Capacitive switch structures for non-discrete tactile and non-tactile switches with customizable minimum actuation thresholds

Abstract

Disclosed embodiments include a strain sensor having a flexible sensor layer including a dielectric layer, a first electrode layer, and a second electrode layer, the first and second electrode layers disposed on opposite sides of the dielectric layer, and a first deformable layer disposed on the first or second electrode layer, wherein deformation of the first deformable layer greater than a predetermined amount is sufficient to generate a deformation of the flexible sensor layer and an impulse signal indicative of deformation above a predetermined threshold. Embodiments may include incorporating the strain sensor into a capacitive button or switch.

Description

[Technical Field]

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

[0002] The present disclosure relates generally to capacitive switches for use in electronic circuits, etc. More particularly, the present disclosure relates to capacitive switches for non-discrete tactile and non-tactile switches with customizable actuation thresholds. [Background technology]

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

[0004] In projected capacitive sensing, rather than charging the entire surface, an XY grid of conductive material is placed between two insulating materials. The grid is often constructed of copper (Cu) or gold (Au) on a printed circuit board (PCB) or indium tin oxide on glass. An integrated circuit (IC) is used to charge and monitor the grid. When an external conductive object, such as a finger or stylus, draws a charge from an area on the grid, the IC calculates the object's position on the touch surface. Touch sensors constructed with projected capacitive technology can be used to detect fingers that are not touching the surface. These act as proximity sensors.

[0005] A resistive touch sensor consists of two conductive layers separated by small spacer dots. The bottom layer is made of glass or film, and the top layer is made of film. The conductive material is coated with a metal film (commonly indium tin oxide) and is essentially transparent. A voltage is applied across the surface of the conductor. Pressure is applied to the sensor's top film using any probe, such as a finger, stylus, or pen, which activates the sensor. When enough pressure is applied, the top film deflects inward and makes contact with the bottom film. This creates a voltage drop, and the contacts create a voltage divider network in the X and Y directions. This voltage and change in voltage are detected by a controller, which calculates the location of the applied touch based on the X and Y coordinates of the touch.

[0006] Switches are also known. For example, dome switches, both tactile and non-tactile, are known to typically rely on the creation of a direct conductive path when the dome is depressed. This results in a switch that toggles between an on and an off state without intermediate states. Dome switches may also include a capacitive sensor, such as U.S. Patent No. 8,963,036, entitled "Capacitive Dome Switch," which is incorporated herein by reference.

[0007] Spring-sensor button sensors also exist. These are typically similar to capacitive dome switches, but employ a spring. When the spring is compressed, the windings move closer together, changing the capacitance of the spring. Typically, there is a ground connection on the surface of the PCB that interacts with the spring. For example, U.S. Pat. No. 4,584,444, "Keyboard Switch," discloses an exemplary capacitive spring switch, which is 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 others. The existing sensors and switches mentioned above do not facilitate or allow for such threshold customization.

[0009] Furthermore, existing switches or detectors are typically not constructed entirely from soft materials, which makes the switch or detector sensitive or detectable when embedded in a soft surface, which may not be desirable.

[0010] Additionally, some applications and environments require localized touch or impact detection over large surface areas. Again, the existing sensors and switches described above do not facilitate or are unable to detect such large areas. Current systems and methods also present other drawbacks, inconveniences, inefficiencies, and challenges. Summary of the Invention [Problem to be solved by the invention]

[0011] Thus, the disclosed embodiments address these and other drawbacks, inconveniences, inefficiencies, and problems associated with current systems and methods. Other advantages and efficiencies exist in the disclosed systems and methods. [Means for solving the problem]

[0012] As used herein, the terms "flexible," "extensible," "compliant," etc. are used somewhat interchangeably and all mean that there is some degree of bending, stretching, compression, twisting, curvature, etc. to the embodiment being described.

[0013] Disclosed embodiments include a strain sensor element for placement at a desired location. The sensor element includes a sensor sub-element having a planar surface and including a dielectric layer, a first ground electrode layer, and a second ground electrode layer, the first and second ground electrode layers disposed on opposite sides of the dielectric layer, the first and second ground layers and the dielectric layer defining first and second air gaps therebetween. The sensor element further includes a deformation layer, the deformation layer and the sensor sub-element defining a third air gap or more compressible region therebetween. When deformation of the deformation layer is greater than a predetermined amount, sufficient to deform the planar surface of the sensor sub-element beyond the third air gap, the surface area of ​​the sensor sub-element increases, generating an impulse signal indicative of deformation above a desired threshold. In some embodiments, the predetermined amount of deformation of the deformation layer is substantially 5 mm.

[0014] In some embodiments, the defined third gap is at least 4.5 mm between the deformation layer and the second ground layer. In other embodiments, the third gap may be a sealed airbag.

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

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

[0017] In some embodiments, the sensor element includes an indicator in electrical communication with the first and second ground electrodes, wherein the impulse signal generated by the strain sensor indicates a deformation greater than a desired threshold.

[0018] In some embodiments, the sensor element includes air, foam, film, and gel composed of silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer, and other deformable and / or elastomeric materials, and the foam material layer is disposed between the first ground layer and the desired location. In other embodiments, the foam material has a lower hardness modulus than the deformation layer, and the support plate is less rigid than the foam material layer and the deformation layer. In some embodiments, the sensor sub-element is more compressible than the deformation layer and the foam material layer. In some embodiments, the foam material layer includes an adhesive layer for adhering the strain sensor element to the desired location.

[0019] In some embodiments, the sensor element comprises a reinforcement material disposed between at least one of the deformation layer and the third void, the third void and the sensor sub-element, or 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 actuation by a user, the button incorporating a sensor element as disclosed herein and having a deformable layer disposed thereon that undergoes contact and deformation for selective actuation by the user.

[0022] Other embodiments also exist. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view of stack layers that make up a compliance sensor system according to a disclosed embodiment. FIG. [Figure 2]FIG. 1 is a schematic diagram of a basic sensor element structure according to an embodiment of the disclosure. [Figure 3] FIG. 1 is a schematic diagram of an application of a sensor element in an EV battery module, according to an embodiment of the disclosure. [Figure 4] FIG. 1 is a schematic diagram of an application of a sensor element in an EV battery module, according to an embodiment of the disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0024] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are herein described in detail. It is to be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0025] As used herein, it is understood that the terms "vertical," "horizontal," "lateral," "upper," "lower," "top," "bottom," "left," "right," "inner," "outer," etc. may refer to the relative orientation or location of features in the disclosed devices and / or assemblies shown in the figures. For example, "upper" or "uppermost" may refer to one feature being located closer to the top of the page than another feature. However, these terms are intended to be broadly interpreted to include devices and / or assemblies having other orientations, such as inverted or tilted orientations, in which top / bottom, upper / lower, above / below, top / bottom, and left / right are interchangeable depending on the orientation.

[0026] As mentioned above, in some applications and environments, it is desirable for a sensor to detect some types of “touch” or impact and ignore others. Additionally, some applications and environments require localized touch or impact detection over a large surface area. For example, in one embodiment directed to an impact sensor for an electric vehicle (EV) battery pack, it may be desirable to be able to detect damage to the road-facing surface of the pack caused by hitting a rock, driving over a curb, etc., and detection must occur over a relatively large surface area. An impact sensor can help manage safety / maintenance situations before additional damage occurs, such as a ruptured cooling tube near the EV battery pack, potentially leaking coolant into the pack and causing an electrical short. However, if the impact is minor or expected, detection is not necessary because there is likely no damage of concern.

[0027] 1 is a schematic cross-sectional view of a stack of layers 100 forming a compliance sensor system. As shown, a dielectric layer 12 is located between a top electrode layer 2 and a signal electrode layer 16. Also shown schematically is a peripheral electrode 140 electrically connecting the top electrode layer 2 and the signal electrode layer 16. Other configurations are also possible.

[0028] In some embodiments, the top electrode layer 2 may comprise an elastomer layer (e.g., silicone) incorporating conductive particles (e.g., nanoparticles such as carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, graphene oxide, etc.). Although shown as a continuous layer in FIG. 1, the top electrode layer 2 may be "hatched" or discontinuous. The top electrode layer 2 may also include a printed circuit board (PCB) interface and a number of conductive trace pads for attaching the PCB, sensor traces, or other electronics for operation and control of the sensor system.

[0029] In some embodiments, dielectric layer 12 may comprise an elastomeric material (e.g., silicone) and may optionally incorporate some conductive material, depending on, among other things, the desired dielectric constant, etc. Although not drawn to scale, in some embodiments, dielectric layer 12 is sized slightly smaller than top electrode layer 2 so that the periphery of top electrode layer 2 is not covered by dielectric layer 12, allowing electrical contact with peripheral electrode 140 as disclosed below.

[0030] In some embodiments, the signal electrode layer 16 may include an elastomeric material (e.g., silicone) with a conductive material (e.g., nanoparticles such as carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, graphene oxide, etc.) limited to the sensor regions, traces, and perimeter electrode 140. Many sensor regions may be distributed throughout the layer 16. The sensor regions may include regions of conductive material. The sensor regions are in electrical communication with the traces printed on the signal electrode layer 16. As shown, embodiments of the signal electrode layer 16 may include a perimeter electrode 140 that is electrically connected to the top electrode layer 2 to, among other things, provide electrical isolation for the entire sensor system. Other configurations are also possible.

[0031] FIG. 2 is a schematic diagram of a basic sensor element 200 structure according to some embodiments. As shown, a skin 22 may be subjected to a deformation force 24. For example, in an EV battery embodiment, the skin 22 may provide a protective cover for the EV battery, and the deformation force 24 may be due to impact with a road surface. In some embodiments, an air gap 26 or other compressible layer may be present between the skin 22 and the sensor layer 28. The sensor layer 28 may include a uniaxial compliance sensor, as described above with reference to FIG. 1. A dielectric layer may also cover the outer surface of the sensor layer 28. An additional compressible layer 30 (e.g., foam, soft rubber, etc.) may be present on the other side of the sensor layer 28. The sensor element 200 may be mounted to a support surface 32 (e.g., a wall or floor of an EV battery, etc.).

[0032] FIG. 3 is a schematic diagram of the application of a sensor element 200 in an EV battery module 32, according to embodiments of the disclosure. As shown, an outer panel 22 protects the bottom of the battery module 32 and may be supported and / or reinforced by suitable supports 34, and the distance between these supports will affect the sensing resolution and deformation characteristics of the outer panel 22. In some embodiments, a cooling system 36 (e.g., coils, tubing, etc., containing a liquid coolant, etc.) may be provided as part of the system. Also, as shown, multiple sensor elements (each including a sensor layer 28 and a compressible layer 30) may be attached to the cooling system 36 to detect deformation of the support panel 22 sufficient to raise concerns about potential damage to the cooling system 36 or the battery module 32. Also, as shown, in this embodiment, an air gap 26 may be included between the sensor layer 28 and the support panel 22. As will be apparent to those skilled in the art having the benefit of this disclosure, components such as the outer panel 22, battery module 32, etc., may be existing parts of other devices and need not be provided as part of the sensor element 200. Similarly, other configurations are possible.

[0033] 4 is a schematic diagram of the application of a sensor element in an EV battery module, according to an embodiment of the disclosure. In this embodiment, a single sensor element 200 with a larger surface area is used to substantially cover the bottom surface of the battery module 32. As shown schematically, a deformation force 24 sufficient to deform the skin 22 and, consequently, the sensor element 200 indicates an impact event. The combination of thicknesses and material properties of the skin 22, air gap (or additional compressible layer) 26, and compressible layer 30 may be optimized for specific sensing applications, such as, but not limited to, detecting an impact associated with a vehicle driving event or detecting finger pressure on a button.

[0034] Additionally, the components of the sensor element 200 may vary depending on the application, sensing needs, sensing environment, etc. For example, the skin 22 may be rigid (e.g., a metal plate), flexible (e.g., a rubber sheet), or semi-rigid / semi-flexible. The higher the flexural modulus and thickness of a given skin 22 material, the higher the minimum load / impact detection threshold. In button / switch applications, the skin 22 may provide a normal tactile feel upon initial actuation of the button.

[0035] Generally, the void (or other compressible layer) 26 is more compressible than the skin 22 and the compressible layer 30. In some embodiments, the void (or other compressible layer) 26 may be a sealed air bladder or the like.

[0036] As mentioned above, embodiments of the sensor layer 28 may include signal and ground electrodes integrated with a Faraday cage, and the mechanical properties of the sensor layer 28 may vary depending on the sensing needs and environment.

[0037] As previously mentioned, compressible layer 30 is typically more compressible than skin 22 and support layer 32, and less compressible than void (or other compressible layer) 26. Compressible layer 30 may include soft rubber, foam, or the like.

[0038] The embodiment of the support surface 32 may likewise vary depending on the application and environment, and is typically expected to have little or no deflection and may be stiffer than the rest of the structure.

[0039] As one of ordinary skill in the art with the benefit of this disclosure will appreciate, the minimum detection threshold will typically be determined by the combined mechanical properties / thickness of the skin 22 and the air gap (or other compressible layer) 26. Similarly, if the compressible layer 30 is stiffer than the skin 22 and the support surface is stiffer than both the skin 22 and the compressible layer, the sensor element may not be able to easily calculate the strain in the sensor layer 28 (i.e., it is essentially sandwiched between two rigid surfaces). Similarly, once the skin 22 deforms down to the support layer 32, further deformation may not be accurately measured.

[0040] Furthermore, the inner conductive layer of sensing layer 28 as well as all other components (i.e., 22, 26, 30, 32) may comprise dielectric or conductive materials selected solely based on the deformation characteristics and sensing requirements of a particular application.

[0041] In some embodiments, localized placement of reinforcement between the skin 22 and the void (or other compressible layer) 26, between the void (or other compressible layer) and the sensor layer 28, or between the sensor layer 28 and the compressible layer 30 can affect deformation characteristics or sensing resolution. Similarly, ribs, thickness variations, embossing, etc. can have a similar effect to providing reinforcement between components.

[0042] Also, although only one sensing layer 28 is shown in the drawings, additional sensing layers 28 and compressible layers 30 may be added if greater accuracy or resolution is desired.

[0043] In button switch embodiments (e.g., FIG. 2), the construction materials can be entirely flexible, allowing embedding in soft surfaces for seamlessly integrated, non-mechanical human-machine interfaces (HMIs). The buttons can also exhibit non-discrete sensing capabilities when a minimum force / pressure is reached, based on the capabilities of the intrinsic capacitive sensors. It may also be desirable for button embodiments to include a graphic overlay, such as on the outer skin 22, indicating the purpose of each button. The graphic overlay may also include an embossed dome whose mechanical properties should be considered for the end use. Other embodiments are also possible.

[0044] While various embodiments have been shown and described above, it is understood that the disclosure is not limited thereto, but includes all such modifications and variations as would become apparent to one skilled in the art.

Claims

1. a flexible sensor layer including a dielectric layer, a first electrode layer, and a second electrode layer, the first and second electrode layers being disposed on opposite sides of the dielectric layer; a first deformable layer disposed on the first or second electrode layer, wherein deformation of the first deformable layer greater than a predetermined amount is sufficient to generate a deformation of the flexible sensor layer and an impulse signal indicative of deformation above a predetermined threshold; A strain sensor comprising:

2. The strain sensor of claim 1 , wherein the predetermined amount of deformation of the first deformation layer is substantially 5 mm.

3. The strain sensor of claim 1 , further comprising a second deformable layer disposed on an opposite side of the flexible sensor layer from the first deformable layer.

4. The strain sensor of claim 3 , wherein the first or second deformable layer may be a sealed airbag.

5. The strain sensor of claim 1 further comprising a Faraday cage element surrounding the flexible sensor layer.

6. 10. The strain sensor of claim 1, wherein the dielectric layer comprises air, foam, film, and gel composed of silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer, and other deformable and / or elastomeric materials.

7. 10. The strain sensor of claim 1, wherein the first and second electrode layers comprise air, foam, film, and gel composed of silicone, urethane, thermoplastic elastomer (TPE), fluoropolymer, and other deformable and / or elastomeric materials.

7. 10. The strain sensor of claim 1, further comprising an indicator in electrical communication with the first and second electrode layers, the impulse signal generated by the flexible sensor layer activating the indicator to indicate a deformation greater than the predetermined threshold.

8. The strain sensor of claim 1 , wherein the flexible sensor layer has a lower hardness modulus than the first deformable layer.

9. The strain sensor of claim 1 , wherein the flexible sensor layer is more compressible than the first deformable layer.

10. The strain sensor of claim 1 , further comprising an adhesive layer for adhering the strain sensor to a desired location.

11. The strain sensor of claim 1 , further comprising one or more stiffeners disposed between the first deformable layer and the flexible sensor layer.

12. The strain sensor of claim 3 , further comprising one or more stiffeners disposed between the first deformable layer and the flexible sensor layer and / or between the second deformable layer and the flexible sensor layer.

13. a deformable skin; and a first compressible layer disposed on one side of the deformable skin; a compliant capacitance sensor layer disposed on the first compressible layer opposite the deformable skin; a second compressible layer disposed on an opposite side of the compliant capacitance sensor layer from the first compressible layer; A capacitive switch comprising:

14. 14. The capacitive switch of claim 13, wherein deformation of the deformable skin greater than a predetermined amount is sufficient to deflect the first compressible layer and the compliant capacitance sensor layer and generate a signal indicative of the deflection above a predetermined threshold.

15. The capacitive switch of claim 13 , wherein the first compressible layer comprises an air gap.

16. The capacitive switch of claim 13 , wherein the first compressible layer is more compressible than the deformable skin and the second compressible layer.

17. The capacitive switch of claim 13 , wherein the compliant capacitance sensor is more compressible than the first compressible layer and the second compressible layer.

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