Electricity: measuring and testing – Magnetic – Displacement
Patent
1996-11-05
1998-08-18
O'Shea, Sandra L.
Electricity: measuring and testing
Magnetic
Displacement
52420725, G01B 730, G01D 514, G01P 1300, F02D 4124
Patent
active
057962472
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
The subject matter of this application is closely related to that of U.S. patent application Ser. No. 08/513,778, filed Sep. 29, 1995, and now U.S. Pat. No. 5,721,486.
BACKGROUND OF THE INVENTION
The invention pertains to a process and a device for determining the angular position of a rotating shaft. With this invention, a Hall sensor in a suitable Hall cell is positioned in front of a pulse wheel that is connected with the shaft; the pulse wheel is provided with at least one tooth, which has one rising tooth flank and one falling tooth flank, and at least one tooth gap. The Hall cell determines the time history of a magnetic flux density, which is generated by the pulse wheel, and delivers a Hall voltage signal. In an output circuit, the Hall voltage signal is converted into a differentiated signal; from that, a square pulse sequence is generated.
A process and a device for determining the position of rotating shafts has been suggested in the published patent application No. DE 43 43 198. A pulse wheel which is provided with teeth is moved with an angular velocity w in front of a Hall sensor with associated magnet. The time history of a magnetic flux density B caused by the pulse wheel is recorded by the Hall sensor as a Hall voltage curve. The recorded signal is differentiated in a dynamic selection circuit, and in a turning point detection circuit, there is generated from the differentiated signal a dynamic output signal which more or less represents the teeth of the pulse wheel. The disadvantage is the fact that by means of the above-mentioned output circuit, a measurement signal is not output until the pulse wheel has attained a certain number of revolutions per unit of time. The angular position cannot be determined below this minimum-revolution number, nor even at the revolution number zero which corresponds to a standstill of the wheel. In addition, the danger exists that noise can superimpose interference on the output signal, which can lead to a corruption of the results of the measurement.
In addition, it is known from published application No. DE 42 09 212 A1 that a differential Hall sensor circuit with two Hall sensors can be placed in the region of a rotating toothed pulse wheel with a permanent magnet. As a result of a specific pitch, the rotating toothed wheel generates a phase-displaced signal in the two Hall sensors. Thus, at least two teeth have to be sensed in order to determine the position of the toothed wheel. This also requires a relatively high velocity of the pulse wheel.
SUMMARY OF THE INVENTION
In accordance with the above, the objective then exists of providing a process and a device for determining the angular position of a rotating shaft which will allow the position of the shaft to be determined beginning from a standstill and going to the highest permissible nominal speed, in conjunction with which, it should be possible for the systematics to suppress noise pulses.
In accordance with the invention, this objective is achieved by means of a process in which with the shaft, rising tooth flank and one falling tooth flank, and at least one tooth gap, revolutions/min.
The advantages achieved with the invention consist particularly in the fact that the position of a shaft can be determined at a standstill, at low revolutions and up to the highest number of revolutions, such as, for example, at 1,500 revolutions/min 3,000 revolutions/min, 10,000 revolutions/min. As a result of the determining of the exact angular position of a shaft, starting from 0, it is, for example, possible to exactly control the injection of gasoline for the individual cylinders right from the start, and subsequently, at higher rotational speeds. Fuel can be saved in this way. Since the dynamic output signal consists of the superimposing of a square pulse sequence on the partial pulse lengths and gaps, noise which may occur and become superimposed on the measurement signal can be suppressed.
The square pulse sequence can be produced by means of processes which a
REFERENCES:
patent: 4982155 (1991-01-01), Ramsden
patent: 5008841 (1991-04-01), McElroy
AB Electronik GmbH
O'Shea Sandra L.
Patidar Jay M.
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