JPH09179434A - Image fixing device and image fixing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To require no oil coating or oil coating of a trace quantity, obtain sufficient fixing performance even when the printing speed is high, miniaturize a device, and reduce the cost. SOLUTION: The unfixed toner image carried on the recording paper 12 is conveyed in contact with the outer peripheral face of a fixing belt 43 for toner fusion. This image fixing device is provided with a pressing roller 45 kept in contact with one of multiple rollers arranged at the terminal end of the conveyance path of the recording paper 12 via a fixing belt 43 and a guide member 46 near the start end of the conveyance path to stabilize toner fusion. The guide member 46 serves as a roller in contact with a heat roller 41 at the start end of the conveyance path, and the pressing force is adjusted so that the nip pressure of a contact section is made smaller than the nip pressure of the terminal end section of the conveyance path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image in which an electrostatic latent image formed on a photoconductor is visualized by toner particles, transferred onto a recording paper, and then fixed on the recording paper by heat and pressure. The present invention relates to a fixing device and an image fixing method.

[0002]

2. Description of the Related Art An image fixing apparatus is important for finally determining the image quality in an image forming apparatus such as a copying machine, a facsimile, a laser printer or the like to which the electrophotographic technology is applied. A conventional image fixing device and image fixing method will be described below.

FIG. 6 is a block diagram of the essential parts of a conventional image forming apparatus.
FIG. 7 is a configuration diagram of main parts of the image fixing device. In FIG. 6, reference numeral 1 denotes a semiconductor laser, a collimator lens, a light source such as a rotating mirror and an f-θ lens, and an LSU unit having an optical system built therein, and 2 denotes an endless belt-shaped polyethylene terephthalate (PET) base material and its outer periphery. It is a photoconductor in which a photosensitive receiving layer such as a selenium (Se) -based photoconductor or an organic photoconductor (OPC) is applied in a thin layer on the surface thereof, and the photoconductor is hung on the driving roller 3 and the driven roller 4 to form an arrow. Rotate in the A direction. Designated by 5Y, 5M, 5C and 5B are developing units opposed to the photoconductor 2 and contain toners of yellow, magenta, cyan and black, respectively.

Reference numeral 6 denotes an endless belt-shaped intermediate transfer member, which is wound around a driving roller 7 and driven rollers 8 and 9 and rotates in the direction of arrow B. Reference numeral 10 denotes a first transfer roller arranged on the inner surface side of the intermediate transfer member 6.
The surface of the intermediate transfer body 6 and the surface of the photoconductor 2 are in contact with each other by the pressing force of. Reference numeral 11 denotes a second transfer roller for transferring the toner image formed on the surface of the intermediate transfer body 6 to the recording paper 12, and comes into contact with the intermediate transfer body 6 when transferring to the recording paper 12. Reference numeral 13 is a paper feed tray for accommodating the recording paper 12, and 14 is a paper feed roller for picking up the recording paper 12 from the paper feed tray 13 on the surface having a high friction coefficient and feeding the recording paper 12 to the second transfer portion in a timely manner.

Reference numeral 15 is a hollow metal heating roller whose surface is thinly coated with silicon rubber or the like, and a heater 16 such as a halogen lamp is disposed inside. Reference numeral 17 denotes a metal pressure roller having a fluororesin film layer on the outermost surface and a rubber layer in the middle, and is pressed against the heating roller 15 by an urging member (not shown). Reference numeral 18 denotes a temperature detector that detects the surface temperature of the heating roller 15. Reference numeral 19 denotes a temperature control unit that adjusts the output of the heater 16 by the heater driver 20 based on the temperature detected by the temperature detector 18 to maintain the surface temperature of the heating roller 15 at a constant temperature. 21,22
Is a discharge roller.

The operation of the image forming apparatus using the conventional image fixing method configured as described above will be described below. A latent image corresponding to a component of a first color (hereinafter, referred to as yellow) is written on the photoconductor 2 by the LSU unit 1 according to a print signal. This latent image is visualized by the developing device 5Y containing yellow toner. The visualized toner image for one color is transferred to the intermediate transfer body 6 by the first transfer roller 10 to which a voltage is applied. Similarly, the magenta, cyan, and black toner images formed on the surface of the photoconductor 2 are also transferred so as to be superimposed on the intermediate transfer body 6, and a single synthetic toner image is formed on the surface of the intermediate transfer body 6. To be done. After that, the recording paper 12 is extracted and conveyed by the paper feed roller 14 from the paper feed tray 13, and the synthetic toner image is transferred to the recording paper 12 by the second transfer roller 11 to which a voltage is applied, and is heated by the heating roller 15. It passes through the nip formed at the contact portion with the pressure roller 17.
At this time, the heating roller 15 whose surface temperature is stable at the control temperature
The synthetic toner image is melted by the contact with, and at the same time, it is semi-permanently fixed on the recording paper 12 by being pressed against the heating roller 15 and the pressure roller 17. Recording paper 12
Is conveyed from the fixing device to the paper discharge rollers 21 and 22 and stored in a paper discharge tray (not shown).

FIG. 7 is a block diagram of the essential parts of a conventional image fixing device. The recording paper 12 carrying an unfixed image is sandwiched between the heating roller 15 and the pressure roller 17, and the toner image is fixed on the recording paper 12 by heat and pressure. Heating roller 1
5 is rapidly heated at the nip portion formed between the contact portion 5 and the pressure roller 17, a large temperature gradient is generated in the toner layer, and a high temperature offset occurs in which the molten toner is offset on the heating roller 15 side. This is particularly noticeable in a color image having multiple toner layers. Therefore, the conventional image fixing device and the image fixing method are characterized in that a release oil such as silicone oil is applied to the roller surface on the unfixed toner contact side in order to prevent high temperature offset. The fixing device and the image fixing method will be described.

The heating roller 15 and the pressure roller 17 are the same as those described above, and a description thereof will be omitted here. 23
Is a tank in which oil 24 is stored. Reference numeral 25 is a pump that utilizes the reciprocating motion of the piston, and pumps the oil 24 in the tank 23 to the oil supply felt 26 in conjunction with the rotation of the heating roller 15. The oil supply felt 26 diffuses the oil in the longitudinal direction and uniformly supplies the oil 24 over the entire length of the rubber oil application roller 27. Reference numeral 28 denotes an oil regulating blade made of fluororubber, which removes excess oil 24 on the surface of the heating roller 15 to form a uniform thin oil layer. The removed oil 24 is collected in the tank 23 through the oil receiver 29. The oil 24 on the heating roller 15 is thinned by an oil regulating blade 28 to form a toner release layer, and prevents the melted toner from being offset to the heating roller 15.

FIG. 8 is a schematic view of a main part of another conventional image fixing device, which is the image fixing device disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-50883. A pair of heat resistant elastic rollers 3
A good heat conductive heat resistant fixing belt 33 is hung between one of the support rollers 32 and the other one, and is sandwiched between the other one of the pair of heat resistant elastic rollers 31, and the good heat conductive heat resistant fixing belt 33 is held. It is composed of a heater 34 for heating.
In this conventional example, a good heat conductive heat resistant fixing belt 33 is used in order to prevent the heat resistant elastic layer of the heat resistant elastic roller 31 from peeling while making the nip portion substantially linear.

[0010]

However, in the above-described conventional image fixing apparatus and image fixing method, high temperature offset is likely to occur, and particularly when fixing a multi-layer toner such as a color image, separation to a heating roller is performed to prevent offset. It is necessary to apply mold oil, and the release oil applying mechanism as described in FIG. 7 causes problems such as an increase in size and cost of the apparatus, complicated maintenance, and residual release oil on the printed matter. There is. Further, as described with reference to FIG. 8, by using the fixing belt, even if it is possible to secure a relatively large nip width for applying heat and pressure to the unfixed toner layer, it is necessary to cope with the speedup. In order to supply heat to the toner, it was necessary to increase the diameter of the heating and pressure roller.

The present invention solves the above-mentioned problems of the prior art. It is not necessary to apply oil, and sufficient fixing performance is obtained even at a high printing speed, and an image fixing device and an image that can be downsized are provided. The purpose is to provide a fixing method.

[0012]

In order to achieve this object, the present invention comprises a plurality of rollers, an endless belt wound around these rollers, and heating means for heating the endless belt, The range of the transport path where the endless belt and the recording medium come into contact with each other using an image fixing device that conveys the toner while the unfixed toner image surface carried on the recording medium is brought into contact with the outer peripheral surface of the endless belt. Toner melts with
The fixing performance is ensured by press-fixing the recording medium and the molten toner between one of the plurality of rollers arranged at the end of the conveyance path and the pressure roller that comes into contact with the endless belt. is there.

Further, in order to realize the above-mentioned image fixing method, a pressure roller which is in contact with one of a plurality of rollers arranged at the end of the conveying path of the recording medium via an endless belt is provided. To do. Here, in order to improve the releasability of the endless belt and the recording paper at the exit of the pressure roller, the surface layer of the roller contacting the pressure roller is made of a heat resistant elastic member. Further, in order to stabilize the melting of the toner, guide means is arranged near the beginning of the conveying path. The guide means is provided with a spring member as a roller that abuts against the roller at the beginning of the conveying path and adjusts the pressure so that the nip pressure at the abutting portion becomes smaller than the nip pressure at the terminal of the conveying path.

[0014]

According to the first aspect of the present invention, since the function of melting unfixed toner and the function of pressing molten toner to the recording paper can be separated, a rapid heating process is eliminated and high temperature offset prevention is performed. Eliminates the need to use mold release oils. Further, the heating member can be brought into contact with the unfixed image for a long time, and since the unfixed toner is brought into contact with the heating member, efficient heat transfer is performed, and printing can be performed at a higher speed than in the past. Further, the temperature gradient of the unfixed toner layer can be suppressed to be small due to the heating for a relatively long time, the occurrence of offset can be suppressed as described above, and the release oil application device is unnecessary. . Moreover, since the heat transfer function and the crimping function are separate processes, the pressing force can be reduced, and the device can be downsized and simplified.

Further, according to the second aspect of the invention, it is possible to prevent the multilayer unfixed toner image from being carelessly crushed, and it is possible to obtain a high-resolution fixed image.

According to the third aspect of the invention, the heating time of the recording paper carrying the unfixed image and the belt is made stable, and a stable fixing process is realized.

According to the structure of claim 4, it is possible to guide more smoothly. Also, since the frictional resistance with the belt is small, the life of the belt and the guide is extended.

Further, according to the structure of claim 5, even if the heat roller is directly contacted with the heat roller, the damage is small and the required durability is secured.

According to the sixth aspect of the invention, it is possible to prevent the belt from sagging in the sheet conveying path, prevent slippage when driving the belt, and realize more stable conveying and heating.

According to the configuration of claim 7, the same operation as that of claim 1 can be obtained. According to the structure of claim 8,
The heating time of the recording paper carrying the unfixed image and the belt is made stable to realize a stable fixing process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic view of a main part of an image forming apparatus according to a first embodiment of the present invention, FIG. 2 is a schematic view of a main part of the image fixing apparatus, and FIG. 3 is a temperature change diagram of the toner layer. is there. Here, the same components as those of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, reference numeral 41 denotes a heat roller, which is provided with a heater 16 in a highly heat-conductive metal tube such as aluminum.
Is included. Reference numeral 42 is a drive roller having an elastic layer such as silicon rubber on the outer circumference of a metal roller, and the drive is transmitted from a drive source (not shown) via a transmission mechanism. A hollow roller may be used as a core material for weight reduction. Reference numeral 43 is a fixing belt having good heat conductivity, and the base is an endless belt made of nickel having good heat conductivity or polyimide having excellent heat resistance. On the outer periphery of the base, a releasable and soft silicone-based rubber coat layer is formed. Other than that, a Teflon-based or fluorine-based coating layer is also conceivable.

The fixing belt 43 is wound around the heat roller 41 and the driving roller 42, and the tension roller 4
4 provides tension. Here, the tension roller 44 may have not only a function of stretching the fixing belt 43, but also a function of a cleaning roller by using a cleaning functional material such as felt for the surface layer. A pressure roller 45 is provided with a fluorine resin coating on the outer circumference of the metal roller in order to reduce the coefficient of friction with the recording paper 12. Reference numeral 46 is a guide member for guiding the recording paper 12 from the second transfer portion to the fixing portion.
The recording paper 12 is guided to the starting end of the straight line portion.

In FIG. 2, 46 is a guide member, 47 is a base, and 48 is an elastic layer, which is a constituent member of the fixing belt 43. As described above, the base 47 is made of a heat-resistant material having good heat conductivity such as nickel, and the elastic layer 48 is made of silicone rubber having releasability. Reference numeral 49 gives an appropriate tension to the heat roller 41 fixed by the belt tension spring and the fixing belt 43 hung around the driving roller 42 to prevent unnecessary slack. In the first embodiment, the outer circumference of the fixing belt 43 is pressed against the fixing belt 43 via the tension roller 44. However, in consideration of damage to the fixing belt 43, the tension roller 4 is provided inside the fixing belt 43.
It is also conceivable that the heat roller 41 is arranged outside and the heat roller 41 is pulled in a direction parallel to the conveying direction of the recording paper 12 and away from the drive roller 42, and the fixing belt 43 is
It is also possible to give tension to the. 50 is a pressure roller 4
5 is a pressure spring for pressing the drive roller 42 through the fixing belt 43. The toner melted by this pressurization is made to enter the fibers of the recording paper 12.

With respect to the image forming apparatus and the image fixing apparatus configured as described above, the operation of the apparatus will be described below focusing on the image fixing method. In FIG. 1, a latent image is formed on the photoconductor 2 according to the print signal, and the recording paper 1 is formed at the second transfer portion.
The operation up to carrying the unfixed image on 2 is the same as the conventional one, and thus the description thereof is omitted here. The recording paper 12 conveyed from the second transfer portion is guided by the guide member 46 to the vicinity of the starting end of the straight portion of the fixing belt 43, and the unfixed toner image comes into contact with the outer peripheral surface of the fixing belt 43. Since the fixing belt 43 and the recording paper 12 are moving at the same linear velocity, the unfixed toner image is conveyed to the pressure unit without being displaced while being in contact with the fixing belt 43. The recording paper 12 conveyed to the pressurizing unit is driven by the driving roller 4 via the fixing belt 43.
2 and the pressure roller 45 are conveyed while being pressurized, and sent to a paper discharge unit (not shown).

FIG. 3 predicts the temperature change of the toner layer during fixing. The vertical axis represents the temperature of the toner layer, and the horizontal axis represents the distance. The schematic configuration of the first embodiment is arranged on the lower side of the figure to facilitate comparison with the distance. In the figure, a is the first embodiment.
Is the temperature change when the image fixing method of 1 is used, and b is the temperature change when the conventional image fixing method is used. In the conventional method, since the heating required for fixing is rapidly performed in the nip, the temperature gradient of the toner layer is large, and the viscosity of the toner is excessively decreased on the heating side of the toner layer (opposite to the recording paper 12 side). Immediately after passing, it is in the high temperature offset area. In the conventional method, this high temperature offset is prevented by using a release oil. On the other hand, in the present embodiment, since the toner is melted for a relatively long time, the temperature gradient in the nip portion is small, and stable fixing can be realized without releasing oil.

(Embodiment 2) FIG. 4 is a schematic view of a main portion of a nip portion of an image fixing device according to Embodiment 2 of the present invention. Drive roller 42, fixing belt 43, pressure roller 4
5, the recording paper 12 is the same as that described above, and the description thereof is omitted here. 51 is the surface layer of the driving roller, which is silicone rubber,
A heat resistant elastic layer such as a silicon foam material, and 52 are metal core members of the drive roller 42. By making the surface layer of the driving roller 42 smaller in hardness than the surface layer of the pressure roller 45, the nip is formed as shown in the drawing, and the recording sheet 1
2 moves in the direction of arrow C. By using this technique, it is possible to prevent unnecessary winding of the recording paper 12 around the heat roller 42, it is not necessary to dispose a member such as a peeling claw at the exit of the fixing device, and the surface layer of the fixing belt 43 is provided. It also prevents unnecessary scratches. Although the nip formation using the heat resistant elastic body and the metal has been described in the second embodiment, it is also possible to realize the nip formation by using the elastic body for both of them so as to maintain the magnitude relationship between the surface layers of both rollers.

(Embodiment 3) FIG. 5 is a block diagram showing the essential parts of an image fixing apparatus according to Embodiment 3 of the present invention. Reference numeral 53 denotes a guide roller which is in contact with the heat roller 41 via the fixing belt 43 in the vicinity of the straight line start end of the fixing belt 43 in order to contact and convey the recording paper 12 to the fixing belt 43. Reference numeral 54 is a guide roller spring that controls the contact force. Reference numeral 55 denotes a surface layer portion of the guide roller 53, which is a heat resistant elastic body layer such as silicon rubber. By using the image fixing device and the image fixing method according to the third embodiment, the recording paper 12 carrying the unfixed toner image can be reliably brought into contact with the outer peripheral surface of the fixing belt 43. Here, it is not necessary to increase the load force on the guide roller 53, and it is provided as guide means. It does not exceed the nip pressure given by at least the pressurizing section.

[0029]

According to the present invention, since the function of melting unfixed toner and the function of pressing molten toner onto recording paper can be separated, a rapid heating process is eliminated, and a releasing oil for preventing high temperature offset. Eliminates the need to use Further, the heating member can be brought into contact with the unfixed image for a long time, and since the unfixed toner is brought into contact with the heating member, efficient heat transfer is performed, and printing can be performed at a higher speed than in the past. Further, the temperature gradient of the unfixed toner layer can be suppressed to be small due to the heating for a relatively long time, the occurrence of offset can be suppressed, and the release oil application device becomes unnecessary. Moreover, since the heat transfer function and the crimping function are separate processes, the applied pressure can be reduced, and the device can be downsized, simplified, and priced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of main parts of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of the image fixing device according to the first embodiment of the present invention.

FIG. 3 is a temperature change diagram of the toner layer according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of essential parts of a nip portion of an image fixing device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of an image fixing device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of main parts of a conventional image forming apparatus.

FIG. 7 is a configuration diagram of main parts of a conventional image fixing device.

FIG. 8 is a configuration diagram of a main part of another conventional image fixing device.

[Explanation of symbols]

 12 recording paper 16 heater 41 heat roller 42 drive roller 43 fixing belt 44 tension roller 45 pressure roller 46 guide member 53 guide roller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junichi Tanizaki 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. An endless belt comprising a plurality of rollers, an endless belt wound around these rollers, and heating means for heating the endless belt. Conveying while abutting on the outer peripheral surface of the belt,
An image fixing device for melting toner, comprising: a pressure roller that is in contact with one of the plurality of rollers arranged at the end of the conveying path of the recording medium via the endless belt. Image fixing device. 2. The image fixing device according to claim 1, wherein a surface layer portion of the roller arranged at the end of the conveying path is composed of a heat resistant elastic member. 3. The image fixing device according to claim 1, wherein a guide means is provided near the start end of the conveying path where the endless belt and the recording medium come into contact with each other. 4. A guide means is provided in the vicinity of the beginning of the conveying path where the endless belt and the recording medium come into contact with each other, and the guide means extends the end of the conveying path among the plurality of rollers via the endless belt. The image fixing device according to claim 1, wherein the image fixing device is a guide roller that comes into contact with a roller that is disposed in the. 5. The image fixing device according to claim 4, wherein the surface layer portion of the guide roller is made of a heat resistant elastic member. 6. The nip pressure between the guide roller and the roller arranged at the beginning of the conveying path is smaller than the nip pressure between the pressure roller and the roller arranged at the ending of the conveying path. The image fixing device described. 7. An endless belt having a plurality of rollers, an endless belt wound around these rollers, and heating means for heating the endless belt. Transport while contacting the outer peripheral surface of the belt,
An image fixing method in which toner is melted, wherein toner is melted in a range of a conveyance path in which the endless belt and the recording medium come into contact with each other, and An image fixing method characterized in that fixing strength is secured by pressing the recording medium and the molten toner between one of them and a pressure roller abutting against the endless belt. 8. A stable device is provided by providing guide means near the start end of a conveying path where the endless belt and the recording medium come into contact with each other and bringing the endless belt and the recording medium into contact with each other to melt the toner. The image fixing method according to claim 7, wherein fixing performance is ensured.