Abstract: A gas sensor for measuring an amount of a measurement gas component, including a solid electrolyte having an internal space, a gas-introducing port for introducing measurement gas from an external space into the internal space, diffusion rate-determining means between the internal space and the gas-introducing port, and inner and outer pumping electrodes for pumping-processing oxygen contained in the measurement gas. The diffusion rate-determining means includes slits each having, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, with at least one dimension of each slit being not more than 10 microns.

Abstract: One of a pair of temperature sensor sections in a combustible gas sensor is covered with porous oxidizing catalytic layers (23, 24) for oxidizing a combustible gas, and the other is not covered with the oxidizing catalyst layers. The temperature sensor sections each have temperature sensitive portions (13, 14) made of a dense ceramic material, resistors (21, 22) buried therein and having a positive resistance temperature coefficient, current leads (31, 32, 41, 42) and voltage leads (33, 34, 43, 44). A method for detecting the deterioration of a catalyst which intends to eliminate the combustible gas, by the use of this combustible gas sensor is further disclosed. When a difference between temperatures of the pair of resistors or a difference between powers fed to the pair of resistors is in excess of a predetermined value, it is judged that the catalyst has been deteriorated.

Abstract: A NOx sensor for measuring NOx concentration including a main pumping cell and a detecting electrode, the main pumping cell-including an electrode having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used to control oxygen concentration in a measurement gas to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode. Accordingly, it is possible to suppress the oxidation of Rh and the reconversion into the metal contained in the detecting electrode, stabilize the impedance, and stabilize the sensitivity to NOx.

Abstract: Temperature of a heater is controlled by switching an increasing rate of a resistance value of a heating unit of the heater. During a period T1 from a time point when heating of the heater is started until the resistance value of the heating unit reaches a reference value, the increasing rate is changed in multiple heating stages. In this manner, temperature and the resistance value of the heating unit are increased. During a period T2 from a time point when the resistance value of the heating unit reaches the reference value, feedback control is performed such that the resistance value is kept at the reference value as a target value.

Abstract: An NOx removal system has a combustion apparatus for applying energy to a load based on a predetermined combustion control process, an NOx remover for reacting NOx emitted from the combustion apparatus with NH3 to produce N2 and H2O, an NH3 and/or urea introducing apparatus connected upstream of the NOx remover, for introducing NH3 and/or urea into a gas passage extending from the combustion apparatus to the NOx remover, and sensor, which is also sensitive connected downstream of the NOx remover, for generating a detected signal based on NH3 and NOx contained in a gas discharged from the NOx remover. A controller controls a rate at which NH3 and/or urea is introduced into the gas passage by the NH3 and/or urea introducing apparatus while repeatedly increasing and reducing the rate, in response to the detected signal generated by the NOx sensor.

Abstract: Disclosed is a NOx sensor for measuring a NOx concentration comprising a main pumping cell and a detecting electrode, the main pumping cell including an electrode (an inner pumping electrode and an outer pumping electrode) having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used so that an oxygen concentration in a measurement gas is controlled to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode.

Abstract: A gas sensor for measuring an amount of a measurement gas component, including a solid electrolyte having an internal space, a gas-introducing port for introducing measurement gas from an external space into the internal space, diffusion rate-determining means between the internal space and the gas-introducing port, and inner and outer pumping electrodes for pumping-processing oxygen contained in the measurement gas. The diffusion rate-determining means includes slits each having, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, with at least one dimension of each slit being not more than 10 microns.

Abstract: Disclosed are a gas sensor and a nitrogen oxide sensor each comprising a first diffusion rate-determining section for giving a predetermined diffusion resistance to a measurement gas to be introduced into a first chamber, the first diffusion rate-determining section being formed with a slit having a laterally extending aperture formed at a front end portion of a second spacer layer to make contact with the lower surface of a second solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber, and a slit having a laterally extending aperture formed at a front end portion of the second spacer layer to make contact with the upper surface of a first solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber.

Abstract: A total of a most adjacent spacing distance in an axial direction between an outer gas-introducing hole of an outer protective cover and a slit provided at a flange of an intermediate protective cover and a most adjacent spacing distance in the axial direction between the slit of the intermediate protective cover and an inner gas-introducing hole of an inner protective cover is at least not less than 10 mm. Gaps for avoiding accumulation of water due to boundary tension are provided in a radial direction between the outer protective cover and the intermediate protective cover and in the radial direction between the outer protective cover and the inner protective cover.

Abstract: It is intended to avoid invasion of oxygen through any route except for an introducing port for a measurement gas so that the amount of oxide or inflammable gas contained in the measurement gas may be measured highly accurately. Insulative layers are provided for respective lead wires at positions corresponding to portions at which the temperature of the oxygen ion-conductive solid electrolyte is increased due to heat generation effected by a heater. Each of the insulative layers is formed to have a pattern in which one end is exposed to a first chamber or a second chamber, and the other end terminates at a position separated by a predetermined distance from a corresponding through-hole. At least the lead wires, which lead to an auxiliary pumping electrode and a detecting electrode, are densified. Preferably, the insulative layers for these lead wires are also densified.

Abstract: Disclosed is a NOx sensor for measuring a NOx concentration comprising a main pumping cell and a detecting electrode, the main pumping cell including an electrode (an inner pumping electrode and an outer pumping electrode) having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used so that an oxygen concentration in a measurement gas is controlled to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode.

Abstract: A sensor for measuring nitrogen oxide (NOx) in a gas by decomposing NOx in the gas and measuring an amount of oxygen generated by the decomposition includes: means for introducing the gas to a first inner space under a first diffusion resistance and connected with an external space, means for controlling an oxygen partial pressure in an atmosphere in the first inner space to be a predetermined low value at which NO is not decomposed substantially by a main pump means, means for introducing a controlled atmosphere of the first inner space into a second inner space which is connected with the first inner space and which is under a second diffusion resistance, and means for converting the atmosphere into an electric signal corresponding to the quantity of oxygen generated by decomposition or reduction of NOx contained in the atmosphere by an electric signal conversion means.

Abstract: Disclosed is a method for controlling a gas sensor comprising the steps of pumping-processing oxygen contained in a measurement gas introduced from external space into a first chamber by using a main pumping cell so that a partial pressure of oxygen in the first chamber is controlled to have a predetermined value at which a predetermined gas component as a measurement objective is not decomposable; decomposing the predetermined gas component contained in the measurement gas in a second chamber by the aid of a catalytic action and/or electrolysis by using a detecting pumping cell to pumping-process oxygen produced during the decomposition; and measuring the predetermined gas component contained in the measurement gas on the basis of a pumping current which flows during the pumping process; wherein the oxygen to be pumped out by the detecting pumping cell is pumped out toward an inner pumping electrode which is fixed to have a base electric potential (ground electric potential), of the main pumping cell.

Abstract: A gas sensor comprises a main pumping cell for pumping-processing oxygen contained in a first chamber, a feedback control system for comparing a partial pressure of oxygen in the first chamber with a first reference value to control the main pumping cell so that the partial pressure of oxygen has a predetermined value at which NO is not decomposable, an auxiliary pumping cell for pumping-processing oxygen in the second chamber, and a measuring pumping cell for pumping-processing oxygen produced by decomposition of NOx.

Abstract: A gas sensor is disclosed in order to decrease the offset value to a degree in which no trouble occurs in the measurement without causing any reduction of NOx so that the measurement accuracy for NOx is improved. In the gas sensor, NOx contained in a measurement gas introduced into a second chamber is decomposed by means of catalytic action and/or electrolysis to pumping-process oxygen produced by the decomposition so that NOx is measured on the basis of a pumping current flowing through a measuring pumping cell thereby. The gas sensor has the following pattern of a heater. That is, a minute pitch is provided for a pattern at a portion corresponding to the forward end of a sensor element, a coarse pitch is provided for a pattern at a central portion, and a pattern is removed at a portion corresponding to the backward end of the sensor element. Thus, the measuring pumping cell is allowed to have a resistivity of electronic conduction of not less than 1 M&OHgr; after conversion into a resistance value.

Abstract: Disclosed is a gas sensor for measuring a NOx concentration comprising a main pumping cell and a detecting electrode, the main pumping cell including an electrode (an inner pumping electrode and an outer pumping electrode) having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used so that an oxygen concentration in a first chamber is controlled to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a buffering space is provided between a gas-introducing port and the first chamber. Accordingly, it is possible to avoid any influence of exhaust gas pressure pulsation generated in a measurement gas and improve the measurement accuracy on the detecting electrode.

Abstract: Disclosed is a NOx concentration-measuring apparatus for measuring a NOx concentration by using a main pumping cell including an electrode (inner pumping electrode and outer pumping electrode) having no or low decomposing/reducing ability with respect to NOx to control an oxygen concentration in a measurement gas to have a predetermined value which substantially does not affect measurement of NOx component, and using a detecting electrode having certain or high decomposing/reducing ability with respect to NOx to decompose NOx so that an amount of oxygen produced during this process is measured, wherein the detecting electrode is a cermet electrode composed of an alloy of Pt—Rh and a ceramic component, and Pt and Rh are contained in a weight ratio of Pt:Rh=20:80 to 1:99.

Abstract: It is intended to avoid invasion of oxygen through any route except for an introducing port for a measurement gas so that the amount of oxide or inflammable gas contained in the measurement gas may be measured highly accurately. Insulative layers are provided for respective lead wires at positions corresponding to portions at which the temperature of the oxygen ion-conductive solid electrolyte is increased due to heat generation effected by a heater. Each of the insulative layers is formed to have a pattern in which one end is exposed to a first chamber or a second chamber, and the other end terminates at a position separated by a predetermined distance from a corresponding through-hole. At least the lead wires, which lead to an auxiliary pumping electrode and a detecting electrode, are densified. Preferably, the insulative layers for these lead wires are also densified.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: A method for producing a NOx sensor comprises the steps of forming electrodes on ceramic green sheets, and stacking and integrating the ceramic green sheets into one unit followed by sintering to prepare a substrate, wherein an oxygen concentration is controlled to be not more than 0.5% in a sintering atmosphere after removal of a binder in the step of sintering the substrate. Specifically, the sintering is performed in an atmospheric atmosphere in Interval 1 in which the temperature in a furnace is changed from room temperature to about 1000.degree. C., and the sintering is performed in a nitrogen atmosphere (oxygen concentration in the atmosphere in the furnace is controlled to be about 400 ppm) in Interval 2 in which the temperature is changed from 1000.degree. C. to a maximum temperature followed by spontaneous radiational cooling.