JPS5810564B2 - internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a combustion chamber equipped with a spark plug with a main intake passage for introducing a mixture into the chamber during the intake stroke of the engine, and a sub-intake passage for introducing air or a lean mixture into the chamber. The intake passages are communicated through the main intake valve and the auxiliary intake valve, respectively, so that the air-fuel mixture can be effectively combusted, especially during low-load operation when it is difficult to achieve good combustion of the air-fuel mixture due to a decrease in charging efficiency.
Stirring and diluting the air-fuel mixture with the air or the lean air-fuel mixture and simultaneously scavenging air around the ignition plug, thereby improving ignition performance and enabling lean combustion of the air-fuel mixture;
The present invention relates to an internal combustion engine that reduces the content of unburned components in exhaust gas.

Conventionally, in such internal combustion engines, the auxiliary intake valves are opened and closed by a valve mechanism consisting of a camshaft and a rocker arm, so the valve mechanism is used together with the valve mechanism for the main intake valve and exhaust valve. Installation in the narrow valve operating chamber of the cylinder head is accompanied by various difficulties and has the drawback of significantly complicating the structure.

The present invention operates the sub-intake valve by the intake negative pressure generated in the combustion chamber, omitting the conventional mechanical valve mechanism for the sub-intake valve, and achieving a simple structure and reliable operation. It is an object of the present invention to provide the above-mentioned internal combustion engine having excellent durability.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 denotes an internal combustion engine body, and a combustion chamber 4 facing a piston 3 is formed in a head portion 2 of the engine. The screwed-on ignition plug 10 is faced.

Further, a main intake passage 5 and an exhaust passage 11 are opened in the combustion chamber 4, and a main intake valve 9 and an exhaust valve 13 are respectively provided in these openings, and these are connected to cams 7a and 7b that move with a crankshaft (not shown) and a rocker. It is opened and closed by the cooperation of arms 8a and ab.

A carburetor 14 is provided at the outer end of the main intake pipe 15 that connects to the main intake passage 5.
An air cleaner 16 is also attached to the carburetor 14.

The carburetor 14 introduces air purified by an air cleaner 16 into an intake passage 18 in a carburetor main body 17, and the negative pressure generated by the air flow causes the fuel stored in a float chamber 19 to be removed. is injected into the intake passage 18 from the main nozzle 20 and the low-velocity injection ports 21, 22, etc., thereby generating an air-fuel mixture, and the air-fuel mixture enters the combustion chamber 4.
The amount supplied to the throttle valve 23 is adjusted by adjusting the opening degree of the throttle valve 23.

The exhaust path 11 includes an exhaust pipe 24 with a silencer 25 interposed in the middle.
is connected.

26 is a sub-intake passage, one end of which is used when the throttle valve 23 is opened at a low opening;
It opens into the intake passage 18 upstream from this point, and the other end opens into the combustion chamber 4, and the opening is formed in the valve seat 27.

A guide cylinder 29 made of an oil-impregnated bearing material is fitted into the downstream inner wall of the sub-intake passage 26, and a bottomed cylindrical valve body 35 of the sub-intake valve 28 is slidably fitted therein.

The valve body 35 includes a hollow valve rod 2 that is slidably fitted onto the guide tube 29.
8a, and an umbrella-shaped valve part 28b that is integrally connected to the lower end of the valve seat 27 and can be brought into contact with and separated from the valve seat 27. A large number of blowholes 30, 30, .

Thus, the valve body 35 can completely shut off the nozzle holes 30, 30, . . . from the combustion chamber 4 when the valve portion 28b is in the closed position seated on the valve seat 27.

Further, a spring seat plate 31 is attached to the upper end of the valve rod 28a, and between this and the guide cylinder 29 is a valve spring 3 that springs the valve body 35 toward the closing position, that is, the sub-intake valve 28 in the closing direction.
2 will be reduced.

An annular shoulder 34 facing the lower surface of the spring seat plate 31 is formed on the inner wall of the sub-intake passage 26, and when the spring seat plate 31 comes into contact with the shoulder 34, the open position of the sub-intake valve 28 is restricted. be done.

Next, to explain the operation of this embodiment, during low load operation of the engine in which the throttle valve 23 of the carburetor 14 is held at a low opening position, during the intake stroke of the engine, the inside of the combustion chamber 4 is lowered as the piston 3 descends. When the main intake valve 9 is opened by the cam 7a moving as the piston 3 descends and the rocker arm 8a, this negative pressure passes through the main intake passage 5 and reaches the low-speed nozzle of the intake passage 18. 21, 22, low speed nozzle 21゜2
Fuel suitable for low-load operation is sucked out from the combustion chamber 2, and the resulting air-fuel mixture is supplied into the combustion chamber 4 through the main intake passage 5.

At the same time, the large negative pressure within the combustion chamber 4 acts on the lower surface of the valve portion 28b of the auxiliary intake valve 28, and moves the valve body 35 against the valve spring 32 to the open position, that is, the valve portion 28b is spaced apart from the valve seat 27. The air purified by the air cleaner 16 passes through the sub-intake passage 26 and the hollow part of the valve rod 28a to the blowhole 30, due to the effect of the negative pressure. The air is injected into the combustion chamber 4 from the nozzle holes 30, 30..., and the negative pressure in the combustion chamber 4 is high, especially when the engine is operating at low load, so the amount of air jetted out from the nozzle holes 30, 30... is large, and therefore the flow rate is low. Moreover, since each blowhole 30 is oriented in the tangential direction of the outer circumference of the valve rod 28a, the air injected into the combustion chamber 4 creates a vortex, which causes the spark plug 1
The burnt gas remaining around the 0 electrode is scavenged all at once, and the air-fuel mixture taken in from the main intake passage 5 is diluted and stirred.

Next, the main intake valve 9 closes in conjunction with the rise of the piston 3 in the compression stroke, and when the pressure in the combustion chamber 4 increases, the auxiliary intake valve 28 closes due to that pressure and the elastic force of the valve spring 32. When a spark discharge occurs at the spark plug 10 at the end of the compression stroke, the air around it has already been scavenged as described above, so ignition is sure to occur, and since the air-fuel mixture is stirred as described above, , even if the air-fuel ratio is lean, good combustion occurs, and as a result, exhaust passage 1 in the next exhaust stroke
The content of unburned components such as carbon monoxide and hydrocarbons in the exhaust gas discharged into the engine is reduced.

Next, during high-load operation of the engine when the throttle valve 23 of the carburetor 14 is opened to a high opening degree, combustion is originally performed well due to the improvement in the charging efficiency in the combustion chamber 4.
It is not necessary to inject air from the auxiliary intake passage 26 into the combustion chamber 4, and in response to this, the auxiliary intake valve 28 is
does not open or opens slightly.

This is because the throttle valve 23 is opened to a high degree, so the negative pressure generated in the combustion chamber 4 during the intake stroke is low, and the sub-intake valve 28
The opening force exerted on the carburetor 1 is significantly reduced, and the
The negative intake pressure introduced into the upper surface of the valve portion 28b of the intake valve 28 from the intake passage 18 of No. 4 through the auxiliary intake passage 26 increases and changes particularly during high-load operation of the engine, causing a relatively large closing of the auxiliary intake valve 28. By acting as a force.

Note that during low-load operation of the engine, the upstream end of the auxiliary intake passage 26 opens upstream from the throttle valve 23, so the valve portion 28
The negative intake pressure acting on the upper surface b is small and hardly acts on the sub-intake valve 28 as a closing force.

As described above, according to the present invention, the auxiliary intake valve 28 is constituted by a negative pressure responsive valve that is sucked and opened when a negative pressure of a certain value or more is generated in the combustion chamber 4 during the intake stroke of the engine. During low load operation of the engine, where it is difficult to achieve good combustion of the air-fuel mixture due to a decrease in efficiency, the sub-intake valve 28 opens wide due to the large negative pressure generated in the combustion chamber 4 during the engine intake stroke, causing combustion to flow from the sub-intake passage 26. Air can be injected into the chamber 4, and the air mixture is agitated and moderately diluted by the air injection, and the scavenging air around the ignition plug works together to make it possible to burn the mixture to dilute it. can reduce unburned components.

Moreover, since the complicated valve operating mechanism of the sub-intake valve 28 as in the prior art is not required, the structure of the engine is significantly simplified and manufacturing is easy.

In particular, the sub-intake valve 28 has a large number of blowholes 30 oriented in the tangential direction of the outer circumferential wall thereof, and is slidably connected to the inner wall of the sub-intake passage 26 and engaged with the inner wall to form the blowholes. 30 and an open position where the engagement is released and the nozzle hole 30 is opened to the combustion chamber 4; and a valve spring 32 that always springs the valve toward the closed position side, and the valve body 35 resists the valve spring 32 when a negative pressure of a certain value or more is generated in the combustion chamber 4 during the intake stroke of the engine. Since the air is sucked toward the open position, the air injected into the combustion chamber 4 from each jet hole 30 of the auxiliary intake valve 28 is directed toward the tangential direction of the outer circumference of the valve body 35, creating a strong swirling flow. As a result, the above-mentioned mixture stirring and scavenging around the spark plug can be performed sufficiently reliably, and the lean combustion of the mixture can be stabilized.

Furthermore, the upstream end of the auxiliary intake passage 26 is opened to the intake passage 18 of the carburetor 14, and only the air purified by the air cleaner 16 of the carburetor 14 can be introduced into the combustion chamber 4 from the auxiliary intake passage 26. Therefore, there is no need to provide a special air cleaner for the auxiliary intake passage 26, and the structure is simple and costs can be reduced.

Moreover, since the upstream end opening of the auxiliary intake passage 26 is located upstream of the throttle valve 23 in the low opening position of the intake passage 18, the opening part at the upstream end of the auxiliary intake passage 26 is located upstream of the throttle valve 23 in the low opening position. Air with a large negative pressure can be introduced, and this negative pressure can act as a relatively large closing force on the valve body 35 of the auxiliary intake valve 28, so that the combustion chamber is closed during high-load operation. Due to the small amount of negative pressure generated within 4,
The closing tendency of the auxiliary intake valve 28 during the same operation can be strengthened, and as a result of the above, the auxiliary intake valve 28 is largely opened during low load operation of the engine, and its opening is narrowed in response to changes in the load. The desired operation can be reliably obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional side view of the main part of an embodiment of the engine of the present invention, and FIG.
The figure is an enlarged longitudinal cross-sectional view of the sub-intake valve and its related components.
The figure is a sectional view taken along the line ■--■ in FIG. 2. 4... Combustion chamber, 5... Main intake path, 9...
...Main intake valve, 10...Ignition plug, 26.
...Sub-intake passage, 28...Sub-intake valve, 30
... Fumarole, 32 ... Valve spring, 35.
...Valve body.

Claims (1)

[Claims] 1. A main intake passage that connects the combustion chamber 4 equipped with the spark plug 10 with the intake passage 18 of the carburetor 14 provided with the throttle valve 23, and introduces the air-fuel mixture generated in the intake passage 18 into the combustion chamber 4. 5
and a sub-intake passage 26 for supplying air to the combustion chamber 4.
In an internal combustion engine in which main and auxiliary intake valves 9 and 28 are provided separately in the main and auxiliary intake passages 5 and 26, the upstream end of the auxiliary intake passage 26 is connected to a low-opening valve of the intake passage 18. The sub-intake valve 28 opens on the upstream side of the throttle valve 23 which is located at the 3-degree position. It can move between a closed position where it is slid onto the inner wall and closes the jet hole 30 and an open position where the engagement is released and the jet hole 30 is opened to the combustion chamber 4. It is composed of a bottomed cylindrical valve body 35 and a valve spring 32 that constantly urges the valve body 35 toward the closed position. The internal combustion engine is configured such that the valve body 35 is drawn toward the open position by pressure.