A cylinder head assembly for an internal combustion engine has a housing (12) in which a plurality of elements (18, 44) are arranged. An optical duct (24) is formed in the housing (12) and is assigned to at least one of the elements (18). The optical duct (24) is assigned an infrared detector (28) that is designed to detect infrared radiation (30) from the at least one element (18) through the optical duct (24) to determine a temperature (T) of the at least one element (18).

A system to detect the presence of a catalyst includes an exhaust gas tube, a first temperature sensing device, a second temperature sensing device, a flow rate measurement device, and a processing device. The first temperature sensing device measures a first temperature of exhaust gas upstream of the exhaust gas tube. The second temperature sensing device measures a second temperature of the exhaust gas downstream of the exhaust gas tube. The processing device estimates an expected time delay between the measured inlet and outlet exhaust gas temperatures corresponding to a system with a catalyst present. The processing device may also determine the presence of a catalyst by comparing the measured second temperature to the measured first temperature and comparing the measured second temperature to an estimated delayed first temperature associated with the expected time delay.

A gas-sensor control device includes a sweep circuit, a return sweep circuit, and a control portion. The sweep circuit energizes a detection current to flow through an oxygen sensor to calculates an impedance of the oxygen sensor. The return sweep circuit energizes a neutralization current to flow through the oxygen sensor in a direction opposite to a direction of the detection current, so as to remove electricity from the oxygen sensor that is energized by the detection current. The control portion executes a detection of an off failure of the sweep circuit and the return sweep circuit, only based on a sensor voltage acquired in a time period where the neutralization current flows through the oxygen sensor, and a threshold.

A combustion speed, for example, is estimated or evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. An increase rate of a heat generation rate relative to a change in a crank angle in a heat generation rate increasing period (e.g., a first-half combustion period a) in which the heat generation rate increases after ignition of an air-fuel mixture is defined as a heat generation rate gradient b/a that is one of characteristic values of the heat generation rate waveform. The heat generation rate gradient is estimated based on a fuel density (e.g., fuel density .sub.fuel@dQpeak at heat generation rate maximum time) at a predetermined time set in advance in the heat generation rate increasing period so as to produce the heat generation rate waveform using the estimated heat generation rate gradient.

In order to provide a flow rate measurement device that can measure a flow rate of a sample fluid passing a tube body with high accuracy even though temperature irregularity of the sample fluid generates along a radial direction of the tube body, the flow rate measurement device comprise a temperature measurement device that measures a mean temperature of a sample fluid discharged from an internal combustion engine or temperature distribution of the sample fluid along a radial direction of the tube body, and a flow rate of the sample fluid is measured based on the mean temperature or the temperature distribution measured by the temperature measurement device.

The present invention pertains to a system for monitoring measured NOx values in an exhaust component, comprising a first NOx sensor having a first predetermined maintenance interval and a second NOx sensor having a second predetermined maintenance interval. The first and second NOx sensors are configured such that their first and second maintenance intervals are staggered. The present invention furthermore pertains to a method for monitoring measured NOx values in an exhaust component, comprising the steps of installing a first NOx sensor having a first predetermined maintenance interval in an exhaust component installing a second NOx sensor having a second predetermined maintenance interval after the first NOx sensor has been operating for a predetermined operation duration such that the first and second maintenance intervals are staggered by a maintenance timing offset.

A system to detect the presence of a catalyst includes an exhaust gas tube, a first temperature sensing device, a second temperature sensing device, a flow rate measurement device, and a processing device. The first temperature sensing device measures a first temperature of exhaust gas upstream of the exhaust gas tube. The second temperature sensing device measures a second temperature of the exhaust gas downstream of the exhaust gas tube. The processing device estimates an expected time delay between the measured inlet and outlet exhaust gas temperatures corresponding to a system with a catalyst present. The processing device may also determine the presence of a catalyst by comparing the measured second temperature to the measured first temperature and comparing the measured second temperature to an estimated delayed first temperature associated with the expected time delay.

An exhaust-gas aftertreatment system including an exhaust-gas module which has an inlet section and an outlet section. The exhaust-gas aftertreatment system has at least one sensor fastening device which comprises at least two, preferably at least three, sensor fastening means that are angularly spaced apart from one another.

The sulfur poisoning of a three-way catalyst is intended to be detected with a high degree of accuracy. It is determined whether the sulfur poisoning of the three-way catalyst is made to be recovered, or a determination is made that the degree of sulfur poisoning of the three-way catalyst is higher when the concentration of NOx detected by an NOx sensor is high than when it is low, based on the concentration of NOx downstream of the three-way catalyst after the air fuel ratio of the exhaust gas flowing into the three-way catalyst has been made to change from a rich air fuel ratio to a lean air fuel ratio and before the air fuel ratio of the exhaust gas flowing out of the three-way catalyst changes to a lean air fuel ratio.

A method to control the temperature of the exhaust gases of a supercharged internal combustion engine, the method comprising: determining the minimum air/fuel ratio of the exhaust gases downstream of the exhaust manifold as a function of the flow rate of air that is not involved in the combustion taking place inside the cylinders and flows directly from the intake manifold into the exhaust pipe; detecting an air/fuel ratio of the exhaust gases downstream of the exhaust manifold by means of a sensor; and controlling the supercharged internal combustion engine as a function of the comparison between the air/fuel ratio of the exhaust gases detected by the sensor and/or the minimum air/fuel ratio of the exhaust gases with a number of threshold values.