WO2009016289A2

WO2009016289A2 - Device and method for monitoring the vibratory state of a rotating machine

Info

Publication number: WO2009016289A2
Application number: PCT/FR2008/000910
Authority: WO
Inventors: Patrick Marconnet; Bernard Pottier; Lanto Rasolofondraibe
Original assignee: Universite De Reims Champagne Ardenne
Priority date: 2007-06-27
Filing date: 2008-06-26
Publication date: 2009-02-05
Also published as: FR2918172B1; WO2009016289A3; FR2918172A1

Abstract

The present invention relates to a device for monitoring the vibrations generated by a bearing of a machine formed by two coaxial races, an outer race and an inner race, with one fixed with respect to the frame of a machine and the other rotating, between which races is trapped at least one rolling element which is able to move, vibrations generated by other members of the machine having a respective frequency signature passing through this bearing, characterized in that the device comprises at least one non-conductive positioning means mounted on an element in contact with an element of the bearing, the positioning means positioning a conductive element, forming a first plate of a capacitor to form a capacitive sensor, at a distance from a conductive part of a race of the bearing, forming the second plate of the capacitor, and the positioning means being secured to a partitioning means so as to create an insulating medium between these two plates.

Description

Device and method for monitoring the vibratory state of a rotating machine

The present invention relates to the field of mechanical components of rotating machines whose rotation mechanisms are sensitive to unbalance or are likely to excite the structure of machines such as turbines, alternators, motors and reducers, etc. and more particularly in the field of ball bearings, needle or roller.

Bearings are mechanical components that guide the rotation of a shaft in a bearing by limiting the friction that could be caused by the movement of one of the two parts relative to the other. The bearings are formed by two coaxial rings, one said inner and the other outer between which movable elements are placed and maintained. These movable elements, generally balls, although trapped between the two coaxial rings ensure the rotation of one of the rings relative to each other.

In some models, the balls are replaced by cylindrical or frustoconical rollers. The bearings are then able to withstand a higher radial force compared to conventional ball bearings. Similarly, some bearings, called needles, use rollers of small diameter compared to their length, having the advantage of being less bulky thanks to a reduced radial space.

However, even if the use of bearings reduces the friction caused by the rotation of a shaft in its bearing, a fatigue of the mechanical components will appear once a certain number of rotations is exceeded. This deterioration affects the rolling bodies such as rings. It can take the form of natural wear, flaking, corrosion, galling, abrasion, etc. that will generate a shock, or take the form of an imbalance of the shaft causing an imbalance. This deterioration of the state of the mechanism then results in a vibration which increases with wear.

Thus, it is known that if the increase of the vibrations makes it possible to detect a defect, the analysis of the characteristics of the vibratory spectrum of the machine will make it possible to identify the cause and thus to define the delay before the critical threshold is achieved. Depending on the type of alteration of the mechanism, the vibration varies. The imbalance of an imbalance of the shaft produces a sinusoidal excitation while the spalling of a track of a bearing will cause a shock which results in an impulse excitation at the passage of each of the movable elements of the bearing on the chipped.

At present, the main method for characterizing and monitoring the state of each essential component of a rotating machine is the use of vibratory sensors of the accelerometric type. The phenomenon used in this type of sensor is called piezoelectricity. Under the action of a mechanical force, some bodies can be polarized. To use this property, the piezoelectric sensors have the shape of a disk, each of whose surfaces is connected to an electrode. Pressure on one side of the sensor generates a mechanical stress that polarizes the sensor. The generated charge is subsequently amplified to be measured.

To be able to measure the vibrations due to deterioration, these piezoelectric sensors are placed close to the strategic points of the main components of the machine under surveillance. The vibration frequency of the bearing results in a stress / pressure frequency at the surface of the sensor, transformed as a variation of a measured electrical signal.

It appears that the use of such sensors has many disadvantages. In addition to their high cost, these sensors can not always be positioned closer to the source at the origin of the possible vibration. Now the vibrations generated by the defects of the bearing have the peculiarity of spreading throughout the structure of the machine. These vibrations can thus change environment because of the change in the nature of the materials, which then causes phenomena of reflection, refraction but also conversion of the propagation mode. It is therefore important to measure the vibrations of a machine correctly that the sensors are positioned on optimum measuring points. In the case of use of accelerometric or piezoelectric sensors, the accession to these optimum measurement points is not always possible. In addition, the vibrations are dampened as they move away from the source that gave them birth. The positioning of these sensors away from the source of the vibrations then causes a significant attenuation of the measured signal.

In addition, it should be noted that these vibratory sensors have a quality of measurement that depends on the surface against which they are positioned. This surface must be able to correctly transmit the measured vibrations without any loss of information.

The present invention aims to provide at least one sensor capable of bearing one or more disadvantages of the prior art while improving the quality of the vibratory signal measured and proposing a low cost solution.

This objective is achieved by a device for monitoring a vibration machine generated by a bearing formed by two rings, one outer and the other inner, one fixed relative to the frame of one machine and the other rotating, coaxial between which at least one rolling element is trapped and capable of moving, vibrations generated by other organs of the machine passing through the bearing, each of the machine members having a respective frequency signature, characterized in that the device comprises at least one non-conducting positioning means mounted on at least one element in contact with at least one element of the bearing or mounted on at least one of the elements of the bearing, the positioning means comprising at least one housing for positioning at least one conductive element, constituting a first armature of at least one capacitor to form a capacitive sensor, at a distance from a conductive portion fixed or integrated with a ring of the bearing, forming the second armature of the capacitor or sensor capacitive, and the non-conductive positioning means being secured to at least one partitioning means which makes it possible to create, between at least two armatures of the same capacitor, a space forming a dielectric insulating medium and this partitioning means ensuring sealing of this insulating medium and being in contact with a portion of the bearing ring fixing or integrating the second armature, the armatures of the capacitive sensor being mounted perpendicularly to the axis of displacement of the vibrations monitored and in that the second reinforcement being integrated or secured in a fixed bearing ring with respect to a frame of the machine at the bottom of a premature In a cavity of the rolling ring, a non-conducting positioning means of at least one armature forms a capacitive sensor by arranging the first armature in front of the second armature, an annular partitioning means closing the insulating medium which separates the armatures. two reinforcements, and in that, a second cavity narrower than the first cavity being formed in the bottom of the first cavity and formed by a bore oriented along an axis perpendicular to the axis of rotation of the bearing and passing through the center of rotation of the bearing, the end of a needle mounted on the first armature perpendicular to a plane tangential to the first armature comes to stay in contact with the bottom of the second cavity located in the depth of the race and in front of the rolling path in contact with at least one rolling element.

According to another variant of the invention, the vibration monitoring device is characterized in that the Young's modulus of the positioning means is smaller than that of the needle mounted on the first armature and / or that of the rolling ring. . According to another variant of the invention, the vibration monitoring device is characterized in that a third armature is integrated or secured to the surface of the frame of the machine located at the orifice of the cavity of the ring. bearing in contact with the frame of the machine, the non-conductive positioning means having the first armature in front of the third armature simultaneously between the second and third armatures so that the first and third armatures, separated by a partitioning means of annular shape for closing an insulating medium, form a second capacitive sensor. According to another variant of the invention, the vibration monitoring device is characterized in that the partitioning means is formed by a metal blade integral with the positioning means and in contact with at least a part of the surface to which the second reinforcement is attached or integrated. According to another variant of the invention, the vibration monitoring device is characterized in that the partitioning means is formed by an integral elastic seal of the positioning means, the elastic seal having a lip in contact with at least a portion of the surface to which the second armature is attached or integrated. According to another variant of the invention, the vibration monitoring device is characterized in that at least three first conductive reinforcements are positioned by a non-conductive positioning means, radially with respect to at least one second conductive reinforcement or integrated in a portion of a bearing ring, the axes respectively passing through the positions of each of the pairs of conductive elements forming a capacitive sensor and the rotation center of the bearing realize between them angles (α) of at most 120 °.

Another advantage of a device according to the invention with several capacitive sensors arranged at 120 ° with respect to the coaxial axis of the rings of the bearing is that the location of the possible defect is achieved with greater precision.

According to another variant of the invention, the vibration monitoring device is characterized in that at least two conductive frames facing each other are one convex and the other concave in a plane perpendicular to the axis of rotation. of the bearing.

According to another variant of the invention, the vibration monitoring device is characterized in that the non-conductive positioning means positions at least one first conductive reinforcement axially with respect to a second conductive reinforcement secured to or integrated in a bearing ring. .

According to another variant of the invention, the vibration monitoring device is characterized in that the non-conducting positioning means positions a pair of conductive reinforcements, one radially, the other axially relative to at least one conductive reinforcement integral or integrated with a bearing ring.

According to another variant of the invention, the vibration monitoring device is characterized in that a single space forming the dielectric insulating medium is common to the pair of capacitors formed by at least two conducting plates positioned by the non-positioning means. -conducteur on the one hand and at least one conductive reinforcement secured to or integrated with a bearing ring on the other hand.

According to another variant of the invention, the vibration monitoring device is characterized in that at least three first armatures are positioned radially by at least one non-conductive positioning means in front of at least one second solidarized reinforcement or integrated in a ring of the bearing forming a first set of at least three capacitive sensors, and in that on at least one face of the bearing, at least three first plates are positioned by at least one non-conductive positioning means in front of the at least one second armature secured to or integral with a ring of the bearing, forming at least a second set of at least three other capacitive sensors, the three capacitive sensors of each of these sets being positioned equidistant from the axis of rotation (ZZ) of the bearing so that, in a plane perpendicular to the axis of rotation (ZZ) of the bearing, the planes passing respectively through the axes of symmetry of each of the capacitive sensors and the center of rotation of the bearing form between them angles (α) of 120.

According to another variant of the invention, the vibration monitoring device is characterized in that the device comprises at least one means for adjusting the distance which separates at least two reinforcements participating in the formation of the same capacitive sensor.

Another advantage of the device of the invention is that the adjustment of the distance between the plates makes it possible to define the sensitivity and the value of the capacitor when empty.

According to another variant of the invention, the vibration monitoring device is characterized in that the pairs of armatures of each of the capacitive sensors are connected to a respective electronic assembly forming a charge amplifier intended to deliver in real time a signal representative of the movements of one armature relative to the other due to vibration during operation of the mechanical bearing.

According to another variant of the invention, the vibration monitoring device is characterized in that each pair of armatures is secured to an electronic assembly forming a charge amplifier (AC), the second armature secured to or integrated into the ring of bearing is connected to ground and the first armature positioned by the non-conductive positioning means is connected to the inverting input (/) of a high impedance Integrated Linear Amplifier (ALI) by a shielded cable whose shield is connected at the non-inverting input of the ALI, the non-inverting input of the ALI being connected to a generator supplying a voltage continuous or alternating (Ve), the output of the ALI being connected to its inverting input via a capacitor (Cή and a resistor connected in parallel.

According to another variant of the invention, the vibration monitoring device is characterized in that each pair of armatures is associated with an electronic assembly forming a charge amplifier (AC), the second armature secured to or integrated in the ring of bearing is connected to a generator supplying a voltage (Ve) and the first armature positioned by the non-conductive positioning means is connected to the inverting input (/) of a high impedance Integrated Linear Amplifier (ALI) by a cable shielded which is connected to a frame of a capacitor (Cs) connected to ground and the other armature is connected to the inverting input (/) of the ALI, a capacitor (Cή being arranged between the inverting input of the ALI and the output of the ALI and three resistors mounted in T, one of the resistors connected to ground, being positioned in parallel with respect to the capacitor (Cή, the non-inverting input se (n.i) of the ALI being connected to the mass

According to another variant of the invention, the vibration monitoring device is characterized in that the output of the linear amplifier

Integrated (ALI) is connected to the input of a digital analog converter whose output is used by a microprocessor circuit to calculate the variation of distance by the execution of a program implementing the formula:

and to trigger an alarm by comparing the result obtained with a stored threshold, Δx representing the variation of the distance (d) separating the two plates of the capacitor, Δ V ₃ representing the variation of the voltage at the output of the amplifier, Ve representing the DC or AC component of the voltage at the input of the amplifier, S _c representing the sensitivity of the capacitance and C _f representing the capacitance of the capacitor connecting the output of the ALI to the inverting input. According to another variant of the invention, the vibration monitoring device is characterized in that it comprises means for detecting the rotational frequency of the bearing to take measurements when the bearing rings are in a defined position. one compared to the other.

According to another variant of the invention, the vibration monitoring device is characterized in that the device comprises at least one means for frequency processing of the vibratory signal measured at the level of the capacitor plates, making it possible to obtain the vibratory signal from at least one of the different members of the machine in comparison with the respective vibratory signatures of each of the members of the machine recorded at at least one storage means.

According to another variant of the invention, the vibration monitoring device is characterized in that the device comprises at least one temporal processing means of the vibratory signal of at least one of the organs of the machine making it possible to obtain several statistical parameters of this signal to be compared with statistical parameters of faults recorded at a storage means.

Another objective of the invention is to propose a method which makes it possible to measure, in real time, precisely and remotely, small variations in capacitances due to the vibrations of the bearing by avoiding the measurement of parasitic capacitances due to an antenna effect.

This objective is achieved by means of a vibration monitoring method involving a monitoring device according to the invention, characterized in that it comprises at least one step of measuring the charges induced by capacitive coupling on a first conductive armature. a variable spacing capacitor positioned by a non-conductive positioning means, a second conductive reinforcement secured to or integral with a bearing ring being at a fixed potential. According to a variant of the invention, the vibration monitoring method is characterized in that the pair of armatures being secured to an electronic assembly forming a charge amplifier (AC), the second armature secured to or integrated with the ring connected to the ground, the first armature being positioned by the non-conductive positioning means and connected to the inverting input (/) of a high impedance integrated linear amplifier (ALI) by a shielded cable whose shield is connected to the non-inverting input of I ¹ ALI, the non-inverting input of the ALI being connected to a generator supplying a DC or AC voltage (Ve), the output of the ALI being connected to its inverting input via a capacitor (C /) and a resistor connected in parallel, the method comprises at least one step of calculating the variation (Δx) of the distance separating the two plates of the capacitor from the variation of the current. ension (ΔV _S ) at the output of a charge amplifier (AC) using the relation:

Δx representing the variation of the distance (d) separating the two plates of the capacitor, ΔV _S representing the variation of the voltage at the output of the amplifier, Ve representing the DC or AC component of the voltage at the input of the capacitor amplifier, S ₀ representing the sensitivity of the capacitance and C _f representing capacitance of the capacitor connecting the output of the ALI to the inverting input.

According to another variant of the invention, the vibration monitoring method is characterized in that the pair of armatures being associated with an electronic assembly forming a charge amplifier (AC), the second

25 armature integral or integrated in the race is connected to a generator providing a DC or AC voltage (Ve) and the first armature positioned by the non-conductive positioning means is connected to the inverting input (/) of a Integrated Linear Amplifier (ALI) with high impedance by shielded cable with shielding connected

30 to a frame of a capacitor (Cs) connected to the ground and the other armature is connected to the inverting input (/) of I ¹ ALI, a capacitor (C /) being arranged between the inverting input of the ALI and the output of the ALI and three resistors mounted in T, the one of the resistors connected to ground, being positioned in parallel with respect to the capacitor (C /), the non-inverting input (ni) of the ALI being connected to the ground, the method comprises at least one step of calculating the variation (Δx) of the distance separating the two plates of the capacitor from the variation of the voltage (ΔV _S ) at the output of a charge amplifier (AC) by using the relation:

Δx representing the variation of the distance (d) separating the two plates of the capacitor, ΔV _S representing the variation of the voltage at the output of the amplifier, Ve representing the DC or AC component of the voltage at the input of the capacitor amplifier, S ₀ representing the sensitivity of the capacitance and C _f representing the capacity of the capacitor connecting the output of the ALI to the inverting input.

According to another variant of the invention, the vibration monitoring method is characterized in that the output of the Integrated Linear Amplifier (ALI) is connected to the input of a digital analog converter (CAN) whose output is used by a microprocessor circuit (MP) to calculate the distance variation by the execution of a program (Prog), the method comprises at least one step of triggering an alarm after comparing the variation (Δx) of the spacing between the two frames with a threshold value.

According to another variant of the invention, the vibration monitoring method is characterized in that, the device comprising means for memorizing the vibratory signature of each of the members of the machine, the method has at least:

a step of measuring the vibratory signal at the level of the armatures of the capacitive sensor positioned at the level of the bearing, a step of comparing the measured vibratory signal with the stored vibratory signature of at least one defined member of the machine,

a step of determining and then extracting the vibratory signal specific to the defined member of the machine from the measured vibratory signal.

According to another variant of the invention, the vibration monitoring method is characterized in that, the device comprising means for storing fault threshold values of several statistical parameters, the method has at least:

a step of measuring the vibratory signal at the level of the armatures of the capacitor positioned at the level of the bearing,

a step of calculating statistical parameters of the measured vibratory signal; a step of comparing the calculated statistical parameters with stored fault threshold values;

a step of determining the importance of the defect.

According to another variant of the invention, the vibration monitoring method is characterized in that, the device comprising at least one display means, the method has at least one step of displaying the position and the importance a defect.

An advantage of the invention is that the method comprising at least one step of processing the signals delivered by the capacitive sensors by the use of at least one vibratory analysis technique, it makes it possible to determine the origin, the nature and / or the importance of the defects of the bearing and the monitored parts of the machine.

Another advantage of the invention is that the method allows continuous monitoring of the bearing and the organs of the machine. The invention, its characteristics and its advantages will appear more clearly on reading the description made with reference to the appended figures in which:

FIGS. 1a and 1b show a known rolling device, represented respectively along an axis perpendicular to the axis of rotation (Z-Z) of the bearing and in a plane passing through the axis of rotation (Z-Z) of the bearing,

FIGS. 2a, 2b and 2c show an embodiment of the invention according to two variant embodiments; FIG. 3 represents a first electronic assembly diagram of the device of the invention;

FIG. 4 represents a second electronic circuit diagram of the device of the invention.

The mechanical bearing is formed of two coaxial rings, one inner (2) and the other outer (1) between which are arranged and held trapped rolling elements (3). These different parts are usually made of steel to remain resistant to compression. The inner face of the outer ring (1), as the outer face of the inner ring (2), has a curved raceway to adapt to the shape of the rolling elements (3). The combination of the two paths located on the respective rings ensures the maintenance of the rolling elements (3) between the two rings (1, 2) while guaranteeing their displacement in a circular circuit centered on the axis of rotation (ZZ) of the bearing, coaxial to both rings. The spacing between the rolling elements (3) is kept constant by means of a cage (4) which is positioned on each face of the bearing, at the level of the radial openings on the rolling elements (3), between the two rings (1, 2) of the bearing.

The rolling elements (3) can be of several types.

Generally, these are balls but in some models, the balls are replaced by cylindrical or frustoconical rollers. The bearings are then able to withstand a higher radial force compared to classic ball bearings. To reduce the radial space, the diameter of the rolls can be decreased in relation to their length; the rolling elements are then called needles. The various rolling elements (3) are generally kept at a distance from each other by a cage (4) which allows their homogeneous distribution in the circular circuit formed by the two rings (1, 2).

To eliminate any possible game and at the same time any useless vibration that could distort the measurements, the mechanical bearing is slightly prestressed. At the level of the bearing, at least one additional non-conductive element: a positioning means (6) is added.

The principle of the invention consists in placing a first conductive reinforcement (7) of the capacitor near and in front of a conductive portion integral with the fixed ring relative to the frame (5) which forms a second armature (8). . The distance that separates the two conductive armatures (7, 8) is then very small, less than or of the order of a tenth of a millimeter. The space (9) separating the two armatures is an insulating medium called dielectric. To form this space (9), the non-conducting positioning means (6) positions firstly a first armature (7) at a distance from the rolling ring and is associated on the other hand with at least one partitioning means (10) which extends on each side of the first frame (7) to come into contact with the second frame secured or integrated with the fixed ring of the bearing. The partitioning means (10) integral with the non-conductive positioning means (6) thus makes a space (9) between the two conductive reinforcements (7, 8) which forms a dielectric insulating medium. In addition, the partitioning means (10) seals the insulating medium of the space (9) thus created.

The variable gap capacitors thus formed by the conductive reinforcements (7, 8) separated by a dielectric insulating medium (9) have capacities of the order of the picofarad with variations of the order of the femto-farad. To allow variations of spacing between these two reinforcement (7, 8), the positioning means (6) has a Young's modulus lower than that of the bearing or frame so as to be deformable when vibrations are encountered therethrough and thus allow a variation of the spacing of the two plates of the capacitive sensor formed by the capacitor.

According to the embodiment chosen, the partitioning means (10) may be formed by a metal blade integral with the positioning means (6), the metal blade coming into contact with the part of the surface of the ring (1 or 2). of the bearing which is secured or integrates the second armature (8) of the capacitor forming the capacitive sensor. According to another embodiment, this partitioning means (10) may also be formed by an integral elastic seal of the positioning means (6), the elastic seal having a lip which comes into contact with the part of the surface of the ring. (1 or 2) of the bearing which is secured or integrates the second armature (8) of the capacitor forming the capacitive sensor.

The embodiment of the device of the invention consists in integrating the capacitive sensor into the thickness of one of the rings (1, 2), inside or outside, of the bearing. The ring (1, 2) which integrates the sensor then comprises at least one bore, a countersink or a bore to come form at least one cavity (11) in the depth of the ring (1, 2) of the bearing. In this cavity (11), a non-conductive positioning means (6) is arranged to position a first conductive reinforcement (7), perpendicular to the axis of the cavity (11), near and opposite the a second armature (8) positioned in the bottom of the cavity (11) where it is secured or integrated with the race (1, 2). Between the two frames, a space (9) defining an insulating medium is formed by a partitioning means (10). According to a particular embodiment, this partitioning means (10) has an annular shape fixed to the positioning means (6). According to a variant of the second embodiment, the positioning means (6) is kept in contact with the frame (5) of the machine, directly or through a particular element such as a steel pellet. The contact surface is then made at the orifice of the cavity (11) which comes to the surface of the bearing ring (1, 2). Through this contact zone, the positioning means (6) is sensitive to vibrations that come directly from the frame (5) of the machine and not only vibrations that come or transit through the bearing.

The detection device of the invention makes it possible to produce a capacitive sensor capable of measuring the vibrations due to the compressive stresses of the rolling elements (3) on the raceway. According to Hertz's theory, the distribution of the stresses due to compression results in a decrease of the deformation with the distance from the point of contact of the rolling element (3) on the raceway (but still outside the zone maximum stress (Hertz) in the under layer). The measurement of this deformation must therefore be carried out, in depth, as close as possible to the point of contact of the rolling element on the raceway.

The capacitive sensor is integrated in the thickness of one of the rings (1, 2) of the bearing. The ring (1, 2) which comprises the sensor then has a first cavity (11) arranged radially relative to the axis of rotation (ZZ) of the bearing. A first armature (7) is then put in place by a positioning means (6) close to and opposite a second armature (8) secured to or integrated into the bottom of the cavity, a partitioning means (10) ensuring sealing a dielectric insulating space between the two frames (7, 8). The surface of the first armature (7) which faces the second armature (8) is mounted with a needle (13) perpendicular to the plane of the armature (7) and arranged along an axis substantially identical to the axis of the first cavity (11). This needle (13) is oriented in the depth of the race in the direction of the raceway. The needle is introduced into a second cavity (12) located in the bottom of the first (11). This second cavity (12) is thus disposed along the same axis as the first cavity, that is to say radially with respect to the axis of rotation (ZZ) of the bearing. The "free" end of the needle (13) is then kept in contact with the bottom of the second cavity (12), the other end being fixed to the first armature.

According to an alternative embodiment, the positioning means (6), alone or with another rigid means, fills the whole of the first cavity (11) and in particular covers the entire surface of the first frame (7) which is on the opposite side to that in contact with the needle (13). The Young's modulus of the positioning means (6) is then much smaller than that of the various elements of the sensor and of the bearing and in particular much smaller than that of the needle (13) and that of the ring (1, 2) of the rolling. Thus, when a rolling element (3) comes to exert a stress on the raceway, this stress dissipates in the depth of the ring (1, 2) of the bearing while it exerts a displacement of the needle (13). ) along its axis proportional to the magnitude of the stress at the point of contact between the needle (13) and the bottom of the second cavity (12) in the rolling ring (1, 2). The displacement of the needle (13) then causes a displacement of the first armature (7) with a crushing of the positioning means (6) against the obstructed orifice of the first cavity (11). This displacement of the first armature (7) is then reflected at the sensor by a spacing of the two armatures (7, 8).

According to another variant embodiment, the positioning means (6) does not position the first armature (7) by coming to cover the surface of the armature (J) which does not face the second armature, but on the contrary leaves the free surface so as to be positioned close to and facing a third armature (8.1). This third reinforcement (8.1) is then positioned at the orifice of the first cavity (11), secured to or integrated into the frame (5) of the machine or to an element in contact with the orifice of the first cavity ( 11) at the surface of the bearing ring. A second partitioning means (10.1), preferably annular, then closes the space (9.1) which separates the first (7) and the third armature (8.1) to isolate a dielectric medium. In this variant of realization, the movement of the needle (13) causes, here again, a spacing of the first (7) and second (8) armatures and at the same time a rapprochement of the first (7) and third (8.1) armatures. The positioning means (6), which, here also, has a Young's modulus lower than that of the various elements of the sensor and of the bearing and in particular much smaller than that of the needle (13) and that of the ring (1 2) of the bearing is pressed against the orifice of the first cavity (11). Thus, from three armatures (7, 8, 8.1) two capacitors and thus two sensing sensors are constructed to obtain two signals for the same vibration.

A regular arrangement of these capacitive sensors on the same side of the bearing makes it easier to locate a possible fault causing vibrations in a plane perpendicular to the axis of rotation of the bearing. The arrangement of these sensors then allows a finer measurement of the vibratory signal, and thus facilitates the correction by rebalancing of any unbalance type defect. Similarly, a regular and symmetrical arrangement of these capacitive sensors on each side of the bearing facilitates the location of the source of vibration in a plane containing the axis of rotation of the bearing. These different sensors thus make it possible to measure, on the one hand, vibratory signals coming directly from the bearing and on the other hand vibratory signals coming from the various members of the machine via the frame (5) and which propagate through the bearing. The vibratory signal of each of the organs of the machine then has a proper frequency signature. An optimal arrangement of the various capacitive sensors consists in positioning the sensors equidistant from the axis of rotation of the bearing so that the planes passing respectively through each of the sensors and by the center of rotation of the bearing have angles between them ( α) of 120 °. Thus the presence of at least three capacitive sensors arranged radially on the bearing and at least three sensors arranged axially on each of the faces of the bearing makes it possible to perform a optimal vibration monitoring through all the bearing elements while facilitating the location of the origin of the vibration.

Furthermore, the armatures (7, 8) arranged axially are preferably flat, while those which are arranged radially, are for a concave and for the other convex so as to be adapted to the curvature of the bearing. In addition, the various frames can be of various shapes, circular, square, oval, etc.

In order to measure the variations of the capacitances of the sensors as a function of the vibrations, the conductive reinforcements (7, 8) of the variable capacitors of the invention are associated with an electronic assembly called a charge amplifier by appropriate connection means (14, 15).

A first armature (8) forms a conductor located opposite but fixed relative to a second (7) integrated at least a portion of the surface of a bearing ring. The variation of the capacity over time of such a capacitor is given by the relation:

C {t) = e- ≠ - = e- ^S ds (t) x (0 with d the distance separating the two armatures, s (t) the amplitude of the variation of the armature considered as moving with respect to its equilibrium point, S the active surface of the reinforcements and ε the permittivity of the vacuum The capacitance sensitivity (S _c ) of the capacitor is then defined by the relation:

This sensitivity can be considered constant for small variations of s (t). Since the displacements of the armature are small, of the order of a few micrometers, it is necessary to have a high sensitivity. The distance d is then of the order of several tens of times s (t), which determines the point of operation of the capacitor. For example for surfaces facing S≈28mm ² , a distance between reinforcement d = 0.01mm, the dielectric being air, a capacitor is obtained whose operating point capacitance is equal to C = 25 pF with a sensitivity Sc = 25 × 10 ⁵ pF / m = 0.25 pF / μm and for a displacement Δd = 0.05μm = 50nm the variation of capacitance ΔC is 0.125pF (ΛC = Sc ^* Λd = 0.25 ^* 0.05 = 0.125pF). The capacitors then have capacities of the order of a few picofarads with variations of the order of a few tens of femtofarads.

The distance d between the armatures must be as small as possible, d = 10 ^"5 ITi = 100μm is ideal, it is possible to increase the sensitivity Sc by placing n active surfaces in view, in this case we obtain: δ and S _c = (n ï ~) ^

^V 'DD ²

The objective being to measure accurately and remotely small variations of capacity to translate in real time the variations in the distance between the two frames due to vibration in the bearing, the so-called two-pole methods can not be suitable because the measurement would indicate then the value of C (t) + Cp, where Cp is the parasitic capacitance of the connecting wires due to an antenna effect.

The method used consists in considering the charges induced by capacitive coupling on only one of the two plates, the other plate being at a fixed potential. The variation of the induced loads is then the analogical image of the displacement s (t).

An electronic circuit diagram of the charge amplifier used is shown in Figure 6. The Integrated Linear Amplifier (ALI) used must be preferably JFET, MOSFET or CMOS with a very high input impedance. This high impedance gives it an important noise immunity with a polarization current of less than 2 fA. In this arrangement, the conductive armature (8) of the capacitor integrated in a portion of the bearing ring is connected to ground. The other conductive armature (7), positioned by the non-conductive positioning means (6), of each of the capacitors is held by a ring and connected to the inverting input (/.) Of an Integrated Linear Amplifier (ALI). ) by a shielded cable (14) whose shield (14.3) is connected to the FALI non-inverting input (/?./.). The ALI is connected by a DC voltage generator at its non-inverting input. In such an arrangement, the parasitic capacitance (Cp) due to the connecting cable which could disturb the measurements is not translated at the output of FALI. Only the DC component and the voltage variations due to the displacement of the so-called mobile armature are then translated at the output of I ¹ ALI. Between the output and the inverting input (/.) Of FALI, a capacity capacitor (C _f ) is connected in parallel with a resistor (R).

A second electronic circuit diagram of the charge amplifier used is shown in FIG. 7. The conductive armature (8) of the capacitor integrated in a part of the ring of the bearing is here connected to a generator. The other conductive reinforcement is here also kept by a ring and connected to the inverting input (/.) Of an Integrated Linear Amplifier (ALI) by a shielded cable (14) whose shielding (14.3) is connected. to ground with a capacitor (Cs). The other capacitor armature (Cs) is also connected to the inverting input (/.) Of FALI. In the same way, between the inverting input (/.) And the FALI output, another capacitor (Cή is positioned on the capacitor (C /), three resistors (R1, R2 and R3) arranged at T and whose one (R3) of them is connected to ground, are also connected in parallel, and the non-inverting input (/ ?./.) of FALI is connected to ground. The relationship between the output voltage Vs (t) and the load Q (t) on the armature (7) whose induced loads are measured is thus:

See Cf

The induced loads being equal to: Q = CV, the load variations due to the relative displacement of the reinforcements are given by: ΔQ = CΔV.

The relationship between the output voltage of the ALI and the vibration of the bearing is then:

where: Δx represents the variation of the distance d separating the two plates of the capacitor, ΔV _S represents the variation of the voltage at the output of the amplifier, Ve represents the DC or AC component of the voltage at the input of the capacitor amplifier, S _c represents the sensitivity of the capacitance and C _f represents the capacitance of the capacitor connecting the output of the ALI to the inverting input.

Thus, for example, if Δx = 1μm = 10 ^'6 m and C _f = 1pF, V = 5V, Sc = 10 ⁴ pF / m ² = 10 ^"8 F / m ² then V _s = 0, 1V. R is negligible in the calculation of the transmittance If it is desired that Δx and ΔV _S be of the same sign, the voltage Ve may then be negative.

The output of the Integrated Linear Amplifier (ALI) can be connected to the input of a digital analog converter (ADC) whose output is used by a microprocessor circuit (MP) to calculate the distance variation (Δx) by executing a program (Prog) using the formula:

and to allow the triggering of an alarm after comparing the calculation result with a stored threshold value.

The device of the invention can be connected to a means of processing the vibratory signal measured. The processing of this signal allows a temporal analysis on the one hand and a frequency analysis on the other hand.

Indeed, each rotating element of a mechanical machine is characterized by one or more characteristic frequency of defects. A bearing, for example, is characterized by three fault frequencies such as the default characteristic frequency of a rolling element (3), and the fault frequencies of each of the rings, inner (2) and outer (1). These frequencies are, previously, calculated from the geometric characteristics of the bearing such as the number of rolling elements (3), the diameter of the inner ring (2) and the diameter of the outer ring (1) as well as the speed of the rotation of the motor and then stored in a storage means. Analysis of the power spectrum of the signal delivered by the capacitive sensor thus makes it possible to locate the defect (s) present in the bearing and to follow in time the evolution of the amplitude of each frequency in order to determine the number of cycles of operation of the component before breaking. Furthermore, the mechanical state of a bearing or other rotating components of a mechanical machine can be characterized by statistical parameters called fault indicators. Among these parameters, the most used are the RMS value, also called rms value, the peak factor, formed by the ratio between the peak value and the rms value of the signal, or even the Kurtosis which corresponds to a measurement of peaks or relative flattening of a distribution of a real random variable with respect to a Gaussian distribution. These different statistical parameters are calculated from the vibratory signal of the bearing. It is then a question of detecting a significant change in these parameters, compared with threshold values recorded in a storage means. The determination of these threshold values is carried out beforehand either by an experimentation of the machine, either by statistical laws. The characterization of the defect and the estimation of its gravity make it possible to establish a diagnosis.

Thus, when a defect appears on an organ of the machine, it is easy to estimate its degree of severity, to follow its evolution and possibly to predict the replacement of the component, either by the temporal analysis of the signal delivered by the sensor. either by frequency analysis of the same signal. The location of this capacitive sensor has the advantage of being able to directly deliver the signature of the fault of the mechanical component and thus makes it possible to avoid diagnostic errors. It is important to point out that the signals from the various sensors of the device of the invention can be used for other applications, such as, for example, the regulation of the rotation speed of the bearing as a function of the unbalance, or even the measurement of the grip of a wheel on the ground. The device of the invention can be connected to a display means to allow, after the variation of the distance (Δx) is calculated, to display the position of a possible bearing fault.

It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration but may be modified in the field defined by the scope of the appended claims;

Claims

1. Device for monitoring the vibrations of a machine generated by a bearing formed by two rings, one outer (1) and the other inner (2), one fixed relative to the frame (5) of the machine and the other rotating, coaxial between which at least one rolling element (3) is trapped and capable of moving, vibrations generated by other organs of the machine passing through the bearing, each of the members of the machine having a signature respective frequency, characterized in that the device comprises at least one positioning means (6) non-conducting mounted on at least one element in contact with at least one element of the bearing or mounted on at least one of the rolling elements, the means positioning device (6) comprising at least one housing for positioning at least one conductive element, constituting a first armature (7) of at least one capacitor for forming a capacitive sensor, at a distance on the one hand the conductor fixed or integrated in a ring (1, 2) of the bearing, forming the second armature (8) of the capacitor or capacitive sensor, and the non-conducting positioning means (6) being integral with at least one partitioning means (10) which makes it possible to create, between at least two armatures (1, 2) of the same capacitor, a space (9) forming a dielectric insulating medium and this partitioning means ensuring the sealing of this insulating medium and being in contact with a portion of the bearing ring fixing or integrating the second armature (8), the armatures (7, 8) of the capacitive sensor being mounted perpendicularly to the axis of displacement of the vibrations monitored. and in that, the second armature (8) being integral or secured in a fixed bearing ring (1, 2) with respect to a frame (5) of the machine at the bottom of a first cavity (11) of the ring rolling, a non-conducting positioning means of at least one armature (7) forms a capacitive sensor by arranging the first armature (7) opposite the second armature (8), a partitioning means (10) annular closing the insulating medium (9) which separates the two armatures (7, 8), and in that a second cavity (12) narrower than the first cavity (11) being formed in the bottom of the first cavity (11) and formed by a bore oriented along an axis perpendicular to the axis of rotation (ZZ) of the bearing and passing through the center of rotation of the bearing, the end of a needle (13) mounted on the first armature (7) perpendicularly at a tangent plane to the first armature (7) is kept in contact with the bottom of the second cavity (12) located in the depth of the ring (1, 2) of rolling and in front of the raceway in contact with at least one rolling element (3).

2. Vibration monitoring device according to claim 1, characterized in that the Young's modulus of the positioning means

(6) is less than that of the needle (13) mounted on the first armature

(7) and / or that of the ring (1, 2) rolling.

3. Vibration monitoring device according to one of claims 1 to 2, characterized in that a third armature (8.1) is integrated or secured to the surface of the frame (5) of the machine located at the orifice of the cavity (11) of the bearing ring (1, 2) in contact with the frame (5) of the machine, the non-conducting positioning means (6) having the first frame (7) facing the third frame ( 8.1) simultaneously between the second (8) and third (8.1) reinforcements so that the first (7) and third (8.1) reinforcements, separated by an annular partitioning means (10.1) to close an insulating medium (9.1) , form a second capacitive sensor.

4. Vibration monitoring device according to one of the preceding claims, characterized in that the partitioning means (10) is formed by a metal plate integral with the positioning means (6) and in contact with at least a portion of the surface to which the second armature (8) is secured or integrated.

5. Vibration monitoring device according to one of the preceding claims, characterized in that the partitioning means (10) is formed by an elastic seal integral with the positioning means (6), the elastic seal having a lip in contact with at least a part of the surface to which the second armature (8) is secured or integrated.

6. Vibration monitoring device according to one of the preceding claims, characterized in that at least three first conductive armatures are positioned by a positioning means (6) non-conductive, radially relative to at least a second frame

(8) Conductive integral or integral with a portion of a ring of the bearing, the axes respectively passing through the positions of each pair of conductive elements forming a capacitive sensor and the center of rotation of the bearing realize between them angles (α ) not more than 120 °.

7. A vibration monitoring device according to one of the preceding claims, characterized in that at least two conductive reinforcements (7, 8) facing each other are convex and concave in a plane perpendicular to the axis. rotation of the bearing.

8. Vibration monitoring device according to one of claims 3 to 6, characterized in that the positioning means (6) non-conductive positions at least a first conductive reinforcement (7.2) axially relative to a second conductive reinforcement (8). secured or integrated to a bearing ring.

Vibration monitoring device according to one of claims 3 to 8, characterized in that the non-conducting positioning means (6) positions a pair of conductive reinforcements (7, 8), one radially (7.1). ), the other axially (7.2) with respect to at least one conductive reinforcement (8) integral or integrated with a bearing ring.

10. Vibration monitoring device according to claim 9, characterized in that a single space (9) forming the dielectric insulating medium is common to the pair of capacitors formed by at least two conductive reinforcements (7.1, 7.2) positioned by the positioning means (6) non-conductive on the one hand and at least one conductive reinforcement (8) secured to or integrated with a bearing ring on the other hand.

11. A vibration monitoring device according to at least one of the preceding claims, characterized in that at least three first armatures are positioned radially by at least one non-conductive positioning means (6) in front of at least one second armature. (8) secured to or incorporated in a bearing ring forming a first set of at least three capacitive sensors, and in that, on at least one face of the bearing, at least three first plates are positioned by at least one positioning means (6) non-conductive in front of at least one second armature (8) secured to or integral with a ring (1, 2) of the bearing, forming at least a second set of at least three other capacitive sensors, the three sensors capacitors of each of these assemblies being positioned equidistant from the axis of rotation (ZZ) of the bearing so that, in a plane perpendicular to the axis of rotation (ZZ) of the bearing, the planes passing through respectively, by the axes of symmetry of each of the capacitive sensors and the center of rotation of the bearing form between them angles (α) of 120.

12. Vibration monitoring device according to one of the preceding claims characterized in that the device comprises at least one distance adjusting means which separates at least two reinforcements (7, 8) involved in the formation of the same capacitive sensor.

Vibration monitoring device according to one of the preceding claims, characterized in that the pairs of armatures of each of the capacitive sensors are connected to a respective electronic circuit. forming a charge amplifier for delivering in real time a signal representative of the movements of one armature relative to the other due to vibrations during operation of the mechanical bearing.

14. Vibration monitoring device according to claim 13, characterized in that each pair of armatures is associated with an electronic assembly forming a charge amplifier (AC), the second armature (8) secured to or integrated with the bearing ring. is connected to ground and the first armature (7) positioned by the non-conductive positioning means (6) is connected to the inverting input (/) of a

High impedance integrated linear amplifier (ALI) with shielded cable (14) whose shield (14.3) is connected to the non-inverting input of PALI, the non-inverting input of PALI being connected to a generator supplying a voltage continuous or alternating (Ve), the output of PALI being connected to its inverting input via a capacitor (Cή and a resistor (R) connected in parallel.

15. Vibration monitoring device according to claim 13, characterized in that each pair of armatures is associated with an electronic assembly forming a charge amplifier (AC), the second armature integral or integrated with the race is connected to a generator supplying a DC or AC voltage (Ve) and the first armature (7) positioned by the non-conductive positioning means (6) is connected to the inverting input (/) of an Integrated Linear Amplifier (ALI) at high impedance by a shielded cable (14) whose shield (14.3) is connected to a capacitor armature

(Cs) connected to the ground and whose other armature is connected to the inverting input (/) of PALI, a capacitor (Cf) being arranged between the inverting input of PALI and the output of PALI and three resistors ( R1, R2, R3) mounted at T, one (R3) of the grounded resistors being positioned in parallel with respect to the capacitor (Cf), the non-inverting input (ni) of PALI being connected to the mass.

Vibration monitoring device according to claims 14 and 15, characterized in that the output of the Integrated Linear Amplifier (ALI) is connected to the input of a digital analog converter whose output is used by a digital circuit. microprocessor for calculating the distance variation by executing a program implementing the formula:

and to trigger an alarm by comparing the result obtained with a stored threshold, Δx representing the variation of the distance (d) separating the two plates of the capacitor, Δ V _s representing the variation of the voltage at the output of the amplifier, Ve representing the DC or AC component of the voltage at the input of the amplifier, S _c representing the sensitivity of the capacitance and Cf representing the capacitance of the capacitor connecting the output of the ALI to the inverting input.

17. Vibration monitoring device according to one of the preceding claims, characterized in that it comprises a means for detecting the rotation frequency of the bearing to perform measurements when the bearing rings are in a defined position relative to one another. to the other.

18. Vibration monitoring device according to claim 16 or 17, characterized in that the device comprises at least one means for frequency processing of the vibratory signal measured at the level of the armatures (7, 8) of the capacitor making it possible to obtain the vibratory signal. at least one of the different members of the machine in comparison with the respective vibratory signatures of each of the members of the machine recorded at at least one storage means.

19. Vibration monitoring device according to claim 18, characterized in that the device comprises at least one temporal processing means of the vibratory signal of at least one of the organs of the device. machine for obtaining several statistical parameters of this signal to be compared with statistical parameters of defects recorded at a storage means.

20. Vibration monitoring method involving a monitoring device according to one of the preceding claims, characterized in that it comprises at least one step of measuring the capacitive coupling induced loads on a first conductive reinforcement (7) of a variable gauge capacitor positioned by a non-conductive positioning means, a second conductive reinforcement (8) secured to or integral with a bearing ring being at a fixed potential.

21. Vibration monitoring method according to the preceding claim, characterized in that the pair of armatures being associated with an electronic assembly forming a charge amplifier (AC), the second armature (8) secured to or integrated with the ring connected to the mass, the first armature (7) being positioned by the non-conductive positioning means (6) and connected to the inverting input (/) of a high impedance Integrated Linear Amplifier (ALI) by a cable (14) shielded, whose shield (14.3) is connected to the non-inverting input of PALI, the non-inverting input of PALI being connected to a generator supplying a DC or AC voltage (Ve), the output of PALI being connected to its inverting input via a capacitor (C /) and a resistor (R) connected in parallel, the method comprises at least one step of calculating the variation (Δx) of the distance separating the two armatures (7, 8) of the capacitor from of the variation of the voltage (ΔV _S ) at the output of a charge amplifier (AC) using the relation:

Δx representing the variation of the distance (d) separating the two plates of the capacitor, ΔV _S representing the variation of the voltage at the output of the amplifier, Ve representing the DC component or alternating the voltage at the input of the amplifier, S _c representing the sensitivity of the capacitance and C _f representing the capacitance of the capacitor connecting the output of the ALI to the inverting input.

22. Vibration monitoring method according to claim 20, characterized in that the pair of armatures being associated with an electronic assembly forming a charge amplifier (AC), the second armature secured to or integrated with the bearing ring is connected to a generator supplying a DC or AC voltage (Ve) and the first armature (7) positioned by the non-conductive positioning means (6) is connected to the inverting input (/) of an amplifier

Integrated linear (ALI) high impedance by a shielded cable (14) whose shield (14.3) is connected to a frame of a capacitor (Cs) connected to the ground and whose other frame is connected to the input inverter (/) of the ALI, a capacitor (Cή being arranged between the inverting input of the ALI and the output of the ALI and three resistors (R1, R2, R3) mounted in T, one (R3 ) of the grounded resistors being positioned in parallel with the capacitor (Cή, the non-inverting input (ni) of the ALI being connected to ground, the method comprises at least one step of calculating the variation (Δx) of the distance separating the two plates (7, 8) of the capacitor from the variation of the voltage (ΔV _S ) at the output of a charge amplifier (AC) using the relation:

23. Vibration monitoring method according to one of the preceding claims, characterized in that the output of the Integrated Linear Amplifier (ALI) is connected to the input of a digital analog converter (ADC) whose output is used by a microprocessor circuit (MP) for calculating the distance variation by executing a program

(Prog), the method comprises at least one step of triggering an alarm after comparing the variation (ZIx) of the spacing between the two plates with a threshold value.

24. Vibration monitoring method according to one of the preceding claims, characterized in that, the device comprising a means of memorizing the vibratory signature of each of the organs of the machine, the method has at least:

a step of measuring the vibratory signal at the level of the armatures (7, 8) of the capacitive sensor positioned at the level of the bearing,

a step of comparing the measured vibratory signal with the stored vibratory signature of at least one defined member of the machine,

25. Vibration monitoring method according to one of the preceding claims, characterized in that, the device comprising means for storing fault threshold values of several statistical parameters, the method has at least:

a step of calculating statistical parameters of the measured vibratory signal, a step of comparing the calculated statistical parameters with stored fault threshold values,

a step of determining the importance of the defect.

26. Vibration monitoring method according to one of the preceding claims, characterized in that, the device comprising at least one display means, the method has at least one step of displaying the position and the importance of a default.