Ngk Spark Plug Company, Limited

Hiroyuki Ishiguro

Takao Kojima

Tetsusyo Yamada

Masahiko Yamada

Masaru Yamano

Toshiki Sawada

Kazuo Taguchi

Yoshihide Kami

Noriaki Kondo

Yutaka Nakayama

Yoshiki Kawachi

Nobuhiro Hayakawa

Yutaka Adachi

Takeshi Kitano

Oxygen sensor element (ZrO.sub.2 solid electrolyte etc) for detecting oxygen concentration in an exhaust gas has a protective layer which is made of a heat-resistant metal oxide and which carries a component of a IIa subgroup element (Ca, Mg etc) on the side exposed to the exhaust gas of the sensor element, at least a part of the protective layer being present as a nonstoichiometric compound (Ti oxide etc) with respect to the heat-resistant metal oxide. Si-poisoning is prevented. Heater for heating the sensor element is provided for preventing Si-poisoning at low temperatures.

Oxygen sensor for preventing silicon poisoning

Oxygen-sensor element comprises reference-gas-side and detection-gas-side electrodes on both surfaces of a solid-electrolyte body, and a porous protective layer on the surface of the detection-gas-side electrode, wherein at least a part (including at least a surface layer) of said porous protective layer is formed by a granular texture of a grain size of 0.1 to 0.5 .mu.m formed mainly of a nonstoichiometric compound of a transition metal oxide (TiO.sub.x), and a catalyst for having gas components of the gas to be measured react is carried in at least a part (including at least a surface layer) of the porous protective layer. Oxidation reaction of gas components is improved to prevent deterioration of the responsive property.

Oxygen-sensor element

Oxygen sensor for air-fuel ratio control is provided with a sensor element having an oxygen ion-conductive main body and electrodes on both sides thereof, and at least one porous protective layer covering the electrode on the exhaust gas side. The protective layer includes an oxygen storage component OSC without copresence of a noble metal catalyst. The protective layer is intermeshingly connected to the main body via spherical protrusions of the main body. Double-layered protective layer structure includes OSC noncontaining layer (optionally containing catalyst) and OSC containing layer, as inner and outer protective layer or vice versa. OSC containing layer is formed by impregnation with OSC-solution through immersing the respective porous protective layer, or by cosintering the OSC containing green coating layer. By impregnation 0.2-8 wt %, or by cosintering 0.2-30 wt %, of OSC metal element is containable. The outer protective layer is thinner and more porous than the inner protective layer. Any of the protective layers can be formed by flame spraying.

Method of producing oxygen sensor for air-fuel ratio control having a

Oxygen sensor for air-fuel ratio control is provided with a sensor element having an oxygen ion-conductive main body and electrodes on both sides thereof, and at least one porous protective layer covering the electrode on the exhaust gas side. The protective layer includes an oxygen storage component OSC without copresence of a noble metal catalyst. The protective layer is intermeshingly connected to the main body via spherical protrusions of the main body. Double-layered protective layer structure includes OSC noncontaining layer (optionally containing catalyst) and OSC containing layer, as inner and outer protective layer or vice versa. OSC containing layer is formed by impregnation with OSC-solution through immersing the respective porous protective layer, or by cosintering the OSC containing green coating layer. By impregnation 0.2 -8 wt %, or by cosintering 0.2-30 wt %, of OSC metal element is containable. The outer protective layer is thinner and more porous than the inner protective layer. Any of the protective layers can be formed by flame spraying.

Oxygen sensor for air-fuel ratio control having a protective layer

As a solid electrolyte suitable for use in oxygen sensors a partially stabilized zirconia, which essentially consists of 4.5-6.0 mol % of Y.sub.2 O.sub.3 and the balance of ZrO.sub.2 and is constituted of tetragonal and cubic crystals, is produced by using a coprecipitated powder of a solid solution of ZrO.sub.2 and Y.sub.2 O.sub.3 as the raw material and performing sintering of a green body at a temperature not higher than 1500.degree. C. The ZrO.sub.2 -Y.sub.2 O.sub.3 powder has a mean particle size not larger than 1 .mu.m and a specific surface area in the range from 2.5 to 7 m.sup.2 /g and is required to be not more than 0.2 wt % in the content of unwanted SiO.sub.2 so that the sintered solid electrolyte may be as low as possible in the content of SiO.sub.2. The obtained solid electrolyte has good mechanical properties and exhibits sufficiently high withstand voltage.

Solid electrolyte of partially stabilized zirconia and method of

A zirconia-base solid electrolyte function element comprising a zirconia-base solid electrolyte substrate, wherein a reinforcing layer is formed directly on each side of said zirconia-base solid electrolyte substrate, the ratio of the shrinkage modulus to the zirconia-base electrolyte substrate to the reinforcing layers is 1.01 to 1.08, and the substrate and the reinforcing layers have been sintered simultaneously.

Reinforced electrolyte function elements

An air/fuel ratio sensor with a solid electrolyte oxygen pump and oxygen sensor defining a closed space therebetween. At least in the oxygen pump, porous electrodes sandwich an ionic oxygen conductive solid electrolyte. The voltage impressed on the electrodes of the pump is limited to a predetermined level, e.g., 6 V, in order to prevent blackening and cracking.

Solid electrolyte air/fuel ratio sensor with voltage control

An apparatus for sensing air-fuel ratio of the present invention is capable of measuring an air-fuel ratio of the air-fuel combustion mixture by sensing a partial pressure of oxygen in the exhaust gas. This apparatus forms a gas regulation chamber by arranging oxygen ion conductive solid electrolytes opposite to each other through a gap. In the gas regulation chamber, diffusion of exhaust gas is regulated. Porous electrodes are formed on both sides of the solid electrolytes. One sensor element formed by one of the solid electrolytes is operated as an oxygen concentration cell element, while the other sensor element formed by the other solid electrolyte is operated as an oxygen pump element. Moreover, the sensor elements are heated in order to activate such elements by heaters provided separately. A constant current is supplied to the oxygen concentration cell element in such a direction as pumping the oxygen into the gas regulation chamber. Supply of a constant current to the oxygen concentration cell element allows existence of a fixed output voltage from the oxygen concentration cell element even when the heater voltage changes. Accordingly, an air-fuel ration can be sensed accurately, independent of change in heater voltage which has been considered as a cause of problem, by controlling a supply current to the oxygen pump element so that an output voltage of the oxygen concentration cell element becomes the fixed voltage and then sensing the air-fuel ratio from such current value.

Apparatus for sensing air-fuel ratio

A heater including an electron-conductive pattern designed to generate heat, which has a partially and/or entirely stabilized ZrO.sub.2 -base substrate, an Al.sub.2 O.sub.3 -base coating layer disposed on the surface of the substrate, and an electron-conductive pattern to generate heat disposed on the coating layer.

Plate-like ceramic heater

An air-fuel ratio sensor including a box member having a wall made of oxygen ion-conductive electrolyte having a pair of porous electrodes on opposite sides and a diffusion-limiting portion providing communication between the inside and outside of the box member, and an oxygen gas sensing element formed within the box member by injection and firing. The oxygen gas sensing element has a resistance which varies in accordance with the oxygen partial pressure of the atmosphere in which the sensor is immersed.

Air/fuel ratio sensor

A heater backed with a ceramic substrate having a ceramic substrate as a base plate and heating element formed thereon, which comprises a conductor for retaining ionized elements, said conductor branching from a terminal lead portion of the minus side connected to the heater element under an applied electric current and extending at the back side of the base plate, along the heating element pattern at least partly thereof. A protecting layer may be provided on the surface of said conductor. The conductor is connected with the lead portion through a conducting through hole.

Heater backed with a ceramic substrate

A pump cell element, for an air-fuel ratio sensor, comprising an oxygen ion conductive zirconia solid electrolyte, a pair of layer electrodes coated on the both surface areas of a measuring portion, and ceramic coating layers each coated on each of said electrodes, at least one of said coating layers disposed on the electrode of a minus side of the pump cell element being provided uniformly and dispersedly with through-pores having a converted diameter of 20-500 .mu.m with an average opening percentage of said through-pores is 5-20%. Blackening at the cathode is effectively eliminated.

Pump cell element for air-fuel ratio sensor

In an oxygen sensor which is provided with an oxygen pump element having electrodes on both front and rear surfaces of a solid electrolyte plate with oxygen ion conductive property, voltage from an external power source is applied between the electrodes and a pumping current flows between the electrodes. Thereby oxygen is pumped out of ambient gases to be measured through a member including a gap with oxygen diffusion limiting property. The limit value of the pumping current accompanied by the oxygen pumping is determined or the oxygen concentration difference produced before and after the diffusive motion of oxygen through the member or oxygen concentration produced after the diffusive motion of oxygen through the member is measured. Thereby the oxygen concentration of the ambient gases is calculated. The oxygen sensor comprises a heater unit installed on the solid electrolyte plate of the oxygen pump element through an electric insulation layer, and a lead wire unit of one electrode of the oxygen pump element connected at one end to the heater unit. Thus the oxygen sensor is excellent in energy saving, detection accuracy, and reduction of use amount of electrode lead wires.

Oxygen sensor

The air-fuel-ratio sensor has a mounting body, a cup-shaped protector enclosing a sensitive element, and gas passage holes and deflectors are provided on the protector wall in such a manner that a gas stream outside the sensor generates swirl of the gas in the cup-shaped protector, the amount of the swirling gas increasing with the distance from the mounting body.

Growing community of inventors

Aichi, Japan

Hiroyuki Ishiguro