JP2008100833A - Paper carrying device and image forming device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable and stable paper carrying device for correcting the skew of paper different in size, thickness and curled condition with the optimum reversing amount of a register roller without giving damage to the front end of the paper. <P>SOLUTION: The paper carrying device comprises a memory device for storing paper information for the size, thickness and type of paper input to an image forming device and printing mode information for single side printing or both side printing, and a drive control device for controlling the reversing operation of the register roller in accordance with the paper information and the printing mode information stored in the memory device. The drive control device is used for adjusting the reversing amount of the register roller 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus used in an image forming apparatus such as a copying machine or a laser printer using electrophotography.

  In image forming apparatuses such as cut paper laser printers and copiers that use electrophotography, the paper transported from the paper feeding device is used for transport and transfer via the paper transport device that corrects the position and skew of the paper. Is transferred to a transfer belt type transfer device using a dielectric belt that also serves as a transfer belt. The transfer device induces an electric charge on the surface of the transfer belt, sucks and conveys the paper with this electric charge, and transfers the image formed on the photosensitive member onto the paper.

  In a conventional sheet conveying device that corrects the position and skew of a sheet, the sheet is fed by a timing roller disposed upstream of the registration roller disposed in front of the transfer device. The timing roller always applies a conveying force to the sheet in the direction of the registration roller. At that time, as described in Japanese Patent Laid-Open No. 5-186102, after the paper has passed through the registration roller by a certain amount, the registration roller is reversed by a certain amount more than the passage amount, and the leading edge of the paper is returned to the registration roller. After releasing from the nip, the leading edge of the sheet is brought into contact with the registration roller again using the waist of the sheet, and the skew is corrected by causing the leading edge of the sheet to follow the registration roller.

JP 05-186102 A

  This method has an advantage that there is no collision when the leading edge of the sheet reaches the registration roller, and therefore the leading edge of the sheet is not damaged when the leading edge of the sheet is brought into contact with the registration roller. However, in this method, the amount of paper passing through the registration roller and the amount of reverse rotation are set regardless of the size and thickness of the paper, so a wide variety of papers, sizes, thicknesses and conditions required for current printing devices are set. It cannot respond to. Generally, since the rigidity of the paper varies depending on the size and thickness of the paper, a difference occurs in the amount of paper movement when the registration roller is reversed due to a difference in paper conveyance resistance, and the leading edge of the paper is completely aligned with the registration roller. There is a case where it is not released from the nip, and the effect of the skew correction is different.

  In recent years, recycled paper with consideration for the global environment has been used in various ministries and companies in place of high-quality paper. However, because recycled paper uses waste paper pulp, its cutting direction and deformation due to moisture absorption are high-quality. It tends to be larger than paper. Further, the curl amount of the paper after heat fixing tends to be larger than that of the high quality paper.

  For this reason, when the leading edge of the sheet is bitten by the registration roller, the entry time of the leading edge of the sheet into the nip may be delayed, so that the passing amount of the leading edge of the sheet in the registration roller nip may be smaller than a specified value. In this case, since the friction distance between the front end of the sheet after the front end of the registration roller is released from the nip of the registration roller and the surface of the registration roller when the registration roller is rotated in reverse, the front end of the sheet is damaged unexpectedly. There is a case. Further, since the leading edge of the sheet is deformed due to thermal curl during double-sided printing, the contact state of the leading edge of the sheet with the nip of the registration roller varies, and the effectiveness of the skew correction may vary.

  An object of the present invention is to provide a highly reliable paper transport apparatus for paper having different sizes, thicknesses, and curled states.

  In order to achieve the above object, the first means of the present invention presses a transfer material against a toner image carrier through a printing paper, and applies a charge having a reverse polarity to the toner to the back surface of the transfer material. Thus, a registration roller capable of rotating in the forward and reverse directions is installed on the upstream side of a transfer device that sucks and conveys the material to be transferred and transfers and conveys the toner image formed on the toner image carrier. In a sheet conveying apparatus that performs skew correction and conveyance of printing paper by bringing the sheet into contact, the sheet size, thickness, and sheet type information input to the image forming apparatus and printing of single-sided printing or double-sided printing A memory device for storing the mode information, and a drive control device for controlling the reverse rotation operation of the registration roller based on the paper information and the printing mode information stored in the memory device. It is obtained by and adjusting a reverse rotation amount of the resist rollers by a control device.

  According to a second means of the present invention, the first means has an input device capable of invalidating the data of the paper information and the printing mode information, and the drive control value of the registration roller can be manually set from the input device. It is characterized by being configured.

  According to a third means of the present invention, there is provided a cassette for storing printing paper, a registration device for transferring a toner image on the toner image carrier to a predetermined position of the printing paper, and the cassette. In the image forming apparatus including a developing / transfer device that forms a toner image on the unloaded printing paper and a fixing device that fixes the toner image transferred onto the printing paper, the first or second registration device is the first or second registration device. It is characterized by using the paper conveying device of the means.

  According to the present invention, skew correction is performed with the optimum amount of reverse rotation of the registration roller even for paper of different sizes, thicknesses, and curl states, and a highly reliable and stable paper that does not damage the leading edge of the paper. Transport can be achieved.

  The paper transport device according to the present invention stops after the paper is brought into contact with the stopped registration roller, and the skew feeding by the registration roller according to information such as the paper size, thickness, paper type, and printing mode. By automatically variably controlling the amount of reverse rotation at the time of correction and setting an optimum skew correction condition for the paper, highly reliable and stable paper conveyance can be achieved.

  In addition, the paper and print mode information is invalidated from the input device of the image forming apparatus, and a function capable of manually inputting a more optimal reverse amount is provided, thereby achieving more reliable and stable paper conveyance. it can.

  An embodiment of the present invention applied to an image forming apparatus such as a cut paper laser printer and a copying machine using electrophotography will be described below with reference to FIG.

  A sheet 3 conveyed from a sheet feeding device (not shown) is subjected to position and skew correction by a timing roller 5 and a registration roller 4 and conveyed onto a transfer belt 6. The conveyed sheet 3 transfers the toner 2 on the photosensitive drum 1 and is conveyed to a fixing device (not shown).

  Conventionally, in the position correction using the registration roller 4 and the skew feeding correction, a predetermined amount of paper is fed after a sensor (not shown) arranged on the upstream side of the registration roller 4 detects the paper regardless of the size and thickness of the paper. Accordingly, the amount of paper that has passed through the registration roller 4 is fixed, and the reverse rotation angle is also set to a fixed amount according to the passage amount.

  For this reason, there is a case where the passing amount and the reverse rotation angle are not optimal for the type and state of the paper, and the skew correction is insufficient or the paper is damaged.

  On the other hand, according to the present invention, after the paper 3 comes into contact with the stopped registration roller 4 and stops according to the information of the printing device such as the paper size, thickness, paper type, and printing mode, By automatically variably controlling the reverse rotation amount of the registration roller 4 for releasing the leading edge of the paper that has entered the nip of the registration roller 4, an optimum skew correction condition is created for the paper, and the skew of the paper 3 Make corrections.

  For example, the optimum reverse rotation amount of the registration roller with respect to the paper size, thickness, and curl state is roughly as follows, and these are the paper size, thickness, and paper type input to the image forming apparatus. A memory device for storing the paper information and print mode information for single-sided printing or double-sided printing, and a drive control device for controlling the reverse operation of the registration roller based on the paper information and the printing mode information stored in the memory device; The registration roller is controlled by the drive control device.

  Narrow paper has a small conveyance resistance (reaction force due to the back of the paper), so the amount of paper movement (the amount of rotation around the registration roller surface) during skew correction when the registration roller is reversed increases. Even if the amount of reverse rotation is small, the correction capability is sufficient. On the other hand, when the amount of reverse rotation is large, the rubbing between the surface of the registration roller after being released from the nip of the registration roller and the front end of the paper increases, which may cause damage.

  Since thin paper has a small conveyance resistance (reaction force due to the back of the paper), the amount of paper movement (the amount of rotation around the registration roller surface) during skew correction when the registration roller is reversed increases, and the amount of rotation of the registration roller At least, the correction capability is sufficient. On the other hand, if the amount of reverse rotation is large, thin paper has low rigidity, and if the amount of reverse rotation of the registration roller is large, buckling is likely to occur when the registration roller is released from the nip, and damage may occur.

  Wide paper has a large conveyance resistance (reaction force due to the back of the paper), so the amount of paper movement (the amount of rotation around the registration roller surface) during skew correction when the registration roller is reversed is reduced, and the leading edge of the paper is In some cases, sufficient skew correction capability cannot be obtained because the resist roller is not sufficiently released from the nip. Therefore, by increasing the reverse rotation amount of the registration roller, the sheet movement amount is increased and the correction capability is enhanced.

  Thick paper has a large conveyance resistance (reaction force due to the back of the paper), so the amount of paper movement (the amount of rotation around the registration roller surface) during skew correction during reverse rotation of the registration roller decreases, and the reverse rotation amount of the registration roller. By increasing, the amount of paper movement is increased and the correction capability is increased.

  For paper with large curl due to thermal curl or the like during double-sided printing, the contact between the registration roller and the leading edge of the paper becomes unstable. In this case, since the leading edge of the paper is caught on the surface of the registration roller, the paper may be skewed or the paper may be damaged due to the reverse rotation of the registration roller. The skew correction ability can be improved.

  Since the deformation and rigidity of paper vary greatly depending on the type and storage state, the skew correction condition may not be optimal even with the reverse rotation specification of the registration roller 4 set in advance under the above conditions. Therefore, in the present invention, a function is provided that makes it possible to individually set the reverse rotation angle by disabling input information from an operation panel of an image forming system (not shown) so that it can be changed to an optimum value.

  FIG. 2 is a top view showing the state of the sheet 3 that has been skew-corrected by the registration rollers 4. The dotted line shows the state before skew correction, and the solid line shows the state after skew correction.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a top view of a sheet whose skew has been corrected by a registration roller.

Explanation of symbols

1 is a photosensitive drum, 2 is toner, 3 is paper, 4 is a registration roller, 5 is a timing roller, and 6 is a transfer belt.

Claims (3)

A transfer material is pressed against a toner image carrier via a printing paper, and a charge having a polarity opposite to that of the toner is applied to the back surface of the transfer material by a transfer device so that the transfer material is sucked and conveyed, and the toner image carrier A registration roller that can rotate forward and backward is installed upstream of a transfer device that transfers and conveys a toner image formed on the body, and the printing paper is brought into contact with the registration roller to perform skew correction and conveyance of the printing paper. In the paper transport device,
Memory device for storing paper information of paper size, thickness, and paper type input to the image forming apparatus and printing mode information for single-sided printing or double-sided printing, and paper information and printing mode stored in the memory device And a drive control device for controlling the reverse rotation operation of the registration roller based on the information, and adjusting the reverse rotation amount of the registration roller by the drive control device.   2. The paper conveyance device according to claim 1, further comprising an input device capable of invalidating the data of the paper information and the print mode information, and configured to manually set the drive control value of the registration roller from the input device. A sheet conveying apparatus characterized by having A cassette for storing printing paper, a registration device for transferring a toner image on the toner image carrier to a predetermined position on the printing paper, and a toner image on the printing paper carried out of the cassette. An image forming apparatus comprising a developing / transferring device to be formed and a fixing device for fixing a toner image transferred onto the printing paper, wherein the paper conveying device according to claim 1 or 2 is used as the registration device. An image forming apparatus.

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