Valve timing adjustment device

A valve timing adjustment device for adjusting a valve timing of a valve that is opened and closed by a camshaft with a torque transmitted from a crankshaft at an internal combustion engine, the valve timing adjustment device comprising:

• a drive-side rotor that is configured to be rotated synchronously with the crankshaft about a rotation center axis that is coaxial with the camshaft;
• a driven-side rotor that is configured to be rotated integrally with the camshaft about the rotation center axis;
• an internal gear section that is formed at one of the driven-side rotor and the drive-side rotor;
• a planetary rotor that has a planetary gear section which is eccentric to the rotation center axis and is meshed with the internal gear section;
• an Oldham coupling that includes:
• a driven Oldham flange that is formed at another one of the driven-side rotor and the drive-side rotor;
• a drive Oldham flange that is formed at the planetary rotor;
• and
• an Oldham intermediate that is configured to synchronize rotation of the driven Oldham flange and rotation of the drive Oldham flange while permitting eccentricity between the driven Oldham flange and the drive Oldham flange;
• and
• a thrust section that is formed at a portion which is other than the Oldham coupling, wherein the thrust section is configured to limit tilting of the planetary rotor relative to the driven Oldham flange when the thrust section contacts the planetary rotor in an axial direction of the rotation center axis, wherein:
• the valve timing adjustment device is configured to satisfy a relationship of θ2>θ1 where:
• θ1 is a maximum tilt amount of the planetary rotor relative to a surface of the driven Oldham flange which is opposed to the Oldham intermediate in the axial direction;
• and θ2 is a maximum tilt amount of the planetary rotor in a clearance formed at the Oldham coupling;
• the valve timing adjustment device is configured to satisfy at least one of a relationship of θ2b>θ1 or a relationship of θ2a>θ1 where:
• a relative moving direction of the Oldham intermediate relative to the drive Oldham flange is defined as a first direction;
• a relative moving direction of the Oldham intermediate relative to the driven Oldham flange is defined as a second direction;
• θ2a is a maximum tilt amount of the planetary rotor in the clearance formed at the Oldham coupling and is a rotation angle of the planetary rotor about a first rotation axis that is parallel to the first direction;
• and
• θ2b is a maximum tilt amount of the planetary rotor in the clearance formed at the Oldham coupling and is a rotation angle of the planetary rotor about a second rotation axis that is parallel to the second direction;
• and
• the valve timing adjustment device is further configured to satisfy all of the relationships of
• θ1=arctan(CL5/L3);
• θ2a=arctan((CL1+CL2/L1)+arctan((CL3+CL4)/L2);
• and
• θ2b=arctan(CL6/L4)+min{arctan((CL7+CL8)/L6), arctan((CL1+CL2)/L5)}
• where:
• CL1 is one of two opposite axial clearances respectively formed between the Oldham intermediate and the drive-side rotor in the axial direction, and CL2 is another one of the two opposite axial clearances respectively formed between the Oldham intermediate and the drive-side rotor in the axial direction;
• L1 is a diameter of an axially contacting part of the Oldham intermediate that is configured to axially contact the drive-side rotor;
• CL3 is one of two opposite circumferential clearances respectively formed between the planetary rotor and the Oldham intermediate in a circumferential direction, and CL4 is another one of the two opposite circumferential clearances respectively formed between the planetary rotor and the Oldham intermediate in the circumferential direction;
• L2 is an axial length of a circumferentially contacting part of the Oldham intermediate that is configured to circumferentially contact the planetary rotor;
• CL5 is an axial clearance between the planetary rotor and the drive-side rotor;
• L3 is a diameter of an axially contacting part of the planetary rotor that is configured to axially contact the drive-side rotor;
• CL6 is an axial clearance between the Oldham intermediate and the driven-side rotor;
• L4 is a maximum distance in a direction perpendicular to the rotation center axis between:
• one axially contacting part of the driven-side rotor that is configured to axially contact another member at one axial side of the driven-side rotor;
• and another axially contacting part of the driven-side rotor that is configured to axially contact further another member at another axial side of the driven-side rotor;
• L5 is a circumferential length of the axially contacting part of the Oldham intermediate that is configured to axially contact the drive-side rotor;
• CL7 is one of two opposite circumferential clearances respectively formed between the Oldham intermediate and the drive-side rotor in the circumferential direction, and CL8 is another one of the two opposite circumferential clearances respectively formed between the Oldham intermediate and the drive-side rotor in the circumferential direction;
• L6 is an axial length of a circumferentially contacting part of the Oldham intermediate that is configured to circumferentially contact the drive-side rotor;
• and
• min denotes a minimum function.