JP2003295739A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a color image of high quality constantly from an in-line type color laser printer by preventing the image forming position or scanning magnification of laser light emitted from a scanning optical device for every color from being changed due to temperature rise within a color image forming apparatus and preventing the generation of a color slippage due to the temperature rise. <P>SOLUTION: The color image forming apparatus is characterized in that it is provided with a cooling fan for suppressing temperature rise in the device, an air duct for efficiently discharging heat from the inside of the device to the outside and a member for separating individual scanning optical devices from the air duct through which heat is carried in order to prevent the generation of temperature differences in the scanning optical devices for respective colors, so that warming or cooling of only a part of the scanning optical devices is prevented. The member for separating the scanning optical devices from the air duct is a cover member for covering these scanning optical devices. <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 a color image forming apparatus for forming a color image by exposing a plurality of laser beams which blink according to image information on a plurality of image carriers.

[0002]

2. Description of the Related Art Conventionally, there has been known an apparatus for forming a color image by using a plurality of scanning optical devices and a plurality of photosensitive drums which are image carriers. As shown in FIG. 5, this color image forming apparatus includes C (cyan), M (magenta),
Four scanning optical devices 1C, 1M, 1Y, 1B corresponding to Y (yellow) and B (black), photoconductor drum 2C,
2M, 2Y, 2B, developing devices 3C, 3M, 3Y, 3B and a conveyor belt 4 and the like. Then, the laser light from each scanning optical device 1C, 1M, 1Y, 1B records image information for each color on the surface of each photoconductor drum 2C, 2M, 2Y, 2B to form a color image at high speed. To do.

In such a color image forming apparatus, in order to form an image by superimposing a plurality of scanning lines, it is important to reduce the scanning line deviation between the respective colors.
Many methods have been proposed, such as a method for adjusting the position of laser light emitted from each scanning optical device and a method for overlapping a plurality of scanning lines by changing the timing of writing an image on a photosensitive drum.

[0004]

However, in the above-mentioned conventional example, even when an image is formed by superimposing a plurality of scanning lines by the above-described method in the initial stage, for example, a large number of printings are continuously performed. In such a case, the temperature inside the image forming apparatus rises due to the heat generated from the fixing device 5 and the electrical component section 6 in the image forming apparatus, and the scanning optical device is also affected by this, so that the overlapped scanning lines are misaligned. The problem of waking up occurs. Scanning optical device 1C, 1M, 1Y,
An image forming lens 7C, 7M, 7Y, 7B for forming an image of the laser beam on the surface of the photosensitive drum is provided in 1B, and this image forming lens is formed by molding an optical resin having good optical characteristics. However, since the refractive index of the optical resin changes depending on the temperature, the scanning magnification of the laser light changes as the temperature of the scanning optical device rises.
Further, since the temperature rise of the scanning optical device also causes the deformation of the optical frame supporting the imaging lens, the deviation of the imaging position of the laser light also occurs. For example, in the case of the scanning optical device described in Japanese Patent Application No. 10-152006 previously proposed by the present applicant, if there is a temperature difference of 10 ° C., the scanning magnification of the laser light and the deviation of the image forming position will be different. It has been confirmed that 60 μm-70 μm occurs. Such a positional deviation of the scanning line becomes more remarkable as the temperature difference of the scanning optical device corresponding to each color becomes larger, and there arises a problem that it appears as a change in tint or a color deviation.

[0005]

Therefore, in order to reduce such a change in color tone and color misregistration and maintain a good color image, the color image forming apparatus of the present invention is configured as follows. It is characterized by

Color image formation having a plurality of scanning optical devices for generating a laser beam that blinks in accordance with image information and a plurality of image carriers for forming images of different colors by the laser beams scanned by the scanning optical devices. The apparatus is provided with a cooling fan for suppressing a temperature rise inside the color image forming apparatus and an air passage for efficiently discharging heat inside the apparatus to the outside, and the air passage and the plurality of scanning optical devices are provided. By providing a member for separating the device from the device, the heat flow generated by the cooling fan does not affect the scanning optical device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 and FIG.
Will be described in detail with reference to the illustrated embodiment.

FIG. 1 is a side view of a color image forming apparatus according to the first embodiment, in which cyan C,
Photoreceptor drums 11C, 11M, 11Y, and 11B, which are image carriers, are provided for each of magenta M, yellow Y, and black B colors. These photosensitive drums 11C, 11M, 11
Primary chargers 12C and 12 are provided around Y and 11B, respectively.
M, 12Y, 12B, scanning optical devices 13C, 13M, 13Y,
13B, developing devices 14C, 14M, 14Y, 14B, transfer rollers 15C, 15M, 15Y, 15B, cleaners 16C, 16
M, 16Y, and 16B are sequentially arranged clockwise.

Four photosensitive drums 11C, 11M, 11
Y and 11B are arranged in a line on the transfer belt 17,
Photosensitive drums 11C, 11M, 1 sandwiching the transfer belt 17
The transfer roller 15 is placed at a position corresponding to each of 1Y and 11B.
C, 15M, 15Y, and 15B are arranged. The transfer belt 17 is stretched between two rollers 18, and one roller 18 is connected to a drive motor with small rotation unevenness in order to feed the transfer belt 17 with high accuracy.

The transfer belt 17 is provided with a paper feed tray 20 having a paper feed roller 19 and a registration roller 21 on the side of the photosensitive drum 11C on which the paper P is fed. On the other hand, the photosensitive drum 11B side of the transfer belt 17 is the discharge side of the paper P, and the detection sensor 22 and the fixing device 23 for detecting whether or not four color images are formed without color misregistration are provided. It is provided and reaches the paper discharge roller 24.

The scanning optical devices 13C, 13M, 13Y and 13B attached to the optical table 25 have a structure as shown by the scanning optical device 13 in FIG. Laser light source unit 30, cylindrical lens 31, optical deflector 32,
A first imaging lens 33 and a second imaging lens 35 having an fθ characteristic, a folding mirror 34, an optical frame 37 for accurately holding and fixing these, a horizontal position for starting the writing of an image from a desired position. The synchronization detector 36 and the like are included.

Laser light L modulated for each color based on image information is emitted from a laser light source unit 30 and linearly condensed by a cylindrical lens 31 on a scanning surface of an optical deflector 32. After the laser beam L is scanned by the optical deflector 32 which is rotating at a high speed in the direction indicated by the arrow, the laser beam L is transmitted through the first imaging lens 33 and guided by the folding mirror 34 toward the photosensitive drum 11. A latent image is formed by passing through the second imaging lens 35 and sequentially scanning the corresponding photosensitive drum surface in the arrow direction.

This latent image is formed on the photosensitive drums 11C, 11M, 11Y and 11B, which are uniformly charged by the primary chargers 12C, 12M, 12Y and 12B shown in FIG. 1, and the developing devices 14C and 14M. , 14Y, and 14B, visible images are formed on the images of cyan C, magenta M, yellow Y, and black B, respectively, and transfer rollers 15C, 15M, 15Y, 1
Paper P conveyed on the transfer belt 17 by 5B
To be sequentially electrostatically transferred to form a color image.

After that, the photosensitive drums 11C, 11M, 1
The residual toner remaining on the 1Y and 11B surfaces is cleaner 1
6C, 16M, 16Y, 16B, and again primary chargers 12C, 12 to form the next color image.
It is uniformly charged by M, 12Y and 12B.

Papers P are stacked on a paper feed tray 20 and are sequentially fed one by one by a paper feed roller 19,
The registration roller 21 sends the image onto the transfer belt 17 in synchronization with the image writing timing. Then, while being accurately conveyed on the transfer belt 17, the cyan C, magenta M, yellow Y, and black B images formed on the surfaces of the photosensitive drums 11C, 11M, 11Y, and 11B are sequentially printed on the paper. A color image is formed by being transferred onto P. Then, after the color image formed on the paper P is thermally fixed by the fixing device 23, the paper P is conveyed by the paper discharge rollers 24 or the like and discharged to the outside of the apparatus.

These scanning optical devices 13C, 13M, 13
The laser light emitted from Y and 13B is applied to the photosensitive drum 11.
The positions for irradiating C, 11M, 11Y, and 11B are aligned by the following method.

First, in the scanning direction of the laser beam (main scanning direction), the image widths (overall magnification) of the four colors and the writing positions of the four colors are aligned.

At the writing position, each color is started to be written from the same position by changing the image writing timing based on a signal obtained from the horizontal synchronization detecting unit 36 arranged immediately before the writing position in the non-image range. Has been adjusted to. In order to make the image width uniform, the modulation frequency for writing the image is changed so that the same image width is obtained for each color.

In the rotation direction of the photosensitive drum (transfer belt conveyance direction), the writing start position of the image front end is adjusted and the inclination of the laser beam scanning line is adjusted so that the left and right heights do not differ.

The writing start position of the image front end is adjusted so that the respective colors are overlapped by changing the timing of starting the modulation according to the image information, and the inclination of the scanning lines is adjusted so that the scanning optical device and the photosensitive drum are substantially parallel. The initial scanning line alignment is performed by adjusting to.

In these adjustments, color misregistration detection patterns of four color images are formed on the transfer belt 17 and the paper P, and the detection sensor 22 reads the detection patterns to calculate and correct the misregistration amount.

Further, in the color image forming apparatus of the present invention, as shown in FIG. 1, the positional deviation of the scanning line of the laser beam between the respective colors may occur due to the influence of the heat generated from the fixing device 23 and the electric component section 27. Configured to not.

The heat generated from the fixing device 23 and the electrical component 27 is efficiently exhausted to the outside of the image forming apparatus by the exhaust cooling fan 26 as indicated by arrows A, B and C in the figure. At this time,
The air passages through which heat flows by the cooling fan 26 are indicated by arrows A, B, C
However, in this embodiment, the optical table 2 is formed.
A defense wall 250 for separating the air passages (arrows A and B) from the scanning optical device is provided on the left end side of 5.

As a result, a part of the heat generated by the fixing device 23 and the heat generated by the electric component section 27 is prevented from flowing from below the scanning optical device 13B.

Further, the scanning optical device 13B located near the cooling fan 26 and the scanning optical device 13C located far from the cooling fan 26 cause a difference in the amount of air generated by the cooling fan 26 and a difference in the effect of heat. Member 2
8 covers the four scanning optics 13C, 13M, 13Y, 13B. The cover member 28 is preferably formed of a material having low thermal conductivity such as plastic, and isolates the air passage C formed by the cooling fan 26 from the scanning optical devices 13C, 13M, 13Y, 13B. The structure can reduce the influence of heat on the scanning optical device. Therefore, the temperature difference generated between the four scanning optical devices can be suppressed to a very small level, and the temperature difference does not occur in the imaging lens in the scanning optical device or the optical frame supporting the imaging lens. It is possible to prevent deviation of the image forming position of light and deviation of the scanning magnification, and it is possible to obtain a high-quality image in which color deviation does not occur even during continuous printing.

(Embodiment 2) In the second embodiment shown in FIG. 3, four scanning optical devices 13C, 13M, 13Y and 1 are provided.
A stirring fan 51 for stirring the internal space is provided inside the cover member 50 that covers 3B.

By operating the stirring fan 51, it is possible to further reduce the temperature gradient in the space surrounded by the cover member 50. Therefore, it is possible to operate the stirring fan 51 during continuous printing for a long time. By incorporating a system or providing a temperature detection sensor 52 in a place where a temperature difference is likely to occur due to the influence of the cooling fan 26 and operating the stirring fan 51 when the temperature difference becomes large, It is possible to more reliably reduce the temperature difference between the scanning optical devices.

(Embodiment 3) Since the cover member in the above-mentioned embodiment can reduce the temperature difference of the scanning optical device, it is not necessary to hermetically seal the periphery of the scanning optical device. For example, as shown in the third embodiment of FIG. 4, by using the cover member 60 whose opening side is small at the temperature of the scanning optical device 13C, the heat (arrows A and B) and cooling of the fixing device 23 and the electrical component 27 are cooled. The heat (arrow C) carried by the fan 26 warms the inside of the cover and the scanning optical device 13C,
13M, 13Y, 13B and the first imaging lens 3 inside thereof
3C, 33M, 33Y, 33B and the second imaging lens 35C,
Since 35M, 35Y, and 35B are prevented from increasing in temperature, the temperature difference generated between them is also small, and the effect of preventing color misregistration can be obtained as in the case of the above-mentioned embodiment.
It is possible to more effectively prevent the shape change of the optical frame or the like due to heat.

[0029]

As described above, in the color image forming apparatus having a plurality of scanning optical devices, the cooling fan for suppressing the temperature rise inside the image forming apparatus and the heat inside the image forming apparatus are efficiently discharged to the outside. By separating the scanning optical device from the air passage for this purpose, only a part of the scanning optical device is warmed, or only a part of the scanning optical device is cooled so that the temperature difference between the scanning optical devices is large. By providing a member that separates the air passage from the scanning optical device so as not to occur, it is possible to reduce the temperature difference between the scanning optical devices and obtain a good color image with no color shift even during continuous printing. it can.

[Brief description of drawings]

FIG. 1 is a side view of essential parts of a color image forming apparatus showing a first embodiment of the present invention.

FIG. 2 is a main part configuration diagram of a scanning optical device showing a first embodiment of the present invention.

FIG. 3 is a side view of essential parts of a color image forming apparatus showing a second embodiment of the present invention.

FIG. 4 is a side view of essential parts of a color image forming apparatus showing a third embodiment of the present invention.

FIG. 5 is a schematic view of a conventional color image forming apparatus.

[Explanation of symbols]

11, 11C, 11M, 11Y, 11B photoconductor drum 13, 13C, 13M, 13Y, 13B scanning optical device 33, 33C, 33M, 33Y, 33B First imaging lens 35, 35C, 35M, 35Y, 35B Second imaging lens 25 optical stand 250 defense wall 26 Cooling fan 28, 50, 60 cover member 51 stirring fan A, B, C Heat flow (wind path)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 CA18 CA39 DA32 DA34                 2H027 JA11 JB12 JB13 JB17 JC05                       JC08 JC16                 2H300 EA01 EA19 EB04 EB07 EB12                       EG02 EH16 EL01 GG28 GG36                       GG46

Claims (2)

[Claims] 1. A color having a plurality of scanning optical devices that generate laser light that blinks in accordance with image information, and a plurality of image carriers that form images of different colors by the laser light scanned by the scanning optical devices. In the image forming apparatus, a cooling fan for suppressing a temperature rise inside the color image forming apparatus and an air passage for efficiently discharging the heat inside the apparatus are provided, and the air passage and the plurality of air passages are provided. A color image forming apparatus, characterized in that a member for separating the scanning optical device is provided so that the flow of heat generated by the cooling fan does not affect the scanning optical device. 2. The color image forming apparatus according to claim 1, wherein the member that separates the air passage from the plurality of scanning optical devices is a cover member that covers the plurality of scanning optical devices.