Exhaust Mechanism

Abstract

An exhaust mechanism includes: an exhaust pipe configured to circulate exhaust gas from an engine; a first outer pipe disposed along the exhaust pipe on an outer periphery of the exhaust pipe; a second outer pipe disposed along the first outer pipe on an outer periphery of the first outer pipe; a pair of intermediate members disposed on the outer periphery of the exhaust pipe, fixed to respective inner peripheral surfaces of a first end portion and a second end portion of the first outer pipe, and being lower in thermal conductivity than the exhaust pipe. A vacuum layer is provided between the first outer pipe and the second outer pipe. At least one of the intermediate members is configured to slide in an axial direction of the exhaust pipe.

What is claimed is: 
     
         1 . An exhaust mechanism comprising:
 an exhaust pipe configured to circulate exhaust gas from an engine;   a first outer pipe disposed along the exhaust pipe on an outer periphery of the exhaust pipe;   a second outer pipe disposed along the first outer pipe on an outer periphery of the first outer pipe, wherein a vacuum layer is provided between the first outer pipe and the second outer pipe; and   a pair of intermediate members disposed on the outer periphery of the exhaust pipe, fixed to respective inner peripheral surfaces of a first end portion and a second end portion of the first outer pipe, and being lower in thermal conductivity than the exhaust pipe, and wherein at least one of the intermediate members is configured to slide in an axial direction of the exhaust pipe.   
     
     
         2 . The exhaust mechanism according to  claim 1 , further comprising:
 a first low-permeability layer disposed on at least one of an inner peripheral surface and an outer peripheral surface of the first outer pipe, and being made of a material with a hydrogen permeability lower than a hydrogen permeability of the first outer pipe; and   a second low-permeability layer disposed on at least one of an inner peripheral surface and an outer peripheral surface of the second outer pipe, and being made of a material with a hydrogen permeability lower than a hydrogen permeability of the second outer pipe.   
     
     
         3 . The exhaust mechanism according to  claim 2 , wherein each of the first low-permeability layer and the second low-permeability layer is one of an aluminum layer and a resin layer. 
     
     
         4 . The exhaust mechanism according to  claim 1 , wherein the pair of intermediate members is made of a material that is at least one of glass wool, metallic mesh, and ceramic.