Electronic device including structure for detecting rotation amount of motor

A power transmission device comprising:

• a motor housing including a first space and a second space distinct from the first space;
• a motor disposed within the first space in the motor housing;
• a shaft disposed within the second space, the shaft extending from the motor and configured to be rotated by the motor;
• a partition wall separating the first space and the second space;
• a pinion gear disposed within the second space, the pinion gear coupled to the shaft and including a plurality of teeth;
• a first magnet;
• a second magnet facing the first magnet with respect to the shaft;
• a hall sensor configured to detect a magnetic field changed by rotation of the pinion gear, and
• a metal plate including a ferromagnetic material to induce magnetic field;
• and
• wherein a relative position among the first magnet, the second magnet and the hall sensor is maintained while the pinion gear is rotated, and
• wherein a polarity of surfaces of the first magnet and the second magnet facing each other is the same.

A power transmission device comprising:

• a motor housing including a first space and a second space distinct from the first space;
• a motor disposed within the first space in the motor housing;
• a shaft disposed within the second space, the shaft extending from the motor and configured to be rotated by the motor;
• a partition wall separating the first space and the second space;
• a pinion gear disposed within the second space, the pinion gear coupled to the shaft and including a plurality of teeth;
• at least one magnet;
• a hall sensor configured to detect a magnetic field changed by rotation of the pinion gear, and
• a metal plate including a ferromagnetic material to induce magnetic field;
• and
• wherein a relative position between the at least one magnet and the hall sensor is maintained while the pinion gear is rotated, and
• wherein the at least one magnet includes a through hole through which the shaft passes.