JP2005035766A - Paper carrying device for electrophotographic printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer equipped with a paper carrying device correcting skewing of a paper edge with a register roller, and correcting the skewing of the entire paper sheet at start of carriage by the register roller to carry the paper sheet. <P>SOLUTION: In the paper carrying device for the electrophotographic printer carrying the paper sheet to a printing part, the paper sheet is fed to the register roller by a timing roller in the rear of the register roller feeding the paper sheet to the printing part without rotating the register roller, the edge part of the paper sheet is fitted along a contact point part of the register roller to correct the skewing of the paper sheet, and immediately after the carriage of the paper sheet to the printing part by the register roller and the timing roller, gripping force of the timing roller is released to correct the skewing of the entire paper sheet and the paper sheet is carried to the printing part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transport device for a printing apparatus using an electrophotographic system.

  A configuration example of a conventional printing apparatus is shown in FIG. First, the printing operation of the printing apparatus 1 in the prior art will be described. The printing paper 2 is conveyed from the paper feeding device 3 to the photosensitive member 5 through the paper conveying device 4. On the other hand, the toner 6 developed on the photoreceptor 5 by the electrophotographic system is transferred to the paper 2 by the transfer device 7. Next, the toner 6 transferred onto the paper 2 is conveyed to a fixing device 8 and fixed on the paper 2 by heat and pressure. In the case of single-sided printing, the sheet 2 on which the toner 6 is fixed is reversed by the reversing device 9 and conveyed to the discharging unit 10 or directly conveyed to the discharging unit 10 without passing through the reversing device 9 and discharged. In the case of double-sided printing, the paper 2 on which the toner 6 is fixed is reversed by the reversing device 9 and conveyed to the paper conveying device 4 by the back surface conveying device 11 to perform the same printing as in the case of single-sided printing.

  When printing the paper 2 in the printing apparatus 1, the paper 2 is transported onto the photoconductor 5 by the paper transport device 4. As shown in FIG. 2, the sheet conveying device 4 includes a registration roller 12 that conveys the sheet 2 onto the photosensitive member 5, a timing roller 13 that conveys the sheet 2 to the registration roller 12, and a sheet conveyance path 14. The sheet 2 conveyed to the sheet conveying device 4 is conveyed to the registration roller 12 stopped by the timing roller 13 as shown in FIG. At that time, the sheet 2 may be conveyed while being skewed as shown in FIG. The correction of the skew of the paper at this time will be described with reference to FIGS.

  As shown in FIG. 4, the leading end portion of the sheet 2 that is skewed and fed to the registration roller 12 is abutted against the contact point of the registration roller 12 that is stopped as shown in FIGS. The slack 15 is generated on the sheet 2, and the skew of the sheet 2 is corrected by the leading edge of the sheet 2 being along the linear contact point of the registration roller 12. Next, the corrected sheet is conveyed by the registration roller 12 in the state shown in FIG. Here, the moment force 16 generated by the slack 15 is applied to the sheet 2. At this time, the registration roller 12 has started conveyance, and the leading edge of the sheet has passed the contact point of the pair of registration rollers. Therefore, when the strain (rigidity) of the sheet to be printed is strong and the moment force 16 is large, Even if the paper tip slips and the skew of the paper once corrects the skew, it returns to its original state due to the moment force generated by the paper stiffness as shown in FIG. The sheet is sent onto the photosensitive member.

  In addition, there is another device that newly attaches another device for reducing or eliminating the conveyance load of the grip roller. However, it is necessary to secure the space of the device and increase the cost (for example, see Patent Document 1).

  In some cases, the registration rollers are rotated in the reverse direction and the skew is corrected to carry the sheet. However, the timing roller pair behind the registration roller grips, so that the sheet re-tilt as described above is performed. A line is generated and conveyed (for example, see Patent Document 2).

JP-A-5-278904

JP 2003-72982 A

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art and to provide a printing apparatus including a transport device that performs skew correction of the entire paper.

  The purpose is to feed the paper to the registration roller without rotating the registration roller by the timing roller behind the registration roller that feeds the paper to the printing unit, and to place the leading edge of the paper along the contact portion of the registration roller. Immediately after correcting the skew of the sheet and transporting the sheet to the printing unit by the registration roller and the timing roller, the gripping force of the timing roller is released to correct the skew of the entire sheet, and the sheet is conveyed to the printing unit. Is achieved.

  According to the present invention, it is possible to correct the skew of the entire sheet without causing the phenomenon that the skew of the sheet corrected by the paper scraping occurs again.

  In addition, by attaching a cam and a one-way clutch to a conventional timing roller and releasing the gripping force when it is reversed, it is not necessary to newly install a device for releasing the gripping force of the timing roller, and the installation space and cost can be reduced.

  Furthermore, when the amount of sag is the same between thick paper and thin paper, the moment force due to the paper scraping is large when the paper is thick, and the moment force is small when the paper is thin. Since the skew correction of paper has an optimal moment force, when the paper is thick, the moment optimal for skew correction of the paper is improved by increasing the timing of releasing the gripping force of the timing roller compared to when the paper is thin. The power can be the same. In this way, by changing the timing of releasing the grip force depending on the type of paper, it is possible to correct the skew of the entire paper.

  Embodiments of the present invention will be described below with reference to FIGS. 1 and 8 to 12.

  The conveyance device 4 includes a registration roller 12 that conveys the sheet 2 onto the photosensitive member 5 and a timing roller 13 that conveys the sheet to the registration roller 12. The timing roller 13 includes a cam 17 and a one-way clutch at both ends as shown in FIG. I have 18. The timing roller 13 has a gripping force in the normal rotation state, but when the reverse rotation occurs, the one-way clutch 18 is locked, and the pressing side of the timing roller 13 is lifted by the cam 17 as shown in FIG. It has become.

The skew correction of the leading edge of the paper 2 shown in FIG. 6 is the same as that described in the prior art, and therefore the present invention will be described after the process of correcting the skew at the leading edge of the paper 2.
In FIG. 10, the skew of the front end of the paper 2 is corrected, and immediately after the paper is transported onto the photoconductor 5 by the registration roller and the front end of the paper is fed, the timing roller is reversed to release the gripping force as shown in FIG. Then, the slack 15 generated in the sheet 2 is eliminated as shown in FIG. 12, and the skew of the entire sheet 2 is corrected.

  In addition, the timing roller drive control unit 19 (not shown) automatically recognizes the thickness and size of the sheet, and can switch the forward, stop, and reverse timings of the registration roller 12 and the timing roller 13.

1 is a configuration diagram of an electrophotographic printing apparatus. The front view of a paper conveyance part. The front view of a paper conveyance part. FIG. 4 is a top view of a sheet that is sent obliquely. FIG. 6 is a top view in which skew feeding is corrected and conveyance is started by a registration roller. FIG. 6 is a front view in which skew correction is performed at the front end of the paper. The top view in which the skew of the sheet occurs again due to slipping of the sheet and the registration roller due to the strain of the sheet even though the skew is corrected. The perspective view of the timing roller based on the Example of this invention. The front view in which the pressing side of the timing roller is lifted to release the gripping force. FIG. 4 is a top view in which skew feeding at the front end of the sheet is corrected in the transport device according to the embodiment of the present invention. FIG. 6 is a front view in which skew feeding at the front end of the sheet is corrected in the transport device according to the embodiment of the present invention. The front view which correct | amends skew of the whole paper in the conveying apparatus based on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Printing apparatus, 2 ... Printing paper, 3 ... Paper feeding apparatus, 4 ... Paper conveyance part, 5 ... Photoconductor, 6 ... Toner, 7 ... Printing part transfer apparatus, 8 ... Printing part fixing machine, 9 ... Paper inversion Apparatus 10... Printing paper discharge unit 11. Backside printing paper transport unit 12. Registration roller 13. Timing roller 14. Paper transport pass 15. Deflection 16. Moment force generated by deflection 17 Cam , 18 ... one-way clutch, 19 ... timing roller drive control unit.

Claims (3)

  In a paper conveyance device of an electrophotographic printing apparatus that conveys paper to a printing unit, the paper is fed to the registration roller without rotating the registration roller by a timing roller behind the registration roller that sends the paper to the printing unit, and the registration roller Immediately after feeding the paper to the printing unit with the registration roller and the timing roller, correct the skew of the paper by aligning the leading edge of the paper with the contact part of the roller. A sheet conveying apparatus for an electrophotographic printing apparatus, wherein the sheet is conveyed to a printing unit.   The timing roller having a grip force relatively lower than that of the registration roller is provided with a mechanism that releases the grip force of the timing roller when rotated in reverse and returns the grip force of the complete timing roller when rotated forward. A sheet conveying apparatus of an electrophotographic printing apparatus, wherein when the image is corrected, the entire timing roller is reversely rotated to cancel the gripping force so that the skew of the entire sheet is corrected and conveyed to the printing unit. An electrophotographic printing apparatus characterized in that the amount of sag produced on a sheet is changed by changing the timing of forward and reverse rotation of the timing roller according to the thickness and size of the sheet, and the skew of the entire sheet is corrected. Paper transport device.

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