Secondary air supply for engine exhaust system

Abstract

A chain chamber of an engine, which accommodates a cam chain for driving a camshaft, is formed between a first cylinder and a second cylinder aligned in the direction along the camshaft. A first-cylinder valve chamber and a second-cylinder valve chamber each accommodate a corresponding valve for supplying secondary air to an exhaust system. The first and second chambers overlap the chain chamber and lie adjacent to each other above the chain chamber. The first-cylinder and second-cylinder valve chambers have first and second valve chamber openings, respectively. A first and a second valve chamber cover for opening and closing the respective valve chamber openings are integrally formed together. This construction reduces the number of engine parts associated with a secondary air system and simplifies the sealing structure of secondary air introduction hoses and cover members.

1 . An engine comprises a cylinder block defining at least two adjacent cylinders, a cylinder head fastened on the cylinder block and supporting at least one camshaft, a head cover mounted on the cylinder head, a cam chain driving the camshaft, a chain chamber housing the cam chain and being formed generally between the adjacent cylinders, and a first-cylinder valve chamber and a second-cylinder valve chamber each being sized to accommodate a reed valve for supplying secondary air to an exhaust system of the engine, the first-cylinder and second-cylinder valve chambers being disposed in a manner such that at least portions of the first-cylinder valve chamber and the second-cylinder valve chamber overlie the chain chamber as viewed in the direction generally parallel to the axes of the cylinders, the first-cylinder and second-cylinder valve chambers also lying adjacent to each other to one side of the chain chamber and each having a valve chamber opening that opens to an exterior side of the engine, and a cover having a portion that closes the valve chamber openings of both the first-cylinder valve chamber and the second-cylinder valve chamber.  
   
   
       2 . The engine of  claim 1 , wherein the first and second valve chambers each have a rectangular shape extending longer in the direction generally parallel to an axis of the camshaft, and each reed valve in the first and second valve chambers includes a rectangular, thin plate that is located with its longer sides extending in the direction generally parallel to the axis of the camshaft.  
   
   
       3 . The engine of  claim 1 , wherein the head cover has a breather chamber for separating oil mist from blow-by gas, the breather chamber being disposed such that at least a portion of the breather chamber overlies the chain chamber as seen in the direction generally parallel to the axes of the cylinders, the breather chamber further lying adjacent to at least one of the first-cylinder and second-cylinder valve chambers.  
   
   
       4 . The engine of  claim 3 , wherein the breather chamber has a breather chamber opening that opens to the exterior side of the engine, and the cover includes a portion that extends over the breather chamber opening, said portion being integrally formed with the portion of the cover that closes the first-cylinder and second-cylinder valve chamber openings.  
   
   
       5 . The engine of  claim 3 , wherein a secondary air hose and a breather hose are bundled together, the secondary air hose connects an air cleaner to the first-cylinder and second-cylinder valve chambers, and the breather hose connects the breather chamber to the air cleaner.  
   
   
       6 . The engine of  claim 3  additionally comprising a second camshaft disposed between the cylinder head and the head cover, the camshafts drivingly engaging each other so as to rotate together.  
   
   
       7 . The engine of  claim 6 , wherein the breather chamber is disposed generally to the side of a space between the camshafts.  
   
   
       8 . The engine of  claim 6 , wherein one of the camshafts is a driving camshaft and the other is a driven camshaft, and wherein the valve chambers are disposed generally to an upper side of the driven camshaft.  
   
   
       9 . The engine of  claim 8 , wherein the driven camshaft opens and closes exhaust valves supported by the cylinder head.  
   
   
       10 . The engine of  claim 1 , wherein the reed valves are orientated so as to deflect in a direction generally parallel to the axes of the cylinders.  
   
   
       11 . The engine of  claim 1 , wherein the cylinder head includes first and second passages, each passage connecting a side of the respective valve chamber, which lies downstream of the corresponding reed valve, with a corresponding exhaust port of the cylinder head.  
   
   
       12 . The engine of  claim 1 , wherein each reed valve includes a base plate that is sandwiched between portions of the cover and the head cover.  
   
   
       13 . The engine of  claim 1 , wherein each valve chamber houses an exhaust gas deflector plate disposed on a downstream side of the corresponding reed valve.  
   
   
       14 . An engine comprising a cylinder block defining at least two adjacent cylinders, a cylinder head fastened to the cylinder block and supporting at least one camshaft, a head cover mounted to the cylinder head, a cam chain driving the camshaft, a chain chamber housing the cam chain and being formed generally between the adjacent cylinders, the chain chamber having a longitudinal axis that lies substantially parallel to axes of the adjacent cylinders, and a first-cylinder valve chamber and a second-cylinder valve chamber each being sized to accommodate a valve for supplying secondary air to an exhaust system of the engine, the first-cylinder and second-cylinder valve chambers being disposed in a manner such that at least portions of the first-cylinder valve chamber and the second-cylinder valve chamber lie to one side of the chain chamber as viewed in a direction along the longitudinal axis of the chain chamber.  
   
   
       15 . The engine of  claim 14 , wherein the first-cylinder and second-cylinder valve chambers lying adjacent to each other and each has a valve chamber opening that opens to an exterior side of the engine  
   
   
       16 . The engine of  claim 15  additionally comprising a cover having a portion that closes the valve chamber openings of both the first-cylinder valve chamber and the second-cylinder valve chamber.  
   
   
       17 . The engine of  claim 16 , wherein the head cover has a breather chamber for separating oil mist from blow-by gas, the breather chamber being disposed such that at least a portion of the breather chamber overlies the chain chamber as seen in the direction generally parallel to the axes of the cylinders, the breather chamber further lying adjacent to at least one of the first-cylinder and second-cylinder valve chambers.  
   
   
       18 . The engine of  claim 17 , wherein the breather chamber has a breather chamber opening that opens to the exterior side of the engine, and the cover includes a portion that extends over the breather chamber opening, which is integrally formed with the portion of the cover that closes the first-cylinder and second-cylinder valve chamber openings.  
   
   
       19 . The engine of  claim 17 , wherein a secondary air hose and a breather hose are bundled together, the secondary air hose connecting an air cleaner to the first-cylinder and second-cylinder valve chambers, and the breather hose connecting the breather chamber to the air cleaner.  
   
   
       20 . The engine of  claim 17  additionally comprising a second camshaft disposed between the cylinder head and the head cover, one of the camshafts being an intake camshaft actuating at least one intake valve supported by the cylinder head and the other camshaft being an exhaust camshaft actuating at least one exhaust valve supported by the camshafts, and wherein the breather chamber is disposed generally to a side of a space between the camshafts and the valve chambers are disposed generally to a side of the exhaust camshaft.