Measuring assembly

Abstract

Measuring assembly having an object (12), which is translationally movable or rotatable about an axis of rotation, and a measuring system (10) for recording a shaft movement, the measuring system (10) comprising: an excitation unit (25) which is connected to the object (12) for conjoint rotation and has at least one permanent-magnetic excitation magnet (26), a Wiegand sensor (36) which interacts with a magnetic field of the excitation magnet (26), a magnetoresistive sensor unit (40) which interacts with the magnetic field of the excitation magnet (26) and is arranged in a manner offset and / or rotated with respect to the Wiegand sensor (36), wherein the magnetoresistive sensor unit (40) has a voltage divider (46, 48) with a first connection (52) and a second connection (54) for supplying the voltage divider (46, 48, 90), at least one magnetoresistive element (60, 62, 64, 66) and a measuring point (70, 72), characterized in that an additional resistor (82) is electrically connected to the measuring point (70, 72), wherein the additional resistor (82) can be electrically connected either to a third connection (86) or to a fourth connection (88) via a changeover unit (84), and wherein the changeover unit (84) is electrically connected to the Wiegand sensor (36), evaluates the voltage pulses from the Wiegand sensor (36) and is designed in such a manner that the changeover between the third connection (86) and the fourth connection (88) is effected on the basis of the polarity of the voltage pulses from the Wiegand sensor (36).

Description

[0001] DESCRIPTION

[0002] Measuring arrangement

[0003] The invention relates to a measuring arrangement with an object that is rotatable or translationally movable about an axis of rotation and a measuring system for detecting an object movement, the measuring system comprising: an excitation unit that is connected to the object in a rotationally fixed manner and has at least one permanent magnetic excitation magnet, a Wiegand sensor that interacts with a magnetic field of the excitation magnet, a magnetoresistive sensor unit that interacts with the magnetic field of the excitation magnet and is arranged offset and / or rotated to the Wiegand sensor, wherein the magnetoresistive sensor unit has a voltage divider with a first connection and a second connection for feeding the voltage divider, at least one magnetoresistive element and a measuring point.

[0004] Such measuring arrangements, in the form of an angle of rotation measuring arrangement, are used to detect the rotational movements of an object, i.e., a shaft rotating about a rotational axis. Angle of rotation measuring systems are often also referred to as angle measuring devices, angle of rotation sensors, or rotary encoders. Such angle of rotation measuring arrangements are used in particular for controlling and monitoring electric motors, in particular servomotors, in machines, systems, or vehicles. One such angle of rotation measuring arrangement is disclosed, for example, in WO 2020 / 015834 A1. The angle of rotation measuring arrangement comprises a shaft rotating about a rotational axis with four excitation magnets attached thereto, a Wiegand sensor, and a further sensor for determining the direction of rotation of the shaft. The excitation magnets are attached to a plate-like support element firmly connected to the rotating shaft and rotate along a circular path.The Wiegand sensor and the additional sensor are arranged together on a rigidly arranged support element. The additional sensor is arranged offset from the Wiegand sensor and is designed as a Hall sensor. DE 10 2012 008 888 A1 also discloses a rotation angle measuring arrangement with a Wiegand sensor and an additional sensor, wherein the additional sensor is designed as a magnetoresistive sensor. The rotation angle measuring arrangement has a bipolar excitation magnet, which is arranged on an end face of a rotating shaft and rotates together with the shaft about an axis of rotation. In the embodiment of DE 10 2012 008 888 A1, both sensors are aligned, i.e., not offset from one another and not rotated relative to one another.

[0005] During operation of the angle of rotation measuring arrangement, the voltage pulses of the Wiegand sensor and the sensor signal of the magnetoresistive sensor unit are usually evaluated in a control unit. To determine the direction of rotation of the rotating shaft, the sensor signal of the magnetoresistive sensor unit is compared with zero at the rotational positions at which a voltage pulse of the Wiegand sensor with a corresponding polarity occurs, i.e. it is determined whether the sensor signal has a negative sensor value or a positive sensor value. For example, it can be defined that with a voltage pulse of the Wiegand sensor with a positive polarity and a positive sensor value of the magnetoresistive sensor unit, or with a voltage pulse of the Wiegand sensor with a negative polarity and a negative sensor value of the magnetoresistive sensor unit, the shaft rotates in a first direction of rotation, for example clockwise.Otherwise, the shaft rotates in a second direction, i.e., counterclockwise, if a voltage pulse from the Wiegand sensor with positive polarity and a negative sensor value from the magnetoresistive sensor unit are present, as well as if a voltage pulse from the Wiegand sensor with negative polarity and a positive sensor value from the magnetoresistive sensor unit are present. In measurement setups with a translationally movable object, the voltage pulses from the Wiegand sensor and the sensor signal from the magnetoresistive sensor unit are also evaluated in a control unit, and the direction of movement of the translationally moved object is determined using the principle described for the rotating shaft.

[0006] If the magnetoresistive sensor unit is offset or rotated relative to the Wiegand sensor, the sensor signal of the magnetoresistive sensor unit is compressed, distorted and / or shifted to such an extent that the problem arises that the sensor signal of the magnetoresistive sensor unit is close to zero in one direction or rotational direction in the range of a voltage pulse of the Wiegand sensor. If this occurs, it is no longer possible to reliably determine whether the sensor signal of the magnetoresistive sensor unit has a negative or a positive sensor value. In extreme cases, the sensor signal of the magnetoresistive sensor unit could be compressed, distorted and / or shifted to such an extent that, with a rotating shaft, two voltage pulses of the Wiegand sensor with the same polarity, caused by rotation in different directions, are in the same range, i.e.both in the negative range or in the positive range, and only differ depending on the direction of rotation. As a result, the direction of rotation of the rotating shaft in this position or in these positions can no longer be determined in the simple manner explained above. Determining the direction of rotation, i.e. signal evaluation, is then only possible using a considerably more complex method. A similar problem also arises with an object moving in translation. The task therefore arises of providing a measuring arrangement with an arrangement of the magnetoresistive sensor unit that is offset and / or rotated relative to the Wiegand sensor, with which the signals from the sensors can be evaluated with relatively little effort.

[0007] This object is achieved by a measuring arrangement having the features of claim 1.

[0008] The measuring arrangement according to the invention comprises an excitation unit with at least one excitation magnet for generating an excitation magnetic field. In a measuring arrangement designed as a rotation angle measuring arrangement, the permanent-magnetic excitation magnet is typically attached to a rotatable shaft in such a way that the alternating excitation magnetic field is generated by a rotational movement of the shaft. Alternatively, however, the excitation magnet can also be attached to a translationally movable object that moves, for example, linearly back and forth. In any case, the movement of the permanent-magnetic excitation magnet generates an alternating excitation magnetic field, i.e., an excitation magnetic field in which the polarity continuously reverses, i.e., the (effective) direction of the field lines continuously changes over time.

[0009] The measuring arrangement according to the invention comprises a Wiegand sensor with a pulse wire—also referred to as a Wiegand wire—and a coil arrangement radially enclosing the pulse wire. The magnetization direction of the pulse wire suddenly reverses under the influence of an external magnetic field as soon as a specific trigger field strength is exceeded. The Wiegand wire maintains its magnetic polarity up to a certain point and reverses to the opposite polarity when exposed to a reversed external magnetic field. This generates a short voltage pulse with a defined electrical energy in the coil arrangement.

[0010] The measuring arrangement according to the invention further comprises a magnetoresistive sensor unit, preferably a TMR or GMR sensor, and serves to continuously detect the magnetic field of the excitation magnet. Magnetoresistive sensors are based on the magnetoresistive effect, whereby the electrical resistance of a material changes when an external magnetic field is applied. The change in the electrical resistance is used to measure the external magnetic field.

[0011] The magnetoresistive sensor unit comprises a voltage divider with a first terminal and a second terminal for supplying the voltage divider, at least one magnetoresistive element, and a measuring point. The sensor signal is derived from the measured value at the measuring point.

[0012] According to the invention, an additional electrical resistor is electrically connected to the measuring point, wherein the additional resistor can be electrically connected via a switching unit either to a third terminal with a third voltage level or to a fourth terminal with a fourth voltage level, and wherein the switching unit is electrically connected to the Wiegand sensor, evaluates the voltage pulses of the Wiegand sensor and is designed such that the switching between the third terminal and the fourth terminal takes place depending on the polarity of the voltage pulses of the Wiegand sensor.The additional resistor allows the sensor signal of the magnetoresistive sensor unit to be shifted in a defined manner so that the sensor signal exhibits either a positive or a negative sensor value when a voltage pulse from the Wiegand sensor is applied. This allows the direction of the object, for example, the direction of rotation of a shaft, to be determined reliably and with minimal effort. The additional resistor is a two-pole passive electrical component and implements an ohmic resistance in electrical and electronic circuits.

[0013] By means of the switching unit, i.e., by selectively connecting the additional resistor to the third or fourth terminal, the sensor signal profile can be shifted either in one direction or the other. Preferably, the third terminal is electrically connected to the first terminal, and the fourth terminal is electrically connected to the second terminal, so that switching is performed by the switching unit between the first terminal and the second terminal.

[0014] By operating the switching unit depending on the polarity of the Wiegand sensor's voltage pulse, it can be ensured that in the movement ranges—i.e., in the case of a rotating shaft, in the rotation angle ranges where a Wiegand sensor's voltage pulse of the same polarity is present—the sensor signal of the magnetoresistive sensor unit has opposite polarity. Based on this, the direction of movement of the object can be determined, since the Wiegand sensor's voltage pulses of the same polarity can be differentiated from one another.

[0015] In a preferred embodiment, a first voltage divider and a second voltage divider are provided, which together form a bridge circuit with two parallel-connected bridge arms. Each bridge arm has two series-connected magnetoresistive elements and a measuring point arranged between the two magnetoresistive elements. One of the two measuring points is electrically connected to an additional resistor. The sensor signal results from the calculation of the measured values ​​at the two measuring points. The measurement signals are fed, for example, to a comparator, and the sensor signal is calculated.

[0016] Alternatively, only a single voltage divider is provided, which comprises the magnetoresistive element and a resistor with a fixed resistance value, with the magnetoresistive element and the resistor connected in series. The measuring point is arranged between the magnetoresistive element and the resistor.

[0017] In a preferred embodiment, a voltage pulse of the Wiegand sensor at a first position, generated in a first direction of the rotating or translationally moving object, and a voltage pulse of the Wiegand sensor at a second position, generated in a second direction of the rotating or translationally moving object, opposite to the first direction, have the same polarity, wherein the sensor signal of the magnetoresistive sensor unit has a negative value at the first position and a positive value at the second position. In this case, for example, a comparator electrically connected to the two measuring points of the bridge circuit outputs a sensor signal from the magnetoresistive sensor unit, wherein it is evaluated whether the sensor signal has a positive or negative sensor value.

[0018] Alternatively, a voltage pulse of the Wiegand sensor at a first position caused in a first direction of the rotating or translationally moving object and a voltage pulse of the Wiegand sensor at a second position caused in a second direction of the rotating or translationally moving object opposite to the first direction have the same polarity, whereby at the first position the measured value of the measuring point is greater than a predefined voltage value and at the second position the measured value of the measuring point is less than the predefined voltage value. The predefined voltage value is, for example, 50% of the supply voltage present at the first connection. In this case, only the value at the measuring point is compared with a predefined voltage value. In contrast to the first variant, it is not the sensor signal that is considered, but the values ​​at the measuring point of the voltage divider.

[0019] Both alternatives serve to distinguish the direction of voltage pulses from the Wiegand sensor with the same polarity. Firstly, the sensor signal from the magnetoresistive sensor unit is compared with zero, i.e., it is determined whether the sensor signal has a negative or a positive sensor value. Secondly, the measured value at the measuring point is compared with a predefined voltage value. In both cases, multiple voltage pulses from the Wiegand sensor with the same polarity result in defined, differing values ​​depending on the direction of the rotating or translationally moving object.

[0020] A measuring arrangement is described below using the attached figures, where

[0021] Figure 1 shows an embodiment of a measuring arrangement according to the invention in cross section,

[0022] Figure 2 shows a schematic representation of a bridge circuit and the switching unit of the measuring arrangement from Figure 1, Figure 3 shows a profile of the sensor signals of a Wiegand sensor and a magnetoresistive sensor unit of the measuring arrangement from Figure 1,

[0023] Figure 4 shows a schematic representation of a voltage divider and the switching unit of the measuring arrangement from Figure 1.

[0024] Figure 1 shows a measuring arrangement 8 designed as a rotation angle measuring arrangement with a rotating shaft 12, which forms the rotating object, and a measuring system 10 designed as a rotation angle measuring system for detecting the rotational movement of the rotating shaft 12. In the present embodiment, the shaft 12 is a hollow shaft that extends essentially in the axial direction and is driven by a drive motor 14 with a static motor housing 16. The measuring system 10 comprises a rotor unit 18, a stator unit 20, and a magnetic shielding arrangement 22.

[0025] The rotor unit 18 has a rotor plate 24 that radially surrounds the shaft 12 and is attached directly to the shaft 12. The rotor unit 18 is thus rotationally fixedly connected to the shaft 12. An excitation unit 25 is arranged on the rotor plate 24. This excitation unit has four excitation magnets 26 evenly distributed along the circumference of the rotor plate 24, which rotate along a circular path upon rotation of the shaft 12. Only two of the four excitation magnets are shown in Figure 1.

[0026] The stator unit 20 has a stator board 32 that radially encloses the shaft 12. A sensor device 34 is arranged on the stator board 32. The sensor device 34 has a Wiegand sensor 36 and an integrated circuit with an evaluation unit and a magnetoresistive sensor unit 40. The integrated circuit further comprises a control logic (not shown in detail) and a power management system (not shown in detail), which enable energy-autonomous operation of the sensor device 34 via the electrical energy obtained from the Wiegand sensor 36. The evaluation unit is also signal-connected to a non-volatile data memory (not shown in detail), in which a revolution count is stored and read by the evaluation unit.

[0027] The sensor device 34 is positioned radially such that, when the shaft 12 rotates, the Wiegand sensor 36 and the magnetoresistive sensor unit 40 detect the magnetic fields of the excitation magnets 26, which rotate with the shaft 12 and are thus guided past the Wiegand sensor 36 and the magnetoresistive sensor unit 40.

[0028] The Wiegand sensor 36 has a Wiegand wire 42 and a coil arrangement 44 radially enclosing the Wiegand wire. The magnetization direction of the Wiegand wire 42 suddenly reverses under the influence of an external magnetic field as soon as a specific trigger field strength is exceeded. The Wiegand wire 42 retains its magnetic polarity up to a certain point and reverses to the opposite polarity when exposed to a reversed external magnetic field. This generates a short voltage pulse with a defined electrical energy in the coil arrangement 44. The polarity of the voltage pulse of the coil arrangement 44 depends on the direction in which the Wiegand wire 42 reverses.

[0029] The magnetoresistive sensor unit 40 is offset circumferentially and thus rotated relative to the Wiegand sensor 36 according to the angular offset. It is based on the magnetoresistive effect, whereby the electrical resistance of a material changes when an external magnetic field is applied. The change in the electrical resistance is used to measure the external magnetic field. The magnetoresistive sensor unit 40 comprises, as shown in Figure 2, two voltage dividers 46, 48 forming a bridge circuit 50, a first terminal 52 to which the supply voltage is applied, and a second terminal 54 to which the ground is applied, for feeding the bridge circuit 50. The bridge circuit 50 comprises two bridge branches 56, 58 connected in parallel, wherein each bridge branch 56, 58 has two magnetoresistive elements 60, 62, 64, 66 connected in series and a measuring point 70, 72 arranged between the two magnetoresistive elements 60, 62, 64, 66.The measuring points 70, 72 are electrically connected to a comparator, whereby the measuring point values ​​of the two measuring points 70, 72 are calculated to form a sensor signal of the magnetoresistive sensor unit.

[0030] According to the invention, an additional resistor 82 is electrically connected to one of the two measuring points 70. The additional resistor 82 is also electrically connected to a switching unit 84, by means of which the additional resistor 82 can be electrically connected optionally to a third terminal 86 or a fourth terminal 88. In the present case, the third terminal 86 is electrically connected to the first terminal 52 and the fourth terminal 88 is electrically connected to the second terminal 54, so that the supply voltage is present at the third terminal 86 and the ground is present at the fourth terminal 88. As a result, the additional resistor 82 is connected in parallel either to one magnetoresistive element 60 of the first bridge branch 56 or to the other magnetoresistive element 62 of the first bridge branch 56.The switching unit 84 is electrically connected to the Wiegand sensor 36, wherein the switching of the switching unit 84 occurs depending on the polarity of the voltage pulses of the coil arrangement 44. Figure 3 shows a diagram with several plotted curves of the sensor signal of the magnetoresistive sensor unit 40 as well as a diagram with a plotted curve of the voltage pulses of the Wiegand sensor 36. The solid line shows the curve of the sensor signal of the magnetoresistive sensor unit 40 without the additional resistor 82. The dashed line shows the curve of the sensor signal of the magnetoresistive sensor unit 40 with a.

[0031] Parallel connection of the additional resistor 82 to the magnetoresistive element 60, ie the connection of the additional resistor 82 to the first terminal 52. The dashed line shows the course of the sensor signal of the magnetoresistive sensor unit 40 with a

[0032] Parallel connection of the additional resistor 82 to the magnetoresistive element 62, ie the connection of the additional resistor 82 to the second terminal 54.

[0033] As already explained above, when the additional resistor 82 is connected to the second terminal 54, i.e. when the voltage pulse from the Wiegand sensor 36 has a positive polarity, the original sensor signal is shifted downwards in the Y direction, and the sensor value of the sensor signal at the rotational position of the corresponding voltage pulse from the Wiegand sensor 36 is evaluated using the downward-shifted, dashed line. In contrast, when the additional resistor 82 is connected to the first terminal 52, i.e. when the voltage pulse from the Wiegand sensor 36 has a negative polarity, the original sensor signal is shifted upwards in the Y direction, and the sensor value of the sensor signal at the rotational position of the corresponding voltage pulse from the Wiegand sensor 36 is evaluated using the upward-shifted dashed line.Such a design ensures a unique assignment of the direction of rotation for each voltage pulse. For a rotation in a first direction, a positive polarity voltage pulse results in a positive sensor value for the sensor signal, and for a negative polarity voltage pulse, a negative sensor value for the sensor signal. In contrast, for a rotation in a second direction opposite to the first direction, a positive polarity voltage pulse results in a negative sensor value for the sensor signal, and for a negative polarity voltage pulse, a positive sensor value for the sensor signal. This allows the shaft's direction of rotation to be determined for each Wiegand sensor voltage pulse.

[0034] In another embodiment, shown in Figure 4, the magnetoresistive sensor unit 40 comprises only a voltage divider 46, which has a single magnetoresistive element 60 and a resistor 90 with a fixed resistance value. The magnetoresistive element 60 and the resistor 90 are connected in series, with the measuring point 70 arranged between them. The measuring point 70 is electrically connected to the additional resistor 82. The additional resistor 82 is electrically connected to a switching unit 84, as in the previously described embodiment. To determine the direction of rotation, the measured value at the measuring point 70 is compared with a predefined voltage value Vref, with the direction of rotation being determined depending on whether the measured value is greater or less than the predefined voltage value Vref.In the same way, in the embodiment of Figure 2, instead of adjusting the two measuring points 70, 72, the measured value at one of the two measuring points 70, 72 could be compared with a predefined voltage value Vref and thereby the direction of rotation of the shaft 12 could be determined.

Claims

P A T E N T A N S P R Ü C H E 1. A measuring arrangement with an object (12) that is rotatable or translationally movable about an axis of rotation and with a measuring system (10) for detecting an object movement, the measuring system (10) comprising: an excitation unit (25) that is connected to the object (12) in a rotationally fixed manner and has at least one permanent-magnetic excitation magnet (26), a Wiegand sensor (36) that interacts with a magnetic field of the excitation magnet (26), a magnetoresistive sensor unit (40) that interacts with the magnetic field of the excitation magnet (26) and is arranged offset and / or rotated relative to the Wiegand sensor (36), wherein the magnetoresistive sensor unit (40) has at least one voltage divider (46, 48) with a first connection (52) and a second connection (54) for supplying the voltage divider (46, 48, 90), at least one magnetoresistive element (60, 62, 64, 66) and a measuring point (70, 72), characterized in that the measuring point (70,72) an additional resistor (82) is electrically connected, wherein the additional resistor (82) can be electrically connected via a switching unit (84) optionally to a third terminal (86) or to a fourth terminal (88), and wherein the switching unit (84) is electrically connected to the Wiegand sensor (36), evaluates the voltage pulses of the Wiegand sensor (36) and is designed such that the switching between the third terminal (86) and the fourth terminal (88) takes place depending on the polarity of the voltage pulses of the Wiegand sensor (36). The measuring arrangement according to claim 1, wherein the third terminal (86) is electrically connected to the first terminal (52) and the fourth terminal (88) is electrically connected to the second terminal (54). The measuring arrangement according to claim 1 or 2, wherein a first voltage divider (46) and a second voltage divider (48) are provided, which together form a bridge circuit (50) with two bridge branches (56, 58) connected in parallel, wherein each bridge branch (56, 58) has two series-connected magnetoresistive elements (60, 62, 64, 66) and a measuring point (70, 72) arranged between the two magnetoresistive elements (60, 62, 64, 66), wherein one of the two measuring points (70, 72) is electrically connected to an additional resistor (82).Measuring arrangement according to claim 1 or 2, wherein the voltage divider (46) comprises the magnetoresistive element (60) and a resistor (90) with a fixed resistance value, which are connected in series, wherein a measuring point is arranged between the magnetoresistive element (60) and the resistor (90). Measuring arrangement according to one of the preceding claims, wherein a voltage pulse of the Wiegand sensor (36) caused in a first direction of the rotating or translationally moving object (12) at a first position and a voltage pulse of the Wiegand sensor (36) caused in a second direction of the rotating or translationally moving object (12) at a second position have the same polarity, wherein the. Sensor signal of the magnetoresistive sensor unit (40) has a negative value at the first position and a positive value at the second position.

6. Measuring arrangement according to one of claims 1 to 4, wherein a voltage pulse of the Wiegand sensor (36) caused in a first direction of the rotating or translationally moving object (12) at a first position and a voltage pulse of the Wiegand sensor (36) caused in a second direction of the rotating or translationally moving object (12) opposite to the first direction at a second position have the same polarity, wherein at the first position the measured value of the measuring point (70) is greater than a predefined voltage value (Vref) and at the second position the measured value of the measuring point (70) is less than the predefined voltage value (Vref).

7. Measuring arrangement according to one of the preceding claims, wherein the magnetoresistive sensor unit (40) is a TMR or a GMR sensor.

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