition, the sealing and cushioning material prevents the unpurified exhaust gas from flowing between the monolith carrier and the catalyst case. In the device according to the fourth aspect, the monolith carrier is elastically held in the catalyst case via the catalyst support metal, and the movement of the monolith carrier in the catalyst case in the radial direction is regulated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an exhaust gas purifying apparatus 1 for a small engine has an expansion chamber 2 and an exhaust gas purifying means 3 interposed at an intermediate portion of an exhaust passage extending from an exhaust port of the engine. The gas purifying means 3 is provided in the expansion chamber 2, and the exhaust gas discharged from the engine is introduced into the expansion chamber 2 through the upstream exhaust pipe 4, and is silenced in the expansion chamber 2. H contained in the exhaust gas while passing through the means 3
Harmful components such as C, CO and NOx are purified and discharged to the outside through the downstream exhaust pipe 5.

A downstream end of an upstream exhaust pipe 4 is connected to an upper wall portion 6a of a hollow box-shaped silencer case 6 forming the expansion chamber 2, and is opened into the expansion chamber 2, and a side wall portion 6b of the silencer case 6 is formed. Downstream exhaust pipe 5 is hermetically mounted in the lower part of the lower part. The shape and size of the expansion chamber 2 can be set as appropriate according to the displacement of the engine and the shape of the device to which the engine is assembled.

The exhaust gas purifying means 3 basically comprises a catalytic converter 10 provided in the expansion chamber 2 and a buffer case 11 for supporting the catalytic converter. As shown in FIG. 1, the buffer case 11 is formed of a tubular member having a substantially oval cross section, and the lower end of the buffer case 11 is hermetically welded to the lower wall 6 c of the sound deadening case 6. A buffer space 12 is formed in the buffer case 11,
A downstream side exhaust pipe 5 that opens into the buffer space 12 is hermetically welded to the peripheral wall of the buffer case 11.

As shown in FIGS. 1 to 4, the catalytic converter 10 includes a monolithic carrier 13 supporting a catalytic substance, a catalyst case 20 covering the monolithic carrier 13, and a catalyst case 20 between the monolithic carrier 13 and the catalyst case 20. Mounted catalyst support means. Reference numeral 14 denotes a rotation restricting member including a pin or a screw for restricting the rotation of the monolith carrier 13.

The catalyst case 20 includes a substantially cylindrical case body 21 with a bottom, and a lid member 22 for closing an upper end opening of the case body 21. The lower half of the case body 21 is mounted in the buffer case 11 and is hermetically welded to the buffer case 11. An annular regulating portion 23 for regulating the downward movement of the monolith carrier 13 is formed on the outer peripheral portion of the bottom wall portion of the case main body 21, and a truncated conical shape projecting downward at the center of the bottom wall portion. A protrusion 24 is formed, and the buffer space 12 is formed on the conical peripheral wall of the protrusion 24.
Are formed at regular intervals.

A flange 26 extending outward is formed at the upper end of the case body 21. The outer periphery of the lid 22 is
6 and is fixed to the case body 21. However,
The cover member 22 and the case body 21 may be integrated by curling the outer peripheral portion. An annular restricting portion 27 for restricting the upward movement of the monolith carrier 13 is formed in the vicinity of the outer periphery of the lid member 22, and a frustoconical protruding portion 28 protruding upward is formed at the center of the lid member 22. Is formed,
A plurality of gas introduction holes 29 that open into the expansion chamber 2 are formed at regular intervals in the conical peripheral wall of the protrusion 28.

The monolithic carrier 13 is a columnar carrier having a plurality of communicating holes 15 formed in the axial direction, on which a catalytic substance such as platinum, palladium or rhodium is carried, and the exhaust gas flows through the communicating holes 15. It is purified in the process of doing. Although the monolithic carrier 13 in the illustrated example is a lattice type, a spiral type or a layered type may be used. Further, although the monolithic carrier 13 having a circular cross section is used, an elliptical shape, an oblong shape, an oval shape, or the like can be used.

As shown in FIGS. 1 to 4, the catalyst support means includes a catalyst support fitting 31 for holding the monolith carrier 13 immovably in the radial direction with respect to the case body 21, and A seal / cushion material 33 for preventing movement of unpurified gas into the annular gap 32 between the monolith carrier 13 and the case main body 21 and a cushion material 3 for regulating movement of the monolith carrier 13 downward.
And 4.

The catalyst support bracket 31 is formed by knitting or weaving a thin metal wire made of stainless steel and the like having excellent heat resistance into a substantially cylindrical shape. The catalyst support bracket 31 is spirally corrugated as shown in FIG. It has enhanced elasticity in the width direction and the radial direction. The inner diameter R1 of the catalyst support fitting 31 is set slightly smaller than the outer diameter of the monolith carrier 13, the outer diameter R2 is set slightly larger than the inner diameter of the case main body 21, and the catalyst support fitting 31 is compressed to the monolith carrier 13 and the case. Body 2
It is mounted in the annular gap 32 between the two. In the illustrated example of the catalyst support bracket 31, the corrugations are drawn so as to draw a spiral in one direction, but the upper half and the lower half may be corrugated so as to draw a spiral in mutually opposite directions. Also, the catalyst support fitting 31 of the illustrated example
For example, a tubular knitted body made by knitting a thin metal wire is folded into a flat plate, corrugated, cut to a certain length, and further rounded into a tube to join both ends. It has been produced.

The cushion member 34 is formed by knitting or weaving a thin heat-resistant metal wire made of stainless steel or the like into a ring shape, and is formed between the annular regulating portion 23 and the outer peripheral portion of the lower end surface of the monolith carrier 13. Thrust receiver 3 to be mounted
4a and a skirt portion 34b extending into the annular gap 32 between the monolith carrier 13 and the case main body 21 and positioning the cushion material 34 in the radial direction are formed in a substantially L-shaped cross section. In addition, this cushion material 34, for example, after cutting a knitted tubular body made by knitting a thin metal wire to a fixed length, winds up a ring from one end thereof,
Further, it is manufactured by compression molding into a substantially L-shaped cross section.

The seal / cushion material 33 basically has a sealing property by holding 20 to 60% by weight of an inorganic fiber material such as ceramic or alumina based on the above-described cushion material 34. Then, the thrust receiving portion 33a mounted between the annular regulating portion 27 and the outer peripheral portion of the lower end surface of the monolith carrier 13 and the seal / cushion material 33 extending to the annular gap 32 between the monolith carrier 13 and the cover member 22 in the radial direction. And a skirt portion 33b positioned at the same position, is formed in a substantially L-shaped cross section. However, the cushion material 34 and the seal and cushion material 33 may be arranged upside down.

Next, the operation and effect of the exhaust gas purifying apparatus 1 will be described. Exhaust gas emitted from the engine is
The gas is introduced into the expansion chamber 2 through the upstream exhaust pipe 4,
After being silenced in, the gas flows into the catalyst case 20 through the gas introduction hole 29 and is purified in the process of flowing through the communication hole 15 of the monolith carrier 13. Then, the purified exhaust gas is once introduced into the buffer space 12 from the gas discharge hole 25 to reduce the circulation speed, and is silenced again, and is discharged from the buffer space 12 to the outside through the downstream exhaust pipe 5. .

In the exhaust gas purifying apparatus 1, since the exhaust gas purifying means 3 is provided inside the expansion chamber 2, the space near the exhaust gas purifying means 3 can be used as a space for noise reduction. Moreover, the expansion chamber 2 and the exhaust gas purifying means 3
This eliminates the need for an exhaust pipe connecting the exhaust gas purifying device and the exhaust gas purifying apparatus 1 as a whole, as compared with a case where the expansion chamber and the exhaust gas purifying means are provided independently. In addition, since the monolith carrier 13 itself acts as a muffler, the muffling performance is greatly improved. Furthermore, the exhaust gas introduced into the expansion chamber 2 heats the entire exhaust gas purifying means 3 at the initial stage of engine startup, rapidly raising the temperature of the monolith carrier 13, and when the engine is cold and lightly loaded. In addition, the entire exhaust gas purifying means 3 is heated so that the temperature of the monolith carrier 13 is suppressed from being lowered. At a high load, the temperature of the exhaust gas purifying means 3 due to the combustion of unburned gas in the monolith carrier 13 is reduced. An abnormal rise is suppressed, and the occurrence of a fire or the like due to the high-temperature exhaust gas purifying means 3 coming into contact with another object is prevented. As described above, the expansion chamber 2 functions as a heating space or a heat retaining space, whereby the temperature of the monolithic carrier 13 is maintained at a desired temperature, the exhaust gas purification performance is improved, and the safety aspect against fire and the like is also improved. .

The monolith carrier 13 is elastically held in the catalyst case 20 via catalyst support means including a catalyst support bracket 31 and cushion members 33 and 34.
The catalyst supporting means effectively absorbs vibrations and impacts acting on the exhaust system, thereby making it possible to effectively prevent the monolith carrier 13 from being damaged.

Further, the sealing and cushioning material 33 provides
The flow of the unpurified gas into the annular gap 32 between the monolith carrier 13 and the case body 21 is prevented, and the unpurified gas is prevented from being discharged to the outside as it is.

Further, a projecting portion 2 projecting outward is provided at the center of the bottom wall of the case body 21 and at the center of the lid member 22.
4 and 28 are formed, and the gas discharge holes 25 and the gas introduction holes 29 are formed in the conical walls of the pair of protrusions 24 and 28, respectively. By disposing the catalyst case 20 in a state where the expansion chamber 2 is in contact with the expansion chamber 2, the expansion chamber 2 can be made compact in the up-down direction.

In this embodiment, the entire exhaust gas purifying means 3 is provided in the expansion chamber 2. However, as in the exhaust gas purifying apparatus 1A shown in FIG.
0, the lower part of the catalyst case 20 is projected downward from the muffling case 6, and the catalyst case 20 is hermetically mounted and fixed in the mounting hole 40.
The buffer case 41 that covers the lower part of the
The downstream exhaust pipe 5 may be connected to the buffer case 41. However, this exhaust gas purifying apparatus 1A constitutes the present invention.
It does not.

[0030]

According to the exhaust gas purifying apparatus for a small engine according to the present invention, the expansion chamber and the exhaust gas purifying means have a simple structure in which the entire exhaust gas purifying means is housed in a muffling case. The exhaust pipe for connecting the exhaust gas can be omitted, and it is not necessary to secure the space for the exhaust gas purifying means, which is completely separate from the space for the expansion chamber. In addition, the exhaust gas purifying device can be made as small as possible. Further, since the exhaust gas purifying means is directly connected to the expansion chamber, the exhaust passage is shortened by that amount, and a decrease in engine performance can be prevented. Further, since the exhaust gas purifying means is heated and kept warm by the exhaust gas in the expansion chamber,
It is possible to quickly raise the temperature of the exhaust gas purifying means to activate the catalytic substance, thereby efficiently improving the purifying performance in the initial stage of the start-up. Sufficient purification performance can be ensured by suppressing temperature drop, temperature rise of exhaust gas purification means at high load can be suppressed, and thermal deterioration of exhaust gas purification means can be prevented. It is possible to prevent the occurrence of a fire or the like due to contact with another object beforehand.

According to the second aspect of the present invention, the monolith carrier is prevented from moving in the axial direction by forming the annular restricting portion and the projecting portion having a simple structure on the bottom wall portion and the lid member of the case body, respectively. At the same time, the expansion chamber can be made smaller in the axial direction of the catalyst case.

According to the third aspect of the present invention, the simple structure of providing the cushion material and the seal / cushion material prevents damage to the monolith carrier due to vibration or the like, while preventing the monolith carrier from being axially moved with respect to the catalyst case. Movement can be regulated. Further, the amount of unpurified gas discharged can be reduced as much as possible by the seal and cushion material. According to the device of claim 4, with a simple configuration of providing the catalyst support bracket, while preventing damage to the monolith carrier due to vibration and the like,
The movement of the monolith carrier in the radial direction with respect to the catalyst case can be restricted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an expansion chamber and a catalytic converter.

FIG. 2 is an exploded perspective view of a catalytic converter.

FIG. 3 is a longitudinal sectional view of a catalyst supporting bracket, a sealing material, and a monolithic carrier.

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

FIG. 5 is a schematic explanatory view of an exhaust gas purifying device having another configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Exhaust gas purifier 2 Expansion chamber 3 Exhaust gas purifying means 4 Upstream exhaust pipe 5 Downstream exhaust pipe 6 Silencing case 6a Upper wall 6b Side wall 6c Lower wall 10 Catalytic converter 11 Buffer case 12 Buffer space 13 Monolith carrier 14 Rotation regulating member 15 Communication hole 20 Catalyst case 21 Case main body 22 Lid member 23 Annular regulating portion 24 Projecting portion 25 Gas exhaust hole 26 Flange 27 Annular regulating portion 28 Projecting portion 29 Gas introduction hole 31 Catalyst support fitting 32 Annular gap 33 Seal and seal Cushion material 33a Thrust receiving portion 33b Skirt portion 34 Cushion material 34a Thrust receiving portion 34b Skirt portion 1A Exhaust gas purifying device 40 Mounting hole 41 Buffer case

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI F01N 3/28 311 F01N 3/28 311S 1/02 1/02 J (72) Inventor Hidetomo Kida 2-chome, Torai, Toyonaka-shi, Osaka No. 6-5 Domestic Parts Industry Co., Ltd. (72) Inventor Toichi Maekawa 2-chome, Torainaka-shi, Osaka 2-6-5 Domestic Produced Parts Industry Co., Ltd. (72) Inventor, Masahiro Tatsumi 2-chome, Torinaka-shi, Osaka No. 5 Domestic Parts Industry Co., Ltd. (72) Inventor Hironao Fukunishi 2-6-5, Asari, Toyonaka City, Osaka Pref. Domestic Parts Industry Co., Ltd. (56) References JP-A-5-179938 (JP, A) JP-A-5-256129 (JP, A) JP-A-58-35217 (JP, A) JP-A-55-170409 (JP, U) JP-A-54-81016 (JP, U) Int.Cl. ⁷ , DB name) F01N 3/28 F01 N 3/24

Claims (4)

(57) [Claims] 1. A have an expansion chamber which is interposed in the middle portion of the exhaust passage and the exhaust gas purification means, bulging into the hollow box-shaped silencer casing
Forming an expansion chamber, and an exhaust gas purifying means in the expansion chamber.
An exhaust gas purifying apparatus for a small engine that houses the entirety of the above, wherein as the exhaust gas purifying means, a cylindrical catalyst case having a gas introduction hole at an upstream end and a gas exhaust hole at a downstream end; A monolithic carrier having a plurality of communication holes extending from the upstream side to the downstream side of the case, fixedly held in the catalyst case, and a cylindrical buffer surrounding the downstream side portion of the catalyst case
The case, the upper end is airtight in the middle of the catalyst case
And the lower end in an airtight manner
And a cylindrical buffer case that forms a buffer space connected to the external space in the expansion chamber.The internal space of the catalyst case is communicated with the expansion chamber through the gas introduction hole, and the gas exhaust hole is formed through the gas discharge hole. An exhaust gas purifying device for a small engine, wherein the exhaust gas purifying device communicates with a buffer space. 2. A catalyst case comprising: a bottomed cylindrical case body;
A lid member that closes the opening of the case body, and an outer peripheral portion of the bottom wall portion of the case body and an outer peripheral portion of the lid member each having an annular regulating portion that regulates movement of the monolith carrier in the axial direction. In the central portion of the bottom wall of the case body and the central portion of the lid member, a protruding portion protruding outward in a truncated cone shape is formed, a gas discharge hole is formed in the conical wall portion of the downstream protruding portion, and 2. The exhaust gas purifying apparatus for a small engine according to claim 1, wherein a gas introduction hole is formed in each of the conical walls of the protruding portions on the side. 3. An annular seal / cushion material is mounted on one side between the annular regulating portion of the lid member and the monolith carrier or between the annular regulating portion on the bottom wall of the case body and the monolith carrier, and the annular cushion material is attached to the other. The exhaust gas purifying apparatus for a small engine according to claim 2, which is mounted. 4. A small engine for a small engine according to claim 1, further comprising a cylindrical catalyst support member for elastically holding the monolith carrier with respect to the catalyst case, between the peripheral wall portion of the catalyst case and the monolith carrier. Exhaust gas purification device.