DE102018107571A1 - Magnetic field sensor arrangement and arrangement for measuring a torque and method for producing the magnetic field sensor arrangement - Google Patents

Abstract

The present invention initially relates to a magnetic field sensor arrangement (03) for measuring a torque on a machine element (01) extending in an axis using the inverse-magnetostrictive effect. The machine element (01) has at least two magnetization areas for magnetization extending circumferentially around the axis. The magnetic field sensor arrangement (03) comprises at least two magnetic field sensors (07) for measuring a differential magnetic field caused by the magnetization and by the torque. According to the invention, the magnetic field sensors (07) each extend circumferentially around the axis in order to enclose the machine element (01) circumferentially. The invention further relates to an arrangement for measuring a torque on a machine element (01) extending in an axis, the arrangement comprising the magnetic field sensor arrangement (03) according to the invention. A further subject of the invention is a method for producing the magnetic field sensor arrangement (03) according to the invention.

Description

The present invention initially relates to a magnetic field sensor arrangement for measuring a torque on a machine element extending in an axis using the inverse magnetostrictive effect. Furthermore, the invention relates to an arrangement for measuring a torque on a machine element extending in an axis, wherein the arrangement comprises the magnetic field sensor arrangement according to the invention. A further subject of the invention is a method for producing the magnetic field sensor arrangement according to the invention.

In the US 6,222,363 B1 a flux gate magnetometer is described with which an external magnetic field of a rotating magnetoelastic wave is measurable.

The US 2002/0162403 A1 shows a magnetoelastic torque sensor with a shaft in which a coil sits on a magnetoelastic region.

From the US 2009/0230953 A1 For example, a magnetoelastic torque sensor is known which comprises a longitudinally extending element having a plurality of magnetoelastically active regions. The torque sensor includes primary and secondary magnetic field sensors connected as a Wheatstone bridge.

The US 2013/0125669 A1 teaches a method of detecting a magnetic interference field in a torque measurement on a magnetoelastic wave. Two signals are measured, the second signal corresponding to the magnetic interference field and being subtracted from the first signal.

From the EP 0 803 053 B1 For example, a torque sensor comprising a magnetoelastic transducer is known. The transducer sits as a cylindrical sleeve on a shaft.

The US 8,893,562 B2 shows a method of detecting a magnetic noise in a magnetoelastic torque sensor. The torque sensor comprises a torque converter with oppositely polarized magnetizations and a plurality of magnetic field sensors, between which can be switched.

The US 8,001,849 B2 shows an arrangement for magnetoelastic torque measurement, in which the effect of external magnetic fields should be compensated. The arrangement comprises a magnetized region of a shaft and at least one passive and one active magnetic field sensor. The passive magnetic field sensors can be arranged on both sides of the magnetized region.

The US 2011/0162464 A1 shows an arrangement for magnetoelastic torque measurement, in which the effect of uniform and non-uniform magnetic fields should be compensated. The arrangement comprises a magnetized region of a shaft and at least three magnetic field sensors. The second and third magnetic field sensors may be disposed adjacent to the magnetized region.

The US 8,087,304 B2 shows a magnetoelastic torque sensor for measuring a torque acting on a shaft. The shaft has one or more extensive magnetizations. 12 of the US 8,087,304 B2 shows an embodiment with only one circumferential magnetization, wherein two primary magnetic field sensors in the region of the magnetization and two secondary magnetic field sensors are arranged adjacent to the region of the magnetization. 18 of the US 8,087,304 B2 shows an embodiment with two circumferential magnetizations, which are alternately polarized, wherein a plurality of magnetic field sensors are arranged at an axial transition between the two magnetizations. 8th of the US 8,087,304 B2 shows an embodiment with three circumferential magnetizations, which are alternately polarized, wherein in each case a magnetic field sensor is arranged in one of the regions of the three magnetizations. Due to the special arrangement of the magnetic field sensors, the influence of magnetic interference fields should be removed.

From the US 9,151,686 B2 a magnetoelastic torque sensor is known, which should have a reduced signal noise. The torque sensor comprises a hollow shaft having three circumferentially magnetized magnetization regions which have alternating polarities. Compared to the magnetization regions, up to eight magnetic field sensors are arranged.

In the article by Michael Melzer et al. (Leibniz Institute for Solid State and Materials Research Dresden): "Ultra-Flexible, Stretchable and Printed GMR Sensors", 14 ^th Symposium "Magnetoresistive Sensors and Magnetic Systems" 21.-22. March 2017, Wetzlar technologies for the arrangement of GMR sensors on highly flexible PET films are described.

The object of the present invention, starting from the prior art, is to minimize rotational errors in a measurement of torques based on the inverse magnetostrictive effect. These rotation-related errors are in particular a so-called RSU error (rotation signal error). Uniformity error), which represents an angle-dependent signal fluctuation of a Sensoroffsets and by basically existing tolerances of the magnetization, fluctuations in the surface quality and mechanical tolerances, such as a parallelism and roundness of a shaft, and tolerances of distances from secondary sensors to the primary sensor is conditional. In a measurement based on the inverse magnetostrictive effect according to the prior art with a magnetic field sensor pair, this error is up to 2.5%.

Said object is achieved by a magnetic field sensor arrangement according to the attached claim 1 and by an arrangement according to the attached independent claim 9 and by a method according to the attached independent claim 10.

The magnetic field sensor arrangement according to the invention is used to measure a torque on a machine element extending in an axis. The torque acts on the machine element, which leads to mechanical stresses and the machine element usually deforms slightly. The axis preferably forms an axis of rotation of the machine element. The following directions, namely the axial direction, the radial direction and the tangential direction are related to the said axis. The arrangement is preferably designed to measure a torque which lies in the axis, so that it is a torsional moment through which the machine element is loaded. The vector of the torque is in the axis.

The machine element has at least two magnetization areas extending circumferentially about the axis for a differential magnetization formed in the machine element. It is thus at least two magnetization areas revolving around the axis or circular magnetization areas. The magnetization regions form a primary sensor for determining the torque.

The magnetization regions preferably have a same spatial extent and are axially spaced apart. Particularly preferably, the magnetization regions are designed in the form of magnetization tracks. Axial adjacent ones of the magnetization regions extending circumferentially around the axis preferably have opposite polarities, i. H. they have an opposite sense of circulation.

The magnetic field sensor arrangement furthermore comprises at least two magnetic field sensors which each form a secondary sensor for determining the torque. The primary sensor is used to convert the torque to be measured in a corresponding magnetic field, while the secondary sensors allow the conversion of this magnetic field into electrical signals. The magnetic field sensors are each designed for the individual measurement of a differential magnetic field caused by the magnetization and by the torque. The said magnetic field occurs due to the inverse magnetostrictive effect. Thus, the measurement possible with the magnetic field sensor arrangement is based on the inverse-magnetostrictive effect.

The magnetic field sensors are preferably arranged in each case for measuring the differential magnetic field emerging from the machine element as a result of the torque-related surface tension change. The magnetic field sensors are preferably arranged in each case for the individual measurement of a tangentially or / and axially aligned direction component of the differential magnetic field caused by the magnetization and by the torque.

The magnetic field sensors are arranged opposite the machine element, wherein preferably only a small radial air gap is present between the magnetic field sensors and an inner or outer surface of the machine element.

The machine element and the magnetic field sensor arrangement are rotatable relative to each other. Preferably, the machine element is rotatable while the magnetic field sensor arrangement rests.

According to the invention, the magnetic field sensors each extend circumferentially about the axis in order to enclose the machine element circumferentially. The magnetic field sensors extend along a path which is suitable for circumferentially enclosing the machine element. This web is preferably circular or elliptical. This web is preferably closed, but may have a short break. The magnetic field sensors each extend circumferentially around the machine element. The magnetic field sensors each extend circumferentially around the machine element at a midpoint angle, which is preferably at least 300 degrees and more preferably is nearly equal to or equal to 360 degrees. Thus, the magnetic field sensors are circumferentially sensitive around the machine element so that rotation between the magnetic field sensor assembly and the machine element does not affect the measurement result.

The magnetic field sensors preferably extend along a circular path around the machine element, wherein the circular paths of the magnetic field sensors preferably have a same radius. The Magnetic field sensors are preferably arranged axially spaced from one another.

A particular advantage of the magnetic field sensor arrangement according to the invention is that the so-called RSU error (rotation signal uniformity error) can be almost completely compensated by a modified design of the magnetic field sensors. Shear force induced magnetic fields also have an influence on the RSU in case of selective magnetic field measurement. This transverse force-related error related to the torque measurement is also compensated by the invention.

The at least two magnetization regions are preferably permanently magnetized on the machine element, so that the magnetization is formed by a permanent magnetization.

The at least two permanently magnetized magnetization regions are preferably magnetically neutral in a state of the machine element which is unloaded from a torque outside the magnetization region, so that no technically relevant magnetic field outside the magnetization region can be measured.

The magnetization regions each represent a part of the volume of the machine element. The magnetization regions are preferably each of annular design, wherein the axis of the machine element also forms a central axis of the respective ring shape. Particularly preferably, the magnetization regions each have the shape of a hollow cylinder coaxial with the axis of the machine element.

The machine element preferably has a high magnetostriction in the magnetization regions.

The magnetization regions are preferably arranged axially spaced from one another, wherein in each case a magnetically neutral region is preferably arranged between two adjacent ones of the magnetization regions. Insofar as more than two of the magnetization regions are present, they preferably each have an equal distance from one another.

At least in the magnetization region, the machine element consists of a magnetostrictive or magnetoelastic material. The machine element preferably consists entirely of the magnetostrictive or magnetoelastic material. Preferably, the machine element consists of a steel. A sleeve of magnetostrictive or magnetoelastic material, which is pressed onto the machine element from a non-magnetoelastic material, is also suitable as long as a suitable air gap is present in the transitional area between the magnetic tracks between the sleeve and the supporting machine element.

The machine element preferably has the shape of a prism or a cylinder, wherein the prism or the cylinder is arranged coaxially to the axis. The prism or the cylinder is preferably straight. Preferably, the machine element has the shape of a straight circular cylinder, wherein the circular cylinder is arranged coaxially to the axis. In particular embodiments, the prism or the cylinder is conical. The prism or the cylinder can also be hollow.

The machine element is preferably formed by a shaft or by a hollow shaft. The shaft or the hollow shaft can be designed for loads due to different torques.

In preferred embodiments of the magnetic field sensor arrangement according to the invention, the magnetic field sensors are each formed by a magnetoresistive sensor or by a Hall sensor. The magnetoresistive sensors are preferably each formed by an AMR sensor or by a GMR sensor. The measurement possible with the AMR sensors is based on the anisotropic magnetoresistive effect (AMR). The measurement possible with the GMR sensors is based on the giant magnetoresistive effect (GMR). The magnetoresistive sensors can also be based on other magnetoresistive effects, so they are generally referred to as xMR sensors.

In preferred embodiments of the magnetic field sensor arrangement according to the invention, the magnetoresistive sensors each have a Barberpol structure which extends circumferentially around the axis and around the machine element. In this embodiment, the magnetoresistive sensors each comprise a strip of a magnetoresistive material on which highly conductive shorting strips are applied, which are preferably rotated by 45 ° or -45 ° to the strip longitudinal direction. The shorting strips are preferably made of aluminum.

Preferred embodiments of the magnetic field sensor arrangement according to the invention comprise four of the magnetoresistive sensors which are electrically connected as a full bridge. The four magnetoresistive sensors are arranged axially spaced. In each case two of the four magnetoresistive sensors preferably have an axial position, such as one of the two magnetization regions, which are oppositely poled. These two magnetoresistive sensors assigned to one of the magnetization regions preferably face one another oppositely oriented Barberpol structures. The magnetoresistive sensors each comprise a strip of magnetoresistive material, the strips of the four magnetoresistive sensors being aligned parallel to each other.

The four full-bridge magnetoresistive sensors are preferably electrically connected to an electronic instrumentation amplifier, which is designed for bridge voltage evaluation of the full bridge. Due to the inventive design of the magnetic field sensor arrangement, the bridge voltage evaluation has no RSU error.

The magnetic field sensors preferably each have an axial position such as one of the magnetization regions. The magnetic field sensors preferably each have an axial position, which equals a middle axial position of one of the magnetization regions.

In preferred embodiments of the magnetic field sensor arrangement according to the invention, the magnetic field sensors are formed on a flexible film, by means of which the machine element can be circumferentially enclosed. Thus, the flexible film surrounds the machine element circumferentially. The magnetic field sensors are applied in particular by a printing technique and by deposition on the film. Insofar as the magnetic field sensors are formed by magnetoresistive sensors, these preferably comprise a magnetoresistive layer which is deposited or printed on the film. The magnetoresistive layer preferably has a strip shape. On the magnetoresistive layer preferably highly conductive shorting strips are applied, which preferably have a Barberpol structure. For applying the shorting strips, a photolithographic method is preferably used. The film is preferably highly flexible and preferably consists of a polymer, preferably PET. The film has a thickness which is preferably less than 10 μm. The magnetoresistive layer preferably comprises cobalt and copper. The shorting strips preferably comprise aluminum. The electronic instrumentation amplifier is preferably also arranged on the film as a semiconductor integrated circuit.

In preferred embodiments of the magnetic field sensor arrangement according to the invention, an additional magnetic field sensor for determining a rotational speed is also formed on the film. The additional magnetic field sensor is opposite to a pole ring formed on the machine element. A combination of a mechanical trigger surface applied to the machine element and an eddy-current sensor printed on the film, which is evaluated with an LDC1101 chip from Texas Instruments, is likewise preferred for speed monitoring. If there is a rotation between the machine element and the magnetic field sensor arrangement, then the pole ring rotates with respect to the additional magnetic field sensor so that the rotational speed and / or an angle of rotation can be measured. The magnetic field sensor arrangement preferably further comprises at least one comparator for an incremental signal evaluation or at least one instrument amplifier for an analog signal evaluation of the additional magnetic field sensor. The comparator or the instrument amplifier is preferably also arranged on the foil. Thus, the magnetic field sensor arrangement allows the measurement of the torque and also the measurement of the rotational speed.

In preferred embodiments of the magnetic field sensor arrangement according to the invention, the film with the magnetic field sensors formed thereon and possibly further components is cast into a hollow cylindrical composite body. Preferably, the film is molded with the magnetic field sensors formed thereon and possibly other components in a synthetic resin, wherein the cured resin largely encloses and mechanically stabilizes the film with the magnetic field sensors and optionally further components formed thereon. The cured resin with the film therein, the magnetic field sensors and possibly other components form the hollow cylindrical composite body.

The arrangement according to the invention is used to measure a torque on a machine element extending in an axis. The machine element has at least two magnetization areas extending around the axis for magnetization. The arrangement further comprises the magnetic field sensor arrangement according to the invention. The magnetic field sensors of the magnetic field sensor arrangement each extend circumferentially around the machine element. The machine element and the magnetic field sensor arrangement are rotatable relative to each other. The arrangement according to the invention preferably comprises one of the described preferred embodiments of the magnetic field sensor arrangement according to the invention. Moreover, the arrangement preferably also has features that are specified in connection with the magnetic field sensor arrangement according to the invention.

The arrangement according to the invention preferably comprises two of the magnetic field sensor arrangements according to the invention. The two magnetic field sensor arrangements, in particular the foils of the two magnetic field sensor arrangements, are preferably galvanically separated. The two hollow cylindrical magnetic field sensor arrangements are preferred arranged coaxially to one another, wherein one of the two hollow cylindrical magnetic field sensor arrangements is arranged in the radial direction over the other of the two hollow cylindrical magnetic field sensor arrangements. Preferably, the foil of the radially outer of the two hollow cylindrical magnetic field sensor arrangements is wound over the foil of the radially inner of the two hollow cylindrical magnetic field sensor arrangements. The two magnetic field sensor arrangements allow the measurement of the torque with a double measurement reliability and / or a two-channel, functionally safe sensor topology.

The method according to the invention serves to produce the magnetic field sensor arrangement according to the invention. In one step of the method, a flexible sheet of polymer is provided. In a further step, magnetoresistive layers or Hall sensor elements are applied to the film in order to form magnetic field sensors on the film. In addition, electrical contacts are applied to the electrical connection of the magnetic field sensors on the film. The magnetoresistive layers are preferably applied by printing or by deposition on the film to form the magnetic field sensors in the form of magnetoresistive sensors. Alternatively, the Hall sensor elements are applied to the film to form the magnetic field sensors in the form of Hall sensors. Preferably, the instrument amplifier is further applied to the film. The film is preferably shaped or wound in the form of a cylinder jacket. The film with the magnetic field sensors thereon and optionally other components is preferably cast in synthetic resin, whereupon, after the curing of the synthetic resin, a composite body is produced which is preferably hollow cylindrical. Moreover, the method preferably also has features which are specified in connection with the magnetic field sensor arrangement according to the invention and the arrangement according to the invention.

• 1 eine bevorzugte Ausführungsform einer erfindungsgemäßen Anordnung in einer perspektivischen Ansicht; und
• 2 eine Magnetfeldsensoranordnung in einem abgewickelten Zustand und eine Welle der in 1 gezeigten Anordnung im Detail.

Further details, advantages and developments of the invention will become apparent from the following description of a preferred embodiment of the invention, with reference to the drawing. Show it:

• 1 a preferred embodiment of an arrangement according to the invention in a perspective view; and
• 2 a magnetic field sensor arrangement in a developed state and a shaft of the in 1 shown arrangement in detail.

1 shows a preferred embodiment of an arrangement according to the invention in a perspective view. The arrangement is for measuring a torque M (shown in FIG 2 ), which on a machine element in the form of a shaft 01 acts.

The wave 01 has two areas of magnetization 02 (shown in 2 ) in the form of circulating tracks. The two magnetization areas 02 (shown in 2 ) are permanently magnetized and oppositely poled. The two magnetization areas 02 (shown in 2 ) form a primary sensor for measuring the torque M (shown in FIG 2 ) using the inverse magnetostrictive effect.

The arrangement includes beside the shaft 01 a magnetic field sensor arrangement 03 , which has a secondary sensor for measuring the torque M (shown in FIG 2 ). The magnetic field sensor arrangement 03 includes a flexible film 04 , which is shaped in the shape of a cylinder jacket and the shaft 01 in the area of magnetization areas 02 (shown in 2 ) completely surrounds. The cylinder jacket shape of the film 04 is coaxial with the shaft 01 arranged. The foil 04 has a radial distance to the shaft 01 on, so that a circumferential air gap 06 between the wave 01 and the foil 04 is trained. The wave 01 is rotatable while the magnetic field sensor arrangement 03 is at rest.

On the slide 04 are four magnetic field sensors 07 formed, which completely circulating on the film 04 and thus completely encircling the shaft 01 extend. The four magnetic field sensors 07 are each formed by an AMR sensor and each comprise a strip 08 of a magnetoresistive material on which highly conductive shorting strips 09 made of aluminum in a Barberpol structure are applied. The Stripes 08 from the magnetoresistive material are on the foil 04 printed. The magnetic field sensor arrangement 03 ie the foil 04 with the magnetic field sensors formed thereon 07 is flexible, so that it can be shaped in various ways and, for example, can be brought back from the cylinder jacket shape in a flat shape.

2 shows the in 1 shown magnetic field sensor arrangement 03 and the wave 01 in detail. The magnetic field sensor arrangement 03 is in a developed flat state away from the shaft 01 shown. The wave 01 has the two permanent magnetized and oppositely poled magnetization regions 02 on. The wave 01 is loaded with the torque M, which is measurable by the arrangement.

By way of illustration, the developed magnetic field sensor arrangement 03 represented within a diagram. A y-axis of the diagram represents an angle β, which represents a center angle with respect to an axis of the shaft. As the magnetic field sensor arrangement 03 in the wound state, the shaft 01 completely surrounds, extends the magnetic field sensor array 03 from β = 0 ° to β = 360 °. An x-axis of the diagram represents a length in the axis of the shaft 01 , The foil 04 is rectangular in the unwound state.

The four magnetic field sensors 07 extend from β = 0 ° to β = 360 °. Two of the four magnetic field sensors 07 stand one of the two magnetization areas 02 opposite, with these two magnetic field sensors 07 the Barberpol structures of the shorting strips 09 aligned with each other. The Stripes 08 of the four magnetic field sensors 07 are rectangular and aligned parallel to each other.

In 2 is also an electrical interconnection of the four magnetic field sensors 07 shown. The four magnetic field sensors 07 are electrically interconnected as a full bridge. The two axially outside magnetic field sensors 07 are on an electrical ground 11 connected. At the two axially inside magnetic field sensors 07 there is a voltage Vcc. The electrical connections of the paired magnetic field sensors 07 form a balanced output signal at an output 12 , which is connected to an instrumentation amplifier (not shown). As instrument amplifier is a standard instrumentation amplifier, such as the type INA826.

LIST OF REFERENCE NUMBERS

01

Machine element in the form of a shaft

02

magnetization field

03

Magnetic field sensor arrangement

04

foil

05

-

06

air gap

07

magnetic field sensor

08

Strips of magnetoresistive material

09

Short strips

10

-

11

electrical mass

12

output

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• US 6222363 B1 [0002]
• US 2002/0162403 A1 [0003]
• US 2009/0230953 A1 [0004]
• US 2013/0125669 A1 [0005]
• EP 0803053 B1 [0006]
• US 8893562 B2 [0007]
• US8001849 B2 [0008]
• US 2011/0162464 A1 [0009]
• US8087304 B2 [0010]
• US 9151686 B2 [0011]

Claims (10)

A magnetic field sensor arrangement (03) for measuring a torque (M) on a machine element (01) extending in an axis, said machine element (01) comprising at least two magnetization regions (02) extending circumferentially about the axis for magnetization, said magnetic field sensor arrangement (03) comprises at least two magnetic field sensors (07) for measuring a caused by the magnetization as well as the torque (M) differential magnetic field, characterized in that the magnetic field sensors (07) each extend circumferentially about the axis to the machine element (01) circumferentially to enclose. Magnetic field sensor arrangement (03) according to Claim 1 , characterized in that the magnetic field sensors are each formed by a magnetoresistive sensor (07) or by a Hall sensor. Magnetic field sensor arrangement (03) according to Claim 2 , characterized in that the magnetoresistive sensors (07) each have a Barberpol structure which extends circumferentially about the axis. Magnetic field sensor arrangement (03) according to one of Claims 1 to 3 , characterized in that it comprises four of the magnetic field sensors (07), which are connected as a full bridge. Magnetic field sensor arrangement (03) according to Claim 4 , characterized in that it comprises an electronic instrumentation amplifier for bridge voltage evaluation of the full bridge. Magnetic field sensor arrangement (03) according to one of Claims 1 to 5 , characterized in that the magnetic field sensors (07) on a flexible film (04) are formed, through which the machine element (01) is circumferentially umschließbar. Magnetic field sensor arrangement (03) according to Claim 6 , characterized in that on the film, an additional magnetic field sensor for determining a speed is further formed. Magnetic field sensor arrangement (03) according to Claim 6 or 7 , characterized in that the film (04) is cast with the magnetic field sensors (07) in a hollow cylindrical composite body. An assembly for measuring a torque (M) on an axially extending machine element (01), the machine element (01) having at least two magnetization regions (02) extending circumferentially about the axis for magnetization, the device further comprising a magnetic field sensor assembly (03) after one of Claims 1 to 8th includes, and wherein the machine element (01) and the magnetic field sensor arrangement (03) are rotatable to each other. Method for producing a magnetic field sensor arrangement (03) according to one of the Claims 1 to 8th : - providing a flexible sheet (04) of a polymer; and - applying magnetoresistive layers (08) or Hall sensor elements as well as electrical contacts to the foil to form magnetic field sensors (07) on the foil (04).

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