JP5078449B2 - Image forming apparatus - Google Patents

Description

  The present invention provides a photoconductor unit including a plurality of toners of different colors, a transfer body that superimposes and holds images of different toner colors formed by the photoconductor unit, and a paper supply control unit that supplies paper to the transfer body. The present invention relates to an image forming apparatus including a paper control unit.

  The time from when a job is received until the first printed material is output (hereinafter referred to as “first print time”) is an important index for expressing the performance of the image forming apparatus, and the first print time. Conventionally, various proposals have been made to shorten the time. For example, Patent Document 1 discloses image formation in which the conveyance speed of the paper is higher than that at the time of image formation after the first paper is sent out by the registration rollers until image formation is started on the paper. A device has been proposed.

JP-A-9-2111915

  In the image forming apparatus, the sheet fed from the sheet storage unit is made to wait in advance by a registration roller, and the sheet is fed from the registration roller in accordance with the leading end of the image formed on the transfer body, and the leading end of the image and the leading end of the sheet are aligned. It is configured to reach the transfer position at the same time. That is, when the paper feeding to the registration roller is delayed, the first print time becomes longer.

  Accordingly, many image forming apparatuses have been configured to start feeding from a sheet storage unit immediately after receiving a job and wait for a sheet with a registration roller. In such an image forming apparatus, at least The first print time does not become long because the sheet to be waited by the registration roller is not fed.

  However, in an image forming apparatus configured to start feeding from a sheet storage unit immediately after receiving a job, if the job is canceled before image formation is started, the sheet already fed to the registration roller Therefore, the paper is unnecessarily discharged.

  Accordingly, it is preferable that paper feeding to the registration roller is as late as possible, and the paper feed timing from the paper storage unit is determined at least within a range that is not delayed from the timing of transferring the image formed on the photoconductor.

  However, in a full-color image forming apparatus including a photoreceptor unit including a plurality of different color toners and a transfer body that holds images of different toner colors formed by the photoreceptor unit in a superimposed manner, generally, there are four transfer members. Since the color toner images are superimposed and transferred to the paper, there is a problem that the first print time becomes long.

  For example, in a tandem type image forming apparatus in which a plurality of photoconductor units are arranged along a transfer body, the paper feed timing is uniformly determined based on the image formation timing of the photoconductor unit that forms the image first, In an image forming apparatus such as a rotary development system in which toner images of respective colors sequentially formed on a single photosensitive unit are transferred onto a transfer body and then transferred onto a sheet, image formation of the photosensitive unit that finally forms an image Since the sheet feeding timing is uniformly determined based on the timing, the first print time is increased by the waiting time until the toner images of the respective colors are formed as compared with the monochrome image forming apparatus.

  In view of the above-described problems, an object of the present invention is to provide an image forming apparatus capable of shortening the first print time while enabling the operation to stop the image forming operation after the color image forming operation is started. In the point.

In order to achieve the above-described object, a first characteristic configuration of an image forming apparatus according to the present invention is, as described in claim 1 of the claims, a photoconductor unit including a plurality of different color toners, An image forming apparatus comprising: a transfer body that superimposes and holds images of different toner colors formed by the photoconductor unit; and a paper feed control unit that controls supply of paper to the transfer body. When the number of toner colors constituting the image formed by the image forming unit is smaller than the number of toner colors provided in the photosensitive unit, the paper feed control unit is configured to store the image for each color component held on the transfer body. Among them, there is a sheet feeding timing determining unit that determines a sheet feeding timing for starting feeding of the sheet stored in the sheet storing unit with reference to the image forming timing of the lowermost layer or the uppermost layer.

  According to the above-described configuration, among the images for each of the color components configured to be superimposed and held on the transfer body, the sheet is fed on the basis of the image formation timing of the lowermost layer or the uppermost layer that is actually involved in image formation. Since the paper feed timing is determined by the timing determining means, the paper feed timing changes depending on the color components constituting the color image, and the opportunity to shorten the first print time can be increased.

  In the second feature configuration, in addition to the first feature configuration described above, a plurality of the photoreceptor units are provided along a circumferential direction of the transfer body, and the sheet feeding timing is provided. Is the image formation timing of the photosensitive unit that forms the lowermost image among the images that are superposed and held on the transfer body.

  In the tandem image forming apparatus, the sheet feeding timing is determined based on the image forming timing of the photosensitive unit that forms the image first. That is, the paper feed timing is determined so as not to be delayed from the transfer timing of the image formed by the photosensitive unit farthest from the transfer position of the toner image onto the paper. Therefore, when the photoconductor unit physically farthest from the transfer position is not involved in image formation, it is not necessary to determine the paper feed timing based on the image formation timing of the photoconductor unit, and the paper feed timing is accordingly increased. Can be accelerated.

  According to the third characteristic configuration, as described in claim 3, in addition to the first characteristic configuration described above, the photoconductor unit includes a single photoconductor and a plurality of developing units, and the sheet feeding timing. Is the image formation timing of the photoconductor unit that forms the uppermost image among the images that are superposed and held on the transfer body.

  In an image forming apparatus such as a rotary development system in which toner images of respective colors sequentially formed on a single photosensitive unit are transferred onto a transfer body and then transferred onto a sheet, The sheet feeding timing is determined based on the image forming timing of the photosensitive unit that forms the uppermost image. That is, the paper feed timing is determined so as not to delay the transfer timing for the color component image finally formed on the photosensitive member. Therefore, when the development unit physically transferred last is not involved in image formation, it is not necessary to determine the paper feed timing based on the image formation timing of the development unit, and the paper feed timing is advanced accordingly. Can do it.

  In the fourth feature configuration, as described in claim 4, in addition to any of the first to third feature configurations described above, from the front end position of the paper before the paper feeding is started, When the paper movement distance to the image transfer position is equal to or greater than the image movement distance from the image formation position of the photosensitive unit that forms the image of the lowermost layer or the uppermost layer to the image transfer position, the paper feed control unit It is that paper feeding is started prior to the image forming timing of the photosensitive unit.

  The sheet moving distance from the leading edge position of the sheet before the start of feeding to the image transfer position to the sheet is the distance from the image forming position of the photosensitive unit that forms the lowermost or uppermost image to the image transfer position. As long as the feed speed is the same as the process speed for image formation when the distance is greater than the image movement distance, even if paper feed is started at the timing when the lowermost or uppermost image leading edge is formed, The leading edge of the sheet reaches the transfer position with a delay from the arrival time at the transfer position. In such a case, the registration can be reliably performed by starting the paper feeding prior to the image forming timing of the photosensitive unit.

  As described above, according to the present invention, it is possible to provide an image forming apparatus capable of shortening the first print time while enabling the operation of stopping the image forming operation after the color image forming operation is started. Can now.

  Hereinafter, an image forming apparatus according to the present invention will be described using a copying machine 1.

  The copying machine 1 is an apparatus for forming an image by an electrophotographic method. The copying machine 1 is placed on an operation unit 10 on which a display unit formed of a liquid crystal screen, a print key for starting a copying operation, and the like are arranged, and a document feeding table 11. An image reading unit 12 that sequentially feeds the read originals, photoelectrically converts the original image to read it as digital image data, and an image processing unit 13 that converts the digital image data read by the image reading unit 12 into output image data. A plurality of photosensitive units and a transfer body, and an image forming unit 2 that forms an image based on output image data and transfers the image to a sheet; and a toner image output on the sheet is heated and fixed on the sheet A fixing unit 15, a sheet storage unit 14 that stores a sheet on which a toner image formed on the photosensitive member is transferred, and a paper feeding / conveying discharge unit that feeds, transports, and discharges the sheet stored in the sheet storage unit 14. A paper mechanism 16; A paper discharge unit 17 whose serial sheet is discharged, and a controller 3 for controlling these function blocks to execute processing as a copying machine 1.

  The image processing unit 13 performs predetermined image processing such as shading correction on the digital image data composed of RGB components input from the image reading unit 12 to obtain M (magenta), C (cyan), Y (yellow), K The image data is converted into output image data composed of (black) color components, and the image data is output for each color component to an exposure device of a photoreceptor unit described later.

  As shown in FIG. 3, the image forming unit 2 is provided with four photosensitive units 20 made of the same hardware at equal intervals along the circumferential direction of the transfer member 21 formed of a transfer belt. From the upstream side, toners of M (magenta), C (cyan), Y (yellow), and K (black) are provided. Each photoconductor unit 20 is provided with a charging charger 20a along the circumferential direction of the photoconductor 20c, an exposure device 20b equipped with a laser beam scanned by a rotary polygon mirror, a developing device 20d, a cleaner 20f, and a static elimination lamp 20g. ing. Further, a transfer roller 20e is disposed at a position facing the photoconductor unit 20 with the transfer body 21 interposed therebetween, and supports the transfer body 21 downstream of the photoconductor unit 20 including black toner disposed on the most downstream side. The transfer roller 22 is disposed at a position opposite to the support roller 23 that is rotationally driven.

  The paper feeding / conveying mechanism 16 includes a pickup roller 16a that picks up the paper from the paper storage unit 14 one by one, a paper feeding roller 16b that transports the picked up paper to the registration roller 16c, and corrects and transfers the leading edge of the paper. A registration roller 16c that feeds the paper at a predetermined timing at which the image leading edge of the image held on the body 21 and the paper leading edge coincide at the transfer position, and a paper discharge roller 16d that discharges the fixed paper to the outside of the apparatus.

  The control unit 3 includes a CPU, a ROM that stores a control program executed by the CPU, a RAM that stores control data and the like, a load such as a motor arranged in each functional block, an interface circuit with a sensor, and the like. Configured. Each functional block is controlled by a control program executed by the CPU of the control unit 3 and related hardware, and a predetermined image forming function of the copying machine 1 is realized.

  As shown in FIG. 1, the control unit 3 forms an image in the image forming unit 2 based on the output image data, and controls an image formation control unit 30 that controls a process of transferring the formed image to a sheet. A paper feed control unit 31 that controls paper feed of the paper stored in the paper storage unit 14 by the paper discharge mechanism 16 is provided.

  The image formation control unit 30 controls each part of the photoconductor unit 20 to form an image and drives and controls the support roller 23 to rotate the transfer body 21 at the same speed as the peripheral speed of the photoconductor 20c. Then, the toner image held on the transfer body 21 is transferred onto the sheet by the transfer roller 22 to which the transfer bias voltage is applied.

  The image formation control unit 30 includes each of the photoconductor units 20 including toners of colors corresponding to the respective color components of M (magenta), C (cyan), Y (yellow), and K (black) constituting the output image data. On the other hand, the surface of the photoreceptor 20c is uniformly charged by the charging charger 20a, the exposure device 20b is driven based on the output image data of the corresponding color component, and a latent image is formed on the surface. After developing and visualizing, the toner image is transferred to the transfer body 21 by the transfer roller 20e to which a transfer bias voltage is applied, and the surface of the photoconductor 20c after transfer is removed by the cleaner 20f, and then the residual charge is removed by the charge eliminating lamp 20g. To control the image forming process of removing.

  When the rotation state of each photoconductor 20c and the rotation state of the rotary polygon mirror are stabilized, that is, when the image formation control state is enabled, the image formation control unit 30 sequentially exposes the image processing unit 13 and each exposure device 20b at a predetermined timing. A start signal is output, and the vertical synchronization signal output from each exposure apparatus 20b is recognized as each image formation start timing (hereinafter referred to as “image formation start timing”).

  When each exposure device 20b detects an exposure start signal, it synchronizes with the scanning start position of the laser by the rotary polygon mirror, and modulates the laser based on the output image data output from the image processing unit 13 to expose the photoconductor 20c. . Each exposure apparatus 20b outputs a vertical synchronization signal to the image formation control unit 30 in synchronization with the first scanning start position of one image.

  Here, the exposure start signal output to each exposure device 20b is output at predetermined time intervals so that the leading edge of the image formed by each photoconductor unit 20 coincides with the transfer body 21 above.

  The output light of the laser modulated based on the output image data has a vertical synchronization signal indicating the tip position of one image as a reference timing in the sub-scanning direction, and a horizontal synchronization signal as a reference timing in the main scanning direction. As described above, raster scanning is performed by a rotating polygon mirror.

  The image formation control unit 30 applies to the transfer body 21 when forming a full-color image in which output component data includes all color component data of M (magenta), C (cyan), Y (yellow), and K (black). The images from the M (magenta) photoreceptor unit 20 arranged on the most upstream side of the transfer body 21 to the most downstream K (black) photoreceptor unit 20 in order so that the areas of the transferred toner images coincide with each other. The formation timing is controlled, and image formation is controlled based on the image data corresponding to each toner color in each photoconductor unit 20.

  Therefore, the toner images transferred from the M (magenta) photoconductor unit 20 disposed on the most upstream side are sequentially superimposed on the transfer body 21 as the lowermost layer, and the most downstream K (black) is superposed. The toner image formed on the photoreceptor unit 20 is transferred to the uppermost layer.

  When the number of toner colors constituting the image formed by the photoreceptor unit 20 is less than the number of toner colors provided in the photoreceptor unit 20, that is, output image data includes M (magenta), C (cyan), and Y (yellow). ) And K (black), when forming a color image in which the color component data is missing, the photosensitivity corresponding to the missing color component is matched so that the areas of the toner images transferred to the transfer body 21 match. Among the photoconductor units 20 excluding the photoconductor unit 20, the image formation timing is sequentially controlled from the photoconductor unit 20 arranged on the most upstream side of the transfer body 21 to the photoconductor unit 20 on the most downstream side. The image formation is controlled based on the image data corresponding to each toner color. At this time, the photoconductor of the photoconductor unit 20 corresponding to the missing color component is rotationally driven, but each process control of charging, exposure, and development is not performed.

  For example, when M (magenta) and C (cyan) components are missing from the output image data, and a color image is formed using the Y (yellow) and K (black) components, M (magenta) and C (cyan) are formed. Since no image is formed on the photoconductor unit 20), image formation is performed in order from the Y (yellow) photoconductor unit 20 arranged on the most upstream side of the transfer body 21 to the K (black) photoconductor unit 20 on the most downstream side. The timing is controlled, and each photoconductor unit 20 controls image formation based on image data corresponding to each toner color.

  Accordingly, the toner image transferred from the Y (yellow) photoreceptor unit 20 arranged on the most upstream side is superimposed on the transfer body 21 as the lowermost layer, and the most downstream K (black) photosensitive is superposed. The toner image formed on the body unit 20 is transferred to the uppermost layer.

  The paper feed control unit 31 feeds the paper stored in the paper storage unit 14 one by one by the pickup roller 16a, and sets the paper feed roller 16b so as to stop at the position of the registration roller 16c with the tip maintained in a loop shape. Control. Next, the registration roller 16c is driven at a timing when the leading edge of the image held on the transfer body 21 and the leading edge of the sheet coincide at the transfer position.

  The paper feed control unit 31 is delayed by a predetermined time so that the front end of the image transferred to the transfer body 21 and the front end of the paper coincide with each other at the transfer position with reference to the earliest image formation timing output from the image formation control unit 30. A paper feed timing determination unit 310 that determines the timing as a paper feed timing is provided, and the paper feed control unit 31 drives the pickup roller 16a based on the paper feed timing determined by the paper feed timing determination unit 310 to form a paper storage unit 14 starts feeding the paper stored in the paper 14.

  Here, the sheet conveying speed of the pickup roller 16a and the sheet feeding roller 16b may be the same as or different from the peripheral speed of the photosensitive member. In this embodiment, the paper transport speed of the pickup roller 16a and the paper feed roller 16b is set to be the same as the peripheral speed of the photoreceptor. Even when the paper transport speed of the paper feed roller 16b is different from the peripheral speed of the photosensitive member, the same speed as the peripheral speed of the photosensitive member should be switched to ensure good transfer characteristics at least when the registration roller 16c is driven. Need to be configured.

  In other words, the paper feed timing determination unit 310 determines the paper feed timing based on the image formation timing of the lowest layer among the images for each color component that are superposed on the transfer body 21.

  Hereinafter, the image forming timing of each photoconductor unit 20 from the start of the image forming operation activated by pressing the print key disposed on the operation unit 10 to the discharge of the paper, and the operation timing of the paper feeding / conveying paper discharge mechanism 16 Will be described based on the time charts of FIGS.

  When the output image data output from the image processing unit 13 is a full-color image having color components of M (magenta), C (cyan), Y (yellow), and K (black), as shown in FIG. When an exposure start signal is output to each photoconductor unit 20 with a predetermined time difference after the print key is pressed, M (magenta) toner arranged on the most upstream side is provided. An image is formed by each of the K (black) photoconductor units 20 arranged on the most downstream side from the photoconductor unit 20.

  The paper feed control unit 31 uses the image forming timing of the photoconductor unit 20 including M (magenta) toner that forms the lowermost image of the superimposed image as a reference, and the leading edge of the image transferred to the transfer body 21 and the paper. Paper feeding is started at a timing delayed by a predetermined time tM so that the leading ends coincide with each other at the transfer position, and the registration roller 16c is driven in accordance with the timing at which the superimposed image held on the transfer body 21 reaches the transfer position.

  In the paper feed control unit 31, the transferred paper is fixed by the fixing unit 15 and discharged to the paper discharge unit 17 by the paper discharge roller 16d. The time T1 from the press operation of the print key to the completion of paper discharge is the first print time.

  When the output image data output from the image processing unit 13 is a color image having only Y (yellow) and K (black) color components, as shown in FIG. 4B, after the print key is pressed. When the image formation control unit 30 outputs an exposure start signal with a predetermined time difference to the photoconductor unit 20 corresponding to the Y (yellow) and K (black) color components, the Y (yellow) disposed on the upstream side. An image is formed by each of the photoconductor unit 20 including the toner and the K (black) photoconductor unit 20 disposed on the most downstream side.

  The paper feed control unit 31 uses the image forming timing of the photoconductor unit 20 having Y (yellow) toner to form the lowermost image of the superimposed image as a reference, and the leading edge of the image transferred to the transfer body 21 and the paper. Paper feeding is started at a timing delayed by a predetermined time tY so that the leading ends coincide with each other at the transfer position, and the registration roller 16c is driven in accordance with the timing at which the superimposed image held on the transfer body 21 reaches the transfer position.

  In the paper feed control unit 31, the transferred paper is fixed by the fixing unit 15 and discharged to the paper discharge unit 17 by the paper discharge roller 16d. The time T2 from the press operation of the print key to the completion of paper discharge is the first print time.

  Since the time until each photoconductor unit 20 is ready to form an image after the print key is pressed is approximately equal, the first print time T1 for the full-color image in FIG. 4A and the color in FIG. There is a difference of T3 = tM−tY from the first print time T2 for the image. That is, the first print time is shortened by T3.

  In other words, among the images for each color component that are superimposed and held on the transfer body 21, the photoreceptor unit 22 that forms the lowermost image is positioned upstream from the photoreceptor unit 22 disposed on the most upstream side. In the case of the photoconductor unit 22, the first print time is shortened.

  However, in the case where the output image data output from the image processing unit 13 is a monotone image having only a K (black) color component, the leading edge position of the paper before the paper feeding is started, that is, the paper storage unit 14. The sheet moving distance from the leading edge position of the sheet accommodated in the sheet to the image transfer position to the sheet is the image movement from the image forming position to the image transfer position of the K (black) photoreceptor unit 22 that forms the lowermost image. Since the distance is equal to or greater than the distance, if the sheet feeding timing is determined based on the image forming timing of the photosensitive unit 22, the image transfer timing is lost.

  In such a case, the paper feed control unit 31 may be configured to start paper feeding ahead of the image formation timing of the photosensitive unit 22. For example, after the print key is operated, the paper feed is started immediately after the main drive system for driving the paper feed roller and the like is started up. Alternatively, an exposure start signal may be output to the image processing unit 13 and the exposure device 20b after the fed paper waits at the registration roller 16c.

  Another embodiment will be described below.

  In the above-described embodiment, the tandem type image forming apparatus in which the four photoconductor units 20 are installed at equal intervals along the circumferential direction of the transfer body 21 has been described. However, the image forming apparatus to which the present invention is applied is described below. Not limited to the tandem method, as shown in FIG. 5 or FIG. 6, the photoconductor unit 20 including a single photoconductor 20 c and a plurality of developing units 20 d and the photoconductor 20 c are sequentially formed. The present invention can also be applied to an image forming apparatus in which toner images of the respective colors are sequentially superimposed on the transfer belt 21 and then transferred onto a sheet.

  5 is an image forming apparatus in which a plurality of developing units 20d are arranged along the peripheral surface of the photoconductor, and FIG. 6 is an image forming apparatus in which a rotary developing device is employed. Are given the same reference numerals to the portions having the same functions as those of the photoconductor unit 20 shown in FIG.

  In this case, when the number of toner colors constituting the image formed by the photoreceptor unit 20 is less than the number of toner colors provided in the photoreceptor unit 20, the paper feed timing determination unit 310 superimposes on the transfer body 21. In this case, the sheet feeding timing may be determined based on the image forming timing of the uppermost layer among the images for each color component held in this manner.

  When a full color image is printed by the image forming apparatus shown in FIG. 5 or FIG. 6, the paper feed timing is determined based on the image formation timing corresponding to the toner color that is finally formed on the photoconductor 20c. This is because it is necessary to transfer the leading edge of the finally formed image and the leading edge of the paper so as to coincide with each other.

  For example, when images are formed in the order of M (magenta), C (cyan), Y (yellow), and K (black), the paper feed timing is determined based on the K (black) image formation timing. It is.

  However, for example, in the case of printing based on output image data that does not include the K (black) color component, the first print time can be determined by determining the paper feed timing based on the Y (yellow) image formation timing. Is shortened.

  In any embodiment, the color order of the toner image transferred to the transfer body 21 is not particularly limited.

  In the above-described embodiment, the case where the image forming apparatus is a copying machine has been described. However, the present invention is applicable to all image forming apparatuses that employ an electrophotographic system such as a printer or a facsimile machine having developing units of different colors. be able to.

  Each of the above-described embodiments is merely an example of the present invention, and the scope of the present invention is not limited by the description. The specific configuration of each part is appropriately selected within the scope of the effects of the present invention. It goes without saying that changes can be designed.

Main functional block diagram of the control unit External view of copier Explanatory drawing of the image forming unit and paper feed conveyance mechanism (A) Timing chart explaining image formation timing and paper feed timing when the color component of the lowermost layer image is magenta, (b) Image formation timing and paper feed timing when the color component of the lowermost layer image is yellow Explaining the timing chart Explanatory drawing of the image forming unit and paper feed conveyance mechanism Explanatory drawing of the image forming unit and paper feed conveyance mechanism

3: Control unit 13: Image processing unit 16a: Pickup roller 16c: Registration roller 20: Photoreceptor unit 30: Image formation control unit 31: Paper feed control unit 310: Paper feed timing determining means

Claims (4)

A photosensitive unit provided with a plurality of toners of different colors, a transfer body that superimposes and holds images of different toner colors formed by the photosensitive unit, and a paper feed control unit that controls supply of paper to the transfer body. An image forming apparatus comprising:
When the number of toner colors constituting the image formed by the photosensitive unit is less than the number of toner colors provided in the photosensitive unit,
The paper feed control unit starts feeding the paper stored in the paper storage unit based on the image forming timing of the lowermost layer or the uppermost layer among the images for each color component held superimposed on the transfer body. An image forming apparatus comprising paper feed timing determining means for determining a paper feed timing to be performed. A plurality of the photoreceptor units are provided along the circumferential direction of the transfer body,
2. The image according to claim 1, wherein the image forming timing serving as a reference for the paper feeding timing is an image forming timing of the photosensitive unit that forms an image of a lowermost layer among images held by being superimposed on the transfer body. Forming equipment. The photoconductor unit includes a single photoconductor and a plurality of developing units,
2. The image according to claim 1, wherein the image forming timing serving as a reference for the paper feeding timing is an image forming timing of the photosensitive unit that forms an uppermost image among images held on the transfer body. Forming equipment. The sheet moving distance from the leading edge position of the sheet before the start of feeding to the image transfer position to the sheet is the distance from the image forming position of the photosensitive unit that forms the lowermost or uppermost image to the image transfer position. When the image moving distance is longer than
4. The image forming apparatus according to claim 1, wherein the paper feed control unit starts paper feeding ahead of an image forming timing of the photosensitive unit. 5.

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