JP3143375B2 - Stratified scavenging two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stratified scavenging two-stroke engine configured to separately inhale an air-fuel mixture and air for scavenging.

[0002]

2. Description of the Related Art As a stratified scavenging two-cycle engine of this kind, a mixture supply system having a carburetor and a throttle valve is connected to a crankcase, and an air supply system for supplying air is connected to a scavenging passage. Is known. The crankcase is provided below the cylinder in which the piston reciprocates, and the scavenging passage is provided so as to communicate from inside the crankcase into the cylinder. In the cylinder, a scavenging port communicating with the scavenging flow path is opened, and an exhaust port for exhausting combustion gas is opened.

In the stratified scavenging two-cycle engine configured as described above, when the piston rises, the pressure in the crankcase starts to decrease, and the scavenging port and the exhaust port close. For this reason, the air-fuel mixture enters the crankcase where the pressure has decreased, and the air also enters the crankcase through the scavenging passage. When the piston reaches the vicinity of top dead center, the air-fuel mixture in the cylinder is ignited, and the piston descends. Then, the pressure in the crankcase starts to rise, and the exhaust port and the scavenging port are opened. For this reason, the combustion gas is discharged from the exhaust port, and the air accumulated in the scavenging passage is ejected from the scavenging port into the cylinder, thereby forcibly discharging the combustion gas from the exhaust port. Then, after the air, the air-fuel mixture enters the cylinder through the scavenging flow path.

Then, the piston starts to rise, and the cycle as described above is repeated again.

[0005] The number of revolutions of the engine varies by adjusting the opening of the throttle valve and controlling the flow rate of the air-fuel mixture flowing into the crankcase.

According to the stratified scavenging two-cycle engine constructed as described above, the inside of the cylinder can be sufficiently scavenged by air, and unburned gas is not discharged during scavenging. Has the advantage of being beautiful.

[0007]

However, in the above-described conventional stratified scavenging two-cycle engine, the amount of air supplied from the air supply system changes depending on the pressure in the crankcase, whereas the amount of air supplied from the mixture supply system varies. However, there is a disadvantage that the amount of air-fuel mixture supplied from the engine varies depending on the pressure in the crankcase and also varies depending on the opening degree of the throttle valve.

For this reason, the air-fuel ratio, which is the ratio of air to fuel, changes depending on the opening of the throttle valve. Therefore, there is a problem that stable engine performance cannot be obtained in the entire speed range. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a stratified scavenging two-cycle engine capable of obtaining stable engine performance in the entire rotation speed range.

[0010]

In order to achieve the above object, the invention according to claim 1 comprises a cylinder (2), a piston (4) reciprocating in the cylinder (2), and the cylinder (2). 2) a crankcase (5) provided at the lower side, an air-fuel mixture supply flow path (15) for supplying an air-fuel mixture into the crankcase (5), and a cylinder (2) from within the crankcase (5). ), A stratified scavenging two-stroke engine including a scavenging passage (9) provided to communicate with the inside of the scavenging passage (9) and an air supply passage (10) for supplying air into the scavenging passage (9). An air flow path (18) branched into the air-fuel mixture supply flow path (15) and the air supply flow path (10) upstream of the air-fuel supply flow path (15) and the air supply flow path (10). ), And the air flow path (18) is provided with the air-fuel mixture supply flow path (15). Air flow control means (30) for controlling the flow rate of air before being branched to the air supply flow path (10) is provided, and the mixture supply flow path (15) is supplied from the air flow path (18). Air-fuel mixture producing means (12) for mixing the fuel with the produced air to produce an air-fuel mixture;
An air-fuel mixture backflow prevention means (16) is provided to allow only the flow of the air-fuel mixture into the crankcase (5), and the air supply flow path (10) is provided with air flow into the scavenging flow path (9). An air check valve (17) that allows only a flow is provided.

Further, according to the present invention, there is provided a cylinder (2), a piston (4) reciprocating in the cylinder (2), and a crankcase (4) provided below the cylinder (2). 5), an air-fuel mixture supply channel (15) for supplying an air-fuel mixture into the crankcase (5), and a scavenging air channel provided to communicate from the crankcase (5) into the cylinder (2). (9) and a stratified scavenging two-cycle engine including an air supply passage (10) for supplying air into the scavenging passage (9), wherein the mixture supply passage (15) and the air supply An air flow path (18) is provided upstream of the flow path (10) and is branched into the mixture supply flow path (15) and the air supply flow path (10). Are provided with the mixture supply channel (15) and the air supply channel (1).
0) and an air flow rate control means (30) for controlling the flow rate of the air before branching to the air supply flow path (15) and the air flow path (10). An air check valve (31) is provided, and the mixture supply passage (15) is provided with an air-fuel mixture mixing means (1) which mixes fuel with air supplied from the air passage (18) to form an air-fuel mixture.
2) is provided.

In the invention according to claim 1,
When the piston (4) moves upward, the pressure in the crankcase (5) decreases, so that the air-fuel mixture enters the crankcase (5), and the air also passes through the scavenging flow path (9) and the crankcase (5). 5) Go inside. When the piston (4) is lowered by the ignition of the air-fuel mixture in the cylinder (2), the pressure in the crankcase (5) increases,
First, the air accumulated in the scavenging flow path (9) enters the cylinder (2) and scavenges the combustion gas in the cylinder (2). After entering the cylinder (2), the cylinder (2) is filled with the air-fuel mixture. At this time, the backflow of the air-fuel mixture to the air-supply flow path (15) is prevented by the backflow prevention means (16), and the airflow to the air-supply flow path (10) is prevented by the air check valve (17). .

Further, by controlling the air flow rate control means (30), the flow rate of the air-fuel mixture flowing from the air-fuel mixture supply passage (15) into the crankcase (5) changes, and the engine speed changes. . Then, the mixture supply channel (1)
5) Since the flow rate of the air is controlled on the upstream side of the air supply flow path (10), the flow rate of the air flowing into the mixture supply flow path (15) and the flow rate of the air flowing into the air supply flow path (10) are controlled. The ratio with the air flow rate is always constant. Therefore, the flow rate of the air-fuel mixture flowing into the crankcase (5) from the air-fuel mixture supply flow path (15) and the air-fuel flow path (10) to the crankcase (5) through the scavenging air flow path (9). The ratio with the flow rate of the inflowing air is always constant.

Therefore, since the air-fuel ratio is always constant, stable engine performance can be obtained in the entire rotational speed range. In addition, since only one air flow control means (30) is required as the flow control means, the structure is simplified and the cost can be reduced.

Further, in the invention according to claim 2,
By the same operation as the invention according to the first aspect, stable engine performance can be obtained in the entire rotation speed range. In addition, only one air check valve (31) is required in place of the air check valve and the air-fuel mixture backflow prevention means as compared with the first aspect of the invention. Can be reduced.

In describing the operation of each of the above-mentioned inventions, air flows from the scavenging passage (9) to the crankcase (5).
Although the flow rate is set such that the air flows through the scavenging passage (9), the flow rate may be set such that the air stays in the scavenging flow path (9).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 shows an embodiment of a reference example, FIG. 2 shows a first embodiment, and FIG. 3 shows a second embodiment.

First, an embodiment of a reference example will be described with reference to FIG. A stratified scavenging two-cycle engine 1 shown in this embodiment includes a cylinder 2, a piston 4 reciprocating in the cylinder 2, a crankcase 5 provided below the cylinder 2, and a cylinder case 5. An air-fuel mixture supply passage 15 for supplying an air-fuel mixture, and a scavenging air passage 9 provided so as to communicate from inside the crankcase 5 into the cylinder 2.
And an air supply passage 1 for supplying air into the scavenging passage 9.
0, and the mixture supply flow path 15
An air-fuel mixture check valve (means for preventing air-fuel mixture backflow) 16 that allows only the flow of the air-fuel mixture into the crankcase 5 is provided. Provided in the air supply channel 10,
An air check valve 17 that allows only the flow of air into the scavenging flow path 9 is provided, and an air flow control unit 20 that controls the flow rate of air is provided, so that the flow rate of the air-fuel mixture and the flow rate of air are substantially constant. It is characterized in that a link mechanism (air-fuel ratio control means) 22 for controlling the air flow rate control means 20 is provided so as to obtain the ratio.

The piston 4 is connected to a crankshaft 6 via a connecting rod 3, and the crankcase 5 has an air-fuel mixture intake port 15 a open to an air-fuel mixture supply passage 15. The cylinder 2 has a scavenging port 9a and an exhaust port 13a which are opened and closed by the movement of the piston 4 itself while the piston 4 reaches the bottom dead center. The scavenging port 9a communicates with the scavenging passage 9 and the exhaust port 13a communicates with the exhaust passage 13. Further, in the vicinity of the scavenging port 9a in the scavenging flow path 9, an air intake port 10a communicating with the air supply flow path 10 is opened.

A mixture check valve 16 is arranged in the mixture supply passage 15 near the mixture intake port 15a, and a throttle valve 14 is arranged upstream of the mixture check valve 16, and a throttle valve 14 is provided. A vaporizer (mixture gas producing means) 12 is arranged further upstream of the valve 14. And
The first air cleaner 11 is connected to the most upstream side of the mixture supply channel 15.

The air supply passage 10 has an air intake port 1
An air check valve 17 is arranged near Oa, and an air flow control means 20 is arranged upstream of the air check valve 17.

A second air cleaner 21 is connected to the most upstream side of the air supply passage 10.

The opening of the throttle valve 14 is adjusted to control the flow rate of the air-fuel mixture flowing into the crankcase 5, thereby controlling the rotation speed of the engine. This throttle valve 14
Is connected to the air flow control means 20 via a link mechanism 22. The link mechanism 22 includes the air flow control unit 2
The air flow control means 20 is controlled so that the opening degree of 0 is substantially the same as the opening degree of the throttle valve 14. Therefore, even if the opening degree of the throttle valve 14 changes, the opening degree of the air flow control means 20 changes in the same manner, and the flow rate flowing through the throttle valve 14 and the flow rate flowing through the air flow control means 20 change. The ratio is to be constant.

In FIG. 1, 7 is a cylinder head, and 8 is a spark plug.

In the stratified scavenging two-cycle engine 1 configured as described above, when the piston 4 rises, the pressure in the crankcase 5 starts to decrease, and the scavenging port 9a and the exhaust port 13a close. For this reason,
The air-fuel mixture formed by the vaporizer 12 enters the crankcase 5 where the pressure has decreased, and air also enters the crankcase 5 through the scavenging flow path 9. Then, when the piston 4 reaches the vicinity of the top dead center, the air-fuel mixture in the cylinder 2 starts burning by the spark plug 8 and the piston 4 starts to descend. Then, the pressure in the crankcase 5 starts to increase, and the exhaust port 13a and the scavenging port 9a are opened.

For this reason, the combustion gas is discharged from the exhaust port 13a, and the compressed air in the scavenging passage 9 is blown out from the scavenging port 9a into the cylinder 2 to force the combustion gas from the exhaust port 13a. Discharge. Then, the mixture in the crankcase 5 enters the cylinder 2 through the scavenging flow passage 9. Further, the backflow to the air-fuel mixture supply passage 15 is prevented by the air-fuel mixture check valve 16, and the backflow to the air supply passage 10 is prevented by the air check valve 17.

When the piston 4 starts to rise, the pressure in the crankcase 5 starts to decrease, and the above-described cycle is repeated again.

Further, by controlling the flow rate of the air-fuel mixture entering the crankcase 5 by the throttle valve 14, the engine speed changes. At this time, the air flow control means 20 is controlled by the link mechanism 22 so that the flow rate of the air-fuel mixture and the flow rate of the air have a substantially constant ratio. The flow rate of the air-fuel mixture
And the flow rate of air entering the crankcase 5 through the scavenging flow path 9 is always constant.

That is, the ratio between the amount of air-fuel mixture and the amount of air filled in the crankcase 5 and the scavenging passage 9 is always constant regardless of the engine speed. Therefore, since the air-fuel ratio is always constant, stable engine performance can be obtained in the entire rotational speed range.

In the above embodiment, the opening of the air flow control means 20 is controlled by the link mechanism 22 so as to be substantially the same as the opening of the throttle valve 14. Instead, a structure using a cable may be used. Further, the opening degree of the air flow control means 20 may be controlled by an electric device so as to be substantially the same as the opening degree of the throttle valve 14.

Next, a first embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. However, components common to the embodiment of the reference example shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be simplified. The difference between the first embodiment and the embodiment of the reference example is that the air-fuel mixture supply passage 15 and the air supply passage 10
On the upstream side of the above, only one air flow control means 30 is provided as air flow control means before being branched into these.

That is, in the stratified scavenging two-cycle engine 1 of the first embodiment, an air flow path 18 branched from the mixture supply flow path 15 and the air supply flow path 10 is provided on the upstream side. The air flow path 18 is provided with an air flow rate control means 30 for controlling the flow rate of air before being branched to the air / fuel mixture supply flow path 15 and the air supply flow path 10. An air-fuel mixture check valve that allows only the flow of the air-fuel mixture into the crankcase 5 while providing a carburetor 12 that mixes fuel with the air supplied from the air flow path 18 (prevention of air-fuel mixture backflow) Means) 16 is provided,
The air supply passage 10 is provided with an air check valve 17 that allows only the flow of air into the scavenging passage 9.

The mixture check valve 16 is disposed near the mixture intake port 15a, and the carburetor 12 is disposed upstream of the mixture check valve 16. Further, the air check valve 17 is arranged near the air intake port 10a.
Further, the air flow control means 30 is disposed near the branch portion 18a in the air flow path 18.

In the stratified scavenging two-cycle engine 1 configured as described above, the flow rate of the air-fuel mixture flowing into the crankcase 5 from the air-fuel mixture supply passage 15 is changed by controlling the air flow control means 30. , The engine speed changes. Since the flow rate of air is controlled on the upstream side of the mixture supply channel 15 and the air supply channel 10, the flow rate of air flowing into the mixture supply channel 15 and the flow rate of air flowing into the air supply channel 10 are controlled. The ratio with the air flow rate is always constant. For this reason, the flow rate of the air-fuel mixture flowing into the crankcase 5 from the air-fuel mixture supply flow path 15 and the air supply flow path 10
And the flow rate of the air flowing into the crankcase 5 through the scavenging flow path 9 is always constant.

Therefore, the air-fuel ratio is always constant irrespective of the engine speed, so that stable engine performance can be obtained over the entire speed range. Moreover, it is only necessary to provide one combined air flow control means 30 as the flow control means, and only one air cleaner 11 is required.
Since there is no need to provide the link mechanism 22 and the like, the structure can be simplified and the cost can be reduced.

Next, a second embodiment will be described with reference to FIG. However, the elements common to the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description will be simplified. The difference between the second embodiment and the first embodiment is that
The only difference is that only one air check valve 31 is provided as a check valve.

That is, in the stratified scavenging two-cycle engine 1 of the second embodiment, an air flow path 18 branched from the mixture supply flow path 15 and the air supply flow path 10 is provided on the upstream side. The air flow path 18 is provided with air flow rate control means 30 for controlling the flow rate of air before being branched to the mixture supply flow path 15 and the air supply flow path 10. An air check valve 31 that allows only the flow of air to the supply flow path 10 side is provided, and the mixture supply flow path 15 is formed by mixing fuel supplied with air supplied from the air flow path 18 to form a gas mixture. It is characterized in that a vessel 12 is provided.

The air flow rate control means 30 is provided in the air flow path 18.
The air check valve 31 is disposed on the upstream side of the air flow control means 30.

In the stratified scavenging two-cycle engine configured as described above, a stable engine performance can be obtained in the entire rotation speed range by the same operation as in the first embodiment. Moreover, the combined air check valve 3 is used as a check valve.
Since only one is required, the structure can be further simplified and the cost can be reduced.

In describing the operation of each of the above embodiments, the flow rate of the air passing through the air flow rate control means 20 is set so as to flow from the scavenging flow passage 9 into the crankcase 5. May be set to a flow rate that remains in the scavenging flow path 9. Further, although a configuration using a carburetor is shown as the air-fuel mixture producing means 12, it may be configured using a fuel injection mechanism instead of the carburetor.

[0041]

According to the first aspect of the present invention, since the flow rate of air is controlled on the upstream side of the mixture supply flow path (15) and the air supply path (10), the mixture supply flow path is controlled. (15)
The ratio between the flow rate of the air flowing into the air supply passage and the flow rate of the air flowing into the air supply passage (10) is always constant. For this reason,
The flow rate of the air-fuel mixture flowing into the crankcase (5) from the air-fuel mixture supply channel (15) and the air flowing into the crankcase (5) from the air supply channel (10) through the scavenging air channel (9). Is always constant.

Therefore, since the air-fuel ratio is always constant, stable engine performance can be obtained in the entire rotation speed range. In addition, since only one air flow control means (30) is required as the flow control means, the structure is simplified and the cost can be reduced.

Further, in the invention according to claim 2,
By the same operation as the invention according to the first aspect, stable engine performance can be obtained in the entire rotation speed range. Moreover, since only one air check valve (31) is required as the check valve, the structure is simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a stratified scavenging two-cycle engine shown as an embodiment of a reference example of the present invention.

FIG. 2 is a sectional view of a stratified scavenging two-cycle engine shown as the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a stratified scavenging two-cycle engine shown as a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stratified scavenging 2 cycle engine 2 Cylinder 4 Piston 5 Crankcase 9 Scavenging flow path 10 Air supply flow path 12 Air-fuel mixture production means (carburetor) 14 Air-fuel mixture flow control means (throttle valve) 15 Air-fuel supply flow path 16 Air-fuel mixture Check valve 17 Air check valve 18 Air flow path 20 Air flow control means 22 Air-fuel ratio control means (link mechanism) 30 Flow control means 31 Air check valve

Continuation of the front page (56) References JP-A-62-113824 (JP, A) JP-A-58-5423 (JP, A) JP-A-58-5424 (JP, A) JP-A-5-33657 (JP) JP-A-60-108530 (JP, A) JP-A-57-183520 (JP, A) JP-A-48-24118 (JP, A) JP-A-4-40236 (JP, A) 3-25611 (JP, B2) Jiko 55-4518 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02B 25/14-25/24

Claims (2)

(57) [Claims] Cylinder (2) and this cylinder (2)
A piston (4) reciprocating in the cylinder, a crankcase (5) provided below the cylinder (2), and a mixture supply passage (15) for supplying a mixture into the crankcase (5). ), A scavenging passage (9) provided to communicate from inside the crankcase (5) into the cylinder (2), and an air supply passage (10) for supplying air into the scavenging passage (9). ), Wherein the mixture supply passage (15) and the air supply flow are provided upstream of the mixture supply passage (15) and the air supply passage (10). And an air flow path (18) branched from the air-fuel mixture supply path (1).
5) and an air flow control means (30) for controlling the flow rate of air before being branched into an air supply flow path (10). The air flow path (18) is provided in the mixture supply flow path (15). ) Is provided with an air-fuel mixture producing means (12) for mixing the fuel with the air supplied from the air supplied from the air-fuel mixture, and means for preventing the air-fuel mixture from flowing back into the crankcase (5). ), And the air supply flow path (10) is provided with an air check valve (17) that allows only the flow of air into the scavenging flow path (9). engine. 2. A cylinder (2) and said cylinder (2)
A piston (4) reciprocating in the cylinder, a crankcase (5) provided below the cylinder (2), and a mixture supply passage (15) for supplying a mixture into the crankcase (5). ), A scavenging passage (9) provided to communicate from inside the crankcase (5) into the cylinder (2), and an air supply passage (10) for supplying air into the scavenging passage (9). ), Wherein the mixture supply passage (15) and the air supply flow are provided upstream of the mixture supply passage (15) and the air supply passage (10). And an air flow path (18) branched from the air-fuel mixture supply path (1).
5) and an air flow control means (30) for controlling the flow rate of air before being branched into an air supply flow path (10), and a mixture supply flow path (15) and an air supply flow path (1).
0) air check valve (3
1) is provided, and the mixture supply flow path (15) is provided with a mixture production means (12) for producing a mixture by mixing fuel with air supplied from the air path (18). Layered scavenging 2
Cycle engine.