FR2506006A1 - APPARATUS FOR DETERMINING THE POSITION OF A MOBILE BODY - Google Patents

Abstract

A STANDARD ELEMENT 21 IN A MAGNETIC MATERIAL IS FIXED ON A MOVING BODY, AND AN E-SHAPED MAGNET 28 IS ADJACENT TO THIS ELEMENT 21. AN ELEMENT 29 HALL EFFECT WITH AN INTEGRATED CIRCUIT DESIGNED TO CONVERT THE VARIATIONS OF THE FLOW DENSITY MAGNETIC OF THE MAGNET IN VARIATIONS OF TENSION IS FIXED AT ONE END OF THE CENTRAL BRANCH OF THE MAGNET 28. THE STANDARD ELEMENT 21 IS AN EXTENDED BAR AND HAS A SERIES OF INDENTATIONS 22 ON ITS TWO SIDES, OF THE PROJECTS 24 , 25 SHAPED BY THE INDENTATIONS AND A COMMON INTERMEDIATE PART 26 HAVING THE SAME HEIGHT AS THE PROJECTS. THE PROJECTS ON BOTH SIDES ARE OFFSET. THE HALL EFFECT ELEMENT WITH INTEGRATED CIRCUIT IS ADJACENT TO THE COMMON INTERMEDIATE PART 26 AND THE TWO POLES AT THE ENDS OF THE MAGNET ARE ADJACENT TO THE SAID PROJECTS.

Description

The present invention relates to an apparatus

  to determine the position of a moving or roaming object

  tation, and to convert the measurement obtained into an electrical signal

  stick. A position sensor is used to detect a position of a moving body of a machine tool or of a crankshaft of an internal combustion engine,

  as a device sensitive to the density of a magnetic flux

tick, a Hall effect element.

  A conventional position sensor cannot determine

  pinpoint the position of a moving body as

  we will describe it in detail below.

  The object of the invention is to provide a position sensor which precisely determines a position of a

  object and which is devoid of provo-

  due to the variation of the distance between the sensor head

  and the object and by variations in temperature.

  The object of the invention is for this purpose an apparatus for determining the position of a mobile body, comprising a magnetic device for producing two magnetic fields, means for converting the variation of the density of the magnetic flux of the field into a variation of voltage, and at least one element calibrated in a magnetic material to form magnetic circuits for magnetic fields, passing through said conversion means and the magnetic device,

  said calibrated member being arranged so that the polar-

  tee of the magnetic circuit of the conversion means either

  paid alternately when the conversion means

  and the calibrated element move relative to each other.

  Other features and advantages of the

  vention will appear during the description which follows

  made with reference to the appended drawings given solely by way of examples and in which:

  Fig 1 is a perspective view of a cap

  classic position marker; Fig 2 a and 2 b are views explaining the operation of the position sensor shown in Fig 1; Fig 3 shows a form of the position sensor output signal;

  Fig 4 is a perspective view of a cap-

  classic angular position tor; Fig S shows a form of the output signal from the angular position sensor; Fig 6 is a perspective view of another position sensor of the prior art; Fig 7 shows a form of the position sensor output signal shown in Fig 6;

  Fig 8 is a perspective view of an apparatus

  position determination reil according to the invention; Fig 9 is a front view showing a position sensor head; Fig l Oa and Ob explain the operation of the position sensor according to the invention; Fig 11 shows a form of the sensor output signal; Fig 12 shows a form of the output signal when the distance between the sensor head and an object varies;

  Fig 13 shows the variations of the character-

  output sensor of the position sensor when the temperature

  ture varies; Fig 14 is a perspective view showing

  another embodiment of the apparatus according to the invention

  tion; Fig. 15 is a diagram of an electrical circuit for producing an output in the position sensor; Fig 16 to 16 h show variants of the

  position sensor according to the invention.

  Referring to Fig 1 which shows a conventional sensor of the position of a movable body, a yoke 1 in U in a permeable material and a permanent cylindrical magnet 2

  are attached together to form a M-shaped device

  me of E to produce a magnetic field A head H of cap-

  tor is arranged adjacent to the generating device

  drant the magnetic field Head H includes a yoke 3 in

  U-shaped and a core 4 fixed to the yoke 3 in the part

  intermediate thereof in order to form an E-shaped element corresponding to the E-shaped device M producing

  the magnetic field A Hall effect element 5 with an internal circuit

  tégré constituting a device sensitive to the density of the magnetic flux is fixed to the end of the core 4 An element 6 forming a screen, made of a permeable material is fixed to a body

  mobile (not shown) and is suitable for crossing in line

  gne right an interval between the device M producing the

  magnetic field and the head H of the sensor Element 6 comprises

  te a series of teeth 7 which are arranged at a distance

equal to each other.

  To describe the operation of the po-

  sition, Fig 2 a shows a state in which an empty gap between the teeth 7 coincides with the head H of the sensor, and Fig 2 b shows a state in which one of the teeth 7

  is interposed between the head H and the device M In the po-

  sition shown in Fig 2 has a magnetic field is pro-

  duit as shown in broken lines to form a closed magnetic circuit passing through the Hall effect element 5

  has integrated circuit Thus this element 5 assumes a conduc-

  When a tooth 7 isolates the magnetic circuit as a

  presented in Fig 2 b, element 5 assumes a non-conductive state

  tor. Fig 3 shows the variation of the density of the magnetic flux This density varies according to a sine wave

  when the screen member 6 moves When the den-

  sity of the magnetic flux exceeds the conductive state, the output of element 5 goes to a high level, and when the density

  of the magnetic flux decreases and falls below the non-state

  conductor, the output of element 5 goes to a low level.

  Thus the distance of movement of a body can be measured

  calculated by counting the output pulses from element 5 to ef-

fet Hall with integrated circuit.

  In the position of the sensor which is represented in FIG. 1, the screen element 6 moves between the device M producing the magnetic field and the head H of the sensor. Consequently element 6 must be produced in the form of a thin plate As a result the resistance of this element 6 is reduced, which does not allow it to be used

  to measure over a long distance.

  FIG. 4 shows a conventional angular position sensor A circular plate 9 is fixed on a rotary shaft 8 and an annular magnetic element J 0 is fixed on

  the periphery of the plate 9 The magnetic element 10 is ai-

  mantled with alternating polarities as shown in the drawing.

  A Hall effect element 11 with integrated circuit is arranged in

  position adjacent to the magnetic element 10.

  The density of the magnetic flux for element 11 varies as shown in Fig 5 Because the polarity

  of the magnetic flux is reversed, pulses having a form

  me defined can be produced by the element 11 However it is difficult to magnetize the magnetic element 10 in an exact configuration A position sensor for eliminating the aforementioned drawbacks is described in the

  Japanese patent application N 055-137222 The position sensor

  tion shown in Fig 6 includes a calibrated body 12 pre-

  feeling a series of cubic projections 13 and a permanent magnet

  14 arranged in position adjacent to the projections An element

  ment 15 with integrated circuit Hall effect is fixed on the North pole The South pole and the element 15 are spaced from the upper surface of the projections 13 by a distance d When the body 12 moves in the longitudinal direction the density of the flow magnetic for the element 15 varies according to the displacement of the projections 13 Consequently the distance of displacement

can be measured.

  However in this position sensor, if the

  tance d varies, the output of element 15 varies, even if the density of the magnetic flux is constant Consequently, the

  body 12 must have a precise configuration and be

  place so as not to cause variation in the distance

  ce d In addition, the output of element 15 varies with the varia-

  room temperature Fig 7 shows the variations

  element 15 output according to variations

  distance d and temperature Because of this variation

  tion of the output of element 15, a strip of values

  ending a switching level must be kept within a narrow range 1 Therefore if this band of values

  is set at an inappropriate level, the position of the body

  bile cannot be determined with precision.

  The invention aims to eliminate the aforementioned drawbacks. With reference to FIG. 8 which shows a position determination device according to the invention, it

  comprises a calibrated body 21 which is fixed on a movable body

  the (not shown) and a position sensor head 27 which

  is carried by any suitable support (not shown

  The element 21 is made of a soft magnetic material such as iron or silicon steel The body 21 consists of an elongated bar and has a series of indentations 22 and 23 on its two sides, projections 24 and 25 delimited by indentations-22 and 23, and an intermediate part

  commune 26 having the same height as the projections 24 and 25.

  The projections arranged on one side are equidistant and are

  offset from the projections formed on the other side 8 t.

  The head 27 of the position sensor comprises a

  mant 28 made of a hard magnetic material such as a magnet

  Alnico or rare earth, and an element 29 with Hall effect with cir-

  integrated baking Magnet 28 has an E-shaped core with N and S poles at its two distant ends, and

  element 29 is fixed to the end of the intermediate part

  diaire Referring to Fig 9, the undersides of the two poles N and S and of the element 29 are at the same level and are arranged so that the pole N is adjacent to a projection 25, that the pole S is adjacent to a projection 24, and

  the element 29 is adjacent to the common part 26 The element

  ment 29 is subjected to the magnetic field in the X direction and

  comprises two conductors 30 forming terminals.

  In operation when the element 21 moves

  this longitudinally as represented by the arrow, each of the projections 24 and 25 in turn crosses the magnetic field generated by the magnet 28 When a projection 25 is adjacent

  at pole N as shown in Fig l Oa, element 29 at ef-

  fet Hall with integrated circuit is in a magnetic field having a polarity represented by the arrow On the contrary when a projection 24 is in the magnetic field,

  element 29 is subjected to the magnetic field of polarity

  pours. Fig 11 shows the density of the magnetic flux

  of the field acting on the element 29 This density varies

  vant a wave of rectangular shape - and the polarity is in-

  paid relative to zero level.

  Fig 12 shows the variation of the density of the magnetic flux when the distance between the calibrated element

  21 and element 29 varies Because the density of the ma-

  genetic varies from zero, we can get

  a wide range L for the above-mentioned value band.

  Fig 13 shows the temperature characteristics

  erection of element 29 The output of this element varies with the variation of the ambient temperature, even if the density of the magnetic flux is constant However, the output of element 29 becomes zero at the zero level of the density of the

  magnetic flux and varies in proportion to this density Ain-

  if according to the invention, it is possible to determine the po-

  sition of a moving body with precision regardless of variations in the distance between the sensor head and

  the calibrated item, and the ambient temperature.

  Fig. 14 shows a position detector

  angular position according to the invention, for example an apparatus for determining the angular position of the crankshaft of a

  internal combustion engine A disc 31 is fixed on an ar-

  rotary bre 31 has two calibrated elements 32 each having the same arrangement of projections as the element shown in FIG.

  Fig 1 are fixed on the periphery of the disc 31 at dis-

  appropriate tances A position sensor head 33 is

  disposed in position adjacent to the projections of the element 32.

  In the device, the angular position "e" from

  firing from one end a is determined by counting the pulses

  output of the integrated circuit Hall effect element

  of the head 33 For example we can thus detect the posi-

  crankshaft top and bottom dead center

as well as the ignition timing.

  Fig. 15 shows a circuit for producing output pulses by means of Hall effect element 29

  with integrated circuit or Hall effect element The output terminals

  tie of element 29 are connected to the inputs of a comparison

  Since the output of the element 29 is inverted at the zero level of the density of the magnetic flux, the output of the comparator 34 is also inverted at the zero voltage of

the exit from Hall 29.

  Fig 16 a to 16 h show different variants of the invention In the device shown in Fig 16 a, a position sensor head comprises branches 41, 44 and 45 and two horizontal magnets 42 and 43 arranged between the branches Un integrated circuit Hall effect element 46 is

  fixed on the end of the intermediate branch 41 The ai-

  mants 42, 43 are arranged with their polarities reversed

  so as to magnetize the branches 44 and 45 with polarities op-

  asked. The position sensor head shown in

  Fig 16 b is constituted by a yoke 47 in the form of T comprising-

  both two vertical magnets 49 and 50 which are fixed in two end parts of the yoke 47 with opposite polarities, and an element 48 of Hall effect with integrated circuit which is fixed

  on the end of the central branch of the yoke 47.

  The sensor head shown in Fig 16 c com-

  takes two U-shaped magnets 51 and 52 which are arranged with their polarities reversed and fixed together to form an E-shaped magnet, and a Hall effect element 53

  has integrated circuit, which is fixed on p 8 the central of the

  mant. FIG. 16 d shows another variant of the sensor head which comprises a single rectangular magnet 54 comprising a cavity and an element 55 of Hall effect with integrated circuit which is embedded in the cavity The two c 8 tees

  the magnet 54 are magnetized with opposite polarities.

  Fig 16 e shows another apparatus for determining

  position nation A calibrated element 56 present in sec-

  tion a U shape and branches 56 a and 56 b which are deca-

  A sensor head comprises a central element 57, two magnets 58 and 59 arranged on either side of the element.

  57 and an integrated circuit Hall effect element 60 which is

  attached to a lower end of the central element Les-

  mants 58 and 59 are arranged with their opposite polarities and

  adjacent to branches 56 a and 56 b respectively.

  Fig 16 f shows another device in which

  several magnetic strips 61 are arranged in the ad position

  adjacent and offset on opposite sides of a cap head

  teur The sensor head comprises a central element 62, two

  magnets 63 and 64 fixed to the two sides of the element 62, an element

  ment 65 Hall effect with integrated circuit attached to the underside

  element 62 and a horizontal element 66 which is

fixed on element 65.

  The sensor head shown in Fig 16 q com-

  takes two magnets 68, 69 arranged with their polarities

  and an integrated circuit Hall effect element 67 which

is placed between the magnets.

  Fig 16 h shows a sensor head comprising

  a U-shaped magnet 70, a Hall effect element 71 with a circle

  integrated baking which is fixed to a central part of the magnet

  and an element 72 fixed to element 71.

  It follows from the above that the invention provides

  nit a measuring device that can accurately determine the position of a moving body even if the distance between

  the sensor head and the moving body varies and if the temperature

  ambient ture also varies although in the modes of

  realization described above the Hall effect element or the

  Hall effect element with integrated circuit be used as devices to convert the variation in flux density

  magnetic in a voltage variation, you can use other

  very means such as a variable resistance as a function of the magnetic field Furthermore it is understood that the invention can be used in an apparatus in which the sensor head is fixed to the movable element and the calibrated element is fixed

on a stationary body.

* REVHNDICATIONS

R B V B N D I C A T I 0 N S

  1 Device for determining the position of a

  body in motion, characterized in that it comprises a dis-

  magnetic positive (28) for producing two magnetic fields, means (29, 33) for converting the variation in the density of the magnetic flux of said field into a variation in voltage

  and at least one calibrated element (21, 32) of a material made of

  genetics to form magnetic circuits of said field,

  going through the means to convert the change in den-

  of the flux and the magnetic device, said element

  lonné (21, 32) being arranged so that the polarity of the circuit

  magnetic baking of said means (29, 33) for converting the den-

  sity of the magnetic flux is alternately reversed when

  that the conversion means (29, 33) and the calibrated element

  (21, 32, 56, 61) move relative to each other.

  2 Apparatus according to claim 1, character-

  in that the magnetic device (28) consists of an E-shaped magnet

  3. Apparatus according to claim 1, character-

  risé in that the calibrated element (21) consists of an elongated bar which has a series of indentations (22) on its two sides, offset projections (24, 25) formed on

  its two sides by said indentations and an inter-

  common medial (26) having the same height as the projections.

  4 Apparatus according to claim 3, character-

  laughed at in that the means (29) for converting the variation

  of the magnetic flux density are mounted on an

  mite of a central branch of said E-shaped magnet (28) Apparatus according to claim 4, characterized

  laughed in that the two poles (N, S) at the ends of the

  E-shaped mant (28) are adjacent to said projections (25,

  26), the means of converting (29) variations in the den-

  sity of the magnetic flux being adjacent to said part

common intermediate (26).

  6 Apparatus according to claim 1, character-

  laughed at in that the means (29) for converting variations there

  of the density of the magnetic flux consist of an element

Hall effect.

  7 Apparatus according to claim 1, character-

  in that the means (29) for converting variations in the density of the magnetic flux consist of an element

  Hall effect with integrated circuit.

  8 Apparatus according to claim 1, character-

  laughed in that the means (29) for converting variations

  of the density of the magnetic flux consist of a re-

  variable resistance, depending on the magnetic field.

  9 Apparatus according to claim 1, character-

  laughed in that it further comprises a yoke for connecting the means (29) for converting variations in the density of the flux

  and the magnetic device (28).

  10 Apparatus according to claim 1, character-

  laughed in that it comprises a yoke (54) fixed on the means for converting the variation in the density of the magnetic flux

  in a position adjacent to said calibrated member (21).

  The apparatus according to claim 1, character-

  laughed in that said calibrated element (56) has in sec-

  tion a U shape and has several projections which are offset.

  12 Apparatus according to claim 1, character-

  laughed in that said calibrated element is constituted by more

several bands (61).