Abstract: An inner peripheral surface and a lower end surface of a bearing sleeve made of a sintered metal are each formed into a smooth cylindrical surface or a flat surface that does not have a dynamic pressure generating portion. Thus, a step of forming the dynamic pressure generating portion can be omitted from a manufacturing step of the bearing sleeve, and cost of dies can be markedly reduced. Further, the inner peripheral surface of the bearing sleeve is formed into the smooth cylindrical surface, and hence a radial dynamic pressure generating portion is formed on an outer peripheral surface of a shaft member. However, the outer peripheral surface of the shaft portion is accessible to tools, and hence the radial dynamic pressure generating portion can be formed easily with high accuracy. As a result, accuracy of a radial bearing gap is enhanced so that a bearing rigidity is enhanced.

Abstract: A fluid dynamic bearing device 1 has a bearing sleeve 8, a shaft member 2 which is inserted in the inner periphery of the bearing sleeve, a housing 7 which is formed by pressing, has the bearing sleeve 8 press-fitted in the inner periphery thereof, and has a stepped section 7d which engages with the end surface of the bearing sleeve and is located ahead in the direction of press-fitting of the bearing sleeve 8, a thrust receiver 9 which is in contact with and supports an end of the shaft member 2, and a seal portion 10 which prevents oil from leaking from the inside of the housing. A dynamic pressure generating groove 8a1 for generating fluid dynamic pressure in a radial bearing gap between the outer peripheral surface of the shaft member 2 and the inner peripheral surface of the bearing sleeve 8 is formed in the inner peripheral surface of the bearing sleeve 8.

Abstract: A housing for a fluid lubrication bearing apparatus is produced. The housing has a cylindrical shape whose inner periphery having a fixing face to which an outer circumferential surface of a bearing sleeve is to be fixed. The method includes providing a forging mold having a groove molding portion extending parallel to a direction of a stroke of said mold and a face molding portion having a convex cylindrical shape on an outer periphery of the forging mold for forming the fixing face of the housing. The method further includes forming the housing with the forging mold, while forging circulation grooves and the fixing face simultaneously on the inner periphery of the housing with the groove molding portion and the face molding portion of the forging mold.

Abstract: A fluid bearing apparatus includes a housing 7 which has a cylindrical shape having a fixing face 7c for fixing the outer circumferential surface 8b of a bearing sleeve 8, and axial circulation grooves 7d for bringing both end faces 8c, 8d of the bearing sleeve 8 into circulation on the inner periphery by forging. A groove molding portion 18a2 is provided on the outer circumference of a rod 18 which serves as a forming mold for the inner periphery of the housing 7, and the circulation grooves 7d are formed by forging with this groove molding portion 18a2. Moreover, after a sealing face 107d and a cylindrical outer circumferential surface 107e provided on the outer periphery of the housing 107 are formed by forging, an inner circumferential surface 107c is formed by forging.

Abstract: A shaft side sealing surface (2a2) provided to an outer peripheral surface of a shaft member (2a) and a bearing side sealing surface (9a) provided to an inner peripheral surface of a bearing member (11) (sealing portion (9)) each has a tapered surface that radially shrinks toward an open-to-air side. In addition, the bearing side sealing surface (9a) has a minimum diameter (r4) set to be larger than a maximum diameter (r5) of the shaft side sealing surface (2a2).

Abstract: A fluid dynamic bearing device (21) includes: a shaft member (22); a housing (29) as an outer member which is arranged on a radially outer side of the shaft member (22) and is opened at both ends; a radial bearing gap which is formed on a radially inner side of the housing (29) and faces an outer peripheral surface of the shaft member (22); and a lid member (30) closing an opening on one end side of the housing (29), wherein the lid member (30) is fitted to an outer peripheral surface of the housing (29) with a fastening allowance which does not affect accuracy of a surface defining an outer diameter dimension of the radial bearing gap so that the housing (29) and the lid member (30) are bonded and fixed to each other.

Abstract: An inner peripheral surface and a lower end surface of a bearing sleeve made of a sintered metal are each formed into a smooth cylindrical surface or a flat surface that does not have a dynamic pressure generating portion. Thus, a step of forming the dynamic pressure generating portion can be omitted from a manufacturing step of the bearing sleeve, and cost of dies can be markedly reduced. Further, the inner peripheral surface of the bearing sleeve is formed into the smooth cylindrical surface, and hence a radial dynamic pressure generating portion is formed on an outer peripheral surface of a shaft member. However, the outer peripheral surface of the shaft portion is accessible to tools, and hence the radial dynamic pressure generating portion can be formed easily with high accuracy. As a result, accuracy of a radial bearing gap is enhanced so that a bearing rigidity is enhanced.

Abstract: A fluid dynamic bearing device includes: a shaft member; a bearing sleeve which forms a radial bearing gap between the bearing sleeve and an outer peripheral surface of the shaft member; a housing which accommodates the bearing sleeve and is opened at both ends; and a lid member which closes an opening on one end side of the housing and forms thrust bearing portions. The housing is an injection-molded product into which the bearing sleeve is inserted, and the housing has another end with which a seal portion forming a seal space is integrally formed. The lid member is fitted with the outer peripheral surface of the housing by loose fitting so that the lid member and the housing are bonded and fixed to each other.

Abstract: A method for producing a housing for a hydrodynamic bearing apparatus includes forming a housing 7 which has a cylindrical shape and which includes a fixing face 7c for fixing the outer circumferential surface 8b of a bearing sleeve 8, and axial circulation grooves 7d for bringing both end faces 8c, 8d of the bearing sleeve 8 into circulation on the inner periphery. The method includes providing a groove molding portion 18a2 on the outer circumference of a rod 18 which serves as a forming mold for the inner periphery of the housing 7, and forming the circulation grooves 7d of the housing by forging with the groove molding portion 18a2 of the mold. Moreover, after a sealing face 107d and a cylindrical outer circumferential surface 107e provided on the outer periphery of the housing 107 are formed by forging, an inner circumferential surface 107c is formed by forging.

Abstract: A method for producing a housing for a hydrodynamic bearing apparatus includes forming a housing 7 which has a cylindrical shape and which includes a fixing face 7c for fixing the outer circumferential surface 8b of a bearing sleeve 8, and axial circulation grooves 7d for bringing both end faces 8c, 8d of the bearing sleeve 8 into circulation on the inner periphery. The method includes providing a groove molding portion 18a2 on the outer circumference of a rod 18 which serves as a forming mold for the inner periphery of the housing 7, and forming the circulation grooves 7d of the housing by forging with the groove molding portion 18a2 of the mold. Moreover, after a sealing face 107d and a cylindrical outer circumferential surface 107e provided on the outer periphery of the housing 107 are formed by forging, an inner circumferential surface 107c is formed by forging.

Abstract: A first axial gap (L1) is formed between a seal portion (9) and a sleeve portion (8). With this, it is possible to set a moving amount of a shaft member (2) in an axial direction with high accuracy irrespective of accuracy of members such as the sleeve portion (8).

Abstract: Providing a fluid dynamic bearing device, wherein the outer member comprises a member formed by a pressing process on a plate member, the radial bearing surface and at least the one of the thrust bearing surfaces of the outer member being formed by the pressing process, and wherein at least a part of the inner member, which forms the radial bearing surface and the thrust bearing surfaces of the inner member, is made of a sintered metal.

Abstract: A fluid dynamic bearing device 1 has a bearing sleeve 8, a shaft member 2 which is inserted in the inner periphery of the bearing sleeve, a housing 7 which is formed by pressing, has the bearing sleeve 8 press-fitted in the inner periphery thereof, and has a stepped section 7d which engages with the end surface of the bearing sleeve and is located ahead in the direction of press-fitting of the bearing sleeve 8, a thrust receiver 9 which is in contact with and supports an end of the shaft member 2, and a seal portion 10 which prevents oil from leaking from the inside of the housing. A dynamic pressure generating groove 8a1 for generating fluid dynamic pressure in a radial bearing gap between the outer peripheral surface of the shaft member 2 and the inner peripheral surface of the bearing sleeve 8 is formed in the inner peripheral surface of the bearing sleeve 8.

Abstract: A lid member (10) is formed in a cup-like shape while having a plate portion (10a) and a cylindrical fixed portion (10b) axially protruding from an outer peripheral end of the plate portion (10a). An outer peripheral surface (10b1) of the fixed portion (10b), which serves as a fixation surface (B), is fixed to an inner peripheral surface (7a) of a housing (7) as an outer member (A). An axial dimension of the fixation surface (B) is larger than a thickness of the plate portion (10a), and hence it is possible to thinly-form the plate portion (10a) and to increase a fixing force between the lid member (10) and the housing (7). As a result, an axial dimension of a fluid dynamic bearing device can be reduced and durability thereof can be simultaneously increased.

Abstract: In order to prevent degradation of accuracy and decrease of strength when a hydrodynamic bearing device is assembled and to reduce a cost of the hydrodynamic bearing device, a guide face serving as a guide when a disc hub is press fitted into a shaft member is formed on the shaft member. Then, the guide face, an outer circumferential surface of the shaft member adjacent to the guide face, and a boundary portion between the guide face and the outer circumferential surface are ground simultaneously, thereby forming a blunting portion having a radius r in the boundary portion. Thus, no edge remains between the guide face and the outer circumferential surface. Therefore, press-fitting resistance when the disc hub is press fitted to an end of the shaft member can be reduced.

Abstract: In order to improve retention strength of a lid member without increase in size and reduction in bearing property of a bearing device, a fluid dynamic bearing device (1) includes: a shaft member (2); a bearing sleeve (8) which forms a radial bearing gap between the bearing sleeve and an outer peripheral surface of the shaft member (2); a housing (4) which accommodates the bearing sleeve (8) and is opened at both ends; and a lid member (10) which closes an opening on one end side of the housing (9) and forms thrust bearing portions (T1 and T2). The housing (9) is an injection-molded product into which the bearing sleeve (8) is inserted, and the housing (9) has another end with which a seal portion (9b) forming a seal space (S) is integrally formed. The lid member (10) is fitted with the outer peripheral surface of the housing (9) by loose fitting so that the lid member (10) and the housing (9) are bonded and fixed to each other.

Abstract: A lid member (10) is formed in a cup-like shape while having a plate portion (10a) and a cylindrical fixed portion (10b) axially protruding from an outer peripheral end of the plate portion (10a). An outer peripheral surface (10b1) of the fixed portion (10b), which serves as a fixation surface (B), is fixed to an inner peripheral surface (7a) of a housing (7) as an outer member (A). An axial dimension of the fixation surface (B) is larger than a thickness of the plate portion (10a), and hence it is possible to thinly-form the plate portion (10a) and to increase a fixing force between the lid member (10) and the housing (7). As a result, an axial dimension of a fluid dynamic bearing device can be reduced and durability thereof can be simultaneously increased.

Abstract: The present invention provides a fluid dynamic bearing device having high durability and capable of being produced at low cost. In the fluid dynamic bearing device, a housing and a disc hub are resin molded parts, and a thrust bearing gap is formed between an upper end surface of the housing and a lower end surface of the disc hub. In this case, the surfaces function as sliding portions temporarily in sliding contact with each other during operation of the bearing. A diameter of PAN-based carbon fibers blended as reinforcement fibers in the resin housing is 12 ?m or less, and the blending amount is within a range of 5 to 20 vol %, thereby making it possible to prevent occurrence of flaws and wear in the sliding portions.

Abstract: A hub (10) is a product formed by injection molding of a resin together with a core metal (13) as an inserted component, and the core metal (13) is exposed on a surface of the hub (10). With this configuration, a cavity of a die for molding the hub (10) is not divided by the core metal (13), and hence it is possible to suppress deterioration in fluidity of a resin due to arrangement of the core metal (13) in the cavity.

Abstract: A first axial gap (L1) is formed between a seal portion (9) and a sleeve portion (8). With this, it is possible to set a moving amount of a shaft member (2) in an axial direction with high accuracy irrespective of accuracy of members such as the sleeve portion (8).