JP2001109288A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device making a service life of a fixing belt prolonged, stable fixing performance demonstrated over a long period, a power saving as a result of improvement in heating efficiency of a heat source, and an image forming device provided with the above fixing device. SOLUTION: In this fixing device provided with the rotatable fixing belt 73 being wound around at least, 2 supporting rollers 74 and 75, a heating source 76 for heating the fixing belt 73, and at least, the 2 pressure rollers 71 and 72 for fixing the toner image on transfer material P in heating/pressing by holding/transporting the transfer material carrying the toner image thereon in a state of laminating the transfer material P and the fixing belt 73, the fixing device is made to arrange the heating source 76 between the pressure roller 71 and the supporting roller 74 on the upstream side in the transporting direction of the fixing belt 73 inside of the fixing belt 73 for heating inner sides of the fixing belt 73 and the heating source 76 is made to heat the upstream side and the downstream side of the fixing belt 73 between the pressure roller 71 and the supporting roller 74.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt-type fixing device for an electrophotographic image forming apparatus and an image forming apparatus provided with the fixing device.

[0002]

2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus includes a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and pressing against the heating roller. A heat roller fixing method in which a recording material on which an unfixed toner image is formed is heated while being nipped and conveyed is often used.

[0003] However, in this type of apparatus, the heat capacity of the heating roller is increased, the warm-up time is lengthened, and the temperature inside the elastic layer is increased, thereby shortening the life of the roller. In addition, many color images have a large solid area, and many of the solid images are other than black, and uneven gloss is conspicuous. When a hard roller is used as the above-mentioned heating and pressing roller, unevenness of gloss is generated according to the unevenness of the paper or the toner layer, so that there is a problem that image quality is reduced.

[0004]

In order to solve the above problems, a fixing system using a rubber roller or a rubber belt has been proposed. Using a rubber roller can provide good image quality, but it takes time to warm up and has a problem such as a short life of the roller.This problem becomes more and more noticeable with the speeding up of copiers and printers. It has become to.

[0005] A fixing device using a fixing belt has the following problems. (1) In a fixing device having a heating source on the inner surface of the fixing belt, if the fixing belt is intensively heated by the heating source immediately before the fixing processing area of the fixing belt, the inner surface of the fixing belt becomes excessive immediately after irradiation by the heating source. And the useful life of the fixing belt may be shortened. (2) A fixing device including a heating source disposed on the inner surface of the fixing belt, a support roller for rotatably supporting the fixing belt, a pressure roller for heating and pressing the fixing belt and the transfer material in a state where the fixing belt and the transfer material are overlapped. In, the irradiation light from the heating source irradiates the support roller and the pressure roller etc. in addition to the surface to be irradiated on the inner surface of the fixing belt, so that the heat of the heating source is wasted and the heating efficiency is reduced. Was.

An object of the present invention is to solve each of the above problems,
Provided is a fixing device that improves the service life of a fixing belt, exhibits stable fixing performance over a long period of time, and achieves power saving by improving the heating efficiency of a heating source, and an image forming apparatus including the fixing device. The purpose is to do.

[0007]

According to the present invention, there is provided a fixing device comprising: a fixing belt rotatable around at least two support rollers; a heating source for heating the fixing belt; A fixing device comprising: at least two pressure rollers for fixing the toner image to the transfer material by nipping and transporting the transfer material carrying the image and the fixing belt in a state of being overlapped with each other and applying heat and pressure. A heating source is disposed inside the fixing belt between the pressure roller and the supporting roller on the upstream side in the fixing belt conveyance direction, and the heating source is provided to the upstream supporting roller of the fixing belt. And heating both the upstream region and the downstream region with respect to the upstream support roller (claim 1).

[0008] The fixing device of the present invention that solves the above-mentioned problems includes:
A fixing belt rotatable around at least two support rollers, a heating source for heating the fixing belt, a transfer material for carrying a toner image, and the fixing belt sandwiched and conveyed in a state of being overlapped and heated; And a pressure source for fixing the toner image to the transfer material by pressing, a heating source is disposed inside the fixing belt, and at least the support roller or the pressure A reflection plate for shielding the irradiation light from the heating source is provided for the roller or both of them (claim 2).

[0009] The image forming apparatus of the present invention is characterized by comprising a fixing device comprising the pressure roller, the support roller, a fixing belt, a heat source, and a reflection plate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fixing device according to the present invention and an image forming apparatus equipped with the fixing device will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a color printer which is an image forming apparatus equipped with the fixing device of the present invention.

In this color printer, a flexible endless belt-shaped photoconductor (hereinafter, referred to as a photoconductor) 1 serving as an image carrier is used.
, Four sets of scorotron chargers (hereinafter referred to as chargers) 2Y, 2M, 2C, 2K, four sets of image exposure devices 3
Y, 3M, 3C, 3K, four sets of developing units 4Y, 4M, 4
The image forming units C and 4K (four sets as shown) are arranged in tandem. The illustrated image exposure apparatus 3
Y, 3M, 3C, and 3K use a laser beam scanning optical device.

The photosensitive member 1 is stretched around a driving roller 11, a lower roller 12, and an upper roller 13, and a tension roller 14
And is rotated clockwise as shown in the drawing while being locally brought into contact with the backup member 15 provided on the inner peripheral surface. The backup member 15 is in contact with the inside of the photoreceptor 1 and develops the developing areas of the developer carriers 41Y, 41M, 41C, 41K of the developing units 4Y, 4M, 4C, 4K and the image exposure devices 3Y, 3M, 3C, 3K. The photoconductor 1 is regulated at the 3K image forming position.

At the start of image recording, a drive motor (not shown) is rotated to rotate the photosensitive member 1 clockwise via a drive roller 11, and the photosensitive member is charged by a charging action of a charger 2Y. Application of the potential to 1 is started. Photoconductor 1
Is the first in the image exposure apparatus 3Y after the potential is applied.
Exposure is started by an electrical signal corresponding to the color signal of the photoconductor 1, ie, the yellow (Y) image signal, and the rotation (sub-scanning) of the photoconductor 1 causes the photosensitive layer on the surface to correspond to the yellow (Y) image of the developed image. An electrostatic latent image is formed. The developing device 4Y reversely develops the latent image in a non-contact state on the developer carrying member 41Y by the developing device 4Y to form a yellow (Y) toner image.

Next, the photoreceptor 1 is further provided with a potential on the yellow (Y) toner image by the charging action of the charger 2M, so that a second color signal of the image exposure device 3M, that is, an image signal of magenta (M) is obtained. Exposure is performed by the corresponding electric signal, and a magenta (M) toner image is formed on the yellow (Y) toner image by non-contact reversal development by the developing device 4M.

By the same process, a cyan (C) toner image corresponding to the third color signal is further formed by the charger 2C, the image exposure device 3C, and the developing device 4C. Further, a black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed by the charger 2K, the image exposure device 3K, and the developing device 4K, and is formed on the peripheral surface within one rotation of the photoconductor 1. A color toner image is formed.

The color toner image formed on the peripheral surface of the photoconductor 1 reaches the transfer area after the potential of the attached toner is adjusted by the charger 2F. From the paper feed cassette 51 or the manual paper feed table 53 of the paper feed device 5,
The transfer material P sent out by the registration rollers 2 and 54 and conveyed to the registration roller pair 55 is fed by the driving of the registration roller pair 55 in synchronization with the passage of the toner image area on the photoconductor 1, and the lower portion of the drive roller 11 The toner image is transferred by the transfer means 6 disposed opposite to the toner image.

The transfer material P on which the toner image has been transferred is separated from the peripheral surface of the photoreceptor 1 and then conveyed to a fixing device 7. The toner image is melted by the fixing device 7 and fixed on the transfer material P. After the completion of the fixing process, the transfer material P is conveyed by a pair of paper discharge rollers 81, 82, and 83 and discharged to a paper discharge tray 84 provided at an upper portion. On the other hand, the photoconductor 1 from which the transfer material P has been separated is cleaned by removing the residual toner by the cleaning blade 91 of the cleaning device 9.
When the formation of the toner image of the next original image is subsequently performed, the pre-charging static eliminator 92 exposes the photoconductor surface of the photoconductor 1 to remove the previous charge.

FIG. 2 is a sectional view showing an embodiment of the fixing device of the present invention, and FIG. 3 is a plan view of the fixing device. In FIG. 2, reference numerals 71 and 72 denote a pair of pressure rollers which can relatively come and go, and reference numeral 73 denotes an endless belt-shaped fixing belt. The support rollers 74 and 75 are a pair of support rollers that support and support the fixing belt 73. 76 is a halogen heater as a heating source, 77A and 77B are reflection plates, 78 is a fixing belt 7
3 is a cleaning means for cleaning the outer peripheral surface.

At least one of the pair of pressure rollers 71 and 72 has a movable rotating shaft position. At the time of fixing, the fixing belt 73 and the transfer material P are nipped and pressed to be conveyed. At the time of non-fixing, at least one of the rollers, for example, the illustrated pressure roller 72 moves in the direction of the arrow against the pressure contact force, and separates from the pressure roller 71 to form a gap. The fixing belt 73 is formed, for example, by laminating a silicone rubber layer and a protective layer on the surface of an endless belt-shaped Ni layer formed by electroforming.

The silicone rubber layer has a thickness of, for example, 0.2 m.
m, rubber elasticity of 3 ° to 60 ° (JISA),
It is a belt layer having a small heat capacity. Further, the fixing belt 73
Is coated with an infrared absorbing material, has a high absorptance of irradiation light, and is heated to a predetermined temperature (for example, 190 ° C.) in a short time by heating by the halogen heater 76.

The fixing belt 73 is stretched between the support roller 74 and the support roller 75 with a very weak tension of 0.5 kg / cm or less, more preferably 0.2 kg / cm or less. Alternatively, it may be in a state where the tension is loosened. The fixing belt 73 is rotated by rotation of the support roller except during the fixing process. Fixing belt 73 during fixing process
Are rotated by being pressed by the pressure rollers 71 and 72. The rotation speed of the fixing belt 73 is the same as the transfer speed of the transfer material P.

As shown in FIG. 3, the support roller 74 has a roller portion 74A formed with a spiral protrusion having an inclination angle with respect to the axial direction of the rotation shaft 74B, and a rotation shaft 74B driven and rotated by a drive source. , A flange member 74C connected to both ends of the roller portion 74A, and a gear 74D fixed to one shaft end of the rotating shaft 74B and connected to a driving source.

The supporting roller 75 is formed by a roller portion 75A having a helical protrusion having an inclination angle with respect to the axial direction of the rotating shaft 75B, a rotating shaft 75B, and a flange member 75C connected to both ends of the roller portion 75A. Become. Roller part 74
A and 75A are materials having heat resistance to the fixing temperature of the halogen heater 76 and having low thermal conductivity, for example,
It is formed of foamed silicone rubber or the like.

The rollers 74A and 75A are
B and 75B were formed by integrally molding silicone rubber or other heat-resistant resin on the outer periphery, or a cord-shaped silicone rubber was spirally wound around the outer peripheral surface of a hollow cylindrical member made of metal or resin to form a projection. The thing etc. are used. Spiral protrusions are formed on the roller portions 74A and 75A in order to reduce the contact area with the fixing belt 73 so as to remove heat from the fixing belt 73 as much as possible. Thus, when the fixing device 7 is warmed up, only the fixing belt 73 needs to be heated, and there is no heat that is taken away by the core metal or the like as compared with the conventional roller fixing method or the like, so that the warming-up time can be significantly reduced. . Further, since the projections are spiral, the fixing belt 73 and the roller 74
A and 75A are continuously in contact with each other, and the operating noise of the fixing belt 73 is reduced.

When both the supporting roller 74 and the supporting roller 75 are driven by the driving device of the main body of the image forming apparatus, the direction of the inclination angle of the helical projection formed on the roller portion 74A of the supporting roller 74 is determined. The direction of the inclination angle of the spiral projection formed on the roller portion 75A of the support roller 75 is reversed. The force that causes the fixing belt 73 to move to one side by the helical protrusions is a roller portion 74A and a roller portion 75A.
, The directions are opposite to each other, and the offset of the fixing belt 73 due to the provision of the spiral protrusion is prevented.

One of the two support rollers 74 and 75 is driven and driven via the fixing belt 73, for example, the support roller 75 is rotated by receiving the driving force from the support roller 74 via the fixing belt 73. In such a case, the direction of the force for biasing the fixing belt 73 is reversed by making the inclination angles of the spiral protrusions the same direction, and similarly, the occurrence of the biasing of the fixing belt 73 is prevented.

The fixing belt 73, which is stretched with a very weak tension, is provided on the inclined surfaces of the flange members 74C provided at both ends of the roller portion 74A and the inclined surfaces of the flange members 75C provided at both ends of the roller portion 75A. Meandering, roller section 74
A, Prevents deviation from 75A. Support roller 74
Is driven and rotated clockwise as indicated by an arrow by a power unit of the image forming apparatus main body. With the rotation of the support roller 74, the fixing belt 73 and the support roller 75 are rotated clockwise. The design value of the driving speed of the fixing belt 73 is the same as the transport speed of the transfer material P. The peripheral speed of the pressure rollers 71 and 72 is driven to be the same as the driving speed of the fixing belt 73.

Inside the fixing belt 73 between the pressing roller 71 and the driving support roller 74 on the upstream side in the conveying direction of the fixing belt 73, one or more rod-shaped halogen heaters 76 are arranged. The halogen heater 76 irradiates and heats the downstream region L and the upstream region U inside the fixing belt 73 between the pressure roller 71 and the support roller 74.

The halogen heater 76 irradiates and heats the downstream region L and the upstream region U inside the fixing belt 73 at the same time, and heats the unit area per unit area as compared with the case where only the downstream region L is irradiated. Of the fixing belt 73 can be reduced, and the temperature rise of the inner surface of the fixing belt 73 can be reduced. The inside of the fixing belt 73 and the support roller 7
In the vicinity of No. 4, a reflector 77A was arranged. Reflector 77A
Is the support roller 7 out of the irradiation light of the halogen heater 76.
4 is reflected and blocked. The reflected light of the halogen heater 76 reflected by the reflection plate 77A irradiates the inner surface of the surrounding fixing belt 73 and heats the fixing belt 73 efficiently without waste.

Further, a reflection plate 77B for shielding the irradiation light of the halogen heater 76 is provided for the pressure roller 71 disposed inside the fixing belt 73. The reflecting plate 77B reflects and blocks the irradiation light reaching the pressure roller 71 among the irradiation light from the halogen heater 76. The reflected light of the halogen heater 76 reflected by the reflection plate 77B irradiates the inner surface of the surrounding fixing belt 73 and heats the fixing belt 73 efficiently without waste.

The irradiation light of the halogen heater 76 and the reflection plate 7
The fixing belt 73 is heated to a predetermined temperature by the reflected lights of 7A and 77B. In the present embodiment, the halogen heater 76 is installed as a heating source between the pressure roller 71 and the support roller 74 on the upstream side of the pressure roller 71, but the present invention is not limited to this. Pressure roller 71
Even if it is disposed between the support roller 75 and the pressure roller 71 on the downstream side of the reflector or both of them, the reflection plate 77A,
By arranging 77B appropriately, a similar effect can be obtained.

As the transfer material P carrying the toner image is conveyed to the fixing area via the conveyance guide plate 56, or before the transfer material P is conveyed to the fixing area, the pressure roller 72 disposed outside the fixing belt 73 is raised. Then, the transfer material P and the fixing belt 73
And pressurized. The toner image on the transfer material P is fixed to the transfer material P by the heating of the fixing belt 73 by the heat and the nipping and pressing by the pressure rollers 71 and 72.

A predetermined load acts on the support shaft 72A at both ends of the pressure roller 72 toward the pressure roller 71 when the support shaft 72A is sandwiched by a spring member, and a constant force acts on the pressure contact portions of the pressure rollers 71 and 72. It is supposed to. The magnitude of this force is 0.2 to 2 kg / cm, preferably 0.6 to 1.0 k per unit length in a direction parallel to the axis of the pressure roller 72.
g / cm.

The pressing by the pressing rollers 71 and 72 may be performed by moving both the pressing roller 71 downward and the pressing roller 72 upward. Since the peripheral speed of the pressure roller 71 or the pressure roller 72 is driven at the same speed as the moving speed of the fixing belt 73, no excessive force is applied to the fixing belt 73 and the transfer material P. I have. After the fixing, the pressure rollers 71 and 72 are released from the pressure contact, so that the distortion and the deviation due to a minute speed difference between the fixing belt 73 and the pressure rollers 71 and 72 are eliminated. , 72 is prevented.

A fixing belt 73 is attached to the toner image on the transfer material P.
Contact with the transfer material P and the unevenness of the toner image due to the elasticity of the silicone rubber, and uniformly contact the heat of the fixing belt 73 heated by the halogen heater 76 and the pressure roller 71, By the pressurization by 72, uniform fixing without gloss unevenness is performed.

An elastic layer made of silicone rubber is provided on the outer periphery of the pressure roller 72 outside the fixing belt 73.
A large nip width is formed at the contact portion between the pressure rollers 71 and 72, and perfect fixing is performed. The fixed transfer material P is transferred to a support roller 7 that supports the fixing belt 73.
The sheet is separated by the fixing belt 73 by the curvature of 5.

The fixed transfer material P is applied to a pressure roller 71,
When the air exits from the nip portion 72, the air is cooled by the outside air, so that offset and improper separation during separation can be avoided.

[0038]

According to the present invention, the following effects can be obtained by the configuration described above. (1) By simultaneously irradiating the upstream side and the downstream side of the fixing belt, which is wound around the driving-side support roller, with a halogen heater, the heating area can be widened and the irradiation energy per unit area can be relatively reduced. And the sharp rise in the temperature inside the fixing belt can be minimized, without causing thermal damage to the fixing belt.
In addition, it has become possible to efficiently provide a fixing device in which the warm-up time is shortened. (2) The reflecting plate arranged inside the fixing belt reflects and blocks the irradiation light of the halogen heater from reaching the supporting roller and the pressing roller, thereby protecting the supporting roller and the pressing roller and reflecting the light. Reflected by the halogen heater irradiates the inner surface of the surrounding fixing belt,
Since the fixing belt is efficiently heated without waste, the heating efficiency of the fixing belt is improved. (3) The image forming apparatus provided with the fixing device including the pressure roller, the support roller, the fixing belt, the heat source, and the reflection plate of the present invention can save power by improving thermal efficiency, shorten warming-up time, achieve high-speed fixing, and achieve high image quality. There is provided an image forming apparatus which has excellent fixability, stabilization and long service life and is excellent in maintenance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a color printer that is an image forming apparatus equipped with a fixing device of the present invention.

FIG. 2 is a sectional view showing an embodiment of the fixing device of the present invention.

FIG. 3 is a plan view of the fixing device.

[Explanation of symbols]

 7 Fixing Devices 71, 72 Pressure Roller 73 Fixing Belt 74 Support Roller 75 Support Roller 74D Gear 76 Halogen Heater (Heat Source) 77A, 77B Reflector P Transfer Material U Upstream Area L Downstream Area

Claims (4)

[Claims] An image forming apparatus comprising: a fixing belt rotatable around at least two support rollers; a heating source for heating the fixing belt; a transfer material for carrying a toner image; A fixing roller having at least two pressure rollers for fixing the toner image to the transfer material by nipping and conveying and applying heat and pressure, wherein the pressing roller and the supporting roller on the upstream side in the fixing belt conveying direction are provided. A heating source is disposed inside the fixing belt between the fixing belt, the heating source is an area of the fixing belt on the upstream side with respect to the upstream support roller, and a heating source with respect to the upstream support roller. A fixing device for heating both downstream regions. A fixing belt rotatable around at least two support rollers, a heating source for heating the fixing belt, a transfer material for carrying a toner image, and the fixing belt in a stacked state. A fixing device including at least two pressure rollers for fixing the toner image to the transfer material by nipping and conveying and applying heat and pressure, wherein a heat source is disposed inside the fixing belt and at least the support A fixing device, wherein a reflection plate for blocking irradiation light from the heating source is provided for the roller, the pressure roller, or both of them. 3. The fixing device according to claim 1, wherein the heating source is a halogen heater. 4. An image forming apparatus comprising a pressure roller, a support roller, a fixing belt, a heat source, and a fixing plate comprising a reflection plate according to claim 1. .