Arrangement and method for measuring a force or a torque, with at least two magnetic sensors spaced apart from one another

Abstract

An arrangement for measuring a force and/or a torque using the inverse-magnetostrictive effect as well a method for a measurement of a force and/or a torque using the inverse-magnetostrictive effect are provided. The force or the torque acts on a machine element (01) that has at least one magnetization area (04) for a magnetization and thus forms a primary sensor for the measurement using the inverse-magnetostrictive effect. The arrangement includes at least two spaced apart magnetic field sensors (06) for measuring a magnetic field (11) caused by the magnetization and also by the force or by the torque, with each of these sensors forming a secondary sensor for the measurement using the inverse-magnetostrictive effect. The arrangement further includes a measurement signal processing unit that is constructed for the signal processing of the measurement signals of the individual magnetic field sensors (06).

Claims

1. An arrangement for measuring at least one of a force or a torque on a rotatable hollow shaft, which has at least one magnetization area for a magnetization; the arrangement comprises: at least three individual magnetic field sensors that are arranged inside of the rotatable hollow shaft and spaced apart for measuring a magnetic field caused by the magnetization and by the at least one of the force or the torque; and a measurement signal processing unit to process signals of the individual magnetic field sensors, wherein each of the magnetic field sensors has an electrical or logical connection that is guided individually to the measurement signal processing unit, such that signals from the magnetic field sensors are processed individually by the measurement signal processing unit.

2. The arrangement according to claim 1, wherein the magnetic field sensors are arranged equidistant or equiangular at least in groups.

3. The arrangement according to claim 1, wherein the magnetic field sensors are arranged in a plane at least group by group.

4. The arrangement according to claim 1, wherein the magnetic field sensors are each constructed for individual measurement of three directional components of the magnetic field caused by the magnetization and also by the at least one of the force or the torque.

5. The arrangement according to claim 1, wherein at least one of the magnetic field sensors is further constructed for measuring an interference magnetic field.

6. The arrangement according to claim 1, wherein the measurement signal processing unit is constructed to evaluate the measurement signals of groups of the magnetic field sensors, and the magnetic field sensors assigned to the groups of the magnetic field sensors is changeable.

7. The arrangement according to claim 1, wherein the magnetic field sensors are not connected together.

8. An arrangement for measuring at least one of a force or a torque on a rotatable hollow shaft, which has at least one magnetization area for a magnetization, the arrangement comprises: a first set of at least three individual magnetic field sensors and a second set of at least three individual magnetic field sensors, the magnetic field sensors being spaced apart for measuring a magnetic field caused by the magnetization and by the at least one of the force or the torque, wherein two or more of the magnetic field sensors are arranged within the rotatable hollow shaft, the first set being arranged in a radially extending plane through the rotatable hollow shaft and the second set being arranged in an axially extending plane through the rotatable hollow shaft; and a measurement signal processing unit to process signals of the individual magnetic field sensors, wherein each of the magnetic field sensors has an electrical or logical connection that is guided individually to the measurement signal processing unit, such that signals from the magnetic field sensors are processed individually by the measurement signal processing unit.

9. The arrangement according to claim 8, wherein the magnetic field sensors are arranged in a matrix.

10. The arrangement of claim 8, wherein at least one magnetic field sensor is common to both the first and second sets.

11. An arrangement for measuring at least one of a force or a torque on a rotatable hollow shaft, which has at least one magnetization area for a magnetization, the arrangement comprises: at least twelve magnetic field sensors for measuring a magnetic field caused by the magnetization and by the at least one of the force or the torque, wherein two or more sensors of the at least twelve magnetic field sensors are arranged within the rotatable hollow shaft, the at least twelve magnetic field sensors including: (i) a first subset of eight magnetic field sensors arranged at a first radial distance from an axis of the rotatable hollow shaft, and the eight magnetic field sensors are spaced apart from each other by 45 degrees, and (ii) a second subset of four magnetic field sensors arranged at a second radial distance from the axis of the rotatable hollow shaft that is less than the first radial distance, and the four magnetic field sensors are spaced apart from each other by 90 degrees; and a measurement signal processing unit to process signals of the magnetic field sensors, wherein each of the magnetic field sensors has an electrical or logical connection that is guided individually to the measurement signal processing unit, such that signals from the magnetic field sensors are processed individually by the measurement signal processing unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional details, advantages, and refinements of the invention are given from the following description of preferred embodiments of the invention, with reference to the drawing. Shown are:

(2) FIG. 1 A first preferred embodiment of an arrangement according to the invention in two views;

(3) FIG. 2 A second preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(4) FIG. 3 A third preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(5) FIG. 4 A fourth preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(6) FIG. 5 A fifth preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(7) FIG. 6 A sixth preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(8) FIG. 7 A seventh preferred embodiment of the arrangement according to the invention in a cross-sectional view;

(9) FIG. 8 An eighth preferred embodiment of the arrangement according to the invention in a longitudinal section view;

(10) FIG. 9 A ninth preferred embodiment of the arrangement according to the invention in a longitudinal section view;

(11) FIG. 10 A tenth preferred embodiment of the arrangement according to the invention in a longitudinal section view;

(12) FIG. 11 An eleventh preferred embodiment of the arrangement according to the invention in a longitudinal section view; and

(13) FIG. 12 A twelfth preferred embodiment of the arrangement according to the invention in two views.

DETAILED DESCRIPTION

(14) FIG. 1 shows a first preferred embodiment of an arrangement according to the invention in a cross-sectional view and in a longitudinal section view. The arrangement comprises a machine element made from a steel in the form of a hollow flange 01 that is mounted on a base body 02 and extends in an axis 03. A torque M.sub.t that can be measured with the arrangement according to the invention acts on the hollow flange 01.

(15) The hollow flange 01 has two magnetization areas 04 in the form of surrounding tracks. The two magnetization areas 04 are permanently magnetized and oppositely poled. The two magnetization areas 04 form a primary sensor for measuring the torque M.sub.t using the inverse-magnetostrictive effect.

(16) The arrangement further comprises twenty magnetic field sensors 06 located in the interior of the hollow flange 01. The twenty magnetic field sensors 06 have an equal distance to the axis 03. The twenty magnetic field sensors 06 are arranged in the form of five groups. Each of the five groups comprises four of the magnetic field sensors 06 that are arranged at an angular distance of 90 with respect to the axis 03 and together in a plane arranged perpendicular to the axis 03. The five groups are arranged equidistant with respect to the axis 03. Only two of the five groups of magnetic field sensors 06 are arranged at an axial position at which one of the two magnetization areas 04 is also arranged. The arrangement of the twenty magnetic field sensors 06 can alternatively also be described in that they are arranged in the form of four groups. Each of the four groups comprises five of the magnetic field sensors 06 that lie together on a straight line arranged parallel to the axis 03 and are arranged equidistant. The arrangement of the twenty magnetic field sensors 06 can alternatively also be described in that they are arranged in the form of two groups. Each of the two groups comprises ten of the magnetic field sensors 06 that are arranged together in a plane surrounding the axis 03 in a matrix-like pattern, wherein the two planes have an angle of 90 to each other.

(17) The described arrangement of the twenty magnetic field sensors 06 leads, among other things, to a group 07 of magnetic field sensors 06 oriented in the axial direction, a group 08 of magnetic field sensors 06 oriented in the diagonal direction, and a group 09 of magnetic field sensors 06 oriented in the tangential direction.

(18) The twenty magnetic field sensors 06 are each shown symbolically by a circle.

(19) The twenty magnetic field sensors 06 each permit a measurement of one or more of the directional components of a magnetic field 11 and also possible interference magnetic fields occurring due to the inverse-magnetostrictive effect.

(20) Each of the twenty magnetic field sensors 06 is connected individually to a microcontroller acting as a measurement signal processing unit 05, shown schematically in FIG. 1, so that the micro-controller can process and evaluate the measurement signals of the twenty magnetic field sensors 06 individually or in variable groups.

(21) The microcontroller controls the polling of the twenty magnetic field sensors 06 and compares their measurement values with a database that is stored in the microcontroller and calculates relative or absolute measurement values and compares them with each other.

(22) In so far as the twenty magnetic field sensors 06 are each formed for measuring all three directional components of the magnetic field 11 occurring due to the inverse-magnetostrictive effect, a spatial vector is measured with the magnitude and direction of the load-dependent magnetic field 11 to be measured. The spatial vector that can be illustrated by the magnetic flux density with the three directional components B.sub.x, B.sub.y and B.sub.z is formed from the measurement values of the magnetic field sensors 06.

(23) The magnetic field 11 produced due to the inverse-magnetostrictive effect is dependent on the torque M.sub.t. Indeed, if necessary, only a few of the twenty magnetic field sensors 06 of this magnetic field 11 can detect, but these magnetic field sensors 06 can be selected and grouped by the microcontroller.

(24) For changing, pure torsion loading of the hollow flange 01 and for a disappearing interference field, at each of the positions of the magnetic field sensors 06, the vector of the magnetic flux density changes only in magnitude, i.e., each of the magnetic field sensors 06 undergoes a change in the vector magnitude, but not in the vector direction. Thus, the magnitude of the magnetic flux density of each vector component B.sub.x, B.sub.y and B.sub.z increases equally, so that the vector direction remains unchanged.

(25) The magnetic flux density of the load-dependent magnetic field 11 is linearly dependent for each of the three vector components B.sub.x, B.sub.y and B.sub.z on the torque M.sub.t, wherein the linear increase is negative or positive as a function of the position of each magnetic field sensor 06 in the axial direction. A slope of zero for one or two of the three vector components is also conceivable.

(26) The load-dependent magnetic field 11 that is measured using the vector of the magnetic flux density B.sub.x, B.sub.y and B.sub.z differs at the positions of the individual magnetic field sensors 06 for a constant torque load. Under the assumption of a disappearing small interference magnetic field, the direction and the magnitude of the vector are equal at each magnetic field sensor 06 with an equal axial position. Accordingly, the direction and the magnitude of the vector differ between the positions of the magnetic field sensors 06 within the axial direction. This relationship offers the ability to combine measurement signals of individual magnetic field sensors 06 into groups and to evaluate them accordingly.

(27) FIG. 2 shows a second preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 1. In contrast to the embodiment shown in FIG. 1, the magnetic field sensors 06 are arranged together in a plane surrounding the axis 03. The magnetic field sensors 06 are arranged in two groups. Each of the two groups comprises several of the magnetic field sensors 06 that are arranged together on a straight line arranged parallel to the axis 03 and equidistant. The magnetic field sensors 06 have an equal distance to the axis 03.

(28) FIG. 3 shows a third preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 2. In contrast to the embodiment shown in FIG. 2, the magnetic field sensors 06 are arranged in different positions about the axis 03 and also in the axis 03. The magnetic field sensors 06 are arranged in four groups. Each of the four groups comprises several of the magnetic field sensors 06 that are arranged together on a straight line arranged parallel to the axis 03 or on the axis 03 and equidistant. The magnetic field sensors 06 not arranged in the axis 03 have an equal distance to the axis 03.

(29) FIG. 4 shows a fourth preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 2. In contrast to the embodiment shown in FIG. 2, the magnetic field sensors 06 are arranged in two planes encompassing the axis 03. These two planes have an angle of 45 to each other.

(30) FIG. 5 shows a fifth preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 3. In contrast to the embodiment shown in FIG. 3, the magnetic field sensors 06 are arranged in seven groups. Each of the seven groups comprises several of the magnetic field sensors 06 that are arranged together on a straight line arranged parallel to the axis 03 or on the axis 03 and equidistant.

(31) FIG. 6 shows a sixth preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 2. In contrast to the embodiment shown in FIG. 2, the magnetic field sensors 06 are arranged in eight groups. Each of the eight groups comprises several of the magnetic field sensors 06 that are arranged together on a straight line arranged parallel to the axis 03 and equidistant. The straight lines of each of four of the eight groups have an angular distance of 90 with respect to the axis 03. The magnetic field sensors 06 of each of four of the eight groups have an equal distance to the axis 03.

(32) FIG. 7 shows a seventh preferred embodiment of the arrangement according to the invention in a cross-sectional view. This embodiment is initially identical to the embodiment shown in FIG. 6. In contrast to the embodiment shown in FIG. 6, the magnetic field sensors 06 are arranged in twelve groups. Eight of the twelve groups of magnetic field sensors 06 are arranged on eight straight lines that have an angular distance of 45 with respect to the axis 03 and an equal distance to the axis 03. The remaining four groups of the twelve groups of magnetic field sensors 06 are arranged on four straight lines that have an angular distance of 90 with respect to the axis 03 and an equal distance to the axis 03.

(33) FIG. 8 shows an eighth preferred embodiment of the arrangement according to the invention in a longitudinal section view. This embodiment is initially identical to the embodiment shown in FIG. 1. In contrast to the embodiment shown in FIG. 1, four of the magnetic field sensors 06 are missing, namely in two of the four groups of magnetic field sensors 06 arranged on straight lines. The magnetic field sensors 06 that have an identical axial position as the magnetization areas 04 are missing.

(34) FIG. 9 shows a ninth preferred embodiment of the arrangement according to the invention in a longitudinal section view. This embodiment is initially identical to the embodiment shown in FIG. 8. In contrast to the embodiment shown in FIG. 8, a different twelve sensors of the magnetic field sensors 06 are missing, namely those that do not have an identical position as the magnetization areas 04.

(35) FIG. 10 shows a tenth preferred embodiment of the arrangement according to the invention in a longitudinal section view. This embodiment is initially identical to the embodiment shown in FIG. 8. In contrast to the embodiment shown in FIG. 8, in two of the four groups of magnetic field sensors 06 arranged on straight lines, those magnetic field sensors 06 that do not have an identical axial position as the magnetization areas are missing. Instead, at the axial positions of the magnetization areas 04, each of four additional magnetic field sensors 06 are arranged with a smaller distance to the axis 03.

(36) FIG. 11 shows an eleventh preferred embodiment of the arrangement according to the invention in a longitudinal section view. This embodiment is initially identical to the embodiment shown in FIG. 8. In contrast to the embodiment shown in FIG. 8, the magnetic field sensors 06 that have an identical axial position as the magnetization areas 04 are missing.

(37) The arrangements of the magnetic field sensors 06 of the embodiments shown in FIGS. 2 to 11 can be combined in the axial direction. For example, the arrangement shown in FIG. 2 can be combined with the arrangement shown in FIG. 9.

(38) The arrangements shown in FIGS. 2 to 11 of the magnetic field sensors 06 enable both a detection of the load-dependent magnetic field 11 and also a detection of a possible interference magnetic field. In particular, it is also possible to determine the intensity and/or the direction of the interference magnetic field. With special calculation types of the measurement signals of the magnetic field sensors 06 and a database stored accordingly in the microcontroller, an interpretation of the measurement and thus the detection of different interference cases and results is possible.

(39) FIG. 12 shows a twelfth preferred embodiment of the arrangement according to the invention in a cross-sectional view and in a longitudinal section view. This embodiment is initially identical to the embodiment shown in FIG. 1. In contrast to the embodiment shown in FIG. 1, all of the magnetic field sensors 06 are arranged in a plane that encompasses the axis 03. The magnetic field sensors 06 are arranged in the form of a matrix in the x and y directions, wherein the axis 03 is in the x-direction. The matrix comprises rows 1, 2, 3, 4, 5 and columns a, b, c, d, e. Each of the matrix elements (1a) to (5e), with the exception of matrix elements (2b), (2d), (3a), (3c), (3e), (4b) and (4d), is provided with one of the magnetic field sensors 06.

(40) The rows 1 and 5 are arranged closest to the inner wall of the hollow flange 01. The distance between the rows 1 and 5 is D. Consequently, the y-coordinate of row 1 is D/2. The y-coordinate of row 5 is D/2. The y-coordinate of row 2 is D/6. The y-coordinate of row 4 is D/6. The y-coordinate of row 3 is zero. The magnetic field sensors 06 in rows 1 and 5 are used mainly for measuring M.sub.t, while the magnetic field sensors 06 in rows 2 to 4 are used mainly for measuring the interference magnetic field.

(41) The load-dependent magnetic field 11 is proportional to the torque M.sub.t. It can be calculated redundantly as M.sub.t_a, M.sub.t_b, M.sub.t_c, M.sub.t_d and M.sub.t_e as follows:
M.sub.t_a=[Y.sub.ta3Y.sub.2a+3Y.sub.4aY.sub.5a].Math.K.sub.1
M.sub.t_c=[Y.sub.1c+3Y.sub.2c3Y.sub.4c+Y.sub.5c].Math.K.sub.2
M.sub.t_e=[Y.sub.1e3Y.sub.2e+3Y.sub.4eY.sub.5e].Math.K.sub.3
M.sub.t_b=[X.sub.1b+2X.sub.3bX.sub.5b].Math.K.sub.4
M.sub.t_d=[X.sub.1d2X.sub.3d+X.sub.5d].Math.K.sub.5

(42) In these formulas, X and Y stand for the respective magnetic field component measured with the magnetic field sensor 06 indicated in the index in the x or y direction. The constants K.sub.1 to K.sub.5 are determined by calibration. It is to be expected that the relationships K.sub.1K.sub.3K.sub.2/2 and K.sub.4K.sub.5 are set.

(43) The terms M.sub.t_a to M.sub.t_e allocate the magnetic field 11 into the columns a to e with reference to different magnetic field spatial components. Depending on the axial position on the hollow flange 01, two different term structures are produced. A largely complete compensation of interference with reference to the terms is achieved at the same time as the measurement of the torque M.sub.t.

(44) By comparing M.sub.t_a, M.sub.t_b, M.sub.t_e, M.sub.t_d and M.sub.t_e, a plausibility check is performed. If the values M.sub.t_a, M.sub.t_b, M.sub.t_e, M.sub.t_d and M.sub.t_e are equal in consideration of a permissible tolerance, then the plausibility check is successful and the measured value can be further processes as a value for M.sub.t. The parameters can move in the permissible tolerance range. The permissible size of the tolerance range is defined in advance and stored in the algorithm.

(45) The terms M.sub.t_a, M.sub.t_b, M.sub.t_e, M.sub.t_d and M.sub.t_e include the compensation of a far field. Likewise, a compensation of a near field that is linearly variable in the plane spanned by the magnetic field sensors 06 takes place in the measured field direction. For a non-linear near field, the linear component of the near field is compensated. The larger the linear component is, the better the compensation of the interference.

(46) In addition, these terms include a compensation of possible transverse forces in the y direction or in a z direction. These terms also include a compensation of possible transverse forces that are caused by possible bending moments in the z direction or in the y direction. The mentioned compensation takes place virtually at the same time as the measurement.

(47) The non-linear component of a near field can be handled using a computational approach. Here, the non-linear component of the near field is defined using the available measured values including directional components of the individual magnetic field sensors 06. Furthermore, a conclusion can be made using the nonlinear component of the near field on the measurement errors caused by this component on the magnetic field sensors 06, including directional components or on the measurement error of groups of magnetic field sensors 06. Starting from this, the measured values of the groups of magnetic field sensors 06 are corrected and thus an increase in the accuracy of the measurement that can be performed with the arrangement according to the invention.

LIST OF REFERENCE SYMBOLS

(48) 01 Machine element in the form of a hollow flange 02 Base body 03 Axis 04 Magnetization area 05 - 06 Magnetic field sensor 07 Group in axial direction 08 Group in diagonal direction 09 Group in tangential direction 10 - 11 Magnetic field