Exhaust system of internal combustion engine

Abstract

An exhaust system of an internal combustion engine includes a main catalyst converter, a bypass catalyst converter, a bypass catalyst converter with a smaller volume and a shift valve device. Upstream-side main exhaust passages have a collecting portion connected with a downstream-side main exhaust passage connected with the main catalyst converter. Bypass exhaust passages have the bypass catalyst converter therein, being connected between the shift valve device and the downstream-side main exhaust passage. The shift valve device is disposed at a position from the upstream-side portions of the upstream-side main exhaust passages to a head flange fixable to a cylinder head of the engine to be shiftable between a first shift position where the upstream-side main exhaust passages are closed and the bypass exhaust passages are opened and a second shift position where the upstream-side main exhaust passages are opened.

1 . An exhaust system of an internal combustion engine comprising:
 a main catalyst converter for purifying exhaust gas discharged from an internal combustion engine;   a bypass catalyst converter for purifying the exhaust gas converter, the bypass catalyst converter having a volume smaller than a volume of the main catalyst converter, the bypass catalyst converter being arranged at a position closer to exhaust ports of the internal combustion engine relative to a position of the main catalyst converter;   upstream-side main exhaust passages having upstream-side portions and downstream-side portions having a collecting portion;   a downstream-side main exhaust passage having an upstream-side portion and a downstream-side portion, the upstream portion thereof being connected with the collecting portion of the upstream-side main exhaust passages, and the downstream-side portion thereof being connected with the main catalyst converter;   bypass exhaust passages including upstream-side bypass passages and a downstream-side bypass passage so that the bypass catalyst converter is disposed between the upstream-side bypass passages and the downstream-side bypass passage, a downstream-side portion of the downstream-side bypass passage being connected with the downstream-side main exhaust passage at a position between the upstream-side main exhaust passages and the main catalyst converter; and   a shift valve device that is disposed at a position from the upstream-side portions of the upstream-side main exhaust passages to a head flange fixed on a cylinder head of the internal combustion engine, the shift valve device being connected with the upstream-side portions of the upstream-side main exhaust valve device and upper portions of the bypass exhaust passages so as to be shiftable between a first shift position where the upstream-side main exhaust passages are closed and the bypass exhaust passages are opened and a second shift position where the upstream-side main exhaust passages are opened.   
   
   
       2 . The exhaust system of the internal combustion engine according to  claim 1 , wherein
 the shift valve device is disposed in the upstream-side portions of the upstream-side bypass passages which are connected with the head flange fixed on the cylinder head.   
   
   
       3 . The exhaust system of the internal combustion engine according to  claim 2 , wherein
 the shift valve device has a plurality of shift valve units that are arranged in line along a longitudinal direction of the cylinder head, the shift valve units being shiftable by one shaft actuated by an actuator.   
   
   
       4 . The exhaust system of internal combustion engine according to  claim 3 , wherein
 the shift valve device includes a housing formed with a valve opening portion, and a rotatable arm rotatable relative to the valve opening portion, the valve opening portion having a seat portion shaped like a taper and being communicatable with the upstream-side portions of the upstream-side main exhaust passages, and the rotatable arm being provided with a valve element having a curved surface seat that is swingable relative to the rotatable arm so that the curved surface seat and the seat portion can be aligned with each other when the shift valve device is shifted to the first shift position.   
   
   
       5 . The exhaust system of internal combustion engine according to  claim 4 , wherein
 the valve element is connected with the rotatable arm though a valve stem thereof, and wherein the valve element contacts with an inner surface of the housing so that the valve element is prevented from oscillating due to contact of the valve element and the inner surface when the shift valve device is at the second shift position.   
   
   
       6 . The exhaust system of internal combustion engine according to  claim 5 , wherein
 the bypass catalyst converter is disposed in an engine room, and the main catalyst converter is mounted under a vehicle floor.   
   
   
       7 . The exhaust system of the internal combustion engine according to  claim 1 , wherein
 the shift valve device has a plurality of shift valve units that are arranged in line along a longitudinal direction of the cylinder head, the shift valve units being shiftable by one shaft actuated by an actuator.   
   
   
       8 . The exhaust system of internal combustion engine according to  claim 7 , wherein
 the shift valve device includes a housing formed with a valve opening portion, and a rotatable arm rotatable relative to the valve opening portion, the valve opening portion having a seat portion shaped like a taper and being communicatable with the upstream-side portions of the upstream-side main exhaust passages, and the rotatable arm being provided with a valve element having a curved surface seat that is swingable relative to the rotatable arm so that the curved surface seat and the seat portion can be aligned with each other when the shift valve device is shifted to the first shift position.   
   
   
       9 . The exhaust system of internal combustion engine according to  claim 8 , wherein
 the valve element is connected with the rotatable arm though a valve stem thereof, and wherein   the valve element contacts with an inner surface of the housing so that the valve element is prevented from oscillating due to contact of the valve element and the inner surface when the shift valve device is at the second shift position.   
   
   
       10 . The exhaust system of internal combustion engine according to  claim 1 , wherein
 the shift valve device includes a housing formed with a valve opening portion, and a rotatable arm rotatable relative to the valve opening portion, the valve opening portion having a seat portion shaped like a taper and being communicatable with the upstream-side portions of the upstream-side main exhaust passages, and the rotatable arm being provided with a valve element having a curved surface seat that is swingable relative to the rotatable arm so that the curved surface seat and the seat portion can be aligned with each other when the shift valve device is shifted to the first shift position.   
   
   
       11 . The exhaust system of internal combustion engine according to  claim 10 , wherein
 the valve element is connected with the rotatable arm though a valve stem thereof, and wherein   the valve element contacts with an inner surface of the housing so that the valve element is prevented from oscillating due to contact of the valve element and the inner surface when the shift valve device is at the second shift position.   
   
   
       12 . The exhaust system of internal combustion engine according to  claim 1 , wherein
 the bypass catalyst converter is disposed in an engine room, and the main catalyst converter is mounted under a vehicle floor.   
   
   
       13 . The exhaust system of internal combustion engine according to  claim 1 , wherein
 the shift valve device and the head flange fixed on the cylinder head are one of one unit thereof and integral parts thereof.   
   
   
       14 . The exhaust system of internal combustion engine according to  claim 13 , wherein
 the shift valve device has a plurality of shift valve units that are arranged in line along a longitudinal direction of the cylinder head, the shift valve units being shiftable by one shaft actuated by an actuator.   
   
   
       15 . The exhaust system of the internal combustion engine according to  claim 14 , wherein
 the shift valve device includes a housing formed with a valve opening portion, and a rotatable arm rotatable relative to the valve opening portion, the valve opening portion having a seat portion shaped like a taper and being communicatable with the upstream-side portions of the upstream-side main exhaust passages, and the rotatable arm being provided with a valve element having a curved surface seat that is swingable relative to the rotatable arm so that the curved surface seat and the seat portion can be aligned with each other when the shift valve device is shifted to the first shift position.   
   
   
       16 . The exhaust system of internal combustion engine according to  claim 15 , wherein
 the valve element is connected with the rotatable arm though a valve stem thereof, and wherein   the valve element contacts with an inner surface of the housing so that the valve element is prevented from oscillating due to contact of the valve element and the inner surface when the shift valve device is at the second shift position.   
   
   
       17 . The exhaust system of internal combustion engine according to  claim 16 , wherein
 the bypass catalyst converter is disposed in an engine room, and the main catalyst converter is mounted under a vehicle floor.   
   
   
       18 . The exhaust system of internal combustion engine according to  claim 13 , wherein
 the shift valve device includes a housing formed with a valve opening portion, and a rotatable arm rotatable relative to the valve opening portion, the valve opening portion having a seat portion shaped like a taper and being communicatable with the upstream-side portions of the upstream-side main exhaust passages, and the rotatable arm being provided with a valve element having a curved surface seat that is swingable relative to the rotatable arm so that the curved surface seat and the seat portion can be aligned with each other when the shift valve device is shifted to the first shift position.   
   
   
       19 . The exhaust system of internal combustion engine according to  claim 18 , wherein
 the valve element is connected with the rotatable arm though a valve stem thereof, and wherein   the valve element contacts with an inner surface of the housing so that the valve element is prevented from oscillating due to contact of the valve element and the inner surface when the shift valve device is at the second shift position.   
   
   
       20 . The exhaust system of internal combustion engine according to  claim 12 , wherein
 the bypass catalyst converter is disposed in an engine room, and the main catalyst converter is mounted under a vehicle floor.