Temperature-compensated strain gauge sensor for automatic truck weighing

Abstract

The utility model relates to sensor technical field, specifically disclose a kind of temperature compensation strain gauge sensor for truck automatic weighing, including semi-rigid base, its top is fixed with the metal sensitive grid wire that is bent into grid shape by adhesive layer, grid wire both ends are welded with lead-out wire, its top is covered with packaging layer, semi-rigid base enables user to paste "adhesive plaster" similarly, by spot gluing or back glue mode, it is quickly installed on the surface of the object to be measured, significantly reduce the requirement to operating technique and surface, and provide impact resistance and anti-scratching protection for sensitive grid wire, packaging layer is used to isolate environmental factors to the interference of measurement. By selecting the sensitive grid wire material that is matched with the thermal expansion coefficient of base, effectively improve the precision and long-term stability of truck automatic weighing under wide temperature environment.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, and more specifically, to a temperature-compensated strain gauge sensor for automatic weighing of trucks. Background Technology

[0002] Strain gauges, or strain sensors, are core components in modern engineering measurement and structural health monitoring. Their basic principle involves attaching a sensitive grid (usually a metal wire or foil) to the surface of the object being measured. When the object deforms, the grid deforms accordingly, causing a change in its resistance. By measuring this change in resistance, the magnitude of the object's strain can be accurately calculated.

[0003] Currently, commercially available traditional strain gauges primarily use flexible films such as polyimide as the substrate. While this structure can adhere well to flat surfaces, it has significant limitations in practical applications. First, the installation process is complex, requiring specialized surface treatment techniques and bonding processes. Inexperienced operators are prone to air bubbles or weak adhesion, leading to inaccurate measurements. Second, the flexible substrate itself has low mechanical strength and is easily scratched or torn in harsh installation or usage environments, resulting in insufficient durability. Furthermore, this type of strain gauge has stringent requirements for the smoothness and cleanliness of the bonding surface, making it unsuitable for rough or unclean industrial environments such as truck beams or leaf springs. Finally, in certain applications requiring specific rigid support or dielectric properties, traditional flexible substrates cannot provide optimal solutions.

[0004] Therefore, the market urgently needs a new type of strain sensor that can overcome the above-mentioned defects and has the advantages of convenient installation, strong mechanical protection, and good adaptability to the bonding surface. Utility Model Content

[0005] In view of the above-mentioned technical problems in related technologies, this utility model provides a temperature-compensated strain gauge sensor for automatic truck weighing, which can solve the above problems.

[0006] To achieve the above-mentioned technical objectives, the technical solution of this utility model is implemented as follows: A temperature-compensated strain gauge sensor for automatic truck weighing includes a semi-rigid substrate. A metal sensitive grid wire is bonded and fixed to the top surface of the semi-rigid substrate via an adhesive layer. Lead wires are welded to both ends of the metal sensitive grid wire. An encapsulation layer covers the top surface of the metal sensitive grid wire and is sealed to the top surface of the semi-rigid substrate. A smart semiconductor temperature sensor is integrated on the top of the semi-rigid substrate, located adjacent to the end of the metal sensitive grid wire. The smart semiconductor temperature sensor internally includes a temperature sensing unit and a non-volatile memory unit.

[0007] Furthermore, the metal-sensitive grid wire includes any one of constantan wire, kamma wire, and nichrome wire, and the metal-sensitive grid wire is bent into a grid shape.

[0008] Furthermore, the two lead wires are welded and fixed to the two ends of the metal sensitive grid wire, respectively.

[0009] Furthermore, the adhesive layer is either epoxy resin or acrylic resin.

[0010] The beneficial effects of this utility model are as follows: The device of this application is a strain sensor that directly bonds the metal sensitive grid wire to a semi-rigid substrate. The sensor has a simple structure, is easy to install, and has low requirements for the bonding surface. Different semi-rigid substrates with different characteristics can be selected according to application requirements, thereby improving the overall performance and application range of the sensor. The semi-rigid substrate has a certain degree of hardness, allowing users to quickly install it directly on the surface of the object to be tested by applying adhesive or backing, just like sticking on a "band-aid" or a hard label. This greatly reduces the technical requirements for operators. The semi-rigid substrate provides better mechanical protection for the fragile metal sensitive grid wires, improving the sensor's impact and scratch resistance. A layer of encapsulation is coated on the surface of the metal sensitive grid wire to protect it and reduce the impact of environmental factors on the measurement of the resistance of the metal sensitive grid wire. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] The present invention will now be described in further detail with reference to the accompanying drawings.

[0013] Figure 1 This is a schematic diagram of the external structure of a temperature-compensated strain gauge sensor; Figure 2 This is a schematic diagram of the structure of the metal sensing grid wire; Figure 3 This is a schematic diagram of the internal structure of a temperature-compensated strain gauge sensor.

[0014] In the picture: 1. Semi-rigid substrate; 2. Lead wire; 3. Encapsulation layer; 4. Metal sensitive grid wire; 5. Adhesive layer. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model are within the protection scope of the present utility model.

[0016] According to this utility model, a temperature-compensated strain sensor is disclosed for automatic weighing of truck suspension systems (especially leaf springs). The sensor is designed to be directly attached to the surface of the leaf spring to monitor the micro-strain caused by load changes. Through a built-in temperature compensation mechanism, the influence of ambient temperature changes on measurement accuracy is eliminated, thereby achieving high-precision vehicle weighing.

[0017] Example 1: 1. Substrate preparation Material Selection and Processing: A 0.8mm thick glass fiber reinforced epoxy resin board was selected as the semi-rigid substrate 1. This material has excellent mechanical strength, fatigue resistance, and a coefficient of thermal expansion similar to steel, which can effectively transmit the strain of the leaf spring while providing good protection. It was processed into a 30mm × 15mm rectangular sheet using a precision cutting machine.

[0018] Surface treatment: Use 400# fine sandpaper to lightly and evenly sand one side of the substrate to create a rough surface to increase the bonding area. Then, thoroughly clean the sanded surface with anhydrous ethanol and acetone in turn to remove oil and dust, and let it dry for later use.

[0019] 2. Sensitive grid fabrication and bonding Sensitive grid selection and forming: Kamama wire with a diameter of 0.025mm is used as the metal sensitive grid wire 4. Kamama wire has high resistivity and sensitivity coefficient, and its resistance-temperature curve can exhibit flat characteristics under specific heat treatment, which is beneficial for temperature compensation. It is bent into a repeating grid shape with a total length of 50mm using a precision wire winding device (e.g., ...). Figure 2 The loop shape shown is used to increase the strain-sensitive area.

[0020] Bonding and Fixing: On the prepared semi-rigid substrate 1, a layer of high-temperature resistant and high-thermal-conductivity epoxy resin is uniformly applied as the bonding layer 5 using a high-precision dispensing device. Under the assistance of a microscope, the formed Kamash grid is precisely placed on the adhesive layer, ensuring its centered position and regular shape. Subsequently, a uniform pressure of 0.1~0.2MPa is applied using a clamp with a flat silicone pad, and excess air bubbles are removed.

[0021] Curing: Place the assembly in a programmable temperature oven and cure it in a stepped manner according to the curing process curve of the epoxy adhesive (e.g., from room temperature to 80°C, hold for 1 hour; then to 120°C, hold for 2 hours) to ensure that the adhesive layer is fully cured and achieves the best bonding strength and cohesion.

[0022] 3. Implementation of lead wire soldering and temperature compensation Lead wire connection: After curing and complete cooling, use a precision spot welding machine to weld two silver-plated copper core high-temperature fluoroplastic wires as lead wires 2 to the beginning and end of the metal sensitive grid wire 4, respectively. The solder joints should be firm, smooth, and have low contact resistance.

[0023] The intelligent semiconductor temperature sensor is positioned close to the end of the metal sensitive grid wire. Using a digital communication interface or a low-power wireless module, it reads the pre-stored, strain gauge-specific compensation coefficient from the non-volatile storage unit of the intelligent semiconductor temperature sensor 3; it simultaneously acquires the strain signal from the strain sensitive grid and the real-time temperature signal from the intelligent semiconductor temperature sensor; using the temperature compensation coefficient read and the real-time temperature signal acquired, it performs mathematical operations on the acquired strain signal to compensate for temperature-induced drift, thereby obtaining the true strain value.

[0024] 4. Encapsulation and protection Encapsulation Layer Coating: To protect the fragile, metal-sensitive grid wires 4 and solder joints from damage caused by moisture, chemicals, oil, and mechanical scratches, a modified silicone rubber layer 3 is applied to the entire grid wire area and part of the lead root. This silicone rubber layer has good elasticity, excellent high and low temperature resistance (-60℃ to 200℃), moisture resistance, insulation, and adhesion to the substrate 1. The coating process is performed in two stages to ensure a uniform coating, no bubbles, and complete coverage of the grid wires.

[0025] Post-curing: After surface drying at room temperature, a moderate post-curing treatment (such as 1 hour at 80°C) can be performed to further improve the mechanical properties and stability of the encapsulation layer 3.

[0026] 5. Sensor Installation and Application At the predetermined measurement location (typically the point of maximum strain) of the truck leaf spring, the surface to be bonded is derusted, sanded, and solvent-cleaned to ensure it is clean, dry, and flat. A layer of high-strength, fast-curing modified acrylic structural adhesive is then applied to the back of the sensor semi-rigid substrate 1 or the surface of the leaf spring.

[0027] The sensor is precisely adhered to the pre-treated leaf spring surface, like a band-aid or a hard label, applying appropriate pressure to ensure uniform contact of the adhesive layer and to expel air. Once the adhesive has fully cured, the sensor becomes an integral part of the leaf spring, accurately sensing its strain.

[0028] Connect the sensor's lead wire 2 to the Wheatstone bridge measurement circuit of the vehicle weighing instrument. Because the sensor itself has an effective temperature compensation function, the instrument does not require a complex software temperature correction algorithm and can stably and accurately output an electrical signal proportional to the load in a wide temperature environment where the truck operates (such as -40℃ to +80℃).

[0029] The sensor described in this embodiment utilizes a semi-rigid glass fiber reinforced epoxy resin substrate, enabling simple and reliable installation, much like a "band-aid," significantly reducing the technical requirements for installers and the stringent conditions of the bonding surface. The substrate provides robust mechanical protection for the internal Kamash sensitive grid, allowing it to withstand the severe vibrations and impacts of truck operation. The modified silicone rubber encapsulation layer effectively isolates it from the corrosive effects of harsh environments such as water, oil, and salt spray. Through material selection and process design, inherent temperature self-compensation is achieved, making this sensor particularly suitable for vehicle-mounted automatic weighing systems where ambient temperatures fluctuate drastically. This significantly improves the long-term stability and measurement accuracy of weighing data, resulting in superior overall performance and a wide range of applications.

[0030] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A temperature-compensated strain gauge sensor for automatic truck weighing, characterized in that, It includes a semi-rigid substrate (1), on the top surface of which a metal sensitive grid wire (4) is bonded and fixedly installed by an adhesive layer (5), and lead wires (2) are welded to both ends of the metal sensitive grid wire (4). The top surface of the metal sensitive grid wire (4) is covered with an encapsulation layer (3), which is sealed and attached to the top surface of the semi-rigid substrate (1). The top of the semi-rigid substrate (1) is integrated with a smart semiconductor temperature sensor, which is located close to the end of the metal sensitive grid wire (4). The smart semiconductor temperature sensor includes a temperature sensing unit and a non-volatile memory unit inside.

2. A temperature-compensated strain gauge sensor for automatic truck weighing according to claim 1, characterized in that, The metal sensitive grid wire (4) includes any one of constantan wire, kamma wire, and nichrome wire, and the metal sensitive grid wire (4) is bent into a grid shape.

3. A temperature-compensated strain gauge sensor for automatic truck weighing according to claim 2, characterized in that, The two lead wires (2) are respectively welded and fixed to the two ends of the metal sensitive grid wire (4).

4. A temperature-compensated strain gauge sensor for automatic truck weighing according to claim 1, characterized in that, The adhesive layer (5) is either epoxy resin or acrylic resin.

Images