Stepping motor drive unit

• US 5,625,268 A
• Filed: 07/20/1994
• Issued: 04/29/1997
• Est. Priority Date: 07/29/1993
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Miyanari, Hiroshi
• Primary Examiner(s): Masih, Karen
• Application Number:
  US08/275,747
• Time in Patent Office: 1,014 Days
• Field of Search: 318/696, 318/685, 318/65, 318/280, 318/286, 363/58, 363/132, 363/136, 363/127, 354/195.1, 359/696
• US Class Current: 318/696
• CPC Class Codes: H02P 8/20 characterised by bidirectional operation

Abstract

A stepping motor drive circuit including a bridge circuit composed of energizing coils constituting a stepping motor and four transistors, and current value switching circuitry for selecting a value of current flow according to the rotation direction of the stepping motor. A value of constant current flow is determined according to the rotation direction of the stepping motor, so that the torque of the stepping motor is optimized relative to a load.

Claims

1. A stepping motor drive unit for a stepping motor including a driven member rotatable in a first direction or a second direction opposite the first direction, and having a first load torque when driven in the first direction and a second load torque when driven in the second direction, the drive unit comprising:

at least two energizing coils;

at least two bridge circuits for providing respective current flow through said energizing coils in forward and reverse flow directions, each of said bridge circuits including a plurality of transistors for switching the current flow between the forward and reverse flow directions;

control means for selectively switching said plurality of transistors in accordance with a direction of rotation of the driven member, so that current flows through said energizing coils in either the forward or reverse flow direction; and

current setting means for setting a value of current flow through said energizing coils in accordance with

current setting means for setting a value of current flow through said energizing coils in accordance with the direction of rotation of the stepping motor,

wherein said current setting means includes a memory in which first and second current value data corresponding to the first and second load torques of a stepping motor are stored, and reference voltage setting means for feeding current value data read from said memory as a reference voltage value to said bridge circuits so that a predetermined current corresponding to a selected one of said first and second current value data will flow through said energizing coils.

2. A stepping motor drive unit for a stepping motor including a driven member rotatable in a first direction or a second direction opposite the first direction, and having a first load torque when driven in the first direction and a second load torque when driven in the second direction, the drive unit comprising:

at least two energizing coils;

at least two bridge circuits for providing respective current flow through said energizing coils in forward and reverse flow directions, each of said bridge circuits including a plurality of transistors for switching the current flow between the forward and reverse flow directions;

control means for selectively switching said plurality of transistors in accordance with a direction of rotation of the driven member, so that current flows through said energizng coils in either the forward or reverse flow direction; and

current setting means for setting a value of current flow through said energizing coils in accordance with the direction of rotation of the stepping motor,

wherein said reference voltage setting means includes a CPU for reading current value data from said memory, and for selecting predetermined current value data according to the direction of rotation of the driven member of a stepping motor, and a D/A converter for converting current value data that is a digital value selected by said CPU into an analog value and feeding the analog value to said bridge circuits.

3. A stepping motor drive unit for driving a stepping motor for a lens array the stepping motor including,

a driving mechanism for moving said lens array in a first direction or a second direction opposite the first direction, said driving mechanism having pressing means for pressing said lens array in said first or second direction, and having a first load torque when said pressing means presses said lens array in said first direction and having a second load torque when said pressing means presses said lens array in the second direction, said stepping motor including a driven member rotatable in forward and reverse directions, such that, when said driven member rotates in the forward direction, said lens array moves in the first direction, and when said driven motor rotates in the reverse direction, said lens array moves in the second direction, said drive unit comprising:

energizing coils;

a circuit for providing current flow through said energizing coils in forward and reverse directions, said circuit providing current flow in the forward direction so as to rotate said driven member in the forward direction, and providing current flow in the reverse direction so as to rotate said driven member in the reverse direction;

control means for controlling said circuit in accordance with current data so as to selectively provide current flow through said energizing coils in the forward or reverse direction; and

current setting means for setting a value of current flow through said energizing coils in accordance with the direction of rotation of said driven member.

4. A stepping motor drive unit, comprising:

a driving mechanism for providing a drive in a first direction or a second direction opposite the first direction, said driving mechanism including pressing means having a first load torque when said pressing means presses in said first direction and a second load torque when said pressing means presses in said second direction;

a stepping motor serving as a driving source for driving said driving mechanism, said stepping motor including energizing coils and a rotor rotatable in forward and reverse directions, said rotor rotating in the forward direction so as to drive said drive mechanism in said first direction, and rotating in the reverse direction so as to drive said driving mechanism in said second direction;

a circuit for providing current flow through said energizing coils in forward and reverse directions, said circuit providing current flow in the forward direction so as to rotate said rotor in the forward direction, and providing current flow in the reverse direction so as to rotate said rotor in the reverse direction;

control means for controlling said circuit so as to selectively provide current flow through said energizing coils in the forward or reverse direction; and

current setting means for setting a value of current flow through said energizing coils in accordance with the direction of rotation of said rotor.

5. A stepping motor drive unit according to claim 4, wherein said current setting means includes a memory in which current value data corresponding to the forward and reverse directions of rotation of said driven member are stored, and a reference voltage setting means for feeding current value data read from said memory as a reference voltage value to said circuit so that a predetermined current corresponding to said current value data flows through said energizing coils.

6. A stepping motor drive unit according to claim 5, wherein said reference voltage setting means includes a CPU for reading current value data from said memory, and for selecting predetermined current value data according to the direction of rotation of the driven member of a stepping motor, and a D/A converter for converting current value data that is a digital value selected by said CPU into an analog value and feeding the analog value to said bridge circuit.