JP2005121692A - Light-deflecting device, image forming apparatus and method for manufacturing the light deflecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-deflecting device from which ample durability can be obtained by allowing the rotational speed of a polygon mirror to be ultra-high rotational speed of 50,000 rpm, and preventing shifting of the polygon mirror. <P>SOLUTION: The optical polarizing device comprises a base member, the polygon mirror formed into a regular polygon and having a reflecting face on each circumference, a flange member holding the polygon mirror to be rotated with respect to the base member, and a pushing member pushing the polygon mirror on the flange member. The polygon mirror is previously pushed against the flange member by a pushing force which is stronger than the pushing force pushed against the flange member by the pushing member, and then the pushing member is pushed and held. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a digital copying machine, a printer, a facsimile, an image forming apparatus such as a multifunction machine having these functions, a light polarizing device used for a barcode reader, and the like, an image forming apparatus provided with the light polarizing device, In addition, the present invention relates to a method for manufacturing an optical polarization device.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a laser beam printer or a digital copying machine, a light polarization device that performs a light beam operation is used to write an image on a photosensitive drum. In such a light polarization device, laser light is incident on a polygon mirror that rotates at high speed in the light polarization device based on the read information, and the reflected light is scanned and projected onto a photoconductor to perform image recording. A number of patent publications disclose light polarizing devices using such polygon mirrors. As an example of this, there is an optical polarization device shown in FIG. (See Patent Document 1)
Below, with reference to FIG. 6, the optical polarization apparatus of patent document 1 is demonstrated.

  A polygon mirror 72 provided with a reflecting surface 72 a for reflecting and polarizing laser light on the outer peripheral surface formed in a regular polygon is inserted into a flange member 71 integrated with an outer cylindrical bearing 73, and a pressing plate 75. The mirror unit 70 is formed by being pressed by the leaf spring 74 supported by the flange member 71 and held and integrated with the flange member 71. On the other hand, an inner cylinder bearing 65 that fits in the radial direction with the outer cylinder bearing 73, an upper thrust bearing 66 that contacts the outer cylinder bearing 73 in the thrust direction, and a lower thrust bearing 64 are inserted into the base member 60. It is positioned in the thrust direction by a fixing plate 67 fixed by screws 68. A fixed yoke 61 is fixed to the base member 60, and a printed wiring board 63 on which a magnet coil 62 is further fixed. On the other hand, a magnet 77 facing the magnet coil 62 is fixed to the flange member 71.

  Accordingly, when the magnet coil 62 is energized, the mirror unit 70 rotates at high speed with respect to the base member 60 via the bearings due to the interaction with the magnet 77.

  Here, although the polygon mirror 72 is held by the holding surface 71c of the flange member 71 at the held surface 72b (processing reference surface), the held surface 72b has an excellent tilt angle of the reflecting surface 72a of the polygon mirror 72. In order to obtain a value, it is necessary to perform machining with high accuracy, and conventionally, machining is performed so that the surface roughness (Ry) of the holding surface 71c and the held surface 72b is a mirror surface of 1 μm or less. However, when the polygon mirror 72 and the flange member 71 are fixed by bringing the holding surface 71c and the holding surface 72b thus mirror-finished into contact with each other, the gap between the inner diameter of the polygon mirror 72 and the outer diameter of the flange member 71 is between. Since there is a gap for inserting and assembling, the polygon mirror 72 is displaced by centrifugal force due to high-speed rotation, and when the mirror unit 70 rotates, there is a possibility that the balance is deteriorated and vibration is increased.

Therefore, in Patent Document 1, surface treatment is performed so that the surface roughness (Ry) of one or both of the holding surface 71c and the held surface 72b is 3 μm ≦ Ry ≦ 20 μm. Ry is the maximum height defined by JISB0601. With this configuration, even if a centrifugal force acts on the polygon mirror 72 when rotating at a high speed, the polygon mirror 72 is not easily displaced due to the frictional force generated between the holding surface 71c and the held surface 72b, which is unnecessary. No longer vibrates.
JP 2002-48997 A

  In recent years, high-speed and high-precision image recording has been demanded. For this reason, it has become necessary to rotate the polygon mirror at a higher speed. Even when the rotation speed of the polygon mirror is 50,000 or higher, it is required that the polygon mirror does not shift and has sufficient durability.

  In this respect, in the invention described in Patent Document 1, the polygon mirror can be prevented from shifting up to about 50,000 rpm, but if it exceeds 50,000 rpm, the polygon mirror may be displaced. It was found by the inventors' investigation.

  In recent years, durability of about several thousand hours to 10,000 hours is required. However, the invention described in Patent Document 1 is insufficient in this respect as well.

  On the other hand, in order to prevent the polygon mirror from shifting, it is necessary to increase the frictional force between the holding surface 71c and the held surface 72b shown in FIG. 5, and for this reason, the pressing force by the leaf spring 74 can be increased. Conceivable. However, it has been found by the inventors that when the pressing force exceeds 150 N, the reflection surface of the polygon mirror is distorted and the image recorded on the photosensitive drum is deteriorated. In order to prevent the image from deteriorating, the flatness of the reflecting surface of the polygon mirror needs to be better than λ / 4 (λ = 633 nm).

  The present invention has been made in view of such problems, and prevents the polygon mirror from shifting even when the rotation speed of the polygon mirror is 50,000 rpm or higher and durability of several thousand hours is required. An object of the present invention is to propose a light polarizing device, an image forming device, and a method for manufacturing the light polarizing device that can be used and have sufficient durability.

The above object can be achieved by any of the following means.
(1) a base member, a polygon mirror formed in a regular polygon and having a reflecting surface on each peripheral surface, a flange member that holds the polygon mirror and rotates with respect to the base member, and the polygon mirror In the optical polarization device provided with a pressing member that presses against the flange member, the polygon mirror is previously pressed against the flange member with a pressing force stronger than the pressing force pressed against the flange member by the pressing member, A light polarization device, which is pressed and held by the pressing member.
(2) a base member, a polygon mirror formed in a regular polygon and having a reflecting surface on each peripheral surface, a flange member that holds the polygon mirror and rotates with respect to the base member, and the polygon mirror And a pressing member that presses the flange member, and a step of mounting the polygon mirror on the flange member, and a pressing force by which the pressing member presses the polygon mirror against the flange member. A method of manufacturing an optical polarizing device, comprising: pressing the polygon mirror against the flange member with a strong pressing force; and pressing and holding the polygon mirror against the flange member with the pressing member.

  According to the method of manufacturing the optical polarizing device of claim 1 and the optical polarizing device of claim 6, the polygon mirror and the flange member slightly bite into close contact with each other, so that the rotational speed of the polygon mirror is 50,000 rpm or higher. Even if the rotation is required and durability for several thousand hours is required, the polygon mirror can be prevented from shifting. Further, even if the polygon mirror is temporarily pressed strongly, it is pressed with a weaker pressing force after assembly, so that the flatness of the reflecting surface of the polygon mirror is maintained well.

  According to the manufacturing method of the light polarizing device of claim 2 and the light polarizing device of claim 7, the amount of biting between the polygon mirror and the flange member is increased by the rough surface processing, and thus the above effect is further increased.

  According to the manufacturing method of the light polarizing device of claims 3 and 4, and the method of manufacturing the light polarizing device of claims 8 and 9, since the film thickness of the adhesive is reduced, the deviation of the polygon mirror caused by the creep phenomenon of the adhesive is smaller. Become.

  According to the image forming apparatus of the fifth aspect, the above effects can be achieved.

  First, an embodiment of a beam scanning optical device having an optical polarization device will be described with reference to FIG.

  In FIG. 1, 1 is an optical polarization device provided with a polygon mirror 1a, 2 is a semiconductor laser, 3 is a collimator lens of a beam shaping optical system, 4 is a first cylindrical lens, 5 and 6 are fθ lenses, and 7 is a second lens. A cylindrical lens, 8 is a mirror, 9 is a cover glass, and 10 is a photosensitive drum. Reference numeral 11 is an index mirror for synchronization detection, and 12 is an index sensor for synchronization detection.

  Beam light emitted from the semiconductor laser 2 is converted into parallel light by the collimator lens 3, passes through the first cylindrical lens 4 of the first imaging optical system, and is reflected on the reflecting surface of the polygon mirror 1 a that rotates at a constant speed in the optical polarization device 1. Is incident on. The reflected light reflected by the reflecting surface of the polygon mirror 1 a passes through the second imaging optical system including the fθ lenses 5 and 6 and the second cylindrical lens 7, and passes around the photosensitive drum 10 via the mirror 8 and the cover glass 9. Main scanning is performed on the surface with a predetermined spot diameter. The main scanning direction is finely adjusted by an adjustment mechanism (not shown), and synchronization detection for each line is performed by making a beam before the start of scanning enter the index sensor 12 via the index mirror 11.

  In such a beam scanning optical device, in order to obtain a good latent image on the photosensitive drum 10, the polygon mirror 1a is formed in a regular polygon and has a plurality of high-precision reflecting surfaces, and is provided on the rotation axis. On the other hand, it is required to rotate at high speed with no inclination and no positional deviation in the direction of the rotation axis.

  Next, the optical polarization device mounted on the beam scanning optical device will be described in detail with reference to FIG. FIG. 2 is a longitudinal sectional view of the light polarization device.

  Reference numeral 20 denotes a base member, which is formed of a metal such as aluminum, holds each member to be described later, and is fixed to the beam scanning optical device described above. A fixed yoke 21 is fixed to the upper surface of the base member 20, and a printed wiring board 23 having a plurality of magnet coils 22 arranged on the same surface is fixed.

  Reference numeral 31 denotes a flange member, which is made of aluminum, brass, stainless steel, or the like, and includes a disc-shaped flange 31a and a cylindrical cylindrical portion 31b. A holding surface 31c that holds the polygon mirror 32 on the lower surface of the flange 31a. have. And the outer cylinder bearing 33 is inserted into the hole provided in the center of the cylindrical part 31b in the flange member 31 by shrink fitting or press fitting, and integrated.

  The polygon mirror 32 is formed into a highly accurate regular polygon using a metal such as aluminum, and has a reflecting surface 32a for reflecting and polarizing laser light on each peripheral surface. The polygon mirror 32 is inserted into the outer peripheral portion of the cylindrical portion 31b of the flange member 31, and the held surface 32b of the polygon mirror 32 is brought into contact with the holding surface 31c. The held surface 32b of the polygon mirror 32 is also a reference surface for processing the reflecting surface 32a, and is mirror-finished.

  Subsequently, a plate spring 34 (pressing member) formed by pressing a stainless steel plate, a phosphor bronze steel plate or a beryllium steel plate is inserted into the outer peripheral portion of the cylindrical portion 31 b, and the mirror pressing plate 35 is attached to the flange member 31 by a small screw 36. Fastened and fixed to the cylindrical portion 31b. As a result, the leaf spring 34 presses the polygon mirror 32 and the held surface 32b of the polygon mirror 32 is pressed against the holding surface 31c of the flange member 31, but no excessive stress is applied to the polygon mirror 32. The deformation of the polygon mirror 32 is prevented.

  In addition, a permanent magnet 37 that opposes the magnet coil 22 and generates rotational torque is bonded to the lower portion of the mirror pressing plate 35 with an adhesive.

  Thus, the mirror unit 30 is constituted by the flange member 31, the polygon mirror 32, the outer cylinder bearing 33, the leaf spring 34, the mirror pressing plate 35, the machine screw 36, and the permanent magnet 37.

  On the other hand, a shaft portion 20a is erected at the center of the base member 20, and the lower thrust bearing 24 is fitted into the shaft portion 20a, and the inner cylinder bearing 25 is further fitted. Subsequently, the outer cylinder bearing 33 of the mirror unit 30 is fitted into the inner cylinder bearing 25, the upper thrust bearing 26 is fitted into the shaft portion 20a, and the machine screw 28 penetrating the plate 27 is screwed to the shaft portion 20a. Fix it. The inner cylinder bearing 25, the outer cylinder bearing 33, the lower thrust bearing 24, and the upper thrust bearing 26 are made of ceramic such as alumina or silicon nitride.

  In this manner, the outer cylindrical bearing 33 that holds the mirror unit 30 is formed with a radial bearing by the inner cylindrical bearing 25 and is subjected to radial dynamic pressure rotation, and a thrust bearing is formed by the lower thrust bearing 24 and the upper thrust bearing 26. Then, thrust dynamic pressure rotation is performed. A dynamic pressure generating groove is formed on at least one of the bearing surface of the lower thrust bearing 24, the bearing surface of the upper thrust bearing 26, or the outer peripheral surface of the inner cylindrical bearing 25. For this reason, wind generated by high-speed rotation flows into the dynamic pressure generating groove, and a gap of about 3 to 10 μm is provided between each bearing fixed by the strong wind pressure generated in the dynamic pressure generating groove and the outer cylindrical bearing 33. Since the resistance between the two is reduced, the mirror unit 30 is in a non-contact state and can smoothly rotate at a high speed.

  Although the light polarization device is formed as described above, since the mirror unit 30 rotates at a high speed, an annoying wind noise due to the turbulence of the air current and noise due to vibration are generated. In particular, in offices where quietness is required, countermeasures for noise reduction are necessary. Therefore, it is desirable to provide a cover facing the base member 20 to cover the mirror unit 30 and the like.

  Next, the manufacturing method of the mirror unit 30 is demonstrated with reference to FIG.3 and FIG.4. 3 is an enlarged view of the mirror unit 30, and FIG. 4 is a side view of the hand press. 3 is upside down with respect to the mirror unit 30 of FIG. 2, and only the right half is depicted.

  First, the outer cylinder bearing 33 is mirror-finished so that the upper end surface 33a and the lower end surface 33b are perpendicular to the central axis, and the inner peripheral surface 33c and the outer peripheral surface 33d are concentric with the central axis. Mirror finish so that The outer cylindrical bearing 33 is fitted into the center hole of the flange member 31, and both are integrated by shrink fitting, press fitting or adhesion.

  Next, the holding surface 31c of the flange member 31 is planarized so as to be parallel to the upper end surface 33a and the lower end surface 33b with reference to the upper end surface 33a or the lower end surface 33b of the outer cylinder bearing 33. Thereby, the holding surface 31c perpendicular to the rotating shaft of the outer cylinder bearing 33 is obtained.

  Subsequently, the polygon mirror 32 is inserted into the cylindrical portion 31b of the flange member 31, and the integrated outer cylindrical bearing 33, the polygon mirror 32, and the flange member 31 are mounted on the cradle 51a of the hand press 51 shown in FIG. Put. Further, a polygon mirror pressing member 52 is placed on the polygon mirror 32. When the grip 51b of the hand press 51 is gripped and rotated downward, the drive unit 51c is lowered to press the polygon mirror pressing member 52, so that the polygon mirror 32 is flanged by the polygon mirror pressing member 52. Pressed by the member 31. Then, the held surface 32b of the polygon mirror 32 is pressure-bonded to the holding surface 31c of the flange member 31, and the held surface 32b slightly bites into the holding surface 31c due to minute irregularities on both surfaces.

  Here, since the polygon mirror pressing member 52 has a built-in pressure sensor such as a strain gauge, the pressing force can be converted and read by the connected voltmeter 53. This pressing force is desirably 150 N to 300 N, and needs to be stronger than the pressing force of the leaf spring 34 after assembly.

  Finally, the plate spring 34 is inserted into the cylindrical portion 31 b of the flange member 31, and the mirror pressing plate 35 is fastened and fixed to the cylindrical portion 31 b of the flange member 31 with the small screw 36. Note that the pressing force of the leaf spring 34 at this time is desirably 70 N to 100 N.

  Note that if the holding surface 31c is processed into a rough surface by masking other than the holding surface 31c of the flange member 31, the held surface 32b of the polygon mirror 32 is deeper than the holding surface 31c by the hand press 51. I will bite in. Furthermore, by using the rough surface processing and adhesion together, there are further effects due to uneven recesses on the surface of each member and adhesion fixing of slight gaps.

  Here, Table 1 shows experimental data when the polygon mirror 32 is not pressed against the flange member 31 and when it is pressed.

  In this experiment, the holding surface 31c of the flange member 31 is blasted.

  The flatness of the reflecting surface is the worst value among the six reflecting surfaces, and λ is 633 nm.

Thickness after assembly, a thickness of the flange member 31 and the polygon mirror 32 after assembly corresponds to T in FIG. 3, the thickness of the pre-assembly, the thickness T ₂ of the thickness T ₁ and the flange member 31 of the polygon mirror 32 Is a value obtained by measuring each of them independently before assembly.

  The amount of change in the running vibration value is the difference between the horizontal vibration value immediately after the start of the experiment and the horizontal vibration value when the polygon mirror 34 is rotated at 55,000 rpm for 3,600 hours.

  According to Table 1, in Experiments 1 and 2, there is no difference in the flatness of the reflection surface 32 a of the polygon mirror 32, but a large difference occurs in the amount of change in the running vibration value. It can be seen that the durability is increased by pressing the polygon mirror 32 against the flange member 31 in advance with a force stronger than the pressing force.

  In addition, an adhesive layer is provided by applying an adhesive between the holding surface 31c and the held surface 32b of the polygon mirror 32 without subjecting the holding surface 31c of the flange member 31 to blasting. The polygon mirror 55 may be pressed against the flange member 31.

  Table 2 shows experimental data obtained in this manner.

  In Table 2, the flatness of the reflecting surface is the worst value among the six reflecting surfaces, and λ is 633 nm.

  As the adhesive, Cemedine Super X was used.

The thickness of the adhesive is the thickness of the flange member 31 and the polygon mirror 32 (corresponding to T in FIG. 3) measured after the assembly and the adhesive is cured, and the thickness of the polygon mirror 32 before assembly (T _{1 in} FIG. 3). And the thickness of the flange member 31 (corresponding to T ₂ ) measured individually and summed.

  The amount of change in the running vibration value is the difference between the horizontal vibration value immediately after the start of the experiment and the horizontal vibration value when the polygon mirror is rotated at 55,000 rpm for 3,600 hours.

  According to Table 2, in Experiments 1 to 3, there is no difference in the flatness of the reflecting surface 32a of the polygon mirror 32. However, if the pressing force of the leaf spring 34 is increased as in Experiment 4, the flatness of the reflecting surface 32a is deteriorated. I understand that. The flatness of the reflecting surface 32a needs to be better than λ / 4.

  Further, there is a large difference in the amount of change in running vibration value between Experiment 1 and Experiments 2 and 3, and the polygon mirror 32 is pressed against the flange member 31 in advance with a force stronger than the pressing force of the leaf spring 34 using the hand press 51. It can be seen that the durability is increased. In Experiment 4, since the flatness was poor, no running vibration was performed.

  Further, in Experiments 2 and 3, since the adhesive film thickness is reduced, the polygon mirror shift due to the adhesive creep phenomenon becomes smaller.

  In addition, the holding surface 31c of the flange member 31 may be roughened and an adhesive may be applied between the holding surface 31c and the held surface 32b. By doing in this way, durability will increase further by the biting of the unevenness | corrugation of the surface of each member, and the adhesion fixation of a few space | gap.

  Note that the light polarization device in the present invention is not necessarily in the form shown in FIGS. 2 and 3, and may be in the form shown in FIG.

  In FIG. 5, the polygon mirror 82 is pressed against the flange member 81 by a leaf spring 84 whose inner diameter is engaged with the cylindrical portion 81 b of the flange member 81.

It is a figure of the beam scanning optical apparatus which has an optical polarization apparatus. It is a longitudinal cross-sectional view of a light polarizing device. It is an enlarged view of a mirror unit. It is a side view of a hand press. It is a figure of the other form of a light-polarizing device. It is a figure of the conventional light polarizing device.

Explanation of symbols

1 Optical polarization device 1a, 32, 72, 82 Polygon mirror 30 Mirror unit 31, 71, 81 Flange member 31c, 71c Holding surface 32a, 72a Reflecting surface 32b, 72b Held surface 33, 73 Outer cylinder bearings 34, 74, 84 Leaf spring 51 hand press

Claims (9)

A base member;
A polygon mirror formed in a regular polygon and having a reflecting surface on each peripheral surface;
A flange member that holds the polygon mirror and rotates with respect to the base member;
A pressing member that presses the polygon mirror against the flange member;
In an optical polarization device comprising:
The polygonal mirror is pressed and held by the pressing member after being pressed against the flange member in advance by a pressing force stronger than the pressing force pressed against the flange member by the pressing member. apparatus. The light polarizing device according to claim 1, wherein a contact surface of the flange member that contacts the polygon mirror is roughened. The light polarizing device according to claim 1, wherein an adhesive layer is provided on a contact surface between the polygon mirror and the flange member. 2. The contact surface of the flange member that contacts the polygon mirror is roughened, and an adhesive layer is provided on the contact surface of the polygon mirror and the flange member. The light polarizing device according to 1. An image forming apparatus comprising the light polarizing device according to claim 1. A base member;
A polygon mirror formed in a regular polygon and having a reflecting surface on each peripheral surface;
A flange member that holds the polygon mirror and rotates with respect to the base member;
A pressing member that presses the polygon mirror against the flange member;
In the manufacturing method of the optical polarization device provided with
Attaching the polygon mirror to the flange member;
The pressing member pressing the polygon mirror against the flange member with a pressing force stronger than the pressing force pressing the polygon mirror against the flange member;
And a step of pressing and holding the polygon mirror against the flange member by the pressing member. The method of manufacturing a light polarizing device according to claim 6, further comprising a step of roughening a contact surface of the flange member that contacts the polygon mirror. The method of manufacturing a light polarizing device according to claim 6, further comprising a step of providing an adhesive layer on a contact surface between the polygon mirror and the flange member. Roughening the contact surface of the flange member that contacts the polygon mirror;
Providing an adhesive layer on the contact surface between the polygon mirror and the flange member;
The manufacturing method of the optical polarizing device of Claim 6 characterized by the above-mentioned.

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