Reducing inductive heating

• US 9,270,797 B2
• Filed: 02/27/2013
• Issued: 02/23/2016
• Est. Priority Date: 02/27/2013
• Status: Expired due to Fees

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Technologies Oy (Nokia Corporation)
• Inventors: Backman, Juha Reinhold
• Primary Examiner(s): Rodas, Richard Isla
• Assistant Examiner(s): Bui, Dung V
• Application Number:
  US13/778,781
• Publication Number:
  US 20140238737A1
• Time in Patent Office: 1,091 Days
• Field of Search: 320/108, 174/396
• US Class Current: 1/1
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H04M 1/03 Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets
• CPC Class Codes: H04R 2209/021 Reduction of eddy currents in the magnetic circuit of electrodynamic loudspeaker transducer
• CPC Class Codes: H04R 2209/022 Aspects regarding the stray flux internal or external to the magnetic circuit, e.g. shielding, shape of magnetic circuit, flux compensation coils
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 9/022 Cooling arrangements

Abstract

An audio transducer apparatus including a component having a first material; and a heating reduction system configured to reduce induced heating in the component. The heating reduction system includes a member at least partially surrounding the component. The member includes a material which has an electrical conductivity that is higher than an electrical conductivity of the first material to thereby reduce induced heating in the component.

Claims

1. An audio transducer apparatus comprising:

a magnet assembly comprising at least two magnet assembly components, where a first one of the components has a first material, where the magnet assembly is part of the audio transducer apparatus;

a heating reduction system configured to reduce induced heating in the first component, where the heating reduction system comprises a member at least partially surrounding the magnet assembly, where the member comprises a material which has an electrical conductivity that is higher than an electrical conductivity of the first material to thereby reduce induced heating in the first component by a field from outside the magnet assembly; and

a heat transfer member extending from the member of the heating reduction system, where the heat transfer member is configured to transfer heat away from the member of the heating reduction system, where the heat transfer member comprises a ground plane of a printed wiring board of an apparatus.

2. An audio transducer apparatus as in claim 1 where the at least two magnet assembly components comprise at least one magnet, a first pole piece connected to a first side of the at least one magnet and a second pole piece connected to an opposite second side of the at least one magnet.

3. An audio transducer apparatus as in claim 1 where the member comprises at least one of:

a ring shape which at least partially surrounds the first component,

a concave shape with the first component being housed at least partially inside the concave shape,

a shape which at least partially surrounds the audio transducer.

4. An audio transducer apparatus as in claim 1 further comprising an insulator located between the first component and the member.

5. An audio transducer apparatus as in claim 1 comprising means for reducing eddy current generation in the first component from an induction battery charging magnetic field generator.

6. A device comprising:

a housing;

a rechargeable battery in the housing;

an induction charging system in the housing coupled to the rechargeable battery; and

an audio transducer apparatus as in claim 1 in the housing.

7. A method comprising:

providing a magnet assembly comprising at least two magnet assembly components, a first one of the components comprising a first material susceptible to heating by induced eddy currents from fields, where the magnet assembly is part of an audio transducer;

connecting a heating reduction system to the magnet assembly, where the heating reduction system is configured to reduce heating in the first component, where the heating reduction system comprises a member at least partially surrounding the magnet assembly, where the member comprises a material which has an electrical conductivity that is higher than an electrical conductivity of the first material to reduce heating in the first component by a field from outside the magnet assembly;

providing a heat transfer member extending from the member of the heating reduction system, where the heat transfer member is configured to transfer heat away from the member of the heating reduction system; and

connecting the heat transfer member to a ground plane of a printed wiring board.

8. A method as in claim 7 where the at least two magnet assembly components are provided as at least one magnet, a first pole piece connected to a first side of the at least one magnet and a second pole piece connected to an opposite second side of the at least one magnet.

9. A method as in claim 7 where the member is provided as a ring shape which at least partially surrounds the first component.

10. A method as in claim 7 where the member is provided with a concave shape, where the first component is located at least partially inside the concave shape.

11. A method as in claim 7 further comprising locating an insulator between the first component and the member.

12. A method as in claim 7 further comprising selecting material for the member based upon electrical conductivity of the material and/or a magnetic property of the material.

13. An apparatus comprising:

a housing;

a rechargeable battery in the housing;

an induction charging system in the housing coupled to the rechargeable battery;

an audio transducer comprising a magnet assembly in the housing, where the magnet assembly comprises at least two magnet assembly components, where a first one of the components comprises a first material susceptible to heating by induced eddy currents from induction charging fields generated externally from the apparatus;

an eddy current heating reduction system configured to reduce induced eddy current heating in the first component by the induction charging fields, where the eddy current heating reduction system comprises a member at least partially surrounding the magnet assembly, where the member comprises a second material which has an electrical conductivity that is higher than an electrical conductivity of the first material, where the member is configured to allow an induced current density to be formed in the member from the induction charging fields from outside the magnet assembly which is higher than an induced current density formed in the first component from the induction charging fields to reduce induced eddy current heating in the first component by the induction charging fields; and

a heat transfer member extending from the member of the eddy current heating reduction system, where the heat transfer member is configured to transfer heat away from the member of the eddy current heating reduction system, where the heat transfer member comprises a ground plane of a printed wiring board of an apparatus.