JP4347010B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a bearing member used in a high-speed digital copying machine, a laser printer, a rotating magnetic head device of a video tape recorder, etc. in which a magnetic disk drive spindle motor or polygon mirror rotary drive device is used. The present invention relates to a hydrodynamic bearing device that uses a lubricant filled in a gap with a shaft member as a pressure generating fluid, and in particular, prevents corrosion generated by an antiwear agent.

  Conventionally, a hydrodynamic bearing device fills a gap between a bearing member and a shaft member with a lubricating fluid and increases dynamic pressure on at least one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member. A generation groove is formed, whereby a pressure increase is generated in the dynamic pressure generation groove when the bearing member or the shaft member is rotated, and both members are maintained in a non-contact state. The lubricants used in these hydrodynamic bearing devices use synthetic oils such as mineral oils, poly-α-olefin oils, ester oils, silicone oils, and fluorine oils as base oils.

When a hydrocarbon base oil is used as the dynamic pressure generating fluid of the hydrodynamic bearing device, it is known to add various additives in the same manner as other industrial lubricants (see, for example, Patent Document 1). The addition amount was also in the range described in the literature. (For example, refer nonpatent literature 1.)
The hydrodynamic bearing device that generates pressure in the dynamic pressure generating groove due to the relative movement of the bearing member and the shaft member and maintains both members in a non-contact state is in a contact state when stopped, and rubs when activated. Therefore, an anti-wear agent has been added to the lubricant, but many anti-wear agents are corrosive due to their performance mechanism, and depending on the amount of addition, the generation of corrosive wear powder is observed. Furthermore, it is well known that the hydrodynamic bearing device is in contact when it is stopped and rubs when it is started, and it is common knowledge that a load such as a side pressure is not applied until the bearing reaches a steady state. However, various known additives were added within a common sense range. (For example, see Patent Document 2.)
Japanese Patent Laid-Open No. 01-185852 Japanese National Patent Publication No. 11-514778 New edition: Petroleum product additive, published by Koshobo, first edition on July 25, 1986

  The problem to be solved is that, as a side effect of adding a large amount of the anti-wear agent among the various additives as described above, corrosive wear powder is generated in the bearing and the lubricant is deteriorated. .

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to provide a highly reliable fluid dynamic bearing device that suppresses the occurrence of corrosion wear powder in the bearing while preventing wear in the bearing.

In order to solve the above problems, the hydrodynamic bearing device of the present invention includes a bearing member and a shaft in which a dynamic pressure generating groove is formed on at least one facing surface of the bearing member and the shaft member, and the dynamic pressure generating groove is opened. In a hydrodynamic bearing device in which a lubricant is filled in a gap with a member, the lubricant has an addition amount of either zinc dithiophosphate or trioctyl phosphate of 0.1 parts by weight to 0.01 parts by weight. Dioctyl sebacic acid diester is used as oil to suppress corrosion wear.

Moreover, well-known various additives, such as antioxidant and a rust preventive agent, can also be mix | blended as needed.

  According to the hydrodynamic bearing device of the present invention, the lubricant sandwiched between the shaft and the bearing sleeve does not generate corrosive wear powder, so that wear in the bearing can be prevented and a highly reliable hydrodynamic bearing device can be realized.

  Further, a highly reliable magnetic disk rotating device can be provided by using the hydrodynamic bearing device of the present invention.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an example of a hydrodynamic bearing device used in a hard disk drive, which has the same configuration as that of a conventional hydrodynamic bearing device except for a lubricant 10, and has a dynamic pressure generating groove 4a and a dynamic pressure generating groove on the outer peripheral surface. One end of the shaft 2 on which 4b is formed is press-fitted into the base 1, and a thrust receiver 3 is fixed to the other end to form a shaft portion. A bearing sleeve 5 is press-fitted into the inner peripheral surface of the hub 6 for attaching a magnetic disk or the like, and a thrust plate 11 is attached to one end of the bearing sleeve 5 to form a bearing body. Then, the bearing sleeve 5 is mounted on the shaft 2 so that the thrust plate 11 and the thrust receiver 3 face each other, and a lubricant 10 is filled in the gap between the shaft portion and the bearing body.

  A stator coil 9 is provided on the outer wall 1a formed on the base 1, and a rotor magnet 7 is attached to the inner peripheral surface of the hub 6 facing the stator coil 9 via a rotor yoke 8, thereby constituting a motor drive unit. The

  When the bearing sleeve 5 and the hub 6 are rotationally driven by the motor driving portion, dynamic pressure is generated in the lubricant 10 by the pumping action of the dynamic pressure generating groove 4a and the dynamic pressure generating groove 4b formed in the shaft 2, and the bearing body is The shaft floats from the shaft portion, and the shaft portion and the bearing body are rotatably supported without contact.

  The dynamic pressure generating groove 4a and the dynamic pressure generating groove 4b may be formed on one or both of the outer peripheral surface of the shaft 2 and the inner peripheral surface of the bearing sleeve 5, and the thrust dynamic pressure generating groove is formed. Alternatively, it may be formed on one or both of the opposing surfaces of the thrust receiver 3 and the thrust plate 11. Also, both the radial and thrust side dynamic pressure generating grooves need only have a shape in which the pressure of the lubricant 10 increases in the gap between the opposing surfaces, and various types such as providing a refracting part and changing the depth of the groove part. Is possible. Further, a fluid bearing device in which the shaft portion rotates and the bearing sleeve 5 is fixed may be used.

  Here, since the characteristic of the hydrodynamic bearing device of the present invention resides in the lubricant 10, it will be described below with an example of an antiwear agent.

  The hydrodynamic bearing device of the present invention is held in a non-contact state in a steady operation state, but rubs at the time of starting. Therefore, the lubricant includes phosphoric acid such as zinc thiophosphate, organomolybdenum compound, tricresyl phosphate, and trialkyl phosphate. An ester wear inhibitor is added. The amount of the anti-wear agent added to the lubricant 10 between the rotating part and the fixed part is 0.1 to 0.01 part by weight (preferably 0.05 to 0.01 part by weight). Thus, it is possible to provide a highly reliable fluid dynamic bearing device while preventing the wear in the bearing and suppressing the occurrence of corrosion wear powder in the bearing.

(Embodiment 2)
Next, an example of the magnetic recording disk rotating device of the present invention will be described. In FIG. 2, in a magnetic disk rotating apparatus incorporating a shaft-rotating type fluid bearing, three magnetic disks 33 are stacked on a hub 30 with a spacer 32 interposed therebetween, and are fixed by a clamp 31. A rotor magnet 29 is provided on the inner peripheral side of the hub 30, and a motor is formed with the stator coil 28 provided on the fixed side, and rotating parts such as the magnetic disk 33 and the hub 30 are rotated at high speed. To drive.

  The stator coil 28 is provided on the outer periphery of the bearing sleeve 22, and the bearing sleeve 22 is fixed to a base 27 connected to the ground. A shaft 21 is press-fitted into the hub 30, and the shaft 21 is inserted into a bearing sleeve 22 to which a thrust receiver 23 is attached. The thrust plate 24 is fixed to the opening on the base 27 side of the bearing sleeve 22.

  A thrust gap and a radial gap between the shaft 21 and the bearing sleeve 22, between the thrust receiver 23 and the bearing sleeve 22, and between the thrust receiver 23 and the thrust plate 24 are filled with a lubricant 26 added with lithium salt as a conductivity-imparting agent. Yes. A dynamic pressure generating groove is provided on at least one of the surfaces where the shaft 21 and the bearing sleeve 22, the thrust receiver 23 and the thrust plate 24 face each other, and the shaft 21 floats due to the dynamic pressure generated by the rotation.

  In the above configuration, the magnetic disk 33, the spacer 32, and the clamp 31 also have a cylindrical shape that is less likely to be unbalanced. The lubricant 10 is rubbed during start-up but does not come into contact during steady operation. The amount of the anti-wear additive added to the bearing is 0.1 to 0.01 parts by weight (preferably 0.05 to 0.01 parts by weight), while preventing wear in the bearing, The generation of corrosive wear powder can be suppressed.

  In addition, in the bearing sleeve rotating type, friction occurs at the time of startup but does not come into contact during steady operation, so the amount of the anti-wear agent added to the lubricant 10 between the rotating part and the fixed part is similarly 0.1 parts by weight. To 0.01 parts by weight (preferably 0.05 parts by weight to 0.01 parts by weight) can prevent the occurrence of corrosive wear powder in the bearing while preventing wear in the bearing.

  The hydrodynamic bearing device of the present invention and the conventional hydrodynamic bearing device are incorporated in the magnetic recording disk rotating device described in the second embodiment, an intermittent test is performed 10,000 times, and the lubricating oil after the test is recovered. The amount of wear powder and the state of occurrence of corrosive wear powder were confirmed by a ferrography analyzer. The results are shown in Table 1.

  Sample A as a lubricating oil was prepared by using 100 parts by weight of dioctyl sebacic acid diester as a base oil and pentaerythryl-tetrakis [3- (3,5-di-tbutyl-4-hydroxyphenyl) as an antioxidant. ) Propionate] and 0.5 parts by weight of methyl-benzotriazole as a corrosion inhibitor and no antiwear agent added.

  Samples B to I shown in Table 1 are obtained by adding 100 parts by weight of the above sample A and further adding the indicated addition amount (parts by weight) of the antiwear agent shown in Table 1. They are arranged in ascending order. In addition, in the evaluation of the amount of wear powder in Table 1, the metal wear powder detected from the recovered oil and the wear marks of the shaft 21 and the bearing sleeve 22 after the decomposition are taken into consideration. A certain thing was evaluated as x and the middle as Δ. Similarly, regarding the evaluation of the corrosive wear powder, a good product was evaluated as “◯”, a product with significant occurrence was evaluated as “X”, and the middle was evaluated as “Δ”.

  As can be seen from Table 1, Sample A to which no antiwear agent is added, and Sample G to Sample I in which 0.2 part by weight of the antiwear agent is added to Sample A, are evaluated in terms of the amount of wear powder or corrosion wear powder. As can be seen, the range from 0.01 parts by weight to 0.1 parts by weight is evaluated as ◯ or Δ. Moreover, evaluation is x also in the sample I which added 0.2 weight part of stearic acid generally considered to be low corrosivity, and it can be said that 0.2 weight part is an excessive addition amount.

  In addition, there is no problem if other than dioctyl sebacic acid diester is used as the base oil, but when the viscosity changes, the friction time at start and stop changes, so it becomes difficult to compare the effects of the additives. For this reason, although the base oil was specified in the present Example, this invention is not limited. Moreover, although the above-mentioned substances were used for the antioxidant and the corrosion inhibitor, this does not limit the present invention.

  Thus, the hydrodynamic bearing device of the present invention can suppress wear due to friction without corroding the inside of the bearing as in the conventional example.

  The hydrodynamic bearing device of the present invention is useful for improving the reliability of precision bearings such as magnetic recording devices that do not have eccentricity or side pressure during steady rotation.

Sectional drawing of the hydrodynamic bearing apparatus in Embodiment 1 of this invention Sectional view of a magnetic recording disk rotating device in Embodiment 2 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 2 Shaft 3 Thrust receiving 4a, 4b Dynamic pressure generating groove 5 Bearing sleeve 6 Hub 7 Rotor magnet 8 Rotor yoke 9 Stator coil 10, 26 Lubricant 11 Thrust plate 31 Clamp 32 Spacer 33 Magnetic disk

Claims (2)

In a hydrodynamic bearing device, a dynamic pressure generating groove is formed on at least one opposing surface of a bearing member and a shaft member, and a lubricant is filled in a gap between the bearing member and the shaft member in which the dynamic pressure generating groove is opened. Is characterized in that the addition amount of either zinc dithiophosphate or trioctyl phosphate is 0.1 parts by weight to 0.01 parts by weight, and dioctyl sebacic acid diester is used as a base oil to suppress corrosion wear. Fluid bearing device. A disk rotating device for magnetic recording on which the hydrodynamic bearing device according to claim 1 is mounted.

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