Abstract: A valve-open-close mechanism is proposed which has parts designed to reduce friction during sliding. The electromagnetic actuator comprises a pair of electromagnets each having a stator and a coil opposed to each other with a gap therebetween, an armature disposed in the gap, and a first stem for transmitting to external the movement of said armature. A retainer and a first return spring are provided on the valve. A second stem is provided at other side of the armature and another retainer and a second return spring are provided for the second stem. A coating film is formed on at least one of the surface or end face of the stem portion of the valve, end faces of the first return spring or second return spring, spring bearing end faces of the retainers, surface or end face of the second stem, and the surface of the armature.

Abstract: An object of this invention is to provide a combination of a shim and a cam for use in a reciprocating mechanical system operated under a severe sliding condition, the combination not only assuring an excellent sliding characteristic by reducing friction work during sliding but also providing a high wear resistance and a high fatigue characteristic. In this combination of the shim and cam, the surface roughness of the sliding surface between the shim surface and cam is 0.08-0.4 &mgr;m in terms of ten-point average surface roughness Rz and the surface hardness of the shim sliding portion is higher than that of the cam and the cam has a plurality of cam mountains.

Abstract: First and second sliding parts of a sliding mechanism slide relative to each other. The first sliding part is held in a recess of a metal holding member, which is bounded by an inner wall that meets an open end of the recess along an edge. The first sliding part has a first side surface portion that contacts the inner wall in the recess away from the edge, and a second side surface portion displaced inwardly away from the inner wall so as not to contact the holding member at the edge. By this structure, generation of stress concentration on the sliding part can be avoided.

Abstract: A silicon nitride ceramic sliding member which includes Si.sub.3 N.sub.4 grains as a main component and is shaped or controlled in dimensions through hot plastic working wherein the Si.sub.3 N.sub.4 particles mainly includes .beta.-type columnar crystal grains. The ceramic sliding member is produced by the step (I) of preparing a preform made of silicon nitride ceramic sintered body including Si.sub.3 N.sub.4 grains as a main component wherein the average grain size (average grain size in minor axis in the case of .beta.-type columnar crystal grains) of the Si.sub.3 N.sub.4 grains is at most 0.5 .mu.m, and the hot plastic working step (II) of placing the preform in a mold and effecting hot plastic deformation of the preform for shaping or dimensional control thereof while simultaneously increasing the average aspect ratio of the .beta.-type columnar crystal grains.

Abstract: A joint body in which aluminum and silicon nitride are strongly joined with each other is provided at a low cost, thereby providing a lightweight part which is excellent in sliding property as a mechanical part of an internal combustion engine of an automobile or the like. The joint body includes a base material which is mainly composed of aluminum, and a member consisting of a silicon nitride sintered body which is substantially directly joined to the base material. A powdery or bulky base material (2) mainly composed of aluminum, and a member (1) consisting of a silicon nitride sintered body are charged in a mold and heated under pressurization, thereby joining the same with each other.

Abstract: The present invention is intended to provide a sliding member that can prevent abnormal wear and partial wear of the mating metal sliding component even when an oil contaminated with exhaust gas components is used.A ceramic sliding component is manufactured as followed. A silicon nitride-based material for the sliding face member is joined to a metal body having a higher thermal expansion coefficient than the sliding face member. A crowned portion is formed on the sliding face of the sliding face member in such a way that the difference between the amounts of crowning (da, db) at two arbitrary points axially symmetric with respect to the center line of the crowned portion is 10% or more and 50% or less of the average of the crowning amounts at the two points.

Abstract: This invention aims at providing a sliding component having a crowning shape formed by applying surface quenching treatment to a portion made of a steel, and a production method thereof. The shape and the quantity of crowning can be controlled by heat-treatment or machining after the surface quenching. The sliding component may be made of a steel alone, or may be formed in such a manner that at least one portion of members forming the crowning-shaped sliding face by the surface quenching is joined or fitted to a sliding component main body made of the steel, and its material is a ceramic.

Abstract: To provide sliding components each comprising a base metal and, joined thereto, a sliding face member having a sliding face of crowning profile, in particular, sliding components such as valve train parts, a cam follower and a rocker arm of an automobile engine. A sliding component having a structure comprising (1) a ceramic forming a sliding face and (2) a base metal joined together, in which the extent of crowning of the sliding face is at least 0.1 to 0.4% of the maximum length of the junction face of the ceramic. The ceramic has a four-point flexural strength of at least 50 Kg/mm as measured in accordance with the Japanese Industrial Standard R1601. The base metal is mainly steel at least the surface of which has preferably a martensite texture and has a hardness of higher than 45 in terms of H.sub.RC. The structure may have an intermediate layer of a metal or cermet.

Abstract: There are provided a process for forming a silicon nitride sintered body, encompassing a sialon sintered body, by making much of the superplasticity of the sintered body intact as a simple material without formation thereof into a composite material, and a formed sintered body produced by the foregoing process. A silicon nitride sintered body (encompassing a sialon sintered body) having a relative density of at least 95% and a linear density of 120 to 250 in terms of the number of grains per 50 .mu.m in length in a two-dimensional cross section of the sintered body is formed through plastic deformation thereof at a strain rate of at most 10.sup.-1 /sec under a tensile or compressive pressure at a temperature of 1,300 to 1,700.degree. C. The formed sintered body has a degree of orientation of 5 to 80% as examined according to a method specified by Saltykov, a linear density of 80 to 200, and excellent mechanical properties especially at ordinary temperatures.

Abstract: The invention aims to offer a method to manufacture a high-strength, high-reliability and low cost silicon nitride based sintered body which is not affected by the amount of metal impurities contained in the silicon nitride powder, without using high-purity silicon nitride powder, and can be sintered for a short sintering time. The invention uses silicon nitride and sintering aids, and the powder mixture containing 500-5000 ppm metal impurities is sintered at temperatures ranging from 1300.degree.-1900.degree. C., and under the conditions wherein the product of sintering temperature and sintering time ranges from 1.times.10.sup.5 to 10.times.10.sup.5 .degree. C. .multidot.seconds.

Abstract: A combination of an adjusting shim and a cam used in a valve train in an internal combustion engine for automobiles, the adjusting shim composed of a ceramic material which sets the surface roughness of a sliding surface of the adjusting shim with respect to a cam to not more than 0.1 .mu.m in ten-point mean roughness Rz, and which contains not less than 60 vol. % of silicon nitride or sialon, and the cam composed of cast iron a surface of which is chill hardened and then provided with a phosphate film thereon. The combination of an adjusting shim and a cam is capable of smoothing a sliding surface of the cam by the break-in of the part even if the cam is not subjected to a super-precision finishing process; preventing the seizure and abnormal abrasion of sliding surfaces; stabilizing a smoothed condition of the sliding surfaces of the cam and shim for a long period of time; and providing excellent sliding characteristics of the sliding surfaces owing to a decrease in the friction coefficient thereof.

Abstract: An industrially feasible method of grinding silicon nitride ceramics is disclosed and provides a sufficiently smooth surface. Namely, the surface has a maximum height-roughness Rmax of 0.1 microns or less and a ten-point mean roughness Rz of 0.05 micron. Further, with this method, surface damage can be repaired while grinding. The vertical cutting feed rate of a grinding wheel into a workpiece should be within the range of 0.005-0.1 micron for each rotation of the working surface of the wheel and change linearly or stepwise. The cutting speed of the grinding wheel in a horizontal (rotational) direction should be within the range of 25 to 75 m/sec. With this arrangement, the contact pressure and grinding heat that is generated between the workpiece and the hard abrasive grains during grinding are combined. In other words, mechanical and thermal actions are combined.

Abstract: A method of producing a silicon nitride ceramic component, comprising: grinding a silicon nitride sintered body comprising .alpha.--Si.sub.3 N.sub.4 having an average grain size of 0.5 .mu.m or smaller and .beta.'-sialon having an average grain size of 3 .mu.m or smaller in major axis and 1 .mu.m or smaller in minor axis into a predetermined size with a surface roughness of 1-7 .mu.m in ten-point mean roughness; heat treating the same at temperature range of 800.degree.-1200.degree. C. in the air; and standing it to allow to be cooled, whereby providing a residual stress in the ground surface before and after the heat treating as a residual compressive stress at a ratio of 1 or higher of the residual compressive stress after the heat treating to that before the heat treating (residual compressive stress after the heat treating/residual compressive stress before the heat treating), preferably 5 or more.

Abstract: An industrially feasible method of grinding silicon nitride ceramics is disclosed and provides a sufficiently smooth surface. Namely, the surface has a maximum height-roughness Rmax of 0.1 microns or less and a ten-point mean roughness Rz of 0.05 microns. Further, with this method, surface damage can be repaired while grinding. The vertical cutting feed rate of a grinding wheel into a work piece should be within the range of 0.005-0.1 micron for each rotation of the working surface of the wheel and change linearly or stepwise. The cutting speed of the grinding wheel in a horizontal (rotational) direction should be within the range of 25 to 75 m/sec. With this arrangement, the contact pressure and grinding heat that is generated between the work piece and the hard abrasive grains during grinding are combined. In other words, mechanical and thermal actions are combined.

Abstract: A ceramic die for cutting and shaping lead frames, in which at least a working section thereof is made of a specific ceramic material having an iron and cobalt content of less than 100 ppm in total. The ceramic die can be formed in a complex shape with a high precision and has a prolonged lifetime because of its superior mechanical properties, such as high wear resistance and high strength, and less probability of adhesion of foreign matter such as solder or the lead frame material thereto. Even if the solder or lead frame material is adhered onto the die, the adhered matter can be removed through a simple procedure in a shortened time. The die is further improved by depositing a hard carbon film onto the surface of the working section.

Abstract: A grind-machining method of ceramic materials characterized in that a peripheral speed of a grinding wheel relative to a working surface is set to 50 to 300 m/sec, a feed stroke speed of the working surface of the grinding wheel in a working direction is set to 50 to 200 m/min, and preferably, a down-feed speed of the working surface of the grinding wheel in a direction orthogonal to the surface of the workpiece is set to 0.05 to 3 mm/min. The grind-machining method of ceramic materials can reduce a grinding force at the time of grinding of ceramic materials and residual defects due to machining, and at the same time, can accomplish high machining efficiency.

Abstract: A zirconia vane used in a rotary compressor, the zirconia vane being formed of a partially stabilized zirconia sintered body containing 92 through 98 molar percent of ZrO.sub.2 and being stabilized with Y.sub.2 O.sub.3, zirconia crystals constituting the zirconia sintered body having a mean grain diameter of 0.1 to 0.6 .mu.m and a maximum grain diameter of not greater than 2 .mu.m, the zirconia sintered body having a mean three-point flexural strength of not less than 120 kg/mm.sup.2 measured in conformity with JIS R1601, a surface of the zirconia sintered body in contact with a rotor of the rotary compressor having a first surface roughness in a direction of rotations of the rotor, specified by a ten-point mean roughness Rz, of not greater than 1 .mu.m and a second surface roughness in a direction perpendicular to the direction of rotation of the rotor, specified by the ten-point mean roughness Rz, of not greater than 0.6 .mu.m.

Abstract: A silicon nitride sintered body characterized by comprising crystal grains having a linear density of 60 to 120 per 50 .mu.m length as measured in an arbitrary two-dimensional section of the sintered body. The silicon nitride sintered body has a shock compressive elasticity limit (Hugoniot-elastic limit) of 15 GPa or more and is substantially composed of crystal phases of .alpha.-silicon nitride and .beta.'-sialon. The percentages of the .alpha.-silicon nitride and .beta.'-sialon are not more than 30% and not less than 70%, respectively. The silicon nitride sintered body is particularly excellent in mechanical strengths at room temperature as well as in productivity and cost efficiency and is useful for applications as the material of parts where a particularly high impact strength is required, such as a valve train mechanism for automobile parts.

Abstract: The preset invention provides a ceramic adjusting shim capable of minimizing the abrasion of parts contacting the adjusting shim, for example, a cam and a tappet. The ceramic adjusting shim is produced from a ceramic material and has a surface roughness of 0.05 to 0.2 .mu.m in ten-point average roughness Rz.

Abstract: The present invention provides an improved adjusting shim used in a valve train for an internal combustion engine for an automobile. The adjusting shim produced from a base material consisting of a ceramic material containing 80 to 98 wt. % of silicon nitride and/or sialon and has a porosity of not more than 3%, a bending strength of not less than 1.0 GPa and an impact compressive elastic limit (Hugoniot elastic limit) of not less than 15 GPa, wherein the base material is provided on the surface thereof which contacts a cam with a ceramic surface layer having a composition different from that of the base material and a hardness lower than that of the base material. The adjusting shim of the present invention enables a power loss of a valve train to be minimized; the abrasion resistance thereof to be improved; and the fuel economy, the performance and durability of an internal combustion engine to be improved.