# US 8,739,581 B2 · Washing machine

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- Number: US 8,739,581 B2
- Document ID: US8739581B2
- Status: Granted
- Kind: B2
- Application number: 12/741,524
- Filed: 2008-11-04
- Published: 2010-12-09
- Granted: 2014-06-03
- Earliest claimed: 2007-11-05
- Assignees: Kabushiki Kaisha Toshiba; Toshiba Consumer Electronics Holdings Corporation; Toshiba Home Appliances Corporation
- Applicants: Tsuyoshi Shiga; Isamu Nitta
- Inventors: Tsuyoshi Shiga; Isamu Nitta
- Web page: https://patentgrep.com/patent/US8739581B2

## CPC

- D06F 37/304: {Arrangements or adaptations of electric motors}
- H02K 1/2788: the rotor consisting of a single magnet or two or more axially juxtaposed single magnets
- D06F 37/36: for rotating the receptacle at more than one speed {(D06F37/304, D06F37/308 take precedence)}
- Y02B 40/00: Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
- D06F: LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A washing machine includes a water tub, an electric motor, and a control device. The motor comprises a stator including a stator coil, a rotor magnet arranged circumferentially with respect to the rotor, and a control device. The rotor magnet includes a permanent magnet. When the control device applies a first voltage to the stator coil in a wash step of the washing operation, the rotor magnet is magnetized so that a magnetic flux of the rotor magnet acting on the stator is increased without reversal of a direction of magnetization. When the control device applies a second voltage to the stator soil in a dehydration step of the washing operation, the rotor magnet is magnetized so that a magnetic flux of the rotor magnet acting on the stator is reduced without reversal of a direction of magnetization as compared with the magnetic flux in the wash step.

## Claims

### Claim 1

A washing machine which includes a water tub and an electric motor configured to rotate a load housed in the water tub and configured to execute a washing operation including a wash step, a rinse step, and a dehydration step, the motor comprising:
a stator including a stator coil;
a rotor including a rotor magnet arranged circumferentially with respect to the rotor, the rotor magnet including a permanent magnet; and
a control device configured to control energizing of the stator coil to change a magnetic flux of the rotor magnet;
wherein the control device is configured to apply a first voltage to the stator coil in the wash step of the washing operation to cause the rotor magnet to be magnetized so that a magnetic flux of the rotor magnet acting on the stator is increased without reversal of a direction of magnetization; and
the control device is configured to apply a second voltage to the stator coil in the dehydration step of the washing operation to cause the rotor magnet to be magnetized so that the magnetic flux of the rotor magnet acting on the stator is reduced without reversal of a direction of magnetization as compared with the magnetic flux in the wash step.

### Claim 2 (depends on 1)

The washing machine according to claim 1, wherein the magnetic flux of the rotor magnet is changed by controlling energization of the stator coil when the load is not substantially driven by the motor.

### Claim 3 (depends on 2)

The washing machine according to claim 2, wherein the magnetic flux of the rotor magnet is increased by controlling energization of the stator coil in a water supply step in which water is supplied into the water tub.

### Claim 4 (depends on 3)

The washing machine according to claim 3, wherein the magnetic flux of the rotor magnet is decreased by controlling energization of the stator coil in a drain step in which water is discharged from the water tub.

### Claim 5 (depends on 4)

The washing machine according to claim 4, wherein the rotor magnet further includes a magnet having a higher coercive force than the permanent magnet, and the permanent magnet is disposed nearer to the stator than the magnet having the higher coercive force.

### Claim 6 (depends on 5)

The washing machine according to claim 5, wherein a voltage, applied to the stator coil in a case where the magnetic flux of the rotor magnet is changed, is set higher than a voltage in a case where the motor is normally operated and lower than a magnetizing voltage in a case where the magnet having the higher coercive force is magnetized.

### Claim 7 (depends on 1)

The washing machine according to claim 1, wherein the magnetic flux of the rotor magnet is increased by controlling energization of the stator coil in a water supply step in which water is supplied into the water tub.

### Claim 8 (depends on 1)

The washing machine according to claim 1, wherein the magnetic flux of the rotor magnet is decreased by controlling energization of the stator coil in a drain step in which water is discharged from the water tub.

### Claim 9 (depends on 1)

The washing machine according to claim 1, wherein the rotor magnet further includes a magnet having a higher coercive force than the permanent magnet, and the permanent magnet is disposed nearer to the stator than the magnet having the higher coercive force.

### Claim 10 (depends on 1)

The washing machine according to claim 1, wherein the rotor magnet further includes a magnet having a higher coercive force than the permanent magnet, and a voltage, applied to the stator coil in a case where the magnetic flux of the rotor magnet is changed, is set higher than a voltage in a case where the motor is normally operated and lower than a magnetizing voltage in a case where the magnet having the higher coercive force is magnetized.