JP2010168141A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device that enhances productivity and prevents the occurrence of wrinkles in a paper sheet. <P>SOLUTION: A first fixing device 17A and a second fixing device 17B are disposed downstream of an image forming part 60. A registration roller 32 is disposed therebetween. An assist roller 33 is disposed upstream of the registration roller 32. Even if a bend occurs in a sheet of paper P in the first fixing device 17A, the bend is corrected on the registration roller 32, thereby suppressing the occurrence of wrinkles in the second fixing device 17B. This shortens the fixing processing time in the first fixing device 17A, enabling good image formation quality. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile including two fixing units.

  As a conventional image forming apparatus, two image forming units are arranged along the paper conveyance path so that a toner image can be transferred to each surface of the paper conveyed through the paper conveyance path. One having a fixing unit on the downstream side is known (see, for example, Patent Document 1).

  In general, when forming an image on a thick sheet, it is known that if the fixing time is short, the toner fixing property is deteriorated. In order to form an image on a thick sheet using the conventional image forming apparatus having the above configuration, it is necessary to set a long time for the sheet to pass through the fixing unit in order to improve the fixing property of the toner on the sheet surface. It becomes. In addition, in order to improve the toner fixability, after fixing on one or both sides, a method such as increasing the number of times of fixing by passing the fixing unit without forming an image in the image forming unit in the state of being back again is performed. It has been broken.

JP 2001-1000047 A

  However, in the conventional image forming apparatus, the fixing time of the toner can be improved by increasing the fixing time in one fixing unit or increasing the number of times of passing through the fixing unit arranged on the downstream side of each image forming unit. Since improvement was aimed at, there was a problem that productivity fell.

  Therefore, in order to solve the above problem, it is conceivable to continuously perform the fixing process in the second fixing unit after passing through the first fixing unit. However, in this case, there is a problem that the sheet is bent at the second fixing unit due to the bending of the sheet during the passage of the first fixing unit or until the second fixing unit is entered after the passage. The reason is that in the fixing process, deformation such as bending is likely to occur under the influence of heat and pressure, and the sheet is easily bent and conveyed in the subsequent conveyance process. Therefore, the sheet is bent when it passes through the first fixing unit or before it enters the second fixing unit, and the sheet that has bent and entered the second fixing unit is likely to be wrinkled.

  The present invention has been made by paying attention to such problems, and an object of the present invention is to provide an image forming apparatus capable of improving productivity and suppressing wrinkles on paper. It is in.

  Another object of the present invention is to provide an image forming apparatus that can efficiently form an image on a thick sheet.

  The present invention is characterized in that a paper conveyance path from a paper feeding section to a paper discharge section, an image forming section that forms a toner image on paper conveyed through the paper conveyance path, and the most downstream of the image forming sections. The first fixing unit and the second fixing unit disposed along the sheet conveyance path on the downstream side of the image forming unit to be corrected, and the skew correction of the sheet disposed between the first fixing unit and the second fixing unit is performed. And a correction mechanism.

  Here, it is preferable that the correction mechanism corrects the skew of the sheet in a state where the rear end of the sheet has passed through the first fixing unit.

In the present invention, it is preferable to include an assist roller that bends the paper in a loop shape downstream of the first fixing unit and upstream of the correction mechanism.
Furthermore, in the present invention, a registration roller can be used as the correction mechanism.

  According to the present invention, it is possible to realize an image forming apparatus capable of improving productivity and suppressing generation of wrinkles on a sheet. Further, according to the present invention, it is possible to efficiently form an image on a thick sheet.

1 is an overall configuration diagram of a color copying machine according to a first embodiment of the present invention. It is explanatory drawing of the copying machine which concerns on the 2nd Embodiment of this invention.

  Hereinafter, details of the image forming apparatus according to each embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is an overall configuration diagram showing an outline of a color copying machine 100 as an image forming apparatus according to a first embodiment of the present invention. The outline of the internal configuration of the color copying machine 100 according to the first embodiment will be described below with reference to FIG. The color copying machine 100 according to the present embodiment is called a tandem type color image forming apparatus.

  The color copying machine 100 reads the color image formed on the original 30 to acquire image information, forms an image of each color on the photosensitive drum based on this image information, and then superimposes the colors on the paper. Is a device for forming Here, an image formed on a sheet output from the color copying machine 100 is referred to as an “output image”. The image forming apparatus according to the present invention is not limited to the color copying machine 100 as in the present embodiment and the monochrome copying machine as in the second embodiment to be described later. The present invention may be applied to a facsimile machine, a multifunction machine of these, and the like.

  In the color copying machine 100, an image input unit 11 and an ADF 40 (automatic document feeder) are disposed on the upper portion of the first main body 101. The ADF 40 operates to automatically feed one or a plurality of originals 30 in the automatic paper feed mode (ADF mode). Here, the ADF mode refers to an operation of automatically feeding a document 30 placed on the ADF 40 and automatically reading a document image.

  The ADF 40 includes a document placement portion 41, a roller 42 a, a roller 42 b, a roller 43, a conveyance roller 44, and a paper discharge tray 46. One or a plurality of originals 30 are placed on the original placing portion 41. A roller 42 a and a roller 42 b are provided on the downstream side of the document placing portion 41. When the ADF mode is selected, the document 30 fed out from the document placing portion 41 is conveyed by the downstream roller 43 so as to rotate in a U-shape. When the ADF mode is selected, the recording surface of the document 30 is placed upward by the document placement unit 41.

  Further, the image input unit 11 operates to read a color image formed on the document 30. For the image input unit 11, for example, a slit scanning scanner for color is used. The image input unit 11 includes an image sensor 58 arranged in an array. For example, when the document 30 is reversed in a U-shape by the roller 43 in the ADF mode, the image reading is performed by reading the surface of the document 30. The signal Sout is output.

For the image sensor 58, for example, a 3-line color CCD (Charge Coupled Device) imaging device is used. The image sensor 58 includes three reading sensors for detecting red (R), green (G), and blue (B) light, which are configured by arranging a plurality of light receiving element arrays in the main scanning direction. The reading sensor divides pixels at different positions in the sub-scanning direction orthogonal to the main scanning direction, and simultaneously reads R, G, and B color light information.

  The document 30 read by the image input unit 11 is conveyed by the conveyance roller 44 and discharged to the discharge tray 46. The image sensor 58 outputs an RGB color-based image reading signal obtained by reading the document 30 in the platen mode. Here, the platen mode refers to an operation of automatically reading an original image by scanning an optical drive system on the original 30 placed on the platen glass.

  In addition to the image sensor 58, the image input unit 11 includes a first platen glass 51, a second platen glass 52 (ADF glass), a light source 53, mirrors 54, 55, and 56, an imaging optical unit 57, and an unillustrated portion. It has an optical drive unit. This optical drive unit operates to move the document 30 or the image sensor 58 relatively in the sub-scanning direction. The sub-scanning direction is a direction orthogonal to the main scanning direction when the arrangement direction of the plurality of light receiving elements constituting the image sensor 58 is the main scanning direction. The mirrors 54 to 56 are arranged so as to return the light reflected by the document 30, and the imaging optical unit 57 forms an image on the image sensor 58 with the returned light. As described above, the document 30 placed on the document placing portion 41 of the ADF 40 is transported by the rollers 42 a, 42 b, 43 and the transport roller 44 described above, and the optical system (light source 53, mirrors 54, 55 of the image input unit 11). , 56, including the imaging optical unit 57 and the optical driving unit), an image on one or both sides of the document 30 is scanned and exposed, and reflected light reflecting image information of the document 30 is read by the image sensor 58.

  The image sensor 58 performs photoelectric conversion according to the amount of incident light. The photoelectrically converted analog image reading signal is A / D converted in the image input unit 11, and a digital image reading signal Sout is output from the image input unit 11. An image processing unit 31 is connected to the image input unit 11 via the control unit 15, and the digital image reading signal Sout is subjected to image compression processing, scaling processing, and the like in the image processing unit 31, and R color, G color, It becomes digital image data of the B color component. Further, the image processing unit 31 converts the image data into Y, M, C, and BK color image data Dy, Dm, Dc, and Dk using the three-dimensional color information conversion table, and the image data after the color conversion. Dy, Dm, Dc, and Dk are transferred to the writing units 3Y, 3M, 3C, and 3K constituting the image forming unit 60.

  The image forming unit 60 forms a color image based on the image data Dy, Dm, Dc, Dk obtained by reading by the image input unit 11. The image forming unit 60 includes a plurality of image forming units 10Y, 10M, 10C, and 10K each having a photosensitive drum for each of Y, M, C, and BK, and an endless intermediate transfer body 6. . The color copying machine 100 has one image forming unit 60, and the image forming unit 60 is the most downstream image forming unit. Further, on the downstream side of the image forming unit 60, a first fixing device 17A is provided as a first fixing unit for fixing the toner image transferred from the intermediate transfer body 6 to the sheet.

  The image forming unit 10Y that forms a yellow (Y) image includes a photosensitive drum 1Y as an image forming body that forms a Y-color toner image, and a Y-color charging disposed around the photosensitive drum 1Y. It includes a section 2Y, a writing unit 3Y, a developing section 4Y, and an image forming body cleaning section 8Y. An image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image forming body that forms an M color toner image, a charging unit 2M for M color, a writing unit 3M, and a developing unit. 4M and an image forming body cleaning unit 8M. An image forming unit 10C that forms a cyan (C) color image includes a photosensitive drum 1C as an image forming body that forms a C color toner image, a charging unit 2C for C color, a writing unit 3C, and a developing unit. 4C and an image forming body cleaning portion 8C. An image forming unit 10K that forms a black (BK) image includes a photosensitive drum 1K as an image forming body that forms a BK color toner image, a charging unit 2K, a writing unit 3K, and a developing unit for BK color. 4K and an image forming body cleaning section 8K.

  The charging unit 2Y and the writing unit 3Y, the charging unit 2M and the writing unit 3M, the charging unit 2C and the writing unit 3C, and the charging unit 2K and the writing unit 3K are based on the image data Dy, Dm, Dc, and Dk. An electrostatic latent image is formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K. The writing units 3Y, 3M, 3C, and 3K are solid scanning type writing units in which a plurality of light modulation elements are arranged on a line in a main scanning direction orthogonal to a conveyance direction (sub-scanning direction) of a sheet on which an image is to be formed. In this example, an LED array head optical system using an LED element as a light modulation element is used.

  The developing units 4Y, 4M, 4C, and 4K develop the electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1K to form Y, M, C, and BK toner images. Development by the developing units 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (for example, negative polarity) as the toner polarity to be used is applied.

  The intermediate transfer body 6 is rotatably supported by a plurality of rollers. The primary transfer rollers 7Y, 7M, 7C, and 7K are installed at positions facing the photosensitive drums 1Y, 1M, 1C, and 1K with the intermediate transfer body 6 interposed therebetween. By applying a primary transfer bias (not shown) having a polarity (for example, positive polarity) opposite to that of the toner to be used to the primary transfer rollers 7Y, 7M, 7C, and 7K, the respective photosensitive drums 1Y, 1M, 1C, The Y, M, C, and BK toner images formed in 1K are sequentially transferred onto the rotating intermediate transfer member 6. In this way, a color toner image in which the toner images of the respective colors are superimposed is formed on the intermediate transfer body 6 by primary transfer.

  Also, below the image forming unit 60, a transport unit 20 that operates to transport the paper P to the image forming unit 60 is provided. The transport unit 20 includes paper feed trays 20A, 20B, and 20C that store the paper P. have. The paper P stored in the paper feed tray 20A and the like is fed by the feed roller 21 and the paper feed roller 22A provided in the paper feed tray 20A and the like, and passes through the transport rollers 22B, 22C and 22D, the registration roller 23, and the like. The color toner image is conveyed to the secondary transfer roller 7 </ b> A and is secondarily transferred from the intermediate transfer body 6 to the paper P on one surface (front surface) on the paper P at a time.

  The first fixing device 17A applies heat and pressure to the paper P on which the color toner image has been transferred to weld the toner onto the paper P and perform a first fixing process. The sheet P after the first fixing process is conveyed to the second main body 102 side, which will be described later, sandwiched between the conveying rollers 24 and disposed adjacent to the first main body 101. The transfer residual toner remaining on the outer peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is removed by the cleaning units 8Y, 8M, 8C, and 8K, and enters the next image forming cycle.

  When images are formed on both sides of the paper P, after the images are formed on the front surface, the paper P discharged from the first fixing device 17A is branched from the transport path toward the second main body 102 by the branching section 26. Next, the sheet P passes through the lower circulating sheet passing path 27A, and is turned upside down by a reversing conveyance path 27B which is a refeed mechanism (ADU mechanism), passes through a refeed conveyance section 27C, and is conveyed to a conveyance roller 22D. To the transfer path described above.

  The reversely conveyed sheet P is conveyed again to the secondary transfer roller 7A through the registration roller 23, and a color image (color toner image) is collectively transferred onto the back surface of the sheet P. On the other hand, after the color image is transferred onto the paper P by the secondary transfer roller 7A, the residual toner remaining on the intermediate transfer body 6 from which the paper P has been subjected to curvature separation is removed by the cleaning unit 8A for the intermediate transfer belt.

  An image quality level measuring unit 65 is installed adjacent to a conveyance path for conveying the paper P after the first fixing process to the second main body 102 side. A gamma curve measurement unit 73 is installed adjacent to the outside of the intermediate transfer member 6. The image quality level measuring unit 65 includes an image quality level measuring sensor, and the gamma curve measuring unit 73 includes a gamma curve measuring sensor. The image quality level measurement sensor and the gamma curve measurement sensor each include four reading sensors for detecting yellow (Y), magenta (M), cyan (C), and black (BK) light.

  The image quality level measuring unit 65 operates to measure the image quality level of the output image output from the color copying machine 100. For example, the image quality level measurement sensor photoelectrically converts light reflected from one surface of the paper P conveyed from the first fixing device 17A to the paper discharge tray 25 to obtain color data of the output image. The image quality level measuring unit 65 outputs color data (output) of the output image and image data Dy, Dm, Dc, Dk (transferred to the writing units 3Y, 3M, 3C, 3K corresponding to the color data of the output image. Relative to the input) is measured as the image quality level of the output image.

  The gamma curve measurement unit 73 operates to measure the image quality level of an intermediate image formed during a series of image forming steps for forming an output image. For example, a gamma curve measurement sensor photoelectrically converts light reflected from the outer peripheral surface of the intermediate transfer body 6 to obtain color data of a color toner image. The gamma curve measurement unit 73 outputs color data (output) of the color toner image and the image data Dy, Dm, Dc, transferred to the writing units 3Y, 3M, 3C, and 3K corresponding to the color data of the color toner image. The relative relationship with Dk (input) is measured as the image quality level of the intermediate image. The image quality level of the intermediate image is corrected under the control of the control unit 15.

  Here, a color toner image formed on the intermediate transfer member 6 will be described as an example of the intermediate image, but in addition to this, Y color and M color formed on the photosensitive drums 1Y, 1M, 1C, and 1K. C, BK color toner images and electrostatic latent images may be used.

  The second main body 102 is provided with a conveyance path 28 into which the paper P is carried in continuously with the conveyance path on the first main body 101 side. The transport path 28 can be switched between the first transport path 28A and the second transport path 28B by a transport path switching means 31 provided in the intermediate portion. Conveying rollers 29A to 29K are arranged at appropriate positions along the conveying path 28, the first conveying path 28A, and the second conveying path 28B.

  A second fixing device 17B as a second fixing unit is disposed in the middle of the first conveyance path 28A, and the paper P fixed by the first fixing device 17A is further added and fixed. ing. That is, the second fixing device 17B re-fixes the fixed paper P that has been fixed by the first fixing device 17A and does not contain an unfixed toner image. In particular, with thick paper P, it is not sufficient to pass the first fixing device 17A in a short time. Therefore, it is possible to perform a reliable fixing process by passing the second fixing device 17B. Become.

  In the present embodiment, a registration roller (pair) 32 as a correction mechanism that corrects the skew of the sheet is disposed on the upstream side of the second fixing device 17B in the first conveyance path 28A. Further, on the upstream side of the registration roller 32, an assist roller (pair) 33 is disposed for bending the paper P whose tip is stopped by the registration roller 32 and the bending of the posture is corrected into a roll shape. The amount of loop formed by the assist roller 33 is set so as to change depending on the size of the paper P. This loop amount can be changed by controlling the time from when the leading edge of the paper P hits the registration roller 32 until the registration roller 32 starts rotating.

  The second transport path 28 </ b> B can be used when transporting the thin sheet P to which the toner is sufficiently fixed only by the first fixing by the first fixing device 17 </ b> A to the paper discharge tray 25.

  In the color copying machine 100 according to the first embodiment having the above configuration, when an image is formed on the thick paper P, it is not necessary to set a long fixing time in the first fixing device 17A, and the second fixing device 17B is installed. By allowing it to pass, sufficient fixing can be performed. For this reason, in this embodiment, the productivity of the color copying machine 100 can be increased.

  Moreover, in the present embodiment, even if the paper P is bent due to passing through the first fixing device 17A, or the paper P is warped due to the heat and pressure accompanying the first fixing, Since the registration roller 32 can correct the bending of the paper P, the second fixing device 17B can suppress wrinkling of the paper P. Therefore, in this embodiment, there is an effect that a high-quality image can be efficiently formed on a thick sheet. By using the assist roller 33, the paper P is fed out while the registration roller 32 is stopped, thereby making it easy to correct the bending of the paper P and smoothly feeding the paper P from the registration roller 32. Have

  In the present embodiment, since the color copying machine 100 is configured using two housings of the first main body 101 and the second main body 102, the first fixing device 17B is used when the second fixing device 17B is not used. The second main body 102 can be removed from the main body 101 and used.

(Second embodiment)
FIG. 2 is an explanatory diagram showing an outline of a monochrome copying machine as an image forming apparatus according to the second embodiment of the present invention. In the present embodiment, the same parts as those in the color copying machine 100 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the present exemplary embodiment, the fixing device 17 is disposed on the downstream side of the image forming unit 60, and another image forming unit 61 is disposed on the opposite side of the conveyance path on the downstream side. A first fixing device 17A and a second fixing device 17B, which are different from the fixing device 17, are provided along the conveyance path on the downstream side of the image forming unit 61 located on the most downstream side among the image forming units 60 and 61. They are arranged sequentially. Also in the present embodiment, the registration roller 32 is arranged on the upstream side of the second fixing device 17B. An assist roller 33 is arranged upstream of the registration roller 32 and downstream of the first fixing device 17A.

  In the present embodiment, when an image is formed on a thick paper P, the toner image transferred on one side of the paper P is subjected to a short-time fixing process by the fixing device 17 to thereby form the first fixing device 17A. Further, since the additional fixing process may be performed in a short time by the second fixing device 17B, the productivity can be improved.

  Further, since the registration roller 32 is arranged on the upstream side of the second fixing device 17B, the sheet P is bent due to passing through the first fixing device 17A, and the influence of heat and pressure associated with the first fixing device. Therefore, even if the paper P is warped, the bending of the paper P can be corrected by the registration roller 32, so that the second fixing device 17B can prevent the paper P from being wrinkled. Therefore, in this embodiment, there is an effect that a high-quality image can be efficiently formed on a thick sheet.

  Also in the present embodiment, by using the assist roller 33, it is possible to easily correct the bending of the paper P by feeding out the paper P while the registration roller 32 is stopped, and from the registration roller 32. This has the effect of smoothly feeding the paper P.

  Also in the present embodiment, when an image is formed on the thick paper P, it is not necessary to set a long fixing time in the fixing device 17 or the first fixing device 17A, and it is sufficient to pass through the second fixing device 17B. Additional fixing can be performed. For this reason, in this embodiment, the productivity of the copying machine can be increased.

Moreover, in the present embodiment, even if the paper P is bent due to passing through the first fixing device 17A, or the paper P is warped due to the heat and pressure accompanying the first fixing, Since the registration roller 32 can correct the bending of the paper P, the second fixing device 17B can suppress wrinkling of the paper P. Therefore, in this embodiment, there is an effect that a high-quality image can be efficiently formed on a thick sheet.

(Other embodiments)
Although the first and second embodiments have been described above, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the first embodiment, the registration roller 32 is used as a correction mechanism for correcting the bending of the paper. Instead of the registration roller 32, for example, a shutter that abuts the front end of the paper in the conveyance direction is disposed. It is of course possible to employ a mechanism that releases the shutter after correcting the bending by applying the leading edge of the sheet to the shutter.

  Further, as a correction mechanism for correcting the bending of the sheet, instead of the registration roller 32, either one of the both edges (right edge and left edge) parallel to the sheet conveyance direction is used as a reference plate (wall). The paper is passed along the so-called one-side reference, and is moved obliquely so as to press one of the edges against the reference plate, and the skew correction is performed by correcting the skew. It is also possible to adopt a configuration to be performed.

  Further, in the first embodiment, the color copying machine 100 is configured to include the first main body 101 and the second main body 102, but it is needless to say that the constituent elements are housed in one housing.

17 fixing device 17A first fixing device 17B second fixing device 28 conveying path 28A first conveying path 28B second conveying path 31 conveying path switching means 32 registration roller (bending correction mechanism)
33 Assist Roller 60 Image Forming Unit 61 Image Forming Unit 100 Color Copier 101 First Main Body 102 Second Main Body P Paper

Claims (4)

An image forming unit that forms a toner image on a sheet conveyed on a sheet conveyance path from a sheet feeding unit to a sheet discharging unit;
A first fixing unit and a second fixing unit disposed along the paper conveyance path on the downstream side of the image forming unit located on the most downstream side of the image forming unit;
A correction mechanism that corrects the skew of the paper disposed between the first fixing unit and the second fixing unit;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the correction mechanism corrects the skew of the sheet in a state where a rear end of the sheet passes through the first fixing unit.   4. The image forming apparatus according to claim 1, further comprising an assist roller configured to bend the sheet in a loop shape downstream of the first fixing unit and upstream of the correction mechanism. 5. apparatus.   The image forming apparatus according to claim 1, wherein the correction mechanism is a registration roller.

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