Abstract: This invention provides a piston in which the moving piston unit can be prevented from rotating with respect the base piston unit, while suppressing the increase of the sliding resistance the piston has with respect to the cylinder. The circumferential wall of the moving piston unit has a pair of skirt parts opposing each other across a piston boss and a pair of side-wall parts coupling the skirt parts and each having an outer circumferential surface concaved toward the central axis X1 of the piston. The side-wall parts have a penetration part each, which penetrates the side-wall part and extends in the directions the moving piston unit reciprocates with respect to the base piston unit. The base piston unit has rotation preventing projections that project perpendicular to the central axis of the piston and are inserted into the penetration parts.

Abstract: This invention provides a piston in which the moving piston unit can be prevented from rotating with respect the base piston unit, while suppressing the increase of the sliding resistance the piston has with respect to the cylinder. The circumferential wall of the moving piston unit has a pair of skirt parts opposing each other across a piston boss and a pair of side-wall parts coupling the skirt parts and each having an outer circumferential surface concaved toward the central axis X1 of the piston. The side-wall parts have a penetration part each, which penetrates the side-wall part and extends in the directions the moving piston unit reciprocates with respect to the base piston unit. The base piston unit has rotation preventing projections that project perpendicular to the central axis of the piston and are inserted into the penetration parts.

Abstract: After hydrostatic pressure is applied to a formed ceramic material, the hydrostatic-pressure-applied formed ceramic material is calcined in such a temperature that shrinkage after calcination is less than one percent. The obtained calcined ceramics has an average pore size of 0.04-0.3 .mu.m and a total pore volume of 0.1-0.3 cc/g and a four-point bending strength of 2-20 kg/mm.sup.2. The calcined ceramics is worked wet by machines to a desired shape, and afterwards the shaped ceramic material is sintered to manufacture a ceramic product.

Abstract: After hydrostatic pressure is applied to a formed ceramic material, the hydrostatic-pressure-applied formed ceramic material is calcined in such a temperature that shrinkage after calcination is less than one per cent. The obtained calcined ceramics has an average pore size of 0.04-0.3 .mu.m and a total pore volume of 0.1-0.3 cc/g and a four-point bending strength of 2-20 kg/mm.sup.2. The calcined ceramics is worked wet by machines to a desired shape, and afterwards the shaped ceramic material is sintered to manufacture a ceramic product.

Abstract: A forming aid to be mixed in a ceramic material for forming the ceramic material into a formed ceramic body of a desired shape, including at least one of a thermoplastic resin and a wax, and a mineral oil in an amount of 30-95% by volume with respect to an entire volume of the aid. Also disclosed is a process of producing a ceramic article from the formed ceramic body containing the aid.

Abstract: A method of extruding ceramic bodies in a downward direction is disclosed, which includes the steps of supporting an extruded body being downwardly extruded through an extruding die to prevent deformation of the extruded body, and cutting the extruded body in a given length. An apparatus for effecting this extruding method is also disclosed, which includes an extruding unit provided with a die at a bottom thereof, a unit for holding the extruded body being downwardly extruded, and a cutter for cutting the extruded body in the given length.

Abstract: A method of machining a ceramic rotor for a pressure wave type supercharger which includes the steps of pressing one end surface of the ceramic rotor against an inner bottom surface of a hydraulic chuck, hydraulically grasping the ceramic rotor with its outer circumference by means of clamping device, and then machining the other end surface and an inner diameter portion of the rotor. Before holding the ceramic rotor in the hydraulic chuck, a metal cylinder is fitted coaxially on the ceramic rotor so that end surfaces and inner circumference of the rotor can be machined with high dimensional accuracy.

Abstract: A ceramic radial turbine rotor made of a ceramic material having a strength s (kg/mm.sup.2) includes blade tips having a thickness t (mm). A product st.sup.2 of strength s and t.sup.2 (square of t) is representative of resistance to breakage of the rotor to foreign objects colliding against blades of the rotor. The product st.sup.2 fulfills a relation st.sup.2 .gtoreq.5.times.10.sup.4 vm+33. In this case, v is a circumferential speed of tip ends of inducers of blades of the rotating rotor when the blades are damaged by steel balls having a mass m (kg) colliding against the blades in a steel ball collision test of blades of a ceramic radial turbine rotor, and vm is a product of v and m.

Abstract: Ceramic rotors for pressure wave superchargers are disclosed, which have a honeycomb structure, wherein a material constituting partition walls of the honeycomb structure has an apparent density of 4.0 g/cm.sup.3 or less, an open porosity of 3.0% or less, a coefficient of thermal expansion in a temperature range from room temperature to 800.degree. C. being 5.5.times.10.sup.-6 /.degree.C. or less, and a four point bending strength of 30 kg/mm.sup.2 or more. A process for producing such ceramic rotors for pressure wave superchargers is also disclosed. The process includes the steps of preparing a ceramic body in which an average particle diameter of a ceramic raw material is controlled to 1 to 10 .mu.m, extruding honeycomb structural bodies by press feeding the ceramic body through body feed holes and extruding channels having a width corresponding to a thickness of partition walls of the honeycomb structure in an extruding die, drying, firing and grinding the thus extruded bodies.

Abstract: Disclosed herein is a method of manufacturing a ceramic honeycomb structural body and a die for extruding a ceramic honeycomb structural body wherein the die includes molding slits having a profile corresponding to a sectional profile of a ceramic honeycomb structural body and ceramic raw batch material supply holes through which a ceramic raw batch material is supplied to the molding slits. The pitch ratio between a short side and a long side of the molding slits is substantially 1:.sqroot.3.

Abstract: The disclosed ceramic heat exchanger has a stress relief layer disposed in the proximity of joint between a hollow hub and a honeycomb structural body integrally joined to the outer circumference of the hub, the stress relief layer having the difference in thermal expansion of not greater than 0.1% at 800.degree. C. relative to the hub.

Abstract: Disclosed herein is a ceramic honeycomb structural body which has cells of a rectangular section in which the pitch ratio between the short side and the long side of the cells is substantially 1:.sqroot.3. A method of manufacturing a ceramic honeycomb structural body and a die for extruding a ceramic honeycomb structural body are also disclosed. The die comprises molding slits having a profile corresponding to a sectional profile of a ceramic honeycomb structural body and ceramic raw batch material supply holes through which a ceramic raw batch material is supplied to the molding slits, wherein the pitch ratio between the short side and the long side of the molding slits is substantially 1:.sqroot.3. Further, a rotary regenerator type ceramic heat exchanger composed of the ceramic honeycomb structural body is disclosed.

Abstract: An extrusion die for a ceramic honeycomb structure having a plurality of different wall thicknesses and at least two through-hole comprises discharge slots corresponding to the cross-sectional shape of the ceramic honeycomb structure and feed passageways formed in communication with said discharge slots. The hydraulic diameters of the feed passageways which communicates with discharge slots which result in thinner wall in the honeycomb structure are comparatively larger than the hydraulic diameters of the feed passageways which communicate with discharge slots which result in thicker walls in the honeycomb structure. The invention can also include a replaceable perforated plate attached on inlet portions of the feed passageways of an extrusion die. The completely novel extrusion die is suitable for use in obtaining a ceramic honeycomb structure having at least two difference types of wall thicknesses and defining through-holes of complex shapes.

Abstract: The disclosed ceramic rotor comprises integrally formed blade portions made of ceramics sintered at atmospheric pressure and a blade-holding portion to which said blade portions are integrally cemented by ceramic material. The blade-holding portion is made of ceramics sintered at atmospheric pressure and has a larger density than that of the blade portions. The thickness of the blade-holding portion is not smaller than the thickness of the blade portions but smaller than the distance between the front and rear surfaces of the blade portions. In the disclosed process, bodies of the blade portions and the blade-holding portion are separately formed and coupled by applying ceramic material therebetween, and the coupled bodies are sintered at atmospheric pressure to produce the ceramic rotor.

Abstract: The disclosed ceramic rotor comprises integrally formed blade portions made of ceramics sintered at atmospheric pressure and a blade-holding portion to which said blade portions are integrally cemented by ceramic material. The blade-holding portion is made of ceramics sintered at atmospheric pressure and has a larger density than that of the blade portions. The thickness of the blade-holding portion is not smaller than the thickness of the blade portions but smaller than the distance between the front and rear surfaces of the blade portions. In the disclosed process, bodies of the blade portions and the blade-holding portion are separately formed and coupled by applying ceramic material therebetween, and the coupled bodies are sintered at atmospheric pressure to produce the ceramic rotor.

Abstract: A low thermal expansion ceramic article having a thermal expansion coefficient of not higher than 2.5.times.10.sup.-6 /.degree.C. within the temperature range of 40.degree.-800.degree. C., and comprising a plural number of ceramic parts bonded into a monolithic structure through glass-ceramics consisting mainly of 10-20% of MgO, 20-40% of Al.sub.2 O.sub.3, 40-60% of SiO.sub.2, 0.1-3% of BaO and 0.01-1% of ZrO.sub.2, is excellent in the heat resistance and in the thermal shock resistance, and can be advantageously used as a rotary regenerator type heat exchanger and a recuperative heat exchanger for gas turbine engine, stirling engine, and industrial apparatuses; and a rotor for turbocharger.