JP2007094000A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent power and toner from being wastefully consumed when failure in paper feed occurs at a paper feed initiation position in a color image forming apparatus. <P>SOLUTION: The image forming apparatus is designed such that a path B is shorter than a conveying path A. The conveying path A extends to a secondary transfer position 16 from the paper feed initiation position 31 of the manual paper insertion part 20. The path B extends to the secondary position 16 from the exposing position 32 of the photoreceptor drum 4a of the first image forming unit 4 of a plurality of image forming units, located farthest (furthest upstream of) from the secondary transfer position, along the surface of the photoreceptor drum 4a and along the lower flat face of the intermediate transfer belt 12 via a primary transfer position 8. A detecting means 29 for detecting success or failure in a paper feed operation is disposed immediately downstream of the conveying path 25 of the paper feed initiation position 31 of the manual paper insertion part 20. In addition, the image forming apparatus is provided with a control means 33 for exerting image formation only when the detecting means detects success in paper feed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus dedicated to monochrome printing, an image formed on an image carrier is transferred onto a sheet at a transfer position immediately downstream. That is, since the distance of the paper feeding start position is longer than the image writing position with respect to the transfer position, writing is performed after the paper feeding is started (see Patent Document 1).

  On the other hand, in a color printing image forming apparatus called a tandem type (hereinafter referred to as “color image forming apparatus”), a toner image formed by a plurality of image forming units corresponding to each color is transferred to an intermediate transfer belt or the like. After being superimposed on the intermediate transfer member (primary transfer), the image is transferred from the intermediate transfer member onto the paper (secondary transfer). Each image forming unit is arranged at a certain distance in the moving direction of the intermediate transfer member, and image formation starts in order from the upstream side.

  In the paper feeding means of the image forming apparatus, it is mainly used when printing on a cassette paper feeding unit that stores standard paper that is frequently used and special paper that is not frequently used (OHP sheet, postcard, cardboard, etc.) A manual paper feed unit is provided. Since various types of paper are used in the manual paper feed unit, the occurrence of paper feed defects increases. In this case, it is particularly in the paper feed portion that separates and feeds the stacked paper one by one, which is likely to cause paper feed failure. In the conveyance path on the way, since the sheet is nipped by one of the conveyance rollers, the frequency of occurrence of conveyance defects is relatively low.

  For this reason, as shown in Patent Document 2 and the like, a manual sheet feeding unit is arranged on the side surface of the apparatus closer to the secondary transfer position, and secondary transfer is performed along the conveyance path from the sheet feeding start position in the manual sheet feeding unit. Primary along the surface of the image carrier from the exposure position of the image carrier of the image forming unit that is farthest from the secondary transfer position (upstream) of the plurality of image forming units than the transport path to the position. The path extending from the transfer position to the secondary transfer position along the lower plane of the intermediate transfer belt is configured to be longer. In other words, the distance to the paper feed start position is shorter than the distance from the secondary transfer position to the exposure position of the most upstream image forming unit.

  In the color image forming apparatus configured as described above, when continuous printing is performed in the shortest time by using the manual sheet feeding unit, the sheet feeding start position is close to the secondary transfer position, so that printing for the second and subsequent sheets is performed. After image formation is started in the most upstream image forming unit, a paper feeding operation for printing the image is started.

  An example of the paper feeding operation will be described based on the timing chart of FIG. At the same time as the output of the image data is started, writing (exposure) of the first image onto the photosensitive drum of the most upstream image forming unit is started by the LSU unit, and writing of the first image is completed. Subsequently, the writing of the second image starts, and the first sheet feeding by the manual sheet feeding unit is started after this. When the paper passes the paper feed start position, the paper is nipped by the transport roller and is transported through the transport path as it is.

In the example of FIG. 6, the paper has been successfully fed up to the third sheet, but the fourth sheet has a feeding failure. However, when the paper feeding failure occurs, the fifth image is being written, and since the fourth image has already been written, it is consumed by writing the fourth and fifth images. Power and toner are wasted.
Japanese Patent Laid-Open No. 2001-234881 (FIG. 1) Japanese Patent Laying-Open No. 2004-29057 (FIG. 1)

  In this way, in a conveyance path configuration in which the distance from the secondary transfer position to the paper feed start position is shorter than the distance to the exposure position of the most upstream image forming unit, when a paper feed failure occurs at the start of paper feed In the upstream image forming unit, the fourth and fifth images are already formed on the intermediate transfer member, and the power and toner consumed for the image formation are wasted.

  An object of the present invention is to prevent wasteful power consumption and toner consumption when a paper feed failure occurs at a paper feed start position in a color image forming apparatus.

  To achieve the above object, the present invention provides an endless intermediate transfer belt, a plurality of image forming units arranged in a line along the intermediate transfer belt, and a toner on the intermediate transfer belt at a secondary transfer position. A secondary transfer unit that transfers an image onto a sheet conveyed along a conveyance path, a manual sheet feeder provided on a side surface of the apparatus, and an electrostatic latent image on an image carrier of each image forming unit according to image data. An image forming unit that develops an electrostatic latent image formed on the image carrier after charging, and a charging unit that charges the image carrier. Developing means for forming a toner image, and primary transfer means for transferring the toner image on the image carrier onto the intermediate transfer belt at a primary transfer position, and a paper feed start position in the manual paper feed section To the secondary transfer position along the transport path From the exposure position of the image carrier of the image forming unit that is farthest from the secondary transfer position among the plurality of image forming units than the path, it passes through the primary transfer position along the surface of the image carrier from the exposure position of the image carrier. The path leading to the secondary transfer position along the lower plane of the transfer belt is configured to be shorter, and image formation is performed only when a successful sheet feeding is detected.

  Further, the present invention is characterized in that a detection unit for detecting the success or failure of the sheet feeding operation is provided immediately downstream of the conveyance path at the sheet feeding start position in the manual sheet feeding unit.

  According to the color image forming apparatus of the present invention, image formation (formation of an electrostatic latent image on the image carrier of the image forming unit) to be output to the paper after detecting that the paper has been successfully fed is detected. ) Is started, and when the paper feed failure occurs, image formation corresponding thereto is not started, so that power and toner are not wasted.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a color image forming apparatus (color printer) according to the present invention. In the color image forming apparatus 1, a first paper feeding unit (automatic paper feeding unit) 2 such as a paper feeding cassette capable of stacking and storing a large number of sheets is disposed at the lower part of the apparatus, and a laser exposure device (LSU unit) is disposed above it. 3) The first to fourth image forming units 4 to 7 are arranged in the horizontal direction corresponding to the colors Y, M, C, and BK.

  FIG. 3 is a schematic configuration diagram of an image forming unit in the color image forming apparatus. Photosensitive drums 4a to 7a as image carriers are respectively provided in four first to fourth image forming units 4 to 7 arranged in a line at substantially constant intervals along the lower plane of the intermediate transfer belt 12. is set up. Around the photosensitive drums 4a to 7a, primary chargers 4b to 7b, developing rollers 4c to 7c, primary transfer rollers 4d to 7d, and drum cleaning rollers 4e to 7e are arranged. Further, the LSU unit 3 (see FIG. 1) irradiates color-spectral image data input from the outside from the laser light emitting element, and passes on the respective photosensitive drums 4a to 7a via a polygon lens, a reflection mirror, and the like. An electrostatic latent image of each color is formed (written).

  The primary transfer rollers 4d to 7d are disposed so as to be in contact with the photosensitive drums 4a to 7a via the intermediate transfer belt 12 at the primary transfer positions 8 to 11, respectively. The intermediate transfer belt 12 is disposed on the upper surface side of each of the photosensitive drums 4a to 7a, and is stretched between the secondary transfer counter roller 13, the driven roller 14, and the tension roller 15, and the secondary transfer counter roller. Reference numeral 13 denotes a secondary transfer position 16 that can be brought into contact with the secondary transfer roller 17 via the intermediate transfer belt 12. The belt cleaning roller 18 is disposed in the vicinity of the driven roller 14 and removes and collects the transfer residual toner remaining on the surface of the intermediate transfer belt 12.

  A fixing roller 19 is disposed above the secondary transfer position 16. A second paper feeding means (manual paper feeding unit) 20 is provided on the right side of the apparatus far from the secondary transfer position 16.

  The sheet conveying means has a conveying path 21 extending vertically from the first sheet feeding means 2 along the left side of the apparatus, and passes through the registration roller 22, the secondary transfer position 16, the fixing roller 19, and the sheet discharging roller 23. , Continues to the discharge tray 24 on the top surface of the apparatus. A transport path 25 from the second paper feed unit 20 extends in the horizontal direction along the upper surface of the first paper feed unit 2 and merges with the transport path 21 in the vertical direction. The second paper feeding means 20 is arranged in order from the upstream side in the paper conveyance direction, and includes a manual feed tray 26, a pickup roller 27a, a feed roller 27b, a retard roller 28 that presses against the feed roller 27b, a paper detection means 29, and a conveyance roller. 30.

  Therefore, starting from the paper feed position (the contact portion between the feed roller 27b and the retard roller 28, hereinafter referred to as “paper feed start position”) 31 in the second paper feed means 20, the second paper feed unit 20 is moved along the transport paths 25 and 21. The first image forming unit 4 located at the furthest position (most upstream) of the image forming units as viewed from the secondary transfer position 16 with respect to the transport path to the next transfer position 16 (path A indicated by a broken line in FIG. 1). Starting from the exposure position 32 of the photosensitive drum 4a, it reaches the secondary transfer position 16 along the lower plane of the intermediate transfer belt 12 via the primary transfer position 8 along the surface of the photosensitive drum 4a in the drum rotation direction. The route (route B indicated by a dotted line in FIG. 1) is configured to be shorter.

  As the sheet detecting means 29, an actuator can be preferably used. In the present embodiment, as shown in the enlarged view of the main part in FIG. 2, the actuator is always in the OFF position, moves to the ON position when the paper is passed, and returns to the OFF position again after the paper passes. As a result, the paper detection means 29 is turned ON / OFF once for each passage of one paper.

  The possibility that the paper will cause a conveyance failure in the conveyance path 21 is much lower than the possibility that the paper will cause a paper feeding failure at the paper feed start position 31. Therefore, when the paper detection means 29 is turned on, the paper detection means 29 Even before the printer is turned off, it can be determined that the paper feeding has been successful. On the other hand, when the paper stops at the paper feed start position 31 due to double feeding of the stacked paper, that is, when the paper detection means 29 does not turn on within a certain time after the paper feeding operation is started. Is determined to be a paper feed failure.

  Next, in the image forming apparatus configured as described above, when five images are continuously output using the paper set on the manual feed tray 26 of the second paper feeding unit 20, there is a paper feeding failure on the fourth paper. An image forming operation when it occurs will be described with reference to FIGS. FIG. 4 is a control block diagram of sheet feeding and image forming operations by the color image forming apparatus of the present invention, and FIG. 5 is a timing chart showing an example of sheet feeding and image forming operations.

  At the same time as the output of image data from a terminal such as a personal computer starts, the control means 33 comprising a microcomputer or the like operates the manual paper feed unit 20 to feed the first sheet and the paper detection means 29 is turned on for a certain period of time. Later, the LSU unit 3 starts the writing (exposure) operation of the first image on the photosensitive drum 4a of the first image forming unit 4. The sheet detection unit 29 is turned off and the second sheet starts to be fed after a certain period of time, and writing of the second sheet is started again at the timing when the sheet detection unit 29 is turned on. Are sequentially and periodically repeated. The fed paper is temporarily stopped by the registration roller 22 and conveyed to the secondary transfer position 16 in accordance with the timing from the writing start of the first image forming unit 4.

  Here, if the sheet detection unit 29 is not turned on within a predetermined time after the start of feeding of the fourth sheet, it is determined that a sheet feeding failure has occurred, and the image writing is immediately stopped. The device continues to operate without stopping, the printing process for the second and third sheets fed first is continued, and when it is finished, an indication that a paper feed failure has occurred is displayed on the operation unit, etc. Stop the device.

  According to this embodiment, after detecting that the paper has been successfully fed, image formation (formation of an electrostatic latent image on the image carrier of the image forming unit) to be output to the paper is started. Therefore, when the paper feeding failure occurs, image formation corresponding to the paper feeding failure is not started, so that power and toner are not wasted.

  It should be noted that the comparative examples and examples described above are merely examples, and the number of images and sheets, the timing of image formation, and the like are not limited thereto, and it goes without saying that various patterns can be changed.

  The present invention can be used in an image forming apparatus such as a printer or a copying machine.

1 is a schematic configuration diagram of a color image forming apparatus (color printer) according to the present invention. FIG. 2 is an enlarged view of the periphery of the paper detection unit in FIG. 1. FIG. 2 is a schematic configuration diagram of an image forming unit in the color image forming apparatus. FIG. 4 is a control block diagram of sheet feeding and image forming operations by the color image forming apparatus. These are timing charts showing an example of operations of paper feeding and image formation by the color image forming apparatus. These are timing charts showing an operation example of paper feeding and image formation by a conventional color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color image forming apparatus 2 1st paper supply means (automatic paper supply part)
3 LSU unit (exposure equipment)
4-7 Image forming unit 4a-7a Photosensitive drum 4b-7b Primary charger 4c-7c Developing roller 4d-7d Primary transfer roller 4e-7e Drum cleaning roller 8-11 Primary transfer position 12 Intermediate transfer belt 13 Secondary transfer facing Roller 14 Driven roller 15 Tension roller 16 Secondary transfer position 17 Secondary transfer roller 18 Belt cleaning roller 19 Fixing roller 20 Second paper feeding means (manual paper feeding unit)
DESCRIPTION OF SYMBOLS 21 Conveyance path 22 Registration roller 23 Paper discharge roller 24 Discharge tray 25 Conveyance path 26 Tray 27a Pickup roller 27b Feed roller 28 Retard roller 29 Paper detection means 30 Conveyance roller 31 Paper feed start position 32 Exposure position 33 Control means

Claims (2)

An endless intermediate transfer belt, a plurality of image forming units arranged in a line along the intermediate transfer belt, and a sheet on which a toner image on the intermediate transfer belt is conveyed along a conveyance path at a secondary transfer position Secondary transfer means for transferring to the image forming apparatus, a manual paper feed unit provided on the side surface of the apparatus, and an exposure device that forms an electrostatic latent image on the image carrier of each image forming unit according to image data,
The image forming unit includes an image carrier, a charging unit that charges the image carrier, and a developing unit that develops an electrostatic latent image formed on the charged image carrier to form a toner image. A primary transfer means for transferring a toner image on the image carrier onto the intermediate transfer belt at a primary transfer position, and a secondary transfer position along a transport path from a paper feed start position in the manual paper feed unit. From the exposure position of the image carrier of the image forming unit located farthest from the secondary transfer position among the plurality of image forming units than the transport path leading to the image, passes through the primary transfer position along the surface of the image carrier. The path to the secondary transfer position along the lower plane of the intermediate transfer belt is configured to be shorter,
An image forming apparatus that forms an image only when a paper feed success is detected.   The image forming apparatus according to claim 1, further comprising a detection unit that detects success or failure of a sheet feeding operation immediately downstream of a conveyance path at a sheet feeding start position in the manual sheet feeding unit.

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