DE102016111879A1 - Unidirectionally sensitive sensor for measuring deformations and brake with such a sensor - Google Patents

Abstract

The invention relates to a unidirectionally sensitive measuring sensor (1) for measuring deformations in a measuring direction (300) by means of a change in resistance with a grid structure (100) which is applied to a carrier body (200). The sensor (1) is characterized in that the grid structure (100) has at least four strain gauges (110, 111, 120, 121) in a Wheatstone bridge arrangement, the strain gauges (110, 111, 120, 121) having different conductor structures in pairs , The invention further relates to a brake which has at least one such sensor (1).

Description

The invention relates to a unidirectionally sensitive sensor for measuring deformations in a measuring direction via a resistance change with a grid structure, which is applied to a support body. The invention further relates to a brake with such a sensor.

Sensors for force related deformation measurements are known in many different designs. Strain gauges are often used.

Such sensors with z. B. electrically vapor-deposited thin-film gratings are designed for example as shear force sensors and are used for force determination from deformations (eg strains) on or in a force-carrying structure or structural component based on resistance changes. Such a structural component can be, for example, an axle body, a wall, a component of a brake, etc.

The publication DE 10 2008 015 873 A1 describes a brake element and a method for producing a brake element for detecting a deformation of a brake for a rail vehicle. The brake is designed to brake a wheel and / or a wheel set of the rail vehicle by means of a friction element of the brake. In this case, the brake element has a first material thickness in a first wall section and a second material thickness in a second wall section. The second material thickness is thinner than the first one. On a surface of the second wall portion, a sensor for measuring a deformation of the brake element in the second wall portion is arranged.

A suitable sensor often has a preferred direction in which it is more sensitive than in other directions. Advantageously, the sensor is even substantially sensitive only in one direction (unidirectional). This succeeds, for example, in that the sensor is bifilar and is compensated for transverse contraction. However, a disadvantage of such a sensor is that changes in the ambient conditions, for example temperature fluctuations, strongly influence the measurement result.

It is an object of the invention to provide an improved unidirectionally sensitive sensor in which the measurement result is influenced as little as possible by ambient parameters, in particular an ambient temperature.

It is another object to provide a brake with improved force measurement.

The object is achieved by a sensor or a brake with a sensor with the respective features of the independent claims.

An inventive sensor of the type mentioned has a grid structure with at least four strain gauges in a Wheatstone bridge arrangement, wherein the strain gauges have pairs of different conductor structures. The arrangement of the four strain gauges in a Wheatstone bridge, an optimal compensation of environmental influences that affect equally on all strain gauges, given, in particular optimal temperature compensation. The pairwise different conductor structure requires pairwise different resistance changes during stretching or contraction in a measuring direction, which leads to a measuring voltage at an output of the bridge arrangement.

In an advantageous embodiment, a pair of strain gauges has a conductor structure in which there are a number of electrically conductive longitudinal conductors arranged parallel to each other and spaced apart from one another, which are each electrically connected in series in an electrical series connection by relatively short connecting pieces and in the measuring direction of Sensor run. The longitudinal conductors can thus perform in their longitudinal direction, the detection of the deformation in the same direction. Based on their total conductor length, these strain gauges with a meander-shaped conductor structure have a large change in resistance when deformed in the direction of measurement.

In a further advantageous embodiment, another pair of strain gauges has a conductor structure in which two conductors are arranged helically next to one another at a certain distance. A structure with two conductors running next to each other at a certain distance is also called a bifilar structure. In this case, the formed screw may preferably have a rectangular basic shape in which sections of the conductors in the measuring direction and further sections transversely, in particular perpendicular to the measuring direction. Such a strain gage is particularly advantageously compensated for transverse contraction. In such a strain gauge, the ratio of the conductor lengths (ie the sum of the lengths of the respective sections) in the measuring direction to the conductor length perpendicular to the measuring direction is inversely proportional to the transverse contraction of a material to be measured. As a result, leads a Deformation perpendicular to the measuring direction does not lead to a resistance change.

In a further advantageous embodiment, it is provided to expose the pair of strain gauges with the meander-shaped conductor structure in a direction transverse, in particular perpendicular to the measuring direction only reduced deformations. In an advantageous embodiment, the support body has a plate-shaped base body, on which the grid structure is applied on. On the one hand, this results in the advantage of easy handling of the lattice structure and, on the other hand, the advantage of adapting the sensor to different installation conditions. In this case, a deformation of the body is transferred to the strain gauges or. To reduce the deformations of the strain gauges, the base body preferably has notches surrounding the strain gauges. As a result of the cuts, the region of the base body in which the strain gages are arranged is less deformed than other regions. The incisions surround the strain gauges preferably clamp-like. The incisions may be straight, angled or arcuate. The latter is particularly advantageous in a round basic shape of the support body.

In a further advantageous embodiment, the grid structure is applied in a thin-film process on the support body or its base body, for example, vapor-deposited. This results in a so-called thin-film sensor. This process is mature and has high qualities. If the support body is metallic, an electrically insulating intermediate layer is applied. In addition to the strain gauges, the lattice structure preferably also includes their connection to the Wheatstone bridge arrangement and / or connection points for contacting.

A further advantage of the support body can offer in that it forms a positive and / or cohesive anti-rotation of the sensor in certain installation situations.

For detecting a deformation which occurs in a deformation direction, the sensor is arranged with its measuring direction in this deformation direction. It is advantageous that a central center line passes through two of the strain gauges in the measuring direction of the sensor.

A brake for a vehicle, in particular a rail vehicle, has at least one sensor as described above. This is a precise detection of deformations and thus of forces acting in the brake, z. B. braking force, in a simple manner possible, the measurement result falsifying environmental influences are compensated as possible.

It is provided that the at least one sensor is arranged in or on a structural component of the brake. This results in a simple integration of the sensor in the brake.

The invention will now be explained in more detail by means of an embodiment with reference to the accompanying drawings. Hereby shows:

1 a perspective view of an embodiment of a brake with a sensor according to the invention;

2 a schematic sectional view of an exemplary structural component;

3 a schematic diagram of a sensor according to the invention;

4a a schematic plan view of an embodiment of a sensor according to the invention; and

4b a sectional view of the sensor according to 4a ,

Identical or similar components and functional groups are provided in the figures with the same reference numerals. Coordinates x, y, z are for orientation.

In 1 is an embodiment of a brake in a perspective view 2 with a sensor according to the invention 1 shown. 2 shows a schematic sectional view of an exemplary structural component 14 ,

The brake 2 is listed here only by way of example and associated with a wheel or wheel set of a rail vehicle, not shown. The wheel or the wheel set has a brake disk 5 with a brake disk axis of rotation 7 on. On the brake disc 5 is on both sides each a brake pad 4 with a friction lining holder 6 arranged.

A structural component 14 the brake 2 , which is a housing here, is with the below described in detail sensor 1 Mistake.

A comprehensive description and detailed explanation of the brake 2 in detail, the document can DE 10 2013 008 185 A1 are taken, wherein the reference numerals used there in FIG 1 and 2 for the sake of simplicity also be used.

The following are the components and functional groups of the brake 2 only briefly indicated and, where appropriate, explained in more detail, if this in connection with the sensor according to the invention 1 necessary is.

The brake 2 includes two clamp levers 8th , each with a brake pad 4 via a friction lining holder 6 coupled; an adjustment device 10 for setting a defined axial distance 20 ; pivot 12 on which the pliers lever 8th are hinged pivotable; the housing 14 as a structural component 14 ; a brake cylinder 16 , where the brake cylinder 16 when pressurized with brake cylinder pressure 18 the pliers lever 8th contracts and in this way a braking force 30 is produced; a reset device 22 ; a bolt 24 which is a console 26 with the housing 14 connects, with the console mounting holes 28 has for attachment.

This in 2 , illustrated housing 14 includes a guide bearing 36 for interaction with the bolt 24 ; a chamber 38 for the brake cylinder 16 ; a connection 40 for the brake cylinder pressure 18 ; a first wall section 33 that with a second wall section 34 connected is. A third wall section 35 connects the second wall section 34 with a wall of the guide bearing 36 ,

In a braking operation by the action of the braking force 30 becomes a frictional force 32 generated as the wheel peripheral force 32 a deformation causes, in principle, anywhere on the brake 2 can be recorded and measured. In the document DE 10 2013 008 185 A1 is described that the deformation of the housing 14 is measured based on this deformation.

This takes place between the first wall section 33 and the third wall section 35 on the second wall section 34 of the housing 14 , On the second wall section 34 acts in an x-direction one between an outer deformation 44 and an inner deformation 46 averaged deformation 48 , A sensor 1 is on the second wall section 34 and in a hollow-cylindrical recess / opening 42 passing through a wall 50 is formed, arranged.

The x-direction extends in the longitudinal direction of the second wall section 34 A y-direction is arranged transversely thereto, and a z-direction runs in the direction of a longitudinal axis of the hollow-cylindrical recess / opening 42 ,

The sensor 1 is for force-related strain measurement in a preferred direction, here in the direction of the force curve of the averaged deformation 48 , educated.

3 shows a schematic representation of a plan view of an exemplary construction of a sensor according to the invention 1 ,

The sensor 1 is constructed as a Wheatstone bridge with four measuring resistors. The four measuring resistors are divided by four individual strain gauges 110 . 111 . 120 . 121 formed, which have pairs of different conductor structures. A pair is from the strain gauges 110 and 111 formed, another pair of strain gauges 120 and 121 ,

The conductor structures can be vapor-deposited or sputtered, for example. For the isolation of a usually metallic carrier, an insulating layer is first applied, for example also sputtered on. Such a layer may be ceramic, for example.

The strain gauges 110 . 111 respectively. 120 . 121 of the different pairs are arranged crosswise within the Wheatstone bridge. There are thus formed two parallel bridge arms, in each of which one of the strain gauges 110 . 111 and one of the strain gauges 120 . 121 are arranged. The two branches of the Wheatstone bridge are in the example shown at connection points 130 . 131 supplied with a supply voltage U _B (GND denotes in the figure, a ground potential to which the supply voltage U _B refers). Between the middle taps of the two branches of the Wheatstone bridge can be at connection points 132 . 133 an output signal U _{A can be} tapped.

Each strain gauge 110 . 111 of the one pair has a number of mutually parallel and spaced apart electrically conductive longitudinal lines 140 on, in each case in an electrical series circuit behind each other in arcuate connections 141 are electrically connected. Such a strain gauge 110 . 111 is basically known and is used for example in strain gauges (DMS). The design of the strain gauges 110 . 111 already leads to a preferred measuring direction of a single strain gauge 110 . 111 , because in this preferred direction, the conductor length of the strain gauge 110 . 111 is not larger than perpendicular to this preferred direction. The preferred direction of the strain gauges 110 . 111 corresponds to just one measuring direction 300 of the sensor 1 , In the in 3 Additionally indicated coordinate system runs the measuring direction 300 parallel to the x-axis.

Each strain gauge 120 . 121 the other pair has two electrically conductive conductors 150 . 151 on, which are arranged side by side at a certain distance helically with a rectangular basic shape. In the middle of this formed snail are both conductors 150 . 151 are electrically connected to each other by a connection 152. The ladder 150 . 151 are arranged in this way bifilar. For clarity, the longitudinal line 140 and the arcuate connection 141 as well as the ladder 150 . 151 and the connection 152 only in each case with a strain gauge 110 respectively. 120 located.

At the strain gauges 110 . 111 If the summed conductor length in the x-direction exceeds the summed conductor length in the y-direction by a multiple. At the strain gauges 120 . 121 is due to the bifilar structure in both the x-, as well as in y-direction set a certain summed ladder length.

The summed ladder length in measuring direction 300 (x-direction) is in the strain gauges 120 . 121 smaller than the strain gauges 110 . 111 , so that the resistance change is correspondingly smaller. When stretch (or contraction) in the direction of measurement 300 Thus, a signal at the output of the bridge arrangement can be measured.

So that the sensor 1 works as unidirectionally as possible, the individual strain gauges 110 . 111 and 120 . 121 in turn, as insensitive as possible to a deformation perpendicular to the measuring direction 300 be.

The strain gauges 110 . 111 already have a low sensitivity in this direction due to the small conductor length in the y direction. In addition, a mechanical decoupling of strains of a support body transversely to the measuring direction 300 intended. This is for example through the cuts shown 202 reached, which the strain gauges 110 . 111 each surrounded like a clip. An expansion or contraction of the material on which the sensor is located 1 is arranged, in the direction of the clasp affects not or only insignificantly on the strain gauges 110 . 111 out.

At the strain gauges 120 . 121 For example, insensitivity in the y-direction can be achieved by a so-called transverse contraction compensation. These are the summed lengths of the ladder 150 . 151 and possibly the connection 152 so dimensioned that with a linear expansion of the sensor 1 perpendicular to the measuring direction 300 (ie in the y-direction) experiences a change in resistance due to a transverse contraction of the underlying material in the x-direction, which compensates for the change in resistance due to the linear expansion in the y-direction.

In other words, the ratio of the summed conductor length in the measuring direction 300 to the accumulated conductor length perpendicular to the measuring direction 300 inversely proportional to the transverse contraction of the material to be measured. The strain gauge thus formed 120 . 121 shows a change in resistance when deformed in the direction of measurement 300 , but no or almost no resistance change with deformation perpendicular to the measuring direction 300 ,

In summary, this creates a sensor 1 in which all four strain gauges 110 . 111 . 120 . 121 no or only negligible change in resistance at a deformation perpendicular to the direction of measurement 300 demonstrate. The sensor is also corresponding 1 not sensitive to deformations perpendicular to the measuring direction 300 ,

In contrast, a deformation leads in the measuring direction 300 to resistance changes in all four strain gauges 110 . 111 . 120 . 121 , but this because of the different line components in the measuring direction 300 to varying degrees for the pair of meandering strain gauges 110 . 111 and the pair of spiral bifilar strain gauges 120 . 121 ,

This creates a sensor 1 , which is unidirectional in the measuring direction 300 sensitive works. At the same time, the arrangement of the strain gauges 110 . 111 . 120 . 121 Temperature compensation is given in the Wheatstone bridge, since temperature influences equally on the strain gauges 110 . 111 . 120 . 121 especially if they use the same conductor material.

The 4a and 4b show a concrete embodiment of a transducer according to the application 1 for example, in the recess / opening 42 can be used to deformation 48 to measure (cf. 1 and 2 ). 4a shows the sensor 1 in a plan view and 4b in a sectional view along in the 4a specified section line AA.

Identical reference numbers in these figures denote the same or equivalent elements as in FIG 3 , With regard to the basic structure corresponds to the in the 4a , b shown sensor 1 the in 3 shown. Its description is hereby expressly referenced.

The sensor 1 has a support body 200 with an applied grid structure 100 on that related to 3 described various pairs of strain gauges 110 . 111 . 120 . 121 includes. The strain gauges 110 . 111 . 120 . 121 are interconnected to a Wheatstone bridge arrangement and with connection points 130 - 133 connected.

The supporting body 200 has a plate-shaped Gundkörper 201 on which the strain gauges 110 . 111 . 120 . 121 and the connection points 130 - 133 are arranged on a surface.

In the example shown, the main body 201 a circular disk. Such a disc-like design can, for. B. in the hollow cylindrical recess 42 of the structural component 14 according to 2 be pressed. Instead of a circular design can also be an oval design or a design with corners, grooves or other protruding or inwardly projecting structures may be formed, thereby simultaneously a positive rotation of the sensor 1 opposite z. B. the structural component 14 can be formed. Of course, a cohesive connection with anti-rotation is possible, for. B. by gluing.

The strain gauges 110 . 111 . 120 . 121 are cruciform on the body 201 positioned, wherein the meandering strain gauges 110 . 111 along a first central axis 301 and the spiral strain gauges 120 . 121 along a second central axis 302 are arranged. The first central axis 301 runs in the measuring direction 300 and the second central axis 302 perpendicular to the measuring direction 300 ,

For decoupling the strain gauges 110 . 111 from a contraction or elongation of the support body 200 in the y-direction, ie perpendicular to the direction of measurement 300 , are incisions 202 in the plate-shaped body 201 introduced in the y-direction like a clip around the strain gauges 110 . 111 are arranged around. Through the cuts 202 is achieved that a deformation of the edge of the main body 201 in the range of strain gauges 110 . 111 not or only insignificantly transfers to this.

As related to 3 is described, the spiral strain gauges 120 . 121 preferably transverse contraction compensated. By combining the strain gauges mechanically decoupled from deformations in the x-direction 110 . 111 and the transverse contraction compensated strain gauge 120 . 121 is the sensor 1 only in the measuring direction 300 and thus unidirectionally sensitive.

In the context of this application is a use of the sensor 1 explained in connection with a brake. Basically, the transducer according to the application not only in connection with brakes, but in many different deformation measurements of different components can be used.

LIST OF REFERENCE NUMBERS

1

sensor

2

brake

4

friction lining

5

brake disc

6

Reibbelaghalter

7

Brake disk rotational axis

8th

caliper lever

10

readjustment

12

pivot

14

Structural component / Housing

16

brake cylinder

18

Brake cylinder pressure

20

Axial distance

22

Reset device

24

bolt

26

console

28

mounting hole

30

braking force

32

Frictional force / wheel peripheral

33-35

wall section

36

guide bearing

38

chamber

40

connection

42

Recess / opening in the first wall section

44

External deformation

46

Inner deformation

48

Average deformation

50

wall

100

lattice structure

110-111

Strain gauge grid

120-121

Strain gauge grid

130-133

connection point

140

longitudinal conductor

141

connection

150, 151

ladder

152

connection

200

supporting body

201

body

202

incision

300

Measuring direction / direction of deformation

301, 302

center line

x, y, z

coordinates

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102008015873 A1 [0004]
• DE 102013008185 A1 [0028, 0032]

Claims (15)

Unidirectionally sensitive sensor ( 1 ) for measuring deformations in a measuring direction ( 300 ) via a resistance change with a grid structure ( 100 ), which on a support body ( 200 ), characterized in that the lattice structure ( 100 ) at least four strain gauges ( 110 . 111 . 120 . 121 ) in a Wheatstone bridge arrangement, wherein the strain gauges ( 110 . 111 . 120 . 121 ) have pairs of different conductor structures. Sensor ( 1 ) according to claim 1, wherein a pair of strain gauges ( 110 . 111 ) a number of mutually parallel and spaced apart electrically conductive longitudinal conductors ( 140 ), which are each electrically connected in series in an electrical series circuit and which in the measuring direction ( 300 ) of the sensor. Sensor ( 1 ) according to claim 1 or 2, wherein a further pair of strain gauges ( 120 . 121 ) two conductors ( 150 . 151 ), which are arranged helically next to each other at a certain distance. Sensor ( 1 ) according to claim 3, wherein a screw having a polygonal basic shape is formed, wherein sections of the conductors ( 150 . 151 ) in the measuring direction ( 300 ) and further sections transversely, in particular perpendicular to the measuring direction ( 300 ). Sensor ( 1 ) according to claim 4, wherein the screw has a rectangular basic shape. Sensor ( 1 ) according to claim 4 or 5, wherein the further pair of strain gauges ( 120 . 121 ) is contra-contraction compensated. Sensor ( 1 ) according to claim 6, wherein a ratio of a summed length of the sections of the conductors ( 150 ) in the measuring direction ( 300 ) to the summed length of the sections of the ladder ( 151 ) perpendicular to the measuring direction ( 300 ) is inversely proportional to the transverse contraction of a material to be measured. Sensor ( 1 ) according to one of claims 2 to 7, wherein the pair of strain gauges ( 110 . 111 ) in a direction transverse, in particular perpendicular to the measuring direction ( 300 ) is exposed only to reduced deformations. Sensor ( 1 ) according to claim 8, wherein the supporting body ( 200 ) a plate-shaped basic body ( 201 ) on which the pair of strain gauges ( 110 . 111 ), and the cuts ( 202 ), which the strain gauges ( 110 . 111 ) surround. Sensor ( 1 ) according to claim 9, wherein the cuts ( 202 ) each of the strain gauges ( 110 . 111 ) surrounded like a clip. Sensor ( 1 ) according to one of claims 1 to 10, in which the lattice structure ( 100 ) in a thin-film process on the support body ( 200 ) is applied. Sensor ( 1 ) according to claim 11, wherein the grid structure ( 100 ) next to the strain gauges ( 110 . 111 . 120 . 121 ) also their connection to the Wheatstone bridge arrangement and / or connection points ( 300 - 303 ) for contacting. Sensor ( 1 ) according to one of claims 1 to 12, wherein at least two of the strain gauges ( 110 . 111 . 120 . 121 ) along a central midline ( 301 ) of the sensor ( 1 ), which in the measuring direction ( 300 ), are arranged. Brake ( 2 ) for a vehicle, in particular a rail vehicle, with at least one sensor ( 1 ) according to any one of the preceding claims. Brake ( 2 ) according to claim 14, characterized in that the at least one sensor ( 1 ) in or on a structural component ( 14 ) of the brake ( 2 ) is arranged.

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