Sensor

• US 20040056753A1
• Filed: 07/22/2003
• Published: 03/25/2004
• Est. Priority Date: 10/28/1998
• Status: Abandoned Application

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Chiang, Justin N., Toth, James, Beadling, William C.
• Application Number:
  US10/624,789
• Publication Number:
  US 20040056753A1
• Time in Patent Office: Days
• US Class Current: 338/22R
• CPC Class Codes: G01K 2003/145 Hotspot localization
• CPC Class Codes: G01K 3/14 in respect of space
• CPC Class Codes: G01K 7/22 the element being a non-linear resistance, e.g. thermistor G01K7/26 takes precedence
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material

Abstract

A laminar sensor (1) for detecting changes on a laminar substrate (35). The sensor includes a laminar sheet (3) which has a first surface (5) and a second opposite surface (7), and is made from a conductive polymer composition which exhibits temperature dependent resistance behavior, preferably PTC behavior. A plurality of sensing elements (12) are electrically connected, preferably in series, on the sensor. Each sensing element is formed as an electrode pair containing a first electrode and a second electrode. The first and second electrodes (9,11) may be on the same surface of the laminar sheet or on opposite surfaces of the sheet. Two electrical leads (17,19) are present for connecting the sensing elements into a circuit, which may be used to detect changes in resistance which occur when a sensing element is exposed to an elevated temperature, a change in pressure, or a solvent.

Claims

1. A laminar sensor for detecting changes on a laminar substrate, the sensor having a resistance at 20°

C. R_T and comprising

(1) a laminar sheet which (a) has a first surface and a second opposite surface, and (b) comprises a conductive polymer composition which (i) exhibits temperature dependent resistance behavior and (ii) has a switching temperature T_s;

(2) a plurality of sensing elements (a) each of which comprises an electrode pair, said electrode pair comprising a first electrode and a second electrode, said electrodes being separated from each other and in contact with the laminar sheet, and (b) which are electrically connected in a resistive network, at least some of said sensing elements connected in series; and

(3) two electrical leads for connecting the sensing elements into a circuit.

2. A sensor according to claim 1 wherein the first electrode is attached to the first surface and the second electrode is attached to the second surface.

3. A sensor according to claim 1 wherein the first and second electrodes are both attached to the first surface.

4. A sensor according to claim 1 wherein the conductive polymer exhibits PTC behavior.

5. A sensor according to claim 1 wherein the laminar sheet has a thickness of at most 1.0 mm (0.040 inch).

6. A sensor according to claim 1 wherein the conductive polymer composition has a resistivity of at most 10 ohm-cm.

7. A sensor according to claim 1 wherein all of the sensing elements are connected in series.

8. A sensor according to claim 1 wherein when at least one sensing element is exposed to a temperature greater than T_s, the resistance of the sensor is at least 1.1R_T, at least 1.3R_T.

9. A sensor according to claim 1 wherein the sensor is positioned directly in contact with and covering at least 75% of one surface of the substrate.

10. A sensor according to claim 1 wherein the substrate is a laminar battery element, preferably a lithium ion polymer battery element.

11. A sensor according to claim 1 which detects temperature changes.

12. A sensor according to claim 1 wherein the total surface area of the first electrodes is at least 10% of the total surface area of the first surface and at most 70% of the total surface area of the first surface.

13. A sensor according to claim 1 which comprises an array comprising at least two groups of sensing elements, preferably wherein the groups comprise lines of sensing elements.

14. A lithium ion polymer battery which comprises

(A) a laminar battery element surrounded by an insulating material, said battery element comprising (1) first and second battery electrodes, (2) an anode, (3) a separator, (4) a cathode, and (5) and electrolyte;

and

(B) a laminar temperature sensor positioned in direct contact with the insulating material and covering at least 75% of one laminar surface of the insulating material, said sensor having a resistance at 20°

C. R_T and comprising

(1) a laminar sheet which (a) has a first surface and a second opposite surface, and (b) comprises a conductive polymer composition which exhibits PTC behavior;

(2) a plurality of sensing elements (a) each of which comprises an electrode pair, said electrode pair comprising a first electrode and a second electrode, said electrodes being separated from each other and in contact with the laminar sheet, and (b) which are electrically connected in a resistive network, at least some of said sensing elements connected in series; and

(3) two electrical leads for connecting the sensing elements into a circuit.

15. An electrical circuit which comprises

(A) a laminar sensor for detecting changes on a laminar substrate, the sensor having a resistance at 20°

C. R_T and comprising

(1) a laminar sheet which (a) has a first surface and a second opposite surface, and (b) comprises a conductive polymer composition which (i) exhibits temperature dependent resistance behavior and (ii) has a switching temperature T_s;

(2) a plurality of sensing elements (a) each of which comprises an electrode pair, said electrode pair comprising a first electrode and a second electrode, said electrodes being separated from each other and in contact with the laminar sheet, and (b) which are electrically connected in a resistive network, at least some of said sensing elements connected in series; and

(3) two electrical leads for connecting the sensing elements into the circuit; and

(B) sensing equipment electrically connected to the electrical leads to detect a change in the sensor.

16. A circuit according to claim 15 wherein the sensing equipment detects a change in resistance of the sensor.

17. A circuit according to claim 15 which further comprises

(C) a source of electrical power which is electrically connected to the sensor, wherein the sensor acts both to detect changes in temperature and as an overcurrent protection device.

18. A circuit according to claim 16 wherein

(1) the sensor comprises an array comprising at least two groups of sensing elements, and

(2) the sensing equipment monitors the groups of sensing elements in the array to allow location of a hot spot.