JPS5853165B2 - 2 cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for purifying exhaust gas from a two-stroke engine using a catalytic converter.

In general, it is desirable to install the catalytic converter as far upstream as possible in the exhaust system from the viewpoint of activation temperature.

However, from a performance standpoint, with a two-stroke engine, if the conditions of the diffuser, front muffler, etc. are compromised, the output will drop significantly and the fuel efficiency will also deteriorate.

This invention purifies exhaust gas and extends the life of the catalyst without degrading engine performance.

The configuration of the present invention will be explained below with reference to the drawings.

As shown in FIG. 1, this invention enables the rear end of the front muffler 2 to be opened without changing the expansion chamber a of the conventional diffuser-type front muffler 2 connected upstream of the exhaust system of the two-stroke engine 1. A pre-catalytic converter 3 is installed in the pre-catalytic converter 3, and air is supplied upstream and downstream of the pre-catalytic converter 3 via an air controller 5 by an air pump 4 driven by an engine.

A main catalytic converter 6 is installed downstream of the pre-catalytic converter 3.

The outlet of the front muffler 2 and the inlet of the main catalyst converter are connected by a flexible pipe 7 for absorbing engine vibrations.

The air supplied upstream of the pre-catalytic converter 3 is
This is to assist the combustion reaction of exhaust gas by the pre-catalytic converter 3, and the air supplied downstream of the pre-catalytic converter 3 is used to prevent the flexible pipe 7 from overheating due to high-temperature exhaust gas and to reduce the exhaust gas from the main catalytic converter 6. This is to assist the combustion reaction of the gas.

The catalyst bed of the catalytic converter is cylindrical or truncated,
Structured so that gas flows from the outside to the inside (
Although a radial flow type is shown in the figure, a cross or other configuration may also be used.

Inner cylinder 3a of catalyst bed screen of pre-catalytic converter 3
A pulp mechanism 8 is provided in the upstream extension of the catalyst bed, and when the catalyst bed temperature rises due to some abnormality on the engine side, a valve is opened to allow some gas to pass through, thereby preventing an abnormal rise in the catalyst temperature.

That is, a small hole is provided in the pre-catalytic converter 3, and a valve mechanism 8 is provided at the entrance of this small hole.

The valve mechanism 8 is a butterfly valve 8a as shown in FIG. 2, which detects the catalyst temperature and operates an actuator 9 to open and close the valve 8a.

Alternatively, as shown in FIG. 3, a reed valve 8b is provided, and when the gas flow rate increases significantly during high-load operation, the reed valve 8b opens due to gas pressure and allows some of the gas to pass through.

Alternatively, the reed valve 8b may be made of bimetal so that the valve 8b opens when the catalyst temperature reaches a predetermined temperature or higher.

Since this invention has the above configuration, it is possible to install the catalytic converter upstream of the exhaust system without changing the conditions of the exhaust tiff user, front muffler, etc. of a 2-cycle engine (that is, without degrading engine performance). In addition, it is possible to improve the activation of the catalyst, solve the problem of installation space for the pre-catalyst device, and improve the ease of attaching and detaching the pre-catalyst device.

In addition, the configuration of the pre-catalyst and main catalyst improves catalyst activation, and the provision of a valve mechanism on the pre-catalyst prevents abnormal rises in catalyst temperature, improving the durability of the catalyst. Air can be supplied to the system to prevent overheating of the exhaust system.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the entire apparatus of the present invention, and FIGS. 2 and 3 are partially enlarged views showing different embodiments of the pre-catalytic converter portion. 1... Engine, 2... Diffuser type front muffler, 3... Pre-catalyst device, 4...
... Air pump, 5 ... Air controller, 6 ... Main catalytic converter.

Claims (1)

[Claims] 1. In the exhaust system of a two-stroke engine that includes a pre-catalytic converter and a main catalytic converter, the pre-catalytic converter is installed at the rear of the diffuser-type front muffler, and air is supplied upstream and downstream of the pre-catalytic converter, and the pre-catalytic converter is A two-stroke engine characterized in that the catalytic converter is provided with a bypass passage and a valve for opening and closing the passage, and the throttle valve is controlled to open when the catalyst temperature is at a predetermined temperature or when the gas pressure increases due to an increase in the gas flow rate. Exhaust purification device.