DE102005013786A1 - Machine capability examination in angular steps - Google Patents

Abstract

For testing screwdrivers (20) with a rotary unit (21) and a first torque sensor (23), a test unit (2) with a counter-torque generating device (3) and a second torque sensor (5) is provided which is connected to the rotary unit (21). a wrench (20) in an initial rotational position of the rotary unit (21) can be brought into contact. A control unit (22) controls rotation of the rotary unit (21) brought into contact with the test unit until the first torque sensor (23) reaches a predetermined target torque. In this case, the second torque sensor (5) measures an actual torque caused by rotation of the rotary unit (21), and a comparison unit (6) compares the predetermined setpoint torque of the screwdriver (20) with the actual torque measured by the second torque sensor (5) , 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. The functional components located in the screwdriver are thereby brought into a defined other position to each other as 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.

Description

AREA OF INVENTION

The The invention relates to a method for testing screwdrivers with a Turntable and a torque sensor and a test system for testing of screwdrivers with a turntable and a torque sensor. In particular, the invention relates to a test method and a test system with the features of the preamble of claim 1 and of Claim 13.

One such test method and such a testing system are typically used in assembly, especially in the Automotive production used. Such a test method and such Test System However, they are also found in other applications in which Screwdrivers are used, e.g. in mass production in the Electronics industry, both fully automated and semi-automated Series production.

traditionally, be screwing tools with torque transducer after assembly, commissioning and during of their commitment checked their ability. at this process, commonly referred to as machine capability testing will check if a Torque that a screwdriver exerts on a screw point corresponds to a torque, which measures a torque sensor of the screwdriver. Especially while of the insert, i. during the Production, screwdrivers are always on their own in certain test cycles Ability checked. kind and frequency the ability checks depend on it For example, from manufacturing and process specifications from. So hangs e.g. the time interval between two ability tests of a screwdriver in automobile manufacturing depends on the safety relevance of bolting, which performs a screwdriver. In so-called screw cases Class A (for example, chassis, brakes, steering, safety belt and airbag, their exact implementation of particular importance for the operational safety of the finished automobile is the skill test cycle usually shorter be as in so-called function critical screwdriving the Class B (such as engine, gearbox or ground screws), whose safety relevance is lower.

BACKGROUND THE INVENTION

to execution a skill test of Screwing tools are currently used in various ways. So z. B. to check the Torque output from the screwing tool is a torque transducer with counter-measuring system attached to the screwdriver. For hand-held screwdrivers come so-called crease keys used by which the operator himself the torque of a with the screwdriver to be checked checked screw tightened. Further comes in the assembly technique often a mobile measuring bench is used, with the several screwdrivers in a row to be checked for their ability can.

Alles These methods have in common that they either increase staff costs and high equipment costs or give inaccurate statements about the accuracy of the screwing tool. For example, e.g. a high staff effort is needed to conduct the skill review of used screwdriver to maintain a high level, as this only possible is when the test cycles as short as possible being held. Extended one the test cycles, z. B. once a week, this carries the risk that a screwdriver, the one after the last skill check as OK (in order) was judged, but then during the further use became defective, i. NIO (not okay) until the next skill test size Number of rejects produced, resulting in elaborate rework or in case of a late notice until a return action the finished pieces can lead. To avoid the latter, has been the increased effort, with short cycles is accepted, in order to get the most accurate statements about the ability to get the screwing tools.

The usual Methods for the ability test of So screwdrivers have the disadvantage that the high effort and costs are associated.

Further the observation was made that an ever further shortening of the Test cycles not more significant to a reduction in the production scrap quota contributes. The conventional ones Procedures for ability testing point thus additionally the disadvantage, the ability can not be reliably checked by screwing tools.

EXPLANATION 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 skill test, a screwdriver is tuned to a particular one 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 The object of the invention is a test method and a test system to provide an effective and reliable test of a Helicopter allows.

These Task is solved by a method (claim 1) for testing screwdrivers with a Rotary unit and a first torque sensor comprising the following Steps: a) Contact at least the turning unit of the screwdriver in an initial rotational position of the rotary unit with a test unit, which is a counter-torque generating device and a second torque sensor; b) specifying a desired torque, which the screwdriver should output; c) turning the turntable, until the first torque sensor of the screwdriver reaches the predetermined target torque; d) measuring an actual torque caused by turning the rotary unit with the second torque sensor; e) Compare the given Target torque the screwdriver with the actual torque measured by the second torque sensor; f) Turn back the turntable over the initial rotational position to a predetermined angle amount in a different initial rotational position.

These Task is further solved through a testing system (Claim 13) for testing screwdrivers with a rotary unit and a first torque sensor, comprising: a test unit with a counter torque generating device and a second torque sensor which is suitable, at least with the rotary unit of at least one screwdriver in an initial rotational position to be brought into contact with the turntable; a control unit for controlling a rotation of the rotary unit brought into contact with the test unit, until the first torque sensor a predetermined target torque achieved, wherein the second torque sensor is suitable, a through measuring the rotation of the turntable caused actual torque; a comparison unit for comparing the predetermined target torque the screwdriver with the actual torque measured by the second torque sensor, wherein the control unit is configured to rotate the unit over Initial rotation position by a predetermined angle in to turn back another initial turning position.

By turning back the turntable over the initial rotational position by a predetermined angle amount in another initial rotational position can be achieved that The functional components of the output located in the screwdriver reliable to each other in a position other than the position of the screwdriver located functional components of the output to each other when Contact the turning unit of the screwdriver in the first initial turning position the turntable with the test unit. This can prevent the screwdriver from accidentally passing in a subsequent check once in the same initial rotational position of the turntable, or in the same of the functional components of the screwdriver Downforce to each other, such. the gears of the output, is checked.

The in the screwdriver functional components are therefore in a defines different position to each other than the position, in the review of the first operating point of the screwdriver to each other. Consequently will be an effective and reliable exam allows the screwdriver.

PREFERRED EMBODIMENTS

Preferably (Claim 2, 14), the rotary unit on the initial rotational position addition to the predetermined angular amount in the other initial rotational position turned back, for the Case that the target torque and the actual torque are at most differ by a given amount. This is achieved that a screwdriver whose actual torque deviates only insignificantly from the nominal torque, still as IO regarding of the checked operating point can be evaluated. The predetermined deviation amount thus forms a tolerance limit for Deviations between nominal torque and 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 after the immediately preceding implementation of step f) is located. Thus, the other initial rotation position attained by turning back the rotary unit beyond an initial rotational position by a predetermined angular amount is thus used as the one initial rotational position upon subsequent rotation of the rotary unit until the first torque sensor of the driver 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.

Further For example, the above-described repetition of steps c) to f) may also be a repetition of steps a) and / or b) include. So can e.g. before repeating steps c) to f) another value for the Target torque to be specified, to be output by the screwdriver.

Preferably gives the product of the number of repetitions, or of the bushings, 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 area the output of a screwdriver is checked at intervals of the predetermined angle. As already explained above, is at least at the first checking a full-angle range of 360 ° no Operating point checked more than once, thereby the entire inspection process is very effective. Furthermore, the screwdriver with each pass of the Steps c) to f) in mutually different positions located in the screwdriver functional components such. B. gears of the Downforce, checked. Consequently will be the whole exam process not only very effective, but also delivers reliable test result because the output is checked in many different operating positions.

Further it is advantageous to change the value of the given angle amount the turntable over the initial rotational position out into another initial rotational position turned back is less than or equal to the quotient of 360 ° and the number of teeth one To choose a gear in a screwdriver, which of all gears in the screwdriver has the most teeth has (claim 5). This can be achieved by repeating of steps c) to f) so often that the product of the number of Repetitions and the value of the predetermined angle amount at least 360 °, the entire downforce of the screwdriver is completely checked. This can be ensured be that an error in the output of the screwdriver, e.g. on the defectiveness of a single tooth of one of the gears in the output the screwdriver is reliable is recognized. Even in this embodiment described above a test procedure of a screwdriver, the entire testing process is extremely effective, since no operating point of the screwdriver is checked more than once.

Further is advantageous that the screwdriver is judged capable if at every comparison of the setpoint torque of the screwdriver with the actual torque the test unit the target torque and the actual torque at most by the predetermined Amount differ from each other. This can be achieved that a screwdriver that malfunctions at least at one operating point has, reliable is judged as NIO (not ok / not capable), and out removed from the production process.

Preferably is the turning unit of the screwdriver with the counter torque generating device the test unit via a Freewheel in contact, which ensures in that the contact between the rotary unit and the counter-torque generating device while of turning back the rotary unit is powerless (claim 7, 16). In this case, the freewheel cause that during turning back the turntable the counter torque generating device is relaxed and the second torque sensor reset is (claim 17). This can be achieved at a turning back the turntable in a step f) located in the screwdriver functional components, such. B. the gears of the output, for a subsequent step c) into a new, defined (i.e., not random) Get home position. This corresponds to a certain initial rotational position the turning unit of the screwdriver a certain position of the screwdriver located functional components to each other.

Further Is it possible, that the counter-torque generating device includes a pair of disc springs (claim 8, 18).

Preferably, the second torque sensor is calibrated (claim 9, 19). For example, the second torque sensor may include a calibrated swivel chain (claim 10, 20). Further, it is possible that the second torque sensor includes a calibrated strain gauge (claim 11, 21).

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

Further advantageous embodiments and improvements of the invention are set forth in the subclaims. It should also be noted that the invention also other embodiments which results from a combination of features that separated in the claims and / or the figures are.

below The invention is based on its advantageous embodiments explained in more detail with reference to the drawings.

SUMMARY THE DRAWINGS

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

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

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

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

4 a cross-sectional view of a test unit and an attached to the test unit screwdriver with rotary unit according to the first or second embodiment of the present invention;

5 a sectional drawing along the line VV in 4 which in plan view a counter torque generating device with a freewheel of in 4 shown embodiment;

6 a flow chart of the test method according to the invention;

7 a flowchart of a test method according to a first embodiment of the present invention;

8th a block diagram of a third embodiment of the test system according to the invention;

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

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

11 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 the 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 according to the invention 1 , The test system 1 includes a screwdriver to be tested 20 with a turntable 21 and a first torque sensor 23 , Furthermore, the test system includes 1 a test unit 2 with a counter torque generating device 3 and a second torque sensor 5 , wherein the test unit 2 is suitable, at least with the rotary unit 21 the screwdriver 20 in an initial rotational position of the rotary unit 21 to be contacted. The test system 1 further comprises a control unit 22 for controlling a rotation of the test unit 2 contacted rotary unit 21 until the first torque sensor 23 reaches a predetermined setpoint torque. In this case, the second torque sensor 5 suitable by turning the turntable 21 to measure caused actual torque. In addition, the test system includes 1 a comparison unit 6 for comparing the predetermined desired torque of the screwdriver 20 with the second torque sensor 5 measured actual torque. Further, the control unit 22 designed, the turntable 21 to turn back beyond the initial rotational position by a predetermined angle to another initial rotational position.

Again 1 can be removed, there is the test system 1 of the present invention mainly from the following components: a screwdriver 20 , a test unit 2 , a comparison unit 6 and a control unit 22 ,

As from the flowchart in 6 can be seen, comprises the test method according to the invention for testing screwdrivers 20 with a turntable 21 and a first torque sensor 23 following steps: a) Contact S6.1 at least the turntable 21 the screwdriver 20 in an initial rotational position of the rotary unit 21 with the test unit 2 that the counter torque generation Facility 3 and the second torque sensor 5 includes; b) Specify S6.2 a target torque, which is the screwdriver 20 to spend; c) Turn S6.3 of the turntable 21 until the first torque sensor 23 the screwdriver 20 reaches the predetermined target torque; d) Measure S6.4 by turning the turntable 21 caused actual torque with the second torque sensor 5 ; e) Compare S6.5 the predetermined desired torque of the screwdriver 20 with the second torque sensor 5 measured actual torque; f) Turn back S6.6 of the turntable 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 according to the present invention described above, 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 to one another, wherein the screwdriver 20 from a first initial rotational position of the rotary unit 21 is checked, the screwdriver in a defined other initial rotational position of the rotary unit 21 with a defined other position of the functional components of the output located in the screwdriver 27 bring to.

By turning back the turntable over the initial rotational position by a predetermined angle amount in another initial rotational position can thus be achieved that the functional components of the output located in the screwdriver reliable to each other in a position other than the position of the screwdriver located functional components of the output to each other when Contact the turning unit of the screwdriver in the first initial turning position the turntable with the test unit. This can prevent the screwdriver from accidentally passing in a subsequent check once in the same initial rotational position of the turntable, or in the same of the functional components of the screwdriver Downforce to each other, such. the gears of the output, is checked.

The in the screwdriver functional components are therefore in a defines different position to each other than the position, in the review of the first operating point of the screwdriver to each other. Consequently will be an effective and reliable exam allows the screwdriver.

2 shows a functional diagram of an embodiment of the test system of the present invention. The reference signs correspond entirely to those in 1 , so as to describe the individual components, which in 2 are referenced with these references, to the description of 1 can be referenced.

The screwdriver 20 includes a turntable 21 and a first torque sensor 23 , the one with the turntable 21 connected is. The turntable 21 may include, for example, a socket whose shape is adapted to the screwing point to be machined. The first torque sensor 23 the screwdriver 20 is suitable, one of the turntable 21 to measure predetermined setpoint torque.

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

The second torque sensor 5 the test unit 2 is about the comparison unit 6 with the first torque sensor 23 the screwdriver 20 connected. Here is the comparison unit 6 designed to the specified torque of the screwdriver 20 from the first torque sensor 23 to receive that from the second torque sensor 5 the test unit 2 to receive measured actual torque, and to compare these two torque values.

The control unit 22 is with the screwdriver 20 connected. In this case, the control unit 22 directly or indirectly via other assemblies of the screwdriver 20 , eg the first torque sensor 23 , with the turntable 21 be connected. The control unit 22 controls a rotation of the with the test unit 2 contacted rotary unit 21 until the first torque sensor 23 the screwdriver 20 reaches a predetermined setpoint torque. Further, the control unit 22 designed, the turntable 21 to turn back beyond a initial rotational position by a predetermined angle amount in another rotational position.

The by reference 20 designated screwdriver is in 2 as a hand-held screwdriver with a handle and a screwdriver head shown schematically. 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 on which is formed, a turntable 21 the screwdriver 20 to record that the turntable 21 and the torque sensor 5 engage each other. For example, the contact surface of the second torque sensor 5 the shape of a screw head and the turntable 21 the shape of a to this screw benkopf matching socket on. One through the turntable 21 mediated rotational movement is thus via the second torque sensor 5 to the counter torque generating device 3 the test unit 2 taught. The counter torque generating device 3 generates one from the turntable 21 caused actual torque output counteracting counter torque. That of the counter torque generating device 3 generated counter torque keeps up with the actual torque caused by the rotation of the turntable. In this equilibrium state, the second torque sensor measures 5 the test unit 2 that from the screwdriver 20 output actual torque by measuring the amount of the second torque sensor 5 applied torque. Preferably, the second torque sensor 5 the test unit 2 to get a calibrated torque sensor to give a reliable indication of the size of the screwdriver 20 output actual torque can be obtained. The second torque sensor 5 can be z. B. include a calibrated swivel chain. According to another example, the second torque sensor comprises 5 a calibrated strain gauge located on the axis of rotation of the test unit 2 is applied. By the torsion of the rotation axis of the test unit 2 The strain gauge is stretched and this strain can be used as a measure of the torque applied to the axis of rotation. Further, the counter torque generating means may include a pair of Belleville springs, which is a soft compression of the counter torque device upon application of the test unit 2 with the torque of the screwdriver 20 allows.

In 2 is the control unit 22 for controlling a rotation of the with the test unit 2 contacted rotary unit 21 separated from the screwdriver 20 intended. The control 22 but also in the screwdriver 20 be integrated or mounted on this. The control unit 22 controls the turntable 21 until the first torque sensor 23 reaches a predetermined setpoint torque. In 2 is the first torque sensor 23 integrated in the screwdriver. The first torque sensor 23 but also on the screwdriver 20 be attached or external to the screwdriver 20 be provided.

The first torque sensor 23 the screwdriver 20 transmits the value of the torque, when the predetermined target torque is reached, to the comparison unit 6 , Furthermore, the second torque sensor transmits 5 the counter torque generating device 3 the measured by him actual torque to the comparison unit 6 , The comparison unit 6 compares the specified torque of the screwdriver 20 with the second torque sensor 5 measured actual torque. Preferably, the screwdriver 20 then judged capable when comparing the desired torque of the screwdriver 20 with the actual torque of the test unit 2 the setpoint torque and the actual torque deviate from each other by at most a predetermined amount.

3 shows a further preferred embodiment of the test system 1 of the present invention. With respect to the components designated by like reference numerals, reference is made to the description in FIG 1 and 2 directed. In 3 is the comparison unit 6 in the control unit 22 , which is also referred to as a nutrunner control integrated. Furthermore, indicates the nutrunner control 22 a unit for detecting the target torque, which with the first torque sensor 23 the screwdriver 20 connected is. The first torque sensor 23 transmits the target torque to the unit for detecting the desired torque, which in turn the value of the target torque to the comparison unit 6 passes. Also includes the nutrunner control 22 a unit for detecting the actual torque. The second torque sensor 5 the test unit 2 transmits the measured by him actual torque to the unit for detecting the actual torque, which in turn the value of the actual torque to the comparison unit 6 passes. The nutrunner control 22 further includes a control for a test procedure for controlling a plurality of tests of a screwdriver 20 in several operating points of the screwdriver 20 behind each other. Furthermore, the nutrunner control includes 22 an evaluation unit with the controller for the test procedure and the comparison unit 6 connected is. After completion of the test procedure, the output of a capability statement is made via the evaluation unit. The ability statement contains either an IO statement, ie the screwdriver 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 sequence is via an angle encoder module 26 , a gearbox 25 , the first torque sensor 23 and a downforce 27 with the turntable 21 connected. The downforce 27 the screwdriver 20 is in 3 exemplified with two bevel gears. The downforce 27 but may also include several and also different types of gears and other components. A drive 28 supplies the screwdriver 20 with the necessary energy. The drive 28 can do it directly with the screwdriver 20 However, it is also possible that the energy is supplied from outside.

A reason for a possible deviation of the of the turntable 21 output actual torque of the predetermined target torque may be in a torque loss within the Ab drive 27 be given. 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. B. in a situation where a defective tooth of one of the gears of the output 27 engages with another gear, torque loss or torque increase in this operating point of the screwdriver 20 be detected, resulting in a deviation between the target torque and the actual torque of the screwdriver 20 can lead. In all other rotational positions of the gear with the defective tooth, however, may be no loss of torque in the output 27 the screwdriver 20 determined, since the target torque and the actual torque do not differ significantly.

To the functional components of the output of a screwdriver 20 After successful testing at an operating point in a defined other position of the functional components to each other, is the control unit 22 designed for the turntable 21 the screwdriver 20 Turning back beyond an initial rotational position by a predetermined angular amount to another initial rotational position. If z. B. the turntable 21 from an initial rotational position (0 °) is first rotated by 10 ° clockwise until the counter torque generating device 3 one from the turntable 21 caused actual torque has generated opposite torque, becomes the turntable 21 turned back 10 ° counterclockwise to its initial starting position (0 °). Then the turntable becomes 21 rotated back past this first initial rotational position (0 °) by a predetermined angular amount (eg 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 controller for the test procedure is designed such that the control of a rotation of the rotating unit brought into contact with the test unit 21 until the first torque sensor 23 reaches a predetermined setpoint torque, and the subsequent turning back the turntable 21 is repeatedly performed over the initial rotational position by the predetermined angular amount to another initial rotational position, it can be achieved that the entire output 27 successively and systematically in steps of the predetermined angle on machine capability is examined.

4 shows a cross-sectional view of a test unit 2 that with the turntable 21 a screwdriver 20 in accordance with an embodiment of the present invention. The screwdriver 20 is fixed in a tray A. The counter torque generating device 3 is with the second torque sensor 5 connected via an axis of rotation, one end of which is shaped to engage with the rotary unit 21 to engage, so by turning the turntable 21 a torque on the axis of rotation of the test unit 2 can be transferred. The test unit 2 is either firmly connected to the tray A or fixed on another immovable base.

On the rotation axis of the test unit 2 a strain gauge DMS is mounted, which torsion at a tapered location of the axis of rotation of the test unit 2 detected when the axis of rotation with that of the rotary unit 21 caused torque is applied. By means of coils S ₁ and S ₂ is a contactless output of measured by the strain gauge DMS actual torque to the comparison unit 6 (not in 4 shown) possible. In the lower part of the 4 is a side view of the cross section of the counter torque generating device 3 shown which disc springs T and a freewheel 7 includes.

A description of this reaction torque generating device 3 is now based on 5 , which is a plan view of the sectional plane along the line VV in 4 represents. In the middle of 5 is the axis of rotation of the test unit 2 Shown in the tightening direction (here in an exemplary clockwise direction) when turning the turntable 21 the screwdriver 20 rotates. A freewheel 7 is such between the axis of rotation of the test unit 2 and a rotating ring DR mounted so 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. While turning back the turntable 21 in the first initial rotational position, the springs T push the rotating ring DR back into its initial position (with force-free springs T). When turning back the Drehein Ness 21 beyond the first initial rotational position by a predetermined angle in a second initial rotational position, the contact between the rotary unit 21 and the test unit 2 due to the freewheel 7 powerless. In other words, the rotation axis of the test unit decreases 2 when turning back the rotary unit over the first initial rotational position of the rotary unit 21 In addition, in the second initial rotational position, the rotating ring DR not with, since the axis of rotation of the test unit 2 in freewheeling direction (counterclockwise here) rotates. Will now be the turntable 21 from the new initial rotational position turned back in the tightening direction (here clockwise) causes the freewheel 7 by locking again a driving of the rotating ring DR in the direction of rotation (clockwise here).

The use of a freewheel 7 in the test unit 2 a test system 1 The present invention has the advantage that when the test cycle is repeated for another operating point of the screwdriver, the rotary unit 21 not from the test unit 2 must be removed and contacted again, leaving a one-time contact the turntable 21 with the test unit 2 sufficient to perform a multi-stage test procedure for several operating points of the screwdriver fully automated without great effort. This means that a user of a hand-held screwdriver 20 this in a break with the test unit 2 or the tray A can be contacted and an automatic Prüfablaufsteuerung is performed, which allows a systematic test of several different operating points of the screwdriver at different positions of the functional components of the output to each other.

With reference to the 7 Embodiments of the inventive method for testing screwdrivers with a rotary unit and a first torque sensor will now be described.

7 shows the flowchart of a method according to a first embodiment for testing screwdrivers 20 with a turntable 21 and a first torque sensor 23 wherein the method comprises steps S6.1 to S6.6 6 includes. These steps are in 7 denoted by S7.1 to S7.6, so here on the description to 6 is referenced.

To step f) of turning back S7.6 of the turntable 21 beyond the initial rotational position by a predetermined angle in another initial rotational position closes according to 7 in step S7.7, 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 7 go through again in turn.

at a repetition of step c), the rotary unit is preferably starting from the initial turning position turned in the the turntable after the immediately preceding execution of the Step f) is located. The one with a previous turning back the turntable on a Initial rotation position by a predetermined angle amount reached other initial rotational position thus becomes as the one initial rotational position a subsequent rotation of the rotary unit until the first torque sensor the screwdriver reaches the predetermined setpoint torque used. This can be achieved that a repeated examination of the Wrench is done at a defined operating point, which is not just random, but certainly different from the operating point of the previous review. This achieves an effective check of the screwdriver, there double checks on one and the same operating point of the screwdriver are avoided. Second, the review of the Overall, screwdriver more reliable, because a larger number different operating points is checked, as if at a random Selection of the initial rotational position of the rotary unit for several consecutive Testing procedures under Some circumstances Operating points are checked several times.

When It also proves advantageous if the product of the number the repetitions, or the executions, the steps c) to f) and the value of the predetermined angle amount at least 360 °. This can be achieved that the full functional area of the Downforce of a screwdriver is checked at intervals of the predetermined angular amount. As explained above, This is at least the first checking a full angle range from 360 ° no Operating point checked more than once, thereby the entire test process very much is effective. Furthermore, the screwdriver with each pass of the Steps c) to f) in mutually different positions located in the screwdriver functional components such. As gears of the output, checked. Consequently will be the whole exam process not only very effective, but also delivers reliable Test result, there 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 be achieved by repeating steps c) to f) so often that the product of the number of repetitions and the value of the pre given angle amount at least 360 °, the entire output of the screwdriver is fully 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.

Further is advantageous that the screwdriver is judged capable if at every comparison of the setpoint torque of the screwdriver with the actual torque the test unit the target torque and the actual torque at most by the predetermined Amount differ from each other. This can be achieved that a screwdriver that malfunctions at least at one operating point has, reliable is judged as NIO (not ok / not capable), and out removed from the production process.

DETAILED DESCRIPTION OF OTHER EMBODIMENTS THE INVENTION

As already described above, comes in the prior art in the Assembly technology often a mobile measuring bench is used, with the several screwdrivers in a row to be checked for their ability can.

Such a mobile measuring bench 2 * is in 11 shown schematically. The measuring bench 2 * includes a test unit 2a * , a manual input unit 2 B* and a test control 2c * , The mobile measuring bench 2 * forms together with a screwdriver 20 who is a turntable 21 includes, and a control unit 22 for controlling a rotation of the rotary unit 21 a screwdriver testing system, as known in the art. At the in 4 shown screwdrivers 20 It is a hand-held electrically controllable machining tool that via a cable with its control unit 22 connected is. The control unit 22 can be z. B. be connected via a connecting rod with a holding unit, which is received in a displacement holding device (not in 4 shown), wherein the holding unit is slidably movable in the displacement holding device. The holding unit is usually a treadmill or a trolley provided with some rollers suspended in a running rail used as a sliding holding device. Both the control unit can be used via the displacement holding device 22 as well as the screwdriver 20 be energized. In addition, the shift holding device can also serve as a control line and data line to the control unit 22 from a central monitoring unit (hereinafter also referred to as 'central unit') to provide control data. If z. B. several such control units 22 can be successively arranged in such a displacement holding device, each individual control unit 22 transmitted from the central unit via the displacement holding device, a control data record, the processing data of the corresponding screwdriver 20 corresponds to a specific screw point. For example, this data is a torque value that the nutrunner uses 20 over the turntable 21 to submit to the screw.

So far, it has been customary for a test person to use the mobile measuring bench 2 * successively to each of the screw stations (consisting of control unit 22 and screwdrivers 20 ) rolls to a machine capability study of the screwdrivers 20 make. The test person first has to use the control unit 22 the current control data for the screwdriver concerned 20 read out, z. B. a torque value with which the screwdriver 20 to tighten a screw. This test value has to be read by the test person as so-called nominal value specification manually via the manual input unit 2 B* into the mobile measuring bench 2 * enter. Optionally, it is also possible that the test person directly a specific setpoint specification for a torque of the screwdriver 20 in the control unit 22 and the same setpoint specification also in the manual input unit 2 B* the mobile measuring bench 2 * enters.

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

After that, the inspector arranges the control unit ( 22 ), the turntable 21 the screwdriver 20 until a first torque sensor of the screwdriver 20 measures the specified setpoint torque. That of the turntable 21 output actual torque is thereby from the test unit 2a * the mobile measuring bench measured. Both from the test unit 2a * measured actual torque as well as the via the manual input unit 2 B* entered nominal value specification of the torque are sent to the test control 2c * passed. In the test control 2c * then takes place a comparison of the desired torque and the actual torque instead. 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 testing system for screwdrivers with a mobile measuring bench 2 * has the disadvantage that it causes increased staff costs and high equipment costs. So z. B. a high personnel costs necessary to keep the ability test of the screwdriver used at a high level, since 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 described above provides 2 * a costly device.

The previously described conventional System for ability testing of So screwing tools has the disadvantage that it is very expensive and costs.

It is therefore desirable a system for testing to provide screwdrivers with an effective and cost-effective testing of screwdrivers allows.

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 testing the screwdriver over the turntable; and a data exchange unit for at least unidirectional exchange of data from the test unit to the control unit.

By the provision of the aforementioned data exchange unit becomes it z. B. allows that z. B. in the test unit obtained data transmitted directly to the control unit of a screwdriver can be. Thereby can Evaluations of the test unit determined test data be performed by the control unit of the screwdriver or by a central unit. As a result, z. B. can be achieved that no test control additionally 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 necessary, because the to be tested Setpoints can already be present in the control unit.

It is possible, that the data exchange unit only for the exchange of data from the test unit is designed for the control unit. In this case, the test unit usually represent a passive element in the test of the screwdriver. But it is also possible that the data exchange unit 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 is designed. In this case, the test unit can also be an active element during the exam represent of screwdrivers.

Preferably include for at least unidirectional replacement of the test unit Data provided for the control unit Torque values of the screwdriver. The data can but also other values such. B. angle of rotation values or others for the screwdriver function authoritative Contain values.

Further It is advantageous that the test unit designed is a torque output by the rotary unit of the screwdriver to check. there is preferably the test unit designed, a result of the review of the torque output by the rotary unit of the screwdriver as Value of an actual torque of the screwdriver via the data exchange unit to replace the control unit.

Thereby is enabled the control unit transmits the actual torque transmitted by the test unit with a nominal torque the control unit can compare.

Further For example, the nutrunner may include a first torque sensor. In addition, can the test unit a counter torque generating device and a second torque sensor.

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

Preferably the control unit is suitable for rotation with the test unit controlled rotary unit until the first torque sensor reaches a predetermined setpoint torque.

Further it is advantageous that the second torque sensor is suitable the actual torque caused by turning the turntable to eat.

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

Preferably the control unit is designed to rotate the unit over the Initial rotation position by a predetermined angle in to turn back another initial turning position. By turning back the turntable over the initial rotational position by a predetermined angle amount in another initial rotational position can be achieved that The functional components of the output located in the screwdriver reliable to each other in a position other than the position of the screwdriver located functional components of the output to each other when Contact the turning unit of the screwdriver in the first initial turning position the turntable with the test unit. This can prevent the screwdriver from accidentally passing in a subsequent check once in the same initial rotational position of the turntable, or in the same of the functional components of the screwdriver Downforce to each other, such. the gears of the output, is checked.

The in the screwdriver functional components are therefore in a defines different position to each other than the position, in the review of the first operating point of the screwdriver to each other. Consequently will be an effective and reliable exam allows the screwdriver.

Preferably the control unit is designed, in the event that the target torque and the actual torque at most by a predetermined amount differ, the turntable on the Initial rotational position by the predetermined angle in the to turn back the other initial turning position.

Further It is advantageous that the control unit is designed to control a rotation of the with the test unit contacted rotary unit until the first torque sensor reaches a predetermined target torque, and the subsequent turning back the turntable over the initial rotational position by the predetermined angle amount repeatedly to another initial rotational position.

Preferably includes the test unit a freewheel that ensures that the contact between the turntable and the test unit during the turndown the turntable becomes powerless.

there it is advantageous that the freewheel causes during the turndown the rotary unit relaxes the counter torque generating device and the second torque sensor is reset.

Preferably includes the counter torque generating device a pair of disc springs. This will give a soft compression of the Anti-torque generator allows, what to an extension the life of the test unit contributes.

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 the second torque sensor has a calibrated strain gauge constitutes. By using a calibrated torque sensor in the test unit becomes an accurate and reliable test result guaranteed.

Further The data exchange unit comprises an electrical line which the test unit and the control unit connects to each other.

It but it is also possible the data exchange unit is a wireless communication link between the test unit and the control unit. In this case, the wireless communication connection an infrared interface can be. Another possibility is that the wireless communication link is a radio interface.

Further it is advantageous that the system has a receiving unit for receiving of the screwdriver. It is advantageous that the receiving unit is designed to take the screwdriver so that the turntable the wrench in the initial rotational position with the counter torque generating means is in contact.

Further, it is possible that the receiving unit is designed as a storage tray for the screwdriver and the test unit is integrated into 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 During a break in production, the wrench is fixed in the storage tray via the clamping bracket and at the same time the test sequence for a machine capability test is started. 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 is the test unit integrated into the control unit. However, it is emphasized that the present Invention not limited thereto is that the test unit is integrated in the control unit.

at the embodiments described above of the system for automatic testing screwdrivers are preferably hand-held screwdrivers. However, the present invention is not limited to the use of hand-held screwdrivers limited, but also includes test systems for testing another screwdriver, z. B. fully automatic Screwdriver or semi-automatic screwdriver, which also completely fixed or can be slidably mounted.

8th shows a block diagram according to a third embodiment of the test system according to the invention. The test system includes a screwdriver to be tested 20 with a turntable 21 , The test system further comprises a control unit 22 for controlling a rotation of the rotary unit 21 , In addition, the test system includes a test unit 2 to check the screwdriver 20 over the turntable 21 , Furthermore, the test system comprises a data exchange unit 22a , which is suitable, at least in one direction (unidirectional) data from the test unit 2 to the control unit 22 exchange.

By the provision of the aforementioned data exchange unit becomes it z. B. allows that z. B. in the test unit obtained data transmitted directly to the control unit of a screwdriver can be. Thereby can Evaluations of the test unit determined test data be performed by the control unit of the screwdriver or by a central unit. As a result, z. B. can be achieved that no test control additionally 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 necessary, because the to be tested Setpoints can already be present in the control unit. Consequently will be an effective and cost effective exam made possible by screwdrivers.

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 8th , so as to describe the individual components, which in 9 are referenced with these references, to the description 8th can be referenced.

The tester to be tested 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 suitable, at least with the turntable 21 the screwdriver 20 in an initial rotational position of the rotary unit 21 to be contacted. Furthermore, the test system comprises a control unit 22 for controlling a rotation of the test unit 2 contacted rotary unit 21 , In this case, the control unit 22 the turntable 21 as long as drive until the first torque sensor of the screwdriver 20 reaches a predetermined setpoint torque. The second torque sensor in the test unit 2 is suitable by turning the turntable 21 to measure caused actual torque.

Preferably, the data being exchanged includes torque values of the driver 20 , Preferably, the test unit 2 designed, one of the turntable 21 the screwdriver 20 check output torque. Furthermore, the test unit 2 designed, a result of the review of the turntable 21 the screwdriver 20 output torque as the value of an actual torque of the screwdriver 20 via the data exchange unit 22a to the control unit 22 exchange. The test unit 2 is about the data exchange unit 22a with the control unit 22 connected. The control unit ( 22 ) is also with the screwdriver 20 connected. The control unit 22 can be z. B. directly with the turntable 21 the screwdriver 20 be connected. But it is also possible that the control unit 22 via the first torque sensor of the screwdriver 20 and / or other assemblies in the screwdriver 20 with the turntable 21 connected is.

The data exchange unit 22a allows one of the turntable 21 output actual torque, which is from the test unit 2 has been measured, via the data exchange unit 22a to the control unit 22 the screwdriver 20 to convey. Therefore, it is basically possible to use the test unit 2 to design as a passive assembly. That means that in the test unit 2 no own test control in addition to the control unit ( 22 ) of the screwdriver 20 must be provided and no manual input unit for specifying a target torque that the test unit 2 from the screwdriver 20 expected. Therefore, in accordance with conventional test systems 11 provided test control 2c * and the manual input unit 2 B* 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 that a test person from the screwdriver 20 output target torque via a manual input unit in the mobile measuring bench 2 * enters. This allows the testing of screwdrivers 20 to run automatically. As a result, personnel expenses and personnel costs are reduced and, moreover, the entire inspection process is effectively designed.

On a manual input unit on the test unit 2 can be waived if the control unit 22 the control data for your screwdriver 20 from a central unit. It may be after As before, be desirable directly on a specific control unit 22 a specific setpoint specification for the screwdriver 20 adjust. Even in this case, however, a setpoint specification which may possibly be made manually is only at the control unit 22 the screwdriver 20 and not in addition to the test unit 2 , It is thus also here the data input effort compared to the prior art reduced, where both a setpoint input in the control unit 22 as well as 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 due to accidentally different setpoint specifications in the control unit 22 and test bench 2 * may occur.

If the control unit 22 has a redundant hardware configuration, the capability test can be carried out via the redundant channel. If this design is not available, the capability test is performed by a separate controller, this separate controller then being connected to the control unit 22 is linked.

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

In 9 is the control unit 22 for controlling a rotation of the with the test unit 2 contacted rotary unit 21 separated from the screwdriver 20 intended. The control 22 but also in the screwdriver 20 be integrated or mounted on this. The control unit 22 controls the turntable 21 until the first torque sensor of the screwdriver reaches a predetermined setpoint torque.

The in the 8th to 10 schematically represented data exchange unit 22a may include an electrical line connecting the test unit 2 and the control unit 22 connects with each other. But it is also possible that the data exchange unit 22a a wireless communication link between the test unit 2 and the control unit 22 includes. Such a wireless communication connection may be an infrared interface or a radio interface.

10 shows a further preferred embodiment of the test system of the present invention. With respect to the components designated by like reference numerals, reference is made to the description in FIG 8th and 9 directed. In 10 is the test unit 2 with the control unit 22 the screwdriver 20 firmly connected via a bracket H. The system according to 10 thus represents a combined Schraubbearbeitungs- / screwdriver testing station.

Preferably, this combined system has a receiving unit for receiving the screwdriver 20 on. It is advantageous that the receiving unit is designed so that the screwdriver 20 to record that the turntable 21 the screwdriver 20 in an initial rotational position with a counter torque generating means of the test unit 2 is in contact, ie engages in this. Preferably, the receiving unit as a storage tray for the screwdriver 20 trained and the test unit 2 integrated into this storage tray. This tray can then via a bracket H fixed to the control unit 22 be connected.

According to a preferred embodiment of the present invention, the tray has a clamping bracket for fixing the screwdriver 20 in the tray on. This allows a user of the screwdriver 20 During a break in production, the wrench is fixed in the storage tray via the clamping bracket and at the same time the test sequence for a machine capability test is started. The test procedure can be fully automatic during the break.

The embodiment described above dan has the advantage that the personnel costs to carry out a review of a Screwdriver is low and the test of screwdrivers thus cost-effective carried out can be.

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 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 another embodiment of the present invention, the test unit 2 also in the control unit 22 the screwdriver 20 be integrated.

The test systems described above are preferably used in the testing of hand-held screwdrivers. However, it is emphasized that the present invention is in its application not on hand-held Screwdrivers limited is.

COMMERCIAL APPLICABILITY

As explained above, is in the test method according to the invention and in the test system according to the invention, Screwdriver effective and reliable on her ability to check. Even though previously isolated references to automotive production have been made, the present invention is not limited thereto but can be used in a variety of other applications where Screwdrivers are used, for example in series production hifi products, washing machines, semiconductor equipment, Etc.

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

reference numeral in the claims are for illustration purposes only and narrow the scope of protection the claims not a.

Claims (36)

Method for testing screwdrivers ( 20 ) with 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 ), which a counter-torque generating device ( 3 ) and a second torque sensor ( 5 ); b) predefining (S6.2) a setpoint torque, which the screwdriver ( 20 to spend); c) turning (S6.3) the turntable ( 21 ) until the first torque sensor ( 23 ) of the screwdriver ( 20 ) reaches the predetermined target torque; d) measuring (S6.4) one by turning the turntable ( 21 ) caused actual torque with the second torque sensor ( 5 ); e) comparing (S6.5) the predetermined desired torque of the screwdriver ( 20 ) with the second torque sensor ( 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 angular amount to another initial rotational position. Method according to claim 1, characterized in that that step f) (S6.6) for carried out the case is that the target torque and the actual torque at most differ by a given amount. A method according to claim 1 or 2, characterized by at least one repetition of steps c) (S6.3) to f) (S6.6). The method of claim 3, wherein the product comprises the number of repetitions and the value of the given angle at least 360 °. Method according to one of the preceding claims, wherein the value of the predetermined angle 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 the gears in the screwdriver ( 20 ) has the most teeth. Method according to one of the preceding claims, wherein the screwdriver ( 20 ) is judged to be capable, if at each comparison of the nominal torque of the screwdriver ( 20 ) with the actual torque of the test unit ( 2 ) the setpoint torque and the actual torque deviate from each other by at most the predetermined amount. Method according to one of the preceding claims, wherein the rotary unit ( 21 ) of the screwdriver ( 20 ) with the counter torque generating device ( 3 ) of the test unit ( 2 ) via a freewheel ( 7 ), which ensures that the contact between the turntable ( 21 ) and counter-torque generating device ( 3 ) while turning back the turntable ( 21 ) becomes powerless. Method according to one of the preceding claims, wherein the counter-torque generating device ( 3 ) includes a pair of disc springs. Method according to one of the preceding claims, wherein the second torque sensor ( 5 ) is calibrated. Method according to one of the preceding claims, wherein the second torque sensor ( 5 ) includes a calibrated swivel chain. Method according to one of claims 1 to 9, wherein the second torque sensor ( 5 ) includes a calibrated strain gauge. Method according to one of the preceding claims, wherein the screwdriver ( 20 ) is a hand-held screwdriver. Testing system ( 1 ) for testing screwdrivers ( 20 ) with a rotary unit ( 21 ) and a first torque sensor ( 23 ), comprising: a test unit ( 2 ) with a counter-torque generating device ( 3 ) and a second torque elementary sensor ( 5 ), which is suitable, at least with the rotary unit ( 21 ) at least one screwdriver ( 20 ) in an initial rotational position of the rotary unit ( 21 ) to be brought into contact; a control unit ( 22 ) for controlling a rotation of the rotary unit brought into contact with the test unit ( 21 ) until the first torque sensor ( 23 ) reaches a predetermined target torque, wherein the second torque sensor ( 5 ) by turning the turntable ( 21 ) to measure actual torque caused; a comparison unit ( 6 ) for comparing the predetermined desired torque of the screwdriver ( 20 ) with the second torque sensor ( 5 ) measured actual torque, characterized in that the control unit ( 22 ), the turntable ( 21 ) to turn back beyond the initial rotational position by a predetermined angle amount to another initial rotational position. Test system according to claim 13, wherein the control unit ( 22 ) is designed, in the event that the desired torque and the actual torque differ by more than a predetermined amount from each other, the rotary unit ( 21 ) to turn back beyond the initial rotational position by the predetermined angle amount in the other initial rotational position. Test system according to one of claims 13 or 14, wherein the control unit ( 22 ), the control of rotation of the rotary unit brought into contact with the test unit ( 21 ) until the first torque sensor ( 23 ) reaches a predetermined setpoint torque, and the subsequent turning back of the rotary unit ( 21 ) beyond the initial rotational position to repeatedly perform the predetermined angular amount to another initial rotational position. Test system according to one of Claims 13 to 15, the test unit ( 2 ) a freewheel ( 7 ), which ensures that the contact between the turntable ( 21 ) and the test unit ( 2 ) while turning back the turntable ( 21 ) becomes powerless. Test system according to claim 16, wherein the freewheel causes, during the turning back of the rotary unit ( 21 ) the counter torque generating device ( 3 ) is relaxed and the second torque sensor ( 5 ) is reset. Test system according to one of claims 13 to 17, wherein the counter torque generating means ( 3 ) includes a pair of disc springs. Test system according to one of claims 13 to 18, wherein the second torque sensor ( 5 ) is calibrated. Test system according to one of the preceding claims, wherein the second torque sensor ( 5 ) includes a calibrated swivel chain. Test system according to one of claims 13 to 19, wherein the second torque sensor ( 5 ) includes a calibrated strain gauge. 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 ) contain. Test system according to claim 22 or 23, wherein the test unit ( 2 ), one of the turntable ( 21 ) of the screwdriver ( 20 ) to check the torque output. Test system according to claim 24, wherein the test unit ( 2 ) is designed to be a result of the review of the turntable ( 21 ) of the screwdriver ( 20 ) output torque as the value of an actual torque of the screwdriver ( 20 ) via the data exchange unit ( 22 ) to the control unit ( 22 ). Test system according to one of Claims 22 to 25, the data exchange unit ( 22a ) comprises an electrical line connecting the test unit ( 2 ) and the control unit ( 22 ) connects to each other. Test system according to claim 26, wherein the data exchange unit ( 22a ) a wireless communication link between the test unit ( 2 ) and the control unit ( 22 ). Test System according to claim 27, wherein the wireless communication link is a Infrared interface is. Test System according to claim 27, wherein the wireless communication link is a Radio interface is. Test system according to one of claims 13 to 29, further comprising a receiving unit for receiving the screwdriver ( 20 ). Test system according to claim 30, wherein the receiving unit is adapted to the screwdriver ( 20 ) so that the turntable ( 21 ) of the screwdriver ( 20 ) in the initial rotational position with the counter torque generating means (FIG. 3 ) is in contact. Test system according to one of the claims 30 or 31, wherein the receiving unit as a storage tray for the screwdriver ( 20 ) and the test unit ( 2 ) is integrated in the tray. Test system according to claim 32, wherein the storage tray is fixed to the control unit ( 22 ) connected is. Test system according to one of claims 32 or 33, wherein the tray a clamping bracket for fixing the screwdriver ( 20 ) in the tray. Test system according to one of claims 13 to 34, wherein the test unit ( 2 ) in the control unit ( 22 ) is integrated. Test system according to one of claims 13 to 35, wherein the screwdriver ( 20 ) is a hand-held screwdriver.