JPH09166020A - Secondary air supply device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply secondary air to the upstream side of a catalyst without using any negative pressure caused by exhaust pulsation. SOLUTION: An output transmission device 4 is provided in the protruding part of a crankshaft protruded to the outside of an engine 1 and a catalyst 18 is provided in the middle way of an exhaustion device 7 (10) connected to the engine 1. In the engine 1 constructed in such a manner, a fan blade 20 for blowing wind is provided in the output transmission 4, this output transmission 4 is covered by a cover 21, this cover 21 is connected to the exhaustion device 7 (10) through a wind guiding duct 22 and the connected part 23 of a wind guiding duct 22 in the exhaustion device 7 (10) side is arranged in the upstream side of the catalyst 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine secondary air supply device.

[0002]

2. Description of the Related Art Exhaust gas emitted from an internal combustion engine such as a gasoline engine includes carbon monoxide (CO) and hydrocarbons (H).
C) and harmful components such as nitrogen oxides (NOx). Exhaust gas purification devices for rendering these harmful components harmless are roughly classified into two.

One is to achieve complete combustion of fuel in a combustion chamber of an engine to prevent generation of harmful components. The other is to make the exhaust gas discharged from the combustion chamber of the engine harmless before it is released to the atmosphere, even if it contains harmful components.

As a means for purifying the latter exhaust gas, a catalyst composed of platinum, rhodium and palladium is provided in the exhaust device, and the exhaust gas discharged from the combustion chamber of the engine is brought into contact with this catalyst to carry out a chemical reaction. In some cases, the harmful substances are converted into carbon dioxide (CO ₂ ), water (H ₂ O), nitrogen (N ₂ ), etc. to render them harmless.

For example, as shown in FIG. 5, an exhaust purification system for an engine Eg used in a small boat is an exhaust system Ex.
Catalyst Ct in the middle of the exhaust pipe Ep which is a part of
Is arranged, and the exhaust gas is purified by passing the exhaust gas through the catalyst Ct.

Secondary air may be supplied to the upstream side of the catalyst in order to accelerate the reaction of the catalyst. Then, it is general to use the negative pressure due to the pulsation of the exhaust gas to supply the secondary air.

[0007]

However, in the case of utilizing the pulsation of exhaust gas to supply the secondary air, there is no particular problem as long as the exhaust pipe length of the exhaust device is set in consideration of the arrangement of the catalyst in advance. However, it is difficult to change the exhaust pipe length when retrofitting a catalyst to an existing engine.

Further, in the case of the two-cycle engine, the negative pressure of the pulsation generated in the exhaust pipe is small and it is not possible to supply sufficient secondary air.

Further, as the engine speed increases, the exhaust pressure increases, making it difficult to utilize the negative pressure due to pulsation.

The present invention has been made in view of the above circumstances, and provides a secondary air supply device for an engine capable of supplying secondary air to the upstream side of the catalyst without utilizing the negative pressure due to the pulsation of exhaust gas. The purpose is to do.

[0011]

In order to solve the above-mentioned problems, a secondary air supply system for an engine according to the present invention is provided.
As set forth in claim 1, in an engine having a catalyst in the middle of an exhaust device connected to the engine, the output transmission device is provided on the protrusion of the crankshaft protruding outside the engine, and A fan blade for blowing air is provided, the output transmission device is covered with a cover, and the cover and the exhaust device are connected by an air guide duct, and the exhaust device side connection portion of the air guide duct is connected to the upstream side of the catalyst. It was placed in.

[0012]

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

FIG. 1 is a left side view of a two-cylinder two-cycle engine used in a water jet propulsion boat or the like. 2 is a plan view of this engine, and FIG. 3 is
It is a rear view of this engine.

As shown in FIGS. 1 to 3, this engine 1
At the top of the crankcase 2 of the cylinder assembly 3
Is provided upright. A crankshaft (not shown), which is an output shaft, is provided in the crankcase 2, and one end of the crankshaft is projected to the outside of the engine 1. The propeller shaft 5 is connected to the protruding portion of the crankshaft via a coupling device 4 which is an output transmission device.

On the other hand, an intake device 6 is provided on the right side of the cylinder assembly 3, and an exhaust device 7 is provided on the left side thereof. The exhaust device 7 includes an exhaust manifold 9 fixed to an exhaust port 8 opening on the left side surface of the cylinder assembly 3, an exhaust pipe 10, an exhaust muffler 11, and an exhaust pipe 1 that are sequentially connected to the exhaust manifold 9.
2 is provided.

The exhaust manifold 9 is formed in a block shape and is fixed to the cylinder assembly 3 with bolts 13. The exhaust manifold 9 has an inverted Y-shaped shape in which a plurality of exhaust gas flows discharged from the exhaust ports 8 in the present embodiment are combined and flowed upward. A joint flange 1 is provided on top of the exhaust manifold 9.
4 is formed, and the joint flange 15 formed on the exhaust pipe 10 is fixed to the joint flange 14 with bolts 16.

The shape of the exhaust pipe 10 extends upward from the junction with the exhaust manifold 9 and immediately curves toward the front, and extends forward while gradually inclining downward, and finally downward. It curves and connects to the exhaust muffler 11. In addition, a split portion 17 is formed at an intermediate portion of the exhaust pipe 10,
Is divided into the first half 10a and the second half 10
and b. Then, the catalyst 18 is arranged on the inner surface of the first half portion 10a of the exhaust pipe 10 on the side of the divided portion 17.

Exhaust pipe 10 and exhaust muffler 11
The connection part with is connected by a joint pipe 19. The exhaust muffler 11 extends downward from the connection portion with the exhaust pipe 10, bends rearward immediately, and extends rearward substantially horizontally and is connected to the exhaust pipe 12. Exhaust muffler 11
The intermediate portion of the is expanded radially to form an expansion chamber (not shown) therein.

A fan blade 20 for blowing air is integrally or integrally provided on the outer peripheral surface of the coupling device 4 which connects the crankshaft and the propeller shaft 5. Further, the periphery of the coupling device 4 is covered with the cover 21. One end of an air guide duct 22 is connected to the cover 21, and the other end of the air guide duct 22 is connected to the vicinity of the split portion 17 of the latter half portion 10b of the exhaust pipe 10.

FIG. 4 is an enlarged sectional view of a connecting portion between the air duct 22 and the rear half portion 10b of the exhaust pipe 10. As shown in FIG. 4, in the vicinity of the split portion 17 of the latter half portion 10b of the exhaust pipe 10, that is, on the upstream side of the catalyst 18, the exhaust device 7 side connection portion 23 of the air duct 22 is integrally or separately formed. The air guide duct 22 is connected to the connecting portion 23. Further, one valve such as a reed valve 24 is arranged in the connecting portion 23 of the air duct 22 to prevent the exhaust gas in the exhaust pipe 10 from flowing back to the air duct 22.

Next, the operation of the present embodiment will be described.

To promote the reaction of the catalyst 18, the catalyst 1
It is desirable to supply secondary air to the upstream side of 8. In the present invention, when the crankshaft of the engine 1 rotates, wind is generated by the fan blade 20 on the outer peripheral surface of the coupling device 4, and this wind is supplied to the upstream side of the catalyst 18 as secondary air through the air duct 22. It

In the case of the two-cycle engine, the negative pressure of the pulsation generated in the exhaust pipe 10 is small, and even if the secondary air cannot be supplied sufficiently, the fan blade 20 forcibly generates the secondary air. Since it is supplied, the amount of secondary air can be increased.

Further, in the present invention, since the fan blades 20 generate the secondary air, it is not necessary to use the pulsation of the exhaust gas to supply the secondary air, and even when the catalyst 18 is retrofitted to the existing engine, Exhaust pipe 1
There is no need to change 0 length.

Furthermore, since the fan blades 20 are directly connected to the crankshaft of the engine 1, the supply amount of secondary air increases as the rotation of the engine 1 increases, and the secondary air supply amount in the high rotation speed range of the engine 1 increases. There is no shortage of secondary air.

[0026]

As described above, according to the secondary air supply system for an engine of the present invention, the output transmission device is provided on the protruding portion of the crankshaft protruding outside the engine, and is connected to the engine. In an engine equipped with a catalyst in the middle of an exhaust device, a fan blade for blowing is provided in the output transmission device, while covering the output transmission device with a cover, the cover and the exhaust device are connected by an air duct, Since the exhaust device side connecting portion of the air guide duct is arranged on the upstream side of the catalyst, when the crankshaft of the engine rotates, wind is generated by the fan blade of the output transmission device, and this wind blows the air guide duct. After that, the secondary air is supplied to the upstream side of the catalyst. As a result, the secondary air can be supplied to the upstream side of the catalyst without using the negative pressure due to the pulsation of exhaust gas.

[Brief description of the drawings]

FIG. 1 is a left side view of a two-cylinder two-cycle engine showing an embodiment of an engine secondary air supply system according to the present invention.

FIG. 2 is a plan view of the engine shown in FIG.

FIG. 3 is a rear view of the engine shown in FIG.

FIG. 4 is an enlarged cross-sectional view of a connection portion between the air duct and the latter half of the exhaust pipe.

FIG. 5 is a diagram showing a general engine.

[Explanation of symbols]

 1 Engine 4 Coupling Device (Output Transmission Device) 7 Exhaust Device 9 Exhaust Manifold (Exhaust Device) 10 Exhaust Pipe (Exhaust Device) 11 Exhaust Muffler (Exhaust Device) 18 Catalyst 20 Fan Blade 21 Cover 22 Wind Guide Duct 23 Wind Guide Duct Exhaust device side connection part

Claims (1)

[Claims] 1. An engine provided with a power transmission device on a protruding portion of a crankshaft projecting to the outside of the engine, and a catalyst provided in the middle of an exhaust device connected to the engine for blowing air to the power transmission device 4. Fan blade 2
0 is provided, the output transmission device 4 is covered with a cover 21, and the cover 21 and the exhaust device 7 (10) are connected by an air guide duct 22. The exhaust device 7 (10) of the air guide duct 22 is connected. A secondary air supply device for an engine, characterized in that the side connecting portion (23) is arranged on the upstream side of the catalyst (18).