Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
  • G01L5/0009—Force sensors associated with a bearing
  • G01L5/0014—Force sensors associated with a bearing by using capacitive sensors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C27/00—Elastic or yielding bearings or bearing supports, for exclusively rotary movement
  • F16C27/04—Ball or roller bearings, e.g. with resilient rolling bodies
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C35/00—Rigid support of bearing units; Housings, e.g. caps, covers
  • F16C35/04—Rigid support of bearing units; Housings, e.g. caps, covers in the case of ball or roller bearings
  • F16C35/042—Housings for rolling element bearings for rotary movement
  • F16C35/045—Housings for rolling element bearings for rotary movement with a radial flange to mount the housing
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
  • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
  • F16C19/04—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly
  • F16C19/06—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for radial load mainly with a single row or balls
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
  • F16C19/52—Bearings with rolling contact, for exclusively rotary movement with devices affected by abnormal or undesired conditions
  • F16C19/522—Bearings with rolling contact, for exclusively rotary movement with devices affected by abnormal or undesired conditions related to load on the bearing, e.g. bearings with load sensors or means to protect the bearing against overload

Definitions

• the present invention relates to the field of capacitive sensor devices for accurately detecting a displacement.
• the present invention relates to the field of the detection and measurement of the load applied to a bearing housing of which a moving part is movable relative to a fixed part under the effect of the load.
• the housing allows the detection of the load applied to said bearing in operation or at a standstill.
• the document FR 2 863 706 describes a device for measuring the load on a washing machine bearing, comprising capacitors provided with an insulator whose thickness can vary according to the load and a means for measuring the capacitance. capacitor, the capacity being representative of the load applied perpendicularly to the electrodes, one of the electrodes being formed by one of the rings of the bearing.
• This device works satisfactorily. However, in some applications, it is desirable to have a high measurement accuracy in at least one direction perpendicular to the axis of the bearing and therefore to benefit from a larger gap variation and negligible hysteresis.
• the sensing zones comprise parts or parts of parts whose thermal expansion coefficients are different.
• the object of the invention is in particular to remedy the defects mentioned above.
• the invention aims at a reliable, economical, compact and precise load measurement, based on the measurement of displacements due to deformations of the housing under the load.
• the capacitive type displacement sensor device comprises a printed circuit comprising a plurality of layers, and two measurement electrodes disposed on opposite external faces of the printed circuit forming two capacitors with a corresponding external electrode, the capacitances of the two capacitors varying in an antagonistic manner. such that a differential measurement of the two capacitors is representative of the relative displacement between the measuring electrodes and the external electrodes.
• the measuring electrodes disposed on opposite external faces of the printed circuit have a small size and a precise and economical positioning.
• the printed circuit may comprise several sandwich layers.
• the measurement electrodes comprise conductive tracks of the printed circuit. Measuring electrodes are compact and inexpensive.
• the printed circuit includes guard electrodes surrounding the measurement electrodes. This forms an electromagnetic shield.
• the guard electrodes are arranged at the same potential as the measurement electrodes.
• the device comprises an integrated signal conditioning circuit.
• the integrated circuit can be arranged on the printed circuit.
• the integrated circuit and the electrodes are connected by tracks of the printed circuit, said tracks being surrounded by guard tracks. This reduces the influence of external parasites on the connection between the integrated circuit and the electrodes.
• the device comprises a displacement measuring means.
• the device comprises a mechanical load measuring means.
• the printed circuit comprises a plurality of conductive layers and insulating layers.
• the electrodes may be formed by conductive layers on two opposite sides of the printed circuit.
• An integrated signal processing circuit may be mounted on the printed circuit on one of said faces in the vicinity of the electrode.
• the displacement sensor device may be disposed in a bearing housing.
• the housing may be provided with an inner portion configured to support a bearing, an outer portion for securing the housing to a mechanical assembly.
• the inner part is connected to the outer part by at least two deformable connecting elements, so that the inner part can move relative to the outer part under the action of a load applied to said bearing.
• the device comprises means for detecting the displacement of one of the parts, internal or external, relative to the other part, external or internal, under the action of a load applied to said bearing.
• the liaison elements are capable of deforming elastically in an applied load range sufficiently wide for the application in question, with negligible hysteresis.
• the device being symmetrical with respect to a plane passing through a geometric axis of said device, the product of the thermal expansion coefficient of the fixed part and the distance between the plane and a face of the fixed part is equal. to the sum of the product of the thermal expansion coefficient of the moving part and the distance between the plane and a face of the moving part and the product of the thermal expansion coefficient of a first electrode and the thickness of the electrode .
• the air gap can be substantially constant over a temperature range, for example from 0 to + 50 ° C. in the field of household appliances.
• the fixed portion and the movable portion may be made of the same material.
• the applied load detection system comprises a movable detection portion rigidly connected to the inner portion and thus movable under the action of the load.
• the detection portion of the inner portion is decoupled from the outer portion with respect to which said detection portion can move without contact, the outer portion comprising a fixed detection portion facing the moving detection portion. to form at least one gap with the movable detection portion.
• the applied load sensing system also includes sensing means for measuring the displacements of the inner portion through variations of the gap between the fixed and movable sensing portions.
• the detection portions may be disposed near an axial plane of symmetry substantially perpendicular to the load to be measured.
• the device may comprise at least two planes of symmetry perpendicular to each other.
• the outer portion, the inner portion and the connecting elements form a one-piece assembly.
• Said one-piece assembly can be obtained in large series by molding a metal alloy or a synthetic material having mechanical properties, including elasticity, desired for the application in question.
• the same mold provided for a one-piece assembly can be used to manufacture monobloc assemblies of different elastic characteristics, depending on the chosen composition of the material, which is particularly economical.
• the fixed detection portion is attached to the inside of the outer portion.
• a housing is provided with a displacement sensor device, an inner portion configured to support a bearing and an outer portion for attaching the device to a mechanical assembly, the inner part being connected to the outer part by one minus two connecting elements deformable, so that the inner portion can move relative to the outer portion under the action of a load applied to said member, the displacement of one of the parts, internal or external, relative to the other part, external or internal, depending on a load applied to said element.
• FIG. 1 is a view in axial section of a housing device provided with a bearing mounted on a shaft;
• FIG 2 is a perspective view of the housing device of Figure 1;
• FIG. 3 is a detail view of FIG. 1;
• FIG 4 is a detail view in radial section of the device of Figure 1;
• FIGS. 5 and 6 are exploded perspective views of a printed circuit
• FIG. 7 is a front elevational view of a displacement sensor
• FIG. 8 is a top view in elevation of the displacement sensor of FIG. 7.
• the housing device is provided with a test body 1 comprising an outer portion 2 and an inner portion 3 separated by a space 4.
• the outer 2 and inner 3 are delimited by two radial planes.
• the inner part 3 is provided with a bore, in which is disposed a rolling bearing 5 mounted on a shaft 6.
• the outer part 2 is intended to be disposed in a mechanical assembly, for example a housing, a frame or a support, not shown.
• the rolling bearing 5 comprises an outer ring 7, an inner ring 8, a row of rolling elements 9, here balls, held at regular circumferential spacings by a cage 10.
• the rolling elements 9 are arranged between an inner race of the outer race 7 and an outer race of the inner race 8.
• the rolling bearing 5 is delimited by the axial outer surface of the outer race 7, the bore of the inner ring 8 and the radial end faces of the outer ring 7 and inner ring 8 which pass from one side and the other of the rolling elements 9, each by a radial plane, coincident on one side with the radial plane delimiting the test body 1.
• the rings 7 and 8 are here made of metal, for example steel, and the raceways are machined with removal of chips.
• the shaft 6 is able to undergo a radial load oriented in the direction of the arrow 11. Said load causes a slight radial displacement of the shaft 6, the rolling bearing 5 and the inner portion 3 relative to the outer portion 2.
• the structure of the test body 1 is explained in more detail in Figures 2 and 3.
• the inner portion 3 comprises a ring-shaped body axially delimited by the aforementioned radial planes and having a substantially constant thickness.
• the inner part 3 also comprises two mobile detection portions 13, in the form of diametrically opposed ears extending outwardly from the body 12. In the example illustrated, the mobile detection portions 13 have an axial length substantially equal to that of the body 12 and the test body 1.
• the inner part 3 also comprises a flange 14, in the form of a plurality of segments separated from each other and circumferentially regularly distributed, flush with one of the radial planes delimiting the test body 1 and extending radially inwards from the bore 12a of the annular body 12.
• the rim 14 serves of axial abutment to the rolling bearing 5, during the mounting of said rolling bearing 5 in the housing, and thus ensures axial positioning of the rolling bearing 5.
• the movable detection portions 13 and the flange 14 are integral with the body 12.
• the outer portion 2 comprises a body 15, adapted to be mounted in the bore of a housing or the like.
• the body 15 comprises two thick portions 16, symmetrical with respect to a plane passing through the axis of the test body 1, and two portions 17 of small radial thickness, each in the shape of a roof, having two panels 17a and 17b, joining in a plane of symmetry passing through the axis of the test body 1.
• the sections 17a and 17b have a substantially constant thickness, except at their junction, because of a wide connection fillet, on the side concave, that is to say on the inside.
• the sections 17a and 17b are connected to the thick portions 16 opposite the roof edge.
• Each thick portion 16 comprises a groove 18 extending axially over the entire length of the test body 1, and in which the movable detection portion 13 of the inner portion 3 projects.
• the thick portion 16 extends radially towards the inside. interior to form jaw-like fixed sensing portions 19 and 20 surrounding the movable detection portion 13.
• the test body 1 is completed by a connecting portion 21 provided with four arms 22, of rounded and deformable shape, connected to the outer portion 3, substantially at the connection between the thick portion 16 and the weak portion. 17, and being connected to the inner portion 3 to the right of the junction between the sections 17a and 17b of the thin portion 17.
• two symmetrical arms 22 are also connected to one another. Between the aforementioned connections, the arms 22 have a rounded shape between the inner portion 3 and the thin portion 17 and extend axially over all or part of the length of the test body 1.
• the outer portion 2, the inner portion 3 and the connecting portion 21 are in one piece and can be made by molding a conductive synthetic material, or by molding a metal, for example an aluminum alloy.
• the test body 1 is symmetrical with respect to two perpendicular planes passing through the axis of said test body 1, one of the planes passing through the junction between the panels 17a and 17b, and the other plane passing through the mobile detection portions 13, which are thus angularly offset by 180 °.
• the gap 25 between the mobile detection portion 13 and the fixed detection portion 19 is equal to the gap 26 between the mobile detection portion 13 and the fixed detection portion 20, and this 1 and both sides of the test body 1.
• a radial load is applied, for example in the direction 1 1, that is to say vertically downward, the outer portion 2 remains substantially immobile , while the inner part 3 moves in the direction of the applied load.
• the gap 25 between the mobile detection portion 13 and the fixed detection portion 19 decreases, and the gap 26 between the mobile detection portion 13 and the fixed detection portion
• a displacement sensor 23 comprises the fixed detection portion 19 and the mobile detection portion 13. More specifically, the mobile detection portion 13 may consist of two conductive fingers 13a, 13b spaced from each other and arranged at the same potential.
• the fixed detection portion 19 comprises a printed circuit 24 fixed to a thick portion 16 for example by partial insertion into a concavity and gluing. The printed circuit 24 is connected to a connecting cable 27 itself connected to a connector 28.
• the printed circuit 24 comprises a plurality of conductive layers and insulating layers. Electrodes 31 and 32 are formed by conductive layers on two opposite sides of the printed circuit 24. An integrated signal processing circuit 29 is mounted on the printed circuit 24 on one of said opposite faces in the vicinity of the electrode 31. Advantageously, the printed circuit board 24 is inserted into a fixing slot and glued. An electrical circuit is thus formed comprising two capacitors of variable capacitance, one being formed by the electrode 31 and the mobile detection portion 13 separated by the gap 26, and the other being formed by the electrode 32 and the mobile detection portion 13 separated by the air gap 25.
• each capacitor is directly representative of the value of the air gaps 25 and 26 and, consequently, of the load applied to the internal part of the test body 1, in the extent that the application of the load causes the displacement of the mobile detection portion 13 relative to the electrodes 31 and 32 which remain fixed.
• the printed circuit 24, in the embodiment illustrated in FIGS. 5 and 6, comprises three insulating layers 33, 34 and 35, at least one of which is in the form of a rigid plate conferring on the whole of the printed circuit board 24 the mechanical characteristics desirable to be able to support the other elements, and in particular the integrated circuit 29.
• the upper insulating layer 33 supports, on the integrated circuit 29 side, the electrode 31, a guard electrode 36 surrounding the electrode measurement 31, and pads 37 and 38 of connection provided to receive the tabs of the integrated circuit 29.
• the pads 37 are also surrounded by the guard electrode 36, while the pads 38 are arranged outside the enclosed area by the guard electrode 36.
• the insulating layer 33 is traversed by a plurality of vias, in particular the via 39 connected to the measuring electrode 31 and the vias 40 and 41, each connected to a stud 37.
• vias 39 to 41 make it possible to provide an electrical connection between the upper surface and the lower surface of the insulating layer 33 and to connect elements of the upper face to elements placed below, for example those visible on the intermediate insulating layer 34 or on the lower insulating layer 35.
• the terms "intermediate”, “lower”, “upper” should be taken relative.
• the insulating layer 34 comprises a large conductive portion 42 disposed under the measuring electrode 31 and the guard electrode 36, thereby forming a guard electrode disposed beneath the measuring electrode 31 and supplementing the protection offered by the electrode 36.
• the guard electrodes 36 and 42 are placed at the same potential via via 43.
• the guard electrode 42 is provided with an opening located in which is disposed a conductive track 44 connecting the lower ends of the vias 39 and 41 and thus making it possible to electrically connect the measuring electrode 31 to one of the legs of the integrated circuit 29.
• the via 40 is extended downwards by a via 45 passing through the intermediate insulating layer 34 and electrically insulated with respect to the guard electrode 42.
• the lower insulating layer 35 has a guard electrode 46 of large size, intended to protect the electrode 32 disposed under said lower insulating layer 35, see FIG. 6.
• the guard electrode 46 is provided with an opening in which is provided a conductive track 47 for connecting the via 45 through the intermediate layer 34 to via 48 through the insulating layer 35.
• the measurement electrode 32 electrically connected to the via 48 and thus to one of the lugs of the integrated circuit 29 via the conducting track 47. , via 45 and via 40.
• the measuring electrode 32 is surrounded by a guard electrode 49 arranged in the same plane and electrically connected to the guard electrode 46 via a via 50.
• the guard electrodes 46 and 49 are thus equipotential.
• On the lower surface of the lower layer 35 are also arranged two capacitors 51 and 51a.
• each of the two capacitors is formed, each capable of cooperating with the fingers 13a and 13b respectively of the mobile detection portion 13.
• a capacitor is formed between the finger 13a and the measuring electrode 31 and another capacitor is formed between the The capacitance of each of the two capacitors varies in the opposite direction during a radial displacement of the mobile part 3 with respect to the fixed part 2 of the test body 1.
• Conductive track 44 is electromagnetically protected by guard electrodes 36, 42 and 46.
• Conductive track 47 is electromagnetically protected by guard electrodes 42, 46 and 49.
• the transfer of the signal between each measuring electrode 31, 32 and the integrated circuit 29 is thus at the heart of the multilayer printed circuit 24 and is protected against electromagnetic disturbances, in particular thanks to the guard layers surrounding the vias and the conductive tracks.
• the conductive tracks and the vias behave as a signal transmission by coaxial cables without having the disadvantages in terms of size and connection.
• it can be provided by a suitable electronic treatment simultaneous excitation of the guard electrodes and measurement electrodes to achieve a particularly effective active shielding.
• a capacitive sensor for differential measurement of micro-displacement integrating both the signal detection and processing system, and an excellent protection against external disturbances thanks to the shielding is available.
• electromagnetic provided in the printed circuit 24 This configuration eliminates the edge forces and perfectly delimit the sensing area of the measuring electrodes. It also allows a reduction of parasitic disturbances caused to the adjacent driver circuit.
• the mobile detection portion 13 comprises a single protuberance facing a printed circuit board face 24 carrying two electrodes 52, 53.
• the mobile detection portion 13 is arranged at a short distance from the electrodes 52, 53 with partial overlap.
• a lateral displacement, in the direction of the arrow 54, of the mobile detection portion 13 with respect to the printed circuit board 24, causes a variation of the respective surfaces opposite the electrode 52 with respect to the mobile detection portion 13 and the electrode 53 with respect to said detection portion mobile 13, whereby a variation of the capacitance of each capacitor formed, on the one hand, by the electrode 52 and the mobile detection portion 13 and, on the other hand, by the electrode 53 and the detection portion mobile 13.
• the electrodes 52 and 53 are each surrounded by a guard electrode 55, 56 also disposed on the upper surface of the printed circuit board 24.
• the printed circuit board 24 may have a structure similar to that illustrated in FIGS. , with a plurality of layers allowing the connections and an electromagnetic shielding on the side of each electrode opposite to the mobile detection portion 13, that is to say at an intermediate layer of the printed circuit board 24.
• the electrodes 52 and 53 are surrounded laterally by a single guard circuit 57, having a generally 8-shaped shape with two openings in which the measuring electrodes 52 and 53 are arranged.
• to be measured causes a parallel relative displacement between the measuring electrodes and the mobile detection portion forming the opposite electrode, the opposing variation of the facing electrode surfaces resulting in linear variations of each capacitance, the differential measurement of said capacitances being representative of the displacement to be measured.
• This embodiment is rather adapted to macrodéplacements, while that illustrated in Figures 1 to 6 is better for the detection of micro-displacements.
• the disclosed embodiments allow for differential capacitance measurements, which greatly increases the reliability and accuracy of. measurement of air gap variations through capacity measurements. Indeed, parasitic variations of capacitances which can be sensitive at the level of each pair of electrodes cancel each other out or attenuate each other by the differential measurement.
• the test body I 5 considered here as a deformable test body, is used in its elastic domain. This use makes it possible to have a relationship between charge and deformation without hysteresis, since there is no friction. To limit the fatigue of the materials, the dimensioning of the connecting arms 21 limits their use under a ceiling. It is possible to choose a maximum applied stress, of the order of 80% of the elastic limit of the housing device, in order to be able to withstand 10 million cycles of elastic deformation without significant permanent deformation.
• the materials of the various elements adjacent to the gap are chosen with expansion coefficients and dimensions such that the dimensional variations of the elements due to temperature changes. offset each other and do not cause significant variations in the gap.
• the ratio between the thermal expansion coefficients of the materials used for said adjacent elements of the gap is chosen close to the inverse ratio of the thicknesses of said elements to allow a constant air gap over a wide temperature range.
• an aluminum alloy proof body with a coefficient of thermal expansion of 23 ppm / ° K is available, leaving an initial air gap Ei of 1.5 mm before assembly of the reported electrode, it is possible to choose an attached electrode composed for example of a glass-teflon type printed circuit, with a coefficient of thermal expansion of the order of 34.5 ppm / ° K and a standard thickness of 1 mm.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 2005
  • 2005-12-20 FR FR0512967A patent/FR2895079B1/fr not_active Expired - Fee Related
• 2006
  • 2006-12-18 WO PCT/FR2006/002768 patent/WO2007080290A2/fr not_active Ceased
  • 2006-12-18 EP EP06841971A patent/EP1963806A2/de not_active Withdrawn

Non-Patent Citations (1)

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