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
  • G01D5/24404—Interpolation using high frequency signals

Definitions

• the object of the invention relates to the technical field of magnetic sensors, of the type comprising an encoder element moving close to a detection cell and adapted to locate at least one angular position in the general sense.
• the object of the invention finds a particularly advantageous application in the automotive field where such a sensor can be used, for example, in the context of ignition functions.
• a magnetic sensor adapted to measure the change in the intensity of a magnetic field
• an encoder provided with a series of elements generating a variable magnetic field
• the detection cell such as for example a Hall effect or magneto-resistive probe
• the detection cell is associated with a hysteresis level comparator, such as a Schmitt trigger, in order to obtain frank transitions of the output voltage for distinct values of the magnetic field, depending on whether it varies in increasing or decreasing.
• the generating elements consist of elements disturbing a magnetic field created by a fixed magnet placed near such disturbing elements.
• such disturbing elements are constituted by teeth arranged in a ferromagnetic ring.
• the elements generating a variable magnetic field are formed by magnetic poles, regularly spaced at a given pitch.
• Such an encoder is thus in the form of a multipolar magnetic ring.
• an encoder produced in the form of a multipolar magnetic ring it can be envisaged either to delete several magnetic poles leaving an empty space, or to replace one or more poles with a sign given by one or more poles of a contrary sign. There is thus produced a given magnetization pole having, between its two adjacent poles of an opposite sign, a different spacing with respect to the spacing pitch of the other poles.
• the usual resolution of the sensors is currently 60-2 pulses per revolution. This level of performance is traditionally obtained using an encoder comprising 60-2 pairs of magnetic poles or 60-2 ferromagnetic teeth and associated with a detection cell delivering a pulse per pair of poles or per tooth.
• the object of the invention aims to remedy the drawbacks stated above by proposing a sensor having a high resolution while presenting an encoder retaining a limited diametral size.
• the object of the invention thus aims to propose a sensor delivering an electrical signal whose resolution is much higher than the resolution of the encoder.
• the object of the invention relates to a sensor comprising at least one rotary magnetic encoder of the type comprising a circular magnetic track formed by a series of elements generating a variable magnetic field, distributed to form P pairs of elements with a period mechanical equal to 360 ° / P, the magnetic track being intended to pass in front of 2n offset detection cells to deliver periodic electrical signals Si (with i varying from 1 to 2n) electrically phase shifted between them by a value equal to l / 2n times the value of the mechanical period and corresponding to the change in the intensity of the magnetic field generated by the elements, the detection cells being connected to means for processing the phase-shifted electrical signals.
• Another object of the invention relates to a sensor, the magnetic track of which comprises elements generating a variable magnetic field, formed by elements disturbing a magnetic field created by a fixed magnet placed nearby.
• the sensor track is formed from an elastomeric or plastic ring loaded with magnetized particles to form the magnetic poles, the ring being mounted on a support ring.
• the senor comprises a low resolution encoder forming a multipolar magnetic ring comprising a series of elements generating a variable magnetic field having a different spacing to form pairs of irregular elements, the low resolution encoder being intended to scroll in front of a detection cell.
• the encoder, and possibly the low resolution encoder are mounted on a target locked in rotation on a shaft of an engine of a motor vehicle " the " 2n cells " ⁇ die “ d ⁇ t ⁇ ctîôn ⁇ t évélTtùèil ⁇ m ⁇ ht " the detection cell for the low resolution coder, being mounted in relation to said coders.
• the target has a peripheral wall and a transverse wall each intended to receive an encoder.
• the target forms a drive pulley.
• the drive pulley is a crankshaft pulley.
• the drive pulley is a cam pulley.
• the target is rotated by a shaft of the gearbox of a motor vehicle.
• the target is mounted inside a support plate of a dynamic seal, mounted in proximity relationship of 2n detection cells, and between the crankshaft and the gearbox of motor vehicle engine speeds.
• the target is rotated by the crankshaft or the camshaft, while being mounted inside the engine block of a motor vehicle and in proximity relationship of 2n cells detection.
• the fig. 1 is a schematic view showing a first embodiment of a sensor according to the invention.
• the fig. 2 shows the shape of the electrical signals obtained and delivered by a position sensor illustrated in FIG. 1.
• the fig. 3 shows the form of the electrical signals obtained and delivered by a second embodiment of a sensor according to the invention.
• the figs. 4 and 5 are views of examples of mounting an encoder according to the invention.
• the figs. 6 and 7 are respectively sectional elevation and perspective views of a complete sensor incorporating high resolution and low resolution encoders.
• the fig. 1 illustrates a first preferred embodiment of a rotary magnetic encoder 1 according to the invention.
• the encoder 1 comprises a circular magnetic track 2 intended to pass in front of 2n detection or measurement cells 3i with n> 1 and with i varying from 1 to 2n, to form a position sensor 4. In the example illustrated in FIG. . 1, the encoder 1 scrolls past four detection cells, respectively 3 ⁇ to 3, (n - 2).
• the magnetic track 2 comprises a series of generating elements 5 of a variable magnetic field, distributed over the circular track to form P pairs of elements 5, with a mechanical period T equal to 360 ° / P.
• the elements generating a variable magnetic field 5 are formed by alternating magnetic poles, so that the magnetic track is constituted by a multipolar magnetic ring.
• the magnetic track of the encoder 1 comprises a series of south poles and north poles arranged to present a regular pitch of spacing between two adjacent poles.
• the magnetic track 2 with elements generating a variable magnetic field 5, formed by elements disturbing a magnetic field created by a fixed magnet, placed near said magnetic track.
• the disturbing elements can be formed by means of teeth arranged in a ring made of ferromagnetic material.
• the magnetic track 2 comprises at least one generating element, said irregular not shown, having a different spacing with respect to the spacing pitch between the other generating elements 5.
• the irregular generating element has a double angular pitch compared to the other generating elements 5.
• the presence of such an irregular generating element constitutes a reference for the magnetic encoder making it possible to determine at least one angular position.
• the annular magnetic track 2 is intended to pass in front of the 2n fixed detection cells 3i which each deliver a periodic analog electrical signal If corresponding to the evolution of the intensity of the magnetic field delivered by the generating elements 5.
• the detection cells 3i are angularly offset between them so that the relative angular offset between the generator elements 5 and the cells 3; is suitable for obtaining 2n electrical signals If electrically phase shifted between them by a value equal to l / 2n times the value of the mechanical period T.
• the detection cells 3i are thus offset in a direction parallel to a direction perpendicular to the axis of rotation ⁇ of encoder 1.
• each detection cell 3j is associated with means, not shown, for processing the phase-shifted electrical signals S, with a view to increasing the resolution of the sensor.
• the processing means comprise means for extracting from each differential signal Sd p , two pulses spaced from T / 2 in order to obtain a digitized signal S s comprising 2n pulses phase shifted by T / 2n.
• the extraction means detect the zero crossing of each differential signal Sd p so that on each zero crossing there corresponds a pulse. It should be understood that such a sensor comprising the processing means described above makes it possible to increase the resolution of the sensor by 2n times without increasing the diametral dimension of the encoder 1. Thus, when the resolution of the encoder is 360 ° / P, the resolution of the associated sensor is 360 ° / 2nP.
• the number P pairs of generator elements 5 is equal to 90 or 60 for example, the sensor has a resolution of 2 ° and 3 ° respectively.
• the magnetic track 2 is formed from an elastomeric or plastic ring loaded with magnetized particles to form the magnetic poles.
• This elastomer ring can be mounted on a support ring, not shown.
• the encoder 1, as described above, is intended to be mounted, being attached or integrated, on a rotating target 6 in the general sense, from which at least one position is determined.
• the description which follows illustrates various variants for mounting the encoder 1 on a rotating target 6.
• the encoder 1 is intended to be mounted on a drive pulley mounted at the outlet of the engine of a motor vehicle, that is to say on a timing pulley or on one auxiliary pulleys.
• the encoder 1 is mounted on the drive pulley 6 located in the axis of the crankshaft, in order to allow detection of the neutral point or of ignition of a cylinder.
• the encoder 1 which consists of a multipolar magnetic ring, is mounted on the internal radial wall or hub 7 (fig. 4) or on the external radial wall 8 (fig. 5) of the pulley d 'drive 6.
• the magnetic multipole elastomer ring is mounted either directly on the pulley 6 which constitutes, by its radial wall a support ring, or indirectly by its support ring which is fixed, by any suitable means, on the pulley.
• the detection cells 3i for example Hall effect, are mounted in the clearance defined between the outer 8 and inner 7 radial walls of the pulley.
• the position sensor comprises, as a drive pulley, a crankshaft pulley provided with a magnetic ring adapted to locate a single position.
• the subject of the invention can, possibly, be applied to the production of a sensor comprising a magnetic encoder 1 provided with several irregular poles, making it possible to identify several positions.
• the magnetic encoder 1 comprises, for example, four irregular poles making it possible to identify the position of the cylinders of an engine.
• the encoder 1 is mounted integral with the camshaft of a motor vehicle engine.
• the encoder 1 can be mounted on the camshaft by having a single irregular pole.
• the encoder 1 according to the invention is intended to be mounted inside a support plate of a dynamic seal for a drive shaft between the crankshaft and the gearbox of an engine of a motor vehicle. Encoder 1 is rotated by the drive shaft and is mounted in proximity relationship of 2n cells 3i detection mounted on the gasket support plate, to form a position sensor.
• the encoder 1 according to the invention is rotated by a shaft of the gearbox of a motor vehicle.
• the encoder 1 according to the invention is rotated by the crankshaft or the camshaft of an engine of a motor vehicle, while being mounted inside the engine block of such a vehicle, in proximity relation of 2n detection cells 3i, in order to constitute a position sensor.
• the sensor 4 according to the invention described above is a so-called high resolution sensor.
• a sensor 4 can comprise, in accordance with FIGS. 6, 7, in addition, a low resolution encoder l 'forming a multipolar magnetic ring comprising a series of generating elements 5 of a variable magnetic field having a different spacing to form P pairs of irregular elements.
• the low resolution encoder 1 ' is intended to pass in front of a detection cell V.
• the generator elements 5 can be formed, as explained above, by elements disturbing a magnetic field or by magnetic poles.
• the low resolution encoder is mounted on the target 6 on which is already mounted the high resolution encoder 1.
• This target generally constituted in the form of a ring, has a radial or peripheral wall 6 ⁇ and a transverse wall 6 2 each intended to receive an encoder 1, l '.
• the invention is not limited to the examples described and shown since various modifications can be made without departing from its scope.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-12-11 FR FR0215628A patent/FR2848663B1/fr not_active Expired - Lifetime
• 2003
  • 2003-12-11 WO PCT/FR2003/003670 patent/WO2004055482A1/fr not_active Application Discontinuation
  • 2003-12-11 EP EP03813162A patent/EP1570238A1/de not_active Withdrawn
  • 2003-12-11 AU AU2003296816A patent/AU2003296816A1/en not_active Abandoned

Non-Patent Citations (1)

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