Welding method and device for assembling hemispherical resonator

Abstract

The present application relates to the technical field of hemispherical resonator assembly, and particularly relates to a welding method and device for an assembled hemispherical resonator, which comprises a vibration welding platform and a clamping assembly above the vibration welding platform; the vibration welding platform is used for bearing a sensitive base and providing a thermal field and a vibration field required for welding, and the clamping assembly is used for clamping a central shaft and feeding the central shaft into a central hole of the base. The platform is internally provided with a heating unit and a composite vibration ultrasonic transducer, which are configured to apply high-frequency vibration of superimposed vertical longitudinal waves and horizontal torsional waves to the base. The present application utilizes the thixotropic effect of high-frequency vibration to reduce the viscosity of molten solder, utilizes the ultrasonic cavitation effect to forcibly discharge bubbles at the bottom of a blind hole, and utilizes the acoustic radiation pressure generated by a vibration standing wave field to drive the central shaft to realize self-centering without friction in the hole. The device solves the problems of air lock virtual welding and rigid assembly jamming in the traditional process, and significantly improves the coaxiality and connection strength of the resonator assembly.

Description

Technical Field

[0001] This invention relates to the field of hemispherical resonator assembly technology, and in particular to a welding method and apparatus for assembled hemispherical resonators. Background Technology

[0002] As a high-precision, high-reliability solid-state inertial sensor, the hemispherical resonator gyroscope's core components mainly consist of a hemispherical resonator made of fused silica and a sensing base. In the manufacturing process of the assembled structure, the central shaft at the bottom of the hemispherical resonator needs to be precisely inserted and welded to the central hole of the sensing base. Traditional connection processes typically use low-melting-point alloys as solder. The solder is melted by external heating, and the central shaft is held by a robotic arm or precision jig and fed into the central hole of the base, which contains pre-filled molten solder. After cooling and solidification, a bond is formed. The quality of this welding directly determines the resonator's mechanical Q-value, impact resistance, and long-term zero-bias stability.

[0003] However, the following shortcomings still exist when welding blind or deep holes with micron-level gaps. First, the center hole of the sensitive base is usually a blind hole structure, and to ensure coaxiality, the fit clearance between the central shaft and the hole wall is extremely small (usually on the order of 10-20 microns). During the insertion of the central shaft, residual air at the bottom of the hole and microbubbles precipitated by the solder due to heat are easily trapped at the bottom, forming high-pressure air cushions or cavitation on the hole wall. This not only hinders the central shaft from sinking to the designed depth, but also reduces the welding contact area, resulting in incomplete welds and reduced connection strength. Second, the molten solder exhibits significant surface tension and viscous resistance within the tiny gaps, easily causing fluid jamming. Existing technologies mostly use rigid robotic arms to clamp and press down the central shaft. Once a slight initial eccentricity or tilt occurs, the rigid system cannot adaptively adjust to the fluid dynamics characteristics, easily leading to hard friction or scraping between the central shaft and the hole wall, causing damage to the quartz component. In addition, traditional welding processes enter a static natural cooling stage after heating stops. Due to the mismatch in thermal expansion coefficients of the solder, quartz, and metal substrate, the solder will generate huge tensile residual stress at the bonding interface during the volume shrinkage process as it changes from liquid to solid. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a welding method and apparatus for an assembled hemispherical resonator.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A welding device for an assembled hemispherical resonator is used to weld the central axis of the hemispherical resonator to the central hole of the sensitive base. The device includes a vibration welding platform and a clamping assembly. The vibration welding platform is used to support and fix the sensitive base and provide the thermal and vibration fields required for welding. The clamping assembly is disposed above the vibration welding platform and is used to clamp the central axis and feed it into the central hole of the sensitive base.

[0007] The vibration welding platform includes an internal heating unit and a composite vibration ultrasonic transducer located below it. The composite vibration ultrasonic transducer is configured to apply high-frequency vibration superimposed with vertical longitudinal waves and horizontal torsional waves to the sensitive base. The welding device uses high-frequency vibration to reduce the viscosity of the molten solder in the hole, uses the cavitation effect generated by the vertical longitudinal waves to expel bubbles, and uses the acoustic radiation pressure generated by the vibration standing wave field to drive the central shaft to achieve self-centering in the central hole.

[0008] Furthermore, the vibration frequency of the composite vibration ultrasonic transducer is set to match the first-order acoustic resonance frequency of the molten solder of the sensitive base, in order to form a standing wave field in the annular gap liquid within the central hole. The pressure node of the standing wave field is located on the geometric central axis of the central hole. The central axis, suspended in the acoustic field, is subjected to a net force pointing towards the sound pressure node. Since the central hole is an axisymmetric structure, its sound pressure node is naturally located on the geometric central axis. Therefore, without the need for high-precision closed-loop position control using external mechanical clamps, the central axis can be forcibly pushed from any initial eccentric position and locked at the center of the central hole solely by the force of the physical field.

[0009] Furthermore, the clamping assembly includes a rigid force-applying end, a flexible suspension spring, and an inertial mass block. The rigid force-applying end is connected to an external robotic arm, and the flexible suspension spring is connected between the rigid force-applying end and the inertial mass block, configured to isolate the vibration of the external robotic arm while allowing the central shaft to generate relative motion with respect to the central hole. The inertial mass block is connected to a chuck for clamping the central shaft. During the welding process, the vibration welding platform will vibrate. The flexible suspension spring breaks the constraint of the robotic arm stiffness on the central shaft in the horizontal direction, while the inertial mass block utilizes the inertial hysteresis effect generated by its large mass to cause the central shaft to generate phase hysteresis in space when the bottom sensitive base vibrates at high frequency, thereby creating a high-frequency relative shearing motion between the central shaft and the hole wall.

[0010] Furthermore, the bearing surface of the vibration welding platform is provided with a vacuum adsorption groove for rigidly coupling the sensitive base to the surface of the vibration source, ensuring that the vibration energy of the composite vibration ultrasonic transducer is transferred to the solder layer. The vacuum adsorption groove can adsorb the sensitive base onto the surface of the vibration welding platform, ensuring that the vibration energy can penetrate the metal base with low loss efficiency and be transferred to the internal liquid solder, thereby ensuring the intensity of cavitation effect and acoustic radiation pressure.

[0011] Furthermore, the heating unit employs a pulsed laser heater, with the laser beam focused on the sidewall of the central hole of the sensitive base. The heating unit melts the solder simultaneously with the start of vibration and maintains the molten state of the solder until the vibration stops. The laser beam can be focused at a specific height on the sidewall of the sensitive base, and heat rapidly melts the internal solder through metal thermal conduction, reducing thermal radiation and thermal shock to the quartz glass material of the upper hemispherical resonator, thus protecting the Q-value characteristics of the resonator. Simultaneously, the solder melts synchronously at the moment of vibration start, utilizing the vibrational thixotropic effect to accelerate heat diffusion, and maintaining the molten state until the vibration stops prevents premature solidification of the solder due to temperature fluctuations, thus preventing stress lock-in.

[0012] Furthermore, the clamping assembly integrates a laser displacement sensor, which monitors the axial settlement displacement of the central shaft relative to the sensitive base in real time. When the settlement displacement value stops changing, it is determined that the air bubble has been emptied and a stop vibration command is issued. In blind hole welding, the laser displacement sensor monitors the Z-axis coordinate of the central shaft in real time with micron-level precision. During the vibration venting stage, as the air bubble is expelled, the central shaft exhibits a stepped or continuous downward movement. When the sensor reading remains constant for a period of time, i.e., the settlement rate is zero, it can be determined that the air bubble at the bottom of the hole has been completely emptied and the central shaft has touched the bottom of the hole. At this point, a command is issued to stop vibration, realizing intelligent control of the process.

[0013] Furthermore, the drive controller of the composite vibration ultrasonic transducer is equipped with an intermittent modulation wave generation module, which inserts periodic pauses into the continuous high-frequency vibration signal. The surface tension restoring force of the molten solder during these pauses corrects the tilt angle of the central axis. The intermittent modulation wave reduces the solder viscosity during continuous high-frequency vibration, facilitating alignment. During the pauses, the acoustic force disappears, and the surface tension of the molten solder in the annular gap becomes dominant. According to the principle of minimum energy, the surface tension tends to flatten the liquid surface, thereby generating a restoring torque that automatically corrects the slight tilt of the central axis, ensuring coaxiality and perpendicularity.

[0014] A welding method for an assembled hemispherical resonator includes the following steps:

[0015] S1: Fix the sensitive base to the vibration welding platform and pre-place the solder in the center hole;

[0016] S2: Clamp the central shaft with the clamping assembly, aligning its axis with the central hole of the sensitive base;

[0017] S3: Start the heating unit to melt the solder, and at the same time start the horizontal torsional vibration mode of the composite vibration ultrasonic transducer to eliminate dry friction of the hole wall;

[0018] S4: Control the central shaft to insert molten solder, superimpose vertical longitudinal wave vibration mode, and use ultrasonic cavitation effect to remove air bubbles from the bottom of the hole;

[0019] S5: Maintain the vibration state and use the acoustic radiation pressure field to radially constrain the central axis, so that it can naturally sink to the theoretical depth and automatically center itself by gravity and inertial micro-motion;

[0020] S6: Stop vibration and allow to cool naturally. Release the central shaft after the solder has solidified to complete the assembly and welding.

[0021] Furthermore, in steps S3-S5 above, by monitoring the impedance or current phase change of the composite vibration ultrasonic transducer, the resonant frequency drift caused by the change in acoustic load of the system due to the insertion of the central shaft into the molten solder is identified in real time. Using the extreme value search algorithm, the driving frequency of the composite vibration ultrasonic transducer is dynamically adjusted so that it is always locked at the amplitude resonance point in the current state. This ensures that the acoustic standing wave field in the central hole always maintains the corresponding acoustic radiation pressure during the process of the central shaft being immersed in the solder, so as to maintain the self-centering constraint on the central shaft.

[0022] Furthermore, in step S6 above, after the heating unit is turned off, the composite vibration ultrasonic transducer is controlled to continue working, but its vibration amplitude is adjusted according to a linearly decreasing attenuation curve. The attenuation process of the vibration amplitude is synchronized with the cooling curve of the solder. The vibration is turned off after the solder temperature is at least 10 degrees Celsius lower than its solidus temperature. The mechanical vibration is used to break up the dendrites generated during the solidification process of the solder, refine the micro-grain structure of the weld, and release the residual stress at the interface caused by volume shrinkage.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention applies vertical longitudinal wave vibration through a composite vibration ultrasonic transducer. By utilizing the cavitation effect generated by ultrasonic waves in molten solder, the tiny bubbles attached to the hole wall and bottom are rapidly merged and floated up against gravity and discharged, completely eliminating the embolism effect. At the same time, the high-frequency vibration utilizes the thixotropic properties of non-Newtonian fluids to significantly reduce the apparent viscosity of molten solder, enabling it to fully fill every corner of the micron-level gaps, achieving effective wetting and connection deep within blind holes.

[0025] 2. This invention utilizes the acoustic radiation pressure generated by standing waves to push the central shaft toward the geometric center with the lowest energy, achieving physical active self-centering. The clamping assembly isolates the rigid constraints of the external robotic arm while vertically feeding, allowing the central shaft to undergo slight adaptive floating relative to the central hole under acoustic radiation pressure.

[0026] 3. This invention utilizes continuous mechanical vibration energy to break up the coarse dendrites generated at the solidification front and promote the formation of fine equiaxed crystals, thereby significantly improving the mechanical strength of the weld. At the same time, the micro-motion during the solidification process is equivalent to performing real-time dynamic aging treatment on the weld, solving the stress concentration problem caused by traditional static cooling, and significantly improving the long-term performance stability and environmental adaptability of the hemispherical harmonic oscillator. Attached Figure Description

[0027] Figure 1 This is a three-dimensional structural schematic diagram of the present invention;

[0028] Figure 2 This is a schematic diagram of the disassembled structure of the present invention;

[0029] Attached diagram labels: 1-Hemispherical resonator, 2-Central shaft, 3-Sensitive base, 4-Vibration welding platform, 5-Composite vibration ultrasonic transducer, 6-Rigid force application end, 7-Flexible suspension spring, 8-Inertial mass block, 9-Clamp, 10-Vacuum adsorption tank. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0031] Example 1, as Figure 1 , 2 As shown, the present invention discloses a welding device for an assembled hemispherical resonator, used to weld the central shaft 2 of the hemispherical resonator 1 to the central hole of the sensitive base 3. It includes a vibration welding platform 4 and a clamping assembly. The vibration welding platform 4 is used to support and fix the sensitive base 3 and provide the thermal and vibration fields required for welding. The clamping assembly is disposed above the vibration welding platform 4 and is used to clamp the central shaft 2 and feed it into the central hole of the sensitive base 3.

[0032] The vibration welding platform 4 includes an internal heating unit and a composite vibration ultrasonic transducer 5 located below it. The composite vibration ultrasonic transducer 5 is configured to apply high-frequency vibration superimposed with vertical longitudinal waves and horizontal torsional waves to the sensitive base 3. The welding device uses high-frequency vibration to reduce the viscosity of the molten solder in the hole, uses the cavitation effect generated by the vertical longitudinal waves to expel bubbles, and uses the acoustic radiation pressure generated by the vibration standing wave field to drive the central shaft 2 to achieve self-centering in the central hole.

[0033] The vibration frequency of the composite vibration ultrasonic transducer 5 is set to match the first-order acoustic resonance frequency of the molten solder in the sensitive base 3, in order to form a standing wave field in the annular gap liquid within the central hole. The pressure node of the standing wave field is located on the geometric central axis of the central hole. Specifically, according to the theory of acoustic radiation force, the central shaft 2 suspended in the sound field will be subjected to a net force pointing towards the sound pressure node (i.e., the lowest pressure point). Since the central hole is an axisymmetric structure, its sound pressure node is naturally located on the geometric central axis. Therefore, without the need for high-precision closed-loop position control using external mechanical clamps, the central shaft 2 can be forcibly pushed from any initial eccentric position and locked at the center of the central hole solely by the force of the physical field. This fundamentally eliminates the frictional damage and mechanical errors caused by traditional rigid contact alignment, achieving precise positioning.

[0034] Preferably, the composite vibration ultrasonic transducer 5 contains a set of piezoelectric ceramic wafers polarized along the thickness direction. When a high-frequency AC voltage signal is applied, based on the inverse piezoelectric effect, the ceramic wafers undergo thickness expansion and contraction deformation, driving the front cover plate to generate axial reciprocating piston motion, i.e., generating vertical longitudinal waves. This mode is mainly used to generate cavitation effects and acoustic radiation pressure. The composite vibration ultrasonic transducer 5 also integrates another set of piezoelectric ceramic wafers polarized tangentially along the circumference. When a specific AC voltage signal is applied, the ceramic wafers undergo shear deformation, driving the front cover plate to generate high-frequency reciprocating torsional motion around the central axis, i.e., generating horizontal torsional waves. This mode is mainly used to shear liquids, eliminate dry friction, and refine grains. By controlling the phase difference and amplitude ratio of the driving signals of the two sets of piezoelectric ceramics, the composite vibration ultrasonic transducer 5 can synthesize complex three-dimensional vibration trajectories in spiral or elliptical shapes at the output end. In this scheme, composite vibration is used to achieve the effect of simultaneously compacting and venting air from top to bottom while rubbing and centering from side to side.

[0035] The clamping assembly includes a rigid force-applying end 6, a flexible suspension spring 7, and an inertial mass block 8. The rigid force-applying end 6 is connected to an external robotic arm, and the flexible suspension spring 7 is connected between the rigid force-applying end 6 and the inertial mass block 8, configured to isolate the vibration of the external robotic arm while allowing the central shaft 2 to generate relative movement with respect to the central hole. The inertial mass block 8 is connected to a chuck 9 for clamping the central shaft 2. Specifically, during the welding process, the vibration welding platform 4 will vibrate. If the top clamping assembly is rigid, the central shaft 2 will be forced to remain stationary with the external robotic arm or generate random vibrations due to rigid transmission. The flexible suspension spring 7 breaks the constraint of the robotic arm stiffness on the central shaft 2 in the horizontal direction, while the inertial mass block 8 utilizes the inertial hysteresis effect generated by its large mass to cause the central shaft 2 to generate a phase lag in space when the bottom sensitive base 3 vibrates at high frequency, thereby creating a high-frequency relative shearing motion between the central shaft 2 and the hole wall. This relative motion significantly reduces fluid resistance and gives the central axis 2 the freedom to finely adjust in response to acoustic radiation pressure, ensuring that it falls into the center point.

[0036] The bearing surface of the vibration welding platform 4 is provided with a vacuum adsorption groove 10, which is used to rigidly couple the sensitive base 3 to the surface of the vibration source, ensuring that the vibration energy of the composite vibration ultrasonic transducer 5 is transferred to the solder layer. Specifically, since the sensitive base 3 is usually lightweight, when the composite vibration ultrasonic transducer 5 applies vibration, relying solely on gravity would cause relative sliding between the sensitive base 3 and the vibration welding platform 4, affecting subsequent welding operations. The vacuum adsorption groove 10 can adsorb the sensitive base 3 onto the surface of the vibration welding platform 4, ensuring that the vibration energy can penetrate the metal base with low loss efficiency and be transferred to the molten solder inside, thereby ensuring the intensity of cavitation effect and acoustic radiation pressure.

[0037] The heating unit employs a pulsed laser heater, with the laser beam focused on the sidewall of the central hole of the sensitive base 3. The heating unit melts the solder simultaneously with the start of vibration and maintains the molten state of the solder until the vibration stops. Specifically, the laser beam can be focused at a specific height on the sidewall of the sensitive base 3. Heat is rapidly melted through metal thermal conduction, minimizing thermal radiation and thermal shock to the quartz glass material of the upper hemispherical resonator 1, thus protecting the Q-value characteristics of the resonator. Simultaneously, the solder melts at the instant vibration starts, utilizing the vibrational thixotropic effect to accelerate heat diffusion, and maintaining the molten state until vibration stops prevents premature solidification of the solder due to temperature fluctuations, thus preventing stress lock-in.

[0038] The clamping assembly integrates a laser displacement sensor, which monitors the axial settlement displacement of the central shaft 2 relative to the sensitive base 3 in real time. When the settlement displacement value stops changing, it is determined that the air bubble has been vented, and a stop vibration command is issued. Specifically, in blind hole welding, the presence of air bubbles forms an air cushion, preventing the central shaft 2 from settling to the designed depth. The laser displacement sensor monitors the Z-axis coordinate of the central shaft in real time with micron-level precision. During the vibration venting stage, as the air bubble is expelled, the central shaft 2 exhibits a stepped or continuous downward movement. When the sensor reading remains constant for a period of time, i.e., the settlement rate is zero, it can be determined that the air bubble at the bottom of the hole has been completely vented, and the central shaft 2 has touched the bottom of the hole or the limiting surface. At this point, a command is issued to stop vibration, realizing intelligent control of the process.

[0039] The drive controller of the composite vibration ultrasonic transducer 5 is equipped with an intermittent modulation wave generation module, which inserts periodic pauses into the continuous high-frequency vibration signal. The surface tension restoring force of the molten solder during these pauses corrects the tilt angle of the central axis 2. Specifically, the intermittent modulation wave reduces the solder viscosity during continuous high-frequency vibration, facilitating alignment. During the pauses, the acoustic force disappears, and the surface tension of the molten solder in the annular gap becomes dominant. According to the principle of minimum energy, the surface tension tends to flatten the liquid surface, thereby generating a restoring torque that automatically corrects the slight tilt of the central axis 2, ensuring coaxiality and perpendicularity.

[0040] Example 2, based on Example 1, proposes a welding method for an assembled hemispherical resonator, including the following steps:

[0041] S1: Fix the sensitive base 3 on the vibration welding platform 4 and pre-place the solder in the center hole; the robot places the sensitive base 3 in the center of the vibration welding platform 4. At this time, the vacuum adsorption system of the vibration welding platform 4 is activated, and the bottom surface of the sensitive base 3 is tightly adsorbed to the surface of the vibration source by using negative pressure.

[0042] S2: The central shaft 2 is clamped by the clamping assembly, so that its axis is aligned with the center hole of the sensitive base 3; the chuck 9 of the clamping assembly grabs the upper end of the central shaft 2 of the hemispherical resonator 1, and the mechanical arm drives the rigid force application end 6 to descend, moving the central shaft 2 directly above the center hole of the sensitive base 3 for alignment under mechanical limitation.

[0043] S3: The heating unit is activated to melt the solder, and the horizontal torsional vibration mode of the composite vibration ultrasonic transducer 5 is activated simultaneously to eliminate dry friction on the hole wall; the pulsed laser heater is activated to focus and heat the side wall of the sensitive base 3, so that the solder in the hole is rapidly heated to above the melting point and turns into a liquid state. At the same time, before the central shaft 2 comes into contact with the solder, the horizontal torsional vibration mode of the composite vibration ultrasonic transducer 5 is activated first.

[0044] S4: Control the insertion of the central shaft 2 into the molten solder, superimpose the vertical longitudinal wave vibration mode, and use the ultrasonic cavitation effect to remove the air bubbles at the bottom of the hole; control the robotic arm to feed on the Z-axis, slowly insert the central shaft 2 into the molten solder, and after insertion, superimpose and start the vertical longitudinal wave vibration mode. At this time, the system is in a multi-dimensional composite vibration state.

[0045] S5: Maintain the vibration state and use the acoustic radiation pressure field to radially constrain the central shaft 2, allowing it to naturally sink to the theoretical depth and automatically center itself by gravity and inertial micro-motion; when the central shaft 2 approaches the theoretical depth, maintain the composite vibration state. At this time, the resonant frequency of the system is tracked in real time through phase-locked loop technology to ensure the formation of a stable acoustic standing wave field in the annular gap liquid inside the central hole.

[0046] S6: Stop vibration and allow to cool naturally. After the solder solidifies, release the central shaft 2 to complete the assembly and welding. After confirming that the central shaft 2 is in place and that the air bubbles have been expelled, turn off the heating unit.

[0047] Example 3, based on Example 2, proposes a specific implementation process for welding an assembled hemispherical harmonic oscillator.

[0048] In steps S3-S5 above, by monitoring the impedance or current phase changes of the composite vibration ultrasonic transducer 5, the resonant frequency drift caused by the acoustic load change of the system due to the insertion of the central shaft 2 into the molten solder is identified in real time. Using an extreme value search algorithm, the driving frequency of the composite vibration ultrasonic transducer 5 is dynamically adjusted to keep it locked at the amplitude resonance point in the current state. This ensures that the acoustic standing wave field in the central hole maintains the corresponding acoustic radiation pressure during the immersion of the central shaft 2 into the solder, thus maintaining the self-centering constraint on the central shaft 2. Specifically, the acoustic load characteristics of the system change dynamically during the welding process. Initially, the sensitive base 3 and the solder vibrate. When the central shaft 2 is inserted into the molten solder, the equivalent mass of the system increases, and the damping also changes due to fluid-structure interaction, causing the natural resonant frequency of the entire system to drift. If the driving power supply remains unchanged at the initial frequency, the amplitude will drop sharply, the acoustic radiation pressure will weaken, and centering failure will occur. By monitoring the impedance characteristics or phase in real time, and in conjunction with the extreme value search algorithm, the power supply can automatically track and lock onto this drifting resonant frequency. This ensures that no matter how deep the central shaft 2 is inserted, the system always operates at its maximum power output point, maintaining the strongest acoustic levitation constraint.

[0049] In step S6 above, after the heating unit is turned off, the composite vibration ultrasonic transducer 5 continues to operate, but its vibration amplitude is adjusted according to a linearly decreasing attenuation curve. The attenuation process of the vibration amplitude is synchronized with the cooling curve of the solder. Vibration is stopped only after the solder temperature is at least 10 degrees Celsius below its solidus temperature. Mechanical vibration is used to break up the dendrites generated during solder solidification, refining the microstructure of the weld and releasing residual interfacial stress caused by volume shrinkage. Specifically, conventional static natural cooling causes volume shrinkage when the solder transitions from liquid to solid. Due to the difference in thermal expansion coefficients between quartz and metal, huge tensile stress is generated at the interface, and coarse dendrites are easily formed, leading to a weak connection. This solution utilizes continuous mechanical vibration energy to physically break up the growing dendritic crystals in the solid-liquid coexistence zone, promoting their transformation into fine and uniform equiaxed crystals, significantly improving the mechanical strength and impact resistance of the weld. Meanwhile, the micro reciprocating motion caused by vibration allows the material to compensate for volume shrinkage through micro-plastic deformation at the moment of solidification, thereby releasing residual stress at the beginning of its generation and greatly improving the long-term stability of the device.

[0050] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A welding method for an assembled hemispherical resonator, the welding method being implemented by a welding device, the welding device being used to weld the central shaft (2) of the hemispherical resonator (1) to the central hole of the sensitive base (3), comprising a vibration welding platform (4) and a clamping assembly, the vibration welding platform (4) being used to support and fix the sensitive base (3) and provide the thermal and vibration fields required for welding, the clamping assembly being disposed above the vibration welding platform (4) for clamping the central shaft (2) and feeding it into the central hole of the sensitive base (3); The vibration welding platform (4) includes a heating unit inside and a composite vibration ultrasonic transducer (5) below it. The composite vibration ultrasonic transducer (5) is configured to apply high-frequency vibration superimposed with vertical longitudinal waves and horizontal torsional waves to the sensitive base (3). The welding device uses high-frequency vibration to reduce the viscosity of the molten solder in the hole, uses the cavitation effect generated by the vertical longitudinal waves to expel bubbles, and uses the acoustic radiation pressure generated by the vibration standing wave field to drive the central shaft (2) to achieve self-centering in the central hole. The vibration frequency of the composite vibration ultrasonic transducer (5) is set to match the first-order acoustic resonance frequency of the molten solder of the sensitive base (3) to form a standing wave field in the annular gap liquid in the central hole. The pressure node of the standing wave field is located on the geometric central axis of the central hole. The heating unit adopts a pulsed laser heater, and the beam is focused on the side wall of the central hole of the sensitive base (3). The heating unit melts the solder when the vibration is turned on and maintains the molten state of the solder before the vibration stops. The drive controller of the composite vibration ultrasonic transducer (5) is equipped with an intermittent modulation wave generation module, which is used to insert periodic pauses in the continuous high-frequency vibration signal and use the surface tension restoring force of the molten solder in the pause gap to correct the attitude tilt angle of the central axis (2). The welding method includes the following steps: S1: Fix the sensitive base (3) on the vibration welding platform (4) and pre-place the welding material in the center hole; S2: Clamp the central shaft (2) with the clamping assembly so that its axis is aligned with the central hole of the sensitive base (3); S3: Start the heating unit to melt the solder, and at the same time start the horizontal torsional vibration mode of the composite vibration ultrasonic transducer (5) to eliminate dry friction of the hole wall; S4: Control the central shaft (2) to insert molten solder, superimpose vertical longitudinal wave vibration mode, and use ultrasonic cavitation effect to remove air bubbles at the bottom of the hole; S5: Maintain the vibration state and use the acoustic radiation pressure field to radially constrain the central axis (2), so that it can naturally sink to the theoretical depth and automatically center itself by gravity and inertial micro-motion; S6: Stop the vibration and allow it to cool naturally. After the solder solidifies, release the central shaft (2) to complete the assembly and welding.

2. The welding method according to claim 1, characterized in that: In steps S3-S5 above, by monitoring the impedance or current phase change of the composite vibration ultrasonic transducer (5), the resonance frequency drift caused by the change in acoustic load of the system due to the insertion of the central shaft (2) into the molten solder is identified in real time. Using the extreme value search algorithm, the driving frequency of the composite vibration ultrasonic transducer (5) is dynamically adjusted so that it is always locked at the amplitude resonance point in the current state, ensuring that the acoustic standing wave field in the central hole always maintains the corresponding acoustic radiation pressure during the process of the central shaft (2) being immersed in the solder, so as to maintain the self-centering constraint of the central shaft (2).

3. The welding method according to claim 1, characterized in that: In step S6 above, after the heating unit is turned off, the composite vibration ultrasonic transducer (5) is controlled to continue to work, but its vibration amplitude is adjusted according to the linearly decreasing attenuation curve. The attenuation process of the vibration amplitude is synchronized with the cooling curve of the solder. The vibration is turned off after the solder temperature is at least 10 degrees Celsius lower than its solidus temperature. The mechanical vibration is used to break the dendrites generated during the solidification of the solder, refine the micro-grain structure of the weld, and release the residual stress at the interface caused by volume shrinkage.

4. The welding method according to claim 1, characterized in that: The clamping assembly includes a rigid force-applying end (6), a flexible suspension spring (7), and an inertial mass block (8). The rigid force-applying end (6) is connected to an external robotic arm. The flexible suspension spring (7) is connected between the rigid force-applying end (6) and the inertial mass block (8) and is configured to isolate the vibration of the external robotic arm while allowing the central shaft (2) to generate relative motion with respect to the central hole. The inertial mass block (8) is connected to a chuck (9) for clamping the central shaft (2).

5. The welding method according to claim 4, characterized in that: The bearing surface of the vibration welding platform (4) is provided with a vacuum adsorption groove (10) to rigidly couple the sensitive base (3) to the vibration source surface, so as to ensure that the vibration energy of the composite vibration ultrasonic transducer (5) is transferred to the solder layer.

6. The welding method according to claim 4, characterized in that: The clamping assembly is equipped with a laser displacement sensor, which is used to monitor the axial settlement displacement value of the central shaft (2) relative to the sensitive base (3) in real time. When the settlement displacement value is no longer changing, it is determined that the bubble has been emptied and a stop vibration command is issued.

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