Flexible pressure sensor for automotive seat and method of manufacturing the same

Abstract

The application provides a flexible pressure sensor for an automobile seat, comprising: a first flexible protective layer; a second flexible protective layer; a first conductive circuit layer, which is formed on one side surface of the first flexible protective layer by screen printing of conductive silver paste; a second conductive circuit layer, which is formed on one side surface of the second flexible protective layer by screen printing of conductive silver paste; and a plurality of pressure-sensitive units, which are arranged between the first flexible protective layer and the second flexible protective layer, and each of the pressure-sensitive units comprises a pressure-sensitive element forming a series loop with the first conductive circuit layer and the second conductive circuit layer, and the resistance value of the pressure-sensitive element changes with the change of the pressure. The first conductive circuit layer and the second conductive circuit layer are formed by screen printing of conductive silver paste, which completely replaces the traditional wire sewing process. The screen printing process is fast, accurate and consistent, and is suitable for large-scale production.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a flexible pressure sensor for automotive seats and a method for manufacturing the same. Background Technology

[0002] The description in this section provides only background information relevant to the disclosure of this application and does not constitute prior art.

[0003] With the continuous improvement of automotive intelligence, seat comfort systems have become an important feature in high-end models. Among these, the seat airbag support system utilizes multiple airbags within the seat cushion and backrest. These airbags dynamically adjust their pressure based on the occupant's body shape, posture, and pressure distribution, providing active support for the occupant's lower back, back, and sides, thus significantly improving ride comfort during long drives. To achieve precise control of the airbag support system, pressure detection devices are installed within the seat to acquire real-time data on the pressure distribution exerted by the occupant on different areas of the seat, serving as the basis for airbag pressure adjustment.

[0004] Currently, pressure detection devices used in seat airbag support systems primarily employ resistive flexible pressure sensors. These sensors typically consist of upper and lower protective layers, with multiple pressure-sensitive units arranged between them. Pressure information at corresponding locations is obtained by detecting changes in the resistance value of each pressure-sensitive unit. To achieve multi-point pressure detection, existing technologies often employ a matrix scanning method—wires extending in a first direction and a second direction are arranged on the two protective layers, respectively. The two wires are electrically connected at their intersections via a pressure-sensitive material, forming pressure detection points.

[0005] Current pressure-sensitive materials typically employ pressure-sensitive carbon paste layers. Carbon paste is a conductive paste containing carbon-based conductive particles (such as graphite, carbon black, and carbon nanotubes), formed on the surface of a protective layer or substrate through methods such as screen printing, spraying, or blade coating. The working principle of the pressure-sensitive carbon paste layer is as follows: when pressure is applied, the contact between the conductive particles within the layer becomes tighter, increasing the conductive path and decreasing the resistance; when the pressure decreases, the contact between the conductive particles loosens, increasing the resistance. Pressure-sensitive carbon paste layers are widely used as pressure-sensitive elements in pressure sensors.

[0006] However, existing pressure detection devices for seat airbag support systems use stitching to fix both layers of wires to non-woven fabric during manufacturing, and the non-woven fabric is then fixed to a protective layer. Specifically, each wire needs to be sewn individually onto the surface of the non-woven fabric, and then the non-woven fabric with the sewn wires is adhered to the protective layer. The wires in the first direction and the wires in the second direction need to be precisely aligned at their intersections, and electrical insulation must be maintained between these intersections. This stitching process, using non-woven fabric as the wire carrier layer, has the following drawbacks: First, the stitching process is complex and difficult to scale up. For sensors with dozens or even hundreds of detection points, a large number of wires need to be sewn onto the non-woven fabric one by one, and the direction, spacing and intersection of each wire need to be precisely controlled, resulting in extremely low production efficiency and difficulty in ensuring consistency.

[0007] Secondly, the double-layer structure of non-woven fabric and protective layer increases the overall thickness of the sensor. The non-woven fabric, as the carrier layer for the conductor, needs to have a certain thickness and mechanical strength; when the protective layer is added, the overall thickness of the sensor increases significantly. When the sensor is installed between the seat foam layer and the seat upholstery, the thicker sensor structure will create a noticeable foreign body sensation, affecting the passenger's comfort.

[0008] Third, the stitching method makes it difficult to achieve precise positioning and reliable insulation of the circuit. The conductors are prone to shifting during the stitching process, leading to deviations in the position of the intersection point. At the same time, the two layers of conductors need to maintain electrical insulation in non-intersection areas, but the stitching method, combined with the fiber structure of non-woven fabric, makes it difficult to achieve reliable insulation over a large area, posing a risk of short circuits.

[0009] Fourth, the material systems of existing sensors lack overall stretchability. In current technologies, protective layers are mostly made of non-stretchable or poorly stretchable materials such as PET, and non-woven fabrics also lack stretchability. When the sensor is attached to the surface of the seat foam layer, the foam layer undergoes significant deformation when the occupant sits on it. The non-stretchable sensor cannot stretch accordingly, affecting not only seating comfort but also potentially causing wire breakage or pressure-sensitive element failure. Although some research has attempted to use TPU as a flexible substrate and stretchable conductive ink as electrodes, the insulating layer, conductive connection layer, and pressure-sensitive element are still non-stretchable materials. This means that when the sensor is stretched as a whole, the non-stretchable components become stress concentration points, leading to delamination, cracking, or functional failure.

[0010] Fifth, the scheme using a pressure-sensitive carbon paste layer as a pressure-sensitive element has problems such as poor adhesion and easy fatigue cracking. The bonding force between the conductive particles in the carbon paste and the flexible protective layer (especially TPU material) is weak. During repeated pressure and bending of the sensor, the pressure-sensitive carbon paste layer is prone to peeling off or cracking from the surface of the protective layer. At the same time, the pressure-sensitive carbon paste layer is a composite system of rigid particles and resin. Under long-term cyclic pressure, microcracks will gradually form inside, eventually leading to the fracture of the pressure-sensitive carbon paste layer, causing irreversible changes in the resistance value of the pressure-sensitive unit.

[0011] In addition to the pressure detection devices used in seat airbag support systems mentioned above, automotive seats are also equipped with another type of pressure detection device—the Safety Belt Reminder (SBR). The SBR device is typically installed between the seat foam and the upholstery, or between the foam and the seat frame, to detect whether the seat is occupied by an occupant. The structure of the SBR device differs fundamentally from the airbag support pressure detection device described in this application: existing SBR sensors use rigid materials as a protective layer, and their structural components include a switch housing consisting of a movable upper shell and a fixed lower shell, non-closed circuit components, and a reset elastic pad, etc. The contact is switched on and off by the up-and-down movement of the upper shell relative to the lower shell. This rigid structure means that the SBR sensor can only provide a binary "on / off" switching signal, unable to output continuous pressure distribution data, making it difficult to meet the precise detection requirements of multi-point pressure distribution in airbag support systems.

[0012] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0013] Based on the aforementioned deficiencies in the prior art, the flexible pressure sensor for automotive seats and its manufacturing method described in this application are intended to solve at least one technical problem in the prior art.

[0014] To achieve the above objectives, this application provides the following technical solution: a flexible pressure sensor for automotive seats, comprising: First flexible protective layer; The second flexible protective layer is disposed opposite to the first flexible protective layer; The first conductive circuit layer is formed on one side surface of the first flexible protective layer by screen printing of conductive silver paste. The second conductive circuit layer is formed on one side surface of the second flexible protective layer by screen printing of conductive silver paste. Multiple pressure-sensitive units are disposed between the first flexible protective layer and the second flexible protective layer. Each pressure-sensitive unit includes a pressure-sensitive element that forms a series circuit with the corresponding first conductive line layer and the second conductive line layer. The resistance value of the pressure-sensitive element changes with the pressure applied.

[0015] This application discloses a method for manufacturing a flexible pressure sensor for automotive seats, comprising the following steps: Provides a first flexible protective layer and a second flexible protective layer; A first conductive circuit layer is formed by screen printing conductive silver paste onto one side surface of the first flexible protective layer. A second conductive circuit layer is formed by screen printing conductive silver paste onto one side surface of the second flexible protective layer. Multiple pressure-sensitive units are disposed on the second flexible protective layer. Multiple insulating units are provided on the first flexible protective layer on which the first conductive line layer is formed or on the second flexible protective layer on which the second conductive line layer is formed. Multiple conductive units are provided on the first flexible protective layer on which the first conductive circuit layer is formed or on the second flexible protective layer on which the second conductive circuit layer is formed. Align and attach the side of the first flexible protective layer having the first conductive circuit layer with the side of the second flexible protective layer having the second conductive circuit layer.

[0016] The beneficial effects of this application, based on the above technical solutions, are as follows: (1) The process is simplified and suitable for mass production. This application uses screen printing of conductive silver paste to form the first and second conductive circuit layers, which completely replaces the traditional wire sewing process. The screen printing process is fast, precise, and consistent, making it suitable for mass production and significantly reducing manufacturing costs and labor hours.

[0017] (2) Eliminating the non-woven fabric layer reduces sensor thickness and improves comfort. In this application, the conductive circuit layer is directly screen-printed onto the surface of the flexible protective layer, eliminating the need to sew wires onto the non-woven fabric and then attach the non-woven fabric to the protective layer as in existing technologies. Eliminating the non-woven fabric layer significantly reduces the overall thickness of the sensor, eliminates the foreign body sensation caused by the double-layer structure of the non-woven fabric and the protective layer, and improves passenger comfort.

[0018] (3) Flexible circuit layout and precise insulation and conduction control. This application sets up multiple independent insulation units and multiple independent conductive units, which are arranged at predetermined positions with intervals. The insulation units control the electrical insulation of the two layers of circuits at the positions where insulation is required, and the conductive units control the electrical connection of the two layers of circuits at the positions where conduction is required. This "independent and spaced" structure avoids the complex process of the traditional single-layer insulation opening scheme, and can flexibly arrange the position of each insulation unit and conductive unit according to the design requirements of the matrix scanning circuit, so as to achieve precise local insulation and local conduction control.

[0019] (4) Improved sensor flexibility and ride comfort. The first and second flexible protective layers of this application are made of stretchable materials such as thermoplastic polyurethane (TPU), polydimethylsiloxane (PDMS), or modified polyethylene terephthalate (modified PET), and there is no need to use non-woven fabric as a conductor carrier layer. The entire sensor has a single flexible protective layer structure. When the sensor is attached to the seat foam layer, it can stretch synchronously with the deformation of the foam layer without relative displacement or stress concentration, avoiding circuit breakage and pressure-sensitive element failure, while significantly improving the ride comfort of the occupants.

[0020] (5) The pressure-sensitive element has strong adhesion and high reliability. In one embodiment of this application, the pressure-sensitive element is a pressure-sensitive carbon paste layer. This pressure-sensitive carbon paste layer is not directly printed on a flexible protective layer such as TPU, but is first set on the surface of a third flexible substrate (PET sheet), and then the PET sheet with the pressure-sensitive carbon paste layer is attached to the second flexible protective layer. Since the adhesion between carbon paste and PET is better than that between carbon paste and TPU, this structure significantly improves the adhesion strength and durability of the pressure-sensitive carbon paste layer, avoiding the peeling or cracking of the pressure-sensitive carbon paste layer during repeated pressure and stretching.

[0021] (6) A variety of pressure-sensitive materials are available, and the application range is wide. This application can use either a pressure-sensitive carbon paste layer or a conductive fiber cloth layer as the pressure-sensitive element. The conductive fiber cloth layer is woven from conductive fibers, which has better flexibility and tensile strength, and its resistance value decreases continuously with increasing pressure, making it suitable for applications requiring high flexibility and high tensile strength.

[0022] (7) The matrix scanning circuit has a complete structure and high detection accuracy. This application uses the first conductive line and the second conductive line to be arranged in a cross pattern. A varistor element can be set at the intersection point. A complete matrix scanning circuit is formed by the control of the conductive unit and the insulating unit. It can realize independent addressing and resistance reading of each detection point, and has high detection accuracy and fast response speed.

[0023] Specific embodiments of this application are disclosed in detail with reference to the following description and accompanying drawings, illustrating how the principles of this application can be employed. It should be understood that the embodiments of this application are not limited in scope. Within the spirit and scope of the appended claims, the embodiments of this application include many changes, modifications, and equivalents.

[0024] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0025] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components. Attached Figure Description

[0026] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this application in any way. Furthermore, the shapes and scales of the components in the drawings are merely illustrative to aid in understanding this application and do not specifically limit the shapes and scales of the components. Those skilled in the art, guided by the teachings of this application, can select various possible shapes and scales to implement this application according to specific circumstances. In the drawings: Figure 1 A schematic diagram of a flexible pressure sensor according to an embodiment of this application is shown.

[0027] Figure 2 A schematic diagram of the structure in an embodiment of this application is shown, showing the first flexible protective layer forming the first conductive line layer.

[0028] Figure 3 A schematic diagram of the structure in an embodiment of this application is shown, showing the second flexible protective layer forming the second conductive line layer.

[0029] The reference numerals in the above figures are as follows: 1. First flexible protective layer; 2. Second flexible protective layer; 3. First conductive circuit layer; 31. First pole circuit unit; 32. Second pole circuit unit; 4. Second conductive circuit layer; 5. Insulating unit; 6. Conductive unit; 7. Varistor unit. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0031] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0034] It should be noted that in the description of this application, the terms "first," "second," etc., are used only for descriptive purposes and to distinguish similar objects; there is no order between them, nor should they be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0035] Reference Figure 1 As shown in the figure, this application discloses a flexible pressure sensor for automotive seats, comprising: First flexible protective layer 1; The second flexible protective layer 2 is disposed opposite to the first flexible protective layer 1; The first conductive line layer 3 is formed on one side surface of the first flexible protective layer 1 by screen printing of conductive silver paste. The second conductive circuit layer 4 is formed on one side surface of the second flexible protective layer 2 by screen printing conductive silver paste. Multiple pressure-sensitive units 7 are disposed between the first flexible protective layer 1 and the second flexible protective layer 2. Each pressure-sensitive unit 7 includes a pressure-sensitive element that forms a series circuit with the corresponding first conductive line layer 3 and second conductive line layer 4. The resistance value of the pressure-sensitive element changes with the pressure applied.

[0036] Combination Figure 2 As shown, specifically, the first flexible protective layer 1 is the bottom supporting structure of the sensor. The first flexible protective layer 1 is a sheet-like flexible insulating material layer with a certain thickness and area. Its function is to serve as the supporting substrate for the first conductive circuit layer 3, providing physical support and electrical insulation for the first conductive circuit layer 3, while also protecting and encapsulating the entire sensor.

[0037] The first flexible protective layer 1 has two opposing surfaces: a first surface (inner surface) facing the second flexible protective layer 2 and a second surface (outer surface) facing away from the second flexible protective layer 2. The first conductive line layer 3 is disposed on the first surface.

[0038] The first flexible protective layer 1 is made of a flexible material, allowing it to bend and deform under external force to adapt to the bonding requirements of curved or irregular surfaces such as seat foam layers. The thickness of the first flexible protective layer 1 is preferably 0.1mm to 0.5mm.

[0039] Combination Figure 3 As shown, the second flexible protective layer 2 is disposed opposite to the first flexible protective layer 1. The second flexible protective layer 2 is a sheet-like flexible insulating material layer corresponding to the first flexible protective layer 1, and it is disposed above the first flexible protective layer 1 (i.e., on the side facing the first surface of the first flexible protective layer 1). The second flexible protective layer 2 and the first flexible protective layer 1 together constitute the top and bottom protective structures of the sensor. The second flexible protective layer 2 also has two opposing surfaces, namely a first surface (inner surface) facing the first flexible protective layer 1 and a second surface (outer surface) facing away from the first flexible protective layer 1. The second conductive circuit layer 4 is disposed on the first surface of the second flexible protective layer 2. Similar to the first flexible protective layer 1, the second flexible protective layer 2 is made of a flexible material. The materials of the first flexible protective layer 1 and the second flexible protective layer 2 can be the same or different. The thickness of the first flexible protective layer 1 and the second flexible protective layer 2 is preferably 0.1mm to 0.5mm, which ensures that the protective layer has sufficient mechanical strength to effectively protect the internal conductive circuit and pressure-sensitive element, while also ensuring the overall flexibility and thinness of the sensor. When the layer thickness is less than 0.1mm, the mechanical strength is insufficient, and it may be damaged or punctured under external force, leading to short circuits in the internal circuitry or damage to the pressure-sensitive components. When the protective layer thickness is greater than 0.5mm, the flexibility is reduced, making it difficult to conform to curved surfaces and affecting ride comfort.

[0040] In particular, when the sensor is used in the seat airbag support system, its thickness of 0.1mm to 0.5mm makes the sensor thin and flexible, which can achieve good conformal adaptation to the curved shape of the seat back. It will not cause foreign body sensation when the passenger sits on it. At the same time, it can stretch synchronously with the deformation of the foam layer, ensuring detection accuracy and service life.

[0041] Specifically, when the flexible pressure sensor of this application is used for pressure distribution detection in an automotive seat airbag support system, the first flexible protective layer 1 and the second flexible protective layer 2 are configured to conformally fit the shape of the seat back. Specifically, since the automotive seat back has a three-dimensional curved surface shape that conforms to the curve of the human back, the curvature of the backrest varies depending on the vehicle model and seat position. The first flexible protective layer 1 and the second flexible protective layer 2 are made of TPU, PDMS, or modified PET materials with good flexibility and stretchability, allowing the sensor as a whole to bend and stretch according to the curved shape of the seat back, tightly adhering to the surface of the seat foam layer. This conformal fitting capability allows the sensor to naturally bend with the curve of the seat back without wrinkles or warping, ensuring good contact between the sensor and the occupant's back, thereby achieving accurate pressure distribution detection. Meanwhile, because the flexible protective layer of the sensor is stretchable, when the foam layer deforms due to the occupant sitting on it, the sensor can stretch along with it, always maintaining a close fit with the surface of the foam layer, thus avoiding stress concentration and foreign body sensation caused by rigid or non-stretchable structures when fitting on curved surfaces.

[0042] The space between the first flexible protective layer 1 and the second flexible protective layer 2 is used to accommodate the first conductive circuit layer 3, the second conductive circuit layer 4, the insulating unit 5, the conductive unit 6, and the varistor unit 7. The fact that the second flexible protective layer 2 is positioned opposite to the first flexible protective layer 1 means that the first surface of the first flexible protective layer 1 and the first surface of the second flexible protective layer 2 are arranged face to face, forming a sandwich space between them.

[0043] The first conductive line layer 3 is formed on one side surface of the first flexible protective layer 1 by screen printing conductive silver paste. Specifically, the first conductive line layer 3 is formed on the first surface of the first flexible protective layer 1 facing the second flexible protective layer 2.

[0044] The first conductive circuit layer 3 is the first set of conductive circuits in the sensor matrix scanning circuit. Conductive silver paste is a conductive paste containing silver particles, possessing excellent conductivity and printability. Screen printing is a process that transfers the paste onto the substrate surface through a screen, characterized by high speed, high precision, good consistency, and suitability for mass production. Compared to existing technologies that sew wires onto non-woven fabric and then attach the non-woven fabric to a protective layer, screen printing directly forms the conductive circuit layer on the surface of the flexible protective layer, eliminating the need for the non-woven fabric layer and significantly reducing the overall thickness of the sensor. The first conductive circuit layer 3 is distributed in a planar configuration as multiple lines arranged as needed.

[0045] The second conductive line layer 4 is formed on one side surface of the second flexible protective layer 2 by screen printing conductive silver paste. Specifically, the second conductive line layer 4 is formed on the first surface of the second flexible protective layer 2 facing the first flexible protective layer 1.

[0046] The second conductive line layer 4 is the second set of conductive lines in the sensor matrix scanning circuit. Similar to the first conductive line layer 3, the second conductive line layer 4 is also formed by screen printing conductive silver paste. The first conductive line layer 3 and the second conductive line layer 4 are formed on the opposing surfaces of two oppositely arranged flexible protective layers. Similarly, the formation of the second conductive line layer 4 eliminates the need for a non-woven fabric layer, which helps to reduce the sensor thickness.

[0047] Multiple pressure-sensitive units 7 are disposed between the first flexible protective layer 1 and the second flexible protective layer 2. The pressure-sensitive unit 7 is a component used to sense pressure and convert the pressure signal into an electrical signal.

[0048] Each pressure-sensitive unit 7 includes a pressure-sensitive element, which is electrically connected to the first conductive circuit layer 3 and the second conductive circuit layer 4. The resistance value of the pressure-sensitive element changes with the applied pressure—when the pressure increases, the resistance value of the pressure-sensitive element decreases accordingly; when the pressure decreases, the resistance value of the pressure-sensitive element increases accordingly. At the location where the pressure-sensitive unit 7 is provided, the first conductive circuit layer 3 and the second conductive circuit layer 4 are electrically connected through a pressure-sensitive element (pressure-sensitive carbon paste layer or conductive fiber cloth layer), and the resistance value of this electrical connection changes with the pressure. This selective electrical connection relationship between the first conductive circuit layer 3 and the second conductive circuit layer 4 constitutes a matrix scanning circuit: each first conductive line and each second conductive line form a detection loop through the pressure-sensitive element. By detecting the resistance value of each pressure-sensitive element, the posture of the passenger in the seat can be obtained, thereby further adjusting and controlling the airbag of the car seat. Of course, this part is similar to the prior art and will not be described in detail here.

[0049] The first conductive circuit layer 3 includes at least one first electrode circuit unit 31 and at least one second electrode circuit unit 32 electrically isolated from the first electrode circuit unit 31. Both the first electrode circuit unit 31 and the second electrode circuit unit 32 are in contact with the corresponding pressure-sensitive element. The second conductive circuit layer 4 is electrically connected to the second electrode circuit unit 32. Specifically, one conductive point of the pressure-sensitive element is in contact with the first end of the first conductive circuit layer 3, and the second end of the first conductive circuit layer 3 extends outward to form a first electrode. Another conductive point of the pressure-sensitive element is in contact with one end of the second electrode circuit unit 32 of the first conductive circuit layer 3, and the other end of each second electrode circuit unit 32 is electrically connected to the second conductive circuit layer 4. Thus, the first conductive circuit layer 3, the pressure-sensitive element, and the second conductive circuit layer 4 constitute a series circuit. The pressure at the corresponding location can be determined by measuring the resistance value of this circuit.

[0050] To improve contact quality, the other end of the second electrode circuit unit 32 is electrically connected to the second conductive circuit layer 4 via a conductive unit 6. The conductive unit 6 has a certain area, so even if there are certain errors in the bonding process of the first flexible protective layer 1 and the second flexible protective layer 2 or in other processing techniques, the quality of the electrical connection between the other end of the second electrode circuit unit 32 and the second conductive circuit layer 4 can still be guaranteed.

[0051] Multiple insulating units 5 may be provided between the first conductive line layer 3 and the second conductive line layer 4. Where insulating units 5 are provided, the first conductive line layer 3 and the second conductive line layer 4 maintain electrical insulation through the insulating units 5. Since this application is a multi-point pressure sensor, multiple detection points need to be arranged over a large area. Therefore, the first conductive line layer 3 and the second conductive line layer 4 may be stacked vertically at certain locations, but it is also required that the first conductive line layer 3 and the second conductive line layer 4 be in an insulating state at those locations. Therefore, insulating units 5 are provided between the first conductive line layer 3 and the second conductive line layer 4 at those locations.

[0052] Each insulating unit 5 is arranged at intervals in a predetermined insulating position. That is, adjacent insulating units 5 are spatially separated from each other, are not connected or continuous, and each insulating unit 5 is an independent entity. "Predetermined insulating position" refers to a specific position in the matrix scanning circuit that is predetermined according to the circuit design and is required to maintain electrical insulation between the first conductive line layer 3 and the second conductive line layer 4.

[0053] The circuit working principle of the flexible pressure sensor in this application is as follows: Multiple first electrode line units 31 in the first conductive line layer 3 serve as the first electrode, and the second electrode is formed by connecting multiple second electrode line units 32 in the first conductive line layer 3 and multiple second conductive lines in the second conductive line layer 4 in series. Each pressure-sensitive element forms a pressure detection point.

[0054] During scanning and detection, the external signal processing circuit sequentially applies driving signals to each of the first electrode line units 31, while simultaneously reading the response signals on the second electrode. When a pressure-sensitive element is subjected to pressure, its resistance decreases, the current between the corresponding electrodes increases, and the response signal changes. By scanning row by row and column by column, the resistance value of each pressure-sensitive element can be obtained, thereby acquiring the pressure distribution information of the entire sensor plane.

[0055] Preferably, the first flexible protective layer 1 and the second flexible protective layer 2 are made of thermoplastic polyurethane (TPU), polydimethylsiloxane (PDMS), or modified polyethylene terephthalate (modified PET).

[0056] Thermoplastic polyurethane (TPU) is a polymer material with excellent flexibility, abrasion resistance, and tensile resilience. Its elongation at break can reach over 500%, allowing it to return to its original shape after being stretched. Using TPU as the material for the flexible protective layer allows the sensor to stretch synchronously with the deformation of the foam layer when applied to the seat surface, preventing relative displacement and stress concentration, thus ensuring both ride comfort and sensor reliability. Simultaneously, the softness of TPU allows the sensor to conform to the curved shape of the seat back, adhering tightly to the foam layer surface without wrinkles or lifting.

[0057] Polydimethylsiloxane (PDMS) is an organosilicon elastomer material with excellent flexibility, breathability and biocompatibility. It also has excellent tensile properties and the ability to conform to the curved surface of a seat back.

[0058] Modified polyethylene terephthalate (modified PET) refers to ordinary PET that has been modified through copolymerization, blending, or the addition of toughening agents to achieve a certain degree of flexibility and tensile strength while maintaining the good electrical insulation properties of PET.

[0059] The first flexible protective layer 1 and the second flexible protective layer 2 can be made of the same material, or different materials can be selected according to actual needs. For example, the first flexible protective layer 1 (bottom layer) can be made of modified PET with higher strength to provide better structural support, and the second flexible protective layer 2 (top layer) can be made of softer TPU to improve contact comfort.

[0060] Preferably, the insulating unit 5 is an insulating sheet, and the insulating sheet is made of any one of polyethylene terephthalate (PET), polyimide (PI), or polyurethane (PU).

[0061] Insulating sheet refers to a thin sheet of insulating material with a certain thickness (preferably 0.02mm to 0.2mm). Each insulating unit 5 is an independent insulating sheet cut into a predetermined shape (such as a circle, square, or rectangle). Multiple insulating units 5 are arranged independently and at intervals.

[0062] PET (polyethylene terephthalate) possesses excellent electrical insulation properties, dimensional stability, and heat resistance, making it a commonly used insulating material. PI (polyimide) offers higher heat resistance and mechanical strength, making it suitable for applications requiring high temperatures or high reliability. PU (polyurethane) exhibits good flexibility and elasticity, and exhibits better compatibility with TPU protective layers.

[0063] The thickness of the insulating unit 5 is matched with the thickness of the conductive unit 6 and the thickness of the pressure-sensitive unit 7 to ensure that the gaps between the layers are uniform after the first flexible protective layer 1 and the second flexible protective layer 2 are bonded together.

[0064] The conductive unit 6 is a conductive sheet, which can be made of any one of conductive cloth, metal foil or conductive adhesive.

[0065] Conductive sheet refers to a thin sheet of conductive material with a certain thickness (preferably 0.02 mm to 0.2 mm). Each conductive unit 6 is an independent conductive sheet cut into a predetermined shape. Multiple conductive units 6 are arranged independently and at intervals.

[0066] Conductive cloth is a flexible conductive material woven from conductive fibers (such as silver-plated nylon fibers, copper-plated polyester fibers, etc.), possessing excellent conductivity, flexibility, and stretchability. Using conductive cloth as the conductive unit 6 can further improve the overall flexibility of the sensor.

[0067] Metal foils (such as copper foil and aluminum foil) have excellent conductivity and low resistance, making them suitable for applications requiring low-resistance connections. Conductive adhesives are adhesives containing conductive particles (such as silver particles and carbon particles), possessing both conductivity and adhesion properties. They can achieve electrical connections while simultaneously fixing the relative positions of two protective layers.

[0068] In an optional embodiment, the pressure-sensitive unit 7 includes a third flexible substrate. The third flexible substrate is a thin flexible sheet, the upper side of which is fixedly disposed on the second flexible protective layer 2 by means of adhesive (such as OCA optical adhesive). The pressure-sensitive element is fixedly disposed on the lower side of the third flexible substrate by means of adhesive. After the first flexible protective layer 1 and the second flexible protective layer are bonded together, the lower side of the pressure-sensitive element contacts the first electrode circuit unit 31 and the second electrode circuit unit 32.

[0069] The third flexible substrate is preferably made of PET. Since the adhesion between carbon paste and PET is better than that between carbon paste and TPU, first applying the pressure-sensitive carbon paste layer to the PET sheet and then laminating the PET sheet onto the TPU protective layer can significantly improve the adhesion strength and durability of the pressure-sensitive carbon paste layer. PET sheets have good dimensional stability, surface flatness, and adhesion to carbon paste, making them an ideal substrate for supporting the pressure-sensitive carbon paste layer. The thickness of the PET sheet is preferably 0.025mm to 0.1mm, providing sufficient mechanical strength to support the pressure-sensitive carbon paste layer while maintaining good flexibility. The PET sheet is adhered to the corresponding position of the second flexible protective layer 2 using an adhesive.

[0070] In an alternative embodiment, a fourth flexible substrate may be disposed on the side of the first flexible protective layer 1 opposite to the second flexible protective layer 2, and the fourth flexible substrate may be positioned directly opposite the third flexible substrate. Furthermore, the third and fourth flexible substrates may be made of materials with higher strength than the first and second flexible protective layers 1, such as PET. More preferably, the areas of the third and fourth flexible substrates attached to the first flexible protective layer 1 are equal. In this way, the pressure-sensitive element is confined between two relatively rigid materials, thereby improving measurement accuracy.

[0071] In one alternative approach, the pressure-sensitive element is a pressure-sensitive carbon paste layer. Carbon paste is a conductive paste containing carbon-based conductive particles (such as graphite, carbon black, carbon nanotubes, etc.), exhibiting excellent piezoresistive effect—when the pressure-sensitive carbon paste layer is subjected to pressure, the contact between its internal conductive particles becomes tighter, increasing the conductive path and decreasing the resistance; when the pressure decreases, the contact between the conductive particles loosens, increasing the resistance. The pressure-sensitive carbon paste layer can be formed on the surface of a third flexible substrate through methods such as screen printing, spraying, or blade coating.

[0072] In another alternative embodiment, the pressure-sensitive element can be a conductive fiber cloth layer, the resistance of which decreases as the applied pressure increases.

[0073] Conductive fiber fabric is a cloth-like material made of conductive fibers (such as silver-plated nylon fibers, carbon fibers, metal fibers, etc.) woven or non-woven. Its working principle is as follows: Under no pressure, the contact between the conductive fibers is relatively loose, resulting in fewer conductive paths and higher resistance. When pressure is applied, the conductive fibers are compressed, the contact between the fibers becomes tighter, and the number of fibers in contact with the conductive silver paste increases, thereby increasing the conductive paths and decreasing the resistance. This piezoresistive effect allows conductive fiber fabric to be used as a pressure-sensitive element. Furthermore, based on this characteristic, the probability of inaccurate measurements due to other factors is low.

[0074] Compared to pressure-sensitive carbon paste layers, conductive fiber cloth layers offer better flexibility and tensile strength, making them more suitable for applications requiring high flexibility or significant deformation. Furthermore, conductive fiber cloth layers can be cut into any shape, allowing for flexible arrangement. Additionally, the resistance of pressure-sensitive carbon paste can change with temperature and is highly sensitive, leading to significant errors in pressure readings. This necessitates simultaneous temperature measurement and resistance compensation, a drawback that conductive fiber cloth does not exhibit.

[0075] This application discloses a method for manufacturing a flexible pressure sensor, which includes the following steps: Step 1: Provide a first flexible protective layer 1 and a second flexible protective layer 2.

[0076] Two independent flexible protective layers, 1 and 2, are provided. The first flexible protective layer 1 supports the first conductive circuit layer 3, and the second flexible protective layer 2 supports the second conductive circuit layer 4 and the varistor. Both protective layers should be cleaned before use to remove surface dust and oil to ensure adhesion for subsequent printing and bonding.

[0077] Step 2: Conductive silver paste is screen-printed onto one side of the first flexible protective layer 1 where the pressure-sensitive element is located to form a first conductive line layer 3. The first conductive line layer 3 is electrically connected to the pressure-sensitive element. Conductive silver paste is screen-printed onto one side of the second flexible protective layer 2 to form a second conductive line layer 4. Multiple pressure-sensitive units 7 are disposed on the second flexible protective layer 2. Generally, the pressure-sensitive units 7 are disposed after the formation of the second conductive line layer 4; however, in other alternative methods, the pressure-sensitive units 7 may be disposed before the formation of the second conductive line layer 4.

[0078] Step 3: Provide a plurality of insulating units 5 on the first flexible protective layer 1 on which the first conductive line layer 3 is formed or on the second flexible protective layer 2 on which the second conductive line layer 4 is formed. Provide a plurality of conductive units 6 on the first flexible protective layer 1 on which the first conductive line layer 3 is formed or on the second flexible protective layer 2 on which the second conductive line layer 4 is formed; In other words, the insulating unit 5 and the conductive unit 6 can be attached to the corresponding positions of the first flexible protective layer 1 where the first conductive circuit layer 3 is formed, or they can be attached to the corresponding positions of the second flexible protective layer 2 where the second conductive circuit layer 4 is formed. Alternatively, the insulating unit 5 can be attached to the corresponding positions of the first flexible protective layer 1 where the first conductive circuit layer 3 is formed, and the conductive unit 6 can be attached to the corresponding positions of the second flexible protective layer 2 where the second conductive circuit layer 4 is formed. Alternatively, the insulating unit 5 can be attached to the corresponding positions of the second flexible protective layer 2 where the second conductive circuit layer 4 is formed, and the conductive unit 6 can be attached to the corresponding positions of the first flexible protective layer 1 where the first conductive circuit layer 3 is formed.

[0079] Step 4: Adhere the side of the first flexible protective layer 1 with the first conductive line layer 3 to the side of the second flexible protective layer 2 with the second conductive line layer 4.

[0080] The surface of the first flexible protective layer 1 containing the first conductive circuit layer 3 is placed facing the surface of the second flexible protective layer 2 containing the second conductive circuit layer 4, and then the two are bonded together by means of heat fusion or the like. After bonding, the first conductive circuit layer 3 and the second conductive circuit layer 4 are positioned opposite each other, the insulating unit 5 and the conductive unit 6 are located between the two circuit layers, and the varistor and the corresponding first conductive circuit layer 3 and second conductive circuit layer 4 form a series circuit.

[0081] The sensor, once bonded, is a thin sheet that can be bent and conform to the curved shape of the seat back, fitting tightly to the surface of the seat foam layer.

[0082] Through the description of the specific embodiments above, those skilled in the art can clearly understand the technical solution of this application and its various modifications. The scope of protection of this application is defined by the claims, but is not limited to the specific embodiments described above.

[0083] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed application subject matter.

Claims

1. A flexible pressure sensor for automotive seats, characterized in that, include: First flexible protective layer; The second flexible protective layer is disposed opposite to the first flexible protective layer; The first conductive circuit layer is formed on one side surface of the first flexible protective layer by screen printing of conductive silver paste. The second conductive circuit layer is formed on one side surface of the second flexible protective layer by screen printing of conductive silver paste. Multiple pressure-sensitive units are disposed between the first flexible protective layer and the second flexible protective layer. Each pressure-sensitive unit includes a pressure-sensitive element that forms a series circuit with the corresponding first conductive line layer and the second conductive line layer. The resistance value of the pressure-sensitive element changes with the pressure applied.

2. The flexible pressure sensor according to claim 1, characterized in that, The first flexible protective layer and the second flexible protective layer are made of one or more of thermoplastic polyurethane, polydimethylsiloxane, or modified polyethylene terephthalate.

3. The flexible pressure sensor according to claim 1, characterized in that, It also includes multiple insulating units, which are disposed between the first conductive line layer and the second conductive line layer. The multiple insulating units are arranged at intervals at each predetermined insulating position to electrically insulate the first conductive line layer and the second conductive line layer at the corresponding predetermined insulating positions. Preferably, the insulating unit is an insulating sheet, and the insulating sheet is made of any one or more of polyethylene terephthalate, polyimide, or polyurethane.

4. The flexible pressure sensor according to claim 1, characterized in that, Each of the pressure-sensitive units includes a third flexible substrate disposed on the second flexible protective layer, and the pressure-sensitive element of the pressure-sensitive unit is disposed on the side of the third flexible substrate facing the first flexible protective layer.

5. The flexible pressure sensor according to claim 4, characterized in that, The third flexible substrate is polyethylene terephthalate sheet.

6. The flexible pressure sensor according to claim 1, characterized in that, The pressure-sensitive element is a conductive fiber cloth layer or a pressure-sensitive carbon paste layer.

7. The flexible pressure sensor according to claim 1, characterized in that, The first conductive circuit layer includes at least one first electrode circuit unit and at least one second electrode circuit unit electrically isolated from the first electrode circuit unit. The first electrode circuit unit and the second electrode circuit unit are in contact with the corresponding varistor element. The second conductive circuit layer is electrically connected to the second electrode circuit unit.

8. The flexible pressure sensor according to claim 7, characterized in that, It also includes multiple conductive units, which are disposed between the first flexible protective layer and the second flexible protective layer. The two sides of each conductive unit are respectively connected to the second conductive line layer to electrically connect the second conductive line layer and the second electrode line unit.

9. The flexible pressure sensor according to claim 7, characterized in that, The conductive unit is a conductive sheet, and the conductive sheet is made of any one or more of conductive cloth, metal foil, or conductive adhesive.

10. A method for manufacturing a flexible pressure sensor for automotive seats, characterized in that, Includes the following steps: Provides a first flexible protective layer and a second flexible protective layer; A first conductive circuit layer is formed by screen printing conductive silver paste onto one side surface of the first flexible protective layer. A second conductive circuit layer is formed by screen printing conductive silver paste onto one side surface of the second flexible protective layer. Multiple pressure-sensitive units are disposed on the second flexible protective layer. Multiple insulating units are provided on the first flexible protective layer on which the first conductive line layer is formed or on the second flexible protective layer on which the second conductive line layer is formed. Multiple conductive units are provided on the first flexible protective layer on which the first conductive circuit layer is formed or on the second flexible protective layer on which the second conductive circuit layer is formed. Align and attach the side of the first flexible protective layer having the first conductive circuit layer with the side of the second flexible protective layer having the second conductive circuit layer.

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