JP2012137593A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that constantly reduces temperature difference between optical scanners that changes over time with a simple configuration, without an increase of power consumption due to an addition of fans.SOLUTION: An image forming apparatus flows cooling air into a space where optical scanners are installed, and provides a plurality of movable radiation fins above the optical scanners. Either one of the number and the height of the radiation fins, or both can be changed, and thereby the amount of heat radiation of the optical scanners can be adjusted, and the temperature difference between the optical scanners is reduced despite the change in temperature of respective optical scanners.

Description

  The present invention relates to a cooling technique for an electrophotographic image forming apparatus such as a copying machine or a laser printer.

  Image forming apparatuses such as copiers and printers mainly form a latent image by an optical scanning device, form a toner image on a photosensitive drum, transfer a toner image onto a recording sheet on a transfer belt, and pressurize toner in a fixing device. Printing is performed through a process of fixing by heating.

  At this time, the surface temperature of the fixing roller for heating in the fixing device is adjusted to about 200 ° C., and this heat is transmitted into the image forming device through the frame constituting the image forming device and convection air. A temperature distribution occurs in the device.

  In particular, a color image forming apparatus has a plurality of optical scanning devices for forming a color image, and a temperature difference occurs between these devices due to heat from the fixing device. When a temperature difference occurs between the optical scanning devices, different thermal deformations occur, and as a result, the latent image formed on the photosensitive drum causes a different position shift for each color, which causes a color shift.

  In order to prevent these problems, in Patent Document 1, a cooling duct and a heat radiating fin are formed in contact with a portion to be cooled that extends in the longitudinal direction where the temperature distribution is desired to be uniform. Furthermore, by increasing the number of radiating fins from upstream to downstream of the cooling air flowing in the duct, a technology has been proposed in which the object to be cooled is uniformly radiated in the longitudinal direction and the temperature distribution is made uniform. . Patent Document 2 proposes a technique for efficiently reducing the temperature rise by changing the interval between the radiation fins depending on whether the temperature is high or low in the developing device casing.

JP 2007-286163 A JP 2007-226148 A

  However, when the number of heat dissipating fins and the arrangement interval are fixed as proposed in the prior art, the temperature distribution can be kept uniform if the temperature distribution of the cooled part is constant over time. If the distribution changes over time, it cannot always be kept uniform. The factors that cause the temperature distribution to change over time are that it takes time for the temperature of the cooled part to stabilize after the heat source starts to generate heat, and that the heat input to the cooled part changes during operation. and so on. Possible causes of the change in the amount of heat input to the cooled part include a change in the print medium to be used, a change in print mode such as single-sided double-sided printing and black-and-white color printing, or an unexpected temperature disturbance such as the user's usage environment. It should be noted that the temperature distribution of the cooled portion at a certain time can take various distributions depending not only on the print medium and print mode at that time but also on the print history up to that point.

  In addition, in order to avoid the above problem, a plurality of fans capable of adjusting the air volume are installed at each location where the temperature distribution occurs, and cooling of the air volume adjusted so as to be uniform when the temperature distribution of the cooled part changes is performed. A technique of flowing wind through the part to be cooled can be considered. However, this technique has a problem that power consumption increases because it is necessary to install a plurality of fans and to adjust the air volume.

  The present invention has been made in view of the above problems, and its purpose is to increase the power consumption by adding a fan or the like, and with a simple configuration, even when the temperature difference of each optical scanning device changes over time. An object of the present invention is to provide an image forming apparatus that can always reduce the temperature difference between the optical scanning devices.

  In order to achieve the above object, according to the first aspect of the present invention, first, in an image forming apparatus having a plurality of optical scanning devices, cooling air is caused to flow in a space where the optical scanning devices are installed. The outer walls of the plurality of optical scanning devices have a protrusion-like structure, and a mechanism for changing the shape of the protrusion-like structure so as to change the area where the outer wall contacts the gas in the installation space. To do.

  The invention described in claim 2 is the invention described in claim 1, characterized in that one or both of the number and the height of the projecting structure whose shape is variable is changed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, setting means for setting a print mode capable of selecting single-sided printing and double-sided printing or color printing and monochrome printing, and the set printing mode And a processing means for determining the shape of the protruding structure. The shape of the protruding structure is changed by the processing means.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the optical scanning is performed based on the temperature information of the plurality of optical scanning devices and the gas temperature in the vicinity thereof, and the detected temperature information. And processing means for determining the shape of the protruding structure of the apparatus. The shape of the protruding structure is changed by the processing means.

  According to the present invention, even when the temperature difference between the optical scanning devices changes with time in the image forming apparatus, the temperature difference can always be reduced, and as a result, the color caused by different thermal deformation between the optical scanning devices. The deviation can be reduced.

1 is a cross-sectional view of a color image forming apparatus according to Embodiment 1. FIG. Sectional drawing which looked at the optical scanning apparatus installation space which concerns on Example 1 from upper direction Sectional drawing which cut | disconnected the optical scanning device which concerns on Example 1 in the direction parallel to the surface of a radiation fin Sectional drawing which cut | disconnected the optical scanning device which concerns on Example 1 in the direction perpendicular | vertical to the surface of a radiation fin Description of steps until the heat radiation fins in Example 1 and Example 2 are driven Sectional drawing which cut | disconnected the optical scanner which concerns on Example 2 in the direction parallel to the surface of a radiation fin, and the perspective view of a radiation fin Sectional drawing which cut | disconnected the space which flows several optical scanning device based on Example 2 and cooling air in the direction parallel to the surface of a radiation fin

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

[Example 1]
FIG. 1 is a cross-sectional view of a color image forming apparatus according to the present embodiment. First, the main configuration and printing process of the color image forming apparatus according to the present embodiment will be described.

  The color image forming apparatus shown in FIG. 1 includes an image forming unit 100 that forms a full-color toner image on a recording sheet, and a fixing device 400 that fixes the toner image formed on the recording sheet to the recording sheet.

  The image forming unit 100 includes photosensitive drums 12Y, 12M, 12C, and 12BK as toner image carriers formed in yellow (Y), magenta (M), cyan (C), and black (BK) colors. ing.

  The photosensitive drums 12Y, 12M, 12C, and 12BK are opposed to the outer peripheral surface, and the primary chargers 13Y, 13M, 13C, and 13BK, the optical scanning devices 11Y, 11M, 11C, and 11BK, the developing device 14Y, in order of the rotation direction. 14M, 14C, 14BK and cleaning devices 15Y, 15M, 15C, 15BK are disposed.

  In the photosensitive drums 12Y, 12M, 12C, and 12BK, first, the primary chargers 13Y, 13M, 13C, and 13BK apply uniform charges to the surfaces of the photosensitive drums 12Y, 12M, 12C, and 12BK. Next, the photosensitive drums 12Y, 12M, 12C, and 12BK are exposed and scanned by the laser beams 16Y, 16M, 16C, and 16BK, which are emitted from the optical scanning devices 11Y, 11M, 11C, and 11BK, and are modulated according to the recording image signal. An electrostatic latent image is formed. Thereafter, in the developing devices 14Y, 14M, 14C, and 14BK, the formed electrostatic latent images are visualized with toner in corresponding colors. Finally, the toner remaining on the surface of the photosensitive drum is cleaned by the cleaning devices 15Y, 15M, 15C, and 15BK.

  The toner images of the respective colors formed on the photosensitive drums 12Y, 12M, 12C, and 12BK are primarily transferred on the intermediate transfer belt 31 and are superimposed. The intermediate transfer belt 31 includes a driving roller 32 for driving the belt and a driven roller 33 driven by the belt.

  The toner image transferred to the intermediate transfer belt 31 is transferred to the recording paper 22 in the secondary transfer portion constituted by the secondary transfer roller 35 and the secondary transfer counter roller 34. The secondary transfer roller 35 is pressed against the intermediate transfer member with an appropriate pressure.

  Here, the recording paper 22 is fed by a paper feed roller pair 23 and a paper feed guide 24 for conveying the recording paper 22 fed from the cassette 21 for storing the recording paper 22 to the registration roller pair 25. Is called. The registration roller pair 25 sends the recording paper 22 to the secondary transfer unit in synchronization with the image formation timing.

  The recording paper 22 transferred in the secondary transfer unit is transported to the fixing device 400 through the transport path 26.

  The fixing device 400 includes a fixing roller pair 41, fixing heat insulating covers 42 and 43, a paper discharge roller 44, and the like. The fixing roller pair 41 includes a heat source such as a halogen heater inside, and the fixing covers 42 and 43 trap the heat of the fixing roller pair 41 inside.

  The unfixed toner image on the recording paper 22 conveyed by the conveyance path 26 is heated and pressurized by the fixing roller pair 41 and fixed on the recording paper 22. After fixing, the recording paper 22 is discharged from the discharge roller 44 to the outside of the apparatus.

  Next, a configuration and a process for reducing a temperature difference between a plurality of optical scanning devices in this embodiment will be described.

  The heat generated from the fixing roller pair 41 is transmitted into the apparatus through a frame constituting the image forming apparatus and a gas circulating in the apparatus, and a temperature difference is generated in the 11Y, 11M, 11C, and 11BK optical scanning devices. Here, since the temperatures of 11Y, 11M, 11C, and 11BK increase from the far side to the near side of the fixing roller pair 41, the temperature increases from 11Y, 11M, 11C, and 11BK in order. In order to reduce this temperature difference, as shown in FIG. 1, the upper portion of the optical scanning device is surrounded by a duct shape as a space 111, and cooling air is flowed by a cooling fan 114. In addition, a plurality of movable radiating fins 112Y, 112M, 112C, 112BK are arranged on the upper lid of 11Y, 11M, 11C, 11BK.

  FIG. 2 is a view of the space 111 as viewed from above. A plurality of radiation fins 112Y, 112M, 112C, 112BK are present on the upper surface of the optical scanning device, and the number of the thermal scanning devices increases as the temperature of the optical scanning device increases. Moreover, the radiation fins 112Y, 112M, 112C, and 112BK are movable, and the number of protrusions in the space 111 can be changed. 2 shows the radiation fin in a state of protruding into the space 111. FIG. The temperature sensors 113Y, 113M, 113C, and 113BK measure the temperature of the upper lid of each optical scanning device in contact with the cooling air, and the temperature sensor 113AIR measures the gas temperature of the cooling air supplied to the space 111.

  FIG. 3 is a cross-sectional view of the optical scanning device 11Y of FIG. 2 cut along a cross section AA, and shows a configuration for making the number of radiating fins variable. The heat dissipating fin 112Y is configured to be freely retracted into the space 111 and housed in a state parallel to the upper lid of 11Y by being rotated by the rotary actuator 116Y about the rotating shaft 115Y. 3A shows a state in which the radiating fin 112Y protrudes into the space 111, and FIG. 3B shows a state in which it is parallel to the upper lid. In order to efficiently dissipate heat by increasing the thermal conductivity between the movable radiating fin 112Y and the casing of the optical scanning device 11Y, for example, means such as heat transport using an elastic heat pipe is taken. .

  FIG. 4 shows a part of a cross-sectional view of the optical scanning device 11Y of FIG. 2 cut along a cross section BB, and shows how to rotate the radiating fin 112Y about the rotation shaft 115Y. 4A corresponds to the state of FIG. 3A corresponding to the state in which the radiating fin protrudes into the space 111, and FIG. 4B corresponds to FIG. 3B corresponding to the state of the optical scanning device 11Y. The state parallel to the upper lid of is shown.

  In the image forming apparatus, the temperature distribution inside the apparatus changes with time depending on the printing medium, the printing mode, the user's operating temperature environment, and the temperature difference of the optical scanning devices 11Y, 11M, 11C, and 11BK changes accordingly. In order to cope with this, in the present embodiment, the movable radiating fins shown in FIGS. 1 to 4 are driven by the process shown in FIG. 5 and the number thereof is made variable over time.

  First, the temperature is measured at certain time intervals by the temperature sensors 113Y, 11M, 11C, and 11BK shown in FIG. 2 and the temperature sensor 113AIR that measures the gas temperature in the space 111. Measure the temperature, and if the maximum temperature difference between the optical scanning devices exceeds a certain allowable value, calculate the heat radiation amount of each optical scanning device based on the temperature information by the processing means that determines the number of radiation fins, Calculate and determine the optimum number of heat dissipating fins to reduce the temperature difference between the scanning devices most. In this step, the number of radiating fins determined by the processing means is realized by the radiating fin driving means such as the rotary actuators 116Y, 116M, 116C, and 116BK.

[Example 2]
In the present embodiment, the image forming apparatus and the printing mechanism in the first embodiment follow the same configuration and process, and the process of changing the heat radiation amount of the radiation fins with time is the same. The point is omitted.

  The difference from the first embodiment is a method of making the heat radiation amount of the optical scanning devices 11Y, 11M, 11C, and 11BK variable.

  That is, in the first embodiment, the amount of heat radiation is changed by changing the number of heat radiation fins, whereas in this embodiment, the heat radiation fins are driven up and down by the drive mechanism 117Y as shown in FIG. The amount of heat release is variable by changing the fin area. 6A is a cross-sectional view of the optical scanning device 11Y cut in a direction parallel to the radiation fins, and FIG. 6B is a perspective view of the radiation fins 112Y and the drive mechanism 117Y. As shown in (B), 117Y is composed of a rotary actuator 117Ya and a roller 117Yb, and by rotating 117Yb, the radiating fin 112Y moves in the vertical direction. As in the first embodiment, in order to efficiently dissipate heat by increasing the thermal conductivity between the movable radiating fin 112Y and the casing of the optical scanning device 11Y, for example, an elastic heat pipe is used to heat between them. Take measures such as transportation.

  FIG. 7 is a cross-sectional view of the image forming apparatus 11Y, 11M, 11C, 11BK of the image forming apparatus according to the present embodiment and the space 111 cut in a direction parallel to the radiation fins. As shown in FIG. 7, the temperature difference is reduced by decreasing the area of the portion that protrudes into the space 111 of the radiating fin in the order from 11Y having the highest temperature to 11BK having the lowest temperature. This can be done by adjusting the height.

[Example 3]
In the present embodiment, the image forming apparatus and the printing mechanism in the first embodiment or the second embodiment follow the same configuration and process, and the configuration in which the shape of the radiating fins is variable is the first or second embodiment. Since either of these may be used, these points are omitted.

  A different point from Example 1 or Example 2 is a process for changing the shape of the radiating fin over time.

  In this embodiment, the temperature of each optical scanning device is not measured, and the physical quantity such as the amount of heat input to the optical scanning device according to the printing medium and the printing mode, the heat capacity of the optical scanning device, and the heat transfer coefficient with the atmosphere is determined. Measure in advance. Then, in the processing means for determining the number of radiating fins or the height of the radiating fins, the temperature change of the optical scanning device is calculated using various physical quantities measured in advance according to the print medium in operation and the heat input amount of the printing mode, The number and height of the heat radiation fins that reduce the temperature difference at each time are determined. Even when the print medium or the print mode is changed during the operation, the temperature change according to the heat input amount of the print medium after the change and the print mode can be calculated using the temperature of the optical scanning device before the change as the initial temperature. Even when there are various printing histories, the optimum number of fins and height can be realized.

100 Image forming unit 400 Fixing device

Claims (4)

  An image forming apparatus having a plurality of rotary polygon mirrors that deflect laser light, an optical lens, and a plurality of optical scanning devices that house the rotary polygon mirror and the optical lens, and having at least one heat source inside the apparatus. Cooling air is supplied to the space in which the plurality of optical scanning devices are installed by cooling means, the plurality of optical scanning devices have a plurality of protrusion-like structures on the outer wall thereof, and the space in which the optical scanning device is installed An image forming apparatus comprising: a mechanism for changing a shape of the protruding structure so as to change an area where an inner gas contacts an outer wall of the optical scanning device.   The image forming apparatus according to claim 1, wherein the mechanism for changing the shape changes one or both of the number and the height of the protruding structures.   One-sided printing and two-sided printing, color printing and black-and-white printing, or setting means capable of setting at least two types of printing media and thicknesses, and the shape of the protruding structure depending on the set printing mode and printing medium 3. The image forming apparatus according to claim 1, further comprising: a processing unit that determines the shape of the protrusion-like structure.   Detection means for detecting temperatures of the plurality of optical scanning devices and at least one temperature in the vicinity of the plurality of optical scanning devices, and processing means for determining the shape of the protruding structure of the optical box based on the detected temperature information The image forming apparatus according to claim 1, wherein the shape of the protruding structure is changed by the processing unit.