Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Reexamination Certificate
1998-06-29
2001-01-16
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
C324S207250, C180S444000
Reexamination Certificate
active
06175231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electronically assisted power steering system for motor vehicles. The power steering system contains a primary shaft, which is in operative connection with a manual steering wheel and is used for transmitting the torque necessary for the steering of the wheels of the vehicle. The power steering system also includes an output member which is in operative connection with the wheels. Using a servo motor, an auxiliary force can be exerted on the primary shaft or the output member. A non-contact detection unit is provided for the non-contact detection of the direction and strength of a steering torque acting on the primary shaft, and/or for detecting the direction and/or the speed of a steering movement of the primary shaft, and/or for detecting another movement and/or movement change of the primary shaft and/or of the output member or of another element of the power steering system. The detection unit includes at least one pulse transmitter connected with the primary shaft and/or the output member or with another element of the power steering system and at least one sensor. The pulse transmitter is arranged in a housing and the sensor is outside of the housing. There is a gap between the pulse transmitter and the sensor.
2. Description of the Prior Art
A similar power steering system is known, for example, from German Patent Publication DE 38 35 955 A1. A non-contacting rotary force sensor is arranged in the area of a steering spindle of this power steering system, by means of which the rotary force in the power steering system can be detected. The rotary force sensor contains two magnetic cylinders, or magnetic rings, and a magnetoresistive unit, or a sensor assembly with magnetoresistive sensors, which project into the interior of the steering system housing from the outside. An air gap exists between the two magnetic cylinders and the magnetoresistive unit.
The opening in the housing, through which the magnetoresistive units project into the interior, is disadvantageous in this version. This opening must be specially produced as an aperture in the housing, thereby creating additional expense. It is also necessary to dependably seal this aperture, so that no impurities can enter the housing.
SUMMARY OF THE INVENTION
It is the object of the invent ion to avoid the disadvantages of the prior art and to make the production of the housing and the required sealing more cost-effective.
This object is attained by means of the power steering system of the present invention. Here, the housing is embodied to be closed in an area located between the pulse transmitter and the sensor. Contrary to the current beliefs of experts in the field, it has been found that the gap between the pulse transmitter and the sensor of a non-contacting rotary steering force sensor or other detection unit can be filled with different materials than air. It is therefore possible to do without an aperture in the housing.
Useful and advantageous embodiments of the invention are disclosed herein. For example, it is advantageous if the housing consists of a non-ferromagnetic material, at least in the area located between the pulse transmitter and the sensor. Structurally the sensor can be usefully arranged on a sensor housing which is bolted to the housing or is fastened to the housing by means of a clamp. It is particularly simple and therefore cost-effective, if the sensor is arranged, together with the electronic unit, on a printed circuit board in the sensor housing.
The invention will be explained in more detail in what follows by means of two exemplary embodiments represented in the drawings.
REFERENCES:
patent: 4874053 (1989-10-01), Kimura
patent: 5248939 (1993-09-01), Brauer
patent: 5523681 (1996-06-01), Hajzler
patent: 38 35 955 A1 (1989-11-01), None
“Durch Die Wand”, elektro Automation 48, Jg. Nr. 3, Mar. 1995, pp. 39-41.
Budaker Martin
H{umlaut over (a)}gele Gerhard
Nagel Willi
Larson & Taylor PLC
Snow Walter E.
ZF Friedrichshafen AG
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