JP2023151919A - Exhaust device - Google Patents

Abstract

To provide an exhaust device which enables an insulator to be held with an exhaust pipe without using a fastening component and can suppress a decrease in heat insulation effect.SOLUTION: An exhaust device comprises an exhaust pipe of an internal combustion engine mounted on a vehicle and an insulator which covers at least a portion of an outer circumference of the exhaust pipe. A heat insulation material is filled in a gap between the exhaust pipe and the insulator. The insulator is held with the heat insulation material. At least portions of the exhaust pipe and the insulator in a pipe line direction have non-circular cross sections with a maximum diameter of an inner periphery of the exhaust pipe larger than a minimum diameter of an outer periphery of the insulator.SELECTED DRAWING: Figure 2

Description

The present invention relates to an exhaust system for a vehicle equipped with an internal combustion engine, and more particularly to an exhaust system including an exhaust pipe and an insulator disposed to block at least a portion of radiant heat from the exhaust pipe.

The exhaust pipe of a vehicle equipped with an internal combustion engine becomes extremely hot due to the passage of high-temperature exhaust gas generated by burning fuel within the cylinder. Therefore, the surrounding members of the exhaust pipe are exposed to high heat due to radiant heat from the high-temperature exhaust pipe, which may lead to deformation or damage.

Therefore, an exhaust pipe is conventionally known that has a heat shielding structure that blocks radiant heat so as to cover a heat source with a heat insulator (hereinafter referred to as an insulator) disposed on the outer circumferential side of the exhaust pipe.

For example, the exhaust pipe includes an exhaust pipe with a flat part formed on a part of the outer periphery and an insulator arranged to cover the outer periphery, and the insulator is an exhaust pipe insulator that is directly fastened to the exhaust pipe body with a fixing clamp. A fixing clamp structure is described in Patent Document 1.

The exhaust pipe has a non-circular cross-sectional shape and an insulator arranged to cover the outer peripheral surface of the exhaust pipe. A retained exhaust system device for an internal combustion engine is described in Patent Document 2.

According to each of the configurations described in Patent Document 1 and Patent Document 2, by fixing the insulator to the fixed portion of the exhaust pipe or peripheral member using a fastening component, a stable heat shielding effect can be maintained. It is said that

The insulators described in Patent Document 1 and Patent Document 2 are fixed to the exhaust pipe or surrounding members using fastening parts, whereas the insulators are fixed to the exhaust pipe without using fastening parts. An exhaust system is described in Patent Document 3. The exhaust pipe with a circular cross-section described in Patent Document 3 is provided with a bracket that projects outward in the radial direction of the exhaust pipe by welding or the like, and is arranged to cover the bracket and the outer peripheral surface of the exhaust pipe. The insulator, which has a circular cross-sectional shape, is fixed by spot welding.

Japanese Patent Application Publication No. 2006-300003 Japanese Patent Application Publication No. 2019-074039 JP2021-076045A

According to the configuration described in Patent Document 3 mentioned above, by fixing the exhaust pipe and the insulator without using fastening parts, the number of members required for fixing can be reduced, and fastening parts are not required. Therefore, it is possible to suppress abnormal noise caused by contact between members and improve quietness. However, the bracket that fixes the exhaust pipe and the insulator tends to transfer heat from the exhaust pipe to the insulator, which means that the heat shielding effect may not be sufficiently exerted.

In addition, the brackets that protrude outward in the radial direction of the exhaust pipe tend to interfere with surrounding parts of the exhaust pipe due to vehicle vibration, and the insulators and brackets are subjected to heavy loads due to repeated high temperatures and cooling, and the above interference There is a risk of damage due to the load.

The present invention has been made in view of the above-mentioned technical problem, and provides an exhaust device that can hold an insulator in an exhaust pipe without using fastening parts, and can suppress a decrease in heat shielding effect. The purpose is to

In order to achieve the above object, the present invention provides an exhaust system including an exhaust pipe of an internal combustion engine mounted on a vehicle, and an insulator that covers at least a part of the outer peripheral surface of the exhaust pipe, A heat shielding agent is interposed between the pipe and the insulator, and the insulator is held by the heat shielding agent, and at least one portion of the exhaust pipe and the insulator in the respective pipe direction. The exhaust pipe has a non-circular cross-sectional shape, and the maximum diameter of the outer peripheral surface of the exhaust pipe is larger than the minimum diameter of the inner peripheral surface of the insulator.

According to the exhaust device of the present invention, the heat shielding agent sealed in a compressed state is interposed in the gap between the exhaust pipe and the insulator, and the insulator can be held by the repulsive force of the heat shielding agent. . Furthermore, since the insulator does not require a holding member such as a bracket or a fastening component, it is difficult to transmit heat from the exhaust pipe to the insulator. Therefore, a decrease in heat shielding effect can be suppressed.

On the other hand, the repulsive force of the heat shielding agent generally decreases at high temperatures due to thermal deformation or changes in the degree of compression, so the decrease in the repulsive force of the heat shielding agent causes a gap between the heat shielding agent and the insulator. This may occur, or the heat shield may peel off, making it impossible to hold the insulator. In addition, when vibrations from the vehicle are transmitted to the insulator through the exhaust pipe, rotational movement occurs in the circumferential direction of the insulator, causing the exhaust pipe and insulator to separate without being held together by the heat shielding agent. , there is a risk of damage due to contact or interference with surrounding members, or unintended rotational movement of the device itself. Therefore, at least a portion of the exhaust pipe and the insulator have a non-circular cross-sectional shape, and the maximum diameter of the outer circumference of the exhaust pipe is larger than the minimum diameter of the inner circumference of the insulator, thereby preventing unintentional rotation of the insulator from the outer circumference of the exhaust pipe. It can be stopped by touching the surface and will not continue to rotate. Therefore, the rotational movement of the insulator is restricted in the heat shield interposed between the exhaust pipe and the insulator, so that peeling and separation can be suppressed. Therefore, even if the repulsive force of the heat shielding agent decreases due to high temperatures or vibrations of the vehicle are transmitted to the exhaust system, the exhaust pipe and insulator can be maintained, and in other words, the decrease in heat shielding effect can be suppressed. can.

FIG. 2 is a schematic diagram for explaining an example of the configuration of an exhaust device according to the present invention. FIG. 3 is a cross-sectional view for explaining the configuration of an exhaust pipe and an insulator in the present invention. FIG. 3 is a cross-sectional view for explaining the operation when the insulator in this invention rotates.

An exhaust system in an embodiment of the present invention will be specifically described with reference to the drawings. Note that this invention is not limited to the embodiments described below.

FIG. 1 is a schematic diagram showing an example of the configuration of an exhaust system 1 in an embodiment of the present invention. The exhaust system 1 includes an exhaust pipe 2 and a heat insulator 3 (hereinafter referred to as the insulator 3), and collects exhaust gases discharged from each cylinder of an internal combustion engine (not shown) mounted on a vehicle. An exhaust manifold (not shown) communicates with a muffler (not shown) that reduces noise generated when exhaust gas is discharged to the outside.

The exhaust pipe 2 has support portions 4 formed at each of its upstream and downstream ends, and a pipe portion 5 between the support portions 4 .

Fixing flanges 6 are formed on the support parts 4 on the upstream and downstream sides of the exhaust pipe 2, respectively, and in the example in FIG. Furthermore, the flange 6 on the downstream side and a member (not shown) that continues to the muffler are connected. Therefore, the exhaust gas that has passed through the exhaust manifold flows in from the direction of arrow B, passes through the pipe portion 5 of the exhaust pipe 2, and is discharged in the direction of arrow C to communicate with the muffler. Note that the exhaust pipe 2 may have a bent portion 7 that changes the flow direction of the exhaust gas, and in the example shown in FIG. 1, the bent portion 7 is provided in the central portion of the exhaust pipe 2. Further, inside the exhaust pipe 2, an exhaust gas purification device such as a catalytic converter or a DPF (particulate matter filter), which is not shown, may be provided.

The insulator 3 is provided so as to cover at least a portion of the outer circumferential surface 8 of the exhaust pipe 2 in the circumferential direction as a heat shielding measure for a portion that becomes particularly high temperature, such as the above-mentioned catalyst. An example of the insulator 3 shown in FIG. 1 covers the entire circumference of the exhaust pipe 2 from the upstream support part 4 to between the bent part 7 of the pipe part 5 and the downstream support part 4. . Note that the insulator 3 may be an exterior pipe and may include a sensor for an exhaust system.

FIG. 2 is a diagram for explaining the configuration of the exhaust pipe 2 and the insulator 3 in the present invention, and is a cross-sectional view taken along arrow A in FIG. 1 and viewed on the upstream side.

In the example shown in FIG. 2, the exhaust pipe 2 has an ellipse that is long in the vertical direction in FIG. It is composed of an elliptical cross section.

In a gap D between the outer circumferential surface 8 of the exhaust pipe 2 and the inner circumferential surface 9 of the insulator 3, a heat shielding agent 10 is sealed substantially uniformly in a compressed state. The insulator 3 is held in the exhaust pipe 2 by the repulsive force of the compressed heat shield 10, that is, via the heat shield 10. Note that the heat shielding agent 10 may be a generally known heat insulating material or heat shielding material. For example, cotton-like glass fiber may be formed into a tape or sheet and attached to the outer circumferential surface 8 of the exhaust pipe 2, or a porous soft material with countless fine holes such as a sponge may be attached. You can. Alternatively, a fluid having a heat insulating or heat shielding effect may be filled in the gap D.

Furthermore, in the example shown in FIG. 2, the insulator 3 has a long ellipse in the vertical direction of FIG. 2 so as to cover the outer circumferential surface 8 of the exhaust pipe 2, and there is a gap around the entire circumference of the outer circumferential surface 8 of the exhaust pipe 2. It is formed larger by D. That is, the insulator 3 has an elliptical cross section formed by a maximum diameter L3 (L1+2D) that is the long axis of the inner circumference of the insulator 3 and a minimum diameter L4 (L2+2D) that is the short axis. The maximum diameter L1 of the exhaust pipe 2 is larger than the minimum diameter L4 of the insulator 3.

Next, the operation of the exhaust system 1 according to the present invention will be explained. According to the exhaust device 1 of the present invention, the heat shield 10 sealed in a compressed state is interposed in the gap D between the exhaust pipe 2 and the insulator 3, and the repulsive force of the heat shield 10 causes the insulator to 3 can be held. Further, since the insulator 3 does not require a holding member such as a bracket or a fastening part, it is difficult to transmit heat from a part that becomes particularly high temperature, such as a catalyst provided inside the exhaust pipe 2, to the insulator 3. Therefore, a decrease in heat shielding effect can be suppressed.

On the other hand, the repulsive force of the heat shielding agent 10 generally decreases due to thermal deformation or changes in the degree of compression when the temperature increases. There is a possibility that an unintended gap will occur between the two, or the heat shielding agent 10 will peel off, making it impossible to hold the insulator 3. In addition, when vibrations from the vehicle are transmitted to the insulator 3 via the exhaust pipe 2, rotational movement occurs in the insulator 3 in the circumferential direction of the insulator 3, and the exhaust pipe 2 and the insulator 3 are held together by the heat shield 10. Otherwise, there is a risk of damage due to contact or interference with surrounding members, or unintended rotational movement of the device itself.

FIG. 3 is a diagram for explaining the operation of the insulator 3 according to the present invention when it rotates due to propagation of vehicle vibration, and is a sectional view when the insulator 3 rotates clockwise in FIG. 3. When the insulator 3 starts rotating clockwise and rotates to the rotation angle θ, the exhaust pipe 2 and the insulator 3 have an elliptical cross-sectional shape, and the maximum diameter L1 of the outer circumference of the exhaust pipe 2 is equal to the inner circumference of the insulator 3. By being larger than the minimum diameter L4, the inner circumferential surface 9 of the insulator 3 and the outer circumferential surface 8 of the exhaust pipe 2 come into contact with each other at the dimensional difference between the maximum diameter L1 and the minimum diameter L4, and the rotation angle is greater than or equal to θ. It is possible to stop the rotation and prevent it from continuing to rotate. If the rotational movement can be stopped, for example, even if the insulator 3 is equipped with a sensor, it is possible to prevent electrical components attached to the sensor from being disconnected.

Therefore, since the rotational movement of the heat shield 10 interposed between the exhaust pipe 2 and the insulator 3 is restricted, unintended peeling or separation of the heat shield 10 can be suppressed. Furthermore, even if the repulsive force of the heat shielding agent 10 is reduced due to high temperature or vibrations of the vehicle are transmitted to the exhaust system 1, the exhaust pipe 2 and the insulator 3 can be maintained, that is, the reduction in heat shielding effect can be prevented. Can be suppressed.

In the embodiment of the present invention, at least a portion of the exhaust pipe 2 and the insulator 3 have an elliptical cross section, but the present invention is not limited to this. For example, it may have a rectangular cross section, or it may have an asymmetric cross-sectional shape that takes into account interference with surrounding members. The point is that at least a portion of the exhaust pipe 2 and the insulator 3 have a non-circular cross-sectional shape in the pipe direction, and the maximum diameter L1 of the outer circumference of the exhaust pipe 2 is equal to the minimum diameter L4 of the inner circumference of the insulator 3. If it is larger, unintended rotational movement of the insulator 3 can come into contact with the dimensional difference between the maximum diameter L1 and the minimum diameter L4, and the rotation can be stopped.

1 Exhaust device 2 Exhaust pipe 3 Insulator 4 Support part 5 Pipe part 6 Flange 7 Bent part 8 Outer peripheral surface 9 Inner peripheral surface 10 Heat shield D Gap L1 Maximum diameter L4 Minimum diameter

Claims (1)

An exhaust system comprising an exhaust pipe of an internal combustion engine mounted on a vehicle, and an insulator that covers at least a part of the outer peripheral surface of the exhaust pipe,
A heat shield is interposed between the exhaust pipe and the insulator,
the insulator is held by the heat shield,
At least a portion of each of the exhaust pipe and the insulator in the pipe direction has a non-circular cross-sectional shape, and the maximum diameter of the outer peripheral surface of the exhaust pipe is larger than the minimum diameter of the inner peripheral surface of the insulator. An exhaust system featuring:

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