JP2008137730A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and accurately straighten the skew of transfer paper P in double-side image formation to prevent the occurrence of a paper conveying failure such as a jammed state. <P>SOLUTION: A conveyance control part for suitably controlling the conveying operation of the transfer paper P used as a recording medium carries out skew straightening by performing end face alignment of the transfer paper P by an adjusting mechanism of a post-processing device 12 simultaneously with the reversing operation (switch-back operation) of the transfer paper P in double-side image formation, and the skew-straightened transfer paper P is reversely conveyed to a double-side conveying path 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus configured to perform image formation on both front and back surfaces of a recording medium.

  In general, when forming an image on a recording medium such as a recording sheet in various image forming apparatuses such as a printer and a copying machine, the recording medium supplied to the recording medium conveyance path is inclined so as not to be sent in an inclined state. Straightening is performed. For example, in the printer of FIG. 1 showing the embodiment of the present invention, the transfer paper (recording medium) P stacked in the paper feed cassette 1 is separated one by one by the paper feed roller 2 and the recording medium transport path. The leading edge of the transfer paper P is abutted against the nip portion of the registration roller 3 provided in the recording medium conveyance path. Accordingly, the transfer paper P is deformed so as to form a loop shape, and the entire length of the leading edge of the transfer paper P is brought into contact with the nip portion of the registration roller 3 by the restoring force at that time. By doing so, matching is performed. As a result, the transfer paper P is corrected to a posture along the recording medium conveyance path, and the subsequent conveyance is performed in this state.

  However, in the operation of correcting the skew by the registration roller 3 described above, it takes time to form a loop and the like. Therefore, when forming images on both the front and back surfaces of the transfer paper (recording medium) P, it is sufficient. In some cases, it is not possible to secure time for performing skew correction. That is, at the time of double-sided image formation, time is required for a control operation such as a reverse operation (switchback operation) of the transfer paper P on which the image is formed on the first surface (front surface) toward the double-sided conveyance path 6 of the double-sided conveyance unit 7. Therefore, it is required to shorten the subsequent transport time as much as possible. For this reason, the skew correction time for the inverted transfer paper P by the registration rollers 3 also tends to be set to a minimum, and as a result, the skew is applied during image formation on the second surface (back surface) of the transfer paper P. If the transfer paper P that is not sufficiently corrected is supplied, it may cause a conveyance failure such as a jam.

Japanese Patent Laid-Open No. 10-218455

  Therefore, the present invention provides an image forming apparatus capable of correcting skew feeding of a recording medium at the time of double-sided image formation quickly and accurately, and reducing the occurrence of paper conveyance defects such as jams. For the purpose.

  In order to achieve the above object, in the image forming apparatus according to the present invention, a recording medium conveyance path provided with a double-side conveyance path that enables image formation on both sides of the recording medium, and the recording discharged from the recording medium conveyance path. In an image forming apparatus provided with a post-processing device provided with an alignment mechanism for aligning the end face of a medium, and a conveyance control unit for appropriately controlling the recording medium conveyance path and the recording medium conveyance operation in the post-processing device, The conveyance control unit feeds a part or all of the recording medium on which an image is formed on one side into the alignment mechanism of the post-processing device to perform end face alignment by forming an oblique surface of the recording medium. It is configured to perform line correction and send the skew-corrected recording medium to the double-sided conveyance path.

  According to the present invention having such a configuration, the reversing operation (switchback operation) of the recording medium after the image formation on the first surface at the time of double-sided image formation is performed simultaneously with the realignment operation (switchback operation) of the recording medium. The skew correction on the two surfaces is performed quickly.

  As described above, in the image forming apparatus according to the present invention, the reversing operation (switchback operation) during double-sided image formation is performed by the conveyance control unit that appropriately controls the recording medium conveyance operation in the recording medium conveyance path and the post-processing apparatus. At the same time, since the post-processing device is configured to correct the skew of the recording medium, the skew correction of the recording medium at the time of double-sided image formation can be performed quickly and accurately, and paper conveyance failure such as a jam. Therefore, the reliability and performance of the image forming apparatus can be improved at the same time.

  Hereinafter, an embodiment in which the present invention is applied to a printer as an image forming apparatus will be described in detail with reference to the drawings.

  The schematic structure and image forming operation relating to the printer shown in FIG. 1 have already been described in the background art section, but will be described again just in case. The transfer paper P accumulated as a recording medium in the paper feed cassette 1 is sent out into the recording medium transport path while being separated one by one by the rotational drive of the paper feed roller 2, and is provided in the recording medium transport path. The leading edge of the transfer paper P is abutted against the nip portion of the registration roller 3 and is deformed into a loop shape. Then, due to the restoring force at that time, the entire length of the leading edge of the transfer paper P is brought into contact with the nip portion of the registration roller 3 for alignment, and as a result, the skew of the transfer paper P is corrected and the recording medium is corrected. Subsequent transport is performed in a posture along the transport path.

  The transfer paper (recording medium) P that has been subjected to the skew correction by the registration roller 3 is sent to the image forming unit 4 adopting the electrostatic recording system, where the first surface (front surface) of the transfer paper P is transferred. A desired image is formed by transferring the toner image thereon, and thereafter, the toner image is conveyed to the fixing unit 5 and the toner image is permanently fixed.

  On the other hand, a double-sided conveyance unit 7 having a double-sided conveyance path 6 is added to the recording medium conveyance path disposed in the printer apparatus main body so as to convey the transfer paper (recording medium) P. A reversing roller 8 is disposed at the discharge portion of the medium conveyance path. When the double-sided image forming mode is selected, after the image is formed on the first surface (front surface) of the transfer paper P as described above, the reverse roller 8 is rotated in the forward direction (Y2 direction). The transfer sheet P on which the image is formed on the first surface (front surface) is drawn into the double-sided conveyance path 6. The transfer paper P with the front and back reversed in this way is sent out again in the front side direction (Y3 direction) of the registration roller 3 by the feeding action of the double-sided conveyance roller 9 arranged in the double-sided conveyance path 6.

  Then, the transfer paper P that has been turned upside down is conveyed again in the direction toward the image forming unit 4 (Y1 direction), and the image forming operation and the fixing operation on the second surface (back surface) of the transfer paper P are described above. This is performed in the same manner as the first surface (front surface), thereby completing image formation on both the front and back surfaces of the transfer paper P.

  Further, on the discharge side of the recording medium conveyance path, a substantially planar discharge tray 11 that can accommodate the transfer paper P sent out from the recording medium conveyance path is disposed, and on the discharge tray 11 Is equipped with a post-processing device 12 that automatically performs operations such as stapling and punching. The post-processing device 12 itself has a well-known structure connected to the discharge portion of the recording medium conveyance path, and accepts the transfer paper P discharged from the recording medium conveyance path in a layered manner and positions the end faces. A well-known alignment mechanism that performs alignment is provided.

  The well-known post-processing device 12 has a top mount structure as shown in FIG. 2, for example, and is mounted on the upper side of the printer apparatus main body described above. Then, the transfer paper P discharged through the recording medium conveyance path in the printer main body is conveyed into the processing arm 12b of the alignment mechanism by the rotational drive of the finisher reversing roller 12a provided in the post-processing device 12. A pair of the processing arms 12b are disposed at both side positions of the transfer paper P in the paper width direction.

  Then, each of the processing arms 12b moves symmetrically in a direction in which the processing arms 12b approach each other with respect to both end surfaces in the paper width direction of the transfer paper P conveyed between the pair of processing arms 12b. Specifically, the transfer paper P is aligned in the paper width direction by the inner end surface of the processing arm 12b being in contact with and pressed against the both side end surfaces of the transfer paper P in the paper width direction. Further, when the transfer paper P is fed into the post-processing apparatus 12, the edge of the transfer paper P in the conveyance direction rear end side comes into contact with the end surface regulating plate (not shown) by its own weight, thereby the transfer paper P P is aligned with the transport direction.

  The alignment process of the transfer paper P by such an alignment mechanism is repeated until one print job is completed, and the whole of the stacked transfer paper P is aligned at the time when one print job is completed. Made. Then, the transfer paper P in the paper bundle state is discharged onto the finisher tray 12c by being opened between the processing arms 12b after post-processing such as stapling is performed, or the finisher reversal described above. The roller 12a is driven to rotate in the reverse direction, and is sent out one by one or in an appropriate amount stacked toward the inside of the duplex conveyance unit 7.

  On the other hand, each transfer operation of the transfer paper P in the above-described image forming operation and the alignment processing operation by the alignment mechanism of the post-processing device 12 is appropriately controlled according to a program provided in a conveyance control unit (not shown). . When the image is formed on both sides of the transfer paper P described above, a part or all of the transfer paper P on which the image is formed on the first surface (front surface) is subjected to the post-processing described above according to the program of the conveyance control unit. After being discharged into the aligning mechanism of the apparatus 12, the aligning mechanism of the processing apparatus 12 performs alignment processing of the transfer paper P by the processing arm 12b, that is, end face alignment, thereby correcting the skew feeding of the transfer paper P. It is made to be done.

  In this way, the transfer paper P that has been skew-corrected by the alignment mechanism of the post-processing device 12 is reversely conveyed toward the double-sided conveyance path 6 of the double-sided conveyance unit 7 by the reverse rotation of the finisher reverse roller 12a. However, at that time, if the finisher reversing roller 12a described above is separated and brought into contact with the upper surface of the transfer paper P at an appropriate timing, the reversing and conveying operation is performed well. A control operation based on a program of such a series of conveyance control units will be described with reference to an embodiment of the continuous duplex printing process shown in FIG.

  That is, as shown in FIG. 3, the continuous duplex printing process of the printer in the present embodiment is first started by a printing process on the first surface (front surface) of the transfer paper P (S1), and is supplied at that time. It is determined whether the transfer sheet P is in the skew state (S2). Whether the transfer paper P is skewed or not is detected, for example, between a pair of sensors (see symbols S1 and S2 in FIGS. 1 and 2) arranged at a specific interval in the transport path. It is possible to carry out the measurement by an appropriate means that monitors the timing between the sensors and determines that the feeding is skewed if the transport time between the sensors is longer than a predetermined time.

  If the skew of the transfer sheet P is not detected (No in S2), a reversing operation (switchback operation) is performed by the duplex conveying unit 7 (S5), and then the second surface of the transfer sheet P is performed. Printing (image formation) processing for (back side) is started (S6).

  On the other hand, when the skew of the transfer paper P is detected (Yes in S2), it is determined whether or not the transfer paper P should be aligned (S3). This determination is made by setting or canceling the duplex skew correction mode for enabling the skew correction operation based on the alignment (end surface alignment) processing of the transfer paper P by the alignment mechanism of the post-processing device 12 described above. If the duplex skew correction mode is set to be canceled, it is determined that a transfer paper conveyance failure has occurred (S8), and the transfer paper P is conveyed to the post-processing device 12 as it is. Thus, the continuous duplex printing operation is interrupted.

  On the other hand, if the double-side skew correction mode is set, the width direction of the transfer paper P is aligned by the alignment mechanism of the post-processing device 12 described above, and the end surface alignment is performed. As a result, the skew of the transfer paper P is corrected (S4). In the skew correction by the alignment mechanism of the post-processing device 12, the above-described finisher reversing roller 12a and the processing arm 12b carry the sheet so that the trailing edge of the transfer paper P does not fall on the finisher tray 12c. The alignment process in the width direction by the processing arm 12b is executed.

  In the above-described determination of the presence / absence of skew (S2), when such a determination is not originally performed, or when it is impossible to determine skew, the above-described case of skew is present (YS in S2). ), It is determined whether or not the transfer paper P is to be aligned (S3), and an operation similar to that described above is performed according to whether or not the double-side skew correction mode is set. (S8, S4) are performed.

  After the skew correction of the transfer paper P is performed, the reverse roller 8 is rotated in the direction opposite to the arrow Y2 in FIG. 1, and the transfer paper P is reversed so that the transfer paper P is drawn into the double-sided conveyance path 6 side. (Switchback operation) is performed (S5). As a result, the transfer sheet P is retransmitted to the image forming unit 4 through the double-sided conveyance path 6, and a printing (image forming) process for the second side (back side) is executed (S6). Finally, it is determined whether or not the printing is finished (S7). If the printing is not finished, the printing process (S1) for the first surface (front surface) of the transfer paper P of the next page is repeated to enter the finished state. If so, the continuous duplex printing operation is terminated.

  As described above, according to the present embodiment, the transfer sheet P as a recording medium sent to the double-sided conveyance path 6 by the reversing operation (switchback operation) is simultaneously with the reversing operation (switchback operation) of the transfer paper P. Since the skew correction is performed by the alignment mechanism of the processing device 12, the skew correction of the transfer paper P at the time of double-sided image formation is performed quickly and accurately, and the occurrence of a paper conveyance failure such as a jam state is prevented. It has become.

  As mentioned above, although the embodiment of the invention made by the present inventor has been specifically described, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the scope of the invention. Nor.

  For example, the embodiment described above applies the present invention to a printer, but the present invention can be similarly applied to other image forming apparatuses such as copying machines.

  As described above, the image forming apparatus according to the present invention can be widely applied to various image forming apparatuses such as copying machines as well as image forming apparatuses such as printers.

1 is a longitudinal sectional view illustrating a schematic configuration of a printer including a post-processing apparatus to which the present invention is applied. FIG. 2 is a longitudinal cross-sectional explanatory diagram illustrating a schematic configuration of a post-processing device mounted on the printer illustrated in FIG. 1. 6 is a flowchart illustrating a control operation of continuous duplex printing processing based on a conveyance control program according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper feed cassette 2 Paper feed roller 3 Registration roller 4 Image forming part 5 Fixing part 6 Double-sided conveyance path 7 Double-sided conveyance unit 8 Reverse roller 9 Double-sided conveyance roller 11 Discharge tray 12 Post-processing device 12a Finisher reverse roller 12b Processing arm 12c Finisher tray

Claims (3)

A recording medium conveyance path provided with a double-side conveyance path that enables image formation on both sides of the recording medium;
A post-processing apparatus provided with an alignment mechanism for aligning the end face of the recording medium discharged from the recording medium conveyance path;
A conveyance control unit for appropriately controlling the conveyance operation of the recording medium in the recording medium conveyance path and the post-processing device;
In the image forming apparatus provided with
The conveyance control unit feeds a part or all of the recording medium on which an image is formed on one side into the alignment mechanism of the post-processing device to perform end face alignment by forming an oblique surface of the recording medium. An image forming apparatus configured to perform line correction and send the skew-corrected recording medium to the double-sided conveyance path.   2. The image forming apparatus according to claim 1, wherein means for detecting skew of the recording medium is disposed in the recording medium conveyance path.   The image forming apparatus according to claim 1, wherein the conveyance control unit is configured to be capable of setting or canceling a double-sided skew correction mode that enables the skew correction operation by the alignment mechanism.

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