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WO2000006972A1 - Detecteur de position - Google Patents

Detecteur de position Download PDF

Info

Publication number
WO2000006972A1
WO2000006972A1 PCT/GB1999/002470 GB9902470W WO0006972A1 WO 2000006972 A1 WO2000006972 A1 WO 2000006972A1 GB 9902470 W GB9902470 W GB 9902470W WO 0006972 A1 WO0006972 A1 WO 0006972A1
Authority
WO
WIPO (PCT)
Prior art keywords
balls
position detector
line
point contact
coils
Prior art date
Application number
PCT/GB1999/002470
Other languages
English (en)
Inventor
Frederick Mark Hudman
Geoffrey Glasgow
Original Assignee
Elliott Industries Limited
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 Elliott Industries Limited filed Critical Elliott Industries Limited
Priority to AU51774/99A priority Critical patent/AU5177499A/en
Publication of WO2000006972A1 publication Critical patent/WO2000006972A1/fr

Links

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
    • G01D5/204—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 by influencing the mutual induction between two or more coils
    • G01D5/2046—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 by influencing the mutual induction between two or more coils by a movable ferromagnetic element, e.g. a core

Definitions

  • This invention relates to improvements in position detectors for measuring relative movement and/or displacement, of the type described in GB 1513567.
  • the present invention provides a position detector comprising a first member; a plurality of substantially contiguous, substantially spherical identical balls of magnetic material carried by the first member, the balls being disposed side by side in a row in point contact with one another and being constrained against movement relative to one another; a second member, the first and second members being relatively movable in a direction parallel to the line of point contact between the balls in said row, and a transducer which is carried by said second member and which comprises transmitting means for producing a periodically varying magnetic field through the row of balls, and means for sensing phase displaced variations produced in the magnetic field as a result of the relative movement between the first and second members and for producing signals denoting the relative positions of the first and second members, said sensing means comprising at least two pick-up coils which are disposed adjacent to and spaced along the row of balls and the line of point contact therebetween; wherein the ratio of the distance between the pick-up coils and the line of point contact between the balls to the diameter of the balls is in the
  • the ratio of the height of the pickup coils from the line of point contact to the ball diameter is 1.28 : 1.34.
  • the ratio of the height of the pickup coils from the line of point contact to the ball diameter is 1.31.
  • the first member comprises a tube for containing the balls which is made from a fibre reinforced plastic material, most preferably carbon fibre reinforced plastic.
  • a fibre reinforced plastic material most preferably carbon fibre reinforced plastic.
  • Use of such materials assists in achieving the desired ratio mentioned above, particularly in small size position detectors m which the ball diameter is in the region of 5mm.
  • FIGURE 1 illustrates diagrammatically one embodiment of the invention, showing only one pair of transmitter and pick-up coils for clarity;
  • FIGURE 2 illustrates diagrammatically the arrangement of four pairs of coils in the measuring device shown in Figure 1;
  • FIGURE 3 illustrates diagrammatically a second embodiment of the invention, showing only one pair of transmitter and pick-up for clarity
  • FIGURE 4 illustrates diagrammatically a third embodiments of the invention, which includes four pick-up coils.
  • a ball container 1, of non-magnetic material, which is preferably be tubular, is fixedly mounted to a part 2 of a machine by a link 3.
  • a transducer comprising several pole pieces 4 (of which only one is shown for clarity) , each pole piece 4 carrying a pair of coils comprising a transmitter coil 5 and a receiver or pick-up coil 6, is fixedly connected to a second part 7 of the machine by a link 8.
  • the parts 2 and 7 are relatively movable in the direction shown by the double-headed arrow and it is the relative displacement resulting from this relative movement which is to be measured.
  • the container 1 houses a plurality of substantially spherical, identical, steel balls la, arranged side by side in contact with each other in a straight line which is parallel to the direction of relative movement of parts 2 and 7.
  • the coils 5 and 6 are placed on opposite sides of the line of balls la, and the pole pieces 4 are aligned so as to execute motion relative to the line of balls la in a direction parallel to that line when the parts 2 and 7 move relative to each other. It is immaterial whether part 2 is stationary and part 7 moves, or vice versa, or whether both parts move in opposite directions and/or at different speeds, so long as relative displacement therebetween occurs parallel to the line of balls la.
  • the transducer employs a number of pole pieces which are periodically spaced along the line of balls la, the relative positions of these pole pieces being determined by the number of poles used and by the diameter of the balls.
  • Each transmitter coil is supplied via lines 50 with a signal of periodic waveform, e.g sinusoidal, rectangular etc., the relationship between the phase of the signal supplied thereto with that of the signal supplied to any other transmitter coil being directly related to the relative spacing of these two transmitter coils along the row of balls.
  • the signal supplied to each transmitter coil produces a magnetic field between that transmitter coil 5 and the associated receiver coil 6, which magnetic field is affected by the relative movement of the balls la between these two coils 5,6.
  • the resulting variation in the magnetic field produces corresponding variations in the signal induced in the receiver coil 6.
  • the resultant signal when the outputs in lines 60 from all the receiver coils are summed, is a constant amplitude sinusoidal wave signal whose phase is directly proportional to the relative displacement between parts 2 and 7 due to relative movement therebetween.
  • the resultant signal after suitable processing, is displayed on a readout panel m digital form which can be connected to a printer for a permanent record to be made.
  • Figure 3 shows an alternative arrangement of the transducer and container 1 which facilitates the accurate aligning of one to the other.
  • the container 1, as in the embodiment of Figure 1 is mounted on the part 2 by a link 3, and the arrangement and operation of the transducer with respect to the container 1 is likewise similar to that described for the embodiment of Figure 1, the difference being that in this embodiment, the pole pieces 4 of the transducer are fixed to a carriage 9 which is mounted on container 1 for sliding motion therealong.
  • the connection between the pole piece 4 and part 7 of the machine is provided by a flexible link 10, replacing the rigid link 8 shown in Figure 1.
  • a plurality of substantially spherical, identical, steel balls la are arranged in a suitable housing 1, side by side in contact with each other in a straight line.
  • a transducer is located around the balls la, the transducer comprising transmitter coils 5 and pick-up coils 6 which are co-axial with the transmitter coils 5 and also co-axial with a line 10 joining the centres of the balls.
  • the balls and the transducer are relatively movable in directions parallel to the line 10, being mounted on respective parts (not shown) of a machine which are also relatively movable in directions parallel to the line 10, and it is the relative displacement of these two machine parts which is to be measured.
  • the manner in which the balls and the transducer are mounted on the machine parts may be similar to the mountings described above with reference to Figures 1 and 3.
  • the transmitter coil 5 comprises a number of transmitter coil portions 5', connected in series, the centre of each coil portion being spaced a distance d/n where d is the diameter or pitch of the balls la and n is the number of pick-up or receiver coils 6.
  • d is the diameter or pitch of the balls la
  • n is the number of pick-up or receiver coils 6.
  • Each pick-up coil, for example 6a comprises a number of pick-up coil portions, for example 6a 1, 6a 2, 6a 3 etc. which are spaced apart at intervals of length d.
  • each pick-up coil portion is surrounded by a respective transmitter coil portion 5', so that the centres of adjacent pick-up coils are interleaved, the centre of pick-up coil portion 6a 1, for example, is spaced by d/4 from the centre of pick-up coil portion 6b 1.
  • the transmitter coil is supplied with a signal of periodic waveform, e.g. sinusoidal, rectangular, etc. which produces a magnetic field parallel to the line 10.
  • a signal of periodic waveform e.g. sinusoidal, rectangular, etc. which produces a magnetic field parallel to the line 10.
  • the variation in the magnetic field resulting from relative axial movement between the balls la and the transducer produces corresponding variations in the signals induced in each pick-up coil 6a, 6b, 6c or 6d.
  • the phase of the output signals from the pick-up coils is then adjusted in correspondence with the relative pitch displacement of the pick-up coils.
  • the resultant signal is a constant amplitude, sinusoidal waveform of which the phase is directly proportional to the relative displacement due to the relative movement of the machine parts.
  • the transmitter coil portions which surround the coil portions of each respective pick-up coil may be connected in series, and a separate signal supplied to each group of transmitter coil portions, the relative phases of the signals supplied corresponding to the pitch displacement of the respective associated pick-up coil output signals is required.
  • coil portions of the pick-up and transmitter coils of the embodiment of Figure 4 are produced on flexible printed circuits which are wrapped around the ball housing.
  • the ratio of the distance of the pick-up coils 6 from the line of point contact of the balls la (the pick-up coil height) to the diameter of the balls la is critical in ensuring optimum accuracy.
  • distortion of the induced signal will also increase. Therefore, it is known that a compromise between these two opposing factors must be found.
  • the actual ball diameter is also important in addition to the distance of the pick-up coils from the balls.
  • the preferred ratio of the pick-up coil height to the ball diameter is in the range of about 1.25 to about 1.37.
  • a preferred ratio is in the range of about 1.28 to about 1.34.
  • the most preferred ratio is 1.31.
  • the minimum signal induced has been found to be 94% of the maximum signal, leaving a useful signal of 6% for processing.
  • the ratio of pick-up coil height to ball diameter rises to 1.56 for example, the minimum voltage induced rises to 98.4% of the maximum signal leaving only 1.6% for processing, thus leading to an increased risk of errors.
  • Typical practical embodiments of the position detecting devices described above use a stainless steel tube for the ball container 1.
  • the ball container must be sufficiently strong and rigid to support a line of balls, ball bearings with a diameter of 12.7mm (0.5"), without bending in the middle when the container itself is only supported at either end. It must also be resistant to fluids including water and industrial coolants since such devices are typically used on machine tools.
  • stainless steel is an particularly attractive choice.
  • the wall of the tube must made very thin, eg approximately 0.3mm. This reduces its strength and rigidity and it is difficult to ensure uniform wall thickness, leading to bowing or buckling of the ball container tube along its length in use.
  • an alternative is to form the ball container from a fibre reinforced plastic material, m particular carbon fibre reinforced plastic.
  • Thin walled tubes of such material can be produced by winding the material round a mandrel which defines the internal diameter of the tube. The exterior surface is then ground to reduce the wall thickness to a desired value.
  • Using such material is advantageous because it can easily be produced to the required dimensions but retains sufficient rigidity, strength and resistance to fluids.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

En ce qui concerne la figure, un détecteur de position comprend une rangée de billes magnétiques (1a) se trouvant en contact les unes avec les autres dans un tube (1) monté sur un premier élément (2) d'une machine. Un transducteur (5) et des bobines détectrices (6) sont montés sur un second élément (7) de la machine. Le premier et le second élément (2, 7) sont mobiles l'un par rapport à l'autre. Le transducteur (5) émet un champ magnétique périodique résultant du mouvement relatif du premier et du second élément (2, 7). Le rapport entre, d'une part, la distance séparant la ligne de point de contact des billes (1a) et les bobines détectrices (6) et, d'autre part, le diamètre des billes (1a) est de l'ordre de 1,25 : 1,37, de façon à optimiser la précision de mesure du détecteur.
PCT/GB1999/002470 1998-07-28 1999-07-28 Detecteur de position WO2000006972A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU51774/99A AU5177499A (en) 1998-07-28 1999-07-28 Position detector

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9816420A GB2340242B (en) 1998-07-28 1998-07-28 Improvements relating to position detectors
GB9816420.5 1998-07-28

Publications (1)

Publication Number Publication Date
WO2000006972A1 true WO2000006972A1 (fr) 2000-02-10

Family

ID=10836308

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/002470 WO2000006972A1 (fr) 1998-07-28 1999-07-28 Detecteur de position

Country Status (3)

Country Link
AU (1) AU5177499A (fr)
GB (1) GB2340242B (fr)
WO (1) WO2000006972A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003006927A1 (fr) * 2001-07-11 2003-01-23 Elliott Industries Limited Detecteur de position inductif

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2343755A (en) * 1998-11-09 2000-05-17 Laurence Ross Petrie Displacement measurement using an elongate magnetic modulating means comprising ferromagnetic balls
GB2392503B (en) * 2002-09-02 2006-02-22 Elliott Ind Ltd Inductive position detectors
DE102006003980A1 (de) 2006-01-27 2007-08-02 Schaeffler Kg Linearführungseinheit mit Längenmesssystem
CN103162609A (zh) * 2011-12-09 2013-06-19 上海球栅测量系统有限公司 位移测量系统和方法
DE102016202403A1 (de) 2016-02-17 2017-08-17 Continental Teves Ag & Co. Ohg Sensor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1188827B (de) * 1959-04-01 1965-03-11 Gen Electric Messgeraet zur Stellungsanzeige
GB1513567A (en) * 1975-08-05 1978-06-07 Newell Eng Co Ltd Position detectors

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB956093A (en) * 1962-07-11 1964-04-22 Gen Electric Improvements in core assembly for a position indicating device
JPH053921Y2 (fr) * 1989-02-09 1993-01-29

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1188827B (de) * 1959-04-01 1965-03-11 Gen Electric Messgeraet zur Stellungsanzeige
GB1513567A (en) * 1975-08-05 1978-06-07 Newell Eng Co Ltd Position detectors

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003006927A1 (fr) * 2001-07-11 2003-01-23 Elliott Industries Limited Detecteur de position inductif
RU2264599C2 (ru) * 2001-07-11 2005-11-20 Ньювол Межермент Системз Лимитед Индукционный детектор положения
US6977594B2 (en) 2001-07-11 2005-12-20 Newall Measurement Systems Limited Inductive position detector

Also Published As

Publication number Publication date
AU5177499A (en) 2000-02-21
GB2340242A (en) 2000-02-16
GB9816420D0 (en) 1998-09-23
GB2340242B (en) 2002-09-25

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