FR2857743A1 - Rotation measurement system for use in bearing, has non rotating unit with passive sensor for detecting angular position of encoder of rotating unit, and connector transmitting signal representing position and power supply - Google Patents

Abstract

The system has a rotating unit with an encoder, and a non rotating unit with a passive sensor (14) for detecting an angular position of the encoder. The passive sensor is distant from the encoder. An electronic counter (25) counts the number of turns of the rotating unit and a temporary supply unit (27) supplies the sensor and the counter. A connector (21) transmits a signal representing the position and power supply to the sensor. An independent claim is also included for a bearing having a rotation measurement system.

Description

Rotation measurement system.

  The present invention relates to the field of multiturn sensors with electronic counting and storage, capable of providing an output signal representative of the absolute position of a rotating part. Such sensors can be used to provide, for example, the position of a linear jack comprising a rotating electric machine.

  It is known to use a mechanical assembly to count and memorize the number of revolutions made by one encoder while another part of the system provides the absolute position inside a lathe. Thus, the number of turns is taken into account, even in the absence of power supply. The electronic processing devices are informed of the exact position of the encoder upon power-up. However, the mechanical assembly is relatively bulky and expensive.

  Furthermore, the current instrumented bearings based on the magnetic, capacitive or inductive phenomena can not operate without external energy supply, in the form of an electrical voltage, and perform an angular measurement and not a multiturn measurement.

  The abstract of JP A 09-273943 discloses an absolute multi-turn encoder, comprising a rotating part equipped with two optical tracks and two magnetic tracks and a non-rotating part comprising two optical sensors and two magnetic sensors, electronic circuits and a reserve power supply for supplying the magnetic sensors. The electronic circuits provide a high power mode and a low power mode depending on whether a main power supply is active or not.

  However, such a system is particularly complex, cumbersome and expensive. The use of optical encoders is undesirable in some applications.

  The invention proposes a simple structure rotation measurement system, adapted to a non-permanent external power supply, compact, very robust and reasonable cost.

  The rotational measuring system, according to one aspect of the invention, comprises a rotary element provided with an encoder, a non-rotating element provided with at least one passive sensor for detecting the angular position of the encoder, said sensor being remote from the encoder, an electronic counter of the number of revolutions or fractions of revolutions made by the rotating element with respect to the non-rotating element, a temporary supply means for the sensor and the encoder and a system for the transmission absolute angular position signals and the power supply. This benefits from a particularly simple system. Passive sensor means a sensor that does not require a power supply for its output state to be changed.

  In one embodiment, the sensor includes a flexible blade switch, also known as a Reed relay.

  In another embodiment, the sensor is of the Wiegand wire type.

  In one embodiment, the power supply means comprises a capacitor of high capacity.

  In one embodiment of the invention, the power supply means comprises a battery or a battery.

  The choice of the type of supply means can be made according to the electrical energy to be supplied and environmental constraints, such as temperature, shock, pollution.

  Advantageously, the connector is connected to the temporary power supply means and the meter.

  Advantageously, the sensor is unlimited rotation.

  The sensor and the counter according to the invention are able to be active when the connector is disconnected.

  Preferably, at least two passive sensors are provided.

  The system for signal and power transmission may comprise a plug-in connector with a complementary connector, or a remote signal and power supply element adapted to cooperate with a remote complementary element. The remote transmission element may form a resonant circuit with the remote complementary element.

  The fact of using a passive sensor, little or no consumer of electrical energy, is particularly interesting for increasing the autonomy of the system. In addition, a sensor of the type proposed is capable of detecting low speed rotations, which is often the case when a rotating element is de-energized, for example manually. The encoder will advantageously be a multipole magnetic pulse ring made from magnets or else from plastoferrite or magnetized elastoferrite.

  The invention also proposes an instrumented bearing comprising two rings, at least one row of rolling elements and a system for measuring rotation. The rolling elements are arranged between the rings. The rotational measuring system comprises a rotating element integral with the rotating race and a non-rotating element integral with the non-rotating race.

  The present invention will be better understood and other advantages will appear on reading the detailed description of some embodiments taken as non-limiting examples and illustrated by the appended drawings, in which: FIG. in axial section of a rolling bearing equipped with a set of rotational detections according to one aspect of the invention; FIG. 2 is an electronic diagram of the rotation detection assembly; FIG. 3 is a front view in elevation of the encoder and sensors of the detection assembly; FIG. 4 is a view in axial section corresponding to FIG. 3; FIGS. 5 and 6 respectively corresponding to FIGS. 3 and 4, illustrate another embodiment of the invention; and FIG. 7 is a variant of FIG.

  As can be seen in Figure 1, a rolling bearing 1 5 comprises an outer ring 2 provided with a raceway 3, an inner ring 4 provided with a raceway 5, a row of rolling elements 6 here balls, arranged between the races 3 and 5, a cage 7 for maintaining the circumferential spacing of the rolling elements 6, and a seal 8 mounted on the outer ring 2 and coming into friction with a cylindrical bearing 4a of the inner ring 4, while being disposed radially between the two rings 2 and 4 and axially between the row of rolling elements 6 and one of the side surfaces of the rings 2, 4.

  The seal 8 is mounted in an annular groove 9 formed in the outer ring 2, near its radial lateral surface 2a. On the opposite side, the outer ring 2 is also provided with a groove 10, symmetrical with the groove 9, with respect to a plane passing through the center of the rolling elements 6.

  A sensor unit, referenced 11 as a whole, is mounted on the outer ring 2 on the side of the groove 10. The sensor unit 11 comprises a metal support 12, a metal cap 13, and two sensor elements 14, of which only one is visible in FIG. 1, embedded in a central part made of synthetic material 15.

  The metal support 12, of generally annular shape, is hooked into the groove 10 and radially surrounds the central portion 15 and the metal cap 13 which has a generally disk-like shape.

  The central portion 15 is limited radially by the support 12 to the outside and has a bore 15a, of diameter such that there remains a sufficient radial space for the encoder to be described later. The sensor elements 14, integral with the central portion 15, are flush with the bore 15a. An end of the central portion 15, radially outwardly projecting, forms a terminal 19 of wire exit 20. The terminal 19 passes through a notch formed in the support 12. The wire 20 is connected to a connector 21, suitable to be connected to a complementary connector, not shown, for the power supply and the transmission of information.

  The encoder 16 comprises an annular support 17 and an active part 18. The support 17 has a T-shaped annular shape and comprises a radial portion 17a, axially in contact with a radial front surface 4b of the inner ring 4, of the same shape. side that the sensor block 11, and a cylindrical portion 17b extending from the outer edge of the radial portion 17a, axially on both sides, being fitted on the side of the inner ring 4 on a cylindrical bearing surface 4c of the ring 4. The span 4c is preferably symmetrical with the span 4a with respect to a radial plane passing through the center of the rolling elements 6.

  The active part 18 of the encoder 16 is of annular shape, of generally rectangular section, disposed on the outer periphery 15 of the cylindrical portion 17b. The active part 18 extends axially in the direction of the rolling elements 6, beyond the radial portion 17a, between the outer and inner rings 2, substantially to the level of the groove 10 of the outer ring 2.

  The active portion 18 extends to near the bore 15a 20 of the central portion 15, with which it forms a radial air gap. During the rotation of the inner ring 4 relative to the outer ring 2, the active part 18 of the encoder 16 rotates in rotation in front of the sensor elements 14, which are capable of outputting an electrical signal. The active part 18 of the encoder 16 is a multipole magnetized ring 25, for example made of plastoferrite. The encoder 16 and the sensor unit 11 form a rotation parameter detection assembly.

  The sensor unit 11 further comprises an electronic module 22 embedded in the central portion 15 and connected, on the one hand, to the sensor elements 14 and, on the other hand, to the connector 21 via the wire 20.

  The electronic module 22 is illustrated in greater detail in FIG. 2. The electronic module 22 can be made in the form of a printed circuit board supporting one or more integrated circuits and one or more discrete elements.

  The electronic module 22 comprises a filtering element 23, a treatment element 24, a counter 25, an interface 26 and a temporary power supply 27. The filtering element 23 is connected to the sensor 14. The temporary power supply 27, under the form of discrete elements, comprises a battery and / or capacitor of high capacity, for example farad, and supplies the filtering element 23, the treatment element 24 and the counter 25. The temporary power supply 27 is connected to the connector 21.

  In Figure 2, is also shown a main power supply 28 connected removably to the connector 21 by a complementary connector 29. The main power supply 28 allows to recharge the temporary power supply 27 when the connectors 21 and 29 are plugged.

  The processing element 24 is mounted downstream of the filtering element 23 and receives from said filtering element 23 one or more signals, preferably digital signals, the filtering element being able to provide preprocessing comprising a scanning step. The counter 25 is mounted downstream of the processing element 24 and receives from said processing element 24 an incrementing or decrementing signal. The interface 26 is mounted downstream of the counter 25 and receives from said counter 25 an n-bit coded position signal.

  The interface 26 is connected to the connector 21 for transmitting the positional formation to external devices via the connector 29 and a wire 30.

  Advantageously, the electronic module 22 is made from a custom circuit, for example an ASIC, and is of very low consumption type, for example less than 10 gA. The electronic module 22 collects the signals from the sensors 14 and increments or decrements the counter according to the direction of rotation. The electronic module 22 can also be made from different components performing the analog and logic operations, from a programmable analog circuit, for example EPLD, or from a microcontroller. The processing element 24 is capable of determining the direction of rotation from the quadrature of the signals of the two sensors 14.

  The temporary power supply 27 may also include a battery which could be turned off when the main power supply 28 is connected to the electronic module 22.

  In the embodiment illustrated in FIGS. 3 and 4, the system comprises an encoder 31 provided with a magnetic double crown with an inner ring provided with six south poles 33 and an outer ring provided with six adjacent north poles 34, unmagnetized zones 35 angularly separating a south pole 33 and a north pole 34 of the neighboring poles. A north pole is radially aligned with a south pole.

  The sensor assembly 32 comprises a printed circuit board 36 whose functions are similar to those of the electronic module 22 of FIG. 2, and supporting two sensors 37 of the type with a flexible blade switch. The soft-blade switches (or Reed relays) are microswitches that close an electrical circuit in the presence of a magnetic field and open said circuit in the absence of a magnetic field. This type of sensor is not in itself power consumer. The encoder 31 and the sensor assembly 32 are here independent of a rolling bearing. The sensors 37 form an open circuit in the absence of a magnetic field and a closed circuit in the presence of a magnetic field. The sensors 37 being angularly offset, generate signals processed by the printed circuit board 36 which make it possible to determine the direction of rotation of the encoder 31 with respect to the sensor 32.

  The embodiment illustrated in FIGS. 5 and 6 will be close to the previous one, except that the magnetized double ring 30 is circularly continuous. The south and north poles are alternately circumferentially and radially. In other words, a north pole 34 of the inner ring is adjacent to a south pole of the outer ring and is surrounded by two south poles of the inner ring.

  A north pole 34 of the outer ring is surrounded by two south poles 33 of the outer ring and adjacent to a south pole 33 of the inner ring. The sensors 37, angularly offset relative to one another, are of the Wiegand wire type and comprise a coil arranged around a Wiegand wire, generating an electric pulse when the polarity of the surrounding magnetic field changes. . The sensors 37 thus detect a succession of fields reversing at each step. Here again, this sensor device is not current consuming.

  As can be seen in FIG. 5, one of the sensors 37 is disposed in the center of a magnetized zone, while the other sensor 37 is disposed astride between a magnetized zone and a non-magnetized zone.

  As a variant, it is possible to provide a rolling bearing comprising an encoder and one or more sensors, the electronic module 22 being disposed externally to the rolling bearing. Such a design is ideal for ball screw actuators where one seeks to know the linear position of the nut set in motion by the rotation of the screw. The reduction of the screw makes it possible to know, with good precision, the position of the nut even with a low resolution of the encoder.

  The electronic counter 25 makes it easy to count a large number of turns. An 8-bit coding makes it possible to code 256 rounds, which generally proves to be largely sufficient. The electronic counter 25 can be active in the absence of the main power supply 28, which is particularly important in the case of a reversible screw whose nut can be moved without control or with the motor disengaged.

  The variant illustrated in FIG. 7 differs from FIG. 2 in that the connectors are replaced by a remote transmission element 38, for example a resonant circuit, and a remote complementary element 39. The element 38 can be part of the electronic module 22, or be connected to the electronic module 22.

  Thanks to the invention, there is a rotation measuring system which remains active, in the absence of external power supply, compact and particularly robust.

Claims (12)

  1-Rotation measuring system, characterized in that it comprises a rotary element provided with an encoder (16), a non-rotating element provided with at least one passive sensor (14) for detecting the position angular encoder (16), said sensor being remote from the encoder, an electronic counter (25) of the number of turns or fractions of a turn, a temporary supply means (27) of the sensor and the counter, and a system for transmitting absolute angular position signals and the power supply.   2-System according to claim 1, characterized in that the sensor (14) comprises a flexible blade switch.   3-System according to claim 1, characterized in that the sensor (14) is of Wiegand wire type.   4-System according to any one of the preceding claims, characterized in that the supply means comprises a capacitor.   5-system according to any one of the preceding claims, characterized in that the supply means comprises a battery or a battery.   6-System according to any one of the preceding claims, characterized in that the connector (21) is connected to the temporary supply means (27) and the counter (25).   7-System according to any one of the preceding claims, characterized in that the sensor (14) is unlimited rotation.   8-System according to any one of the preceding claims, characterized in that the sensor (14) and the counter (25) are able to be active when the connector (21) is disconnected.   9-System according to any one of the preceding claims, characterized in that the non-rotating element is provided with at least two passive sensors.   10-System according to any one of the preceding claims, characterized in that the system for the transmission of signals and power supply comprises a connector (21) adapted to be connected with a complementary connector (29).   11-System according to any one of claims 1 to 9, characterized in that the system for signal transmission and power supply comprises a remote signal transmission element and the power supply adapted to cooperate with a remote complementary element.   12-instrumented bearing comprising an outer ring, an inner ring and at least one row of rolling elements, characterized in that it comprises a rotation measuring system according to one   any of the preceding claims.