FR2752806A1 - HOT BOX DETECTOR - Google Patents

Abstract

The invention concerns a sensor (1) for monitoring the temperature of axle boxes (5) of a moving train (100) comprising: an optical block (21) for remote measuring of temperatures of the train (100) axle boxes (5) including a bar (30) of infrared elements, and an electronic block (24) for processing temperature signals. The bar (30) is associated with an optical system (29) forming an assembly arranged for observing according to an observation field transversal in cross section (51) substantially constant along an optical axis (37) of the optical system (29). The invention is useful for monitoring high speed trains (HST).

Description

HOT BOX DETECTOR
In the rail sector, transport safety is the subject of preventive accident surveillance, which notably consists of regularly checking certain train parameters in order to detect dangerous anomalies or local malfunctions. The invention relates more particularly to the monitoring of the temperature of the axle boxes, also called "hot boxes", of the cars of a train, mounted at the ends of each axle connecting two wheels.

An axle box includes an axle bearing embedded in grease, which can heat up abnormally through wear to the point of causing not only the explosion of the axle box but also, and consequently, the rupture of the axle causing the train to derail. Such an accident risk is all the more increased as the train travels quickly, high speed trains (TGV), capable of reaching a speed of nearly 400 kilometers per hour, being particularly exposed to it.

The monitoring of the temperatures of the axle boxes of a train is ensured from a monitoring station, connected to a set of hot box detectors (DBC) intended to measure the temperatures of the axle boxes, by means of devices. called "Trackside Electronics". For reasons of reliability and connectivity, the DBC detectors are mounted not on the axle boxes themselves, but fixed to the ground, near the track, All the DBC detectors being placed along both sides of the railway. The temperatures of the axle boxes of a train can thus be measured remotely, when the train is passing, by infrared detection.

There are in particular four generations of infrared DBC detectors, all of the single-beam type. A monobeam type DBC detector comprises a cell with a single infrared detection element. In operation, the detection cell fixedly observes a small elementary field, and, when a train passes, takes a sampling of temperatures from a series of elementary surfaces, corresponding to the field of observation, of the axle boxes moving in its field of observation. The sampling speed is adapted to the train speed.

The first three generations of DBC detectors include single-element Photo Magneto Electric (PME) type detection cells, more particularly suitable for monitoring conventional, non-TGV trains. The fourth generation includes a photoconductive type monodetector in
Hg-Cd-Te (Mercury, Cadmium and Tellurium), faster than the PME single detector, and better suited to the needs of TGV train monitoring.

However, these four generations of single-beam DBC detectors have the common disadvantage of being able to monitor only a narrow field of observation.

However, there are nearly four hundred types of axle boxes, of structure and above all of variable size. As a result, axle boxes risk, in a non-negligible way, of passing in front of the DBC detectors but outside their field of observation.

To avoid this problem, it is known to use DBC detectors comprising a single infrared monodetector, associated with a mirror placed in a vibrating tuning fork or truly pivoting, to scan a wider field of observation.

However, this type of detector has the double disadvantage of measuring temperatures with very poor precision and of being limited to monitoring trains traveling at a maximum of around 200 km / h.

The present invention provides a DBC detector allowing precise and faithful measurements to be made, and suitable for monitoring all types of axle boxes.

To this end, the invention relates to a hot box detector (DBC), for monitoring the temperatures of the axle boxes of a running train, comprising: - means for remote measurement of the temperatures of the axle boxes of the train comprising a remote detection element, - electronic means for processing temperature signals, characterized in that the measurement means comprise a plurality of remote detection elements.

Thanks to the invention, the field of observation, consisting of all the fields of observation of the plurality of elements, is wide. The invention is ultimately a multi-beam DBC detector.

In addition, the DBC detector of the invention performs measurements with much more precision than the scanning DBC detectors because the elementary surfaces observed are all identical unlike those scanned using the mirror.

Advantageously, the plurality of detection elements is associated with an optical system forming an assembly arranged to observe according to an observation field of substantially constant cross section along the optical axis of the optical system.

Thanks to this, whatever the distance of sight separating the DBC detector and the axle box, variable from simple to triple according to the type of axle box and the diameter of the wheel, the surface observed perpendicular to the axis optical is substantially constant, and therefore the accuracy of the measurements is also.

Advantageously also, the optical system is arranged to return the image of its entrance pupil far behind the optical system, along the optical axis.

Thanks to this, the DBC detector monitors a substantially constant field of observation for variable observation distances.

In a preferred embodiment of the invention, the measurement means have a spectral analysis band arranged so that the precision of the measurements is insensitive to variations in ambient brightness, and in particular to solar reflections.

Therefore, the DBC detector of the invention does not risk causing false alarms of abnormal heating of an axle box, frequent with the DBC detectors of the prior art when the rays of the sun become grazing.

In the preferred embodiment of the detector of the invention, the detection elements are infrared elements and are organized in a detection strip.

The invention will be better understood with the aid of the following description of a preferred embodiment of the hot box detector (DBC) 1 of the invention, with reference to the appended drawing in which: - Figure 1 shows a view in section of the DBC detector 1 on a railroad track 2 when a train 100 passes, - Figure 2 represents a schematic view of a train monitoring network, - Figure 3 represents a functional block diagram of the DBC detector 1 of Figure 1, and - Figure 4 shows schematically the DBC detector 1 of Figure 1 and its field of observation.

In the description which follows, the DBC 1 hot box detector is coupled to another identical DBC 1 detector, the pair of DBC 1 forming part of the train monitoring network.

In a train, the wheels 3 of the cars and the locomotive are linked, two by two, by axles 4 at the ends of which are mounted axle boxes 5, or "hot boxes", comprising axle bearings. When running, the axle boxes 5 are liable to explode, causing the derailment of the train 100, following the abnormal heating of an axle bearing.

The train monitoring network is intended to monitor the temperatures of the axle boxes of trains 100.

The pair of hot box detectors (DBC) 1 is intended to measure remotely, by infrared detection, the respective temperatures of the pairs of hot boxes 5 of the axles 4 of a train 100.

The two DBC detectors 1 are respectively fixed on the two opposite ends of neighboring sleepers 6 of the railroad track, facing each other on track 2, and connected to Trackside Electronics (EBV) 7 .

The EBV 7 of the pair of detectors 1 is also connected, here by wire connection, to: - two devices 8 for announcing the passage of a train mounted, in the middle of the track, on sleepers located on either side on the other side of the sleepers 6 for fixing the DBC detectors 1, - a synchronization pedal 10 for determining measurement time windows, mounted on one of the sleepers for fixing the DBC 1, and - a train monitoring station 9, connected to a plurality of EBVs associated with a plurality of pairs of DBC detectors, and here in radio link with the trains,
The whole forming the surveillance network.

Each DBC detector 1 integrates a central electronic control and power supply unit 20 comprising power supplies and a microcontroller associated with electronic controls, intended to manage the operation of the detector
DBC 1. The central block 20 is connected to: - an optical block 21 for infrared detection for measuring temperature signals, associated with a modulator disk 22 with one hundred slots rotatably mounted on the output axis of a motor 23 , - an electronic block 24 for acquisition and digital processing of temperature signals, - a shutter 25 of an input 26 of the DBC detector 1, mounted movably under the control of a motor 27 and connected to a mirror assembly - motor 31-32, and - a heating circuit 28 of the optical unit 21 at a reference temperature, here equal to 40 "C, comprising heating resistors.

The central block 20 is connected to the on-board electronics 7.

The optical unit 21 here comprises eight infrared detection cells arranged in a strip 30, associated with an optical system 29.

Each cell comprises a single photoconductive detection element, made of HgCdTe, having an area of approximately 1 × 1 millimeter and an observation field of approximately 10 × 10 millimeters for a nominal viewing distance of 400 millimeters.

The strip 30 is coupled to a Peltier component intended to cool the photoconductive elements to -35 C.

The optical system 29 comprises, between the input 26 and the detection bar 30: - the shutter 25, - the mirror 31 mounted to rotate on the motor output axis 32 to avoid dirt, and pivoting in order to orient photon radiation received, - a silicon lens (L1) 33 associated with an anti-reflection diaphragm 34, - a first optical assembly 35 comprising two lenses (L2 and L3), in germanium and silicon, associated with a diaphragm intended for limit parasitic reflections, and - a second optical assembly 36 comprising two lenses (L4 and L5), made of silicon.

The optical system 29 is designed to return the image of its entrance pupil 33 far behind itself, along its optical axis 37.

A reference source 38, placed in the vicinity of the mirror 31, plays the role of observation target of the bar 30 in the rest state of the DBC detector 1.

The modulator disk 22 is disposed at the common focal point of the two optical assemblies 35, 36, situated between them.

The optical unit 21 can analyze an infrared flux in an analysis spectral band comprising the wavelengths between 3 and 5 micrometers, in other words in band II, so that the accuracy of the measurements is insensitive to variations in the ambient light.

The field of observation of the bar 30 in cross section along the optical axis 37 of the optical unit 21 is an area 51 of approximately 100 × 10 millimeters, for a nominal viewing distance 50 equal to 400 millimeters. The side of the largest dimension of the observation surface of the bar 30 perpendicular to the optical axis 37, is parallel to the crosspieces 6 of the railway 2.

In addition, the field of observation of the bar 30 has a cross section, along the optical axis 37 of the optical unit 21, constant to within 20%, in other words substantially constant, for viewing distances (53.50 , 54) variables from simple to triple, here between 200 and 600 millimeters approximately.

After the structural description of the DBC 1 detectors and the train monitoring network, their operations will now be described.

When a train 100 approaches the pair of DBC detectors 1, one of the two warning devices 8 detects the passage of the train and transmits a train warning signal to the EBV 7 which activates the operating state of the two DBC detectors 1 at rest.

The synchronization pedal 10, in association with the EBV 7, determines the measurement time windows, in order to synchronize the measurements with the passages of the axle boxes of the train above the DBC detectors 1.

In each DBC detector 1, the central block 20 controls the opening of the shutter 25, the pivoting of the mirror 31 in order to orient the optical axis 37 towards the entrance pupil 33, the anti-fouling rotation of this mirror 31 , and the rotation, at a sampling speed of 3600 revolutions per minute, of the modulating disk 22.

When the train 100 passes, and more precisely from each axle box 5 of the train above the DBC detector 1, the latter picks up, through the slots of the modulator disc 22, the photonic radiation emitted by the axle box 5, and, alternately those emitted by the modulating disk 22 which is at a known temperature, thereby carrying out a sampling of temperature samples from a series of surfaces of the moving axle box 5, corresponding to the surfaces 51 observed by bar 30.

The measurements are synchronized using pedal 10.

For each sample, the bar 30 measures eight temperatures of elementary surface portions 52 respectively observed by the eight detection elements.

The bar 30 observes the moving axle box 5, over the entire length of this along the track 2, and performs at least eight sampling, the train 100 running at a maximum speed of 360 kilometers per hour.

The measured temperature signals are received by the acquisition and processing block 24 which converts the analog signals into digital signals transmitted to the EBV 7.

In EBV 7, the temperature signals of the axle box 5 are processed, and if one of the temperatures, of a basic surface portion of the axle box 5, is higher than the reference temperature , the EBV 7 informs the monitoring station 9 so that the latter alerts the train 100 of an abnormal heating of the axle box 5.

Claims (6)

1. Hot box detector (DBC) (1) for monitoring the temperatures of the axle boxes (5) of a running train (100), comprising: - means (21) for remote measurement of the temperatures of the axle boxes (5) of the train (100) comprising a remote sensing element, - electronic means (24) for processing temperature signals, characterized in that the measuring means (21) comprise a plurality of 'remote sensing elements. 2. Hot box detector according to claim 1 wherein the plurality of detection elements are associated with an optical system (29) forming an assembly arranged to observe according to an observation field of cross section (51) substantially constant along the optical axis (37) of the optical system (29). 3. Hot box detector according to claim 2, in which the optical system (29) is arranged to return the image of its entrance pupil (33) far behind the optical system (29), along the axis optics (37). 4. Hot box detector according to one of claims 1 to 3, in which the measuring means (21) have a spectral analysis band arranged so that the measurement accuracy is insensitive to variations in ambient luminosity. 5. Hot box detector according to one of claims 1 to 4, wherein the detection elements are infrared elements. 6. Hot box detector according to one of claims 1 to 5, wherein the detection elements are organized in a detection strip (30).