Valve mechanism of internal combustion engine

A valve mechanism of an internal combustion engine which has two engine valves for each cylinder which are biased in a closing direction by valve springs, the valve mechanism comprising:

• a supporting shaft;
• a swing member having a through bore, the swing member being swingably disposed on the supporting shaft having the supporting shaft received in the through bore, the swing member operating the engine valves to open against a biasing force of the valve springs when swung;
• and
• a drive mechanism that applies a drive force to the swing member to effect the swing movement against the biasing force of the valve springs, the drive mechanism being constructed to apply the drive force to one end portion of the swing member with respect to an axial direction of supporting shaft,
• wherein, when the engine valves are maximally opened by the swing member, a distance from a second diametrically center position of the through bore of the swing member to a head member of the corresponding engine valve is longer than a distance from a first diametrically center position of the through bore of the swing member to a head member of the corresponding engine valve, the first diametrically center position being in the vicinity of the one end portion of the swing member.

A valve mechanism of an internal combustion engine having first and second engine valves for each cylinder, comprising:

• a drive shaft rotated synchronously together with a crankshaft of the engine;
• a cylindrical hollow cam shaft rotatably disposed about the drive shaft keeping a first cylindrical clearance therebetween, the cam shaft being formed with first and second cams that respectively actuate the first and second engine valves for opening and closing the same;
• a bearing which bears a given portion of the cam shaft keeping a second cylindrical clearance therebetween, the given portion being positioned between the first and second cams;
• and
• a movement transmitting mechanism which transmits a torque of the drive shaft to the cam shaft while converting a rotation movement of the drive shaft to a swing movement of the cam shaft, the movement transmitting mechanism being arranged to apply the torque to one axial end of the cam shaft where the first cam is provided,
• wherein the thickness of the first cylindrical clearance is smaller than that of the second cylindrical clearance.