METHOD FOR CONDITION ANALYSIS OF AN ELECTROMETAL JOINING SYSTEM AND ELECTROMETAL JOINING SYSTEM FOR PERFORMING THIS METHOD

Description

Technical area

[0001] The invention relates to a method for analyzing the condition of an electromechanical joining system. Furthermore, the invention relates to an electromechanical joining system designed to implement the method according to the invention. State of the art

[0002] WO2005124488A1 discloses a method for analyzing the condition of an electric drive for controlling axes within a technical process. The known method is used, for example, in an electrical automation system and serves to monitor components subject to wear, such as a brake, a gear, a belt drive, a bearing, a screw drive, a guide, etc. In particular, the known method serves to detect emerging wear on the aforementioned components at an early stage. This can, for example, enable the relevant component to be replaced at a time when failure of the electrical automation system is possible at minimized cost, for example, during normal maintenance intervals or during operational downtimes of the electrical automation system.To this end, the method known from the aforementioned document proposes using a monitoring device to process actual values ​​from the electric drive and, if necessary, additional measured values ​​acquired by sensors. The measured values ​​are processed using an algorithm and displayed, for example, on a suitable display unit.

[0003] The applicant is a manufacturer of electromechanical joining systems, as documented in data sheet 2160A_000-764d-02.17. Electromechanical joining systems are used in automated joining processes. The electromechanical joining system comprises an electric drive with an electronically commutated servomotor and a lead screw drive. The lead screw drive converts the rotary motion of a servomotor drive shaft into a linear motion. For this purpose, the lead screw drive has a lead screw and a lead screw nut. A plunger for tool mounting is attached to one end of the lead screw nut. The electromechanical joining system comprises wear-prone components such as a brake, a gear, a belt drive, the lead screw drive, bearings, a lead screw nut guide, a plunger anti-rotation device, etc. The rotary motion of the drive shaft is detected by an absolute encoder, enabling highly precise positioning of the plunger.A force sensor records the temporal progression of forces and torques acting during the joining process. WO2016205846A1 is directed to a method for determining a usage characteristic of a pressing tool in a joining press. The joining press has a usage timer that determines the usage time of the joining press. The joining press also has a force measuring device that determines the force applied by the joining press. The joining press also has an analysis and evaluation module that determines a tool service status based on the usage time and the force applied.

[0004] The object of the present invention is to detect wear of components of an electromechanical joining system at an early stage in order to largely avoid failure of the electromechanical joining system. Disclosure of the invention

[0005] The invention relates to a method for analyzing the condition of an electromechanical joining system according to claim 1.

[0006] The inventive method for analyzing the condition of an electromechanical joining system with the features of claim 1 has the advantage that it enables the detection of impending wear of a component of the electromechanical joining system in a particularly simple manner. To this end, the teaching of the invention proposes determining the additional measured values ​​required for the condition analysis using a sensor that serves to measure temporal force or torque curves during the joining process, and that the algorithm of the control device links the actual values ​​with the additional measured values.

[0007] In other words, this means that the control system's algorithm links actual values ​​of the electric drive (e.g., current, angular velocity of a drive shaft, etc.) with additional measured variables (force or torque) measured by the sensor in the electromechanical joining system. Such a link or quotient is also referred to as the efficiency of the electromechanical joining system.

[0008] A typical characteristic of impending wear of a component of the electromechanical joining system is that, for example, an increased current is required to achieve a certain value (force or torque) compared to a new or run-in condition. As soon as the aforementioned connection or relationship between the actual values ​​of the electric drive and the additional measured values ​​in the electromechanical joining system falls below or exceeds a certain ratio, this relationship can be interpreted and used as a warning signal for impending wear or the necessary replacement of a wear-prone component of the electromechanical joining system.

[0009] Advantageous further developments of the method according to the invention for the condition analysis of an electromechanical joining system are listed in the subclaims.

[0010] An electromechanical joining system within the meaning of the invention is generally understood to mean any device designed to effect a joining process. In particular, this also includes an electromechanical joining system for joining components such as pressing, screwing, forming (e.g., riveting, clinching, rolling, caulking, flanging, pressing, or pressure joining).

[0011] In a preferred variant of the method according to the invention, which has been generally described so far, it is provided that the actual values ​​and the additional measured values ​​are only taken into account by the algorithm during a portion of the duration of the joining process, wherein the actual values ​​are preferably at least virtually constant during the taken-in period. The background to this preferred variant is that, particularly at the beginning and end of the joining process, irregularities occur, for example in the current consumption of the electric drive or the angular speed of a drive shaft of the electric drive. In contrast, the actual values ​​of the electric drive are typically at least virtually constant or do not exhibit any peaks in a middle phase of the joining process. In particular, the algorithm should also make it possible to filter out or eliminate any irregularities that may exist during the period to be taken into account.to smooth out these irregularities, if necessary. It is also conceivable, for example, to average out linearly changing measured values ​​during the period under consideration, or to calculate a mean.

[0012] While the method described above allows the required state variables to be recorded during the joining process or during operation of the electromechanical joining system, an alternative implementation of the method provides for the actual values ​​and the additional measured values ​​to be taken into account by the algorithm during additional operation outside the joining process, in particular during operation of the electromechanical joining system in which the electromechanical joining system is not subjected to force or torque. In other words, this means that the actual values ​​and the additional measured values ​​are recorded during an "idle stroke" of the electromechanical joining system without any input side of the electromechanical joining system being subjected to force.Furthermore, it is conceivable to perform the "idle stroke" during the return movement phase of an output element of the electromechanical joining system until the next component is joined, so that no additional time is required.

[0013] In order to determine an emerging trend or emerging wear in the electromechanical joining system, it is also important that the actual values ​​and the additional measured values ​​are determined at the same time (i.e. simultaneously) so that the algorithm links the actual values ​​and the additional measured values ​​transmitted to the control device at the same time.

[0014] As already explained above, it is particularly advantageous if the actual values ​​and the additional measured values ​​are taken into account during a constant angular speed of the electric drive.

[0015] The actual values ​​are values ​​of the rotary movement of a drive shaft of the electric drive acting on the screw drive and / or actual values ​​of the electric drive in the form of the current consumption of the electric drive. Both the rotary movement of the drive shaft and the current consumption of the electric drive can usually be monitored or determined using relatively simple sensors.

[0016] For the early detection of an emerging trend or impending wear of a wear-prone component of the electromechanical joining system, it is essential that the control device creates or evaluates a temporal correlation between the actual values ​​and the additional measured values. In other words, this means that appropriate display means, for example in the form of a graph on a screen or in a numerical representation, make it possible to depict a trend in the interlinked measured values ​​over the operating life of the electromechanical joining system.

[0017] In the latter variant, it is particularly advantageous if the control device also extrapolates, i.e., extrapolates, the temporal progression of the link between the actual values ​​and the additional measured values ​​for the future. Such a method makes it possible, in particular, to determine the (safe) remaining operating time of the electromechanical joining system until a worn component needs to be replaced, or to infer the potential service life of the corresponding component.

[0018] In principle, the control device can be located within the electric drive or external to the electric drive, for example, in an external computer. Preferably, the control device is an integral part of the electric drive's control unit. The external computer can be located anywhere on Earth. The actual values ​​of the electric drive and other measured values ​​from the sensor can then be fed to the external computer as digital data via a network such as the Internet.

[0019] The invention further comprises an electromechanical joining system with an electric drive that acts on a rotatably or linearly movable output element for a joining process by means of a screw drive. The electromechanical joining system is further characterized by first means for detecting actual values ​​of the electric drive and second means for detecting further measured values ​​from a sensor for measuring temporal force or torque curves during the joining process. The electromechanical joining system has a control device to which the actual values ​​and the further measured values ​​can be fed. Furthermore, the control device has an algorithm that is designed to link the actual values ​​and the further measured values ​​according to a method according to the invention as described so far.

[0020] In the concrete design of the electromechanical joining system, it is provided that the electric drive is designed as a servo drive and that the servo drive has a control device for controlling the electric drive. Short description of the characters

[0021] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the figures. Fig. 1 a perspective view of a part of an embodiment of an electric drive of an electromechanical joining system for joining two components; Fig. 2 a first embodiment of an electromechanical joining system for joining two components, with an electric drive according to Fig. 1, which is designed, in a schematic representation, with a control device integrated in an electric drive for carrying out the method according to the invention; Fig. 3 a second embodiment of an electromechanical joining system for joining two components, with an electric drive according to Fig. 1 , which is designed, in a schematic representation, with an external control device for carrying out the method according to the invention; and Fig. 4 and Fig. 5 Representations of an efficiency or a lifetime curve of the electromechanical joining system according to Fig. 2 or 3 as a result of a condition analysis carried out by the control device using an algorithm. Ways to implement the invention

[0022] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0023] Fig. 1shows, in perspective, part of an embodiment of an electric drive 10 of an electromechanical joining system 100 for joining two components. The electric drive 10 advantageously has a servomotor 12 and a brake 4. The main task of the brake 4 is to hold a plunger of the screw drive 20 in a position with high precision when the servomotor 12 is not energized. A further task of the brake 4 is to brake the servomotor 12. The servomotor 12 drives a drive shaft 18 via a gear 5 and a belt drive 6. The drive shaft 18 is supported by at least one bearing 7. The servomotor 12 rotates the drive shaft 18 at a speed n clockwise or counterclockwise. An absolute encoder 11 detects the speed n of the drive shaft 18. The absolute encoder 11 is preferably arranged spatially close to the brake 4 or the servomotor 12. In Fig. 1The absolute encoder 11 is not shown in the figure. With knowledge of the present invention, the servo motor can also drive the drive shaft gearlessly and beltlessly.

[0024] The electric drive 10 has a screw drive 20. The screw drive 20 comprises a threaded spindle with a spindle nut, a guide 8 and an anti-twist device 9. The spindle nut sits on the threaded spindle. The threaded spindle has an external thread, the spindle nut has an internal thread, and the external and internal threads are cut to match each other. One end of the drive shaft 18 is connected to the threaded spindle in a rotationally fixed manner and rotates the threaded spindle. A rotational movement of the threaded spindle results in a linear movement of the threaded nut. The guide 9 guides the threaded nut during the linear movement. An end of the threaded nut facing away from the drive shaft 18 has a tappet. The tappet serves as a tool holder, in Fig. 1Such a tool is not depicted in the figure. The anti-rotation device 8 secures the plunger against rotation.

[0025] In Fig. 2 and 3 Two embodiments of an electromechanical joining system 100 for joining two components 1, 2 are shown schematically in a highly simplified manner. By way of example, the electromechanical joining system 100 is intended to press a first component 1 into an opening of a second component 2 in the direction of arrow 3 up to a specific position.

[0026] The electromechanical joining system 100 has an electric drive 10 according to Fig. 1 The electric drive 10 is controlled by a control device 13. Advantageously, the electric drive 10 is a servo drive with a servo motor 12, and the control device 13 is a servo amplifier. The control device 13 is a computer. The control of the servo motor 12 by the control device 13 is in Fig. 2 and3 marked by a double arrow. A housing of the electric drive 10 is Fig. 2 and 3 Shown in dashed lines. Servo motor 12, control unit 13, drive shaft 18, and absolute encoder 11 are arranged in the housing.

[0027] Subject to wear within the meaning of the invention means that, for example, due to abrasion or increasing tolerances between components of the electromechanical joining system 100, the efficiency of the electromechanical joining system 100 decreases over the service life of the electromechanical joining system 100. This means that to achieve one and the same result at an output element 22, which is operatively connected to the screw drive 20 and carries out the actual joining process, increased electrical energy is required at the electric drive 10. The output element 22 in question is operatively connected to the first component 1 to be pressed into the component 2.

[0028] The electromechanical joining system 100 has various wear-prone components 21 such as the brake 4, the gear 5, the belt drive 6, the bearing 7, the guide 8, the anti-twist device 9, etc. For example, the brake 4 may not be installed in the housing as specified in the operating instructions and may drag during operation, leading to increased wear on the brake lining. Alternatively, the brake 4 may be electrically connected to the control device 13 in a manner different from that specified in the operating instructions, resulting in excessively high braking forces and, in turn, increased wear on the brake lining. The gearbox 5 contains oil, which can age prematurely due to excessively high operating temperatures. The belt drive 6 is also subject to wear. The belt drive 6 comprises a belt and pulleys, which are supported by bearings. The belt may not be seated properly on the pulleys, leading to increased wear on the belt material. The pulleys may be rotating out of true, resulting in premature wear on the bearings. The same applies to bearing 7 of the drive shaft 18.Bearing 7 can also wear out prematurely due to overload or damage. Furthermore, the guide 8 can become contaminated during operation, leading to increased frictional resistance on the guide surfaces of the guide 8 and premature wear of the guide surfaces. Finally, the anti-rotation device 9 is also exposed to high forces during operation and can wear out prematurely due to overload or damage.

[0029] Furthermore, the output element 22 is operatively connected to a sensor 24. The sensor 24 serves to determine a force or torque (depending on the type of joining process) applied by the output element 22 during the joining process of the component 1. The sensor 24 can be a strain gauge or a piezoelectric sensor. The sensor 24 can be integrated into the ram or attached to the ram. The value for the force or torque determined by the sensor 24 represents an additional measured value ZMW and is fed by the sensor 24 to a monitoring device 30 as an input variable. With knowledge of the present invention, the person skilled in the art can also use a sensor to determine a pressure applied by the output element 22.

[0030] Likewise, at least one actual value IW, IW' of the electric drive 10 is supplied as an input variable by the control device 13 of the servo motor 12. An actual value IW is a rotational speed n of the drive shaft 18, or an actual value IW' is a required current I of the servo motor 12.

[0031] Both the actual values ​​IW, IW' of the electric drive 10 and the additional measured values ​​ZMW of the sensor 24 are determined at the same time during the joining process and fed to the control device 14.

[0032] According to the invention, a control device 14 is provided. Fig. 2 the control device 14 is arranged in the electric drive 10. Preferably, the control device 14 is an integral part of the control device 13. According to Fig. 3The control device 14 is configured as an external computer outside the electric drive 10. The control device 14 has an algorithm 16 configured to link the actual values ​​IW, IW' of the electric drive 10 with the additional measured values ​​ZMW of the sensor 24. The result of the linking is used for a condition analysis of the electromechanical joining system 100, which serves to detect incipient wear and, therefore, an impending failure or a necessary replacement of a wear-prone component 21 in a timely manner. The linking of the actual values ​​IW, IW' of the electric drive 10 with the additional measured values ​​ZMW of the sensor 24 preferably takes place in real time.For the purposes of the present invention, real time is defined such that a result of the linking in the control device 14 is available more quickly than the time it takes to supply the actual values ​​IW, IW` of the electric drive 10 and the additional measured values ​​ZMW of the sensor 24.

[0033] In the Fig. 41 is a diagram of the efficiency η over time t over a longer operating period of the electromechanical joining system 100. A curve 34 connects the individual points in time at which the corresponding actual values ​​IW, IW' of the electric drive 10 and the additional measured values ​​ZMW of the sensor 24 were fed to the control device 14. The algorithm 16 has determined the efficiency η at the respective points in time as a quotient between the actual values ​​IW, IW` of the electric drive 10 and the additional measured values ​​ZMW of the sensor 24. Furthermore, an extrapolation for the future can be seen starting from the dashed time course of curve 34.

[0034] In particular, it can be seen that the magnitude of the efficiency η decreases with increasing time t. A limit value GW indicates a threshold at which, for example, it is economically worthwhile to replace a worn component of the electromechanical joining system 100 due to the decreasing efficiency η or the impending wear of a wear-prone component 21—before the wear leads to an unwanted interruption in the operation of the electromechanical joining system 100. The time t 1 at which the limit value GW will be reached can be extrapolated by the algorithm 16. The time t 1 is called the service life of the wear-prone component 21.

[0035] In the Fig. 5In contrast, a curve 36 is shown, which represents the expected remaining service life LD of the electromechanical joining system 100 over time t. The actual values ​​IW, IW' of the electric drive 10 and the additional measured values ​​ZMW of the sensor 24 were used by means of the algorithm 16 using a service life formula, whereby the service life formula may include further factors or values ​​that may need to be determined using additional measured values ​​or information.

[0036] For example, a lifetime LD can be determined from actual values ​​IW of the speeds n of the drive shaft 18 measured by the absolute encoder 11 and additional measured values ​​ZMW of forces F measured by the sensor 24 according to the following lifetime formula: LD ∼ B − 1 3 = ∑ i m q i ∑ i m q i n i F i 3 Accordingly, the service life LD is inversely proportional to the cube of an average load B during a number of m operating cycles, where i is the index of the individual operating cycles. qi denotes the length of an operating cycle. And ni represents an average speed measured during an operating cycle. Finally, F i is an average force measured during an operating cycle. With knowledge of the present invention, the person skilled in the art can also use a different service life formula. For example, they can use a service life LD 10 , which is achieved by 90% of the components subject to wear, or they can use a service life LD 5 , which is achieved by 95% of the components subject to wear. Here, too, the following applies: LD 10 = K 10 B − 1 3 LD 5 = K 5 B − 1 3 Where K 10 and K 5 are experimentally determined proportionality factors.

[0037] Here, too, a critical limit value GW and the reaching of the limit value GW at time t 2 can be predicted using algorithm 16. The time t 2 is called the service life of the electromechanical joining system 100.

[0038] The Fig. 4 and 5 The curves 34, 36 shown can be displayed, for example, on a display device 30, in particular a screen, connected to the control device 16. Furthermore, the curves 34, 36 or the numerical values ​​resulting from the curves 34, 36, as well as the underlying actual values ​​of the electric drive 10 or the additional measured values ​​of the sensor 24, can also be stored using a storage medium 32. The storage medium 32 is preferably a Transducer Electronic Data Sheet (TEDS) according to the IEEE 1451.4 standard. List of reference symbols

[0039] 1 Component 2 Component 3 Arrow 4 Brake 5 Gearbox 6 Belt drive 7 Bearing 8 Anti-twist device 9 Guide 10 Electric drive 11 Absolute encoder 12 Servo motor 13 Control device 14 Monitoring device 16 Algorithm 18 Drive shaft 20 Screw drive 21 Wear-prone component 22 Output element 24 Sensor 30 Display device 32 Storage medium 34 Curve 36 Curve 100 Electromechanical joining system LD Service life GW Limit value t Time t 1 Calculated service life of the wear-prone component t 2 Calculated service life of the electromechanical joining system or the screw drive IWIst-Wert Speed ​​of the drive shaft IW`Actual value Current of the servo motor ZMW Additional measured value η Efficiency

Claims

1. A method for analyzing the status of an electromechanical joining system (100) wherein an output force or output torque for a joining method carried out by the electromechanical joining system (100) is generated by an electrical drive (10) by means of a screw drive (20), which drive (10) comprises a servo motor (12), which servo motor (12) drives a drive shaft (18) by means of a gear (5) and a belt drive (6); wherein a monitoring device (14) is supplied with actual values (IW, IW`) of the electrical drive (10) as input variables, wherein an actual value (IW, IW`) is a rotational speed (n) of the drive shaft (18) or a required current of the servo motor (12); wherein a sensor (24) determines additional measurement values (ZMW), which sensor (24) is used to measure the course of forces or torques over time during the joining method; wherein the monitoring device (14) is supplied with the additional measurement values (ZMW) as input variable, wherein the actual values (IW, IW`) of the electrical drive (10) as well as the additional measurement values (ZMW) of the sensor (24) are determined at the same point of time in the joining process and transmitted to the monitoring device (14); wherein the monitoring device (14) uses an algorithm (16) to link the actual values (IW, IW`) with the additional measurement values (ZMW); wherein the algorithm (16) calculates an efficiency (η) from the ratio of the actual values (IW, IW') and the additional measurement values (ZMW); and wherein the monitoring device (14) uses this linkage to detect upcoming wear of a wear-prone component (21) of the electromechanical joining system (100).

2. The method according to claim 1, characterized in that the algorithm (16) uses the actual values (IW, IW`) and the additional measurement values (ZMW) only during part of the time period the joining method takes, wherein preferably during that period the actual values (IW, IW') are at least nearly constant.

3. The method according to claim 1, characterized in that the algorithm (16) uses the actual values (IW, IW`) and the additional measurement values (ZMW) during an additional operation outside of the joining method, in particular during an operation of the electromechanical joining system (100) where no force or torque acts on the electromechanical joining system (100).

4. The method according to any of the claims 1 to 3, characterized in that the algorithm (16) links actual values (IW, IW`) and additional measurement values (ZMW) with one another that are transmitted to the monitoring device (14) at the same time.

5. The method according to any of the claims 1 to 4, characterized in that the algorithm (16) uses actual values (IW, IW`) and additional measurement values (ZMW) during a constant rotational angular speed of the electrical drive (10).

6. The method according to any of the claims 1 to 5, characterized in that the algorithm (16) uses amounts of a rotary movement of a drive shaft (18) of the electrical drive (20) acting on the screw drive (20) as the actual values (IW) or the algorithm (32) uses amounts of the power consumption (I) of a servo drive (12) of the electrical drive (10) as the actual values (IW').

7. The method according to any of the claims 1 to 6, characterized in that the monitoring device (14) calculates a time course of the linkage of the actual values (IW, IW`) and the additional measurement values (ZMW).

8. The method according to claim 7, characterized in that the monitoring device (14) extrapolates the time course of the linkage of the actual values (IW, IW`) and the additional measurement values (ZMW) into the future.

9. The method according to claim 7 or 8, characterized in that the monitoring device (14) determines an amount of time remaining until the at least one wear-prone component (21) of the electromechanical joining system (100) must be replaced or a service life (LD) of the electromechanical joining system (100), respectively.

10. The method according to any of the claims 8 to 10, characterized in that the results of the linkage of linking the actual values (IW, IW`) with the additional measurement values (ZMW) are stored in a storage medium (32) of the electromechanical joining system (100).

11. An electromechanical joining system (100) comprising an electrical drive (10), which electrical drive (10) acts by means of a screw drive (20) on a rotatable or linearly movable output element (22) for performing a joining method, which drive (10) comprises a servo motor (12), which servo motor (12) drives a drive shaft (18) by means of a gear (5) and a belt drive (6), comprising first means of detecting actual values (IW, IW`) of the electrical drive (10) and second means of detecting additional measurement values (ZMW) by means of a sensor (24) for measuring the course of forces or torques over time during the joining method, wherein an actual value (IW, IW`) is a rotational speed (n) of the drive shaft (18) or a required current of the servo motor (12), and comprising a monitoring device (14) which may be supplied by the actual values (IW, IW`) and the additional measurement values (ZMW), wherein the first means determine the actual values (IW, IW') of the electrical drive (10) and the second means determine the additional measurement values (ZMW) of the sensor (24) at the same point of time in the joining process and transmit them to the monitoring device (14); wherein the monitoring device (14) comprises an algorithm (16) designed to link the actual values (IW, IW') and the additional measurement values (ZMW) with one another according to a method as defined in any of the claims 1 to 10; wherein the algorithm (16) calculates an efficiency (η) from the ratio of the actual values (IW, IW`) and the additional measurement values (ZMW).

12. The electromechanical joining system according to claim 11, characterized in that a control device (13) controls the electrical drive (10).

13. The electromechanical joining system according to claim 11 or 12, characterized in that a storage medium (32) for storing the linkage of the actual values (IW, IW') with the additional measurement values (ZMW) that is carried out by the monitoring device (14) is provided.

14. The electromechanical joining system according to any of the claims 11 to 13, characterized in that the monitoring device (14) is arranged in the electrical drive (10) or in that the monitoring device (14) is positioned outside the electrical drive (10).