JP2007086133A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image of high quality by suppressing wax stripes formed of wax accumulated on a cleaning web. <P>SOLUTION: The cleaning web uses woven fabric or non-woven fabric whose fiber alignment angle is ≥65°. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and a fixing device used in the image forming apparatus.

  In such a fixing device, generally, a recording material is nipped and conveyed by a heating member and a pressure member pressed against the heating member, and when the recording material passes through a nip formed between the heating member and the pressure member, the toner image Is fixed by heating.

  Since the heating member comes into contact with the recording material carrying the toner image, the heating member is cleaned so that toner and paper dust adhere to the heating member. However, various improvements have been made regarding this cleaning. I came.

  In Patent Document 1, the force for pressing the cleaning member against the surface to be cleaned is locally increased with respect to the moving direction of the surface to be cleaned, thereby preventing dirt due to toner or the like from accumulating on the surface to be cleaned.

Further, in Patent Document 2, in order to prevent gloss memory generated by the wax contained in the toner being deposited on the heating member and transferred to the recording material, the contact portion between the heating rotator and the cleaning rotator and It has been proposed that the temperature of the contact portion where the cleaning rotator and the cleaning member come in contact is higher than the melting point of the wax.
JP 2002-189373 A JP 2005-43532 A

  In the conventional technique for cleaning the heating member, the problem that the cleaning is not sufficient and dirt accumulates on the heating member due to long-term use has not been solved.

  In particular, when fixing a toner image made of a wax-containing toner, the wax accumulates in a portion where the cleaning web is in contact with the surface to be cleaned, and the accumulated wax is transferred to a recording material so that a wax streak appears in the image. The problem is not solved. This wax streak is a phenomenon in which the glossiness can be non-uniformly streaked in the recording paper conveyance direction, and lowers the image quality.

  As is well known, in the fixing process of a single recording material, the cleaning web is stationary with little movement and moves continuously or intermittently at a very slow moving speed. Therefore, the accumulation of the wax described above occurs on the cleaning web and causes a reduction in image quality.

  The present invention provides an image forming apparatus that forms a high-quality image by preventing cleaning defects, in particular, wax streaks, by improving the cleaning performance of the cleaning web, and a fixing device used in the image forming apparatus. The purpose is to provide.

The object is achieved by the following invention.
1.
In a fixing device having a heating member, a pressure member pressed against the heating member, and a cleaning web for cleaning the heating member,
The fixing device, wherein the cleaning web is made of fibers and has a fiber orientation angle of 45 ° or more with respect to a moving direction of the heating member.
2.
2. The fixing device as described in 1 above, which fixes a toner image made of wax-containing toner.
3.
3. The fixing device according to claim 1, wherein the cleaning web contacts the heating member to clean the heating member.
4).
3. The fixing device according to 1 or 2, further comprising a cleaning roller that contacts the heating member, wherein the cleaning web contacts the cleaning roller to clean the heating member.
5.
5. The fixing device according to claim 1, further comprising an update unit configured to update a used portion of the cleaning web with an unused portion.
6).
An image forming apparatus comprising: an image forming unit that forms a toner image on a recording material using a wax-containing toner; and the fixing device according to any one of 1 to 5 above.

  According to the invention of any one of claims 1 to 6, a high quality image in which wax streaks generated due to the wax adhered and accumulated on the cleaning web are satisfactorily suppressed is formed.

  According to the invention of claim 4, since the heating roller is not directly rubbed and cleaned, the surface of the heating roller is prevented from being damaged and the durability of the heating roller is increased.

Hereinafter, the present invention will be described by way of embodiments of the present invention, but the present invention is not limited to the embodiments.
<Image forming apparatus>
FIG. 1 schematically shows an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes an automatic document feeder A, an image reading unit B, and an image forming unit C. In the image forming portion C, reference numeral 1 denotes a photoconductor, and the photoconductor is preferably an organic photoconductor having a photosensitive layer in which an organic photoconductor is dispersed in a resin from the viewpoints of environment and cost, but is not limited thereto. Any known photoreceptor can be used.

  The photosensitive member 1 is not limited to the drum-shaped photosensitive member illustrated, and may be a belt-shaped photosensitive member. Reference numeral 2 denotes a charging device that charges the photoreceptor 1 and forms a uniform potential on the photoreceptor 1. The charging device 2 is preferably a scorotron charger having a control grid and a discharge electrode or a contact charging type charger using a roller to which a voltage is applied.

  Reference numeral 3 denotes an exposure apparatus that exposes the photoreceptor 1. As the exposure apparatus, a scanning exposure apparatus having a scanning optical system composed of a polygon mirror, a lens, and a mirror using a laser diode as a light source, and a scanning optical apparatus having a light emitting diode array and an imaging optical fiber are preferable. Any known exposure apparatus can be used. The exposure device 3 performs dot exposure of the photoreceptor 1 according to the image data.

  A developing device 4 accommodates a two-component developer or a one-component developer, develops an electrostatic latent image on the photoreceptor 1, and forms a toner image on the photoreceptor 1. As the toner, a polymerized toner containing a wax is preferably used. A transfer device 5 includes a corona charger. The transfer device 5 charges the recording material P with a polarity opposite to that of the toner on the photoreceptor 1, and transfers the toner image to the recording material P. Reference numeral 6 denotes a separation device including a corona charger, which performs AC corona charging on the recording material P to remove the charge from the recording material P and separate it from the photoreceptor 1.

  A fixing device 7 includes a heating roller 71 as a heating member, a pressure roller 73 as a pressure member, and a heater 73. Reference numeral 8 denotes a cleaning device. Untransferred toner and untransferred toner adhere to the photoreceptor 1 after the transfer, and it is necessary to clean the photoreceptor 1 in order to perform the next image formation. The cleaning device 8 has a cleaning blade made of an elastic blade such as urethane rubber.

Reference numeral 9 denotes a recording material storage unit that stores the recording material P. The recording material storage unit 9 includes a tray or a cassette, and can be pulled out from the image forming apparatus to replenish the recording material P.
<Fixing device>
FIG. 2 is a cross-sectional view of an example of a fixing device according to an embodiment of the present invention.

  Reference numeral 71 denotes a heating roller as a heating member, which contacts the unfixed toner on the recording material P and heats and melts the toner image to be fixed. The heating roller 71 includes, from the inside, a core metal 71A, an elastic layer 71B made of a heat-resistant elastic material such as silicon rubber, and a surface layer 71C made of a releasable material such as PFA or PPFE. As the heating member, in addition to a so-called soft roller having a heat-resistant elastic layer, a so-called hard roller having no heat-resistant elastic layer and having a surface layer formed on a cored bar can be used. Further, a belt can be used instead of the roller.

  Reference numeral 72 denotes a pressure roller as a pressure member that comes into pressure contact with the heating roller 71, and is formed from the inside with a core metal 72A, an elastic layer 72B made of a heat-resistant elastic material such as silicon rubber, and a releasable material such as PFA and PPFE. A surface layer 72C is provided. As the heating member, a roller or a belt having no surface layer and having a heat-resistant elastic layer on a core metal can be used.

  Reference numeral 73 denotes a heater disposed in the fixing roller 71, which is a halogen lamp. As the heater, a resistance heating element or dielectric heating means can be used.

  The heating roller 71 and the pressure roller 72 rotate as indicated by arrows to sandwich and convey the recording material P, and the toner image T on the recording material P is heated and fixed at the nip between the two.

  74 is a cleaning roller that contacts the heating roller 71 and rotates at the contact position so that its surface moves in the same direction as the surface of the heating roller, and is made of metal or heat-resistant resin.

  75 is a cleaning web that contacts and cleans the cleaning roller 74, and is made of a woven or non-woven fabric of heat-resistant fibers such as aramid fibers.

The cleaning web 75 is updated by an original winding roll 76 serving as an updating unit and a winding roller 77 serving as an updating unit. That is, the cleaning web 75 is continuously or intermittently drawn out at a very slow speed, and is taken up from the original winding roll 76 onto the winding roll 77. Reference numeral 78 denotes a pressing member that brings the cleaning web 75 into contact with the cleaning roller 74. Examples of specific materials and configurations of the fixing device are as follows.
Fixing roller 71 · · · Outer diameter: 50mm
Core metal 71A ... 7 mm thick steel pipe elastic layer 71B ... 2mm thick silicon rubber surface layer 71C ... 30µm thick PFA
Fixing roller 72 ... Outer diameter: 50 mm
Core metal 71A ... 7mm thick iron pipe elastic layer 71B ... 1mm thick silicon rubber surface layer 71C ... 30µm thick PFA
Heat source 73... Halogen lamp cleaning roller 74 SUS pipe cleaning web 75 Aramid fiber woven fabric In the illustrated embodiment, the surface of the heating member 71 is cleaned by the cleaning roller 74, and The surface of the cleaning roller 74 is cleaned with the cleaning web 75. The surface of the cleaning roller 74 moves in the same direction as the surface of the heating member 71. In such a configuration, since the surface of the heating member 71 is not directly rubbed with the cleaning member, the surface of the heating member is prevented from being damaged by the cleaning member, and a soft roller whose surface is easily damaged is used as the heating roller. Preferred when used.

However, the cleaning web 75 may be brought into contact with the heating roller 71 to directly clean the surface of the heating roller 71.
<Cleaning web>
As described above, the cleaning web 75 is in contact with the cleaning roller 74 in a substantially stationary state during the fixing operation. Accordingly, a part of the toner image and paper dust adhere to and accumulate on the contact portion of the cleaning web 75 with the cleaning roller 74.

  In the present embodiment, for the purpose of preventing offset and winding of a recording material, an image is formed and fixed using a wax-containing toner.

  Conventionally known waxes such as paraffin waxes, polyolefin waxes, modified products thereof (oxides and grafted products), higher fatty acids, metal salts of higher fatty acids, amide waxes and ester waxes can be used. .

  The wax content of the toner is preferably about 7 to 23% by mass.

  Wax has the property of imparting gloss to the surface of the recording material, but if the distribution of the amount of wax present on the surface of the recording material is not uniform, unevenness in the glossiness of the surface of the recording material occurs, resulting in image quality. Reduce.

  However, as described above, when the wax accumulates on the cleaning web 75, a part of the wax moves and adheres to the surface of the recording material via the cleaning roller 75 and the heating roller 71, and the wax amount distribution on the surface of the recording material is reduced. It has been found that it becomes non-uniform and reduces the quality of the image.

  That is, it has been found that streaky gloss unevenness occurs in the transport direction on the surface of the recording material.

  As a result of studying to prevent such streaky uneven gloss (hereinafter referred to as “wax streaks”), a web made of fibers is used as the cleaning web 75, and the moving direction of the cleaning roller 74 with which the cleaning web 75 comes into contact is used. By using a woven or non-woven fabric having a large number of fibers oriented in a direction perpendicular to the cleaning web 75 as a cleaning web 75, the wax streaks were successfully prevented.

  Thus, a cleaning web having a fiber orientation is schematically shown in FIG.

  In FIG. 3, the number Nx (number per unit length) of fibers oriented in the X direction is larger than the number Ny (number per unit length) of fibers oriented in the Y direction. In an actual woven fabric or non-woven fabric, the fibers are not oriented regularly as shown in FIG. 3, but are oriented irregularly, but the number of fibers (Nx) observed in the cross section in the Y direction and the X direction The fiber orientation can be shown by comparison with the number of fibers (Ny) observed in the cross section.

  In the present invention, the direction of movement of the cleaning roller 74 in which the cleaning web 75 contacts the direction in which the number of oriented fibers is the largest, that is, the direction perpendicular to the cross section in which the number of observed fibers is the largest. (Or the moving direction of the heating roller) By setting the fiber orientation angle θ, which is an acute angle between Y and 45 °, to 45 ° or more, wax streaks could be prevented.

  Whether the fiber orientation angle θ in FIG. 4 is 45 ° or more depends on the tensile strength of the cleaning web 75 in the X direction (direction perpendicular to the moving direction of the cleaning roller 74) and the Y direction (moving direction of the cleaning roller). It can be determined by comparing the tensile strength of That is, if the tensile strength Fx in the X direction is equal to or greater than the tensile strength Fy in the Y direction, it can be said that the fiber orientation angle θ is equal to or greater than 45 °.

As a test method of tensile strength, for example, when a web is cut to a size of 150 mm (X direction) × 150 mm (Y direction), a tensile test is performed, and the load when it breaks or when it does not break and stretches The weight when extending 20% or more is compared between the X direction and the Y direction.

  When the fiber orientation angle θ is less than 45 °, wrinkles are likely to occur.

  A toner image was formed using a polymerized toner containing 14% by mass of paraffinic wax as the wax, and fixing was performed.

  A woven fabric made of 2-denier aramid fibers was used for cleaning.

  Table 1 shows the occurrence of wax streaks.

  As is apparent from the table, when the acute angle formed by the fiber orientation angle and the moving direction of the cleaning roller is 45 ° or more, no wax streaks occurred when the tensile strength Fx was equal to or higher than the tensile strength Fy.

1 is a diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of an example of a fixing device according to an embodiment of the present invention. It is a figure which shows typically the woven fabric or nonwoven fabric which has orientation. It is a figure which shows a fiber orientation angle.

Explanation of symbols

71 Heating roller 72 Pressure roller 73 Heater 74 Cleaning roller 75 Cleaning web θ Fiber orientation angle

Claims (6)

In a fixing device having a heating member, a pressure member pressed against the heating member, and a cleaning web for cleaning the heating member,
The fixing device, wherein the cleaning web is made of fibers and has a fiber orientation angle of 45 ° or more with respect to a moving direction of the heating member. The fixing device according to claim 1, wherein a toner image made of a wax-containing toner is fixed. The fixing device according to claim 1, wherein the cleaning web contacts the heating member to clean the heating member. The fixing device according to claim 1, further comprising a cleaning roller that contacts the heating member, wherein the cleaning web contacts the cleaning roller to clean the heating member. The fixing device according to claim 1, further comprising an update unit that updates a used portion of the cleaning web with an unused portion. An image forming apparatus comprising: an image forming unit that forms a toner image on a recording material using a wax-containing toner; and a fixing device according to claim 1.

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