EP1969318A1 - Magnetic detector arrangement - Google Patents

Magnetic detector arrangement

Info

Publication number
EP1969318A1
EP1969318A1 EP06824473A EP06824473A EP1969318A1 EP 1969318 A1 EP1969318 A1 EP 1969318A1 EP 06824473 A EP06824473 A EP 06824473A EP 06824473 A EP06824473 A EP 06824473A EP 1969318 A1 EP1969318 A1 EP 1969318A1
Authority
EP
European Patent Office
Prior art keywords
magnetic
detector arrangement
magnetic field
sensor element
sensor
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.)
Withdrawn
Application number
EP06824473A
Other languages
German (de)
French (fr)
Other versions
EP1969318A4 (en
Inventor
Pierre Van Glabeke
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.)
Volvo Truck Corp
Original Assignee
Volvo Lastvagnar AB
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 Volvo Lastvagnar AB filed Critical Volvo Lastvagnar AB
Publication of EP1969318A1 publication Critical patent/EP1969318A1/en
Publication of EP1969318A4 publication Critical patent/EP1969318A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/025—Compensating stray fields
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2861—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using magnetic means
    • 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
    • G01D5/142—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 using Hall-effect devices
    • G01D5/145—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 using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields

Definitions

  • the present invention relates to a magnetic detector arrangement according to the preamble to claim 1. This magnetic detector arrangement allows for improved magnetic sensors .
  • a switch or a sensor with a high resolution and which at the same time is insensitive to an external magnetic field it is desirable to position the magnet and the detector close to each other. In this way, it is possible to use a detector with a low sensitivity, obtaining a switch or a sensor that is more or less insensible to external magnetic fields.
  • One problem with magnetic sensors is that the sensitivity of the detector must increase with an increased detection distance.
  • a problem with the detector being very sensitive is that it will more easily be disturbed by an external, interfering magnetic field. This can e.g. occur when the sensor is close to a high current cable or a large transformer.
  • a magnetic sensor can e.g. be built into a hydraulic cylinder in order to give the position of the piston head.
  • a magnet is mounted to the piston head and a magnetic sensor detects the position of the magnet.
  • This integrating of a magnetic detector in the cylinder leads to a greater distance between the magnet and the detector element, thus making the detector sensitive to external magnetic fields .
  • the object of the invention is therefore to achieve an improved magnetic detector arrangement that is less sensitive to the influence of an outer magnetic field.
  • the object of the invention is achieved in that the arrangement also comprises magnetic deflector means adapted for directing an external magnetic field in a direction parallel to the magnetic sensor element.
  • a magnetic detector is obtained where the sensitivity to an outer magnetic field is reduced. This is achieved by using a magnetic deflector that direct the field lines of the outer magnetic field in a direction parallel to the magnetic sensor element. This allows for magnetic detector arrangements that have an improved resistance to a disturbing external magnetic field and/or an improved resolution.
  • the magnetic means comprises two equally polarised magnets positioned at a predefined distance apart next to each other with the polarisation in the same direction. This improves the resolution and/or the resistance to external magnetic fields even further.
  • the magnetic deflector means may be in the shape of one or more rods or a tube.
  • the magnetic deflector means may be positioned in different positions.
  • Fig. 1 shows a known hydraulic cylinder with a magnetic detector arrangement
  • Fig. 2a shows an embodiment of the magnetic detector arrangement according to the invention
  • Fig. 2b shows a side view of the embodiment in 2a
  • Figs. 3a, 4a shows further embodiments of the magnetic detector arrangement according to the invention
  • Figs. 3b, 4b shows a side view of the embodiment in
  • Figs . 5, 6, 7 shows further embodiments of the magnetic detector arrangement according to the invention
  • Fig. 8 shows a schematic view of a magnetic detector arrangement according to the invention.
  • Fig 1 shows a known hydraulic cylinder 8 comprising a magnetic detector arrangement 1.
  • the magnetic detector arrangement 1 consists of a magnetic element 4 and a magnetic sensor 2.
  • the magnetic element 4 can comprise one or more magnets and is in this embodiment a circular ring magnet mounted to the piston head. In this way, the magnetic element will indicate the position of the piston head. The position is detected by the sensor which is mounted on the outside of the cylinder.
  • the magnetic field of the magnetic arrangement will influence the softmagnetic core of the sensor and this influence can be detected by using the detector coil in a known manner. In this way, a contactless position detection is possible.
  • the sensor can be analogue or with a number of discrete steps.
  • the sensor preferably comprises a linear coil 9 and at least one softmagnetic core 10 that is to be saturated. Such a linear magnetic sensor is well known to the skilled person and is not described further.
  • the circular magnets are used because the piston head is not fixed in a rotational direction inside the cylinder.
  • a hydraulic cylinder where the rotation of the piston head is known or fixed, it is also possible to use a magnetic arrangement that does not cover the complete periphery of the piston head.
  • the hydraulic cylinder is made of non-magnetic material, preferably stainless steel, but also other non-magnetic materials such as aluminium or a composite is possible, depending on e.g. the pressure in the cylinder.
  • the piston rod is preferably made of hardened steel .
  • the cylinder has inlets and outlets for the hydraulic oil. These are not shown in the figure.
  • Such a hydraulic cylinder with a magnetic position detector is also well known to the skilled person.
  • the hydraulic cylinder can e.g. be used for a steerable rear axle on a truck to indicate the position of the piston head and thus the steered wheel angle.
  • a tubular extension is mounted to the hydraulic cylinder.
  • This extension is made from a ferro-magnetic material, e.g. iron, and is mounted on the side of the cylinder along the longitudinal axis 12 of the cylinder.
  • the extension tube can be either open at the end or be closed with a sealing to the rod.
  • the purpose of this extension is to influence the magnetic field lines of the earth magnetic field in such a way that the magnetic field lines are forced to be more or less parallel to the magnetic sensor. In this way, the earth magnetic field will not influence the position detection of the piston head.
  • the tubular extension is thus used as a magnetic deflector that directs the magnetic field lines in a direction parallel to the magnetic detector.
  • the magnetic deflector functions in the following way.
  • the magnetic field lines from a magnetic field are drawn to the magnetic deflector material since the magnetic deflector is made from a ferro-magnetic material. Consequently, some of the magnetic field lines from the magnetic field will be lead through the magnetic deflector and some field lines, with a distance to the magnetic deflector, will follow the same direction and thus will be parallel with the field lines passing through the magnetic deflector.
  • By placing magnetic deflector means symmetrically in respect to the magnetic sensor will thus create a magnetic field that is substantially parallel to the magnetic sensor. This creates an area around the magnetic sensor with a magnetic field that is substantially homogenous and directed parallel with the sensor. Magnetic field lines passing in other directions through the magnetic sensor will thus be reduced significantly.
  • the magnetic sensor is parallel to the travelling direction of the piston, i.e. the sensor extends in the same direction as the travelling of the piston.
  • This longitudinal axis is denoted 12 in the figures. It is along this axis that the magnetic field lines of the external magnetic field are directed with the magnetic deflector. The centre of the tubular extension coincides with this axis 12.
  • the magnetic detector arrangement comprises two magnetic deflectors 7 positioned parallel to the magnetic sensor and symmetric to a symmetry axis 11 running through the sensor element 2 and the magnet 4.
  • the magnetic deflectors are made from a ferro-magnetic material, such as iron.
  • the properties of the magnetic deflectors are selected such that the material, e.g. iron, is not saturated by the external magnetic field.
  • the external magnetic field may be the earth magnetic field and or another external magnetic field, e.g. a magnetic field induced by a high-current cable.
  • the properties of the magnetic deflectors are selected such that they do not saturate by magnetic fields that can be expected or defined by e.g. a standard or regulation.
  • the two magnetic deflectors having the dimensions of 5 x 10 mm are made from iron and extend the length of the hydraulic cylinder.
  • the length of a magnetic deflector is preferably longer than the magnetic detector, but may also be shorter depending on e.g. the material properties and/or the positioning of the magnetic deflector.
  • the magnetic deflectors are fastened to the outside of the hydraulic cylinder in a symmetric way, as is shown in fig. 3b.
  • the magnetic detector arrangement comprises three magnetic deflectors 7 positioned parallel to the magnetic sensor and symmetric to the symmetry axis 11 running through the sensor element 2 and the magnet 4.
  • the three magnetic deflectors are fastened to the outside of the hydraulic cylinder in a symmetric way, with one deflector opposing the sensor and the other two positioned with an offset of 120 degrees around the cylinder, as is shown in fig. 4b.
  • the magnetic deflectors do not need to be fixed to the hydraulic cylinder. As is shown in fig. 5, they may also be positioned around the cylinder in space, somewhat distance from the outside surface of the cylinder. This positioning may be advantageous in some installations, e.g. when the cylinder itself needs to be changed or maintained.
  • Figs. 6 and 7 show embodiments with a tube-like magnetic deflector that will not disturb the magnetic sensor.
  • the magnetic deflector is a tube with a cut-out extending the length of the magnetic deflector. The cut-out is in the order of 90 degrees and preferably in the range between 60 and 180 degrees.
  • the magnetic deflector is a tube with a diameter that is large enough to enclose the complete cylinder with the magnetic detector arrangement. The distance between the tube and the sensor is chosen so that the tube does not disturb the sensor.
  • magnétique deflectors prevent the piston rod from being magnetised by the external magnetic field. Since the magnetic deflectors direct the external magnetic field parallel to the sensor, the magnetic field will also be parallel to the piston rod. Since the piston rod does not move perpendicular to a magnetic field, the magnetisation of the piston rod will be greatly reduced.
  • the magnetic element 4 comprises two permanent magnets .
  • a schematic magnetic detector comprising two permanent magnets is shown in fig. 8.
  • the magnets have approximately the same magnetic properties .
  • the magnets are equally polarised and positioned next to each other in a symmetrical way with their symmetry axes parallel and with the polarisation in the same direction.
  • the distance between the magnets is small compared with the size of the magnets .
  • the distance between the magnets is selected so that the magnetic field is as wide as possible with an equal density. This is possible due to the fact that the magnetic field from the magnets will deform symmetrically in respect to a plane in between the magnets when positioned close to each other. By doing this, a well-defined magnetic field is obtained.
  • This embodiment allows for an improved sensitivity of the magnetic detector arrangement.
  • the optimal distance between the magnets depends on various magnetic properties of the magnets .
  • the optimal distance is small or equal compared to the thickness of the magnets.
  • the optimal distance for two ceramic type magnets with the size 12*6 mm and 4 mm thick can be between 0.9 mm to 4 mm when the two planes with the size 12*6 mm are side by side.
  • the easiest way to obtain the optimal distance is by empirical measurements .
  • the optimal distance between the magnets depends on various magnetic properties of the magnets.
  • the optimal distance is small compared to the magnets .
  • the optimal distance for two ceramic type magnets with the size 12*6*4 mm can be approximately 0.9 mm.
  • the easiest way to obtain the optimal distance is by empirical measurements .
  • the invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims .
  • the magnetic arrangement can, for example, also be used for other types of detectors or switches. 1 : Magnetic detector arrangement

Abstract

The invention discloses a magnetic detector arrangement with a magnetic sensor element (2) and a magnetic means (4) for imposing a magnetic field on the magnetic sensor element (2) , and also comprises magnetic deflector means (7) operable to direct an external magnetic field in a direction substantially parallel to the magnetic sensor element (2) . The magnetic means (4) comprise two equally polarised magnets positioned at a predefined distance apart next to each other with the polarisation in the same direction so that a magnetic field generated in operation by the two magnets is forced to be substantially parallel to the magnetic sensor element (2) . The advantage of the invention is to provide a magnetic detector arrangement with a reduced sensitivity to an outer magnetic field.

Description

TITLE: Magnetic detector arrangement
TECHNICAL FIELD: The present invention relates to a magnetic detector arrangement according to the preamble to claim 1. This magnetic detector arrangement allows for improved magnetic sensors .
BACKGROUND ART:
In modern vehicles, there are many functions that are controlled electronically. Some of these functions are of the on/off type, some can be switched to several positions and some are analogue. Mechanically operated switches and sensors control most functions, but some functions require a contact-less operation. An example of functions where a contact-less operation is preferred is e.g. ABS-sensors (ABS = Automatic Brake System) , chassis height detection or switches that are exposed to weather, pollutions and direct friction. One kind of contact-less switches and sensors are based on a magnetic principle. There exist different types of magnetic detectors, e.g. reed-contacts, hall-sensors and other kinds of integrated magnetic detectors . A magnetic field is used to influence the detector. The detector and the magnet thus form the switch or the sensor.
To obtain a switch or a sensor with a high resolution and which at the same time is insensitive to an external magnetic field, it is desirable to position the magnet and the detector close to each other. In this way, it is possible to use a detector with a low sensitivity, obtaining a switch or a sensor that is more or less insensible to external magnetic fields. One problem with magnetic sensors is that the sensitivity of the detector must increase with an increased detection distance. A problem with the detector being very sensitive is that it will more easily be disturbed by an external, interfering magnetic field. This can e.g. occur when the sensor is close to a high current cable or a large transformer.
Thus, it is preferred not to raise the sensitivity too much for the detector.
A problem that arises when the magnetic field is increased by using a larger magnet is that the magnetic field is not only stronger, it is also more distributed in space. This gives the effect that, when an analogue detector is used, the resolution will be degraded due to the imprecise magnetic field.
A magnetic sensor can e.g. be built into a hydraulic cylinder in order to give the position of the piston head. In such an arrangement, a magnet is mounted to the piston head and a magnetic sensor detects the position of the magnet. This integrating of a magnetic detector in the cylinder leads to a greater distance between the magnet and the detector element, thus making the detector sensitive to external magnetic fields .
DISCLOSURE OF INVENTION: The object of the invention is therefore to achieve an improved magnetic detector arrangement that is less sensitive to the influence of an outer magnetic field.
The solution to this problem according to the invention is described in the characterizing part of claim 1. The other claims contain advantageous embodiments and further developments of the magnetic detector arrangement according to the invention.
With a magnetic detector arrangement, comprising a magnetic sensor element and a magnetic means for imposing a magnetic field on the magnetic sensor element, the object of the invention is achieved in that the arrangement also comprises magnetic deflector means adapted for directing an external magnetic field in a direction parallel to the magnetic sensor element.
By this first embodiment of the magnetic detector arrangement according to the invention, a magnetic detector is obtained where the sensitivity to an outer magnetic field is reduced. This is achieved by using a magnetic deflector that direct the field lines of the outer magnetic field in a direction parallel to the magnetic sensor element. This allows for magnetic detector arrangements that have an improved resistance to a disturbing external magnetic field and/or an improved resolution.
In an advantageous further development of the magnetic detector arrangement according to the invention, the magnetic means comprises two equally polarised magnets positioned at a predefined distance apart next to each other with the polarisation in the same direction. This improves the resolution and/or the resistance to external magnetic fields even further.
In advantageous further developments of the magnetic detector arrangement according to the invention, different magnetic deflector means are disclosed. The magnetic deflector means may be in the shape of one or more rods or a tube. The magnetic deflector means may be positioned in different positions. BRIEF DESCRIPTION OF DRAWINGS
The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which
Fig. 1 shows a known hydraulic cylinder with a magnetic detector arrangement,
Fig. 2a shows an embodiment of the magnetic detector arrangement according to the invention,
Fig. 2b shows a side view of the embodiment in 2a,
Figs. 3a, 4a shows further embodiments of the magnetic detector arrangement according to the invention, Figs. 3b, 4b shows a side view of the embodiment in
3a, 4a,
Figs . 5, 6, 7 shows further embodiments of the magnetic detector arrangement according to the invention, and Fig. 8 shows a schematic view of a magnetic detector arrangement according to the invention.
MODES FOR CARRYING OUT THE INVENTION
The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims .
Fig 1 shows a known hydraulic cylinder 8 comprising a magnetic detector arrangement 1. The magnetic detector arrangement 1 consists of a magnetic element 4 and a magnetic sensor 2. The magnetic element 4 can comprise one or more magnets and is in this embodiment a circular ring magnet mounted to the piston head. In this way, the magnetic element will indicate the position of the piston head. The position is detected by the sensor which is mounted on the outside of the cylinder. The magnetic field of the magnetic arrangement will influence the softmagnetic core of the sensor and this influence can be detected by using the detector coil in a known manner. In this way, a contactless position detection is possible. The sensor can be analogue or with a number of discrete steps. The sensor preferably comprises a linear coil 9 and at least one softmagnetic core 10 that is to be saturated. Such a linear magnetic sensor is well known to the skilled person and is not described further.
The circular magnets are used because the piston head is not fixed in a rotational direction inside the cylinder. In a hydraulic cylinder where the rotation of the piston head is known or fixed, it is also possible to use a magnetic arrangement that does not cover the complete periphery of the piston head.
The hydraulic cylinder is made of non-magnetic material, preferably stainless steel, but also other non-magnetic materials such as aluminium or a composite is possible, depending on e.g. the pressure in the cylinder. The piston rod is preferably made of hardened steel . The cylinder has inlets and outlets for the hydraulic oil. These are not shown in the figure. Such a hydraulic cylinder with a magnetic position detector is also well known to the skilled person. The hydraulic cylinder can e.g. be used for a steerable rear axle on a truck to indicate the position of the piston head and thus the steered wheel angle.
In a first embodiment of the invention, shown in fig. 2, a tubular extension is mounted to the hydraulic cylinder. This extension is made from a ferro-magnetic material, e.g. iron, and is mounted on the side of the cylinder along the longitudinal axis 12 of the cylinder. The extension tube can be either open at the end or be closed with a sealing to the rod. The purpose of this extension is to influence the magnetic field lines of the earth magnetic field in such a way that the magnetic field lines are forced to be more or less parallel to the magnetic sensor. In this way, the earth magnetic field will not influence the position detection of the piston head. The tubular extension is thus used as a magnetic deflector that directs the magnetic field lines in a direction parallel to the magnetic detector. To direct the field lines of the earth magnetic field parallel to the detector will reduce the sensitivity for disturbances of this external magnetic field and thus to improve the accuracy of the detector. This is due to the fact that the magnetic sensor element is not influenced by magnetic field lines parallel to the detector coil in the detector.
The magnetic deflector functions in the following way. The magnetic field lines from a magnetic field are drawn to the magnetic deflector material since the magnetic deflector is made from a ferro-magnetic material. Consequently, some of the magnetic field lines from the magnetic field will be lead through the magnetic deflector and some field lines, with a distance to the magnetic deflector, will follow the same direction and thus will be parallel with the field lines passing through the magnetic deflector. By placing magnetic deflector means symmetrically in respect to the magnetic sensor will thus create a magnetic field that is substantially parallel to the magnetic sensor. This creates an area around the magnetic sensor with a magnetic field that is substantially homogenous and directed parallel with the sensor. Magnetic field lines passing in other directions through the magnetic sensor will thus be reduced significantly.
The magnetic sensor is parallel to the travelling direction of the piston, i.e. the sensor extends in the same direction as the travelling of the piston. This longitudinal axis is denoted 12 in the figures. It is along this axis that the magnetic field lines of the external magnetic field are directed with the magnetic deflector. The centre of the tubular extension coincides with this axis 12.
In a second embodiment of the invention, shown in fig. 3 , the magnetic detector arrangement comprises two magnetic deflectors 7 positioned parallel to the magnetic sensor and symmetric to a symmetry axis 11 running through the sensor element 2 and the magnet 4. By using magnetic deflectors positioned around the magnetic element instead of mounting the deflector as an extension of the cylinder allows for a shorter hydraulic cylinder installation, which is an advantage both in weight and cost.
The magnetic deflectors are made from a ferro-magnetic material, such as iron. The properties of the magnetic deflectors are selected such that the material, e.g. iron, is not saturated by the external magnetic field. The external magnetic field may be the earth magnetic field and or another external magnetic field, e.g. a magnetic field induced by a high-current cable. Preferably the properties of the magnetic deflectors are selected such that they do not saturate by magnetic fields that can be expected or defined by e.g. a standard or regulation. In this example, the two magnetic deflectors having the dimensions of 5 x 10 mm are made from iron and extend the length of the hydraulic cylinder. The length of a magnetic deflector is preferably longer than the magnetic detector, but may also be shorter depending on e.g. the material properties and/or the positioning of the magnetic deflector. The magnetic deflectors are fastened to the outside of the hydraulic cylinder in a symmetric way, as is shown in fig. 3b.
In a further embodiment of the invention, shown in fig. 4, the magnetic detector arrangement comprises three magnetic deflectors 7 positioned parallel to the magnetic sensor and symmetric to the symmetry axis 11 running through the sensor element 2 and the magnet 4. In this example, the three magnetic deflectors are fastened to the outside of the hydraulic cylinder in a symmetric way, with one deflector opposing the sensor and the other two positioned with an offset of 120 degrees around the cylinder, as is shown in fig. 4b.
The magnetic deflectors do not need to be fixed to the hydraulic cylinder. As is shown in fig. 5, they may also be positioned around the cylinder in space, somewhat distance from the outside surface of the cylinder. This positioning may be advantageous in some installations, e.g. when the cylinder itself needs to be changed or maintained.
There are a number of possible combinations with regards to the number and positioning of the magnetic deflectors. It is however important not to position a magnetic deflector too close to the magnetic sensor, since the magnetic deflector will disturb the sensor if it is mounted too close. It is therefore advantageous to use rod-like magnetic deflectors as described above.
It is also possible to use a tube-like magnetic deflector on the side of the cylinder, and not just next to the cylinder as the extension tube described above. Figs. 6 and 7 show embodiments with a tube-like magnetic deflector that will not disturb the magnetic sensor. In fig. 6, the magnetic deflector is a tube with a cut-out extending the length of the magnetic deflector. The cut-out is in the order of 90 degrees and preferably in the range between 60 and 180 degrees. In fig. 7, the magnetic deflector is a tube with a diameter that is large enough to enclose the complete cylinder with the magnetic detector arrangement. The distance between the tube and the sensor is chosen so that the tube does not disturb the sensor.
Another advantage of the magnetic deflectors is that they prevent the piston rod from being magnetised by the external magnetic field. Since the magnetic deflectors direct the external magnetic field parallel to the sensor, the magnetic field will also be parallel to the piston rod. Since the piston rod does not move perpendicular to a magnetic field, the magnetisation of the piston rod will be greatly reduced.
In an advantageous embodiment the magnetic element 4 comprises two permanent magnets . A schematic magnetic detector comprising two permanent magnets is shown in fig. 8. Preferably, the magnets have approximately the same magnetic properties . The magnets are equally polarised and positioned next to each other in a symmetrical way with their symmetry axes parallel and with the polarisation in the same direction. The distance between the magnets is small compared with the size of the magnets . The distance between the magnets is selected so that the magnetic field is as wide as possible with an equal density. This is possible due to the fact that the magnetic field from the magnets will deform symmetrically in respect to a plane in between the magnets when positioned close to each other. By doing this, a well-defined magnetic field is obtained. This embodiment allows for an improved sensitivity of the magnetic detector arrangement.
The optimal distance between the magnets depends on various magnetic properties of the magnets . The optimal distance is small or equal compared to the thickness of the magnets. As an example, the optimal distance for two ceramic type magnets with the size 12*6 mm and 4 mm thick can be between 0.9 mm to 4 mm when the two planes with the size 12*6 mm are side by side. The easiest way to obtain the optimal distance is by empirical measurements .
The optimal distance between the magnets depends on various magnetic properties of the magnets. The optimal distance is small compared to the magnets . As an example, the optimal distance for two ceramic type magnets with the size 12*6*4 mm can be approximately 0.9 mm. The easiest way to obtain the optimal distance is by empirical measurements .
The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims . The magnetic arrangement can, for example, also be used for other types of detectors or switches. 1 : Magnetic detector arrangement
2 : Magnetic sensor
3 : Piston head
4 : Magnetic means 5: Piston rod
6 : Extension
7 : Magnetic deflector
8 : Hydraulic cylinder
9: Coil 10: Softmagnetic core
11: Symmetry axis
12 : Longitudinal axis

Claims

1. A magnetic detector arrangement, comprising a magnetic sensor element (2) and a magnetic means (4) for imposing a magnetic field on the magnetic sensor element (2) , the arrangement also comprising magnetic deflector means (7) operable to direct an external magnetic field in a direction substantially parallel to the magnetic sensor element (2),
characterized in that
the magnetic means (4) comprises two equally polarised magnets positioned at a predefined distance apart next to each other with the polarisation in the same direction so that a magnetic field generated in operation by the two magnets is forced to be substantially parallel to the magnetic sensor element (2).
2. A magnetic detector arrangement as claimed in claim 1, characterised in that the magnetic deflector means (7) are positioned parallel to the magnetic sensor element (2) .
3. A magnetic detector arrangement as claimed in any one of claims 1 to 2, characterized in that the magnetic deflector means (7) consists of a tube positioned at one of the detector arrangement with the central axis parallel with the magnetic sensor.
4. A magnetic detector arrangement as claimed in any one of claims 1 to 3, characterized in that the magnetic deflector means (7) consists of two magnetic deflectors (7) .
5. A magnetic detector arrangement as claimed in any one of claims 1 to 3 , characterized in that the magnetic deflector means (7) consists of three magnetic deflectors (7) .
6. A magnetic detector arrangement as claimed in any one of claims 1 to 5, characterized in that the magnetic deflector means (7) is made from a ferromagnetic material .
7. A hydraulic cylinder comprising a magnetic detector arrangement as claimed in any one of claims 1 to 6.
8. A vehicle comprising a hydraulic cylinder as claimed in claim 7.
9. A vehicle comprising a hydraulic cylinder as claimed in claim 8, wherein the hydraulic cylinder is connected to a steerable axle.
EP06824473A 2005-12-02 2006-11-24 Magnetic detector arrangement Withdrawn EP1969318A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0502659A SE530319C2 (en) 2005-12-02 2005-12-02 Magnetic detector arrangement, hydraulic cylinder and vehicles with such arrangement
PCT/SE2006/001334 WO2007064271A1 (en) 2005-12-02 2006-11-24 Magnetic detector arrangement

Publications (2)

Publication Number Publication Date
EP1969318A1 true EP1969318A1 (en) 2008-09-17
EP1969318A4 EP1969318A4 (en) 2010-10-06

Family

ID=38092505

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06824473A Withdrawn EP1969318A4 (en) 2005-12-02 2006-11-24 Magnetic detector arrangement

Country Status (3)

Country Link
EP (1) EP1969318A4 (en)
SE (1) SE530319C2 (en)
WO (1) WO2007064271A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0812903D0 (en) 2008-07-15 2008-08-20 Rota Eng Ltd Linear actuator and position sensing apparatus therefor
EP2696219B1 (en) 2012-08-06 2017-01-04 Ampass-Explorer Corp. Header device for improving the reception quality of a material detector device
JP6779645B2 (en) * 2016-03-30 2020-11-04 Ntn株式会社 Electric actuator
CN113289700B (en) * 2021-05-14 2022-04-29 北京航空航天大学 Density gradient microstructure, preparation method of density gradient microstructure and magnetic control switch

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2044461A (en) * 1979-03-16 1980-10-15 Moog Inc Armature position detector
GB2389659A (en) * 2002-06-12 2003-12-17 Imi Vision Ltd A position measuring system

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE8901770U1 (en) * 1989-02-15 1990-07-26 Schaltbau Gmbh, 8000 Muenchen, De
JPH04169881A (en) * 1990-11-02 1992-06-17 Fujitsu Ten Ltd Magnetic shield structure of magnetic sensor
JPH07260745A (en) * 1994-03-22 1995-10-13 Tokyo Gas Co Ltd Magnetic shield structure of magnetic sensor
DE19956313A1 (en) * 1999-11-12 2001-05-23 Atecs Mannesmann Ag Magnetic field sensor for determining the position of a moving object
US6720764B2 (en) * 2002-04-16 2004-04-13 Thomas Energy Services Inc. Magnetic sensor system useful for detecting tool joints in a downhold tubing string

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2044461A (en) * 1979-03-16 1980-10-15 Moog Inc Armature position detector
GB2389659A (en) * 2002-06-12 2003-12-17 Imi Vision Ltd A position measuring system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO2007064271A1 *

Also Published As

Publication number Publication date
SE530319C2 (en) 2008-04-29
EP1969318A4 (en) 2010-10-06
SE0502659L (en) 2007-06-03
WO2007064271A1 (en) 2007-06-07

Similar Documents

Publication Publication Date Title
JP3447076B2 (en) Position sensor device
US5231352A (en) Power actuator including magnetic position detector
KR101891347B1 (en) Magnetic proximity sensor
US20150323346A1 (en) Magnetic Measuring Arrangement and Corresponding Sensor Arrangement for Detecting Motion of a Moving Component
EP0707195B1 (en) Magnetic detector of movement of an object
JPH0441921B2 (en)
KR900014893A (en) Accelerometer with Dual Magnetic Sensors
US6577123B2 (en) Linear position sensor assembly
EP1969318A1 (en) Magnetic detector arrangement
US7285950B2 (en) Position measuring system and pneumatic cylinder
US7308975B2 (en) Velocity sensing system for a damper
US7463023B1 (en) Non-contacting rotary and linear travel sensor
US20050012500A1 (en) Path sensor with an magnetoelectric transformer element
US7508288B2 (en) Magnetic switch arrangement
ES2222268T3 (en) PEDAL SYSTEM FOR AUTOMOBILE, PROVIDED BY A DISPLACEMENT RECEIVER.
US7342394B2 (en) Magnetic detector arrangement and method for obtaining a symmetric magnetic field
US20120242332A1 (en) Measurement method and magnetic sensor for the contactless detection of movements
US20030048100A1 (en) Magnetic sensor of the position of a moving member over a trajectory followed by the moving member
US20240067260A1 (en) Steering system comprising a shielded magnetic torque sensor device
US20090184707A1 (en) Electromagnetic barrier for use in association with inductive position sensors
US6426618B1 (en) Magnetostrictive linear displacement transducer for a vehicle steering system
JP3326903B2 (en) Travel detector
CN114364947B (en) Linear actuator comprising a measuring device for determining the position of a linearly movable part
JP6201629B2 (en) Vehicle detection device
JPH0694404A (en) Height sensor with built-in shock absorber

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20080702

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

A4 Supplementary search report drawn up and despatched

Effective date: 20100907

DAX Request for extension of the european patent (deleted)
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20130601