Electricity: measuring and testing – Magnetic – Displacement
Patent
1994-08-29
1997-02-25
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Displacement
123414, 324166, 327 18, 327 79, 377 17, H03K 5153, F02P 767, G01D 5244, G01B 730
Patent
active
056062575
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to a device for signal shaping or regeneration and for detecting reference marks, in which a square-wave signal is formed from a sinusoidal signal with a singularity and the singularity is unambiguously detected.
As is known for evaluation of a sinusoidal signal, this signal must first be transformed into a square-wave signal to simplify evaluation. Such sinusoidal signals occur, for example, as output signals of inductive sensors which sense bodies with different markings which move past these sensors.
In particular, in detecting the position of the crankshaft or camshaft of an internal combustion engine, transmitter disks which are connected with these shafts and have a number of markings are sensed by inductive sensors and the output signal obtained in so doing is evaluated in the control device of the motor vehicle. Before being evaluated, the output signal of the inductive sensor is changed into a square-wave signal. The sinusoidal signal is compared with a threshold value and a change in the flank or edge of the square-wave signal occurs when this threshold value is exceeded. Such an arrangement is known, for example, from DE-OS 31 27 220.
In this known device, it is necessary to change the threshold value as a function of the anticipated signal height, since the height of the output signal of the inductive transmitter depends extensively on the speed at which the markings pass by and a fixed threshold value would therefore cause excessive inaccuracy.
SUMMARY OF THE INVENTION
The device according to the invention for forming a square-wave signal and detecting a reference mark from a sinusoidal signal with at least one singularity characteristic of the reference mark includes means for testing whether a transition between a positive value and a negative value of the sinusoidal signal occurs at zero-axis crossing of the sinusoidal signal; means for monitoring the negative half-wave immediately following each of the zero-axis crossings to determine whether the negative half-wave is greater than or less than a predetermined threshold value; logic means for producing a level change to form a square pulse when the transition between the positive value and the negative value is detected at a zero-axis crossing and when, at the same time, the negative half-wave is greater than the predetermined threshold value immediately following the detected transition and means for measuring a time interval between the pulse edges of the square-wave signal to detect the at least one singularity and thus the reference mark.
The device according to the invention has the advantage over the prior art that the sinusoidal signal is transformed into a square-wave signal in a very accurate manner, interference is extensively suppressed, and the singularity of the sinusoidal signal caused by the reference mark is detected in a particularly reliable manner and the square-wave signal is also formed in the region of the singularity at the correct location.
This advantage is achieved in that the zero-axis crossing of the sinusoidal signal is used to form the reversing edges of the square-wave signal or to change the level and the direction of crossover of the signal is detected and checked in order to ascertain whether the sensor element is located opposite an angle mark or a gap when crossing the zero axis. In addition, the negative half-wave is monitored to determine whether or not it falls short of the threshold value.
For positive identification of the singularity of the sinusoidal signal, the distances between the switching edges are determined; the falling edge of the square-wave signal following the singularity is used for synchronization.
The circuit arrangement used in the device according to the invention has the advantage of a simple construction and can advantageously be integrated by CMOS technique and can accordingly be used according to the specific application. The linear processing of the input signal within a broad range and the extensive frequency response a
REFERENCES:
patent: 3767938 (1973-10-01), Kueper
patent: 4233592 (1980-11-01), Leichle
patent: 4262251 (1981-04-01), Fujishiro et al.
patent: 4797827 (1989-01-01), Cockerham
patent: 5430370 (1995-07-01), Rooke
patent: 5446375 (1995-08-01), Perkins
Buro Davide
Krauter Immanuel
Robert & Bosch GmbH
Strecker Gerard R.
Striker Michael J.
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