JPS6255417A - Exhaust control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To obtain appropriate exhaust by providing an enlarged chamber in a passage, which connects an auxiliary port and an exhaust pipe both situated at the upper part of an exhaust port of a two-cycle engine, and providing a change-over valve at the intersection between the passage and the enlarged chamber so that both opening/ closing of the auxiliary port and opening of the enlarged chamber can be conducted in accordance with the engine speed. CONSTITUTION:An auxiliary port 10a is provided on the upper part of an exhaust port 3a of a two-cycle engine, while an enlarged chamber 7 is provided in a passage 11 which connects the port 10a and an exhaust pipe 3. At the intersection between the chamber 7 and passage 11 is installed a change-over valve 12, and when the engine speed is low the direction of the valve 12 is as illusted here. At this time, since the auxiliary port 10a is closed, the blowby from the exhaust port 3 can be prevented. In addition, since the enlarged chamber 7 is connected to the exhaust pipe 3, the exhaust passage capacity corresponding to the low engine speed can be ensure. When the engine speed is high, the change-over valve is turned counterclockwise in the figure by an angle of 90 deg.. As a result, the auxiliary port 10a is opened, thereby the exhaust timing being made earlier. At the same time, the enlarged chamber 7 is closed, thereby making the exhaust pipe capacity meet the high engine speed condition.

Description

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

[Prior art]

Generally, in order to improve the output of a two-stroke engine, it is necessary to improve the filling efficiency of the air-fuel mixture filled into the cylinder and to quickly exchange gas between the exhaust gas and the air-fuel mixture.

Two-stroke engines have an exhaust structure that uses air-fuel mixture to push exhaust gas out, so-called scavenging, so a portion of the air-fuel mixture is exhausted from the exhaust port along with the exhaust gas, resulting in a decrease in the output of the two-stroke engine. (The so-called atrium is a phenomenon). Conventionally, in order to prevent the above-mentioned blow-out phenomenon during exhaust, an expansion chamber (sub-chamber) was formed in the exhaust pipe, and the exhaust pressure pulsations generated within this expansion chamber were used to prevent the gas from being discharged from the exhaust port. The combustion air-fuel mixture is pushed back into the cylinder by pressure, improving the filling efficiency of the air-fuel mixture. Furthermore, in a two-stroke engine, the exhaust timing varies depending on the position of the exhaust port. The most preferable exhaust timing differs depending on the engine rotation range. In other words, in order to obtain high output at high revolutions, it is desirable to position the exhaust port relatively close to the cylinder head side and advance the exhaust timing. , the output will decrease in the low rotation range, and conversely, if the exhaust port is set to a position where the exhaust timing is late, the output will decrease in the high rotation range.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an exhaust control device for a two-stroke engine that improves output over a wide range of rotations, from low rotation to high rotation. Structure of the Invention] In order to achieve the above-mentioned object, the present invention provides a first passage that opens to an exhaust port, a 20th passage that opens to a subchamber for varying exhaust pipe volume, and a passage that opens from the opening of the exhaust port. A hole is provided in one peripheral surface between a third passage located on the cylinder head side and opened, and a fourth passage opened to the exhaust port downstream of the opening position of the first passage. A cylindrical valve is provided, and by rotating the valve, a state in which the exhaust port and the subchamber communicate with each other and a state in which the exhaust port and the subexhaust port communicate with each other are selected. That's what I do.

〔Example〕

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

FIG. 1 is a sectional view of a main part of a two-stroke engine 2 to which an exhaust gas control device 1 of the present invention is applied.

This two-stroke engine 2 has a first passage 4 that opens into an exhaust bow 3.

Further, an O subchamber 7 for varying exhaust pipe volume is formed in the cylinder head 5 and cylinder block 6 of the two-stroke engine 2, and extends across the cylinder head 5 and cylinder block 6. teeth,
The second passage 8 is open. Furthermore, above the exhaust port 3, that is, between the exhaust port 3 and the cylinder head 5, there is a third
A passageway 10 and a fourth passageway 11 having one end opened to an exhaust topo (3) downstream of the first passageway 4 are formed.

Note that these passages 10, 11 are formed at two locations in the cylinder block 6, as shown in FIG. 2, which is shown along the BB cross section in FIG. A cylindrical valve 12 is rotatably arranged in relation to the first passage 4, second passage 8, third passage 1°, and fourth passage 11. This valve 12 has three openings 12a on its side.

A communication hole 12d having a T-shaped cross section is formed with 12b and 12c. In FIG. 1, reference numeral 13 is an inlet boat, 14 is a scavenging boat opened to the cylinder 9, and 15 is a water jacket.

Next, the operation of the exhaust control device 10 described above will be explained, and the configuration will also be explained in more detail.

When the two-cycle engine 2 is started and its rotational speed is in a low/medium rotational speed range, the valve 12 is operated by a drive device (not shown) (for example, a servo motor or mechanical type driven according to the engine rotational speed). Drive bag for governor mechanism, etc. (fit) K
Therefore, it rotates and stops at the position iK shown in FIG.

According to the stop position of the valve 9 shown in FIG.
The third passageway 10 is closed and the opening 12a of the valve 12 is closed.

12b and 12C face the first passage 4, the fourth passage 11, and the second passage 8, respectively, so that the subchamber 7
communicates with the exhaust bow 3 via the communication hole 12d of the valve 12. Therefore, the valve 12 shown in FIG.
At the stop position, the exhaust pipe volume increases, ensuring a suitable exhaust pipe volume in the low and medium rotational speed ranges, as well as providing suitable exhaust timing in the low and medium rotational speed ranges.

On the other hand, when the two-stroke engine 2 reaches a high rotational speed range, the valve 12 is instantaneously rotated from the stop position shown in FIG. 1 to the stop position shown in FIG. 3 by a drive device (not shown).

In the stop position of the valve 12 shown in FIG. 3, the second passage 8 is closed by the peripheral surface of the valve 12, and the openings 12a and 12C of the valve 12 are closed to the third passage 10 and the fourth passage 12, respectively. Facing the passage 11 and the opening 12b
faces the first passage 4, the third passage 10 connects to the exhaust port aVc through the communication hole 12d of the valve 12.
communicate. Note that FIG. 4 is a sectional view taken along the line EE in FIG. 3.

Therefore, in the stop position of the valve 12 shown in FIG.
When a piston (not shown) descends during exhaust, the third passage 10 opens before the exhaust port 3, and therefore the exhaust timing is advanced. In addition, since the third passage 10 and the fourth passage 11 are formed with a gentle curvature, the exhaust resistance of the exhaust gas passing through these passages 10 and 11 is extremely small (this allows for smooth exhaust gas flow). In addition, since the space between the subchart/buff and the exhaust port 3 is closed by the surface of the valve 12, the exhaust pipe volume decreases, and the optimal exhaust pipe volume in the high rotation speed range is reduced. It is secured.

In the above embodiment, the upper edge 3a of the opening of the exhaust port 3 is positioned below the opening 10a of the third passage 10, as shown in FIG. Without being limited to the above embodiments, as shown in FIG. 5, in which the same parts as in FIGS. 1 and 2 are denoted by the same reference numerals, and in FIG. is formed on the upper edge 3a of the opening of the exhaust port 3 located between the third passages 10 and 10, and the upper edge 3b' of the notch 3b is formed on the upper edge 10a' of the opening 10a of the third passage 10. They may be formed at matching positions. Note that the notch 3b is formed in a shape 5 such that its cross-sectional area decreases toward the downstream side of the exhaust port 3, as shown in FIG. By forming the opening upper edge 3aK notch 3b of the exhaust port 3 in this manner, the opening area between the third passage 10 and the exhaust port 3 increases during high rotation, and exhaust gas can be discharged quickly. becomes.

Further, in each of the above embodiments, the subchamber 7 is formed in the cylinder head 5, but the present invention is not limited to the above embodiments. As shown in the figure, the subchamber 7 may be formed in front of the crankcase 20 of the two-stroke engine 2. An exhaust passage 21 communicating with the exhaust port 3 is formed on the side of the cylinder block 6 of the two-stroke engine 2 shown in FIG.
a communicates with a subchamber 7 formed at the front of the crankcase 20. Note that this two-stroke engine 2 has a 5K engine as shown in FIG. 8, which is shown by the GG cross section in FIG.

A drive device 22 consisting of a mechanical governor mechanism that rotates the cylindrical valve 12 in a predetermined engine speed range is disposed on the side of the crankcase 20. In addition, the seventh
Reference numeral 23 in the figures and FIG. 8 is an oil discharge hole formed at the bottom of the subchamber 7. When the subchamber 7 is formed in the crankcase 20 as shown in FIGS. 7 and 8, the center of gravity of the engine 2 is lowered compared to when the subchamber 7 is formed in the cylinder head 5.

〔Effect of the invention〕

This invention uses a simple valve as described in 5 above to change the exhaust pipe volume and exhaust timing according to the engine speed range, so it is suitable for low/medium speed ranges and high speed ranges. It is possible to obtain tζ exhaust pipe volume and exhaust timing, and therefore it is possible to provide a two-stroke engine with improved output over a wide range of rotation speeds from low rotation range to high rotation range.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the essential parts of a two-stroke engine showing the exhaust control device k of the present invention, Fig. 2 is a top view of the BBm of Fig. 1, and Fig. 3 shows the operating mode of the exhaust control device according to the present invention. FIG. 4 is a cross-sectional view of main parts of a two-stroke engine; FIG. 4 is a cross-sectional view taken along line EE of FIG. 3; FIG. 5 is a cross-sectional view of a two-stroke engine showing another embodiment of the exhaust control device according to the present invention; FIG. FIG. 5 is a sectional view taken along line Ii'F, FIG. 7 is a sectional view of a two-stroke engine showing still another embodiment of the exhaust control device according to the present invention, and FIG. 8 is a sectional view taken along line GG in FIG. 1... Exhaust control device, 2... 2-stroke engine,
3... Exhaust port, 4... First passage, 7
...Subchamber, 8...Second passage, 9...Cylinder, 10...Third passage, 11...Fourth passage, 12...Valve, 12d...Communication Hole. Applicant Suzuki Motor Co., Ltd. 1, -1 Representative Patent Attorney Takahisa Kimura 1□. Figure 1 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] a first passage that opens to the exhaust port; a second passage that opens to the subchamber for varying exhaust pipe volume; and a third passage that opens at a position closer to the cylinder head than the opening of the exhaust port; A cylindrical valve having a hole penetrated through its circumferential surface is disposed between the first passage and a fourth passage opening to the exhaust port downstream of the opening position of the first passage, and the valve is rotated. a state in which the exhaust port and the subchamber are in communication;
An exhaust control device for a two-cycle engine, characterized in that a state in which the exhaust port and the sub-exhaust port are in communication is selected.