JP3114127B2 - Exhaust valve device for two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust valve device for a two-cycle engine having an exhaust valve facing an exhaust port.

[0002]

2. Description of the Related Art Conventionally, this type of exhaust valve device includes a main exhaust passage communicating with a main exhaust port of an engine cylinder and an auxiliary exhaust passage communicating with auxiliary exhaust ports on both sides of the main exhaust port. There is a type in which valves are provided, and the cross-sectional area of the entire exhaust passage is changed by these valves (for example, see JP-A-63-173817).

In the conventional exhaust valve device disclosed in this publication, when the engine is rotating at a low speed, both valves are closed to reduce the cross-sectional area of the exhaust passage, and the two valves are switched as the engine speed increases. It had an open structure.

The main exhaust valve provided in the main exhaust passage has a structure in which a substantially plate-shaped valve body is supported so as to be vertically swingable above the main exhaust passage, and an end portion thereof faces the main exhaust port. As the auxiliary exhaust valve provided in the auxiliary exhaust passage, a rotary valve that rotates with respect to the cylinder has been used. The auxiliary exhaust valves are driven by a rack-and-pinion type power transmission mechanism, and the main exhaust valve is connected to the auxiliary exhaust valve via a power transmission mechanism separate from the power transmission mechanism so as to interlock with the auxiliary exhaust valve. Had been linked. In addition, the main exhaust valve and the sub exhaust valve are configured to open simultaneously.

That is, in the conventional exhaust valve device, the cross-sectional area of the exhaust passage is small when the engine is rotating at a low speed, and increases as the engine speed increases. For this reason, an exhaust passage cross-sectional area commensurate with the engine speed can be obtained, and high output can be obtained over the entire rotation range.

[0006]

However, even if the auxiliary exhaust passage is provided on the side of the main exhaust passage so as to change the cross-sectional area of the exhaust passage to a size corresponding to the engine speed, it is not always necessary to perform the full rotation. No high power was obtained over the region. This is considered to be related to the exhaust timing when the auxiliary exhaust valve opens as described below.

When the engine speed increases from the middle speed range to the high speed range, the opening of the auxiliary exhaust valve is increased to increase the sectional area of the auxiliary exhaust passage, and the opening of the main exhaust valve is increased to increase the exhaust. Accelerating the timing is important for obtaining high output.

In the above-described conventional exhaust valve device, the substantial exhaust timing of the engine is such that when the auxiliary exhaust valve opens, the piston passes through the upper edge of the auxiliary exhaust port even if the opening degree is small, It will be accelerated rapidly. When the opening is small, the position of the main exhaust valve is
This is a position where the exhaust timing in the main exhaust passage is slightly advanced from that at the time of medium speed rotation.

That is, the exhaust timing in the main exhaust passage is later than the substantial exhaust timing of the engine, and the output tends to decrease when the engine speed increases from the middle speed range to the high speed range.

Further, the above-mentioned conventional exhaust valve device requires a gear type power transmission mechanism for driving the auxiliary exhaust valve and a power transmission mechanism for interlocking the main exhaust valve with the auxiliary exhaust valve. In addition, since each valve is supported on the cylinder by a pivot, there is a problem that the structure is complicated.

[0011]

An exhaust valve device of a two-stroke engine according to the present invention is arranged side by side along a cylinder axis direction, faces a main exhaust port, and moves in parallel according to the engine speed to project. A low-speed main exhaust valve and a high-speed main exhaust valve, the amount of which is changed and the exhaust timing is changed, and a pair of sub-exhaust valves that face the auxiliary exhaust port on the side of the main exhaust port and change the passage cross-sectional area, For each valve,
When the engine speed is smaller than the set speed, the valves are fully closed, and when the engine speed exceeds the set speed, the low-speed main exhaust valve and the sub exhaust valve are simultaneously opened, and thereafter, the high-speed main exhaust valve is opened. An exhaust valve drive mechanism for opening the valve is connected.

[0012]

The exhaust timing in the main exhaust passage is gradually increased by opening the high-speed main exhaust valve after the low-speed main exhaust valve opens. In other words, when each main exhaust valve is opened, the exhaust timing in the main exhaust passage is instantaneously increased by a large amount. For this reason, by opening the low-speed region main exhaust valve at the same time as opening the sub exhaust valve, the exhaust timing in the main exhaust passage approaches the substantial exhaust timing of the engine.

Further, since the low-speed main exhaust valve and the high-speed main exhaust valve move in parallel with each other, they can be driven by one rotating shaft.

[0014]

1 to 11 show an embodiment of the present invention.
This will be described in detail. 1 is a cross-sectional view of a two-stroke engine equipped with an exhaust valve device according to the present invention, FIG. 2 is an enlarged cross-sectional view showing a main exhaust valve driving section of the exhaust valve device according to the present invention, and FIG. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1, FIG. 5 is an enlarged sectional view showing a sub-exhaust valve driving section of the exhaust valve device according to the present invention, and FIG. 6 is a main exhaust valve. FIG. 7 is a sectional view of FIG.
FIG. 5 is a view as viewed from the direction of the arrow A in FIG.

FIG. 8 is an exploded perspective view of the exhaust valve driving mechanism.
9A and 9B are cross-sectional views for explaining the operation of the high-speed main exhaust valve. FIG. 9A shows a fully closed state, and FIG. 9B shows a state when the high-speed main exhaust valve starts to open. (C) shows a fully opened state. 10 is a development view of an exhaust port portion of a cylinder, FIG. 11 is a graph showing a relationship between an engine speed and a valve stroke amount of an exhaust valve device according to the present invention, FIG. 12 is a graph showing a change in exhaust timing, and FIG. 4 is a graph showing a relationship between an engine speed and an output of an engine equipped with the exhaust valve device according to the present invention.

In these figures, reference numeral 1 denotes a motorcycle 2
In the cycle engine, a cylinder body 3 is mounted on a crankcase 2 of the engine 1, a cylinder head 4 is further mounted on the cylinder body 3, and an ignition plug 5 is provided on the cylinder head 4.

A piston 6 is slidably provided in the cylinder of the cylinder body 3, and the piston 6 is connected to a crank arm 9 of a crank shaft 8 via a connecting rod 7. The crank arm 9 is housed in a crank chamber 10 of the crank case 2.
Reference numeral 0 denotes a scavenging port 11a which is opened in the middle of the cylinder body 3 through a scavenging passage 11 formed in the cylinder body 3.
Is in communication with

An intake passage 12 communicating with the crank chamber 10 is formed in the cylinder body 3 below the scavenging port 11a, and a main exhaust passage communicating with the inside of the cylinder of the cylinder body 3 is provided at a position facing the intake passage 12. The main exhaust passage 13 and the inside of the cylinder of the cylinder body 3 communicate with each other through auxiliary exhaust passages 14 located on both sides of the main exhaust passage 13.

The upper side of the main exhaust passage 13 (cylinder head 4
The main exhaust valve 15 for the low-speed range and the main exhaust valve 16 for the high-speed range for varying the exhaust timing and the cross-sectional area of the main exhaust passage according to the engine speed are provided in the valve mounting hole 3a formed on the cylinder side. They are mounted in a state where they are arranged along the axial direction.

The high-speed main exhaust valve 16 of the two main exhaust valves is disposed so as to face a part of the cylinder opening 13a of the main exhaust passage 13 which is on the side of the cylinder head 4, and is provided with a low-speed main exhaust valve. The exhaust valve 15 is disposed at a position below (on the crankshaft side) the main exhaust valve 16 for the high-speed range. Note that the main exhaust valve 1 for the low-speed range
As shown in FIG. 10, 5 is positioned below the cylinder opening 14 a of the auxiliary exhaust passage 14 (on the crankshaft side). In FIG. 10, the two main exhaust valves are hatched so that their positions are clear.

As shown in FIG. 8, the low-speed main exhaust valve 15 comprises a substantially plate-shaped valve element 15a and a rod-shaped valve shaft 15b. It is supported by an exhaust valve 16. And the valve shaft 1
A pin 15c erected on 5b is connected to a valve drive mechanism described later. The end of the valve body 15a on the exhaust passage side (tip 15d) is formed in a shape that matches the shape of the main exhaust passage 13.

As shown in FIG. 8, the high-speed main exhaust valve 16 has a valve body 16a formed in a substantially plate shape, a valve guide 16b inserted into a valve mounting hole 3a of the cylinder body 3, and a valve guide 16b. And an operation block 17 screwed to the valve guide 16b. In addition, valve element 1
The end of the exhaust passage 6a (tip 16c) on the exhaust passage side is formed in a shape conforming to the shape of the main exhaust passage 13 in the same manner as the low-speed main exhaust valve 15. The operation block 17 is connected to a valve drive mechanism described later.

Further, a valve shaft 15b of the low speed range main exhaust valve 15 is supported on the valve guide 16b and the operation block 17 so as to be able to advance and retreat.

The operation block 17 is fixed to the valve guide 16b by a mounting screw 17a.
7b and a connecting portion 17 formed integrally with the main body 17b.
c.

As shown in FIG. 2, the lower portion of the connecting portion 17c has two upper and lower arcuate surfaces 17d and 17e, and a projection 1 which opposes an end of the upper arcuate portion through a notch 17f.
7 g are formed.

The main exhaust valve 15 for the low speed region and the main exhaust valve 16 for the high speed region thus configured are connected to the main exhaust passage 13.
, The exhaust timing and the cross-sectional area of the main exhaust passage 13 can be changed.

Further, as shown in this embodiment, by forming the valve bodies 15a and 16a of these main exhaust valves 15 and 16 in a plate shape, the exhaust timing and the passage in the main exhaust passage 13 having a large cross-sectional area are provided. The cross-sectional area can be easily changed.

Above the auxiliary exhaust passage 14, a columnar auxiliary exhaust valve 18 is provided for the low and high speed main exhaust valve 1.
The auxiliary exhaust passage 14 is provided in the auxiliary exhaust passage 14 so as to be able to advance and retreat in the direction of the cylinder opening 14a in the same manner as in the case of 5 and 16. I have.

As shown in FIG. 8, the auxiliary exhaust valve 18 has a columnar valve body 18a and a valve shaft 18b, and the valve shaft 18b is connected to the cylinder body 3 by a valve guide 18c.
It is supported to move forward and backward. The sub-exhaust valve 18 is connected to a valve driving mechanism described later via a pin 18d provided upright on the valve shaft 18b, and is opened and closed according to the engine speed.

By forming the sub-exhaust valve 18 in a columnar shape and making the cross section of the tip 18e substantially coincide with the cross section of the passage, the valve itself can be easily formed and the valve hole can be easily formed. Further, the influence on the strength of the partition wall 19 between the auxiliary exhaust passage 14 and the main exhaust passage 13 is reduced.

Reference numeral 21 denotes a valve drive mechanism for driving the three types of exhaust valves (the main exhaust valve 15 for the low speed range, the main exhaust valve 16 for the high speed range, and the sub exhaust valve 18).

The valve driving mechanism 21 is formed as shown in FIG. 8, and the three kinds of exhaust valves are opened at a predetermined timing by changing the rotation angle of one shaft 22 according to the engine speed. It is configured to operate.

The shaft 22 is disposed in a direction perpendicular to the cylinder axis, and is provided with a pin 1 of the main exhaust valve 15 for the low speed range.
5c is engaged with a drive plate 24 connected to the operation block 17 of the high-speed main exhaust valve 16
The drive fork 25 and the like with which the pin 18d of the sub exhaust valve 18 is engaged are fixed.

A drive device (not shown) for changing the rotation angle of the shaft 22 according to the engine speed is connected to the shaft end of the shaft 22.

The drive forks 23 and 25 are connected to the pin 15c of the main exhaust valve 15 for the low speed range and the one of the sub exhaust valves 18 respectively.
Grooves 23a and 25a into which 8d are fitted are respectively formed, and are configured to change the rotational operation of the shaft 22 into a reciprocating operation to move the low-speed main exhaust valve 15 and the sub exhaust valve 18 forward and backward.

The drive plate 24 is mounted on the operation block 17.
The pressing portion 24a that abuts on the projection 17g and the fan-shaped portion 24b that slides on the lower arc surface 17e of the operation block 17 are integrally formed. The pressing portion 24a has an end surface that is an arc surface that is in sliding contact with the upper arc surface 17d of the operation block 17. The outer peripheral surface of the fan-shaped portion 24b is an arc surface having a curvature substantially equal to that of the arc surface 17e.

The thus configured valve driving mechanism 21
According to this, by rotating the shaft 22, the low-speed main exhaust valve 15, the high-speed main exhaust valve 16 and the sub exhaust valve 18 move forward and backward in conjunction with each other.

The low-speed main exhaust valve 15 and the sub exhaust valve 18 advance and retreat with the rotation of the shaft 22 to open and close.
The main exhaust valve 16 for the high-speed range is opened and closed with the main exhaust valve 15 for the low-speed range and the sub-exhaust valve 18 opened by a predetermined opening degree by the time difference drive structure by the operation block 17 and the driving plate 24. 1 and 2
Reference numeral 26 denotes a cover which is housed so as to cover the valve drive mechanism 21, and is fixed to the cylinder body 3 of the engine 1.

Next, the operation of the three types of exhaust valves will be described with reference to FIG.

When the engine speed is in the low speed range below the set speed, the shaft 22 of the valve drive mechanism 21
, The low-speed main exhaust valve 15, the high-speed main exhaust valve 16 and the sub exhaust valve 18 are fully closed. FIG. 9A shows the state at the time of fully closing.

At this time, the auxiliary exhaust valve 18 is advanced by the driving fork 25 of the shaft 22 toward the cylinder opening 14a of the auxiliary exhaust passage 14. The pressing portion 24 a of the driving plate 24 has an arc surface at the tip thereof in contact with the arc surface 17 d of the operation block 17. Note that the exhaust timing of the engine 1 at this time is set relatively late so as to be suitable for low-speed operation. The position of the tip of each exhaust valve when fully closed is indicated by a two-dot chain line a in FIGS. 2 and 5. The fully closed position of the sub-exhaust valve 18 shown in FIG. 5 is such that the tip end 18e of the sub-exhaust valve 18 is slightly separated from the bottom wall of the auxiliary exhaust passage 14.
Since the auxiliary exhaust passage is brought into a state equivalent to the fully closed state by moving forward, there is no problem in operation and effect. In the present embodiment, the position of the auxiliary exhaust valve 18 when the auxiliary exhaust passage 14 is substantially fully closed as described above is simply referred to as the fully closed position.

When the engine speed exceeds the set speed and the engine rotates at a medium speed, the shaft 22 rotates counterclockwise as shown in FIG. 9B. At this time, the low speed main exhaust valve 15 and the sub exhaust valve 18 are opened together with the rotation of the shaft 22. By opening the low-speed region main exhaust valve 15, the main exhaust passage 13 is opened.
And the exhaust timing in the main exhaust passage 13 is instantaneously increased with a large amount of change.

[0043] shown by R ₁ engine speed at this time in FIGS. In FIG. 11, a straight line a indicates a change in the opening degree of the sub exhaust valve 18 and the low speed main exhaust valve 15, and a straight line b indicates a change in the opening degree of the high speed main exhaust valve 16.

When the auxiliary exhaust valve 18 is opened, the engine 1 is exhausted when the piston 6 passes the upper edge of the cylinder opening 14a of the auxiliary exhaust passage 14. That is, as shown by the broken line in FIG. 12, the exhaust timing is earlier than the exhaust timing determined by the low-speed range main exhaust valve 15 (shown by the solid line in FIG. 12).

The drive plate 24 also rotates together with the shaft 22, but since the pressing portion 24a slides on the circular arc surface 17d, the operating block 17 and the high-speed main exhaust valve 16 are maintained at the fully closed position. . That is, the low-speed main exhaust valve 15 and the sub-exhaust valve 18 are opened before the high-speed main exhaust valve 16 is opened.

In this state, the high-speed main exhaust valve 1
Even if the exhaust pressure is applied to the actuator block 6 and the operation block 17 is urged to the left in FIG. 9, the pressing portion 24 a and the fan-shaped portion 24 b contact the arc surfaces 17 d and 17 e of the operation block 17 and function as a stopper. The movement of the operation block 17 is restricted.

When the shaft 22 further rotates counterclockwise as the engine speed increases, FIG.
As shown in FIG. 9, the pressing portion 24a of the driving plate 24 comes into contact with the projection 17g of the operation block 17, and urges the operation block 17 to the left in FIG. The rotation angle of the shaft 22 at this time is about 40 ° in the apparatus of the present embodiment. The positions of the distal ends of the low-speed range main exhaust valve 15 and the sub-exhaust valve 18 at this time are indicated by a two-dot chain line b in FIGS. 2 and 5. Incidentally, it denoted by R ₂ of the engine rotational speed at this time in FIGS.

When the engine speed increases and the shaft 22 further rotates leftward from the position shown in FIG. 9B, the operation block 17 moves to the left in FIG. 16 will open. By opening the high-speed region main exhaust valve 16, the passage cross-sectional area of the main exhaust passage 13 further increases, and the exhaust timing of the main exhaust passage 13 is accelerated. Also at this time, as in the case where the low-speed range main exhaust valve 15 is opened, the speed is instantaneously increased with a large change amount.

Thereafter, as shown in FIG. 9C, the shaft 22 is rotated so that the low-speed main exhaust valve 15, the high-speed main exhaust valve 16 and the sub exhaust valve 1
8 is fully opened. When the valve is fully opened, the exhaust timing becomes the fastest and the full exhaust passage cross-sectional area becomes maximum, so that a high output can be easily obtained when the engine is fully opened.

The position of the tip of each valve at this time is shown in FIG.
And the position shown by the solid line in FIG. The rotation angle of the shaft 22 when each valve is fully opened is about 54 ° in the apparatus of the present embodiment.

When the engine speed decreases from the fully open operation state, all the valves begin to close at the same time, and after the high-speed main exhaust valve 16 is fully closed, the low-speed main exhaust valve 15 and the sub exhaust valve 18 are closed. It is fully closed. When the high-speed main exhaust valve 16 is closed, the drive plate 24
Presses the side surface of the notch 17f of the operation block 17.

That is, the period when the high-speed region main exhaust valve 16 is open is in the range indicated by A in FIG. 9, and the period when the low-speed region main exhaust valve 15 and the sub exhaust valve 18 are open is in the range indicated by B. Become.

As shown in FIG. 11, the amount of change in the opening degree of each valve (valve stroke amount) with respect to the rotation amount of the shaft 22 is equal to that of all exhaust valves when the high-speed main exhaust valve 16 is open. It is almost equal.

Further, the exhaust timing of the engine 1 is as follows.
Once faster when the rotation speed R ₁ of the low-speed range for main exhaust valve 15 and the auxiliary exhaust valve 18 begins to open, then it becomes even faster when a high speed range for main exhaust valve 16 is opened. And it becomes constant after all the exhaust valves are fully opened. Incidentally, FIGS. 11 and 12 in R ₃ is an engine rotational speed that all of the exhaust valve is fully opened.

Therefore, according to the exhaust valve device of the present invention, the exhaust timing in the main exhaust passage 13 is gradually adjusted by opening the high-speed main exhaust valve 16 after the low-speed main exhaust valve 15 is opened. Be faster. In other words, when each of the main exhaust valves 15 and 16 is opened, the exhaust timing in the main exhaust passage 13 is instantaneously increased with a large change amount. Therefore, by opening the low-speed region main exhaust valve 15 at the same time as opening the sub-exhaust valve 18, the exhaust timing in the main exhaust passage 13 becomes substantially equal to the engine exhaust timing (the cylinder opening 14 a of the auxiliary exhaust passage 14). (Exhaust timing determined by the above).

In the two-stroke engine equipped with the exhaust valve device according to the present invention, the output characteristics indicated by the solid line in FIG. 13 were obtained. In FIG. 13, a broken line indicates a case where no exhaust valve is mounted, a dashed line indicates a case where only one main exhaust valve is mounted, and a two-dot chain line indicates a case where one main exhaust valve and one auxiliary exhaust valve are mounted.

As shown in FIG. 13, it can be seen that when the configuration of the present invention is adopted, high output can be obtained in the low and medium speed ranges.

In this embodiment, the main exhaust valve 15 for the low speed range, the main exhaust valve 16 for the high speed range, and the sub exhaust valve 1
Since the driving of the valve driving mechanism 8 is performed by the rotation of the shaft 22 of the valve driving mechanism 21, the valve driving mechanism 21 can have a simple structure, and the parts can be shared, and the increase in the number of parts can be minimized. Can be suppressed.

[0059]

As described above, the exhaust valve device of the two-stroke engine according to the present invention is arranged side by side along the cylinder axis direction, faces the main exhaust port, and moves in parallel in accordance with the engine speed. A main exhaust valve for a low speed range and a main exhaust valve for a high speed range, the amount of protrusion of which is changed to change the exhaust timing, and a pair of auxiliary exhaust valves for changing a passage cross-sectional area facing the auxiliary exhaust port on the side of the main exhaust port, In each of the valves, when the engine speed is smaller than the set speed, the valves are fully closed, and when the set speed is exceeded, the low-speed main exhaust valve and the sub-exhaust valve are simultaneously opened, Since the exhaust valve drive mechanism that opens the high-speed main exhaust valve is connected, the exhaust timing in the main exhaust passage is such that the high-speed main exhaust valve opens after the low-speed main exhaust valve opens. It becomes gradually faster by.
In other words, when each main exhaust valve is opened, the exhaust timing in the main exhaust passage is instantaneously increased by a large amount. For this reason, by opening the low-speed region main exhaust valve at the same time as opening the sub exhaust valve, the exhaust timing in the main exhaust passage approaches the substantial exhaust timing of the engine.

Therefore, a high output can be obtained even when the engine speed increases from the middle speed range to the high speed range, so that a high output can be obtained over a wide engine speed range.

Since the low-speed main exhaust valve and the high-speed main exhaust valve move in parallel with each other, they can be driven by one rotating shaft. For this reason,
The structure of the exhaust valve driving mechanism is simplified, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a two-stroke engine equipped with an exhaust valve device according to the present invention.

FIG. 2 is an enlarged sectional view showing a main exhaust valve driving section of the exhaust valve device according to the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is an enlarged sectional view showing a sub exhaust valve driving section of the exhaust valve device according to the present invention.

FIG. 6 is a sectional view of a main exhaust valve.

FIG. 7 is a view on arrow A in FIG. 1 with a cover removed.

FIG. 8 is an exploded perspective view of an exhaust valve driving mechanism.

9A and 9B are cross-sectional views for explaining the operation of the high-speed main exhaust valve. FIG. 9A shows a fully closed state, and FIG. 9B shows a state when the high-speed main exhaust valve starts to open. State,
FIG. 3C shows a fully opened state.

FIG. 10 is a development view of an exhaust port portion of the cylinder.

FIG. 11 is a graph showing a relationship between an engine speed and a valve stroke amount of the exhaust valve device according to the present invention.

FIG. 12 is a graph showing a change in exhaust timing in a main exhaust passage.

FIG. 13 is a graph showing a relationship between an engine speed and an output of an engine equipped with the exhaust valve device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 13 main exhaust passage 14 auxiliary exhaust passage 15 main exhaust valve for low speed range 16 main exhaust valve for high speed range 17 operation block 18 auxiliary exhaust valve 21 valve drive mechanism 23 drive fork 24 drive plate 25 drive fork

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 25/20 F02D 13/02

Claims (1)

(57) [Claims] 1. A main exhaust valve for a low-speed region and a high-speed region, wherein the main exhaust valve is arranged side by side along the cylinder axis direction and faces the main exhaust port, and moves in parallel according to the engine speed to change the amount of projection to change the exhaust timing. A main exhaust valve, and a pair of auxiliary exhaust valves that face the auxiliary exhaust port on the side of the main exhaust port and change the cross-sectional area of the passage, wherein each of the valves is provided when the engine speed is smaller than a set speed. Is fully closed, and when the set number of revolutions is exceeded, the low-speed main exhaust valve and sub-exhaust valve are simultaneously opened, and then the exhaust valve drive mechanism that opens the high-speed main exhaust valve is connected. An exhaust valve device for a two-stroke engine.