Oil drain structure of valve timing adjusting device for internal combustion engine

An oil drain structure of a valve timing adjusting device between a crank shaft and a cam shaft of an internal combustion engine, the oil drain structure comprising:

• a housing coupled with a ratchet plate interlocking with the crank shaft and having an inner space;
• a rotor configured to partition the inner space of the housing into an advance chamber and a retard chamber while interlocking with the cam shaft, the rotor having a plurality of vanes relatively rotating in the advance chamber and the retard chamber with respect to the housing by a pressure of a working fluid to adjust a phase;
• and
• a rotation preventing means configured to suppress a position change between the rotor and the housing by regulating the relative rotation of the rotor with respect to the housing,
• wherein the rotation preventing means includes:
• a locking pin member elastically installed in a mounting hole of at least one of the vanes;
• a plurality of locking grooves connected to each other at different depth on a surface of the ratchet plate so that the plurality of locking grooves are coupled with the locking pin member during a locking operation of the locking pin member;
• a drain groove connected to at least one locking groove of the plurality of locking grooves and configured to discharge the working fluid within the at least one locking groove during the locking operation;
• and
• a drain hole formed in the rotor and configured to communicate with the drain groove.