ARRANGEMENT FOR MEASURING A TORQUE ACTING ON A STEERING SHAFT OF A MOTOR VEHICLE AND METHOD FOR CHECKING THE ARRANGEMENT

Abstract

A method test an arrangement for measuring a torque acting on a steering shaft of a motor vehicle. The measurement is carried out using the inverse magnetostrictive effect. The steering shaft has an axis and at least two magnetization areas extending circumferentially around the axis. The arrangement comprises at least four magnetic field sensors for measuring an axial component of a magnetic field caused by the magnetization as well as by the torque. There are at least two combinations of at least two of the magnetic field sensors each, each of which is sufficient to measure the torque. First and second measurement values of the torque are determined with first and second combinations of the magnetic field sensors. The first measurement value and the second measurement value are compared, as a result of which a malfunction of the arrangement can be recognized.

Claims

1. A method for testing an arrangement for measuring a torque acting on a steering shaft of a motor vehicle, the steering shaft having an axis and at least two magnetization areas extending circumferentially around the axis, wherein said arrangement comprises at least four magnetic field sensors for measuring an axial component of a magnetic field caused by said magnetization as well as by the torque, wherein there are at least two combinations of at least two of said magnetic field sensors, each of said combinations being sufficient for measuring said torque, and wherein said method comprises: Determining a first measurement value of the torque with a first one of the combinations of the magnetic field sensors; Determining a second measurement value of the torque with a second one of the combinations of the magnetic field sensors; and Comparing the first measurement value with the second measurement value.

2. A method according to claim 1, wherein a third measurement value of the torque is also determined with a third combination of the at least four magnetic field sensors, the first measurement value, the second measurement value and the third measurement value being compared.

3. A method according to claim 1, wherein, in order to compare the measurement values, absolute amounts of differences between the measurement values are calculated.

4. A method according to claim 2 wherein a sum of the absolute amounts of the differences between the measurement values is calculated.

5. A method according to claim 4, wherein an error signal is output if the sum of the absolute amounts exceeds a previously defined maximum.

6. A method according to claim 1, wherein the magnetic field sensors each have a same tangential position as at least one other of the magnetic field sensors.

7. A method according to claim 1, wherein the each of the magnetic field sensors is axially located opposite one of the magnetization areas.

8. A method according to claim 7, wherein at least one of the magnetization areas has a same axial position as two of the magnetic field sensors, these two magnetic field sensors being arranged opposite one another with respect to the axis.

9. A method according to claim 8, wherein each of the magnetization area is axially located opposite a respective two of the magnetic field sensors, the respective two magnetic field sensors arranged opposite one another with respect to the axis, wherein two of the magnetic field sensors have a same tangential position and are axially adjacent, a first of the magnetic field sensors outputting a measurement signal a.sub.1, the magnetic field sensor opposite the first magnetic field sensor with respect to the axis forming a second one of the magnetic field sensors which outputs a measurement signal a.sub.2, the measurement signals a.sub.1 and a.sub.2 representing the axial directional components of the magnetic field occurring with opposite direction, wherein the magnetic field sensor axially adjacent to the first magnetic field sensor forms a third of the magnetic field sensors which outputs a measurement signal b.sub.1, wherein the measurement signals a.sub.1 and b.sub.1 represent the axial direction components of the occurring magnetic field with the same direction, wherein the magnetic field sensor opposite the third magnetic field sensor with respect to the axis forms a fourth of the magnetic field sensors which outputs a measurement signal b.sub.2, wherein the measurement signals b.sub.1 and b.sub.2 represent the axial direction components of the occurring magnetic field with opposite direction, and wherein the at least two measurement values are each determined according to one of the following rules: $M_1=\frac{a_1-a_2-b_1+b_2}{4}{M}_2=\frac{a_1+b_2}{2}{M}_3=-\frac{a_2+b_1}{2}$

10. An arrangement for measuring a torque acting on a steering shaft of a motor vehicle, the steering shaft having an axis and at least two magnetization areas extending circumferentially around said axis, said arrangement comprising at least four magnetic field sensors for measuring an axial directional component of a magnetic field caused by the magnetization as well as by the torque, wherein there are at least two combinations of at least two of said magnetic field sensors, respectively, each of said combinations being sufficient for measuring said torque, and wherein said arrangement further comprises a measurement signal processing unit adapted to perform a method according to claim 1.

11. A method according to claim 1, wherein, in order to compare the measurement values, squares of differences between the measurement values are calculated.

12. A method according to claim 2 wherein a sum of the squares of the differences between the measurement values is calculated.

13. A method according to claim 12, wherein an error signal is output if the sum of the squares of the differences exceeds a previously defined maximum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Further details, advantages and developments arise from the following description of embodiments with reference to the drawing. In the figures:

[0066] FIG. 1 a first embodiment of an arrangement is shown in two views;

[0067] FIG. 2 a second embodiment of the arrangement is shown in two views;

[0068] FIG. 3 a third embodiment of the arrangement is shown in two views; and

[0069] FIG. 4 a fourth embodiment of the arrangement is shown in two views.

DETAILED DESCRIPTION

[0070] FIG. 1 is a first embodiment of an arrangement in a cross-sectional view and in a longitudinal sectional view. The arrangement comprises a steering shaft 01 of a motor vehicle. The steering shaft 01 is made of steel and extends into an axis 03. A torsional torque Mt acts on the steering shaft 01, which can be measured with the arrangement.

[0071] The steering shaft 01 has two magnetization areas 04 in the form of circumferential tracks. The two magnetization areas 04 are permanently magnetized and polarized in opposite directions, which is shown in each case by an arrow 05 illustrating the direction of rotation. The two magnetization areas 04 form a primary sensor for measuring the torsional torque Mt using the inverse magnetostrictive effect.

[0072] The arrangement also includes four magnetic field sensors 06, which are located near the steering shaft 01. The four magnetic field sensors 06 are located at the same distance from the axis 03.

[0073] The four magnetic field sensors 06 each serve to measure an axial directional component of a magnetic field occurring due to the magnetization of the magnetization areas 04 and the torsional torque Mt due to the inverse magnetostrictive effect. A magnetic field direction of this magnetic field is shown at the positions of the magnetic field sensors 06 by an arrow 07 illustrating the respective magnetic field direction. A positive measuring direction of the magnetic field sensors 06 is illustrated by the symbol used for the magnetic field sensors 06 with an arrow drawn in.

[0074] Two of the four magnetic field sensors 06 have the same axial position as a first one of the magnetization areas 04. Two more of the four magnetic field sensors 06 have the same axial position as a second one of the magnetization areas 06.

[0075] A first magnetic field sensor 11 of the four magnetic field sensors 06 outputs a signal a.sub.1. The magnetic field sensor 06 opposite the first magnetic field sensor 11 in relation to the axis 03 forms a second magnetic field sensor 12 which outputs a signal a.sub.2. The magnetic field sensor 06 axially adjacent to the first magnetic field sensor 11 forms a third magnetic field sensor 13 which outputs a signal b.sub.1. The magnetic field sensor 06 opposite the third magnetic field sensor 13 in relation to the axis 03 forms a fourth magnetic field sensor 14 which outputs a signal b.sub.2.

[0076] The arrangement further comprises a microcontroller (not shown) which is used for measurement signal processing and is configured to carry out a method for checking the arrangement.

[0077] FIG. 2 is a second embodiment of the arrangement in a cross-sectional view and in a longitudinal sectional view. This embodiment is initially similar to the embodiment shown in FIG. 1. In contrast to the first embodiment shown in FIG. 1, the steering shaft 01 has three magnetization areas 04, which are alternately polarized. The first magnetic field sensor 11 of the four magnetic field sensors 06 in turn outputs the signal a.sub.1. The second magnetic field sensor 12 is axially adjacent to the first magnetic field sensor 11 and outputs the signal b.sub.1. The third magnetic field sensor 13 is arranged opposite the first magnetic field sensor 11 with respect to the axis 03 and outputs the signal b.sub.2. The fourth magnetic field sensor 14 is axially adjacent to the third magnetic field sensor 13 and outputs the signal c.sub.2.

[0078] FIG. 3 is a third embodiment of the arrangement in a cross-sectional view and in a longitudinal sectional view. This embodiment is initially the same as the embodiment shown in FIG. 2. In contrast to the second embodiment shown in FIG. 2, the arrangement comprises six of the magnetic field sensors 06. The first magnetic field sensor 11 of the six magnetic field sensors 06 in turn outputs the signal a.sub.1. The second magnetic field sensor 12 is arranged opposite the first magnetic field sensor 11 with respect to the axis 03 and outputs the signal a.sub.2. The third magnetic field sensor 13 is axially adjacent to the first magnetic field sensor 11 and outputs the signal b.sub.1. The fourth magnetic field sensor 14 is arranged opposite the third magnetic field sensor 13 with respect to the axis 03 and outputs the signal b.sub.2. A fifth magnetic field sensor 15 of the six magnetic field sensors 06 is axially adjacent to the third magnetic field sensor 13 and outputs the signal c.sub.1. A sixth magnetic field sensor 16 of the six magnetic field sensors 06 is arranged opposite the fifth magnetic field sensor 15 with respect to the axis 03 and outputs the signal c.sub.2.

[0079] FIG. 4 is a fourth embodiment of the arrangement in a cross-sectional view and in a longitudinal sectional view. This embodiment is initially similar to the embodiment shown in FIG. 3. In contrast to the third embodiment shown in FIG. 3, the arrangement comprises eight of the magnetic field sensors 06. The first magnetic field sensor 11 of the six magnetic field sensors 06 in turn outputs the signal a.sub.1. The second magnetic field sensor 12 is arranged opposite the first magnetic field sensor 11 with respect to the axis 03 and outputs the signal a.sub.2. The third magnetic field sensor 13 is axially adjacent to the first magnetic field sensor 11 and outputs the signal b.sub.11. The fourth magnetic field sensor 14 is located directly adjacent to the third magnetic field sensor 13 and outputs the signal b.sub.12. The fifth magnetic field sensor 15 is arranged opposite the third magnetic field sensor 13 with respect to the axis 03 and outputs the signal b.sub.21. The sixth magnetic field sensor 16 is located directly adjacent to the fifth magnetic field sensor 13 and outputs the signal b.sub.22. A seventh magnetic field sensor 17 of the eight magnetic field sensors 06 is axially adjacent to the third magnetic field sensor 13 and outputs the signal c.sub.1. An eighth magnetic field sensor 18 of the six magnetic field sensors 06 is arranged opposite the seventh magnetic field sensor 17 with respect to the axis 03 and outputs the signal c.sub.2.

LIST OF REFERENCE SIGNS

[0080] 01 Steering shaft [0081] 02 - [0082] 03 Axis [0083] 04 Magnetization area [0084] 05 Direction of rotation [0085] 06 Magnetic field sensor [0086] 07 Magnetic field direction [0087] 08 - [0088] 09 - [0089] 10 - [0090] 11 First magnetic field sensor [0091] 12 Second magnetic field sensor [0092] 13 Third magnetic field sensor [0093] 14 Fourth magnetic field sensor [0094] 15 Fifth magnetic field sensor [0095] 16 Sixth magnetic field sensor [0096] 17 Seventh magnetic field sensor [0097] 18 Eighth magnetic field sensor