JP2007065312A - Rotary driving apparatus for polygon mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary driving apparatus for polygon mirror in which an air flow rectification member is arranged at a proper position, thus the air flow, which is made non-uniform in the circumferential direction of the rotation of a polygon mirror due to the rotation of the polygon mirror which takes in the air into a projected part, is turned into a streamlined flow, the motion of a rotor supporting the polygon mirror is suppressed and the plane tilt of the polygon mirror and the deterioration of jitter value are prevented. <P>SOLUTION: The rotary driving apparatus for polygon mirror comprises: a polygon mirror 2; the rotor 31 which supports the polygon mirror 2; a motor 3 which rotationally drives the rotor 31; and a cover member 4 which covers the polygon mirror 2 and is provided with an open part 41 for passing a laser beam. The cover member 4 is provided with a projected part 44 which is projected to surround the periphery of the open part 41 and the air flow rectification member 6 is formed at the front side end part 48 of the open part 41 in the rotating direction of the polygon mirror 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a polygon mirror rotation driving device used as an optical scanning device such as a laser beam printer or a facsimile. More specifically, the present invention relates to a polygon mirror rotation driving device in which a polygon mirror is covered with a cover member.

In recent years, polygon mirror rotation driving devices used as optical scanning devices such as laser beam printers have been increased in processing speed, and polygon mirrors are required to rotate at a high speed of 40,000 revolutions per minute or more. It has become to.
When the polygon mirror is rotated at such a high speed, there arises a problem that windage loss increases due to air resistance caused by the rotation of the polygon mirror. In other words, the load on the motor and bearing that drives the polygon mirror to rotate due to windage increases, and the rise time of the motor also increases, causing problems such as an increase in the steady current and starting current of the motor.
Therefore, a method of reducing windage loss by covering the polygon mirror with a cover member has been proposed, but in the case where the size of the internal space sealed by the cover member is different between the upper side and the lower side of the polygon mirror Although the windage loss can be reduced, the flow velocity of air generated as the polygon mirror rotates increases, and negative pressure is generated above and below the polygon mirror. As described above, since the size of the internal space sealed by the cover member differs between the upper side and the lower side of the polygon mirror, the negative pressure does not have the same negative pressure. There arises a new problem that the rotor supporting the mirror moves up and down during rotation, which may adversely affect the so-called plane collapse and jitter value.

For this reason, in the Japanese Utility Model Publication No. 4-26525 (see Patent Document 1) according to the applicant's application, the present applicant provides an air flow suppressing means including protrusions and grooves on the inner surface of the cover member covering the polygon mirror. Therefore, it has been proposed to prevent the flow of air around the polygon mirror as it rotates and to balance the negative pressure generated above and below the polygon mirror.

Patent Document 1 Japanese Utility Model Publication No. 4-26525

In the polygon mirror rotation driving device according to Patent Document 1, air flow suppression means including protrusions and grooves is provided on the inner surface of the cover member that covers the polygon mirror, so that surrounding air generated as the polygon mirror rotates is reduced. It is disclosed that the problem of the rotor supporting the polygon mirror moving up and down during rotation is solved by preventing the flow and balancing the negative pressure generated above and below the polygon mirror.

However, as shown in FIGS. 1A and 3, the polygon mirror rotation driving device in which a protruding portion 44 is formed on the cover member so as to surround the opening 41 for entering and exiting laser light. In this case, there is a problem that the rotor that supports the polygon mirror moves during rotation due to the protruding portion 44.

Accordingly, the present invention provides an air rectifying member disposed at a suitable position in a polygon mirror rotation driving device in which a protrusion is formed on the cover member so as to surround the periphery of the laser light incident / exit opening. As a result of the rotation of the polygon mirror, the air flow that has entered the projecting portion and becomes non-uniform in the circumferential direction of the rotation of the polygon mirror can be adjusted to a good air flow, and the polygon mirror is supported. It is an object of the present invention to provide a polygon mirror rotation driving device that can suppress the movement of the rotor to prevent the polygon mirror from being tilted and the jitter value from being deteriorated.

In order to achieve the above object, the present invention provides a polygon mirror, a rotor that supports the polygon mirror, a motor that rotationally drives the rotor, and a cover that covers the polygon mirror having an opening for entering and exiting laser light. In the polygon mirror rotation driving device comprising the member, the cover member includes a protruding portion protruding so as to surround the opening, and the air rectifying member rotates the polygon mirror at the opening. It formed in the front end side edge part of a direction.

According to the present invention, in the polygon mirror rotation driving device, air is generated at the front end side end in the rotation direction of the polygon mirror in the laser light entrance / exit opening that causes uneven air flow in the rotation direction of the polygon mirror. Since the flow regulating member is arranged, the air flow that has entered the projecting portion and becomes nonuniform in the circumferential direction of the rotation of the polygon mirror can be adjusted to a good air flow, and the shaft of the rotor that supports the polygon mirror The movement in the direction (vertical direction), the movement in the circumferential direction, and the swinging can be suppressed, the deterioration of the surface of the polygon mirror is deteriorated, and the angle of each reflecting surface (mirror surface) formed on the so-called polygon mirror is changed. And deterioration of jitter value can be prevented.

In this invention, it is preferable that the said cover member is formed from the cylindrical part which covers the outer periphery of the said polygon mirror, and has the said protrusion part and the said opening part, and the cover part which covers the upper surface of the said polygon mirror. .

With this configuration, the mirror surface of the polygon mirror can be protected from dust and the like, and further, the motor and the polygon mirror can be easily installed on the cover member.

In the present invention, a polygon mirror comprising a polygon mirror, a rotor that supports the polygon mirror, a motor that rotationally drives the rotor, and a cover member that covers the polygon mirror having an opening for entering and exiting laser light. In the rotation driving device, the cover member includes a projecting portion projecting so as to surround the periphery of the opening, and the air rectifying member is provided at an end of the opening in the rotational direction of the polygon mirror in the opening. Since it is formed, it is possible to adjust the air flow that has entered the projecting part and becomes uneven in the circumferential direction of the rotation of the polygon mirror to a good air flow, and suppresses the movement of the rotor that supports the polygon mirror It is possible to prevent the polygon mirror from falling down and the jitter value from deteriorating.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

Fig.1 (a) is a top view which shows the polygon mirror rotational drive apparatus concerning embodiment of this invention. FIG.1 (b) is explanatory drawing cut | disconnected along the chain line EOH of FIG. 1 (a). FIG. 2 is an explanatory view showing a main part of the motor 3 shown in FIG.

(Configuration of polygon mirror rotation drive device)
As shown in FIGS. 1 (a), 1 (b), and 2, the polygon mirror rotation drive device 1 in this embodiment is roughly composed of a polygon mirror 2, a rotor 31 that supports the polygon mirror 2, and an iron-made device. The motor 3 is configured on the substrate 5 and rotationally drives the rotor 31, and the laser beam incident / exit opening 41 is provided, and the polygon mirror 2 and the cover member 4 that covers the entire motor 3 are configured.

(Motor configuration)
In the motor 3 according to the present embodiment shown in FIG. 2, a connector 51 for outputting a drive signal to the motor 3 is mounted on the iron substrate 5 with screws 52. A frame 7 for fixing the motor 3 is provided on the lower end side.
The frame 7 is formed with a shaft fixing hole 53 through which the proximal end side of the rotating shaft 32 of the motor 3 is inserted. The fixed shaft 32 is inserted into the shaft fixing hole 53 and is screwed into the frame by bolts 33. Tightened and fixed.

A substantially hollow cylindrical core holder 34 is fixed on the iron substrate 5, and a stator core 35 made of a laminate of electromagnetic steel plates or the like is attached to the cylindrical outer peripheral surface of the core holder 34. A drive coil 36 is wound around each salient pole portion of the stator core 35.

A rotating pedestal portion 31 a constituting a part of the rotor 31 is rotatably mounted on the fixed shaft 32. That is, a radial dynamic pressure bearing RB that generates dynamic pressure in the air present in the gap between the two members between the outer peripheral surface of the fixed shaft 32 and the inner peripheral surface of the central hole of the rotating pedestal 31a. The entire rotor 31 is rotatably supported by the radial dynamic pressure bearing RB.

At this time, in order to improve wear resistance and seizure resistance, the outer surface of the fixed shaft 32 is subjected to a surface treatment such as polyamideimide resin coating, and the surface of the polyamideimide resin coating layer is applied. Is formed with a dynamic pressure generating groove having a herringbone shape or a spiral shape (not shown) by a method such as cutting.
When the rotor 31 rotates, dynamic pressure is generated in the gap between the outer peripheral surface of the fixed shaft 32 and the inner peripheral surface of the central hole of the rotating pedestal 31a. On the other hand, the rotary pedestal 31a is supported in a state where it floats by a predetermined amount.

On the other hand, the thrust bearing SB is configured by using a magnetic force acting between the permanent magnet 32 a disposed at the upper end portion of the fixed shaft 32 and the permanent magnet 31 b disposed at the upper end portion of the rotor 31. .
The pair of permanent magnets 32 a and 31 b are arranged to face each other with different poles, and are configured to float and hold the entire rotor 31 at a predetermined position in the axial direction with respect to the fixed shaft 32. .

Further, a rotor case 31c formed in a substantially cup shape is fixed to the rotary base 31a of the rotor 31 by caulking so as to protrude radially outward from the rotary base 31a. An annular rotor magnet 31e is attached to the inner peripheral surface of the standing wall yoke 31d provided on the outer peripheral portion so as to be close to each salient pole portion of the stator core 35 from the outside in the radial direction.

(Fix polygon mirror)
Next, fixing of the polygon mirror 2 will be described with reference to FIG.

On the outer peripheral surface of the rotary pedestal 31a in the rotor 31, there are provided a mounting peripheral surface 31a2 and a mounting bottom surface 31a3 that form a stepped shape that supports the polygon mirror 2, and these mounting peripheral surface 31a2 and mounting bottom surface A substantially planar heptagonal polygon mirror 2 made of metal such as aluminum or aluminum alloy is attached to the polygon mirror mounting portion 31a1 made of 31a3.

A central hole 22 is formed at the center of the polygon mirror 2, and seven reflecting surfaces 21 are formed on the outer peripheral surface of the polygon mirror 2. The reflecting surface 21 reflects laser light, and all the seven reflecting surfaces 21 are finished with extremely high accuracy so as to have the same reflection angle.

The center hole 22 formed in the central portion of the polygon mirror 2 is in contact with the mounting peripheral surface 31a2 of the rotating pedestal portion 31a or fitted with an appropriate gap. Further, the lower end surface of the polygon mirror 2 is in axial contact with the mounting bottom surface 31 a 3, and the upper end surface of the polygon mirror 2 is brought into contact with the mounting bottom surface 31 a 3 by the axial pressing force of the mirror pressing member 23. It is fixed so that it can be pressed against.

(Configuration of cover member)
Next, the cover member 4 according to the embodiment of the present invention will be described with reference to FIG. 1 (a), FIG. 1 (b) and FIG.
FIG. 3 is a cross-sectional view of the cover member 4 taken along the chain line AA ′ in FIG.

In this embodiment, the cover member 4 covers the polygon mirror 2 and the motor 3 to prevent windage damage and protect from dust, and is used to install the polygon mirror 2 and the motor 3.

The cover member 4 is formed from a metal such as aluminum or an aluminum alloy, and the entire inner peripheral surface of the cover member 4 is coated with an adhesive material. This adhesive material is for adsorbing dust such as aluminum powder generated by the rotation of the polygon mirror 2 to prevent the reflection surface 21 (mirror surface) of the polygon mirror 2 from being damaged.

The cover member 4 has an opening 41 for entering and exiting the laser beam located on the optical path, and a cylindrical portion 42 that covers the outer periphery of the polygon mirror 2 and a lid portion 43 that covers the upper surface of the polygon mirror are separated. Constructed in the body.
Three screw holes 42b are formed at equal intervals on the top portion 42a of the cylindrical portion 42, and the lid portion 43 is formed integrally with the cylindrical portion 42 using the screws 42b1 through the screw holes 42b. ing.

An opening 41 for entering and exiting the laser beam is formed in the standing wall portion 42c of the cylindrical portion 42, and a protruding portion 44 protruding so as to surround the outer periphery of the opening 41 is formed on the outer peripheral surface of the standing wall portion 42c. The glass plate 45 is fixed to the outer peripheral surface of the projecting portion 44 with an adhesive or the like.

Reference numeral 46 denotes a flange portion for installing the motor 3 to which the polygon mirror 2 is fixed using the screw 46 a 1 in the cover member 4. In the present embodiment, three screw holes 46 a are formed at equal intervals in the flange portion 46, and the frame 7 to which the motor 3 is attached is fixed integrally with the cover member 4 using the screws 46 a 1.

A projecting portion 44 projecting so as to surround the outer periphery of the opening 41 is formed with a deformed space 47 having a triangular shape. Therefore, the air generated with the rotation of the polygon mirror 2 enters the deformed space 47 formed in the projecting portion 44, and an uneven air flow occurs in the circumferential direction of the rotation of the polygon mirror 2. .
For this reason, the air rectifying member 6 is provided in the cover member 4 in order to adjust the air flow that is not uniform in the circumferential direction of the rotation of the polygon mirror 2 in the cover member 4 to a good air flow.
The air rectifying member 6 has a substantially quadrangular protrusion shape, and the air rectifying member 6 entirely faces the laser light incident / exit opening 41 of the cylindrical portion 42, and the rotation direction of the polygon mirror 2 (the center of FIG. 3). It is located at the front end 48 in the direction of the arrow and is provided on the flange 46 so as to face the lower surface of the polygon mirror 2.
Since the air rectifying member 6 is integrally formed when the cylindrical portion 42 of the cover member 4 is molded, the air rectifying member 6 can be easily formed, and the air rectifying member 6 can be formed at an appropriate position. It is.

Furthermore, the cover member 4 is formed to have substantially the same space on the upper side and the lower side of the polygon mirror 2 installed in the cover member 4.

The size of the air rectifying member 6 in the present embodiment is about 1/6 the size of the opening length in the circumferential direction of the inner peripheral surface of the opening 41, and the air rectifying member 6 is formed to be approximately the same as the width of the flange 46, and the height of the air rectifying member 6 is such that it does not extend from the flange 46 to the opening 41.
In the present embodiment, the air rectifying member 6 is integrally formed when the cylindrical portion 42 of the cover member 4 is molded as described above, but is not formed integrally with the cylindrical portion 42 and is separately provided. Then, it may be fixed to the flange portion 46 of the cylindrical portion 42 using a screw, an adhesive, or the like.
In the present embodiment, the air rectifying member 6 has a substantially quadrangular protrusion, but may have various protrusions such as a plate or a triangle. In other words, any shape may be used as long as the air flow that has become non-uniform in the circumferential direction of rotation of the polygon mirror 2 with the rotation of the polygon mirror 2 is adjusted to a good air flow.

Next, with reference to FIG. 4A and FIG. 4B, an experiment regarding the surface tilt of the polygon mirror 2 in the present embodiment will be described.

FIG. 4A is a graph obtained by measuring the surface tilt of the polygon mirror 2 when the air rectifying member 6 is not provided on the cover member 4.
FIG. 4B shows that the air rectifying member 6 having a protruding shape is provided on the flange portion 46 at one end 48 in the rotational direction of the polygon mirror 2 in the laser light incident / exit opening 41 of the cover member 4. It is the graph which measured the surface tilt of the polygon mirror 2 in the case of.

As shown in FIG. 4A, in the case where the air rectifying member 6 is not provided on the cover member 4, when the surface tilt of the polygon mirror 2 is continuously measured over a certain number of times, the number of seconds of the surface tilt is positive. It can be seen that there is a large error between the sides and the minus side, which is not stable and has a large error.

On the other hand, as shown in FIG. 4 (b), an air rectifying member formed in a protruding shape on the flange portion 46 at the distal end 48 in the rotational direction of the polygon mirror 2 in the laser light incident / exit opening 41 of the cover member 4. In the case where 6 is provided at one place, when the surface tilt of the polygon mirror 2 is continuously measured over a certain number of times, the number of seconds for the surface tilt is negative and negative compared to the graph shown in FIG. It can be seen that it is stable, not shaking sideways. That is, it can be seen that the error of the tilting is small.

Thus, by providing the air rectifying member 6 having a protruding shape on the flange portion 46 at one end 48 in the rotation direction of the polygon mirror 2 in the laser light incident / exit opening 41 of the cover member 4, Compared to the case where the air rectifying member 6 is not provided in the cover member 4, it was confirmed that the error of the surface tilt of the polygon mirror 2 can be reduced.
That is, in the deformed space 47 formed in the projecting portion 44 of the cover member 4, the air flow that has become non-uniform in the circumferential direction of the rotation of the polygon mirror 2 is efficiently and effectively adjusted to a good air flow. As a result, the movement of the rotor 31 supporting the polygon mirror 2 in the axial direction (vertical direction), the movement in the circumferential direction, and the swinging can be suppressed, and deterioration of the surface tilt of the polygon mirror 2 can be prevented. This was confirmed by this experiment.

(Main effects of this form)
In the polygon mirror rotation driving device 1 of the present embodiment, the air rectification is formed in a protruding shape at the flange portion 46 at the front end 48 in the rotation direction of the polygon mirror 2 in the laser light incident / exit opening 41 of the cover member 4. When the member 6 is formed and provided at a position facing the lower surface of the polygon mirror 2, air that has become uneven in the circumferential direction of rotation of the polygon mirror 2 in the deformed space 47 formed in the projecting portion 44. The flow can be efficiently and effectively adjusted to a good air flow, and the movement of the rotor 31 supporting the polygon mirror 2 in the axial direction (vertical direction) and the movement and swing in the circumferential direction are suppressed, and the polygon It is possible to prevent the mirror 2 from falling down.

(Other embodiments)
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the embodiment described above, the air rectifying member 6 is formed in the flange portion 46 formed in the cylindrical portion 42 of the cover member 4, but the air rectifying member 6 may be formed in the lid portion 43.
In this case, it is preferable that the air rectifying member 6 is also provided in the lid portion 43 at the front end side end portion 48 in the rotation direction of the polygon mirror-2 in the laser light incident / exit opening portion 41 of the cover member 4.

Moreover, in the form mentioned above, although the air rectification member 6 is provided only in one place, you may provide in several places. Furthermore, the air rectifying member 6 may be provided on both the cylindrical portion 42 and the lid portion 43. In short, the air rectifying member 6 is arranged at a necessary position so that the air flow that becomes non-uniform in the circumferential direction of the rotation of the polygon mirror 2 during the rotation of the polygon mirror 2 can be adjusted to a good air flow. Just do it.

Fig.1 (a) is a top view which shows the polygon mirror rotational drive apparatus concerning embodiment of this invention. FIG.1 (b) is explanatory drawing cut | disconnected along the chain line EOH of FIG. 1 (a). It is explanatory drawing which shows the principal part of the motor 3 shown in FIG.1 (b). It is sectional drawing of the cover member 4 at the time of cut | disconnecting by the dashed line A-A 'of FIG.1 (b). FIG. 4A is a graph obtained by measuring the surface tilt of the polygon mirror when the air rectifying member is not provided on the cover member. FIG. 4B shows a polygon mirror in the case where one air rectifying member having a protruding shape is provided on the flange portion at the tip end side in the rotation direction of the polygon mirror in the laser light incident / exit opening of the cover member. It is the graph which measured the surface inclination of.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polygon mirror rotation drive device 2 Polygon mirror 3 Motor 31 Rotor 32 Fixed shaft 33 Core holder 34 Stator core 35 Drive coil 4 Cover member 41 Opening part 42 Cylindrical part 43 Lid part 44 Projection part 46 Flange part 47 Deformed space 48 Polygon mirror rotation End 5 in the direction 5 substrate 6 air rectifying member

Claims (2)

In a polygon mirror rotation driving device comprising a polygon mirror, a rotor that supports the polygon mirror, a motor that rotationally drives the rotor, and a cover member that covers the polygon mirror having an opening for emitting and emitting laser light,
The cover member includes a projecting portion projecting so as to surround the periphery of the opening,
The polygon mirror rotation driving device characterized in that the air rectifying member is formed at a tip side end portion in the rotation direction of the polygon mirror in the opening. 2. The cover member according to claim 1, wherein the cover member includes a cylindrical portion that covers an outer periphery of the polygon mirror and has the protruding portion and the opening, and a lid portion that covers an upper surface of the polygon mirror. Polygon mirror rotation drive device.

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