JP2001075410A - Fixing device and fixing nip width changing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device equipped with a fixing nip width changing mechanism capable of improving heat efficiency. SOLUTION: This fixing device 90 is equipped with a fixing roller 92 and a pressure roller 98 forming a nip with the roller 92, and further equipped with the fixing nip width changing mechanism 100 constituted of a 1st belt guiding roller 102 performing positioning on the entrance side of the nip 99, a 2nd belt guiding roller 104 performing positioning on the exit side of the nip 99, and an endless belt member attached to pass through the upper sides of the roller 102 and the roller 104 and the nip 99 and forming a loop. The loop is held in the nip 99 by the rollers 92 and 98 so as to be bent. The crimped closed-loop presses the rotatable fixing roller 92 and forms the wide nip 110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION This invention relates generally to electrostatographic duplicators, and more particularly to fusing nip widths used in electrostatographic duplicators to increase fusing dwell time and improve fusing heat efficiency. The present invention relates to a small (compact) fixing device provided with a conversion mechanism.

[0002]

2. Description of the Related Art In a typical electrostatographic (electrophotographic) printing process, a photoconductive member is charged to a substantially uniform potential to render its surface photosensitive. The charged portion of the photoconductive member is exposed to selectively erase charge in the illuminated area. Thereby, an electrostatic latent image is recorded on the photoconductive member. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by contact with a developer. Generally, the developer consists of carrier particles and toner particles adhered to the carrier particles by triboelectric action.
The toner particles are attracted from the carrier particles to a donor roller or latent image on the photoconductive member. The toner particles attracted to the donor roller are then typically deposited on an electrostatic latent image on a photoreceptor charge retentive surface to form a toner powder image. The toner powder image is then transferred from the photoconductive member to the copy medium, and then the toner particles are heated to permanently fix the toner powder image to the copy medium.

In order to permanently fix or fuse toner particles onto a support member or sheet by heat,
It is necessary to raise the temperature of the toner particles to a point where the components of the toner particles fuse and become tacky. By this action,
Toner flows to some extent over the fibers or pores of the support member, or else over the surface of the support member. Thereafter, when the toner cools, it solidifies and is firmly bonded to the support member.

One technique for thermally fixing a toner powder image on a support member is to provide a support having an unfixed toner image between a pair of opposed roller members (at least one of which is internally heated). It was through the member. During operation of this type of fixing device, a support member to which a toner image is attached by electrostatic action is passed through a nip formed between a pair of rollers. The toner image contacts the heated fixing roller and is heated in the nip. In the case of a nip forming fusing roller, one or more layers that are deformed by a pressure roller that is harder than when the two rollers are pressed are provided on the heated fusing roller. The nip length determines the residence time, ie, the time that the toner particles are in contact with the surface of the heating roller.

[0005]

When a color image is fixed at a low speed, the required processing state such as temperature, pressure and dwell time can be easily realized, so that the roller fixing device works very well. . As the processing speed approaches 100 pages per minute (100 ppm), the fusing performance of the rollers begins to degrade. At such higher speeds, the dwell time must be kept constant, which requires an increase in nip width. Increasing the nip width can be achieved very simply by increasing the thickness of the fuser roller rubber, or by increasing the outer diameter of the roller, or both. Each of those solutions reaches a limit at about 100 ppm. In particular, the thickness of the rubber is limited by the maximum heat resistance of the rubber and the temperature gradient across the elastic layer. Also, the size of the rollers becomes an important issue for space, weight, cost, and peeling reasons.

Next, a conventional technique which is considered to be related to the patentability of the present invention will be examined. The relevant literature probably has some relevance to patentability issues,
A better understanding and appreciation of the present invention can be given together with the detailed description that follows.

No. 5,250,998 (199)
Issued on November 5, 2013) includes a heating roller, an endless belt looped around a conveying roller, and a pressing roller for pressing a sheet having a toner image against the heating roller. A toner image fixing device in which an endless belt is interposed therebetween is disclosed. To detect the temperature of the heating roller, a sensor is disposed inside the loop of the belt so as to contact the heating roller. The fixing temperature of the toner image is controlled based on the temperature of the heating roller detected by the sensor. A first nip region is formed in a pressure portion between the heating roller and the fixing roller. Following the first nip area, but without contacting the heating roller, a second nip area is formed between the belt and the fixing roller.

No. 5,465,146 (199)
No. 5, November 7, 2005) relates to a fixing device for an electrophotographic copying apparatus which can obtain a clear fixed image without offset by using no oil or using only a small amount of oil. An endless fixing belt in which a release thin film is coated on a metal body is stretched tight between a fixing roller having an elastic surface and a heating roller. The pressure roller is configured to push the surface of the elastic fixing roller upward from below via the fixing belt to form a nip portion between the fixing belt and the pressure roller. A guide plate for the support member having an unfixed image provided between the heating roller and the nip portion below the fixing belt forms a substantially straight heating passage between the guide plate and the fixing belt. The heat capacity of the metal body of the fixing belt is 0.001 per cm ²
~ 0.02 cal / ° C.

[0009]

SUMMARY OF THE INVENTION The present invention provides a fixing nip width conversion mechanism used in a copying apparatus and a small (compact) fixing apparatus having a long nip width and having the same. The fixing device includes a rotatable fixing roller and a rotatable pressure roller for pressing the fixing roller to form a roller nip. What is important is that the fixing nip width conversion mechanism has a first belt guide roller positioned at an entrance side of a roller nip formed by a rotatable fixing roller and a rotatable pressure roller, and a second belt positioning roller positioned at an exit side of the roller nip. A two-belt guide roller and an endless belt member mounted over the first belt guide roller, the second belt guide roller, and the roller nip to form a closed loop.
When attached, the closed loop of the belt member is pinched and deflected by a rotatable fixing roller and a rotatable pressure roller in a roller nip. The clamped closed loop presses the rotatable fusing roller to form a long nip, thereby increasing fusing residence time and improving fusing heat efficiency as compared to the roller nip. Such a small fixing device with a long nip width
Electrostatography (electrophotography) that produces high quality fixed toner images
Suitable for use in a portable duplicator.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments, but it is not intended to limit the invention to those embodiments. The invention encompasses the spirit of the invention and all alternatives, modifications and equivalents which fall within the scope of the invention as set forth in the appended claims.

[0011] To aid in a general understanding of the features of the present invention, reference is made to the drawings. In the drawings, identical elements are denoted by the same reference numeral throughout. The drawings described are only illustrative of preferred embodiments of the invention and do not limit the invention. First, various processing units used in the electrostatographic (electrophotographic) copying apparatus shown in FIG. 1 will be briefly described.

As shown, an electrostatographic (electrophotographic) reproduction apparatus 8 in which the present invention is usefully used comprises a photoconductive belt comprising a photoconductive surface 11 and a light-transmitting conductive support. A charge-bearing image support member in the form of 10 is used. The belt 10 is attached so as to pass through a series of electrophotographic processing sections including a charging section AA, an exposure section BB, a developing section CC, a transfer section DD, a fixing section EE, and a cleaning section FF.
The belt 10 moves in the direction of arrow 16 and advances a continuous portion thereof to sequentially pass through various processing units arranged around the belt moving path. The belt 10 includes a plurality of rollers 1
It is wrapped around 8,20,22. Roller 18
Can be used to apply an appropriate tension to the photoreceptor belt 10. The roller 20 is connected to the motor 23 via any suitable means, for example a belt transmission. Motor 23 rotates roller 20 to advance belt 10 in the direction of arrow 16.

As can be seen in detail with reference to FIG. 1, initially a continuous portion of belt 10 passes through charging station AA. In the charging section AA, the corona discharge device 24 (for example, a scorotron, a corotron, or a dicorotron) is connected to the belt 10.
Selectively to a high uniform positive or negative potential.
The corona discharge device 24 can be controlled using any suitable control device known in the art.

Next, the charged portion of the photoreceptor surface passes through the exposed portion BB. In the exposure section BB, the uniformly charged photoreceptor surface, ie, the charge holding surface 10, is exposed to a laser input scanning device and / or an output scanning device 25. The scanning device 25 is controlled by a controller or ESS 26 and discharges the charge retaining surface according to its output. ESS 26 is the main multitasking processor for operating and controlling printing operations with all other device subsystems, including, for example, features of the present invention.
The scanning device is a three-level laser raster output scanner (R
OS). Thus, the photoreceptor contains both a charged area image and a discharged area image.

In the developing section CC, a developing system 30 contacts a developer with the electrostatic latent image to develop the latent image. The developing system 30 includes a first developing device 32 and a second developing device 34 as illustrated. The developing device 32 has a housing containing a pair of magnetic brush rollers 35 and 36. The magnetic brush rollers 35 and 36 bring the developer 40 into contact with the photoreceptor to develop a discharge area image. Developer 40
Include, for example, negatively charged color toner. The electrical bias is provided by a power supply 41 electrically connected to the developing device 32. The power supply 41 applies a DC bias to the magnetic brush rollers 35 and 36.

The developing device 34 includes a pair of magnetic brush rollers 3
It has a housing containing 7,38. The magnetic brush rollers 37 and 38 bring the developer 42 into contact with the photoreceptor,
Develop the charged area image. The developer 42 includes, for example, a positively charged color toner that develops a charged area image. Appropriate electrical bias is provided by a power supply 43 electrically connected to the developing device 34. The power supply 43 applies a DC bias to the magnetic brush rollers 37 and 38.

Since the developed composite image on the photoreceptor consists of positive and negative toner, a corona discharge of the desired polarity, either positive or negative, is used to effectively transfer the toner to the image support. A pre-transfer corona discharge member 56 for adjusting the state of the toner is provided.

A support or sheet 58 of support material is fed from a supply tray (not shown) to a transfer station DD. The sheet 58 is sent out of a supply tray by a sheet supply device (not shown), passes through the corona charging device 60, and is conveyed to the transfer unit DD. After the transfer, the sheet continues to move in the direction of arrow 62 toward the fixing unit EE.

As shown in the drawing, a small belt fixing device 90 according to the present invention having a nip width converting mechanism 100 according to the present invention is installed in the fixing unit EE. The fixing device 90 has a rotatable fixing roller 92. Fixing roller 9
2 is heated, for example, by a heating device 94 (shown as an internal ramp, but could be an external heater) to raise the temperature of its surface 96 to the appropriate toner fusing temperature. The fixing device 90 further includes a rotatable pressure roller 98 that presses the rotatable fixing roller 92 to form a roller nip 99.

What is important is that the small fixing device 90 has a fixing nip width conversion mechanism 1 for increasing the fixing residence time and improving the fixing heat efficiency as compared with the roller nip 99.
00 is provided. Referring to FIGS. 1 to 3, and particularly to FIG. 2, the nip width conversion mechanism 100 includes a first belt guide roller 102 that positions the belt at the entrance side of the roller nip 99 and a second belt that positions the belt at the exit side of the roller nip 99. It has a belt guide roller 104.
Each of the belt guide rollers 102 and 104 can be made of an extruded aluminum member. As illustrated, the nip width conversion mechanism 100 further has an endless belt 108. Endless belt 108 is the first
Belt guide roller 102 and second belt guide roller 104
, Thus forming a deflectable, squeezable, closed loop 108 around the guide rollers 102 and 104 (FIG. 2).

When assembling the nip width conversion mechanism 100 to form the nip width conversion type fixing nip according to the present invention (FIG. 3), the endless belt member 106 is placed on the first belt guide roller 102 and the roller nip is 99 and is mounted on the second belt guide roller 104. The closed loop 108 is pinched and bent by the rotatable fixing roller 92 and the rotatable pressure roller 98 in the illustrated roller nip 99. Conveniently, the closed loop 108 in the pinched state presses the rotatable fuser roller 92 to release the long width fuser nip 110.
Is formed and converted into a fixing nip 110 having a considerably longer width than the roller nip 99 having a shorter width. This conversion increases the fixing residence time as compared with the roller fixing nip 99, and improves the fixing heat efficiency.

In accordance with another aspect of the present invention, the long fusing nip 110 includes an entrance area 11 to the long fusing nip.
It has two relatively high nip pressure regions, including two and an outlet region 114. As shown, the first high nip pressure area at the entrance area 112 to the long width fixing nip is such that the fixing roller 92 sandwiching one section of the closed loop 108 presses the first belt guide roller 102. Generated by Similarly, the second high nip pressure region 114 at the outlet region is generated by the fixing roller 92 sandwiching one section of the closed loop 108 pressing the second belt guide roller 104.

Two belt guide rollers 102, 104
Is preferably a floating idler roller that is independently held in place by a closed loop 108 of the belt member 106, but even if only one of the belt guide rollers is an idler roller, The nip width conversion mechanism 100 works equally well. In a preferred embodiment where the two belt guide rollers are idler rollers, either the rotatable fixing roller 92 or the rotatable pressure roller 98 is the drive roller.

In summary, fuser 90 uses a unique floating idler roller and belt mechanism 100. The pair of floating idler rollers 102 and 104 are
6 is held alone in place by the closed loop 108. The idler rollers 102, 104 themselves do not have a conventional radial bearing or positioning mechanism. This is because it allows for a compact, thermally efficient, low cost and simple design compared to other belt fusing devices having similar long width fusing nips. As noted above, the pressure characteristics of the long width fusing nip 110 of the present invention are also unique in that the highest pressure areas (two) can be located in the nip entry area 112 and the nip exit area 114. It is.

Continuing the description with reference to FIGS. 1 to 3, the fixing roller 92 is a driving roller, and is preferably mounted at a suitable fixed position on the frame 93 by a pair of end bushes (not shown). On the other hand, the pressure roller 98 is similarly mounted on the frame 93, but can approach and retreat with respect to the fixing roller 92 (arrow 11).
8) A load can be applied to the fixing roller 92 by a force F by a spring 120 or the like. Accordingly, the nip load and the belt tension are determined by the load of the force F applied to the pressure roller 98. The floating idler rollers 102, 104 are independently held in their respective belt guidance positions by the closed loop 108 of the belt member 106. As noted above, these idler rollers assembled in mechanism 100 and fuser 90 do not have a conventional radial bearing or positioning mechanism. All that is required of the idler rollers is a shaped thrust bushing 124 at each end thereof (FIG. 2) for laying the idler rollers aside from the end bushing of the fuser roller 92.
The mechanism 100 (the combination of the idler roller and the belt loop) is held at the nip conversion position in the roller nip 99 by only the fixing roller 92 and the pressure roller 98.

In operation, the copy media or sheet 58 having the unfixed toner image 89 on the top surface enters the wide fusing nip 110 through the entrance area 112 and exits the nip 110 through the exit area 114. The high pressure zone nip inlet will advantageously minimize wrinkles and other deformations on the incoming media or sheet 58. On the other hand, the high pressure area nip exit will serve to improve the adhesion of the fused image to the media or sheet 58. As can be clearly seen, the toner image is in contact with the heated surface 96 of the fuser roller 92 and, for example, a roller nip 99
And travels a very long distance past the nip 110 as compared to traveling through the nip 110. Thus, the fusing residence time through the long fusing nip 110 at the determined travel speed will be much longer than, for example, the roller nip 99.

Advantageously, the nip width conversion mechanism 10
The zero and fixing device 90 result in a small belt fixing device having a relatively small total belt surface area as compared to other belt fixing devices. The compact construction and small belt surface area minimize heat loss and reduce the energy required for its operation. When a fixing test was performed with the compact fixing device according to the present invention, it was found that the required fixing temperature was reduced by 84 ° F. as compared with a normal heating and pressing roller fixing device. further,
Since the belt member 106 is relatively short, the cost is relatively low, and the belt guide roller can also be low in cost.

As can be seen from the above, a small and long nip width fixing device provided with a fixing nip width conversion mechanism used in a copying apparatus and the same was obtained. The small long nip width fixing device has a rotatable fixing roller and a rotatable pressure roller that presses the fixing roller to form a nip roller. Importantly, the fusing nip width conversion mechanism positions a belt at the entrance side of a roller nip formed by a rotatable fusing roller and a rotatable pressure roller, and a belt at an exit side of the roller nip. And an endless belt member mounted on the first and second belt guide rollers and through the roller nip to form a closed loop. The closed loop, when mounted, is bent between a rotatable fixing roller and a rotatable pressure roller in a roller nip. The pinched closed loop presses the rotatable fusing roller to form a long width fusing nip, thereby increasing fusing residence time and improving fusing heat efficiency as compared to the roller fusing nip.

While the present invention has been described with respect to particular embodiments thereof, it is evident that those skilled in the art will envision many alternatives, modifications and equivalents. Accordingly, this invention is intended to embrace all such alternatives, modifications and equivalents as fall within the spirit and broad scope of the invention as set forth in the appended claims.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an electrophotographic (electrophotographic) copying apparatus incorporating a nip width conversion mechanism and a fixing device of the present invention.

FIG. 2 is a perspective view of the nip width conversion mechanism of FIG.

FIG. 3 is a detailed end view of the nip width conversion mechanism and the fixing device of FIG. 1 according to the present invention.

[Explanation of symbols]

 AA charging unit BB exposure unit CC developing unit DD transfer unit EE fixing unit FF cleaning unit 8 electrophotographic duplicating device 10 photoconductive belt 11 photoconductive surface 16 belt moving direction 22 roller 23 drive motor 24 corona discharge device 25 raster output Scanner (ROS) 26 ESS (controller) 30 Developing system 32, 34 Developing device 35, 36, 37, 38 Magnetic brush developing roller 40 Developer 41, 43 Power supply 56 Corona discharge member before transfer 58 Copy medium (sheet) 60 Corona charging Device 62 Sheet moving direction 90 Small belt fixing device according to the present invention 92 Rotatable fixing roller 93 Frame 94 Heating device 96 Surface of fixing roller 98 Rollable pressure roller 99 Roller nip 100 Nip width conversion mechanism 102 First belt guide roller 104 Second belt Induction roller 106 Endless belt member 108 Closed loop 110 Long width fixing nip 112 Inlet area 114 Outlet area 118 Pressure roller moving direction 120 Spring 122 End bushing 124 Thrust bushing

Claims (3)

[Claims] 1. A fixing nip width conversion mechanism for converting a short-width roller fixing nip into a long-width belt fixing nip in order to increase a fixing residence time and improve fixing heat efficiency, comprising: (a) a rotatable fixing roller; A first belt guide roller positioned at an inlet side of a roller fixing nip formed by a pressure roller rotatable with the first belt; (b) a second belt guide roller positioned at an outlet side of the roller fixing nip; An endless belt member mounted on the first belt guide roller and the second belt guide roller, the belt member forming a closed loop in the mounted state, The closed loop can be clamped in the roller fixing nip by the rotatable heat fixing roller and pressure roller. And,
The closed loop forms a belt fusing nip that, when pinched, is wider than the roller fusing nip, thereby increasing fusing residence time and improving fusing heat efficiency. mechanism. 2. A compact fixing device having a long nip width, comprising: (a) a rotatable fixing roller; and (b) a rotatable pressurizing device for pressing the rotatable fixing roller so as to form a roller nip. (C) a fixing nip width conversion mechanism, (i) a first belt guide roller positioned at an entrance side of the roller nip formed by the rotatable fixing roller and the rotatable pressure roller; and (Ii) a second positioning at the outlet side of the roller nip;
A fixing nip width conversion mechanism having a belt guide roller; and (d) a closed loop formed so as to pass over the first belt guide roller, the second belt guide roller, and the roller nip. A closed loop of the belt member is pinched and deflected by the rotatable heat fixing roller and the pressure roller in the roller fixing nip. The closed loop formed forms a long width fusing nip to press the rotatable fusing roller, thereby
A fixing device, wherein the fixing residence time is increased and the fixing heat efficiency is improved as compared with the roller fixing nip. 3. An electrostatographic duplicating apparatus, comprising: (a) a movable image support member having a toner image supporting surface forming a moving path; and (b) the toner disposed along the moving path. Various devices for electrostatographic processing for forming a toner image on an image support surface; (c) means for transferring the toner image from the toner image support surface to a support; (d) the toner image A small, long nip width fixing device for heating and fusing to the support, the fixing device comprising a fixing roller forming a roller nip and a pressure roller, the fixing device comprising: A fixing device comprising: (i) a first belt guide roller positioned at an entrance side of the roller nip;
(Ii) a second belt guide roller positioned at the outlet side of the roller nip; and (iii) a closed loop formed by being mounted on the first belt guide roller, the second belt guide roller, and the roller nip. The closed loop presses against the rotatable fusing roller to form a long width belt fusing nip when pinched, thereby providing a relatively wide belt fusing nip as compared to the roller fusing nip. An electrophotographic duplicating apparatus characterized in that the fixing residence time is increased and the fixing heat efficiency is improved.