JPH0893482A - Exhaust control device for 2-cycle engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an exhaust control device for a two-cycle engine that can obtain optimum exhaust conditions in all low, medium, and high engine speed ranges, and can obtain good power feeling and throttle response. [Composition] Arranged on the upper wall 10 of the exhaust passage 9 so as to be movable back and forth
A valve body 11 having a tip 11b protruding above the exhaust gas inlet 9a in the exhaust passage 9 to lower the upper edge position of the exhaust gas inlet 9a according to the engine speed, and a valve drive for moving the valve body 11 forward and backward. In the exhaust control device of the two-cycle engine, which includes the mechanism 18 and the valve drive mechanism accommodating chamber 12 that accommodates the valve drive mechanism 18, the exhaust timing is changed by advancing and retracting the valve body 11, An opening part communicating with the outdoor space is provided, and an opening part changing means for changing the opening area of the opening part according to the engine speed is provided.

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 engine speed range, on the contrary, the engine output decreases due to the leakage of exhaust gas from the breather pipe.

The present invention has been made in view of the above circumstances, 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 the exhaust control device of a two-cycle engine, which comprises advancing and retracting the valve element to change the exhaust timing, an opening communicating with an outdoor space of the valve drive mechanism accommodating chamber is provided, and an opening area of the opening is reduced. It is characterized in that it is provided with an opening variable means for changing the rotation speed of the engine.

In the exhaust control device for a two-cycle engine according to a second aspect of the present invention, the opening varying means reduces the opening area in a high engine speed range and increases the opening area in a low to middle engine speed range. It is characterized by doing.

In the exhaust control device for a two-cycle engine according to a third aspect of the present invention, the opening varying means operates in conjunction with the forward / backward movement of the valve body.

[0010]

According to the first aspect of the present invention, the opening is provided to communicate with the outdoor space of the valve drive mechanism accommodating chamber, and the valve body communicates with the outdoor space of the valve drive mechanism accommodating chamber. The valve body can move accurately and quickly without being affected by the pressure in the valve drive mechanism housing chamber, and the power feeling and the throttle response in the low-medium speed range of the 2-cycle engine performance are improved. Further, by changing the opening area of the opening communicating with the outdoor space of the valve drive mechanism accommodating chamber according to the engine speed, exhaust gas leaks from the opening communicating with the outdoor space of the valve drive mechanism accommodating chamber. This can be alleviated, and a decrease in engine output can be prevented.

According to the second aspect of the present invention, the opening varying means reduces the opening area in the high engine speed range and increases the opening area in the low and middle engine speed range. Leakage from the opening communicating with the space outside the valve drive mechanism accommodating chamber is reduced, and a reduction in engine output can be prevented. On the other hand, throttle response is improved especially in the low and middle speed range.

According to the third aspect of the invention, since the opening varying means operates in conjunction with the forward / backward movement of the valve body, a special mechanism for driving the opening varying means is unnecessary, and the structure is simple and reliable. Works.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust control system for a two-cycle engine of the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view of a 2-cycle engine, FIG. 2 is a side view of a partially-broken 2-cycle engine, and FIG. 3 is a partially-broken 2
FIG. 4 is a plan view of a cycle engine, FIG. 4 is a cross-sectional view of an exhaust control device of a two-cycle engine, FIG. 5 is a cross-sectional view showing an operating state in a low / medium speed range, and FIG. 6 is a cross-sectional view showing an operating state in a high speed range. , FIG. 7 is a sectional view taken along the line VII-VII 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 attached to the inside of the valve drive mechanism accommodating chamber 12 by a screw 14, and the valve drive mechanism accommodating chamber 12 is covered with a lid 16 attached by a screw 15.

The connecting shaft 1 is attached to the shaft portions 11a of the pair of valve bodies 11.
7 is inserted, and the pair of valve bodies 11 are connected by the connecting shaft 17. 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 a boss 4.
7, the boss 47 is integrally rotatably provided on the valve drive shaft 48. A lever 49 is fastened and fixed to the end of the valve drive shaft 48 with a bolt 50.
A spring 51 is provided between the boss 50 and the boss 50.

The valve drive shaft 48 is rotatably supported on the side walls 12a and 12b of the valve drive mechanism accommodating chamber 12, and the valve drive shaft 4
A valve actuating lever 52 is fastened and fixed to a central portion of the bolt 8 with a bolt 53, and a concave portion 5 formed at a tip portion of the valve actuating lever 52.
2a is engaged with the connecting pin 17. Therefore, when the valve drive shaft 48 rotates, the valve operating lever 52 operates in conjunction with each other to move the valve element 11 forward and backward via the connecting pin 17, and the exhaust inlet 9a in the exhaust passage 9 depending on the engine speed. The tip portion 11b of the exhaust gas projects from the upper part to lower the upper edge position of the exhaust gas inlet, and the valve body 11 is advanced and retracted to change the exhaust gas timing.

A large-diameter opening 60 and a small-diameter opening 61 are formed on the side wall 12b of the valve drive mechanism accommodating chamber 12 near the valve drive shaft 48 so as to communicate with the space outside the valve drive mechanism accommodating chamber 12. The large-diameter opening 60 and the small-diameter opening 6
1 is open to the atmosphere through breather pipes 62 and 63, respectively. The valve drive shaft 48 is provided with a control plate 64 that constitutes an opening varying means so as to be integrally rotatable and axially movable. The control plate 64 opens and closes a large-diameter opening 60 and a small-diameter opening 61. It is located at the position. A spring 65 is provided between the control plate 64 and the valve actuating lever 52 to constantly press the control plate 64 against the side wall 12b of the valve drive mechanism accommodating chamber 12 to prevent the opening 60 having a large diameter and the opening 61 having a small diameter. The sealing property is secured.

Therefore, the valve body 1 is rotated by the rotation of the valve drive shaft 48.
1 moves forward and backward, and the control plate 64 operates in conjunction with the forward movement of the valve element 11. As described above, since the valve element 11 operates in conjunction with the advancing / retreating operation, the mechanism operates easily and reliably.

In the low and medium engine speed range of the engine, the valve element 11 moves forward and the exhaust timing is delayed as shown in FIG.
On the other hand, the control plate 64 closes the small diameter opening 61 and opens the large diameter opening 60 to increase the opening area.

Further, in the high engine speed range, as shown in FIG. 6, the valve body 11 is retracted and the exhaust timing is early, while the control plate 64 closes the large-diameter opening 60 and the small-diameter. The opening area is reduced by opening the opening 61.

As described above, the opening area of the opening is changed according to the engine speed, but since the valve body 11 communicates the valve drive mechanism housing chamber 12 with the atmosphere, the valve body 11 is opened.
Can make accurate and quick movements without being affected by the pressure in the valve drive mechanism housing chamber 12, and improves the power feeling and throttle response in the low to middle speed range of the two-cycle engine performance. Further, since the opening area of the opening that communicates the valve drive mechanism accommodating chamber 12 with the atmosphere is changed according to the rotation speed of the engine, exhaust gas is less likely to leak from the opening that communicates with the atmosphere. Therefore, it is possible to prevent the engine output from decreasing.

In this embodiment, the opening area of the opening is reduced by opening the small-diameter opening 61 particularly in the high engine speed range, so that the exhaust gas slides on the valve body 11 in the high engine speed range. Leakage from the moving portion through the opening communicating with the atmosphere in the valve drive mechanism housing chamber 12 is reduced, and a decrease in engine output can be prevented. On the other hand, in the low to middle speed range, the opening area is increased by opening the large diameter opening 60, so that the throttle response is improved.

8 to 10 show another embodiment of the exhaust control system for a two-cycle engine, FIG. 8 is a cross-sectional view showing an operating state in a low to medium revolution range, and FIG. 9 is an operating state in a high revolution range. 10 is a sectional view taken along line XX in FIG.

In this embodiment, the members designated by the same reference numerals as those in FIGS. 1 to 7 have the same structure, and the description thereof will be omitted.
In this embodiment, on the side wall 12b of the valve drive mechanism accommodating chamber 12, a large-diameter opening 70 communicating with the space outside the valve drive mechanism accommodating chamber 12 is formed near the valve drive shaft 48.
The large-diameter opening 70 is open to the atmosphere via a breather pipe 71. The valve drive shaft 48 is integrally rotatably provided with a control plate 72 that constitutes an opening varying means. The control plate 72 is sized to open and close a part of the large-diameter opening 70.

Therefore, in the low and medium engine speed range of the engine, as shown in FIG. 8, the valve body 11 advances and the exhaust timing is delayed, while the control plate 72 opens the large-diameter opening 70 to open the opening area. To increase.

Further, in the high engine speed range, as shown in FIG. 9, the valve element 11 is retracted and the exhaust timing is early, while the control plate 72 blocks a part of the large-diameter opening 70. The opening area is reduced by opening a part of the large-diameter opening 70.

As described above, the opening area of the single opening 70 is changed according to the engine speed to provide the opening 70 for communicating the valve drive mechanism accommodating chamber 12 with the atmosphere. Since the mechanism housing chamber 12 communicates with the atmosphere,
The valve body 11 can be moved accurately and quickly without being affected by the pressure in the drive mechanism housing chamber 12, and the power feeling and the throttle response in the low-medium speed range of the 2-cycle engine performance are improved. Further, since the opening area of the opening 70 that communicates the valve drive mechanism accommodating chamber 12 with the atmosphere is changed according to the engine speed, the exhaust gas is discharged from the valve drive mechanism accommodating chamber 1.
Leakage of 2 from the opening 70 communicating with the atmosphere is reduced, and a decrease in engine output can be prevented.

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 through 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.

Further, although the control plates 64 and 72 are operated in association with the advancing / retreating operation of the valve element 11 by the rotation of the valve drive shaft 48, the control plates 64 and 72 are not operated by the valve drive shaft 48 but are operated independently by a motor or the like. May be.

[0035]

As described above, according to the first aspect of the present invention, the valve body is not affected by the pressure in the valve drive mechanism accommodating chamber because the opening portion communicating with the space outside the valve drive mechanism accommodating chamber is provided. It enables accurate and 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 area of the opening communicating with the outdoor space of the valve drive mechanism accommodation chamber is changed according to the engine speed, exhaust gas may leak from the opening communicating with the outdoor space of the valve drive mechanism accommodation chamber. Can be reduced, and a decrease in engine output can be prevented.

According to the second aspect of the invention, since the opening varying means reduces the opening area in the high engine speed range and increases the opening area in the low and middle engine speed range, the exhaust gas is exhausted particularly in the high engine speed range. Is prevented from leaking from the opening communicating with the space outside the valve drive mechanism accommodating chamber, and it is possible to prevent a decrease in engine output, while improving the throttle response, especially in the low to medium speed range.

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

[0038]

[Brief description of drawings]

[0039]

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

[0040]

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

[0041]

FIG. 3 is a plan view of a partially broken two-cycle engine.

[0042]

FIG. 4 is a sectional view of an exhaust control device of a two-cycle engine.

[0043]

FIG. 5 is a cross-sectional view showing an operating state in a low / medium speed range.

[0044]

FIG. 6 is a cross-sectional view showing an operating state in a high rotation speed range.

[0045]

7 is a cross-sectional view taken along the line VII-VII of FIG.

[0046]

FIG. 8 is a cross-sectional view showing an operating state in a low / medium speed range.

[0047]

FIG. 9 is a sectional view showing an operating state in a high rotation speed range.

[0048]

10 is a cross-sectional view taken along line XX of FIG.

[0049]

[Explanation of symbols]

 1 2 Cycle Engine 9 Exhaust Passage 9a Exhaust Inlet 10 Upper Wall 11 Valve Body 12 Valve Drive Mechanism Storage Chamber 18 Valve Drive Mechanism

Claims (3)

[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. In the exhaust control device, an opening communicating with an outdoor space of the valve drive mechanism accommodating chamber is provided, and an opening changing unit that changes the opening area of the opening according to the engine speed is provided. Exhaust control device for 2-cycle engine. 2. The two-cycle engine according to claim 1, wherein the opening varying means reduces the opening area in a high engine speed range and increases the opening area in a low and middle engine speed range. Exhaust control device. 3. The exhaust control device for a two-cycle engine according to claim 1 or 2, wherein the opening varying means operates in conjunction with an advancing / retreating operation of the valve element.