JP2013018614A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximally suppress a cost increase and the upsizing of an apparatus even if recording is performed on a large-sized sheet.SOLUTION: A both-side reversing part comprising a both-side unit 61 and an extension unit 65 is provided at the back of an image forming apparatus body where an image is formed by a recording head 7. Conveyance rollers 63a, 63b, 63c are arranged in a both-side conveyance path 62 of the both-side unit 61. No conveyance roller is not arranged in the extension conveyance path 67 of the extension unit 65. When recording is performed on both sides of the large-sized sheet, the sheet is reversed by the extension conveyance path 67 having a longer path than the both-side conveyance path 62.

Description

  The present invention relates to an image forming apparatus capable of recording on both sides of a sheet (recording medium).

  In recent years, double-sided printing functions have been widely installed in image forming apparatuses from the viewpoint of reducing environmental burden and reducing costs. In an electrophotographic image forming apparatus, it is necessary to fix an unfixed toner image transferred to a sheet, and as a configuration for reversing the front and back of the sheet, the sheet after single-sided recording is completely removed from the image forming unit. In general, the configuration is such that it is sent to the double-side reversing unit (normally after passing through the fixing device), the front and back sides are reversed, and sent again to the image forming unit.

  On the other hand, in the inkjet recording system, a configuration in which non-contact printing with the paper is utilized, and after the single-side printing, the paper runs backward from the printing unit and is sent to the double-side reversing unit (hereinafter referred to as an inkjet double-side pass method). It is well known and commonly used.

  However, in the case of adopting the inkjet double-sided pass method in the conventional inkjet recording apparatus capable of double-sided recording, if double-sided printing is possible on large-size paper (large-size paper can be reversed), the paper of the double-sided reversing unit The number of transport means (conveying rollers, etc.) placed in the transport path is required to extend the path according to the large-size paper and to transport normal-size or small-size paper along the transport path. There is a problem that the image forming apparatus is increased in size and cost is increased.

  Specifically, the path length capable of accommodating postcards is 148 mm, but 420 mm is required to accommodate A3 paper. In other words, it is necessary to secure a path length of at least 420 mm in order to provide a double-sided function corresponding to A3, and 420 ÷ 105 = four conveying means (conveying rollers) to convey a postcard on a conveying path of 420 mm or more. Etc.) is required. Generally, A4 paper (297 mm), such as A4 paper (297 mm), is often used rather than large paper, so it is not possible to have a double-sided reversing unit for large paper that is used less frequently. This results in a cost for the less necessary part.

  Japanese Patent Application Laid-Open No. 2010-215376 (Patent Document 1) describes an image forming apparatus that can perform double-sided recording using a larger size paper while minimizing the enlargement of the apparatus. In the device, there is a limit on the expansion of the path length in the double-sided reversing unit, so double-sided recording on large-size paper is difficult, and if it is possible to handle large-size paper, the transport placed in the transport path The problem that the number of means (conveying rollers and the like) increases is not solved at all.

  The present invention solves the above-mentioned problems in a conventional image forming apparatus, and an image forming apparatus capable of suppressing an increase in cost and an increase in the size of the apparatus as much as possible even when the double-sided recording using large-size paper is possible. The issue is to provide.

  According to the present invention, according to the present invention, after recording on the first surface of the recording medium by the image forming unit, the recording medium is reversely fed to pass through the double-side reversing unit, and the recording medium is reversed to reverse the recording medium. In the image forming apparatus capable of performing double-sided recording by feeding again to the image unit and recording on the second side of the recording medium, the double-side reversing unit includes a first reverse conveyance path and a second reverse conveyance path length different from each other. And the second reverse transfer path is provided so as to join the first reverse transfer path after branching from the first reverse transfer path.

  According to the image forming apparatus of the present invention, the double-side reversing unit includes the first reverse conveyance path and the second reverse conveyance path having different conveyance path lengths, and the second reverse conveyance path is the first reverse conveyance path. Since it is provided to join the first reverse conveyance path after branching from the conveyance path, double-sided recording using large-size paper can be realized at low cost and in a small space.

1 is a cross-sectional view illustrating a configuration of an ink jet recording apparatus that is an example of an image forming apparatus according to the present invention. It is a schematic diagram explaining the attachment / detachment mechanism of an extension unit and a duplex unit. It is a fragmentary perspective view which shows the branch part of a double-sided conveyance path | route and an extended conveyance path | route. It is a fragmentary perspective view which shows the Example comprised so that a switching claw might be switched by attachment or detachment of an extension unit. It is a schematic diagram explaining operation | movement of the switching nail | claw and the member which switches it. It is sectional drawing which shows the structure of the inkjet recording device of 2nd embodiment of this invention. 1 is a cross-sectional configuration diagram illustrating an example of an inkjet double-pass image forming apparatus. FIG. 8 is a cross-sectional configuration diagram illustrating a recording apparatus having a duplex conveyance path having a path length larger than that of the apparatus of FIG.

Prior to the description of the embodiments of the invention, an example of an image forming apparatus having a double-sided printing function and an example of a method that enables handling of large-size paper based on the apparatus configuration will be described.
FIG. 7 is a cross-sectional configuration diagram illustrating an example of an “inkjet double-pass method” image forming apparatus that reverses a sheet after single-sided printing from a printing unit. In the ink jet recording apparatus shown in this figure, in the main body of the apparatus, the paper 12 stored in the paper feed cassette 10 is sent out by the paper feed roller 13, further transported to the printing position by the transport belt 21, and recorded by the recording head 7. Do. A duplex unit 61 is mounted on the back of the main body of the apparatus. When duplex printing is performed, the sheet after one-sided recording is transported into the duplex unit 61 by reverse rotation of the transport belt 21 and passed through the duplex transport path 62. Then, the paper is reversed (with the back surface being the printing surface), and is fed again. After recording on the back surface of the paper, the paper is discharged onto the paper discharge tray 54.

  In an apparatus that allows paper to be reversed with such a configuration and performs double-sided printing, the paper size that allows double-sided printing is limited to the paper size that can be reversed by the duplex unit 61. That is, since the reversible paper size is determined by the path length of the double-sided conveyance path 62 of the duplex unit 61, the length of the double-sided conveyance path (reversal conveyance path) is increased in order to enable reversal of larger-size paper. It is possible.

  FIG. 8 is a cross-sectional configuration diagram illustrating an inkjet recording apparatus including a duplex unit 161 having a duplex transport path 162 having a path length larger than the duplex transport path 62 in the apparatus of FIG.

  In the apparatus of FIG. 8, since the path length of the duplex conveyance path 162 is long, a total of five conveyance roller pairs are provided so that the sheet can be conveyed in the conveyance path. Compared with the apparatus of FIG. 7, in addition to the three pairs of conveyance rollers that the apparatus of FIG. 7 has, conveyance rollers 63d and 63e are provided. In this way, if the path length of the double-sided conveyance path is increased in order to invert a larger size sheet to enable double-sided recording, the number of conveyance roller pairs required for the double-sided conveyance path increases and the cost increases. There is a problem. In addition, for users who do not require double-sided recording on large-size paper, an unnecessary cost is borne, but the double-sided recording on large-size paper is not possible with the apparatus of FIG. It is desirable that the function can be expanded so that double-sided recording can be performed on large-size paper at that time.

In view of such a point, an embodiment of the invention in which the present inventor has made extensive studies will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a configuration of an ink jet recording apparatus which is an example of an image forming apparatus according to the present invention. The ink jet recording apparatus according to the present embodiment is roughly configured from an image forming apparatus main body having an image forming unit and a double-sided unit (reversing unit) attached to the image forming apparatus main body.

  The main body of the image forming apparatus holds the carriage 3 slidably in the main scanning direction by a guide rod 1 which is a guide member installed on left and right side plates (not shown), and is bridged between a driving pulley and a driven pulley by a main scanning motor (not shown). The carriage 3 is moved and scanned in the main scanning direction (direction perpendicular to the drawing) via the timing belt 5 passed.

  The carriage 3 includes, for example, four recording heads 7 each including a droplet discharge head that discharges yellow (Y), cyan (C), magenta (M), and black (Bk) ink droplets. The outlets are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.

  As a droplet discharge head constituting the recording head 7, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses film boiling of a liquid using an electrothermal transducer such as a heating resistor, or a metal phase change due to a temperature change is used. For example, a shape memory alloy actuator, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink (recording liquid) can be used.

  On the carriage 3, sub tanks for each color (not shown) for supplying ink of each color to the recording head 7 are mounted. Ink is supplied to the sub tank from a main tank (ink cartridge) (not shown) via an ink supply tube. In addition to the recording head 7 that discharges ink droplets, a recording head that discharges a fixing treatment liquid (fixing ink) that reacts with the recording liquid (ink) to improve the fixing property of the ink can be provided.

  On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feeding cassette 10, a paper feed roller for separating and feeding the paper 12 one by one from the paper stacking unit 11 13 is provided with a separation pad 14 made of a material having a large friction coefficient, and this separation pad 14 is urged toward the paper feed roller 13 side.

  As a transport unit for transporting the recording medium (paper) 12 fed from the paper feed unit below the recording head 7, a transport belt 21 for attracting and transporting the paper 12 with electrostatic force; A counter roller 22 for transporting the paper 12 sent from the paper supply unit via the guide 15 between the transport belt 21 and the paper 12 fed substantially vertically upward is changed by about 90 ° and the transport belt. 21 is provided with a conveying guide 23 for following the upper surface 21 and a tip pressure roller 25 urged toward the conveying belt 21 by a pressing member 24. Further, a charging roller (not shown) that constitutes a charging means for charging the surface of the conveying belt 21 is provided.

  Here, the conveyance belt 21 is an endless belt, is stretched between the conveyance roller 27 and the tension roller 28, and the conveyance roller 27 is rotated via a timing belt and a timing roller from a sub-scanning motor (not shown). Thus, the belt is configured to circulate in the belt conveyance direction (sub-scanning direction).

  In addition, an encoder scale 42 having slits is provided on the front side of the carriage 3, and an encoder sensor 43 including a transmission type photosensor that detects the slits of the encoder scale 42 is provided on the front side of the carriage 3. An encoder 44 for detecting the position of the carriage 3 in the main scanning direction is configured.

  Further, as a paper discharge unit for discharging the paper on which recording has been performed by the recording head 7, a separation claw (not shown) for separating the paper from the transport belt 21, a paper discharge roller 52 and a paper discharge roller. 53 and a paper discharge tray 54 for stocking the paper 12 to be discharged.

  A duplex unit 61 is attached to the back of the image forming apparatus main body. The duplex unit 61 includes conveyance rollers 63a, 63b, and 63c disposed along the duplex conveyance path 62, and rollers 64a, 64b, and 64c that are in contact with the conveyance rollers.

  The transport direction (counterclockwise direction in FIG. 1) in the duplex unit 61 does not change regardless of whether the sheet drive system on the image forming apparatus main body is rotated forward or backward. The drive system for driving the paper conveyance system provided in the double-sided paper feeding unit 61 is composed of, for example, a gear train composed of an odd number of gears on a bracket that swings in accordance with the rotation direction, and an even number of gears. There are two gears connected to the two gear trains, and either one of the gear trains is engaged with the rotation direction of the paper transport system on the apparatus main body side, so that in the double-sided paper feed unit 61 The rotation is kept in one direction. In addition to the swinging bracket, a one-way clutch or an electromagnetic clutch may be used.

  Furthermore, in the present embodiment, an optional extension unit 65 can be mounted outside the duplex unit 61. In FIG. 1, the extension unit 65 is attached. In the extension unit 65, an extension conveyance path 67 surrounded by a guide plate is formed. The extension unit 65 is configured to be easily attached to and detached from the duplex unit 61. The double-sided unit 61 and the extension unit 65 constitute a double-sided reversing unit having two reverse conveying paths with different sheet conveying path lengths.

  It should be noted that the duplex unit 61 includes a branch side connection path (upper side of the apparatus) branched from the duplex transport path 62 and communicated with the extension transport path 67 of the extension unit, and the extension transport path 67 of the extension unit. And a merging-side communication path (lower side of the device) for merging with each other. A switching claw 66 for switching the paper transport direction is disposed at the entrance of the branch side communication path. The position of the switching claw 66 is switched by driving means such as a solenoid (not shown). By switching the position of the switching claw 66, the traveling direction of the paper that has been fed back from the printing unit is switched between a direction that passes through the normal duplex conveyance path 62 and a direction that passes through the extension conveyance path 67 of the extension unit. Can do.

  When the sheet is reversed using the extended conveyance path 67, the sheet is conveyed in the duplex unit 61 (part of the conveyance path 62) until entering the extension unit 65 and after exiting the extension unit 65. However, in the following explanation, “passing through the extended transport path 67”, “using the extended transport path 67”, and the like will be described.

  In the ink jet recording apparatus of the present embodiment configured as described above, the paper 12 is separated and fed one by one from the paper feed unit, and the paper 12 fed substantially vertically upward is guided by the guide 15 and the transport belt 21. And the counter roller 22, and the front end is guided by the transport guide 23 and pressed against the transport belt 21 by the front end pressure roller 25, thereby changing the transport direction by approximately 90 °.

  At this time, a positive (plus) output and a minus (negative electrode) output are alternately applied to a charging roller (not shown), that is, an alternating voltage is applied, and the conveying belt 21 is in the sub-scanning direction which is the circumferential direction. In addition, positive and negative charges are alternately applied in a band shape with a predetermined width. When the sheet 12 is fed onto the conveyance belt 21 charged alternately with plus and minus, the sheet 12 is attracted to the conveyance belt 21 by electrostatic force, and the sheet 12 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 21. Is done.

  Therefore, by driving the recording head 7 according to the image signal while moving the carriage 3, the ink droplets are ejected onto the stopped paper 12 to record one line, and after the paper 12 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  As for the relationship between the scanning direction of the carriage 3 and printing, there are a unidirectional recording mode in which an image is formed only during scanning in one direction and a bidirectional recording mode in which an image is formed in both directions of scanning of the carriage 3. It is optional to set this according to the designation from the user and the print image, or to perform only one of the modes.

  In the case of duplex printing, when recording on the front surface (surface to be printed first) is completed, the conveyance belt 21 is rotated in the reverse direction so that the recorded paper 12 is fed into the duplex unit 61 and conveyed on both sides. The paper 12 is reversed by passing the path 62 or the extended conveyance path 67 (with the back surface being the printing surface), and is fed again between the counter roller 22 and the conveyance belt 21, and timing control is performed. In the same manner as described above, the sheet is conveyed onto the conveying belt 21 and recorded on the back surface, and then discharged onto the discharge tray 54.

  At the time of reverse feeding of the paper, the paper driving system on the image forming apparatus main body side is returned to the normal rotation direction at a predetermined timing after the trailing edge of the paper is removed from the printing unit (after entering the duplex unit 61). As a result, the paper that has been turned upside down and re-fed between the counter roller 22 and the conveyor belt 21 is fed to the printing unit.

  In duplex printing, which of the duplex conveyance path 62 and the extended conveyance path 67 is passed through is determined (controlled) by the sheet size. Temporarily, in the ink jet recording apparatus of the present embodiment, it is possible to use a sheet up to the maximum A3 size (longitudinal sheet). In that case, when using paper up to B4 size, for example, A4 (vertical) size or B4 (vertical) size paper, the switching claw 66 is switched so that the paper passes through the double-sided conveyance path 62. When A3 size (vertical) paper is used, the switching claw 66 is switched so that the paper passes through the extended conveyance path 67. Hereinafter, A3 size paper is referred to as “large size paper”, and B4 size or less paper is referred to as “normal size”.

  By the way, the length (path length) of the reverse path 62 of the duplex unit 61 is longer than the length of the normal size sheet, and when a sensor (not shown) detects that the trailing edge of the regular size sheet has entered the duplex unit 61. Then, the length is set so that the leading edge of the sheet does not reach the conveying belt 21. Further, the path length (path length including a part of the transport path 62) when using the reverse path 67 of the extension unit 65 is longer than the length of the large size sheet, and the rear end of the large size sheet is in the duplex unit 61. When a sensor (not shown) detects that it has entered, the length is set so that the leading edge of the sheet does not reach the conveyor belt 21. By setting in this way, the entire sheet is taken into the duplex unit 61 or the duplex unit 61 + extension unit 65 without remaining in the image forming apparatus main body when the sheet is reversed.

  Furthermore, the path length of the extended portion, more precisely, the path length from the transport roller 63a (and the roller 64a) to the transport roller 63c (and the roller 64c) via the reverse path 67 of the extension unit 65 is large. The length is set to be shorter than the length of the paper (for example, A3 length). By setting in this way, when the large-size sheet is reversed through the reversing path 67, the sheet can be conveyed by the conveyance rollers (here, the conveyance roller 63a and the conveyance roller 63c) in the duplex unit 61. For this reason, it is not necessary to dispose the transport roller and its drive system in the extension unit 65 (in the reverse path 67) for transporting large-size paper, and it is possible to prevent the apparatus configuration from becoming complicated and to prevent an increase in cost. it can.

  Even if a large-size sheet is jammed in the extension unit 65, the sheet is exposed to the outside of the unit (outside of the extension unit 65) from either the branching section or the joining section. Jam processing can be performed simply by removing from the duplex unit 61. Therefore, it is not necessary to provide an opening for jam processing or the like in the extension unit 65, and in this respect as well, it is possible to prevent a complicated configuration and an increase in cost.

  Furthermore, since there is no transport roller, it is possible to cope with various paper sizes by arbitrarily setting the length of the extended transport path (by preparing an extension unit having an appropriate path length). . For example, when it is desired to use strip-shaped long paper, double-sided recording using long paper can be performed by attaching an extension unit having a path length corresponding to the long paper to the double-side unit 61. .

  Further, a branching portion from the duplex unit 61 to the extension unit 65 (a branching portion from the reversing path 62 to the reversing path 67) is a sheet transporting means (in this example, a pair of transporting rollers by a transporting roller 63a and a roller 64a). ) Immediately after the branch path to the extension unit 65, that is, the pair of transport rollers (in this example, the transport roller 63a) and the pair of transport rollers after the merging section. The distance (distance) from the (conveying roller 63c in this example) can be minimized. At the same time, the paper can be stably conveyed with respect to the conveyance load at the branching portion.

  As described above, the extension unit 65 is configured to be detachable from the duplex unit 61. FIG. 2 shows a configuration of an attaching / detaching mechanism (locking mechanism) for the extension unit 65 and the duplex unit 61. As shown in this figure, fitting portions 68b and 68b fitted to receiving portions 68a and 68a provided on the double-sided unit 61 are provided at the upper and lower portions of one end (double-sided unit side) of the extension unit 65. Is formed. By fitting the fitting portions 68b and 68b to the receiving portions 68a and 68a and pushing the extension unit 65 into the double-sided unit 61, the fitting portion 68b is fitted into the receiving portion 68a and the extending unit 65 becomes the double-sided unit 61. It can be easily installed. Further, the extension unit 65 can be easily detached from the duplex unit 61 by pulling the extension unit 65 in the direction indicated by the arrow in the drawing. In addition, you may provide the fastener etc. which fix to the double-sided unit 61 after attaching the extension unit 65. FIG.

  In the illustrated example, a configuration in which the extension unit 65 can be completely detached (removed) from the duplex unit 61 is shown, but a configuration in which the extension unit 65 is pulled out from the duplex unit 61 by a slide rail or the like is also possible. Furthermore, the extension unit 65 can be mounted and supported on the double-sided unit 61 via a rotating shaft, and the extension unit 65 can be provided to be openable by rotating the extension unit 65.

  Since there is no need to provide a transport roller and its drive system in the extension unit 65, it is possible to easily realize a high degree of freedom of attachment and removal of the extension unit 65 from the double-sided unit 61 with the above-described appropriate configuration. it can.

  FIG. 3 is a partial perspective view showing a branch portion of the double-sided conveyance path 62 and the extended conveyance path 67. As described above, in this embodiment, the double-sided conveyance path 62 is used when reversing normal size paper, and the extended conveyance path 67 is used when reversing large size paper. The width of the duplex conveyance path 62 (the length in the direction orthogonal to the sheet conveyance direction) is set to a width corresponding to the normal size sheet. The switching claw 66 arranged at the branching portion is set to the width of the double-sided conveyance path 62 (narrower than the width of the extended conveyance path 67). With such a configuration, the switching claw 66 can be reduced in size and the cost can be reduced. Further, it is possible to enclose a mechanism for operating the switching claw and an attaching / detaching mechanism (locking mechanism) for the extension unit without enlarging the outer shape of the unit by using a space that is free in the width direction.

4 and 5 show an embodiment in which the switching claw 66 is switched by attaching and detaching the extension unit 65. FIG.
As shown in FIG. 4, a striker 71 protrudes from one end portion in the width direction of the extension unit 65. A hole 69 into which the striker 71 is inserted is provided on the duplex unit 61 side. As shown in the upper part of FIG. 5, a lever 70 is attached and fixed to one side (side corresponding to the striker 71) of the rotation shaft of the switching claw 66. The lever 70 may be formed integrally with the rotation shaft of the switching claw 66. The switching claw 66 and the lever 70 are set to have a predetermined angle as shown in the middle part of FIG. Then, when the extension unit 65 is attached to the duplex unit 61, the striker 71 is inserted into the hole 69, and as shown in the lower part of FIG. To be configured.

  A torsion spring (not shown) is attached to the rotation shaft of the switching claw 66, and imparts a turning behavior so that the switching claw 66 is positioned as shown in the upper part of FIG. As a result, the switching claw 66 guides the sheet that has been fed back from the printing unit to the duplex conveyance path 62 of the duplex unit 61. That is, when the extension unit 65 is not attached to the duplex unit 61, the switching claw 66 is held at a switching position that guides the sheet that has been fed back from the printing unit to the duplex conveyance path 62 of the duplex unit 61.

  By attaching the extension unit 65 to the duplex unit 61, as shown in the lower part of FIG. 5, when the striker 71 rotates the switching claw 66, the switching claw 66 extends the paper that has been fed back from the printing unit. The position is switched to the position leading to the extended conveyance path 67 of the unit 65. As a result, in a state in which the extension unit 65 is attached, the sheet that has been fed back from the printing unit is conveyed through the extended conveyance path 67.

  With such a configuration, the switching claw 66 is automatically switched by attaching and detaching the extension unit 65. The extension unit 65 may be configured to be completely removed from the duplex unit 61 or may be configured to be pulled out by a slide rail or the like. Moreover, the structure open | released by rotating may be sufficient.

  Here, the configuration in which the striker 71 directly operates the switching claw 66 is shown, but a configuration in which the switching claw 66 is operated using a link member or the like may be used. Moreover, the structure which drives the said power source and operates the switching nail | claw 66 by the striker 71 pushing a switch or detecting the striker 71 using a power source may be sufficient. Further, the striker 71 can be used to detect that the extension unit 65 is attached to and removed from the duplex unit 61.

  FIG. 6 shows a second embodiment in which a part of the duplex unit and the extension unit are integrated and provided as an extension unit. Since the basic configuration is the same as that of the first embodiment described with reference to FIG. 1 and the like, different portions will be described, and redundant description will be omitted.

  In the ink jet recording apparatus according to the second embodiment shown in FIG. 6, an expansion unit 80 including a normal reversing unit 60 and an extended reversing unit 75 is attached to the back of the image forming apparatus main body. The extension reversing portion 75 is provided so as to be openable and closable with respect to the normal reversing portion 60 by a rotation shaft 77 located at the lower end portion of the unit cover 76. In the figure, the extension inversion part 75 is shown in an open state. A configuration in which the extension reversing part 75 is completely removed (detached) from the normal reversing part 60 is also possible. Moreover, the structure which pulls out the extension inversion part 75 from the normal inversion part 60 by a slide rail etc. is also possible.

  In the second embodiment, of course, the extended conveyance path 67 is formed on the extended reversing unit 75 side, but an outer guide plate that forms the double-sided conveyance path 62 is also provided on the extended reversing unit 75 side. Yes. In addition, the rollers 64a and 64b and the switching claw 66 are also provided on the extended inversion portion 75 side, that is, supported in the unit cover 76. When the extension reversing portion 75 is closed, the switching claw 66 is connected to the drive system provided on the normal reversing portion 60 side and can be switched. Alternatively, the switching claw 66 is switched using the configuration described in FIGS. 4 and 5 (in that case, a striker is provided on the normal reversing unit 60 side, and the switching claw 66 is switched by the striker when the extension reversing unit 75 is closed). You may comprise as follows.

  According to the configuration of the second embodiment, when the paper is jammed, the nip of the plurality of conveyance roller pairs in the double-side conveyance path 62 is opened by opening the extension reversing unit 75 (in this example, the conveyance roller). 63a and 63b), the jammed paper (normal size paper) can be easily taken out. The nip is not opened at the conveyance roller 63c, but the sheet can be taken out because the trailing edge of the sheet is sufficiently exposed. When a sheet enters the extended conveyance path 67 (when a large size sheet is jammed), the sheet can be taken out from the branching section or the merging section.

  In addition, according to the configuration of the second embodiment, paper jam has occurred in both normal size paper and large size paper while providing two transport paths for paper reversal to enable duplex printing of large size paper. In this case, it is possible to maintain a good workability (similar to a single reverse device) because jam processing can be performed by one-action operation of opening the extended reversing unit 75. Operability can be provided.

  As described above, according to the present invention, the first reverse conveyance path in which the recording medium conveyance unit is disposed in the double-side reversing unit and the second reverse conveyance path in which the recording medium conveyance unit is not disposed are provided. The second reversing transport path is provided so as to join the first reversing transport path after branching from the first reversing transport path, so that double-sided recording using large-size paper is low cost and space-saving. Can be realized.

  In addition, since the path length of the second reverse transport path is longer than the path length of the first reverse transport path, double-sided recording using a larger size paper is performed using the second reverse transport path. be able to.

  Further, the branch portion from the first reverse transfer path to the second reverse transfer path is provided in the vicinity of the downstream side of one transfer means arranged in the first reverse transfer path, so that the second reverse transfer It is possible to minimize the arrangement interval of the sheet conveying means for feeding the sheet for conveying the path. At the same time, the sheet can be stably conveyed with respect to the conveyance load at the branching portion.

  In addition, since a switching unit that switches the conveyance direction of the recording medium is arranged at a branch portion from the first reverse conveyance path to the second reverse conveyance path, the sheet conveyance direction is changed to the first reverse conveyance path or the second reverse conveyance path. It is possible to surely switch to the second reverse conveyance path.

  Then, the size of the switching unit in the direction orthogonal to the paper conveyance direction is set to a size corresponding to the paper passing width of the first reverse conveyance path, so that the cost can be reduced and driving is performed using the vacant space. It is possible to enclose the system and the unit attaching / detaching mechanism without enlarging the outer shape.

  Moreover, since the part provided with the second reverse conveyance path is configured as a detachable unit with respect to the part provided with the first reverse conveyance path, the unit provided with the second reverse conveyance path when necessary. It becomes possible to mount the apparatus, and the initial cost of the apparatus can be reduced, and the initial installation space of the apparatus can also be reduced.

  In addition, by attaching a unit including the second reverse conveyance path, the paper conveyance direction in the double-side reversing unit can be automatically switched from the first reverse conveyance path to the second reverse conveyance path. In addition, it is possible to detect the mounting of the unit in conjunction with the switching of the conveyance direction, and it is possible to reduce the cost because it is not necessary to provide a separate detection means.

Further, by separating the unit having the second reverse conveyance path, a part of the first reverse conveyance path is opened, so that the jam processing can be easily performed.
As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. Appropriate configurations can be adopted as the configuration of the image forming apparatus main body, that is, the configuration of the paper feeding unit and the printing unit.

  The length of the reverse conveyance path is also an example, and can be set to a length corresponding to an appropriate paper size. An appropriate configuration can also be adopted as the configuration of the drive system of the conveyance roller in the double-side reversing unit.

  The image forming apparatus is not limited to a printer, and may be a copier, a facsimile, or a multifunction machine having a plurality of functions.

3 Carriage 7 Recording Head 10 Paper Feed Cassette 21 Conveying Belt 61 Double Sided Unit 62 Double Sided Conveying Path 63 Conveying Roller 64 Roller 65 Extension Unit 66 Switching Claw 67 Extended Conveying Path 68a Receiving Portion 68b Fitting Portion 69 Hole 70 Lever 71 Striker 75 Extension Reversal Part 80 Expansion unit

JP 2010-215376 A

Claims (9)

After recording on the first surface of the recording medium in the image forming unit, the recording medium is reversely fed to pass through the both-side reversing unit, the front and back of the recording medium are reversed, and the recording unit is fed again to the image forming unit for recording. In an image forming apparatus capable of recording on the second side of the medium and capable of double-sided recording,
The double-side reversing unit includes a first reverse conveyance path in which a recording medium conveyance unit is disposed and a second reverse conveyance path in which a recording medium conveyance unit is not disposed,
2. The image forming apparatus according to claim 1, wherein the second reverse conveyance path is provided so as to join the first reverse conveyance path after branching from the first reverse conveyance path.   The image forming apparatus according to claim 1, wherein a path length of the second reverse transport path is longer than a path length of the first reverse transport path.   The branch portion from the first reverse conveyance path to the second reverse conveyance path is provided in the vicinity of the downstream side of one conveyance means arranged in the first reverse conveyance path. Item 3. The image forming apparatus according to Item 1 or 2.   The switching unit for switching the conveyance direction of the recording medium is arranged at a branch portion from the first reverse conveyance path to the second reverse conveyance path. The image forming apparatus described in the item.   5. The image according to claim 4, wherein a size of the switching unit in a direction perpendicular to the paper transport direction is set to a size corresponding to a paper passing width of the first reverse transport path. Forming equipment.   The part provided with said 2nd inversion conveyance path is comprised as a unit which can be attached or detached with respect to the part provided with said 1st inversion conveyance path, The any one of Claims 1-5 characterized by the above-mentioned. The image forming apparatus described in 1.   By mounting the unit including the second reverse transfer path on the portion including the first reverse transfer path, the sheet transfer direction in the double-side reverse unit is changed from the first reverse transfer path to the second reverse transfer path. The image forming apparatus according to claim 6, wherein the image forming apparatus is switched to a path.   The attachment of the unit having the second reverse conveyance path to the portion having the first reverse conveyance path is detected in conjunction with switching of the paper conveyance direction in the double-side reversing unit. Item 8. The image forming apparatus according to Item 7. The part of the first reverse transport path is opened by separating the unit including the second reverse transport path from the portion including the first reverse transport path. The image forming apparatus according to any one of 6 to 8.

Images