JP2959323B2 - Exhaust pipe structure of internal combustion 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 pipe structure of an internal combustion engine, and more particularly to an axial end structure of a double pipe exhaust pipe.

[0002]

2. Description of the Related Art In order to release a difference in thermal expansion between inner and outer pipes, a metal mesh interposed between the inner and outer pipes at the other end is used, while the exhaust pipe of the internal combustion engine is a double pipe. A structure in which the inner and outer tubes can be slid via a hole is known (for example, Japanese Utility Model Laid-Open No. 63-170519). In this conventional structure, the inner tube is enlarged at the slidable end side,
It is engaged with the stopper.

[0003]

However, since the inner tube comes into direct contact with the exhaust gas, it is hotter than the outer tube. The inner tube is
If the portion of the inner tube that has not expanded has come to the position of the metal mesh when it expands in the axial direction relatively to the outer tube due to thermal expansion, the metal mesh falls off or the inner tube cannot be supported. There is a risk.

An object of the present invention is to provide a double exhaust pipe structure having an inner pipe and an outer pipe which are slidable at one end and slidable at the other end.
It is an object of the present invention to provide an exhaust pipe structure that can maintain the support of the inner pipe from the outer pipe even when the inner pipe extends by thermal expansion relative to the outer pipe.

[0005]

An exhaust pipe structure for an internal combustion engine according to the present invention for achieving the above object has the following structure. That is, the inner tube and the outer tube are joined at one end in the axial direction of the inner tube and the outer tube, and the inner tube and the outer tube are connected between the two tubes at the other end in the axial direction. In the exhaust pipe structure of the internal combustion engine, which is slidable via a support member mounted on the inner pipe and the outer pipe are both reduced in diameter at the other end side from the mounting portion of the support member, An exhaust pipe structure for an internal combustion engine, wherein a clearance between the inner pipe and the outer pipe at the reduced diameter portion is equal to or less than the thickness of the support member.

[0006]

In the exhaust pipe structure of the internal combustion engine of the present invention, the inner and outer pipes are both reduced in diameter at the slidable end side, and the clearance of the reduced diameter portion is less than the thickness of the support member. Even so, the support member is prevented from moving relative to the reduced diameter portion, and the support of the inner tube from the outer tube does not come off or loosen.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust pipe structure for an internal combustion engine according to a preferred embodiment of the present invention will be described below with reference to the drawings. FIG.
In addition, a not-shown horizontal V-type engine (an engine whose longitudinal direction extends in the left-right direction of the vehicle, has left and right banks, and has a V-shape when the engine is viewed in the longitudinal direction)
1 shows the entire exhaust pipe including a front pipe connected to the exhaust pipe. 1, 2 are flanges for attaching to exhaust manifolds (not shown) of both the left and right banks, 3 and 4 are exhaust pipes from both banks, 5 is a junction where exhaust gases from both banks are merged, and 6 is a merged portion. A conduit 7 for guiding the exhaust gas to a downstream such as a catalytic converter (not shown) is a flexible pipe for absorbing the thermal expansion between the two banks.

FIG. 2 is an enlarged view of the end of the exhaust pipe 4 on the flange 2 side, and FIG. 3 is an enlarged view of the end of the exhaust pipe 4 on the flexible pipe 7 side. The exhaust pipes 3 and 4 have a double pipe structure of an inner pipe 11 and an outer pipe 12. The inner tube 11 has a small thickness (for example, 0.8 mm in thickness) in order to reduce the heat capacity and suppress a decrease in the exhaust gas temperature when the engine is warmed up, and the outer tube 12 has a large thickness in order to maintain strength. (For example, a thickness of 1.2 mm).

The outer tube 12 is reduced in diameter at its front and rear ends, and its front end (on the side of the flanges 1 and 2) is in close contact with the outer peripheral surface of the inner tube 11 and is fixed to the flanges 1 and 2 together with the inner tube 11 by welding. . The rear end (on the side of the flexible pipe 7) is welded and fixed to the flexible pipe 7 by the outer pipe 12 alone.

A wire mesh ring 13 as a support member is provided between the inner and outer pipes at a position farther from the flexible pipe side end than the reduced diameter portion of the outer pipe 12 at the rear end,
The clearance between the inner and outer pipes is secured, and the exhaust gas is prevented from flowing into the space between the inner and outer pipes. The wire mesh ring 13 is fixed to only one of the inner pipe 11 and the outer pipe 12 by spot welding or the like, and is slidable with the other. With this slide structure, it is possible to absorb the difference in the amount of thermal expansion due to the temperature difference between the inner and outer tubes by the axial movement of the inner tube 11 with respect to the outer tube 12. The support member (wire mesh ring) is preferably provided on the downstream side in consideration of deterioration due to the exhaust temperature of the support member.

The rear end of the inner pipe 11 (the flexible pipe 7
Side) is reduced in diameter, like the outer tube 12, and extends into the flexible pipe 7, avoiding gas contact with the joint between the outer tube 12 and the flexible pipe 7, and transferring heat to the outer tube 12. Minimized. In addition, with a contraction tube having such a length, almost no increase in engine back pressure occurs.

The clearance between the inner pipe 11 and the outer pipe 12 at the reduced diameter portion at the rear end is set to be equal to or less than the thickness of the wire mesh ring 13 as a support member.
In cooperation with the diameter reduction toward the tip of the outer tube 12, even when the wire mesh ring 13 is not fixed to one of the inner and outer tubes when the inner and outer tubes are relatively displaced in the axial direction, the wire mesh ring 13 is removed.
Is prevented from shifting toward the reduced diameter portion of the inner and outer tubes. Further, as shown in FIG.
Even if it ends near the diameter reduction start point, there is almost no effect on the function, and therefore it may be as shown in FIG. In this case, the displacement of the wire mesh ring 13 is prevented only by reducing the diameter of the outer tube 12.

Next, the operation will be described. During operation of the engine, the inner pipe 11 comes into contact with high-temperature exhaust gas,
Is 200 ° C. to 300 ° C. higher than the outer tube 12. The inner pipe 11 is fixed to the outer pipe 12 at one end on the flange side, and is slidable at the other end, so that the inner pipe 11 moves relatively to the outer pipe 12 at the end on the slide side. Accordingly, the wire mesh ring 13 as a support member also moves relatively in the axial direction with respect to one of the inner tube 11 and the outer tube 12 or both when the wire mesh ring 13 and the inner and outer tubes are not fixed. While the cycle of stopping and starting the engine is repeated, even if the wire mesh ring 13 moves from the initial position between the inner and outer pipes to the side deviating from the inner and outer pipes, the clearance of the inner and outer pipes of the reduced diameter portion is increased. Movement in the direction in which the ring 13 is not more than the thickness of the ring 13 and the reduced diameter of the outer tube are hindered and prevented from being removed.

Further, since the outer pipe 12 is reduced in diameter to the outer diameter surface of the inner pipe 11 and the diameter of the inner pipe 11 is not reduced except at the reduced diameter portion, there is almost no increase in engine back pressure and almost no decrease in engine output. Absent. Although the diameter of the inner tube 11 is reduced at the reduced diameter portion in FIG. 3, the length thereof is short, so that the engine back pressure hardly increases.

Further, the conventional front pipe is fixed to a flange and a flexible pipe with a diameter based on the inner pipe, and an insulator with a heat insulating material attached around its outer circumference to a diameter equivalent to the outer pipe. The insulator has several flanges along its length, where bolts and nuts cover the inner tube. Therefore, many considerations are required in terms of mounting, pipe path, and interference with other components. However, if the outer tube 12 is formed of a pipe and is directly joined to a flange or a flexible pipe with the outer tube 12 as in the structure of the present invention, only the pipe diameter is a constraint on mounting, and this pipe diameter is also a conventional pipe diameter. Since the front pipe insulator is equal to or smaller than the front pipe insulator, the degree of freedom in design is increased, and the increased degree of design freedom is improved by engine performance (increased pipe bending radius and reduced back pressure), vibration and noise performance Can be distributed to improvement).

In the type in which the inner pipe 11 is reduced in diameter and extended inside the flexible pipe as shown in FIG. 3, there is no direct gas contact with the band portion of the flexible pipe, that is, the temperature does not rise so much. In addition, the reliability of the joint between the bellows pipe and the blade is improved, and heat damage to peripheral components is eliminated.

The pressure pulsation to the wire mesh ring 13 is also attenuated because the distance from the end of the inner tube to the wire mesh ring 13 is increased, and the settling of the wire mesh ring 13 is reduced, thereby improving reliability. I do.

[0018]

According to the present invention, the inner and outer tubes are both reduced in diameter at the (flexible side) end, and the clearance between the inner and outer tubes is reduced by the thickness of the support member (wire mesh ring) at the reduced diameter portion. As described below, the support member is prevented from moving to the end of the exhaust pipe, and the reliability of the slidable support structure for the inner pipe is increased.

[Brief description of the drawings]

FIG. 1 is a front view of an exhaust pipe structure of an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a front view showing a part of the end of the exhaust pipe of FIG.

FIG. 3 is a cross-sectional view of a flexible pipe side end of the exhaust pipe of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 flange 2 flange 3 exhaust pipe 4 exhaust pipe 7 flexible pipe 11 inner pipe 12 outer pipe 13 support member (wire mesh ring)

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01N 7/08

Claims (1)

(57) [Claims] An inner tube and an outer tube are joined at one end in the axial direction of the inner tube and the outer tube, and the inner tube and the outer tube are connected at the other end in the axial direction. In an exhaust pipe structure of an internal combustion engine that is slidable via a support member mounted between pipes, the inner pipe and the outer pipe are both reduced in diameter at the other end side from a mounting portion of the support member. An exhaust pipe structure for an internal combustion engine, wherein a clearance between the inner pipe and the outer pipe at the reduced diameter portion is equal to or less than the thickness of the support member.