LOW-VOLTAGE DIRECT CURRENT MOTOR

• US 20160372981A1
• Filed: 06/17/2016
• Published: 12/22/2016
• Est. Priority Date: 06/19/2015
• Status: Active Grant

• Current Assignee: Johnson Electric International AG (Johnson Electric Holdings Limited)
• Original Assignee: Johnson Electric SA 125 Rue de Progres La Chaux de Fonds Switzerland (Johnson Electric Holdings Limited)
• Inventors: LU, Ming Cen, LAW, Chi Keung, LEUNG, Ngai Ming
• Granted Patent: US 10,218,230 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02K 1/02 characterised by the magnetic material
• CPC Class Codes: H02K 1/17 Stator cores with permanent magnets
• CPC Class Codes: H02K 2213/03 Machines characterised by numerical values, ranges, mathematical expressions or similar information
• CPC Class Codes: H02K 23/04 having permanent magnet excitation

Abstract

A low-voltage direct current motor has a stator and a rotor rotatable relative to the stator. The rotor includes a rotary shaft, a rotor core fixed to the shaft, a commutator fixed to the shaft adjacent to the rotor core, and rotor windings wound about poles of the rotor core and electrically connected to the commutator. The stator includes a round housing, a permanent magnet mounted to an inner surface of the housing, and brushes disposed in sliding contact with the commutator. An input voltage of the motor is in the range of 7 to 36V, and a ratio of an outer diameter of the rotor core to an outer diameter of the housing is in the range of 67% to 75%.

Claims

1. A low voltage direct current motor, comprising:

a stator comprising a round housing, a permanent magnet mounted to an inner surface of the housing, and brushes; and

a rotor rotatable relative to the stator, the rotor comprising a rotary shaft, a rotor core fixed to the shaft, a commutator fixed to the shaft adjacent to the rotor core, and rotor windings wound about poles of the rotor core and electrically connected to the commutator,

wherein the brushes of the stator are disposed in sliding contact with the commutator, an input voltage of the motor is in the range of 7 to 36V, and a ratio of an outer diameter of the rotor core to an outer diameter of the housing is in the range of 67% to 75%.

2. The motor of claim 1, wherein the ratio of the outer diameter of the rotor core to the outer diameter of the housing is in the range of 67.6% to 73.8%.

3. The motor of claim 1, wherein the permanent magnet is a ferrite magnet.

4. The motor of claim 3, wherein the ferrite magnet is made of a material with a maximum energy product BHmax of 35.8±

1.6 kj/m³.

5. The motor of claim 3, wherein the ferrite magnet is made of a material with a residual magnetic flux density Br of 430±

10 mT, a coercive force Hcb of 318.5±

7.9 kA/m, and an intrinsic coercive force Hcj of 358.3±

7.9 kA/m.

6. The motor of claim 3, wherein the ferrite magnet is made of a material with a maximum energy product BHmax of 34.2±

1.6 kj/m³.

7. The motor of claim 6, wherein the ferrite magnet is made of a material with a residual magnetic flux density Br of 430±

10 mT, a coercive force Hcb of 258.7±

7.9 kA/m, and an intrinsic coercive force Hcj of 270.7±

7.9 kA/m.

8. The motor of claim 3, wherein the outer diameter of the housing is 27.5 mm±

0.3 mm, and the outer diameter of the rotor core is 19 mm±

0.2 mm.

9. The motor of claim 8, wherein when an axial length of the magnet is 21.0 mm±

2.1 mm, 27.5 mm±

0.3 mm, or 34 mm±

0.3 mm, the motor is capable of achieving a rated power output of 20 W, 50 W, or 80 W, respectively.

10. The motor of claim 1, wherein the rotor core has five or ten poles, the stator has two permanent magnetic poles, and the commutator has five commutator segments.

11. The motor of claim 1, wherein a wire diameter of the rotor windings of the motor is in the range of 0.1 mm to 0.5 mm.

12. The motor of claim 1, wherein a wire diameter of the rotor windings of the motor is in the range of 0.3 mm to 0.35 mm.

13. The motor of claim 1, wherein the permanent magnet comprises a number of individual permanent magnet pieces.

14. A brush roller for a vacuum cleaner, the brush roller being driven by a low-voltage direct current motor, the low-voltage direct current motor comprising:

a stator comprising a round housing, a permanent magnet mounted to an inner surface of the housing, and brushes; and

a rotor rotatable relative to the stator, the rotor comprising a shaft, a rotor core fixed to the shaft, a commutator fixed to the shaft adjacent to the rotor core, and rotor windings wound about poles of the rotor core and electrically connected to the commutator,

wherein the brushes of the stator are disposed in sliding contact with the commutator, an input voltage of the motor is in the range of 7 to 36V, and a ratio of an outer diameter of the rotor core to an outer diameter of the housing is in the range of 67% to 75%.

15. The brush roller of claim 14, wherein the ratio of the outer diameter of the rotor core to the outer diameter of the housing is in the range of 67.6% to 73.8%.

16. The brush roller of claim 14, wherein the permanent magnet is a ferrite magnet made of a material with a maximum energy product BHmax of 35.8±

1.6 kj/m³.

17. The brush roller of claim 14, wherein the permanent magnet is a ferrite magnet made of a material with a residual magnetic flux density Br of 430±

10 mT, a coercive force Hcb of 318.5±

7.9 kA/m, and an intrinsic coercive force Hcj of 358.3±

7.9 kA/m.

18. The brush roller of claim 14, wherein the permanent magnet is a ferrite magnet made of a material with a maximum energy product BHmax of 34.2±

1.6 kj/m³.

19. The brush roller of claim 18, wherein the permanent magnet is a ferrite magnet made of a material with a residual magnetic flux density Br of 430±

10 mT, a coercive force Hcb of 258.7±

7.9 kA/m, and an intrinsic coercive force Hcj of 270.7±

7.9 kA/m.

20. The brush roller of claim 14, wherein the outer diameter of the housing is 27.5 mm±

0.3 mm, and the outer diameter of the rotor core is 19 mm±

0.2 mm.

21. A home appliance comprising a low-voltage direct current motor, the low-voltage direct current motor comprising:

a stator comprising a round housing, a permanent magnet mounted to an inner surface of the housing, and brushes; and

a rotor rotatable relative to the stator, the rotor comprising a shaft which is rotatably mounted, a rotor core fixed to the shaft, a commutator fixed to the shaft adjacent to the rotor core, and rotor windings wound about poles of the rotor core and electrically connected to the commutator,

wherein the brushes of the stator are disposed in sliding contact with the commutator, an input voltage of the motor is in the range of 7 to 36V, and a ratio of an outer diameter of the rotor core to an outer diameter of the housing is in the range of 67% to 75%.