JP2008250092A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which prevents toner or paper powder accumulating on an auxiliary roller from falling, that is transferred to a recording medium via fixing rotors and prevents image noise to be generated. <P>SOLUTION: The fixing device 6 has the two fixing rotors 22 and 23, with which a recording medium S having on its surface an image formed from toner T is heated under pressure, while being held in between them, and thereby the toner T is melted and fixed to the recording medium S; and the auxiliary roller 24, disposed abutted against at least the fixing rotor 22 or 23, to aid the function of the fixing rotor 22 or 23, wherein a coating layer formed by baking PFA powder resin is formed on the surface of the auxiliary roller 24. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device for an image forming apparatus.

  In an image forming apparatus, a pair of fixing rotators such as a heating roller having a heat source and a pressure roller pressed by the heating roller sandwich a recording medium such as a recording sheet on which a toner image is formed and heat while pressing. Thus, a fixing device that melts and fixes the toner image on the recording paper is used.

  In some cases, a part of toner on the recording paper or paper dust adheres to the fixing rotator of the fixing device. If there is an auxiliary roller such as a soaking roller that contacts the fixing rotator and makes the heat uniform, the toner adhering to the fixing rotator moves and accumulates on the auxiliary roller, and eventually the grown toner In some cases, the lump may fall off the auxiliary roller and be transferred onto the recording paper via the fixing rotating body. As described above, the toner dropped from the auxiliary roller and transferred onto the recording paper has a problem of generating image noise that is an unintended toner image on the recording paper and lowering the image quality.

For example, Patent Document 1 discloses a technique for providing a cleaning roller that comes into contact with a fixing rotator to collect toner and paper dust adhering to the fixing rotator. In the fixing device of Patent Document 1, a bias voltage is applied to the cleaning roller to hold the collected toner and the like. However, holding the toner collected by applying the bias voltage increases the cost of the fixing device and generates electromagnetic noise.
JP-A-8-110742 JP 2002-351248 A JP-A-8-69197 JP-A-8-286546 JP-A-9-2118607 JP-A-11-65346 JP 2002-182508 A JP 2005-49512 A JP 2001-166626 A JP 2003-29563 A

  In view of the above problems, an object of the present invention is to provide a fixing device in which toner and paper powder accumulated on an auxiliary roller are dropped and transferred to a recording medium via a fixing rotating body, and image noise is not generated. To do.

  In order to solve the above-described problems, a fixing device according to the present invention is a pair of fixing and fixing a toner on the recording medium by sandwiching and heating the recording medium having an image formed with toner on the surface. A coating roller formed by baking PFA powder resin on the surface of the auxiliary roller. It is assumed that a layer has been formed.

  According to this configuration, the releasability of the auxiliary roller can be made higher than that of the fixing rotator, so that the toner and paper powder adhering to the fixing rotator can be immediately applied to the recording medium as fine powder that is difficult to see. Transcribed. For this reason, toner and paper dust do not collect and adhere to the recording medium, and no visible image noise is generated.

  In the fixing device of the present invention, when the thickness of the coating layer on the surface of the auxiliary roller is 20 μm or more, the film is not cut, and when it is 40 μm or less, a uniform coating layer can be formed without unevenness.

  In the fixing device of the present invention, the auxiliary roller may be in contact with the fixing rotating body and driven to rotate.

  The fixing device of the present invention may further include a heating unit that heats the auxiliary roller.

  According to the present invention, by forming a coating layer having high releasability on the surface of the auxiliary roller, the toner and paper powder adhering to the fixing rotator are not collected, but agglomerated and visually recognized. By attaching to the recording medium before growing, no visible image noise is generated on the recording medium.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows an image forming apparatus 1 having a fixing device of the present invention. The image forming apparatus 1 includes four developing units 2 that form images with yellow, magenta, cyan, and black toners, a transfer belt 3, and toner images formed by the developing units 2 on the transfer belt 3 by electrostatic force. 1 is a primary transfer roller 4 for transferring, a secondary transfer roller 5 for transferring a toner image transferred to a transfer belt 3 to a recording paper (recording medium) S by electrostatic force, and an embodiment of the present invention. The image forming apparatus includes a fixing device 6 for fixing the toner image by heating the recording paper S, and four toner cartridges 7 for supplying yellow, magenta, cyan, and black toners to the developing units 2, respectively.

  Each developing unit 2 includes a rotating drum-shaped photoconductor 8, a charger 9 that charges the photoconductor 8, an exposure device 10 that exposes the charged photoconductor 8 to form an electrostatic latent image, and A developing device 11 that forms a toner image by attaching toner T to the electrostatic latent image, and a cleaner 12 that scrapes off the toner on the surface of the photoreceptor 9 are provided.

  The transfer belt 3 is stretched around a driving roller 13 that is rotationally driven, a driven roller 14, and a tension roller 15 that applies tension, and is rotated in the direction of the arrow by the driving roller 13. Further, the image forming apparatus 1 includes a cleaner unit 16 that removes toner remaining on the surface of the transfer belt 3.

  The recording paper S is supplied to the paper supply unit 17, fed one by one by the supply roller 18, transported to the secondary transfer roller 5 by the transport roller 19, passes through the fixing device 6, and is discharged by the paper discharge roller 20. 21 is discharged.

  Further, FIG. 2 shows details of the fixing device 6. The fixing device 6 includes a fixing roller 22, a pressure roller 23 pressed toward the fixing roller, a soaking roller (auxiliary roller) 24 pressed against the pressure roller 23, and a fixing heater that heats the fixing roller 22. 25 and a soaking heater 26 for heating the soaking roller 24.

  The fixing roller 22 is provided with a silicon sponge rubber layer 22b on the surface of a stainless steel core 22a, and an endless belt 22c in which a silicon electroforming sleeve is covered with silicon rubber and a PFA tube on the surface. Become.

  The pressure roller 23 is formed by providing a silicon sponge rubber layer 23b on an iron core metal 23a and covering the surface with a PFA tube 23c.

  The soaking roller 24 sand blasts the surface of an aluminum alloy cored bar (for example, a pipe having an outer diameter of 21 mm and a wall thickness of 3 mm) 24a, applies a primer with an air spray gun, and blows and drys it for about 30 minutes. The body resin is powder-coated with an electrostatic coating machine and baked at 380 ° C. to 400 ° C. for 20 minutes to 40 minutes to form a coating layer 24b having a thickness of 20 μm to 40 μm on the surface of the core metal 24a. . Due to this coating layer 24b, the surface of the soaking roller 24 has a very high release property of 110 ° to 115 ° by the contact angle method.

  The fixing roller 22 is rotationally driven by a motor (not shown), and the pressure roller 23 is pressed against the fixing roller 22 so as to be driven and rotated by the fixing roller 22. The soaking roller 24 is in pressure contact with the pressure roller 23 and is driven to rotate by the pressure roller 23.

  In this embodiment, the fixing roller 22 is heated by a fixing heater 25 which is an induction heating device, and the pressure roller 23 is heated mainly by heat conduction from the fixing roller 22. The soaking roller 24 made of an aluminum alloy having a high thermal conductivity contacts the pressure roller 23 and moves the heat of the high-temperature portion of the pressure roller 23 to the low-temperature portion. Uniform in the direction. That is, the soaking roller 24 assists its function so that the pressure roller 23 can uniformly heat the recording paper S. The soaking heater 26 compensates for heat dissipated from the soaking roller 24 to the outside.

  The fixing roller 22 and the pressure roller 23 sandwich a recording sheet S on which an image is formed with the toner T, and heat while applying pressure to melt the toner T and fix the recording sheet S on the recording sheet S. Function as. The recording paper S is passed so that the surface on which the image of the toner T is formed comes into contact with the fixing roller 22.

  In the fixing device 6 of the present embodiment, since the releasability of the soaking roller 24 is higher than that of the pressure roller 23, foreign matters such as toner and paper dust attached to the pressure roller 23 are transferred to the soaking roller 24. And remains on the pressure roller 23. Here, when the recording sheet S is newly passed, the foreign matter adhering to the pressure roller 23 is transferred to the recording sheet S.

  In this way, foreign matters such as toner adhering to the pressure roller 23 are transferred to the next recording sheet S without changing the position on the pressure roller 23, and therefore do not agglomerate with other foreign matters to generate a lump. . For this reason, the toner transferred from the pressure roller 23 to the recording paper S is merely a single particle dispersed therein and does not have a size that can be recognized by human vision.

  Further, foreign matters such as toner adhering to the fixing roller 22 may be transferred to the pressure roller 23 in a state in which the recording paper S is not passed. Since the image is transferred to the recording paper S and discharged before the recording becomes, the possibility that the recording paper S is recognized as image noise is extremely low.

  Further, since no foreign matter adheres to the soaking roller 24 with high releasability, it is not necessary to clean the soaking roller 24 and the cost can be reduced.

  The fixing device of the above embodiment and the conventional fixing device having the same temperature equalizing roller made of an aluminum alloy that is not coated on the surface, and the other structure is the same as that of the above embodiment, and fluorine on the surface of the aluminum alloy cored bar. Recording is actually performed using a comparative fixing device having a heat equalizing roller formed by forming a coating layer having a release layer of 108 ° to 112 ° by a contact angle method with a film thickness of 20 μm to 40 μm made of resin. An experiment was conducted to confirm the stain generated on the paper S.

In the experiment, black and white characters with an image density of 20% were printed continuously on 1000 sheets of A4 size copy paper of 90 g / m ² , and unplanned toner images with a minimum diameter of 0.3 mm or more were printed on the front and back of the copy paper. A total of 5 or more developed images were counted as image noise.

As a result of this experiment, the following image noise generation rates were obtained in the respective fixing devices.

  Thus, the image noise occurrence rate is greatly improved by the present invention. Note that this image noise occurrence rate is a number counted based on criteria that are considerably stricter than in practical use, and general users are conscious of noise when these image noises are densely generated. is there. Actually, when the image noise occurrence rate in this experiment is about 20% or less, there is almost no large image noise that would be worrisome for general users.

1 is a schematic diagram of an image forming apparatus including a fixing device of the present invention. 1 is a cross-sectional view of a fixing device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 6 Fixing apparatus 22 Fixing roller (fixing rotary body)
23 Pressure roller (fixing rotator)
24 Soaking roller (auxiliary roller)
24a cored bar 24b coating layer 25 fixing heater 26 soaking heater S recording paper (recording medium)
T Toner

Claims (4)

A pair of fixing rotators for fusing and fixing the toner to the recording medium by sandwiching and heating the recording medium having an image formed with toner on the surface; and
An auxiliary roller in contact with any one of the fixing rotator and assisting the function of the fixing rotator,
A fixing device comprising a coating layer formed by baking a PFA powder resin on a surface of the auxiliary roller.   The fixing device according to claim 1, wherein the coating layer on the surface of the auxiliary roller has a thickness of 20 μm or more and 40 μm or less.   The fixing device according to claim 1, wherein the auxiliary roller is driven to rotate in contact with the fixing rotating body.   The fixing device according to claim 1, further comprising a heating unit that heats the auxiliary roller.

Images