JP2010276906A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the occurrence of conveyance dust of a recording paper due to the sliding of a guide plate from a secondary transfer body to a fixing nip is prevented, and the occurrence of wrinkles of the recording paper when the recording paper enters the fixing nip is prevented. <P>SOLUTION: An image recording device transfers a black toner image to the recording medium P conveyed from a pair of resist rollers in a paper feeder, between a black photoreceptor 11B and the secondary transfer body 18, and then, transfers color toner images except black between an intermediate transfer body 16 to which the color toner images are transferred and the secondary transfer body 18, and next, fixes the transferred toner images by the fixing nip N formed by a fixing roller 101 and a pressure roller 102. In the image recording device of the image forming apparatus, a separation point S, to which the recording medium P is conveyed and at which the recording medium P is separated from the secondary transfer body 18, is arranged within 10 mm from the fixing nip N. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, for example, an image forming apparatus such as a copying machine, a printer, a facsimile machine, a multifunction machine, and a printing machine.

  The color electrophotographic apparatus includes a developing device for each of a plurality of photoconductors, and forms a single color toner image on each photoconductor, and sequentially transfers the single color toner images to record a composite color image. There is a so-called tandem type. The demand for high-speed monochrome images is increasing, and the number of tandem products is increasing.

  The tandem type electrophotographic apparatus includes a direct transfer system that sequentially transfers an image on each photosensitive member to a sheet conveyed by a sheet conveying belt by a transfer device, and a primary transfer device that transfers an image on each photosensitive member. There is an indirect transfer type in which images are sequentially transferred to an intermediate transfer member once and then images on the intermediate transfer member are collectively transferred to a sheet by a secondary transfer device.

  Comparing the direct transfer type and the indirect transfer type, the former requires that a paper feeding device is arranged upstream of the tandem type image forming apparatus in which the photoconductors are arranged, and a fixing device is arranged downstream. , There is a drawback of increasing the size. In contrast, in the latter, the secondary transfer position can be installed relatively freely, and the paper feeding device and the fixing device can be arranged so as to overlap the tandem type image forming device, thereby reducing the installation space and reducing the size. There are advantages that are possible. For these reasons, recently, tandem type electrophotographic apparatuses, particularly indirect transfer type products, are increasing.

  2. Description of the Related Art An image forming apparatus, which is an electrophotographic apparatus such as a conventional printer or copier, after recording paper is secondarily transferred, enters a fixing nip while sliding a fixing inlet guide plate from a transfer outlet guide plate. The problem here is that the transfer exit guide plate and the fixing entrance guide plate are frictionally charged by the recording paper, repelling with the unfixed toner on the recording paper, causing conveyance dust and image deterioration (image dust). It is a point. Further, wrinkles of the recording paper may occur due to the condensation of the guide plate adhering to the recording paper.

  Patent Document 1 discloses an apparatus that transports recording paper to a fixing unit using a transfer belt as an image forming apparatus that cleans transfer residual toner and time-stained toner, and Patent Document 2 discloses primary transfer transfer dust. And an image forming apparatus that prevents reverse transfer and prevents secondary transfer pre-transfer and transfer dust. However, since the recording paper is configured to land on the guide plate provided in the fixing unit and enter the fixing nip, there is a problem that conveyance dust due to rubbing of the guide plate cannot be improved.

  On the other hand, in Patent Documents 3 and 4, as an image forming apparatus that satisfies the image quality and printing speed of full-color images and monochrome images and can form a stable and high-quality image, a fixing unit for recording paper without a guide plate is disclosed. However, there is no description of a method for preventing wrinkling when entering the fixing nip.

The problem of the present invention has been made in view of the problems in the prior art described above, and prevents the occurrence of conveyance dust generated by sliding of the guide plate between the secondary transfer member of the recording paper and the fixing nip, An object of the present invention is to provide an image forming apparatus that prevents the occurrence of wrinkling of recording paper when entering a fixing nip.
Another object of the present invention is to provide an image forming apparatus equipped with a toner recycling function and realizing a low printing cost (low CPP).

In order to solve the above problems, the present invention is as follows.
[1] A black toner image is transferred between a black photosensitive member and a secondary transfer member onto a recording medium conveyed from a pair of registration rollers of a paper feeding device, and then a color toner image other than black is transferred to the color medium. An image recording apparatus for transferring between the intermediate transfer member to which the toner image has been transferred and the secondary transfer member, and then fixing the transferred toner image at a fixing nip formed by a fixing roller and a pressure roller. In
The separation point at which the recording medium is transported and separated from the secondary transfer member is disposed within 10 mm from the fixing nip.
[2] The separation point according to [1], wherein a separation point at which the recording medium is conveyed and separated from the secondary transfer member is disposed on the fixing roller side with respect to a tangent line of the fixing nip. An image forming apparatus.
[3] An angle formed by a straight line connecting a contact point between the intermediate transfer member and the secondary transfer member and a separation point where the recording medium is conveyed and separated from the secondary transfer member with a tangent line of the fixing nip. The image forming apparatus according to any one of [1] to [2], wherein the angle is 30 degrees or less.
[4] The image forming apparatus according to any one of [1] to [3], wherein the surface potential of the fixing roller and the surface potential of the secondary transfer member are the same.
[5] The linear velocity of the roller pair of the fixing roller and the pressure roller is 1.0 to 2.0% faster than the linear velocity of the secondary transfer member. An image forming apparatus according to any one of the above.
[6] The above-mentioned [1], characterized in that a static eliminator is provided on a conveyance path of the recording medium between a separation point where the recording medium is conveyed and separated from the secondary transfer member and the fixing nip. To [5].
[7] The configuration according to any one of [1] to [6], wherein the shape of the separation roller constituting the separation point of the secondary transfer member is either a straight shape or a crown shape. An image forming apparatus.
[8] From the above [1], characterized in that a guide member is provided on the back surface of the secondary transfer body, and a rib guide member capable of idling is provided at both ends of a separation roller constituting the separation point of the secondary transfer body. [7] The image forming apparatus according to any one of [7].
[9] The image forming apparatus according to any one of [1] to [8], wherein a diameter of a separation roller constituting the separation point of the secondary transfer member is 20 mm or less.

As an effect of the present invention, according to the first aspect of the present invention, the black toner image is transferred between the black photosensitive member and the secondary transfer member onto the recording medium conveyed from the registration roller pair of the paper feeding device. Thereafter, a color toner image other than black is transferred between the intermediate transfer member to which the color toner image has been transferred and the secondary transfer member, and then the transferred toner image is transferred to a fixing roller and a pressure roller. In the image recording apparatus to be fixed at the fixing nip formed in Step 1, the separation point where the recording medium is transported and separated from the secondary transfer member is disposed within 10 mm from the fixing nip. The recording medium can be conveyed without interposing a transfer outlet guide plate or a fixing inlet guide plate, and can enter the fixing nip, so that conveyance dust caused by charging of the guide is not generated. From further the separation point, by shortening the distance to the fixing nip, to prevent the collision of the pressure roller due to sagging of the recording medium, it is possible to prevent the occurrence of wrinkles.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a separation point at which the recording medium is conveyed and separated from the secondary transfer member is on the fixing roller side with respect to a tangent line of the fixing nip. By being arranged, the recording medium separated from the secondary transfer member first contacts the fixing roller, and then is stretched and enters the fixing nip. Therefore, the recording medium is placed on a rubber roller such as the pressure roller. It is possible to more reliably prevent wrinkles caused by contact of the leading end of the recording medium (recording paper).
According to a third aspect of the present invention, in the image forming apparatus according to any one of the first to second aspects, the contact point between the intermediate transfer member and the secondary transfer member and the recording medium are conveyed to the secondary transfer member. Since the angle formed between the straight line connecting the separation point and the tangent line of the fixing nip is 30 degrees or less, the leading edge of the recording medium (recording paper) smoothly enters the fixing nip, and the thickness When a certain recording sheet or the like is passed, it is possible to prevent transfer blur caused by the impact of the leading end of the recording sheet contacting the fixing roller or the pressure roller.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, since the surface potential of the fixing roller and the surface potential of the secondary transfer member are set to the same potential, the secondary transfer is performed. Generation of an electric field between the body and the fixing roller can be prevented, and generation of image dust can be prevented in advance.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the linear velocity of the roller pair of the fixing roller and the pressure roller is 1 relative to the linear velocity of the secondary transfer member. Since the recording medium separated from the secondary transfer body is expanded by the temperature change of the fixing roller, the recording medium is separated from the secondary transfer body even if the linear velocity is increased. The phenomenon that the recording medium is pulled can be prevented, and the occurrence of transfer deviation can be prevented.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the separation point between the separation medium where the recording medium is conveyed and separated from the secondary transfer member, and the fixing nip. Since a static eliminator is provided on the recording medium conveyance path, it is possible to prevent the occurrence of image dust due to a sudden flow of electric charge that occurs when the charged recording medium comes into contact with the fixing roller having a low potential. Can do.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the shape of the separation roller constituting the separation point of the secondary transfer member is either a straight shape or a crown shape. Therefore, the recording medium after being separated from the secondary transfer member can be warped to the fixing roller side according to the shape of the separation roller, and the leading end of the recording medium is always directed to the fixing roller side. Further, when the end of the recording medium hits the pressure roller and the other part contacts the fixing roller, entry into the fixing nip is hindered, and the stress causes the recording medium to enter the recording medium. Although a phenomenon of wrinkles is observed, this can be prevented beforehand.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the separation roller is provided with a guide member on the back surface of the secondary transfer body and constitutes the separation point of the secondary transfer body. Since the rib guide members capable of idling are provided at both ends of the belt, lateral displacement of the belt of the secondary transfer member can be prevented, and the belt of the secondary transfer member moves toward the side with the larger flare during the rotation of the belt. Accordingly, it is possible to prevent a phenomenon in which a lateral stress is generated between the fixing roller and the pressure roller pair and leads to wrinkles.
According to the ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the diameter of the separation roller constituting the separation point of the secondary transfer member is 20 mm or less, and therefore the curvature is small. Can be used to smoothly separate the recording medium from the secondary transfer member, stabilize the entry of the recording medium into the fixing nip, and suppress the occurrence of wrinkles.

1 is a cross-sectional view showing a schematic configuration of an embodiment of an image forming apparatus of the present invention. FIG. 3 is a schematic explanatory diagram of the vicinity of the fixing unit of the image forming apparatus of the present invention. FIG. 3 is a schematic view of an aspect in which a bias applying device is connected to a fixing roller of the image forming apparatus of the present invention. FIG. 3 is a schematic diagram of an aspect in which a static eliminator of the image forming apparatus of the present invention is connected. FIG. 4 is a cross-sectional view showing an example of a shape of a separation roller that constitutes a separation point of a secondary transfer member of the image forming apparatus of the present invention.

  Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of a full-color image forming apparatus as an embodiment of the image forming apparatus of the present invention. The image forming unit has a tandem configuration including a photoconductor, a charging device, an exposure device, a developing device, and a transfer device for each color other than black and black, and directly transfers black toner and applies color toner other than black. It is configured to perform intermediate transfer.

A recording medium (hereinafter referred to as “recording paper”) P is nipped and conveyed by a registration roller 20 and a registration counter roller 21, and is nipped by a black photoconductor 11 </ b> B and a secondary transfer body (secondary transfer belt) 18. Black toner is transferred.
Regarding the color color, the yellow color will be described as a representative example. The photosensitive member 11Y is charged by the charging roller 12, a latent image is formed by the laser of the optical writing device 15, and then the yellow toner is transferred to the latent image portion by the developing roller 13. Adhere to. After the yellow toner is transferred to the intermediate transfer member (intermediate transfer belt) 16, the cyan toner is transferred from the cyan photosensitive member 11C and the magenta toner is transferred from the magenta photosensitive member 11M in the same procedure while moving in the right direction in the figure. The toner image thus transferred is transferred to the recording paper P sandwiched between the secondary transfer belts 18.

  The residual toner on the intermediate transfer belt 16 after the transfer is collected by the belt cleaning device 17. The remaining toner is returned to the developing unit of the photoconductor unit on which the black photoconductor 11B is mounted. Similarly, residual toner adhering to the secondary transfer belt 18 is also collected by the secondary transfer belt cleaning device 19 and returned to the developing unit of the photoconductor unit on which the black photoconductor 11B is mounted.

  The recording paper P onto which the toner image of each color has been transferred is separated from the secondary transfer member, and then conveyed to the fixing unit 10 and enters a fixing nip formed by the fixing roller 101 and the pressure roller 102, and the toner The image is fixed by heating. Thereafter, the recording paper P is discharged out of the apparatus.

FIG. 2 is a schematic diagram showing an aspect of the configuration in the vicinity of the fixing unit 10 of the image forming apparatus of the present invention.
In the image forming apparatus of the present invention, the distance L between the separation point S where the recording paper P is conveyed and separated from the secondary transfer body 18 and the fixing nip N formed by the fixing roller 101 and the pressure roller 102 is It is within 10 mm.

  In the image forming apparatus of the present invention, the separation point S where the recording paper P is conveyed and separated from the secondary transfer body 18 is arranged on the fixing roller 102 side with respect to the tangent line of the fixing nip N. With this arrangement, wrinkles of the recording paper P can be prevented.

  Further, in the image forming apparatus of the present invention, a straight line connecting the contact point between the intermediate transfer member 16 and the secondary transfer member 18 and the separation point S where the recording paper P is conveyed and separated from the secondary transfer member 18 is fixed. The angle θ formed with the tangent line of the nip N is 30 degrees or less. By setting such an angle, it is possible to prevent transfer blur caused by the impact of the leading edge of the recording paper contacting the fixing roller or the pressure roller.

(Second Embodiment)
FIG. 3 is a schematic diagram of a mode in which a bias applying device to the fixing roller is connected in the image forming apparatus of the present invention.
As shown in FIG. 3, a high voltage power source 103 and a CPU are connected to the fixing roller 101 and the transfer roller 22 of the secondary transfer body 18, and a bias is applied from the high voltage power source 103 to the surface potential of the fixing roller 101. The surface potential of the secondary transfer body 18 is set to the same potential. By making the surface potentials of the fixing roller and the secondary transfer body equal, the generation of an electric field can be prevented and the occurrence of image dust can be prevented beforehand.

(Third embodiment)
In the image forming apparatus of the present invention, the linear velocity of the pair of the fixing roller 101 and the pressure roller 102 is set to be 1.0 to 2.0% faster than the linear velocity of the secondary transfer body 18. . By setting such a linear velocity, it is possible to prevent the recording paper from sagging.

(Fourth embodiment)
FIG. 4 is a schematic diagram illustrating a mode in which static elimination is applied in the image forming apparatus of the present invention.
As shown in FIG. 4, a neutralization device (neutralization needle) 104 is provided in front of the fixing nip N between the fixing roller 101 and the pressure roller 102, and after the recording paper P is separated from the secondary transfer body 18, the fixing is performed. Before entering the nip N, the recording paper P is discharged. A high-voltage power source 103 and a CPU are connected to the static elimination device (static elimination needle) 104.

(Fifth embodiment)
In the image forming apparatus of the present invention, for example, the shape of the separation roller 23 constituting the separation point S of the secondary transfer member 18 shown in FIG. 2 is either a straight shape or a crown shape.
FIG. 5 is a cross-sectional view showing an example of a secondary transfer body (belt) and a separation roller constituting the separation portion of the secondary transfer body.
As shown in FIG. 5, a guide member 83 is provided on the back surface of the belt 82 of the secondary transfer member, and rib guide members 84 capable of idling are provided at both ends of the separation roller 81. Thereby, the belt running stability of the secondary transfer member can be achieved.

  The diameter of the separation roller is preferably 20 mm or less (φ20 or less). Since the recording medium is smoothly separated from the secondary transfer member due to the small curvature, entry of the recording medium into the fixing nip can be stabilized and generation of wrinkles can be suppressed.

[Reference example]
In the image forming apparatus shown in FIG. 1, a separation point S where the recording paper P shown in FIG. 2 is conveyed and separated from the secondary transfer body 18, and a fixing nip N formed by the fixing roller 101 and the pressure roller 102. The separation point was set so that the distance L was 10 mm, and printing was performed, and the presence or absence of wrinkling of the recording paper during paper feeding was examined.
When fifteen sheets of recording paper were passed on both sides, no wrinkles were observed during continuous feeding.

  Further, when the image forming apparatus shown in FIG. 1 was checked for the occurrence of wrinkles due to the sheet passing immediately after startup, the image forming apparatus according to the present invention in which the distance L between the separation point S and the fixing nip N is 10 mm is wrinkled. The occurrence of was not seen. On the other hand, in a conventional image forming apparatus provided with a guide plate and having a distance L of 13.2 mm, wrinkles were observed on 13 of 15 sheets. This is considered to be a result of the leading edge of the recording paper getting wet due to condensation on the fixing separation plate and drooping and hanging down, making it difficult to enter the fixing nip due to the longer distance.

DESCRIPTION OF SYMBOLS 10 Fixing unit 11 Photoconductor 12 Charging roller 13 Developing roller 14 Cleaning device 15 Optical writing device 16 Intermediate transfer body (intermediate transfer belt)
17 Belt cleaning device 18 Secondary transfer body (secondary transfer belt)
DESCRIPTION OF SYMBOLS 19 Photoconductor cleaning device 20 Registration roller 21 Registration counter roller 22 Transfer roller 23 Separation roller 101 Fixing roller 102 Pressure roller P Recording medium (recording paper)
S Separation point N Fixing nip

JP 2008-89770 A JP 2007-248931 A JP 2006-85138 A JP 2002-296867 A

Claims (9)

After the black toner image is transferred between the black photosensitive member and the secondary transfer member to the recording medium conveyed from the registration roller pair of the paper feeding device, the color toner image other than black is transferred to the recording medium. In the image recording apparatus for transferring between the transferred intermediate transfer member and the secondary transfer member, and then fixing the transferred toner image at a fixing nip formed by a fixing roller and a pressure roller.
An image forming apparatus, wherein a separation point at which the recording medium is conveyed and separated from the secondary transfer member is disposed within 10 mm from the fixing nip.   The image forming apparatus according to claim 1, wherein a separation point at which the recording medium is conveyed and separated from the secondary transfer member is disposed on the fixing roller side with respect to a tangent line of the fixing nip.   A straight line connecting a contact point between the intermediate transfer member and the secondary transfer member and a separation point where the recording medium is transported and separated from the secondary transfer member forms an angle of 30 degrees with the tangent line of the fixing nip. The image forming apparatus according to claim 1, wherein the image forming apparatus is:   The image forming apparatus according to claim 1, wherein the surface potential of the fixing roller and the surface potential of the secondary transfer member are set to the same potential.   5. The linear velocity of the roller pair of the fixing roller and the pressure roller is 1.0 to 2.0% faster than the linear velocity of the secondary transfer body. 6. Image forming apparatus.   6. The static eliminator is provided on a conveyance path of the recording medium between a separation point where the recording medium is conveyed and separated from the secondary transfer member and the fixing nip. An image forming apparatus according to claim 1.   7. The image forming apparatus according to claim 1, wherein a shape of a separation roller constituting the separation point of the secondary transfer member is one of a straight shape and a crown shape.   The guide member is provided on the back surface of the secondary transfer body, and rib guide members capable of idling are provided at both ends of a separation roller constituting the separation point of the secondary transfer body. The image forming apparatus described in 1.   9. The image forming apparatus according to claim 1, wherein a diameter of a separation roller constituting the separation point of the secondary transfer member is 20 mm or less.

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