JPH08158870A - Exhaust control structure of two-cycle engine - Google Patents

Abstract

PURPOSE: To decrease the stick of a valve due to adherence of exhaust carbon as well as to improve an exhaust characteristic at intermediate opening of an auxiliary exhaust control valve of a two-cycle engine. CONSTITUTION: A main exhaust passage 6 and an auxiliary exhaust passage 7 separately opening a main exhaust port 6a and an auxiliary exhaust port 7a to an inwall of a cylinder 3 are formed on a cylinder block 2, a main exhaust control valve 8a is set in the main exhaust passage 6, and an auxiliary exhaust control valve 91 to open and close the auxiliary exhaust passage 7 interlocked with the main exhaust control valve 8a is set in the auxiliary exhaust passage 7. The auxiliary exhaust control valve 91 to open and close the auxiliary exhaust passage 7 in the vertical direction is made as a revolving valve consisting of a cutout surface formed by cutting out a part of a sectionally circular revolving shaft member 9 and a circular arc outer peripheral surface, offset to the side of a shaft center of the cylinder 3 rather than the main exhaust control valve 8a, arranged in the neighbourhood of the auxiliary exhaust port 7a and set so as to revolve in a direction where the cutout surface is directed to the exhaust upstream side at the time of closing the valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust passage formed in a cylinder block, which comprises a main exhaust passage and an auxiliary exhaust passage each of which opens in the cylinder separately and joins at the downstream of the main exhaust passage. And a two-cycle engine in which an exhaust control valve is installed in each of the auxiliary exhaust passage.

[0002]

2. Description of the Related Art The piston itself acts as an exhaust valve 2
In a cycle engine, the exhaust passage formed in the cylinder block has a main exhaust passage whose one end opens into the cylinder as a main exhaust port, and one end which opens laterally to the main exhaust port into the cylinder as an auxiliary exhaust port. The auxiliary exhaust passage has its end joined to the main exhaust passage, and the main exhaust passage is equipped with a main exhaust control valve that opens and closes the upper part of the main exhaust port according to the engine speed, etc. By installing an auxiliary exhaust control valve that opens and closes the auxiliary exhaust passage in conjunction with the main exhaust control valve, the exhaust start timing is accelerated at high speed rotation to increase the exhaust area, and vice versa at low speed rotation. As described above, it has been conventionally performed to control the exhaust timing and the exhaust area of the exhaust passage.

Therefore, as a structure thereof, an exhaust control valve for the main exhaust passage and the auxiliary exhaust passage is formed on one rotating shaft (Japanese Patent Laid-Open No. 59-101534), or for the main exhaust passage and the auxiliary exhaust passage. The exhaust control valve is formed as a separate valve body and is linked by a mechanism such as a pinion, a rack, a cam (Japanese Patent Laid-Open No. 63-173817).
Also, there has been conventionally known an exhaust control valve for the main exhaust passage and an auxiliary exhaust passage, which are linked by eccentric interlocking pins formed in the respective exhaust passage and an elongated hole (Japanese Patent Laid-Open No. 4-66721). .

[0004]

In the conventional exhaust control structure for a two-cycle engine as described above, a rotary valve formed by cutting out a part of a rotary shaft member having a circular cross section is used as an auxiliary exhaust control valve. When used, the auxiliary exhaust control valve is shown in FIG. 9 from the fully open state in which the cutout surface 91a serves as the ceiling wall of the auxiliary exhaust passage 7 and the arc-shaped outer peripheral surface 91b contacts the cylinder block, as shown in FIG. like,
When the valve is closed, the arcuate outer peripheral surface 91b that is in sliding contact with the cylinder block comes out to the exhaust gas upstream side of the auxiliary exhaust passage 7, and the cutout surface 91a rotates in a direction so as to face the exhaust gas downstream side. It is installed in.

That is, as the opening / closing position of the auxiliary exhaust control valve becomes farther from the auxiliary exhaust port of the cylinder, it becomes more difficult to secure the gas sealability in the vicinity of the auxiliary exhaust port by the auxiliary exhaust control valve, and it is difficult to control the exhaust timing. When the auxiliary exhaust control valve is fully closed during low speed operation, there is an ineffective volume part integrated with the combustion chamber between the auxiliary exhaust control valve and the auxiliary exhaust port. In this case, the farther the auxiliary exhaust control valve is from the auxiliary exhaust port, the larger the portion of the ineffective volume and the lower the output.

Therefore, even if the rotary shaft member is installed at the same position, the opening / closing operation position of the auxiliary exhaust control valve should be as close to the exhaust upstream side of the auxiliary exhaust passage (as close to the auxiliary exhaust port) as possible. Normally, the auxiliary exhaust control valve is installed so as to rotate in the direction shown in FIG.

However, as shown in FIG. 9, when the auxiliary exhaust control valve is rotated in such a direction that the arcuate outer peripheral surface 91b faces the exhaust upstream side and the notch surface 91a faces the exhaust downstream side, the intermediate opening degree Because the exhaust flow does not flow smoothly in the exhaust gas, the control accuracy of the auxiliary exhaust flow rate commensurate with the rotation angle of the auxiliary exhaust control valve deteriorates, and it becomes difficult to obtain the exhaust characteristics according to the control of the auxiliary exhaust control valve. Also, an arcuate outer peripheral surface 91 which is a sliding contact surface with the cylinder block.
Since the exhaust gas flowing from the inside of the cylinder directly hits b, carbon in the exhaust gas adheres to this portion, so that a so-called valve stick that hinders the rotation of the valve easily occurs.

When the auxiliary exhaust control valve is linked with the main exhaust control valve via a link mechanism including a main exhaust side lever, an auxiliary exhaust side lever, and a rod for connecting the levers, the auxiliary exhaust control valve In order to rotate the levers in the directions as shown in FIG. 9, as shown in FIG. 13, the connecting portions 20, 22 of the levers 18, 23 and the rod 21 are connected to the rotation shafts of the levers 18, 23. If it is located on the same side with respect to the line X connecting the two, the operating angle of the rod 21 with respect to the auxiliary exhaust side lever 23 becomes worse, and the turning force of the main exhaust side lever 18 is effectively transmitted to the auxiliary exhaust side lever 23. I can't.

An object of the present invention is to eliminate the inconvenience of the conventional exhaust control structure for a two-cycle engine as described above. More specifically, the auxiliary exhaust control valve, which is a rotary valve, is By making it as close as possible to the exhaust port and rotating it in the opposite direction to the conventional one, the flow of the auxiliary exhaust at the intermediate opening becomes smooth, and the auxiliary exhaust control valve at the intermediate opening of the auxiliary exhaust becomes It is an object of the present invention to provide an exhaust control structure for a two-cycle engine, which can improve exhaust characteristics in accordance with control of exhaust gas and can reduce the valve stick of an auxiliary exhaust control valve due to adhesion of exhaust carbon. Is something
Further, in such an exhaust control structure of a two-cycle engine, when the auxiliary exhaust control valve is interlocked with the main exhaust control valve via a link mechanism, it is an object to effectively transmit the driving force thereof. Is.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention is designed so that a main exhaust port and an auxiliary exhaust port are separately opened in a cylinder inner wall and are joined downstream thereof. The main exhaust passage and the auxiliary exhaust passage are formed in the cylinder block, the main exhaust passage is equipped with a main exhaust control valve that opens and closes the upper part of the main exhaust port, and the auxiliary exhaust passage is equipped with a main exhaust control valve. In a two-cycle engine in which an auxiliary exhaust control valve that opens and closes the auxiliary exhaust passage is installed, the auxiliary exhaust control valve that opens and closes the auxiliary exhaust passage in a vertical direction partially covers a rotary shaft member having a circular cross section. A rotary valve that is formed by cutting out and that includes a cutout surface and an arc-shaped outer peripheral surface, is offset toward the axial center side of the cylinder with respect to the main exhaust control valve, and is arranged in the vicinity of the auxiliary exhaust port, Closed Sometimes truncated face is characterized in that it is installed so as to rotate in a direction such as to face the exhaust upstream side.

Further, in such an exhaust control structure for a two-cycle engine, as described in claim 2, in order to interlock the auxiliary exhaust control valve with the main exhaust control valve, the main exhaust side lever and the auxiliary exhaust A link mechanism including a side lever and a rod for connecting the levers is installed on the outer side of the cylinder block, and in the link mechanism, each connecting portion of each lever and the rod is connected to each lever. It is characterized in that they are located on different sides with respect to the line connecting the rotation axes of the levers so that the rotation directions are opposite.

[0012]

[Operation] With the above configuration, when the auxiliary exhaust control valve is rotated and is in the intermediate opening state, the cutout surface of the auxiliary exhaust control valve faces the upstream side of the exhaust gas, and moreover, it flows in. Since the angle of the notch surface with respect to the incoming exhaust gas changes according to the opening of the auxiliary exhaust control valve, the flow of exhaust along the auxiliary exhaust control valve at the intermediate opening becomes smooth, and the auxiliary exhaust control valve The auxiliary exhaust flow rate is controlled according to the turning angle, and the control accuracy of the engine output according to the turning angle of the auxiliary exhaust control valve is improved.

Further, the arcuate outer peripheral surface of the auxiliary exhaust control valve, which is the sliding contact surface with the cylinder block, moves in and out on the downstream side of the exhaust as the auxiliary exhaust control valve rotates, Exhaust gas immediately after flowing from the inside of the cylinder does not directly contact the part, and the amount of carbon in the exhaust gas that adheres to this part is small, and the carbon adheres to the sliding contact surface of the valve and prevents it from turning. Sticking is hard to occur.

Even though the rotation direction of the auxiliary exhaust control valve is opposite to the normal direction, the auxiliary exhaust control valve itself is arranged closer to the auxiliary exhaust port than the conventional one. In comparison, the opening / closing operation position of the auxiliary exhaust control valve does not move away from the auxiliary exhaust port.

Further, according to the structure described in claim 2, the auxiliary exhaust control valve is driven in association with the main exhaust control valve by the link mechanism including the main exhaust side lever, the rod and the auxiliary exhaust side lever. In this case, the operating angle of the rod with respect to the auxiliary exhaust side lever is improved, and the turning force of the main exhaust side lever can be effectively transmitted to the auxiliary exhaust side lever.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust control structure for a two-cycle engine of the present invention will be described below with reference to the drawings.

1 to 4 show a main part of a two-cycle engine to which an embodiment of an exhaust control structure of the present invention is applied, and FIG. 1 is a vertical cross section of a cylinder block to which a cylinder head is connected. 2 shows a cross section near the exhaust passage, FIG. 3 shows one side surface of the cylinder block,
FIG. 4 shows the other side surface of the cylinder block.

The two-cycle engine has a cylinder head 1
Is integrally connected to a lower portion of the cylinder block 2, and a crankcase (not shown) is integrally connected to a lower portion of the cylinder block 2. The crankcase is connected to a piston via a connecting rod. The crankshaft is pivotally supported, the intake passage leading to the carburetor is opened in the crankcase (neither is shown), and the cylinder block 2 has a cylinder 3 in which a piston (not shown) moves up and down. Are formed so as to penetrate vertically.

On the inner surface of the cylindrical peripheral wall of the cylinder 3 of such a two-cycle engine, each end of a plurality of scavenging passages 5 communicating with the inside of the crankcase is opened as a scavenging port 5a.
The respective ends of the main exhaust passage 6 and the auxiliary exhaust passage 7 forming the exhaust passage are opened as a main exhaust port 6a and an auxiliary exhaust port 7a, respectively.

The main exhaust port 6a is opened so that its upper end is located above the scavenging port 5a, and the auxiliary exhaust ports 7a are located above the scavenging port 5a. 6a are respectively opened on both sides in the cylinder circumferential direction, and the downstream ends of the respective auxiliary exhaust passages 7 extending from the respective auxiliary exhaust ports 7a to the exhaust downstream are connected to the main exhaust passage 6 continuing from the main exhaust port 6a to the exhaust downstream. It joins from both sides.

The main exhaust passage 6 is provided with a main exhaust control valve 8a, which is located in the vicinity of the main exhaust port 6a and extends obliquely downward from the top wall of the main exhaust passage 6 toward the main exhaust port 6a. Auxiliary exhaust control valves 91 projecting from the side wall on the side opposite to the main exhaust passage 6 side into the auxiliary exhaust passage 7 are installed in the auxiliary exhaust passage 7 near the auxiliary exhaust port 7a.

The main exhaust control valve 8a is a sliding valve that moves in and out of the main exhaust passage 6 from the top wall of the main exhaust passage 6, and other than the sliding shaft 8b provided with the main exhaust control valve 8a at its tip. An engagement pin 8c is provided at the end.
A rotation shaft 12 in which a pin engaging portion 10 for rotatably holding c is integrally fixed near the center thereof with a bolt 11 is provided.
The cylinder block 2 is pivotally supported by the cylinder block 2 so that both ends 12a and 12b thereof project from the cylinder block 2 to both sides.

By rotating the rotating shaft 12, the pin engaging portion 10 rotates and the engaging pin 8c.
Is moved in the axial direction of the sliding shaft 8b, and the rotating shaft 12
The main exhaust control valve 8a moves in and out of the main exhaust passage 6 from the top wall of the main exhaust passage 6 in conjunction with the reciprocating rotation of the rotating shaft 12 because the sliding shaft 8b orthogonal to the slide shaft 8b slides. Will be done.

At the end 12a of the rotary shaft 12 projecting to one side of the cylinder block 2, a cylindrical collar 13 whose outer peripheral surface is partially cut away in the axial direction is formed on the bolt 1.
It is fixed by 4, and the pulley 13 is attached to the collar 13.
Is non-rotatably fitted and fixed, and the pulley 1
Each end of wires 16a and 16b for transmitting reciprocal rotation of a servo motor unit (not shown) controlled according to the number of revolutions of the engine is connected to 5.

A collar 13 is fixed to the end 12b of the rotary shaft 12 projecting to the other side of the cylinder block 2 with a bolt 14 like the end 12a, and a pulley 15 is attached to the collar 13. Instead of, the plate 17 is non-rotatably fitted and fixed.

Further, both ends 12a of the rotary shaft 12 are
The main exhaust side lever 18 is rotatably fitted to the collar 13 so as to overlap the outsides of the pulley 15 and the plate 17, which are respectively fixed to the 12b,
By tightening the bolts 19 to the pulley 15 or plate 17, the pulley 15 or plate 1
The positional relationship with respect to 7 is fixed so as to be adjustable.

Regarding the structure of the main exhaust side lever 18 itself, as shown in FIGS. 5A and 5B, a connecting portion 20 for rotatably connecting one end of a rod 21 described later.
Is fixed to the outer surface of its upper part, and the collar 13 is attached to its lower part.
A circular fitting hole 18b for rotatably fitting in is opened, and a long hole 1 for inserting the bolt 19 in the center thereof.
8a is opened and is rotatably fitted in the collar 13. After that, the mounting angle with respect to the pulley 15 or the plate 17 is adjusted within the range of the elongated hole 18a to adjust the bolt 19.
It is fixed in.

On the other hand, with respect to the respective auxiliary exhaust control valves 91 installed in the respective auxiliary exhaust passages 7, all the auxiliary exhaust control valves 91 are introduced into the auxiliary exhaust passage 7 from the side of the auxiliary exhaust passage opposite to the main exhaust passage 6 side. In the cantilevered rotary valve, the rotary shaft member 9 having a circular cross section whose diameters are changed stepwise has an enlarged diameter end projecting into the auxiliary exhaust passage 7 having a substantially half-moon to crescent cross-section. Is formed by partially cutting out the outer peripheral surface thereof.

As shown in FIGS. 7 and 8, the auxiliary exhaust control valve 91 has a cutout surface 91a and an arcuate outer peripheral surface 9 as shown in FIG.
1b and the auxiliary exhaust control valve 9
7, the cutout surface 91a is flush with the top wall of the auxiliary exhaust passage 7, and the arc-shaped outer peripheral surface 9 is open.
The entire 1b is buried in the cylinder block 2, and when the valve is closed, as shown in FIG. 8, the cutout surface 9b is rotated in a direction toward the exhaust upstream, that is, the side of the auxiliary exhaust port 7a. The auxiliary exhaust passage 7 is opened and closed from the top wall side.

The rotary shaft members 9 arranged symmetrically with respect to the main exhaust passage 6 are in parallel relationship with the rotary shaft 12, and are located in the cylinder 3 more than the position of the main exhaust control valve 8a. In order that the axes of the rotary shaft members 9 and 9 coincide with one virtual axis line that is brought closer to the axis,
It is arranged on the line.

Then, in any of the rotating shaft members 9,
The enlarged diameter end of the auxiliary exhaust passage 7 is the auxiliary exhaust control valve 9
1, the intermediate diameter portion of the rotary shaft member 9 is rotatably supported by the cylinder block 2 via a bearing portion 30 as a valve bearing portion, and the diameter of the rotary shaft member 9 is reduced. The other end side 92 thus formed projects laterally from the cylinder block 2 as an input shaft.

The cylinder block 2 of the rotary shaft member 9
As for the mounting of the auxiliary exhaust control valve 91 to the valve mounting hole 2a penetrating the auxiliary exhaust passage 7 from the side of the cylinder block 2, the intermediate portion of the auxiliary exhaust control valve 91 is protruded into the auxiliary exhaust passage 7. The rotating shaft member 9 is inserted from the side together with the surrounding bearing portion 30, and the retaining portion 24 presses the bearing portion 30 from the outside into the valve mounting hole 2a. It is carried out by fixing to 2.

At the respective end portions 92 of the rotary shaft members 9 projecting to the left and right sides of the cylinder block 2, a cylindrical collar 26 whose cylindrical outer peripheral surface is partially cut away in the axial direction is provided with a pin 27. The auxiliary exhaust side lever 23, to which the connecting portion 22 for rotatably connecting the other end of the rod 21 described later is fixed to the outer surface of the collar 26, is fixed to the collar 26 in a non-rotatable manner. It is fixed firmly.

Between the main exhaust side lever 18 and the auxiliary exhaust side lever 23, which are respectively installed outside the cylinder block 2 on both sides as described above, the rods 21 for connecting and linking them are provided. That is, that is, one end of the rod 21 is rotatably connected to the connecting portion 20 fixed to the outer surface of the main exhaust side lever 18, and the rod 21 is connected to the connecting portion 22 fixed to the outer surface of the auxiliary exhaust side lever 23. Since the other end of the cylinder block 2 is rotatably connected, the rotation of the rotation shaft 12 on the main exhaust side on both sides of the cylinder block 2 causes the rotation shaft member 9 on the auxiliary exhaust side to rotate.
A link mechanism for interlocking with each is formed.

On both sides of the cylinder block 2, the connecting portion of the connecting portion 20 and one end of the rod 21 is covered with the cover 31, and the connecting portion of the connecting portion 22 and the other end of the rod 21 is covered with the cover 32. Has been done.

In the above link mechanism, the positional relationship among the main exhaust side lever 18, the rod 21, and the auxiliary exhaust side lever 23 is as shown in FIGS. 3 and 4.
Extends upward from the rotation shaft (12a or 12b), and the connecting portion 20 with the rod 21 has a main exhaust side lever 1
8 is located at the upper end of the auxiliary exhaust side lever 23, the auxiliary exhaust side lever 23 extends downward from its rotation shaft (92), and the connecting portion 22 with the rod 21 is located at the lower end of the auxiliary exhaust side lever 23. positioned.

That is, in the comparative example shown in FIGS. 10 and 11, as shown in FIG. 13, the connecting portions 20 and 22 of the levers 18 and 23 and the rod 21 connect the rotating shafts of the levers 18 and 23. Are on the same side of the virtual line X,
The rotation direction of the auxiliary exhaust side lever 23 is the same as the rotation direction of the main exhaust side lever 18 without the rod 21 crossing the imaginary line X, whereas in the present embodiment shown in FIGS. 3 and 4, As shown in FIG. 12, the connecting portions 20 and 22 of the levers 18 and 23 and the rod 21 are located on different sides with respect to the virtual line X connecting the rotation axes of the levers 18 and 23,
The rod 21 crosses the virtual line X, and the rotation direction of the auxiliary exhaust side lever 23 is opposite to the rotation direction of the main exhaust side lever 18.

By the way, the auxiliary exhaust control valve 9a provided in the auxiliary exhaust passage 7 as described above is heated considerably by directly receiving the heat of the exhaust gas, but in the two-stroke engine of the present embodiment. 1 has a bolt tightening structure for connecting the cylinder block 2 below the cylinder head 1. As shown in FIG. 1 and FIG. It is screwed into the bolt hole,
The connecting bolt 41 is screwed in such a manner that its tip portion 41 a projects into the water jacket 2 b of the cylinder block 2.

Therefore, the bolt is embedded in the cylinder block side, and the bolt projecting upward from the upper surface of the cylinder block is inserted into the through hole of the cylinder head from below, and the bolt protruding upward from the through hole of the cylinder head. As shown in FIG. 6, the water jacket 2b formed in the cylinder block 2 in the vicinity of the valve mounting hole 2a into which the rotary shaft member 9 is loaded is compared with a structure in which the upper end of the cylinder is tightened with a nut. Since the water passage portion is not blocked by the embedded portion of the bolt and the water flow is not interfered with, the cooling performance of the auxiliary exhaust control valve 9a in the cylinder block 2 is not hindered.

The operating states of the exhaust control valves 8a and 91 of the two-cycle engine of the present embodiment having the above structure will be described below.

During low speed operation where the engine speed is low, the main exhaust control valve 8a has its leading edge approaching the inner surface of the cylinder 4 and largely advancing into the main exhaust passage 6, and the auxiliary exhaust control valve 91a. Is rotated so as to close the auxiliary exhaust passage 7 from the upper part, the upper part of the main exhaust port 6a is closed by the main exhaust control valve 8a, and the auxiliary exhaust port 7a is closed by the auxiliary exhaust control valve 91. Is in a state.

In this state, when the piston moves downward, the exhaust start timing from the main exhaust port 6a is delayed,
Exhaust gas is prevented from flowing out from the auxiliary exhaust port 7a, and the cross-sectional area of all the exhaust passages becomes a size commensurate with the low speed, so that the torque conversion of combustion energy is efficiently performed.

When the rotational speed of the engine increases from this state, the servomotor is rotated by the amount corresponding to the engine rotational speed by the control based on the detection of the engine rotational speed, and the rotation of the servomotor is changed by the wire. 16a,
16b is transmitted to the pulley 15 and the pulley 15
The rotary shaft 12 fixed to the main exhaust control valve 8a is rotated so that the sliding shaft 8b is slid through the pin engaging portion 10 and the engaging pin 8c. It retreats away from the inner surface of the cylinder 3, and the upper portion of the main exhaust port 6a opens from below.

At the same time, with the rotation of the rotation shaft 12, the main exhaust side levers 18 provided on both ends 12a and 12b thereof are simultaneously rotated, and the main exhaust side lever 18 is rotated by the rod 21. Auxiliary exhaust side lever 2 via
3, the rotation shaft member 9 is rotated by the rotation of the auxiliary exhaust side lever 23, the auxiliary exhaust control valve 91 is rotated in the valve opening direction, and the auxiliary exhaust port 7a is opened from below. .

During high-speed operation with a high engine speed, the main exhaust control valve 8a and the auxiliary exhaust control valve 91 are operated in conjunction with the servomotor that rotates in accordance with the engine speed as described above. The leading edge portion of the main exhaust control valve 8a substantially coincides with the top wall of the main exhaust passage 6,
Further, as shown in FIG. 7, the cutout surface 91a of the auxiliary exhaust control valve 91 is substantially aligned with the top wall of the auxiliary exhaust passage 7, and both the main exhaust port 6a and the auxiliary exhaust port 7a are fully opened. It becomes a state.

In this state, when the piston moves downward, the exhaust start timing from the main exhaust port 6a is advanced,
Exhaust gas sufficiently flows out from the auxiliary exhaust port 7a, and the cross-sectional area of all exhaust passages is of a size commensurate with high speed, and a large amount of exhaust is performed early and scavenging is performed well,
High output can be obtained.

When the engine speed decreases from high speed operation, the servomotor rotates in the direction opposite to the above case by the amount corresponding to the engine speed, and contrary to the above case, the main The exhaust control valve 8a advances so that its tip edge approaches the inner surface of the cylinder 3, and in conjunction with this, the auxiliary exhaust control valve 91 is rotated in the valve closing direction as shown in FIG. 6a upper part and auxiliary exhaust port 7
At the same time, a is closed from top to bottom.

By the way, as described above, the main exhaust control valve 8a and the auxiliary exhaust control valve 91 simultaneously move through the link mechanism in conjunction with the movement of the servomotor according to the engine speed, so that the main exhaust port 6a is moved. In the two-cycle engine of the present embodiment, the upper part of which and the auxiliary exhaust port 7a are opened and closed synchronously by the respective control valves 8a and 91,
The mutual positional relationship (opening) and the operation amount of the main exhaust control valve 8a and the auxiliary exhaust control valve 91 can be arbitrarily adjusted, and thereby the effect of the exhaust control valve according to the improvement purpose can be brought out. Is possible.

That is, the rotary shaft 12 on the main exhaust side and the rotary shaft member 9 on the auxiliary exhaust side are provided on both outer sides of the cylinder block 2 as shown in FIGS. Since it is configured to be interlocked via a link mechanism composed of the rod 21 and the auxiliary exhaust side lever 23, each member 18, 21, 23 of the link mechanism with respect to the rotating shaft 12 and the rotating shaft member 9. Can be easily replaced, and the pulley 15 and the plate 1 can be easily replaced.
7, the relative angle of the main exhaust side lever 18 is
It can be easily changed by loosening 9 and moving in the range of the long hole 18a of the main exhaust side lever 18 and adjusting and then tightening the bolt 19 again.

Therefore, the pulley 15 and the plate 1
By changing the relative angle of the main exhaust side lever 18 with respect to 7, the mutual positional relationship between the main exhaust control valve 8a and the auxiliary exhaust control valve 91 (with respect to the opening degree of the main exhaust control valve 8a at the main exhaust port 6a, The opening degree of the auxiliary exhaust control valve 91 at the auxiliary exhaust port 7a can be changed, and the lever ratio of the main exhaust side lever 18 and the auxiliary exhaust side lever 23 can be changed to change the main exhaust control valve 8a and the auxiliary exhaust control valve. It is possible to change the mutual operation amount of 91 (the moving amount of the auxiliary exhaust control valve 91 that moves in conjunction with the moving amount of the main exhaust control valve 8a).

According to the exhaust control structure of the two-cycle engine of the present embodiment as described above, as compared with the comparative example as shown in FIG. 9, as shown in FIG. At the opening degree, the flow of the exhaust gas along the auxiliary exhaust control valve 91 becomes smooth, and moreover, depending on the opening degree of the auxiliary exhaust control valve 91, the cutout surface 91a of the cutout surface 91a against the flow of the exhaust gas on the exhaust upstream side. Since the angle is changed, the amount of exhaust gas commensurate with the rotation angle of the auxiliary exhaust control valve 91 is discharged from the auxiliary exhaust passage 7, and the rotation angle of the auxiliary exhaust control valve 91 is changed. Control accuracy of engine output is improved.

Further, the arcuate outer peripheral surface 91b, which is the sliding contact surface with the cylinder block, moves in and out on the downstream side of the exhaust gas as the auxiliary exhaust control valve 91 rotates, so this portion 91b. The exhaust gas immediately after flowing into the cylinder from
Adhesion of carbon in the exhaust gas to b is reduced, so that a so-called valve stick that prevents the carbon from adhering to the sliding contact surface of the valve and hinders its rotation is less likely to occur.

Since the auxiliary exhaust control valve 91 takes the rotating direction as shown in FIG. 8, the opening / closing operation position of the auxiliary exhaust control valve 91 on the rotating shaft member 9 is as shown in FIG. 9 as a comparative example. However, in the present embodiment, the rotating shaft member 9 itself is more auxiliary than in the case of the conventional exhaust control structure of a two-cycle engine. Since the auxiliary exhaust control valve 91 is located closer to the exhaust port 7a, the opening / closing operation position of the auxiliary exhaust control valve 91 is not far from the auxiliary exhaust port 7a as compared with the conventional exhaust control structure of a two-cycle engine.

Further, in this embodiment, the main exhaust side lever 1
When the auxiliary exhaust control valve 91 is driven in conjunction with the main exhaust control valve 8a by the link mechanism including the rod 8, the rod 21, and the auxiliary exhaust side lever 23, the main exhaust side lever 18
Since the positional relationship between the rod 21 and the auxiliary exhaust side lever 23 is as shown in FIG. 12, the operating angle of the rod 21 with respect to the auxiliary exhaust side lever 23 is larger than that of the comparative example shown in FIG. Has been improved, the main exhaust side lever 18
It is possible to effectively transmit the turning power of the above to the auxiliary exhaust side lever 23.

Although one embodiment of the exhaust control structure for a two-cycle engine of the present invention has been described above, the present invention is not limited to the specific structure as described above. For example, main exhaust control In order to open and close each of the valve and the auxiliary exhaust control valve, the structure is not limited to the one in which the two are interlocked via the link mechanism by the one drive source as shown in the above embodiment, and the main exhaust side and the auxiliary exhaust side are connected. Needless to say, the specific structure of the control valve can be appropriately changed as long as it is described in the scope of the claims, for example, the control valve can be driven separately.

[0056]

According to the exhaust control structure of the two-cycle engine of the present invention as described above, the turning direction of the auxiliary exhaust control valve is opposite to that of the conventional one, so that the auxiliary exhaust at the intermediate opening degree is controlled. The flow becomes smooth, the exhaust characteristics at the intermediate opening degree in the auxiliary exhaust can be improved, and the occurrence of valve stick due to the adhesion of exhaust carbon in the auxiliary exhaust control valve can be reduced.

According to the structure described in claim 2, the driving force can be effectively transmitted when the auxiliary exhaust control valve is interlocked with the main exhaust control valve via the link mechanism. .

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part (a cylinder head and a cylinder block) of a two-cycle engine to which an embodiment of an exhaust control structure of the present invention is applied.

2 is a cross-sectional view of the vicinity of an exhaust passage of the two-stroke engine shown in FIG.

FIG. 3 is a side view showing one side of a main part of the two-cycle engine shown in FIG. 1 (however, a cylinder head part is omitted).

FIG. 4 is a side view showing the opposite side of the main part of the two-cycle engine shown in FIG.

5 (A) is a side view and FIG. 5 (B) is a sectional view showing a main exhaust side lever member in the embodiment shown in FIG.

6 is a partial cross-sectional side view showing a water jacket in the vicinity of a support portion of the auxiliary exhaust control valve of the two-cycle engine shown in FIG.

7 is an explanatory view showing a fully opened state of the auxiliary exhaust control valve in the embodiment shown in FIG.

8 is an explanatory diagram showing a state of an intermediate opening degree of the auxiliary exhaust control valve in the embodiment shown in FIG.

FIG. 9 is an explanatory diagram showing a state of an intermediate opening degree of an auxiliary exhaust control valve in a comparative example.

FIG. 10 is a side view showing one side of a main part of a two-cycle engine in a comparative example.

FIG. 11 is a side view showing the opposite side of the main part of the two-cycle engine of the comparative example shown in FIG. 10 (however, the cylinder head part is omitted).

12 is an explanatory view showing the outline of the link mechanism of the embodiment shown in FIG.

13 is an explanatory diagram showing an outline of a link mechanism of the comparative example shown in FIG.

[Explanation of symbols]

 2 Cylinder Block 3 Cylinder 6 Main Exhaust Passage 6a Main Exhaust Outlet 7 Auxiliary Exhaust Exhaust 7a Auxiliary Exhaust Exhaust 8a Main Exhaust Control Valve 9 Rotating Shaft Member 18 Main Exhaust Side Lever 20 Coupling (Main Exhaust Side Lever and Rod) 21 Rod 22 Connection Part (for Auxiliary Exhaust Side Lever and Rod) 23 Auxiliary Exhaust Side Lever 91 Auxiliary Exhaust Control Valve 91a Notch Surface (for Auxiliary Exhaust Control Valve) 91b Arc-Shaped Outer Surface (for Auxiliary Exhaust Control Valve)

Claims (2)

[Claims] 1. A main exhaust passage and an auxiliary exhaust passage are formed in a cylinder block so that a main exhaust opening and an auxiliary exhaust opening are separately opened on an inner wall of a cylinder and merge downstream thereof. A two-cycle engine in which a main exhaust control valve that opens and closes the upper portion of the exhaust port is installed, and an auxiliary exhaust control valve that opens and closes the auxiliary exhaust passage in conjunction with the main exhaust control valve is installed in the auxiliary exhaust passage. In the above, the auxiliary exhaust control valve that opens and closes the auxiliary exhaust passage in the vertical direction is a rotary valve that is formed by cutting out a part of a rotary shaft member having a circular cross section, and that has a notched surface and an arc-shaped outer peripheral surface,
It is offset closer to the axial center of the cylinder than the main exhaust control valve, and is located near the auxiliary exhaust port. The exhaust control structure of a two-cycle engine, which is characterized in that 2. A link mechanism including a main exhaust side lever, an auxiliary exhaust side lever, and a rod for connecting these levers is provided outside the cylinder block in order to interlock the auxiliary exhaust control valve with the main exhaust control valve. In addition, the link mechanism of the lever is connected to the line connecting the rotating shafts of the levers so that the connecting directions of the levers and the rods are opposite to each other. The two according to claim 1, characterized in that they are located on different sides.
Exhaust control structure for cycle engine.