Capacitive transducer and a method for manufacturing a transducer

• US 8,891,222 B2
• Filed: 02/14/2012
• Issued: 11/18/2014
• Est. Priority Date: 02/14/2012
• Status: Expired due to Fees

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Benslimane, Mohamed Yahia
• Primary Examiner(s): Ha, Nguyen T
• Application Number:
  US13/396,137
• Publication Number:
  US 20130208397A1
• Time in Patent Office: 1,008 Days
• Field of Search: 361/286, 361277-278, 361290-292, 361/272, 361/273, 3612831-2833, 310/328, 310/369
• US Class Current: 361/286
• CPC Class Codes: G01D 5/241 by relative movement of capacitor electrodes
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 7/023 of macromolecular compounds
• CPC Class Codes: H04R 19/00 Electrostatic transducers
• CPC Class Codes: H04R 31/003 for diaphragms or their outer suspension

Abstract

A capacitive transducer (1) comprises a polymer film (2) having a first surface and a second surface, a first electrically conductive layer (3) arranged on the first surface of the polymer film (2), and a second electrically conductive layer (3) arranged on the second surface of the polymer film (2). The polymer film (2) is at least partly made from a material having a molecular weight which is at least 21,000 g/mol. The inventors have surprisingly found that silicone polymer materials with high molecular weights, such as liquid silicone rubbers (LSR) or high temperature vulcanizing (HTV) elastomers, have high electrical breakdown strengths, even though technical data sheets from manufacturers state almost identical electrical breakdown strengths similar to that of RTV-2 elastomers. Using such materials in capacitive transducers allows high electrical fields to be applied to transducers without risking electrical breakdown, thereby increasing performance of transducers.

Claims

1. A capacitive transducer comprising:

a polymer film having a first surface and a second surface,

a first electrically conductive layer arranged on the first surface of the polymer film, and

a second electrically conductive layer arranged on the second surface of the polymer film,

wherein the polymer film is at least partly made from a material having a molecular weight which is at least 21,000 g/mol,

wherein the polymer film is a structure comprising at least two layers of polymer material,

wherein at least a first of the layers of polymer material is made from a material having a molecular weight which is at least 21,000 g/mol, and at least a second of the layers of polymer material is made from a material having a molecular weight which is between 7,000 g/mol and 21,000 g/mol.

2. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material having a degree of polymerization which is at least 300.

3. The capacitive transducer according to claim 2, wherein the polymer film is at least partly made from a material having a degree of polymerization which is at least 500.

4. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material having a SiO₂ filler content of at least 10% by weight.

5. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material having a pyrogenic silica filler content of at least 10% by weight.

6. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material comprising an additive which increases the relative permittivity or the dielectric constant of the polymer film.

7. The capacitive transducer according to claim 1, wherein the polymer film is made from an elastomer.

8. The capacitive transducer according to claim 7, wherein the elastomer is a silicone elastomer.

9. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material having a molecular weight which is at least 35,000 g/mol.

10. The capacitive transducer according to claim 1, wherein the polymer film is at least partly made from a material having a molecular weight which is at least 350,000 g/mol.

11. The capacitive transducer according to claim 1, wherein the first surface of the polymer film and/or the second surface of the polymer film comprises a surface pattern of raised and depressed surface portions, and

wherein the first electrically conductive layer and/or the second electrically conductive layer is/are deposited onto the surface pattern of the first and/or second surface, the first electrically conductive layer and/or second electrically conductive layer thereby having a corrugated shape.

12. The capacitive transducer according to claim 11, wherein the raised and depressed surface portions of the first and/or second surface have a shape and/or size which varies periodically along at least one direction of the respective surface.

13. The capacitive transducer according to claim 11, wherein the surface pattern comprises waves forming troughs and crests extending in essentially one common direction, each wave defining a height being a shortest distance between a crest and neighbouring troughs.

14. The capacitive transducer according to claim 13, wherein an average height of the waves is between ⅓

and 20 μ

m.

15. The capacitive transducer according to claim 1, wherein the first electrically conductive layer and/or the second electrically conductive layer has/have a thickness in the range of 0.01-0.2 μ

m.

16. The capacitive transducer according to claim 1, wherein the polymer film is a structure comprising at least three layers of polymer material,

wherein at least a first of the layers of polymer material is made from a material having a molecular weight which is at least 21,000 g/mol, at least a second of the layers of polymer material is made from a material having a molecular weight which is between 7,000 g/mol and 21,000 g/mol, and at least a third of the layers of polymer material is made from a material having a molecular weight which is between 7,000 g/mol and 21,000 g/mol, and

wherein the first layer is arranged between the second layer and the third layer.

17. The capacitive transducer according to claim 1, wherein at least the second of the layers of polymer material is made from a material having a degree of polymerization which is at least 300.