Easily started DC motor apparatus

• US 5,486,742 A
• Filed: 01/21/1994
• Issued: 01/23/1996
• Est. Priority Date: 09/17/1991
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Iwata, Minoru, Chino, Hiroyuki, Akasaka, Toshiya
• Primary Examiner(s): Cabeca, John W.
• Application Number:
  US08/183,775
• Time in Patent Office: 732 Days
• Field of Search: 318/254, 318/138, 318/257, 318/439, 318/436, 318/696
• US Class Current: 318/400.11
• CPC Class Codes: H02P 6/185 using inductance sensing, e.g. pulse excitation

Abstract

A DC motor apparatus which can be started with a power supply having a small current capacity and which provides a large driving force. The DC motor apparatus comprises a permanent magnet in a rotor of the DC motor, a plurality of coils provided at a stator of the DC motor, a distributor for controlling the switching of current paths to the coils and a position detector for detecting a rotational position of the rotor of the motor to output switching signal to the distributor. A pulsating unit is further provided for pulsating currents supplied to the coils whereby a current flowing from the distributor to any one of the coils can be pulsated when the DC motor is activated, resulting in easy starting the DC motor.

Claims

1. A DC motor comprising:

a rotary member for rotating about an axis;

a stationary member having a pluarlity of coils;

a position setecting means for detecting a pluarlity of positions of said rotary member as said rotary member rotates about said axis;

a DC current distributing means responsive to the output of said position detecting means for sequentially swithcing DC current supplied to said plurality of coils;

a pulsating means for pulsating the DC current flowing through at least one of said plurality of coils selected on the basis of a position of said rotary member detected by said position detector during a period that said DC current is being supplied to said at least one coil; and

wherein, during start-up of the motor, the DC current is pulsed in a timed sequence such that a driving force due to the DC current coincides with a back-and-forth swing of the rotary member resulting from the inertial force of the rotary member when the DC current pulses are supplied thereto.

2. A DC motor apparatus according to claim 1, wherein said pulsating means is disposed between said position detecting means and said distributing means.

3. A DC motor apparatus according to claim 2, further comprising an excitation;

detector for detecting the completion of starting of said motor to stop or bypass the operation of said pulsating means.

4. A DC motor apparatus according to claim 1, wherein said pulsating means is disposed between said plurality of coils and a power supply which supplies currents to these coils.

5. A DC motor apparatus according to claim 4, further comprising an excitation detector for detecting the completion of starting of said motor to stop or bypass the operation of said pulsating means.

6. A DC motor comprising:

a magnetic rotor being rotatable about an axis;

a stator adjacent said rotor and having a plurality of coils;

a position detecting means for detecting a magnetic position of the rotor with respect to the stator;

a DC current distributor connectable to the coils for supplying current and creating magnetic fields around the coils for causing the rotor to rotate;

a pulsating unit for pulsating the current supplied by the distributor;

a detector for detecting when the DC motor is in an initial start-up state and when the DC motor reaches a steady-state;

wherein, during the initial start-up state of the DC motor, current is supplied to a single coil selected on the basis of the magnetic position of the rotor, the pulsating unit pulsates the current supplied to said single coil at a rate which causes the rotor to pendulate back and forth with increasing momentum; and

wherein, during the steady-state of the DC motor, the pulsating unit no longer pulsates the current and the DC distributor supplies current to each of the coils in sequential order to cause the rotor to continuously rotate.