Brushless DC motor actuator having remote commutation sensing apparatus
View Patent ↗A brushless DC motor and Hall Effect commutation sensors are mounted on a common circuit board, and ferromagnetic elements partially embedded in the motor stator in proximity to the periphery of the rotor magnetically couple the rotor magnet to the Hall Effect sensors. Preferably, the ferromagnetic elements are embedded in the stator adjacent the radial periphery of the rotor magnet. Alternately, the ferromagnetic elements can be embedded in the stator adjacent the axial periphery of the rotor magnet.
1. A brushless motor actuator, comprising:
a printed circuit board;
a Hall Effect sensor surface mounted on said printed circuit board;
a wound stator assembly affixed to said printed circuit board, including an annular core fixed in a non-magnetic housing and having an axis that is perpendicular to said printed circuit board,
a rotor supported for rotation about said axis, said rotor having an annular permanent magnet disposed adjacent a radial periphery of said annular core; and
a ferromagnetic element at least partially embedded in the non-magnetic housing of said wound stator assembly for coupling magnetic flux from the annular permanent magnet of said rotor to said Hall Effect sensor, said ferromagnetic element having a first end disposed in proximity to a periphery of said annular permanent magnet and a second end that terminates in proximity to said Hall Effect sensor,
where the first end of said ferromagnetic element is disposed in proximity to a radial periphery of said annular permanent magnet, and
where a radial periphery of said annular core adjacent said annular permanent magnet is undercut to define an axially extending region of non-magnetic housing material in proximity to the radial periphery of said annular permanent magnet, and said ferromagnetic element is at least partially embedded in said axially extending region of non-magnetic housing material.
2. The brushless motor actuator of claim 1 , where said ferromagnetic element has a longitudinal axis that is parallel with the axis of said annular core.
3. The brushless motor actuator of claim 1 , where said ferromagnetic element extends into said axially extending region of non-magnetic housing material to substantially overlap an axial dimension of said annular permanent magnet.
4. A brushless motor actuator, comprising:
a printed circuit board;
a Hall Effect sensor surface mounted on said printed circuit board;
a sound stator assembly affixed to said printed circuit board, including an annular core fixed in a non-magnetic housing and having an axis that is perpendicular to said printed circuit board,
a rotor supported for rotation about said axis, said rotor having an annular permanent magnet disposed adjacent a radial periphery of said annular core; and
a ferromagnetic element at least partially embedded in the non-magnetic housing of said wound stator assembly for coupling magnetic flux from the annular permanent magnet of said rotor to said Hall Effect sensor, said ferromagnetic element having a first end disposed in proximity to a periphery of said annular permanent manget and a second end that terminates in proximity to said Hall Effect sensor,
where the first end of said ferromagnetic element is disposed in proximity to an axial periphery of said annular permanent magnet; and
where a periphery of said non-magnetic housing adjacent said annular permanent magnet is undercut to define an axially extending region of non-magnetic housing material in proximity to the axial periphery of said annular permanent magnet, and said ferromagnetic element is at least partially embedded in said axially extending region of non-magnetic housing material.
5. A brushless motor actuator, comprising:
a printed circuit board;
a Hall Effect sensor carried with said printed circuit board;
a wound stator assembly carried with said printed circuit board, including an annular core fixed in a non-magnetic housing and having an axis that is substantially perpendicular to said printed circuit board,
a rotor supported for rotation about said axis, said rotor having an annular permanent magnet disposed adjacent a radial periphery of said annular core; and
a ferromagnetic element at least partially embedded in the non-magnetic housing of said wound stator assembly for coupling magnetic flux from the annular permanent magnet of said rotor to said Hall Effect sensor, said ferromagnetic element having a first portion disposed in proximity to a periphery of said annular permanent magnet and a second portion disposed in proximity to said Hall Effect sensor,
where the first portion of said ferromagnetic element is disposed in proximity to a radial periphery of said annular permanent magnet, and
where a radial periphery of said annular core adjacent said annular permanent magnet is undercut to define an axially extending region of non-magnetic housing material in proximity to the radial periphery of said annular permanent magnet, and said ferromagnetic element is at least partially embedded in said axially extending region of non-magnetic housing material.