Method for processing a signal of a pressure measuring device inside an internal combustion engine

A method of measuring a pressure in a combustion chamber of a cylinder in a precise manner using a device for processing a signal of a pressure measuring device (DP) inside an internal combustion engine, said device including:

• a pressure measuring sensor (800) supplying an output voltage signal (SB) representing the pressure within the internal combustion engine, the signal (SB) including “plateau” phases during which the voltage changes according to a more or less linear function as a function of time, and voltage peak phases representing the combustion pressure peaks,
• a processing unit (500) connected to said pressure measuring sensor,
• the method including the following steps:
• I) acquisition of the values of the signal (SB) by the processing unit (500),
• II) detection by the processing unit (500) of the voltage peaks of the signal (SB) representing the combustion pressure peaks,
• the method being characterized in that it furthermore includes the following steps:
• III) calculation by the processing unit (500) of a first duration (Dt1) between a first time (t0) corresponding to a first combustion pressure peak (P0) and a second time (t1) corresponding to a second combustion pressure peak (P1), consecutive to the first combustion pressure peak (P0),
• IV) calculation by the processing unit (500) of a correction start time (tc1), located in a plateau phase between two combustion peaks, and defined by:
• tc1=t1±x1*Dt1
• where:
• tc1 is the correction start time,
• T1 is a second time corresponding to a second combustion pressure peak,
• Dt1 is a first duration between the first time (t0) and the second time (t1),
• x1 is a first constant with a value varying between 0.1 and 0.9,
• V) measurement by the processing unit (500) of a value of the signal (VOFF1) at the correction start time (tc1),
• VI) correction by the processing unit (500) of the signal (SB), on the basis of the correction start time (tc1) in relation to a reference value (VREF) and obtaining of a first processed signal (S) such that:
• S=SB−VOFF1+VREF
• Where SB is the signal at the pressure measuring sensor output,
• VOFF1 is the value of the signal at the correction start time (tc1),
• VREF is the reference value.