Brushless motor with rotor position detection compensation caused by induced voltage in rotor

• US 5,982,133 A
• Filed: 07/23/1996
• Issued: 11/09/1999
• Est. Priority Date: 07/28/1995
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Murakami, Hiroshi, Ito, Hiroshi, Asano, Yoshinari, Honda, Yukio, Narazaki, Kazushige, Kadoya, Naoyuki, Shinto, Masayuki
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/685,081
• Time in Patent Office: 1,204 Days
• Field of Search: 318/254, 318/439, 318/138, 318/650, 318/432, 318/434, 318/798-811
• US Class Current: 318/650
• CPC Class Codes: H02P 23/009 using field weakening
• CPC Class Codes: H02P 6/153 wherein the commutation is advanced from position signals phase in function of the speed
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

A brushless motor having at least one current influence detector (10a, 10b, 10c) for detecting influence of an induced voltage caused by variations of current flowing in an armature winding (3). Furthermore, a positional signal detecting circuit means (11) detects a positional signal corresponding to rotational position of the rotor (2) in accordance with the voltage signal appearing at the armature winding (3) and the output signal issued from the at least one current influence detector (10a, 10b, 10c).

Claims

1. A brushless motor comprising:

a rotor having a magnet,

an armature winding having three coils connected in three-phase star connection, said armature winding being arranged in interlinkage with a magnetic field generated by said magnet,

a semiconductor commutator means having six switching elements connected in a three-phase bridge connection, three output terminals of said semiconductor commutator means being connected with said three coils, respectively,

at least one current influence detector for detecting the influence of an induced voltage generated by variations of current flowing in said armature winding,

a positional signal detecting circuit means for receiving a voltage signal appearing at said armature winding and an output signal issued from said at least one current influence detector, said positional signal detecting circuit means detecting a positional signal corresponding to the rotational position of said rotor in accordance with said voltage signal and said output signal,

a phase signal output circuit means for determining a phase of the current to be supplied in said armature winding responding to said positional signal issued from said positional signal detecting circuit means, and

a control circuit means for issuing six control signals to said six switching elements responding to a phase signal issued from said phase signal output circuit means,

said at least one current influence detector having a ring-shaped core and a winding wound around said ring-shaped core in a toroidal shape, said ring-shaped core being disposed at a wiring for connecting said positional signal detecting circuit means and said semiconductor commutator means so that said wiring goes through the inside of said ring-shaped core so that the least one current influence detector and the wiring constitute a current transformer, and mutual inductance of the at least one current influence detector is equal to self-inductance of each of the three coils.

2. A brushless motor in accordance with claim 1, wherein said positional signal detecting circuit means subtracts said output signal from said voltage signal.

3. A brushless motor comprising:

a rotor having a magnet,

an armature winding having three coils connected in three-phase star connection, said armature winding being arranged in interlinkage with a magnetic field generated by said magnet,

a semiconductor commutator means having six switching elements connected in a three-phase bridge connection, three output terminals of said semiconductor commutator means being connected with said three coils, respectively,

at least one current influence detector for detecting the influence of an induced voltage generated by variations of current flowing in said armature winding,

a positional signal detecting circuit means for receiving a voltage signal appearing at said armature winding and an output signal issued from said at least one current influence detector, said positional signal detecting circuit means detecting a positional signal corresponding to the rotational position of said rotor in accordance with said voltage signal and said output signal, and thereby eliminating the influence of the induced voltage,

a phase signal output circuit means for determining a phase of the current to be supplied in said armature winding responding to said positional signal issued from said positional signal detecting circuit means, and

a control circuit means for issuing six control signals to said six switching elements responding to a phase signal issued from said phase signal output circuit means,

said at least one current influence detector having a ring-shaped core and a winding wound around said ring-shaped core in a toroidal shape, said ring-shaped core being disposed at a wiring for connecting said positional signal detecting circuit means and said semiconductor commutator means so that said wiring goes through the inside of said ring-shaped core so that the least one current influence detector and the wiring constitute a current transformer, and mutual inductance of the at least one current influence detector is equal to self-inductance of each of the three coils.

4. A brushless motor in accordance with claim 3, wherein said positional signal detecting circuit means subtracts said output signal from said voltage signal.