JP2005156905A - Fixing device, image forming apparatus, and guide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image of high quality which is free of scatter of a toner image even when a polymerizable toner is used. <P>SOLUTION: A fixing device 60 which fixes a toner image carried on a form P has a fixing roll 61, an endless belt 62 which can move in contact with the fixing roll 61 while forming a nip part N, and a fixation entrance guide 56 which guides the form P to the nip part N, and the fixation entrance guide 56 has an upstream-side guide part 562 which guides the form P to an area where heat which is much enough to mutually fuse toner images is conducted while holding a state where the toner image is electrostatically restrained to the form P and a downstream-side guide part 561 which guides the form P to vicinity of the nip part N in a state where the toner images are mutually fused. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device and the like, and more particularly to a fixing device used in an image forming apparatus using an electrophotographic system.

  In an image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, a photosensitive member formed in a drum shape is uniformly charged, and the photosensitive member is exposed to light controlled based on image information. An electrostatic latent image is formed on the photoreceptor. The electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is electrostatically transferred onto a recording sheet by a transfer device, and is fixed by a fixing device to form an image.

  In a fixing device used in such an image forming apparatus, as shown in FIG. 8, a heating source 113 is provided inside a cylindrical metal core 111, and a release layer 112 is formed on the outer peripheral surface of the metal core 111. The fixing roll 110 was pressed against the fixing roll 110, and a heat-resistant elastic body layer 122 and a release layer 123 made of a heat-resistant resin film or heat-resistant rubber film were formed on the outer peripheral surface of the core metal 121. It is composed of a pressure roll 120. Then, when the recording paper P carrying the unfixed toner image is guided to the roll nip portion N formed between the fixing roll 110 and the pressure roll 120 by the guide member 130 and the recording paper P is passed through the roll nip portion N. The toner image is fixed on the recording paper P by heating and pressing the unfixed toner image. Such a fixing device is called a heating roll method and is generally widely used.

  Further, the pressure pad includes a rotatable fixing roll whose surface is elastically deformed, an endless belt capable of running while being in contact with the fixing roll, and a pressure pad disposed in a non-rotating state inside the endless belt. The endless belt is pressed against the fixing roll so as to form a contact surface with the fixing roll, and a belt nip portion is provided so that the sheet can pass between the endless belt and the fixing roll. In the fixing device configured to locally elastically deform the exit side of the sheet of the surface of the sheet, the guide member guides the recording paper to the belt nip portion, and when passing the recording paper through the belt nip portion, There is also a technique related to a fixing device that fixes an unfixed toner image by heating and pressing (for example, a special technique). References 1).

  In particular, in the fixing device described in Patent Document 1, since the endless belt is pressed against the fixing roll using a pressure pad instead of the pressure roll in the conventional heating roll type fixing device, the fixing roll and the endless belt The width of the belt nip formed by the above can be easily made larger than the width of the conventional roll nip between the fixing roll and the pressure roll, so that it is possible to cope with higher speeds and to reduce the size of the apparatus. It has the advantage that it is also easy.

  In the fixing device as described above, the recording paper onto which the toner image has been transferred by the transfer device is guided to the nip portion by the guide member. At this time, the toner image is conveyed while being restrained by the electrostatic force on the recording paper. The That is, for the charged toner, a charge having the opposite polarity to the charged charge of the toner is applied to the back surface of the recording paper by the transfer device, and the coulomb between the toner and the opposite polarity charge on the back surface of the recording paper is applied. The toner image is bound to the recording paper by the force. For this reason, the binding force on the toner image on the recording paper is unstable, and the toner image is likely to be disturbed due to fluctuations in the amount of charge carried on the back surface of the recording paper. For example, when the electrostatic force applied to the toner image decreases, for example, the charge applied to the back surface of the recording paper decreases for some reason, the toner image scatters around the toner image, causing an image defect.

  Therefore, as a method for preventing the disturbance of the toner image on the path from the transfer device to the fixing device, a guide member for guiding the transfer material (recording paper) from the transfer portion to the fixing portion, an insulating layer in contact with the transfer material, and this There is a technique that includes a conductive layer provided on the side opposite to the side in contact with the transfer material of the insulating layer (see, for example, Patent Document 2). With this configuration, the toner image is prevented from being disturbed and fixing offset by stably holding the charge on the back side of the recording paper.

Japanese Patent No. 3298354 (pages 4-7) JP-A-6-308846 (page 3-4, FIG. 1)

Incidentally, in recent years, with the advancement of xerographic (electrophotographic) technology, conversion of conventional pulverized toner to polymerized toner is being attempted in toner. Polymerized toners are formally called emulsion polymerization toners or EA (Emulsion Aggregation) toners, and can form spherical toners with a small particle size of several μm and high uniformity. It becomes possible to make it clear. Also, in production, compared with the mechanical energy consumption used in the conventional kneading and pulverization methods, the use of a chemical brewing plant requires less energy consumption, reducing CO ₂ generation by about 30%. It also has the advantage of being able to. Furthermore, since the toner transfer efficiency to the recording paper is high, the residual toner is reduced, and as a result, the toner consumption can be suppressed, and the fixing temperature of the toner transferred to the recording paper more uniformly can be set low. Also excellent in terms of environment.

However, the polymerized toner has a structure in which the ratio of the surface area to the volume is high because it is a spherical shape having a small particle size of several μm and high uniformity as described above. For this reason, the charge amount per unit weight (specific charge amount) of the toner is high, and the toner is easily scattered electrostatically. Further, since it is spherical in shape, the surface energy of the toner is very small, and scattering is likely to occur due to slight physical and electrical stress. As a result, even on the path from the transfer device to the fixing device, the toner image may be scattered on the recording paper during conveyance by the guide member, resulting in an image defect. In particular, in the vicinity of the entrance of the fixing nip portion, it is necessary to adjust the conveyance direction of the recording paper in order to accurately enter the recording paper into the nip portion. Spattering is also likely to occur. Further, in a low-temperature and low-humidity environment or during the second side printing in the double-sided printing mode, the toner moisture content tends to decrease and the specific charge amount tends to increase, so that the toner image is particularly easily scattered.
Note that the technique described in Patent Document 2 described above is insufficient to suppress the disturbance of the toner image when using a polymer toner that is likely to scatter.

  Therefore, the present invention has been made to solve the technical problems as described above, and the object of the present invention is to produce a high-quality image without scattering of a toner image even when a polymerized toner is used. It is to form.

  For this purpose, the fixing device of the present invention is provided with a fixing member that heats and fixes a toner image carried on a recording material and an end portion on the fixing member side in a temperature region where the toner images are fused together. And a first guide portion that contacts the recording material and frictionally charges the recording material to a polarity opposite to the charging polarity of the toner image, and a second guide portion having heat resistance extending to the vicinity of the fixing member. And a guide member.

Here, the first guide portion of the guide member may be disposed outside a temperature region where the first guide portion is thermally deformed. In the guide member, the first guide portion can be formed of a high-resistance material positioned on the minus side in the triboelectric charging series with respect to the recording material. In particular, the first guide portion may be formed of polypropylene.
Moreover, the guide member can form the 2nd guide part with a metal. Furthermore, the first guide portion and the second guide portion can be integrally configured.
On the other hand, the toner image may be formed of a polymerized toner.

  The fixing device of the present invention is a fixing device for fixing a toner image carried on a recording material, and is movable while forming a nip portion in contact with a rotating member having a heat source and a rotating member. A pressure member and a guide member that guides the recording material to the nip portion. The guide member holds the toner image electrostatically restrained with respect to the recording material while the recording material is held in the toner image. And a downstream guide portion that guides the recording material to the vicinity of the nip portion in a state where the toner images are fused to each other. Here, the term “fusion” refers to a state in which the toner particles are not completely melted but at least the toner particles and the toner particles on the surface of the toner image adhere to each other and restrain each other. The same applies hereinafter.

Here, the rotating member may be a fixing roll having a heat source inside. The pressurizing member may be an endless belt, and may include a pressure member that presses the endless belt against the rotating member at the nip portion.
Moreover, the guide member can form an upstream guide part in a rib shape. In particular, the cross section of the upstream guide portion can be formed narrower toward the contact portion with the recording material. Furthermore, it can be characterized by embossing the surface of the downstream guide portion that conveys the recording material. In addition, the surface of the downstream guide portion on which the recording material is conveyed can be covered with a fluororesin. Furthermore, the end of the downstream guide portion on the nip portion side may be hemmed.

Further, the fixing device of the present invention has a pressure roll that can be elastically deformed, a rotatable pressure belt, a heat generating source, a fixing belt that can be driven while being in contact with the pressure roll and forming a nip portion, A pressure member that is disposed inside the fixing belt and presses the fixing belt against the pressure roll at the nip portion, and a guide member that guides the recording material to the nip portion. And holding the recording material in a state in which the toner image is fused with each other, and an upstream guide portion that guides the recording material to a region where heat is applied to the extent that the toner images are fused to each other. And a downstream guide portion that leads to the vicinity of the nip portion.
Here, the pressure member may be formed of a heat source disposed on the fixing belt.

Further, the present invention is regarded as an image forming apparatus. The image forming apparatus of the present invention includes a toner image forming unit that forms a toner image, and a transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material. And a fixing means for fixing the toner image transferred onto the recording material to the recording material, the fixing means contacting the rotating member and forming a nip portion while contacting the rotating member. The movable pressure member and the end on the nip side are arranged in a temperature region where the toner images are fused to each other, and the recording material comes into contact with the recording material and has a polarity opposite to the charging polarity of the toner image. A guide member having a first guide portion to be frictionally charged and a second guide portion having heat resistance extending to the vicinity of the nip portion is provided.
Here, the toner image forming means can form a toner image with a polymerized toner. The fixing unit can also ground the second guide portion of the guide member via a diode.

Further, the present invention is regarded as a guide member, and the guide member of the present invention is formed of a recording material carrying a toner image by a rotating member having a heat generation source and a pressure member movable while contacting the rotating member. A guide member that is transported to a nip portion that is heated to a region where heat is applied to the recording material while the toner image is electrostatically restrained with respect to the recording material. An upstream guide portion that guides the recording material and a downstream guide portion that guides the recording material to the vicinity of the nip portion in a state where the toner images are fused to each other are provided.
Here, the upstream guide portion can be formed of a high resistance material located on the minus side in the triboelectric charging series with respect to the recording material. Further, the downstream guide portion can be made of metal.

  As an effect of the present invention, it is possible to provide an image forming apparatus capable of forming a high-quality image without scattering of a toner image even when polymerized toner is used.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Embodiment 1]
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is an intermediate transfer type image forming apparatus generally called a tandem type. In the image forming apparatus 1, a plurality of image forming units 1Y, 1M, 1C, on which toner images of respective color components of yellow (Y), magenta (M), cyan (C), and black (K) are formed by electrophotography. 1K, upstream first intermediate transfer roll 21 to which Y and M toner images formed by image forming units 1Y and 1M are sequentially transferred, and C and K toner images formed by image forming units 1C and 1K are sequentially transferred. The downstream first intermediate transfer roll 22, the upstream first intermediate transfer roll 21, and the second intermediate transfer roll 23 to which the respective color component toner images transferred to the downstream first intermediate transfer roll 22 are sequentially transferred, the second intermediate A transfer roll 30 that collectively transfers the superimposed toner images transferred to the transfer roll 23 onto the paper P, and a fixing device 60 that fixes the toner images transferred by the transfer roll 30 onto the paper P are provided. There. Moreover, it has the control part 40 which controls operation | movement of each apparatus.

  In the image forming apparatus 1 of the present embodiment, each of the image forming units 1Y, 1M, 1C, and 1K has a charger 12 that charges the photosensitive drum 11 around the photosensitive drum 11 that rotates in the direction of arrow A. A laser exposure device 13 for writing an electrostatic latent image on the photosensitive drum 11 (exposure beam is indicated by a symbol Bm in the figure), each color component toner is accommodated, and the electrostatic latent image on the photosensitive drum 11 is made of toner. Electrophotographic devices such as a developing unit 14 for visualizing and a drum cleaner 17 for removing residual toner on the photosensitive drum 11 are sequentially arranged. Further, the image forming units 1Y and 1M are arranged around the upstream first intermediate transfer roll 21, and the image forming units 1C and 1K are arranged around the downstream first intermediate transfer roll 22, and each photosensitive drum. 11 is in contact with the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22.

The upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 are elastic materials in which an appropriate amount of a conductive agent such as carbon black is contained in a rubber material such as silicone rubber in a shaft made of metal such as iron or SUS. A cylindrical roll having a diameter of 60 mm, which is formed by covering a body layer and further laminating a release layer on the surface of the elastic body layer. The volume resistivity of the elastic body layer is formed to be 10 ⁵ to 10 ⁹ Ωcm. The upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 are rotated at the same speed as the photosensitive drum 11 in the direction B shown in FIG. 1 by a drive motor (not shown). Further, the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 are installed in contact with the second intermediate transfer roll 23.

The second intermediate transfer roll 23 is formed by coating a shaft made of a metal such as iron or SUS with an elastic body layer containing a suitable amount of a conductive agent such as carbon black in a rubber material such as silicone rubber. A cylindrical roll having a diameter of 60 mm, which is formed by laminating a release layer on the surface. The volume resistivity of the elastic layer is formed to be 10 ⁸ to 10 ¹² Ωcm. The second intermediate transfer roll 23 is driven by a drive motor (not shown) at a speed equal to the rotational speed of the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 in the direction C shown in FIG. It is rotating.
The transfer roll 30 includes a shaft, an elastic layer fixed around the shaft, and a resin layer covered with the elastic body layer. The shaft is a cylindrical bar made of metal such as iron or SUS. The elastic layer is a cylindrical roll made of urethane rubber containing an appropriate amount of a conductive agent such as carbon black and having a volume resistivity of 10 ⁶ to 10 ⁹ Ωcm.
Further, the upstream first intermediate transfer roll 21, the downstream first intermediate transfer roll 22, and the second intermediate transfer roll 23 have a cleaner 21a for removing residual toner and paper dust on the surface of the roll after transfer and cleaning. , 22a, and 23a are provided.

  In the image forming apparatus according to the present embodiment, as a paper transport system, a paper tray 50 that stores paper P, a pick-up roll 51 that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing, and a pickup After the transfer rolls 52 and 53 for transporting the paper P fed by the roll 51, the paper P transported by the transport rolls 52 and 53 is transferred to the transfer roll 30 at a predetermined timing, and after being transferred by the transfer roll 30. A conveyance guide 55 for conveying the conveyed paper P to the fixing device 60 is provided.

Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described.
In the image forming apparatus 1 as shown in FIG. 1, image data output from an image reading device (IIT) not shown or a personal computer (PC) not shown is subjected to predetermined image processing by an image processing device (IPS) not shown. Is applied, the image forming operation is executed by the image forming units 1Y, 1M, 1C, and 1K. In IPS, the input reflectance data is subjected to predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing. Is done. The image data subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to each laser exposure unit 13.

  The laser exposure unit 13 irradiates the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, for example, with an exposure beam Bm emitted from a semiconductor laser in accordance with the input color material gradation data. Yes. In each of the photoconductive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged to, for example, −380 V by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13, so that the bright portion potential is − A 70V electrostatic latent image is formed. The formed electrostatic latent image is reversely developed by the negatively charged toners of Y, M, C, and K by the developing devices 14 of the respective image forming units 1Y, 1M, 1C, and 1K. At this time, the developing device 14 is applied with a developing bias obtained by superimposing a DC component of −300 V with an AC component of 4 kHz and 1.6 kVpp. Here, as the toner of each color of Y, M, C, and K, a polymerized toner manufactured by an emulsion polymerization method (EA method) is used. Since the polymerized toner is a spherical toner having a small particle size of several μm and high uniformity, the specific charge amount can be relatively high as −20 to −40 μC / g, and the image quality of the color print can be remarkably sharpened. It becomes possible.

The toner images formed on the photoconductive drums 11 of the image forming units 1Y and 1M are transferred to the upstream first intermediate transfer roll 21, and the toner formed on the photoconductive drums 11 of the image forming units 1C and 1K. The image is transferred to the downstream first intermediate transfer roll 22. Thereafter, the toner images transferred to the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 are transferred to the second intermediate transfer roll 23. Further, the toner image finally transferred to the second intermediate transfer roll 23 is collectively transferred onto the paper P by the transfer roll 30.
Here, FIG. 2 is a diagram illustrating a flow until the toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the paper P. An electric field (primary transfer bias) having a polarity opposite to the charging polarity (minus polarity) of the toner is applied to the upstream first intermediate transfer roll 21 by applying a voltage of usually +250 to 500 V, for example, +320 V. Yes. Therefore, the magenta (M) toner image is first primarily transferred from the photosensitive drum 11M of the image forming unit 1M along the rotation direction (arrow B) of the upstream first intermediate transfer roll 21, and then the image forming unit 1Y. A yellow (Y) toner image is primarily transferred from the photosensitive drum 11Y, and the M toner image and the Y toner image are sequentially superimposed on the surface of the upstream first intermediate transfer roll 21.

Similarly, a voltage of +250 to 500 V, for example, +320 V is normally applied to the downstream side first intermediate transfer roll 22. Therefore, the black (K) toner image is first primarily transferred from the photosensitive drum 11K of the image forming unit 1K along the rotation direction (arrow B) of the downstream first intermediate transfer roll 22 and then the image forming unit 1C. A cyan (C) toner image is primarily transferred from the photoreceptor drum 11 </ b> C, and the K toner image and the C toner image are sequentially superimposed on the surface of the downstream first intermediate transfer roll 22.
The voltage value applied to the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 is set to an optimum value by the control unit 40 based on the charged state of the toner, the ambient temperature, the humidity, and the like. Can do.

After the toner images are sequentially primary transferred onto the surfaces of the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22, the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 rotate. Then, the toner image is conveyed to a contact portion with the second intermediate transfer roll 23. The second intermediate transfer roll 23 is usually applied with a voltage of +600 to 1200 V, for example, +700 V, and the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 to which a voltage of +320 V is applied, In the meantime, an electric field (secondary transfer bias) having a polarity opposite to the charging polarity (minus polarity) of the toner is applied. For this reason, the toner images carried on the upstream first intermediate transfer roll 21 and the downstream first intermediate transfer roll 22 are first, along the rotation direction (arrow C) of the second intermediate transfer roll 23, first the upstream first intermediate transfer roll 21. The M toner image and the Y toner image are secondarily transferred from the transfer roll 21, and then the K toner image and the C toner image are secondarily transferred from the downstream first intermediate transfer roll 22, so that the surface of the second intermediate transfer roll 23 is transferred. In addition, the M toner image, the Y toner image, the K toner image, and the C toner image are superimposed.
Note that the writing timing in each laser exposure unit 13 is controlled by the control unit 40 so that the registration of the toner images of each color on the surface of the second intermediate transfer roll 23 is performed with high accuracy.

  After the toner images are sequentially secondary transferred onto the surface of the second intermediate transfer roll 23, the second intermediate transfer roll 23 rotates and the toner image is conveyed to a contact portion (final transfer portion) E with the transfer roll 30. Is done. On the other hand, in the paper transport system, the pickup roll 51 rotates in accordance with the timing at which the toner image is transported to the final transfer portion E, and the paper P of a predetermined size is supplied from the paper tray 50. The paper P supplied by the pickup roll 51 is conveyed by the conveyance rolls 52 and 53 and reaches the final transfer portion E. When reaching the final transfer portion E, the registration roll 54 rotates in accordance with the movement timing of the second intermediate transfer roll 23 carrying the toner image, so that the position of the paper P and the position of the toner image are changed. Alignment is made.

  In the final transfer portion E, the transfer roll 30 is pressed against the second intermediate transfer roll 23. At this time, the sheet P conveyed at the same timing is sandwiched between the second intermediate transfer roll 23 and the transfer roll 30 that rotates in the same direction (arrow D direction). At that time, a voltage of +1200 to 5000 V, for example +1200 V, is normally applied to the transfer roll 30, and the toner charging polarity (minus polarity) with the second intermediate transfer roll 23 to which a voltage of +700 V is applied. In contrast, an electric field having a reverse polarity (final transfer bias) is applied. The unfixed toner image carried on the second intermediate transfer roll 23 is collectively electrostatically transferred onto the paper P in the final transfer portion E pressed by the transfer roll 30 and the second intermediate transfer roll 23. Is done.

Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the second intermediate transfer roll 23 by the transfer roll 30, and is provided downstream of the second intermediate transfer roll 23 in the sheet transport direction. Passes through the conveyance guide 55.
A plurality of ribs are formed on the surface of the conveyance guide 55 along the conveyance direction of the paper P, and a metal plate is disposed between the ribs at a position 1.5 mm lower than the rib surface. The metal plate is grounded via a diode and exerts an electrostatic adsorption force on the paper P passing through the rib surface. The diode is provided in order to prevent the transfer current supplied to the transfer roll 30 from leaking from the conveyance guide 55 through the paper P when the resistance of the paper P decreases in a high temperature and high humidity environment. . With this diode, the potential of the metal plate is maintained at +1 to 2 kV when the potential difference between the transfer roll 30 and the second intermediate transfer roll 23 is set to 500V. Note that a fan for sucking and transporting the paper P is provided in the transport guide 55 in order to attract and transport the paper P to the rib surface even in a high temperature and high humidity environment.

The ribs of the conveyance guide 55 are electrically high resistance (insulating), and are configured to have a characteristic of frictionally charging the paper P to a positive polarity opposite to the toner polarity by contact with the paper P. ing. That is, the rib itself is made of a high resistance material located farther from the paper in the triboelectric charging series. Examples of such a material include polypropylene (PP), polyethylene (PE), Teflon (trade name), and the like, and the substrate is made of PP having excellent processability, for example.
In this way, the rib is formed of a material that is frictionally charged with a positive polarity opposite to the toner polarity with respect to a paper such as PP, so that the paper P is frictionally charged by contacting the rib, and the back surface of the paper P The amount of positive polarity charge held on the side increases. Further, since the rib is formed of a high-resistance material, electric charges are not leaked from the back surface of the paper P. Therefore, since the toner image is more strongly restrained with respect to the paper P, a phenomenon in which the toner image is scattered around can be suppressed.
On the other hand, the area where the rib contacts the paper P is made as small as possible. The ribs frictionally charge the paper to the positive polarity, but the ribs themselves are charged to the negative polarity. Therefore, when the contact area between the ribs and the paper P increases, the toner image (negative polarity) is generated by the negative charge held on the surface of the ribs. This is because the repulsive force against the toner becomes strong, and conversely, the toner image is likely to be scattered. Therefore, the rib is formed in an elongated shape along the conveyance direction of the sheet P, and the cross-sectional shape in the vicinity of the rib surface is formed so as to have a semicircular or triangular shape with a small tip area.

The sheet P that has passed through the conveyance guide 55 is conveyed to the fixing device 60. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed by a paper discharge roll 57 to a paper discharge mounting portion 58 provided in a discharge portion of the image forming apparatus 1.
On the other hand, after the transfer to the paper P is finished, the residual toner remaining on the surfaces of the upstream first intermediate transfer roll 21, the downstream first intermediate transfer roll 22, and the second intermediate transfer roll 23 is the With rotation, it is conveyed to the cleaning unit and removed by cleaners 21a, 22a, and 23a, respectively.

Next, the fixing device 60 used in the image forming apparatus of the present embodiment will be described.
FIG. 3 is a side sectional view showing a configuration of the fixing device 60 of the present embodiment. The fixing device 60 includes a fixing roll 61 as an example of a rotating member, an endless belt 62 as an example of a pressure member, a pressure pad 64 that is pressed from the fixing roll 61 via the endless belt 62, and a sheet P through a nip portion N. A main part is constituted by a fixing entrance guide 56 as an example of a guide member that guides the light. In the fixing device 60 of the present embodiment, a fixing member is constituted by the fixing roll 61 and the endless belt 62, and the pressure pad 64 constitutes a part of the pressure member.

The fixing roll 61 is configured by laminating a heat-resistant elastic layer 612 and a release layer 613 around a metal core (cylindrical core) 611.
Inside the fixing roll 61, a halogen heater 66 is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. The control unit 40 of the image forming apparatus 1 controls the lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69, and the surface temperature of the fixing roll 61 is maintained at a predetermined set temperature (for example, 170 ° C.). It is adjusted so that.
The endless belt 62 is rotatably supported by a pressure pad 64 and an edge guide 80 described later. The nip portion N is disposed in pressure contact with the fixing roll 61.

The pressure pad 64 is disposed inside the endless belt 62 while being pressed against the fixing roll 61 via the endless belt 62, and forms a nip portion N with the fixing roll 61.
In the pressure pad 64, a pre-nip member 64a for securing a wide nip portion N (the length in the moving direction of the endless belt 62 and the fixing roll 61) is arranged on the inlet side of the nip portion N, and the fixing roll 61 is distorted. Is provided on the outlet side of the nip portion N. Further, in order to reduce the frictional resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64, a low friction sheet 68 is provided on the surface of the pre-nip member 64a and the peeling nip member 64b in contact with the endless belt 62. . The pressure pad 64 and the low friction sheet 68 are held by a metal holder 65.

  The fixing roll 61 is rotated in the direction of arrow F by a drive motor (not shown), and the endless belt 62 is also rotated by this rotation. The sheet P on which the toner image is electrostatically transferred in the final transfer portion E of the image forming apparatus 1 shown in FIG. 1 is guided by the fixing inlet guide 56 and conveyed to the nip portion N. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the fixing roll 61. In the fixing device 60 of the present embodiment, since the nip portion N can be configured widely by the concave pre-nip member 64a that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

In addition, in the fixing device 60, by disposing the peeling nip member 64b so as to protrude from the outer peripheral surface of the fixing roll 61, distortion of the fixing roll 61 is locally caused in the exit region (peeling nip portion) of the nip portion N. It is configured to be large. If the separation nip member 64b is arranged in this way, the fixed paper P passes through the locally formed distortion when passing through the separation nip portion, and therefore is wound around the fixing roll 61. The sheet P can be effectively peeled off.
In particular, by locally increasing the distortion of the fixing roll 61, it is possible to obtain high peeling performance with a small amount of distortion. Therefore, even when a thin heat-resistant resin is used as the release layer 613 of the fixing roll 61, generation of paper wrinkles on the paper P can be suppressed. Further, peeling between the heat-resistant elastic layer 612 and the release layer 613 hardly occurs, and the reliability of the component performance over a long period can be improved together with maintaining the peeling performance.

Furthermore, since the distortion amount of the fixing roll 61 can be reduced, the heat-resistant elastic body layer 612 of the fixing roll 61 can be thinned. Therefore, since the heat capacity of the fixing roll 61 can be reduced, the warm-up time can be shortened and the power consumption can be reduced. Further, since the heat-resistant elastic body layer 612 having a low thermal conductivity can be thinned, the thermal resistance between the inner surface and the outer surface of the fixing roll 61 can be reduced and the thermal response can be improved. Suitable for high speed.
Note that a peeling member 70 may be disposed on the downstream side of the nip portion N of the fixing roll 61 as an auxiliary means for peeling. The peeling member 70 is held by a holder 72 in a state in which the peeling baffle 71 is close to the fixing roll 61 in a direction (counter direction) opposite to the rotation direction of the fixing roll 61.

Next, each member constituting the fixing device 60 will be described in detail.
First, the fixing roll 61 is a roll having an outer diameter of 26.5 mm. The core 611 is composed of a cylindrical body made of metal such as iron, aluminum, SUS or the like with high thermal conductivity. The outer diameter and thickness of the core 611 can be reduced in diameter and thickness in the fixing device 60 of the present embodiment because the pressing force of the pressure pad 64 is small.
Any material can be used for the heat-resistant elastic layer 612 as long as it is an elastic body having high heat resistance. In particular, it is preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 25 to 40 ° (JIS-A), and specific examples include silicone rubber and fluorine rubber.

  The release layer 613 may be any resin as long as it is a heat resistant resin. For example, a silicone resin, a fluorine resin, or the like can be used. From the viewpoint of safety, a fluororesin is suitable. As the fluororesin, PFA, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer), or the like can be used. The thickness of the release layer 613 is preferably 5 to 30 μm, more preferably 10 to 20 μm. If the thickness of the release layer 613 is less than 5 μm, the paper P is likely to be wrinkled due to the distortion of the fixing roll 61, while if it exceeds 30 μm, the release layer 613 becomes hard and the image has defects such as uneven gloss. This is because there is an increase in the possibility of the occurrence of both.

The endless belt 62 is an endless belt whose original shape is formed in a cylindrical shape with a diameter of 30 mm. The endless belt 62 includes a base layer and a release layer coated on the surface or both surfaces of the base layer on the fixing roll 61 side. . The base layer is formed of a polymer such as polyimide, polyamide, or polyimideamide, or a metal such as SUS, nickel, or copper, and has a thickness of 30 to 200 μm, preferably 50 to 125 μm, and more preferably about 75 to 100 μm. The release layer coated on the surface of the base layer is formed of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm.
Further, the inner peripheral surface of the endless belt 62 has a surface roughness Ra (arithmetic average roughness) set to 0.4 μm or less in order to reduce the frictional resistance with the pressure pad 64. Further, the outer peripheral surface of the endless belt 62 is set to have a surface roughness Ra of 1.2 to 2.0 μm so that the driving force from the fixing roll 61 is easily received.

As described above, the pressure pad 64 includes the pre-nip member 64 a and the peeling nip member 64 b and is supported by the holder 65. An elastic body such as silicone rubber or fluorine rubber, a leaf spring, or the like can be used for the prenip member 64 a, and the surface on the fixing roll 61 side is formed in a concave shape that substantially follows the outer peripheral surface of the fixing roll 61.
The peeling nip member 64b is formed of a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the peeling nip member 64b, the outer surface shape in the nip portion N is formed in a convex curved surface shape having a constant radius of curvature.

The low friction sheet 68 is provided to reduce the frictional resistance (friction resistance) between the inner peripheral surface of the endless belt 62 and the pressure pad 64, and is formed of a material having a small friction coefficient and excellent wear resistance and heat resistance. doing. Further, minute unevenness is formed on the surface of the low friction sheet 68 on the endless belt 62 side so that the lubricant applied to the inner peripheral surface of the endless belt 62 can enter the sliding portion with the endless belt 62. Yes. The roughness of the irregularities is Ra (arithmetic mean roughness) of 5 to 30 μm. This is not appropriate if the roughness of the unevenness is smaller than Ra = 5 μm, and it is not appropriate because it is difficult to allow a sufficient lubricant to enter the sliding portion with the endless belt 62. This is based on the fact that the mark is not preferable because it is noticeable as uneven gloss when OHP or coated paper is fixed. Furthermore, the low-friction sheet 68 is configured so as not to infiltrate the lubricant (difficult to pass through) so that the lubricant does not penetrate and leak from the back surface. Specifically, a porous resin fiber cloth made of a fluororesin is used as a base layer, and a surface of the pressure pad 64 is wrapped with a PET resin sheet, a sintered PTFE resin sheet, and Teflon (trade name) are impregnated. A glass fiber sheet or the like can be used.
The low friction sheet 68 may be configured separately from the pre-nip member 64a and the peeling nip member 64b, or may be configured integrally with the pre-nip member 64a and the peeling nip member 64b.

  The holder 65 is provided with a lubricant application member 67 along the longitudinal direction of the fixing device 60. The lubricant application member 67 is made of heat-resistant felt, and is impregnated with about 3 g of a lubricant such as amino-modified silicone oil having a viscosity of 300 cs, for example. The lubricant application member 67 is disposed so as to be in contact with the inner peripheral surface of the endless belt 62, and always supplies an appropriate amount of lubricant to the inner peripheral surface of the endless belt 62 by osmotic pressure from the heat-resistant felt. . The lubricant application member 67 is configured such that only the edge portion of the heat resistant felt is in contact with the inner peripheral surface of the endless belt 62 so that the supply of lubricant from the heat resistant felt is not excessive. Thus, the lubricant is supplied to the sliding portion between the endless belt 62 and the low friction sheet 68, and the friction resistance between the endless belt 62 and the pressure pad 64 via the low friction sheet 68 is further reduced, so that the endless belt 62 is smoothly rotated.

Next, a configuration for supporting the endless belt 62 in the fixing device 60 will be described.
FIG. 4 is a cross-sectional view of the end portion of the fixing device 60 for explaining a state in which the endless belt 62 is supported, and is a view seen from the downstream side in the conveyance direction of the paper P.
As shown in FIG. 4, edge guides 80 are disposed at both ends of the holder 65. The edge guide 80 is provided outside the belt traveling guide portion 801 and the belt traveling guide portion 801 having a cylindrical shape in which a notch is formed in a portion corresponding to the nip portion N and the vicinity thereof, that is, a C-shaped cross section, and an endless belt. A flange portion 802 formed with an outer diameter larger than the inner diameter of 62 and a holding portion 803 provided outside the flange portion 802 for positioning and fixing the edge guide 80 to the fixing device 60 main body. .
Both ends of the holder 65 are fixed and supported on the inner side surface of the flange portion 802. Further, the belt traveling guide portion 801 is disposed so as to overlap with a certain region of the end portion of the holder 65.

The endless belt 62 is supported by the outer peripheral surface of the belt traveling guide portion 801 except for the nip portion N and the vicinity thereof, and rotates along the outer peripheral surface of the belt traveling guide portion 801. (See also FIG. 3). Accordingly, the belt traveling guide portion 801 is formed of a material having a small coefficient of static friction so that the endless belt 62 can smoothly rotate, and further has a thermal conductivity so that it is difficult to take heat away from the endless belt 62. Made of low material.
Further, the flange portion 802 is disposed such that the interval between the inner side surfaces of the flange portion 802 disposed at both ends of the holder 65 substantially coincides with the width of the endless belt 62, and the endless belt 62 moves in the width direction ( Belt walk) is regulated. As described above, the endless belt 62 is set so that the movement in the rotation direction and the width direction is restricted by the edge guide 80.
The endless belt 62, except for the nip portion N, is made of only the lubricant application member 67 and the edge guide 80, so that the frictional resistance can be made as small as possible, and heat loss is also reduced. Can be small.

In the fixing device 60 according to the present embodiment, the fixing inlet guide 56 that guides the sheet to the nip portion N is provided on the lower side of the conveyance path of the sheet P, and a heat resistant surface in which a plane toward the nip portion N is formed. A downstream guide portion (second guide portion) and an upstream guide portion (first guide portion) that forms a plane for guiding the paper P to a plane formed in the downstream guide portion. The end portion on the nip portion N side of the upstream guide portion is disposed so as to be located upstream of the end portion on the nip portion N side of the downstream guide portion in the transport direction of the paper P.
FIG. 5 is a perspective view for specifically explaining the configuration of the fixing inlet guide 56. As shown in FIG. 5, the fixing entrance guide 56 includes a downstream guide portion 561 and an upstream guide portion 562. The downstream guide portion 561 is formed with a flat portion 561a facing the nip portion N, and an end surface 561b that is hemmed on the nip portion N side. The end surface 561 b on the nip portion N side is formed substantially parallel to the rotation shafts of the fixing roll 61 and the endless belt 62.
Further, the upstream guide portion 562 has a plate-like rib 562a arranged in the upstream direction in the transport direction of the paper P of the downstream guide portion 561 toward the paper P transport direction along the longitudinal direction of the downstream guide portion 561. It is configured by arranging multiple. The rib 562a is formed with a convex portion 562b protruding from the flat surface portion 561a of the downstream guide portion 561. Furthermore, the end portion 562c on the nip portion N side of the rib 562a is disposed so as to be located upstream of the end surface 561b on the nip portion N side of the downstream guide portion 561 in the conveyance direction of the paper P.

Here, FIG. 6 is a perspective view illustrating the configuration of the downstream guide portion 561 and the upstream guide portion 562 of the fixing inlet guide 56 in more detail. As shown in FIG. 6, in the upstream guide portion 562, the convex portions 562b of all the ribs 562a arranged in the conveyance direction of the paper P form a virtual plane (virtual plane) 562d as a whole, The virtual plane 562d is configured to be positioned closer to the paper P side than the plane portion 561a of the downstream guide portion 561. That is, a step is provided between the flat portion 561a of the downstream guide portion 561 and the virtual plane 562d formed by the convex portion 562b, and the sheet P is conveyed along the virtual plane 562d formed by the convex portion 562b in the upstream guide portion 562. The downstream guide portion 561 is configured not to contact the flat surface portion 561a.
Further, the end 562c on the nip portion N side of the rib 562a is positioned on the upstream side in the transport direction of the paper P from the end surface 561b on the nip portion N side of the downstream guide portion 561. Further, the end surface 561b on the nip portion N side of the downstream guide portion 561 is subjected to a hemming process that is bent to the opposite side (lower side in FIG. 6) to the conveyance side of the paper P.

Next, the effect of the fixing entrance guide 56 on the paper P will be described.
The paper P onto which the toner images are collectively transferred from the second intermediate transfer roll 23 in the final transfer portion E of the image forming apparatus 1 is conveyed to the fixing inlet guide 56 of the fixing device 60 through the conveying guide 55. In the fixing entrance guide 56, the paper P first contacts the convex portion 562b of the upstream guide portion 562, and is conveyed along a virtual plane 562d formed by the convex portion 562b. At this time, since a step is provided between the flat surface portion 561a of the downstream guide portion 561 and the virtual plane 562d formed by the convex portion 562b, the paper P does not directly contact the flat surface portion 561a of the downstream guide portion 561. It is conveyed in the state.
When the paper P passes through the upstream guide portion 562, the toner image is carried on the paper P, but the charge of the toner image (minus) is applied to the back surface of the paper P by the transfer roll 30 in the final transfer portion E. The toner image is constrained to the paper P by the Coulomb force between the positive polarity and the charge on the back side of the paper P. When the paper P comes into contact with the convex portion 562b of the upstream guide portion 562, the back surface in a state where a positive polarity charge is held comes into contact with the convex portion 562b.

Here, the convex portion 562b is electrically high resistance (insulating), and is configured to have a characteristic of frictionally charging the paper P to a positive polarity by contact with the paper P. That is, the convex portion 562b itself is made of a high-resistance material located far from the paper in the triboelectric charging series. Examples of such a material include polypropylene (PP), polyethylene (PE), Teflon (trade name), and the like, and the convex portion 562b is formed of PP having excellent workability, for example.
As described above, the convex portion 562b is formed of a material that is frictionally charged with a positive polarity with respect to paper such as PP, so that the paper P comes into contact with the convex portion 562b of the upstream guide portion 562 and is frictionally charged. The amount of positive polarity charge held on the back side of P increases. Further, since the convex portion 562b is formed of a high-resistance material, electric charges are not leaked from the back surface of the paper P. Therefore, since the toner image is more strongly restrained with respect to the paper P, a phenomenon in which the toner image is scattered around can be suppressed.
In particular, when a polymerized toner is used, the polymerized toner has a structure in which the ratio of the surface area to the volume is high because the polymerized toner has a small particle diameter of several μm and a highly uniform spherical shape. For this reason, the charge amount per unit weight (specific charge amount) of the toner is high, and the toner is easily scattered electrostatically. Further, since it is spherical in shape, the surface energy of the toner is very small, and scattering is likely to occur due to slight physical and electrical stress. Therefore, the effect of forming the convex portion 562b with a material that is triboelectrically charged to a positive polarity with respect to paper such as PP is great.

  On the other hand, the area where the convex portion 562b contacts the paper P is made as small as possible. The convex portion 562b frictionally charges the paper with a positive polarity, but the convex portion 562b itself is charged with a negative polarity. Therefore, when the contact area between the convex portion 562b and the paper P increases, the negative charge held on the surface of the convex portion 562b is increased. This is because the electric repulsive force with respect to the toner image (negative polarity) becomes strong, and conversely, the toner image is easily scattered. Accordingly, as shown in FIG. 6, the convex portion 562b of the upstream guide portion 562 is formed in an elongated shape with a width of 0.5 to 0.7 mm along the conveyance direction of the paper P, and the cross-sectional shape is substantially semicircular. It is formed so that the area of the tip becomes small like a substantially triangular shape.

By the way, the fixing entrance guide 56 is a member provided to accurately guide the paper P to the nip portion N, and therefore is arranged to extend to the vicinity of the nip portion N so that the paper P is directed toward the nip portion N with high accuracy. There is a need to. In a configuration in which the fixing entrance guide 56 cannot accurately guide the paper P to the vicinity of the nip portion N, the paper P hits a member such as the fixing roll 61 or the endless belt 62 before reaching the nip portion N, and a paper jam or This is because it causes paper breakage and further image disturbance.
However, when a material such as the PP described above that is triboelectrically charged with a positive polarity is used as the material constituting the convex portion 562b, the material is a resin, so that it extends to the vicinity of the nip portion N. May be deformed or melted by the heat from the fixing roll 61.

Therefore, the fixing inlet guide 56 of the present embodiment is arranged by extending the downstream guide portion 561 formed of a material such as a metal resistant to heat to the vicinity of the nip portion N, and the upstream guide portion 562 is the fixing roller 61. The end portion on the nip portion N side is disposed so as to be located in a region where heat is applied to the extent that the toner particles are fused to each other from the fixing roll 61.
As described above, the upstream guide portion 562 can maintain a state in which the toner image is strongly restrained with respect to the paper P to such an extent that the toner image is prevented from scattering around. However, when the paper P leaves the upstream guide portion 562 and reaches the downstream guide portion 561, the downstream guide portion 561 is formed of a heat-resistant material such as a metal that is resistant to heat. By contacting the side guide portion 561, the positive charge held on the back surface of the paper P becomes unstable, and the toner image is likely to be scattered. Therefore, the upstream guide portion 562 is disposed so as to be located in a region that receives heat from the fixing roll 61 such that the toner particles are fused to each other on the nip portion N side. Therefore, in the downstream area of the upstream guide portion 562, the toner image on the paper P is not completely melted, but at least toner particles and toner particles present on the surface of the toner image adhere to each other and are restrained. Since “bonding” occurs, the occurrence of scattering can be suppressed. In particular, when a polymerized toner is used as the toner, the polymerized toner has a characteristic of being easily scattered, and can be fused to each other at a relatively low temperature as compared with a conventional pulverized toner. Therefore, it is easy to fuse the toners even at a position relatively away from the fixing roll 61.

As described above, in the fixing device 60 of the present embodiment, the fixing inlet guide 56 is formed of a highly heat-resistant downstream guide portion 561 such as metal and a high-resistance material that frictionally charges the paper with a positive polarity. The downstream guide portion 561 extends to the vicinity of the nip portion N, and the upstream guide portion 562 is not deformed by the heat of the fixing roll 61. The nip portion N side is disposed so as to be located in a region where heat is applied so that the toner particles are fused to each other from the fixing roll 61. With this configuration, in a region where the toner particles are not heated to such a degree that the toner particles are fused to each other, the upstream guide portion 562 suppresses the toner image from being scattered to the sheet P to the extent that the toner image is prevented from scattering. Maintain a state of being restrained electrically. Further, in the state as it is, the paper P is conveyed on the upstream guide portion 562 from the fixing roll 61 to a region where heat is applied to the extent that the toner particles are fused with each other, and the toner particles are fused with each other. Then, the sheet P is conveyed to the nip portion N using the downstream guide portion 561 having high heat resistance. As a result, scattering of the toner image can be suppressed, and the paper P can be accurately guided to the nip portion N.
Here, in the fixing device 60 of the present embodiment, when PP is used as the material of the rib 562a of the upstream guide portion 562, the heat resistant temperature at which PP does not deform is about 120 ° C. or less, and the polymerized toner is melted. Since the temperature at which adhesion occurs is about 100 ° C. or higher, the end portion 562c of the rib 562a is positioned so that the region on the nip portion N side of the rib 562a of the upstream guide portion 562 is located within the temperature region of 100 to 120 ° C. The nip portion N is set to a distance of 18 mm.

  In the fixing entrance guide 56 of the fixing device 60 of the present embodiment, the downstream guide portion 561 having high heat resistance and the rib-shaped upstream side formed of a high resistance material that frictionally charges the paper in a positive polarity. The guide portion 562 is configured as a separate body (two-piece structure), but the fixing inlet guide 56 is formed of a rib-shaped guide member having high heat resistance such as aluminum extending to the vicinity of the nip portion N, and this guide. On the surface of the rib in contact with the paper P in the member, the toner particles are fused by the fixing roll 61 from the upstream end of the guide member in the conveyance direction of the paper P in the region where the fixing roll 61 is not deformed by heat. A one-piece structure (one-piece structure) coated with a high-resistance material that is triboelectrically charged with positive polarity to the paper until it reaches the nip N side end located in the region where the heat reaches a certain level. It is also possible.

  By the way, as described above, when the polymerized toner is used, the toner is easily scattered even by a slight physical and electrical stress, and the toner is scattered in the final transfer portion E where the toner physically moves. A small amount of toner particles float around the final transfer portion E. The floating toner adheres to the leading edge portion of the paper P although the amount is small as the paper P is conveyed. Therefore, as the prints are overlapped, the toner gradually adheres and accumulates on the flat surface portion 561a of the downstream guide portion 561 and the end surface 561b on the nip portion N side of the fixing entrance guide 56 where the leading edge portion of the paper P contacts. . The accumulated toner becomes a stain on the back side of the paper P and causes image quality to deteriorate.

Therefore, the flat surface portion 561a and the end surface 561b of the downstream guide portion 561 are covered with a fluororesin. With this configuration, the toner attached to the leading edge portion of the paper P becomes difficult to adhere to the downstream guide portion 561 and toner accumulation can be suppressed, so that the backside contamination of the paper P can be suppressed. . Further, by covering the flat portion 561a with a fluororesin, the slipperiness is improved and the paper P can be transported smoothly.
Further, a hemming process is performed on the end surface 561b on the nip portion N side so that the end portion (edge) of the downstream guide portion 561 is away from the flat portion 561a with which the paper P contacts. Since there is a step at the edge, a slight physical vibration is generated at the leading edge portion of the paper P passing through the edge. For this reason, the toner adhering to the leading edge portion of the paper P is peeled off, and toner is likely to accumulate on the edge. Therefore, the end surface 561b on the nip portion N side is hemmed so that the end surface 561b is smoothly curved to prevent physical vibrations from occurring on the paper P passing through the end surface 561b. With this configuration, the toner adhering to the leading edge portion of the paper P becomes difficult to peel off at the end surface 561b, and the occurrence of back dirt on the paper P due to toner accumulation can be suppressed.

  Furthermore, embossing is performed on the flat surface portion 561a of the downstream guide portion 561, and a plurality of convex portions that are elongated in the conveyance direction of the paper P are formed at predetermined intervals in the longitudinal direction. Such a convex portion can reduce the contact area between the paper P and the flat portion 561a, so that the toner adhering to the leading edge portion of the paper P adheres to the flat portion 561a and the end surface 561b of the downstream guide portion 561. Can be further suppressed.

In the fixing device 60 of the present embodiment, the downstream guide portion 561 of the fixing inlet guide 56 is grounded via a diode. By using the diode, the potential of the downstream guide portion 561 can be maintained at +1 to 2 kV when the potential difference between the transfer roll 30 and the second intermediate transfer roll 23 is set to 500V. Therefore, it is possible to prevent the transfer current supplied to the transfer roll 30 from leaking from the downstream guide portion 561 via the paper P even when the resistance of the paper P is reduced in a high temperature and high humidity environment.
Note that when the distance between the fixing inlet guide 56 and the transfer roll 30 is set to be equal to or longer than the length of the maximum sheet P, or when the transfer voltage applied to the transfer roll 30 is set to 0 V, the fixing is performed. The downstream guide portion 561 of the inlet guide 56 can be directly grounded without using a diode.

  As described above, in the fixing device 60 according to the present embodiment, the fixing inlet guide 56 is a high-resistance material that frictionally charges the paper with the downstream guide portion 561 having high heat resistance, such as metal, and the paper with a positive polarity. The rib-shaped upstream guide portion 562 is formed by extending the downstream guide portion 561 to the vicinity of the nip portion N, and the upstream guide portion 562 is deformed by heat of the fixing roll 61. The end portion on the nip portion N side is disposed so as to be located in a region where heat is generated so that the toner particles are fused to each other from the fixing roll 61. With this configuration, in the fixing entrance guide 56, in the region where the heat from which the toner particles are fused to each other from the fixing roll 61 does not reach, the upstream guide portion 562 suppresses the scattering of the toner image. The state in which the toner image is electrostatically strongly restrained with respect to the paper P can be maintained. Further, while maintaining the state on the upstream guide portion 562 as it is, the sheet P is transported from the fixing roll 61 to a region where heat is applied to the extent that the toner particles are fused with each other, and the toner particles are fused with each other. Thus, it is possible to suppress the scattering of the toner image even when the electrostatic force is weakened. Then, the sheet P can be conveyed to the nip portion N by being guided to the downstream guide portion 561 having high heat resistance in a state where scattering of the toner image is suppressed. Therefore, even when polymerized toner is used as the toner, it is possible to suppress scattering of the toner image. Furthermore, since the paper P can be accurately guided to the nip portion N, it is possible to suppress the occurrence of paper jam, paper breakage, and image distortion.

  In this embodiment, the belt nip type fixing device 60 in which the endless belt 62 is pressed against the fixing roll 61 by the pressure pad 64 to form the belt nip portion N has been described. However, the fixing inlet of this embodiment is described. The guide 56 can be applied to any method as long as it is a fixing device that fixes by applying heat. For example, a heating roll method in which a pressure roll is pressed against a fixing roll to form a roll nip portion. The same effect can be obtained in the fixing device.

[Embodiment 2]
In the first embodiment, the image forming apparatus is described in which the fixing roll 61 having a heat source is used as the heating unit and the fixing device 60 using the endless belt 62 with the pressure pad 64 pressed as the pressing unit is mounted. In the second embodiment, a fixing device mounted on the image forming apparatus shown in FIG. 1 is a fixing device using a fixing belt with a heat generation source pressed as a heating unit and a pressure roll as a pressing unit. explain. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

FIG. 7 is a side cross-sectional view showing the configuration of the fixing device 90 in the present embodiment. As shown in FIG. 7, in the fixing device 90 of the present embodiment, the fixing belt 92 is disposed on the toner image carrying surface side of the paper P. A ceramic heater 82 which is a resistance heating element as an example of a heat source is disposed inside the fixing belt 92, and heat is supplied from the ceramic heater 82 to the nip portion N.
The ceramic heater 82 has a substantially flat surface on the pressure roll 91 side and is disposed over the entire width of the fixing region. The nip portion N is formed by being supported by the holder 65 and being pressed by the pressure roll 91 via the fixing belt 92. Therefore, the ceramic heater 82 also functions as a pressure member. The sheet P that has passed through the nip portion N is peeled off from the fixing belt 92 by the change in the curvature of the fixing belt 92 in the exit region (peeling nip portion) of the nip portion N.

Further, a low friction sheet 68 is disposed between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82 in order to reduce the frictional resistance between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82. The low friction sheet 68 may be configured separately from the ceramic heater 82 or may be configured integrally with the ceramic heater 82.
In addition, the lubricant application member 67 is supported on the holder 65 at a position opposite to the position where the ceramic heater 82 is supported. The lubricant application member 67 is made of heat-resistant felt, and is impregnated with about 3 g of a lubricant such as amino-modified silicone oil having a viscosity of 300 cs, for example. The lubricant application member 67 is disposed so as to be in contact with the inner peripheral surface of the fixing belt 92, and always supplies an appropriate amount of lubricant to the inner peripheral surface of the fixing belt 92 by osmotic pressure from the heat-resistant felt. . Note that the lubricant application member 67 is configured such that only the edge portion of the heat resistant felt is in contact with the inner peripheral surface of the fixing belt 92 so that the supply of the lubricant from the heat resistant felt is not excessive. Thus, the lubricant is supplied to the sliding portion between the fixing belt 92 and the low friction sheet 68, and the friction resistance between the fixing belt 92 and the ceramic heater 82 via the low friction sheet 68 is further reduced, so that the fixing belt 92 is smoothly rotated.

On the other hand, the pressure roll 91 is disposed so as to face the fixing belt 92, and is configured to rotate in the direction of arrow G by a drive motor (not shown), and the rotation of the fixing belt 92 is driven by this rotation. The pressure roll 91 includes a core (cylindrical cored bar) 911, a heat-resistant elastic body layer 912 coated on the outer peripheral surface of the core 911, and a release layer 913 made of a heat-resistant resin coating or a heat-resistant rubber coating. Has been configured. In the fixing device 90 of the present embodiment, the fixing belt 92 is an endless belt whose original shape is formed in a cylindrical shape, and is formed of a polymer such as polyimide, polyamide, or polyimideamide, or a metal such as SUS, nickel, or copper. And a release layer that is formed by PFA, PTFE, or FEP and is coated on the surface or both surfaces of the base layer on the pressure roll 91 side.
Further, a peeling member 70 can be disposed on the downstream side of the nip portion N of the fixing belt 92 as an auxiliary means for peeling. The peeling member 70 is held by the holder 72 in a state where the peeling baffle 71 is close to the fixing belt 92 in a direction (counter direction) opposite to the rotation direction of the fixing belt 92.

  Then, the sheet P on which the toner image is electrostatically transferred in the final transfer portion E of the image forming apparatus 1 shown in FIG. 1 is guided to the nip portion N of the fixing device 90 by the fixing inlet guide 56. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the ceramic heater 82 on the fixing belt 92 side. Also in the fixing device 90 of the present embodiment, since the nip portion N can be configured widely between the pressure roll 91 and the ceramic heater 82, stable fixing performance can be ensured.

  Here, in the fixing device 90 according to the present embodiment, as in the first embodiment, the fixing inlet guide 56 has a positive polarity with respect to the downstream guide portion 561 having high heat resistance such as metal and the paper. A rib-shaped upstream guide portion 562 made of a high-resistance material that is frictionally charged. The downstream guide portion 561 extends to the vicinity of the nip portion N, and the upstream guide portion 562 includes a fixing belt. It is arranged such that the end of the nip portion N side is located in a region where the heat is such that toner particles are fused to each other from the fixing belt 92.

With such a configuration, in the fixing inlet guide 56, in the region where the heat is not reached to the extent that the toner particles are fused from the fixing belt 92, the upstream guide portion 562 suppresses the scattering of the toner image. The state in which the toner image is electrostatically strongly restrained with respect to the paper P can be maintained. Further, while maintaining the state on the upstream guide portion 562 as it is, the sheet P is transported from the fixing belt 92 to a region where heat is applied to the extent that the toner particles are fused with each other, and the toner particles are fused with each other. Thus, it is possible to suppress the scattering of the toner image even when the electrostatic force is weakened. Then, the sheet P can be conveyed to the nip portion N by being guided to the downstream guide portion 561 having high heat resistance in a state where scattering of the toner image is suppressed.
Therefore, even when polymerized toner is used as the toner, it is possible to suppress scattering of the toner image. Furthermore, since the paper P can be accurately guided to the nip portion N, it is possible to suppress the occurrence of paper jam, paper breakage, and image distortion.

  As an application example of the present invention, application to an image forming apparatus such as a copying machine or a printer using an electrophotographic method, for example, application to a fixing apparatus that fixes an unfixed toner image carried on a recording paper (paper). is there. Further, there is application to an image forming apparatus such as a copying machine or a printer using an ink jet method, for example, to a fixing device that dries an undried ink image carried on a recording paper (paper).

1 is a schematic configuration diagram showing an image forming apparatus of the present invention. FIG. 6 is a diagram illustrating a flow until a toner image formed on a photosensitive drum is transferred to a sheet. FIG. 3 is a side cross-sectional view illustrating a configuration of the fixing device according to the first embodiment. FIG. 3 is a cross-sectional view of an end portion of the fixing device. FIG. 6 is a perspective view illustrating a configuration of a fixing entrance guide. FIG. 5 is a perspective view for explaining a configuration of a substrate and an insulating member of a fixing entrance guide. FIG. 4 is a side sectional view illustrating a configuration of a fixing device according to a second embodiment. FIG. 10 is a side sectional view showing a configuration of a conventional fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1Y, 1M, 1C, 1K ... Image forming unit, 11 ... Photoconductor drum, 12 ... Charger, 13 ... Laser exposure device, 14 ... Developer, 17 ... Drum cleaner, 21 ... First upstream intermediate transfer roll, 22 ... downstream first intermediate transfer roll, 23 ... second intermediate transfer roll, 30 ... transfer roll, 40 ... control part, 56 ... fixing inlet guide, 561 ... downstream guide part, 561a ... flat part, 561b ... end face, 562 ... Upstream guide part, 562a ... Rib, 562b ... Convex part, 562c ... End, 60,90 ... Fixing device, 61 ... Fixing roll, 62 ... Endless belt, 64 ... Pressure pad, 64a ... Pre-nip member, 64b ... Peeling Nip member, 65 ... holder, 66 ... halogen heater, 67 ... lubricant application member, 68 ... low friction sheet, 69 ... temperature sensor, 70 ... peeling member, 80 ... edge guide, 80 DESCRIPTION OF SYMBOLS 1 ... Belt travel guide part, 82 ... Ceramic heater, 91 ... Pressure roll, 92 ... Fixing belt

Claims (23)

A fixing member that heats and fixes the toner image carried on the recording material;
The end on the fixing member side is disposed within a temperature region where the toner images are fused to each other, and contacts the recording material to frictionally charge the recording material to a polarity opposite to the charging polarity of the toner image. A guide member having a first guide portion and a second guide portion having heat resistance extending to the vicinity of the fixing member;
A fixing device comprising:   The fixing device according to claim 1, wherein the first guide portion of the guide member is disposed outside a temperature region in which the first guide portion is thermally deformed.   2. The fixing device according to claim 1, wherein the guide member is formed of a high resistance material in which the first guide portion is positioned on the minus side in the triboelectric charging series with respect to the recording material.   The fixing device according to claim 3, wherein the first guide portion of the guide member is made of polypropylene.   The fixing device according to claim 1, wherein the second guide portion of the guide member is made of metal.   The fixing device according to claim 1, wherein the first guide portion and the second guide portion are integrally configured in the guide member.   The fixing device according to claim 1, wherein the toner image is formed of a polymerized toner. A fixing device for fixing a toner image carried on a recording material,
A rotating member having a heat source;
A pressure member that is movable while in contact with the rotating member to form a nip portion;
A guide member for guiding the recording material to the nip portion,
The guide member guides the recording material to an area where heat is applied to the extent that the toner images are fused to each other while the toner image is electrostatically restrained with respect to the recording material. And a downstream guide portion that guides the recording material to the vicinity of the nip portion in a state where the toner images are fused to each other.   The fixing device according to claim 8, wherein the rotating member is a fixing roll having the heat generation source therein.   The fixing device according to claim 8, wherein the pressure member includes an endless belt, and includes a pressure member that presses the endless belt against the rotating member in the nip portion.   The fixing device according to claim 8, wherein the guide member has the upstream guide portion formed in a rib shape.   12. The fixing device according to claim 11, wherein the guide member is formed such that a cross section of the upstream guide portion is narrowed toward a contact portion with the recording material.   9. The fixing device according to claim 8, wherein the guide member is embossed on a surface of the downstream guide portion that conveys the recording material.   The fixing device according to claim 8, wherein the guide member is coated with a fluororesin on a surface of the downstream guide portion that conveys the recording material.   The fixing device according to claim 8, wherein the guide member has an end portion on the nip portion side of the downstream guide portion that is hemmed. While the surface is elastically deformed, the pressure roll can be rotated,
A fixing belt having a heat source and being driven while being in contact with the pressure roll and forming a nip portion;
A pressure member that is disposed inside the fixing belt and presses the fixing belt against the pressure roll at the nip portion;
A guide member for guiding the recording material to the nip portion,
The guide member guides the recording material to an area where heat is applied to the extent that the toner images are fused to each other while the toner image is electrostatically restrained with respect to the recording material. And a downstream guide portion that guides the recording material to the vicinity of the nip portion in a state where the toner images are fused to each other.   The fixing device according to claim 16, wherein the pressure member includes a heat source disposed on the fixing belt. Toner image forming means for forming a toner image;
Transfer means for transferring the toner image formed by the toner image forming means onto a recording material;
Fixing means for fixing the toner image transferred onto the recording material to the recording material,
The fixing means is
A rotating member having a heat source;
A pressure member that is movable while in contact with the rotating member to form a nip portion;
The end on the nip side is disposed in a temperature region where the toner images are fused to each other, and contacts the recording material to frictionally charge the recording material to a polarity opposite to the charging polarity of the toner image. An image forming apparatus comprising: a first guide portion; and a guide member having a heat-resistant second guide portion extending to the vicinity of the nip portion.   The image forming apparatus according to claim 18, wherein the toner image forming unit forms a toner image with a polymerized toner.   The image forming apparatus according to claim 18, wherein the fixing unit includes a second guide portion of the guide member that is grounded via a diode. A guide member that conveys a recording material carrying a toner image to a nip portion formed by a rotating member having a heat source and a pressure member movable while contacting the rotating member;
An upstream guide portion for guiding the recording material to a region where heat is applied to the extent that the toner image is fused to each other while maintaining the state in which the toner image is electrostatically restrained with respect to the recording material;
And a downstream guide portion for guiding the recording material to the vicinity of the nip portion in a state where the toner images are fused to each other.   The guide member according to claim 21, wherein the upstream guide portion is formed of a high-resistance material positioned on the minus side in the triboelectric charging series with respect to the recording material.   The guide member according to claim 21, wherein the downstream guide portion is made of metal.

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