JPH079180B2 - Exhaust control device for 2-cycle engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust control device for a two-cycle engine, and in particular, the exhaust timing is changed according to the engine speed to improve the output of the two-cycle engine. The present invention relates to improvement of an exhaust control device.

[Prior art]

Conventionally, in a two-cycle engine, an exhaust valve that changes the position of the upper edge of the exhaust port is provided immediately after the opening on the cylinder side of the exhaust port.
Alternatively, by driving with a drive device such as a mechanical governor mechanism, the exhaust timing is changed according to the engine speed, and the output of the two-cycle engine from the low speed range to the high speed range is improved. is there.

FIG. 4 is a conceptual cross-sectional view of a two-cycle engine 2 equipped with the conventional exhaust control device 1 described above.

The exhaust control device 1 is composed of a valve body 4 forming an upper wall 3b immediately after the cylinder side opening 3a of the main exhaust passage 3. The valve body 4 is composed of a plate slidably arranged in the main exhaust passage 3, and the upper end 4a of the valve body 4 is provided with a main exhaust gas according to the engine speed. The above-mentioned drive device (not shown) for moving a predetermined stroke into the passage 3 is connected.

According to such an exhaust control device 1, when the rotation of the two-cycle engine 2 rises and reaches a predetermined high rotation speed range, the valve device 4 is moved from the initial position shown by the solid line in FIG. 4 by the drive device. Move to the position indicated by the chain line.

When the valve body 4 moves in this manner, the lower end surface 4b of the valve body 4 apparently raises the position of the upper edge 3c of the cylinder-side opening of the main exhaust passage 3 by H, which changes the exhaust timing. Exhaust timing suitable for each engine speed range is secured, and the output of the two-cycle engine 1 is improved.

Note that FIG. 5 is a fragmentary sectional view taken along the line A of FIG. In FIG. 4, reference numeral 5 is a cylinder, 6 is a cylinder sleeve, 7 is a cylinder block, and 8 is a cylinder head.

By the way, according to the conventional exhaust control device 1 described above, the plate-shaped valve body 4 is retracted into the main exhaust passage 3 and the exhaust timing is changed by the lower end surface 4b thereof. When the valve body 4 projects into the main exhaust passage 3 as indicated by the solid line, a part (arrow B) of the exhaust gas discharged from the cylinder side opening 3a of the main exhaust passage 3 is discharged to the valve body 4.
Since the course of the exhaust gas is suddenly changed, the exhaust gas is not discharged smoothly, which hinders rapid gas exchange and reduces the output of the engine.

[Object of the Invention]

In view of the above-mentioned circumstances, the present invention changes the exhaust timing according to the engine speed while maintaining the smooth discharge of exhaust gas, and has a wide engine speed range from the low speed range to the high speed range of the engine. Provided is an exhaust control device for a two-cycle engine, which is designed to improve the output as much as possible.

[Structure of Invention]

In order to achieve the above object, in an exhaust control system for a two-cycle engine according to the present invention, a main exhaust passage opening to a cylinder, and a cylinder circumference between an upper edge of a cylinder side opening of the main exhaust passage and a cylinder head. A sub-exhaust passage having one opening on its surface and the other opening downstream of the main exhaust passage, and an exhaust pipe volume varying sub-chamber having one end communicating with the main exhaust passage and the sub-exhaust passage, respectively. A cylindrical valve having a cutout recess formed in a peripheral surface and having an arcuate cross-section, and a communication hole formed between the peripheral surfaces, wherein one end of the sub-chamber, the main exhaust passage, and the sub-exhaust gas are provided. A cylindrical valve rotatably disposed at a position where each of the passages intersects with each other, and drive means for rotationally driving the cylindrical valve according to an engine speed range, wherein the cylindrical valve is used in an engine low speed range. Bar The sub-chamber and the main exhaust passage are communicated with each other by the communication hole, and rotationally driven to a position where the peripheral surface of the cylindrical valve closes the main exhaust passage and the sub-exhaust passage, Further, in the high engine speed region, the peripheral surface of the cylindrical valve closes the space between the sub-chamber and the main exhaust passage, and the arcuate cutout concave portion of the cylindrical valve forms the main exhaust passage and the sub-exhaust. Drive means for communicating with the exhaust passage.

〔Example〕

An embodiment of the exhaust control device according to the present invention will be described in detail below.

FIG. 1 is a conceptual diagram of a main part of a two-cycle engine 20 equipped with an exhaust control device 10 of the present invention, and the same parts as in FIG.

The exhaust control device 10 includes a main exhaust passage 3, an auxiliary exhaust passage 12 formed in a cylinder 5 between a cylinder side opening upper edge 3c of the main exhaust passage 3 and a cylinder head 8, and a cylinder head 8. And a sub-chamber 21 for changing the exhaust pipe volume, one end of which is connected to the main exhaust passage 3, and the sub-exhaust passage 12
And a cylindrical valve 22 that opens and closes between the main exhaust passage 3 and the main exhaust passage 3 and the sub chamber 21.

Of these, the auxiliary exhaust passage 12 is formed such that the downstream end thereof communicates with the downstream of the main exhaust passage 3 and the axis thereof is substantially parallel to the axis of the main exhaust passage 3.

The valve 22 is rotatably supported in the cylinder block 7 at a position where one end of the sub chamber 21 and the main exhaust passage 3 and the sub exhaust passage 12 intersect with each other.

The valve 22 has a peripheral surface 22b formed with a notched concave portion 22c having a substantially arcuate cross section facing the auxiliary exhaust passage 12 and the main exhaust passage 3, and the sub-chamber 21 and the main exhaust passage 3 are provided between the peripheral surfaces. A communication hole 22a is formed to allow communication between and.

Also, this valve 22 depends on the engine speed.
It is connected to a drive device (not shown) for rotating 22 (for example, a mechanical governor device using a centrifugal force of a ball, or a servomotor). Note that FIG. 2 is a fragmentary sectional view taken along the line C of FIG.

Next, the operation of the above-described exhaust control device 20 will be described, and the configuration will be described in more detail.

When the two-cycle engine 20 is started and its rotation speed is within a predetermined low rotation speed range, the valve 22 is rotated by the drive device and stopped at the initial position shown in FIG.

According to the initial position of the valve 22 shown in FIG. 1, the valve
The peripheral surface 22b of 22 closes the space between the sub exhaust passage 12 and the main exhaust passage 3, and the communication hole 22a closes the sub chamber 21.
The main exhaust passage 3 and the main exhaust passage 3 communicate with each other.

Therefore, all the exhaust gas is discharged through only the cylinder side opening 3a of the main exhaust passage 3, and the discharge timing is a suitable exhaust timing in the low rotation speed range defined by the upper edge 3c of the cylinder side opening 3a. Has been maintained.

Further, since the sub-chamber 21 and the main exhaust passage 3 are communicated with each other, the volume of the exhaust pipe is increased, and a suitable exhaust pipe volume is secured in the low rotation speed range.

On the other hand, when the rotation speed of the two-cycle engine 20 reaches a predetermined high rotation speed range, the valve 22 is rotated by the drive device, and the arc-shaped cutout concave portion 22c formed on the peripheral surface 22b thereof is shown in FIG. As shown, it stops at the position facing the sub exhaust passage 12 and the main exhaust passage 3.

According to the stop position of the valve 22 shown in FIG. 3, the sub exhaust passage 12 and the main exhaust passage 3 are communicated with each other by the notch recess 22c of the valve 22, and the exhaust gas (arrow D) at the initial stage of exhaust is the sub exhaust gas. It is discharged to the main exhaust passage 3 through the exhaust passage 12.

The space between the sub chamber 21 and the main exhaust passage 3 is closed by the peripheral surface 22b of the valve 22.

Therefore, according to the stop position of the valve 22 shown in FIG. 3, since the exhaust gas is discharged through the auxiliary exhaust passage 12, the position of the cylinder side opening upper edge of the main exhaust passage 3 is
From the upper edge 3c of the cylinder side opening 3a to the upper edge 12 of the auxiliary exhaust passage 12
The distance H up to a is increased, so that the exhaust timing is advanced, and a suitable exhaust timing is secured in the high rotation speed range.

The course of the exhaust gas passing through the sub exhaust passage 12 is gently changed by the arcuate recess 22c, so that the exhaust gas passing through the sub exhaust passage 12 is smoothly discharged.

Further, since the sub-chamber 21 and the main exhaust passage 3 are closed, the volume of the exhaust pipe is reduced, and a suitable exhaust pipe volume can be secured at the same time in a high rotational speed range.

〔The invention's effect〕

As described above, in the exhaust control device of the present invention, since the exhaust timing changing valve is not exposed at the cylinder side opening of the main exhaust passage, the resistance of the exhaust gas flowing in the main exhaust passage is reduced, and the upper portion of the main exhaust passage is reduced. A sub-exhaust passage is formed in the sub-exhaust passage so that the length of the exhaust passage between the sub-exhaust passage and the main exhaust passage is hardly changed. Since the resistance of the exhaust gas flowing through the engine is also reduced, the exhaust gas flowing in the main exhaust passage and the sub-exhaust passage becomes smooth, and the exhaust timing is changed while achieving quick gas exchange, thus improving the output of the 2-cycle engine. In addition to being able to achieve, it is also possible to secure a suitable exhaust pipe volume according to each engine speed range with one cylindrical valve,
Suitable exhaust timing and exhaust pipe volume are secured over a wide range of engine speeds from the low speed range to the high speed range, so that a wide range of engine speeds from the low speed range to the high speed range is achieved. The output of the 2-cycle engine can be greatly improved.

[Brief description of drawings]

1 is a conceptual cross-sectional view of a two-cycle engine equipped with an exhaust control device according to the present invention, FIG. 2 is a fragmentary cross-sectional view taken along the line C of FIG. 1, and FIG. 3 is an exhaust control device according to the present invention. 2 is a fragmentary cross-sectional view of a two-cycle engine showing the action of FIG. 4, FIG. 4 is a fragmentary cross-sectional view of a conventional two-cycle engine showing an exhaust control device, and FIG. Is. 3 ... Main exhaust passage, 3a ... Cylinder side opening, 3c ... Cylinder side opening upper edge, 5 ... Cylinder, 8 ... Cylinder head, 10 ... Exhaust control device, 12 ... Sub exhaust passage, twenty two…
… Cylindrical valve, 13a, 20 …… Two-cycle engine, 22a
...... Communication hole, 22b …… Peripheral surface, 22c …… Notched recess.

Claims (1)

[Claims] 1. A main exhaust passage opening to a cylinder, and one opening on a cylinder circumferential surface between a cylinder head opening upper edge of the main exhaust passage and a cylinder head, the main exhaust passage being provided downstream of the main exhaust passage. An auxiliary exhaust passage having the other opening, an exhaust pipe volume-changing sub-chamber having one end communicating with the main exhaust passage and the auxiliary exhaust passage, and a cutout recess having an arc-shaped cross section formed on the peripheral surface, A cylindrical valve having a communication hole formed between peripheral surfaces,
A cylindrical valve rotatably disposed at a position where one end of the sub-chamber and the main exhaust passage and the sub-exhaust passage intersect, and a drive for rotationally driving the cylindrical valve according to an engine speed range. In the low engine speed region, the sub-chamber and the main exhaust passage are communicated with each other by the communication hole of the cylindrical valve, and the main exhaust passage and the main exhaust passage are connected by the peripheral surface of the cylindrical valve. The sub-exhaust passage is occluded between the sub-chamber and the main exhaust passage by the peripheral surface of the cylindrical valve in a high rotational speed range of the engine. An exhaust control device for a two-cycle engine, comprising: a drive unit that connects the main exhaust passage and the auxiliary exhaust passage with each other by an arcuate cutout recess of the valve.