DE102007049741B4 - Magnetic scale carrier - Google Patents

Abstract

Magnetic scale carrier with alternately magnetized or magnetizable sections (14, 16) in one measuring direction (22, 24), characterized in that the scale carrier has at least two carrier elements (10, 12) on which sections are spaced apart in the measuring direction (22, 24) (14, 16) of the same magnetization are provided, with magnetized or magnetizable sections (14) of a carrier element (10) coming to lie in the spaces between magnetized or magnetizable sections (16) of the other carrier element (12) and in the measuring direction (22, 24) mutually adjacent sections (14, 16) of different carrier elements (10, 12) each have different magnetic polarities.

Description

The present invention relates to a magnetic scale carrier or a magnetic material measure having alternating magnetized or magnetizable sections in one measuring direction. The invention further relates to a method for producing the scale carrier.

Background and state of the art

Magnetoresistive (MR) sensors are widely used for measuring physical quantities, in particular distances and rotational movements. These make use of the so-called magnetoresistive effect, after which the electrical resistance of a conductive material changes under the action of a magnetic field. In this case, MR sensors according to the prior art in particular use the so-called anisotropic magnetoresistive effect (AMR) and the giant magnetoresistive effects (GMR), by means of which not only the amplitude but also the direction of an applied magnetic field can be precisely determined.

To use these magnetic effects for the measurement technique, individual AMR or GMR resistors are arranged as a Wheatstone bridge on an integrated chip.

Such MR sensors are designed to detect magnetic field changes precisely. For the length or angle measurement therefore reference objects, such as magnetic scales or Polräder are necessary, which have a well-defined inducible or permanent spatially inhomogeneous or a geometric default following alternating magnetic field. The available reference objects distinguish between magnetic and non-magnetic scales.

Non-magnetic scales are, for example, non-magnetized gear wheels or toothed racks made of a ferromagnetic material, which however generate measurable spatial magnetic field inhomogeneities in the presence of an external magnetic field during a relative movement with respect to the MR sensor. From the geometry of the reference object and the known distance of the individual teeth, which are responsible for the magnetic inhomogeneities, precise conclusions about the translation or rotational movement of the reference object can be drawn from the sensor signal.

In contrast, magnetized scales have a permanent, inhomogeneous and / or alternating magnetic field in the direction of measurement or movement. Such magnetic scales are made of magnetizable, in particular hard magnetic or soft magnetic material and have a periodically alternating polarity along the movement or rotation direction to be measured.

In the DE 10 2004 063 462 B3 Such a scale carrier for magnetic length or angle measurements is described. This has a groove incorporated on its surface along the scale track, which is filled with a curable magnetic powder paste. To cure this powder paste, the scale carrier is heated, and after curing, a magnetic layer is applied over the groove surface. Such a scale carrier is at best suitable for the generation of periodic magnetic structures in the millimeter range. For smaller structures in the submillimeter range, such a production process is hardly applicable. For applications in microsystems technology, such scale carriers are therefore almost unsuitable. In addition, their production is relatively complex and labor intensive.

In the production of magnetic scales or material measures, moreover, the magnetization of a given magnetic pattern on the scale to be magnetized is quite problematic. In particular, if, as customary in microsystem technology, particularly small scales for correspondingly miniaturized MR sensors are to be manufactured. At most magnet magnetic structures in the submillimeter range can be produced by means of the magnetizing devices available today.

However, such known pole structures have a relatively weak magnetic field, so that the sensors of the measuring systems must be arranged very close to the pole structures in order to obtain an evaluable measuring signal. Due to the small distance of the sensors to the pole structures, however, a high susceptibility to interference by any fouling that settles in the gap between the sensor and the pole structure is considerable in these systems.

A generic magnetic scale carrier is from the JP 560 168 01 AA known. The scale carrier has in the X direction on a support member in spaced-apart portions of the same magnetization, each having different poles of the sections facing each other.

From the DE 93 11 045 U1 a scale carrier is known in which a magnetic film has alternating poles, which are arranged one behind the other in the measuring direction.

task

The object of the present invention is to provide a magnetic scale or a magnetic material measure with significantly smaller magnetic structure sizes, which have a precise and sharply demarcated pole pitch. In addition, the magnetic scale according to the invention should be suitable for industrial mass production and have a high potential for optimization in terms of production time and production costs.

Invention and advantageous effects

The object underlying the invention is achieved by means of a magnetic scale carrier according to claim 1, a method for its production according to claim 10 and a device for measuring distances and / or angles of rotation. Further advantageous embodiments of the invention are specified in the respective subclaims.

The magnetic scale carrier according to the invention has alternately magnetized or magnetizable sections along a measuring direction. These magnetically poled alternating in the measuring or in the direction of movement adjacent magnetized or magnetizable sections specify a spatial magnetic coding, which allows for a relative movement of scale and associated MR sensor an incremental or even absolute measurement of a distance or a rotation angle.

According to the invention, the magnetic scale carrier has at least two carrier elements, on each of which sections of equal magnetization spaced apart from one another in the direction of measurement or movement are provided. The two carrier elements are arranged in such a way to each other that magnetized or magnetizable portions of a support element come to lie in the interstices of corresponding magnetized or magnetizable portions of the other support element, so that in the measuring or moving direction, an alternating magnetic pole structure is generated.

Thus, it is provided according to the invention that in the measurement or movement direction adjacent magnetizable or magnetized portions of different carrier elements each have different magnetic polarity. In this case, the magnetized or magnetizable portions of a respective carrier element are provided with the same polarity.

By joining two in the region of their magnetized or magnetizable sections substantially homogeneously magnetically poled carrier elements and their corresponding interlocking geometric configuration can be generated in an overlap region of the scale carrier carrier combined a sharply demarcated, precise and at the same time miniaturized spatial magnetic coding. By means of the simplest magnetizing devices, it is therefore possible to produce minute magnetic structures in the sub-millimeter range in a cost-effective and simple manner. These structures also have a relatively strong magnetic field, so that any sensors can be arranged without loss of the quality of the measurement signal at a greater distance to it. In this respect, this also reduces the susceptibility to interference due to any contamination.

The objective and structural separation of magnetic poles by the interlocking and quasi-toothed arrangement in the overlap region of the support elements allows the generation of a particularly high number of pole pairs per unit length or area. This allows a further miniaturization of magnetic scales without a significant increase in production costs and manufacturing costs.

According to a first advantageous embodiment of the invention, it is provided that the magnetized or magnetizable sections of the carrier elements extend substantially perpendicular to the measuring direction of movement of the associated carrier elements. Between the magnetized or magnetizable portions of a carrier element that extend perpendicularly from the carrier plane, intermediate spaces are provided into which those oppositely poled magnetized or magnetizable portions of a corresponding carrier element when immersing two carrier elements are immersed or come to rest.

It is provided in particular that the magnetized or magnetizable sections of different and mutually to be joined carrier elements intermesh claw-like or interlocking. In this way, a parallel to the plane of the support elements extending pattern can be generated with alternating magnetic polarity.

According to a further advantageous aspect of the invention, it is provided that the magnetized or magnetizable sections and / or the intermediate spaces between a carrier element can be produced lithographically. For this purpose, all common lithographic processes are considered. The advantage for generating the magnetized or magnetizable sections is the so-called LIGA method or LIG method provided. This is based on a combination of depth lithography, galvanic and micro-impression. By means of such lithographic processes, microstructures with smallest dimensions of up to 0.2 μm, structural heights of up to 3 mm and aspect ratios of up to 50 can be produced.

The starting material for the carrier elements is a flat substrate, such as a silicon wafer, which, unless already electrically conductive, is provided with a metallic conductive layer. On this layer, a thick radiation-especially photo- or X-ray-sensitive film (resist) is applied, which is exposed by irradiation. After development of the resist, a negative mold remains in the applied metal structure.

In a subsequent galvanic process, a metal is deposited on the substrate in the areas where the film has been removed during development. After removal of the film or the photoresist, the substrate, the starting layer and the electrodeposited metal remain behind. For the further method, either the starting layer can be etched away, the structure "overgrown" by a further galvanic process step, or alternatively the lithographically produced microstructure can be directly cut out of the substrate.

According to a further advantageous embodiment, at least the magnetizable sections of the carrier elements are magnetizable prior to joining the carrier elements. This magnetization can be largely homogeneous over the surface of the carrier elements. The inhomogeneous and alternating in the measuring direction magnetic polarity is only generated by the subsequent joining of the carrier elements.

It is further provided that the magnetized or magnetizable sections are integrally connected to the associated carrier element or integrally formed thereon. According to the invention, provision is made in particular for the magnetized or magnetizable sections to be produced by a photolithographic process from the planar substrate of a carrier element. Alternatively, however, the geometric shape of the carrier element can also be produced by casting or stamping. The choice of the manufacturing process depends primarily on the selection of the material and the size of the structure to be produced in the material.

According to a further advantageous aspect, it is provided that the structure size of the magnetized or magnetizable sections of the carrier elements is in the range of a few micrometers to millimeters. In particular, feature sizes in the range of minimally 5 to 10 microns are provided. Such structure sizes allow a drastic miniaturization of magnetic scales and their implementation in correspondingly small-scale magnetoresistive sensory measurement systems.

This miniaturization not only reduces the size of corresponding measuring systems, but also significantly increases the accuracy of the measuring system. In addition, since no expensive high-resolution magnetization device is required more, at the same time the production costs for such miniaturized and at the same time high-resolution magnetic scales can be drastically reduced.

According to a development of the invention, the carrier elements which are adapted to one another and which can be arranged on one another have an essentially rectilinear or rod-like outer geometry. Such trained measure embodiments are preferably used for a length measurement. In this case, the scale along its longitudinal direction, in which it has alternately different magnetic polarity, moved relative to a sensory element.

Furthermore, it is provided that the support elements also have a disk-like geometry and can be arranged coaxially with each other. In this embodiment, the scale acts as a pole wheel with circumferentially alternately arranged permanent magnet. The pole wheel is used as an incremental encoder for a speed or rotation angle sensor. It is sufficient if the support elements also have only a ring-like structure.

The individual magnetizable sections of adjacent carrier elements extend in the axial direction. The free end of the rod-shaped or tooth-like magnetizable sections comes to rest in intermediate spaces of corresponding magnetizable sections of the carrier element arranged adjacently in the axial direction. In this way, a circumferentially alternating magnetic polarity can be generated in a simple manner.

According to an advantageous embodiment of the invention, at least one preferably separate permanent magnet and / or electromagnet is provided, through which the sections and possibly the carrier elements are magnetizable. As a result, the scale carrier can be realized in a particularly cost-effective manner, since the sections and preferably also the carrier elements themselves do not have to be magnetized and insofar as they are relatively small inexpensive materials can be used, which need only be magnetizable. For as a source of magnetization acts in this case at least one permanent magnet or electromagnet, are magnetized by the magnetic field, the sections or support elements in the manner according to the invention.

It makes sense that the sections and possibly the support elements made of soft magnetic material, since these materials are particularly cost.

According to a further independent aspect, the invention relates to a method for producing a magnetic scale carrier, wherein at least two support elements are provided, each having magnetizable sections. In this case, the carrier elements are assembled in such a way that the magnetized or magnetizable sections of a carrier element come to lie in intermediate spaces of magnetized or magnetizable sections of the adjacent to be arranged or the other carrier element.

Perpendicular to the interface between the two support elements thus creates an alternating pattern of different magnetic poled sections.

Advantageously, the carrier elements are produced by means of lithographic methods from magnetized or magnetizable carrier substrates. As support substrates are all hard magnetic and / or soft magnetic materials in question. In particular nickel cobalt or nickel-iron alloys, but also powder materials and soft ferrites such as NiZn and MnZn are provided as good starting materials for the carrier substrates.

The magnetization of the individual carrier elements, which is largely homogeneous in the plane of the interface between individual carrier elements, can be effected after a photolithographic or galvanic shaping of the carrier elements. Alternatively or additionally, sufficient magnetization can also be created directly in the galvanic deposition of the geometric structure on the carrier substrate by applying suitable fields.

Moreover, the invention relates to a device for measuring distances and / or angles of rotation with a scale carrier according to the invention and a magnetoresistive sensor device. The latter is arranged in or on the measuring device in the immediate vicinity of the movable scale carrier and is designed to generate electrical signals as a function of a translatory or rotary movement of the scale carrier relative to the sensor device, by means of which the movement performed by the scale can be qualitatively and quantitatively determined.

embodiment

Other objects, advantages, features and applications of the present invention will be explained below with reference to an embodiment with reference to the drawings.

Show it:

1 a cross-sectional view of a scale carrier with claw-like intermeshing alternately magnetized sections and

2 a schematic cross section of a magnetic scale in the embodiment as a pole in plan view.

In the 1 is a scale carrier with two carrier elements 10 . 12 shown in cross section. On the carrier elements 10 . 12 are each extending in the vertical direction single magnetizable sections 14 . 16 formed when joining the two support elements 10 . 12 as it is in 1 is hinted claw-like mesh. In the measuring or moving direction 22 , what a 1 Thus, a sharply demarcated and in miniature version easily realizable magnetic periodic pole structure, which is universally usable as magnetic material measure both for the measurement of translational and rotational movements in combination with conventional MR sensors.

The individual web or comb-like magnetizable sections 14 . 16 are in particular produced by means of lithographic processes, such as the LIGA or LIG process. However, alternative production methods, such as stamping or metal injection molding, are also conceivable. In any case, it is necessary for the invention that the individual sections 14 . 16 are largely permanently magnetizable.

It is particularly provided that the two support elements 10 . 12 be magnetized differently. Im in 1 example shown has the overhead support element 10 at its upper continuous portion of a magnetic north pole not explicitly shown and in its downwardly corresponding into the interstices sections 16 protruding magnetizable sections 14 a magnetic south pole. Correspondingly, the inverse is in 1 underlying support element 12 poled. Thus, the continuous part lying down there has a magnetic south pole and the upwardly projecting sections 16 a magnetic north pole.

By means of the technique according to the invention, therefore, the smallest possible alternating magnetic structures in the micrometer range can be produced without the need for high-resolution magnetizing devices. The spatial resolution and density of magnetic polarity is solely due to the size of the carrier elements 10 . 12 essentially perpendicular to the direction of measurement or movement 22 extending structures 14 . 16 specified.

This in 1 shown claw-like intermeshing differently polarized and equipped with corresponding geometric shapes support elements 10 . 12 is almost universally applicable to rod-shaped magnetic scales for length measurement as well as disc-like scales for the rotation angle measurement. So is in 2 an example of a pole along a section line AA 'according to 1 shown. The pole wheel is along the by reference numeral 24 marked rotational directions rotatably mounted either counterclockwise or clockwise.

On its outer circumference are alternately poled magnetic sections 14 . 16 arranged the corresponding magnetic fields, passing through the magnetic field lines 18 are shown as examples. These of the alternately arranged differently polarized magnetic sections 14 . 16 generated magnetic fields can during a rotational movement of the pole wheel from the associated MR sensor 20 both qualitatively and quantitatively.

The microsystem technology for the generation of geometric structures in the micrometer range allows the production of such Polräder on a micrometer scale.

According to a possible embodiment of the magnetic scale carrier, not shown here, it may be provided that a preferably separate permanent magnet or electromagnet is provided, by means of which the sections and optionally the carrier elements can be magnetized. In this case, the sections and / or the carrier elements are preferably made of soft magnetic material. If the sections and support elements are produced by means of lithographic processes, the preferred soft magnetic material is a nickel-iron alloy.

Of course, the magnetizable structures, such as the sections and support elements may be made of other ferritic materials and / or of ferritic materials.

LIST OF REFERENCE NUMBERS

10

support element

12

support element

14

Magnetizable section

16

Magnetizable section

18

magnetic field lines

20

MR sensor

22

measuring direction

24

direction of rotation

Claims (14)

Magnetic scale carrier in a measuring direction ( 22 . 24 ) alternately magnetized or magnetizable sections ( 14 . 16 ) characterized in that the scale carrier at least two support elements ( 10 . 12 ), in each case in the measuring direction ( 22 . 24 ) spaced apart sections ( 14 . 16 ) are provided with the same magnetization, wherein magnetized or magnetizable sections ( 14 ) of a carrier element ( 10 ) in spaces of magnetized or magnetizable sections ( 16 ) of the other carrier element ( 12 ) and in the measuring direction ( 22 . 24 ) adjacent sections ( 14 . 16 ) of different carrier elements ( 10 . 12 ) each have different magnetic polarity. Scale carrier according to claim 1, wherein the magnetized or magnetizable sections ( 14 . 16 ) substantially perpendicular to the measuring direction ( 22 ) on the associated carrier elements ( 10 . 12 ). Scale carrier according to one of the preceding claims, wherein the magnetized or magnetizable sections ( 14 . 16 ) of different carrier elements ( 10 . 12 ) claw-like. Scale carrier according to one of the preceding claims, wherein the magnetized or magnetizable portions and / or the intermediate spaces are lithographically generated. Scale carrier according to one of the preceding claims, wherein the at least the magnetizable sections ( 14 . 16 ) before joining the carrier elements ( 10 . 12 ) are magnetizable. Scale carrier according to one of the preceding claims, wherein the magnetized or magnetizable sections are integral with the carrier elements ( 10 . 12 ) are connected or integrally formed thereon. Scale carrier according to one of the preceding claims, wherein the structure size of the magnetized or magnetizable sections ( 14 . 16 ) is in the range of a few μm to mm. Scale carrier according to one of the preceding claims, wherein the carrier elements ( 10 . 12 ) have a substantially rectilinear or rod-like geometry. Scale carrier according to one of the preceding claims 1 to 7, wherein the carrier elements ( 10 . 12 ) have a disc-like geometry and are arranged coaxially with each other. Scale carrier according to one of the preceding claims, characterized in that a, preferably separate permanent magnet or electromagnet is provided, through which the sections ( 14 . 16 ) and possibly the carrier elements ( 10 . 12 ) are magnetizable. Scale carrier according to one of the preceding claims, characterized in that the sections ( 14 . 16 ) and possibly the carrier elements ( 10 . 12 ) consist of soft magnetic material. Method for producing a magnetic scale carrier, wherein at least two carrier elements ( 10 . 12 ) with sections protruding from the substrate plane ( 14 . 16 ) and the sections ( 14 . 16 ) of different carrier elements ( 10 . 12 ) are polarized differently magnetically, wherein the support elements are joined together so that magnetized sections ( 14 ) of a carrier element ( 10 ) in interspaces of magnetized sections ( 16 ) of the other carrier element ( 12 ) come to rest. Method according to claim 12, wherein the carrier elements ( 10 . 12 ) are produced by means of lithography from magnetized or magnetizable carrier substrates. Device for measuring distances and / or angles of rotation with a scale carrier according to one of the preceding claims 1 to 11 and a magnetoresistive sensor device ( 20 ), which is adapted to detect a movement of the scale carrier quantitatively.

Images