JPH01154115A - Rotating body supporting device - Google Patents

Abstract

PURPOSE:To guarantee the inclination accuracy and stability of a rotating body during high speed rotation and to thin the device by permitting a dynamic pressure gas bearing part provided on the flat plane of the rotating body and opposing a base table to support the rotating body in the axial direction and to maintain the inclination supporting accuracy and stability. CONSTITUTION:A spiral groove 63 is provided on the flat plane 61a of the base table 61, and a rotating member 51 is placed outside of the fixed shaft 60 in the center of the base table 61, and the dynamic pressure gas bearing is composed of one herringbone groove 62 on the peripheral plane of the fixed axis. When the rotating assembly body 56 is rotated at high speed, air flows into the space between a flat plane 51b of the rotating member 51 and a flat plane 61a of the base table 61 by the herringbone groove 63, and into the space between the rotating member 51 and the fixed shaft 60 by the herringbone groove 62, and air pressure is generated. Therefore, the rotating assembly body is supported without contacting with the base table 61 and the fixed shaft 60 and accurately revolves with extremely small frictional resistance. Thus, the stability and the inclination accuracy of the rotating body the maintained and the rotating body supporting device is greatly thinned and miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotating body support device that is applied to, for example, a rotating polyhedral mirror light deflector and stably supports a rotating body that rotates with high accuracy and high speed.

Conventional technology In recent years, with the development of office equipment, there has been a demand for printer-related equipment that records and prints information to be faster, smaller, and lower in cost. Printers with high print quality and high speed are now appearing.

Generally, as shown in FIG. 4, this laser beam printer scans a photoreceptor 1, which has been uniformly charged in advance, with a laser beam from an optical scanning section 2 to form an electrostatic latent image on the photoreceptor l. The optical scanning unit 2 shapes the laser beam 3 emitted from the semiconductor laser beam tA4 into an appropriate beam shape through the beam shaping optical system 5, and then converts the laser beam 3 into a rotating polygon mirror. The light is deflected through a light deflector 6 and scanned onto the photoreceptor 1 through an imaging optical system 7.

In addition, the deflection speed of the rotating polyhedral optical deflector 6, that is, the high speed and high precision of the optical deflector, mainly determines the high speed and high quality of the laser beam printer. configured.

Conventionally, a rotating polyhedral light deflector is disclosed in Japanese Patent Application Laid-open No. 59-2, for example.
There is a configuration to which a rotating body support device as shown in Publication No. 3319 is applied. Its configuration is shown in FIG.

In FIG. 5, a rotating polygonal light deflector 10 is composed of a rotating polygonal mirror II and a rotation drive unit 12 that rotates the rotating polygonal mirror 1) in a predetermined direction at high speed.

A fixed shaft 13 is defined on the motor housing I4, and a hollow cylindrical rotary member 15 is rotatably fitted around the outer circumference of the fixed shaft 13 with a slight gap therebetween.

Further, the upper and lower ends 28 and 29 of the outer circumferential surface of the fixed shaft 13 are
Dog-shaped herringbone grooves 26 and 27 are formed in the inner peripheral surface of the rotating member 15 to generate dynamic pressure in the radial direction due to the relative speed with the inner circumferential surface of the rotating member 15.

On the other hand, an inner magnetic ring 17 of a magnetic bearing 16 for thrust support is attached to the lower end of the rotating member 15, and a rotor magnet 1B is fixed to the rotating member 15 near the center in the vertical direction.

Also, above the rotor magnet 18 is a rotating polyhedral mirror 1).
While the lower end surface is in contact with the rotating member 15, the upper end surface is pressed and fixed by the mirror holding member 20. On the other hand, the motor housing 14 has a stator 2 provided with a drive coil 21 surrounding the outer periphery of the rotor magnet 18.
2 is fixed and rotating polyhedral mirror 1). Rotor magnet 18
The rotating assembly 23 consisting of the magnetic ring 17 and the inner magnetic ring 17 is rotatably driven by a well-known direct current brushless drive system.

Further, an outer magnetic ring 24 is similarly fixed below the motor housing 14 so as to surround the inner magnetic ring 17 with a certain gap, and the inner magnetic ring 17 and the outer magnetic ring 24 have an attractive force with each other. It constitutes a thrust support magnetic bearing 16 that is magnetized to work and supports the rotary assembly 23 in the vertical direction (direction of its own weight). moreover,
A sealing cover 25 is attached to the upper part of the motor housing 14, and clean air is sealed therein.

With the above configuration, when the drive coil 21 is energized, a rotating magnetic field is generated in the stator 22, and the rotating assembly 23 is rotated by the magnetic attraction force with the rotor magnet 18.

As a result, a relative speed is generated between the rotating member 15 and the fixed shaft 13, and air flows into the gap between the herringbone grooves 26 and 27 at the upper and lower ends of the fixed shaft 13, generating air pressure in the radial direction, forming a so-called dynamic pressure gas bearing. The rotating assembly 23 rotates at high speed with extremely low frictional resistance and stability in a non-contact state.

Therefore, the rotating polygon mirror 1) is also rotated at high speed, and accordingly, the laser beam is deflected at high speed within the optical scanning section. At this time, the accuracy of the trajectory of the deflected laser beam is determined by the inclination and deformation of each mirror surface of the rotating polygon mirror 1) during rotation. Considerably high specifications are required for the stability and rotation accuracy of the deflector itself during high-speed rotation.

Problems to be Solved by the Invention However, in the above configuration, the rotating member 1
5 is supported in the radial direction by two dynamic pressure gas bearings 28 and 29 provided at the upper and lower ends of the fixed shaft 13,
In addition, since the thrust magnetic bearing 16 holds the load only in the thrust direction, the fixed shaft 1 can support the tilt due to the gyro moment etc. that occurs when the rotating member 15 rotates at high speed.
3 by means of a gas bearing.

Therefore, the load capacity, stability, and accuracy of rotating members during high-speed rotation, such as runout and tilt accuracy, are determined by the bearing spacing between the gas bearings 28 and 29 at the upper and lower ends of the fixed shaft 13 and the bearing specifications, such as the herringbone groove 26. and a depth of 27,
It is determined by the gas spring constant of the bearing, which is determined by the number of grooves or the gap between the rotating member 15 and the fixed shaft 13.

In particular, the bearing spacing of the gas bearing section on the fixed shaft has a great influence on the stability and accuracy, and a sufficiently long bearing spacing is required.

However, in order to make this rotating polyhedral optical deflector stable under high-speed rotation and to make it thinner, it is necessary to shorten the bearing spacing in the above configuration, which results in the stability of the rotating polyhedral mirror. However, there have been problems in that the accuracy and inclination accuracy are reduced, and the printing quality as a laser beam printer is also deteriorated.

In particular, the need for the above-mentioned reduction in size and thickness becomes apparent when the rotating polyhedral optical deflector 6 is incorporated into the optical scanning section unit 2. That is, in the optical scanning section 2, an optical unit excluding the optical deflector 6, for example, a beam shaping optical system 5 mainly composed of a lens group. While the imaging optical system 7 can be made thin to a thickness close to the spot diameter formed by the laser beam 3, the optical deflector 6 requires the above-mentioned configuration including the rotating polygonal mirror 1), and is capable of optical scanning. When assembled into a unit 2, only the optical deflector 2 protrudes from the unit 2, as shown in FIG.

For this reason, when this optical scanning section 2 is incorporated into the main body of a laser beam printer, there is a problem that the space occupied by the optical scanning section 2 in the entire main body becomes large and the main body itself becomes large.

On the other hand, in order to significantly reduce the thickness and size of the rotating body support device, the content of Japanese Patent Application No. 1983-5301 has already been filed, but in this configuration, external disturbances, especially vibrations, Depending on the degree of impact or gyro moment, etc., the load capacity of this configuration has a limit in holding the rotating member, and in the worst case, it may come into contact with the opposing base or regulating member (fixed shaft) and cause seizure. had sex.

Means for Solving the Problems In order to solve the above-mentioned problems, the rotating body support device of the present invention includes a rotating body and the rotating body, and a flat portion is formed on the end face facing the rotating shaft, and a flat portion is formed in the rotating shaft direction. a rotating member having a hollow cylindrical shape; a base having a gas bearing disposed opposite to a flat surface of the rotating member and generating dynamic pressure through relative motion with the rotating member; A rotating member having a circumferential surface and a fixed shaft having a constant gap in the radial direction and provided with a gas bearing portion that generates dynamic pressure in the radial direction by relative movement with the rotating body, and having the rotating body. The center of gravity is located approximately at the center of the gas bearing portion on the fixed shaft.

Function: With the above-described configuration, the present invention provides tilt accuracy and stability that occur when the rotating body rotates at high speed, instead of having the two hydrodynamic pressure gas bearings on the circumferential surface of the fixed shaft bear the burden mainly on the flat surface of the rotating body. The hydrodynamic gas bearing installed on the base facing the rotating body supports the rotating body in the axial direction and maintains the accuracy and stability of its inclination. The unbalanced force caused by the unbalance is borne by the hydrodynamic gas bearing installed on the fixed shaft, and the center of gravity of the rotating member having the rotating body is set approximately at the center of the hydrodynamic gas bearing. It acts on the center of gravity (to reduce the moment due to the inertial force of the rotating member, and reduces the load on the hydrodynamic gas bearing provided on the base table).

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 1 shows a cross-sectional view of a rotating polyhedral mirror light deflection device using the rotational drive device of the present invention, and FIG. 2 is an exploded perspective view of the rotating polyhedral mirror light deflection device using the rotational drive device of the present invention. FIG. 3 shows the dynamic pressure distribution in the radial direction of the rotating body.

In FIG. 1, reference numeral 51 is a rotating member having a flange-like shape and having a center of rotation in the vertical direction. ing.

Reference numeral 53 denotes a ring-shaped rotor magnet, which is magnetized with multiple poles in the direction of the rotational axis while being bonded to a back yoke 54 made of a soft magnetic material. It is fixed by adhesive or other means. Further, the diameters of the flange portion of the rotating member 51 and the back yoke 54 are made larger than the outer diameter of the rotating polygon mirror 52.

That is, the rotating polygon mirror 52 is sandwiched between the flange portion of the rotating member 51 having a larger diameter and the back yoke 54. Reference numeral 55 denotes a sub-rotor made of a soft magnetic material, configured to allow magnetic flux to flow from the rotor magnets 53 and the rotor magnets arranged with a certain gap in the axial direction, and fixed to the rotating member 52 by adhesive or other means. has been done.

That is, the rotating member 519 rotates the rotating body mirror 52 . Roke magnet 53, back yoke 54. The sub-rotors 55 are fixed to each other and constitute a rotating assembly 56.

A smooth plane part 51b is formed on the lower end surface of the flange part of the rotating member 51, and facing the plane part 51b,
A base 61 having a smooth flat surface 61a is arranged, and the base 61 is fixed to a casing (not shown). Further, a spiral groove 63 is formed on the flat surface 61a of the base 61 so that its centripetal direction coincides with the rotational direction of the rotating assembly 56, and a spiral groove 63 is formed in the flat surface 61a of the rotating member 51 to face the flat surface 1b of the rotating member 51. It constitutes a gas bearing. Also, the flat part 51
Parts not involved in the dynamic pressure gas bearing shown in b are coated with Nusumi 51C. Moreover, 61b is a pressure regulating hole that communicates with the outside from this Nusumi 51C.

A fixed shaft 60 that restricts movement of the rotation assembly 56 in the radial direction is disposed at the center of the base 61, and is fixed to the base 61 by press fitting or the like. Further, the rotating member 51 of the rotating assembly 56 is rotatably fitted onto the fixed shaft 60 with a certain gap between it and the outer circumference of the fixed shaft.
A herringbone groove 62 is formed at one location on the circumferential surface of the fixed shaft so that an arrow-shaped tip thereof faces in the rotational direction of the rotating assembly 56, thereby forming a hydrodynamic gas bearing. In addition, the portions of the fixed shaft that are not involved in the dynamic pressure gas bearing are provided with a pad 60a.

Furthermore, grooves 57 and 58 are formed on the outer circumference of the lower flat part 51b of the rotating member 51 and on the outer circumference of the upper part of the sub-rotor 55 for attaching weights for adjusting the dynamic balance. The dynamic balance can be adjusted with high precision under the same conditions. Further, the center of gravity of the rotating assembly 56 is located on the fixed shaft 60, and moreover, the center of gravity of the rotating assembly 56 is located at a substantially central portion 70 of the one herringbone groove 62.
It is set up nearby. In other words, in this embodiment, in the vicinity of the maximum dynamic pressure generating area on the fixed shaft 60 as shown in FIG. Anywhere is fine.

Further, in FIG. 2, reference numeral 65 denotes fixed coil substrates 65a and 65b which are fixed to the motor frame 64 with screws 71 and can be divided into two pieces, and a plurality of flat coils 65 are attached to the motor frame 64.
6, a rotor magnet position detection sensor 67, and two printed circuit boards 68a.

68b. In this embodiment, the flexible printed circuit board is the printed circuit board 68a.

Used for 68b. A plurality of flat coils 66 and a rotor magnet position detection sensor 67 are wired on printed circuit boards 68a and 68b, and are further molded with resin 70. Therefore, the fixed coil substrate 65 can be divided into two parts and placed in the gap between the rotor magnet 53 and the sub-rotor 55 after adjusting the dynamic balance of the rotating assembly 56.

In the rotating polyhedral mirror light deflecting device configured as described above, by energizing the fixed coil board 65, rotational torque is generated in the magnetic flux in the air gap between the rotor magnet 53 and the sub-rotor 55, and the rotating assembly 56 rotates at high speed. However, a spiral groove 63 is formed in the gap between the opposing plane part 51b of the rotating member 51 and the plane part 61a of the base 61, and a herringbone groove 6 is formed in the gap between the rotating member 51 and the fixed shaft 60.
2, air flows in and air pressure is generated, and the rotating assembly 56 is supported without contact with the base 6] and the fixed shaft 60, and can rotate with high precision with extremely small frictional resistance. .

As described above, according to this embodiment, since the center of gravity of the rotating assembly 56 is set approximately at the center 70 of the herringbone groove 62 on the fixed shaft 60, the gas bearing in the structure of this embodiment In particular, this has the effect of reducing the load capacity of the gas bearing section on the base 61.

That is, external forces and moments applied to the gas bearing on the fixed shaft 60 are applied in the radial direction at the center of gravity of the rotating assembly 56 due to unbalanced forces due to dynamic balance adjustment on the rotating assembly 56 and resulting couples or external vibrations. There is an inertial force and a moment from the support point of the rotating assembly 56 due to the inertia force, but in the structure of this embodiment, the moment is mostly generated by the gas bearing part provided on the base 61 and the rotating assembly 56 is generated by the moment. In order to maintain the load of
The burden on the gas bearing section on the base 61 can be reduced, and damage to the bearing caused by a relatively large moment of inertia can be prevented.

In addition, in response to abnormally large disturbances such as external shocks or gyroscopic moments generated by external vibrations during high-speed rotation, the load capacity of the gas bearings provided on the base 61 and the fixed shaft 60 is increased. A rotating member 51 and a fixed shaft 60 in a rotating assembly 56 constituting a gas bearing. The base 61 is made of a wear-resistant ceramic material, such as SiC or alumina (A) in this embodiment.
By using ItzO+), it is possible to prevent seizure damage during high-speed rotation and rotation failures due to contact during startup and shutdown, which are characteristics of hydrodynamic gas bearings.

At this time, the base stand 61. The fixed shaft 60 and the rotating member 51 facing it are preferably made of the same ceramic material. Further, instead of using a ceramic material, the same effect can be obtained by surface-treating the metal base with a wear-resistant material by thermal spraying, ion blasting, or the like.

Furthermore, since the structure of this embodiment has a spiral groove 63, which is a hydrodynamic gas bearing, formed on the plane of the base 61, press processing, resin molding, etc. A highly productive processing method can be applied, and as described above, the ceramic material can be applied to the base 61. By using the fixed shaft 60, grooves can be formed using plastic processing, which is extremely easy to handle and requires a short processing time, thereby further improving productivity.

Although the above embodiment is a rotating body support device that supports a rotating body having a rotating polyhedral mirror, the present invention is not limited thereto and can be applied to any rotating body.

Effects of the Invention As described above, the present invention provides a rotating body, a rotating member including the rotating body and having a flat portion formed on an end face in the rotation axis direction and having a hollow cylindrical shape in the rotation axis direction, and a flat surface of the rotating member. A base is provided with a gas bearing that generates dynamic pressure in the direction of the rotating shaft due to the relative speed of the rotating body disposed opposite the rotating body, and a constant gap is formed in the radial direction between the cylindrical inner circumferential surface of the rotating member and the rotating body. and a fixed shaft provided with a gas bearing at one location that generates dynamic pressure in the radial direction due to relative speed with the rotating body, the center of gravity of the rotating member having the rotating body is controlled by the dynamic pressure on the fixed shaft. Due to the configuration, which is characterized by being placed almost in the center of the gas bearing part,
Compared to the conventional structure with two dynamic pressure gas bearings provided on the circumferential surface of a fixed shaft, the rotating body support device can be made significantly thinner while guaranteeing tilt accuracy and stability during high-speed rotation of the rotating body. At the same time, a rotating polyhedral dawn light deflector to which this device is applied also has the excellent effect of being thinner and smaller.

Furthermore, reliability can be obtained even against abnormal disturbances such as external vibrations and shocks, and productivity can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional side view of a rotating polyhedral dawn light deflector to which the rotating body support device of the present invention is applied, FIG. 2 is an exploded perspective view of the rotating polyhedral dawn light deflector in this embodiment, and FIG. 3 is an exploded perspective view of the rotating polyhedral dawn light deflector in this embodiment. 4 is a perspective view of an optical scanning device to which a conventional rotating polyhedral optical deflector is applied, and FIG. 5 is an explanatory diagram showing the dynamic pressure distribution in the radial direction of a rotating body support device. FIG. 2 is a configuration diagram of a rotating polyhedral light deflector. 51... Rotating member, 51b... Rotating member plane part, 52... Rotating polyhedral mirror, 53...
... Rotor magnet, 56 ... Rotating assembly, 60
...Fixed shaft, 61 ...Base stand, 61
b...Pressure adjustment hole, 62...Herringbone groove, 63...Spiral groove. Name of agent: Patent attorney Toshio Nakao Haka1 person S/---
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−1 fixed axis

Claims (2)

[Claims] (1) a rotating body, a rotating member including the rotating body and having a flat portion formed on an end face in the rotating shaft direction and having a hollow cylindrical shape in the rotating shaft direction; A base having a gas bearing that generates dynamic pressure in the direction of the rotating shaft due to the relative speed with the rotating body, and a base having a certain gap in the radial direction from the cylindrical inner peripheral surface of the rotating member, and the relative speed with the rotating body. and a fixed shaft provided with a gas bearing that generates dynamic pressure in the radial direction, and the center of gravity of the rotating member having the rotating body is located approximately at the center of the dynamic pressure gas bearing on the fixed shaft. A rotating body support device characterized by: (2) The rotating body support device according to claim (1), wherein the rotating member constituting the hydrodynamic gas bearing and the base and fixed shaft opposing the rotating member are made of a ceramic material.