JP2012189704A - Fixing device and image forming device having the same - Google Patents

Abstract

A fixing device capable of preventing wrinkling of a recording medium and obtaining uniform image quality over the entire width of the recording medium and an image forming apparatus having the same.
A fixing device includes a fixing roller that is rotationally driven by a driving source, and a pressed roller that is in pressure contact with the fixing roller. (A) The fixing roller includes a cored bar a. And (b) the pressure roller 44 is composed of a core metal 42a and an elastic layer 44b, and (c) at least one of the fixing roller 42 and the pressure roller 44. In the vicinity of the surface of the one elastic layer, grooves M and soft protrusions J are alternately provided in a direction perpendicular to the axes of the fixing roller 42 and the pressed roller 44.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and the like, in which a wrinkle is prevented from being generated on a recording paper and fixing failure is prevented, and an image forming apparatus having the same.

  An image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile is an apparatus that forms an image including characters and symbols on a recording medium such as paper, cloth, or OHP sheet based on image information. In particular, an electrophotographic image forming apparatus is widely used in offices because it can form high-definition images on plain paper at high speed. In such an electrophotographic image forming apparatus, the toner is heated and melted on the surface of the recording medium, and the toner is fixed on the surface of the recording medium by pressurizing the melted toner. Things are widely used. This thermal fixing method is widely used in the field because it can provide a high fixing speed and high fixed image quality.

  In a fixing device in an image forming apparatus using a conventional electrophotographic system, a recording medium on which a toner image is transferred passes through a fixing nip formed by a fixing roller and a pressure roller, and the toner is placed on the recording medium. The image is fixed. This type of fixing device has a problem that the recording medium is wrinkled during the fixing process. In order to solve such a problem, a fixing device (see Patent Document 1) having a fixing roller having an “inverted crown shape” has been proposed. This fixing roller is shown in FIG. As shown in FIG. 8, the fixing roller 42 has a core shaft 42b and an elastic layer 42a formed on the core shaft 42b. The fixing roller 42 is so-called "reverse" by making the thickness of both ends of the elastic layer 42b thicker than the thickness of the center and making the shape of the fixing roller 42 smaller in diameter than the both ends. Crown shape ". In this way, when the shape of the fixing roller 42 is an inverted crown shape, the peripheral speed of the end portion having a large outer diameter becomes faster than that of the central portion, so that a force to pull the recording medium in the fixing nip outward in the paper width direction acts. It becomes. In this way, when a pulling force is exerted on the recording medium in the fixing nip in the paper width direction outside, the recording medium receives a pulling force in the paper width direction outside, so that generation of wrinkles in the recording medium can be prevented.

  However, when the fixing roller 42 has an inverted crown shape, there is a problem that the nip pressure at the center portion is lowered. In particular, when thick paper is used as the recording medium, there is a problem that fixing failure occurs in the center. Accordingly, an attempt has been made to reduce the difference between the outer diameter of the both ends of the fixing roller 42 and the outer diameter of the central portion, thereby suppressing the decrease in the nip pressure in the central portion and suppressing the deterioration in the fixing performance in the central portion. However, in this case, since the distance from the fixing nip to the center of rotation of the fixing roller 42 is substantially the same at both end portions and the central portion of the fixing roller 42, wrinkles of the recording medium cannot be prevented over time. There was a problem. Furthermore, in the case of a recording medium that tends to cause wrinkles such as thin paper, there is a problem that the generation of wrinkles cannot be sufficiently prevented.

  The present invention aims to solve this problem.

  That is, an object of the present invention is to provide a fixing device that can prevent wrinkling of a recording medium and obtain uniform image quality over the entire width of the recording medium, and an image forming apparatus having the same.

  In order to achieve the above object, a first aspect of the present invention provides a fixing device including: a fixing roller that is rotationally driven by a driving source; and a pressed roller that is pressed against the fixing roller. (B) the fixing roller is composed of a cored bar and an elastic layer; (b) the pressed roller is composed of a cored bar and an elastic layer; and (c) the fixing roller and the pressed roller. In the fixing device, grooves and soft protrusions are alternately provided in the vicinity of the surface of at least one of the elastic layers in a direction perpendicular to the axes of the fixing roller and the pressed roller. .

  According to a second aspect of the present invention, in the first aspect of the present invention, the control unit, a drive motor in which the number of rotations of the fixing roller is controlled by the control unit, and the fixing roller and the control unit by the control unit. And a power source that controls the amount of fixing heat of a heater provided on at least one of the pressed rollers.

  According to a third aspect of the present invention, a fixing roller that is rotationally driven by a driving source, a heating roller that is provided in parallel to the fixing roller, and a rotation roller that is provided between the fixing roller and the heating roller. In a fixing device, comprising: a fixing belt; and a pressed roller that is pressed against the fixing roller via the fixing belt and rotated in a forward direction with respect to the fixing belt. (B) the pressure roller is composed of a metal core and an elastic layer, and (c) the elasticity of at least one of the fixing roller and the pressure roller. In the vicinity of the surface of the layer, the fixing device is characterized in that grooves and soft protrusions are alternately provided in a direction orthogonal to the axes of the fixing roller and the pressed roller.

  According to a fourth aspect of the invention, there is provided the control unit according to the third aspect of the invention, a drive motor in which the rotation speed of the fixing roller is controlled by the control unit, and the heating roller by the control unit. And a power source for controlling the amount of fixing heat of the heater provided.

  The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein the elastic layer formed on the fixing roller and the pressed roller is made of a silicone resin. It is characterized by being.

  The invention described in claim 6 is the invention described in any one of claims 1 to 5, wherein the surface of the elastic layer formed on the fixing roller and the pressed roller is fluorine-based. A release layer made of a resin is provided.

  The invention described in claim 7 comprises an unfixed toner image forming means for forming an unfixed toner image on the surface of a recording medium, and a fixing means for fixing the unfixed toner image with a foamy fixing liquid. An image forming apparatus comprising the fixing device according to claim 1 as the fixing unit.

  According to the first aspect of the present invention, in the fixing device that includes a fixing roller that is rotationally driven by a driving source and a pressure-receiving roller that is pressed against the fixing roller, (A) the fixing roller includes: (B) the pressure roller is composed of a metal core and an elastic layer, and (c) the elasticity of at least one of the fixing roller and the pressure roller. In the vicinity of the surface of the layer, grooves and soft projections are alternately provided in a direction perpendicular to the axes of the fixing roller and the pressure-applied roller, so that the recording medium is prevented from wrinkling. It is possible to provide a fixing device capable of obtaining uniform image quality over the entire width of the image forming apparatus.

  According to the second aspect of the present invention, at least one of the control unit, the drive motor in which the rotation speed of the fixing roller is controlled by the control unit, and the fixing roller and the pressed roller by the control unit. And a power supply in which the amount of fixing heat of the heater is controlled is provided, so that a fixing device that can prevent wrinkling of the recording medium and obtain uniform image quality over the entire width of the recording medium is provided. can do.

  According to the third aspect of the present invention, a fixing roller that is rotationally driven by a driving source, a heating roller provided in parallel to the fixing roller, and a rotation roller provided between the fixing roller and the heating roller. (A) the fixing roller having a fixing belt and a pressed roller that is pressed against the fixing roller via the fixing belt and rotated in a forward direction with respect to the fixing belt. (B) the pressed roller is formed of a core metal and an elastic layer, and (c) at least one of the fixing roller and the pressed roller. Near the surface of the elastic layer, grooves and soft protrusions are alternately provided in a direction perpendicular to the axes of the fixing roller and the pressure-applied roller, thereby preventing the recording medium from wrinkling. Uniform across the entire width of the recording medium It is possible to provide a fixing device capable of obtaining a quality.

  According to the fourth aspect of the present invention, the control unit, the drive motor whose rotation speed is controlled by the control unit, and the fixing heat amount of the heater provided on the heating roller by the control unit are as follows. Therefore, it is possible to provide a fixing device that can further prevent wrinkling of the recording medium and obtain uniform image quality over the entire width of the recording medium.

  According to the invention described in claim 5, since the elastic layer formed on the fixing roller and the pressed roller is made of a silicone resin, the heat resistance of the elastic layer is improved. Thus, it is possible to provide a fixing device that can prevent the occurrence of wrinkling of the recording medium and prevent a fixing defect that can obtain uniform image quality over the entire width of the recording medium P.

  According to the sixth aspect of the present invention, since the release layer made of a fluorine-based resin is provided on the surface of the elastic layer formed on the fixing roller and the pressed roller, the elasticity It is possible to provide a fixing device in which the heat resistance of the layer is further improved, wrinkling of the recording medium is further prevented, and uniform image quality can be obtained over the entire width of the recording medium.

  According to the invention described in claim 7, unfixed toner image forming means for forming an unfixed toner image on the surface of a recording medium, and fixing means for fixing the unfixed toner image with a foamy fixing liquid. In the image forming apparatus, the fixing device according to any one of claims 1 to 6 is provided as the fixing unit, so that wrinkles of the recording medium are prevented and the entire width of the recording medium is prevented. Thus, it is possible to provide an image forming apparatus which can obtain a uniform image quality and prevent fixing failure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fixing device showing an embodiment of the present invention, wherein (a) is a front view, (b) is a side view, and (c) is a partially enlarged longitudinal sectional view of an elastic layer. It is. 1 is a schematic explanatory diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 3 is a block diagram illustrating a control mechanism in the fixing device according to the embodiment of the present invention. It is a schematic explanatory drawing of the image forming apparatus which shows other one Embodiment of this invention. It is a block diagram explaining the control mechanism in the fixing device which shows other one Embodiment of this invention. FIG. 3 is a perspective view illustrating a configuration of an intermediate transfer belt. FIG. 4 is an explanatory diagram showing a width direction velocity distribution in a fixing nip, where (a) shows a state in which a convex velocity distribution is exhibited in the conveyance direction B of the recording medium in the fixing nip, and (b) Indicates a state in which a concave velocity distribution is exhibited in the conveyance direction B of the recording medium in the fixing nip. FIG. 7 is an explanatory diagram showing a widthwise out-of-plane deformation shape of a recording medium in a fixing nip, and (a) shows a state in which a convex velocity distribution is exhibited with respect to a recording medium conveyance direction B in the fixing nip; (B) shows a state in which paper wrinkles are generated as the recording medium is conveyed. FIG. 9 is an operation explanatory diagram when a corrugated sheet is sandwiched between fixing rollers in a fixing device according to an embodiment of the present invention. It is explanatory drawing which shows the conventional fixing roller.

  As shown in FIGS. 1 and 2, the fixing device 40 a according to the present invention includes a fixing roller 42 that is rotationally driven by a driving source (not shown), and a pressure roller 44 that is in pressure contact with the fixing roller 42. And have. In the fixing device 40a, (a) the fixing roller 42 is composed of a cored bar 42a and an elastic layer 42b, and (b) the pressed roller 44 is composed of a cored bar 42a and an elastic layer 44b. (C) near the surface of the elastic layer of at least one of the fixing roller 42 and the pressed roller 44 and in a direction perpendicular to the axes of the fixing roller 42 and the pressed roller 44. Grooves M and soft protrusions J are provided alternately.

  FIG. 1 shows the external shapes of the fixing roller 42 and the pressed roller 44 in the fixing device 40a of the present invention. In the fixing device 40a, in the vicinity of the surface of at least one of the elastic layers 42b and 44b of the fixing roller 42 and the pressure-receiving roller 44, a “cut” is made in a direction perpendicular to the axes of the fixing roller 42 and the pressure-receiving roller 44. A groove (in this specification, referred to as a “groove”) M and a soft protrusion (in this specification, referred to as “soft protrusion”) J are provided alternately. The grooves M and the soft protrusions J are provided at an equal pitch. As shown in FIGS. 1B and 1C, the flexible protrusion J does not need to be formed in the entire thickness direction of the elastic layers 42b and 44b, and may be provided only in the vicinity of the surface thereof. That's fine.

  According to the fixing device 40a of the present invention, the ease of deformation in the vicinity of the surface of the elastic layer of at least one of the fixing roller (drive roller) 42 and the pressed roller 44 depends on the conveyance direction of the recording medium P. Since the recording medium P is small in a direction perpendicular to the conveyance direction, the fixing roller is caused by the distortion energy of the out-of-plane deformation of the recording medium P when the recording medium P undergoes out-of-plane deformation as the recording medium P is conveyed. At least one surface of the pressure roller 42 and the pressed roller 44 is deformed in a direction perpendicular to the conveyance direction of the recording medium P, and as a result, the recording medium P moves in a direction perpendicular to the conveyance direction of the recording medium P. Thus, the out-of-plane deformation of the recording medium P is reduced. Therefore, it is possible to prevent the out-of-plane deformation of the recording medium P from accumulating as the recording medium P is conveyed and causing “wrinkles”.

  In addition, since the ease of deformation of the surface of the recording medium P at the fixing roller 42 and the pressed roller 44 can be sufficiently increased in the transport direction, the transport accuracy of the recording medium P can be ensured. Further, according to the present invention, in the vicinity of the surface of the elastic layer of at least one of the fixing roller 42 and the pressed roller 44, a direction orthogonal to the axes of the fixing roller 42 and the pressed roller 44 is provided. Since the grooves M and the soft protrusions J are alternately provided (that is, parallel to the conveyance direction of the recording medium P), the wrinkle prevention performance can be controlled by the geometric shape, and therefore, wrinkles are not easily generated. The system can be designed. Further, according to the fixing device 40a of the present invention, unlike the conventional system using the reverse crown shape, the surface pressure distribution in the width direction of the recording medium can be made substantially constant, so that the entire width of the recording medium P is covered. And uniform image quality.

  Accordingly, in the fixing device 40a having the fixing roller 42 that is rotationally driven by a driving source (not shown) and the pressure-applying roller 44 that is pressed against the fixing roller 42, (a) the fixing roller 42 includes: (B) the pressed roller 44 includes a cored bar 42a and an elastic layer 44b; and (c) the fixing roller 42 and the pressed roller. In the vicinity of the surface of at least one of the elastic layers 44, the grooves M and the soft protrusions J are alternately provided in the direction perpendicular to the axes of the fixing roller 42 and the pressed roller 44. It is possible to provide a fixing device capable of preventing the occurrence of wrinkling of the medium and obtaining uniform image quality over the entire width of the recording medium P.

  As shown in FIG. 3, the fixing device 40 a includes a control unit 63, a drive motor 67 in which the number of rotations of the fixing roller 42 is controlled by the control unit 63, and the fixing by the control unit 63. And a power source 68 in which the amount of fixing heat of the heater in at least one of the roller 42 and the pressed roller 44 is controlled. Thus, at least one of the control unit 63, the drive motor 67 in which the rotation speed of the fixing roller 42 is controlled by the control unit 63, and the fixing roller 42 and the pressed roller 44 by the control unit 63. If the power supply 68 in which the fixing heat amount of the heater is controlled is provided, it is possible to provide the fixing device 40a that further prevents the recording medium P from being wrinkled and prevents the fixing failure.

  Next, the fixing device 40a showing an embodiment of the present invention will be described in detail.

As shown in FIG. 7A, when a convex velocity distribution is exhibited in the conveyance direction B of the recording medium P in the fixing nip, the conveyance direction of the recording medium P in the fixing nip. As a result, an inward velocity vector is generated, so that both ends in the width direction of the recording medium P are gradually conveyed inward as the recording medium P is conveyed through the fixing nip, and thus wrinkles are finally generated in the recording medium. The possibility increases. On the other hand, as shown in FIG. 7B, when the concave velocity distribution is exhibited with respect to the conveyance direction B of the recording medium P at the fixing nip, the conveyance direction of the recording medium P at the fixing nip. An outward velocity vector is generated. Therefore, since both ends in the width direction of the recording medium P are pulled outward in the fixing nip, the recording medium is less likely to be wrinkled. In FIG. 7, V _a is a conveyance direction speed distribution over the width direction of the recording medium P, V _C is a maximum conveyance speed over the width direction of the recording medium P, and V _E is the recording medium P. Is the minimum transport speed in the width direction, and _Pa is the transport direction speed distribution measurement position (width direction) of the recording medium P.

  In the prior art, an inverted crown roller as shown in FIG. 10 is used as the fixing roller 42 so that a velocity distribution as shown in FIG. 7B is obtained in the fixing nip. When a reverse crown roller is used as the fixing roller 42, the pressure applied to the pressed roller 44 at the center of the fixing roller 42 is greater than the applied pressure to the pressed roller 44 at both ends of the fixing roller 42. Therefore, the peripheral speed near the both ends of the fixing roller 42 in the fixing nip becomes faster than that near the center. In one embodiment of the present invention, since the fixing roller 42 transports the recording medium P in the fixing nip, the peripheral speed near the both ends of the fixing roller 42 in the fixing nip becomes faster than the vicinity of the center. Then, the velocity distribution of the recording medium in the fixing nip becomes as shown in FIG. 7B, and the wrinkle of the sheet is suppressed.

FIG. 8 shows an out-of-plane deformation shape of the recording medium in the fixing nip. As shown in FIG. 8A, when the fixing nip has a convex velocity distribution with respect to the conveyance direction B of the recording medium P, the fixing nip is directed inward with respect to the conveyance direction of the recording medium P. Therefore, as the recording medium P is conveyed through the fixing nip, both end portions in the width direction of the recording medium P are gradually conveyed inward, so that the recording medium P is deformed out of plane. W ₁ ″ is generated. At the initial stage of paper conveyance with a small waviness W1, “waviness W ₁ ” is absorbed by elastic deformation of the fixing roller 42 and the like, so that no wrinkle is generated. However, as the conveyance of the recording medium P progresses, the “waviness W ₁ ” grows because the amount of conveyance of the recording medium P in the width direction increases, and as a result, the “paper wrinkle W ₂ ” eventually grows. It will occur.

Will now be described with reference to FIG. 9 the operation when the waviness W ₁ of the recording medium P is sandwiched between the rollers formed of villi J. In FIG. 9, only the surface portion of the lower roller, that is, the vicinity of the surface of the elastic layer in the roller to be pressed is illustrated, and the upper roller is not illustrated. As shown in FIG. 8, before the occurrence of wrinkles, waviness W ₁ is generated on the recording medium P, which grows along with the conveyance of the recording medium P and leads to generation of paper wrinkles W ₂ . However, as shown in FIG. 9 (a), in the roller on which the soft protrusion J is formed, when the paper P on which the swell W1 is formed is caught in the roller nip portion, the paper P 9A and 9B, it receives a force in the axial direction of the roller (left and right in the figure) corresponding to the strain energy of the swell W1, as shown in Fig. 9B, soft protrusions J are formed on the surface of the roller. Therefore, the force corresponding to the strain energy bends in the axial direction (left and right in the figure), and the waviness W ₁ of the recording medium P is deformed in a decreasing direction. The growth of ₁ can be suppressed and the generation of wrinkles can be prevented, while the rigidity of the soft protrusion J in the rotation direction of the roller is ensured, so that the conveyance accuracy is maintained. Does not change the roller diameter in the axial direction The pressure distribution in the axial direction becomes substantially constant, so that the fixing property can be kept uniform in the axial direction, and the width and height of the soft protrusion J and the material are optimized according to the use condition of the apparatus. As a result, it is possible to prevent wrinkling of the recording medium while ensuring good fixability for a wide range of paper types.

  As shown in FIGS. 1 and 4, the fixing device 40 b of the present invention includes a fixing roller 42 that is rotationally driven by a driving source (not shown), and a heating roller 41 that is provided in parallel to the fixing roller 42. A fixing belt 43 rotatably provided between the fixing roller 42 and the heating roller 41, and is pressed against the fixing roller 42 via the fixing belt 43 and is forwardly directed to the fixing belt 43. And a pressed roller 44 that is rotated in the direction. In the fixing device 40b, (a) the fixing roller 42 is constituted by a cored bar 42a and an elastic layer 42b, and (b) the pressed roller 44 is constituted by a cored bar 42a and an elastic layer 44b. (C) near the surface of the elastic layer of at least one of the fixing roller 42 and the pressed roller 44 and in a direction perpendicular to the axes of the fixing roller 42 and the pressed roller 44. Grooves M and soft protrusions J are provided alternately.

  As described above, the fixing roller 42 rotated by a driving source (not shown), the heating roller 41 provided in parallel to the fixing roller 42, and the fixing roller 42 and the heating roller 41 can be rotated. A fixing belt 40b, and a pressure roller 44 that is pressed against the fixing roller 42 via the fixing belt 43 and rotated in the forward direction with respect to the fixing belt 43. (B) The fixing roller 42 is composed of a core metal 42a and an elastic layer 42b, and (b) the pressed roller 44 is composed of a core metal 42a and an elastic layer 44b. ) In the vicinity of the surface of the elastic layer of at least one of the fixing roller 42 and the pressed roller 44, a groove M and a soft projection J are formed in a direction perpendicular to the axis of the fixing roller 42 and the pressed roller 44. There When are alternately provided, as in the fixing device 40a, it is possible to provide a fixing device 40b which was prevented prevented to defective fixing even creasing of the recording medium P.

   As shown in FIG. 5, the fixing device 40 b includes a control unit 63, a drive motor 67 in which the rotation speed of the fixing roller 42 is controlled by the control unit 63, and the heating by the control unit 63. And a power source 68 for controlling the amount of fixing heat of the heater provided on the roller 45. As described above, the control unit 63, the drive motor 67 in which the rotation speed of the fixing roller 42 is controlled by the control unit 63, and the fixing heat amount of the heater provided in the heating roller 45 are controlled by the control unit 63. In the same way as the fixing device 40a, it is possible to provide the fixing device 40b that further prevents the recording medium P from being wrinkled and prevents the fixing failure.

  In the fixing device 40b, the heating roller 41 serving as a heating means incorporates a heater 45 such as a halogen lamp in a hollow metal core, and heats the fixing belt 43 from the inside by this radiant heat. ing. The heating roller 41 is rotationally driven by a drive source (not shown), the fixing roller 42 is rotationally driven through the fixing belt 43, and the pressure-sensitive roller 44 is driven to rotate through the fixing nip. That is, in the fixing device 40b, the fixing roller 42 functions as a driving member that transmits the driving force of the driving source to the recording medium P and applies a conveying force to the recording medium P, and the pressed roller 44 Functions as a counter member that rotates following the fixing nip. The control unit 63 controls the entire apparatus. The control unit 63 controls the drive motor 67 to control the rotation speed of the fixing roller 42 and the power source 68 of the heater 45. The amount of fixing heat can be controlled.

  As shown in FIG. 1, the elastic layers 42b and 44b formed on the fixing roller 42 and the pressed roller 44 are made of silicone resin. As described above, when the elastic layers 42b and 44b are made of a silicone resin, the heat resistance of the elastic layer is improved. For this reason, the occurrence of wrinkling of the recording medium P is further prevented and fixing failure is prevented. A fixing device can be provided.

  Further, as shown in FIG. 1, a release layer (not shown) made of a fluorine-based resin is formed on the surfaces of the elastic layers 42b and 44b formed on the fixing roller 42 and the pressed roller 44. ) Is provided. As described above, if a release layer made of a fluororesin is provided on the surfaces of the elastic layers 42b and 44b formed on the fixing roller 42 and the pressed roller 44, the heat resistance of the elastic layer is increased. Therefore, like the fixing device 40a, it is possible to provide the fixing device 40b that further prevents the recording medium P from being wrinkled and prevents fixing failure.

  As shown in FIGS. 2 and 4, the image forming apparatuses 1A and 1B according to the present invention include an unfixed toner image forming unit that forms an unfixed toner image on the surface of a recording medium, and bubbles the unfixed toner image. Fixing means for fixing with a state fixer. In the image forming apparatus of the present invention, the fixing device according to any one of claims 1 to 6 is provided as the fixing unit. Thus, in the image forming apparatus, comprising: an unfixed toner image forming unit that forms an unfixed toner image on the surface of a recording medium; and a fixing unit that fixes the unfixed toner image with a foamy fixing solution. When the fixing device according to any one of 1 to 6 is provided, it is possible to provide an image forming apparatus in which the occurrence of wrinkling of the recording medium is prevented and fixing failure is prevented.

  Next, the image forming apparatus will be described in more detail.

  As shown in FIG. 4, the image forming apparatus 1A of the present invention is an electrophotographic color image forming apparatus capable of forming a full color image by adopting a tandem method, and includes four image forming units 10 ( Y, M, C, Bk) are juxtaposed along the upper running side of the intermediate transfer belt 20. The intermediate transfer belt 20 will be described later with reference to FIG. The image forming unit 10 has the same configuration except for the color of the toner to be handled. In FIG. 4, only the leftmost yellow image forming unit 10Y is provided with reference numerals for the devices constituting the unit. That is, the image forming unit 10 includes a photosensitive drum 11 as an image carrier. Around the photosensitive drum 11, a charging unit 12, a developing device 13, a cleaning device 14, and the like are provided. Further, a primary transfer unit is configured inside the intermediate transfer belt 20 so as to face each photosensitive drum 11. A transfer roller 15 is provided. In the image forming apparatus 1A, each image forming unit 10 (Y, M, C, Bk) is provided with an exposing unit. For example, an exposing unit 16 such as an LED is disposed between the charging unit 12 and the developing unit 13. It is arranged so that optical writing is possible. As the exposure means 16, an exposure apparatus common to the image forming units 10 (Y, M, C, Bk), for example, a laser writing apparatus can be used.

  A transfer roller 31, which is one of the supporting members of the intermediate transfer belt 20 and functions as a backup member, is a transfer member so as to face the transfer counter roller 32 with the intermediate transfer belt 20 interposed therebetween. . A registration roller pair 54 is disposed on the right side of the transfer roller 31, and a conveyance belt 55 is disposed on the left side of the transfer roller 31. A fixing device 40b is provided on the left side of the transport belt 55. The fixing device 40b is a belt fixing device having a fixing belt 43 stretched between a heating roller 41 and a fixing roller 42 as heating means, and the pressed roller 44 is pressed against the fixing roller 42 with the fixing belt 43 interposed therebetween. It is provided to do. A paper feed tray 50 for storing a recording medium (recording paper) P is disposed in the lower part of the image forming apparatus 1A, and a pickup roller 51 and a separation feeding roller 52 are provided as paper feeding means. Further, a conveyance roller 53 is disposed at an appropriate position in the sheet conveyance path indicated by a one-dot chain line in FIG. Further, although not shown, a paper guide is provided as appropriate. In addition, a manual paper feed unit and a paper reversing unit can be provided as necessary. It is also possible to mount an image reading device (scanner), an automatic document feeder (ADF), or the like.

  Next, an image forming operation in the image forming apparatus 1B will be briefly described.

  The photosensitive drum 11 of the image forming unit 10 is rotationally driven counterclockwise in the figure by a driving unit (not shown), and the surface of the photosensitive drum 11 is uniformly charged to a predetermined polarity by the charging unit 12. The charged photosensitive member surface is irradiated with scanning light from the exposure unit 16, whereby an electrostatic latent image is formed on the surface of the photosensitive drum 11. At this time, the image information exposed to each photosensitive drum 11 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device 13 to the electrostatic latent image formed in this manner, and visualized as a toner image. Further, the intermediate transfer belt 20 is driven to run in the clockwise direction in the drawing, and the respective color toner images are sequentially transferred from the photosensitive drum 11 to the intermediate transfer belt 20 by the action of the primary transfer roller 15 in each image forming unit 10. In this way, the intermediate transfer belt 20 carries a full-color toner image on its surface. Note that a single color image can be formed using any one of the image forming units 10, or a two-color or three-color image can be formed using a plurality of image forming units. In the case of monochrome printing, image formation is performed using the rightmost black unit 10Bk in the drawing among the four image forming units.

  The residual toner adhering to the surface of the photosensitive drum 11 after transferring the toner image is removed from the surface of the photosensitive drum by the cleaning device 14, and then the surface is subjected to the action of a static eliminator (not shown) so that the surface potential is initially set. To prepare for the next image formation. On the other hand, the paper is fed from the paper feed tray 50 and is sent out toward the secondary transfer position by the registration roller pair 54 in timing with the toner image carried on the intermediate transfer belt 20. The toner image on the surface of the intermediate transfer belt is collectively transferred onto the sheet by the transfer roller 31 as the second transfer unit. The sheet on which the toner image has been transferred is sent to the fixing device 40 by the conveying belt 55, and when passing through the fixing device 40, the toner image is fused and fixed to the sheet by heat and pressure. The paper on which the toner image is fixed is discharged to a paper discharge tray (not shown).

  Next, the intermediate transfer belt 20 will be described.

  As shown in FIG. 6, the intermediate transfer belt 20 is stretched over a drive roller 21, a driven roller 22, an external stretching roller 23, a transfer counter roller 32, and a transfer guide roller 33. When the roller 21 is rotationally driven by the motor 26, it travels in the direction of arrow A in FIG. The driven roller 22 applies a tension to the intermediate transfer belt 20 by a load applying unit (not shown) to generate a friction conveying force between the driving roller 21 and the intermediate transfer belt 20. As described with reference to FIG. 4, the photosensitive drum 11 of each color image forming unit is located on the upper running side of the intermediate transfer belt 20, which is a belt stretching surface formed by the driving roller 21 and the driven roller 22. A transfer roller 15 serving as a primary transfer unit is disposed in the loop of the intermediate transfer belt 20 so as to face each of the photosensitive drums 11 arranged in parallel. A transfer roller 31 is disposed below the transfer counter roller 32 and is pressed against the transfer counter roller 32 with the intermediate transfer belt 20 interposed therebetween.

  A predetermined high voltage is applied to the transfer counter roller 32 from a transfer power source (not shown) to form a transfer electric field in a transfer nip between the transfer roller 31 and the transfer roller 31 that is electrically grounded. In addition, the transfer roller 31 conveys the recording medium P with a predetermined pressing force together with the transfer counter roller 32 and the intermediate transfer belt 20. Further, a transfer guide roller 33 is disposed on the back side of the intermediate transfer belt 20 in the vicinity of the upstream side of the transfer counter roller 32 in the belt rotation direction. The transfer roller 30, the transfer roller 31, and the transfer counter roller 32 constitute a secondary transfer unit.

  As shown in FIG. 4, the transfer guide roller 33 is disposed slightly outside the straight line connecting the outer peripheral surfaces of the drive roller 21 and the transfer counter roller 32, and the intermediate transfer belt 20 is moved from the belt inner side to the outer side. It is provided at a position to push it out. Therefore, the arrangement relationship between the transfer counter roller 32 and the transfer roller 30 is such that the intermediate transfer belt 20 is sandwiched between transfer nips formed by the transfer roller 30 and the transfer counter roller 32 after the intermediate transfer belt 20 is wound around the surface of the transfer roller 30, and The arrangement relationship is such that the portion of the recording paper P sandwiched between the transfer nips is closer to the surface of the image carrier by the waist of the recording paper P than the portion of the recording paper P. Although not shown in FIG. 6, a belt cleaning unit 24 (see FIG. 4) for cleaning the intermediate transfer belt 20 is disposed outside the belt between the transfer counter roller 32 and the external stretching roller 23. A backing roller 25 (see FIG. 4) corresponding to the cleaning blade of the belt cleaning means 24 is disposed inside the belt. The recording medium P is conveyed in the direction of arrow B in the figure, and after the posture of the recording medium P is corrected by the registration roller pair 54, the recording medium P is conveyed between the transfer roller 31 and the intermediate transfer belt 20 to be subjected to intermediate transfer. The toner image on the belt 20 is electrostatically transferred onto the paper.

  The image forming apparatus according to the present invention has been described above with reference to the image forming apparatus illustrated in FIG. 4, but can be similarly described with reference to FIG. 2.

40a, 40b Fixing device 42 Fixing roller 42a Core metal 42b Elastic layer 44 Pressurized roller 44a Core metal 44b Elastic layer J Soft projection M Groove

JP 2005-195856 A

Claims (7)

In a fixing device having a fixing roller that is rotationally driven by a driving source, and a pressed roller that is pressed against the fixing roller,
(A) The fixing roller is composed of a cored bar and an elastic layer,
(B) the pressed roller is composed of a cored bar and an elastic layer, and
(C) Grooves and soft protrusions are alternately provided in the vicinity of the surface of the elastic layer of at least one of the fixing roller and the pressed roller in a direction perpendicular to the axes of the fixing roller and the pressed roller. A fixing device.   A control unit, a drive motor in which the number of rotations of the fixing roller is controlled by the control unit, and a fixing heat amount of a heater provided in at least one of the fixing roller and the pressed roller are controlled by the control unit. The fixing device according to claim 1, further comprising: a power source. A fixing roller rotated by a driving source, a heating roller provided in parallel to the fixing roller, a fixing belt rotatably provided between the fixing roller and the heating roller, and the fixing belt A pressure-applying roller that is pressed against the fixing roller and rotated in a forward direction with respect to the fixing belt;
(A) The fixing roller is composed of a cored bar and an elastic layer,
(B) the pressed roller is composed of a cored bar and an elastic layer, and
(C) Grooves and soft protrusions are alternately provided in the vicinity of the surface of the elastic layer of at least one of the fixing roller and the pressed roller in a direction perpendicular to the axes of the fixing roller and the pressed roller. A fixing device.   A control unit; a drive motor in which the rotation speed of the fixing roller is controlled by the control unit; and a power source in which a fixing heat amount of a heater provided in the heating roller is controlled by the control unit. The fixing device according to claim 3.   The fixing device according to claim 1, wherein an elastic layer formed on the fixing roller and the pressed roller is made of a silicone-based resin.   6. A release layer made of a fluorine-based resin is provided on the surface of an elastic layer formed on the fixing roller and the pressed roller. The fixing device according to 1.   An image forming apparatus comprising: an unfixed toner image forming unit that forms an unfixed toner image on a surface of a recording medium; and a fixing unit that fixes the unfixed toner image with a foamy fixing solution. An image forming apparatus comprising the fixing device according to any one of items 1 to 6.

Images