Automatic calibration method for a motor vehicle a camshaft sensor

Automatic calibration method for a motor vehicle camshaft sensor, said engine having at least one camshaft (16), a toothed encoded target (14) associated with this camshaft, and a magnetic field sensor (10) placed in the proximity of the target to detect magnetic field variations caused by the passage of the teeth of the target in the proximity of the sensor, said sensor delivering an electrical signal representing teeth and intervals of the target as a function of a predetermined detection threshold K which is a function of the amplitude of the magnetic field, said method consisting of continuously measuring the value of the magnetic field during a time corresponding to at least one revolution of the target, said method being characterized in that it also consists of:

• determining the maximum amplitude Amax of the field measured during this time, by determining:
• the minimum value Bmin of the field received by the sensor during at least one revolution of the target,
• the maximum value Bmax-max of the field received by the sensor during at least one revolution of the target,
• the difference between the maximum value Bmax-max of the field received for the set of teeth and the minimum value Bmin of the field received during at least one revolution of the target, and
• determining the minimum amplitude Amin of the field measured during this time, by determining:
• the minimum value Bmax-min of the field received by the sensor during at least one revolution of the target,
• the minimum value Bmax-min of the maximum field for the set of teeth during at least one revolution of the target, and
• the difference between the minimum value Bmax-min of the field received and the minimum value Bmin of the field received during at least one revolution of the target, and
• determining the auto-adaptive threshold K′ of the detection of the teeth and intervals of the target, to be applied to the signal received from the magnetic sensor, with allowance for the geometrical and/or assembly imperfections of the target, according to the following formula:
• K
• ′
• =
• A
• min
• A
• max
• ×
• K
• .