JPH0764010A - Light deflector - Google Patents

Abstract

PURPOSE:To miniaturize a motor driving the rotation of a polygon mirror and to reduce the power consumption thereof by reducing windage-loss torque when the polygon mirror is rotated at a high speed. CONSTITUTION:In a light deflector rotating the polygon mirror 1, which is obtained by forming plural reflecting mirror surfaces 1a on the outside circumference, at a prescribed speed, reflecting and deflecting light beams made incident on the mirror surfaces 1a, circumferential walls 21 and 22 brought close to the mirror 1 are provided in an area outside the circumscribed circle of the mirror 1 and in an area on the upper and/or lower side of the mirror 1. Then, air convection generation by the peripheral atomosphere of the mirror 1 is maintained to be in a stable laminar flow state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention scans an original image or a photoconductor with a light beam emitted from a laser light source in an image reading system such as a digital copying machine or a facsimile or an image writing system such as a laser beam printer. For the optical deflector.

[0002]

2. Description of the Related Art Conventionally, as a document image reading system, there is known a method of exposing and scanning a document image with a light beam to obtain density information for each pixel from the reflected light, and as a recording image writing system. A method of forming an electrostatic latent image by exposing and scanning a photoconductor with a light beam modulated according to information is known. In any of these systems, a scanning method using an optical deflector equipped with a polygonal mirror is known as a method of scanning an original image or a photoconductor with a light beam emitted from a laser light source.

FIG. 7 is a schematic diagram showing an image writing system using this scanning system. Reference numeral 100 is a laser light source and reference numeral 1 is a laser light source.
Reference numeral 01 is a collimator lens, and reference numeral 102 is a polygon mirror 102a.
Reference numeral 103 denotes a mirror cover having an opening 103a through which a light beam incident on and reflected by the polygon mirror 102a passes, reference numeral 104 denotes an f-θ lens, and reference numeral 105 denotes a photoconductor drum. . The light beam emitted from the laser light source 100 is reflected by the reflecting mirror surface of the polygon mirror 102a and enters the photoconductor drum 105. At this time, the light beam is deflected as the polygon mirror 102a rotates in the direction of arrow A. , The photosensitive drum 105 is scanned in the direction of arrow B. Along with this, the photoconductor drum 105 rotates in the direction of arrow C, and a two-dimensional electrostatic latent image is formed on the photoconductor drum 105.

Conventionally, as an optical deflector used for such a purpose, one disclosed in Japanese Patent Laid-Open No. 3-17611 is known. Specifically, the rotating member is rotatably supported on a fixed shaft erected on the housing, and
A polygonal mirror is fixed to the mirror flange formed on the rotating member, and the polygonal mirror is rotated together with the rotating member by a motor unit incorporated in the housing. Further, in this optical deflector, the peripheral wall is erected close to the circumscribed circle of the polygon mirror, and the wind loss torque generated as the polygon mirror rotates is reduced.

[0005]

By the way, when a polygon mirror rotates at a high speed, air convection occurs around it.
This air convection is mainly caused by friction between the upper surface, the lower surface and the outer peripheral surface of the polygon mirror and the surrounding atmosphere. That is, as shown in FIG. 5, in the upper area A and the lower area B of the polygon mirror 50, air convection occurs due to friction between the upper surface 50a or the lower surface 50b of the polygon mirror 50 and the surrounding atmosphere, while the outer peripheral area of the polygon mirror 50. At C, air convection different from the upper region A and the lower region B is generated due to the friction between the outer peripheral surface 50c of the polygon mirror 50 and the surrounding atmosphere. Incidentally, reference numeral 5 in the drawing
Reference numeral 1 denotes a mirror cover that prevents dust from adhering to the polygon mirror 50.

However, the air convection generated in these regions A, B and C is a region outside the circumscribed circle of the polygon mirror 50 and above and / or below the polygon mirror 50, ie region A. And C diffuse to the region D adjacent to C and C or the region E adjacent to B and C, so that two different air convections are mixed in the above regions D and E. Therefore, in the regions D and E, two different air convections interfere with each other to generate a turbulent flow, and the polygon mirror 5
There is a problem that the air resistance acting on zero, that is, the windage loss torque increases. The increase in the windage loss torque has led to an increase in the size of the motor that rotationally drives the polygon mirror 50 and an increase in power consumption.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce a windage torque when the polygon mirror rotates at a high speed, and thereby to rotate the polygon mirror. An object of the present invention is to provide an optical deflector capable of downsizing and power consumption thereof.

[0008]

In order to achieve the above object, the optical deflector of the present invention rotates a polygonal mirror having a plurality of reflecting mirror surfaces on its outer periphery at a predetermined speed and makes it incident on the reflecting mirror surface. In the optical deflector for reflecting and deflecting the light beam, the peripheral wall adjacent to the polygonal mirror is provided in an area outside the circumscribed circle of the polygonal mirror and in an area above and / or below the polygonal mirror. It is characterized by being provided.

In such a technical means, the peripheral wall may be formed at any position above the polygonal mirror or below the polygonal mirror as long as it is outside the circumscribed circle of the polygonal mirror. It may be formed in both the upper side and the lower side of the polygon mirror.

As for the shape of the peripheral wall, if the mixing of the air convection generated in the upper region of the polygon mirror and the air convection generated in the outer peripheral region can be reduced, the shape of the peripheral wall can be appropriately changed in design. However, from the viewpoint of preventing the mixing of these air convections as much as possible, it is preferable that the shape is such that the upper region and the outer peripheral region of the polygon mirror can be divided.

Further, in the present invention, a well-known technical means such as an air dynamic pressure bearing can be applied to the bearing for supporting the rotation of the polygon mirror. As for the motor that drives the polygon mirror to rotate, well-known technical means such as an inner magnet type scanner motor, an outer magnet type scanner motor, and an axial type scanner motor may be applied.

[0012]

According to the above technical means, as shown in FIG.
In the region outside the circumscribed circle of the polygon mirror 50 and in the region above and / or below the polygon mirror, the polygon mirror 5
Since the peripheral wall close to 0 is provided, the air convection generated in the upper area A or the lower area B of the polygon mirror 50 and the polygon mirror 50
It is possible to prevent mutual interference with the air convection generated in the outer peripheral region C. This suppresses the occurrence of turbulent air flow in the atmosphere around the polygon mirror 50, and reduces the air resistance acting on the polygon mirror 50.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical deflector of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of an optical deflector to which the present invention is applied. In the figure, reference numeral 1 is a polygonal mirror having eight reflecting mirror surfaces 1a on the outer circumference, reference numeral 2 is a rotary sleeve that holds the polygonal mirror 1 and rotates, and reference numeral 3 is a mirror flange projecting from the rotary sleeve 2. Reference numeral 4 denotes a mirror cap for sandwiching the polygon mirror 1 with the mirror flange 3, and reference numeral 5 denotes a fixing screw penetrating the mirror cap 4 and the polygon mirror 1 and screwed into the mirror flange 3.

The rotary sleeve 2 is loosely fitted to a fixed shaft 7 provided upright on the shaft flange 6a with a predetermined gap (hereinafter, bearing gap) held therebetween. It constitutes an air dynamic pressure bearing in the radial direction. That is, the dynamic pressure generating grooves 7a are formed on the outer peripheral surface of the fixed shaft 7 in a herringbone pattern, and when the rotary sleeve 2 rotates, air dynamic pressure is generated in the bearing gap, and the rotary sleeve 2 has a high pressure. It is supported by the air lubrication film and rotates around the fixed shaft 7 in a non-contact state. Although the dynamic pressure generating groove 7a is formed on the outer peripheral surface of the fixed shaft 7 in this embodiment, the dynamic pressure generating groove may be formed on the inner peripheral surface of the rotary sleeve 2 instead.

Further, in FIG. 1, reference numeral 8 is a motor for rotationally driving the rotary sleeve 2, and comprises a rotor portion 8a fixed to the outer periphery of the rotary sleeve 2 and a stator portion 8b fixed to the housing 6. It is configured.

The rotor portion 8a includes a magnet 9 and a magnet yoke 10, which are fixed to the rotary sleeve 2 by press fitting or bonding. As shown in FIG. 2, the magnet 9 is arranged on the inner circumference of a stator core 11 which will be described later, and is magnetized to have two poles so as to divide the circumference.

A magnetic attraction force always acts between the magnet 9 and the stator core 11, and these constitute a magnetic thrust bearing. That is, the rotating sleeve 2
Is moved in a thrust direction (axial direction of the fixed shaft) from a predetermined position, the rotary sleeve 2 is pulled back to a predetermined position where the magnet 9 and the stator core 11 face each other by the magnetic attraction force, and the rotary sleeve 2 is always thrust. It is held at a predetermined position in the direction.

On the other hand, the stator portion 8b is provided with a stator core 11 erected on the housing 6 with a screw 13 via a collar 12, and an electromagnetic coil 14 is wound around the stator core 11 in a toroidal shape. A circuit board 16 is fixed to the stator core 11 via studs 15, and the electromagnetic coil 14 is connected to wiring printed on the circuit board 16. The circuit board 16 is connected to a control circuit unit (not shown).

The direction of the current flowing through the electromagnetic coil 14 is
It is determined based on the detection signal of the magnetic detection sensor 17 provided upright on the circuit board 16. That is, the magnetic detection sensor 17 detects the leakage magnetic flux of the magnet 9 of the rotor section 8a and transmits the detection signal to the control circuit section, while the control circuit section detects the vicinity of the magnetic detection sensor 17 based on the detection signal. It is determined whether the magnetic pole of the magnet 9 that has passed through is the N pole or the S pole, and the direction of the current flowing through the electromagnetic coil 14 wound around each portion of the stator core 11 is determined. As a result, a force in a direction for continuing the rotation of the rotary sleeve 2 always acts between the electromagnetic coil 14 and the magnet 9, and a predetermined number of rotations is given to the rotary sleeve 2.

The polygonal mirror 1 is fixed to the rotating sleeve 2 by using the mirror cap 4 and the fixing screw 5. That is, a fixing screw 5 penetrating the mirror cap 4 and the polygon mirror 1 is screwed into the mirror flange 3, and the polygon cap 1 is sandwiched and fixed by the mirror cap 4 and the mirror flange 3. Further, when the polygonal mirror 1 is fixed, an air pocket 18 is formed between the upper end of the fixed shaft 7 and the mirror cap 4 to suppress damping in the thrust direction. The air pocket 18 is communicated with the outside air through the fine holes 19, so that the damping effect described above is stabilized.

In the optical deflector of the present embodiment constructed as described above, the mirror cover 20 for covering the polygon mirror 1 and the mirror cap 5 from above is arranged on the housing 6.
Dust is prevented from adhering to the reflecting mirror surface 1a of the polygon mirror 1 and the motor. The mirror cover 20 is provided with an opening 20a through which a light beam entering and reflected by a reflecting mirror surface passes,
A glass plate is fitted in the opening 20a. Therefore, as shown in FIG. 3, a light beam emitted from a laser light source (not shown) passes through the opening 20a, enters the reflecting mirror surface 1a of the polygon mirror 1, is reflected and deflected, and then is opened again. And is irradiated onto a photosensitive drum or the like (not shown).

A peripheral wall 21 adjacent to the polygonal mirror 1 is provided on the inside of the mirror cover 20, and the peripheral wall 21 is an area outside the circumscribed circle of the polygonal mirror 1 and the polygonal mirror 1. It is located in the upper region. A peripheral wall 22 is also projectingly provided on the upper edge of the housing 6, and the peripheral wall 22 is located in an area outside the circumscribed circle of the polygonal mirror 1 and below the polygonal mirror 1. .

That is, the peripheral wall 21 projecting from the mirror cover 20 separates the upper space 23a and the outer peripheral space 23c of the polygonal mirror 1 from each other.
The air convections generated at 23c are prevented from interfering with each other. Similarly, the peripheral wall 22 projecting from the housing 6 has a lower space 23b of the polygonal mirror 1 and an outer peripheral space 2.
3c is separated from the two spaces 2 as the polygon mirror 1 rotates.
The air convections generated in 3b and 23c are prevented from interfering with each other.

Therefore, according to the optical deflector of this embodiment,
Since the air convection around the polygon mirror maintains a stable laminar flow state without generating turbulence, the air resistance acting on the polygon mirror 1 is reduced as compared with the conventional optical deflector, and the wind loss torque is reduced. be able to.

Although the peripheral wall 21 is formed integrally with the mirror cover 20 in this embodiment, the peripheral wall 21 may be formed by fixing a ring-shaped member inside the mirror cover 20. Also, with respect to the peripheral wall 22 on the housing 6 side, a ring-shaped member can be fixed to the upper edge of the housing 6 to form the peripheral wall 22.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, the shape of the inside of the mirror cover 20 and the shape of the upper edge of the housing 6 are changed as shown in comparison with those of the first embodiment. That is, the peripheral wall 30 of the mirror cover 20 and the peripheral wall 31 of the housing 6 were molded so that their cross sections were tapered. Since other configurations are the same as those of the first embodiment, the same reference numerals as those of the first embodiment are given in the drawings and the description thereof will be omitted.

Also in this second embodiment, the air convection generated in the space above the polygon mirror 1 or the air convection generated in the space below the polygon mirror 1 and the air convection generated in the outer space of the polygon mirror 1 mutually. Since the space that interferes with each other is reduced, the air resistance acting on the polygon mirror becomes smaller than that of the conventional one, and the wind loss torque can also be reduced.

[0028]

As described above, according to the optical deflector of the present invention, the polygon mirror is provided in the area outside the circumscribed circle of the polygon mirror and in the area above and / or below the polygon mirror. Since the neighboring peripheral walls are provided to prevent air convection from interfering with each other in the surrounding atmosphere of the polygon mirror, it is possible to reduce windage torque when the polygon mirror rotates at high speed, and rotate the polygon mirror. It is possible to reduce the size of the driving motor and reduce its power consumption.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of an optical deflector of the present invention.

FIG. 2 is a plan view showing a motor of the optical deflector according to the first embodiment.

FIG. 3 is a plan view showing an operating state of the optical deflector according to the first embodiment.

FIG. 4 is a schematic view showing a second embodiment of the optical deflector of the present invention.

FIG. 5 is a reference diagram for explaining a problem of a conventional optical deflector.

FIG. 6 is a reference diagram for explaining the operation of the present invention.

FIG. 7 is a schematic view showing a usage example of an optical deflector.

[Explanation of symbols]

1 ... Polyhedral mirror, 1a ... Reflective mirror surface, 2 ... Rotating sleeve, 3 ...
Mirror flange, 4 ... Mirror cap, 20 ... Mirror cover, 20a ... Opening part 21, 22 ... Peripheral wall

Claims (1)

[Claims] 1. An optical deflector that rotates a polygonal mirror having a plurality of reflecting mirror surfaces on its outer periphery at a predetermined speed to reflect and deflect a light beam incident on the reflecting mirror surface, wherein the circumscribed circle of the polygonal mirror is An optical deflector characterized in that a peripheral wall adjacent to the polygon mirror is provided in an outer region and an upper region and / or a lower region of the polygon mirror.