WO2011111724A1

WO2011111724A1 - Die for forming dynamic pressure grooves and method for manufacturing dynamic pressure-type oil-impregnated sintered bearing

Info

Publication number: WO2011111724A1
Application number: PCT/JP2011/055448
Authority: WO
Inventors: 洋赤井; 正明戸田; 晃也大平; 英之筒井; 直子伊藤
Original assignee: Ntn株式会社
Priority date: 2010-03-12
Filing date: 2011-03-09
Publication date: 2011-09-15
Also published as: JP2011190827A

Abstract

Provided are a die for forming dynamic pressure grooves and a method for manufacturing a dynamic pressure-type oil-impregnated sintered bearing using the die. The die has excellent abrasion resistance and thus can be used for a long time before being replaced. The die (3) for forming dynamic pressure grooves is used in a method for manufacturing a dynamic pressure-type oil-impregnated sintered bearing in which a bearing main body is formed by molding a bearing surface which has oblique dynamic pressure grooves in the inner circumferential surface of a cylindrical sintered metal material, and the bearing main body is made to contain oil by means of the impregnation of lubricating oil or lubricating grease into pores within the bearing main body, wherein the die (3) has a molding part on an outer circumferential surface thereof to mold a dynamic pressure groove region. When the bearing main body is being formed, the die (3) is inserted into the inner circumferential surface of the sintered metal material and pressure is applied, and the dynamic pressure groove region is molded in the inner circumferential surface by means of plasticity processing. The die (3) for forming dynamic pressure grooves has a hard coating of at least one selected from a hard nitride coating, a hard carbide coating, and a hard carbon coating.

Description

Method for manufacturing dynamic pressure groove forming mold and dynamic pressure type sintered oil-impregnated bearing

The present invention is a hydrodynamic type in which a sintered metal bearing body is impregnated with lubricating oil or lubricating grease to have a self-lubricating function, and the outer peripheral surface of a shaft is levitated and supported by a hydrodynamic oil film of oil interposed in a bearing gap. The present invention relates to a method for producing a sintered oil-impregnated bearing and a dynamic pressure groove forming mold used in the production.

Hydrodynamic sintered oil-impregnated bearings are used for equipment that requires high rotational accuracy at high speeds, such as polygon mirrors for laser beam printers (LBP) and spindle motors for magnetic disk drives (HDD, etc.) and DVD-ROMs. Like a spindle motor, it is suitably used for a device that is driven at a high speed by applying a large unbalance load when a disk is placed thereon.

In the above-mentioned small spindle motors related to information equipment, further improvement in rotational performance and cost reduction are required. As a means for that, it has been studied to replace the bearing portion of the spindle with a sintered oil-impregnated bearing from a rolling bearing. However, since the sintered oil-impregnated bearing is a kind of a perfect circle bearing, unstable vibration is likely to occur where the shaft eccentricity is small, and so-called whirling that tends to swing at half the rotational speed is likely to occur. There are drawbacks. Therefore, as a hydrodynamic sintered oil-impregnated bearing, a dynamic pressure groove such as a herringbone type or a spiral type is provided on the bearing surface, and a dynamic oil film is generated in the bearing gap by the action of the dynamic pressure groove due to the rotation of the shaft. Conventionally, floating support (non-contact support) has been attempted.

Conventionally, as a method for forming a dynamic pressure groove on a bearing surface, a shaft-shaped jig in which a plurality of balls harder than the bearing material are arranged and held at equal intervals around the circumference is inserted into the inner circumferential surface of the bearing material. A method is known in which the ball is pressed against the inner peripheral surface of the material while the ball is subjected to a spiral motion by rotation and feed of the material to plastically process the formation region of the dynamic pressure groove (see Patent Document 1). Further, as a method for improving this method, a method is known in which a material bulge that occurs in a region adjacent to a dynamic pressure groove during molding is removed by a lathe or reamer (see Patent Document 2).

In addition, the methods of Patent Document 1 and Patent Document 2 require a jig rotation drive mechanism and a feed mechanism, which complicates manufacturing equipment. Moreover, since post-processing of the area | region adjacent to the dynamic pressure groove in a bearing surface is required, a manufacturing man-hour increases. As these measures, a molding die (sizing pin) having a first molding part for molding a dynamic pressure groove forming region on the bearing surface and a second molding part for molding a region other than the dynamic pressure groove forming region. Is inserted into the inner peripheral surface of the cylindrical sintered metal material, and the outer peripheral surface of the sintered metal material is press-fitted into the die while the sintered metal material is constrained from both sides in the axial direction by the first punch and the second punch. Then, a method of simultaneously forming the formation region of the dynamic pressure groove on the bearing surface and the other region by applying a pressing force and plastically deforming the inner peripheral surface by pressing the inner peripheral surface of the forming die is known ( (See Patent Document 3). In this method, the molding process of the bearing surface having the inclined dynamic pressure groove can be performed with a simple facility, with a small number of steps and with high accuracy.

Japanese Patent No. 2541208 JP-A-8-232958 JP-A-11-190344

However, in Patent Document 3, the material of the sizing pin, which is a dynamic pressure groove forming die for transferring the groove, is not limited, and a cemented carbide having excellent wear resistance is used as the die material of the sizing pin. Even when the number of products to be produced increases, the sizing pin for transferring the groove may wear, and the inner diameter dimension and groove depth of the product may not fall within the required tolerances. Therefore, it is necessary to replace the sizing pin with a new sizing pin according to the wear situation of the sizing pin, and it is desired to improve the wear resistance of the sizing pin in order to extend the replacement life of the sizing pin.

The present invention has been made in order to cope with such problems, and is a dynamic pressure groove forming mold having excellent wear resistance and extending the replacement life, and a dynamic pressure type sintered oil impregnation using the mold. It aims at providing the manufacturing method of a bearing.

The die for forming a dynamic pressure groove of the present invention forms a bearing body by forming a bearing surface having an inclined dynamic pressure groove on the inner peripheral surface of a cylindrical sintered metal material. A dynamic pressure groove forming mold used in a method for manufacturing a hydrodynamic sintered oil-impregnated bearing in which oil is retained by impregnation of lubricating oil or lubricating grease in pores, for forming a region of the dynamic pressure groove When forming the bearing body with the forming part on the outer peripheral surface, it is inserted and pressed into the inner peripheral surface of the sintered metal material, and the region of the dynamic pressure groove is formed on the inner peripheral surface by plastic working The dynamic pressure groove forming mold has at least one hard coating selected from a nitride hard coating, a carbide hard coating, and a hard carbon coating on the outer peripheral surface.

The film thickness of the hard coating is 0.2 to 8 μm. Further, the indentation hardness of the hard coating is 10 GPa or more.

The hard coating is a hard carbon coating. Further, the dynamic pressure groove forming mold has a metal intermediate layer between the mold and the hard carbon coating. The metal intermediate layer is at least one selected from tungsten (hereinafter referred to as W), chromium (hereinafter referred to as Cr), silicon (hereinafter referred to as Si), and titanium (hereinafter referred to as Ti). It contains a metal element. The hard carbon film is formed by an unbalanced magnetron sputtering (hereinafter referred to as UBMS) method.

The hard coating is characterized in that the indentation hardness increases continuously or stepwise from the outer peripheral surface side of the dynamic pressure groove forming mold to the outermost surface side of the hard coating.

The dynamic pressure groove forming mold base material is made of a cemented carbide material.

The method of manufacturing a hydrodynamic sintered oil-impregnated bearing according to the present invention forms a bearing body having an inclined dynamic pressure groove on the inner peripheral surface of a cylindrical sintered metal material to form a bearing body. A method of manufacturing a hydrodynamic sintered oil-impregnated bearing in which oil is retained in an internal pore by impregnation with lubricating oil or lubricating grease, wherein the forming step of the bearing surface includes the above-described gold for forming a dynamic pressure groove according to the present invention. A mold is inserted into the inner peripheral surface of the sintered metal material, and a forming portion for forming the dynamic pressure groove region of the dynamic pressure groove forming mold is pressed onto the inner peripheral surface of the sintered metal material. And a step of forming the region of the dynamic pressure groove on the inner peripheral surface by plastic working.

The hydrodynamic sintered oil-impregnated bearing targeted by the above manufacturing method is a bearing used for a spindle motor for a magnetic disk drive.

As described above, the dynamic pressure groove forming mold of the present invention is a sizing pin having inclined dynamic pressure grooves on the outer peripheral surface, and on the outer peripheral surface, a nitride-based hard coating, a carbide-based hard coating, a hard carbon Since it has at least one hard coating selected from coatings, it has excellent wear resistance. For this reason, dynamic pressure type sintering including a step of inserting and pressurizing the dynamic pressure groove forming die into the inner peripheral surface of the sintered metal material and forming a region of the dynamic pressure groove on the inner peripheral surface by plastic working. Even when used in the manufacture of oil-impregnated bearings, the replacement life of the die (sizing pin) can be extended.

In particular, a hard carbon film is adopted as the hard film, and (1) a metal intermediate layer is provided between the mold and the hard carbon film, or (2) the indentation hardness of the hard carbon film is set on the mold substrate side. By continuously or stepwise increasing from the hard carbon coating to the outermost surface side, the wear resistance and adhesion can be further improved, and the replacement life of the die (sizing pin) can be further extended. I can plan.

The method of manufacturing a hydrodynamic sintered oil-impregnated bearing according to the present invention forms a bearing body having an inclined dynamic pressure groove on the inner peripheral surface of a cylindrical sintered metal material to form a bearing body. This is a method for manufacturing a hydrodynamic sintered oil-impregnated bearing in which oil is retained in the internal pores by impregnation with lubricating oil or lubricating grease, and the bearing surface molding step sinters the dynamic pressure groove forming mold described above. Insert into the inner peripheral surface of the metal material, press the molded part of this dynamic pressure groove forming mold to the inner peripheral surface of the sintered metal material, and shape the region of the dynamic pressure groove on the inner peripheral surface by plastic working Therefore, it is possible to manufacture with a simple equipment and a small number of man-hours. In addition, the replacement life of the dynamic pressure groove forming die (sizing pin) is long, and the manufacturing cost can be reduced.

It is sectional drawing which shows an example of a dynamic pressure type sintered oil-impregnated bearing. It is a partially enlarged view of a sizing pin that is a die for forming a dynamic pressure groove of the present invention. It is sectional drawing which shows the sintered metal raw material used as the raw material of a bearing main body. It is sectional drawing which shows an example of the formation process of a bearing surface. It is sectional drawing which shows an example of the formation process of a bearing surface. It is a principal part expanded sectional view which shows the process (c) in FIG. 4, and a process (e). It is a schematic diagram which shows the film-forming principle of UBMS method. It is a schematic diagram of the UBMS apparatus provided with the AIP function. It is a figure which shows a friction tester. It is sectional drawing which shows the other example of the formation process of a bearing surface. It is sectional drawing which shows the other example of the formation process of a bearing surface.

The dynamic pressure groove forming mold of the present invention is used in a method of manufacturing a dynamic pressure type sintered oil-impregnated bearing described later. A hydrodynamic sintered oil-impregnated bearing targeted by this manufacturing method will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of a hydrodynamic sintered oil-impregnated bearing. The hydrodynamic sintered oil-impregnated bearing 1 includes, for example, a bearing body 1a made of sintered metal mainly composed of copper or iron, or both, and the pores of the bearing body 1a by impregnation with lubricating oil or lubricating grease. It is made up of retained oil (base oil of lubricating oil or lubricating grease). The hydrodynamic sintered oil-impregnated bearing 1 is used, for example, in a spindle motor for a magnetic disk drive, a scanner motor for a laser beam printer, or the like.

A bearing surface 1b is formed on the inner periphery of the bearing body 1a so as to face the outer peripheral surface of the shaft to be supported via a bearing gap, and an inclined dynamic pressure groove 1c is formed on the bearing surface 1b. In the embodiment shown in FIG. 1, the two bearing surfaces 1b are formed to be separated from each other in the axial direction. Each bearing surface 1b has a first region in which a plurality of dynamic pressure grooves 1c inclined in one direction with respect to the axial direction are arranged in the circumferential direction, and is spaced apart from the first region in the axial direction. And a second region in which a plurality of dynamic pressure grooves 1c inclined to the other side are arranged in the circumferential direction, and an annular smooth region 1d positioned between the first region and the second region. The backs (regions between the dynamic pressure grooves 1c) 1e of the first region and the second region are each continuous with the smooth region 1d. On the bearing surface 1b, the surface openings are distributed almost uniformly over the entire region including the region where the dynamic pressure grooves 1c are formed. When relative rotation occurs between the bearing body 1a and the shaft, the oil in the bearing gap is drawn toward the smooth region 1d by the dynamic pressure grooves 1c formed in the first region and the second region so as to incline in opposite directions. Thus, a dynamic pressure oil film is formed, and the outer peripheral surface of the shaft is levitated and supported (non-contact support) with respect to the bearing surface 1b by the dynamic pressure oil film.

The die for forming a dynamic pressure groove of the present invention is used for forming a bearing body 1a of a dynamic pressure type sintered oil-impregnated bearing 1 as shown in FIG. An example of the dynamic pressure groove forming mold of the present invention will be described with reference to FIG. FIG. 2 is a partially enlarged view of a sizing pin that is a die for forming a dynamic pressure groove. As shown in FIG. 2, the sizing pin 3, which is a dynamic pressure groove forming mold, has a convex first molding part 3a and a concave second molding part 3b on its outer peripheral surface. The 1st shaping | molding part 3a shape | molds the area | region (refer FIG. 1) of the dynamic pressure groove 1c in the bearing surface 1b. The 2nd shaping | molding part 3b shape | molds areas | regions (annular smooth area | region 1d, spine 1e) other than the dynamic pressure groove 1c. The step (depth) between the first molded portion 3a and the second molded portion 3b is about 2 to 4 μm, which is the same as the depth of the dynamic pressure groove 1c (see FIG. 1) on the bearing surface 1b, but is exaggerated in FIG. It is illustrated as follows.

The material of the sizing pin 3 includes carbon tool steel, alloy tool steel, high speed tool steel, cemented carbide and the like. In particular, cemented carbide is excellent in wear resistance and is therefore suitable as a mold material. Further, in order to increase the surface hardness of the mold, a surface treatment such as nitriding treatment or shot peening may be performed.

In the present invention, in the sizing pin 3, at least one selected from a nitride-based hard coating, a carbide-based hard coating, and a hard carbon coating is provided on the outer peripheral surface of the mold including the first molded portion 3a and the second molded portion 3b. One hard coating is formed.

Examples of the nitride hard coating include TiN, TiBN, CrN, CrAlN, TiAlN, SiN, SiAlN, AlCrSiN, TiBON, ZrN, SiCN, and AlN. Examples of the carbide hard coating include SiC and TiC. In addition, the hard carbon coating in the present invention has an intermediate structure in which a diamond structure and a graphite structure are mixed structurally, and is called a diamond-like carbon (hereinafter referred to as DLC). It is. Each of the above coating films can be formed alone or in a laminate of two or more. In addition, a hard film can be formed by doping with an element effective for improving mechanical properties such as wear resistance, friction characteristics, hardness, and non-adhesiveness.

The film thickness of the hard coating is preferably 0.2 to 8 μm. If it is too thick, the stress generated in the film during film formation becomes excessive, and cracks may occur during film formation. Even if a crack does not occur, a film that is too thick tends to be peeled off because the residual stress is high. On the other hand, if the thickness is too thin, the effect of extending the life of the mold is reduced when the hard coating is worn. It is more preferable that the film thickness of the hard coating is 0.4 to 8 μm because at least the effect of extending the life of the mold can be confirmed, and it does not peel off due to high residual stress. Further, if it exceeds 5 μm, it may be easy to peel off at the edge portion, so that the film thickness of the hard coating is more preferably 0.4 to 5 μm.

The indentation hardness of the hard coating of the present invention is preferably 10 GPa or more. If it is less than 10 GPa, the surface of the mold is easily damaged, the wear resistance is poor, and the replacement life of the mold is shortened.

Among the hard coatings described above, the hard carbon coating (DLC) is particularly suitable as the hard coating formed on the dynamic pressure groove forming mold of the present invention because it has excellent frictional wear characteristics and the coating surface is smooth. . For example, by using a hard carbon coating (DLC) as the hard coating, the surface roughness of the mold surface (coating surface) can be made the same as that of the mold substrate, so that post-processing such as polishing and lapping is unnecessary. Become. This post-processing such as polishing and lapping is necessary to match the surface roughness required for the product surface because the surface of the coating becomes rough when other hard coating is used.

The film formation method of the hard carbon coating (DLC) is not particularly limited, but for example, a CVD method using heat, light, plasma (DC plasma, holocathode plasma, RF plasma, pulsed plasma, surface wave plasma), Examples thereof include PVD film forming methods such as ion beam, ionized vapor deposition, holocathode arc, vacuum arc vapor deposition, UBMS, plasma sublimation, and electron beam vapor deposition. Among these, it is preferable to employ a UBMS film formation method that can provide a hard coating having particularly excellent wear resistance.

The film forming principle of the UBMS method using the UBMS apparatus will be described with reference to the schematic diagram shown in FIG. As shown in FIG. 7, an inner magnet 14 a and an outer magnet 14 b having different magnetic characteristics are arranged in the central portion and the peripheral portion of a round target 15, and the above magnet is formed while forming a high-density plasma 19 near the target 15. A part 16 a of the magnetic force lines 16 generated by 14 a and 14 b reaches the vicinity of the base material 12 connected to the bias power source 11. The Ar plasma generated during the sputtering along the magnetic force lines 16a can be diffused to the vicinity of the base material 12. By such an UBMS method, the ion assist effect that Ar ions 17 and electrons reach the base material 12 more than the normal sputtering, along the magnetic field lines 16a reaching the vicinity of the base material 12, due to the ion assist effect. A dense film (layer) 13 can be formed. In forming the hard carbon film (DLC), a graphite target is used as the solid target 15. Further, if necessary, a carbon hydrogen gas such as methane gas can be introduced into the apparatus to serve as a carbon supply source.

When a hard carbon film (DLC) is employed as the hard film, the film has a high hardness and Young's modulus, but has a characteristic that the deformability is extremely small and the adhesion to the substrate is weak, and thus the substrate is a base material. In order to improve the adhesion of the hard carbon film to the mold, it is preferable to form a metal intermediate layer between the mold and the hard carbon film. The metal intermediate layer can be formed using, for example, the target 15 corresponding to the metal intermediate layer in FIG.

The metal intermediate layer preferably contains at least one metal element selected from W, Cr, Si, and Ti. By including these metal species, adhesion to a die (sizing pin) substrate made of carbon tool steel, alloy tool steel, high-speed tool steel, cemented carbide, or the like can be further improved. Moreover, a metal intermediate | middle layer can also be made into several layers from which a composition differs as needed.

Also, the metal intermediate layer adjacent to the hard carbon coating (DLC) reduces the metal content from the mold or other metal intermediate layer side toward the hard carbon coating side, while the carbon content is continuously increased. It is preferable to use a graded layer that is gradually or stepwise increased. This inclined layer becomes a stress relaxation layer, and the adhesion between the metal intermediate layer and the hard carbon coating can be improved.

The hard film is preferably a hardness gradient film whose indentation hardness increases continuously or stepwise from the outer peripheral surface side of the mold toward the outermost surface layer side of the film. By adopting a hardness gradient coating, it is possible to eliminate a steep hardness difference from the metal intermediate layer, and to improve adhesion. A hard carbon film (DLC) with a gradient in hardness can be obtained by using a graphite target in the UBMS method and forming a film by continuously or stepwise increasing the bias voltage for a mold as a base material. The reason why the hardness increases continuously or stepwise is that the composition ratio between the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter as the bias voltage increases.

The sizing pin, which is a die for forming a dynamic pressure groove of the present invention, forms the hard coating as described above on the outer peripheral surface, so it has excellent wear resistance and is replaced in comparison with sizing pins that do not have these hard coatings. The service life can be greatly extended.

The method of manufacturing a hydrodynamic sintered oil-impregnated bearing according to the present invention forms a bearing body having an inclined dynamic pressure groove on the inner peripheral surface of a cylindrical sintered metal material to form a bearing body. A method for manufacturing a hydrodynamic sintered oil-impregnated bearing in which oil is retained in an internal pore by impregnation with lubricating oil or lubricating grease, and in the molding process of the bearing surface, the above-described dynamic pressure groove forming mold (sizing pin) ) Is inserted into the inner peripheral surface of the sintered metal material, and a molding portion for forming the dynamic pressure groove region of the dynamic pressure groove forming mold is pressed onto the inner peripheral surface of the sintered metal material, This includes a step of forming the region of the dynamic pressure groove on the inner peripheral surface by plastic working.

As an example of the manufacturing method of the hydrodynamic sintered oil-impregnated bearing of the present invention, in the bearing surface forming step, the above-mentioned hydrodynamic groove forming mold (sizing pin) is inserted into the inner periphery of the sintered metal material, and then sintered. In a state in which the sintered metal material is constrained from both sides in the axial direction by the first punch and the second punch, the outer peripheral surface of the sintered metal material is pressed into the die to apply a pressing force, and the inner peripheral surface is formed with the dynamic pressure groove. A method of simultaneously forming the formation region of the dynamic pressure groove on the bearing surface and the other region by pressurizing and plastically deforming the outer peripheral surface of the metal mold will be described below.

In this manufacturing method, in order to suppress the axial extension of the sintered metal material due to the press-fitting into the die and prevent the displacement of the bearing surface, the sintered metal material is axially formed by the first punch and the second punch. A configuration is adopted in which the die is pressed into the die while restrained from both sides.

The press-fitting operation of the sintered metal material to the die can be performed by fixing the die and interlocking the dynamic pressure groove forming mold with the first punch and the second punch. It can also be performed by holding the restraint position of the material by the mold and the first punch and the second punch and moving the die in the axial direction with respect to the sintered metal material.

The sintered metal material is shown in FIG. FIG. 3 is a cross-sectional view showing an example of a sintered metal material. As shown in FIG. 3, the sintered metal material 1 ′ is obtained by mixing one or more kinds of metal powders and compacting them, followed by firing to form a predetermined cylindrical porous sintered body. The sintered metal material 1 'is preferably made of copper, iron, or both as a main component. A bearing body 1a of the hydrodynamic sintered oil-impregnated bearing 1 shown in FIG. 1 can be manufactured, for example, by subjecting the cylindrical sintered metal material 1 'to the bearing surface forming process described above.

The molding process of the bearing surface is performed by pressurizing a molding die having a shape corresponding to the bearing surface 1b of the bearing body 1a, which is a finished product, on the inner peripheral surface of the sintered metal material 1 ′ subjected to a predetermined sizing process. This is a step of simultaneously forming the formation region of the dynamic pressure groove 1c on the bearing surface 1b and the other regions (smooth region 1d, spine 1e). This step includes steps (a) to (h) shown in FIGS. FIG. 6 is an enlarged cross-sectional view of the main part showing step (c) and step (e) in FIG.

The molding apparatus used in the bearing surface molding process includes a cylindrical die 2 for press-fitting the outer peripheral surface of the sintered metal material 1 ′, a sizing pin (core rod) 3 for molding the inner peripheral surface of the sintered metal material 1 ′, The upper punch 4 and the lower punch 5 that press both end surfaces of the sintered metal material 1 ′ from the up and down direction (axial direction) are configured as main elements. Reference numeral 6 denotes a ram (hydraulic ram or the like) for driving the sizing pin 3 and the upper punch 4. The sizing pin 3 is connected to the ram 6 and moves up and down integrally with the ram 6. The upper punch 4 is not connected to the ram 6, and after the ram 6 is lowered to some extent, it is pushed by the ram 6 to perform a lowering operation. The lower punch 5 is fixed. The die 2 is driven up and down by driving means (not shown). Here, the sizing pin 3 is the dynamic pressure groove forming die of the present invention, and the dynamic pressure groove forming portion is shown enlarged in FIG.

In the initial state shown in FIG. 4A, the die 2 is in the lower position, and the sizing pin 3, the upper punch 4 and the ram 6 are in the upper position. The die 2 is slidably inserted in the lower punch 5, and the lower punch 5 waits at the upper end entrance of the forming hole of the die 2 and receives the lower end surface of the sintered metal material 1 ′. The sizing pin 3 is slidably inserted into the upper punch 4.

From the initial state, the ram 6 is lowered and the sizing pin 3 is inserted into the inner peripheral surface of the sintered metal material 1 '(see FIG. 4B). At this time, there is an internal clearance T between the inner peripheral surface of the sintered metal material 1 ′ and the molding die of the sizing pin 3 (based on the first molding part 3 a). The size of the inner diameter clearance T is, for example, 50 μm (diameter amount).

The ram 6 is further lowered and applied to the upper punch 4. The upper punch 4 is lowered together with the sizing pin 3 and pressed against the upper end surface of the sintered metal material 1 ′. The lower punch 5 is pressed and restrained from above and below (see FIGS. 4C and 6C).

Thereafter, the die 2 is raised while maintaining the restrained state of the sintered metal material 1 ′ in the vertical direction, and the outer peripheral surface of the sintered metal material 1 ′ is pressed into the forming hole of the die 2 (FIG. 4D). (E), FIG. 6 (e)). The press-fitting allowance S at this time is, for example, 150 μm (diameter amount).

The sintered metal material 1 ′ is deformed by receiving a pressing force from the die 2 and the upper and

lower punches

4, 5, and the inner peripheral surface is pressed against the outer peripheral surface of the sizing pin 3. The amount of pressurization on the inner peripheral surface is substantially equal to the difference of 100 μm (diameter amount) between the press-fitting allowance S (diameter amount 150 μm) and the inner diameter clearance T (diameter amount 50 μm), and from the inner peripheral surface to a depth of 50 μm (radial amount). The surface layer portion of the sizing pin 3 is pressed against a molding die composed of the first molding portion 3a and the second molding portion 3b to cause plastic flow and bite into the molding die. As a result, the shape of the molding die is transferred to the inner peripheral surface of the sintered metal material 1 ′, and the bearing surface 1 b is molded into the shape shown in FIG. 1.

After the formation of the bearing surface 1b is completed, the die 2 is moved down while the vertical restraint state of the sintered metal material 1 ′ is maintained (see FIG. 5 (f)), and the sintered metal material 1 ′ is moved to the die. 2 is removed (see FIG. 5G). Thereafter, the sizing pin 3 and the upper punch 4 are raised by the raising of the ram 6 (the raising of the upper punch 4 is performed by a driving means or a returning means not shown), and the sizing pin 3 is moved to the sintered metal material 1 ′. (See FIGS. 5G and 5H). When the sintered metal material 1 ′ is pulled out of the die 2, a spring back is generated in the sintered metal material 1 ′ and the inner diameter thereof is enlarged, so that the sintered metal material is not destroyed without breaking the dynamic pressure groove 1c of the bearing surface 1b. The molding die of the sizing pin 3 can be extracted from the inner peripheral surface of 1 ′. Thereby, the bearing main body 1a is completed.

As another example of the method for producing the hydrodynamic sintered oil-impregnated bearing of the present invention, the above-mentioned hydrodynamic groove forming mold (sizing pin) is inserted into the inner peripheral surface of the sintered metal material in the bearing surface molding step. Thereafter, the outer peripheral surface of the sintered metal material is press-fitted into the die (the die is fixed) with the first punch, and then the material is compressed with the die, the first punch, and the second punch to form a dynamic pressure groove. The method will be described below. The process of forming the bearing surface is shown in FIGS.

The molding apparatus used in the bearing surface molding process in this example is the same as the above-described molding apparatus, and the cylindrical die 2 for press-fitting the outer peripheral surface of the sintered metal material 1 ′ and the inner periphery of the sintered metal material 1 ′. A sizing pin (core rod) 3 for forming the surface, and an upper punch 4 and a lower punch 5 for pressing both end surfaces of the sintered metal material 1 ′ from the vertical direction (axial direction) are configured as main elements.

Both the sizing pin 3 and the upper punch 4 are lowered, and the signing pin 3 is inserted into the inner peripheral surface of the sintered metal material 1 ′, and the upper punch 4 is pressed against the upper end surface of the sintered metal material 1 ′ ( FIG. 10 (a)). Thereafter, the sintered metal material 1 ′ is pressed by the upper punch 4, and the outer peripheral surface of the sintered metal material 1 ′ is press-fitted into the forming hole of the die 2 (see FIG. 10B). The press-fitting allowance at this time is the same as that described above. Since the sintered metal material 1 ′ is press-fitted into the die 2, the inner peripheral surface thereof is shaped to hug the sizing pin 3.

Thereafter, the lower punch 5 is pressed against the lower end surface of the sintered metal material 1 'to pressurize the sintered metal material 1' from above and below (see FIG. 11 (a)). The sintered metal material 1 ′ is deformed by receiving a pressing force from the die 2 and the upper and

lower punches

4, 5, and forms a molding die whose inner peripheral surface is composed of the first molding part 3 a and the second molding part 3 b of the sizing pin 3. Pressurized. The amount of pressurization of the inner peripheral surface is substantially equal to the difference between the outer diameter interference and the inner clearance, and the surface layer portion from the inner peripheral surface to a predetermined depth is pressed to the mold of the sizing pin 3 to cause plastic flow. Biting into the mold. As a result, the shape of the molding die is transferred to the inner peripheral surface of the sintered metal material 1 ′, and the bearing surface 1 b is molded into the shape shown in FIG. 1.

After the molding of the bearing surface 1b is completed, as shown in FIG. 11B, the lower punch 5 and the sizing pin 3 are raised in conjunction with the sizing pin 3 inserted into the sintered metal material 1 ′. Then, the sintered metal material 1 ′ is removed from the die 2. When the sintered metal material 1 ′ is pulled out of the die 2, a spring back is generated in the sintered metal material 1 ′ and the inner diameter thereof is enlarged, so that the sintered metal material is not destroyed without breaking the dynamic pressure groove 1c of the bearing surface 1b. The molding die of the sizing pin 3 can be extracted from the inner peripheral surface of 1 ′. Thereby, the bearing main body 1a is completed.

In each of the above-described methods, the radius of the springback amount of the sintered metal material 1 ′ is smaller than the depth of the dynamic pressure groove 1c, and the forming die slightly interferes with the inner peripheral surface of the sintered metal material 1 ′. However, it is only necessary to add a diameter expansion amount (radius amount) due to material elasticity of the sintered metal material 1 ′ and release the molding die without breaking the shape of the bearing surface 1b. Even in the case where the interference occurs when the sizing pin 3 is pulled out from the inner peripheral surface of the sintered metal material 1 ′, a hard coating having excellent wear resistance is formed on the outer peripheral surface of the sizing pin 3 in the present invention. Therefore, it is possible to suppress wear on the outer peripheral surface of the sizing pin 3 including the mold composed of the first molding part 3a and the second molding part 3b.

When the bearing main body 1a is manufactured through the above-described processes, and this is impregnated with lubricating oil or lubricating grease to hold the oil, the hydrodynamic sintered oil-impregnated bearing 1 shown in FIG. 1 is completed. The shape of the bearing surface is not limited to that shown in the figure, and may be one in which, for example, a V-shaped or spiral dynamic pressure groove is formed. Moreover, what formed one bearing surface in the bearing main body may be used. These can be dealt with by changing the shape and number of sizing pin molds.

The base materials used in the examples and comparative examples and the apparatuses used for film formation are as follows.
(1) Substrate material: cemented carbide or cold die steel SKD-11 (in the table, “carbide” is an abbreviation for cemented carbide, and “SKD-11” is an abbreviation for cold die steel) .)
(2) Base material dimensions: mirror surface (Ra = 0.005 μm or less) 30 mm square, thickness 5 mm
(3) UBMS method: manufactured by Kobe Steel; UBMS202 / AIP combined device (4) Plasma CVD method: manufactured by Shinko Seiki Co., Ltd .; experimental pulsed plasma CVD device (5) Arc ion plating (hereinafter referred to as AIP) method : Kobe Steel; UBMS202 / AIP combined device (6) HCD method: Interface Corporation; 3-target HCD-PCD device

The outline of the UBMS202 / AIP combined apparatus is shown in FIG. FIG. 8 is a schematic diagram of a UBMS device having an AIP function. As shown in FIG. 8, the UBMS 202 / AIP composite apparatus instantaneously vaporizes and ionizes the AIP evaporation source material 20 using a vacuum arc discharge to the base material 22 arranged on the disk 21, The AIP function for depositing this on the substrate 22 to form a film and the sputter evaporation source materials (targets) 23 and 24 with a non-equilibrium magnetic field increase the plasma density in the vicinity of the substrate 22 to increase the ion assist effect. It is an apparatus having a UBMS function capable of controlling the characteristics of a film deposited on a substrate by increasing the number of films. With this apparatus, a composite film in which an AIP film and a plurality of UBMS films (including a composition gradient) are arbitrarily combined can be formed on a substrate.

Examples 1 to 19 and Comparative Examples 1 to 2
The substrate shown in Table 1 was ultrasonically cleaned with acetone and then dried. After drying, the base material was attached to each apparatus shown in Table 1, and a metal intermediate layer and a hard film of the kind shown in Table 1 were respectively formed to obtain test pieces. In addition, with the hardness gradient, the indentation hardness of the hard coating is gradually increased from the base material or metal intermediate layer side toward the outermost layer side. The Cr, Ti, and WC layers, which are metal intermediate layers, are evacuated to about 5 × 10 ⁻³ Pa inside the film forming chamber of the UBMS202 / AIP composite apparatus, and the base material is baked with a heater. It formed by each method after etching the base-material surface with plasma. The obtained test piece was subjected to a film thickness test, a surface roughness test, a hardness test and an abrasion test shown below, and the film thickness, maximum surface roughness, hardness and specific wear amount were measured and / or evaluated. The results and the overall judgment results shown below are also shown in Tables 1 and 2.

<Film thickness test>
The film thickness of the obtained test piece was measured by using a surface shape / surface roughness measuring instrument (manufactured by Taylor Hobson Co., Ltd .: Foam Talysurf PGI830). The film thickness was obtained from the step difference between the non-film forming part and the film forming part by masking a part of the film forming part.

<Surface roughness test>
The surface maximum roughness Rz of the obtained test piece was measured using Taylor Tobs Surf PGI830 manufactured by Taylor Hobson. The measurement results are also shown in Table 1. In addition, since the surface shape of a product becomes smooth, the one where surface maximum roughness is small is preferable.

<Hardness test>
The indentation hardness of the obtained test piece was measured using a nanoindenter (G200) manufactured by Agilent. The measurement results are also shown in Table 1. In addition, the measured value has shown the average value of the depth (location where hardness is stabilized) which is not influenced by surface roughness, and is measuring 10 each test piece.

<Abrasion test>
The obtained test piece was subjected to an abrasion test using a friction tester shown in FIG. FIG. 9A shows a front view, and FIG. 9B shows a side view. Material: Sintered alloy Cu 58.6% -Fe 39% -Sn 1.5% -C 0.5% -Stearic acid 0.4%, surface roughness Ra: 0.2 to 0.3 μm, curvature: 60 mm A sintered alloy is attached to the rotating shaft 25 as a counterpart material 27, a test piece 26 is fixed to an arm portion 28, and a predetermined load 29 is applied from the upper side of the drawing, whereby the maximum contact surface pressure of Hertz is 0.5 GPa, room temperature (25 )) At a rotational speed of 0.1 m / s for 30 minutes when the mating material 27 is rotated without interposing a lubricant between the test piece 26 and the mating material 27. The frictional force generated between the piece 26 was detected by the load cell 30. The specific wear amount was calculated from the test conditions and the wear amount after the test.

Examples 1 to 19 showed excellent results with respect to each comparative example in which a hard coating was not formed.

The method of manufacturing a hydrodynamic sintered oil-impregnated bearing according to the present invention can be manufactured with a simple facility, with a small number of man-hours and with high accuracy, and in addition, replacement of a dynamic pressure groove forming die (sizing pin) Since the lifetime is long and the manufacturing cost can be reduced, it can be suitably used for manufacturing a hydrodynamic sintered oil-impregnated bearing used for a spindle motor for a magnetic disk drive, a scanner motor for a laser beam printer, or the like.

DESCRIPTION OF SYMBOLS 1 Dynamic pressure type sintered oil-impregnated bearing 1a Bearing body 1b Bearing surface 1c Dynamic pressure groove 1d Annular smooth area 1e Area between dynamic pressure grooves 1 'Sintered metal material 2 Die 3 Sizing pin (dynamic pressure groove forming die)
3a 1st molding part 3b 2nd molding part 4 Upper punch 5 Lower punch 6 Ram 11 Bias power supply 12 Base material 13 Film (layer)
14a Inner magnet 14b Outer magnet 15 Target 16 Magnetic field line 16a Part of magnetic field line 17 Ar ion 18 Target 19 High-density plasma 20 AIP evaporation source material 21 Disk 22

Base material

23, 24 Sputter evaporation source material (target)
25 Rotating shaft 26 Test piece 27 Mating material 28 Arm part 29 Load 30 Load cell

Claims

A bearing body having a slanted dynamic pressure groove is formed on the inner peripheral surface of a cylindrical sintered metal material to form a bearing body, and the fine pores inside the bearing body are impregnated with lubricating oil or lubricating grease. A dynamic pressure groove forming mold used in a manufacturing method of a dynamic pressure type sintered oil-impregnated bearing for retaining oil,
The die for forming a dynamic pressure groove has a molding part for forming the region of the dynamic pressure groove on the outer peripheral surface, and is inserted into the inner peripheral surface of the sintered metal material when forming the bearing body. And pressurizing to form the region of the dynamic pressure groove on the inner peripheral surface by plastic working,
The dynamic pressure groove forming mold has at least one hard film selected from a nitride-based hard film, a carbide-based hard film, and a hard carbon film on an outer peripheral surface. Type.
2. The dynamic pressure groove forming mold according to claim 1, wherein the thickness of the hard coating is 0.2 to 8 μm.
2. The dynamic pressure groove forming mold according to claim 1, wherein the indentation hardness of the hard coating is 10 GPa or more.
2. The dynamic pressure groove forming mold according to claim 1, wherein the hard coating is a hard carbon coating.
5. The dynamic pressure groove forming mold according to claim 4, wherein the dynamic pressure groove forming mold has a metal intermediate layer between the mold and the hard carbon coating.
6. The dynamic pressure groove forming mold according to claim 5, wherein the metal intermediate layer contains at least one metal element selected from tungsten, chromium, silicon, and titanium.
5. The dynamic pressure groove forming die according to claim 4, wherein the hard carbon coating is formed by an unbalanced magnetron sputtering method.
The hard coating is a coating whose indentation hardness increases continuously or stepwise from the outer peripheral surface side of the dynamic pressure groove forming mold to the outermost surface side of the hard coating. 1. The dynamic pressure groove forming mold according to 1.
2. The dynamic pressure groove forming mold according to claim 1, wherein a base material of the dynamic pressure groove forming mold is made of a cemented carbide material.
A bearing body having a slanted dynamic pressure groove is formed on the inner peripheral surface of a cylindrical sintered metal material to form a bearing body, and the fine pores inside the bearing body are impregnated with lubricating oil or lubricating grease. A method for producing a hydrodynamic sintered oil-impregnated bearing that retains oil,
In the molding process of the bearing surface, the dynamic pressure groove forming mold according to claim 1 is inserted into the inner peripheral surface of the sintered metal material, and the dynamic pressure groove region of the dynamic pressure groove forming mold is molded. And pressurizing a molded portion to the inner peripheral surface of the sintered metal material, and forming a region of the dynamic pressure groove on the inner peripheral surface by plastic working. Manufacturing method of bearing.
The method of manufacturing a hydrodynamic sintered oil-impregnated bearing according to claim 10, wherein the hydrodynamic sintered oil-impregnated bearing is a bearing used in a spindle motor for a magnetic disk drive.