JP2002106549A - Dynamic pressure bearing device, rotation device and deflection scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an oil of a dynamic pressure bearing device from leakage. SOLUTION: The dynamic pressure bearing device has a bearing of polyhedral mirrors comprised of a sleeve 2 integrally with a circuit substrate 14 setting a stator 12 and shaft 1 fitted therein. When an opening width W of an opening 2a of the sleeve 2 is small, the oil 6 leaks out due to enclosure of air in a spacing of the bearing and when the opening width W is large, the oil 6 is feared to leak out on tilting the device. Then the oil is prevented from leakage by setting the opening width W not less than 0.15 mm, not greater than 0.20 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device, a rotating device, and a deflection scanning device used for a laser printer, an optical disk device, a magnetic disk device, and the like.

[0002]

2. Description of the Related Art In an image forming apparatus of a laser printer or a digital copying machine, a scanner optical system for scanning a laser beam is mounted on a bearing supporting a rotating polygon mirror rotating at a high speed so that a stable and smooth rotation can be obtained. Use pressure bearings. Also, in information storage devices such as optical disks and magnetic disks, dynamic pressure bearings have been widely used as bearings for supporting disks rotating at high speed.

FIG. 7 shows a conventional dynamic pressure bearing device of a deflection scanning device, which comprises a sleeve 102 rotatably supporting a shaft 101 in a bearing hole, and a sleeve 10.
Disk 103 fixed to the lower end of the second and closing the bearing hole
The thrust plate 104 is supported by the oil filled between the inner surface of the bearing hole of the sleeve 102 and the outer surface of the shaft 101 and between the thrust plate 104 and the end surface of the shaft 101.

The upper end, lower end, and center of the bearing hole of the sleeve 102 have recesses 102a to 102a, respectively.
2c, which are large-diameter portions disposed as so-called oil reservoirs, between the upper end recess portion 102a and the center recess portion 102c, and the center recess portion 102c.
Herringbone-shaped dynamic pressure generating grooves 105a and 105b are formed between the recessed portion 102b and the lower end portion 102b. Further, a spiral groove is formed on the upper surface of the thrust plate 104. The upper end of the shaft 101 is a sleeve 102
Projecting above the bearing hole of
10 is fixed.

[0005] In the thus configured dynamic pressure bearing device, when the shaft 101 rotates, a dynamic pressure is generated in the oil by the action of the dynamic pressure generating grooves 105a and 105b provided in the bearing hole of the sleeve 102, and the shaft 101 It rotates without contact with the bearing hole of the sleeve 102. Also in the thrust direction, a 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.

A rotating polygon mirror 111 having a reflecting surface 111a is integrally connected to a flange member 110 at the upper end of the shaft 101. To rotate the rotating polygon mirror 111, a permanent magnet 112a is used.
The rotor 112 is also fixed and is disposed so as to face the stator 113 including the stator coil 113a and the core 113b.

The volume of the recess 102a at the upper end is set to be larger than the amount of lubricating oil in order to prevent leakage of the oil filled in the sleeve 102.

[0008]

However, according to the above-mentioned prior art, when the shaft rotates at a high speed, the oil sump, which is the recess at the upper end, becomes negative pressure, and air flows into the oil sump. On the other hand, the oil level in the sleeve rises due to the centrifugal force caused by the high-speed rotation of the shaft, and the rising oil accumulates in the oil sump near the sleeve opening. The volume of the oil sump at the upper end is larger than the volume of the oil filled in the sleeve, and has a structure in which oil that leaks is prevented by storing all the rising oil. However, when the shaft rotates at a higher speed, the oil liquid level is transmitted along the inner surface of the sleeve by centrifugal force and further rises and adheres to the gap between the sleeve opening and the shaft. If this gap is too narrow, the adhering oil wraps around the entire circumference of the sleeve opening, and wraps the air in the oil reservoir and seals it.

In this state, when the shaft is stopped next time, the air in the oil reservoir tries to flow out of the sleeve in a direction opposite to the rotation, so that the oil leaks.

On the other hand, when the motor is used at an angle, if the gap between the shaft and the sleeve opening is too large, oil leaks through this gap.

If such a leakage phenomenon occurs for a long time, the amount of oil in the bearing device decreases, and the accuracy of the bearing device deteriorates and the durability decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and has a high performance capable of easily and extremely effectively preventing leakage of a working fluid such as oil from an opening of a sleeve. It is an object of the present invention to provide a dynamic bearing device, a rotating device, and a deflection scanning device.

[0013]

In order to achieve the above object, a hydrodynamic bearing device according to the present invention is injected into a bearing gap between a shaft and a sleeve which are relatively rotatably fitted. A working fluid for generating a dynamic pressure, wherein an opening width of the bearing gap at an opening of the sleeve is 0.15 to 0.5.
It is characterized by being within a range of 20 mm.

It is preferable that a recess having a volume larger than the working fluid injection amount is provided in the opening of the sleeve.

A dynamic pressure generating groove may be provided on at least one of the shaft and the sleeve.

[0016] A rotating device according to the present invention includes the above-described hydrodynamic bearing device, and a brushless motor including a rotor integrated with a shaft or a sleeve of the hydrodynamic bearing device.

A deflection scanning device according to the present invention includes the above-described dynamic pressure bearing device, and a rotary polygon mirror that is rotatably supported by the dynamic pressure bearing device.

[0018]

If the width of the gap between the sleeve and the shaft at the opening of the sleeve, that is, the opening width of the bearing gap is too wide or too narrow, the working fluid leaks. Therefore, as a result of various experiments, it was found that setting the opening width in the range of 0.15 to 0.20 mm can avoid leakage of the working fluid.

That is, by setting the opening width at the opening of the sleeve to 0.15 mm or more, the bearing gap is closed due to the working fluid adhering to the opening of the sleeve, and troubles in which air is trapped are prevented. 0.20m
By setting m or less, it is possible to realize a hydrodynamic bearing device, a rotating device, and a deflecting scanning device that do not have a risk of leakage of a working fluid even when the device is tilted.

[0020]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a rotary device using a hydrodynamic bearing device according to an embodiment. This rotary device includes a reflecting surface 1 for deflecting and scanning a light beam in a deflection scanning device described later.
This is a brushless motor for rotationally driving the rotary polygon mirror 11 having the lens 1a.

As shown in FIG. 1A, the shaft 1 is integrated with a rotor 12 composed of a permanent magnet 12a and a yoke 12b and a rotary polygon mirror 11, and the sleeve 2 is composed of a stator coil 13a and a stator core 13b. 1
3 is integrated.

The stator core 13b has a multi-pole pole shoe, and a stator coil 13a is wound around each pole shoe. The energization is sequentially switched according to the rotational position of the multi-magnetized permanent magnet 12a, and a rotational force is generated between the rotor 12 and the stator 13.

The stator core 13b around which the stator coil 13a is wound is fixed to a circuit board 14 together with circuit components constituting a drive circuit.
It is fixed to. Such a rotor section and a stator section are separately produced, and a total set as a motor is performed. At this time, a predetermined amount of a working fluid for generating a dynamic pressure, ie, an oil 6, is injected into the sleeve 2 by an oil injection device (see FIG. 1 (b)). The shaft 1 that fits into the shaft is inserted to complete the motor.

As described above, the dynamic pressure bearing device for rotatably supporting the motor has a sleeve 2 rotatably supporting the shaft 1 in the bearing hole, and is fixed to a lower end of the sleeve 2 to close the bearing hole. The bearing gap between the disk 3 and the thrust plate 4 supported by the disk 3 and the inner surface of the bearing hole of the sleeve 2 and the outer surface of the shaft 1 and the oil filled between the thrust plate 4 and the end surface of the shaft 1 6.

The upper end, the lower end, and the center of the bearing hole of the sleeve 2 are each formed with an oil reservoir 5a formed of a recess.
5c between the upper oil reservoir 5a and the central oil reservoir 5c, and between the central oil reservoir 5c and the lower oil reservoir 5b, each having a herringbone-shaped dynamic pressure generating groove. Pressure generating portions 7a and 7b are formed. A spiral groove is formed on the upper surface of the thrust plate 4. The upper end of the shaft 1 protrudes above the bearing hole of the sleeve 2, and the rotary polygon mirror 11 is fixed to the upper part.

The groove depth of the herringbone-shaped dynamic pressure generating groove is about several microns. The amount of oil injected into the bearing gap between the shaft 1 and the sleeve 2 is an amount that satisfies the height from the lower end of the shaft 1 to the upper end of the upper dynamic pressure generating portion 7a, and the volume of the oil reservoir 5a at the upper end is It is set larger than the injection amount of the oil 6.

Next, the operation of the hydrodynamic bearing device will be described. When the motor is stopped, shaft 1 and sleeve 2
However, when the shaft 1 starts rotating, dynamic pressure is generated by the herringbone-shaped dynamic pressure generating grooves provided in the dynamic pressure generating portions 7a and 7b, and the shaft 1 comes into contact with the sleeve 2. Become a state of support without.

However, if the rotary drive is performed for a long time, leakage of the oil 6 becomes a problem. More specifically, when the shaft 1 starts rotating at a high speed from the stop state shown in FIG. 5A, the oil reservoir 5a is in a negative pressure state, and as shown in FIG. appear. The oil 6 injected into the sleeve 2 rises in the bearing gap due to centrifugal force caused by high-speed rotation. The raised oil is retained in the oil reservoir 5a, but when the shaft 1 rotates at a higher speed, the oil is pushed out to the opening 2a of the sleeve 2 and is shown in FIGS. 5 (c) and 5 (d). Thus, the shaft 1 and the sleeve 2 are attached to each other.

At this time, if the width of the gap between the opening 2a of the sleeve 2 and the shaft 1, that is, the opening width W is small, the oil adhering to the opening 2a of the sleeve 2 goes around the entire circumference, and ( As shown in e), the oil reservoir 5a encloses air and is sealed. When the shaft 1 is stopped in this state, the air in the oil reservoir 5a pushes the oil out of the sleeve 2 due to the pressure difference so as to come out of the sleeve 2 in a direction opposite to the rotation, and an oil leak occurs (see FIG. 5 (f), (g)).

As described above, the leakage of the oil caused by sealing the sleeve opening by the oil occurs when the opening width between the shaft and the sleeve is small.

As shown in FIG. 6, when the motor is used at an angle, the following problem occurs. Even if the shaft 1 and the sleeve 2 are inclined, as shown in FIG. 6A, the level of the oil 6 is kept horizontal when the motor is stopped. At this time, if the opening width W between the shaft 1 and the sleeve 2 is large, the flow path resistance of the oil passing through this gap is low, so that when stopping after the rotation state shown in FIG. As shown in (c), the oil comes out of the sleeve 2 and oil leakage easily occurs.

In any of the above cases, if the motor is repeatedly started and stopped for a long period of time, oil leakage will progress, and eventually the amount of oil will decrease to maintain the accuracy of the hydrodynamic bearing device. Becomes impossible. Oil leaks thus contribute to reduced durability.

Therefore, as shown in FIG. 1C, in the opening 2a of the sleeve 2 disposed on the oil reservoir 5a having a volume larger than the volume of the oil 6 filled in the bearing gap, The opening width W between the shaft 1 is 0.15 mm
As described above, the oil is prevented from leaking by being set within the range of 0.20 mm or less.

That is, by setting the opening width W between the opening 2a of the sleeve 2 and the shaft 1 to 0.15 mm or more, oil is prevented from adhering to the entire periphery of the opening 2a of the sleeve 2. Even when used in an inclined state, the opening width W is set to 0.20 mm or more in order to have a sufficient flow resistance between the shaft 1 and the opening 2a of the sleeve 2, so that oil leakage can be prevented. It is to prevent.

More specifically, as shown in FIG. 2, when the shaft 1 starts rotating at a high speed from the stop state shown in FIG. 2A, the oil reservoir 5a is in a negative pressure state as shown in FIG. Inflow of air occurs. In addition, FIG.
As shown in FIG.
Is transmitted through the inner surface of the sleeve 2 by the centrifugal force generated by the high-speed rotation, rises, is pushed out to the opening 2 a of the sleeve 2, and adheres to the shaft 1. Is 0.15 mm or more, and there is a sufficient amount of oil allowance in this gap, so that the oil does not flow around the entire circumference (FIG. 2 (d),
(E)). When the shaft 1 stops in this state, as shown in FIGS. 2 (f) and 2 (g), the air in the oil reservoir 5a tries to come out of the sleeve 2 due to the pressure difference, but the gap is closed. As the air passage is secured, only air flows out.

Also, when used in an inclined state as shown in FIG. 3, if the opening width W between the shaft 1 and the opening 2a of the sleeve 2 is 0.20 mm or less, a sufficient flow path can be obtained. Since the resistance is generated, the oil is held in the opening 2a of the sleeve 2 and does not leak out even when the rotation is stopped as shown in FIGS. 3 (b) and 3 (c).

According to the present embodiment, even if the motor is repeatedly started and stopped for a long time, there is no decrease in bearing accuracy or durability due to oil leakage. Greatly improve reliability,
This can greatly contribute to improving the performance and durability of a rotating device and a deflection scanning device using this.

FIG. 4 shows a main part of the deflection scanning device, which comprises a light source 51 for generating a light beam (light flux) such as a laser beam and the like, and a light reflecting surface 1 of a rotary polygon mirror 11.
A cylindrical lens 51a for linearly condensing the light beam on the rotary drum 11a, and deflects and scans the light beam by the rotation of the rotary polygon mirror 11; An image is formed on 53. The imaging lens system 52 includes a spherical lens 52a, a toric lens 52b, and the like, and has a so-called fθ function of correcting a scanning speed and the like of a point image formed on the photoconductor 53.

When the rotary polygon mirror 11 is rotated by the motor, its reflecting surface 11a rotates at a constant speed around the axis of the rotary polygon mirror 11. As described above, the angle between the optical path of the light beam generated from the light source 51 and collected by the cylindrical lens 51a and the normal to the reflecting surface 11a of the rotary polygon mirror 11, that is, the incident angle of the light beam on the reflecting surface 11a Changes over time with the rotation of the rotating polygon mirror 11, and similarly, the reflection angle also changes. Therefore, the point image formed by condensing the light beam on the photoreceptor 53 is in the axial direction (main scanning direction) of the rotating drum. (Scan).

The imaging lens system 52 focuses the light beam reflected by the rotary polygon mirror 11 on the photosensitive member 53 into a point image having a predetermined spot shape, and scans the point image in the main scanning direction. Is designed to keep the speed constant.

The point image formed on the photoreceptor 53 is electrostatically generated by the main scanning by the rotation of the rotating polygon mirror 11 and the sub-scanning by the rotation of the rotating drum having the photoreceptor 53 around its axis. Form a latent image.

Around the photosensitive member 53, a charging device for uniformly charging the surface of the photosensitive member 53, and a charging device for visualizing an electrostatic latent image formed on the surface of the photosensitive member 53 into a toner image. A developing device, a transfer device (not shown) for transferring the toner image to recording paper, and the like are arranged, and recording information by a light beam generated from the light source 51 is printed on recording paper or the like.

The detection mirror 54 reflects the light beam on the upstream side in the main scanning direction from the optical path of the light beam incident on the write start position of the recording information on the surface of the photoreceptor 53, and receives a light receiving element 55 having a photodiode or the like. To the light receiving surface of The light receiving element 55 outputs a scanning start signal for detecting a scanning start position (write start position) when the light receiving surface is irradiated with the light beam.

The light source 51 generates a light beam corresponding to a signal given from a processing circuit for processing information from the host computer. The signal given to the light source 51 corresponds to information to be written on the photoconductor 53, and the processing circuit represents information corresponding to one scanning line which is a locus formed by a point image formed on the surface of the photoconductor 53. The signal is given to the light source 51 as one unit. This information signal is transmitted in synchronization with a scanning start signal given from the light receiving element 55.

The rotating polygon mirror 11 and the imaging lens system 52
Are housed in the optical box 50, and the light source 51 and the like are attached to the side wall of the optical box 50. A rotating polygon mirror 11 in an optical box 50,
After the imaging lens system 52 and the like are assembled, a lid (not shown) is attached to the upper opening of the optical box 50.

[0047]

Since the present invention is configured as described above, the following effects can be obtained.

Leakage of working fluid such as oil from the opening of the sleeve of the dynamic pressure bearing device can be easily and extremely effectively avoided. By using such a dynamic pressure bearing device, it is possible to realize a high-performance rotating device and a deflection scanning device that do not have a risk of malfunction due to leakage of oil or the like.

[Brief description of the drawings]

FIGS. 1A and 1B show a rotating device having a hydrodynamic bearing device according to an embodiment, wherein FIG. 1A is a schematic sectional view thereof, FIG. 1B is a sectional view showing only the shaft and sleeve of FIG. () Is an enlarged view of a portion surrounded by a circle A in (b).

FIG. 2 is a view for explaining that oil does not leak if the opening width of the sleeve in FIG. 1 is 0.15 mm or more.

FIG. 3 is a view for explaining that oil does not leak if the opening width of the sleeve in FIG. 1 is 0.20 mm or less.

FIG. 4 is a diagram illustrating the entire deflection scanning device.

FIG. 5 is a diagram illustrating oil leakage that occurs because the opening width of the dynamic pressure bearing device is too narrow.

FIG. 6 is a diagram illustrating oil leakage that occurs because the opening width of the hydrodynamic bearing device is too large.

FIG. 7 is a schematic sectional view showing a hydrodynamic bearing device according to a conventional example.

[Explanation of symbols]

 1 shaft 2 sleeve 2a opening 3 disk 4 thrust plate 5a-5c oil sump 6 oil 7a, 7b dynamic pressure generating part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // F16C 17/08 F16C 17/08 F term (reference) 2H045 AA25 AA27 AA43 3J011 AA07 AA12 BA04 CA02 JA02 KA02 KA03 5H605 BB05 BB19 CC04 CC05 DD03 EB03 EB06 EB21 EB28 GG21 5H607 AA05 BB09 BB17 CC01 DD03 DD16 GG12 GG15 GG25

Claims (6)

[Claims] A shaft and a sleeve fitted relatively rotatably, and a working fluid for generating dynamic pressure injected into a bearing gap between the shaft and the sleeve, wherein the bearing gap at an opening of the sleeve is provided. Wherein the width of the opening is in the range of 0.15 to 0.20 mm. 2. The hydrodynamic bearing device according to claim 1, wherein a recess having a volume larger than a working fluid injection amount is provided in an opening of the sleeve. 3. At least one of the shaft and the sleeve,
2. A dynamic pressure generating groove is provided.
Or the dynamic pressure bearing device according to 2. 4. A rotating device comprising a dynamic pressure bearing device according to claim 1, and a brushless motor provided with a rotor integral with a shaft or a sleeve of the dynamic pressure bearing device. 5. A deflection scanning device comprising: the dynamic pressure bearing device according to claim 1; and a rotary polygon mirror rotatably supported by the dynamic pressure bearing device. 6. A deflection scanning device comprising: the rotation device according to claim 4; and a rotary polygon mirror driven to rotate by the rotation device.