Disclosed is an apparatus for detecting a position of a drawbar unit
installed in a spindle unit. The apparatus is a part of an automatic tool
exchange device for exchanging tools in the spindle unit of a machine
tool. The apparatus transmits a signal to a main controller after
detecting the position of the drawbar such that the main controller
checks a state of a tool clamped by the drawbar unit. The drawbar unit is
installed in the spindle unit forming the automatic tool exchange device
and clamps the tool at a front thereof. A core is installed at a rear
peripheral portion of the drawbar unit and a coil section having a
cylindrical shape is wound around an outer peripheral portion of the
core. An LC oscillating circuit is provided such that the LC oscillating
circuit includes the coil section as a part thereof. An oscillating
frequency of the LC oscillating circuit varies depending on a position of
the core made of magnetic material, so the apparatus detects the position
of the drawbar unit based on the oscillating frequency of the LC
oscillating circuit. A position detecting section transmits present
position information of the drawbar unit to a main controller, so the
main controller detects the present position of the drawbar unit.