WO2022089689A1

WO2022089689A1 - Proximity switch, method for operating such a switch, and arrangement and method for monitoring a track section

Info

Publication number: WO2022089689A1
Application number: PCT/DE2021/100860
Authority: WO
Inventors: Dr. Martin KNEPPE; Markus Mende
Original assignee: Pintsch Gmbh
Priority date: 2020-10-27
Filing date: 2021-10-27
Publication date: 2022-05-05
Also published as: DE112021005736A5; EP4237311A1

Abstract

Proximity switch (10) having a first sensor element (S1) with a first sensing region (16) for sensing an object moving through the first sensing region (16), a second sensor element (S2) with a second sensing region (18) for sensing an object moving through the second sensing region (18), and a third sensor element (S3) with a third sensing region (20) for sensing an object moving through the third sensing region (20), wherein the sensing regions (16, 18, 20) of the three sensor elements (S1, S2, S3) are arranged in a spatially distributed manner such that an object moving in a particular direction through the sensing regions enters the sensing regions (16, 18, 20) in succession and leaves the latter again in the same order, wherein there is an overlapping region (22) in which the sensing regions (16, 18, 20) overlap such that an object situated there is sensed by all three sensor elements (S1, S2, S3), and wherein provision is made of an evaluation logic unit (24) having a state machine (40) for detecting the direction of movement and for identifying a defective sensor element.

Description

PROXIMITY SWITCH, METHOD FOR OPERATING SUCH AS WELL AS ARRANGEMENT AND EXPERIENCE FOR MONITORING A TRACK SECTION

TECHNICAL FIELD OF THE INVENTION

The invention relates to a proximity switch, a method for operating such a switch and an arrangement and a method for monitoring a track section.

BACKGROUND OF THE INVENTION

Proximity switches have long been known, in particular in the form of inductive proximity switches for use as so-called wheel sensors, e.g. from DE 23 26 089 A1, DE 32 34 651 A1 and DE 33 13 805 A1. They comprise at least one sensor element, typically in the form of an AC-powered oscillating circuit coil, which responds to a relative movement between the sensor element and a metal object, e.g. a railway wheel rolling past the sensor element, and triggers a pulse which is used, e.g. for counting or for triggering certain control signals can. If the sensor element is an AC-powered oscillating circuit coil, also known as a response coil, this is typically connected to a capacitor to form an L-C oscillating circuit and is part of a quiescent current monitoring circuit. If a metallic object moves through the electromagnetic field of the coil, the electrical behavior of the monitoring circuit changes, so that counting or control pulses, for example, can then be generated in a manner known per se via corresponding trigger circuits.

A typical application of proximity switches is the monitoring of track sections of a rail system, using proximity switches arranged at the beginning and at the end of a track section to be monitored to count whether the number of tracks in the track section retracted wheels (and thus also the corresponding number of axles of a rail vehicle, which is why in the railway sector one typically does not speak of a wheel but of an axle count) corresponds to the number of wheels or axles that have been pulled out of the track section, in order to then assign the corresponding track section to a to be able to report to the higher-level controller as free or occupied.

If a proximity switch has two sensor elements arranged one behind the other, the direction of travel and possibly even the speed of travel can also be determined from the order in which the sensor elements respond.

Inductive proximity switches of the type mentioned have proven themselves in practice for many years, but the increasing density of rail traffic, especially public transport in metropolitan areas, where e.g sensors with you. If a track that is actually free is reported as occupied, this can result in massive traffic disruptions. Of course, it can have catastrophic effects if an actually occupied track section is reported as free, which is why the standard design of corresponding systems is always such that, in case of doubt, an actually free track section is reported as occupied rather than erroneously releasing an occupied track section.

Various proposals have already been made to increase the reliability and operational safety, ie the reliability of the detection of, for example, the wheels of a passing rail vehicle. For example, DE 199 15 597 A1 proposes a wheel sensor with two oscillating circuit coils fed with alternating current, each coil consisting of two coil parts which have a common winding and whose individual windings are guided around two coil centers in the form of a figure eight when viewed from above, which advantageously allows to suppress induced interference voltages and to achieve a particularly high level of immunity to interference from electromagnetic interaction with the eddy current brakes used in many rail vehicles when they work in the detection range of the coils. If, in the case of the known proximity switches with two sensor elements, i.e. typically with two response coils, one sensor element fails due to a line interruption, the design is usually such that the sensor element goes into a "permanently occupied" state, i.e. it reacts as if its detection range was permanent a corresponding metallic object, from which it can usually be easily concluded that the corresponding sensor element has failed. However, it can also happen that sensor elements mistakenly do not respond, which is why, for safety reasons, several proximity switches always have to be installed in order to be able to decide from the sum of the information supplied by the corresponding sensor elements whether a sensor element is defective and is supplying an incorrect signal.

For conceptual clarification, it should be pointed out at this point that a track section is considered occupied if at a certain point in time more axles have entered it than exited, while a sensor element is said to be occupied if there is a detectable object in the detection range of the sensor element sensor element is located or the sensor element incorrectly indicates that a detectable object is located in its detection range due to a fault. Accordingly, a track section is considered free at a certain point in time if the same number of axles have moved out of it as previously moved into it, while a sensor element is said to be in a free state if there is no detectable object in the detection range of the sensor element or that Sensor element incorrectly indicates that there is no detectable object in its detection range due to a malfunction.

Particularly in the case of heavily frequented routes, there is a need to further increase the reliability of detection and, in particular, to ensure operational safety even if a sensor element fails at peak times and immediate maintenance of the system leads to operational interruptions.

For at least a partial solution to this problem, DE 196 28 884 A1 proposes a proximity switch with three micro-power pulsed radar elements serving as sensor elements, whose detection ranges partially overlap and whose signals are evaluated in the form of a "majority decision" in such a way that an occupied or free message only occurs when at least two of the three sensor elements output an occupied or a free signal. The occupancy reports are then used in a manner known per se to generate counting pulses, so that by using a plurality of proximity switches it can be counted how many wheels and thus how many train axles have entered and exited a track section.

With the solution proposed in DE 196 28 884 A1 it is possible to continue to operate the proximity switch even if one of the sensor elements fails, but it is only possible with great circuitry complexity (individual monitoring of the individual sensor elements) to determine which of the sensor elements may be defective. In addition, in the solution proposed in DE 19628 884 A1, the direction of travel should be determined solely from the sequence in which the individual sensor elements respond, which can be problematic if a sensor element fails.

SUMMARY OF THE INVENTION

The invention is based on the object of specifying a proximity switch which has been improved taking into account the above-mentioned problems, as well as a method for operating the same. The invention is also based on the object of specifying an arrangement and a method for monitoring a track section using a proximity switch according to the invention.

The object is achieved by a proximity switch having the features of claim 1 and a method for operating a proximity switch having the features of claim 6. The independent claims 8 and 10 relate to an arrangement and a method for monitoring a track section. The corresponding subclaims relating to advantageous configurations and developments. The invention allows a proximity switch to be configured compactly and inexpensively in such a way that there is a high level of operational reliability and it can be easily determined whether one of the sensor elements installed in the proximity switch is defective. This increases what is known as the availability of an arrangement, such as in particular an arrangement for monitoring a track section with regard to the presence of a rail vehicle in the track section, ie if a sensor element fails, the system is still available. In addition, the invention makes it possible to reliably determine the direction of movement in which an object is moving past the proximity switch, even when a sensor element has failed.

According to the invention, a proximity switch comprises a first sensor element with a first detection range for detecting an object moving through the first detection range, a second sensor element with a second detection range for detecting an object moving through the second detection range, and a third sensor element with a third detection range for detecting a moving object through the third detection area, wherein the detection areas of the three sensor elements are spatially distributed in such a way that an object moving in a specific direction through the detection areas enters the detection areas one after the other and these in the same order in which it entered them is, leaves again, with there being an overlapping area in which the detection areas overlap in such a way that an object located there is detected by all three sensor elements. The proximity switch also includes an evaluation logic with a state machine for detecting the direction of movement and for identifying a defective sensor element.

The evaluation logic can be arranged together with the sensor elements in a common housing or it can be separated from the sensor elements and, for example, be part of a higher-level controller. The proximity switch therefore does not have to be a single component. Rather, the proximity switch is implemented as a functional unit through the interaction of sensor elements and evaluation logic. The evaluation logic and in particular the state machine can be implemented, for example, with the aid of programmable logic controllers, logic gates, flip-flops or relays. For the hardware implementation of a state machine, a register for storing states, a first logic unit that determines transitions from one state to another, a second logic unit that is responsible for outputting the state, and a clock generator or a delay element can be used in a manner known to those skilled in the art , to be able to advance/distinguish between previous, current and next states. However, the state machine can also be implemented in software, for example as an event-controlled finite machine or virtual finite machine. Here, the invention advantageously allows the person skilled in the art to choose the most favorable implementation depending on the application and local conditions.

In one embodiment, the detection areas each have the same width, which makes it easy to evaluate corresponding sensor signals, for example with regard to the speed of an object moving through the detection area.

In one embodiment, at least one further sensor element is provided, the detection area of which can, but does not have to, overlap with one of the other detection areas, which enables additional information to be obtained.

In one embodiment, the sensor elements work inductively and each comprise at least one resonant circuit coil fed with alternating current.

In one embodiment, the sensor elements are arranged in a common housing in such a way that, when the housing is installed as intended, their detection areas lie one behind the other at a location to be monitored in the expected direction of movement of an object to be detected.

In a method for operating a proximity switch according to the invention, each sensor element has an occupancy status, which indicates that an object is in the detection range of the respective sensor element is located, and a free state, which indicates that there is no object in the detection range of the respective sensor element, is assigned, the occupied and free states of the three sensor elements being mapped by the state machine in eight switch states and the sequence in transitions from one switch state to another and is evaluated to determine the direction of movement of the object and, if necessary, to identify a defective sensor element. In this way, it is possible to determine movement directions simply from the sequence in which the switch states change, cost-effectively and reliably, even if a sensor element is defective and, for example, is permanently in an occupied or free state. In addition, the defective element can be easily identified.

In one embodiment of the method, a free message is generated when none of the sensor elements or only one of the sensor elements detects the presence of an object, and an occupancy message is generated when at least two sensor elements detect the presence of an object. As explained above, these free or occupied reports can then be used in a manner known to those skilled in the art to generate counting pulses.

In one implementation of the method, when the sensor elements are arranged such that an object moving in a specific direction through the detection areas first enters the detection area of the first sensor element, then enters the detection area of the second sensor element and then enters the detection area of the third sensor element , generates an error message if only the second sensor element or only the first and third sensor elements detect the presence of an object in the corresponding detection area.

In an arrangement for monitoring a track section with regard to the presence of a rail vehicle in the track section, at least one inventive proximity switch is arranged at the beginning and at the end of the track section, both of which are communicatively coupled to a higher-level controller. At the beginning and at the end of the track section there can also be at least two according to the invention Proximity switches are provided and coupled in such a way that each proximity switch provided at the beginning of the track section forms an independent counting circuit with each proximity switch provided at the end of the track section.

Further details and advantages of the invention result from the purely exemplary and non-limiting description of an exemplary embodiment in connection with the drawing comprising three figures.

BRIEF DESCRIPTION OF THE DRAWING

1 shows a highly schematic plan view of a proximity switch according to the invention with three sensor elements.

FIG. 2 shows a diagram of the response of three sensor elements when a metal train wheel drives past.

3 shows a state machine that models the behavior of a proximity switch according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

1 shows a highly schematized top view of a proximity switch, denoted in its entirety by 10, with three sensor elements S1, S2 and S3 arranged in a housing 12. For clarification, the housing 12 is shown here as if one could see the three sensor elements S1, S2 and S3 in a plan view, which can actually be the case, but does not have to be. If the sensor elements are AC-powered resonant circuit coils, it is important that the housing does not form a Faraday cage, so that the sensor elements can interact with metallic objects moving past. Typically, these are those to be detected by means of the sensor elements objects around wheels of rail vehicles, and in Fig. 1 a section of rail 14 is shown.

The sensor elements S1, S2 and S3 are arranged in the housing in such a way that the detection areas 16, 18, 20 of the individual sensor elements shown here in a highly schematic form and only for basic understanding, i.e. those spatial areas within which the sensor elements S1, S2 and S3 detect the presence of an object, typically a wheel of a rail vehicle, are spatially offset from one another in such a way that an object moving in a specific direction through the detection areas enters the different detection areas one after the other and then leaves them again in the same order. In the schematic representation of Fig. 1, the sensor element S1 has the detection area 16 shown by the dashed line, the sensor element S2 has the detection area 18 shown by the dotted line and the sensor element S3 has the detection area 20 shown by the dash-dotted line. The detection areas 16, 18 1 and 20 overlap in an overlap area 22 hatched in the manner of a grid, and an object located there is detected by all three sensor elements S1, S2 and S3.

It should be emphasized at this point that the numbering of the detection areas is arbitrary and is only used for illustration. Depending on the design of the sensor elements, it is theoretically possible to have the detection areas cross, arranging the sensor elements such that a sensor element on the right in the drawing covers a central area in the drawing and a central sensor element covers the right area. It is not important which sensor element covers which detection area, but that it is known in which order an object moving in a certain direction enters the detection area. Finally, it is also not important that the sensor elements are separate components, but rather that there are separate, partially overlapping detection areas. In this sense, three corresponding sensor fields realized in a single sensor can also be regarded as "sensor elements". The sensor elements S1, S2 and S3 interact with an evaluation logic 24, which evaluates signals generated by the individual sensors, eg voltage changes, and includes a state machine for detecting the direction of movement and for identifying a defective sensor element. In the example shown, the evaluation logic is arranged in the housing 12 together with the sensor elements. However, it can also be separated from the sensor elements and, for example, be part of a higher-level controller.

For a simple explanation of the mode of operation, it is now assumed that a wheel moving from left to right on the rail 14 first enters the detection area 16 of the sensor element S1, then enters the detection area 18 of the sensor element S2 and finally enters the detection area 20 of the sensor element S3. there is an overlap of the detection areas, so that, as will be explained in more detail below in connection with FIGS. 2 and 3, two or even all three sensor elements respond at specific times.

If the wheel continues to move in the same direction, it leaves the detection areas in the same order in which it entered the detection areas, i.e. in the example in Fig. 1 it first leaves the detection area 16 of the sensor element S1, then the detection area 18 of the Sensor element S2 and finally the detection area 20 of the sensor element S3. This advantageous arrangement of the detection areas makes it possible, as will be seen in more detail from the following description, to reliably distinguish between incorrect reports and actual events and also to ensure that the proximity switch functions even if one of the sensor elements has a malfunction.

To explain the mode of operation of the invention, FIG. 2 shows diagrammatically the time curves 26, 28 and 30 of signals from the three sensor elements S1, S2 and S3, thus forming a diagram of the response of the three sensor elements from FIG. 1 when a metal train wheel passes by . "Signal progression" here means the change in a specific measured variable over time, and accordingly the time is plotted in any desired unit on the abscissa. Above are dimensionless and on top of each other for ease of understanding the signal curves 26, 28 and 30 are shown offset. In reality, if the sensor elements are oscillating circuit coils, the measured variable can be, for example, a current through the respective coil, which then does not rise or fall in a strictly rectangular manner, as shown in FIG. 2, but rather sinusoidally. If this were plotted on the ordinate and if the coils had the same quiescent current, the curves 26, 28 and 30 would be superimposed and would only be offset in time. However, the steepness of the fall or rise is not relevant for understanding the invention, which is why it can simply be assumed here that each sensor element S1, S2 and S3 has two states, namely a so-called occupied state, which indicates that an object is in the detection area of the respective sensor element (S1, S2, S3) and a free state, which indicates that there is no object in the detection range (16, 18, 20) of the respective sensor element, with an occupied state being indicated below and in particular in Fig. 3 by 1 and an idle state is represented by 0, and that the states of the respective sensor elements change suddenly at certain points in time.

If, for the sake of simplicity, it is said here that "a sensor element has a state", this means that specific information can be taken from the signal it outputs, which can be analog or digital, namely whether an object is in the detection range of the sensor element is (state 1) or not (state 0). This information does not always have to be correct: due to a defect or a fault, it can happen that sensor elements "display" incorrectly, i.e. permanently go into an occupied or free state, whereby the invention - as explained in detail below - advantageously makes it possible to recognize such "false states" and still determine the direction of movement of an object and even identify the faulty sensor element.

In the example explained in connection with the figures, the three sensor elements S1, S2 and S3 are arranged such that an object moving from left to right in FIG. 1, e.g. a train wheel, first enters the detection range 16 of the first sensor element S1 , which takes place at time T1 shown in FIG. 2, so that the signal generated by sensor element S1 and thus signal curve 26 changes. The object then moves further and enters the detection range 18 of the second sensor element S2 at time T2, as a result of which the signal curve 28 also changes. If this object then continues to move in the same direction, it finally enters the detection range 20 of the third sensor element S3 at time T3, as a result of which the signal profile 30 also changes. Since the detection areas are arranged such that they spatially overlap, there are also temporal overlapping areas for objects moving in one direction, in particular a temporal overlapping area 32 in which the object is simultaneously detected by all three sensor elements. In a temporal overlap region 34 the object is detected only by the first and second sensor element, in a temporal overlap region 36 only by the second and third sensor element.

At time T4, if the object continues to move in the specific direction, it leaves the detection range of sensor element S1. It is then still in the temporal overlap area 36 and is correspondingly detected by the two sensor elements S2 and S3. At time T5 it leaves the detection range of the second sensor element S2 and is only detected by sensor element S3. Finally, at time T6, the object also leaves the detection range of the third sensor element S3.

If the proximity switch comprises three sensor elements, as in the example shown, which can each be in an occupied and free state, then there are eight possible combinations of the states, referred to below as switch states, which are mapped by the state machine 40 shown in FIG. 3 . Each switch state 41, 42, ..., 48 therefore corresponds to a combination of the states in which the three sensor elements S1, S2 and S3 of the proximity switch are located at a specific point in time, with Fig. 3 being read as follows: In the so-called Basic state 41, if there is no object in any of the three detection ranges of the three sensor elements of the proximity switch (or one of the sensor elements incorrectly indicates that no object is detected due to a fault), all sensor elements are in state 0.

As already explained, it is assumed in this example that the detection areas are arranged in such a way that an object moving from left to right in Fig. 1 first enters the detection area 16 of the sensor element S1, then into the detection area 18 of the sensor element S2 and finally into the detection area 20 of the sensor element S3 and then leaves the corresponding detection areas again in the same order, i.e. first from the detection area 16 of the sensor element S1, then from the detection area 18 of the sensor element S2 and finally exits the detection area 20 of the sensor element S3. This case corresponds to a clockwise rotation in the state machine of FIG. 3 through the switch states 41, 42, 43, 44, 45, 46 shown in the outer circles. If the object moved in the opposite direction, it would first enter the detection range of the sensor element S3 on. A movement of the object in the opposite direction thus corresponds to a state change from state 41 via states 46, 45, 44, 43, 42 back to 41, and thus a counter-clockwise movement through the outer circles in Fig. 3. The state machine 40 for evaluating the information actually supplied by the individual sensor elements, which can be digital or analog, can be implemented in the form of software, but also as a hardware circuit.

When an object first enters the detection range of the sensor element S1, its state changes from "free" to "occupied", which is represented by a 1 in the state machine 40 of FIG. 3, so S1 = 1 means nothing other than that the sensor element S1 has detected the presence of an object. Correspondingly, S2=0 and S3=0 mean that the object has not yet been detected by the sensor elements S2 and S3.

If the object moves further, it enters the detection range of the second sensor element and the status of sensor element S2 changes from 0 to 1. Since the detection ranges overlap as described above, it continues to be detected by the first sensor element (S1 = 1 | S2 = 1 | S3 = 0). If the object continues to move, it will eventually be detected by all three sensor elements (S1 = 1 | S2 = 1 | S3 = 1). The object then leaves the detection range of the first sensor element, but is still detected by sensor elements S2 and S3 (S1 = 0 | S2 = 1 | S3 = 1). When the object has also left the detection range of the second sensor element, the status of the three sensor elements changes to S1=0| S2 = 0 | S3 = 1 before the object is finally no longer detected by any sensor element (S1 = 0 | S2 = 0 | S3 =0). The two inner circles in FIG. 3 show "impossible" switch states 47 and 48 for the arrangement of the sensor elements that is made here, which can only come about if a sensor element is working incorrectly. The switch state 47 with S1 = 0 | S2 = 1 | S3 = 0 cannot exist in this exemplary embodiment if the sensor elements are working correctly, since the detection areas are arranged here in such a way that objects either first enter the detection area of sensor element S1 or that of sensor element S3, depending on the direction of movement, and there is an overlapping area in which all three detection areas overlap. Together with the fact that the detection areas are arranged according to the invention in such a way that objects moving in one direction enter the individual detection areas one after the other and leave them again one after the other in the same order, it follows that there is not just one overlapping area, in where all three detection areas overlap, but also an overlap area where the first and second detection areas overlap, and an overlap area where the second and third detection areas overlap, while it is impossible for an object to be detected only in the detection area of the Sensor element S2, which is in the example between the detection areas of the sensor elements S1 and S3.

Switch state 47 is therefore impossible and is recognized as an error, so that a corresponding error message can be generated and sent to a higher-level control unit. In the same way, the switch state 48 with S1=1 | S2 = 0 | S3=1 impossible because the object in the arrangement of the detection areas according to the example must also be in the detection area of the second sensor element when it is in the overlapping area of the detection areas of the first and third sensor elements. This signal aspect is also recognized as an error and can be reported to a higher-level control unit.

The evaluation of the order in which the switch states 41, 42, . . to be identified, even reliably if a sensor element is defective and should, for example, be permanently in an occupied or free state. This is evident from Table 1 below, in which possible

State changes are shown:

Table 1 - State change of the switch states from Fig. 3

Different sequences of the switch states 41 to 48 from FIG. 3 are shown in the left column. The abbreviation "iO" means "okay", the abbreviation "FR LR" means "direction of travel from left to right" (i.e. with reference to Fig. 3 a movement of the object past the proximity switch from left to right) and the abbreviation "FR RL" means "direction of travel from right to left" (that is, with reference to FIG. 3, the object moves past the proximity switch from right to left). As the table shows, the state machine allows, from the sequence of the switch states, even if a sensor element should be in a permanent occupied or free state due to a defect, to clearly detect the direction of travel, to identify the defective sensor element and even to identify the type of the defect (wrongly assigned, wrongly free). This also enables appropriate notifications for To generate maintenance and repair teams so that they then know exactly what needs to be repaired in a proximity switch.

In the typical application of a corresponding proximity switch for monitoring a track section of a rail system, the object to be detected is a wheel of a rail vehicle that moves past the proximity switch either from left to right or from right to left if this is installed as intended and the sensor elements are practical lie horizontally next to each other. If the exact time of a status change is recorded, since the distances between the detection areas are known, the relative speed at which the object and proximity switch move past one another can also be determined, although in most applications it will be the case that only the object moves , but the proximity switch is installed in a fixed position.

A proximity switch according to the invention also allows the signal images to be evaluated in a particularly reliable manner and used, for example, to generate counting pulses and, by arranging at least one proximity switch at the beginning and one proximity switch at the end of a track section, to monitor the track section with regard to the presence of a rail vehicle . The signal images can be evaluated in a manner known per se according to a "2 out of 3" evaluation: Since each signal image contains three states, the evaluation always leads to an operationally reliable result even if the sensor element is defective. If only one of the three sensor elements indicates the presence of an object, the signal reported by the proximity switch to a higher-level controller is still evaluated as free. If at least two of the three sensor elements indicate the presence of an object, the signal reported by the proximity switch to a higher-level controller is evaluated as occupied. All switch states 41, 42, 46 and 47 in the upper half A of FIG. 3 delimited by the broken line correspond to a free message, and all switch states 43, 44, 45 and 48 shown in the lower half B of FIG. 3 correspond to an occupancy message. By capturing the sequence of the status changes, eg from 42 to 43 and back to 42, a so-called "pendulum" can also be achieved, in which a wheel does not completely run over the switch, in the example but only in the detection ranges of the sensor elements S1 and S2 and then rolls back again, distinguished from a complete overrun of the sensor and a "in" or "count out", ie a count of whether a wheel has entered or left a track section, only with complete crossing of the switch. To monitor the track section, a comparison is then made as to whether the number of counted wheels matches the number of counted wheels. If this is the case, it can be assumed that a rail vehicle that has entered the track section has left it again, ie the corresponding track section is free.

Numerous modifications and developments are possible within the scope of the inventive idea, which relate, for example, to the number and design of the sensor elements and the detection areas. Due to the properties described above, the proximity switch offers extremely high reliability. Nevertheless, if additional redundancy is desired, e.g. These additional sensor elements can be integrated into the proximity switch. It is also possible, for example, to arrange two proximity switches according to the invention at the beginning and at the end of a track section to be monitored and each of the two proximity switches located at the beginning with each of the proximity switches arranged at the end of the track section to form an axle counting circuit consisting of a proximity switch at the beginning and a proximity switch to couple at the end of the track section.

It goes without saying that the chosen expressions first, second, third detection area or first, second and third sensor element are arbitrary and instead of the arrangement shown, in which the second sensor element is located between the first and the third sensor element, other arrangements can also be used can be met. It is important that the detection areas differ in terms of their beginning and end, i.e. an object does not leave or enter the detection areas of two sensor elements at the same time, but that all three are in a common overlapping area overlap. The sensor elements also do not have to work inductively, although inductive sensor elements have proven particularly effective for applications in the railway sector and are therefore used in a preferred embodiment of the invention.

REFERENCE LIST

10 proximity switches

12 housing

14 rail

16, 18, 20 detection range

22 Overlap area

24 evaluation logic

26, 28, 30 waveform over time

32, 34, 36 temporal overlap area

40 state machine

41 , 42, 43, 44, 45, 46, 47, 48 Switch state

S1 , S2, S3 sensor element

T1 , T2, T3, T4, T5, T6 point in time

Claims

PATENT CLAIMS

1. Proximity switch (10) with a first sensor element (S1) with a first detection area (16) for detecting an object moving through the first detection area (16), a second sensor element (S2) with a second detection area (18) for detecting a moving through the second detection area (18) and a third sensor element (S3) with a third detection area (20) for detecting an object moving through the third detection area (20), wherein the detection areas (16, 18, 20) of the three Sensor elements (S1, S2, S3) are arranged spatially distributed in such a way that an object moving through the detection areas in a specific direction enters the detection areas (16, 18, 20) one after the other and leaves them again in the same order, and wherein it there is an overlap area (22) in which the detection areas (16, 18, 20) overlap in such a way that an object located there is different from all of them three sensor elements (S1, S2, S3) is detected, characterized by an evaluation logic (24) with a state machine (40) for detecting the direction of movement and for identifying a defective sensor element.

2. Proximity switch (10) according to claim 1, characterized in that the evaluation logic (24) is arranged together with the sensor elements (S1, S2, S3) in a common housing (12).

3. Proximity switch (10) according to claim 1, characterized in that the evaluation logic (24) is separated from the sensor elements (S1, S2, S3).

4. Proximity switch according to one of claims 1 to 3, characterized in that the detection areas each have the same width.

5. Proximity switch according to one of claims 1 to 4, characterized in that at least one further sensor element is provided, the detection area can overlap with one of the other detection areas.

6. Proximity switch according to one of claims 1 to 5, characterized in that the sensor elements work inductively, in particular by means of AC-powered resonant circuit coils.

7. Proximity switch (10) according to one of claims 1 to 6, characterized in that the sensor elements (S1, S2, S3) are arranged in a common housing (12) so that they in the intended assembly state of the housing (12) on a location (14) to be monitored in the expected direction of movement of an object to be detected one behind the other.

8. A method for operating a proximity switch (10) according to any one of claims 1 to 7, wherein each sensor element (S1, S2, S3) has an occupancy state which indicates that an object is in the detection area (16, 18, 20) of the respective sensor element (S1, S2, S3) and a free state, which indicates that there is no object in the detection range (16, 18, 20) of the respective sensor element, is assigned, characterized in that the occupied and free states of the three sensor elements ( S1, S2, S3) are mapped by the state machine in eight switch states (41, 42, ..., 48) and the order in transitions from one switch state (41, 42, ..., 48) to another is detected and to Determination of the direction of movement of the object and, if necessary, to identify a defective sensor element (S1, S2, S3) is evaluated.

9. Method for operating a proximity switch (10) according to claim 8, wherein a clear message is generated if none of the sensor elements (S1, S2, S3) or only one of the sensor elements (S1, S2, S3) detects the presence of an object, and an occupancy message is generated when at least two sensor elements (S1, S2, S3) detect the presence of an object.

10. Method for operating a proximity switch (10) according to claim 8 or claim 9, wherein the sensor elements (S1, S2, S3) are arranged in such a way that an object moving in a specific direction through the detection areas first enters the detection area (16). of the first sensor element (S1), then into the detection area (18) of the second sensor element (S2) and then into the detection area (20) of the third sensor element (S3), and an error message is generated if only the second sensor element (S2) or only the first and third sensor elements (S1, S3) detect the presence of an object in the corresponding detection area.

11. Arrangement for monitoring a track section with regard to the presence of a rail vehicle in the track section, characterized in that at least one inductive proximity switch according to one of claims 1 to 7 is provided at the beginning and at the end of the track section, which communicates with a higher-level controller are coupled.

12. Arrangement according to claim 11, characterized in that two proximity switches according to one of claims 1 to 7 are provided at the beginning and at the end of the track section, each of the proximity switches provided at the beginning of the track section being connected to both of the proximity switches provided at the end of the track section linked to two independent counting circles.

13. Method for monitoring a track section with regard to the presence of a rail vehicle in the track section using an arrangement according to one of claims 11 or 12 and a method according to one of claims 8 to 10, characterized in that the monitored track section is considered to be of a rail vehicle occupied if the number of occupancy reports issued by the proximity switch(es) located at the start of the track section exceeds the number of occupancy reports issued by the proximity switch(es) provided at the end of the track section.