JPH0816449B2 - Exhaust system for 2-cycle engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a main exhaust passage and an auxiliary
The present invention relates to an exhaust system for a two-cycle engine, which has an exhaust passage and an auxiliary exhaust control member, and in which a piston itself acts as an exhaust valve.

[0002]

2. Description of the Related Art Conventionally, a two-cycle engine has been mainly used.
Auxiliary exhaust passage is provided in addition to the exhaust passage.
There is an exhaust device that opens and closes the
For example, see JP-A-63-272916). this
This type of exhaust system closes the auxiliary exhaust passage at low speed and closes it at high speed.
The exhaust passage to the engine speed.
Improve the output at high speed by making the area suitable
Let

[0003]

[Problems to be Solved by the Invention] But this exhaust system
, The auxiliary exhaust control member is separated from the cylinder bore.
The auxiliary exhaust passage is closed because it is installed in
At this time, from the auxiliary exhaust control member in the auxiliary exhaust passage
Also near the cylinder bore (hereinafter referred to as "passage space")
U ), The exhaust gas collects and flows back into the cylinder.
There is a case. Therefore, LowDecrease output at high speed
There are cases.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an exhaust system for a two-cycle engine capable of improving the output at low speed.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is provided with an auxiliary exhaust control member for changing the state of the exhaust gas from the auxiliary exhaust passage so as to be slidably movable. A drive device is provided for moving the exhaust control member to a position close to the auxiliary exhaust port of the cylinder.

According to the first aspect of the present invention, since the auxiliary exhaust control member moves to a position close to the auxiliary exhaust port of the cylinder, there is no possibility of forming a large passage space in the vicinity of the cylinder bore.

According to a second aspect of the present invention, in the first aspect of the invention, the auxiliary exhaust control member closes the upper part of the auxiliary exhaust port with the lower part of the auxiliary exhaust port opened. This makes it possible to control the timing at which the auxiliary exhaust port opens.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Follow the instructions below. First, the main exhaust system will be described. In FIG. 1, a main exhaust port 2 is provided inside a cylinder 1.
The main exhaust passage 3 communicates with each other. A storage hole 4 formed in the cylinder 1 is opened in the upper portion of the main exhaust passage 3. A main exhaust control member 5 that changes the state of the exhaust gas G from the main exhaust passage 3 and a main guide member 6 are stored in the storage hole 4.

The main exhaust control member 5 is slidably provided in the housing hole 4 and slides into the main exhaust passage 3 from the housing hole 4 and is shown by a chain line in FIG. By protruding to the vicinity of the main exhaust port 2,
The state of the exhaust gas G is changed by delaying the timing of the exhaust gas G. On the other hand, the main guide member 6 guides the inclined upper surface 5 a of the main exhaust control member 5. The inclined lower surface 5b of the main exhaust control member 5 of FIG. 1 is guided by the storage hole 4. The main exhaust control member 5 is integrally formed with a tongue-shaped control portion 5c and a shaft portion 5d shown in FIG. 2 (a). The tip surfaces 5e, 6e of the main exhaust control member 5 and the main guide member 6 in FIG. 1 are shaped along the inner surface of the main exhaust passage 3, and when the main exhaust control member 5 retracts into the storage hole 4, Are smoothly connected to the inner surface of the main exhaust passage 3.

FIG. 2 (b) is a view of the storage hole 4 as seen obliquely from below. As shown in this figure, the main exhaust control member 5 is
The main guide member 6 and the main guide member 6 are in contact with each other at approximately the upper and lower centers of the horizontally long storage hole 4, and the inclined upper surface 5a of the main exhaust control member 5 extends laterally over the entire width of the storage hole 4.
The cross-sectional shape of the main exhaust control member 5 is set to a horizontally long shape that is long in the circumferential direction R of the cylinder 1. On the other hand, as shown in FIG. 2 (c), the main exhaust control member 5 has a shape in the vicinity of the main exhaust port 2 that is substantially the same as the planar cross-sectional shape of the main exhaust passage 3. . In addition,
The main exhaust control member 5 is provided with a pair of stopper surfaces 5f and 5g, and these stopper surfaces 5f and 5g respectively correspond to the pair of stopper surfaces 6 of the main guide member 6 of FIG.
The main exhaust control member 5 is positioned in contact with f and 6g.

Next, the auxiliary exhaust system will be described. As shown in FIG. 3, the inside of the cylinder 1 and the main exhaust passage 3 are connected by an auxiliary exhaust passage 7 as an auxiliary exhaust passage. A pair of auxiliary exhaust passages 7 are provided, and as shown in FIG. 1, a storage hole 8 is opened in the upper portion of the auxiliary exhaust passage 7. An auxiliary exhaust control member 9 for changing the state of the exhaust gas G from the auxiliary exhaust passage 7 and an auxiliary guide member 10 are housed in the housing hole 8. The auxiliary exhaust control member 9 is slidably provided in the storage hole 8 and slides into the auxiliary exhaust passage 7 from the storage hole 8 to move the lower part of the auxiliary exhaust port 11 as shown in FIG. The upper part of the auxiliary exhaust port 11 is closed in the opened state. On the other hand, the auxiliary guide member 10 is
The inclined upper surface 9a of the auxiliary exhaust control member 9 is guided.

FIG. 5A is a perspective view showing the auxiliary exhaust control member 9 and the auxiliary guide member 10. In this figure, there is a space Ss between the auxiliary guide member 10 and the inclined upper surface 9a of the auxiliary exhaust control member 9.
Is a dead end surrounded by the auxiliary exhaust control member 9 and the auxiliary guide member 10 and the wall surface 1a forming the auxiliary exhaust passage 7 of FIG. 3, and therefore, at the low speed shown in FIG. The top is closed.

The auxiliary guide member 10 has a tip portion 10a.
Has a shape along the inner surface of the cylinder 1 and always closes the upper portion of the auxiliary exhaust port 11, and a piston (not shown) makes sliding contact with the tip portion 10a. On the other hand, in the fully open state of FIG. 1, the auxiliary exhaust control member 9 and the auxiliary guide member 1
The lower surfaces 9e and 10e of 0 form part of the wall surface of the auxiliary exhaust passage 7.

As shown in FIG. 5B, the auxiliary exhaust control member 9 is integrally formed with a control portion 9c and a shaft portion 9d. The auxiliary exhaust control member 9 is provided with a pair of stopper surfaces 9f and 9g.
f and 9g are the auxiliary guide members 1 of FIG.
The auxiliary exhaust control member 9 is positioned by contacting the stopper surfaces 10f and 10g of No. 0. The main guide member 6 and the auxiliary guide member 10 in FIG. 1 are fixed to the cylinder 1 with screws 13.

Next, the drive unit 2 shown in FIG. 6 and FIG.
0 will be described. In FIG. 6, the drive device 20 is
The main exhaust control member 5 and the auxiliary exhaust control member 9 are moved to positions close to the main exhaust port 2 and the auxiliary exhaust port 11, respectively. This drive 2
Reference numeral 0 has a pulley 21 to which a rotational force from a motor (not shown) which is a drive source is transmitted. The pulley 21 is fixed to the drive shaft 22 and rotates the drive shaft 22 forward or backward by about 40 ° to 50 ° by the rotational force of the motor. The drive shaft 22 is rotatably supported by the cylinder 1 of FIG. 7 and the cover 12 of FIG.

The drive shaft 22 has a U-shaped cutout 23.
A pair of arms 23 having a are provided as shown in FIG. 7. A first pin 24 and a second pin 25 are inserted into and engaged with the notch 23a of the arm 23. The first pin 24 and the second pin 25 are inserted into the pin insertion hole 5h of the main exhaust control member 5 and the pin insertion hole 9h of the auxiliary exhaust control member 9, respectively. Therefore, as the drive shaft 22 and the arm 23 in FIG. 1 rotate in the direction of arrow A, the main exhaust control member 5 and the auxiliary exhaust control member 9 reach positions near the main exhaust port 2 and the auxiliary exhaust port 11, respectively. Moving. That is,
The arm 23 transmits the driving force from the motor, which is one driving source, to both the exhaust control members 5 and 9.

The first pin 24 is provided closer to the drive shaft 22 than the second pin 25. Therefore, the movement stroke of the main exhaust control member 5 is the movement of the auxiliary exhaust control member 9. Smaller than stroke. The pin insertion hole 5h of the main exhaust control member 5 is an oval hole that is long in the moving direction of the main exhaust control member 5.

Next, an example of the operation of the above configuration will be described. First, when the engine speed is low and low, the arm 23 is held at the position shown in FIG. 4, and the main exhaust control member 5 and the auxiliary exhaust control member 9 are held in the state shown in this figure. Therefore, at low speed, the upper portions of the main exhaust port 2 and the auxiliary exhaust port 11 are closed, and the timing of opening the main exhaust port 2 and the auxiliary exhaust port 11 is delayed.

Thereafter, when the rotation speed of the engine reaches a predetermined speed, the pulley 21 is rotated by the rotation of a motor (not shown).
The drive shaft 22 and the arm 23 rotate in the direction of arrow B via (FIG. 6). By this rotation, the pair of pins 24,
While 25 moves in the direction of arrow C, both exhaust control members 5 and 9 slide in the direction of arrow C to retract from both exhaust ports 2 and 11 to both storage holes 4 and 8. This allows
As shown in FIG. 1, both exhaust ports 2 and 11 are widely opened, and the exhaust timing becomes a fast timing commensurate with the engine rotation speed, and as is well known, the output at high speed improves.

[0020] In the exhaust system of a two-cycle engine of this is,
The auxiliary exhaust control member 9 shown in FIG.
Since it slides and moves to a position close to, the space Ss generated near the auxiliary exhaust port 11 at low speed
(Passage space) is significantly reduced. Therefore, the exhaust G is because can suppress the amount of backflow into the cylinder 1, output when the low speed is improved.

By the way, in this embodiment, with the auxiliary exhaust control member 9 opening the lower part of the auxiliary exhaust port 11,
The upper part of the auxiliary exhaust port 11 is closed. Therefore, the exhaust timing of the auxiliary exhaust port 11 can also be controlled, so that the output of the engine is further improved. However, according to the present invention, the auxiliary exhaust control member 9 is not shown in FIG.
The auxiliary exhaust passage 7 may be fully closed or fully opened.

In the above embodiment, the auxiliary exhaust control member 9 was slid in the direction parallel to the main exhaust passage 3 in FIG. 6, but this is not always necessary. For example, from the auxiliary exhaust control member 9 to the auxiliary exhaust port 11 to the cylinder 1
It may be long in the radial direction and slidably moved in the radial direction of the cylinder 1. Further, the inclination angle of the auxiliary exhaust control member 9 with respect to the cylinder 1 of FIG. 1 and the inclination angle of the main exhaust control member 5 may be different from each other.

Further, in this embodiment, a motor (not shown) is used as a drive source of the drive unit 20, but in the present invention, the drive unit 20 may be a mechanical drive unit. In addition, as a mechanical drive device, by rotation of a governor connected to a crank shaft (not shown),
There is a known device in which a steel ball moves along the inclination of a dish-shaped spherical plate when the rotational speed of a crankshaft exceeds a predetermined value. (See, for example, JP-A-60-249614).

Further, in the above embodiment, the main exhaust control member 5 is moved in accordance with the engine speed. However, in the present invention, the throttle opening is taken into consideration in addition to the engine speed to control both exhausts. The members 5 and 9 may be controlled.

[0025]

As described above, according to the first aspect of the present invention, at the time of low speed, a large space is not formed in the auxiliary exhaust passage in the vicinity of the auxiliary exhaust port, so that the exhaust gas is prevented from flowing back into the cylinder. Can be suppressed. It was but <br/>, output when low speed is improved. In this case, the engine output can be further improved by controlling the exhaust timing of the auxiliary exhaust port.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a cylinder at a high speed showing an embodiment of the present invention.

FIG. 2 (a) is a perspective view showing a main exhaust control member and a main guide member, and FIG. 2 (b) is a front view of both members as viewed from a storage hole.
(C) is a plane sectional view of a cylinder showing a main exhaust control member.

FIG. 3 is a plan sectional view of a cylinder showing a main exhaust passage and an auxiliary exhaust passage.

FIG. 4 is a vertical cross-sectional view of a cylinder at low speed.

5A is a perspective view showing an auxiliary exhaust control member and an auxiliary guide member, and FIG. 5B is a perspective view of the auxiliary exhaust control member.

FIG. 6 is a plan view showing a driving device.

FIG. 7 is a rear view of the same.

[Explanation of symbols]

1 ... Cylinder, 2 ... Main exhaust port, 3 ... Main exhaust passage, 4
... Storage hole, 5 ... Main exhaust control member, 6 ... Main guide member, 7
... auxiliary exhaust passage, 9 ... auxiliary exhaust control member, 11 ... auxiliary exhaust port, 20 ... drive device, R ... circumferential direction.

Claims (2)

[Claims] 1. A main exhaust passage communicating with the inside of a cylinder and an upper exhaust passage.
Auxiliary exhaust communication is provided between the cylinder and the main exhaust passage.
Of the auxiliary exhaust passage connected as a passage and the auxiliary exhaust passage
2 with an auxiliary exhaust control member that changes the state of exhaust
An exhaust system for a cycle engine, wherein the auxiliary exhaust control member is slidably provided, and
Place the auxiliary exhaust control member close to the auxiliary exhaust port of the cylinder.
2 cycle engine equipped with a driving device to move
Gin exhaust system. 2. The auxiliary exhaust control unit according to claim 1.
Material is auxiliary with the lower part of the auxiliary exhaust port open.
Exhaust from a 2-cycle engine with the top of the exhaust port closed
apparatus.