JPS61275519A - Exhaust pipe structure in exhaust device - Google Patents

Abstract

PURPOSE:To improve exhaust efficiency, by joining an inner pipe to an outer pipe at an inlet end of an exhaust pipe, directly contacting a gasket with the inlet end, and tapering an inner surface of the inner pipe at its inlet portion from the gasket to a position of an elementary pipe diameter. CONSTITUTION:A combustion chamber 5 is formed at an upper portion of a cylinder 2, and is communicated through an exhaust valve 6 to an exhaust passage 7 in a cylinder head 4 which passage is open at an exhaust opening 7a. The exhaust opening 7a is connected through a gasket 8 to an exhaust pipe 9. The exhaust pipe 9 is constructed in a double structure having an inner pipe 9i and an outer pipe 9o with an air layer defined therebetween. The inner pipe 9i is diverged at its inlet portion to form a tapered portion 10, and is joined by spot welding 11 to the outer pipe 9o at an inlet end. Thus, an inner surface of the inner pipe 9i at the inlet portion is tapered at 10 to gradually converge a sectional area of the exhaust passage from the gasket 8 to the position of an elementary pipe diameter De.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exhaust pipe structure of an exhaust system attached to a motorcycle or the like.

[Prior art]

Some exhaust pipes installed on motorcycles have a double structure consisting of an inner pipe and an outer pipe with an air layer in between. When the exhaust pipe has such a double structure, the outer pipe is prevented from overheating due to the heat insulating effect of the air layer, and discoloration of the plating or painting applied to the surface of the outer pipe can be prevented.

In the conventional double-structured exhaust pipe 29, as shown in FIG. 2, the inlet side of the inner pipe 29i is expanded via a step 34, and the expanded portion 30 is in contact with the inner surface of the outer pipe 29o. , and the ends of the flanges 32 covering the outside thereof are bead welded 31. The end of the flange 32 of the exhaust pipe 29 was brought into contact with the exhaust lower a opening in the cylinder head via the gasket 28, and was pressed and fixed by the mounting bracket 33.

However, according to the exhaust pipe 29, the base pipe diameter De of the inner pipe 291 and the diameter De' of the expanded portion 30 suddenly change through the step 34, and the inner diameter Db of the weld bead 31 also changes from the diameter De. and Da'. Therefore,
Exhaust gas discharged from the exhaust lower a to the exhaust pipe 29 experiences flow resistance due to a passage cross-sectional area that suddenly increases or decreases, causing a reduction in exhaust efficiency.

In addition, the step 34 is weakened due to localized large distortion due to processing deformation, and the high temperature exhaust gas is likely to shine directly on that area, which further tends to cause a decrease in strength. was.

[Purpose of the invention]

An object of the present invention is to provide an exhaust pipe structure that improves exhaust efficiency by making exhaust gas flow smoothly in a double-structured exhaust pipe, and improves the durability of the exhaust pipe.

[Structure of the invention]

The present invention achieves the above object by making the exhaust pipe a double structure with an air layer between the inner pipe and the outer pipe, and the inlet end of the exhaust pipe is
In an exhaust device connected to an exhaust port opening in a cylinder head via a gasket, the inner pipe and the outer pipe are joined to each other at an inlet end of the exhaust pipe, and the inlet end is brought into direct contact with the gas get, and The inner surface of the inner tube on the artificial side is tapered from the gasket to the diameter of the original tube.

〔Example〕

The present invention will be explained below with reference to embodiments shown in the drawings.

In FIG. 1, 1 is an engine mounted on a motorcycle with its head tilted forward, 2 is its cylinder, 3 is a piston, and 4 is a cylinder head. A combustion chamber 5 is provided in the upper part of the cylinder 2, and an exhaust passage 7 communicates with the combustion chamber 5 through an exhaust valve 6 provided therein. An exhaust pipe 9 is connected to an exhaust lower a through which an exhaust passage 7 opens from the cylinder head 4 via a gasket 8.

The exhaust pipe 9 has a double structure including an inner pipe 91 and an outer pipe 9o with an air layer interposed therebetween. Of both the inner and outer pipes, inner pipe 9
1 is widened at its inlet side to form a tapered portion 10, and is spot welded 11 to the outer tube 9o at the inlet end. On the other hand, a ring-shaped flange 12 is welded to the outer periphery of the outer tube 9o. The exhaust pipe 9 configured in this manner is mounted so that its inlet end is in direct contact with the gasket 8 and is strongly pressurized toward the gasket 8 by the mounting bracket 13 engaged with the flange 12. ing.

The inner pipe 91 of the exhaust pipe 9 installed in this manner has a tapered portion 10 on its inlet-side inner surface, so that the cross-sectional area of the exhaust gas passage is smooth from the position of the gasket 8 to the base pipe diameter De. It has a tapered shape with a convergence change. Therefore, the exhaust gas discharged from the exhaust passage 7 to the exhaust pipe 9 flows smoothly and is not subjected to large flow resistance unlike the conventional double-structured exhaust pipe.

Therefore, exhaust efficiency can be improved and engine performance can be improved.

Further, since the inner pipe 91 having the above structure does not have a deformed part where strain is locally concentrated unlike a conventional exhaust pipe, the strength does not decrease by 4 degrees due to high temperature exhaust gas.

〔Effect of the invention〕

As described above, the present invention provides an exhaust pipe in which the exhaust pipe has a double structure with an air layer between the inner pipe and the outer pipe, and the inlet end of the exhaust pipe is connected to the exhaust port opening in the cylinder head via a gasket. In the device, the inner tube and the outer tube are joined to each other at the inlet end of the exhaust pipe, the inlet end is brought into direct contact with the gasket, and the inner surface on the inlet side of the inner tube is at the base pipe diameter from the gasket. Since the exhaust gas is tapered and converged, the flow of exhaust gas discharged from the exhaust port to the exhaust pipe is smoothed, thereby improving exhaust efficiency.

In addition, the inner pipe has 2, like a conventional double structure exhaust pipe,
Since there are no deformed parts where strain is locally concentrated,
The durability of the exhaust pipe can be improved without causing a decrease in strength, which occurs when the local strain is exposed to high-temperature exhaust gas.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing the main parts of an exhaust pipe according to an embodiment of the present invention provided in a motorcycle engine, and FIG. 2 is a longitudinal cross-sectional view showing the main parts of a conventional exhaust pipe provided in a motorcycle engine. It is a diagram. 1-engine, 7--exhaust passage, 7a--exhaust port, 8--gasket, 9-exhaust pipe, 91-inner pipe,
9o--outer pipe, 10--tapered part, De--original pipe diameter.

Claims (1)

[Claims] The exhaust pipe has a double structure with an air layer between the inner and outer pipes,
In an exhaust system in which the inlet end of the exhaust pipe is connected to an exhaust port opening in the cylinder head via a gasket, the inner pipe and the outer pipe are joined to each other at the inlet end of the exhaust pipe, and the inlet end is connected to the gasket. in direct contact with the
An exhaust pipe structure for an exhaust device, characterized in that an inner surface on the inlet side of the inner pipe is tapered and converged from the gasket to the diameter of the base pipe.