DE10307978A1 - Force measurement device for determining the force applied to brake shoes or blocks, has a disk-shaped force sensor with a resistive measurement bridge - Google Patents

Abstract

Device for determining the force applied by an actuator to a brake shoe comprises deformation sensitive measurement resistances (3) mounted on a deformable disk-shaped force sensor (2).

Description

The invention relates to a device for determining a force, for example one from an actuator on the brake blocks exercised in a motor vehicle Force resulting from strain sensitive measuring resistors geometry-dependent have electrical resistance values and an extensible force transducer is built up, with the strain-sensitive measuring resistors the surface of the stretchable force transducer are applied and in the force transducer initiated force over whose elongation causes an elongation of the strain-sensitive measuring resistors.

A device for determining a force of the type mentioned is known from the DE 101 51 561 A1 known. Here, strain gauge pairs are arranged on a measuring ring, in which axial input forces are introduced from one end face via axial projections and passed on as reaction forces via the other end face. A support area for the respective reaction force is provided in the middle between the projections on the opposite side. A pair of strain gauges is arranged between a projection and a support area of the measuring ring on a bending section.

A disadvantage of this device is that the force ring when used as a sensor in a motor vehicle brake, as an additional Component must be integrated into the brake. This component must be very positioned close to the thermally heavily loaded components of the brake become. Due to dirt on the surface of the force ring and thermal Loads on the measuring strips can significant measurement errors arise. In addition, the power ring a relatively complex external shape according to the prior art on.

The invention is based on the object a device for determining a force of the aforementioned Specify the type that is part of the power flow anyway Components can be easily formed and easily before thermal loads and be protected from contamination can.

According to the invention the object is achieved in that the stretchable force transducer is disc-shaped.

The invention has the advantage that the force transducer as a simple, rotationally symmetrical component is trained. Such a component is usually in the power flow of power transmission Assemblies available anyway, which is the integration of another Component unnecessary in the power flow makes.

At a first training course the strain sensitive measuring resistors on the surface of the Force transducer on at least two to the center of the disk-shaped force transducer arranged in concentric circles. With this arrangement of the measuring resistors results a particularly good measurement signal.

In one embodiment of the invention shows the disc-shaped Force transducers have a central hole. This has the advantage that another component, for example the spindle of an electromechanical Motor vehicle brake, can reach through the central hole and so the necessary powers the power transmission System can deliver. Through an advantageous adjustment of the diameter the central hole can affect the elongation behavior of the force transducer to be influenced.

In the case of further training, one is first group of strain-sensitive measuring resistors on one to the central one Hole concentric inner circle arranged on the force transducer and a second group of strain sensitive measuring resistors is on an outer circle concentric to the central hole on the force transducer arranged, with adjacent measuring resistors of the respective group equidistant are arranged. The arrangement of the measuring resistors on two concentric Circles create a particularly clear measurement effect, since the resistances at Load of the force transducer according to the invention stretched significantly differently on the inner circle than that on the outer circle.

At a next training are at least four strain-sensitive measuring resistors to at least one electrical measuring bridge connected. Electric bridge circuits deliver very precise measurement results, since there is a small change the electrical resistance value of a measuring resistor belonging to the bridge leads to a clearly measurable detuning of the measuring bridge.

In a next embodiment, the force is applied concentric in the area of the hole of the force transducer and the force is diverted concentric in the area of the outer edge of the Force transducer. Due to the symmetrical load on the load cell there are optimal elongation values, with the load cell very much high forces can record.

In one possible embodiment the force transducer is in one piece with a sleeve educated. For example, in the electromechanical motor vehicle brake anyway a leadership element that is made up of a perforated disc and a sleeve, it is advantageous the disc-shaped Section of the guide element to be designed as a force transducer and in combination with the measuring resistors To create a device for determining a force.

In one embodiment, the strain-sensitive measuring resistors are applied to an expandable, disk-shaped substrate, the diameter of which is preferably less than or equal to that of the force transducer and which is arranged concentrically on the force transducer and firmly attached to it sem is connected. It can be advantageous if the measuring resistors are first connected to a substrate, which can be formed, for example, as a thin film, and then applied to the force transducer together with the substrate. On the one hand, it is conceivable that the substrate is retained during the connection process with the force transducer and from then on forms an intermediate layer between the measuring resistors and the force transducer. On the other hand, it is also possible to thermally destroy the substrate, for example in a baking process, the measuring resistors in turn coming into direct contact with the force transducer. The person skilled in the art can choose from these possibilities according to the circumstances.

Alternatively, they are strain sensitive Sense resistors applied directly to the force transducer. Because the force transducer usually consists of metallic material, is in this embodiment to form an insulation layer on the metal beforehand. This succeeds for example in a so-called scaling process, in which a layer of metal oxide using oxygen and high temperatures on the metal surface is developed. Such a metal oxide layer forms a well-adhering one Insulation layer with which the measuring resistors can be intimately connected.

It is particularly advantageous if the force transducer is made of steel or a steel alloy. Steel or steel alloys have excellent ductility and the scaling process described above can with these Metals performed very well become.

In one configuration, the steel is or the steel alloy is thermally hardenable. Thermally hardenable steels change at the thermal treatment its elasticity, which is advantageous in used to manufacture the device for determining a force can be.

In the case of further training, those that are sensitive to stretching are Sense resistors form-fitting connected to the substrate and / or the force transducer. You can do this at Example recesses may be present on the substrate, in the one Resistance paste is introduced, which is then in a thermal Process for measuring resistance is cured. Through the recesses a well-defined volume can be filled with resistance paste and after curing the paste is form-fitting Connection between the substrate and / or the force transducer and the measuring resistors. This achieves precisely defined resistance values and the Sense resistors can can hardly separate from the substrate and / or the force transducer.

It is beneficial if the stretch sensitive Sense resistors and / or the measuring resistors connecting electrical lines on the substrate and / or Force transducers are applied in thick-film technology. alternative for this are the strain-sensitive measuring resistors and / or the electrical connecting the measuring resistors Lines to the substrate and / or the force transducer using thin-film technology applied. Both thick-film technology and thin-film technology are modern processes with which conductor tracks can be easily carried out and resistors in good quality made on planar surfaces can be.

In one configuration, the Sleeve out Steel or a steel alloy. The ductility and Strength properties of steel can be used to advantage. If the wall thickness the sleeve bigger or equal to the thickness of the disc-shaped Is force transducer, the expansion takes place primarily in the force transducer and the sleeve reserves their shape unchanged at. this makes possible a very accurate force measurement.

With an advantageous further education the force is applied concentrically via an additional one Ring, the ring being a wedge-shaped Has cross section and the wedge shape is selected such that the force transducer only up to that of the wedge-shaped Ring can stretch predetermined limit. This arrangement enables one very effective overload protection for the device according to the invention to determine a force, since the force transducer certain load completely on the wedge-shaped Cross-section of the ring creates and not be bent further can.

In a next embodiment, the force transducer and / or the substrate by radial boundaries in several the same size Sectors divided, each with a measuring resistor on the inner and another measuring resistor on the outer circle centrally in each Sector is arranged and at least one arranged on the inner circle Measuring resistor with at least one measuring resistor arranged on the outer circle to an electrical measuring bridge connected is. It is advantageous that with this device to determine a force, every possible stretch of the disk-shaped force transducer can be measured precisely.

It is advantageous if on the Force transducer and / or another measuring resistor on the substrate is arranged, the temperature on the force transducer and / or on the substrate. With a measured value for that on the force transducer and / or temperature prevailing on the substrate can cause a temperature drift the measuring bridge be compensated effectively.

In a further embodiment, a glass layer with a high electrical resistance is applied to the stretchable force transducer and the strain-sensitive measuring resistors are arranged on the glass layer. A glass layer can be melted easily and inexpensively onto a metallic force transducer and it forms an electrically very dense resistance layer. Short circuits of the measuring resistors to the earthed This effectively prevents force transducers.

The invention leaves numerous embodiments to. One of these is said to be based on that shown in the drawings Figures explained become. These show in

1 a device according to the invention for determining a force,

2 an advantageous embodiment of the device for determining a force,

3 : the in 2 force transducer shown in combination with a sleeve,

4 : an electromechanical motor vehicle brake,

5 : an interconnection of the strain-sensitive resistors to measuring bridges,

6 . 7 . 8th : various configurations for introducing the force into the force transducer,

9 : a force transducer with substrate and measuring resistors.

1 shows a device according to the invention 1 to determine a force. The device 1 a force transducer is used to determine a force 2 and a variety of strain-sensitive measuring resistors 3 , The strain-sensitive measuring resistors 3 are on an inner circle 8th and an outer circle 9 arranged. The force transducer 2 is designed according to the invention as a disc-shaped, flat component. The center on the surface of the disk-shaped force transducer is also the center of the inner circle 8th and the outer circle 9 , The measuring resistors 3 on the inner circle 8th are arranged equidistant to their respective neighboring measuring resistor. The measuring resistors too 3 on the outer circle 9 are arranged equidistant to their neighboring measuring resistors. In this embodiment there is a measuring resistor 3 on the inner circle 8th and a measuring resistor 3 on the outer circle 9 on one from the center of the disc-shaped force transducer 2 radial to the outer edge 6 the line of the force transducer.

But it is also conceivable that on the outer circle 9 arranged measuring resistors 3 to those on the inner circle 8th arranged measuring resistors 3 are arranged offset by a certain angle. If, as shown in this exemplary embodiment, four measuring resistors each 3 on the inner circle 8th and the outer circle 9 are arranged, it would be useful, for example, an offset between the measuring resistors 3 of the inner circle 8th and the outer circle 9 to choose from 45 °. It should be expressly pointed out that a larger or a smaller number of measuring resistors 3 on the inside 8th or the outer circle 9 can be arranged. As in this example, they can be arranged on radial lines or offset against one another as desired. In addition, the invention is not limited to two circles 8th . 9 with measuring resistors 3 limited. A larger number of concentric circles 8th . 9 on which measuring resistors 3 are arranged can be advantageous.

The measuring resistors are among each other 3 with electrical wires 13 to measuring bridges 10 connected. The measuring resistors and also the electrical lines 13 can be applied directly to the force transducer using thick-film technology or thin-film technology 2 be applied. For this it is necessary to use the mostly metallic force transducer 2 electrically isolate on the surface. Such insulation, for example of steel, can be carried out in a so-called scaling process, in which an oxide layer is formed on the surface of the steel at high temperatures and has an electrically insulating effect. However, it is also possible to melt a highly insulating layer of glass that adheres particularly well to the scale layer.

The strain-sensitive measuring resistors 3 have geometry-dependent ohmic resistance values. As long as in the force transducer 2 If no force is applied, all measuring resistors are located 3 in the unstretched state. The measuring bridge 10 is, apart from a compensatable offset, in the adjusted state. This creates the measuring bridges 10 no measurable signal in the power-free state. However, it becomes the center of the force transducer 2 a force is initiated which is a counterforce at the outer edge 6 of the force transducer 2 experiences, the force transducer deforms 2 and with it the measuring resistances deform 3 , Because the measuring resistors 3 on the inner circle 8th deform differently than the measuring resistors 3 on the outer circle 9 , experience the measuring bridges 10 Upsets. Such detuning manifests itself as a voltage shift at the measuring points of the measuring bridges 10 , This voltage shift at the measuring points of the measuring bridges 10 is the one on the load cell 2 initiated force proportional. The force on the force transducer 2 proportional electrical voltage shift will be evaluated by subsequent electronics, not shown here.

An advantageous embodiment of the device 1 to determine a force is in 2 shown. A disc-shaped force transducer 2 is again on an inner circle 8th and an outer circle 9 with four strain-sensitive measuring resistors each 3 stocked. Here too are the strain-sensitive measuring resistors 3 directly onto the surface of the force transducer 2 applied. At the center of the force transducer 2 there is a hole 4 , Through the hole 4 For example, a drive shaft for a ball screw can be guided. The introduction of force 11 now takes place on the inner edge 5 of the perforated force transducer 2 , The diversion of force 12 takes place on the outer edge 6 of the force transducer 2 , The force sensor becomes the force transducer 2 deformed what again in order to deform the strain-sensitive measuring resistors 3 leads. The strain-sensitive measuring resistors 3 are deformed to different degrees on the inner and on the outer circle, which leads to a shift in the electrical voltage at the measuring points of the measuring bridge, not shown here. Depending on the position of the measuring resistors 3 and the type of design of the force transducer 2 are the strain-sensitive measuring resistors 3 on the inner circle 8th and the outer circle 9 either stretched or compressed. It is possible that the measuring resistors 3 on the inner circle 8th or on the outer circle 9 are stretched or compressed to different degrees or the measuring resistances 3 on the inner circle 8th are stretched with the measuring resistors 3 on the outer circle 9 are compressed or the measuring resistors 3 on the outer circle 9 are stretched and the measuring resistances on the inner circle 8th are compressed. The possibilities mentioned depend heavily on the thickness 14 of the disk-shaped force transducer 2 in terms of attacking forces. The diameter of the hole also plays a role 4 in the load cell 2 play an essential role in the behavior of the entire component.

3 shows the in 2 described force transducer 2 in combination with a sleeve 7 that can be used as a guide element in a brake for a motor vehicle. In this embodiment, the force transducer according to the invention 2 in one piece with a sleeve 7 educated. On the sleeve 7 is a collar 21 formed. The force to be measured is on the inner edge 5 of the perforated force transducer 2 initiated and it plants itself over the force transducer 2 and its outer edge 6 to the sleeve 7 continued. The force transducer is deformed 2 instead, which also means the strain-sensitive measuring resistors 3 be deformed. This deformation leads to the detuning of the measuring resistors 3 formed measuring bridges, which in turn gives the measurement signal. The collar 21 on the sleeve 7 is used to transfer the applied force to a next component. Such a component can be, for example, the floating caliper of a disc brake installed in the motor vehicle.

Such a use of the force transducer according to the invention 2 is in 4 shown. 4 shows the application of the device according to the invention for determining a force in an electromechanical motor vehicle brake. Some components known from conventional hydraulic brake systems are also used in an electromechanical motor vehicle brake. 4 shows for example the floating saddle 20 , the brake disc 24 and the brake pads 23a and b. The brake blocks 23a . b during a braking maneuver using the floating caliper 20 and a component generating the braking force against the brake disc 24 pressed. In a conventional brake system, the mechanical braking force is generated by a hydraulic cylinder.

In the case of the electromechanical brake, the hydraulic cylinder is operated by a ball screw 19 replaced. The ball screw drive 19 is from a wave 18 driven by the second gear 17 and the first gear 16 with the electric motor 15 connected is. The electric motor 15 receives its electrical energy from a driver stage 27 with a signal processing system 26 connected is. The signal processing system 26 receives a brake signal 28 from the driver. With this brake signal 28 the electric motor is supplied by the driver 15 driven, causing the gears 16 and 17 are set in rotation, which in turn is over the shaft 18 the ball screw 19 drives. The ball screw drive 19 generates a force that the force-introducing element 36 against the force transducer 2 pressed. The opposing force is created via the foot 22 of the ball screw drive 19 on the first brake block 23a issued. The force-introducing element 36 is based on the force transducer 2 off, which in turn transfers the force over the sleeve 7 and the collar 21 to the floating saddle 20 emits. The floating saddle 20 includes the second brake pad 23b , which in turn against the brake disc 24 is pressed.

To the contact pressure of the brake pads 23a . b to the brake disc 24 To be able to control precisely, the force introduced must be measured. This measurement is carried out by the device according to the invention 1 to determine a force. Because the force-introducing element 36 against the force transducer 2 which in turn presses the force onto the sleeve 7 passes on, takes place with advantageous dimensioning of the force transducer 2 an expansion of the force transducer 2 , which in turn leads to a deformation of the strain-sensitive measuring resistors 3 leads. Because the strain-sensitive measuring resistors 3 are connected to a measuring bridge, they generate a measured value 25 , the signal processing system 26 is fed. With the help of this measured value 25 calculates the signal processing system 26 a manipulated variable that the on the brake pads 23a . b force required to perform the braking maneuver desired by the driver. This manipulated variable in turn becomes the driver stage 27 fed the electric motor 15 drives accordingly.

The connection of the strain sensitive resistors necessary for this regulation 3 to measuring bridges 10 is in 5 shown. 5 shows a schematic plan view of the device according to the invention 1 to determine a force with a force transducer 2 and strain-sensitive measuring resistors 3 , The strain-sensitive measuring resistances are indicated by the ellipses 3 combined into two groups. The two groups of strain-sensitive measuring resistors 3 will be according to the above The circuit diagrams shown are connected to measuring bridges.

For this exemplary embodiment, the interconnection became the Wheatstone measuring bridge 30 selected. Four measuring resistors each 3 are interconnected to a four-pole, the first pole with a voltage source 32 , the second pole with a ground point 31 and the two remaining poles with measuring points 33 are occupied. As long as in the force transducer 2 no force is applied, there is no deformation of the force transducer 2 and therefore no deformation of the strain-sensitive measuring resistors 3 , The measuring bridge 30 is therefore in a balanced state and at the measuring points 33 there is the same potential. Because the differential amplifier 29 no voltage difference registered in this state, it also generates no output signal.

However, there will be a force in the load cell 2 initiated, the strain-sensitive measuring resistors are deformed 3 , which in turn leads to potential differences at the measuring points 33 leads, the differential amplifier 29 measures a voltage from the differential amplifier 29 is amplified according to its wiring. This signal can be used as a direct measurement for the force transducer 2 introduced force are considered and the signal processing system 26 can be supplied as a controlled variable.

The 6 . 7 and 8th show different configurations for introducing the force into the force transducer 2 , where options are also shown, the force transducer 2 protect against mechanical overload. In each of the 6 . 7 and 8th is the force transducer 2 in one piece with the sleeve 7 educated. In the load cell 2 is a central hole 4 introduced and the strain-sensitive measuring resistors 3 are directly on the force transducer 2 positioned. In these exemplary embodiments, the force is generated by the force-introducing element 36 initiated.

In 6 the force is planted by the force-introducing element 36 via a washer 35 to a ring 34 with wedge-shaped cross section. First, the force introduced is over the highest point of the wedge to the inner edge 5 of the force transducer 2 forwarded. The force transducer 2 deforms in accordance with the force applied until a predetermined maximum force is reached. The gap closes when the maximum force is reached 40 between the ring 34 with the wedge-shaped cross-section and the force transducer 2 , The force transducer 2 has now reached a maximum intended stretch and will not be stretched further because of the force transducer 2 now completely on the ring 34 with the wedge-shaped cross section. This will overload the load cell 2 effectively prevented.

The design according to 7 effectively prevents overloading of the load cell 2 , Here is the lower ring 35 with a paragraph 37 Mistake. Paragraph 37 is in direct contact with the inner edge 5 of the force transducer 2 , With the introduction of a force via the force-introducing element 36 becomes the washer 35 against the force transducer 2 pressed. Paragraph 37 on the washer 35 enables the deformation of the load cell 2 , The washer bumps when a predetermined maximum force is reached 35 with its outer circumference against the force transducer 2 , causing further deformation of the force transducer 2 is effectively prevented.

A similar principle is in 8th shown with the washer 35 now with a ring 38 is combined with a square cross-section. The ring 38 with a square cross-section replaces the 7 known paragraph 37 , Because the ring 38 with a square cross-section is slightly higher than the washer 35 is that of the force-introducing element 36 force initially applied via the ring 38 with a square cross-section on the force transducer 2 transfer. The force transducer 2 will stretch due to the force introduced. When a predetermined maximum force is reached, the force transducer sets 2 near its outer edge 6 on the washer 35 on, which in turn causes the force transducer to overstretch 2 is effectively prevented.

In all of the exemplary embodiments considered so far, it has been assumed that the strain-sensitive measuring resistors 3 directly on the force transducer 2 be put on. Because the strain-sensitive measuring resistors 3 mostly manufactured in thick or thin film technology and the force transducer 2 Made of metallic material, mostly made of steel, are technologically demanding finishing processes of the force transducer 2 necessary to have liability between the force transducer 2 and the strain-sensitive measuring resistors 3 to enable and at the same time isolation of the measuring resistors from the metallic body of the force transducer 2 to reach.

9 offers an alternative embodiment in which the strain-sensitive measuring resistors 3 first on a substrate 39 are applied, which then with the force transducer 2 is connected. The substrate 39 should have the same or similar expansion coefficients as the force transducer 2 have. It is quite conceivable the substrate 39 to be made from insulating material such as ceramic, glass fiber reinforced material or thin film.

With the force transducer 2 can the substrate 39 for example by gluing, sintering, soldering, positive clamping or welding. Both the use of a substrate 39 as well as the direct loading of the force transducer 2 with the strain-sensitive measuring resistors 3 provide technological advantages ready, which will be applied according to the circumstances.

10 shows the top view of a force transducer according to the invention 2 , The force transducer 2 is by eight radial boundaries 42 in eight equal sectors 43 divided. On the force transducer 2 are two concentric circles 8th . 9 created whose centers with the center of the disc-shaped force transducer 2 coincide. In these circles 8th . 9 and at the center of each sector 43 are strain-sensitive measuring resistors 3 arranged. These strain-sensitive measuring resistors 3 are connected to measuring bridges. The interconnection of the measuring bridges is not shown here. In 10 is also the central hole 4 in the load cell 2 to recognize.

It is also on the load cell 2 another measuring resistor 41 arranged, which is used for temperature measurement. With this additional measuring resistor 41 the temperature currently prevailing on the force transducer can be recorded. With that of the further measuring resistor 41 The signal provided and proportional to the temperature can measure the temperature drift of the measuring bridges from the strain-sensitive measuring resistors 3 be compensated effectively.

1.

contraption to determine a force

Second

Load cell

Third

strain-sensitive measuring resistor

4th

hole in the load cell

5th

internal Edge of the force transducer

6th

outer edge of the force transducer

7th

shell

8th.

internal circle

9th

outer circle

10th

measuring bridge

11th

application of force

12th

Kraftausleitung

13th

electrical cables

14th

thickness of the disc-shaped load cell

15th

electric motor

16th

first gear

17th

second gear

18th

wave

19th

Ball Screw

20th

floating caliper

21st

collar on the sleeve

22nd

foot

23rd

brake pad

24th

brake disc

25th

reading

26th

signal processing

27th

driver stage

28th

brake signal from driver

29th

differential amplifier

30th

Wheatstone measuring bridge

31st

Dimensions

32nd

voltage source

33rd

measuring points

34th

ring with wedge-shaped cross-section

35th

washer

36th

powerful introductory element

37th

paragraph

38th

ring with a square cross section

39th

substratum

40th

gap

41st

Another measuring resistor

42nd

radial limit

43rd

sector

Claims (28)

Contraption ( 1 ) to determine a force, for example one from an actuator on the brake pads ( 23a, b ) force exerted by a motor vehicle, which consists of strain-sensitive measuring resistors ( 3 ), which have geometry-dependent electrical resistance values and an extensible force transducer ( 2 ) is constructed, whereby the strain-sensitive measuring resistors ( 3 ) on the surface of the stretchable force transducer ( 2 ) are applied and which are in the force transducer ( 2 ) The force introduced over its elongation is an elongation of the strain-sensitive measuring resistor stands ( 3 ), characterized in that the extensible force transducer ( 2 ) is disc-shaped. Contraption ( 1 ) for determining a force according to claim 1, characterized in that the strain-sensitive measuring resistors ( 3 ) on the surface of the force transducer ( 2 ) on two to the center of the disc-shaped force transducer ( 2 ) concentric circles ( 8th . 9 ) are arranged. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the disk-shaped force transducer ( 2 ) a central hole ( 4 ) having. Contraption ( 1 ) for determining a force according to claim 3, characterized in that a first group of strain-sensitive measuring resistors ( 3 ) on an inner circle concentric to the central hole ( 8th ) on the force transducer ( 2 ) is arranged and a second group of strain-sensitive measuring resistors ( 3 ) on one to the central hole ( 4 ) concentric outer circle ( 9 ) on the force transducer ( 2 ) is arranged, with adjacent measuring resistors ( 3 ) of the respective group are arranged equidistant. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that at least four strain-sensitive measuring resistors ( 3 ) to at least one electrical measuring bridge ( 10 ) are connected. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the force introduction is concentric in the region of the hole ( 4 ) of the force transducer ( 2 ) takes place and the force is distributed concentrically in the area of the outer edge ( 6 ) of the force transducer ( 2 ) he follows. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the force transducer ( 2 ) in one piece with a sleeve ( 7 ) is trained. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the strain-sensitive measuring resistors ( 3 ) on a stretchable, disc-shaped substrate ( 39 ) are applied, the diameter of which is preferably less than or equal to that of the force transducer ( 2 ) and that is concentric on the force transducer ( 2 ) arranged and firmly connected to it. Contraption ( 1 ) for determining a force according to claim 8, characterized in that the stretchable substrate ( 39 ) has a central hole whose diameter is greater than or equal to that in the force transducer ( 2 ) is. Contraption ( 1 ) for determining a force according to claims 8 or 9, characterized in that the material of the stretchable substrate ( 39 ) has a surface expansion coefficient which is essentially that of the material of the force transducer ( 2 ) corresponds. Contraption ( 1 ) for determining a force according to at least one of claims 1 to 7, characterized in that the strain-sensitive measuring resistors ( 3 ) directly on the force transducer ( 2 ) are applied. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the force transducer ( 2 ) consists of steel or a steel alloy. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the stretchable substrate ( 39 ) consists of steel or a steel alloy. Contraption ( 1 ) to determine a force according to claims 12 or 13, characterized in that the steel or the steel alloy is thermally hardenable. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the surface of the force transducer ( 2 ) and / or the substrate ( 39 ) after scaling is an electrical insulator. Contraption ( 1 ) for determining a force according to claims 8 or 9, characterized in that the substrate ( 39 ) consists of at least one ceramic material. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the strain-sensitive measuring resistors ( 3 ) are positively connected to the substrate and / or the measuring element. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the strain-sensitive measuring resistors ( 3 ) with the substrate ( 39 ) and / or the force transducer ( 2 ) are glued, sintered, soldered or welded. Contraption ( 1 ) to determine a force according to at least one of the preceding claims, characterized in that the strain-sensitive measuring resistors ( 3 ) and / or the measuring resistors ( 3 ) connecting electrical lines ( 13 ) on the substrate ( 39 ) and / or the force transducer ( 2 ) are applied using thick film technology. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the strain-sensitive measuring resistors ( 3 ) and / or the measuring resistors ( 3 ) connecting electrical lines ( 13 ) on the substrate ( 39 ) and / or the force transducer ( 2 ) are applied using thin-film technology. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the disc-shaped substrate ( 39 ) with the force transducer ( 2 ) is firmly connected by gluing, sintering, soldering, positive locking or welding. Contraption ( 1 ) for determining a force according to claim 7, characterized in that the sleeve ( 7 ) consists of steel or a steel alloy. Contraption ( 1 ) for determining a force according to claim 7 or 22, characterized in that the wall thickness of the sleeve ( 7 ) greater than or equal to the thickness ( 14 ) of the disc-shaped force transducer ( 2 ) is. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the force introduction concentrically via at least one additional ring ( 34 . 35 . 38 ) he follows. Contraption ( 1 ) for determining a force according to claim 24, characterized in that the ring ( 34 ) has a wedge-shaped cross-section and the force transducer ( 2 ) only up to that of the wedge-shaped ring ( 34 ) can stretch the specified limit. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that the force transducer ( 2 ) and / or the substrate ( 39 ) by radial limits ( 42 ) in several sectors of the same size ( 43 ) is divided, with one measuring resistor ( 3 ) on the inside ( 8th ) and another measuring resistor ( 3 ) on the outer circle ( 9 ) central in each sector ( 43 ) is arranged and at least one on the inner circle ( 8th ) arranged measuring resistor ( 3 ) with at least one on the outer circle ( 9 ) arranged measuring resistor ( 3 ) to an electrical measuring bridge ( 10 ) connected is. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that on the force transducer ( 2 ) and / or on the substrate ( 39 ) another measuring resistor ( 41 ) is arranged, the temperature on the force transducer ( 2 ) and / or on the substrate ( 39 ) measures. Contraption ( 1 ) for determining a force according to at least one of the preceding claims, characterized in that on the extensible force transducer ( 2 ) a glass layer with a high electrical resistance is applied and the strain-sensitive measuring resistors ( 3 ) are arranged on the glass layer.