JP2008101729A - Dynamic pressure bearing device and deflection type scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life dynamic pressure bearing device capable of preventing a deterioration of oil as a working fluid and exhibiting a stable bearing performance. <P>SOLUTION: A base material of either a shaft 1 or a sleeve 2 rotatably fitted to each other is made from copper alloy. A surface of the base material is provided with a surface treated film subjected to lead-free electroless nickel plating. The content of lead contained in the copper alloy composing the base material is equal to or less than 0.01% by weight. By applying the lead-free electroless nickel plating as the surface treatment, the deterioration of the oil caused by lead can be prevented. As the content of lead in the base material is smaller, the affinity of the base material with the electroless nickel plating becomes better, so that there hardly occurs unevenness of plating or a pinhole. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device and a deflection scanning device used in a laser beam printer, an optical / magnetic disk device, and the like.

  In a deflection scanning device mounted on a laser beam printer, a digital copying machine, or the like, a dynamic pressure bearing device for obtaining a stable and smooth rotation is used for a bearing portion that supports a rotating polygon mirror that rotates at high speed. Also, in information recording devices such as optical disks and magnetic disks, dynamic pressure bearings are widely used to support disks that rotate at high speed.

  FIGS. 2A and 2B show a hydrodynamic bearing device according to a conventional example. FIG. 2A shows a state where the shaft 101 is attached, and FIG. 2B shows a state where the shaft 101 is not attached. The hydrodynamic bearing device includes a shaft 101, a sleeve 102 that rotatably supports the shaft 101 in the bearing hole 105, a disk 103 that is fixed to the lower end of the sleeve 102 and seals the bearing hole 105, and a disk 103 And a thrust plate 104 supported by the cylinder. In addition, the bearing 106 between the bearing hole 105 of the sleeve 102 and the shaft 101 and the space between the thrust plate 104 and the end surface of the shaft 101 are filled with oil 106 that is a working fluid.

  Large diameter portions 105a, 105b, and 105c are provided at the upper end, the lower end, and the center of the bearing hole 105 of the sleeve 102, respectively. Further, a herringbone-like dynamic pressure having one fold line is provided between the large diameter portion 105a at the upper end and the large diameter portion 105c at the center, and between the large diameter portion 105c at the center and the large diameter 105b at the lower end. Generation grooves 107a and 107b are formed. A spiral groove is formed on the upper surface of the thrust plate 104. The upper end portion of the shaft 101 protrudes upward from the bearing hole 105 of the sleeve 102, and a boss portion (not shown) is fixed to the upper portion thereof.

  When the shaft 101 rotates, dynamic pressure is generated in the oil 106 by the action of the dynamic pressure generating grooves 107 a and 107 b provided in the bearing hole 105 of the sleeve 102, and the shaft 101 rotates without contact with the bearing hole 105 of the sleeve 102. Also in the thrust direction, dynamic pressure is generated by the action of the spiral groove provided in the thrust plate 104, and the shaft 101 is supported in a floating state. When this hydrodynamic bearing device is used in a deflection scanning device, a rotary polygon mirror (not shown) is integrally coupled to the upper end of the shaft 101 via a boss portion. Etc. are also fixed to the shaft 101.

  In the hydrodynamic bearing device configured as described above, the lead contained in the shaft or the sleeve and the oil of the working fluid are liable to react as the temperature becomes higher. For this reason, when the motor is operated for a long time or is intermittently started and stopped, the oil of the working fluid becomes a gel, the viscosity is deteriorated, and the bearing life is reduced.

  Therefore, as disclosed in Patent Document 1, the shaft or sleeve is made of a copper alloy, and the contained lead is suppressed to 0.003 to 0.5% by weight, thereby suppressing the deterioration of oil due to the reaction with lead. The configuration is known.

In addition, as disclosed in Patent Document 2, there is a method of performing electroless nickel plating on the surface of the shaft or sleeve.
JP 2003-97557 A JP 2000-321522 A

  However, in the configuration of Patent Document 1, it is unavoidable that the shaft and the sleeve come into contact with each other and cause sliding wear when a low-speed rotation region that cannot be supported by dynamic pressure or intermittent start / stop operation is performed.

  Moreover, the thing disclosed by patent document 2 tends to generate | occur | produce a plating nonuniformity and a pinhole in the electroless nickel plating formed in the surface of a axis | shaft or a sleeve. Therefore, in order to improve the dimensional accuracy, there are cases where a cutting process or a ball burnishing process is required as a post process.

  The present invention relates to a hydrodynamic bearing device and deflection scanning that can suppress reaction between lead contained in a shaft and sleeve and oil of a working fluid and reduce sliding wear at the start and stop of a motor, low speed operation, and the like. The object is to provide an apparatus.

  In order to achieve the above object, a hydrodynamic bearing device of the present invention includes a shaft and a sleeve that are rotatably fitted to each other, and oil interposed between the shaft and the sleeve, and at least one of the shaft and the sleeve. Is a dynamic pressure bearing device provided with dynamic pressure generating means for generating dynamic pressure in the oil, wherein the shaft or the base material of the sleeve has a lead content of 0.01% by weight or less. It is made of a copper alloy, and the base material is subjected to a surface treatment of electroless nickel plating not containing lead.

  The smaller the lead content contained in the shaft or sleeve made of a copper alloy, the better the compatibility with electroless nickel plating, the less uneven plating and pinholes after the surface treatment, and the more likely the dimensional accuracy is stabilized.

  If the base fluid of the working fluid is a combination of an oil mainly composed of an ester and a shaft or sleeve that has been subjected to a surface treatment that does not contain lead in electroless nickel plating, Reaction with oil is suppressed. Accordingly, the bearing life is improved without deteriorating the viscosity of the oil.

  As a result, it is possible to realize a hydrodynamic bearing device having a long life and stable bearing performance.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1A is a cross-sectional view showing a main part of a deflection scanning apparatus according to an embodiment, and a rotary polygon mirror 11 having a reflection surface 11a for deflecting and scanning a light beam and for rotationally driving the mirror. The drive part is shown. FIGS. 1B and 1C are sectional views showing the hydrodynamic bearing device of FIG. 1A, FIG. 1B is a state where the shaft 1 is attached to the sleeve 2, and FIG. Show.

  As shown in FIG. 1A, the shaft 1 is integrated with a rotor 12 composed of a permanent magnet 12 a and a yoke 12 b and a rotary polygon mirror 11. The sleeve 2 is integrated with the stator 13 and the circuit board 14 including the drive coil 13a and the stator core 13b, and the shaft 1 and the sleeve 2 are rotatably fitted to each other.

  The base material of the sleeve 2 is a copper alloy, and the lead content contained in the copper alloy is 0.01% by weight or less, and this base material is first processed into a sleeve shape.

  The processed sleeve 2 is subjected to electroless nickel plating not containing copper. As a pretreatment process, the sleeve 2 is degreased, activated, washed with water, and the like, and then the sleeve 2 is immersed in an electroless nickel plating bath not containing copper. The plating may be performed by a general electric conduction method or a catalyst method, and an optimum plating thickness may be applied. Then, if washing, drying, etc. are performed, the surface treatment film | membrane of the electroless nickel plating which does not contain copper in the sleeve 2 will be formed.

  The stator core 13b has multi-pole pole shoes, and a drive coil 13a is wound around each pole shoe. The energization is sequentially switched depending on the rotational position of the permanent magnet 12 a magnetized in multiple poles, and a rotational force is generated between the rotor 12 and the stator 13. The stator core 13b around which the drive coil 13a is wound is fixed to the circuit board 14 together with circuit components constituting the drive circuit, and the circuit board 14 is integrated with the sleeve 2. Such a rotor part and a stator part are produced individually and assembled as a motor. After a predetermined amount of oil 6 as a working fluid is injected into the sleeve 2 by an oil supply device, the shaft 1 that is rotatably fitted inside the sleeve 2 is inserted to complete the motor.

  The oil 6 that is a working fluid uses an oil mainly composed of an ester.

  As described above, the hydrodynamic bearing device, which is a bearing portion that rotatably supports the rotating polygon mirror 11, has a sleeve 2 that rotatably supports the shaft 1 in the bearing hole 5, and a lower end of the sleeve 2 that is fixed to the bearing hole. 5 and a thrust plate 4 supported by the disc 3. Oil 6 is filled between the inner surface of the bearing hole 5 of the sleeve 2 and the outer surface of the shaft 1 or between the thrust plate 4 and the end surface of the shaft 1.

  The upper end portion, the lower end portion, and the central portion of the bearing hole 5 of the sleeve 2 are large diameter portions 5a, 5b, and 5c, respectively. Between the large-diameter portion 5a at the upper end and the large-diameter portion 5c at the center, and between the large-diameter portion 5c at the center and the large-diameter portion 5b at the lower end, herringbone-like dynamic pressure generating grooves (dynamic pressure generating means) ) 7a and 7b are formed. A spiral groove is formed on the upper surface of the thrust plate 4.

  When the shaft 1 rotates, dynamic pressure is generated in the oil 6 by the action of the dynamic pressure generating grooves 7a and 7b provided in the bearing hole 5 of the sleeve 2, and the shaft 1 rotates without contact with the bearing hole 5 of the sleeve 2. . Also in the thrust direction, dynamic pressure is generated by the action of the spiral groove provided in the thrust plate 4, and the shaft 1 is supported in a floating state. The disc 3 is fixed by caulking in order to close the opening at the lower end of the sleeve 2. Since the disc 3 is easily affected by the deterioration of the cylindricity, it is necessary to assemble with an appropriate pressure.

  As described above, since the sleeve 2 is a copper alloy base material whose lead content is suppressed to 0.01% by weight or less and is subjected to a surface treatment of electroless nickel plating not containing lead. There is no risk of oil deterioration due to the reaction with. In addition, pinholes and plating unevenness can be prevented from occurring in the electroless nickel-plated surface treatment film, thereby contributing to stabilization of dimensional accuracy. As a result, a long-life dynamic pressure bearing device with stable bearing performance can be realized. By using such a dynamic pressure bearing device for the bearing portion of the rotary polygon mirror, it is possible to greatly contribute to extending the life of the deflection scanning device.

1 shows a deflection scanning device according to an embodiment, in which (a) is a schematic sectional view thereof, (b) is a sectional view showing a bearing portion of (a), and (c) is a schematic sectional view showing only a sleeve. . It is a figure which shows the hydrodynamic bearing apparatus by one prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 axis | shaft 2 sleeve 3 disc 4 thrust plate 6 oil 7a, 7b dynamic pressure generating groove 11 rotating polygon mirror 12 rotor 13 stator 14 circuit board

Claims (3)

  A dynamic pressure generating means for generating dynamic pressure on the oil in at least one of the shaft and the sleeve; and a shaft and a sleeve that are rotatably fitted to each other, and oil interposed therebetween The base material of the shaft or the sleeve is made of a copper alloy having a lead content of 0.01% by weight or less, and the base material contains no lead. A hydrodynamic bearing device that is subjected to electrolytic nickel plating surface treatment.   The hydrodynamic bearing device according to claim 1, wherein the oil is mainly composed of an ester.   3. A deflection scanning apparatus comprising: a bearing portion comprising the hydrodynamic bearing device according to claim 1; and a rotary polygon mirror rotatably supported by the bearing portion.

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