JPH0816450B2 - Exhaust system for 2-cycle engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for a two-cycle engine in which a piston itself acts as an exhaust valve.

[0002]

2. Description of the Related Art Conventionally, in a two-cycle engine, there is an exhaust device in which an auxiliary exhaust passage is provided in addition to the main exhaust passage, and the auxiliary exhaust passage is opened and closed by an auxiliary valve (for example, Japanese Patent Laid-Open No. 63-272916). reference). In this type of exhaust system, the auxiliary exhaust passage is closed at low speed and opened at high speed, and the cross-sectional area of the exhaust passage is made to be an area corresponding to the rotation speed of the engine, thereby improving the output at high speed.

Here, the above prior art is as shown in FIG.
The valve shaft portion 10d of the auxiliary valve 10A is projected above the cylinder head 1, and the rotational force is input from the projected valve shaft portion 10d. In this way, by making the valve shaft portion 10d project from the cylinder head 1, the auxiliary valve 10
It is not necessary to provide a drive rack or the like for rotating A in the cylinder 2, and therefore it is easy to provide a water jacket in the vicinity of the auxiliary valve 10A, which facilitates cooling of the engine.

[0004]

However, in the case of the above-mentioned prior art, the auxiliary valve 10A is inserted and housed in the valve box 2a formed in the cylinder 2 from above. Therefore, the upper valve shaft portion 10d having a smaller diameter than the lower valve body 10b.
It is unavoidable that a useless space 2b is generated around the engine, which may cause the engine performance to not be improved. In addition, hot exhaust gas may pass through or the auxiliary valve 10A exposed to the exhaust gas may not be sufficiently cooled.

The present invention has been made in view of the above problems of the prior art. In a two-cycle engine exhaust system having an auxiliary valve, the space around the auxiliary valve is effectively used to improve engine performance. At the same time, the purpose is to sufficiently cool the auxiliary valve.

[0006]

In order to achieve the above object, the present invention is directed to a cylinder in which both ends are provided with a seal member therebetween.
A cylindrical valve holder fixed to
While supporting the cylindrical valve shaft part of
The middle part of the rudder faces the space where the cooling liquid flows.

According to the present invention, the cylindrical valve shaft portion is
Support with a tubular valve holder, and fix both ends of the valve holder.
Since it is fixed to the cylinder via the seal member, the valve shaft is
Insert it into the valve holder and attach this valve holder to the cylinder.
Since it can be supported just by fitting it into the
It is easy to form and does not move relative to the valve holder and the cylinder.
Because it is sealed with the seal member between the
Surely done. Also, set the middle part of the valve holder to
Since it faces the space where the
And the auxiliary valve can be effectively cooled.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical section of a two-cycle engine, 1 is a cylinder head, 2 is a cylinder, 3 is a scavenging passage, and 4 is a water jacket. The main exhaust port 5 communicates the inside of the cylinder 2 with the main exhaust passage 7 of FIG. The pair of auxiliary exhaust passages 9 connects the auxiliary exhaust port 8 on the side of the main exhaust port 5 and the main exhaust passage 7 as an auxiliary exhaust passage. That is, the cross-sectional area of the auxiliary exhaust passage 9 is formed smaller than that of the main exhaust passage 7. A resonance chamber 30 communicates with the main exhaust passage 7 at a low speed to prevent the output from decreasing at a low speed.
In the present invention, it is not always necessary to provide it.

The rotary valve (auxiliary valve) 10 is
The auxiliary exhaust passage 9 is provided in the middle of the auxiliary exhaust passage 9 and, in response to a change in the rotation speed of the engine, through a transmission device 12 (FIG. 3),
The auxiliary exhaust passage 9 is opened and closed by being rotationally driven in opposite directions by a driving device (not shown). The rotary valve 10 includes a valve passage 10a and a valve body 10b.
And are formed on the cylindrical portion 10c of FIG. In this rotary valve 10, the rotary valve 10 is arranged with respect to the cylinder 2 so that the valve body 10b is close to the cylinder bore 6 and the valve shaft portion 10d that rotationally drives the rotary valve 10 is farther from the cylinder bore 6 than the valve body 10b. Is inclined. The rotary valve 10 is made of iron-based metal, for example.

The valve shaft portion 10d is, as shown in FIG.
A valve holder 11 fixed to the cylinder 2 is rotatably supported by screws 13 and the like. Valve holder 11
Is made of aluminum, for example, and has a cylindrical shape with large upper and lower ends. Small diameter portion 11a in the middle of the valve holder 11
That is, a part of the valve holder 11 faces the water jacket 4 which is a space in which the cooling liquid flows. O-ring grooves 11 b are formed on the outer circumference of the upper end and the lower end of the valve holder 11, and an O-ring 15 seals between the valve holder 11 and the cylinder 2.
That is, the water jacket 4 is formed so as to surround the small diameter portion 11 a of the valve holder 11, and cools the rotary valve 10 and the cylinder 2 via the valve holder 11. An oil seal 31 seals between the valve holder 11 and the valve shaft portion 10d.

The valve shaft portion 10d penetrates the cylinder 2 obliquely and protrudes above the cylinder 2 so that the cylinder 2
Above, is connected to the first or second pulleys 19 and 20 of the transmission device 12 via screws 14. The pulleys 19 and 20 described above receive the rotational force from a motor (not shown) to rotate the rotary valve 10 shown in FIG.

Next, an example of the operation of the above configuration will be described. First, when the engine speed is low and low, the rotary valve 10 is held at the position shown, and the auxiliary exhaust passage 9 is closed by the rotary valve 10. Therefore, the exhaust gas G is exhausted only from the main exhaust passage 7, and as is well known, the cross-sectional area of the entire exhaust passage becomes small corresponding to a low speed, and a decrease in output at a low speed is prevented.

After that, when the rotation speed of the engine reaches a predetermined speed, the rotary valve 10 is rotated by the rotation of a motor (not shown). As a result, the auxiliary exhaust passage 9 communicates with the main exhaust passage 7, and exhaust is performed from both exhaust passages 7, 9. Therefore, when the engine speed is high and the engine speed is high, the cross-sectional area of all exhaust passages is large at the high speed and the output is improved as is well known.

In the above structure, the valve holder 11 supporting the rotary valve 10 shown in FIG. 3 is fixed to the cylinder 2, so that the O-ring 15 can seal between the cylinder 2 and the valve holder 11, for example. it can. Therefore, by providing the water jacket 4 around, for example, the small diameter portion 11a of the valve holder 11, the valve body 10b of the rotary valve 10 and the like can be sufficiently cooled via the valve holder 11 and the valve shaft portion 10d. . Further, the outer circumference of the valve shaft portion 10d of the rotary valve 10 is used as the water jacket 4, so that no wasted space is generated and engine performance is improved.

By the way, in the case of the conventional example of FIG. 4, in addition to the upper valve shaft portion 10d, the valve shaft portion 1 below the valve body 10b.
At 0d, the auxiliary valve 10A is pivotally supported on the cylinder 2 and the like. Therefore, the valve shaft portion 1 is provided below the valve body 10b.
Since 0d projects, the valve shaft portion 10d and the scavenging passage 3 in FIG. 1 may interfere with each other, and thus the scavenging passage 3 may not be formed into a smooth shape.

On the other hand, in this embodiment, the upper valve shaft portion 10d is rotatably supported by the long valve holder 11 to support the rotary valve 10 on the cylinder 2. In other words, the other valve shaft portion is not projected from the lower end of the valve body 10b, so that the scavenging passage 3 shown by the broken line is less likely to interfere with the lower end portion of the rotary valve 10, and therefore the scavenging passage 3 has a smooth shape. Can be As a result, the output of the engine is improved.

By the way, in this embodiment, a motor (not shown) is used as a drive source of the drive unit, but in the present invention, the drive unit may be a mechanical drive unit. As a mechanical drive device, when the rotation speed of the crankshaft (not shown) rotates above a predetermined value by the rotation of a governor connected to the crankshaft, the steel balls follow the inclination of the dish-shaped spherical plate. There are known devices that move. (See, for example, JP-A-60-249614).

In the above embodiment, water is flowed in the space 4 in which the cooling liquid flows, but it goes without saying that a cooling liquid other than water may be flowed. Further, although the rotary valve 10 is tilted in the above embodiment, this is not always necessary in the present invention, and the rotary valve 10 may be provided in parallel with the cylinder 1, for example.

As described above, according to the present invention,
Support the cylindrical valve shaft with the cylindrical valve holder, and
Secure both ends of the lube holder to the cylinder through the seal members.
Fit the valve stem into the valve holder and
Can it be supported simply by fitting the lube holder into the cylinder?
It is easy to form a support mechanism for the valve shaft and
There is a seal between the valve holder and the cylinder.
Because it is sealed, it is surely done. Also the valve
The middle part of the holder is exposed to the space where the coolant flows.
Use the space around the auxiliary valve to
It can be cooled sufficiently over
The resulting auxiliary valve can be effectively cooled to improve engine performance.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a two-cycle engine showing an embodiment of the present invention.

FIG. 2 is a plan sectional view.

FIG. 3 is a sectional view of a valve holder.

FIG. 4 is a vertical cross-sectional view showing a conventional support structure for an auxiliary valve.

[Explanation of symbols]

2 ... Cylinder, 4 ... Space (water jacket), 7 ... Main exhaust passage, 9 ... Auxiliary exhaust passage, 10 ... Auxiliary valve (rotary valve), 10d ... Valve shaft part, 11 ... Valve holder.

Claims (1)

[Claims] 1. A main exhaust passage communicating with the inside of a cylinder, an auxiliary exhaust passage connecting the inside of the cylinder and the main exhaust passage as an auxiliary exhaust passage, and an auxiliary valve opening and closing the auxiliary exhaust passage. , A drive device for driving the auxiliary valve in accordance with a change in the rotational speed of the engine 2
Exhaust device for cycle engine with both ends sealed
Cylindrical valve holder fixed to a cylinder through a member supports the cylindrical valve shaft portion of the auxiliary valve, and the intermediate portion of the valve holder is exposed to the space through which the cooling liquid flows. 2 cycles Exhaust system of the engine.