JPH07189704A - Two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent fuel loss by preventing a blow-by phenomenon that air-fuel mixture jetted to a combustion chamber from the scavenging port of an engine is exhausted directly from an exhaust port. CONSTITUTION:A two-cycle engine is provided with a branch passage 59 branching off from between a throttle valve 53 in an intake passage 51 and a main nozzle hole 55 opened in the rear of the throttle valve 53, and a carburetor 37 provided with an auxiliary nozzle hole 57 opened frontward from the branching position of the branch passage 59. The branch passage 59 is opened to the inner wall of a cylinder 15 near a scavenging port 31 or to a scavenging passage, and the intake passage 51 is communicated with the inside of a crankcase 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine provided with a scavenging passage which connects a scavenging port which opens into a combustion chamber when a piston descends with a crankcase.

[0002]

2. Description of the Related Art Conventionally, in a two-cycle engine of this type, as shown in FIG. 4, a mixture of fuel sucked into a crankcase 3 from a carburetor when the piston 1 is raised is a piston after the engine explodes. It was configured to jet into the combustion chamber 9 from the scavenging port 7 that opens immediately before the end of the descent through the scavenging passage 5 when descent.

[0003]

Since the exhaust port 11 is provided so as to start opening immediately before the scavenging port 7 is opened,
A portion of the air-fuel mixture jetted from the scavenging port 7 at the beginning of the jet flowed to the exhaust port 11, causing a so-called blow-through phenomenon, resulting in fuel loss.

[0004]

SUMMARY OF THE INVENTION In a two-stroke engine, the present invention is provided with a branch passage branching between a throttle valve in an intake passage and a main nozzle opening that is open to the rear of the throttle valve. A carburetor with an auxiliary nozzle opening that opens forward from the branch position of the passage was provided, and this branch passage was connected to the cylinder inner wall near the scavenging opening or the scavenging passage, and the intake passage was provided to communicate with the crankcase. It is a thing.

[0005]

In the present invention, when the piston rises, the inside of the crankcase has a negative pressure, the air in the intake passage of the carburetor is sucked into the crankcase, and the fuel ejected from the main nozzle port is mixed. At the same time, air is sucked into the scavenging passage from the branch passage. At this time, the throttle valve is open and fuel is not ejected from the auxiliary nozzle port. Next, when the piston descends due to the explosion, the exhaust port opens near the end of the descent and the exhaust gas is released, and then the scavenging port opens, and the positive pressure in the crankcase first ejects the air in the scavenging passage, Subsequently, the air-fuel mixture in the crankcase is ejected, but while the exhaust port is open, only the air initially ejected from the scavenging port is discharged, and then the air-fuel mixture is exhausted by the exhaust port before the air-fuel mixture is exhausted from the exhaust port. Will be closed.

When the throttle valve is adjusted to perform the idle operation, the fuel is jetted from the auxiliary nozzle port and the fuel at the main nozzle port is stopped, but the air-fuel mixture is sent to both the branch passage and the crankcase to perform the idle operation. Retained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

A cylinder 15 is fixed to the upper part of the crankcase 13, and a piston 17 is fitted inside the cylinder 15 so as to be vertically movable.
Are connected to a crank 21 of a crankshaft 19 which is pivotally supported by the crankcase 13 by a connecting rod 23. The spark plug 2 is provided on the upper surface of the combustion chamber 25 in the upper portion of the cylinder 15.
7 is attached, and the exhaust port 2 is at the end of the downward movement of the piston 17.
9. The scavenging port 31 is open. The exhaust port 29 communicates with the atmosphere through the muffler 33, and the scavenging port 31 communicates with the inside of the crankcase 13 through a scavenging passage 34.

At the end of rising of the piston 17, the intake port 3
5 opens to communicate with the crankcase 13, and the intake port 35
Is communicated with the atmosphere through a vaporizer 37 and an air cleaner 39.

A rear end of the intake passage 51 in the carburetor 37 communicates with the inside of the crankcase 13 through an intake port 35 opened and closed by the piston 17, and a check valve 52 that communicates only in the intake direction is provided near the front end. Has been. A main nozzle opening 55 is opened behind the throttle valve 53 in the intake passage 51, and an auxiliary nozzle opening 57 is opened close to the throttle valve 53. The other end of the branch passage 59 that branches from the intake passage 51 between the throttle valve 53 and the main nozzle port 55 communicates with the scavenging passages 34, 34 that face each other via a branching communication pipe 61.

In this embodiment, when the piston 17 rises, the inside of the crankcase 13 has a negative pressure, and the air is sucked from the air cleaner 39 into the crankcase 13 through the intake passage 51 of the carburetor 37. Mouth 5
Fuel jetted from 5 is mixed. Branch passage 5 at the same time
Air is sucked into the scavenging passage 34 from 9. At this time,
The throttle valve 53 is in the open state, the flow velocity of the air near the auxiliary nozzle port 57 decreases, and fuel is not ejected from the auxiliary nozzle port 57.

Next, when the piston 17 descends due to the explosion, the exhaust port 29 opens near the end of the downward descent, and exhaust gas is released, and subsequently the scavenging port 31 opens and the positive pressure in the crankcase 13 causes the scavenging passage to begin. The air in 34 is ejected, and then the air-fuel mixture in the crankcase 13 that is ejected is ejected, but while the exhaust port 29 is open,
Only the air initially ejected from the scavenging port 31 is discharged, and then the exhaust port 29 is closed before the air-fuel mixture is exhausted from the exhaust port 29.

At this time, the intake passage 51 is connected to the piston 1
Since it is closed by 7 and the check valve 52 is provided, the mixture does not flow back into the branch passage 59.

In the present invention, the fuel injected from the auxiliary nozzle port 57 is interlocked with the throttle valve 53 to stop the fuel injection from the auxiliary nozzle port 57 during normal operation to prevent the fuel from entering the branch passage 59. Alternatively, it may be provided so that only air is reliably sent.

Further, instead of the check valve 52 in the intake passage 51, a check valve 63 may be provided in the branch passage 59 as shown in FIG.

[0016]

The present invention has the following effects. (1) It is possible to prevent the air-fuel mixture ejected from the scavenging port from being directly discharged from the exhaust port, prevent fuel loss, and improve the fuel consumption rate. (2) A butterfly valve in the air passage communicating with the scavenging passage and a mechanism for interlocking this butterfly valve with the throttle valve are not required, and only one check valve is required, and the structure is simple and inexpensive to manufacture. (3) With the configurations of claims 2 and 3, it is possible to prevent the air-fuel mixture from flowing back from the scavenging passage to the branch passage. (4) According to the configuration of claim 4, it is possible to prevent the fuel from being mixed with the air ejected from the branch passage into the cylinder during the normal operation, and to further improve the fuel consumption rate.

[Brief description of drawings]

FIG. 1 is a side sectional view of an embodiment of the present invention.

FIG. 2 is a front sectional view of the present invention.

FIG. 3 is a side view of another embodiment of the main part of the present invention.

FIG. 4 is a front sectional view of a conventional example.

[Explanation of symbols]

 13 Crankcase 15 Cylinder 31 Scavenging Port 34 Scavenging Passage 37 Vaporizer 51 Intake Passage 52 Check Valve 53 Throttle Valve 55 Main Nozzle Port 57 Auxiliary Nozzle Port 59 Branch Passage 63 Check Valve

Claims (4)

[Claims] 1. A throttle valve 53 in the intake passage 51,
Main nozzle port 55 that opens behind the throttle valve 53
And a carburetor 37 having an auxiliary nozzle port 57 that opens forward from the branching position of the branch passage 59.
1 is communicated with the inner wall of the cylinder 15 or the device passage 34, and the intake passage 51 is connected to the crankcase 13
A two-cycle engine characterized by communicating with the inside. 2. The two-stroke engine according to claim 1, further comprising a check valve 52 that communicates the intake passage 51 only in the intake direction. 3. The two-cycle engine according to claim 1, further comprising a check valve 63 which connects the branch passage 59 only in the direction of the cylinder 15. 4. The two-cycle engine according to claim 1, further comprising an auxiliary nozzle port 57 which is closed in conjunction with the throttle valve 53 when the throttle valve 53 is opened.