WO2020057973A1

WO2020057973A1 - Measuring system and measuring method for determining wear of a brake lining of a friction brake

Info

Publication number: WO2020057973A1
Application number: PCT/EP2019/073542
Authority: WO
Inventors: Sebastian Kuss; Ovidiu Parasca
Original assignee: Knorr-Bremse Systeme für Schienenfahrzeuge GmbH
Priority date: 2018-09-18
Filing date: 2019-09-04
Publication date: 2020-03-26
Also published as: EP3853494A1; DE102018122884A1

Abstract

The invention relates to a measuring system and to a method for determining wear of a brake lining (6) of a friction brake, wherein a wear element (11), the wear of which is detected as representative of the brake lining (6) or by which wear of the brake lining (6) is detected, is integrated into the brake lining (6). The measuring system comprises a permanent magnet (13) and a magnetic field sensor which are arranged in a ferromagnetic core (16) in a closed first magnetic circuit, and the wear element (11) is ferromagnetic and is designed in such a way that a second magnetic circuit leads through the wear element (11) and the permanent magnet (13).

Description

DESCRIPTION

Measuring system and measuring method for determining wear of a brake lining of a friction brake

The invention relates to a measuring system and a measuring method for determining wear of a brake lining of a friction brake, wherein a wear element is incorporated into the brake lining, the wear of which is representative of the

Brake pad is determined.

Measuring systems and measuring methods for determining wear can record the reaching of a wear limit of the brake pad during the operation of the vehicle and give an indication of a necessary replacement of the brake pad. In this way, the length of an inspection interval in which a visual inspection of the covering thickness takes place can be extended, as a result of which the costs of the inspection and also follow-up costs are reduced by increased downtimes.

From the document DE 10 2006 042 777 B3, for example, a device is known in which an adjusting spindle of an application device of the brake is coupled to an encoder via a reduction gear. A sensor, which preferably interacts with the sensor in a contactless manner, detects a wear value of the brake lining based on the position of the sensor. In this arrangement, a current wear value of the brake lining is advantageously output. In this way, excessive wear can be detected before a wear limit is reached. However, due to the mechanical coupling of the sensor and adjusting spindle of the application device, the system is structurally complex.

US 2006/0273148 A1 describes a non-contact type

Measuring system of the type mentioned is known, in which a contactless readable sensor is incorporated as a wear element in the brake pad. The

Document DE 10 2008 011 288 B4 shows a similar system, in which, however, the sensor is not arranged in the brake pad, but on the outside thereof. According to the two publications, the sensor is, for example, as RFID (Radio Frequency Identification) sensor designed. An intact function of the embedded sensor can be checked regularly via a transceiver arranged externally from the brake pad. If the brake pad reaches a predetermined wear limit, the embedded sensor is also worn and destroyed, whereupon a request from the transceiver is no longer answered. The transceiver thus detects when the wear limit has been reached and transmits it preferably wirelessly to a display device. The construction is structurally simple, since no mechanically moving components are involved.

Compared to the system mentioned above, however, no information reflecting the current wear is available, but only the achievement of the

Wear limit detected. The system described is structurally simple

feasible, especially if the sensor is arranged on the outside of the brake pad. Suitable mass-produced sensors are also available at low cost. Due to its arrangement in or on the brake pad, the sensor may be exposed to high temperatures. This can be his

Service life must be reduced.

It is an object of the present invention to provide a device and a method for detecting wear of a brake pad, which is constructed in a contactless manner and without additional mechanically moved components, and which also operates reliably at the high temperatures which can occur in the area of the brake pad .

This object is achieved by a device or a method with the features of the respective independent claim. Advantageous configurations and

Further developments are the subject of the dependent claims.

A measuring system according to the invention of the type mentioned at the outset is characterized in that the measuring system comprises a permanent magnet and one

Magnetic field sensor, which are arranged in a ferromagnetic core in a closed first magnetic circuit, the wear element being ferromagnetic and such formed that a second magnetic circuit leads through the wear element and the permanent magnet.

In the measuring system according to the invention, two coupled magnetic circuits are thus formed, the magnetic fluxes of which they pass from the

Permanent magnets are caused and which influence each other with a sufficiently small reluctance of the two magnetic circuits in such a way that a sinking flux in one of the circles leads to an increase in the flux in the other circle and vice versa. A measurement of the magnetic flux in the first circle thus provides information about the flux in the second circle, which in turn is due to the abrasion of the brake pad and thus the embedded wear element when the brake is used.

In a method according to the invention for determining wear of a brake lining of a friction brake, there is at least one in the brake lining

Wear element incorporated, the wear of which is determined on behalf of the brake pad or by which wear of the brake pad is recorded. The

The method has the following steps: in a first magnetic circuit, a measuring sensor and in a second magnetic circuit coupled to the first magnetic element, the wear element is subjected to a magnetic field by the permanent magnet. A magnetic field strength is detected in the first magnetic circuit and an

The wear value of the wear element and / or the brake lining is determined on the basis of the magnetic field strength detected.

As stated in connection with the measuring system, the magnetic field strength in the first magnetic circuit depends on the magnetic reluctance of the second

Magnetic circuit and thus the geometry of the wear element, which changes when worn. With the wear of the brake disc, which is accompanied by abrasion of the wear element, the measured one changes accordingly

Magnetic field strength, whereby the wear value can be determined. This enables a contactless, immediate measurement of the current wear of the brake pad. The wear element itself is inexpensive and robust and especially heat-resistant, so that it is reliable even at high

Temperatures that can be reached in or on the brake pad can be used.

In an advantageous embodiment of the measuring system, the wear element is inserted into the brake lining essentially perpendicular to the brake disc and is positioned on one side opposite the brake disc with an end face in front of the magnetic field sensor. In the unused state of the brake pad, the wear element can extend over its entire thickness or even only in a rear part of the brake pad. A progressive wear of the

Brake pads can in the first case for the entire area of wear

Brake pads are recorded and in the second case only from a certain

State of wear.

In a further advantageous embodiment of the measuring system, the ferromagnetic core is formed in several parts from at least two L-shaped sections which complement each other to form a U-shaped basic shape with a base and two legs. The

Magnetic field sensor is between the two sections e.g. arranged in the base to detect the magnetic flux flowing through the core. The

Permanent magnet is arranged between the two legs. End faces of the two legs are positioned adjacent to a rear side of the brake pad, both end faces abutting the wear element. The wear element preferably has a geometry similar to a ladder, with two columns spaced apart from one another, which extend perpendicular to the friction surface of the brake lining, and at least one rung connecting the columns and oriented transversely to the columns. One of the two end faces of the legs of the core lies opposite one end face of one of the two pillars of the wear element, as a result of which the two coupled magnetic circuits are formed. Said ladder-shaped wear element can be made in one piece from several cuboid

Sections can be formed or assembled in several parts from several cuboid elements. The ladder-shaped geometry leads to a measurement signal of the magnetic field sensor that does not change linearly with the wear of the brake lining. When the rungs are abraded, the measurement signal changes more than in the sections between the rungs. The abrasion of the rungs and the associated Wear conditions can be detected robustly and reliably. The position (s) and the number of rungs can, for example, be matched to relevant wear conditions, for example in such a way that two first stages indicate necessary brake maintenance intervals and a third prompts for replacement of the pads.

In a further advantageous embodiment of the measuring system

Magnetic field sensor is a Hall sensor. The magnetic field sensor and / or the permanent magnet and / or the core are preferably arranged in a sensor head. To evaluate the signals of the magnetic field sensor, the measuring system in one embodiment has an electronic unit with an evaluation unit, which is connected to the magnetic field sensor. A wear value determined by the evaluation unit can

for example by a radio module which is arranged in the electronics unit and is coupled to the evaluation unit, e.g. to a

superordinate monitoring and / or display device. The electronics unit further preferably has a battery for supplying power to the evaluation unit, the magnetic field sensor and / or the radio module. Such a self-sufficient

Energy supply makes it easy to retrofit the measuring system, even if an on-board power supply is not available on a brake to be retrofitted.

The measured field strength is not only dependent on the geometry of the wear element, but also changes when the wear element comes into mechanical contact with the brake disc. When the wear element comes into contact, part of the flux emanating from the permanent magnet is passed through the brake disc, which results in a sudden change in the magnetic field

Magnetic field sensor results.

In an advantageous embodiment of the method, with the aid of this effect an additional application and / or release of the friction brake is determined on the basis of a change in the detected magnetic field strength. This is preferred

Applying and / or releasing the friction brake using a

Differentiated the rate of change of the detected magnetic field strength from wear of the brake pad. So it becomes possible, besides the wear measurement Measuring system can also be used to check the functionality of the friction brake.

The invention is explained in more detail below with reference to figures. The figures show:

Fig. 1 shows a part of a friction brake of a rail vehicle with a

Device for detecting wear of a brake pad in a first embodiment;

Fig. 2a-c each an enlarged detail of Fig. 1, in which the device for

Monitoring of wear is shown in more detail on different wear conditions of the brake pad;

Fig. 3 is a schematic representation of a measurement signal for measuring a

Wear depending on a wear time;

Fig. 4 shows a sensor head of a device for measuring wear with connected electronics unit in a schematic block diagram.

1 shows a section of a friction brake 1 of a rail vehicle, for example a freight wagon, partially cut.

The friction brake 1 is a disc brake, in which on a scar 2 of the

Vehicle a brake disc 3, in the present case an internally ventilated disc, is attached. There is an application mechanism 4, not shown here, which acts on two brake pads 6, each carried by a pad carrier 5. The

Clamping mechanism 4 is not shown in greater detail here. It can be actuated pneumatically, hydraulically or by an electric motor in a known manner. When applying the friction brake 1, the brake pads 6 are on the

Application mechanism 4 pressed against the brake disc 3 and thus into one

Frictional intervention brought with the brake disc 3. When the brakes are used, both the brake disc 3 and the brake pads 6 wear out, as the lining thickness (lining thickness) decreases. To avoid direct frictional contact between the brake pad carrier 5 and the brake disc 3, the brake pads 6 may only wear to a maximum of a predetermined permissible wear level, which is symbolized in FIG. 1 by a dashed line, for example.

To observe the increasing wear of the brake pads 6 and

Monitoring whether the brake pads 6 have reached the maximum permissible degree of wear is a measuring system 10 for monitoring the friction brake 1

Pad thickness of the brake pads 6 provided. The measuring system 10 includes a

Wear element 11 and a sensor head 12. In the one shown in FIG. 1

In the exemplary embodiment, the measuring system 10 is formed only on one side of the friction brake 1, that is to say on one of the brake pads 6. In an alternative embodiment, it is possible to use a corresponding measuring system 10 for both brake pads 6

to provide.

The braking system 10 is in each case a schematic in FIGS. 2a-c

Sectional drawing shown in more detail. 2a shows an arrangement with a brake pad 6 in the delivery state or with a brake pad thickness which is far above the wear limit. 2b shows the same arrangement as wear progresses. In the arrangement shown in Fig. 2c, the brake pad 6 has reached its wear limit.

In the exemplary embodiment shown, the wear element 11 is a ferromagnetic element which is inserted into the brake lining 6. In the example shown, the wear element 11 consists of an arrangement of a plurality of cuboid elements 111-115, two spaced-apart cuboid elements 111, 113, 115 alternating with larger rod-shaped elements 112, 114. The smaller cuboid elements 111, 113, 115 are also referred to below as longitudinal elements 111, 113, 115 and the longer rod-shaped elements 112, 114 as transverse elements 112, 114. The cuboid elements 111-115 thus form a ladder-shaped structure, the cross section of which varies in stages in the wear direction of the brake lining (ie in a direction perpendicular to the braking surface of the brake lining 6 or to the surface of the brake disk 3). The wear element 11 is preferably made of a mechanically soft ferromagnetic metal and is worn off the brake disc 3 when the brake pad 6 wears without the brake disc 3 being excessively worn, ie more than by the brake pads 6.

In the example shown, the wear element 11 is flush with the brake pad 6 on the side opposite the brake disc 3, the

Cover carrier 5 is shortened or recessed in this area, so that

Wear element 11 is not in mechanical contact with the lining carrier 5. The wear element 11 could alternatively also protrude beyond the brake pad 6. The wear element 11 ends in front of the sensor head 12. In the example shown, this comprises a permanent magnet 13 and a magnetic field sensor, advantageously a Hall sensor 14, which is coupled via a connecting cable 15 to an electronic unit not shown in FIGS. 2a-c.

The permanent magnet 13 and the Hall sensor 14 are arranged together with a core 16 within the sensor head 12. The core 16 is ferromagnetic,

for example an iron core. In the exemplary embodiment shown, it is formed in two parts from two L-shaped sections which together form a U-shaped section

Complete the basic shape with a base and two legs. The Hall sensor 14 is positioned in the base between the two sections. In the illustrated

In the exemplary embodiment, the two sections are completely separated from one another by the Hall sensor 14. Correspondingly, the Hall sensor 14 measures the entire magnetic flux running through the core 16.

The core 16, which is U-shaped in its overall shape, is arranged within the sensor head 12 such that end faces of its legs face the brake lining 6 and preferably bear against the brake lining 6. Between the legs is the Permanent magnet 13 arranged. In this way, a first magnetic circuit is formed, which is also referred to below as the primary circuit.

The two spaced-apart cuboid elements of the wear element 11 are embedded in the brake lining 6 in such a way that they are each positioned centrally in front of the end faces of the legs of the core 16. The wear elements 11 extend in the direction of the thickness of the brake pad 6 from the back approximately to its friction surface.

The wear element 11 and the permanent magnet 13, as well as the edge regions of the core 16 facing the wear element 11, in addition to the

Primary circuit formed a second magnetic circuit, which is also referred to below as a secondary circuit. Both run through the permanent magnet 13 itself

magnetic circles.

In the situation shown in FIG. 2a, the magnetic flux generated by the permanent magnet 13 is divided between the primary circuit and the secondary circuit. The Hall sensor 14 measures a correspondingly small magnetic flux in the primary circuit.

With increasing wear (see FIG. 2b) of the brake pad 6, this also becomes

Wear element 11 removed. This goes for an increase in magnetic

Reluctance of the secondary circuit, through which the ratio of the magnetic fluxes of the two circuits to one another is changed. As a result, the flow in the primary circuit measured by Hall sensor 14 increases.

The flow in the primary circuit becomes maximum when the wear element 11 has been completely removed and the flow in the secondary circuit has dropped to zero. In the wear element 11 used here, the transverse elements 112, 114 contribute more to the magnetic flux in the secondary circuit than the longitudinal elements 111, 113, 115, since the transverse elements 112, 114 close the secondary circuit. Removal of the elements 112, 114 is clearly shown in the measured magnetic flux, whereas removal of the elements 111, 113, 115 has only a minor effect on the magnetic flux. For this reason, the maximum flow is essentially already reached in the wear situation according to FIG. 2c. The magnetic flux in the primary circuit measured by the Hall sensor 14 that does not change linearly with the abrasion of the wear element or the brake pad 6 is shown in FIG.

3 schematically represented in the form of a diagram. On the x axis of the

The diagram shows the wear in% and the magnetic flux in arbitrary units on the y-axis. A measurement curve 21 shows the measured flow. The measurement curve 21 runs within the different sections of the

Wear element 11 linear, the slope in sections of the longer cuboid elements 112, 114 being many times greater than in sections of the spaced smaller elements 111, 113, 115. In the latter, the measurement curve 21 runs approximately horizontally.

The course of the measurement curve with the pronounced shoulders during the abrasion of one of the elements 112, 114 enables reliable and robust detection of the wear states associated with the position of the elements 112, 114. The position and the number of cross elements 112, 114 can be matched to relevant wear conditions, for example in such a way that two first stages indicate necessary brake maintenance intervals and a third prompts for a pad replacement.

The system described is designed to measure the magnetic flux when the brake is not in use. When the friction brake 1 is actuated, the brake pad 6 is pressed against the brake disc 3 and the brake disc 3 becomes part of the secondary circuit. This also changes the flow in the primary circuit, specifically it is lowered when the brake is applied.

4 shows a possible evaluation of the Hall sensor 14 of the sensor head 12 in a block diagram. The sensor head 12 can, for example, be that shown in FIG. 2 or FIGS. 3a, b, with further depictions being shown

Components of the sensor head 12 was dispensed with.

4, the sensor head 12 is connected to a via the connection cable 15

Electronics unit 17 is connected. This can, for example, in the area of Friction brake, for example attached to the application mechanism 4.

The electronics unit 17 comprises an evaluation unit 18 which applies a suitable operating current to the Hall sensor 14 and evaluates the signals of the Hall sensor 14. In the example shown, the evaluation unit is coupled to a radio module 19, via which the evaluated signals of the Hall sensor 14 are forwarded to a higher-level diagnostic unit, not shown here. Retrofitting can also advantageously be carried out in this way without corresponding cables for the transmission of the signals being laid in the rail vehicle.

It can be provided that a wear value is determined by the evaluation unit 18 and passed on by the radio module 19. In this way, the higher-level diagnostic unit can understand the continuous wear of one or both of the brake linings 6 of the friction brake 1. It is then possible, for example, to compare excessive wear on different axles and / or different brakes on one axle

To detect brake pads 6 before its wear limit is reached.

In addition, a comparison of the determined can already be made in the evaluation unit 18

Wear value take place with a predetermined maximum wear value, so that the radio module 19 can immediately output a signal indicating that the wear limit has been reached.

In the example shown, the electronics unit 17 further comprises a battery 20 for the self-sufficient energy supply of the electronics unit 17. This is also of particular interest in retrofit solutions which are made possible even if there is no cable for energy supply from an electrical system. To be as large as possible

To achieve operating time of the electronics unit 17 with the battery 20 before it has to be exchanged or charged, it can be provided that

Information about the determined degree of wear is only output intermittently, for example hourly or initiated by braking processes. In the first embodiment of FIG. 2, the measuring system 10 can be set up to apply or release the friction brake 1 independently of the

To detect wear of the brake pad. This is possible because when the friction brake 1 is applied, the side of the wear element 11 facing the brake disc 3 comes into contact with the brake disc 3, which likewise changes the

Magnetic field on the opposite, positioned in front of the Hall sensor 14

Front side of the wear element 11 results. A change in the magnetic field detected by the Hall sensor 14 due to the application of the friction brake 1 leads to a rapid, almost abrupt change in the detected field strength. In this way alone, such an application event can be distinguished from a change in the magnetic field that results from wear of the brake lining 6 and the wear element 11.

The evaluation unit 18 can be designed to detect a change resulting from the application or release of the friction brake 1 and to emit a corresponding signal about the application or release of the brake. In this context, it can further be provided that after the brake has been released, a measurement is taken of the wear of the brake lining 6, which is then output by the evaluation unit 18 via the radio module 19.

Reference numerals

1 friction brake

2 scar

3 brake disc

4 locking mechanism

5 brake pads

6 brake pad

10 measuring system

1 1 wear element

111 -115 cuboid element

12 sensor head

13 permanent magnet

14 Hall sensor

15 connection cables

16 core

17 electronics unit

18 evaluation unit

19 radio module

20 battery

21 measurement curve

Claims

PATENT CLAIMS

1. Measuring system (10) for determining wear of a brake lining (6) of a friction brake (1), wherein a wear element (11) is incorporated into the brake lining (6), the wear of which is determined on behalf of the brake lining (6) or by Wear of the brake lining (6) is detected, characterized in that the measuring system comprises a permanent magnet (13) and a magnetic field sensor, which are arranged in a ferromagnetic core (16) in a closed first magnetic circuit, and in that the wear element (11) is ferromagnetic is and designed so that a second by the wear element (11) and the permanent magnet (13)

Magnetic circuit leads.

2. Measuring system (10) according to claim 2, wherein the wear element (11) in

Is inserted substantially perpendicular to the brake disc (3) in the brake lining (6) and is positioned on an opposite side of the brake disc (3) with an end face in front of the magnetic field sensor.

3. Measuring system (10) according to claim 2, wherein the wear element (11) extends in the unused state of the brake pad (6) over its entire thickness.

4. Measuring system (10) according to claim 2 or 3, wherein the wear element (11) on the side opposite the brake disc (3) protrudes with a section over the brake lining (6) or is flush with the brake lining (6).

5. Measuring system (10) according to one of claims 1 to 4, in which the core (16)

is formed in several parts from at least two L-shaped sections which complement each other to form a U-shaped basic shape with a base and two legs, the magnetic field sensor being arranged between the two sections in the base and the permanent magnet (13) being arranged between the two legs is.

6. Measuring system (10) according to claim 5, wherein the core (16) with end faces of the two legs is positioned adjacent to a rear side of the brake pad (6), both end faces abutting the wear element (11).

7. Measuring system (10) according to claim 6, wherein the wear element (11)

The geometry of a ladder has two columns spaced apart from one another, which extend perpendicular to the friction surface of the brake pad, and at least one rung connecting the columns.

8. Measuring system (10) according to claim 6 and 7, in each of which one of the two

End faces of the legs of the core (16) lie opposite one end face of one of the two pillars of the wear element (11).

9. Measuring system (10) according to one of claims 6 to 8, in which the

Wear element (11) has a plurality of cuboid sections or elements (111-115).

10. Measuring system (10) according to one of claims 1 to 9, in which the

Magnetic field sensor is a Hall sensor (14).

11. Measuring system according to one of claims 1 to 10, in which the magnetic field sensor and / or the permanent magnet (13) and / or the core (16) are arranged in a sensor head (12).

12. Measuring system according to one of claims 1 to 11, comprising a

Electronics unit (17) with an evaluation unit (18), which with the

Magnetic field sensor is connected.

13. Measuring system according to claim 12, wherein the electronics unit (17) has a radio module (19) which is coupled to the evaluation unit (18).

14. Measuring system according to claim 12 or 13, wherein the electronics unit (17) has a battery (20) for power supply.

15. A method for determining wear of a brake pad (6)

Friction brake (1), with at least one in the brake lining (6)

ferromagnetic wear element (11) is incorporated, comprising the following steps:

- Applying a magnetic field to a measuring sensor by the

Permanent magnets (13) in a first magnetic circuit;

- Applying the wear element (11) with the magnetic field of the

Permanent magnets (13) in a second magnetic circuit coupled to the first magnetic circuit;

- detecting a magnetic field strength in the first magnetic circuit;

- Determining a wear value of the wear element (11) and / or the brake lining (6) on the basis of the magnetic field strength detected.

16. The method according to claim 15, wherein the magnetic field strength is detected by a Hall sensor (14) as a measuring sensor.

17. The method according to claim 15 or 16, in which additionally applying and / or releasing the friction brake (1) is determined on the basis of a change in the detected magnetic field strength.

18. The method according to claim 17, in which the application and / or release of the friction brake (1) is differentiated from wear of the brake lining (6) on the basis of a rate of change of the detected magnetic field strength.