Patent Application
20230074765
This application claims priority from German Application No. 10 2021 123 392.5 filed on Sep. 9, 2021, which is incorporated herein by reference in its entirety.
The invention relates to a load measuring arrangement comprising a test object and a load measuring device for measuring a load applied between a first region and a second region of the test object by means of active magnetization. Further, the invention relates to a load measuring method for measuring a load applied between a first region of a test object and a second region of a test object by means of active magnetization.
Load measuring arrangements and load measuring methods are known in which a load such as a torque, force or even mechanical stresses in a test object are measured magnetostrictively. While some of these measuring methods and measuring arrangements require the measuring zone to be permanently magnetized in advance, the invention relates to such measuring methods and measuring arrangements in which a magnetic field is only actively applied during the measurement and magnetic field parameters, which are present when the measuring zone of the test object located in the magnetic field is subjected to a load, are detected to determine the load.
Such load measuring arrangements and load measuring methods are known from the following literature:
The aforementioned load measuring methods and load measuring arrangements have been proven to measure torques, forces, stresses. However, for some test objects, there are conflicting objectives with respect to the desired function of the test object and the measurement of the load on the test object. For example, it may be desirable to manufacture the test object, such as shafts, chassis components, power transmission elements, gear elements, bicycle parts or the like, from materials and/or in geometries that are optimized in terms of weight, power transmission, adaptation to environmental conditions, stiffness, main function fulfillment, etc., but that are less suitable for magnetostrictive load measurement.
The invention is based on the problem of improving load measuring arrangements and load measuring methods of the kind mentioned in literature [1] to [17] with regard to function of the test object and measurement of the load.
To solve this problem, the invention provides a load measuring arrangement and a load measuring method according to the independent claims.
Advantageous embodiments are the subject of the subclaims.
The invention provides a load measuring arrangement comprising a test object and a load measuring device for measuring a load applied between a first region and a second region of the test object, wherein the test object has a main transmission region receiving a majority of the load between the first region and the second region, wherein a secondary transmission element is attached to the first and second regions of the test object so as to receive a smaller portion of the load between the first and second regions in parallel with the main transmission region, the load measuring apparatus comprising magnetic field generating means for generating a magnetic field at the secondary transmission element, and a magnetic field detection device for detecting a magnetic field parameter changing due to the load on the secondary transmission element.
Thus, the material and/or structure of the secondary transmission element can be formed for optimal load measurement, while the transmission region can be formed for optimal functional performance of the test object.
The load measuring device can be designed as described in the aforementioned literature [1] to [17] and thus have, for example, a measuring sensor, such as sensor head with coils, in particular planar coils, more particularly in V or X arrangement, in order to generate a magnetic field by means of a generator coil and to detect magnetic field parameter changes dependent on loads by means of measuring coils.
Accordingly, it is preferred that the load measuring device comprises a first and a second magnetic field detection device for detecting the magnetic field parameter changing due to the load on the secondary transmission element.
It is preferred that the load measuring device comprises a generator coil and at least two measuring coils.
It is preferred that the load measuring device comprises planar coils.
It is preferred that the load measuring device comprises at least three coils arranged in a V-shape or five coils arranged in an X-shape.
It is preferred that the load measuring device comprises a measuring sensor having the magnetic field generating device and the at least one magnetic field detection device, and a supply and evaluation unit connected to the measuring sensor. Preferred further details of the supply and evaluation unit are described in particular in [5], [7] and [17].
The secondary transmission element can be optimally designed for load measurement by active magnetization, in particular with regard to material selection. Preferred materials for the secondary transmission element or at least of a measuring zone thereof are:
Preferably, the secondary transmission element can be more easily fabricated separately from any other base body of the test object. For example, a smaller secondary transmission element is easier to handle for material processing or coating than, for example, larger shafts or chassis parts or the like. The secondary transmission element can then be attached to the base body of the test object so that part of the load is received via the secondary transmission element and can be measured there. From this, it is then possible to determine the load on the test object, for example after calibration.
It is preferred that the load measuring device is designed to measure a force, strain, torque or axial stress using an active magnetic sensor system.
It is preferred that the load measuring device comprises a measuring sensor fixedly connected to the test object and having the magnetic field generating device and the at least one magnetic field detection device.
It is preferred that the load measuring device comprises a measuring sensor fixedly connected to the secondary transmission element and having the magnetic field generating device and the at least one magnetic field detecting device.
It is preferred that the secondary transmission element is magnetostrictive and is attached to the first and second regions of the test object such that deformation of the test object results in deformation of the secondary transmission element, wherein the load measuring device is configured to determine the load on the secondary transmission element.
In one embodiment, it is preferred that the secondary transmission element is formed from the same material as the transmission region. This allows measurement errors, for example due to different temperature expansions, to be reduced. By using the secondary transmission element, the geometry of the secondary transmission element can be optimized for load measurement independently of the geometry of the transmission area.
In one embodiment, it is preferred that the secondary transmission element is formed from the same material as the transmission region, but material properties differ due to different heat treatment or different mechanical processing. For example, the secondary transmission element may be subjected to work hardening. Experiments have shown that this can improve load measurements with active magnetization.
It is preferred that the secondary transmission element is coated with a layer of a material with a relative permeability >2.
It is preferred that the secondary transmission element is coated with a layer of a material selected from the group consisting of electroless nickel, nickel, metallic glass, μ-metal, ferrite, permalloy.
It is preferred that the secondary transmission element is fixedly connected to the first region of the test object by a first connecting region and is fixedly connected to the second region of the test object by a second connecting region, wherein a measuring zone of the secondary transmission element arranged between the first and second connecting regions is not connected to the transmission region and is loaded in parallel when the transmission region is loaded, wherein the load measuring device is designed to measure the load on the measuring zone by active magnetization and to determine a magnetic parameter changing due to the load.
It is preferred that the secondary transmission element is connected to the base body of the test object by means of a connection technique selected from the group consisting of rivets, screws, material connection, welding, soldering, bonding, shrinking-on, crimping.
It is preferred that the secondary transmission element is formed, at least at a measuring zone, of a work-hardened metal having a dislocation density >5e8/cm2 or a residual compressive stress >400 MPa in amount.
It is preferred that the measuring zone bridges the first and second connecting regions.
It is preferred that the measuring zone has a smaller thickness and/or width than the connecting regions.
It is preferred that the secondary transfer member is configured with respect to the construction and relative geometry of the connecting regions and the measuring zone such that strain between the first region and the second region of the test object results in greater strain at the measuring zone.
It is preferred that the secondary transmission element is designed with respect to the construction and relative geometry of the connecting regions and the measuring zone such that a strain between the first region and the second region of the test object leads to strain at the measuring zone changed in such a way that an average strain or average stress at a measuring position of the measuring zone, which measuring position extends from a surface facing a measuring sensor of the load measuring device to a depth corresponding to the penetration depth of the magnetic field, deviates by at least 20% from the average strain or average stress of the secondary transmission element.
It is preferred that the connecting regions are formed to be substantially more rigid than the measuring zone.
It is preferred that the first connecting region, the measuring zone and the second connecting region are formed as sleeves which are fastened axially successively to one another and in which the transmission region is accommodated, the connecting regions having a greater wall thickness than the measuring zone, the ends of the connecting regions which are arranged away from one another being fixedly connected to the first and second regions, respectively, of the test object, but relative movements between the sleeves and the transmission region being possible between the first and second regions.
It is preferred that the measuring zone is more elastic than the transmission region.
It is preferred that the test object has an at least piecewise cylindrical surface which is rotatable by at least 5° about the cylinder axis of the cylindrical surface, wherein the secondary transmission element is also at least piecewise cylindrical in shape and is attached to the cylindrical surface of the test object in such a way that it is deformed when loads are applied to the test object, wherein a measuring sensor of the load measuring device which comprises the magnetic field generating device and the at least one magnetic field detection device is arranged such that it does not rotate along with the cylindrical surface when the latter is rotated.
It is preferred that the test object is a shaft for transmitting a torque.
It is preferred that the test object is a gear element for transmitting a force or torque.
It is preferred that the test object is a part of a vehicle or lifting tool loaded in operation.
According to another aspect, the invention provides a load measuring method for measuring a load applied to a test object between a first region and a second region, the test object having a transmission region between the first region and the second region, comprising:
Preferably, the load measuring arrangement is configured to perform the load measuring method. Preferably, the load measuring method is performed with the load measuring arrangement according to one of the previously described embodiments.
According to a further aspect, the invention provides a manufacturing method of a load measuring arrangement according to one of the previously described embodiments, comprising providing a base body of the test object, providing a secondary transmission element, wherein the secondary transmission element is manufactured and processed separately from the base body, in particular coated, work-hardened or subjected to a heat treatment, attaching a first connecting region of the auxiliary transmission element to the first region of the test object and a second connecting region to the second region of the test object so that the measuring zone of the secondary transmission member located between the first and second connecting regions and the transmission region can move relative to each other for performing different deformations, and arranging the load measuring device for measuring the load at the measuring zone.
Some features and advantages of preferred embodiments of the invention will be explained in more detail below.
Embodiments of the invention relate to load measurement using a secondary transmission element inserted in a secondary force or torque or load flow.
Embodiments of the invention relate to force/strain/axial load measurement using an active magnetic field sensor.
Preferably, a magnetostrictive secondary transmission element (sometimes also referred to as a shunt element) is attached to the measurement object in such a way that a deformation of the measurement object results in a deformation of the secondary transmission element, wherein the determination of the force/strain/load is performed via the secondary transmission element.
Embodiments of the invention relate to a load measuring arrangement on objects having an at least piecewise cylindrical surface that can rotate by at least 5° about the cylinder axis, wherein a likewise at least piecewise cylindrical secondary transmission element is attached to the surface, which transmission element is also deformed by loads on the base body, and wherein the measuring sensor does not follow rotations of the base body.
It is preferred that the secondary transmission element is designed to serve as a signal amplifier, which is preferably achieved by structurally designing it such that strain of the base body results in non-uniform strain in the secondary transmission element, wherein the strain or average stress at the measurement position deviates by at least 20% from the average strain or average stress of the secondary transmission element, wherein the measurement position corresponds to the surface facing the measuring sensor to a depth corresponding to the penetration depth of the magnetic field.
It is preferred in some embodiments that a secondary transmission element is made of the same alloy/steel grade, although the mechanical and heat treatment may differ.
In some embodiments, it is provided that the secondary transmission element is coated with a magnetic (relative permeability >2) layer, in particular electroless nickel, nickel, metallic glass, p-metal, ferrite, permalloy.
Preferably, the secondary transmission element is formed at least in some regions, in particular in a measuring zone, from work-hardened metal (e.g. cold-rolled sheet, deep-drawn cylinder) with a dislocation density >5e8/cm2 or a residual compressive stress of greater than 400 MPa in amount.
Preferably, the secondary transmission element is made of μmetal or Metglass.
Preferably, the secondary transmission element is connected to the main body by one of the following attachment methods:
In some embodiments, it is provided that the measuring sensor is fixedly connected to the base body. In some embodiments, it is provided that the measuring sensor is fixedly connected to the secondary transmission element.
Some embodiments of the invention relate to a load measuring device comprising a test object and a load measuring device for measuring a load on the test object, wherein the load measuring device comprises a magnetic field detection device for detecting a magnetic field parameter which changes due to load, wherein at least one measuring zone (here on a secondary transmission element of the test object) has been plastically deformed at least in a region from the surface to a depth of 20 μm, at a temperature below the recrystallization temperature, to obtain a dislocation density of at least 5e8/cm2.
Accordingly, a preferred embodiment of the manufacturing process comprises plastically deforming at least a measuring zone of the secondary transmission element at least in a region from the surface to a depth of 20 μm, at a temperature below the recrystallization temperature, to obtain a dislocation density of at least 5e8/cm2.
Preferably, a near-surface region is or will be plastically deformed using one of the following methods:
In one embodiment, the secondary transmission element is/are made of a previously work-hardened material.
Preferably, the secondary transmission element is/are made of a work-hardened material.
Embodiments of the invention will be explained in more detail below with reference to the accompanying drawings wherein it is shown by
The load measuring device 14 has at least one magnetic field detecting device 16, 16a, 16b for measuring a magnetic field parameter changing due to stresses in a measuring zone 18 of the test object 12.
Further, the load measuring device 14 has a magnetic field generating device 20 with which a magnetic field is actively generated in the measuring zone 18. This means that the measuring zone 18 does not itself have to be permanently magnetized.
As indicated in
The test object 12 or the measurement object 32 is, for example, a shaft, a chassis component, a power transmission element, a transmission element, a bicycle crank or any other element on which a load, such as a force, mechanical stress, torque is to be measured.
The measurement object 32 has a base body 34 with a first region 36, a transmission region 38 and a second region 40. Between the first region 36 and the second region 40, the load to be measured is applied. The first region 36 is, for example, an input region, such as an input end of a shaft or an input region of an area of interest of the measurement object 32 with respect to the load to be measured. The second region 40 is, for example, an output end of a shaft or an output region of an area of interest of the measurement object 32 with respect to the load to be measured. The transmission region 38 connects the first region 36 to the second region 40, such that the majority of the load is received by the transmission region 38. The base body 34 and, in particular, the transmission region 38 are configured to be optimized with respect to the function that the measurement object 32 is intended to perform. In particular, the base body 34 and the transmission region 38 need not be formed of a material which is optimized or even formed for magnetostrictive load measurement. For example, the base body 34 could be formed of fiber-reinforced materials, non-metals, or metals with no magnetic properties or only poor magnetic properties. If a base body 34 of steel is selected, the steel grade need not be selected for magnetostrictive properties or machined or coated.
The test object 12 further comprises the secondary transmission element 42, which is subject to load parallel to the transmission region 38 and receives a smaller portion of the load between the first region 36 and the second region 40. The secondary transmission element 42 and the transmission region 38 are not connected to each other, so that local relative displacements between the secondary transmission element 42 and the transmission region 38 are possible and, in particular, locally different deformations of the transmission region 38 and the secondary transmission element 42 are possible.
The measuring zone 18 is formed on the secondary transmission element 42. The secondary transmission element 42 is optimized with respect to design and material selection and/or material processing with respect to magnetostrictive load measurement substantially independently of the base body 34.
In particular with respect to material selection, the secondary transmission element 42 can be optimally formed for load measurement by active magnetization. Preferred materials for the secondary transmission element 42 or at least of the measuring area 18 thereof are:
The secondary transmission element 42 has a first connecting region 44, the measuring zone 18 and a second connecting region 46. The first connecting region 44 attaches the secondary transmission element 42 to the first region 36 of the base body 34. With the second connecting region 46, the secondary transmission element 42 is attached to the second region 40 of the base body 34. Possible fastening methods for fastening the connecting regions 44, 46 to the regions 36, 40 of the base body 34 are:
As the embodiment of
In the embodiment of
Further, the force flow 58 of the load on the secondary transmission element 42 is shown when a torque is transmitted via the solid shaft—measurement object 32. The arrangement of
With this design, the full angle of rotation that is created across the solid shaft carrying the main force can be conveyed to the measurement tube by means of two welded or soldered stiff tubes. The measurement tube can be designed to utilize the full safety factor margin.
The measurement tube—measuring zone sleeve 56—is designed to be more elastic than the solid shaft so that only a fraction of the total torque is introduced into the measurement tube.
As can be seen from the illustration in
In particularly preferred embodiments, at least the measuring zone 18, in this case in particular the near-surface region from the surface facing the measuring sensor 24 to a depth of about 20 μm, is work-hardened.
This can be done, for example, by local mechanical work-hardening. According to embodiments, the near-surface regions of at least the measuring zone 18 of the secondary transmission element 42 is plastically work-hardened using one of the following methods:
In another possible embodiment, a material such as a metal sheet is first provided from one of the above possible materials and is correspondingly plastically cold-formed, and the test object 12 or the secondary transmission element 42 is then produced from this material, for example by punching.
As can be seen from these examples, the effect of cold deformation is present for different materials.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 123 392.5 | Sep 2021 | DE | national |
