DE102019125653A1 - Sensor for the qualitative and / or quantitative detection of forces and / or pressures - Google Patents

Abstract

Disclosed is a sensor (1) for the qualitative and / or quantitative detection of forces and / or pressures exerted on the sensor (1) with an electrical resistance which is at least partially exposed to contact surfaces and can be connected to two electrical poles of a measurement current source Conductor track structure (3), • a flexible, deformable, flat contact element (5) which is spaced apart from the contact surfaces in a zero position of the sensor (1) and has an electrically conductive conductive surface facing the contact surfaces, and • a flexible, deformable contact element (5), Pressure piece (6) arranged on a side of the contact element (5) opposite the conductor track structure (3), which has a pressure surface with which it faces the contact surfaces of the conductor track structure (3) and which extends in a cross-sectional circumference starting from a base in the direction of the contact element (5) seen tapers. The pressure piece (6) is arranged and set up to be displaced in the direction of the contact element (5) in the event of a force acting on the sensor (1) or pressure exerting on the sensor (1), and the contact element (5) in the direction of the contact surfaces of the To press the conductor track structure (3).

Description

The present invention relates to a sensor for the qualitative and / or quantitative detection of forces and / or pressures on the sensor.

In many technical applications it is desirable or even necessary to be able to record or determine forces and / or pressures at least qualitatively, but often also quantitatively. In the corresponding applications, pressure sensors or force sensors, which can be of completely different shapes, are used for this purpose.

The present invention particularly addresses an area that is becoming increasingly important, namely the integration of pressure or force sensors in everyday objects, in which a force or pressure on a surface is to be recorded and determined qualitatively, but advantageously also quantitatively. In particular, it is about applications for pressure or force measurements in objects with a flexible or elastic surface on which the pressures or forces to be determined or recorded are applied. Examples of this are in the insoles of shoes, in particular sports shoes, such as running shoes, integrated pressure or force sensors or such sensors in seat cushions or backrests of seating furniture or the like.

In these applications, sensors for the detection of pressure and / or force are required which, on the one hand, are compact and, in particular, flat in construction, and, on the other hand, preferably do not reduce or completely eliminate the flexibility of the material or object in which they are integrated.

In such fields of application, it is often necessary not only to collectively record forces or a pressure applied there, but also to determine it spatially and / or temporally resolved, be it qualitative, be it also in a quantitative measurement. Further information can then be obtained from the results of the measurements. For example, this can be done when detecting forces that are dynamically on a person's foot when walking or running, resolved in particular also according to different sections of the foot's anatomy. The recording of such forces or such pressure loads allows information about malpositions of the musculoskeletal system, for example, and can also be helpful in training an athlete, e.g. to improve his running style.

Various force or pressure sensors and sensor arrangements formed with them, which enable a temporally and / or spatially resolved detection of forces or pressures applied to the surface, have already been proposed.

In the DE 3704870 describes a flat arrangement with capacitive sensors for measuring compressive forces in a shoe. The limits of this system, which is currently still available on the market, lie in the high technical effort, power consumption and the disruptive influence of humidity and temperature. Sensors according to the DE 3704870 must be calibrated by specialists at short intervals, and the complicated electronics result in short battery life and high sales prices.

Furthermore, there are sensors, so-called force sensing resistors, built on the basis of force or pressure-dependent electrical resistances formed in film form, which have been proposed, for example, also for use for measuring loads in shoes (integrated in insoles) . The basic function of the sensors mentioned above is described, for example, in US Pat U.S. 4,314,227 .

Examples of shoe insoles (or shoe insoles) equipped with such or comparable sensor technology are described in US 2010/0063779 A1 , U.S. 5,033,291 and DE 11 2012 000 006 T5 .

The sensors made in foil form based on the Force Sensing Resistor principle have a crucial weakness that has hitherto prevented their mass use, especially for private users: The sensor cells formed according to this principle are inconsistent and change their electrical resistance, sometimes temporarily, sometimes permanently after strong mechanical loads . This means that measurements cannot be reproduced. If a sensor arrangement, e.g. in an insole, contains fifteen individual sensors working on the principle of force sensing resistors, it is normal for four or five of these sensor cells to have a permanently changed characteristic curve after loading, while the less loaded sensors remain undamaged . The measurements distorted in this way are not trustworthy and the values of several of the individual sensors cannot be compared with one another. Users help themselves by replacing the sensor foils of the sensor arrangement after a few hours of use, which alleviates the problem, but does not solve it.

All the systems currently on offer have three decisive weaknesses: They are expensive, can only be used in a stationary manner and require intensive use Maintenance. This means that these systems are far from being a product aimed at the end user for the mass market. Because they do not produce large quantities, the cost reductions otherwise expected for electronic products are impossible. The high price arises not only from the complicated technology and the relatively high power consumption, but also from the constantly necessary calibrations and the replacement of the parts equipped with the sensors, e.g. worn sensor soles, in the case of the technology described last with sensors based on Force Sensing resistors. Specially trained specialists are required for the calibration, which further impedes mass use. As a result, for example, insoles equipped with a flat sensor arrangement for space- and / or time-resolved force or pressure measurement can hardly be found or used worldwide in department stores, sports clubs and medical practices. Instead, treadmills with video cameras and Kistler force plates are used there for the purpose of recording loads and strains that occur when walking or running, which are expensive, but at least require little maintenance.

Another sensor design is the as yet unpublished German patent application 10 2018 127 320.7 at. There, a sensor arrangement with individual sensors is disclosed, which achieves a force- or pressure-dependent change in resistance of the sensor component in that a contact element opposite a conductor path arrangement, which has a cross-sectional contour tapering in the direction of the conductor paths, is less dependent on the external force or pressure is pressed strongly or more strongly against the conductor tracks and deforms in the process. As a result of the deformation, an area with which the contact element touches the conductor tracks becomes larger or remains smaller - in the case of lower pressure or lower applied force. Depending on the size of the area with which the contact element touches the conductor tracks, electrical connections between conductor track sections that are connected to different poles are larger or smaller in cross section, so that the resistance increases as the pressure increases or the applied force increases of the individual sensor or sensor element is reduced.

In principle, this design has proven to be well suited for inexpensive production and robustness of the individual sensors, which also relates to the durability of the sensors with regard to the reproducibility of their sensor outputs or measured values. However, it has been shown that the formation of the conductive surface on the contact elements, which for production-related reasons is done with a coating of an electrically conductive material that is firmly applied to a carrier element made of a non-electrically conductive elastomer, the individual sensors formed in this way often clearly showed deviations from one another in their electrical sensor characteristics that were insufficient for compliance with specified tolerance values. In other words, it was not possible to reproduce the electrically conductive coating so precisely that the electrical properties of the contact elements formed in this way always matched within a technically usable tolerance window. Because of these fluctuations, problems then arose when calibrating sensor arrangements formed with these sensors, since they could not simply work with predetermined characteristics of the individual sensors, since these characteristics partly differ from sensor to sensor due to the deviations in the electrical conductive properties of the coatings of the individual contact elements clearly and just too strongly differentiated.

The use of sensors as mentioned at the beginning and any sensor arrangements formed therefrom is, as already mentioned, but not limited to an arrangement in an insole or insole of a shoe and the acquisition of dynamic measured values there. Corresponding sensor arrangements can also be envisaged for use in other applications, for example in the area of a seat surface of a chair, in order to dynamically record and monitor the sitting behavior of a user. In such an application, for example, warnings could be issued if a user of such a technology sits at a workplace for too long, too long in a certain posture or in an unhealthy posture at all, in order to motivate the user to leave his seated position or to prevent back damage from sitting too long or incorrectly, for example.

Against the background of the above, it was the object of the present invention to provide a sensor for the qualitative and / or quantitative detection of forces and / or pressures on the sensor, which is particularly comparable to the sensors of the unpublished patent application DE 10 2018 127 320.7 The sensor arrangement disclosed can be manufactured inexpensively with a good service life and durability of the sensor properties, with at the same time improved comparability of individual sensors that are industrially manufactured in a corresponding design. In other words, the sensors to be specified according to the invention should have the same characteristic curves for sensors formed under the same production conditions, so that they can in particular also be combined in several sensor arrangements containing such sensors without the need for a later evaluation of differences in the characteristic curves of the individual sensors must be taken into account.

This object is achieved according to the invention by a sensor for the qualitative and / or quantitative detection of forces and / or pressures on the sensor having the features of claim 1. Advantageous developments of such a sensor according to the invention are shown in claims 2 to 11. In a further aspect, the invention also consists in specifying a flat sensor arrangement for the temporally and / or spatially resolved force or pressure measurement with the features of claim 12. Advantageous embodiments of such a sensor arrangement are given in claims 13 to 15 with special features.

According to the invention, the sensor for the qualitative and / or quantitative detection of forces and / or pressures on the sensor initially has a conductor track structure which is partially exposed with contact surfaces and can be connected to two electrical poles of a measuring current source and has an electrical resistance. In the conductor track structure, in particular, branches or branches of conductor tracks that are not connected to one another in the conductor track structure and can be connected to one of the two electrical poles of the measuring current source can be provided, the respective contact surfaces of which are exposed.

The sensor also has a flexible, deformable, flat contact element which is spaced apart from the contact surfaces when the sensor is in a zero position and has an electrically conductive conductive surface facing the contact surfaces. This contact element can in particular be made conductive overall, but can also have a conductive coating or the like. The contact element is in particular planar, with particular advantage being designed to be planar. It can be, for example, and in particular by means of an elastic film or a membrane of this type, electrically configured at least on a surface facing the contact surfaces, the conductive surface.

The sensor according to the invention also has a pressure piece formed from a flexibly deformable material, for example an elastomer, arranged on a side of the contact element opposite the conductor track structure, which has a pressure surface with which it faces the contact surfaces of the conductor track structure and which is in a cross-sectional circumference starting from a base of the pressure piece tapered in the direction of the contact element. The pressure piece can in particular advantageously be formed from an electrically non-conductive material. According to the invention, the pressure piece is further arranged and set up to be displaced in the direction of the contact element when a force acts on the sensor or when pressure is applied to the sensor and to press the contact element in the direction of the contact surfaces of the conductor track structure.

A sensor formed in this way has a compared to that in the unpublished DE 10 2018 127 320.7 The described sensor initially appears to have a more complex structure, since an additional element, namely the flat contact element, is to be provided. However, this aspect, which initially appears to be a disadvantage, is clearly overcome and actually to an advantage that the contact element can be reproducibly produced with a significantly more homogeneous conductivity, so that elements can be achieved in the industrial production of such sensors with within a narrow and justifiable tolerance range , characteristic curves running the same within the tolerance range.

The sensor according to the invention can in particular also be designed to be integrated in a flat sensor arrangement, the sensor arrangement being formed as a fixed and cohesive unit. For example, several conductor track structures, for example arranged in a matrix-like manner, can be applied to a circuit board, each of which is part of an individual sensor of its own. The contact elements can be formed, for example, on a continuously formed film or membrane by means of appropriate coatings, wherein the continuous film or membrane can be stretched over, for example, the entire printed circuit board, for example a flexible printed circuit board. The pressure pieces can in turn be formed as integral components of a continuously manufactured unit, for example a type of mat, and their arrangement can be set and distributed in accordance with the arrangement of the conductor track arrangements, so that they also form components of the individual sensors. In this way, a sensor arrangement or several sensor arrangements can be formed very easily from sensors according to the invention, which can then be used, for example, in a spatially resolved and / or time-resolved detection of onerous pressures or forces, in particular with the help of a suitable interconnection of the individual ones in a sensors according to the invention formed in such a sensor arrangement.

As already mentioned, the pressure piece of a sensor according to the invention can advantageously be formed from an elastomer material.

The contact element can be made entirely of an electrically conductive material or just as well from an electrically non-conductive, coated with an electrically conductive material on its side facing the conductor track arrangement, that is to say formed with an electrically conductive coating.

The pressure surface of the pressure piece can in any case taper conically in one section starting from the base in the direction of the contact element. Such a configuration, it has been shown, results in a good characteristic curve, which can be easily evaluated over a wide measuring range, of the changing resistance as a function of a pressure or a force on the sensor. Although a zero position of the sensor can also be selected so that the pressure piece in it already touches the contact element, possibly even tensioning and pushing the contact element in the direction of the contact surfaces of the conductor tracks, the zero position is advantageously selected so that the pressure piece is in a state of the sensor, in which this is not subjected to pressure or force (i.e. in the zero position) is placed in such a way that it does not touch the contact element. This results in a maximum resistance of the sensor (the conductor tracks) when the sensor is in the zero position.

The conductor track structures can in particular be formed by mutually insulated conductor tracks or conductor track sections, of which a first conductor track or a first conductor track section can be connected to a first pole of a measuring current source and a second conductor track or a second conductor track section can be connected to a second pole of the measuring current source that is different from the first pole is. This can be formed, for example, in the form of two nested, mutually electrically insulated finger structures as first and second conductor tracks. In this case, a mask made of an insulating material can be applied to the conductor tracks, more precisely on their exposed surface, which causes a shape adaptation of a geometry of the exposed surface conductor tracks or conductor track sections to a cross-sectional geometry of the pressure piece. If the pressure piece is essentially circular in cross section (with a diameter that increases in the direction of the base), the mask can provide a correspondingly circular section of the conductor tracks in order to reproduce the geometry of the pressure piece.

In order to ensure that the contact element maintains a sufficient distance from the conductor tracks in a zero position, it is advantageously provided that the contact element is fixed to spacers which ensure a corresponding distance between the contact surfaces of the conductor track structure and the contact element. These can, for example, be wall-like elevations which are arranged around the conductor tracks and on which the contact element rests, in particular is fixed there, for example by gluing. Only when the pressure piece is now moved from the side opposite the conductor track arrangement towards the contact element and presses it down in the direction of the conductor track structures, the electrical contact is formed, i.e. the electrical resistance of the conductor track structure decreases as a measure of the applied pressure or an applied force . Due to the elasticity of the contact element, when the pressure piece springs back after the applied force or pressure has ceased, the contact element will also spring back against a spring force resulting from the deformation when it is pressed in and will return to the starting position in which it does not touch the contact surfaces of the conductor tracks.

As already mentioned, part of the invention is also a flat sensor arrangement for the temporally and / or spatially resolved force or pressure measurement with an arrangement of individual sensors designed as described above and with a controller with which the sensors are connected distributed over a detection area. As already mentioned above, the pressure pieces of several sensors of the sensor arrangement can be connected to one another in a pressure piece support. This pressure piece support can, as already mentioned, be designed like a mat. The contact elements of the sensors can also be formed on a continuous film or membrane or another corresponding flat element. As already mentioned, the conductor track structures can be arranged on a common circuit board, in particular a flexible circuit board.

The control of the sensor arrangement can advantageously be set up to record sensor signals from the individual sensors repeatedly in a predetermined time cycle and to supply them to an evaluation. This leads to a good temporally and / or spatially resolved detection of pressures or forces on the sensor arrangement, so that dynamic and / or spatially distributed processes can also be better detected here.

• 1 in drei Ansichten a, b und c eine stark schematisierte Querschnittsdarstellung eines erfindungsgemäß gebildeten Sensors in einer Nullstellung (a), einer Stellung bei mäßiger auflastender Kraft / mäßigem auflastendem Druck (b) und einer Stellung bei hoher auflastender Kraft / hohem auflastendem Druck (c);
• 2 eine Aufsicht auf eine aus erfindungsgemäßen Sensoren in erfindungsgemäßer Weise gestaltete Sensoranordnung (ohne die Steuerung);
• 3 eine Explosionsdarstellung der Sensoranordnung aus 2;
• 4 in zwei Ansichten, einer Aufsicht (4a), und einer isometrischen Ansicht (4b) ein erstes Sensorteil eines Sensors der Sensoranordnung;
• 5 in drei Ansichten, einer Aufsicht (5a), einer isometrischen und explodierenden Ansicht (5b) und einem Längsschnitt (5c) ein zweites Sensorteil eines Sensors der Sensoranordnung;
• 6 in drei Ansichten, einer Aufsicht von der Rückseite her (6a), einer Aufsicht von der Vorderseite her (6b) und einer Seitenansicht ( 6c) zwei über Leitungsabschnitte zusammenhängende Leiterplatten mit darauf ausgebildeten ersten Sensorteilen der Sensoranordnung nach 2;
• 7 in drei Ansichten, einer Aufsicht von der Rückseite her (7a), einer Aufsicht von der Vorderseite her (7b) und einer Seitenansicht ( 7c) zwei mattenartig zusammenhängend gebildete Anordnungen mit zweiten Sensorteilen der Sensoranordnung nach 2;
• 8 eine Kennlinie eines Sensors nach 1, wie er in der der Sensoranordnung nach 2 eingebunden sein kann; und
• 9 in einer schematischen Darstellung eine weitere Anwendungsmöglichkeit einer mit erfindungsgemäßen Sensoren gebildeten erfindungsgemäßen Sensoranordnung für die Bestimmung einer Auflast und Lastverteilung in einer Sitzfläche eines Sitzmöbels, z.B. eine Stuhls.

Further advantages and features of the invention emerge from the following description of an exemplary embodiment on the basis of the attached figures. Show:

• 1 in three views a, b and c a highly schematic cross-sectional representation of a sensor formed according to the invention in a zero position (a), a position with a moderate load / moderate load Pressure (b) and a position at high loading force / high loading pressure (c);
• 2 a plan view of a sensor arrangement designed from sensors according to the invention in the manner according to the invention (without the controller);
• 3rd an exploded view of the sensor assembly 2 ;
• 4th in two views, one top view ( 4a) , and an isometric view ( 4b) a first sensor part of a sensor of the sensor arrangement;
• 5 in three views, one top view ( 5a) , an isometric and exploding view ( 5b) and a longitudinal section ( 5c ) a second sensor part of a sensor of the sensor arrangement;
• 6th in three views, a top view from the rear ( 6a) , a top view from the front ( 6b) and a side view ( 6c ) two printed circuit boards connected by line sections with first sensor parts of the sensor arrangement formed thereon 2 ;
• 7th in three views, a top view from the rear ( 7a) , a top view from the front ( 7b) and a side view ( 7c ) two mat-like interconnected arrangements with second sensor parts of the sensor arrangement 2 ;
• 8th a characteristic curve of a sensor 1 as shown in the sensor arrangement 2 can be involved; and
• 9 in a schematic representation a further possible application of a sensor arrangement according to the invention formed with sensors according to the invention for determining a load and load distribution in a seat surface of a chair, for example a chair.

In the figures, possible exemplary embodiments or possible embodiments of a sensor according to the invention or a sensor arrangement according to the invention are shown. These are only examples of possible realizations of the invention. The invention is not restricted to these exemplary embodiments, but rather, as will become clear to the person skilled in the art, can also be implemented in different forms. Nonetheless, features essential to the invention are once again shown and explained with reference to the figures and the exemplary embodiments shown there, wherein such features can also be implemented and incorporated in general in modified embodiments.

1 shows, in three different representations and in a highly schematic manner, a cross section through a sensor designed according to the invention in a zero position, i.e. without any pressure or force ( 1a) , in a position subject to moderate pressure and moderate force ( 1b) and in a high pressure, high force position ( 1c ).

The inventively designed, in 1 shown sensor 1 initially has a printed circuit board as a first sensor part 2 , in particular a flexible printed circuit board made with conductive traces 3rd is equipped. The conductor tracks 3rd have in an in 1 Direction shown above free and exposed contact surfaces. Between the conductor tracks 3rd are insulating protrusions 4th formed that a vertical distance to the conductor tracks 3rd form. About the insulating protrusions 4th a contact element is placed 5 in the form of a flexible and elastic film or membrane, which in any case on their the conductor tracks 3rd and whose exposed side facing the contact surfaces is formed in an electrically conductive manner, has a guide surface, for example by a firmly adhering one applied there. electrically conductive coating.

There is also a pressure piece 6th to see that starting from a base in the direction of the contact element 5 reduced in cross-sectional diameter or cross-sectional circumference. The pressure piece 6th is made of an elastically deformable, flexible material, for example an elastomer, and is electrically non-conductive. It is also made of an elastic material, for example an elastomer, in particular with the pressure piece 6th integrally connected or part of the pressure piece 6th forming, flexible supports 7th , the edge of the pressure piece 6th are formed on the contact element 5 up and holds in a like in 1a shown zero position of the sensor a distance to the contact element 5 one, which in turn, a distance to the contact surfaces of the conductor tracks 3rd adheres to. In this position, the resistance of the conductor paths contacted by two poles of a measuring current source is 4th maximum high. The pressure piece can be referred to as the second sensor part and the contact element as the third sensor part.

Now weighs on the sensor 1 , more precisely on the pressure piece 6th a force or a pressure, the pressure piece becomes 6th in the direction of the conductor tracks 4th emotional. The flexible supports deform in the process 7th and presses the pressure piece 6th with its the contact element 5 facing side against the contact element 5 and presses it against the conductor tracks in a central area 4th . This is how it arises between the conductor tracks 4th an electrical contact, the electrical resistance of the sensor decreases 1 . In the 1 b this is shown very schematically.

If the pressure or the force is increased, the pressure piece pushes 6th even further against the contact element 5 , whereby it is - like this also the flexible supports 7th do - further deformed and presses against the contact element with a larger contact surface. The contact element then makes contact 5 the contact surfaces of the conductor tracks on a larger area 4th and the electrical resistance of the sensor 1 continues to sink.

If the loading pressure is now from the sensor 1 taken, if there is no loading force, then due to the elastic properties of the pressure piece 6th and the flexible supports 7th the pressure piece 6th put back in the in 1a position shown. Also the flexible and elastic contact element 5 then returns to the in 1a position shown. The sensor 1 is then back in the zero position.

In the representations of the 1 is in particular also the contact element 5 shown very schematically, especially in its deformation. The steps that can be seen in the figures are in particular not discontinuities in the contact element 5 . In reality, there are gentle, curved transitions here.

In 2 is now a possible embodiment of a flat sensor arrangement according to the invention 10 to see. It contains a plurality, in this exemplary embodiment 15th , individual sensors 1 which, as explained above and in the 1 are formed very schematically shown. The sensors 1 are in the sensor array 10 connected in a manner to be described in more detail below with supply and signal lines leading to a connector 13th to lead. The controller can use the rest of the sensor arrangement 10 alternatively also be firmly connected.

To the connector 13th is in use of the sensor array 10 a controller connected, the measurement signals from the sensors 1 receives and the sensors 1 applied with a supply voltage. This control is part of the sensor arrangement 10 . An evaluation of the sensor signals for the acquisition of data on the respective sensor can also be carried out in the controller 1 on the load or the pressure exerted on it. The controller can have an, in particular wireless, interface for transmitting data. It can also contain an energy source, such as, in particular, a battery or an accumulator, for supplying itself and also the sensors 1 with the required electrical energy.

In the exemplary embodiment shown, the sensor arrangement is 10 formed in order to be integrated into an inner sole or an insole for a shoe, for example for a running shoe. In this exemplary embodiment, the outline of the sensor arrangement is adapted to the shape of a left foot, which can be size 40, for example. As the sensors 1 can be arranged largely freely, adjustments to different shoe sizes are easily possible. Adaptations can also be made to the sensor arrangement for other applications 10 , for example for the detection of pressures and / or forces in a seat surface of a chair, advantageous forms or forms required by such applications can be made simply by changing the number and / or the arrangement of the sensors 1 can be adjusted and varied accordingly.

In the arrangement shown, the sensor arrangement 10 three sensors 1 in a section provided for the arrangement in the area of the heel and twelve sensors 1 for an arrangement in the area of the front of the shoe in which the ball of the foot is supported. This arrangement reflects the fact that for one application of the sensor arrangement 10 to absorb dynamic forces that arise during locomotion (walking, running) can be measured at the heel with a lower resolution, while the rolling movements of the toes and the forefoot should be measured more precisely.

In 3rd is an exploded view of the vertical structure of the sensor arrangement 10 recognizable. On one flexible circuit board each 14th who have favourited the circuit board 2 in 1 are the first sensor parts 15th educated. The flexible circuit boards 14th (or sections of a flexible circuit board) are over a ridge 16 connected with each other. Electrical signal and supply lines, which are the first sensor parts, also run along this web 15th to the connector 13th in order to be able to connect it to the controller. In the assembled state on the flexible circuit boards 14th lie mats 17th with second sensor parts molded therein 18th who have favourited the thrust pads 16 contain. The mats are preferably connected to the second sensor parts 18th formed from an elastomer, in particular from silicone rubber. The mats 17th lie with the second sensor parts 18th matching the first sensor parts 15th on the flexible circuit boards 14th aligned and are with the circuit boards 14th firmly connected, for example by means of circumferential adhesive layers 19th or by means of welds. There are between the first sensor parts 15th and the second sensor parts 18th the third sensor parts (not shown here) are arranged, the contact elements 5 form. These can for example be on one between the first and second sensor parts 15th , 18th arranged foils or membranes be formed, for example by partially conductive coating.

4th shows an isolated, in the embodiment shown in the flexible circuit board 14th integrally formed, first sensor part 15th . The first sensor part 15th is in the form of a conductor track structure also known as an electrode 20th formed, especially on the flexible circuit board 14th upset. This conductor track structure 20th consists of conductor tracks or conductor track sections made of a material with good electrical conductivity, such as copper, while the flexible circuit board 14th consists of an electrically insulating material such as polyimide. The conductor tracks of the conductor track structure correspond to those in 1 schematically shown conductor tracks 3rd who have favourited Circuit Board 14th the in 1 circuit board shown schematically 2 . The conductor tracks of the conductor track structure 20th are in any case in a section (or sections) with their conductive material exposed to a contact surface. Both the circuit board 14th per se as well as the conductor tracks should be flexibly deformable for the application selected here. In particular, a realizable bending radius of down to 3 cm is aimed for. Circuit board 14th and conductor tracks must also be mechanically robust so that they can cope with the stress in the respective application and do not lose their function even after long use. In the application highlighted here, they must be in the sensor arrangement 10 withstand the rolling movements of the foot in an inner or insole of a shoe.

The conductor track structure 20th consists of two separate conductor tracks that are in an unloaded starting position of the sensor 1 have no electrical connection (compare also 1a) .

To the track structure 20th to the geometric shape of the second sensor part 18th to adapt (see also 4th ) is on the track structure 14th a mask 25th applied from an insulating material, for example printed on. The mask can also use the in 4th insulating projections shown 4th form.

In 5 is the mechanical structure of a second sensor part 18th shown in more detail (as an excerpt from one of the mats 17th the in 1 sensor arrangement shown). This includes all of the second sensor parts 18th a mat 17th in particular and advantageously constructed identically.

The second sensor part 18th has a pressure piece as a central element 21 (according to the pressure piece 6th out 1 ) starting from a base with which it is attached to the mat 17th is formed, in an assembled state of the sensor 1 to the first sensor part 15th pointing direction reduced in cross-section. In the embodiment shown, the pressure piece is 21 in a perpendicular to the base, hence to a plane of the mat 17th , guided cut conically shaped in a large section, has a flattened, approximately spherical tip.

The pressure piece 21 exists as the mat 17th , made of a soft elastomer such as silicone rubber, which on the one hand can be easily deformed, but returns to its original shape in the absence of forces. The pressure piece is with a throwing surface 21 in operation one between the first and the second sensor part 15th , 18th facing the contact element arranged as a third sensor part, the one in the direction of the conductor track structures 20th Has exposed electrically conductive surface. The contact element is also elastically deformable.

The pressure piece 21 surrounding it are flexible and elastic supports made of the same material 23 shaped that the supports 7th according to 1 correspond. These flexible supports 23 are ring-shaped around the pressure piece 21 and have roughly the cross-sectional shape of an isosceles triangle.

When the sensor is installed 1 is the second sensor part 18th so on the first sensor part 15th put on that the pressure piece 21 the conductor track structure 20th with the interposition of the contact element (compare 5 in 1 ) opposite, with a central section of the pressure piece 21 to a center of the conductor track structure 20th shows.

The conductor tracks of the conductor track structure 20th are designed so that a small contact surface of the pressure piece 21 as described above against the conductor tracks 20th pressed contact element to a high electrical resistance between two conductor tracks of the conductor track structure 20th leads, while a large contact surface of the pressure piece 21 on the contact element and thus the contact element with its electrically conductive surface on the conductor tracks 20th as it is caused by a deformation of the pressure piece obtained due to a load-bearing force or a load-bearing pressure 21 results (compare also 1 c) , leads to less resistance. For this purpose, for example, a meander-shaped structure of the conductor track structure as used in the exemplary embodiment 20th be suitable. Instead of such a meandering structure, however, other arrangements are also possible. The only decisive factor is that there is a deformation of the pressure piece 21 and a resulting contact element with a larger surface area leads to a correlated change in resistance.

When the pressure piece 21 as in an unloaded state of the sensor 1 the contact element not at all and the contact element the conductor track structure 20th accordingly not touched either (compare 1a) , the contact is open, the resistance so theoretically infinite. With a light touch, the resistance can be, for example, 1 kΩ, with a medium touch, for example, 100 Ω and with a maximum contact surface of the pressure piece 21 Contact element pressed onto the conductor tracks, for example at 10 Ω. The variable electrical resistance is due to the fact that with an increasing contact surface of the pressure piece 21 on the contact element and thus the contact element on the conductor track structure 20th larger parts of the electrically conductive contact element from the conductor track structure 20th to be contacted.

The flexible supports 23 lie in an assembled state of the sensor 1 on the circuit board 14th or on the contact element 5 (compare 1 ) and prevent the pressure piece 21 the contact element permanently on the conductor track structure 20th depresses. At low transverse to the plane of the circuit board 14th or the mat 17th acting forces are only the flexible supports 23 on while the pressure piece 21 and thus also the contact element with greater forces increasingly on the flexible circuit board 14th trained conductor track structure 20th rest on, deforming it further and further. The pressure piece 21 is, so to speak, pressed more and more flat, and presses the contact element against the conductor track structure over an ever larger area 20th which, as mentioned above, causes an ever decreasing electrical resistance. Recesses 24 between the supports formed as ring segments 23 serve as air channels to prevent air bubbles when squeezed.

As mentioned are the mats 17th at its edge, for example by means of an adhesive, welding or adhesive tape to the respective flexible circuit board 14th connected. The contact element with the conductor track is also similar 14th connected. By mechanical pressure from above, the pressure pieces 21 individually or together, independently of one another, across the plane of the mat 17th towards the flexible circuit board 14th are pressed and press the respective contact element onto the circuit board and the conductor tracks there.

In one application for forming one with the sensor array 10 provided insole or insole of a shoe should be the pressure pieces 21 With regard to the hardness of the material and the shape, be dimensioned and designed so that a slight vertical pressure (pressure force <10 N) only leads to a minimum deformation, while the maximum deformation (depending on body weight and movement load up to approx. 500 N ) per unit area to an almost complete support of the pressure piece 21 on the flexible circuit board 14th , or the conductor track structure 10 , and the one between the pressure piece 21 and circuit board 14th arranged contact element should lead. This is because no additional forces can be measured with a complete support. The shape of the pressure piece 21 and the hardness of its material, especially the elastomer used, determine the measuring range.

Depending on the application, the sensor arrangement 10 with their integrated sensors 10 thus designed for lighter or heavier loads. When used in an inner or insole of a shoe, however, the load per unit area is approximately the same for heavier and lighter people, because taller people usually also have larger feet. Therefore, the same construction of the pressure pieces 21 be suitable for very different shoe sizes.

In 6th is the entire flexible circuit board 14th to be seen with the first sensor parts formed on an insulating carrier material 15th in the form of the conductor track structures 20th . In the circuit board 14th Conductor tracks are formed that form the conductor track structures 20th with the connector 13th connect. This the conductor track structures 20th with the connector 13th connecting traces are not shown here. The course and the arrangement of these conductor tracks correspond to the technology customary for flexible conductor tracks. Every pressure piece 21 is exactly one contact element (see 5 in 1 ) and exactly one track structure 20th assigned. Together, these three components each form a sensor 1 .

In the exemplary embodiment, each sensor 1 in addition, exactly one channel of an analog / digital converter is assigned to the controller. A matrix arrangement for measurement is also conceivable and would reduce the number of conductor tracks and the channels to be provided in the analog / digital converter, but such an arrangement increases the risk of interference from mutual influencing of sensors 1 .

7th shows the mats 17th with a group of one pressure piece each formed on it 21 having second sensor parts 18th . The mats 17th are arranged here in a shape adapted to the foot. In the exemplary embodiment, the second sensor parts are 18th with the pressure pieces 21 arranged in a regular grid. But this is not absolutely necessary, they can be arranged freely. The sensor parts 18th and their pressure pieces 21 can also be made larger or smaller than in the exemplary embodiment. For larger pressure pieces 21 however, the position information of the measurements would be less precise. For very small print pieces 21 (<6mm) there would be the risk that saturation would be reached more quickly with larger forces, ie the force measuring range would be limited, but the position resolution would be higher.

In 8th is a characteristic curve of a sensor 1 pictured. As long as the contact element has the conductor track structure 20th not touched, the contact is open and the resistance is extremely high (in the megohm range). As can be seen from this characteristic curve, the resistance drops here with a load of around 5N to around 1 kΩ, then drops with a load of 10N to below 250 Ω and then approaches when the sensor is saturated 1 with around 80N a resistance of less than 10 Ω.

This characteristic curve is in direct proportion to the mechanical construction of the contact element and the conductor track structure 20th pressing pressure piece 21 . Depending on the shape and material of the pressure piece 21 if the characteristic curve also changes, a flatter shaped pressure piece would be created 21 lead to saturation more quickly (the measuring range would be smaller, the sensor 1 more sensitive), while a pressure piece made of harder material 21 can also register higher forces.

The semi-linear characteristic in 8th In the exemplary embodiment, it is deliberately chosen because it enables precise measurement with lower forces of less than 10N, but can still differentiate between forces of more than 50N.

• Sohlensensoren auf kapazitiver Basis liefern nur schwache elektrische Signale mit hohem Rauschanteil, die leicht durch Feuchtigkeit in der Messumgebung, z.B. in einem Schuh, oder durch andere Störeinflüsse, wie z.B. bei einer Integration in einer Sohle durch Fußbewegungen, gestört werden können. Im Unterschied dazu liefert die erfindungsgemäße Lösung bei einer Beschaltung der resistiven Sensoren, z.B. der Sensoren 1, mit einem üblichen Spannungsteiler vergleichsweise starke Signale im 100mV-Bereich. Dadurch ist es nicht erforderlich, die Zuleitungen abzuschirmen.

A sensor arrangement according to the invention, for example a sensor arrangement as shown in the figures and described above 10 , has the following advantages over the known solutions:

• Sole sensors on a capacitive basis deliver only weak electrical signals with a high level of noise, which can easily be disturbed by moisture in the measuring environment, e.g. in a shoe, or by other interfering influences, e.g. when integrated in a sole by foot movements. In contrast to this, the solution according to the invention delivers when the resistive sensors, for example the sensors, are connected 1 , with a common voltage divider, comparatively strong signals in the 100mV range. This means that it is not necessary to shield the supply lines.

Usual sensor arrangements based on foils with so-called force sensing resistors, when used as sole sensors, supply signals with tremors in the frequency range of over 20 Hz, which must be filtered out separately. The cause lies in the strong vibrations when running, which lead to changeable contacts of the film. In particular, when running with a sports shoe, the inserted sensor film is considerably curved and deformed in accordance with the movements of the foot. The release path of a force sensor based on a force sensing resistor is around 0.01 to 0.05 mm, i.e. 10-50 µm. Correspondingly, a vibration or a shock with a movement of 0.01 to 0.05mm acting on the sensor leads to a full deflection of the sensor system. The short triggering path of the sensor in the manner of the previously known force sensing resistor causes a high resonance frequency of well over 100 Hz, which worsens the signal / noise ratio of the measurements.

In contrast to this, the spring travel, that is to say the release travel in the solution according to the invention, is in the range of 0.5 mm, which is 10 to 50 times as much as with the previously customary sensors in the manner of a force sensing resistor. Correspondingly, a deformation with a movement of 0.01 to 0.05 mm acting on the sensor according to the invention only leads to a deflection of 2-10%, so it does not confuse the measurement. The resonance frequency is well below 100 Hz and therefore outside of the frequency ranges that are important for the measurement.

The construction of the sensors according to the invention ensures that each electrically measurable signal is directly proportional to the deformation of the pressure piece 21 and driven by this, the contact element behaves. The precision of the system, a constant conductive contact surface of the contact element and a constant conductor track structure, for example the conductor track structure, are correspondingly 14th , provided that it is just as reproducible as the mechanics of the pressure piece 21 and des. of the contact element. By arranging a flat contact element, which with the help of the tapered pressure piece 21 against the conductor track structures 20th is pressed, a high reproducibility of the individual sensors is achieved 1 and also from sensors 1 get with each other, since the electrical conductivity of the flat contact element, for example a film or membrane, can be adjusted very precisely and reproducibly.

In addition, the construction according to the invention ensures that the measured electrical resistances are always related to the total resistance of the contact element. Without contact between the contact element and the conductor track structure, in an implementation as described in the exemplary embodiment or a comparable implementation with conductor tracks separated in the normal state in the conductor track structure, no electrical connection can be made to the conductor track structure. With maximum contact of the pressure piece and thereby obtained maximum contact of the guide surface of the contact element, that is, maximum triggering of a sensor, for example a sensor 1 , the electrical resistance of this sensor is always the same value that corresponds to the resistance of the conductive surface of the contact element.

In 9 is finally another possible application of one of the sensors according to the invention 1 formed sensor arrangement 29 outlined. In the application form shown there, with a sensor arrangement according to the invention 29 that of a seated person on a seat 26th a chair, for example a chair, such as an office chair, the load exerted and the distribution of this load can be determined. This is done in the seat 26th between a base that forms a solid base and thus results in a stable abutment 27 and one on this basis 27 applied seat pad 28 the essentially flat sensor arrangement 29 arranged. This sensor arrangement 29 contains a large number of sensors designed according to the invention 1 , which are arranged here like a matrix. The sensors 1 are in the sensor array 29 interconnected and connected to evaluation electronics.

With this in the seat 26th a seating furniture arranged sensor arrangement 29 can be based on one with the sensor array 29 feasible spatially and time-resolved measurement of the loading forces or pressures on the sitting posture assumed by the person sitting on the seating furniture and on changes in the same. It is also possible, simply by determining the duration of the application of pressure (force), to infer a time that a user spends in a sitting position on the seating furniture. / For example, a signal can be sent to the person that they have reached or exceeded a recommended maximum length of stay in a sitting position. If the dynamics and / or the specific pressure and force distribution indicate a poor sitting posture, the person can be requested, for example, to change (improve) the sitting posture via appropriate software and output.

List of reference symbols

1

sensor

2

Circuit board

3

Track

4th

insulating protrusion

5

Contact element

6th

Pressure piece

7th

flexible support

10

Sensor arrangement

13th

Connector

14th

flexible circuit board

15th

first sensor part

16

web

17th

flexible mat

18th

second sensor part

19th

Adhesive layer

20th

Track structure

21st

Pressure piece

22nd

electrically conductive coating

23

flexible support

24

Recess

25th

mask

26th

Seat

27

Base

28

Padding

29

Sensor arrangement

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 3704870 [0007]
• US 4314227 [0008]
• US 2010/0063779 A1 [0009]
• US 5033291 [0009]
• DE 112012000006 T5 [0009]
• DE 102018127320 [0012, 0015, 0020]

Claims (15)

Sensor (1) for the qualitative and / or quantitative detection of forces and / or pressures on the sensor (1) • a conductor track structure (3; 20) which has an electrical resistance and is located at least partially exposed with contact surfaces and can be connected to two electrical poles of a measuring current source, • a flexible, deformable, flat contact element (5) which is spaced apart from the contact surfaces in a zero position of the sensor (1) and has an electrically conductive conductive surface facing the contact surfaces, and • a pressure piece (6; 21) formed from a flexibly deformable material and arranged on a side of the contact element (5) opposite the conductor track structure (3; 20), which has a pressure surface with which it touches the contact surfaces of the conductor track structure (3; 20) opposite and which tapers in a cross-sectional circumference starting from a base in the direction of the contact element (5), the pressure piece (6; 21) being arranged and set up when a force acting on the sensor (1) or on the sensor (1) burdening pressure to be shifted in the direction of the contact element (5), and to press the contact element (5) in the direction of the contact surfaces of the conductor track structure (3; 20). Sensor (1) Claim 1 , characterized in that the pressure piece (6; 21) is formed from an elastomer material. Sensor (1) according to one of the preceding claims, characterized in that the contact element (5) is provided with an electrically conductive coating on its guide surface facing the contact surfaces of the conductor track arrangement (3; 20). Sensor (1) after one of the Claims 1 or 2 , characterized in that the contact element (5) is formed from an electrically conductive material. Sensor (1) according to one of the preceding claims, characterized in that the pressure surface of the pressure piece (6; 21) tapers conically starting from the base in the direction of the contact element (5) at least in one section. Sensor (1) according to one of the preceding claims, characterized in that the pressure piece (6; 21) does not touch the contact element (5) when the sensor (1) is not subjected to a force or a pressure. Sensor (1) according to one of the preceding claims, characterized in that the conductor track structure (3; 20) having an electrical resistance is formed by conductor tracks or conductor track sections isolated from one another, of which a first conductor track or a first conductor track section can be connected to a first pole of a measuring current source and a second conductor track or a second conductor track section can be connected to a second pole of the measurement current source that is different from the first pole. Sensor (1) Claim 7 , characterized by two nested, mutually electrically isolated finger structures as a first and a second conductor track. Sensor (1) after one of the Claims 7 or 8th , characterized by a mask made of an insulating material applied to the exposed surface of the conductor tracks or conductor track sections, the mask causing a shape adaptation of a geometry of the exposed surface of the conductor tracks or conductor track sections to a cross-sectional geometry of the pressure piece (6; 21). Sensor (1) according to one of the preceding claims, characterized by an elastic film or membrane as the contact element (5). Sensor (1) according to one of the preceding claims, characterized in that the contact element (5) is fixed to spacers (4) which keep it at a distance from the contact surfaces of the interconnect structure (3; 20) in the zero position. Flat sensor arrangement (10) for temporally and / or spatially resolved force or pressure measurement with an arrangement of individual sensors (1) according to one of the preceding claims distributed over a detection area and with a controller to which the sensors (1) are connected. Sensor arrangement (10) according to Claim 12 , characterized in that the pressure pieces (6; 21) of several sensors (1) of the sensor arrangement (10) are connected to one another in a pressure piece support (17). Sensor arrangement (10) according to one of the Claims 12 or 13th , characterized in that the conductor track structures (3; 20) are arranged on a common circuit board (14), in particular a flexible circuit board (14). Sensor arrangement (10) according to one of the Claims 12 to 14th , characterized in that the controller is set up to send sensor signals from the individual sensors (1) at a predetermined time To record timing repeatedly and to submit an evaluation.

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