JPH09242546A - Crank chamber pre-load type spark ignition type two-stroke internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the irregular combustion at the time of low-load operation, and while to improve the fuel consumption, and to purify the exhaust gas by respectively supplying the rich air-fuel mixture and the lean air-fuel mixture to a combustion chamber through a separate scavenge air passage in the layered condition, and igniting the rich air-fuel mixture with an ignition plug in a crank chamber pre-load type spark ignition type two-stroke internal combustion engine. SOLUTION: In a crank chamber pre-load type spark ignition type two-stroke internal combustion engine 1, a rich air-fuel mixture intake passage 12 is arranged at a position, in which an extension line of a rich air-fuel mixture intake passage 12 contacts with a rotation focus of a large end 8 of a connecting rod 7 and while the rich air-fuel mixture flow flowed from the rich air-fuel mixture intake passage 12 into a crank chamber 11 coincides with the rotating direction of the large end 8 of the connecting rod 7, and a rich air-fuel mixture scavenge air passage 16 is formed on the extension line of the rich air-fuel mixture passage 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankcase precompression type spark ignition type two-stroke internal combustion engine, in which a rich air-fuel mixture and a lean air-fuel mixture or air are scavenged into a combustion chamber in layers through separate scavenging passages. However, the residual gas is scavenged mainly with a lean air-fuel mixture or air to reduce fuel blow-through, improve fuel efficiency, and purify exhaust gas.

[0002]

2. Description of the Related Art A conventional crank chamber precompression type spark ignition two-stroke internal combustion engine for supplying a rich mixture and a lean mixture to a combustion chamber in a layered manner is disclosed in JP-A-55-14992. is there.

In the internal combustion engine described in the above publication, as shown in FIG. 4, one of a plurality of scavenging passages 03, 04, 05 connecting the lower part of the crank chamber 01 and the combustion chamber 02 with respect to the exhaust port 06 is provided. The air-fuel mixture intake passage 07 is connected to the scavenging passage 03 opened on the side opposite to the cylinder diameter, and the fuel-air supply means 08 such as a carburetor is provided in the air-fuel mixture intake passage 07 and is located immediately below the exhaust port 06. An air intake passage 09 opening to the crank chamber 01 was provided.

In addition to the Japanese Patent Laid-Open Publication No. 55-14992, there is a crank chamber precompression type spark ignition type two-stroke internal combustion engine (see FIG. 5) described in Japanese Patent Laid-Open Publication No. H2-45614, which faces the exhaust port 06. Although it is unclear in which part of the crank chamber 01 the lower end of the scavenging passage 03 whose upper end is opened is opened, the other parts are configured in substantially the same manner.

[0005]

In the conventional internal combustion engine shown in FIG. 4, the residual gas is scavenged only with a lean air-fuel mixture by making a difference in the air-fuel mixture concentration in the scavenging air to reduce the fuel blow-through. Although considered, the lower end of the scavenging passage 03 communicating with the mixture intake passage 07 is opened at the lower part of the crank chamber 01, so that the rich mixture mixed with the fuel by the fuel supply means 08 is in the latter half of the ascending stroke. Of the scavenging passage 03 because it descends and flows into the crank chamber 01 during intake of the crank chamber and rises and flows into the combustion chamber 02 during scavenging in the latter half of the descending stroke.
The mixed air flow inside changes its direction according to the ascending and descending strokes of the piston, and the rich air-fuel mixture diffuses into the air in the crankcase, so there is a drawback that the fuel blow-through reduction effect is small.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an improvement of a crank chamber precompression type spark ignition type two-stroke internal combustion engine which overcomes the above drawbacks, and the intake air is cranked in a combustion chamber compression stroke by a piston. In a crank chamber pre-compression type spark ignition two-stroke internal combustion engine in which the intake air is introduced into a room, the intake air is compressed when the piston descends, and the intake air is introduced into the combustion chamber through a scavenging passage by utilizing the pressure of the compression. A rich mixture intake passage for introducing a rich mixture into the crank chamber, and a lean mixture / air intake passage for introducing a lean mixture or air into the crank chamber, and an extension of the rich mixture intake passage The line is in contact with the rotation locus of the outer periphery of the crank web, and the rich mixed airflow flowing into the crank chamber from the rich mixture intake passage is connected to the crankshaft. The rich mixture intake passage is disposed at a position corresponding to the rotation direction of the outer periphery of the cylinder, and the rich mixture scavenging passage is formed on an extension line of the rich mixture intake passage.

Since the present invention is constructed as described above, the rich air-fuel mixture flowing into the crank chamber from the rich air-fuel mixture intake passage is assisted by viscous resistance force and intake inertia force due to rotation of the crank end face, Since it is guided to the rich air-fuel mixture scavenging passage, there is little fuel diffusion into the air in the crankcase. As a result, the amount of fuel in the scavenging air flow blown to the exhaust port is extremely small, which makes it possible to significantly improve fuel efficiency and purify exhaust gas.

By configuring the present invention as set forth in claim 2, the mixture in the combustion chamber can be separated into a rich mixture and air to form a layered structure. Ignition by the air spark plug can be carried out smoothly, and irregular combustion can be avoided.
It is possible to improve fuel efficiency and reduce HC emissions.

Further, according to the third aspect of the present invention, by configuring the present invention, the rich air-fuel mixture that has flowed into the combustion chamber from the rich air-fuel mixture scavenging passage is opened and exhausted in the rich air-fuel mixture scavenging passage. The lean air-fuel mixture or air flow that is placed on both sides of the line connecting the mouth is sandwiched by the lean air-fuel mixture or air flow that has flowed in from the opening, and a vertical vortex of rich air-fuel mixture is formed along the center line of the piston hole. Since the rich air-fuel mixture can stably contact the spark plug, the air-fuel mixture is ignited more reliably.

According to the fourth aspect of the present invention, by constructing the present invention, the rich mixture in the crank chamber from the rich mixture intake passage toward the rich mixture scavenging passage is cranked during the ascending stroke. Since it can be brought into contact with the outer circumference, the moving air flow along the rotation direction of the outer circumference of the crank web promotes the flow of the rich mixture fresh air,
With sufficient supply of the rich air-fuel mixture, normal combustion is secured and the output is maintained at a high level.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention shown in FIGS. 1 to 3 will be described below.

A single cylinder crank chamber precompression type spark ignition two-stroke internal combustion engine 1 of the present invention is mounted on a motorcycle (not shown) with a cylinder head 4 facing forward (to the left in FIG. 1). In the chamber precompression type spark ignition type two-stroke internal combustion engine 1, a cylinder block 3 and a cylinder head 4 are sequentially stacked in front of a crankcase 2 and integrally coupled to each other.

A piston 6 is slidably fitted in a cylinder hole 5 formed in the cylinder block 3 back and forth, and the piston 6 and the crank web 9 are interconnected by a connecting rod 7. The crank web 9 is rotationally driven in accordance with the sliding.

Further, the crankcase is arranged so that the extended line of the rich mixture intake passage 12 is in contact with the rotation paths of the large end portion 8 of the connecting rod 7, the crank pin 10 of the crank web 9 and the fitting portion in the crank chamber 11. 2, a rich air-fuel mixture intake passage 12 is disposed below the rear part of the crankshaft 2, and the direction of the rich air-fuel mixture flowing into the crank chamber 11 from the rich air-fuel mixture intake passage 12 and the rotation of the crankpin 10 in contact with the rich air-fuel mixture flow. The crank web 9 can rotate clockwise in FIG. 1 so as to match the direction.

Further, a reed valve 13 is provided at a connection portion of the rich mixture intake passage 12 with the crank chamber 11, and a throttle valve (not shown) is provided in the rich mixture intake passage 12 on the upstream side thereof. ) A vaporizer 14 and a lubricating oil supply means (not shown) are provided.

A rich mixture scavenging passage 16 communicating between the crank chamber 11 and the combustion chamber 15 is located on a substantially extended line of the rich mixture intake passage 12, and gently bends between the crankcase 2 and the cylinder block 3. And the exhaust port at the diameter position of the scavenging opening 17 of the rich mixture scavenging passage 16 and the cylinder hole 5.
18 and an exhaust passage 19 communicating therewith are formed.
An exhaust valve 20 is provided at 19.

Further, a lean mixture / air intake passage 21 is communicated with an upper portion of the crank chamber 11 in the vicinity of a joint between the crankcase 2 and the cylinder block 3, and a lead is provided at a downstream end of the lean mixture / air intake passage 21. A valve 22 is provided and
A throttle valve 23 is provided on the upstream side, and the throttle valve (not shown) of the carburetor 14, the throttle valve 23, and the exhaust valve 20 are connected to each other via a link 24, and the throttle of the carburetor 14 is reduced. When the valve is opened / closed, the throttle valve 23 and the exhaust valve 20 are adapted to be opened / closed in conjunction with this.

Furthermore, the cylinder head 4 is provided with an ignition plug 25 located on a plane passing through the center line of the cylinder hole 5 and along the scavenging opening 17 and the exhaust port 18.
The scavenging opening 26 is connected to both sides of a plane that connects the exhaust port 18 with the exhaust port 18 at substantially the same front and rear position as the scavenging opening 17.
Is opened, and the scavenging opening 26 is communicated with the crank chamber 11 via an air scavenging passage (not shown).

The embodiment shown in FIGS. 1 to 3 is
As configured as described above, in the operating state, the fuel supplied to the rich mixture intake passage 12 by the carburetor 14 is mixed with the air passing through the rich mixture intake passage 12 to form a rich mixture. The lubricating oil supplied from the lubricating oil supply means (not shown) is the rich mixture intake passage.
It is uniformly mixed with the rich air-fuel mixture in 12 and is sucked into the crank chamber 11 which has a negative pressure in the ascending stroke.

The fresh air sucked into the crank chamber 11 is compressed in the descending stroke, and when the scavenging opening 17 and the scavenging opening 26 are opened in the descending stroke of the piston 6, the compressed fresh air is rich in the mixture scavenging. It is supplied into the combustion chamber 15 through the scavenging opening 17 and the scavenging opening 26 via the passage 16 and a scavenging passage (not shown). When the scavenging opening 17, the scavenging opening 26, and the exhaust port 18 are closed by being discharged to the exhaust passage 19 and rising of the piston 6, the air-fuel mixture in the combustion chamber 15 is compressed by the rising of the piston 6, and the top dead center is reached. In the vicinity, ignition by the spark plug 25 or self-ignition by the thermal energy of the residual gas in the previous cycle is performed.

In this way, the rich mixture intake passage in the rising stroke
The intake amount of the rich mixture fresh air sucked into the crank chamber 11 from 12 is approximately at the central time when the piston 6 closes the scavenging opening 17 and the scavenging opening 26 from the vicinity of the bottom dead center to reach the top dead center. Since it is the largest, the large end portion 8 of the connecting rod 7 and the crank pin of the crank web 9 are provided at the lower center of the crank chamber 11.
By the moving wind force to the rich mixture scavenging passage 16 of the fitting portion at the approximate center time of the ascending stroke where the fitting portion with 10 is located, the rich mixture intake passage 12 through the crank chamber 11 As a result of the flow of the rich mixture fresh air flowing toward the mixture scavenging passage 16 being promoted, normal combustion is ensured and a large reduction in output is prevented by sufficient supply of the rich mixture fresh air.

Further, a lean air-fuel mixture containing almost no fuel or fresh air containing only air flows into the combustion chamber 15 through the scavenging openings 26 on both sides of the line connecting the scavenging opening 17 and the exhaust port 18. Since the rich air-fuel mixture fresh air that has flowed into the combustion chamber 15 through the scavenging opening 17 is sandwiched from both sides of the lean air-fuel mixture or fresh air containing only air, it flows out from the exhaust port 18 to the exhaust passage 19, so that burned gas is generated. As a result of being smoothly discharged to the exhaust passage 19 with the lean air-fuel mixture or fresh air containing only air, the filling effect is increased,
Fuel efficiency is improved. In the combustion chamber 15, a rich air-fuel mixture and a lean air-fuel mixture or a fresh air containing only air can be formed separately in layers, and the center line of the cylinder hole 5 connecting the scavenging opening 17 and the exhaust port 18 can be formed. A vertical vortex of the rich air-fuel mixture can be formed along the vertical plane passing through and can be surely brought into contact with the spark plug 25, so that the average air-fuel ratio of all the air-fuel mixture sucked into the combustion chamber 15 is increased. However, it is possible to reliably perform ignition by the spark plug 25, avoid irregular combustion, and improve fuel consumption and reduce HC emissions in this respect.

Further, since the carburetor 14, the throttle valve 23, and the exhaust valve 20 are connected by the link 24, the opening degree of the throttle valve 23 and the exhaust valve 20 can be adjusted according to the increase or decrease of the fuel supply amount of the carburetor 14. As a result, the air-fuel ratio can always be set within an appropriate range, exhaust gas emission can be suppressed during low-speed or low-load operation, and active-heat atmosphere combustion can be promoted. The cost reduction can be achieved by simplifying the control system of the carburetor 14, the throttle valve 23, and the exhaust valve 20.

[Brief description of drawings]

FIG. 1 is a crank chamber precompression type spark ignition type 2 according to the present invention.
It is a vertical side view at the bottom dead center of a stroke internal combustion engine.

FIG. 2 is a vertical cross-sectional side view of a crank chamber precompression type spark ignition type two-stroke internal combustion engine at a substantially central time during an ascending stroke.

FIG. 3 is a cross-sectional view of a crank chamber precompression type spark ignition two-stroke internal combustion engine cut along the line III-III in FIG.

FIG. 4 is a vertical cross-sectional side view of a conventional crank chamber precompression type spark ignition type two-stroke internal combustion engine described in JP-A-55-14992.

FIG. 5 is a vertical cross-sectional side view of a crank chamber precompression type spark ignition type two-stroke internal combustion engine described in JP-A-2-45614.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crank chamber precompression type spark ignition type 2-stroke internal combustion engine, 2 ... crankcase, 3 ... cylinder block, 4 ...
Cylinder head, 5 ... Cylinder hole, 6 ... Piston, 7 ...
Connecting rod, 8 ... Large end, 9 ... Crank web, 10 ... Crank pin, 11 ... Crank chamber, 12 ... Rich mixture air intake passage, 13 ... Reed valve, 14 ... Vaporizer, 15 ... Combustion chamber,
16 ... Rich mixture scavenging passage, 17 ... Scavenging opening, 18 ... Exhaust port,
19 ... Exhaust passage, 20 ... Exhaust valve, 21 ... Lean mixture / air intake passage, 22 ... Reed valve, 23 ... Throttle valve, 24 ... Link, 25 ... Spark plug, 26 ... Scavenging opening.

Claims (4)

[Claims] 1. An intake air is introduced into a crank chamber in a combustion chamber compression stroke by a piston, the intake air is compressed when the piston descends, and the intake air is introduced into the combustion chamber via a scavenging passage by utilizing a pressure due to the compression. In a crank chamber precompression type spark ignition type two-stroke internal combustion engine to be introduced, a rich mixture intake passage for introducing a rich mixture into the crank chamber and a lean mixture for introducing only a lean mixture or air into the crank chamber.・ An air intake passage is provided,
The line connecting the rich mixture intake passage and the fuel supply device is in contact with the outer circumference of the crank web, and the rich mixed air flow that has flowed into the crank chamber from the fuel supply device is aligned with the rotation direction of the outer circumference of the crank web. A crankcase precompression type spark ignition type two-stroke internal combustion engine, characterized in that a rich mixture intake passage is provided, and a rich mixture scavenging passage is formed on an extension of the rich mixture intake passage. 2. The crank chamber precompression type spark ignition system according to claim 1, wherein the lean mixture / air intake passage is mainly supplied with the lean mixture or air sucked from an intake port. Two-stroke internal combustion engine. 3. The inlet opening of the rich mixture scavenging passage is located at a position farthest from the exhaust port, and the inlet openings of other scavenging passages connect the exhaust outlet and the inlet opening of the rich mixture scavenging passage. The crankcase precompression type spark ignition type two-stroke internal combustion engine according to claim 1 or claim 2, wherein the crankcase precompression type spark ignition type two-stroke internal combustion engine is disposed on both sides of the cabling and is disposed on a cylinder wall surface. 4. The large end portion of the outer periphery of the crank web is in contact with the extension line of the rich air-fuel mixture intake passage during the piston rising stroke.
2. A crank chamber precompression type spark ignition type two-stroke internal combustion engine described in any one of 1.