JPH0420979Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to an exhaust control device for a two-stroke engine, and in particular changes the exhaust timing according to the engine rotation speed to improve the output of the two-stroke engine. Concerning improvements to exhaust control devices.

[Prior Art] Conventionally, in a two-stroke engine, an exhaust valve that changes the position of the upper edge of the opening is provided immediately after the cylinder side opening of the exhaust port, and this exhaust valve is operated by a servo motor or a mechanical governor mechanism. By driving with a drive device,
Some engines improve the output of a two-stroke engine from low to high speeds by changing the exhaust timing depending on the engine speed. As the above-mentioned exhaust valve, conventionally there is an hourglass-shaped valve that is rotatably disposed within the exhaust port and changes the position of the upper edge of the cylinder-side opening of the exhaust port on its circumferential surface.

By the way, in the conventional exhaust control device mentioned above,
The valve used to change the exhaust timing is an hourglass-shaped valve that is extremely difficult to work with and requires a high level of processing precision, resulting in high costs and poor mass production.

[Effect of idea]

In view of the above-mentioned circumstances, this invention provides a two-stroke engine exhaust control device that is low cost, highly mass-producible, and highly reliable.

[Structure of the idea]

In order to achieve the above-mentioned purpose, this invention:
A hole with a circular cross section is bored in the upper wall located immediately after the cylinder side opening of the exhaust port, and the lower end surface forms the upper surface of the exhaust port, and the center axis is the center axis of the cylinder. A columnar valve body is arranged so as to be inclined upward when viewed from a plane perpendicular to the cylinder side, and is slidably arranged in the hole toward the cylinder side opening. The end face protrudes into the exhaust port to lower the upper edge position of the cylinder side opening, and the lower end face of the valve body escapes from the exhaust port to lower the upper edge position of the cylinder side opening. I'm trying to raise it.

〔Example〕

Hereinafter, one embodiment of the exhaust gas control device according to the present invention will be described in detail.

Figure 1 shows 2 installed in the exhaust control device 1 of the present invention.
FIG. 2 is a sectional view of main parts of a cycle engine 2. FIG.

This exhaust control device 1 has an exhaust port 3
The upper wall 3b located immediately after the cylinder side opening 3a of
It consists of a hole 4 with a circular cross section bored in the hole 4, a spacer 7 filling the approximately upper semicircular part of the hole 4, and a columnar valve body 5 slidably disposed within the hole 4. . The valve body 5 is arranged such that its lower end surface 5a forms the upper surface of the exhaust port 3, and its central axis is inclined upward when viewed from a plane perpendicular to the central axis of the cylinder 9. Further, its cross section is approximately semicircular as shown in FIG. 2, which is indicated by the AA cross section in FIG. Further, the hole 4 has a lower end surface 5a of the valve body 5 disposed in the hole 4.
It is bored in the direction of sliding toward the cylinder side opening 3a (Fig. 1). On the other hand, the upper end surface 5b of the valve body 5 is connected to a drive device (not shown) (for example, a mechanical governor mechanism using ball centrifugal force, a servo motor, etc.) via a link mechanism 6. The valve body 5 is moved by the device and the link mechanism 6 by a predetermined stroke length along the direction in which the hole 4 is formed. Note that in FIGS. 1 and 2, reference numeral 7 denotes a spacer having a substantially semicircular cross section fixed in the hole 4;
One end surface 7a forms the upper surface of the exhaust port 3. Further, in FIG. 1, reference numeral 8 is a cylinder block, 9 is a cylinder, 10 is a cylinder head, and 11 is a lid that covers the link mechanism 6.

Next, the operation of the above-mentioned exhaust control device 1 will be explained,
The configuration will also be explained in more detail.

When the two-stroke engine 2 is started and its rotational speed range is low, the valve body 5 is projected by the drive device toward the cylinder side opening 3a of the exhaust port 3, and is moved to the initial position shown in FIG. Stop at. According to the initial position of the valve body 5 shown in FIG. 1, the upper edge position (arrow C) of the opening 3a formed in the cylinder 9 is as shown in FIG.
The lower end surface 5a of the valve body 5 allows the opening 3
The height H of the semicircular notch 3c forming the upper edge 3a' of a is apparently lowered. Therefore, the exhaust timing of the 2-cycle engine 2 is delayed by the lowered position of the upper edge of the cylinder-side opening of the exhaust port 3. Therefore, suitable exhaust timing is ensured in the low rotation speed range, and the 2-cycle engine 2 This will improve the output.

Further, according to the exhaust control device 1 described above, the first
As shown in the figure, the valve body 5 is located at the opening 3a on the cylinder side.
When the valve body 5 protrudes toward the cylinder, the tip of the valve body 5 receives strong exhaust pressure from the exhaust gas discharged from the exhaust port 3, but the valve body 5 is located upward when viewed from a plane in which the central axis intersects at right angles with the central axis of the cylinder. Since the exhaust pressure applied to the valve body 5 is mainly received by the surface where the valve body 5 and the hole 4 are in sliding contact, it does not act in the sliding direction of the valve body 5. Therefore, excessive exhaust pressure is not transmitted to the link mechanism 6 of the drive device that drives the valve body 5.

On the other hand, when the engine speed of the two-stroke engine 2 increases and reaches a predetermined high speed range, the valve body 5 of the exhaust control device 1 is pulled into the hole 4 by the drive device, as shown in FIG. Stop at the position shown. According to the stop position of the valve body 5 shown in FIG. 4, the upper edge position (arrow D) of the opening 3a formed in the cylinder 9 as shown in FIG. Since it coincides with the upper edge 3a' of the notch 3c, the height of the notch 3c is raised by the height H compared to the apparent upper edge position (arrow C) of the opening 3a shown in FIG. . Therefore, the exhaust timing of the two-stroke engine 2 is
The position of the upper edge of the cylinder-side opening becomes earlier as the position of the upper edge of the cylinder side opening increases, and therefore, suitable exhaust timing is ensured in the high rotational speed range, and the output of the two-cycle engine 2 is improved.

In the above embodiment, a case has been described in which one valve body 5 is used in the exhaust control device 1, but of course the present invention is not limited to the above embodiment, and the same parts as in FIG. 3 are designated by the same reference numerals. As shown in FIG. 6, the width W of the cylinder side opening 3a of the exhaust port
If the valve body 5 is wide, a plurality of the valve bodies 5 may be installed in parallel and operated simultaneously. In addition, when installing a plurality of valve bodies 5, a semicircular notch 3 is formed on the upper edge of the cylinder side opening 3a.
c are formed in a number corresponding to the number of valve bodies 5.

In the above embodiment, in the hole 4 having a circular cross section,
Although the valve body 5 having a semicircular cross section is disposed through the spacer 7 having a semicircular cross section, the present invention is not limited to the above embodiment. As shown in FIG. 8 and the EE cross section of FIG. 7, a valve body 12 with a circular cross section may be used instead of the valve body 5 with a semicircular cross section, and the use of the spacer 7 may be eliminated. . The above-mentioned valve body 12 having a circular cross section has a surface 12b at the tip of its lower end surface 12a, which has approximately the same height as the height H of the notch 3c of the cylinder side opening 3a, so that it runs along the circumferential surface of the cylinder 9. is formed.

When the above-mentioned valve body 12 is made to protrude a predetermined stroke toward the cylinder-side opening 3a as shown in FIG. 7 in a low rotational speed range, the opening 3a will move as shown in FIG. 9 shown in view B of FIG. The upper edge position (arrow C) is lowered by the height H of the notch 3c by the lower end surface 12a of the valve body 12, and the exhaust timing is delayed. In addition, when the valve body 12 is pulled into the hole 4 in a high rotational speed range as shown in FIG. 10, the upper edge position of the opening 3a (arrow D) coincides with the upper edge 3a' of the semicircular notch 3c, and the exhaust timing becomes earlier.

[Effect of idea]

This idea consists of a hole with a circular cross section drilled in the upper wall located immediately after the cylinder-side opening of the exhaust port, and a cylindrical hole slidably placed inside the hole. Since the hole and the valve body are constructed with a valve body, machining of the hole and the valve body is extremely easy, and therefore mass productivity can be improved and a two-stroke engine with an exhaust control device can be provided at a low cost.

In addition, in this invention, the cylindrical valve body is arranged so that its central axis is inclined upward when viewed from a plane perpendicular to the central axis of the cylinder, so that the exhaust pressure is applied to the valve body in the sliding direction. Therefore, damage to the drive device that drives the valve body can be prevented as much as possible, and a highly reliable exhaust control device can be provided.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of a two-stroke engine showing the exhaust control device according to the present invention, and Figure 2 is the same as that of Figure 1.
AA sectional view, FIG. 3 is a broken sectional view taken from B in FIG. 6 is a broken sectional view of the cylinder side opening showing another embodiment. FIG. 7 is a sectional view of the main parts of a two-cycle engine showing another embodiment of the valve body. Fig. 8 is a sectional view of EE in Fig. 7, Fig. 9 is a broken sectional view taken from B in Fig. 7, Fig. 10 is a sectional view of essential parts of a two-stroke engine showing the operation of another embodiment, and Fig. 11. is a broken cross-sectional view taken from B in FIG. 10. DESCRIPTION OF SYMBOLS 1... Exhaust control device, 2... 2-cycle engine, 3... Exhaust port, 3a... Cylinder side opening, 3b... Upper wall, 4... Hole, 5, 12
...Valve body, 5a, 12a...lower end surface.

Claims (1)

[Claims for Utility Model Registration] (1) A hole with a circular cross section is bored in the upper wall located immediately after the cylinder-side opening of the exhaust port, and a hole with a circular cross section is formed in the hole so that the lower end surface touches the upper surface of the exhaust port. A columnar valve body formed and arranged so as to be inclined upward when viewed from a plane whose central axis intersects at right angles with the central axis of the cylinder is slid in the hole toward the cylinder side opening. The valve body is arranged so as to be freely slidable, and the lower end surface of the valve body protrudes into the exhaust port to lower the upper edge position of the cylinder side opening, and the lower end face of the valve body is allowed to escape from the inside of the exhaust port. . An exhaust gas control device for a two-stroke engine, characterized in that the upper edge position of the cylinder side opening is raised. (2) The second aspect of the utility model registration claim (1), wherein the valve body has a substantially semicircular cross section.
Cycle engine exhaust control device.