JP2001254624A - Stratified scavenging two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of acceleration failure and engine stop by avoiding fuel concentration from leaning due to excess of an air quantity to achieve normal combustion in sudden acceleration of the engine in the stratified scavenging two-cycle engine to improve sudden accelerating performance in particular in the cold mode, and to prevent the occurrence of combustion failure due to excess of fuel by avoiding fuel from being stored on the under side of the air-fuel mixture passage when the engine is operated with inclination. SOLUTION: This stratified scavenging two-cycle engine is provided with an air passage for supplying scavenging air from an air cleaner to a scavenging passage, a check valve for opening and closing the air passage according to the negative pressure in the scavenging passage, and an insulator having an air passage and an air fuel mixture passage arranged side by side. The engine is provided with a communicating passage with a small passage area for communicating the air passage with the air fuel mixture passage and feeding the air-fuel mixture in the air fuel mixture passage to the air passage according to the negative pressure in the air passage, and with a check valve fitted to the insulator to be operated by a bimetal plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a stratified scavenging two-stroke engine of a crankcase compression type, and more particularly to an air and mixture supply system for an air-driven stratified scavenging two-cycle engine in which scavenging air is used to perform advance scavenging. Regarding improvement.

[0002]

2. Description of the Related Art In a conventional two-stroke engine,
Utilizing that the pressure in the crankcase formed in the crankcase becomes negative when the piston moves to the top dead center, the air-fuel mixture is sucked into the crankcase and the piston moves toward the bottom dead center. The air-fuel mixture compressed in the crank chamber is introduced into the combustion chamber from the crank chamber when the scavenging port is opened,
The combustion gas is charged into the combustion chamber while extruding the combustion gas. In this scavenging stroke, since the open section between the scavenging port and the exhaust port overlaps in a wide range, about 30% of the air-fuel mixture flows through with the combustion gas,
This is the main cause of excessive THC (total hydrocarbon) emissions, which results in wasted fuel.

[0003] In order to reduce such blow-by of the air-fuel mixture, an air-driven stratified scavenging method has been provided. In such a scavenging method, during the intake stroke of the piston toward the top dead center, the crank chamber is filled with air-fuel mixture, and at the same time, air is sucked into the crank chamber through the scavenging passage connected to the scavenging port and charged into the scavenging passage. When the scavenging port is opened during the combustion and exhaust strokes that descend from TDC,
The air in the scavenging passage is introduced into the combustion chamber prior to the air-fuel mixture to scavenge the combustion exhaust gas, and subsequently the air-fuel mixture is introduced into the combustion chamber. In such a scavenging method, blow-by of the air-fuel mixture is significantly reduced to about one third of that of the conventional engine.

[0004] Such an air-driven stratified scavenging two-cycle engine is disclosed in Japanese Patent Application Laid-Open Nos. 7-139358 and 10-108.
Inventions such as JP-A-252565 and JP-A-9-125966 are provided.

In the invention disclosed in Japanese Patent Application Laid-Open No. 7-139358, an air passage opening in a position close to the scavenging port is provided in a scavenging passage communicating between the scavenging port and the inside of the crankcase. A check valve communicating only in the direction of the scavenging passage is provided to prevent the mixture supplied from the scavenging port into the cylinder from flowing through to the exhaust side.

In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 10-252565, the end of an air passage is connected to a portion of a scavenging passage that connects a scavenging opening and a crank chamber, and the air passage is connected to the scavenging opening. A check valve to allow the flow of
A fuel control valve that adjusts the amount of fuel in the air-fuel mixture passage so as to be rotatable around a shaft that intersects the air-fuel mixture passage and the air air passage that are provided parallel to the carburetor, and air that adjusts the air amount in the air air passage A control valve is provided.

In the invention of Japanese Patent Application Laid-Open No. 9-125966, an air-fuel mixture control valve that opens and closes an air-fuel mixture passage connecting a carburetor and a crankcase, and an air control valve that opens and closes an air passage connecting an air cleaner are provided. The mixture control valve and the air control valve are connected to each other so that the mixture flow rate and the air flow rate can be controlled so as to have a substantially constant ratio.

[0008]

In such an air-driven stratified scavenging two-cycle engine, during idling operation, the negative pressure on the air passage side is higher than that on the air-fuel mixture passage side. With further rapid acceleration, transient fuel concentration leaning due to the delay in following the fuel supply is promoted by a rapid increase in the amount of leading air,
Excessive air causes the fuel concentration to be too low.

For this reason, when the acceleration operation is performed, the fuel amount cannot follow the increase in the air amount, and the fuel concentration becomes too low to perform normal combustion, resulting in poor acceleration or engine stop.

[0010] However, Japanese Patent Application Laid-Open No. 7-139358,
JP-A-10-252565, JP-A-9-125966
In the invention of No. 3, etc., although the ratio control of the air flow rate and the air-fuel mixture flow rate is performed during the steady operation, no preventive measures against the excessive air amount state at the time of rapid acceleration of the engine as described above are taken. .

When such a two-stroke engine is used for a brush cutter, the engine is often operated in an inclined state. During such a tilting operation, fuel is stored in the lower portion of the mixture passage, and when the attitude of the engine changes, the fuel is rapidly aspirated.
It causes poor combustion due to excess fuel. However,
In the above-mentioned prior art, no measures are taken to prevent such a trouble at the time of the tilting operation.

Further, in such a stratified scavenging two-cycle engine, at the time of sudden acceleration immediately after starting from a cold state,
As described above, the tendency that the fuel amount cannot follow the increase in the air amount strongly appears and often causes the engine to stop, and it is desired to prevent the occurrence of such a problem and improve the rapid acceleration in a cold state. ing.

The present invention has been made in view of the above-mentioned problems of the prior art,
In a stratified scavenging two-cycle engine, by avoiding leaning of the fuel concentration due to excess air volume during rapid acceleration of the engine, normal combustion is achieved, thereby improving the rapid acceleration especially in a cold state. A first object is to prevent occurrence of poor acceleration or engine stop.

It is a second object of the present invention to prevent the occurrence of combustion failure due to excess fuel by preventing fuel from being stored below the mixture passage during the lean operation of the engine.

[0015]

According to the present invention, an exhaust port and a scavenging port are provided on the side of a cylinder and open when the piston rises to open the crank chamber. An intake port that communicates with an air-fuel mixture supply port that supplies air-fuel mixture to the scavenging port; a scavenging passage connected to the scavenging port; an air passage that supplies scavenging air from an air cleaner to the scavenging passage; A non-return valve that opens and closes the air passage with a negative pressure, and an insulator in which the air passage and the air-fuel mixture passage are arranged side by side. A layer having a small passage area communicating with the mixture passage and supplying the mixture in the mixture passage to the air passage by a negative pressure in the air passage. To propose a scavenging two-cycle engine.

According to this invention, the mixture in the mixture passage is supplied into the air passage through the communication passage having a small passage area in the air passage having a higher negative pressure than the mixture passage during the idling operation. When the amount of air in the air passage becomes excessive during rapid acceleration, the air-fuel mixture from the communication passage is mixed into the air. As a result, the air-fuel mixture is mixed into the air flowing through the air passage, and the fresh air supplied from the scavenging port into the cylinder is prevented from being in an excessive air state. The occurrence of thinning is prevented and the acceleration is improved. In addition, during high-speed operation, the throttle opening increases, and the pressure difference between the mixture passage and the air passage is almost eliminated, so that the mixture flows into the air passage from the mixture passage through the communication passage having the small passage area. There is almost no air-fuel mixture, so that the air-fuel mixture is prevented from being included in the leading air, and required exhaust gas performance can be maintained.

Further, during the lean operation of the engine, the air-fuel mixture in the air-fuel mixture passage can flow into the air passage through the communication passage having the small passage area. The fuel is stored in the portion of the cylinder, and the fuel is not suddenly sucked into the cylinder due to a change in the engine attitude, resulting in an excess of fuel. This prevents the occurrence of poor combustion.

Therefore, according to the present invention, the small passage area between the air passage and the mixture passage which can supply the mixture in the mixture passage to the air passage by the negative pressure in the air passage. A stratified scavenging two-cycle engine having the above-mentioned effects can be obtained with a very simple device without providing a control device having a complicated structure in which a communication passage is provided.

The invention according to claims 2 to 12 relates to a specific structure of the communication passage having a small passage area. The invention according to claim 2 is characterized in that the communication passage in claim 1 is larger than the check valve. It is provided between the air passage and the mixture passage on the downstream side.

According to a third aspect of the present invention, in the second aspect, the communication passage is formed in an insulator gasket interposed on a mounting surface between the insulator and the cylinder.

According to a fourth aspect of the present invention, in the second aspect, the communication passage is formed on a mounting surface of the insulator with the cylinder.

According to a fifth aspect of the present invention, in the second aspect, the communication passage is formed in a mounting surface of the cylinder with the insulator.

According to the second to fifth aspects of the present invention, the communication passage is opened at a position downstream of the check valve of the air passage, so that the operation during the above-described tilt operation of the engine is performed. The effect, that is, when the engine is operated near 180 ° when the engine is tilted, the fuel accumulated under the mixture passage can be caused to flow into the air passage through the communication passage when the engine is operated near 180 °. The effect and the effect of preventing the occurrence of fuel failure due to the above are remarkable.

In particular, the communication passage may be provided between the insulator gasket provided on the mounting surface of the insulator and the cylinder, or between the carburetor and the insulator. If formed on the carburetor gasket interposed on the mounting surface, the insulator gasket or the carburetor gasket is formed with only a slit corresponding to the width of the communication passage. Can be provided.

According to a sixth aspect of the present invention, in the first aspect, the communication passage is provided between the air passage upstream of the check valve and the mixture passage. Features.

The invention according to claim 7 is characterized in that, in claim 6, the communication passage is formed in a carburetor gasket interposed on a mounting surface between the carburetor and the insulator.

According to an eighth aspect of the present invention, in the sixth aspect, the communication passage is formed in a mounting surface of the insulator with a carburetor.

According to a ninth aspect of the present invention, in the sixth aspect, the communication passage is formed on a mounting surface of the carburetor with the insulator.

In the case where the communication passage is provided between the air passage downstream of the check valve and the air-fuel mixture passage as in the present invention, Since the passage is communicated with the scavenging passage downstream of the check valve, increasing the passage area of the passage leads to a reduction in engine output. By providing between the air passage upstream of the check valve and the air-fuel mixture passage, it is possible to increase the passage area of the communication passage without a decrease in engine output. Acceleration performance can be further improved.

The invention according to claims 10 to 11 is the first invention.
According to a modified embodiment of the communication passage in the invention described in claim 10, the invention described in claim 10 is characterized in that in claim 1, the communication passage is one of the insulator, the carburetor or the cylinder, and the air passage and the mixture passage. It is characterized by comprising a small hole communicating between the two.

According to an eleventh aspect of the present invention, in the tenth aspect, the small hole is provided with a check valve that allows only a flow from the mixture passage to the air passage.

According to a twelfth aspect of the present invention, the invention of the second aspect is combined with the invention of the sixth aspect. In the first aspect, the communication passage is located downstream of the check valve. Are provided at two places between the air passage and the mixture passage, and between the air passage and the mixture passage upstream of the check valve.

According to this aspect of the invention, one of the communication passages is provided between the air passage downstream of the check valve and the air-fuel mixture passage. The air-fuel mixture can flow into the air passage through the communication passage having the small passage area, and fuel is stored in the lower portion of the air-fuel mixture passage, which is rapidly sucked into the cylinder due to a change in engine attitude. And the occurrence of combustion failure due to excess fuel is prevented, and the other of the communication passages is provided between the air passage upstream of the check valve and the air-fuel mixture passage, whereby the engine It is possible to increase the passage area of the communication passage without lowering the output, and it is possible to obtain a synergistic effect that the acceleration performance at the time of rapid acceleration can be improved.

According to a thirteenth aspect of the present invention, an exhaust port and a scavenging port are provided on the side of the cylinder, and the mixture passage is opened when the piston rises and communicates with an intake port for supplying the mixture into the crank chamber. A scavenging passage connected to the scavenging port, an air passage for supplying scavenging air from an air cleaner to the scavenging passage, a check valve for opening and closing the air passage by a negative pressure in the scavenging passage, and the air In an air-driven stratified scavenging two-cycle engine including a passage and an insulator in which the mixture passage is juxtaposed, the check valve is attached to and detached from a valve seat formed at an air passage outlet of the insulator. A valve body plate that opens and closes the air passage outlet, and a contact member that comes into contact with an engine member including the cylinder. A bimetallic strip which is curved in the valve seat side,
A stopper whose free end is curved to the opposite side of the valve seat is cantilevered in this order from the side of the valve seat, and a root portion thereof is fixed to the insulator.

According to a fourteenth aspect of the present invention, in addition to the thirteenth aspect, the air passage and the air-fuel mixture passage communicate with each other, and the air-fuel mixture in the air-fuel mixture passage is caused by the negative pressure in the air passage. And a communication passage having a small passage area for feeding the small passage.

According to a fifteenth aspect, in the thirteenth aspect, the contact member for the bimetal plate is omitted.

According to a sixteenth aspect of the present invention, an exhaust port and a scavenging port are provided on the side of the cylinder, and the mixture passage is opened when the piston rises and communicates with an intake port for supplying the mixture into the crank chamber. A scavenging passage connected to the scavenging port, an air passage for supplying scavenging air from an air cleaner to the scavenging passage, a check valve for opening and closing the air passage by a negative pressure in the scavenging passage, and the air In an air-driven stratified scavenging two-cycle engine including a passage and an insulator in which the mixture passage is juxtaposed, the check valve is attached to and detached from a valve seat formed at an air passage outlet of the insulator. The free end of the valve body plate that opens and closes the air passage outlet and the engine member including the cylinder is bent toward the valve seat at normal temperature and bent toward the valve seat side as the temperature rises. And a bimetal plate which also serves as a stopper in the opening direction of Rutotomoni the valve body plate overlaid in a cantilever in this order from the valve seat side, characterized by comprising fixed the base portion to the insulator.

According to the thirteenth to sixteenth aspects of the present invention, when the temperature of the engine member including the cylinder is low in a cold state, the valve body plate of the check valve is pressed by the bimetal plate to form an air passage to the cylinder. Is closed, scavenging air is not supplied from the air passage into the cylinder at the time of rapid acceleration after the start in the cold state, and operates in the same manner as an engine that does not perform stratified scavenging. This prevents the scavenging air flowing through the air passage from causing a problem that the air-fuel mixture becomes too thin to cause the engine to stop. Also, when the temperature of the engine members including the cylinder rises,
Due to the deformation of the bimetal plate, the valve body plate of the check valve can open and close the air passage in the same manner as during normal load operation.

According to the present invention, since the stopper 73 is omitted, the structure is simplified and the number of parts is reduced. Further, according to the structure of claim 15, since the contact member of the bimetal plate is omitted,
Since the check valve does not receive direct conduction heat from the cylinder,
It has a characteristic that the temperature rise of the bimetal plate is delayed, and the time required for the predetermined deformation depending on the temperature is lengthened.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and other relative arrangements of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Not just.

FIG. 1 is a cross-sectional view of the air-driven stratified scavenging two-cycle engine according to the first embodiment of the present invention, which is perpendicular to the crankshaft center including the cylinder center axis, FIG. 2 is a front view of a carburetor gasket, and FIG. FIG. 4 is an end view of the insulator on the side of the carburetor gasket (as viewed in the direction of arrows AA in FIG. 1), FIG. 4 is an enlarged cross-sectional view near a connecting portion between the insulator and the cylinder (an enlarged view of a Z part in FIG. 1), FIG. 6 is a front view of the gasket, FIG. 6 is an end view of the insulator gasket side (a view taken along the line BB in FIG. 4), and FIG. 7 is a view corresponding to FIG. FIG. 8 is a sectional view of a principal part around an insulator of an air passage in the two-stroke engine according to the second embodiment of the present invention, and FIG.
FIG. 10 is a plan view in FIG. 8 showing a plan shape of the check valve portion, and FIG. 11 is an exploded perspective view of the insulator and the check valve portion. FIG. 12 shows a third embodiment of the present invention.
FIG. FIG. 13 is a temperature characteristic diagram of the bimetal.

In FIG. 1 showing the first embodiment, reference numeral 2 denotes a cylinder, 4 denotes a piston, 6 denotes a crankshaft, 6a denotes a crank web constituting the crankshaft 6, 5 denotes a crankcase, 3 denotes a piston 4 and a crankshaft. 6, a connecting rod, 7 is a cylinder head, 8 is a spark plug, 11 is an air cleaner, and 12 is a carburetor. Also,
25 is a combustion chamber, 5a is a crank chamber formed inside the crankcase 5, 15 is the carburetor 12 and the crank chamber 5
a is a mixture passage connecting the a. 13a is the cylinder 2
Is connected to the exhaust pipe 13 at an exhaust port opened on the side of the.

Reference numeral 9a denotes scavenging ports provided on the left and right sides of the exhaust port 13a of the cylinder 2 so as to be opposed to the exhaust port 13a at a position substantially perpendicular to the exhaust port 13a. Each of the pair of scavenging ports 9a includes a pair of scavenging passages 109e provided in the cylinder 2 in an oblique direction, a pair of scavenging passages (not shown) which are the merging places of the scavenging passages, and both sides of the crankcase 5. A pair of scavenging passages 109d formed in the wall of the surface in an arc shape and a pair of scavenging passage openings 109b, 109
b and is communicated with the crank chamber 5a.

The scavenging passage openings 109b, 109b
Are openable and closable by the crank web 6a of the crankshaft 6, in the direction of the crankshaft center 60, the end faces of the openings 109b, 109b and the crank web 6a.
Are close to each other with a small gap.

Reference numeral 10 denotes an air supply chamber provided inside the side portion of the cylinder 2, and an upstream side thereof has an insulator 30 described later.
The downstream side is connected to a pair of air branch passages 10a. The air branch passage 10
a shows the paired scavenging passages and the paired scavenging passages 10;
9e and 109e. The air supply chamber 1
In the opening 0 to the left and right air branch passages 10a and 10a, a reed valve type check valve 16 that allows only the flow toward the air branch passages 10a and 10a is provided.

Reference numeral 30 denotes an insulator for thermally isolating the engine body from the intake system. The insulator 30 is bolted to the side surface of the cylinder 2. The air passage 10 is provided above the inside of the insulator 30.
b, a mixture passage 15 is formed in parallel on the lower side. The upstream side of the mixture passage 15 is connected to an air cleaner 11 through a mixture control valve 14 for controlling the mixture flow rate in the carburetor 12 and a gas passage 10e, and the downstream side is a cylinder through an intake port 15a. (Combustion chamber 25).

Reference numeral 110 denotes an air passage tube integrated with the carburetor 12 for connecting the air cleaner 11 and the insulator 30. The air passage tube 110 is provided with an air control valve 20 for changing the area of the air passage. The valve 20 is linked to the mixture control valve 14 of the carburetor 12.

The above configuration is similar to that of Japanese Patent Application No. 11-122599 filed by the present applicant. In the present invention, the leading air supply system and the mixture supply system are improved.

That is, 41 is an insulator gasket interposed on the mounting surface between the insulator 30 and the cylinder 2, and 42 is a carburetor gasket interposed on the mounting surface between the insulator 30 and the carburetor 12. As shown in FIG. 2, the carburetor gasket 42 has an air passage 10b on the upper side and a mixture passage 15 on the lower side, which are formed in parallel with the insulator 30. A communication passage 43 communicating between the air passage 10b and the mixture passage 15 is formed in a slit shape. 46 is a bolt hole.

The insulator gasket 41
As shown in FIG. 5, an air passage 10b on the upper side and an air-fuel mixture passage 15 on the lower side are formed in parallel with the pitch of the insulator 30, and are formed in parallel between the air passage 10b and the air-fuel mixture passage 15. In the figure, a communication passage 44 for communicating the two is formed in a slit shape. 61 is a hole for installing the check valve 16, and 49 is a bolt hole. As shown in FIG. 4, the communication passage 44 of the insulator gasket 41 is connected to the mixture passage 15 and a seat surface 45 of the check valve 16.
While communicating with the air supply chamber 10 on the downstream side,
The width, that is, the passage area is formed smaller than the width of the communication passage 43 of the carburetor gasket 42, and the communication passage 44 is formed.
To minimize output reduction.

Instead of providing the communication passages 44 and 43 in the insulator gasket 41 and the carburetor gasket 42, as shown in FIG. 3, a groove-like communication passage 47 is formed in the joint surface of the insulator 30 with the carburetor gasket 42. And, as shown in FIG. 6, the insulator 3
A groove-shaped communication passage 51 may be formed in the joint surface with the insulator gasket 41 of No. 0. Further, the communication passage may be formed on the side of the cylinder 2 on which the insulator 30 is mounted, or may be formed on the side of the carburetor 12 on which the insulator 30 is mounted.

Air-driven stratified scavenging 2 having such a configuration
During operation of the cycle engine, when the piston 4 is lowered by the combustion pressure in the combustion chamber 25 and the exhaust port 13a is opened, the combustion gas (exhaust gas) in the combustion chamber 25 passes through the exhaust port 13a and exhaust pipe 13 Is discharged to the outside air through a muffler (not shown). Piston 4
Is further lowered, the left and right scavenging ports 9a, 9a are opened, and the air stored in the scavenging passage 109e and the like flows into the combustion chamber 25 and pushes the combustion gas toward the exhaust port 13a.

Next, the air-fuel mixture stored in the crank chamber 5a forms a pair of scavenging passage openings 109b,
The gas flows into the combustion chamber 25 from the scavenging port 9a via the scavenging passage 109d and the scavenging passage 109e. When the piston 4 is lowered and is at the bottom dead center, the exhaust port 13a and the scavenging port 9a are open, and the supply of the air and the air-fuel mixture into the combustion chamber 25 is finished or is about to be finished.
When the piston 4 rises from the bottom dead center, the scavenging port 9a is closed by the piston 4, and the inside of the crank chamber 5a becomes a closed space, and expansion, that is, a decrease in pressure starts.

When the piston 4 further rises, the exhaust port 13a is closed, and the compression of the mixed gas in the combustion chamber 25 starts. On the other hand, the pressure in the crank chamber 5a increases due to the increase in the volume of the crank chamber 5a due to the rise of the piston 4. Further decline. When the piston 4 further rises, an intake port 15a formed on the side surface of the cylinder 2 opens, and the air-fuel mixture generated by the carburetor 12 and controlled in flow rate by the air-fuel mixture control valve 14 passes through the air-fuel mixture passage 15 into the crank chamber 5a. Supplied to

The decrease in the pressure in the crank chamber 5a is transmitted to the left and right air branch passages 10a via the scavenging passage opening 109b, the scavenging passage 109d and the scavenging passage 109e, so that the reed valve check valve 16 is opened. The air supplied to the air supply chamber 10 through the check valve 16 is supplied to the crank chamber 5.
a.

Here, the paired scavenging passages 109e and 109d from the scavenging port 9a to the crank chamber 5a form a long scavenging passage, and are supplied to the scavenging passage. The air that has flown into such a long scavenging passage first flows into the crank chamber 5a.

When the piston 4 reaches the vicinity of the compression top dead center,
Spark discharge is generated in the combustion chamber 25 by the ignition plug 8, and the compressed air-fuel mixture is ignited and burned. Due to this combustion, the piston 4 is pushed down by the generated pressure, and a rotational torque is generated on the crankshaft 6.

When the exhaust port 13a is opened by lowering the piston 4, the combustion gas in the combustion chamber 25 is discharged from the exhaust port 13a.
a flows into the exhaust pipe 13 and is then discharged outside through a muffler (not shown). On the other hand, as the piston 4 descends, the gas in the crank chamber 5a is compressed on the back side of the piston 4. When the piston 4 is further lowered to open the side scavenging port 9a, the air-fuel mixture supplied into the crank chamber 5a is paired with the scavenging passage opening 109b, the scavenging passage 109d, Then, the gas is blown into the combustion chamber 25 from the scavenging port 9a through the scavenging passage 109e, and a scavenging action of pushing out the combustion gas (exhaust gas) in the combustion chamber 25 from the exhaust port 13a is performed.

During the idling operation of the engine, the negative pressure in the air passage 10b, the air supply chamber 10, the air branch passage 10a and the like is higher than that in the mixture passage 15 side.

However, according to the embodiment of the present invention, the communication passages 43 and 44 having a small passage area provided between the air passage 10b and the mixture passage 15 in the insulator gasket 41 and the carburetor gasket 42, respectively. Alternatively, the communication in the groove-shaped communication passages 47 and 51 formed in the insulator 30 allows the air-fuel mixture in the air-fuel mixture passage 15 to flow through the communication passages 43 and 44 having a small passage area during idling operation.
Alternatively, the air is supplied into the air passage 10 b and the air supply chamber 10 through 47 and 51.

As a result, the air passage 1 at the time of sudden acceleration
When the air amount on the 0b side becomes excessive, an air-fuel mixture is mixed into the air flowing through the air passage 10b side, and the fresh air supplied from the scavenging port 9a into the combustion chamber 25 is prevented from being in an excessive air state. As a result, the occurrence of excessive fuel concentration during rapid acceleration of the engine is prevented, and the acceleration is improved.

Further, during high-speed operation, the throttle opening becomes large, and the pressure difference between the mixture passage 15 and the air passage 10b and the air supply chamber 10 is almost eliminated. Communication passages 43 and 44
Alternatively, almost no air-fuel mixture flows into the air passage 10b or the air supply chamber 10 through the air passages 47 and 51, so that the air-fuel mixture is prevented from being included in the leading air, and required exhaust gas performance can be maintained.

Further, during the lean operation of the engine, the air-fuel mixture in the air-fuel mixture passage 15 forms a communication passage downstream of the check valve 16, that is, on the combustion chamber 25 side, that is, the communication passage 44 of the insulator gasket 41 or Since fuel can flow into the air supply chamber 10 through the communication passage 51 on the insulator gasket 41 side of the insulator 30, fuel is stored in a portion below the mixture passage 15, and this changes the engine attitude. This prevents sudden suction into the cylinder and prevents the occurrence of poor combustion due to excess fuel.

In order to solve the problem at the time of the tilting operation, the communication passage 44 or 51 is provided between the air supply chamber 10 downstream of the check valve 16 and the mixture passage 15. Since the communication passage 44 or 51 is communicated with the scavenging passage 109e or the like downstream of the check valve 16, the passage area is increased.
Although the engine output is reduced, the provision of the communication passage 43 or 47 in the carburetor gasket 42 upstream of the check valve 16 or the carburetor gasket 42 of the insulator 30 causes a reduction in engine output. Thus, it is possible to increase the passage area of the communication passage, thereby improving the acceleration performance during sudden acceleration.

Therefore, according to this embodiment, the space between the mixture passage 15 and the air passage 10b and the air supply chamber 10 is
The communication passages 43 and 44 having a small passage area capable of supplying the air-fuel mixture in the air-fuel mixture passage 15 to the air passage side by the negative pressure in the air passage 10b and the air supply chamber 10 are provided.
The above-mentioned effects can be obtained with a very simple device without installing a control device having a complicated structure.

Further, the communication passage 43 or 44 is
If formed on the insulator gasket 41 or the carburetor gasket 42, the insulator gasket 4
1 or the carburetor gasket 42, the communication passage 43
Or just process the slit corresponding to the width of 44,
The communication passage can be provided with a simple and small number of processing steps.

In FIG. 7 showing another embodiment of the communication passage, reference numeral 63 denotes a communication passage formed of a small hole, which communicates between the air passage 10b and the mixture passage 15 of the insulator 30. Reference numeral 64 denotes a check valve provided in the communication passage 63.
It is configured to allow only the flow toward the side.
Note that the check valve 64 may be omitted and only the communication passage 63 formed of a small hole may be provided. Further, the insulator 3
Instead of 0, the communication passage 63 and the check valve 64 as described above may be provided in the carburetor 12 or the cylinder 2.

In FIGS. 8 to 11 showing the second embodiment, FIG.
Numeral 0 denotes a check valve. A valve plate (lead valve plate) 71 which comes into contact with the valve seat 30a and a bimetal plate 7 which comes into contact with the valve plate 71 are provided on a valve seat 30a provided on the insulator 30.
2 and a stopper 73 that contacts the bimetal plate 72
And are attached by small screws 74.
The valve body plate 71 is made of, for example, a thin and smooth stainless steel spring plate having a thickness of about 0.2 mm, and has a bottle shape having a constricted upper portion as shown in FIG. The valve seat 3 having two mounting holes 71a into which circular protrusions 30c to be described later are inserted, and a lower portion formed on the outlet side of the air passage 10b of the insulator 30.
0a, and closes the passage opening of the air passage 30b.

The bimetal plate 72 is connected to the valve body plate 71.
The side in contact with is made of a metal plate having a high coefficient of thermal expansion and is made of a bimetal material thicker than the valve body plate 71.
As shown in FIG. 11, the planar shape of the bimetal plate 72 is substantially the same as that of the valve body plate 71, and has two mounting holes 72a at the top. The bimetal plate 72 is provided with a contact member 72b that bends at a right angle from one side and then turns at an obtuse angle so as to promote heat transfer from the cylinder 2 of the engine. ing.

Further, the lower portion of the bimetal plate 72
At normal temperature, the tip is curved toward the valve seat 30a as shown by a two-dot chain line in FIG. 11, and when attached to the valve seat 30a, the valve body plate 71 is shown as a solid line in FIG. And presses it toward the valve seat 30a to smoothen it. When the temperature rises, it curves to the opposite side of the valve seat 30a as shown by the two-dot chain line in FIG. Has become. The stopper 73 is formed to be thicker than the bimetal plate 72, as shown in FIG. 11, made of a rigid metal plate having a T-shape in plan view, having two mounting holes 73a in the upper part, and the lower part in the lower part. Side is the valve seat 30a
To restrict the upper limit of the bending of the bimetal plate 72.

A female screw 30f and a circular projection (dwell) 3 are provided on the insulator 30 at a position corresponding to the mounting hole 71a of the valve body plate 71 above the valve seat 30a.
0c are provided respectively, and the valve body plate 71, the bimetal plate 72, and the stopper 73 are provided with respective mounting holes 71a,
One of the holes 72a and 73a is positioned by being fitted into the circular projection 30c, and the small screw 74 is screwed into the female screw 30f through the other hole to thereby form the insulator 30.
It can be attached to. When the insulator 30 is connected to the cylinder 2, the tip of the contact member 72b of the bimetal plate 72 comes into contact with the inner wall of the air supply chamber 10 of the cylinder 2 with a sufficient elastic force.

That is, in this embodiment, the check valve 70 is attached to and detached from the valve seat 30a formed at the outlet of the air passage 10b of the insulator 30 to open and close the outlet of the air passage 10b. The free end (lower portion) is in contact with the engine member including the cylinder 2 and its free end (lower portion) is bent toward the valve seat 30a at normal temperature, and is bent toward the opposite side to the valve seat 30a as the temperature rises. A stopper 73 curved to the opposite side to the valve seat 30a is stacked in a cantilever manner in this order from the valve seat 30a side, and the root portion is fixed to the insulator 30 by a small screw 74.

In the stratified scavenging two-cycle engine having the check valve 70 having the above-described structure, when the engine is in a cold state, the bimetal plate 72 presses the valve body plate 71 by the initial pressing force, and the air passage 10b Is closed. Immediately after starting the engine in such a state, a rapid acceleration operation is performed and the mixture control valve 14 is rapidly opened.
The air control valve 20 linked to this also opens greatly rapidly,
The air control valve 20 is in a state where a large amount of scavenging air can flow.

According to this embodiment, however, the cylinder 2
In a cold state where the temperature of the check valve 7 is low, as described above,
Since the valve body plate 71 of 0 is pressed by the bimetal plate 72 to close the air passage 10b, the scavenging air flows from the air passage 10b into the cylinder 2 during rapid acceleration after the start in the cold state. It operates similarly to an engine that is not supplied and does not perform stratified scavenging. This prevents the scavenging air flowing through the air passage 10b from causing a problem that the air-fuel mixture becomes too thin to cause the engine to stop. When the temperature of the cylinder 2 rises, the deformation of the bimetal plate 72 causes the valve plate 7 of the check valve 70 to move.
1 can open and close the air passage 10b in the same manner as during normal load operation.

FIG. 13 is an explanatory view showing an example of the temperature-opening degree characteristic of the air passage in the bimetal plate 72. As shown in FIG.
In this example, when the temperature reaches 70 ° C., the bimetal plate 72 becomes flat and loses the initial pressing force on the valve body plate 71. When the temperature further rises, the bimetal plate 72 curves to the opposite side of the valve seat 30a (see FIG. 8). Opening of the valve plate 71 is allowed, and then the allowable opening of the valve plate 71 is increased in proportion to the temperature rise. When the bimetal plate 72 comes into contact with the stopper 73, the maximum opening is reached. It is locked at a time. FIG.
The upper and lower dashed lines indicate the degree of warpage of the bimetal plate 72 in the free state as an opening, and the lower side of the deformation in the free state is determined by the valve seat 30a of the insulator 30.
The upper side is 0% and 1% by the stopper 73.
It is constrained to the state of 00%.

Therefore, according to this embodiment, when the engine is started from a cold state, the air passage 10b is closed by the check valve 70, whereby the supply of the scavenging air into the cylinder 2 is cut off. The engine can be operated in the same manner as an engine that does not perform stratified scavenging, whereby an excessive air phenomenon caused by scavenging air that occurs transiently during acceleration of the engine can be prevented, and high acceleration performance can be secured.

In FIG. 12 showing the third embodiment, two members, a valve body plate 71 contacting the valve seat 30a of the insulator 30 and a bimetal plate 72 'contacting the valve body plate 71, are overlapped with each other. Stopper 7 in the second embodiment
The check valve 75 is configured by removing 3. In this embodiment, the valve body plate 71 is the same member as in the second embodiment, and the bimetal plate 72 'is made thicker and more rigid than the bimetal plate 72 in the second embodiment. The stopper function is provided, and a curvature similar to that of the stopper 73 in the second embodiment occurs near the maximum temperature during use of the engine.

That is, in this embodiment, the check valve 75 is attached to and detached from the valve seat 30a formed at the outlet of the air passage 10b of the insulator 30, and the valve body plate 71 opens and closes the outlet of the air passage 10b. When the free end (lower portion) contacts the engine member including the cylinder 2 at normal temperature, it curves toward the valve seat 30a at normal temperature, curves toward the opposite side to the valve seat 30a as the temperature rises, and moves in the opening direction of the valve body plate. And a bimetal plate 72 ′ also serving as a stopper is cantilevered in this order from the valve seat 30 a side, and a root portion thereof is fixed to the insulator 30 by a small screw 74.

Therefore, according to this embodiment, the stopper 73 in the first and second embodiments is omitted, so that the structure is simplified and the number of parts is reduced. Other configurations are the same as those of the second embodiment, and the same members are denoted by the same reference numerals.

Although not shown in the drawings, in the second and third embodiments, the contact members 72b of the bimetal plates 72 and 72 'in the check valves 70 and 75 are removed to remove the flat surfaces of the bimetal plates 72 and 72'. The shape may be the same as that of the valve body plate 71. In this case, since the check valves 70 and 75 do not receive direct conduction heat from the cylinder 2, the temperature rise of the bimetal plates 72 and 72 ′ is delayed, and the time required for a predetermined deformation depending on the temperature is increased. Having. Other configurations are the same as those of the second and third embodiments.

[0081]

As described above, according to the first to twelfth aspects of the present invention, the air passage and the mixture passage communicate with each other through the communication passage having a small passage area. An air-fuel mixture is supplied into the air passage through a communication passage having a small passage area. Thereby, it is avoided that the air-fuel mixture is mixed into the air flowing in the air passage, and the fresh air supplied from the scavenging port into the cylinder is in an excess air state,
The occurrence of excessive fuel concentration during rapid acceleration of the engine is prevented, and the acceleration is improved.

During high-speed operation, the pressure difference between the mixture passage and the air passage is almost eliminated, so that the mixture flowing from the mixture passage through the communication passage having the small passage area into the air passage is also reduced. There is almost no air-fuel mixture in the leading air, so that the required exhaust gas performance can be maintained.

Further, during the lean operation of the engine, the air-fuel mixture in the air-fuel mixture passage can flow into the air passage through the communication passage. The fuel does not accumulate in the cylinder due to a change in the engine attitude, and the occurrence of combustion failure due to excessive fuel is prevented.

According to the present invention, a communication passage having a small passage area is provided between the air passage and the mixture passage.
A stratified scavenging two-cycle engine having the above-described effects can be obtained with a very simple device without providing a control device having a complicated structure.

In particular, according to the twelfth aspect, by providing one of the communication passages between the air passage downstream of the check valve and the air-fuel mixture passage, the engine can be used during the tilt operation of the engine. In other words, the above-mentioned effect, that is, the occurrence of poor combustion due to excess fuel can be prevented, and the other of the communication passages is provided between the air passage and the mixture passage upstream of the check valve. Thus, it is possible to increase the passage area of the communication passage without lowering the engine output, and to obtain a synergistic effect that the acceleration performance at the time of rapid acceleration can be improved.

According to the invention of claims 13 to 16, at the time of rapid acceleration after starting in a cold state, the valve plate of the check valve is pressed by the bimetal plate and the air to the cylinder is released. Since the passage is closed, scavenging air is not supplied into the cylinder from the air passage, whereby the scavenging air flowing through the air passage becomes too lean to cause an engine stop. Can be prevented. When the temperature of the engine member including the cylinder rises, the valve plate of the check valve can open and close the air passage in the same manner as during normal load operation due to the deformation of the bimetal plate.

In particular, according to the present invention, since the stopper 73 is omitted, the structure is simplified and the number of parts is reduced. Further, according to the structure of claim 15, since the contact member of the bimetal plate is omitted,
Since the check valve does not receive direct conduction heat from the cylinder,
It has a characteristic that the temperature rise of the bimetal plate is delayed, and the time required for the predetermined deformation depending on the temperature is lengthened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view perpendicular to a crank axis including a cylinder center axis of an air-driven stratified scavenging two-cycle engine according to an embodiment of the present invention.

FIG. 2 is a front view of a carburetor gasket.

3 is an end view of the insulator on the vaporizer gasket side (a view taken along the line AA in FIG. 1).

FIG. 4 is an enlarged cross-sectional view (enlarged view of a Z portion in FIG. 1) near a connection portion between the insulator and the cylinder.

FIG. 5 is a front view of an insulator gasket.

FIG. 6 is an end view of the insulator on the side of the insulator gasket (a view taken along the line BB in FIG. 4).

FIG. 7 is a view corresponding to FIG. 4, showing a second embodiment of the communication passage.

FIG. 8 is a sectional view of a principal part around an insulator in an air passage in the two-stroke engine according to the second embodiment of the present invention.

FIG. 9 is a view as viewed in the direction of arrows CC in FIG. 8;

FIG. 10 is a plan view in FIG. 8 showing a plan shape of the check valve portion.

FIG. 11 is an exploded perspective view of an insulator and a check valve portion.

FIG. 12 is a view corresponding to FIG. 8, showing a third embodiment of the present invention.

FIG. 13 is a temperature characteristic diagram of a bimetal.

[Explanation of symbols]

 Reference Signs List 2 cylinder 4 piston 5 crankcase 5a crankcase 6 crankshaft 7 cylinder head 8 spark plug 9a scavenging port 10 air supply chamber 10a air branch passage 10b air passage 11 air cleaner 12 carburetor 13a exhaust port 14 mixture control valve 15 mixture passage 15a intake port 16 check valve 20 air control valve 25 combustion chamber 30 insulator 30a valve seat 41 insulator gasket 42 carburetor gasket 43, 44, 47, 51, 63 communication passage 64 check valve 70, 75 check valve 71 valve body Plate 72, 72 'Bimetal plate 73 Stopper 74 Machine screw 109b Scavenging passage opening 109d, 109e Scavenging passage

Continued on front page (72) Inventor Yasuhiro Hattori Nagoya City, Nakamura-ku, Iwatsuka-cho, Takamichi 1 Industrial Equipment Division Mitsubishi Heavy Industries, Ltd. Nagoya Laboratory Co., Ltd.

Claims (16)

[Claims] An exhaust port and a scavenging port are provided on a side of a cylinder, and are connected to the scavenging port, the mixture passage being opened when the piston is raised and communicating with an intake port for supplying an air-fuel mixture into a crank chamber. Scavenging passage, an air passage for supplying scavenging air from an air cleaner to the scavenging passage, a check valve for opening and closing the air passage by a negative pressure in the scavenging passage, the air passage and the mixture passage In the air-driven stratified scavenging two-stroke engine provided with an insulator arranged in parallel with the inside thereof, the air passage communicates with the air-fuel mixture passage, and a negative pressure in the air passage causes the air-fuel mixture inside the air-fuel mixture passage. A stratified scavenging two-stroke engine, comprising: a communication passage having a small passage area for supplying an air-fuel mixture to the air passage. 2. The stratified scavenging two-stroke engine according to claim 1, wherein the communication passage is provided between the air passage and the mixture passage downstream of the check valve. . 3. The stratified scavenging two-stroke engine according to claim 2, wherein the communication passage is formed in an insulator gasket interposed on a mounting surface between the insulator and the cylinder. 4. The stratified scavenging two-stroke engine according to claim 2, wherein the communication passage is formed in a surface of the insulator to be attached to the cylinder. 5. The stratified scavenging two-stroke engine according to claim 2, wherein the communication passage is formed in a mounting surface of the cylinder with the insulator. 6. The stratified scavenging two-stroke engine according to claim 1, wherein the communication passage is provided between the air passage upstream of the check valve and the air-fuel mixture passage. . 7. The stratified scavenging two-cycle engine according to claim 6, wherein the communication passage is formed in a carburetor gasket interposed on a mounting surface between the carburetor and the insulator. 8. The stratified scavenging two-stroke engine according to claim 6, wherein the communication passage is formed in a surface of the insulator to be attached to a carburetor. 9. The stratified scavenging two-stroke engine according to claim 6, wherein the communication passage is formed in a mounting surface of the carburetor with respect to the insulator. 10. The layered structure according to claim 1, wherein the communication passage comprises a small hole communicating between an air passage and an air-fuel mixture passage in one of the insulator, the carburetor, and the cylinder. Scavenging two-cycle engine. 11. The stratified scavenging two-stroke engine according to claim 10, wherein a check valve is provided in the small hole to allow only a flow from the air-fuel mixture passage toward the air passage. 12. The communication passage is provided between the air passage and the mixture passage downstream of the check valve, and between the air passage and the mixture passage upstream of the check valve. 2. The stratified scavenging two-stroke engine according to claim 1, wherein the engine is provided at two places between the two. 13. An exhaust port and a scavenging port are provided on the side of the cylinder, and are connected to the scavenging port, the mixture passage being open when the piston rises and communicating with an intake port for supplying an air-fuel mixture into the crank chamber. Scavenging passage, an air passage for supplying scavenging air from an air cleaner to the scavenging passage, a check valve for opening and closing the air passage by a negative pressure in the scavenging passage, the air passage and the mixture passage In the air-driven stratified scavenging two-cycle engine including an insulator arranged in parallel with the inside, the check valve is attached to and detached from a valve seat formed at an air passage outlet of the insulator, and the air passage outlet is connected to the check valve. A valve having a valve body plate that opens and closes and a contact member that comes into contact with an engine member including the cylinder, and a free end that curves toward the valve seat side at normal temperature and curves toward the opposite valve seat side as the temperature rises. A layered scavenging device comprising a metal plate and a stopper having a free end curved toward the non-valve seat side in a cantilevered manner in this order from the valve seat side, and a root portion fixed to the insulator. Two-cycle engine. 14. A communication passage having a small passage area which communicates the air passage with the mixture passage and supplies the mixture in the mixture passage to the air passage by a negative pressure in the air passage. 14. The stratified scavenging two-stroke engine according to claim 13, wherein: 15. The stratified scavenging two-cycle engine according to claim 13, wherein a contact member of said bimetal plate is omitted. 16. An exhaust port and a scavenging port are provided on the cylinder side, and are connected to the scavenging port, the mixture passage being opened when the piston rises and communicating with an intake port for supplying an air-fuel mixture into the crank chamber. Scavenging passage, an air passage for supplying scavenging air from an air cleaner to the scavenging passage, a check valve for opening and closing the air passage by a negative pressure in the scavenging passage, the air passage and the mixture passage In the air-driven stratified scavenging two-cycle engine including an insulator arranged in parallel with the inside, the check valve is attached to and detached from a valve seat formed at an air passage outlet of the insulator, and the air passage outlet is connected to the check valve. A valve body plate that opens and closes, and a free end that is in contact with an engine member including the cylinder and curves at the normal temperature toward the valve seat side at an ordinary temperature, and is bent toward the opposite valve seat side according to a temperature rise, and the valve body plate A layered scavenging two-stroke engine, wherein a bimetal plate also serving as a stopper in the opening direction is cantilevered in this order from the valve seat side, and a root portion thereof is fixed to the insulator.