Patent Application
20070289395
The combination of the measurement arrangements 10 and 12 illustrated in the Figures produces a device which is particularly suitable to determine the absolute steering wheel rotation angle in a motor vehicle. The steering wheel (not shown) is coupled non-rotatably to a rotary shaft 14 (steering column), which can carry out several revolutions in both directions of rotation, starting from an original position (central position of the steering wheel).
The first measurement arrangement 10 includes a rotor 16, which is coupled to the rotary shaft 14. For example, the rotor 16 is a disc which is connected non-rotatably to the rotary shaft 14 and oriented perpendicularly thereto. The rotor 16 has several coded zones 18. The coded zones 18 are electrically conductive zones which have different geometries and are arranged distributed in the peripheral direction approximately at the same radial distance r from the center of rotation C of the rotary shaft 12.
An inductive first sensor 20 is mounted approximately at the radial distance r from the rotation center C of the rotary shaft 12 on a carrier (not shown), which is stationary in relation to the rotor 16. The first sensor 20 is arranged and designed so that it detects the coding of the coded zones 18 when the rotary shaft 12 rotates, by measuring the inductivity of the coded zones 18 which are passing by.
The angle position of the rotor 18 is determined in a measurement range of 0° to 360° from the actually measured inductivity and/or from the inductivity change in an electronic evaluation arrangement.
In order to make an absolutely distinct measurement possible, the coding of the individual zones 18 is distinct at every location in the peripheral direction.
To increase the accuracy of measurement, a plurality of first sensors 20 can be provided, arranged at suitable different locations.
Instead of inductive first sensors 20, capacitive first sensors 20 may also be provided, by which a change in the capacity of the coded zones 18 can be detected. A combination of inductive and capacitive first sensors 20 is also conceivable.
It is basically also possible to realize the measurement principle described above in reverse, i.e. the first sensor or sensors 20 are mounted on the rotor 16 and the coded zones 18 are mounted on the stationary carrier.
The second measurement arrangement 12 likewise includes a rotor which is coupled to the rotary shaft 14. The rotor of the second measurement arrangement 12 may be identical to the rotor 16 of the first measurement arrangement 10 or, for example, may be a housing cover of the measurement device. For the sake of simplicity, it will be assumed below that the rotor is the same rotor 16 as used in the first measurement arrangement 10.
A spiral-shaped connecting link guide 22 is formed in the rotor 16. A deflection element 24 engages into the connecting link guide 22. The deflection element 24 undergoes a deflection which is dependent on the rotation of the connecting link guide 22. The deflection element 24 may, for example, be an arm which performs a rotary movement, or a slider which performs a linear movement.
The deflection element 24 also has at least one coded zone 26. The coded zone 26 of the deflection element 24 may again be an electrically conductive zone with a special geometry and/or may have sections of differing capacity.
The second measurement device 12 further includes a second sensor 28 which is arranged so as to be stationary in the deflection zone of the deflection element 24. The second sensor 28 is an inductive and/or capacitive sensor, coordinated with the coded zone 26 of the deflection element 24.
It is possible to detect the change in inductivity or capacity of the coded zone 26 with the second sensor 28. From this data, conclusions can be drawn by means of the evaluation electronics regarding the direction and number of revolutions which the rotary shaft 12 has carried out.
Several second sensors 28 may again be provided, arranged at suitable different locations, in order to increase the accuracy of measurement.
The second measurement arrangement 12 can analyse a sufficient number of revolutions (or portions thereof), in order to cover the entire rotation range of the steering wheel. The determining of the absolute steering wheel rotation angle then takes place by combining the measurement results of the first and second measurement arrangements 10 and 12.
The device according to the invention can check itself for plausibility by means of the evaluation electronics and is redundant. In addition, with the device according to the invention it is possible to maintain the detection of the angle to a limited extent, if one of the measurement arrangements fails, by means of the other measurement arrangement (which is still functionable), owing to the use of the two measurement arrangements 10, 12 which are designed to be continuous.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2006 009 621.3 | Jun 2006 | DE | national |
