JP2006201693A - Image forming apparatus - Google Patents

Abstract

An object of the present invention is to realize a high-speed printing process of an image forming apparatus by a method different from the conventional one.
A sheet feeding unit that accommodates sheets and selectively feeds and conveys one sheet at a time from the accommodated sheets, and image formation that forms an image on the sheet fed from the sheet feeding unit. The image forming apparatus including the unit 3 and the paper discharge tray 6 that discharges the paper after the image formation by the image forming unit 3 is provided with two sets of left and right image forming units 3L and 3R. In this configuration, a printing unit that transfers using an unfixed developer and a fixing device that melts and fixes the unfixed developer transferred onto the paper are provided.
[Selection] Figure 1

Description

  The present invention relates to an electrophotographic image forming apparatus used for a copying machine, a laser printer, a facsimile machine, a multifunction machine, and the like, and more particularly to an image forming apparatus capable of high-speed printing processing.

  In recent years, development of image forming apparatuses capable of high-speed image forming processing (printing processing) has been progressing. In order to speed up the printing process of the image forming apparatus, the peripheral speed of the photosensitive member called process speed, the speed of the conveyed paper, etc. are increased, or the interval between the conveyed sheets is reduced. Has been done.

  However, there are various technical demands for achieving a high-speed printing process of the image forming apparatus by the method described above. For example, in order to increase the process speed, it is indispensable to improve at least the sensitivity characteristics of the photoreceptor and improve the stirring performance and charging characteristics of the developer. In order to increase the sheet conveyance speed, it is necessary to improve the sheet conveyance accuracy by securing the linearity of the sheet conveyance path or improving the mounting accuracy of the components of the sheet conveyance mechanism. As the distance between the sheets is shortened, it is necessary to take measures that can effectively prevent the jamming of the conveyance sheets. Further, as a common request, it is necessary to improve the temperature control performance of the fixing device, and it is necessary to secure a heat source for the fixing device capable of such highly accurate temperature control.

Patent Document 1 discloses an image forming apparatus that attempts to speed up the printing process by adjusting the paper feed timing without increasing the process speed. Specifically, a paper storage unit that stores paper, an image forming unit that forms an image on the paper, a paper feeding unit that takes out the paper from the paper storage unit and feeds the paper to the image forming unit, and the paper storage unit An alignment unit that delays the progress of the sheet fed between the image forming unit and the image forming unit and conveys the sheet to the image forming unit, and the sheet feeding unit and the aligning unit according to the start timing of the image forming process Control means for controlling the drive, and a paper detector for detecting the paper length of the fed paper is provided, so that the control means can advance the paper feed timing based on the detected paper length. An image forming apparatus to be controlled is disclosed.
Japanese Patent Laid-Open No. 2000-272781

  As described above, when it is attempted to increase the speed of the printing process in the image forming apparatus by the method as described above, conventionally, various technical problems have been accompanied.

  The present invention has been made in view of such a point, and an object of the present invention is to realize high-speed printing processing in an image forming apparatus by a method different from the conventional one. That is, an object of the present invention is to provide an image forming apparatus capable of performing high-speed printing processing by a method other than increasing the process speed, increasing the sheet conveying speed, and reducing the distance between sheets.

  In the present invention, means for solving the above-described problems are configured as follows. That is, a sheet feeding unit that accommodates sheets, selectively feeds and conveys one sheet at a time among the accommodated sheets, an image forming unit that forms an image on sheets fed from the sheet feeding unit, and an image In an image forming apparatus including a paper discharge unit that discharges a sheet after image formation by the forming unit, two or more sets of the image forming units are provided, and each image forming unit is printed using an unfixed developer. And a fixing device for melting and fixing the unfixed developer transferred onto the paper. Here, the printing unit is a part other than the fixing device in the image forming unit.

  According to the image forming apparatus having such a configuration, when image formation is continuously performed on a plurality of sheets, image formation is performed by two or more sets of image forming units, thereby increasing the process speed, The image forming process (printing process) in the image forming apparatus can be speeded up by a method other than increasing the sheet conveying speed and shortening the distance between sheets. In other words, even if the process speed of the image forming apparatus, the sheet conveyance speed, and the distance between sheets are the same as the conventional one, the printing process can be accelerated.

  As described above, according to the present invention, the printing process of the image forming apparatus is speeded up by a method different from the conventional one. Therefore, it is not always indispensable to satisfy various technical requirements in order to increase the printing speed of the image forming apparatus, and the burden of developing the apparatus can be reduced accordingly. Specifically, in order to increase the process speed, it is not always necessary to improve the sensitivity characteristics of the photosensitive member or improve the stirring performance and charging characteristics of the developer. Also, in order to increase the paper transport speed, to ensure the straightness of the paper transport path, to improve the mounting accuracy of the parts of the paper transport mechanism, and to reduce the distance between paper, It is not always necessary to take measures to prevent it. Furthermore, it is not always necessary to secure a heat source for the fixing device capable of highly accurate temperature control.

  In the image forming apparatus of the present invention, when two sets of the image forming units are provided and image formation is continuously performed on a plurality of sheets, the image forming units may be used alternately. it can.

  According to the image forming apparatus having such a configuration, when image formation is continuously performed on a plurality of sheets, by performing image formation by alternately using two sets of image forming means, the process speed can be increased. Further, it is possible to realize a high-speed printing process in the image forming apparatus by a method other than a high paper conveyance speed and a short paper distance. In other words, even if the process speed of the image forming apparatus, the sheet conveyance speed, and the distance between sheets are the same as the conventional one, the printing process can be accelerated.

  In the image forming apparatus according to the aspect of the invention, the sheet feeding unit includes a sheet feeding cassette that stores sheets, and a pickup roller unit that can feed sheets in the sheet feeding cassette in a plurality of directions. And

  According to the image forming apparatus having such a configuration, when image formation is continuously performed on a plurality of sheets, the sheet in the sheet feeding cassette is fed in a plurality of directions by the pickup roller unit, and each image forming unit By performing image formation for each, it is possible to realize a high-speed printing process in the image forming apparatus by a method other than a high process speed, a high paper conveyance speed, and a short inter-paper distance. In other words, even if the process speed of the image forming apparatus, the sheet conveyance speed, and the distance between sheets are the same as the conventional one, the printing process can be accelerated. In addition, since the paper can be fed in a plurality of directions by the pickup roller unit from only one paper feeding cassette, the paper feeding means can be made compact, and the image forming apparatus can be made compact.

  In the image forming apparatus of the present invention, inside the paper feed cassette, corresponding to the size of the paper to be stored, a conveyance guide member at both ends in the paper feed direction, and a partition plate at the center in the paper feed direction Can be selectively provided. As a result, the paper feed cassette can be configured such that each size of paper is just accommodated therein.

  In the image forming apparatus of the present invention, image data is written on the photosensitive member of each printing unit by an optical unit using a two-beam, one-polygon mirror system.

  According to the image forming apparatus having such a configuration, since the polygon mirror and the polygon motor that drives the same are shared in the optical unit, the number of parts can be reduced, the apparatus can be made compact, and the cost can be reduced. When image formation is continuously performed on a plurality of sheets, image data is written on each photoconductor by an optical unit using a two-beam, one-polygon mirror system, and image formation is performed in each image forming unit. As a result, it is possible to realize a high-speed printing process in the image forming apparatus by a method other than an increase in process speed, an increase in sheet conveyance speed, and a reduction in the distance between sheets. In other words, even if the process speed of the image forming apparatus, the sheet conveyance speed, and the distance between sheets are the same as the conventional one, the printing process can be accelerated.

  In the image forming apparatus of the present invention, when two sets of image forming means are alternately used to form images on a plurality of sheets continuously, the optical unit should write an odd number of images on the photosensitive member. One of the data and the even-numbered image data to be written is subjected to image processing that rotates a predetermined angle with respect to the other. Here, the rotation angle of the image processing can be set to 180 degrees, for example.

  According to the image forming apparatus having such a configuration, when the rotation angle of image processing is 180 degrees, for example, image data to be written oddly by the optical unit with respect to one photoconductor (on an odd number of sheets). Assuming that image data to be imaged is written from one side (for example, the front end side), the image data to be written evenly by the optical unit to the other photoconductor (images on even-numbered sheets of paper) The image data to be formed) is written from the opposite side (for example, the rear end side). Thus, when the paper on which the image is formed by each image forming unit is discharged to the paper discharging unit, the direction of the image formed by one image forming unit and the image formed by the other image forming unit The direction can be aligned.

  In the image forming apparatus of the present invention, the paper discharge unit is provided with a pair of alignment members that align the paper discharged in the paper discharge direction after image formation by each image forming unit. To do.

  In the image forming apparatus as described above, when image formation is continuously performed on a plurality of sheets, the printing process can be speeded up. Since the performed sheets are each discharged, the positions of the discharged sheets are staggered and the stacking property may be deteriorated. For this reason, by providing an alignment member and aligning the paper discharged in the paper discharge direction in the paper discharge direction, the positions of the discharged paper in the paper discharge direction are aligned, and the stacking property is improved. it can.

  In the image forming apparatus of the present invention, the pair of alignment members are disposed symmetrically with respect to the center of the paper discharge unit in the paper discharge direction, and are provided so as to reciprocate in the paper discharge direction. The alignment member according to the size of the sheet discharged to the sheet discharge means can be performed by the alignment member.

  Since the present invention is configured as described above, when image formation is continuously performed on a plurality of sheets, image formation is performed by two or more sets of image forming units, thereby increasing the process speed. Further, it is possible to realize a high-speed printing process in the image forming apparatus by a method other than a high paper conveyance speed and a short paper distance. In other words, even if the process speed of the image forming apparatus, the sheet conveyance speed, and the distance between sheets are the same as the conventional one, the printing process can be accelerated.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

  In the present embodiment, a case where the present invention is applied to a digital copying machine as an image forming apparatus will be described. FIG. 1 schematically shows an internal configuration of a digital copying machine 1 according to the present embodiment. As shown in FIG. 1, a digital copying machine 1 includes a scanner unit 2, two sets of left and right image forming units (image forming units) 3L and 3R for forming an image on a sheet as a recording medium, each image forming unit 3L, Two sets of sheet conveying mechanisms 4L and 4R that respectively convey sheets to 3R, a sheet feeding unit (sheet feeding means) 5 that feeds and conveys the sheets stored in the sheet conveying mechanisms 4L and 4R one by one, and each image formation A discharge tray 6 is provided as a discharge unit (discharge unit) that discharges the sheet on which the image is formed by the units 3L and 3R. Hereinafter, each part of the digital copying machine 1 will be described.

  The scanner unit 2 includes a document placing table 21 made of transparent glass or the like, and a double-sided automatic document feeder (RADF) 22 serving as a document feeding unit that feeds a document onto the document placing table 21. This is a part for reading the image of the document on the document table 21 and creating image data.

  The RADF 22 includes an automatic paper feed tray 22a for automatically feeding a plurality of set originals one by one onto the document placement table 21. The RADF 22 can cause the scanner unit 23 (described later) to read one side or both sides of a document according to the user's selection. Specifically, a transport path for transporting a document on the automatic paper feed tray 22a onto the document placement table 21 and a reversing path for reversing the document so that the scanner unit 23 can read both sides of the document are provided. When only one side of the document is read, only the conveyance path is used. On the other hand, when both sides of the document are read, the document conveyed on the document table 21 via the conveyance path is reversed on the reversal path. Thus, it is conveyed again onto the document table 21. For this reason, each path is provided with a transport path switching means and a sensor group (both not shown) for recognizing the transport position of the document. The configuration of the RADF 22 is well known in the art and will not be described in detail.

  Further, the scanner unit 2 includes a scanner unit 23 for reading an image of a document conveyed on the document placement table 21. The scanner unit 23 includes a lamp reflector assembly 24, a plurality of reflection mirrors 25a, 25b, and 25c, an optical lens body 26, and a photoelectric conversion device (CCD) 27.

  The lamp reflector assembly 24 irradiates light on the document placed on the document placement table 21. Each of the reflecting mirrors 25a, 25b, and 25c reflects the reflected light from the original in the left direction in the drawing and then reflects downward as indicated by the one-dot chain line in FIG. Reflected in the right direction in the figure so as to go to.

  As a document image reading operation, when a document is placed on the document placing table 21, the first scanning unit 23 a composed of the lamp reflector assembly 24 and the reflecting mirror 25 a scans along the document placing table 21 in the horizontal direction. The whole document is irradiated with light. At this time, the second scanning unit 23b composed of the reflection mirrors 25b and 25c moves in the same direction at a predetermined speed (half the speed relative to the first scanning unit 23a) with respect to the first scanning unit 23a. The light reflected by the reflecting mirrors 25a, 25b, and 25c and passed through the optical lens body 26 forms an image on the photoelectric conversion element 27, and the reflected light is converted into an electric signal (original image data) in the photoelectric conversion element 27. It has been converted to. The image data obtained in this way is transmitted to the control unit (image processing unit) 3A, where various processing is performed, and then temporarily stored in the memory of the control unit 3A. The image data in the memory is read out and used for the image forming operation by the image forming units 3L and 3R.

  Two sets of image forming units 3L and 3R and paper transport mechanisms 4L and 4R are provided on the left and right sides of the digital copying machine 1. The left and right image forming units 3L and 3R and the paper transport mechanisms 4L and 4R have substantially the same configuration. The left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R are substantially symmetric with respect to the left and right center position of the digital copying machine 1. The digital copying machine 1 may be provided with three or more sets of image forming units and paper transport mechanisms. However, in view of the arrangement configuration of the image forming units and paper transport mechanisms described later, two sets are preferable. It is. Therefore, an example in which the digital copying machine 1 is provided with two sets of image forming units and a paper transport mechanism will be described below.

  When the digital copying machine 1 forms an image on only one sheet, one of the left and right image forming units 3L and 3R and the sheet conveying mechanisms 4L and 4R and the sheet conveying unit. The mechanism 4 (in this case, the left image forming unit 3L and the paper transport mechanism 4L) is used.

  On the other hand, when image formation is continuously performed on a plurality of sheets, the left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R are alternately used. For image formation on odd-numbered sheets, one of the left and right image forming units 3L and 3R, and the sheet transport mechanisms 4L and 4R, and the image transport unit 4 (in this case) The left image forming unit 3L) is used, and for image formation on even-numbered sheets, the remaining one of the image forming unit 3 and the sheet transport mechanism 4 (in this case, the right image forming unit 3R and the sheet transport) Mechanism 4R) is used. Here, the image forming unit 3L and the paper transport mechanism 4L disposed on the left side of the digital copying machine 1 will be described, and the image forming unit 3R and the paper transport mechanism 4R disposed on the right side of the digital copying machine 1 will be described in detail. Description is omitted.

  The image forming unit 3L includes a laser writing unit 31L and an electrophotographic process unit 32L as optical units that write image data on the photosensitive drum 33L. The laser writing unit 31L irradiates the surface of the photosensitive drum 33L of the electrophotographic process unit 32L with laser light based on the document image data converted by the photoelectric conversion element 27. Details of the laser writing unit will be described later.

  The photosensitive drum 33L rotates in a direction indicated by an arrow in FIG. 1, and an electrostatic latent image is formed on the surface of the photosensitive drum 33L by being irradiated with laser light from the laser writing unit 31L.

  In the electrophotographic process section 32L, a charger 34L, a developing device 35L, a transfer device 36L, a cleaning device 37L, a fixing device (fixing means) 39L, and the like are arranged around the photosensitive drum 33L. The charger 34L charges the surface of the photosensitive drum 33L before the electrostatic latent image is formed to a predetermined potential. The developing device 35L develops the electrostatic latent image formed on the surface of the photosensitive drum 33L into a visible image with toner as an image forming material. The transfer device 36L transfers the toner image formed on the surface of the photoreceptor drum 33L onto a sheet. The cleaning device 37L removes the toner remaining on the surface of the photosensitive drum 33L after the toner transfer. The fixing device 39L melts and fixes the unfixed developer on the paper with a heat source incorporated therein, and fixes the toner image transferred onto the paper on the paper by heating.

  When forming an image on a sheet, the surface of the photosensitive drum 33L is charged to a predetermined potential by the charger 34L, and the laser writing unit 31L irradiates the surface of the photosensitive drum 33L with laser light based on the image data. To form an electrostatic latent image. Thereafter, the developing unit 35L develops a visible image with toner on the surface of the photosensitive drum 33L, and the toner image is transferred by the transfer unit 36L to a sheet fed from a sheet transport mechanism 4L described later. Thereafter, the sheet is heated by the fixing device 39L, and the toner image is fixed. On the other hand, the toner remaining on the surface of the photosensitive drum 33L is removed by the cleaning device 37L. This completes one cycle of the image forming operation on the paper.

  The sheet conveying mechanism 4L conveys the sheets stored in the sheet feeding cassettes 51 and 51 constituting the sheet feeding unit 5 one by one to cause the image forming unit 3L to perform image formation, and the image-formed sheet Is discharged to a paper discharge tray 6 serving as a discharge unit.

  One end (upstream end side in the paper transport direction) of the transport path 41L of the paper transport mechanism 4L is branched to face the discharge side of the paper feed cassettes 51 and 51, and the other end (downstream end in the paper transport direction). Side) is opposed to the paper discharge tray 6 via the transfer device 36L and the fixing device 39L. A pickup roller 52L of the pickup roller unit 52 is disposed at the upstream end (portion facing the paper feed cassette 51) of the conveyance path 41L. On the downstream side of the pickup roller 52L, there is provided a separation unit 42L for preventing double feeding of sheets fed to the transport path 41L, that is, for feeding sheets one by one to the transport path 41L. Yes. In addition, a discharge roller 43L that discharges the sheet to the discharge tray 6 is disposed at the downstream end (portion facing the discharge tray 6) of the conveyance path 41L, and a sheet is disposed in the middle of the conveyance path 41L. A conveying roller 44L that conveys to the downstream side is disposed.

  The paper feed unit 5 includes a paper feed cassette 51 that contains paper, and a pickup roller unit 52 that selectively feeds the paper stored in the paper feed cassette 51 to the paper transport mechanisms 4L and 4R one by one. . As will be described in detail later, paper feed from the paper feed cassette 51 is performed not only in one direction but in a plurality of different directions (in this example, left and right directions). That is, paper can be supplied from the paper feed cassette 51 to either the left or right paper transport mechanism 4L, 4R. The pickup roller unit 52 is a pendulum type. 2 to 5 are used as the paper feed cassette 51, which will be described later in detail. Although FIG. 1 shows an example in which two stages of paper feed cassettes 51 and 51 are provided on the top and bottom, the number of paper feed cassettes 51 may be one, three or more, and a manual feed tray. Can also be provided.

  As described above, in the digital copying machine 1, when image formation is continuously performed on a plurality of sheets, image formation is performed by alternately using the left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R. As a result, it is possible to realize high-speed image formation processing (printing processing) by a method other than the conventional method (higher process speed, higher paper conveyance speed, shorter paper distance). In other words, even if the process speed, paper transport speed, and paper distance of the digital copying machine 1 are the same as the conventional one, the printing process can be speeded up.

  Therefore, it is not always indispensable to satisfy various technical requirements for speeding up the printing process of the digital copying machine 1, and the burden of developing the apparatus can be reduced accordingly. Specifically, in order to increase the process speed, it is always necessary to improve the sensitivity characteristics of the photoconductive drums 33L and 33R, and improve the toner stirring performance and charging characteristics of the developing units 35L and 35R. Is not. Further, in order to increase the paper transport speed, the linearity of the transport paths 41L and 41R of the paper transport mechanisms 4L and 4R is ensured, the mounting accuracy of components of the paper transport mechanisms 4L and 4R is improved, or the transport path is increased. It is not always necessary to take measures to prevent jamming of transported paper in order to shorten the distance between the papers transported through 41L and 41R. Furthermore, it is not always necessary to secure a heat source for the fixing devices 39L and 39R capable of highly accurate temperature control.

  Next, the paper feeding unit 5 will be described in detail with reference to FIGS.

  As described above, the paper feed unit 5 is configured to be capable of paper feeding on both sides, and can feed paper from the paper feed cassette 51 to the paper transport mechanisms 4L and 4R on the left and right sides. Both-side paper feeding from the paper feed cassette 51 is performed by the following pickup roller unit 52.

  As shown in FIG. 1 and the like, the pickup roller unit 52 is configured as a pendulum type pickup roller so that both-side paper feeding is possible. The pickup roller unit 52 includes left and right pickup rollers 52L and 52R, and a connecting member 53 that rotatably supports the left and right pickup rollers 52L and 52R. The pickup rollers 52L and 52R are arranged on both the left and right sides of the connecting member 53 having a shape bent at the center. A rotation fulcrum 53a is provided at the top (center) of the bent connection member 53, and the connection member 53 is rotatable about the rotation fulcrum 53a. The connecting member 53 includes a left paper feed position where the left pickup roller 52L contacts the paper stored in the paper feed cassette 51 by driving a motor or the like (as shown in the upper paper feed tray 51 in FIG. 1), and a right The pickup roller 52 </ b> R rotates to switch between the right paper feed position (in the case of the lower paper feed tray 51 in FIG. 1) that contacts the paper stored in the paper feed cassette 51.

  Here, when supplying paper from the paper feed cassette 51 to the left paper transport mechanism 4L, the connecting member 53 is rotated to the left paper feed position, and the pickup roller 52L is stored in the paper feed cassette 51. Abut. In this state, the motor or the like is driven to operate the pickup roller 52L, and the uppermost sheet stored in the sheet feeding cassette 51 is conveyed to the sheet conveying mechanism 4L (left-side sheet feeding). Conversely, when paper is supplied from the paper feed cassette 51 to the right paper transport mechanism 4R, the connecting member 53 is rotated to the right paper feed position, and the pickup roller 52R is stored in the paper feed cassette 51. Abut. In this state, the motor or the like is driven to operate the pickup roller 52R, so that the uppermost sheet stored in the sheet feeding cassette 51 is conveyed to the sheet conveying mechanism 4R (right-side sheet feeding).

  When an image is formed on only one sheet, the left image forming unit 3L and the sheet transport mechanism 4L are used as described above. In this case, the connecting member 53 is rotated to the left sheet feeding position, and only one sheet of the sheet feeding cassette 51 is fed to the sheet transport mechanism 4L by the pickup roller 52L. Then, the paper supplied from the paper feed cassette 51 to the paper transport mechanism 4L is transported along the transport path 41L, image formation is performed by the image forming unit 3L, and then from the paper discharge roller 43L to the paper discharge tray 6. Discharged.

  In contrast, when image formation is continuously performed on a plurality of sheets, the left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R are alternately used as described above. In this case, continuous sheet feeding is performed from the sheet feeding cassette 51 and sheets are alternately supplied to the left and right sheet transport mechanisms 4L and 4R. At this time, for the odd-numbered sheets, the connecting member 53 is rotated to the left sheet feeding position, the left sheet is fed by the pickup roller 52L, and the sheet is fed from the sheet feeding cassette 51 to the sheet conveying mechanism 4L. Then, the odd-numbered sheets supplied to the sheet transport mechanism 4L by the left sheet feeding are transported along the transport path 41L, the image is formed by the image forming unit 3L, and then discharged from the discharge roller 43L. It is discharged to the tray 6.

  On the other hand, for the even number of sheets, the connecting member 53 is rotated to the right sheet feeding position, the right side sheet is fed by the pickup roller 52R, and the sheet is fed from the sheet feeding cassette 51 to the sheet transport mechanism 4R. The even-numbered sheets supplied to the sheet transport mechanism 4R by the right-side sheet feeding are transported along the transport path 41R, image formation is performed by the image forming unit 3R, and then the sheet is discharged from the sheet discharge roller 43R. It is discharged to the tray 6.

  The timing for switching the rotation position between the left sheet feeding position and the right sheet feeding position of the connecting member 53, in other words, the timing for switching between the left sheet feeding and the right sheet feeding by the pickup roller unit 52 is the left and right image forming units. The timing matches the timing of image formation by 3L and 3R, and is controlled by the control unit 3A. Here, since the pick-up roller unit 52 is a pendulum type, it is possible to smoothly switch between the left-side paper feeding and the right-side paper feeding, and to realize quick both-side paper feeding. In addition, since the paper feeding to the left and right sides as described above can be performed from only one paper feeding cassette 51, the paper feeding section 5 and the digital copying machine 1 can be made compact. Can do.

  When the digital copying machine 1 continuously forms images on a plurality of sheets, the sheets in the sheet feeding cassette 51 are alternately supplied to the left side and the right side by the pickup roller unit 52, and the left and right image forming units 3L. 3R and the paper transport mechanisms 4L and 4R are used alternately to form an image, so that a method other than the conventional method (higher process speed, higher paper transport speed, shorter inter-paper distance) is used. Thus, the printing process can be speeded up. In other words, even if the process speed, paper transport speed, and paper distance of the digital copying machine 1 are the same as the conventional one, the printing process can be speeded up.

  The paper feed cassette 51 is formed as shown in FIGS. 2 to 5 according to the size of the paper to be stored. FIG. 2 is a cross-sectional view showing a paper feed cassette 51A that accommodates A3 paper, FIG. 3 is a cross-sectional view that shows a paper feed cassette 51B that contains B4 paper, and FIG. FIG. 5 is a cross-sectional view showing a paper cassette 51C, and FIG. 5 is a cross-sectional view showing a paper feed cassette 51D that accommodates B5 paper.

  As shown in FIGS. 2 to 5, the outer shapes of the paper feed cassettes 51 corresponding to the respective sizes of paper are equal to each other. Therefore, each paper feed cassette 51 can be handled in substantially the same manner, and the paper feed cassette 51 mounted on the digital copying machine 1 can be easily replaced from one paper feed cassette 51 to another paper feed cassette 51. it can. For example, when the paper feed cassette 51 containing the paper of the size desired by the user is not loaded in the digital copying machine 1, the paper feed cassette 51 containing the paper of the desired size is replaced. It can be done easily. In addition, the pickup roller unit 52 having the same configuration can be used for all the paper feed cassettes 51.

  As shown in FIGS. 2 to 5, inside each paper feed cassette 51, there are transport ribs (in this case, both right and left ends) corresponding to the size of the paper to be stored. Partition plates 55 are selectively provided at the conveyance guide members 54L and 54R, and in the central part (in this case, the left and right central part) in the paper feeding direction.

  The inside of the paper feed cassette 51 </ b> A shown in FIG. 2 has a size that fits just the maximum size A3 paper that can be printed by the digital copying machine 1. When image formation is performed on A3 paper, the paper feed cassette 51A is mounted on the digital copying machine 1. When image formation is continuously performed on a plurality of A3 sheets, the A3 sheets accommodated in the sheet feeding cassette 51A are left and right by the pickup roller unit 52 as described above. 4R are alternately supplied. By attaching a partition plate 55 as described later (see FIG. 4), the paper feed cassette 51A can be used as a paper feed cassette for storing A4 paper.

  The inside of the paper feed cassette 51B shown in FIG. 3 is formed so that B4 paper having a size slightly smaller than A3 paper can be accommodated. That is, as described above, the outer shape of the paper feed cassette 51B is equal to the outer shape of the other paper feed cassettes 51A, 51C, 51D shown in FIGS. Are provided with conveying ribs 54L and 54R at the left and right ends of the paper feed cassette 51B. The lengths of the transport ribs 54L and 54R in the direction along the paper feeding direction are substantially equal to half the length obtained by subtracting the length of the B4 paper in the paper feeding direction from the length of the A3 paper in the paper feeding direction. Further, the transport ribs 54L and 54R are symmetrical to each other, and are disposed at symmetrical positions with respect to the left and right center of the paper feed cassette 51B. By providing such transport ribs 54L and 54R in the paper feed cassette 51B, B4 paper can be stored just inside the paper feed cassette 51B.

  When image formation is performed on B4 paper, the paper feed cassette 51B is mounted on the digital copying machine 1. When image formation is continuously performed on a plurality of B4 sheets, the B4 sheets housed in the sheet feeding cassette 51B are left and right by the pickup roller unit 52 as described above. 4R are alternately supplied. By attaching a partition plate 55 as described later (see FIG. 5), the paper feed cassette 51B can be used as a paper feed cassette for storing B5 paper.

  The inside of the paper feed cassette 51C shown in FIG. 4 is formed so that A4 paper can be accommodated. That is, since the A4 paper is exactly half the size of the A3 paper, the partition plate 55 is disposed at the center of the left and right sides of the paper feed cassette 51C in order to make the inside of the paper feed cassette 51C suitable for accommodating the A4 paper. Has been. By providing such a partition plate 55 in the paper feed cassette 51C, A4 paper can be stored exactly in the left and right regions inside the paper feed cassette 51C partitioned by the partition plate 55. In addition, A4 paper can be accommodated twice as much as A3 paper. Further, by removing the partition plate 55, the paper feed cassette 51C can be used as a paper feed cassette for storing A3 paper.

  When image formation is performed on A4 paper, a paper feed cassette 51C is mounted on the digital copying machine 1. When image formation is continuously performed on a plurality of A4 sheets, the A4 sheets housed in the sheet feeding cassette 51C are left and right by the pickup roller unit 52 as described above. 4R are alternately supplied. At this time, regarding the left side paper feeding by the pickup roller 52L, the A4 paper accommodated in the left half region of the paper feeding cassette 51C partitioned by the partition plate 55 is fed to the paper transport mechanism 4L, while the pickup roller For the right side paper feeding by 52R, A4 paper housed in the right half area of the paper feeding cassette 51C partitioned by the partition plate 55 is fed to the paper transport mechanism 4R.

  The inside of the paper feed cassette 51D shown in FIG. 5 is formed so that the B5 paper just fits. That is, conveyance ribs 54L and 54R similar to those in the case of the paper feed cassette 51B shown in FIG. 3 are provided at the left and right ends of the paper feed cassette 51D. Further, a partition plate 55 similar to that in the case of the paper feed cassette 51C shown in FIG. By providing the transport ribs 54L and 54R and the partition plate 55 in the paper feed cassette 51D, the B5 paper can be stored in the left and right regions inside the paper feed cassette 51D partitioned by the partition plate 55. . In addition, B5 paper can be accommodated twice as much as B4 paper. Further, by removing the partition plate 55, the paper feed cassette 51D can be used as a paper feed cassette for storing B5 paper.

  When image formation is performed on B5 paper, the paper feed cassette 51D is mounted on the digital copying machine 1. When image formation is continuously performed on a plurality of B5 sheets, the B5 sheets housed in the sheet feeding cassette 51D are left and right by the pickup roller unit 52 as described above. 4R are alternately supplied. At this time, regarding the left side paper feeding by the pickup roller 52L, the B5 paper accommodated in the left half area of the paper feeding cassette 51D partitioned by the partition plate 55 is fed to the paper transport mechanism 4L, while the pickup roller For the right side paper feeding by 52R, B5 paper housed in the right half region of the paper feeding cassette 51D partitioned by the partition plate 55 is fed to the paper transport mechanism 4R.

  Next, the laser writing units 31L and 31R of the image forming units 3L and 3R will be described in detail with reference to FIGS. FIG. 6 is a plan view showing the laser writing units 31L and 31R using the two-beam one polygon mirror system, and FIG. 7 is a front view showing the left laser writing unit 31L. The right laser writing unit 31R is arranged symmetrically with the laser writing unit 31L shown in FIG.

  As shown in FIG. 6, the laser writing units 31L and 31R are configured as optical units that write image data on the photosensitive drums 33L and 33R by a two-beam one-polygon mirror system. That is, the laser writing units 31L and 31R are provided with the left and right semiconductor laser light sources 71L and 71R for irradiating laser light corresponding to the image data, whereas the laser writing units 31L and 31R are provided with the laser light units 71L and 71R. There is only one polygon mirror 72 that deflects the laser beam at an equal angular velocity.

  Specifically, as shown in FIGS. 6 and 7, the left laser writing unit 31L that writes image data to the photosensitive drum 33L of the image forming unit 3L has one left and right laser that irradiates laser light corresponding to the image data. Each semiconductor laser light source 71L, a polygon mirror 72 that deflects the laser light emitted from the semiconductor laser light source 71L at an equal angular velocity, first and second mirrors 73L and 74L that reflect the laser light from the polygon mirror 72, a polygon mirror The f-θ lens 75L corrects the laser beam deflected at a constant angular velocity 72 to scan the photosensitive drum 33L at a constant velocity, and the third mirror 76L reflects the laser beam corrected by the f-θ lens 75L. It has. The right laser writing unit 31R for writing image data to the photosensitive drum 33R of the image forming unit 3R is disposed at a point-symmetrical position with respect to the laser writing unit 31L and the rotation shaft 72a of the polygon mirror 72. . The polygon mirror 72 is irradiated with laser light from the left and right semiconductor laser light sources 71L and 71R at an angle different by 180 degrees.

  Thus, only one polygon mirror 72 and a polygon motor (not shown) for driving the polygon mirror 72 are provided for the left and right laser writing units 31L and 31R. That is, the polygon mirror 72 and the polygon motor that drives the polygon mirror 72 are shared by the left and right laser writing units 31L and 31R. It is conceivable to provide two polygon mirrors 72 and two polygon motors. However, by sharing the polygon mirror 72 and the polygon motor, the number of parts can be reduced, the apparatus can be made compact, and the cost can be reduced.

  Here, when an image is formed on only one sheet, the left image forming unit 3L and the sheet transport mechanism 4L are used as described above. At this time, laser light is irradiated by the laser writing unit 31L to the photosensitive drum 33L whose surface is charged to a predetermined potential by the charger 34L, and an electrostatic latent image is formed on the surface. The image data on which the image is written on the photosensitive drum 33L by the laser writing unit 31L is developed by the developing device 35L, and is transported along the transport path 41L of the paper transport mechanism 4L by the transfer device 36L. The toner image is transferred onto the paper, and further, the toner image is fixed by the fixing device 39L, and then discharged to the paper discharge tray 6.

  In contrast, when image formation is continuously performed on a plurality of sheets, the left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R are alternately used as described above. In this case, laser light corresponding to the image data is alternately radiated from the left and right laser writing units 31L and 31R to the photosensitive drums 33L and 33R whose surfaces are charged to a predetermined potential by the chargers 34L and 34R. An electrostatic latent image is formed. At this time, with respect to image data to be written odd-numbered (image data to be formed on odd-numbered sheets of paper), image writing to the photosensitive drum 33L is performed by the laser writing unit 31L, and the image to be written even-numbered. With respect to data (image data to be formed on even-numbered sheets of paper), image writing to the photosensitive drum 33R is performed by the laser writing unit 31R.

  The odd-numbered image data to be written on the photosensitive drum 33L by the laser writing unit 31L is developed by the developing unit 35L, and the transfer path 36L of the paper transport mechanism 4L is transferred by the transfer unit 36L. The toner image is transferred to the sheet conveyed along the line. Further, after the toner image is fixed by the fixing device 39L, the toner image is discharged from the paper discharge roller 43L to the paper discharge tray 6. Further, the even-numbered image data to be written on the photosensitive drum 33R by the laser writing unit 31R is developed by the developing unit 35R, and the transfer path 36R of the paper transport mechanism 4R by the transfer unit 36R. The toner image is transferred to the sheet conveyed along the line. Further, after the toner image is fixed by the fixing device 39R, the toner image is discharged from the paper discharge roller 43R to the paper discharge tray 6.

  As described above, in the digital copying machine 1, when images are continuously formed on a plurality of sheets, images are alternately applied to the photosensitive drums 33L and 33R by the laser writing units 31L and 31R using the two-beam one-polygon mirror system. By writing data and performing image formation in the image forming units 3L and 3R, a method other than the conventional method (higher process speed, higher paper conveyance speed, shorter paper distance) The printing process can be speeded up. In other words, even if the process speed, paper transport speed, and paper distance of the digital copying machine 1 are the same as the conventional one, the printing process can be speeded up.

  The distribution of the image data written by the left and right laser writing units 31L and 31R and the timing of writing the image data by the laser writing units 31L and 31R as described above are controlled by the control unit 3A. Here, the control unit 3A performs the following image processing on the image data to be written by the laser writing units 31L and 31R when continuously forming images on a plurality of sheets. The control unit 3A performs image processing for rotating image data to be written evenly by the laser writing unit 31R by a predetermined angle (in this case, 180 degrees). When the image is written, the rotated image data is read out. Note that, instead of the above-described image processing, the image data to be written in an odd number can be rotated 180 degrees by the laser writing unit 31L.

  As a result, if image data to be written odd-numbered by the laser writing unit 31L is written to the photosensitive drum 33L from one side (for example, the front end side), the laser writing unit is written to the photosensitive drum 33R. The image data to be written even-numbered by 31R is written from the opposite side (for example, the rear end side). Thus, when the paper on which image formation has been performed by the left and right image forming units 3L and 3R is discharged to the paper discharge tray 6, the direction of the image formed by one image forming unit 3 and the other image forming unit 3 can align the direction of the image formed.

  Next, the paper discharge tray 6 will be described with reference to FIGS. FIG. 8 is a cross-sectional view showing the paper discharge tray 6, and FIG. 9 is a cross-sectional view showing a paper alignment operation in the paper discharge tray 6.

  The paper discharge tray 6 is disposed at the left and right center of the digital copying machine 1. The paper on which the image is formed is discharged from the paper discharge rollers 43L and 43R to the paper discharge tray 6. The bottom surface of the paper discharge tray 6 is formed horizontally.

  Here, when an image is formed on only one sheet, the left image forming unit 3L and the sheet transport mechanism 4L are used as described above. In this case, the sheet on which the image is formed by the image forming unit 3L is discharged from the discharge roller 43L to the discharge tray 6.

  In contrast, when image formation is continuously performed on a plurality of sheets, the left and right image forming units 3L and 3R and the sheet transport mechanisms 4L and 4R are alternately used as described above. In this case, the paper on which the image has been formed is alternately discharged to the paper discharge tray 6 from the left and right paper discharge rollers 43L and 43R. At this time, for odd-numbered sheets, the sheet on which the image is formed by the image forming unit 3L is discharged from the discharge roller 43L to the discharge tray 6. On the other hand, for the even number of sheets, the sheet on which the image is formed by the image forming unit 3R is discharged from the discharge roller 43R to the discharge tray 6.

  The timing of discharging the paper to the paper discharge tray 6 is controlled by the control unit 3A so that the order of the paper discharged alternately is not changed. The sheet discharge timing is, for example, a sheet on which image formation has been performed first after the sheet on which image formation has been performed is discharged from one of the discharge rollers 43 and comes into contact with the bottom surface of the discharge tray 6. Is discharged from the other discharge roller 43. Here, the sheet discharged from the sheet discharge roller 43 reaches a position where the leading end of the sheet exceeds at least the left and right center position of the sheet discharge tray 6 by the conveying force when the sheet is discharged.

  The paper discharge tray 6 includes left and right alignment plates (alignment members) 61L and 61R that align the paper discharged to the paper discharge tray 6 in the paper discharge direction (in this case, the left-right direction). . The alignment plates 61 </ b> L and 61 </ b> R are substantially L-shaped members and are arranged symmetrically with respect to the left and right center of the paper discharge tray 6. The alignment plates 61L and 61R are provided so as to be reciprocally movable left and right. Moreover, they are provided so as to move symmetrically with respect to the left and right center of the paper discharge tray 6.

  The reciprocating movement of the left and right alignment plates 61L and 61R is enabled by, for example, a rack and pinion mechanism. Specifically, the rack member connected to one alignment plate 61L and the rack member connected to the other alignment plate 61R are arranged to face each other with a predetermined interval. A pinion gear is arranged between the rack members and meshes with the rack members. Here, both rack members are provided so as to be able to reciprocate along the paper width direction, whereas the pinion gear is provided so as not to move. Then, by driving a drive source such as a motor to rotate the pinion gear, the left and right alignment plates 61L and 61R move symmetrically with respect to the left and right center.

  The left and right alignment plates 61L and 61R collectively align the sheets discharged to the sheet discharge tray 6. The sheet alignment operation of the alignment plates 61L and 61R will be described. This sheet alignment operation is controlled by the control unit 3A. FIG. 9 shows a case where A4 paper alignment is performed in the paper discharge tray 6.

  The alignment plates 61L and 61R are at the initial positions as shown in FIG. 9A before the sheet alignment operation is started. The initial position is a position where the distance between the alignment plates 61L and 61R at this position is equal to the maximum sheet width (in this case, A3 sheet width) that can be printed by the digital copying machine 1.

  The sheet alignment operation is started after all print jobs are completed and all sheets are discharged to the discharge tray 6. First, as shown in FIG. 9B, the alignment plates 61L and 61R are moved from the initial position to the alignment position by driving the drive source. The alignment position is a position determined based on the print paper size, that is, the size of the paper discharged to the paper discharge tray 6. For example, when the printing paper size is A4 paper, the alignment position is determined such that the interval between the alignment plates 61L and 61R at this position is equal to the A4 paper width or slightly longer than the A4 paper width. it can. When the print paper size is A3 paper, the initial position is the alignment position, so that the alignment plates 61L and 61R do not need to be moved.

  After the alignment plates 61L and 61R reach the alignment position, next, as shown in FIG. 9C, the alignment plates 61L and 61R are reciprocated several times by a minute distance by driving the drive source. Thereby, alignment of the paper discharged on the paper discharge tray 6 in the paper discharge direction is performed. Then, after the above-described reciprocating movement, the alignment plates 61L and 61R are returned to the initial position, and the sheet alignment operation is completed. Note that when image formation is performed on only one sheet, the sheet alignment operation may not be performed.

  In the digital copying machine 1, when image formation is continuously performed on a plurality of sheets, the printing process can be speeded up by the above-described method. Since the performed paper is alternately discharged from the left and right paper discharge rollers 43L and 43R, the positions of the discharged paper are alternately shifted in the paper discharge direction, which may deteriorate the stacking property. In this example, the alignment plates 61L and 61R are provided to align the paper discharged in the paper discharge tray 6 in the paper discharge direction. Therefore, the positions of the discharged paper in the paper discharge direction are aligned and the stacking property is good. Can be. Further, the sheet alignment according to the sheet size can be performed by the sheet alignment operation of the alignment plates 61L and 61R as described above.

1 is a diagram showing an outline of an internal configuration of a digital copying machine to which the present invention is applied. It is sectional drawing which shows the paper feed cassette which accommodates A3 paper. It is sectional drawing which shows the paper feed cassette which accommodates B4 paper. It is sectional drawing which shows the paper feed cassette which accommodates A4 paper. It is sectional drawing which shows the paper feed cassette which accommodates B5 paper. It is a top view which shows the laser writing unit using a 2 beam 1 polygon mirror system. It is a front view which shows the left laser writing unit. FIG. 6 is a cross-sectional view illustrating a paper discharge tray. FIG. 6 is a cross-sectional view illustrating a paper alignment operation in a paper discharge tray.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital copier 2 Scanner part 3L, 3R Image formation part 4L, 4R Paper conveyance mechanism 5 Paper feed part 6 Paper discharge tray 31L, 31R Laser writing unit 32L, 32R Electrophotographic process part 33L, 33R Photosensitive drum 39L, 39R Fixing Container 41L, 41R Conveyance path 51 Paper feed cassette 52 Pickup roller section 52L, 52R Pickup roller 54L, 54R Conveying rib 55 Partition plate 61L, 61R Alignment plate 71L, 71R Semiconductor laser light source 72 Polygon mirror

Claims (9)

A sheet feeding unit that accommodates a sheet, selectively feeds and conveys each of the stored sheets, an image forming unit that forms an image on the sheet fed from the sheet feeding unit, and an image forming unit In an image forming apparatus comprising a paper discharge means for discharging paper after image formation by
Two or more sets of the image forming means are provided, and each image forming means is provided with a printing section that transfers using an unfixed developer and a fixing device that melts and fixes the unfixed developer transferred onto the paper. An image forming apparatus.   The image forming apparatus according to claim 1, wherein when two sets of the image forming units are provided and image formation is continuously performed on a plurality of sheets, the image forming units are alternately used.   3. The sheet feeding unit according to claim 1, wherein the sheet feeding unit includes a sheet feeding cassette for storing sheets, and a pickup roller unit capable of feeding sheets in the sheet feeding cassette in a plurality of directions. The image forming apparatus described.   In the sheet feeding cassette, a conveyance guide member is selectively provided at both ends in the sheet feeding direction and a partition plate is selectively provided in the center in the sheet feeding direction, corresponding to the size of the sheet to be accommodated. The image forming apparatus according to any one of claims 1 to 3.   5. The image forming apparatus according to claim 1, wherein image data is written on the photosensitive member of each printing unit by an optical unit using a 2-beam, 1-polygon mirror system.   When two sets of image forming means are used alternately to form images continuously on a plurality of sheets, the optical unit is used to store the odd-numbered image data and even-numbered image data on the photosensitive member. 6. The image forming apparatus according to claim 5, wherein image processing is performed in which one of them is rotated by a predetermined angle with respect to the other.   The image forming apparatus according to claim 6, wherein a rotation angle of the image processing is 180 degrees.   8. A pair of alignment members for aligning sheets discharged in the sheet discharge direction after the image formation by each image forming unit is provided in the sheet discharge unit. An image forming apparatus according to claim 1.   The pair of alignment members are arranged symmetrically with respect to the center of the paper discharge means in the paper discharge direction, and are provided so as to be able to reciprocate in the paper discharge direction, and are discharged to the paper discharge means by the pair of alignment members. The image forming apparatus according to claim 8, wherein paper alignment is performed according to a size of the paper to be printed.

Images