Motorcycle Exhaust System and Motorcycle Provided with Exhaust System

Abstract

An exhaust system for a motorcycle that inhibits generation of flow noise without diminishing external appearance. The exhaust system has a tail cap and a ring shaped outer cap that is fixed to a rear end edge of a casing. An inner cap is fixed to a rear end wall of the casing and has a tail hole having a size that allows a tail pipe to pass through it with a gap therebetween. A gap s is formed in a boundary region between the inner cap and the outer cap.

1 . An exhaust system for a motorcycle comprising:
 an engine;   an exhaust pipe connected to the engine; and   a muffler connected to the exhaust pipe, wherein   the muffler includes a casing, provided in a rear end section of the muffler, that has a rear end wall and that surrounds a rear section of the exhaust pipe, and a tail cap that surrounds an outer side of the rear end wall of the casing, and   a tail hole is formed in the rear end wall such that a gap is left with respect to an outer diameter of a rear end of the exhaust pipe, the gap between the tail hole and the rear end of the exhaust pipe is in communication with a space formed between the rear end wall and the tail cap, and a passage is formed that communicates the space and an outside space.   
   
   
       2 . The exhaust system for a motorcycle according to  claim 1 , wherein the exhaust pipe includes an engine side exhaust pipe that is connected to the engine, and a tail pipe that is connected to the engine side exhaust pipe and that is surrounded by the casing. 
   
   
       3 . The exhaust system for a motorcycle according to  claim 2 , wherein the tail cap includes a ring shaped outer cap that is attached to an outer side of the rear end wall of the casing, and an inner cap which is attached to the rear end wall of the casing and in which the tail hole is formed such that a gap is left with respect to the outer diameter of the tail pipe, wherein
 the passage is the gap formed in a boundary region between the inner cap and the outer cap.   
   
   
       4 . The exhaust system for a motorcycle according to  claim 3 , wherein the tail pipe is formed such that a rear end surface of the tail pipe is generally flush with an opening edge of the tail hole of the inner cap. 
   
   
       5 . The exhaust system for a motorcycle according to  claim 3 , wherein the inner cap includes a cap body that is fixed to the rear end wall of the casing and in which the tail hole is formed, and a flange that protrudes outward to the rear from an outer periphery edge of the cap body, and
 the outer cap includes a bent back section that bends around from an outer side to an inner side of the flange, and a gap is formed between the bent back section and the flange.   
   
   
       6 . The exhaust system for a motorcycle according to  claim 3 , wherein the outer cap is fixed to a rear end edge of the casing by a fixing member. 
   
   
       7 . The exhaust system for a motorcycle according to  claim 3 , wherein the inner cap is fixed from the rear to the rear end wall of the casing by a fixing member. 
   
   
       8 . The exhaust system for a motorcycle according to  claim 3 , wherein the tail pipe includes a main pipe connected to the engine side exhaust pipe and that extends to the rear, and a first branch pipe and a second branch pipe that are connected to the main pipe and that branch out from the main pipe. 
   
   
       9 . The exhaust system for a motorcycle according to  claim 8 , wherein sound absorbing material is filled in an area between the casing and the tail pipe. 
   
   
       10 . The exhaust system for a motorcycle according to  claim 9 , wherein a hole is formed in the main pipe. 
   
   
       11 . The exhaust system for a motorcycle according to  claim 1 , wherein the casing has an elliptical shape when viewed in a cross section, and is formed such that, when viewed from an exhaust gas flow direction, a cross sectional area of the casing becomes larger as the casing extends from an upstream side to a downstream side thereof. 
   
   
       12 . The exhaust system for a motorcycle according to  claim 1 , wherein an exhaust gas chamber is connected to the exhaust pipe, the exhaust gas chamber is partitioned in to a plurality of expansion chambers, and the muffler is connected to one of the expansion chambers. 
   
   
       13 . The exhaust system for a motorcycle according to  claim 12 , wherein the exhaust gas chamber includes a first expansion chamber that is connected to the engine side exhaust pipe, a third expansion chamber that is connected to the muffler, and a second expansion chamber that is positioned between the first expansion chamber and the third expansion chamber when viewed from an exhaust gas flow direction. 
   
   
       14 . A motorcycle comprising an engine and an exhaust system connected to the engine, wherein
 the exhaust system comprises an exhaust pipe connected to the engine and a muffler connected to the exhaust pipe, and   the muffler comprises a casing, provided in a rear end section of the muffler, that has a rear end wall and that surrounds a rear section of the exhaust pipe, and a tail cap that surrounds an outer side of the rear end wall of the casing, and   a tail hole is formed in the rear end wall such that a gap is left with respect to an outer diameter of a rear end of the exhaust pipe, the gap between the tail hole and the rear end of the exhaust pipe is in communication with a space formed between the rear end wall and the tail cap, and a passage is formed that communicates the space and an outside space.   
   
   
       15 . The motorcycle according to  claim 14 , wherein the casing is shaped as an ellipsis when viewed in a cross section, and is disposed such that a long axis of the ellipsis extends in a generally upward-downward direction. 
   
   
       16 . The motorcycle according to  claim 15 , wherein a recessed portion that extends in an exhaust gas flow direction is formed in an upward-downward direction central portion of the casing. 
   
   
       17 . The motorcycle according to  claim 14 , wherein the muffler is disposed to the front of a vertical line that passes through a rotational centre of a rear wheel. 
   
   
       18 . The motorcycle according to  claim 17 , wherein the muffler extends diagonally upward toward the rear and protrudes outwards in a vehicle width direction outer side.