EP1288098B1 - Wheel sensor and arrangement - Google Patents

Abstract

An inductive sensor on a railway line detects a change in a magnetic field as the iron wheels of a railway vehicle pass over a rail. A system with first (La) and second (Li) coreless coils compensates for interfering magnetic fields (\=Fs). The first coreless coil optimizes this compensating effect along with the second coreless coil that fits inside the first coreless coil and generates a magnetic field in an opposite direction during a combined supply of current.

Description

The invention relates to a wheel sensor according to the preamble of claims 1 and 3 and a Radsensoranordnung according to the preamble of claims 8 and 10. Radsensoren be used in railways for the track vacancy, but also for other switching and reporting tasks. In this case, the magnetic field influencing effect of the iron wheels of rail vehicles is predominantly utilized. By means of inductive sensors mounted on the track, which generate a specific magnetic field, the retroactivity of the iron wheels can be detected, whereby a wheel pulse is registered with each wheel detection or axle detection. The number of wheel pulses in conjunction with another wheel sensor provides information about the occupancy state of the intermediate track section. This track vacancy is an essential decision criterion for the control of switches and signals. Based on the occupancy state of track sections, the decision is made whether a rail vehicle may enter this track section or not. Consequently, the alarm signals of the axle counters must meet extremely high reliability requirements. It must be ensured that only the iron wheels of the rail vehicles passing over the sensors are detected by the sensors and interference magnetic fields of other origin are ignored. This applies, for example, magnetic fields that arise in electric traction through rail currents and by vehicle components such as transformers, chokes and electronic rail brakes. The latter pose a particular problem because the magnetic fields generated are very strong. This is especially true for the ICE (Intercity Express) developed eddy current brake, which generates a fault magnetic field in the excited state, which greatly overlaps the working magnetic field of the inductive sensor.

An approach that relies on placing the operating frequencies of the sensors in seemingly harmonic frequency-free magnitudes, can not guarantee lasting success, since the development of new vehicle components constantly new interference fields with sometimes very high frequencies added. Frequency selection also makes it impossible to avoid interference fields containing frequency components in the range of the operating frequency of the inductive sensor. Usually, the operating frequencies are in the range of 30 kHz to 1 MHz, while interference fields can certainly reach frequencies up to 2 MHz.

Another approach is based on compensation efforts of the kind that the disturbance magnetic field is quasi neutralized by building an opposing field. According to the DE-A1-197 09 844 For this purpose, a coil arrangement with a magnetic core is provided. Two coils arranged concentrically to one another are connected in such a way that opposing magnetic fields arise when the current flows together. On the other hand, a magnetic interference field induces interference voltages in both coils, which compensate each other because of the opposing wiring of the two coils. The coil arrangement is part of an inductive sensor for generating a working magnetic field is maintained. The iron mass of a traveling wheel changes the properties of the working magnetic field, which is sensed. The problem with this approach, however, is that a very strong interference magnetic field, such as an excited eddy current brake, the coil core so can magnetize that an undesirable response of the sensor is caused.

A similar, but coreless coil assembly is from the DE-A1-199 15 597 known. However, the sensitivity of this generic axle counter is low, since the magnetic field generated for the detection of the wheel does not optimally penetrate the area of the wheel flange of the wheel. In addition, wetness on the sensor housing may result in a further reduction in sensor sensitivity at the usually high operating frequencies of coreless coil assemblies.

The invention has for its object to overcome these disadvantages and to provide a wheel sensor with inductive sensor whose parameters are optimized in terms of sensitivity and thus in terms of the reliability of the overall system.

The object is achieved alternatively by the features of claims 1 and 3. According to claim 1, an optimization is achieved in that the inner coil has an area ratio corresponding to the higher number of turns than the outer coil. In this way, not only a partial compensation of the same, but a complete compensation is achieved in homogeneous interference fields. The special coil dimensioning also has the consequence that the induction occurring in opposite directions when driving in both coils are not the same size and consequently a sufficiently high total induction remains for the detection of a wheel. Since disturbing effects are virtually completely eliminated and the working magnetic field has a very high field strength and optimally passes through the wheel flange of the wheel to be detected Compared to the prior art, a significant improvement in the sensitivity of the sensor and thus increasing the reliability of the overall system. If the disturbance magnetic field is inhomogeneous, differences between the disturbing voltages of the partial coils can occur as a result of the different coil dimensions. In this case, a partial compensating effect is present, with the effectively remaining total noise voltage being extremely small and ultimately negligible.

The second coil is preferably arranged centrally within the first coil according to claim 2. However, the compensation effect is also present when the inner coil is arranged eccentrically. The coil shapes can be very different. For example, the inner coil may have circular turns and be arranged eccentrically within an oval shaped outer coil.

Claim 3 characterizes a further solution of the task, wherein in addition to the solution according to claim 1, a simplification is achieved. Coils of different geometry and different number of turns are not required in this alternative solution. Instead, an overlapping in the vertical projection arrangement of similar coils is provided, the winding planes are arranged quasi one above the other. Since the coils are not interdigitated or interpenetrated, the magnetic field generated by one coil passes through the other coil in equal parts with opposing inner and outer magnetic fluxes, that is, the coils are magnetically decoupled from each other.

The coils are preferably designed according to claim 4 as a very flat, spirally wound disc coils. In this way, the coils can be easily installed in the housing of a wheel sensor.

According to claim 5, the winding planes of the coils in both alternative solutions can run parallel to the track plane.

In a special coil arrangement for the alternative solution characterized in claim 6 according to claim 3, both coils are tilted at the same inclination angle to a horizontal surface in the track direction. Magnetic interference fields then pass through both coils in the same intensity and direction and thus cancel each other, even if the field is not parallel to the coil longitudinal axes.

Simple coil or winding geometries, which are based on a round base, are preferred according to claim 7. Conceivable, however, for both alternatives also square, in particular square or rectangular bases.

In an advantageous development described in claim 8, two wheel sensors are arranged one behind the other. In this way, the direction of travel of a rail vehicle passing over the two wheel sensors can be determined on the basis of the time interval of the wheel pulse registration.

In order to keep the distance between the two wheel sensors as low as possible, in particular with common housing, and yet sufficiently timed to obtain mutually offset wheel pulses, according to claim 9 roof-shaped inclined winding planes of the coil pairs are provided.

Claim 10 characterizes a Doppelradsensoranordnung in which also overlap the adjacent coils of the two wheel sensors. The magnetic decoupling according to claim 3 also has an effect in this area. The advantage of this arrangement is that the geometric overlapping of the wheel sensors has a longer overlapping phase of the influence exerted by a wheel on both sensors.

Figur 1

eine schematische Darstellung des Kompensationsprinzips, wie sie aus dem Stand der Technik bekannt ist,

Figur 2

eine erste erfindungsgemäße Ausführungsform einer Spulenanordnung,

Figur 3a

eine Seitenansicht und eine Draufsicht einer Spulenanordnung gemäß Figur 2 mit Arbeitsfeldbeaufschlagung,

Figur 3b

die Seitenansicht gemäß Figur 3a mit Störfeldbeaufschlagung,

Figur 4

eine Abwandlung der ersten Ausführungsform in Seitenansicht und in Draufsicht,

Figur 5

eine zweite erfindungsgemäße Ausführungsform einer Spulenanordnung,

Figur 6

eine Seitenansicht und eine Draufsicht der zweiten Ausführungsform gemäß Figur 5,

Figur 7a

eine Seitenansicht gemäß Figur 6 mit Arbeitsfeldbeaufschlagung,

Figur 7b

eine Seitenansicht gemäß Figur 6 mit Störfeldbeaufschlagung,

Figur 8

eine Doppelradsensoranordnung,

Figur 9

eine Spulenanordnung und

Figur 10

eine weitere Doppelradsenoranordnung.

The invention will be explained in more detail with reference to figurative representations. Show it:

FIG. 1

a schematic representation of the compensation principle, as known from the prior art,

FIG. 2

a first embodiment of a coil arrangement according to the invention,

FIG. 3a

a side view and a plan view of a coil assembly according to FIG. 2 with fieldwork,

FIG. 3b

the side view according to FIG. 3a with interference field,

FIG. 4

A modification of the first embodiment in side view and in plan view,

FIG. 5

A second embodiment of a coil arrangement according to the invention,

FIG. 6

a side view and a plan view of the second embodiment according to FIG. 5 .

Figure 7a

a side view according to FIG. 6 with fieldwork,

FIG. 7b

a side view according to FIG. 6 with interference field,

FIG. 8

a double wheel sensor arrangement,

FIG. 9

a coil assembly and

FIG. 10

another Doppelradsenoranordnung.

FIG. 1 schematically illustrates the operation of an inductive sensor with interference field compensation according to the prior art. The sensor consists essentially of an oscillator 1 and a resonant circuit 2 with a capacitor C and two coils L1 and L2. With this arrangement, it is possible, the interference voltages U _StörL1 and U _StörL2 a on both coils L1 and L2 similarly acting disturbance magnetic field φ _s ( FIG. 2 and FIG. 5 ) to compensate. For this purpose, the two coils L1 and L2 in the LC resonant circuit 2 are connected in such a way that the interference voltages U _StörL1 and U _{StörL2 are opposite} in _direction for the same absolute value and thus cancel each other out. On the other hand, a voltage applied by the oscillator 1 to the LC resonant circuit 2 working _voltage U _oszL1 or U _oszL2 for generating a working _{magnetic field is} hardly affected by this arrangement.

FIG. 2 shows a track body 3 in perspective view with a first embodiment of a coil arrangement according to the invention for interference magnetic field compensation. It is seen that a noise magnetic field φ _s of a rail current I _s is generated. In order to virtually neutralize this disturbing magnetic field φ _s , here the two coils L1 and L2 connected in series are formed as inner coil Li and outer coil La, wherein the winding orientations of the two coils Li and La are opposite to each other, like the FIGS. 3a and 4 show symbolized by arrows. In addition, the number of turns n _{Li of} the inner coil Li is greater than the number of turns n _{La of} the outer coil La.

bzw. $$\mathrm{U}\mathrm{=}\mathrm{\mu }\mathrm{\cdot }\mathrm{n}\mathrm{\cdot }\frac{1}{\mathrm{A}}\cdot \frac{\mathrm{dB}}{\mathrm{dt}}$$

und
U_Li = U_La ergibt sich für die Dimensionierung der Spulen: $$\frac{{\mathrm{n}}_{\mathrm{Li}}}{{\mathrm{n}}_{\mathrm{La}}}\mathrm{=}\frac{{\mathrm{A}}_{\mathrm{La}}}{{\mathrm{A}}_{\mathrm{Li}}}\mathrm{,}$$

wobei

• µ die Permeabilität,
• φ der magnetische Fluss,
• B die magnetische Induktion und
• A die Fläche der Spule La bzw. Li
  bedeuten. Die innere Spule Li hat also eine dem Flächenverhältnis entsprechende höhere Windungszahl n_Li als die äußere Spule La. Dieser Umstand hat zur Folge, dass die durch den Schwingkreisstrom des Oszillators 1 in beiden Spulen Li und La entgegengesetzt auftretenden Induktionen B_Li und B_La nicht gleich groß sind und im Bereich der inneren Spule Li gemäß Figur 3a eine ausreichend hohe Gesamtinduktion B_Li-B_La zur Detektion eines den induktiven Sensor überfahrenden Rades eines Schienenfahrzeuges verbleibt. Dagegen kompensieren sich der innere und der äußere Anteil eines Störmagnetfeldes mit der Gesamtinduktion B_Stör gegenseitig, wie Figur 3b in symbolhafter Darstellung zeigt.

Out $$\mathrm{U}\mathrm{=}\mathrm{\mu }\mathrm{\cdot }\mathrm{n}\mathrm{\cdot }\frac{\mathrm{d\phi }}{\mathrm{dt}}$$

respectively. $$\mathrm{U}\mathrm{=}\mathrm{\mu }\mathrm{\cdot }\mathrm{n}\mathrm{\cdot }\frac{1}{\mathrm{A}}\cdot \frac{\mathrm{dB}}{\mathrm{dt}}$$

and
U _Li = U _La results for the dimensioning of the coils: $$\frac{{\mathrm{n}}_{\mathrm{Li}}}{{\mathrm{n}}_{\mathrm{La}}}\mathrm{=}\frac{{\mathrm{A}}_{\mathrm{La}}}{{\mathrm{A}}_{\mathrm{Li}}}\mathrm{.}$$

in which

• μ the permeability,
• φ the magnetic flux,
• B is the magnetic induction and
• A is the area of the coil La or Li
  mean. The inner coil Li thus has a higher number of turns n _Li corresponding to the area ratio than the outer coil La. This circumstance has the consequence that the inductances B _Li and B _La which occur in opposite directions due to the resonant circuit current of the oscillator 1 in both coils Li and _{La are} not the same and in the region of the inner coil Li according to FIG FIG. 3a a sufficiently high total induction B _Li -B _La for the detection of a inductive sensor passing wheel of a rail vehicle remains. In contrast, the inner and the outer portion of a disturbing magnetic field with the total inductance B _sturge compensate each other, as FIG. 3b in symbolic representation shows.

The compensation effect is present even if, as in FIG. 4 , the inner coil Li is not arranged centrically in the outer coil La. In a further modification, the coils Li and La can be of almost any shape, such as circular, square, rectangular or oval. With exact compliance with the above-mentioned dimensioning rule, namely the reverse proportionality of the number of turns to the coil surfaces, an almost complete compensation of disturbing homogeneous magnetic fields can be achieved. In the case of inhomogeneous interference fields, differences between the interference voltages of the coils Li and La can occur as a result of the different coil dimensions. However, the effectively remaining total noise voltage is always smaller than that of a single coil, so that at least partially compensating effect is guaranteed.

The FIGS. 5 to 10 refer to a further embodiment according to the invention of an interference field compensating coil arrangement. Opposite in the FIGS. 2 to 4 illustrated variant, this embodiment differs in particular in that the coils used L1 and L2, in contrast to the coils Li and La have similar geometry. This results in a reduction of the effort or costs.

FIG. 5 shows in an analogous representation FIG. 2 in that two mutually offset and partially overlapping coils L1 and L2 of the same geometry and number of turns are provided. Since both coils L1 and L2 are identical, the disturbance magnetic field φ _s induces in both coils L1 and L2 the same interference voltage U _StörL1 and U _StörL2 ( FIG. 1 ). For compensation, the coils L1 and L2, as for FIG. 1 executed, interconnected. In the overlapping, but not penetrating arrangement of the two coils L1 and L2, these are magnetically decoupled from each other, that is, the magnetic field generated by a coil L1 and L2 passes through the another coil L2 or L1 in equal parts with the opposing inner and outer magnetic fluxes φ _i and φ _a , as FIG. 6 shows. This effect is achieved by the partial overlap of the coils L1 and L2, wherein the distance X between the longitudinal axes of the two coils L1 and L2 is always smaller than the diameter thereof. For the required for the detection of wheels working magnetic field B _L1 and B _L2 , the result in Figure 7a shown conditions, while a disturbance magnetic field B _sturgeon according to FIG. 7b is compensated. Each coil L1 and L2 generates a magnetic field as a single coil, since the magnetic decoupling no mutual interference occurs. Therefore, it has no influence that the magnetic fields B _L1 and B _{L2 of} both coils L1 and L2 are directed in oscillator operation. Both coils L1 and L2 contribute in equal parts to the detection of a wheel, because their magnetic fields B _L1 and B _L2 from the flange 4 ( FIG. 8 ) of a wheel are influenced in the same way. Compared to an arrangement with only one sensor coil, that is, without including this single coil in a coil majority for interference field compensation, the Einwirkbereich of the wheel extends approximately to the lateral offset X of the two coils L1 and L2.

FIG. 8 shows the coils L1_1, L2_1 and L2_2 two wheel sensors relative to the track body 3. The coils L1_1, L2_1 and L2_2 and L1_2 are such, for example, within a sensor housing, mounted so that their centers have a constant height to the horizontal base surface of the track body 3 , wherein the winding planes are inclined to the track plane. Magnetic interference fields then pass through the two coils L1_1 and L2_1 or L2_2 and L1_2 in the same intensity and direction and thus cancel each other, even if the Interference field is not parallel to the coil longitudinal axes. The in FIG. 8 shown double sensor is run over by the wheel flange 4 of the wheel in a specific time sequence, so that it can be concluded from the signal sequence on the direction of travel of the rail vehicle.

In FIG. 9 a preferred coil form for wheel sensors is shown. The coils L1 and L2 are disc-shaped and wound in spirals. The height of the disk coils corresponds to the diameter of the winding wire and is therefore so small that the two overlapping coils L1 and L2 can be installed without inclination in the housing of a wheel sensor.

FIG. 10 illustrates a dual sensor with disk coils L1_Sys1 and L2_Sys1 and L1_Sys1 and L2_Sys2, with the adjacent coils L2_Sys1 and L1_Sys2 of the two sensor systems overlap Sys1 and Sys2

Claims (10)

1. Wheel sensor, in particular for a track-free signalling installation, having at least one trackside inductive sensor for detection of a magnetic field change resulting from iron wheels of a rail vehicle moving over the track and having an arrangement which has coreless coils (L1, L2; La, Li) in order to compensate for disturbing magnetic fields (ϕ_s, B_dist) ,
   characterized in that
   a first coreless coil (La) and a second coreless coil (Li), which is arranged within the first and when current flows through them jointly produces a magnetic field (B_Li) in the opposite sense, are provided, with the turn planes of the coils (La, Li) essentially matching and with the numbers of turns (n_Li and n_La) of the coils (Li and La) being inversely proportional to the coil areas (A_La and A_Li) .
2. Wheel sensor according to Claim 1
   characterized in that
   the second coil (Li) is arranged centrally within the first coil (La).
3. Wheel sensor, in particular for a track-free signalling installation, having at least one trackside inductive sensor for detection of a magnetic field change resulting from iron wheels of a rail vehicle moving over the track and having an arrangement which has coreless coils (L1, L2) in order to compensate for disturbing magnetic fields (ϕ_S, B_dist),
   characterized in that
   two coreless coils (L1, L2) are provided which have essentially the same geometry and the same numbers of turns, and whose turn planes run essentially parallel to one another, with the coils (L1, L2) overlapping in a vertical projection and producing magnetic fields in opposite senses when current flows through them jointly.
4. Wheel sensor according to one of the preceding claims,
   characterized in that
   the coils (L1, L2; L1Sys1, L2Sys1, L1_Sys2, L2_Sys2) are in the form of disc coils whose height corresponds to the diameter of the conductor used.
5. Wheel sensor according to one of the preceding claims,
   characterized in that
   the turn planes of the coils (L1, L2; La, Li) run essentially parallel to the track plane.
6. Wheel sensor according to Claim 3,
   characterized in that
   the turn planes of the coils (L1_1, L2_1; L2_2, L2_1) are at an angle, which is oriented essentially in the track longitudinal direction, with respect to the track plane, and the connecting line between the coil centre points runs parallel to the track on a horizontal plane.
7. Wheel sensor according to one of the preceding claims,
   characterized in that
   the coils (L1, L2; Li, La) have round, in particular circular and/or oval, turns.
8. Wheel sensor arrangement, which is dependent on the direction of travel,
   characterized by
   the wheel sensors, which are at a distance from one another in the track direction, according to one of the preceding claims being used in pairs.
9. Wheel sensor arrangement, which is dependent on the direction of travel, according to Claim 8,
   characterized by
   the use of wheel sensors according to Claim 5, with the turn planes of the coil pairs (L1_1 and L2_1; L2_2 and L1_2) having inclinations which are oriented in opposite directions, in the form of a roof.
10. Wheel sensor arrangement, which is dependent on the direction of travel,
    characterized by
    wheel sensors which overlap in the track direction, according to one of Claims 1-7, being used in pairs.

Images