Patent Application
20080148492
1. Field of the Invention
The present disclosure is related to washing machines. More particularly, the present disclosure is related to washing machines having motor braking circuits and methods of braking.
2. Description of Related Art
Vertical axis washing machines, also known as top loading washing machines, represent a large portion of the overall washing machine consumer market.
Most vertical axis washing machines include a spin cycle for removing water and/or detergents from the laundry using centrifugal force. During a typical spin cycle, the washing machine spins the laundry tub at relatively high speed. At the termination of the spin cycle and/or when the door of the machine is opened during the spin cycle, it is desirable to brake the motor to minimize spin tub run down speed.
Conventionally, the braking of the motor has been achieved by connecting resistors across the motor windings. This technique has the disadvantage that relatively high power resistors are required and these add to the cost of the laundry machine.
Accordingly, there is a need for washing machines that overcome, alleviate, and/or mitigate one or more of the aforementioned and other deleterious effects of prior art washing machines.
A washing machine is provided that includes a motor, an inductive winding device, a motor control unit, and a braking circuit. The motor control unit is in electrical communication with the motor and the inductive winding device. The braking circuit is in electrical communication with the inductive winding device and the motor control unit. The braking circuit dissipates a braking energy from the motor through the inductive winding device and the motor control unit controlling the braking energy so as to avoid activation of the inductive winding device.
A washing machine is also provided that includes a motor, a motor control unit, a mode shifter, a basket, an agitator, and a mode-shifting braking circuit. The motor control unit is in electrical communication with the motor. The mode shifter is controlled by the motor control unit between a first state and a second state. The basket and agitator configured to be driven by the motor via the mode shifter. The agitator is driven by the motor when the mode shifter is in the first state, while the basket and agitator are driven by the motor when the mode shifter is in the second state. The mode-shifting braking circuit is resident on the motor control unit so that the circuit can dissipate a braking energy from the motor through the mode shifter only to a level sufficient to maintain the mode shifter in the first state.
A method of controlling a washing machine during a braking operation is also provided. The method includes dissipating a braking energy from a motor generated during the braking operation through an inductive winding device only to a level sufficient to maintain the inductive winding device in an un-activated state.
The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
Referring to the drawings and in particular to
Washer 10 includes a motor 12, a motor control unit 14, and a mode shifter 16. Motor 12 is three-phase alternating current (AC) induction motor and, in some embodiments includes motor control unit 14 integral therewith. Motor control unit 14 includes a mode-shifting braking circuit 18 resident thereon. Circuit 18 is configured, upon receipt of a stopping signal, to place motor 12 into generating mode in a known manner. In this manner, the mechanical energy of washer 10 is transformed into electrical energy on the motor inverter's DC bus voltage.
Advantageously, circuit 18 is configured to dissipate the energy from the DC bus voltage through mode shifter 16. Thus, washer 10 having circuit 18 takes advantage of an existing washing machine component (e.g., mode shifter 16) to dissipate the energy and, thus, eliminates the need for the high power resistors of the prior art. However, motor control unit 14 is configured to vary the energy supplied to mode shifter 16 so as to avoid activation of the mode shifter.
Washer 10 includes an outer housing 20 supporting a tub 22, a basket 24, an agitator 26, motor 12, motor control unit 14, and mode shifter 16 in a known manner. Basket 24 is configured to hold articles such as clothes to be washed.
During a spin cycle, basket 24 and agitator 26 are configured to be driven by motor 12 to rotate at a high speed about vertical axis 28. In this manner, liquid within the articles is removed by the centrifugal force imparted by the spin cycle and is allowed to exit the basket through openings (not shown). However, during a washing cycle, only agitator 26 is configured to be driven by motor 12 to rotate back-and-forth about a vertical axis 28 so that the clothes in the basket are agitated. Mode shifter 16 is configured to prevent rotation of basket 24 during the washing cycle in a known manner.
For example, agitator 26 is secured to an agitator drive shaft 30 and basket 24 is secured to a basket drive shaft 32. Motor 12 is coupled to mode shifter 16 by a transmission 34. Transmission 34 is configured to transmit rotary motion imparted on a motor shaft 36 by motor 12 to mode shifter 16.
During the washing or agitating cycle, mode shifter 16 is in a first state where the mode shifter is configured to transmit the rotary motion from transmission 34 to agitator drive shaft 30. In the first state, mode shifter 16 is engaged/activated so as to lock inner basket 24 to outer basket 22 so that the inner basket does not rotate. However, in the spin cycle, mode shifter 16 is in a second state (e.g., disengaged/deactivated) where the mode shifter is configured to transmit the rotary motion from transmission 34 to both agitator and basket drive shafts 30, 32 so that inner basket 24 is rotated.
Mode shifter 16 is in electrical communication with motor control unit 14. Thus, mode shifter 16 can be selectively switched by motor control unit 14 between the first and second states.
In the illustrated embodiment, mode shifter 16 includes a solenoid 38 that moves the shifter between the first and second states. During the wash or agitate cycle, mode shifter 16 is engaged and placed into the first state where the mode shifter is configured to transmit the rotary motion from transmission 34 only to agitator drive shaft 30. To do so, the motor control unit 14 applies an engage voltage to solenoid 38 of about 130 volts AC. Once engaged, motor control unit 14 reduces the control voltage to solenoid 38 to a hold-in level of about 30 volts AC.
During the spin cycle, motor control unit 14 removes the mode shifter control voltage and gravitational forces cause the mode shifter to go to the second state where the mode shifter is configured to transmit the rotary motion from transmission 34 to both agitator and basket drive shafts 30, 32.
Advantageously, circuit 18 is configured to dissipate the energy generated during braking through solenoid 38 instead of the power resistor as in prior art devices.
However, it has been determined by the present disclosure that applying the energy generated during braking to solenoid 38 can cause mode shifter 16 to activate. It was further determined by the present disclosure that activation of mode shifter 16 while inner basket 24 is spinning would be detrimental to one or more components of washer 10. Advantageously, motor control unit 14 is configured to control the amount of energy dissipated from circuit 18 through solenoid 38 so as to prevent activation of mode shifter 16. More particularly, control unit 14 is configured to dissipate the braking energy from motor 12 through mode shifter 16 only to a level sufficient to maintain the mode shifter in the second or un-activated state.
For example, motor control unit 14 can apply a braking voltage to solenoid 38 when tub 24 is required to stop to dissipate the energy. The braking voltage applied to solenoid 38 during mode-shift braking is below the control voltage necessary to engage mode shifter 16. In this manner, motor control unit 14 ensures that mode shifter 16 is not activated during braking. In one embodiment, circuit 18 is controlled by motor control unit 14 to apply a braking voltage of between about 30 VAC to about 80 VAC to solenoid 38 when tub 24 is required to stop.
Accordingly, washer 10 allows for the elimination of the brake resistor and its associated control circuitry, which reduces the cost of the washer and increases the reliability of the washer due to the decreased number of components.
In the illustrated embodiment, transmission 34 is shown as a pulley-and-belt transmission. However, it is contemplated by the present disclosure for transmission 34 to be a direct drive transmission, a geared transmission, and others.
Also in the illustrated embodiment, mode shifter 16 is shown as including solenoid 16 for moving the shifter between the first and second states. However, it is contemplated by the present disclosure for mode shifter 16 to include any other inductive winding component for moving the shifter between the first and second states. Moreover, it is contemplated by the present disclosure for circuit 18 to dissipate the energy of braking through any other inductive winding component of washer 10, which is controlled by motor control unit 14, where the control unit 14 controls the dissipated energy so as to avoid activating that component.
Washer 10 is configured to utilize the braking provided by circuit 18 during one or more conditions. For example, during the spin cycle of washer 10, the user is able to lift the lid 40 to gain access to tub 24. In order to mitigate against the danger of the user having access to tub 24 when spinning at high speeds, washer 10 is configured to bring the tub to a complete stop in under 7 seconds via circuit 18. In other examples, washer 10 can bring tub 24 to a stop via circuit 18 any time braking of the tub is desired.
Referring now to
The circuit shown in
Referring now to
Advantageously, method 60 includes a mode shift brake algorithm 62. Algorithm 62 is resident on motor control unit 14 and is configured to apply a braking voltage to solenoid 38 when tub 24 is spinning and is required to stop. The braking voltage applied to solenoid 38 by mode-shift braking algorithm 62 is below the control voltage necessary to engage mode shifter 16. In this manner, algorithm 62 ensures that mode shifter 16 is not activated during braking.
When algorithm 62 is braking the embodiment where motor 12 is an AC induction motor, the algorithm is configured to drive the stator of the motor at a lower frequency then the rotor. Algorithm 12 achieves this by monitoring the rotor speed and applying a voltage to the stator that has a smaller frequency than the voltage to the rotor. By driving the stator at a slower speed, algorithm 62 generates a negative torque on the rotor and causes the motor to go into a generating mode. Algorithm 62 continues to lower the driving frequency all the while dumping the generated voltage to solenoid 38 until the rotor speed is zero. Moreover, algorithm 62 balances the negative torque on the rotor, so that the generated voltage, when applied to solenoid 38, is insufficient to activate or engage mode shift 16.
It should also be noted that the terms “first”, “second”, “third”, “upper”, “lower”, and the like may be used herein to modify various elements. These modifiers do not imply a spatial, sequential, or hierarchical order to the modified elements unless specifically stated.
While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims.
