Sanden Corporation

Tadashi Miyazawa

Toshiyuki Teshigawara

A brushless dc motor having 3-phase stator windings and a permanent-magnet rotor is driven on a dc voltage through a 3-phase electronic switching circuit. Back emf voltages across the stator windings are individually phase-delayed and the phase-delayed voltages are individually compared in comparators with a common sawtooth-wave comparator reference voltage having a frequency proportional to a current rotor speed and an amplitude whose center voltage is one-half of the motor driving dc voltage. A drive control unit, a microcomputer, transmits to the switching circuit switching control signals in sequential driving steps according to 3-phase output signals of the comparators so that the switching circuit performs commutation of the motor drive voltage in a first motor driving mode. The time constant of the phase-delay circuits is increased when the rotational speed of the rotor is below a predetermined speed or the motor driving current is above a predetermined level. When the time constant is increased, the motor driving mode is switched from the first motor driving mode to a second motor drive mode for a predetermined time period at fixed driving steps regardless of the 3-phase comparator output signals. The motor driving mode reverts to the first motor driving mode when the predetermined time period for the second motor driving mode has lapsed.

Apparatus and method for driving and controlling brushless motor

A coin return control system for vending machines is disclosed which includes a predetermined coin denomination detecting portion for detecting the coin denomination predetermined by a coin denomination predetermination switch every time change may have to be paid out by the vending machine. A memory memorizes the coin denomination detected by the coin denomination detecting portion immediately after operating an inventory switch which is a switch other than the coin denomination predetermination switch. A variation detecting portion detects the variation of the coin denomination predetermined by the coin denomination predetermination switch based on the coin denomination detected by the predetermined coin denomination detecting portion and the coin denomination memorized by the memory. An instruction portion instructs the coin paying-out mechanism to return a coin from the auxiliary change retaining tube when the number of coins retained in the change retaining tube corresponding to the coin denomination memborized by the memory is below a predetermined value. A determination portion determines whether or not the instruction portion should instruct the coin paying-out mechanism to return a coin from the auxiliary change retaining tube based on the detected result of the variation detecting portion. Therefore, the coin return control system for vending machines always correctly pays out a necessary coin despite the position of the coin denomination predetermination switch or a faulty read out of the position of the switch.

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Tatebayshi, Japan

Tadashi Miyazawa