Laser welding system for dissimilar metals of copper pipe and heat absorbing plate of flat plate type solar heat collector

Abstract

The invention discloses a dissimilar metal laser welding system for a copper pipe and a heat absorbing plate of a flat plate type solar heat collector, and belongs to the technical field of heat collector laser welding. According to the mobile laser welding compensation device, the single process that a traditional welding device firstly conducts fitting and then conducts welding is broken through, the thermal stress compensation unit and the laser welding unit are integrated in the mobile laser welding compensation unit, and the thermal stress compensation unit and the laser welding unit are integrated in the mobile laser welding compensation unit; a compensation wheel of the thermal stress compensation unit directly acts on a welding area, real-time stress compensation in the welding process is achieved in cooperation with elastic buffering of a compensation spring, deformation and cracking caused by stress release after traditional welding are avoided, the stress value of a welding spot area is stably controlled to be below a welding seam anti-cracking threshold value, and the welding quality is improved. The stress cracking problem of laser welding of the copper and aluminum dissimilar metal is thoroughly solved, and the laser welding qualification rate of the heat collector is increased.

Description

Technical Field

[0001] This invention relates to the field of laser welding of solar collectors, specifically a laser welding system for dissimilar metals, such as copper tubes and absorber plates, in flat-plate solar collectors. Background Technology

[0002] As a core component of solar thermal utilization systems, flat-plate solar collectors consist of copper tubes made of copper and absorber plates made of aluminum alloy. These two components must be welded together to form a tight heat transfer connection. This dissimilar metal laser welding process directly determines the heat transfer performance and structural stability of the collector. With the expanding application scenarios of flat-plate solar collectors, higher requirements are placed on the quality precision and structural reliability of the welding between the copper tubes and absorber plates. Traditional welding equipment is gradually becoming unable to meet the demands for stable and precise welding.

[0003] Existing laser welding systems for dissimilar metals, such as copper tubes and absorbers in flat-plate solar collectors, have several technical shortcomings in practical applications:

[0004] Traditional methods often employ a single process of bonding first and then welding, lacking a real-time stress compensation mechanism. Due to the significant differences in the thermal expansion coefficients and melting points between the copper tube and the heat absorber plate, the welding area is prone to severe internal stress during the welding process due to sudden temperature rises and falls. When the stress value exceeds the weld crack resistance threshold, it is very easy to cause the weld to crack, resulting in unqualified welding. This not only increases material waste but also affects the overall structural strength of the collector.

[0005] Traditional designs employ fixed compensation forces and lack temperature-linked adaptive adjustment structures. During welding, the temperature of different welding areas dynamically changes due to differences in laser energy and workpiece thickness. Fixed compensation forces cannot match these temperature fluctuations. In the high-temperature stage, insufficient compensation can exacerbate the risk of weld cracking, while in the low-temperature stage, excessive compensation can cause deformation of the copper tube or heat absorber. This makes it difficult to adapt to the needs of different specifications and welding conditions, resulting in poor versatility.

[0006] The welding unit lacks an effective pre-pressing and bonding structure and a precise transmission mechanism. Before welding, the interface between the copper tube and the absorber plate is prone to small gaps due to positioning deviations, leading to defects such as incomplete welds and porosity during welding. Furthermore, the force transmission during welding lacks guiding constraints, resulting in insufficient positioning accuracy and large fluctuations in welding quality at different weld points, making it difficult to ensure a tight heat transfer connection between the copper tube and the absorber plate. This not only increases the labor and time costs of subsequent inspection and repair but also reduces the overall thermal efficiency of the collector due to the loose heat transfer interface, affecting the collector's performance.

[0007] Therefore, there is an urgent need for a laser welding system for dissimilar metals, such as copper tubes and absorber plates, in flat-plate solar collectors to solve the aforementioned problems with existing equipment. Summary of the Invention

[0008] The purpose of this invention is to provide a dissimilar metal laser welding system for copper tubes and absorber plates of flat-plate solar collectors, in order to solve the problems mentioned in the background art regarding existing laser welding of solar collectors.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a fixed frame is included, on which a welding object body to be welded is disposed, and the welding object body includes a copper tube and a heat absorption plate. A movable laser welding compensation unit for welding the welding object is disposed on the upper side of the welding object body, and a heat adaptation drive unit for adjusting the applied pressure by adjusting the welding temperature is disposed on one side of the movable laser welding compensation unit. The movable laser welding compensation unit transmits the bending force of the bimetallic strip, which senses the heat generated by laser welding, to the laser welding position of the copper tube and the heat absorption plate.

[0010] The mobile laser welding compensation unit includes a laser welding unit for laser welding the workpiece body and a thermal stress compensation unit driven by a heat adaptation drive unit. The heat adaptation drive unit includes a thermal stress transmission component that transmits heat generated during welding by the laser welding unit, and the heat adaptation drive unit also includes a hydraulic transmission component that is driven by the thermal stress transmission component.

[0011] As a further preferred embodiment of this technical solution: the laser welding unit includes a connecting frame installed inside the fixed frame, and one end of the connecting frame is connected to a first connecting plate, and a pressing welding wheel is provided on the lower side of the first connecting plate, while one side of the first connecting plate is connected to;

[0012] As a further preferred embodiment of this technical solution: the pressing welding wheel is attached to the connecting frame that is rolled on the upper surface of the copper tube, and the pressing welding wheel is rotatably connected to the connecting block provided on the lower side of the first connecting plate, and the fixing plate is fixedly provided on one side of the first connecting plate, while the shape of the compensation wheel is U-shaped;

[0013] As a further preferred embodiment of this technical solution: the thermal stress compensation unit includes a connecting cylinder fixedly disposed in the middle position of the fixed plate, and a sliding rod is provided on the inner side of the connecting cylinder, and a driven pressure plate is connected to the upper side of the sliding rod, a compensation spring is provided on the inner side of the connecting cylinder, and a support frame is connected to the lower side of the fixed plate, and a compensation wheel is connected to the inner side of the support frame.

[0014] As a further preferred embodiment of this technical solution: the end of the sliding rod away from the driven lower pressure plate is slidably connected to the inner side of the connecting cylinder, and the two ends of the compensation spring are respectively connected to the end of the sliding rod away from the driven lower pressure plate and the middle position of the upper side of the support frame, and the upper side of the support frame is slidably connected to the lower side of the fixed plate through the provided sliding rod, and the compensation wheel is rotatably connected to the inner side of the support frame.

[0015] As a further preferred embodiment of this technical solution: the thermal stress transmission assembly includes a support seat that is bolted to the inside of the fixed frame, and a connecting lever is connected to the upper side of the support seat. One end of the connecting lever is connected to a first transmission shaft. Meanwhile, a first transmission connecting frame is provided on the outside of the first transmission shaft, and a connecting rod is connected to the upper side of the first transmission connecting frame. The upper end of the connecting rod is connected to a second transmission connecting frame. Meanwhile, a transmission sliding shaft is connected to the inside of the second transmission connecting frame, and a bimetallic strip is connected to the upper side of the transmission sliding shaft.

[0016] As a further preferred embodiment of this technical solution: the thermal stress transmission assembly further includes a second transmission shaft disposed at the end of the connecting lever away from the first transmission shaft, and a third transmission connection frame is disposed on the outer side of the second transmission shaft;

[0017] As a further preferred embodiment of this technical solution: the connecting lever is rotatably connected to the upper side of the support base, and the connecting lever is connected to the support base by bolts. The first transmission shaft is slidably connected to the inner groove of the first transmission connecting frame, while the connecting rod is slidably disposed on the inner side of the fixed frame. The end of the bimetallic strip away from the transmission shaft is fixedly disposed on the inner side of the fixed frame, and the bimetallic strip is attached to the lower surface of the heat absorption plate. The transmission shaft is slidably connected to the inner side of the second transmission connecting frame, and the second transmission shaft is slidably connected to the inner side of the third transmission connecting frame.

[0018] As a further preferred embodiment of this technical solution: the hydraulic transmission assembly includes a second connecting plate disposed on the upper side of the third transmission connecting frame, and a first piston slide rod is connected to the upper side of the second connecting plate. The hydraulic transmission assembly also includes a connecting pipe connected to the fixed frame, and the first piston slide rod is slidably connected to the inner side of the connecting pipe. Meanwhile, a return spring is sleeved on the outer side of the first piston slide rod, and a second piston slide rod is connected to the inner side of the end of the connecting pipe away from the first piston slide rod. A compensation pressure plate is connected to one end of the second piston slide rod.

[0019] As a further preferred embodiment of this technical solution: the two ends of the return spring are respectively connected to the upper side of the second connecting plate and the side of the connecting tube near the second connecting plate, and the second piston slide rod is slidably connected to the end of the connecting tube away from the first piston slide rod, and the compensating lower pressure plate is slidably attached to the upper side of the driven lower pressure plate.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention breaks through the traditional welding equipment's single process of first bonding and then welding. It integrates a thermal stress compensation unit and a laser welding unit in a mobile laser welding compensation unit. The compensation wheel of the thermal stress compensation unit directly acts on the welding area, and with the elastic buffer of the compensation spring, it realizes real-time stress compensation during welding, rather than the traditional stress release after welding that leads to deformation and cracking. It stably controls the stress value of the weld area below the weld crack resistance threshold, completely solves the problem of stress cracking in laser welding of dissimilar metals such as copper and aluminum, and improves the pass rate of laser welding of solar collectors.

[0022] 2. Simultaneously, the pressing welding wheel of the laser welding unit pre-presses the copper tube and heat absorption plate along with the workpiece conveyor, eliminating tiny gaps at the interface through rolling and bonding, thus preventing incomplete welding and porosity from the source.

[0023] 3. Among them, the thermal stress driving unit innovatively adopts a combination structure of bimetallic sheet and hydraulic transmission. The bimetallic sheet is attached to the heat absorption plate to sense the temperature in real time. The temperature signal is directly converted into mechanical bending force by utilizing the difference in thermal expansion coefficient of different metals, without the need for additional electronic control sensors.

[0024] Furthermore, by lever conversion of the thermal stress transmission component and pressure amplification of the hydraulic transmission component, adaptive adjustment is achieved, where the compensation force increases with higher temperatures and decreases with lower temperatures, rather than through traditional manual adjustment. This design precisely matches the stress changes caused by temperature fluctuations during welding, avoiding both insufficient high-temperature compensation leading to cracking and excessive low-temperature compensation causing deformation, thereby reducing the workpiece deformation rate.

[0025] 4. Furthermore, this invention features multiple guiding and transmission safeguards. In the mobile laser welding compensation unit, the connecting cylinder provides axial guidance for the sliding rod, and the support frame restricts lateral displacement through the sliding rod, ensuring that the compensation force is not offset. In the thermal stress drive unit, the support seat is double-fixed with a rotating shaft and bolts, and the connecting pipe uses a sealed hydraulic transmission to ensure efficient force transmission. At the same time, the two work together to achieve integrated welding and compensation operations without manual intervention. This system solves the problem of large quality fluctuations in the large-scale production of traditional equipment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 1 ;

[0027] Figure 2 This is a schematic diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 2 ;

[0028] Figure 3 This is a partial structural diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 1 ;

[0029] Figure 4 This is a partial structural diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 2 ;

[0030] Figure 5 This is a partial structural diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 3 ;

[0031] Figure 6 This is a partial structural diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 4 ;

[0032] Figure 7 This is a partial structural cross-section of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 1 ;

[0033] Figure 8 This is a partial structural diagram of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 5 ;

[0034] Figure 9 This is a partial structural cross-section of the dissimilar metal laser welding system for copper tubes and absorber plates in a flat-plate solar collector according to the present invention. Figure 2 .

[0035] In the diagram: 1. Fixed frame; 2. Welded object body; 201. Copper pipe; 202. Heat absorber plate;

[0036] 3. Mobile laser welding compensation unit;

[0037] Laser welding unit: 301, connecting frame; 302, first connecting plate; 303, pressing welding wheel; 304, fixing plate;

[0038] Thermal stress compensation unit: 305, connecting cylinder; 306, sliding rod; 307, driven lower pressure plate; 308, compensation spring; 309, support frame; 310, compensation wheel;

[0039] 4. Thermal stress driving unit;

[0040] Thermal stress transmission assembly: 401, support base; 402, connecting lever; 403, first transmission shaft; 404, first transmission connecting frame; 405, connecting rod; 406, second transmission connecting frame; 407, transmission slide shaft; 408, bimetallic strip; 409, second transmission shaft; 410, third transmission connecting frame;

[0041] Hydraulic transmission components: 411, second connecting plate; 412, first piston slide rod; 413, connecting pipe; 414, return spring; 415, second piston slide rod; 416, compensating pressure plate. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example

[0044] Please see Figures 1-9 This is a schematic diagram of some embodiments of the dissimilar metal laser welding system for copper tubes and absorber plates in the flat-plate solar collector of this application.

[0045] In some embodiments, the dissimilar metal laser welding system for copper tubes and absorber plates of flat-plate solar collectors can be applied to the large-scale manufacturing of flat-plate solar collectors. Specific applications include the processing of core components for household flat-plate solar water heater collectors and commercial pressurized flat-plate solar collectors. Figure 1 In this embodiment, the welding system is used as an example to describe the welding process of copper tubes and absorber plates in a household flat-plate solar water heater collector. Of course, similar structures can also be used for dissimilar metal laser welding scenarios of other types of flat-plate solar collectors, which will not be described in detail below.

[0046] Understandable, Figure 1 The diagram only schematically illustrates some of the components included in the laser welding system; the actual shape, size, location, and construction of these components are not subject to change. Figure 1 Due to limitations, laser welding systems can also include, compared to... Figure 1 More or fewer components. For example, to improve welding accuracy, a visual positioning camera can be added; to achieve automated loading and unloading, a robotic arm gripping component can be added, etc.

[0047] In some embodiments, the dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector may include a fixed frame 1, a welding object body 2, a movable laser welding compensation unit 3, and a heat adaptation drive unit 4. The welding object body 2 is mounted on the fixed frame 1, the movable laser welding compensation unit 3 is located on top of the welding object body 2, and the heat adaptation drive unit 4 is located on one side of the movable laser welding compensation unit 3. When the laser welding system is running, the fixed frame 1 serves as the installation base for the entire system. The welding object body 2 is placed at a designated position on the fixed frame 1, the movable laser welding compensation unit 3 performs the welding operation on both, and the heat adaptation drive unit 4 adjusts the compensation force according to the welding temperature.

[0048] In some embodiments, the welding object body 2 includes a copper pipe 201 and a heat absorber plate 202. The copper pipe 201 is made of copper and is used to transmit the heat transfer medium. The heat absorber plate 202 is made of aluminum alloy and has a selective absorption coating on its surface. It is used to absorb solar energy and transfer heat to the copper pipe 201. The copper pipe 201 is laid parallel to the upper surface of the heat absorber plate 202. During welding, it is necessary to ensure that the two are in close contact to avoid gaps that could lead to welding defects.

[0049] It should be noted that the dimensions of the copper tube 201 and the absorber plate 202 can be adjusted according to the specifications of the flat-plate solar collector. This description only uses a common household specification as an example. Understandably, the arrangement of the copper tube 201 and absorber plate 202 shown in the figure is for illustrative purposes only. The specific arrangement can be adjusted according to the thermal efficiency requirements of the collector and is not limited here.

[0050] In some embodiments, the laser welding unit includes a connecting frame 301, a first connecting plate 302, a pressing welding wheel 303, and a fixing element, wherein:

[0051] The connecting frame 301 is bolted to the inside of the fixed frame 1. It is made of Q235 steel and has a rectangular cross-section to ensure support stability.

[0052] The first connecting plate 302 is made of stainless steel and is fixed to one end of the connecting frame 301 by welding, and is used to install the pressing welding wheel 303.

[0053] The pressing welding wheel 303 is made of Cr12MoV alloy and its surface is hardened. It is rolled and attached to the upper surface of the copper tube 201 and rotatably connected to the connecting block on the lower side of the first connecting plate 302. It can roll synchronously with the copper tube 201 to pre-press and attach the copper tube 201 and the heat absorption plate 202.

[0054] The fixing plate 304 is made of stainless steel and is fixed to one side of the first connecting plate 302 by bolts. It is used to install the components of the thermal stress compensation unit.

[0055] It should be noted that the pressure of the welding wheel 303 can be adjusted by adjusting the connection position between the connecting block and the first connecting plate 302 to ensure that the copper tube 201 and the heat absorber plate 202 are in close contact. In this embodiment, the pre-pressure of the welding wheel 303 can eliminate the small gap between the copper tube 201 and the heat absorber plate 202, avoiding defects such as incomplete welding and porosity during laser welding. At the same time, it can assist in conveying the welding object body 2, improving welding efficiency.

[0056] In some embodiments, the thermal stress compensation unit includes a connecting cylinder 305, a sliding rod 306, a driven lower pressure plate 307, a compensation spring 308, a support frame 309, and a compensation wheel 310, wherein:

[0057] The connecting cylinder 305 is made of stainless steel and is fixedly installed in the middle of the fixed plate 304, with the sliding rod 306 providing guidance on the inner side.

[0058] The sliding rod 306 is made of No. 45 steel. The end away from the driven lower pressure plate 307 is slidably connected to the inner side of the connecting cylinder 305 and can slide along the axial direction of the connecting cylinder 305.

[0059] The driven lower pressure plate 307 is made of aluminum alloy and is bolted to the upper side of the sliding rod 306 to receive the compensation force transmitted by the hydraulic transmission assembly.

[0060] The compensating spring 308 is made of piano wire, and its two ends are respectively connected to the end of the sliding rod 306 away from the driven lower pressure plate 307 and the upper middle position of the support frame 309. The initial state is a pre-compressed state, providing basic compensation force.

[0061] The support frame 309 is made of stainless steel and has a U-shaped structure. Its upper side is slidably connected to the lower side of the fixed plate 304 via a slide rod, and it can move laterally along the slide rod.

[0062] The compensation wheel 310 is made of polyurethane and is rotatably connected to the inside of the support frame 309, which can apply lateral compensation force to the copper tube 201.

[0063] In this embodiment, when the heat adaptation drive unit 4 transmits the compensation force to the driven lower pressure plate 307, the driven lower pressure plate 307 pushes the sliding rod 306 to move downward along the connecting cylinder 305. The sliding rod 306 compresses the compensation spring 308, and the compensation spring 308 transmits the force to the support frame 309. The support frame 309 drives the compensation wheel 310 to apply pressure to the copper tube 201, thereby relieving the internal stress generated when the heat absorber plate 202 is restricted by the copper tube 201. This makes the stress value in the weld area lower than the crack resistance threshold of the weld between the copper tube 201 and the heat absorber plate 202, thus preventing the weld from cracking.

[0064] It should be noted that the stiffness of the compensation spring 308 can be adjusted according to the material of the welded object. In some other embodiments, a disc spring can be used instead of a cylindrical helical spring. It is not limited to using only the compensation spring 308, as long as the elastic compensation function can be achieved.

[0065] In some embodiments, the thermal stress transmission assembly includes a support base 401, a connecting lever 402, a first transmission shaft 403, a first transmission connecting frame 404, a connecting rod 405, a second transmission connecting frame 406, a transmission sliding shaft 407, a bimetallic strip 408, a second transmission shaft 409, and a third transmission connecting frame 410, wherein:

[0066] The support base 401 is made of cast iron and is installed inside the fixed frame 1 by bolts. A rotating shaft is provided on the upper side to support the connecting lever 402.

[0067] The connecting lever 402 is made of steel and is rotatably connected to the upper side of the support base 401. It can rotate around the axis of the support base 401 to realize the transmission and amplification of force.

[0068] The first drive shaft 403 is made of stainless steel and is fixedly connected to one end of the connecting lever 402. It is slidably connected to the inner groove of the first drive connecting frame 404 and can drive the first drive connecting frame 404 to move up and down.

[0069] The first transmission connecting frame 404 is made of aluminum alloy and has a U-shaped structure. The upper side is connected to the connecting rod 405 by bolts.

[0070] The connecting rod 405 is made of stainless steel and is slidably set in the guide hole opened on the inner side of the fixed frame 1, and can slide along the axial direction of the guide hole;

[0071] The second transmission connecting frame 406 is made of aluminum alloy and is bolted to the upper end of the connecting rod 405. A transmission slide shaft 407 is connected to the inner side.

[0072] The transmission shaft 407 is made of stainless steel and is slidably connected to the inner side of the second transmission connection frame 406, and can slide within the second transmission connection frame 406.

[0073] The bimetallic strip 408 is made of Invar alloy and brass composite. One end away from the transmission slide shaft 407 is fixedly set on the inner side of the fixed frame 1 and attached to the lower surface of the heat absorber plate 202. It can be bent by induction of the heat generated by laser welding.

[0074] The second drive shaft 409 is made of stainless steel and is fixedly connected to the end of the connecting lever 402 away from the first drive shaft 403. It is slidably connected to the inner side of the third drive connecting frame 410 and can drive the third drive connecting frame 410 to move up and down.

[0075] The third transmission connecting frame 410 is made of aluminum alloy, and the upper side is connected to the second connecting plate 411 of the hydraulic transmission component.

[0076] It should be noted that the diagram illustrates the bending direction of the bimetallic strip 408. When the heat generated by laser welding raises the temperature of the heat absorber plate 202, the coefficient of thermal expansion of the brass in the bimetallic strip 408 is greater than that of the Invar alloy. The bimetallic strip 408 bends towards the Invar alloy side, pushing the transmission slide shaft 407 to move. The transmission slide shaft 407 drives the second transmission connecting frame 406 to move down. The second transmission connecting frame 406 drives the first transmission connecting frame 404 to move down through the connecting rod 405. The first transmission connecting frame 404 pulls one end of the connecting lever 402 down through the first transmission shaft 403. The connecting lever 402 rotates around the support base 401 shaft, and the other end moves up. Through the second transmission shaft 409, it drives the third transmission connecting frame 410 to move up, thus realizing the transfer of thermal stress.

[0077] Understandably, the length of the bimetallic strip 408 can also be other sizes to achieve different bending displacements. The length of the bimetallic strip 408 is not limited here, as long as it can sense heat and transfer power.

[0078] In some embodiments, the hydraulic transmission assembly includes a second connecting plate 411, a first piston slide 412, a connecting pipe 413, a return spring 414, a second piston slide 415, and a compensating pressure plate 416, wherein:

[0079] The second connecting plate 411 is made of stainless steel and is bolted to the upper side of the third transmission connecting frame 410 for mounting the first piston slide rod 412.

[0080] The first piston slide rod 412 is made of stainless steel and is slidably connected to the inside of the connecting pipe 413. A sealing ring is provided on the surface to ensure hydraulic sealing.

[0081] The connecting pipe 413 is made of seamless steel pipe and is fixedly connected to the fixed frame 1 by a bracket. The inside is filled with hydraulic oil to transmit hydraulic pressure.

[0082] The return spring 414 is made of piano wire and is sleeved on the outside of the first piston slide rod 412. Its two ends are respectively connected to the upper side of the second connecting plate 411 and the side of the connecting tube 413 near the second connecting plate 411. Its initial state is the natural state and it is used to reset the first piston slide rod 412.

[0083] The second piston slide rod 415 is made of stainless steel and is slidably connected to the end of the connecting tube 413 away from the first piston slide rod 412. The surface is also provided with a nitrile rubber sealing ring.

[0084] The compensating lower pressure plate 416 is made of aluminum alloy and is bolted to one end of the second piston slide rod 415. It slides against the upper side of the driven lower pressure plate 307 and is used to transmit hydraulic pressure to the driven lower pressure plate 307.

[0085] In this embodiment, when the third transmission connecting frame 410 moves upward, it drives the second connecting plate 411 to move upward. The second connecting plate 411 pulls the first piston slide rod 412 to slide upward along the connecting pipe 413. The hydraulic oil pressure inside the connecting pipe 413 increases, pushing the second piston slide rod 415 to slide downward. The second piston slide rod 415 drives the compensating lower pressure plate 416 to move downward, applying a compensating force to the driven lower pressure plate 307. The higher the welding temperature, the greater the bending degree of the bimetallic strip 408, the longer the sliding distance of the first piston slide rod 412, the greater the hydraulic pressure, and the greater the compensating force, thus realizing the function of adaptively adjusting the magnitude of the compensating force according to the welding temperature.

[0086] It should be noted that the hydraulic oil capacity in the connecting pipe 413 can be adjusted according to the required compensation force range. Understandably, the installation position of the hydraulic transmission component shown in the figure is only schematic, and the specific installation position can be adjusted according to the structure of the fixed frame 1, which is not limited here.

[0087] In some embodiments, the drive unit that moves the laser welding unit includes a Z-axis drive assembly (not shown) for vertical movement, an X-axis drive assembly (not shown) for movement along the length of the copper tube 201, and a mounting base (not shown). All components are integrated on the upper side of the fixed frame 1 and rigidly connected to the connecting frame 301 of the laser welding unit, ensuring no relative wobbling of the laser welding unit during movement. This is suitable for welding scenarios involving the copper tube 201 and the absorber plate 202 of a flat-plate solar collector. Wherein:

[0088] Z-axis drive assembly: may include Z-axis linear guide, Z-axis slide block and Z-axis servo motor; Z-axis servo motor is connected to Z-axis slide block through ball screw. When the motor is running, it converts the rotational motion into the linear motion of Z-axis slide block, which drives the laser welding unit to move downwards closer to the welding object body 2 or upwards away from the welding object body 2. In the initial state, the laser welding unit is located at the high position of Z-axis, and moves downwards to the working position before welding.

[0089] Specifically, in the initial state, the Z-axis sliding seat is in a high position. After welding starts, the control system first sends a signal to move the Z-axis downward. The motor drives the lead screw to rotate, and the sliding seat moves the laser welding unit downward. The laser range sensor provides real-time feedback of the distance. When the detected distance reaches the preset position, the motor stops and the brake locks.

[0090] X-axis drive assembly: Installed on the lower side of the Z-axis slide seat, including X-axis linear guide, X-axis slide seat and X-axis servo motor; X-axis servo motor drives X-axis slide seat to move through ball screw, and laser welding unit connecting frame 301 is fixed on the lower side of X-axis slide seat, which can drive laser welding unit to move along the length of copper tube 201, adapting to the welding requirements of fixed welding points of copper tubes 201 of different lengths.

[0091] Specifically, the X-axis servo motor receives pulse signals from the control system through pulse control mode, and the 17-bit encoder provides real-time feedback on the motor's rotation angle position, forming a closed-loop control.

[0092] Mounting base: It is fixed to the upper side of the fixed frame 1 by expansion bolts and is used to support the Z-axis guide rail and servo motor; shock-absorbing pads are set between the base and the guide rail to absorb the vibration generated when the servo motor is running and prevent the vibration from being transmitted to the laser welding unit and causing the weld point to shift.

[0093] It should be noted that the figure only shows a simplified structure of the drive unit. In actual installation, the Z-axis guide rail needs to be calibrated with a verticality instrument to ensure that the guide rail is vertical; the X-axis guide rail needs to be parallel to the length direction of the copper tube 201 to ensure the compatibility of the movement path with the copper tube 201.

[0094] For example, the movement of the drive unit strictly follows the sequence of first moving downwards along the Z-axis, then moving along the X-axis along the copper tube 201, and finally moving upwards along the Z-axis. It is also equipped with protective components and a lubrication system to ensure movement stability.

[0095] Movement sequence control: In the initial state, the laser welding unit is located at the high position of the Z-axis and the starting position of the X-axis. After welding starts, the control system first sends a Z-axis drive signal, the Z-axis servo motor runs, and drives the laser welding unit to move downward. After the Z-axis is in place, the control system sends an X-axis drive signal, the X-axis servo motor runs, and drives the laser welding unit to move along the length of the copper tube 201, aligning with the fixed welding points one by one for welding. After the welding of a single copper tube 201 is completed, the Z-axis first moves upward to the high position, and then the X-axis resets to the starting position, waiting for the next copper tube 201 to be delivered to the position before repeating the above process.

[0096] In this embodiment, by first moving the Z-axis downward, then moving the X-axis along the copper tube 201, and finally moving the Z-axis upward, interference between the laser welding unit and other components can be avoided when the laser welding unit moves at a high position, while ensuring that the laser focus is always accurately aligned with the fixed welding point.

[0097] As a preferred implementation, a coordinate library of fixed welding points for flat-plate solar collectors of different specifications is preset in the control system: the X-axis starting position and Z-axis working position of the fixed frame 1 are used as the reference origin, and the X-axis spacing of the fixed welding points is set according to the diameter of the copper tube 201. The coordinate library can be edited and modified through the human-machine interface (not shown) to adapt to the replacement needs of different specifications of products.

[0098] Working principle or structural principle: In the initial state, the welding object body 2 is placed at the designated position of the fixed frame 1, the pressing welding wheel 303 is attached to the upper surface of the copper tube 201, the compensation spring 308 is in a pre-compressed state, providing basic pre-pressure for the thermal stress compensation unit; the bimetallic strip 408 is in a natural state, the first piston slide 412 and the second piston slide 415 of the hydraulic transmission assembly are both in the initial position, and the compensation lower pressure plate 416 is in slight contact with the driven lower pressure plate 307;

[0099] When the laser welding system is started, the conveying unit transports the workpiece 2 to the welding station, and the laser welding unit begins laser welding at the joint between the copper tube 201 and the heat absorber plate 202. The heat generated during welding is transferred to the heat absorber plate 202, causing its temperature to rise. The bimetallic strip 408, attached to the lower surface of the heat absorber plate 202, senses the heat and bends towards the side with the smaller coefficient of thermal expansion, pushing the transmission shaft 407 to move. The transmission shaft 407 drives the second transmission connecting frame 406 downwards, which, through the connecting rod 405 and the first transmission connecting frame 404, drives the first transmission shaft 403 downwards, causing the connecting lever 402 to rotate around the support base 401. The other end of the connecting lever 402 moves upwards, driving the second transmission shaft 409 to... The third transmission connecting frame 410 moves upward; the third transmission connecting frame 410 pulls the second connecting plate 411 upward, the second connecting plate 411 drives the first piston slide rod 412 to slide upward along the connecting pipe 413, the hydraulic oil pressure in the connecting pipe 413 increases, pushing the second piston slide rod 415 downward, the second piston slide rod 415 drives the compensating lower pressure plate 416 to apply a compensating force to the driven lower pressure plate 307; the driven lower pressure plate 307 transmits the compensating force to the sliding rod 306, the sliding rod 306 compresses the compensating spring 308, pushing the support frame 309 downward, the support frame 309 drives the compensating wheel 310 to apply a lateral compensating force to the copper pipe 201, relieving the internal stress generated when aluminum is restricted by copper, so that the stress value in the weld area is lower than the weld crack resistance threshold;

[0100] When welding is completed, the welded object body 2 leaves the welding station, the temperature of the heat absorber plate 202 gradually decreases, the bimetallic strip 408 returns to its natural state and no longer applies a thrust to the transmission slide shaft 407; the reset spring 414 pushes the second connecting plate 411 down, the second connecting plate 411 drives the first piston slide rod 412 to reset, the hydraulic oil pressure in the connecting pipe 413 decreases, the second piston slide rod 415 resets under the action of the compensation spring 308, the compensation wheel 310 no longer applies a compensation force to the copper pipe 201, the entire system returns to its initial state, waiting for the next welding operation.

[0101] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0102] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art, inspired by this description, design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the scope of protection of this invention.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser welding system for dissimilar metals, consisting of copper tubes and absorber plates in a flat-plate solar collector, characterized in that: The system includes a fixed frame (1), on which a welding object body (2) to be welded is mounted. The welding object body (2) includes a copper tube (201) and a heat absorber plate (202). A movable laser welding compensation unit (3) for welding the welding object is mounted on the upper side of the welding object body (2). A heat adaptation drive unit (4) for adjusting the applied pressure by adjusting the welding temperature is mounted on one side of the movable laser welding compensation unit (3). The movable laser welding compensation unit (3) transmits the bending force generated by the heat generated by the laser welding through the bimetallic strip (408) to the laser welding position of the copper tube (201) and the heat absorber plate (202). The mobile laser welding compensation unit (3) includes a laser welding unit for laser welding the workpiece body (2) and a thermal stress compensation unit driven by a heat adaptation drive unit (4). The heat adaptation drive unit (4) includes a thermal stress transmission component that transmits heat generated during welding by the laser welding unit. The heat adaptation drive unit (4) also includes a hydraulic transmission component that is driven by the thermal stress transmission component.

2. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 1, characterized in that: The laser welding unit includes a connecting frame (301) installed on the inner side of the fixed frame (1), and one end of the connecting frame (301) is connected to a first connecting plate (302), and a pressing welding wheel (303) is provided on the lower side of the first connecting plate (302), while one side of the first connecting plate (302) is connected to a...

3. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 2, characterized in that: The pressing welding wheel (303) is attached to the connecting frame (301) that is rolled on the upper surface of the copper tube (201), and the pressing welding wheel (303) is rotatably connected to the connecting block provided on the lower side of the first connecting plate (302). The fixing plate (304) is fixedly provided on one side of the first connecting plate (302), and the compensation wheel (310) is U-shaped.

4. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 3, characterized in that: The thermal stress compensation unit includes a connecting cylinder (305) fixedly installed in the middle of the fixed plate (304), and a sliding rod (306) is provided on the inner side of the connecting cylinder (305). A driven lower pressure plate (307) is connected to the upper side of the sliding rod (306), a compensation spring (308) is provided on the inner side of the connecting cylinder (305), a support frame (309) is connected to the lower side of the fixed plate (304), and a compensation wheel (310) is connected to the inner side of the support frame (309).

5. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 4, characterized in that: The end of the sliding rod (306) away from the driven lower pressure plate (307) is slidably connected to the inner side of the connecting cylinder (305), and the two ends of the compensating spring (308) are respectively connected to the end of the sliding rod (306) away from the driven lower pressure plate (307) and the middle position of the upper side of the support frame (309). The upper side of the support frame (309) is slidably connected to the lower side of the fixed plate (304) through the provided sliding rod, and the compensating wheel (310) is rotatably connected to the inner side of the support frame (309).

6. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 5, characterized in that: The thermal stress transmission assembly includes a support base (401) installed on the inner side of the fixed frame (1) by bolts, and a connecting lever (402) is connected to the upper side of the support base (401). One end of the connecting lever (402) is connected to a first transmission shaft (403). A first transmission connecting frame (404) is provided on the outer side of the first transmission shaft (403). A connecting rod (405) is connected to the upper side of the first transmission connecting frame (404). A second transmission connecting frame (406) is connected to the upper end of the connecting rod (405). A transmission sliding shaft (407) is connected to the inner side of the second transmission connecting frame (406). A bimetallic strip (408) is connected to the upper side of the transmission sliding shaft (407).

7. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 6, characterized in that: The thermal stress transmission assembly also includes a second transmission shaft (409) disposed at the end of the connecting lever (402) away from the first transmission shaft (403), and a third transmission connecting frame (410) is disposed on the outside of the second transmission shaft (409).

8. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 7, characterized in that: The connecting lever (402) is rotatably connected to the upper side of the support base (401), and the connecting lever (402) is connected to the support base (401) by bolts. The first transmission shaft (403) is slidably connected to the inner groove of the first transmission connecting frame (404). At the same time, the connecting rod (405) is slidably disposed on the inner side of the fixed frame (1). The end of the bimetallic strip (408) away from the transmission slide shaft (407) is fixedly disposed on the inner side of the fixed frame (1), and the bimetallic strip (408) is attached to the lower surface of the heat absorption plate (202). The transmission slide shaft (407) is slidably connected to the inner side of the second transmission connecting frame (406), and the second transmission shaft (409) is slidably connected to the inner side of the third transmission connecting frame (410).

9. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 8, characterized in that: The hydraulic transmission assembly includes a second connecting plate (411) disposed on the upper side of the third transmission connecting frame (410), and a first piston slide rod (412) is connected to the upper side of the second connecting plate (411). The hydraulic transmission assembly also includes a connecting pipe (413) connected to the fixed frame (1). The first piston slide rod (412) is slidably connected to the inner side of the connecting pipe (413). Meanwhile, a return spring (414) is sleeved on the outer side of the first piston slide rod (412). The inner side of the end of the connecting pipe (413) away from the first piston slide rod (412) is connected to a second piston slide rod (415), and one end of the second piston slide rod (415) is connected to a compensating pressure plate (416).

10. The dissimilar metal laser welding system for copper tubes and absorber plates of a flat-plate solar collector according to claim 9, characterized in that: The two ends of the return spring (414) are respectively connected to the upper side of the second connecting plate (411) and the side of the connecting tube (413) close to the second connecting plate (411), and the second piston slide rod (415) is slidably connected to the end of the connecting tube (413) away from the first piston slide rod (412), and the compensating lower pressure plate (416) is slidably connected to the upper side of the driven lower pressure plate (307).

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