JPH09105331A - Exhaust controller of two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optimum exhaust condition securable at the whole of low, medium and high speed ranges, thereby enabling it to realize a good power feeling and a throttle response. SOLUTION: In this exhaust controller of a two-cycle engine, which is equipped with a valve element 11 being retractably installed in an upper wall 10 of an exhaust passage 9, and lowering an upper edge position of an exhaust inflow port 9a as its tip part 11b is projected to an upper part of this exhaust inflow port 9a in the exhaust passage 9 according to engine speed, a valve driving mechanism having this valve element 11 retractably operated, and a valve driving mechanism storage chamber 12 storing this valve driving mechanism, and varies a span of exhaust timing by making the valve element 11 retractable, it is provided with an opening part 16a being interconnected to the outdoors of this valve driving mechanism storage chamber 12. In addition, it is also provided with an opening part on-off means A opening or closing this opening part 26a according to engine speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for a two-cycle engine, and more particularly, to an exhaust control device for a two-cycle engine in which an exhaust timing is changed by advancing and retracting a valve element provided on an upper wall of an exhaust passage. It relates to the device.

[0002]

2. Description of the Related Art In an exhaust control device for a two-cycle engine of this type, for example, it is disposed on an upper wall of an exhaust passage so as to be capable of advancing and retreating, and the exhaust control device is provided above the exhaust inlet in the exhaust passage in accordance with the engine speed. The valve body is provided with a valve body having a tip portion protruding to lower the upper edge position of the exhaust gas inlet, a valve drive mechanism for advancing and retracting the valve body, and a valve drive mechanism accommodating chamber for accommodating the valve drive mechanism. Some of them change the exhaust timing.

When the engine is operated in the low speed range and the high speed range, the valve body is placed in the forward position and the reverse position, respectively, whereby a wide speed range from the low speed to the high speed is achieved. A high engine output can be obtained at. By the way, exhaust gas flows into the valve drive mechanism accommodating chamber that accommodates the valve drive mechanism through a minute gap existing between the valve element and its guide means. As a result, the internal pressure of the valve drive mechanism accommodating chamber becomes higher than the pressure of the exhaust inflow port. The pressure in the valve drive mechanism accommodating chamber acts in such a direction as to hinder the backward movement of the valve body in the forward position when the valve body is moved backward. It causes the situation that it cannot be fully retracted to the position of. Therefore, conventionally, for example, Japanese Patent Laid-Open No. 5-8686
As disclosed in Japanese Patent Publication No. 8, a breather pipe is provided in the valve drive mechanism accommodating chamber.

[0004]

This breather pipe has the effect of keeping the pressure in the valve drive mechanism accommodating chamber constant and allowing the valve element to move accurately and quickly, and also has the same effect as the one in which a resonator is attached to the exhaust system. It has a great effect on improving the power feeling and the throttle response in the low and middle rpm range of the 2-cycle engine performance.

However, in the high rotational speed range, on the contrary, exhaust gas that has entered the valve drive mechanism accommodating chamber from the sliding portion between the valve body and the valve body holding portion further leaks from the breather pipe, resulting in engine output. The inconvenience of lowering occurs.

The present invention has been made in view of the above situation, and it is possible to obtain optimum exhaust conditions in all low, medium and high engine speed ranges, and to obtain a good power feeling and throttle response. The purpose is to provide a control device.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is arranged so as to be capable of advancing and retreating on the upper wall of the exhaust passage, and the exhaust gas in the exhaust passage is arranged according to the engine speed. A valve body having a tip portion protruding above the inflow port to lower the upper edge position of the exhaust inflow port, a valve drive mechanism for moving the valve body forward and backward, and a valve drive mechanism accommodating chamber for accommodating the valve drive mechanism. In an exhaust control device for a two-cycle engine, wherein the exhaust timing is changed by advancing and retracting the valve element, an opening communicating with the outside of the valve drive mechanism accommodating chamber is provided, and the opening is set to the engine speed. It is characterized in that it is provided with an opening / closing means for opening / closing in response to the opening.

As described above, since the opening portion communicating with the outside of the valve drive mechanism accommodating chamber is provided and the valve body communicates with the outside of the valve drive mechanism accommodating chamber, the valve body is in the valve drive mechanism accommodating chamber. Accurate and quick movement is possible without being affected by the pressure of the engine, and the power feeling and throttle response in the low / medium speed range of the 2-cycle engine performance are improved. Also,
By opening and closing the opening that communicates with the outside of the valve drive mechanism accommodating chamber according to the engine speed, it is possible to reduce exhaust leakage from the opening that communicates with the outside of the valve drive mechanism accommodating chamber and reduce engine output. Can be prevented.

In the invention of the exhaust control device for a two-cycle engine according to claim 2, the opening opening / closing means closes the opening in a high engine speed range and opens the opening in a low to medium engine speed range. It is characterized by that.

As described above, the opening / closing means closes the opening in the high engine speed range and opens the engine in the low / medium engine speed range. In particular, in the high engine speed range, the valve body and the valve body holding section are opened. The amount of exhaust gas that enters the valve drive mechanism accommodating chamber from the sliding part between the two increases, but at this time, exhaust gas is less likely to leak from the opening that communicates with the outside of the valve drive mechanism accommodating chamber, and engine output decreases. Can be prevented, while the throttle response is improved especially in the low and middle rpm range.

The invention of an exhaust control system for a two-cycle engine according to claim 3 is characterized in that the opening / closing means operates in conjunction with the forward / backward movement of the valve body.

As described above, since the opening / closing means operates in conjunction with the forward / backward movement of the valve body, a special mechanism for driving the opening / closing means is unnecessary, and the structure is simple and reliable.

In the invention of the exhaust control device for a two-cycle engine according to claim 4, the opening opening / closing means is configured to directly open / close the opening at its end portion by the forward / backward movement of the valve body. Is characterized by.

As described above, the opening / closing means opens / closes the opening directly at the end of the valve element by the forward / backward movement of the valve element, and opens / closes without the interposition of other parts. Therefore, the responsiveness is good and the structure is simple. Works reliably.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an exhaust control system for a two-cycle engine according to the present invention will be described below with reference to the drawings. 1 is a vertical cross-sectional view of a 2-cycle engine, FIG. 2 is a side view of a partially-broken 2-cycle engine, FIG. 3 is a cross-sectional view of an exhaust control device of a 2-cycle engine, and FIG. 4 is IV of FIG.
-A cross-sectional view taken along line IV, FIG. 5 is a view taken along line VV in FIG. 2, and FIG.
Is a front view of the cover, FIG. 7 is a rear view of the cover, and FIG.
FIG. 8 is a sectional view taken along line VIII-VIII of FIG.

This two-cycle engine 1 is mounted on a motorcycle and is mounted on a crankcase 2 of the two-cycle engine 1.
A cylinder block 3 is mounted on the cylinder block 3, and a cylinder head 4 is attached to the cylinder block 3. A crankshaft 5 is rotatably supported by the crankcase 2. The crankshaft 5 is connected to a piston 7 provided on the cylinder block 3 via a connecting rod 6, and the crankshaft 5 is rotated by the reciprocating movement of the piston 7.

A scavenging passage 8 and an exhaust passage 9 are formed in the cylinder block 5, and a pair of valve bodies 11 are arranged on an upper wall 10 of the exhaust passage 9 so as to be able to move forward and backward. The shaft portion 11a of the pair of valve bodies 11 is provided in the holder 1 in the valve drive mechanism accommodating chamber 12 formed integrally with the cylinder block 3.
3 is slidably supported, and its tip 11b projects above the exhaust gas inlet 9a in the exhaust passage 9 to lower the upper edge position of the exhaust gas inlet 9a. The holder 13 is mounted in the valve drive mechanism housing chamber 12 by a screw 14, and the valve drive mechanism housing chamber 12 is covered with a cover 16 mounted by a screw 15.

A valve drive mechanism 18 for advancing and retracting the valve body 11 is accommodated in the valve drive mechanism accommodating chamber 12, and the valve drive mechanism 18 can be operated by a power transmission mechanism 19.

The power transmission mechanism 19 is composed of a centrifugal governor 20 and a link mechanism 21, and transmits the rotation of the crankshaft 5 to the valve drive mechanism 18. Governor shaft 22 of centrifugal governor 20
Is rotatably supported from the crankcase 2 to a cover 23 provided on the cylinder block 3 via bearings 24 and 25, and a gear 26 fixed to the governor shaft 22 has a gear 26.
Is engaged with a gear 27 fixed to the crankshaft 5
The governor shaft 22 rotates in conjunction with. A fixed body 28 and a movable body 29 are provided on the governor shaft 22 so as to face each other.
A centrifugal weight 30 is provided between 8 and the movable body 29. A collar 31 is provided on the shaft portion 29a of the movable body 29, bearings 34 and 35 are provided on both sides of the collar 31 via washers 32 and 33, and one bearing 34 is disposed in contact with the movable body 29. The other bearing 35 is arranged in contact with the plate 36. Plate 36 and gear 2
A spring 37 is provided between the movable body 29 and the movable body 29, and the movable body 29 is constantly urged toward the fixed body 28 via the plate 36. A spacer 38 is provided at the shaft end of the movable body 29,
When the spacer 38 contacts the gear 26, the movable body 2
Position control is performed when 9 is moved in the axial direction by the centrifugal force of the centrifugal weight 30.

A fork 41, which is fastened and fixed to the drive shaft 39 with a bolt 40, is engaged between the washers 32 and 33 of the movable body 29. Therefore, when the governor shaft 22 rotates and the centrifugal weight 30 moves outward due to the centrifugal force, the movable body 29 moves on the governor shaft 22 in the direction away from the fixed body 28, thereby driving through the fork 41. The shaft 39 rotates. A link 42 is fixed to an end of the drive shaft 39, and the link 42 is connected to a drive link 44 via a connecting pin 43. The drive link 44 is connected to the bracket 46 of the valve drive mechanism 18 via the connection pin 45, and transmits the rotation from the drive link 44 to the valve drive mechanism 18. In this way, the rotation of the crankshaft 5 is transmitted to the valve drive mechanism 18 via the link mechanism 21 by the operation of the centrifugal governor 20.

The bracket 46 of the valve drive mechanism 18 is applied to the end of the valve drive shaft 48 via a collar 49, and the bolt 4
It is tightened and fixed by 7 and can rotate integrally. The lever 5 is inserted into the annular groove 48a formed at the end of the valve drive shaft 48.
0 is applied and the lever 50 is fixed to the side surface of the cylinder block 3 with a bolt 51 to fix the valve drive shaft 48 at a predetermined position with respect to the cylinder block 3.

The valve drive shaft 48 is rotatably supported by the side walls 12a and 12b of the valve drive mechanism accommodating chamber 12, and the valve drive shaft 4
The valve actuation cylinder 52 is fastened and fixed to the center of the valve 8 with bolts 53, and a pair of springs 90 are wound around the valve drive shaft 48. The both ends 90a of each spring 90 together with the convex portion 52a of the valve actuation cylinder 52 act as a valve. The operating pin 17 of the body 11 is engaged so as to be sandwiched from both sides. Collars 91 are inserted through the valve drive shaft 48 to prevent the springs 90 from tilting and falling.

Therefore, when the valve drive shaft 48 rotates, the valve operating cylinder 52 operates in conjunction with each other to move the valve element 11 forward and backward via the operating pin 17 via the pair of springs 90, and the engine speed is increased. Accordingly, the tip portion 11b projects above the exhaust gas inlet 9a in the exhaust passage 9 to lower the upper edge position of the exhaust gas inlet 9 and move the valve body 11 back and forth to change the exhaust timing. Therefore, the left and right valve bodies 11 can be independently driven without being restricted by the movement of the other valve body 11. That is, even if there is a manufacturing error in the assembled state of the pin 17 and the valve body 11, the left and right valve bodies 11 are independently driven without being restricted by the movement of the other valve body 11,
Even if one valve body 11 comes into contact with the exhaust gas inlet port 9a first and closes, the other valve body 11 also comes into contact with the exhaust gas inlet port 9a and is closed without being affected by this.

The cover 16 of the valve drive mechanism accommodating chamber 12 includes:
The opening 16a is formed so as to communicate with the atmosphere, and the opening 16a
16b is formed at a position facing the head portion 11c of the valve body 11. A breather pipe 62 is connected to the opening 16 a, and is open to the atmosphere via the breather pipe 62. The peripheral wall of the opening 16b, that is, the valve body 11
The contact surface with the head portion 11c is formed as the same surface as the peripheral wall of the cover 16, that is, the seal surface with the cylinder block 3 for forming the valve drive mechanism accommodating chamber 12, and both seal surfaces can be processed simultaneously. The processing man-hour is reduced.

As described above, the opening 16a communicating with the outside of the valve drive mechanism accommodating chamber 12 is provided, and the opening 16a is provided.
The opening / closing means A is configured to open / close directly by the head 11c of the valve body 11 by the forward / backward movement of the valve body 11 and open / close the opening 16a in accordance with the engine speed.

Therefore, the valve body 1 is rotated by the rotation of the valve drive shaft 48.
1, the valve element 11 moves forward as shown in FIG. 1 and the exhaust timing is delayed, and the head portion 11c of the valve element 11 opens the opening 16b of the opening 16a in the low and middle engine speed range.
And communicates with the outside of the valve drive mechanism housing chamber 12. When the valve body 11 is moving backward while the valve body 11 is moving forward, the air in the valve drive mechanism accommodating chamber 12 is compressed, but the valve drive mechanism accommodating chamber 12 is open to the atmosphere. The opening 16a serves as an escape path for air and can be smoothly retracted.

Further, in the high engine speed range, the valve body 1
1 is retracted and the exhaust timing is early,
The head 11c of No. 1 directly blocks the opening 16b of the opening 16a, and the communication with the outside of the valve drive mechanism housing chamber 12 is blocked.

In this way, the opening 16a is changed according to the engine speed, and in the low and middle engine speed range,
Since the valve body 11 communicates the valve drive mechanism accommodating chamber 12 with the atmosphere, the valve body 11 can move accurately and quickly without being affected by the pressure in the valve drive mechanism accommodating chamber 12. Improves the power feeling and throttle response in the low and middle rpm range.

Further, in the high engine speed range, the opening 1 of the opening 16a for communicating the valve drive mechanism accommodating chamber 12 with the atmosphere.
6b is closed, and particularly in a high rotational speed range, the amount of exhaust gas that enters the valve drive mechanism accommodating chamber from the sliding portion between the valve body and the valve body holding portion increases, but at this time, the exhaust gas Leakage from the opening 16a communicating with the atmosphere in the drive mechanism housing chamber 12 is reduced, and a decrease in engine output can be prevented.

Further, the opening opening / closing means A is constructed so as to directly open and close the opening 16a at its end by the forward / backward movement of the valve body 11, and the head 16c at the end directly opens the opening 16a. Since the opening 16b is opened and closed, a special mechanism for driving the opening opening / closing means A is unnecessary, and since the opening 16a is directly opened / closed without interposing other parts, the response is good and the number of parts is small. The structure is simple and can operate reliably.

In both of the above embodiments, the space outside the valve drive mechanism accommodating chamber 12 is the atmosphere, but the space is not limited to the atmosphere and has a larger volume than the valve drive mechanism accommodating chamber 12.
For example, it may be connected to a muffler or the like.

The rotation of the crankshaft 5 is controlled by the operation of the centrifugal governor 20 via the link mechanism 21 to drive the valve drive mechanism 1.
However, the valve drive mechanism 18 may be operated by an actuator such as a motor according to the engine speed.

[0033]

As described above, according to the first aspect of the present invention, since the opening communicating with the outside of the valve drive mechanism accommodating chamber is provided, the valve body is not affected by the pressure of the valve drive mechanism accommodating chamber and is accurate. It enables quick movements and improves the power feeling and throttle response in the low to medium rpm range of the 2-cycle engine performance. Further, since the opening communicating with the outside of the valve drive mechanism accommodating chamber is changed according to the number of revolutions of the engine, exhaust gas is less likely to leak from the opening communicating with the outside of the valve drive mechanism accommodating chamber. The decrease can be prevented.

According to the second aspect of the present invention, the opening opening / closing means closes the opening in the high engine speed range and opens the opening in the low and medium engine speed range. Therefore, particularly in the high engine speed range, the valve body is opened. The amount of exhaust gas that enters the valve drive mechanism accommodating chamber from the sliding part between the valve and the valve holding part increases, but at this time, the exhaust gas is less likely to leak from the opening communicating with the outside of the valve drive mechanism accommodating chamber. As a result, it is possible to prevent the engine output from being lowered, and on the other hand, the throttle response is improved particularly in the low and middle speed range.

According to the third aspect of the present invention, since the opening / closing means operates in conjunction with the forward / backward movement of the valve element, a special mechanism for driving the opening / closing means is unnecessary, and the structure is simple and simple. It can operate reliably.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a two-cycle engine.

FIG. 2 is a side view of a partially broken two-cycle engine.

FIG. 3 is a sectional view of an exhaust control device of a two-cycle engine.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2;

5 is a view taken along line VV of FIG.

FIG. 6 is a front view of the cover.

FIG. 7 is a rear view of the cover.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG.

[Explanation of symbols]

 1 2 Cycle Engine 9 Exhaust Passage 9a Exhaust Inlet 10 Upper Wall 11 Valve Body 11c Head 12 Valve Drive Mechanism Housing Chamber 16 Cover 16a Opening 16b Opening 18 Valve Driving Mechanism

Claims (4)

[Claims] 1. An upper wall of an exhaust passage is provided so as to be capable of advancing and retreating, and a tip portion thereof protrudes above an exhaust inlet of the exhaust passage in accordance with the number of revolutions of an engine so that an upper edge position of the exhaust inlet is located. A two-cycle engine having a valve body to be lowered, a valve drive mechanism for moving the valve body forward and backward, and a valve drive mechanism accommodating chamber for housing the valve drive mechanism, the exhaust timing being changed by moving the valve body forward and backward. The exhaust control device is provided with an opening communicating with the outside of the valve drive mechanism accommodating chamber, and an opening opening / closing means for opening / closing the opening according to the number of revolutions of the engine. Control device. 2. The two-cycle engine according to claim 1, wherein the opening / closing means closes the opening in a high engine speed range and opens the opening in a low / medium engine speed range. Exhaust control device. 3. The exhaust control device for a two-cycle engine according to claim 1, wherein the opening / closing means operates in conjunction with the advancing / retreating operation of the valve body. 4. The opening / closing means according to claim 1 or 2, wherein the opening / closing means is configured to directly open / close the opening at its end portion by advancing and retracting the valve body. Exhaust control device for cycle engine.