PTC heater for use in liquid with close electrical and thermal coupling between electrode plates and thermistors

• US 5,598,502 A
• Filed: 08/05/1994
• Issued: 01/28/1997
• Est. Priority Date: 08/20/1993
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Takahashi, Minoru, Ono, Makoto
• Primary Examiner(s): Jeffery, John A.
• Application Number:
  US08/285,449
• Time in Patent Office: 907 Days
• Field of Search: 392/502, 392/500, 219/505, 219/541, 219/544, 219/530, 219/523, 219/537, 338/22 R, 338/254, 338/256, 338/257, 338/271, 338/272, 338/306, 338/328
• US Class Current: 392/502
• CPC Class Codes: H05B 3/14 the material being non-metallic

Abstract

A heater for heating a liquid in which the electrical contact between a PTC thermistor and electrode plates is surely realized, and the thermal coupling and the thermal efficiency are excellent. In a case 1, an internal space 13 has an opening 14 at one side portion, and the whole of the periphery of the case is closed except the opening 14. A pair of electrode plates 21 and 22 have projections 211 and 221 on faces 212 and 222, and are housed in the internal space 13 of the case 1 in such a manner that their other faces 223 are opposed to heat radiating faces 11 and 12. The PTC thermistors are disposed between the electrode plates 21 and 22 in such a manner that projections 211 and 221 are contacted with the electrodes 32 and 33, respectively. Thermal conductive fillers 41 and 42 made of a resin are charged between the electrodes 32 and 33 of the PTC thermistors 3 and the electrode plates 21 and 22 so as to fill the gaps which are formed by the projections 211 and 221.

Claims

1. A PTC heater for use in liquid comprising:

a case including first and second radiating members having peripheries which engage each other and which are shielded to define an internal space inside said case, said case having an opening between said first and second radiating members;

plural electrode plates arranged in said internal space, each of said electrode plates having elastic projections on both of opposing sides of each of said electrode plates;

at least one positive temperature coefficient thermistor having electrodes provided on opposing surfaces, said at least one positive temperature coefficient thermistor being arranged between said electrode plates while the projections on one of said opposing sides of said electrode plates are in contact with said electrodes;

projections on another of said opposing sides of said electrode plates being engaged with an inside wall of said case; and

a thermally conductive adhesive resin disposed between said electrodes of said at least one positive temperature coefficient thermistor and said electrode plates.

2. A PTC heater according to claim 1, further comprising at least one insulating frame member provided between said electrode plates, said insulating frame member having at least one hole in which said at least one positive temperature coefficient thermistor is arranged.

3. A PTC heater according to claim 2, wherein said opening communicates said internal space with outside of said case, said insulating frame member has at least one air path communicating each at least one said hole with the outside of said case via said opening.

4. A PTC heater according to claim 1, further comprising an additional thermally conductive adhesive resin disposed between said electrode plates and said inside wall of said case.

5. A PTC heater according to claim 1, further comprising a pair of insulating frame members provided between said electrode plates and fixed to said electrode plates respectively, each said insulating frame members having at least one hole for positioning said at least one positive temperature coefficient thermistor, a sum of thickness of said insulating frame members being smaller than a thickness of said at least one positive temperature coefficient thermistor.

6. A PTC heater according to claim 1, wherein said case is made of metal, further comprising electrical insulating layers interposed between said case and said electrode plates.

7. A PTC heater according to claim 1, further comprising a thermal fuse for interrupting a power supply to said at least one positive temperature coefficient thermistor when said at least one positive temperature coefficient thermistor abnormally generates heat.