System for discrimination of spurious crank encoder signals
View Patent ↗A system for discrimination of spurious crankshaft encoder signals. A position encoder connected to an engine crankshaft sends a pulsed signal indicative of crankshaft rotational performance to an engine controller. The controller is programmed to trigger an interrupt service routine (ISR) on every falling or rising edge of each pulse. The ISR calculates and stores the period of each pulse and the period of the previous pulse and calculates the rotational speed and instantaneous acceleration or deceleration of the engine at all times. The controller is further programmed with realistic engine acceleration and deceleration limits and recognizes a next signal only within a time window corresponding to those limits and the engine speed. Signals arriving outside the calculated time window are considered spurious and are rejected. The system improves engine performance by preventing loss of synchronization between spark and fuel injection and piston and valve timing.
1. A system for discrimination of spurious crank encoder signals in an internal combustion engine, comprising:
a) a crankshaft position encoder for generating a pulsed signal indicative of rotational performance of said crankshaft; and
b) an engine controller for receiving said pulsed signal from said encoder and for generating signals controlling engine functions including but not limited to spark and fuel injection timing,
wherein said controller
computes from said encoder generated signals a period between a first pulsed signal and a second pulsed signal indicative of engine speed,
applies a calculation to determine a rate of engine acceleration/deceleration,
calculates an expected time window for receiving a third pulsed signal,
recognizes said third pulsed signal that arrives within the expected time window, and
rejects said third pulsed signal that arrives outside the expected time window.
2. A method for discrimination of spurious crankshaft encoder signals in an internal combustion engine having a crankshaft and a target wheel mounted for rotation with said crankshaft, said target wheel having a predetermined number of spaced apart teeth, each tooth having a rising edge and falling edge, said engine further having a crankshaft position encoder for generating a pulsed signal indicative of rotational performance of the crankshaft, and an engine controller for receiving the pulsed signal from the encoder and for controlling the timing of engine functions including but not limited to spark and fuel injection timing,
the method comprising the following steps:
a) triggering an interrupt service routine that generates a pulsed signal from every falling and rising edge of each tooth;
b) calculating and storing a period of interrupt from each successive pulsed signal;
c) comparing the periods of interrupt from successive pulsed signals to calculate engine speed and an instantaneous rate of acceleration or deceleration of the engine;
d) using the calculated rate of engine acceleration or deceleration and the engine speed to calculate a predicted a time window for reception of the next successive pulsed signal;
e) recognizing a next successive pulsed signal arriving within the predicted time window; and
f) rejecting as spurious a next successive pulsed signal arriving outside the predicted time window.
3. A method in accordance with claim 2 comprising the further step of regulating the timing of spark and fuel injection in said engine in response to said received signal from said encoder.