JP2007327604A - Hydrodynamic bearing device and rotary device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lubricating oil from being discharged from the inside of a fixed sleeve by rotation of a rotary shaft, in a scanner motor, etc. which use a hydrodynamic bearing. <P>SOLUTION: The rotary shaft 1 connected to a polygonal mirror 5 is rotatably fit in a fixed sleeve 10. Dynamic pressure is developed by dynamic pressure-developing grooves 16 in the lubricating oil in the gap between the rotary shaft 1 and the fixed sleeve 10. The rotary shaft 1 keeps a clearance groove 17 between both the dynamic pressure-developing grooves 16 with the groove face coated with a porous film 20 having oil-retention function by a chemical conversion treatment. Thus, the lubricating oil is prevented from being discharged from the bearing gap to stabilize the motor drive for a long period of time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device and a rotating device mounted on a scanner motor such as a laser beam printer (LBP).

  The operation principle of a general recording device such as LBP scans the photosensitive surface on the outer periphery of the photosensitive drum with laser light emitted from a laser source, and exposes and charges the portion of the photosensitive surface that receives the laser light. Recording is performed by attaching toner to the charging portion and transferring the toner to paper or another recording medium. Normally, a rotating polygon mirror (rotating polygon mirror) is used to scan the outer circumference of the photosensitive drum with laser light emitted from a laser transmission source.

  In such an LBP, in recent years, with the increase in recording speed and accuracy, there is an increasing demand for high performance such as high-speed rotation of 20000 rpm or more and reduction of rotation unevenness with respect to the scanner motor.

  In general, an LBP scanner motor includes a polygon mirror and a spindle motor. That is, a polygon mirror is attached to the rotation shaft of the spindle motor, and the polygon mirror is rotated by the rotation of the rotation shaft of the spindle motor. The polygon mirror is fixed so that the normal vector of the mirror surface is orthogonal to the axis of the spindle motor, and the polygon mirror rotates at high speed, so that the laser beam is scanned on the photosensitive drum of the LBP with high accuracy. Is done.

  FIG. 3 shows a conventional scanner motor with a polygon rotating mirror. A mounting ring 102 is fixed to the rotating shaft 101 of the motor. A rotor yoke 103 is fixed to the mounting ring 102, and a drive magnet 104 is fixed to the rotor yoke 103. A polygon mirror 105 is attached to the upper reference surface of the attachment ring 102, and is pressed and fixed by a wave washer 106, a flat washer 107 and a stopper 108. The rotating shaft 101, the rotor yoke 103, and the polygon mirror 105 that are coupled in this manner serve as a rotating body of the motor.

  On the other hand, a fixing sleeve 110, an iron substrate 111, and a stator core 112 for applying a rotational force are fixed to a housing 109 which is a fixing member. A circuit component 114 such as a drive IC is mounted on the iron substrate 111. A fixed magnet 113 is fixed to the lower end portion of the fixed sleeve 110, and a levitating magnet 115 is fixed to the lower end portion of the rotating shaft 101. The rotating shaft 101 is rotatably held. In order to generate dynamic pressure on the outer periphery of the rotating shaft 101, dynamic pressure generating grooves 116 are formed at two locations, upper and lower. In addition, lubricating oil is filled between the fixed sleeve 110 and the rotating shaft 101, and smooth rotation can be performed.

  The fixed sleeve 110 is fitted into the central through hole of the housing 109, and the rotary shaft 101 is inserted into the inner diameter of the fixed sleeve 110 with a clearance of about 1 to 2 μm. In a state where the rotating shaft 101 is inserted into the fixed sleeve 110, the lower end portion of the through hole of the housing 109 is closed by the sealing member 118. Thereby, the stability of the dynamic pressure generation and the rotation stability during the high-speed rotation of the rotating shaft 101 are ensured. A winding coil 119 for generating a rotating magnetic field is attached around the salient poles of the stator core 112.

  The coaxiality of the rotor yoke 103 with respect to the rotating shaft 101 and the parallelism with the iron substrate 111 are guaranteed by the processing accuracy of the housing 109. That is, the rotor yoke 103 to which the drive magnet 104 is fixed is caulked and fixed to the first reference surface (lower surface side) of the mounting ring 102, and the mounting ring 102 is press-fitted into the rotating shaft 101. Further, a polygon mirror 105 is firmly attached to the second reference surface (upper surface side) of the mounting ring 102 by a flat washer 107 and a stopper 108 fitted in a stopper groove of the rotating shaft 101 via a wave washer 106. It is pressed and fixed to. For this reason, even when rotating at a high speed of 20000 rpm or more, the balance of rotational motion does not shift.

  Usually, the movement balance is adjusted by aligning the aperture portion of the outer edge of the rotor yoke 103 and the outer peripheral groove (not shown) of the upper surface of the polygon mirror 105 with UV adhesive or the like. Since the parallelism between the outer peripheral mirror surface of the polygon mirror 105 and the rotating shaft 101 is guaranteed by the respective reference surfaces of the mounting ring 102 and the polygon mirror 105 as described above, good optical scanning is possible.

  In such a configuration, a current is passed through the winding coil 119 attached to the stator core 112, and the current flowing through the winding coils of each phase (for example, three phases) is switched in accordance with a signal from the rotation phase detection means (not shown). A rotating magnetic field is generated. This magnetic field generates a repulsive force in the drive magnet 104, and the drive magnet 104, the rotor yoke 103, the rotating shaft 101, and the polygon mirror 105 rotate integrally.

  With these components, the scanner motor serves as the heart of the LBP.

  However, there is a problem that the lubricating oil that plays an important role in the stability of rotation comes out of the gap between the fixed sleeve and the rotating shaft due to the rotation of the rotating shaft. This phenomenon causes a problem with respect to driving stability such as rotation stop due to running out of lubricating oil and a problem that scattered lubricating oil adheres to the mirror surface of the polygon mirror and adversely affects the optical system.

  With respect to such problems, Patent Document 1 discloses a technique for absorbing the scattered lubricating oil by a material having an oil retaining function so that the lubricating oil does not adhere to the mirror surface of the polygon mirror. .

In addition, as an example of improving the oil retaining function, Patent Document 2 discloses an example in which a microcrystalline structure of manganese phosphate is provided on the shaft surface to improve the oil retaining function. Further, a technique for producing microcrystals is disclosed in Patent Document 3. Further, Patent Document 4 discloses various motors and compressors using manganese phosphate microcrystals.
JP-A-9-197323 JP 2003-049754 A Japanese Patent Laid-Open No. 7-090611 Japanese Patent Laid-Open No. 4-036458

  However, all of the techniques disclosed in Patent Documents 2 to 4 are for reducing friction of sliding surfaces such as gears and splines. Further, in the configuration disclosed in Patent Document 1, there is a problem that the bearing oil is discharged from the inside of the fixed sleeve due to the rotation of the rotation shaft of the scanner unit, and the scanner motor can be driven stably for a long time. Is difficult.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and realizes long-term stable driving of a scanner motor and the like by holding long-term lubricating oil that generates dynamic pressure. It is an object of the present invention to provide a hydrodynamic bearing device and a rotating device that can be used.

  The hydrodynamic bearing device of the present invention includes a shaft and a sleeve that are relatively rotatably fitted, and a hydrodynamic bearing device that generates dynamic pressure by lubricating oil filled between the shaft and the sleeve. The shaft and the sleeve include a dynamic pressure generating part having a bearing gap for generating the dynamic pressure, and a relief part that forms a bearing gap larger than the dynamic pressure generating part. A porous film formed by chemical conversion treatment is formed on at least one of the shaft and the sleeve.

  By configuring the porous film to be immersed in the lubricating oil, the lubricating oil can be stably held in the bearing gap. As a result, it is possible to improve the driving stability by preventing the lubricating oil from leaking out of the sleeve and running out of the lubricating oil, and to be applied to high-speed rotation driving.

  Further, in order to prevent the porous film from coming into contact with the sleeve or the shaft at the time of high-speed rotation driving or at the start or stop of rotation, an escape portion is formed. Thereby, chipping of the porous film can be prevented, and it can be avoided that the porous material is mixed into the lubricating oil and has an adverse effect.

  As described above, according to the present invention, it is possible to provide a dynamic bearing device having a long life and high performance by preventing the deterioration of the lubricating oil due to the peeling of the porous material and stabilizing the driving.

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

  FIG. 1 shows an overall configuration of a scanner motor which is a rotating device. A mounting ring 2 is fixed to a rotating shaft (shaft) 1 of the motor. A rotor yoke 3 is fixed to the mounting ring 2, and a drive magnet 4 is fixed to the rotor yoke 3. A polygon mirror (rotating polygon mirror) 5 is attached to the upper reference surface of the attachment ring 2, and is pressed and fixed by a wave washer 6, a flat washer 7 and a stopper 8. The rotating shaft 1, the rotor yoke 3 and the polygon mirror 5 which are combined in this way become a rotating body of the scanner motor.

  On the other hand, a fixing sleeve (sleeve) 10, an iron substrate 11, and a stator core 12 for applying a rotational force to the drive magnet 4 are fixed to the housing 9 that is a fixing member. A circuit component 14 such as a driving IC is mounted on the iron substrate 11. A fixed magnet 13 is fixed to the lower end portion of the fixed sleeve 10, and a levitating magnet 15 is fixed to the lower end portion of the rotary shaft 1, and the rotary shaft 1 is rotatably held. On the outer periphery of the rotating shaft 1, dynamic pressure generating grooves 16 are formed at two locations, upper and lower, and a concave relief portion formed on the surface of the rotating shaft 1 is formed between the upper and lower dynamic pressure generating grooves 16. An escape groove (annular groove) 17 is disposed. This relief groove may be provided on the inner surface of the fixed sleeve 10 facing the rotation shaft, or the same effect can be obtained even if it is provided on both. Further, the bearing gap between the fixed sleeve 10 and the rotating shaft 1 is filled with lubricating oil, and smooth rotation can be performed.

  The fixed sleeve 10 is fitted in the central through hole of the housing 9, and the rotary shaft 1 is inserted into the inner diameter of the fixed sleeve 10 with a clearance of about 1 to 2 μm. In a state where the rotating shaft 1 is inserted into the fixed sleeve 10, the lower end portion of the through hole of the housing 9 is closed by the sealing member 18. Thereby, the stability of the dynamic pressure generation and the rotational stability during the high-speed rotation of the rotary shaft 1 are guaranteed. A winding coil 19 for generating a rotating magnetic field is attached around the salient poles of the stator core 12.

  On the inner surface (groove surface) of the relief groove 17 formed on the rotating shaft 1, a porous film 20 which is a polycrystalline oil retaining material having fine irregularities mainly composed of manganese phosphate microcrystals is formed. (See (b) of FIG. 1). Other than manganese phosphate microcrystals, any material having an oil retaining function may be used, but manganese phosphate is technically established as a chemical conversion treatment film that is harder than other types of chemical conversion treatment films and has excellent wear resistance. It is preferable to use this material. In addition, the fine unevenness | corrugation was confirmed also in the chemical conversion treatment using phosphates, such as zinc manganese phosphate and zinc phosphate other than manganese phosphate processing, and shows an oil retention effect.

  The escape grooves may be arranged on the sleeve side, and the same effect can be obtained regardless of whether the porous coating is formed in the inside of these escape grooves or on the other side facing the escape grooves. be able to.

  If the microcrystal aggregate is not in the escape groove portion but in the dynamic pressure generating portion or in the vicinity thereof, when the motor rotates at a high speed, it peels off due to the high dynamic pressure. Further, when the rotation starts from the rotation stop state in which the shaft and the bearing are in contact, or when the rotation is stopped, the microcrystal aggregate comes into contact and comes off. When the fine crystal aggregates are peeled off in this manner, the lubricating oil becomes finely greased including the fine crystals separated, and the rotational load increases. In order to prevent this, the microcrystalline oil retaining portion is formed in a concave relief portion to prevent the microcrystalline aggregate from peeling off. The depth and size of the concave relief portion can be arbitrarily set, but it is desirable to adjust the depth according to the size of the microcrystal. The shape of the relief portion may be arbitrarily formed between the shaft and the sleeve that are relatively rotatably fitted, but the ease of formation and masking for forming the microcrystalline aggregate only in the relief portion. From the viewpoint of ease of work such as, it is desirable to form the ring.

  According to the present embodiment, it is possible to prevent the lubricating oil from being discharged out of the fixed sleeve 10 and increase the driving stability. In addition, it is possible to increase the oil retention state of the lubricating oil and to apply it to high-speed rotation driving. Furthermore, as an additional function, the influence of the lubricating oil on the polygon mirror optical system can be reduced.

  Further, by mounting the scanner motor on the LBP, the operation reliability of the LBP can be improved.

  In the present embodiment, the results of studies on extending the life of a scanner motor by manganese phosphate film formation will be described, but the material and manufacturing method of the porous film are not limited to this.

  A porous film of the manganese phosphate microcrystal aggregate was formed in the concave portion (relief groove) of the rotating shaft made of stainless steel. The rotating shaft was made of stainless steel, and Phosnin 130R (trade name, manufactured by Riko Kyosan Co., Ltd.) was used as the manganese phosphate chemical conversion treatment material.

  In order to clean the surface of the rotary shaft, cleaning with acetone and alkali degreasing were performed in advance. Thereafter, chemical conversion treatment, water washing and drying were performed.

  The rotary shaft was subjected to chemical conversion treatment by masking the portion that generates dynamic pressure facing the fixed sleeve with a ring-shaped masking jig. Thereby, the phosphate microcrystal aggregate is not formed on the surface other than the concave portion of the rotating shaft, and the phosphate microcrystal aggregate can be prevented from peeling off due to the rotation of the motor.

  A porous film of phosphate microcrystal aggregates is formed in the recesses not masked, and fulfills an oil retaining function. FIG. 2 is an SEM image of the chemical conversion film on the rotating shaft made of stainless steel. Observation by SEM reveals that fine irregularities are formed by manganese phosphate microcrystals of 50 to 100 μm scale. Lubricating oil is captured in the uneven portions and exhibits an oil retaining effect.

  The chemical conversion treatment was carried out by diluting phosnin 130R with pure water so as to have a concentration of 10 vol%, performing chemical conversion for 10 minutes under the condition of a processing temperature of 90 ° C., thoroughly washing with water after chemical conversion, and then drying.

(Comparative Example 1)
As Comparative Example 1, a rotating shaft that does not form a manganese phosphate chemical conversion film having the same configuration as that of Example 1 was incorporated into the scanner motor unit shown in FIG.

(Comparative Example 2)
As Comparative Example 2, a concave portion was not provided on the surface of the rotating shaft facing the fixed sleeve, and a manganese phosphate chemical conversion film was formed on the entire surface of the rotating shaft including the dynamic pressure generating portion. Using this rotating shaft, an endurance test was conducted in the same manner as in Comparative Example 1.

  Table 1 shows the durability test results of Example 1 and Comparative Examples 1 and 2.

  As a condition for the durability test, the change with time of the starting current value was examined under the condition that the rotation speed of the scanner motor was 40,000 rpm and the environmental temperature was 80 ° C.

実施例１および比較例１、２においては初期状態において駆動電流値が同じであり、初期特性に違いは見られない。しかしながら、耐久性に違いが見られる。リン酸マンガン化成処理を行った実施例１においては７，０００ｈでも起動電流が安定しているが、化成処理を行っていない比較例１では、５，０００ｈ付近で一度電流値が下がり、その後、駆動電流が上昇し、モータの回転が止まってしまった。また、凹部を設けず、動圧発生部を含む全面にリン酸マンガン処理を行った比較例２は、６，０００ｈを超えると電流の上昇が起り、実施例１ほどの駆動安定はなかった。

In Example 1 and Comparative Examples 1 and 2, the drive current values are the same in the initial state, and there is no difference in the initial characteristics. However, there are differences in durability. In Example 1 where the manganese phosphate chemical conversion treatment was performed, the starting current was stable even at 7,000 h, but in Comparative Example 1 where the chemical conversion treatment was not performed, the current value decreased once around 5,000 h, and then The drive current increased and the motor stopped rotating. Further, in Comparative Example 2 in which the entire surface including the dynamic pressure generating part was subjected to the manganese phosphate treatment without providing the concave part, the current increased when exceeding 6,000 h, and the driving stability was not as high as that of Example 1.

  When the scanner unit was disassembled and confirmed for the cause of the rotation stopping, in Comparative Example 1, the lubricant was almost gone. In Comparative Example 2, peeling of the phosphate microcrystal aggregate was observed, and contamination of the lubricating oil was observed. On the other hand, with respect to Example 1, changes in the amount of lubricating oil and viscosity do not appear significantly, and the drive current value is also stable. From this, it was found that the manganese phosphate chemical conversion treatment was performed on the recesses other than the dynamic pressure generating part, which contributed to the extension of the motor life and the stabilization of the quality.

  In this embodiment, the escape portion for forming the porous film that holds the lubricating oil is provided on the rotating shaft side, but it goes without saying that the same effect can be obtained even if this escape portion is provided on the fixed sleeve side. .

  In addition to the scanner motor mounted on the LBP or the like, the present invention can be widely applied to various rotating devices having rotating members.

1 shows a hydrodynamic bearing device according to an embodiment, in which (a) is a schematic sectional view thereof, and (b) is a partial sectional elevational view showing only a rotating shaft. It is a SEM observation image of manganese phosphate microcrystal. It is a schematic cross section which shows one prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Mounting ring 3 Rotor yoke 4 Drive magnet 5 Polygon mirror 6 Wave washer 7 Flat washer 8 Fastener 9 Housing 10 Fixed sleeve 11 Iron substrate 12 Stator core 13 Fixed magnet 14 Circuit component 15 Floating magnet 16 Dynamic pressure generating groove 17 Escape Groove 18 Sealing member 19 Winding coil 20 Porous film

Claims (5)

  In the hydrodynamic bearing device, which has a shaft and a sleeve that are relatively rotatably fitted, and generates a dynamic pressure by a lubricating oil filled between the shaft and the sleeve, the shaft and the sleeve have the dynamic A dynamic pressure generating part having a bearing gap for generating pressure, and a relief part that forms a bearing gap larger than the dynamic pressure generating part, and at least one of the shaft and the sleeve in the relief part A hydrodynamic bearing device characterized by forming a porous film by chemical conversion treatment.   2. The hydrodynamic bearing according to claim 1, wherein the escape portion has an annular groove formed in at least one of the shaft and the sleeve, and the porous coating is formed on a groove surface of the annular groove. apparatus.   3. The hydrodynamic bearing device according to claim 1, wherein the porous film has a phosphate microcrystal aggregate.   4. The hydrodynamic bearing device according to claim 3, wherein the phosphate microcrystal aggregate is manganese phosphate.   5. A rotating device, wherein the rotary polygon mirror is rotatably supported by the hydrodynamic bearing device according to claim 1.

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