Abstract: 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.

Abstract: A method of making a cylindrical ferromagnetic body and cover assembly for a rotor of a dc motor is provided. In a first embodiment, a blend of a powdered ferromagnetic material and a heat-curable binder is compressedly molded into a cylindrical form in a generally cylindrical non-magnetic cover material having an annular flange around the top thereof, while heat is applied to the material from a heated stationary mold through the cover material, so that the cylindrically-molded ferromagnetic body firmly adheres to the cover material in the molding process. After the ferromagnetic body is cured, an non-magnetic annular protector is placed on the top of the cylindrically-molded body and the annular flange is radially inwardly bent over onto the protector. In a second embodiment, a heated block of a powdered ferromagnetic material is deposited in a cup-shaped non-magnetic cover material.

Abstract: An apparatus is provided for allowing simple entry and display of location information in a vehicle travel guide system. Spot information corresponding to contents carried on an atlas is stored in a memory card 24, and by designating a retrieval condition such as an atlas name corresponding to an atlas, a page, an area or an attribute of a spot, spot information which satisfies the retrieving condition is retrieved from the spot information stored in the memory card 24 and a result of the retrieval is displayed on a display unit 23 in a superimposed relationship with an over wide image of the atlas. Further, desired spot information as the result of the retrieval is selected, and the selected spot information is stored as position information of a current location or a destination into a position information memory 12. The disclosed apparatus allows a beginner who is not familiar with the operation of the device to input position information such as a destination readily in a short time without confusion.

Abstract: A flat motor is disclosed comprising a motor housing having a first engaging mechanism, a magnet fixed to the motor housing, a holder plate attached to the motor housing and provided with a pair of brush holders. The holder plate has a second engaging mechanism engaging the first engaging mechanism. A third engaging mechanism engages an inside surface of the magnet. The holder plate can be positioned coaxially with the motor housing by the engagement of the first engaging mechanism with the second engaging mechanism, the magnet can be positioned coaxially with the holder plate by the engagement of the third engaging mechanism with the magnet. The motor housing, the holder plate and the magnet can all be positioned coaxially with one another without use of a particular jig, thereby improving the assembly of the flat motor and increasing the productivity of the motor.