WO2005124171A1 - Sintered bearing, method of manufacturing the same, and motor with sintered bearing - Google Patents

Abstract

[PROBLEMS] To provide a sintered bearing manufacturable at low cost and having high performance and a motor having the sintered bearing. [MEANS FOR SOLVING PROBLEMS] This sintered bearing is so formed that the distribution of the dispersive density of a solid lubricating powder mixed in the bearing base material powder of a bearing powder material is varied continuously or stepwise in the axial or radial direction to segregate a solid lubricant with high density to a necessary portion such as that to which high load is applied so that the function of the bearing can be improved without so increasing the amount of the solid lubricating powder. Thus, the function of the bearing can be improved without increasing the added amount of the rather expensive solid lubricant.

Description

 Specification

 TECHNICAL FIELD The present invention relates to a sintered bearing, a method for manufacturing the same, and a motor provided with the sintered bearing.

 The present invention relates to a sintered bearing in which a bearing body material is formed by sintering a bearing powder material in which a solid lubricant powder is mixed with a bearing base powder, a method for manufacturing the same, and a sintered bearing And a motor having the same.

 Background art

 [0002] In general, a bearing body of a sintered bearing containing a solid lubricant is filled with a bearing powder material in which a solid lubricant powder is mixed with a bearing base powder in a die, and the die is filled in the die. Bearing A powder material is formed into a substantially cylindrical shape by sintering. The bearing powder used for the bearing is iron, iron copper, iron bronze, iron brass, bronze, phosphor bronze, or a mixture thereof. Examples thereof include graphite, molybdenum disulfide, BN, and tungsten disulfide, as well as copper plating powder obtained by plating these with metallic copper or the like.

 [0003] In such a sintering process of a bearing powder material in which a solid lubricating powder is mixed with a bearing base powder, the bearing powder material is pressed and molded into a predetermined shape. It is heated and fired, and the fired body of the bearing powder material containing the solid lubricant is subjected to a sizing step to perform oil impregnation.

 [0004] The solid lubricant powder force generated in the bearing base material as described above is considered so as to be contained as uniformly dispersed as possible in the bearing body having the bearing base material as a matrix. . For example, in order to prevent segregation due to the specific gravity difference between the solid lubricating powder and the bearing base powder, the specific gravity of the two powders is adjusted by applying copper plating to the solid lubricating powder before firing. Measures have been taken.

[0005] When the solid lubricant is uniformly dispersed in the bearing body having the bearing base material as a matrix, the solid lubricant, which is a relatively expensive material, functions as a bearing. !! ヽ ヽ The entire sintered bearing becomes extremely expensive, especially if the amount of solid lubricant added is increased to improve bearing performance. I will. [0006] In addition, when the amount of the solid lubricant added is increased, the flowability of the entire bearing material is reduced, so that good moldability cannot be obtained. There's a problem. Further, since the solid lubricant which has lost the base material of the bearing as a matrix also increases, problems such as fluctuation of bearing friction and seizure, or contamination by the solid lubricant are caused.

 Disclosure of the invention

 Problems to be solved by the invention

[0007] Therefore, an object of the present invention is to provide a sintered bearing capable of enhancing the bearing function without increasing the amount of solid lubricant added, and a method of manufacturing the same.

 Means for solving the problem

 [0008] In order to solve the above-mentioned problems, in a method of manufacturing a sintered bearing according to claim 1 of the present invention, a solid lubricating powder mixed with a bearing base powder of a bearing powder material filled in a die is provided. The bearing powder has a specific gravity smaller than the specific gravity of the bearing base material powder, and the two powders are mixed to produce a bearing powder material. According to this manufacturing method, it is possible to bias the solid lubricating powder to a necessary portion, for example, a portion to which a high load force is applied, by utilizing the specific gravity difference between the two powders. Therefore, the bearing function can be improved without significantly increasing the amount of the solid lubricating powder.

 In the method for manufacturing a sintered bearing according to claim 2 of the present invention, when the bearing powder material according to claim 1 is filled in a die, the molding cavity inside the die is kept in a negative pressure state. The bearing powder material is sucked into the molding cavity and charged. Thus, when the bearing powder material is sucked into the die, the solid lubricating powder can be biased toward a necessary portion by utilizing a specific gravity difference with the bearing powder material.

 [0010] Further, in the method for manufacturing a sintered bearing according to claim 3 of the present invention, in the pressing and compression molding step constituting the sintering step according to claim 1, the bearing powder is formed. The compression ratio of the body material is set to 2 or more. By setting the compression ratio to 2 or more, the concentration difference in the axial direction is likely to occur in the axial direction as the filling depth increases.

[0011] In the method for manufacturing a sintered bearing according to claim 4 of the present invention, since the solid lubricating powder according to claim 1 is used without being subjected to metal plating. The specific gravity is reduced by the amount that the metal is not applied to the powder. Also, the metal plating step is omitted, and the productivity is improved.

 [0012] In the method for manufacturing a sintered bearing according to claim 5 of the present invention, the solid lubricating powder according to claim 1 or 2 includes graphite powder, and is usually used frequently. The sintered bearing is easily manufactured by the solid lubricating powder.

 [0013] Further, in the sintered bearing according to claim 6 of the present invention, the sintered bearing is formed by molding the bearing main body by using the manufacturing method according to claim 1, wherein the bearing main body is formed of a powdered bearing base material. Solid lubricant powder is formed in the sintered body so that the solid lubricant generated is contained in a dispersed state. Further, the dispersion concentration distribution of the solid lubricant in the bearing main body changes in the axial direction in the bearing main body. For this reason, it is possible to bias the solid lubricating powder to a portion where a high load is applied, and it is possible to improve the bearing function without increasing the amount of the solid lubricating powder so much.

 [0014] The sintered bearing according to claim 7 of the present invention includes a bearing main body containing a solid lubricant generated from the solid lubricant powder in a dispersed state in a sintered body of the bearing base powder. In the sintered bearing, the dispersion concentration distribution of the solid lubricant in the bearing body changes in the axial direction in the bearing body. This force can bias the part where the solid lubricant powder is subjected to a high load. Furthermore, the bearing function can be improved without increasing the amount of the solid lubricating powder.

 [0015] In the sintered bearing according to claim 8 of the present invention, the dispersion concentration distribution of the solid lubricating powder according to claim 6 or 7 is changed from one end portion in the axial direction of the bearing body to the other end portion. Since the direction force is continuously increasing or decreasing, the solid lubricating powder can be biased toward a required portion at one end or the other end in the axial direction, for example, a portion where a high load force S is applied. . Therefore, the bearing function can be improved without increasing the amount of the solid lubricating powder.

[0016] Further, in the sintered bearing according to claim 9 of the present invention, the sintered bearing is formed by molding the bearing main body using the manufacturing method according to claim 1, wherein the bearing main body is formed of the bearing base material. The solid lubricant is formed so as to contain the generated solid lubricant in a dispersed state in a powdered sintered body, and the dispersed concentration distribution of the solid lubricant in the bearing body is determined by the bearing main body. It changes radially in the body.

 [0017] The sintered bearing according to claim 10 of the present invention is provided with a bearing body containing a solid lubricant generated from the solid lubricant powder in a dispersed state in a sintered body of the bearing base powder. In the sintered bearing, the dispersion concentration distribution of the solid lubricant in the bearing body changes radially in the bearing body.

 [0018] For example, the sintered bearing according to claim 11 of the present invention is configured such that the dispersion concentration distribution of the solid lubricant in claim 9 or 10 is increased in the inner peripheral wall portion of the bearing body. . As a result, the solid lubricating powder can be biased toward the radially inner portion where the load is applied, and the bearing function can be improved without increasing the amount of the solid lubricating powder so much. .

 [0019] Furthermore, the motor according to claim 12 of the present invention includes a sintered bearing capable of biasing a part where a high load is exerted, so that the bearing function can be enhanced at low cost. . The invention's effect

 [0020] As described above, the sintered bearing and the method of manufacturing the sintered bearing according to the present invention are characterized in that the solid lubricating powder mixed with the bearing base powder has a specific gravity higher than that of the bearing base powder. A small material is adopted, and a powder material of the bearing is manufactured by mixing these two powders. According to this manufacturing method, the solid lubricating powder mixed with the bearing base powder of the bearing powder material can be biased toward a necessary portion, for example, a portion where a high load is applied. In addition, the segregation can improve the bearing function without increasing the amount of the solid lubricant powder. Further, the bearing function can be enhanced without increasing the amount of the relatively expensive solid lubricant, and a low-cost, high-performance sintered bearing and a motor having the sintered bearing can be obtained.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment in which the present invention is applied to a spindle motor used in a rotary drive device of various media disks such as a DVD and a CD-ROM will be described in detail with reference to the drawings. I do.

First, as shown in FIG. 1, the overall structure of a spindle motor used in a media disk rotation drive device includes a stator set 10 as a fixing member and a stator set 10. And a rotor set 20 as a rotating member that is mounted so as to be relatively rotatable relative thereto. In the stator assembly 10, a bearing sleeve 12 made of a sintered bearing is fitted inside a bearing holder 12 fixed to a substantially central portion of a fixed base plate (base plate) 11. And so on.

 [0023] Further, a stator core 14 having a laminated body of electromagnetic steel plates and the like is fitted on a core mounting surface provided on the outer peripheral side wall surface of the bearing holder 12. A drive coil 15 is wound around each radial salient pole portion provided on the stator core 14.

 Further, the above-described rotating shaft 21 constituting the rotor set 2 is rotatably inserted into a bearing hole formed through the bearing sleeve 13 along the central axis thereof. The rotating shaft 21 in the present embodiment is formed of stainless steel.

 At this time, the bearing sleeve 13 has a so-called middle relief bearing structure, as shown in FIG. 2, particularly a force constituted by a sintered bearing made of a substantially hollow cylindrical metal sintered body. ing. In other words, the inner peripheral surface of the bearing hole 13a formed in the bearing sleeve 13 has, at both end portions in the axial direction (vertical direction in the drawing), convex bearing surfaces 13b, 13c protruding inward in the radial direction. Are formed so as to form an annular shape, and a relief recessed surface 13d, which is an enlarged inner diameter of the inner peripheral surface of the bearing hole 13a, is formed in a stepped portion between the bearing surfaces 13b, 13c in the axial direction. It is formed to be depressed! The detailed structure of such a bearing sleeve 13 and a method for manufacturing the same will be described later in detail as a main part of the present invention.

 At this time, the bearing surfaces 13b and 13c are arranged so as to face the cylindrical bearing surface formed on the outer peripheral surface of the rotating shaft 21 in the radial direction, and the two bearing surfaces are opposed to each other. Radial bearings RBI and RB2 are formed in the minute bearing gap between them. In each of these radial bearing portions RBI, RB2, the bearing surfaces 13b and 13c on the bearing sleeve 13 side and the bearing surface on the rotating shaft 21 side are circumferentially opposed via a minute gap of, for example, about several / zm. A predetermined lubricating oil such as a lubricating oil or a magnetic fluid is interposed in a bearing clearance space formed by the minute clearance.

Further, the bearing surfaces 13b and 13c on the bearing sleeve 13 side are configured to support a shaft of a port hub 22 described later together with the rotating shaft 21. [0028] On the other hand, a pivot portion 21a that forms a part of a spherical surface is provided at the illustrated lower end portion of the rotating shaft 21, and a thrust plate 16 is attached to an opening at the illustrated lower end side of the bearing holder 12. Has been. Further, a disc-shaped thrust receiving member 17 is mounted inside the thrust plate 16. The pivot portion 21a on the lower end of the rotary shaft 21 described above is disposed so as to make point contact with the upper surface of the thrust receiving member 17 in the illustrated direction, whereby the entire rotary shaft 21 is moved in the thrust direction. Become supported.

 A boss portion 22a of an outer rotor type mouth hub 22 having a thin bottom shape is fixed to an upper protruding portion of the rotating shaft 21. At the outermost peripheral portion of the rotor hub 22 extending radially outward from the boss portion 22a, an annular cylindrical upright wall 22b is provided, and an inner peripheral surface of the cylindrical upright wall 22b is provided. A drive magnet (permanent magnet) 23, also formed in an annular shape, is attached. Driving magnetizing surface forces formed along the inner and outer circumferential surfaces of the annular driving magnet 23 are arranged so as to approach each salient pole portion of the stator core 14 from the radially outer side. .

 Further, on the upper surface side of the rotor hub 22 in the figure, a hub stand 24 as a disk mounting portion is provided. The hub base 24 is fixed so as to be inserted into the outside of the boss portion 22a of the rotor hub 22. A mounting hole for a recording media disk (not shown) is passed through the hub base 24. As a result, the entire recording media disk is mounted in a state of being positioned in the radial direction.

 On the other hand, the above-described bearing sleeve 13 is formed of a porous sintered bearing having a large number of pores, and the porous interior of the sintered bearing is impregnated with the above-described lubricating oil. I have. As shown in FIGS. 3 and 4, the bearing sleeve 13 has a large-diameter shape projecting radially outward at a substantially central portion in the axial direction on the outer peripheral surface of the bearing sleeve 13. The fixed portion 13e is provided so as to form an annular shape. The fixing portion 13e is fixed to the inner peripheral surface side of the bearing holder 12 by press fitting or the like, so that the entire bearing sleeve 13 is held.

[0032] Further, on both sides of the fixing portion 13e of the bearing sleeve 13 in the axial direction, the outer peripheral surface of the bearing sleeve 13 (the surface facing the bearing holder 12) has a smaller diameter than the fixing portion 13e. Shaped portions 13f and 13g are provided, and a step is formed at a boundary portion with the fixed portion 13e. These small diameter portions 13f, 13g are provided on the inner peripheral surface thereof at positions corresponding to the bearing surfaces 13b, 13c of the radial bearing portions RB1, RB2 described above, respectively.

 [0033] An annular gap is formed between the small diameter portions 13f and 13g and the inner peripheral surface of the bearing holder 12, and the two annular oil reservoirs 13h are formed by the formed annular gap. , 13i are defined respectively. The lubricating oil described above is injected and stored in these two oil reservoirs 13h and 13i, as shown in particular in FIG.

 On the other hand, the metal sintered bearing constituting such a bearing body of the bearing sleeve 13 is filled with a bearing powder material in a die and molded into a substantially cylindrical shape, as described later. Is made by sintering. A solid lubricant such as graphite or molybdenum disulfide is contained in a dispersed state in the matrix of the bearing body of the bearing sleeve 13 that also has such a sintered body force.

 [0035] In the present embodiment, the dispersed concentration distribution determined by the content of the solid lubricant changes in the axial direction inside the above-described bearing main body, and the solid lubricant is segregated. . For example, in FIG. 2, the radial bearing portion RB1 arranged on the upper side of the drawing has a solid lubricant in which the content of the solid lubricant is increased to be in a high concentration distribution state, and the radial bearing portion arranged on the lower side of the drawing has In part RB2, the content of the solid lubricant is reduced to achieve a low concentration distribution state. That is, the content of the solid lubricant is continuously increased from the lower end in the drawing to the upper end in the drawing of the bearing body, so that the dispersion concentration distribution is obtained.

 [0036] In the structure of the spindle motor as shown in Fig. 1, this is caused by the unbalanced load of the motor portion arranged on the upper side in the figure and the bearing surface 13b of the radial bearing portion RB1 arranged on the upper side in the figure. The structure is such that a large load is applied. For this reason, the content of the solid lubricant is increased so as to enhance the bearing function of the radial bearing portion RB1 on the upper side in the figure where the load load is large, so that a high concentration distribution state is achieved.

For example, when the load applied to the upper radial bearing RB1 in the figure is “twice” the load applied to the lower radial bearing RB2 in the figure, the solid in the upper radial bearing RB1 in the figure is correspondingly corresponding thereto. The content of the lubricant is set to be "twice" the content of the solid lubricant in the radial bearing portion RB2 on the lower side in the figure. [0038] Such a segregated state of the solid lubricant is realized by setting a specific gravity difference in the bearing powder material. More specifically, first, as a bearing powder material in the present embodiment, a solid lubricating powder having a force such as graphite is used as a matrix by using a bearing base powder such as iron-copper-tin or iron-copper as a matrix. A mixture obtained by adding only the components is used.

 At this time, in the present embodiment, the specific gravity of the solid lubricating powder is reduced by omitting the copper plating as a metal plating applied to the solid lubricating powder. The specific gravity of the body is set to, for example, 1Z2 or less, preferably 1Z3 or less. Then, a bearing powder material is manufactured by mixing a solid lubricating powder having a small specific gravity with a bearing base powder having a large specific gravity as a matrix. In addition, no oil or the like for preventing segregation of the solid lubricating powder should be used when mixing them.

 When the thus obtained bearing powder material is filled in a die, the solid lubricating powder can be biased by utilizing the above-described specific gravity difference, and the solid lubricating powder can be dispersed during firing. The solid lubricant produced from the powder can be biased in the axial direction. This point will be described below together with the manufacturing process of the bearing sleeve 13.

 Next, a method and an apparatus for manufacturing the bearing sleeve 13 will be described with reference to FIGS. 5 and 6 (A) to (F). FIG. 5 is a process diagram schematically illustrating a method and an apparatus for manufacturing a bearing sleeve. FIG. 6 is a process diagram schematically illustrating a method and an apparatus for manufacturing a bearing sleeve.

 First, as shown in FIG. 5, an outline of a manufacturing apparatus for manufacturing the bearing sleeve 13 is a core rod 104 having an outer diameter substantially the same as the inner diameter of the bearing sleeve 13, and arranged on the outer circumference of the core rod 104. Dies 100, an upper punch 103 and a lower punch 101 for compressing the bearing powder material stored between the core rod 104 and the die 100, and a feeder cup 102 for supplying the bearing powder material. RU

 Further, in FIG. 5, the molding cavity 100a is a space formed between the core rod 104 and the die 100, in other words, a filling space in which the bearing powder material is filled.

 Next, a method for manufacturing the bearing sleeve 13 will be described with reference to FIGS. 6 (A) to 6 (F).

First, the entire manufacturing process of the bearing sleeve 13 is schematically shown in FIGS. The “powder filling step”, the “pressing and compression molding step” shown in FIGS. 6 (D) and (E), and the “unloading step” shown in FIG. 6 (F), It is composed of a “heat treatment step” and a “pressure sizing molding step” not shown! RU

The “powder filling step” will be described with reference to FIGS. 6 (A), 6 (B) and 6 (C). In the initial state, as shown in FIG. 6A, the upper end surface of the die 100 and the upper end surfaces of the lower punch 101 and the core rod 104 are arranged at the same surface position. In addition, the upper punch 10

3 is waiting.

Next, the feeder cup 102 moves toward the dice 100 and stops on the dice 100 as shown in FIG. 6 (B).

 In this state, the bearing powder material obtained by mixing the above-described specific gravity! / Bearing base powder and solid lubricating powder having a low specific gravity is passed through the feeder cup 102 into the molding cavity 100a of the die 100. Is now being supplied to

 Then, as shown in FIG. 6 (C), the die 100 and the core rod 104 are moved upward by an appropriate amount in the upward direction in the drawing together with the core rod 104. By rising, the inside of the molding cavity 100a is in a negative pressure state. The bearing powder material is sucked into the negative pressure die 100, so-called “suction filling” is performed. That is, as described above, the bearing powder material is supplied from the feeder cup 102, and is filled in a predetermined filling space so as to be full, thereby completing the “powder filling step”.

 At the time of “absorption and filling” of the bearing powder material, the difference in specific gravity between the bearing base powder and the solid lubricating powder causes the bearing base powder having a large specific gravity to move downward in the axial direction. The solid lubricant powder having a low specific gravity drops in the axial direction as the amount of the solid lubricant powder drops in the axial direction, and as a result, the solid lubricant powder is biased toward the upper side in the axial direction as described above. State.

 After “suction filling”, as shown in FIG. 6 (D), the feeder cup 102 moves to the retracted position, and the upper punch 103 descends from the upper side to enter the forming cavity 100a of the die 100. Inserted. At the same time, in the present embodiment, the dice 100 itself slightly descends.

As a result, as shown in FIG. 6 (E), the bearing powder material in the molding cavity 100a of the die 100 is pressurized from both the upper and lower directions, and compression-molded into the shape of a pressurized intermediate molded body. "Pressure compression molding process" is completed. If the compression ratio ε at the time of molding is increased so as to be, for example, 2 or more, there is an advantage that the filling depth becomes large and a concentration difference easily occurs in the axial direction.

 [0053] Here, the compression ratio is obtained by dividing the volume of the bearing powder material filled in the molding cavity 100a by the volume when it is compression molded into a pressurized intermediate compact (compact). The values shown are shown. In some cases, a value obtained by dividing the filling height by the height of the pressed intermediate compact (compact) is used instead of the volume ratio. In this embodiment, the volume ratio is designed to be 2 or more.

 Then, as shown in FIG. 6 (E), the upper punch 103 moves up to the original standby position, and further lowers to the position of the initial state (A) of the die 100 and the core rod 104. By these operations, the compression intermediate molded body of the compression-molded bearing sleeve 13 is taken out, and the “pulling-out step” is completed.

 Although not shown, the pressurized intermediate molded body of the bearing sleeve 13 taken out is fired, and further subjected to a pressure sizing molding step by a pressure molding step, as shown in FIGS. The bearing sleeve 13 as a simple sintered bearing is formed.

 As described above, according to the sintered bearing and the manufacturing method thereof according to the present embodiment, the bearing base powder of the bearing powder material to be filled in the die 100 is mixed with the bearing base powder. Utilizing the difference in specific gravity with solid lubricating powder, it is possible to segregate the solid lubricating powder to the area where high load is applied, and to improve the bearing function without significantly increasing the amount of solid lubricating powder. Is planned.

 When the content of the solid lubricant, ie, the concentration distribution, is continuously changed in the axial direction as in the above-described embodiment, the inner diameter d of the sintered bearing and the total length L in the axial direction are reduced. Therefore, the condition that LZd> 1 holds is a condition for obtaining the above-described operation.

 [0058] The segregation state of the solid lubricating powder is a ratio of the total length L to the outer diameter D of the force bearing main body, which is preferably obtained particularly in a sintered bearing having a long length in the axial direction. By setting the LZD to be greater than or equal to a specific value, it is possible to surely obtain a bias in the axial direction of the solid lubricant powder.

Next, the results of measuring the content of the solid lubricating powder (graphite) of the sintered bearing in the present embodiment will be described with reference to FIGS. 7 (a), (b) and FIG. In the present embodiment, since the bearing body is substantially cylindrical, the segregation state of the solid lubricant powder is considered to affect the thickness of the bearing body. And a wall thickness T (= (Dd) / 2) indicating a relationship between the diameter and the outer diameter D.

 For example, in FIG. 7 (a), the outer diameter D of the sintered bearing is 6 mm, the inner diameter d is 3 mm, the wall thickness Tl. Is 5 mm, and the total length L is changed to 6 mm, 9 mm, 12 mm, and 15 mm. Assuming that the position of the upper end surface in the axial direction of the sintered bearing is 0% and the position of the lower end surface in the figure is 100%, the upper end surface force corresponds to the 0% position. The results of measuring the content of lubricating powder (graphite) using the above-mentioned LZT as a parameter are shown.

 [0061] Further, in FIG. 7 (b), the outer diameter D of the sintered bearing is 6 mm, the inner diameter d is 3 mm, and the total length L is 6 mm, 9 mm, 12 mm, By changing it to 15 mm, the upper end surface force corresponding to the 0% position The solid lubricant powder at the position corresponding to 90% below the axial direction (for example, when the total length L is 6 mm, the position 5.4 mm from the upper end surface) Assuming that the content of the body (graphite) is “1”, the degree of bias in each position is calculated.

 FIG. 8 is a graph showing the relationship between LZT and biased prayer. Based on Figs. 8 (a) and 8 (b), the vertical axis indicates the degree of bias, and the horizontal axis indicates the position of the upper end surface.

 [0063] From the measurement results, if the LZT force or higher, the bearing body of the sintered bearing contains the solid lubricant generated in the sintered body of the bearing base material powder in a dispersed state in a solid lubricant. It can be seen that the dispersion concentration distribution of the solid lubricant in the bearing main body changes in the axial direction throughout the bearing main body.

 Further, as is clear from the graph shown in FIG. 8, if the ratio LZT, which is the ratio of the thickness T of the bearing body to the overall length L, is set to be “8 or more”, the sintered bearing is It can be seen that the degree of bias of the solid lubricant gradually decreases from the upper end surface to the lower end surface of the solid lubricant. Therefore, in the manufacturing process described above, the degree of bias of the solid lubricant in the axial direction of the sintered bearing is appropriately controlled by determining the dimensions of the sintered bearing so that the LZT is 8 or more. And the segregation in the axial direction of the solid lubricating powder can be reliably obtained.

At this time, in particular, in the present embodiment, when filling the bearing powder material into the die 100, “suction filling” is performed in which the molding cavity 100a inside the die 100 is in a negative pressure state. I have to. For this reason, when the bearing powder material is sucked into the die 100, the solid lubricating powder can be surely biased by utilizing the difference in specific gravity from the bearing base powder. . That is, since the bearing base material powder having a higher specific gravity is filled into the molded cavity 100a first, and the solid lubricating powder having a smaller specific gravity is charged into the molded cavity 100a with a delay, the solid lubricant can be reliably supplied to the sintered bearing. Can be made to pray.

Further, in the above-described embodiment, since the solid lubricating powder without metal plating is adopted, the specific gravity is reduced by the amount of no metal plating on the solid lubricating powder. A difference can be provided in the filling speed between the base powder and the solid lubricating powder. In addition, the productivity can be improved as much as the metal plating step is omitted.

 When graphite powder or molybdenum disulfide is used as the solid lubricating powder as in the present embodiment, these are solid lubricating powders that are easily obtained on a daily basis. Strong bearing powder material is easily produced.

 Although the embodiments of the invention made by the inventor have been specifically described above, the present invention is not limited to the above embodiments, and can be variously modified without departing from the gist of the invention. Uno is not even!

 For example, as shown in FIG. 3, by changing the outer diameter from a perfect circle to a shape with a longitudinal groove, a thick part and a thin part are formed. As a result, the fixed lubricant is more likely to be biased in the thin portion, and a thick portion and a thin portion of the fixed lubricant are formed in the angle direction. This makes it possible to use the fixed lubricant more effectively by arranging the shaft on the side where the shaft load is high (side pressure is applied) in the dark part.

 [0070] Furthermore, by providing a step in the bearing outer diameter, if the outer diameter is large and the small side is different in thickness, and if the thinner side is arranged as the higher load side, More and more individual lubricants begin to pray!

[0071] Further, the present invention can be applied to a sintered bearing that does not have a middle relief structure, such as a hubstan motor or a geared motor that exerts a lateral pressure load. Also in this case, segregation should be performed so that a large amount of solid lubricant is distributed in a portion where the applied load is large. [0072] The segregation of the solid lubricant content is not limited to the concentration distribution as in the above-described embodiment. For example, the solid lubricant having a large particle diameter is changed by changing the particle diameter of the solid lubricant. You may arrange so that it may gather in the part with a large load. Solid lubricants generally have a weak bonding force and are liable to fall off from the matrix. However, the larger the particle size, the more difficult it is to fall off. Also in this case, by using the above-described manufacturing process, a solid lubricant having a large particle diameter can be collected at a portion where a large load is applied. In other words, the larger the solid lubricant, the larger the filling resistance in the filling process and the lower the filling speed.Therefore, the size of the solid lubricant gradually increases in the axial direction of the sintered bearing. Or you can make them pray so that they become smaller gradually.

 [0073] Further, segregation of the content of the solid lubricant can also be performed by changing the shape of the solid lubricant. For example, by arranging a flat solid lubricant in a portion with a large load, the bearing function can be enhanced. Also in this case, since the flat solid lubricant has a larger filling resistance in the filling step and a lower filling speed, the flat solid lubricant is applied to a portion having a larger load by using the above-described manufacturing process. It can be collected.

 Further, the segregation of the content of the solid lubricant can be performed in the radial direction.

 For example, by arranging the solid lubricant on the inner peripheral side of the bearing surface to which a large load is directly applied, the slidability is improved. Also in this case, the above-described manufacturing process can be used. That is, since the filling resistance in the filling step becomes larger in the portion closer to the wall surface of the molding cavity, the solid lubricating powder having a low specific gravity can be filled more in the inner peripheral surface or the outer peripheral surface of the sintered bearing.

 [0075] On the other hand, in order to segregate the content of such a solid lubricant, it is also possible to use two-color molding. That is, if two types of bearing powder materials are sequentially filled into the die by two-color molding, the content of the solid lubricant changes in the axial direction.

 Further, in the above-described embodiment, it is also possible to manufacture the bearing powder material by the usual “drop-in filling” in which “suck-in filling” is used.

Further, the above-described embodiment is one in which the present invention is applied to a spindle motor for a DVD or CD-ROM disk drive. The present invention is not limited to this. The present invention can be similarly applied to a motor for rotationally driving various media disks such as a hard disk and a flexible disk, and to a sintered bearing used in various other devices.

 Brief Description of Drawings

 FIG. 1 is an explanatory longitudinal sectional view showing a structural example of a DVD, CD-ROM drive motor provided with a bearing device to which the present invention is applied.

 FIG. 2 is an explanatory longitudinal sectional view showing a structure of a bearing portion of a bearing device used for the motor shown in FIG. 1;

 FIG. 3 is an external perspective explanatory view showing the shape of a bearing body of a bearing sleeve made of the sintered bearing shown in FIG. 2.

 FIG. 4 is a semi-longitudinal sectional view showing an enlarged bearing portion of a sintered bearing.

 FIG. 5 is a process drawing schematically showing a method and an apparatus for manufacturing a bearing device to which the present invention is applied.

 FIG. 6 (A) to (F) are process diagrams schematically showing a method and an apparatus for manufacturing a bearing device to which the present invention is applied.

 FIG. 7 is a table showing an example of measurement results of the content of solid lubricating powder (graphite) in the sintered bearing according to the present invention.

 FIG. 8 is a diagram showing an example of a measurement result of a solid lubricating powder (graphite) content in a sintered bearing according to the present invention.

 Explanation of symbols

[0079] 12 bearing holder

 13 Bearing sleeve (bearing body)

 13a Bearing hole

 RBI, RB2 Radial bearing

 21 Rotary axis

 100 dice

 100a molding cavity

101 Lower punch 102 Feeder cup 103 Upper punch

Claims

The scope of the claims  [1] A die is filled with a bearing powder material in which a solid lubricating powder is mixed with a bearing base powder, and the bearing powder material filled in the die is sintered to form a bearing body. There are several methods for manufacturing bearings.  The bearing powder material is manufactured by mixing the solid lubricating powder having a specific gravity smaller than that of the bearing substrate powder / ヽ with the bearing substrate powder. The method of manufacturing the bearing.  [2] When filling the bearing powder material into the die, the molding cavity inside the die is set to a negative pressure state, and the bearing powder material is sucked into the molding cavity and filled. 2. The method for producing a sintered bearing according to claim 1, wherein: 3. The method for producing a sintered bearing according to claim 1, wherein a compression ratio of the bearing powder material in the pressure compression molding step constituting the sintering step is 2 or more. 4. The method for producing a sintered bearing according to claim 1, wherein a metal plating is applied as the solid lubricating powder. 5. The method for producing a sintered bearing according to claim 1, wherein the solid lubricating powder includes a graphite powder. [6] A sintered bearing in which the bearing main body is formed using the manufacturing method according to claim 1, wherein the bearing main body is formed from the solid lubricating powder in a sintered body of the bearing base powder. The solid lubricant is formed so as to contain the solid lubricant in a dispersed state, and the dispersion concentration distribution of the solid lubricant in the bearing body changes in the bearing body in the axial direction. A sintered bearing. [7] A sintered bearing having a bearing body containing a solid lubricant produced in a dispersed state in a sintered body of a bearing base powder in the form of a solid lubricant powder,  A sintered bearing characterized in that the dispersion concentration distribution of the solid lubricant in the bearing body changes in the axial direction in the bearing body. [8] The claim, wherein the dispersion concentration distribution of the solid lubricating powder continuously increases or decreases toward one end side component force in the axial direction of the bearing body toward the other end side. A sintered bearing according to claim 6 or claim 7. [9] A sintered bearing in which the bearing main body is formed using the manufacturing method according to claim 1, wherein the bearing main body is formed from the solid lubricating powder in a sintered body of the bearing base powder. The solid lubricant is formed so as to contain the solid lubricant in a dispersed state, and the dispersion concentration distribution of the solid lubricant in the bearing body changes radially throughout the bearing body! / Sintered bearing characterized by the following characteristics:  [10] In a sintered bearing having a bearing body containing a solid lubricant generated from a solid lubricant powder in a sintered body of a bearing base powder in a dispersed state, the solid lubricant in the bearing body is provided. A sintered bearing characterized in that the dispersion concentration distribution of the agent varies radially and radially within the bearing body.  11. The sintered bearing according to claim 9, wherein a content of the solid lubricant is configured to increase in an inner peripheral wall portion of the bearing main body. [12] A motor provided with the sintered bearing according to any one of claims 6 to 11,