A linear motor includes a slider unit having a magnet row in which plural permanent magnets are arranged in series so that the same poles are opposed to each other, a stator unit including electromagnetic coils for plural phases arranged along a movement direction of the slider unit, and plural magnetic detector devices, wherein the plural magnetic detector devices are provided in response to the phases of the electromagnetic coils for plural phases and detect magnetic flux radially extending in a direction perpendicular to the arrangement direction of the permanent magnets at boundaries between the permanent magnets of the magnet row and output signal waveforms for plural phases at phases equal to phases of waveforms of back electromotive forces generated in the respective electromagnetic coils for plural phases when the magnet row moves.
1. A linear motor comprising:
a slider unit having a magnet row in which plural permanent magnets are arranged in series so that the same poles are opposed to each other and moving in an arrangement direction of the magnet row by electromagnetic force;
a stator unit including electromagnetic coils for plural phases arranged along a movement direction of the slider unit and receiving supply of drive currents at different phases with respect to each phase; and
plural magnetic detector devices that detect changes of magnetic flux with movement of the magnetic row for controlling movement of the slider unit,
wherein the plural magnetic detector devices are provided in response to the phases of the electromagnetic coils for plural phases and arranged along the movement direction of the slider unit at an outer circumferential side of the electromagnetic coils for plural phases, and thereby, detect magnetic flux radially extending in a direction perpendicular to the arrangement direction of the permanent magnets at boundaries between the permanent magnets of the magnet row and output signal waveforms for plural phases at phases equal to phases of waveforms of back electromotive forces generated in the respective electromagnetic coils for plural phases when the magnet row moves.
2. The linear motor according to claim 1 , further comprising a control unit that controls drive signals of the linear motor based on output signals for at least two phases output by the plural magnetic detector devices and detects a position of the slider unit for controlling the position of the slider unit.
3. The linear motor according to claim 2 , wherein the electromagnetic coils for plural phases are electromagnetic coils for three phases,
the plural magnetic detector devices output signal waveforms for three phases corresponding to the electromagnetic coils for three phases, and
the control unit transforms the signal waveforms for three phases into signal waveforms for two phases corresponding to positions of the boundaries between the permanent magnets in the magnet row and detects the position of the slider unit based on the signal waveforms for two phases.
4. The linear motor according to claim 1 , wherein aback yoke is provided between the plural magnetic detector devices and the electromagnetic coils for plural phases, and
plural slits along the movement direction of the slider unit are formed in the back yoke.