JP2007025052A - Scanning optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and compact scanning optical apparatus in which vibration is reduced. <P>SOLUTION: The scanning optical apparatus includes: a light source unit which emits a light beam; a rotary polygon mirror which deflects and scans the light beam from the light source unit; a driving means which supports the rotary polygon mirror and rotationally drive it; an imaging means which provides the image of the light beam from the rotary polygon mirror on a photoreceptor; an optical box which supports the light source unit, the driving means and the imaging means. The leg parts of the optical box are fixed on a frame of the image forming apparatus. The scanning optical apparatus is mounted on the image forming apparatus with a viscoelastic body inserted between at least one of the leg parts of the scanning optical apparatus and the frame. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning optical device provided in an image forming apparatus such as a laser beam printer or a digital copying machine.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic method, a latent image is formed on a charged photosensitive member by exposing and scanning a light beam corresponding to image information with a scanning optical device, and developing the latent image. An image is formed by transferring an image onto a sheet.

  In this exposure scanning, the rotary polygon mirror is rotationally driven to deflect and scan the light beam. However, this rotational driving generates vibration, which adversely affects images and noise.

  Conventional techniques for solving such problems include those in which the leg of the scanning optical device is fixed to the device main body via a spherical surface or an elastic body (see Patent Document 1), and vibration in the scanning optical device. There is one provided with a dynamic vibration absorber (see Patent Document 2).

  Hereinafter, conventional vibration reduction techniques will be described.

In the scanning optical device disclosed in Patent Document 1, as shown in FIG. 9, the leg portion of the scanning optical device is made spherical or an elastic member is used to reduce vibration. In the scanning optical device disclosed in Patent Document 2, as shown in FIG. 10, a dynamic vibration absorber is attached to the scanning optical device to reduce vibration.
JP 2000-249955 A (No. 4, FIG. 2, FIG. 3) Japanese Patent No. 3184370 (Section 3, FIGS. 1 to 4)

  However, the scanning optical device disclosed in Patent Document 1 has the following problems.

  That is, the leg of the scanning optical device is made spherical or an elastic body is sandwiched, but a screw is used to fix the scanning optical device, and vibration is transmitted from the screw to the device main body. The vibration transmitted to the frame or the like is not reduced, and the vibration of the scanning optical device itself is not reduced.

  On the other hand, the scanning optical device disclosed in Patent Document 2 has the following problems.

  That is, vibration is reduced by providing a separate weight for attaching the dynamic vibration absorber to the scanning optical device. However, a place for the attachment is required, and the cost increases.

  Moreover, although vibration is reduced by the dynamic vibration absorber, the attachment direction of the viscoelastic body and the weight is parallel to the direction of vibration, and the efficiency of vibration reduction by the viscoelastic body is deteriorated.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a scanning optical device that can reduce vibration at low cost without taking up space.

In order to achieve the above object, the invention according to claim 1
A light source unit that emits a light beam;
A rotary polygon mirror that deflects and scans the light beam from the light source unit;
Driving means for supporting and rotating the rotary polygon mirror;
Imaging means for forming an image of the light beam from the rotary polygon mirror on the photosensitive member;
An optical box for holding the light source unit, the driving means, and the imaging means;
A scanning optical device comprising: a leg portion of the optical box fixed to a frame of the image forming apparatus;
The scanning optical device is attached to the image forming apparatus via a viscoelastic body between at least one leg portion and the frame.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the viscoelastic body is attached so that a shearing force acts on the viscoelastic body in a direction in which the rigidity of the frame is weak. To do.

  According to a third aspect of the present invention, in the first aspect of the present invention, the leg portion is in pressure contact with the frame through the viscoelastic member.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, at least one of the leg portions attached to the frame via the viscoelastic body is located closest to the deflector.

  The invention according to claim 5 is the invention according to claim 3, wherein the pressing direction is a direction perpendicular to a direction in which a shearing force acts on the viscoelastic member.

  According to the first aspect of the present invention, the vibration optical energy is converted into thermal energy by attaching the scanning optical device to the image forming apparatus via the viscoelastic body between the leg portion of the optical box and the frame of the image forming apparatus. The vibration that is converted and transmitted to the image forming apparatus can be reduced, and the vibration of the scanning optical device itself can also be reduced.

  According to the second aspect of the present invention, the vibration in the direction in which the rigidity of the frame is weak can be efficiently reduced by attaching the viscoelastic body so that the shearing force acts in the direction in which the rigidity of the frame is weak.

  According to invention of Claim 3, a vibration becomes difficult to be transmitted to a flame | frame by pressing a leg part to a flame | frame via a viscoelastic body.

  According to the fourth aspect of the present invention, since the attachment portion in the vicinity of the deflector which is the vibration source of the scanning optical device is most easily transmitted to the frame, the vibration transmitted to the frame can be effectively reduced.

  According to the fifth aspect of the present invention, the force for fixing the scanning optical device to the frame can be efficiently transmitted to the viscoelastic body by setting the pressure contact direction to a direction perpendicular to the direction in which the shearing force acts on the viscoelastic body. This improves the efficiency of vibration reduction.

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

  FIG. 7 is a diagram showing an image forming apparatus according to an embodiment of the present invention. In the figure, reference numeral 101 denotes a scanning optical device having a configuration described later, and reference numeral 102 denotes a photosensitive drum as an image carrier. In the present embodiment, a light beam (laser beam) L that is light-modulated based on image information is emitted from the scanning optical device 101 and irradiated onto the surface of the photosensitive drum 102 to form a latent image. This latent image is formed on the surface of the photosensitive drum 102 that is uniformly charged by the charger 103, visualized as an image by the developing device 104, and transferred to the transfer material P conveyed by the transfer roller 105. An image is formed by electrostatic transfer.

  Thereafter, the residual toner remaining on the surface of the photosensitive drum 102 is removed by the cleaner 106 and is uniformly charged again by the charger 103 to form the next image. The transfer material P is stacked on the paper feed tray 107, fed one by one by the paper feed roller 108, and sent to the transfer roller 105 by the registration roller 109 in synchronization with the image writing timing. .

  The toner is transferred onto the transfer material P by the transfer roller 105 to form an image. The image formed on the transfer material P is heat-fixed by the fixing device 110 and then conveyed by the paper discharge roller 111 or the like and output to the outside of the image forming apparatus.

  FIG. 8 is a diagram illustrating the configuration of the scanning optical device 101 according to the present embodiment.

  In FIG. 8, 131 is a laser unit in which a semiconductor laser as a light source, a semiconductor laser driving circuit, and a collimator lens that converts emitted light from the semiconductor laser into parallel light are integrated, and 132 is a cylindrical that has power only in the sub-scanning direction. A lens, 133 is a scanner motor unit for deflecting and scanning the laser light, 134 is an fθ lens for making the scanning light scanning speed constant on the photosensitive drum surface, and 135 is a constant image writing position. , A synchronous folding mirror for guiding a laser beam to the synchronous sensor, 137 an optical box for holding these optical elements, and 137a an exit window for emitting the laser beam from the inside of the optical box , 101a, 101b, 101c are for attaching the scanning optical device to the image forming apparatus. It is a part.

  FIG. 1 is a diagram illustrating a configuration of a portion for attaching a scanning optical device 101 according to the present embodiment to an image forming apparatus.

  In FIG. 1, 1a, 1b, and 1c are viscoelastic bodies, 2a, 2b, and 2c are frames of the image forming apparatus, and 3a, 3b, and 3c are frame attachment portions for attaching the scanning optical device 101 to the frames 2a, 2b, and 2c. Reference numerals 4a, 4b and 4c denote fixing springs for fixing the scanning optical device 101 to the frames 2a, 2b and 2c.

  Since the frames 2a, 2b, and 2c have low rigidity in the Xa, Xb, and Xc directions, respectively, the frames 2a, 2b, and 2c are likely to vibrate when vibration is transmitted in that direction from the scanning optical device. 2a, 2b, 2c itself vibrates and generates noise.

  The viscoelastic bodies 1a, 1b, and 1c are provided between the leg portions 101a, 101b, and 101c of the scanning optical device and the frame mounting portions 3a, 3b, and 3c so that the shearing force works efficiently in the directions of Xa, Xb, and Xc, respectively. The fixing springs 4a, 4b, and 4c extend the leg portions 101a, 101b, and 101c of the scanning optical device in a direction perpendicular to the direction in which the shearing force acts on the viscoelastic bodies 1a, 1b, and 1c. Each is attached so as to be in pressure contact with the frame attaching portions 3a, 3b, 3c.

  At this time, the portion of the scanning optical device where the vibration is the largest is the leg portion 101a closest to the scanner motor unit 133 that is the vibration source, so that the leg portion 101a is attached to the frame 2a via the viscoelastic body 1a. Accordingly, vibration transmitted to the image forming apparatus can be efficiently reduced.

  FIG. 2 is a view showing a relationship among the leg portion 101a, the frame attachment portion 3a, and the viscoelastic body 1a.

  Since the leg portion 101a has the viscoelastic body 1a, the leg portion 101a is configured not to directly contact the frame attachment portion 3a.

  FIG. 3 shows the case where nothing is attached between the leg portion 101a and the attachment portion 3a closest to the scanner motor 133, the case where the viscoelastic body 1a is attached, and the case where the elastic body is attached as a reference. It is the graph which measured how the vibration of the Xa direction of the flame | frame 3a changed with a laser Doppler vibrometer, performed frequency analysis, and compared the power in the frequency of the vibration generated by scanner motor rotation. With this index, the smaller the vibration, the smaller the power value.

  Here, VEM (Viscoelastic Material) (thickness 50 μm) manufactured by Sumitomo 3M Limited was used as the viscoelastic body, and rubber (thickness 50 μm) was used as the elastic body.

  Here, the characteristics of the VEM used as the viscoelastic body will be described.

  VEM is a polymer compound that has a mechanical behavior that has both fluid-like viscosity and spring-like elasticity. When it is deformed, it generates internal resistance, and vibration is generated by converting the energy of this deformation into thermal energy. It works to attenuate.

  It can be seen from the graph of FIG. 3 that vibration is reduced by attaching the viscoelastic body 1a between the leg portion 101a and the mounting portion 3a of the scanning optical apparatus 101, and the effect is reduced by half with the elastic body.

  FIG. 4 shows that the motor balance is relatively poor (2.5 mg · cm) and the good one (1) when nothing is attached between the leg portion 101a and the attachment portion 3a and when the viscoelastic body 1a is attached. .0 mg · cm) is a graph comparing the pitch unevenness of the image. In this index, if the banding is small, the Amplitude value is small. If the motor balance is good, the vibration generated by the rotation of the motor is small, so the banding is small.

  It can also be seen from the graph in the figure that the banding is reduced when the viscoelastic body 1a is attached, and that the banding reduction effect by the viscoelastic body is larger as the motor balance is worse.

  The reason why these phenomena occur is that when periodic strain is applied, there is not much phase loss between stress and strain in an elastic body, so there is not much energy loss. This is because a large phase difference occurs between stress and strain, resulting in a large energy loss.

  As a result, the attachment of the viscoelastic body not only makes it difficult for vibration to be transmitted from the scanning optical device 101 to the frame 2a, but also attenuates the vibration itself, which is effective in reducing image banding.

  FIG. 5 is a view showing a relationship when the viscoelastic body 1a is attached between the leg portion 101a and the attachment portion 3a and fastened with the fixing screw 5. FIG.

  The leg portion 101a does not directly contact the frame attachment portion 3a because of the viscoelastic body 1a, but is fastened to the frame attachment portion 3a by the fixing screw 5.

  In FIG. 6, the viscoelastic body 1a is attached between the leg 101a and the attachment part 3a, and the leg 101a is pressed against the attachment part 3a by the fixing spring 4a, and the leg 101a is attached to the attachment part 3a by the fixing screw 5. This graph shows how the vibration in the Xa direction of the frame 2a changes when it is fastened to the laser, measured with a laser Doppler vibrometer, analyzed for frequency, and compared the power at the frequency of vibration generated by scanner motor rotation. is there.

  It can be seen from the graph of the figure that when the leg portion 101a and the attachment portion 3a of the scanning optical device 101 are fastened with the fixing screw 5, the effect is lowered.

  This is because the vibration is directly transmitted from the leg portion 101a to the attachment portion 3a via the fixing screw 5 without being transmitted to the viscoelastic body, and as a result, the frame 2a vibrates.

  Here, an example of pressure contact with a spring is given as a method of holding the scanning optical device on the frame, but as a method of holding the scanning optical device, the viscoelastic body, the scanning optical device, and the frame are in close contact with each other, and As long as the scanning optical device and the frame are not fastened to each other, any method can be used to obtain the vibration damping effect. For example, a method of bonding them together may be used.

FIG. 3 is a diagram illustrating a mounting portion between the scanning optical device and the image forming apparatus according to the present invention. FIG. 3 is a diagram illustrating details of a mounting portion of the scanning optical device and the image forming apparatus according to the present invention. It is the graph explaining the vibration change by the viscoelastic body attachment in embodiment of this invention. It is the graph explaining the banding change by the viscoelastic body attachment in embodiment of this invention. It is a figure explaining the screw fastening method for comparing with the attachment method of the scanning optical apparatus and image forming apparatus in embodiment of this invention. It is the graph explaining the vibration change at the time of the spring pressure welding in embodiment of this invention, and a screw fastening. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a figure explaining the scanning optical apparatus in embodiment of this invention. It is a figure which shows the conventional scanning optical apparatus of Unexamined-Japanese-Patent No. 2000-249955. It is a figure which shows the conventional scanning optical apparatus described in the patent 3184370.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a-1c Viscoelastic body 2a-2 Frame 3a-3c Frame attaching part 4a-4c Fixing spring 5 Fixing screw 101 Scanning optical apparatus 101a-101c Leg part 102 Photosensitive drum 103 Charger 104 Developer 105 Transfer roller 106 Cleaner 107 Paper feed Tray 108 Paper feed roller 109 Registration roller 110 Fixing device 111 Paper discharge roller 131 Laser unit 132 Cylindrical lens 133 Scanner motor unit 134 fθ lens 135 Synchronous sensor 136 Synchronous folding mirror 137 Optical box 137a Output window

Claims (5)

A light source unit that emits a light beam;
A rotary polygon mirror that deflects and scans the light beam from the light source unit;
Driving means for supporting and rotating the rotary polygon mirror;
Imaging means for forming an image of the light beam from the rotary polygon mirror on the photosensitive member;
An optical box for holding the light source unit, the driving means, and the imaging means;
A scanning optical device comprising: a leg portion of the optical box fixed to a frame of the image forming apparatus;
A scanning optical apparatus, wherein the scanning optical apparatus is attached to the image forming apparatus via a viscoelastic body between at least one leg of the scanning optical apparatus and the frame.   The scanning optical apparatus according to claim 1, wherein the viscoelastic body is attached so that a shearing force is applied to the viscoelastic body in a direction in which the rigidity of the frame is weak.   The scanning optical apparatus according to claim 1, wherein the leg portion is pressed against the frame via the viscoelastic member.   2. The scanning optical apparatus according to claim 1, wherein at least one of the leg portions attached to the frame via the viscoelastic body is located closest to the deflector.   4. The scanning optical apparatus according to claim 3, wherein the press-contact direction is a direction perpendicular to a direction in which a shearing force acts on the viscoelastic member.

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