Resonant bottom mold for ultrasonic welding, resonance bottom mold design method and welding system

Abstract

The present invention belongs to the field of ultrasonic welding technology and discloses a resonant bottom mold for ultrasonic welding, a resonant bottom mold design method, and a welding system. The resonant bottom mold for ultrasonic welding includes a bottom mold body, which is disposed on a workbench of the ultrasonic welding system and has a welding working surface for supporting a workpiece. The material and geometric dimensions of the bottom mold body determine that its inherent resonant frequency matches the preset ultrasonic working frequency of the ultrasonic welding system. When the bottom mold body is excited by the upper welding head of the ultrasonic welding system, it can resonate in a predetermined direction, and the welding working surface is disposed at the position of the vibration antinode. In the resonant bottom mold for ultrasonic welding of the present invention, during the ultrasonic welding process, the bottom mold body can resonate at the same frequency and in the opposite direction as the upper welding head, thereby increasing the relative motion and friction between the workpieces at the welding interface, improving the efficiency of welding energy transfer, and ultimately achieving the effect of improving welding quality and increasing welding efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic welding, and in particular to a resonance bottom mold for ultrasonic welding, a resonance bottom mold design method and a welding system. Background Art

[0002] The base die (also known as the lower die / positioning fixture) in ultrasonic welding equipment is a component installed on the welding workbench to position and support the workpiece. The ultrasonic welding head and the base die form a pressure closed loop, so that the vibration energy is concentrated on the welding interface, so that the two work together to complete the welding operation.

[0003] Traditional bottom molds are usually passive rigid structures, that is, the bottom mold mainly undertakes the functions of workpiece positioning and energy reflection, and the natural frequency of the bottom mold is usually much lower than the ultrasonic welding frequency (15-40kHz). Its rigidity characteristics make it impossible to synchronously respond to high-frequency vibrations. It is understandable that during the ultrasonic welding process, the bottom mold does not participate in the vibration or does not match the vibration of the ultrasonic welding head, which ultimately leads to low energy transfer efficiency and affects the welding quality and consistency. Summary of the Invention

[0004] The purpose of the present invention is to provide a resonant bottom mold for ultrasonic welding, a resonant bottom mold design method and a welding system, so that the vibration of the bottom mold and the ultrasonic welding head are matched, thereby improving the efficiency of energy transfer and achieving improved welding quality and consistency.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] Resonant bottom mold for ultrasonic welding, including:

[0007] A bottom mold body is arranged on a workbench of the ultrasonic welding system, and the bottom mold body has a welding working surface for supporting a workpiece;

[0008] In which, the material and geometric dimensions of the bottom mold body determine that its inherent resonant frequency matches the preset ultrasonic working frequency of the ultrasonic welding system, and when the bottom mold body is excited by the upper welding head in the ultrasonic welding system, it can resonate along a predetermined direction, and the predetermined direction is configured to be opposite to the vibration direction of the upper welding head, and the welding working surface is set at the position of any vibration antinode when the bottom mold body resonates.

[0009] Preferably, the predetermined direction is a horizontal direction.

[0010] Preferably, the distance between the position of the vibration antinode and the position of the adjacent vibration node is an odd multiple of 1 / 4 wavelength of the resonance.

[0011] Preferably, the bottom mold body is arranged in a columnar shape, and the bottom mold body has a fixed end connected to the workbench and a free end away from the workbench, and the welding working surface is located at the free end.

[0012] Preferably, the bottom mold body comprises:

[0013] a vibrating rod; and

[0014] A fixed base is arranged at one end of the vibration rod close to the workbench, and the fixed base is connected to the workbench.

[0015] Preferably, the vibration rod and the fixed base are integrally formed.

[0016] Preferably, the base mold body is made of steel, titanium alloy or aluminum alloy.

[0017] A resonant bottom mold design method is used to design a resonant bottom mold for ultrasonic welding, comprising the following steps:

[0018] Determine the operating frequency of the ultrasonic welding system matched with the bottom mold body, select the material of the bottom mold body and obtain its acoustic characteristics;

[0019] Based on the working frequency and the acoustic characteristics, the geometric dimensions of the bottom mold body are determined to match the working frequency and have a resonance direction opposite to the vibration direction of the upper welding head, and the welding working surface is at the vibration antinode position when the bottom mold body resonates.

[0020] Preferably, determining the geometric dimensions of the bottom mold body includes:

[0021] Finite element analysis software is used to perform modal analysis and inherent characteristic analysis on the base mold body with different geometric dimensions, and the geometric dimensions that meet the design requirements are selected.

[0022] The welding system includes an acoustic component and an upper welding head, wherein the upper welding head is connected to the acoustic component. The welding system also includes a resonant bottom mold for ultrasonic welding, and the upper welding head is configured to excite the resonant bottom mold for ultrasonic welding.

[0023] Beneficial effects of the present invention:

[0024] The resonant bottom mold for ultrasonic welding of the present invention is provided with a welding working surface for placing workpieces on the bottom mold body. During the ultrasonic welding process, the bottom mold body whose inherent resonant frequency matches the ultrasonic working frequency preset by the ultrasonic welding system is excited by the upper welding head, so that the bottom mold body resonates in a direction opposite to the vibration direction of the upper welding head, that is, the bottom mold body produces a resonance with the same frequency and opposite direction as the upper welding head. Since the welding working surface is at the vibration antinode position, the relative movement and friction between the workpieces at the welding interface are increased, thereby improving the efficiency of welding energy transfer; in this way, the weld strength and welding consistency can be improved to improve the welding quality, and the welding efficiency can also be improved by shortening the welding time.

[0025] The resonant bottom mold design method of the present invention selects the material of the bottom mold body through the operating frequency of the ultrasonic welding system, and then determines the geometric dimensions of the bottom mold body based on the operating frequency and the acoustic characteristics of the bottom mold body. In this way, the material and geometric dimensions of the bottom mold body can be quickly determined, thereby improving the design speed of the resonant bottom mold.

[0026] The welding system of the present invention works in conjunction with an upper welding head and a resonant bottom mold for ultrasonic welding. During the ultrasonic welding process, the upper welding head is used to excite the bottom mold body, causing the bottom mold body to resonate in a direction opposite to the vibration direction of the upper welding head, thereby increasing the relative movement and friction between the workpieces at the welding interface, thereby improving the efficiency of welding energy transfer, and thus improving welding quality and welding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the resonant bottom mold for ultrasonic welding of the present invention;

[0028] Figure 2 It is a schematic diagram of the resonant bottom mold for ultrasonic welding of the present invention in a resonant state.

[0029] In the picture:

[0030] 100. Workpiece; 1. Bottom mold body; 11. Vibrating rod; 12. Fixed base; 2. Welding work surface; 3. Antinode; 4. Node; 5. Upper welding head. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0032] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0033] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0034] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0035] Refer to the following Figures 1 to 2 The resonance bottom mold for ultrasonic welding, the resonance bottom mold design method and the welding system provided by the present invention are described.

[0036] The welding system includes a frame, a workbench, an acoustic assembly, an upper horn 5, and a resonant base die for ultrasonic welding. The workbench and acoustic assembly are both connected to the frame. The acoustic assembly includes an ultrasonic generator and a transducer, and the resonant base die for ultrasonic welding is connected to the workbench. The ultrasonic generator is connected to the frame, and the ultrasonic transducer is slidably connected to the frame along a predetermined direction. The ultrasonic transducer is driven by a transfer mechanism and is electrically connected to the ultrasonic generator. The upper horn 5 is connected to the ultrasonic transducer. The transfer mechanism can drive the upper horn 5 to move in a predetermined direction relative to the resonant base die for ultrasonic welding to perform ultrasonic welding on a workpiece 100.

[0037] The resonant bottom die for ultrasonic welding is designed to generate resonance with the same frequency and opposite direction as the upper welding head 5 during ultrasonic welding, thereby improving the efficiency of energy transfer and achieving improved welding quality and consistency. Please refer to the following content of this embodiment for the specific structure of the resonant bottom die for ultrasonic welding.

[0038] The resonant bottom mold for ultrasonic welding includes a bottom mold body 1, which is connected to the workbench of the ultrasonic welding system, and has a welding working surface 2 for supporting the workpiece 100; wherein, the material and geometric dimensions of the bottom mold body 1 determine that its inherent resonant frequency matches the ultrasonic working frequency preset by the ultrasonic welding system, and when the bottom mold body 1 is excited by the upper welding head 5, it can resonate along a predetermined direction, and the predetermined direction is configured to be opposite to the vibration direction of the upper welding head 5, and the welding working surface 2 is set at any vibration antinode 3 position when the bottom mold body 1 resonates.

[0039] It should be noted that the natural resonant frequency of the base mold body 1 refers to the natural vibration frequency of the base mold body 1 in a free vibration state (without external excitation), which is determined by its own material properties and structure. This natural resonant frequency is determined by the elastic modulus, density, and geometry of the base mold body 1 and reflects its mechanical vibration characteristics. When the external ultrasonic excitation frequency matches this natural resonant frequency, the base mold body 1 enters a resonant state, and the energy transfer efficiency reaches its peak. The vibration antinode 3 is the location of the maximum amplitude in the vibration wave, i.e., the vibration amplitude reaches its maximum value here. The vibration node 4 is the location of the minimum amplitude in the vibration wave, i.e., the vibration amplitude reaches its minimum value here.

[0040] As described above, a welding working surface 2 is provided on the base mold body 1. During the ultrasonic welding process, the upper welding head 5 excites the base mold body 1, whose inherent resonant frequency matches the ultrasonic operating frequency preset by the ultrasonic welding system, so that the base mold body 1 resonates in a direction opposite to the vibration direction of the upper welding head 5. That is, during the ultrasonic welding process, the base mold body 1 resonates at the same frequency and in the opposite direction as the upper welding head 5. Since the welding working surface 2 is located at the position of the vibration antinode 3, the relative movement and friction at the welding interface between the base mold body 1 and the workpiece 100 are increased, thereby improving the efficiency and concentration of the welding energy transfer. In addition, the strength of the weld point and the consistency of the welding quality can be improved, thereby achieving an improvement in welding quality. In addition, due to the improved efficiency of energy transfer, the time of each welding can be shortened, thereby improving welding efficiency.

[0041] For example, the preset direction in this embodiment is the vertical direction, and the vibration direction of the upper welding head 5 is the horizontal direction, that is, the predetermined direction is also the horizontal direction and is opposite to the vibration direction of the upper welding head 5. Optionally, in some other embodiments, the predetermined direction is also an inclined direction. It should be noted that the vibration direction of the bottom mold body 1 is opposite to the vibration direction of the upper welding head 5, which is an inherent characteristic. In this embodiment, the waveform of the upper welding head 5 takes a sine wave as an example. The displacement of the upper welding head 5 is y1, y1=sin(ωx+φ), and the acceleration of the upper welding head 5 is a1. Differentiating the above formula twice yields the acceleration formula of the upper welding head 5, a1=-ω2sin(ωx+φ); since the force of the upper welding head 5 on the bottom mold body 1 is relative and opposite, the acceleration of the bottom mold body 1 is a2, a2=ω2sin(ωx+φ), and the displacement of the bottom mold body 1 is y2. Integrating the above formula twice yields the displacement formula of the bottom mold body 1, that is, y2=-sin(ωx+φ), so the vibration direction of the bottom mold body 1 is opposite to that of the upper welding head 5. From another perspective, based on the forced vibration theory, the present invention designs the natural resonant frequency of the bottom mold body 1 to be slightly lower than the system operating frequency, so that the system operates in a region where its own operating frequency is greater than the natural resonant frequency of the bottom mold body 1. In this region, the displacement response phase of the excited body (i.e., the bottom mold body 1) naturally lags behind the driving force by about 180 degrees, thereby achieving reverse vibration with the upper welding head.

[0042] Based on the above, the upper welding head 5 vibrates in the horizontal direction (parallel to the welding surface). First, the horizontal vibration can effectively destroy the oxide layer on the metal interface and achieve solid-state connection through high-frequency friction. It is particularly suitable for welding soft metals such as aluminum and copper, and the conductivity after welding is close to zero resistance, and the applicability of metal welding is wide. Secondly, the lateral friction force generated by the horizontal vibration can quickly remove contaminants on the surface of the workpiece 100, thereby shortening the welding time and significantly improving production efficiency. Furthermore, the heat generated by the parallel vibration is concentrated on the contact surface, avoiding the overall heating of the material, reducing the risk of thermal deformation of the workpiece 100, and is suitable for the welding of precision components. In addition, the plastic flow generated by the horizontal vibration can promote the atomic diffusion of dissimilar metals (such as copper-aluminum) and achieve high-strength metallurgical bonding.

[0043] Furthermore, since the vibration waveform in this embodiment is a sine wave, a complete sine wave has 3 vibration nodes 4 positions and 2 vibration antinodes 3 positions, and the vibration antinode 3 position is located exactly in the middle of two adjacent vibration nodes 4 positions, that is, the distance between the vibration antinode 3 position and the adjacent vibration node 4 position is an odd multiple of the 1 / 4 wavelength of resonance.

[0044] Furthermore, the bottom mold body 1 is arranged in a columnar shape, and the bottom mold body 1 has a fixed end connected to the workbench and a free end away from the workbench. The welding working surface 2 is located at the free end, so that the ultrasonic mechanical vibration energy is focused on the free end to increase the local amplitude of the free end, which is more conducive to high-frequency vibration transmission and reduces energy loss.

[0045] Specifically, the bottom mold body 1 includes a vibrating rod 11 and a fixed base 12. The fixed base 12 is connected to the end of the vibrating rod 11 closest to the workbench. The fixed base 12 is connected to the workbench. At the end where the vibrating rod 11 and the fixed base 12 are close to each other, the cross-sectional area of ​​the vibrating rod 11 is smaller than the cross-sectional area of ​​the fixed base 12. In this way, the fixed base 12 can increase the contact area between the bottom mold body 1 and the workbench, thereby ensuring the stability of the connection between the bottom mold body 1 and the workbench.

[0046] In addition, the end of the vibration rod 11 in this embodiment is provided with a plurality of positioning teeth away from the fixed base 12, so that the top of the vibration rod 11 is provided with a tooth surface, which can pre-position the workpiece (such as a terminal), so that the workpiece is positioned through the bottom mold body 1 during welding. The upper welding head 5 placed above the bottom mold body 1 excites the welding material and the bottom mold body 1 to resonate, so that the ultrasonic energy is more concentrated on the welding surface, thereby saving the energy required for welding.

[0047] Optionally, the vibration rod 11 and the fixed base 12 are integrally formed, thereby ensuring the connection strength between the vibration rod 11 and the fixed base 12, so that the bottom mold body 1 is not easily disintegrated during resonance. Of course, in other embodiments, the vibration rod 11 and the fixed base 12 can also be fixedly connected.

[0048] Furthermore, a base plate is connected between the bottom mold body 1 and the workbench. The base plate is fixed to the mounting surface of the workbench via multiple screws. Positioning pins and holes are provided on the side of the base plate adjacent to the workbench. The positioning pins and holes ensure stable positioning of the base plate, allowing only elastic deformation of the bottom mold body 1 during welding. Optionally, in other embodiments, positioning bosses and slots may be provided between the base plate and the workbench.

[0049] Optionally, the base mold body 1 is made of steel, titanium alloy or aluminum alloy. In this embodiment, steel is taken as an example, specifically W18Cr4V high-speed steel. W18Cr4V high-speed steel has high hardness and wear resistance, excellent high-temperature stability and high process compatibility.

[0050] This embodiment also provides a resonant bottom mode design method, which includes the following steps:

[0051] S1. Determine the operating frequency of the ultrasonic welding system that matches the bottom mold body 1, select the material of the bottom mold body 1 and obtain its acoustic characteristics.

[0052] In step S1, the ultrasonic operating frequency can be 15kHz, 20kHz or 40kHz; the Young's modulus of the material of the bottom mold body 1 is 180-220GPa, and the density of the material of the bottom mold body 1 is 8000-10000kg / m 3 The sound velocity of the material of the bottom mold body 1 is 4200~5200m / s.

[0053] Specifically in this embodiment, taking the ultrasonic working frequency as 20kHz as an example, the material of the bottom mold body 1 in this embodiment is W18Cr4V high-speed steel, which has a Young's modulus of 190GPa and a density of 8500kg / m 3 , the speed of sound is 4728m / s.

[0054] S2. Based on the working frequency and acoustic characteristics, determine the geometric dimensions of the bottom mold body 1 that matches the working frequency and has a resonance direction opposite to the vibration direction of the upper welding head 5, and make the welding working surface 2 at the vibration antinode 3 position when the bottom mold body 1 resonates.

[0055] In step S2, determining the geometric dimensions of the bottom mold body 1 that matches the working frequency and has a resonance direction opposite to the vibration direction of the upper welding head 5 includes: estimating the geometric dimensions of the bottom mold through theoretical calculations, and then performing modal analysis and inherent characteristic analysis on the bottom mold bodies 1 of different geometric dimensions through finite element analysis software, and selecting the geometric dimensions that meet the design requirements.

[0056] Specifically, with one end of the bottom mold body 1 fixed, based on the Young's modulus, density and sound velocity of the material of the bottom mold body 1, the vibration mode function of the free vibration of the cantilever beam (derived from the Euler-Bernoulli beam theory) is used to calculate the length L and diameter D of the vibration rod 11 when the bottom mold body 1 produces a resonance of 1 / 4 wavelength (or an odd multiple of 1 / 4) at 20 kHz. In this embodiment, L is 60 to 80 mm, and D is 20 to 25 mm, and different combinations of length L and diameter D are listed.

[0057] Finite element analysis software is then used to perform modal and inherent characteristic analysis on the base mold body 1 of varying geometric dimensions, selecting the geometry that meets the design requirements. It should be noted that modal analysis involves using the surface of the base mold body 1 adjacent to the workbench as a fixed surface, and using mesh simulation to confirm whether the base mold body 1 produces a vibration mode that matches the upper welding head 5 at the welding frequency. The welding active surface must be located near a point of maximum amplitude. Inherent characteristic analysis involves determining whether the base mold body 1 exhibits a resonant mode of the aforementioned vibration mode near the welding frequency under the action of a horizontal excitation force, and confirming whether its amplitude is greater than 10 microns.

[0058] It should be added that if the analysis results of all geometric dimensions of the bottom mold body 1 do not meet the requirements of modal analysis and inherent characteristics, the length L and diameter D of the bottom mold body 1 need to be readjusted and analyzed until the bottom mold body 1 meets the design requirements.

[0059] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A resonant bottom die for ultrasonic welding, characterized in that: include: A bottom mold body (1) is arranged on a workbench of an ultrasonic welding system, wherein the bottom mold body (1) has a welding working surface (2) for supporting a workpiece (100); The material and geometric dimensions of the bottom mold body (1) determine that its inherent resonant frequency matches the preset ultrasonic working frequency of the ultrasonic welding system, and when the bottom mold body (1) is excited by the upper welding head (5) in the ultrasonic welding system, it can resonate along a predetermined direction, and the predetermined direction is configured to be a direction opposite to the vibration direction of the upper welding head (5), and the welding working surface (2) is set at the position of any vibration antinode (3) when the bottom mold body (1) resonates.

2. The resonant bottom mold for ultrasonic welding according to claim 1, characterized in that: The predetermined direction is a horizontal direction.

3. The resonant bottom mold for ultrasonic welding according to claim 1, characterized in that: The distance between the position of the vibration antinode (3) and the position of the adjacent vibration node (4) is an odd multiple of 1 / 4 wavelength of the resonance.

4. The resonant bottom mold for ultrasonic welding according to any one of claims 1 to 3, characterized in that: The bottom mold body (1) is arranged in a columnar shape, and has a fixed end connected to the workbench and a free end facing away from the workbench, and the welding working surface (2) is located at the free end.

5. The resonant bottom mold for ultrasonic welding according to any one of claims 1 to 3, characterized in that: The bottom mold body (1) comprises: a vibrating rod (11); and A fixed base (12) is arranged at one end of the vibration rod (11) close to the workbench, and the fixed base (12) is connected to the workbench.

6. The resonant bottom mold for ultrasonic welding according to claim 5, characterized in that: The vibration rod (11) and the fixed base (12) are integrally formed.

7. The resonant bottom mold for ultrasonic welding according to any one of claims 1 to 3, characterized in that: The bottom mold body (1) is made of steel, titanium alloy or aluminum alloy.

8. A method for designing a resonant bottom mold for ultrasonic welding, wherein: The following steps are involved: Determining the operating frequency of the ultrasonic welding system that the bottom mold body (1) cooperates with, selecting the material of the bottom mold body (1) and obtaining its acoustic characteristics; Based on the working frequency and the acoustic characteristics, the geometric dimensions of the bottom mold body (1) are determined to match the working frequency and have a resonance direction opposite to the vibration direction of the upper welding head (5), and the welding working surface (2) is at a vibration antinode (3) position when the bottom mold body (1) resonates.

9. The resonant bottom mode design method according to claim 8, characterized in that: The geometrical dimensions of the bottom mold body (1) that are determined to match the operating frequency and whose resonance direction is opposite to the vibration direction of the upper welding head (5) include: Finite element analysis software is used to perform modal analysis and inherent characteristic analysis on the bottom mold body (1) of different geometric dimensions, and a geometric dimension that meets the design requirements is selected.

10. A welding system comprising an acoustic component and an upper welding head (5), wherein the upper welding head (5) is connected to the acoustic component, characterized in that: The welding system further comprises a resonant bottom mold for ultrasonic welding as claimed in any one of claims 1 to 7, and the upper welding head (5) is configured to excite the resonant bottom mold for ultrasonic welding.

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