JP3097089B2 - Exhaust control device for two-stroke engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device that changes the exhaust timing of a two-cycle engine according to the engine speed.

[Conventional technology]

Conventionally, in the case of a two-cycle engine, the position of the upper edge of the exhaust port is raised and lowered in accordance with the engine speed, thereby securing an optimal exhaust timing in accordance with each engine speed range, thereby ensuring a two-cycle engine in a wide engine speed range. There is provided an exhaust control device that improves the output of the exhaust gas.

FIG. 2 is a conceptual sectional view of a main part of a two-stroke engine 2 to which the above-described exhaust control device 1 is mounted.

The exhaust control device 1 has a plate-shaped first valve body 4 and a second valve body 5 which are disposed on the upper wall 3a of the exhaust passage 3 so as to be able to protrude and retract. (L position)
As shown in the figure, both the first and second valve bodies 4 and 5 are made to protrude toward the exhaust port 6, and the tip 4 a of the first valve body 4 is
As a result, the upper edge position of the exhaust port 6 is lowered by A, thereby delaying the exhaust timing to improve the output of the two-cycle engine 2 in the low engine speed range. As shown in the figure, only the first valve element 4 is retracted from the exhaust port 6, and the upper edge position of the exhaust port 6 is raised by B by the tip 5a of the second valve element 5, thereby reducing the exhaust timing. The output of the two-stroke engine 2 in the middle rotation speed range is slightly improved.

As shown in FIG. 3, the front end surfaces of the first valve body 4 and the second valve body 5 are formed so as to rise frontward and become substantially flush with each other in the middle rotation range of the engine. I have.

In the high rotation range (H position) of the engine, as shown in FIG. 4, both the first and second valve bodies 4 and 5 are retracted from the exhaust port 6 so that the upper edge position of the exhaust port 6 is further reduced by C. As a result, the exhaust timing is made the fastest to improve the output of the two-stroke engine 2 in the high rotation speed range.

The first and second valve bodies 4 and 5 described above are disposed so as to overlap each other as shown in the figure, and when the second valve body 5 is retracted from the exhaust port 6, it is necessary to use FIG. As shown, the pin 7 which is an engaging portion press-fitted to the second valve body 5 is engaged with the long groove 4b which is an engaging portion formed on the upper surface of the first valve body 4, The second valve element 5 is retracted into the upper wall 3a of the exhaust passage 3 following the retraction of the first valve element 4. In addition, the second valve element 5 is always in the second position via the pin 7 by the pressing force of the spring 8 disposed in the cylinder.
As shown in the figure, it is urged to protrude toward the exhaust port 6 side.

In FIGS. 2 to 4, reference numeral 9 denotes a cylinder sleeve, and 9 'denotes a scavenging port.

On the other hand, as shown in FIG. 2, the drive device for the first and second valve bodies 4 and 5 has a U-shape which is inserted into a shaft 10 supported on the rear end of the first valve body 4. Lever with cutout 11
And a drive shaft 12 for rotating the lever 11. When the drive shaft 12 rotates, the first
The second valve bodies 4 and 5 sequentially protrude and descend from the upper wall 3a of the exhaust passage 3 toward the exhaust port 6.

The drive shaft 12 described above is driven by an exhaust valve drive pulley 13 (hereinafter simply referred to as a drive pulley) fixed to one end of the drive shaft 12 shown in FIG. The drive pulley 13 is driven by a servo motor (not shown) at a predetermined engine speed via a drive cable 14 wound around the pulley 13.

On the other hand, the first and second valve bodies 4 and 5 described above have the L position shown in FIG. 2 in the low rotation speed region, the M position shown in FIG. 3 in the middle rotation speed region, and the M position shown in FIG. Since it is necessary to move to the H position shown in FIG. 4, the plate supporting the drive shaft 12 is adjusted to adjust to the above-mentioned L, M and H positions in each of these rotation speed ranges. Forming an alignment mark 16 at the L position, an alignment mark 17 at the M position, and an alignment mark 18 at the H position at predetermined positions of 15,
An alignment mark 19 is formed at a predetermined position on the upper surface of the driving pulley 13, and as shown in FIG. 5, when the mark 19 of the pulley 13 and the alignment mark 16 at the L position match, as shown in FIG. The first and second valve bodies 4 and 5 are set so as to be positioned, and as shown in FIG. 6, when the mark 19 of the pulley 13 and the alignment mark 17 at the M position match, the third
The first and second valve bodies 4 and 5 are set so as to be positioned at the M position shown in the figure. Further, as shown in FIG. 7, the mark 19 of the pulley 13 and the alignment mark 18 at the H position are aligned. When they match, the first and second valve bodies 4 are moved to the H position shown in FIG.
5 was adjusted so as to be positioned.

[Problems to be solved by the invention]

By the way, according to the exhaust control device described above, the distal end face 4c of the first valve element 4 and the second valve element 5 at the position M shown in FIG.
At the time of adjustment, the mark 19 of the pulley 13 and the alignment mark 17 at the M position are matched as shown in FIG. When the pulley 13 is rotated by a servomotor (not shown), the play of the operating cable 14 (actually, the play is usually 0.3 to 0.5 mm and the amount of bending is about 1 mm) causes the pulley 13 to rotate as shown in FIG. The mark 19 and the alignment mark 17 at the M position do not reach the position where they match, and as a result, as shown in FIG. 8 which is an enlarged view of a main part of FIG. 3, the first valve body 4 and the second valve body 5 Do not coincide with each other, the first valve element 4 projects or retracts by the amount of play, as shown by the dashed-dotted lines 20 and 21.

Although there is no problem in the first valve element 4 being retracted as shown by the one-dot chain line 20 due to the play of the cable, if the first valve element 4 protrudes as shown by the one-dot chain line 21, the flow of the exhaust gas is obstructed, and the mid-speed range is reduced. At the optimal exhaust timing,
There is a problem that causes a decrease in the output of the two-cycle engine.

Note that such a problem is caused when the first and second valve bodies 4 and 5 are both retracted into the upper wall 3a of the exhaust passage 3 in a high rotation speed range, and the tip of the first valve body 4 Tip surface of second valve element 5
In some cases, it may protrude from 5a. In this case, too, the flow of the exhaust gas is obstructed, so that an optimal exhaust timing cannot be obtained in a high rotational speed range, which causes a decrease in the output of the two-stroke engine.

The present invention has been made in view of the above circumstances, and has as its object to provide an exhaust control device for a two-stroke engine that can secure a suitable exhaust timing in a middle / high speed range.

[Means for solving the problem]

In order to achieve the above object, in the present invention, a first valve body and a second valve body formed in a plate shape are vertically overlapped,
Further, a driving device is connected to the first valve body and engaged with the second valve body at a position retracted by a predetermined distance to advance and retreat along the radial direction of the cylinder. A second valve body is provided on the side wall of the cylinder so as to protrude and retract above an exhaust port communicating with an exhaust passage, and the first valve body and the second valve body are disposed in a low-speed range of the engine. Both are protruded to the exhaust port side, and the upper edge position of the exhaust port is lowered by the tip of the first valve body located on the lower side, and the engine is in the medium speed range with respect to the low speed range. Only the first valve element located on the lower side is retracted by a predetermined distance from the exhaust port side to raise the upper edge position of the exhaust port to the tip position of the second valve element, and the first and second valves The front end surface of the body rises forward and is formed on a substantially flat inclined surface, and the engine rotates at high speed In the range, the relative positions of the first and second valve bodies with respect to the medium speed range are further retreated by connecting the first valve body to the driving device in a state of substantially the middle speed range by engagement of the two. In the exhaust control device of the two-cycle engine, wherein the second valve body is retracted from the exhaust port side to further raise the upper edge position of the exhaust port, only the first valve element is retracted by a predetermined distance, A tip end surface of the first valve body and the second valve body;
The engagement between the first valve body and the second valve body is relative to the relative position of the first and second valve bodies in the middle speed range where the tip surface of the valve body is substantially flush with the front surface. The relative position at which the joint is engaged is such that at least the first valve body is further retracted by a small amount.

[Action]

According to the exhaust control device described above, the second valve body is
The first and second valve bodies are positioned on the upper wall of the exhaust passage because the distal end surface of the valve body is set so as to engage at a position slightly smaller than the distal end surface of the second valve body. Even when the vehicle is retracted, the above-described positional relationship between the first and second valve bodies is maintained, so that the first valve body does not protrude from the distal end surface of the second valve body and does not become exhaust resistance.

〔Example〕

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

FIG. 1 is an enlarged perspective view of a main part of a two-stroke engine 31 equipped with an exhaust control device 30 according to the present invention. The same parts as those in FIG. ing.

In the exhaust control device 30, when setting the positioning of the first and second valve bodies 4 and 5 in the middle rotation speed range of the engine, as shown in FIG. When the mark 17 matches, as shown in FIG. 1, the distal end face 4c of the first valve body 4 is moved to the distal end face 5c of the second valve body 5.
The position is set in advance so as to be retracted to a position a predetermined distance deeper than that, that is, at a position slightly retreated.

Note that the distance for retreating is as shown in FIG.
And the tip surface of the first valve body 4
In order to retreat 4c by a predetermined distance less than the distal end face 5c of the second valve element 5, the mounting position of the lever 11 and the drive shaft 12 is changed.

Therefore, according to the control device 30 described above, when the pulley 13 is rotated via the cable 14 by a servo motor (not shown) during operation of the engine as shown in FIG. 6, the play of the operation cable 14 actually causes the play as shown in FIG. Pulley 13 mark
Even if the first valve body 4 protrudes to the position of the dashed line 32 shown in FIG. The amount of protrusion is absorbed in advance by a distance obtained by retreating the distal end surface 4c of the first valve body 4 by a predetermined distance from the distal end surface 5c of the second valve body 5.

For this reason, even if the distal end face 4c of the first valve element 4 protrudes to the maximum due to the play amount of the cable 14, the distal end face 4c of the first valve element 4 and the second valve element 4 as shown by the one-dot chain line 32 in FIG. 5 tip surface 5c
, That is, an inclined surface which is substantially flush with the front and rises, and the front end surface of the first valve body 4 in the middle rotation speed region of the engine.
4c does not protrude from the distal end face 5c of the second valve body 5.

That is, according to the above-described configuration, even when the first and second valve bodies 4 and 5 retreat to the upper wall 3a of the exhaust passage 3 in a high rotation speed range, the first and second valve bodies 4 and 5 described above are used. In other words, the second valve body 5 maintains the positional relationship in which the distal end face 4c of the first valve body 4 is slightly retracted from the distal end face 5c of the second valve body 5, As a result, the first valve body 4 does not protrude from the distal end surface 5a of the second valve body 5 and does not provide exhaust resistance.

〔The invention's effect〕

As described above, in the exhaust control device of the present invention,
Since the second valve body is set so as to engage at a position where the distal end surface of the first valve body is slightly retracted from the distal end surface of the second valve body, the first and second valve bodies are engaged. Even when the valve body retreats to the upper wall of the exhaust passage, the above-described positional relationship between the first and second valve bodies is maintained. It is possible to prevent the tip end face from protruding from the tip end face of the second valve body as much as possible, thereby securing a suitable exhaust timing in a middle / high speed range and further improving the output of the two-stroke engine. it can.

[Brief description of the drawings]

FIG. 1 is a conceptual cross-sectional view of a two-stroke engine to which an exhaust control device according to the present invention is applied, FIGS. 2 to 4 are conceptual cross-sectional views of main parts of a two-stroke engine showing the operation of the exhaust control device, and FIGS. FIG. 8 is a diagram showing the operation of the driving pulley, and FIG. 8 is an enlarged view of a main part of FIG. 3 ... exhaust passage, 3a ... upper wall, 4 ... first valve body, 4b ...
… Groove, 4c, 5c… Tip end face, 5… Second valve body, 6… Exhaust port, 7… Pin.

Claims (1)

(57) [Claims] 1. A first valve body formed in a plate shape and a second valve body are vertically overlapped with each other, and a driving device is connected to the first valve body, and the first valve body is retracted by a predetermined distance to a first position. The first valve body and the second valve body are opened on the side wall of the cylinder so as to engage with the second valve body so as to advance and retreat along the radial direction of the cylinder. The first valve body and the second valve body both protrude toward the exhaust port side in the low-speed rotation range of the engine, and the upper edge position of the exhaust port is located at the lower side. The first valve body is lowered by the tip of the first valve body, and only the first valve body located below the low-speed rotation area in the middle rotation speed range of the engine is retracted by a predetermined distance from the exhaust port side. The upper edge position of the exhaust port is raised to the tip position of the second valve body, and the first and second valves are moved. The front end face of the first valve body is formed to be substantially flush with the front end face, and the relative positions of the first and second valve bodies with respect to the medium speed range in the high speed range of the engine by engagement of the two. By further retreating the first valve body connected to the driving device in a state of a substantially middle speed range, the second valve body is retreated from the exhaust port side to further raise the upper edge position of the exhaust port. Done 2
In the exhaust control device for a cycle engine, only the first valve body is retracted by a predetermined distance, and a medium-speed rotation speed in which a front end surface of the first valve body and a front end surface of the second valve body are substantially flush with each other. The relative position where the engaging portion of the first valve body and the engaging portion of the second valve body engage with at least the first valve body relative to the relative position of the first and second valve bodies in the region. An exhaust control device for a two-stroke engine, wherein the exhaust control device is further retracted.