JPH04112920A - Exhaust timing controller of 2-cycle engine - Google Patents

Abstract

PURPOSE:To prevent the distal end of a controlling valve from projecting in an exhaust path when the controlling valve is fully opened in two plate-like controlling valves moved back and forth to very exhaust timing by providing the controlling valve such that its widthwise center line is at a predetermined angle to a plane perpendicular to the sliding direction of a piston. CONSTITUTION:A cylinder body 1 is provided on the upper position of an exhaust path 3 slidably two plate-like controlling valves 7 which have their longitudinal axis l1 inclined by a predetermined angle theta1 to the sliding direction of a piston and the widthwise axis l2 inclined by a predetermined angle theta2 to a plane perpendicular to the sliding direction of the piston. The respective controlling valves 7 are formed on one end adjacent no the cylinder 2 side with an arcuate surfaces 7a having the same curvature as that of the cylinder 2. Thus, when the controlling valve 7 in a high rotation region retreats from the exhaust path 3 to be fully opened, the outside distal end of the valve project in the exhaust path 3 so that exhaust flows smoothly in the exhaust path 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust timing control device for a two-stroke engine.

(Prior Art) As shown in FIG. 7, such an exhaust timing control device includes a plate-shaped control valve 107 that is slidably provided at an angle inclined with respect to the sliding direction of the piston 113 and is connected to the exhaust passage 103. By moving the engine forward and backward near the exhaust boat 105, the exhaust timing is changed between the low rotation range and the high rotation range, thereby improving the engine output over the entire rotation range. That is, in the high rotation range, the control valve 10 is closed as shown by the solid line in FIG.
7 from the exhaust passage 103, and in the low rotation range, the exhaust timing is delayed by protruding the control valve 107 into the exhaust passage 103 as shown by the chain line in Fig. 7. This improves engine output by properly discharging air throughout the entire rotation range.

However, in recent years, there has been a trend to increase the opening area of the exhaust passage in order to increase exhaust efficiency and increase the output direction of the engine, and as the opening area of the exhaust passage increases, the width of the control valve also increases. growing.

However, as the width of the control valve increases, the thermal distortion of the control valve increases, causing a problem that the sliding resistance of the control valve increases.

Therefore, as shown in FIG. 8, two control valves 207 and 207 are provided above the exhaust passage 203 with a large opening area, and the amount of thermal distortion of each control valve 207 and 207 is kept small and these resistance resistances are reduced. Attempts have been made to reduce this (for example, see Japanese Patent Laid-Open No. 6232216). In addition, FIG. 8 shows the cylinder 202, exhaust passage 203, and control valve 207°20.
7 is a plan view schematically showing the relationship between the control valves 207 and 7.
207 is slid in the direction of arrow C in the figure.

(Problem to be solved by the invention) By the way, the end face 207a of the tip of the control valve 207, 207
, 207a are arcuate surfaces with a curvature equal to that of the cylinder 202, so the control valve 20 as shown in FIG.
The outer tip portions a, a of each of the control valves 207 and 207 protrude by an amount Δ relative to the inner tip portions s and b in the sliding direction of the control valve 207 (in the direction of arrow C in the figure). For this reason, the 9th
As shown in the figure, the control valves 207, 207 or the exhaust passage 203
Even if it is fully opened by retreating from the
, a protrudes into the exhaust passage 203 and disturbs the exhaust flow, resulting in an increase in exhaust resistance and a problem in that the exit direction of the engine is obstructed. In addition, Fig. 9 is shown in the direction of the arrow in Fig. 8.
The direction is shown, and in the figure, 205, 205 are exhaust ports.

The present invention has been made in view of the above problem, and its purpose is to prevent the outer tip of the control valve from protruding into the exhaust passage when the control valve is fully opened, thereby suppressing the increase in exhaust resistance. An object of the present invention is to provide an exhaust timing control device for a two-stroke engine that is capable of controlling the exhaust timing of a two-stroke engine.

(Means for Solving the Problems) In order to achieve the above object, the first invention provides two plate-shaped controls that are slidably provided in the circumferential direction of the cylinder at an angle inclined with respect to the sliding direction of the piston. In an exhaust timing control device for a two-stroke engine that changes the exhaust timing by moving a valve forward and backward in the upper part of the exhaust passage near the exhaust boat, the control valve is moved relative to its widthwise centerline or to a plane perpendicular to the sliding direction of the piston. It is characterized by being inclined at a predetermined angle.

A second aspect of the invention is the exhaust timing control device for a two-stroke engine, characterized in that the control valves are arranged radially around the cylinder axis.

(Function) According to the present invention, since it follows the shape of the inner end surface of each control valve or the shape of the inner wall of the exhaust passage, when the control valve retreats from the exhaust passage and becomes fully open, its outer tip or the exhaust passage The exhaust flows smoothly through the exhaust passage without protruding. As a result, the exhaust resistance can be suppressed to a small level, and the engine can be moved in a further direction.

(Example) An example of the first invention will be described below based on the accompanying drawings.

Fig. 1 is a vertical cross-sectional view of the main parts of a two-stroke engine showing an exhaust timing control device according to the present invention, Fig. 2 is a view taken in the direction of the arrow (■) in Fig. 1, and Fig. 3 is a cylinder, exhaust passage, and control. FIG. 4, a schematic plan view showing the relationship with the valve, is a view taken in the direction of the arrow {circle around (2)} in FIG.

As shown in Fig. 1, a cylinder 2 is installed through the center of the cylinder body l, and an exhaust passage 3 and a plurality of scavenging passages (only one is shown) 4 are formed around the cylinder 2. The exhaust passage 3, exhaust passage 4... are each connected to an exhaust port 5. A scavenging boat 6 is opened on the inner circumferential surface of the cylinder 2.

Further, the cylinder body l is provided with two plate-shaped control valves 7, 7 slidably located above the exhaust passage 3, or these control valves 7, 7 are provided as shown in FIG. The axis line in the longitudinal direction, or the sliding direction of the piston (not shown)
The axis mi of the cylinder 2 is inclined at a predetermined angle θ with respect to the force direction, and the axis of the cylinder 2 is oriented in the width direction as shown in FIG.
It is provided so as to be inclined at a predetermined angle θ with respect to a plane perpendicular to the sliding direction of the piston (the direction in which the axis of the cylinder 2 is viewed).

One end of each of the control valves 7 facing the cylinder 2 side forms an arcuate surface 7a having the same curvature as that of the cylinder 2, as shown in FIG. It is worn. This lot 8 faces into a housing 9 that is formed integrally with the upper part of the exhaust passage 3 of the cylinder body 1, and a bottle 10 is provided at the end of the lot 8 to penetrate in a direction perpendicular to the axis. .

On the other hand, inside the housing 9, a rotatably supported shaft 11 is disposed long in the direction perpendicular to the paper surface of FIG. (see FIG. 2), and the pin 10 is engaged with a 0-shaped recess 12a formed at the tip of each arm 12.

When the shaft 11 is rotated by a drive source (not shown) that is controlled based on information on the engine speed, the arms 12 are rotated in the same direction, and the two control valves are rotated. 7.7 and the arrow A direction at the same time, the tips of these control valves 7.7 or the upper part of the exhaust passage 3 move back and forth to change the timing when the exhaust boat 5 is opened by the piston, that is, the exhaust timing, The upward direction of the engine is maintained over the entire rotation range. That is, when the engine is operating in a low rotation range, the control valves 7, 7 are made to protrude from the upper part of the exhaust passage 3, and thereby the upper part of the exhaust boat 5 is closed by the control valves 7, 7. By delaying the exhaust timing, exhaust can be properly performed at low rotation speeds, thereby improving engine output in the low rotation speed range.

Also, when the engine is operating in a high rotation range, the control valve 7.7 withdraws from the exhaust passage 3 and becomes fully open, and as a result, the upper part of the exhaust boat 5 is opened, the exhaust timing is advanced, and the high rotation speed is increased. By properly discharging the engine at certain times, it is possible to improve the engine output in the high rotation range.

In the above, in this embodiment, as described above, the control valves 7, 7
is a predetermined angle θ with respect to the axis line 2 in the width direction or a plane perpendicular to the sliding direction of the piston (the direction in which the axis of cylinder 2 is viewed)
2 (see FIG. 2), the shape of the inner end surface of the control valve 7 follows the shape of the inner wall of the exhaust passage 3 as shown in FIG. 4, and the control valve 7. When the outer tips 7 and 7 are in the fully open state after retreating from the exhaust passage 3, the outer tips a and a do not protrude into the exhaust passage 3. Therefore, the exhaust gas flows smoothly in the exhaust passage 3, the exhaust resistance is kept small, and the engine output is further increased.

Next, an embodiment of the second invention will be described based on FIGS. 5 and 6. Furthermore, FIG. 5 is a vertical sectional view of the essential parts of a two-cycle engine showing the exhaust timing control device according to the present invention, and FIG. 6 is a schematic plan view showing the relationship between the cylinder, exhaust passage, and control valve. In these figures, the first invention according to the first invention is shown.
The same elements as shown in FIGS. 4 to 4 are designated by the same reference numerals.

In this embodiment as well, two control valves 7, 7 are slidably provided above the exhaust passage 3, and as shown in FIG. It is arranged so as to be inclined by a predetermined angle θ□ with respect to the sliding direction (direction in which the axis of the cylinder 2 is viewed).

In this embodiment, the control valves 7, 7 are arranged radially around the axis of the cylinder 2, as shown in the sixth section. If the control valves 7, 7 are arranged in this way,
Amount Δ of the control valve 7.7 protruding in the sliding direction (in the direction of the arrow) with respect to its outer tips a, a and its inner tips S, b
L2 is smaller than the conventional protrusion amount ΔL shown in Fig. 8 (Δ
Therefore, when the control valves 7, 7 or 7 are fully open by retreating from the exhaust passage 3 in the high rotation range, the outer tips a, a or the exhaust passage 3
It doesn't stick out inward. As a result, in this embodiment as well, the exhaust gas flows smoothly in the exhaust passage 3, the exhaust resistance is suppressed to a low level, and the engine output is further improved.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, when the control valve retreats from the exhaust passage and becomes fully open, its outer tip does not protrude into the exhaust passage, so that the exhaust gas is The effect is that the exhaust gas flows smoothly through the passage, the exhaust resistance is kept low, and the engine can be moved in a further direction.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the essential parts of a two-stroke engine showing an exhaust timing control device according to the first invention, and Fig. 2 is a view taken in the direction of the arrows in Fig. 1.
FIG. 3 is a schematic plan view showing the relationship between the cylinder, the exhaust passage, and the control valve. Fig. 4 is a view taken in the direction of the arrow (■) in Fig. 1, Fig. 5 is a longitudinal cross-sectional view of the main parts of a two-stroke engine showing the exhaust timing control device according to the second invention, and Fig. 6 is a view showing the cylinder and exhaust passage. A schematic plan view showing the relationship with the control valve; FIG. 7 is an Ijl sectional view of the main part of a two-stroke engine equipped with a conventional exhaust timing control device;
FIG. 8 is a plan view schematically showing the relationship between cylinders, exhaust passages, and control valves in a two-stroke engine, and FIG. 9 is a view taken in the direction of the arrow {circle around (2)} in FIG. 2...Cylinder, 3...Exhaust passage, 5...Exhaust boat, 7...Control valve, Dan...Cylinder axis, sentence,...
...Longitudinal center line of the control valve, intersection...Radial center line of the control valve, θ1. θ2...Inclination angle of control valve 6 Patent applicant Yamaha Motor Co., Ltd. Representative Patent attorney Ryo Yamashita Figure 1 Figure 2 Figure 3 Figure 4 Figure 6

Claims (2)

[Claims] (1) The exhaust timing is controlled by moving two plate-shaped control valves, which are slidably provided in the cylinder circumferential direction at an angle inclined to the sliding direction of the piston, to the upper part of the exhaust passage near the exhaust port. In the exhaust timing control device for a two-stroke engine, the control valve is provided so that its center line in the width direction forms a predetermined angle with respect to a plane perpendicular to the sliding direction of the piston. Exhaust timing control device for 2-stroke engine. (2) The exhaust timing is controlled by moving two plate-shaped control valves, which are slidably provided in the cylinder circumferential direction at an angle inclined to the sliding direction of the piston, to the upper part of the exhaust passage near the exhaust port. 1. An exhaust timing control device for a two-stroke engine, characterized in that the control valves are arranged radially around a cylinder axis.