JPS61296325A - Kinetic fluid bearing type scanner unit - Google Patents

Abstract

PURPOSE:To obtain high rotational precision by forming center holes at both ends of a rotating shaft and boring a case so that the center shaft of a center pressing base or adjusting jig is inserted into the center hole of the rotating shaft. CONSTITUTION:When a motor stator 20 begins to be powered on, a motor rotor 19 rotates the rotating shaft 12, a disk 15, and a polygonal mirror 17. This polygonal mirror has its outer peripheral surface worked into about 4-12 flat specular surfaces and reflects laser light from an incidence window 13A out of the window. At this time, two herringbone groups of a sleeve 11C produce pressure as the relative speed to the rotating shaft 12 increases, and the rotating shaft 12 is centered to maintain high rotational precision. Further, the spiral groove 16A of a thrust bearing 16 generates pressure with the lower end surface 15A of the disk 15 and rotates stably without contacting. Consequently, the constitution with the high rotational precision is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a polygon mirror scanner for a laser printer or a rotary head scanner for a video tape recorder, etc., which uses a hydrodynamic fluid bearing in the rotating main shaft. Regarding scanners.

2. Description of the Related Art A conventional dynamic pressure fluid bearing type scanner of this type will be described. FIG. 4 shows a conventional dynamic pressure fluid bearing type scanner unit for a laser printer.

A fixed shaft 3 passing through a lower case 1 and an upper case 2 having an entrance window 2A is fixed by nuts 4A, 4B. A rotatable sleeve 5 is provided on the outer periphery of the fixed shaft 3, and the lower end surface of the sleeve 5 is in contact with a thrust bearing 6. A polygon mirror 7 and a motor rotor 8 are attached to this sleeve 5. 9 is a motor stator. Here, herringbone groups 3A and 3B are provided at two locations on the outer periphery of the fixed shaft 3, and a spiral-shaped group 6A is provided on the upper end surface of the thrust bearing 6, which is rotated by motors 8 and 9. When this starts, the pumping action of these groups increases the pressure of air or lubricant (not shown), and the sleeve rotates with high precision without contact. Then, the laser beam incident through the entrance window 2A is reflected by the polygon mirror 7.

Problems to be Solved by the Invention However, such a dynamic pressure fluid bearing type scanner unit has the following problems. This type of scanner unit requires the scanner (in this case, the polygon mirror) to have a high precision of 0.5 micrometers, but the rotation of the hydrodynamic bearing has an extremely high precision of about 0.2 micrometers. However, it is difficult to attach the polygon mirror 7 to the rotating sleeve 5 with the same precision as a hydrodynamic bearing,
The rotational vibration of the micron meter was occurring. In general, this mounting accuracy can be maintained by readjusting after assembly, but when the sleeve 5 is stopped, the sleeve 5 will play against the fixed shaft 3 by the amount of the bearing clearance, so readjusting the mounting is not recommended. There was a problem that adjustments could not be made because there were no standards. The present invention provides a highly accurate dynamic pressure fluid bearing type scanner unit configuration in which the mounting of the scanner can be easily adjusted based on the shaft after assembly.

Means for Solving the Problems In order to solve the above problems, the dynamic pressure fluid bearing type scanner unit of the present invention includes a sleeve and a rotating shaft on which a disk and a scanner are mounted inside the sleeve. Two sets of herringbone groups are provided on one side of the outer periphery of the rotating shaft, and a spiral group is provided on one of the contact surfaces of the end face of the disk and the sleeve, and a circular hole is provided at both ends of the rotating shaft. A hole is provided in the case so that a center shaft such as a center push stand or an adjustment jig can be inserted into the center hole of the rotating shaft.

By using the above technical means, after assembling the scanner unit, insert the center shaft of the center pusher through the hole in the case with the bearing stopped, support both ends of the rotating shaft, and finely adjust the mounting of the polygon mirror using this shaft as a reference. can be done. Furthermore, since the bearing of this scanner unit is combined with a dynamic pressure fluid bearing that has high rotational precision due to the pumping action of the group, the precision between the sleeve and the shaft during rotation is sufficiently high. in this way,
By combining the polygon mirror installation fine-adjustable configuration and dynamic pressure type fluid bearings, the sleeve and shaft can be rotated.

Accuracy is maintained between the polygon mirrors, ensuring high rotation accuracy.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. 1 and 2 show a dynamic pressure fluid bearing type scanner unit for a laser printer. In the same figure, 11 is the lower case, and 11 has two herringbone groups 1 on the inner diameter.
It integrally has sleeves 11 and 11C having sleeves 1A and 11B. A radial bearing is formed between the sleeve 11C and the rotating shaft 12 which is freely inserted into the sleeve 11C. Rotating axis 1
Center holes 12A and 12B are machined at both ends of 2.

Reference numeral 13 denotes a cover that prevents the incidence of random light and the incorporation of dust, and has an entrance window 13A, a center window 13B, and an adjustment hole 13C. 14 is a C I that prevents the rotating shaft 12 from coming off upwards.
This is J-ng. A disk 15 is fixed to the rotating shaft 12, and a thrust bearing 16 having a spiral group 16A shown in FIG. do.

A polygon mirror 17 is fixed to the disk 15 with adjustment screws 18. 19 is a motor rotor, and 20 is a motor stator. Here, the rotating shaft 12 and the sleeve 1 of the lower case
The radial dynamic pressure fluid bearing consisting of 1C is 0.2
It has the ability to rotate concentrically with high rotational precision on the order of micrometers, and the center holes 12A and 12B are machined to be coaxial with the outer peripheral surface of the rotating shaft 12 on the order of 0.1 micrometers. In addition, the lower case 11 has a sleeve 11C.
A hole 11D is opened in communication with the hole 11D.

The operation of the dynamic pressure fluid bearing type scanner configured as described above will be explained. When the motor stator 20 starts to be energized, the motor rotor 19 moves to the rotating shaft 12. disc 1
5. Rotate the polygon mirror 17. This polygon mirror has 4 outer peripheral surfaces.
It is processed into a flat mirror surface with about 12 sides, and the entrance window 1
The laser light entering from 3A is reflected outside from the same window. At this time, the two sets of herringbone groups of the sleeve 11C generate pressure as the relative speed with the rotating shaft 12 increases, centering the rotating shaft 12, and maintaining high rotation accuracy of 0.2 micrometer. Further, the spiral group 16A of the thrust bearing 16 is also connected to the lower end surface 1 of the disk 16.
It generates pressure between 5A and rotates stably without contact.

At this time, the rotational accuracy of the polygon mirror 170 can be expressed as the sum of the rotation accuracy of the hydrodynamic bearing and the mounting accuracy of the polygon mirror 17 with respect to the rotating shaft 13, but normally, poor accuracy is a problem for the polygon mirror 1.
The installation accuracy is 7. It is reasonable to adjust this by receiving the reflected light of the laser beam incident from the light emitter 24 with the light receiver 25 and measuring the angle in the final adjustment step after assembling the scanner in FIG. 3. Therefore, in this case, while the scanner is stopped, the center holes 13A, 13B of the rotary shaft 13 are moved by the center pushers 21A, 21B to the center shafts 21A, 21B with the tapered center shafts 21A, 21B, while the outer circumferential surface of the shaft 13 is moved to the shaft with the tapered hole, etc. The mounting of the polygon mirror 17 can be readjusted by adjusting the tightening method of the adjusting screw 18 using the driver 23 with reference to the rotating shaft 13.

In this way, the rotation accuracy of the polygon mirror 17 (scanner) relative to the sleeve (ie, the fixed body) can be adjusted to a high accuracy of about 0.5 micrometer. In the conventional example, this high rotational accuracy can only be guaranteed to about 2 microns due to the poor mounting accuracy of the polygon mirror, and although it is not shown in the figure, in scanners using ball bearings, the ball bearing itself has a runout of 1 micron or more. It was not possible to guarantee high precision as in the present invention.

Still, in the configuration of the present invention, the cover 13 does not require precision and the case can be made of resin as a sheet metal, resulting in low cost.

The polygon mirror 17 has a center window 13B and an adjustment hole 13C in the cover 13, so that it can be adjusted even with the cover 13 attached.

In addition, the two herringbone groups are sub IJ-B11.
It may be provided on the outer circumferential surface of the rotating shaft 13 instead of on the inner circumference of C.

Note that the spiral group may be provided not on the surface of the thrust bearing 6 but on the lower end surface 15A of the disk 15.

Although not shown, an upper rotating cylinder having a magnetic head for a video tape recorder may be attached instead of the polygon mirror 17. In this case, the cover 13 is not necessary.

Note that the lower hole of the case 11, the center window of the cover 13, and the adjustment hole 13C may be covered with an adhesive tape (not shown) or the like after the adjustment is completed.

Incidentally, a lubricant may be retained in the two sets of herringbone groups and the one set of spiral groups.

Effects of the Invention The present invention improves rotational accuracy by using a hydrodynamic bearing having a rotating shaft, and by providing a center hole in the end face of the rotating shaft and leaving it open so that the scanner can be finely adjusted when the scanner is stopped. A high dynamic pressure fluid bearing type scanner unit configuration can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a dynamic pressure fluid bearing type scanner unit according to an embodiment of the present invention, Fig. 2 is an explanatory view of the thrust bearing of the same scanner unit, Fig. 3 is an explanatory view of the installation adjustment method while the scanner unit is stopped, FIG. 4 is a sectional view of a conventional dynamic pressure bearing type scanner unit. 11...Lower case, 11A, 11B...
... Herringbone group, 11C ... Sleeve, 11D ... Hole, 12 ... Rotating shaft, 12A, 12B ... Center hole, 15 ...
...Disk, 16A...Spiral group, 17...Scanner.

Claims (2)

[Claims] (1) It has a sleeve and a rotating shaft that can freely rotate inside the sleeve, the rotating shaft has a disk equipped with a scanner, and either the inner periphery of the sleeve or the outer periphery of the rotating shaft has a It has two sets of herringbone groups, and has a spiral group on one of the abutting surfaces where the end surface of the disk and the end surface of the sleeve abut, and the lower end of the rotating shaft is provided integrally with the sleeve. A dynamic pressure fluid bearing type scanner unit, characterized in that the shaft is opened from a hole provided in the lower case and has a center hole at both ends of the shaft. (2) The dynamic pressure fluid bearing type scanner unit according to claim 1, wherein the scanner is a polygon mirror.