Capacitive switching structure for non-discrete, haptic, and non-haptic switches with custom minimum activation threshold

Abstract

The present invention relates to a strain sensor having a flexible sensor layer comprising a dielectric layer, a first electrode layer and a second electrode layer disposed on opposite sides of the dielectric layer, and a first deformable layer located on the first electrode layer or the second electrode layer, a deformation of the first deformable layer greater than a predetermined amount is sufficient to deform the flexible sensor layer and generate a pulsed signal indicating that the deformation exceeds a predetermined threshold. The invention also relates to a capacitive button or switch comprising said strain sensor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 379,958, filed on October 18, 2022, entitled “Capacitive Switch Structure For Non-Discrete, Tactile and Nontactile Switches With Customizable Minimum Activation Thresholds,” under 35 U.S.C. 119, the contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure generally relates to capacitive switches for use in electronic circuits and the like. More particularly, the present disclosure relates to a capacitive switch for non-discrete tactile and non-tactile switching with custom activation thresholds. Background Art

[0003] Capacitive and resistive sensors are known. For example, surface capacitive sensing and projected capacitive sensing are existing touch sensing technologies. In surface capacitive sensing, an insulator is applied on one side of a surface along with a conductive coating. A thin layer of insulator is applied on top of this conductive coating. Current is applied to all corners of the conductive coating. When an external conductor, such as a human finger or stylus, comes into contact with the surface, capacitance forms between them, drawing more current from the corners. The current at each corner is measured, and the ratio of the currents determines the touch location on the surface.

[0004] In projected capacitive sensing, the entire surface is not charged. Instead, an XY grid of conductive material is placed between two insulating materials. This grid is typically made of copper (Cu) or gold (Au) on a printed circuit board (PCB) or indium tin oxide on glass. An integrated circuit (IC) charges and monitors this grid. When charge is pulled from areas on the grid by an external conductive object, such as a finger or stylus, the IC calculates the object's position on the touch surface. Touch sensors made with projected capacitive technology can be used to sense a finger that is not touching the surface. They function as proximity sensors.

[0005] Resistive touch sensors consist of two conductive layers separated by a small spacer. The bottom layer is made of glass or film, and the top layer is made of film. The conductive material is coated in the form of a metal film, usually indium tin oxide, which is transparent in nature. Voltage is applied to the surface of the conductor. When pressure is applied to the top film of the sensor using any probe such as a finger, stylus, pen, etc., it activates the sensor. When enough pressure is applied, the top film bends inward and contacts the bottom film. This causes a voltage drop, and the contact point creates a voltage divider network in the XY direction. This voltage and the change in voltage are detected by the controller, and the touch position where the pressure was applied is calculated based on the XY coordinates of the touch.

[0006] In addition, various switches are known. For example, tactile (metal) dome switches and non-tactile (metal) dome switches are known, both of which generally rely on creating a direct conductive path when the dome is pressed. This allows the switch to switch between an on and off state without an intermediate state. Some (metal) dome switches may also include a capacitive sensor, such as U.S. Patent No. 8,963,036, entitled "Capacitive Dome Switch," the contents of which are incorporated herein by reference.

[0007] There are also spring-sensor button sensors. These are generally similar to capacitive (metal) dome switches, but use a spring. When the spring is compressed, the windings move closer together, and the capacitance of the spring changes. There is usually a ground connection on the PCB surface for the spring to interact with. For example, U.S. Patent No. 4,584,444, entitled "Keyboard Switch," discloses an exemplary capacitive spring switch, and its contents are incorporated herein by reference. Other switches also exist.

[0008] In some applications and environments, it is desirable for a sensor to detect some types of "touch" or impact and ignore other types of "touch" or impact. The above-mentioned existing sensors and switches do not easily lend themselves to such threshold setting or are unable to do so.

[0009] In addition, existing switches or detectors are usually not made entirely of soft materials. Therefore, when a switch or detector is embedded in a soft surface, it can be sensed or felt, which may be undesirable.

[0010] Furthermore, in some applications and environments, it is necessary to sense a localized touch or impact over a larger area. Similarly, the aforementioned existing sensors and switches are not easy or even impossible to perform such large-area detection. Existing systems and methods also have other drawbacks, inconveniences, inefficiencies, and problems. Summary of the Invention

[0011] Thus, the disclosed embodiments solve the above-mentioned problems and other shortcomings, inconveniences, inefficiencies and problems with existing systems and methods. The disclosed systems and methods also have other advantages and efficiencies.

[0012] As used herein, "flexible," "stretchable," "compliant," and the like are used somewhat interchangeably and all mean that there is a certain amount of flexing, stretching, compression, torsion, bending, and the like for the described embodiment.

[0013] Disclosed embodiments include a strain sensor element for placement at a desired location. The sensor element includes a sensor subelement having a planar surface and comprising a dielectric layer, a first ground electrode layer, and a second ground electrode layer, the first and second ground electrode layers being disposed on opposite sides of the dielectric layer, the first and second ground electrode layers and the dielectric layer defining first and second air gaps therebetween. The sensor element also includes a deformable layer, wherein the deformable layer and the sensor subelement define a third air gap or further compressible region therebetween, and wherein when deformation of the deformable layer is greater than a predetermined amount and sufficient to exceed the third air gap and deform the planar surface of the sensor subelement, the surface area of ​​the sensor subelement is increased, and a pulse signal is generated indicating that the deformation has exceeded a desired threshold. In some embodiments, the predetermined amount of deformation of the deformable layer is substantially 5 mm.

[0014] In some embodiments, the third air gap defined between the deformable layer and the second ground plane is at least 4.5 mm. In other embodiments, the third air gap may be a hermitically sealed air bag.

[0015] In some embodiments, the sensor element further comprises a Faraday cage element.

[0016] In some embodiments, the dielectric layer includes air, foam, film, and gel including silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer, and other deformable and / or elastic materials.

[0017] In some embodiments, the sensor element includes an indicator in electrical communication with the first ground electrode and the second ground electrode, wherein the pulse signal generated by the strain sensor provides an indication that the deformation is greater than a desired threshold.

[0018] In some embodiments, the sensor element comprises air, foam, a film, and a gel, wherein the gel comprises silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer, and other deformable and / or elastomeric materials, wherein a foam layer is disposed between a first ground plane and a desired location. In other embodiments, the foam has a hardness factor less than that of the deformable layer, and the support plate has a stiffness less than that of the foam layer and the deformable layer. In some embodiments, the sensor subelement is more compressible than the deformable layer and the foam layer. In some embodiments, the foam layer comprises an adhesive layer for attaching the strain sensor element to the desired location.

[0019] In some embodiments, the sensor element includes a reinforcement member disposed at least one of the following locations: between the deformable layer and the third air gap, between the third air gap and the sensor sub-element, and between the sensor sub-element and the foam material layer.

[0020] In some embodiments, the sensor element is disposed between the battery pack floor structure and the surrounding environment.

[0021] Also disclosed are embodiments of a button for selective activation by a user, the button comprising a sensor element as disclosed herein, wherein the deformable layer is configured to be contacted and deformed by a user for selective activation.

[0022] Other implementations are also possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic cross-sectional view of a laminate used to form a compliant sensor system according to disclosed embodiments.

[0024] Figure 2 is a schematic diagram of a basic sensor element structure according to the disclosed embodiments.

[0025] Figure 3 is a schematic diagram of an application of a sensor element in an EV battery module according to the disclosed embodiment.

[0026] Figure 4 is a schematic diagram of an application of a sensor element in an EV battery module according to the disclosed embodiment.

[0027] While specific embodiments are shown by way of example in the accompanying drawings and will be described in detail herein, the present invention is susceptible to various modifications and alternative forms. However, it should be understood that the present disclosure is not limited to the particular forms disclosed. Rather, it is intended to cover all variations, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. DETAILED DESCRIPTION

[0028] It should be understood that the terms "vertical," "horizontal," "lateral," "upper," "lower," "top," "bottom," "left," "right," "inner," "outer," and the like as used herein may refer to the relative orientation or position of features in devices and / or components as shown in the accompanying drawings. For example, "upper" or "topmost" may refer to a feature that is positioned closer to the top of the page than another feature. However, these terms should be broadly interpreted to include devices and / or components having other orientations, such as inverted or oblique orientations, where top / bottom, above / below, over / below, up / down, and left / right may be interchanged based on orientation.

[0029] As described above, in some applications and environments, it is desirable for a sensor to detect some types of "touches" or impacts and ignore other types of "touches" or impacts. Additionally, in some applications and environments, it is desirable to sense localized touches or impacts over a larger area. For example, in an embodiment involving an impact sensor for an electric vehicle (EV) battery pack, it may be desirable to be able to sense whether the road-facing side of the battery pack has been damaged by a rock impact, driving on a curb, etc., and sensing over a relatively large area is desired. The impact sensor can help manage safety / repair situations before additional damage occurs (such as a ruptured coolant line near the EV battery pack, causing coolant to leak into the battery pack, potentially causing a short circuit, etc.). However, if the impact is small, or anticipated, no sensing is required because no worrisome damage may be caused.

[0030] Figure 1 is a schematic cross-sectional view of a laminate 100 for forming a compliant sensor system. As shown, dielectric layer 12 is positioned between top electrode layer 2 and signal electrode layer 16. As schematically shown, peripheral electrode 140 electrically connects top electrode layer 2 and signal electrode layer 16. Other configurations are also possible.

[0031] In some embodiments, the top electrode layer 2 may include an elastomeric layer (e.g., silicone) incorporating conductive particles (e.g., nanoparticles such as carbon black, nickel nanowires, silver nanoparticles, graphene flakes, graphene oxide, etc.). Figure 1Although shown as a continuous layer in FIG, the top electrode layer 2 may also be "hatched" or otherwise discontinuous. The top electrode layer 2 may also include a printed circuit board (PCB) interface and a plurality of conductive trace pads for attaching the PCB, sensor traces, or other electronic devices for operation and control of the sensor system.

[0032] In some embodiments, the dielectric layer 12 can include an elastomeric material (e.g., silicone) and, if desired, can incorporate some conductive material therein, depending, inter alia, on the desired magnitude of the dielectric constant. While not drawn strictly to scale, in some embodiments, the dielectric layer 12 is sized slightly smaller than the top electrode layer 2 so that the peripheral edge of the top electrode layer 2 is not covered by the dielectric layer 12 and allows electrical contact with the peripheral electrode 140 as described below.

[0033] In some embodiments, the signal electrode layer 16 can include an elastomeric material (e.g., silicone) with a conductive material (e.g., nanoparticles such as carbon black, nickel nanowires, silver nanoparticles, graphene microplatelets, graphene oxide, etc.) confined to the sensor area, traces, and peripheral electrodes 140. Multiple sensor areas can be distributed throughout the signal electrode layer 16. The sensor areas can include areas of conductive material. The sensor areas are electrically connected to the traces printed on the signal electrode layer 16. As shown, embodiments of the signal electrode layer 16 can include a peripheral electrode 140 electrically connected to the top electrode layer 2, thereby providing electrical isolation for the entire sensor system, in particular. Other configurations are also possible.

[0034] Figure 2 2 is a schematic diagram of the basic structure of a sensor element 200 according to the disclosed embodiment. As schematically shown, the outer plate 22 may be subjected to a deformation force 24. For example, in an EV battery embodiment, the outer plate 22 may include a protective cover for the EV battery, and the deformation force 24 may be caused by impact with the road surface. In some embodiments, an air gap 26 or other compressible layer may be located between the outer plate 22 and the sensor layer 28. The sensor layer 28 may include the above-mentioned Figure 1 The dielectric layer can cover the outer surface of the sensor layer 28. An additional compressible layer 30 (e.g., foam, soft rubber, etc.) can be located on the other side of the sensor layer 28. The sensor element 200 can be mounted on a support surface 32, such as a wall or floor of an EV battery.

[0035] Figure 3Schematic diagram of a sensor element 200 in an EV battery module 32 according to a disclosed embodiment. As shown, an outer plate 22 protects the bottom of the battery module 32 and is supported and / or reinforced by appropriate supports 34. The distance between these supports will also affect the sensing resolution and deformation characteristics of the outer plate 22. In some embodiments, a cooling system 36 (e.g., coils, pipes, etc. with a liquid coolant) may be provided as part of the system. As shown, multiple sensor elements (each including a sensor layer 28 and a compressible layer 30) may be mounted in the cooling system 36 to sense any deformation of the support plate 22 sufficient to cause potential damage to the cooling system 36 or the battery module 32. As shown in this embodiment, an air gap 26 may be included between the sensor layer 28 and the support plate 22. It will be apparent to those skilled in the art having the benefit of this disclosure that components such as the outer plate 22 and the battery module 32 can be existing parts of other equipment and need not be provided as part of the sensor element 200. Similarly, other configurations are possible.

[0036] Figure 4 is a schematic diagram illustrating the use of a sensor element in an EV battery module according to the disclosed embodiments. In this example, a single, relatively large-area sensor element 200 is used to substantially cover the bottom surface of battery module 32. As schematically illustrated, a deformation force 24 sufficient to deform outer panel 22, and therefore sensor element 200, indicates an impact event. The combination of the thickness and material properties of outer panel 22, air gap (or additional compressible layer) 26, and compressible layer 30 can be optimized to suit specific sensing scenarios, such as, but not limited to, sensing impact caused by vehicle driving events or sensing finger pressure on a button.

[0037] Furthermore, the components of sensor element 200 may vary depending on the application, sensing requirements, sensing environment, and so on. For example, outer plate 22 may be rigid (e.g., a metal plate), flexible (e.g., a rubber sheet), or semi-rigid / semi-flexible. The greater the flexural modulus and thickness of the outer plate 22 material, the higher the minimum load / impact sensing threshold. In button / switch applications, outer plate 22 may provide a typical tactile feel for initial engagement of the button.

[0038] Typically, the air gap (or other compressible layer) 26 is more compressible relative to the outer panel 22 and the compressible layer 30. In some embodiments, the air gap (or other compressible layer) 26 may be a sealed bladder or the like.

[0039] As described above, embodiments of the sensor layer 28 may include signal and ground electrodes with an integrated Faraday cage.The mechanical properties of the sensor layer 28 may also vary depending on the sensing needs and environment.

[0040] As described above, the compressible layer 30 is more compressible relative to the outer panel 22 and the support layer 32, and less compressible relative to the air gap (or other compressible layer) 26. The compressible layer 30 may include a soft rubber, foam material, or the like.

[0041] The implementation of the support surface 32 may also vary depending on the application and environment, and is generally assumed to have little or no deflection and may generally be stiffer than the rest of the structure.

[0042] As will be understood by those of ordinary skill in the art having the benefit of this disclosure, the combined mechanical properties / thickness of the outer panel 22 and the air gap (or other compressible layer) 26 will generally determine the minimum sensing threshold. Similarly, if the compressible layer 30 is stiffer than the outer panel 22, and the supporting surface is stiffer than both the outer panel 22 and the compressible layer, the sensor element may not allow the sensor layer 28 to strain in an easily calculable manner (i.e., the sensor layer 28 is essentially sandwiched between two hard surfaces). Similarly, if the outer panel 22 deforms all the way to the supporting layer 32, further deformation may not be accurately measured.

[0043] Furthermore, with the exception of the conductive layers within sensing layer 28, all other components (ie, 22, 26, 30, 32) may comprise dielectric or conductive materials selected solely based on the deformation characteristics and sensing requirements of a particular application.

[0044] In some embodiments, reinforcements may be locally positioned between the outer panel 22 and the air gap (or other compressible layer) 26, between the air gap (or other compressible layer) and the sensor layer 28, or between the sensor layer 28 and the compressible layer 30 to affect deformation characteristics or sensing resolution. Similarly, by employing ribs, varying thicknesses, or embossing, similar effects may be provided as having reinforcements between components.

[0045] Additionally, although only one sensing layer 28 is shown, additional sensing layers 28 and compressible layers 30 may be added if higher accuracy or resolution is required.

[0046] For push button switch implementations (e.g., Figure 2), all component materials can be flexible so they can be embedded in soft surfaces for seamlessly integrated non-mechanical human machine interface (HMI) applications. Based on the capabilities of the underlying capacitive sensors, the buttons can also have non-discrete sensing capabilities once a minimum force / pressure is reached. For button embodiments, a graphic overlay indicating the purpose of each button can also be included on the outer plate 22, etc. The graphic overlay can also include an embossed dome(s), the mechanical properties of which need to be considered for the final application. Other embodiments are also possible.

[0047] Although various embodiments have been shown and described, the present disclosure is not limited thereto, but should be construed to include all changes and modifications that are obvious to those skilled in the art.

Claims

1. A strain sensor comprising: a flexible sensor layer comprising a dielectric layer, a first electrode layer, and a second electrode layer, the first electrode layer and the second electrode layer being disposed on opposite sides of the dielectric layer; as well as a first deformable layer, which is located on the first electrode layer or the second electrode layer; The deformation of the first deformable layer greater than a predetermined amount is sufficient to deform the flexible sensor layer and generate a pulse signal indicating that the deformation exceeds a predetermined threshold.

2. The strain sensor according to claim 1, wherein Said predetermined amount of deformation of said first deformable layer is substantially 5 mm.

3. The strain sensor according to claim 1 , further comprising: A second deformable layer is located on an opposite side of the flexible sensor layer from the first deformable layer.

4. The strain sensor according to claim 3, wherein: The first deformable layer or the second deformable layer is a sealed airbag.

5. The strain sensor according to claim 1 , further comprising: A Faraday cage element surrounds the flexible sensor layer.

6. The strain sensor according to claim 1, wherein The dielectric layer includes air, foams, films, and gels including silicone, urethane, thermoplastic elastomers (TPE), fluoropolymers, and other deformable and / or elastic materials.

7. The strain sensor according to claim 1, wherein The first electrode layer and the second electrode layer include air, foam, film and gel, and the gel includes silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer and other deformable and / or elastic materials.

8. The strain sensor according to claim 1, further comprising: An indicator is in electrical communication with the first electrode layer and the second electrode layer, wherein the pulse signal generated by the flexible sensor layer activates the indicator to indicate a deformation greater than the predetermined threshold.

9. The strain sensor according to claim 1, wherein: The flexible sensor layer has a stiffness coefficient smaller than that of the first deformable layer.

10. The strain sensor according to claim 1, wherein The flexible sensor layer is more compressible than the first deformable layer.

11. The strain sensor according to claim 1 , further comprising: An adhesive layer for attaching the strain sensor to a desired location.

12. The strain sensor according to claim 1, further comprising: One or more reinforcement members are disposed between the first deformable layer and the flexible sensor layer.

13. The strain sensor according to claim 3, further comprising: one or more reinforcement members disposed at at least one of the following locations: between the first deformable layer and the flexible sensor layer; between the second deformable layer and the flexible sensor layer.

14. A capacitive switch, comprising: Deformable outer panels; a first compressible layer disposed on one side of the deformable outer panel; a compliant capacitive sensor layer disposed on a side of the first compressible layer opposite the deformable outer plate; as well as A second compressible layer is disposed on a side of the compliant capacitive sensor layer opposite the first compressible layer.

15. The capacitive switch according to claim 13, wherein: Deformation of the deformable outer plate greater than a predetermined amount is sufficient to deform the first compressible layer and the compliant capacitive sensor layer and generate a signal indicative of deformation exceeding a predetermined threshold.

16. The capacitive switch according to claim 13, wherein: The first compressible layer includes an air gap.

17. The capacitive switch according to claim 13, wherein: The first compressible layer is more compressible than the deformable outer panel and the second compressible layer.

18. The capacitive switch according to claim 13, wherein: The compliant capacitive sensor is more compressible than the first compressible layer and the second compressible layer.

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