OMNIDIRECTIONAL ROTATIONAL SPEED AND ROTATIONAL DIRECTION SENSOR

Abstract

A magnetic-field (MF) sensor, including: a chip having first, second and third MF measuring-elements (ME) to output first, second and third MF signals, amplitudes of which are proportional to a MF emanating from a rotating-object (RO), in which directions of the normal vectors of the MF MEs are linearly independent; a signal acquisition unit to determine first/second differential-signals (DS), in which the first DS is based on a difference between the MF signals of the first and second MF MEs, and in which the second DS is based on a difference between the MF signals of the first/third MF MEs, and in which the signal acquisition unit is configured to determine a combined signal from the MF signal of the first MF ME and the first/second DS; and an evaluation unit to generate an output signal, which contains a speed and direction of motion of the RO.

Claims

1-14. (canceled)

15. A magnetic field sensor, comprising: a chip having at least a first, a second and a third magnetic field measuring element, which are configured to output a first, second and third magnetic field signal respectively, the amplitudes of which are proportional to a magnetic field emanating from a rotating object, wherein directions of the normal vectors of the at least three magnetic field measuring elements are linearly independent of each other; a signal acquisition unit to determine a first differential signal and a second differential signal, wherein the first differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the second magnetic field measuring element, and wherein the second differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the third magnetic field measuring element, and wherein the signal acquisition unit is further configured to determine a combined signal from the magnetic field signal of the first magnetic field measuring element and the first differential signal and second differential signal; and an evaluation unit to generate an output signal, which contains a speed of motion and a direction of motion of the rotating object.

16. The magnetic field sensor of claim 15, wherein the at least three magnetic field measuring elements include Hall sensors.

17. The magnetic field sensor of claim 15, wherein the normal vectors of the three magnetic field measuring elements each include an angle of 90° to one another.

18. The magnetic field sensor of claim 16, wherein the first magnetic field measuring element includes a lateral Hall sensor, and the second and third magnetic field measuring elements each include a vertical Hall sensor.

19. The magnetic field sensor of claim 15, wherein the chip is arranged in a plane which is essentially parallel to a tangential plane of the rotating object.

20. The magnetic field sensor of claim 15, wherein the chip, with the at least three magnetic field measuring elements, is in a housing.

21. The magnetic field sensor of claim 15, further comprising: a current or voltage interface.

22. The magnetic field sensor of claim 15, wherein the magnetic field measuring elements include magneto-resistive elements.

23. The magnetic field sensor of claim 15, wherein the evaluation unit is configured to perform a temperature compensation of the measurement signals of the at least three magnetic field measuring elements.

24. A system, comprising: a magnetic field sensor, including: a chip having at least a first, a second and a third magnetic field measuring element, which are configured to output a first, second and third magnetic field signal respectively, the amplitudes of which are proportional to a magnetic field emanating from a rotating object, wherein directions of the normal vectors of the at least three magnetic field measuring elements are linearly independent of each other; a signal acquisition unit to determine a first differential signal and a second differential signal, wherein the first differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the second magnetic field measuring element, and wherein the second differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the third magnetic field measuring element, and wherein the signal acquisition unit is further configured to determine a combined signal from the magnetic field signal of the first magnetic field measuring element and the first differential signal and second differential signal; and an evaluation unit to generate an output signal, which contains a speed of motion and a direction of motion of the rotating object; and a pole wheel with teeth and gaps, the pole wheel being magnetically coded.

25. A system, comprising: a magnetic field sensor, including: a chip having at least a first, a second and a third magnetic field measuring element, which are configured to output a first, second and third magnetic field signal respectively, the amplitudes of which are proportional to a magnetic field emanating from a rotating object, wherein directions of the normal vectors of the at least three magnetic field measuring elements are linearly independent of each other; a signal acquisition unit to determine a first differential signal and a second differential signal, wherein the first differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the second magnetic field measuring element, and wherein the second differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the third magnetic field measuring element, and wherein the signal acquisition unit is further configured to determine a combined signal from the magnetic field signal of the first magnetic field measuring element and the first differential signal and second differential signal; and an evaluation unit to generate an output signal, which contains a speed of motion and a direction of motion of the rotating object; and a pole wheel with teeth and gaps, the chip of the magnetic field sensor being magnetically pre-stressed, by providing a permanent magnet on the chip.

26. The system of claim 24, further comprising: an additional differential element to determine the rotational direction of the pole wheel.

27. The system of claim 24, further comprising: an additional differential element to determine and/or compensate for extraneous fields.

28. A method for determining a rotational speed and a rotational direction of a rotating object using a magnetic field sensor, the method comprising: a) detecting one magnetic field signal each from the first magnetic field measuring element, the second magnetic field measuring element and the third magnetic field measuring element; b) determining a first differential signal from a difference between the magnetic field signals of the first magnetic field measuring element and the second magnetic field measuring element; c) determining a second differential signal from a difference between the magnetic field signals of the first magnetic field measuring element and the third magnetic field measuring element; d) calculating a combined signal from the magnetic field signal of the first magnetic field measuring element and the first differential signal and second differential signal; e) calculating and outputting an output signal, which contains a speed of motion and a direction of motion of the rotating object; wherein the magnetic field sensor includes: a chip having at least the first, the second and a third magnetic field measuring element, which are configured to output a first, second and third magnetic field signal respectively, the amplitudes of which are proportional to a magnetic field emanating from a rotating object, wherein directions of the normal vectors of the at least three magnetic field measuring elements are linearly independent of each other; a signal acquisition unit to determine the first differential signal and the second differential signal, wherein the first differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the second magnetic field measuring element, and wherein the second differential signal is based on a difference between the magnetic field signals of the first magnetic field measuring element and the third magnetic field measuring element, and wherein the signal acquisition unit is further configured to determine the combined signal from the magnetic field signal of the first magnetic field measuring element and the first differential signal and second differential signal; and an evaluation unit to generate the output signal, which contains the speed of motion and the direction of motion of the rotating object.

29. The magnetic field sensor of claim 15, wherein the normal vectors of the three magnetic field measuring elements each include an angle of 90° to one another, and wherein further magnetic field measuring elements are included.

30. The magnetic field sensor of claim 15, wherein the chip, with the at least three magnetic field measuring elements, is in a housing, and the chip can be fastened with a holder, and wherein the interior of the housing is at least partially filled with a plastic material, and flux guide plates are provided to minimize interference signals in the region of the chip.

31. The magnetic field sensor of claim 15, wherein the magnetic field measuring elements include magneto-resistive elements, which include anisotropic magneto-resistive elements, giant magneto-resistors, or magnetic tunnel resistors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a plan view and a schematic view of a magnetic field sensor 1 according to the invention and a pole wheel 20 in three different orientations (FIGS. 1a to 1c).

[0037] FIG. 2 shows typical magnetic field signals of the individual magnetic field elements in each of the three orientations of FIG. 1, where here the curve of the magnetic field signals is recorded over time, i.e. when the pole wheel rotates (FIGS. 2a to 2c).

[0038] FIG. 3 shows an arrangement of a magnetic field sensor according to the invention in a housing.

DETAILED DESCRIPTION

[0039] FIG. 1 shows the magnetic field sensor 1 according to the invention and a pole wheel 20. The magnetic field sensor 1 is arranged above the pole wheel 20 in plan view. The pole wheel 20 has teeth 21 and gaps 22. The magnetic field sensor contains a chip 2 on which three magnetic field measuring elements 2a, 2b and 2c are arranged. Furthermore, the magnet 2d is arranged on this chip. The magnetic field measuring elements 2a, 2b and 2c are essentially rectangular in shape, with a larger base surface and each with small, narrow side faces. The first magnetic field measuring element 2a as a lateral Hall element is mounted flat on the chip 2, and rests with its large base surface on the chip 2. A Hall voltage can always be measured when the pole wheel 20 rotates. The two other magnetic field measuring elements 2b and 2c are vertical magnetic field measuring elements and are positioned with the small surface on the chip and are therefore arranged perpendicular to the chip. The chip 2 is parallel to a tangential plane of the pole wheel 20. In FIG. 1b) the chip 2 of FIG. 1a is rotated by 45°, so the position of the magnetic field measuring elements 2a, 2b and 2c has also changed. Despite this, the chip 2 is still located in a plane parallel to a tangential plane of the pole wheel 20. In FIG. 1c) this view is rotated again by 45°; here also the chip 2 is located in a plane parallel to the tangential plane of the pole wheel 20.

[0040] In FIG. 2 the curve of the magnetic field strengths, i.e. the signal of sensors 2a, 2b and 2c, is plotted against time (or in this case: as a function of the rotational angle) and as a function of the orientation of the chip 2. FIG. 2a) corresponds to the view in FIG. 1a).

[0041] The signal of the second magnetic field measuring element 2b (drawn as Bx in FIG. 2) has a significantly lower amplitude here than the signals of the first magnetic field measuring element 2a (designated as Bz in FIG. 2) and of the third magnetic field measuring element 2c (designated as By in FIG. 2), since here the magnetic field lines of the magnet 2d, which are deflected by the pole wheel 20, can only induce a Hall voltage in the second magnetic field measuring element 2b (since the magnetic field lines are not perpendicular to the extension direction of the second magnetic field measuring element 2b). The signals of the first and third magnetic field measuring elements 2a and 2c have a larger amplitude, since here the magnetic field lines run perpendicular to the respective Hall element and can thus induce a stronger Hall voltage. The two amplitudes of the magnetic field measuring elements 2a and 2c are phase-shifted, which can be explained by the fact that the magnetic field change on these two elements occurs in a temporally offset manner, since they are separated from each other in the rotational direction of the pole wheel 20 and thus the teeth 21 of the pole wheel pass over the chip 2 in a temporally offset manner - and thus the deflection of the magnetic field lines of the permanent magnet 2d takes place with a phase offset.

[0042] FIG. 2b) illustrates that the signals of the magnetic field measuring elements 2b and 2c have a similar shape, since the components acting here are those of the magnetic field acting from the permanent magnet 2d, which is deflected by the rotation of the pole wheel 20, and are accordingly perpendicular to the Hall elements and can thus induce a Hall voltage.

[0043] FIG. 2c) shows the measurement signals of the sensors in the arrangement shown in FIG. 1c). Here, strong excursions of the signals of the first and second magnetic field measuring elements 2a and 2b are shown, phase-shifted in each case. This is explained by the spatial distance between the first and second magnetic field measuring elements 2a and 2b in the direction of rotation. However, only small oscillations from the third magnetic field measuring element 2c are apparent, since only a very small component of the magnetic field lines enters perpendicular to the Hall sensor and therefore no strong Hall voltage can be generated in the extension direction of the third magnetic field measuring element 2c.

[0044] These signals can be used to determine both a rotational speed and a rotational direction. In particular, the phase offset allows the direction of rotation to be detected. Two channels are sufficient for detecting a direction, three channels are not required here. This saves computing time, which means that the results of the calculations for rotational direction and speed can be provided more quickly.

[0045] FIG. 3 shows an arrangement of the chip 2 in a housing 5. The chip 2 is attached to the housing 5 with a holder 6. The interior of the housing 5 is partially filled with a plastic material. This fixes the chip more securely in the housing. The position of the housing relative to a pole wheel is also shown. The air gap L between the pole wheel 20, which has teeth 21 and gaps 22, and the housing 5 can vary accordingly. It is also indicated that the signal acquisition unit 3, evaluation unit 4 and the current or voltage interface 7 are located on the chip.

[0046] In the region of the chip 2, a flux guide plate 8 is also shown, which is configured to keep magnetic interference fields away from the chip 2.

[0047] The present embodiment is not limited to the embodiment described. It is important that there are at least three Hall elements present, the normal vectors of which are linearly independent of each other. However, other elements can be arranged in between them, for example additional Hall elements at a 45° angle to the corresponding measuring elements 2a, 2b and 2c. This would increase the accuracy even further.

[0048] The present invention relates to a magnetic field sensor 1, which is configured to determine the movement of a rotating object 20, which either generates a rotating magnetic field itself or deflects an existing magnetic field accordingly, in particular the rotational direction and rotational speed of the rotating object. For this purpose, a chip 2 with at least three magnetic field measuring elements 2a, 2b, 2c is used, which may be a 3D Hall sensor. Such magnetic field sensors 1 are used in particular in commercial vehicles.

TABLE-US-00001 THE LIST OF REFERENCE SIGNS IS AS FOLLOWS 1 magnetic field sensor 2 chip 2a first magnetic field measuring element 2b second magnetic field measuring element 2c third magnetic field measuring element 2d permanent magnet 3 signal acquisition unit 4 evaluation unit 5 housing 6 holder 7 current or voltage interface 8 flux guide plate 20 pole wheel 21 tooth 22 gap D1 first differential signal D2 second differential signal KS combined signal AS output signal