DE102006047683B3 - Defective force or form-fitting connection i.e. screw connection, recognizing method for use by on-screwing device, involves measuring torque or force characterizing connection as parameter during movement between screw and clamping section - Google Patents

Abstract

The method involves moving a screw (3) and a clamping section (1), and/or a counter piece (2) relative to each other and provided in force or form-fitting contact such that a screw connection is force-balanced and/or a form-fit is partially released. A torque or force characterizing the connection is measured as a parameter during a relative movement between the screw and the section, and/or the piece and is compared with a reference parameter. A friction force path or a friction moment path is determined between the screw and the clamping section, and/or the counter piece. An independent claim is also included for a device for recognizing a defective force or form-fitting connection i.e. screw connection.

Description

The The present invention relates to a method and an apparatus for detecting a faulty non-positive or positive connection.

Strong connections arise through the transfer of forces, for example, pressure forces or friction forces counting. The cohesion of non-positive Connection becomes exclusive ensured by the acting force. tensile forces can with non-positive Only transfer connections as long as the static friction is greater than or equal to the tensile force. To the non-positive Belong to connections For example, screw / tapped holes after reaching the tightening torque. The screw is tightened, i. biased, and keeps the connection, because The friction prevents the screw from pulling turned back again, i.e. is solved. In the connection technology automatic screwing devices are known, non-positively connected to screw connections secure with a controlled tightening torque.

Positive connections arise from the interaction of at least two connection partners. Due to the mechanical connection, the connection partners can even without or with interrupted power transmission does not solve. To positive Counting connections including rivets / holes, keyways / grooves or screw connections, if the screw has no compressive forces on the parts to be joined, i. not biased is. In purely positive Screwed connections will tighten the screw either on or off Shearing claimed.

A faulty positive or positive connection is present, if by foreign influences e.g. Form and / or surface defects, plastic deformation or foreign substances a connection between materials not predetermined target parameters, e.g. Torque or force enough.

In the DE 39 30 306 A1 describes a torque measurement with tolerance monitoring in the production of threaded holes, wherein the tapping machine has a distance measuring device. The production process of a threaded hole is not comparable with the dismantling of a screw connection with respect to the occurring forces and moments.

In the DE 90 07 394 U1 a device for measuring a static and dynamic friction torque in driven bearings is described, wherein an equal sized electromagnetically generated torque on the outer ring of the bearing compensates for the frictional torque. Such a device is for example unsuitable for disassembly of a screw.

In the DE 41 18 595 C2 A tester for monitoring the tolerance of the maximum tightening torque and maximum angle of rotation when making a screw connection is described, in which the measured value profile is stored, compared with a desired value and can be displayed to the operator. However, this tester is not at the same time suitable for significantly lower measured values of the torques (<0.1 Nm) and does not solve the detection of a faulty connection during disassembly.

It It is an object of the present invention to provide a method and a device for detecting a faulty non-positive or positive connection which are used when disassembling the connection can.

These The object is achieved by a method for detecting a faulty non-positive or positive connection, in particular a screw connection, wherein at least two elements, initially in a frictional or positive engagement with each other stand, relative to each other are moved so that the connection relieves strain is and / or the fit is at least partially solved, where at least one parameter characterizing the compound during the Movement is measured and compared with a desired parameter.

By the inventive method Is it possible, while the disassembly of a non-positive or positive connection a faulty Automatically detect connection and reliable from a faultless differ.

Preferably becomes at least one parameter characteristic of the connection during the Motion measured and compared with a nominal parameter run. hereby Is it possible, not just evaluate the dismantling process at a single time, but to record and compare the corresponding parameter course. This allows a more reliable Detecting if a faulty non-positive or positive connection is present.

Preferably the parameter course becomes over evaluated the time. This is for example a frequency analysis the parameter course possible, or its integration or differentiation by time, from which additional Clues to detect a faulty positive or positive connection result.

According to one another preferred embodiment becomes the parameter course after reaching a threshold value evaluated. The threshold value can be, for example, a breakaway torque, i.e. overcoming the tightening torque of the screw and thus the overcoming be the bias of the screw.

Preferably a gradient of the parameter course is determined, which with a Target gradient is compared. In particular, through the differentiation of the parameter course, i. by evaluating the slope of the corresponding parameter curve, can be faulty force or positive Reliable connections recognize and distinguish from faultless connections.

According to one another preferred embodiment it is decided that there is a faultless connection when the threshold is less than a set threshold, and if a absolute gradient of the parameter profile is less than a nominal gradient. For example with a faultless screw connection takes when unscrewing the number of thread-locking threads is linear starting, so that the torque curve at the beginning of a low threshold and subsequently has a low gradient.

Preferably it is decided that there is a faulty connection if the threshold is greater than is the target threshold and if the magnitude gradient of the parameter history is less than a target gradient. Here, an impurity, e.g. one dried impregnating agent, or a shape and surface defect to an increased threshold at the beginning of disassembly of the compound, and then to a steeply sloping gradient.

According to one another preferred embodiment it is decided that there is a faulty connection if the threshold is less than a desired threshold, and if the absolute gradient the parameter history is greater than is a nominal gradient. For example, when loosening a screw connection to lead smallest chips on the screw or eccentricity of the screw to torque peaks within one or more revolutions. A ridge on the screw or shavings in lead the threaded hole to a rising torque curve. This is also this Error type reliable recognizable.

Further preferred embodiments of the inventive method are in the further dependent claims explained.

The the above task will be over In addition, according to the invention solved by a device for detecting a faulty non-positive or positive connection between at least two elements that are connected together in a or positive locking Engage, in particular a screw, with a Movement device for generating a force-relieving and / or the positive connection at least partially solving relative movement between the two elements, a measuring device that at least one the Measuring compound characterizing parameter during relative motion, and a comparator that includes the measured parameter a setpoint parameter.

By the device according to the invention Is it possible, reliable faulty power or positive Detect connections and distinguish from faultless connections.

Preferably a position allocation device is provided which has a positional relationship the interengaging elements and the moving means checked and / or corrected. The location allocator allows inclination or eccentricity of each other to recognize engaged elements and the device or exclude. Are the inter-engaging elements with respect to the Device inclined or eccentric to a center of rotation of a This may lead to a faulty assessment of the force or positive locking Lead connection.

Preferably the measuring device has a force or torque sensor. Thus, you can also form and surface defects as a result of plastic deformation, for example at excessive tightening torque or repeatedly tightening a screw, resulting in a setting of the Material leads, be detected and evaluated by means of the friction torque.

Preferably The torque sensor has a measuring range between 0 and 0.1 Nm.

Previous Monitor automatic screwdrivers only the tightening torque and / or the tightening angle for the pretensioning of a screw connection and are therefore unsuitable for a screwdriving process with a fraction to monitor the torque or incorrect positive locking Recognize connections. This disadvantage is due to the use a torque sensor with a measuring range between 0 and 0.1 Nm fixed.

According to a further preferred embodiment, the comparison device has a circuit and / or a program which precedes a method according to at least one of the preceding NEN exemplary embodiments executes. As a result, a cost-effective implementation of the device is possible.

Further preferred embodiments of Device according to the invention are in the further dependent claims explained.

The The present invention will now be described in terms of preferred embodiments in conjunction with the associated Figures closer explained. In these show:

1 a side view of a detacher, and

2 a block diagram of a Entschraubvorrichtung.

In 1 is a side view of a detacher 21 shown. The helicopter 21 has an electric motor 11 on, which has an electrical connection 12 with an in 2 shown power supply 24 connected is. Alternative to the electric motor 11 Piezo drive or a hydraulic or pneumatic drive is conceivable, if it is possible to regulate the torque curve of this drive accurately enough, or to control by suitable monitoring and control devices. Thus, the electric motor 11 In the exemplary embodiment, a part of a movement device for generating a force-relieving or positive locking at least partially releasing relative movement between a screw 3 and a clamping piece 1 , or a counterpart 2 represents.

The electric engine 11 is with a screw device 10 connected by a rack 9 is held. The electric engine 11 drives the screwing device 10 by a rotary motion. In the screwing device 10 For example, a measuring device may be provided in the form of a force or torque sensor. Preferably, the torque sensor has a measuring range between 0 and 0.1 Nm and allows by a corresponding connection with a in 2 The control unit shown a feedback of the measured values, which are included in the release of the screw. As with respect to 2 will be explained, however, is the use of a force or torque sensor when using an electric motor 11 not necessarily required.

When in 1 embodiment shown is the screw 10 with the frame 9 over an elastic component 8th screwed between a screw head and the frame 9 is arranged. The elastic component 8th may for example be a rubber washer. For the screw connection is in the frame 9 a hole is provided which has an inner diameter which is slightly larger than an outer diameter of the screw. Through the elastic component 8th Thus, there is a quasi-floating storage of screwing 10 on the rack 9 , Thus, the elastic component 8th a simple location allocation device that prevents the movement device on a screw head 4 the screw 3 eccentric or inclined, which can lead to errors in the assessment of the screw connection.

Apart from the elastic component 8th However, more complex position-allocation devices are conceivable to prevent the movement device eccentric and / or inclined to the screw head 4 is put on. Active elements, such as piezoactuators, may be provided for positional correction. The correct position can also be checked by means of inclination sensors and, if necessary, corrected by the piezoactuators in the sense of a control loop.

The electric engine 11 is about an axial shaft of the screw 10 with a screw element 6 connected. In the in 1 illustrated preferred embodiment is the screw 6 designed as a hexagon nut. Depending on the type of screw head used 4 but are also other screw 6 such as Allen inserts, Torx inserts or cross-slot inserts to use.

Below a projecting collar of the screw 6 is a holding element 7 a lifting device (not shown). In the preferred embodiment, the retaining element allowed 7 by movement in the longitudinal direction of the Axialschaftes the screwing 10 a lifting of the screw 6 to the said screw 6 from the screw head 4 to loosen and / or engaged with a new screw head 4 bring to. For the said lifting device, at least one actuator, not shown, is provided. Furthermore, the axial shaft of the screw device 10 For example, at least a two-part, telescopic linkage, which is slidable into each other and by movement of the retaining element 7 the lifting device in the direction of the electric motor 11 is pushed into each other. By the said holding element 7 An assessment of several screw connections can take place in succession in an automated manner.

The electric engine 11 , the screwing device 10 , the frame 9 , the elastic component 8th , the screw element 6 and the holding element 7 the lifting device make components of a Entschrau bers 21 represents.

The screw element 6 of the detacher 21 is in 1 in engagement with the screw head 4 the screw 3 , The clamping piece 1 , the counterpart 2 and the screw 3 with her screw head 4 form a non-positive or positive connection 20 , The screw 3 connects the counterpart 2 with the clamping piece 1 , Here, both the clamping piece 1 and the counterpart 2 as well as only the counterpart 2 be provided with a corresponding screw thread. In the latter case, the clamping piece 1 a bore having an inner diameter larger than an outer diameter of the screw 3 ,

With the reference numerals 5a and 5b are two contaminants in the bore of the clamp 1 , or the screw thread of the counterpart 2 shown. The contamination 5a This represents a chip, which is located in the threaded hole, while the contamination 5b represents an impregnating agent, before screwing into the bore of the clamping piece 1 flowed.

In the in 1 As shown, the screw is already released and is only in positive engagement, as from the distance s between the surface of the clamping piece 1 and the bottom of the screw head 4 is apparent.

In 2 a block diagram of a Entschraubvorrichtung is shown. In the embodiment shown, the Entschraubvorrichtung consists of the screwdriver 21 , which engages with the non-positive or positive connection 20 stands, the control unit 25 , a personal computer (PC) 27 and a monitor 28 , The control unit 25 has a current clamp 22 , a control device 23 and a power supply 24 on. The control unit 25 , the computer 27 and the monitor 28 draw electrical energy from a network connection 26 to which they are connected.

A measured value feedback of the parameters characterizing the connection, for example the force or the torque can in the sense of a control circuit to or in the control unit 25 respectively.

In the control unit 25 draws the power supply 24 the electrical energy from the grid connection 26 and is with its output to the input of the controller 23 connected. Outputs of the control device 23 are on the one hand with the current clamp 22 connected and the other with the PC 27 , As output of the current clamp 22 is the electrical connection 12 with the engine 11 of the detacher 21 connected. A monitor output of the PC 27 is with the monitor 28 connected.

In the in 2 shown embodiment, the current clamp 22 a measuring device, the current consumption of the electric motor 11 of the detacher 21 supervised. About this power consumption can be in the control unit 25 determine the torque that the electric motor 11 generated, or with the said electric motor 11 is charged. This can be done, for example, by a corresponding evaluation in the control unit 25 determine the swelling moment or the momentary friction torque of the screw connection. Thus, the current clamp 22 an ammeter.

The control device 23 is part of a comparison device having a circuit and / or a program that / performs a method for detecting a faulty non-positive or positive connection. However, the corresponding program may also be partially or entirely in the PC 27 , which is equipped with a corresponding control interface, expire. The method will be described below.

In the preferred embodiment, the frictional connection is made by the deicer 21 relieved of force by the bias of the screw 3 and the tightening torque of the screw through a breakaway torque that of the electric motor 11 is applied, is degraded. Thus, a positive connection with surface pairing of the dissolved screw remains 3 in the tapped hole, as in 1 is shown.

A positive connection exists with a defined fit, the surface contact during disassembly typical frictional forces or friction generated. When unscrewing a loosened screw from the threaded hole, these frictional / friction moments of the shape and position tolerances of the engaging elements, as well as the surface of the screw 3 and the threaded hole dependent. These include, for example, parameters and influences such as friction coefficient, eccentricity, Krad, chips and foreign matter.

Thus, the method for detecting a faulty non-positive or positive connection is not only applicable to a non-positive screw, but also, for example, on a positive screw connection, ie a Schraubver bond, in which the screw 3 is no longer biased. However, other applications with different positive or positive connections are conceivable, for example, at feather keys and grooves.

Through the extractor 21 will be a relative movement between the screw 3 and the clamping piece 1 , or the counterpart 2 generated. There by the connection is relieved of force either in the first step, or in the second step, the positive connection is at least partially solved. It is also possible, for example, that the screw 3 is held stationary, and the counterpart 2 and / or the clamping piece 1 be rotated by a corresponding drive.

During the Relative movement becomes at least one characterizing the compound Parameter measured. This can, for example, the previously mentioned frictional force, or be the friction torque. However, for more precise determination, whether a faulty or error-free connection exists, a combination of parameters, for example the breakaway torque and the subsequent friction torque curve, the angle of rotation, which can be achieved with a certain drive torque Angular velocity, or the like respectively.

As a general rule it is conceivable to have only one parameter that characterizes the connection, record at a fixed time, such as the Breakaway. A more accurate evaluation is by measuring a Parameter course, for example, the torque curve during a part or the entire Unschraubungsvorgang possible. The obtained Torque curve can with a setpoint torque curve in the context of a Evaluation can be compared. Furthermore, a more detailed one Evaluation of the force or torque curve over time, the distance traveled, or the angle of rotation after reaching an initial threshold, or by differentiation, integration or frequency analysis possible.

Particularly advantageous is the combination of the evaluation of the threshold value when the frictional screw is relieved of force, and the torque curve during the screw 3 at least partially from the counterpart 2 and the clamping piece 1 is rotated out, that is, the positive connection is at least partially solved. If a comparison of the measured torque threshold value and the setpoint threshold value reveals that the torque threshold value is greater than the setpoint threshold value, an outage logic is set in the controller 23 or in the PC 27 determines that there is a faulty connection.

Preferably the torque curve is derived according to the time, so that a Gradient of the torque curve is determined with a target gradient is compared. The Aussagelogik notes that a flawless Connection exists when the torque threshold is less than is a target threshold, and if the magnitude gradient of the torque curve is less than a target gradient. It is assumed that for a faultless unscrewing the number of threads linear decreases and the torque curve to a low threshold Beginning and has a low gradient.

The look-out logic also determines that a faulty connection exists when the torque threshold is greater than a desired threshold and when the magnitude gradient of the torque curve is less than a desired gradient. For example, the penetration of an impregnating agent or other adhesive foreign substances into the screw hole or form and surface defects of the screw 3 or the screw hole to a higher torque threshold at the beginning and a sharply decreasing torque gradient.

The look-out logic further determines that a faulty connection exists when the torque threshold is less than the desired threshold and when the magnitude gradient of the torque curve is greater than a desired gradient. Smallest chips on the screw 3 or an eccentricity of the screw 3 lead to torque peaks within one or more revolutions. A ridge on the screw 3 or chips in the threaded hole lead to an increasing torque curve, which is reflected in an evaluation of the torque gradient. For example, a combined measurement of the angle of rotation traveled would allow accurate location of the fault in the tapped hole, if required.

Generally, the evaluation can be done manually on the monitor 28 done, or completely automated in the PC 27 , or in the control device 23 , For this purpose, for example, in the PC 27 a database with possible connection errors in a screw connection be deposited. The database can also contain for different screw types, which are characterized by diameter, thread length, thread pitch or the like, error-free force and / or torque thresholds, error-free force and / or torque curves according to the thresholds, as well as differentiations, integrations and / or frequency analyzes of the courses ,

By combined data analysis, a secure and accurate detection of faulty positive or positive connections is possible. The evaluation is preferably carried out in a measured value interface of the PC or directly in its digital memory by the arithmetic unit of the PC 27 , The result of the evaluation is preferably from the monitor 28 represented numerically and / or graphically. Also, a direct further processing of the results of the evaluation, for example by returning the results to the control device 23 and adaptation of the control of the Ent screwdriver 21 while unscrewing on the basis of these results in the sense of a rule circle is possible.

The The above description discloses an embodiment of a method for detecting a faulty force or positive connection, in particular a screw connection, wherein at least two elements, which are initially in a frictional or positive engagement with each other, relative to each other are moved so that the connection relieved of force is and / or the fit is at least partially solved, where at least one parameter characterizing the compound while the movement is measured and compared with a target parameter, and a corresponding device for detecting a faulty non-positive or positive Connection.

Claims (18)

Method for detecting a faulty force or positive locking Connection, in particular a screw connection, wherein at least two elements, initially in a positive or positive engagement with each other, are moved relative to each other so that the connection is relieved of force and / or the positive connection at least partially solved where at least one parameter characterizing the compound is during the Movement is measured and compared with a desired parameter. The method of claim 1, wherein at least one of Compound characterizing parameter course during the Movement is measured and compared with a desired parameter course becomes. A method according to claim 1 or 2, wherein force or Torque as the compound characterizing parameter during the Movement are measured, and from it a Reibkraftverlauf or a Reibmomentverlauf between the relatively moving Elements is determined. The method of claim 2 or 3, wherein the parameter profile over the Time is evaluated. Method according to at least one of claims 2 to 4, wherein the parameter course after reaching a threshold value is evaluated. Method according to claim 5, wherein it is decided that a faulty connection exists when the threshold value of the parameter progression is greater as a target threshold. Method according to at least one of claims 2 to 6, wherein a gradient of the parameter profile is determined with the a desired gradient is compared. Method according to claim 7, wherein it is decided that there is an error-free connection when the threshold value is less than the target threshold, and if the magnitude gradient of the parameter profile is less than a nominal gradient. The method of claim 7 or 8, wherein decided is that there is a faulty connection when the threshold value greater than is the target threshold and if the magnitude gradient of the parameter history is less than a target gradient. Method according to at least one of claims 7 to 9, deciding that there is a faulty connection, if the threshold is less than the target threshold, and if the magnitude gradient the parameter history is greater than one Target gradient is. Device for detecting a faulty force or positive locking Connection between at least two elements that are in each other a non-positive or positive Engage, in particular a screw, with one Movement device for generating a force-relieving and / or the positive connection at least partially releasing relative movement between the two elements, a measuring device, the at least one measuring the compound characterizing parameter during the relative movement, and a comparator that measures the measured parameter compared with a target parameter. Apparatus according to claim 11, wherein a location allocation device is provided, which is a positional relationship of each other standing elements and the moving device checked and / or corrected. Apparatus according to claim 11 or 12, wherein a Evaluation is provided, the measured parameters as Parameter history over evaluates the time. Device according to at least one of claims 11 to 13, wherein the measuring device is a force or torque sensor having. Apparatus according to claim 14, wherein the torque sensor has a measuring range between 0 and 0.1 Nm. Device according to at least one of claims 11 to 15, wherein the moving means is driven by an electric motor is. Apparatus according to claim 16, wherein the measuring device an ammeter having a current consumption of the electric motor certainly. Device according to at least one of claims 11 to 17, wherein the comparison means a circuit and / or a Program, the / a method according to at least one of claims 1 to 10 executes.