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

• US 7,095,193 B2
• Filed: 05/19/2004
• Issued: 08/22/2006
• Est. Priority Date: 05/19/2004
• Status: Active Grant

• Current Assignee: HR Textron, Inc.
• Original Assignee: HR Textron, Inc.
• Inventors: Kellogg, Michael I., Mock, M. Robert
• Primary Examiner(s): Duda, Rina
• Assistant Examiner(s): Horn, Robert
• Application Number:
  US10/848,888
• Publication Number:
  US 20050258786A1
• Time in Patent Office: 825 Days
• Field of Search: 318/138, 318/254, 318/439, 318722-724, 310/68.B, 310/156.05, 310/156.06, 324/179
• US Class Current: 318/400.38
• 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,

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.

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. A brushless DC motor apparatus according to claim 1, wherein:

the Hall-effect sensors are disposed distally from the windings outside one end of the housing in a direction parallel to the axis of rotation of the magnetic rotor assembly;

the rotor magnets are disposed on a generally cylindrical shaft of the magnetic rotor assembly and have an elongated shape generally aligned with the axis of the shaft;

the magnetic circuit elements are elongated in a direction generally aligned with the axis of the shaft and extend through the one end of the housing, and the first end portion of each magnetic circuit element is disposed immediately opposite the rotor magnets at one end thereof.

9. A brushless DC motor apparatus according to claim 8, wherein the magnetic circuit members for each position sensor describe an elongated U shape with the first end portions located at respective tips of one end of the elongated U shape and the second end portions curving towards each other to form a curved middle section at the other end of the elongated U shape.

10. A brushless DC motor apparatus according to claim 9, wherein each magnetic circuit member has a step-like bend in a respective mid-portion between the first and second end portions.

11. A brushless DC motor apparatus according to claim 9, wherein:

the elongated rotor magnets are disposed on an outer cylindrical surface of the shaft of the magnetic rotor assembly and are 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 first end portions of the magnetic circuit members position sensors;

the first end portion of each magnetic circuit member defines a respective first surface facing the elongated rotor magnets; and

the second end portion of each magnetic circuit member defines a respective interfacing portion which defines a second surface facing the respective Hall effect sensor, the surface area of the second surface being substantially less than the surface area of the first surface.

12. 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, 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.

13. 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,

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; and

a controller coupled to the interface, the wind ings 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.

14. The DC motor system of claim 13 wherein the position sensors of the brush less 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.

15. The DC motor system of claim 13 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.

16. A DC motor system according to claim 13, wherein:

the Hall-effect sensors are disposed distally from the windings outside one end of the housing in a direction parallel to the axis of rotation of the magnetic rotor assembly;

the rotor magnets are disposed on a generally cylindrical shaft of the magnetic rotor assembly and have an elongated shape generally aligned with the axis of the shaft;

the magnetic circuit elements are elongated in a direction generally aligned with the axis of the shaft and extend through the one end of the housing, and the first end portion of each magnetic circuit element is disposed immediately opposite the rotor magnets at one end thereof.

17. 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 wind ings 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,

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.