Wheel detector, method for operating a wheel detector and components therefor
The wheel detector addresses interference issues by adjusting its transmission frequency to distinguish between interference and actual wheel presence, ensuring reliable operation.
Patent Information
- Authority / Receiving Office
- AU · AU
- Patent Type
- Applications
- Current Assignee / Owner
- SIEMENS MOBILITY GMBH
- Filing Date
- 2025-12-11
- Publication Date
- 2026-07-09
AI Technical Summary
Conventional wheel detectors are highly susceptible to external interference, leading to false malfunction signals and errors.
A wheel detector with an adjustable transmission frequency that can select from multiple frequencies, allowing it to differentiate between interference and actual wheel presence by adjusting its frequency based on specific switching criteria.
Reduces susceptibility to external interference, preventing false fault reports and ensuring continuous operation by adjusting transmission frequency to avoid interference frequencies.
Smart Images
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Abstract
Description
Wheel detector, method for operating a wheel detector and components thereof The invention relates to wheel detectors for railway track installations for detecting wheels of passing rail vehicles. Wheel detectors are generally known for use in railway track installations. Wheel detectors currently in use are based on a generation of an electromagnetic field on the transmitter side and a measurement of this field on the receiver side. When a wheel of a rail vehicle traveling on the railway track installation enters the area of the electromagnetic field, the wheel changes the field so that the presence of the wheel can be inferred and a wheel detection signal can be generated. Document EP 3 296 181 A2 describes a method for tuning an inductive sensor to detect the presence of rail vehicle wheels. The sensor comprises a generator system, a resonant circuit, a detection system, an amplifier system, and an output stage. An internal signal and an output signal are generated in the inductive sensor. A reference value is stored in the internal signal values and used to obtain a reference value in the output signal that is characteristic of the absence of a wheel above the inductive sensor in accordance with the invention. A basic tuning of the internal signal value is performed to the reference level by adjusting a frequency of the generator system. Document EP 2 240 357 B1 relates to a method for increasing the interference immunity of a wheel sensor, in particular for a track vacancy detection system, wherein in at least one sensor channel a transmit signal is generated, which is 2025279734 11 Dec 2025 inductively coupled to a receive signal, which is fed to an evaluating facility for detecting a change in the magnetic field resulting from a rail vehicle running over the track, as well as a corresponding wheel sensor. Document EP 4 180 300 A1 relates to a sensor facility for detecting a change in the magnetic field caused by an object approaching the sensor facility, in particular by a wheel of a rail vehicle. The sensor facility comprises at least one transmitting resonant circuit for generating a magnetic field, at least one receiving resonant circuit for generating at least one measurement signal caused by the magnetic field, and at least one processing facility for processing the at least one measurement signal. Document DAVID GOERES: “Compatibilite du materiel roulant avec les detecteurs electroniques de rouers” [“Compatibility of rolling stock with electronic wheel detectors”],” REVUE GENERALE DES CHEMINS DE FER: RCGF, HG EDITIONS, FR, No. 236, March 1, 2014 (2014-03-01), pages 18-35, XP001526399, ISSN: 0035-3183 describes the interference phenomena caused by rolling stock in infrastructure facilities in connection with the approval process for the TGV2N2 in Germany. These interferences are introduced by the harmonic components generated by the commissioning of the new converters with IGBT technology. The object of the invention is to specify a wheel detector that is less sensitive to external interference than conventional wheel detectors. In accordance with the invention, this object is achieved by a wheel detector with the features according to patent claim 1. 2025279734 11 Dec 2025 Advantageous embodiments of the wheel detector in accordance with the invention are specified in subordinate claims. In accordance with the invention, a transmitting facility of the wheel detector which is designed to generate an electromagnetic alternating field can be adjusted with regard to its active transmission frequency by means of a control signal and renders it possible to select the active transmission frequency from at least two different transmission frequencies, and an evaluating facility of the wheel detector is configured in such a way that it adjusts the transmission frequency by means of the control signal if a receive signal of a receiving facility of the wheel detector fulfills a specified switching criterion. A significant advantage of the wheel detector in accordance with the invention is that it is less susceptible to interference than conventional wheel detectors. If, for example, an external interference signal is coupled in, for example by a current flowing in the rails, this can influence the receive signal of the receiving facility in a conventional wheel detector in such a way that the impression of a malfunction or even the impression of a failure of the wheel detector is created and an error signal is falsely generated by an evaluating facility. In the case of the wheel detector in accordance with the invention, such false triggering can be prevented in many cases because, due to the adjustability of the transmission frequency, the wheel detector can check whether the interference is also present at transmission frequencies other than the current one. As recognized by the inventor, the inventive idea is that external interference often occurs only in very narrow frequency bands and that, by selecting a different transmission frequency, the wheel detector can continue to operate without interference despite 2025279734 11 Dec 2025 the influence of external interference. In other words, in many cases, the ability to adjust the transmission frequency allows continued operation without a false fault report of a malfunction being sent to a higher-level control center. Adjusting the transmission frequency preferably provides for a frequency change of at least 200 Hz in each case. It is advantageous if the receive signal is assigned a signal strength band that is limited by a trigger threshold and a dropout threshold. The trigger threshold is preferably selected so that it enables wheel detection, and the dropout threshold is preferably selected so that it signals an error. During undisturbed operation and without a wheel running over the track, the receive signal of the receiving facility is preferably in the range of a quiescent level, which thus indicates undisturbed operation or the operational readiness of the wheel detector. The quiescent level lies between the trigger threshold and the dropout threshold and is preferably closer to the dropout threshold than to the trigger threshold. The evaluating facility preferably generates a wheel detection signal indicating a wheel is running over the track if the signal strength passes the trigger threshold or lies outside the signal strength band in a signal strength range adjacent to the dropout threshold. The signal strength range adjacent to the dropout threshold and outside the signal strength band is the range above the trigger threshold if the trigger threshold is higher than the dropout threshold and otherwise the range is below the trigger threshold if the trigger threshold is lower than the dropout threshold. 2025279734 11 Dec 2025 The evaluating facility preferably generates an error signal if, over a specified time period, the signal strength passes the dropout threshold or lies outside the signal strength band in a signal strength range adjacent to the trigger threshold. The signal strength range adjacent to the dropout threshold outside the signal strength band is the range below the dropout threshold if the trigger threshold is higher than the dropout threshold, and otherwise the range is above the dropout threshold if the trigger threshold is lower than the dropout threshold. In the case of one embodiment variant regarded as advantageous, the evaluating facility preferably regards the switching criterion as being fulfilled if the signal strength of the receive signal passes the dropout threshold or lies outside the signal strength band in the signal strength range adjacent to the dropout threshold. Alternatively or in addition, it is possible in an advantageous manner to assign to the receive signal a signal strength sub-band which is delimited by the trigger threshold and a switching threshold. The switching threshold preferably lies between the trigger threshold and the dropout threshold. If such a switching threshold is defined, it is of advantage if the evaluating facility already regards the switching criterion as fulfilled if the signal strength of the receive signal passes the switching threshold or lies outside the signal strength sub-band in a signal strength range adjacent to the switching threshold. The transmitting facility is preferably assigned a signal frequency range which is delimited by a lower transmission frequency and an upper transmission frequency. 2025279734 11 Dec 2025 The transmission frequency is preferably assigned a large number of transmission frequencies which lie in the transmission frequency range and have a specified minimum frequency spacing between one another. The minimum frequency spacing of the transmission frequencies preferably lies in a range between 200 Hz and 500 Hz. The transmission frequency range can extend for example from 30 kHz to 50 kHz. The transmission frequency range preferably comprises at least eight, for example ten, transmission frequencies which are separated from one another by the minimum frequency spacing. The evaluating facility is preferably configured in such a manner that, when the switching criterion is fulfilled, it starts a specified switching algorithm in which at least one adjustment step is performed. Each adjustment step preferably includes in each case setting a new transmission frequency, evaluating the receive signal and checking whether the switching criterion continues to be fulfilled with the newly set transmission frequency or not, and continuing the switching algorithm by triggering a new adjustment step if the switching criterion continues to be fulfilled and otherwise terminating the switching algorithm and a normal continuous operation with the actually set transmission frequency. In the case of the last-mentioned embodiment, it is of advantage if the switching algorithm provides for the consecutive setting of specified transmission frequencies from a predefined group of transmission frequencies in accordance with a specified selection scheme and the switching algorithm is continued with in each case the next transmission frequency in accordance with the selection scheme if, in the case of the respective prevailing transmission frequency, the switching criterion remains fulfilled. 2025279734 11 Dec 2025 The selection scheme preferably provides for a large as possible frequency change during an adjustment, and namely on the condition that transmission frequencies which have already been set within the scope of any previous adjustment steps and recognized as unsuitable are not activated again. After unsuccessful testing of all transmission frequencies specified in the selection scheme, the switching algorithm can also advantageously provide for the switching algorithm to be continued by restarting the selection scheme. After unsuccessful testing of all transmission frequencies specified in the selection scheme, the switching algorithm can also advantageously provide for a warning message to be output. It is advantageous if a warning message is output if the duration of the performance of the switching algorithm reaches or exceeds a specified warning time period. The invention also relates to a transmitting facility for a wheel detector, in particular for such a wheel detector as described above. With regard to the transmitting facility, it is provided in accordance with the invention that this is designed so as to generate an electromagnetic alternating field and for its transmission frequency to be adjustable by means of a control signal and that it renders it possible to select the active transmission frequency from at least two different transmission frequencies. With regard to the advantages of the transmitting facility in accordance with the invention and advantageous embodiments of the transmitting facility in accordance with the invention, 2025279734 11 Dec 2025 reference is made to the above statements in connection with the wheel detector in accordance with the invention and its advantageous embodiments. The invention also relates to an evaluating facility for a wheel detector, in particular for such a wheel detector as described above, in order to evaluate a receive signal of the wheel detector and generate a wheel detection signal as a function of the result of the evaluation. With regard to the evaluating unit, it is provided in accordance with the invention that this is configured in such a manner that it adjusts the transmission frequency of a transmitting facility of the wheel detector by means of a control signal if the receive signal fulfills a specified switching criterion. With regard to the advantages of the evaluating facility in accordance with the invention and advantageous embodiments of the evaluating facility in accordance with the invention, reference is made to the above statements in connection with the wheel detector in accordance with the invention and its advantageous embodiments. The invention also relates to a method for operating a wheel detector, in particular one such as described above, for a railway track installation for detecting wheels of passing rail vehicles. In accordance with the invention, it is provided with regard to the method that a transmitting facility of the wheel detector, which is designed to generate an electromagnetic alternating field, can be adjusted with regard to its active transmission frequency by means of a control signal and renders it possible to select the active transmission frequency from at least two different transmission frequencies, and the active transmission frequency is adjusted by means of the control signal if a 2025279734 11 Dec 2025 receive signal of a receiving facility of the wheel detector fulfills a specified switching criterion. With regard to the advantages of the method in accordance with the invention and advantageous embodiments of the method in accordance with the invention, reference is made to the above statements in connection with the wheel detector in accordance with the invention and its advantageous embodiments. The invention is explained in detail below with the aid of exemplary embodiments, by way of example in the drawing: Fig. 1 shows an exemplary embodiment for a wheel detector in accordance with the invention which is equipped with one exemplary embodiment for a transmitting facility in accordance with the invention and with another exemplary embodiment for an evaluating facility in accordance with the invention and with the aid of which various embodiment variants of methods in accordance with the invention are explained, Figs. 2-10 show possible operating scenarios of the wheel detector in accordance with Figure 1. Fig. 11 shows an exemplary embodiment for a controllable resonant circuit of the transmitting facility in accordance with Figure 1 in more detail, and Fig. 12 shows an exemplary embodiment for a evaluating facility of the wheel detector in accordance with Figure 1 in more detail. 2025279734 11 Dec 2025 For the sake of clarity, the same reference characters are always used in the figures for identical or comparable components. Figure 1 shows an exemplary embodiment for a wheel detector in accordance with the invention which is mounted in the region of a rail 1 of a railway track installation and is used to detect wheels of passing rail vehicles. The wheel detector can form a component of an axle counting facility which renders it possible to monitor a track section of the railway track installation. The wheel detector comprises a transmitting facility 10 emitting a transmit signal S, a receiving facility 20 and an evaluating facility 30. In the case of the exemplary embodiment shown in Figure 1, the transmitting facility 10 and the receiving facility 20 are arranged on different sides of the rail 1. The transmitting facility 10 is equipped with a transmissionside resonant circuit 11 which can be adjusted from the outside and which renders it possible to generate an electromagnetic alternating field in the region of the wheel detector. The frequency of the alternating field or the active transmission frequency f of the transmitting facility 10 can be adjusted from the outside by means of a control signal ST, for example by adjusting the resonance frequency of the resonant circuit 11. By way of example, it is assumed below that the transmitting facility 10 is assigned a transmission frequency range which is delimited by a lower transmission frequency and an upper transmission frequency. A large number of selected transmission frequencies which have a specified minimum 2025279734 11 Dec 2025 frequency spacing between one another lies in the transmission frequency range. The respective active transmission frequency f is specified in the case of the exemplary embodiment in accordance with Figure 1 by the evaluating facility 30 by means of transmitting the control signal ST via a control line 31 connecting the transmitting facility 10 and the evaluating facility 30. The control signal ST can be, for example, a digital control signal with which, in cooperation with a (not further illustrated) control module arranged within the transmitting facility 10, internal switches of the transmitting facility 10 are switched on or off in order to adjust the transmission frequency f. In the case of the exemplary embodiment in accordance with Figure 1, the evaluating facility 30 comprises a receiving resonant circuit 21 which outputs a receive signal Se, a rectifier 22 arranged downstream of the receiving resonant circuit 21, a low-pass filter 23 arranged downstream of the rectified 22, and an amplifier 24. The function of the rectifier 22 of the low-pass filter 23 and the amplifier 24 is to pre-process the receive signal Se and generate a signal strength signal Ss which indicates the respective signal strength of the receive signal Se. The rectifier 22 can be a diode rectifier but with a view to efficiency a synchronous rectifier is preferred. The clock signal T required for operating such a synchronous rectifier can be transmitted, for example, by the evaluating facility 30 via a clock line 32 to the receiving facility 20. The evaluating facility 30 can derive this clock signal T from a feedback signal Rs corresponding to the transmit signal S 2025279734 11 Dec 2025 which the transmitting facility 10 continuously transmits to the evaluating facility 30 via a return line 33. Figure 2 shows how the wheel detector in accordance with Figure 1 works with the aid of the temporal curve of the signal strength signal Ss over the time t. In this case, it is assumed that, for example, during trouble-free operation without a wheel running over the track, the signal strength signal Ss has a quiescent level RP. The quiescent level RP lies in a specified signal strength band B which is delimited by a trigger threshold G1 and a dropout threshold G2. In the case of the exemplary embodiment in accordance with Figure 2, the trigger threshold G1 lies above the quiescent level RP and the dropout threshold lies below the quiescent level RP but this can also be inverse depending upon the design of the wheel detector. The dropout threshold G2 generally lies closer to the quiescent level RP than the trigger threshold G1. The evaluating facility 30 generates a wheel detection signal Z indicating a wheel running over the track if the signal strength or the signal strength signal Ss passes or lies outside the signal strength band B in a signal strength range adjacent to the trigger threshold G1, in this case therefore above the trigger threshold G1. The evaluating facility 30 generates an error signal F if over a specified time period the signal strength or the signal strength signal Ss passes the dropout threshold G2 or lies outside the signal strength band B in a signal strength range adjacent to the dropout threshold G2, in this case therefore below the dropout threshold G2. 2025279734 11 Dec 2025 In the case of the exemplary embodiment in accordance with Figure 1, it is provided that the evaluating facility 30 adjusts the active transmission frequency f by means of the control signal ST if the signal strength signal Ss or the signal strength of the receive signal Se passes the dropout threshold G2 or lies below the dropout threshold G2. The transmission frequency f is preferably adjusted in accordance with a specified switching algorithm. Within the scope of the switching algorithm, the transmission frequency f is adjusted in successive steps until a suitable new transmission frequency f is found. Each adjustment step includes in each case setting a new transmission frequency f, evaluating the receive signal Se or the signal strength signal Ss and checking whether the switching criterion continues to be fulfilled with the newly set transmission frequency f or not, and continuing the switching algorithm by triggering a new adjustment step if the switching criterion continues to be fulfilled and otherwise terminating the switching algorithm and normal continuous operation with the actually set transmission frequency f. In so doing, the switching algorithm provides for the specified transmission frequencies to be set consecutively from a predefined group of transmission frequencies already mentioned above in accordance with a specified selection scheme. In this case, the switching algorithm is continued with in each case the next transmitting frequency f in accordance with the selection scheme if in the case of the respective prevailing transmission frequency f the switching criterion remains fulfilled. During the adjustment, a large as possible frequency change is preferably performed in each case, and namely on the condition 2025279734 11 Dec 2025 that transmission frequencies which have already been set within the scope of any previous adjustment steps and recognized as unsuitable are not activated again. A possible sequence of transmission frequencies is illustrated below with the aid of a simple example in which a transmission frequency range with seven possible transmission frequencies f1 to f7, preferably equidistant with regard to frequency, is assumed; the first transmission frequency f1 forms the lower frequency limit of the transmission frequency range, the seventh transmission frequency f7 forms the upper frequency limit of the transmission frequency range and the fourth transmission frequency f4 lies in the middle of the transmission frequency range. Figure 3 illustrates the transmission frequency range with the seven possible transmission frequencies f1 to f7, wherein it is assumed that initially the middle transmission frequency f4 is active. If the switching criterion is now fulfilled because the signal strength of the receive signal Se drops below the dropout threshold G2, the evaluating facility 30 will set either the first transmission frequency f1 or the seventh transmission frequency f7 because this selection at this point in time leads to the greatest frequency jump. By way of example, Figure 4 assumes that the evaluating facility 30 has selected the seventh transmission frequency f7, in other words the highest transmission frequency f of the transmission frequency range and the transmitting facility 10 has switched accordingly. If the switching criterion continues to be fulfilled because the signal strength of the receive signal Se still lies below 2025279734 11 Dec 2025 the dropout threshold G2, the evaluating facility 30 will now set the first transmitting frequency f1 because this selection at this point in time leads to the greatest possible frequency jump. Figure 5 shows the adjustment. If the switching criterion continues to be fulfilled because the signal strength of the receive signal Se still lies below the dropout threshold G2, the evaluating facility 30 will now set the sixth transmitting frequency f6 (see Figure 6) because this selection at this point in time leads to the greatest possible frequency jump, on the condition that transmission frequencies that have previously been tested unsuccessfully within the selection scheme are not tested twice. If the switching criterion continues to be fulfilled, the other transmission frequencies in the further sequence f2 -> f5 -> f3 are tested (see Figures 7-9). After all the transmission frequencies specified in the selection scheme have been successfully tested, the evaluating facility 30 can terminate the switching algorithm by restarting the selection scheme or switching the transmission frequency f. It is advantageous if a warning message W is output if this situation occurs. The evaluating facility 30 can also output a warning message W if the duration of the performance of the switching algorithm reaches or exceeds a specified warning time period. Referring again to Figure 2, the section a shows a phase in which the signal strength of the receive signal Se or the signal strength signal Ss has the quiescent level RP. 2025279734 11 Dec 2025 In section b, the signal strength signal Ss drops under the influence of an interference variable ab, until the dropout threshold G2 is reached. After reaching this dropout threshold G2, another transmission frequency is switched to after a defined time period has elapsed in which the signal level must continue to remain below the dropout threshold G2. In section c, the original quiescent level RP is reached again after a settling period because an interference variable is no longer coupled in to the newly set frequency. In section d, an interference variable is likewise coupled in, however its influence increases the reception voltage or the signal strength signal Ss, in other words allows it to increase in the direction of wheel influence. Since this signal remains below the wheel recognition threshold, the frequency is not changed. In section e, this interference has subsided and the original quiescent reception level RP is again present, for example, in the form of a resting reception voltage. In section f, the signal strength signal Ss has dropped due to a coupled interference and lies below the dropout threshold G2. As in section b, after a defined time period has elapsed, the transmission frequency is changed in order to set an interference-free frequency. If this new working frequency does not lead to an increase in signal strength beyond the dropout threshold G2, it is assumed that this frequency is likewise subject to interference and a further frequency is set. After a definite time period, the original working frequency can also be re-set and consequently checked. 2025279734 11 Dec 2025 The procedure of checking the signal strength is repeated after the defined time period. The changing of the frequency is continued until the quiescent level RP or the quiescent reception voltage is reached again or the interference threshold is exceeded. In section g, the quiescent level RP or the quiescent reception voltage is reached again. In section h, the typical signal curve of a wheel running over the track is represented: The reception voltage increases until the wheel recognition threshold or trigger threshold G1 is exceeded. As long as the wheel recognition threshold is exceeded, a wheel detection signal Z is generated or output. If in section f it is not possible to set an interference-free frequency and thus the level can no longer increase beyond the interference threshold, after a defined time period has elapsed an interference message SM is generated by the evaluating facility 30 of the wheel detector and transmitted to a higher-level system. Figure 10 shows an alternative way of operating the wheel detector in accordance with Figure 1 with the aid of the temporal curve of the signal strength signal Ss over the time t. In this case, it is assumed that, during trouble-free operation without a wheel running over the track, the signal strength signal Ss has a quiescent level RP. In contrast to the embodiment variant in accordance with Figure 2, a signal strength sub-band SSB is also provided which is delimited by the trigger threshold G1 and a switching threshold Gm. The switching threshold Gm lies between the quiescent level RP and the dropout threshold G2. 2025279734 11 Dec 2025 The evaluating facility 30 regards the switching criterion as being fulfilled if the signal strength of the receive signal Se passes the switching threshold Gm or lies outside the signal strength sub-band in a signal strength range adjacent to the switching threshold Gm. In other words, the adjustment of the transmission frequency f is started even earlier than in the case of the exemplary embodiment in accordance with Figure 2, because the search for a new transmission frequency f begins earlier and it is not necessary to be below the dropout threshold G2. Moreover, the above statements in connection with Figure 2 apply. Figure 11 shows components of an exemplary embodiment for a transmitting facility 10 which can be used in the case of the wheel detector in accordance with Figure 1. It specifically shows a switchable capacitor circuit 100 which together with an inductance L forms a component of the transmitter-side resonant circuit 11 and its n capacitors can be individually switched on or off by means of switching signals ST1-Stn contained in the control signal ST. The selection of switching capacitors C1-Cn on or off determines the resonance frequency of the resonant circuit 11 and thus the active transmission frequency f of the transmitting facility 10 of the wheel detector. A control module 12 can be provided in order to extract the switching signals ST1-STn from the control signal ST. Figure 12 shows components of an exemplary embodiment for an evaluating facility 30 which can be used in the case of the wheel detector in accordance with Figure 1. The evaluating facility 30 comprises a computing facility 300 and a memory 301. Stored in the memory 301 is a control program SPM which, 2025279734 11 Dec 2025 when executed by the computing facility 300, causes this to operate the wheel detector as described above, in particular to execute the switching algorithm UA according to a stored selection scheme AS, for the purpose of selecting the respective active transmission frequency f. Finally, it should be mentioned that the features of all above described exemplary embodiments can be combined with one another in any way in order to form further other exemplary embodiments of the invention. All the features of the subclaims can also be combined individually with each of the independent claims, and namely individually or in any combination with one or more other subclaims, in order to obtain further other exemplary embodiments. 2025279734 11 Dec 2025 List of reference characters 1 Rail 10 Transmitting facility 11 Resonant circuit 12 Control module 20 Receiving facility 21 Receiving resonant circuit 22 Rectifier 23 Low-pass filter 24 Amplifier 30 Evaluating facility 31 Control line 32 Clock line 33 Return line 100 Capacitor circuit 300 Computing facility 301 Memory a-h Sections AS Selection scheme B Signal strength band C1-Cn Capacitors f Transmission frequency f1-f7 Transmission frequencies F Error signal G1 Trigger threshold G2 Dropout threshold Gm Switching threshold Rp Quiescent level Rs Feedback transmit signal S Transmit signal Se Receive signal SM Interference message 2025279734 11 Dec 2025 SPM Control program Ss Signal strength signal SSB Signal strength sub-band ST Control signal ST1-STn Switching signal t Time T Clock signal UA Switching algorithm W Warning message Z Wheel detection signal
Claims
1. A wheel detector for a railway track installation for detecting wheels of passing rail vehicles,- wherein a transmitting facility (10) of the wheel detector, which is designed to generate an electromagnetic alternating field, can be adjusted with regard to its activetransmission frequency (f) by means of a control signal (ST)and renders it possible to select the active transmission frequency (f) from at least two different transmission frequencies,- an evaluating facility (30) of the wheel detector is designed in such a way that it adjusts the transmission frequency (f) by means of the control signal (ST) if a receive signal (Se) of a receiving facility (20) of the wheel detector fulfills a specified switching criterion, characterized in that- after unsuccessful testing of all transmission frequencies specified in the selection scheme (AS), the switching algorithm (UA) provides for the switching algorithm (UA) to be continued by restarting the selection scheme, and / or- after unsuccessful testing of all transmission frequencies specified in the selection scheme (AS), the switchingalgorithm (UA) outputs a warning message, and / or- a warning message (W) is output if the duration of the performance of the switching algorithm (UA) reaches or exceeds a specified warning time period.
2. The wheel detector as claimed in claim 1, characterized in that- the receive signal (Se) is assigned a signal strength band (B) which is delimited by a trigger threshold (G1) and a dropout threshold (G2), and2025279734 11 Dec 2025- the evaluating facility (30) generates a wheel signal (Z) indicating a wheel is running over the track if the signal strength passes the trigger threshold (G1) or lies outside the signal strength band (B) in a signal strength range adjacent to the trigger threshold (G1).- the evaluating facility (30) generates an error signal (F) if over a specified time period the signal strength passesthe dropout threshold (G2) or lies outside the signalstrength band (B) in a signal strength range adjacent to the dropout threshold (G2).
3. The wheel detector as claimed in claim 2, characterized in thatthe evaluating facility (30) regards the switching criterion as being fulfilled if the signal strength of the receive signal (Se) passes the dropout threshold (G2) or lies outside the signal strength band (B) in a signal strength range adjacent to the dropout threshold (G2).
4. The wheel detector as claimed in one of the preceding claims 2 to 3,characterized in that- the receive signal (Se) is assigned a signal strength subband (SSB) which is delimited by the trigger threshold (G1)and a switching threshold (Gm) lying between the triggerthreshold (G1) and the dropout threshold (G2), and- the evaluating facility (30) regards the switching criterion as being fulfilled if the signal strength of the receive signal (Se) passes the switching threshold (Gm) or lies outside the signal strength sub-band (SSB) in a signal strength range adjacent to the switching threshold (Gm).
5. The wheel detector as claimed in one of the preceding claims,2025279734 11 Dec 2025characterized in thatthe transmitting facility (10) is assigned a signal frequencyrange which is delimited by a lower transmission frequency(f1) and an upper transmission frequency (f7).
6. The wheel detector as claimed in claim 5,characterized in thatthe transmitting facility (10) is assigned a large number of transmission frequencies (f1-f7) which lie in the transmission frequency range and have a specified minimum frequency spacing between one another.
7. The wheel detector as claimed in one of the preceding claims, characterized in thatthe evaluating facility (30) is configured in such a manner that when the switching criterion is fulfilled it starts a specified switching algorithm (UA), in which at least one adjustment step is performed, wherein each adjustment step includes in each case:- setting a new transmission frequency (f), evaluating the receive signal (Se) and checking whether the switching criterion continues to be fulfilled with the newly set transmission frequency (f) or not, and- continuing the switching algorithm (UA) by triggering a new adjustment step if the switching criterion continues to befulfilled and otherwise terminating the switching algorithm (UA) and normal continuous operation with the actually settransmission frequency (f).
8. The wheel detector as claimed in claim 7, characterized in thatthe switching algorithm (UA) provides for the consecutive setting of specified transmission frequencies from a2025279734 11 Dec 2025predefined group of transmission frequencies in accordance with a specified selection scheme (AS) and the switching algorithm (UA) is continued with in each case the next transmission frequency (f) in accordance with the selectionscheme (AS) if in the case of the respective prevailing transmission frequency (f) the switching criterion remainsfulfilled.
9. The wheel detector as claimed in claim 8, characterized in thatthe selection scheme (AS) provides for a large as possiblefrequency change during an adjustment, and namely on thecondition that transmission frequencies which have already been set within the scope of any previous adjustment steps andrecognized as unsuitable are not activated again.
10. The wheel detector as claimed in one of the preceding claims, characterized in that- the evaluating facility (30) is configured in such a manner that adjusting the transmission frequency (f) provides for a frequency change of at least 200 Hz in each case, and / or- the minimum frequency spacing of the transmission frequencies lies in a range between 200 Hz and 500 Hz,and / or- the transmission frequency range extends from 30 kHz to 50kHz, and / or- the predefined group of transmission frequencies comprisesat least eight, preferably ten, transmission frequencies which are separated from one another by the minimum frequency spacing.2025279734 11 Dec 202511. A transmitting facility (10) for a wheel detector, in particular for a wheel detector as claimed in one of the preceding claims, characterized in thatthe transmitting facility (10) is designed so as to generatean electromagnetic alternating field and for its transmission frequency (f) to be adjustable by means of a control signal(ST) and renders it possible to select the active transmissionfrequency (f) from at least two different transmission frequencies.
12. An evaluating facility (30) for a wheel detector, in particular for a wheel detector as claimed in one of thepreceding claims, for evaluating a receive signal (Se) of a receiving facility (20) of the wheel detector and generating awheel detection signal as a function of the result of the evaluation, characterized in that the evaluating unit (30) is configured in such a manner that it adjusts the transmission frequency (f) of a transmitting facility (10) of the wheel detector by means of a control signal (ST) if the receive signal (Se) fulfills a specified switching criterion.
13. A method for operating a wheel detector, in particular onesuch as claimed in the preceding claims, for a railway track installation for detecting wheels of passing rail vehicles,characterized in that- a transmitting facility (10) of the wheel detector, which is designed to generate an electromagnetic alternating field, can be adjusted with regard to its active transmission frequency (f) by means of a control signal (ST) and renders it possible to select the active transmission frequency (f) from at least two different transmission frequencies, and2025279734 11 Dec 2025- the active transmission frequency (f) is adjusted by means of the control signal (ST) if a receive signal (Se) of a receiving facility (20) of the wheel detector fulfills a specified switching criterion.