JP2003320699A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of improving the image quality by restraining displacement of a laser beam by reducing vibration of optical parts in an inexpensive and simple configuration. <P>SOLUTION: An imaging apparatus comprises an optical scanning unit having a plurality of optical parts for guiding a light beam outputted from a light source to a surface to be scanned, a photosensitive member for receiving the light beam for imaging, a main body driving part for driving the photosensitive member, or the like, and a housing for supporting these component. A vibration receiving member with the resonance frequency in phase with at least one optical member is provided in the vibration propagation path of the housing for fixing the optical scanning unit. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of reducing vibrations affecting images with an inexpensive and simple structure.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as laser printers, copying machines, and facsimiles have an optical scanning device for scanning a photosensitive member with a laser beam to form an electrostatic latent image. In the scanning device, if the vibration frequency propagating from the drive unit of the image forming apparatus main body through the housing and the natural frequency of the optical components in the optical scanning device are close to each other, the optical components resonate and generate a large vibration. ing. When the optical components in the optical scanning device vibrate, the position of the laser beam applied to the photoconductor is periodically displaced depending on the vibration frequency, and the pitch between scanning lines becomes non-uniform and appears in the image. Was there.

Further, in recent years, as the density of recorded images has increased, the pitch between scanning lines has become finer, so that there has been a problem in that even a small laser beam positional deviation may become apparent. Further, as the printing speed becomes higher, the driving motor and the like have to be rotated at higher speed, so that the vibrating force is increased and the problem becomes more severe.

[0004]

In order to reduce the positional deviation of laser light due to vibration, a method of reducing the primary vibration of the drive system of the image forming apparatus main body, a method of reducing transmission efficiency, a method of suppressing resonance, etc. There is. For example, as a method for reducing the transmission efficiency, Japanese Patent Application Laid-Open No. 2-253274 discloses an "optical scanning device" in which the optical scanning device itself is attached to a main body via a cushioning material. However, it is difficult to suppress the vibration while maintaining the positional accuracy of the optical scanning device. Further, as a method of suppressing resonance, Japanese Patent Laid-Open No. 9-269460 discloses a "scanning optical device", in which the resonance frequency of a folding mirror is changed to a frequency range in which image unevenness is not noticeable. However, this method has a problem in that it is necessary to dispose optical components that are strict in terms of accuracy and have a very limited installation space while maintaining the functions of light transmission and light reflection.

Further, as another method for suppressing the resonance of the optical component, the "optical scanning device" of Japanese Unexamined Patent Publication No. 2000-258712 and the "optical scanning device and image forming apparatus" of Japanese Unexamined Patent Publication No. 2000-171744 include: There has been proposed an optical scanning device including a vibration absorbing unit that causes a vibration receiving member to absorb vibration propagating through a bottom wall of an optical box. However, in this conventional technique, the effect is small unless the vibration transmission efficiency up to the vibration receiving member (the cover that covers the optical box) is better than the part where the optical component is attached, but downsizing is also required. In the existing optical box, it was difficult to properly transmit the vibration to only the vibration receiving member without propagating the vibration to the optical component.

[0006] Some of the methods for suppressing the resonance mentioned above can easily reduce the vibration because the vibration frequency can be specified for the rotational vibration by the deflection motor used in the optical scanning device. Since the vibration frequency band of the vibration propagating from the drive unit is wide, it was insufficient to suppress it.

The present invention has been made in view of the above circumstances, and at least one of a plurality of optical components in the optical scanning device is provided in the middle of the vibration propagation path of the housing for fixing the optical scanning device.
By attaching a vibration receiving member that matches the resonance frequency with two optical parts, and applying a vibration to the vibration receiving member to dissipate the vibration energy that causes the optical parts to resonate, the vibration of the optical parts can be performed with a cheap and simple configuration. An object of the present invention is to provide an image forming apparatus capable of reducing the positional deviation of laser light and improving the image quality.

Further, the length, mass and material of the vibration receiving member may be changed in order to match the resonance frequency with at least one optical component, and the vibration receiving member may be fixed in the vibration propagation path of the casing for fixing the optical scanning device. By making the vibration receiving member more resonable and diverging the vibration energy, the vibration of the optical component can be reduced with a cheap and simple structure, the positional deviation of the laser light can be suppressed, and the image quality can be improved. An object of the present invention is to provide an image forming apparatus that can be improved.

[0009]

In order to achieve such an object, the invention according to claim 1 has an optical scanning device having a plurality of optical components for guiding light emitted from a light source to a surface to be scanned, and the light scanning device. In an image forming apparatus having a photoconductor that receives light to form an image, a main body drive unit that drives the photoconductor and the like, and a housing that holds these, a vibration propagation path of the housing that fixes the optical scanning device. It is characterized in that it has at least one optical component and a vibration receiving member characterized by having a resonance frequency.

According to a second aspect of the present invention, in the first aspect of the invention, the vibration receiving member includes means for changing the material, length and mass of the member in order to match the resonance frequency with at least one optical component. The optical scanning device is characterized by being fixed to a casing for fixing the optical scanning device.

The invention according to claim 3 is the invention according to claim 1 or 2.
The invention is characterized in that the resonance frequency has means for obtaining it from the material and shape of at least one optical component and vibration calculation such as the finite element method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic view of the overall configuration showing an example of an image forming apparatus having the configuration of the present invention and an optical scanning device.
The present configuration has a main body 1 of a digital copying machine and a document reading device 2.
, Contact glass 3, light source 4, mirrors 5, 6,
7, an imaging lens 8, a CCD image sensor 9, a photoconductor 11, a charger 12, an optical scanning device 13, a developing device 14, a transfer device 15, a separator 16, and a cleaning device 17. A paper feed roller 20, a paper feed guide plate 21, a registration roller 23, a conveyor belt 24, and a fixing roller 2.
5, a paper discharge roller 26, a paper feed cassette 27, a deflection motor 30, a polygon mirror 31, an fθ lens 32, a folding mirror 33, a toroidal lens 34, and a dustproof glass 35. ing.

A document reading device 2 is provided above the main body 1. The document reading device 2 illuminates a document set on the contact glass 3 with a light source 4, reflects a reflected image of the document with a plurality of mirrors 5, 6, and 7, and a CCD lens (solid-state image pickup) with an imaging lens 8. Element) 9
To form an image. The CCD image sensor 9 converts the image of the document into an electric signal corresponding to the density. The image data converted into an electric signal is converted by an image processing unit (not shown) and output to the optical scanning device 13. Optical scanning device 1
3 is a beam emitting element such as a laser diode (2 in FIG. 2).
8) The divergent beam light emitted from the collimator lens (not shown) is converted into substantially parallel light, which is condensed in the sub-scanning direction by the cylindrical lens (29 in FIG. 2). The condensed beam light is driven by the deflection motor 30. Polygon mirror 31
And the deflected beam light is deflected by the fθ lens 32, the folding mirror 33, the toroidal lens 34, and the dustproof glass 3.
It is to irradiate the photoconductor 11 via 5.

Below the document reading device 2, a charger 12, an optical scanning device 13, a developing device 14, a transfer device 15, a separator 16, and a cleaning device are provided around a photoconductor 11 which rotates in a direction indicated by C in the drawing. 17 is arranged, and an electrostatic latent image is formed by the optical scanning device 13 on the charged portion of the photoconductor 11 uniformly charged by the charger 12. After that, the developing device 14
Is visualized as a toner image by the transfer device 15, the toner image is transferred onto the paper P, and the residual toner is removed by the cleaning device 1.
It was configured to collect at 7. The paper transport unit includes a paper feed roller 20, a paper feed guide plate 21, a registration roller 23, a transport belt 24, a fixing roller 25, and a paper discharge roller 26. The paper feed roller 20 is driven to feed the paper. The paper P is taken out from the paper cassette 27 one by one and the transfer device 1
5, the toner image is transferred, the toner image is heated by the fixing roller 25 to be fixed, and then the toner image is discharged onto the pedestal.

FIG. 2 is an explanatory top view showing a state in which the optical scanning device used in the image forming apparatus of the present invention is attached to the main body casing. FIG. 3 is a front view and a cross-sectional explanatory view showing a state in which the optical scanning device 13 which is also used in the image forming apparatus of the present invention is attached to the main body housing. This configuration includes an LD 28, a cylindrical lens 29, and a polygon mirror. 31, fθ lens 32, folding mirror 33, toroidal lens 34
, Dustproof glass 35, optical base 36, and rear side plate 50
A front plate 51, a right stay 52, a left stay 53,
The vibration receiving member 100 is included.

The rear side plate 50 to the left stay 53 are a part of the casing of the image forming apparatus, and the rear side plate 50 and the front side plate 51.
And a right stay 52 and a left stay 53 that connect them. Although not shown, the rear side plate 50 has a main body drive unit that drives the photoconductor 11, the developing device 14, and the paper transport unit described in FIG. 1, and drives and transmits drive motors, gears, timing belts, and the like. Means are provided. The optical scanning device 13 is positioned and screwed to the right stay 52 and the left stay 53 with a predetermined accuracy.

According to the structure up to this point, the vibration generated in the main body drive portion causes the rear side plate 50, the right stay 52, and the left stay 53.
And the optical base 36 and the optical components in the optical scanning device 13 are vibrated to cause the above problem. Therefore, in the present invention, the vibration receiving members 100a and 100b are respectively fixed to the left and right stays with screws.

The optical parts mentioned here include a polygonal mirror 31 for scanning light, a lens for correcting the beam spot position, a folding mirror 33 for reflecting the light to bend the optical path, and mainly for dust-proof purpose, but transmitting light. A dustproof glass 35 and the like are included. The fθ lens 32 tends to be made plastic for cost reduction, which is disadvantageous to vibration. The toroidal lens 34 has a role of correcting pitch unevenness of scanning lines due to a surface tilt error between the reflecting surfaces of the polygonal mirror 31. The lens surface shape is, for example, a normal toroidal surface and a barrel toroidal surface and is an anamorphic surface, so it is made plastic.
Since it is better to use a reduction optical system to improve the correction accuracy,
Since it is arranged in the last stage of the optical path among the imaging lenses, it becomes long in the scanning direction, and is weak against vibration. Since the folding mirror is also long, it often causes a vibration problem.

FIG. 4 is a perspective view of the vibration receiving members 100a and 100b. The lengths of the members and the mass of the weight 101 are different between the vibration receiving members 100a and 100b, and the plurality of optical components arranged in the optical scanning device 13 easily vibrate and have a large influence on the image, or The resonance frequency is matched with the optical base 36 to which the parts are attached. The material of the vibration receiving member 100 can be changed according to the resonance frequency to be combined, such as sheet metal or mold. The resonance frequency is determined by the material, shape, etc., and can be easily obtained from vibration calculation by the finite element method or the like. In this embodiment, an example in which there are two vibration receiving members is given, but in the case of one, it is sufficient if it is large enough to be installed on both the right stay and the left stay, and it is also possible to install three or more. .

According to the above construction, the vibration generated in the main body drive portion flows to the vibration receiving member, and the vibration energy for resonating the optical parts and the optical base can be diverged, and the above problems can be solved. .

[0022]

As is apparent from the above description, according to the present invention, at least one optical component of a plurality of optical components in the optical scanning device is provided in the vibration propagation path of the housing for fixing the optical scanning device. Since the vibration receiving member having the same resonance frequency as that of the component is attached, it is possible to apply vibration to the vibration receiving member to radiate the vibration energy that causes the optical component to resonate.

Further, by changing the material, length, mass and the like of the vibration receiving member according to the resonance frequency, resonance with the optical component can be facilitated and vibration energy can be easily dissipated.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an overall configuration showing an example of an image forming apparatus having a configuration of the present invention and an optical scanning device.

FIG. 2 is an explanatory top view showing a state in which the optical scanning device used in the image forming apparatus of the present invention is attached to the main body casing.

FIG. 3 is a front view and a cross-sectional explanatory view showing a state in which the optical scanning device used in the image forming apparatus of the present invention is attached to a main body casing.

FIG. 4 is a perspective view of vibration receiving members 100a and 100b.

[Explanation of symbols]

11 photoconductor 13 Optical scanning device 36 Optical base 52 Right stay 53 Left stay 100, 100a, 100b Vibration receiving member 101 weight

Claims (3)

[Claims] 1. An optical scanning device having a plurality of optical components that guide light emitted from a light source to a surface to be scanned, a photoconductor that receives the light to form an image, and a main body drive that drives the photoconductor and the like. In an image forming apparatus having a unit and a housing that holds these, at least one optical component has a resonance frequency that matches a resonance frequency in a vibration propagation path of the housing that fixes the optical scanning device. An image forming apparatus having a receiving member. 2. The vibration receiving member has means for changing the material, length and mass of the member in order to match the resonance frequency with at least one optical component, and is fixed to a casing for fixing the optical scanning device. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: 3. The image forming apparatus according to claim 1, further comprising means for obtaining the resonance frequency from a material and a shape of at least one optical component and a vibration calculation such as a finite element method.