Clamp-type pneumatic clamping device and method for welding work

Abstract

The present application relates to the technical field of welding tooling, and discloses a clamp type pneumatic clamping device and method for welding processing. The clamp type pneumatic clamping device for welding processing comprises a front section exhaust pipe clamping module and a control module. The front section exhaust pipe clamping module comprises a base, two clamping units and an upper locking unit. The base is provided with a V-shaped support surface for bearing and initially centering the front section of the exhaust pipe. The two clamping units are respectively located on the two sides of the V-shaped support surface. Each clamping unit comprises a horizontal telescopic actuator and a clamping head connected with the horizontal telescopic actuator. The front section exhaust pipe clamping module and the control module are cooperatively arranged to collect the strain signals of the bent pipe area in real time before clamping, analyze the end offset trend, and drive the left and right clamping heads to implement asymmetric pre-biasing, so that the pipe is automatically centered after natural rebound, thereby effectively eliminating dynamic misalignment and significantly improving the welding precision and air tightness reliability.

Description

Technical Field

[0001] This invention relates to the field of welding tooling technology, and more specifically, to a caliper-type pneumatic clamping device and method for welding processing. Background Technology

[0002] A typical automotive exhaust system consists of a front exhaust pipe, a three-way catalytic converter, and a rear exhaust pipe, welded together sequentially. During the actual welding process, specialized welding clamps are used to precisely align and reliably secure these components. Then, welding equipment is used to seal each connection point, ensuring the structural strength and airtightness of the exhaust system.

[0003] Currently, existing welding fixtures generally employ rigid positioning and symmetrical clamping. While this effectively constrains exhaust pipe assemblies under static conditions, it falls short when dealing with complex front-end exhaust pipes. Particularly when the front-end exhaust pipe is composed of multiple thin-walled sections with varying curvatures, residual stress inevitably accumulates during cold bending. When such components are installed in the fixture, if traditional static clamping strategies are used, the components often experience slight but significant positional shifts or angular torsions due to elastic rebound, leading to misalignment at the joint with the three-way catalytic converter. This dynamic misalignment is not only difficult to detect visually or through conventional inspection methods, but it also directly causes uneven weld gaps, insufficient penetration, and even leakage defects, severely impacting welding quality and product reliability.

[0004] Therefore, there is an urgent need for an intelligent welding clamping device that can actively sense the springback trend and implement asymmetric pre-offset clamping based on the prediction results, so as to achieve high-precision, adaptive dynamic centering and stable locking while preserving the natural springback degree of freedom of the pipe fitting. Summary of the Invention

[0005] The purpose of this invention is to provide a caliper-type pneumatic clamping device and method for welding processing to solve the above-mentioned technical problems.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions: This invention provides a caliper-type pneumatic clamping device for welding processing, comprising: a front exhaust pipe clamping module and a control module; The front exhaust pipe clamping module includes: The base has a V-shaped support surface for supporting and initially centering the front section of the exhaust pipe; Two clamping units are located on both sides of the V-shaped support surface, and each clamping unit includes a horizontal telescopic actuator and a clamping head connected to the horizontal telescopic actuator; The upper locking unit is located above the V-shaped support surface. It includes a vertical telescopic actuator and a top pressure head connected to the vertical telescopic actuator, which is used to press down and lock the exhaust pipe after horizontal clamping is completed. The springback sensing unit is used to sense the strain changes caused by elastic springback at the bending part of the front section of the exhaust pipe, which is spliced ​​from pipe segments with different curvatures, and outputs corresponding electrical signals. The control module, which is communicatively connected to the two clamping units, the springback sensing unit, and the upper locking unit, is configured as follows: Receive strain release signals and analyze the predicted offset direction and offset amount at the end of the exhaust pipe; Based on the predicted offset, an asymmetric position adjustment command is generated, which controls two horizontal telescopic actuators to move the corresponding gripping heads to the pre-biased position, so that an initial gap is formed between the two gripping heads that is in the opposite direction to the predicted offset. After the exhaust pipe naturally springs into place due to elastic rebound, the two clamping units are driven to clamp synchronously, and the upper locking unit is triggered to perform a vertical downward pressing action to complete the final locking.

[0007] Preferably, the rebound sensing unit includes a movable support base and a strain sensor disposed on the support base, wherein the strain sensor contacts the high-stress area on the inner side of the curved section when the exhaust pipe is placed at the front section.

[0008] Preferably, the contact surface of the clamping head is an arc-shaped concave surface that matches the outer diameter of the exhaust pipe, and the surface is covered with an elastic buffer layer.

[0009] Preferably, the horizontal telescopic actuator and the vertical telescopic actuator are any one of a servo electric cylinder, an electric push rod, or a proportional cylinder with position feedback.

[0010] Preferably, the top pressure head is connected to the vertical telescopic actuator via a floating connection mechanism, which is used to adapt to minor unevenness of the curved surface at the top of the exhaust pipe.

[0011] Preferably, the floating connection mechanism is any one of a ball joint, a universal joint, or a compression spring assembly.

[0012] Preferably, the control module has a pre-stored strain-offset mapping table for the exhaust pipe of a specific vehicle model. The mapping table is established based on offline calibration data and is used to convert the strain change signal into the corresponding predicted offset.

[0013] Preferably, the timing sequence of the actions performed by the control module is as follows: after the workpiece is placed, the springback sensing unit is activated to collect data; before the upper locking unit is pressed down, the pre-bias adjustment of the left and right clamping units is completed; and after the exhaust pipe springs back and stabilizes, synchronous clamping and vertical locking are performed.

[0014] Preferably, the clamping device further includes a catalyst clamping module and a rear exhaust pipe clamping module, which are integrated on the same workbench.

[0015] A method for controlling a clamping device includes the following steps: Step S100: After the front section of the exhaust pipe is placed on the V-shaped support surface, the strain release signal of its bending part is collected by the spring-loaded sensing unit. Step S200: Determine the predicted offset direction and offset amount of the exhaust pipe end based on the strain release signal; Step S300: Based on the predicted offset, control the horizontal telescopic actuators of the left and right gripping heads to move to the asymmetrical pre-offset positions respectively, so that an initial gap is formed between the two gripping heads that compensates for the predicted offset. Step S400: Wait for the exhaust pipe to naturally fall within the initial gap due to elastic rebound; Step S500: Drive the left and right clamping heads to clamp the exhaust pipe simultaneously, and control the upper vertical locking head to press down to complete the final locking.

[0016] The beneficial effects of this invention are as follows: This invention, by setting up a front exhaust pipe clamping module and a control module to work together, can collect strain signals in the bend area in real time before clamping, analyze the end offset trend, and drive the left and right clamping heads to perform asymmetrical pre-offset, so that the pipe can automatically center after natural springback, thereby effectively eliminating dynamic misalignment, significantly improving welding accuracy and airtight reliability, and overcoming the positioning inaccuracies and assembly stress problems caused by traditional tooling that clamps first and then welds. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a caliper-type pneumatic clamping device for welding processing according to the present invention; Figure 2 This is a front view of a caliper-type pneumatic clamping device for welding processing according to the present invention; Figure 3 This is a schematic diagram of the front exhaust pipe clamping module in a caliper-type pneumatic clamping device for welding processing according to the present invention. Figure 4 This is a front view of the front exhaust pipe clamping module in a caliper-type pneumatic clamping device for welding processing according to the present invention. Figure 5 This is a block diagram showing the relationship between the control end and the front exhaust pipe clamping module in a caliper-type pneumatic clamping device for welding processing according to the present invention. Figure 6 This is a flowchart of a clamping device control method according to the present invention.

[0018] In the diagram: 10, rear exhaust pipe clamping module; 20, catalytic converter clamping module; 30, front exhaust pipe clamping module; 301, base; 302, horizontal telescopic actuator; 303, clamping head; 304, vertical telescopic actuator; 305, top pressure head; 306, support seat; 307, strain sensor; 308, floating connection mechanism. Detailed Implementation

[0019] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0020] Please refer to the following: Figures 1 to 6 A caliper-type pneumatic clamping device for welding processing includes: a front exhaust pipe clamping module 30, a control module, a catalytic converter clamping module 20, and a rear exhaust pipe clamping module 10. The rear exhaust pipe clamping module 10, the catalytic converter clamping module 20, and the front exhaust pipe clamping module 30 are sequentially integrated onto the same workbench. The rear exhaust pipe clamping module 10, the catalytic converter clamping module 20, and the front exhaust pipe clamping module 30 respectively clamp and fix the various components of the exhaust pipe assembly, ensuring accurate alignment of each component.

[0021] The front exhaust pipe clamping module 30 includes: a base 301, two clamping units, an upper locking unit, and a springback sensing unit. The base 301 has a V-shaped support surface for holding the front exhaust pipe, which is composed of two pipe sections with different curvatures. The included angle of the V-shaped support surface is 90°–120°, and its surface is coated with a ceramic-based high-temperature resistant coating to reduce the impact of welding heat radiation on the positioning reference. The V-shaped structure enables the pipe to self-center in the vertical direction, providing a reference for subsequent horizontal adjustment.

[0022] Two clamping units are located on either side of the V-shaped support surface. Each clamping unit includes a horizontal telescopic actuator 302 and a clamping head 303. The horizontal telescopic actuator 302 can be any of a servo electric cylinder, an electric push rod, or a proportional cylinder with position feedback. In this embodiment, a servo electric cylinder is preferred. The two horizontal telescopic actuators 302 are independently controlled and their extension amounts can be adjusted separately to achieve asymmetrical clamping or pre-biasing. The clamping head 303 is connected to the telescopic end of the horizontal actuator. Its contact surface is an arc-shaped concave surface that matches the outer diameter of the exhaust pipe. The inner surface of the clamping head 303 is covered with an elastic buffer layer (such as polyurethane) to adapt to the pipe diameter and prevent damage.

[0023] The upper locking unit is located directly above the V-shaped support surface and is used to press down and lock the exhaust pipe after horizontal clamping. The upper locking unit includes a vertical telescopic actuator 304 and a top pressure head 305. The vertical telescopic actuator 304 can be any one of a servo electric cylinder, an electric push rod, or a proportional cylinder with position feedback; in this embodiment, a servo electric cylinder is preferred. The top pressure head 305 is connected to the telescopic end of the vertical telescopic actuator 304, and its contact surface is also provided with an arc-shaped concave surface that matches the outer diameter of the exhaust pipe, and a flexible protective layer is provided on this concave surface. In addition, the top pressure head 305 is connected to the vertical telescopic actuator 304 through a floating connection mechanism 308. The floating connection mechanism 308 can be any one of a ball joint, a universal joint, or a compression spring assembly; in this embodiment, a compression spring assembly is used. By setting the floating connection mechanism 308, the top pressure head 305 can adapt to the slight unevenness of the curved surface at the top of the exhaust pipe, preventing local overpressure deformation caused by slight unevenness of the pipe fitting.

[0024] Two springback sensing units are provided, located in the bending areas of the two curved sections of the front exhaust pipe. Each springback sensing unit includes a movable support 306 and a strain sensor 307 mounted on the support 306. When the front section of the exhaust pipe is placed, the strain sensor 307 contacts the high-stress area on the inner side near the curved section. The strain sensor 307 can be fine-tuned by adjusting the position of the support 306, giving it a certain degree of adaptability. During workpiece loading, the sensor is temporarily attached to the high-stress area on the inner side of the front exhaust pipe near the curved section to collect the strain release signal at the moment of placement. This signal directly reflects the residual stress release trend and is a key input for predicting end-point offset.

[0025] The control module can be implemented using an embedded controller (such as an industrial PLC), and communicates with the two clamping units, the springback sensing unit, and the upper locking unit respectively. It integrates the following functional units: Signal acquisition unit: Receives the voltage signal output by strain sensor 307 through analog input interface, and performs filtering and amplification; Feature extraction unit: Analyzes the acquired strain time series signal and extracts key feature parameters, such as the initial strain change rate (dε / dt) or the strain decay amplitude within the first 500ms; Predictive mapping unit: Based on a pre-stored "strain-offset mapping table", the characteristic parameters are converted into predicted offset (Δy) and predicted torsion angle (Δθ) at the end of the exhaust pipe. This mapping table is obtained through offline calibration. For example, for the front pipe of a specific vehicle model, the correspondence between its strain response and actual misalignment is tested multiple times under standard operating conditions, and a lookup table or lightweight regression model is established. Instruction generation unit: Calculates the target positions of the left and right gripping heads 303 based on the prediction results. For example, if the predicted end offsets to the right by Δy, the left gripping head 303 is controlled to extend Δy / 2 more and the right gripping head 303 to extend Δy / 2 less, forming an initial gap with a total width of W0-Δy (W0 is the theoretical centering width), thus achieving reverse compensation. Timing control unit: Strictly manages the action sequence of each actuator to ensure that the process of "sensing first, then pre-biasing, waiting for rebound, synchronous clamping, and finally vertical locking" is executed in an orderly manner.

[0026] It should be noted that the prediction mapping unit is the core functional module of the control module for intelligent compensation. Its function is to accurately convert the strain characteristic parameters collected by the rebound sensing unit into the predicted lateral offset (Δy) and predicted torsional angle (Δθ) of the exhaust pipe end relative to the three-way catalytic converter interface. This conversion process is based on a pre-built "strain-offset mapping table" stored in the control module's internal memory, and its implementation includes the following steps: a. Offline calibration stage Before the device is put into use, the following calibration procedure is performed for the exhaust pipe front section of each vehicle model that needs to be processed: Several exhaust pipe front sections of the same model are sequentially installed into this clamping device; after each installation and before clamping, the actual misalignment of the end flange in its free state (including lateral offset) is measured in real time using a high-precision non-contact displacement sensor (such as a laser displacement gauge) or an industrial camera system. and angle deviation Simultaneously, the strain signal output by the rebound sensing unit at the same moment is recorded, and key feature parameters, such as the peak strain value, are extracted. The strain rate of change (dε / dt) within the first 300ms; the time required for the strain to decay to 90% of the steady-state value (τ); pair each set of "strain feature vectors" with the corresponding "measured misalignment" to form a calibration dataset.

[0027] b. Mapping Model Construction Based on the above calibration dataset, a lookup table method is used to construct the mapping relationship: Lookup table method: The strain characteristic space is divided into several intervals (e.g., using dε / dt as the main index), with each interval corresponding to an average misalignment. During runtime, the control module searches for the nearest neighbor interval based on the real-time characteristic values ​​and outputs the corresponding Δy and Δθ. This method has low computational cost and is suitable for resource-constrained embedded systems.

[0028] c. Online prediction stage In actual welding operations, the control module performs the following operations: The strain signal is acquired in real time and its characteristic parameters are extracted; a pre-stored mapping table or model is called to quickly calculate the predicted offset Δy and predicted torsion angle Δθ of the current workpiece; if a differential clamping strategy is adopted (i.e., the left and right clamping heads 303 are adjusted independently), Δθ is further converted into the position difference correction amount of the left and right clamping heads 303, for example: ; Wherein, k is the geometric transformation coefficient, k=L / 2, and L is the distance from the clamping point to the end of the exhaust pipe, which is determined by the distance from the clamping point to the end; finally, the target position command of the two horizontal telescopic actuators 302 is generated.

[0029] d. Model updates and maintenance To address the drift in springback characteristics caused by mold wear or material batch variations, the system supports uploading new calibration data via a human-machine interface and updating the mapping table or model parameters online to ensure long-term accuracy.

[0030] The working process of the caliper-type pneumatic clamping device for welding processing designed in this invention is as follows: Step 1: Workpiece Placement and Signal Acquisition After the operator places the front exhaust pipe into the V-shaped support surface, a start signal is triggered. The control module immediately activates the rebound sensing unit, which completes the acquisition and preliminary filtering of the strain release signal within 500ms.

[0031] Step 2: Offset Prediction The feature extraction unit calculates the strain rate of change, queries the mapping table, and outputs the predicted offset direction and magnitude (e.g., Δy = +1.1 mm, indicating a rightward offset).

[0032] Step 3: Asymmetric pre-biasing The instruction generation unit generates target position instructions for the left and right gripping heads 303 based on this and sends them to the corresponding horizontal telescopic actuators 302. The two gripping heads 303 move synchronously to the pre-biased position, at which point the gripping gap is slightly smaller than the theoretical value, reserving "springback space".

[0033] Step 4: Natural rebound into place The fitting rebounds elastically towards the center of the preset gap, stabilizing within approximately 1-2 seconds. During this phase, the upper locking unit remains raised without applying any constraint, ensuring free rebound.

[0034] Step 5: Simultaneous clamping and vertical locking After confirming that the rebound is stable (which can be judged by the stabilization of the strain signal or by setting a fixed delay), the control module drives the left and right clamping units to apply the rated clamping force synchronously, and then triggers the upper locking unit to press down, completing the final rigid fixation.

[0035] Step Six: The welding allow output system self-checks whether the clamping force is within the set range. If it is normal, it outputs a "welding allowed" signal to the welding robot or manual operation interface and proceeds to the next process.

[0036] This invention provides a caliper-type pneumatic clamping device, method, and control method for welding processing. It addresses the problem of elastic springback and misalignment caused by residual stress from cold bending of automotive exhaust pipes, achieving a technological breakthrough from "passive rigid clamping" to "active intelligent compensation." Its main technical effects are summarized as follows: Significantly reduces misalignment: This invention detects the strain release signal in the bend area before clamping, predicts the end offset trend, and drives the left and right clamping heads 303 to perform asymmetrical pre-biasing, effectively counteracting the effect of elastic rebound and greatly improving the alignment accuracy before welding.

[0037] Achieving dynamic adaptive clamping: Adopting a timing control strategy of "sensing first, then pre-adjusting, waiting for springback, and then locking", the pipe fitting retains its natural springback degree of freedom, avoids the additional stress introduced by the forced constraint of traditional tooling, and improves the quality of weld and airtightness reliability.

[0038] Simple structure and strong compatibility: Based on conventional V-shaped support and upper and lower clamping, only independently adjustable left and right clamping units and strain sensing modules are added. No complex vision or laser system is required, which is low cost and easy to integrate into existing automated production lines.

[0039] Supports flexible switching between multiple vehicle models: By pre-storing strain-offset mapping tables for different vehicle models, the device can quickly adapt to various exhaust pipe structures. Precise compensation can be achieved simply by switching parameter files, demonstrating good engineering practicality and scalability.

[0040] In summary, this invention precisely solves a common industry problem in the welding of thin-walled double-bend exhaust pipes through a combination of hardware and software, achieving high-precision and high-efficiency intelligent clamping without significantly increasing hardware complexity.

[0041] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention, all of which are within the protection scope of the present invention.

Claims

1. A caliper-type pneumatic clamping device for welding processing, characterized in that, include: Front exhaust pipe clamping module and control module; The front exhaust pipe clamping module includes: The base has a V-shaped support surface for supporting and initially centering the front section of the exhaust pipe; Two clamping units are located on both sides of the V-shaped support surface, and each clamping unit includes a horizontal telescopic actuator and a clamping head connected to the horizontal telescopic actuator; The upper locking unit is located above the V-shaped support surface. It includes a vertical telescopic actuator and a top pressure head connected to the vertical telescopic actuator, which is used to press down and lock the exhaust pipe after horizontal clamping is completed. The springback sensing unit is used to sense the strain changes caused by elastic springback at the bending part of the front section of the exhaust pipe, which is spliced ​​from pipe segments with different curvatures, and outputs corresponding electrical signals. The control module, which is communicatively connected to the two clamping units, the springback sensing unit, and the upper locking unit, is configured as follows: Receive strain release signals and analyze the predicted offset direction and offset amount at the end of the exhaust pipe; Based on the predicted offset, an asymmetric position adjustment command is generated, which controls two horizontal telescopic actuators to move the corresponding gripping heads to the pre-biased positions, so that an initial gap is formed between the two gripping heads that is in the opposite direction to the predicted offset. After the exhaust pipe naturally springs into place due to elastic rebound, the two clamping units are driven to clamp synchronously, and the upper locking unit is triggered to perform a vertical downward pressing action to complete the final locking.

2. The caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The rebound sensing unit includes a movable support base and a strain sensor mounted on the support base. When the strain sensor is placed at the front of the exhaust pipe, it contacts the high-stress area on the inner side of the curved section.

3. The caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The contact surface of the clamping head is an arc-shaped concave surface that matches the outer diameter of the exhaust pipe, and the surface is covered with an elastic buffer layer.

4. The caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The horizontal telescopic actuator and the vertical telescopic actuator are any one of a servo electric cylinder, an electric push rod, or a proportional cylinder with position feedback.

5. A caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The top pressure head is connected to the vertical telescopic actuator via a floating connection mechanism, which is used to adapt to minor unevenness on the curved surface of the exhaust pipe top.

6. A caliper-type pneumatic clamping device for welding processing according to claim 5, characterized in that, The floating connection mechanism is any one of a ball joint, a universal joint, or a compression spring assembly.

7. A caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The control module has a pre-stored strain-offset mapping table for exhaust pipes of specific vehicle models. The mapping table is established based on offline calibration data and is used to convert strain change signals into corresponding predicted offsets.

8. A caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The timing sequence of actions performed by the control module is as follows: after the workpiece is placed, the springback sensing unit is activated to collect data; before the upper locking unit is pressed down, the pre-bias adjustment of the left and right clamping units is completed; and after the exhaust pipe springs back and stabilizes, synchronous clamping and vertical locking are performed.

9. A caliper-type pneumatic clamping device for welding processing according to claim 1, characterized in that, The clamping device also includes a catalyst clamping module and a rear exhaust pipe clamping module, which are integrated on the same workbench.

10. A control method for a clamping device, using a caliper-type pneumatic clamping device for welding as described in any one of claims 1-8, characterized in that, The following steps are included: Step S100: After the front section of the exhaust pipe is placed on the V-shaped support surface, the strain release signal of its bending part is collected by the spring-loaded sensing unit. Step S200: Determine the predicted offset direction and offset amount of the exhaust pipe end based on the strain release signal; Step S300: Based on the predicted offset, control the horizontal telescopic actuators of the left and right gripping heads to move to the asymmetrical pre-offset positions respectively, so that an initial gap is formed between the two gripping heads that compensates in the opposite direction to the predicted offset. Step S400: Wait for the exhaust pipe to naturally return to the initial gap due to elastic rebound; Step S500: Drive the left and right clamping heads to clamp the exhaust pipe simultaneously, and control the upper vertical locking head to press down to complete the final locking.

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