US 9,176,159 B2 · Variable reluctance sensor interfaces with signal pre-processing and methods of their operation

Abstract

The embodiments described herein can provide a variable reluctance sensor (VRS) interface that may reduce the probability of erroneous transitions in a resulting generated detect signal. As such, the VRS interface can improve the accuracy of position and/or motion determinations, and thus can improve the performance of a wide variety of devices that use variable reluctance sensors. To facilitate this, the VRS interface includes a pre-processing circuit configured to modify a VRS signal to prevent the modified VRS signal from dropping below a threshold value and generating erroneous transitions in the detect signal pulse between leading and lagging edges of a tooth. In one embodiment the pre-processing circuit comprises a peak and hold circuit. In another embodiment the pre-processing circuit comprises a resistor-capacitor circuit. In either case the pre-processing circuit can prevent erroneous transitions in the detect signal and thus may improve the performance and accuracy of the system.

Claims20

Dependent claims

A variable reluctance sensor interface for processing a variable reluctance sensor signal that reflects a magnetic flux variation that occurs when a tooth passes by a variable reluctance sensor, wherein the tooth has a leading tooth edge and a trailing tooth edge, the variable reluctance sensor interface comprising:

a pre-processing circuit configured to modify the variable reluctance sensor signal to prevent the variable reluctance sensor signal from dropping below a second threshold value between a first portion of the variable reluctance sensor signal corresponding to the leading tooth edge and a second portion of the variable reluctance sensor signal corresponding to the trailing tooth edge;
a leading edge comparator including a first input configured to receive the modified variable reluctance sensor signal and including an output configured to provide a leading edge signal responsive to the modified variable reluctance sensor signal reaching a first threshold value;
a trailing edge comparator including a first input configured to receive the modified variable reluctance sensor signal and including an output configured to provide a trailing edge signal responsive to the modified variable reluctance sensor signal reaching the second threshold value;
and
a post-processing circuit configured to receive the leading edge signal and the trailing edge signal and generate a detect signal pulse having a width corresponding to a timing difference between the leading edge signal and the trailing edge signal.

2 more elements

A capacitor discharge ignition system for an internal combustion engine, comprising:

a variable reluctance sensor configured to sense passing of at least one tooth on a wheel in an internal combustion engine, the variable reluctance sensor configured to generate a variable reluctance sensor signal;
a pre-processing circuit configured to modify the variable reluctance sensor signal to prevent the variable reluctance sensor signal from dropping below a second threshold value between a first portion of the variable reluctance sensor signal corresponding to a leading tooth edge and a second portion of the variable reluctance sensor signal corresponding to a trailing tooth edge;
a leading edge comparator including a first input configured to receive the modified variable reluctance sensor signal and including an output configured to provide a leading edge signal responsive to the modified variable reluctance sensor signal reaching a first threshold value;
a trailing edge comparator including a first input configured to receive the modified variable reluctance sensor signal and including an output configured to provide a trailing edge signal responsive to the modified variable reluctance sensor signal reaching the second threshold value;
a post-processing circuit configured to receive the leading edge signal and the trailing edge signal and generate a detect signal pulse having a width corresponding to a timing difference between the leading edge signal and the trailing edge signal;
and
an ignition control unit configured to control ignition timing based at least in part on the detect signal pulse.

4 more elements

Dependencies are inferred from the claim text.

Variable reluctance sensor interfaces with signal pre-processing and methods of their operation

Life of this patent

Variable reluctance sensor interfaces with signal pre-processing and methods of their operation

Life of this patent

Abstract

Claims20