JPH07139358A - Two cycle engine - Google Patents

Abstract

PURPOSE:To prevent the generation of a blow-by phenomenon and fuel loss by installing an air passage which opens in the position adjacent to a scavenging port inside a scavenging passage and installing a check valve. CONSTITUTION:A spark plug 27 is mounted on the upper surface of a combustion chamber 25 in the upper part inside a cylinder 15, and an exhaust port 29 and a scavenging port 31 are opened at the end point of the falling down of a piston 17. An air passage 43 is opened in the position adjacent to the scavenging port 31 inside a scavenging passage 41 which connects the scavenging port 31 to a crank case 13. A check valve 49 which communicates only in the direction of the scavenging passage 41 is installed in the air passage 43. Direct exhaust of a mixed gas ejected from the scavenging port 31 is prevented and fuel loss is prevented for enhancing a fuel consumption rate.

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. 5, a mixture of fuel sucked from a carburetor into a crankcase 3 when a 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]

According to the present invention, an air passage opening at a position near a scavenging port is provided in a scavenging passage, and a check valve is provided in this air passage. Further, as a second aspect, an adjusting device for adjusting the air flow rate of the air passage in association with the throttle operation of the engine is provided.

[0005]

In the present invention, when the piston rises, the inside of the crankcase has a negative pressure, and the air-fuel mixture containing the fuel mixed by the carburetor is sucked into the crankcase from the intake port, and at the same time, the check is performed from the air passage. When the valve is opened, air is sucked in and the air enters the entire scavenging passage or a part of the scavenging port side. 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, which continues. 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 exhausted, and then the exhaust port is closed before the air-fuel mixture is exhausted. is there.

[0006]

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 via the muffler 33, and the scavenging port 31 communicates with the inside of the crankcase 13 via a scavenging passage 41 described later.

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 via a vaporizer 37 and an air cleaner 39.

An air passage 43 is opened at a position close to the scavenging port 31 in the scavenging passage 41 which connects the scavenging port 31 and the crankcase 13, and the air passage 43 is provided with an internal butterfly valve 45 to adjust the flow rate. The device 47 communicates with the scavenging passage 4
A check valve 49 that communicates only in the one direction is provided.

An arm 57 is fixed to a shaft 55 to which a butterfly valve 53 for opening and closing an intake passage 51 in the carburetor 37 is fixed, and an arm 61 fixed to a shaft 59 of a butterfly valve 45 of an adjusting device 47 is connected by a rod 63. The arm 67 pivotally attached to the other end of the rod 65 connected to the throttle lever is fixed to the shaft 55, and the butterfly valve 53 and the butterfly valves 45, 45 are provided so as to open and close in conjunction with each other.

In the above structure, when the piston 17 moves up, the pressure in the crankcase 13 becomes a negative pressure, and the air-fuel mixture by which the fuel is mixed by the carburetor 37 is sucked into the crankcase 13 from the intake port 35. At the same time, the check valve 49 is opened from the air passage 43 and air is sucked into the scavenging passage 41. When the piston 17 descends due to the explosion, the exhaust port 29 opens near the end of the descending and the exhaust gas is released, and then the scavenging port 31 opens, and the positive pressure in the crankcase 13 causes the air in the scavenging port 31 to burn. Gush into chamber 25, then crankcase 1
Although the air-fuel mixture in 3 is ejected, only the air initially ejected from the scavenging port 31 is discharged while the air outlet 29 is open, and then the air outlet 29 is closed before the air-fuel mixture is discharged. It is what is done.

When the throttle lever is operated to shift the engine from the high speed rotation to the low speed rotation, the rod 65 of FIG. 4 is pulled in the direction of arrow A, and the butterfly valve 53 of the carburetor 37 is pulled.
Is rotated in the closing direction to perform idle rotation, and the butterfly valve 45 of the adjusting device 47 is rotated in the closing direction via the rod 63 to reduce the air flow rate.

The scavenging passage is
The shape such as the length and the cross-sectional area is appropriately set, and the shape may be largely curved or an air pocket may be provided on the way.

Further, in the present embodiment, the adjusting device is directly interlocked with the throttle operation, but in the present invention, it may be indirectly interlocked with the throttle operation such as interlocking with the rotational speed of the engine.

[0015]

According to the present invention, the air-fuel mixture ejected from the scavenging port can be prevented from being directly discharged from the exhaust port, the fuel loss can be prevented, and the fuel consumption rate can be improved. is there.

According to the second aspect, the air amount can be adjusted and the output can be stabilized in accordance with the throttle operation.

[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 same.

FIG. 3 is a side sectional view of the adjusting device.

FIG. 4 is a plan view of an interlocking mechanism.

FIG. 5 is a front sectional view of a conventional example.

[Explanation of symbols]

 13 crankcase 31 scavenging port 41 scavenging passage 43 air passage 47 adjusting device 49 check valve

Claims (2)

[Claims] 1. An air passage 43, which opens to a position close to the scavenging port 31, is provided in a scavenging passage 41 which connects the scavenging port 31 and the inside of the crankcase 13, and the air passage 43 is provided.
The two-cycle engine is characterized in that a check valve 49 communicating only in the direction of the scavenging passage 41 is provided in the. 2. The two-cycle engine according to claim 1, further comprising an adjusting device 47 which adjusts an air flow rate of the air passage 43 in association with a throttle operation of the engine.