JPS62266515A - Rotary mechanism for optical scanning polygon mirror - Google Patents

Abstract

PURPOSE:To prevent the reflecting faces of an optical scanning polygon mirror from being spoiled by lubrication oil by arranging a rotor and a stator constituting a driving motor having an external diameter shape larger than the outer diameter of the polygon mirror on the lower end of a rotary shaft holding the polygon mirror on its upper end and the lower part of a housing opposed to said lower end. CONSTITUTION:The optical scanning polygon mirror 35 is fixed on the upper end part of the rotary shaft 32 with a screw 37 or the like through a rubber ring 36 and the rotor 38 and the stator 39 constituting the driving motor, e.g. an axial gap type motor, having the external diameter shape larger than the outer diameter of the polygon mirror 35 are arranged on the lower end part and the lower surface of the bearing housing opposed to the lower end part. Since the rotating peripheral speed of the rotor 38 is larger than that of the rotating polygon mirror 35, an air flow is generated in the maximum peripheral speed direction of the rotor 38 and a gap around the rotary shaft in the bearing housing 31 is turned to a pressure-reduced state. The air flow generated at that time flows to the driving motor side in the lower direction along the rotary shaft 32 and the lubricating oil is not dispersed to the polygon mirror side, so that the reflecting faces of the polygon mirror 35 can be prevented from dirt due to the lubricating oil.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a rotation mechanism for an optical scanning polygon mirror used in a laser scanning optical system of a laser printer, etc. A rotating shaft holding an optical scanning polygon mirror on the upper part is supported via a bearing, and the fixed base and the optical scanning polygon mirror are mounted on the lower part of the rotating shaft and on the housing wall facing the lower part. By adopting a structure that includes a rotor and a stator that constitute a shaft-opposed motor with an outer diameter larger than the outer diameter, the direction of scattering of lubricating oil from each bearing on the polygon mirror during high-speed rotation can be controlled. It is designed to change downward to prevent the polygon mirror from becoming dirty.

[Industrial application field]

The present invention relates to a rotation mechanism for an optical scanning polygon mirror used in a laser scanning optical system such as a laser printer, and uses a special configuration to prevent the polygon mirror from becoming contaminated by lubricating oil splashed from a bearing during high-speed rotation. This article relates to a new rotation mechanism that prevents this from happening.

An electrophotographic transfer printer that uses a laser scanning optical system, that is, a laser printer, modulates a continuously oscillated laser beam from a laser device using an optical modulator using an electrical signal corresponding to the printing information, and uses a polygon mirror that rotates at high speed. The light is reflected and focused on the surface of a rotating photoreceptor, and is scanned and exposed in the direction of the rotation axis to form an electrostatic latent image.

The electrostatic latent image is developed with a developing device, and black powder called toner is electrostatically attached thereto to form a visible image. This visible image is transferred to recording paper to which an electric field is applied and then fixed. Thereafter, such a process is repeated to perform print recording.

In order to obtain clear print quality in such laser printers, it is necessary to keep the reflective surface of the rotating polygon mirror used in the laser scanning optical system always clean and to ensure that the polygon mirror has a high surface tilt accuracy. extremely important.

[Conventional technology]

As shown in the cross-sectional view of FIG. 4, the conventional rotation mechanism of a polygon mirror for laser beam scanning is constructed such that an upper bearing 3 and a lower bearing 4 are installed in a bearing housing l equipped with a stator 2 that constitutes a motor at the bottom. A rotary shaft 5 having a rotor 6 at its lower end is pivotally supported, and on an upper fixed base 7 of the rotary shaft 5, for example, 8 to 1
A dihedral polygon mirror 8 is secured to a screw 10 via a rubber ring 9.
It is fixed by etc. The polygon mirror 8 can be rotated at high speed by a drive motor comprising a rotor 6 at the lower end of the rotating shaft 5 and a stator 2 provided on the opposite side of the housing.

In addition, in order to minimize the rotational runout of the rotating shaft 5 and improve the rotation precision of the surface tilt of the polygon mirror 8, the distance between the upper bearing 3 and the lower bearing 4, which fit and support the rotating shaft 5, is set to a certain degree. For example, a ball bearing or the like is passed through the lower bearing 4 of the upper bearing 3 and the lower bearing 4, and the fitting part of the lower bearing 4 with the bearing housing 1 side is loosely fitted. A loose fitting portion of the bearing 4 is pressed by a spring 11 provided around the rotating shaft 5 to eliminate play within the lower bearing 4.

[Problem that the invention seeks to solve]

By the way, in the rotation mechanism of such a conventional optical scanning polygon mirror, when the polygon mirror 8 rotates at high speed, lubricant flows out from the upper bearing 3 and the lower bearing 4 that fit and support the rotating shaft 5. There is an inconvenience that oil scatters from the gap between the upper surface of the bearing housing l and the upper fixing base 7 of the rotary shaft 5 and stains the reflective surface of the polygon mirror 8. A labyrinth seal portion 12 is provided between the upper surface and the upper fixing base 7 of the rotary shaft 5 to prevent lubricating oil from leaking or scattering.

However, providing such a labyrinth seal part 12 for preventing lubricant oil leakage requires a complicated machining process, which increases the machining cost. Alternatively, a structure that prevents scattering is required.

In view of such conventional circumstances, the present invention provides a system in which, for example, when a disk with a rotating shaft provided at the center is rotated, air around the rotating shaft flows toward the outer periphery of the disk where the maximum circumferential speed is achieved. Focusing on the phenomenon, the bearing housing 21 as shown in FIG.
A rotating shaft 24, which is supported by an upper bearing 22 and a lower bearing 23, has an upper disk 25 corresponding to a polygon mirror on the upper part, and a drive having an outer diameter larger than the outer diameter of the disk 25 on the lower part. A lower disk 26 corresponding to a rotor constituting a motor
When the rotating shaft 24 is rotated,
Since the rotational circumferential speed of the lower disk 26 having a larger outer diameter than the rotational circumferential speed of the upper disk 25 is greater, the area around the rotating shaft 24 in the bearing housing 21 is under reduced pressure, and the air flow is as shown by the arrow. Occurs in the direction shown. Utilizing this principle, when the optical scanning polygon mirror is rotated at high speed, the lubricating oil flowing out from the upper and lower bearings is prevented from scattering toward the polygon mirror, thereby lubricating the polygon mirror. The object of the present invention is to provide a novel rotation mechanism for an optical scanning polygon mirror that prevents contamination by oil.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention pivots a rotating shaft that holds an optical scanning polygon mirror at its upper end within a main bearing housing through an upper bearing and a lower bearing, and also supports a rotating shaft that holds an optical scanning polygon mirror at its upper end. , a rotor and a stator constituting a drive motor having an outer diameter larger than the outer diameter of the optical scanning polygon mirror are provided in a lower part of the housing that faces the lower part.

[For production]

In the rotation mechanism of the present invention, when the rotating shaft is rotated, the rotational peripheral speed of the rotor side constituting the drive motor having a larger outer diameter is greater than the rotational peripheral speed of the polygon mirror side, so that The gap around the axis of rotation is under reduced pressure, and this custom airflow flows along the axis of rotation and downward toward the drive motor.

Therefore, even if the elHh oil leaks from the upper and lower bearings that support the rotating shaft, the air flow prevents the /II1 oil from scattering toward the polygon mirror, preventing contamination. Ru.

〔Example〕

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

FIG. 1 is a sectional view of essential parts showing an embodiment of a rotation mechanism for an optical scanning polygon mirror according to the present invention.

In the figure, 31 is a bearing housing, 32 is a rotating shaft that is supported by an upper bearing 33 and a lower bearing 34 made of ball bearings etc. disposed inside the bearing housing 31, and a loose fitting portion of the lower bearing 34. is pressed by a spring 40 disposed around the rotating shaft 32 to eliminate play within the bearing and improve rotational runout accuracy of the rotating shaft 32.

Also, at the upper end of the rotating shaft 32, there is a multifaceted IJ for optical scanning.
35 is fixed by a screw 37 or the like via a rubber ring 36, and the lower end and the lower surface of the bearing housing 31 facing the lower end have an outer diameter larger than the outer diameter of the polygon mirror 35. A rotor 38 and a stator 39 that constitute a drive motor, for example an axial gap type motor, are provided.

In the rotation mechanism of the optical scanning polygon mirror 35 configured in this manner, the rotation circumferential speed of the rotor 38 constituting the drive motor having a larger outer diameter shape is higher than the rotation circumferential speed of the rotating polygon mirror 35. As a result, an air flow is generated in the direction of the maximum circumferential speed of the rotor 38, and the gap around the rotating shaft in the bearing housing 31 is reduced in pressure. Flows to the drive motor side.

Therefore, even if lubricating oil flows out from the upper bearing 33 and lower bearing 34 that pivotally support the rotating shaft 32, the lubricating oil is drawn downward by the air flow and is scattered toward the polygon mirror. Therefore, the reflective surface of the polygon mirror 35 is prevented from becoming dirty.

In addition, in the above embodiment, an example was explained in which an axial gap type motor was configured as the drive motor having an outer diameter larger than the outer diameter of the polygon mirror 35, but the present invention is limited to this example. Rather, for example, as shown in FIG. 3, a flanged rotor 41 with an outer diameter larger than the outer diameter of the polygon mirror 35 is attached to the lower end of the rotating shaft 32, and a wall surface of the bearing housing 31 that faces the rotor 41. A similar effect can be obtained when a radial gap type motor is constructed in which the stator 42 is disposed at the radial gap type motor.

〔Effect of the invention〕

As is clear from the above description, according to the rotation mechanism of the optical scanning polygon mirror according to the present invention, the lower end of the rotating shaft holding the optical scanning polygon mirror at the upper end, and the lower part of the housing opposite to the lower end, By providing a rotor and a stator constituting a drive motor having an outer diameter larger than the outer diameter of the pre-scanning and scanning polygon mirrors, air around the rotation axis when the polygon mirror rotates can be reduced. The airflow flows in the direction of the maximum circumferential speed of the rotor constituting the drive motor, which has an outer diameter larger than that of the polygon mirror, and the lubricating oil flowing out from the upper and lower bearings is dragged and transferred downward by this airflow. This has an excellent advantage in that the lubricating oil is prevented from scattering toward the polygon mirror, and the lubricating oil is easily prevented from staining the reflective surface of the polygon mirror.

Therefore, it is possible to provide a highly reliable rotation mechanism for an optical scanning polygon mirror that can be used in this type of rotation mechanism and exhibits excellent effects.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of the rotation mechanism of a polygon mirror for light scanning according to the present invention, and FIG. 2 is a main part illustrating the principle of the rotation mechanism of a polygon mirror for light scanning according to the present invention. 3 is a cross-sectional view of a main part showing another embodiment of the rotation mechanism of a polygon mirror for optical scanning according to the present invention, and FIG. 4 is a sectional view for explaining the rotation mechanism of a conventional polygon mirror for optical scanning. It is a sectional view of the main part. In FIGS. 1 to 3, 21 and 31 are bearing housings, 22 and 33 are upper bearings,
23.34 is a lower bearing, 24.32 is a rotating shaft, 25 is an upper disk, 26 is a lower disk, 35 is a polygon mirror, 38 is a rotor, 39.42 is a stator, 41 is a flanged rotor. Each is shown below. An example of 3 points on 4 slopes.

Claims (1)

[Claims] A rotating shaft (32) holding an optical scanning polygon mirror (35) on the upper part is rotated through an upper bearing (33) and a lower bearing (34) arranged in a main bearing housing (31). The optical scanning polygon mirror (
35) A rotation mechanism for a polygon mirror for optical scanning, characterized in that it is provided with a rotor (38) and a stator (39) that constitute an axially opposed motor having an outer diameter larger than the outer diameter of the mirror.