DEVICE FOR DETECTING PRESSURE FORCES BETWEEN TWO BODIES

Abstract

The invention relates to a device for detecting the pressure forces between two bodies (1) that can be brought into contact by applying a force, said device comprising a multilayer measuring sheet (3) which can be inserted into the butt joint between the two bodies (1) and, between two electrically conductive layers (5) connected to an evaluation circuit (6), has a sensor layer (4) with pressure-responsively varying electrical properties. To improve the measurement result, it is proposed for two superposed measuring sheets (3) having an electrically insulating separation layer (9) interposed therebetween to form a measuring insert (2) insertable into the butt joint, and for the two measuring sheets (3) to each be separately connected to the evaluation circuit (6), which comprises a signal processing unit (11) which, in accordance with a predetermined algorithm, combines the measurement signals from the two measuring sheets (3) into a measurement result.

Description

1 / 7 DEVICE FOR DETECTING PRESSURE FORCES BETWEEN TWO BODIES FIELD OF TECHNIQUE

[0001] The invention relates to a device for detecting pressure forces between two bodies, which can be placed in contact with each other under the influence of a force, with a multilayer measuring sheet that can be inserted into the butt joint between the two bodies, which has a sensing layer with pressure-dependent variable electrical properties between two electrically conductive layers connected to an evaluation circuit. STATE OF THE ART

[0002] In order to detect the clamping forces of disc or drum brakes, it is known (AT 524 872 B1) to insert a multilayer measuring film composed of a sensing layer with pressure-dependent electrical properties between the brake body and the brake rotor. With the aid of two electrically conductive layers, the pressure-dependent electrical measuring signal from the sensing layer is captured and supplied to an evaluation circuit, in which the clamping forces are determined based on the known pressure dependence of the electrical measuring signal. Due to unavoidable local irregularities in the sensing layer with respect to the pressure dependence of its electrical properties, measurement errors are expected. Measurement errors may also occur if the measuring foil is not uniformly loaded across its entire measuring surface.

[0003] In order to take into account measurement errors, it is known (AT 524 872 B1) to provide the measuring sheet to assign the determined clamping forces to the area of ​​the sensor layer exposed to the respective pressure with two layers of electrodes connected to the evaluation circuit to determine the sheet's capacity between the electrode layers. If the brake body does not actuate Petition 870250079626, dated 05 / 09 / 2025, page 13 / 22 2 / 7 across the entire surface of the disc or drum brake rotor, there will be different distances between the brake body and the brake rotor, which will influence the capacity of the measuring sheet fixed between the brake body and the brake rotor, so that the contact surface can also be determined with a corresponding capacity measurement, in order to relate the clamping forces detected by the sensor layer to that contact surface.

[0004] However, an additional capacitance measurement has no influence on the irregularities that occur in the sensor layer measurement area with respect to the pressure-dependent electrical properties of the sensor layer. DESCRIPTION OF THE INVENTION

[0005] The invention is therefore based on the problem of providing a device for detecting the pressure forces between two bodies that can be placed in contact with each other, with a measuring sheet that can be inserted into the butt joint between the two bodies, in such a way that the accuracy of the measurement can be improved with a relatively small constructive effort.

[0006] Based on a device of the type described above, the invention solves the problem by means of two measuring sheets arranged one above the other, with the interposition of an electrically insulating separating layer, forming a measuring insert that can be inserted into the butt joint, and each of the two measuring sheets being separately connected to the evaluation circuit, which comprises a signal processing unit that combines the measuring signals from the two measuring sheets into a measurement result according to a predetermined algorithm.

[0007] Since, according to these measures, the electrical parameters dependent on the pressure forces to be measured between the two bodies are measured independently of each other. Petition 870250079626, dated 05 / 09 / 2025, page 14 / 22 3 / 7 another by two measuring sheets and due to the fact that the irregularities in relation to the electrical properties of the sensor layers of the two measuring sheets are distributed differently over the common measuring surface of the two measuring sheets, the electrical measurement signals recorded independently of each other for the pressure forces to be recorded can be combined with each other, so as to improve the measurement result. For this purpose, the measurement signals of the two measuring sheets are compared in a signal processing unit of the evaluation circuit according to a predetermined algorithm, and a measurement result processed according to the algorithm is output. In the simplest case, the algorithm can lead to an average, which already results in a noticeable improvement in measurement accuracy.

[0008] Providing a measuring insert with two measuring blades, which supply independently recorded measuring signals, can also be used advantageously to monitor the functionality of the measuring insert. If the measuring signals from the two measuring blades deviate from each other by a certain amount, this means that at least one of the two measuring blades is defective. In the evaluation circuit, the measuring signals from the two measuring blades can therefore be compared with each other and an error signal can be issued if a predetermined difference between the two measuring signals is exceeded.

[0009] Furthermore, at least one of the two measuring sheets may have two layers of electrodes connected to the evaluation circuit to determine the sheet's capacitance between the electrode layers, so as to be able to infer the respective contact surface between the two bodies pressed against each other from the sheet's capacitance in a manner known to itself and thus detect the effective pressure forces depending on the respective contact surface. Since, in Petition 870250079626, dated 05 / 09 / 2025, page 15 / 22 4 / 7 In the case of a congruent arrangement of the two measuring sheets, the contact surfaces for both measuring sheets coincide, so at least in this case, the area detection for one of the measuring sheets is sufficient. BRIEF DESCRIPTION OF THE INVENTION

[00010] The drawing shows an example of the invention.

[00011] Figure 1 shows a device according to the invention in a schematic block diagram, and Figure 2 shows a schematic layered structure of a multilayer measuring sheet, which can be used according to the invention. WAYS TO IMPLEMENT THE INVENTION

[00012] According to the invention, to detect the pressure forces acting between two bodies 1, a multilayer measuring insert similar to a sheet 2 is inserted into the butt joint between the two bodies 1, comprising two corresponding measuring sheets 3 arranged one above the other in a congruent manner. These multilayer measuring sheets 3 have a sensing layer 4 made of a material whose electrical properties change with the applied pressure, as is particularly the case with piezoresistive materials, preferably suitably doped semiconductors, for example, silicon or germanium-based or III-V semiconductors.

[00013] The sensing layer 4 of the two measuring sheets 3 is arranged between two electrically conductive layers 5, through which a measuring voltage is applied to the sensing layer 4, preferably piezoresistive. Since the specific electrical resistance of the sensing layer 4 changes with the applied pressure, the pressure load on the sensing layer 4 and therefore the magnitude of the forces acting on it can be deduced from the magnitude of the electric current flowing through the sensing layer 4 due to the dependence of the given pressure on the specific electrical resistance. The area of ​​the sensing layer 4 Petition 870250079626, dated 05 / 09 / 2025, page 16 / 22 5 / 7 is predetermined by the construction and is therefore known.

[00014] An evaluation circuit 6 is provided for evaluating the measurement signals, to which the two measuring sheets 3 are connected separately, namely according to Figure 1, through corresponding couplings 7 to the signal lines 8 connected to the conductive layers 5, through which not only can the measurement signals be transmitted to the evaluation circuit 6, but also the energy required for the measurement operation can be transmitted from the evaluation circuit 6 to the measuring sheets 3. However, the measurement signals can also be transmitted wirelessly to the evaluation circuit 6, which normally requires a separate power supply assigned to the measuring insert 2.

[00015] To ensure that the two measuring sheets 3 measure the pressure forces acting between the two bodies 1 independently of each other, the two measuring sheets 3 must be electrically separated from each other by an insulating separating layer 9. Known measuring sheets of this type have two electrically insulating covering layers 10, as shown in Figure 2. The two inner covering layers 10, which are close to each other when two conventional measuring sheets 3 are used for a measuring insert 2 according to the invention and which, in this case, form a two-layer separating layer 9, can advantageously be replaced by a common single-layer separating layer 9.

[00016] Since, according to these construction measures, the pressure forces existing between the two bodies 1 are detected independently of each other by the two measuring sheets 3, the measurement signals from these measuring sheets 3 can be combined with each other in order to obtain a measurement result that, in particular, compensates for irregularities in the structure of the sensor layers 4. To this end, the evaluation circuit 6 comprises a unit of Petition 870250079626, dated 05 / 09 / 2025, page 17 / 22 6 / 7 signal processing 11 in which the measured values ​​detected by the two measuring sheets 3 are calculated according to a predetermined algorithm, in order to produce an improved measurement result and, for example, send it to a screen 12.

[00017] If it is possible that the applied pressure is not uniformly distributed over the measuring surface of the measuring insert 2, a capacitance measurement can also be performed to estimate the size of the area of ​​the two measuring sheets 3 that is exposed to the pressure. For this purpose, at least one of the two measuring sheets 3 is provided with two electrode layers 13, which cover the electrically conductive layers 5 with the interposition of an insulating layer 14, as shown in Figure 2. Since the capacitance of the sheet depends on the respective area over which the pressure is transmitted between the two bodies 1, this capacitance measurement can be used to infer the area of ​​the sensor layer 4 that is exposed to the applied pressure due to the acting forces, which allows the determined forces to be attributed to the area of ​​the sensor layer 4 exposed to the respective pressure.

[00018] The additional capacitance measurement, for which two separate electrode layers 13 are not necessarily required, since one of the electrically conductive layers 5 can also be used as an electrode layer for capacitance measurement, does not increase handling effort. The additional construction effort required for the electrode layers 13 and their connecting lines 15 also remains low. It is only necessary to ensure that the pressure-sensitive area detectable by capacitance measurement is adequately considered in the calculation of the measurement result. If both measuring sheets are supplied with electrode layers for separate capacitance measurements, error compensation can also be activated with respect to Petition 870250079626, dated 05 / 09 / 2025, page 18 / 22 7 / 7 determination of the fraction of the area subjected to pressure, although this generally does not have a significant influence on the measurement result.

[00019] Although the embodiment provides two matching measuring blades 3 arranged identically one above the other, which simplifies construction and measurement conditions, an arrangement of mutually offset measuring blades is also possible. In this case, the measuring surface common to both measuring blades is decisive for comparing the measurement results. With a corresponding adjustment of the algorithm, it is also possible to use non-matching measuring blades. Petition 870250079626, dated 05 / 09 / 2025, pages 19 / 22

Claims

1 / 1 CLAIMS 1. Device for detecting pressure forces between two bodies (1), which can be placed in contact with each other under the influence of force, with a multilayer measuring sheet (3) that can be inserted into the butt joint between the two bodies (1), which has a sensing layer (4) with pressure-dependent variable electrical properties between two electrically conductive layers (5) connected to an evaluation circuit (6), CHARACTERIZED in that two measuring sheets (3) arranged one above the other under the interposition of an electrically insulating separating layer (9) form a measuring insert (2) that can be inserted into the butt joint, and that the two measuring sheets (3) are separately connected to the evaluation circuit (6), which comprises a signal processing unit (11) that combines the measurement signals from the two measuring sheets (3) into a measurement result according to a predetermined algorithm.

2. Device according to claim 1, CHARACTERIZED in that at least one of the two measuring sheets (3) has two electrode layers (13) connected to the evaluation circuit (6) to determine the capacitance of the sheet between the electrode layers (13). Petition 870250079626, dated 05 / 09 / 2025, p. 20 / 22

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