DE102019216988A1 - Position measuring system - Google Patents

Abstract

The invention relates to a position measuring system (10), comprising a permanent magnet (12) and a magnetic field sensor (16) which is movably arranged along a measuring section (14) running laterally next to the permanent magnet (12), in order to use a magnetic field sensor (16) specific direction of the magnetic field to be able to determine a position of the magnetic field sensor (16) along the measuring section (14). In order to reduce the susceptibility of the position measuring system (10) to interference with regard to interference fields and to be able to specify the dependency of the direction of the magnetic field on the position along the measuring section (14) more flexibly and to be able to reduce the impairment of the measuring accuracy due to mechanical tolerances or mechanical play, the position measuring system (10) according to the invention furthermore has at least one ferromagnetic flux guide piece (20-1, 20-2) which extends in a plate shape below or above the measuring section (14) on the one hand in the direction of the measuring section (14) and at least part of the measuring section (14 ) following and on the other hand extends in the lateral direction.

Description

The present invention relates to a position measuring system, comprising a permanent magnet and a magnetic field sensor arranged movably along a measuring section running laterally next to the permanent magnet, in order to be able to determine a position of the magnetic field sensor along the measuring section using a direction of the magnetic field determined by means of the magnetic field sensor.

In such a position measuring system, for. B. the determination of the position of the magnetic field sensor or a component provided with the magnetic field sensor can be provided along a straight measuring section provided. Alternatively, however, in such a measurement, z. B. a curved measuring section can be provided, for. B. a circular arc curved measuring section.

The function of such a "magnetic" position measuring system is based on the fact that the magnetic field of a permanent magnet is location-dependent and thus a direction of the magnetic field determined for a specific location by means of a magnetic field sensor is a value representative of the corresponding position (of the magnetic field sensor relative to the permanent magnet) represents or can be inferred from the result of a measurement of the direction of the magnetic field on this position. It goes without saying that the position, the movability and the movement of the magnetic field sensor along the measuring section are to be understood here and also within the scope of the invention as the relative position or relative mobility or relative movement of the magnetic field sensor relative to the permanent magnet.

Such generic position measuring systems are known in various designs from the prior art. For example, refer to the publications EP 0 979 988 B1 , DE 199 10 636 A1 , EP 1 989 505 B1 and WO 2011/135063 A2 referenced.

The disadvantage of the position measuring systems known from the prior art is that they are more or less susceptible to impairment of the measurement result due to any magnetic interference fields that may occur in the installation environment of the system. In addition, known systems often have the disadvantage that, due to the properties of a magnetic field, which are predetermined in principle, the dependency of the magnetic field of the permanent magnet on the position of the magnetic field sensor along the measurement path is caused by the construction (e.g. through the shape and magnetization of the permanent magnet, and the course of the Measuring distance relative to the permanent magnet) can be influenced, but cannot be specified as desired. Another disadvantage of known systems is the sensitivity of the measurement to mechanical tolerances such. B. Manufacturing and assembly tolerances and mechanical play. In particular, changes in the position of the magnetic field sensor caused by play at right angles to the direction of the magnetic field to be measured cause considerable measurement uncertainty.

It is an object of the present invention to eliminate or at least alleviate the disadvantages explained above in a position measuring system of the type mentioned at the beginning. In particular, the invention is intended to enable a position measuring system of the type mentioned at the outset that is less susceptible to interference and in which the dependence of the magnetic field on the position along the measuring section can be specified more flexibly.

According to the invention, this object is achieved by a position measuring system according to claim 1. The dependent claims relate to advantageous developments of the invention.

The position measuring system according to the invention is characterized in that it furthermore has (at least) one ferromagnetic flux guiding piece, which extends below or above the measuring section in the form of a plate on the one hand in the direction of the measuring section and following at least part of the measuring section and on the other hand in the lateral direction.

With the invention, the (at least one) ferromagnetic flux guide piece can advantageously at least partially screen any magnetic interference fields that may occur. Therefore, the influence of interference fields on the measurement result is reduced. The shielding effect depends on the spatial arrangement and extent of the ferromagnetic material and can thus be advantageously adapted to the specific application through the design. The shielding effect proves to be particularly favorable if ferromagnetic flux guide pieces extending below and above the measuring section are attached.

The terms used here in the description of the position measuring system to define relative spatial arrangements and spatial directions, such as B. "below", "below", "above", "above", "vertical", "side" or "lateral", "horizontal" are only used to simplify the description of the position measuring system. The terms define, so to speak, a spatial coordinate system of the position measuring system as such, but were chosen arbitrarily insofar as ultimately only in Use situation of the position measuring system z. B. determines where is up and where is down.

Another advantage of the invention is that the (at least one) ferromagnetic flux guide piece can be used to influence and thus modify the dependency of the direction of the magnetic field of the permanent magnet on the position of the magnetic field sensor along the measurement path. In the invention, the dependence of the magnetic field on the position of the magnetic field sensor can be influenced not only by the shape and magnetization of the permanent magnet and the course of the measuring path relative to the permanent magnet, but also advantageously by the specific arrangement and shape of the flux guide (s).

It has turned out to be advantageous that there are many arrangements and shapes of the flux guiding piece or pieces that can be used, with which at the same time both a large shielding effect against interference fields and an advantageous modification of the dependence of the direction of the magnetic field on the position of the magnetic field sensor, which co-determines the measuring system characteristics can be achieved.

In particular, z. B. any kind of linearization of the mentioned dependency or the measuring system characteristic represent such an advantageous modification. In this context, linearization means that the relationship between the direction of the magnetic field (or the corresponding sensor signal) on the one hand and the position to be determined on the other hand can be described more precisely by a relatively simple mathematical function, in particular a linear function, than without the inventive use of a or several flux guide pieces would be the case.

Yet another advantage of the invention is that a dependency of the direction of the magnetic field on the position of the magnetic field sensor that is relatively insensitive with regard to any tolerances can be achieved. For example, with the invention by a homogenization of the magnetic field in the area of the measuring section z. B. mechanical play of the magnetic field sensor with regard to its arrangement on the measuring section and / or when it is guided along the measuring section can be advantageously compensated.

The measuring section runs laterally next to the (at least one) permanent magnet along the permanent magnet. In one embodiment, the measuring section is provided to run in a straight line. Alternatively, however, a non-rectilinear measuring section can also be provided, in particular z. B. a curved measuring section, z. B. a circular arc curved measuring section. A curved measuring section can, for. B. correspond to an arc angle of at least 20 °, in particular at least 40 ° and / or a maximum of 180 °, in particular a maximum of 120 °. The course of the measuring section can in particular, for. B. parallel (i.e. with a predetermined uniform distance in the lateral direction of the position measuring system) to a course of an in particular e.g. B. elongated shaped permanent magnets can be provided. In a preferred embodiment, the magnetic field sensor retains its orientation with respect to the (local) orientation of the measuring section during its movement along the measuring section (i.e. relative to the permanent magnet).

In an embodiment of the invention that is described in more detail below, the permanent magnet is designed as an annularly closed body. In this case, the measuring section can also run in a closed ring laterally next to the permanent magnet along the permanent magnet. In particular, closed, concentric courses of the permanent magnet and the measuring section which are curved in the shape of an arc of a circle can be provided, so that the course of the measuring section corresponds to an arc angle of 360 °.

In the context of the invention, it should not be ruled out that several permanent magnets are provided, in particular, for. B. at least two permanent magnets, the magnetic field sensor z. B. along a laterally next to the two permanent magnets (that is, viewed in the lateral direction between the two permanent magnets) along both permanent magnets can be arranged movable measuring section.

In the context of the invention, it should not be excluded that several magnetic field sensors are provided, in particular z. B. at least two magnetic field sensors, both of which are arranged movably along the measuring section running laterally next to the (at least one) permanent magnet along the same, but offset from one another in the course of the measuring section. In this case, a position along the measurement path can be determined using the multiple magnetic fields (measured by multiple magnetic field sensors).

In one embodiment of the invention, the permanent magnet is formed from a piece of a hard magnetic material, in particular, for. B. an alloy containing iron (z. B. ferrite) and z. B. cobalt and / or nickel. Alternatively, the permanent magnet z. B. be formed from a composite material, such as. B. a plastic matrix with therein embedded particles of magnetic material. The latter magnets can, for. B. be produced by pressing or spraying.

In one embodiment of the invention it is provided that the permanent magnet is designed as an elongated profile.

In this case, the permanent magnet has a uniform cross-section (profile cross-section) over its length (profile). The profile cross-section can in particular, for. B. a rectangular, z. B. approximately square, or z. B. have an approximately trapezoidal shape.

In one embodiment it is provided that a profile axis of the profile runs in a straight line. In this case, the permanent magnet can, for. B. a prismatic, e.g. B. have cuboid shape.

In another embodiment it is provided that a profile axis of the profile is curved. For example, a profile axis curved in the shape of a circular arc can be provided.

In one embodiment of the invention it is provided that the permanent magnet is designed as an elongated profile and the measuring section running laterally next to the permanent magnet along the same runs parallel to a profile axis of the profile.

In this context, the term “parallel” should be understood regardless of whether the profile axis and the measuring section both run in a straight line or both run in a curved manner.

In particular, it can be provided here that the profile axis and the measuring section both run in a straight line, laterally spaced from one another, parallel to one another, or that the profile axis and the measuring section z. B. with respective curvatures, laterally spaced from each other, run parallel to each other (for example on respective arcs of two concentric circles).

In one embodiment of the invention it is provided that the permanent magnet is designed as an elongated body with a cross section that varies over its length (course).

The term “cross-section” is to be understood in such a way that the cross-section is determined both by its shape (cross-sectional shape) and its size (cross-sectional area). In this respect, a cross-section that varies over the length of the permanent magnet can result due to a variation in the cross-sectional shape and / or a variation in the cross-sectional area content.

In one embodiment of the invention it is provided that the permanent magnet is designed as an elongated body with a uniform (not varying) cross-sectional area over its length.

In one embodiment of the invention it is provided that the permanent magnet is designed as an elongated body with a cross-sectional shape that varies over its length. For this purpose, in particular z. For example, it can be provided that the cross section has the shape of a square (z. B. shape of a trapezoid), in which the orientation of a side of the square facing the measuring section varies over the length of the permanent magnet.

In a further development of this embodiment it is provided that the mentioned side of the square runs vertically at a central point along the length of the permanent magnet (and the cross-section there is at least approximately rectangular, for example), but increases with increasing distance from the central point runs obliquely (with respect to the vertical).

Alternatively or additionally it can be provided that the mentioned side of the quadrilateral extends at an angle with respect to the vertical which varies monotonically, in particular strictly monotonically, in particular proportionally to the position in the course of this length over the course of the length of the permanent magnet. In a preferred development, the angle with respect to the vertical varies overall (over the full length of the permanent magnet) by an angular amount of at least 10 °, in particular at least 30 ° or at least 60 °. On the other hand, it is advantageous in many cases if this angular amount is a maximum of 120 °, in particular a maximum of 90 °. In particular, it can also be provided here that the cross-section of the permanent magnet has a uniform (not varying) cross-sectional area over the length of the same. In one embodiment, said square is a trapezoid in which two parallel trapezoid sides run at least approximately in the lateral direction of the position measuring system and one side of the trapezoid facing away from the measuring section runs at least approximately in the vertical direction of the position measuring system.

In one embodiment, the permanent magnet is designed as an annular (z. B. circular) closed body, wherein the measuring path z. B. also ring-shaped (z. B. circular ring) closed radially outside of the permanent magnet.

In this case too, the above-described configurations of the permanent magnet can advantageously be provided, with The following should be noted with regard to the terminology: "along the length (of the permanent magnet)" then means "along the circumference", and "a full length (of the permanent magnet)" then means "a full 360 ° circumference / rotation". In addition, the following restriction must be observed: A cross-section at a certain point must be reproduced every 360 ° after progressing along the circumference (at the latest). This is always the case with the design of the permanent magnet as a profile, but with a design with a cross-section that varies over the length (course, ie here 360 ° rotation), this represents a restriction.

Taking this restriction into account, an annularly closed permanent magnet requires the configuration described above, in which "the mentioned side of the quadrangle runs vertically at a central point along the length of the permanent magnet (and the cross-section there, for example, is at least approximately rectangular). , but with increasing distance from the central point runs increasingly obliquely (with respect to the vertical) ”, a modification. In the case of an embodiment with a cross-section that varies over the 360 ° rotation, a modified embodiment provides that the mentioned side of the quadrilateral runs vertically at (at least) a certain first point in the course of the permanent magnet (and the cross-section there, for example, at least approximately rectangular) and with increasing distance from this first point up to (at least) a second point runs increasingly obliquely (with respect to the vertical), but after each such second point is exceeded, the side of the square again runs decreasingly obliquely (with respect to the vertical).

Furthermore, taking into account the restriction in an annularly closed permanent magnet, the configuration described above requires a modification in which “the mentioned side of the quadrilateral extends at an angle with respect to the vertical that is monotonous, in particular strictly monotonous, in particular proportional, over the length of the permanent magnet to the position in the course of this length varies ”, whereby in a preferred development“ the angle with respect to the vertical varies here overall (over the full length of the permanent magnet) by an angular amount of at least 10 °, in particular at least 30 ° or at least 60 ° ”. In the case of an embodiment with a cross-section that varies over the 360 ° circumference, a modified embodiment provides that the mentioned side of the quadrilateral extends at an angle with respect to the vertical that is monotonous in sections, in particular strictly monotonous, in particular proportional to the course of the circumference of the permanent magnet Position varies over the course of this circumference, at least a portion of the circumference with a monotonic increase and at least a portion of the circumference with a monotonic decrease is provided, in a preferred development the angle with respect to the vertical over the full circumference of the permanent magnet and / or each of the mentioned Sections varied by an angular amount of at least 10 °, in particular at least 30 ° or at least 60 ° (and varied, for example, by a maximum of 120 °, in particular by a maximum of 90 °).

There are various possibilities with regard to the magnetization of the permanent magnet.

In one embodiment of the invention it is provided that the permanent magnet is magnetized homogeneously, in which case the permanent magnet can be designed, for example, as an elongated profile and in particular be magnetized orthogonally to a profile axis of the profile (e.g. vertically).

In the case of a homogeneous magnetization of the permanent magnet, a magnetization direction oriented at least approximately orthogonally to a course of the permanent magnet is preferably provided, in particular z. B. an at least approximately vertically oriented direction of magnetization.

Homogeneous magnetization in the direction of the profile axis of the profile, or generally in the direction of the length of the permanent magnet, should not, however, be excluded within the scope of the invention.

1. 1. Beispiel: Bei einem Permanentmagneten, der als ein langgestrecktes (z. B. geradlinig) verlaufendes Profil ausgebildet und homogen in Richtung seiner Profilachse magnetisiert ist, ergibt sich entlang einer parallel zur Profilachse verlaufenden Messstrecke eine qualitativ relativ komplizierte und quantitativ relativ schwache Abhängigkeit des Magnetfeldes von der Position entlang der Messstrecke. Mit dem Einsatz eines oder mehrerer über die Länge des Permanentmagneten betrachtet ungleichmäßiger Flussleitstücke lässt sich die Abhängigkeit jedoch vorteilhaft sowohl qualitativ (z. B. Linearisierung) als auch quantitativ (z. B. Vergrößerung eines „Hubs“ der vom Magnetfeldsensor gemessenen Größe(n)) modifizieren bzw. verbessern.
2. 2. Beispiel: Bei einem Permanentmagneten, der als ein langgestrecktes (z. B. geradlinig) verlaufendes Profil ausgebildet und homogen orthogonal zu seiner Profilachse (z. B. vertikal) magnetisiert ist, ergibt sich entlang einer seitlich neben dem Permanentmagneten entlang desselben parallel zur Profilachse verlaufenden Messstrecke überhaupt keine Abhängigkeit des Magnetfeldes von der Position entlang der Messstrecke (abgesehen von „Randeffekten“ an den Enden einer bis an die beiden Enden des Permanentmagneten heranreichenden Messstrecke). Mit dem Einsatz eines oder mehrerer über die Länge des Permanentmagneten betrachtet ungleichmäßiger Flussleitstücke lässt sich eine solche Abhängigkeit jedoch vorteilhaft hervorrufen und sogar qualitativ in einem gewissen Ausmaß in gewünschter Weise einstellen.

In a particularly advantageous further development of the embodiment with homogeneous magnetization, it is provided that the arrangement and / or shape of the flux guide piece (s), viewed over the length of the permanent magnet, is so uneven that as a result, the dependence of the magnetic field on the position of the magnetic field sensor along the measurement path and thus the measuring system characteristic is significantly modified, or that this dependency is even caused in the first place. Two examples of this:

1. 1st example: In the case of a permanent magnet, which is designed as an elongated (e.g. straight) profile and is magnetized homogeneously in the direction of its profile axis, there is a qualitatively relatively complicated and quantitatively relatively weak dependency of the measurement path running parallel to the profile axis Magnetic field from the position along the measuring section. With the use of one or more non-uniform flux guide pieces viewed over the length of the permanent magnet, the dependency can be advantageously reduced both qualitatively (e.g. linearization) as well as quantitatively (e.g. increasing a "stroke" of the variable (s) measured by the magnetic field sensor) or improving it.
2. 2nd example: In the case of a permanent magnet, which is designed as an elongated (e.g. straight) profile and is magnetized homogeneously orthogonally to its profile axis (e.g. vertically), the result is along a side next to the permanent magnet along the same parallel to Measuring section running along the profile axis, there is absolutely no dependence of the magnetic field on the position along the measuring section (apart from "edge effects" at the ends of a measuring section that extends to both ends of the permanent magnet). With the use of one or more non-uniform flux guide pieces viewed over the length of the permanent magnet, however, such a dependency can advantageously be brought about and can even be set qualitatively to a certain extent in the desired manner.

According to a more specific embodiment, the permanent magnet is magnetized homogeneously with a magnetization direction oriented essentially orthogonally to a course of the permanent magnet, in particular with an essentially vertically oriented magnetization direction, with a lower and an upper flux guide being provided, which extend laterally over the entire course of the measuring section Viewed in direction, each extend up to the permanent magnet and lie against the permanent magnet (and e.g. end flush with the permanent magnet), and each at one point in the course of the measuring section, viewed in a lateral direction, up to the measuring section or beyond the measuring section extend and have a varying lateral extent over at least part of the course of the measuring section. The contours (viewed from above or below) of the two flux guide pieces can in particular, for. B. run mirror images of each other, based on a mirror plane extending vertically in a central region of the measuring section. A longitudinal center line of the permanent magnet can be straight or curved.

In another embodiment of the invention it is provided that the permanent magnet is magnetized inhomogeneously, wherein in this case too the permanent magnet can be designed, for example, as an elongated profile, and where in particular, for. B. a “helical” along a profile axis of the profile, or more generally along the length of the permanent magnet, varying magnetization can be provided.

Such a helical variation can in particular be provided such that a (local) direction of magnetization depends essentially exclusively on the position along the profile axis of the profile (generally: along the length of the permanent magnet).

In the case of an inhomogeneous magnetization of the permanent magnet, a magnetization direction which is at least approximately orthogonal to a course of the permanent magnet and which varies in the course of the permanent magnet is preferably provided.

In a further development of the embodiment with inhomogeneous magnetization, it is provided that the arrangement and shape of the flux guide piece (s) are uniform over the length of the permanent magnet. For this purpose, the flux guide or z. B. each of two flux guide pieces arranged below or above the measuring section can each be designed as a plate, which extends below or above the measuring section on the one hand in the direction of the measuring section and here the measuring section over its entire length and on the other hand in the lateral direction with constant extension ( e.g. plate width). In this case, there is no significant qualitative change in the measuring system characteristic, which can essentially already be predetermined by the inhomogeneous (e.g. helical) magnetization. However, there is advantageously a high shielding effect with regard to interference fields and, furthermore, a certain quantitative modification of the measuring system characteristics can advantageously be achieved by amplifying and homogenizing the magnetic field in the area of the measuring section.

In another development of the embodiment with inhomogeneous magnetization, it is provided that the The arrangement and / or shape of the flux guide piece (s) over the length of the permanent magnet is uneven, in order to modify the measuring system characteristics in a desired way (e.g. linearization) by modifying the dependence of the magnetic field on the position of the magnetic field sensor along the measuring section ).

Here is an exemplary embodiment: In the case of a permanent magnet, which is designed as an elongated (e.g. straight) profile and is magnetized inhomogeneously, orthogonally to its profile axis, "helically", a qualitatively simple and quantitative result is obtained along a measurement section running parallel to the profile axis Relatively strong dependence of the magnetic field on the position along the measuring section. The inventive use of one or more flux guide pieces can then, for. B. serve primarily to shield interference fields. Nevertheless, in this example too, the measuring system characteristics can advantageously be modified (e.g. linearized) through a targeted non-uniformity of the arrangement and / or shape of the flux guide piece (s) considered over the length of the permanent magnet.

For this purpose, the flux guide or z. B. each of two flux guide pieces arranged below or above the measuring section can each be designed as a plate that extends below or above the measuring section on the one hand in the direction of the measuring section and here the measuring section z. B. following over the entire length and on the other hand in the lateral direction with uneven extension (z. B. plate width).

According to a more specific embodiment, the permanent magnet is inhomogeneously magnetized with a magnetization direction oriented essentially orthogonally to a course of the permanent magnet and varying in the course of the permanent magnet, with a lower and an upper flux guide being provided, which are viewed in the lateral direction over the entire course of the measuring section on the one hand extend up to the permanent magnet and bear against the permanent magnet and on the other hand each extend up to the measuring section or beyond the measuring section. The permanent magnet can here, for. B. be designed as an elongated body with a varying cross-section over its length, in particular wherein the cross-section has the shape of a square, in which the orientation of a side of the square facing the measuring section varies over the length of the permanent magnet. In particular, the direction of magnetization, which varies in the course of the permanent magnet, can be provided as a (“helical”) rotation of the direction of magnetization. B. can result in a twist angle which is at least 10 °, in particular at least 20 °. On the other hand, it is sufficient in many cases if this angle of rotation is a maximum of 120 °, in particular a maximum of 90 °. A longitudinal center line of the permanent magnet can run straight or curved.

As already mentioned, within the scope of the invention, the permanent magnet can be designed as an annularly closed body (e.g. profile). In this case, too, the configurations described above with homogeneous or inhomogeneous magnetization can advantageously be provided if, with regard to the terminology, it is noted that “along the length (of the permanent magnet)” then means “along the circumference” and “a full length (of the Permanent magnets) "then z. B. can mean "a full 360 ° circumference / rotation", and the restriction is observed that a magnetization (in amount and direction) at a certain point after progressing along the circumference (at the latest) must be reproduced every 360 °. The term “in the lateral direction” is then to be understood as “in the radial direction”. In one embodiment, a periodically changing direction of magnetization is provided along the circumference, with only one period or several periods (e.g. 2, 3, 4 or more periods) of a circumferential angle-dependent curve viewed over the full circumference (360 °) the direction of magnetization can be provided.

In one embodiment of the invention, the position measuring system has (at least) one lower ferromagnetic flux guiding piece, which extends below the measuring section in the form of a plate on the one hand in the direction of the measuring section and following at least part of the measuring section and on the other hand in a lateral direction, and (at least) one of the position measuring system upper ferromagnetic flux guiding piece, which extends above the measuring section in the form of a plate on the one hand in the direction of the measuring section and following at least part of the measuring section and on the other hand in the lateral direction.

When describing particular details or embodiments relating to the design of a flux guide piece, this description can be related to one or more or all of these flux guide pieces in the case of the presence of several flow guide pieces, for example a lower and an upper flow guide piece as mentioned above.

In one embodiment, the flux guide piece is formed from a soft magnetic material, in particular a metal or a metal alloy.

In the case of the material of the flux guide piece, it can in particular be e.g. B. iron or a metal alloy containing iron (z. B. iron-nickel alloy) act.

In one embodiment it is provided that the flux guide piece is designed as a solid sheet metal (“flux guide sheet”), in particular as a sheet with a uniform thickness. Suitable sheets can, for. B. be designed or manufactured as a stamped sheet.

In an advantageous embodiment, a thickness (or a thickness averaged over a sheet metal area) is at least 0.05 times, in particular at least 0.1 times, and / or is at least 0.1 times the (possibly maximum) extension of the permanent magnet in the vertical direction Thickness a maximum of 0.5 times, in particular a maximum of 0.4 times this extension.

In one embodiment it is provided that the flux guiding piece has the shape of a flat plate, a plate plane on the one hand being able to extend at least approximately parallel to the measuring section (below or above the same) and on the other hand in the lateral direction, in particular at least approximately in the horizontal direction.

In one embodiment, it is provided that the flux guiding piece extends at least at one point in the course of the measuring section as far as the permanent magnet when viewed in the lateral direction (e.g. extends horizontally), in particular rests against the permanent magnet. So z. B. a flux guide arranged below the measuring section with a front edge or with part of its upper flat side rest on the permanent magnet, whereas a flux guide arranged above the measurement section can rest with a front edge or with part of its lower flat side on the permanent magnet.

A flat contact of the (plate-shaped extending) flux guide piece on a corresponding contact surface of the permanent magnet is preferably provided. The contact surface can, for. B. be designed as a flat surface. The contact surface can, for. B. represent a lower or an upper end surface of the permanent magnet, in which case it is preferred that the flux guide piece in question is in full contact with this contact surface. The contact surface can, for. B. be oriented horizontally.

In one embodiment of the invention it is provided that the flux guiding piece extends at least at one point in the course of the measuring section viewed in the lateral direction up to the measuring section or beyond the measuring section.

In a further development of this embodiment it is provided that the flux guiding piece extends over the entire course of the measuring section viewed in the lateral direction up to the measuring section or beyond the measuring section. In the case of a rectilinear measuring section, this z. B. be provided a flux guide with a rectangular contour. In the case of an annular (z. B. circular) closed measuring section, this can be, for. B. a flux guide with a uniformly wide annular or with a circular contour can be provided.

In one embodiment of the invention, it is provided that the flux guide piece extends as far as the permanent magnet and rests on the permanent magnet in the entire course of the measuring section viewed in the lateral direction, and on the other hand extends to the measuring section or beyond the measuring section.

In one embodiment of the invention it is provided that the flux guide piece has a varying lateral extent over at least part of the course of the measuring section. Preferably, only the lateral extension of the part of the flux guide piece facing away from the permanent magnet varies, whereas the part of the flux guide piece facing the permanent magnet has a uniform lateral extension and z. B. with an end face or (preferably) a part of the flat side rests on the permanent magnet.

In a further development of this embodiment it is provided that the flux guiding piece has a varying lateral extent over the entire course of the measuring section. In this case too, only the lateral extent of the part of the flux guide piece facing away from the permanent magnet preferably varies. In the case of a rectilinear measuring section, this z. B. be provided a flux guide with a trapezoidal contour.

As already mentioned, within the scope of the invention, the permanent magnet can be designed as a ring-shaped (for example circular ring-shaped) body (for example profile) running in a closed manner. Even then, the above-described configurations of the flux guide piece can advantageously be provided, in particular, for. B. also with (at least) one annularly closed flux guide. Note the restriction that the cross-section of the flux guide must be reproduced at a certain point after progressing along the circumference (at the latest) every 360 °. The term “in the lateral direction” is then to be understood as “in the radial direction”. The restriction is e.g. B. fulfilled when the or each flux guide has a uniform cross section over the circumference. However, designs are also possible in which the flux guide piece has a non-uniform cross-section in the course of the circumference (in particular, for example, a non-uniform lateral or radial extension, e.g. on its (radially outer) side facing the measuring section). In one embodiment, a periodically changing radial extension of the flux guide piece is provided along the circumference, with only one period or several periods (e.g. 2, 3, 4 or more periods) viewed over the full circumference (360 °) of the system. a circumferential angle-dependent course of this radial extension can be provided.

With the (at least one) magnetic field sensor used in the invention, the magnetic field is measured at the location of the magnetic field sensor to determine a direction of the magnetic field in order to determine the position of the magnetic field sensor based on the determination of this direction of the magnetic field to be determined along the measuring section running next to the permanent magnet.

In one embodiment, the magnetic field sensor is designed to provide (at least) one analog sensor signal (e.g. voltage signal).

In one embodiment, the magnetic field sensor is designed to provide (at least) one digital sensor signal (data signal).

The term “magnetic field sensor” is to be understood broadly in the sense of the invention insofar as it is generally neither necessary nor expedient to completely, i.e., completely divide the magnetic field vector at the location of the magnetic field sensor. H. in terms of amount and direction.

In a preferred embodiment, by means of the magnetic field sensor z. B. (at least) two different magnetic field components are measured and the direction of the magnetic field is determined from them.

In one embodiment of the invention it is provided that the magnetic field sensor is designed to measure at least two magnetic field components of the magnetic field and to provide a sensor signal that is dependent on the direction of the magnetic field. The latter sensor signal can in particular, for. B. be representative of an angle or angle of rotation by which the direction of the magnetic field deviates from a direction defined by the magnetic field sensor or is rotated. Such magnetic field sensors are commercially available in diverse designs and can advantageously be used in the invention.

In one embodiment, the magnetic field sensor is designed as a magnetoresistive sensor, e.g. B. as a so-called XMR sensor, so z. B. as AMR ("anisotropic magneto-resistive") - sensor, GMR ("giant magneto-resistive") - sensor or TMR ("tunneling magneto-resistive") - sensor. Alternatively, the magnetic field sensor z. B. as a Hall sensor such as in particular z. B. a 2D Hall sensor or 3D Hall sensor.

In a more specific embodiment of the invention, it is provided that the magnetic field sensor is designed to transmit a sensor signal (e.g. analogue sensor signal) representative of an angle of rotation by which the direction of the magnetic field is rotated from a direction defined by the magnetic field sensor and its arrangement in the position measuring system Voltage signal or digital data signal).

The direction defined in this way can in particular be a lateral direction of the position measuring system, i. H. a horizontal direction orthogonal to the direction of the measurement section, wherein as the angle of rotation to be measured in particular z. B. the angle of rotation resulting in a plane orthogonal to the direction of the measurement section can be provided.

In one embodiment of a magnetic field sensor that measures an angle of rotation of the magnetic field, the latter is designed to measure the angle of rotation in an angle of rotation range of at least 10 °, in particular at least 20 ° (e.g. +/- 10 °). On the other hand, in many cases it is sufficient if the measurable angle of rotation range is a maximum of 90 ° (e.g. +/- 45 °).

In one embodiment it is provided that a position dependency of a rotation angle of the magnetic field determined by means of the measurement of the magnetic field sensor along the measurement path can be described at least in sections by an at least approximately linear function or by an at least approximately sinusoidal function. If the course of the measuring section is not closed in a ring shape, an at least approximately linear function is preferred in many cases, whereas if the measuring section is closed in a ring shape, an at least approximately sinusoidal function is preferred in many cases.

In one embodiment of the invention it is provided that the measuring system has a device for characteristic curve compensation, which is designed to modify (at least) one measuring signal generated by the magnetic field sensor as a function of the magnetic field in a predetermined manner and thus a modified sensor signal (for further use or further processing).

In one embodiment, the device for characteristic curve compensation is formed by a circuit arrangement for signal processing, which is an integral part of the magnetic field sensor. As an alternative or in addition, the device for characteristic curve compensation or at least part of a circuit arrangement for signal processing which forms it can also be provided structurally separate from the magnetic field sensor. For example, the position measuring system can have an evaluation device (e.g. program-controlled electronic evaluation device) to which a sensor signal generated by the magnetic field sensor is supplied and which is designed to carry out the characteristic curve compensation (or at least part of it) in order to achieve the modified Provide sensor signal.

In one embodiment, the device for characteristic curve compensation is designed as a digital signal processing device to which (at least) one sensor signal generated by the magnetic field sensor in the form of a digital data signal is fed. Alternatively, z. For example, it can be provided that (at least) one digital data signal is fed to the digital data processing device, which was obtained by analog / digital conversion from a sensor signal provided in analog form by the magnetic field sensor.

In one embodiment, the device for characteristic curve compensation is designed to implement a modification of the measuring system characteristic in such a way that the relationship between on the one hand the value (analog or digital) of a signal provided by the magnetic field sensor, such as e.g. B. a sensor signal representative of an angle of rotation of the magnetic field and, on the other hand, the position (along the measurement path) can be described more precisely by a relatively simple mathematical function, in particular a linear function ("linearization"), than without the use of characteristic curve compensation would be the case.

In one embodiment, the device for characteristic curve compensation is designed to carry out a so-called “multipoint calibration” in which the relevant sensor signal is within the relevant value range (e.g. +/- 45%) is calibrated (modified) using a compensation curve, this compensation curve being defined for this value range by several interpolation points. For example, the support points (or data representing them) can be stored in the device for characteristic curve compensation. When the position measuring system is in operation, the device can use the support points or a compensation curve determined therewith to carry out the corresponding compensation (e.g. by multiplying the value represented by the sensor signal with a correction factor resulting from the compensation curve for this value).

Although, as already mentioned, a certain setting of the measuring system characteristics can already advantageously be implemented in the invention by suitable arrangement and shape of one or more flux guiding pieces, an additional use of the characteristic curve compensation described can advantageously further improve this setting in terms of its accuracy and / or further degrees of freedom enable adjustability.

In an embodiment that is also advantageous in this regard, a tilting of a course of the measuring section with respect to a (horizontal) course of the permanent magnet and / or one or more flux guide pieces is provided in such a way that the (vertical) positions of the two ends of the measuring section differ significantly from one another , so that the measuring section between the two ends is inclined (with respect to the course of the permanent magnet or the flux guide, or with respect to the horizontal) from one end to the other end. In particular, a uniform angle of inclination of the inclined course of the measuring section with respect to the course of the permanent magnet and / or a flux guide piece, viewed over the length of the measuring section, can be provided.

Equivalent to this, one could also speak of a tilting of the arrangement formed from the permanent magnet and flux guide piece (s) with respect to a (horizontal) course of the measuring section. What is essential for this embodiment is the tilting of the components mentioned relative to one another.

The tilting leads to a corresponding modification of the measuring system characteristics. It has been shown to be particularly advantageous that with the defined tilting the magnetic field sensor can be guided along the measuring section in a more homogeneous field and thus a reduction in the sensitivity of the measuring system characteristics or the measuring accuracy to mechanical tolerances (e.g. play in horizontal and / or vertical direction, as well as e.g. manufacturing and / or assembly tolerances) can be achieved.

In one embodiment, the above-mentioned angle of inclination (or, in the case of a non-uniform angle of inclination, its value averaged over the course of the measurement section) is at least 1 °, in particular at least 2 °. On the other hand, a value of a maximum of 10 °, in particular a maximum of 5 °, is expedient in many cases.

According to a further aspect of the invention, the use of a position measuring system of the type described here as a linear position measuring device or an angular position measuring device on a linearly adjustable component or rotationally adjustable component of a vehicle is proposed. As a rotatable component comes z. B. a turbocharger flap or a valve flap of a motor vehicle into consideration.

• 1 ein Positionsmesssystem gemäß eines ersten Ausführungsbeispiels,
• 2 ein Diagramm zur Veranschaulichung einer idealen und einer realen Positionsabhängigkeit des Magnetfeldes am Beispiel des in 1 gezeigten Positionsmesssystems,
• 3 einen bei einem Positionsmesssystem einsetzbaren Magnetfeldsensor,
• 4 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels,
• 5 eine Darstellung zur Veranschaulichung des Magnetfeldes für das in 4 gezeigte Positionsmesssystem,
• 6 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels,
• 7 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels,
• 8 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels,
• 9 eine Darstellung zur Veranschaulichung einer Kennlinien-Kompensation bei einem Positionsmesssystem,
• 10 ein Blockschaltbild eines Magnetfeldsensors eines Positionsmesssystems gemäß eines Ausführungsbeispiels,
• 11 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels, in einer Draufsicht,
• 12 das Positionsmesssystem von 11 in mehreren Querschnittsansichten,
• 13 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels, in einer Draufsicht,
• 14 das Positionsmesssystem von 11 in mehreren Querschnittsansichten,
• 15 ein Positionsmesssystem gemäß eines weiteren Ausführungsbeispiels, in einer Draufsicht, und
• 16 und 17 beispielhafte Verläufe von mittels Magnetfeldsensoren bei dem Positionsmesssystem von 15 bestimmten Magnetfeldwinkeln.

The invention is described in more detail below on the basis of exemplary embodiments with reference to the accompanying drawings. They represent:

• 1 a position measuring system according to a first embodiment,
• 2 a diagram to illustrate an ideal and a real position dependency of the magnetic field using the example of the in 1 position measuring system shown,
• 3 a magnetic field sensor that can be used in a position measuring system,
• 4th a position measuring system according to a further embodiment,
• 5 a representation to illustrate the magnetic field for the in 4th shown position measuring system,
• 6th a position measuring system according to a further embodiment,
• 7th a position measuring system according to a further embodiment,
• 8th a position measuring system according to a further embodiment,
• 9 a representation to illustrate a characteristic curve compensation in a position measuring system,
• 10 a block diagram of a magnetic field sensor of a position measuring system according to an embodiment,
• 11 a position measuring system according to a further embodiment, in a plan view,
• 12th the position measuring system from 11 in several cross-sectional views,
• 13th a position measuring system according to a further embodiment, in a plan view,
• 14th the position measuring system from 11 in several cross-sectional views,
• 15th a position measuring system according to a further embodiment, in a plan view, and
• 16 and 17th exemplary courses of by means of magnetic field sensors in the position measuring system of 15th certain magnetic field angles.

1 shows a first embodiment of a position measuring system 10 , comprising a permanent magnet 12th and one along a side next to the permanent magnet 12th along the same measuring section 14th movably arranged magnetic field sensor 16 .

With this position measuring system 10 can be based on a means of the magnetic field sensor 16 specific direction of the magnetic field a position of the magnetic field sensor 16 along the measuring section 14th to be determined. It is irrelevant here whether the permanent magnet is fixedly mounted and the magnetic field sensor is moved in this installation environment in the practical use of the position measuring system in a certain installation environment (technical facility, e.g. vehicle), or, conversely, whether the magnetic field sensor is fixedly mounted and the permanent magnet (including flux guide pieces described below) is moved. In this respect, only the relative position or relative movement of the magnetic field sensor relative to the permanent magnet is important for the measurement. In the 1 three arrows 18th illustrate for three different positions along the measuring section 14th the direction of the respective magnetic field present there.

In the example shown, the permanent magnet is 12th made of a hard magnetic metal alloy and designed as an elongated profile. The permanent magnet 12th has a cross-section (profile cross-section) of rectangular shape that is uniform over its length (profile) and is designed with a profile axis running in a straight line.

The one next to the permanent magnet 12th measuring section running along the same 14th is also provided to run in a straight line in the example shown and here runs parallel to the profile axis of the profile of the permanent magnet 12th . The measuring section 14th thus runs in a lateral direction of the position measuring system 10 viewed at a certain distance parallel to the permanent magnet 12th or its profile axis.

The position measuring system 10 is therefore particularly suitable for linear position detection on a component (e.g. the plunger of an electromechanical actuator or the like) which is arranged displaceably in a technical device (e.g. vehicle).

In the example shown, the permanent magnet is 12th homogeneously magnetized, with one direction of magnetization oriented vertically, ie orthogonal to the profile axis and orthogonal to the lateral direction of the position measuring system 10 .

The position measuring system 10 also has two ferromagnetic flux guide pieces in the example shown 20-1 , 20-2 on, namely a lower ferromagnetic flux guide 20-1 that is below the measuring section 14th plate-shaped on the one hand in the direction the measuring section 14th and the measuring section 14th following and on the other hand in the lateral direction (lateral direction) extends, and an upper ferromagnetic flux guide 20-2 that is above the measuring section 14th plate-shaped on the one hand in the direction of the measuring section 14th and the measuring section 14th following and on the other hand extends in the lateral direction.

The flux guide pieces 20-1 , 20-2 extend in the example shown in the lateral direction on the one hand (in 1 left) up to the permanent magnet 12th and lie there, so that the relevant side edges of the flux guide pieces 20-1 , 20-2 flush with the permanent magnet 12th to lock. On the other hand (in 1 right) the flux guide pieces extend 20-1 , 20-2 viewed in the lateral direction at one of their longitudinal ends in the course of the measuring section 14th clearly over the measuring section 14th but each have one over the course of the measuring section 14th continuously decreasing lateral extension, so that the flux guide pieces 20-1 , 20-2 at their respective other longitudinal end in the area of the permanent magnet 12th end and thus the permanent magnet in the lateral direction 12th not tower above.

The contours of the two flux guide pieces (viewed from above or below) 20-1 , 20-2 run, based on one in the middle of the measuring section 14th vertically extending mirror plane, mirror images of each other.

In this embodiment it is advantageous in addition to one through the flux guide pieces 20-1 , 20-2 The shielding effect achieved against any interference fields is primarily the fact that due to the uneven shape of the flux guide pieces 20-1 , 20-2 over the length of the permanent magnet 12th considers a dependency of the magnetic field (see arrows 18th in 1 ) from the position of the magnetic field sensor 16 along the measuring section 14th is caused. It should be noted here that with the permanent magnet 12th without such flux guide pieces 20-1 , 20-2 no dependence of the magnetic field at all on the position along the measuring section 14th would result (apart from "edge effects" at the ends of the example shown up to the two ends of the permanent magnet 12th approaching measuring section 14th ).

With the use of the irregularly shaped flux guide pieces 20-1 , 20-2 however, the named dependency can advantageously be brought about and even qualitatively adjusted to a certain extent in the desired manner. For this purpose, deviating from the straight lines provided in the example shown, the curves in 1 right side edges of the flux guide pieces 20-1 , 20-2 For example, curved and / or angled courses can be provided in such a way that the dependence of the magnetic field on the position along the measurement section 14th is modified accordingly.

2 shows an exemplary, for this purpose the embodiment of 1 Dependence of the direction of the magnetic field on the position shown.

The direction of the magnetic field is in 2 represented by an angle "ang" of the direction of the magnetic field with respect to the vertical direction, and the position along the measuring section 14th is represented by a standardized position parameter "pos" (pos = 0% at the beginning of the measuring section, pos = 50% in the middle of the measuring section, pos = 100% at the end of the measuring section).

When the magnetic field sensor 16 along the measuring section 14th is moved ( 1 ), the angle "ang" varies between the values a1 (with pos = 0%) and a2 (with pos = 100%). In the example of 1 we have a2 = -α1.

The solid line in 2 shows the real position dependency of the angle "ang", whereas the dashed line in 2 represents a dependency, which is mostly to be preferred as ideal in practice, in which the angle “ang” changes linearly with the position “pos”.

With an appropriately selected arrangement and shape of one or more flux guide pieces (stationary relative to the permanent magnet, and in particular e.g. connected to or adjacent to it), the position dependency of the magnetic field can be advantageously influenced in the invention, for example in order to achieve the ideal dependency explained above or at least approximate.

3 shows again isolated in the embodiment of 1 used magnetic field sensor 16 that provides a sensor signal that is dependent on the direction of the magnetic field and that is representative of the angle or angle of rotation "ang" by which the direction of the magnetic field is rotated from a direction defined by the magnetic field sensor.

3 also illustrates the angular measuring range of the magnetic field sensor 16 , which in this example is z. B. extends over a range of +/- 45 °. When used in the position measuring system 10 of 1 the angle of rotation "ang" to be measured lies in a plane orthogonal to the direction of the measuring section 14th .

In the following description of further exemplary embodiments, the same reference numbers are used for components with the same effect, each supplemented by a small letter to distinguish the embodiment. Essentially, only the differences from the exemplary embodiment (s) already described are discussed here, and for the rest herewith express reference is made to the description of previous exemplary embodiments.

4th shows a further embodiment of a position measuring system 10a which, as can be seen from the following explanation, differs in two aspects from the example of 1 differs: On the one hand, the position measuring system 10a an inhomogeneously magnetized permanent magnet, and on the other hand uniformly shaped flux guide pieces are used.

This in 4th Position measuring system shown 10a as in the example of 1 a permanent magnet designed as an elongated profile with a rectangular profile cross-section and with a straight profile axis 12a to the laterally offset a measuring section 14a runs along which a magnetic field sensor 16a is movable.

The permanent magnet 12a is, however, inhomogeneously magnetized, whereby in the example shown one is orthogonal to the profile axis of the permanent magnet 12a oriented, "helically" varying magnetization along the profile axis is provided. A (local) direction of magnetization only depends on the position along the profile axis of the permanent magnet 12a from.

The position measuring system 10a includes as in the example of 1 also a lower ferromagnetic flux guide 20-1 that is located below a measuring section 14a plate-shaped on the one hand in the direction of the measuring section 14a and following this and on the other hand in the lateral direction (lateral direction) extends, as well as an upper ferromagnetic flux guide 20a-2 that is above the measuring section 14a plate-shaped on the one hand in the direction of the measuring section 14a and following this and on the other hand extends in the lateral direction.

However, in the position measuring system 10a the arrangement and shape of the flux guide pieces 20a-1 , 20a-2 over the length of the permanent magnet 12a considered evenly as the flux guide pieces 20a-1 , 20a-2 extend in the lateral direction with a constant extension (plate width). This results in no significant qualitative change in the position dependency of the magnetic field (see arrows 18th in 4th ), which is already caused here by the inhomogeneous helical magnetization. However, there is advantageously a high shielding effect with regard to interference fields, and a certain amplification of the magnetic field in the area of the measuring section is also advantageous 14a achieved.

In the example shown, the flux guide pieces have 20a-1 , 20a-2 each a rectangular contour.

The arrangement and / or the shape of the flux guiding pieces could deviate from this 20a-1 , 20a-2 over the length of the permanent magnet 12a considered, however, should be modified in order to modify the dependence of the magnetic field on the position of the magnetic field sensor 16a along the measuring section 14a to accomplish. The straight lines of the in 4th right side edges of the flux guide pieces 20-1 , 20-2 be replaced by curved and / or angled courses.

In the case of such a modification, too, it is mostly advantageous if the contours of the two flux guide pieces are related to one in a central region of the measuring section 14a vertically extending mirror planes continue to run mirror images of one another. It is also mostly advantageous if the modified side edges continue to cover the measurement section when viewed in the lateral direction 14a tower above.

5 shows in three different cross-sections of the in 4th position measuring system shown 10a , for positions with pos = 0%, pos = 50% and pos = 100% along the measuring section 14a , magnetic field lines of the magnetic field determined by corresponding simulation calculations.

Also illustrated 5 exemplary one compared to the examples of 1 and 4th Modified embodiment, which consists in the fact that the course of the measuring section is tilted with respect to a horizontal course of one or more flux guide pieces in such a way that the vertical positions of the two ends of the measuring section differ significantly from one another. This variation is in 5 evident. While in the middle of the measuring section (pos = 50%) the magnetic field sensor 16a (and thus the measuring section) viewed vertically in the middle between the flux guide pieces 20a-1 , 20a-2 is arranged or runs, so are the magnetic field sensor 16a or the corresponding sections of the measuring section at the two ends of the measuring section (pos = 0% and pos = 100%) offset vertically upwards (for pos = 0%) or downwards (for pos = 100%). In particular, a uniform angle of inclination of the inclined course of the measuring path with respect to the horizontal direction in the range of z. B. be provided about 1 ° to 5 °. With this modification, a reduction in the sensitivity of the measurement system characteristics and thus the measurement accuracy with respect to mechanical play and mechanical manufacturing and assembly tolerances can advantageously be achieved, since the magnetic field sensor 16a is moved in an area in which there is a more homogeneous magnetic field.

6th shows a further embodiment of a position measuring system 10b which differs from the in 4th position measuring system shown 10a differs in that a profile axis of a permanent magnet 12b and accordingly a measuring section running parallel to it 14b run not in a straight line, but curved in a circular arc. The in 6th The arc angle α drawn in is approximately 45 °, but can also assume other values adapted to the specific application. In particular, could differ from 6th an arc angle α of 360 ° can also be provided. In this case, the permanent magnet would be designed as a circular, closed profile, in which the measuring section can also in particular also run circularly closed around the permanent magnet (radially outside of the permanent magnet), with a “helical” magnetization varying along the profile axis as it progresses along the Must be reproduced every 360 ° (at the latest) (examples of this are described below with reference to the 11 and 12th as 13th and 14th explained).

The position measuring system 10b is therefore suitable for. B. for detecting the angle of rotation on a rotatably mounted component (e.g. rotary shaft on a turbocharger flap or on a valve flap) of a technical device (e.g. vehicle). When used in this way, the permanent magnet 12b and flux guide pieces 20b-1 , 20b-2 formed arrangement are attached to a respective rotary shaft, so that this rotates with a rotation of the rotary shaft, whereas a magnetic field sensor 16b can be fixed stationary at the appropriate lateral distance. When the rotating shaft rotates, the magnetic field sensor moves 16b then relative to the permanent magnet 12b along the measuring section 14b .

Apart from the curved, here circular arc shape of the position measuring system 10b and thus measuring along an arc of a circle, this system works like the one with reference to 4th described system.

Also related to 1 position measuring system described 10 can according to a modification be curved, in particular curved in the shape of a circular arc, be it with an arc angle of less than 360 ° or with an arc angle of 360 ° (ie closed in a ring). The one for the position measuring system 10 (or 10a) with reference to the length of the permanent magnet or the measuring section, and possible details and configurations described with reference to the lateral direction can also be used for curved modifications. It should be noted that the length is then curved and therefore there is no longer a uniform lateral direction of the system, but the lateral direction varies over the length (the lateral direction then runs orthogonally at each point to the orientation of the longitudinal direction at this point and can then also be used as a radial direction are designated).

7th shows a further embodiment of a position measuring system 10c which differs from the in 4th position measuring system shown 10a differs in that it is a permanent magnet 12c is designed as an elongated body with a cross-section that varies over its length (course).

In the illustrated embodiment, the permanent magnet is 12c is designed with a uniform (not varying) cross-sectional area over its length. However, the cross-sectional shape varies. The cross section has the shape of a square, in which over the length of the permanent magnet 12c the orientation of one of the measuring sections 14c facing side of the square varies. Said side of the square runs vertically in the middle of the course of the length of the permanent magnet, and the cross-section there is rectangular. However, as the distance from the center increases, the side runs increasingly obliquely with respect to the vertical.

In the example shown, the side of the square runs at an angle with respect to the vertical which is strictly monotonous and in particular z. B. varies proportionally to the position in the course of this length.

In the example shown, the angle with respect to the vertical varies as a whole (over the full length of the permanent magnet 12c) by an angle of 90 °.

The permanent magnet 12c is like the example of 4th inhomogeneously magnetized, one everywhere orthogonal to the profile axis of the permanent magnet 12c oriented, "helically" varying magnetization along the profile axis is provided.

In many cases it is preferred that the angle by which the magnetization moves in the course of the permanent magnet 12c rotates, is at least approximately equal to that angle (e.g. with a deviation of a maximum of 20 °, in particular a maximum of 10 °) by which the permanent magnet moves 12c the orientation of the said quadrangle side rotates. This is in the example of 7th the case in which in the course of the permanent magnet 12c the direction of magnetization rotates by 90 °.

8th shows a further embodiment of a position measuring system 10d which differs from the in 7th position measuring system shown 10c is distinguished by the fact that a course (e.g. longitudinal center axis) of a permanent magnet 12d and accordingly a measuring section running parallel to it 14d run not in a straight line, but curved in a circular arc. Otherwise the example corresponds to 8th in structure and function the example of 7th .

The position measuring system 10d is therefore suitable (like e.g. the one in 6th Position measuring system shown 10b) For example, for detecting the angle of rotation on a rotatably mounted component of a technical device (e.g. vehicle).

That related to 8th position measuring system described 10d can, according to a modification, be designed in a ring-shaped manner (e.g. circular ring-shaped). To reproduce the cross-section and the magnetization every 360 ° there would be a possible modification z. B. in the in 8th The variation of the cross-section and the magnetization shown should be provided for a first 180 ° partial circumference and provided inverted for an adjoining second 180 ° partial circumference (so that the cross-section and magnetization at the end of the second 180 ° partial circumference match those at the beginning of the first 180 ° - Partial scope). More generally, a variation in cross-section and magnetization (such as that in 8th shown variation of the cross-section and the magnetization) and their inverted variation are provided alternately for an even number “n” of more than two successive partial circumferences that complement each other to the full 360 ° circumference. For n = 4 this would be e.g. B. four 90 ° partial circumferences, for n = 6 six 60 ° partial circumferences, for n = 8 eight 45 ° partial circumferences, etc.

9 illustrates a characteristic curve compensation, which can be optionally used in every position measuring system of the type described here, which serves to modify (at least) one measurement signal generated by the (at least one) magnetic field sensor as a function of the magnetic field in a predetermined manner and thus a modified sensor signal (for a further use or further processing).

9 shows in the upper part an exemplary plot of a relative error "err" of the sensor signal generated by the magnetic field sensor depending on the position or here the standardized position parameter "pos" (pos = 0% at the beginning of the measuring section, pos = 50% in the middle of the Measuring section, pos = 100% at the end of the measuring section).

If an annular (e.g. circular) closed course of the measuring section is provided, 0% and 100% designate the same point on the measuring section, and pos = 0% can e.g. B. can be interpreted as an angular position of 0 ° and pos = 100% as an angular position of 360 °.

The relative error "err" to be eliminated or at least reduced by means of the characteristic curve compensation can in principle be freely defined as the ratio between the "real" value represented by the sensor signal (e.g. digital value) and a (arbitrarily) specified "Ideal" value. In practice, a value that varies linearly with the position is usually desirable as an ideal value (linearization). In contrast to this, however, a different mathematical function for describing an “ideal” measuring system characteristic could also be desirable in the specific application.

The relative error "err" or its position-dependent progression "err (pos)" can e.g. B. be determined empirically. Then a z. B. digital representation of this course in a device for characteristic compensation, z. B. a (in particular e.g. program-controlled) digital signal processing device can be stored, in particular as an error curve defined by several interpolation points (cf. 9 above), which can then be used as a compensation curve (or to determine a compensation curve) in the operation of the relevant position measuring system.

When the position measuring system is in operation, each measured value generated by the magnetic field sensor during its magnetic field measurement can be modified (corrected) using the previously stored support points or a compensation curve resulting therefrom so that the modified value corresponds exactly (more) to the "ideal" value. For this purpose, z. B. each value represented by the original sensor signal can be multiplied by a correction factor resulting from a compensation curve for this value.

9 shows in the lower part an exemplary plot of the relative error “err” for a sensor signal modified (corrected) in this way as a function of the normalized position parameter “pos”. As can be seen, the relative error has advantageously been drastically reduced.

In one embodiment it is provided that the characteristic curve compensation is carried out entirely or at least partially by the magnetic field sensor, which in this case is equipped with appropriate electronics, in particular z. B. is equipped with digital signal processing electronics. Alternatively, however, the characteristic curve compensation can also take place in an evaluation device (e.g. program-controlled electronic) used separately from the magnetic field sensor, which (at least) one of the Magnetic field sensor generated (and z. B. for an angle of the magnetic field direction representative) sensor signal is supplied and which generates the correspondingly modified sensor signal therefrom and optionally z. B. further evaluates (depending on the purpose of the position measurement).

10 shows in a block diagram an embodiment of a magnetic field sensor that can be used for a position measuring system of the type described here 16 . The magnetic field sensor shown 16 can thus in particular z. B. in each of the above with reference to the 1 , 4th , 6th , 7th and 8th systems described are used.

The magnetic field sensor 16 has two magnetoresistive sensor units 30-1 and 30-2 which are designed to measure magnetic field components of the magnetic field assigned to two orthogonally oriented directions, ie to provide two analog electrical signals “x” and “y” each representing one of these components.

In the example shown, the signals x and y are each generated by means of one of two amplifiers 32-1 and 32-2 amplified and by means of a respective A / D converter 34-1 or. 34-2 converted into digital signals.

The digital signals become an angle calculation unit 36 supplied, in which the direction (angle) of the magnetic field is calculated from the two component signals.

The one from the angle calculation unit 36 The calculated angle of the magnetic field is made by means of a characteristic compensation unit 38 corrected, and the thus corrected angle via an interface unit 40 issued.

The angle calculation unit 36 and the characteristic compensation unit 38 can in particular z. B. implemented as functional parts of a computing unit, which is designed in the form of a program-controlled electronic computing device (z. B. microcontroller). The data required for the characteristic curve compensation can be stored in advance in a memory unit 42 to which the characteristic curve compensation unit 38 when correcting the angle.

In summary, the in 10 shown magnetic field sensor 16 is designed to measure two magnetic field components of the magnetic field and to provide therefrom a sensor signal that is dependent on the direction of the magnetic field but is advantageously linearized in this case.

The 11 to 17th show exemplary embodiments of position measuring systems 10e ( 11 and 12th ), 10f ( 13th and 14th ) and 10g ( 15th to 17th ) to illustrate the embodiment, which is interesting within the scope of the invention for certain applications, in which an annular, here circularly closed course of a measuring section radially outside of a permanent magnet that runs parallel to it and here also circularly closed 12e , 12f or. 12g is provided.

A further advantageous common feature of these exemplary embodiments is that both a lower (first) flux guide piece extending below the measuring section 20e-1 , 20f-1 or. 20g-1 as well as an upper (second) flux guide piece extending above the measuring section 20e-2 , 20f-2 or. 20g-2 is provided, these flux guide pieces each terminating radially on the inside flush with an inner circumference of the permanent magnet.

The 11 and 12th show an embodiment in which the flux guide pieces 20e-1 , 20e-2 have a uniform lateral (radial) extension over the entire course (circumference) of the measuring section, and in this case, as shown, in this radial direction z. B. can each extend somewhat radially outward beyond the measuring section. The flux guide pieces are therefore 20e-1 , 20e-2 each circular with a uniform width.

A dependency of the direction of the magnetic field of the permanent magnet required for position measurement 12e from the position (circumferential position or circumferential angular position) of a magnetic field sensor 16e ( 12th ) along the measuring section is caused by an inhomogeneous magnetization, here a helical one along the length (circumference) of the permanent magnet 12e varying magnetization, realized.

The 12A to 12D are cross-sections at the in 11 The circumferential positions "A" (circumferential angular position = 0 °) to "D" (circumferential angular position = 270 °) drawn in and illustrate the magnetization that varies helically along the circumference.

In the example shown, a direction of magnetization varies over a full circumference (360 °) z. B. at least approximately sinusoidal in a range of +/- 15 ° (deviation from the vertical). As from the 12A to 12D seen over the full circumference (360 °), a period of a circumferential angle-dependent course of the magnetization direction is provided. In a departure from this example, however, several periods (e.g. 2, 3, 4 or more) periods could also be provided.

The 13th and 14th show an embodiment in which the flux guide pieces 20f-1 , 20f-2 Considered over the course (circumference) of the measuring section have a non-uniform lateral (radial) extension, and in this case, as shown, in this radial direction in each case z. B. extend radially outward over part of its circumference slightly beyond the measuring section and over another part of its circumference less far than the measuring section.

The dependence of the direction of the magnetic field of the permanent magnet required for position measurement 12f from the position (circumferential position or circumferential angular position) of a magnetic field sensor 16f ( 14th ) along the measuring section is in this example due to an inhomogeneous magnetization, here a helical one along the length (circumference) of the permanent magnet 12f varying magnetization, realized, and by the inconsistent lateral (radial) extension of the flux guide pieces 20f-1 , 20f-2 to a certain extent still beneficially reinforced.

The 14A to 14D are cross-sections at the in 13th circumferential positions "A" (circumferential angular position = 0 °) to "D" (circumferential angular position = 270 °) and illustrate the magnetization that varies helically along the circumference, which is exactly the same as in the example of 11 and 12th can be provided, so viewed along the circumference z. B. can vary at least approximately sinusoidally and / or can perform one or more periods (z. B. sinusoidal periods) of a circumferential angle-dependent course over the full circumference (360 °).

According to a modification of the 13th and 14th example shown could be the permanent magnet ( 12f) be magnetized homogeneously, in particular with an at least approximately vertically oriented direction of magnetization.

The 15th shows an embodiment in which a permanent magnet 12g and flux guide pieces 20g-1 , 20g-2 as well as for the example of 11 and 12th are designed as described. The permanent magnet could deviate from this 12g and the flux guide pieces 20g-1 , 20g-2 however, it can also be designed differently.

The in 15th Example shown two magnetic field sensors 16g-1 and 16g-2 used, each along the side (radially) next to the permanent magnet 12g are arranged movably along the same running measuring section, but are offset by 90 ° to each other in the course of the measuring section. The determination of the position along the measurement section can thus advantageously be carried out using the two magnetic field sensors 16g-1 and 16g-2 measured magnetic fields can be realized.

The 16 and 17th show exemplary courses of the by means of the magnetic field sensors 16g-1 and 16g-2 certain angles "ang1" and "ang2" of the magnetic field direction with respect to the vertical depending on a position (circumferential angular position) along the measuring section.

When the magnetic field sensor 16g-1 is moved along the measuring section, the angle "ang1" varies in the example shown as from 16 can be seen at least approximately sinusoidally, whereas the angle "ang2" here as from 17th evidently varied at least approximately in the shape of a cosine. In the example, the position (circumferential position) can advantageously be clearly determined from the two simultaneously determined values of "ang1" and "ang2".

The real position dependency of the angles "ang1" and "ang2" can be modified by a suitably adapted shape of the flux guiding pieces and / or by using a characteristic curve compensation (as already described above) so that the position dependency is more exact by a desired mathematical function, here z. B. a sine or cosine function is described than would be the case without characteristic curve compensation.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 0979988 B1 [0004]
• DE 19910636 A1 [0004]
• EP 1989505 B1 [0004]
• WO 2011/135063 A2 [0004]

Claims (17)

Position measuring system (10), comprising a permanent magnet (12) and a magnetic field sensor (16) arranged movably along a measuring section (14) running laterally next to the permanent magnet (12), in order to measure the direction of the magnetic field based on a direction of the magnetic field determined by means of the magnetic field sensor (16) to be able to determine a position of the magnetic field sensor (16) along the measuring section (14), characterized in that the position measuring system (10) furthermore has at least one ferromagnetic flux guide piece (20-1, 20-2) which is located below or above the measuring section ( 14) plate-shaped on the one hand in the direction of the measuring section (14) and following at least part of the measuring section (14) and on the other hand extending in the lateral direction. Position measuring system (10) according to Claim 1 , wherein the permanent magnet (12) is designed as an elongated profile. Position measuring system (10) according to one of the preceding claims, wherein the permanent magnet (12) is designed as an elongated body with a cross section that varies over its length. Position measuring system (10) according to one of the preceding claims, wherein the permanent magnet (12) is magnetized homogeneously. Position measuring system (10) according to Claim 4 , wherein the permanent magnet (12) is designed as an elongated profile and is magnetized orthogonally to a profile axis of the profile. Position measuring system (10) according to one of the Claims 1 to 3 , wherein the permanent magnet (12) is magnetized inhomogeneously. Position measuring system (10) according to one of the preceding claims, comprising: - A lower ferromagnetic flux guide piece (20-1, 20-2), which extends below the measuring section (14) in the form of a plate on the one hand in the direction of the measuring section (14) and at least part of the measuring section (14) and on the other hand in the lateral direction, and - An upper ferromagnetic flux guide piece (20-1, 20-2) that extends above the measuring section (14) in the form of a plate on the one hand in the direction of the measuring section (14) and following at least part of the measuring section (14) and on the other hand in the lateral direction. Position measuring system (10) according to one of the preceding claims, wherein the flux guide piece (20-1, 20-2) extends at least one point in the course of the measuring path (14) viewed in the lateral direction up to the permanent magnet (12), in particular on the permanent magnet (12) is applied. Position measuring system (10) according to one of the preceding claims, wherein the flux guide piece (20-1, 20-2) is viewed in the lateral direction at at least one point in the course of the measuring section (14) up to the measuring section (14) or over the measuring section ( 14) extends beyond. Position measuring system (10) according to one of the preceding claims, wherein the flux guide piece (20-1, 20-2) has a varying lateral extent over at least part of the course of the measuring section (14). Position measuring system (10) according to one of the preceding claims, a tilting of a course of the measuring section (14) with respect to a course of the permanent magnet (12) and / or the flux guide piece is provided such that the vertical positions of the two ends of the measuring section (14 ) differ from each other, so that the measuring section (14) between these two ends runs inclined with respect to the course of the permanent magnet (12) or the flux guide piece from one end to the other end. Position measuring system (10) according to one of the Claims 1 to 10 , wherein the permanent magnet (12) is designed as an annularly closed body. Position measuring system (10) according to one of the preceding claims, wherein the magnetic field sensor (16) is designed to measure at least two magnetic field components of the magnetic field and to provide a sensor signal dependent on the direction of the magnetic field. Position measuring system (10) according to one of the preceding claims, in particular wherein the permanent magnet (12) is magnetized homogeneously, in particular with a direction of magnetization that is essentially orthogonal to a course of the permanent magnet (12), in particular with a direction of magnetization that is essentially vertically oriented, the flux guide piece (20-1, 20-2) extends over the entire course of the measuring section (14) viewed in the lateral direction up to the permanent magnet (12) and rests on the permanent magnet (12), at at least one point in the course of the measuring section (14) viewed in the lateral direction as far as the measuring section (14) or beyond the measuring section (14), and has a varying lateral extent over at least part of the course of the measuring section (14). Position measuring system (10) according to one of the preceding claims, wherein the permanent magnet (12) is magnetized inhomogeneously, in particular with a magnetization direction which is essentially orthogonal to a course of the permanent magnet (12) and which varies in the course of the permanent magnet (12), wherein the flux guide piece (20-1, 20-2) over the entire course of the measuring section (14), viewed in the lateral direction, extends on the one hand up to the permanent magnet (12) and rests against the permanent magnet (12) and on the other hand up to the measuring section (14) ) or extends beyond the measuring section (14). Position measuring system (10) according to Claim 15 , the permanent magnet (12) being designed as an elongated body with a cross-section that varies over its length, in particular the cross-section being in the shape of a square, in which the orientation of one of the measuring path (14) faces over the length of the permanent magnet (12) Side of the square varies. Position measuring system (10) according to one of the preceding claims, wherein the permanent magnet (12) is designed as an annularly closed body and the measuring section (14), for example, also annularly closed laterally next to the permanent magnet (12) along the permanent magnet (12).

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