EP2566660B1 - Device for producing precise tightening torque for screw connections - Google Patents

Description

The invention relates to a device for generating a torque-precise torque for screw according to the preamble of claim 1 and a method for calibrating such a device according to the preamble of claim. 6

Torque wrenches and torque multipliers are known in various embodiments from the prior art.

So revealed the WO 2009/115889 A1 an electronic torque wrench with replaceable torque sensors that is calibrated to produce a defined torque.

From the DE 32 37 325 A1 goes out a transmission power key with overload protection, which allows a translation of the applied torque and thus represents a Drehmomentvervielfältiger. This is characterized by the fact that upon reaching a desired torque torque transmission is interrupted by an overload protection. With such a transmission power key high-precision tightening torques can not be realized.

A torque wrench with an RFID reader and an RFID antenna for identification of the torque wrench is in the US 2008/0115636 A1 disclosed. With such a torque wrench can be determined whether a desired torque has been generated.

Torque multipliers, also referred to as force multipliers in the following, generally have highly-geared planetary gears. Spur gears or epicyclic gears are also used occasionally in torque multipliers. The input torque is set manually and usually generated with the help of a ratchet or with the help of a torque wrench. The output torque of the transmission can then be determined on the basis of a previously determined and known transmission ratio stored, for example, in a table. However, the transmission efficiency is not considered. Alternatively, the output torque of a torque setting table, which is also previously determined, taken. Here, the transmission efficiency is taken into account, with interpolation being carried out at intermediate values.

There is now a desire, in the context of quality assurance with manual torque and force multipliers, to randomly check and document the applied torque values.

For detecting the torque, different devices and methods are known for this purpose. A first known from the prior art solution provides to integrate a torque sensor in the transmission of the force multiplier. In this case, the sensor must be supplied with energy via an external evaluation unit, also called a datalogger. In this the data is recorded and stored.

Another solution known from the prior art provides a torque sensor connected downstream of the force multiplier. This will be on the output shaft of the transmission arranged a suitable torque sensor. Again, the power supply and data recording by means of a wired external device.

In both solutions known from the prior art, the energy supply of the sensor or the data evaluation and storage takes place from outside or outside. For this purpose, electrical cables in the form of cables and evaluation devices are required, which are exposed to harsh site conditions. Often, the sensitive, loose cables are accidentally torn or damaged. Also plug connections are provided which can be damaged and bent in contact with other components. Also so-called interface boxes containing connectors for the cable, and are arranged on the gear housing as an additional and projecting beyond the gear housing out, usually cuboid-shaped housing, can be damaged. It is also disadvantageous that the required evaluation devices, in addition to the other devices, have to be either umgehängt by the operator or carried in the form of belt bags or the like. The data transmission between the sensors and the evaluation device is usually done via "flying" cables, which hinder the operator in addition.

The invention is therefore based on the object to provide a device which allows the operator to be used without restrictions by cables or external devices and on the other hand ensure the greatest possible security in determining the output torque.

The object is achieved by a device for generating a torque-precise tightening torque for screw according to claim 1. Advantageous developments and refinements of the device according to the invention are the subject of the dependent claims on claim 1.

Thus, an advantageous development of the device according to the invention, that the electronic torque wrench has a display to display the output torque described above, wherein input and output torque are related to the transmission.

In the memory is - among other data - advantageously also stored in the calibration gear ratio of the torque multiplier stored.

The gear ratio is preferably stored as an interpolation curve of the functional relationship of the output torque in dependence on the input torque of the torque multiplier in the memory.

A particularly advantageous embodiment provides that the transmission have an RFID transponder and the torque wrench an RFID reader, which are matched to each other. In this case, the torque wrench detects the gearbox. It can be stored in the memory, the transmission characterizing data used to determine the tightening torque of the screw.

Another object of the invention is to provide a method which can easily be used for a common calibration of torque multipliers and electronic torque wrenches, in particular, specific data of the torque multiplier and in particular its transmission should be taken into account in the calibration.

This object is achieved by a method for calibrating a device for generating a torque-precise tightening torque for screw with the features of claim 6. The common calibration of the torque multiplier together with the electronic torque wrench is carried out so that the transmission ratio based on at least one over the entire torque range obtained Average value takes place. This so determined gear ratio is stored in the memory of the torque wrench and taken into account in the determination of the tightening torque of the screw in subsequent screwing.

In this case, the actual transmission ratio over the entire torque range is determined and stored at different angular positions of the output shaft of the torque multiplier. For this purpose, the transmission ratio is first determined and stored over the entire Drehömentbereich at a first angle, then the output shaft is further rotated by predeterminable angle and determined at each of these angular positions over the entire torque range, the transmission ratio and stored.

For this purpose, the output shaft is further rotated by an angle of 90 ° until it is twisted overall by an angle of 180 °. This further rotation by predeterminable angles is based on the knowledge that the torque curve of the output torque as a function of the input torque substantially shows a periodic curve which can be described by a sine or cosine function. A further rotation by multiples of 90 ° allow the determination of this periodic sine / cosine progression. If it is rotated further by angles smaller than 90 °, for example by 45 °, then it is necessary to continue rotating until the output shaft of the torque multiplier has rotated by 180 °. From the values thus obtained, a mean transmission ratio is then calculated and stored in the memory of the electronic torque wrench.

An advantageous embodiment of the method is the subject of the back claim to claim 6. Thus, advantageously, an interpolation curve, in the first approximation, an interpolation straight line is set between the gear ratios determined in this way at different angular ratios, and the output torque is determined as a function of the input torque on the basis of this interpolation curve.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Fig. 1

schematisch eine von der Erfindung Gebrauch machende Vorrichtung zur Erzeugung eines drehmomentgenauen Anzugsmoments für Schraubverbindungen;

Fig. 2

der Drehmomentvervielfältiger der in Fig. 1 dargestellten Vorrichtung;

Fig. 3

eine Draufsicht auf den in Fig. 2 dargestellten Drehmomentvervielfältiger;

Fig. 4

das Ausgangsdrehmoment über dem Eingangsdrehmoment und

Fig. 5

das Ausgangsdrehmoment über dem Eingangsdrehmoment zur Erläuterung einer Variante des erfindungsgemäßen Verfahrens.

In the figures show:

Fig. 1

schematically a device making use of the invention for generating a torque-tight torque for screw;

Fig. 2

the torque multiplier of in Fig. 1 illustrated device;

Fig. 3

a top view of the in Fig. 2 illustrated torque multiplier;

Fig. 4

the output torque over the input torque and

Fig. 5

the output torque on the input torque to explain a variant of the method according to the invention.

The device shown in the figure for generating a torque-accurate torque comprises a torque multiplier, in general Both the input and the output shaft each end, for example, with a square, to which acts in the case of the input shaft, a torque wrench 200 and the case in the case of the input shaft the output shaft 102 in a so-called "power nut" or simply "nut" 140 engages. By means of the nut 140, a tightening torque is transmitted to a (not shown) screw connection. The torque multiplier 100 further includes a known reaction arm 130 which prevents the torque multiplier from spinning during the tightening operation by striking a stationary object.

The torque multiplier 100 is manually operated by a torque wrench 200. For this purpose, the torque wrench 200 has a handle 210. The torque wrench 200 itself is an electronic torque wrench 200 having a display 205 and an input device 220. The input device 220 serves, for example, for inputting data characterizing the screwdriving process. The adjustment of the torque wrench 200 via a selection menu. After selecting a menu item, the desired output torque and the desired limit values are entered. During the application of torque, an operator is visually informed of the progress, for example by means of light bars. Shortly before reaching the target torque, the operator can also be informed by an acoustic signal. After reaching the torque, a likewise preferably optical and optionally also acoustic "okay" or "non-kay" display is performed and the torque value achieved is stored in a data memory provided in the torque wrench 200 (not shown). All values stored in the torque wrench can be transferred to a PC or laptop after completion of all work and further evaluated there.

The basic idea of the invention is firstly to provide a self-sufficient device which manages without additional cables, an external power supply, remote input and display devices and the like. For this purpose, the torque wrench is battery or battery operated. In addition, it can be provided that the torque multiplier 100 or the transmission gear 110 of the torque multiplier 100 has an RFID transponder which cooperates with an RFID reader arranged in the torque wrench 200. In this case, the torque wrench 200 effectively recognizes the torque multiplier 100 or the transmission 110 of the torque multiplier 100 and by resorting to values stored in the memory of the torque wrench 200 which were determined and stored in a common calibration to be described in greater detail below Torque values can be set exactly. In the memory for this purpose, translation values are stored, which are each associated with the transmission 110 of the torque multiplier 100. These values are used in a computing unit provided in the torque wrench 200. The combination of RFID transponder and RFID reader completely excludes system confusion.

The calibration of the torque multiplier 100 and torque wrench 200 system is accomplished by first determining the actual gear ratio over the entire torque range of the torque multiplier 100. The procedure of this calibration will be described below with reference to FIGS. 2 to 5 explained. In Fig. 2 schematically a side view of the torque multiplier 100 is shown. An input shaft 101 terminating in, for example, a square on which the electronic torque wrench 200 engages is engaged via the transmission 110 with an output shaft which also terminates with a square 102 which engages a keyed nut, also referred to as a "power nut" 140 , The power nut 140 is adapted on the output side to the screw head or to the nut of the screw connection. At the input shaft becomes an input torque M _E applied and at the output of the transmission 110 is an output torque M _A on. The transmission ratio between input torque M _E and output torque M _A is determined by the transmission 110. It is first determined this gear ratio, wherein the input torque M _{E is} determined by the electronic torque wrench 200, and the output torque M _A is detected by a sensor 400 which is arranged on the output shaft. This sensor 400 is intended only for calibration. In later operation, the arrangement of such a sensor 400 is not required.

The determination of the transmission ratio now takes place in that the output shaft and thus the output square 102 are first brought into a first position, which corresponds to an angle of 0 ° ( Fig. 3b1 )). Then, the screw is "tightened" by the input torque M _{E is} applied and the output torque M _{A is} determined. This results in a functional relationship between the output torque M _A and the input torque M _E , the in Fig. 4 is shown schematically by a dashed line. In principle, such a series of measurements suffices for determining this functional relationship between the output torque M _{A and} the input torque M _E. In this case, the interpolation curve of the function M _A (M _E ) is then determined and this interpolation curve, in particular an interpolation straight line, as in FIGS FIGS. 4 and 5 represented, saved as a kind of characteristic.

In order to further increase the accuracy, a particularly advantageous embodiment of the method according to the invention provides further measurement series.

In a second series of measurements, the output square 102, that is to say the output shaft, is rotated by 90 °, as shown on the right in FIG Fig. 3b2 ) is shown schematically and again the relationship between output torque M _A and input torque M _{E is} determined, in Fig. 4 shown as a solid line.

Finally, in a third series of measurements, the output shaft and thus the output square 102 is further 90 ° ( Fig. 3b3 )) and again the dependence of the output torque M _A on the input torque M _{E is} determined. This is in Fig. 4 represented by a dotted line. From these three lines, an interpolation curve is then determined, in the first approximation an interpolation straight line which is stored in a memory 250 of the torque wrench 200 and which represents the dependence of the output torque M _A on the input torque M _E.

At the in Fig. 4 In the embodiment shown, the interpolation curve (the straight line shown) is formed over the entire torque range. A further increase in accuracy results when, to determine the interpolation, the curve, as in Fig. 5 is divided, for example, into four sub-areas I, II, III, IV of the input torque M _{E is} divided and an interpolation is performed in each of these sub-areas. Again, this results in a substantially linear course. The number of these subdivisions can be further increased, so that in the limit case an exact approximation of the function M _A (M _E ) is possible. After completion of the calibrations, the sensor 400 is removed and the dependence of the output torque M _A on the input torque M _E is - as mentioned - stored in the memory of the electronic torque wrench 200 and used in later Schraubschrauben. In this way, very accurately the tightening torque of screw can be determined.

The calibration over different angular ranges is required because all known types of transmissions have due to the engagement conditions of the tooth flanks more or less sinusoidal fluctuations in the torque curve and thus the force curve. This means that over the entire torque curve of the torque multiplier deviations from theoretically calculated torque are detectable. Due to the calibration, these deviations can be taken into account and eliminated.

Claims (7)

1. An apparatus for producing a precise tightening torque for screw connections, with a combination of torque multiplier (100) and a torque wrench (200) which is adjusted to said torque multiplier and is calibrated together with said torque multiplier, wherein the torque wrench (200) comprises an input unit (220) for the input of a torque limit value and that torque wrench (200) comprises a memory (250) for storing the data characterizing the torque.
2. An apparatus according to claim 1, characterized in that the torque wrench (200) comprises a display (205) for displaying an input and output torque.
3. An apparatus according to claim 1, characterized in that the gear ratio of the torque multiplier (100) which is determined during calibration is stored in the memory.
4. An apparatus according to claim 3, characterized in that the gear ratio is stored in the memory (250) as an interpolation curve of the functional connection of the output torque (M_A) depending on the input torque (M_E) of the torque multiplier (100).
5. An apparatus according to one of the claims 1 to 4, characterized in that the torque multiplier (100) comprises an RFID transponder, and that the torque wrench (200) comprises an RFID reader, which communicate with one another and by means of which a transmission of the characteristic gear ratio (100) to the torque wrench (200) occurs.
6. A method for calibrating an apparatus for producing a precise tightening torque for screw connections according to one of the claims 1 to 5, wherein the output torque (M_A) is determined depending on the input torque (M_E) over the entire torque progression as the gear ratio, and that the gear ratio (M_A(M_E)) occurs on the basis of at least one average value obtained over the entire torque range, that the gear ratio is determined at several gear engagement angles (0°, 90°, 180°), and that thereafter an output shaft of the torque multiplier (100) will be further rotated about respectively predeterminable angles, especially twice about 90°, and the gear ratio over the entire torque range will be determined in this process and a mean gear ratio will be calculated therefrom, which will be stored in the memory (250) of the torque wrench (200).
7. A method according to claim 6, characterized in that the average value is determined by forming an interpolation curve, especially a straight interpolation line.

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