Abstract: The present invention has the objective of providing a hydrodynamic bearing device that has high reliability and that is suitable for miniaturization through superior heat resistance and by utilizing a dynamic pressure-generating liquid with little loss due to evaporation. A hydrodynamic bearing device comprises at least one of a shaft structure and a sleeve having a dynamic pressure-generating mechanism, and a dynamic pressure-generating liquid present in a gap between the shaft structure and the sleeve; wherein the main component of the dynamic pressure-generating liquid is ionic liquid.

Abstract: In the present invention, in order to provide a fluid dynamic bearing, having heat resistance, wherein the electrical charging on a rotation portion is prevented and the torque loss caused by a lubricant is made lower, an ionic liquid or the like is added to the lubricant filled in the clearance between the opposed faces of a shaft and a sleeve unit as an electrical conductivity imparting agent.

Abstract: The invention provides a hydrodynamic bearing device, comprising at least one of a shaft and a sleeve having a dynamic pressure-generating mechanism, and a lubricant present in a gap between the shaft and the sleeve; wherein the lubricant contains at least one compound selected from the group consisting of aliphatic ethers having a total carbon number of 24 to 32 as represented in Formula (1) or Formula (2) R1—O—R2??(1) R3—O-A-O—R4??(2) and wherein R1 represents a C16 or higher alkyl group having at least one side-chain, R2 represents a C4 or higher alkyl group, the carbon number of R1 is greater than the carbon number of R2, R3 and R4 represent C8 or higher alkyl groups, A represents a C5 or higher CnH2n group, and at least one of R3, R4, and A have a branched structure.

Abstract: A hydrodynamic bearing device is provided for use with a spindle motor. The hydrodynamic bearing device has a sleeve made of a sintered metal that is obtained by sintering a sintering material that is iron, an iron alloy, copper, a copper alloy or a mixture thereof. This sintered metal has independent pores, which do not communicate with each other, by selecting conditions for forming a desired sintered body within a predetermined range. The conditions includes a grain size of powdered metal of a material for the sintered metal, a molding pressure when the molded body is formed, sintering temperature and sintering period in the sintering step.

Abstract: A hydrodynamic bearing device being low in torque, low in power consumption, high in reliability and best suited for miniaturization and a spindle motor using the same. The hydrodynamic bearing device in accordance with the present invention, dynamic pressure generation grooves being provided on at least one of a shaft or a sleeve, and a lubricant being present in a clearance where the above-mentioned shaft and the above-mentioned sleeve are opposed to each other, is characterized in that the above-mentioned lubricant contains diesters obtained from a divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the ? position and one or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms.

Abstract: A hydrodynamic bearing device capable of inhibiting leakage of a working fluid to an outside of a bearing and preventing reduction in radial bearing rigidity, and capable of keeping a gap between a thrust bearing and a radial bearing favorable and rotating stably. The hydrodynamic bearing device includes a shaft relatively rotatably inserted into a bearing hole of a sleeve, a radial bearing surface having dynamic pressure generating grooves formed on at least one of an outer peripheral surface of the shaft and an inner peripheral surface of the sleeve, and a gap filled with a working fluid between the shaft and the sleeve. The shaft is made of high manganese chrome steel or stainless steel, and the sleeve is entirely made of sintered metal of metal particles including at least 60% by weight of iron or copper. Resin, metal or water glass is impregnated in pores on a surface of the sintered metal and cured.

Abstract: In order to suppress the increase of torque loss at low temperature and the increase of shaft swinging at high temperature and to improve the workability of the sleeve, high manganese chromium steel or austenitic stainless steel is used as the material of the shaft, sulfur free-machining steel is used as the material of the sleeve, and the surface thereof is coated with plating primarily containing nickel and phosphorus. Hence, it is possible to obtain a hydrodynamic bearing wherein the changes in the characteristics of the bearing owing to the change in the viscosity of a lubricant depending on temperature change can be prevented, in addition, the workability of the sleeve and the dynamic pressure generation grooves and the wear resistance of the bearing can be made best.

Abstract: In the present invention, in order to provide a fluid dynamic bearing, having heat resistance, wherein the electrical charging on a rotation portion is prevented and the torque loss caused by a lubricant is made lower, an ionic liquid or the like is added to the lubricant filled in the clearance between the opposed faces of a shaft and a sleeve unit as an electrical conductivity imparting agent.

Abstract: In a hydrodynamic bearing according to the present invention a fixed shaft has different diameter sizes by positions so that overflow or splashing of lubricant out of the apparatus is prevented due to a centrifugal force during high-speed rotation, and lubricant reservoirs are provided in narrower clearances and in wider clearances so that the lubricant is induced to move toward lubricant reservoirs in narrower clearances due to surface tension while the hydrodynamic bearing is in stop, therefore overflow of the lubricant is prevented at the time of starting up.

Abstract: In a hydrodynamic bearing according to the present invention a fixed shaft has different diameter sizes by positions so that overflow or splashing of lubricant out of the apparatus is prevented due to a centrifugal force during high-speed rotation, and lubricant reservoirs are provided in narrower clearances and in wider clearances so that the lubricant is induced to move toward lubricant reservoirs in narrower clearances due to surface tension while the hydrodynamic bearing is in stop, therefore overflow of the lubricant is prevented at the time of starting up.

Abstract: A fluid-bearing apparatus comprising a shaft, a sleeve, dynamic pressure-generating grooves that are provided on either the shaft or on the bearing surface of the sleeve that faces the shaft, wherein a single-component composition is used as the base oil of a lubricant, and accordingly segregation of the lubricant components does not occur, thereby preventing both the development of cavitation arising from decreases in the local vapor pressure and the washing away of the lubricant to the outside of the region of the bearing resulting from the enhancement of the gradient of surface tension of the lubricant.

Abstract: A fluid bearing device including a shaft, a sleeve rotatably supported by the shaft, a thrust bearing plate supported by the sleeve, a radial groove formed on one of an outer periphery of the shaft and an inner periphery of the sleeve, and a spiral groove formed on one of one end face of the shaft and one face of the thrust bearing plate such that the radial groove retains oil, while the spiral groove retains grease containing thickener and base oil identical, in compositions and viscosity, with the oil of the radial groove.

Abstract: Automatic focusing apparatus in an optical drawing machine, comprising a drawing optical means having a dichroic mirror which transmits light for drawing and reflects light for detecting the focus to apply the focus detecting light to which a photosensitive material is insensitive onto the latter, an imaging lens means, and a focus detecting device for detecting whether the surfaces of the photosensitive material are located in the depth of focus of the drawing optical means.