JP2020046421A - Planar force sensor unit for sensor system - Google Patents

Abstract

To provide a planar force sensor unit for force sensor systems and/or pressure sensor systems.SOLUTION: A force sensor unit includes first and second insulating thin films, and the thin films are mutually-superposedly arranged and support conductor path patterns. Elastically-deformable spacer elements between conductor path patterns divide the conductor path patterns into multiple individual areas. The conductor path patterns include evaluation circuit connection parts that are formed at mutually opposite terminal ends of the sensor unit. When the conductor path patterns are contacted and connected to each other, respectively different resistance values are generated between the connection parts in the individual areas. A microcontroller of the evaluation circuit measures the resistance values at the connection parts in sequentially continuing clock periods, and stores them. A comparator unit is configured to compare a current resistance value with the stored resistance values and to output an output signal when the current resistance value is deviated from the stored respective resistance values by a prescribed value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a planar force sensor unit for a sensor system, comprising a first insulating thin film and a second insulating thin film, wherein the insulating thin films overlap each other. A first conductor track pattern and a second conductor track pattern that are arranged on their facing surfaces and between which a resiliently deformable spacer element is arranged. . The membrane is preloaded by spacer elements so that they are elastically separated from one another. The force acting on at least one of these thin films forms a contact connection between the first conductor pattern and the second conductor pattern. At least one of the first conductor pattern and the second conductor pattern is separated by a spacer element into a number of contact areas, wherein a force acts on one of the thin films. Then, contact connection occurs between the conductor path patterns of the first thin film and the second thin film. Here, these conductor track patterns are formed at least partially on the thin film by means of a resistive coating. These coatings have a certain electrical sheet resistance. The first conductor track pattern and the second conductor track pattern have connections for connection to an evaluation circuit, which is related to the position and by the action of forces and the crushing of the spacer element. An output signal is output in relation to the resulting resistance value.

  Sensor systems that sense pressure or force are used in many monitoring systems. For example, these sensor systems are used in automobiles and the like to determine whether the driver is firmly gripping the steering wheel, whether the hand is acting on the steering wheel, or whether the driver is overworked or has health problems. Determines whether the steering wheel or another control element has been released. Here, for example, see DE 10 201 0035 940 B4 and DE 10 201 400 163. Similar pressure-sensitive sensor systems are furthermore generally suitable for applications in which pressure effects or force effects caused by occupancy of vehicle seats or by forces are to be detected or measured, for example in the event of an accident. . This should trigger, for example, the action of a control or accessory element of the motor vehicle. Another example is a shelf system, where the occupancy of individual surfaces should be continuously monitored. These are only a few special application possibilities with many application possibilities.

  In many applications, this type of sensor system is located under the outer cover, so that in order not to affect the appearance of the object on which the sensor unit is mounted, the sensor unit is: It should have only a small thickness perpendicular to its main surface. The cover must be partially attached to the original object whose operation is to be verified under relatively high mechanical stress, so if the dimensions of the spacer element are small or In the case of an action or a force action, there is also a danger of continuous local crushing of the membrane and thus misoperation. This is the case, for example, with the rim of a steering wheel in a motor vehicle in which a leather cover is provided and under which the sensor system is arranged, but for example to reduce the occupancy of the vehicle seat or other loads. This also occurs in other application cases, such as a seat sensor used in a car seat to confirm. With known pressure-sensitive sensors, the action of pressure through the seat covering can cause at least partial misoperation of a large number of individual contact elements.

  The task of the present invention is to evaluate the output signal of the sensor system, since this type of misoperation, which can also be caused by temperature effects, aging, partial damage, etc., is not unavoidable, and in particular is often not constant. Is to realize a sensor system that is not affected by this kind of action.

  The above-mentioned problem is solved by the invention described in claim 1.

  Advantageous configurations and developments of the invention are described in the dependent claims.

  The invention will be described in more detail hereinafter on the basis of the illustrated embodiments.

FIG. 3 is a perspective view of a non-limiting example of an embodiment of the structure of the sensor system, separated from one another, using an embodiment of the sensor unit. FIG. 2 is a cross-sectional view of the embodiment shown in FIG. 1 is a perspective view of a thin film with a first embodiment of a conductor track pattern. FIG. 5 is a first thin-film embodiment of a sensor unit having a planarly extending conductor track pattern usable with the conductor track patterns shown in FIGS. 3 and 4b. FIG. 11 is a plan view of a third embodiment of the second thin film of the sensor unit on which the spacer elements are arranged. FIG. 9 is a plan view of another embodiment of a first thin film having an extended conductor track pattern. FIG. 5b is a plan view of an embodiment of a second film having a strip-like conductor track pattern to be used with the first film shown in FIG. 5a. FIG. 9 is a plan view of another embodiment of a second membrane with a number of individual conductor tracks connected in series and in parallel with one another via conductor tracks with resistance. Diagram used in the steering wheel of a vehicle, connected to the first membrane shown in FIGS. 4a and 5a, with the second membrane shown in FIG. 3, 4b or 5b. 3 is an embodiment of the use of one or more sensor units shown in FIGS. 4a, 4b or 5a, 5b. FIG. 3 is an embodiment of a number of sensor units that may be woven or embedded in a textile or helmet and their evaluation. 9 is an embodiment of an evaluation circuit for the sensor unit shown in FIGS. 1 to 8.

  FIG. 1 shows a perspective view of a sensor part of a sensor system arranged on a carrier part 20. This may be the rim of the steering wheel or another component of the vehicle, the inner surface of a garment or helmet, the mounting surface or another surface 24 of the shelf system, on which force or pressure acts, Should be detected and evaluated.

  The upper surface of the sensor part may be covered by a cover 23, which is for example an outer leather cover in the case of a steering wheel rim, or a leather cover in the case of a vehicle seat. It may be stuck and sewn around the rim or seat of the steering wheel under the action of a large pulling force.

  Below the cover 23 may be located a cushion layer or insulator layer 22, which is used to compensate for undulations in the underlying structure.

  Below the cover 23 or the cushion layer 22, the first thin film 1 of the sensor unit is arranged. 1 and 2, the first thin film 1 has a first conductive path pattern 3 on its lower surface. 4a and 5a, this may be a full coating of a material with sheet resistance, but may also have a structure as described below for the second thin film 2.

  In FIGS. 1 and 2, a heat conductor layer 21 may be disposed on the upper surface of the first thin film 1.

  Below the first membrane 1 is arranged a second membrane 2 of the sensor unit, which carries a second conductor track pattern 4. For this purpose, advantageous embodiments are shown in FIGS. 3, 4b, 5b and 6.

  Arranged between the track patterns 3, 4 is a spacer element 7, which is elastically squashable, and is composed of the first track pattern 3 and the track pattern 4 of the second membrane 2. A gap is maintained between them and only when a force or pressure is applied does a contact connection between the conductor traces 3, 4 of the two membranes 1, 2 result.

  The second membrane 2 is advantageously mounted directly on the carrier part 20. The carrier part 20 forms an abutment upon application of force or pressure.

  FIG. 1 shows a relatively simple conductor track pattern 4 of the second membrane 2, which consists of a central conductor track 24, from which perpendicular and spaced apart from each other. Of the conductor track section 25 extends. Both the central conductor track 24 and the further conductor track section 25 are separated by spacer elements 7 into individual areas, where a contact connection is made when a force or pressure is applied.

  In the first embodiment of FIG. 1, a first connection portion 6 for an evaluation circuit is provided at the end of the conductor path 24 at the center of the second conductor path pattern 4 on the left side. This will be described in more detail. The conductor path 3 of the first conductor path pattern 3 is provided with a second connection 5 for an evaluation circuit at a right end opposite to the first end. This is in FIG. 1 opposite the right-hand second end of the central conductor track 24, but is separated therefrom by a spacer element 7 when no force is applied. In the event of a continuous crushing of the conductor track patterns 3, 4 at this end, which may be caused by the construction and manufacture of the outer cover 23, this should also be detected in the region between the ends described above. Under the action of force or pressure, a measurable and evaluable change in the resistance between these connections occurs at connections 5 and 6.

  FIG. 3 shows an embodiment of the conductor track pattern 4 of the second thin film 2 of the sensor unit, which allows easy differentiation between signals in two different areas of the sensor unit. Here, the spacer elements are not shown, but correspond to the spacer elements 7 in FIGS. 1 and 4b, 5b and 6 according to the purpose. In such an embodiment, the central conductor track 24 of FIG. 1 is divided into two mutually parallel halves 26, 27 with each connection 6 for the evaluation circuit. I have. The conductor sections, which extend at right angles to the halves 26, 27, are each interrupted in their own longitudinal direction and are connected by conductor sections 30 having a very narrow width and a curvature and thus a high resistance.

  The conductor halves 26, 27 also have a smaller width than the central conductor 24 in FIG. This results in a significantly increased resistance difference during operation at different points of the conductor track pattern. The same measures may of course also be applied in the conductor track pattern of the membrane 2 shown in FIG.

  The conductor track pattern shown in FIG. 3 is the same as the conductor track pattern of the second thin film 2 shown in FIG. Not only can it be used with the pattern 3, but also with the conductor track pattern of the first thin film 1 having the segmented structure shown in FIGS. 3, 4b and 5b. The important condition here is that the connection parts 5, 6 of the thin films 1, 2 for the evaluation circuit are arranged at mutually opposite ends of each conductor path pattern.

  4a and 4b show another embodiment of the first thin film 1 and the second thin film 2 of the sensor unit. In such an embodiment of the sensor unit, the first membrane 1 likewise has a full-surface coating 3 with a track pattern, which consists of a material having a measurable sheet resistance. For the connection of the evaluation circuit, the first membrane 1 has a first connection 5 on the left in FIG. 4a.

  Such a first thin film 1 is used together with a second thin film 2 shown in FIG. 4b. It likewise has as conductor track pattern 4 a full-surface coating of a resistive material with a measurable sheet resistance. Here, spacer elements 7, 8 are arranged on the surface of such a coating, which extend in a linear or vertical direction in FIG. 4b over the electrically conductive coating. . This divides the surface of the circuit traces 3, 4 into a number of regions, in which, when a force or pressure acts on one or two thin films 1, 2, the contact between the coatings forming the conductor traces A connection can be made.

  As can be seen from FIG. 4b, the second membrane 2 has, on the right side of FIG. 4b, a second connection 6 for connection to an evaluation circuit.

  To form a sensor unit, a first thin film is placed on a second thin film as follows. That is, the conductive coatings are opposed on the inner surface of the sensor unit and are positioned so that they are resiliently spaced from one another by the spacer elements 7,8. Here, the first thin film is arranged on the second thin film such that the connection part 5 is arranged on the edge of the sensor unit opposite to the connection part 6.

  Since the spacer element has a relatively small thickness and is elastically deformable, the action of a force or pressure on one or two membranes 1, 2 corresponds to the action of this force. Where a contact is made between the coatings. This gives rise to a resistance which varies between the connections 5 and 6 in relation to its position and in relation to the position of such a contact point. By arranging the connections in this way at the opposite edges of the membranes 1, 2, whether in the case of contact connections due to manufacturing or in the case of continuous contact connections caused by external influences, In one or more regions located between the spacer elements, deliberate squashing of the thin film causes a measurable change in resistance between the connections 5, 6 in another region.

  In the embodiment shown in FIGS. 5a and 5b as well, a first thin film 1 with a connection 5 on a full-surface coating 3 is used. Here, however, the second membrane has a strip-like conductor track pattern with strips 41, 42, 43, transversely to the extension of the strips 41, 42, 43 and over these spacer sections. 7 are arranged. This spacer section holds the gap between the first thin film 1 and the second thin film 2 with no force applied when the first thin film 1 is placed on the second thin film 2 so that the conductive coatings face each other. . The use of separated conductor track strips 41, 42, 43 allows, on the right-hand side of the second membrane 2, a connection 6 at the connection 6 with a plurality of inputs of the evaluation circuit, whereby a force or pressure Additional elucidation of the location of the impact and contact connections is obtained. However, the connection parts 6 may be connected to each other, and the evaluation circuit may be connected to one input side.

  In the embodiment of FIG. 6, the second membrane 2 is coated with a number of mutually separated conductor track surfaces 50. It is interconnected both in series and in parallel via narrow conductor tracks 10, 11. The conductor tracks 10, 11 may be bent for their extension, or may be otherwise extended, to increase their resistance. Such a second thin film 2 may work with a fully coated first thin film as described with reference to FIGS. 4a and 5a.

  5a, 5b and 6 as long as the condition is met that the connections 5, 6 of the two thin films are arranged at mutually opposite ends of the sensor unit formed by them. In the embodiment shown, it is possible to use, instead of the fully coated conductor pattern of the first thin film 1, a conductor pattern corresponding to each described conductor pattern of the second thin film. It is possible.

  The membranes 1, 2 themselves may be made of an elastomeric material, are very flexible and may be thin, for example in the range of 0.2 to 0.6 mm. However, it should have sufficiently low ductility to avoid breaking of the coating that forms the conductor track pattern. Such a coating with sheet resistance may be printed on a thin film having a thickness of 40 to 100 micrometers in the form of a resistive paste.

  After the conductor track pattern has been printed on one or two films, the spacer elements may also be printed on the film. The thickness of the spacer element, in relation to the intended use of the sensor unit, is advantageously in the range from 0.25 to 0.55 mm.

  This results in a very flexible sensor unit, which can be stuck around a bent carrier structure or sewn to a garment part.

  FIG. 7 thus illustrates the use of the sensor unit 100 consisting of the first and second membranes to evaluate the fact that hand force is acting or not acting on the rim 101 of the steering wheel. Are shown. For this purpose, one or more sensor units 100 are glued around the rim 101 of the steering wheel and inserted below the leather cover, as described with reference to FIG. Is done.

  The connections 5, 6 of the sensor unit 100 are connected to the input of an evaluation circuit 102, which may include a microcontroller.

  FIG. 7 further shows an electronic unit. The electronic unit may possibly trigger an emergency deployment when no / acting forces are applied to the rim of the steering wheel for a certain period of time. For this purpose, the sensor unit 100 is connected to the microcontroller 102 via the steering wheel, if it is integrated in the steering wheel, together with the connection line of such a steering wheel. As indicated by the dashed lines, one or more of the sensor units 100 may form part of a steering wheel cover that can be additionally installed, which in this case is a separate microcontroller. It is connected. Such a microcontroller 102 is now fed via a feed circuit 107 and outputs an output signal to the transponder 104 and the acoustic unit 105. The acoustic unit is shown as a handset in FIG. 5, but may include a speaker or a mobile phone. In the case of an undesired false alarm, this may be shut off via the shut-off device 106.

  The transponder 104 is connected via a wireless connection to another transponder 108 at the rescue station, to which an alert signal may be transmitted. The alarm signal can also receive vehicle location data as long as the microcontroller 102 is connected to the location unit 115.

  FIG. 8 shows an embodiment of a sensor system including a large number of sensor units. This may for example be embedded in the clothing of the motorcycle driver. As shown in the lower part of FIG. 8, the sensor unit may be embedded in the lower leg of the driver or the upper body of the driver, and additionally in the helmet. Here, these sensor units are separately connected to the microcontroller 102 and, in the event of an accident, not only give an alarm, but also convey information about the extent of the accident and the relevant body area of the driver. Which may be communicated wirelessly via interconnected transponders 104, 108 and via antennas 112, 113. Again, a shut-off device 106 is provided, which allows the shut-off of false alarms. The spacer elements may be formed with different stiffnesses in different sensor units and within them, so that only severe impacts on the sensor units are possible at the contact connection and at each connection 5, 6 resulting therefrom. This causes a change in resistance.

  In FIG. 9, the evaluation unit, shown in FIGS. 7 and 8 in simplified form as microcontroller 102, is shown in more detail. As can be seen from FIG. 9, such a microcontroller 102 is connected to the connections 5 and 6 of the sensor unit and has a separate memory unit 120 or is connected to a separate memory unit 120 I have. The microcontroller is clocked and evaluates the resistance appearing at the connections 5, 6 at predetermined time intervals and stores this in one or two memories 120. Here, each current measured value of the resistance is compared in the comparator 121 with the preceding measured value stored in the memory 120. If the current resistance value has changed by a predetermined value with respect to the stored resistance value, the comparator 121 outputs an output signal to the line 122 connected to the transponder 104.

  In this way, instead of evaluating the actual state of each of the operated or non-operated sensor units, such a change in state in successive clock cycles is evaluated.

Claims (9)

A planar force sensor unit for a force sensor system and / or a pressure sensor system,
The force sensor unit has a first insulating thin film (1) and a second insulating thin film (2), wherein the insulating thin films are arranged to overlap each other and face each other. Surface, carrying a first conductor track pattern (3) and a second conductor track pattern (4), wherein the thin films (1, 2) are preloaded so as to be elastically separated from each other. A force acting on at least one of the thin films to form a contact connection between the first conductor track pattern (3) and the second conductor track pattern (4). An elastically deformable spacer element (7) is arranged between the conductor track patterns;
At least one of the first conductor track pattern (3) and the second conductor track pattern (4) is divided into a number of contact areas by the spacer element (7), When a force acts on one of them, a contact connection occurs between the conductor track patterns of the first and second thin films,
The conductor track pattern (3, 4) is at least partially formed by a resistive coating, the coating having a predetermined electrical sheet resistance;
The first conductor path pattern (3) and the second conductor path pattern (4) have connecting portions (5, 6) for connecting to an evaluation circuit (102), and the evaluation circuit A planar force sensor unit that outputs an output signal in relation to the position and / or in relation to the force action and the numerical value of the resistance value caused by the crushing of said spacer element,
The connection portions (5, 6) for the evaluation circuit (102) are formed at opposite ends of the sensor unit, at least in the axial direction;
The conductor track pattern (3, 4) is divided by the spacer element into a number of sub-regions, the sub-regions in one or more individual regions upon contact connection between the conductor track patterns Providing different resistance values between the connections (5, 6) of the evaluation circuit (102),
The evaluation circuit includes a clock-controlled microcontroller, and the microcontroller measures the resistance value at the connection unit (5, 6) in successive clock cycles, and determines a memory unit (120). )
A comparator unit (121) is connected to the microcontroller (102), and the comparator unit compares a current resistance value with a resistance value stored in the memory unit (120) and When the current resistance value deviates by a predetermined value from the stored resistance value, an output signal (122) is output.
A planar force sensor unit, characterized in that: At least one of the conductor track patterns (4) is divided into individual surfaces (28, 29; 50), on which the spacer elements (7) are arranged; The individual surfaces are interconnected by connection lines (30; 10, 11) having resistance.
The sensor unit according to claim 1. The individual faces (50) of the conductor track pattern (4) are arranged in groups of individual faces connected in series to one another via a connection part (11) having a resistance,
Said groups are also interconnected on their own side via connection parts (10) which have a resistance.
The sensor unit according to claim 2. The conductor track pattern entirely covers the first thin film (1) and / or the second thin film (2), and is divided into individual regions by the spacer element (7);
The spacer element extends in both a first direction and a direction substantially perpendicular to the first direction, and divides the overall coating into a number of discrete regions;
The sensor unit according to claim 1. The first thin film (1) and / or the second thin film (2) are formed as elastic thin films, which elastic thin films can extend in their own longitudinal and lateral directions. Is,
The sensor unit according to claim 1. In the case of a continuous contact connection of the individual areas of the conductor track, the individual areas are arranged such that a change in resistance is measured and occurs at the connection (5, 6).
The sensor unit according to claim 1. The sensor unit is arranged under a leather cover of a steering wheel,
The sensor unit according to claim 1. The sensor unit is sewn to a garment part,
The sensor unit according to claim 1. One or more sensor units are located on a bottom surface of the shelf system and are configured to determine an occupancy of the shelf system;
The sensor unit according to claim 1.