Variable Valve Drive Device, Engine, and Motorcycle

Abstract

A cam sprocket 211 is driven to rotate by the drive force transmitted from a crankshaft 130 to by turn drive an eccentric plate 250 around an axis running in parallel with the axis of rotation of the cam sprocket 211. The eccentric plate 250 is movable from a position concentric with the cam sprocket 211 to an eccentric position. As it is driven to rotate at the eccentric position, it drives an intake cam block 240 by way of a variable camshaft 230 with a rotary phase difference that changes periodically relative to the cam sprocket 211. The intake cam block 240 drives an intake valve. The phase angle of the eccentric plate 250 at the connection section with the cam sprocket 211 and at the connection section with the movable camshaft 230 is s defined to be between 80° and 160° or between 200° and 290° when the direction in which the eccentric plate 250 rotates is assumed to be the forward direction.

1 . A variable valve drive device comprising: 
 a cam drive member adapted to be driven to rotate by the drive force transmitted from a crankshaft;    an eccentric member adapted to be driven to rotate around an axis of rotation running in a direction same as the rotary shaft of the cam drive member, by operation of the cam drive member, the axis being movable from a concentric position on the rotary shaft to an eccentric position;    a camshaft arranged concentrically on the rotary shaft and adapted to be driven to rotate around the rotary shaft by the eccentric member with a rotary phase difference changing periodically relative to the cam drive member when it is driven by the eccentric member at the eccentric position; and    a cam block adapted to be driven to rotate by the camshaft with a rotational phase same with the camshaft and drive an exhaust valve or an intake valve, the device characterized in that    the eccentric member includes: 
 an input connection section connected to the cam drive member to receive as input the rotary force of the cam drive member; and  
 an output connection section connected to the camshaft to output the rotary force of the eccentric member itself driven to rotate by the rotary force input by way of the input connection section, and  
   the timing of opening the exhaust valve or the intake valve as a function of the shift of the axis of rotation of the eccentric member in a direction is angularly unequivocally advanced and/or the timing of closing the exhaust valve or the intake valve is angularly unequivocally delayed for the phase angle of the input connection section and that of the output connection section relative to the axis of the eccentric member.    
   
   
       2 . The variable valve drive device according to  claim 1 , characterized by comprising an eccentricity moving section for moving the axis of the eccentric member from a concentric position to an eccentric position relative to the axis of rotation of the cam drive member.  
   
   
       3 . The variable valve drive device according to  claim 2 , characterized in that the eccentricity moving section is adapted to move the axis of the eccentric member along an arc line.  
   
   
       4 . The variable valve drive device according to  claim 1 , characterized by comprising another cam block that is driven to rotate by the cam drive member with a rotary phase same as the cam drive member and arranged at a position adjacent to the cam block.  
   
   
       5 . The variable valve drive device according to  claim 4 , characterized in that the cam block drives the intake valve by revolutions while the other cam block drives the exhaust valve by revolutions.  
   
   
       6 . An engine characterized in that the engine is equipped with a variable valve drive device according to  claim 1  and that the crankshaft is arranged substantially in parallel with the axis of rotation of the cam drive member and the cam drive member is interlocked with the revolutions of the crankshaft by way of a drive force transmission section arranged orthogonally relative to the crankshaft.  
   
   
       7 . A motorcycle characterized in that an engine according to  claim 6  is mounted thereon with the crankshaft arranged transversally.