Linear actuator comprising a brushless polyphase electric motor

• US 20050218727A1
• Filed: 03/04/2003
• Published: 10/06/2005
• Est. Priority Date: 03/05/2002
• Status: Active Grant

• Current Assignee: Moving Magnet Technologies
• Original Assignee: Moving Magnet Technologies
• Inventors: Foucaut, Antoine, Gandel, Pierre, Prudham, Daniel, Alzingre, Jean-Daniel
• Granted Patent: US 7,589,445 B2
• Time in Patent Office: Days
• US Class Current: 310/80
• CPC Class Codes: F16H 2025/2075 Coaxial drive motors
• CPC Class Codes: F16H 2025/2087 using planetary gears
• CPC Class Codes: F16H 25/20 Screw mechanisms with automatic reversal F16H25/12
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02K 7/06 Means for converting reciprocating motion into rotary motion or vice versa

Abstract

A linear actuator includes a brushless polyphase synchronous electric motor having a stator and a rotor. The rotor acts on a control element via a driver which can transform the rotation movement thereof into a linear movement over several rotations. Preferably, the inventive actuator comprises elastic and/or magnetic return device which can systematically return the control element to a reference position when the power supply to the motor is cut. The motor has a position detection device which, together with an electronic control unit, is used for the automatic control and regulation of the position of the rotor and, therefore, the control element.

Claims

1. Linear actuator comprising

a brushless multiphase synchronous electric motor having a stator and a rotor acting on a control organ through a driving means for converting, over several revolutions, rotational movement into a linear displacement;

a springy and/or magnetic restoring means for systematically restoring the control organ into a reference position in the event of interruption of the power supply to the motor;

a position-detection device of the motor contributing, in combination with an electronic control unit, to the control or the adjustment of the position of the rotor and the control organ; and

an independent reversible reduction device associated with the driving means.

2. Linear actuator according to claim 1, wherein said springy and/or magnetic restoring means are comprised of at least one springy and/or magnetic element actionable on said rotor to restore the control organ and startable from any position previously imparted by the motor, into said reference position.

3. Linear actuator according claim 1, wherein said springy and/or magnetic restoring means are comprised of a springy and/or magnetic element actable directly on the control organ in order to restore the control organ and startable from any position imparted by the motor, into said reference position.

4. Actuator according to claim 1, wherein said springy and/or magnetic restoring means are comprised of a combination of a springy and/or magnetic element controlling the rotation of the rotor and a springy and/or magnetic element actable directly on the control organ so as to restore the control organ into a reference position, and being startable from any position previously imparted by the motor.

5. Linear actuator according to claim 1, wherein said driving means for converting the rotational motion of the rotor into a linear movement is reversible.

6. Linear actuator according to claim 1, wherein said driving means for converting the rotational movement of the rotor into a linear movement are comprised of a screw and nut system, the rotor having, at the level of an axial bored, a nut engaged with a coaxial threaded rod defining, directly or indirectly, the control organ.

7. Linear actuator according to claim 6, wherein said nut carried by the rotor is mounted moveably on a fixed threaded rod so as to be movable, according a helical motion, under the stator and having a linear displacement thereof transmittable to the control organ immobilized in rotation.

8. Linear actuator according to claim 6, wherein the screw and nut system is of the ball screw type with low friction coefficient.

9. Linear actuator according to claim 1, wherein said driving means for converting the rotational motion of the rotor into a linear displacement is comprised of a system of the type roller and cam, the roller associated with the control organ evolving along a circular cam put into rotation, directly or indirectly, by the rotor.

10. Linear actuator according to claim 1, wherein said driving means for converting the rotational motion of the rotor into a linear displacement comprises a first cam and a second cam with crossed profiles rotated rotatable with a differential speed, in order to impart to a roller, in the form of a pin, an axial sliding causing the translation of the control organ (O).

11. Linear actuator according to claim 1, wherein said detection device comprises magneto-sensitive elements, such as Hall sensors, integrated into the stator of the motor magnetic poles of the rotor being detectable to the elements.

12. Linear actuator according to claim 11, wherein said detection device comprises a linear position sensor associated with the control organ.

13. Linear actuator according to claim 1, wherein said motor comprises a rotor including N pairs of rotor poles radially magnetized in an alternate direction, N being greater or equal to four, while being different from a multiple of three, the stator comprising P×

9 identical poles spaced apart by 40°

/P, said stator poles being grouped consecutively three by three, so as to define a W-shaped circuit, grouping three consecutive stator poles the central stator pole of which carries the coil of the corresponding phase, said central stator poles of two W-shaped circuits, each corresponding to a phase, being angularly spaced apart by 120°

.