WO1995034456A1

WO1995034456A1 - Method of determining the position of flat spots on the running surfaces of rail-vehicle wheels

Info

Publication number: WO1995034456A1
Application number: PCT/CH1995/000133
Authority: WO
Inventors: Paul Matthias Arnoczky
Original assignee: Knorr-Bremse Electronic Gmbh
Priority date: 1994-06-10
Filing date: 1995-06-12
Publication date: 1995-12-21
Also published as: AU2559395A

Abstract

The invention uses high-frequency circuits connected up with the rails (14) to detect and determine the position of flat spots. Above a particular speed of travel (v), the interruption in the electrical contact caused by a flat spot as a result of the weight acting on the axle and the inertia of the wheel is measured and analysed. At at least one measurement point, one of the two rails (14) is cut through and the cut HF-insulated. In the immediate vicinity of the cut (15) with its insulated joint, HF signals are fed into the rails (14), with the sleepers insulated, on each side of the cut by respective test-signal feed units (28) with an HF generator (30) feeding through first LC components (35, 36). The cut (15) is preferably bridged by an HF choke (16). These signals form, through second LC components (37, 38) of a test-signal feed unit (28) connected to the rails on each side of the cut (15), at the same distance (lx) from the cut, resonant circuits (44, 45) of the same frequency. The wheels pass over the limited measurement path (l1 + l2) at a measured and recorded speed (v). The wheels, together with their axles, form a short circuit between the rails which is interrupted by a flat spot. The installation has all the advantages of that proposed in WO,A 88/01956, but offers the additional advantage that only one cut (15) needs to be made in the rail per measurement point and hence the installation is simpler.

Description

Location of flat spots in the tread of rail vehicle wheels

The invention relates to a method and a device for determining and locating flat spots in the tread of wheels of rail vehicles made of electrically conductive material, using high-frequency circuits connected to the rails, the sequence from a corresponding driving speed of the axle weight and inertia of a wheel is measured and evaluated due to a break in contact with the supporting rail caused by a flat spot.

Since its inception, the railroad has faced the problem of flat spots on wheels. This is still the case today because on the one hand many vehicles are not equipped with brake control systems (ABS) and on the other hand flat spots can arise for many other known and unknown reasons. Flat spots mostly occur when wheels lock when braking. Brake systems can freeze and ice up, especially in winter. Under the influence of friction and high local temperature, the tread of wheels is flattened and deformed.

Flat spots cause an out-of-round run with strong blows of the damaged wheel against the running surface of the rail. This leads to serious consequential damage to the rails and the superstructure, but also to the axle bearings, the body and the load of the vehicles. In addition, the development of noise is an increasing burden on the environment.

The overall high repair costs and the dangers that arise mean that vehicles with flat spots are quickly detected and removed from traffic. With getting higher at the speeds that are reached, this requirement becomes more and more important, since the impact increases approximately quadrant to the driving speed. These impact effects can cause damage, especially in winter.

WO, A 88/01956 describes a method and a device which detect the flat spots with great accuracy when passing through a train, even at high speed. The type and size of the damage and the affected axles are immediately signaled to the operations-monitoring departments with very high selectivity, so that they can plan and initiate all necessary measures until the train arrives. This largely reduces maintenance on the rails and consequential damage.

The system of W0, A 88/01956 essentially consists of a double, isolated measuring section and an electronic measuring system, which e.g. is housed in a cabin near the measurement section. Data transfers from the measuring system lead to operational monitoring.

The signal acquisition according to W0, A 88/01956 has proven to be very good. Thanks to the 2 x 1.6 m rail insulation, it is possible to simultaneously scan both wheels of a bogie and selectively record flat spots.

The reliability of this system with regard to the axis-precise detection, the length determination and the selective verification of flat spots on the bogie is almost 100%. A disadvantage of the system that hinders broad purchasing is on a psychological level: the rail insulation requires three cuts with an insulating joint over a measuring distance of 3.2 m. Therefore, the trust and necessary understanding among railway experts could not be found to the extent that technical progress had promised. Although this isolation is neither static still shows safety-related disadvantages, the prejudice has so far hardly been overcome.

The present invention has for its object to provide a method and a device of the type mentioned, which works without HF-isolated measuring sections cut from the rails on both sides, and the electronic measuring system according to W0, A 88/01956 can largely be used, including the measurement of the speed and the axle load. The method and the system should work equally reliably and economically even without isolated measuring sections.

With regard to the method, the object is achieved according to the invention in that at least one measuring point is cut through at least one of the two rails and this single interface is HF-isolated, in the immediate vicinity of the cut with an isolating joint, one measurement signal supply with a high frequency Generator feeds RF signals into the rails with isolated thresholds via first LC elements, which signals form resonance circuits with the same frequencies via second LC elements of a measurement signal feed arranged at the same distance from the cut with an insulating joint, the resonance circuits with the first measurement distance formed by proximity initiators and the cut with an isolating joint, the second measuring distance is monitored by a processor, the measuring section is overrun by wheels at a measured and registered speed, which with its axis interrupts a short circuit between the tracks caused by possible flat spots These form the measurement signals generated by the interruptions on the LC elements, digitally recorded with the aid of a processor and evaluated with precise assignment of flat spots to the wheel in question. Special embodiments and further developments of the method are the subject of dependent patent claims. With this solution, which is surprisingly simple in the knowledge of the invention, trains can be measured and evaluated with at least the same precision and safety as in accordance with W0, A 88/01956 with only one cut in a rail at a minimum speed of preferably about 40 km / h, largely the same electronic device is used. Good results can also be achieved if trains with today's maximum speeds in the range of 300 to 400 km / h break through. The retrofitting of systems already created according to W0, A 88/01956 is therefore simple; all that is required is to insert a new rail, which is only interrupted once, and to arrange the measurement signal supply according to the invention.

The computer system controls the gate times of the axes for the signal acquisition as a function of the measured speed of the rolling train. No signals are recorded outside of these gate times for each axis.

Furthermore, some processors expediently control corresponding threshold voltages for the optimal measurement signal acquisition.

Finally, other processors preferably control some digital / analog converters of known design, which ensure the necessary bias voltage limit for a comparator and for the optimal switching points of the measuring electronics.

For the greatest possible security for the detection of flat spots, several measuring points with measuring signal feeds are preferably arranged in such a way that a wheel is scanned in full several times, preferably shifted twice, which can be referred to as a tandem system.

The high-frequency generator of a measurement signal feed preferably works in a frequency range of at least about 400 kHz, in particular 400 kHz - 1 MHz, measured at a voltage in the range of 6 - 36 V, in particular of about 24 V. from peak to peak.

A flat spot detected with RF measurement signal feed-in can be verified not only by its length, but also by the size or intensity of the impact generated.

If there are several flat spots in the same wheel, only the largest is preferably registered and evaluated by the computer system.

With regard to the device for carrying out the method, the object is achieved according to the invention in that the measurement signal feeds arranged on both sides of an HF-insulated cut comprise a high-frequency generator with a primary winding for inductive action on a first LC element that connects the rails in a conductive manner on the one hand, at equal intervals from the cut with an insulating joint, at least a second each, which also connects the rails of the LC element for generating resonant circuits, and comprise means for detecting, processing and transmitting the signals to processors. Special embodiments and further developments of the system are the subject of dependent patent claims.

The cut in a rail, which does not impair the mechanical stability, is isolated in such a way that an RF signal (high-frequency signal) can work on both sides of the insulation, independently of others, for the acquisition of measurement data (speed, flat spots, etc.).

Such a cut with an insulating joint is preferably bridged with an HF choke. As mentioned, the RF signals remain isolated from one another, but the route monitoring signals, traction currents from locomotives and the like are not interrupted.

The length of a measurement distance, corresponding to the distance of the Cut with an insulating joint from the LC links, preferably corresponds to about half the circumference of a wheel.

The distance between the measurement sections of two adjacent measurement signal feeds suitably corresponds to somewhat more than a multiple of the full circumference of a wheel, in particular approximately 2.25 times the circumference.

The data acquisition preferably comprises a plurality of processors or microprocessors, digital / analog converters, comparators, etc. Some microprocessors work as an axis counter for the rail contact control and as a time measuring device for determining the train speed. Further microprocessors monitor the switching points generating the route occupancy signals with respect to the beginning and the end of the measuring routes. If a switching point is not in the specified range, for example, some processors regulate the switching point after each train passage by optimally adjusting the comparator bias of the transmitter / receiver box via digital / analog converter.

The method according to the invention and the corresponding system have all the advantages of W0, A 88/01956, but additionally offer a solution with only one cut with rail insulation, no rails have to be cut more than once per measuring point, and a correspondingly simple installation .

The invention is explained in more detail with reference to exemplary embodiments shown in the drawing, which are also the subject of dependent patent claims. They show schematically:

1 shows a rolling railway wheel with a flat point,

2 shows an arrangement of strain gauge strips for the detection of the axle load, 3 shows a measuring point with measurement signal feeds,

Called sender / receiver box,

4 shows a signal curve, and

5 shows a section of an electronic data acquisition.

1 shows a railroad wheel 10 rolling slowly on a rail 14 in the direction of arrow v with a flat 12 in three positions. Slow here means, for example, a speed of about 10 km / h. If the flat 12 lies parallel to the rail 14, which corresponds to the middle position, then the wheel 10 and thus the wheel axis 18 (r - r_) lower, r being the normal distance of the tread 20 of the wheel 10 from the center Z, r the corresponds to the smallest distance of the flat 12 from the center Z.

At higher speeds, e.g. from 40 km / h, the flat 12 briefly loses contact with the rail 14 and, according to known physical laws, bounces more and more with increasing speed. The contact is re-established with an increasingly violent impact on the rail.

Fig. 2 shows a mechanical arrangement for detecting the axle load Q (Fig. 1). For a better determination of the effective length of a flat point 12 (FIG. 1), it is necessary to approximate the axle weight. Strain gauges (DMS) 24 known per se are arranged on the neutral line 22 of a rail 14. Four pairs of connecting leads 26 lead to four strips above the track, two of which are attached on the left and two on the right rail, exactly opposite, and connected to form a known bridge circuit.

3 shows the basic arrangement of a measurement signal feed 28 in the rails 14 of a railroad track. The rails 14 have only one cut 15 per measuring point, which rather isolated and bridged with an RF choke 16.

A high-frequency generator 30 generates electromagnetic waves of a high frequency f with greater power. The circuit of the HF generator 30 comprises a winding 32 which induces a current in the winding 34 of a first LC element 35. A second identical LC element 37 is connected to the left of the first LC element 35, at a distance 1 ___. The two LC elements 35, 37 together form a resonance circuit 44 with the optimal resonance frequency f.

DerResonanzkreis 44 induced in an receiver winding 42 a voltage U .. If a measured distance is not short-circuited with a wheel axle 1 _1, the voltage is U., as shown in Figure 4, high (H).

The resonance circuit 44 shown in the left measuring distance 1 ₁ is repeated in the same way in the right measuring distance 1 ₂ as the resonance circuit 45 of the LC elements 36, 38. The sum of the same measuring distances 1. + 1 ₂ , measuring distance 1, is normally 3.2 m, corresponding to the circumference of a European standard wheel. With two measuring distances 1. = 1 ₂ = 1.6 m, flat spots of a multi-axis bogie can be detected simultaneously.

The measurement signal feed 28 could consist of more than two resonance circuits 44, 45 by connecting further LC elements at the same distance as 1 and 1 ₂ .

On the right side of FIG. 3, an LC element 37 of a next measuring point with measurement signal feed is shown, the distance between the two outermost LC elements 37, 38 is 4 x 1 + 2 ^' x (1- - 1) = L. At a radius r of a wheel of 1 m, L is at least a little over 7 m, but usually about 20-30 m long, which is about n, 25 times the circumference of the wheel, where n is an integer of at least 2. This arrangement ensures that each wheel is twice scanned at different angles, thereby increasing the accuracy of the system.

Not shown, a third and a fourth measuring point can follow at the same distance L, which are always constructed according to the pattern of the measuring signal feeds 28 shown in FIG. 3. Accuracy is further increased by additional measuring points, but it also entails higher costs, which is why in practice there are usually two measuring points.

In the left area of FIG. 3, the inlet side of the railway wheels, magnetic proximity initiators 46, 48 are installed to determine the speed v of a train. These double initiators 46, 48 also ensure that each axis is counted at least once. The initiators are monitored individually and together by a microprocessor 50 (FIG. 5).

The speed measurement by the initiators 46, 48 takes place in cooperation with the cut 15 with an insulating joint. The measured throughput time of an axis is transmitted for the measuring distance 1 "from the computer system as the gate opening time.

With the measured speed v, the distances between the lines are calculated as functions of times. With

_

With the aid of the calculated speeds, the individual times which are necessary for the acquisition of measurement signals are determined.

4 shows the amplitudes U of the resonance vibrations as a function of the path length 1. Without traversing trains, the amplitudes of the voltages U .. and U ₂ according to FIG. 3 remain large without damping: U ₁ = U ₂ = H within 1.

If a train passing through with its rolling axes, the two rails 14 (FIG. 3) on the points SP limited measuring path 1, + 1_ = 1, the voltages U, or U ₂ collapse during this path length, the amplitudes of the resonance vibrations become small: L.

In the case of a flat point 12, the voltages U .. or U-, expressing the characteristics of this flat point, are increased for a very short time, the amplitudes of the resonance vibrations increase from L to H during this time.

From these data and distances, a flat spot length Fl can be determined as follows:

'Fl

Fl = 1. v

in which

Fl = flat point length 1. = length of the measuring distance; e.g. 1.6 mt _F1 = break time of the flat t = roll time of an axis over 1. v 1

C »s. f (v, Q), correction factor dependent on the speed and the axle load

5, part of processor 50 is shown. This includes a comparator 52 with associated resistors, capacitors and diodes, which are known to the person skilled in the art and are therefore generally not described in more detail.

A microprocessor ES simulator 54 of the processor 50 opens and blocks the measurement signals S.,, S "with the signals TM-, TM ~, which limit the gate time TM of the corresponding axis, and simultaneously monitors S ', S-'. The microprocessor 54 simultaneously controls a digital / analog converter 56, which generates the necessary bias voltage limit for the comparator 52. In addition to the door opening for detecting flat spots 12, the TM processors have the following tasks:

- Fault detection in the case of defective rail contacts

Detection of piggyback axles (more than two axles per bogie)

Gate control without axis counting errors with multiple assignment of the measuring distance 1. of axes - optimal setting of the switching points SP (Fig. 4).

The measuring, control and evaluation electronics used according to the invention comprise several microprocessors, digital / analogue converters, comparators, memories and other known electronic components, also with the addition of a PC, which can replace microprocessors.

Claims

1. A method for determining and locating flat spots (12) in the tread (20) of wheels (10) of rail vehicles made of electrically conductive material, using high-frequency circuits connected to the rails (14), whereby from one ent speaking driving speed (v) which is measured and evaluated due to the axle weight (Q) and the inertia of a wheel (10) caused by a flat point (12) interruption of the contact with the supporting rail (14),

characterized in that

cut at least one measuring point through one of the two rails (14) once and this single interface is HF-insulated, in the immediate vicinity of both sides of the section (15) with an isolating joint, one measurement signal supply (28) each with a high-frequency generator (30) Via first LC elements (35, 36), HF signals are fed into the rails (14) with insulated sleepers, which signals are connected to the rails (14) with the rails (14) and are insulated from both sides at the same distance (1) from the cut (15). Connected LC elements (37, 38) of a measurement signal feed (28) form resonant circuits (44, 45) with the same frequencies, the first measurement distance (1.) from proximity initiators (46, 48) and the section (15) with an insulating joint formed, the second measuring distance (1 ₂ ) is monitored ^by a processor, the measuring section (1. + 1 ₂ ) is rolled over at a measured and registered speed (v) by wheels (10) which have their axis (18 ) one due to any flat spots (12) and Interrupted short circuit between the rails (14), the measurement signals generated on the LC elements (37, 38) by the interruptions tapped, digitally recorded with the aid of a processor (50) and evaluated with precise assignment of flat spots to the wheel in question.

2. The method according to claim 1, characterized in that the processor (50) in function of the measured speed (v) of the rolling train the gate times (TM ₁ , TM ₂ ) of the axes (18) for the signal transmission , and the corresponding threshold voltages are controlled.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that the processor (50) controls a digital / analog converter (56), which generates the necessary bias voltage limits for a comparator (52).

4. The method according to any one of claims 1 to 3, characterized ge indicates that a wheel (10) is scanned several times over the full extent of its tread (20), preference being given by several flat spots (12) of a wheel (10) only the largest is registered and evaluated.

5. The method according to any one of claims 1 to 4, characterized ge indicates that the high-frequency generator (30) with at least about 400 kHz, at a voltage in the range of 6-36 V, preferably about 24 V, works.

6. The method according to any one of claims 1 to 6, characterized in that a flat spot (12) detected with HF measurement signal feed-in is verified by the impact intensity generated.

7. Device for carrying out the method according to one of claims 1 to 6,

characterized in that 14

the measurement signal feeds (28) arranged on both sides of an HF-insulated cut (15) have a high-frequency generator (30) with a primary winding (32) for inductive action on a first LC element which connects the rails (14) in a conductive manner (36), on both sides at equal distances (1) from the cut (15) with an insulating joint, at least one second LC element (37, 38) also connecting the rails (14) to produce resonant circuits (44, 45) , and comprise means for acquiring, processing and transmitting the signals to processors (50).

8. The device according to claim 7, characterized in that the section (15) is bridged with an insulating joint with an HF choke (16).

9. The device according to claim 8, characterized in that the length of a measuring distance (1-, 1-,) corresponds approximately to the length of half the tread (20) of a rail vehicle wheel (10).

10. The device according to claim 8 or 9, characterized gekenn¬ characterized in that the distance (L) between the measuring distances (1-, 1 ₂ ) from two adjacent measuring points with measurement signal feeds (28) is approximately an integral multiple of the length of the full tread (20) of a rail vehicle wheel (10), each plus about a quarter of a full tread.