Measuring device for determining the overall starting torque, the friction moment of a screw head and the pre-stressing force of a tightened screw connection

The invention relates to a measuring device for determining the overall tightening torque M_A, The head frictional moment M_K and the biasing force F_V one dressed and content Erten in a force / torque transducer Screw resulting by measuring voltages in accordance with the Preamble of claim 1.

It is known from the literature, for example, from Dubbel, Taschenbuch für den Maschinenbau, 14th ed. 1981, pp 374 et seq., That the essential characteristic of an Screw, which for example, two components such as plates or flanges braced, the mating threads of a bolt with the Internal thread of a nut or a component is. The rotation of at least one the parts leads to their displacement relative to each other along a common Axis of the screw axis. The relative longitudinal movement and the relative Rotary movement of a part (z. B. Mother) relative to another part (eg. B. the bolts) are proportional to each other. If by further turning the tightened screw, then formed in a bolt tension (Tension), which is sometimes referred to as bias force, and an equal high pressure force (compressive stress) between the components. As a result, elongates the Bolts somewhat and the plates are in a by suction. "Rötscher-cone" limited range together. One speaks of a resilient Resilience in the screw.

When turning the parts must be an engagement with the tension F_V Rising thread friction torque M_G and a head frictional moment M_K be overcome. The Thread friction torque M_G results from the form-fitting to today sliding action areas, the so-called. helicoids (mostly ruled surfaces) of the two Parts. The head frictional moment M_K results from the friction of sliding on one another Surfaces under the nut and under the head, depending on What part is rotated while tightening a joint. The entire, while tightening a joint applied torque M_A sits down additively of the frictional moments M_G and M_K together and is therefore dependent of biasing force F_V and coefficients of friction, the latter of course depending on material are.

A calculation of the often not directly measurable thread friction torque M_Gprepares insofar trouble when that partially measurable parameter, M_A, M_K and F_V, But especially the head frictional moment M_K, means Known measuring devices are not determined with sufficient accuracy. In order a reliable statement about the quality and reliability of a screw difficult, which in particular in the automotive industry, which according to international Standards and building standards works, is a hindrance.

A measuring device for determining the overall tightening torque M_A, The head friction torque M_K and the biasing force F_V For example, from DE 25 21 428 C2 known. The measuring instrument consists of a substantially cylindrical housing with an oriented parallel to the cylinder axis of the housing lower base plate. At a first end, the housing provided a with an internal shoulder Inner flange onto. On the inner shoulder is the outer ring of a ball bearing attached. At the opposite second end of the housing is a Inner flange performing steel ring screwed which in an upper recess receives the outer ring of a further ball bearing, the integrally formed with, annular portion protrudes into the housing. A chucking is near its two ends rotatably on ball bearings and friction in the housing supported, however, they two diametrically from the scope of the fixed sleeve projecting, resiliently flexible arms is tied to the housing-fixed steel ring. The poor have at their chucking the adjacent end necking on. The free ends of the arms are each connected via a cylindrical Pin hinged to the ring. Upon rotation of the chucking due to the Tightening of the screw within the steel ring can to arms acting as joint axes pins pivot friction.

The test screw is inserts into the fixed sleeve, which in its central region than relatively thin Torsionszelle is formed, is clamped. In embodied as Torsionszelle field of Chucking by means of at least two externally mounted sets of Strain from the head frictional moment M_K dependent Torsional and axial of the biasing force F_V dependent Compressive stress measured in the fixed sleeve, the amount of interest Tensile stress in the screw corresponds. The whole while tightening the Screw applied torque M_A occurs as a bending stress in the Field of resiliently flexible arms is on and also in the Cross-sectional reductions of arms arranged strain detected. The thread friction torque M_G can be the difference between the Overall tightening torque M_A and the head friction torque M_K to calculate. During the tightening of the screw connection occurs a deformation of the fixed sleeve on. The total deformation of the fixed sleeve consists of a pure Compression (compressive stress) and a pure shear (torsional), which can be described by the angle conditions: The upsetting (Compressive stress) can preferred by two at 90 ° to each other Strain gauges, one parallel to and the other transverse to the longitudinal axis Chucking is arranged to be detected completely. The shear (Torsional), by two at 90 ° to each location and to the longitudinal axis the chucking inclined at 45 ° strain entirely captured will. The chucking is along its longitudinal axis by the biasing force F_Vcompressed and perpendicular to it by M_K/ R sheared, where R is the radius of the Chucking is, which is assumed to be large compared to its wall thickness D.

The head of the frictional torque M_K dependent Torsionspannung has no further Compression (compressive stress) along the longitudinal axis of the chucking result. Likewise, axial compression (compressive stress) does not lead to a further shear (Torsional).

However, a so-called crosstalk place (disturbance) of a measured variable in the other and vice versa take place. In particular, the aufder ultimately as a feather acting torsion and pressure elastic chucking applied sets of Strain both of the head frictional moment M_K dependent Torsional and axial of the biasing force F_V dependent Compressive stress exposed. Since the above-described angle conditions, especially when mounting the strain gauges are not always reliable can be complied with, the strain gauges detect, for example, the head from the friction torque M_K dependent torsional a small Share the axial of the biasing force F_V dependent compressive stress as well with as vice versa.

Decisive for the compression (compressive stress) of the fixed sleeve and the elongation (Tensile stress) of the bolt under the biasing force F_V are your supporting cross-sections and the elastic moduli of their materials. Of the Modulus of elasticity of the bolt is usually the same as that of chucking; both are preferably made of steel. The supporting cross-section of the Chucking is as small as possible in the interests of a well measurable, large Compression (compression stress). The supporting cross-section of the bolt is in the Interest of saving material also My. The lower limit of the supporting Cross-sections is determined by the requirement that no permanent deformation may occur during operation This requirement applies to fixed sleeve and screw alike. Therefore, the biasing force is F_V supporting cross-sections the bolt and the chucking sleeve is substantially equal.

The situation is different when the torsional deformation. Even here, the elastic material properties, namely the shear modulus, identical. It should also the screw bolt designed so that nearly the maximum allowable Torsional deformation occurs. Decisive for the torsional deformation is, however, next to the shear modulus and the amount of the supporting cross-section, the radius with respect to the rotation axis, ie the axis or longitudinal axis of the screw Chucking, and this is necessarily much larger in the fixed sleeve than that of the bolt, as the former surrounding the latter coaxially. thats why considerably smaller when chucking the torsional deformation than in Bolts. An electrical output signal (useful quantity) of the associated Strain gauge is thus considerably less than that for the compression of (Compression stress), or in other words, markedly more sensitive to the Crosstalk (disturbance) of other variables. So is, for example, after DE 25 21 428 C2, the ratio of the measured signals (Nutzgrößen) for the head friction torque M_K dependent torsional only about 5/1 to 3/1 of that for by the biasing force F_V dependent compressive stress. Due to the relatively small Torsional deformation, which to a small measuring signal (useful quantity) for the Head frictional moment M_K dependent torsional leads, and the same applied axial preload force F_VThat in a large compression (compressive stress) results, carried out by the crosstalk (disturbance) of the variables a serious Falsification of the measurement signal (useful quantity) of the measuring point for the head friction torque M_K dependent torsional stress.

Conversely, however, is due to the conditions described distortion the variable (useful variable) for the biasing force F_V dependent compressive stress by crosstalk (disturbance) of the head frictional moment M_Kdependent torsional stress in the measuring point for the biasing force F_V very low and without meaning.

It is an object of the invention to provide a measuring device of the type mentioned such further develop that particular head frictional moment M_K or which depend on torsional stress with increased accuracy determined is.

This object is solved by the features of claim 1. advantageous Developments of the invention are in the dependent claims indicated.

The inventive measuring device for determining the overall tightening torque M_A, The head frictional moment M_K and the biasing force F_V a tightened and held in a force / torque transducer screw by measuring resultant tensions, in particular:<ul><li>one from the total torque M_A dependent bending stress about at least one measuring station;</li><li>one from the head frictional moment M_K dependent torsional or Bending stress of at least one measuring station; as</li><li>one of the axial preload force F_V pressure dependent voltage across at least one measuring station;</li></ul>by strain gauges / torque transducer are arranged on the motor, that they at least each one of the measuring points to determine the M_A, M_K or F_V form-dependent voltages, characterized by the fact that the measuring point for the head from the friction torque M_K dependent torsional or bending stress by mechanical means of an influence of the axial force of the biasing F_V dependent pressure voltage is decoupled.

By the provision of means for mechanical decoupling is in advantageously crosstalk (disturbance) a measured quantity in the measuring point the other measured variable largely prevented and an increased measurement accuracy, especially for the head frictional moment M_K, Obtained so that one hand, the thread friction torque M_G be determined more accurately and thereby more secure statement about quality and reliability of Screw allows the screw and on the other hand so interpretable is that risks in terms of loosening or disengagement of the screw exclude better under operating load. The operational area of Invention hereby extends not only to the quality assurance, but also eg incoming goods inspection and research and development, preferably in the automotive industry.

According to the invention is characterized a force / torque transducer, which a torsion and pressure flexible cylindrical central chucking having, on the at least one measuring point for the head frictional moment M_K dependent Torsional strain and at least one measuring point for the axial of the biasing force F_V pressure dependent voltage is arranged, characterized in that the means for decoupling the measuring point for the head frictional moment M_K dependent Torsional stress at least partially, the compressive stresses in the fixed sleeve cancel or channel the torsional stresses.

To decouple the measuring point for the head frictional moment M_K dependent Torsional stress is proposed, for example, that at least one adjacent this is applied in the central chucking and to the longitudinal axis transversely, preferably approximately at right angles, erstrekender relief slot provided is, which advantageously at least partially Compressive stresses in the chucking cancels.

The decoupling can preferably be reinforced by the fact that in addition to Relief slot at least one adjacent the decoupled measuring point for the the head frictional moment M_K dependent torsional stress in the central chucking introduced and to their longitudinal axis approximately parallel extending is provided in the substantially rectangular relief cut.

A further increase of the decoupling effects is preferably characterized achieved that adjacent to the measuring point for a second relief slot from Head frictional moment M_K dependent torsional stress is provided, which in the is disposed substantially parallel to the first relief slot, wherein as with Long sides of a rectangle the length of the relief slots greater than their Distance from one another, preferably at least one and a half times as large, in particular twice as large as that between the discharge slots a web-like formed section is.

To increase the torsional deformation in the area of ​​the measuring point for the Head frictional moment M_K dependent torsional stress is proposed that the web-shaped portion has a lower wall thickness or material thickness d as the rest of the wall thickness D of the central chucking.

For the targeted transfer or introduction of torsional stress in the web-shaped section is proposed that at least one relief slot and at least one relief cut, preferably two opposing relief recesses, approximately at right angles to each other so are arranged without contact, that between them a narrow tongue, preferably two narrow tongues, are formed, which the web-shaped portion with the other chucking connect, the narrow and thin tongues in advantageously by the relief recesses of the influences of by the biasing force F_V dependent compressive stress maximum exempted.

In the simplest embodiment, the measuring point for the Head frictional moment M_K dependent torsional stress facing sides of the Relief recesses preferably as a straight line formed.

To increase the torsional deformation in the area of ​​the measuring point for the Head frictional moment M_K dependent torsional if necessary while maintaining the Material thickness D is proposed that the measurement point for the head friction torque M_K dependent torsional stress facing sides of the Relief recesses are formed extended so that the web-shaped portion at least in the area of ​​the measuring point for the head frictional moment M_Kdependent torsional having a local constriction, wherein preferably the lateral extension of the relief recesses in the middle The area of ​​the measuring point for the head frictional moment M_K dependent Torsional stress facing sides of the relief recesses formed and circular segment shaped or triangular or other geometrical Form is reproduced.

According to the invention on the central chucking the measuring point for Determining one of the biasing force F_V pressure dependent voltage and the thereof mechanically decoupled measuring point for determining a head from friction torque M_K dependent torsional alternately and evenly spaced apart, preferably in each case two pairs of measuring points and partly at an angle of 90 ° to each other, respectively.

An alternative design of a force / torque transducer with a torsion and pressure flexible cylindrical central chucking, on which only the Measuring points for the axial of the biasing force F_V dependent compressive stress are arranged, is inventively preferred by the fact that the Measuring points for the head frictional moment M_K dependent torsional stress on an outer sleeve which encloses the central chucking coaxially, are arranged, which via means for additional mechanical decoupling of the Measuring points for the head frictional moment M_K dependent torsional stress of the axial of the biasing force F_V dependent compressive stress to the central is chucking connected without play in particular, said means advantageously Manner are pressure elastically and torsionally rigid.

For mechanical decoupling at least one of the outer sleeve arranged measuring point for the head frictional moment M_K dependent Torsional stress and the central chucking at which the forces and moments primary attack, and, at one end face of a first, preferably cylindrical Flange and at the opposite end face of a second, preferably rectangular, having flange, is preferred according to between the outer sleeve and the central chucking least one pressure elastic torsion circular diaphragm arranged.

For pressure-elastic and torsionally rigid support of the outer sleeve on the central chucking it is proposed that the outer sleeve a mutually open cylinder having both ends each having an inner flange, wherein between opposing flanges of central chucking and outer sleeve, a circular diaphragm is arranged in each case.

Alternatively, the outer sleeve has a preferably cup-like shape, with an adjacent molded to the outer edge of its open side and inner flange a circular base plate with a hole through which the central Chucking extending therethrough, so that the bottom side, the outer sleeve on the bottom plate the second, preferably rectangular, the central flange Chucking and on its open side by a between the opposing flanges of central chucking and outer sleeve arranged circular diaphragm is mounted pressure-elastic and torsionally rigid

To Mimimierung of crosstalk of the biasing force F_V dependent Compressive stress in one measuring point for the head frictional moment M_K dependent Torsion stress, it is proposed that the circular membrane at least having a circumferential bead.

Alternatively to a diaphragm is proposed that for mechanical decoupling the measuring point for the head frictional moment M_K dependent Torsional stress between the outer sleeve and the central chucking provided at least one pressure-elastic torsion bellows or compensator is, which is preferably between the first, preferably cylindrical flange and arranged on the outer sleeve of the measuring point from the head frictional moment M_K dependent torsional stress is disposed.

As an alternative to a membrane or a first bellows or compensator suggested that a second pressure-elastic torsion bellows or compensator is provided, preferably between the measuring point for the Head frictional moment M_K dependent torsional stress and to the second, preferably rectangular, arranged flange associated circular Plane is.

To Mimimierung of crosstalk of the biasing force F_V dependent Compressive stress in one measuring point for the head frictional moment M_K dependent Torsional stress is proposed that the or the bellows or expansion joints have at least one rotating shaft.

Outer sleeve, diaphragm, bellows or compensator and / or central chucking preferably by known connecting techniques, especially by Screwing and / or welding, rigidly and without play connected.

Another mechanical decoupling of the measuring point for the head friction torque M_K dependent torsional stress from the axial of the biasing force F_Vdependent pressure voltage is preferable in the invention by appropriate selection a geometrical arrangement of the measuring point for the head friction torque M_K dependent torsional stress on the outer sleeve, especially by selection of a length L of Meßstellenbereiches for the head frictional moment M_Kdependent torsional stress on the outer sleeve, a radius R of the outer Sleeve, and a thickness d of the outer sleeve (17) in the region of the measuring point for the the head frictional moment M_K dependent torsional stress, which for Enlargement of a torsional deformation, the wall thickness d of the outer sleeve in Area of ​​the measuring point for the head frictional moment M_K dependent Torsional stress is preferably less than the remaining wall thickness of the D outer sleeve.

To increase the measuring sensitivity of which is arranged on the outer sleeve Measuring points for the head frictional moment M_K dependent torsional stress is proposed that the outer sleeve additionally has radial holes.

Alternatively and / or cumulatively, it is proposed that adjacent to that on the outer sleeve disposed at least one measuring point relief slot and / or at least one relief cut analogous one of the claims 3 to 10 is provided.

According to the invention, the measuring points are to determine one of the biasing force F_V dependent compressive stress on the central chucking and thereof mechanically decoupled measuring point for determining a from Head frictional moment M_K dependent torsional stress on the outer sleeve relative to each other partly, preferably in pairs alternately, ie. preferably two pair of measurement points relatively fair and at an angle of 90 ° arranged to each other.

For placement of suitable strain gauges in the measuring points for one of the biasing force F_V pressure dependent voltage is proposed that the outer Sleeve respectively over the aufder central chucking arranged measuring points for by the biasing force F_V dependent compressive stress has a recess, which is at least as measured in their dimensions that the strain gauges on the central chucking can be placed and still redirect or initiation of the head frictional moment M_K dependent torsional stress in the designated measurement point is guaranteed aufder outer sleeve.

An inventively preferred alternative force / torque transducer with a torsion and pressure elastic cylindrical central chucking, on the only the measuring points for the axial of the biasing force F_V dependent compressive stress are arranged, wherein the central chucking a at its Front end of a first, preferably cylindrical flange, and on the opposite Front end a second, preferably rectangular flange which is characterized in an advantageous manner by the fact that the second flange two diametrically arranged connecting arms are formed in one piece, in which an outer cylindrical sleeve is arranged so that a friction torque from the head M_K dependent torsional stress as a pressure-elastic torsion Membrane and / or at least one bellows or compensator, and on the outer Sleeve aufdie link arms acts that aufwenigstens a connecting arm in at least one measurement site with suitable strain of a Head frictional moment M_K dependent bending stress is measurable.

Here, the outer sleeve is characterized by a simple construction especially characterized in that the outer sleeve in all areas preferably an approximately uniform material thickness D has.

The force / torque transducer according to the invention with a torsion and pressure elastic cylindrical central chucking sleeve rotatably mounted in a housing is supported, with the support of the fixed sleeve in the housing at a End face, preferably on the front end, at which the second, preferably rectangular, flange is formed, via two diametrically of the chucking projecting resiliently flexible arms takes place, distinguished by the fact that the biegelastischen arms at least one, preferably each one, that is on each Arm at least one measuring point for the total torque M_A dependent Bending stress is provided, which advantageously compared to the prior art known solutions a simplified measure of Total torque M_A is dependent bending stress.

Further advantages and embodiments of the present invention will become apparent exemplary embodiments and described with reference to the drawing:

Show it:<dl tsize="8"><dt>Fig. 1</dt><dd>schematically a torsion and pressure flexible cylindrical central Chucking a force / torque transducer in perspective Representation, on the at least one measuring point for the head friction torque M_K dependent torsional stress and at least one Measuring point for an axial of the biasing force F_V dependent Compressive stress is placed;</dd><dt>FIG. 2</dt><dd>schematic is a developed one on the central arranged chucking according to FIG. 1 measuring point for the head friction torque M_K dependent torsional stress;</dd><dt>Fig. 3</dt><dd>schematically a total unwound portion of the center Chucking according to FIG. 1 with partly arranged measuring points for the the head frictional moment M_K dependent torsional strain and the Biasing force F_V dependent compressive stress;</dd><dt>Fig. 4</dt><dd>a further exemplary embodiment as shown in Fig. 2;</dd><dt>Fig. 5</dt><dd>a further exemplary embodiment as shown in Fig. 2;</dd><dt>Fig. 6</dt><dd>schematically a torsion and pressure flexible cylindrical central Chucking a force / torque transducer, at least one of Measuring point for an axial of the biasing force F_V dependent Compressive stress is disposed and coaxially by an outer sleeve is surrounded, on the at least one measuring point for the head friction torque M_K dependent torsional stress is arranged which is decoupled by a pressure-elastic torsion membrane; </dd><dt>Fig. 7</dt><dd>a further exemplary embodiment as shown in Fig. 6, wherein the measuring site for one from the head frictional moment M_K dependent torsional by two pressure-elastic torsion membranes is decoupled;</dd><dt>Fig. 8</dt><dd>schematically a torsion and pressure flexible cylindrical central Chucking a force / torque transducer, at least one of Measuring point for an axial of the biasing force F_V dependent Compressive stress is disposed and coaxially by an outer sleeve is surrounded, that the head frictional moment M_K dependent Torsional stress as a pressure-elastic torsion membrane and acting on the outer sleeve to two link arms that particular tothe side surfaces of the link arms in at least one Measuring point a from the head frictional moment M_K dependent bending stress is measurable;</dd><dt>Fig. 9</dt><dd>schematically a torsion and pressure flexible cylindrical central Chucking a force / torque transducer, at least one of Measuring point for an axial of the biasing force F_V dependent Compressive stress is disposed and coaxially by an outer sleeve is surrounded, on the at least one measuring point for the head friction torque M_K dependent torsional stress is arranged which by at least one pressure-elastic torsionally rigid bellows or Compensator is decoupled; and</dd><dt>Fig. 10</dt><dd>schematically a torsion and pressure flexible cylindrical central Chucking a force / torque transducer, at least one of Measuring point for an axial of the biasing force F_V dependent Compressive stress is disposed and coaxially by an outer sleeve is surrounded, that the head frictional moment M_K dependent Torsional so through at least one elastic pressure torsionally rigid bellows or compensator and the outer sleeve two connecting arms acts, that in particular on the side faces the connecting arms in at least one measuring point from a Head frictional moment M_K dependent bending stress is measurable.</dd></dl>

Fig. 1 shows schematically a torsionally and compressively elastic cylindrical central Chucking 7 a force / torque transducer 1 in a perspective view, at least one measuring point 5 for the head frictional moment M_K dependent Torsional strain and at least one measuring point 6 for the axial Biasing force F_V pressure dependent voltage are arranged. The central Chucking 7 has two ends on to a front end is a first, preferably a circular or cylindrical flange 22 having a through opening 30 formed on the introduction of a bolt. 2 At the other Front end is a second, preferably a rectangular, flange 23 with two diametrically projecting from the periphery, flexible elastic arms 28, 29 are formed, which are integrally formed on the second flange 23rd Flange 23 has, as is the first flange 22, at its center in the longitudinal center a through hole 30 through the guided the free end 2a of the bolt 2 and fixed with a nut 3 is screwed, that the screw head 2b of the screw bolt 2 on the first Flange 22. To absorb radial forces is the first, preferably cylindrical flange 22 mounted on roller bearings in an outer casing, not shown. Via the second, preferably rectangular, the flange 23, the entire When tightening the screw (2, 3) applied torque M_A about the two flexurally elastic arms 28, 29 are also derived in the housing.

For the measurement of a head frictional moment M_K dependent torsional is represented slightly enlarged on the central chucking 7 at least one Point Number 5 provided. Preferably two similar to 180 ° relative to each other on the periphery of the chucking sleeve 7 arranged offset measuring points 5 for a Measurement of the head frictional moment M_K dependent torsional provided. The arranged thereto in a measuring point 5 strain gauges 50 are in offset an angle of 90 ° to each other. To the longitudinal axis 8 of the Chucking 7, the angle of the strain gauges 50 respectively 45 °.

Another measuring point 6 is used to measure one of the axial preload force F_Vdependent compressive stress and is also on the central chucking 7 arranged. In the measuring point 6 two strain gauges 60 are arranged, wherein a wire strain gauge parallel and the other transverse to the longitudinal axis 8 of central chucking 7 is arranged.

For the measurement of the total torque M_A dependent bending stress is on the two preferably rectangular shaped resiliently flexible arms 28, 29 provided at least one measuring point 4, the two strain gauges 40 includes, like the strain gauge 60 to each other and to the longitudinal axis 8 of the central chucking 7 aligned.

Preferably, each always at least two pairs of strain gauges 40, 50, 50a, 60 arranged so that a Wheatstone measuring bridge can be formed.

For maximum or full decoupling of the influences of the Biasing force F_V dependent compressive stress on a measuring point 5 of the Head frictional moment M_K dependent torsional stresses is inventively the measuring point 5, 5a for the head frictional moment M_K dependent Torsional stress by mechanical means of an influence of the axial Biasing force F_V dependent pressure voltage decoupled.

According to FIG. 1, the mechanical decoupling in particular by the central Chucking 7 introduced relief slots 9, 10 and relief recesses 11, 12 achieved. The relief slots 9, 10 are on the central Chucking 7 transversely introduced to the longitudinal axis 8 of the fixed sleeve. 7 The Length of the relief slots 9, 10 is preferably greater than the distance between them, preferably one and a half as large, in particular twice as large as its Distance from each other by the discharge slots 9, 10, as schematized and fragmentary enlarged in FIG. 2 with a portion of a abgewikelten arranged on the central chucking 7 of FIG. 1 from the measuring point for the Head frictional moment M_K dependent torsional shown, a web-like Section 13, also referred to as web 13, formed in the center of the measuring point 5 is disposed with the strain gauges 50th Lift the relief slots 9, 10 the voltage waveforms in the cylindrical chucking 7 at least partially on or channel these. Particularly upsetting (compressive stress) of the central Chucking 7 through the axial preload force F_V is by the Relief slots 9, 10 maximum or completely in the measuring point 5 collected. A shear (torsion stress) of the cylindrical surface of the central chucking 7 by a Unifangskraft M_K/ R in FIG. 2 represented disproportionately and additionally by means of a dashed line in is a maximum or completely tothe web 13 and thus undiminished transferred to the strain gauges arranged there 50th On Crosstalk of the biasing force F_V in the measuring point 5 for the head friction torque M_K is reliably switched off.

Targets and action directions of forces and moments, especially F_V, M_Aand M_KAre schematically indicated by arrows in FIGS. 1 to 9.

Fig. 3 shows how the measuring points 5 and 6, preferably on the central chucking 7 can be arranged. This is shown schematically a total of unsettled 7 disposed portion of the central chucking according to FIG. 1 with partly Measuring points 5, 6 for the head frictional moment M_K dependent torsional and the biasing force F_V dependent compressive stress shown. Preferably are each two identical measuring points 5, 6 offset by 180 ° to each other arranged on the periphery of the central chucking 7th During the Measuring point 6 by the biasing force F_V dependent compressive stress undiminished can act, the measuring point 5 is for the head frictional moment M_K dependent Torsional stress by the relief slots 9, 10 with respect to the biasing force F_V relieved. The shear (torsional) in the fixed sleeve 7 is unabated onto the web 13 between the discharge slots 9, 10 and thus on the Point Number 5 transmitted. Since the determined by the relief slots 9, 10 share the total cross section no longer apply the biasing force F_V to disposal is, wherein this and the following embodiments of the invention the wall thickness D of the central chucking 7 adapted accordingly, that a Congestion is avoided. To the torsional deformation at the measuring point 5 of the Head frictional moment M_K compared to designs according to the prior art to Zoom, is preferred according to the wall thickness D in the range of Web 13 selectively reduced to a wall thickness d. This is also possible, because at this point just a burden by the biasing force F_V occurs. A Such a reduction of the wall thickness D, for example, by milling, grinding or spark erosion removal done, so that in the region of the web 13 or the Point Number 5 for the head frictional moment M_K dependent torsional a flattening of the cylindrical chucking the rest 7 or even a Bag arises. The relief slots 9, 10 are for example likewise by Milling or spark erosion cutting to produce.

In FIG. 4 a further preferred embodiment according to the invention shown. For mechanical decoupling of the measuring point 5 for the head friction torque M_K dependent torsional stress of the of the biasing force F_Vpressure dependent voltage is used here, as shown, at least one Relief slot 9. For the targeted transfer of shear (torsional) on the web 13 are two thin tongues 14, 15 which in alternating directions of rotation one from the head frictional moment M_K dependent torsional alternately Train and pressure are claimed. The web 13 for the point 5 of the Head frictional moment M_K dependent torsional stress is through two rectangular Relief recesses 11, 12 is limited, the approximately perpendicular to Longitudinal extent of the relief slot 9 are arranged and the thin Tongues 14, 15 form. The thin blades 14, 15 are through the relief recesses 11, 12 from the influence of the biasing force F_V dependent Compressive stress maximum exempted. In this embodiment, which are the Point Number 5 for the head frictional moment M_K facing dependent torsional Side walls of the relief recesses 11, 12 as straight lines executed, and the side walls thereby form the web 13, the wall thickness d in the area of ​​the measuring point 5 for the head frictional moment M_K dependent Torsional stress is carried out less than the rest of the wall thickness D of the central Chucking. 7

The increase in the torsional deformation at the measuring point 5 for the head friction torque M_K dependent torsional stress, according to the Embodiment of FIG. 5 in addition in by a local constriction 16 central region of the web 13, possibly while retaining the material thickness D be achieved, said local constriction 16 by preferably semicircular extensions in the central region of the measuring station 5 for the the head frictional moment M_K facing dependent torsional Side wall of the relief recesses 11, 12 is formed. The measuring point of 5 for the head frictional moment M_K remote dependent torsional Pages do not extend preferably over the length of the relief slot 9 and 10 respectively.

Finally, a combination of the foregoing is possible, which all measures for at least partial local repealing particular Compressive stress curves show in the central chucking 7, wherein the Measuring points 5 and 6 are arranged on the central chucking 7th

In the following embodiments are only the measuring points 6 to the Measuring one of the biasing force F_V dependent on the compressive stress central chucking 7 arranged.

Fig. 6 shows schematically a torsionally and compressively elastic cylindrical central Chucking 7 a force / torque transducer 1, on the at least one measuring point 6 for an axial of the biasing force F_V dependent compressive stress is arranged, and of an outer sleeve 17 coaxially surrounded, on the at least one measuring point 5 for the head frictional moment M_K dependent torsional is arranged, which by a pressure-elastic torsion Membrane is decoupled 18; the head from the friction torque M_K dependent torsional is thus measured on an outer sleeve 17th Observation point 5 for the head from the friction torque M_K dependent torsional stress is to do so by Influences of the preload force F_V pressure dependent voltage across at least one diaphragm 18 largely decoupled.

The bearing or support of the torsion and pressure elastic central Chucking sleeve 7 is effected as described above to FIG. 1, described in a not shown Housing. The measurement of the total torque M_A dependent bending stress takes place also on the flexurally elastic arms 28, 29, the integrally the second, preferably rectangular, flange 23 of the central chucking 7 formed. The outer sleeve 17 has in the embodiment of FIG. 6 is a cup-like shape with a adjacent to the outer edge 33 of its open Side molded inner flange 24 and a circular bottom plate 26 a hole 27 through which the central chucking 7 extending therethrough, so that the base side the outer sleeve 17 via the rectangular bottom plate 26 at Flange 23 of the central chucking 7 and on its open side via an intermediate the flanges 22, 24 arranged circular diaphragm 18 elastically pressure and is held torsionally.

The diameter of the hole 27 in the bottom plate 16 is greater than that of the central chucking 7 and smaller than the edge length of the second, preferably rectangular, nearly square, flange 23. At their, the resiliently flexible arms 28, 29 facing page supports the bottom plate 26 the outer sleeve 17 from the flange 23 and forms in the area where a especially play-free connection. Through this connection, the process variable or the measured value for the head frictional moment M_K dependent torsional stress in the measuring point 4 for the total torque M_A derived. The total moment therefore does not rely on centralized chucking 7, but will her passing directly above the two resiliently flexible arms 28, 29 in the housing derived. In the area of ​​the measuring point 5 for the head frictional moment M_K dependent Torsional stress includes the outer sleeve 17 have a smaller thickness d, as in the region extending from the measuring point 5 for the head frictional moment M_Kdependent torsional extends away.

Finally, the circular diaphragm 18 has at least one circumferential bead 19, the crosstalk of the biasing force F_V in the measuring point 5 for the Head frictional moment M_K dependent torsional largely minimized.

Alternatively, to a bottom plate 26, as shown in Fig. 7, a second pressure elastic torsion circular diaphragm 18 between the outer its sleeve 17 and flange 23 is attached, like a lid between a circular, is integrally formed on the outer sleeve 17, inner flange 25 and the second flange 23 extends.

Another mechanical decoupling of the measuring point 5 for the head friction torque M_K dependent torsional stress from the axial of the biasing force F_Vdependent pressure voltage is preferable in the invention by appropriate selection a geometrical arrangement of the measuring point 5 for the head friction torque M_K dependent torsional stress on the outer sleeve 17, in particular by Choice of a length L of Meßstellenbereiches 5 on the outer sleeve 17, a Radius R of the outer sleeve 17, and a thickness d of the outer sleeve 17 in the region the measuring point 5 for the head frictional moment M_K dependent torsional stress, so that the influence of shearing (torsion stress) at the measuring points 6 for by the biasing force F_V dependent compressive stress on the inner chucking 7 is significantly minimized.

In addition to reducing the material thickness D in the field of measuring points for 5 the head from the friction torque M_K dependent torsional stress on the outer Sleeve 17, the sensitivity of the measuring points 5 for the head friction torque M_K dependent torsional by example radial bores or relief slots 9, 10 and relief recesses 11, 12 as in the description of Figs. 1 - 5 were discussed above, can be increased.

Also in the embodiment of Fig. 8 by the biasing force F is_Vdependent compressive stress measured on the central chucking. 7 Schematically shown in FIG. 8 is a torsion and pressure flexible cylindrical central Chucking 7 a force / torque transducer 1, in which at least one Measuring point 6 for an axial of the biasing force F_V dependent compressive stress is arranged, and of an outer sleeve 17 is coaxially surrounded so that a the head frictional moment M_K dependent torsional stress as a pressure elastic torsion membrane and the outer sleeve 17 in two Connecting arms 31, 32 acts, that in particular on the side surfaces of the link arms 31, 32 in at least one measuring point 5 a head from friction torque M_K dependent bending stress is measurable. The decoupling of the measuring points 5a, 6 from each other via a disposed between the flanges 22, 24 Membrane 18, a circumferential bead has 19th The outer sleeve 17 is as open at both ends cylindrical design and has over its entire axial length of a uniform material thickness on D, ie, the outer sleeve 17 serves as the diaphragm 18 only for the transfer of the head frictional moment M_K dependent Torsional stress. On rectangular flange 23 in addition to the flexurally elastic arms 28, 29 on the side walls 34, the one-piece connection arms 31, 32, which in its length and / or thickness of up to resiliently flexible arms 28, 29 may differ, formed. By appropriate Determining the length and the thickness of the connecting arms 31, 32 can Sensitivity of the measuring point 5a of the head frictional moment M_K dependent Bending stress be optimally designed. At its the connecting arms 31, 32 side facing the outer sleeve 17 with the arms 31, 32 of the flange 23, especially without play, connected, for example by screwing and / or Welding. The strain gauges 50a in the measuring point 5a are like Strain gages 40 and 60 to each other and to the longitudinal axis 8 of the central Chucking 7 arranged. The measurement of the head friction torque M_K done thus subjected to bending stress on the connecting arms 31, 32 of the second, preferably rectangular, flange 23. All that while tightening Screw applied torque M_A will turn on the resiliently flexible arms 28, 29 measured in the measuring points 4 and on the resiliently flexible arms 28, 29 derived in a non-illustrated housing.

Fig. 9 shows schematically a torsion and pressure flexible cylindrical central Chucking 7 a force / torque transducer 1, in which at least one Measuring point 6 for an axial of the biasing force F_V dependent compressive stress is arranged, and of an outer sleeve 17 coaxially surrounded, on the at least one measuring point 5 for the head frictional moment M_K dependent torsional is arranged, which by at least one elastic pressure torsionally rigid bellows or compensator 20, 35 is mechanically decoupled. For this purpose, the bellows or compensator 20, 35 at least one shaft 21.

A first, known per se bellows or compensator 20 with at least one shaft 21 is in the embodiment of Fig. 9 between the flange 22 and the outer Sleeve 17 mounted form-fitting. A second bellows or compensator 35 with at least one shaft 21 connects the outer sleeve 17 via a bottom 36 with the rectangular flange 23. The connection is form-fitting, said positive connection, for example by screwing, clamping, Gluing or welding can be made. The first, preferably cylindrical flange 22 is for reasons of assembly in this embodiment, not integrally formed on the central chucking 7 but is applied to the central chucking 7 plugged. The Ste ckverbindung can both loose be formed and for example screwed. To measure the head friction torque M_K dependent torsional stress is on the outer sleeve 17 arranged measuring point. 5

FIG. 10 shows schematically a torsion and pressure flexible cylindrical central Chucking 7 a force / torque transducer 1, in which at least one Measuring point 5a for an axial of the biasing force F_V dependent compressive stress is disposed, which by an outer sleeve 17 is coaxially surrounded so that one from the head frictional moment M_K dependent torsional so on at least one pressure-elastic torsionally rigid bellows or compensator 20, 35 and acting on the outer sleeve 17 at two connecting arms 31, 32 that in at least one measuring point 5 a head from friction torque M_K dependent Bending stress is measurable.

A first a conventional bellows or compensator 20 with at least one shaft 21 is like the embodiment of FIG. 9 between the first flange 22 and the outer sleeve 17 is mounted form-fitting. A second bellows or compensator 35 with at least one shaft 21 connects the outer sleeve 17 directly to the second flange 23 integrally formed connecting arms 31, 32. The Connection is positively locking, wherein the positive connection for example by screwing, clamping, gluing or welding may be made. The cylindrical flange 22 is also as shown in FIG. 9 describes running plugged. To measure the head friction torque M_K dependent torsional stress is placed on the two offset by 180 ° Connecting arms 31, 32 at least one measuring point 5a, preferably in each case a Measuring point 5a for measuring the head frictional moment M_K dependent Bending stress placed.

The embodiments according to the figures 6 to 10, it should be noted that in particular through appropriate design of the central chucking 7, the Membrane 18, the bellows or compensator 20, 35 and / or the outer sleeve 17 the relationship of the preload force F_V or compressive stress dependent Crosstalk signal (disturbance) to the measured signal (useful variable) for the head friction torque M_K pending torsional or bending stress is so influenced that the ratio is sufficiently small. In addition, by suitably designing in particular the central chucking 7 and the outer sleeve 17, the ratio the measurement signals (Nutzgrößen) for the head frictional moment M_K dependent Torsion and bending stress and for the biasing force F_V dependent Compressive stress so influenced, for example, that about the same high measurement signals (Nutzgrößen) are achievable.

The special shapes of a force / torque transducer 1 according to the inventively preferred embodiments allow advantageously Thus, the determination of the total tightening torque M_A, The head friction torque M_K and the biasing force F_VAs in international standards and domestic standards For example, the major car manufacturers are required. Moreover, with a measuring device according to the invention, the inherently difficult to accurately measuring head frictional moment M_K detected with increased accuracy and in conformity evaluable. This also the thread friction torque is M_Gbe determined more accurately and a more secure statement about quality and reliability of the screw 2, 3 possible.

By means of additional hardware Soff- and have the results of friction coefficients output protocols and if curves and tables will. Screws manufacturers can with existing software quickly and without Retrofitting various bolt 2 according to different standards Check and mitliefern the protocols to its customers.

The invention is preferably suitable for use in quality assurance, in particular in the automotive industry. Überschraubmomente of self-locking nuts 3 are another area of ​​application, as well Incoming inspection and research and development.

LIST OF REFERENCE NUMBERS

<dl tsize="7" compact="compact"><dt>1</dt><dd>Force / torque transducer</dd><dt>2</dt><dd>bolt</dd><dt>2a</dt><dd>free end of the bolt 2</dd><dt>2 B</dt><dd>Head of the bolt 2</dd><dt>3</dt><dd>mother</dd><dt>4</dt><dd>Measuring point for the total torque M_A dependent bending stress</dd><dt>5</dt><dd>Measuring point for the head frictional moment M_K dependent torsional</dd><dt>5a</dt><dd>Measuring point for the head frictional moment M_K dependent bending stress</dd><dt>6</dt><dd>Measuring point for the axial of the biasing force F_V dependent compressive stress</dd><dt>7</dt><dd>central chucking</dd><dt>8th</dt><dd>Longitudinal axis of the chucking sleeve 7</dd><dt>9, 10</dt><dd>relief slot</dd><dt>11, 12</dt><dd>relief cut</dd><dt>13</dt><dd>web</dd><dt>14, 15</dt><dd>tongue</dd><dt>16</dt><dd>constriction</dd><dt>17</dt><dd>outer sleeve</dd><dt>18</dt><dd>membrane</dd><dt>19</dt><dd>Bead of the diaphragm 18</dd><dt>20, 35</dt><dd>Bellows or compensator</dd><dt>21</dt><dd>Wave of the bellows 20, 35 and the compensator 20, 35</dd><dt>22</dt><dd>first, preferably cylindrical flange of the central chucking 7 </dd><dt>23</dt><dd>second, preferably rectangular, the central flange chucking 7</dd><dt>24, 25</dt><dd>Internal flanges of the outer sleeve 17</dd><dt>26</dt><dd>baseplate</dd><dt>27</dt><dd>hole</dd><dt>28, 29</dt><dd>resiliently flexible arms</dd><dt>30</dt><dd>Through hole</dd><dt>31, 32</dt><dd>connecting arms</dd><dt>33</dt><dd>Outer edge of the outer sleeve 17</dd><dt>34</dt><dd>Side walls of the rectangular flange 23</dd><dt>36</dt><dd>plate</dd><dt>40</dt><dd>Strain gauges for measuring the total torque M_A dependent bending stress</dd><dt>50</dt><dd>Strain gauges for measuring the head friction torque M_K dependent torsional</dd><dt>50a</dt><dd>Strain gauges for measuring the head friction torque M_K dependent bending stress</dd><dt>60</dt><dd>Strain gauges for measuring an axial of the biasing force F_V dependent compressive stress</dd></dl>