Automatic riveting method for pressure plate and force transmission sheet of clutch cover assembly

Abstract

The invention relates to the technical field of automobile part assembly, in particular to an automatic riveting method for a pressure plate and a force transmission piece of a clutch cover assembly. The method comprises the steps that a first mechanical arm grabs and positions a pressure plate to a riveting die, a second mechanical arm penetrates a rivet into stacked force transmission pieces to form a force transmission piece assembly, the assembly is grabbed by the first mechanical arm after preliminary detection is conducted on the assembly, and real-time dynamic detection is conducted in the transferring process. And the first mechanical arm assembles the assembly which is detected to be qualified to the pressing disc to form a to-be-riveted assembly, and after the to-be-riveted assembly is subjected to final detection, the qualified product is subjected to riveting forming. According to the automatic assembling machine, manual operation can be replaced by full-automatic operation, multiple online detection is combined, the assembling efficiency and quality consistency are greatly improved, and the problems of low efficiency, poor quality and inaccurate positioning caused by manual operation are accurately solved.

Description

Technical Field

[0001] This invention relates to the field of automotive parts assembly technology, and in particular to an automated riveting method for the pressure plate and force transmission plate of a clutch cover assembly. Background Technology

[0002] The clutch is a key component widely used in vehicle transmission systems, its core function being to transmit or interrupt power through engagement and disengagement. As the core component of the clutch, the assembly quality of the clutch cover directly determines its overall performance and reliability. Within this assembly, the pressure plate is a ring-shaped metal component typically featuring a central bore and notches in a specific circumferential orientation; its main function is to withstand spring pressure and press the friction plates together. The force transmission plate is a thin-walled, strip-shaped metal part connected to the pressure plate by rivets, playing a crucial role in transmitting torque and compensating for installation misalignments. Therefore, precise riveting between the pressure plate and the force transmission plate is fundamental to ensuring reliable clutch operation.

[0003] Currently, the riveting process of the pressure plate and transmission plate in the clutch cover assembly mainly relies on manual operation and visual confirmation by the operator. Specifically, in the traditional assembly method, the operator must first manually place the pressure plate on the riveting die, and then manually pick up the transmission plate and rivet and insert them into the lower punch hole of the riveting die. This process requires repeating the above tedious picking, hole alignment, insertion, and positioning operations for the transmission plate and rivet. Only after all parts have been manually placed can the operator wait for the riveting die to close and rivet.

[0004] The above-mentioned manual assembly mode has significant limitations: (1) low production efficiency, highly dependent on the operator's skill level and work rhythm, making it difficult to standardize and speed up the production cycle; (2) poor assembly quality stability, key quality control points such as whether the parts are placed in place, whether the rivets and holes are aligned, and whether the number of transmission plates is correct, rely entirely on the operator's visual observation and personal experience, which is very easy to cause problems such as missing parts, incorrect parts, or positioning deviations due to fatigue, negligence, or individual differences, thereby affecting the performance and reliability of the clutch assembly and bringing potential quality risks; (3) high labor intensity, repetitive fine operations are easy to cause operator fatigue, which is not conducive to improving the working environment and optimizing labor costs in the long run. With the development of intelligent manufacturing trend and the urgent need for the construction of automated production lines, this traditional manual assembly mode has become a bottleneck restricting the improvement of production efficiency and the guarantee of product quality consistency. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide an automated riveting method for the pressure plate and the force transmission plate of the clutch cover assembly, so as to solve the problems of low production efficiency, poor assembly quality stability and inaccurate positioning in the prior art due to the fact that the riveting and assembly of the clutch pressure plate and the force transmission plate are completely dependent on manual operation.

[0006] This invention discloses an automated riveting method for the pressure plate and force transmission plate of a clutch cover assembly, comprising: The first robotic arm is controlled to grab the pressure plate to be riveted and transfer the pressure plate to be riveted to a preset circumferential angle and place it on a preset riveting mold. A preset number of force transmission plates are stacked sequentially. The second robotic arm is controlled to pick up rivets and align the rivets with the first end hole at one end of the force transmission plate, passing them through all the stacked force transmission plates to obtain a force transmission plate assembly. The number of force transmission plates in the force transmission plate assembly is initially detected, and the first robotic arm is controlled to grasp the force transmission plate assembly that has passed the initial detection. The number of force transmission plates grasped by the first robotic arm is dynamically detected in real time until the first robotic arm transfers the force transmission plate assembly that has passed the dynamic detection to the top of the riveting mold. The first robotic arm is controlled to insert the transferred rivets into the riveting holes of the pressure plate, and the positioning pin on the riveting mold is aligned with the second end hole of the other end of the force transmission plate and passes through all the stacked force transmission plates to obtain the assembly to be riveted. The quantity and position of the force transmission plate components in the assembly to be riveted are finally inspected, and the assembly to be riveted that passes the final inspection is riveted and formed.

[0007] Optionally, controlling the first robotic arm to grasp the pressure plate to be riveted and transferring the pressure plate to be riveted at a preset circumferential angle onto a preset riveting mold includes: The first coordinate information after the pressure plate is loaded is pre-calibrated, and the height information of the pressure plate to be riveted is obtained by a contact displacement sensor set on the first robotic arm; Based on the first coordinate information and the height information, the first robotic arm is controlled to grasp the pressure plate to be riveted; The target coordinate information of the assembly position on the riveting mold is pre-calibrated. Based on the target coordinate information, the first robotic arm is controlled to transfer the gripped pressure plate to the assembly position of the riveting mold at a preset circumferential angle.

[0008] Optionally, controlling the first robotic arm to transfer the gripped pressure plate at a preset circumferential angle and place it on the assembly position of the riveting mold includes: The circumferential angle of the assembly between the pressure plate and the riveting mold is pre-calibrated; The first image information of the pressure plate on the first robotic arm is acquired by an image acquisition device set on the first robotic arm, and the spatial coordinates of the notch feature on the pressure plate are extracted from the first image information. The current circumferential angle of the pressure plate is calculated based on the extracted spatial coordinates. The current circumferential angle of the pressure plate is compared with the assembly circumferential angle to obtain the angle deviation value. Based on the angle deviation value, the first robotic arm is controlled to rotate and grasp the circumferential angle of the pressure plate until the current circumferential angle of the pressure plate is consistent with the pre-assembly circumferential angle. Then, the pressure plate is transferred and placed on the assembly position of the riveting mold.

[0009] Optionally, the sequential stacking of a preset number of force transmission plates includes: The force transmission plates that are manually stacked in the initial storage position are extracted in a preset quantity using an extraction device and then transferred to a preset pickup slot for stacking. The presence status of the force transmission plate in the pickup slot is detected by a first positioning detection sensor installed in the pickup slot. If the force transmission piece is not detected in the pickup slot, the extraction device is activated to continue extracting the force transmission piece and transferring it to the pickup slot for stacking.

[0010] Optionally, controlling the second robotic arm to pick up the rivet and align the rivet with the first end hole at one end of the force transmission plate, passing it through all the stacked force transmission plates, includes: The rivet vibrating feeder is used to sort and output multiple rivets in a preset posture to a preset pickup channel, and the second coordinate information of the rivets located at the end of the pickup channel is pre-marked. The second robotic arm is controlled to pick up the rivet by acquiring the arrival signal of the rivet in the rivet vibrating plate reaching the end of the pick-up channel through the second positioning detection sensor preset at the end of the picking channel, and the second robotic arm is controlled to pick up the rivet according to the positioning detection signal and the second coordinate information. Based on the position and orientation of the force transmission plate within the pickup slot, the third coordinate information of the first end hole on the force transmission plate is pre-calibrated; Based on the third coordinate information, the second robotic arm is controlled to align the picked-up rivet with the first end hole on the force transmission plate and pass it through all the stacked force transmission plates.

[0011] Optionally, the step of performing a preliminary detection of the number of force transmission plates in the force transmission plate assembly, and controlling the first robotic arm to grasp the force transmission plate assembly that has passed the preliminary detection, includes: The first thickness information of a preset number of force transmission plates is pre-calibrated; The second thickness information of the force transmission plate assembly in the pickup slot is obtained by using a laser scanning displacement sensor installed on the second robotic arm. The second thickness information is compared with the first thickness information, and the number of force transmission plates in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a first grasping instruction is generated. The first grasping instruction includes controlling the first robotic arm to grasp the force transmission plate assembly and transfer it to the riveting mold. If the material is determined to be unqualified, a first rejection instruction is generated. The first rejection instruction includes controlling the second robotic arm to grab the force transmission plate assembly and transfer it into a preset unqualified material frame.

[0012] Optionally, the real-time dynamic detection of the number of force transmission plates grasped by the first robotic arm includes: The third thickness information of the force transmission plate assembly on the first robotic arm is obtained by using a contact displacement sensor installed on the first robotic arm. The third thickness information is compared with the first thickness information, and the number of force transmission plates in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a continue transfer instruction is generated. The continue transfer instruction includes controlling the first robotic arm to continue transferring the force transmission plate assembly it has grasped to the riveting mold. If the result is deemed unqualified, a second rejection instruction is generated. The second rejection instruction includes controlling the first robotic arm to interrupt its transfer to the riveting mold and transferring the gripped force transmission plate assembly into a preset unqualified material frame.

[0013] Optionally, controlling the first robotic arm to insert the transferred rivet into the riveting hole of the pressure plate includes: Based on the position and orientation of the force transmission piece placed in the pickup slot, the fourth coordinate information of the force transmission piece is pre-calibrated after it is moved into the pickup slot; Based on the fourth coordinate information, the first robotic arm is controlled to grasp the force transmission plate assembly located in the pickup slot; Based on the assembly position and orientation of the pressure plate and the riveting mold, the fifth coordinate information of the riveting hole on the pressure plate is pre-calibrated after the pressure plate is assembled with the riveting mold; Based on the fifth coordinate information, the first robotic arm is controlled to transfer the rivet from the force transmission plate assembly and insert it into the riveting hole of the pressure plate.

[0014] Optionally, aligning the locating pin on the riveting die with the second end hole at the other end of the force transmission piece through all the stacked force transmission pieces includes: Based on the distribution of the positioning pins on the riveting mold, the sixth coordinate information of the positioning pins is pre-calibrated; According to the sixth coordinate information, the first robotic arm is controlled to move the second end hole of the force transmission plate in the force transmission plate assembly to above the positioning pin, and the positioning pin on the riveting mold is aligned with the second end hole and passes through all the stacked force transmission plates.

[0015] Optionally, the final detection of the number and position of the force transmission components in the assembly to be riveted includes: The second image information of the assembly to be riveted is obtained by an image acquisition device installed on the first robotic arm; The acquired second image information is preprocessed, and the contour and position information of the force transmission plate assembly are identified and extracted from the preprocessed second image information. Based on the extracted contour and position information, the actual position and actual number of all force transmission plate components in the assembly to be riveted are counted. If the actual number of each group of force transmission plate components is consistent with the preset number, and the deviation between the actual position of each force transmission plate component and the preset standard position is within the preset qualified threshold range, then the final inspection of the assembly to be riveted is deemed qualified. If the actual number of the force transmission plate components is inconsistent with the preset number, or if the deviation between the actual position of any group of force transmission plate components and the preset standard position exceeds the qualified threshold range, the final inspection of the assembly to be riveted is determined to be unqualified, and an alarm signal is generated.

[0016] Compared with the prior art, the automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly provided in this embodiment of the invention has the following advantages: By controlling the first robotic arm to precisely place the pressure plate onto the riveting mold at a preset circumferential angle, the positioning benchmark of the pressure plate is fundamentally ensured, thus solving the problem of inaccurate circumferential positioning in traditional methods. The assembly of the force transmission plates is automatically prefabricated by sequentially stacking the force transmission plates and having the second robotic arm pick up the rivets. Based on this, the force transmission plate assemblies undergo preliminary inspection, with the first robotic arm picking up qualified products. Real-time dynamic monitoring is performed during the transfer process, forming a dual process monitoring of the number of force transmission plates, effectively avoiding omissions and misassemblies. Subsequently, the first robotic arm precisely inserts the rivets into the riveting holes of the pressure plate and uses the mold positioning pins to complete the alignment of the force transmission plates, ensuring the accurate assembly relationship of the assemblies to be riveted. Finally, a vision system performs a final inspection of the quantity and position of the assemblies to be riveted, ensuring that only fully qualified products enter the riveting forming process. Therefore, this invention significantly improves assembly efficiency, stability, and product consistency through multi-step automated execution and a multi-level quality inspection closed loop. Attached Figure Description

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a schematic diagram of the overall system structure of the automated riveting method for pressure plate and force transmission plate provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the assembly of the pressure plate and the force transmission plate provided in an embodiment of the present invention.

[0018] The markings in the attached diagram are as follows: 1. First robotic arm; 2. Pressure plate; 3. Riveting mold; 4. Force transmission plate; 5. Second robotic arm; 6. Rivet; 7. Extraction device; 8. Rivet vibrating plate. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] This invention discloses an automated riveting method for the pressure plate and force transmission plate of a clutch cover assembly, such as... Figure 1 and Figure 2 As shown, it includes: Control the first robotic arm 1 to grab the pressure plate 2 to be riveted, and transfer the pressure plate 2 to be riveted to be placed on the preset riveting mold 3 at a preset circumferential angle; A preset number of force transmission plates 4 are stacked in sequence. The second robotic arm 5 is controlled to pick up the rivet 6 and align the rivet 6 with the first end hole at one end of the force transmission plate 4 and pass it through all the stacked force transmission plates 4 to obtain the force transmission plate assembly. The number of force transmission plates 4 in the force transmission plate assembly is initially checked, and the first robotic arm 1 is controlled to grab the force transmission plate assembly that has passed the initial check. The number of force transmission plates 4 grasped by the first robotic arm 1 is dynamically detected in real time until the first robotic arm 1 transfers the force transmission plate assembly that has passed the dynamic detection to the top of the riveting mold 3. The first robotic arm 1 is controlled to insert the transferred rivet 6 into the riveting hole of the pressure plate 2, and the positioning pin on the riveting mold 3 is aligned with the second end hole of the other end of the force transmission plate 4 and passes through all the stacked force transmission plates 4 to obtain the assembly to be riveted. The quantity and position of the force transmission plate components in the riveting assembly are finally inspected, and the riveting assembly that passes the final inspection is riveted and formed.

[0021] Through the implementation of the above-described automated riveting method for pressure plates and force transmission plates, the first robotic arm 1 is controlled to automatically grasp and orient the pressure plate 2. That is, by utilizing the high repeatability and motion flexibility of the first robotic arm 1 (preferably a six-degree-of-freedom serial industrial robot) and combining it with the preset circumferential angle control, it is ensured that the pressure plate 2 to be riveted is transferred and placed on the preset riveting mold 3 in the correct orientation in one go. This eliminates the problems of circumferential positioning deviation and poor placement consistency that are difficult to avoid in manual placement, and establishes an accurate and reliable benchmark for the entire assembly process.

[0022] In the process of forming the force transmission plate assembly, a preset number of force transmission plates 4 are sequentially stacked, and the second robotic arm 5 (preferably a small high-speed SCARA robot) is controlled to complete the picking up and insertion of rivets 6, thereby achieving automated prefabrication of the assembly. The second robotic arm 5 preferably uses a vacuum suction cup (preferably a polyurethane contour suction cup) at its end to reliably pick up individual rivets 6 from the vibratingly sorted rivets 6, and can be controlled according to spatial coordinates to accurately align the rivets 6 with and pass them through the first end hole at one end of all the stacked force transmission plates 4, thereby efficiently and stably obtaining a force transmission plate assembly with a consistent structure, replacing the inefficient and error-prone operation of manually inserting rivets one by one.

[0023] To achieve full-process quality control, a multi-level automated inspection mechanism is introduced. First, a preliminary inspection is conducted immediately after the force transmission plate assembly is formed. By measuring the assembly's characteristics and comparing them with standard parameters, the quantity of force transmission plates 4 in the assembly is quickly determined to be acceptable, thus achieving automated interception at the first quality checkpoint. Force transmission plate assemblies that pass the preliminary inspection are then picked up by the first robotic arm 1.

[0024] Secondly, during the process of the first robotic arm 1 grasping and transferring the force transmission plate assembly, the force transmission plate assembly in the grasping state is dynamically detected in real time to verify the number of force transmission plates 4 again. This forms a secondary verification and process monitoring of the same quality attribute during the movement, effectively preventing unqualified products caused by grasping instability or previous missed inspections from flowing into the core assembly station. This dynamic detection mechanism continues until the first robotic arm 1 safely transfers the confirmed qualified force transmission plate assembly above the riveting mold 3.

[0025] Subsequently, the first robotic arm 1 performs a precision assembly operation, accurately inserting the transferred rivet 6 into the pre-positioned riveting hole of the pressure plate 2, while simultaneously ensuring that the second end hole of the other end of the force transmission plate 4 is precisely aligned with and passes through the positioning pin on the riveting mold 3. This action simultaneously completes the mechanical connection between the pressure plate 2 and the force transmission plate assembly, as well as the final positioning of the force transmission plate 4 on the mold, thereby forming a structurally complete assembly to be riveted.

[0026] Before final riveting, a final inspection is conducted to verify that the actual number of all force transmission plate components in the assembly to be riveted is complete and that the position of each force transmission plate component matches the insertion state of the locating pins (i.e., whether the position is accurate). This final inspection constitutes the last barrier of quality control, ensuring that any assembly defects that may have escaped in previous steps are identified. Only assemblies that pass the final inspection are authorized to undergo the final riveting process.

[0027] In summary, the method of this invention, through a triple quality protection system consisting of "preliminary inspection - dynamic inspection - final inspection," is deeply integrated with the collaborative operation process of the first robotic arm 1 and the second robotic arm 5. This enables full-process, multi-dimensional, and automated monitoring and assurance of the key quality attribute of the quantity of force transmission plates 4. As a result, while improving the production cycle of the assembly line, it ensures that the output products have extremely high consistency, reliability, and quality stability. This fundamentally solves a series of technical problems existing in traditional manual methods, such as low production efficiency, large quality fluctuations, and excessive reliance on human experience and visual inspection.

[0028] It should be noted that the riveting method in this embodiment of the invention is to perform the final riveting forming operation on the end of the force transmission plate 4 where the rivet 6 is provided, so as to achieve a firm fixation on that side. The other end of the force transmission plate 4 is mainly precisely positioned and supported by the positioning pin on the riveting mold 3, thereby meeting the functional and motion compensation requirements of the force transmission plate 4 in the actual operation of the clutch cover assembly.

[0029] Further, controlling the first robotic arm 1 to grasp the pressure plate 2 to be riveted, and transferring the pressure plate 2 to be riveted at a preset circumferential angle onto the preset riveting mold 3, includes: The first coordinate information of the pressure plate 2 after loading is pre-calibrated, and the height information of the pressure plate 2 to be riveted is obtained by a contact displacement sensor set on the first robotic arm 1. Based on the first coordinate information and height information, control the first robotic arm 1 to grab the pressure plate 2 to be riveted; The target coordinate information of the assembly position on the riveting mold 3 is pre-calibrated. Based on the target coordinate information, the first robotic arm 1 is controlled to transfer the gripped pressure plate 2 to the assembly position of the riveting mold 3 at a preset circumferential angle.

[0030] Furthermore, controlling the first robotic arm 1 to transfer the gripped pressure plate 2 at a preset circumferential angle and place it on the assembly position of the riveting mold 3 includes: The circumferential angle of the assembly between the pressure plate 2 and the riveting mold 3 is pre-calibrated; The first image information of the pressure plate 2 on the first robotic arm 1 is obtained by an image acquisition device set on the first robotic arm 1, and the spatial coordinates of the notch feature on the pressure plate 2 are extracted from the first image information. The current circumferential angle of pressure plate 2 is calculated based on the extracted spatial coordinates. The current circumferential angle of pressure plate 2 is compared with the assembly circumferential angle to obtain the angle deviation value. Based on the angle deviation value, the first robotic arm 1 is controlled to rotate and grasp the circumferential angle of the pressure plate 2 until the current circumferential angle of the pressure plate 2 is consistent with the pre-assembly circumferential angle. Then, the pressure plate 2 is transferred and placed on the assembly position of the riveting mold 3.

[0031] Through the implementation of the above-described automated riveting method for pressure plates and force transmission plates, the first coordinate information of the pressure plate 2 after loading is pre-calibrated, providing the first robotic arm 1 with a precise grasping target position, effectively solving the uncertainty of position when manually picking up parts visually. After the first robotic arm 1 moves above the pressure plate 2 according to the first coordinate information, it actively detects and obtains the height information of the surface of the pressure plate 2 to be riveted through a contact displacement sensor (preferably a high-precision inductive or laser triangular reflective displacement sensor) equipped at its end. This step can automatically adapt to the slight height changes of the pressure plate 2 caused by stacking in the tray, ensuring the stability and reliability of the grasping action. Combining the first coordinate information and the real-time acquired height information, a precise three-dimensional grasping point can be calculated based on a conventional control system, thereby controlling the first robotic arm 1 to successfully grasp the pressure plate 2 to be riveted.

[0032] In the transfer and placement phase, the target coordinate information of the assembly position on the pre-calibrated riveting mold 3 is used as the endpoint of the movement to guide the transport path of the first robotic arm 1. To achieve precise circumferential positioning, the necessary assembly circumferential angle for the mating of the pressure plate 2 and the riveting mold 3 is pre-calibrated. This angle is crucial to ensuring the alignment of the riveting holes on the pressure plate 2 with the subsequent tooling of the mold. Before placement, the first image information of the pressure plate 2 to be grasped is acquired by an image acquisition device (preferably a high-resolution industrial CCD camera with a coaxial light source) set on the first robotic arm 1. The spatial coordinates of the notch features on the pressure plate 2 in the camera coordinate system are extracted from the first image information using an image processing algorithm, and then the current circumferential angle of the pressure plate 2 is calculated.

[0033] By comparing the calculated current circumferential angle with the pre-calibrated assembly circumferential angle in real time, an accurate angle deviation value can be obtained. The control system generates a compensation command based on this angle deviation value, controlling the end effector of the first robotic arm 1 to rotate by the corresponding angle, thereby adjusting the circumferential angle of the gripping pressure plate 2 until the current circumferential angle is completely consistent with the assembly circumferential angle. In this state, the first robotic arm 1 can finally transfer the pressure plate 2 to the assembly position of the riveting mold 3 according to the target coordinate information. This process completely eliminates the defect of inaccurate control of the circumferential angle during manual placement, achieving fully automatic, high-repeatability positioning of the pressure plate 2 on the mold, laying a crucial foundation for the subsequent automated assembly of the force transmission plate 4 and the rivet 6.

[0034] Preferably, forty pressure plates 2 are neatly stacked in the tray in ten layers, with four pieces per layer.

[0035] Further, a predetermined number of force transmission plates 4 are stacked sequentially, including: Using the extraction device 7, extract the force transmission plates 4 that are manually stacked in the initial storage position in a preset quantity as a group, and transfer them to the preset pickup slot for stacking. The presence status of the force transmission piece 4 in the pickup slot is detected by the first positioning detection sensor set in the pickup slot. If the force transmission piece 4 is not detected in the pickup slot, the extraction device 7 is activated to continue extracting the force transmission piece 4 and transferring it to the pickup slot for stacking.

[0036] Furthermore, the second robotic arm 5 is controlled to pick up the rivet 6 and align the rivet 6 with the first end hole at one end of the force transmission plate 4, passing it through all the stacked force transmission plates 4, including: The rivet vibrating feeder 8 is used to sort and output multiple rivets 6 into a preset pickup channel in a preset posture, and the second coordinate information of the rivet 6 at the end of the pickup channel is pre-calibrated. The second robotic arm 5 is controlled to pick up the rivet 6 by obtaining the arrival detection signal of the rivet 6 in the rivet vibrating plate 8 reaching the end of the picking channel through the second positioning detection sensor preset at the end of the picking channel, and the second robotic arm 5 is controlled to pick up the rivet 6 according to the positioning detection signal and the second coordinate information. Based on the position and posture of the force transmission plate 4 placed in the pickup slot, the third coordinate information of the first end hole on the force transmission plate 4 is pre-calibrated. Based on the third coordinate information, the second robotic arm 5 is controlled to align the picked-up rivet 6 with the first end hole on the force transmission plate 4 and pass it through all the stacked force transmission plates 4.

[0037] Through the implementation of the above-described automated riveting method for the pressure plate and the force transmission plate, in the automated supply stage of the force transmission plate 4, a set of force transmission plates 4 is accurately extracted from the force transmission plates 4 neatly stacked in the initial storage position by the operator using an extraction device 7 (such as a precision push rod mechanism driven by a servo motor), according to a preset quantity, and stably transferred to the preset pickup slot for stacking. This process replaces the manual operation of picking up and placing the force transmission plates 4 one by one, ensuring the consistency of the quantity of each set of force transmission plates 4 and the rhythmic supply.

[0038] To ensure the material status within the pickup slot is known and controllable, a first positioning detection sensor (such as a diffuse reflection photoelectric sensor) installed in the pickup slot monitors the presence of the force transmission piece 4 in real time. If the sensor detects that the force transmission piece 4 is not present in the pickup slot, indicating an empty material state, the control system immediately generates a replenishment command and automatically activates the extraction device 7 to continue the extraction and transfer actions until the force transmission piece 4 is placed back into the pickup slot. This closed-loop feedback mechanism effectively avoids assembly interruptions caused by material supply interruptions, achieving continuous and automated management of the force transmission piece 4 supply.

[0039] In the automated feeding and assembly process of rivets 6, a large number of bulk rivets 6 are first oriented and sorted using a rivet vibrating feeder 8 (such as an electromagnetic vibrating feeder equipped with a linear feeder), so that they are neatly output into the preset pick-up channel with their heads facing upwards in a preset posture. In order to accurately locate the gripping point, the second coordinate information of the rivets 6 when they are transported to the end of the pick-up channel and ready is pre-marked.

[0040] A second positioning detection sensor (such as a fiber optic sensor or a microswitch) installed at the end of the pick-up channel monitors the end of the channel. When the sensor receives a positioning detection signal indicating that the rivet 6 has reached the end of the pick-up channel, it indicates that the single rivet 6 is in a state where it can be stably grasped. The control system then combines this positioning detection signal with the pre-calibrated second coordinate information and sends a command to the second robotic arm 5 (preferably a high-precision SCARA robot) to control its end effector (such as a vacuum nozzle) to move to the precise position and reliably pick up the rivet 6.

[0041] To achieve precise assembly of the rivet 6 and the force transmission plate 4, the system pre-calibrates the third coordinate information of the center of the first end hole on the stacked force transmission plate 4 based on the fixed position and posture of the force transmission plate 4 stacked in the pickup slot. Finally, the second robotic arm 5, based on this third coordinate information, controls the rivet 6 it carries to move to the alignment position and stably pushes the rivet 6 along the axial direction, so that it passes through the first end hole of all the force transmission plates 4 stacked in the pickup slot in sequence. This efficiently and accurately completes the automated assembly of the force transmission plate assembly, completely eliminating the quality and efficiency bottlenecks caused by manual rivet insertion, which results in misalignment and low efficiency.

[0042] Preferably, the force transmission plate 4 is a thin-walled strip-shaped part with a thickness of about 1 mm. The operator neatly stacks the force transmission plates 4 into the extraction device 7. The extraction device 7 can extract the force transmission plates 4 in groups of four, and can extract four plates * four groups of force transmission plates 4 at once and neatly stack them into four pickup slots. The second robotic arm 5 picks up the rivet 6 and inserts it into the first end hole of the force transmission plate 4, and then inserts the rivet 6 from the force transmission plate assembly into the rivet 6 hole of the pressure plate 2, so that the four groups of force transmission plates 4 and rivets 6 can be quickly assembled in sequence, so that the riveting mold 3 can enter the riveting position to close the mold and rivet, thus completing the entire riveting process.

[0043] Furthermore, a preliminary inspection is performed on the number of force transmission plates 4 in the force transmission plate assembly, and the first robotic arm 1 is controlled to grasp the force transmission plate assembly that has passed the preliminary inspection, including: Pre-calibrate the first thickness information of the preset number of force transmission plates 4; The second thickness information of the force transmission plate assembly in the pickup slot is obtained by using a laser scanning displacement sensor installed on the second robotic arm 5. The second thickness information is compared with the first thickness information, and the number of force transmission plates 4 in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a first grasping instruction is generated. The first grasping instruction includes controlling the first robotic arm 1 to grasp the force transmission plate assembly and transfer it to the riveting mold 3. If the material is deemed unqualified, a first rejection instruction is generated. The first rejection instruction includes controlling the second robotic arm 5 to grab the force transmission plate assembly and transfer it into a preset unqualified material frame.

[0044] Furthermore, the number of force transmission plates 4 grasped by the first robotic arm 1 is dynamically detected in real time, including: The third thickness information of the force plate assembly on the first robotic arm 1 is obtained by a contact displacement sensor installed on the first robotic arm 1. The third thickness information is compared with the first thickness information, and the number of force transmission plates 4 in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a continue transfer instruction is generated. The continue transfer instruction includes controlling the first robotic arm 1 to continue transferring the gripped force transmission plate assembly to the riveting mold 3. If the result is deemed unqualified, a second rejection instruction is generated. The second rejection instruction includes controlling the first robotic arm 1 to interrupt the transfer to the riveting mold 3 and transferring the gripped force transmission plate assembly into a preset unqualified material frame.

[0045] Through the implementation of the above-described automated riveting method for pressure plates and force transmission plates, in the core stage of quality control, a precise quantitative benchmark is provided for automated inspection by pre-calibrating the standard first thickness information formed by stacking a preset number of force transmission plates 4. For preliminary inspection, a laser scanning displacement sensor (preferably a non-contact laser rangefinder sensor based on the triangulation principle) mounted on the second robotic arm 5 is used to scan and measure the assembled force transmission plate assembly in the slot, quickly obtaining its overall second thickness information. The system automatically compares the real-time acquired second thickness information with the preset first thickness information. Since the thickness of a single force transmission plate 4 is known and stable, the consistency between the second thickness information and the first thickness information directly reflects whether the actual number of force transmission plates 4 contained in the force transmission plate assembly matches the preset number.

[0046] If the comparison result is within the allowable tolerance range, the number of force transmission plates 4 in the force transmission plate assembly is preliminarily qualified. The system then generates a first gripping instruction, which includes controlling the first robotic arm 1 to move to the pick-up slot and grip the qualified force transmission plate assembly, and then initiating the action sequence of transferring the assembly to the riveting mold 3. If the comparison result exceeds the tolerance range, it is determined to be unqualified. The system immediately generates a first rejection instruction, which will drive the second robotic arm 5 to grip the unqualified force transmission plate assembly after placing the rivets 6, and transfer it to the preset unqualified material frame. Thus, at the beginning of the assembly process, components with missing or extra assembly defects are automatically rejected to prevent them from entering the subsequent core work stations.

[0047] To more reliably verify the number of force transmission plates 4 and monitor their status during movement, real-time dynamic detection was further implemented. During the process of the first robotic arm 1 grasping the force transmission plate assembly and beginning its transfer, a contact displacement sensor (such as a micro-displacement measurement probe employing a high-precision spring guide rod structure and integrating a linear encoder) mounted on the end effector of the first robotic arm 1 performs real-time physical contact measurement of the end face of the force transmission plate assembly in the grasping state, obtaining its third thickness information during grasping and movement.

[0048] This contact measurement method is less affected by ambient light and component surface reflections, and maintains stable contact during robotic arm movement, providing another independent and reliable data source. The system also compares the real-time acquired third thickness information with the preset first thickness information. If the comparison result is satisfactory, a continue transfer command is generated, instructing the first robotic arm 1 to continue the predetermined transfer task to the riveting mold 3. If the comparison result is unsatisfactory, it indicates that the part may have fallen off after gripping or that the initial detection was incorrect. The system will immediately generate a second rejection command, which will force the first robotic arm 1 to interrupt its current transfer path to the riveting mold 3 and instead control the robotic arm to move the unsatisfactory force transmission plate component into a preset unsatisfactory material frame.

[0049] This dual quality verification mechanism, combining "preliminary inspection" and "dynamic inspection" based on thickness information comparison, constitutes a progressive closed-loop process quality control. It not only performs initial inspection at static workstations but also conducts secondary verification during the dynamic process of material transfer. This significantly enhances the monitoring and reliability of the key quality characteristic of "the quantity of force transmission plates 4," effectively eliminating the risk of potential failure in single-point inspections. It ensures that only force transmission plate assemblies that have passed both verifications can be delivered to the riveting mold 3 for final assembly, thereby improving production flow while maximizing the consistency and reliability of product assembly quality.

[0050] Furthermore, controlling the first robotic arm 1 to insert the transferred rivet 6 into the riveting hole of the pressure plate 2 includes: Based on the position and posture of the force transmission plate 4 placed in the pickup slot, the fourth coordinate information of the force transmission plate 4 being moved into the pickup slot is pre-calibrated. Based on the fourth coordinate information, the first robotic arm 1 is controlled to grasp the force transmission plate assembly located in the pickup slot; Based on the assembly position and posture of the pressure plate 2 and the riveting mold 3, the fifth coordinate information of the riveting hole on the pressure plate 2 is pre-calibrated after the pressure plate 2 is assembled into the riveting mold 3. Based on the fifth coordinate information, the first robotic arm 1 is controlled to transfer the rivet 6 in the force transmission plate assembly and insert it into the riveting hole of the pressure plate 2.

[0051] Furthermore, the positioning pin on the riveting die 3 is aligned with the second end hole at the other end of the force transmission piece 4 and passes through all the stacked force transmission pieces 4, including: Based on the distribution of the locating pins on the riveting die 3, the sixth coordinate information of the locating pins is pre-calibrated; According to the sixth coordinate information, the first robotic arm 1 controls the transfer of the second end hole of the force transmission plate 4 in the force transmission plate assembly to the top of the positioning pin, and makes the positioning pin on the riveting mold 3 align with the second end hole and pass through all the stacked force transmission plates 4.

[0052] Through the implementation of the above-described automated riveting method for the pressure plate and force transmission plate, the accurate position and posture of the force transmission plate 4 after being stacked in the pickup slot are pre-calibrated, obtaining the fourth coordinate information characterizing the target grasped by the force transmission plate assembly. This enables the first robotic arm 1 to accurately and repeatedly locate and grasp the force transmission plate assembly located in the pickup slot based on this fourth coordinate information, completely eliminating the randomness of positioning that may exist in manual or simple mechanized grasping. At the same time, by pre-calibrating the spatial orientation of the riveting hole on the pressure plate 2 after it is successfully assembled into the riveting mold 3, accurate fifth coordinate information is obtained. After grasping the force transmission plate assembly, the first robotic arm 1 plans its motion path based on this fifth coordinate information, controls the rivet 6 in the force transmission plate assembly it carries, accurately transfers it and aligns it with the riveting hole on the pressure plate 2, and finally completes the insertion action.

[0053] This assembly process, guided by dual coordinate information (fourth and fifth coordinate information), transforms the uncertain operation of aligning and inserting rivets 6 into rivet holes from one that relies on the operator's feel and eyesight into a deterministic, highly repeatable, automated operation driven by coordinate data and executed by the first robotic arm 1 (such as a high-precision six-axis articulated robot). This fundamentally solves the quality problems of skewing and jamming that easily occur when manually inserting rivets, and ensures the assembly consistency of the connecting pairs.

[0054] While inserting the rivet 6, the sixth coordinate information, which pre-calibrates the precise distribution of each locating pin on the riveting mold 3, provides a spatial reference for positioning the other end of the force transmission plate 4. When controlling the movement of the force transmission plate assembly, the first robotic arm 1 simultaneously adjusts the assembly's posture and planar position based on this sixth coordinate information, aligning the central axis of the second end hole on the force transmission plate 4 with the corresponding locating pin axis. Subsequently, in coordination with the continued riveting action, the first robotic arm 1 controls the force transmission plate assembly to move along the locating pin axis, allowing the locating pins on the riveting mold 3 to smoothly and without interference align with and pass through the second end holes of all the stacked force transmission plates 4. This process achieves precise synchronous establishment of the spatial relationship between the pressure plate 2, the force transmission plate assembly (connected by the rivet 6), and the riveting mold 3 (connected by the locating pins), ensuring uniform internal stress distribution and that the relative positions of each part meet design expectations before final fastening of the entire assembly to be riveted.

[0055] Furthermore, a final inspection is conducted on the number and location of the force transmission plate assemblies in the riveted assembly, including: The second image information of the assembly to be riveted is obtained by an image acquisition device installed on the first robotic arm 1; The acquired second image information is preprocessed, and the contour and position information of the force transmission plate assembly are identified and extracted from the preprocessed second image information. Based on the extracted contour and position information, the actual position and quantity of all force transmission plate components in the assembly to be riveted are counted. If the actual number of force transmission plate components is consistent with the preset number, and the deviation between the actual position of each force transmission plate component and the preset standard position is within the preset qualified threshold range, then the final inspection of the assembly to be riveted is deemed qualified. If the actual number of force transmission plate components is inconsistent with the preset number, or if the deviation between the actual position of any group of force transmission plate components and the preset standard position exceeds the qualified threshold range, the final inspection of the assembly to be riveted will be deemed unqualified, and an alarm signal will be generated.

[0056] Through the implementation of the above-described automated riveting method for pressure plates and force transmission plates, in the final stage of quality control, an image acquisition device (such as an industrial camera equipped with a high-resolution CMOS sensor and a telecentric lens, coupled with a high-brightness LED ring light source) mounted on the first robotic arm 1 directly acquires the second image information of the assembled assembly to be riveted, ensuring the real-time and accurate detection of the object's state. After acquiring the second image information, it is first preprocessed, including noise reduction, contrast enhancement, and geometric correction, to eliminate interference caused by uneven ambient lighting, part reflections, and viewing angle distortion, laying the foundation for subsequent accurate analysis. Subsequently, from the preprocessed second image information, machine vision algorithms (such as edge detection or contour extraction algorithms based on the Canny operator) are used to stably identify and extract the complete contours of all force transmission plate components and their precise position information in the image coordinate system.

[0057] Based on the extracted contour and position information, the system can automatically determine the actual positions of all force transmission plate components in the assembly to be riveted. By analyzing the contour region of each force transmission plate component (e.g., calculating features within the contour or measuring its coverage pixel height), the system further determines the actual number of all force transmission plate components. Then, the system automatically compares the actual number of force transmission plate components with the preset number required by the process. Simultaneously, it compares the actual position of each force transmission plate component with the preset standard positions corresponding to the ideal assembly state, which are pre-calibrated and stored in the system, and calculates the positional deviation.

[0058] If the test results meet two conditions—that is, the actual number of all force transmission plate components matches the preset number, and the deviation of the actual position of each force transmission plate component from the preset standard position is within the acceptable threshold range set according to the assembly accuracy requirements—then the system determines that the final test result of the assembly to be riveted is qualified, allowing it to proceed to the subsequent riveting and forming process. Conversely, if the test finds that the actual number of force transmission plate components is inconsistent with the preset number (there are missing or insufficient components), or the actual position deviation of any group of force transmission plate components exceeds the acceptable threshold range (there is misalignment or offset), the system will immediately determine that the final test result of the assembly to be riveted is unqualified.

[0059] Upon determining non-conformity, the system automatically generates an alarm signal containing the specific defect type (quantity discrepancy or location deviation). This signal can trigger the production line's audible and visual alarms, display warning messages on the control screen, or communicate with the upper-level manufacturing execution system to record production anomalies. This enables the immediate detection, accurate location, and process interception of defects, ensuring that only products that fully conform to design specifications can be shipped out. It fundamentally eliminates the oversights and misjudgments that may occur during final visual inspection by humans, transforming quality control from qualitative judgments relying on human experience to a quantitative, objective, traceable, and automated closed loop based on data and standards.

[0060] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the present invention.

Claims

1. An automated riveting method for the pressure plate and force transmission plate of a clutch cover assembly, characterized in that, The automated riveting method for the pressure plate and the force transmission plate includes: The first robotic arm is controlled to grab the pressure plate to be riveted and transfer the pressure plate to be riveted to a preset circumferential angle and place it on a preset riveting mold. A preset number of force transmission plates are stacked sequentially. The second robotic arm is controlled to pick up rivets and align the rivets with the first end hole at one end of the force transmission plate, passing them through all the stacked force transmission plates to obtain a force transmission plate assembly. The number of force transmission plates in the force transmission plate assembly is initially detected, and the first robotic arm is controlled to grasp the force transmission plate assembly that has passed the initial detection. The number of force transmission plates grasped by the first robotic arm is dynamically detected in real time until the first robotic arm transfers the force transmission plate assembly that has passed the dynamic detection to the top of the riveting mold. The first robotic arm is controlled to insert the transferred rivets into the riveting holes of the pressure plate, and the positioning pin on the riveting mold is aligned with the second end hole of the other end of the force transmission plate and passes through all the stacked force transmission plates to obtain the assembly to be riveted. The quantity and position of the force transmission plate components in the assembly to be riveted are finally inspected, and the assembly to be riveted that passes the final inspection is riveted and formed.

2. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 1, characterized in that, The process of controlling the first robotic arm to grasp the pressure plate to be riveted and transferring the pressure plate to be riveted at a preset circumferential angle onto a preset riveting mold includes: The first coordinate information after the pressure plate is loaded is pre-calibrated, and the height information of the pressure plate to be riveted is obtained by a contact displacement sensor set on the first robotic arm; Based on the first coordinate information and the height information, the first robotic arm is controlled to grasp the pressure plate to be riveted; The target coordinate information of the assembly position on the riveting mold is pre-calibrated. Based on the target coordinate information, the first robotic arm is controlled to transfer the gripped pressure plate to the assembly position of the riveting mold at a preset circumferential angle.

3. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 2, characterized in that, The control of the first robotic arm to transfer the gripped pressure plate at a preset circumferential angle and place it on the assembly position of the riveting mold includes: The circumferential angle of the assembly between the pressure plate and the riveting mold is pre-calibrated; The first image information of the pressure plate on the first robotic arm is acquired by an image acquisition device set on the first robotic arm, and the spatial coordinates of the notch feature on the pressure plate are extracted from the first image information. The current circumferential angle of the pressure plate is calculated based on the extracted spatial coordinates. The current circumferential angle of the pressure plate is compared with the assembly circumferential angle to obtain the angle deviation value. Based on the angle deviation value, the first robotic arm is controlled to rotate and grasp the circumferential angle of the pressure plate until the current circumferential angle of the pressure plate is consistent with the pre-assembly circumferential angle. Then, the pressure plate is transferred and placed on the assembly position of the riveting mold.

4. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 1, characterized in that, The sequential stacking of a preset number of force transmission plates includes: The force transmission plates that are manually stacked in the initial storage position are extracted in a preset quantity using an extraction device and then transferred to a preset pickup slot for stacking. The presence status of the force transmission plate in the pickup slot is detected by a first positioning detection sensor installed in the pickup slot. If the force transmission piece is not detected in the pickup slot, the extraction device is activated to continue extracting the force transmission piece and transferring it to the pickup slot for stacking.

5. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 4, characterized in that, The control of the second robotic arm to pick up the rivet and align the rivet with the first end hole at one end of the force transmission plate, passing it through all the stacked force transmission plates, includes: The rivet vibrating feeder is used to sort and output multiple rivets in a preset posture to a preset pickup channel, and the second coordinate information of the rivets located at the end of the pickup channel is pre-marked. The second robotic arm is controlled to pick up the rivet by acquiring the arrival signal of the rivet in the rivet vibrating plate reaching the end of the pick-up channel through the second positioning detection sensor preset at the end of the picking channel, and the second robotic arm is controlled to pick up the rivet according to the positioning detection signal and the second coordinate information. Based on the position and orientation of the force transmission plate within the pickup slot, the third coordinate information of the first end hole on the force transmission plate is pre-calibrated; Based on the third coordinate information, the second robotic arm is controlled to align the picked-up rivet with the first end hole on the force transmission plate and pass it through all the stacked force transmission plates.

6. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 5, characterized in that, The step of performing a preliminary detection of the number of force transmission plates in the force transmission plate assembly, and controlling the first robotic arm to grasp the force transmission plate assembly that has passed the preliminary detection, includes: The first thickness information of a preset number of force transmission plates is pre-calibrated; The second thickness information of the force transmission plate assembly in the pickup slot is obtained by using a laser scanning displacement sensor installed on the second robotic arm. The second thickness information is compared with the first thickness information, and the number of force transmission plates in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a first grasping instruction is generated. The first grasping instruction includes controlling the first robotic arm to grasp the force transmission plate assembly and transfer it to the riveting mold. If the material is determined to be unqualified, a first rejection instruction is generated. The first rejection instruction includes controlling the second robotic arm to grab the force transmission plate assembly and transfer it into a preset unqualified material frame.

7. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 6, characterized in that, The real-time dynamic detection of the number of force transmission plates grasped by the first robotic arm includes: The third thickness information of the force transmission plate assembly on the first robotic arm is obtained by using a contact displacement sensor installed on the first robotic arm. The third thickness information is compared with the first thickness information, and the number of force transmission plates in the force transmission plate assembly is determined according to the comparison result. If the judgment is qualified, a continue transfer instruction is generated. The continue transfer instruction includes controlling the first robotic arm to continue transferring the force transmission plate assembly it has grasped to the riveting mold. If the result is deemed unqualified, a second rejection instruction is generated. The second rejection instruction includes controlling the first robotic arm to interrupt its transfer to the riveting mold and transferring the gripped force transmission plate assembly into a preset unqualified material frame.

8. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 5, characterized in that, The step of controlling the first robotic arm to insert the transferred rivet into the riveting hole of the pressure plate includes: Based on the position and orientation of the force transmission piece placed in the pickup slot, the fourth coordinate information of the force transmission piece being moved into the pickup slot is pre-calibrated; Based on the fourth coordinate information, the first robotic arm is controlled to grasp the force transmission plate assembly located in the pickup slot; Based on the assembly position and orientation of the pressure plate and the riveting mold, the fifth coordinate information of the riveting hole on the pressure plate is pre-calibrated after the pressure plate is assembled with the riveting mold; Based on the fifth coordinate information, the first robotic arm is controlled to transfer the rivet from the force transmission plate assembly and insert it into the riveting hole of the pressure plate.

9. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 8, characterized in that, The step of aligning the positioning pin on the riveting die with the second end hole at the other end of the force transmission piece and passing it through all the stacked force transmission pieces includes: Based on the distribution of the positioning pins on the riveting mold, the sixth coordinate information of the positioning pins is pre-calibrated; According to the sixth coordinate information, the first robotic arm is controlled to move the second end hole of the force transmission plate in the force transmission plate assembly to above the positioning pin, and the positioning pin on the riveting mold is aligned with the second end hole and passes through all the stacked force transmission plates.

10. The automated riveting method for the pressure plate and force transmission plate of the clutch cover assembly according to claim 1, characterized in that, The final inspection of the number and position of the force transmission plate assemblies in the riveting assembly includes: The second image information of the assembly to be riveted is obtained by an image acquisition device installed on the first robotic arm; The acquired second image information is preprocessed, and the contour and position information of the force transmission plate assembly are identified and extracted from the preprocessed second image information. Based on the extracted contour and position information, the actual position and actual number of all force transmission plate components in the assembly to be riveted are counted. If the actual number of the force transmission plate components is consistent with the preset number, and the deviation between the actual position of each force transmission plate component and the preset standard position is within the preset qualified threshold range, then the final inspection of the assembly to be riveted is deemed qualified. If the actual number of the force transmission plate components is inconsistent with the preset number, or if the deviation between the actual position of any group of force transmission plate components and the preset standard position exceeds the qualified threshold range, the final inspection of the assembly to be riveted is determined to be unqualified, and an alarm signal is generated.

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