Rotation detecting sensor

Abstract

Disclosed is a rotation detecting sensor suitable for use under a vibration-abundant condition as e.g. a sensor disposed in an automobile body for detecting rotation of an engine or ABS. The sensor includes a detecting element for detecting rotation of a rotary body as a change in a magnetic flux and outputting a signal and an integrated circuit for processing the amplified signal into a pulse corresponding to the detected rotation of the rotary body. The signal processing includes an initialization such as a gain adjustment for obtaining an appropriate gain for use in the subsequent process of conversion of the amplified signal to the pulse. According to this invention, a re-initialization is effected to obtain a new initial value such as a new gain if the previously effected initialization is determined inappropriate.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a rotation detecting sensor comprising a detecting element for detecting rotation of a rotary body as a change in magnetic flux and outputting an output signal corresponding thereto, initializing means for effecting an initialization including at least a gain adjustment for obtaining a desired gain as an initial value based on variation in the output signal upon lapse of a predetermined number of rotations of the rotary body, means for amplifying said output signal together with said gain to provide an amplified signal, and pulse generating means for generating a pulse corresponding to the rotation of said rotary body based variation in said amplified signal amplified based on said gain. [0003] 2. Related Art [0004] A rotation detecting sensor of the above-noted type is designed for detecting change in a magnetic flux which occurs in association with rotation of a rotary body. More p...

AI Technical Summary

Benefits of technology

The present invention provides a rotation detecting sensor that can accurately detect the rotation of a rotary body and generate a pulse with minimal disturbance in the pulse generation timing. The sensor includes an initializing means for adjusting the initial gain of the sensor based on the variation in magnetic flux during the rotation. The sensor also has a threshold value for delimiting the pulse generating timing, and can re-initialize to obtain a new initial value if the initial value is determined to be inappropriate. The sensor can be used in various applications such as vibration detection in machines and can still effect an optimal pulse waveform even in the presence of vibration. The sensor is designed to be integrated into a single integrated circuit for mass production and stability of performance.

Problems solved by technology

In such case, the vibration of the machine body per se such as the automobile body can cause a periodic change in the separating distance between the rotary body and the detecting element even when the rotary body is not rotating.

Then, if the initialization is effected under such condition in the presence of inadvertent vibration-associated variation (i.e. vibration noise) in the output signal from the detecting element, the gain adjustment will result in an excessively large gain, since the vibration noise is a very small change in the magnetic flux.

Hence, when this output signal is amplified together with the excessively large gain previously obtained, the resultant amplified signal will have a value exceeding a maximum signal processing range of the integrated circuit.

Then, if the pulse generation is effected under this condition, there will occur such inconvenience as disturbance in the pulse generation timing.

Obviously, such solutions are undesirable because of disadvantageous reduction in the sensor sensitivity.

Hence, there is the possibility of disturbance in the output pulse while the initialization is being effected.

This solution is also disadvantageous or not practical because of significant cost increase expected from the provision of the additional sensor.

In this condition, however, the hysteresis widths of the pulse generation threshold values are extremely small.

Thereafter, when the rotary body actually begins to rotate, because of the excessively large gain obtained previously, the resultant amplified signals should exceed the maximum signal processing range of the circuit.

As a result, if the sensor detects the rotational speed of the rotary member and effects the predetermined control scheme in the manners described above, proper performance cannot be obtained with this sensor.

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