JP2565396Y2 - Muffler cooling system in forced air-cooled overhead valve engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure of an exhaust silencing system in a forced air-cooled overhead valve engine.

[0002]

2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 52-120242, air cleaners are arranged on one side of an engine body and muffler bodies are arranged on the other side of the engine body. In some cases, the muffler body and the muffler tail tube are covered with a muffler cover.

[0003]

However, in the above-mentioned prior art, the muffler tail tube extends straight from the muffler body to the outside of the bonnet, and its dimension is shortened.
For this reason, the amount of heat radiation in the muffler tail tube is reduced, and the exhaust gas passing through the muffler tail tube is not cooled much. As a result, the outlet temperature of the exhaust gas cannot be reduced too much, and as a result, the exhaust gas expands rapidly at the outlet of the muffler tail pipe to generate noise, thereby causing a problem that the noise reduction performance of the exhaust noise cannot be improved so much. . The present invention has been made in view of such a point, and an object of the present invention is to provide a muffler cooling device capable of sufficiently lowering the exhaust gas outlet temperature and improving the noise reduction performance of exhaust noise.

[0004]

In order to achieve the above object, according to the present invention, air cleaners are arranged on one side of the engine body and left and right sides of the engine body, and muffler bodies are arranged in the front and rear directions on the other side of the engine body. The muffler tail pipe derived from the front end of the muffler body is formed by folding back and piping backward, and the muffler body, muffler tail pipe and exhaust introduction pipe are covered with a muffler cover. The muffler body and muffler tail are communicated with the inside and blow a part of the engine cooling air blown up in the fan case into the muffler cover to allow the engine cooling air introduced into the muffler cover to flow backward. It is characterized in that the pipe and the exhaust introduction pipe are configured to be cooled.

[0005]

The present invention operates as follows, for example, as shown in FIGS. A part of the engine cooling air blown in the fan case (10) by the cooling fan (11) is blown into the muffler cover (18), and flows backward through the muffler cover (18) so that the muffler body ( 16), cool the muffler tail pipe (17) and the exhaust introduction pipe (23). And the muffler tail tube (17)
However, by being folded back in the muffler cover (18), the size of the muffler tail tube (17) in the muffler cover (18) becomes longer, and the amount of heat radiation from the muffler tail tube (17) increases. I do.
As a result, the exhaust gas passing through the muffler tail pipe (17) is exposed to the low-temperature engine cooling air for a long time and is strongly cooled.

[0006]

1 shows an embodiment of the present invention, FIG. 1 is an enlarged view of a main part, FIG. 2 is a partially longitudinal front view of an engine unit, FIG. 3 is a partially cross-sectional plan view of an engine unit, and FIG. FIG. 5 is a partial perspective rear view of the engine unit, and FIG. In this engine unit, an engine body (1) of a forced air-cooled overhead valve engine is housed in a decorative cover (2), and the interior of the decorative cover (2) is divided into two parts by a partition wall (3). Are partitioned into an engine body accommodating chamber (4), a muffler accommodating chamber (5), and an air cleaner accommodating chamber (6).

Engine body of a forced air-cooled overhead valve engine
(1) The intake port on the front wall of the head block (7)
(8), an exhaust port (9) is opened in the rear wall, the front of the engine body (1) is covered with a fan case (10), and a cooling fan (11) arranged in the fan case (10). The engine cooling air generated by the above is formed so as to flow from the front to the rear in the engine body accommodating chamber (4). Further, an air cleaner (12) and a carburetor (13) are housed in an air cleaner housing chamber (6) formed on the left side of the engine body housing chamber (4).

An exhaust muffler unit (14) is disposed in the muffler housing chamber (5) formed on the right side of the engine body housing chamber (4) along the front-rear direction. This exhaust silencer unit (1
4) is a cylindrical muffler body (16) containing a catalyst (15) inside, a muffler tail pipe (17) derived from the muffler body (16), and a muffler body (16) and a muffler tail pipe (17) Muffler cover (1
8).

The muffler tail tube (17) is led out forward from the front end wall (19) of the muffler main body (16), and then folded back in a vertical plane to face backward along the upper surface of the muffler main body (16). The muffler cover (18) is located at the rear end wall (2
It is arranged so as to face the exhaust port (21) formed at the opening (0). An exhaust port (22) corresponding to the exhaust port (21) is formed on the wall surface of the decorative cover (2) facing the rear end wall (20) of the muffler cover (18). The muffler cover (18) is formed in a shape capable of covering the outer periphery of the other surface except for the front side of the exhaust introduction pipe (23) connecting the exhaust port (9) and the muffler body (16).

The inside of the muffler cover (18) communicates with the inside of the fan case (10) at a portion near the front end thereof, and a part of the engine cooling air blown by the cooling fan (11) is supplied to the muffler cover (18). It is configured to be introduced into (18) and flow through the muffler cover (18) from front to back. The engine cooling air introduced into the muffler cover (18) is diverted at a portion near the rear end in the muffler cover (18), and opens to the rear end wall (20) of one muffler cover (18). Through the exhaust port (21), the makeup cover (2) from the air outlet (22) of the makeup cover (2)
Discharged outside, the other flows along the exhaust inlet pipe (23),
The cooling air flows into the decorative cover (2) through the cooling air vent (24) formed at the end thereof, and joins the cooling exhaust air after cooling the engine body (1) to form the engine body housing chamber (4). ), The exhaust outlet (28) formed in the decorative cover (2) corresponding to the back side
From the makeup cover (2).

In the drawing, reference numeral (25) denotes an air guide plate disposed on the engine body (1), (26) denotes an outside air intake passage formed in a decorative cover (2), and the outside air intake passage (26). Is the air cleaner containment room
A compartment is formed at the lower end of (6), and the outside air intake (27) is open at the lower part on the back side of the decorative cover (2). Then, a part of the intake outside air flowing in the outside air intake passage (26) is sucked into the air cleaner (12) in the air cleaner accommodation chamber (6) as combustion air, and the remaining intake outside air is supplied to the engine body accommodation chamber ( It flows into the portion near the front end of 4) and flows into the fan case 10 as engine cooling air.

[0013]

The present invention has the following effects since it is constructed and operates as described above. Since the muffler tail tube is folded back in the muffler cover, the size of the muffler tail tube cooled by the engine cooling air in the muffler cover becomes longer, and the amount of heat radiation from the muffler tail tube can be increased.

That is, the exhaust gas passing through the muffler tailpipe is exposed to the low temperature engine cooling air for a long time and is strongly cooled, whereby the exhaust outlet temperature is lowered and the exhaust gas at the outlet of the muffler tailpipe is reduced. Abrupt expansion can be suppressed, and the noise reduction performance of exhaust noise can be improved.

Moreover, since the muffler tail pipe is thinner than the muffler main body and the exhaust introduction pipe, even if the muffler tail pipe is folded and piped, it does not become too bulky, thereby preventing the muffler cover from being enlarged. .

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part.

FIG. 2 is a partial longitudinal front view of the engine unit.

FIG. 3 is a partial cross-sectional plan view of the engine unit.

FIG. 4 is a partial longitudinal rear view of the engine unit.

FIG. 5 is a perspective view of the muffler device taken out.

[Explanation of symbols]

1: engine body, 8: intake port, 9: exhaust port, 10: fan case, 11: cooling fan, 12
... air cleaner, 16 ... muffler body,
17… Muffler tail tube, 18… Muffler cover,
23 ... exhaust pipe.

Claims (1)

(57) [Scope of request for utility model registration] 1. An engine body of a forced air-cooled overhead valve engine.
The fan case (10) is arranged so as to surround the cooling fan (11) arranged in front of (1), and the intake port (8) is provided on the front of the engine body (1) and on the rear surface of the engine body (1). In a forced air-cooled overhead valve engine having an exhaust port (9) opened, air cleaners (12) are arranged on one side of the engine body (1) and muffler bodies (16) are arranged on the other side of the engine body (1). The muffler tail pipe (17) led out from the front end of the muffler main body (1) is folded back to form a pipe backward, and the muffler body (16), the muffler tail pipe (17) and the exhaust introduction pipe Cover (23) with muffler cover (18)
The part near the front end inside (18) communicates with the inside of the fan case (10), and a part of the engine cooling air blown in the fan case (10) is blown into the muffler cover (18). , The engine cooling air introduced into the muffler cover (18) is blown backward, and the muffler body (16) and the muffler tail pipe (1
7) A muffler cooling device for a forced air-cooled overhead valve engine, wherein the muffler cooling device is configured to cool the exhaust introduction pipe (23).