Abstract: In a method of detecting defects generated in a honeycomb structural body, both end sections of the honeycomb structural body is sealed along a flowing direction of exhaust gas. Air is supplied in the flowing direction of the exhaust gas from one end section to the other end section of the honeycomb structural body. Microphones are arranged at outer periphery of the honeycomb structural body and detect sounds of air leaking from a skin layer of the honeycomb structural body. A judgment step judges whether or not defects such as holes having not less than a predetermined diameter and cracks are generated on the basis of a magnitude of the detected sounds of the leaking air.

Abstract: In a method of detecting defects generated in a honeycomb structural body, both end sections of the honeycomb structural body is sealed along a flowing direction of exhaust gas. Air is supplied in the flowing direction of the exhaust gas from one end section to the other end section of the honeycomb structural body. Microphones are arranged at outer periphery of the honeycomb structural body and detect sounds of air leaking from a skin layer of the honeycomb structural body. A judgment step judges whether or not defects such as holes having not less than a predetermined diameter and cracks are generated on the basis of a magnitude of the detected sounds of the leaking air.

Abstract: A multilayered air-fuel ratio sensor consists of a plurality of substrate layers. At least one heterogeneous boundary layer is interposed between the plurality of substrate layers. The heterogeneous boundary layer has a thickness in a range of 10 to 100 ?m. The heterogeneous boundary layer absorbs thermal shocks or any other stresses acting on the substrate layers and stops the growth of cracks.

Abstract: A gas sensing element and related manufacturing method are disclosed with a solid electrolyte body having one surface formed with a measuring-gas-side electrode and the other surface formed with a reference-gas-side electrode, wherein a measuring-gas-side lead portion is formed on the solid electrolyte body in connection with the measuring-gas-side electrode and a reference-gas-side lead portion is formed on the solid electrolyte body in connection with the reference-gas-side electrode. A dense protective layer is formed on the solid electrolyte body so as to cover the measuring-gas-side lead portion, and a porous protective layer is laminated on the dense protective layer so as to cover the measuring-gas-side electrode, wherein the relationship is established as QB?0.8 QA where QB represents a porosity rate of a base end region of the measuring-gas-side lead portion in an area spaced from the base end of the dense protective layer by a distance of approximately 0.

Abstract: A gas sensor includes a sensor element and a porcelain insulator in which the sensor element is retained. The sensor element includes a measurement gas electrode, an electric lead extending from the measurement gas electrode, a dense protective layer covering the lead, and a porous protective layer disposed on the dense protective layer to cover the measurement gas electrode. The dense protective layer protrudes from an end of the porous protective layer by a distance of 5 mm or less, thereby ensuring the mechanical strength of the porous protective layer to minimize physical separation of the lead from the solid electrolyte layer. The base end of the porous protective layer lies inside porcelain insulator, thereby covering the whole of a portion of the sensor element exposed directly to the measurement gas with the porous protective layer to minimize the separation of the lead.

Abstract: A method of manufacturing an elliptic deep-drawn product including a first step of providing an intermediate product and a second step of providing an end product. In the first step, a rotary forming die is used to form in a blank a substantially round formed portion of a U-shaped cross-section. In the second step, the formed portion is deformed at its semicircular portion by press working to form an elliptic portion, being formed into a final shape.

Abstract: A gas sensor element which may be employed in measuring the concentration of gas such O2, NOx, or CO. The gas sensor element consists of an electrochemical cell made up of a solid electrolyte body formed by a partially stabilized zirconia and a pair of electrodes disposed on the solid electrolyte body. The electrochemical cell is subjected to an aging treatment in which the dc current is applied to the electrodes at a given voltage to enhance the activation of the electrochemical cell.

Abstract: A gas sensing element includes a solid electrolytic substrate having oxygen ion conductivity, a measured gas side electrode provided on a surface of the solid electrolytic substrate so as to be exposed to a measured gas, and a reference gas side electrode provided on another surface of the solid electrolytic substrate so as to be exposed to a reference gas. The measured gas side electrode is covered by a porous electrode protecting layer. A limit current density of the electrode protecting layer is in a range from 0.04 mA/mm2 to 0.15 mA/mm2 on a unit area of the reference gas side electrode.

Abstract: A method of manufacturing an elliptic deep-drawn product including a first step of providing an intermediate product and a second step of providing an end product. In the first step, a rotary forming die is used to form in a blank a substantially round formed portion of a U-shaped cross-section. In the second step, the formed portion is deformed at its semicircular portion by press working to form an elliptic portion, being formed into a final shape.

Abstract: In a gas sensor element, a sensor portion has a solid electrolyte member and a pair of electrodes. The solid electrolyte member has first and second surfaces opposite thereto. The first and second electrodes are mounted on the first and second surfaces of the solid electrolyte member, respectively. A heater member has a heating element and one and other surfaces opposite thereto. The sensor portion is integrally laminated on the one surface of the heater member. The other surface of the heater member is contactable to the target gas. At least a part of the other surface of the heater member has a ten points average roughness that is no more than 1.71 &mgr;m.

Abstract: A nonfragile ad quickly activatable structure of a gas sensor element which may be built in a gas sensor employed in an air-fuel ratio control system for automotive vehicles for measuring the concentration of gas such O2, NOx, or CO. The gas sensor element is made of a lamination of a measurement gas electrode, a reference gas electrode, and a heater. The heater works to elevate the temperature of the gas sensor element up to a given value required to bring the gas sensor element into an activated condition. The heater includes a heater substrate, a heating element, and power supply leads. A minimum distance X between an edge of the heater substrate and an edge of the heating element meets a relation of 0.1 mm≦X≦0.6 mm, thereby minimizing a thermal expansion difference between the heater element and the heater substrate to avoid cracks in a portion of the heater substrate near the heater element.

Abstract: A gas sensor element which may be employed in measuring the concentration of gas such O2, NOx, or CO. The gas sensor element consists of an electrochemical cell made up of a solid electrolyte body formed by a partially stabilized zirconia and a pair of electrodes disposed on the solid electrolyte body. The electrochemical cell is subjected to an aging treatment in which the dc current is applied to the electrodes at a given voltage to enhance the activation of the electrochemical cell.

Abstract: A gas sensing element includes a solid electrolytic substrate having oxygen ion conductivity, a measured gas side electrode provided on a surface of the solid electrolytic substrate so as to be exposed to a measured gas, and a reference gas side electrode provided on another surface of the solid electrolytic substrate so as to be exposed to a reference gas. The measured gas side electrode is covered by a porous electrode protecting layer. A limit current density of the electrode protecting layer is in a range from 0.04 mA/mm2 to 0.15 mA/mm2 on a unit area of the reference gas side electrode.

Abstract: A nonfragile ad quickly activatable structure of a gas sensor element which may be built in a gas sensor employed in an air-fuel ratio control system for automotive vehicles for measuring the concentration of gas such O2, NOx, or CO. The gas sensor element is made of a lamination of a measurement gas electrode, a reference gas electrode, and a heater. The heater works to elevate the temperature of the gas sensor element up to a given value required to bring the gas sensor element into an activated condition. The heater includes a heater substrate, a heating element, and power supply leads. A minimum distance X between an edge of the heater substrate and an edge of the heating element meets a relation of 0.1 mm≦X≦0.6 mm, thereby minimizing a thermal expansion difference between the heater element and the heater substrate to avoid cracks in a portion of the heater substrate near the heater element.

Abstract: A composite gas sensor comprises a pump cell, a NOx sensor cell and an oxygen sensor cell. The NOx sensor cell is connected to a first ammeter and a constant power source to measure the NOx concentration of a sample gas. The pump cell is connected to a second ammeter and a variable power source to measure an air-fuel ratio of the sample gas. The oxygen sensor cell is connected to a voltmeter. A controller adjusts the variable power source to produce a constant value from the voltmeter.

Abstract: A bonding boundary intervenes between a zirconia-series solid electrolytic sheet and an alumina-series insulating sheet. The bonding boundary includes at least partly a crystal phase containing SiO2.

Abstract: A multilayered air-fuel ratio sensing element comprises a solid electrolytic substrate having oxygen ion conductivity. A measuring gas sensing electrode is provided on one surface of the solid electrolytic substrate so as to be exposed to a measuring gas. A reference gas sensing electrode is provided on another surface of the solid electrolytic substrate so that the reference gas sensing electrode is exposed to a reference gas introduced into a reference gas chamber. The measuring gas sensing electrode is covered by a porous diffusive resistor layer. And, a hollow space is provided between the measuring gas sensing electrode and the porous diffusive resistor layer.

Abstract: A gas sensor includes a body having a measurement-gas chamber and a reference-gas chamber. The measurement-gas chamber is supplied with a measurement gas. The reference-gas chamber is supplied with a reference gas. A detecting cell provided in the body includes (1) a solid electrolyte member, (2) a measuring electrode provided on the solid electrolyte member and facing the measurement-gas chamber, and (3) a reference electrode provided on the solid electrolyte member and facing the reference-gas chamber. A heater portion operates for heating the detecting cell. The heater portion includes (1) a first substrate, (2) a heating member provided on the first substrate, (3) a high-voltage-side lead portion provided on the first substrate and electrically connected to the heating member, (4) a low-voltage-side lead portion provided on the first substrate and electrically connected to the heating member, and (5) a second substrate covering the heating member.

Abstract: A composite gas sensor comprises a pump cell, a NOx sensor cell and an oxygen sensor cell. The NOx sensor cell is connected to a first ammeter and a constant power source to measure the NOx concentration of a sample gas. The pump cell is connected to a second ammeter and a variable power source to measure an air-fuel ratio of the sample gas. The oxygen sensor cell is connected to a voltmeter. A controller adjusts the variable power source to produce a constant value from the voltmeter.

Abstract: A multilayered air-fuel ratio sensor consists of a plurality of substrate layers. At least one heterogeneous boundary layer is interposed between the plurality of substrate layers. The heterogeneous boundary layer has a thickness in a range of 10 to 100 &mgr;m. The heterogeneous boundary layer absorbs thermal shocks or any other stresses acting on the substrate layers and stops the growth of cracks.