Patent ID: 8773114

Claim:
An apparatus for detecting a displacement of an electromagnetic actuator, comprising: an electromagnetic actuator including: a movable core; a drive coil which causes a displacement of the movable core by giving a drive force to the movable core; and a detection coil which is disposed at a position where a mutual coupling coefficient with the drive coil changes in accordance with the displacement of the movable core, the electromagnetic actuator transmitting a drive force of the movable core to a mechanical system; a drive portion configured to supply a drive current to the drive coil, the drive current being synchronized with a pulse width modulation signal; and a displacement detecting portion to which an output voltage of the detection coil is inputted and which is configured to output a displacement detection signal corresponding to the displacement of the movable core, wherein the displacement detecting portion includes: a sampling-signal generating portion configured to generate a sampling signal in synchronism with the pulse width modulation signal; and a synchronous sampling portion configured to output the displacement detection signal by sampling the output voltage of the detection coil in synchronism with the sampling signal.