Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
  • G01D5/245—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains using a variable number of pulses in a train
  • G01D5/2454—Encoders incorporating incremental and absolute signals
  • G01D5/2455—Encoders incorporating incremental and absolute signals with incremental and absolute tracks on the same encoder
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
  • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
  • G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D2205/00—Indexing scheme relating to details of means for transferring or converting the output of a sensing member
  • G01D2205/20—Detecting rotary movement
  • G01D2205/26—Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation

Definitions

• the present invention relates to the field of detecting the angular position of an electric motor shaft.
• the present invention also relates to the field of steering columns of motor vehicles, in which it is desired to know accurately the angular position.
• Electric power steering frequently use brushless direct current electric motors which it is necessary to control the phase switching finely and thus to know the absolute angular position of the rotor.
• the assistance electric motors thus actuate the orientation system of the zones with which they are mechanically linked.
• the mechanical connection between the assistance motor and the wheel alignment system can be done in different possible places, for example on the steering column shaft or on the rack of the steering wheel. wheel orientation.
• a steering column In a steering column, there is generally a reduction between the rotational speed of the steering column and that of the electric motor of the order of 10 to 20, so that the steering column makes a turn while the The engine shaft is 10 to 20.
• the number of accumulated turns for the steering column from one maximum steering direction to another is of the order of 4 revolutions. It is therefore necessary to determine the absolute angle of the motor shaft over 40 to 80 turns of the shaft and the absolute angle of the steering column over 4 turns.
• EP 1 026 068 discloses an electric power steering comprising a steering shaft, an electric motor having a rotor operably connected to the steering shaft through a gearbox having a gear ratio. non-integer reduction, first sensing means for producing an output dependent on the angular position of the steering shaft and second sensing means adapted to produce an output dependent on the angular position of the rotor, and processing means adapted for processing both output signals to produce an angular position signal indicating the angular position of the steering shaft over a range greater than one full revolution.
• An absolute angle sensor can be provided on the motor shaft or on the steering column shaft, which is costly in the case of an absolute multi-turn sensor.
• an index can be provided on the steering shaft, or on the motor shaft. However, the index does not provide sufficient accuracy.
• EP 1 413 499 discloses an electric power steering provided with two sensors on the steering column and a sensor on the engine. Having three sensors is expensive and also requires a relatively sophisticated processing electronics.
• US 5,646,523 discloses an apparatus for determining the angular wheel steering position comprising a fine sensor and a coarse sensor associated with the steering column shaft, the thin sensor having quadruple reduction thanks to to gears for driving faster the corresponding encoder.
• This device is relatively complicated and does not know the position of the poles of the electric motor.
• US 6,248,993 discloses a steering angle sensor for determining the absolute steering angular position of a wheel, comprising two sensor units, one detecting the angular position in a corner segment of the complete steering rotation range, the other unit detecting the steering rotation through gears with a ratio other than 1, so that the rotational speeds detected by the two sensors are different for the purpose of detect an absolute angular position.
• this document does not make it possible to know the absolute angular position of the rotor of the electric drive motor.
• the abstract of JP 2005 053 416 discloses a steering apparatus for a fully electric steering type vehicle. The electric steering motor is associated with two gearboxes, one for the steering of the wheels and the other for the detection of the rotation with a rotation on a lap from a neutral position is a total rotation on two turns.
• the present invention aims to overcome the disadvantages and limitations of the above documents.
• the object of the present invention is to provide, by means of a single module, an absolute angular position of the shaft of the electric steering motor and the steering angle of the steering wheels.
• the steering angle of the steering wheels is uniquely related to the angular position of the steering column.
• the object of the present invention is to provide said angular positions by reliable and inexpensive means.
• the angular position detection device of an electric motor shaft with respect to a rotating element comprises a gearbox comprising an input rotatably connected to the shaft, and an output, so that the output of the gearbox moves on an angle less than 2 ⁇ , a single-turn angular position sensor being arranged to measure the angle of the output of the gearbox, and an angular position sensor being disposed on the input of the gearbox.
• a gearbox provided with an input angular position sensor and an output angular position sensor and capable, when mounted in a steering mechanism, of providing two signals making it possible to determine with a sufficient accuracy the angular position of the rotor of the electric motor and the angular position of the wheels.
• the gearbox with its two sensors forms a subassembly that can be mounted on a conventional electric power steering motor.
• the reducing ratio of the reducing agent can be between 5 and 100.
• the reducer comprises a rolling bearing and a housing.
• the rolling bearing may comprise an inner ring mounted on the shaft and an outer ring mounted in the housing.
• An encoder may be supported by the inner ring and cooperate with the angular position sensor.
• the single-turn sensor is an absolute angular position sensor.
• An absolute single-turn angular position sensor is significantly less expensive than a multiturn absolute angular position sensor.
• the single-turn sensor is mounted on an electronic card supported by a housing of the reducer. Both sensors can be mounted on the electronic board.
• An encoder can be mounted on a rolling bearing.
• the device comprises a rolling bearing comprising a rotating inner ring adapted to be mounted on the shaft and a non-rotating outer ring.
• the reducer comprises at least one epicyclic gear train. It is thus possible to obtain a reduction ratio of the order of 5 to 20.
• the reducer comprises at least one harmonic reducer. It is thus possible to obtain a reduction ratio of between 15 and 100.
• the output is sized in pairs for the device's own drag torque.
• the drag torque of the device may consist essentially of the drag torque of the rolling bearing of the gearbox and the drag torque of the gears of the gearbox.
• the drag torque of the device is very low.
• the input angular position sensor is capable of measuring a modulo 2 ⁇ angle. It is therefore possible to use an economic angular position sensor of absolute or incremental type.
• the shaft is bonded to a gear driven member with a reduction ratio of 1 to 5.
• the input angular position sensor comprises a multipole encoder.
• the angular position sensor may be radially outside the encoder.
• the single-turn angular position sensor may have an axial air gap with an encoder.
• the single-turn angular position sensor may be disposed radially outside the angular position sensor.
• a sensor may comprise one or more sensitive elements arranged facing an encoder element, for example one or more Hall effect cells arranged opposite a multipole magnetic encoder ring.
• the electric motor comprises a rotor, a stator, a shaft supporting the rotor and a device for detecting the angular position of the shaft relative to a non-rotating element.
• the reducer comprises an input rotatably connected to the shaft, and an output.
• the reduction ratio of the gearbox is chosen between 5 and 100 so that the output of the gearbox moves at an angle of less than 2 ⁇ .
• a single-turn angular position sensor is arranged to measure the angle of the output of the gearbox and an angular position sensor is disposed on the input of the gearbox.
• a power steering device may comprise an electric motor as above and a shaft driven by the electric motor is provided to cause steering of the wheels of a vehicle.
• a gearbox may include a reduction mechanism, an input, an output, a single-turn angular position sensor arranged to measure the angle of the output, and an angular position sensor disposed on the input, the reduction ratio of the reducer being chosen so that the output of the reducer moves on an angle less than 2 ⁇ .
• the reducer may comprise a rolling bearing and a housing, the rolling bearing comprising an inner ring adapted to be mounted on a shaft, an outer ring mounted in the housing, and an encoder supported by the inner ring and cooperating with the angular position sensor.
• FIG. 1 is an axial sectional view of a device angular position detection
• Figure 2 is an exploded perspective view of the device of Figure 1
• Figure 3 is a side elevational view of the device of Figure 1.
• the angular position detection device 1 is mounted on the shaft 2 of an electric motor.
• the shaft 2 also supports a pinion 3 keyed by a key 4 and for example intended to drive a complementary gear of a steering column.
• the detection device 1 comprises a gearbox 5, here harmonic type, a rolling bearing 6 and a detection part 7.
• the gearbox 5 which is here harmonic type comprises a ring 8 provided with an inwardly directed toothing, a flexible gear 9 radially meshing with the ring 8 in two diametrically opposed zones (see FIG. 3), and a generator of wave 10, mounted concentrically.
• the flexible gear 9 is provided with an axial inner surface.
• the wave generator 10 comprises a ring 1 1 whose bore is mounted on the shaft 2 integrally in rotation by means of a key 12. From the ring 1 1 extend radially towards the outside two arms diametrically opposed.
• the wave generator 10 comprises two support fingers 13 each mounted on an arm. The ring, the arms and the fingers can be monobloc.
• the wave generator 10 is completed by two smooth bearings 14 each mounted on a finger 13.
• the pads 14 are in contact with the inner surface of the flexible gear 9 which they cause the radial deformation by constraining said flexible gear 9 to come mesh in the toothing of the crown 8 in two diametrically opposite areas. It could be envisaged to replace the bearings 14 by bearings.
• the wave generator 10 is keyed on the shaft 2 by a key 12.
• the rolling bearing 6 is mounted on the shaft 2 axially between the pinion 3 and the gearbox 5.
• the rolling bearing 6 comprises an inner ring 15, for example fitted on the shaft 2, an outer ring 16, a row of rolling elements 17, here balls, maintained at regular circumferential spacing by a cage and a sealing flange 18 mounted in a groove of the outer ring 16 and forming a narrow passage with an axial bearing of the inner ring 15.
• the Rings 15 and 16 each have a raceway in the form of a toroidal portion for receiving the rolling elements 17.
• the rings 15 and 16 are of the deep groove type.
• the bearing 6 can be of a standard type mass produced economically.
• the detection device 1 comprises a housing 19, for example made of synthetic material, surrounding the gearbox 5 and the bearing 6.
• the housing 19 is annular and comprises an axial portion of small diameter 20 in the bore of which is rigidly fixed the outer ring 16 of the bearing 6.
• the axial portion of small diameter 20 is extended by a short radial flange 21 directed inwards and in contact with a front surface of the ring 16, thus forming an axial stop.
• the housing 19 also comprises a radial portion 22 extending outwardly from the end of the axial portion of small diameter 20 opposite to the radial flange 21 and having a substantially coplanar face with the radial front surfaces of the inner rings 15 and outer 16 of the bearing 6.
• the housing 19 comprises an axial portion of large diameter 23 extending axially opposite the pinion 3 from the end of large diameter of the radial portion 22.
• the ring 8 is integral with the axial portion of large diameter 23.
• the parts of the housing 19 and the ring 8 are made integrally, for example integrally molded.
• the housing 19 may be made of polyamide reinforced with a mineral filler.
• the detection part 7 is generally arranged in a space delimited axially on one side by the gearbox 5 and on the other side by the bearing 6, and radially on one side by the shaft 2 and on the other. another side by the large diameter axial portion 23 of the housing 29.
• the detection portion 7 comprises an electronic card 24 occupying a limited angular sector (see Figures 2 and 3), for example of the order of 90 ° and fixed against the internal radial face of the radial portion 22 of the housing 19 and in contact with the end face of the outer ring of the bearing 16 on the side of the gearbox 5.
• the electronic card can be fixed on the outer ring 16 and in contact with the housing 19.
• the electronic card 24 supports an electronic processing circuit 25 and two sensors 26 and 27, for example magnetosensitive type.
• the sensor 26 is fixed angularly substantially in the middle of the card 24 and radially at the level of the flexible gear 9.
• the sensor 27 is fixed angularly substantially in the middle of the card 24 and radially on its inner edge facing radially towards the inside. Thus the sensor 26 is disposed radially outside the sensor 27.
• the sensors 26 and 27 may each be optical or magnetic type. In what follows, we will consider the case of two sensors 26 and 27 magnetosensitive type.
• the detection part 7 comprises two annular encoders 28 and 29.
• the encoder 28 is in the form of a multipole ring of elongated rectangular section radially fixed, for example by gluing or overmoulding, to a radial face of the flexible gear 9, and facing the sensor 26 with a small axial gap.
• the encoder 28 having a rigidity lower than that of the flexible element 9 is capable of accompanying the radial deformations of said flexible gear 9 and of generating a magnetic signal in the sensor 26.
• the encoder 28 and the gear 9 could form a single piece.
• the encoder 29 is supported by the inner ring 15 of the bearing 6 and generates a magnetic signal in the sensor 27.
• the encoder 29 comprises a support 30, for example in the form of a sheet metal cup provided with an axial portion fitted on an outer surface of the inner ring 15, a radial portion in abutting contact against the radial end face of the inner ring 15 on the side of the reducer 5 and an axial portion of smaller diameter extending towards the reducer 5, and an active portion 31, for example of the plastoferrite type, overmolded on the support 29 by surrounding the axial portion of small diameter and a portion of the axial portion of large diameter and having an axial outer surface in front of the sensor 27 with a small radial air gap.
• the bearing 6 does not have a sealing flange on the encoder 29 side.
• the detection part 7 thus comprises the same electronic card supporting two sensors and an electronic circuit receiving the output signals of said sensors and capable of transmitting to the outside, for example by a wired or radio link, not shown, information representative of the absolute angular position of the shaft 2 and information relating to the steering angle.
• the electronic circuit 25 can transmit output signals from the sensors 26 and 27 after a simple shaping or, alternatively, carry out a treatment to determine with the desired accuracy the absolute angular position of the shaft 2 of the electric motor of a motor. on the basis of the information provided by the sensor 27 and, on the other hand, the steering angle of the vehicle wheels as a function of the output signal of the sensor 26 and the output signal of the sensor 27.
• the detection device 1 can therefore comprise a single bearing, a gearbox, two encoders, two sensors and a single electronic card supporting the sensors, which is particularly economical and compact.
• the Detection 1 forms a subset that can be easily assembled on an electric motor shaft end 2, for example between a steering column drive gear and the housing, not shown, of the motor.
• the shaft 2 of the electric motor is rotatable by driving the pinion 3, which actuates the steering device of the wheels, the shaft 2 of the motor being mechanically connected with the wheel alignment system so that that the reduction ratio between the angular displacement of the motor shaft 2 and the angular displacement of the steering column shaft is of the order of 10 to 20.
• the inner ring 15 of the bearing 6, and consequently the encoder 29, are driven at the same speed as the shaft 2.
• the angular displacement of the shaft 2 is thus detected by the sensor 27 and transmitted to the electronic circuit 25 for transmission to an external member and, where appropriate, treatment.
• the wave generator 10 of the gearbox 5 is also driven at the same speed of rotation of the shaft 2, which causes rotation of the flexible gear 9 with a reduction ratio of 5 to 100, preferably of In other words, the flexible gear 9 and the encoder 28 move by one degree of angle for 40 to 80 ° of displacement angle of the shaft 2.
• the angular displacement of the encoder 28 and the flexible gear 9 is detected by the sensor 26 and transmitted to the electronic circuit 25 for transmission to an external member and, where appropriate, treatment.
• the reduction ratio of the gearbox 5 is designed to be greater than or equal to the product of the gear ratio of the shaft 2 relative to at the steering column by the number of revolutions of the steering column from one stop to another, ie from the extreme steering position to the left at the extreme steering position to the right of the vehicle wheels .
• This ensures that the encoder 28 has a range of rotation less than 360 °. It is thus possible to use an encoder 28 and a monotour-type sensor 26 that is considerably more economical than a multiturn sensor.
• the resolution of the sensor 26 and the encoder 28 may be relatively small insofar as the precise angular position of the shaft 2 is provided by the sensor 27 and the encoder 29 while the sensor 26 and the encoder 28 only provide one. signal of lesser precision. Given the gear ratio offered by the gear 5, it is thus possible to determine an angular position of the steering column with a very good precision of the order of 0.1 °.
• the encoder 28 may be of the circumferentially alternating pole type or the quadrupole type with an outer north pole and an inner south pole on 180 ° and an inner north pole and an outer south pole on 180 °.
• the magnetic field seen by the sensor varies according to the angular position and the radial position of the encoder 28 taking into account the radial deformation of the flexible gear 9.
• the sensor 27 and the encoder 29 are multiturn type with high resolution or providing an absolute angle.
• the housing 19 is provided to be non-rotating, for example rotatably connected to the housing of the electric motor while one of the encoders is associated with the inner ring of the bearing and the other with the gearing. flexible gearbox.
• the encoder 29 may be mounted on the axial annular portion 1 of the wave generator 10 or directly on the shaft 2, which may make it possible to use a bearing of standard type with two sealing elements. also of standard type. There is thus a reducer whose crown can be provided to support the sensors, the bearing ensuring the concentricity of the crown and the shaft of the electric motor.
• dashed lines in FIG. 1 illustrate the housing 32 of the electric motor and the steering column 33. Thanks to the invention, it benefits from an extremely compact and economical device mounted as a subassembly on a fully electric electric steering or electric steering motor shaft and provided with an electronic card providing at the same time a signal representative of the precise angular position of the electric motor shaft and a signal representative of the steering angle of the wheels. Only two sensors can provide this data. In addition, other additional detection systems can be dispensed with, for example arranged on a steering column bearing or on a steering rack.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Power Steering Mechanism (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Steering Controls (AREA)
• Retarders (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2006
  • 2006-03-14 FR FR0602204A patent/FR2898676B1/fr not_active Expired - Fee Related
• 2007
  • 2007-03-13 JP JP2008558865A patent/JP4875111B2/ja not_active Expired - Fee Related
  • 2007-03-13 EP EP07731733A patent/EP1994369A2/fr not_active Withdrawn
  • 2007-03-13 WO PCT/FR2007/050917 patent/WO2007104890A2/fr active Application Filing
  • 2007-03-13 CN CNA2007800087408A patent/CN101400972A/zh active Pending

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