FR3085480A1 - SENSOR FOR CONTROLLING THE QUALITY OF CURRENT CAPTURE BY A PANTOGRAPH OF A RAIL TRACTION MACHINE - Google Patents

Abstract

The invention relates mainly to a sensor (15) for controlling the quality of the current collection on a catenary by a pantograph of a railway traction machine, which clevis-shaped sensor (15) intended to be fixed on a support of a bow of the pantograph, which sensor comprises at least one optical fiber suitable for measuring the mechanical stresses undergone by the yoke (15), the sensor thus being able to determine the contact force of the bow on the catenary.

Description

SENSOR FOR THE CONTROL OF THE QUALITY OF CURRENT CAPTURE BY A PANTOGRAPH OF A RAIL TRACTION MACHINE

Field of the Invention The invention is in the field of quality control of the capture, by a pantograph of a railway traction machine, of the electric current flowing on a catenary.

PRIOR ART [0002] A pantograph is a device installed on the roof of an electric motor to transmit electric current to its motor organs. It generally consists of a frame, articulated around pivots to deploy or fold, and a head supporting a bow with one or two friction bands, by other pivots or suspensions called bow suspensions.

When, under the combined action of pneumatic cylinders and damping springs, the articulated frame is deployed, the head rises against the catenary and is held there with a contact force, for example of about seventy Newtons. As the powerplant advances, the bow slides against the catenary and remains in contact with it.

However, at high speeds, the relatively low contact force is insufficient to prevent contact breakdowns between the friction bands and the catenary, which causes electric arcs and fluctuations in the intensity of the current transmitted to the engines. On these fluctuations depends the quality of the capture of the electric current. Conversely, a too strong catenary pantograph contact force can lead to significant lifting of the contact wire with a risk of damage to the catenary and the supports.

There are many methods for controlling the quality of the current collection.

We can directly measure the fluctuations in the intensity of the current. It is alternatively possible to measure the frequency of the electric arcs occurring during contact breakdowns or to make measurements of the power dissipated by these same electric arcs.

But we can also measure in real time the instantaneous contact force with which the bow remains applied against the catenary, with a strain gauge sensor secured to a test piece integrated in the mechanical chain supporting the pantograph. .

The test piece is located near the bow, so that the measurements are not affected by the part of the chain separating the test piece from the bow, for example by the presence of springs. shock absorbers, in particular those which may be provided in bow suspensions.

[0009] Rail traction machine pantographs are known for capturing current on a catenary, comprising a frame, a friction bow on the catenary, at least one bow support, a yoke fixed to the frame and to which is pivotally fixed the bow support and at least one force sensor of the type with piezoresistive stress gauges.

Generally, the yoke is mounted on a spring suspension box fixed to a cross member itself fixed to the upper fork of the frame and the bow support is inserted between the two cheeks of the yoke with a securing pivot of the yoke and of the support passing through it and fixed to the two cheeks of the yoke, the sensor being fixed for example under the friction bands of the bow.

However, the mechanical chain of the pantograph needs to be modified to introduce the test piece forming the strain gauge sensor. These modifications are therefore complex and costly to implement.

In addition, the mounting of the sensor, necessarily aerial, involves respecting an aerodynamic profile of the test piece. In particular, its presence on the pantograph must not induce a change in contact force greater than 5% of its nominal value, this up to speeds of up to 350 kn / hour.

To overcome these problems, patent publication FR0512194 proposes a piezoresistive strain gauge sensor which also forms a fixing yoke.

Disadvantage of the Prior Art In this configuration, the sensor test body being at the potential of the catenary, it is necessary to use a conditioning and galvanic isolation chain on the roof of the traction machine. Such equipment is particularly bulky and expensive.

Furthermore, the sensor being located near the catenary, it is very sensitive to electromagnetic disturbances. It is therefore necessary to implement measures to isolate the strain gauges.

Objects of the invention The invention thus aims to propose a force sensor which is simple to implement and install, while remaining as least disruptive as possible once integrated in the mechanical chain of the pantograph.

Disclosure of the invention To this end, the invention relates to a sensor for controlling the quality of the current collection on a catenary by a pantograph of a railway traction machine, which clevis-shaped sensor intended to be fixed on a pantograph bow support and comprises at least one optical fiber suitable for measuring the mechanical stresses undergone by the yoke, the sensor thus being able to determine the contact force of the bow on the catenary.

Thus, by the use of optical strain gauges, it overcomes electromagnetic disturbances from the catenary. In addition, mounting is simplified because the gauges can be mounted in series: several optical strain gauges can thus be present within the same optical fiber. Finally, the sensor is able to determine, from the contact force, the longitudinal friction force of the bow on the catenary and the transverse contact force of the bow on the catenary.

The sensor of the invention may also include the following optional characteristics considered in isolation or according to all possible technical combinations:

- The optical fiber comprises at least one Bragg grating.

- The yoke includes a sole intended to be secured to the pantograph suspension means, and two cheeks each comprising at least one test piece.

- Each yoke of the yoke comprises a pivot in which a shaft of the pantograph bow support is intended to be embedded, and two opposite arches arranged on either side of the pivot connecting said pivot to the sole of the yoke and forming each proof piece.

- Optical fiber includes at least one Bragg grating arranged at the level of a test piece.

- The optical fiber comprises four Bragg gratings of substantially identical sensitivity arranged at the level of the respective test pieces.

- Each Bragg network of optical fiber is integral with the arch considered.

- Each Bragg grating of the optical fiber is integral with the concave face of the arch considered.

- Each Bragg grating of the optical fiber is arranged at a median zone considered in relation to the width of the arch considered.

- Each hoop has a radius of curvature between six and nine millimeters, and a thickness between two and four millimeters.

- Each Bragg grating is positioned at the level of a portion of the arch considered between the part joining said arch to the arched portion considered and the top of said arch.

The invention also relates to a pantograph of a railway traction machine for capturing the current on a catenary, comprising at least one friction bow on the catenary, at least one bow support, at least one yoke fixed to means for suspending the pantograph and to which the bow support is fixed, which clevis forms the sensor for measuring the contact force of the bow on the catenary as described above.

The invention also relates to a railway traction machine comprising at least one pantograph as described above.

Presentation of the figures [0022] Other characteristics and advantages of the invention will emerge clearly from the description which is given below, for information and in no way limitative, with reference to the appended figures among which:

- Figure 1 shows a perspective view of the pantograph bow of the invention and its support, incorporating the sensor of the invention forming a fixing yoke;

- Figure 2 shows a perspective view of a detail of Figure 1 according to the circled part I illustrating the sensor of the invention;

- Figure 3 shows a perspective view of the sensor of the invention of Figure 1 forming a fixing yoke, isolated from the rest of the pantograph;

- Figure 4 shows a cross-sectional view of the yoke sensor of Figure 3, illustrating in particular the arches and the position of two Bragg gratings of an optical fiber integrated in the arches.

- Figure 5 shows an elevational view of a detail of Figure 4 according to the circled part V illustrating a portion of a bow provided with the optical fiber.

Detailed description of the invention It is first of all specified that in the figures, the same references designate the same elements regardless of the figure on which they appear and whatever the form of representation of these elements. Similarly, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to another figure.

It is also specified that the figures essentially represent an embodiment of the object of the invention but that there may be other embodiments which meet the definition of the invention.

The system of the invention finds its application in the field of quality control of the capture, by a pantograph of a railway traction machine, of the electric current flowing on a catenary, and more precisely in the determination in real time of the contact force F of the pantograph bow on the catenary.

Referring to Figure 1, a pantograph 1, of which only the head has been shown comprises, in the upper part of its frame 2, suspension members 12a, 12b, here shock absorbers and, in this case, spring boxes, to hold a bow 3 against a catenary wire (not shown) for distributing electric current. The area of electrical contact of the bow 3 with the catenary wire is formed by a central portion 4 of said bow 3. This central portion 4 comprises two elements 5a, 5b substantially rectilinear and parallel to each other, each covered by a friction strip 10a, 10b.

When the powerplant moves, a mechanism controls the deployment of the articulated frame 2 of the pantograph 1 so that the friction strips 10a and 10b of the straight elements 5a and 5b are applied against the contact wire with an overall contact force F.

This overall contact force F can be broken down into its transverse component F ± representative of the bearing force of the bow 3 against the catenary, and its longitudinal component F // representative of the longitudinal friction forces of the bow 3 against the catenary. Thus, each of the two rectilinear elements 5a, 5b of the central portion 4 of the bow 3 supports a transverse contact force F ± / 2 and a longitudinal force F /// 2 (shown in FIG. 1 only for the element straight 5a). Of course, the result of the sum of the longitudinal component F // (or of the sum of the longitudinal forces F /// 2) and of the transverse component F ± (or of the sum of the two transverse contact forces F ± / 2) corresponds to the overall contact force F.

The bow 3 also includes two peripheral portions 6a, 6b secured to the respective ends of the central portion 4. Each peripheral portion 6a, 6b comprises a main arm 7a, 7b and two secondary arms 8a, 9a; 8b, 9b extending from an end portion of the main arm 7a, 7b located on the side of the bow 3 to the free ends of the two rectilinear elements 5a, 5b of the central portion 4 of the bow 3.

The bow 3 further comprises two bow supports 11 (only one of which is shown in Figure 1) integral with the main arms 7a, 7b of the respective peripheral portions 6a, 6b, and formed at the parts of ends of said peripheral portions 6a, 6b, between the secondary arms 8a, 9a; 8b, 9b. Each bow support 11 has a substantially cylindrical shape and includes a bore whose function will be explained below.

The suspension members 12a, 12b are each secured, in their upper part, to a fixing yoke 15 (only one is visible in Figure 1). Each bow support 11 is pivotally mounted in the corresponding fixing yoke 15 so as to provide support for the bow 3, as will be explained below, in particular with reference to FIGS. 2 to 4.

Each yoke 15 is in one piece and has two parallel cheeks 21 and 22 seated on a sole 23 of generally rectangular shape and ensuring the attachment of the yoke 15 to the corresponding suspension boxes 12a, 12b.

Each cheek 21, 22 has a pivot 27, 28 in which is formed a bore 27 ', 28' intended to receive the shaft 13 passing through the arch support considered 11 (Figure 2). The cheeks 21, 22 of a yoke 15, the bow support 11 and the shaft considered 13 thus form a hinge joint. The two bores 27 ', 28' of the pivots 27, 28 are arranged coaxially around an axis XX 'parallel to the sole 23 of the yoke 15, which axis XX' forms the pivot axis of the arch support considered 11 relative to the yoke 15. Thus and as shown in Figure 2, the mounting of the bow support 11 in the yoke considered 15 is effected by embedding said support 11 between the cheeks 21, 22 of the yoke considered 15, the shaft 13 of the bow support 11 then being pivotally mounted in the bores 27 ', 28' of the pivots 27 and 28 and in the bore (not shown) of the bow support 11.

The bow support 11 can not pivot relative to the yoke 15 only at an angle with sufficient travel so that the two friction strips 10a and 10b can, under the action of the force F, remain in contact with the catenary wire regardless of the inclination of the wire. The pivots 27 and 28 are sufficiently distant from the sole 23 so that the lower faces of the supports 11 do not, by pivoting, abut on the sole 23.

The two yokes 15 are arranged to jointly measure the force F permanently. Each clevis 15 thus forms a force sensor at the same time as the support element for the bow 3.

According to the invention, each cheek 21, 22 of the yoke 15 forming the sensor comprises two arches 29, 30; 31, 32 of convex shapes, of general rectangular sections, of substantially identical thicknesses and radii of curvature, interconnected by an arcuate central portion of concave shape 33, 34 which supports the pivot considered 27, 28. The external ends of the hoops 29, 30; 31, 32 are integral with the opposite longitudinal edges of the sole 23. Said hoops 29, 30; 31, 32 and the arcuate portion considered 33, 34 thus form a corrugated structure resting on the sole 23, as shown in FIGS. 3 and 4, and the lower face of which is formed by the two concave lower faces of the respective arches 29 - 32 and by the convex underside of the arcuate portion considered 33, 34.

Each hoop 29, 30, 31, 32 acts as a test piece adapted to undergo deformations causing displacements detectable by strain gauges of the force sensor of the invention. The thickness and curvature of each hoop 29, 30, 31, 32 is defined so as to ensure sufficient deformation of said hoops 29, 30, 31, 32 to be measurable.

By way of nonlimiting example, for a constraint force F of the bow against the catenary of the order of seventy Newtons, the radius of curvature of each arch 29, 30, 31, 32 is included between seven and eight millimeters, while the thickness of each hoop 29, 30, 31, 32 is between two and three millimeters. Thus, the deformation of the arches 29, 30, 31, 32 remains elastic under the stress F.

According to the invention and with reference to Figures 4 and 5, the yoke sensor 15 comprises at least one optical fiber 19 adapted to measure the deformations undergone by the yoke 15 due to mechanical stresses resulting from the contact force F between the bow and the catenary whose transverse component Fi propagates towards said clevis 15 perpendicular to the substantially horizontal plane which passes through the two rectilinear elements 5a, 5b. Preferably, and in order to protect the optical fiber from frictional forces, part of said fiber 19 is integrated into the thickness of the sole 23 of the yoke 15 forming a sensor.

In order to measure as precisely as possible the deformations undergone by the yoke 15, the optical fiber 19 is arranged at at least one hoop 29 32, and preferably at least at the level of the four hoops 29 - 32, since c 'is the part of the yoke 15 which supports the most significant deformations by being arranged closest to the pivots 27, 28 subjected to the transverse force F ± substantially vertical.

The use of an optical fiber 19 explains the need to use arches 29, 30, 31, 32 without right angles, because the optical fiber 19 must have a minimum radius of curvature of about six millimeters to ensure correct functioning of the yoke sensor 15.

The optical fiber 19 comprises at least one optical strain gauge 20, each gauge preferably being a Bragg grating 20, the structure and operation of which are well known to those skilled in the art, namely in particular that the deformations undergone by the Bragg network 20 are proportional to the applied stress.

According to the invention, the optical fiber 19 of the yoke sensor 15 comprises at least one Bragg grating 20, and preferably comprises four Bragg grids 20 each arranged at the level of a test piece considered 29, 30, 31, 32. Thus, each Bragg grating 20 is adapted to measure the mechanical deformation undergone by the test piece 29, 30, 31, 32 in which it is integrated and to determine the force inducing this deformation of the piece of test considered 29 - 32. In addition, the technology of the Bragg networks 20 makes it possible to connect them in series on the same optical fiber 19, which simplifies the wiring of the optical fiber 19 to a detector suitable for collecting the measurements coming from said networks. from Bragg 20. For example, this detector can be secured to the sole 23 of the yoke 15 and connected to control means of the electronic card type, itself secured to the sole 23 of the yoke 15 forming sensor.

Each arch 29 - 32 has its own Bragg network 20, the four Bragg networks having the same sensitivity. This makes it possible to discriminate the longitudinal component F // of the force F due to the friction of the bow 3 on the catenary, that is to say along the catenary in the substantially horizontal plane passing through the two rectilinear elements 5a , 5b, of the transverse component F ± due to the contact support of the bow 3 against the catenary. In other words, the Bragg gratings 20 of the arches considered 29 - 32 are configured to determine the longitudinal component F // of the force F and the transverse component F ± of the force F independently of one another.

The longitudinal forces F // induce a measurement offset between the Bragg gratings 20 of a yoke 15 positioned on either side of the axis passing through the pivots 27, 28. Thus, by choosing networks of Bragg 20 with the same sensitivity for the same yoke 15, the control means determine and then remove the longitudinal component by summing the deformations measured by the Bragg gratings 20, in order to finally retain only the transverse component F ± proportional to the contact force F, this transverse component F ± extending in a plane perpendicular to the catenary, this plane being substantially vertical.

As a corollary, the horizontal component F // of the force F due to the friction of the bow 3 on the catenary can be determined by comparing the deformations measured by the Bragg gratings 20 of a yoke 15 positioned on the side and on the other side of the axis passing through the pivots 27, 28.

More precisely, the transverse component F ± of the force F is obtained by adding the values of the forces undergone by each arch 29 - 32 and determined by the Bragg gratings 20 considered, while the longitudinal component F // of the force F is obtained by subtracting the sum of the values of the forces undergone by the poles 29 - 32 of one of the cheeks 21, 22 from the sum of the values of the forces undergone by the poles 29 - 32 of the other cheek 21, 22 .

It is particularly interesting to directly determine the transverse component F ± of the force F, that is to say without taking into account the longitudinal component F // due to friction, because the current approval criteria do not take take into account that the vertical bearing force, ie the transverse component F ± of the overall contact force F.

On the other hand, the determination of the longitudinal component F // of the force F gives information on the nature of the sliding of the bow 3 along the catenary. For example, a sudden increase in the longitudinal component F // reflects the existence of a point on the catenary where the bow 3 hangs on the latter. Such an attachment point on the catenary may cause premature wear of the friction strips 10a, 10b of the bow 3. It is therefore particularly advantageous that the clevis sensor 15 is able to identify such attachment points existing on the catenary from the determination of the longitudinal component F // of the force F.

Referring to Figure 4, each Bragg grating 20 is preferably positioned at a portion Z1 of the arch considered 29, 30, 31, 32 between the part joining said arch 29 - 32 to the portion arched considered 33, 34 and the vertex 29a, 31a; 30a, 32a, or “crest” of said arch 29, 30, 31, 32. It is indeed at this portion that the deformations of the arch 29, 30, 31, 32 are of greatest amplitude, since they are closest to the corresponding pivot 27, 28 which undergoes the contact force F. The precision and the quality of the measurements are therefore improved.

According to the invention and with reference to Figures 4 and 5, at least the part of the optical fiber comprising the Bragg gratings 20 is integral with the arches 29 32 of the yoke 15. More precisely and according to the embodiment presented in the figures, each Bragg grating 20 of the optical fiber 19 is integral with the concave underside of the arch considered 29 - 32. In this way, the optical fiber 19 and the Bragg grids 20 are protected by the hoop considered 29 - 32. More precisely still, each Bragg grating 20 is integral with the hoop considered 29, 30, 31, 32 at the level of a median zone M (shown partially in FIG. 3) of said hoop 29, 30 , 31, 32 considered with respect to the width of the arch 29, 30, 31, 32. This arrangement makes it possible to have the Bragg grating 20 in a median plane of the arch considered 29 - 32 passing through the neutral fiber of the latter, which neutral fiber is the portion of a deformable material not influenced by mechanical stresses.

By positioning the optical fiber 19 as close as possible to the plane passing through the neutral fiber of the arch considered 29, 30, 31, 32, the transverse horizontal stresses of the force F, that is to say perpendicular to the catenary, have no influence on the measurement by the Bragg gratings 20 of the optical fiber 19.

An optimal measurement is thus obtained which makes it possible to differentiate the horizontal stresses F // from the vertical component F ± of the stress force F. A precise measurement of the vertical stress F ± is thus obtained. As specified above, the measurement provided by the Bragg gratings 20 is proportional to the vertical component of the force F, the value of the measurement depending in particular on the angle a formed between the vertical and a straight line D passing through the center of one of the networks and the center 35 of the pivot considered 27, 28.

According to one embodiment of the invention and with reference to FIG. 4, the arrangement of the optical fiber 19 in the yoke 15 is as follows:

The optical fiber 19 enters, from one of the longitudinal edges of the sole 23, into the thickness of the yoke 15 at the base of a cheek 21, 22, then comes out at the foot from one of the arches 29 - 32 to traverse the entire underside of the corrugated structure formed by the arches 29 - 32 and the arcuate portion 33, 34 supporting the pivot 27, 28, to the opposite longitudinal edge of the sole 23. The fiber 19 again enters the thickness of the yoke 15 and then extends along a channel or a groove 36 formed in the sole 23 to the base of the other cheek 27, 28 at which it emerges from the yoke 15, then runs through the entire underside of the corrugated structure of the other cheek 21, 22 to finally move away from the yoke 15 towards the detector if the latter is not integrated into the yoke 15 forming a sensor.

Finally, note that the yokes 15 being the force sensors, the aerodynamic resistance of the pantograph 1 remains unchanged.

The embodiment described above is by no means limiting, and modifications can be made without departing from the scope of the invention. As an example, it is possible to integrate several optical fibers 19 into the yoke 15, each comprising a Bragg grating 20.

Claims (11)

1. Sensor for controlling the quality of the current collection on a catenary by a pantograph (1) of a railway traction machine, which clevis-shaped sensor (15, 16) intended to be fixed on a support of bow (11) pantograph (1), characterized in that it (15) comprises at least one optical fiber (19) adapted to measure the mechanical stresses undergone by the yoke (15), the sensor thus being able to determine the contact force ( F) of the bow (3) on the catenary. 2. Sensor according to the preceding claim, characterized in that the optical fiber (19) comprises at least one Bragg grating (20). 3. Sensor according to claim 1 or 2, characterized in that the yoke (15) comprises a sole (23) intended to be secured to suspension means (12a, 12b) of the pantograph (1), and two cheeks (21 , 22) each comprising at least one test piece (29, 30, 31, 32). 4. Sensor according to the preceding claim, characterized in that each cheek (21, 22) of the yoke (15) comprises a pivot (27, 28) in which a shaft (13) of the pantograph bow support (11) (1) is intended to be embedded, and two opposite arches arranged on either side of the pivot (29, 30, 31, 32), connecting said pivot (27, 28) to the sole (23) of the yoke ( 15) and each forming a test piece. 5. Sensor according to the preceding claim, characterized in that the optical fiber (19) comprises at least one Bragg grating (20) disposed at the level of a test piece (29, 30, 31, 32), preferably four Bragg gratings (20) of substantially identical sensitivity arranged at the level of the respective test pieces (29, 30, 31, 32). 6. Sensor according to the preceding claim, characterized in that each Bragg grating (20) of the optical fiber (19) is integral with the arch considered (29, 30, 31, 32). 7. Sensor according to the preceding claim, characterized in that each Bragg grating (20) of the optical fiber (19) is integral with the concave face of the arch considered (29, 30, 31, 32). 8. Sensor according to the preceding claim, characterized in that each Bragg grating (20) of the optical fiber (19) is arranged at a median zone considered with respect to the width of the arch considered (29, 30 , 31, 32). 9. Sensor according to any one of claims 5 to 8, characterized in that each Bragg grating (20) is positioned at a portion (Z1) of the arch considered (29, 30, 31, 32) between the part joining said hoop (29, 30, 31, 32) to the arcuate portion considered (33, 34) and the top (29a, 31a; 30a, 32a) of said hoop (29, 30, 31, 32 ). 10. Pantograph (1) of a railway traction machine for capturing the current on a catenary, comprising at least one bow (3) of friction on the catenary, at least one bow support (11), at least one yoke ( 15) fixed to suspension means (2; 12a, 12b) of the pantograph and to which is fixed the bow support (11), characterized in that the yoke (15) forms the sensor for measuring the contact force (F) of the bow (3) on the catenary according to any one of claims 1 to 9. 11. Railway traction machine comprising at least one pantograph (1) according to claim 10.