JP2008037528A - Sheet stacking device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for contributing to reducing the number of components and the size of a device by utilizing a tray of a sheet reversing part as a second sheet discharge part. <P>SOLUTION: The sheet reversing part is served as the second sheet discharge part and a sheet reversing and carrying means is served as a second sheet carrying and discharging means. When transfer materials (sheets) are such media that sheets such as OHT or gross paper are easily stuck to each other, they are discharged alternately to the first discharge part and the second discharge part so as to be prevented from being stuck to each other. Thus, no imaging defect occurs. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet conveying device that has a function of reversing and conveying sheets such as a printer, a copying machine, and a facsimile, a reversing tray that substantially covers the sheet in a sheet reversing unit, and uses the reversing tray as a sheet discharge tray It relates to the device.

Conventionally, as an image forming apparatus in which a sheet discharge unit is a sheet reversal unit, as disclosed in Patent Document 1, it is easy to distinguish between a sheet being reversed and conveyed by the discharge unit and a sheet discharged to the discharge unit. In addition, there is a case where the upper surface of the pair of conveyance guides covering the sheet reversing path portion is used as a stacking tray for the sheets discharged from the second sheet discharge portion.
JP 2005-280856 A

  However, in the above method, a second sheet discharge unit other than the first sheet discharge unit and the sheet reversing unit is required, and the number of components increases, and the apparatus cannot be increased in size.

  The object of the invention according to the present application is to solve the problems of the above-described method by using the tray of the sheet reversing unit as the second sheet discharge unit, thereby reducing the number of components and reducing the size of the apparatus. Is to provide.

  Further, by using the sheet reversing unit as the second sheet discharging unit (stacking unit), the first discharging unit is used when the transfer material (sheet) is a medium in which sheets such as OHT and glossy paper are easily stuck to each other. By alternately discharging to the second discharge unit (stacking unit), sticking between sheets can be prevented, and image defects do not occur. This is particularly effective in preventing sticking by switching the paper discharge section (stacking section) alternately, as sticking between transfer materials (sheets) tends to be a problem, especially in double-sided printing with high image density. is there.

  Accordingly, in order to achieve the above object, the present invention provides an image forming apparatus including a first stacking unit that stacks sheets and a first sheet discharge unit that discharges sheets to the first stacking unit. , A sheet reversing path unit for reversing and conveying the sheet, and a reversing conveying unit for reversing and conveying the sheet, wherein the sheet reversing path unit is a second sheet stacking unit, and the reversing and conveying unit is a second sheet discharging unit. It is characterized by becoming.

  As described above, according to the present invention, the tray of the sheet reversing unit is used as the second sheet discharging unit, thereby reducing the number of components, downsizing the apparatus, and sticking transfer materials (sheets) to each other. It leads to prevention of image defects.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not intended to limit the scope of the invention only to them.

  1 and 2 are schematic configuration model diagrams of a color laser printer which is an example of a color image forming apparatus having a sheet reversing tray unit according to the first embodiment of the present invention.

  As shown in FIGS. 1 and 2, yellow (hereinafter abbreviated as “Y”), magenta (hereinafter abbreviated as “M”), cyan (hereinafter referred to as “C”), which are image holders arranged side by side in an oblique direction. ) And black (hereinafter abbreviated as “Bk”) four photosensitive drums 1a, 1b, 1c, 1d (hereinafter simply abbreviated as “photosensitive drum 1”). 1, an intermediate transfer belt 12e serving as an intermediate transfer body on which a toner image formed on the surface of the photosensitive drum 1 is primarily transferred is stretched by a driving roller 12f and a driven roller 12g. The secondary transfer means 16 is disposed at a position facing the driven roller 12g with the belt 12e interposed therebetween.

  The toner images formed on the respective photosensitive drums 1 are primarily transferred to the intermediate transfer belt 12e by the action of the transfer units 12a, 12b, 12c, and 12d. Around each photosensitive drum 1, primary chargers 2a, 2b, 2c, and 2d (hereinafter simply referred to as "charging means" for uniformly charging the surface of the photosensitive drum 1 in order from the upstream side in the rotation direction). Exposure means for forming an electrostatic latent image by irradiating the surface of the photosensitive drum 1 uniformly charged by the primary charger 2 with a laser beam based on image information. 3a and 3b (hereinafter simply referred to as “exposure means 3”) are arranged.

  Then, developing means 40a, 40b, 40c, and 40d (hereinafter referred to as toner images) are formed by attaching toners of colors Y, M, C, and Bk to the surface of the photosensitive drum 1 on which the electrostatic latent image is formed. Cleaning means 8a, 8b, 8c, 8d (hereinafter simply referred to as “cleaning means 8”) for removing the toner remaining on the surface of the photosensitive drum 1 after transfer. Has been.

  The developing unit includes process cartridges 7a, 7b, 7c, and 7d (hereinafter simply referred to as “process cartridge 7”) and toner cartridges 5a, 5b, 5c, and 5d (hereinafter simply referred to as “toner cartridge 5”). It is unitized.

  On the other hand, the transfer material (sheet) 11a fed from the paper feed cassette 11 by the pickup roller 9 is separated and fed one by one by the separating means of the feed roller 51a and the retard roller 52a, and then the registration roller by the conveying roller pair 13a. When the sheet is fed to the pair 17 and fed from the multi-tray 50, the sheet is separated and fed one by one by the separating means of the feed roller 51b and the retard roller 52b, and then the registration roller pair 17 by the conveying roller pair 13b. Is transferred between the intermediate transfer belt 12e and the secondary transfer means 16 by the registration roller pair 17 at a predetermined timing, and is primarily transferred to the intermediate transfer belt 12e by the action of the secondary transfer means 16. The toner image is secondarily transferred.

  The transfer material 11a on which the toner image has been transferred is fixed by the discharge roller pair when the switching lever 55 is switched to a position 55a shown in FIG. 20 and is discharged onto a discharge tray 21 provided in the upper part of the apparatus main body. When the switching lever 55 is at the position 55b shown in FIG. 2, the conveying roller pair 13c conveys it to the switchback roller pair 31 of the double-sided conveyance path 30, and the switchback roller pair 31 switches the conveying direction. At this time, the transfer material 11a protruding from the apparatus main body 100 is substantially covered with the reverse tray unit 300 so that the user does not touch it by mistake. Then, it passes through the transport roller pairs 13d, 13e, and 13f and is transported again to the registration roller pair 17.

  Here, a fixing device used in a general image forming apparatus will be described with reference to FIG.

  In FIG. 3, the fixing roller 140 is provided with a releasable resin layer 142 such as PFA or PTFE on a metal core 141 such as aluminum or iron as an example, and the inside is heated by a heater 143. Yes. The surface temperature of the fixing roller 140 is detected by the temperature detecting element 150 contacting the fixing roller 140, and the temperature control circuit intermittently operates the heater 143, whereby the surface temperature of the fixing roller 140 is changed. It is controlled to a predetermined temperature.

  On the other hand, the pressure roller 160 that is pressed against and rotates against the fixing roller 140 is provided with an elastic layer 162 such as silicon rubber or silicon sponge having heat resistance and low hardness on a metal core 161 such as aluminum or iron. The surface has a coating layer 163 made of a resin having high releasability such as PFA or PTFE, and the inside is heated by a heater 163. The temperature of the pressure roller 160 is detected by the surface temperature of the pressure roller 160 by the temperature detecting element 151 that is in contact with the pressure roller 160, and the temperature control circuit intermittently operates the heater 163, whereby the pressure roller 140. Similarly to the fixing roller 140, the surface temperature of is controlled to a predetermined temperature.

  In addition, the offset deteriorates because the releasability of the surface of the fixing roller 140 decreases due to the adhesion of the charcoal powder. The offset toner is transferred from the surface of the fixing roller 140 to the surface of the pressure roller 160 due to the difference in releasability in the transfer material conveyance interval, and is accumulated on the surface of the pressure roller 160. In such a process, the toner adhering or accumulating on the pressure roller 160 returns to the back surface of the transfer material or returns to the fixing roller 140, and causes the surface of the transfer material to become dirty.

  Furthermore, when an image larger than the paper size is drawn and “marginless” printing is performed without margins, toner is attached to the surfaces of the fixing roller 140 and the pressure roller 160, causing the front and back surfaces of the transfer material to become dirty. For this reason, the cleaning roller 145 is brought into contact with the fixing roller 140 and the cleaning roller 165 is brought into contact with the pressure roller 160, whereby the toner attached to the surface of the roller is collected. The cleaning roller 145 can be brought into contact with and separated from the fixing roller 140, and the cleaning roller 165 can be brought into contact with and separated from the pressure roller 160 by a cam mechanism (not shown).

  In addition, the image forming apparatus has a special transfer material mode, and a special transfer material can be set from an operator operation panel (not shown) or a host computer. Depending on the type and thickness of the material, part of the process conditions such as the transfer speed of the transfer material and the fixing temperature can be changed.

  Further, in the color image forming apparatus as described above, in recent years, there has been a demand for higher output image quality. In particular, the gradation of the density and its stability have a great influence on the judgment of the quality of an image given by a human.

  However, in the color image forming apparatus, the density of the obtained image fluctuates if there are fluctuations in each part of the apparatus due to environmental changes or prolonged use.

  In particular, in the case of an electrophotographic color image forming apparatus, several kinds of exposure amounts and development biases corresponding to absolute humidity are applied to toners of each color Y, M, C, and Bk, whose color balance is lost even by slight variations in density. The process conditions and the optimum values for gradation correction are selected based on the absolute humidity measured by the temperature and humidity sensor.

  In addition, a toner patch for density detection is created on the intermediate transfer member, drum, etc. with toner of each color so that a constant density-gradation characteristic can be obtained even if fluctuations occur in each part of the apparatus, and the unfixed toner patch Is detected by the density detection sensor 201 for unfixed toner, and the density control is performed by feeding back to the process conditions such as the exposure amount and the development bias based on the detection result, thereby obtaining a stable image. Yes.

  However, density control using the density detection sensor 201 for unfixed toner is to detect a patch by forming a patch on an intermediate transfer member, a drum, or the like. There is no control over changes in balance.

  The color balance also changes depending on the transfer efficiency in transferring the toner image to the transfer material, and heating and pressurization by fixing.

  This change cannot be handled by density control using the density detection sensor for unfixed toner.

  Therefore, a density or chromaticity detection sensor (hereinafter referred to as “color sensor”) 200 for detecting the density of a single color toner image on a transfer material or the chromaticity of a full color image after transfer and fixing is installed to control density or chromaticity. A color toner patch is formed on a transfer material, and the detected density or chromaticity is fed back to process conditions such as exposure amount, process condition, look-up table (LUT), and the density or density of the final output image formed on the transfer material. Chromaticity control is performed.

  Next, the reverse tray unit 300 will be described.

  The reversing tray unit 300 includes a reversing tray 301 and a reversing tray cover 302, and is configured to substantially cover a transfer material (sheet) that is conveyed in a reversed manner. By conveying the reversed sheet into the reversing tray unit 300, the user is prevented from touching the transfer material (sheet) being reversed and conveyed from the outside.

  The reversing tray cover 302 can be opened and closed with respect to the reversing tray 301 as shown in FIG.

  Further, when the switching lever 55 is at the position 55b shown in FIG. 2, the transfer material 11a is conveyed to the switchback roller pair 31 in the duplex conveyance path 30 by the conveyance roller pair 13c.

  Here, when the switchback roller pair 31 is set by the user, the transfer material 11a is transferred to the reverse tray unit 300 by continuing to rotate in the arrow A direction without switching the rotation in the arrow B direction in FIG. It will be possible to send in completely. At this time, the reverse tray unit 300 that has received the transfer material 11a becomes the second paper discharge unit (stacking unit), and the transfer material 11a is stacked on the reverse tray 301 as shown in FIG.

  As shown in FIG. 6, the reverse tray unit 300 is configured to be detachable from the apparatus main body 100.

  As described above, according to the present embodiment, by using the reverse tray unit 300 as the second paper discharge unit, components such as the conveyance roller (pair) normally provided in the second sheet discharge unit can be provided. Since the number of components can be reduced, the size of the apparatus can be reduced.

  Further, by making the reverse tray cover 302 openable and closable with respect to the reverse tray 301, the transfer material (sheet) stacked when the reverse tray 301 in the reverse tray unit 300 is used as the second discharge tray is taken out. It becomes easy. Even if a transfer material (sheet) remains in the reversing tray unit 300, it is easy to recognize the transfer material (sheet) and to access the transfer material (sheet), thereby improving the processability. To do.

  Further, by using the reversing tray unit 300 that is a transfer material (sheet) reversing unit as the second paper ejection unit, a total of two paper ejection units are provided in addition to the first paper ejection unit. Therefore, the first paper discharge unit and the reverse tray unit unit can be switched and discharged. In addition, sticking of OHT, glossy paper, moisture-absorbing paper, and transfer materials (sheets) on which high-density images are printed is prevented by alternately discharging paper to the first paper discharge unit and reverse tray unit. And no image defects occur.

  For example, in the case of 10 jobs from P1 to P10, when the first discharge unit is A and the second discharge unit is B, P1 (A) ⇒P6 (B) ⇒P2 (A) ⇒ P7 (B) ⇒P3 (A) ⇒P8 (B) ⇒P4 (A) ⇒P9 (B) ⇒P5 (A) ⇒P10 (B) {P1 (A) discharges P1 to the first discharge section By alternately disposing the discharge portions, the sticking between the transfer materials can be prevented. Further, by changing the print page order of the job, when the transfer materials (sheets) stacked on the first discharge unit and the transfer materials (sheets) stacked on the second discharge unit are combined, Since there is no need to replace the job, the job may be processed in this way.

  The image forming apparatus according to the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist thereof. For example, the optical system may be one that uses an LED array in addition to one that scans laser light with a polygon mirror, or a copier type that has an image reading unit in addition to a printer type image forming apparatus that does not have an image reading unit. The image forming apparatus may be used. The switching setting for determining whether or not to use the reversing unit as the second paper discharge unit is not limited to the time set by the user, but the information from the media sensor for determining the type of the transfer material and the information such as the temperature / humidity sensor. It may be switched automatically based on In addition to the electrophotographic method, the recording method may be another recording method such as an inkjet method.

1 is a schematic cross-sectional view of an image forming apparatus illustrating a technique according to an embodiment of the present invention. 1 is a schematic cross-sectional view of an image forming apparatus illustrating a technique according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device for explaining a technique according to an embodiment of the present invention. It is a schematic structure sectional view of the inversion tray unit explaining the art concerning the example of the present invention. It is a schematic structure sectional view of the inversion tray unit explaining the art concerning the example of the present invention. 1 is a schematic cross-sectional view of an image forming apparatus illustrating a technique according to an embodiment of the present invention.

Explanation of symbols

1 (1a, 1b, 1c, 1d) Photosensitive drum 2 (2a, 2b, 2c, 2d) Primary charger 3 (3a, 3b) Exposure device 5 (5a, 5b, 5c, 5d) Toner cartridge 7 (7a, 7b, 7c, 7d) Process cartridge 8 (8a, 8b, 8c, 8d) Cleaning means 9 Pickup roller 11 Paper feed cassette 11a Transfer material (sheet)
12 Intermediate transfer belt unit 13 (13a, 13b, 13c, 13d, 13e, 13f) Transport roller pair 14 Fixing means 16 Secondary transfer means 17 Registration roller pair 20 Discharge roller pair 21 Discharge tray 30 Duplex transport path 31 Switchback roller pair 40 (40a, 40b, 40c, 40d) Developing means 50 Multi-tray 51 (51a, 51b) Feed roller 52 (52a, 52b) Retard roller 55 Switching lever 100 Main body 140 Fixing roller 145 Cleaning roller 160 Pressure roller 165 Cleaning roller 200 Color sensor 300 Reverse tray unit 301 Reverse tray 302 Reverse tray cover

Claims (6)

  A sheet reversing path unit that reversely conveys a sheet, and a sheet in an image forming apparatus comprising: a first stacking unit that stacks sheets; and a first sheet discharging unit that discharges sheets to the first stacking unit; A sheet stacking apparatus, wherein the sheet reversing path unit serves as a second sheet stacking unit, and the reverse transporting unit serves as a second sheet discharge unit.   2. The sheet reversing path unit includes a reversing tray, and an upper surface of the reversing tray has a function of a stacking tray for stacking sheets discharged by the second sheet discharging unit. Sheet stacking device.   The sheet stacking apparatus according to claim 1, wherein the sheet reversing path unit is detachable from the apparatus main body.   4. The sheet stacking apparatus according to claim 1, wherein the sheet reversing path unit includes the reversing tray and a reversing tray cover that covers the reversing tray.   The sheet stacking apparatus according to claim 4, wherein the reverse tray cover is openable and closable.   6. An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the sheet stacking device according to claim 1, which stacks the sheet formed by the image forming unit. apparatus.

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