JPH0223774Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a muffler in a general-purpose engine used in a power pest control machine, a lawn mower, an agricultural work machine, etc.

[Prior art and its problems]

Generally, the casing of a muffler for a general-purpose engine has an exhaust gas inlet on one side, an exhaust gas outlet on the other side, and a partition plate with an exhaust gas vent in the middle.

Inside this muffler housing, a through pipe for muffler mounting bolts is installed, and an exhaust gas passage for noise reduction is formed (for example,
No. 56-17314, Utility Model Application No. 56-83628), the structure is complicated and manufacturing is extremely troublesome.

For this reason, recently, as shown in Figs. 1 and 2, a sound-muffling pipe 3, which is a combination of two half-pipe pipes that integrate the through-pipe 1 of the muffler mounting bolt and the muffling exhaust gas passage 2, has been developed. The muffler is held within the casing.

By the way, these muffling pipes 3 have a large number of circular or oval exhaust gas vent holes 8 in the circumferential direction of the cylindrical part forming the exhaust gas passage 2 in order to flow gas from the exhaust gas passage 2 into the muffler chamber. It is drilled. The ventilation holes 8 are formed by punching with a press, but since the pitch of the ventilation holes 8 is small and there are a large number of them, the punching process requires several steps, which causes an increase in costs. Moreover, the total dimension of the inner circumferential edge of the gas vent hole 8 is large and acts as a resistance to the gas flow passing through the gas vent hole 8, generating frictional noise and becoming a new source of secondary noise.

[Purpose of invention]

The present invention was developed to solve the above problems, and consists of forming a noise-reducing exhaust gas passage by combining two half pipes, and forming a large gas vent by cutting out a part of the butt part of the half pipes. The object of the present invention is to provide a muffler for a general-purpose engine in which a muffler pipe is retained and fixed in a muffler casing, which eliminates the need to press many small gas vent holes and improves the muffler effect.

[Structure of the idea]

An embodiment of a muffler for a general-purpose engine according to the present invention will be described with reference to FIGS. 3, 4, and 5. The muffler housing 10 includes an outer housing 12 having an exhaust gas inlet 11 at the lower part of one side, and an outer housing 12 having an exhaust gas inlet 11 at the lower part of the other side. An outer casing 14 having an exhaust gas outlet 13 is butted against the partition plate 16 having an exhaust gas vent 15 therebetween, and the peripheral edges thereof are crimped and fixed to form muffler chambers 17 and 18 inside. be. The exhaust gas vent 15 of the partition plate 16 is offset from the exhaust gas inlet 11 and the exhaust gas outlet 13 so as not to overlap with each other.

Inside the muffler housing 10, there is a half pipe 19.
are put together to form an exhaust gas passage 20 with a circular cross section, and one side of each abutting portion is rolled outward in a circular shape alternately to form a through chamber 22 for the muffler mounting bolt 21, A muffling pipe 24 is held in which an exhaust gas vent hole 23 is formed by shallowly notching the front half of the other side in the longitudinal direction. That is, a through hole 25 having the same external shape as the sound deadening pipe 24 bored in the lower part of the partition plate 16
, penetrate the sound deadening pipe 24 and connect its front end to the outer casing 1.
The outer protrusion 26 on the periphery of the exhaust gas inlet 11 of No. 2
It abuts against a backing plate 28 having an exhaust gas vent 27 inserted therein, and its rear end is held by being fitted into an inner protrusion 29 provided at the lower part of the outer casing 14.

Muffler attachment bolts of the noise-reducing pipe 24 are passed through both upper and lower sides of the exhaust gas introduction hole 11 of the outer protrusion 26, upper and lower sides of the exhaust gas vent 27 of the backing plate 28, and upper and lower sides of the inner protrusion 29, respectively. Room 22
A bolt insertion hole 30 is provided that matches the .

In addition, although the exhaust gas passage 20 of the muffler pipe 24 in the muffler of the above embodiment has a circular cross section,
The exhaust gas passage 20' is not limited to this, but may have a rectangular cross section as shown in FIG. 6, for example.
Furthermore, the exhaust gas passage 20'' may have an oval cross section as shown in FIG. 7. Furthermore, the through chamber 22 of the muffler mounting bolt 21 is not limited to a circular cross section; A rectangular through-hole 22' may be used.Furthermore, a lip 34 curved outward may be formed at the opening edge of the exhaust gas vent 23 of the muffling pipe 24, as shown in FIG.

[Effect of invention]

The general-purpose engine muffler of the present invention constructed as described above has an exhaust gas vent 27' in the center on the end face of the exhaust pipe of the engine, as shown in FIG.
A gasket 32 having bolt insertion holes 30' formed above and below the gasket 32 is interposed therebetween for installation. That is, the outer protrusion 2 is formed on the end surface of the exhaust pipe 31 with the gasket 32 interposed therebetween.
6, align the exhaust gas inlet 11 with the exhaust pipe 31, and insert the muffler mounting bolt 21 into the bolt insertion hole 30 of the outer casing 14, the bolt penetration chamber 22 of the muffling pipe 24, and the bolt of the backing plate 28. insertion hole 30,
The muffler is mounted by passing through the bolt insertion hole 30 of the outer casing 12 and the bolt insertion hole 30' of the gasket 32, and screwing into the bolt hole 33 of the end face of the exhaust pipe 31.

In the muffler of the present invention attached to the end face of the exhaust pipe 31 in this way, the exhaust gas is passed through the gasket 32.
It enters the exhaust gas passage 20 of the muffling pipe 24 through the exhaust gas vent 27', the exhaust gas inlet 11 of the outer casing 12, and the exhaust gas vent 27 of the backing plate 28,
Half pipe 1 forming the passage 20 from here
It enters the muffler chamber 17 in the outer casing 12 through the exhaust gas vent 23 in the other front half of the abutting portion of the 9, and further passes through the exhaust gas vent 15 in the partition plate 16 to enter the muffler chamber 18 in the outer casing 14. The exhaust gas enters the inside and is discharged to the outside from the exhaust gas outlet 13.

In the flow of exhaust gas inside this muffler, when the exhaust gas that has entered the exhaust gas passage 20 of the muffler pipe 24 passes through the exhaust gas vent 23, one side smoothly flows out along the inner wall of the exhaust gas passage 20. do,
Since it enters the muffler chamber 17 inside the outer casing 12, there is little frictional resistance and air flow friction noise is reduced. Especially the 8th
When an outwardly curved lip 34 is formed on the opening edge of the exhaust gas vent 23 as shown in the figure, the exhaust gas flows out smoothly, resulting in extremely low frictional resistance and significantly reducing airflow friction noise. Can be reduced.
Further, as the exhaust gas flows along the inner wall of the exhaust gas passage 20 of the muffling pipe 24 toward the upper and lower exhaust gas vents 23, a circulation flow is generated in the exhaust gas, which attenuates acoustic pressure waves and also reduces the gas flow. Since the airflow is smoothly discharged, the effective opening area of the exhaust gas vent 23 is increased, and the actual opening area is required to be small, which effectively reduces exhaust noise.

[Effect of idea]

In the muffler for a general-purpose engine according to the present invention, the exhaust gas that enters the exhaust gas passage of the muffling pipe flows along its inner wall as described above, and smoothly flows through the muffler from the exhaust gas vent at the butt part of the two half pipes. Since it flows into the chamber, there is less frictional resistance.
Airflow friction noise is reduced, and the exhaust gas flows along the inner wall of the exhaust gas passage of the muffling pipe, creating a circular flow, which attenuates the acoustic pressure waves of the exhaust gas and allows the gas flow to be smoothly discharged. Ru. Therefore, exhaust noise is significantly reduced and the silencing function is greatly improved.

In addition, in the muffler of the present invention, the exhaust gas vent of the muffler pipe in the muffler housing is formed by a notch formed when punching the material at the butt part of the two halves of the pipe. There is no need to punch out a large number of circular or oval gas vent holes in the circumferential direction of the half-split pipe, and therefore the muffler and the muffler can be manufactured easily and inexpensively.

Furthermore, improving the noise reduction function through the muffler internal structure (the structure of the muffler pipe that circulates the exhaust gas) as described above is extremely difficult to achieve in general-purpose engines because the muffler volume cannot be increased due to design layout conditions. This is an important item, in other words, the improvement of the muffler's internal structure's silencing function is
Since the muffler itself can be made smaller, it has a great effect on making the engine smaller and reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a muffler pipe held inside a muffler of a conventional general-purpose engine, Fig. 2 is a sectional view of a conventional improved type of muffler pipe, and Fig. 3 is a muffler of a general-purpose engine according to the present invention. FIG. 4 is a cross-sectional view taken along line A-A in FIG. 3, FIG. 5 is a cross-sectional view taken along line B-B in FIG. 3, and FIGS. The figures are sectional views showing other examples of the muffler pipe in the muffler of the present invention. 10...Muffler housing, 11...Exhaust gas inlet, 13...Exhaust gas outlet, 15...Exhaust gas vent, 16...Partition plate, 19...Half pipe, 2
0... Exhaust gas passage, 21... Muffler mounting bolt, 22... Penetration chamber, 23... Exhaust gas vent, 24... Sound deadening pipe.

Claims (1)

[Scope of utility model registration request] A muffler chamber is partitioned in the front and rear by vertically oriented partition plates, and an exhaust gas passage is formed in the vertically oriented partition plates by combining two half pipes, and the extensions on one side of the abutting portion are staggered. A noise-reducing pipe that is wound outward to form a through-hole for a muffler mounting bolt is passed through, and an exhaust gas vent is formed by cutting out a part of the side of the exhaust gas passage that does not form a bolt-through-chamber, thereby forming an exhaust gas passage. A general-purpose engine muffler characterized by a communicating muffler chamber at the front.