JP2006347725A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing reduction in an output quality, by reducing a curl in a thermal fixation. <P>SOLUTION: This image forming device is characterized in that an openable-closable recording paper delivery cover is arranged for cutting off from outside air, and a humidity detecting means is arranged in a paper delivery part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile, or a multifunction machine having a printer function added thereto, and more specifically, for stacking sheets discharged outside the apparatus after image formation. The present invention relates to a mechanism around the sheet stacking unit.

  FIG. 4 is a schematic cross-sectional view (front view) showing the overall configuration of a conventional image forming apparatus (a composite copying machine having a printer function and a facsimile function in addition to a copy function). First, an overall schematic configuration of a conventional image forming apparatus 500 will be described with reference to FIG.

  The image forming apparatus 500 includes a document reading unit 510 (including an automatic document feeder 511 in the present embodiment) disposed at an upper portion, an image forming unit 520 disposed at a substantially central portion, and an image forming unit. The sheet feeding unit 530 is disposed below and on the right side of the 520. In the image forming unit 520, a photosensitive drum 521 that is an electrophotographic photosensitive member, a charging roller 522 that performs charging processing on the surface of the photosensitive drum 521, a developing device 523 that visualizes an electrostatic latent image on the photosensitive drum 521, A process cartridge 525 that integrally includes a cleaning device 524 that removes and collects a residual toner image on the photosensitive drum 521, an exposure device (laser scanner unit) 526 disposed above the process process cartridge 525, and the photosensitive drum 521. The transfer roller 527 that transfers the toner image on the photosensitive drum 521 facing the sheet S to the sheet S, the fixing device 528 that performs heat fixing processing on the sheet S after image transfer, and the fixing device 528 are integrally configured. A paper discharge roller pair 529 for discharging the subsequent sheet S to the outside of the apparatus is disposed.

  The paper feed unit 530 includes a paper feed cassette 531 capable of storing a horizontally placed A4 size sheet S or a smaller size sheet S, and a paper feed roller for sending out the sheet S toward the image forming unit 520. An intermediate plate 533 and the like are disposed for lifting the 532 and the vicinity of the leading edge of the sheet S so as to contact the paper feed roller 532. The sheet S sent out by the paper feed roller 532 is temporarily stopped by the registration roller pair 535 via the conveyance roller pair 534 and sent out after the timing of the toner image formed on the photosensitive drum 521 is matched. In some cases, the image forming unit 520 is fed to the registration roller pair 535 from a manual sheet feeding unit 536 provided on the right side in the drawing.

  The document reading unit 510 is provided with a document table glass 512, a contact image sensor (CIS) 513, a support shaft 514 of the CIS 513, a reader motor 515 for driving the CIS 513, and the like. The document is placed on the platen glass 512 and scanned by the CIS 513 to convert the image reflected light into an electrical signal.

  In this way, when the original image reflected light is converted into an electric signal by the original reading unit 510 on the photosensitive drum 521 uniformly charged by the charging roller 522, and the electric signal is exposed as the image light L from the laser scanner unit 526, An electrostatic latent image is formed on the photosensitive drum 521. The electrostatic latent image is developed by the developing device 523 along with the rotation of the photosensitive drum 521 and is visualized as a toner image, and is then conveyed from the paper feeding unit 530 by the transfer roller 527 and is timed by the registration roller pair 535. Is transcribed. The photosensitive drum 521 that has been transferred is cleaned by a cleaning device 524 and is prepared for the next image formation. After the transfer, the sheet S is thermally fixed when the toner image on the sheet S passes through the fixing device 528, and after fixing, the sheet S is placed on the sheet stacking portion 551 and the extension tray 552 outside the apparatus by the discharge roller pair 529. Is discharged.

As another conventional example, the sheet S becomes a high temperature when thermally fixed, and the contained water evaporates from the sheet S. When the sheet S is then cooled, the sheet S is curled. Therefore, in order to suppress such curling, a device for giving moisture to the sheet S in the process of paper discharge has been proposed (see, for example, JP-A-4-291277 and JP-A-2001-026352).
JP-A-4-291277 JP 2001-26352 A

  However, in the image forming apparatus 500 shown in the conventional example, the sheet S becomes a high temperature when thermally fixed, and moisture contained in the sheet S evaporates, and when it is cooled, the sheet S is curled. End up.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image forming apparatus capable of reducing curling during heat fixing and preventing deterioration in output quality. is there.

  A first configuration of an image forming apparatus according to the present invention includes an image forming unit that forms an image by an electrophotographic method, a fixing unit that thermally fixes a sheet after image formation, and a sheet after fixing. And a sheet stacking unit for stacking the discharged sheets, wherein the sheet discharge stacking unit includes a cover member for surrounding the sheet discharge stacking unit and separating it from the peripheral space. The image forming apparatus configured to include a humidity detection unit in the sheet discharge stacking unit.

  A second configuration of the image forming apparatus according to the present invention is characterized in that in the first configuration, there is a humidity detecting means for the inner peripheral space outside the sheet discharge stacking portion.

  A third configuration of the image forming apparatus according to the present invention is characterized in that, in the first and second configurations, the cover member includes a lid that can be opened and closed.

  According to a fourth configuration of the image forming apparatus of the present invention, in any one of the first to third configurations, the open / close state of the cover member is determined based on detection information from the humidity detection unit. To do.

  According to the above configuration, it is possible to reduce the curl amount of the sheet material generated in the drying process of the sheet material after fixing, and to prevent the quality of the discharged sheet material from being deteriorated.

  As described above, according to the present invention, the sheet discharged from the apparatus can be dried uniformly while maintaining moisture in the atmosphere as much as possible in the drying process of the sheet material after fixing. By drying in the staying space, the curl amount of the sheet can be reduced, and the output quality of the output sheet can be prevented from being lowered.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  FIG. 1 is a schematic sectional view (front view) showing an overall configuration of an image forming apparatus (copier) according to an embodiment of the present invention, FIG. 2 is an enlarged view of a main part according to the embodiment of the present invention, and FIG. FIG. 2 is a plan sectional view (upper view) showing the discharge sheet tray portion according to the embodiment of the present invention. The image forming apparatus 100 according to the present embodiment has the same basic configuration as the conventional image forming apparatus 500 except for the configuration of the paper discharge tray unit 150. Accordingly, descriptions of individual components such as the document reading unit, the paper feeding unit, and the image forming unit are omitted, and the same components are denoted by the same reference numerals.

  Hereinafter, a description will be given focusing on the paper discharge tray unit 150, which is a main part of the present invention.

  First, the overall configuration of the paper discharge tray unit 150 will be described with reference to FIG. The paper discharge tray unit 150 in the present embodiment has the same basic configuration as the copier 500 shown in FIG. 4, except for the configuration of the paper discharge tray unit 610 for stacking the discharged sheets S. The paper discharge tray 150 of the copying machine 100 is provided with a cover member 151 that covers the upper side of the extension tray 170 and shields it from the outside of the machine. The cover member 151 is provided with a lid 153 that can be opened and closed with the hinge 155 as a rotation center, and the sheet S discharged outside the apparatus can be taken out by opening the lid 153 (the opened state is indicated by a broken line). Show).

  By including the paper discharge tray unit 150 having such a configuration, water vapor that is radiated from the sheet S heated by the fixing 528 and flows out from the discharge port 541 is surrounded by the cylinder interior 553 and the cover member 151 without escaping to the outside of the apparatus. It can be stored in the water vapor retention space A. For this reason, since the sheet S immediately after recording does not come into contact with the surrounding outside air in a state where the temperature is high, the sheet S absorbs moisture again in a stable humidity state and reduces the curl amount in the drying process after discharge. It becomes possible.

  In order to form the water vapor retention space A, the cover member 151 is shielded from the space outside the machine. The cover member 151 mainly includes a cover portion 152 and a lid portion 153 having the hinge portion 155 as a rotation center. The cover member 151 is a fastening member (not shown) on the exterior surface 515 of the document reading portion 510. It is fixed by.

  As a feature of the paper discharge tray unit 150 of the present invention, the cover unit 152 is provided with a humidity detection sensor 160. Further, a humidity detection sensor (not shown) is also provided outside the apparatus of the paper discharge tray unit 150.

  A dehumidifying agent 171 is detachably incorporated in the extension tray unit 170. By doing so, the amount of water vapor in the water vapor retention space A is stabilized.

  FIG. 2 is an enlarged view of the paper discharge tray unit 150. The humidity detection sensor 160 is generally a sensor that can be easily purchased.

  In the extension tray section 170, a dehumidifying agent 171 whose main component is calcium chloride (in some cases, silica gel or raw coal) is incorporated in a portion other than the stacking area of the sheets S. The dehumidifying agent 171 is placed in a recess 170a formed in the extension tray 170 so that it can be easily replaced.

  FIG. 3 shows the extension tray 170 viewed from above. A region indicated by a two-dot chain line in FIG. In the present embodiment, as shown in the figure, the dehumidifying material 171 is configured to be placed one by one on the front side and the far side of the apparatus outside the sheet S stacking area. The dehumidifying agent 171 is configured so that the number of the dehumidifying agent 171 can be selected according to the installation environment of the image forming apparatus 100.

  The above is the configuration of the paper discharge tray unit 150 in this embodiment. The operation of the dehumidifying agent 171 will be described.

  In the image forming apparatus 100, the water vapor that diverges from the sheet S and flows out of the apparatus from the discharge port 541 during heat fixing is stored in the water vapor retention space A. The sheet S discharged outside the apparatus is dried while resorbing moisture in the water vapor retention space A, whereby curling of the sheet S itself is suppressed (contents described in the section of the prior art). At this time, depending on the degree of moisture absorption (= water content) of the sheet S left in the cassette 531 or the like, the amount of water vapor that diverges from the sheet S and flows out from the discharge port 541 at the time of heat fixing increases, and the water vapor retention space. A situation may occur where the saturated water vapor amount at the ambient temperature in A is exceeded. In this case, condensation occurs on the inner side surface (the entire area of each surface facing the sheet S such as the cover member 151, the extension tray portion 170, the sheet stacking portion 551, etc., hereinafter referred to as the inner side surface), and the discharged sheet S is Since it gets wet, the output quality of the sheet S is greatly impaired.

  Therefore, by energizing the heater unit 160 to generate heat, the temperature in the water vapor retention space A is increased to increase the amount of saturated water vapor in the water vapor retention space A, thereby preventing condensation on the inner surface. .

  Actually, the situation where the amount of water vapor in the water vapor retention space A exceeds the saturated water vapor amount at the atmospheric temperature at that time due to the outflowing water vapor is only when the continuous sheet S is output, and the time required for this continuous output. The amount of heat generated by the heater unit 160 may be set so that the atmospheric temperature in the water vapor staying space A can be increased by generating heat through the heater unit 160. For example, the saturated water vapor amount can be increased by about 40% as long as the heat generation capacity of the heater unit 160 that raises the temperature of the water vapor retention space A at 15 ° C. to 20 ° C. within the time required for a predetermined number of output sheets. The heat generation capability of the heater unit 160 at a predetermined number of output sheets is set in consideration of the power consumption of the entire apparatus required when the image forming apparatus 100 is movable (image formation) based on experiments. The control unit 191 of the heater unit 160 shown in FIGS. 1 and 2 is depicted as a dedicated part outside the apparatus, but is a display for easy understanding and is actually an image forming apparatus 100. Is incorporated in a control unit (not shown).

  When the image formation is completed, the heating of the heater unit 160 stops. When the temperature of the atmosphere in the water vapor staying space A decreases with time, and the temperature around the image forming apparatus 100 (normal room temperature) is particularly low (for example, about 7.5 ° C.), A situation in which the relative humidity exceeds 100% may occur in the water vapor retention space A, and as a result, condensation occurs on the inner surface (condensation due to a drop in the dew point). In order to prevent dew condensation in this case, it is necessary to reduce the amount of water vapor in the water vapor retention space A. Here, the moisture absorption action by the dehumidifying agent 171 exhibits the effect of preventing dew condensation. In the case of a device installed in a situation where the room temperature is low, the atmospheric temperature in the water vapor retention space A is also low, so the amount of saturated water vapor in the water vapor retention space A when the device is stopped is small. Even the output of the sheet S may cause condensation on the inner surface of the water vapor retention space A due to water vapor generated from the sheet S during heat fixing.

  In this case, it is better that the amount of water vapor in the water vapor retention space A before image formation is small, and moisture absorption by the dehumidifying agent 171 is effective. Thus, in a device installed in a low temperature environment such as in a cold region, it is better to equip with a sufficient dehumidifying agent to prevent the output sheet from getting wet due to condensation, and in this embodiment, both near and far It is desirable to provide a dehumidifying agent in the recess 170a. Further, in an apparatus installed in a room temperature environment (for example, room temperature of about 20 ° C.), the degree of curling of the output sheet (in order to suppress curling, the amount of water vapor in the water vapor retention space A is desired to be increased (wet side). )) And the degree of condensation on the inner surface after the machine is stopped (if you want to prevent the sheet S from getting wet, you want to reduce the amount of water vapor in the water vapor retention space A (dry side)) The number can be adjusted. In the present embodiment, one or two dehumidifying agents 171 can be selected.

  In this way, in the image forming apparatus according to the present embodiment, the discharged sheet can absorb moisture again during the drying process in the water vapor staying space to reduce the curl amount. In addition, the moisture absorption action of the dehumidifying agent can prevent condensation due to a dew point drop due to a decrease in the ambient temperature in the moist water vapor retention space after sheet output. As a result, it is possible to form a sheet with good output quality that suppresses curling and suppresses moisture due to condensation.

1 is a front sectional view showing an overall configuration of an image forming apparatus (copier) according to an embodiment of the present invention. 1 is a front cross-sectional view showing a main part of an image forming apparatus (copier) according to an embodiment of the present invention. Main part supplementary explanatory drawing (plan view) according to the embodiment of the present invention Front sectional view showing the entire configuration of a conventional image forming apparatus (copier)

Explanation of symbols

100 Image Forming Apparatus (Embodiment)
DESCRIPTION OF SYMBOLS 150 Paper discharge tray part 151 Cover member 152 Cover part 153 Cover part 155 Hinge part 160 Humidity sensor 170 Extension tray part 171 Dehumidifier 200 Image forming apparatus (another embodiment)
Reference Signs List 250 discharge tray section 500 conventional image forming apparatus 510 document reading section 520 image forming section 525 process cartridge 530 sheet feeding section 551 sheet stacking section A water vapor retention space S sheet

Claims (4)

  An image forming unit for forming an image by an electrophotographic method, a fixing unit for thermally fixing a sheet after image formation, a discharging unit for discharging a sheet after fixing, and a sheet stacking for stacking the discharged sheet An image forming apparatus comprising: a cover member for enclosing the sheet discharge stacking unit and surrounding the sheet discharge stacking unit with a peripheral space; An image forming apparatus comprising humidity detection means in the sheet discharge stacking section.   The image forming apparatus according to claim 1, further comprising a humidity detecting unit in an inner peripheral space outside the sheet discharge stacking unit.   The image forming apparatus according to claim 1, wherein the cover member includes a lid that can be opened and closed.   The image forming apparatus according to claim 1, wherein an open / close state of the cover member is determined based on detection information from the humidity detection unit.

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