JPH06299848A - Exhaust pipe structure for internal combustion engine - Google Patents

Abstract

PURPOSE:To keep supporting of an inner pipe by an outer pipe in a double exhaust pipe structure even when relative motion is generated eut to thermal expansion difference between an inner and an outer pipes. CONSTITUTION:A double exhaust pipe has one end being fixed and the other end being slidable. An inner pipe 11 and an outer pipe 12 are reduced in their diameters at the end portion on the sliding side. The clearance between the inner and outer pipes at the diameter-reduced portion is not more than the thickness of a wire mesh ring 13 installed between the inner and outer pipes. In the above exhaust pipe structure for an internal combustion engine, the wire mesh ring 13 is not demounted from a space between the inner and outer pipes 11, 12 even when relative motion due to thermal expansion is repeated.

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 an exhaust pipe composed of a double pipe.

[0002]

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

[0003]

However, since the inner pipe is in direct contact with the exhaust gas, it becomes hotter than the outer pipe. The inner tube
When it expands in the axial direction relative to the outer pipe due to thermal expansion, if the unexpanded part of the inner pipe comes to the position of the metal mesh, the metal mesh will fall off or the inner pipe cannot be supported. There is a risk.

An object of the present invention is to provide a dual exhaust pipe structure having inner and outer pipes which are joined at one end and slidable at the other end,
An object of the present invention is to provide an exhaust pipe structure capable of maintaining the support of the inner pipe from the outer pipe even when the inner pipe expands due to thermal expansion relative to the outer pipe.

[0005]

An exhaust pipe structure of an internal combustion engine according to the present invention for achieving the above object comprises the following structure. That is, a double pipe of an inner pipe and an outer pipe is formed, and the inner pipe and the outer pipe are joined at one axial end of the double pipe, and the inner pipe and the outer pipe are located between the two pipes at the other axial end. In an exhaust pipe structure of an internal combustion engine that is slidable via a support member mounted on, the inner pipe and the outer pipe are both reduced in diameter on 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 is equal to or less than a thickness of the support member in the reduced diameter portion.

[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 on the slidable end side, and the clearance of the reduced diameter portion is set to be equal to or less than the thickness of the support member, so that the inner pipe is elongated. However, the support member is prevented from moving relatively to the reduced diameter portion, and the support of the inner pipe from the outer pipe is not disengaged or loosened.

[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. Figure 1
A horizontal V-type engine (not shown) (engine whose longitudinal direction extends in the left-right direction of the vehicle and has left-right banks and which is V-shaped when the engine is viewed in the longitudinal direction)
The whole exhaust pipe which consists of the front pipe connected to is shown. Reference numerals 1 and 2 are flanges for attaching to the exhaust manifolds (not shown) of both the left and right banks, 3 and 4 are exhaust pipes from both banks, 5 is a confluence section for converging exhaust gas from both banks, and 6 is confluence. A conduit 7 that guides the exhaust gas to the downstream such as a catalytic converter (not shown) is a flexible pipe for absorbing the thermal expansion amount between both banks.

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

The outer pipe 12 has a reduced diameter at its front and rear ends, and its front end (on the side of the flanges 1 and 2) is closely attached to the outer peripheral surface of the inner pipe 11 and is welded and fixed to the flanges 1 and 2 together with the inner pipe 11. . Further, the rear end portion (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 supporting member is provided between the inner and outer pipes at a portion 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 to the other. With this slide structure, it is possible to absorb the difference in 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 exhaust temperature of the support member.

The rear end of the inner pipe 11 (the flexible pipe 7
Like the outer tube 12, the side) has a reduced diameter and extends into the flexible pipe 7 to prevent gas from hitting the joint between the outer tube 12 and the flexible pipe 7 and to transfer heat to the outer tube 12. Keep it to a minimum. Further, if the contracted tube has such a length, an increase in engine back pressure hardly occurs.

The clearance between the inner pipe 11 and the outer pipe 12 at the reduced diameter portion of the rear end portion is set to be equal to or less than the thickness of the wire mesh ring 13 which is a supporting member.
The wire mesh ring 13 cooperates with the diameter reduction toward the tip of the outer pipe 12 to prevent the wire mesh ring 13 from being fixed to one of the inner and outer pipes when the inner and outer pipes are relatively displaced in the axial direction.
Is prevented from being displaced toward the reduced diameter portion of the inner and outer tubes. Further, as shown in FIG.
Even if it is ended near the diameter reduction start point of, since it has almost no effect on the function, it may be made as shown in FIG. In this case, the wire mesh ring 13 is prevented from being displaced only by reducing the diameter of the outer tube 12.

Next, the operation will be described. When the engine is operating, the inner pipe 11 comes into contact with high-temperature exhaust gas, so the inner pipe 11
Is higher than the outer tube 12 by 200 ° C to 300 ° C. 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 relative to the outer pipe 12 at the end portion on the slide side. Along with this, the wire mesh ring 13, which is a support member, also moves axially relative to one of the inner pipe 11 and the outer pipe 12, or when the wire mesh ring 13 and the inner and outer pipes are unfixed. While the engine stop and start cycles are repeated, even if the wire mesh ring 13 tries to move from the initial position between the inner and outer pipes to the side away from the inner and outer pipes, the clearance of the inner and outer pipes in the reduced diameter portion causes the wire mesh. The fact that the thickness of the ring 13 is less than or equal to the thickness of the ring 13 and the reduced diameter of the outer tube impedes the movement in the releasing direction and prevents the detaching.

Further, since the outer pipe 12 is reduced to the outer diameter surface of the inner pipe 11 and the diameter of the inner pipe 11 is not reduced except for the reduced diameter portion, there is almost no increase in engine back pressure and almost no decrease in engine output. Absent. In FIG. 3, the diameter of the inner pipe 11 is reduced at the reduced diameter portion, but since the length is short, the engine back pressure is hardly increased.

Further, the conventional front pipe is fixed to the flange and the flexible pipe with a diameter of the inner pipe standard, and an insulator having a heat insulating material is attached to the outer periphery thereof with a diameter corresponding to the outer pipe. The insulator has several flanges along its length, and the inner tube is covered with bolts and nuts there. Therefore, many considerations are required in terms of mounting, pipe paths, and interference with other parts. However, if the outer cylinder 12 is formed of a pipe and is directly joined to the flange or the flexible pipe by the outer pipe 12 as in the structure of the present invention, only the pipe diameter is a constraint condition for mounting. The degree of freedom in design is increased because it is equal to or smaller than the insulator of the front pipe, and the increased degree of freedom in design is achieved by engine performance (increasing the bend R of the pipe to reduce back pressure), vibration, and noise performance (optimizing the position of the front pipe stay). It is possible to divert 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. The reliability of the joint between the bellows pipe and the braider is improved, and heat damage to peripheral parts is eliminated.

Further, the pressure pulsation on the wire mesh ring 13 is also attenuated because the distance from the end of the inner pipe to the wire mesh ring 13 is long, and the fatigue of the wire mesh ring 13 is reduced, so that the reliability is improved. To do.

[0018]

According to the present invention, both the inner and outer pipes are reduced in diameter at the ends (on the flexible side), and the clearance between the inner pipe and the outer pipe 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 portion of the exhaust pipe, and the reliability of the slidable support structure for the inner pipe is increased.

[Brief description of drawings]

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

FIG. 2 is a front view showing a part of a flange-side end portion of the exhaust pipe of FIG. 1 in a sectional view.

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

[Explanation of symbols]

 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)

Claims (1)

[Claims] 1. A double pipe having an inner pipe and an outer pipe, wherein the inner pipe and the outer pipe are joined at one axial end of the double pipe and the inner pipe and the outer pipe are joined at the other axial end. In an exhaust pipe structure of an internal combustion engine, which is slidable via a support member mounted between pipes, the inner pipe and the outer pipe are both reduced in diameter on the other end side with respect to the mounting portion of the support member. The exhaust pipe structure of the internal combustion engine, wherein the clearance between the inner pipe and the outer pipe is equal to or less than the thickness of the support member at the reduced diameter portion.