JPH0234409Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a muffler for a spark ignition gasoline engine with a carburetor.

[Conventional technology]

FIG. 6a shows this type of spark ignition gasoline engine. In the figure, 1 is an engine, and 2 is a carburetor that supplies fuel, which supplies an appropriate amount of fuel depending on the amount of air that the engine takes in. 3 is a silencer. Figure 6b shows a sectional view of the silencer, where 3a is the silencer body, 3b is the inlet pipe, 3d is the outlet pipe, and 3f
7 is the inlet pipe, 7 is the exhaust flow, and 8 is the hot spot at the corner. Generally, an engine can be stopped by turning on a stop switch (not shown), but the air-fuel mixture is supplied from the carburetor even when the engine is idling between the time the engine starts to stop and the engine completely stops, and is discharged unburned. For this reason, the silencer may be filled with unburned air-fuel mixture, which may ignite and explode at hot spots, producing an abnormally loud sound (afterburn).

In order to prevent this afterburn, a solenoid valve is provided in the fuel system, and the solenoid valve is closed at the same time as a stop switch is turned on, thereby stopping the fuel supply to the engine.

[Problem that the invention attempts to solve]

The occurrence of afterburn is not only undesirable in terms of noise countermeasures, but also poses problems such as damage to the silencer.

In addition, the method of installing a solenoid valve in the fuel system requires a power source to operate the solenoid valve, so it is applicable only to engines with batteries, and as a result of inserting the solenoid valve into the fuel system, vapor lock etc. In addition, there are other problems such as an increase in the number of engine parts and an increase in cost.

[Means for solving problems]

The purpose of this invention is to focus on the above points and provide an afterburn countermeasure other than the fuel stop method (electromagnetic valve).The main feature of this invention is that it connects to the engine exhaust port and opens into the silencer body. an inlet pipe extending downwardly within the silencer body;
It consists of an inlet pipe and a U-shaped pipe extending upward from the lower end, and an outlet pipe is provided at the lower part of the muffler main body.

[Effect]

In this case, an unburned mixture reservoir is provided in the silencer inlet pipe, that is, the exhaust passage that connects to the engine exhaust port and opens into the silencer body, to store the rich mixture that is discharged when the engine is stopped. and prevent afterburn.

The present invention can be widely applied to general-purpose engines.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

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

In the figure, 3a is a main body of the muffler, 3b is an inlet pipe, 3c is a U-shaped pipe arranged in the vertical direction, and 3d is an outlet pipe. In addition, 1 is an engine, 3 is a silencer, 4 is a baffle plate, 5 is an exhaust valve, 6 is an exhaust port,
7 indicates the flow of exhaust gas.

The operation in the case of the above configuration will be described.

The volume of the U-shaped tube 3c is larger than the capacity of the unburned mixture discharged when the engine is stopped, that is, the highly concentrated gas exceeding the explosion limit, which is of particular importance. Concentrated gas remains in the area.

FIG. 2 is a sectional view showing a silencer according to a second embodiment. The distal end portion 30c of the U-shaped tube 3c in FIG. 1 is made to protrude to the outside of the muffler main body 3a.
Since the U-shaped tube tip 30c is exposed to the atmosphere,
The combustion exhaust gas is further cooled and the muffler temperature is lowered.

FIG. 3 is a sectional view showing a muffler according to a third embodiment. A double pipe 31 is used instead of the U-shaped pipe 3c.

FIG. 4 is an explanatory diagram showing a silencer according to a fourth embodiment. A U-shaped tube 3c is provided outside the muffler main body 3a.

FIG. 5 is a sectional view showing a silencer according to a fifth embodiment. In this way, the muffler cover 3e may be provided in the muffler of the above invention, and the engine cooling air from the air guide plate 4 may be guided into the muffler cover to forcibly cool the muffler 3.

[Effect of idea]

The above case has the following effects.

In the case of the first embodiment, the mixture remains in the U-shaped pipe portion as a rich gas. Therefore, the hot spot will not become an ignition source and explode because it will not flow into the silencer body and be diluted to reach the explosive limit concentration.

In the case of the second embodiment, the silencer is further cooled by exposure to the atmosphere and the temperature of the muffler is lowered, which is more effective in preventing afterburn.

The operations and effects of the third embodiment and the fourth embodiment are the same as those of the first embodiment.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a silencer according to a first embodiment of the present invention, FIG. 2 is a sectional view showing a silencer according to a second embodiment, and FIG. 3 is a sectional view showing a silencer according to a third embodiment. , FIG. 4 is an explanatory diagram showing the silencer of the fourth embodiment,
FIG. 5 is a sectional view showing the silencer of the fifth embodiment, and FIG.
FIG. 6a is a sectional view showing a spark ignition gasoline engine, and FIG. 6b is a sectional view showing the muffler of FIG. 6a. 3a...silencer body, 3b...inlet pipe, 3c...
...U-shaped pipe, 3d...exit pipe, 6...exhaust port.

Claims (1)

[Scope of utility model registration request] In a spark ignition gasoline engine with a carburetor, the exhaust passage connected to the exhaust port of the engine and opening into the muffler main body is formed by an inlet pipe extending downward within the muffler main body and a U extending upward from the lower end of the inlet pipe.
What is claimed is: 1. A silencer characterized in that the silencer is composed of a square tube and an outlet tube is provided at the bottom of the silencer main body.