Ultrasonic welding device

Abstract

The utility model relates to the technical field of ultrasonic welding, in particular to an ultrasonic welding device which comprises a supporting frame. The servo linear motor is fixed to the supporting frame; the ultrasonic welding pile is arranged on the servo linear motor, the servo linear motor is used for driving the ultrasonic welding pile to move up and down, and the ultrasonic welding pile is used for vibration welding; the pressure sensor is arranged between the servo linear motor and the ultrasonic welding pile; the displacement sensor is arranged on the supporting frame, corresponds to the ultrasonic welding pile and is used for collecting the displacement of the ultrasonic welding pile relative to the supporting frame; the control system is electrically connected with the servo linear motor, the pressure sensor and the displacement sensor, and the control system is used for controlling the power of the servo linear motor according to the change ratio of the pressure sensor and the displacement sensor; and the power monitoring module is integrated in the control system and is used for collecting the instantaneous power of the transducer. The ultrasonic welding device aims at improving the consistency of welding seams during ultrasonic welding.

Description

Technical Field

[0001] This utility model relates to the field of ultrasonic welding technology, and more specifically, to an ultrasonic welding device. Background Technology

[0002] When ultrasound is applied to the contact surfaces of thermoplastic plastics, it generates high-frequency vibrations of tens of thousands of times per second. These high-frequency vibrations, reaching a certain amplitude, transmit ultrasonic energy to the welding area through the upper welding component. Due to the high acoustic impedance at the welding area—the interface between the two welded parts—localized high temperatures are generated. Furthermore, because plastics have poor thermal conductivity, the heat cannot dissipate quickly enough, accumulating in the welding area. This causes the contact surfaces of the two plastics to melt rapidly. With the application of pressure, they fuse together. After the ultrasound stops, the pressure is maintained for a few seconds to allow solidification, thus forming a strong molecular chain and achieving the purpose of welding.

[0003] Utility model patent CN214161737U discloses an ultrasonic welding device, including a device body, a base, a support column, a sensor bracket, and a parts clamp. A support frame is installed inside the device body on one side of the drive frame. A cylinder is installed inside the support frame, and a push rod is installed at the end of the cylinder near the drive frame, enabling fine-tuning of the internal structure of the ultrasonic welding device.

[0004] In actual use, it was found that the compressibility of the gas in the starting system caused unstable welding force, affecting the consistency of the weld. Utility Model Content

[0005] The main objective of this invention is to provide an ultrasonic welding device that aims to improve the consistency of welds during ultrasonic welding.

[0006] To address the aforementioned technical problems, an ultrasonic welding device is proposed, comprising: a support frame;

[0007] A servo linear motor is fixedly mounted on the support frame;

[0008] An ultrasonic welding stack is mounted on the servo linear motor, which drives the ultrasonic welding stack to move up and down. The ultrasonic welding stack is used for vibration welding.

[0009] A pressure sensor is disposed between the servo linear motor and the ultrasonic welding stack;

[0010] A displacement sensor is disposed on the support frame, corresponding to the ultrasonic welding stack, and is used to collect the displacement of the ultrasonic welding stack relative to the support frame;

[0011] The control system is electrically connected to the servo linear motor, pressure sensor, and displacement sensor respectively. The control system is used to control the power of the servo linear motor according to the change ratio of the pressure sensor and displacement sensor.

[0012] The power monitoring module, integrated into the control system, is used to collect the instantaneous power of the transducer.

[0013] In any of the above technical solutions, the ultrasonic welding stack further includes:

[0014] A transducer, installed with the servo linear motor and connected to a power supply, is used to convert electrical energy into mechanical vibration;

[0015] A booster, disposed on the transducer, is used to amplify the amplitude of the transducer;

[0016] A welding head is provided on the booster.

[0017] In any of the above technical solutions, the control system further includes an adaptive speed regulation module based on Lyapunov stability.

[0018] In any of the above technical solutions, the servo linear motor further integrates a power failure brake, and the braking response time of the power failure brake is ≤10ms.

[0019] In any of the above technical solutions, the surface of the welding head is further coated with a silicon nitride wear-resistant coating.

[0020] The beneficial effects are:

[0021] 1. The ultrasonic welding device of this application drives the ultrasonic welding pile through a servo linear motor, collects the pressure of the ultrasonic welding pile on the workpiece at various times through a pressure sensor, and collects the displacement change of the ultrasonic welding pile during welding through a displacement sensor. The control system can adjust the output power of the servo linear motor in real time by calculating the collected pressure and displacement change rate.

[0022] 2. The ultrasonic welding device of this application can achieve delayed welding. At the beginning of welding, the servo linear motor is turned on to drive the ultrasonic welding pile to contact the workpiece to be welded, for example, to maintain the contact pressure in the range of 5-50N (the contact pressure is fed back by a pressure sensor). Then the ultrasonic welding pile is turned on to soften the workpiece to be welded. Then the servo linear motor is controlled by the pressing speed limited by the control system to carry out welding. This can avoid premature compression of the workpiece to be welded and avoid the weld seam being too thin.

[0023] 3. The ultrasonic welding device of this application adjusts the downward pressing speed Vt in real time according to the force change rate (∆F / ∆t). The formula for adjusting the speed Vt is as follows:

[0024] When ∆F / ∆t>Fth

[0025]

[0026] When ∆F / ∆t≤Fth

[0027]

[0028] V0 is the predetermined descent speed of the servo linear motor during welding, k is the energy loss rate of the ultrasonic wave propagating in the material, and Fth is the critical rate of change when the trigger speed is adjusted.

[0029] This allows the servo linear motor to automatically slow down when the rate of change of force (∆F / ∆t) exceeds Fth, thus preventing energy overload.

[0030] 4. The power monitoring module is integrated into the control system, which can directly monitor the power of the transducer, accurately calculate the energy accumulation, and terminate welding when the accumulated energy reaches the set value, thus avoiding welding quality errors caused by relying solely on time control. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0032] Figure 1 This is a three-dimensional structural schematic diagram of an ultrasonic welding device according to an embodiment of the present invention.

[0033] The annotations in the attached figures are explained as follows:

[0034] 1. Supporting framework;

[0035] 2. Servo linear motor;

[0036] 3. Ultrasonic welding stack; 301. Transducer; 302. Booster; 303. Welding head;

[0037] 4. Pressure sensor;

[0038] 5. Displacement sensor;

[0039] 6. Control system. Detailed Implementation

[0040] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of this application, and not all of the embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0041] It should be noted that, as shown in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list; the method or apparatus may also include other steps or elements.

[0042] If the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0043] In this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0044] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0045] The ultrasonic welding apparatus of this application will be described in detail below through the following embodiments.

[0046] In this embodiment, as Figure 1 As shown, the ultrasonic welding device includes: a support frame 1;

[0047] Servo linear motor 2 is fixedly mounted on support frame 1;

[0048] The ultrasonic welding stack 3 is mounted on the servo linear motor 2. The servo linear motor 2 is used to drive the ultrasonic welding stack 3 to move up and down. The ultrasonic welding stack 3 is used for vibration welding.

[0049] Pressure sensor 4 is positioned between servo linear motor 2 and ultrasonic welding stack 3;

[0050] Displacement sensor 5 is installed on the support frame 1, corresponding to the ultrasonic welding stack 3, and is used to collect the displacement of the ultrasonic welding stack 3 relative to the support frame 1.

[0051] The control system 6 is electrically connected to the servo linear motor 2, the pressure sensor 4, and the displacement sensor 5 respectively. The control system 6 is used to control the power of the servo linear motor 2 according to the change ratio of the pressure sensor 4 and the displacement sensor 5.

[0052] The power monitoring module (not shown in the figure) is integrated into the control system 6 and is used to collect the instantaneous power of the transducer 301.

[0053] In this technical solution, the frame includes a base with shock-absorbing pads, a vertically mounted column perpendicular to the base, and an adjustable housing on the column. The top of the housing is fixed with a control system 6 and a port for power connection. The servo linear motor 2 is a permanent magnet synchronous linear motor, fixed to the housing. The motor rotor is connected to a lead screw, and the lead screw is equipped with a ball screw slider. The slider is connected to the ultrasonic welding stack 3. As the motor rotor rotates, the height of the ultrasonic welding stack 3 can be adjusted. The speed of position adjustment of the ultrasonic welding stack 3 varies with the motor output power.

[0054] In this embodiment, the ultrasonic welding stack 3 includes:

[0055] Transducer 301 is installed on servo linear motor 2 and connected to power supply to convert electrical energy into mechanical vibration;

[0056] The booster 302 is disposed on the transducer 301 and is used to amplify the amplitude of the transducer 301;

[0057] Welding head 303 is located on booster 302.

[0058] In this technical solution, the transducer 301 is a piezoelectric ceramic, fixed to the sliding structure of the servo linear motor 2, and threadedly connected to the booster 302. The transducer 301 can convert electrical energy into 20kHz mechanical vibration with an amplitude of approximately 20 micrometers. The booster 302 can increase the amplitude, amplifying the vibration amplitude output by the transducer 301 through the mechanical lever principle, with a gain ratio of 0.5 to 3. The length of the booster 302 must be an integer multiple of half the wavelength of the ultrasonic wave (e.g., 20kHz corresponds to approximately 125mm in titanium alloy) to ensure frequency resonance with the transducer 301. The welding head 303 is made of aluminum alloy and is connected to the booster 302 via a tapered thread. The welding head 303 is installed at the point of maximum vibration antinode at the output end of the booster 302 to ensure efficient energy output. The transducer 301 drives the welding head 303 to generate high-frequency vibration, melting the workpiece to be welded, thus performing welding.

[0059] Pressure sensor 4 is fixed between servo linear motor 2 and transducer 301, and can measure the force exerted by welding head 303 on the welded material in real time. Displacement sensor 5 is a laser sensor, which is fixed on the bottom side of the outer shell of support frame 1 and is set on a plane corresponding to welding head 303. This plane is provided with a reflective layer to enhance laser reflectivity.

[0060] The power monitoring module (not shown in the figure) synchronously measures the operating current and voltage of transducer 301 during operation, calculates the instantaneous power, and calculates the energy accumulation during operation. It can monitor the input power of transducer 301 and prevent overload. By calculating the accumulated energy, the completion of welding can be determined, which improves welding quality and reduces welding deviation compared to determining completion by welding time. Depending on the application requirements, the power monitoring module can be configured as an INA219 module, a Hall sensor + external ADC, or a dedicated power meter chip, etc.

[0061] During welding, the welding quality is affected by the contact pressure, descent speed, and displacement. The contact pressure is measured by the pressure sensor 4, the displacement is measured by the displacement sensor 5, and the descent speed is determined by the power of the servo linear motor 2 controlled by the control system 6.

[0062] During welding, the control system 6 controls the servo linear motor 2 to descend until the pressure from the pressure sensor 4 is within the range of 5-50N, bringing the welding head 303 into contact with the workpiece. The transducer 301 is then activated, causing the welding head 303 to vibrate and heat and soften the workpiece. After softening, the pressure either slowly or abruptly drops below the set pressure value, indicating that softening is complete. Then, the control system 6 controls the servo linear motor 2 to descend the welding head 303 at a predetermined speed V0 to begin welding. As welding progresses, the measured pressure gradually increases, while the descent displacement gradually shortens over the same time interval. Simultaneously, the power monitoring module tracks the accumulated energy, stopping welding once the predetermined accumulation is reached. During the process of reaching the predetermined accumulation, the rate of change of force (∆F / ∆t) may exceed the critical rate of change Fth. If this occurs, the control system 6 automatically reduces the power of the servo linear motor 2, ensuring that the speed at which the servo linear motor 2 lowers the welding head 303 matches the adjusted speed Vt.

[0063] This ensures that the welding energy is consistently maintained at a predetermined accumulation level during each weld, improving welding results and avoiding the instability of welding force caused by pneumatic transmission in existing technologies, thus enhancing weld consistency. Furthermore, by coordinating the displacement sensor 5 and the servo linear motor 2, displacement control can reach the micrometer level, supporting the welding needs of various materials (such as PP and ABS).

[0064] Furthermore, the ultrasonic welding device of this application can be used for multi-mode welding: ① Prioritizing pressure stability, suitable for thin-walled parts; ② Pressing down according to a preset displacement curve, suitable for deep cavity structures; ③ Energy-displacement coupling mode: When the accumulated energy reaches the set value, the speed curve is switched to prevent overheating.

[0065] In this embodiment, the control system 6 includes an adaptive speed control module based on Lyapunov stability.

[0066] In this technical solution, when the load changes abruptly (such as when a welding machine encounters uneven material thickness), traditional PID control is prone to oscillation. The Lyapunov function is used to calculate the system's energy state in real time, ensuring error convergence. Specifically, the setup involves establishing a reference model, defining an ideal system response speed curve, defining the speed error equation, constructing the Lyapunov function, deriving the adaptive law, and finally synthesizing the control signal.

[0067] In this embodiment, the servo linear motor 2 integrates a power failure brake (not shown in the figure), and the braking response time of the power failure brake is ≤10ms.

[0068] In this technical solution, a power failure brake is installed to prevent the weld pile from falling when power is cut off.

[0069] In this embodiment, the surface of the welding head 303 is coated with a silicon nitride wear-resistant coating.

[0070] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An ultrasonic welding apparatus, characterized in that, include: Supporting framework (1); A servo linear motor (2) is fixedly mounted on the support frame (1); An ultrasonic welding stack (3) is mounted on the servo linear motor (2). The servo linear motor (2) is used to drive the ultrasonic welding stack (3) to move up and down. The ultrasonic welding stack (3) is used for vibration welding. A pressure sensor (4) is disposed between the servo linear motor (2) and the ultrasonic welding stack (3); A displacement sensor (5) is disposed on the support frame (1) and is disposed corresponding to the ultrasonic welding stack (3) for collecting the displacement of the ultrasonic welding stack (3) relative to the support frame (1); The control system (6) is electrically connected to the servo linear motor (2), pressure sensor (4) and displacement sensor (5) respectively. The control system (6) is used to control the power of the servo linear motor (2) according to the change ratio of the pressure sensor (4) and displacement sensor (5). A power monitoring module is integrated into the control system (6); The ultrasonic welding stack (3) includes: A transducer (301) is provided with the servo linear motor (2) and connected to a power source to convert electrical energy into mechanical vibration; A booster (302) is disposed on the transducer (301) for amplifying the amplitude of the transducer (301); A welding head (303) is disposed on the booster (302); The power monitoring module is used to collect the instantaneous power of the transducer (301).

2. The ultrasonic welding apparatus according to claim 1, characterized in that, The control system (6) includes an adaptive speed regulation module based on Lyapunov stability.

3. The ultrasonic welding apparatus according to claim 1, characterized in that, The servo linear motor (2) integrates a power failure brake, and the braking response time of the power failure brake is ≤10ms.

4. The ultrasonic welding apparatus according to claim 1, characterized in that, The surface of the welding head (303) is coated with a silicon nitride wear-resistant coating.

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