Method for adapting a detection threshold of a crankshaft sensor for motor vehicle

Patent metadata

Field	Value
Publication number	US-10215591-B2
Application number	US-201514727356-A
Country	US
Kind code	B2
Filing date	Jun 1, 2015
Priority date	Jun 3, 2014
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

Disclosed is a method for adapting a detection threshold (S 1 ) of a magnetic field sensor for a crankshaft of a motor vehicle equipped with the “stop & go” function, the sensor delivering a signal (B) of variations of magnetic field having two states, such as: State 1 : when the crankshaft is rotating: the signal includes rising fronts and falling fronts, State 2 : when the crankshaft is stopped: the signal has an aperiodic progressive drift (ΔT AR ). The method includes for state 2 steps making it possible to estimate the variation (Δ 1 , Δ 2 , Δ 3 , Δ 4 . . . Δ i ) of the value (V 1 , V 2 . . . V i ) of the signal (B) during the stopped phase of the crankshaft in order to adapt the detection threshold (S 1 ) to a new value (S 4 ) applicable for the detection of the first tooth upon restart of the engine (R).

First claim

The invention claimed is:

1. A method for adapting a detection threshold of a magnetic field sensor for a crankshaft of an engine of a motor vehicle, the engine including a processor, the crankshaft including at least one toothed target, the magnetic field sensor being configured to deliver a signal of variations of magnetic field to the processor, the processor being configured to process the signal delivered by the sensor, the signal of variations of magnetic field delivered by said sensor having two States that include:
State 1 : when the crankshaft is rotating, the signal comprises rising fronts and falling fronts, representative of teeth and troughs of the target, and
State 2 : when the crankshaft is stopped, the signal has an aperiodic progressive drift,
in order to account for a thermal drift sustained by the signal when the crankshaft is stopped to improve precision of the sensor when the engine is restarted from a warm condition, the adaptation method comprising:
detecting, in the State 1 , the rising fronts and falling fronts of the signal on the basis of at least one detection threshold; and
in the State 2 ,
step 1: detecting the stopping of the crankshaft by the absence during a predetermined period of detection of rising fronts and falling fronts over the signal based on the detection threshold,
step 2: after the predetermined period, measuring the value of the signal at successive intervals,
step 3: for each interval, calculating the variation of the value of the signal,
step 4: calculating a new detection threshold by the addition, to the detection threshold previously used over the previous interval, of the variation of the value of the signal calculated over said previous interval, and
step 5: repeating steps 3 and 4 as long as there is no rising front or falling front detected on the basis of the antepenultimate detection threshold used prior to the addition in step 4; and

subsequently detecting, by the magnetic field sensor and the processor, a position of the crankshaft using the new calculated detection threshold after the engine is restarted from the warm condition after the crankshaft is stopped.

2. The adaptation method as claimed in claim 1 , wherein the successive intervals are of identical duration.

3. The adaptation method as claimed in claim 2 , wherein the predetermined period is proportional to a speed of rotation of the crankshaft.

4. The adaptation method as claimed in claim 2 , wherein the predetermined period is at least equal to a period comprising a rising front and a falling front prior to the stopping of the crankshaft.

5. The adaptation method as claimed in claim 1 , wherein the predetermined period is proportional to a speed of rotation of the crankshaft.

6. The adaptation method as claimed in claim 1 , wherein the predetermined period is at least equal to a period comprising a rising front and a falling front prior to the stopping of the crankshaft.

7. A system for device for measuring the position of a crankshaft of a motor vehicle engine, said device comprising:
a crankshaft;
at least one toothed target associated with said crankshaft;
a magnetic field sensor, arranged in the proximity of the toothed target, said sensor delivering a signal of variations of magnetic field caused by the rotation of the toothed target:
when the crankshaft is rotating, the signal comprising rising fronts and falling fronts, representative of the teeth and troughs of the target, and
when the crankshaft is stopped, the signal having an aperiodic progressive drift; and

a processor configured to process the signal delivered by the sensor, the processor being configured to:
detect rising fronts and falling fronts of the signal on the basis of at least one detection threshold,
detect the stopping of the crankshaft by the absence during a predetermined period of detection of rising fronts and of falling fronts over the signal,
after the predetermined period, measure the value of the signal at successive intervals,
for each interval, calculate the variation of the value of the signal,
for each interval, calculate a new detection threshold by the addition, to the threshold detection previously used over the previous interval, of the variation of the value of the signal calculated over said previous interval,
detect the rotation of the crankshaft by using the antepenultimate calculated detection threshold,

subsequently detecting, by the magnetic field sensor and the processor, a position of the crankshaft using the new calculated detection threshold after the engine is restarted from a warm condition after the crankshaft is stopped.

8. A detection system comprising:
a processor; and
a magnetic field sensor for a motor vehicle crankshaft having at least one toothed target, said sensor being associated with the processor and configured to deliver a signal of variations of magnetic field to said processor, the magnetic field sensor being configured to:
when the crankshaft is rotating, provide the signal comprising rising fronts and falling fronts, representative of teeth and troughs of a target, and
when the crankshaft is stopped, provide the signal having an aperiodic progressive drift,

wherein the processor is configured to:
detect rising fronts and falling fronts of the signal on the basis of at least one detection threshold,
detect the stopping of the crankshaft by the absence, during a predetermined duration of detection of rising fronts and falling fronts, over the signal,
after the predetermined duration, measure the value of the signal at successive intervals,
for each interval, calculate the variation of the value of the signal,
for each interval, calculate a new detection threshold by the addition, to the detection threshold used previously over the previous interval, of the variation of the value of the signal calculated over said previous interval, and
detect the rotation of the crankshaft by using the antepenultimate calculated detection threshold,

wherein a position of the crankshaft is subsequently detected by the magnetic field sensor and the processor, using the new calculated detection threshold after the engine is restarted from a warm condition after the crankshaft is stopped.

9. A motor vehicle comprising a sensor as claimed in claim 8 .

Assignees

• Continental Automotive France
• Continental Automotive Gmbh

Inventors

• Mirassou David
• Larue Marie-Nathalie

Classifications

• G01D18/002

  Automatic recalibration (G01D18/008 takes precedence) · CPC title

• G01P21/00

  Testing or calibrating of apparatus or devices covered by the preceding groups · CPC title

• G01P3/488

  delivered by variable reluctance detectors · CPC title

• G01P3/487

  delivered by rotating magnets · CPC title

• G01D5/145 Primary

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title