DE19802064B4 - Sensor magnet, in particular for position detection in combination with a sensor element, and magnetizing coil for its magnetization - Google Patents

Sensor magnet, in particular for position detection in combination with a sensor element, and magnetizing coil for its magnetization

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Publication number
DE19802064B4
DE19802064B4 DE1998102064 DE19802064A DE19802064B4 DE 19802064 B4 DE19802064 B4 DE 19802064B4 DE 1998102064 DE1998102064 DE 1998102064 DE 19802064 A DE19802064 A DE 19802064A DE 19802064 B4 DE19802064 B4 DE 19802064B4
Authority
DE
Germany
Prior art keywords
magnetization
sensor magnet
sensor
switching
characterized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
DE1998102064
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German (de)
Other versions
DE19802064A1 (en
Inventor
Martin Dr. Grönefeld
Jacek Dipl.-Phys. Krzywinski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WINDHORST BETEILIGUNGSGESELLSCHAFT MBH
WINDHORST BETEILIGUNGSGMBH
Original Assignee
WINDHORST BETEILIGUNGSGESELLSCHAFT MBH
WINDHORST BETEILIGUNGSGMBH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by WINDHORST BETEILIGUNGSGESELLSCHAFT MBH, WINDHORST BETEILIGUNGSGMBH filed Critical WINDHORST BETEILIGUNGSGESELLSCHAFT MBH
Priority to DE1998102064 priority Critical patent/DE19802064B4/en
Publication of DE19802064A1 publication Critical patent/DE19802064A1/en
Application granted granted Critical
Publication of DE19802064B4 publication Critical patent/DE19802064B4/en
Anticipated expiration legal-status Critical
Application status is Expired - Fee Related legal-status Critical

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01DMEASURING 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
    • G01D5/00Mechanical 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
    • G01D5/12Mechanical 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
    • G01D5/244Mechanical 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
    • G01D5/249Mechanical 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 pulse code
    • G01D5/2497Absolute encoders

Abstract

sensor magnet with magnetization pattern with at least two different widths Switching areas between the pole transitions one or more tracks for field generation for sampling in combination with a bipolar switching sensor, characterized in that each Switching area (1a, 1b) of the sensor magnet (1) in the middle between the pole transitions (2) has a greatly reduced magnetization and the magnetization in the area of pole transitions (2) the highest is and there as possible quickly reversing in the direction.

Description

  • The The invention relates to a sensor magnet according to the preamble of Claim 1 and further relates to a magnetizing coil for the Magnetization.
  • To the Detecting lengths, Angles and absolute positioning are used in measuring and automation technology so far mainly optical measuring systems used. Although these measuring systems have a high accuracy, they prove under harsh operating conditions as susceptible to failure. In the last Time is therefore attempted to such measuring systems on the basis of Form magnetic field sensors and multi-pole magnetized permanent magnet. The coding of the sensor magnets is carried out by means of an impressed north-south pole pattern on one or more tracks. The location of North and South Poland can evaluated with one or more digital magnetic field sensors become. However, practice has shown that when not symmetrically magnetized Permanent magnets (wide and narrow north or south poles as immediate or indirect neighbors) there is a shift in field strength and the steepness of the flanks of the induction curve in a defined Distance (position of the sensor) comes in the area of north-south transitions.
  • aggravating is added that the for use coming magnetic field sensors a switching hysteresis own and thus also a certain inaccuracy in the evaluation cause the position. These physical processes have one direct influence on the accuracy and use of such positioning systems.
  • by virtue of the switching hysteresis, this magnetization should be as possible huge Field gradients nearby have the switching sensitivity of the sensor magnet.
  • In addition to this It should be noted that in increasing Dimensions of permanent magnets in combination with a sensor element (eg Hall sensor, field plate, GMR or GIANT MAGNETO RESISTANT sensor or similar) can be used for position detection. This can be a linear displacement between magnet and sensor or even a rotary motion of a magnet rotor at the front or lateral magnetization.
  • The European patent application EP 0 718 494 A2 relates to an apparatus for magnetizing a magnetic material for producing magnetic poles of nonuniform strength in a magnetic encoder. The described magnetization device is designed such that in the magnetization pattern of the coder the north pole is symmetrical with the maximum magnetization in the middle between the pole junctions, while the maximum magnetization of the south pole is shifted towards a pole transition.
  • at Many applications have high accuracy requirements the position of the pole transition posed. This transitional sharpness will generally determined by the accuracy of the magnetizing coil.
  • In some cases are instead of regular switching patterns same pole width irregular switching pattern demanded, that is the width of the poles, about which the switching state of the sensor defined on or off is, varies from pole to pole. Even with arbitrary exact magnetization This is by the law the stray fields magnetostatically the zero crossing of the detected induction between the poles opposite moved the magnetization change. The shift is down other from the measuring distance so that too with exact magnetization the switching points opposite to their ideally located. The same problem occurs multi-track magnetizations on which the poles of the neighboring tracks the zero crossing over to move a track.
  • Of the Invention is based on the object, the magnetization of the sensor magnet to influence in the development of such positioning systems so that these Displacement is reasonably least, and a magnetization in which the stray field effect of wide poles is only marginal near located Polübergänge acts.
  • According to the invention this task is solved by that everybody Switching range of the sensor magnet in the middle between the pole transitions has greatly reduced magnetization and the magnetization is highest in the area of pole transitions and there as possible quickly reversing in the direction.
  • Especially advantageous developments of the invention are in the claims 2 to 9 marked while claim 10 to a magnetizing coil for magnetizing Sensor magnet is directed according to the invention.
  • to Detection of the magnetization according to the invention bipolar switching sensors are particularly suitable in which the switching states switch to fields of opposite sign. These sensors have a switching hysteresis that covers the zero crossing, this means the switching state of the sensor remains at the fall of the field to a even received small field value of opposite sign.
  • One Another advantage of this magnetization is that for magnetization the permanent magnets used relatively simple coils are used can, there fields in the order of magnitude the saturation fields be required only in the region of the pole transitions Magnetisierpuls. The power conductors have to so that the entire pole area does not necessarily enclose.
  • The magnetic preferred direction of the magnetic material can be in either Moving direction or perpendicular to the direction of movement. Such Sensor magnets can also be formed multi-track and as part of a switching unit be used in combination with a bipolar magnetic field sensor.
  • A Magnetizing coil for magnetizing such sensor magnets also stands out especially in that the Current conductor of the magnetizing coil, the Polbereiche not completely and tightly enclose.
  • When especially beneficial for both the magnetization as well the sampling of such sensor magnets has been found when the Magnetization of the sensor magnet within the wider switching ranges between the pole transitions less than 60% of the absolute magnetization decreases near the pole junctions. The magnetization can be in the middle of the wider switching ranges almost disappear and go back below 10% of the saturation magnetization.
  • Such Sensor magnets can advantageously as a rotor magnet with frontal magnetization or as a rotor magnet with magnetization on the outer circumference be educated. Deviating configurations come according to Use and purpose as well in question.
  • The The invention will be apparent from the accompanying schematic drawings explained in more detail. In show the drawing
  • 1 a conventionally magnetized sensor magnet with four opposing poles of different widths and the induction measured above, as well as the resulting switching states of a bipolar sensor with the corresponding switching thresholds,
  • 2 a sensor magnet magnetized according to the invention, in which the pole transitions were generated by three individual conductors,
  • 3 the magnetization in a sensor magnet having anisotropic orientation in the direction of displacement, with the same magnetization as in 2 in which the sensitivity of the sampled signal to interference fields is reduced,
  • 4 a corresponding sensor magnet to 2 and 3 in the preferred direction perpendicular to the surface, whereby the switching sharpness and accuracy is positively influenced,
  • 5 the current path between current input and current output of a coil for 7-track recording of a digital pattern for the rotational position detection of a disk in the case of an end-side scanning,
  • 6 one with the coil of 5 magnetically magnetized rotor magnet and
  • 7 a magnetized on the periphery rotomagnet with associated bipolar switching sensors that can be configured as a Hall sensor, field plate or GMR sensor.
  • In the 1 to 4 shown sensor magnets 1 have magnetization patterns with at least two different width switching ranges 1a . 1b between the pole transitions 2 on one or more tracks for field generation for sampling in conjunction with a bipolar switching sensor.
  • At the sensor magnet 1 from 1 It is a conventional magnetized magnet with four poles 3 opposite polarity 4 , being about the four poles 3 the magnetic flux density "B" is plotted in conjunction with the level "a" for turning ON a bipolar switch and the level "b" for turning OFF such a bipolar switch. The resulting ON or OFF switching states are shown above, and it is particularly noticeable that the ON and OFF switching points E and A are opposite the zero crossing at the pole junctions 2 between the different wide switching ranges 1a . 1b with opposite polarity 4 with an amount X A or X E are shifted relatively strong.
  • The size of the shift X A and X E depends inter alia on the measuring distance, so that even with exact magnetization, the switching points E and A between the poles 3 shifted from their ideal position. The same problem occurs in multi-track magnetizations in which the poles of the neighboring tracks shift the zero crossing over a track.
  • To the shift at the pole transitions 2 As low as possible, therefore, according to the embodiments of the invention 2 to 4 every switching range 1a . 1b of the sensor magnet 1 in the middle between the pole crossings 2 a greatly reduced magnetization, so that the Magnetization in the area of pole transitions 2 is highest and reverses as quickly as possible in the direction.
  • It has proved to be particularly advantageous for the highest possible switching accuracy if the magnetization of the sensor magnet 1 within the wider switching ranges 1b between the pole transitions 2 to less than 60% of the absolute magnetization near the pole junctions.
  • The magnetization can also be in the middle of the wider switching ranges 1b almost disappear and go back below 10% of the saturation magnetization.
  • Such conditions are in the magnetized according to the invention sensor magnet of 2 to 4 given.
  • At the sensor magnet 1 from 2 became the pole crossings 2 with the magnetization directions shown there 4a generated by three individual conductors. The magnetic flux density "B" lies in the middle part between the pole junctions 2 just above the zero crossing between the two levels "a" and "b" for the ON and OFF switching of a bipolar switch and only increases in the immediate vicinity of the pole transitions 2 on the relevant level, so that the ON and OFF switching points E and A of the bipolar switch always in a consistently small distance X a , X e , with respect to the Polübergängen 2 are shifted.
  • In the embodiment of 3 are practically the same conditions as in the sensor magnet 1 from 2 before, except that in this second sensor magnet 1 the magnetic preferred direction of the magnetic material is in the direction of movement and has an anisotropic orientation in the direction of displacement. The sensitivity of the sampled signal to interference fields is thereby reduced.
  • Also in this type of magnetization, the magnetic flux density "B" moves in the middle part of the different width switching ranges 1a . 1b in the immediate vicinity of the zero crossing between levels "a" and "b" for turning ON and OFF a bipolar switch to close at the highly magnetized pole junctions 2 suddenly rise and reverse as quickly as possible in the direction, which is a very small shift of the switching points E and A of the bipolar switch against the pole transitions 2 entails.
  • This also applies to the in 4 shown third magnetization of such a sensor magnet 1 with different wide switching ranges 1a . 1b and a very small magnetization in the middle part between the pole junctions 2 , This sensor magnet 1 has a magnetization of the magnetic material in the preferred direction 4c perpendicular to the direction of movement in the immediate vicinity of the pole transitions 2 , As a result, the switching sharpness and accuracy of a bipolar switching sensor, such as a Hall sensor, a field plate, a GMR sensor or the like, also positively influenced, such as the course of the magnetic flux density "B" in 4 and the above curve for the switching points ON and OFF or E and A of such a switch or sensor can be seen. Such sensor magnets may be multi-tracked.
  • In 5 is the power path 5 between power input 5a and current output 5b a coil 6 for the seven-track recording of a digital pattern for the rotational position detection of a disk in frontal scanning shown. The winding of the coil 6 is arranged so that in the frontal magnetization of a rotor magnet 10 , as in 6 shown, an alternating succession of NORTH and SOUTH poles N and S results, the tightly packed in the outer part immediately adjacent to each other and increase towards the center in size and decrease in number accordingly, so that finally only in the middle part two NORD- and two SOUTH poles N and S diametrically opposite each other and offset by 180 ° to each other, wherein at all NORD and SÜD poles of different widths each of the middle part between the pole junctions magnetized very low and the magnetization in the pole junctions is highest and there, as in the embodiments of 2 to 4 shown, reversed as quickly as possible in the direction. For better clarity are in the rotor magnet 10 from 6 the NORTH and SOUTH poles N and S are complete only in the upper right quadrant and only partially in the remaining quadrants.
  • This type of magnetization on such a rotor magnet with frontal magnetization is in 7 in one opposite 6 shown enlarged view. The dash-dot line indicates this 7a each the edge region of the maximum flux density at the NORD poles and the dashed line 7b the range of maximum flux density at the SOUTH poles. The current conductors of the magnetizing coil of 5 are arranged for this kind of magnetization so that they do not completely and tightly enclose the pole regions N and S on the disk-shaped or cylindrical sensor magnet to be magnetized. This can be easily determined by the representation of the magnetizing coil 6 from 5 with the rotor magnet 10 from 6 is brought to cover.
  • In the further embodiment of 8th it is a magnetized on the outer circumference rotor magnet 11 with with a plurality of switching areas of different widths and these associated bipolar switching sensors 12 , which can be designed either as a Hall sensor, field plate, GMR sensor or similar.
  • Again, the NORTH and SOUTH poles have a similar sequence and different widths as in the front-side magnetization of the rotor magnet 10 from 7 , The dash-dotted lines 7a show the regions of maximum magnetic flux density of the NORD poles at the pole junctions and the dashed lines 7b the area of the maximum flux density of the south poles in each case in the immediate vicinity of Polübergänge.
  • In addition to the magnetized on the outer circumference sensor magnet 1 There are several bipolar switching magnetic field sensors 12 for scanning the different width switching ranges of the sensor magnet with the greatly reduced magnetization in the middle of each switching range between the edge magnetizations 7a . 7b , which is highest in the area of the pole transitions and thus only in very narrow, narrow areas and reverses there as quickly as possible in the direction. The magnetic field sensors 12 can, as already mentioned above, each optionally Hall sensors, field plates, GMR sensors or similar components.
  • 1
    sensor magnet
    1a
    switching range
    1b
    switching range
    2
    pole transitions
    3
    Pole
    4
    polarity
    4a
    magnetization direction
    4b
    magnetic preferred direction
    4c
    magnetic preferred direction
    5
    current path
    5a
    current input
    5b
    current output
    6
    magnetizing
    7a
    dot-dash Line =
    Area the maximum flux density at the NORD Poland
    7b
    dashed Line =
    Area the maximum flux density at the SOUTH Poland
    10
    rotor magnet
    11
    rotor magnet
    12
    bipolar Magnetic field sensors
    B
    magnetic flux density
    "A"
    level for the Turning ON a bipolar switch
    "B"
    level for the Turning off a bipolar scaler
    e
    ON switching point
    A
    OFF switching point
    X A
    amount a shift of the OFF switching point
    X E
    amount a shift of the ON switching point
    N
    North Pole
    S
    South Pole

Claims (10)

  1. Sensor magnet having a magnetization pattern with at least two differently wide switching ranges between the pole transitions on one or more tracks for field generation for scanning in conjunction with a bipolar switching sensor, characterized in that each switching range ( 1a . 1b ) of the sensor magnet ( 1 ) in the middle between the pole transitions ( 2 ) has a greatly reduced magnetization and the magnetization in the region of the pole junctions ( 2 ) is highest and reverses as quickly as possible in the direction.
  2. Sensor magnet according to claim 1, characterized in that the magnetization of the sensor magnet ( 1 ) within the wider switching ranges ( 1b ) between the pole transitions ( 2 ) to less than 60% of the absolute magnetization near the pole junctions ( 2 ) goes back.
  3. Sensor magnet according to claim 1 or 2, characterized in that the magnetization in the region of the middle of the wider switching areas ( 1b ) almost disappears, that is less than 10% of the saturation magnetization.
  4. Sensor magnet according to one of Claims 1 to 3, characterized in that it is in the form of a rotor magnet ( 10 ) is formed with frontal magnetization.
  5. Sensor magnet according to one of Claims 1 to 3, characterized in that it is in the form of a rotor magnet ( 11 ) is formed with magnetization on the outer circumference.
  6. Sensor magnet according to one of claims 1 to 5, characterized in that the magnetic preferred direction ( 4b ) of the magnetic material in the direction of movement.
  7. Sensor magnet according to one of claims 1 to 5, characterized in that the magnetic preferred direction ( 4c ) of the magnetic material is perpendicular to the direction of movement.
  8. Sensor magnet according to one of claims 1 to 7, characterized in that it is multi-tracked is trained.
  9. Sensor magnet according to one of Claims 1 to 8, characterized in that it is part of a switching unit in combination with a bipolar magnetic field sensor ( 12 ).
  10. Magnetizing coil for magnetizing a sensor magnet according to one of Claims 1 to 9, characterized in that the current conductors (current path 5 ) of the magnetizing coil ( 6 ) do not completely and tightly enclose the pole regions (N and S).
DE1998102064 1998-01-21 1998-01-21 Sensor magnet, in particular for position detection in combination with a sensor element, and magnetizing coil for its magnetization Expired - Fee Related DE19802064B4 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE1998102064 DE19802064B4 (en) 1998-01-21 1998-01-21 Sensor magnet, in particular for position detection in combination with a sensor element, and magnetizing coil for its magnetization

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Application Number Priority Date Filing Date Title
DE1998102064 DE19802064B4 (en) 1998-01-21 1998-01-21 Sensor magnet, in particular for position detection in combination with a sensor element, and magnetizing coil for its magnetization

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DE19802064A1 DE19802064A1 (en) 1999-07-22
DE19802064B4 true DE19802064B4 (en) 2007-05-24

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Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19944203A1 (en) * 1999-09-15 2001-03-22 Zahnradfabrik Friedrichshafen Means for detecting a position of a control element
DE102007063006A1 (en) * 2007-12-21 2009-06-25 Baumer Holding Ag Method and device for producing a material measure for position measuring systems and material measure

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0303676B1 (en) * 1987-02-24 1991-03-20 Renishaw plc Scales for position determining apparatus
US5117183A (en) * 1990-02-21 1992-05-26 The Torrington Company Asymmetric magnetization fixture
US5519393A (en) * 1993-07-22 1996-05-21 Bouens, Inc. Absolute digital position encoder with multiple sensors per track
EP0718494A2 (en) * 1990-02-21 1996-06-26 Snr Roulements Asymmetric magnetization fixture
DE19534995A1 (en) * 1995-09-21 1997-03-27 Bosch Gmbh Robert Sensor for steering angle detection
DE69312109T2 (en) * 1992-02-13 1998-01-08 Japan Servo absolute encoder

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0303676B1 (en) * 1987-02-24 1991-03-20 Renishaw plc Scales for position determining apparatus
US5117183A (en) * 1990-02-21 1992-05-26 The Torrington Company Asymmetric magnetization fixture
EP0718494A2 (en) * 1990-02-21 1996-06-26 Snr Roulements Asymmetric magnetization fixture
EP0443938B1 (en) * 1990-02-21 1997-04-16 Snr Roulements High resolution sensor system for internal combustion engines
DE69312109T2 (en) * 1992-02-13 1998-01-08 Japan Servo absolute encoder
US5519393A (en) * 1993-07-22 1996-05-21 Bouens, Inc. Absolute digital position encoder with multiple sensors per track
DE19534995A1 (en) * 1995-09-21 1997-03-27 Bosch Gmbh Robert Sensor for steering angle detection

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