Pressure measuring device and corresponding method

A device for measuring the cylinder pressure of an internal combustion engine, the operation of which comprises a plurality of successive cycles, each cycle being broken down into at least first and second strokes, the measuring device comprising at least one pressure sensor (1) consisting of at least one piezoelectric element associated with a capacitive element, and an output (10) generating a first voltage (V1) representative of a pressure (F) applied to the piezoelectric element, the device further comprising:

• a filtering module (2) comprising at least one input (20) and one output (21), capable of filtering parasitic low-frequency voltages present at its input (20), and of generating on its output (21) a second voltage (V2) free of these parasitic low-frequency voltages;
• a control module (3) capable of delivering a control signal (Scom) that is dependent on a switching parameter correlated with a stroke, among the first and second strokes, in which the engine is operating;
• a switching module (4), in response to the control signal (Scom), capable of disconnecting the input (20) of the filtering module (2) from the output (10) of the pressure sensor (1) during the first stroke, and of connecting the input (20) of the filtering module (2) to the output (10) of the pressure sensor (1) during the second stroke;
• and
• an output (5) generating an output voltage (Vout) equal to the first voltage (V1) during the first stroke, and equal to the second voltage (V2) during the second stroke,
• characterized in that the first stroke corresponds to a compression stroke or to a combustion-expansion stroke, and in which the second stroke corresponds to an intake stroke or to an exhaust stroke.

A method for measuring the cylinder pressure of an internal combustion engine, the operation of which comprises a plurality of successive cycles, each cycle being broken down into at least first and second strokes, the method consisting in at least generating a first voltage (V1) representative of a pressure (F) applied to a piezoelectric element associated with a capacitive element, characterized in that it further consists in:

• delivering a control signal (Scom) that is dependent on a switching parameter correlated with an engine stroke, among the first and second strokes, in which the engine is operating;
• when the switching parameter is correlated with the first stroke, generating an output signal (Vout) equal to the first voltage (V1), in response to the control signal (Scom);
• and
• when the switching parameter is correlated with the second stroke, filtering the parasitic low-frequency voltages present in the first voltage (V1), and generating an output signal (Vout) equal to a second voltage (V2) representative of the first voltage (V1) free of these low-frequency voltages, in response to the control signal (Scom),
• the first stroke corresponding to a compression stroke or to a combustion-expansion stroke, and the second stroke corresponding to an intake stroke or to an exhaust stroke.