EP0530743B1 - Detection arrangement of railway vehicle wheels - Google Patents

Abstract

In a wheel sensor for detecting wheels of railway vehicles, preferably for counting the wheels (6) in a section of track, metal-detecting, inductive sensors (1, 3, 41, 43) are attached symmetrically to travel rails (4) and their relative levels are evaluated, as a result of which interference influences of an electrical, inductive, thermal or mechanical kind are suppressed and flanged wheels can be distinguished from metal components which give the false impression of other wheels. Train types can be determined from the patterns (Fig. 4) of the signals (51, 55) when satisfactory wheels pass by and from metallic objects. The earliest arrival of the train at positions relative to the wheel sensor is calculated from the maximal speeds assigned to the train types. <IMAGE>

Description

The invention relates to a wheel sensor for detecting wheels of rail-bound vehicles, preferably for counting the wheels in a track section, with the features specified in the preamble of claim 1. Such a sensor arrangement is known from DE-C-958 848.

Wheel sensors on rails are known in which a coupling change or a damping change occurs in the wheel sensors by driving over the wheels of rail-bound vehicles (SANDER, "rail contacts - a system comparison" in Signal + Draht, 1973, H.10, S.179-183) . The wheel sensors are attached on one side to the running rail (US Pat. No. 4,283,031) or act only on one side, even if e.g. the transmitter coil of the wheel sensor on one side, whose receiver coil is attached to the other side of the rail (SCHMIDT, "Der Achszähler Standarrd Elektrik Lorenz AG type Azl 70 - Teil 1" in Signal + Draht, 1976, H.6, p.116- 123). The wheel sensors essentially react to the wheel flange of a wheel. With the known wheel sensors, the direction of travel can be detected by arranging them one behind the other (FRECH, SCHMIDT, "The axle counter of Standard Elektrik Lorenz AG" in Signal + Draht, H.11, 1967, p.165-174).

In the case of wide wheels without a wheel flange, there is so much metal mass protruding from the inside of the rail that the mass of a wheel flange can be sporadically simulated on the the known wheel sensors react and incorrectly count the wheels.

When the magnetic rail brakes are lowered onto the running rail, the large mass and the excitation also cause the same problem of incorrect counting, made more difficult by raising the unused magnetic brakes.

Likewise, the known wheel sensors react incorrectly when driving over eddy current brakes (KRÖGER, "Principle, Development and Design of Linear Eddy Current Brakes" in ZEV-Glasers Annalen, 1985, H.9, pp. 368-374) by their excitation, although here too no clear one Wheel counting is possible. An unsolved problem is also the short-term, considerable heating of the travel rail and the wheel sensors arranged on it when the eddy current brake is excited, because the short-term temperature compensation of the copper coils of the wheel sensors fails.

The safety of the wheel detection of the known wheel sensors also depends on their precise adjustment on the rail, which is more difficult with different rail profiles.

The wear of the rail head gives rise to the further problem of the need for timely and frequent readjustment on the rail in the known wheel sensors.

Short-circuit currents in the rails can also have a negative effect on the reliability of the wheel count in the known wheel sensors.

From German Auslegeschrift DE-AS 1 268 650 it is known that sensors are equipped with evaluation devices that count axes moving in and out of a district and transmit the counting results to the signal box for further processing for the purpose of free reporting of the district. It is also known to process sensor signals in two channels and to transmit them to a central location via a data transmission device (KORTHAUER, MÜLLER, "Anrückmelder zur Rottenwarnung" in Signal + Draht 1977, H.1 / 2, p.32-33). It is not possible to make a timely notification of the arrival of trains to locations relative to the sensors with these devices. There is also a plausibility check of the wheel detection not possible.

It is therefore an object of the invention to provide a wheel sensor which has no incorrect counts when it is driven over by flange-free wheels, magnetic rail brakes or eddy current brakes, places low demands on the adjustment and is insensitive to electrical interference.

This object is achieved in a generic wheel sensor by the characterizing features of claim 1.

The wheel sensor according to the invention has the particular advantage that a symmetrical arrangement of at least two inductive sensors and a relative evaluation of their level compensates for interference influences of an electrical, inductive, thermal or mechanical nature by comparing them directly or indirectly.

Advantageous variants and developments of the invention are mentioned below.

If there is limited space in the sleeper compartment or with coils of a sensor arranged on both sides of a travel rail, the second sensor can expediently be arranged on the opposite travel rail.

By using a controlled, delayed memory, sensors can also be arranged one behind the other on a running rail, if, for example a rail hike cannot be ruled out.

The asymmetry of a wheel with a wheel flange can be used to check the plausibility of the sensor, which is mainly influenced and faces the wheel crane.

Filters arranged differently in the processing and output branches of the levels can reduce interference and suppress runtime differences, suppress levels that are too low or too high by means of threshold switches, and adapt the level of the wheel sensor to its task by forming quotients and / or differences.

A longitudinal arrangement of the wheel sensors, even with only two individual sensors, makes it possible to recognize the direction of passage and a reversal of the direction after the vehicle has come to a standstill.

By measuring the chronological sequence of wheels and other metallic objects passing over the wheel sensor, it is possible to recognize train types and to trigger timely reports of the arrival of trains relative to the wheel sensor from assigned speeds. For slow trains, e.g. preventing the track from being cleared too early at construction sites at some distance.

Further refinements describe improvements in wheel detection, the modification of the wheel sensors as a data transmission device and a secure processing unit.

Fig. 1

eine Anordnung eines Radsensors an einer Fahrschiene im Gleis,

Fig. 2

eine Auswerteschaltung eines Radsensors,

Fig. 3

weitere Anordnungen von Radsensoren im Gleis,

Fig. 4

eine weitere Auswerteschaltung eines Radsensors,

Fig. 5

Zusätze zur Auswerteschaltung eines Radsensors,

Fig. 6

eine weitere Auswerteschaltung eines Radsensors,

Fig. 7

eine Verknüpfungsschaltung in der Auswerteschaltung,

Fig. 8

eine richtungserkennende Schaltung in der Auswerteschaltung,

Fig. 9

ein aktuelles Datenmuster.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. It shows

Fig. 1

an arrangement of a wheel sensor on a running rail in the track,

Fig. 2

an evaluation circuit of a wheel sensor,

Fig. 3

further arrangements of wheel sensors in the track,

Fig. 4

another evaluation circuit of a wheel sensor,

Fig. 5

Additions to the evaluation circuit of a wheel sensor,

Fig. 6

another evaluation circuit of a wheel sensor,

Fig. 7

a logic circuit in the evaluation circuit,

Fig. 8

a direction-recognizing circuit in the evaluation circuit,

Fig. 9

a current data pattern.

1 shows a typical arrangement of a wheel sensor with two associated inductive sensors (1, 3) known per se. The sensors (1, 3) are arranged symmetrically to a travel rail (4) in the track (2). A wheel (6) rolling over the travel rail (4) influences the sensors (1, 3) differently due to its asymmetry. The sensor (3) facing the wheel rim is influenced more because of the relatively closer, larger mass of the wheel (6), so that there is a more influenced level (9) at the output of this sensor (3). By comparing the levels (7, 9) of the sensors (1, 3), a wheel with a wheel flange can be clearly identified despite all interfering influences that act symmetrically or almost symmetrically on the sensors (1, 3). These interferences can be eliminated by comparing the levels (7, 9) of the sensors (1, 3). As already mentioned, such interferences can be electrical, inductive, thermal or mechanical, among other things.

If sensor 1 is influenced to a greater extent, this indicates an error that can be displayed on an output (11) of a comparator (5).

A typical evaluation circuit of a wheel sensor is shown in FIG. The levels (7, 9) of two assigned inductive sensors (1, 3) are routed to a comparator (5), which outputs a wheel-recognizing level (11) at the output if the levels are not the same.

If the influence of the level (9) of the sensor (3) assigned to the wheel flange of the wheel (6) does not prevail, the wheel-recognizing output level (11) can be suppressed in the comparator (5) and / or a further output level (13) indicating an error are given by the comparator (5).

The variable levels (7, 9) of the sensors (1, 3) known per se can e.g. rectified or non-rectified voltages or currents based on changes in the influence of their inductance, inductance coupling, resonant circuit damping, phase or frequency by a wheel (6) of a rail vehicle.

Fig. 3 shows different arrangements of typical wheel sensors in the track (2). The assigned sensors (1, 3) can, for. B. consist of a damped by a wheel (6) resonant circuit or a transmitting and receiving coil, the coupling of which is influenced by a wheel (6). Insofar as the transmitting and receiving coils of a sensor (1, 3) are arranged horizontally apart from one another, the transmitting coils are shown in FIG. 3 as a triangle and the receiving coils as a square. The coils can be, for example, concentrated air coils, a ferrite core contain or be designed as larger frame coils.

3a corresponds to the top view of the inductive sensors (1, 3) of a wheel sensor according to FIG. 3. The sensors (1, 3) can contain only one coil or vertically arranged transmitting and receiving coils.

In Fig. 3b sensors (1, 3) of a wheel sensor are attached to both rails (4) in the same transverse direction. Since the wheel flanges of the wheels (6) of one axle face each other, the same effect results as in the arrangement according to FIG. 3a.

3c shows a wheel sensor with horizontally offset transmission and reception coils of sensors 1 and 3.

FIG. 3d shows a further arrangement of a wheel sensor with sensors (1, 3) having several coils.

The wheel sensor according to FIG. 3e consists of two sensors (1, 3) arranged along a track, with the level (23) of the sensor first traveled being delayed until the other sensor is used for the purpose of comparison (5).

In a manner known per se in terms of circuit technology, with an arrangement of the wheel sensors according to FIGS. 3e, 3f or 3g, the direction of travel can be recognized by the sensors traveled in succession and their output levels which are offset in time, and if the zones of influence and the resulting level overlap, a reversal of direction after a standstill . For an arrangement according to FIG. 3g, only two sensors (1, 3), but a level delay as mentioned in FIG. 3e are necessary for the purpose of comparison.

4 shows a circuit principle for comparison of sensors (1, 3) of a wheel sensor arranged along the travel rail (4). The levels (7, 9) of the sensors (1, 3) are fed to a switch (15) which detects the change in level of the sensor first traveled and transfers this level (23) to a memory (19) which stores the level or level curve with a delay and then only outputs to the comparator (5) when the switch (15) detects the change in level when the other sensor is driven, the level (21) of which supplies the switch (15) to the comparator (5) directly or via an adapter circuit (17) so that this level and the level delayed by the memory can be compared as if the sensors (1, 3) had been run over at the same time. The memory (19) can, for example, be based on the known, not known, basis of a sample / hold circuit, a bucket chain circuit, a signal processor or an analog / digital converter with a serial FIFO memory connected downstream. In some of these circuits, a matching circuit (17), for example an analog / digital converter, is necessary in order to achieve the same type of level at the input of the comparator (5).

5 has expedient additives (25 to 35) in order to increase the interference immunity of the circuit according to FIG. 2, these additives also having to be introduced analogously into the circuit according to FIG. 4, which is not shown in more detail.

The filters (25, 27, 29) can reduce interference and suppress runtime differences. The filter 29 after the level comparison essentially serves to suppress runtime differences.

Threshold switches (31, 33, 35) suppress levels that are too low in order to eliminate only small deviations or changes in the levels. By responding to levels that are too high and suppressing them, excessive influences can be eliminated with the threshold switches (31, 33, 35); the influences of a very strongly excited eddy current brake can e.g. B. combat in addition to the symmetrical suppression properties of the wheel sensor.

The comparator (5) can also compare the input levels (7, 9) in a manner known per se, not shown in more detail, on the basis of the formation of the quotient and / or difference, the unwanted dependence on absolute levels being better suppressed.

6 shows a typical evaluation circuit of a wheel sensor which contains a logic circuit (61). Depending on the levels (47, 49) of two assigned inductive sensor pairs (41, 43), the sensor pair gives the predominant level of the sensor (43) facing the wheel flange (41, 43) corresponding to the passage of a proper wheel, a wheel signal (51), at approximately the same level of both sensor pairs (41, 43) corresponding to a metallic object passing symmetrically to the rail head, a detection signal (55) and at a predominant level of that facing away from the wheel flange Sensor (41) an error signal (53).

7a shows a possible, highly simplified logic circuit (61) with the properties mentioned above.

The levels (47, 49) in Fig. 7b are approximately the same size corresponding to a symmetrical, metallic object above the pair of sensors (41, 43), which leads to the detection signal (55) at the output of the associated AND gate in Fig. 7a, if the switching threshold S in Fig. 7b is exceeded by both levels.

The levels (47, 49) shown by way of example in FIG. 7c differ in size according to a correct wheel above the sensor pair (41, 43), which leads to the wheel signal (51) at the output of the associated AND gate in FIG. 7a if the switching threshold S in FIG. 7c falls below the level 47 and is exceeded by the level 49 and the levels are lowered with the same resistances R to such an extent that the level 47 is below the switching threshold in the fault-free case shown.

The same applies to the error signal (53) as mentioned for the wheel signal (51), but the sizes of the levels (47, 49) are interchanged. It would almost correspond to a wheel rim on the wrong side of a passing wheel. The error signal (53) is expediently used to reject the entire measuring process of the wheel sensor.

The temporal sequence (56) of the wheel signals (51) or the detection signals (55) is obtained from the latter signals by an OR gate (FIG. 7a).

The logic circuit (61) is better constructed from analog elements already mentioned at the beginning for better interference suppression.

9 shows an example of a current data pattern, this occurs when the wheel signal (51) is clocked out as a 1-bit sequence with the temporal sequence signal (56). The wheels are recorded as binary ones and the symmetrical metal objects as binary zeros. The data pattern can be seen in the example
3 wheels
1 symmetrical metal object
2 wheels
1 symmetrical metal object
n wheels
Train types can thus be set as data patterns on the train and recorded with the sensor pairs (41, 43), primarily from the first bit sequences, which are assigned to the train's drive unit, for example. If there is insufficient identification due to the consequence of wheel and eddy current brakes and / or magnetic rail brakes, coding plates on the train can also be used.

The number of binary ones in the example corresponds to the number of axles of the train and can easily be separated for evaluation.

FIG. 6 shows how the signals or current data patterns mentioned (FIG. 9) are fed to a computer (63) in the evaluation circuit (45). The computer (63) has a memory (not shown) and a program and is connected to a timer (57).

If the computer has stored data patterns of different train types with assigned data about the possible speed and acceleration of the train type, it can recognize the train type and its possible speed and acceleration by comparing the current data pattern (FIG. 9) detected by the sensor pairs and the evaluation circuit. The computer can use these known calculation methods to determine the time span from which these trains travel, for example, on average or at the earliest a certain distance. If the calculation is based on the maximum possible speed, the earliest arrival of the train at a location with a known distance from the wheel sensor can be predetermined. Data or messages about this can be output (65) or via a data transmission (67) at their output (69). If the data or messages are transmitted via the data transmission (67), for example, to a location of a construction site in the track area on which the calculation is based and evaluated there, a time-delayed but nevertheless timely warning can be triggered there, which results from the calculation. Construction work does not have to be interrupted prematurely. A computer (not described in more detail) with equivalent properties such as the computer 63 together with a data transmission similar to the data transmission 67 can be used for the evaluation.

The computer (63) can, however, also measure the temporal sequence of at least the first wheel and / or recognition signals (51, 55) and stored data associated with the train type about the absolute distances of at least the first wheel axles and / or metallic passing by symmetrically to the rail head Objects determine the current speed of the train. With this current speed and the maximum possible acceleration, the arrival of the train at locations relative to the wheel sensor can be determined more precisely according to known calculation methods.

If the distance between the coils and sensor pairs (41, 43) arranged along the track is known, the computer (63) can determine the levels (47a, 47b or 49a, 49b) of the coils of the sensor pairs (41, 43) also easier to determine the current speed of the train.

8 shows a D flip-flop circuit (41a, 41b, or 43a, 43b), which is contained in the evaluation circuit (45) and with which the direction of pull can be detected. As before, two coils per sensor (41, 43) arranged along the track are assumed. The designations 41a, 41b, 47a, 47b, 47c and 47c are assigned to the sensor 41, the rest to the sensor 43. The mode of operation is identical for both sensors.

The inductively influenced coils of the sensor pairs (41, 43) arranged along the track in succession are given correspondingly successive levels (47a, 47b, or 49a, 49b) from the inputs of the D flip-flop circuit (41a, 41b, or 43a, 43b). For example, if the level 47a at the data input of the D flip-flop 41a occurs before the level 47b at its clock input, the former level is passed to the output of the D flip-flop 41a as a direction signal 49c when the level 47b arrives. The D flip-flop 41b, on the other hand, does not pass any level to its output. With the reverse order of the levels, the D flip-flops behave in reverse. The outputs (47c, 47d, or 49c, 49d) differ according to the order of the levels and show the direction of travel of the train. After the direction signals have been recognized, the D flip-flops are reactivated by resetting, which is not shown in FIG. 8 for reasons of clarity. The information about the train direction can be used, for example, in connection with the notification of the arrival of the train at certain locations or for the direction-dependent axle counting.

The computer (63) in FIG. 6 can also contain analog / digital converters (not shown), advantageously one for each signal-emitting coil of the sensor pair (41, 43). If the levels (47, 49) of the sensor pairs (41, 43) are converted into digital values so quickly that at least 3 values are stored when a sensor and a wheel and / or a metallic object are affected, then an increasing number of values per Influencing a better and better resolved equivalent recognition pattern of the measured object in the form of a table of values. In contrast to angular brakes, a wheel is characterized, for example, by small increments in the associated value table because of its round shape. The significance of the measured objects can be determined by known calculation methods using comparison tables permanently stored in the computer (63). The safety of the wheel sensor can be increased to a level necessary for signal-technical safety in modern railroad operation in a logical connection with wheel signals (51) or detection signals (55) or error signals (53).

The signals 51, 53, 55, 56 of the evaluation circuit (45) in FIG. 6 and / or the current data pattern (FIG. 9) or the like can also be transmitted to a remote location via the data transmission 67 and processed there in a similar or identical manner are in the computer 63. The data can be compressed, for example the current data pattern in the example of FIG as a sequence of digits 3, 1, 2, 1, n instead of the bit sequence.

6, the pair of sensors (41, 43) can each contain a first transmitter and / or receiver (71). If the trains themselves each contain a second transmitter and / or receiver (73) immediately above the rail, data can be exchanged wirelessly between the transmitters and / or receivers (71, 73) in a manner known per se, the computer (63) corresponds to the first transmitter and / or receiver (71) via a data line (65) and the train corresponds to the second transmitter and / or receiver (73) via line 75. The first transmitter and / or receiver (71) can also be part or all of the coils of the sensor pair (41, 43) on an inductive basis, in particular if the coils to prevent the mutual influence of the transmission of the data and the measurements in a generally known compensating manner Bridge circuit are arranged.

Signal security can be achieved if the evaluation circuit (45), possibly also the data transmission (67) and / or the transmitter / receiver (71, 73) and the corresponding connections (47, 49, 65, 69, 75) as a second decoupled functional unit are present again, the functional units work in the same way and monitor each other for the same and simultaneous output signals.

Claims (15)

1. Wheel sensor for detecting the wheels of rail-mounted vehicles, principally for counting the number of wheels in a track section,

   - using pairs of metal-detecting inductive sensors (1, 3, 41, 43) attached to the running rails

   - whose electrical level is fed to an evaluation circuit (5, 45), whereby

   - the sensors of sensor pairs (1, 3, 41, 43) are located so that one sensor (1, 41) is situated on the side of a running rail (4) on which a wheel flange does not pass and the other sensor (3, 43) is situated on the side of a running rail (4) on which a wheel flange passes, with the distinguishing feature

   - that the evaluation circuit (5, 45) contains a comparator and

   - that the comparator (5) emits an output signal (11, 51) in the event of unequal levels at its inputs which corresponds to the passing of a proper wheel or wheel pair on an axle if the level of the sensor (3, 43) facing the wheel flange dominates the level of the other sensor (1, 41).
2. Wheel sensor according to Claim 1 with the distinguishing feature that the sensors (1, 3, 41, 43) are located immediately opposite one another along the track (2) (Figs. 3a to 3d).
3. Wheel sensor according to Claim 1 with the distinguishing feature that the sensors (1, 3, 41, 43) are located in an offset pattern along the track (2) (Figs. 3e, 3g) and a storage device (19) that delays the level or level characteristic of the sensor triggered first until the associated sensor is triggered is situated in front of the comparator (5) and a separating filter (15) that detects the time sequence of the sensor levels (7, 9, 47, 49) directs the first incoming level (23) to the comparator via the storage device (19) and the other level (21) directly or via an interface circuit (17) to the comparator (5).
4. Wheel sensor according to one of the preceding Claims with the distinguishing feature
   that the comparator (5) operates on the basis of the quotients and/or differences formed from its input levels and the sensor and/or output levels are taken either to filters (25, 27, 29) that absorb faults or running time differences and/or to triggers (31, 33, 35) that delimit the response range.
5. Wheel sensor according to one of the preceding Claims with the distinguishing feature
   that two pairs of sensors (1, 3, 41, 43) are located along the track (2) (Fig. 3f) and each wheel (6) is inductively influenced in a chronological sequence and preferably with an overlap.
6. Wheel sensor according to one of the Claims 1 to 4 with the distinguishing feature
   that one pair of sensors (1, 3, 41, 43) is located in an offset pattern along the track (2) (Figs. 3e, 3g) and each wheel (6) is inductively influenced in a chronological sequence and preferably with an overlap.
7. Wheel sensor according to one of the preceding Claims with the distinguishing feature

   - that the evaluation circuit (5, 45) contains a timer (57), an associated computer (63) - containing a memory and a program - and a logic circuit (61)which, in the event of the level of the sensor (43) of the sensor pair (1, 3, 41, 43) facing the wheel flange dominating, writes a wheel signal (11, 51) corresponding to the passing of a proper wheel in the memory of the computer (63) and, in the event of the level of both sensor pairs (1, 3, 41, 43) being more or less the same, differentiated by the time sequence (56) of the two signals (51, 55), writes a recognition signal (55) corresponding to a metal object passing symmetrically to the rail head in the memory of the computer (63), the two signals being written together as a current data pattern (Fig. 4) corresponding to the train type, and

   - that the current data pattern (Fig. 4) is available at the output (65) of the computer and, if appropriate - preferably compressed in a familiar manner - by way of a data transfer module (67), at its output (69).
8. Wheel sensor according to Claim 7 with the distinguishing feature
   that the symmetrical metal object is an eddy-current brake and/or an electromagnetic rail brake and/or a coding plate on the train.
9. Wheel sensor according to one of the preceding Claims with the distinguishing feature

   - that known data patterns of the train types, with assigned data concerning the possible speed and acceleration of the train type, are stored in the computer (63),

   - that the computer (63) compares the current data pattern (Fig. 4) with known data patterns of the train types stored in the computer (63) and recognizes the train type in the event of convergence, reads the stored data concerning the possible speed and acceleration of the train type assigned to the train type, and derives from said information data concerning the time of arrival of the train at places relative to the wheel sensor according to known calculation methods and makes this data available at the output (65, 69), and/or

   - that the computer (63) makes the data contained in the current data pattern (Fig. 4), having been derived from the wheel signal (51) and corresponding to the number of axles on the train, available at the output (65, 69).
10. Wheel sensor according to Claim 9 with the distinguishing feature
    that the computer (63) determines the current speed of the train and data concerning the time of arrival of the train at places relative to the wheel sensor according to known calculation methods by measuring the time sequence of at least the first wheel and/or recognition signals (51, 55) and with reference to data stored in the computer (63) concerning the absolute spacing of at least the first wheel axles and/or metal objects passing symmetrically to the rail head, said data being assigned to the train type, and makes the results available at the output (65, 69).
11. Wheel sensor according to one of the preceding Claims with the distinguishing feature

    - that the evaluation circuit (5, 45) has a resettable delay flipflop (41a, 41b and/or 43a, 43b),

    - that the coils of the pairs of sensors (1, 3, 41, 43) located along the track, the coils being inductively influenced in a chronological sequence, accordingly conduct sequential levels (47a, 47b and/or 49a, 49b) to one data input and one clock input of each delay flipflop (41a, 41b and/or 43a, 43b) which, depending on the sequence of the levels, issue directional signals (47a, 47b and/or 49c, 49d) corresponding to the direction of the train and are then reset, and

    - that the computer (63) determines the current speed of the train and data concerning the time of arrival of the train at places relative to the wheel sensor according to known calculation methods by measuring the time spacing of the levels (47a, 47b and/or 49a, 49b), the spacing of the coils of the pairs of sensors (1, 3, 41, 43) being known, and makes the results available at the output (65, 69) together with the directional signals (47c, 47d and 49c, 49d).
12. Wheel sensor according to one of the preceding Claims with the distinguishing feature
    that the interface circuit (61) emits an error signal (53) and/or makes said signal available at the output (65, 69) in the event of the level of the sensor (1, 41) facing away from the wheel flange dominating.
13. Wheel sensor according to one of the preceding Claims with the distinguishing feature

    - that the computer (63) contains analog-to-digital converters,

    - that the levels (7, 9, 47, 49) of the pairs of sensors (1, 3, 41, 43) are converted into digital signals in a time sequence, that at least 3 values are stored in the event of a sensor being influenced by a wheel and/or metal object, and

    - that the computer (63) compares these values with its stored value patterns of significant wheels, metal objects and sources of interference to ascertain similarities according to known calculation methods and, in the event of correspondence, makes message signals - preferably in a logic operation with wheel signals (51) and/or recognition signals (55) and/or error signals (53) - available at the output (65, 69).
14. Wheel sensor according to one of the preceding Claims with the distinguishing feature

    - that each pair of sensors (1, 3, 41, 43) contains a first, preferably inductive, transmitter and/or receiver (71),

    - that trains each contain a second, preferably inductive, transmitter and/or receiver (73) located immediately above the rail,

    - that the first transmitter and/or receiver (71) corresponds with the computer (63) and/or the data transfer module (67) via the data cable (65), and

    - that data are exchanged between the transmitters and/or receivers (71, 73) without wires by known means.
15. Wheel sensor according to one of the preceding Claims with the distinguishing feature

    - that the evaluation circuit (5, 45) and, if appropriate, the data transfer module (67) and/or the transmitters/receivers (71, 73) as well as the relevant connections (7, 9, 47, 49, 65, 69, 75), are present twice, that is also in the form of a second, decoupled function unit, and

    - that the function units work in the same way and monitor one another for the occurrence of identical and concurrent output signals.

Images