Electrical generator or motor structure – Dynamoelectric – Linear
Patent
1996-01-16
1998-02-17
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Linear
318135, G01P 4702
Patent
active
057194513
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a linear magnetic actuator. Magnetic actuators are known which typically operate in a reciprocating fashion to actuate the diaphragm of a diaphragm pump, for example. Magnetic actuators operate by interaction between a magnetic field and electric current flowing in one or more coils or windings. Typically magnetic actuators include an electromagnet incorporating a fixed core and a winding associated with the core, influencing a movable armature also of soft ferromagnetic material. It is also known to include one or more permanent magnets mounted on the movable actuator member, again influenced by an electromagnet.
Generally, designs known hitherto are intended for low power applications such as aerators for aquariums and little attention has been given to ensuring good magnetic and electrical efficiency.
The present invention provides a linear magnetic actuator comprising a pair of stator windings arranged to carry currents providing magnetic fields of opposed polarity and arranged adjacent to one another along a line substantially perpendicular to the directions of current flow in the windings, a permanent magnet actuator member mounted for movement along a path parallel to said line and having opposite magnetic poles with a predetermined spacing along said path such that in a de-energised state of the actuator each magnetic pole is proximate a respective one of the stator windings, and a slotless stator back iron piece extending parallel to said line behind the stator windings relative to the actuator member and having a face closest to the actuator member which is flat in directions parallel to said line over the extent of the back iron piece.
With this arrangement, the air gap between the magnetic poles of the permanent magnet actuator member and the slotless stator back iron piece is constant as the actuator moves along its path. As a result, high magnetic efficiency can be obtained if this air gap is kept small. Importantly also, there will be no saliency force on the actuator.
Preferably, each magnetic pole has a face which extends a predetermined width along said line and each stator winding comprises a plurality of turns extending evenly along said line for not less than said width of the corresponding pole face. Then, more preferably, the actuator member has a predetermined maximum displacement and each stator winding extends along said line for a distance not substantially greater than said width plus said predetermined displacement.
In fact, each stator winding normally extends for approximately the width of the corresponding magnetic pole face plus the predetermined maximum displacement of the actuator member. Extending the stator coils evenly in the direction of movement of the actuator member has a number of effects and advantages. Firstly, the coil can be made very thin (in the direction of the air gap between the magnetic pole face and the back iron piece) so that the air gap can be minimised. Secondly, the magnetic field distribution relative to the magnetic pole pieces does not vary as the magnetic actuator member moves along its stroke. So long as the stator winding extends along the stroke of the actuator member for a sufficient length, a consistent number of turns of the stator winding interact with the magnetic field for all positions of the actuator member. The result can be an actuator of high magnetic efficiency and highly consistent performance over a range of power outputs.
The stator windings will normally be arranged to carry currents of the same magnitude and may typically be connected in series. However, arrangements may also be contemplated in which currents of different magnitudes flow in the different windings.
It will be understood that energising the stator windings with current of one polarity produces a force on the permanent magnet actuator member, which can move the member along said path unless otherwise restrained at least until one of the poles of the magnet reaches the interface between the two stator windings. If by this positio
REFERENCES:
patent: 3903437 (1975-09-01), Mori
patent: 4371800 (1983-02-01), Brander
patent: 4422060 (1983-12-01), Matsumoto
patent: 4690371 (1987-09-01), Bosley et al.
patent: 4945269 (1990-07-01), Kamm
patent: 5231337 (1993-07-01), Van Namen
patent: 5339064 (1994-08-01), Bessho
patent: 5345206 (1994-09-01), Morcos
Clark Richard Edward
Cook Stephen John
Huntleigh Technology PLC
LaBalle Clayton E.
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