A system for an engine to determine in situ under specified conditions the auto-ignition quality of the fuel used in a compression ignition engine is provided. The system may include an ion current sensor. The ion current sensor may access an engine cylinder for obtaining ion current data. A control unit may be in communication with the ion current sensor for receiving the ion current data. The control unit being configured to determine the auto-ignition quality of the fuel based on features of the ion current data.

A pressure-measuring glow plug device includes a module housing, a glow plug configured to ignite a combustion mixture in a combustion chamber of an internal combustion engine, and a pressure-measuring device. The pressure-measuring device has a pressure sensor configured to detect the pressure in the combustion chamber. The glow plug is connected to the module housing by a flexurally elastic membrane. The force acting on the glow plug in the combustion chamber is transferred to the pressure sensor, which is supported on a supporting element by a preloading force. The supporting element is fastened rigidly to the module housing by a sensor housing. The glow plug device further includes a separate loading sleeve that is connected at one end to the pressure-transferring piece and at the other end to the supporting element. The loading sleeve is configured to apply the preloading force for the pressure sensor.

A pressure-measuring glow plug has a heating pin for igniting a combustion mixture of an internal combustion engine and a pressure sensor for detecting a combustion chamber pressure of the internal combustion engine. The pressure-measuring glow plug has a contacting unit which includes a carrier for accommodating a signal processing unit and a plug connection having connecting contacts in a plug housing. A glow module housing for accommodating the heating pin and the pressure sensor and an electronic module housing for accommodating the carrier are provided. The electronic module housing is connected at a glow module-sided connecting location to the glow module housing and, at a plug-sided connecting location, to the plug housing.

A combustion pressure sensor having a tubular housing extending in an axial direction DX, a displacement member disposed within the housing, and a tubular connection member which elastically connects the displacement member to the housing. The combustion pressure sensor has a housing weld W1 that connects the housing and the connection member At least a circumferential portion of the housing weld is a bulge housing weld RW1 which bulges in a radial direction DR.

A pressure sensor integrated glow plug inserted inside a cylinder of an internal combustion engine and used, the pressure sensor integrated glow plug being equipped with a housing, a rod-like heater element held with its distal end projecting from the housing, and a pressure sensor, with the heater element being held in the housing by a flexible member and configured in such a way that its position relative to the housing is displaceable, and with the pressure sensor being configured in such a way that it can receive pressure inside the cylinder because of the displacement of the heater element, wherein a heat-resistant fiber member carrying an oxidation catalyst component is disposed in an interstice between the housing and the heater element on the distal end side of the flexible member.

In a combustion pressure sensor, a sensor holder is installed in a housing. The sensor holder has an end contact surface. A load transfer member is installed in the housing. The load transfer member has a contact surface facing the end contact surface of the sensor holder. The contact surface of the load transfer member is in contact with the end contact surface of the sensor holder. One of the contact surface of the load transfer member and the end contact surface of the sensor holder has a concavely curved shape, and the other thereof has a convexly curved shape.

In an internal combustion engine which includes a combustion pressure sensor incorporated glow plug and sensor nonincorporated glow plugs, a first plug regression line Lp1 and the second plug regression line Lp2 are in such a relation that, at any temperature Tx within the temperature range Tr, a second voltage Vp2x is lower than a first voltage Vp1x; the resistance of a second electricity supply line is greater than the resistance of a first electricity supply line; and a first section regression line and a second section regression line are in such a relation that, at any temperature Tx within the temperature range Tr, an overall voltage deviation |Vc1xVc2x|, which is the absolute value of the difference between a third voltage Vc1x and a fourth voltage Vc2x, is smaller than a first-second plug voltage difference (Vp1xVp2x).

A glow plug adaptor for pressure measurement in a combustion chamber of an internal combustion engine includes an adaptor sleeve attached to an adaptor head that contains a pressure sensor with a diaphragm. A sealing shoulder can be screwed into an opening in a combustion chamber to provide a pressure-tight seal and permit passage of signal conductors from the pressure sensor through the adaptor sleeve. The adaptor head is tapered at the proximal combustion chamber end, and in the adaptor head a cavity is formed in such a way that the cavity is bounded by the diaphragm of the pressure sensor mounted therein and by a closed end wall of the adaptor head.

A pressure measuring glow plug includes: a housing in which a heating pin for igniting a combustion mixture of an internal combustion engine and a pressure measuring unit for recording a combustion chamber pressure of the internal combustion engine are situated. The heating pin has a glow current contact for an electric heating element. At the end of the heating pin facing away from the combustion chamber, a pressure transmitting element is fastened, which transmits the combustion chamber pressure acting on the heating pin to the pressure measuring unit. The pressure transmitting element is sleeve-shaped and forms an accommodation space for the glow current contact of the heating element.

What is described is a method for igniting a fuel/air mixture in a combustion chamber of an engine, wherein a pencil, which is electrically insulated with respect to walls of the combustion chamber and contains a heating resistor, is electrically heated to a temperature of at least 800 C. in the combustion chamber of the engine by applying a heating voltage, and a high voltage of at least 500 V, which is different from the heating voltage, is applied to the pencil and thereby ions are generated in the combustion chamber by field emission of electrons. The invention additionally relates to an ignition system and a glow plug.