JP2001117397A - Fixing device and electrophotographic device equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of improving an efficiency of transmitting heat to a toner image, and also, capable of attaining the stabilization with a simple constitution. SOLUTION: The device is provided with a belt-like member which is stretched to be laid between plural rolls, a heating source for heating the belt- like member, a roller transfer unit for bringing a recording member in electrically press contact with the surface of the belt-like member, and a pressure roller for holding the recording material with the belt-like member and pressurizing the recording material, and the belt-like member is heated in a state where the recording material surface with the toner image formed is brought into tight contact with the belt-like member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for a printer, a facsimile, a copying machine, and the like, and an electrophotographic apparatus provided with the fixing device.

[0002]

2. Description of the Related Art A fixing method using a belt designed to make up for the drawbacks of the conventional heat roll fixing method has excellent characteristics such as quick start, low temperature fixing and non-offset property. The belt fixing system is roughly classified into the following three configurations.

One is a system in which one fixing belt is fixed by one pressure roll as disclosed in Japanese Patent Application Laid-Open No. 10-31377. The other is JP2
Japanese Patent Application Laid-Open No. 4-199169 discloses a method of fixing a single fixing belt by two pressure rolls. This is a method in which fixing is performed using a book fixing belt.

A feature or aim of these belt fixing systems is that the use of a fixing belt can increase the heating time which cannot be obtained by the conventional heat roll fixing system. Further, when the sheet is separated from the fixing belt, the non-offset property can be secured by adding a cooling effect.

For example, Japanese Patent Application Laid-Open No. Hei 10-31377 discloses a system in which guide means for stably bringing a sheet into contact with a fixing belt is provided, and fixing is performed while conveying the sheet while keeping it in contact with a heating element. By the guide means, the recording material makes smooth and reliable contact with the belt-shaped heating element, and the heating time can be stably secured for a long time.

As another technique, Japanese Patent Laid-Open Publication No. 5-196
No. 42 discloses a simultaneous transfer-fixing method in which a recording medium is brought into close contact with a toner image melted by heating and pressing on an intermediate transfer member, and the recording material is peeled off together with the toner image after being cooled in the closely contacted state.

[0007]

SUMMARY OF THE INVENTION
In the method disclosed in Japanese Patent Application Laid-Open No. 10-31377, the contact of the recording material with the belt-shaped heating body after passing through the guide means depends only on gravity, and therefore, there is a restriction on the arrangement of the heating body flat portion. Is big. Further, as described above, since the recording paper expands and contracts due to heating, if it is performed as it is, the state of contact with the fixing belt becomes unstable, and it is inevitable that fixing unevenness occurs. In this method, there is no description about a peeling means such as a peeling nail or a peeling roll. If it is carried out as it is, it is difficult to peel off the recording material together with the toner image from the heating body, and particularly when a recording material having low rigidity such as thin paper is used,
It is inevitable that winding occurs along the slope of the heating element. In order to avoid these problems, the arrangement of a plurality of guide rollers and peeling rolls is complicated and large, and the cost is unavoidable.

In the system disclosed in Japanese Patent Application Laid-Open No. 5-19642, a forced cooling mechanism must be provided in order to realize cooling separation, which also leads to an increase in cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small and inexpensive fixing device which can make the most of the advantages of the belt fixing system, has a simple structure, improves the heat transfer efficiency to a toner image, and is stable and uniform. And an electrophotographic apparatus having the same.

Further, a fixing device capable of supplying a high-efficiency and stable amount of heat to a toner image and constantly and stably obtaining a high-quality image regardless of the size and material of the recording material or the gravity. And an electrophotographic apparatus having the same.

Further, since the heating time can be efficiently and prolonged, heat required for fixing can be supplied to the toner image at a low surface temperature, so that power consumption can be reduced and high-speed printing can be performed. It is an object of the present invention to provide a fixing device capable of obtaining a sufficient fixing performance even with respect to the above, and an electrophotographic apparatus provided with the fixing device.

Another object of the present invention is to provide a fixing device in which an offset hardly occurs and in which the supply amount of an anti-offset agent can be reduced or completely eliminated, and an electrophotographic apparatus including the same.

[0013]

In order to achieve the above object, the present invention provides a fixing device for heating and fixing a recording material having a toner image formed thereon, comprising: a belt-like member stretched by a plurality of rolls; A heating source for heating the belt-shaped member, a transfer device for electrostatically bringing the recording material into close contact with the surface of the belt-shaped member, and a transfer source disposed at the most downstream of the plurality of rolls with respect to a conveying direction of the recording material. And a pressure roll that is disposed at a position facing the roll, and presses and presses the recording material with the belt-shaped member, wherein the belt-shaped member includes a recording material surface on which the toner image is formed and the recording material surface. The belt-like member is configured to be heated in a close contact state.

According to this configuration, the recording material having the unfixed toner image formed on the surface thereof is brought into close contact with the belt-shaped member as the heating body via the unfixed toner image by the roll transfer device, and is conveyed. While being heated. Further, by applying pressure by a pressure roll immediately before the recording material is separated from the belt-shaped member, separation of the toner image from the belt-shaped member is promoted, non-offset properties can be improved, and an anti-offset agent can be used. The supply can be reduced or completely eliminated. Further, the conveyance of the recording material and the contact of the toner image with the heating element are stabilized, and the toner image can be stably and efficiently heated uniformly for a long time regardless of the material and size of the recording material.

Also, since the fixing temperature can be set low, the power consumption of the fixing device can be reduced.
Also, sufficient fixing performance can be obtained even at high speed.

Further, since the behavior of the recording material does not depend on gravity, the belt-shaped member can be freely arranged vertically, horizontally, and obliquely, which is effective in reducing the size of the entire apparatus.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fixing device according to an embodiment of the present invention and an electrophotographic apparatus provided with the fixing device will be described with reference to the drawings.

FIGS. 2 and 3 show a schematic configuration of an electrophotographic apparatus having a fixing device according to an embodiment of the present invention. 2 and 3 show a full-color image recording apparatus using a belt-shaped photoreceptor and an intermediate transfer member. FIG. 2 shows an example in which a flat portion of a belt-shaped member is arranged in a horizontal state, and FIG. 3 is arranged in a substantially vertical state. It is an example.

As shown in FIGS. 2 and 3, the belt-shaped photoconductor 11 having the organic photoconductive layer formed on the surface thereof is moved in the direction of the arrow (FIG. 2).
Are at the contact position with the intermediate transfer drum 18 from below to above,
FIG. 3 rotates in the opposite direction). A predetermined charge is uniformly applied to the surface of the belt-shaped photoreceptor 11 by the charger 12 to form a charge layer. Next, the belt-shaped photoreceptor is controlled by a laser beam of an exposure unit 13 controlled according to input image information. Body 11
The upper portion is illuminated, the charge of the illuminated portion is erased, and an electrostatic latent image is formed on the surface of the belt-shaped photoconductor 11.

Next, the electrostatic latent image formed on the surface of the belt-like photoreceptor 11 is made visible by toner charged to a polarity opposite to that of the electrostatic latent image stored in the developing machine (yellow) 14. The visible image is transferred onto the intermediate transfer drum 18. This process is further performed by a developing machine (magenta) 15,
The development is sequentially performed using a developing machine (cyan) 16 and a developing machine (black) 17 to form a visible image superimposed on four colors on the intermediate transfer drum 18.

Next, the visible image is transferred to
The image is transferred onto a recording material 9 made of paper or a plastic sheet. The recording material 9 after the transfer is removed by static elimination, and the fixing device 20
Is fixed by heating.

Next, one embodiment of the fixing device according to the present invention will be specifically described with reference to FIG. In FIG. 1, the fixing device 2
0 is the first fixing roll 1, the second fixing roll 2, and the first fixing roll 2.
A fixing belt 3 stretched between a fixing roll 1 and a second fixing roll 2, a pressure roll 4, a roller transfer unit 5 as an electrostatic adhesion unit 5, a heating source 6, a thermistor 7 as a temperature control unit, and a toner image 8 , A recording material 9 such as paper.

The fixing belt 3 is stretched by a rotatable first fixing roll 1 and a second fixing roll 2, and a pressure roll 4 is pressed against the second fixing roll 2 with the fixing belt 3 interposed therebetween. .

A roller transfer device 5 is disposed below the first fixing roll 1 as an electrostatic contact portion.

The first fixing roll 1 is made of a hollow aluminum core bar, and has a step (not shown) larger than the thickness of the fixing belt 3 at both ends in the axial direction for preventing the fixing belt 3 from shifting. I have. Further, in order to apply tension to the fixing belt 3 stretched between the first fixing roll 1 and the second fixing roll 2, a load is applied to the first fixing roll 1 in the right direction in the figure by a spring (not shown). ing.

A heating source 6 such as a heater lamp is provided inside the first fixing roll 1, and heat of the heating source 6 is transmitted to the fixing belt 3 through the first fixing roll 1. A thermistor 7 is provided on the outer peripheral surface of the fixing belt 3 in contact with the first fixing roll 1, and the temperature of the surface of the fixing belt 3 is controlled by adjusting the amount of electricity supplied to the heating source 6.

The second fixing roll 2 and the pressure roll 4 are both formed by providing a heat-resistant elastic layer such as silicone rubber on an aluminum core. The heat-resistant elastic layers of the second fixing roll 2 and the pressure roll 4 have a nip shape formed at a pressure contact portion between the second fixing roll 2 and the pressure roll 4 so that the toner image 8 on the recording material 9 adheres. The pressure roller 4 uses an elastic layer having a higher hardness than the second fixing roll 2 in order to make the surface having a convex shape.

That is, in order to make the hardness of the heat-resistant elastic layer of the pressure roll 4 higher than the hardness of the heat-resistant elastic layer of the second fixing roll 2, the heat-resistant elastic layer itself of the pressure roll 4 has a high hardness. Or the thickness of the heat-resistant elastic layer is made smaller than that of the second fixing roll 2. Therefore, a metal roller of aluminum or the like may be used as it is without intentionally providing the heat-resistant elastic layer on the pressure roll 4.

The fixing belt 3 has a thickness of, for example, 30 to 50.
Endless nickel belt by electroforming of μm, thickness of 60
An endless upper belt made of polyimide resin having a thickness of 100 μm is used. Also, the thickness of the endless belt is 50 to 1 on the outer peripheral surface.
A silicone rubber layer having a thickness of 50 μm or having an outer peripheral surface subjected to mold release treatment with PFA or fluororesin is used.

The roller transfer device 5 as an electrostatic contact portion has an elastic roll electrode having a predetermined resistance value around a conductive metal shaft, and a solenoid for moving a roll electrode (not shown) forward and backward. As the material of the elastic layer, sponge or rubber using a polymer resin such as urethane and silicone is suitable. Next, the operation of the present fixing device will be described with reference to FIG. The recording material 9 on which the unfixed toner image 8 formed by each process of electrophotography is placed, with the toner image surface in contact with the fixing belt 3 from the right side in FIG. 2 and the lower side in FIG. Invade from the side.

The roller transfer unit 5 is retracted to a rest state until the step of forming the unfixed toner image 8 on the recording material 9, and the recording material 9 bearing the toner image 8 is guided to the fixing device 20. In this step, the recording material 9 is brought into contact with the fixing belt 3 in synchronization with the entry of the recording material. In synchronization with this operation, a voltage is applied to the roll electrode, and a voltage is applied to the back surface of the recording material 9 (the surface on which the toner image is not formed, the back surface).

As a result, the recording material 9 on which the unfixed toner image 8 is placed is guided to the fixing belt 3, and the surface on which the toner image 8 is placed comes into close contact with the fixing belt 3, and is conveyed while being heated. You. Thereafter, pressure is applied between the second fixing roll 2 and the pressure roll 4 together with the fixing belt 3, and the fixing belt 3 is pressed.
The recording material 9 on which the toner image 8 is placed is separated from the surface, and the fixing process is completed.

As described above, according to the present embodiment, the recording material 9 is conveyed and heated in a state where the recording material 9 is in electrostatic contact with the surface of the fixing belt 3. Therefore, it is possible to supply a high-efficiency, stable and uniform heat quantity without being influenced by the size and material of the recording material 9 and further by gravity. Further, unlike the above-described embodiment (see FIGS. 2 and 3), there is no restriction on the arrangement,
It can be arranged vertically, horizontally and diagonally in an electrophotographic apparatus.

Further, since the flat portion of the fixing belt 3 where the recording material 9 extends from the first fixing roll 1 to the second fixing roll 2 is formed as a heating section for the toner image, a long heating time can be ensured. Can be. Therefore, the toner image can be fixed at a low surface temperature without increasing the surface temperature of the fixing belt 3 so much.

Further, even if the printing speed is increased, heat required for fixing can be supplied to the toner image, and sufficient fixing performance can be obtained.

Further, by setting the surface temperature of the fixing belt 3 to be low, the viscosity of the molten toner in the vicinity of the surface of the fixing belt 3 does not decrease, thereby making it difficult for offset to occur.

According to the present invention, offset does not easily occur even if a large amount of a release agent such as silicone oil is not applied, and the supply amount of the release agent can be reduced or completely eliminated. Also, the paper peeling section such as a separation claw can be omitted.

In this embodiment, a roller transfer device is used as the electrostatic contact portion. However, other forms, for example, a conductive brush or a conductive belt may be used.

In this embodiment, the voltage is applied to the recording material in synchronization with the recording material entering the fixing device.
The timing of applying the voltage or charge is not particularly limited, and may be before, during, or after entering the fixing device. Alternatively, it may be provided by a combination thereof.

Further, the amount of charge elimination of the recording material when the unfixed toner image is transferred from the intermediate transfer drum to the recording material is adjusted to be lower, and the amount of electric charge necessary to adhere to the belt member is left on the recording material. Can also respond.

Further, in this embodiment, the voltage is applied to the recording material, but the object to which the voltage or charge is applied by the electrostatic contact portion is not limited to the recording material, but is applied to the belt-shaped member. May be.

In this case, the form of the electrostatic contact portion and the timing of voltage / charge application are not particularly limited, and any combination of the forms and timings described above can be used.

FIG. 4 shows a schematic configuration of a fixing device according to another embodiment of the present invention.

As an electrostatic contact portion, instead of a roller transfer unit 5 which applies a charge or a voltage by contacting the recording material 9 as in the above-described embodiment (see FIG. 1), the first fixing roll 1 on the surface of the fixing belt 3 A charging charger 22 is provided along the portion wound around the belt, and a static elimination charger 10 as a static elimination mechanism for static elimination of the fixing belt 3 and the recording material 9 is provided in the vicinity of a pressure unit having the pressure roll 4. In this example, a charge or a voltage is applied to the recording material 9 in a non-contact manner.

The separation of the recording material 3 from the surface of the fixing belt 3 is performed by forming the pressure contact portion between the second fixing roll 2 and the pressure roll 4 such that the recording material 9 bites into the second fixing roll 2 side. Is achieved. However, since electric charges remain on the surface of the fixing belt 3 and the recording material 9, there are cases where the separation cannot be performed only by pressing. Therefore, in the present embodiment, in order to make it easier for the recording material 9 after fixing to be separated from the surface of the fixing belt 3, the fixing device 20 is provided with a static elimination charger 1 as a static elimination mechanism.
0 is provided.

That is, the fixing device 20 and the peeling mechanism (static elimination mechanism) are formed as one unit.

This charge eliminating mechanism can be applied to other embodiments.

In the present embodiment, the AC corona discharge is used for the charge eliminating mechanism. However, a method such as brush electricity removal in which a conductive brush or the like is brought into contact from the back of the paper can be applied.

Further, in addition to these electric methods,
A mechanical method such as providing a peeling claw on the charge removing mechanism for peeling can also be applied.

FIG. 5 shows a schematic configuration of a fixing device according to another embodiment of the present invention. A heating source is provided in the first roll on which the fixing belt 3 is stretched in the above-described embodiment (FIGS. 1 and 4), and a heating source 6 such as a heater lamp is provided on the inner peripheral portion of the fixing belt 3. It is an example. Since the fixing belt 3 is directly heated, it can be said that the efficiency is high and the stability is excellent as compared with the embodiment.

The heating source 6 is PT
A planar heater such as a C ceramic heater may be used. When using a planar heater such as PTC ceramic,
It is preferable that the sheet heater is brought into contact with the back side of the fixing belt 3 and is slid. A configuration may be adopted in which a thermistor is attached to this planar heater, and the temperature can be controlled by controlling the amount of current supplied to the planar heater.

FIG. 6 shows a schematic configuration of a fixing device according to another embodiment of the present invention. The fixing belt cooling device is provided between the first fixing roll 1 and the second fixing roll 2 and on the inner peripheral portion of the fixing belt 3. This is an example in which a mechanism 21 is provided.

The fixing belt cooling mechanism 21 is provided with radiating fins on a metal plate of aluminum or the like, and is provided such that the bottom surface thereof slides in contact with the fixing belt 3.
At this time, abrasion resistance can be improved by forming a lubricating protective film such as a hard carbon film on a portion sliding with the fixing belt 3 or applying a lubricant to the inner peripheral surface of the fixing belt 3. Good.

With this configuration, the temperature of the toner image 8 is reduced before the recording material 9 is separated from the fixing belt 3, so that the recording material 9 can be reliably separated from the fixing belt 3. . Further, the traveling distance to the pressurizing section can be reduced.

The fixing belt cooling mechanism 21 includes
Regardless of the above embodiment, a device that generates forced convection such as a fan may be used.

Also, since a compact and highly efficient fixing device with a simple configuration and less restrictions on arrangement can be realized as in the present invention, a tandem-type electronic device having a plurality of photoconductors which is likely to have a large device configuration. This is effective for photographic devices.

[0057]

As described above, according to the present invention, heat can be supplied to a toner image with high efficiency and stability, and it is always stable regardless of the size and material of the recording material or the gravity. High quality images can be obtained.

Further, since the heating time can be efficiently and prolonged, heat required for fixing can be supplied to the toner image at a low surface temperature, so that power consumption can be reduced and high-speed printing can be performed. , Sufficient fixing performance can be obtained.

Further, since the fixing temperature can be set low, the viscosity of the molten toner at the interface between the fixing belt and the toner image does not decrease, and offset hardly occurs. In addition, by applying pressure immediately before the recording material is separated from the fixing belt, separation of the toner image from the fixing belt is promoted, and non-offset properties can be improved. Therefore, the supply amount of the offset preventing agent can be reduced or completely eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electrophotographic apparatus including a fixing device according to one embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an electrophotographic apparatus including a fixing device according to one embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a fixing device according to another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a fixing device according to another embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a fixing device according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st fixing roll, 2 ... 2nd fixing roll, 3 ... Fixing belt, 4 ... Pressure roll, 5 ... Roller transfer device, 6 ... Heat source, 7 ... Thermistor, 8 ... Toner image, 9 ... Recording material, 11
... belt-like photoreceptor, 12 ... charger, 13 ... exposure unit, 14
... developing machine (yellow), 15 ... developing machine (magenta), 1
6 developing machine (cyan), 17 developing machine (black), 1
8 intermediate transfer drum 19 transfer device 20 fixing device
21 ... Fixing belt cooling mechanism.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masashi Yamamoto 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 2H032 AA05 AA15 BA08 BA21 BA23 BA28 2H033 AA02 AA09 AA21 AA32 BA11 BA12 BA13 BB01 BB28

Claims (6)

[Claims] 1. A fixing device for heating and fixing a recording material on which a toner image is formed, a belt-like member stretched by a plurality of rolls, a heating source for heating the belt-like member, and a surface of the belt-like member. An electrostatic adhesion unit that electrostatically adheres the recording material to the recording material, and is disposed at a position facing a roll disposed at the most downstream of the plurality of rolls with respect to a conveyance direction of the recording material, and A fixing device, comprising: a pressure roll for sandwiching and pressing the belt-shaped member, wherein the surface of the recording material on which the toner image is formed and the belt-shaped member are heated in close contact. 2. The fixing device according to claim 1, wherein the electrostatic contact portion has a function of applying a charge or a voltage to the recording material. 3. The fixing device according to claim 1, wherein said electrostatic contact portion is a roll transfer device. 4. The fixing device according to claim 1, wherein a hardness of a surface of the pressure roll is higher than a hardness of the opposite roll. 5. A fixing device for heating and fixing a recording material on which a toner image is formed, comprising: a belt-shaped member stretched by a first roll and a second roll; and a heating source for heating the belt-shaped member. A roller transfer unit that is disposed to face the first roll, applies a charge or voltage to the back surface of the recording material on which the toner image is formed, and electrostatically adheres to the belt-shaped member; And a pressure roll disposed opposite to the second roll and pressing the recording material with the belt-shaped member. 6. A photoconductor, a charger for charging the surface of the photoconductor, an exposure device for forming an electrostatic latent image on the surface of the photoconductor, and forming a toner image of a different color on the surface of the photoconductor. A plurality of developing machines; an intermediate transfer member that forms a color toner image by superimposing the toner images of different colors; a transfer device that transfers the color toner image to a recording material; and a color toner image on the recording material. A fixing device for fixing the belt-shaped member stretched by a plurality of rolls, a heating source for heating the belt-shaped member, and forming the color toner image on the belt-shaped member. An electrostatic adhesion unit that applies a charge or voltage to the back surface of the recording material to electrostatically adhere the recording material, and a pressure roll that sandwiches and presses the recording material with the belt-shaped member. Electrophotographic equipment.