Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2000-04-05
2001-07-24
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207120, C324S202000
Reexamination Certificate
active
06265866
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a measuring device for determining the position of a control element.
BACKGROUND OF THE INVENTION
To determine the position of a control element, such as a throttle valve, which is exposed to high temperatures, there are used in known manner mechanical potentiometers which are mechanically connected to the control element. Analog signals are output to an A/D converter and then to an evaluation unit.
A disadvantage of such devices, however, is that the mechanical potentiometers undergo considerable wear, whereby additional interfering variables falsify the measured result.
German Patent Application DE 3345804 A1 discloses an instrument for contactless electronic measurement of the angle of a mechanical actuator. In this instrument a shaft, connected mechanically to the actuator protrudes form the instrument and a rotatable magnet is attached to the shaft. A sensor element is disposed in the casing opposite the rotatable magnet. A Hall element cannot be utilized under these conditions, since the instrument is exposed to relatively high temperatures and thereby output signals of the Hall element drift very greatly. Therefore a flux gate principle and not the Hall effect is used for this purpose.
Various contactless devices containing Hall generators using the Hall effect for measuring lengths and/or angles are disclosed in German Patent Application DE 4405513 A1, German Patent DE 4408056 C2 and German Patent Application DE 1970987 A1. These measuring devices are also imprecise as regards their measured results at relatively high temperatures, since here also the influence of temperature on the magnet and its flux density is not precluded.
SUMMARY OF THE INVENTION
An object of the invention is to provide a measuring device to determine the position of a control element, accurately and at high temperatures.
A further object of the invention is to provide such a measuring device which obviates the need for a mechanical potentiometer by the use of a temperature-resistant Hall sensor and the special design of a permanent magnet, which is connected to a control element by a spindle. By virtue of the Hall effect, the Hall sensor delivers an output signal, during adjustment movement of the control element and thus of the position of the permanent magnet relative to the Hall sensor, that is preferably linearly proportional to the adjustment movement of the control element. At the same time, the Hall sensor is programmed to correct temperature-related measurement errors.
The permanent magnet is configured axially and radially or diametrally and is mounted centrally or eccentrically on the spindle, so that, for example, the position of an exhaust-gas return valve (EGR valve) can be determined.
Since the Hall sensor is programmable, the measuring device can be designed in modular form by means of a switching circuit such as an ASIC unit. The measuring device has space-saving design, and it has constant interface outputs. Calibration and programming of the Hall sensor of the measuring device are achieved during in-circuit use, i.e. when it is being used for the design purpose, and otherwise necessary preprogramming is obviated.
By virtue of this feature of the measuring device, it is capable of checking its functional response by an additional self-test signaling errors that have occurred.
REFERENCES:
patent: 4893502 (1990-01-01), Kubota et al.
patent: 5659389 (1997-08-01), Hieb et al.
patent: 3345804 (1985-06-01), None
patent: 4405513 (1995-08-01), None
patent: 4408056 (1997-04-01), None
patent: 197 09 087 (1998-09-01), None
Burger Frank
Ludwig Norbert
Ladas and Parry
Patidar Jay
Pierburg AG
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