JP2012177467A - Fluid dynamic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid dynamic bearing device which is excellent in quietness, high in accuracy, does not cause the deterioration of bearing performance, and can be manufactured at a low cost.SOLUTION: The fluid dynamic bearing device 10 is composed of: an outer member 20 formed with respective radial dynamic grooves 12a and having a radial bearing face 29R formed with a trust bearing between and among thrust bearing faces 13T, 23T and 24T of the outer member 20 and an inner member 11 and the thrust bearing faces 23T, 24T formed at both ends of the radial bearing face; and the inner member 11. In the fluid dynamic bearing device, a lubrication fluid is interposed at the a dynamic bearing, a portion forming at least a radial bearing face 12R and the thrust bearing face 13T of the inner member 11 is formed of a sintered metal, and spaces 30a, 30b between the radial bearing face 12R and the thrust bearing face 13T are kept at positive pressure.

Description

  The present invention relates to a fluid dynamic bearing device that rotatably supports a rotating body by a dynamic pressure action of lubricating oil generated in a bearing gap between an inner member and an outer member.

  A bearing is incorporated in a fan motor mounted on a personal computer or OA device, and a rotating shaft to which the fan is attached is rotatably supported by the bearing. In this type of application, a so-called rolling bearing is generally used that includes a plurality of rolling elements between an outer ring and an inner ring and includes a cage that holds the rolling elements (for example, Patent Documents). 1).

  On the other hand, as a fluid dynamic pressure bearing device, fluid dynamics having a structure comprising a cylindrical bearing ring, an outer member composed of a bearing plate fitted to both ends thereof, and an inner bearing plate member disposed inside the outer member. There is a pressure bearing device (Patent Document 2).

JP 2000-249142 A JP 2008-275159 A

  Incidentally, fan motors and the like mounted on personal computers and OA devices are continuously operated for a long time, and in recent years, quietness and high reliability are required. However, rolling bearings avoid the generation of so-called cage noise caused by collision between the cage pocket and rolling elements during operation, and friction noise caused by rolling of the rolling elements on the raceway surface of the inner and outer rings. Since it is not possible, it is difficult to meet the demand for further improvement in quietness.

  With regard to this problem, the present inventors paid attention to a fluid dynamic pressure bearing device. As an example, a fluid dynamic pressure bearing device disclosed in Patent Document 2 includes a first bearing ring (12) and a pair of first bearing plates that protrude from the first bearing ring (12) to the inner diameter side. (16, 20) constitute an outer member (first bearing member), and a cylindrical second bearing ring (14) attached to the rotary shaft and an outer periphery of the second bearing ring (14) An inner member (second bearing member) is constituted by the second bearing plate (18) fixed to the surface. When the inner member rotates, a radial bearing gap is formed between the inner peripheral surface of the first bearing ring (12) and the second bearing plate (18), and the pair of first bearing plates (16 20) and a second bearing plate (18), a thrust bearing gap is formed. When the pair of first bearing plates (16, 20) and the second bearing plate (18) are engaged in the axial direction, the withdrawal of the inner member from the inner periphery of the outer member is restricted, and the fluid movement Since the pressure bearing device can be integrated, it can be easily assembled to a fan motor or the like.

  However, in the fluid dynamic bearing device described above, the outer member is composed of many parts, so that the processing cost of each part and the assembly cost of these parts increase, making it difficult to reduce the cost. In addition, it is difficult to process a dynamic pressure groove with high accuracy.

  In addition, if the supply of lubricating oil is insufficient in the space between the radial bearing gap and the thrust bearing gap and this part becomes negative pressure, the performance of the bearing part deteriorates and the contact between the inner member and the outer member May cause problems.

  An object of the present invention is to provide a fluid dynamic bearing device that is excellent in quietness, highly accurate, has no deterioration in bearing performance, and can be manufactured at low cost.

  As a result of various studies to solve the above problems, the present inventors intervene in the space between the radial bearing gap and the thrust bearing gap in order to prevent deterioration of the bearing performance of the fluid dynamic bearing device. The new idea of keeping the lubricating oil pressure positive has been reached.

  The present invention includes a radial bearing surface, an outer member having a thrust bearing surface formed at both ends thereof, and a radial bearing surface disposed inside the outer member and opposed to each of the radial bearing surface and the thrust bearing surface. And a thrust bearing surface, and an inner member having a fixed surface with the shaft on the inner periphery, and a radial bearing gap is formed between the outer member and the radial bearing surface of the inner member, and the radial bearing surface A radial dynamic pressure groove is formed in either one of the outer member and the inner member, and a thrust bearing gap is formed between the thrust bearing surfaces of the outer member and the inner member, and a thrust dynamic pressure groove is formed in either one of the thrust bearing surfaces. In the fluid dynamic pressure bearing device in which lubricating oil is interposed in the bearing gap, at least the radial bearing surface and the thrust bearing surface of the inner member are made of sintered metal, It is characterized in that the space between the dialkyl bearing gap and the thrust bearing gap is maintained at a positive pressure.

  As described above, at least the radial bearing surface and the thrust bearing surface forming part of the inner member are made of sintered metal, so that the radial bearing can be manufactured with high accuracy, excellent quietness and low cost. Since the space between the gap and the thrust bearing gap is maintained at a positive pressure, deterioration of the bearing performance can be prevented. Here, the positive pressure means a pressure higher than the atmospheric pressure.

  The outer member is composed of two members, an outer member on the outside and an outer member on the inner side. Both of the two outer members are formed of an integral material of a cylindrical portion and a radial portion, and the cylindrical portion Is fixed by fitting. As a result, the fitting portions of the outer and inner outer members have sufficient lengths, so that stable fitting and fixing can be obtained, the rigidity of the outer members is high, and the bearing clearance is set with high accuracy. can do. Furthermore, in the case where the outer member is formed by pressing a plate material, the radial bearing surface and the thrust bearing surface can be formed with high accuracy by this pressing, and can be manufactured at low cost.

  Since the inner member is made of sintered metal, when forming the dynamic pressure groove on the radial bearing surface of the inner member, the plastic flow when rolling the dynamic pressure groove can be absorbed by the internal pores of the sintered metal, For this reason, the rise of the surface due to plastic flow is suppressed, and the dynamic pressure grooves can be formed with high accuracy. Further, when the dynamic pressure groove is formed on the thrust bearing surface of the inner member, it can be molded at the same time as pressing or sizing of the inner member, so that it can be manufactured with high accuracy and at low cost.

  Specifically, the material of the sintered metal in the part forming the bearing surface is made of copper-iron, and the blending ratio of copper is 10 to 80%. If the blending ratio of copper is less than 10%, there will be a problem with the formability and lubricity of the dynamic pressure grooves, while if the blending ratio of copper exceeds 80%, it is difficult to ensure wear resistance. Therefore, the blending ratio of copper is desirably 10 to 80%.

  The surface opening ratio of the radial bearing surface of the sintered metal is set to 2 to 20%. When the surface opening ratio is less than 2%, the circulation of the lubricating oil is not sufficient, and when the surface opening ratio exceeds 20%, a pressure drop generated in the lubricating oil occurs. Therefore, the surface porosity is preferably 2 to 20%.

  A radial dynamic pressure groove and a thrust dynamic pressure groove are formed on the radial bearing surface and the thrust bearing surface of the inner member, respectively. Thereby, the dynamic pressure groove of the inner member made of sintered metal can be manufactured with high accuracy and low cost by rolling, pressing, or molding at the time of sizing.

  Since the thrust dynamic pressure groove is a pump-out type, the lubricating oil is sent to the outer diameter side, and the pressure of the lubricating oil existing in the space between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure. Therefore, deterioration of bearing performance can be prevented. Herringbone shape is preferable as the pump-out type thrust dynamic pressure groove.

  The surface opening of the inner member is provided by providing a region having a surface opening ratio larger than that of each bearing surface in the outer surface portion of the inner member located in the space between the radial bearing gap and the thrust bearing gap. The internal lubricating oil is guided to the outer surface portion having a large rate, and the pressure of the lubricating oil in this portion is maintained at a positive pressure. Thereby, deterioration of bearing performance can be prevented.

  At least one of the radial dynamic pressure groove and the thrust dynamic pressure groove of the inner member is formed by pressing, but the region where the surface opening ratio of the outer surface portion of the inner member is large is the above-mentioned pressing process. By not using a surface, it can be easily formed without additional processing.

  At least one of the radial dynamic pressure groove and the thrust dynamic pressure groove of the inner member is formed by rolling, but the region where the surface area ratio of the outer surface portion of the inner member is large is the above rolling processing. By not using the processed surface, it can be easily formed without additional processing.

  At least one of the radial bearing surface and the thrust bearing surface of the inner member is sealed. Thereby, the pressure drop of lubricating oil can be suppressed.

  According to the present invention, since at least the radial bearing surface and the thrust bearing surface of the inner member are made of sintered metal, high accuracy and excellent quietness can be produced at low cost. Since the space between the bearing gap and the thrust bearing gap is maintained at a positive pressure, deterioration of the bearing performance can be prevented.

It is a longitudinal cross-sectional view of the fluid dynamic pressure bearing apparatus of the 1st Embodiment of this invention. It is the front view and side view which show the dynamic pressure groove formed in the inward member. It is the longitudinal cross-sectional view which expanded the fluid dynamic pressure bearing apparatus partially. It is a longitudinal cross-sectional view of the fan motor incorporating the fluid dynamic pressure bearing device. It is a longitudinal cross-sectional view of the fluid dynamic pressure bearing apparatus of the modification of 1st Embodiment. It is a longitudinal cross-sectional view of the fluid dynamic pressure bearing apparatus of the 2nd Embodiment of this invention. It is a right view of the fluid dynamic pressure bearing apparatus of 2nd Embodiment. It is a cross-sectional view of the BB line of FIG. It is a longitudinal cross-sectional view which shows an assembly method. It is a longitudinal cross-sectional view which shows an assembly method. It is a cross-sectional view which shows the state which inject | pours an adhesive agent into the fitting part of an outward member.

  Embodiments of the present invention will be described below with reference to the drawings.

  A fluid dynamic pressure bearing device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the fluid dynamic bearing device 10 includes an inner member 11 and an outer member 20 that rotatably supports the inner member 11. The inner member 11 is attached to a rotating shaft (not shown), and the outer member 20 is attached to a housing (not shown). Lubricating oil is interposed between the surfaces of the inner member 11 and the outer member 20 facing each other in the axial direction and the radial direction (radial bearing gap R and thrust bearing gap T).

  The inner member 11 is made of sintered metal. The inner member 11 has an outer peripheral surface 12 and both side surfaces 13 and 13, the outer peripheral surface 12 forms a radial bearing surface 12R, and both side surfaces 13 and 13 form thrust bearing surfaces 13T and 13T. The outer peripheral surface 12 has a cylindrical shape, and both side surfaces 13 and 13 are flat surfaces in the radial direction perpendicular to the axis A. A radial bearing gap R is formed between the radial bearing surface 12R of the inner member 11 and the radial bearing surface 29R of the outer member 20, and the thrust bearing surfaces 13T, 13T of the inner member 11 and the thrust bearing of the outer member 20 are formed. Thrust bearing gaps T and T are formed between the surfaces 23T and 24T. Chamfered portions 11 b and 11 c are formed at both ends of the outer peripheral surface 12 of the inner member 11, and spaces 30 a and 30 b are formed between the outer member 20 and the outer member 20. The radial bearing gap R, the thrust bearing gaps T and T, and the spaces 30a and 30b are filled with lubricating oil. In order to show the details of the state of filling with this lubricating oil, FIG. 3 shows a partial vertical cross-section in which the upper half of the fluid dynamic bearing device 10 of FIG. Lubricating oil is filled in the radial bearing gap R, the thrust bearing gaps T and T, and the spaces 30a and 30b located between the radial bearing gap R and the thrust bearing gaps T and T. A dynamic pressure groove 12 a is formed on the outer peripheral surface 12 of the inner member 11. Specifically, as shown in FIG. 2 (b), a dynamic pressure groove 12a formed on the entire outer peripheral surface 12 and bent in a V shape, and a hill portion 12b partitioning the dynamic pressure groove 12a (shown by cross-hatching in the figure) And a herringbone shape alternately arranged in the circumferential direction. Chamfered portions 11 b and 11 c are formed at both ends of the outer peripheral surface 12. The dynamic pressure groove 12a is formed by rolling, for example. Since the inner member 11 is formed of sintered metal, the plastic flow of the outer peripheral surface 12 of the inner member 11 due to the compression of the rolling process can be absorbed by the internal pores of the sintered metal. For this reason, the rise of the surface of the inner member 11 due to plastic flow is suppressed, and the dynamic pressure groove 12a and the hill portion 12b can be formed with high accuracy. When the dynamic pressure groove 12a is rolled, the chamfered portions 11b and 11c at both ends of the outer peripheral surface 12 are not rolled. That is, the chamfered portions 11b and 11c are formed only in the powder forming process of the sintered metal constituting the inner member 11, and remain as the forming surfaces by the process. Therefore, the surface open area ratio of the chamfered portions 11b and 11c is larger than that of the radial bearing surface.

  As shown in FIG. 1, both side surfaces 13 and 13 of the inner member 11 form a flat surface in the radial direction perpendicular to the axis A, and dynamic pressure grooves 13 a and 13 a are formed on both side surfaces 13 and 13. . Details are shown in FIGS. 2 (a) and 2 (c). FIG. 2A shows the left side surface 13 of the inner member 11, and FIG. 2C shows the right side surface 13 of the inner member 11. As shown in the figure, dynamic pressure grooves 13a, 13a formed on the entire surfaces of both side surfaces 13, 13 and bent in a V shape, and hill portions 13b, 13b (indicated by cross-hatching in the figure) partitioning the grooves, It exhibits a herringbone shape that is alternately arranged in the circumferential direction.

As shown in FIGS. 2 (a) and 2 (c), lubricating oil is sent to the outer diameter side by rotation of the dynamic pressure grooves 13a and 13a of the thrust bearing surfaces 13T and 13T formed on both side surfaces 13 and 13 of the inner member. Use pump-out specifications. The herringbone shape of the thrust dynamic pressure grooves 13a, 13a is a pump-out specification in which lubricating oil is sent to the outer diameter side by rotation. Generally, the herringbone-shaped dynamic pressure grooves 13a and 13a are provided with a folded portion P. The radius r _h of the folded portion P, the outer radius r ₁ and the inner radius r _{2 of} the dynamic pressure grooves 13a and 13a, When r _h ² = (r ₁ ² + r ₂ ² ) / 2 holds, the fluid pressure in the pump-in direction generated on the outer diameter side of the folded portion P and the pump generated on the inner diameter side of the folded portion P The fluid pressure in the out direction becomes equal. For example, when the diameter is φ2, the outer diameter is φ4, and the diameter (2r _h ) of the folded portion P is φ3.16, the fluid pressure is equal on the inner diameter side and the outer diameter side. At this time, the radius r _h of the folded portion P is larger than the intermediate point between the outer radius r ₁ and the inner radius r ₂ . On the other hand, in the present embodiment, the radius r of the folded portion is made larger than r _h [= (r ₁ ² + r ₂ ² ) ^1/2 / 2 ^1/2 ] obtained by the above formula (r > R _h ). In this case, since the fluid pressure in the pump-out direction generated on the inner diameter side with respect to the turn-back portion P is dominant over the fluid pressure in the pump-in direction, the thrust bearing surfaces 13T and 13T as a whole are in the pump-out direction (outer diameter direction). The lubricating oil flows, and the pressure of the lubricating oil in the spaces 30a and 30b (see FIG. 3) between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure. Thereby, deterioration of bearing performance can be prevented. The form of the thrust dynamic pressure grooves 13a and 13a is arbitrary as long as it is a pump-out specification, and a spiral shape can be adopted in addition to a herringbone shape.

  Since the inner member 11 is formed of sintered metal, the dynamic pressure grooves 13a and 13a on the side surfaces 13 and 13 are formed by, for example, rolling. Also in the rolling process of the dynamic pressure grooves 13a and 13a on the both side surfaces 13 and 13, the plastic flow of the both side surfaces 13 and 13 due to the compression of the rolling process is baked in the same manner as the rolling process of the dynamic pressure grooves 12a on the outer peripheral surface 12. Can be absorbed by the internal pores of the metal. For this reason, the rise of the surface of the inner member 11 due to plastic flow is suppressed, and the dynamic pressure groove 13a and the hill portion 13b can be formed with high accuracy. Further, the chamfered portions 11b and 11c are not rolled when the dynamic pressure groove 13a is rolled. Therefore, the surface opening ratio of the chamfered portions 11b and 11c is larger than the surface opening efficiency of the thrust bearing surface 13T, similarly to the relationship with the radial bearing surface 12R described above. The chamfered portions 11b and 11c correspond to regions where the surface area ratio is larger than that of each bearing surface provided on the outer surface portion of the inner member 11. Thereby, even if the space 30a, 30b between the radial bearing gap and the thrust bearing gap facing the chamfered portions 11b, 11c becomes negative pressure for some reason, the chamfered portion 11b, Lubricating oil can be supplied to the spaces 30a and 30b via 11c, and the spaces 30a and 30b can be maintained in a positive pressure state.

  As shown in FIG. 3, the internal space of the fluid dynamic pressure bearing device 10 in which the outer member 20 and the inner member 11 are assembled is filled with lubricating oil including the internal pores of the inner member 11 made of sintered metal. Therefore, in addition to the lubricating oil being sent to the outer diameter side by the pump-out specification of the thrust dynamic pressure grooves 13a and 13a described above, the chamfered portions 11b and 11c having a large surface opening ratio are In combination with the fact that the lubricating oil inside the member 11 is guided, the pressure of the lubricating oil in the spaces 30a, 30b is maintained at a positive pressure more reliably. Thereby, deterioration of bearing performance can be prevented. The thrust dynamic pressure grooves 13a, 13a for the pump-out specification and the chamfered portions 11b, 11c having an increased surface opening ratio do not necessarily have to be employed at the same time, and either one of the configurations is used depending on the bearing size and use conditions. You may adopt only.

  The radial dynamic pressure groove 12a and the thrust dynamic pressure grooves 13a and 13a of the inner member 11 can be molded by pressing as another processing method. In this case, since it is press working with a mold, it can be formed with high accuracy. Further, the radial dynamic pressure groove 12a and the thrust dynamic pressure grooves 13a, 13a can be molded simultaneously with the sizing of the inner member 11. The radial dynamic pressure groove 12a formed on the outer peripheral surface 12 of the inner member 11 can be taken out from the mold using a spring back after molding. Even when the radial dynamic pressure groove 12a and the thrust dynamic pressure grooves 13a and 13a are pressed, the chamfered portions 11b and 11c are not pressed. Therefore, as in the case of the rolling process described above, the surface open area ratio of the chamfered portions 11b and 11c is larger than both the bearing surfaces of the radial bearing surface 12R and the thrust bearing surface 13T. The chamfered portions 11b and 11c correspond to regions where the surface area ratio is larger than that of each bearing surface provided on the outer surface portion of the inner member 11.

  As shown in FIGS. 1 and 3, chamfered portions 11 d and 11 d are provided at both axial ends of the cylindrical inner peripheral surface 11 a of the inner member 11. The inner member 11 is formed by, for example, press-fitting (light press-fitting) the inner peripheral surface 11a into the outer peripheral surface of the rotating shaft (not shown) or interposing an adhesive between the inner peripheral surface 11a and the outer peripheral surface of the rotating shaft. By this, it is fixed to the rotating shaft. The inner peripheral surface 11a corresponds to a fixed surface with the shaft.

The material of the sintered metal that forms the inner member 11 is copper iron-based, and the blending ratio of copper is 10 to 80%. If the copper blending ratio is less than 10%, there will be a problem with the formability and lubricity of the dynamic pressure grooves, while if the copper blending ratio exceeds 80%, it is difficult to ensure wear resistance. In consideration of lubricity, copper iron is preferable, but other materials such as iron, copper, and stainless steel can be used. In any case, the surface open area ratio can take any value as long as the circulation of the lubricating oil and the dynamic pressure effect can be obtained, but a range of 2 to 20% is desirable. When the surface opening ratio is less than 2%, the circulation of the lubricating oil is not sufficient, and when the surface opening ratio exceeds 20%, the pressure generated in the lubricating oil decreases. Further, as long as the oil circulation is not hindered, at least one of the radial bearing surface 12R and the thrust bearing surface 13T of the inner member 11 can be sealed. Thereby, the pressure drop of lubricating oil can be suppressed. The density of the copper-iron-based sintered member is set to 6 to 8 g / cm ³ in order to maintain the lubricity and plastic workability.

  Next, the outer member 20 will be described. As shown in FIG. 1, the outer member 20 is composed of two members, an inner outer member 20a and an outer outer member 20b. The inner outer member 20a has a cylindrical portion 20a1 and a radial direction portion 20a2. The outer outer member 20b is also formed of an integral material with the cylindrical portion 20b1 and the radial direction portion 20b2. The inner outer member 20a and the outer outer member 20b are both formed in a substantially L-shaped longitudinal section. The outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a is lightly press-fitted into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer outer member 20b and fixed with an adhesive 45 interposed therebetween.

  Since the chamfered portion 28 (see FIG. 3) is provided on the inner periphery of the end surface of the cylindrical portion 20b1 of the outer member 20b on the outer side, the adhesive 45 can be easily injected. Both the inner outer member 20a and the outer outer member 20b are formed in a substantially L shape by pressing a plate material. Specifically, the plate material is a stainless steel plate, a cold rolled steel plate or the like, and the plate thickness is about 0.1 to 1 mm. In this embodiment, the inner peripheral surface 29 of the cylindrical portion 20a1 of the inner outer member 20a forms a radial bearing surface 29R. The inner side surface 23 of the radial direction portion 20a2 of the inner outer member 20a and the inner side surface 24 of the radial direction portion 20b2 of the outer outer member 20b form thrust bearing surfaces 23T and 24T, respectively. Both the inner peripheral surface 29 and the inner side surfaces 23 and 24 are formed as smooth surfaces without irregularities, and the dynamic pressure grooves 12 a and 13 a are formed in the outer peripheral surface 12 and the both side surfaces 13 and 13 of the inner member 11. . A small-diameter inner peripheral surface 26 is formed at the inner diameter side end of the radial direction portion 20b2 of the outer outer member 20b, and a small-diameter inner peripheral surface 25 is formed at the inner diameter side end of the radial direction portion 20a2 of the inner outer member 20a. Has been. In this structure, since the fitting portion between the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outer side and the outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a has a sufficient length, Stable assembly and adhesive fixing can be realized.

  Lubricating oil is filled in the internal space of the fluid dynamic bearing device 10 having the above structure including the internal pores of the inner member 11 made of sintered metal. As shown in FIG. 3, the lubricating oil is filled in the radial bearing gap R, the thrust bearing gaps T and T, and the spaces 30a and 30b. Lubricating oil inside the inner member 11 is guided to the chamfered portions 11b and 11c having a large surface opening ratio, and the pressure of the lubricating oil in the spaces 30a and 30b is maintained at a positive pressure. In addition to this, the herringbone shape of the thrust dynamic pressure grooves 13a, 13a has a pump-out specification in which the lubricating oil is sent to the outer diameter side by rotation, so that the lubricating oil is sent to the outer diameter side, and the space The pressures of the lubricating oils 30a and 30b are more reliably maintained at a positive pressure. Thereby, deterioration of bearing performance can be prevented.

  On the sealing surface, the lubricating oil is drawn to the outer diameter side (radial bearing gap R side) by the capillary force of the bearing gap. Further, as the rotating shaft rotates, the lubricating oil in the thrust bearing gap T is subjected to a centrifugal force or a pushing force by the dynamic pressure groove, whereby the lubricating oil is pushed into the outer diameter side (radial bearing gap R side). Leakage of the lubricating oil can be prevented by the centrifugal force, the pushing force, and the capillary force due to the bearing gap.

  FIG. 4 shows a fan motor 1 incorporating the fluid dynamic bearing device 10 of the present embodiment. This fan motor 1 is used for discharging heat generated inside a personal computer, OA equipment, etc. to the outside and cooling the inside, and is a fluid dynamic bearing that rotatably supports the rotary shaft 2 in a non-contact manner. The apparatus 10 includes a fan 3 attached to the rotary shaft 2, a stator coil 50 and a rotor magnet 51 that are opposed to each other via a radial gap, and a case 52. The stator coil 50 is attached to the outer periphery of the housing portion 53 of the case 52, and the rotor magnet 51 is attached to the inner periphery of the fan 3. The fluid dynamic bearing device 10 is incorporated in the housing portion 53 of the case 52. In the fan motor 1 configured as described above, when the stator coil 50 is energized, the rotor magnet 51 is rotated by the magnetic force between the stator coil 50 and the rotor magnet 51, and accordingly, the fan 3 is connected to the rotating shaft 2. Rotates together.

  As shown in FIG. 1, in the fluid dynamic bearing device 10, since the inner member 11 is provided between the axial directions of both inner side surfaces 23, 24 of the outer member 20, both inner side surfaces 23 of the outer member 20, 24 and the both side surfaces 13 and 13 of the inner member 11 are engaged in the axial direction, so that the inner member 11 is prevented from coming off from the inner periphery of the outer member 20. Thereby, since separation of the inner member 11 and the outer member 20 can be prevented and the fluid dynamic bearing device 10 can be handled integrally, the attachment to the rotating shaft 2 and the housing part 53 becomes easy.

  Next, a modification of the first embodiment is shown in FIG. Parts having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted. The same applies to the following embodiments.

  In this modification, thrust dynamic pressure grooves 23a, 24a are formed on the inner side surface 23 of the radial direction portion 20a2 of the inner outer member 20a and the inner side surface 24 of the radial direction portion 20b2 of the outer outer member 20b, respectively. Has been. And both the side surfaces 13 and 13 of the inward member 11 are formed by the smooth surface without an unevenness | corrugation. The dynamic pressure grooves 23a and 24a for thrust are formed by press work when the inner outer member 20a and the outer outer member 20b are formed from a plate material by press work, for example. Therefore, the dynamic pressure grooves 23a and 24a can be formed with high accuracy. The shapes of the thrust dynamic pressure grooves 23a and 24a are the same as those shown in FIGS. 2 (a) and 2 (c). Other parts are the same as those in the first embodiment. In this modification, the radial dynamic pressure groove 12a is formed in the inner member 11. However, the radial dynamic pressure groove 12a can also be formed in the inner outer member 20a.

  A second embodiment will be described with reference to FIG. In this embodiment, sleeve portions 11e and 11f are formed to protrude from both ends of the inner member 11 in the axial direction. The outer diameter surfaces of the sleeve portions 11e and 11f are formed at the inner diameter side end portion of the radial direction portion 20a2 of the inner outer member 20a at the inner diameter side end portion of the small diameter inner peripheral surface 25 and the radial direction portion 20b2 of the outer outer member 20b. It faces the small-diameter inner peripheral surface 26 with a seal gap. The small-diameter inner peripheral surface 25 and the small-diameter inner peripheral surface 26 are formed in a tapered shape that expands toward the outside of the bearing, and seal spaces S1, S2 are formed between the outer-diameter surfaces 41, 42 of the sleeve portions 11e, 11f. Is formed. The oil surface of the lubricating oil is held in the seal spaces S1 and S2.

  Also in the first embodiment and the present embodiment described above, the dynamic pressure grooves 12a and 13a have a herringbone shape and are for one-way rotation. In the present embodiment, the following display is provided to identify the rotation direction. As shown in FIG. 6, an identification groove 44 is formed in the end surface 43 of the right sleeve portion 11 f of the inner member 11. When the end portion of the sleeve portion 11f having the identification groove 44 is arranged on the right side as shown in the figure, it can be seen that the rotation direction of the inner member 11 is the right direction (clockwise). In the above description, when the identification display is arranged on the right side, the rotation direction is set to the right direction. On the contrary, the rotation direction may be set to the left direction (counterclockwise direction).

  FIG. 7 shows details of the identification groove 44. 3 is a right side view of the fluid dynamic bearing device 10. FIG. An identification groove 44 is formed on the end face 43 of the sleeve portion 11 f of the inner member 11. The identification grooves 44 are formed at two locations on the diameter, and the identification grooves 44 are formed by a powder forming process or a sizing process of the inner member 11 made of sintered metal. Therefore, since the identification groove is formed in the manufacturing process of the inner member 11, the cost does not increase. The identification groove 44 is not limited to the groove having the above shape, and may be, for example, an arrow-shaped identification groove that directly indicates the rotation direction. In addition to the above, the indication for identifying the rotation direction is, for example, a display indicating the rotation direction on the outer surface of the outer member 20, or the hues of the inner outer member 20a and the outer outer member 20b being different. It may be formed on the surface. For this purpose, materials of different hues are used or surface treatment is performed.

  In 2nd Embodiment, as shown in FIG. 6, the convex part 21a is provided in the opening edge part of the outer peripheral surface 21 of the cylindrical part 20a1 of the inner side outer member 20a. FIG. 8 shows a cross section taken along line BB including the convex portion 21a. The convex portions 21a are formed on the outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a at eight locations in the circumferential direction. This convex portion 21a is press-fitted into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outside. And it is temporarily fixed by the convex part 21a in the state which set the thrust bearing clearance gap, and it fixes with the adhesive agent 45 intervening. Since the convex portion 21a is partially pressed into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b, the accuracy of the inner member 20a and the outer member 20b is not impaired. . In addition, although the convex part 21a was formed in eight places on the outer peripheral surface 21 of the cylindrical part 20a1 of the inner outer member 20a, if the number of the convex parts 21a is three or more, it can be an appropriate number. The shape of the convex portion 21a is not limited to a round protrusion, and may be a shape extending in the axial direction. Further, the convex portion can be formed on the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outside. In short, the convex portion can be press-fitted within a range in which the accuracy of the inner outer member 20a and the outer outer member 20b is not impaired, and is temporarily fixed by the convex portion with a thrust bearing gap set. Any form is acceptable. Other parts are the same as those in the first embodiment. Further, the form of formation of the dynamic pressure grooves is not limited to that of the present embodiment, and may be a form of modification of the above-described first embodiment.

  In FIG. 6, the end surfaces 43a and 44b, the end outer peripheral surfaces 41 and 42, and the chamfered portion 11d are sealed in order to prevent the lubricating oil from seeping out from the end portions of the sleeve portions 11e and 11f of the inner member 11. It is desirable to do. Further, as another method for preventing the lubricating oil from seeping out, an oil repellent may be applied to the end portions of the sleeve portions 11e and 11f. Furthermore, the effect can be further enhanced by combining these.

  In the first embodiment and the present embodiment, the radial direction portion 20a2 of the inner outer member 20a, the radial direction portion 20b2 of the outer outer member 20b, and the side surfaces 13 and 13 of the inner member 11 opposite to the radial direction portion 20b2 are axial lines. Although shown what was formed at right angle with respect to H, it is not restricted to this, The radial direction part 20a2, the radial direction part 20b2, and the side surfaces 13 and 13 which oppose this can also be inclined and formed in cone shape.

  Next, a method for assembling the fluid dynamic pressure bearing device of the present invention will be described with reference to FIGS. This assembly method shows the fluid dynamic bearing device of the second embodiment, but the same applies to the first embodiment and its modifications.

  The gap setting device shown in FIG. 9 includes a fixing jig F and a moving jig G that is arranged inside the fixing jig F and is movable in the vertical direction. The fixing jig F has an inner peripheral surface 35 that is slidably fitted to the mounting surface 30, the guide surface 34, and the moving jig G. The moving jig G has an outer peripheral surface 38 slidably fitted to the shoulder surface 36, the guide surface 37 and the fixing jig F. Outside this gap setting device, the inner member 11 is accommodated in the inner outer member 20a and the outer member 20b, and the inner outer member 20a is moved outside to the state where there is no thrust bearing gap T. It pushes in relative to the direction member 20b. A set of the outer member 20b on the outer side, the outer member 20a on the inner side, and the inner member 11 in this state is placed on the fixing jig F and the moving jig G as shown in FIG. That is, after the inner peripheral surface 11a of the inner member 11 is fitted to the guide surface 37 of the moving jig G, the outer outer member 20b, the inner outer member 20a, and the inner member 11 are set downward. It is inserted, fitted to the guide surface 34 of the fixing jig F, and further inserted downward, and the outer surface of the radial direction portion 20b2 of the outer member 20b on the outer side is placed in contact with the mounting surface 30. At this time, the moving jig G is retracted downward.

  Thereafter, the moving jig G is raised and moved to the lower end surface of the sleeve portion 11f of the inner member 11 where the thrust bearing gap T is zero between the outer member 20b on the outer side and the outer member 20a on the inner side. The shoulder surface 36 of the tool G is brought into contact. With this position as the reference position, as shown in FIG. 10, the moving jig G is further raised to move the inner member 11 upward, and from the outer member 20b that has been press-fitted through the convex portion 21a. The inner outer member 20a is separated. The clearance between the inner side surface 24 of the outer member 20b on the outer side and the side surface 13 of the inner member 11 is stopped at a position where the total amount Δ of the thrust bearing clearances T on both sides is reached, and the clearance setting is completed.

  In this assembling method, the outer member 20b on the outer side, the outer member 20a on the inner side, and the inner member 11 can be set and temporarily fixed outside the gap setting device including the fixing jig F and the moving jig G. . Since the gap setting device including the fixing jig F and the moving jig G performs only the gap setting, the workability is good.

  As described above, with the thrust bearing gap T set and the outer member 20b on the outer side and the outer member 20a on the inner side being temporarily fixed, as shown in FIG. The outer member 20b and the inner outer member 20a are injected into the fitting portion. Since the chamfered portion 28 is provided on the inner peripheral surface 22 of the end surface of the cylindrical portion 20b1 of the outer member 20b on the outer side, it is easy to inject adhesive. Thereafter, the adhesive is solidified by baking. An adhesive that can omit firing, such as an anaerobic adhesive, may be used. Alternatively, the thrust bearing gap T may be set after first applying an adhesive. In any case, since the outer member 20b on the outer side and the outer member 20a on the inner side are temporarily fixed, a special jig for maintaining the set thrust bearing gap T is unnecessary, and workability is improved. Will improve.

  Lubricating oil is injected between the assembled inner member 11 and outer member 20 including the internal pores of the sintered metal inner member 11. After that, the fluid dynamic pressure bearing device 10 is heated to a set temperature exceeding the maximum temperature (upper limit) assumed in the usage environment, and the lubricating oil overflowing from the inner diameter side end portion of the thrust bearing gap T due to thermal expansion at this time Wipe off. Thereafter, by cooling to room temperature, the lubricating oil contracts, the oil surface moves backward to the bearing inner side (outer diameter side), and is held in the seal spaces S1 and S2. Thereby, if it is in the assumed temperature range, lubricating oil will not leak by thermal expansion. Thus, the fluid dynamic bearing device 10 is completed.

  In the above embodiment, the dynamic pressure grooves 12a, 13a, 23a, and 24a are formed in a herringbone shape, but can be formed in appropriate dynamic pressure grooves such as a spiral shape, a step shape, and an arc shape. Moreover, you may form the radial bearing surface 12R which has the dynamic-pressure groove | channel 12a in several places of an axial direction.

DESCRIPTION OF SYMBOLS 1 Fan motor 2 Rotating shaft 3 Fan 10 Fluid dynamic pressure bearing apparatus 11 Inner member 11a Inner peripheral surface 12a Radial dynamic pressure groove 12R Radial bearing surface 13a Thrust dynamic pressure groove 13T Thrust bearing surface 20 Outer member 20a Inside outside Outer member 23a Outer outer member 23a Thrust dynamic pressure groove 23T Thrust bearing surface 24a Thrust dynamic pressure groove 24T Thrust bearing surface 29R Radial bearing surface R Radial bearing gap T Thrust bearing gap

Claims (12)

An outer member having a radial bearing surface and thrust bearing surfaces formed at both ends thereof, and a radial bearing surface and a thrust bearing surface disposed inside the outer member and facing the radial bearing surface and the thrust bearing surface, respectively. A radial bearing gap is formed between the outer member and the radial bearing surface of the inner member, and the radial bearing surface is opposed to the radial bearing surface. A radial dynamic pressure groove is formed on one side, a thrust bearing gap is formed between the thrust bearing surfaces of the outer member and the inner member, and a thrust dynamic pressure groove is formed on one of the opposing thrust bearing surfaces. In the fluid dynamic pressure bearing device in which lubricating oil is interposed in the bearing gap,
A portion of the inner member that forms at least a radial bearing surface and a thrust bearing surface is made of sintered metal, and a space between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure. Fluid dynamic bearing device.   The outer member is composed of two members, an outer member on the outside and an outer member on the inner side. Both of the two outer members are formed of an integral material of a cylindrical portion and a radial portion, The fluid dynamic bearing device according to claim 1, wherein the cylindrical portion is fitted and fixed.   The fluid dynamic bearing device according to claim 2, wherein the outer member is formed by pressing a plate material.   2. The fluid dynamic bearing device according to claim 1, wherein the sintered metal is copper-iron based, and a mixing ratio of copper is 10 to 80%.   The fluid dynamic pressure bearing device according to claim 1 or 2, wherein the sintered metal has a surface opening ratio of at least a radial bearing surface of 2 to 20%.   The fluid dynamic pressure bearing according to any one of claims 1 to 5, wherein the radial dynamic pressure groove and the thrust dynamic pressure groove are respectively formed on a radial bearing surface and a thrust bearing surface of an inner member. apparatus.   The fluid dynamic pressure bearing device according to claim 1, wherein the thrust dynamic pressure groove is a pump-out type.   The fluid dynamic pressure bearing device according to claim 7, wherein the pump-out type thrust dynamic pressure groove has a herringbone shape.   The region having a larger surface opening ratio than each bearing surface is provided in an outer surface portion of the inner member located in a space between the radial bearing gap and a thrust bearing gap. The fluid dynamic pressure bearing device according to 1.   10. The fluid according to claim 9, wherein at least one of a radial dynamic pressure groove and a thrust dynamic pressure groove of the inner member is formed by pressing, and the region is not a processing surface of the pressing. Hydrodynamic bearing device.   10. The radial dynamic pressure groove and the thrust dynamic pressure groove of the inner member are formed by rolling processing, and the region is not a processing surface of the rolling processing. Fluid dynamic bearing device.   The fluid dynamic bearing device according to any one of claims 1 to 11, wherein a sealing treatment is applied to at least one of a radial bearing surface and a thrust bearing surface of the inner member.

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