Brushless motor driving system

#1. Field of the Invention

#The present invention relates to brushless motor driving systems and more particularly to a brushless motor driving system which will detect positions of a rotor composed of a permanent magnet by way of magnetic flux sensing elements such as Hall generators to suitably distribute the driving exciting current flown into field coils thereby imparting a rotative force to the motor, wherein alternating signals of low frequencies are applied as a power source, the direction of power supply to the motor being inverted by said alternation to reversely rotate the motor.

#2. Description of the Prior Art

#FIG. 1 is an electrical circuit diagram of one preferred embodiment of a brushless motor driving system in accordance with the present invention.

#FIG. 2 is an electrical circuit diagram of another preferred embodiment of a brushless motor driving system in accordance with the present invention.

#FIG. 3 is a sectional view illustrating the construction of a brushless motor applicable to the present invention.

#The arrangement of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram of one preferred embodiment of a Hall motor driving system in accordance with the present invention. In FIG. 1, the system comprises a D.C. power source E and a change-over switch S, polarities of terminals A and B being inverted by changing over said switch S between the left and the right. The system further comprises a Hall generator unit H, a motor driving unit D, and diodes D.sub.1 -D.sub.4 connected in the form of a bridge, to the outputs of which said Hall generator H and motor driving unit D are connected. A circuit I is provided to invert and control the order of applying a Hall generator output to the driving unit D. The Hall generator unit H has Hall generators H.sub.1 and H.sub.2 connected with an emitter output circuit in a constant-voltage circuit consisting of a resistor R.sub.1, diodes D.sub.5, D.sub.6 and a transistor Q.sub.1, said Hall generators H.sub.1, H.sub.2 being arranged on a stator of the motor in a suitable manner opposite to the magnetic poles of the rotor. The Hall generators have output terminals a, b, c, d, outputs of which are received into a signal composer M in the inversion and control circuit I, and a trigger signal generator T is triggered by the output from the signal composer M to generate pulse signals. The reference character C denotes a reversible shift type ring counter. The motor driving circuit D comprises field coils L.sub.1 -L.sub.4 of the motor, driving transistors Q.sub.2 -Q.sub.5, AND circuits G.sub.1 -G.sub.4, and a resistor R.sub.2.

#Operation of this circuit will now be described with reference to FIGS. 1 and 4.

#Assume that change-over switch S is changed-over so that the terminal A thereof occupies the positive position (+) while the terminal B thereof occupies the negative position (-), the Hall generators H.sub.1 and H.sub.2 will have current flown into a circuit of ##EQU1## Hence, the positive (+) Hall voltages are produced, as shown in FIGS. 4 (A) - (D), on the order of a, b, c, and d in the output terminals of Hall generators H.sub.1, H.sub.2 in response to rotation of the rotor, and these Hall voltages are successively applied to the composer M. The trigger signal generator circuit T is triggered by the output of the composer M as shown in FIG. 4 (E), and a trigger pulse shown in FIG. 4 (F) is produced from the output thereof in response to rotation of the motor. This trigger pulse is received into an input terminal e of the reversible ring counter C. This counter C is designed to be selectively shifted to the right or left in response to the input signal when the positive (+) potential as shown in FIG. 4 (G) is applied to input terminal f or g. When the positive (+) pole of the power source is connected with the terminal A, diode D.sub.7 is energized while diode D.sub.8 is deenergized so that, the positive (+) potential is applied to the terminal f, causing the counter to shift to the right such that the trigger pulse to the terminal e is received. Consequently, the outputs of the counter C produce outputs as shown in FIGS. 4 (H) - (K) on the order of O.sub.4 - O.sub.3 - O.sub.2 - O.sub.1, which are then received into AND circuits G.sub.1 - G.sub.4 in the motor driving unit. These AND circuits are designed to be turned ON by the output of the counter C and the potentials in the driving circuits. For instance, the AND circuit G.sub.1 is turned ON by the output O.sub.1 of the counter C and the potential in the circuit of coil L.sub.4, that is, by the signal from O.sub.1 when the circuit of coil L.sub.4 is in the OFF state. The AND circuits so designed as just described above are used to make sure that conduction of current to the preceding coil has been completed and to allow conduction of current to the successive coil so that an overlapped portion of operating time between both coils may be eliminated to produce no irregularities in producing torque.