TEMPERATURE-SENSING  TAPE BASED UPON BIMETAL SWITCH, AND METHOD OF TEMPERATURE CONTROL

A temperature-sensing tape including a flexible, electrically insulating substrate, a plurality of temperature-sensing elements disposed on the substrate, wherein a temperature-sensing element includes a bimetallic switch.

FIELD

The present embodiment relate generally to temperature-sensing devices. More specifically, the present embodiments relate to a temperature-sensing tape having a plurality of integrated temperature-sensing elements.

DESCRIPTION OF RELATED ART

Systems and devices such as electrical devices, batteries, or other equipment can be damaged by overtemperature conditions if such conditions are allowed to persist. Thus, it is common for systems and/or devices to be equipped with temperature-sensing devices that can be used to measure temperature variations at discrete locations on the surface of an electrical device. If a measured temperature exceeds a predetermined threshold, the electrical device may be automatically shut off until the overtemperature condition subsides or is remedied, thereby mitigating damage to the device or system being protected.

Batteries, such as Lithium ion batteries are designed to operate below a threshold or maximum safe operating temperature. Accordingly, a protection sensor to protect such a battery will optimally operate to prevent operation of the battery above the threshold temperature. To this end, temperature sensors such as PTC sensors, have been developed to trip at a targeted temperature in the range of the threshold temperature of the device or system to be protected. Ideally, in operation, given PTC sensor will trip at a corresponding temperature characteristic of the PTC material used to form the PTC sensor.

However, for a given product, such as a battery system, maximum operating temperature requirements may change. Accordingly, different sensors, having different trip temperatures, may be called for to accommodate changing requirements for thermal protection.

It is with respect to these and other considerations that the present improvements may be useful.

SUMMARY

In one embodiment, a temperature-sensing tape is provided. The temperature-sensing tape may include a plurality of flexible conductor portions. The temperature-sensing tape may also include a sensor array, comprising at least one temperature-sensing element, disposed in electrical series with the plurality of flexible conductor portions, where the at least one temperature-sensing element comprises a bimetallic switch.

In another embodiment, a thermal protection arrangement is provided, including a protected component; and a temperature-sensing tape, thermally coupled to the protected component. The temperature-sensing tape may include a plurality of flexible conductor portions; and a sensor array, comprising at least one temperature-sensing element, disposed in electrical series with the plurality of flexible conductor portions, where the at least one temperature-sensing element comprises a bimetallic switch.

In a further embodiment, a method of protecting a component ma include ,adhering a temperature-sensing tape to at least one protected area of the component, where the temperature-sensing tape has at least one temperature-sensing element, where the at least one temperature-sensing element includes a bimetallic switch. The method may also include determining a safe state corresponding to a logical “0” when an electrical resistance of the temperature-sensing tape is below a first threshold; and determining an unsafe state corresponding to a logical “1” when the electrical resistance of the temperature-sensing tape is above a second threshold.

DETAILED DESCRIPTION

Exemplary embodiments of a temperature-sensing tape in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The temperature-sensing tape may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will convey certain exemplary aspects of the temperature-sensing tape to those skilled in the art.

The present embodiments provide a temperature-sensing tape and a thermal protection arrangement and techniques, based upon a sensor array that is formed of temperature-sensing elements having a bimetallic switch. As used herein, a “tape,” “temperature-sensing tape,” or similar term, may refer to a structure having an array of temperature-sensing elements that are arranged in electrical series with a conductor, where the conductor may be integrated in a flexible tape material, integrated in a cloth material or woven structure, or may be a freestanding conductor, such as a wire. The tape may be adapted to be affixed to a protected element where temperature is to be measured, such as a battery. In particular, the tape may be affixed at least in locations of the tape where the temperature-sensing element is present, so as to impart thermal contact between the temperature-sensing element and protected element.

Referring toFIG.1A, a top view illustrating a temperature-sensing tape (hereinafter “the tape10”) in accordance with an exemplary embodiment of the present disclosure is shown. According to some embodiments, the tape10may include an electrically insulating support structure, such as a flexible substrate, shown as substrate12. The substrate12may be formed of a strip of dielectric material having an adhesive material on one or both sides thereof for allowing the tape10to be adhered to a surface (e.g., a surface of an electrical device). In various, non-limiting embodiments, the substrate12may be Scotch Tape, polyvinyl chloride (PVC) tape, Mylar, etc. In other embodiments, the substrate12may be formed of a cloth or woven material.

A plurality of temperature-sensing elements14may be disposed on the substrate12and may be spaced apart from one another along a length of the substrate12. Each of the temperature-sensing elements14may include a bimetal switch16, acting as a temperature-sensitive switch. By way of example, the tape10is shown inFIG.1Aas including a total of four temperature-sensing elements. In various embodiments, the tape10may include a greater or fewer number of temperature-sensing elements14without departing from the present disclosure, with the total number of temperature-sensing elements14generally being dictated by the length of the tape10and the distance between the temperature-sensing elements14. While the temperature-sensing elements14are shown inFIG.1Aas being evenly spaced apart from one another along the length of the substrate12, various embodiments of the tape10may include temperature-sensing elements14, disposed at irregular intervals along the length of the substrate12, such as may be dictated by the requirements of a particular application of the tape10.

The tape10may further include a conductive circuit, formed within an electrical conductor, arranged in electrical series with the temperature-sensing elements14. In the specific example illustrated inFIG.1A, the ‘electrical conductor’ is formed of a plurality of flexible conductor portions, shown as flexible conductors18, disposed on the substrate12. The flexible conductors18may extend between, and may be electrically connected to, the temperature-sensing elements14as further described below. The flexible conductors18may be formed of elongated segments of flexible, electrically conductive material that may be adhered to, printed on, or otherwise applied to the substrate12. Examples of such materials include, but are not limited to, copper mesh, silver epoxy, various types of metal wire or ribbon, conductive ink, etc. As such, the flexible conductors18may have the shape of a flat foil, a round cross-section wire, a single strand wire, a multistrand wire, a flat wire, a rod, or other suitable shape.

As noted, the tape10may be sufficiently flexible to be applied to protected elements or arrays of elements that define various surfaces, including multiple surfaces extending at angles to one another, curved surfaces, and so forth.FIG.1Bis a top view illustrating a variant of the temperature-sensing tape shown inFIG.1A. In this example, the tape50includes a flexible substrate56, with a flexible conductor54integrated onto the flexible substrate56. The flexible conductor54includes a plurality of conductive segments, arranged in electrical series with a plurality of temperature-sensing elements, shown as temperature-sensing elements52.

FIG.2Ais a side view illustrating an exemplary embodiment of a bimetallic switch according to some embodiments of the present disclosure. The bimetallic switch80may be incorporated in a temperature-sensing element, such as temperature-sensing element14or temperature-sensing element52. The bimetallic switch80may be formed of any suitable known bimetallic material system. As shown, a bimetallic switch80is arranged in an open configuration, where a bimetallic element82is spaced apart from a contact84. The bimetallic element82may be formed of two separate metal elements, arranged on top of one another, where the two different elements may be selected from any suitable pair of metal materials, as known in the art. As in known bimetal switches, the bimetallic element82may be formed of two different metals having two different thermal expansion coefficients (such as steel/copper, steel brass, or any other suitable bimetallic material system as known in the art). The two different metals may be formed as strips, for instance that are joined together to one another, such that the different thermal expansions force the bimetallic element82to change configuration when heated. For example, at a normal operating temperature range, the bimetallic element82may tend to be flat, while as temperature increases, the bimetallic element82may tend to bend in a given direction. Upon cooling the bimetallic element82may bend in the opposite direction as the bend direction upon heating.

Depending upon the exact configuration of the bimetallic element82and contact84, and the normal operation temperature designed for the bimetallic switch80, the bimetallic switch80may be considered a normally open switch or a normally closed switch.FIG.2Billustrates the examples of normally closed switch operation and normally open switch operation. In normally closed configuration, electrical current may pass through the bimetallic switch80, such as through conductors86, attached to the contact84and to the bimetallic element82. In an open configuration, the bimetallic switch80will not pass electrical current. According to embodiments of the disclosure, the bimetallic switch80may be arranged with a targeted switch temperature, suitable for thermal protection of an element to be protected, such as a battery. For example, a switch temperature to protect an element, such as a lithium ion battery, may range from 50° C. to 100° C., according to just some non-limiting embodiments. As used herein, the term switch temperature, in the context of an overtemperature protection application, may refer to the temperature where a bimetallic switch changes from a closed configuration to an open configuration as the bimetallic switch heats up. In other words, according to various embodiments of the disclosure, a bimetallic switch, such as bimetallic switch16, may be configured as a normally closed switch, where electrical current passes through the bimetallic switch16under normal operation. “Normal operation” may mean that the temperature of the protected element attached to the bimetallic switch is within a targeted operating range, such as a lithium ion battery designed for operating below 60° C. Under normal operation, the bimetallic element remains touching an external contact to complete an electrical circuit. The switch temperature denotes that temperature where the bimetallic element deforms or changes shape during an increase in temperature, to the extent to no longer touch the electrical contact and thus to switch to an open circuit condition.

Note that in accordance with known bimetallic switches, the bimetallic switches of the present disclosure may act reversibly so that when cooled from a temperature above the switch temperature, the bimetallic switch will close and return an electrical circuit to a closed circuit condition. Note also that an electrical hysteresis may be present in the bimetallic switches of the present embodiments. In particular, the switch temperature upon heating may be greater than the return temperature upon cooling, where the ‘return temperature’ refers to the temperature of the bimetallic switch during cooling from above the switch temperature, where the bimetallic switch returns to a closed configuration.

Generally, the degree of hysteresis of a bimetallic switch of the present embodiments may vary, but may be equal to one degree C. or more, several degrees, or up to tens of degrees according to some embodiments of the disclosure.FIG.2Cis an idealized graph that illustrates the concept of electrical hysteresis for a bimetallic switch. In this example, the switch temperature is 102° C., which temperature may represent the temperature where electrical resistivity of a circuit markedly increases, while the return temperature is 100° C. As such, the hysteresis in temperature between heating and cooling is 2° C.

FIG.3illustrates one example of electrical hysteresis for a bimetallic switch, whileFIG.4illustrates another example of electrical hysteresis for a bimetallic switch. In the example ofFIG.3, the switch temperature is 61° C. while the return temperature is 45° C. In the example ofFIG.4, the switch temperature is 105° C. and the return temperature is 85° C.

Note that the above examples illustrate that a temperature-sensing element configured with a bimetallic switch may provide a truly digital response where current flow is abruptly cut off or returned at a given temperature. While the above examples may be implemented in a bimetallic switch configured with a bimetal strip foil, in other non-limiting embodiments, a bimetallic switch may be a bi-metal arm, a bi-stable disk, a micro-electromechanical system (MEMs) structure, or a metal wire structure. Moreover, a bimetallic switch using a MEMs structure, may include a MEMs structure formed on a printed circuit board substrate.

Referring toFIG.5, a schematic illustration of an exemplary protection arrangement100implementing the above-described tape (tape10) is shown. The protection arrangement100may include one or more components (hereinafter “the protected component”) that may be protected by the tape10. In the exemplary embodiment shown inFIG.5, the protected component is a battery110having a plurality of cells112that are electrically connected in series. The battery110may be connected to a load114for supplying electrical power thereto. In various examples, the battery110may be a Li-ion battery, a Li-Polymer battery, a Ni-MH rechargeable battery, or the like. The present disclosure is not limited in the regard, and it is contemplated that the protected component may alternatively be, or may alternatively include, any of a variety of electrical power sources and/or electrical devices that may benefit from overtemperature protection.

The tape10may be adhered to the battery110, with the temperature-sensing elements14disposed on surfaces of respective cells (cells112) of the battery110. Particularly, each of the temperature-sensing elements14may be positioned so as to be under the thermal influence of a respective one of the cells112such that an increase in a temperature of one of the cells112may cause an increase in a temperature of a respective one of the temperature-sensing elements14disposed thereon.

The protection arrangement100may further include a control element116(e.g., a digital control element such as an ASIC, a microprocessor, etc.) that may be electrically connected to the flexible conductors18of the tape10and that may be configured to monitor a resistance in the tape10as further described below. The control element116may also be operatively connected to a disconnect switch118(e.g., a FET, a relay, etc.) that may be connected in electrical series intermediate the battery110and the load114.

During normal operation of the protection arrangement100, the battery110may supply electrical power to the load114, and the temperatures of the cells112may be within a normal operating range (e.g., less than 60 degrees Celsius, less than 80 degrees Celsius, etc.). However, upon the occurrence of an overtemperature condition, the temperature of one or more of the cells112may increase above the normal operating range, which increase may in-turn cause the temperatures of respective temperature-sensing elements14of the tape10to increase. If the temperature of one or more of the temperature-sensing elements14increases above the switching temperature, the resistance in the tape10may increase sharply as the bimetallic switch16causes an electrical open. An increase in the temperatures of the cells112may result from exposure to an external heat source (e.g., the protection arrangement100sitting out in the sun), or from an overcurrent condition caused by an internal fault in the battery110, for example.

The control element116may be configured to monitor a resistance of the tape10, or a voltage change, for example, and to control operation of the protection arrangement100accordingly. For example, when a bimetallic switch of the temperature-sensing element14is closed, the control element116measures a relatively low resistance in the tape10, indicating that the temperatures of the temperature-sensing elements14are below the switch temperature. The control element116may determine that the temperatures of the cells112are within a normal, safe operating range. However, if the control element116measures a relatively high resistance in the tape10, indicating that the temperature of one of more of the temperature-sensing elements14is above the switch temperature, the control element116may determine that the temperature of one or more of the cells112has exceeded the normal, safe operating range. If the control element116determines that the temperature of one or more of the cells112has exceeded the normal, safe operating range, the control element116may open the disconnect switch118, thereby arresting the flow of current in the protection arrangement100and preventing or mitigating damage that could otherwise result if the overtemperature or overcurrent condition were allowed to persist.

In additional non-limiting embodiments, a protected component may include a power tool having a battery pack, an e-scooter or other electric vehicle, a laptop computer, a notebook computer, a large battery system. Ad advantage afforded by a flexible tape of the present embodiments is the ability to conveniently place a sensor of plurality of temperature sensors, as well as fuse elements at any suitable location in a three-dimensional object having any arbitrary shape.

Regarding the aforementioned embodiments, in some variants, the substrate12may have an adhesive on a bottom side of the tape10, for attachment to a device being protected, on a bottom side of the tape10, for attachment to a device being protected. In some embodiments, adhesive can be applied to just sections under a temperature-sensing element14, to improve thermal contact to a surface of a device being protected. In particular embodiments, additives that have high thermal conductivity may be arranged within an adhesive, such as a high thermal conductivity powder, to improve thermal conductivity of the adhesive, and thus provide better thermal contact between a temperature-sensing element14and device being monitored or protected. Non-limiting examples of thermal high conductivity materials include intrinsic (low electrical conductivity) ZnO, Al2O3, AlN diamond paste, or high-thermal-conductivity electrically conductive particles including ceramic, metal or carbon based particles, fibers etc.

FIG.6presents a logic flow600, in accordance with embodiments of the disclosure. At block602, a temperature-sensing tape is adhered to a protected area of a component to be monitored. In some embodiments, the protected area may multiple different areas. The component to be monitored may be a battery in some embodiments. The temperature-sensing tape may include one or more sensing areas (such as a given sensing area and an additional sensing area), where a given sensing area overlaps with the protected area. The sensing area may include a bimetallic switch, arranged in an electrical circuit. The bimetallic switch may be arranged in a normally closed configuration according to some embodiments. In some embodiments, the multiple different sensing areas are arranged to overlap with the protected area where the temperature-sensing tape is adhered to the component. As such, the sensing area(s) are arranged in good thermal contact with the component.

At block604, a safe state corresponding to a logical “0” (or alternatively a logical “1”) is determined when the resistance of the temperature-sensing tape lies below a first threshold. At block606an unsafe state corresponding to a logical “1” (or alternatively a logical “0”) is determined when the resistance of the temperature-sensing tape is above a second threshold. The second threshold may generally be greater than the first threshold.

In sum, the present embodiments provide various advantages for temperature-sensing and overtemperature control. For one, the use of a bimetallic switch provides a truly digital response as the switch transitions abruptly between an open circuit and closed circuit configuration. A tape arranged with bimetallic switch sensor of the present embodiments may be configured to provide switching temperatures over a wide temperature range, based on the same device. In addition, such a tape should pass reliability requirements well above an activation temperature.

While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.