US3688170A - Reversing motor system for a laundry appliance - Google Patents

Reversing motor system for a laundry appliance Download PDF

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Publication number
US3688170A
US3688170A US134580A US3688170DA US3688170A US 3688170 A US3688170 A US 3688170A US 134580 A US134580 A US 134580A US 3688170D A US3688170D A US 3688170DA US 3688170 A US3688170 A US 3688170A
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Prior art keywords
input terminals
circuit
motor
winding
rotor
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Expired - Lifetime
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US134580A
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English (en)
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Joseph Karklys
Stephen A Becker
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Whirlpool Corp
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Whirlpool Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/24—Controlling the direction, e.g. clockwise or counterclockwise

Definitions

  • the motor is provided with a pair of stator windings connected in opposite polarity sense, one of these windings being connected to an alternating voltage source for continuously receiving an altemating voltage wave while the other winding is selectively and/or cyclically connected across the voltage input terminals for a very brief period to reverse the motor.
  • the motor with an electronic control circuit forms the basis of a simplified drive system for an automatic laundry appliance.
  • the various techniques for reversing single phase motors have a number of disadvantages when the techniques are applied to laundry appliance drive systems which require frequent periodic reversal. These disadvantages include: overheating of the motor due to operation for long periods at low efficiency and low self-ventilating speeds; poor switch life; high cost due to requirements for large capacitors, switches, complex feedback circuitry and additional ventilating means; and difficulty in providing a drive system which has good agitator action as well as good spin characteristics.
  • a motor is provided with a rotor and a pair of stator windings, each of the stator windings taking a general form which is typical of conventional stator windings for induction motors.
  • the two stator windings are connected in opposite polarity sense with respect to each other and, contrary to the switching of applied voltage from one winding to the other as done in the aforementioned Nystuen application, one of the windings is connected to an alternating voltage power source to continuously receive an alternating voltage wave, while the other winding is selectvely and cyclically connected across the voltage source at or near time spaced zero crossings of the alternating voltage wave.
  • Such energization of the motor creates a very rapid reversal of the direction of rotation of the motor, and the motor is periodically reversed in this manner to provide the alternating drive for the agitator of an automatic washing apparatus.
  • the motor may be connected to the agitator by means of a torsion spring which is intended to absorb mechanical transients and promotes a smooth agitating operation.
  • a unijunction transistor relaxation oscillator is included in a control circuit connected to the motor, and
  • conduction of the unijunction transistor is utilized to develop a gating pulse for a controlled conduction device which serves as a switch to connect and disconnect the second stator winding from the voltage input terminals at appropriate times.
  • FIG. 1 is a schematic elevational view of a laundry appliance which may advantageously employ a reversing motor system constructed in accordance with the principles of the present invention
  • FIGS. 2a-2d are graphical illustrations of several voltage wave fomrs which may be applied to the stator windings to effect a rapid reversal of the motor;
  • FIGS. 3a and 3b are graphical illustrations of motor torque and synchronous speed with respect to time illustrating the speed of motor reversal according to the invention.
  • FIG. 4 is a schematic circuit diagram of a motor having two stator windings and the associated control circuit according to the present invention.
  • an agitator 15 Also mounted within the tub l1 and further within the interior of the spin basket 13 is an agitator 15.
  • the agitator l5 and the spin basket 13 are driven by a drive motor 16 which is coupled thereto by way of a pulley 17, a belt 18, a pulley 19 and a drive shaft 20.
  • the spin basket 13 and the agitator 15 may be secured for common movement, or a clutch mechanism (not shown) may be provided as is well known in the art to drivingly engage the spin basket 13 and the agitator drive shaft 20.
  • the agitator 15 may be resiliently coupled to the agitator drive shaft 20 as illustrated by means of a pair of torsion springs 21 and 22.
  • the springs may be housed in an upper portion of the agitator l and coupled to this portion of the agitator and to the upper portion of the agitator drive shaft 20.
  • One of the springs 21 and 22 couples motion to the agitator when the drive shaft is rotating in a first direction and the other of springs 21 and 22 couples motion to the agitator when the drive shaft 20 is rotating in the opposite direction.
  • Different types of springs or other resilient driving connections may be used to couple the drive shaft 20 to the agitator 15 to ease the dynamic torsional loading of the motor 16 during its cyclic reversals.
  • the drive motor 16 has a first winding connected across an alternating voltage power source 45 and is operated in a unidirectional or in an oscillator mode by means of a control circuit 24 which is efiective to apply voltage pulses to a second winding of the motor at or near zero crossings of the applied voltage.
  • the net effect of a properly synchronized voltage pulse from the control circuit 24 is to create a negative torque pulse of large magnitude and brief duration.
  • the impulse created by the negative torque pulse is sufiicient to overcome the inertia of the rotor and the driven load to provide an extremely rapid reversal of the motor.
  • the control circuit 24 is operative only during the agitation portion of a washing cycle in accordance with a signal supplied via a lead 25 by an appliance timer 26.
  • the timer 26 may be of the conventional electromechanical type in which a series of switch contacts are sequentially operated by a set of rotatably driven cams. Such timers are well known in the art, and the timer 26 effectively controls the various machine operations including spin, as indicated by a lead 27 to the motor 16.
  • the lead 27 may serve to energize an additional winding, a high speed winding, of the motor 16 to achieve a high spin speed during the extract portion of a washing cycle.
  • the induction motor may be provided with two windings, both located on the same axis and connected in opposite polarity sense to each other.
  • a rapid reversal of the motor may be effected by simply energizing one of the stator windings continuously in the normal fashion and applying a voltage pulse to the second winding at a zero crossing point of the applied voltage. It has been found that a rapid motor reversal can be obtained by energizing the second winding for 1/2 cycle, 3/2 cycle, or 5/2 cycle of the applied voltage.
  • These modes of energization are illustrated in FIG. 2, the motor reversal being initiated at 28.
  • the inertia of the rotor and machine load usually are important in the selection of the most optimum of the aforementioned modes for fast reversal.
  • the motor windings for a period comprising an odd number of half cycles, thereby insuring that the number of half cycles aiding the initial half cycle will be greater than the number of half cycles opposing it, and that the last half cycle will be of the same polarity as the initial half cycle.
  • FIG. 3a illustrates the nature of the torque pulse which is developed within the motor 16 when the windings are energized by one of the methods of FIGS. 2a-2d.
  • the torque pulse illustrated at 29 always opposes the previous direction of motor rotation, and is of large magnitude and short duration.
  • the attendant rapid motor reversal is depicted by the lower curve of FIG. 3b, and as illustrated the motor can almost immediately achieve synchronous speed in the opposite direction, typically within approximately milliseconds.
  • FIG. 4 illustrates the motor 16 having two stator windings 30 and 31 of the type described in connection with a control circuit 24 for effecting a periodic or cyclic reversal of the motor.
  • the control circuit 24 is economical and operates directly 45) a conventional alternating current input line L1, L2 (source 45() and eliminates the necessity for any additional power supplies.
  • the control circuit 24 employs a unijunction transistor connected in a relaxation oscillator configuration for timing the reversal pulses; however, other means, as for example digital 60H countdown, could be utilized for the same purpose.
  • a position sensing device for initiating motor reversal could also be employed when synchronized to the positive half cycle of the input line voltage.
  • the circuit illustrated in FIG. 4 comprises a pair of stator windings 30, 31 for providing the excitation field of the motor 16.
  • the first winding 30 is connected across the alternating voltage input terminals L1, L2 and the second winding 31 is connected in series with a controlled conduction device, here illustrated a silicon controlled rectifier 32, the series combination being connected across the input terminals L1, L2.
  • a relaxation oscillator 33 is provided for controlling the conduction of the controlled conduction device 32.
  • the relaxation oscillator 33 includes a resistor 34, a diode 35 and a capacitor 36 connected in series across the input terminals L1, L2 for deriving a bias potential at conductor 37 by charging of the capacitor 36 through the diode 35 and the resistor 34.
  • the direct current potential on conductor 37 is utilized for charging a capacitor 39 through a resistor 38 to provide the firing potential at the emitter of a unijunction transistor 40.
  • the unijunction transistor 40 has one base thereof connected by way of a resistor 41 to the conductor 37 and the DC potential thereat, and the other base thereof connected to the input terminal L2 by way of a resistor 42.
  • the resistor 42 is employed to develop a gating pulse thereacross upon conduction of the unijunction transistor .40, which gating pulse is applied to a gate electrode 43 of the controlled conduction device 32 to render that device conductive and connect the second winding 31 across the input terminals L1, L2.
  • the RC time constant of the resistor 38 and the capacitor 39 determines the periodic firing of the unijunction transistor 40 and accordingly the periodic application of line voltage to the second stator winding 31.
  • the periodic firing of the unijunction transistor 36 as determined by the resistor 38 and the capacitor 39 is synchronized to voltage zero crossings preceding positive half cycles of the AC line voltage by the supply voltage ripple.
  • the time between timings of transistor 36 may comprise numerous half cycles of the AC line voltage. Such synchronization to the zero crossing points of the AC voltage waveform is important if reliable and repeatable motor reversals are to be obtained.
  • the lead 25 from the electromechanical timer referred to earlier is seen as connected to the junctionof the resistor 38, the capacitor 39, and the emitter lead 44 of the unijunction transistor 40.
  • This enables the emitter of the unijunction transistor to be shorted to power supply lead L2 by means of an appropriate timer contact (not shown), thereby stopping operation of the relaxation oscillator 33 and preventing the periodic energization of SCR 32 and stator winding 31.
  • the periodic reversal of motor 16 can be halted as desired to perform other portions of a washing cycle.
  • the apparatus disclosed herein provides a simple and economical driving system for a laundry appliance which operates equally well in a unidirectional rotational mode and in an oscillatory mode. Further, the system eliminates the necessity for complex feedback networks and additional cooling and ventilating apparatus previously required in prior art reversible motor systems in that the mechanical transients are short lived and reversal is almost instantaneous so that motor speed is sufiiciently high to prevent overheating and to provide conventional self-ventilating action.
  • a motor reversing circuit comprising: input terminals for receiving an alternating voltage wave having cyclic zero crossover points; a rotor; first and second stator windings inductively coupled to said rotor and wound in opposite polarity sense to each other and respectively connected across said input terminals; and reversing means including switching means serially interposed in the connection between said second winding and one of said input terminals, and switch control means connected across said input terminals and connected to said switching means for actuating said switching means in response to and at selected zero crossover points to efiect controlled reversal of said rotor.
  • a motor reversing circuit comprising: input terminals for receiving an alternating voltage wave having cyclic zero crossover points; a rotor; first and second stator windings inductively coupled to said rotor and wound in opposite polarity sense to each other and respectively connected across said input terminals; and reversing means including switching means serially interposed in the connection between said second winding and one of said input terminals, and switch control means interconnected between said input terminals and connected to said switching means for actuating said switching means to effect controlled reversal of said rotor, wherein said switch control means includes a relaxation oscillator circuit connected to said switching means.
  • a motor reversing circuit comprising: input terminals for receiving an alternating voltage wave having cyclic zero crossover points; first and second stator windings inductively coupled to said rotor and wound in opposite polarity sense to each other and respectively connected across said input terminals; and reversing means including switching means serially interposed in the connection between said second winding and one of said input tenninals, and switch control means interconnected between said input terminals and connected to said switching means for actuating said switching means to effect controlled reversal of said rotor, wherein said switching means includes a semi-conductor switch connected in circuit with said second winding and having a gate electrode connected to said switch control means, wherein said switch control means includes a unijunction transistor having an emitter and a pair of bases, first circuit means including a diode and a first capacitor connected in series across said input terminals so as to develop a bias potential for said transistor, second circuit means including an RC circuit connected across said first capacitor to develop the firing potential of said transistor in response to the
  • a motor reversing circuit comprising means connected to said RC circuit and operable to inhibit the development of the firing potential for providing unidirectional rotation of said rotor.
  • a motor circuit for a laundry appliance having a movable part comprising: alternating voltage input terminals for receiving an alternating voltage wave of positive and negative polarity; a first winding connected across said input terminals; a second winding; a rotor inductively coupled to said first and second windings and connected to the movable part of said laundry appliance; switch means having a control terminal, said switch means and said second winding connected in series across said input terminals with said second winding in an opposite polarity sense relative said first winding; and circuit means connected to said input terminals and to said control terminal to cyclically close said switch means during predetermined time-spaced half cycles of the alternating voltage wave to effect cyclic reversals of direction of rotation of said rotor and said movable part of said laundry appliance.
  • a motor reversing circuit includes a unijunction transistor having an emitter and a pair of bases, first circuit means including a diode and a first capacitor connected in series across said input terminals to provide a bias potential for said transistor, second circuit means including an RC circuit connected across said first capacitor to develop the firing potential for said transistor in response to the direct current potential derived across said first capacitor, and a resistance connected in circuit with one of said bases and connected to said switching means for developing a switch operating pulse upon conduction of said transistor.
  • a laundry appliance comprising: means defining a laundry treatment zone for receiving laundry including a rotatable member; a motor including a rotor connected to said rotatable member, and a pair of field windings inductively coupled to said rotor; a pair of input terminals for receiving an alternating voltage wave, said input terminals connected to one of said windings and connectable to the other of said windings in an opposite polarity sense relative said one winding; and reversing means connected to said input terminals and to said other winding for periodically connecting said other winding to said input terminals for at least one half cycle of the alternating wave to provide a reversing torque to periodically reverse the direction of rotation of said rotor and rotatable member for agitating the laundry in said treatment zone.
  • said reversing means includes a control terminal
  • said appliance includes a timer circuit connected between said input terminals and said control terminal for controlling the initiation and duration of operation of said reversing means.
  • a motor reversing circuit comprising: alternating voltage input terminals for receiving an alternating voltage wave of positive and negative polarity; a motor including a first stator winding connected tosaid input terminals for constant energization, a second stator winding disposed in opposite polarity sense to said first stator winding for connection across said input terminals, and a rotor inductively coupled to said first and second windings; and reversing means for reversing the direction of rotation of said rotor, said reversing means including switch means connected in circuit with said input terminals and said second winding and having a control terminal, and switch control means connected to said input terminals and synchronized with the zero crossings of the alternating wave and operable to cyclically operate said switch means at a frequency less than that of the alternating wave to cyclically reverse the direction of rotation of said rotor.
  • said switch control means includes a relaxation oscillator circuit connected to said switch means.
  • a motor reversing circuit includes a unijunction transistor having an emitter and a pair of bases, first circuit means including a diode and a first capacitor connected in series across said input terminals to apply a bias potential to said transistor, second circuit means including an RC circuit connected across said first capacitor to develop the firing potential for said transistor in response to the direct current potential derived across said first capacitor, and a resistance connected in circuit with one of said bases and connected to said switching means for developing a switch operating pulse upon conduction of said transistor.
  • a method of cyclically reversing the direction of rotation of the rotor of a single phase induction motor having first and second oppositely wound field windings comprising the steps of: continuously applying an alternating voltage wave of positive and negative polarity across said first field winding; and periodically applying one-half cycle of the alternating voltage wave to said second field winding simultaneously with the ap plication of the same half cycle voltage to said first winding.
  • the method of cyclically reversing the direction of rotation of a single phase induction motor having first and second oppositely wound field windings comprising the steps of: continuously applying an alternating voltage of positive and negative polarity across the step of generating is further defined as including the step of synchronizing the generation of motor reversal signals with zero voltage points of the alternating voltage.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Ac Motors In General (AREA)
US134580A 1971-04-16 1971-04-16 Reversing motor system for a laundry appliance Expired - Lifetime US3688170A (en)

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US13458071A 1971-04-16 1971-04-16

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BR (1) BR7202250D0 (it)
CA (1) CA954932A (it)
DE (1) DE2217847A1 (it)
IT (1) IT952665B (it)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025830A (en) * 1975-02-03 1977-05-24 Computer Peripherals, Inc. Motor control and web material drive system
US4081726A (en) * 1976-01-05 1978-03-28 Linear International Corporation Electric motor
US4409532A (en) * 1981-11-06 1983-10-11 General Electric Company Start control arrangement for split phase induction motor
US4779431A (en) * 1987-01-12 1988-10-25 Whirlpool Corporation Drive system for automatic washer
US4950969A (en) * 1988-04-28 1990-08-21 Whirlpool Corporation Variable motor speed control for automatic washer

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3021701A (en) * 1959-08-07 1962-02-20 Gen Motors Corp Clothes washing machine and single phase induction motor therefor
US3248908A (en) * 1962-05-18 1966-05-03 Sidney B Pope Washing machine
US3528103A (en) * 1968-01-11 1970-09-08 Gen Electric Induction motor and starting and reversing circuit therefor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3021701A (en) * 1959-08-07 1962-02-20 Gen Motors Corp Clothes washing machine and single phase induction motor therefor
US3248908A (en) * 1962-05-18 1966-05-03 Sidney B Pope Washing machine
US3528103A (en) * 1968-01-11 1970-09-08 Gen Electric Induction motor and starting and reversing circuit therefor

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025830A (en) * 1975-02-03 1977-05-24 Computer Peripherals, Inc. Motor control and web material drive system
US4081726A (en) * 1976-01-05 1978-03-28 Linear International Corporation Electric motor
US4409532A (en) * 1981-11-06 1983-10-11 General Electric Company Start control arrangement for split phase induction motor
US4779431A (en) * 1987-01-12 1988-10-25 Whirlpool Corporation Drive system for automatic washer
US4950969A (en) * 1988-04-28 1990-08-21 Whirlpool Corporation Variable motor speed control for automatic washer

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CA954932A (en) 1974-09-17
IT952665B (it) 1973-07-30
DE2217847A1 (de) 1973-10-25
BR7202250D0 (pt) 1974-12-31

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