JP2503862Y2 - Engine exhaust system - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust system, and more particularly, to a structure of an exhaust pipe connecting portion in the exhaust system.

[0002]

2. Description of the Related Art The exhaust passage formed in the engine body is
Generally, in a two-stroke engine, it is formed into a cylinder,
In a 4-cycle engine, it is formed in the cylinder head. Also, the opening of the exhaust passage on the combustion chamber side (exhaust port)
In particular, in the case of a two-cycle engine, an oblong shape such as an ellipse or an ellipse is used in consideration of exhaust timing and the like. In that case, the relatively short exhaust passage is also formed to have a laterally long sectional shape as a whole, following the shape of the exhaust port. An exhaust pipe (exhaust pipe) is connected to the outlet side of the exhaust passage. A base is provided at a connection portion of the exhaust pipe with the exhaust passage. References disclosing the conventional structure of such an exhaust device include, for example, Japanese Utility Model Publication No. 60-194122 and Japanese Utility Model Publication No. 1-4346.
There is No. 3 etc.

[0003]

However, in the conventional exhaust system, since the cross-sectional shape of the mouthpiece and the exhaust pipe (cross-sectional shape of the exhaust gas passage) is circular, the exhaust passage of the engine body has a horizontally long cross-sectional shape. In the case where it has, the cross section of the passage changes stepwise at the portion of the mouthpiece (exhaust pipe connecting portion), and the exhaust efficiency may not be sufficiently high. In addition, since the exhaust pipe connecting section has a substantially circular cross section and the vertical dimension is relatively large, it is not possible to sufficiently reduce the overall cylinder height in the case of a two-cycle engine, and the weight is reduced and the primary compression ratio is improved. There is a problem that it is difficult to do. Further, there is a problem that an extra mechanism for circumferential positioning is required at the exhaust pipe connecting portion.

The present invention has been made in view of the above technical problems, and an object of the present invention is to make the flow passage shape of the exhaust pipe connecting portion smooth even if the exhaust passage of the engine body has a horizontally long cross-sectional shape. It is possible to improve the exhaust efficiency, and when connecting the exhaust pipe to the cylinder, it is possible to reduce the overall height of the cylinder, which reduces the size and weight of the engine and improves the primary compression ratio to improve the charging efficiency. It is an object of the present invention to provide an exhaust system for an engine that can be easily improved.

[0005]

This invention Means for solving the problems], in exhaust apparatus for connecting an exhaust pipe to an exhaust passage formed in the engine body, an exhaust passage that will be formed in the engine body, shea
From the exhaust port that opens to the Linda bore to the exhaust pipe connection
Therefore, it has a horizontal major axis and a smooth cross-sectional area.
It is formed with a laterally elongated elliptical cross-sectional shape that slightly increases.
The exhaust pipe connecting portion formed on the engine body has a fixed
Inner diameter part for connection with a predetermined length having a horizontally long elliptical cross-sectional shape
Of the exhaust pipe connected to the engine body.
A fixed airtight fit is fitted to the inner diameter of the exhaust pipe connection at the end.
A die having a laterally oblong cross-sectional shape is fixed, and
The tip of the trachea has a length of about 50 mm to about 500 mm.
Enclosed from the same horizontal cross-sectional shape as the above-mentioned mouthpiece to a normal circular cross-section
With smooth that is formed so as to cross changed configuration to the shape, it is intended to achieve the above object.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 is a schematic horizontal sectional view showing an embodiment of an engine exhaust system to which the present invention is applied, and FIG. 2 is a vertical sectional view taken along line 2-2 in FIG. This embodiment shows a case where the present invention is applied to a two-cycle engine. 1 and 2, a bore 3 in which a piston 2 slides is formed inside a cylinder 1 of a two-cycle engine, and an exhaust passage 4 and a scavenging passage (not shown) are formed in the cylinder 1. A cylinder head 5 is fastened to the upper end of the cylinder 1 in an airtight state, and a combustion chamber 6 is formed between the cylinder head 5 and the piston 2.

The exhaust passage 4 opens in the bore 3 as an exhaust port (exhaust port) 7. In the illustrated example, auxiliary exhaust ports 8 and 8 are formed on both sides of the exhaust port 7, and these exhaust ports 8 and 8 communicate with the middle of the exhaust passage 4 through the auxiliary exhaust passages 9 and 9. . In addition, a control valve (not shown) that is controlled to open and close according to the engine speed is provided in each auxiliary exhaust passage 9, 9.

The lower end of the cylinder 1 is air-tightly connected to a crank case (not shown), and the crank case is provided with an intake port (not shown) for sucking the air-fuel mixture. The scavenging passage is formed so that the crankcase communicates with a predetermined position (not shown) of the bore 3. The air-fuel mixture sucked into the crankcase is subjected to a predetermined compression (primary compression) by the stroke motion of the piston 2, and is supplied into the combustion chamber 6 through the scavenging passage at a predetermined timing. Then, the air-fuel mixture supplied into the combustion chamber 6 is ignited at a predetermined timing, explosive combustion expansion of the air-fuel mixture generates power, and burned exhaust gas (exhaust gas) is opened at a predetermined timing. It is discharged to the outside through the exhaust passage 4.

The cylinder 1, the cylinder head 6 and the crankcase (not shown) constitute a so-called engine body. Therefore, the exhaust passage 4 formed in the cylinder 1 has a laterally long cross-sectional shape. Specifically, the exhaust port 7 has a horizontally long shape, and the outer opening 10 of the exhaust passage 4 has a horizontally long shape with a cross section slightly larger than that of the exhaust port 7, and the exhaust gas has a horizontally long cross section in which the cross-sectional area changes smoothly. It is configured to communicate with each other through the passage 4. This "laterally long shape" refers to a smooth shape (shape without sharp corners) having a lateral dimension larger than the vertical dimension (axial direction of the cylinder 1) including an ellipse, an ellipse, or an oval shape.

At the outer opening 10 of the exhaust passage 4, an exhaust pipe connecting portion 11 having the same laterally long cross-sectional shape as the inner and outer circumferences is formed. On the other hand, the exhaust pipe connecting portion 11 is provided at the tip of the exhaust pipe 12 (the side connected to the exhaust passage 4).
The cylindrical base 13 fitted to the inner diameter of the is fixed (welded or brazed). The inner and outer peripheries of the mouthpiece 13 also have a laterally long cross-sectional shape similar to that of the exhaust pipe connecting portion 11, and can be fitted in an airtight state as shown in the drawing. It should be noted that the outer circumference of the base 13 is filled with O for ensuring airtightness.
Seal members 14, 14 such as rings are attached.

Furthermore, the inner and outer peripheries of the tip 15 of the exhaust pipe 12 also have the same laterally long cross-sectional shape as the base 13. The cross-sectional shape of the exhaust pipe 12 is formed so that the cross-section smoothly changes from the laterally long shape of the tip 15 to the circular shape of the normal portion within the range of the predetermined length L of the tip portion. The length L of the range in which the cross section changes is selected so that the flow of exhaust gas becomes smooth, and can be selected, for example, from about 50 mm to 500 mm.

In this embodiment, as a fixing mechanism for attaching the exhaust pipe 12 to the engine body (cylinder 1 in the illustrated example), as shown in FIG. 2, it is provided at two locations on the outer periphery of the exhaust pipe connecting portion 11. The formed hooking portions 16, 16 and the outer periphery of the exhaust pipe 12 are fixed to corresponding two places (welding, brazing, etc.).
A method is adopted in which tension springs 18 and 18 are mounted between the hooks 17 and 17, and the spring forces of these springs 18 and 18 are used for fixing. As a fixing mechanism for mounting the exhaust pipe 12 to the engine body, other mounting structures such as a method of screwing a mounting flange provided on the engine body side and a flange provided on the exhaust pipe side with a gasket or the like are used. Of course, it can be adopted.

FIG. 3 is a schematic cross-sectional view showing the cross-sectional shape of the flow passage in each part of the exhaust passage and the exhaust pipe in FIG. 3A to 3F are lines A- indicating the cross-sectional position in FIG.
The cross-sectional shape of the part corresponding to each of A-line FF is shown. As is apparent from FIG. 3, in the illustrated exhaust device, the exhaust passage 4 formed in the cylinder 1 has a cross-sectional shape of a horizontally elongated shape such as a horizontally oriented ellipse.
The cross-sectional shape of the exhaust pipe 12 connected to the exhaust passage 4 is a horizontally long shape (substantially the same) corresponding to the shape of the opening 10 of the exhaust passage 4 at the portion of the mouthpiece 13. Further, in the portion of the exhaust pipe 12 itself, in the range of the predetermined length L of the tip portion thereof, the cross-section is smoothly changed from the same cross-sectional shape as the mouthpiece 13 to the shape of the exhaust pipe 12 which is essentially a true circle. Has been done.

According to the embodiment [0014] described above, the cross section of the exhaust passage in the exhaust pipe connecting portion 1 1 and the vicinity thereof in the engine exhaust system, while the horizontally long shape, so to cross changed smoothly in the direction of flow, next The effect like this was obtained. That is, first, the shape of the exhaust passage was made smooth, and the exhaust efficiency could be improved. Secondly, especially in a two-cycle engine, since the vertical dimension of the connecting portion to the cylinder 1 can be reduced, it is possible to drive the working surface of the cylinder base (the mating surface with the upper end surface of the crankcase) upward. This enables the size and weight of the cylinder to be reduced by reducing the height of the cylinder and the stroke / bore ratio to be set with a high degree of freedom, and the volume of the crankcase can be reduced. It is now possible to easily improve efficiency. Thirdly, since the connecting portion of the exhaust pipe 12 has a horizontally long shape, it becomes possible to easily and accurately perform circumferential positioning when attaching the exhaust pipe.

In the above-described embodiment, the case where the exhaust pipe 12 is connected to the cylinder 1 as in the 2-cycle engine has been described, but the present invention is as in the 4-cycle engine.
The same can be applied to the case where the exhaust pipe is connected to the cylinder head, and the same effect can be achieved.

[0016]

As apparent from the above description, according to the invention] According to the present invention, the exhaust passage in the exhaust system of the engine connecting the exhaust pipe to the exhaust passage formed in the engine body, that will be formed in the engine body, a cylinder bore Exhaust opening to
Extend the horizontal major axis from the port to the exhaust pipe connection.
It has an oblong elliptical shape with a slightly increased cross-sectional area
Before being formed into a cross-sectional shape and into the engine body
Note that the exhaust pipe connection part has a certain oblong cross-sectional shape.
A predetermined length of the connecting inner diameter portion is formed,
At the tip of the exhaust pipe connected to the main body,
Has a constant oblong cross-sectional shape that is airtightly fitted to the inner diameter
The mouthpiece is fixed and the tip of the exhaust pipe is about 50m.
Horizontal length similar to the above-mentioned mouthpiece in the range of m to about 500 mm
Smooth cross-section change from cross-sectional shape to normal circular cross-sectional shape
Since the formed have that configured to, even if the cross-sectional shape of the exhaust passage of the engine body is horizontally long elliptical, it can exhaust flow of the exhaust pipe connecting portion to smoothly increase the exhaust efficiency, excess The exhaust pipe can be easily positioned in the circumferential direction without the need for a structure, and the overall height of the cylinder is made smaller, making it easier to reduce the size and weight of the engine and to improve the filling efficiency by improving the primary compression ratio. An exhaust system for an engine is provided. 』

[Brief description of drawings]

FIG. 1 is a schematic horizontal sectional view schematically showing a main part of an embodiment of an exhaust system for an engine to which the present invention is applied.

2 is a vertical cross-sectional view taken along the line 2-2 in FIG.

3 is a schematic cross-sectional view showing the cross-sectional shape of the flow passage of each part of the exhaust passage and the exhaust pipe shown in FIG.

[Explanation of symbols]

 1 Cylinder 2 Piston 3 Bore (Cylinder) 4 Exhaust Passage 5 Cylinder Head 6 Combustion Chamber 7 Exhaust Port 10 Outer Opening of Exhaust Passage 11 Exhaust Pipe Connection (Cylinder) 12 Exhaust Pipe 13 Base (Exhaust Pipe) 15 Exhaust Pipe Engine Side tip

Claims (1)

(57) [Scope of utility model registration request] In the exhaust device according to claim 1 engine for connecting the exhaust pipe to the exhaust passage formed in the engine body, an exhaust passage that will be formed in the engine body (4), bore
From the exhaust port (7) opening to (3) to the exhaust pipe connection
(11) Has a horizontal major axis and has a cross-sectional area
Formed with a horizontally elongated elliptical cross-section that increases slightly
And the exhaust pipe connecting portion formed in the engine body
In (11), there is a cross-sectional shape of a certain oblong ellipse.
A constant length inner diameter for connection is formed on the engine body.
The exhaust pipe connecting part is provided at the tip of the exhaust pipe (12) to be connected.
A certain oblong elliptical cut that is airtightly fitted to the inner diameter of (11).
The exhaust pipe is fixed with a base (13) having a surface shape.
The tip of (12) has a length of about 50 mm to about 500 mm.
Within the range of the same as that of the above-mentioned base (13),
Formed so that the cross-section changes smoothly to a regular circular cross-section
The exhaust apparatus according to which do characterized Rukoto is.