Isuzu Ceramics Research Institute Co. Ltd.

Isuzu Motors Limited

Hideki Kita

Hideo Kawamura

Takayuki Suzuki

Yasuaki Unno

Wenjea J Tseng

Toshiyuki Yamada

Tetsuya Isshiki

Kazuo Miyajima

Hisataka Numao

Hideo Yamamuro

A thermocouple-type temperature-detecting device excellent in the temperature measurement responsiveness constituted of an outer protective pipe and an inner protective pipe the outer protective pipe is formed in a laminated layer structure of a 2nd layer made of a ceramic containing molten metal-repelling BN and a 1st layer made of a ceramic, the inner protective pipe is formed of a front protective pipe made of a ceramic having a good heat conductivity and a heat-shielding rear protective pipe extending into the outer protective pipe through an air layer furthermore, the head portion of the front protective pipe is projected from the outer protective pipe and a temperature-sensitive portion of a thermocouple is disposed in the inside of the head portion

Thermocouple-type temperature-detecting device

&lsqb;0081&rsqb; A thermocouple lance for measuring temperatures in molten metals has a protective sheath of multi-layered structure that makes it possible to improve the life expectancy of repetitive measuring devices. The thermocouple lance has a protective sheath with one closed end and one opened end wherein porous heat-resisting ceramic filler is compacted. Embedded in the filler is a pair of W&mdash;Re alloy wires dissimilar in their composition from each other. The protective sheath has a layered structure made from cermet layers each having a molybdenum matrix and other layers of at least one boundary layer selected from the class consisting of C, MgO, CaO, Al,O,and ZrO,, the cermet layers and boundary layers overlapping each other in alternate layers. At least the outermost shell layer of the protective sheath is made of a cermet layer composed of any one of Mo&mdash;ZrN, Mo&mdash;ZrB,, Mo&mdash;ZrO,, Mo&mdash;ZrC and composite thereof. In one embodiment, a protective sheath is composed of layers in which are embedded filaments oriented predominantly in the circumferential direction of the sheath, and boundary layers which are provided between confronting surfaces of any adjoining filament-embedded layers, the boundary layer being weaker in bonding power than the filament-embedded layers. The filaments are of carbon or ceramic whereby the protective sheath may be enhanced in strength against the tensile stress that will occur due to the temperature difference in the protective sheath.

Thermocouple lance with layered sheath for measuring temperature in molten metal

A thermocouple lance for measuring temperatures in molten metals has a protective sheath of multi-layered structure that makes it possible to improve the life expectancy of repetitive measuring services. The thermocouple lance comprises a protective sheath with one closed end and one open end wherein porous heat-resisting ceramic filler is compacted. Embedded in the filler is a pair of W&mdash;Re alloy wires dissimilar in their composition from each other. The protective sheath has the layered structure made from the cermet layers each having a molybdenum matrix and other layers of at least one selected from the class consisting of C, MgO, CaO, Al,O,and ZrO,, both of which layers are overlapped each other in alternate layer. At least the outermost shell layer of the protective sheath is made of a cermet layer composed of any one of Mo&mdash;ZrN, Mo&mdash;ZrB,, Mo&mdash;ZrO,, Mo&mdash;ZrC and composite thereof.

Thermocouple lance with alternating molybdenum layered sheath for measuring temperature in molten metal bath

This ceramic heater is increased in bulk density and decreased in production cost by using an unsintered composite as an unsintered filling member filled in a protective pipe without application thereto of a filling pressure while preventing a heating element from deteriorating. In this ceramic heater, the heating element capable of heating by flowing electricity therethrough is disposed in the protective pipe, which is filled with the unsintered composite. In the unsintered composite, inorganic compound particles are disposed between insulating ceramic particles. In this ceramic heater, the heating element is fixed to the inner wall surface of the protective pipe with a heat-resistant glass layer. The heat-resistant glass layer is partially penetrated into the unsintered composite. The open end portion of the protective pipe is hermetically sealed with a heat-resistant sealing member while allowing extension of lead wires from the end portion of the protective pipe.

Ceramic heater and process for producing the same

This ceramic sheath type thermocouple has a long service life, an improved temperature measuring responsibility and an improved temperature measuring precision, and enables repetitive use. The ceramic sheath type thermocouple has its protective tube 1 formed of a heat resisting ceramics selected from silicon nitride, sialon and silicon carbide. In the protective tube 1 are installed a pair of W--Re wires that are connected to form a joint portion constituting a temperature measuring point 5. A filler made of Si.sub.3 N.sub.4 reaction-sintered ceramics is loaded into the front end portion of the protective tube to enclose the W--Re wires. Another filler made of SiC whisker with a heat conductivity smaller than that of the filler of the front end portion is loaded into the rear portion of the protective tube. An inert gas is sealed in the protective tube. Alternatively, the temperature measuring portion may be formed by exposing from the front end portion of the protective tube the joint portion where the ends of the W--Re wires are connected. The temperature measuring portion is coated with a cover film that is made of silicon carbide, silicon nitride or a composite of these, all having excellent heat resisting and corrosion resisting properties.

Ceramic sheath type thermocouple

A method for producing a reaction sintered ceramic, including forming a green sheet by mixing an Si powder and an oxide including Al and O. A ceramic fiber can be added to the green sheet. The green sheet is reaction sintered and oxidized to yield a ceramic of high toughness and low thermal conductivity.

Method for producing a reaction sintered ceramic

The present invention provides a unit sheath adaptable to a glow plug or a thermocouple, which is improved in durability by the protection from burn-out of the conductive filament. The unit sheath is preferably adapted to a glow plug 10. A protective envelope 1 of ceramics high in density includes a metallic filament 4 of any one of pure tungsten, molybdenum or alloy thereof. A high-density sealant 3 hermetically closes the envelope 1 at its opened end 5. Filler 2 of non-conductive, unburned material is packed in the space around the metallic filament 4 in the envelope 1. The filler contains therein an additive 7 that may be subjected to the oxidation at the temperature lower than that of the metallic filament 4. The additive 7 is composed of at least any one of a free oxygen absorber selected from the group of carbon, titanium, boron, aluminum and nitride thereof, or the mixture thereof.

Unit sheath

In the ceramics having a low heat conductivity, silicon nitride is contained as a main component, a composite oxide or a separate phase thereof and transition metal elements having 66 to 75 of atomic number are dispersed into a substrate, and a minute layer grown continuous to the substrate is formed on the surface of the substrate. The composite oxide is at least one of 3Al.sub.2 O.sub.3. 2SiO.sub.2, 2MgO.2Al.sub.2 O.sub.3.5SiO.sub.2, 2MgO.SiO.sub.2 and 4MgO.5Al.sub.2 O.sub.3.2SiO.sub.2. The adding quantity of the composite oxide and the separate phase thereof is 15 to 60 wt. % in terms of the composite oxide. The adding component of transition metal elements having 66 to 75 of atomic number is less 10 wt. % in terms of oxide of the transition metal elements.

Ceramics having a low heat conductivity

A slidably engaged surface of a sliding member has a first travel length portion formed of a composite material providing a small contact angle with respect to lubricating oil and an adjoining second travel length portion formed of a composite material providing a higher contact angle with the lubricating oil. The first length portion preferably corresponds to boundary and mixed lubricating areas and the second length portion corresponds to a fluid lubricating area.

Low friction engine cylinder and production method therefor

A ceramic sheath capable of preventing damage to conductive wire rod exhibits excellent thermal resistance and a thermal shock resistance. A conductive wire rod is provided in a protective pipe of silicon nitride, silicon carbide or SiAlON so as to extend longitudinally from one end toward the other, and buried in a filler of reaction sintered silicon nitride. The filler comprises two layers, i.e. a core portion having a low sintering time size variation ratio, and a seal portion constituting a boundary layer between the core portion and the protective pipe and having a sintering time size variation ratio higher than that of the core portion. The conductive wire rod comprises a coil of a metal wire. The coil is formed helically along its whole length, and the winding pitch of the coil is set small, large and small in this order from the front end portion of the shell of the protective pipe toward its base end portion.

Ceramic sheath device with multilayer silicon nitride filler insulation

A thermocouple structure capable of measurement of a high temperature with a high accuracy is constituted of a protective pipe made of a heat-resistant ceramic; a pair of wires differing in kind and extending in the protective pipe from one end thereof to the other end thereof in the longitudinal direction thereof in a state of being spaced away from each other; a thin film constituting a temperature-sensing portion, made of a tungsten alloy, disposed on one end portion of said protective pipe, and connected to the wires; and a covering layer made of a heat-resistant ceramic and covering the thin film in such a way as to disallow exterior exposure of the thin film. The protective pipe is made of Si.sub.3 N.sub.4, and a filling member made of a powder mixture of Si.sub.3 N.sub.4 and TiN is filled in the protective pipe. Alternatively, a pair of printed strips differing in kind may be formed as wires in a protective pipe to provide such a thermocouple structure.

Thermocouple structure

The present invention provides a low-friction ceramic having a lowered coefficient of friction and an enhanced strength. The ceramic comprises as the matrix phase a nonoxide ceramic containing silicon, such as Si.sub.3 N.sub.4 or SiC and an iron compound in an amount of about 5 to 40% by weight dispersed in the matrix phase. This ceramic is excellent in the ability to adsorb lubricating oil, has a low coefficient of friction, is almost free from pores, and has a strength equal to or higher than that of a ceramic containing no iron oxide.

Low-friction ceramics

A composite ceramic is produced by forming a mixed powder of Si and a compound oxide as the starting material into a formed material, nitriding and firing the formed material to form a sinter, and subjecting the sinter to oxidation treatment. The composite ceramic, which is:lightweight and reduced in heat conductivity, has a specific gravity of at most 2.6, and comprises a phase composed of all of elements Si, O and N, and at least one element selected from the element group consisting of A1, Zr, Li, P and Mg, in which phase a subphase composed of Si, Al, 0 and N and a subphase composed of Si, O and N are formed. Another composite ceramic has pores and a disperse phase in a matrix phase composed of Si.sub.3 N.sub.4 crystal grains, an oxide and an oxynitride, and further comprises coarse Si.sub.3 N.sub.4 grains dispersed in the matrix phase with O-containing boundary reaction product layers formed in the boundaries between the matrix phase and the coarse Si.sub.3 N.sub.4 grains. Thus, this composite ceramic, though reduced in heat conductivity, has a high toughness and a high strength due to dispersion of the coarse Si.sub.3 N.sub.4 grains in the matrix phase.

Composite ceramic

A silicon nitride based sintered product produced with Si powder, a Si.sub.3 N.sub.4 powder, and an assistant component effective for sintering silicon nitride as raw materials. A resultant sintered product has fine tissue, exhibits little presence of pores and remaining silicon, and possesses high mechanical strength which can be enhanced by calcinating the product under low pressure after it has been reacted and first sintered.

Silicon nitride based sintered product

The low thermal conductivity ceramic of the present invention comprises a sialon (Si--Al--O--N) and at least one element selected from among La, Dy, Ce, Hf and Zr and has an average grain size of 1.5 .mu.m or less and a thermal conductivity of 0.01 cal/cm.multidot.s.multidot..degree.C. or less. It can be produced by raising the temperature of a molding containing a sialon and the above elements in a gas atmosphere having a pressure of 5 arm or more at a high rate to conduct firing. The present invention enables the ceramic structure to be hyperfined and the phonon scattering to be enhanced, so that it is possible to provide a low thermal conductivity ceramic having a high strength and a low thermal conductivity.

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Fujisawa, Japan

Hideki Kita