To improve responsiveness to variation operation of a rotation angle phase by effecting further rapid engagement release operation of an engaging means.
Drive torque of a drive means 21 is controlled such that, at the initial stage of engagement release operation of an engaging means 14, initial drive torque higher than proper drive torque necessary to variation of a given amount of a rotation angle phase is operated for a given period and after a lapse of the given period, drive torque is reduce to the proper drive torque. Through control of energization described above, the drive force in the disengaging direction of the engaging means 14 is generated on tooth surfaces of the tapered-off teeth 20A, 20A,..., 20B, 20B,... of the engaging means 14 by drive torque of the drive means 21. The drive torque is set to initial drive torque higher than proper drive torque. Encouraging operation of disengagement of the engaging means 14 through drive torque of the drive means 21 is enhanced. Disengagement of the engaging means 14 is rendered rapid by an amount equivalent to enhancement of the encouraging operation, resulting in improvement of responsiveness to variation operation of a rotation angle phase between first and second rotation transmission members 1 and 2.
OKUDA TSUNEHISA
HARADA TSUKASA
