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Lin Engineering, Inc.

Ryan C Lin

Ted T Lin

Richard L Badgerow

A step motor integrates its mounting face and heat sink into the stator design. In particular, mounting holes (typically, four in number) are provided through the stator stack in outer perimeter areas. The stator stack itself becomes the mounting surface, allowing the heat generated from the stator to conduct directly to the mounting plate. The front end cap for holding the rotor in alignment is situated inside of the stator's mounting surface and takes no part in mounting the motor to the mounting surface. The end caps only hold the rotor in proper relation within the stator and contain the bearing assembly for the rotor's axial drive shaft. The perimeter of the stator assembly between the mounting screw holes may have saw-tooth cutouts that define heat-dissipation fins.

Motor having stator assembly with integrated mounting and heat sink features

A rotary machine (e.g., motor or generator) has end caps with plastic piloting rings that engage a stator's plastic winding frame in an interference fit, so that a rotor seated by bearings in the end caps is properly aligned with the stator. The flexibility of the plastic-to-plastic fit allows looser tolerances in comparison to machining of all-metal end caps, while the average circle of the piloting ring's outer diameter still assures proper concentricity of rotor shaft, bearings, piloting rings and stator.

Motor end cap with interference fit

A half-stepping motor with bifilar coil windings about its stator poles has two layers of stator coils with different numbers of turns per pole for each layer. The ratio between the number turns is selected to provide a desired angular phase shift in the torque profile. A first layer wound about a first group of poles is connected in series in a forward sense with a second layer wound about a second distinct group of poles and driven by a first phase, while a second layer wound about the first group of poles is connected in series in a reverse sense with a first layer wound about the second group of poles and driven by a second phase in quadrature relation to the first phase. For a motor with 8 stator poles, the desired phase shift is 22.5 degrees, resulting from a turn ratio between the layers of about 0.4142.

Half-stepping motor with bifilar winding ratio for smooth motion

A two-phase step motor with bifilar winding around the stator poles is connected to phases &agr; and &bgr; (90&deg; apart) of a two-phase driver in a manner that maximizes torque at medium speed operation and minimizes vibrations. In particular, the coils that are wound around different groups of stator poles are connected in series. In one set, both coils are connected in a forward sense around the stator, while in the other set, the two coils are connected in opposite senses. All coils are energized in every phase of a pulse cycle. The properties are intermediate between that of convention series and parallel stator coil connections.

Stator coil T-connection for two-phase step motors

Disclosed is a stator of 2-phase step motor that has 4 stator coils, two in each phase. The coils are wound around 8 stator poles in a standard bifilar winding pattern. The first center-tap of the first phase and the second center tap of the second phase are connected. One end of the first phase makes a first terminal. One end of the second phase makes a second terminal. The other end of the first phase and the other end of the second phase are connected to make a third terminal. A three-phase driver can drive the step motor via these three terminals. Performance of the stator of the step motor can be improved by increasing the number of turns of the two coils whose ends make the first and second terminals. Then the three phase resistances of the stator can be adjusted to have similar resistances by reducing the wire gauge of the other two coils. This reduction of the wire size compensates for the space needed for the increase in the numbers of coil turns mentioned above. This connection scheme applies in general to a 4N-pole stator of a 2-phase step motor.

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Cupertino, CA, United States of America

Ryan C Lin