EP1861688A1

EP1861688A1 - Machine power test in angular increments

Info

Publication number: EP1861688A1
Application number: EP06707617A
Authority: EP
Inventors: Baltes Alfing Montagetechnik GmbH GASS
Original assignee: Alfing Montagetechnik GmbH
Current assignee: Alfing Montagetechnik GmbH
Priority date: 2005-03-24
Filing date: 2006-03-21
Publication date: 2007-12-05
Also published as: WO2006100032A1; DE102005013786A1; DE102005013786B4

Abstract

In order to test screwing devices (20) with a rotating unit (21) and with a first torque sensor (23), a testing unit (2) with a counter-torque generating device (3) and with a second torque sensor (5) is provided, this test unit being able to be brought into contact with the rotating unit (21) of a screwing device (20) in an starting rotation position of the rotating unit (21). A control unit (22) controls a rotation of the rotating unit (21) brought into contact with the testing unit until the first torque sensor (23) reaches a predetermined set torque. The second torque sensor (5) measures an actual torque caused by the rotation of the rotating unit (21), and a comparison unit (6) compares the predetermined set torque of the screwing device (20) with the actual torque measured by the second torque sensor (5). The control unit (22) is designed for rotating the rotating unit (21) back beyond the starting rotating position about a predetermined angle into another starting rotation position. The functional components located inside the screwing device are brought together in a defined position different from the position in which they stood together during the testing of the first operating point of the screwing device. This enables an effective and reliable testing of the screwing device.

Description

MACHINE SKILLS IN ANGLE STEPS

FIELD OF THE INVENTION

The invention relates to a method for testing screwdrivers with a rotary unit and a torque sensor and a test system for testing screwdrivers with a rotary unit and a torque sensor. In particular, the invention relates to a test method and a test system with the features of the preamble of patent claim 1 or. of claim 13.

Such a test method and 'such a test system are typically in the

Assembly technology, especially used in automotive production. However, such a test method and such a test system can be found in other fields of application in which screwdrivers are used, for. B. in mass production in the electronics industry, both in fully automated and semi-automated series production.

Traditionally, bolting tools are tested for torque on transducers after assembly, commissioning, and during their use. In ■ this process, generally as a machine capability study is determined, it is checked whether a torque exerted by a screwdriver on a screw, with a torque that measures a torque sensor of the screwdriver. In particular, during use, ie during production, screwdrivers are repeatedly checked for their ability in certain test cycles. The type and frequency of the capability tests depend, for example, on manufacturing and process specifications. Thus, for example, the time interval between two capability tests of a screwdriver in automobile production depends on the safety relevance of the screwdriving operations performed by a screwdriver. In so-called class A (eg on chassis, brakes, steering, seatbelt and airbag, the exact implementation of which is of particular importance to the reliability of the finished automobile, the capability test cycle will generally be shorter than in so-called class B critical (class B) such as on engine, gearbox or ground screws) whose safety relevance is lower.

BACKGROUND OF THE INVENTION

Various methods are currently used to perform a capability test of screwdrivers. So z. B. for checking the torque output by the screwing tool, a torque transducer with counter-measuring system is attached to the screwing tool. With hand-held screwdriving tools, so-called crease keys are used An insert that allows the operator to check the torque of a screw tightened with the screwdriver being tested. Furthermore, a mobile measuring bench is often used in assembly technology, with the succession of several screwdrivers can be checked for their ability.

All these methods have in common that they either cause increased personnel costs and high equipment costs or provide only inaccurate statements about the accuracy of the screwing tool. For example, e.g. a high personnel expenditure is necessary in order to keep the ability check of the used screwdrivers at a high level, since this is only possible if the test cycles are kept as short as possible. Extend the test cycles, z. Once per week, there is a risk that a screwdriver judged to be IO (OK) after the last capability check but then become faulty during further use, i. E. NIO (not in order), produces a large number of rejects until the next proficiency check, which can lead to costly rework or, in the case of a late notice, to a return action of the finished pieces. To avoid the latter, so far the increased effort associated with short test cycles has been accepted in order to obtain the most accurate statements possible about the ability of the screwing tools.

The conventional methods for testing the ability of screwing tools thus have the disadvantage that they are associated with high costs and costs. It has also been observed that a further reduction in the number of test cycles is no longer noteworthy for a reduction in the number of test cycles

Contribution rate. The conventional methods of capability testing thus also have the disadvantage of being unable to reliably verify the ability of screwing tools.

EXPLANATION OF THE INVENTION

As explained above, it is not possible in the prior art to effectively and reliably check screwdrivers for their ability, essentially because the check of the screwdriver at each capability check is only ever checked at a single operating point. Thus, in the prior art during a capability test, a screwdriver to a certain nominal torque in a position of the functional components located in the screwdriver to each other, such. As gears of the output, checked. The position of the functional components in the nutrunner is purely coincidental during each capability test, so that in a number of successive capability tests the nutrunner is not checked at all times in several positions of the functional components in the nutrunner and in other positions of the nutrunner at all.

The object of the invention is to provide a test method and a test system, which allows an effective and reliable testing of a screwdriver.

This object is achieved by a method (claim 1) for testing screwdrivers with a rotary unit and a first torque sensor, comprising the following steps: a) contacting at least the rotary unit of the screwdriver in an initial rotational position of the rotary unit with a test unit, which has a counter-torque generating device and a second torque sensor; b) presetting a setpoint torque which the screwdriver is to output; c) rotating the rotary unit until the first torque sensor of the screwdriver reaches the predetermined So11 torque; d) measuring an actual torque caused by rotation of the rotary unit with the second torque sensor; e) comparing the predetermined setpoint torque of the screwdriver with the actual torque measured by the second torque sensor; f) turning back the turntable beyond the initial rotational position by a predetermined angular amount to another initial rotational position.

This object is further achieved by a test system (claim 13) for testing screwdrivers having a rotary unit and a first torque sensor, comprising: a test unit having a counter torque generating means and a second torque sensor suitable, at least with the rotary unit of at least one screwdriver brought into contact in an initial rotational position of the rotary unit to become; a control unit for controlling a rotation of the rotating unit brought into contact with the testing unit until the first torque sensor reaches a predetermined target torque, the second torque sensor being adapted to measure an actual torque caused by the rotation of the rotating unit; a comparison unit for comparing the predetermined target torque of the screwdriver with the actual torque measured by the second torque sensor, wherein the control unit is configured to rotate the rotary unit back beyond the initial rotational position by a predetermined angle to another initial rotational position.

By turning back the rotary unit on the initial rotational position addition to a given angular amount to another initial rotational position can be achieved that located in the screwdriver functional components of the output to each other reliably in a different position than the position of the screwdriver located in the functional components of the output to each other when contacting the rotary unit of the screwdriver in the first initial rotational position of the rotary unit with the test unit. In this way, it can be prevented that the screwdriver is randomly checked again in the same initial rotational position of the rotary unit or in the same of the functional components of the output located in the screwdriver, such as the gear wheels of the output drive. The functional components in the screwdriver are thus brought into a defined other position to each other than the position in which they were in the review of the first operating point of the screwdriver to each other. Thus, an effective and reliable testing of the screwdriver is made possible.

PREFERRED EMBODIMENTS

Preferably (claim 2, 14), the rotary unit is rotated back beyond the initial rotational position by the predetermined angular amount in the other initial rotational position, in the event that the desired torque and the actual torque differ by more than a predetermined amount. This ensures that a screwdriver whose actual torque deviates only insignificantly from the setpoint torque, can still be rated as IO with respect to the checked operating point. The predetermined deviation amount thus forms a tolerance limit for deviations between the setpoint torque and the actual torque.

Preferably, the following steps are repeated at least once: c) turning the rotary unit until the first torque sensor of the screwdriver reaches the predetermined setpoint torque; d) measuring an actual torque caused by rotation of the rotary unit with the second torque sensor; e) comparing the predetermined setpoint torque of the screwdriver with the actual torque measured by the second torque sensor; f) turning back the rotary unit over the initial rotational position by a predetermined angular amount to another rotational position (claim 3, 15). In this case, preferably, in a repetition of step c), the rotary unit is rotated starting from the initial rotational position in which the rotary unit is located after the immediately preceding execution of step f). The other initial rotational position reached by a predetermined angular amount in a previous turning back of the rotary unit over an initial rotational position is thus used as the one initial rotational position in a subsequent rotation of the rotary unit until the first torque sensor of the screwdriver reaches the predetermined target torque. It can thereby be achieved that a repeated check of the screwdriver takes place at a defined operating point which differs not only accidentally but with certainty from the operating point of the preceding check. As a result, on the one hand an effective check of the screwdriver is achieved, since double checks are avoided at one and the same operating point of the screwdriver. On the other hand, the check of the screwdriver becomes more reliable as a whole, since a larger number of different operating points is checked than if a random selection of the initial rotational position of the rotary unit for several consecutive test procedures may check several operating points several times.

Furthermore, the above-described repetition of steps c) to f) may also be a repetition of the steps a) and / or b). Thus, for example, before the repetition of steps c) to f), a different value for the setpoint torque to be output by the screwdriver can be specified.

Preferably, the product of the number of repetitions, or the feedthroughs, the steps c) to f) and the value of the predetermined angle amount at least 360 ° (claim 4). This can be achieved that the full functional range of the output of a screwdriver is checked at intervals of the predetermined angle. As already explained above, at least during the first testing of a full angle range of 360 °, no operating point is checked more than once, whereby the entire checking process is very effective. Furthermore, the screwdriver with each pass of steps c) to f) in each different positions of the screwdriver located in the functional components such. As gears of the output, checked. Thus, the entire test procedure is not only made particularly effective, but also provides a reliable test result, since the output is checked in many different operating positions.

Further, it is advantageous to select the value of the predetermined angular amount by which the rotary unit is rotated back to a different initial rotational position beyond the initial rotational position, less than or equal to the quotient of 360 ° and the number of teeth of a gear in a screwdriver, which of all Gears in the screwdriver most teeth has (claim 5). This can be achieved that when the steps c) to f) are repeated so often that the product of the number of repetitions and the value of the predetermined angle amounts to at least 360 °, the entire output of the screwdriver is completely checked. This can be ensured that a fault in the output of the screwdriver, which is based for example on the defectiveness of a single tooth of the gears in the output of the screwdriver, reliably detected. Even in this previously described embodiment of a test procedure of a screwdriver, the entire test procedure is extremely effective since no operating point of the screwdriver is checked more than once.

Furthermore, it is advantageous that the screwdriver is judged to be capable of deviating from the setpoint torque and the actual torque at most by the predetermined amount in each comparison of the setpoint torque of the screwdriver with the actual torque of the test unit. It can thereby be achieved that a screwdriver, which has a malfunction at least at one operating point, is reliably assessed as NIO (not in order / not capable) and is removed from the production process.

Preferably, the rotary unit of the screwdriver is in contact with the counter torque generating means of the test unit via a freewheel which ensures that the contact between the rotary unit and counter torque generating means during the turning back of the rotary unit is powerless (claim 7, 16). In this case, the freewheel can cause, during the turning back of the rotary unit, the counter torque torque Generation device is relaxed and the second torque sensor is reset (claim 17). It can thereby be achieved that in a turning back of the rotary unit in a step f) located in the screwdriver functional components such. B. the gears of the output, for a subsequent step c) get into a new, defined (ie not randomly determined) starting position. In this case corresponds to a certain initial rotational position of the rotary unit of the screwdriver a certain position of the functional components located in the screwdriver to each other.

Further, it is possible that the reaction torque generating means includes a pair of disc springs (claims 8, 18).

Preferably, the second torque sensor is calibrated (claim 9, 19). For example, the second

Torque sensor include a calibrated rotation chain (claim 10, 20). Furthermore, it is possible for the second torque sensor to be calibrated

Strain gauge includes (claim 11, 21).

Preferably, the screwdrivers described above are hand-held screwdrivers (claim 12, 36).

Further advantageous embodiments and improvements of the invention are specified in the subclaims. It should also be noted that the invention also includes other embodiments, which consist of a Combination of features that are listed separately in the claims and / or figures.

The invention will be explained in more detail below on the basis of its advantageous embodiments with reference to the drawings.

1 BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, the same or similar reference numerals designate the same or similar parts. In the drawings show:

Fig. 1 is a block diagram of the test system according to the invention;

2 shows an overview diagram of the test system according to the invention according to a first embodiment;

3 is an overview diagram of a second embodiment of the test system according to the invention;

4 is a cross-sectional view of a test unit and a rotary unit type wrench in contact with the test unit according to the first or second embodiment of the present invention; Fig. 5 is a sectional drawing taken along the line VV in Fig. 4, showing in plan view a counter-torque generating device with a freewheel of the embodiment shown in Fig. 4;

6 is a flowchart of the test method according to the invention;

7 is a flow chart of a test method according to a first embodiment of the present invention;

Fig. 8 is a block diagram of a third

Embodiment of the test system according to the invention;

9 is an overview diagram of the test system according to the third embodiment;

10 is an overview diagram of the test system according to the invention according to a fourth embodiment; and

Fig. 11 shows a conventional system for testing

Screwdrivers with a mobile measuring bench according to the prior art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION With reference to FIGS. 1 and 6, the test system according to the invention or the test method according to the invention will now be described in principle first.

1 shows a block diagram of the test system 1 according to the invention. The test system 1 comprises a screwdriver 20 to be tested with a rotary unit 21 and a first torque sensor 23. Furthermore, the test system 1 comprises a test unit 2 with a counter-torque generating device 3 and a second torque sensor 5, wherein the test unit 2 is adapted to be brought into contact at least with the rotary unit 21 of the screwdriver 20 in an initial rotational position of the rotary unit 21. The test system 1 further includes a control unit 22 for controlling rotation of the rotary unit 21 brought into contact with the test unit 2 until the first torque sensor 23 reaches a predetermined target torque. In this case, the second torque sensor 5 is adapted to measure a caused by the rotation of the rotary unit 21 actual torque. In addition, the test system 1 comprises a comparison unit 6 for comparing the predetermined setpoint torque of the screwdriver 20 with the actual torque measured by the second torque sensor 5. Further, the control unit 22 is adapted to turn the rotary unit 21 back beyond the initial rotational position by a predetermined angular amount to another initial rotational position.

As can be seen from Figure 1, the test system 1 of the present invention consists mainly of the following components: a screwdriver 20, a test unit 2, a comparison unit 6 and a control unit 22.

As can be seen from the flowchart in FIG. 6, the test method according to the invention for testing screwdrivers 20 with a rotary unit 21 and a first torque sensor 23 comprises the following steps: a) contacting S6.1 at least the rotary unit 21 of the screwdriver 20 in an initial rotational position of Rotary unit 21 with the test unit 2, which includes the counter torque generating device 3 and the second torque sensor 5; b) specify S6.2 a desired torque, which the screwdriver 20 is to output; c) turning S6.3 the rotary unit 21 until the first torque sensor 23 of the screwdriver 20 reaches the predetermined target torque; d) measuring S6.4 the actual torque caused by the rotation of the rotary unit 21 with the second torque sensor 5; e) comparing S6.5 of the predetermined setpoint torque of the screwdriver 20 with the actual torque measured by the second torque sensor 5; f) turning back Sβ .6 of the rotary unit 21 beyond the initial rotational position by the predetermined angular amount to the other initial rotational position.

With the test system described above or with the test method described above according to the present invention, it is possible, after checking a screwdriver 20 at an operating point corresponding to a certain position of the functional components located in the screwdriver, wherein the screwdriver 20 of a first Initial rotation position of the rotary unit 21 is checked from the screwdriver in a defined other Initial rotational position of the rotary unit 21 to bring with a defined other position of the functional components of the output 27 located in the screwdriver.

By turning back the rotary unit on the initial rotational position addition to a given angular amount to another initial rotational position can thus be achieved that located in the screwdriver functional components of the output to each other reliably in a different position than the position of the screwdriver located in the functional components of the output to each other when contacting the rotary unit of the screwdriver in the first initial rotational position of the rotary unit with the test unit. As a result, it can be prevented that the screwdriver in a subsequent check at random again in the same initial rotational position of the rotary unit, or in the same of the functional components of the output in the screwdriver, such. the gears of the output, is checked.

The functional components in the screwdriver are thus brought into a defined other position to each other than the position in which they were in the review of the first operating point of the screwdriver to each other. Thus, an effective and reliable testing of the screwdriver is made possible.

Fig. 2 shows a functional diagram of one embodiment of the test system of the present invention Invention. The reference numerals correspond entirely to those in FIG. 1, so that reference may be made to the description of FIG. 1 for the description of the individual components, which are referenced in FIG. 2 with these reference symbols.

The screwdriver 20 in this case comprises a rotary unit 21 and a first torque sensor 23, which is connected to the rotary unit 21. The rotary unit 21 may e.g. comprise a socket whose shape is adapted to the screwing point to be machined. The first torque sensor 23 of the screwdriver 20 is suitable for measuring a setpoint torque predetermined by the rotary unit 21.

The test unit 2 includes a second torque sensor 5 and a counter torque generating device 3, which is connected to the second torque sensor 5.

The second torque sensor 5 of the test unit 2 is connected to the first torque sensor 23 of the screwdriver 20 via the comparison unit 6. In this case, the comparison unit 6 is designed to receive the predetermined setpoint torque of the screwdriver 20 from the first torque sensor 23, to receive the actual torque measured by the second torque sensor 5 of the test unit 2, and to compare these two torque values with one another.

The control unit 22 is connected to the screwdriver 20. In this case, the control unit 22 directly or indirectly via other assemblies of the screwdriver 20, for example the first torque sensor 23 to be connected to the rotary unit 21. The control unit 22 controls rotation of the rotary unit 21 brought into contact with the test unit 2 until the first torque sensor 23 of the screwdriver 20 reaches a predetermined target torque. Further, the control unit 22 is configured to rotate the rotary unit 21 back to a different rotational position by a predetermined angular amount beyond an initial rotational position.

The designated with reference numeral 20 screwdriver is shown schematically in Fig. 2 as a hand-held screwdriver with a handle and a nutrunner head. However, the invention is not limited to the use of manual wrenches. Rather, fully automatic screwdriver can be found in the test system and the test method according to the present invention input.

The test unit 2 has a second torque sensor 5, which is designed to receive a rotary unit 21 of the screwdriver 20 in such a way that the rotary unit 21 and the torque sensor 5 engage with one another. For example, the contact surface of the second torque sensor 5 has the shape of a screw head and the rotary unit 21 has the shape of a socket fitting to this screw head. A mediated by the rotary unit 21 rotational movement is thus via the second torque sensor 5 to the counter torque generating means 3 of the test unit

2 mediates. The counter torque generating device

3 produces an output actual torque outputted from the rotary unit 21 Counter torque. The counter torque generated by the counter torque generating means 3 keeps the balance with the actual torque caused by the rotation of the rotary unit. In this equilibrium state, the second torque sensor 5 of the test unit 2 measures the actual torque outputted from the driver 20 by measuring the amount of the torque applied to the second torque sensor 5. Preferably, the second torque sensor 5 of the test unit 2 is a calibrated torque sensor in order to be able to obtain a reliable statement about the magnitude of the actual torque output by the screwdriver 20. The second torque sensor 5 can be z. B. include a calibrated swivel chain. According to another example, the second torque sensor 5 comprises a calibrated strain gauge, which is applied to the axis of rotation of the test unit 2. By the torsion of the axis of rotation of the test unit 2 of the strain gauge is stretched and this strain can be used as a measure of the voltage applied to the axis of rotation torque. Further, the counter torque generating means may include a pair of Belleville springs, which allows a soft compression of the counter torque device upon application of the test unit 2 with the torque of the screwdriver 20.

In FIG. 2, the control unit 22 for controlling rotation of the rotary unit 21 brought into contact with the check unit 2 is provided separately from the driver 20. The controller 22 may also be integrated in the screwdriver 20 or be mounted on this. The control unit 22 controls the rotary unit 21 until the first torque sensor 23 reaches a predetermined setpoint torque. 2, the first torque sensor 23 is integrated in the screwdriver. The first torque sensor 23 may also be mounted on the screwdriver 20 or provided externally to the screwdriver 20.

The first torque sensor 23 of the screwdriver 20 transmits the value of the torque to the comparison unit 6 when the predefined setpoint torque is reached. Furthermore, the second torque sensor 5 of the counter-torque generating device 3 transmits the actual torque measured by it to the comparison unit 6. The comparison unit 6 compares the predetermined setpoint torque of the screwdriver 20 with the actual torque measured by the second torque sensor 5. Preferably, the screwdriver 20 is then judged to be capable of differing in the comparison of the desired torque of the screwdriver 20 with the actual torque of the test unit 2, the target torque and the actual torque at most by a predetermined amount.

Fig. 3 shows another preferred embodiment of the test system 1 of the present invention. With regard to the components designated by the same reference numbers, reference is made to the description in FIGS. 1 and 2. In Fig. 3, the comparison unit 6 in the control unit 22, which is also referred to as a nutrunner control integrated. Furthermore, the nutrunner control 22 has a unit for detecting the setpoint torque, which is connected to the first torque sensor 23 of the screwdriver 20 connected is. The first torque sensor 23 transmits the So11 torque to the unit for detecting the setpoint torque, which in turn passes on the value of the setpoint torque to the comparison unit 6. In addition, the nutrunner control 22 comprises a unit for detecting the actual torque. The second torque sensor 5 of the test unit 2 transmits the actual torque measured by it to the unit for detecting the actual torque, which in turn passes on the value of the actual torque to the comparison unit 6. The nutrunner control 22 further comprises a control for a test sequence for controlling a plurality of tests of a screwdriver 20 in several operating points of the screwdriver 20 in a row. Furthermore, the nutrunner control 22 comprises an evaluation unit, which is connected to the control for the test procedure and the comparison unit 6. After completion of the test procedure, the output of a capability statement is made via the evaluation unit. The ability statement includes either an IO statement, ie, the driver 20 is judged to be capable, or includes an NIO statement, according to which the screwdriver 20 is rated as faulty.

The control for the test procedure is connected via an angle encoder assembly 26, a transmission 25, the first torque sensor 23 and an output 27 with the rotary unit 21. The output 27 of the screwdriver 20 is shown in FIG. 3 by way of example with two bevel gears. The output 27 can still contain several and also different types of gears and other components. A drive 28 supplies the nutrunner 20 with the necessary energy. The drive 28 can thereby be directly connected to the screwdriver 20, but it is also possible that the power is supplied from outside.

One reason for a possible deviation of the actual torque output by the rotary unit 21 from the predetermined setpoint torque may be a loss of torque within the output 27. The torque loss in the output 27 may depend on the position of the functional components located in the output to each other. So z. Example, in a situation where a defective tooth of one of the gears of the output 27 engages another gear, a torque loss or torque increase are detected in this operating point of the screwdriver 20, resulting in a deviation between the target torque and torque of the screwdriver 20 can lead. In all other rotational positions of the gear with the defective tooth, however, under certain circumstances no loss of torque in the output 27 of the screwdriver 20 is detected, since the target torque and the actual torque do not differ significantly from each other.

In order to bring the functional components of the output of a screwdriver 20 after checking at an operating point in a defined other position of the functional components to each other, the control unit 22 is adapted to the rotary unit 21 of the screwdriver 20 beyond an initial rotational position by a predetermined angle in a to turn back the other initial turning position. If z. B. the rotary unit 21 from an initial rotational position (0 °) is initially rotated by 10 ° clockwise until the reaction torque generating means 3 has generated an opposite of the actual torque caused by the rotary unit 21, the rotary unit 21 is again rotated by 10 ° counterclockwise to its initial initial rotational position (0 °) , Then, the rotary unit 21 is rotated back beyond this first initial rotational position (0 °) by a predetermined angular amount (for example, 5 °) in a counterclockwise direction to another second initial rotational position (-5 °). This ensures that a subsequent test procedure takes place at a defined other position of the functional components located in the output to each other. The terms 'clockwise' and 'counterclockwise' in the above example are to be understood as exemplary. More generally, it can be said to refer to a clockwise rotation (clockwise in the example above) and a counterclockwise rotation (in the above counterclockwise example). The tightening direction can also be counterclockwise and the direction against the tightening direction can also be clockwise.

By now the control unit 22 or the control for the test procedure is designed so that the control of rotation of the rotating unit 21 brought into contact with the test unit until the first torque sensor 23 reaches a predetermined target torque, and the subsequent turning back of the rotary unit 21st beyond the initial rotational position by the predetermined angle amount to another Initial rotation position is repeatedly performed, it can be achieved that the entire output 27 is examined successively and systematically in steps of the predetermined angular amount on machine capability.

4 shows a cross-sectional view of a test unit 2 brought into contact with the rotary unit 21 of a screwdriver 20 according to an embodiment of the present invention. The screwdriver 20 is fixed in a tray A. The reaction torque generating device 3 is connected to the second torque sensor 5 via an axis of rotation of which one end is shaped to engage with the rotary unit 21, so that rotation of the rotary unit 21 transmits torque to the rotation axis of the test unit 2 can be. The test unit 2 is either firmly connected to the tray A or fixed on an otherwise immovable pad.

On the axis of rotation of the test unit 2, a strain gauge DMS is mounted, which can detect a torsion at a tapered position of the axis of rotation of the test unit 2, when the axis of rotation is caused by the rotation unit 21 caused torque. By means of coils S ^ and S2 is a contactless

Output of measured by the strain gauge DMS actual torque to the comparison unit 6 (not shown in Fig. 4) possible. In the lower part of FIG. 4, the cross-section of the counter-torque generating device 3 is shown in side view, which disc springs T and a freewheel 7 comprises. A description of this counter-torque generating device 3 will now be given with reference to FIG. 5, which shows a plan view of the sectional plane along the line VV in FIG. In the middle of Fig. 5, the axis of rotation of the test unit 2 is shown, which rotates in the tightening direction (here by way of example in a clockwise direction) during rotation of the rotary unit 21 of the screwdriver 20. A freewheel 7 is mounted in such a way between the axis of rotation of the test unit 2 and a rotating ring DR, that the rotation axis in a clockwise rotation entrains the rotating ring DR (locking the freewheel in the tightening direction, here in a clockwise direction). The rotating ring DR, which has two outwardly directed lugs, rotates with respect to a fixed ring FR, which in turn has two fixed indentations E. Between the lugs of the rotating ring DR and the recesses E of the fixed ring FR springs can be mounted, which cause a soft interception of the torque absorbed by the screwdriver. These springs may be in the form of cup springs T. During the turning back of the rotary unit 21 in the first initial rotational position, the springs T push the rotating ring DR back to its original position (with force-free springs T). When the rotary unit 21 is rotated back beyond the first initial rotary position by a predetermined angle in a second initial rotary position, the contact between the rotary unit 21 and the test unit 2 becomes powerless due to the freewheel 7. In other words, the rotational axis of the test unit 2 does not take the rotating ring DR when turning back the rotary unit beyond the first initial rotational position of the rotary unit 21 in the second initial rotational position, since the axis of rotation the test unit 2 in freewheeling direction (counterclockwise here) rotates. If the rotary unit 21 is now rotated again in the tightening direction (here in a clockwise direction) from the new initial rotational position, the freewheel 7 again causes locking of the rotating ring DR in the direction of rotation (here in a clockwise direction).

The use of a freewheel 7 in the test unit 2 of a test system 1 of the present invention has the advantage that in a repetition of the test cycle for another operating point of the screwdriver, the rotary unit 21 does not have to be removed from the test unit 2 and contacted again, so that a one-time bring in contact the rotary unit 21 with the test unit 2 sufficient to perform a multi-stage test procedure for several operating points of the screwdriver fully automated without much effort. This means that a user of a hand-held screwdriver 20 can contact him during a break with the test unit 2 and the tray A and an automatic Prüfablauf- control is performed, the systematic testing of several different operating points of the screwdriver at different positions of the functional components of the output to each other allows.

Embodiments of the inventive method for testing screwdrivers with a rotary unit and a first torque sensor will now be described with reference to FIG. 7 shows the flow diagram of a method according to a first embodiment for testing screwdrivers 20 with a rotary unit 21 and a first torque sensor 23, the method comprising the steps S6.1 to Sβ .6 from FIG. These steps are designated in FIG. 7 by S7.1 to S7.6, so that reference is made to the description of FIG. 6 here.

The step f) of turning back S7.6 of the rotary unit 21 beyond the initial rotational position by a predetermined angle to another initial rotational position is followed, as shown in FIG. 7 in step S7.7, by a decision as to whether steps c) to f) (S7 .3 to S7.6) should be repeated. If a repetition is to take place (YES to S7.7), the steps c) to f) (S7.3 to S7.6) in FIG. 7 are executed again in sequence.

In a repetition of step c), the rotary unit is preferably rotated starting from the initial rotational position in which the rotary unit is after the immediately preceding implementation of step f). The other initial rotational position reached by a predetermined angular amount in a previous turning back of the rotary unit over an initial rotational position is thus used as the one initial rotational position in a subsequent rotation of the rotary unit until the first torque sensor of the screwdriver reaches the predetermined target torque. As a result, it can be achieved that a repeated examination of the screwdriver takes place at a defined operating point, which is not only accidental, but with certainty of the Operating point of the previous review is different. As a result, on the one hand an effective check of the screwdriver is achieved, since double checks are avoided at one and the same operating point of the screwdriver. On the other hand, the check of the screwdriver becomes more reliable as a whole, since a larger number of different operating points is checked than if a random selection of the initial rotational position of the rotary unit for several consecutive test procedures may check several operating points several times.

It also proves to be advantageous if the product of the number of repetitions or of the feedthroughs, the steps c) to f) and the value of the predetermined angle amount results in at least 360 °. This can be achieved that the full functional range of the output of a screwdriver is checked at intervals of the predetermined angle. As already explained above, at least during the first testing of a full angle range of 360 °, no operating point is checked more than once, whereby the entire checking process is very effective. Furthermore, the screwdriver with each pass of steps c) to f) in each different positions of the screwdriver located in the functional components such. As gears of the output, checked. Thus, the entire test procedure is not only made particularly effective, but also provides a reliable test result, since the output is checked in many different operating positions. In addition, it is advantageous to choose the value of the predetermined angular amount by which the rotary unit is rotated back to a different initial rotational position beyond the initial rotational position, less than or equal to the quotient of 360 ° and the number of teeth of a gear in a screwdriver, which of all Gears in the screwdriver has the most teeth. It can thereby be achieved that when the steps c) to f) are repeated so often that the product of the number of repetitions and the value of the predetermined angle amount is at least 360 °, the entire output of the screwdriver is completely checked. This can be ensured that a fault in the output of the screwdriver, which is based for example on the defectiveness of a single tooth of the gears in the output of the screwdriver, reliably detected. Even in this previously described embodiment of a test procedure of a screwdriver, the entire test procedure is extremely effective since no operating point of the screwdriver is checked more than once.

Furthermore, it is advantageous that the screwdriver is judged to be capable of deviating from the setpoint torque and the actual torque at most by the predetermined amount in each comparison of the setpoint torque of the screwdriver with the actual torque of the test unit. It can thereby be achieved that a screwdriver, which has a malfunction at least at one operating point, is reliably assessed as NIO (not in order / not capable) and is removed from the production process. DETAILED DESCRIPTION OF FURTHER EMBODIMENTS OF THE INVENTION

As already described, a mobile measuring bench is frequently used in the prior art in assembly technology, with which several screwdrivers can be checked successively for their ability.

Such a mobile measuring bench 2 * is shown schematically in FIG. The measuring bench 2 * comprises a test unit 2a *, a manual input unit 2b * and a test control 2c *. The mobile measuring bench 2 * together with a screwdriver 20, which comprises a rotary unit 21, and a control unit 22 for controlling a rotation of the rotary unit 21 form a system for testing screwdrivers, as is known from the prior art. The screwdriver 20 shown in FIG. 4 is a hand-operated, electrically controllable machining tool that is connected to its control unit 22 via a cable. The control unit 22 may be z. B. be connected via a connecting rod with a holding unit which is received in a displacement holding device (not shown in Figure 4), wherein the holding unit slidably in the

Move holding device is movable. The holding unit is usually a trolley or a trolley provided with some rollers suspended in a track which is used as a slide holding means. Both the control unit 22 and the screwdriver 20 can be energized via the displacement holding device be supplied. In addition, the shift-holding device can also serve as a control line and data line in order to supply control unit 22 with control data from a central monitoring unit (also referred to below as 'central unit ¹ '). If z. B. several such control units 22 successively in such

Shift holding device are arranged, each control unit 22 can be transmitted from the central unit via the displacement holding device, a control data set corresponding to the processing data of the corresponding screwdriver 20 at a certain Schraubstelle. These data are, for example, a torque value which the screwdriver 20 is to deliver via the rotary unit 21 to the screwing point.

So far, it has been customary for a test person to roll the mobile measuring bench 2 * successively to each of the screw stations (consisting of control unit 22 and screwdriver 20) in order to carry out a machine capability examination of the screwdrivers 20. In this case, the test person must first read out via the control unit 22, the current control data for the screwdriver 20 in question, z. B. a torque value with which the screwdriver 20 should tighten a screw. The test person has to enter this read-out torque value as a so-called preset value by hand via the manual input unit 2b * into the mobile measuring bench 2 *. Optionally, it is also possible that the test person directly enters a specific setpoint specification for a torque of the screwdriver 20 in the control unit 22, and the same setpoint specification in the manual input unit 2b * of the mobile measuring bench 2 * enters.

Then the test person couples the screwdriver 20 with the test unit 2a * of the mobile measuring bench 2 *, so that the rotary unit 21 of the screwdriver 20 engages in the test unit 2a *. The test unit 2a * includes a counter torque generating device that generates a counter torque to the torque generated by the rotary unit 21.

Thereafter, the inspector causes the control unit (22), the rotary unit 21 of the screwdriver 20 to rotate until a first torque sensor of the screwdriver 20 measures the predetermined target torque. The actual torque output by the rotary unit 21 is measured by the test unit 2a * of the mobile measuring bench. Both the actual torque measured by the test unit 2a * and the setpoint specification of the torque input via the manual input unit 2b * are forwarded to the test controller 2c *. In the test control 2c * then a comparison of the setpoint torque and the actual torque takes place. If the two values coincide, the nutrunner will be judged to be capable, in the event of a deviation the nutrunner will be judged incapable.

This conventional test system for screwdrivers with a mobile measuring bench 2 * has the disadvantage that it causes an increase in personnel costs and high equipment costs. So z. For example, a high level of human resources is required to complete the capability review of the To keep the used screwdriver at a high level, as this is only possible if the test cycles are kept as short as possible. If you extend the test cycles z. At one time per week, there is a risk that a screwdriver judged to be IO (OK, ie capable) after the last capability check, but then become faulty during further use, ie NOK (not OK, ie not capable) until the next capability test produces a large number of broke pieces, which can lead to elaborate rework or in case of late notice to a return action of the finished pieces. To avoid the latter, so far the increased effort associated with short test cycles has been accepted in order to obtain the most accurate statements possible about the ability of the screwing tools. Furthermore, the mobile measuring bench 2 * described above represents a cost-intensive device.

The above-described conventional system for testing the ability of screwing tools thus has the disadvantage that it is associated with high costs and costs.

It is therefore desirable to provide a system for testing screwdrivers which allows for an effective and inexpensive testing of screwdrivers.

This allows a system for automatic testing of screwdrivers, comprising: at least one screwdriver with a rotary unit; a control unit for controlling a rotation of the rotary unit; a test unit for Checking the screwdriver via the turntable; and a data exchange unit for at least unidirectional exchange of data from the test unit to the control unit.

By providing the aforementioned data exchange unit, it is z. B. allows z. B. in the test unit data can be transmitted directly to the control unit of a screwdriver. As a result, evaluations of the test data determined by the test unit can be carried out by the control unit of the screwdriver or by a central unit. As a result, z. B. be achieved that no PrüfSteuerung in addition to the control unit for controlling the screwdriver for testing is needed. Furthermore, it can be achieved that no manual input of a setpoint specification is necessary, since the setpoint values to be checked can already be present in the control unit.

It is possible that the data exchange unit is designed only for the exchange of data from the test unit to the control unit. In this case, the test unit will usually be a passive element in the test of the screwdriver. But it is also possible that the data exchange unit is designed both for an exchange of data from the test unit to the control unit, as well as for an exchange of data from the control unit to the test unit. In this case, the test unit can also be an active element in the testing of screwdrivers. Preferably, the data provided for at least unidirectional exchange from the test unit to the control unit comprises torque values of the screwdriver. The data can also be other values such. B. rotational angle values or other relevant for the nutrunner function values.

Furthermore, it is advantageous that the test unit is designed to check a torque output by the rotary unit of the screwdriver. In this case, the test unit is preferably designed to exchange a result of the verification of the torque output by the rotary unit of the screwdriver as the value of an actual torque of the screwdriver via the data exchange unit to the control unit.

This makes it possible for the control unit to compare the actual torque transmitted by the test unit with a So11 torque of the control unit.

Furthermore, the screwdriver may comprise a first torque sensor. In addition, the test unit may include a counter torque generating device and a second torque sensor.

Furthermore, it is advantageous that the test unit is suitable to be brought into contact at least with the rotary unit of at least one screwdriver in an initial rotational position of the rotary unit.

Preferably, the control unit is adapted to cause rotation of the test unit in contact Turn unit to control until the first torque sensor reaches a predetermined So11 torque.

Furthermore, it is advantageous that the second

Torque sensor is suitable, which by turning the

Turn unit caused to measure actual torque.

Preferably, the system further comprises a comparison unit for comparing the predetermined desired torque of the screwdriver with the actual torque measured by the second torque sensor.

Preferably, the control unit is adapted to turn back the rotary unit over the initial rotational position by a predetermined angle amount to another initial rotational position. By turning back the rotary unit over the initial rotational position by a given angular amount to another initial rotational position can be achieved that the functional components of the output are in each other reliably in a different position than the position of the screwdriver ■ functional components of the output to each other when contacting the rotary unit of the screwdriver in the first initial rotational position of the rotary unit with the test unit. In this way, it can be prevented that the screwdriver is randomly checked again in the same initial rotational position of the rotary unit or in the same of the functional components of the output located in the screwdriver, such as the gear wheels of the output drive. The functional components in the screwdriver are thus brought into a defined other position to each other than the position in which they were in the review of the first operating point of the screwdriver to each other. Thus, an effective and reliable testing of the screwdriver is made possible.

Preferably, in the event that the So11 torque and the actual torque deviate from each other by at most a predetermined amount, the control unit is configured to rotate the rotary unit back beyond the initial rotational position by the predetermined angular amount to the other initial rotational position.

Furthermore, it is advantageous that the control unit is designed to control the rotation of the rotary unit brought into contact with the test unit until the first torque sensor reaches a predetermined setpoint torque, and the subsequent turning back of the rotary unit beyond the initial rotary position by the predetermined angle in FIG to perform another initial rotation position repeatedly.

Preferably, the test unit comprises a freewheel which ensures that the contact between the rotary unit and the test unit during the turning back of the rotary unit is powerless.

It is advantageous that the freewheel causes, during the turning back of the rotary unit, the counter-torque generating device is relaxed and the second torque sensor is reset. Preferably, the counter torque generating means includes a pair of Belleville springs. This allows a soft compression of the counter torque generating device, which contributes to an extension of the life of the test unit.

Preferably, the second torque sensor is calibrated. It is possible that the second torque sensor includes a calibrated rotating chain. But it is also possible that the second torque sensor includes a calibrated strain gauge. The use of a calibrated torque sensor in the test unit ensures an accurate and reliable test result.

Furthermore, the data exchange unit comprises an electrical line which connects the test unit and the control unit with each other.

But it is also possible that the data exchange unit a wireless

Communication link between the test unit and the control unit comprises. In this case, the wireless communication connection can be an infrared interface. Another possibility is that the wireless communication connection is a radio interface.

Furthermore, it is advantageous that the system comprises a receiving unit for receiving the screwdriver. It is advantageous that the receiving unit is designed to receive the screwdriver so that the rotary unit of the screwdriver in the initial rotational position is in contact with the counter torque generating means.

Further, it is possible that the receiving unit is designed as a storage tray for the screwdriver and the test unit is integrated in the tray. It is possible that the tray is firmly connected to the control unit. It is also possible that the tray has a clamping bracket for fixing it screwdriver in the tray. This allows a user of the screwdriver 20, in a production break, to fix the screwdriver over the clamp in the tray and simultaneously start the test procedure for a machine capability test. The test procedure can be fully automatic during the break. This has the advantage that the personnel costs for carrying out a check of a screwdriver is low and the testing of screwdrivers can thus be carried out inexpensively.

Preferably, the test unit is integrated in the control unit. It is emphasized, however, that the present invention is not limited to the fact that the test unit is integrated into the control unit.

The previously described embodiments of the system for automatic testing of screwdrivers are preferably hand-held screwdrivers. However, the present invention is not limited to the use of hand-held screwdrivers, but also includes test systems for testing other screwdrivers, e.g. B. fully automatic screwdriver or semi-automatic screwdriver, which can also be stored completely fixed or displaceable.

FIG. 8 shows a block diagram according to a third embodiment of the test system according to the invention. The test system comprises a tester 20 having a rotary unit 21. The test system further comprises a control unit 22 for controlling a rotation of the rotary unit 21. In addition, the test system comprises a test unit 2 for testing the screwdriver 20 via the rotary unit 21. Furthermore, the test system comprises a Data exchange unit 22a, which is suitable for exchanging data from the test unit 2 to the control unit 22 at least in one direction (unidirectionally).

By providing the aforementioned data exchange unit, it is z. B. allows z. B. in the test unit data can be transmitted directly to the control unit of a screwdriver. As a result, evaluations of the test data determined by the test unit can be carried out by the control unit of the screwdriver or by a central unit. As a result, z. B. be achieved that no PrüfSteuerung in addition to the control unit for controlling the screwdriver for testing is needed. Furthermore, it can be achieved that no manual input of a setpoint specification is necessary, since the setpoint values to be checked can already be present in the control unit. Thus, an effective and cost-effective testing of screwdrivers is made possible. Figure 9 shows a functional diagram of the third embodiment of the test system of the present invention. The reference numerals correspond entirely to those in FIG. 8, so that reference may be made to the description of FIG. 8 for the description of the individual components which are referenced with these reference symbols in FIG.

The test driver 20 includes a first torque sensor (not shown). The test unit 2 includes a counter torque generating device and a second torque sensor (not shown). The test unit 2 is adapted to be brought into contact at least with the rotary unit 21 of the screwdriver 20 in an initial rotational position of the rotary unit 21. Furthermore, the test system comprises a control unit 22 for controlling a rotation of the rotary unit 21 brought into contact with the test unit 2. The control unit 22 can control the rotary unit 21 until the first torque sensor of the screwdriver 20 reaches a predetermined So11 torque. The second torque sensor in the test unit 2 is adapted to measure an actual torque caused by the rotation of the rotary unit 21.

The data that is exchanged preferably contains torque values of the screwdriver 20. Preferably, the test unit 2 is designed to check a torque output by the rotary unit 21 of the screwdriver 20. Further, the test unit 2 is configured to exchange a result of the check of the torque output from the rotary unit 21 of the screwdriver 20 as the value of an actual torque of the screwdriver 20 to the control unit 22 via the data exchange unit 22a. The test unit 2 is connected via the data exchange unit 22a with the Control unit 22 connected. The control unit (22) is also connected to the screwdriver 20. The control unit 22 may be z. B. be connected directly to the rotary unit 21 of the screwdriver 20. But it is also possible that the control unit 22 is connected via the first torque sensor of the screwdriver 20 and / or other assemblies in the screwdriver 20 with the rotary unit 21.

The data exchange unit 22a makes it possible to transmit an actual torque output by the rotary unit 21, which has been measured by the test unit 2, to the control unit 22 of the screwdriver 20 via the data exchange unit 22a. Therefore, it is basically possible to design the test unit 2 as a passive assembly. This means that in the test unit 2 no separate test control in addition to the control unit (22) of the screwdriver 20 must be provided and also no manual input unit for specifying a target torque that expects the test unit 2 of the screwdriver 20. Therefore, the test control 2c * provided in conventional test systems according to FIG. 11 and the manual input unit 2b * are not necessary in the test system according to the invention. The test unit 2 is thus easier and cheaper to manufacture.

Furthermore, it is no longer necessary for a test person to enter a setpoint torque to be output by the driver 20 via a manual input unit into the mobile measuring bench 2 *. This makes it possible to run the test of screwdrivers 20 automatically. As a result, personnel expenses and Reduced staff costs and beyond the entire audit process effectively designed.

A manual input unit on the test unit 2 can be dispensed with if the control unit 22 receives the control data for its screwdriver 20 from a central unit. However, it may still be desirable to set a specific nominal value specification for the screwdriver 20 directly at a specific control unit 22. Even in this case, however, a setpoint specification which may possibly be made manually is only to be carried out on the control unit 22 of the screwdriver 20 and not additionally on the test unit 2. Thus, also here the data input effort compared to the prior art is reduced, where both a setpoint input in the control unit 22 and in the mobile measuring bench 2 * was necessary. In addition, the test method is safer by the only one-time setpoint specification, since no errors by accidentally different setpoint specifications in the control unit 22 and test bench 2 * can occur.

If the control unit 22 has a redundant hardware configuration, the capability check can be performed via the redundant channel. If this embodiment is not present, the capability test is performed by a separate controller, this separate controller is then linked to the control unit 22.

The designated by reference numeral 20 screwdriver is shown schematically in Figure 9 as a hand-held screwdriver with a handle and a screwdriver head. The However, the invention is not limited to the use of handheld wrenches. Rather, fully automatic and / or fixed screwdriver can be found in the test system according to the present invention input.

In FIG. 9, the control unit 22 for controlling a rotation of the rotary unit 21 brought into contact with the test unit 2 is provided separately from the screwdriver 20. The controller 22 may also be integrated in the screwdriver 20 or be mounted on this. The control unit 22 controls the rotary unit 21 until the first torque sensor of the screwdriver reaches a predetermined setpoint torque.

The data exchange unit 22a shown schematically in FIGS. 8 to 10 can comprise an electrical line which connects the test unit 2 and the control unit 22 to one another. However, it is also possible that the data exchange unit 22a comprises a wireless communication connection between the test unit 2 and the control unit 22. Such a wireless communication connection may be an infrared interface or a radio interface.

Figure 10 shows another preferred embodiment of the test system of the present invention. With regard to the components designated by the same reference numbers, reference is made to the description in FIGS. 8 and 9. In Figure 10, the test unit 2 with the control unit 22 of the screwdriver 20 via a bracket H is firmly connected. The system according to FIG. 10 thus constitutes one combined screwing / screwdriver testing station.

Preferably, this combined system has a receiving unit for receiving the screwdriver 20. In this case, it is advantageous that the receiving unit is designed to receive the screwdriver 20 in such a way that the rotary unit 21 of the screwdriver 20 is in an initial rotational position in contact with a counter-torque generating device of the test unit 2, i. engages in these. Preferably, the receiving unit is designed as a storage tray for the screwdriver 20 and the test unit 2 integrated in this tray. This tray can then be connected via a bracket H fixed to the control unit 22.

According to a preferred embodiment of the present invention, the tray has a clamping bracket for fixing the screwdriver 20 in the tray. This allows a user of the screwdriver 20, in a production break, to fix the screwdriver over the clamp in the tray and simultaneously start the test procedure for a machine capability test. The test procedure can be fully automatic during the break.

The embodiment described above has dan advantage that the personnel costs for carrying out a review of a screwdriver is low and the test of screwdrivers can thus be carried out inexpensively. After the test process, the test data are evaluated with a test statement. The test statement may indicate that the tool is capable; then the screwdriver 20 is released for further production. If the test statement indicates that the tool is not capable, the screwing system is locked for production to avoid any production scrap. The test statement can be issued visually, eg via a display / warning lamp or via a display, or acoustically, eg via a warning tone / confirmation tone. According to a further embodiment of the present invention, the test unit 2 can also be integrated into the control unit 22 of the screwdriver 20.

The test systems described above are preferably used in the testing of hand-held screwdrivers. It is emphasized, however, that the present invention is not limited in its application to hand-held screwdrivers.

INDUSTRIAL APPLICABILITY

As explained above, in the test method according to the invention and in the test system according to the invention, screwdrivers can be effectively and reliably tested for their ability. Although references to automobile manufacturing have been made infrequently hereinabove, the present invention is not limited thereto, but can be used in a variety of other applications where screwdrivers are used, for example, in the mass production of hi-fi. Products, washing machines, semiconductor equipment, etc.

Therefore, numerous other embodiments and improvements of the invention are possible without departing from the scope as defined in the appended claims. Numerous variations and changes may therefore be made by one of ordinary skill in the art based on the above teachings.

Reference signs in the claims are merely illustrative and do not limit the scope of the claims.

Claims

A method of testing screwdrivers (20) having a rotary unit (21) and a first torque sensor (23), comprising the following steps:

a) contacting (S6.1) at least the rotary unit (21) of the screwdriver (20) in an initial rotational position of the rotary unit (21) with a test unit (2) comprising a counter-torque generating means (3) and a second torque sensor (5) ;

b) predetermining (S6.2) a So11 torque which the screwdriver (20) is to output;

c) turning (S6.3) the rotary unit (21) until the first torque sensor (23) of the screwdriver (20) reaches the predetermined setpoint torque;

d) measuring (S6.4) an actual torque caused by the rotation of the rotary unit (21) with the second torque sensor (5);

e) comparing (S6.5) the predetermined initial torque of the screwdriver (20) with that of second Drehiαomentsensor (5) measured actual torque;

characterized by the following step:

f) turning back (S6.6) of the rotary unit (21) beyond the initial rotational position by a predetermined angle to another initial rotational position.

2. The method according to claim 1, characterized in that step f) (S6.6) is performed in the event that the desired torque and the actual torque deviate from each other by a predetermined amount at most.

3. The method according to claim 1 or 2, characterized by an at least one repetition of steps c) (S6.3) to f) (S6.6).

4. The method of claim 3, wherein the product of the number of repetitions and the value of the predetermined angular amount is at least 360 °.

5. The method according to any one of the preceding claims, wherein the value of the predetermined angular amount is less than or equal to the quotient of 360 ° and the number of teeth of a gear in the screwdriver (20), which of All gears in the screwdriver (20) has the most teeth.

6. Method according to one of the preceding

Claims, wherein the screwdriver (20) is judged to be capable of, if at each comparison of the desired torque of the screwdriver (20) with the actual torque of the test unit (2) the desired torque and the actual torque at most by the predetermined amount differ from each other.

7. Method according to one of the preceding

Claims, wherein the rotary unit (21) of the screwdriver (20) is in contact with the counter-torque generating device (3) of the test unit (2) via a freewheel (7) which ensures that the contact between the rotary unit (21) and counter torque Generating means (3) during the turning back of the rotary unit (21) becomes powerless.

8. The method according to any one of the preceding claims, wherein the counter torque generating means (3) includes a pair of disc springs.

9. Method according to one of the preceding

Claims, wherein the second Drehmorαentsensor (5) is calibrated.

10. The method according to any one of the preceding claims, wherein the second torque sensor (5) includes a calibrated rotating chain.

11. The method of claim 1, wherein the second torque sensor includes a calibrated strain gauge.

12. The method according to any one of the preceding claims, wherein the screwdriver (20) is a hand-held screwdriver.

13. A test system (1) for testing screwdrivers (20) with a rotary unit (21) and a first torque sensor (23), comprising:

a test unit (2) having a counter torque generating means (3) and a second torque sensor (5) adapted to be brought into contact at least with the rotary unit (21) of at least one screw driver (20) in an initial rotational position of the rotary unit (21) become;

a control unit (22) for controlling a rotation of the rotary unit (21) brought into contact with the test unit until the first torque sensor (23) reaches a predetermined target torque, wherein the second torque sensor (5) is adapted to measure an actual torque caused by the rotation of the rotary unit (21);

a comparison unit (6) for comparing the predetermined setpoint torque of the screwdriver (20) with the actual torque measured by the second torque sensor (5),

characterized in that

the control unit (22) is adapted to rotate the rotary unit (21) back beyond the initial rotational position by a predetermined angle to another initial rotational position.

14. A test system according to claim 13, wherein the control unit (22) is designed, in the event that the desired torque and the actual torque deviate from each other by at most a predetermined amount, the rotary unit (21) beyond the initial rotational position by the predetermined Turn back angle amount in the other initial rotational position.

15. The test system of claim 13, wherein the control unit is configured to control rotation of the turntable (21) brought into contact with the test unit until the first torque sensor (23) reaches a predetermined So11 torque. and the following Turning back the rotary unit (21) beyond the initial rotational position to repeatedly perform the predetermined angular amount to another initial rotational position.

16. Test system according to one of claims 13 to 15, wherein the test unit (2) comprises a freewheel (7), which ensures that the contact between the rotary unit (21) and the test unit (2) during the turning back of the rotary unit (21) becomes powerless.

17. A test system according to claim 16, wherein the freewheel causes during the turning back of the rotary unit (21) the counter torque generating means (3) is relaxed and the second torque sensor (5) is reset.

18. Test system according to one of claims 13 to 17, wherein the counter torque generating means

(3) includes a pair of disc springs.

19. A test system according to any one of claims 13 to 18, wherein the second torque sensor (5) is calibrated.

20. Test system according to one of the preceding claims, wherein the second torque sensor (5) includes a calibrated rotary chain.

21. A test system according to any one of claims 13 to 19, wherein the second torque sensor (5) includes a calibrated strain gauge.

22. Test system according to one of claims 13 to 21, further comprising a data exchange unit (22a) for at least unidirectional exchange of data from the test unit (2) to the control unit (22).

The test system of claim 22, wherein the data includes torque values of the driver (20).

24. Test system according to claim 22 or 23, wherein the test unit (2) is designed to check a torque output by the rotary unit (21) of the screwdriver (20).

25. A test system according to claim 24, wherein the test unit (2) is adapted to display a result of checking the torque output from the rotary unit (21) of the screwdriver (20) as a value of an actual torque of the screwdriver (20) via the data exchange unit (22 ) to the control unit (22).

The test system according to any one of claims 22 to 25, wherein the data exchange unit (22a) comprises an electrical lead interconnecting the test unit (2) and the control unit (22).

27. The test system of claim 26, wherein the data interchange unit (22a) comprises a wireless communication link between the test unit (2) and the control unit (22).

The test system of claim 27, wherein the wireless communication link is an infrared interface.

The test system of claim 27, wherein the wireless communication link is a radio interface.

30. Test system according to one of claims 13 to 29, further comprising a receiving unit for receiving the screwdriver (20).

31. The inspection system according to claim ^'30, wherein the receiving unit is adapted to the screwdriver

(20) so that the rotary unit (21) of the screwdriver (20) in the initial rotational position with the counter torque generating means

(3) is in contact.

32. Test system according to one of claims 30 or 31, wherein the receiving unit is designed as a storage tray for the screwdriver (20) and the test unit (2) is integrated in the storage tray.

33. Test system according to claim 32, wherein the tray is firmly connected to the control unit (22).

34. Test system according to one of claims 32 or 33, wherein the tray has a clamping bracket for fixing the screwdriver (20) in the tray.

35. Test system according to one of claims 13 to 34, wherein the test unit (2) in the control unit

(22) is integrated.

36. Test system according to one of claims 13 to 35, wherein the screwdriver (20) is a hand-held screwdriver.