JPH0510142A - Exhaust control device for 2-cycle engine - Google Patents

Abstract

(57) [Abstract] The purpose of the invention is to control the exhaust of a two-cycle engine so as to improve the output as much as possible over a wide range of engine speeds from a low speed range to a high speed range. To provide a device. An exhaust control device for a two-cycle engine according to the present invention includes an exhaust passage opening to a cylinder, an auxiliary exhaust passage opening to a cylinder with an opening area smaller than an opening area of the exhaust passage, and one end communicating with the exhaust passage. A two-cycle engine having a sub-chamber for varying the exhaust pipe volume, wherein the sub-chamber and the exhaust passage are communicated with each other and the exhaust passage and the sub-exhaust passage are communicated with each other in a low speed rotation range of the engine. So that the sub-chamber and the exhaust passage are closed and the exhaust passage and the sub-exhaust passage are communicated with each other in the high-speed rotation range of the engine according to the engine speed. It is equipped with an on-off valve that closes the communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine, and more particularly to improvement of its exhaust system structure.

[0002]

2. Description of the Related Art In a conventional two-cycle engine, exhaust is performed by adding a so-called scavenging process in which combustion gas is extruded by a mixture gas. At present, there is no certain gas exchange, that is, the exchange of air-fuel mixture and exhaust gas.

[0003]

By the way, in the conventional two-cycle engine in which the modest gas exchange is not performed as described above, a part of the air-fuel mixture comes out from the exhaust port during exhaust (so-called blow-through phenomenon). ), The efficiency of charging the air-fuel mixture is reduced, and the engine has reduced output.

Conventionally, in order to prevent such blow-through phenomenon, an expansion chamber is formed in the exhaust pipe, and exhaust gas pulsation generated in the expansion chamber is used to prevent blow-through of the air-fuel mixture and to fill the air-fuel mixture. Although the efficiency is improved and the output is improved, the optimum volume for forming this expansion chamber also differs depending on each rotation range of the 2-cycle engine, and therefore, 2 cycles over a wide rotation range. The engine output could not be improved.

In view of the above-mentioned circumstances, the present invention provides an exhaust control device for a two-cycle engine, which is designed to improve the output as much as possible over a wide range of engine speeds from a low speed rotation range to a high speed rotation range. The purpose is to do.

[0006]

In order to solve the above-mentioned problems, in the exhaust control system for a two-cycle engine according to the present invention, an exhaust passage opening to the cylinder and an opening area smaller than the opening area of the exhaust passage are provided in the cylinder. A two-cycle engine having an opening sub-exhaust passage and an exhaust pipe volume varying sub-chamber, one end of which communicates with the exhaust passage, wherein the sub-chamber and the exhaust passage are provided between the sub-chamber and the exhaust passage in a low engine speed region. The exhaust passage and the sub-exhaust passage are closed while being communicated with each other, and the sub-chamber and the exhaust passage are closed in the high-speed rotation region of the engine, and the exhaust passage and the sub-exhaust passage are closed. An open / close valve is provided to open and close the passages according to the engine speed so that the passages are in communication.

[0007]

According to the exhaust control system for a two-cycle engine according to the present invention described above, the volume of the exhaust pipe is increased and the cross-sectional area of the exhaust hole is increased in the low speed rotation region by the on-off valve that communicates and blocks each passage according to the engine speed. Is reduced, which makes it possible to obtain a suitable exhaust pipe volume and displacement in the low speed rotation range.
Further, in the high speed rotation range, the volume of the exhaust pipe is reduced and the cross sectional area of the exhaust hole is enlarged, so that an appropriate exhaust pipe volume and exhaust amount can be obtained in the high speed rotation range.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust control device according to the present invention will be described in detail below.

FIG. 1 shows an exhaust control device 23 according to the present invention.
FIG. 3 is a fragmentary cross-sectional view of a two-cycle engine 2 to which is applied.

In the exhaust control device 23, a sub chamber 3 for varying the exhaust pipe volume is formed in the cylinder head 4, and the sub chamber 3 is provided immediately after the exhaust port 7 via a passage 6 formed in the cylinder block 5. To the exhaust passage 8.

On the other hand, the cylinder block 5 is formed with a sub-exhaust passage 30 opening to the cylinder with an opening area smaller than the opening area of the exhaust passage 8. The auxiliary exhaust passage 30 has a first auxiliary exhaust passage 20 having one end opened above the upper edge of the exhaust port 7 and the other end communicating with the passage 6, and one end communicating with the passage 6. The second auxiliary exhaust passage 2 whose other end communicates with the downstream of the exhaust port 8
1 and 1.

Further, as shown in FIG. 1, the sub-chamber 3 and the exhaust passage 8 are located at positions where the exhaust passage 8, the sub-chamber 3 and the sub-exhaust passage 30 communicate with each other. When the two are connected, the first and second
Between the sub-exhaust passages 20 and 21, that is, when the sub-exhaust passage 30 is closed and the sub-chamber 3 and the exhaust passage 8 are closed, the first and second sub-exhaust passages 20 , 21, that is, the opening / closing valve 31 that connects the auxiliary exhaust passage 30 and the exhaust passage 8 with each other. The on-off valve 31 is composed of a cylindrical valve 9.

Further, the sub-chamber 3 and the exhaust passage 8 are communicated with the peripheral surface 9a of the cylindrical valve 9 constituting the opening / closing valve 31, or the first and second valves are connected.
A hole 9b is formed between the secondary exhaust passages 20 and 21, that is, the auxiliary exhaust passage 30 and the exhaust passage 8 are communicated with each other.

Further, the cylindrical valve 9 constituting the opening / closing valve 31 is fitted in a hole formed in the passage 6 and is rotatably supported at that position. In FIG. 1, reference numeral 11
Is an exhaust pipe connected to the exhaust passage 8, 12 is a water jacket, and 13 is a piston.

Next, the operation of the exhaust control device 23 described above will be described.

In a predetermined low speed rotation range of the two-cycle engine 2, the cylindrical valve 9 constituting the open / close valve 31 is stopped at the rotational position shown in FIG. 1 by an open / close valve drive device (not shown).

At the rotation stop position of the valve 9 shown in FIG. 1, the subchamber 3 is formed by the hole 9b formed in the valve 9.
Since the exhaust passage 8 and the exhaust passage 8 communicate with each other, the exhaust pipe volume is increased, and a suitable exhaust pipe volume is secured in the low speed rotation range. At the rotation stop position of the valve 9 shown in FIG.
And the second auxiliary exhaust passages 20, 21 are closed, that is, the auxiliary exhaust passage 30 and the exhaust passage 8 are closed, and the exhaust hole cross-sectional area is an exhaust port formed at one end of the exhaust passage 8. Since there is only the opening area of 7, the exhaust hole cross-sectional area is reduced and a suitable exhaust amount is secured in the low speed rotation range.

Therefore, at the rotation stop position of the cylindrical valve 9 constituting the on-off valve 31 in the engine low speed rotation range shown in FIG. 1, the exhaust pipe volume increases and the exhaust hole cross-sectional area decreases, so that the low speed rotation range. Therefore, the suitable exhaust pipe volume and exhaust amount can be secured, and the output of the two-cycle engine 2 in the low speed rotation range can be improved.

Next, when the two-cycle engine 2 reaches a predetermined medium speed rotation range, the open / close valve driving device (not shown) causes the cylindrical valve 9 constituting the open / close valve 31 to rotate to the position shown in FIG. And then stop at that position.

According to the rotation stop position of the valve 9 shown in FIG. 2, the peripheral surface 9a of the valve 9 causes the space between the first and second auxiliary exhaust passages 20 and 21, that is, the auxiliary exhaust passage 30 and the exhaust passage. 8 is maintained, and the subchamber 3 and the exhaust passage 8 are also closed, so that both the exhaust pipe volume and the exhaust amount are reduced, and the exhaust pipe volume suitable for the medium speed rotation range is obtained. And the displacement are secured, and the engine output in this rotation range is improved.

Further, when the engine 2 reaches a predetermined high speed rotation range, the cylindrical valve 9 constituting the opening / closing valve 31 is rotated to the position shown in FIG. Stop.

At the rotation stop position of the valve 9 shown in FIG. 3, since the peripheral surface 9a of the valve 9 closes the space between the sub chamber 3 and the exhaust passage 8, the exhaust pipe volume decreases,
A suitable exhaust pipe volume is secured in the high speed rotation range. See also FIG.
At the rotation stop position of the valve 9 shown in FIG.
Between the first and second auxiliary exhaust passages 20 and 21,
That is, since the auxiliary exhaust passage 30 and the exhaust passage 8 communicate with each other, the entire exhaust hole cross-sectional area is the opening area of the exhaust port 7 plus the opening area of the auxiliary exhaust passage 30. The cross-sectional area is increased and a suitable displacement is secured in the high speed rotation range.

Therefore, at the rotation stop position of the valve 9 in the engine high-speed rotation region shown in FIG. 3, the exhaust pipe volume decreases and the exhaust hole cross-sectional area increases, so that a suitable exhaust pipe volume and exhaust gas in the high-speed rotation region are obtained. Is secured, and the output of the two-cycle engine 2 in the high speed rotation range is improved.

[0024]

As described above, in the exhaust control device of the present invention, the volume of the exhaust pipe is increased in the low speed rotation region and the exhaust hole is blocked by the open / close valve that communicates and blocks each passage according to the engine speed. In addition to reducing the area, the exhaust pipe volume is reduced in the high-speed rotation range and the exhaust hole cross-sectional area is increased, so the exhaust pipe volume and exhaust volume suitable for a wide engine rotation range from the low-speed rotation range to the high-speed rotation range can be obtained. Therefore, the output of the 2-cycle engine can be greatly improved.

[Brief description of drawings]

FIG. 1 is a view showing an exhaust control device according to the present invention 2
A fragmentary sectional view of a cycle engine.

FIG. 2 is a fragmentary cross-sectional view of a two-cycle engine showing the operation of the exhaust control device according to the present invention.

FIG. 3 is a fragmentary cross-sectional view of a two-cycle engine showing the operation of the exhaust control device according to the present invention.

[Explanation of symbols]

 1 ... 2-cycle engine 3 ... Sub chamber 8 ... Exhaust passage 23 ... Exhaust control device 30 ... Sub exhaust passage 31 ... Open / close valve

Claims (1)

Claim: What is claimed is: 1. An exhaust passage opening to the cylinder, an auxiliary exhaust passage opening to the cylinder with an opening area smaller than the opening area of the exhaust passage, and an exhaust pipe volume having one end communicating with the exhaust passage. A two-cycle engine having a variable sub-chamber, wherein the sub-chamber and the exhaust passage are communicated with each other and the exhaust passage and the sub-exhaust passage are closed in a low speed rotation range of the engine, In the high speed rotation region of the engine, the sub-chamber and the exhaust passage are closed, and the exhaust passage and the sub-exhaust passage are communicated with each other according to the engine speed so as to communicate with each other. An exhaust control device for a two-cycle engine, which is equipped with an on-off valve.