JPH05321673A - Exhaust device for two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent generation of a dead volume in an auxiliary exhaust passage by providing a main exhaust valve of which exhaust timing is controllable at a main exhaust port, and providing a switching valve interlocked with the main exhaust valve at a downstream end of the auxiliary exhaust passage. CONSTITUTION:A main exhaust port 16a is opened in an inner surface of a cylinder bore 14. A pair of auxiliary exhaust ports 17a, 18a are opened on both sides of the main exhaust port 16a. Downstream ends 17b, 18b of a pair of auxiliary exhaust passages 17, 18 connected to the auxiliary exhaust ports 17a, 18a respectively are connected to a downstream part 16b of a main exhaust passage 16. A main exhaust valve 25 of which exhaust timing from the main exhaust passage 16 is provided at the main exhaust port 16a. Upstream switching valves 32, 33 and downstream switching valves 34, 35 interlocked with the main exhaust valve 25 are provided at the auxiliary exhaust ports 17a, 18a and the downstream ends 17b, 18b of the auxiliary exhaust passages 17, 18 respectively. Generation of a dead volume when the auxiliary exhaust passages are closed is thus prevented, thereby desired operation performance can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is provided on the inner surface of a cylinder bore.
The main exhaust port is opened, and a pair of auxiliary exhaust ports are opened on both sides of the main exhaust port, and a pair of auxiliary exhaust passages individually communicating with both auxiliary exhaust ports are provided downstream of the main exhaust passage communicating with the main exhaust port. The present invention relates to an exhaust system for a two-cycle engine to which a downstream end is connected.

[0002]

2. Description of the Related Art Conventionally, such an apparatus has been disclosed in, for example, Japanese Patent Laid-Open No. HEI-2.
It is known from Japanese Patent Publication No. 49922.

[0003]

By the way, a pair of auxiliary exhaust ports are opened to the inner surface of the cylinder bore on both sides of the main exhaust port, and the auxiliary exhaust passage is opened / closed according to the operating state of the engine, thereby exhausting the exhaust gas as a whole. By changing the cross-sectional area of the passage, it becomes possible to control the output according to the operating state of the engine. However, in the above-mentioned conventional one, an on-off valve such as a rotary valve for controlling the exhaust of the auxiliary exhaust passage is provided in an intermediate portion of the auxiliary exhaust passage, and when the on-off valve is closed, the upstream side and the upstream side of the on-off valve and If the auxiliary exhaust passage is closed, the dead volume will be adversely affected on the combustion chamber and the exhaust system when the auxiliary exhaust passage is closed, and the desired operating performance may not be obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust system for a two-cycle engine in which dead volume does not occur when the auxiliary exhaust passage is closed.

[0005]

To achieve the above object, according to the present invention, the main exhaust port is provided with a main exhaust valve capable of controlling the exhaust timing from the main exhaust passage. An upstream opening / closing valve and a downstream opening / closing valve that interlock with the main exhaust valve are provided at the downstream ends of the port and both auxiliary exhaust passages, respectively.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a two-cycle engine, FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1, and FIG. Is 3 in FIG.
3 is a sectional view taken along line -3, FIG. 4 is a sectional view taken along line 4-4 of FIG. 2, FIG. 5 is a sectional view taken along line 5-5 of FIG. 3, and FIG. 6 is a sectional view taken along line 6-6 of FIG.

First, in FIGS. 1 and 2, an engine body 10 of this two-cycle engine is connected to a cylinder block 11, a cylinder head 12 connected to the upper surface of the cylinder block 11, and a lower part of the cylinder block 11. A cylinder bore 14 formed in the cylinder block 11 and a piston 1
5 is slidably fitted.

The cylinder block 11 includes a main exhaust passage 1
6 and a pair of auxiliary exhaust passages 17 and 18, and the upstream end of the main exhaust passage 16 is opened to the inner surface of the cylinder bore 14 as a main exhaust port 16a.
The upstream end of 18 is opened as an auxiliary exhaust port 17a, 18a on the inner surface of the cylinder bore 14 on both the left and right sides of the main exhaust port 16a. Moreover, the downstream ends 17b and 18b of both auxiliary exhaust passages 17 and 18 are connected to the downstream portion 16b of the main exhaust passage 16. An intake port 19 and a plurality of scavenging ports 20 are provided in the cylinder block 11, and an ignition plug 21 is attached to the cylinder head 12 so as to face the center of the top of the cylinder bore 14.

A valve housing chamber 2 is provided on the upper surface of the main exhaust port 16a.
4 is formed, and the main exhaust is configured to be rotatable between the valve open position stored in the valve storage chamber 24 and the valve open position lowered from the valve storage chamber 24 as shown in FIG. A valve 25 is provided. The main exhaust valve 25 is formed in a flat and substantially rectangular shape, and a regulating surface 26 that is substantially flush with the inner surface of the cylinder bore 14 when the valve is closed is provided at the front end of the main exhaust valve 25. A rear end portion 25 is swingably supported by the cylinder block 11 via a support shaft 27 orthogonal to a plane including the axis of the cylinder bore 14.

The cylinder block 1 is provided on both sides of the main exhaust valve 25.
A pair of auxiliary valves 28 and 29 are rotatably supported by the first valve 1 so as to traverse both auxiliary exhaust passages 17 and 18. These sub-valves 28, 29 have cutout-shaped flow passages 28a, 29a in the portions corresponding to the auxiliary exhaust passages 17, 18, and are configured as rotary valves. Thus, the sub-valves 28 and 29 are connected to each other by the connecting shaft 30 that connects the eccentric positions, and rotate integrally.

On the other hand, an elongated hole 31 through which the connecting shaft 30 penetrates is provided in the middle portion of the main exhaust valve 25, and the main exhaust valve 25 also rotates in response to the turning operation of both the sub valves 28 and 29. It can be operated. Thus, when both the sub valves 28 and 29 are in the valve opening positions in which the flow passages 28a and 29a correspond to the auxiliary exhaust passages 17 and 18, the main exhaust valve 25 is operated in the valve storage chamber 24.
When the sub-valves 28 and 29 are rotated to the closed position where the auxiliary exhaust passages 17 and 18 are closed, the main exhaust valve 25 is lowered from the valve storage chamber 24 to the closed position. Therefore, both auxiliary valves 28 and 29 and the main exhaust valve 25 are interlocked and connected.

The auxiliary exhaust ports 17a and 18a are respectively provided with upstream side opening / closing valves 32 and 33 which interlock with the auxiliary valves 28 and 29, that is, the main exhaust valve 25.
At the downstream ends 17b and 18b of the valves 7 and 18, auxiliary valves 28 and 29 are provided.
That is, the downstream opening / closing valves 34, 3 that are interlocked with the main exhaust valve 25
5 are arranged respectively.

Referring also to FIGS. 3 and 4, the upstream side opening / closing valves 32, 33 are connected to the auxiliary exhaust port 17 by guide members 36, 37 attached to the cylinder block 11.
a, a lower position where 18a is closed, and an auxiliary exhaust port 17a,
It is guided up and down between the upper position that opens 18a. Thus, springs 40, 41 for sandwiching the locking pins 38, 39 planted at the eccentric positions of the sub-valves 28, 29 from both sides are attached to the upstream side on-off valves 32, 33. When 29 operates in the valve closing direction, the upstream side opening / closing valves 38, 39 are driven in the valve closing direction, and when the auxiliary valves 28, 29 operate in the valve opening direction, the upstream side opening / closing valves 38, 39 are driven in the valve opening direction. Will be done.

The downstream opening / closing valves 34 and 35 are opened from the storage recesses 42 and 43 in the storage recesses 42 and 43 provided on the side surfaces of the downstream ends 17b and 18b of the auxiliary exhaust passages 17 and 18, respectively. The downstream ends 17 of the auxiliary exhaust passages 17 and 18 can be rotated so as to project and rotate between the valve closing positions where the connection opening ends of the auxiliary exhaust passages 17 and 18 to the main exhaust passage 16 are closed.
The shafts 44 and 45 fixed to the cylinder block 11 are rotatably supported by the shafts 44 and 45, respectively.

At the intermediate portion of the downstream side on-off valves 34, 35, one ends of drive shafts 46, 47 supported by the cylinder block 11 so as to be slidable in the axial direction are provided with one ends of the drive shafts 46, 47 in accordance with the axial operation of the drive shafts 46, 47. The downstream side opening / closing valves 34 and 35 are connected so as to be rotationally driven, and followers 48 and 49 are fixed to their drive shafts 46 and 47, respectively. On the other hand, the sub valves 28 and 2
9, drum portions 50 and 51 having a fan-shaped cross section are integrally provided, and cam grooves 52 and 53 as shown in FIG. 5 are provided on the side surfaces of the drum portions 50 and 51, respectively. The followers 48 and 49 are fitted into the cam grooves 52 and 53. As a result, the drive shafts 46 and 47 are connected to the drum unit 5.
The axial opening and closing operations of the auxiliary valves 28 and 29 actuate in the axial direction in response to the rotation of 0 and 51, and the downstream side opening and closing valves 34 and 35 are opened and closed accordingly. The downstream side opening / closing valves 34, 35 are operated in the valve opening direction when the valve is opened, and the downstream side opening / closing valves 34, 35 are operated in the valve closing direction when the auxiliary valves 28, 29 are operated in the valve closing direction.

With particular attention to FIG. 4, a lever 54 is rotatably supported on one of the two sub-valves 28 and 29, and a locking pin 55 embedded in the sub-valve 29 is provided on both sides. A spring 56 sandwiched between them is attached to the lever 54. Thus lever 5
The sub-valve 29 is rotationally driven according to the rotational operation of No. 4.

The gear 58 provided on the crankshaft 57 meshes with the input gear 60 of the water pump 59, and the input gear 60 is the gear 6 of the governor 61.
Meshed with 2.

In FIG. 6, the governor 61 is a rotary shaft 63.
A plate-shaped support member 64 fixed to the support member, a gear 62 provided on the outer periphery of the support member 64, a movable member 65 facing the support member 64 and slidably supported by the rotating shaft 63, and a support member. 64 and a plurality of centrifugal balls 66 interposed between the movable member 65, and a pair of bearings 67, 67 on the movable member 65.
A movable rack 68 supported via the movable member 65 and a governor spring 69 that elastically urges the movable member 65 toward the supporting member 64. The set load of the governor spring 69 is greater than or equal to a predetermined number of revolutions of the crankshaft 57, and the centrifugal ball 66 is rotated. It is set to allow centrifugal movement. Therefore, when the engine enters a predetermined high speed rotation range, the annular rack 68 is driven to the left side in FIG. 6 by the centrifugal movement of the centrifugal balls 66.

On the other hand, a shaft 71 having a pinion 70 meshing with the movable rack 68 is rotatably supported on the crankcase 13, and a lever 72 is fixed to one end of the shaft 71. Moreover, the lever 72 and the lever 54
Are connected via a connecting rod 73 whose length is adjustable, and the movable rack 68 of the governor 61 moves axially in the high-speed operation range of the engine, whereby the lever 72 rotates via the pinion 70. Then, the lever 54 is rotationally driven via the connecting rod 73. Thus, the connecting rod 73 causes the lever 54 to rotate in the valve opening direction of the main exhaust valve 25 in response to the rotation of the lever 72 when the engine enters the high speed operation range. , 5
Connect between the four.

By the way, restriction projections 74 and 75 are provided at both circumferential ends of the outer peripheral portion of the drum 51.
In the cylinder block 11, the main exhaust valve 25 is in the closed position, and the stopper 76 that protrudes from the restriction projection 74 to restrict the turning end of the lever 54 while the main exhaust valve 25 is in the open position. In this state, there is provided a stopper 77 that comes into contact with the regulation protrusion 75 and regulates the turning end of the lever 54.

Next, the operation of this embodiment will be described. When the engine is in the high speed rotation range, the governor 61 is used.
1, the lever 54 is rotationally driven via the movable rack 68, the pinion 70, the lever 72, and the connecting rod 73, and the sub valve 29 is rotationally driven counterclockwise in FIG. 1 via the spring 56 and the locking pin 55. It At this time, since the auxiliary valve 28 is connected to the auxiliary valve 29 via the connecting shaft 30, the auxiliary valve 28
Also rotates together with the auxiliary valve 29, and both auxiliary valves 28, 29 are driven in the valve opening direction. The main exhaust valve 25 is driven by the connecting shaft 30 in the valve opening direction. Further, the upstream side opening / closing valves 32 and 33 and the downstream side opening / closing valves 34 and 35 are also driven to the valve opening side.

In this way, when the engine is in the high speed rotation range, the main exhaust passage 16 and both auxiliary exhaust passages 1
7, 18 are in communication with each other, the exhaust timing is advanced, and the distribution area of the entire exhaust passage is increased to improve the engine output.

When the engine enters the low speed rotation range,
The sub valves 28 and 29 rotate in the opposite direction to the high speed rotation range, whereby the sub valves 28 and 29 are closed and the main exhaust valve 25 is closed, and the exhaust timing is delayed and the entire circulation of the exhaust passage is achieved. The area becomes smaller. Moreover, the upstream opening / closing valve 3
2, 33 and the downstream opening / closing valves 34, 35 are the main exhaust valves 2
5 and is closed together with the main exhaust valve 25, the upstream and downstream parts of the auxiliary exhaust passages 17 and 18 are closed respectively.
18 never becomes a dead volume. Therefore, the exhaust pulsation wave as set by the exhaust system is obtained in the low speed rotation range of the engine, and the cylinder bore 14
It is possible to avoid the influence of the dead volume on the volume of the combustion chamber inside, and to obtain a predetermined operating performance.

Moreover, when the engine moves from the high speed rotation range to the low speed rotation range, the upstream side opening / closing valves 32, 33 are lowered from their open positions, so that the upstream side opening / closing valves 32, 33 are formed.
It is possible to control the exhaust timing from the auxiliary exhaust passages 17 and 18 at the lower edge, and more precise exhaust control can be performed.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims. It is possible to

[0027]

As described above, according to the present invention, the main exhaust port is provided with the main exhaust valve capable of controlling the exhaust timing from the main exhaust passage, and the auxiliary exhaust ports and the downstream of both auxiliary exhaust passages are provided. The upstream side opening / closing valve and the downstream side opening / closing valve interlocking with the main exhaust valve are respectively provided at the ends, so that when the auxiliary exhaust passage is closed, dead volume is prevented from occurring in the auxiliary exhaust passage, and the dead volume is prevented. It is possible to obtain a desired driving performance by avoiding adversely affecting the driving performance.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a two-cycle engine.

FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 of FIG.

4 is a sectional view taken along line 4-4 of FIG.

5 is a sectional view taken along line 5-5 of FIG.

6 is a sectional view taken along line 6-6 of FIG.

[Explanation of symbols]

 14 Cylinder bore 16 Main exhaust passage 16a Main exhaust port 16b Downstream part of main exhaust passage 17,18 Auxiliary exhaust passage 17a, 18a Auxiliary exhaust port 17b, 18b Downstream end of auxiliary exhaust passage 25 Main exhaust valve 32, 33 Upstream opening / closing valve 34 , 35 Downstream valve

Claims (1)

[Claims] 1. A main exhaust port (16a) is opened on an inner surface of a cylinder bore (14), and a pair of auxiliary exhaust ports (17a, 18a) are opened on both sides of the main exhaust port (16a) to provide a main exhaust port (16a). The downstream end (17b, 18b) of the pair of auxiliary exhaust passages (17, 18) individually communicating with both auxiliary exhaust ports (17a, 18a) is provided at the downstream portion (16b) of the main exhaust passage (16) communicating with 16a). In the exhaust system of the connected two-cycle engine, the main exhaust port (16a) is provided with a main exhaust valve (25) capable of controlling the exhaust timing from the main exhaust passage (16), and both auxiliary exhaust ports (17a) are provided. , 18a) and both auxiliary exhaust passages (1
7. The downstream end (17b, 18b) of (7, 18) is provided with an upstream side opening / closing valve (32, 33) and a downstream side opening / closing valve (34, 35) which are interlocked with the main exhaust valve (25), respectively. A two-cycle engine exhaust system.