JPS5853631A - Scavenge device of crank chamber compression 2-cycle engine - Google Patents

Abstract

PURPOSE:To ensure optimum area for a scavenge passage in a full range of load, by providing a rotary valve which changes area of the scavenge passage in such a manner as to increase the area of the scavenge passage synchronously with increase of a throttle opening. CONSTITUTION:A pressure relief passage 10 is provided between one of the plural scavenge passages 6, 6 and the internal surface 12 of a cylinder wall in the upper from an exhaust port 7, and a rotary valve 11, interlocking to a throttle pedal 26, is provided in a connection part of said passage to the scavenge passage 6. Then the rotary valve 11 is constituted in such a manner that the pressure relief passage 10 is communicated to the scavenge passage 6 only when a throttle is fully closed or almost fully closed, and area of the scavenge passages 6, 6 are increased synchronously with increase of a throttle opening. In this way, optimum area of the scavenge passage can be obtained in a full range of load, and scavenge flow speed of a mixture, flowing into a combustion chamber 31 from the scavenge passages 6, 6, can be increased to fully perform scavenge action, then a turbulence flow for effective combustion can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a crank chamber compression type 24# V engine t) return air system*ecsg, and is aimed at improving output and fuel economy at partial load, and improving startability. There is.

Generally, in a crank high-pressure wheel type two-cycle μ engine, the scavenging passage area (effective cross-sectional area) is constant.

(Slot for O) j'l/A minute with small opening area During load fluctuation, the intake mixture is small and the pressure inside the crankcase is also small, so the passage area designed for full load operation is O.
When the air-fuel mixture flows into the cylinder through a large scavenging passage, the scavenging flow rate is low and sufficient scavenging action cannot be performed, and turbulence is also obtained to improve effective combustion, resulting in poor atomization. On the other hand, there are known decompression devices that release the pressure in the combustion chamber at the time of startup to reduce the starting torque. If the relief passage is kept open all the time, the output will decrease during normal operation and the fuel consumption rate will increase, which is a drawback.However, if a dedicated opening/closing mechanism is provided as a countermeasure to this problem, the cost will increase.

In the present invention, the slot/L/
By providing a tally valve that can change the scavenging passage area so that the scavenging passage area increases as the M degree increases, the optimum scavenging passage area can be maintained in all areas from partial load to full load. This makes it possible to improve the output and fuel economy at partial load.

In addition, by providing a pressure relief passage that opens only when the throttle is fully closed or nearly fully closed (by providing a pressure relief passage that is opened by the rotary valve described above), it is possible to reduce starting trouble and improve smooth starting performance, as well as during normal operation. First, the present invention will be described with reference to the drawings.

@Figures 1 to 3 are crank chamber compression type 2 to which the present invention is applied.
This is a longitudinal cross-sectional view of a cycle engine, showing the times of startup, partial load operation, and full load operation, respectively. @2+ in 1 diagram
Iku y engine 1 has cylinder hef F2. The cylinder 3 and the crankcase 4 are integrally provided, and the inner surface 12 of the cylinder 3
A piston 5 is fitted to the piston 5 so as to be able to move up and down, and the piston S is fitted to the piston shin 13, the connecting sink 14. Connect the crankshaft 1G to the crankshaft 1G.
is rotatably supported by the crankcase 4 by a bearing 17. ? The crank lN1g in the rank case 4 is sealed by a seal ring 19 installed between the crank case 4 and the crankshaft 160, and the crank! 1g passes through the crankcase 4 and a scavenging passage provided within the thickness of the cylinder 30, and opens into the cylinder wall rM12 at the scavenging port 80. Scavenging port) 8. Inner surface of cylinder wall between 8!
An exhaust port 7 is opened, and this exhaust port 7 communicates with the atmosphere through an exhaust pipe (not shown) having a muffler.

Further, an intake port (not shown) is provided in the crankcase 4 facing the cylinder wall inner surface 12 facing the exhaust port 7 or the crank chamber 18, and this intake port is connected to the crankcase chamber 1.
It communicates with the carburetor via a reed valve (both not shown) that allows flow only in eight directions, or via a piston valve that opens and closes as screws 1 and 5 move up and down.

A pressure relief hole 9 is opened in the inner surface 12 of the cylinder wall at a position higher than the exhaust port 7, and this relief hole 9 communicates with one of the scavenging passages 6 (through the pressure relief passage 10 and the scavenging rotary valve 11. The valve 11 is a cylindrical body that is rotatably fitted into a 9-cylindrical valve seat 21, and is located at the connection between the pressure relief passage 10 and the scavenging passage 6.
A is provided with an arcuate notch 22. The scavenging passage 6 on the side where the rotary valve 11 is located is near the scavenging port) 81iD #
At C, the entire passage passes through the inside of the valve seat 21. Therefore, at the time of starting in FIG.
connects the pressure relief passage 10 to the scavenging passage 6.

Center vc[i! of rotary valve 11! The operating shaft 23 is provided with an arm 24 on the part that protrudes outside the cylinder 3, and the arm 24 is connected to a throttle pedal 26 (27) via a cape A/25.
8 is a stopper, and 29 is a fulcrum of the pedal 26.

At the time of starting as shown in Figure 111 (in this case, the throttle pedal 2
6 is depressed and the scavenging rotary valve 11 is V%'&%/% rounding! 11, the pressure relief passage 10 communicates with the scavenging passage 6 through the notch 22, and the scavenging passage 6 and the scavenging boat 8 on the side where the rotary valve 110 is located are closed. When the starter is operated in this state to give starting rotation to the crankshaft 16, the piston 5 rises and the piston 5 moves to the exhaust port. Combustion chamber 3 after passing the upper edge of C1
1 has been supplied to the combustion chamber 31 via the scavenging passage 6 and is open to the other side, so that the compressed pressure in the combustion chamber 31 is released through the pressure relief hole 9. It is released to the scavenging passage 6 through the pressure relief passage 10 and the notch 22, the pressure rise of combustion 11$1 becomes gradual, and the piston S rises easily. That is, the starting torque is reduced and the starting rotation of the crankshaft 16 becomes lighter, thereby improving starting performance. After the piston 5 passes upward through the pressure relief hole 9, the O pressure inside the combustion W131 increases, and at a predetermined timing (a spark supplied from the spark plug 20 causes an explosion, the screw cylinder 5 receives downward explosive pressure, Apply rotational force to the crankshaft 16.After starting, the return air rotary valve 11 is operated at
The posture shown in the figure is maintained, so the compression in the combustion chamber 31 is appropriately released, and gentle idling rotation with low output and low vibration continues.

When throttle pedal A/26 is depressed a certain amount in the direction of arrow A (partial load operation), when pedal A/260m is reached, cape A/
25, the operating shaft 231C and the rotary valve 11 are rotated in the direction of arrow B via the arm 24, the pressure relief passage 10 is immediately closed (Fig. 2), and the scavenging passage 6 is opened to the second g.
The scavenging passage area increases as the throttle opening increases from the initial opening state shown in FIG. Then, when the throttle pedal is fully depressed and the throttle opening is fully opened, the notch 22 of the rotary valve 11 reaches the position where the scavenging passage area 6 is maintained at its maximum.

When operating with a small throttle opening area I/% sardine load,
The air-fuel mixture sucked into the crank chamber 18 is small, and the pressure in the crank chamber is also small.However, the false scavenging passage 6 with the rotary valve 11 is rounded, with its passage area narrowed by the rotary valve 11, and the scavenging flow rate is high. 1, the opposite @O scavenging passage 6 also has an overall decrease in the area of the scavenging passage (
Scavenging, flow rate increases, scavenging air) 8, 8 to combustion chamber 3
The scavenging air tM flowing into the combustion chamber 31 effectively improves the pressure and fuel economy of the exhaust gas in the combustion chamber 31. Set it wI3
During full-load operation (shown in the figure), the air-fuel mixture of the device flows into the combustion chamber at a high flow rate from the scavenging passages 6.6 on both sides, which have large passage areas designed for full-load operation, and sufficient scavenging action is achieved. It will be done.

As explained above, in the Kg of the present invention, a pressure relief passage 1O is provided between one of the plurality of scavenging passages 6.6 and the cylinder wall inner surface 120 above the exhaust boat 7, and the pressure relief passage 10 and scavenging Connection g of passage 6 [throttle pedal A/
26 or a rotary valve 11 that interlocks with the throttle lever is provided, and a pressure relief passage, . . . 10, communicates with the scavenging passage 6 only when the throttle is fully closed or almost fully closed, and the area of the scavenging passage increases as the throttle opening increases. As a result, the optimum scavenging passage area can be obtained in all regions from partial load to full load, and the combustion chamber 31 (
By increasing the scavenging flow rate of the air-fuel mixture flowing into the cylinder), it is possible to perform a sufficient scavenging action and improve performance. Also, the relief passage 1G opens at the time of starting with the throttle fully closed, so
If the starting torque can be reduced, that is, the starting performance can be improved, the O pressure relief passage is blocked during normal operation, so there is an advantage that it can prevent a decrease in output and fuel efficiency during normal operation. . Scavenging communication area OP] lJ control and opening and closing of the pressure relief passage 100 are performed by one rotary valve 11, so an increase in the number of parts and an increase in cost F can be minimized.

[Brief explanation of drawings]

Claims (1)

[Claims] A pressure relief passage is provided on the inner surface of the cylinder wall above one of the plurality of scavenging passages and the exhaust boat, and a rotary valve that interlocks with the exhaust valve is installed at the interface between the pressure relief passage and the scavenging passage. Crank chamber compression type 2 characterized in that the pressure relief passage communicates with the scavenging passage only when fully closed or almost fully closed, and the area of the scavenging passage increases as the throttle opening increases. Cycle engine O scavenging device