Resistance spot welding apparatus for welding dissimilar metals and welding method thereof

Abstract

This invention provides a resistance spot welding apparatus for welding dissimilar metals, used to continuously feed fasteners with shaft and cap structures and weld them to the weld points of dissimilar metals. The apparatus includes a feeding assembly for continuously supplying fasteners during the welding process and a gripping assembly surrounding a welding electrode. The feeding assembly drives a feeding rod to continuously supply fasteners via a driver. The gripping assembly uses a plurality of gripping rods to grip the fasteners using a combination of vacuum suction. The gripping heads on the gripping rods automatically reset and close under the coordinated action of first and second elastic components. During welding, each gripping head is passively opened by pressure from the welding electrode or actively opened by a first driver, preventing the gripping heads from interfering with the welding of the fasteners to the dissimilar metal. This invention also provides a method for welding dissimilar metals using the apparatus of this invention.

Description

Technical Field

[0001] This invention belongs to the field of welding dissimilar metals, specifically relating to a resistance spot welding device and welding method for welding dissimilar metals. Background Technology

[0002] In the technology of joining dissimilar metals, two important connection methods are known: welding and mechanical joining. Welding methods include laser welding, friction stir welding, and resistance spot welding, among others. Due to the significant differences in thermophysical and mechanical properties between dissimilar metals (such as aluminum and steel), brittle intermetallic compounds and cracks easily form in the weld seam during welding, resulting in extremely poor mechanical properties of the welded joint. Therefore, it is currently difficult to obtain high-strength joints using welding processes to join dissimilar metals, leading to relatively few dissimilar metal components joined by welding in fields such as automobiles. In mechanical joining technology, techniques such as self-piercing riveting and flowdrill screws are commonly used. These mechanical joining processes typically require additional nails to be driven into the weld point to achieve the connection. Because the joint is not affected by brittle intermetallic compounds, the connection usually has reliable performance. However, with the widespread application of advanced high-strength steel and even ultra-high-strength steel in the automotive field, as well as the gradual promotion and application of large-scale one-piece die-cast aluminum alloys, it has become more difficult to mechanically join these dissimilar metals with high strength and poor deformation ability, such as joining ultra-high-strength hot-formed steel and aluminum alloys.

[0003] CN115780980A describes a welding element and welding method that pierces a low-melting-point metal layer and welds it to a high-melting-point metal, demonstrating high-quality connection results in welding aluminum and advanced high-strength steel. However, in practical applications, the continuous and stable supply of welding elements is crucial to the effectiveness and quality of dissimilar metal welded joints. CN205008532U discloses a strip for continuously supplying rivets, which is wound around a welding torch and driven to move in a stepping motion to achieve continuous rivet supply. Since the rivets must first be pressed onto the strip, this adds extra preparation time, and separating the rivets from the strip during welding is complex. Furthermore, the installation and replacement of the strip on the welding equipment is cumbersome. In addition, the strip is usually made of plastic, which is easily deformed by high temperatures and is typically a disposable consumable. Therefore, the strip conveying solution is not suitable for solving the problem of continuous conveying of welding elements when resistance spot welding dissimilar metals.

[0004] The purpose of this invention is to provide an apparatus for resistance spot welding dissimilar metals, and a welding method using the apparatus. The apparatus can quickly supply fasteners (welding elements) to the weld point, achieving precise positioning of the fasteners and efficient, high-quality welding results. Summary of the Invention

[0005] The purpose of this invention is to provide a resistance spot welding device and a welding method for welding dissimilar metals, thereby improving the conveying efficiency of fasteners during resistance spot welding of dissimilar metals, reducing equipment manufacturing costs, and improving the welding efficiency and quality of dissimilar metals.

[0006] According to one aspect of the present invention, a gripping assembly is provided, mounted on an electrode link of a resistance spot welding device for welding dissimilar metals, for gripping fasteners welded to dissimilar metals, characterized in that it includes gripping rods, a sliding assembly, a first mounting assembly, a second mounting assembly, a first elastic assembly, a second elastic assembly, a first driver, and a connector; the first mounting assembly is mounted on the electrode link; one end of the sliding assembly is connected to the first mounting assembly, and the sliding assembly is axially slidable relative to the first mounting assembly; the first elastic assembly is mounted between the first mounting assembly and the sliding assembly, for resetting the sliding assembly after axial sliding; at least two gripping rods are mounted on the sliding assembly at equal circumferential angles, and the top of the gripping rods extends out of the sliding assembly and is distributed around the periphery of the welding electrode ends of the electrode link; The second elastic component is the same number as the gripping rod and is installed between the gripping rod and the sliding component. It drives the gripping rod to rotate around its installation position, causing the top of the gripping rod to move towards the periphery of the welding electrode. The first driver is connected to the sliding component via a connector and drives the sliding component to slide axially. The first driver is also mounted to the electrode connecting rod via a second mounting component. When the sliding component is driven, it slides away from the welding electrode, causing the first elastic component to store energy and pulling the gripping rod to move in the same direction. Simultaneously, the tops of each gripping rod open under the pressure of the welding electrode, causing the second elastic component to store energy. After the driving force of the sliding component is removed, the first elastic component drives the sliding component to reset and slide, while the second elastic component drives the gripping rod to reset, causing the tops of each gripping rod to move towards the periphery of the electrode and close.

[0007] Furthermore, the top of the gripping rod is provided with an arc-shaped surface, so that at least a portion of the outer surface of the fastener is in contact with the arc-shaped surface, and the arc-shaped surface is provided with adsorption holes for adsorbing the fastener.

[0008] Furthermore, the gripper rod is equipped with a vacuum adsorption pipe, one end of which is connected to an external air pipe that connects to a vacuum pump, and the other end is connected to an adsorption hole at the top of the gripper rod.

[0009] Furthermore, the top of the gripping rod is provided with an electrode pressing surface, which is used to withstand the compression of the outer periphery of the welding electrode, so that the top of each gripping rod in the closed state surrounding the outer periphery of the welding electrode can be opened.

[0010] Furthermore, the electrode pressing surface forms an acute angle α1 with the vertical line, and the acute angle α1 is smaller than the acute angle α3, wherein the acute angle α3 is the acute angle formed by the sidewall of the outer periphery of the electrode welding surface and the sidewall of the electrode body. Preferably, the value of the acute angle α1 is in the range of 10° to 35°.

[0011] Furthermore, the top of the gripping rod, serving as the gripping head, can be disassembled and replaced.

[0012] According to another aspect of the present invention, a feeding assembly is provided for delivering fasteners on demand to the gripping assembly, characterized in that it includes a feeding rod, a second driver, and a feed tube; one end of the feeding rod is provided with a discharge nozzle, and the feeding rod is provided with a feeding pipe and a gas pipe; the end of the feeding pipe is connected to the discharge nozzle, so that the fastener enters the feeding pipe through the feed tube and is then transported to the discharge nozzle; the gas pipe is connected to the discharge nozzle for connecting high-pressure gas to assist the discharge nozzle in releasing the fastener; the discharge nozzle is provided with a check valve and a third elastic component, the check valve preventing the fasteners delivered into the discharge nozzle from rebounding along the feeding pipe, and the third elastic component for clamping the fasteners in the discharge nozzle; the second driver causes the feeding rod to telescopically move to continuously supply fasteners to the gripping assembly.

[0013] Furthermore, the feeding assembly is independently mounted on the side of the spot welding device. The second driver causes the feeding rod to extend and retract in the axial direction perpendicular to the electrode connecting rod. The feeding assembly also includes a third driver for driving the feeding assembly to move in the axial direction parallel to the electrode connecting rod. Preferably, the second driver is a high-pressure gas driver, and the third driver is a motor driver.

[0014] Furthermore, the feeding assembly is integrated into the side panel of the gripping assembly, and the second driver drives the feeding rod to extend and retract in a direction parallel to the axial direction of the electrode connecting rod. When the feeding rod extends downward, it causes the discharge nozzle to rotate from the direction toward the side wall of the welding electrode to the direction toward the end of the welding electrode.

[0015] According to another aspect of the present invention, a resistance spot welding apparatus for welding dissimilar metals is provided. This apparatus continuously supplies fasteners for welding and welds the fasteners to the weld points of a first metal and a second metal stack. The resistance spot welding apparatus includes a welding clamp, a welding robot, a robot control cabinet, a feeding cabinet, a vacuum pump, and a main control cabinet. The dissimilar metals welded by the resistance spot welding apparatus include a first metal and a second metal. The first metal has a melting point below 750°C, and the second metal has a melting point above 1300°C. The fasteners supplied include a shaft portion and a cap surrounding the shaft portion. During welding, the spot welding apparatus delivers the fasteners to the front end of the welding electrode and welds the dissimilar metals. Specifically, the spot welding apparatus includes a gripping assembly and a feeding assembly. The feeding assembly receives fasteners fed from the feeding cabinet via a feed pipe and delivers the fasteners to the gripping assembly as needed. The gripping assembly grips the fasteners and cooperates with the spot welding apparatus to weld the fasteners to the weld points of the dissimilar metals.

[0016] According to another aspect of the present invention, a method for resistance spot welding is provided for welding dissimilar metals using the aforementioned resistance spot welding apparatus, characterized in that the welding process specifically includes the following steps:

[0017] a. During the feeding stage, the feeding cabinet uses high-pressure gas to transport the fasteners to the discharge nozzle of the feeding rod. The gripping assembly and the feeding assembly work together to align the welding electrode with the discharge nozzle of the gripping rod, and the fasteners discharged from the discharge nozzle are gripped by the vacuum suction force of the gripping head.

[0018] b. During the pre-compression stage, the welding rod moves toward the first and second metal stacks. When the fastener or gripper head contacts the first metal surface, the welding clamp continues to apply electrode pressure to the weld point. The gripper head opens under the pressure of the outer peripheral sidewall of the electrode end face, so that the welding surface of the electrode presses the fastener onto the first metal with a set pressure.

[0019] c. During the welding stage, at least one current pulse is input into the weld joint by the welding electrode. The current pulse causes the first metal covered by the fastener shaft to melt at high speed and be sprayed into the cap of the fastener. After the fastener shaft is squeezed by the electrode pressure, it quickly penetrates the first metal layer and comes into contact with the second metal. The resistance heat generated by the current pulse causes the common melt nugget formed between the fastener shaft and the second metal to achieve a firm connection.

[0020] d. At the end of the welding stage, the electrode connecting rod retracts, causing the electrode and gripper assembly to move away from the weld point. The sliding component and gripper rod of the gripper assembly are reset under the drive of the first elastic component and the second elastic component, so that the gripper head returns to the closed state and surrounds the outer periphery of the welding electrode.

[0021] Furthermore, when the thickness of the first metal is less than or equal to 1.5 mm, the current pulse input in the welding stage consists of 2 to 6 short current pulses, each with a duration of less than 60 ms, and a cooling time of 2 to 40 ms between each current pulse. When the thickness of the first metal is greater than 1.5 mm, the welding stage employs a multi-stage welding current pulse process including a preheating stage, a fastener piercing stage, and a joining stage. In the fastener piercing stage, each current pulse has a duration of less than 80 ms, and the current pulse in this stage causes molten first metal to be ejected from the weld joint.

[0022] The beneficial effects of this invention are:

[0023] (1) The spot welding device of the present invention has a simple structure, compact size, is easy to manufacture and has low manufacturing cost.

[0024] (2) The gripper assembly structure of the present invention can be directly installed on the electrode connecting rod of the welding clamp, which is easy to install and highly compatible with welding clamps on the market, reducing the upgrade cost of welding machine; in addition, the gripper assembly structure is compact, ensuring the achievable performance of the welding clamp in welding complex components.

[0025] (3) Since at least two gripping rods are set, it is beneficial for the gripping head to open and release the fastener. In addition, an electrode pressing surface is set on the gripping head, so that the gripping head can automatically open under the pressure of the electrode during the welding process, which promotes the contact and compression between the electrode and the fastener. This reduces the additional energy input to drive the gripping head to open, thus achieving energy saving.

[0026] (4) Since the gas pipe in the feeding rod is connected to the discharge nozzle, high-pressure gas is used to assist the fasteners to be sprayed from the discharge nozzle to the gripper head, which ensures that the fasteners are smoothly transferred from the feeding assembly to the gripper assembly.

[0027] (5) The gripping rod can be opened and moved up to the periphery or above the welding electrode by the first driver, so as to avoid the gripping assembly interfering with the grinding and replacement process of the welding electrode, and at the same time achieve the effect of the spot welding device to weld the same metal using traditional welding process. Attached Figure Description

[0028] Figure 1 This is a cross-sectional schematic diagram of the gripper assembly in one embodiment of the present disclosure;

[0029] Figure 2 This is a schematic diagram of the four gripping heads after they are closed in one embodiment of the present disclosure;

[0030] Figure 3 A three-dimensional schematic diagram of the gripper assembly in another embodiment of this disclosure;

[0031] Figure 4 A three-dimensional schematic diagram of the first mounting component in another embodiment of this disclosure;

[0032] Figure 5 A three-dimensional schematic diagram of the sliding component in another embodiment of this disclosure;

[0033] Figure 6 This is a three-dimensional schematic diagram of the gripper in another embodiment of the present disclosure;

[0034] Figure 7 This is a schematic diagram showing the detailed features of the grab head in another embodiment of the present disclosure;

[0035] Figure 8 This is a schematic diagram of a welding electrode that may be used in another embodiment of the present disclosure;

[0036] Figure 9 This is a schematic diagram showing the positions of the welding electrode, the gripper head, and the fastener in another embodiment of the present disclosure;

[0037] Figure 10 This is a three-dimensional schematic diagram of the gripper rod and sliding assembly after installation, according to another embodiment of the present disclosure;

[0038] Figure 11 This is a schematic diagram of the gripper heads after closure in another embodiment of the present disclosure;

[0039] Figure 12 This is a top view of the arc-shaped surface of each gripper head after it is closed, as described in another embodiment of the present disclosure.

[0040] Figure 13 A three-dimensional schematic diagram of the delivery rod in another embodiment of this disclosure;

[0041] Figure 14 This is a schematic diagram of the working process of the delivery rod in another embodiment of the present disclosure;

[0042] Figure 15 This is a schematic diagram of a resistance spot welding apparatus system in another embodiment of the present disclosure;

[0043] Figure 16 This is a schematic diagram of a fastener conveying system in another embodiment of the present disclosure, in which the gripping assembly and the feeding assembly are integrated into one unit;

[0044] Figure 17 This is a schematic diagram of the gripper assembly in another embodiment of the present disclosure;

[0045] Figure 18 This is a diagram illustrating the closed state of the gripper head and the effect of gripping the fastener in another embodiment of the present disclosure.

[0046] Figure 19 This is a schematic diagram of the pre-compression process of the electrode on the fastener in another embodiment of the present disclosure;

[0047] Figure 20 A diagram showing the change of the gripper rod when the electrode is preloaded on the fastener in another embodiment of this disclosure;

[0048] Figure 21 This is a diagram illustrating the effect of the first driver opening the gripper lever in another embodiment of the present disclosure.

[0049] Figure 22 In another embodiment of this disclosure, the electrode pre-pressing process on the workpiece is performed without fasteners;

[0050] Figure 23 In another embodiment of this disclosure, the electrode pre-presses the workpiece after the first driver drives the gripping rod to open;

[0051] Figure 24 This is a schematic diagram illustrating the preferred changes in current, electrode pressure, and time in Embodiment 1 of this disclosure;

[0052] Figure 25 The surface and cross-sectional morphology of the solder joint in Embodiment 1 of this disclosure are shown in the diagram.

[0053] Figure 26 This is a schematic diagram illustrating the preferred changes in current, electrode pressure, and time in Embodiment 2 of this disclosure;

[0054] Figure 27 This is a schematic diagram of joint formation during welding of dissimilar metals in Embodiment 2 of this disclosure;

[0055] Figure 28 The image shows the surface morphology of the weld point after continuous welding of dissimilar metals using the resistance spot welding device in Embodiment 2 of this disclosure.

[0056] Figure 29 This is a diagram illustrating the effect of continuous welding of dissimilar metals using a resistance spot welding device in Embodiment 3 of this disclosure.

[0057] Figure 30 The image shows the morphology of the solder joint surface and the solder joint cross-section in Embodiment 3 of this disclosure. Detailed Implementation

[0058] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0059] One embodiment of the present invention provides a gripper assembly. For example... Figure 1The diagram shows a cross-sectional view of the gripper assembly 900. The gripper assembly 900 is mounted on the electrode connecting rod 63 and includes gripper rods 10, a sliding assembly 20, a first mounting assembly 30, a second mounting assembly 52, a first elastic assembly 41, a second elastic assembly 42, a first driver 50, and a connector 43. In this embodiment, four gripper rods 10 are provided, and the top of each gripper rod, serving as a gripper head 11, is detachable and replaceable. The gripper rods are mounted on the sliding assembly 20 at equal circumferential angles, so that the gripper heads 11 of the gripper rods are distributed around the periphery of the welding electrode 60. Figure 2 This provides a more intuitive demonstration of the distribution of the four gripping heads (11-1, 11-2, 11-3, and 11-4) around the welding electrode after they are closed. The gripping heads 11 are connected to the sliding assembly 20 via pins 27, allowing the gripping rods to rotate around the pins 27 at their mounting positions, thus enabling the opening and closing movements of the four gripping heads. A second elastic assembly 42 is installed between the sliding assembly and the gripping rods. This second elastic assembly drives the gripping rods 10 to adhere to the limiting terminal 22, ensuring that the four gripping heads 11 remain in a tightly closed state (e.g., ...). Figure 2 (As shown). The sliding component 20 is mounted on the first mounting component 30. A slider is provided between the sliding component and the first mounting component, allowing the sliding component to slide axially relative to the first mounting component. The first mounting component 30 is mounted on the electrode connecting rod 63. A first elastic component 41 is provided between the sliding component and the first mounting component. When the sliding component 20 slides axially upward, the first elastic component 41 is compressed and stores energy. Once the driving force that drives the sliding component to move upward is released, the first elastic component releases the stored elastic energy and drives the sliding component to slide downward back to its initial position. The driving force that drives the sliding component to slide can come from the first driver 50, or from the force formed when the gripper head 11 squeezes against the workpiece to be welded. The first driver 50 is mounted on the electrode connecting rod 63 via the second mounting component 52. The telescopic rod 51 on the first driver is connected to the connector 43, which in turn is connected to the sliding assembly 20. When the telescopic rod 51 retracts, the connector 43 drives the sliding assembly 20 to move upward, and the sliding assembly simultaneously drives the gripping rod 10 to move upward. The welding electrode pushes against the gripping head, thus pushing the gripping rod away. After the telescopic rod 51 extends downward, the first elastic component drives the sliding assembly to reset and slide, while the second elastic component drives the gripping rod to reset, causing the gripping heads of each gripping rod to move towards the periphery of the electrode and close.

[0060] In another embodiment of the present invention, such as Figures 3 to 15 As shown. The 3D schematic diagram of the 900-type gripper assembly is shown below. Figure 3As shown, the first actuator 500 uses a compression cylinder. The telescopic rod 51 of the compression cylinder is connected to the block-shaped connector 43. The connector 43 has a through hole (not shown), which is connected to the bolt 44 with an overfit, allowing the bolt 44 to slide upward relative to the connector 43. When the telescopic rod 51 retracts upward, it drags the connector 43 to move. The connector 43 can then drive the bolt 44 to move the sliding component 20 upward. However, the first actuator 50 cannot drive the sliding component 20 to slide downward. The driving force for the sliding component 20 to slide downward comes from the elastic force of the first elastic component 41.

[0061] Figure 4 The diagram shows a three-dimensional schematic of the first mounting component 30. A sliding groove 31 is provided on the body of the first mounting component. When the sliding component is matched with the first mounting component, the slider of the sliding component first slides upward from the open sliding groove 31', then rotates horizontally through the transverse sliding groove 31' into the relatively closed sliding groove 31. The bolt hole 34 is on the same vertical line as the longitudinal sliding groove 31. After the bolt 44 is installed with the sliding component 20, the sliding component is limited to sliding up and down along the sliding groove 31 (e.g., ...). Figure 3 Mounting hole 35 is used for mating and mounting with electrode connecting rod, and threaded hole 33 is used for screwing in screws to fix the first mounting assembly.

[0062] Figure 5 The diagram shows a three-dimensional schematic of the sliding assembly 20. Three pairs of gripping rods are mounted on the lower circumferential side at equal angles, and each pair of mounting brackets has a limiting terminal 22. The sliding assembly 20 body has a second elastic component mounting port 23 and a first elastic component mounting port 25. A threaded hole 24 is provided at the upper end of the sliding assembly for mounting bolts that connect to the connector. Inside the sliding assembly 20 is a sliding component mounting hole 26, within which a fixed slider (not shown) is provided for matching with the sliding groove 31 on the first mounting assembly.

[0063] Figure 6 The diagram shows a three-dimensional and cross-sectional view of the gripping rod 10. At its tail end is a second mounting port 16 for the second elastic component. After the gripping rod is installed onto the sliding assembly, the second mounting port 16 is opposite to the mounting port 25 on the sliding assembly, used for mounting the second elastic component between them (see reference). Figure 3 A mounting hole 15 is located near the center of the gripper rod 10. A limiting slot 14 is also located near the mounting hole to mate with the limiting terminal 22 on the sliding assembly. When the limiting slot 14 contacts the limiting terminal 22 on the sliding assembly, the three gripper heads 11 close in a ring shape (see reference). Figure 11The gripping head 11 is located at the top of the gripping rod 10. Preferably, the gripping head can be disassembled and replaced. A vacuum adsorption pipe 13 is provided inside the gripping rod 10, which has a threaded port 37 at the tail end of the gripping rod for connecting to an air pipe. The vacuum adsorption pipe on the gripping head side is connected to the adsorption hole 12. When the vacuum pump draws a vacuum, the adsorption hole forms an adsorption force to adsorb the fastener.

[0064] like Figure 7 As shown, an arc-shaped surface (composed of a side surface 11a and a top surface 11b) is arranged on the gripper head 11 to accommodate the fastener in a conformal fit. Therefore, a portion of the arc-shaped surface fits and matches the outer surface of the fastener; and the adsorption holes are distributed on the arc-shaped surface. Preferably, there is an angle α2 between the side surface 11a of the arc-shaped surface and the vertical line, ranging from 1° to 5°, so that the fastener is more smoothly adsorbed into the gripper head. The top surface 11b of the arc-shaped surface gradually curves upward to connect to the electrode pressing surface 11c. This upwardly curved top surface 11b facilitates the gripper head 11 to open quickly and detach from the fastener after being subjected to force. In order to allow each closed gripper head to open smoothly under the pressure of the electrode, an electrode pressing surface 11c is provided on the gripper head. The electrode pressing surface forms an acute angle α1 with the vertical line Q1, and the acute angle α1 is smaller than the acute angle α3, where the acute angle α3 is the acute angle formed by the sidewall of the outer periphery of the electrode welding surface and the sidewall of the electrode body. For example... Figure 8 The figure shows a commonly used arc-shaped electrode in this field. Figure 8 1A), spherical electrode ( Figure 8 1B), conical electrode ( Figure 8 1C) and pointed electrode ( Figure 8 The acute angle α3 of (1D) is given by the given angle. Figure 9 As shown, setting the acute angle α1 to be smaller than the acute angle α3 allows the outer periphery of the electrode to preferentially contact the electrode pressing surface 11c, while reducing the contact area between the electrode and the electrode pressing surface 11c, which is more conducive to the gripper head opening under the pressure of the outer periphery of the electrode. To improve the surface hardness and wear resistance of the electrode pressing surface 11c, a plating layer including molybdenum and chromium metal plating, a ceramic plating, and a tungstate plating can be applied to the electrode pressing surface 11c.

[0065] like Figure 10 As shown, after the gripping rod 10 is installed onto the mounting bracket 21 of the sliding assembly, the gripping rod 10 can rotate around the pin 27. For example... Figure 10 When the upper gripper rotates clockwise, the gripper head 11 moves closer to the welding electrode 60, achieving the effect of closing all gripper heads; while when it rotates counterclockwise, the gripper heads move away from the welding electrode. Since a second elastic component 42 is provided at the tail of the gripper rod, when the gripper head 11 opens, the second elastic component 42 is compressed and stores energy. Once the force driving the gripper head to open is removed, the second elastic component will drive the three gripper heads to close. Figure 11 The diagram shows the closed state of the three gripping heads 11-1, 11-2, and 11-3. In this state, the arc-shaped surfaces of the three gripping heads assemble into a ring shape, with the electrode welding surface 61 located at the center. During welding, the gripping head 11 must open outwards to allow the welding electrode to smoothly press against the fastener 100, avoiding interference from the gripping head during the welding process. (Reference) Figure 19 To reduce the opening stroke of the gripper head and further improve the smooth opening effect, in a preferred embodiment, both ends of the top surface 11b of the arc-shaped surface of the gripper head are cut off, such as... Figure 12 As shown in 2A. In another preferred embodiment, the inner contour of the top surfaces (11b-1, 11b-2, and 11b-3) of the three arc-shaped surfaces is formed after being joined, as shown in Figure 2A. Figure 12 As shown in 2B, the gripper head can be adapted to fasteners of different sizes and shapes by replacing the gripper head with an arc-shaped surface of different sizes, thereby reducing the operating cost of the equipment.

[0066] Figure 13 A three-dimensional schematic diagram of the feeding rod 70 in this embodiment is shown. An annular discharge nozzle 71 is provided at the end of the feeding rod, and the discharge nozzle is connected to the feeding pipe 72. To prevent the fastener 100, transported by high-pressure gas, from rebounding along the feeding pipe after entering the discharge nozzle, a check valve 76 is provided near the connection between the discharge nozzle 71 and the feeding pipe 72. A third elastic component 75 is provided on both sides of the discharge nozzle. When the fastener is fed into the discharge nozzle, the third elastic component 75 applies a certain pressure to clamp the fastener. According to a preferred embodiment, the third elastic component 75 applies clamping force to the fastener in an electrically controlled manner, allowing the fastener to be transmitted more smoothly into the discharge nozzle. In addition, the third elastic component is also connected to a trigger switch 74. When the trigger switch is opened, the elastic force of the third elastic component is released, allowing the fastener to be smoothly discharged from the discharge nozzle.

[0067] Figure 14 This illustrates the process of fastener 100 being transferred from the feed rod to the gripper assembly. (Example) Figure 14 In section 3A, the material pipe 77 is connected to the feeding pipe 72, and the fasteners are carried into the discharge nozzle by a high-speed airflow. For example... Figure 14 In step 3B, after receiving the instruction, the second driver drives the feed rod to move towards the welding electrode 60. As the gripper head 11 aligns with the discharge nozzle, it simultaneously triggers the switch 74 to release the clamping force applied to the fastener by the third elastic component; at the same time, the feed tube 77 is connected to the gas pipe 73 and only high-pressure gas is blown out. With the assistance of high-pressure gas and the vacuum suction force on the gripper head, the fastener is quickly transferred from the discharge nozzle to the gripper head.

[0068] According to another aspect of the present invention, a resistance spot welding apparatus for welding dissimilar metals is provided. This apparatus can continuously supply fasteners during the welding of a first metal and a second metal stack by welding electrodes. The spot welding apparatus includes a welding clamp 200, a welding robot 400, a first driver 500, a feed cabinet 300, a vacuum pump 600, and a main control cabinet 800. Figure 15 As shown. The spot welding device welds dissimilar metals including a first metal and a second metal. The first metal has a melting point below 750°C, and the second metal has a melting point above 1300°C. The fastener being transported includes a shaft and a cap surrounding the shaft. During welding, the spot welding device transports the fastener to the welding point area and welds the first metal and the second metal. The resistance spot welding device is characterized by comprising a feeding assembly and a gripping assembly. The feeding assembly acts as a transfer station during fastener transport, receiving fasteners from the feeder. During welding, the feeding assembly transports the fastener to the gripping head of the gripping assembly according to instructions. The gripping assembly then grips the fastener onto the welding point area, thereby achieving welding of the fastener to the dissimilar metal welding point using welding electrodes.

[0069] In a preferred embodiment, the feeding assembly includes a feeding rod 70, a feed tube 77, a second actuator 78, and a third actuator 79. The feeding assembly is mounted on a welding clamp on the side of the electrode connecting rod 63. The second actuator 78 causes the feeding rod 70 to move laterally, continuously supplying fasteners to the gripping assembly 900. The third actuator 79 causes the feeding assembly to move axially parallel to the electrode connecting rod 63, adjusting the position of the feeding assembly. Furthermore, the third actuator 79 can move in conjunction with the movement of the electrode connecting rod 63; for example, if the electrode connecting rod moves upward, the third actuator 79 drives the feeding rod 70 to move downward, improving the efficiency of fastener delivery. The feed tube 77, the second actuator 78, and the third actuator 79 are connected to the feeding cabinet 300 to continuously supply fasteners and compressed gas. The gripping assembly 900 is mounted on the electrode connecting rod 63, wherein the gripping rod is connected to a vacuum pump 600 to adsorb the fasteners. A sensor system 700 is also installed around the part gripping assembly and the part feeding assembly to monitor and provide feedback on the fastener feeding information in real time, and transmits the monitored information to the main control cabinet 800 for analysis and processing. The main control cabinet 800 is used for process adjustment and control of the normal operation of the entire spot welding device system.

[0070] To improve the efficiency of fastener transfer from the feed assembly to the gripper assembly, in another preferred embodiment, the feed assembly is integrated into the side panel of the gripper assembly, such as... Figure 16As shown. The feeding rod 70 is divided into two sections and connected by a mounting pin 70a, with a fourth elastic component 70b located near the mounting pin 70a. The fourth elastic component is used to drive the end where the discharge nozzle 71 is located to rotate around the mounting pin 70a. In the initial state, the second driver 78 is in a retracted state, so that the entire feeding rod 70 is located on the right side of the electrode connecting rod 63. At this time, the material tube 77 is connected to the feeding pipe 72 in the gripping rod, and the fastener is conveyed to the discharge nozzle 71 through the feeding pipe 72; while the fastener 100' still located on the gripping head 11 can be used for welding, such as Figure 16 As shown in Figure 4A, after the previous weld point is prepared, the feeding assembly receives an instruction to cause the second driver 78 to drive the feeding rod 70 to slide downwards. The lower end of the gripping rod rotates under the drive of the fourth elastic component 70b, causing the ejector nozzle to rotate from the direction facing the side wall of the welding electrode 60 to directly below the welding electrode. Under the combined effect of high-pressure gas and vacuum suction force, the fastener 100 is transferred from the ejector nozzle to the gripping head 11. The device of this embodiment can deliver the next fastener to the ejector nozzle while welding, further shortening the fastener transfer path, reducing the waiting time for the gripping head to deliver the fastener, and improving welding efficiency.

[0071] In another embodiment, the gripper assembly of the resistance spot welding device is as follows: Figure 17 As shown. Two first actuators 50 are mounted opposite each other on both sides of the electrode connecting rod 63 and connected to the sliding assembly via connectors and bolts. Three gripping rods 10 are arranged circumferentially at equal angles around the sliding assembly 20. Their tail ends are connected to a vacuum adsorption pipe to achieve adsorption. The gripping heads at the lower ends of the three gripping rods surround the welding electrode 60. In the free state, the gripping rods 10 are subjected to pressure from the second elastic component, causing the three gripping heads 11 to close tightly, as shown. Figure 18 As shown in Figure 5A, a total of six suction holes 12 are provided circumferentially on the three gripping heads (11-1, 11-2, and 11-3), enabling the gripping heads to generate a large suction force to adsorb the fasteners. Figure 18 The 5B model demonstrates the effectiveness of the gripper head in firmly adhering to fasteners.

[0072] Figure 19 A schematic diagram is shown showing the gripper head 11 opening when the electrode is pre-pressed onto the fastener. When the gripper head 11 is closed, the electrode pressing surface 11c is in contact with a localized area around the electrode, while the fastener is adsorbed within the arc-shaped surface of the gripper head. At this time, a gap still exists between the welding surface 61 of the welding electrode and the fastener 100, such as... Figure 19As shown in Figure 6A, as the upper and lower welding electrodes move toward the workpiece, the fastener first contacts the surface of the first metal 80. The periphery of the fastener exerts a force F2 on the gripper head, restricting its further downward movement. On the other hand, as the electrode continues to press down onto the fastener surface, the outer periphery of the welding electrode exerts an outward pushing force F1 on the electrode pressing surface 11c. Under the action of these two forces F1 and F2, the gripper head 11 gradually opens, as shown in Figure 6A. Figure 19 As shown in Figure 6B. During further welding, the shaft portion of the fastener 100 pierces the first metal 80, causing the welding electrode 60 to continue pressing down. The gripper head 11 will continue to be squeezed by the electrode and further open, thus avoiding obstructing the welding process of the electrode to the fastener.

[0073] Figure 20 This demonstrates the effect of the gripper head opening during actual preloading. Before the fastener 100 contacts the first metal 80, the gripper head is tightly closed, as shown... Figure 20 7A. As the welding electrode 60 continues to press down, the gripping heads (such as 11-1 and 11-2) gradually open to both sides until the electrode welding surface is pressed against the fastener, as shown in Figure 7A. Figure 20 7B. When the gripper head opens, the second elastic component 42 is compressed, and simultaneously the sliding component 20 moves upward, driving the first elastic component 41 to also be compressed. Once the electrode is moved away from the first metal 80, the compressed first and second elastic components drive the gripper head and the sliding component to return to their original positions. In another preferred embodiment, such as... Figure 21 As shown, when the electrode presses the fastener against the surface of the first metal 80, the first driver 50 can be activated to pull the sliding component 20 upward through the connector 43, thereby pulling the gripper rod to quickly open the closed gripper head, thus avoiding interference of the gripper head with the welding process.

[0074] Figure 22 This diagram illustrates the welding process of a spot welding device on a metal workpiece when the gripper head 11 is not gripping a fastener. As the welding electrode 60 moves the gripper head 11 toward the surface of the first metal 80, the gripper head first contacts the metal tool, such as... Figure 22 As shown in (a), as the welding electrode 60 is pressed downwards, the gripper head 11 is gradually pushed away by the outer periphery of the electrode, causing the welding electrode 60 to contact the metal workpiece, as shown in (a). Figure 22 As shown in (b), the spot welding device can then use traditional welding processes to weld the metal structure. For example... Figure 22(c) Further illustrates the state of the gripper assembly after the gripper head is pressed against the workpiece without gripping the fastener. The gripper heads (e.g., 11-1 and 11-2) open smoothly, allowing the welding electrode to successfully contact the workpiece surface. The sliding assembly 20 moves upward under the drive of the gripper rod, causing the first elastic assembly 41 to be compressed and energy stored. Due to the overfit connection between the bolt 44 and the connector 43, the bolt 44 can move upward relative to the connector. Of course, when welding the same first or second metal using conventional spot welding processes, the resistance spot welding equipment of the present invention preferentially allows the sliding assembly to be driven upward by the first driver 50, causing the gripper heads (e.g., 11-1 and 11-2) to open and distribute around the welding electrode 60, such as... Figure 23 As shown. Furthermore, after the gripper head opens and rises to either side or above the welding electrode under the drive of the first driver 50, the welding electrode can be replaced or its end face can be refurbished using a commercially available grinder. This reduces the need to disassemble the gripper assembly 900 when replacing or refurbishing the welding electrode.

[0075] According to another embodiment of the present invention, a method for resistance spot welding is provided for welding dissimilar metals using the aforementioned resistance spot welding apparatus. The welding process of this method specifically includes the following steps:

[0076] a. During the feeding stage, the feeding cabinet uses high-pressure gas to deliver the fasteners to the discharge nozzle of the feeding rod. The gripping assembly and the feeding assembly work together to align the welding electrode with the discharge nozzle of the gripping rod. The vacuum suction force of the gripping head grips the fasteners ejected from the discharge nozzle, such as... Figure 14 As shown.

[0077] b. During the pre-compression stage, the welding connecting rod moves towards the first and second metal stacks. Once the fastener or gripper head contacts the first metal surface, the welding clamp continues to apply electrode pressure to the weld joint. The gripper head opens under the pressure of the outer peripheral sidewall of the electrode end face, causing the welding surface of the electrode to press the fastener onto the first metal at a set pressure. Figure 19 As shown.

[0078] c. During the welding stage, at least one current pulse is input into the weld joint from the welding electrode. This current pulse causes the first metal covering the fastener shaft to melt at high speed and be sprayed into the fastener cap. Under the pressure of the electrode, the fastener shaft rapidly penetrates the first metal layer and comes into contact with the second metal. The resistance heat generated by the current pulse promotes a strong connection between the fastener shaft and the second metal through a common weld nugget. Figure 27As shown. The resistance heat generated by the current pulse has the characteristic of rapidly melting the first metal and causing it to be ejected from the solder joint onto the fastener cap, rather than the process of the first metal being slowly heated and plasticized by resistance heat and extruded from the fastener shaft. Preferably, when the thickness of the first metal is less than or equal to 1.5 mm, the welding process in the welding stage is as follows: Figure 24 As shown, the input current pulse consists of 2 to 6 short current pulses, and each current pulse lasts for less than 60 ms (milliseconds). Figure 24 (where t1, t3, t5, or t7 are all less than 80 ms), and there is a 2-40 ms cooling time between each current pulse (i.e., Figure 24 (t2, t4, and t6). When the thickness of the first metal is greater than 1.5 mm, a multi-stage welding current pulse process is adopted, including a preheating stage, a fastener piercing stage, and a joining stage, such as... Figure 26 As shown, each current pulse in the fastener puncture phase lasts for less than 80 ms, and during this phase, the current pulse causes molten first metal to be ejected from the solder joint.

[0079] d. At the end of the welding stage, the electrode connecting rod retracts, causing the electrode and gripper assembly to move away from the weld point. The sliding component and gripper rod of the gripper assembly are reset under the drive of the first elastic component and the second elastic component, so that the gripper head returns to the closed state and surrounds the outer periphery of the welding electrode.

[0080] Example 1:

[0081] In this embodiment, the first metal 80 is made of 1.1 mm thick six-series aluminum alloy (AA6016), and the second metal 90 is made of 1.2 mm thick quenched and tempered steel (Q&P1180). Since the first metal is relatively thin, it is preferred to use... Figure 24 The process shown involves applying multiple short current pulses, with two current pulses, each 14 kA, lasting for 45 ms, and a 20 ms cooling time between the two pulses. The spot welding apparatus of this invention is used during welding, with a fixed electrode pressure of 6 kN. Figure 25 The weld surface and cross-sectional morphology after welding are shown. The central shaft of fastener 100 successfully pierced the first metal 80 and formed a common weld nugget 91 with the second metal 90, resulting in a strong weld between the fastener and the steel. In the closed cavity structure formed by the outer cap of fastener 100 and the surface of the first metal, short current pulses can be observed inducing the melting of the first metal and ejecting it at high speed as exhaust metal 82. This prevents the first metal from mixing into the weld nugget 91 and forming brittle intermetallic compounds.

[0082] Example 2:

[0083] refer to Figures 26 to 28 In this embodiment, the resistance spot welding device of the present invention is used to perform continuous welding tests on dissimilar metals. During the welding process, the fixed electrode pressure is 6 kN. The first metal 80 is made of 2 mm thick AA6111 aluminum alloy, and the second metal 90 is made of 1.4 mm thick aluminum-silicon coated hot-formed steel with a strength of 1500 MPa. The current process during the welding stage is as follows... Figure 26 As shown, the current settings include I1 for the preheating stage, I2 for the fastener puncture stage, and I3 for the final connection stage. The following section combines... Figure 27 The welding process diagram further illustrates the weld point formation process:

[0084] During the preheating phase, from t1 to t2, a pulsed preheating current I1 is applied to the solder joint, with an effective current value of 3 kA and a duration of 100 ms. During this period, the fastener 100, the first metal 80, and the second metal 90 achieve close contact, and the low-melting-point first metal 80 forms a molten zone 81 in a localized area within the solder joint.

[0085] During the fastener piercing stage, specifically the time interval t3 to t4, several short, high-effectiveness current pulses are applied. These pulses cause the first metal in the solder joint to melt rapidly, forming ejected metal 82 that is sprayed at high speed into the cap structure surrounding the fastener shaft. The fastener shaft 101 then rapidly pierces the first metal 80 under electrode pressure, forming a direct contact surface 83 with the second metal 90. Because the current pulse duration is relatively short during this stage, neither the fastener surface layer nor the second metal surface layer in contact with the first metal melts, effectively controlling the mixing of the molten first metal in the melting zone 81 into the solder joint. In this embodiment, the current I2 for this stage is set to four pulses, each with an effective value of 14 kA and a duration of 56 ms. A 30 ms cooling time is set between each pulse to control excessive resistance heat input, allowing the fastener shaft to pierce the first metal layer at high speed.

[0086] During the connection phase, specifically the time interval t5 to t6, a current pulse is applied. This current pulse melts the direct contact surface 83 between the fastener shaft and the second metal 90, forming a common weld nugget 91. Because the second metal and the fastener have higher melting points, the duration of the input current pulse is set relatively longer, allowing sufficient resistance heat to form within the weld joint for nucleation and weld nugget growth, thereby improving the connection strength of the joint. In this embodiment, the effective value and duration of the current pulse in this phase are set to 12 kA and 260 ms, respectively.

[0087] Figure 28The surface morphology of the weld joint after continuous welding using the device of the present invention is shown. The welding process is stable, and weld joints with good surface condition are obtained. This proves that using the device and welding method of the present invention, high-quality direct welding of dissimilar metals can be achieved without the need for prefabrication of the first metal.

[0088] Example 3:

[0089] In this embodiment, the first metal 80 is made of 2.5 mm thick six-series aluminum alloy (AA6082), and the second metal 90 is made of 1.5 mm thick aluminum-silicon coated hot-formed steel with a strength of 1500 MPa. The electrode pressure is maintained at 6 kN during welding. Due to the further increase in the thickness of the first and second metals, [the following is preferred]. Figure 26 The multi-stage welding process is shown. In the preheating stage, the effective value and duration of current I1 are set to 5 kA and 150 ms, respectively. In the fastener piercing stage, current I2 is set with four current pulses, each with an effective value of 16.5 kA and a duration of 55 ms, and a 20 ms cooling time interval between each pulse. In the joining stage, the effective value and duration of current I3 are set to 13 kA and 340 ms, respectively. Figure 29 The welding process of the spot welding device of the present invention is demonstrated. It can be seen that even with a relatively thick first metal, the spot welding device can continuously grip fasteners and achieve efficient welding. The surface and cross-sectional morphology of the weld point after welding are shown below. Figure 30 As shown, the surface condition of the weld joint is good, and the partially melted first metal in the weld joint is discharged into the cap of the fastener 100. The shaft of the fastener successfully penetrates the first metal layer and forms a common weld nugget 91 with the second metal 90, achieving a strong welding effect.

[0090] It should be understood that the above embodiments are only intended to illustrate the technical concept of the present invention to facilitate understanding by those skilled in the art, and are not intended to limit the scope of protection of the present invention. Within the scope of the claims of the present invention, any improvements and equivalent substitutions to the parts, structures, or method steps involved in the above embodiments, especially combinations of different embodiments without causing structural or principle conflicts, fall within the scope of protection of the present invention.

Claims

1. A grabber assembly mounted on an electrode link of a resistance spot welding apparatus for welding dissimilar metals, for grabbing a fastener to be welded to a dissimilar metal, characterized by, It includes a gripping rod, a sliding assembly, a first mounting assembly, a second mounting assembly, a first elastic assembly, a second elastic assembly, a first driver, and a connector; The first mounting assembly is mounted on the electrode connecting rod; One end of the sliding component is connected to the first mounting component, and the sliding component can slide axially relative to the first mounting component; The first elastic component is installed between the first mounting component and the sliding component, and is used to reset the sliding component after axial sliding. The gripping rods are at least two in number and are mounted on the sliding assembly at equal angles in the circumferential direction. The top of the gripping rods extends out of the sliding assembly and surrounds the welding electrode ends of the electrode connecting rod. The second elastic component is the same number as the gripping rod and is installed between the gripping rod and the sliding component. It is used to drive the gripping rod to rotate around the installation position, so that the top of the gripping rod moves closer to the periphery of the welding electrode. The first driver is connected to the sliding assembly via a connector to drive the sliding assembly to produce axial sliding, and the first driver is mounted to the electrode connecting rod via a second mounting assembly; When the sliding component is driven, it slides away from the welding electrode, causing the first elastic component to store energy and the gripping rod to move in the same direction. At the same time, the top of each gripping rod opens under the pressure of the welding electrode, causing the second elastic component to store energy. After the driving force of the sliding component is removed, the first elastic component drives the sliding component to reset and slide, and the second elastic component drives the gripping rod to reset, causing the top of each gripping rod to move towards the periphery of the electrode and close. The fastener's outer surface is made to fit at least a portion of the curved surface, and the curved surface is provided with adsorption holes for adsorbing the fastener.

2. The gripper assembly according to claim 1, characterized in that, The gripper rod is equipped with a vacuum adsorption pipe. One end of the vacuum adsorption pipe is connected to an external air pipe that connects to a vacuum pump, and the other end is connected to an adsorption hole at the top of the gripper rod.

3. The gripper assembly according to claim 1, characterized in that, The top of the gripping rod is provided with an electrode pressing surface, which is used to withstand the compression of the outer periphery of the welding electrode, so that the top of each gripping rod in the closed state surrounding the welding electrode can open.

4. The gripper assembly according to claim 3, characterized in that, The electrode pressing surface forms an acute angle α1 with the vertical line, and the acute angle α1 is smaller than the acute angle α3, where the acute angle α3 is the acute angle formed by the side wall of the outer periphery of the electrode welding surface and the side wall of the electrode body.

5. The gripper assembly according to claim 1, characterized in that, The top of the gripping rod, serving as the gripping head, can be disassembled and replaced.

6. A delivery assembly for delivering fasteners on demand to the gripping assembly according to any one of claims 1-5, characterized in that, Includes a feed bar, a second driver, and a feed tube; The feeding rod is equipped with a discharge nozzle at one end, and a feeding pipe and a gas pipe are provided in the feeding rod. The end of the feeding pipe is connected to the discharge nozzle, so that the fastener enters the feeding pipe through the material pipe and is then transported to the discharge nozzle. The gas pipeline is connected to the discharge nozzle and is used to connect high-pressure gas to assist the discharge nozzle in releasing the fasteners; The discharge nozzle is equipped with a check valve and a third elastic component. The check valve prevents the fasteners fed into the discharge nozzle from springing back along the feeding pipe. The third elastic component is used to clamp the fasteners in the discharge nozzle. The second driver causes the feed rod to extend and retract, continuously supplying fasteners to the gripper assembly.

7. The delivery assembly according to claim 6, characterized in that, The feeding assembly is independently mounted on the side of the spot welding device. The second driver causes the feeding rod to extend and retract in the direction perpendicular to the axial direction of the electrode connecting rod. The feeding assembly also includes a third driver for driving the feeding assembly to move in the direction parallel to the axial direction of the electrode connecting rod.

8. The delivery assembly according to claim 6, characterized in that, The feeding assembly is integrated into the side of the gripping assembly. The second driver drives the feeding rod to extend and retract in a direction parallel to the axial direction of the electrode connecting rod. When the feeding rod extends downward, the discharge nozzle rotates from the direction toward the side wall of the welding electrode to the direction toward the end of the welding electrode.

9. A resistance spot welding device for welding dissimilar metals, the device continuously supplies fasteners for welding and welds the fasteners to the weld points of a first metal and a second metal stack, the resistance spot welding device comprising a welding clamp, a welding robot, a robot control cabinet, a feeding cabinet, a vacuum pump, and a main control cabinet, wherein the dissimilar metals welded by the resistance spot welding device comprise a first metal and a second metal, the first metal having a melting point below 750°C and the second metal having a melting point above 1300°C, the fasteners being fed include a shaft portion and a cap surrounding the shaft portion, and during welding, the spot welding device feeds the fasteners to the front end of the welding electrode and welds the dissimilar metals, characterized in that: The invention includes the gripping assembly as described in any one of claims 1-5 and the feeding assembly as described in any one of claims 6-8; the feeding assembly is used to receive fasteners conveyed from the feed tube by the feed cabinet and deliver the fasteners to the gripping assembly as needed; the gripping assembly is used to grip the fasteners and, in conjunction with a spot welding device, weld the fasteners to the weld points of dissimilar metals.

10. A method for resistance spot welding, used in the resistance spot welding apparatus of claim 9 for welding dissimilar metals, characterized in that: The welding process specifically includes the following steps: a. During the feeding stage, the feeding cabinet uses high-pressure gas to transport the fasteners to the discharge nozzle of the feeding rod. The gripping assembly and the feeding assembly work together to align the welding electrode with the discharge nozzle of the gripping rod, and the fasteners discharged from the discharge nozzle are gripped by the vacuum suction force of the gripping head. b. During the pre-compression stage, the welding rod moves toward the first and second metal stacks. When the fastener or gripper head contacts the first metal surface, the welding clamp continues to apply electrode pressure to the weld point. The gripper head opens under the pressure of the outer peripheral sidewall of the electrode end face, so that the welding surface of the electrode presses the fastener onto the first metal with a set pressure. c. During the welding stage, at least one current pulse is input into the weld joint by the welding electrode. The current pulse causes the first metal covered by the fastener shaft to melt at high speed and be sprayed into the cap of the fastener. After the fastener shaft is squeezed by the electrode pressure, it quickly penetrates the first metal layer and comes into contact with the second metal. The resistance heat generated by the current pulse causes the common melt nugget formed between the fastener shaft and the second metal to achieve a firm connection. d. At the end of the welding stage, the electrode connecting rod retracts, causing the electrode and gripper assembly to move away from the weld point. The sliding component and gripper rod of the gripper assembly are reset under the drive of the first elastic component and the second elastic component, so that the gripper head returns to the closed state and surrounds the outer periphery of the welding electrode.

11. The resistance spot welding method according to claim 10, characterized in that, When the thickness of the first metal is less than or equal to 1.5 mm, the current pulse input during the welding stage is: A series of short current pulses, each lasting less than 60 ms, with intervals between the current pulses. Cooldown time; When the thickness of the first metal is greater than 1.5 mm, the welding stage adopts a multi-stage welding current pulse process including a preheating stage, a fastener piercing stage and a connection stage. In the fastener piercing stage, each current pulse is maintained for less than 80 ms, and the current pulse in this stage causes molten first metal to be ejected from the weld joint.

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