JP2000304036A - Dynamic pressure type bearing and dynamic pressure type bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a manufacturing process of a dynamic pressure type bearing having a radial bearing surface and a thrust bearing surface and to facilitate precision control. SOLUTION: A radial bearing surface 10r having a dynamic pressure groove 11 inclined against the axial direction and opposed to an outer peripheral surface of a shaft member to support through a radial bearing clearance is provided on an inner peripheral surface of a bearing main body 10. Additionally, a thrust bearing surface 10s having a dynamic pressure groove 14 is provided at least on one end surface of the bearing main body 10, and this thrust bearing surface 10s is compressed simultaneously with the radial bearing surface 10r.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing, a method of manufacturing the same, and a dynamic pressure bearing unit using the dynamic pressure bearing. This dynamic pressure bearing is used especially in the field of information equipment, such as optical disk devices such as DVD-ROM and DVD-RAM, magneto-optical disk devices such as MO,
It is suitable as a bearing for a spindle motor of a magnetic disk device such as an FDD or an HDD, or a bearing for a polygon scanner motor such as an LBP, and is particularly suitable as a bearing for a thin motor.

[0002]

2. Description of the Related Art The spindle motors of the above information equipment are required to have higher rotational accuracy, higher speed, lower cost, lower noise, and the like. There is a bearing for supporting a motor spindle. In recent years, the use of a dynamic pressure bearing having a dynamic pressure groove for generating dynamic pressure has been studied as this type of bearing. This dynamic pressure bearing has features such as high rotational accuracy and low noise while being low in cost, and is considered to be able to sufficiently meet the required performance.

In this dynamic pressure type bearing, a dynamic pressure groove of a herringbone type or a spiral type is formed on an inner peripheral surface (radial bearing surface) of a substantially cylindrical sleeve material for generating dynamic pressure. Conventionally, a dynamic pressure groove is formed by inserting a shaft-shaped jig having a plurality of balls harder than the bearing material arranged at equal circumferential intervals into the inner peripheral surface of the bearing material and rotating the jig. A method of rolling (plastic working) a dynamic pressure groove by pressing the ball against the inner peripheral surface of the material while giving a spiral motion to the ball by feed and feeding (Patent No. 2541208) is known.

In this type of dynamic pressure bearing, in order to support the spindle in a non-contact manner in the thrust direction, there is a case where a thrust bearing surface having a dynamic pressure groove is provided on an end face of the bearing or a face on the spindle side opposed thereto. This dynamic pressure groove machining of the thrust bearing surface is usually performed by a press.

[0005]

However, in the dynamic pressure groove machining by the above-described rolling, since the material rises in a region adjacent to the dynamic pressure groove at the time of molding, it is necessary to remove the material with a lathe or a reamer. (JP-A-8-232958), which complicates the process. In addition, during removal processing, it is necessary to press the end face of the bearing against the jig to position it.Therefore, it is necessary to finish the end face of the bearing with high precision, and to maintain the end face precision during the processing, which is troublesome. Take it.

[0006] Further, since the processing of the thrust bearing surface is performed in a separate step from the processing of the radial bearing surface, the precision of the bearing surface formed in the previous step may be reduced during the subsequent step, and precision control is difficult.

Accordingly, an object of the present invention is to simplify a manufacturing process of a dynamic pressure bearing having a radial bearing surface and a thrust bearing surface, to facilitate accuracy control, and the like.

[0008]

In order to achieve the above object, according to the present invention, a bearing body has a hydrodynamic groove which is inclined with respect to an axial direction on an inner peripheral surface thereof, and an outer periphery of a shaft member to be supported. A thrust bearing surface having a dynamic pressure groove is formed on at least one end surface of the bearing body at the same time as the radial bearing surface on a bearing provided with a radial bearing surface opposed to the bearing surface via a radial bearing clearance.

This dynamic pressure type bearing can be constituted by forming a bearing main body with a sintered metal and impregnating it with oil, or a bearing main body formed with a soft metal.

A dynamic pressure type bearing unit according to the present invention includes a shaft member having a flange portion, and any of the above dynamic pressure type bearings, wherein the thrust bearing surface and the end face of the flange portion opposed to the thrust bearing surface have thrust. A bearing clearance is formed.

In the above dynamic pressure type bearing, a radial forming die for forming a dynamic pressure groove on a radial bearing surface is arranged on an inner peripheral portion of a bearing material, and both ends of the bearing material are provided on at least one of the dynamic pressure grooves on a thrust bearing surface. By holding a pair of punch surfaces provided with a thrust forming die for forming the bearing material, and applying a pressing force to the bearing material in this state, the bearing material has a dynamic pressure groove on the inner peripheral surface and at least one end surface, respectively. It is manufactured by simultaneously forming a radial bearing surface and a thrust bearing surface.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view of a dynamic pressure bearing unit according to the present invention. This bearing unit comprises a dynamic pressure bearing 1
And a substantially cylindrical housing 2 in which the dynamic pressure bearing 1 is fixed to the inner diameter portion, and a shaft member 3 inserted into the inner diameter portion of the dynamic pressure bearing 1. At one end of the shaft member 3, a flange portion 3 a projecting in the radial direction is provided by a method such as integral molding or press-fitting of another member, and the flange portion 3 a is a bottom plate for closing one opening of the housing 2. 4 and one end face of the dynamic pressure bearing 1. The other end opening of the housing 2 is closed by a seal member 5 such as a seal washer or the like, so that leakage of oil to the outside is prevented.

The hydrodynamic bearing 1 of this embodiment is a hydrodynamic sintered oil-impregnated bearing in which a cylindrical bearing metal body 10 is impregnated with lubricating oil or lubricating grease. The bearing body 10 is formed of a sintered metal containing copper or iron or both as a main component, and desirably contains 20 to 95% by weight of copper.
Molded using.

On the inner peripheral surface of the bearing body 10, a radial bearing surface for supporting the shaft member 3 serving as a rotating shaft in a radially non-contact manner.
10r is provided. The radial bearing surface 10r is opposed to the outer peripheral surface of the shaft member 3 via a radial bearing clearance Cr.
This embodiment exemplifies a case in which a pair of radial bearing surfaces 10r are provided apart from each other in the axial direction as shown in FIG.
On both radial bearing surfaces 10r, a plurality of dynamic pressure grooves 11 (herringbone type) inclined with respect to the axial direction are formed in the circumferential direction. The dynamic pressure groove 11 may be inclined with respect to the axial direction, and may have a shape other than the herringbone type, for example, a spiral type as long as this condition is satisfied. On the outer periphery of the sintered oil-impregnated bearing 1, one or more (two in the drawing) grooves 12 are provided.
The groove 12 is formed along the axial direction. When the dynamic pressure type bearing 1 is installed in the housing 2 as shown in FIG. 1, the air enters and exits from the space surrounded by the bearing body 10 and the bottom plate 4 and the outside. Function as a ventilation path to ensure

The radial bearing surface 10r has a first groove region m1 in which the dynamic pressure grooves 11 inclined to one side are arranged, and a first groove region m1.
A second groove region m2 in which the dynamic pressure grooves 11 inclined to the other are arranged in the axial direction, and an annular smooth portion n located between the two groove regions m1 and m2, Two groove areas m1,
The dynamic pressure groove 11 of m2 is partitioned by the smooth portion n and is discontinuous. The back portion 13 between the smooth portion n and the dynamic pressure groove 11 is at the same level. This type of non-continuous type dynamic pressure groove 11 is a continuous type, that is, in which the smooth portion n is omitted, and the dynamic pressure groove 11 is formed in a V-shape that is continuous with each other between the two groove regions m1 and m2. Smoothing part n
Therefore, there is an advantage that the oil film pressure is high because the oil is collected around the center, and that the bearing has high rigidity because it has a smooth portion n without a groove.

In the sintered oil-impregnated bearing 1, the lubricant (lubricating oil or base oil of lubricating grease) inside the bearing body 10 is generated by the pressure generation due to the rotation of the shaft member 3 and the thermal expansion of the oil due to the temperature rise. The fluid oozes out from the surface of the bearing 10 and is drawn into the radial bearing clearance Cr by the action of the dynamic pressure groove 11. The oil drawn into the radial bearing clearance Cr forms a lubricating oil film and supports the shaft member 3 in a non-contact manner in the radial direction. That is, the lubricant inside the bearing body 10 oozed out by the dynamic pressure action of the inclined dynamic pressure groove 11 is drawn into the radial bearing clearance Cr, and the lubricant continues to be pushed into the radial bearing surface 10r, so that the oil film force increases. Thus, the rigidity of the bearing can be improved. When a positive pressure is generated in the radial bearing clearance 10r, the lubricant flows back into the bearing body 10 because there is a hole in the surface of the radial bearing surface 10r, but new lubricant is pushed into the radial bearing clearance 10r one after another. As it continues, the oil film strength and stiffness are kept high. In this case, since a continuous and stable oil film is formed, high rotation accuracy is obtained, and shaft runout, NRRO, jitter and the like are reduced. Further, since the shaft member 3 and the bearing main body 10 rotate in a non-contact manner, the noise is low and the cost is low.

A thrust bearing surface 10s formed simultaneously with the radial bearing surface 10r is provided on one end surface of the bearing body 10 (an end surface facing the flange portion 3a of the shaft member 3). On the thrust bearing surface 10s, a plurality of dynamic pressure grooves 14 having a portion inclined with respect to a radial imaginary line drawn on the bearing end surface are arranged at regular intervals in the circumferential direction. In the present embodiment, as the dynamic pressure groove 14 of the thrust bearing surface 10s, a herringbone type, that is, a substantially V-shaped one having a bent portion at a substantially central portion in the radial direction is exemplified. Other shapes may be used as long as they are satisfied.

In the bearing unit shown in FIG. 1, while the shaft member 3 is rotating, the shaft member 3 receives a levitation force due to an exciting force between the rotor 8 and the stator 7 (see FIG. 9) and floats from the bottom plate 4. Becomes At this time, a hydrodynamic oil film is formed on the thrust bearing clearance Cs between the thrust bearing surface 10s and the end face of the flange portion 3a opposed thereto by the same action as above.
The shaft member 3 is supported in a non-contact manner in the thrust direction. A thrust washer 4a made of a highly lubricating resin material or the like is disposed on the upper surface of the bottom plate 4 and directly below the shaft member 3, so as to reduce friction between the motor and the shaft end at the time of starting or immediately before stopping. I have.

The bearing body 10 of the above-mentioned hydrodynamic sintered oil-impregnated bearing 1
Can be manufactured by subjecting a cylindrical sintered metal material (bearing material) obtained by compression-molding the above metal powder and further firing to, for example, sizing → rotational sizing → bearing surface forming. it can.

The sizing step is a step of sizing the outer peripheral surface and the inner peripheral surface of the sintered metal material to correct a bending or the like in the sintering process. The outer peripheral surface of the sintered metal material is pressed into a cylindrical die. At the same time, the sizing pin is pressed into the inner peripheral surface. The rotation sizing process is performed by rotating a rotation sizing pin having a substantially polygonal cross section (the outer peripheral surface of a pin having a circular cross section is partially flattened and an arc portion is left at a position equidistant in the circumference) in the sintered metal material. This is a step of sizing the inner peripheral surface by rotating the sizing pin while pressing against the peripheral surface. This rotation sizing corrects the roundness and cylindricity of the inner peripheral surface of the sintered metal material, and reduces the surface porosity to, for example, 3%.
Finished to ~ 15%. The bearing surface forming step includes, on the inner peripheral surface and at least one end surface of the sintered metal material subjected to the sizing processing as described above, a forming die having an uneven shape corresponding to the shapes of the radial bearing surface 10r and the thrust bearing surface 10s. By applying pressure, dynamic pressure grooves on both bearing surfaces 10r and 10s
This is a step of simultaneously forming the regions 11 and 14 and the other regions (for example, the back 13 and the annular smooth region n in the radial bearing surface 10r).

FIG. 3 illustrates a schematic structure of a forming apparatus used in the bearing surface forming step. This device is a sintered metal material
Cylindrical die 20 for forming 10 'outer peripheral surface, sintered metal material
A core rod 21 made of cemented carbide for forming the inner peripheral surface of 10 ′ and upper and lower punches 22 and 23 for pressing both end surfaces of the sintered metal material 10 ′ from above and below are configured as main elements.

As shown in FIG. 4, an outer peripheral surface of the core rod 21 is provided with a concave-convex forming die 21a (radial forming die) corresponding to the shape of the pair of radial bearing surfaces 10r.
The convex part 21a1 of the molding die 21a forms the area of the dynamic pressure groove 11 on the radial bearing surface 10r, and the concave part 21a2 forms the area other than the dynamic pressure groove 11 (the back 13 and the annular smooth area n). . The step between the convex portion 21a1 and the concave portion 21a2 in the molding die 21a is as small as the depth of the dynamic pressure groove 11 in the radial bearing surface 10r (for example, about 2 to 5 μm), but is considerably exaggerated in the drawing. It is drawn. In addition, on the punch surface of one of the punches (for example, the upper punch 22),
A mold 22a (thrust mold) having an uneven shape corresponding to the dynamic pressure groove 14 on the thrust bearing surface 10s is provided. Which of the upper and lower punches 22 and 23 is provided with the thrust forming die can be arbitrarily determined according to the workability of the work in the subsequent process, and the thrust forming die 23 a May be provided. Thrust mold 22a (or
Although the specific shape of 23a) is not shown, a region of the dynamic pressure groove 14 of the thrust bearing surface 10s is formed by a convex portion in the same manner as the radial molding die 21a, and a region other than the dynamic pressure groove 14 is formed by a concave portion. It shall be molded.

The molding by this molding apparatus is performed according to the procedures shown in FIG.

First, after positioning the sintered metal material 10 ′ on the upper surface of the die 20, the upper punch 22 and the core rod 21 are lowered, and the sintered metal material 10 ′ is pressed into the die 20,
Further, it is pressed against the lower punch 23 to apply pressure from above and below ().

The sintered metal material 10 ′ is made up of a die 20 and upper and lower punches.
The inner peripheral surface is pressed against the forming die 21 a of the core rod 21, and one end surface is pressed against the forming die 22 a of the upper punch 22, respectively, by receiving a compressive force from 22 and 23. Thereby, the molding die 21
a and 22a are transferred to the inner peripheral surface and one end surface of the sintered metal material 10 ', and the radial bearing surface 10r and the thrust bearing surface 10s are simultaneously formed into predetermined shapes and dimensions (simultaneously with sintering). The outer peripheral surface and both end surfaces of the metal material 10 'are also sized).

After the forming of both bearing surfaces 10r and 10s is completed,
While maintaining the positional relationship between the sintered metal material 10 ′ and the core rod 21, the upper and lower punches 22 and 23 and the core rod 21 are integrally raised (), and the sintered metal material 10 ′ is pulled out of the die 20.
Next, hot air is blown onto the outer peripheral surface of the sintered metal material 10 ′ by a heater such as a hot air generator to heat the sintered metal material 10 ′, and then the sintered metal material 10 ′ is pulled out of the core rod 21. (). At this time, when the sintered metal material 10 'is pulled out of the die 20, springback occurs in the sintered metal material 10' and the inner diameter of the sintered metal material 10 'increases. Further, the temperature of the sintered metal material 10 ′ becomes higher than that of the core rod 21 due to the heating, and the sintered metal material 10 ′ becomes higher than the core rod 21 (made of cemented carbide).
Since the coefficient of thermal expansion of (mainly copper) is large, the inner diameter of the sintered metal material 10 'is further increased. for that reason,
Interference between the core rod 21 and the sintered metal material 10 'is avoided,
The core rod 21 can be removed from the inner peripheral surface of the sintered metal material 10 'without breaking the dynamic pressure groove 11 of the radial bearing surface 10r. In the case where the sintered metal material 10 'can be smoothly pulled out only by the spring back, the heating step by the heater may be omitted.

The sintered metal material 1 manufactured through the above steps
When 0 ′ is cleaned and impregnated with lubricating oil or lubricating grease to retain the oil, the sintered oil-impregnated bearing 1 shown in FIG. 2 is completed. The bearing 1 is fixed to the inner peripheral surface of the housing 2 by, for example, bonding. The housing 2 of the bearing 1
If the bearing clearances Cr and Cs and the space around the bearings are filled with oil by lubricating separately from the impregnating oil after incorporation into the lubricating oil, the lubricity is significantly improved.

As described above, if the bearing surfaces 10r and 10s are formed by compression-molding the sintered metal material 10 ', the process can be simplified, the cycle time can be shortened, and the production cost can be improved through mass productivity. Can be reduced. Further, a high-precision dynamic pressure-type bearing can be easily manufactured only by performing the final bearing surface forming process (dynamic pressure sizing) with high accuracy, so that accuracy control is also easy. Simultaneous molding of the radial bearing surface 10r and the thrust bearing surface 10s is also easy. In this case, the problem of molding both bearing surfaces 10r and 10s in separate processes, that is, a decrease in accuracy of the bearing surface formed in the previous process, and the like. Problem can also be avoided.

FIGS. 6 to 9 show another embodiment of a bearing unit using the above-mentioned hydrodynamic sintered oil-impregnated bearing 1. FIG.

FIG. 6 shows the other of the bearing body 10 (the housing 2).
In the embodiment in which the thrust bearing surface 10s is provided on the end surface (opening side), a thrust bearing clearance Cs is formed between the thrust bearing surface 10s and the end surface (lower end surface) of the flange portion 3a provided on the shaft member 3. Is done. In the drawing, the bottom plate 4 and the housing 2
An elastic material 4b such as resin, rubber or the like is stacked on the bottom plate 4 and used as a packing to prevent oil leakage from the joint with the bottom plate.

FIG. 7 shows an embodiment in which thrust bearing surfaces 10s1 and 10s2 are provided on both end surfaces of the bearing body 10, respectively.
10 and the thrust bearing clearances C with the end faces of the two flange portions 3a1 and 3a2 provided at two places of the shaft member 3.
They face each other via s1 and Cs2. In this case, the thrust loads in both directions can be supported, and the shaft member 3 is prevented from coming off, so that damage to the motor when an impact load is applied to the shaft member 3 can be avoided. Thrust bearing surface
10s1 and 10s2 are thrust forming dies having an uneven shape corresponding to the dynamic pressure groove shape on the punch surfaces of the upper and lower punches 22 and 23 in FIG.
By providing 22a and 23a, molding can be performed simultaneously with the radial bearing surface 10r in exactly the same procedure as in FIG.

FIG. 8 shows the thrust bearing surface on one end face (bottom side of the housing 2) of the bearing body 10 as in FIG.
10s1 and a similar thrust bearing surface 10s2 on one of the opposing surfaces of the flange portion 3a and the bottom plate 4 (for example, the upper surface of the bottom plate 4). The same effect as the structure of FIG. Is done.

FIG. 9 shows the housing 2 shown in FIG.
And a bottomed cylindrical housing 2 ′ (bag-shaped housing).
The thrust bearing surfaces 10s1 and 10s2 are provided on one of the opposed surfaces of the flange portion 3a and the housing bottom surface 2a (for example, the housing bottom surface 2a) (the width of the radial bearing clearance Cr and the thrust bearing clearance Cs1 and Cs2). Is exaggerated). In this case, in addition to the same effect as the structure of FIG. 7, it is possible to completely prevent oil leakage from the joint between the bottom plate 4 and the housing 2 and further reduce the cost by reducing the number of parts. The same effect can be obtained by applying a similar bag-shaped housing 2 'to the bearing units of FIGS. 6 and 7. Reference numeral 6 in the figure denotes a disk hub, which holds a magnetic disk or the like and is coupled to the upper end of the shaft member 3.
Denotes a motor stator fixed to the bag-shaped housing 2 ', 8
Denotes a motor rotor fixed to the disk hub 6.

In the above description, the case where the bearing main body 10 is formed of a sintered metal is exemplified. However, the present invention is also applied to the case where the bearing main body 10 is formed of a soft metal such as aluminum, brass, and bronze. In this case, the radial bearing surface 10r and the thrust bearing surface 10s can be simultaneously formed in the same procedure as in FIGS. If the bearing material after forming the bearing surface is difficult to come off from the core rod 21, the bearing material may be heated in the process. In this case, the lubricating oil as a lubricant is filled in the radial bearing clearance Cr and the thrust bearing clearance Cs.

[0036]

According to the present invention, a dynamic pressure bearing for supporting a shaft member in a non-contact manner in both a radial direction and a thrust direction can be manufactured at a low cost and with high accuracy by a simple method. In addition, since the radial bearing surface and the thrust bearing surface are molded at the same time, the accuracy of the bearing surface molded in the previous process may decrease during the subsequent process, as in the case where both bearing surfaces are molded in separate processes. Thus, each bearing surface can be formed at low cost and with high precision.

[Brief description of the drawings]

FIG. 1 is a sectional view of a dynamic pressure bearing unit according to the present invention.

2A is a cross-sectional view of a dynamic pressure bearing according to the present invention, and FIG. 2B is a plan view as viewed from a direction b.

FIG. 3 is a schematic sectional view of a forming apparatus used in a bearing surface forming step.

FIG. 4 is a front view of a core rod.

FIG. 5 is a sectional view showing a bearing surface forming step.

FIG. 6 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

FIG. 7 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

FIG. 8 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

FIG. 9 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing 2 Housing 3 Shaft member 3a Flange part 4 Bottom plate 10 Bearing body 10r Radial bearing surface 10s Thrust bearing surface 21a Radial molding die 22a Thrust molding die 23a Thrust molding die Cr Radial bearing clearance Cs Thrust bearing clearance

Claims (5)

[Claims] 1. A radial bearing surface having a dynamic pressure groove inclined with respect to an axial direction and facing an outer peripheral surface of a shaft member to be supported via a radial bearing clearance is provided on an inner peripheral surface of a bearing body. A dynamic pressure bearing, wherein a thrust bearing surface having a dynamic pressure groove is formed on at least one end surface of the bearing body at the same time as the radial bearing surface. 2. The dynamic pressure bearing according to claim 1, wherein the bearing body is formed of a sintered metal and impregnated with oil. 3. The bearing body according to claim 1, wherein the bearing body is formed of a soft metal.
The dynamic pressure bearing described. 4. A shaft member having a flange portion, and a shaft member having a flange portion.
4. A dynamic pressure bearing unit comprising: the dynamic pressure bearing according to any one of claims 3 to 3, wherein a thrust bearing clearance is formed by the thrust bearing surface and an end surface of a flange portion facing the thrust bearing surface. 5. A thrust for forming a dynamic pressure groove of a thrust bearing surface on both ends of the bearing material and at least one of the both ends of the bearing material while disposing a radial molding die for forming a dynamic pressure groove of the radial bearing surface. By holding with a pair of punch surfaces provided with a molding die and applying a pressing force to the bearing material in this state, the inner peripheral surface and at least one end surface of the bearing material,
A method of manufacturing a dynamic pressure bearing, wherein a radial bearing surface and a thrust bearing surface each having a dynamic pressure groove are simultaneously formed.