JP2005140339A - Spindle motor for information equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve further cost reduction of a spindle motor for information equipment comprising a fluid dynamic bearing device. <P>SOLUTION: A housing 7 is formed by injection-molding a metallic material and has a cylindrical side part 7b and an annular seal part 7a integrally extended from an upper end of the side part 7b to an inner diameter side. A bottom member 6 is made out of a resin material and fixed to a lower end of the side part 7b of the housing 7. The fluid dynamic bearing device 1 is assembled by fixing a bearing sleeve 8 and the bottom member 6 to the housing 7 formed in a state of opening its bottom part, and further mounting a shaft member 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spindle motor for information equipment including a hydrodynamic bearing device that non-contact supports a shaft member in a radial direction with an oil film of lubricating oil generated in a bearing gap. This spindle motor is, for example, a spindle motor such as a magnetic disk device such as HDD or FDD, an optical disk device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO, It is suitable as a polygon scanner motor for a laser beam printer (LBP).

  The various spindle motors are required to have high speed, low cost, low noise, etc. in addition to high rotational accuracy. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, as this type of bearing, the use of a fluid bearing having characteristics excellent in the required performance has been studied, or It is actually used.

  This type of hydrodynamic bearing includes a so-called hydrodynamic bearing provided with dynamic pressure generating means for generating dynamic pressure in the lubricating oil in the bearing gap, and a so-called perfect bearing having no dynamic pressure generating means (the bearing surface is a perfect circle). The bearings are roughly classified into shapes.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD or a polygon scanner motor of a laser beam printer (LBP), a radial bearing portion that rotatably supports a shaft member in a radial direction and a shaft member A thrust bearing portion that is rotatably supported in the thrust direction, and a dynamic pressure in which a dynamic pressure generating groove (dynamic pressure groove) is provided on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member as the radial bearing portion A bearing is used. As the thrust bearing portion, for example, a motion in which dynamic pressure grooves are provided on both end surfaces of the flange portion of the shaft member, or surfaces facing the flange portion (the end surface of the bearing sleeve, the end surface of the thrust member fixed to the housing, etc.). A pressure bearing or a bearing having a structure in which one end surface of a shaft member is in contact and supported by a thrust plate or the like (so-called pivot bearing) is used.

  Normally, the bearing sleeve is fixed at a predetermined position on the inner periphery of the housing, and a seal member is provided at the opening of the housing in order to prevent the lubricating oil injected into the inner space of the housing from leaking to the outside. There are many.

  The hydrodynamic bearing device having the above configuration is composed of parts such as a housing, a bearing sleeve, a shaft member, a thrust member (or a thrust plate), and a seal member, and is a high bearing required as the performance of information equipment increases. Efforts are being made to increase the processing accuracy and assembly accuracy of each part in order to ensure performance. On the other hand, with the trend of lowering the price of information equipment, the demand for cost reduction for spindle motors equipped with this type of hydrodynamic bearing device has become increasingly severe.

  An object of the present invention is to further reduce the cost of a spindle motor for information equipment provided with a hydrodynamic bearing device.

  In order to solve the above-mentioned problems, the present invention includes a shaft member, a hydrodynamic bearing device that rotatably supports the shaft member, a motor stator and a motor rotor, and the shaft member is driven by an exciting force between the motor stator and the motor rotor. In a rotating spindle motor for information equipment, a hydrodynamic bearing device is provided between a housing, a bearing sleeve fixed to the inner periphery of the housing, an inner peripheral surface of the bearing sleeve, and an outer peripheral surface of the shaft member. A radial bearing portion that supports the shaft member in the radial direction in a non-contact manner with an oil film of the lubricating oil generated in the above, and a thrust bearing portion that supports the shaft member in the thrust direction, and the housing is formed by injection molding of a metal material I will provide a.

  As said metal material, an aluminum alloy, a magnesium alloy, stainless steel etc. can be used, for example.

  By injection-molding the housing with a metal material, the manufacturing cost can be reduced as compared with the case where the housing is formed by turning or the like.

  As a method for injection molding the housing with a metal material, a metal injection molding (MIM) method or a thixo molding method can be employed. In general, the MIM method is a molding method in which a metal powder and a resin binder are kneaded, then injected into a mold and molded, and then the molded body from which the binder has been removed by degreasing is sintered to obtain a finished product ( After sintering, post-processing is performed as necessary.) And has the following features. In other words, small parts with complex shapes can be formed in near net shape, mold shapes can be transferred and mass-produced with the same shape, shrinkage during molding, degreasing and sintering By determining the shrinkage rate, etc., parts with high dimensional accuracy can be produced, and the mold shape can be transferred, ensuring the same surface accuracy (surface roughness, etc.) as the mold finish accuracy. It is possible to make near-net shapes for difficult-to-process materials such as stainless steel. In the thixomolding method, a chip such as a magnesium alloy is heated to a semi-molten state in a cylinder, stirred with a screw, and formed into a slurry to be injection-molded from a nozzle. The thixomolding method is a process that is friendly to the global environment because it can produce parts with high dimensional accuracy and does not require a flameproof gas such as SF6 gas.

  By using a magnesium alloy as the metal material for forming the housing, it is possible to further reduce the weight of the hydrodynamic bearing device and thus the spindle motor. Magnesium alloy is the metal with the lowest specific gravity among practical metals, and its specific gravity is about 1.8, which is about one-fourth that of iron and about two-thirds that of aluminum alloy. Moreover, it is excellent in thin-wall formability as compared with aluminum alloys and the like.

  Furthermore, the magnesium alloy has good heat dissipation, and the hydrodynamic bearing device of the present invention having a housing made of magnesium alloy is suitable for a rotation support portion of a spindle motor mounted on information equipment. For example, in a personal computer, as the clock frequency of a CPU (central processing unit) is rapidly increasing, heat is easily trapped inside the personal computer, and the operating environment of a hydrodynamic bearing device incorporated in a disk drive device or the like is also increased. The severity is increasing. In addition, with the increase in the speed of disk drive devices and the like, the internal heat generation amount of the bearing itself tends to increase. On the other hand, when heat is accumulated inside the hydrodynamic bearing device, the deterioration of the lubricating oil is promoted, which causes a decrease in the bearing life. By forming the housing of the hydrodynamic bearing device with a magnesium alloy having good heat dissipation, it is possible to prevent heat from being accumulated inside the hydrodynamic bearing device and prevent a reduction in bearing life.

  Magnesium alloys are excellent in recyclability with almost no deterioration in quality due to remelting and refining. Therefore, it is preferable to form the housing of the hydrodynamic bearing device with a magnesium alloy from the viewpoint of reducing the environmental load.

  In the above configuration, the radial bearing portion can be a dynamic pressure bearing that generates dynamic pressure in the lubricating oil in the bearing gap.

  According to the present invention, it is possible to provide a spindle motor for information equipment that is much cheaper and lighter.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to this embodiment. This spindle motor is used for a disk drive device such as an HDD, and has a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 mounted on the shaft member 2, and a radial gap, for example. A motor stator 4 and a motor rotor 5 which are opposed to each other. The stator 4 is attached to the outer periphery of the casing 6, and the rotor 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the casing 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor 5 is rotated by the exciting force between the stator 4 and the rotor 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows a fluid dynamic bearing device (fluid dynamic pressure bearing device) 1. The hydrodynamic bearing device 1 includes a housing 7, a bearing sleeve 8, a shaft member 2, and a bottom member 6 that forms the bottom of the housing 7.

  Between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2, the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart from each other in the axial direction. A thrust bearing portion S <b> 1 is provided between the lower end surface 2 b of the shaft member 2 and the end surface of the bottom member 6. For convenience of explanation, the description will proceed with the side of the bottom member 6 as the lower side and the side opposite to the bottom member 6 as the upper side.

  The shaft member 2 is formed of, for example, a metal material such as stainless steel, and the lower end surface 2b thereof is formed in a convex spherical shape.

  The bearing sleeve 8 is formed in a cylindrical shape, for example, with a porous body made of sintered metal, particularly a sintered body of sintered metal mainly composed of copper. On the inner peripheral surface 8a of the bearing sleeve 8 formed of this sintered metal, two upper and lower regions serving as radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart in the axial direction. In the two regions, for example, herringbone-shaped dynamic pressure grooves are formed. In addition, as the shape of the dynamic pressure groove, a spiral shape, an axial groove shape, or the like may be adopted.

  The housing 7 is formed by injection molding (metal injection molding or thixo molding) of a metal material such as a magnesium alloy, and extends integrally from the upper end of the cylindrical side portion 7b and the side portion 7b to the inner diameter side. And an annular seal portion 7a. The inner peripheral surface 7a1 of the seal portion 7a faces the outer peripheral surface 2a1 of the shaft member 2 via a predetermined seal space. In this embodiment, the tapered shape of the outer peripheral surface 2a1 of the shaft member 2 that forms the seal space facing the inner peripheral surface 7a1 of the seal portion 7a is gradually reduced upward (outward direction of the housing 7). Is formed. When the shaft member 2 rotates, the tapered outer peripheral surface 2a1 also functions as a so-called centrifugal force seal.

  The bottom member 6 is formed of a resin material and is fixed to the lower end of the side portion 7b of the housing 7.

  The hydrodynamic bearing device 1 of this embodiment can be assembled by fixing the bearing sleeve 8 and the bottom member 6 to the housing 7 formed in the state where the bottom portion is opened by the above-described molding, and further mounting the shaft member 2. it can.

  First, the bearing sleeve 8 is mounted on the inner peripheral surface of the side portion 7b from the opened bottom portion of the housing 7, and is pushed forward until the upper end surface comes into contact with the inner surface of the seal portion 7a. At that position, the bearing sleeve 8 is fixed to the housing 7 by appropriate means such as bonding, press-fitting, laser beam welding, and high-frequency pulse bonding. Next, the resin bottom member 6 is fixed to the lower end of the side portion 7b of the housing 7 by an appropriate means. In this embodiment, while forming the annular rib 7b1 in the lower end of the side part 7b, forming the annular recessed part 6a in the end surface of the bottom member 6, and fitting the recessed part 6a to the rib 7b1, Is attached to the lower end of the side portion 7b, and is fixed by ultrasonic welding or induction heating. In order to strengthen the fixed state of the bottom member 6, it is preferable that at least one of the inner peripheral surface and the outer peripheral surface of the rib 7 b 1 is formed with screw-like unevenness or knurled unevenness. Further, the rib 7b1 and the recess 6a may be discontinuous in the circumferential direction as long as they can be fitted to each other. Thereafter, the shaft member 2 is inserted into the inner peripheral surface 8 a of the bearing sleeve 8, and the lower end surface 2 b is brought into contact with the end surface of the bottom member 6. Then, lubricating oil is supplied to the internal space of the housing 7 sealed by the seal portion 7a.

  When the shaft member 2 rotates, the regions (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a of the shaft member 2 via a radial bearing gap. As the shaft member 2 rotates, dynamic pressure of lubricating oil is generated in the radial bearing gap, and the shaft member 2 is non-contacting freely in the radial direction by an oil film of lubricating oil formed in the radial bearing gap. Supported. Thus, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are configured. At the same time, the lower end surface 2 b of the shaft member 2 is contact-supported by the bottom member 6. Thereby, the thrust bearing part S1 which supports the shaft member 2 rotatably in the thrust direction is configured.

  FIG. 3 shows a modification of the embodiment shown in FIG. In this modification, the resin bottom member 9 is press-fitted and fixed to the inner periphery of the lower end of the side portion 7 b of the housing 7.

  FIG. 4 shows a hydrodynamic bearing device 11 according to another embodiment. The hydrodynamic bearing device 11 of this embodiment is different from the hydrodynamic bearing device 1 shown in FIG. 2 in that the bottom portion 17 c is integrally formed with the housing 17, and the lower end surface 2 b of the shaft member 2 is contact-supported by the thrust plate 20. In other words, the resin seal member 10 is attached to the upper end opening of the housing 17. The seal member 10 includes an inner peripheral surface 10b that forms a seal space facing the outer peripheral surface 2a1 of the shaft member 2.

  The housing 17 is formed by injection molding (metal injection molding or thixo molding) of a metal material such as a magnesium alloy, for example, and has a cylindrical side portion 17b and a bottom portion 17c continuous with the lower end of the side portion 17b. And.

  The thrust plate 20 is formed of a low friction material, for example, a resin material, and is disposed on the bottom portion 17 c of the housing 17.

  In the hydrodynamic bearing device 11 of this embodiment, the bearing sleeve 8 and the seal member 10 are fixed to the housing 17 formed with the upper end opened by the above-described molding, and the thrust plate 20 and the shaft member 2 are further mounted. Can be assembled by.

  First, the bearing sleeve 8 is mounted on the inner peripheral surface of the side portion 17b from the upper end opening of the housing 17, and is advanced until the lower end surface comes into contact with the inner surface of the bottom portion 17c. At that position, the bearing sleeve 8 is fixed to the housing 17 by appropriate means such as adhesion, press-fitting, laser beam welding, and high-frequency pulse bonding. Next, the resin seal member 10 is fixed to the upper end of the side portion 17b of the housing 17 by an appropriate means. In this embodiment, the annular rib 17b1 is formed on the upper end of the side portion 17b, the annular recess 10a is formed on the end surface of the seal member 10, and the seal member 10 is fitted to the rib 17b1. Is attached to the upper end of the side portion 17b, and is fixed by ultrasonic welding or induction heating. In order to strengthen the fixing state of the seal member 10, it is preferable that at least one of the inner peripheral surface and the outer peripheral surface of the rib 17b1 is formed with screw-shaped unevenness or knurled unevenness. Further, the rib 17b1 and the recess 10a may be discontinuous in the circumferential direction as long as they can be fitted to each other.

  Thereafter, the thrust plate 20 is mounted on the bottom portion 17 c of the housing 17, and the shaft member 2 is further inserted into the inner peripheral surface 8 a of the bearing sleeve 8, and the lower end surface 2 b is brought into contact with the end surface of the thrust plate 20. Then, lubricating oil is supplied to the internal space of the housing 17 sealed with the seal member 10.

  FIG. 5 shows a hydrodynamic bearing device 21 according to another embodiment. The hydrodynamic bearing device 21 includes a housing 27, a bearing sleeve 28, a shaft member 22, and a bottom member 26 that constitutes a bottom portion of the housing 27.

  Between the inner peripheral surface 28a of the bearing sleeve 28 and the outer peripheral surface 22a1 of the shaft portion 22a of the shaft member 22, the first radial bearing portion R21 and the second radial bearing portion R22 are provided apart in the axial direction. A first thrust bearing portion S21 is provided between the lower end surface 28c of the bearing sleeve 28 and the upper end surface 22b1 of the flange portion 22b of the shaft member 22, and the lower end surface of the end surface 26a of the bottom member 26 and the flange portion 22b. A second thrust bearing portion S22 is provided between 22b2.

  The shaft member 22 is formed of a metal material such as stainless steel, for example, and includes a shaft portion 22a and a flange portion 22b provided integrally or separately at the lower end of the shaft portion 22a.

  The bearing sleeve 28 is formed in a cylindrical shape, for example, with a porous body made of sintered metal, particularly a sintered body of sintered metal mainly composed of copper.

  On the inner peripheral surface 28a of the bearing sleeve 28 formed of this sintered metal, two upper and lower regions serving as radial bearing surfaces of the first radial bearing portion R21 and the second radial bearing portion R22 are provided apart in the axial direction. In the two regions, for example, herringbone-shaped dynamic pressure grooves are formed. In addition, as the shape of the dynamic pressure groove, a spiral shape, an axial groove shape, or the like may be adopted.

  Further, for example, a spiral dynamic pressure groove is formed on the lower end surface 28c of the bearing sleeve 28, which is the thrust bearing surface of the first thrust bearing portion S21. In addition, as a shape of the dynamic pressure groove, a herringbone shape, a radiation groove shape, or the like may be adopted.

  The housing 27 is formed, for example, by injection molding (metal injection molding or thixo molding) of a metal material such as magnesium alloy, and extends integrally from the upper end of the cylindrical side portion 27b to the inner diameter side of the side portion 27b. And an annular seal portion 27a. The inner peripheral surface 27a1 of the seal portion 27a faces the outer peripheral surface 22a1 of the shaft member 22 via a predetermined seal space. In this embodiment, the outer peripheral surface 22a1 of the shaft member 22 that forms the seal space facing the inner peripheral surface 27a1 of the seal portion 27a is tapered so that the diameter gradually decreases upward (outward direction of the housing 27). Is formed.

  The bottom member 26 is formed of a resin material and is fixed to the lower end of the side portion 27b of the housing 27. For example, a herringbone-shaped dynamic pressure groove is formed on the end surface 26a of the bottom member 26, which is a thrust bearing surface of the second thrust bearing portion S22. When the bottom member 26 is formed by resin injection molding, the dynamic pressure groove of the end face 26a can be formed simultaneously with molding (transferred by a molding die). Further, as the shape of the dynamic pressure groove, a spiral shape, a radiation groove shape, or the like may be adopted. The bottom member 26 can be fixed to the housing 27 in the same manner as in the embodiment shown in FIG. Or it can also carry out in the aspect similar to embodiment shown in FIG.

  The shaft portion 22 a of the shaft member 22 is inserted into the inner peripheral surface 28 a of the bearing sleeve 28, and the flange portion 22 b is accommodated in a space portion between the lower end surface 28 c of the bearing sleeve 28 and the end surface 26 a of the bottom member 26. Lubricating oil is supplied to the internal space of the housing 27 sealed by the seal portion 27a.

  When the shaft member 22 rotates, the regions (two upper and lower regions) of the inner peripheral surface 28a of the bearing sleeve 28 face the outer peripheral surface 22a1 of the shaft portion 22a via a radial bearing gap. Further, the region that becomes the thrust bearing surface of the lower end surface 28c of the bearing sleeve 28 faces the upper end surface 22b1 of the flange portion 22b via the thrust bearing gap, and the region that becomes the thrust bearing surface of the end surface 26a of the bottom member 26 is the flange. It faces the lower end surface 22b2 of the portion 22b via a thrust bearing gap. As the shaft member 22 rotates, the dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft portion 22a of the shaft member 22 rotates in the radial direction by the oil film of the lubricating oil formed in the radial bearing gap. It is supported non-contact freely. Thereby, the first radial bearing portion R21 and the second radial bearing portion R22 that support the shaft member 22 in a non-contact manner so as to be rotatable in the radial direction are configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the flange portion 22b of the shaft member 22 is rotatably supported in both thrust directions by the lubricating oil film formed in the thrust bearing gap. . Thereby, the first thrust bearing portion S21 and the second thrust bearing portion S22 that support the shaft member 22 in a non-contact manner so as to be rotatable in the thrust direction are configured.

  In addition, the structure which fixes a resin-made sealing member to the upper-end opening part of a housing is also applicable to the hydrodynamic bearing apparatus which employ | adopted the dynamic pressure bearing for the thrust bearing part according to embodiment shown in FIG. .

It is sectional drawing of the spindle motor which concerns on embodiment of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus which concerns on the modification of embodiment shown in FIG. It is sectional drawing which shows the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus which concerns on other embodiment of this invention.

Explanation of symbols

1, 11, 21 Fluid bearing device 2, 22 Shaft member 4 Motor stator 5 Motor rotor 7, 17, 27 Housing 8, 28 Bearing sleeve R1, R21 First radial bearing portion R2, R22 Second radial bearing portion S1, S21, S22 Thrust bearing

Claims (3)

In an information equipment spindle motor comprising a shaft member, a hydrodynamic bearing device that rotatably supports the shaft member, a motor stator and a motor rotor, and rotating the shaft member by an excitation force between the motor stator and the motor rotor.
The hydrodynamic bearing device is provided between a housing, a bearing sleeve fixed to the inner periphery of the housing, and an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member, and the lubricating oil generated in the bearing gap. A radial bearing portion that supports the shaft member in a radial direction in an oil film in a non-contact manner; and a thrust bearing portion that supports the shaft member in a thrust direction.
A spindle motor for information equipment, wherein the housing is formed by injection molding of a metal material. The hydrodynamic bearing device according to claim 1, wherein the metal material is a magnesium alloy. The hydrodynamic bearing device according to claim 1, wherein the radial bearing portion is a dynamic pressure bearing that generates dynamic pressure in the lubricating oil in the bearing gap.

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