JP2019120389A - Fluid dynamic pressure bearing device and motor including the same - Google Patents

Abstract

To provide a fluid dynamic pressure bearing device which can maintain desired bearing rigidity while achieving reduction of an axial dimension of the entire device and can be assembled at low costs.SOLUTION: A fluid dynamic pressure bearing device 1 according to the invention includes: a housing 7 having a shape of a cylinder with a closed bottom; a bearing sleeve 8 disposed at an inner periphery of the housing 7; and a shaft member 2 having a shaft part 2a inserted into an inner periphery of the bearing sleeve 8 in a removable manner. One part of an internal space of the housing 7 is filled with lubrication oil L and the other part forms a cavity part which is not filled with the lubrication oil L. One axial end surface 8c of the bearing sleeve 8 located at the opening side of the housing 7 opens to atmospheric air. An inclined surface part 11 forming an oil buffer space 12 with an outer peripheral surface 2a1 of the shaft part 2a is provided between an inner peripheral surface 8a of the bearing sleeve 8 and the one axial end surface 8c.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fluid dynamic bearing device and a motor provided with the same.

  As well known, a fluid dynamic bearing device has features such as high speed rotation, high rotation accuracy and low noise. For this reason, the fluid dynamic pressure bearing device is a bearing device for a motor mounted on various electric devices including an information device, specifically, for a fan motor incorporated in a PC or the like, or a laser beam printer ( It is suitably used as a bearing device for a polygon scanner motor incorporated in LBP).

  An example of a fluid dynamic bearing device is described in Patent Document 1 below. This fluid dynamic pressure bearing device has a bottomed cylindrical (a shape integrally having a cylindrical portion and a bottom portion closing one end in the axial direction) a housing, a bearing sleeve disposed on the inner periphery of the housing, and a bearing A shaft member inserted into the inner periphery of the sleeve, a radial bearing portion supporting the shaft member in the radial direction by an oil film of lubricating oil formed in a radial bearing gap, a thrust bearing portion supporting one end of the shaft member, a housing And an annular member (seal member) fixed to the inner periphery of the opening of

  This fluid dynamic pressure bearing device is used in a so-called full fill state in which the entire inner space of the housing is filled with lubricating oil, and a seal space (the inner peripheral surface of the annular member and the outer peripheral surface of the shaft member A radial gap) having a larger gap width than the radial bearing gap is provided. The seal space has a buffer function to absorb the volume change caused by the temperature change of the lubricating oil, and is designed to always keep the oil surface of the lubricant within the seal space within the assumed temperature change range. There is. As a result, it is possible to prevent the deterioration of the bearing performance due to the external leakage of the lubricating oil and the contamination of the surrounding environment.

  However, if a so-called full-filled oil-impregnated structure in which the entire internal space of the housing is filled with lubricating oil is adopted, the entire internal space of the housing is lubricated using a complicated method such as vacuum impregnation after assembly of the fluid dynamic bearing device. It is necessary to fill with oil and precisely manage the oil level position in the sealing space of the lubricating oil (finely adjust the filling amount of the lubricating oil). Therefore, in the conventional oil-containing structure, it has been difficult to meet the demand for further cost reduction for the fluid dynamic bearing device.

  Therefore, the applicant has proposed a fluid dynamic bearing device as described in Patent Document 2 in order to solve the above-mentioned problems. That is, the fluid dynamic bearing includes: a bottomed cylindrical housing; a bearing sleeve disposed on the inner periphery of the housing; a shaft member inserted on the inner periphery of the bearing sleeve; and an upper end surface of the bearing sleeve An annular seal member fixed to the inner periphery of the housing in a contact state and forming a seal space with the outer peripheral surface of the shaft member, and a radial between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member A radial bearing portion for supporting the shaft member in the radial direction by an oil film of lubricating oil formed in the bearing gap, and a thrust bearing portion for supporting one end of the shaft member in the thrust direction. The part is filled with lubricating oil, and the remaining part is a void part not filled with lubricating oil.

  Thus, by providing the void portion not filled with lubricating oil in the internal space of the housing, the amount of lubricating oil filled in the internal space of the housing becomes smaller than the total volume of the internal space, and An area not filled with lubricating oil is provided. Therefore, after fixing the bearing sleeve and the annular member to the inner periphery of the housing, and before inserting the shaft member into the inner periphery of the bearing sleeve, lubricating oil in the inner space using a suitable filler (eg, micropipette) The necessary amount of lubricating oil can be supplied to the internal space simply by Therefore, it is possible to eliminate the need for extensive equipment for lubricating and highly precise adjustment and management of the oil level, and to reduce the cost of lubricating the fluid dynamic bearing device, and hence the cost of assembling the fluid dynamic bearing device. .

JP 2003-307212 JP, 2014-59014, A

  By the way, recently, thickness reduction of various motors (for example, fan motor for cooling etc.) mentioned above is progressing, and in order to maintain cooling performance equivalent to the fan motor of conventional size, the size of the impeller is large. For this reason, the load acting on the bearings tends to increase. If the axial dimension of the bearing in the fluid dynamic pressure bearing device is shortened along with the thinning of the motor, the bearing rigidity is reduced, and it is difficult to allow the load on the bearing which tends to increase as described above.

  In view of the above-described circumstances, the present invention provides a fluid dynamic bearing device capable of maintaining a required bearing rigidity while reducing the axial dimension of the entire device, and capable of being assembled at low cost. , And technical issues to be solved.

  The solution to the above problems is achieved by the fluid dynamic bearing device according to the present invention. That is, this bearing device has a bottomed cylindrical housing closed at one end in the axial direction and open at the other end in the axial direction, a bearing sleeve disposed on the inner periphery of the housing, and a bearing that can be inserted and removed. The shaft member is radially oriented by an oil film of lubricating oil formed in a radial bearing gap between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member, and a shaft member having a shaft portion inserted into the inner periphery of the sleeve In a fluid dynamic bearing device comprising a radial bearing portion to support and a thrust bearing portion to support one end of a shaft member in a thrust direction, a part of the internal space of the housing is filled with lubricating oil and the remaining part is lubricated An axial end surface of the bearing sleeve which is an oil-free gap and is an opening side of the housing is open to the atmosphere, and an axial portion is formed between the inner peripheral surface of the bearing sleeve and the axial end surface. Between the outer surface of the Inclined surface is characterized with a point that is provided for forming a-buffered space. The “thrust bearing portion” referred to here may be, for example, a pivot bearing portion which contacts and supports one end of the shaft member in the thrust direction.

  As described above, in the fluid dynamic bearing device according to the present invention, the bearing on the opening side of the housing is adopted while adopting an oil-impregnated structure in the form of a so-called partial fill in which a part of the internal space of the housing is filled with lubricating oil. An inclined surface portion is formed between the inner peripheral surface of the bearing sleeve and the axial end surface to form an oil buffer space between the inner peripheral surface of the bearing sleeve and the axial end surface, with one end surface in the axial direction of the sleeve being open to the atmosphere. The As a result, since the seal member which is essential in the fluid dynamic bearing having the oil-impregnated structure in the form of the conventional partial fill can be eliminated, the entire shaft of the fluid dynamic bearing can be obtained without changing the axial dimension of the bearing sleeve. Directional dimensions can be shortened. In addition, when using the oil filling structure of the partial fill, it is not necessary to require a large oil buffer volume as compared with the case of using the oil filling structure in the form of the full fill. Therefore, the oil buffer space of sufficient volume can be obtained only by utilizing a part of axial direction one end side of a bearing sleeve as formation of an oil buffer space as a slope part. As described above, according to the present invention, it is possible to assemble at low cost a fluid dynamic bearing device capable of effectively preventing the leakage of lubricating oil. In addition, it becomes possible to cope with thinning of the motor and high load capacity.

  Further, in the fluid dynamic bearing device according to the present invention, the inclined surface portion is continuous with the chamfered portion continuous with the inner peripheral surface of the bearing sleeve and the chamfered portion, and the inclination angle with respect to the central axis of the bearing sleeve is smaller than the chamfered portion. It may consist of a large, large inclined surface.

  For example, in the case where the inclined surface portion is constituted only by the inclined surface having a large inclination angle to allow sufficient oil buffer, the insertion of the shaft portion is smooth when the shaft portion is inserted into the inner periphery of the bearing sleeve. There is a possibility that can not be done. If the inclination angle of the inclined surface is reduced for the purpose of smooth insertion of the shaft, there arises a problem that the oil buffer space is reduced. Therefore, as described above, by forming the inclined surface portion with the chamfered portion and the large inclined surface having a larger inclination angle than the chamfered portion, it is possible to smoothly insert the shaft portion, but with a sufficient volume of oil. It is possible to form the buffer space with the outer peripheral surface of the shaft portion.

  In this case, the inclination angle with respect to the central axis of the large inclined surface may be larger than 45 ° and smaller than 90 °.

  By thus setting the inclination angle of the large inclined surface within a predetermined range, it is possible to form the oil buffer space having a sufficient volume while enabling the smooth insertion of the shaft portion described above. ) Can be enjoyed effectively.

  Further, in the fluid dynamic bearing device according to the present invention, the bearing sleeve has a receding surface portion between the axial one end surface and the outer peripheral surface, which is receded to the axial center side of the bearing sleeve than the axial one end surface. The bearing sleeve may be held between the pressing member and the housing by pressing the receding surface portion in the axial direction by the pressing member.

  Thus, by holding the bearing sleeve in the axial direction by the pressing member and holding the bearing sleeve between the pressing member and the housing, the bearing sleeve is fixed to the housing at the same time as fixing the pressing member to the housing. It can be fixed. Therefore, the effort required for the assembly of members (especially the assembly of a bearing sleeve and a housing) can be reduced. Further, the bearing sleeve is provided with a receding surface portion receding to the axial center side of the bearing sleeve from one end surface in the axial direction, and the bearing surface is held by pressing the receding surface portion by the pressing member. A part or all of the axial direction can be accommodated on the axial center side of the bearing sleeve rather than the upper end surface. Therefore, the axial dimension of the fluid dynamic bearing can be shortened as much as possible while using the pressing member.

  In this case, the pressing member may be fixed to the housing by press-fitting the outer peripheral surface thereof into the inner peripheral surface of the housing.

  As described above, when the pressing member is fixed to the housing by press-fitting the outer peripheral surface of the pressing member to the inner circumferential surface of the housing, the axial direction of (the retreating surface portion of) the bearing sleeve by the pressing member The center can be pushed in. Thus, the pressing member, the bearing sleeve and the housing can be fixed to each other with a minimum of work.

  Further, in the fluid dynamic bearing device according to the present invention, the bearing sleeve may be made of a porous body in which the inner holes are impregnated with the lubricating oil.

  As described above, when the bearing sleeve is formed of a porous body and the internal pores thereof are impregnated with the lubricating oil, the radial bearing clearance and the thrust bearing are generated due to the bleeding of the lubricating oil from the surface opening of the bearing sleeve. The area around the department can be filled with ample lubricating oil. Therefore, the bearing performance of the radial bearing portion and the thrust bearing portion can be stably maintained. In addition, if the bearing sleeve impregnated with lubricating oil can be fixed to the housing in advance, the amount of lubricating oil injected into the internal space of the housing can be reduced accordingly. Therefore, it becomes possible to perform the oiling operation to the inside of a housing more simply.

  Further, in the fluid dynamic bearing device according to the present invention, the lubricating oil may be an ester type, a PAO type or a fluorine type lubricating oil.

  As described above, by using an ester-based, PAO-based or fluorine-based lubricating oil, it is possible to obtain an oil-impregnated structure that is resistant to temperature changes and the like during use and transportation of the fluid dynamic bearing device 1.

  As described above, the fluid dynamic bearing device according to the above description can maintain the required bearing rigidity while reducing the axial dimension of the entire device, and can be assembled at low cost. For example, as a motor provided with the above-mentioned fluid dynamic pressure bearing device, it can be suitably provided especially as a fan motor etc. which are required to be thinned.

  As described above, according to the present invention, it is possible to maintain the required bearing rigidity while shortening the axial dimension of the entire device, and provide a fluid dynamic bearing device that can be assembled at low cost. It becomes.

It is a sectional view of a fan motor concerning one embodiment of the present invention. It is sectional drawing of the fluid hydrodynamic bearing apparatus shown in FIG. 3 is a cross-sectional view of the bearing sleeve shown in FIG. It is a principal part expanded sectional view of a fluid hydrodynamic bearing apparatus shown in FIG. It is a figure which shows the assembly process of the fluid hydrodynamic bearing apparatus shown in FIG. 2, (a) is a figure which shows the initial stage (at the time of oiling) of the process, (b) is the middle stage of the process (when inserting a shaft member) FIG. FIG. 5 is a view for conceptually explaining the action of the oil buffer space shown in FIG. 4, in which (a) is a main part enlarged sectional view showing a state in which the lubricating oil is held in the oil buffer space, (b) is a lubricating oil It is a principal part expanded sectional view when pull-in of a has occurred.

  Hereinafter, an embodiment of the present invention will be described based on the drawings.

  FIG. 1 conceptually shows one configuration example of a fan motor according to the present embodiment. The fan motor includes a fluid dynamic pressure bearing device 1, a shaft member 2 serving as a rotating portion of the fluid dynamic pressure bearing device 1, a rotor 3 to which the shaft member 2 is attached and has blades not shown, and a rotor 3 And a stator coil 5 opposed to the rotor magnet 4 via a radial gap, and a motor base 6 as a holding member to which the stator coil 5 is attached and which constitutes the stationary side of the fan motor. The housing 7 of the fluid dynamic bearing 1 is fixed to the inner periphery of the motor base 6, and the rotor 3 is fixed to one end of the shaft member 2 of the fluid dynamic bearing 1. In the fan motor configured as described above, when the stator coil 5 is energized, the rotor magnet 4 is rotated by the electromagnetic force between the stator coil 5 and the rotor magnet 4, and along with this, the shaft member 2 and the shaft member 2 The rotor 3 fixed to the shaft rotates integrally.

  When the rotor 3 rotates, wind is sent upward or downward in FIG. 1 according to the configuration of the blades provided on the rotor 3. For this reason, while the rotor 3 is rotating, a thrust downward or upward in FIG. 1 acts on the shaft member 2 of the fluid dynamic pressure bearing device 1 as a reaction force of the blowing action. Between the stator coil 5 and the rotor magnet 4, a magnetic force (repulsive force) in the direction to cancel this thrust acts, and the thrust load generated by the difference between the thrust and the magnetic force is the fluid dynamic bearing device 1 Acting on the thrust bearing T of the The magnetic force in the direction to cancel the thrust can be generated, for example, by displacing the stator coil 5 and the rotor magnet 4 in the axial direction (detailed illustration is omitted). Further, when the rotor 3 rotates, a radial load acts on the shaft member 2 of the fluid dynamic bearing device 1. The radial load acts on the radial bearings R1, R2 of the fluid dynamic bearing device 1.

  FIG. 2 is a cross-sectional view of the fluid dynamic bearing device 1 according to the present embodiment. The fluid dynamic bearing device 1 includes a housing 7, a bearing sleeve 8 disposed on the inner periphery of the housing 7, a shaft member 2 inserted on the inner periphery of the bearing sleeve 8, and the bearing sleeve 8 in the axial direction Here, it mainly includes a pressing member 9 for pressing in a direction along the central axis X of the bearing sleeve 8 (the same applies hereinafter) and holding the same with the housing 7. The inner space of the housing 7 is filled with a predetermined amount of lubricating oil L (indicated by dense hatching in FIG. 2), and at least the radial bearing portions R1 and R2 supporting the shaft member 2 in the radial direction. The radial bearing gap Gr (see FIG. 4) and the bottom gap Gb accommodating the thrust bearing portion T supporting the lower end of the shaft member 2 in the thrust direction are filled with the lubricating oil L. In the following, for convenience of explanation, one side in the axial direction in which the housing 7 is open is referred to as the upper side, and the opposite side in the axial direction is the lower side. However, the posture of the fluid dynamic bearing device 1 in use is limited. It is not a thing.

  The housing 7 has a shape (a so-called bottomed cylindrical shape) having a cylindrical portion 7a and a bottom portion 7b closing the lower end side of the cylindrical portion 7a, and in the present embodiment, the cylindrical portion as shown in FIG. 7a and the bottom 7b are integrally formed of metal. A stepped portion 7c is formed integrally with the cylindrical portion 7a and the bottom portion 7b on the inner periphery of the boundary portion between the cylindrical portion 7a and the bottom portion 7b, and the lower end surface 8b of the bearing sleeve 8 abuts on the upper end surface 7c1 of the stepped portion 7c. There is. In the present embodiment, on the upper end surface 7b1 of the bottom 7b of the housing 7, for example, the thrust plate 10 made of resin is disposed. Thus, the upper end surface 10a of the thrust plate 10 is made lower than the upper end surface 7c1 of the step 7c by a predetermined height. In this case, the upper end surface 10 a of the thrust plate 10 is a thrust bearing surface. However, the thrust plate 10 is not necessarily provided, and may be omitted. In that case, the upper end surface 7b1 of the bottom 7b is a thrust bearing surface. Of course, the housing 7 can also be an injection-molded product of resin.

  The shaft member 2 has a shaft portion 2 a inserted into the inner periphery of the bearing sleeve 8. In this case, at least the shaft portion 2a of the shaft member 2 is formed of a highly rigid metal material including a steel material such as stainless steel. The outer peripheral surface 2a1 of the shaft portion 2a is formed to be a smooth cylindrical surface, and is formed so that the outer diameter dimension is constant over the entire length of the shaft portion 2a except for the convex spherical tip 2a2. The outer diameter of the shaft member 2 is smaller than the inner diameter of the bearing sleeve 8 (the diameter of the inner circumferential surface 8 a). As described above, the shaft member 2 is insertable into and removable from the bearing sleeve 8. The tip 2 a 2 of the shaft 2 a is in contact with the upper end surface 10 a of the thrust plate 10 disposed at the bottom of the housing 7.

  The bearing sleeve 8 is either a porous body, in this case copper-based powder (including not only pure copper powder but also copper alloy powder) and / or iron-based powder (including not only pure iron powder but also iron alloy powder) It is formed in a cylindrical shape by a porous body of sintered metal which is a main component. In this case, the lubricating oil L may be impregnated in the internal holes of the bearing sleeve 8. The bearing sleeve 8 may be formed of a porous body other than sintered metal, for example, a porous resin, or may be formed of a solid body of metal without internal pores (copper, stainless steel, etc.).

  Cylindrical radial bearing surfaces forming radial bearing gaps Gr (see FIG. 4) between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the opposing shaft portion 2a are provided at two axial positions. Provided. As shown in FIG. 3, dynamic pressure generating portions (radial dynamic pressure generating portions) A1 and A2 for generating dynamic pressure action on the lubricating oil L in the radial bearing gap Gr are formed on the respective radial bearing surfaces. ing. The radial dynamic pressure generating portions A1 and A2 of the present embodiment are respectively inclined in opposite directions and axially spaced from each other, and are provided with a plurality of upper dynamic pressure grooves Aa1 and lower dynamic pressure grooves Aa2, It has a convex-shaped hill part which divides dynamic-dynamic-pressure groove Aa1 and Aa2, and has a herringbone shape as a whole. The hill portion of the present embodiment is an annular portion provided between the inclined hill portion Ab provided between adjacent dynamic pressure grooves in the circumferential direction and the upper and lower dynamic pressure grooves Aa1 and Aa2 and having substantially the same diameter as the inclined hill portion Ab. It consists of hill part Ac.

  In the upper radial dynamic pressure generating portion A1, the axial dimension of the upper dynamic pressure groove Aa1 is larger than the axial dimension of the lower dynamic pressure groove Aa2. On the other hand, in the lower radial dynamic pressure generating portion A2, the axial dimension of the lower dynamic pressure groove Aa2 is larger than the axial dimension of the upper dynamic pressure groove Aa1. Further, the axial dimension of the upper dynamic pressure groove Aa1 constituting the radial dynamic pressure generating portion A1 is equal to the axial dimension of the lower dynamic pressure groove Aa2 constituting the radial dynamic pressure generating portion A2, and The axial dimension of the lower dynamic pressure groove Aa2 constituting the pressure generating portion A1 is equal to the axial dimension of the upper dynamic pressure groove Aa1 constituting the radial dynamic pressure generating portion A2. Therefore, when the shaft member 2 rotates, the lubricating oil L in the radial bearing gap Gr on the upper side (radial bearing portion R1) and the lower side (radial bearing portion R2) respectively corresponds to the lower side (radial bearing portion R2) and the upper side (radial bearing portion R2). It is pushed into the radial bearing gap of the radial bearing portion R1).

  For example, the radial dynamic pressure generating portions A1 and A2 simultaneously perform the forming of the bearing sleeve 8 (more specifically, the sintered body formed by compacting the metal powder and then sintering is subjected to a sizing process Therefore, the bearing sleeve 8 may be formed by molding at the same time as molding the bearing sleeve 8 of finished dimensions, and in view of the good workability of the sintered metal, the inner peripheral surface is rolled to a smooth bearing surface. You may form by giving plastic processing, such as construction. Further, the form of the radial dynamic pressure generating portions A1, A2 (each dynamic pressure groove) is not limited to this. For example, any one or both of the radial dynamic pressure generating portions A1 and A2 may have a plurality of spiral dynamic pressure grooves arranged in the circumferential direction. Further, either or both of the radial dynamic pressure generating portions A1 and A2 may be formed on the outer peripheral surface 2a1 of the opposing shaft portion 2a. The radial dynamic pressure bearing portions A1 and A2 do not necessarily have to be separated in the axial direction. For example, although not shown, they may be provided adjacent to each other in the axial direction.

  Further, in the present embodiment, the bearing sleeve 8 is located on the outer peripheral side of the upper end surface 8c and on the center side of the central axis X of the bearing sleeve 8 than the upper end surface 8c (in FIG. It has a receding surface 8g which is retracted to the side closer to the axial middle position). The receding surface portion 8g has, for example, a flat shape, and is formed parallel to the lower end surface 8b and the upper end surface 8c. In this case, the first outer peripheral surface 8d1 having a relatively small outer diameter is provided between the upper end surface 8c and the receding surface portion 8g, and the outer diameter is relatively provided between the lower end surface 8b and the receding surface portion 8g. A large second outer circumferential surface 8d2 is provided. In this case, both the lower end surface 8 b and the upper end surface 8 c have a flat shape without irregularities such as dynamic pressure grooves. However, this does not deny the existence of surface openings resulting from the porous structure (in particular, the sealing treatment such as coating may not be performed).

  Further, as shown in FIG. 4, an inclined surface portion 11 forming an oil buffer space 12 with the outer peripheral surface 2a1 of the shaft portion 2a is provided between the inner peripheral surface 8a and the upper end surface 8c. In this embodiment, the inclined surface portion 11 is continuous with the inner peripheral surface 8a and the chamfered portion 8e continuous on the upper end side, and the chamfered portion 8e and the upper end side, and the inclined surface portion 11 with respect to the central axis X of the bearing sleeve 8 The inclination angle θ2 is composed of a large large inclined surface 8f. The large inclined surface 8f is continuous with the upper end surface 8c. Here, the inclination angle θ1 of the chamfered portion 8e with respect to the central axis X is usually 45 °, but it is of course possible to increase or decrease it by adjusting the molding conditions or the like. The inclination angle θ2 of the large inclined surface 8f with respect to the central axis X is arbitrary as long as the above conditions are satisfied, and is set, for example, in a range larger than 45 ° and smaller than 90 °. It is set in the range of ° or less. Further, in this case, the radial dimension of the large inclined surface 8 f can be arbitrarily set within the range of the upper end surface 8 c.

  The bearing sleeve 8 having the above-mentioned shape is accommodated in the housing 7 in a state where the lower end surface 8 b is in contact with the upper end surface 7 c 1 of the step 7 c of the housing 7. As a result, relative positioning between the housing 7 and the bearing sleeve 8 in the axial direction is achieved, and a predetermined volume of space between the lower end surface 8 b of the bearing sleeve 8 and the upper end surface 10 a of the thrust plate 10 provided at the bottom of the housing 7 is Bottom clearance Gb is formed.

  The bearing sleeve 8 can be fixed to the housing 7 by an appropriate means such as press-fitting (press-fitting with a large interference), bonding, press-bonding (combination of press-fitting and bonding), but in the present embodiment The bearing sleeve 8 is held between the pressing member 9 and the housing 7 by axially pressing the receding surface portion 8g provided radially outward with the pressing member 9, thereby fixing the bearing sleeve 8 to the housing 7 (see FIG. See Figure 2). At this time, if the pressing member 9 is fixed to the housing 7, the outer peripheral surface (here, the second outer peripheral surface 8d2) of the bearing sleeve 8 does not have to be fixed directly to the inner peripheral surface 7a1 of the housing 7 Because the bearing sleeve 8 may be assembled, the operation of assembling the bearing sleeve 8 to the housing 7 is simplified. The means for fixing the pressing member 9 to the housing 7 is optional. For example, the outer peripheral surface 9 b of the pressing member 9 is moved to a position where the lower end surface 9 a of the pressing member 9 abuts on the receding surface 8 g of the bearing sleeve 8. The means etc. which press-fit to inner skin 7a1 of 5 are employable. In this case, a slight gap may exist between the inner circumferential surface 9 c of the pressing member 9 and the first outer circumferential surface 8 d 1 of the bearing sleeve 8.

  As described above, when the bearing sleeve 8 is fixed to the housing 7 by holding the bearing sleeve 8 between the housing 7 and the pressing member 9, the upper end surface 8c is open to the atmosphere, and in the present embodiment, The upper end surface 9 d of the pressing member 9 is at the same height position (the same position in the central axis X direction) as the upper end surface 8 c of the bearing sleeve 8.

  When the fluid dynamic bearing device 1 having the above configuration is disposed in the posture shown in FIG. 2, at least the radial bearing gap Gr and the thrust bearing portion T of the radial bearing portions R1 and R2 in the internal space of the housing 7 A part of the area including the bottom gap Gb contained therein is filled with the lubricating oil L. In the present embodiment, an annular space (a part of the oil buffer space 12) formed between the chamfered portion 8e located on the upper inner periphery of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a is also lubricating oil L (See Figure 2). On the other hand, the area of the remaining part of the internal space of the housing 7 (the area excluding the above-described part of the area) is not filled with the lubricating oil L at normal time (for example, at room temperature in terms of temperature). Specifically, the annular space (the remaining portion of the oil buffer space 12) between the large inclined surface 8f of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a is not usually filled with the lubricating oil L.

  As described above, in the fluid dynamic bearing device 1, the amount (volume) of the lubricating oil L filled in the internal space of the housing 7 is smaller than the volume of the internal space of the housing 7. The internal space of the pressure bearing device 1 (housing 7) is provided with a gap where the lubricating oil L does not exist.

  Here, as the lubricating oil L, an ester-based, PAO-based or fluorine-based lubricating oil is suitably used in consideration of temperature change and the like during use and transportation of the fluid dynamic pressure bearing device 1.

  The fluid dynamic bearing device 1 having the above configuration is assembled, for example, in the procedure shown in FIGS. 5 (a) and 5 (b).

  First, the bearing sleeve 8 in which the inner hole is impregnated with the lubricating oil L is prepared. Then, until the lower end surface 8b of the bearing sleeve 8 abuts on the upper end surface 7c1 of the step portion 7c of the housing 7, the bearing sleeve 8 is lightly press-fit onto the inner periphery of the housing 7 or fitted with a predetermined gap therebetween. . Subsequently, the lower end surface 9a of the pressing member 9 is fixed to the upper end portion of the inner peripheral surface 7a1 of the housing 7 in a state where the lower end surface 9a is in contact with the receding surface 8g of the bearing sleeve 8. It clamps from the axial direction both sides with bottom 7b (step 7c), and fixes to housing 7. With the housing 7 and the bearing sleeve 8 and the pressing member 9 thus subassembled, a predetermined amount of lubricating oil L is filled in the internal space of the housing 7 (for example, the inner periphery of the bearing sleeve 8) (see FIG. 5 (a)). Then, as shown in FIG. 5 (b), the shaft 2a is inserted into the inner periphery of the bearing sleeve 8, and the tip 2a2 of the shaft 2a is brought into contact with the upper end surface 10a of the thrust plate 10 (FIG. Reference), the outer peripheral surface 2a1 of the shaft 2a is opposed to the inclined surface 11 of the bearing sleeve 8, which in the present embodiment is the chamfer 8e and the large inclined surface 8f (see FIG. 4). Thereby, the oil buffer space 12 is formed, and the fluid dynamic bearing 1 shown in FIG. 2 is completed.

  In the fluid dynamic bearing device 1 configured as described above, when the shaft member 2 rotates, radial bearing surfaces provided to be separated at two locations above and below the inner peripheral surface 8a of the bearing sleeve 8 and a shaft portion opposed thereto Radial bearing gaps Gr and Gr are respectively formed between the outer peripheral surface 2a1 and the outer peripheral surface 2a. Then, with the rotation of the shaft member 2, the pressure of the oil film formed in the both radial bearing gaps Gr, Gr is increased by the dynamic pressure action of the radial dynamic pressure generating portions A1, A2, and the shaft member 2 is supported non-contact in the radial direction. The radial bearing portions R1 and R2 are formed at two places in the axial direction. At the same time, a thrust bearing portion T is formed which contacts and supports the shaft member 2 in the thrust direction on the upper end surface 10 a of the thrust plate 10 disposed at the bottom of the housing 7. As described with reference to FIG. 1, the shaft member 2 exerts a magnetic force as an external force that presses the shaft member 2 downward (to the bottom 7 b of the housing 7). Therefore, excessive rotation of the shaft member 2 as the shaft member 2 rotates can be prevented as much as possible from being pulled out of the inner periphery of the bearing sleeve 8.

  In addition, between the shaft portion 2a and the bearing sleeve 8, which is the only communication portion between the internal space of the housing 7 and the atmosphere, an inclined surface portion provided between the inner peripheral surface 8a and the upper end surface 8c of the bearing sleeve 8. An oil buffer space 12 is formed between the shaft portion 2a and the outer peripheral surface 2a1 of the shaft portion 2a (see FIG. 4). Therefore, when the internal space of the housing 7 changes to a high temperature state, for example, the environment in which the fluid dynamic bearing device 1 is placed becomes a high temperature environment, the lubricating oil L filling the internal space of the housing 7 expands. Even if it does, the lubricating oil L which was expanded in the oil buffer space 12 mentioned above can be hold | maintained, and the leaking out of the lubricating oil L can be prevented (refer Fig.6 (a)). Further, as in the present embodiment, the inclination angle θ2 with respect to the central axis X of the large inclined surface 8f located on the bearing outer side is made relatively large, and the central axis X of the chamfered portion 8e located on the inner side of the bearing from the large inclined surface 8f. By relatively reducing the inclination angle θ1 with respect to the angle θ1, a pull-in function to the inside of the bearing due to the capillary phenomenon is effectively generated for the lubricating oil L held in the oil buffer space 12. Therefore, the lubricating oil L in the state of being held in the oil buffer space 12 returns to the inside of the bearing (a radial bearing gap or the like) via the annular space between the chamfered portion 8e and the outer peripheral surface 2a1 of the shaft portion 2a See FIG. 6 (b)).

  As described above, in the fluid dynamic pressure bearing device 1 according to the present invention, when the radial bearing gap Gr and the bottom gap Gb are filled with the lubricating oil L (see FIG. 2), A void is provided. This means that the amount of lubricating oil L filled in the inner space is smaller than the total volume of the inner space. In the fluid dynamic bearing device 1 according to the present invention, since the shaft member 2 is attachable to and detachable from the bearing sleeve 8, as described above, after the bearing sleeve 8 is fixed to the inner periphery of the housing 7. A necessary amount of lubrication can be provided to the internal space of the housing 7 simply by filling the internal space of the housing 7 with the lubricating oil L using an appropriate oil supply tool before inserting the shaft member 2 into the inner periphery of the bearing sleeve 8. Oil L can be supplied. Therefore, a large-scale equipment for oil supply such as vacuum impregnation or a highly precise adjustment or management operation of the oil surface is not necessary, and the manufacturing cost of the fluid dynamic bearing 1 can be reduced.

  Further, in the fluid dynamic bearing device 1 according to the present invention, as described above, the bearing is adopted while filling a part of the internal space of the housing 7 with the lubricating oil L, so-called oil-filled structure in the form of a partial fill. The upper end surface 8c of the sleeve 8 is open to the atmosphere, and an oil buffer space 12 is formed between the inner peripheral surface 8a and the upper end surface 8c of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a. The inclined surface portion 11 was provided (see FIGS. 2 and 4). As a result, the seal member, which is essential in the fluid dynamic pressure bearing device having an oil-impregnated structure in the form of a conventional partial fill, can be eliminated, so the entire fluid dynamic pressure bearing device 1 can be obtained without changing the axial dimension of the bearing sleeve 8 The axial dimension of can be shortened. In addition, when using the oil filling structure of the partial fill, it is not necessary to require a large oil buffer volume as compared with the case of adopting the oil filling structure in the form of the full fill. Therefore, the oil buffer space 12 having a sufficient volume can be obtained only by utilizing a part of the upper end side of the bearing sleeve 8 as the inclined surface portion 11 to form the oil buffer space 12. As described above, according to the present invention, it is possible to assemble the fluid dynamic bearing device 1 capable of effectively preventing the leakage of the lubricating oil L at low cost.

  Further, in the present embodiment, the inclined surface portion 11 is continuous with the chamfered portion 8e continuous with the inner peripheral surface 8a of the bearing sleeve 8 and the chamfered portion 8e, and the inclination angle θ1 of the chamfered portion 8e with respect to the central axis X of the bearing sleeve 8 The inclination angle θ2 with respect to the central axis X of the bearing sleeve 8 is larger than that of the large inclination surface 8f. Thereby, for example, when inserting the shaft portion 2a into the inner periphery of the bearing sleeve 8 (see FIG. 5B), the shaft portion 2a is made smooth by the chamfered portion 8e having a relatively small inclination angle θ1 with respect to the central axis X Be inserted. On the other hand, the volume of the oil buffer space 12 can be increased by setting the inclination angle θ2 of the large inclined surface 8f relatively large.

  Further, in the present embodiment, since the bearing sleeve 8 is axially pressed by the pressing member 9 and the bearing sleeve 8 is held between the pressing member 9 and the housing 7, the pressing member 9 is fixed to the housing 7. The bearing sleeve 8 can be fixed to the housing 7 only by doing this. Therefore, the effort required for the assembly of members (especially the assembly of bearing sleeve 8 and housing 7) can be reduced. Further, the bearing sleeve 8 is provided with a receding surface portion 8g receding from the upper end surface 8c to the axial center side of the bearing sleeve 8, and the bearing surface 8 is held by pressing the receding surface portion 8g with the pressing member 9. Therefore, a part or all (in the present embodiment, all) of the pressing member 9 in the axial direction can be accommodated on the axial center side of the bearing sleeve 8 with respect to the upper end surface 8c. Therefore, the axial dimension of the fluid dynamic bearing 1 can be shortened as much as possible while using the pressing member 9.

  As mentioned above, although one Embodiment of this invention was described, the fluid hydrodynamic bearing apparatus 1 which concerns on this invention, and its manufacturing method take any form in the range of this invention, without being limited to the form of the said illustration. obtain.

  For example, in the above embodiment, the inclined surface portion 11 is exemplified by the chamfered portion 8e both having a tapered shape and the large inclined surface 8f having a larger inclination angle θ2 with respect to the central axis X than the chamfered portion 8e. Other forms are also possible. For example, although not shown, the inclined surface portion 11 may be configured of one or more curved surfaces (for example, a shape in which the inclination angle with respect to the central axis X increases outward in the axial direction), or a tapered inclined surface The inclined surface portion 11 may be configured by the curved surface described above.

  In the above embodiment, the receding surface portion 8g has a flat shape and is parallel to the upper end surface 8c (see FIG. 2), but other shapes may of course be adopted. For example, the receding surface portion 8g can have any shape as long as the bearing sleeve 8 can be axially pressed by the pressing member 9, such as an inclined surface or a concave surface. Similarly, the shape of the pressing member 9 is arbitrary as long as the bearing sleeve 8 can be pressed in the axial direction, and may have a shape other than illustrated.

  Further, in the embodiment described above, the housing 7 provided separately from the motor base 6 is fixed to the inner periphery of the motor base 6, but the part corresponding to the motor base 6 is integrally fixed to the housing 7 It can also be provided.

  Further, either or both of the radial bearing portions R1 and R2 may be configured by other known dynamic pressure bearings such as so-called multi-arc bearings, step bearings, and wave-shaped bearings. When the thrust bearing portion T is configured by a dynamic pressure bearing, the dynamic pressure bearing can also be configured by another known dynamic pressure bearing such as a so-called step bearing or a wave type bearing.

  Further, in the embodiment described above, by arranging the rotor magnet 4 and the stator coil 5 in the axial direction, an external force for pressing the shaft member 2 against the bottom 7 b of the housing 7 can be applied to the shaft member 2. Although it was made to act, the means for making such an external force act on shaft member 2 is not restricted to the above-mentioned. Although illustration is omitted, for example, the magnetic force can be applied to the rotor 3 by arranging a magnetic member capable of attracting the rotor magnet 4 so as to face the rotor magnet 4 in the axial direction. Further, when the thrust as the reaction force of the blowing action is sufficiently large and the shaft member 2 can be pressed downward only by this thrust, the magnetic force (magnetic attraction force) as the external force for pressing the shaft member 2 downward is You may omit it.

  Further, although the case where the present invention is applied to the fluid dynamic pressure bearing device 1 in which the rotor 3 having blades as the rotating member is fixed to the shaft member 2 has been described above, the present invention uses the rotating member as: The present invention can be preferably applied to the fluid dynamic bearing device 1 in which a disk hub having a disk mounting surface or a polygon mirror is fixed to the shaft member 2. That is, according to the present invention, not only the fan motor as shown in FIG. 1, but also a fluid dynamic pressure bearing incorporated in other electric devices such as a spindle motor for a disk drive and a polygon scanner motor for a laser beam printer (LBP). It can be preferably applied to the device 1 as well.

DESCRIPTION OF SYMBOLS 1 fluid dynamic pressure bearing device 2 shaft member 2a shaft portion 2a1 outer peripheral surface 3 rotor 4 rotor magnet 5 stator coil 6 motor base 7 housing 7a cylindrical portion 7b bottom portion 7c step portion 8 bearing sleeve 8e chamfered portion 8f large inclined surface 8g receding surface portion 9 pressing member 10 thrust plate 11 inclined surface portion 12 oil buffer space A1, A2 radial dynamic pressure generating portion Aa1, Aa2 dynamic pressure groove Gb bottom gap Gr radial bearing gap L lubricating oil R1, R2 radial bearing portion T thrust bearing portion X central axis θ1 Inclination angle (Chamfered portion)
θ2 inclination angle (large inclination surface)

Claims (8)

A bottomed cylindrical housing closed at one axial end and open at the other axial end, a bearing sleeve disposed on the inner periphery of the housing, and an insertable and removable inner periphery of the bearing sleeve The shaft member is supported in the radial direction by an oil film of lubricating oil formed in a radial bearing gap between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member, and a shaft member having an inserted shaft portion. In a fluid dynamic bearing device comprising: a radial bearing portion; and a thrust bearing portion supporting one end of the shaft member in a thrust direction,
A part of the internal space of the housing is filled with the lubricating oil, and the remaining part is a void not filled with the lubricating oil,
One axial end face of the bearing sleeve on the opening side of the housing is open to the atmosphere, and between the inner peripheral face of the bearing sleeve and the axial one end face, between the outer peripheral face of the shaft portion A fluid dynamic bearing device comprising an inclined surface portion forming an oil buffer space.   The inclined surface portion includes a chamfered portion continuous with the inner circumferential surface of the bearing sleeve, and a large inclined surface continuous with the chamfered portion and having a larger inclination angle with respect to the central axis of the bearing sleeve than the chamfered portion. The fluid dynamic bearing device according to 1.   The fluid dynamic bearing according to claim 1 or 2, wherein an inclination angle of the large inclined surface with respect to the central axis is larger than 45 ° and smaller than 90 °. The bearing sleeve has, between the one axial end surface and the outer peripheral surface, a receding surface portion which is retracted to the axial center side of the bearing sleeve with respect to the one axial end surface,
The fluid dynamic bearing according to any one of claims 1 to 3, wherein the bearing sleeve is sandwiched between the pressing member and the housing by pressing the receding surface portion in the axial direction by the pressing member.   The fluid dynamic bearing according to claim 4, wherein the pressing member is fixed to the housing by press-fitting the outer peripheral surface thereof to the inner peripheral surface of the housing.   The fluid dynamic pressure bearing device according to any one of claims 1 to 4, wherein the bearing sleeve is made of a porous body in which internal holes are impregnated with the lubricating oil.   The fluid dynamic pressure bearing device according to any one of claims 1 to 6, wherein the lubricating oil is an ester-based, PAO-based or fluorine-based lubricating oil.   A motor comprising the fluid dynamic bearing device according to any one of claims 1 to 7.

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