JPH08144768A - Exhaust control structure of 2-cycle engine - Google Patents

Abstract

PURPOSE: To enable the control for exhaust timing of an auxiliary exhaust passage by an auxiliary exhaust control valve and to prevent lowering of output during low speed operation. CONSTITUTION: A two-cycle engine is so constructed that a main exhaust port 6a and an auxiliary exhaust port 7 are separately opened in the inner wall of a cylinder 3, a main exhaust passage 6 and an auxiliary exhaust passage 7 are formed on a cylinder block 2 in such a manner as to join in the downstream, a main exhaust control valve 8a for opening and closing the upper part of the main exhaust port 6a is installed in the main exhaust passage 6, and an auxiliary exhaust control valve 9a for opening and closing the auxiliary exhaust passage 7, interlocking with the main exhaust control valve 8a is installed in the auxiliary exhaust passage 7. Accordingly, the auxiliary exhaust control valve 9a for opening and closing the auxiliary exhaust passage 7 in the vertical direction is disposed in the vicinity of the auxiliary exhaust port 7a in such a manner as to be offset from the main exhaust control valve 8a to the shaft center side of the cylinder 3.

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 any of the conventionally known exhaust control structures for a two-cycle engine as described above, the main exhaust control valve in the main exhaust passage and the auxiliary exhaust control valve in the auxiliary exhaust passage are both known. Are arranged substantially side by side, and the main exhaust control valve opens and closes in a position close to the main exhaust port, and the auxiliary exhaust control valve opens and closes in a position recessed from the auxiliary exhaust port. .

Therefore, it is impossible to secure the gas sealability in the vicinity of the auxiliary exhaust port by the auxiliary exhaust control valve,
There is a problem that it is difficult to control the exhaust timing of the auxiliary exhaust passage by opening and closing the auxiliary exhaust control valve, and desired engine characteristics cannot be obtained.

Further, even if the auxiliary exhaust control valve is controlled so that the auxiliary exhaust passage is fully closed at low speed operation, the auxiliary exhaust passage upstream of the auxiliary exhaust control valve functions as a part of the combustion chamber. Since this portion has a large ineffective volume, the output during low speed operation is reduced.

An object of the present invention is to eliminate the inconveniences of the conventional exhaust control structure for a two-cycle engine, and more specifically, the auxiliary exhaust that opens and closes in conjunction with the main exhaust control valve. By installing the control valve as close to the auxiliary exhaust port as possible, the exhaust timing of the auxiliary exhaust passage can be controlled by the auxiliary exhaust control valve, and the desired engine characteristics can be obtained. An object of the present invention is to provide an exhaust control structure for a two-cycle engine that can prevent a reduction in output.

[0008]

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 the vertical direction is closer to the cylinder axis than the main exhaust control valve. And is arranged in the vicinity of the auxiliary exhaust port.

Further, in such an exhaust control structure for a two-cycle engine, as described in claim 2, the rotating shaft member is provided on the side of the auxiliary exhaust passage opposite to the main exhaust passage. The block is rotatably supported with respect to the block, and one end of the rotary shaft member is formed as an auxiliary exhaust control valve that projects laterally into the auxiliary exhaust passage to open and close the auxiliary exhaust passage. The other end of the rotating shaft member is projected laterally from the cylinder block as an input shaft of the auxiliary exhaust control valve.

[0010]

[Operation] With the above-mentioned configuration, since the gas sealability can be secured to some extent by the auxiliary exhaust control valve near the auxiliary exhaust port, the timing of the opening / closing timing of the auxiliary exhaust port that opens and closes by the vertical movement of the piston Can be controlled by.

Further, the ineffective volume upstream of the auxiliary exhaust passage, which is caused by the auxiliary exhaust control valve being recessed from the auxiliary exhaust port, is reduced, and output reduction during low speed operation is prevented.

Further, according to the above-mentioned structure, the auxiliary exhaust control valve is installed on the side opposite to the main exhaust passage in a cantilevered manner by the cylinder block. Therefore, the auxiliary exhaust control valve can be installed as close as possible to the auxiliary exhaust port without reducing the wall thickness of the cylinder wall of the cylinder block.

[0013]

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 an essential part of a two-cycle engine to which an embodiment of an exhaust control structure of the present invention is applied. 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 to which the cylinder head is connected, and FIG. 4 shows the other side surface of the cylinder block.

A 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 the upper end thereof 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 passage 6a and extends obliquely downward from the top wall of the main exhaust passage 6 toward the main exhaust outlet 6a. The auxiliary exhaust passage 7 is provided with auxiliary exhaust control valves 9a that protrude into the auxiliary exhaust passage 7 from the side wall opposite to the main exhaust passage 6 side in the vicinity of 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 out in a plane in the axial direction is provided with a 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 9a installed in the respective auxiliary exhaust passages 7, all the auxiliary exhaust control valves 9a from the side of the auxiliary exhaust passage opposite to the side of the main exhaust passage 6 into the auxiliary exhaust passage 7. In the cantilever-shaped rotary valve, which has a columnar rotary shaft member 9 having different diameters in a stepwise manner, the enlarged diameter end projecting into the auxiliary exhaust passage 7 has a substantially half-moon to crescent cross-section. 6 and 7 are formed by partially cutting out the outer peripheral surface thereof.
As shown in FIG. 5, the rotation shaft member 9 is rotated to rotate in the auxiliary exhaust passage 7 to open and close the auxiliary exhaust passage 7 from the top wall side in the vertical direction.

The rotary shaft members 9 arranged symmetrically with respect to the main exhaust passage 6 are in parallel with the rotary shaft 12, and the main exhaust control valve 8a is fully closed.
Are arranged on a straight line so that the axes of the rotary shaft members 9, 9 are aligned with one virtual axis that is closer to the axial center of the cylinder 3 than the tip position of.

Then, in any of the rotary shaft members 9,
The enlarged diameter end of the auxiliary exhaust passage 7 is the auxiliary exhaust control valve 9
The intermediate diameter portion of the rotating shaft member 9 is rotatably supported by the cylinder block 2 via the bearing portion 30 as a valve bearing portion, and the diameter of the rotating shaft member 9 is reduced. The other end 9b 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 9a in 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 9a is protruded into the auxiliary exhaust passage 7. After inserting the rotating shaft member 9 from the side together with the surrounding bearing portion 30 and holding the bearing portion 30 from the outside by the retaining member 24 into the valve mounting hole 2a, the retaining member 24 is fixed to the cylinder block by the bolt 25. It is carried out by fixing to 2.

At each end 9b of each rotary shaft member 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 out 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 so as not to rotate. It is fixed firmly.

Rods 21 for connecting and linking the main exhaust side lever 18 and the auxiliary exhaust side lever 23, which are respectively installed outside the cylinder block 2 as described above, 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 the rod 21 at one end is covered by the cover 31, and the connecting portion of the connecting portion 22 and the other end of the rod 21 is covered by the cover 32. Has been done.

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 this 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, 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. 8, the water jacket 2b formed in the cylinder block 2 in the vicinity of the valve mounting hole 2a in which the rotary shaft member 9 is loaded is compared to a connection 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 9a of the two-cycle engine of the present embodiment having the above structure will be described below.

During low-speed operation at a low engine speed, 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 9a. 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 9a. 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, the main exhaust side levers 18 provided on both ends 12a and 12b of the rotary shaft 12 are simultaneously rotated with the rotation of the rotary shaft 12, 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 9a 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 9a operate 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,
The cutout surface of the auxiliary exhaust control valve 9a substantially coincides 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.

In this state, when the piston moves downward, the timing of starting exhaust 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 servo motor 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 9a is rotated in the valve closing direction.
The upper part of the main exhaust port 6a and the auxiliary exhaust port 7a are simultaneously closed from above to below.

By the way, as described above, the main exhaust control valve 8a and the auxiliary exhaust control valve 9a move simultaneously via the link mechanism in conjunction with the movement of the servomotor according to the engine speed, so that the main exhaust port 6a. 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 control valves 8a and 9a
The mutual positional relationship (opening) and operation amount of the main exhaust control valve 8a and the auxiliary exhaust control valve 9a 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 9a (with respect to the opening of the main exhaust control valve 8a at the main exhaust port 6a, The opening degree of the auxiliary exhaust control valve 9a at the auxiliary exhaust port 7a can be changed, and by changing the lever ratio of the main exhaust side lever 18 and the auxiliary exhaust side lever 23, the main exhaust control valve 8a and the auxiliary exhaust control valve It is possible to change the mutual operation amount of 9a (the moving amount of the auxiliary exhaust control valve 9a that moves in conjunction with the moving amount of the main exhaust control valve 8a).

For example, the pulley 1 of the main exhaust side lever 18
5 and the relative angle with respect to the plate 17, the position of the auxiliary exhaust control valve 9a when the main exhaust control valve 8a is fully closed (the main exhaust port 6a is a half open state in which the upper part is closed) is shown in FIG. The main exhaust port 6
By adjusting the ratio of the movement amounts of the main exhaust control valve 8a and the auxiliary exhaust control valve 9a so that the auxiliary exhaust port 7a is fully opened when the valve a is fully opened, the main exhaust port 6a is lowered by lowering the piston during low speed operation. It is possible to first release the pressure of the exhaust gas from the auxiliary exhaust port 7a before opening the.

When adjusted in this way, the exhaust port 6a
Even if the gas sealability at the time of closing the main exhaust control valve 8a is improved, the pressure of the exhaust gas is released from the auxiliary exhaust port 7a prior to the main exhaust port 6a, so that the pressure in the muffler is rapidly increased at the same time as the exhaust. It is suppressed that it rises to
It is possible to reduce the radiated sound from the muffler that is generated due to the rapid increase in the pressure inside the muffler.

Also, the pulley 15 of the main exhaust side lever 18
And the relative angle with respect to the plate 17 is adjusted so that the positional relationship between the main exhaust control valve 8a and the auxiliary exhaust control valve 9a is set to the state shown in FIG. When the main exhaust control valve 8a is fully closed, the auxiliary exhaust port 7a is fully closed.) When the main exhaust port 6a is fully opened, the auxiliary exhaust port 7a and the auxiliary exhaust control valve 8a are fully opened. By adjusting the ratio of the moving amount of the valve 9a, the auxiliary exhaust control valve 9a is brought closer to the auxiliary exhaust port 7a and the gas sealing property in the vicinity of the auxiliary exhaust port 7a is improved. By the time the main exhaust port 6a opens, there is almost no leakage of exhaust gas from the auxiliary exhaust port 7a.

With this adjustment, when the main exhaust control valve 8a is fully closed, the gas sealability of the entire exhaust port is improved, and gas is not blown out from the auxiliary exhaust port 7a.
The control of the exhaust timing by the main exhaust control valve 8a becomes more faithful.

According to the exhaust control structure of the two-cycle engine of the present embodiment as described above, the gas sealing property by the auxiliary exhaust control valve 9a near the auxiliary exhaust port 7a can be secured, so that the vertical movement of the piston causes The timing of opening and closing of the auxiliary exhaust port 7a to be opened and closed can be controlled by the auxiliary exhaust control valve 9a, and the main exhaust control valve 8a when the auxiliary exhaust control valve 9a is closed.
The control of the exhaust timing of the main exhaust port 6a by means of becomes more faithful, and desired engine characteristics can be obtained.

Further, since the auxiliary exhaust control valve 9a is located close to the auxiliary exhaust port 7a, the ineffective volume upstream of the auxiliary exhaust passage 7 is reduced, and it is possible to prevent output reduction during low speed operation. .

Further, since the auxiliary exhaust control valve 9a is installed on the side opposite to the main exhaust passage 6 in a cantilevered manner with respect to the cylinder block 2, the cylinder wall portion of the cylinder block 2 is provided. The auxiliary exhaust control valve 9a can be installed as close as possible to the auxiliary exhaust port 7a without reducing the thickness of the auxiliary exhaust valve 7a.

Although one embodiment of the exhaust control structure for a two-cycle engine according to the present invention has been described above, the present invention is not limited to the specific structure as described above. As long as the tip of the valve 9a is closer to the cylinder axis than the tip of the main exhaust control valve 8a, the direction of the rotation axis of each auxiliary exhaust control valve 9a located on both sides of the main exhaust passage 6 is It does not necessarily have to be parallel to the moving shaft 12.

Further, even when the auxiliary exhaust control valve 9a is fully closed, the auxiliary exhaust passage 7 is not always set to be fully closed when the auxiliary exhaust control valve 9a is fully closed. The degree to which the auxiliary exhaust passage 7 is closed at the time of closing is arbitrarily set.

[0054]

According to the exhaust control structure of the two-cycle engine of the present invention as described above, the exhaust timing of the auxiliary exhaust passage can be controlled by the auxiliary exhaust control valve, and desired engine characteristics can be obtained. The ineffective volume upstream of the auxiliary exhaust passage can be reduced to prevent the output from decreasing during low speed operation.

According to the second aspect of the invention, the auxiliary exhaust control valve, which opens and closes in conjunction with the main exhaust control valve, can be used as much as possible without reducing the wall thickness of the cylinder wall. Can be installed close to.

[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.

FIG. 4 is a side view showing the opposite side of the two-stroke engine shown in FIG. 3 (however, the cylinder head portion is omitted).

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

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

8 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.

9 is an explanatory diagram showing an example of adjustment of the positional relationship between the main exhaust control valve and the auxiliary exhaust control valve in the embodiment shown in FIG.

10 is an explanatory view showing another example of adjustment of the positional relationship between the main exhaust control valve and the auxiliary exhaust control valve in the embodiment shown in FIG.

[Explanation of symbols]

2 cylinder block 3 cylinder 6 main exhaust passage 6a main exhaust outlet 7 auxiliary exhaust passage 7a auxiliary exhaust outlet 8a main exhaust control valve 9 turning shaft member 9a auxiliary exhaust control valve 9b other end of turning shaft member (auxiliary exhaust control valve Input axis)

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[Procedure amendment]

[Submission date] December 7, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG.

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 two cycles, the auxiliary exhaust control valve for opening and closing the auxiliary exhaust passage in the vertical direction is arranged closer to the axial center of the cylinder than the main exhaust control valve and is arranged near the auxiliary exhaust port. Exhaust control structure of engine. 2. A rotating shaft member is rotatably supported with respect to a cylinder block at a side of the auxiliary exhaust passage opposite to the main exhaust passage, and one end portion of the rotating shaft member is a side. Is formed as an auxiliary exhaust control valve that projects into the auxiliary exhaust passage and opens and closes the auxiliary exhaust passage, and the other end of the rotating shaft member acts laterally from the cylinder block as an input shaft of the auxiliary exhaust control valve. The exhaust control structure for a two-cycle engine according to claim 1, wherein the exhaust control structure is projected.