WO2019115764A1 - Detection device and method for the detection of magnetic particles in lubricants - Google Patents

Abstract

The invention relates to a detection device (10) for the detection of at least one characteristic value of magnetic particles (20, 22) incorporated in a lubricant, particularly a particle density, wherein the detection device (10) comprises the following components (12, 18, 24, 30): a receiving unit (12) in which a receiving space (14) for a specimen (16) of the lubricant is formed, a magnet unit (18) for a focused magnetic effect on the magnetic particles (20, 22) of the specimen (16) introduced into the receiving space by means of a variable magnetic field generated by the magnet unit (18), which magnetic field penetrates the receiving space (14), an xMR sensor (24) for measuring the magnetic flux density μ in the receiving space (14) and an evaluating unit (30) for determining the characteristic value from the sensor signal issued by the xMR sensor (24). According to the invention, the detection device (10) is configured to measure the differential signal between the xMR sensor (24) with the specimen (16) and an xMR sensor (24) without the specimen (16), wherein the detection device (10) comprises two xMR sensors (24), one of which measures the magnetic flux density μ of the specimen (16) in the receiving space (14) and the other of which is decoupled from the influence of the specimen (16) as a reference sensor, and/or the receiving unit (12) is mounted removably and/or replaceably on the remainder of the detection device (10) to carry out a measurement of the magnetic flux density μ with the specimen (16) and a reference measurement of the magnetic flux density μ without the specimen (16). The invention further relates to a corresponding use of the detection device (10), a system for determining an instantaneous actual condition of a lubricant in use and a method for the detection of at least one characteristic value of magnetic particles (20, 22) incorporated in a lubricant.

Description

 Detection device and method for the detection of magnetic particles in

 Lubricants B e c o rp e c ts

The invention relates to a detection device for detecting at least one characteristic of magnetic particles incorporated in a lubricant, in particular a particle density of these magnetic particles.

The invention further relates to a corresponding use of the detection device and a method for detecting at least one characteristic of embedded in a lubricant magnetic particles. The use of magnetic particles in lubricants is known for a variety of applications, such as in heavy cranes, elevators, ski lifts. In the application examples explicitly mentioned here, the lubricant is used for equipment that is usually operated "on the field" or stationary. By determining certain

Characteristics of the magnetic particles incorporated in the respective lubricant can be used to make a statement about the safety-relevant properties of the lubricant.

The ability to determine such characteristics on site is therefore desirable.

The detection of magnetic particles themselves is well known from other applications. For example, US 8,728,825 B2 describes one on the GMR effect (GMR: Giant Magneto Resistance magnetoresistive biosensor for detecting small magnetic particles adhering to biological molecules. The magnetic particles can act as a kind of magnetic marker

biological molecules. They are, for example, superparamagnetic particles with well-defined properties and are also referred to as "beads".

It is the object of the invention to provide measures for the detection of at least one characteristic of magnetic particles incorporated in a lubricant, which permit a measurement which is simple to carry out.

The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are specified in the subclaims.

In the detection device according to the invention for detecting at least one parameter of magnetic particles incorporated in a lubricant, it is provided that the detection device has the following components:

 (A) a receiving unit in which a receiving space for a sample of the lubricant is formed,

 (B) a magnet unit for the targeted magnetic influence of the magnetic particles of a sample introduced into the receiving space by means of a variable magnetic field generated by the magnet unit, which penetrates the receiving space,

 (c) an XMR sensor for measuring the magnetic flux density m in the receiving space and

(D) an evaluation unit for determining the characteristic from the sensor signal of the XMR sensor. The parameter of the particles is in particular a particle density of the magnetic particles. The XMR sensor can be based on any magneto-resistive effect summarized under the term XMR (X-Magneto-Resistive). These are the following sensor types: Giant Magneto-Resistive (GMR), Anisotropic Magneto-Resistive (AMR), Colossal Magneto-Resistive (CMR), Tunneling Magneto-Resistive (TMR) and Extraordinary Magneto-Resistive (EMR) Sensors. The use of a GMR sensor for the detection of at least one characteristic of magnetic particles per se is - as mentioned - known. The detection device according to the invention now makes it possible to determine the characteristics of magnetic particles that are incorporated in a lubricant in a simple manner on site relatively accurately. The detection device is for this purpose a mobile detection device, in particular a portable detection device.

According to an alternative of the invention, the detection device has two XMR sensors, one of which measures the magnetic flux density m of the sample in the receiving space and the other is "uncoupled from the influence of the sample" as a reference sensor.

According to a further alternative of the invention, the receiving unit is detachably and / or replaceably attached to the remainder of the detection device. Such an embodiment of the detection device allows a convenient implementation of a measurement of the magnetic flux density m with sample and a reference measurement of the magnetic flux density m without a sample.

This detection device allows a later described use for determining a current actual state of a lubricant in use.

According to a preferred embodiment of the invention it is provided that the

Magnet unit is a magnet unit for a targeted passage through a magnetic field strength loop for receiving a hysteresis curve by means of the XMR sensor. It is preferably provided that the receiving unit is set up such that a well-defined sample can be introduced into the receiving space by means of doctor blade technology. The

Aufhahmeeinheit forms, for example, a trogformige limitation of

Storage room with a flat edge area, over which one with a suitable squeegee can stroke to fill the receiving space to the edge with lubricant. The resulting sample then completely occupies the holding space.

The detection device preferably has a housing which houses at least one of the components (i) XMR sensor, (ii) evaluation unit and (iii) magnet unit. Preferably, the housing houses at least the XMR sensor and the evaluation unit.

According to a preferred embodiment of the invention it is provided that the magnetic particles are ferromagnetic particles and / or superparamagnetic particles. Such particles are generally used in lubricants.

It is advantageously provided that the evaluation unit is set up, the characteristics of simultaneously present in the sample ferromagnetic particles and

Separate superparamagnetic particles.

According to a further preferred embodiment of the invention, it is provided that the magnetic particles have a particle size in the sub-micrometer range, in particular in the nanometer range. The term sub-micrometer range is to be understood as meaning, in particular, dimensions of the particles which are smaller than 1 micron (1 pm).

In the inventive use of a detection device for detecting at least one characteristic of magnetic particles, in particular a particle density of these particles, in a lubricant is provided that the detection device is designed as the above-mentioned detection device.

According to a preferred embodiment of the use according to the invention it is provided that for determining a current actual state of the lubricant in use in this lubricant, a predetermined number or concentration and type of magnetic particles is integrated independent of use, via the means of Detection device determined characteristic is closed to the actual state of the lubricant. The magnetic particles that are used in the lubricant regardless of use (ie even before use) are a type of sensor for certain external influences on the lubricant, which critically affect its condition. These influences are for example (a) a chemical influence, which causes an oxidation process with the magnetic particles, (b) a temperature influence, in particular an overheating of the

Lubricant, which affects magnetization of the magnetic particles, (c) the influence of strong magnetic fields, which makes the magnetic particles clusters, etc. The invention further relates to a corresponding system for determining a current actual state of a lubricant in use, with lubricant in which a predetermined number or concentration and type of magnetic particles is integrated independent of use and with an aforementioned detection device for detecting at least one characteristic of the magnetic particles incorporated in the lubricant. This kit (kit-of-parts) allows the above-mentioned use to determine a current actual state of the lubricant in use.

In the method according to the invention for the detection of at least one parameter of magnetic particles incorporated in a lubricant, in particular a particle density, the following steps are provided:

 (a) introducing a sample of the lubricant into a receiving space,

 (B) targeted magnetic influencing of the magnetic particles of the introduced into the receiving space sample by means of a variable magnetic field H, which the

Penetration space penetrates,

(c) measuring the magnetic flux density m in the receiving space by means of an XMR sensor in at least two different magnetic field settings and

(d) determining the characteristic from the sensor signal of the XMR sensor. In the detection method it is provided that a measurement of the magnetic

Flux density m with sample and a reference measurement of the magnetic flux density m without a sample is performed. The measurement with sample is then set in relation to the measurement without sample. In the simplest case, a difference measurement is made. In this way possible magnetic interference can be eliminated.

According to a preferred embodiment of the method according to the invention it is provided that the targeted magnetic influence of the magnetic particles targeted passing through a magnetic field loop and measuring the magnetic

Flux density m is a picking up of a corresponding hysteresis curve by means of the XMR sensor.

Finally, the invention also relates to a computer program product comprising

Program parts which are set up in a processor of a computer-based control and evaluation unit for carrying out the aforementioned method.

The invention will now be described by way of example with reference to the accompanying drawings with reference to a preferred embodiment, wherein the features shown below, both individually and in combination may represent an aspect of the invention. Show it:

Fig. 1 is a schematic representation of a detection device for detecting at least one characteristic of embedded in a lubricant magnetic particles according to a preferred embodiment of the invention and

2 shows a plan view of an active sensor region of an XMR sensor of the detection device designed as a GMR sensor. 1 shows a schematic representation of a detection device 10 for detecting at least one characteristic of magnetic particles incorporated in a lubricant. The detection device 10 shown can be roughly divided into five main components. These are: (a) a receiving unit 12 in which a receiving space 14 for a sample 16 of the lubricant is formed, (b) a magnet unit 18 for targeted magnetic influencing of the magnetic particles 20, 22 of the introduced into the receiving space sample 16 by means of one of Magnetic unit 18 generated variable magnetic field, which penetrates the receiving space 14, (c) designed as a GMR sensor XMR sensor 24 for measuring the magnetic flux density m in

Aufhahmeraum 14, (d) a computer-based control and evaluation 26 with a control unit 28 (also called control unit or control unit) for controlling the

Detection process of the detection device 10 and an evaluation unit 30 for determining the characteristic from the sensor signal of the XMR sensor 24 and (e) a - preferably openable - housing 32, which einhaust the XMR sensor 24, and the control and evaluation 26. The mentioned units 28, 30 of the computer-based control and evaluation device 26 are essentially software modules.

In principle, the receiving unit 12 may also be disposed within the housing 32 or be formed by the housing 32. In the example shown, however, the receiving unit 12 is detachably or exchangeably attached to the housing 32. The

 Aufhahmeeinheit 12 is designed in such a way that by means Rakeltechnik a

well-defined sample 16 in the receiving space 14 can be introduced. The receiving unit 12 forms a trough-shaped boundary of the receiving space 12 with a flat edge region 34, over which one can stroke with a corresponding doctor blade 36 to the

To fill the receiving space 14 to the edge with lubricant. The resulting sample 16 then completely occupies the receiving space 14.

The magnet unit 18 has an electromagnet 38, which is actuated by the control unit 28 of the control and evaluation device 26 during the measurement. thanks to this Control, the magnet unit 18 for a targeted driving through a

Magnetic field strength loop for receiving a hysteresis curve by means of the XMR sensor 24 are used. In the simplest case, only two well-defined points are approached on the hysteresis curve and from the measurements of the magnetic flux density m at these points the characteristic of the magnetic particles 20, 22 incorporated in the lubricant is determined. In the example, the magnet unit 18 is fixedly mounted on or in the housing 32. In an alternative embodiment of the detection device 10, the magnet unit 18 is also detachably or exchangeably attached to / in the housing 32 (not shown). The so-designed magnetic unit 18 is also referred to as a magnetic attachment.

In the example shown, the electromagnet 38 has a coil pair 40. The coils of the coil pair 40 may be formed as air coils or as coils with ferromagnetic Kem. Furthermore, the device 10 comprises a power supply 42 for the coils of the coil pair 40. The power supply 42 as well as the evaluation unit 30 are of the

 Control unit 28 activated (arrows). The evaluation unit 30 communicates with the sensor 24 (double arrow) and an output interface 44 (double arrow), for example an HMI interface such as a display, etc. In addition to the structure shown in FIG. 1, in which the magnetic field with respect to the XMR Sensor 24 is an in-plane field, a structure is also possible and quite desirable, in which the magnetic field generated by the magnet unit 18 is a perpendicular to the sensor 24 field. Such a magnetic field can be easily generated with a permanent magnet, which is pushed under the sensor 24. The different magnetic field settings can be in this structure, for example, by removing and / or replacing the

Achieve permanent magnets.

The XMR sensor 24 may be based on any magneto-resistive effects summarized by the term XMR (X-Magneto-Resistive). Besides the GMR sensor, these are Sensors based on the following effects: Anisotropy Magneto-Resistive (AMR), Colossal Magneto-Resistive (CMR), Tunneling Magneto-Resistive (TMR) and the

Extraordinary Magneto-Resistive (EMR). Especially preferred are GMR and TMR sensors.

The XMR sensor 24 constructed as a GMR sensor from the example consists in particular of a cobalt (Co) copper (Cu) GMR layer system in which the Cu layer thickness is selected such that it couples at the first antiferromagnetic RKKY maximum. The stacking sequence is as follows: substrate / (Co 3nm / Cu -1 nm) ₃₉ / Co 3nm / Ru 3nm.

FIG. 2 shows the active sensor region 46 of the GMR sensor 24. The active

Sensor region 46 has a meander structure with a conductor width of 1 mhi and is contacted via four interconnects 48, 50, 52, 54. About two of the tracks 48, 50, a constant current is fed, while two further tracks 52, 54 of the

Voltage drop across the sensor 24 is measured. The corresponding resistance measurement is thus, as usual, realized as a four-point measurement, at the power source and

Voltage tap have separate contact points. The power source is preferably one

Constant current source. To prevent leakage currents, the GMR sensor 24,

except the contact pads, passivated with a Ta ₂ 0 ₂ layer whose layer thickness should be smaller than the average particle diameter, In the sensor 24 shown in Fig. 2, the Ta ₂ 0 ₅ layer 10 nm for magnetic particles 20, which as Co nanoparticles with a diameter of about 20 nm are formed.

The size of the active sensor region 44 (ie the meander surface) and the structure width must be adapted to the concentration ranges and magnetic particles 20, 22 used. For a given measuring surface, the measuring signal must be different

Particle concentrations in the lubricant are calibrated for quality determination. To determine the quality of the particle dispersion in the lubricant, which is necessary for calibration, then takes place via a dual beam FIB system (FIB: Focused Ion Beam). This results in the following basic principle of the detection method:

First, a well-defined sample 16 of the lubricant is introduced into the receiving space 14, then the magnetic particles 20, 22 of the introduced into the receiving space 14 sample 16 by means of a variable magnetic field H, which penetrates the receiving space 14, targeted magnetically influenced, while the magnetic Melted flux density m in the receiving space 14 by means of the XMR sensor 24 at least two different magnetic field settings and finally determined from the sensor signal of the XMR sensor 24, the characteristic of the magnetic particles incorporated in the lubricant 20, 22.

In order to be able to calculate possible disturbance variables, this basic principle is supplemented as follows:

The difference signal between the XMR sensor 24 without lubricant sample 16 and the XMR sensor 24 with lubricant sample 16 is measured once without the magnetic attachment 18 and once with the magnetic attachment 18. The difference signal can be measured in different ways:

The sensors 24 can be measured without particles once and once with magnetic attachment 18 and the values are stored. Thereafter, these measurements are performed for the same sensors 24 with applied lubricant sample 16.

 Subsequently, the measurement results for the sensor 24 with lubricant sample 16 are subtracted from the stored measurement results without lubricant sample 16.

A sensor 24 is covered while a reference sensor 24 is covered by a protective layer so that no stray fields reach the reference sensor 24. Again, once without and once measured with magnetic attachment 18. The particle concentration is proportional to the magnitude of the difference signal between uncoated and coated XMR sensor 24.

reference numeral

10 detection device

 12 receiving unit

14 storage room

 16 sample

 18 magnet unit

 20 ferromagnetic particles

22 superparamagnetic particles 24 XMR sensor

 26 control and evaluation device

28 control unit

 30 evaluation unit

 32 housing

34 edge area (recording unit)

36 squeegee

 38 electromagnet

 40 coil pairs

 42 power supply

44 output interface

 46 active sensor area

 48 trace

 50 trace

 52 trace

54 trace

Claims

Patent claims 1. A detection device (10) for detecting at least one characteristic of embedded in a lubricant magnetic particles (20, 22), in particular a particle density, wherein  the detection device (10) comprises the following components (12, 18, 24, 30): a receiving unit (12) in which a receiving space (14) for a sample (16) of the lubricant is formed,  a magnet unit (18) for selectively influencing magnetically the magnetic particles (20, 22) of the sample (16) introduced into the receiving space by means of a variable magnetic field generated by the magnet unit (18), which magnet  Receiving space (14) penetrates,  an XMR sensor (24) for measuring the magnetic flux density in  Aufhahmeraum (14) and an evaluation unit (30) for determining the characteristic from the sensor signal of XMR sensor (24),  characterized in that  the detection device (10) is arranged for measuring the difference signal between the XMR sensor (24) with sample (16) and an XMR sensor (24) without sample (16), wherein  - The detection device (10) comprises two XMR sensors (24), one of which measures the magnetic flux density m of the sample (16) in the receiving space (14) and the other is decoupled as a reference sensor from the influence of the sample (16) and / or the receiving unit (12) for performing a measurement of the magnetic  Flux density m with sample (16) and a reference measurement of the magnetic  Flux density m without sample (16) removable and / or replaceable at the rest of the Detection device (10) is attached. 2. Detection device according to claim 1, characterized in that the  Magnet unit (18) is a magnet unit (18) for a targeted passage through a magnetic field strength loop for receiving a hysteresis curve by means of the XMR sensor (24). 3. Detection device according to claim 1 or 2, characterized in that the receiving unit (12) is arranged such that by means of doctor blade technique a well-defined sample (16) in the receiving space (14) can be introduced. 4. Detection device according to one of claims 1 to 3, characterized in that the magnetic particles (20, 22) are ferromagnetic particles (20) and / or superparamagnetic particles (22). 5. Detection device according to claim 4, characterized in that the  Evaluation unit (30) is arranged to separately determine the characteristics of simultaneously present in the sample (16) of ferromagnetic particles (20) and superparamagnetic particles (22). 6. Detection device according to one of claims 1 to 5, characterized in that the magnetic particles (20, 22) have a particle size in the sub-micrometer range, in particular in the nanometer range. 7. Use of a detection device (10) according to any one of claims 1 to 6 for the detection of at least one characteristic of magnetic particles (20, 22), in particular a particle density, in a lubricant. 8. Use according to claim 7, characterized in that for determining a current actual state of the lubricant in use in this lubricant magnetic particles (20, 22) of predetermined type and concentration are independent of use involved, using the means of  Detection device (10) determined characteristic to the actual state of  Lubricant is closed. 9. System for determining a current actual state of a lubricant in the  Use, with  Lubricant, in the magnetic particles (20, 22) of predetermined type and  Concentration are independent of use involved and  A detection device (10) according to any one of claims 1 to 6 for detecting at least one characteristic of the magnetic incorporated in the lubricant Particles (20, 22). 10. A method for detecting at least one characteristic of in a lubricant  integrated magnetic particles (20, 22), in particular a particle density, with the steps:  Introducing a sample (16) of the lubricant into a receiving space (14), targeted magnetic influencing of the magnetic particles (20, 22) of the sample (16) introduced into the receiving space (14) by means of a variable  Magnetic field, which penetrates the receiving space (14), - Measuring the magnetic flux density in the receiving space (14) by means of at least one XMR sensor (24) at least two different  Magnetic field settings and  Determining the parameter from the sensor signal of the at least one XMR sensor (24),  marked by  a measurement of the magnetic flux density m with sample (16) and a Reference measurement of the magnetic flux density m without sample, wherein the measurement with sample (16) is then set in relation to the measurement without sample and - The detection device (10) comprises two XMR sensors (24), one of which measures the magnetic flux density m of the sample (16) in the receiving space (14) and the other is decoupled as a reference sensor from the influence of the sample (16) and / or the receiving unit (12) for performing a measurement of the magnetic  Flux density m with sample (16) and a reference measurement of the magnetic  Flux density m without sample (16) removable and / or replaceable at the rest of the  Detection device (10) is attached. 11. The method according to claim 10, characterized in that the targeted magnetic influencing of the magnetic particles (20, 22) a targeted passage through a magnetic field loop and the measurement of the magnetic flux density m a Aufhehmen a corresponding hysteresis curve by means of the XMR sensor (24) is. 12. Computer program product comprising program parts which are set up in a processor of a computer-based control and evaluation device (26) for carrying out the method according to claim 10 or 11.