A pressure sensor includes a sensor assembly and an evaluation unit. The; sensor assembly includes a sensor and an electrode arrangement. The sensor is configured to generate signals under the action of a pressure profile. The electrode arrangement is configured to transmit the signals to the evaluation unit. The evaluation unit includes an electric circuit board. The electric circuit board includes a base material that is electrically insulating with a specific volume resistance that is at least equal to 10.sup.15 cm at room temperature. The electric circuit board includes a high temperature region facing the sensor assembly and a normal temperature region that faces away from the sensor assembly.

A pressure sensor includes a sensor assembly and an evaluation unit. The; sensor assembly includes a sensor and an electrode arrangement. The sensor is configured to generate signals under the action of a pressure profile. The electrode arrangement is configured to transmit the signals to the evaluation unit. The evaluation unit includes an electric circuit board. The electric circuit board includes a base material that is electrically insulating with a specific volume resistance that is at least equal to 10.sup.15 cm at room temperature. The electric circuit board includes a high temperature region facing the sensor assembly and a normal temperature region that faces away from the sensor assembly.

A pressure sensor includes a connection portion provided with a screw portion configured to fix the pressure sensor to a combustion chamber of a vehicle engine; a hollow liquid-enclosing container fixed to one end of the connection portion; a pressure transmission fluid enclosed inside the liquid-enclosing container; a diaphragm fixed to one end of the liquid-enclosing container and elastically deformed when receiving pressure to transmit the pressure to the pressure transmission fluid; a pressure detection element fixed to the other end of the liquid-enclosing container and detecting the pressure transmitted to the pressure transmission fluid and converts the detected pressure into an electric signal; and a heat-dissipating rod provided inside the liquid-enclosing container. The connection portion and the liquid-enclosing container, and the connection portion and the diaphragm are mechanically connected to each other by welding or the like.

A knock sensor including a body, having a detection assembly able to measure vibrations, and a metal mount having a support ring on which the detection assembly rests, a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body. The mount includes a lower flange below the support ring and the lower flange is bored with attachment holes, which improve its sealing.

A knock sensor including a body, having a detection assembly able to measure vibrations, and a metal mount having a support ring on which the detection assembly rests, a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body. The mount includes a lower flange below the support ring and the lower flange is bored with attachment holes, which improve its sealing.

A pressure sensor including a housing extending along an axial line, a diaphragm fixed to a front-end side of the housing, a piezoelectric unit disposed in a hole in the housing and including a piezoelectric element, a transmission member that transmits deformation of the diaphragm to the piezoelectric unit, and a guide member having a through hole extending along the axial line and surrounding the piezoelectric unit in the through hole. (SL/AL)0.26 is satisfied in the cross section perpendicular to the axial line passing through the piezoelectric element, where SL is the maximum value of the distance in the radial direction between the center of the through hole and the center of the piezoelectric element and AL is the maximum value of the distance in the radial direction between the outside surface of the piezoelectric element and the center of the through hole.

A pressure sensor including a housing extending along an axial line, a diaphragm fixed to a front-end side of the housing, a piezoelectric unit disposed in a hole in the housing and including a piezoelectric element, a transmission member that transmits deformation of the diaphragm to the piezoelectric unit, and a guide member having a through hole extending along the axial line and surrounding the piezoelectric unit in the through hole. (SL/AL)0.26 is satisfied in the cross section perpendicular to the axial line passing through the piezoelectric element, where SL is the maximum value of the distance in the radial direction between the center of the through hole and the center of the piezoelectric element and AL is the maximum value of the distance in the radial direction between the outside surface of the piezoelectric element and the center of the through hole.

A pressure sensor includes an evaluation unit and a sensor assembly, which includes a sensor and an electrode arrangement. The sensor generates signals under the action of a pressure profile, and the electrode arrangement transmits the signals to the evaluation unit, which includes an evaluation unit housing, an electric circuit board and a reinforcement element, which is arranged in a radial plane between the electric circuit board and the evaluation unit housing. The reinforcement element is mechanically connected to the electric circuit board and dampens mechanical resonance vibrations of the electric circuit board that occur in the radial plane.

A pressure sensor includes an evaluation unit and a sensor assembly, which includes a sensor and an electrode arrangement. The sensor generates signals under the action of a pressure profile, and the electrode arrangement transmits the signals to the evaluation unit, which includes an evaluation unit housing, an electric circuit board and a reinforcement element, which is arranged in a radial plane between the electric circuit board and the evaluation unit housing. The reinforcement element is mechanically connected to the electric circuit board and dampens mechanical resonance vibrations of the electric circuit board that occur in the radial plane.

An in-cylinder pressure sensor is provided. It is determined whether a cylinder for which the in-cylinder air-fuel ratio is to be calculated is a rich cylinder or a lean cylinder. A polytropic index in the expansion stroke is calculated from the in-cylinder pressure detected by the in-cylinder pressure sensor. The calculated polytropic index m is corrected based on an operational condition parameter of an internal combustion engine. An in-cylinder air-fuel ratio is calculated based on the corrected polytropic index m in the expansion stroke, the result of the determination of whether the cylinder is a rich cylinder or a lean cylinder, and an m-A/F curve.