WO2017082831A1 - Magnetic rotary displacement encoder with a protected elasto-ferrite layer - Google Patents

Magnetic rotary displacement encoder with a protected elasto-ferrite layer Download PDF

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Publication number
WO2017082831A1
WO2017082831A1 PCT/SI2016/000023 SI2016000023W WO2017082831A1 WO 2017082831 A1 WO2017082831 A1 WO 2017082831A1 SI 2016000023 W SI2016000023 W SI 2016000023W WO 2017082831 A1 WO2017082831 A1 WO 2017082831A1
Authority
WO
WIPO (PCT)
Prior art keywords
layer
elasto
ferrite
encoder
rotary displacement
Prior art date
Application number
PCT/SI2016/000023
Other languages
French (fr)
Inventor
Branko Cvetkovic
Ljubo Slabajna
Janez Novak
Matjaz Sivec
Original Assignee
Rls Merilna Tehnika D.O.O.
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 Rls Merilna Tehnika D.O.O. filed Critical Rls Merilna Tehnika D.O.O.
Publication of WO2017082831A1 publication Critical patent/WO2017082831A1/en

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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
    • G01D5/14—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
    • G01D5/20—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 by varying inductance, e.g. by a movable armature
    • 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
    • G01D5/24428—Error prevention
    • G01D5/24433—Error prevention by mechanical means
    • G01D5/24438—Special design of the sensing element or scale
    • 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
    • G01D2205/80—Manufacturing details of magnetic targets for magnetic encoders

Definitions

  • the object of the invention is a magnetic rotary displacement encoder with a protected elasto-ferrite layer.
  • a position encoder is a device that senses a physical change that appears in linear or rotary displacement and translates it to an analogue or digital electrical signal. Generally, it consists of two parts that move relative to each other: a data carrier and a reading head that contains sensors for detecting physical changes upon its displacement along the data carrier. As to the basically applied principle of sensing a physical change, encoders can be magnetic, optical, capacitive, inductive, and others. Encoders can be rotary encoders measuring an angle, or linear encoders measuring distance.
  • the invention relates to rotary type magnetic encoders.
  • Data carriers of magnetic encoders are:
  • the task and the goal of the invention are to provide for high rotation speed of rotary encoders with elasto-ferrite carriers of magnetic recordings, and at the same time their protection against harmful influences of vapours of cooling lubricants.
  • the task of the invention is solved by a protective layer applied over an elasto-ferrite carrier.
  • a rotary encoder i. e. a magnetic data carrier
  • a rotary encoder is a ring that is put onto a shaft that rotates and allows measurement of a position, i. e. an angle or revolution speed, i. e. angular velocity of this shaft.
  • the encoder consists of layers.
  • a layer 2 is a known layer of an elasto-ferrite carrier and is applied onto the metallic first layer 1 in known ways.
  • a protective layer 3 is applied over the layer 2 of the elasto-ferrite carrier.
  • the layer 3 covers only an external wall of the layer 2 of the elasto-ferrite carrier.
  • the protective layer 3 of the embodiment is made from stainless steel; its thickness is smaller than the width of the magnetic poles in the elasto-ferrite layer 2 by one order of magnitude, i. e. an order lOx, which practically means 50 to 100 micrometres.
  • Other metals can be used instead of stainless steel, e. g. brass or bronze.
  • the material of the layer 3 is not ferromagnetic.
  • a ferromagnetic material is acceptable only as a very thin layer that is thinner than the non-ferromagnetic variant by an order of 5-10x.
  • the layer 3 is made as follows: a metallic strip is first cut to a selected length, both ends are then joined to a ring and butt-welded with a fibre laser for instance.
  • the length, at which the strip is cut, is selected in a way that, after the strip is welded into a ring, the inner diameter of the layer 3 is slightly smaller than the outer diameter of the elasto-ferrite layer 2.
  • the metallic layer 1 with the elasto-ferrite layer 2 is cooled while the protective layer 3 is heated.
  • the inner diameter of the layer 3 is larger than the outer diameter of the elasto-ferrite layer 2 due to thermal expansion, the ring is put onto the elasto-ferrite layer 2. Once the temperatures get equalized, the protective layer 3 tightly envelops the elasto-ferrite layer 2.
  • the protective layer 3 is preferably from metal; ratios as specified in the description of the embodiment hold true for the metallic layer 3.
  • the protective layer 3 can be made from a suitable non-metallic material.
  • the second embodiment of Figure 3 is identical to the first embodiment of Figure 2, only that the protective layer 3, after having been assembled onto the layer 2, is bent 4 over a side edge of the layer 2 of the elasto-ferrite carrier. Conventional methods of plastic deformation of metals are used for bending, for instance a bending moment.
  • the third embodiment of Figure 4 is identical to the first embodiment of Figure 2 and the second embodiment of Figure 4, except that the protective layer 3 is bent over a side wall of the layer 2 of the elasto-ferrite carrier and approximately up to a half 9 of a side wall of the first layer 1.
  • the protective layer 3 is welded onto the layer 1 at a position of the half 9. This weld continues over the entire circumference of the ring, such that the layer 2 is impermeably protected from the environment.
  • the protective layer 3 is butt- welded or welded with overlaped joints preferably by a fibre laser.

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

Abstract

The object of the invention is a magnetic rotary displacement encoder with a protected elasto-ferrite layer. A position encoder is a device that senses a physical change that appears in linear or rotary displacement and translates it to an analogue or digital electrical signal. The encoder of the invention is characterized in that at least over an external wall of a layer (2) of the elasto-ferrite carrier a protective layer (3) made from a non-ferromagnetic material is applied having a thickness of an order of magnitude of 10x smaller than the width of magnetic poles in the elasto-ferrite layer (2), or made from a ferromagnetic material having a thickness of an order of magnitude of 5-10x smaller than the thickness of the layer (3) made from a non-ferromagnetic material.

Description

MAGNETIC ROTARY DISPLACEMENT ENCODER WITH A PROTECTED ELASTO-FERRITE LAYER
The object of the invention is a magnetic rotary displacement encoder with a protected elasto-ferrite layer.
A position encoder is a device that senses a physical change that appears in linear or rotary displacement and translates it to an analogue or digital electrical signal. Generally, it consists of two parts that move relative to each other: a data carrier and a reading head that contains sensors for detecting physical changes upon its displacement along the data carrier. As to the basically applied principle of sensing a physical change, encoders can be magnetic, optical, capacitive, inductive, and others. Encoders can be rotary encoders measuring an angle, or linear encoders measuring distance.
The invention relates to rotary type magnetic encoders.
Data carriers of magnetic encoders are:
- from ferrite ceramics:
- drawbacks: fragility, due to which shrink-fitting is impossible;
- advantages: simplicity, magnetic pole widths are of an order of magnitude of mm which provides for a larger distance between a reading head and rings, low production cost, low price, allow high resolution;
- with metallic carriers:
- drawbacks: expensive materials, thermal treatment is needed to reach magnetic properties, low widths of magnetised poles (order of magnitude of 0.1 mm) and thus a short sensing distance, sensitivity to superficial damages;
- advantages: long-term metrological stability, high accuracy, high resolution. - with gear wheels:
- drawbacks: low resolution, high interpolation error, loudness of a sound, high initial production cost due to expensive tools, a permanent magnet in a reading head, due to which the reading head is larger, a magnetic field shield is needed for the magnet not to attract filings, ...
- advantages: simplicity, high speeds.
- with elasto-ferrite carriers
- drawbacks: unreachably high speeds (>20,000 RPM), a binding material (NBR, HNBR...) ages rapidly due to vapours of cooling lubricants;
- advantages: simplicity, high resolution, magnetized poles have widths of an order of magnitude of mm and therefore a distance between a reading head and rings can be longer, low production cost.
The task and the goal of the invention are to provide for high rotation speed of rotary encoders with elasto-ferrite carriers of magnetic recordings, and at the same time their protection against harmful influences of vapours of cooling lubricants.
The task of the invention is solved by a protective layer applied over an elasto-ferrite carrier.
The invention will be described by way of drawings representing in: Fig. 1: a ring of a rotary encoder, projective view, Fig. 2: cross-section of the rotary encoder in a first embodiment, Fig. 3: cross-section of the rotary encoder in a second embodiment, Fig. 4: cross-section of the rotary encoder in a third embodiment. According to Figure 1, a rotary encoder, i. e. a magnetic data carrier, is a ring that is put onto a shaft that rotates and allows measurement of a position, i. e. an angle or revolution speed, i. e. angular velocity of this shaft. As seen from the cross-section from Figure 2, the encoder consists of layers. In the interior of the ring there is a known metallic first layer 1 that contacts the shaft, on which the ring is put. A layer 2 is a known layer of an elasto-ferrite carrier and is applied onto the metallic first layer 1 in known ways. According to the invention, a protective layer 3 is applied over the layer 2 of the elasto-ferrite carrier.
According to the first embodiment, the layer 3 covers only an external wall of the layer 2 of the elasto-ferrite carrier.
The protective layer 3 of the embodiment is made from stainless steel; its thickness is smaller than the width of the magnetic poles in the elasto-ferrite layer 2 by one order of magnitude, i. e. an order lOx, which practically means 50 to 100 micrometres. Other metals can be used instead of stainless steel, e. g. brass or bronze. Desirably, the material of the layer 3 is not ferromagnetic. A ferromagnetic material is acceptable only as a very thin layer that is thinner than the non-ferromagnetic variant by an order of 5-10x. The layer 3 is made as follows: a metallic strip is first cut to a selected length, both ends are then joined to a ring and butt-welded with a fibre laser for instance. The length, at which the strip is cut, is selected in a way that, after the strip is welded into a ring, the inner diameter of the layer 3 is slightly smaller than the outer diameter of the elasto-ferrite layer 2. During the assembly of the protective ring of the layer 3 the metallic layer 1 with the elasto-ferrite layer 2 is cooled while the protective layer 3 is heated. When the inner diameter of the layer 3 is larger than the outer diameter of the elasto-ferrite layer 2 due to thermal expansion, the ring is put onto the elasto-ferrite layer 2. Once the temperatures get equalized, the protective layer 3 tightly envelops the elasto-ferrite layer 2. The protective layer 3 is preferably from metal; ratios as specified in the description of the embodiment hold true for the metallic layer 3.
It is understandable, that the protective layer 3 can be made from a suitable non-metallic material. The second embodiment of Figure 3 is identical to the first embodiment of Figure 2, only that the protective layer 3, after having been assembled onto the layer 2, is bent 4 over a side edge of the layer 2 of the elasto-ferrite carrier. Conventional methods of plastic deformation of metals are used for bending, for instance a bending moment.
The third embodiment of Figure 4 is identical to the first embodiment of Figure 2 and the second embodiment of Figure 4, except that the protective layer 3 is bent over a side wall of the layer 2 of the elasto-ferrite carrier and approximately up to a half 9 of a side wall of the first layer 1. In a special embodiment, the protective layer 3 is welded onto the layer 1 at a position of the half 9. This weld continues over the entire circumference of the ring, such that the layer 2 is impermeably protected from the environment. Again, one of conventional methods of plastic deformation of metals is used for bending. The protective layer 3 is butt- welded or welded with overlaped joints preferably by a fibre laser.
All the above is also valid for an example when the carrier layer 1 is somewhat wider than the elasto-ferrite layer 2 and the layer 1 is provided with a groove, into which the layer 2 is inserted over part of its height.

Claims

PATENT CLAIMS
1. A magnetic rotary displacement encoder wherein a data carrier is an elasto-ferrite layer, characterized in that at least over an external wall of a layer (2) of the elasto-ferrite carrier a protective layer (3) made from a non-ferromagnetic material is applied having a thickness of an order of magnitude of lOx smaller than the width of magnetic poles in the elasto-ferrite layer (2), or made from a ferromagnetic material having a thickness of an order of magnitude of 5-10x smaller than the thickness of the layer (3) made from a non- ferromagnetic material.
2. Encoder of claim 1, characterized in that the layer (3) is bent (4) over a side edge of the layer (2) in a rotary displacement encoder.
3. Encoder of claim 1, characterized in that the protective layer (3) is bent over a side wall of the layer (2) of the elasto-ferrite carrier and approximately up to a half (9) of a side wall of the first layer (1).
4. Encoder of claim 3, characterized in that the protective layer (3) is butt-welded or welded with an overlapped joint to the layer (1) preferably by a fibre laser.
5. Encoder of claim 1, characterized in that the layer (3) is fastened to the layer (2) of the rotary displacement encoder such that for the assembly of a protective ring the metallic layer (1) with the elasto-ferrite layer (2) is cooled while the protective layer (3) is heated and the ring is put onto the elasto-ferrite layer (2).
PCT/SI2016/000023 2015-11-13 2016-09-20 Magnetic rotary displacement encoder with a protected elasto-ferrite layer WO2017082831A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SI201500272A SI25094A (en) 2015-11-13 2015-11-13 A magnetic encoder with a protected elasto-ferite layer
SIP-201500272 2015-11-13

Publications (1)

Publication Number Publication Date
WO2017082831A1 true WO2017082831A1 (en) 2017-05-18

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020140418A1 (en) * 2001-03-28 2002-10-03 Shinzaburo Ichiman Rotor for rotation sensor
US20060226830A1 (en) * 2005-04-11 2006-10-12 Hutchinson Encoder for a movable shaft, a device including such an encoder, and a method of fabricating such an encoder
US20070209438A1 (en) * 2006-03-06 2007-09-13 Bernard Branchereau Shaft Encoder, Device Comprising Such An Encoder And Method Of Manufacturing Such An Encoder
EP2535722A1 (en) * 2010-06-16 2012-12-19 Ströter Antriebstechnik GmbH Transmitter in the form of a plastoferrite ring and device comprising such a transmitter
EP2830074A2 (en) * 2013-07-26 2015-01-28 Wacom Co., Ltd. Electromagnetic induction sensor, overlay member for electromagnetic induction sensor, and manufacturing method of electromagnetic induction sensor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020140418A1 (en) * 2001-03-28 2002-10-03 Shinzaburo Ichiman Rotor for rotation sensor
US20060226830A1 (en) * 2005-04-11 2006-10-12 Hutchinson Encoder for a movable shaft, a device including such an encoder, and a method of fabricating such an encoder
US20070209438A1 (en) * 2006-03-06 2007-09-13 Bernard Branchereau Shaft Encoder, Device Comprising Such An Encoder And Method Of Manufacturing Such An Encoder
EP2535722A1 (en) * 2010-06-16 2012-12-19 Ströter Antriebstechnik GmbH Transmitter in the form of a plastoferrite ring and device comprising such a transmitter
EP2830074A2 (en) * 2013-07-26 2015-01-28 Wacom Co., Ltd. Electromagnetic induction sensor, overlay member for electromagnetic induction sensor, and manufacturing method of electromagnetic induction sensor

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