Ultrasonic assisted welding equipment and method capable of accurately applying pressure

Abstract

The present application discloses an ultrasonic assisted welding equipment and method that can accurately apply pressure. The equipment of the present invention is composed of an ultrasonic welding head, a pressure sensor, a transition spring, a limit plate, a limit contact piece, a motion module and a servo controller. In this technical solution, the motion module uses the transition spring to push the ultrasonic welding head to achieve feed pressurization. After the ultrasonic welding head contacts the sample, the transition spring generates a continuously changing loading pressure on the ultrasonic welding head, thereby improving the stability and accuracy of the loading pressure control. When the motion module is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor, the limit plate contacts the limit contact piece, and the servo controller controls the motion module to cut off the power output. The transition spring immediately drives the moving seat to reverse feed to release the compressive elastic force acting on the limit plate, thereby improving the timeliness of the early warning under high-speed loading.

Description

Technical Field

[0001] The present application relates to the technical field of ultrasonic welding, and in particular to an ultrasonic assisted welding device and method capable of applying pressure precisely. Background Art

[0002] In recent years, ultrasonic welding has attracted widespread attention as an emerging welding technology. This technology is an advanced technology that uses high-frequency ultrasonic vibration and pressure to make the base material plastically deform or produce cavitation effect on the welding surface to form an interface bond by using the energy of the acoustic field. This technology is suitable for the connection and manufacturing of difficult-to-wet metals and thermoplastic materials, and is therefore widely used in aerospace, communications, batteries and other industries.

[0003] However, ultrasonic welding equipment mostly uses longitudinal vibration, which requires stable and accurate pressure to be applied during ultrasonic welding to ensure that the welding surfaces are tightly fitted while avoiding pressure load changes. In addition, in order to improve welding accuracy and quality, a step-by-step ultrasonic welding scheme is often adopted during connection, that is: first, a stronger ultrasonic vibration is applied under a smaller welding pressure to achieve accurate alignment of the sample, and then a weaker ultrasonic vibration is applied under a larger welding pressure to achieve a firm connection. However, this step-by-step ultrasonic welding scheme places higher requirements on the loading accuracy and response speed of the welding device.

[0004] At present, there is still a lack of ultrasonic assisted welding equipment and methods that can accurately apply pressure on the market. Patent No. CN201721280155.0 discloses a cylinder tightening device for ultrasonic welding. The patent uses a driving cylinder to drive the turntable adjustment block to move longitudinally, and pressurization is achieved by lifting the cylinder, but the cylinder pressurization adjustment accuracy is low and pressure step loading cannot be achieved. Patent No. CN201910018517.6 discloses an electro-hydraulic composite servo loading method and device. The patent uses a servo motor to drive the lead screw to push the hydraulic cylinder to output loading pressure, and automatic loading is achieved by equipping a servo controller. Patent No. CN202111666981.X discloses a welding method and system based on servo motor pressure control. The invention uses a servo motor to drive the ultrasonic welding head for feedback pressurization and triggers ultrasonic vibration through PID position adjustment.

[0005] In the above-mentioned related technologies, although equipped with pressure loading for the ultrasonic welding head, the pressure loading is generated by the feeding of the motion module, and the loading pressure is removed by the return movement of the motion module. This method does not have a high enough control response speed for the welding pressure, and the loading pressure control is not accurate enough. Summary of the invention

[0006] In view of this, the present application provides an ultrasonic assisted welding equipment and method that can accurately apply pressure, which can improve the accuracy of pressure control and the timeliness of response.

[0007] In a first aspect, the present application provides an ultrasonic assisted welding device capable of accurately applying pressure, comprising:

[0008] An ultrasonic welding head for producing welding action;

[0009] A pressure sensor for detecting pressure load in real time;

[0010] A movable seat is fixedly provided with a spring pressure pin and a limit contact piece;

[0011] A motion module, used for driving the movable seat to move linearly back and forth relative to the ultrasonic welding head;

[0012] A transition spring, mounted on the spring pressure pin;

[0013] A limiting plate, used to be compressed by the elastic force of one end of the transition spring away from the spring pressure pin, and the limiting plate is fixedly connected to the ultrasonic welding head;

[0014] a limit contact piece, configured with the limit piece to form a limit switch;

[0015] a servo controller, electrically connected to the pressure sensor and the limit contact, to control the feeding of the motion module;

[0016] Among them, the motion module uses the transition spring to push the ultrasonic welding head to achieve feed pressurization, and the transition spring generates a continuously changing loading pressure on the ultrasonic welding head; when the motion module is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor, the limit plate contacts the limit contact piece, and the servo controller controls the motion module to cut off the power output. The transition spring releases the compressive elastic force acting on the limit plate by driving the moving seat to reverse feed, thereby immediately removing the loading pressure caused by the compressive elastic force on the ultrasonic welding head.

[0017] Optionally, it further comprises a support column with both ends mounted on the spring pressure pin and the limiting plate, and the transition spring is sleeved on the outer circumference of the support column.

[0018] Optionally, the motion module is disposed on a fixed seat for carrying the linear motion of the movable seat.

[0019] Optionally, the servo controller for generating a control instruction for causing the motion module to receive a stop driving is also configured to preset a target welding pressure, and when the actual pressure of the ultrasonic welding head exceeds the target welding pressure, the servo controller controls the motion module to stop driving.

[0020] Optionally, a pressure sensor is further included, two ends of the pressure sensor are fixedly connected to the limit plate and the ultrasonic welding head, and the pressure sensor is electrically connected to the servo controller.

[0021] Optionally, the limit switch contact piece and the limit plate cooperate, that is, when the forward feed stroke of the ultrasonic welding head reaches a predetermined stroke, the transition spring can instantly drive the return stroke of the ultrasonic welding head.

[0022] In a second aspect, the present application provides an ultrasonic assisted welding device capable of accurately applying pressure to perform a step-by-step ultrasonic welding method, comprising:

[0023] S1: Assemble the polished and cleaned welding materials, and adjust the relative position to ensure that the sample and the ultrasonic welding head are on the same central axis;

[0024] S2: Raise the motion module to the upper limit of motion, adjust the position of the pressure sensor and the limit contact, set the contact pressure, safety factor, fast feed speed, slow feed speed, target pressure 1, target pressure 2 and holding time;

[0025] S3: Edit the program, the motion module first pressurizes at a fast feed rate to reach the contact pressure, then adjusts the pressure to the value of target pressure 1 at a slow feed rate and applies the first ultrasonic vibration, then adjusts the pressure to the value of target pressure 2 and applies the second ultrasonic vibration;

[0026] S4: After the pressure maintenance is completed, the welding pressure is released and the weldment is taken out.

[0027] The ultrasonic assisted welding equipment that can accurately apply pressure provided above, the motion module generates loading pressure on the ultrasonic horn by driving the moving seat to move forward in a straight line relative to the ultrasonic horn, in which process, the transition spring will apply a compressive elastic force to the limit plate, and the compressive elastic force cooperates with the motion module drive to realize pressure loading. When the motion module is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor, the motion module receives a control instruction to stop driving, and the transition spring releases the compressive elastic force acting on the limit plate by driving the moving seat to reverse feed, thereby removing the welding pressure on the ultrasonic horn. On the one hand, since the adjustment of the loading pressure brought by the transition spring is a continuous change rather than a step-like change, the stability and accuracy of the loading pressure control are improved. On the other hand, the cooperation of the limit contact and the limit plate limits the forward feed stroke of the ultrasonic horn, and the transition spring can immediately drive the return stroke of the ultrasonic horn, thereby avoiding overload damage to the pressure sensor, improving the response timeliness of removing the welding pressure, and improving the stability and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0029] Figure 1 A schematic diagram of a working state of an ultrasonic assisted welding equipment capable of accurately applying pressure provided in an embodiment of the present application.

[0030] Figure 2 This is a welding appearance diagram of an ultrasonic assisted welding operation according to an embodiment of the present application.

[0031] Figure 3 This is a welding appearance diagram of an ultrasonic assisted welding operation according to another embodiment of the present application.

[0032] The components in the figure are marked as follows:

[0033] 1-ultrasonic welding head; 2-ultrasonic transducer; 31-pressure sensor; 32-limiting plate; 33-support column; 34-transition spring; 35-spring pressure pin; 36-moving seat; 37-limiting contact piece; 4-motion module; 5-servo controller; 6-fixed seat; 7-slide plate; 8-guide rail. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0035] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0036] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0038] Before introducing the technical solution of the present application, it is necessary to explain the background of the invention of the present application.

[0039] It is common that in the related art, the loading pressure on the ultrasonic horn 1 depends on the motion module 4, that is, the motion module 4 drives the linear motion of the forward feed of the ultrasonic horn 1 to generate loading pressure on the ultrasonic horn 1, and the reverse return generates unloading pressure. Since the linear motion stroke of the motion module 4 is directly related to the accuracy of the pressure loaded on the ultrasonic horn 1. In order to improve the accuracy of the loading pressure, it is usually focused on improving the accuracy of the minimum feed amount of the motion module 4 (which can be understood as the minimum adjustment value of the feed amount), that is, the smaller the minimum feed amount, the more accurate the control of the loading pressure. However, the improvement of the accuracy of the minimum feed amount is very limited at the technical level. The adjustment of the forward feed amount of the motion module 4 is determined by the minimum feed amount, that is, the level of the forward feed amount is an integer multiple of the minimum feed amount, which results in the adjustment of the forward feed amount of the motion module 4 being discrete (or called step-type), non-continuous. In addition, the longitudinal vibration of the ultrasonic horn 1 in the working state will also react to the motion module 4 to cause pressure instability and load variation. Therefore, the motion module 4 directly drives the ultrasonic horn 1 to bring about a very limited control accuracy of the loading pressure.

[0040] More importantly, pressure loading usually faces a high driving speed, and steps such as pressure relief or early warning protection rely on the motion module 4 to start the return movement only when the actual pressure of the ultrasonic horn 1 is obtained. That is, the motion module 4 needs a certain amount of time to respond to the actual pressure of the ultrasonic horn 1. This response is not only reflected in the feedback of the actual pressure of the ultrasonic horn 1 to the motion module 4, but also in the response of the driving stroke caused by the system deformation or gap of the power component of the motion module 4, that is, there is a certain amount of time between the motion module 4 generating a driving instruction and the ultrasonic horn 1 actually generating a driving action. The pressure sensor 31 is very prone to overload damage, and the equipment reliability and stability are poor.

[0041] Based on the inventor's awareness of the above-mentioned difficulties, the inventor has proposed an ultrasonic assisted welding equipment that can accurately apply pressure. The motion module 4 uses the transition spring 34 to push the ultrasonic welding head 1 to achieve feed pressurization. In this process, the transition spring 34 will apply a compressive elastic force to the limit plate 32, and the compressive elastic force cooperates with the motion module 4 to drive. According to Hooke's quantitative method, it can be known that the change of the compressive elastic force is a linear function with the deformation variable, so that the adjustment of the loading pressure is a continuous change rather than a step-like, thereby achieving stable and accurate pressure loading. In addition, when the motion module is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor, the servo controller 5 controls the motion module 4 to cut off the power output, that is, the motion module 4 is directly powered off and its servo stops loading, and the transition spring 34 releases the compressive elastic force acting on the limit plate 32 by driving the moving seat 36 to reverse feed, thereby immediately removing the welding pressure caused by the compressive elastic force on the ultrasonic welding head 1. The cooperation of the limiting contact member 37 and the limiting sheet 32 ​​limits the forward feeding stroke of the ultrasonic horn 1, and the transition spring 34 can instantly drive the ultrasonic horn 1 to return, thereby avoiding overload damage to the pressure sensor 31 and improving the stability and reliability of the device. Thus, the present invention is created.

[0042] refer to Figure 1 The present application provides an ultrasonic assisted welding device capable of accurately applying pressure, comprising:

[0043] An ultrasonic welding head 1, used to produce welding action;

[0044] A pressure sensor 31 for detecting pressure load in real time;

[0045] A movable seat 36 is fixedly provided with a spring pressure pin 35 and a limit contact member 37;

[0046] A motion module 4, used to drive the moving seat 36 to perform linear reciprocating motion relative to the ultrasonic welding head 1;

[0047] A transition spring 34, mounted on the spring pressure pin 35;

[0048] A limiting piece 32, used to be compressed by the elastic force of one end of the transition spring 34 away from the spring pressing pin 35, and the limiting piece 32 is fixedly connected to the ultrasonic welding head 1;

[0049] a limit contact member 37 mounted on the movable seat 36 and configured with the limit plate 32 to form a limit switch;

[0050] a servo controller 5, electrically connected to the pressure sensor 31 and the limit contact 37, to control the feeding of the motion module 4;

[0051] Among them, the motion module 4 uses the transition spring 34 to push the ultrasonic welding head 1 to achieve feed pressurization, and the transition spring 34 generates a continuously changing loading pressure on the ultrasonic welding head 1; when the motion module 4 is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor 31, the limit plate 32 contacts the limit contact piece 37, and the servo controller 5 controls the motion module 4 to cut off the power output, that is, the motion module 4 is directly powered off and its servo stops loading, and the transition spring 34 releases the compressive elastic force acting on the limit plate 32 by driving the moving seat 36 to reverse feed, thereby immediately removing the loading pressure caused by the compressive elastic force on the ultrasonic welding head 1.

[0052] The type and size of the transition spring 34 can be selected according to the loading range and sensitivity.

[0053] The limit contact member 37 has been widely used in various fields. Its working principle and type, model or source are well known and will be briefly described again.

[0054] It has been mentioned above that "the motion module 4 is used to drive the linear reciprocating motion of the above-mentioned moving seat 36 relative to the above-mentioned ultrasonic horn 1". Here, the installation relationship between the motion module 4, the moving seat 36, and the ultrasonic horn 1 is easy to think of. As a demonstrative implementation method, a fixed seat 6 can be provided to carry the linear motion of the moving seat 36, and both the fixed seat 6 and the moving seat 36 can be plate-shaped. The motion module 4 can be fixedly mounted on the fixed seat 6, and the power component of the motion module 4 is fixedly connected to the moving seat 36. A slide plate 7 is fixedly arranged on the moving seat 36, and a guide rail 8 is fixedly arranged on the fixed seat 6. The guide rail 8 cooperates with the slide plate 7 so that the moving seat 36 can slide linearly on the fixed seat 6. The ultrasonic horn 1 can be located on the fixed seat 6 or on the non-power component of the motion module 4, so that the spring pressure pin 35 and the limit contact member 37 are driven to move relative to the ultrasonic horn 1 as the moving seat 36 is driven.

[0055] The motion module 4 can be implemented by any linear reciprocating motion mechanism such as an electric cylinder or electric push rod known in the art. The minimum feed distance of the motion module 4 is maintained at 0.02-0.1 mm or other forms.

[0056] As an exemplary implementation, an ultrasonic transducer 2 may be configured, and countersunk holes (not shown in the figure) are added to the upper and lower ends of the ultrasonic transducer 2, which are connected to the ultrasonic welding head 1 by a connection method such as bolts.

[0057] In a typical embodiment, it also includes a support column 33 with two ends mounted on the spring pressure pin 35 and the limiting plate 32 , and the transition spring 34 is sleeved on the outer circumference of the support column 33 .

[0058] In a typical embodiment, the servo controller 5 used to generate a control instruction for causing the motion module 4 to receive a stop driving is also configured to preset a target welding pressure. When the actual pressure of the ultrasonic welding head 1 exceeds the target welding pressure, the servo controller 5 controls the motion module 4 to stop driving.

[0059] In a typical embodiment, a pressure sensor 31 is further included. Two ends of the pressure sensor 31 are fixedly connected to the limit plate 32 and the ultrasonic welding head 1 . The pressure sensor 31 is electrically connected to the servo controller 5 .

[0060] Thus, through the arrangement of the pressure sensor 31 and the servo controller 5, the design objective is to realize the real-time detection of the pressure load and the feedback regulation of the feeding motion of the motion module 4. The servo controller 5 adopts the segmented loading mode of the pressure contact control. When the pressure is less than the contact threshold, the motion module 4 feeds quickly. As the pressure exceeds the contact threshold, the servo controller 5 performs speed limiting processing on the motion module 4.

[0061] The servo controller 5 adopts a segmented loading mode of pressure contact control, and the contact pressure, target pressure, feed speed of the motion module 4 at different stages and the pressure holding time can be preset. The feed speed after reaching the contact pressure should be less than the speed before reaching it. Once the measured pressure of the pressure sensor 31 reaches the contact pressure, the servo controller 5 will limit the speed of the motion module 4, and perform PI adjustment according to the difference between the measured pressure and the given target pressure, so as to ensure rapid pressure loading while avoiding problems such as overload and overshoot.

[0062] The servo controller 5 automatically generates the overload pressure by multiplying the target pressure by the safety factor. When the measured pressure exceeds the overload pressure, the servo controller 5 senses and sends an excitation signal for power-off protection, and the motion module 4 stops the pressurization action, so that it has an overload protection function. The safety factor can be in the range of 1 to 3.

[0063] It is easy to imagine that, in practice, when the measured pressure reaches the target pressure, the servo controller 5 will start recording the pressure holding time.

[0064] The pressure sensor 31 can be a tension and compression bidirectional sensor, with a range of 0.5 to 2000N, an available temperature range of -50 to 300°C, a hysteresis of 0.02 to 5%, and a sensitivity error of 0.01 to 5%.

[0065] The servo controller 5 can be selected as a PID controller or a PLC controller.

[0066] It is understandable that the distance between the limiting piece 32 and the limiting contact member 37 multiplied by the elastic coefficient of the transition spring 34 should be smaller than the range limit of the pressure sensor 31 .

[0067] The servo controller 5 can realize real-time detection of the pressure load and feedback regulation of the feed motion of the motion module 4, and provide constant pressure, variable pressure loading conditions and load detection functions through editing programs.

[0068] Now, the operation process of the ultrasonic assisted welding equipment that can accurately apply pressure in the present application is described in several common application scenarios. It should be noted that this common implementation scheme cannot be used as a basis for understanding the essential feature identification of the technical problem claimed to be solved by the present application, and it is only a demonstration.

[0069] Application Example 1:

[0070] The Ni / Sn-Pb composite solder reinforced by homemade foam Ni was used to perform single pressure and ultrasonic brazing connection of silver-plated Al alloy by ultrasonic assisted welding equipment which can apply precise pressure.

[0071] Specific steps:

[0072] 1. Use wire cutting machine to cut the surface silver-plated Al alloy into 10×10×3mm 3 The homemade Ni / Sn-Pb composite solder was cut and rolled into 10×10×0.1mm 3 The size of the experimental material was then polished and ultrasonically cleaned;

[0073] 2. Place the workpieces to be welded with the solder assembled on a heating plate with a positioning plate, and adjust the relative positions of the positioning plate and the ultrasonic welding head 1 to ensure that they are on the same central axis;

[0074] 3. Raise the motion module 4 to the upper limit of motion, and adjust the position of the pressure sensor 31 and the limit contact 37. Set the contact pressure, target pressure, safety factor, fast feed speed, slow feed speed and holding time to 0.03MPa, 0.6MPa, 1.5, 150mm / s, 10mm / s and 30min respectively;

[0075] 4. The ultrasonic frequency is selected as 20kHz, the ultrasonic time is set to 8s, and the ultrasonic power is set to 120W;

[0076] 5. Set the heating plate brazing temperature to 250°C and keep it warm for 30 minutes. After the solder melts, start the program;

[0077] 6. The motion module 4 first pressurizes at a fast feed rate to reach the contact pressure, then adjusts the pressure to the target pressure at a slow feed rate, and applies ultrasonic vibration;

[0078] 7. After the pressure holding is completed, wait for the weldment to cool to room temperature, release the welding pressure and take out the weldment.

[0079] refer to Figure 2, is the SEM image of the silver-plated Al alloy joint. Although the joint can be welded after single pressure and ultrasonic treatment, there are obvious holes in the weld layer, the solder overflow is serious, and the connection quality is not high.

[0080] Application Example 2:

[0081] The self-made Ni foam reinforced Ni / Sn-Pb composite solder was used to perform step-by-step ultrasonic-assisted brazing of silver-plated Al alloy by ultrasonic-assisted welding equipment that can apply precise pressure.

[0082] Specific steps:

[0083] 1. Use wire cutting machine to cut the surface silver-plated Al alloy into 10×10×3mm 3 The homemade Ni / Sn-Pb composite solder was cut and rolled into 10×10×0.1mm 3 The size of the experimental material was then polished and ultrasonically cleaned;

[0084] 2. Place the workpieces to be welded with the solder assembled on a heating plate with a positioning plate, and adjust the relative positions of the positioning plate and the ultrasonic welding head 1 to ensure that they are on the same central axis;

[0085] 3. Raise the motion module 4 to the upper limit of motion, and adjust the position of the pressure sensor 31 and the limit contact 37. Set the contact pressure, safety factor, fast feed speed, slow feed speed and holding time to 0.03MPa, 1.3, 150mm / s, 10mm / s and 30min respectively;

[0086] 4. The ultrasonic frequency was selected as 20kHz, and a two-step brazing procedure was set up: the target pressure 1, ultrasonic power 1, and ultrasonic time 1 were set to 0.4MPa, 120W, and 3s respectively; the target pressure 2, ultrasonic power 2, and ultrasonic time 2 were set to 0.6MPa, 105W, and 5s respectively;

[0087] 5. Set the heating plate brazing temperature to 250°C and keep it warm for 30 minutes. After the solder melts, start the program;

[0088] 6. The motion module 4 first pressurizes at a fast feed speed to reach the contact pressure, then adjusts the pressure to the value of target pressure 1 at a slow feed speed and applies the first ultrasonic vibration, then adjusts the pressure to the value of target pressure 2 and applies the second ultrasonic vibration;

[0089] 7. After the pressure is maintained, remove the welding pressure and take out the weldment after the weldment cools to room temperature.

[0090] The joints are brazed in stages to achieve a tight fit and effectively reduce the risk of flashing. Figure 3, is the SEM image of the silver-plated Al alloy joint. The solder and the plated metal interface are well bonded, the weld layer has no obvious defects, and the weld width remains consistent. The device can achieve accurate and fast step-by-step pressure loading, has high stability, and significantly improves the brazing quality.

[0091] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. An ultrasonic assisted welding device capable of applying pressure accurately, characterized in that: include: An ultrasonic welding head for producing welding action; A pressure sensor for detecting pressure load in real time; A movable seat is fixedly provided with a spring pressure pin and a limit contact piece; A motion module, used for driving the movable seat to move linearly back and forth relative to the ultrasonic welding head; A transition spring, mounted on the spring pressure pin; A limiting plate, used to be compressed by the elastic force of one end of the transition spring away from the spring pressure pin, and the limiting plate is fixedly connected to the ultrasonic welding head; a limit contact piece, configured with the limit piece to form a limit switch; a servo controller, electrically connected to the pressure sensor and the limit contact, to control the feeding of the motion module; The motion module uses a transition spring to push the ultrasonic welding head to achieve feeding and pressurization. After the ultrasonic welding head contacts the sample, the transition spring generates a continuously changing loading pressure on the ultrasonic welding head. When the motion module is overspeed or the welding pressure exceeds the target pressure monitored by the pressure sensor, the limit plate contacts the limit contact piece, and the servo controller controls the motion module to cut off the power output. The transition spring releases the compressive elastic force acting on the limit plate by driving the moving seat to reverse feed, thereby immediately removing the loading pressure on the ultrasonic welding head caused by the compressive elastic force. The servo controller adopts a segmented loading mode of pressure contact control, which can pre-set the contact pressure, target pressure, feed speed of the motion module at different stages and the holding time; the feed speed after reaching the contact pressure should be less than the speed before reaching the contact pressure; The servo controller automatically generates the overload pressure by multiplying the target pressure by the safety factor. When the measured pressure exceeds the overload pressure, the servo controller senses it and sends an excitation signal for power-off protection. The motion module stops pressurizing, giving it an overload protection function. The safety factor ranges from 1 to 3. The ultrasonic assisted welding equipment capable of applying pressure accurately is applied to ultrasonic brazing.

2. The ultrasonic assisted welding equipment capable of accurately applying pressure according to claim 1, characterized in that: It also includes a support column with two ends mounted on the spring pressure pin and the limiting plate, and the transition spring is sleeved on the outer periphery of the support column.

3. The ultrasonic assisted welding equipment capable of accurately applying pressure according to claim 1, characterized in that: The motion module is arranged on a fixed seat for bearing the linear motion of the moving seat.

4. The ultrasonic assisted welding equipment capable of accurately applying pressure according to claim 1, characterized in that: The servo controller for generating a control instruction for causing the motion module to receive a stop driving is also configured to preset a target welding pressure. When the actual pressure of the ultrasonic welding head exceeds the target welding pressure, the servo controller controls the motion module to stop driving.

5. The ultrasonic assisted welding equipment capable of accurately applying pressure according to claim 4, characterized in that: It also includes a pressure sensor, both ends of which are fixedly connected to the limiting piece and the ultrasonic welding head, and the pressure sensor is electrically connected to the servo controller.

6. The ultrasonic assisted welding equipment capable of accurately applying pressure according to claim 1, characterized in that: The cooperation of the limit switch contact and the limit plate means that when the forward feed stroke of the ultrasonic welding head reaches a predetermined stroke, the transition spring can instantly drive the return stroke of the ultrasonic welding head.

7. A step-by-step ultrasonic welding method using an ultrasonic assisted welding device capable of accurately applying pressure according to any one of claims 1 to 6, characterized in that: include S1: Assemble the polished and cleaned welding materials, and adjust the relative position to ensure that the sample and the ultrasonic welding head are on the same central axis; S2: Raise the motion module to the upper limit of motion, adjust the position of the pressure sensor and the limit contact, set the contact pressure, safety factor, fast feed speed, slow feed speed, target pressure 1, target pressure 2 and holding time; S3: Edit the program, the motion module first pressurizes at a fast feed rate to reach the contact pressure, then adjusts the pressure to the value of target pressure 1 at a slow feed rate and applies the first ultrasonic vibration, then adjusts the pressure to the value of target pressure 2 and applies the second ultrasonic vibration; S4: After the pressure maintenance is completed, the welding pressure is released and the weldment is taken out.

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