JP4599738B2 - Motor and disk device provided with the same - Google Patents

Description

表１から明らかなように、実施例は３０万回回転で１０台中２台しか停止していないが、比較例１は動圧溝底面の硬度が高いために、異物を吸収できずに焼付きが生じている。比較例２は動圧溝底面の硬度が高い上、溝深さが浅いために十分な軸受剛性が得られず、多くのモータが停止している。比較例３は停止しているモータの数は少ないが、このモータを分解すると摩耗粉により潤滑油は黒くゲル化していることが確認できた。表面の硬度が低いため焼き付くことはないが、摩耗により駆動電流値が増加し停止している。
【００４７】
【発明の効果】
以上述べたように、本発明のモータは、優れた耐摩耗性を有し、潤滑油中に金属粉等の異物が混入し動圧発生部に集中したとしても、このような異物により引き起こされる焼き付きを防止することができ、長期間にわたって優れた性能を維持することができる。
【００４８】
本発明のディスク装置では、ハウジング内部に固定され、記録媒体を回転部に装着したモータを備え、このモータとして前記のモータを用いるので、装置の長寿命化を測ることができる。
【図面の簡単な説明】
【図１】本発明のモータに使用される流体動圧軸受の概略構成を示す部分拡大断面図である。
【図２】周回溝の一実施態様を示す概設図である。
【図３】本発明のモータの概略構成図である。
【図４】本発明のディスク装置の概略構成図である。
【図５】実施例・比較例で作製したサンプルの概略構成図である。
【符号の説明】
１ 基材
２ 金属層
３，３１，３２，３３，３４ 動圧溝
４ 周回溝
７ モータ
８ ディスク装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor and a disk device including the motor, and more particularly to a motor having a fluid dynamic pressure bearing that is excellent in wear resistance and hardly causes seizure, and a disk device including the motor.
[0002]
[Prior art]
In a disk drive that rotates a recording disk such as a hard disk, high deflection accuracy is required as the capacity of the recording disk increases. Is growing.
[0003]
This fluid dynamic pressure bearing includes a shaft and a sleeve that can rotate relative to each other, a lubricating oil interposed as a working fluid therebetween, and a dynamic pressure groove that induces a dynamic pressure in the lubricating oil when the motor rotates. The dynamic pressure groove is generally provided on the sleeve side in many cases.
[0004]
[Problems to be solved by the invention]
For shafts used for fluid dynamic pressure bearings, stainless steel, particularly martensite-based slenless material, is often used because of its mechanical strength, workability, and availability of wires. A stainless steel material is suitable for the sleeve material opposed to this, but for the same reason, when a stainless steel material is used for the sleeve, seizure due to adhesion is likely to occur during contact / sliding because the material has a similar composition. Therefore, various coatings and heat treatments are applied to the stainless steel, but it is not sufficient.
[0005]
In addition, a copper-based material is often used for the sleeve because of its ease of processing. However, when a copper-based material is used, the wear is large, the runout accuracy deteriorates over time, and the lubricating oil is caused by wear powder. There is a risk that the viscosity increases and the current value increases.
[0006]
For this reason, it is also proposed to apply plating to the surface of the grooved copper-based sleeve, but cutting powder, burrs, etc. generated during groove processing remain around the groove, causing unevenness on the plating surface, The cutting powder itself is plated to produce protrusions. The protrusions formed in this way are higher in hardness than stainless steel and may damage the shaft or cause abnormal rotation. Further, the foreign matter and wear powder are concentrated on the dynamic pressure generating part by the pumping action by the dynamic pressure groove when the motor rotates, and seizure due to biting is likely to occur.
[0007]
In addition, cutting powder and burrs generated by groove formation by rolling or other machining are sticky and cannot be easily removed by cleaning, and the inside of the groove is technically difficult to polish and wear powder is generated in reverse. Become. Groove formation by electrolytic processing is not suitable because it is difficult to ionize a copper-based material, and it is difficult to form a sharp groove.
[0008]
The present invention has been made in view of such conventional problems, and has excellent wear resistance, and even if foreign matter such as metal powder is mixed in the lubricating oil and concentrated on the dynamic pressure generating portion, It is an object of the present invention to provide a motor having a fluid dynamic pressure bearing capable of preventing seizure caused by foreign matter and maintaining excellent performance for a long period of time, and a disk device including the motor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a motor according to the present invention includes a sleeve member, a shaft member that is rotatable relative to the sleeve member, and a lubricating oil filled between the sleeve member and the shaft member. In the motor having a fluid dynamic pressure bearing constituted by the sleeve member, the sleeve member has a base material made of copper, aluminum, magnesium and an alloy containing these as a main component, and has a higher hardness than the base material on the base material surface. And a dynamic pressure groove is formed in the metal layer so that the bottom surface of the base material is exposed.
[0010]
The base material (metal material) used here may be any material having a hardness lower than that of stainless steel and having a Hv of 180 or less. However, from the viewpoint of ease of handling including workability and cost, copper or a copper alloy is used. preferable.
[0011]
The metal layer provided on the surface of the substrate is preferably nickel or an alloy containing nickel as a main component from the viewpoint of hardness and workability. In order to obtain sufficient bearing characteristics, wear resistance and seizure resistance, The film thickness is set in the range of 3 to 15 μm, preferably 5 to 10 μm.
[0012]
Although this metal layer can be provided by various methods, it is recommended that the metal layer be formed by plating in terms of uniformity and cost. The plating in this case can be either electroless plating or electrolytic plating.
[0013]
Further, the groove processing needs to be performed so that the plating layer is completely removed and the material is exposed on the bottom surface, and it is preferable to perform the processing by electrolytic processing in which fine cutting powder and burrs are not generated during processing.
[0014]
In addition, when cutting powder or the like is mixed in the lubricating oil and concentrates on the dynamic pressure generating part, to increase the allowable volume of foreign matter and prevent local accumulation, It is preferable to provide a circumferential groove in advance in the base material before providing the metal layer so as to communicate the end portion on the downstream side in the flow direction or the bent portion of the dynamic pressure groove where the highest dynamic pressure is generated. The width of the circumferential groove may be in a range that is not completely blocked when the metal layer is formed and that does not affect the bearing characteristics.
[0015]
Further, the disk device of the present invention is a disk device comprising a housing, a motor fixed inside the housing, and information access means for writing and / or reading information on the recording disk, wherein the recording disk The motor is used as a motor for rotationally driving the motor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows an example of a fluid dynamic pressure bearing. As shown in FIG. 1, a metal layer 2 having a hardness higher than that of the substrate 1 is formed on the substrate 1 having a hardness of Hv 180 or less, and the metal layer 2 is moved so that the surface of the substrate 1 is exposed on the bottom surface. A pressure groove 3 is provided to form a sleeve. When the motor rotates, the lubricating oil flows downstream in the flow direction of the dynamic pressure groove 3 or in the direction of the bent portion, so that foreign matters such as metal powder mixed in the lubricating oil concentrate and accumulate on the dynamic pressure generating portion. If the gap between the opposing shafts becomes narrow due to accumulated foreign matter or if foreign matter is caught larger than the gap between the shafts, contact and sliding between the shaft and the sleeve will occur. Further, since the bottom surface of the dynamic pressure groove 3 is soft, foreign matter is embedded in the surface, so that the seizure does not occur. On the other hand, since the metal layer 2 having high hardness is formed on the surface of the base material other than the dynamic pressure groove 3, the sleeve will not be worn even after long-term use. In FIG. 1, the dynamic pressure grooves 3 are formed up to a depth at which the surface of the base material 1 is exposed. However, the dynamic pressure grooves 3 may also be formed in the base material 1.
[0018]
As the material for the shaft, stainless steel is suitable because of its mechanical strength, workability, and availability of wire. Further, examples of the metal material having a hardness of Hv 180 or less used as the base material 1 of the sleeve include copper, aluminum, magnesium and alloys containing these as main components. From the viewpoint, copper or a copper alloy is preferable. As an alloy containing copper as a main component, for example, an alloy containing one or more elements such as Zn, Ni, Pb, Sn, P, and Be can be used.
[0019]
The material of the metal layer 2 having high hardness formed on the surface of the base material 1 of the sleeve is not particularly limited, but nickel or an alloy containing nickel as a main component is used from the viewpoint of hardness and workability. preferable. One or more elements of Fe, Nb, Cr, Co, P, B, W, etc. are blended in the alloy containing nickel as a main component.
[0020]
Examples of the method for forming the metal layer 2 include, but are not limited to, plating, physical vapor deposition, and CVD. However, the electroless plating method is a preferable forming method because a uniform film can be formed when a metal layer made of nickel or an alloy containing nickel as a main component is formed.
[0021]
The thickness of the metal layer 2 is preferably in the range of 3 to 15 μm. When the film thickness of the metal layer 2 is less than 3 μm, when a strong force is applied, the metal layer is broken. On the other hand, when the thickness exceeds 15 μm, there are problems in workability and cost, such as a decrease in bearing rigidity and a longer processing time until the base material is exposed on the bottom surface of the dynamic pressure groove 3. The more preferable lower limit value of the film thickness is 5 μm, and the upper limit value is 10 μm.
[0022]
In order to make the hardness of the metal layer 2 higher, an annealing treatment may be performed after the formation of the metal layer 2. The conditions for the annealing treatment may be appropriately determined from the composition, film thickness, etc. of the metal layer 2. The annealing process may be performed before or after the dynamic pressure groove 3 is processed.
[0023]
As a method for forming the dynamic pressure groove 3 in the metal layer 2, conventionally known processing methods such as electrolytic processing, cutting processing, rolling processing, press processing, and laser processing can be used, but are not particularly limited. . However, since rolling and pressing tend to cause distortion and burrs of the bearing member due to processing, and laser processing has particle problems, electrolytic processing is preferable. Electrolytic machining is a particularly preferred machining method because the metal material in the groove portion is electrolyzed and processed, so that fine burrs, peeling, and chips that cause foreign matters in the lubricating oil are not generated.
[0024]
The shape of the dynamic pressure groove 3 is not particularly limited as long as it is a shape in which lubricating oil is caused to flow by a pumping action to exert a bearing action. Examples include herringbone grooves and spiral grooves. Further, from the viewpoint of effectively preventing seizure, as described in detail later, a circumferential groove may be further provided so as to communicate the downstream end portion or the bent portion of the dynamic pressure groove 3 in the flow direction of the lubricating oil.
[0025]
FIG. 2 shows an embodiment example of the dynamic pressure groove and the circumferential groove. As shown in FIG. 2 (a), when the herringbone dynamic pressure groove 31 is formed, it circulates so as to communicate the downstream end portion in the flow direction of the lubricating oil, that is, the bent portion B of the "<"-shaped groove. Groove 4 is formed. When the motor rotates in the direction of the arrow X, the lubricating oil flows in the opposite direction and travels along the dynamic pressure groove 31 toward the circumferential groove 4, where two flows collide with each other and flow in the vertical direction on the paper surface. Accordingly, foreign matter in the lubricating oil accumulates in the dynamic pressure groove 31 and the circumferential groove 4.
[0026]
As shown in FIG. 2B, when the spiral dynamic pressure groove 32 is formed, the circumferential groove 4 is formed at the upper end portion of the spiral groove 32 inclined upward to the right. When the motor rotates in the direction of the arrow X, the lubricating oil flows in the opposite direction, so that the lubricating oil moves upward along the spiral groove 32, collides with the side wall of the circumferential groove 4, and flows in the vertical direction on the paper surface. Accordingly, the foreign matter in the lubricating oil accumulates in the dynamic pressure groove 32 and the circumferential groove 4 as in the case of FIG.
[0027]
As shown in FIG. 2C, when two spiral dynamic pressure grooves 33 are formed at a predetermined interval, when the motor rotates in the arrow X direction, the lubricating oil moves along the spiral groove 33 in the arrow Y direction. The two flows collide with each other at the center of the circular groove 4 and flow in the vertical direction on the paper surface.
[0028]
FIG. 2D shows an external view in which the circumferential groove 4 is formed in the central bent portion B of the herringbone dynamic pressure groove 34 formed in the thrust plate.
[0029]
Thus, when forming a circumference groove in a dynamic pressure groove, after forming the above-mentioned metal layer on the substrate surface, a circumference groove is formed simultaneously with a dynamic pressure groove. Alternatively, after the circumferential groove is directly processed on the substrate surface, a metal layer is formed on the substrate surface by a plating method, and then the dynamic pressure groove is formed. In this case, if the circumferential groove width is about 5 to 10 μm wider than the film thickness of the metal layer, the metal layer is not formed in each groove portion, so just plating the metal layer on the substrate on which the groove is formed, Circumferential grooves are also formed in the metal layer.
[0030]
FIG. 3 is a schematic sectional view of a motor for driving a hard disk as an embodiment of the motor of the present invention. The motor 7 includes a bracket 71, a shaft 72 whose one end is fitted and fixed to the central opening of the bracket 71, and a rotor 73 that is rotatably held relative to the shaft 72. A stator 711 is fixed to the bracket 71, and a rotor magnet 731 is provided on the rotor 73 at a position facing the stator 711, and a rotational driving force is generated between the stator 711 and the rotor magnet 731.
[0031]
A disc-shaped upper thrust plate 721 and a lower thrust plate 722 projecting outward in the radial direction are provided at the upper end and the lower end of the shaft 72. Is formed.
[0032]
On the other hand, the rotor 73 is supported by the shaft 72 via a rotor hub 732 on which the recording disk D is placed on the outer peripheral portion and a minute gap in which the lubricating oil 75 is held, which is positioned on the inner peripheral side of the rotor 73. And a sleeve 734. Further, the sleeve 734 is provided with an upper counter plate 76a and a lower counter plate 76b so as to cover the outer sides of the upper and lower thrust plates.
[0033]
Here, the shaft 72 and the upper and lower thrust plates 721 and 722 correspond to the shaft member in the present invention, and the sleeve 734 corresponds to the sleeve member in the present invention. In this sleeve member, a plating layer mainly composed of nickel is formed on the surface of a base material mainly composed of copper. As will be described later, a herringbone-like dynamic pressure groove 78 is formed on the upper and lower portions of the inner peripheral surface of the through hole 77 of the sleeve 734, and a spiral shape is formed on the lower surface of the upper thrust plate 721 and the upper surface of the lower thrust plate 722. The dynamic pressure grooves 79 are respectively formed by electrolytic processing.
[0034]
A portion extending from the outer periphery of the shaft 72 adjacent to the upper portion of the gas intervening portion 74 provided at the center of the shaft 72 to the lower surface, the outer peripheral surface, and the upper surface of the upper thrust plate 721 has an opposing sleeve 734. A minute gap is formed between the upper part of the inner peripheral part through-hole 77 and the part from the upper counter plate 76a to the lower surface, and the lubricating oil 75 is held. A spiral dynamic pressure groove 79 that generates dynamic pressure in the lubricating oil 75 as the rotor 73 rotates is formed on the lower surface of the upper thrust plate 721 and the upper surface of the lower thrust plate 722. The dynamic pressure groove 79 exerts an action of pressing the lubricating oil 75 in the direction of arrow A during rotation of the motor and generating a supporting force for holding the rotor portion in the axial direction. Further, herringbone-like dynamic pressure grooves 78 are formed in the upper and lower lubricating oil retaining portions on the inner peripheral surface of the through hole 77 of the sleeve 734. The dynamic pressure groove 78 acts to generate a support force that presses the lubricating oil 75 in the direction of arrow B when the motor rotates and holds the rotor portion in the radial direction.
[0035]
The distribution of the dynamic pressure of the lubricating oil 75 in the minute gap generated by the dynamic pressure grooves 78 and 79 is highest near the inner peripheral portion P of the lower surface of the upper thrust plate. As a result, when the air dissolved in the lubricating oil 75 is bubbled, the bubbles are diffused and excluded to the outside of the inner peripheral portion P, and the gap in the lower gas intervening portion 74 or the upper counter plate 76a in the upper portion The bottom gap is reached. Since these gaps are opened to the atmosphere directly or through the outside air communication hole 70, the bubbles are released to the outside air from here, and the lubricating oil leakage due to the expansion of the bubbles is prevented.
[0036]
Further, a taper seal portion is formed between the lower surface of the counter plate 76a, which is an end portion of the lubricating oil holding portion, and the upper surface of the upper thrust plate 721. The taper seal portion gradually widens in the axial direction. An oil repellent agent is applied to the end of each of these. Similarly, the upper portion of the gas intervening portion 74 at the center of the shaft 72, which is the other end of the lubricating oil holding portion, also extends from the lubricating oil holding portion between the outer peripheral surface of the shaft 72 and the inner peripheral surface of the sleeve 734. A taper seal part is formed in which the gap gradually increases as the distance from the lower side in the axial direction decreases, and an oil repellent is applied to the end of the taper seal part. By the taper seal portions formed at both ends, a gas-liquid interface of the lubricant is formed and held at a position where the dynamic pressure generated in the lubricant, the atmospheric pressure, and the surface tension of the taper seal are balanced. The oil repellent applied to the taper seal portion also has an action of preventing so-called lubricating oil migration in which the lubricating oil diffuses along the metal surface of the shaft or sleeve. With these lubricating oil retaining structures, a fluid bearing structure with no lubricating oil leakage and high load bearing capacity is realized.
[0037]
The structure of the same minute gap, dynamic pressure groove, and lubricating oil holding part is formed in the lower thrust plate 722 and the lower counter plate 76b from the lower part of the gas intervening part 74 provided at the center part of the shaft 72 in an upside down arrangement. The lower dynamic pressure bearing supports the rotor portion more stably.
[0038]
FIG. 4 is a schematic explanatory diagram showing an embodiment of the disk device of the present invention. Inside the housing 81, a spindle motor 82 that rotatably supports a recording disk 83 that stores information at high density, and an information access means 87 that reads and writes information from and to the recording disk 83 are arranged. The information access means 87 includes at least a head 86 for reading and writing information on the recording disk 83, an arm 85 for supporting the head 86, and an actuator unit 84 for moving the head 86 and the arm 85 to a required position on the recording disk 83. It is configured. The above motor is used as the spindle motor 82.
[0039]
Incidentally, the information density that can be stored in the recording disk has been dramatically improved in recent years, and a clean environment with extremely few dusts and dirt is indispensable as an installation environment of the recording disk. Therefore, in order to provide a highly clean space in which the inside of the housing 81 is shielded from the outside air, the information access means 87 and the spindle motor 82 should be of a mechanism that does not leak lubricating oil mist or the like. desirable.
[0040]
【Example】
Examples of the present invention will be described below. FIG. 5 shows schematic sectional views of Examples and Comparative Examples in which the following evaluation tests were performed.
[0041]
(Example)
A sleeve was produced using an alloy (BC6C) having a hardness of Hv100 as a main component of copper (BC6C), and a nickel layer having a thickness of 5 μm was formed on the surface thereof by electroless plating. Thereafter, the dynamic pressure grooves were processed so that the base material was exposed by electrolytic processing to prepare a sample. FIG. 5A shows a schematic sectional view of the sample.
[0042]
(Comparative Example 1)
A sample was prepared in the same manner as in the example except that stainless steel having a hardness of Hv250 was used as the base material of the sleeve. FIG. 5B shows a schematic sectional view of the sample.
[0043]
(Comparative Example 2)
A sample was prepared in the same manner as in the example except that the depth of the dynamic pressure groove was shallower than the thickness of the metal layer and the base material was not exposed on the bottom surface of the dynamic pressure groove. FIG. 5C shows a schematic cross-sectional view of the sample.
[0044]
(Comparative Example 3)
A sleeve was prepared using an alloy (BC6C) containing copper having a hardness of Hv100 as a main component (BC6C) as a base material, and a dynamic pressure groove was processed by direct cutting on the surface to prepare a sample. FIG. 5D shows a schematic sectional view of the sample.
[0045]
(Evaluation measurement method)
A motor was produced from the sleeve sample produced above and a stainless steel shaft. Furthermore, before the evaluation test, 1 mg of particles having a particle diameter of about 1 μm is mixed in advance in the lubricating oil filled between the sleeve and the shaft. Ten such motors were prepared for each sample, and intermittent operation (10 second operation / 10 second stop) was performed in an environment at a temperature of 80 ° C. until the cumulative number of rotations reached 300,000 times, and stopped halfway. Evaluation was performed by the number of motors. The evaluation results are shown in Table 1. After the evaluation, the motor was disassembled and the state of the bearing portion was observed.
[0046]
[Table 1]

As can be seen from Table 1, in Example, only 2 out of 10 were stopped at 300,000 rotations, but Comparative Example 1 was seized without absorbing foreign matter because of the high hardness of the bottom surface of the dynamic pressure groove. Has occurred. In Comparative Example 2, since the hardness of the bottom surface of the dynamic pressure groove is high and the groove depth is shallow, sufficient bearing rigidity cannot be obtained, and many motors are stopped. In Comparative Example 3, the number of stopped motors was small, but it was confirmed that when this motor was disassembled, the lubricating oil was blackened by wear powder. Although the surface hardness is low, no seizure occurs, but the drive current value increases due to wear and stops.
[0047]
【The invention's effect】
As described above, the motor of the present invention has excellent wear resistance, and even if foreign matter such as metal powder is mixed in the lubricating oil and concentrated on the dynamic pressure generating portion, it is caused by such foreign matter. Burn-in can be prevented and excellent performance can be maintained over a long period of time.
[0048]
The disk device of the present invention includes a motor fixed inside the housing and having a recording medium mounted on the rotating portion. Since the motor is used as the motor, the life of the device can be increased.
[Brief description of the drawings]
FIG. 1 is a partially enlarged sectional view showing a schematic configuration of a fluid dynamic pressure bearing used in a motor of the present invention.
FIG. 2 is a schematic view showing an embodiment of a circumferential groove.
FIG. 3 is a schematic configuration diagram of a motor according to the present invention.
FIG. 4 is a schematic configuration diagram of a disk device of the present invention.
FIG. 5 is a schematic configuration diagram of samples manufactured in Examples and Comparative Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base material 2 Metal layer 3, 31, 32, 33, 34 Dynamic pressure groove 4 Circumferential groove 7 Motor 8 Disk apparatus

Claims (7)

In a motor having a fluid dynamic pressure bearing comprising a sleeve member, a shaft member rotatable relative to the sleeve member, and a lubricating oil filled between the sleeve member and the shaft member,
It said sleeve member is copper, aluminum, a substrate made of an alloy composed mainly of magnesium and these, on the surface, has a metal layer higher than the substrate hardness, the bottom surface of the base material is exposed As described above, a motor is characterized in that a dynamic pressure groove is formed in the metal layer.   The motor according to claim 1, wherein the base material is copper or an alloy containing copper as a main component.   3. The motor according to claim 1, wherein the metal layer is nickel or an alloy containing nickel as a main component and has a thickness of 3 to 15 μm.   The motor according to claim 1, wherein the metal layer is formed by plating.   The motor according to claim 1, wherein the dynamic pressure groove is formed by electrolytic processing.   The motor according to any one of claims 1 to 5, wherein a circumferential groove is formed so as to communicate an end portion or a bent portion of the dynamic pressure groove on the downstream side in the flow direction of the lubricating oil. A disk drive device comprising a housing, a motor that is fixed in the housing and rotationally drives the recording disk, and information access means for writing and / or reading information on the recording disk,
A disk device using the motor according to claim 1 as the motor.

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