Anti-bubble automobile radar damping fin and preparation method and installation method thereof

Abstract

The invention discloses an anti-bubble automobile radar damping fin as well as a preparation method and an installation method thereof. The damping fin is of a multi-layer composite structure and comprises an aluminum foil layer, a damping layer and a key hot melt adhesive net film layer from outside to inside. Through a matched pressurizing and heating installation process, hot melt adhesive is melted and flows during installation, all air gaps between the damping fin and the complex curved surface automobile door metal plate are actively filled and discharged, and permanent strong bonding without bubbles is formed after cooling. According to the method, the industrial problem that the radar performance is reduced due to the fact that bubbles are easily generated in traditional manual rolling of the damping fin is fundamentally solved, the high consistency of the attaching quality and the environmental durability are achieved, and the detection precision and reliability of the vehicle-mounted radar under the limiting working condition are remarkably improved; and important basic part guarantee is provided for high-level automatic driving and intelligent vehicle body functions.

Description

Technical Field

[0001] This invention relates to the field of automotive parts technology, and in particular to an anti-bubble automotive radar damping sheet, its preparation method and installation method, which is especially suitable for suppressing the interference of door vibration on vehicle radar sensors, belonging to the intersection of automotive intelligent sensing system and NVH (noise, vibration and harshness) control technology.

[0002] More specifically, this invention relates to a multi-layer composite functional damping sheet, which, through an innovative hot melt adhesive interface layer design and a matching pressurized heating installation process, completely solves the technical problem of air bubbles generated when traditional damping sheets are bonded to car door sheet metal due to air residue, thereby ensuring the detection accuracy and reliability of vehicle radar under complex working conditions and extreme temperature environments. Background Technology

[0003] With the rapid advancement of automotive intelligence and electrification, the adoption rate of Advanced Driver Assistance Systems (ADAS) and vehicle comfort features is increasing daily. Among these, features such as automatic door opening / closing, collision warning, and blind spot monitoring significantly enhance vehicle convenience and safety. The implementation of these functions relies heavily on accurate and reliable environmental perception sensors, such as millimeter-wave radar and ultrasonic radar, which are typically integrated into vehicle body components such as doors and bumpers.

[0004] As a dynamic component, a car door is subject to various vibration sources during driving and opening / closing, including road surface excitation, motor drive, air turbulence, and the impact of closing. These vibrations are transmitted to the radar sensors installed inside the door, causing modulation of the transmitted and received electromagnetic wave signals and generating parasitic phase-modulation or amplitude-modulation noise, also known as "vibration clutter." This clutter can overwhelm weak effective echo signals, severely reducing the radar's signal-to-noise ratio, detection range, angular resolution, and target recognition accuracy. In extreme cases, it may lead to malfunctions or failures, posing a safety hazard.

[0005] To isolate or attenuate the transmission of door sheet metal vibrations to radar sensors, the industry commonly employs a solution of attaching damping sheets to the inner side of the door sheet metal corresponding to the radar mounting area. The core function of these damping sheets is to convert the structural vibration energy of the door sheet metal into heat energy and dissipate it through intramolecular friction of their viscoelastic material. This creates a "mechanical filter" along the vibration transmission path, effectively suppressing the vibration energy transmitted to the radar mounting point and providing a relatively stable mechanical mounting foundation for the radar.

[0006] Currently, most mainstream automotive radar damping sheets on the market use viscoelastic damping materials based on butyl rubber, asphalt-modified materials, or acrylate polymers. These materials exhibit good damping loss factors within their glass transition temperature range. Their typical structure consists of a single or multiple layer of damping material combined with a layer of aluminum foil. The aluminum foil layer primarily serves as electromagnetic shielding, preventing the radar's own electromagnetic signals from leaking and interfering with other electronic equipment, or allowing external electromagnetic interference to intrude into the radar. It also provides some reinforcement and shaping.

[0007] However, these traditional damping plates have significant inherent defects in terms of actual installation process and long-term environmental reliability, specifically in the following aspects: 1. High dependence on installation process, resulting in poor consistency in bonding quality: Currently, the installation of damping sheets mainly relies on manual rolling. The process is roughly as follows: first, the release paper on the adhesive side of the damping sheet is removed; then, it is initially aligned with the preset position on the door sheet metal for initial pasting and positioning; finally, workers use manual rollers (mostly made of rubber or silicone) to repeatedly press and roll the surface of the damping sheet, attempting to squeeze out the air between the damping sheet and the door sheet metal to achieve a tight fit. The inner side of the door sheet metal usually has complex three-dimensional curved surfaces and concave and convex features (such as reinforcing ribs, holes, welds, etc.). The pressure, speed, and uniformity of the path coverage of the manual rolling depend entirely on the experience and skill of the operator. This highly human-dependent process leads to significant fluctuations in bonding quality. In curved surfaces, edges, or areas of concavity and convexity transition, tiny air gaps are easily left due to insufficient or incomplete rolling. These initial, imperceptible air gaps create hidden dangers for subsequent problems.

[0008] 2. Subsequent high-temperature processes lead to the manifestation and deterioration of bubbles: During the painting process, the car body undergoes an electrophoretic baking process at temperatures as high as 150°C to 180°C. Under this high-temperature environment, the air initially remaining in the air gap between the damping sheet and the door sheet metal is heated, and according to the ideal gas law (PV=nRT), its volume expands significantly. Simultaneously, some low-molecular-weight volatiles in the damping layer material may also be released by heat. These gases cannot escape from the closed or semi-closed space formed by the damping sheet and the door sheet metal, generating enormous internal pressure, causing localized bulging of the damping sheet, forming visible bubbles or bulges. Microscopic misalignment areas left by manual rolling evolve into macroscopic defects after baking.

[0009] 3. The Fatal Impact of Air Bubbles on Damping Performance and Radar Functionality: The presence of air bubbles disrupts the necessary rigid coupling between the damping plate and the door sheet metal from a mechanical perspective. Vibrational energy, when passing through the interface, undergoes strong reflection and attenuation at the air bubbles (air layer), significantly reducing the efficiency of vibration transmission to the effective damping layer of the damping plate. Essentially, the air bubble introduces a low-impedance "spring" unit at the interface, severely reducing the overall structural loss factor of the damping plate-door sheet metal system. This greatly diminishes the damping performance of the damping plate, making it unable to effectively filter vibrations from the door sheet metal.

[0010] From a long-term reliability perspective, automobiles undergo harsh environmental temperature cycles in real-world use (e.g., interior temperatures can reach above 85°C under summer sun and below -30°C in winter). The air within the bubble region repeatedly expands and contracts due to these drastic temperature changes, generating periodic stress on the damping sheet. This can lead to fatigue and weakening of the adhesive layer, or even cause the bubble region to expand or the damping sheet to peel off locally. This dynamically unstable interface state makes the mechanical environment of the radar sensor unpredictable and degrades its performance, directly manifesting as increased vibration noise (clutter) levels in the radar output signal, fluctuations in the target detection threshold, and a shrinking detection envelope. In the worst-case scenario, strong vibration noise may trigger the radar's fault protection mechanism, causing temporary malfunctions and seriously threatening the safety and reliability of functions such as automatic doors and blind spot monitoring that rely on this radar.

[0011] 4. Existing Technological Improvement Attempts and Their Limitations: Several attempts have been made to address the air bubble problem, but none have fundamentally solved it: Improving Adhesives: Using pressure-sensitive adhesives (PSA) with stronger initial tack or better flowability. However, this only slightly improves initial bonding and cannot solve the fundamental problem of air expansion during baking. Furthermore, an overly soft adhesive layer may creep under prolonged high temperatures, reducing shear strength. Optimizing Roller Tools: Using custom rollers or pneumatic pressurization tools with shapes more closely matching the curved surface. This improves pressure uniformity to some extent, but still cannot guarantee 100% air removal on complex three-dimensional curved surfaces, and still requires highly skilled operators, increasing costs. Pre-molded Damping Sheets: Pre-molding damping sheets into a shape perfectly matching the curved surface of the car door sheet metal. While this improves bonding, the car door sheet metal itself has manufacturing tolerances, and the shapes of door sheet metal vary between different car models and locations, resulting in extremely high pre-molding mold costs, poor versatility, and difficulty in large-scale application.

[0012] In summary, existing traditional damping sheet technology based on manual roll bonding, due to inherent process defects, cannot ensure a bubble-free, durable, and reliable rigid bond with complex curved automotive door sheet metal, becoming a key bottleneck restricting the performance improvement of high-reliability automotive radar. There is an urgent need in this field for a novel solution that innovates from both material systems and installation processes to systematically solve the bubble problem and achieve a high-quality, highly consistent, and environmentally durable bond. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the purpose of this invention is to provide an anti-bubble automotive radar damping sheet, its preparation method, and its installation method. The primary objective of this invention is to fundamentally eliminate the generation of bubbles at the interface between the damping sheet and the vehicle door sheet metal through innovative product structural design. The second objective is to provide a highly reliable, automated, and standardized installation process that matches the product structure, eliminating reliance on manual skills and ensuring consistent bonding quality. The third objective is to ensure that the damping sheet maintains excellent vibration damping performance and a stable interface bonding state even after experiencing the high temperatures of automotive manufacturing processes and extreme high and low temperature environments throughout the vehicle's lifespan. This provides durable and effective mechanical vibration isolation for the vehicle radar, ensuring its long-term stability and reliability in detection performance.

[0014] The above-mentioned objective of this invention is achieved through the following technical solutions: This invention provides an anti-bubble automotive radar damping sheet, which is a multi-layer composite structure, comprising at least: a damping layer made of viscoelastic material; a hot melt adhesive mesh layer, laminated on one main plane of the damping layer as a bonding surface with the door sheet metal; and an aluminum foil layer, laminated on another main plane of the damping layer opposite to the hot melt adhesive mesh layer.

[0015] According to one embodiment of the present invention, the material of the damping layer is selected from butyl rubber, asphalt-based polymer materials or acrylate polymers, and the present invention also provides one such material.

[0016] According to one embodiment of the present invention, the material of the hot melt adhesive web layer is EVA-based or polyamide-based hot melt adhesive, and its activation temperature is 80°C to 180°C.

[0017] According to one embodiment of the present invention, the thickness of the aluminum foil layer is 0.05 mm to 0.15 mm, and it is a 0-state aluminum foil.

[0018] According to one embodiment of the present invention, the overall thickness of the damping sheet is 1.5 mm to 3.5 mm.

[0019] 6. The present invention, as described in the above embodiments, also provides a method for preparing an anti-bubble automotive radar damping sheet, comprising the following steps: S1: Raw material preparation, weighing damping layer material (such as aluminum foil, butyl rubber, tackifying resin, filler, etc.) and hot melt adhesive particles or hot melt adhesive film according to the formula; S2: Co-extrusion composite molding, melting the damping layer material and hot melt adhesive particles separately and then co-extruding, cooling and shaping, and then composite with aluminum foil. Specifically, melting the damping layer material and hot melt adhesive particles separately and extruding them through an extruder with a composite die head. Co-extrusion combines the molten damping layer material with the molten hot melt adhesive at the die head. After cooling and shaping by cooling rollers, an integrated damping sheet blank is formed. After extrusion, it is simultaneously laminated with aluminum foil on the side without the hot melt film. The overall thickness of the resulting damping sheet is between 1.5-3.5mm. S3: Die-cutting. Die-cutting punches or cuts the laminated blank into the required shape, matching the shape to the door sheet metal fitting area. S4: Inspection and packaging. The finished product is inspected for appearance, size, and performance. After passing the inspection, it is packaged and stored.

[0020] According to one embodiment of the present invention, step S2 further includes: forming a damping sheet substrate with aluminum foil and a hot melt adhesive film by an extrusion process, and then bonding the two together by a heated rolling process.

[0021] This invention also provides a method for installing an anti-bubble automotive radar damping sheet, comprising the following steps: laser positioning on the door sheet metal; placing the damping sheet in the corresponding position; applying a pressure of 1 kPa to 5 kPa to the damping sheet using a pressurizing device to ensure tight contact between the damping sheet and the door sheet metal; and heating the area where the door sheet metal and the damping sheet are in contact to 80°C to 180°C on the other side of the door sheet metal using a heating device, maintaining the temperature for 5 to 30 seconds to complete the installation of the damping sheet.

[0022] According to one embodiment of the present invention, after installation, the door is further placed in an oven for baking to simulate electrophoretic baking conditions.

[0023] The present invention also provides an automobile door, including a door sheet metal and the aforementioned anti-bubble automobile radar damping sheet, wherein the damping sheet is bonded to the door sheet metal by a hot melt adhesive mesh layer.

[0024] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: Eliminating the bubble problem and achieving perfect adhesion: This invention creatively uses a hot melt adhesive web layer as the interface medium, combined with a synchronous pressure heating process, fundamentally eliminating the conditions for bubble formation. The fluidity of the molten hot melt adhesive ensures that interface gaps are actively filled, which passive rolling cannot achieve. This ultimately forms an ideal bonding interface free of bubbles and voids, achieving full contact, thus fundamentally preventing the degradation of damping performance caused by bubbles.

[0025] Significant leaps in bonding quality consistency, eliminating reliance on manual skills: Core installation parameters (pressure, temperature, time) are precisely controlled by the equipment, achieving process standardization and repeatability. Regardless of operator changes, as long as the equipment parameters are set correctly, the bonding quality of each damping sheet remains highly consistent. This greatly improves product reliability and production yield, and reduces the risk of quality fluctuations.

[0026] Exceptional environmental durability and vibration damping performance: The bubble-free rigid interface ensures efficient transfer of vibration energy from the door sheet metal to the damping layer for dissipation. After high-temperature baking and extreme temperature cycling (-40℃ to +85℃) testing, the damping sheet of this invention exhibits long-term stable interfacial bond strength and damping factor. It provides a stable, reliable, and low-noise mechanical mounting platform for radar sensors throughout their entire lifecycle, from vehicle manufacturing to scrapping, significantly improving radar performance retention in harsh environments.

[0027] Excellent process compatibility and production efficiency: The installation method of this invention is fast (single-piece operation time can be controlled within 1 minute) and easy to integrate into automated door production lines or sub-assembly lines. It does not conflict with existing painting and final assembly processes. The one-step production method is highly efficient and suitable for large-scale manufacturing. This helps reduce overall production costs (although material costs increase slightly, improved yield, reduced rework, and increased efficiency lead to overall cost optimization).

[0028] Wide applicability and design flexibility: This solution is not sensitive to the complexity of the curved surface of the car door sheet metal and has strong versatility. By adjusting the activation temperature of the hot melt adhesive and the formula and thickness of the damping layer, it can be flexibly adapted to the specific needs of different car models, different radar models (such as 24GHz, 77GHz radar), and different installation locations (doors, rearview mirrors, bumpers, etc.).

[0029] In summary, this invention, through synergistic innovation in product structure, material system, and installation process, systematically solves the long-standing problem of "bubbles" in automotive radar damping sheets, providing a crucial foundational component guarantee for the widespread adoption of high-precision, high-reliability vehicle radar, and has positive significance for promoting the intelligent development of automobiles. Attached Figure Description

[0030] Figure 1 This is a front view of the anti-bubble automotive radar damping sheet of the present invention.

[0031] Figure 2 for Figure 1 A sectional view.

[0032] Figure 3 for Figure 2 A magnified view of part A in the diagram.

[0033] Figure 4 This is a schematic diagram of the installation of the anti-bubble automotive radar damping sheet of the present invention.

[0034] Reference numerals: 1. Damping sheet; 2. Damping layer; 3. Hot melt adhesive film layer; 4. Aluminum foil layer. Detailed Implementation

[0035] 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. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0036] In the description of this application, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] The primary objective of this invention is to fundamentally eliminate air bubbles at the interface between the damping sheet 1 and the vehicle door sheet metal through innovative product structural design. The second objective is to provide a highly reliable, automated, and standardized installation process that matches the product structure, eliminating reliance on manual skills and ensuring consistent bonding quality. The third objective is to ensure that the damping sheet 1 maintains excellent vibration damping performance and a stable interface bonding state even after experiencing the high-temperature processes of automotive manufacturing and the extreme high and low temperature environments throughout the vehicle's lifespan. This provides durable and effective mechanical vibration isolation for the vehicle radar, ensuring its long-term stability and reliability in detection performance.

[0039] To achieve the above-mentioned objectives, refer to Figures 1-4This invention proposes a systematic technical solution covering three aspects: product structure, preparation method, and installation method. These three aspects complement each other and together constitute a complete technical system for solving the bubble problem.

[0040] 1. Product Structure of Anti-Bubble Automotive Radar Damping Sheet: The anti-bubble damping sheet 1 provided by this invention is a functional multi-layer composite sheet specifically designed for automotive door radar applications. Its core design concept lies in introducing an "intelligent" interface layer—a hot-melt adhesive mesh layer 3—between the damping layer 2 and the door sheet metal. During installation, this interface layer, under heat and appropriate pressure, undergoes viscous deformation, actively filling all microscopic and macroscopic gaps between the damping sheet 1 and the irregular surface of the door sheet metal, completely expelling and replacing residual air. Subsequently, it cools and solidifies to form a strong, gapless, permanent bond.

[0041] Specifically, the damping plate 1 comprises at least the following layered structure stacked in sequence: Aluminum foil layer 4: Serves as the back layer of damping sheet 1 (the side away from the door sheet metal). Preferably, it is 0.05mm to 0.15mm thick O-state (fully annealed) aluminum foil. O-state aluminum foil has excellent flexibility and ductility, allowing it to perfectly conform to the complex three-dimensional curved surface of the door sheet metal along with damping layer 2 without cracking or wrinkling. This aluminum foil layer 4 must maintain good electrical continuity; its main function is electromagnetic shielding to prevent radar signal interference or external interference. Simultaneously, it also serves as a composite substrate for damping layer 2, providing dimensional stability and ease of processing.

[0042] Damping layer 2: As the core functional layer of damping sheet 1, it is laminated on top of aluminum foil layer 4. It is composed of a viscoelastic polymer material with a high damping loss factor (tan δ). Optional matrix materials include, but are not limited to: butyl rubber (IIR), halogenated butyl rubber (XIIR), asphalt-modified polymers, acrylate polymers, polyurethane elastomers, or blends thereof. This layer typically also contains tackifying resins (such as terpene resins, petroleum resins), fillers (such as calcium carbonate, mica powder, carbon black), plasticizers, antioxidants, etc., and through formulation optimization, it achieves a broad and gentle damping peak within the common operating temperature range of vehicles (e.g., -40℃ to +120℃). The thickness of damping layer 2 is a key parameter affecting the damping effect, typically between 1.3mm and 3.3mm, and can be designed according to the vibration spectrum and damping requirements of a specific vehicle model.

[0043] Hot melt adhesive web layer 3: This layer serves as the bonding layer for the damping sheet 1 (the side in contact with the door sheet metal) and is laminated onto the damping layer 2. This is the key innovative layer of the present invention. This layer is composed of hot melt adhesive material and exists in the form of a web. Preferably, it is an EVA (ethylene-vinyl acetate copolymer), polyamide (PA), polyester (PES), or polyolefin (PO) based hot melt adhesive. These materials are solid at room temperature and possess a certain initial tack, facilitating the initial positioning of the damping sheet 1 on the door sheet metal and preventing slippage. Its core characteristic lies in having a defined activation temperature range (typically 80°C to 180°C). When heated to this temperature range, the hot melt adhesive web melts rapidly, its viscosity drops sharply, and it transforms into a viscous liquid with good fluidity and wettability. Driven by moderate external pressure (1-5 kPa), the molten hot melt adhesive flows like a liquid, filling all microscopic depressions and gaps between the damping sheet 1 and the door sheet metal surface caused by roughness, curvature variations, and installation clearances, while completely squeezing out any residual air at the interface. Heating is then stopped, and the hot melt adhesive cools and re-cures within tens of seconds, forming a high-strength, gapless adhesive interface that combines mechanical and chemical adhesion with the door sheet metal surface. The mesh structure facilitates uniform melting during heating and allows trace amounts of air or volatiles to escape laterally under pressure, further preventing porosity.

[0044] Release layer: Covering the outer surface of the hot melt adhesive web layer 3, it protects the hot melt adhesive web layer 3 from contamination, scratches, or adhesion to other objects before transportation, storage, and installation. Release paper or release film is typically used, with carefully selected release force to ensure reliable protection while allowing for easy peeling during installation. Positioning marks or operating instructions may be printed on the release layer.

[0045] The total thickness of the damping sheet 1 is preferably controlled within the range of 1.5mm to 3.5mm to achieve a balance between spatial constraints (door interior panel gap) and optimal damping performance.

[0046] 2. Preparation method of anti-bubble automotive radar damping sheet: To achieve the above-mentioned multi-layer composite structure, this invention provides two efficient preparation methods suitable for large-scale production: Method 1: One-step co-extrusion composite molding (preferred): This method features a continuous process flow, high production efficiency, and good interlayer bonding. Specific steps include: S1: Raw Material Preparation and Pretreatment: Prepare the composite raw material for damping layer 2 and the hot melt adhesive granules separately. The raw material for damping layer 2 typically includes a polymer matrix (such as butyl rubber), tackifying resin, fillers, additives, etc., and may exist in the form of compounded granules or premixed powder. The hot melt adhesive granules are prepared according to the selected type. Aluminum foil rolls and release film rolls are also ready.

[0047] S2: Co-extrusion and Online Lamination: A multi-channel co-extruder is used. The damping layer 2 raw material and hot melt adhesive particles are melted and plasticized in different extruder screws to achieve a uniform melt state. The two melts are precisely metered and conveyed to a specially designed composite flat die. Inside the die, the molten damping layer 2 material and the molten hot melt adhesive are laminated at a preset thickness ratio, and then co-extruded from the die lip to form an integrated "damping layer 2 / hot melt adhesive web layer 3" double-layer melt sheet. This melt sheet is immediately drawn onto a set of cooling and shaping rollers (usually mirror cooling rollers) for rapid cooling and solidification, forming a base sheet with good interfacial bonding.

[0048] S3: Online Release Film Coating and Cooling Traction: When the molten sheet is freshly extruded, its temperature is high and its texture is soft. A release film (or release paper) must be immediately applied to the surface of its hot melt adhesive web layer 3. The release film plays a dual role at this stage: firstly, it protects the surface of the hot melt adhesive; secondly, in conjunction with the traction belt, it provides support and isolation in the softened state of the sheet, preventing adhesion and maintaining sheet flatness. After the release film is applied, the sheet undergoes rapid cooling and curing via a set of cooling and setting rollers (usually mirror-finish cooling rollers) to form a base sheet with good interfacial bonding.

[0049] S4: Aluminum Foil Layer 4 Lamination and Online Slitting: On one side of the damping layer 2 of the cooled and shaped base sheet, a hot-press lamination device is used to firmly bond the pre-unfolded aluminum foil to the surface of the damping layer 2 under appropriate temperature and pressure. This step can be completed online simultaneously with the extrusion process. Subsequently, according to the product design dimensions, online rolling and slitting are performed directly on the production line to cut the composite sheet into sheet units of a certain length, without the need for winding into large coils. This method reduces intermediate steps and improves continuity.

[0050] S5: Die-cutting process: Die-cut the segmented "aluminum foil layer 4 / damping layer 2 / hot melt adhesive mesh layer 3 (release film)" units. Since the damping sheet itself is a soft material, it can naturally conform to the curved surface of the car door sheet metal during application. Therefore, there is no need to cut according to the three-dimensional curved surface projection. It is only necessary to use a CNC die-cutting machine to perform two-dimensional planar cutting based on the predetermined length and width dimensions and the necessary positioning holes and other features.

[0051] S6: Inspection and Packaging: The finished damping sheet 1 shall be inspected for appearance (no damage, no foreign matter), dimensions (compared with the digital model), and initial tack sampling test. Qualified products shall be packaged into boxes according to the order quantity and labeled with product model, batch number, and other information.

[0052] Furthermore, there is an even better process from S4 to S5: after the aluminum foil is laminated, it is rapidly cooled and then rolled online (the release paper is not cut, and the rolling is also done with a die, directly rolling into the finished product shape, replacing the die cutting of S5). Then the release paper is cut into pieces to obtain the finished product. The temperature before rolling is below 40℃.

[0053] Method 2: Two-step layered preparation followed by composite preparation: This method offers greater flexibility and is suitable for small-batch, multi-variety production or the modification of existing production lines. Specific steps include: S1': Raw material and substrate film preparation: Prepare the composite raw material for damping layer 2 (such as butyl rubber-based compound granules), aluminum foil rolls, and separately prepared hot melt adhesive web rolls (usually already laminated with release film or release paper). The hot melt adhesive web is a porous or dense film-like material pre-made by methods such as melt extrusion, casting, or spunbonding.

[0054] S2': Synchronous Hot Press Lamination: A single extruder melts and plasticizes the damping layer 2 raw material, forming a molten sheet through a flat extrusion die. In this crucial process, pre-unfolded aluminum foil rolls and hot melt adhesive web rolls are simultaneously fed into a set of precision hot press lamination rollers from both sides of the molten damping layer sheet. The aluminum foil is laminated to the upper surface of the molten damping layer. The hot melt adhesive web (with its release liner facing outwards) is laminated to the lower surface of the molten damping layer.

[0055] Under the temperature and pressure of the composite roller, the molten damping layer material achieves a firm interface bond with the aluminum foil and hot melt adhesive web on both sides, completing the three-layer composite structure of "aluminum foil layer 4 / damping layer 2 / hot melt adhesive web layer 3 (release film)" in one step.

[0056] S3': Cooling, Shaping, and Post-processing: The composite sheet is shaped by cooling rollers. Then, according to product size requirements, it is slit or rolled online to form sheet units or rolls ready for die-cutting.

[0057] The subsequent S4' die-cutting and S5' inspection and packaging steps are the same as in Method 1: Die-cutting: Cutting sheet material into predetermined two-dimensional dimensions.

[0058] Inspection and Packaging: After inspecting the appearance, dimensions, and performance, the product is packaged and put into storage.

[0059] 3. Installation method of anti-bubble automotive radar damping sheet: The structural characteristics of the damping sheet 1 of this invention determine that it needs a special installation method to match it. The core of this method is an automated or semi-automated process of "positioning-pressurization-heating" in one body, which completely replaces the traditional manual rolling.

[0060] Preparation before installation: Peel off the release layer from the damping sheet 1 to expose the clean hot melt adhesive film layer 3.

[0061] S100: High-precision positioning: On the door sheet metal assembly, a laser projection positioning system or a vision-based robotic positioning system is used to precisely project or indicate the predetermined fitting contour line of the damping plate 1 onto the door sheet metal surface. This step ensures that the damping plate 1 is placed in the theoretically optimal position, covering the radar mounting point and avoiding interference.

[0062] S200: Initial Placement and Pre-fixation: The operator or robot places the damping sheet 1 (with release paper removed) aligning it with the projected outline. Relying on the initial adhesion of the hot melt adhesive web layer 3 at room temperature, the damping sheet 1 can be temporarily fixed to the door sheet metal and will not fall off due to gravity or slight movement.

[0063] S300: Synergistic effect of pressure and heating (critical step): This step is performed using a dedicated bonding device. This device typically includes a pressure head with appropriate flexibility that matches the shape of the damping sheet 1 (which may be made of silicone, airbags, or arrayed micropillars), and heating elements (such as infrared heaters, hot air nozzles, or resistance heating plates) integrated inside the pressure head or located on the back of the door sheet metal.

[0064] Pressurization process: Under program control, the pressure head moves above the damping plate 1 and applies a uniformly distributed, controllable vertical pressure to the damping plate 1. The pressure range is preferably 1 kPa to 5 kPa. This pressure is sufficient to ensure that the damping plate 1 makes tight contact with the door sheet metal and provides driving force for the flow of molten hot melt adhesive, but will not cause excessive irreversible deformation of the damping layer 2 material.

[0065] Heating process: Almost simultaneously with pressurization, the heating system starts, rapidly heating the bonding interface area (including the door sheet metal, hot melt adhesive film layer 3, and part of the damping layer 2) to above the activation temperature of the hot melt adhesive, i.e., reaching the target temperature of 80°C to 180°C. The heating time needs to be precisely controlled to ensure that the hot melt adhesive melts fully but does not undergo excessive thermal degradation; the typical temperature holding time is 5 to 30 seconds.

[0066] Synergistic effect: Under the combined action of heat and force, the solid hot melt adhesive web melts, its viscosity decreases, and its fluidity increases. Driven by uniform pressure, the molten hot melt adhesive, like a liquid, fully wets the cleaned, roughened surface of the bare car door sheet metal and flows into any microscopic gaps and depressions that may exist between them. At the same time, any trace air that may remain at the interface is completely "squeezed out" and discharged through the edges of the web structure. This process achieves a high degree of interfacial tightness during bonding.

[0067] More importantly, the components that have completed the initial bonding will proceed with the door assembly to the subsequent electrophoresis and high-temperature baking processes. The heat provided during the baking process will cause the hot melt adhesive to undergo secondary melting, full flow, and finally complete curing, thereby forming a stronger, more durable interface bond between the sheet metal (ultimately the electrophoretic paint surface) and the damping sheet, achieving true 100% solid area contact. This process cleverly utilizes the inherent high-temperature processes in vehicle manufacturing to optimize the performance of the hot melt adhesive.

[0068] S400: Cooling, Curing, and Pressure Relief: After the predetermined heating time is reached, turn off the heating source. Maintain pressure or slightly reduce pressure with the pressure head to allow the bonding interface to cool naturally or with forced air cooling under pressure. The hot melt adhesive re-solidifies within tens of seconds, changing from a viscous flow state to a solid state, forming a strong physical anchor and chemical bond with the door sheet metal surface. The pressure head is then lifted and removed.

[0069] S500: Post-process compatibility treatment: The door assembly with damping pad 1 installed can seamlessly proceed to subsequent automotive manufacturing processes, especially electrophoresis baking. At this point, since there are no air gaps at the interface, and the heat resistance temperature of the hot melt adhesive is usually higher than the baking temperature, or has already undergone a similar thermal history in step S300, the baking process will not generate new bubbles or bulges. On the contrary, moderate post-baking may help the hot melt adhesive crosslink or further cure, improving long-term bond strength.

[0070] Example 1: Butyl rubber based damping sheet 1 1. Preparation of damping plate 1: Structure: It adopts a four-layer structure of "aluminum foil layer 4 / damping layer 2 / hot melt adhesive film layer 3 / release layer" (aluminum foil and damping layer 2 have been composited into one).

[0071] Aluminum foil layer 4: 0.10mm thick 1070-O state aluminum foil is selected, with a clean surface and electrical conductivity ≥58 MS / m.

[0072] Damping layer 2: The matrix material is halogenated butyl rubber (XIIR), combined with terpene resin tackifier, flake mica powder (to enhance the damping temperature range), calcium carbonate filler, antioxidants, etc. It is compounded through internal mixing. The designed thickness of damping layer 2 is 2.8mm.

[0073] Hot melt adhesive web layer 3: EVA-based hot melt adhesive web is selected. The model is a commercially available medium-temperature activated type commonly used for automotive interior bonding. The activation temperature range is 90-120℃, the weight is about 80g / m², and the thickness is about 0.1mm.

[0074] Release layer: 75g / m² glassine release paper is selected.

[0075] Preparation process: Method 1 (co-extrusion composite molding) is adopted. The damping layer 2 compound is granulated and fed into the main extruder, while the EVA hot melt adhesive granules are fed into the auxiliary extruder. A 2.9mm thick double-layer sheet (damping layer 22.8mm + hot melt adhesive web layer 30.1mm) is co-extruded at the composite die head and cooled and shaped by cooling rollers. Subsequently, aluminum foil is laminated onto the back of the damping layer 2 online using hot press rollers. Finally, release paper is laminated onto the surface of the hot melt adhesive web layer 3 and the sheet is wound up. The roll is then cut into specific shapes of damping sheet 1 according to the drawings of the front door radar installation area of ​​a certain SUV model using a CNC die-cutting machine.

[0076] 2. Installation and testing of damping plate 1: Installation target: The inner door sheet metal of the left front door of the above-mentioned SUV models (already coated with electrophoretic paint).

[0077] Installation equipment: Semi-automatic laminating machine, equipped with a visual positioning camera, a flexible silicone pressure head, and a bottom infrared heating plate.

[0078] Installation steps: The operator secures the door assembly to the tooling frame. The equipment's vision system identifies the reference holes on the door sheet metal and projects the outline of damping sheet 1. The operator peels off the release paper from damping sheet 1 and attaches it to the projected area.

[0079] Automatic program activated: The silicone pressure head presses down, applying a uniform pressure of 2.0 kPa; the bottom infrared heating plate activates, heating the back of the door panel bonding area to 110 ± 5℃ and maintaining this temperature for 10 seconds. After heating, the pressure head maintains pressure and cools for 15 seconds.

[0080] Lift the pressure head and visually inspect the bonding surface for bubbles, wrinkles, and complete sealing of the edges.

[0081] Simulated post-processing: The car door with damping plate 1 installed was placed into the experimental oven and baked at 180℃ for 30 minutes to simulate the electrophoretic baking process.

[0082] Performance testing: High and low temperature cycling test: The door assembly equipped with the damping plate 1 and the actual 77GHz radar module was placed in a walk-in environmental test chamber. Five cycles of temperature change test were performed: -30℃ (held for 2 hours) → room temperature (1 hour) → +85℃ (held for 2 hours) → room temperature (1 hour). During each temperature stabilization phase, the acceleration transfer function of the radar mounting point was measured using a vector network analyzer and a vibration exciter test system to calculate the insertion loss (IL) of damping plate 1; at the same time, the radar self-test mode was run to collect the noise level of its baseband output.

[0083] Results: Throughout the high and low temperature cycling, damper 1 showed no signs of bulging or delamination. At 25°C, the insertion loss averaged 25 dB in the critical frequency band of 100-500 Hz; at -30°C, it was 22 dB; and at +85°C, it was 23 dB, with minimal performance fluctuations. The radar self-test noise level remained below -95 dBm / Hz throughout the entire cycle, with no abnormal clutter peaks appearing, indicating normal radar function.

[0084] Example 2: Acrylic polymer-based damping sheet 1 1. Preparation of damping plate 1: Structure: Same as Example 1.

[0085] Aluminum foil layer 4: 0.08mm thick 0-state aluminum foil.

[0086] Damping layer 2: The matrix material is a self-adhesive acrylic pressure-sensitive polymer, mixed with hollow glass microspheres (for weight reduction and improved damping), silica filler, etc. This material exhibits high damping characteristics over a wide temperature range. The designed thickness is 2.2 mm.

[0087] Hot melt adhesive web layer 3: Copolyamide (Co-PA) based hot melt adhesive web is selected, with a higher activation temperature (130-160℃), better heat resistance, and a thickness of about 0.15mm.

[0088] Preparation process: Method 2 (layer lamination) is adopted. First, an acrylic damping slurry is coated onto an aluminum foil through a coating line, and then cured in an oven to form an "aluminum foil / damping layer 2" substrate. A Co-PA hot melt adhesive film (with release film) is purchased separately. On a laminating machine, the surface of the substrate damping layer 2 and the hot melt adhesive film are hot-pressed together at 120℃ and 0.3 MPa pressure. Finally, it is die-cut into shape.

[0089] Installation and Testing: Installation pressure: 3.0 kPa; heating temperature: 140℃; holding time: 15 seconds. Post-baking conditions are the same as in Example 1.

[0090] High and low temperature test results: The insertion loss is 24 dB, 26 dB, and 25 dB at -30℃, 25℃, and 85℃, respectively, demonstrating extremely stable performance. The radar operating noise level is better than -100 dBm / Hz.

[0091] Comparative Example 1 (Traditional manual roller pressing installation) The same materials as those used for the damping layer 2 and aluminum foil layer 4 in Example 1 are used, but instead of composite hot melt adhesive web layer 3, a layer of high-performance acrylic pressure-sensitive adhesive (PSA) is directly coated on the surface of the damping layer 2 and covered with release paper.

[0092] Installation: The most experienced technicians use rubber rollers of various curvatures to carefully roll and paste the product by hand, visually inspecting and tapping to confirm that there are no air bubbles initially.

[0093] Post-baking and testing: After baking at 180℃ for 30 minutes, a small bulge with a diameter of approximately 3mm appeared at the edge of a slightly dented area on the door panel. During high and low temperature cycling tests, this bulge area exhibited a slight "breathing" phenomenon with temperature changes. The radar noise level rose to -88 dBm / Hz at -30℃, exhibiting slight periodic clutter. The insertion loss decreased to 18 dB at low temperatures.

[0094] Comparative Example 2 (Simulated installation failure) The same conventional damping sheet 1 as Comparative Example 1 was used.

[0095] Installation: Simulate novice operation, with excessively fast rolling speed and uneven pressure, intentionally leaving a visible, tiny unfitted area (approximately 1 cm² in area, containing air and tiny air bubbles) in the middle region of damping sheet 1.

[0096] Post-baking and testing: After baking, several distinct bubbles developed in the area. During high and low temperature tests, radar noise increased dramatically, with significant clutter appearing at both -30℃ and +85℃, and the radar's near-field detection function intermittently failing. Insertion loss testing was meaningless.

[0097] Comparative Example 3 (Simulated installation malfunction) The same conventional damping sheet 1 as Comparative Example 1 was used.

[0098] Installation: Simulate novice operation, with excessively fast rolling speed and uneven pressure, intentionally leaving a visible small unfit area (approximately 5cm², containing air and large air bubbles) in the middle area of ​​damping sheet 1.

[0099] Post-baking and testing: After baking, several distinct bubbles developed in the area. During high and low temperature tests, radar noise increased dramatically, with significant clutter appearing at both -30℃ and +85℃, and the radar's near-field detection function intermittently failing. Insertion loss testing was meaningless.

[0100] Comparative Example 4 (without damping plate 1) As a blank control, the radar sensor was directly mounted on the exposed door sheet metal via a bracket (there was a standard rubber pad between the door sheet metal and the radar bracket, but no large-area damping sheet1).

[0101] Test: In the environmental test chamber, even with slight vibration excitation, the radar signal is filled with strong clutter related to the vibration frequency, the signal-to-noise ratio is severely degraded, and the target detection function is basically lost.

[0102] Summary of Performance of Examples and Comparative Examples The key test results of the above examples are summarized in the table below for clear comparison:

[0103] Conclusion: Examples 1 and 2, relying on the core technology of "hot melt adhesive mesh layer 3 + pressurized heating installation," demonstrated excellent and stable performance in all test items, fully achieving the invention's objectives. Comparative Example 1 shows that even the best conventional processes cannot avoid the risk of air bubbles and suffer from insufficient long-term reliability. Comparative Examples 2, 3, and 4, on the contrary, demonstrate the fatal harm of air bubbles and the indispensable role of the damping sheet 1.

[0104] Examples 1 and 2 compare the damping sheet 1 of the present invention using different material combinations. The test results are all valid, indicating that the filtering performance of the damping sheet 1 is stable and reliable. Meanwhile, Example 2 is better than Example 1, showing that the present invention can achieve excellent and consistent radar performance guarantee with different material combinations.

[0105] Examples 1 and 2 effectively solve the problem of reduced radar performance or even failure caused by air bubbles during the installation of damping sheet 1 by adding a hot-melt mesh structure. In Comparative Example 1, because the hot-melt mesh structure was not used, the installation required a very high level of skill from the operator, as it relied entirely on manual pasting and pressing. Even if the initial state was good, due to physical adhesion, slight changes in the interface could occur after harsh temperature cycling, causing fluctuations in radar performance parameters at high and low temperatures, resulting in performance inferior to the embodiments of the present invention. In Comparative Examples 2 and 3, because the structure of the present invention was not used and the conditions of inadequate manual pasting were simulated, the radar failed directly at high and low temperatures, and the test failed. Comparative Example 4, as a blank control, demonstrates the necessity of the damping sheet 1. Without the damping sheet 1, sheet metal vibration directly interferes with radar detection performance, and the radar cannot function normally.

[0106] Other possible implementations: Those skilled in the art will understand that various modifications and combinations can be made to the above implementations without departing from the core concept of the present invention: Material selection: Damping layer 2 can be made of any polymer with good viscoelasticity, such as polyurethane or silicone rubber modified materials. Hot melt adhesives can also be TPU (thermoplastic polyurethane), PES, etc., as long as they possess clear solid-liquid transition characteristics.

[0107] Structural variations: A layer of non-woven fabric or fiberglass cloth can be added between the aluminum foil layer 4 and the damping layer 2 to enhance dimensional stability and tear resistance. The hot melt adhesive web layer 3 can also be a discontinuous pattern such as dot matrix or stripe, as long as it can form a continuous bonding interface after heating.

[0108] Installation equipment: The pressurizing device can be a vacuum film press, which uses negative pressure adsorption to generate uniform pressure. The heating method can also be electromagnetic induction heating (for metal car door sheet metal), ultrasonic heating, etc.

[0109] Application Extension: This invention is not only applicable to door radar, but also to any part that needs to install radar and is subject to vibration interference, such as trunk door, fender, and roof. It can even be extended to other automotive acoustic or vibration control components that require high-reliability bonding.

[0110] The implementation principle of this invention is as follows: This invention discloses an anti-bubble automotive radar damping sheet, its preparation method, and its installation method. The damping sheet 1 has a multi-layer composite structure, including an aluminum foil layer 4, a damping layer 2, and a crucial hot melt adhesive mesh layer 3 from the outside to the inside. Through a matching pressure heating installation process, the hot melt adhesive melts and flows during installation, actively filling and expelling all air gaps between the damping sheet 1 and the complex curved surface of the car door sheet metal. After cooling, a permanent and strong bond without bubbles is formed. This invention fundamentally solves the industry problem of traditional hand-rolled damping sheets 1 easily generating bubbles, leading to a decrease in radar performance. It achieves high consistency in bonding quality and environmental durability, significantly improving the detection accuracy and reliability of automotive radar under extreme conditions, and providing an important basic component guarantee for high-level autonomous driving and intelligent body functions.

[0111] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An anti-bubble automotive radar damping sheet which is a multi-layer composite structure, characterized by, At least comprising: a damping layer (2) composed of viscoelastic material; a hot melt adhesive mesh film layer (3) compounded on one main plane of the damping layer (2) as the bonding surface with the door panel; an aluminum foil layer (4) compounded on the other main plane of the damping layer (2) away from the hot melt adhesive mesh film layer (3).

2. The anti-bubble automotive radar damping sheet according to claim 1, wherein The material of the damping layer (2) is selected from at least one of butyl rubber, asphalt-based polymer material or acrylate polymer.

3. The anti-bubble automotive radar damping sheet according to claim 1, wherein The material of the hot melt adhesive mesh film layer (3) is EVA-based or polyamide-based hot melt adhesive, and the activation temperature is 80-180℃.

4. The anti-bubble automotive radar damping sheet according to claim 1, wherein The thickness of the aluminum foil layer (4) is 0.05-0.15mm, and it is 0-state aluminum foil.

5. The anti-bubble automotive radar damping sheet according to claim 1, wherein The total thickness of the damping sheet (1) is 1.5-3.5mm.

6. The method of claim 1 to 5, wherein the method is characterized by, Comprising the following steps: S1: raw material preparation, weighing the damping layer (2) material and hot melt adhesive particles or hot melt adhesive film according to the formula; S2: co-extrusion molding, co-extruding the damping layer (2) material and hot melt adhesive particles after melting respectively, and compounding with aluminum foil after cooling and setting; S3: die cutting molding, punching or die cutting the compounded blank into the required shape, and the shape matches the bonding area of the door panel; S4: inspection and packaging, appearance, size and performance inspection of the finished product, and packaging into the warehouse after passing the inspection.

7. The method of claim 6, wherein the method further comprises the step of: 7.

1. applying a pressure to the dampening sheet to remove air bubbles from the dampening sheet. The step S2 further comprises: making damping sheet (1) substrate with aluminum foil and hot melt adhesive film respectively through extrusion process, and then compounding them through heating roller pressing method.

8. A method of mounting an anti-bubble automotive radar damping sheet according to any one of claims 1 to 5, wherein Comprising the following steps: Using laser positioning on the door panel; Placing the damping sheet (1) in the corresponding position; Applying 1-5kPa pressure to the damping sheet (1) through the pressing device to make the damping sheet (1) and the door panel tightly bonded; On the other side of the door panel, heating the bonding area of the door panel and the damping sheet (1) to 80-180℃ through the heating device, and keeping for 5-30 seconds to complete the installation of the damping sheet (1).

9. The method of claim 8, wherein the method further comprises the step of: 9-1) applying a pressure to the mounting surface of the damping sheet to prevent air bubbles from being generated in the mounting surface of the damping sheet. After installation, the door is also placed in an oven for baking to simulate electrophoresis baking conditions.

10. An automobile door characterized by comprising: A door panel and a bubble-proof automotive radar damping sheet according to any one of claims 1-5, wherein the damping sheet (1) is bonded to the door panel through the hot melt adhesive mesh film layer (3).

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