Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-06-30
2001-06-19
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231160
Reexamination Certificate
active
06248993
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to detecting the angle position of a steering wheel of a motor vehicle. More particularly, the present invention relates to a steering angle sensor for determining the absolute angle position of a steering wheel. In greater particularity, the present invention is a steering angle sensor having a sensor unit for detecting the steering angle position of a steering wheel within an angle segment of the entire rotational range of the steering wheel in which the rotor of this sensor unit is coupled to the rotational movement of the steering wheel.
BACKGROUND ART
The steering angle and steering angle lock in motor vehicles are required for influencing a driving dynamics control system. In addition to the steering angle values, this driving dynamics control system obtains further measurement data, such as wheel rotational speed and the rotation of the motor vehicle about its vertical axis. The driving dynamics control system evaluates the absolute steering angle lock and the steering speed values with the other detected data. The driving dynamics control system uses these values and other data for controlling actuators such as brakes and engine management.
DE 4022837 A1 discloses an optoelectronic steering angle sensor. The steering angle sensor includes a light source and a line sensor arranged in parallel and spaced apart from each other. An encoder disc is disposed between the light source and the line sensor. The encoder disc is non-rotatable connected to the steering spindle. The line sensor is a CCD-sensor line. The code transmitter is formed as a light slit disc and as a code trace in the form of a spiral which increases in size from the inside outwards. The exposure of the image points of the line sensor in a specific steering lock makes it possible to obtain information regarding the actual steering angle lock.
An Archimedean spiral extending over 360° provides the coding for this encoder disc. This steering angle sensor determines absolute steering wheel angle positions only in the range of the coding and thus only in the range of 360°. However, it is possible to rotate steering wheels much more than 360°. On the basis of a straight position of the wheels and thus a zero position of the steering angle sensor it is desirable to detect the absolute steering angle in an angular range of the entire rotational range of the steering wheel.
The steering angle sensor disclosed in DE 4022837 A1 only detects an angle segment in the range of a complete steering wheel lock of 180° to the right and 180° to the left starting from the zero position of the steering angle sensor. However, steering wheels in motor vehicles can make, for example, three complete turns to the right and to the left starting from the zero position. Thus, a steering angle sensor which measures in the absolute steering angle position would have to be able to cover 2160°, i.e., six revolutions.
Steering angle sensor systems are disposed in the region of the steering spindle of the motor vehicle. The installation space available in this region for installing the steering angle sensor is limited both in the axial direction and, in particular, in the radial direction with respect to the steering spindle. For this reason, an attempt is made to connect steering angle sensor systems to existing modules such as the flat spiral spring cartridge or to integrate them therein. In many cases, this is only possible if the steering angle sensor requires the smallest possible allowable installation space.
DISCLOSURE OF INVENTION
Accordingly, it is an object of the present invention to provide a steering angle sensor for determining the absolute angle position of a steering wheel of a motor vehicle within the entire rotational range of the steering wheel.
In carrying out the above object and other objects, the present invention provides a steering angle sensor for determining absolute angle position of a steering wheel in a motor vehicle within the rotational range of the steering wheel. The steering angle sensor includes a first sensor unit for detecting steering angle position of the steering wheel within a first angle segment of the rotational range of the steering wheel. The first sensor unit has a driving rotor coupled to the rotational movement of the steering wheel. The steering angle sensor further includes a second sensor unit for detecting steering angle position of the steering wheel within a second angle segment of the rotational range of the steering wheel. The second sensor unit has a driven rotor coupled to the driving rotor such that during rotational movement of the steering wheel the driven rotor and the driving rotor rotate at different speeds. The absolute angle position of the steering wheel is determined from the steering angle position detected by the first sensor unit and the steering angle position detected by the second sensor unit.
In contrast to prior art steering angle sensors, the steering angle sensor of the present invention includes two sensor units. Each sensor unit has a rotor. The rotors are coupled together with gears such that during a steering wheel movement the rotors move at slightly different rotational speeds. The rotor of one sensor unit is coupled to the rotational movement of the steering spindle. This rotor is the driving rotor. The driving rotor drives the rotor of the other sensor unit. The other rotor is the driven rotor. Both sensor units detect angle position of the steering wheel within respective predetermined angle segments of the entire rotational range of the steering wheel. It is expedient if the predetermined angle segments monitored by the two sensor units are different, for example, if they differ from each other by 5° to 15°.
The absolute angle position of the steering wheel of a motor vehicle is defined over the entire rotational range of the steering wheel by a first measurement value, i.e., steering angle position within a first predetermined angle segment, detected by the first sensor unit and a second measurement value, i.e., steering angle position within a second predetermined angle segment, detected by the second sensor unit. If the sensor units detect the angle position with different degrees of accuracy the steering angle sensor functions according to a type of nonius sensor.
The advantages accruing to the present invention are numerous. For example, two sensor units each monitor only one predetermined angle segment of the entire rotational range of the steering wheel while the rotor of one sensor unit is disposed within the rotor of the other sensor unit. This arrangement is particularly space-saving, so that the installation space required for steering angle sensor in comparison to the prior art steering angle sensors, which use only one single sensor unit, is only slightly increased in size or not increased in size at all.
Preferably, the outer rotor is coupled to the movement of the steering spindle and the inner rotor is driven by a planetary gear. Advantageously, in accordance with an alternate embodiment of the present invention, the rotors are geared coupled together wherein the geared coupling is produced by rotational axes of the two rotors being disposed in parallel with each other in an offset position. In this alternate embodiment, the inner rotor has external, circumferential toothing which engage into internal toothing of the outer rotor. Expediently, the diameters of the rotors of the two sensor units are only slightly different and, therefore, the speed difference between the two rotors is small. Consequently, this substantially obviates noise resulting from considerably different rotational speeds in the case of a different geared coupling of the two rotors.
The inner rotor is preferably held in the outer rotor by an eccentric bearing ring. The bearing ring has fixing means which non-rotatable fix the bearing ring to the stator of the inner rotor. In so doing, it is expedient for the fixing means to be in the form of a hollow spigot equipped with an elongate hole extending in the radial d
Bläsing Frank
Bunselmeier Dirk
Hinteresch Klaus
Rimke Kersten
Brooks & Kushman P.C.
Lee John R.
Leopold Kostal GmbH & Co. KG
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