Stepper motor with stator biasing magnets

Claim 2

An electric rotating machine comprising permanent magnet rotor means, two pairs of pole pieces with each pair cooperating with a separate axial portion of the rotor means, each pole piece having a salient stator pole which is radially spaced from the rotor means, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating a magnetic biasing flux passing through the rotor means, energizing means for generating a magnetic stator flux in the salient stator poles, the generated flux passing from said poles through selected axial portions of the rotor means, the strength and direction of the stator flux being respectively greater than and opposed to the bias flux flowing through the rotor means to produce a net magnetic flux, each pair of pole pieces being so aligned with respect to the rotor means and with respect to the other pair of pole pieces that in the quiescent condition and for a given energization of the energizing means the influence of the net magnetic flux on separate axial portions of the rotor means exerts substantially equal torque on the rotor means in opposite directions whereby the rotor means is stabilized in a predetermined angular orientation.

Claim 3

An electric rotating machine as recited in claim 1 wherein the permanent magnet biasing means comprises a pair of annular biasing magnets, one for each pair of stator pole pieces.

Claim 4

An electric rotating machine comprising permanent magnet rotor means, two pairs of pole pieces with each pair cooperating with separate axial portions of the rotor means, each pole piece having a salient stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the rotor means, field coils encircling a portion of at least one of the stator pole pieces for generating magnetic flux in the salient stator poles, the generated flux passing from the poles through selected axial portions of the rotor means, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating a magnetic biasing flux passing through the rotor means, means for energizing at least one of the field coils to produce a magnetic stator flux through a selected axial portion of the rotor means, the strength and direction of the stator flux being respectively greater than and opposed to the bias flux flowing through the rotor means, each pair of pole pieces being so aligned with respect to the rotor means and with respect to the other pair of pole pieces that with said field coils de-energized the bias magnetic flux exerts substantially equal torque on different axial portions of the rotor means in opposite directions to stabilize the rotor means in a first predetermined angular orientation and for a given energization of at least one of the field coils the influence of the bias and stator magnetic fluxes on different axial portions of the rotor means exerts substantially equal torque on the rotor means in opposite directions whereby the rotor means is stabilized in a different pre-determined angular orientation.

Claim 5

An electric rotating machine comprising permanent magnet rotor means, two pairs of pole pieces with each pair cooperating with separate axial portions of the rotor means, each pole piece having a salient stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the rotor means, field coils encircling a portion of at least one of the stator pole pieces for generating magnetic flux in the salient stator poles, the generated flux passing from the poles through selected axial portions of the rotor means, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating a magnetic biasing flux passing through the rotor means, means for energizing at least one of the field coils to produce a magnetic stator flux through a selected axial portion of the rotor means, the strength and direction of the stator flux being respectively greater than and opposed to the bias flux flowing through the rotor means, each pair of pole pieces being so aligned with respect to the rotor means and with respect to the other pair of pole pieces that with said field coils de-energized the bias magnetic flux exerts substantially equal torque on different axial portions of the rotor means in opposite directions to stabilize the rotor means in a first predetermined angular orientation and for a given energization of at least one of the field coils the influence of the bias and stator magnetic fluxes on different axial portions of the rotor means exerts substantially equal torque on the rotor means in opposite directions whereby the rotor means is stabilized in a different pre-determined angular orientation.

Claim 6

An eleCtric rotating machine comprising permanent magnet rotor means, two pairs of pole pieces with each pair cooperating with separate axial portions of the rotor means, each pole piece having a salient stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the rotor means, a first and a second field coil mounted co-axially with the rotor means for generating magnetic flux in the salient stator poles, the generated flux passing from the poles through selected axial portions of the rotor means, means for selectively energizing the field coils independently of one another, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating a magnetic biasing flux passing through the rotor means, the strength and direction of which is respectively less than and opposed to the stator flux, each pair of pole pieces being so aligned with respect to the rotor means and with respect to the other pair of pole pieces that when the first field coil is energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it from an initial position and stabilize it in a first predetermined angular orientation, when the second field coil is energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it to and stabilize it in a second predetermined angular orientation, when both of the field coils are energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it to and stabilize it in a third predetermined angular orientation, and when both of the field coils are de-energized the bias magnetic flux through different axial portions of the rotor means exerts forces on the rotor means to return and stabilize it in its initial position.

Claim 7

An eleCtric rotating machine comprising permanent magnet rotor means, two pairs of pole pieces with each pair cooperating with separate axial portions of the rotor means, each pole piece having a salient stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the rotor means, a first and a second field coil mounted co-axially with the rotor means for generating magnetic flux in the salient stator poles, the generated flux passing from the poles through selected axial portions of the rotor means, means for selectively energizing the field coils independently of one another, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating a magnetic biasing flux passing through the rotor means, the strength and direction of which is respectively less than and opposed to the stator flux, each pair of pole pieces being so aligned with respect to the rotor means and with respect to the other pair of pole pieces that when the first field coil is energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it from an initial position and stabilize it in a first predetermined angular orientation, when the second field coil is energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it to and stabilize it in a second predetermined angular orientation, when both of the field coils are energized the bias and stator magnetic fluxes through different axial portions of the rotor means exert forces on the rotor means to rotate it to and stabilize it in a third predetermined angular orientation, and when both of the field coils are de-energized the bias magnetic flux through different axial portions of the rotor means exerts forces on the rotor means to return and stabilize it in its initial position.

Claim 8

An electric rotating machine as recited in claim 4 wherein the field coils each include a first and a second lead, and the field coil energizing means comprises a two terminal source of direct current, means for connecting one of the direct current source terminals to the first leads of the field coils, a switch having a neutral position and a first, a second, and a third terminal and a contact arm which selectively connects to each of the three switch terminals, means for connecting the contact arm to the other direct current source terminal, the second lead of one of the field coils being connected to the first switch terminal, the second lead of the other field coil being connected to the third switch terminal, a first and a second diode, the first diode being connected between the first and the second switch terminals, the second diode being connected between the second and the third switch terminals, the first and second diodes having polarities such that when the contact arm connects to the second switch terminal, current from the direct current source flows through the diodes and both of the field coils.

Claim 9

An electric rotating machine comprising a shaft, means for rotatably mounting the shaft, a pair of permanent magnet rotors mounted on the shaft, two pairs of centrally orificed cup-shaped pole pieces with each pair encompassing a separate one of the rotors, each pole piece having a salient stator pole projecting perpendicularly from a portion of the edge of the orifice in a direction parallel to the axis of rotation of the encompassed rotor and radially spaced therefrom, field coils mounted co-axially with the rotors for generating magnetic flux in the pole pieces, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating magnetic bias flux passing through the rotors, means for selectively energizing the field coils independently of one another to generate a magnetic stator flux through at least one of the rotors, the strength and direction of the stator flux Being respectively greater than and opposed to the bias flux flowing through the rotor to produce a net stator flux, each pair of pole pieces being so aligned with respect to the rotor encompassed by it and with respect to the other pair of pole pieces that when said field coils are de-energized the bias flux acts on both of said rotors to cause the rotors to exert substantially equal torque on the shaft in opposite directions to stabilize the shaft in a first pre-determined angular orientation and for given energizations of the field coils the influence of the bias and net stator fluxes on the rotors causes the rotors to exert substantially equal torque on the shaft in opposite directions whereby the shaft is stabilized in a different predetermined angular orientation, said shaft automatically returning to said first pre-determined angular orientation upon the de-energization of said field coils.

Claim 10

An electric rotating machine comprising a shaft, means for rotatably mounting the shaft, a pair of permanent magnet rotors mounted on the shaft, two pairs of centrally orificed cup-shaped pole pieces with each pair encompassing a separate one of the rotors, each pole piece having a salient stator pole projecting perpendicularly from a portion of the edge of the orifice in a direction parallel to the axis of rotation of the encompassed rotor and radially spaced therefrom, field coils mounted co-axially with the rotors for generating magnetic flux in the pole pieces, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating magnetic bias flux passing through the rotors, means for selectively energizing the field coils independently of one another to generate a magnetic stator flux through at least one of the rotors, the strength and direction of the stator flux Being respectively greater than and opposed to the bias flux flowing through the rotor to produce a net stator flux, each pair of pole pieces being so aligned with respect to the rotor encompassed by it and with respect to the other pair of pole pieces that when said field coils are de-energized the bias flux acts on both of said rotors to cause the rotors to exert substantially equal torque on the shaft in opposite directions to stabilize the shaft in a first pre-determined angular orientation and for given energizations of the field coils the influence of the bias and net stator fluxes on the rotors causes the rotors to exert substantially equal torque on the shaft in opposite directions whereby the shaft is stabilized in a different predetermined angular orientation, said shaft automatically returning to said first pre-determined angular orientation upon the de-energization of said field coils.

Claim 11

An electric rotating machine as recited in claim 6 in which one of the rotors is of a material that has high magnetic coercivity, low permeability and low specific gravity, and a magnetic energy product of at least 3.0 X 106 gauss-oersteds along the axis of magnetic orientation.

Claim 12

An electric rotating machine as recited in claim 10 wherein the permanent magnet biasing means comprises a permanent magnet having opposite magnetic poles affixed to the pole pieces of one of the pairs of pole pieces.

Claim 13

An electric rotating machine as in claim 8 wherein the magnet comprises a strip of material one portion of which is adhesively secured to one of the paired cup-shaped pole pieces and is polarized generally in a radially outward direction, and another portion of which is adhesively secured to the other of the paired cup-shaped pole pieces and is polarized generally in the opposite direction.

Claim 14

An electric rotating machine comprising a rotor shaft, means for rotatably mounting the rotor shaft, a pair of bipole permanent magnet rotors mounted on the rotor shaft, said rotors respectively having first and second sets of rotor poles, two pairs of stator pole pieces, the respective pairs of stator pole pieces cooperating with separate rotors and having first and second sets of stator poles, one of said first sets of poles having a fixed mechanical angular displacement with respect to the corresponding set of said second sets of poles which is less than 180 degrees, the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the cooperating rotor, a pair of field coils mounted coaxially with the rotors for generating magnetic flux in the salient stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors, and means for energizing at least one of the field coils to produce magnetic flux through at least one of the rotors in opposition to, and greater in magnitude than, the bias flux whereby the rotors will rotate through a predetermined arc in a predetermined direction.

Claim 15

An electric rotating machine comprising a rotor shaft, means for rotatably mounting the rotor shaft, a pair of bipole permanent magnet rotors mounted on the rotor shaft, said rotors respectively having first and second sets of rotor poles, two pairs of stator pole pieces, the respective pairs of stator pole pieces cooperating with separate rotors and having first and second sets of stator poles, one of said first sets of poles having a fixed mechanical angular displacement with respect to the corresponding set of said second sets of poles which is less than 180 degrees, the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the cooperating rotor, a pair of field coils mounted coaxially with the rotors for generating magnetic flux in the salient stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors, and means for energizing at least one of the field coils to produce magnetic flux through at least one of the rotors in opposition to, and greater in magnitude than, the bias flux whereby the rotors will rotate through a predetermined arc in a predetermined direction.

Claim 16

An electric rotating machine as recited in claim 10 wherein the rotors are mounted on the rotor shaft such that their magnetic polarities are angularly displaced substantially ninety degrees and wherein the stator poles of one of the pairs of pole pieces are aligned with the corresponding stator poles of the other pair of pole pieces.

Claim 17

An electric rotating machine comprising a rotor shaft, means for rotatably mounting the rotor shaft, a pair of bipole permanent magnet rotors mounted on the rotor shaft such that there is a substantial angular displacement between the magnetic polarities of the respective rotors, two pairs of stator pole pieces, each pair of stator pole pieces cooperating with separate rotors, each pole piece having a stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radIally spaced from the cooperating rotor, a pair of field coils, each encircling a portion of at least one of the stator pole pieces for generating magnetic flux in the stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors to stabilize the same in a quiescent stationary position with each rotor pole displaced from the corresponding stator pole of opposite polarity by approximately forty-five degrees, and means for automatically energizing the field coils in a predetermined sequence to produce flux through select ones of the rotors in opposition to, and greater in magnitude than, the bias fluxes so as to advance the rotors through a revolution of 360 mechanical degrees upon completion of the energization sequence.

Claim 18

An electric rotating machine comprising a rotor shaft, means for rotatably mounting the rotor shaft, a pair of bipole permanent magnet rotors mounted on the rotor shaft such that there is a substantial angular displacement between the magnetic polarities of the respective rotors, two pairs of stator pole pieces, each pair of stator pole pieces cooperating with separate rotors, each pole piece having a stator pole and the stator poles of each pair of pole pieces being diametrically opposed to each other and radIally spaced from the cooperating rotor, a pair of field coils, each encircling a portion of at least one of the stator pole pieces for generating magnetic flux in the stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors to stabilize the same in a quiescent stationary position with each rotor pole displaced from the corresponding stator pole of opposite polarity by approximately forty-five degrees, and means for automatically energizing the field coils in a predetermined sequence to produce flux through select ones of the rotors in opposition to, and greater in magnitude than, the bias fluxes so as to advance the rotors through a revolution of 360 mechanical degrees upon completion of the energization sequence.

Claim 19

An electric rotating machine as recited in claim 12 wherein the means for sequentially energizing the field coils comprises a source of electric pulses, first bistable means responsive to the pulses generated by the pulse source for generating a first and a second output signal which are 180 degrees out of phase with each other, the first and the second output signals having frequencies which are one half the frequency of the pulse source, second bistable means responsive to the first output signal for generating a third output signal having one half the frequency of the first output signal, third bistable means responsive to the second output signal for generating a fourth output signal having one half the frequency of the second output signal, means responsive to the third output signal for energizing a selected one of the field coils while the third output signal is of a pre-determined polarity and magnitude, and means responsive to the fourth output signal for energizing the other field coil while the fourth output signal is of a pre-determined polarity and magnitude.

Claim 20

Electric rotating machine comprising a shaft, means for rotatably mounting the shaft, a pair of permanent magnet rotors mounted on the shaft, a pair of stator frames, each stator frame being formed of two opposed, ''''C'''' shaped pole pieces, separate field coils encircling portions of the pairs of pole pieces for generating a magnetic flux in the pole pieces, the pole pieces of each pair being spaced apart from each other and terminating at their distal ends from the encircling field coil in stator poles, the stator poles of each stator frame being radially spaced from a separate one of the rotors, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating magnetic bias flux passing through the rotors to stabilize the same in a quiescent stationary position with each rotor pole displaced from the corresponding stator pole of opposite polarity by approximately forty-five degrees, means for selectively energizing the field coils independently of one another to generate a magnetic stator flux through at least one of the rotors, the strength and direction of the stator flux being respectively greater than and opposed to the bias flux flowing through the rotor to produce a net stator flux, each pair of pole pieces being so aligned with respect to the rotor from which their pole faces are radially spaced and with respect to the other pair of pole pieces that for given energizations of the field coils the influence of the bias and net stator fluxes on the rotors causes the rotors to exert substantially equal torque on the shaft in opposite directions whereby the shaft is stabilized in a pre-determined angular orientation.

Claim 21

Electric rotating machine comprising a shaft, means for rotatably mounting the shaft, a pair of permanent magnet rotors mounted on the shaft, a pair of stator frames, each stator frame being formed of two opposed, ''''C'''' shaped pole pieces, separate field coils encircling portions of the pairs of pole pieces for generating a magnetic flux in the pole pieces, the pole pieces of each pair being spaced apart from each other and terminating at their distal ends from the encircling field coil in stator poles, the stator poles of each stator frame being radially spaced from a separate one of the rotors, permanent magnet means in magnetic circuit relationship with each pair of stator pole pieces for generating magnetic bias flux passing through the rotors to stabilize the same in a quiescent stationary position with each rotor pole displaced from the corresponding stator pole of opposite polarity by approximately forty-five degrees, means for selectively energizing the field coils independently of one another to generate a magnetic stator flux through at least one of the rotors, the strength and direction of the stator flux being respectively greater than and opposed to the bias flux flowing through the rotor to produce a net stator flux, each pair of pole pieces being so aligned with respect to the rotor from which their pole faces are radially spaced and with respect to the other pair of pole pieces that for given energizations of the field coils the influence of the bias and net stator fluxes on the rotors causes the rotors to exert substantially equal torque on the shaft in opposite directions whereby the shaft is stabilized in a pre-determined angular orientation.

Claim 22

An electric rotating machine as recited in claim 14 wherein the permanent magnet biasing means comprises a permanent magnet having opposite magnetic poles affixed to the pole pieces of one of the stator frames.

Claim 23

An electric rotating machine comprising a rotor shaft, a pair of permanent magnet rotors moUnted on the rotor shaft, said rotors respectively having first and second sets of rotor poles, two pairs of stator pole pieces, the respective pairs of stator pole pieces cooperating with separate rotors and having first and second sets of stator poles, one of said first sets of poles being angularly displaced substantially ninety degrees from the corresponding set of said second sets of poles, the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the cooperating rotor, separate field coils encircling portions of the pairs of stator pole pieces for generating magnetic flux in the stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors, and means for energizing at least one of the field coils to produce magnetic flux through at least one of the rotors in opposition to, and greater in magnitude than, the bias flux whereby the rotors will rotate through a pre-determined arc in a pre-determined direction.

Claim 24

An electric rotating machine comprising a rotor shaft, a pair of permanent magnet rotors moUnted on the rotor shaft, said rotors respectively having first and second sets of rotor poles, two pairs of stator pole pieces, the respective pairs of stator pole pieces cooperating with separate rotors and having first and second sets of stator poles, one of said first sets of poles being angularly displaced substantially ninety degrees from the corresponding set of said second sets of poles, the stator poles of each pair of pole pieces being diametrically opposed to each other and radially spaced from the cooperating rotor, separate field coils encircling portions of the pairs of stator pole pieces for generating magnetic flux in the stator poles, the generated flux passing from the stator poles through the cooperating rotors, permanent magnet biasing means in magnetic circuit relationship with each pair of stator pole pieces for generating a biasing flux through the rotors, and means for energizing at least one of the field coils to produce magnetic flux through at least one of the rotors in opposition to, and greater in magnitude than, the bias flux whereby the rotors will rotate through a pre-determined arc in a pre-determined direction.

Claim 25

An electric rotating machine as recited in claim 16 wherein the rotors are mounted on the rotor shaft such that their magnetic polarities are angularly displaced substantially ninety degrees and wherein the stator poles of one of the pairs of pole pieces are aligned with the corresponding stator poles of the other pair of pole pieces.