Ngk Spark Plug Company, Limited

Honda Giken Kogyo Kabushiki Kaisha

Kazunori Yokota

Nobuhiro Hayakawa

Tetsusyo Yamada

Junichi Kagawa

Akihiro Toya

Takashi Yamaguchi

Shigeru Miyata

Toyohei Nakajima

Yasushi Okada

Hiroaki Mori

Tetsusho Yamada

Keiichi Hayashi

A method of treating a porous body in a gas concentration sensor to regulate the gas diffusion. The porous body is impregnated with a impregnant containing a component that adheres to or binds with the pore surfaces. The component may be a metal salt, examples of which are Al(NO.sub.3).sub.3, CaCl.sub.2 and H.sub.2 PtCl.sub.2. A colloidal solution may be used.

Method of adjusting a gas sensor

An air-fuel ratio sensor in which the temperature dependence as well as the pressure dependence of a detection signal obtained by the air-fuel ratio sensor are suppressed to thereby improve the accuracy in air-fuel ratio by the air-fuel ratio sensor, which is not influenced by deposits in an exhaust gas and which is high in durability. The suppression is achieved by using a gas-diffusion limiting portion having such critical parameters as 10-30% porosity, 1-3 micrometers mean pore size and 200-1000 micrometers thickness. Alternatively the parameters may be 15-25% porosity, 0.1-7 micrometers pore size and 400-800 micrometers thickness.

Air-fuel ratio sensor

At least one of center and ground electrodes of a spark plug has a thin layer formed by bonding noble metal powder on a discharge-related surface area of the electrode stock of said at least one of said center and ground electrodes in accordance with ultrasonic bonding. Instead of the thin layer, a discharge tip may be formed there by boring a hole in the electrode stock, filling noble metal powder, which has been obtained by coating spherical or flaky metal particles with a corresponding noble metal or noble metal alloy, in the hole and then bonding the thus-filled noble metal powder in accordance with ultrasonic bonding. As a further alternative, a tip made of a noble metal or an alloy thereof may be bonded by ultrasonic bonding or resistance welding in the hole with a layer of metal powder of a metal having good high-temperature erosion resistance or an alloy thereof interposed therebetween. The spark plug enjoys a long operating life.

Spark plug

An air/fuel ratio sensor having an unambiguous output with respect to both the fuel-rich and the fuel-lean regions and which does not require the introduction of atmospheric air. The sensor is composed of first and second elements, each having porous electrodes formed on opposite sides of an oxygen-ion-conductive electrolyte plate. The two elements are arranged to define between them a gas compartment communicating with the atmosphere to be detected via one or more diffusion limiting portions. One of the elements serves as an oxygen concentration differential electrochemical cell and the other one as an oxygen pump. An internal reference oxygen source is formed on the side of one of the elements opposite the gas compartment, and a small current is caused to flow the first element so as to transfer oxygens from the gas compartment to the oxygen source. The second element pumps oxygen into or out of the gas compartment in such a manner that the air/fuel ratio of the gas in the gas compartment is held at a predetermined value.

Air/fuel ratio sensor

At least one of center and ground electrodes of a spark plug has a thin layer formed by bonding noble metal powder on a discharge-related surface area of the electrode stock of said at least one of said center and ground electrodes in accordance with ultrasonic bonding. Instead of the thin layer, a discharge tip may be formed there by boring a hole in the electrode stock, filling noble metal powder, which has been obtained by coating spherical or flaky metal particles with a corresponding noble metal or noble metal alloy, in the hole and then bonding the thus-filled noble metal powder in accordance with ultrasonic bonding. As a further alternative, a tip made of a noble metal or an alloy thereof may be bonded by ultrasonic bonding or resistance welding in the hole with a layer or metal powder of a metal having good high-temperature erosion resistance or an alloy thereof interposed therebetween. The spark plug enjoys a long operating life.

An air/fuel ratio sensor having two units of probe is disclosed each of which comprises two sensing elements, each having a pair of porous electrodes on oppostie sides of an oxygen ion-conductive solid electrolyte; a gas compartment which is formed in contact with one porous electrode for each sensing element and which communicates with the gaseous atmosphere of interest by way of a gas diffusion limiting portion; and an internal reference oxygen source which is formed in contact with one sensing element on the porous electrode side which is opposite the side where said gas compartment is provided. The oxygen source communicates with the outside by way of a leakage resisting portion. The gas compartment in the first unit of probe communicates directly with the gaseous atmosphere of interest by way of a first gas diffusion limiting portion while the gas compartment in the second unit of probe communicates with the gas in the first unit of probe by way of a second gas diffusion limiting portion.

The invention relates to a gas sensor having first and second solid electrolyte cells each of which has a solid electrolyte plate, e.g. a zirconia plate, and a pair of porous electrode layers formed on the opposite surfaces of the plate, spacing means to hold the first and second cells in a narrowly spaced, opposite and parallel arrangement and to define a gas chamber, which admits a gas atmosphere subject to measurement, within the gap between the two cells such that the inner electrode layers of the two cells face each other across the gas chamber and means to appropriately restrict diffusion of the gas atmosphere into the gas chamber. Usually one of the two solid electrolyte cells is used as a concentration cell and the other as an ion pump. To prevent unintentional changes in the distance between the two electrode layers facing each other across the gas chamber during the manufacturing process including sintering treatment, at least one support pillar is disposed in the gas chamber so as to fixedly extend from the inner electrode layer of the first cell to the inner electrode layer of the second cell.

Gas sensor with gas diffusion chamber between two platy solid

A spark plug having a center electrode comprises a ceramic insulator whose leg portion is shaped at the tip in a bag form so as to close the insulator bore. A firing tip is provided at the bag-shaped tip in a face-to-face relation with a side electrode by fixing an electrode element made of a sinter of a ceramic powder containing particles of a size between 10 and 200 .mu.m which are coated with a noble metal to a thickness of 0.1-20 .mu.m. An electrode axis extends from the top end of the plug and is inserted through the insulator bore.

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Aichi, Japan

Kazunori Yokota