Hysteresis-poor sensor.

[0001] The invention concerns a hysteresis-poor sensor, for example a current sensor and a position sensor, whereby the river and/or the position by the change of a produced magnetic field in the open magnetic circuit measured wird.

Sensors can measure changes of a magnetic field, which are produced for events which can be measured from one to. The produced magnetic field is concentrated with one or more river-prominent soft-magnetic elements to a flux valve, which is in an air gap in the river-prominent soft-magnetic element. Due to the air gap is the magnetic circuit offen.

The magnetic field can be produced for example by a river or a movement of a permanent magnet. Dependent on the source of the produced magnetic field the sensor can be a current sensor or a position sensor. The DE 10,011,047 A1 reveals a current sensor and the DE 19825 433 A1 a position sensor, those in each case on this measurement principle basieren.

It exhibits this kind of sensors however the disadvantage that due to the material hysteresis of the river-prominent soft-magnetic element the accuracy of the measurement limits ist.

The DE 4,229,948 A1 reveals a current sensor, with which this hysteresis is avoided, in order to improve the accuracy of the measurement. This current sensor covers a only one closed soft-magnetic magnet core coupled with a primary coil, which is flowed through by the signal current, and a secondary winding, those with the primary coil over the magnet core magnetically ist.

The magnet core is reset periodically into the saturation and the voltage drop is scanned, whereby this voltage drop of the secondary amperage is proportional. From the current and the preceding measured value of the voltage drop an average value is formed, whereby the contributions of the additional magnetizing current waive themselves mutually. By this periodic remagnetization of the magnet core into the saturation, independently of the primary-carrier flow which can be measured, magnetic conditions are independent with the scanning of the prehistory of the core. It steps thus no hysteresis auf.

This sensor has however the disadvantage that its structure as well as its enterprise complicate ist.

Task of the available invention is to indicate a sensor a simple structure exhibits as well as a precise measurement of a magnetic field-witnessing event, for example an electric current or the movement of the permanent magnet, ermöglicht.

This is solved with the subject of the independent requirements. Further favourable further educations are article of the dependent Ansprüche.

A sensor is indicated according to invention, which covers a source of magnetic field, at least a river-prominent soft-magnetic element with at least an air gap, and at least a magnetic field sensor. The magnetic field sensor is arranged in the air gap and measures a change of the magnetic field of the source of magnetic field. The river-prominent soft-magnetic element partly consists or all of an alloy, those of 35 Gew. - % # Ni # 50 Gew. - %, 0 Gew. - % # CO # 2 Gew. - %, 0 Gew. - % # Mn # 1.0 Gew. - % 0 Gew. - % # SI # 0.5 Gew. - % as well as 0.5 Gew. - % # CR # 8 Gew. - % and/or 0.5 Gew. - % # Mo # 8 Gew. - %, whereby (Mo+Cr) # is 8, remainder iron as well as unavoidable impurities besteht.

The change of the magnetic river of the source of magnet is produced from one to event which can be measured. The produced magnetic field is concentrated with the river-prominent soft-magnetic element to the magnetic field sensor in the air gap. This event which can be measured knows for example a flowing river, in case of a current sensor, or a movement of a permanent magnet, in case of a position sensor, sein.

For a removing Koerzitivfeldstärke the material hysteresis of the river-prominent soft-magnetic element is increasingly reduced and therefore sensor hysteresis. As consequence the linearity of the sensor increases. A low sensor hysteresis and a increased sensor linearity make a precise measurement possible of the magnetic river, which develops with shifting or with the rotation of the permanent magnet regarding the river-prominent soft-magnetic element and/or when flowing the river. The accuracy of the sensor becomes by the use of this alloy for the river-prominent soft-magnetic element verbessert.

The use soft-magnetic 80% NiFe of a Permalloylegierung has the disadvantage of a very low saturation under 0,8T and high material costs due to the high Ni-content. The sensor according to invention contains at least in part with a material a saturation of more largely than 0.85 T. over a waste of the saturation of the material with increased operatings temperature small to hold, should not curie temperature Tc not too low liegen.

Curie temperature of the river-prominent soft-magnetic element within the range over 200°C makes the enterprise possible of the sensor with 125°C. This temperature corresponds to the upper limit of the ambient temperature range desired from -40°C to 125°C, that typically with sensors for applications of automobiles ist.

The alloy of the river-prominent soft-magnetic element exhibits thus a combination of characteristics, which is particularly suitable for sensors such as position sensors and current sensors, there working off hysteresis reduced and the accuracy of the sensor increased wird.

The impurities can be O, N, C, S, mg or approx. or mixtures of two or several of these elements, whereby the impurities lie below the following borders: Approx. # 0.0025 Gew. - %, mg # 0.0025 Gew. - %, S # 0.01 Gew. - %, 0 # 0.01 Gew. - %, N # 0.005 Gew. - % and C # 0.02 Gew. - %.

The impurity level knows for example by a cerium deoxidation or a VlM (Vacuum Induction Melting), VAR (Vacuum of acres Remelting), ESU (Electro cinder Umschmelz procedure) and or with other actually well-known procedures low held werden.

An increasing chrome content or an increasing molybdenum content can lead according to invention to a further lowering of the Koerzitivfeldstärke. The effect depends however on the nickel content. If the nickel content is too high or too low, no clear lowering of the Koerzitivfeldstärke is reached. Therefore the alloy according to invention points a nickel content within the range of 35 up to 45 weight percentage and a chrome content and/or a molybdenum content from 0,5 to 8 weight percentage auf.

beside iron The sum of the two elements Mo and CR is held below 8 weight percentage, thus the saturation not too far absinkt.

In further remark examples the nickel content is defined closer and amounts to 38 Gew. - % # Ni # 45 Gew. - % or 38 Gew. - % # Ni # 42 Gew. - %.

In further remark examples is 1 Gew. - % # CR # 8 Gew. - % and/or 1 Gew. - % # (Cr+Mo) # 8 Gew. - %.

In a further remark example the alloy consists of 35 Gew. - % # Ni # 45 Gew. - %, 0 Gew. - % # CO # 2 Gew. - %, O Gew. - % # Mn # 1.0 Gew. - % 0 Gew. - % # SI # 0.5 Gew. - % as well as 0.5 Gew. - % # CR # 8 Gew. - % and/or 0.5 Gew. - % # Mo # 8 Gew. - %, whereby (Mo+Cr) # is 8, remainder iron as well as unavoidable Verunreinigungen.

The alloy can exhibit also Mn and/or SI, whereby O Gew. - % # Mn # 0.5 Gew. - %, 0 Gew. - % # SI # 0.2 Gew. - %. Mn and SI can serve the deoxidation and be able to do in particular them with higher chrome contents used werden.

In a further remark example the alloy furthermore CO exhibits, whereby 0 Gew. - % # CO # 0.5 Gew. - %.

CO knows the saturation erhöhen.

In a first remark example the source of magnetic field exhibits a direct current or an alternating current, which produces a magnetic field, if it flows by a leader. The size of the produced magnetic field is proportional to the size of the flowing river. Furthermore the sensor can exhibit at least a coil, which is wound around the river-prominent soft-magnetic element. The river which can be measured flows by this Wicklung.

In a second remark example the source of magnetic field exhibits a permanent magnet, which is movable in the reference to the river-prominent soft-magnetic element. The size of the change of the produced magnetic river is proportional to the size of the change of position of the permanent magnet. Therefore the position of the permanent magnet from the change of the magnetic river can be determined. The permanent magnet can be connected with an article, whose position is to be measured. This can be a relative linear or a rotation, those with the sensor determined wird.

The permanent magnet can exhibit a multiplicity of ranges, which exhibit alternating directions of magnetization. These ranges can be planned with a multiplicity of magnets, those installed on a yoke sind.

Alternatively the permanent magnet can be einstückig and exhibit ranges, those differently magnetized sind.

The river-prominent soft-magnetic element can exhibit different shapes. In a remark example only one U river-prominent soft-magnetic element is planned, whereby the distance between the arms of the U-form plans the air gap. In a further remark example the river-prominent soft-magnetic element exhibits several separate parts, whereby an air gap between the parts develops. The river-prominent soft-magnetic element can exhibit one or more slots, those in each case an air gap vorsehen.

In a remark example the produced magnetic river is measured contactless with a magnetic field sensor in form of a Hallsonde. Alternatively the magnetic field sensor knows a strip from amorphous soft-magnetic material aufweisen.

A suitable material is commercially, available under the trade name VlTROVAC of the company Vaccumschmelze GmbH and CO kg. A magnet sensor from this material is in the EP 0,294,590 a2 offenbart.

In a remark example are two or three magnetic field sensors vorgesehen.

Remark examples become now on the basis the designs more near beschrieben.

Fig. 1 Fig. a schematic opinion of a sensor shows, shows 2 after a first remark example with a river-prominent soft-magnetic element from an alloy according to invention a schematic opinion of a sensor after a second remark example with a river-prominent soft-magnetic element from an alloy according to invention, Fig. 3 Fig. 4 Fig.

the measured Koerzitivitätsfeld for alloys with 47 Gew shows. - % or 37 Gew. -, The measured Koerzitivitätsfeld for alloys with 40 Gew shows % Ni and different chrome contents. -, And the measured Koerzitivitätsfeld for further Legierungen.

according to invention shows % Ni and different Chromoder molybdenum contents The Fig. 1 and 2 shows two sensors 1 and 1 “, which exhibit a river-prominent soft-magnetic element 2 from a soft-magnetic alloy in each case, some Koerzivitätsfeldstärke of less than 100 mA/Cm aufweist.

Fig. 1 shows a sensor 1 after a first remark example, which is designed as current sensor. Fig. 2 shows a sensor 1 " after a second remark example, which is designed as position sensor. Both sensors 1, 1 “point the following parts auf.

The sensors 1 and 1 " cover in each case a source of magnetic field 3, a river-prominent soft-magnetic element 2 with an air gap 4 and a magnetic field sensor 5, which are arranged in the air gap 4 and a change of the magnetic flow of the source of magnetic field 3 measures. The magnetic field sensor 5 can be for example a Hallsonde. The two sensors 1 and 1 " differ by the source of the Magnetfeldes.

In the sensor 1 of the first remark example a magnetic field is produced by a river 6, which flows by an electrically leading circle, which is formed by a wire or a cable. This magnetic field is led with the river-prominent soft-magnetic element 2 and concentrated at the magnetic field sensor 5, which is arranged in the air gap 4. The produced magnetic field depends on the amperage, so that the amperage from the measured produced magnetic field can be determined. The sensor 1 after the first remark example, is thus a Stromsensor.

In the sensor 1 “, after the second remark example, the magnetic field of a permanent magnet 7 becomes erzeugt.

The permanent magnet 7 exhibits a multiplicity of ranges 8, the alternating directions of magnetization 9 aufweisen.

The direction of magnetization 9 is with the magnetic poles north (N) and south (s) in Fig. 2 dargestellt.

In the sensor 1 “of the second remark example the permanent magnet 7 is moved by a not represented article. In Fig. 2 is thereby a linear or rotatorische movement möglich.

The movement of the permanent magnet 7 produces a changed magnetic field, which is concentrated with the river-prominent soft-magnetic element 2 on the magnetic field sensor 5 in the air gap 4. The size of the changes of the magnetic field depend on the range of the movements of the permanent magnet 7. The position of the article, which is connected with the permanent magnet 7, can be determined from this measured magnetic field. The sensor 1 " is, after the second remark example, thus a Positionssensor.

The river-prominent soft-magnetic element 2 of the current sensor 1 as well as the position sensor 1 " consists those of an alloy with a composition, with the following formula 35 Gew. - % # Ni # 45 Gew. - %, O Gew. - % # CO # 2 Gew. - %, O Gew. - % # Mn # 0.5 Gew. - % O Gew. - % # SI # 0.2 Gew. - % as well as 0.5 Gew. - % # CR # 8 Gew. - % and/or 0.5 Gew. - % # Mo # 8 Gew. - %, whereby (Mo+Cr) # is 8, remainder iron as well as unavoidable impurities described wird.

This alloy is iron nickel a based alloy with chrome and/or molybdenum. The elements chrome and molybdenum can reduce the Koerzivitätsfeldstärke clearly opposite the pure NiFe alloy, while the saturation is appropriate above 0,85 T and so that higher, than with that 80% NiFe Permalloy alloys is. This combination of the characteristics leads to a reduced material hysteresis. Therefore a sensor 1 and/or 1 can be manufactured ", which exhibits a reduced sensor hysteresis and a increased sensor linearity. The accuracy of the sensor 1 and/or 1 " becomes thus erhöht.

Fig. the measured Koerzitivitätsfeldstärke for alloys with 47 Gew shows 3. - % and 37 Gew. - % Ni and a chrome content of 1 Gew. - % up to 6,65 Gew. - %.

The compositions, the measured Koerzivitätsfeld and the induction, with H = 10 A/cm (B (10)) of these alloys are summarized in the table 1 and 2. The compositions are in each case in weight percentage angegeben.

1150°C/H2 Fe Ni CR HC (mA/cm) bio (T) 93/4759 remainder of 47.4 0.96 24 1.39 93/4760 remainder of 47.45 1.67 26 1.33 93/4867 remainder of 47.4 2.17 35 1.31 93/4868 remainder of 47.4 3.14 28 1.228 1150°C/H2 Fe Ni CR HC (mA/cm) Bie (T) 93/4869 remainder 47.4 4, 10 34 1.146 93/4870 remainder of 47.4 5, 05 46 1.08 93/4525 remainder of 47.6 6, 04 31 0, 99 table 1 1150°C/H2 Fe Ni CR Mn SI HC (mA/cm) bio (T) 93/4444 remainder of 36.95 2.10 0.50 0.21 72 1.17 93/4443 remainder 36.95 4.15 0.5,0.2 60 1 93/4442 remainder of 36.95 6.65 0.5 0.22 42 0.81 table 2 in the comparison example of the table 1 points the alloy to approximately 47 Gew. - % Ni up. With this nickel content no connection between the chrome content and the Koerzivitätsfeld shows up. With a lower nickel content of approximately 37 Gew. - % the Koerzitivitätsfeld sinks with increasing chrome content of over 70 mA/cm on approximate mA/cm ab.

Fig. two remark examples of an alloy of the river-prominent soft-magnetic element 2 of the sensor 1 and/or 1 shows 4 “, those in each case 40 Gew. - % nickel exhibit. With the first remark example 2 Gew become. - % and 4 Gew. - % chrome and with the second remark example 2 Gew. - % and 4 Gew. - % Mo caused. In both remark examples the Koerzivitätsfeldstärke sinks with increasing Chromund molybdenum content ab.

Table 3 summarizes the compositions as well as the values of B10, HC and Tc (curie temperature) for further alloys, of which the river-prominent soft-magnetic element 2 of the sensor 1 and/or 1 can consist ". The values of the Koerzivitätsfeldstärke HC of these alloys are also in Fig. 5 graphically dargestellt.

Fe Ni CR Mo bio HC Tc (Gew. - %) (Gew. - %) (Gew. - %) (T) (mA/cm) (°C) remainder 36.1 2.1 1.05 72.9 164 remainder 38.0 3.3 1.10 59.3 184 remainder 40.1 2.1 1.33 51 248 remainder 40.0 4.5 1.09 37.4 208 remainder 40.0 5, 8 0.99 32 187 remainder 40.0 7.1 0.87 30.2 164 remainder 43.0 5.8 1.02 31.1 248 remainder 44.0 4.5 1.15 32, 6,291 remainder 44.0 5.8 1.05 35.5 270 remainder 44.0 7.1 0, 95 38.7 248 remainder 40.0 1.9 1.30 36.5 279 remainder 39.9 4.3 1.15 31.5 277 remainder of 41.7 5.5 1.12 36.5 316 Fe Ni CR Mo bio HC Tc (Gew. - %) (Gew. - %) (Gew. - %) (T) (mA/cm) (°C) remainder of 40.0 2.2 2, 1 1.12 30.6 243 table 3 the air gap 4 in the river-prominent soft-magnetic element 2 leads to a shearing of the magnetic circle, i.e. the BH loop measured at the river-prominent soft-magnetic element 2 becomes flatter the more broadly the air gap 4 ist.

The Koerzitivfeldstärke HC of the soft-magnetic material determines the remanence of the loop in the open magnetic circuit. The remanence enters directly hysteresis and thus accuracy of the sensor 1 and/or 1 “. By the use of a FeNiCr material according to invention with low Koerzitivfeldstärke Iässt itself sensor hysteresis reduzieren.

In applications of sensors soft-magnetic materials serve e.g. as river-prominent soft-magnetic elements or river concentrators. Sensors are usually an input value as linear as possible into a sensor signal abbilden.

For the soft-magnetic material a low Koerzitivfeldstärke and thus a weak Hysterese.

means By the ambient temperatures of the application of sensors, e.g. for automobile sensors from -40 to 125°C, the saturation between ambient temperature and maximum temperature no more than around should not 30% abfallen.

Reference symbol list 1 current sensor 1 " position sensor 2 river-prominent soft-magnetic element 3 source of magnetic field 4 air gap magnetic field sensor 6 river 7 permanent magnet 8 range of the continuous magnet 9 direction of magnetization