Brushless DC motors with remote Hall sensing and methods of making the same

• US 20050258786A1
• Filed: 05/19/2004
• Published: 11/24/2005
• Est. Priority Date: 05/19/2004
• Status: Active Grant

• Current Assignee: HR Textron, Inc.
• Original Assignee: HR Textron, Inc.
• Inventors: Mock, M. Robert, Kellogg, Michael I.
• Granted Patent: US 7,095,193 B2
• Time in Patent Office: Days
• US Class Current: 318/400.400
• CPC Class Codes: H02K 15/00 Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence

Abstract

A brushless DC motor apparatus includes a housing and a stator assembly coupled to the housing. The apparatus further includes a magnetic rotor assembly rotatably coupled to the housing. The magnetic rotor assembly is configured to rotate within the housing in response to electric currents through windings of the stator assembly. The apparatus further includes position sensors which are configured to provide position signals identifying angular position of the magnetic rotor assembly relative to the stator assembly. Each position sensor includes (i) a Hall-effect sensor disposed distally from the windings, and (ii) magnetic circuit members having first end portions adjacent the windings and proximate rotor magnets and second end portions adjacent the Hall-effect sensor. Use of such magnetic circuit members enables the Hall-effect sensors to reside a greater distance from the windings vis-à-vis conventional brushless DC motors which position sensors adjacent to stator coils within motor casings.

Claims

1. A brushless DC motor apparatus, comprising:

a housing;

a stator assembly coupled to the housing, the stator assembly having a support and windings coupled to the support;

a magnetic rotor assembly rotatably coupled to the housing, the magnetic rotor assembly being configured to rotate within the housing in response to electric currents through the windings; and

position sensors which are configured to provide position signals identifying angular position of the magnetic rotor assembly relative to the stator assembly, each position sensor including (i) a Hall-effect sensor disposed distally from the windings, and (ii) magnetic circuit members having first end portions adjacent to the windings and proximate to rotor magnets and second end portions adjacent to the Hall-effect sensor.

2. The brushless DC motor apparatus of claim 1 wherein the position sensors include:

a first position sensor, a second position sensor, and a third position sensor, which extend through the housing and are disposed around a periphery of the magnetic rotor assembly in a manner consistent with proper motor commutation and position sensing.

3. The brushless DC motor apparatus of claim 2 wherein the Hall-effect sensors of the first, second and third position sensors are configured to generate, as the position signals, analog output signals to effectuate precise angular position identification.

4. The brushless DC motor apparatus of claim 2 wherein the Hall-effect sensors of the first, second and third position sensors are configured to generate, as the position signals, digital output signals to effectuate precise angular position identification.

5. The brushless DC motor apparatus of claim 4 wherein the magnetic rotor assembly includes:

a shaft which is rotatably coupled to the housing; and

permanent magnets disposed on the shaft, the permanent magnets being configured to concurrently provide (i) torque to rotate the shaft in response to the electric currents through the windings, and (ii) a magnetic field to the Hall-effect sensors of the first, second and third position sensors through the magnetic circuit members of the first, second and third position sensors.

6. The brushless DC motor apparatus of claim 1 wherein the magnetic circuit members of each position sensor includes:

a pair of ferromagnetic material elements, each ferromagnetic material element having a first portion which defines a surface that faces the magnetic rotor assembly, and an interfacing portion which defines a surface that serves as a Hall-effect sensor interface.

7. The brushless DC motor apparatus of claim 6 wherein the surface defined by the first portion of each ferromagnetic material element has a first surface area, wherein the surface defined by the interfacing portion of each ferromagnetic material element has a second surface area, and wherein the first surface area is substantially greater than the second surface area.

8. The brushless DC motor apparatus of claim 1 wherein the windings of the stator assembly are configured to provide a temperature environment which is greater than 100 degrees Celsius, and wherein the Hall-effect sensors of the position sensors are configured to operate in a temperature environment which is less than 150 degrees Celsius.

9. The brushless DC motor apparatus of claim 1 wherein the windings of the stator assembly are configured to operate at a maximum temperature which is greater than 150 degrees Celsius, and wherein the Hall-effect sensors of the position sensors are configured to operate at a maximum temperature which is less than 150 degrees Celsius.

10. A brushless DC motor apparatus, comprising:

a housing;

a stator assembly coupled to the housing, the stator assembly having a support and windings coupled to the support;

a magnetic rotor assembly rotatably coupled to the housing, the magnetic rotor assembly being configured to rotate within the housing in response to electric currents through the windings; and

position sensors which are configured to provide position signals identifying angular position of the magnetic rotor assembly relative to the stator assembly, each position sensor including (i) a Hall-effect sensor disposed distally from the windings, and (ii) means for conducting a magnetic field from a location adjacent to the windings to a location adjacent to the Hall-effect sensor.

11. A DC motor system, comprising:

an interface;

a brushless DC motor apparatus which includes;

a housing;

a stator assembly coupled to the housing, the stator assembly having a support and windings coupled to the support,

a magnetic rotor assembly rotatably coupled to the housing, the magnetic rotor assembly being configured to rotate within the housing in response to electric currents through the windings, and

position sensors which are configured to provide position signals identifying angular position of the magnetic rotor assembly relative to the stator assembly, each position sensor including (i) a Hall-effect sensor disposed distally from the windings, and (ii) magnetic circuit members having first end portions adjacent to the windings and second end portions adjacent to the Hall-effect sensor; and

a controller coupled to the interface, the windings of the stator assembly and the position sensors, the controller being configured to receive the position signals provided by the position sensors and generate the electric currents through the windings in response to commands from the interface.

12. The DC motor system of claim 11 wherein the position sensors of the brushless DC motor apparatus include:

a first position sensor, a second position sensor, and a third position sensor, which are coupled to the housing and disposed around a periphery of the magnetic rotor assembly.

13. The DC motor system of claim 11 wherein the magnetic circuit members of each position sensor include:

a pair of ferromagnetic material elements, each ferromagnetic material element having a first portion which defines a surface that faces the magnetic rotor assembly, and an interfacing portion which defines a surface that serves as a Hall-effect sensor interface.

14. The DC motor system of claim 11 wherein the windings of the stator assembly are configured to operate at a maximum temperature which is greater than 150 degrees Celsius, and wherein the Hall-effect sensors of the position sensors are configured to operate at a maximum temperature which is less than 150 degrees Celsius.

15. A method for manufacturing a brushless DC motor apparatus, the method comprising:

coupling a stator assembly to a housing, the stator assembly having a support and windings supported by the support;

installing position sensors adjacent to the stator assembly, the position sensors being configured to provide position signals identifying angular position of a magnetic rotor assembly relative to the stator assembly, each position sensor including (i) a Hall-effect sensor disposed distally from the windings, and (ii) magnetic circuit members having first end portions adjacent to the windings and second end portions adjacent to the Hall-effect sensor; and

rotatably coupling the magnetic rotor assembly to the housing, the magnetic rotor assembly being configured to rotate within the housing in response to electric currents through the windings.

16. A magnetic circuit adapted for use in a brushless DC motor, the magnetic circuit comprising:

a first magnetic circuit member and a second magnetic member, each of the first and second magnetic members including (i) a first end portion configured to reside in a fixed position adjacent to windings of the brushless DC motor, and (ii) a second end portion configured to reside adjacent to a Hall-effect sensor to conduct a magnetic field from a magnetic rotor assembly, which is rotatable relative to the windings, to the Hall-effect sensor enabling the Hall-effect sensor to provide a position signal identifying an angular position of the magnetic rotor assembly relative to the windings.

17. The magnetic circuit of claim 16 wherein each magnetic circuit member includes:

a ferromagnetic material element having a first portion which defines a surface configured to face the magnetic rotor assembly, and an interfacing portion which defines a surface configured to serve as a Hall-effect sensor interface to the Hall-effect sensor.