JPH0721869Y2 - Two-stroke engine scavenging passage variable mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a variable scavenging passage mechanism for a crankcase compression type two-stroke gasoline engine.

[Conventional technology]

4 to 6 show a schematic structure of a conventional Suniire scavenging two-stroke gasoline engine. In FIG. 4, 1 is a cylinder, 2 is a crankcase, 3 is a piston, 4 is a spark plug, 5 is an intake hole, and 6 is an exhaust hole. Reference numeral 7 denotes a scavenging hole, which is provided symmetrically with respect to a center line (an alternate long and short dash line in FIG. 5) connecting the intake hole and the exhaust hole.

Reference numeral 8 denotes a scavenging passage, the inlet of which is provided on the outer peripheral portion (outside) of the crankcase 2.

FIG. 5 shows the positional relationship and shape of the exhaust hole 6, the scavenging hole 7, and the scavenging passage 8 as viewed from above. Next, the operation of the conventional example will be described. Fresh air (mixture) when piston 3 rises
Is sucked into the crankcase 2 through the intake hole 5. Next, when the piston 3 descends, the scavenging hole 7 is opened before bottom dead center, and fresh air flows into the combustion chamber in the cylinder 1 through the scavenging passage 8. At this time, since the exhaust hole 6 has already been opened, a part of the fresh air flowing into the cylinder 1 is blown through the exhaust hole 6 without participating in combustion. For this reason, the direction of the scavenging hole 7 and the scavenging passage 8 is directed to the opposite side of the exhaust hole 6 to reduce blow-through of fresh air.

When the scavenging airflow is strong (the throttle valve opening is large when the load is high), it is as shown in FIG. 9, and when the scavenging airflow is weak (the throttle valve opening is small when the load is low), it is as shown in FIG.

[Problems to be solved by the device]

In the conventional example, the direction of the scavenging hole 7 is directed to the opposite side of the exhaust hole 6 in order to reduce blow-through of the air-fuel mixture. However, especially at a low load, the flow rate of scavenging air from the crankcase 2 to the cylinder 1 is small, so the penetration force of the scavenging air flow is weak, and as shown in the schematic diagrams of FIGS. Hard to hold.
Therefore, blow-through of fresh air into the exhaust hole 6 is increased, and the amount of fresh air filled in the cylinder 1 is reduced.

Further, while the fresh air is supplied to the cylinder, the exhaust hole 6 is open and fresh air flows in at a pressure close to the atmospheric pressure. Even when the exhaust hole is closed, the pressure in the cylinder is close to the atmospheric pressure. . When the exhaust hole is closed, the pressure inside the cylinder is almost the same for both low and high loads, but the throttle valve opening of the carburetor is small when the load is low,
The amount of fresh air flowing in is reduced and the amount of fresh air blown through is large, so that the amount of fresh air in the cylinder is reduced and the residual gas ratio becomes very large.

Therefore, at low load, abnormal combustion with many misfires is observed, causing problems such as vibration and noise.

In addition, as shown in Fig.8, depending on the movement of the throttle valve,
The scavenging passage control valve 10 is driven by the link mechanism of 6, 15, 14, and 13 to control the flow direction and strength of the scavenging air. Since this method is directly connected to the throttle valve by the link mechanism, it operates only in proportion to the opening of the throttle valve, and the optimum passage area and passage shape for the load condition cannot be obtained.

[Means for Solving the Problems]

A variable valve that works in conjunction with a throttle valve via a cam mechanism is provided on one (one side) or both of the symmetrical scavenging passages to optimally control the scavenging passage area according to the throttle valve opening, and also to perform scavenging. Control the flow direction and strength of.

[Action]

The opening / closing movement of the throttle valve is transmitted to the scavenging passage control valve via the cam mechanism and the rod, and the scavenging passage is opened / closed according to the load.

Therefore, it is possible to prevent abnormal combustion at low load, which is peculiar to a two-cycle gasoline engine, improve combustion at low load, and improve fuel efficiency.

〔Example〕

1 and 2 show an embodiment of the present invention. The valve for controlling the scavenging passage area is basically driven by the link mechanism as in FIG. However, the drive wheel 16 is not directly driven by the throttle valve, but via the scavenging passage control drive shaft 22 driven by the cam mechanism composed of the cam profile plates 21a, 22a according to the movement of the throttle valve 21, Controlled. The details will be described below.

In FIGS. 1 and 2, 9 is a cylinder and 10 is a scavenging passage.
Control valve that closes 11 from the lateral direction, 12 is a valve storage space, 13, 14, 16
Is a control valve drive shaft, 15 is a rotary shaft, 17 is a carburetor, and 21 is a throttle valve shaft for adjusting the inflow amount of the air-fuel mixture. A cam plate half-rotating shaft 22 is provided with a cam profile plate 22a. The cam profile plate 21a provided on the throttle valve shaft 21 is contacted with D as a contact point and driven. Also cam profile plate 22a
Is always pressed by a return spring (not shown) in the direction in which it contacts the cam profile plate 21a on the throttle valve shaft side. The drive shaft 16 is mounted on the cam profile plate 22a, and rotates the rotary shaft 15 according to the movement of the throttle valve shaft 21 via the cam plate rotary shaft 22. Reference numeral 20 is a support portion of the rotating shaft 15. The drive shaft 14 drives the drive shaft 13 by the rotation of the rotary shaft 15 to move the control valve 10 to make the area of the scavenging passage 11 variable. 19 is an O-ring that prevents gas leakage. Although the present embodiment is applied to only one side of the scavenging passage, the same mechanism may be provided in both passages.

The operation of this device will be described with reference to FIGS. In FIG. 3, the straight line indicates the conventional example, and the broken line indicates the performance of the present invention. When the throttle valve opening of the high load carburetor is close to full opening, the drive shaft 16 moves in the B direction, and the link mechanism of 16, 15, 14, 13 moves the control valve 10 in the B'direction, and the scavenging passage 11 is almost fully open. At this time, the scavenging passage area is sufficiently secured as in the conventional example, and the scavenging flow rate is sufficiently secured.
The output is large.

When the load is low, the drive shaft 16 moves in the C direction,
The control valve 10 is moved in the C'direction by the link mechanism of 5,14,13 to reduce the area of the scavenging passage 11.

If this mechanism is used only on one side of the two scavenging passages, the scavenging passage area becomes smaller and the school becomes larger depending on the opening of the throttle valve, so the combustion performance at light load is improved. Also, when it is provided in both passages, the flow direction of scavenging air can be controlled, the amount of fresh air filled can be increased, and combustion and fuel consumption can be improved.

A conventional example provided with the variable mechanism described with reference to FIGS. 7 and 8 is shown by the one-dot chain line in FIG. 3 and ---. In this case, the passage area can be controlled only in proportion to the movement of the throttle valve. However, in the example of the present invention (dotted line), the throttle valve shaft side cam profile plate 21a
The scavenging passage control cam profile of the contact portion of the drive shaft side cam profile plate 22a can be freely selected, and more optimal scavenging air flow control can be performed as compared with the conventional example shown in FIGS.

[Effect of device]

The present invention has the following effects in the sineile scavenging type crankcase compression two-cycle engine by providing a valve in the scavenging passage, which is interlocked with the throttle valve and adjusts the scavenging passage area according to the load.

The scavenging passage area can be freely varied according to the load, abnormal combustion at low load can be eliminated, combustion at low load can be improved, and fuel efficiency of the engine can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a scavenging passage varying mechanism according to an embodiment of the present invention. FIG. 1 is a horizontal sectional view of a main part, and FIG. 2 is a sectional view taken along the line II-II of FIG. . FIG. 3 is a performance diagram of the present invention and the conventional example. 4 to 6 are schematic views of a conventional Siuniere scavenging two-stroke gasoline engine, FIG. 4 is a vertical sectional view, FIG. 5 is a horizontal sectional view of the air passage portion of FIG.
The figure is a sectional view taken along the line VI-VI in FIG. 7 and 8 are configuration diagrams of a conventional scavenging passage varying mechanism, FIG. 7 is a horizontal sectional view of a main portion, and FIG. 8 is a sectional view taken along the line VIII-VIII of FIG. 9th
Figures 10 and 10 are explanatory views of the scavenging flow of a conventional two-cycle gasoline engine with scavenging scavenging system. Fig. 9 shows a strong scavenging air flow and Fig. 10 shows a weak scavenging air flow. 9 ... Cylinder, 10 ... Control valve 11 ... Scavenging passage, 13, 14, 16 ... Drive shaft 15, 22 ... Rotation shaft, 21 ... Throttle valve shaft 21a, 22a ... Cam profile plate

Claims (1)

[Scope of utility model registration request] 1. A Siuniere scavenging type crankcase compression two-cycle engine, in which a scavenging passage is interlocked with a throttle valve,
A scavenging passage variable mechanism for a two-cycle engine, which is provided with a valve for adjusting a scavenging passage area according to a load.