Valve actuation apparatus of internal combustion engine

Abstract

In a valve actuation apparatus of a multi-cylinder engine employing a drive shaft rotatably arranged to extend over a plurality of cylinders, a drive cam attached to the drive shaft, and a motion transmitter provided for each of the cylinders for converting a rotary motion of the drive cam into an oscillating motion, a rockable-cam structural member is provided for each of the cylinders in a state where a shaft is inserted through inner peripheries of the rockable-cam structural members, for operating engine valves by the transmitted oscillating motion. A plain bearing is provided in at least one axial position between the axially-spaced rockable-cam structural members. An inner periphery of the plain bearing is in contact with an outer periphery of the shaft, whereas an outer periphery of the plain bearing is in contact with an inner periphery of a bearing portion mounted on the engine.

1 . A valve actuation apparatus of an internal combustion engine having a plurality of engine cylinders comprising:
 a drive shaft adapted to be driven by a crankshaft of the engine and rotatably arranged to extend over the plurality of engine cylinders in a direction of a cylinder row of the engine cylinders;   a drive cam attached to the drive shaft and provided for each of the engine cylinders;   a motion transmission mechanism provided for each of the engine cylinders for converting a rotary motion of the drive cam into an oscillating motion;   a rockable-cam structural member provided for each of the engine cylinders in a state where a shaft is inserted through inner peripheries of the rockable-cam structural members, for operating at least one engine valve by an oscillating force transmitted from the motion transmission mechanism; and   a cylindrical collar member provided in at least one axial position between the rockable-cam structural members spaced apart from each other in an axial direction of the shaft, an inner peripheral surface of the collar member being in contact with an outer peripheral surface of the shaft, and an outer peripheral surface of the collar member being in contact with an inner peripheral surface of a bearing portion mounted on the engine.   
     
     
         2 . The valve actuation apparatus as claimed in  claim 1 , wherein:
 the shaft, which is inserted through the inner peripheries of the rockable-cam structural members, is the drive shaft.   
     
     
         3 . The valve actuation apparatus as claimed in  claim 2 , wherein:
 the drive shaft has a pair of shaft-end journal portions formed at both axial ends, the shaft-end journal portions being rotatably supported by a pair of shaft-end bearing portions mounted on the engine; and   the bearing portion, which is mounted on the engine, is arranged between the shaft-end bearing portions for rotatably supporting the collar member.   
     
     
         4 . The valve actuation apparatus as claimed in  claim 3 , wherein:
 the collar member is provided for each of the engine cylinders; and   the bearing portion, which is mounted on the engine for rotatably supporting the collar member, is also installed for each of the engine cylinders for rotatably supporting the collar members by the respective bearing portions.   
     
     
         5 . The valve actuation apparatus as claimed in  claim 3 , wherein:
 the collar member is arranged between the drive cam and the rockable-cam structural member, so that one axial end of the collar member is in abutted-engagement with the drive cam and the other axial end of the collar member is in abutted-engagement with the rockable-cam structural member.   
     
     
         6 . The valve actuation apparatus as claimed in  claim 4 , wherein:
 an axial movement of the rockable-cam structural member is restricted by both the collar member and the drive cam.   
     
     
         7 . The valve actuation apparatus as claimed in  claim 4 , wherein:
 the rockable-cam structural member comprises:
 a pair of rockable cams configured to oscillate by the oscillating force transmitted from the motion transmission mechanism for operating a pair of engine valves by respective oscillating motions of the rockable cams, resulting from the transmitted oscillating force; 
 a first cylindrical portion formed integral with the rockable cams and arranged between the rockable cams so that an outer peripheral surface of the first cylindrical portion is rotatably supported by a bearing portion mounted on the engine; and 
 a second cylindrical portion configured to protrude axially outward from at least one of the rockable cams, 
   wherein an outer peripheral surface of the second cylindrical portion, together with the outer peripheral surface of the collar member, is in contact with the inner peripheral surface of the bearing portion, which is mounted on the engine for rotatably supporting the collar member.   
     
     
         8 . The valve actuation apparatus as claimed in  claim 7 , wherein:
 a contact-surface area of the outer peripheral surface of the collar member in contact with the inner peripheral surface of the bearing portion, which is mounted on the engine for rotatably supporting the collar member, is dimensioned to be greater than a contact-surface area of the outer peripheral surface of the second cylindrical portion in contact with the inner peripheral surface of the bearing portion, which is mounted on the engine for rotatably supporting the collar member.   
     
     
         9 . The valve actuation apparatus as claimed in  claim 8 , wherein:
 an outside diameter of the collar member and an outside diameter of the second cylindrical portion are set to be identical to each other.   
     
     
         10 . The valve actuation apparatus as claimed in  claim 7 , wherein:
 the outer peripheral surface of the second cylindrical portion of the rockable-cam structural member is rotatably supported by the bearing portion, which is mounted on the engine for rotatably supporting the collar member.   
     
     
         11 . The valve actuation apparatus as claimed in  claim 2 , wherein:
 the collar member is loosely fitted onto the drive shaft to permit a rotary motion as well as an axial sliding motion of the collar member relative to the drive shaft.   
     
     
         12 . The valve actuation apparatus as claimed in  claim 11 , wherein:
 a clearance between the inner peripheral surface of the collar member and the outer peripheral surface of the drive shaft is dimensioned to be less than a clearance between an inner peripheral surface of the rockable-cam structural member and the outer peripheral surface of the drive shaft.   
     
     
         13 . The valve actuation apparatus as claimed in  claim 12 , wherein:
 the clearance between the inner peripheral surface of the rockable-cam structural member and the outer peripheral surface of the drive shaft is set to a clearance that there is no contact between the inner peripheral surface of the rockable-cam structural member and the outer peripheral surface of the drive shaft during operation of the engine.   
     
     
         14 . The valve actuation apparatus as claimed in  claim 1 , wherein:
 the motion transmission mechanism comprises:
 a control shaft arranged to extend over the plurality of engine cylinders; 
 a control cam provided for each of the engine cylinders and attached to the control shaft, a geometric center of the control cam being radially displaced from an axis of the control shaft; 
 a rocker arm pivotably supported on the control cam of the control shaft; and 
 a link arm mechanically linking the drive cam and the rocker arm for converting the rotary motion of the drive cam into the oscillating motion and for transmitting the oscillating motion to the rocker arm, 
   wherein the control shaft is rotatably supported by a further bearing portion configured to extend from the bearing portion, whose inner peripheral surface is in contact with the outer peripheral surface of the collar member, toward the control shaft.   
     
     
         15 . A valve actuation apparatus of an internal combustion engine having a plurality of engine cylinders comprising:
 a drive shaft adapted to be driven by a crankshaft of the engine and rotatably arranged to extend over the plurality of engine cylinders in a direction of a cylinder row of the engine cylinders;   a drive cam attached to the drive shaft and provided for each of the engine cylinders;   a motion transmission mechanism provided for each of the engine cylinders for converting a rotary motion of the drive cam into an oscillating motion; and   a rockable-cam structural member provided for each of the engine cylinders in a state where a shaft is inserted through inner peripheries of the rockable-cam structural members, for operating at least one engine valve by an oscillating force transmitted from the motion transmission mechanism,   wherein the shaft is rotatably supported at a plurality of points including at least one axial position between the rockable-cam structural members spaced apart from each other in an axial direction of the shaft.   
     
     
         16 . The valve actuation apparatus as claimed in  claim 15 , wherein:
 the shaft, which is inserted through the inner peripheries of the rockable-cam structural members, is the drive shaft.   
     
     
         17 . A valve actuation apparatus of an internal combustion engine having a plurality of engine cylinders comprising:
 a drive shaft adapted to be driven by a crankshaft of the engine and rotatably arranged to extend over the plurality of engine cylinders in a direction of a cylinder row of the engine cylinders;   a drive cam attached to the drive shaft and provided for each of the engine cylinders;   a motion transmission mechanism provided for each of the engine cylinders for converting a rotary motion of the drive cam into an oscillating motion;   a rockable-cam structural member provided for each of the engine cylinders in a state where a shaft is inserted through inner peripheries of the rockable-cam structural members, for operating at least one engine valve by an oscillating force transmitted from the motion transmission mechanism; and   the rockable-cam structural member comprising:
 a pair of rockable cams configured to oscillate for operating a pair of engine valves by respective oscillating motions of the rockable cams; 
 a first cylindrical portion formed integral with the rockable cams and arranged between the rockable cams so that an outer peripheral surface of the first cylindrical portion is rotatably supported by a first bearing portion mounted on the engine; and 
 a second cylindrical portion configured to protrude axially outward from at least one of the rockable cams, 
   wherein both of the shaft and the second cylindrical portion are rotatably supported by a second bearing portion mounted on the engine.   
     
     
         18 . The valve actuation apparatus as claimed in  claim 17 , wherein:
 the shaft, which is inserted through the inner peripheries of the rockable-cam structural members, is the drive shaft.