JP2009048057A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a guide member, which can be rocked and fixed, between two conveying means for keeping the entering position/angle of the front end of advancing paper to the conveying means on the downstream side constant and for reducing fluctuation in conveying tension of conveyed paper. <P>SOLUTION: The image forming apparatus comprises a first conveying means and a second conveying means for conveying paper by opposed rotating members, and a guide member, which is brought into contact with the surface of the advancing paper to be oscillated, for guiding the front end of the paper fed from the first conveying means to a predetermined sheet entering position in the second conveying means. The image forming apparatus also has a fixing means stopping oscillation of the guide member to fix it in a predetermined position, a paper detection sensor arranged on the downstream of the guide member, and a control means controlling the fixing means based on a detection signal sent from the paper detection sensor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a conveying unit that conveys a sheet by a roller or a belt.

  Image forming apparatuses such as copiers, printers, facsimiles, and the like based on electrophotography are apparatuses that are widely used.

  In these image forming apparatuses, a sheet fed from a sheet feeding device is conveyed by a conveying path set by a plurality of conveying means and a guide member made up of rotating members arranged opposite to each other, for example, rotating rollers or belts. And a predetermined process is performed during the process.

  The transport path is provided with a plurality of transport means at a predetermined interval. The leading edge of the paper entering the transport means has a fixed entrance position or entrance angle by a guide member located upstream of the transport means. Guided to be.

  Thus, in a conveyance path in which a plurality of conveyance units exist, the state where the rear end portion of the sheet nipped by a certain conveyance unit is also nipped by the conveyance unit upstream of the conveyance unit, that is, A state in which the sheet is nipped and conveyed by a plurality of conveying units is created.

  However, the conveying speed of all the conveying means is not always maintained constant depending on the processing performed on the sheet, the size, thickness, and type of the sheet.

  In particular, the conveyance speed of a fixing device that is a conveyance unit that conveys a sheet while fixing and fixing a toner image on the sheet by pressurizing and heating the nipped sheet, and the conveyance speed of a delivery roller that is a conveyance unit upstream thereof are: Differences occur due to changes in conditions as described above.

  As a result, the paper between the two conveying means is loosened or pulled.

  Proposal to provide a guide member that swings in contact with the surface of the paper between the two conveying means in order to regulate the slack generated in this way and to keep the tension applied to the paper between the two conveying means constant. (For example, refer to Patent Document 1).

  However, such a guide member that swings following the slack of the paper between the two conveying means can be used although the tension applied to the paper between the two conveying means can be made constant. Since there are various types of paper and their rigidity is different, it is difficult to make the entrance position and the entrance angle of the paper entering the downstream transport means constant.

  Furthermore, when the conveyance speed of the conveyance means located downstream becomes larger than the conveyance speed of the conveyance means located upstream, the paper is pulled by the downstream conveyance means. It is not a solution.

  As a technique for making the paper entrance position and the entrance angle to the downstream transport means constant, a proposal is known in which the position of the guide member is changed according to conditions relating to the paper (see, for example, Patent Document 2).

However, with this proposal, although the approach position and the approach angle can be made constant, it is not possible to suppress the occurrence of slack or pulling of the paper between the two transporting means.
JP 61-45251 JP-A-9-197735

  The present invention has been made in view of the situation as described above, and an object of the present invention is to provide a guide member that can be swung and fixed between two transporting means so that the leading edge of the paper that advances is downstream. An object of the present invention is to realize an image forming apparatus that makes the position and angle of entering the conveying means constant, and that suppresses fluctuations in the conveying tension of the conveyed paper.

The above-mentioned subject is achieved by realizing the following invention.
1. A first conveying means and a second conveying means for conveying a sheet by a member that rotates oppositely; and
An image forming apparatus comprising: a guide member that guides a leading edge of the sheet fed from the first conveying unit to a predetermined sheet entering position of the second conveying unit;
A guide member that swings in contact with the surface of the traveling paper;
A fixing means for stopping swinging of the guide member and fixing the guide member at a preset position;
A paper detection sensor provided downstream of the guide member;
An image forming apparatus comprising: a control unit that controls the fixing unit based on a detection signal sent from the paper detection sensor.
2. The control means includes
Until the conveyance of the paper is started by the second conveyance means, the guide member is fixed at a preset position, and when the conveyance of the paper is started by the second conveyance means, the guide The image forming apparatus according to claim 1, wherein the fixing unit is controlled to release the fixing of the member.
3. A rotation amount detecting means for detecting a rotation amount from a reference position of the guide member;
The control means includes
3. The image forming apparatus according to claim 1, wherein a transport speed of the first transport unit or the second transport unit is changed based on a detection signal of the rotation amount detection unit.
4). The image forming apparatus according to any one of claims 1 to 3, wherein the fixing unit fixes the guide member at a preset position within a swingable range of the guide member.

  According to the present invention, the conveyance of the paper in the image forming apparatus is stabilized, and the conveyance failure of the paper and the accompanying image defect are prevented from occurring.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram of the image forming apparatus G.

  The image forming apparatus G has an automatic document feeder F at the top of the main body. The main body includes a reading unit 1, a writing unit 2, an image forming unit 3, an operation display unit 4, a paper feeding unit 5, and a paper discharge refeed. The paper unit 6, the fixing device 7, the control unit C, and the like are included.

  The automatic document feeder F feeds the documents placed on the document table 11 to the document conveying means 13 one by one by the document separating means 12, and the document conveying means 13 conveys the sent documents to the document discharging means 14. Then, the document discharge means 14 discharges the sent document to the document discharge table 15.

  The document image is read by a slit 21 provided in the document conveyance path, which is a document image reading position of the reading unit 1.

  When reading images on both sides of the document, the document which has been read on the first surface is reversed by the document reversing means 16 having a pair of rollers, and is sent again to the document conveying means 13 to re-feed the second surface. Reading is done.

  The reading unit 1 is a unit for reading an original image and obtaining image data. The original image irradiated with light by the lamp 231 at the position of the slit 21 is a first mirror unit 23, a second mirror unit 24, and the like. The image forming lens 25 forms an image on the image sensor 26 which is a linear CCD.

  The signal output from the image sensor 26 is A / D converted by the image processing unit of the control means C, subjected to processing such as shading correction and image compression, and is stored in the memory M as image data.

  The writing means 2 is based on the image data that has been called from the memory M and subjected to predetermined image processing. The writing means 2 is charged by the charging means 32 with the laser beam and the polygon mirror and is rotated by the charging means 32. The surface is scanned to form an electrostatic latent image corresponding to the original image on the surface of the photoreceptor 31.

  The electrostatic latent image is reversely developed by the developing unit 34 of the image forming unit 3 to form a toner image on the photoreceptor 31.

  Corresponding to the timing of toner image formation, the paper P is fed from the manual paper feeding means 55 or the paper feeding means 5 having a cassette or tray for accommodating the paper P as a transfer material.

  The fed paper P is transported by the transport roller 56, and is synchronized with the toner image formed on the photosensitive member by the timing roller 39 and sent out to the transfer region.

  In the transfer area, the toner image formed on the surface of the photoreceptor 31 is transferred to the paper P charged to the opposite polarity by the action of the transfer means 35.

  The paper P carrying the toner image is separated from the surface of the photoreceptor 31 by the action of the separating means 36 and sent to the fixing device 7.

  In the fixing device 7, the paper P carrying a toner image is conveyed while being heated and pressurized by a heating roller 71 and a pressure roller 72 arranged to face each other, and the toner image is fixed on the paper P and discharged. It is sent out of the apparatus by a roller 63.

  When the paper P is turned upside down and sent out, the switching guide 62 guides the paper P to the paper discharge / refeed means 6 and switches the paper P back to the discharge roller 63.

  Further, when forming an image on both sides of the paper P, the paper P that has been fixed on the first side is guided to the paper discharge refeed means 6 by the switching guide 62 and reversed by the reversing unit 65. Then, the sheet is fed to a conveyance path 66 for paper feeding and used for image formation on the second surface.

  On the other hand, the surface of the photoconductor 31 after the transfer of the toner image onto the paper P is prepared for the next image formation after the residual toner is removed by the cleaning means 37.

  FIG. 2 is a block diagram illustrating a control relationship of the image forming apparatus G.

  The control means C is a computer system including a CPU, a memory M, an arithmetic unit, an I / O port, a communication interface, etc. (not shown), and also has a circuit for driving each means. Yes.

  Each unit is controlled by executing a program corresponding to the job stored in the memory M.

  The control means C is connected to a LAN or a public line via the communication means T1, and can exchange data with other information devices.

  In addition, about the block which is not directly related to description of embodiment of this invention, description in a figure is abbreviate | omitted.

  FIG. 3 is a view for explaining the guide member 80 and its periphery.

  The sheet P is sent out toward the photoreceptor 31 as indicated by an arrow a by a registration roller 39 which is a first transport unit.

  The toner image formed on the photoconductor 31 is transferred to the paper P sent out by the action of the transfer means 35, and the paper P carrying the toner image is separated from the surface of the photoconductor 31 by the action of the separating means 36. .

  The leading edge of the sheet P separated from the surface of the photosensitive member 31 advances along the belt 301 of the belt conveyance unit 300 and is guided to the guide member 80 to determine the heating roller 71 or the pressure roller 72 of the fixing device 7 in advance. Hit the position.

  The leading end portion of the paper P that hits the rotating heating roller 71 or the pressure roller 72 proceeds to a nip portion formed by the heating roller 71 and the pressure roller 72 and is sandwiched between these two rollers.

  The toner image on the paper is fixed to the paper P by the pressure heating to the paper P by the heating roller 71 and the pressure roller 72, and the paper P after the image fixing proceeds in the direction of arrow b.

  The heating roller 71 and the pressure roller 72 described above serve as a second conveying unit because they fix the image while conveying the paper P.

  The guide member 80 is a member that can swing around a shaft 81 as shown by a dotted line in the figure, and swings while contacting the lower surface of the paper P.

  A paper detection sensor S for detecting the paper P is provided downstream of the guide member 80, and the detection signal is sent to the control means C.

  FIG. 4 is a view for explaining the guide member 80 and the fixing means 90.

  A spring attachment member 82, a protrusion member 83, and a rotary encoder E are attached to the guide member 80.

  The springs B1 and B2 are attached to the end of the spring attachment member 82, and the guide member 80 swings and rotates within a preset maximum rotation angle (w) about the fulcrum 81 by the contact of the paper P. To do.

  The amount of rotation of the guide member 80 from the reference position is detected by a rotary encoder E which is a rotation amount detection means, and the detection information is sent to the control means C.

  The fixing means 90 is composed of a fixed guide member 91 facing the protruding portion of the guide member, and a mechanism for moving the fixed guide member 91 in the arrow x and y directions in the figure. Note that the specific technical configuration is appropriately determined at the time of design.

  As shown in the drawing, the fixed guide member 91 is rotated in the direction of the arrow y around the rotation shaft 81, stopped at a preset position, and then moved in the x direction toward the rotation shaft.

  Due to the movement of the fixed guide member 91 described above, the protruding member 83 fixed to the guide member 80 rotates and stops so as to be fitted to the fixed guide member 91. As a result, the guide member 80 is fixed at the fitting position indicated by z in the drawing, and the swinging stops.

  That is, by controlling the fixing means 90, the guide member 80 can be fixed at an arbitrary position within the range of the maximum rotation angle w, and the swinging can be stopped.

  By controlling the operation of the guide member 80 and the fixing means 90 as described above, the guide member 80 is fixed at a predetermined position within the swingable range in accordance with the progress of the paper P, or by contact with the paper P. It is possible to perform control such as swinging.

  FIG. 5 is a flowchart showing the flow of such a fixed control 100.

  Until the image formation on the paper P is performed, the guide member 80 is fixed by a fixing unit 90 at a preset position within the swingable range.

  The leading end portion of the paper P carrying the toner image is guided to a fixed guide member 80, and is sandwiched between a heating roller 71 and a pressure roller 72, which are rollers of a second transport unit.

  The fixing position of the guide member 80 is determined so that the leading end portion of the sheet P enters a predetermined position of the roller of the second conveying unit at a predetermined angle, and is determined by an experiment. Is.

  A paper detection sensor S is provided downstream of the guide member 80, the leading edge of the paper P traveling is detected, and a detection signal is sent to the control means C (step S1: Y).

  The control means C executes a timing determination process 101 that is a program based on the detection signal (step S2).

  The timing determination process is to calculate the time when the leading edge of the paper P is detected by the paper detection sensor S, the leading edge of the paper P is sandwiched by the second conveying means, and the conveyance is started. A conveyance start flag is set at the calculated timing.

  When the conveyance start flag is set (step S3: Y), the control unit C cancels the fixing operation of the fixing unit 90 by executing the fixing operation release process 102, and the guide member 80 is allowed to swing. (Step S4).

  That is, a constant conveyance tension is applied to the sheet P conveyed by the first conveyance unit and the second conveyance unit by the swinging guide member 80.

  When the trailing edge of the paper P is detected by the paper detection sensor S and a detection signal is sent to the control means C (step S5: Y), the control means C fixes the guide member 80 at a preset position. The fixing operation execution process 103 of the fixing means 90 is executed (step S6), and the routine is exited.

  When the paper P is transported by both the first transport means and the second transport means, and the paper P between them is slack, the slack is absorbed by the swinging guide member, and the first P Although the transport tension of the paper P between the transport unit and the second transport unit is maintained almost constant, the transport tension may increase without causing slack.

  Such an increase in the transport tension causes the fixing device as the second transport means to pull the paper P in the middle of the transfer of the toner image from the photoconductor. It can also lead to a decline.

  Note that, as examples of image quality deterioration, there are known variations in the aspect ratio of the image, poor transfer at the trailing edge of the paper P, and the like.

  Therefore, in order to prevent an excessive increase in the transport tension, the transport speed of the second transport means on the downstream side of the transport path is decreased or the transport speed of the first transport means on the upstream is increased. It is necessary to suppress an increase in tension.

  FIG. 6 is a flowchart showing the flow of the conveyance speed control 200 of the conveyance means.

  The conveyance speed control 200 is a control executed when the guide member 80 is in a swingable state.

  Detection information L of the rotary encoder E that detects the amount of rotation from the reference position of the guide member 80 that is swinging in contact with the surface of the paper P is taken into the control means at a predetermined cycle (step S11).

  If the value of the read detection information L exceeds the preset upper limit LU (step S12: Y), it is determined that the slack of the paper P is greater than or equal to the preset amount, and the second The drive unit of the transport unit is controlled to increase the transport speed of the transport unit or to decrease the transport speed of the first transport unit (step S13).

  Further, when the value of the read detection information L is equal to or less than the preset upper limit LU (step S12: N) and is equal to or greater than the preset lower limit LL (step S14: N), It is determined that the slack of the paper P is within a preset range, and the processing routine is exited.

  On the other hand, if it is equal to or smaller than the preset lower limit value LL (step S14: Y), it is determined that the slackness of the paper P is smaller than the preset range, and the second conveying means The drive unit of the transport unit is controlled to decrease the transport speed or increase the transport speed of the first transport unit (step S15).

  Thus, by controlling the conveyance speed of the first conveyance unit or the second conveyance unit based on the swing position of the guide member, the amount of looseness of the paper P between the two conveyance units is large. Can always be within a certain range.

  As described above, the control for permitting and prohibiting the swinging motion of the guide member capable of swinging allows the leading end of the sheet to always enter the desired position of the second transport unit from the desired angle, The transport tension of the paper P between the first transport unit and the second transport unit can be kept constant.

  Further, by changing the transport speed of the first transport unit or the second transport unit based on the position information of the guide member, the slackness of the paper P being transported can be kept within a certain range. The increase in the conveyance tension of the paper can be kept within a certain range.

  As a result, it is possible to prevent a change in the aspect ratio of the image due to an excessive increase in the conveyance tension, and a decrease in image quality caused by abrupt separation of the trailing edge of the paper P from the photoreceptor 31.

  In the present invention, the case where the first transport unit is a registration roller and the second transport unit is a fixing roller has been described as an example. However, other transport paths of the image forming apparatus, for example, paper discharge re-feeding The paper means 6 can also be applied.

1 is a conceptual diagram of an image forming apparatus. 2 is a block diagram illustrating a control relationship of the image forming apparatus. FIG. It is a figure explaining a guide member and its periphery. It is a figure explaining a guide member and a fixing means. It is a flowchart which shows the flow of fixed control. It is a flowchart which shows the flow of conveyance speed control.

Explanation of symbols

7 Fixing device 80 Guide member 90 Fixing means 91 Fixed guide member C Control means E Rotary encoder (rotation amount detection means)
G Image forming device S Paper detection sensor

Claims (4)

A first conveying means and a second conveying means for conveying a sheet by means of opposing rotating members;
An image forming apparatus comprising: a guide member that guides a leading edge of the sheet fed from the first conveying unit to a predetermined sheet entering position of the second conveying unit;
A guide member that swings in contact with the surface of the traveling paper;
A fixing means for stopping swinging of the guide member and fixing the guide member at a preset position;
A paper detection sensor provided downstream of the guide member;
An image forming apparatus comprising: a control unit that controls the fixing unit based on a detection signal sent from the paper detection sensor. The control means includes
Until the conveyance of the paper is started by the second conveyance means, the guide member is fixed at a preset position, and when the conveyance of the paper is started by the second conveyance means, the guide The image forming apparatus according to claim 1, wherein the fixing unit is controlled to release the fixing of the member. A rotation amount detecting means for detecting a rotation amount from a reference position of the guide member;
The control means includes
3. The image forming apparatus according to claim 1, wherein a transport speed of the first transport unit or the second transport unit is changed based on a detection signal of the rotation amount detection unit. The image forming apparatus according to claim 1, wherein the fixing unit fixes the guide member at a preset position within a swingable range of the guide member.

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