JP2006063938A - Engine exhaust system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust system, for example, for an automobile in which an exhaust emission control device is provided in the system and a double tube exhaust duct is formed from an engine to the above device to improve the thermal insulation between inner and outer tubes. <P>SOLUTION: The exhaust emission control device 2 is provided in the exhaust system of an engine 1, and the double tube exhaust duct 3 is formed from the engine 1 to the device 2. On the outer peripheral face of an inner tube 31 composing the duct 3, a thermal insulation layer 7 is disposed in such a state as not to contact an outer tube 32. The insulation layer 7 is formed by performing a heat resistant coating or plating on the outer peripheral face of the inner tube or may be formed by covering that face with a heat resistant fiber or chip. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust system (exhaust system) of an engine such as an automobile. More specifically, the present invention relates to an engine exhaust system in which an exhaust purification device is provided in the exhaust system, and exhaust pipes extending from the engine to the exhaust purification device are formed in multiple inside and outside.

  2. Description of the Related Art Conventionally, in an exhaust system of an engine such as an automobile as in Patent Document 1 and Patent Document 2, for example, an exhaust purification device such as a catalytic converter and a DPF is provided in the system, and an exhaust pipe line from the engine to the exhaust purification device Are formed in a multi-layered manner.

  As described above, the exhaust pipe from the engine to the exhaust gas purification device is formed in multiple inside and outside, so that the temperature rise on the outer surface of the exhaust pipe can be suppressed and the exhaust temperature introduced into the exhaust gas purification device Is maintained at a predetermined temperature or higher so that the purification efficiency can be promoted.

  In this case, between the inner pipe and the outer pipe constituting the above-described inner and outer multiple exhaust pipes, as in Patent Document 1, nothing is filled and a simple space is formed as an air heat insulating layer, and Patent Document There are some which are filled with a heat insulating material such as glass wool between the inner and outer pipes as in 2, but there is a problem that a sufficient heat insulating effect cannot always be obtained in either case.

  For example, in the case where the space between the inner and outer pipes is simply made into a space as described above to form an air heat insulating layer, convection occurs in the space and the heat insulating effect is lowered, and the one filled with the heat insulating material is passed through the heat insulating material. As a result, heat is transferred from the inner pipe to the outer pipe, and the heat insulation effect is reduced. For this reason, particularly in the current situation where the exhaust gas temperature is required to be maintained at a high temperature due to the recent tightening of exhaust gas regulations, further improvement of the heat insulation effect is required.

JP 2002-138825 A JP-A-9-151730

  The present invention has been proposed to meet the above demands, and an object of the present invention is to provide an exhaust system for an engine having an exhaust pipe having an inner / outer multiple structure that is more excellent in heat insulation.

  In order to achieve the above object, an engine exhaust system according to the present invention has the following configuration. That is, in an engine exhaust system in which an exhaust purification device is provided in the engine exhaust system and exhaust pipes extending from the engine to the exhaust purification device are formed in an inner and outer multiple, the inner pipes constituting the inner and outer multiple exhaust conduits A heat insulating layer is provided on the outer peripheral surface in a non-contact manner with the outer tube. The heat insulating layer is formed, for example, by applying heat resistant coating or plating to the outer peripheral surface of the inner tube. Alternatively, it can be formed by coating the outer peripheral surface of the inner tube with heat-resistant fibers or chips.

  As described above, by providing a heat-insulating layer on the outer peripheral surface of the inner pipe constituting the inner and outer multiple exhaust pipes in a non-contact manner with the outer pipe, the exhaust heat in the inner pipe is radiated to the outside of the inner pipe. In addition to reducing the temperature difference between the outer surface of the inner tube and the inner surface of the outer tube, the occurrence of convection in the space between the inner and outer tubes can be reduced as much as possible. In addition, since the heat insulation layer is not in contact with the outer pipe, the exhaust heat in the inner pipe is prevented from being directly transmitted from the heat insulation layer to the outer pipe, and the surface temperature of the outer pipe is prevented from rising, and the engine has an excellent heat insulation effect. It is possible to provide an exhaust system.

  Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings. FIG. 1 is a front view showing an embodiment of an engine exhaust system according to the present invention, and FIG. 2 is a partially cutaway enlarged view of a main part thereof.

  In the figure, 1 is an engine, 2 is an exhaust purification device such as a catalytic converter (catalyzer), 3 is an exhaust pipe line from the engine 1 to the exhaust gas purification apparatus 2, and the exhaust pipe line 3 is an exhaust manifold in this embodiment. 3a and an exhaust pipe 3b. The exhaust pipe 3b is formed into an inner / outer multiple, and in the case of the figure, an inner pipe 31 and an outer pipe 32 are formed into an inner and outer double. In the figure, reference numeral 4 denotes a rear exhaust pipe for guiding the exhaust gas purified by the exhaust gas purification device 2 to a silencer omitted in the figure disposed at the rear of the vehicle body.

  A short cylindrical spacer made of a metal wire such as stainless wool as shown in FIG. 2 is provided between the inner and outer pipes 31 and 32 at the upstream and downstream ends of the exhaust pipe 3b constituting the exhaust pipe 3 described above. The spacers 5 are disposed in a ring-shaped recess 32a formed on the inner surface of the outer tube 32 so that the spacers 5 are fixed to the outer tube 32 so as not to move relative to each other in the axial direction. A relative movement (sliding movement) is possible in the axial direction with respect to the tube 31.

  The exhaust manifold 3a and the exhaust pipe 3b are connected to each other via a flange joint 6. The connection flange 6b on the exhaust pipe 3b side is welded to the upstream end of the outer pipe 32 of the exhaust pipe 3b. It is fixed with etc. The exhaust purification device 2 has a configuration in which the honeycomb catalyst 22 is accommodated in the outer cylinder 21, and the upstream end of the outer cylinder 21 is gradually reduced in diameter so that the outer pipe at the downstream end of the exhaust pipe 3b. It fits to the outer peripheral surface of 32 and is fixed by welding or the like.

  In the present embodiment, the heat insulating layer 7 is provided in a non-contact manner with the outer pipe 32 on the outer peripheral surface of the inner pipe 31 in the inner and outer multiple exhaust pipes 3b constituting the exhaust pipe 3 extending from the engine 1 to the exhaust gas purification device 2. It is a thing. The materials of the inner and outer tubes 31 and 32 are appropriate, and for example, a ferritic metal such as stainless steel can be used. In addition, although the formation method and material of the heat insulating layer 7 are also appropriate, in the present embodiment, the heat insulating layer 7 is formed by applying heat resistant coating to substantially the entire outer peripheral surface of the inner tube 31. As the heat-resistant coating material (coating material), for example, a silicon-based resin coating material to which a silane-based curing agent or the like is appropriately added can be used, and a heat insulating layer formed by the coating. What is necessary is just to form the thickness of 7 to about 15-40 micrometers.

  The heat insulating layer 7 is not limited to the above-described coating, and may be formed by plating or the like, and the plating material is preferably a metal having a low thermal conductivity as much as possible. For example, a chromium-based metal or the like is used. it can. The heat insulating layer 7 is formed by winding a heat-resistant fiber or synthetic resin such as glass wool, rock wool or stainless wool around the outer peripheral surface of the inner tube 31, or a heat-resistant fiber around the synthetic resin, It is also possible to form the chip by finely chopping a chip impregnated with a heat-resistant synthetic resin binder or the like by spraying the outer peripheral surface of the inner tube 31 or the like.

  In the above-described embodiment, the heat insulating layer 7 is provided on the outer peripheral surface of the inner pipe of the exhaust pipe 3b in the exhaust pipe 3 extending from the engine 1 to the exhaust purification device 2. However, the exhaust manifold 3a is formed in an inner and outer multiple. The heat insulating layer 7 may be provided on the outer peripheral surface of the inner pipe of the manifold, or the heat insulating layer 7 may be provided on the outer peripheral surfaces of the inner pipes of both the exhaust manifold 3a and the exhaust pipe 3b. Further, the heat insulating layer 7 may be provided only on a part of the outer peripheral surface of the inner pipe of the exhaust manifold 3a and / or the exhaust pipe 3b. For example, a running wind hits an engine such as an automobile and the exhaust temperature tends to decrease. It can also be provided only at the location.

  As described above, the exhaust pipe 3 extending from the engine 1 to the exhaust purification device 2 is formed in an inner / outer multiple, and the outer pipe 32 is not in contact with the outer peripheral surface of the inner pipe 31 constituting the inner / outer multiple exhaust pipe 3. By providing the heat insulating layer 7, it is possible to reduce the exhaust heat in the inner pipe 31 from being radiated to the outside of the inner pipe 31, and the temperature difference between the outer surface of the inner pipe 31 and the inner surface of the outer pipe 32. As a result, the occurrence of convection in the space between the inner and outer pipes 31 and 32 can be reduced as much as possible. Further, since the heat insulating layer 7 is not in contact with the outer tube 32, it is possible to prevent the exhaust heat in the inner tube 31 from being directly transmitted from the heat insulating layer 7 to the outer tube 32 and increasing the surface temperature of the outer tube 32. It is possible to provide an engine exhaust system having an excellent heat insulation effect.

  As described above, the engine exhaust system according to the present invention is an extremely simple system in which the heat insulating layer 7 is provided in a non-contact manner with the outer pipe on the outer peripheral surface of the inner pipe of the inner and outer multiple exhaust pipe lines 3 extending from the engine 1 to the exhaust purification device 2. An exhaust system having an excellent heat insulating effect can be provided with a simple configuration. As a result, in the automotive industry, where exhaust gas regulations have been increasingly tightened recently, the exhaust gas temperature introduced into the exhaust gas purification device is as high as possible without increasing the surface temperature of the exhaust pipe from the engine to the exhaust gas purification device. Therefore, it is possible to sufficiently satisfy the demand for maintaining the exhaust system, and it is possible to increase the degree of freedom of design and industrial applicability of this type of exhaust system.

The front view which shows one Embodiment of the exhaust system of the engine by this invention. The partially cut-out enlarged view of the main part of the exhaust system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust gas purification device 3 Exhaust pipe line 3a Exhaust manifold 3b Exhaust pipe 31 Inner pipe 32 Outer pipe 4 Rear exhaust pipe 5 Spacer 6 Flange joint 6a, 6b Flange 7 Heat insulation layer

Claims (4)

  In an engine exhaust system in which an exhaust purification device is provided in the exhaust system of the engine, and exhaust pipes extending from the engine to the exhaust purification device are formed in an inner and outer multiple, an outer peripheral surface of an inner pipe constituting the inner and outer multiple exhaust pipe An engine exhaust system characterized in that a heat insulating layer is provided in a non-contact manner with the outer pipe.   2. The engine exhaust system according to claim 1, wherein the heat insulating layer is formed by applying a heat resistant coating to an outer peripheral surface of the inner tube.   The engine exhaust system according to claim 1, wherein the heat insulating layer is formed by plating the outer peripheral surface of the inner tube.   2. The engine exhaust system according to claim 1, wherein the heat insulating layer is formed by coating a heat resistant fiber or a synthetic resin on an outer peripheral surface of the inner tube.

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