DE4229569C1 - Machine tool with telemetry monitoring system for tool shaft - uses sensor element attached to shaft and coupled to amplifier on outside of housing half shell enclosing shaft - Google Patents

Abstract

The telemetry monitoring system uses a sensor element (3) attached to a reduced dia. shaft section (16), coupled to an amplifier and an antenna supported by the shaft, with a cooperating stationary transmission/reception antenna (8), coupled to an evaluation and display circuit. The larger and smaller dia. shaft sections (15, 16) are enclosed by a housing (28) comprising two half shells (29, 30) at a given distance from the sensor element. The amplifier is attached to the outside face of one of the shells. Both shells are balanced so that no imbalance force is exerted on the amplifier. USE/ADVANTAGE - For wear monitoring during machine operation. Suitable for relatively small machine tool rotating at high r.p.m.

Description

The invention relates to a tool according to the preamble of Claim 1.

From "Technical Notices AEG-Telefunken 63 (1973), 7, pp. 278-284" is already a contactless measuring device for continuous detection temperature values on rotating parts. This messein direction can also be used with a tool for other purposes come, so generally serves to measure electrical and not electrical shear quantities, the measured value information rotating without contact the parts are transferred to a stationary apparatus.

A tool therefore already emerges from the cited literature reference With:

• - at least one telemetrically monitored wave, the first Shaft section and an adjacent second shaft section with ge has a reduced diameter compared to the former,
• a sensor element fastened on the second shaft section,
• - A sensor signal amplifier and a coupling antenna, which on the Shaft are mounted, and
• - A stationary connected to an evaluation and display unit ren transmit / receive antenna.

DE 28 46 583 C2 also describes a device for transmitting Measurement signals known via a transformer. There is a ring on a shaft flange mounted, which carries a first transformer part, which is coaxial lies to the shaft and rotates with it. On the face opposite the first Transmitter part is coaxially to the shaft, a second arranged stationary Transformer part.

It is also a power meter for a crank drive from the DE 37 22 728 C1 known. This is where a lei is measured stung z. B. on the bottom bracket of a bicycle. The pedaling force is determined by the ver Forming a suitable bending element on the strain gauge are arranged, converted into an electrical signal and by in  ductive transmission to one connected to the bicycle frame Delivered to recipient.

Sensor telemetry systems or sensor signal rotary transmitters are used for contactless sensor signal tapping on moving objects, in particular Waves, through contactless HF transmission of sensor signal and Power supply between with moving sensor and stationary emp Catch antenna using highly integrated microelectronics. With  you can z. B. torques, forces, accelerations, temp temperatures, pressures and speeds in test benches, gearboxes, motors, etc., record. They therefore represent an alternative to the conventional ones Slip ring or mercury rotary transmitters.

Such a sensor signal rotary transformer is shown in FIGS. 1 and 2 of the present application. It consists of the sensor 1 already mentioned, which is firmly connected to a shaft 2 and rotated with it, as shown in FIG. 2. Sensor 1 includes a sensor element 3 , a sensor signal amplifier 4 with coupling antenna 5 and a voltage supply 6 , as shown in FIG. 1. The sensor element 3 Sen can be a strain gauge sensor, a pressure sensor, a semiconductor sensor, a thermocouple, etc.

The sensor signal amplifier 4 amplifies, depending on the selection of the amplification factor, the sensor signal from the sensor element 3 and converts it into a digital signal. A double modulation process (FM / AM) is used to guarantee high immunity to electromagnetic interference and mechanical vibrations. The modulated sensor signal is transmitted to a stationary evaluation unit 7 , specifically via a receiving antenna 8 , which is connected to the evaluation unit 7 via a coaxial cable 9 . At the same time, the sensor signal amplifier 4 and the sensor element 3 are supplied with energy via the receiving antenna 8 and the coupling antenna 5 . For this purpose, the receiving antenna 8 generates a high-frequency magnetic field, which is received by the coupling antenna 5 and is converted by the sensor signal amplifier 4 into the supply energy for the sensor signal amplifier 4 and the sensor element 3 . The voltage source 6 serves to keep this supply voltage constant.

The evaluation unit 7 converts the digital sensor signal coming from the sensor signal amplifier 4 into an amplified analog sensor signal, with the aid of an input-side evaluation circuit 10 and a downstream sensor signal channel 11 . The converted and amplified sensor signal can then be fed to a processing device 12 for further processing. It can also be a digital display 13 to be displayed. An integrated trigger brand generator circuit 14 allows rotating shafts 2 egg ne rotation angle-related measurement signal processing. If an amplitude pulse is generated per shaft revolution, this can be determined in the evaluation circuit 10 and reported to the trigger mark generator circuit 14 . Its output is also connected to units 12 and 13 for further processing or display of speeds.

Standard sensors can be used as sensors. Strain gauge resistors (strain gauge resistors) can be used in full, half or quarter circuit since a sufficient sensor supply voltage is provided by the sensor signal amplifier 4 . For thermocouples, a temperature compensation compensation can be provided in the sensor signal amplifier 4 . In addition, photo resistors, magnetic field sensors, piezo crystal sensors, etc. can also be used as sensor elements. A further suitable voltage is available at sensor signal amplifier 4 for active sensors.

In the structure according to FIG. 2, a moment measurement is carried out per revolution, this structure when tapping static measured variables, eg. B. the temperature or a static torque, can be used. However, there are problems with the circumferential arrangement of the sensor with regard to balancing, the safe positioning of the sensor on the shaft circumference and problems in accommodating the sensor, particularly in the case of small and compact tools.

The invention is based, the To design the tool structure so that wear monitoring continuous operation under harsh operating conditions. In particular in particular, this type of monitoring should also be used for relatively small and compact tools and especially with high ones Unbalanced speeds are possible.

The solution to the problem is in the characteristic ning part of claim 1 specified.  

Advantageous embodiments of the invention are can be found in the subordinate claims.

The tool according to the invention has the following advantages:

• 1. Since the sensor element is in a shaft section, the ge compared to other shaft sections on a reduced diameter has practically no axially directed forces from the outside act on the sensor element, thereby preventing damage or an unwanted move is protected.
• 2. The enveloping body also completely covers the sensor element, so that it is also protected against radial external forces.  
• 3. The envelope consists of 2 half-shells, one of which is the Sen signal amplifier carries. The weight from the half carrying the sensor signal amplifier shell and the sensor signal amplifier can at least approx be selected equal to the weight of the other half-shell, so that the overall device also shows good balancing behavior.

According to a very advantageous development of the invention, the first and the second shaft section between further shaft sections that larger diameter than the first shaft section exhibit. This results in an even better protection of the enveloping body pers and the underlying sensor element, which immediately on the second shaft section is attached.

The coupling antenna is ring-shaped around the first or second wave cut around so that it could be used in the case where the first and the second wave section is lower, on one of the other waves can support cuts. This ensures good axial securing of the Coupling antenna achieved. The coupling antenna also projects radially Direction not very far beyond the other wave sections, see above that several waves of the type mentioned are arranged closely adjacent can. Preferably, the coupling antenna with the other waves sections are aligned. Also the Sen attached to one of the half-shells The signal signal amplifier does not protrude very far in the radial direction the other shaft sections out, so that he too a compact off design of the tool, even in the case of multiple shafts.  

The enveloping body can on its first shaft section facing end facing inwards have pointing noses, which are located on the second shaft section support. These noses serve to stabilize the envelope for the In case the first wave section does not give it enough support. The noses can also be omitted if the enveloping body is the first wave cut overlaps and is relatively stable so that it is on cannot execute radial vibrations at its free end.

The half-shells are preferably equipped with flanges over which connected them together, e.g. B. are screwed. The flanges are on the axially extending sides of the half-shells and ste hen radially outwards from these. Instead of the flanges Half shells on these sides but also thickening areas sen, with tangential through holes / through passage openings for screw admission are provided.

According to a very advantageous development of the invention, one of the Half-shells in two lying one behind the other in the wavelength direction Half-shell sections divided, of which only one is in engages a groove running tangentially in the first shaft section, while the other half shell carries the sensor signal amplifier.

The sensor signal amplifier is therefore on the undivided half scha le, during one of the half-shell sections, which over the sensorele ment comes to rest, is carried by the other half-shell. Of the second half-shell section, which lies above the groove and also from the other half shell is worn in its inner area trained that there is an approach, which in the Groove can grip. In other words, both have half-shell sections te in the inner area on a different structure, so that it easy is to make them separately.

The half-shell carrying the sensor signal amplifier is flat  Outside surface equipped to the sensor signal amplifier to be able to attach better, preferably a cuboid structure door. Both components are e.g. B. glued together.

To the signal amplifier and the envelope body carrying it and the To protect the coupling antenna from contamination, the shaft in it Section, wear a shrink tube that sits firmly on the shaft and thus fulfills the protective effect mentioned above.

Are several tools lying parallel to one another in one plane There are waves on which there is a sensor signal amplifier ker and a coupling antenna are located so that they are tele can be monitored metrically, so all waves are preferred driven simultaneously and in the same way, so that for the case where e.g. B. the sensor signal amplifier protrudes beyond the wave range, there is no danger that the sensor signal amplifiers are adjacent the waves touch each other.

The parallel shafts are located in one factory witness head, which on the inside contains the transmitting and receiving antennas for carries the respective sensor signal amplifier. This send and receive so antennas are the respective coupling antennas of the differ Chen waves and are ge by shielding from each other separates, which prevents crosstalk of signals. This Shielding plates are more suitable on the inside of the tool head Fastened way, for example by screwing or by Ver welding.

A tool with one or more of the above telemetrically Watched shafts can be a thread forming tool, for example differs from a tap in that the wall material to form the thread is compressed and not cut. In this case, threads are formed in the end faces of the shafts mentioned always applicable.  

However, other machining devices can also be used with the shafts be connected, for example drills, milling cutters, taps, and the same. In all these cases, z. B. a torque over Carry out a watch to prevent signs of wear from the above-mentioned Bear processing elements such as thread formers, taps, drills, etc., to be able to determine.

For this purpose, the sensor element is preferably made of Deh voltage measurement strips, which are firmly glued to the second shaft section are. The strain gauges run at 45 ° to the shaft se. Preferably, the strain gauge resistors are in full, half or quarter circuit switched, with a suitable sensor supply voltage is provided by the sensor signal amplifier. The DMS Full and half bridges can be connected without additional elements the. The resulting resistance depending on the torque change in the strain gauge bridge is converted into a frequency change and transmitted to the evaluation unit via the receiving antenna. At the exit the evaluation unit stands next to the one proportional to the torque Voltage signal (sensor signal) additionally the speed signal available supply, which is also obtained in the receiving antenna.

The invention is described below with reference to the drawing in described. Show it:

Fig. 1: the circuit design of a conven tional sensor signal resolver,

FIG. 2 shows the arrangement of the conventional rotary transformer sensor signal with respect to a, to be monitored shaft

FIG. 3 shows an embodiment of the invention a, to be monitored shaft

Sift according to the invention configured waves in side and top view with the corresponding Schnittan: Fig. 4

FIG. 5 shows a front view of a threaded drill head,

FIG. 6 shows the output of an evaluation unit of the Sen-sorsignal rotary transformer at a kontinuierli chen manufacturing process in which repeated threads are formed,

FIG. 7 shows the output signal of the evaluation unit for a single thread forming process,

Fig. 8: formers the time-dependent rotational speed profile of a thread,

Fig. 9: the time-dependent feeding of the thread,

Fig. 10: the associated time-dependent Momentenver run, and

Fig. 11: the time-dependent torque curve during the formation of a thread with a new thread form and with a thread former with which 36,000 threads have already been formed.

An embodiment of the invention will be described in more detail with reference to FIGS . 3 to 11.

According to FIG. 3, a shaft 2 has a first shaft section 15 and a second shaft section 16 adjacent thereto. The diameter of the first shaft section 15 is larger than the diameter of the second shaft section 16 . Both shaft sections 15 and 16 are delimited by further shaft sections 17 on the left in FIGS. 3 and 18, 19 on the right in FIG. 3. The drive of the shaft 2 takes place on the right-hand side via the further shaft section 19 , while in the further shaft section 17 z. B. a thread former, not shown, can be placed on the end face. For this purpose, the further shaft section 17 has a blind hole 20 , which is provided with a thread 21 at its lower end. The further shaft sections 17 , 18 and 19 are larger in diameter than the first shaft section 15 .

In the area of the first shaft section 15 there are two parallel tangential grooves 22 on opposite shaft sides. They serve to hold an enveloping or clamping body, as will be explained below.

On the far right in FIG. 3, sections along line AA and line BB are shown.

Fig. 4 shows two of the shafts shown in Fig. 3 in Parallelanord voltage, which are rotated 90 ° against each other. These waves each carry a sensor 23 , to which a sensor element 3 , a sensor signal amplifier 4 and a coupling antenna 5 belong.

In the present case, the sensor element 3 is designed as a strain gauge element whose strain gauge resistances run at 45 ° to the longitudinal axis 24 of the shafts 2 . The sensor element 3 is on the second wel lenabschnitt 16 and is firmly connected to this, for. B. glued. The sensor element 3 Sen does not protrude in the radial direction of the first shaft section 15th

The coupling antenna 5 is located on the first shaft section 15 and abuts the end face of the adjacent further shaft section 17 . More precisely, the coupling antenna 5 consists of an annular carrier 25 which has a circumferential groove for receiving a coil winding 26 which is connected to the sensor signal amplifier 4 via wires 27 . The coil winding 26 can e.g. B. have only a single turn. The carrier body 25 consists of two half-shells which are glued to one another after being placed on the first shaft section 15 . At the same time, the carrier body 25 is adhesively connected to the further shaft section 17 , so that it is firmly positioned in this area.

As can be seen in FIG. 4, the transmitting / receiving antennas 8 are arranged in the immediate vicinity of the coupling antenna 5 , the antennas 8 being attached to a housing (not shown).

The sensor signal amplifier 4 , which is designed as a cuboid block, is fixedly arranged with its one main surface on an enveloping or clamping member 28 , which is positioned in the region of the first and second Wellenab section 15 , 16 . Sensor signal amplifier 4 and Klemmkör by 28 can be glued together.

The clamping body 28 consists of two half-shells 29 and 30 which are screwed together mitein. For this purpose, the half-shells 29 , 30 lateral flanges 31 , 32 , which are equipped with corresponding through / threaded openings 33 for receiving screws. In the axial direction, the clamping body 28 extends so far that it completely overhangs the grooves 22 in the first shaft section 15 and the sensor element 3 in the second shaft section 16 .

As can be seen in FIG. 4 in its lower part, the half-shell 30 is formed in one piece and rests on the left on the first shaft section 15 . The inner diameter of the half-shell 30 thus corresponds to the outer diameter of the first shaft section 15 . In contrast, the inner diameter is the half-shell 30 carries in its right area is larger than the outer diameter of the second shaft portion 16, which element the Sensorele 3, so that the sensor element 3 does not come with the half-shell 30 in contact. At the far right end of the half-shell 30 in FIG. 4, this can have inwardly pointing lugs 34 in order to be supported on the second shaft section 16 via these lugs. These lugs 34 can also be omitted with a stable design of the half-shell 30 .

The aforementioned half-shell 30 need not have a shoulder on its left side in FIG. 4 in order to engage in the groove 22 opposite it in the first shaft section 15 . This takes over the other half-shell 29 in connection with the other groove 22 , as will be explained.

This other half-shell 29 consists of two half-shell sections 35 and 36 lying one behind the other in the axial direction. They are assembled separately from one another, the one half-shell section 35 coming to the left above the groove 22 , while the other half-shell section 36 has a greater axial length and essentially covers the sensor element 3 . Both half-shell sections 35 , 36 are, as already indicated, screwed to the half-shell 30 , each separately.

The left half-shell section 35 has an inwardly projecting set 37 which engages in the opposite groove 22 . Through the sen approach 37 it is achieved that the clamping body 28 can no longer move in the axial direction of the shaft when the half-shell section 35 is connected to the half-shell 30 . The same applies to the other half-shell section 36 after connection to the half-shell 30 . This other half-shell section 36 can still be supported in the left region on the first shaft section 15 , that is to say have the same inner diameter as this. He then just comes to lie at a distance above the sensor element 3 and can also be supported at its right or free end via further lugs 34 on the two th shaft section 16 . A plurality of strain gauge elements 3 can be arranged distributed over the circumference of the second shaft section 16 .

The half-shell 30 carrying the sensor signal amplifier 4 can be made of material which is more easily than the half-shell sections 35 and 36 , so that the weight of the sensor signal amplifier 4 and half-shell 30 corresponds at least approximately to the weight of the half-shell sections 35 and 36 . In this way, an imbalance of the waves can be largely avoided. For example, the half-shell sections 35 and 36 can be made of copper, while the half-shell 30 can be made of aluminum.

The remaining space at the axial ends of the clamping body between this and the coupling antenna 5 on the one hand and the further Wellenab section 18 on the other hand can be filled with a non-conductive plastic material al to prevent dirt from getting inside the clamping body 28 . In addition, the shaft in the entire region of the first and second shaft sections 15 , 16 can be covered with a shrink tube 38 , which also overlaps part of the shaft sections 17 and 18 , in order to thus additionally protect the sensor from contamination.

On the right in FIG. 4, sections along line CC (top) and line DD (bottom) are shown.

Fig. 5 shows a tool head 39 , which is designed to receive four Wel len 2 , which are arranged in a plane and at equal distances from each other in parallel. This is a front view of the tool head 39 , the shafts 2 being cut in the area of the grooves 22 . The shafts 2 are designed in accordance with FIGS. 3 and 4. In the interior of the tool head 39 are located above or below the respective shafts 2 in the region of the coupling coil 5 shown in dashed lines and dot-dash line, the respective transmission / reception antennas 8. A mutual arrangement above and below is also possible. These transmit / receive antennas 8 are arranged on the inside of the tool head 39 . In Fig. 5, only the left hand shown at the antennas 8. They are also present over the right waves, although not shown in detail. A shielding plate 40 is located between the respective transmitting / receiving antennas 8 in order to prevent crosstalk phenomena during signal evaluation. It extends z. B. on both sides beyond the horizontal plane, as is provided. These shields 40 are fixed to the inside of the tool head 39 , z. B. screwed to this or welded ver. The tool head 39 itself contains a gear (not shown) for synchronously driving all shafts 2 and is, for. B. filled with gear oil, which is under positive pressure. To connect the sensors to the shafts 2 to protect against external influences even better 23, this can take place with a shrink tube 38 for also with a metallic sleeve. B. aluminum coated.

In the tool head 39 z. B. from the front insert four thread formers, which can then simultaneously form four threads.

The wear monitoring during thread forming using the shafts shown in FIG. 4 is described in detail below with reference to FIGS. 6 to 11.

It is assumed that only one thread former is monitored, the is new, is coated with TiN, is able to thread one size of M 2.5 and with a molding speed of v = 25 m / min. is moved. The sensor signal obtained is low-pass filtered (f = 10 Hz).

If a continuous manufacturing process takes place, threads are formed in an uninterrupted sequence, the signal curve according to FIG. 6 will be maintained, in which the torque in Nm is applied over time in seconds. This is the low-pass filtered sensor signal at the output of the evaluation unit 7 in FIG. 1. This sensor signal is fed to the processing device 12 for further processing.

Fig. 7 shows a section of the sensor signal shown in Fig. 6 for a single manufacturing process. This signal is thus obtained when only one thread is formed. A weak maximum M _{1 first} appears in the signal, which is obtained as a result of the acceleration of the thread former. In other words, its inertial mass must first be overcome here. Then a large maximum M _{2 appears} , which results directly from the thread forming. The signal then swings out.

The relationships are shown in more detail in FIGS. 8 to 10. Thus, Fig. 8 shows that the thread former is driven first with a posi tive speed and then with a negative speed. In the area of the positive speed it is led into the prepared hole to form the thread, while in the area of the negative speed it is pulled out of the then available hole. The feed is plotted in Fig. 9. These processes are in turn assigned to the signal curve in FIG. 10, that is to say the time curve of the torque for the formation of a thread. This course corresponds to that in FIG. 7.

In contrast, FIG. 11 for a single thread forming process the difference in the signal curve when using a new threads have been formed formers and using an old thread former, with the already 36000 thread. In the case of the new thread former, the maximum M ₂ assigned to the thread forming process lies far below the corresponding maximum M ₂ 'which is obtained when the old thread former is used.

If the sensor signal in FIG. 11 is recorded using the new thread former and stored as a calibration curve, the maximum M ₂ can be determined from this and also stored as a threshold value. In the subsequent thread forming processes with the same thread former, the maxima M ₂ ′ obtained in this way, which are likewise assigned to the corresponding thread forming processes, are compared with the maximum M ₂ , when the maximum M ₂ ′ is a predetermined distance from the maximum M ₂ exceeds an error signal is generated, which indicates that the thread form mer is worn. Such comparisons can be carried out for a wide variety of thread formers under the most diverse boundary conditions, for example for different materials into which threads are to be formed, for different thread sizes, under different material coatings of the thread formers, etc.

As already mentioned, the signal curve is stored in the new thread former and the maximum M _{2 is} stored in the processing device 12 . It also determines the maxima M ₂ ', compares this with the maximum M ₂ and possibly generates the error signal. This can be used directly to switch off the thread forming tool.

Claims (14)

1. Tool with

• - At least one telemetrically monitored shaft ( 2 ), which has a first shaft section ( 15 ) and an adjacent second shaft section ( 16 ) with a reduced diameter compared to the former,
• - A sensor element ( 3 ) lying on the second shaft section ( 16 ),
• - A sensor signal amplifier ( 4 ) and a coupling antenna ( 5 ), which are mounted on the shaft ( 2 ), and
• - A stationary transmitting / receiving antenna ( 8 ) connected to an evaluation and display unit ( 7 , 13 ), characterized in that
• the first and the second shaft section ( 15 , 16 ) are surrounded by an enveloping body ( 28 ) which has two half-shells ( 29 , 30 ) and which is supported on the first shaft section ( 15 ),
• - The enveloping body ( 28 ) comes to lie at a distance above the sensor element ( 3 ),
• - The sensor signal amplifier ( 4 ) on the outside of one ( 30 ) of the half-shells ( 29 , 30 ) is attached, and
• - Both enveloping bodies ( 29 , 30 ) are designed in terms of weight so that the sensor signal amplifier ( 4 ) does not cause any imbalance.

2. Tool according to claim 1, characterized in that the first and second shaft sections ( 15 , 16 ) lie between further shaft sections ( 17 , 18 ) which have a larger diameter compared to the first shaft section ( 15 ). 3. Tool according to claim 2, characterized in that the Kop pelantenne ( 5 ) is placed in a ring around the first or second shaft section ( 15 , 16 ) and is supported on one of the further shaft sections ( 17 , 18 ). 4. Tool according to one of claims 1 to 3, characterized in that the weight of the sensor signal amplifier ( 4 ) carrying egg NEN half-shell ( 30 ) and the sensor signal amplifier ( 4 ) at least approximately equal to the weight of the other half-shell ( 29 ) is. 5. Tool according to one of claims 1 to 4, characterized in that the first shaft section ( 15 ) has at least one tangential de groove ( 22 ) into which an extension ( 37 ) of the enveloping body ( 28 ) engages. 6. Tool according to claim 5, characterized in that the enveloping body ( 28 ) on its end facing away from the groove ( 22 ) has inwardly facing lugs ( 34 ) which are supported on the second shaft section ( 16 ). 7. Tool according to one of claims 1 to 5, characterized in that the half-shells ( 29 , 30 ) have flanges ( 31 , 32 ) via which they are connected to one another, preferably screwed. 8. Tool according to one of claims 1 to 7, characterized in that one of the half-shells ( 29 ) is divided into two half-shell sections ( 35 , 36 ) one behind the other in the longitudinal direction of the shaft, of which only one ( 35 ) into the groove ( 22nd ) engages, and that the other half-shell ( 30 ) carries the sensor signal amplifier ( 4 ). 9. Tool according to one of claims 1 to 8, characterized in that the half-shell ( 30 ) carrying the sensor signal amplifier ( 4 ) has a flat outer surface for receiving it. 10. Tool according to one of claims 1 to 9, characterized in that the shaft ( 2 ) carries a shrink tube ( 38 ), the sensor signal amplifier ( 4 ) and the envelope body carrying it ( 28 ) and the Kop pelantenne ( 5 ) covers. 11. Tool according to one of claims 1 to 10, characterized in that it has several in a plane parallel to each other wel len ( 2 ), each of which is monitored telemetrically, and that all waves simultaneously and in the same way are driven. 12. Tool according to claim 11, characterized in that between the respective transmitting and receiving antennas ( 8 ) shielding plates ( 40 ) are arranged. 13. Tool according to one of claims 1 to 12, characterized in that in the end faces of the shafts ( 2 ) thread formers can be used. 14. Tool according to one of claims 1 to 13, characterized in that the sensor element ( 3 ) from strain gauges is built up, which are glued to the second shaft section ( 16 ).