JPH10142972A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance fixing efficiency, to attain high speed fixing, and to improve the image quality after fixing, in a fixing device. SOLUTION: A fixing belt is formed of a conductive elastic body having heat resistance, and it is pressed inside by a pressing roller 502 to constitute a fixing nip part N. The toner image T on a recording material P is fixed by allowing the fixing belt 501 to generate heat by providing respective electrode 503 and 504 on the upstream side and the downstream side of the nip part N, conducting the current by a power source 508, and heating the transfer material P. Since the fixing belt 501 itself can generate the heat, the heat can be efficiently fed corresponding to the transfer material P and the toner image T, and since the fixing belt 501 is composed of an elastic body, the width of the fixing nip part N is widened, the fixing efficiency is enhanced, the fixing speed is increased, the fixing belt 501 can excellently follow up unevenness even if the unevenness is present on the transfer material surface, contact to the toner image becomes close, and thus the image quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device mounted on a copying machine, a laser beam printer, or the like, for heating and fixing a toner image on a transfer material.

[0002]

2. Description of the Related Art Conventionally, as a fixing device for fixing an unfixed toner image formed on a transfer material in an image forming section in an image forming apparatus such as a copying machine or a laser beam printer, a so-called fixing device shown in FIG. Roller type fixing devices are well known.

This fixing device of the transfer roller type has a fixing roller Rf having a release layer on the surface and a pressure roller Rp having an elastic layer. Inside the fixing roller Rf, the surface temperature of the fixing roller Rf is set. To maintain a predetermined temperature
Are arranged.

The above-mentioned fixing roller Rf and pressure roller Rp are in pressure contact with each other, and the unfixed toner image T
The non-fixed toner image Ta is fixed on the transfer material P by applying heat and pressure by nipping and transporting the transfer material P carrying a. In the figure, Da is an application roller for applying silicone oil to the surface of the fixing roller Rf to improve the releasability, and W is a fixing roller Rf and a pressure roller Rp.
This is a cleaning device for removing silicone oil and toner adhering to the surface.

The above-described roller-type fixing device has an advantage that its structure is relatively simple. However, since the heat capacity of the roller is large, the temperature of the roller is set to a temperature at which the toner can be fixed to the transfer material P. (Hereinafter "fixable temperature"
(It takes a long time to warm up). Even during the operation other than the fixing operation (for example, standby = standby state), the heater H must be appropriately energized to generate heat and adjust the temperature, so that power is wasted (contrary to energy saving). It has such disadvantages.

As a fixing device which solves these disadvantages and achieves a fixing temperature in a relatively short time and achieves energy saving, for example, a heater through a fixing film having high heat resistance and high releasability as shown in FIG. Currently, a fixing device of a so-called fixing film type in which a toner is heated and fixed on a transfer material is practically used.

In FIG. 1, reference numeral 401 denotes an endless belt type thin film heat-resistant fixing film. 402 is a pressure roller, 403 is a heating element (thermal heater), 404 is a driving roller for driving the fixing film 401, and 405 is a driven roller also serving as a tension roller. Drive roller 40
4, the driven roller 405 and the heating element 403 are arranged in parallel with each other, and the fixing film 401 is wound and stretched between these three members. Drive roller 404
Is rotated counterclockwise in the figure by a drive system (not shown), and accordingly, the fixing film 401 travels (moves) in the direction of arrow a due to friction with the outer peripheral surface of the drive roller 404. At this time, the fixing film 401 runs at the same speed as the transfer material P so as to rub against the heating body 403.

[0008] The pressure roller 402 is made of a heat-resistant rubber elastic material such as silicone rubber, for example. Like a general pressure roller, PFA (PFA) is applied on the rubber elastic material to enhance the surface release property. A highly releasable surface layer such as tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) or PTFE (polytetrafluoroethylene) is formed. The pressure roller 402 is urged in the direction of the heating element 403 by an urging means (not shown), thereby pressing the fixing film 401 against the heating element 403 with a predetermined pressing force. , A fixing nip portion N1.

The heating element 403 is a low-heat-capacity linear heating element whose longitudinal direction is the axial direction of the fixing film 401 (a direction orthogonal to the moving direction a of the fixing film; hereinafter, referred to as “fixing film width direction”). Yes, heater substrate 403a
And a heater 403b formed in a narrow band or linear shape along the longitudinal direction substantially in the center of the lower surface of the substrate 403a,
The heater 403b includes a surface protection layer 403c made of heat-resistant glass or the like for protecting the surface of the heater 403b, a temperature detecting element 403d provided on the upper surface of the substrate 403a, a heater support 403e for insulatingly supporting the substrate 403a, and the like.

In FIG. 1, P denotes a transfer material, which is supplied from the left side and passes through the fixing nip N1.
Move right. Before being introduced into the fixing device, the transfer material P carries the unfixed toner image Ta on the surface. The transfer material P enters the fixing nip portion N1, where
The fixing film 4 whose surface carrying the unfixed toner image Ta moves in the same direction at substantially the same speed as the transfer speed of the transfer material P
01, overlaps with the fixing film 401, and passes through the fixing nip N1 while receiving a squeezing pressure.

As a result, the unfixed toner image Ta on the transfer material P is heated and pressurized in the fixing nip portion N1 to become a softened and fused toner image Tb, and further discharged to a fixed state Tc.

In the fixing device using the fixing film having the above-described structure, quick start is possible, and it is not necessary to perform standby temperature control in which the heating element 403 is energized and heated in advance. There is an advantage that a rise in temperature can also be prevented.

[0013]

However, the above-mentioned fixing device using the fixing film 401 has the following problems. It is difficult to further increase the speed. Poor image quality after fixing.

First, to speed up the problem, it is necessary to further reduce the thickness of the fixing film 401 and increase the thermal conductivity.

However, the fixing film 401 mainly used at present is, for example, a polyimide resin film as a base material coated with a fluorine resin as a high release layer and having a thickness of about 30 μm. Thinning results in a decrease in film strength, which is not preferable in terms of the device configuration.

Further, BN is added to the base material to increase the thermal conductivity.
(Boron nitride), AlN (aluminum nitride), SiC
It is effective to add a filler such as (silicon carbide), but if added excessively, the film strength is reduced.
It is rather disadvantageous for an increase in mechanical stress due to speeding up.

The fixing film 401 and the pressure roller 4
It is also effective to increase the fixing nip N1 formed by the pressure roller 402 and the pressure roller 402 in this case.
It is necessary to reduce the elasticity of the material No. 2 and problems such as an increase in the size of the fixing device and deformation of the pressure roller 402 in a long-term pressing state occur.

Next, although the image quality after fixing is low, the transfer material P nipped and conveyed by the fixing film 401 which comes into contact with the heating member 403 which is a rigid body and the pressing roller 402 which is an elastic body. At the fixing nip N1
When receiving heat and pressure, the contact state is as shown in FIG. That is, since the transfer material P generally has irregularities on the surface, the contact state between the fixing film 401 and the individual toners Tb on the transfer material P becomes uneven. Therefore, as shown in FIG. 11B, the toner x formed on the convex portion of the surface of the transfer material P that comes into contact with the fixing film 401 receives sufficient heat and pressure, and thus melts as indicated by Tb. The toner y formed in the concave portion on the surface of the transfer material P cannot be brought into contact with the fixing film 401, so that energy is supplied only by radiant heat, and the melting condition is insufficient. The individual toners thereafter retain their granularity.

As described above, the difference between the surfaces of the toner fixed on the transfer material P having the irregularities visually looks uneven as a solid image because the surface irregular reflection is increased (image quality after fixing is low).

FIGS. 12A and 12B show the fixing nip portion N1 when a rubber elastic material such as silicone rubber is used as the surface material of the fixing member D instead of the fixing film 401. FIG. 5 is a diagram illustrating a contact state between the fixing member D and the toner Tb on the transfer material P and a fixing state of the toner Tc on the transfer material P after passing through the fixing nip N1.

In this configuration, the contact of the fixing member D, which is a rubber elastic body, follows the unevenness of the surface of the transfer material P. That is, since the surface of the fixing member D follows the unevenness of the surface of the transfer material P, The surface condition of the toner Tc is uniform, and a solid image is visually uniform (image quality after fixing is high).

However, in the case where a rubber elastic material such as silicone rubber is used as the fixing member D of the above-described fixing device, in order for the fixing member D to follow the general unevenness of the surface of the transfer material, 100 μm or more, preferably 15
That a thickness of the rubber elastic body D of 0 μm or more is required,
Applicants have confirmed by experiments and the like.

Accordingly, as described above, when the thickness of the fixing film increases, the heat conduction time from the heating element 403 increases, so that the fixing member D made of such a rubber elastic material is used for the fixing device. Is not preferred.

Therefore, according to the present invention, the temperature at which the toner can be fixed to the transfer material in a short time is reached (quick start property), and it is not necessary to perform standby temperature control in which the heating element is energized and heated in advance, thereby saving energy. It is an object of the present invention to provide a fixing device that can perform fixing at a high speed while being capable of achieving high image quality after fixing.

[0025]

According to a first aspect of the present invention, there is provided a movable fixing belt in which a conductive member which generates heat by energization is formed in a belt shape, and the fixing belt is brought into contact with the fixing belt to contact the fixing belt. A pressurizing member for forming a fixing nip portion between the fixing belt and an energizing means for generating heat at a portion corresponding to the fixing nip portion of the fixing belt, and fixing the transfer material having an unfixed toner image on a surface thereof. The unfixed toner image is fixed on the surface of the transfer material while being nipped and conveyed in the nip portion.

According to a second aspect of the present invention, the fixing belt is formed of a conductive elastic material having heat resistance.

According to a third aspect of the present invention, the fixing belt has a highly releasable surface layer on a surface side in contact with the unfixed toner image.

According to a fourth aspect of the present invention, the fixing belt has a reinforcing layer on the back surface side.

In the present invention according to claim 5, the energizing means includes electrodes that contact the fixing belt on an upstream side and a downstream side of the fixing nip portion in the running direction of the fixing belt, respectively. And a power supply for conducting electricity.

According to a sixth aspect of the present invention, the fixing belt is formed in an endless shape, and further includes a roller member around which the fixing belt is wound. Perforation is applied to one of the fixing belt and the roller member. And the other is provided with a tooth portion that engages with the perforation.

[Operation] Based on the above configuration, since the fixing belt itself generates heat when energized, heat can be efficiently supplied to the transfer material and the toner image.

If the fixing belt is formed of a heat-resistant conductive elastic material, the width of the fixing nip can be easily changed and the fixing efficiency can be increased.
Higher speed is possible. Furthermore, when the surface of the transfer material carrying the toner image has irregularities, the fixing belt follows the irregularities well, and the contact with the toner image becomes dense, so that the toner image after fixing is visually uniform. be able to.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIGS. 1 and 2 are a longitudinal sectional view and a perspective view, respectively, showing a schematic configuration of a fixing device according to the present invention.

The fixing device 50 shown in these figures has an endless belt-like heat-resistant elastic belt (hereinafter referred to as “fixing belt”) 501. The fixing belt 5
01 will be described later.

The fixing belt 501 includes a driving roller 505
And a driven roller 506 also serving as a tension roller, and is urged inward by a pressing roller (pressing member) 502 disposed between the rollers 505 and 506, thereby fixing the image. A fixing nip N is formed between the belt 501 and the pressure roller 502. Fixing belt 501, drive roller 505 by a driving means (not shown) based on that rotates in the arrow a ₁ direction, runs in the direction of arrow a at a speed equal to the conveying speed of the transfer material P (transfer).

With respect to the running direction of the fixing belt 501,
Current-carrying electrodes (electrodes) 503 and 504 are arranged on the upstream and downstream sides of the fixing nip N so as to sandwich the fixing nip N therebetween. The energizing electrodes 503 and 504 are rotatably supported by supporting means (not shown) and are in contact with the inner peripheral surface of the fixing belt 501. A power supply 508 is connected to the energizing electrodes 503 and 504, and the energizing electrodes 503 and 504 of the fixing belt 501 are connected.
It is configured to supply power to the portion between 504.

A portion of the inner peripheral surface of the fixing belt 501 corresponding to the above-described fixing nip portion N is provided with a fixing belt 501.
A temperature detecting element 507 for measuring the surface temperature of the fixing belt 501 is provided in contact with the driving roller 505 on the outer peripheral surface of the fixing belt 501. And a cleaning and oil supply member 509 for cleaning the outer peripheral surface is provided in contact therewith.

The pressure roller 502 is a heat-resistant rubber elastic material such as silicone rubber. Like a general pressure roller, a P-type rubber is applied on the rubber elastic material to enhance the surface release property.
A highly releasable surface layer such as FA or PTFE is formed. As the pressure roller 502, for example, a silicone rubber layer having a thickness of about 7 mm is provided on the surface of a cored bar, and this surface is covered with a PFA tube having a thickness of 100 μm, and is configured to have a diameter of about 30 mm as a whole. Are arranged between the energizing electrodes 503 and 504 so as to contact a part of the outer peripheral surface of the fixing belt 501.

In this embodiment, the contact pressure between the fixing belt 501 and the pressure roller 502 is determined by the tension of the fixing belt 501 or the nip area between the fixing belt 501 and the pressure roller 502. , 7 kg / cm ² or less per unit area, more preferably 0.5 to
It may be set to a value of about 5.0 kg / cm ² .

The above-mentioned pressure roller 502 is used for the fixing belt 5.
01 of travel of the arrow a running speed of with the (mobile) arrow a ₂ direction to the fixing belt 501 in the same direction (forward direction) driven to rotate at the same speed.

The current-carrying electrodes 503 and 504 have a diameter of 5 to 10 m.
For example, platinum plating, rhodium plating, or the like is applied to a rigid material of about m, and the fixing belt 501 is uniformly abutted in the width direction.

The temperature detecting element 507 is constituted by, for example, an NTC thermistor which is a low-heat-capacity temperature measuring resistor. The fixing belt 501 may be disposed on the outer peripheral surface or the inner peripheral surface of the fixing belt 501 in contact with the fixing belt 501, but a portion where the toner image is actually fixed, that is, a fixing nip portion N is preferably provided in the vicinity of the fixing belt 50, as shown in FIG.
1 is preferably disposed on the inner peripheral surface.

The power supply 508 has, for example, a pulsed waveform with a DC voltage of 100 V and a period of 200 ms.
, And a pulse corresponding to a desired temperature and energy release amount controlled by the temperature detection element 507 is given while changing the pulse width. The pulse width at this time is approximately 0.
5 to 5 ms. In addition, at 100 VAC, the temperature sensor 5
The energized power may be controlled by controlling the phase angle to be energized by an energization control circuit (not shown) including a triac based on the detected temperature of 07.

When the current-carrying electrodes 503 and 504 are energized, Joule heat is generated in the Z portion of the fixing belt 501 shown in FIG.
07, the result of the temperature measurement is fed back to a control circuit (not shown), and the current-carrying electrodes 503, 504
, And the temperature of the fixing belt 501 is controlled to a predetermined fixing temperature (for example, 150 ° C.).

The cleaning and oil supply member 50
Reference numeral 9 denotes a structure in which a felt pad 509b is attached to the lower surface of a base material 509a. The felt pad 509b is impregnated with an oil having a good releasability, such as silicone oil, and abuts on the outer peripheral surface of the fixing belt 501 so as to sandwich the fixing belt 501 between itself and the driving roller 505. Have been.

In the fixing device 50 having the above-described structure, there is no equivalent to the heating element 403 in the above-mentioned fixing film type fixing device (see FIG. 10).
Since the fixing belt 501 itself is a heating element, the heat capacity of the fixing belt 501 is extremely small, and most of the heat energy of the fixing belt 501 is supplied to the toner T on the transfer material P. To a temperature at which the image can be fixed on the transfer material P.

For this reason, in the fixing device 50 of the fixing belt type having the above-described configuration, quick start is possible, and there is no need for standby temperature control in which the fixing belt 501, which is a heating element, is energized and heated in advance. Energy saving can be achieved, and the temperature inside the image forming apparatus can be prevented from rising.

The surface of the fixing belt 501 is made of an elastic material (described later).
As shown in (a) and (b), even when the surface of the transfer material P has irregularities, the toner image Tb in the fixing nip N is as shown in FIG. The image Tc is in a uniform fixed state.

In the example shown in FIG.
Although the fixing belt 501 is not limited to the endless belt shape, the fixing belt 501 is not limited to the endless belt shape, and may be a long film having an end and run at a predetermined speed from the feeding roller to the winding roller. You may make it contact a pressure roller between rollers.

FIG. 4 is a schematic sectional view of a layer structure showing an example of the fixing belt 501 used in the first embodiment. The fixing belt 501 is made of a rubber elastic material G made of a heat-resistant, highly releasable rubber material such as silicone rubber, fluorine rubber, or fluorosilicone rubber, and a conductive material C having various shapes such as a strip, a fiber, and a powder. The rubber elastic body D to which a metal material, a metal oxide, graphite, carbon black, an ionic conductive material or the like is added is used. The rubber elastic body D is configured as a low-resistance material having a volume resistance of 100 Ω · cm or less, preferably 10 Ω · cm or less by appropriately adjusting the amount of the conductive substance C to be added.

As shown in FIG. 5, PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) and PTFE (polyethylene) are applied to the surface of the rubber elastic body D in order to improve the surface release performance of the fixing belt 501. It is also possible to adopt a multilayer structure in which a fluororesin layer such as tetrafluoroethylene) or a high-release layer (surface layer) F made of a heat-resistant, high-release rubber material without the above-mentioned conductive substance is provided.

The high release layer F is provided with a fixing belt 501 for preventing electrostatic offset of toner due to surface charging.
It is preferable to lower the resistance by adding a conductive material in the same manner as described above. However, in this case, the surface releasability decreases due to the addition of the conductive substance C to the high releasability layer F.
The volume of the high release layer F can be reduced by making the amount of the conductive substance C smaller than that of the rubber elastic body D layer, or by changing the type of the conductive substance C internally added to the rubber elastic body D layer. It is desirable that the resistance be 10 ² to 10 ⁹ Ω · cm.

It is desirable that the high release layer F be as thin as possible in order to reduce the thermal conductivity. However, considering the wear of the release layer due to long-term use of the fixing device 50,
A certain thickness is required. Therefore, the high release layer F
Is preferably 3 to 20 μm, more preferably 5 to 10 μm.

Further, in order to increase the strength of the fixing belt 501, a base layer (base film) B as shown in FIG.
As a heat-resistant resin, for example, a film made of a high heat-resistant resin such as polyphenylene sulfide, polyamide imide, polyimide, polyether ether ketone, liquid crystal polymer, a metal sheet such as aluminum and nickel, or a ceramic, metal, glass, etc. The fixing belt 501 may be formed by laminating the above-described low-resistance rubber elastic body D on the composite material of the above. This base layer B is desirably made thinner in order to reduce the heat capacity of the fixing belt 501.

As described above, the thickness of the fixing belt 501 is 100 to 2000 μm as a whole, preferably 150 to 50 μm.
It is preferably 0 μm.

As shown in FIG. 7, a perforation 510 is formed in at least one end of the fixing belt 501 in the width direction, and a gear (not shown) is provided on the outer peripheral surface of the driving roller 505. Tooth part) 5
11 may be hooked on the perforations 510 to drive the fixing film 501. According to this, in addition to ensuring the conveyance of the fixing belt 501, it is possible to prevent the fixing belt 501 from shifting in the width direction.

4 to 7 described above,
Details will be described later.

Next, an image forming apparatus provided with the fixing device 50 having the above-described configuration will be described with reference to FIG. In addition,
FIG. 2 shows a schematic configuration of an electrophotographic four-color full-color laser beam printer as an example of an image forming apparatus provided with a fixing device 50 according to the present invention.

The image forming apparatus shown in FIG.
And a reader unit 2. The printer unit 1 includes a transfer material transport system I that transports a transfer material P, and an image forming unit II that forms a toner image on a photosensitive drum 20 as an image carrier.
And a rotary developing device III, which is one of the main components of the image forming section II, and a fixing section V for fixing the toner image formed on the transfer material P by the image forming section II.

The transfer material transport system I is a printer unit 1 shown in FIG.
The cassettes 101 and 102 for supplying a transfer material which are detachable from the opening formed on the right side of the cassette 101, and the paper feed rollers 103 disposed above the leading ends (downstream) of the cassettes 101 and 102 , 104 and these rollers 10
Transport roller 105, paper feed guide 107, transport roller 106, paper feed guide 108
Further, around the transfer drum 110, the transfer material contacting roller 109, the gripper 111, and the separation charger 11 are arranged in order from the bottom to the top along the rotation direction.
4 and a separation claw 115, and a transfer charger 112 and a separation charger 113 for the transfer material P provided inside the transfer drum 110. In addition, the aforementioned separation claw 11
On the downstream side of 5, a conveyor belt means 116 is provided.

Further, on the extension of the end portion of the conveying belt means 116 in the conveying direction, that is, on the right side of the printer section 1,
A fixing unit V including the above-described fixing device 50, discharge roller 51, and discharge tray 52 is provided.

The image forming section II includes a photosensitive drum (image carrier) 20 disposed above and in contact with the transfer drum 110 and rotating in the direction of arrow R20, and disposed above the photosensitive drum 20. Primary charger 21 and a cleaning device 22 disposed on the right side.
Above the primary charger 21, an image exposure means 24 for irradiating a laser beam E for forming an electrostatic latent image on the surface of the photosensitive drum 20, and an image exposure reflection means 25 such as a polygon mirror
And

The rotary developing device III provided on the left side of the image forming section II has a rotating body 3 composed of a rotatable housing.
And four color developing devices mounted on the rotating body 3, namely, a yellow developing device 3Y, a magenta developing device 3M, and a cyan developing device 3.
C and a black developing device 3Bk. In these developing devices, a developing device containing a developer of a color to be used for developing an electrostatic latent image formed on the surface of the photosensitive drum 20 is moved to a developing position facing the photosensitive drum 20 by rotation of the rotating body 3. Here, a predetermined color toner is attached to the electrostatic latent image and developed as a toner image. In the first embodiment, the developer contains a so-called two-component developer containing a carrier and a toner as main components.

As the developer, in addition to the above-described two-component developer, a so-called one-component developer can be used. It is also possible to use a magnetic toner. Further, it goes without saying that a conventionally known liquid toner can also be used as the developer.

The reader unit 2 is mounted on the upper surface of the printer unit 1 described above. The reader unit 2 includes a movable table 203 that can move in the direction of arrow K while scanning a document G set with the read image surface facing downward. Moving table 203
Has a light source 202 that irradiates the image surface of the document G, and a CCD 201 that reads an image by reflected light from the image surface.

In the above-described image forming apparatus, when the photosensitive drum 20 rotates in the direction of arrow R20 in FIG. 3 and the surface thereof is uniformly charged to the surface potential of -670 V by the primary charger 21, the yellow image of the original is obtained. P according to the signal
Image exposure is performed by the W-modulated laser light E, and an electrostatic latent image of a yellow image is formed on the photosensitive drum 20.
The electrostatic latent image of this yellow image is transferred to the rotating body 3 of the developing section III.
The yellow toner is attached by the yellow developing device 3Y which is disposed at the developing position in advance by the rotation of
It is developed as a yellow toner image. At this time, the developing bias applied to the developing sleeve 31 of the yellow developing device 3Y is such that the peak-to-peak voltage V _PP is 2 kV and the frequency f is 2 kHz.
a rectangular wave alternating voltage of z, are those direct voltage V _DC are superimposed, and a -410V the V _DC as contrast voltage V _cont becomes 260 V.

On the other hand, the cassette 101 (or the cassette 10
The transfer material P stored in 2)
(Or the paper feed roller 104), the paper is fed one by one, and is held by the gripper 111 at a predetermined timing via the transport roller 105, the paper feed guide 107, the transport roller 106, and the paper feed guide 108, and is used for contact. Roller 109
And is electrostatically wound around the surface of the transfer drum 110 by electrodes facing the transfer drum 110. The transfer drum 110
Synchronization with the photosensitive drum 20 is rotating in the arrow R110 direction, the yellow toner image developed on the photosensitive drum 20 surface by the yellow developing device 3Y, the transfer nip portion N ₁
Is transferred to the transfer material P on the transfer drum 110 by the transfer charger 112. Then, the transfer drum 110
Keeps rotating while holding the transfer material P, and prepares for transfer of the toner image of the next color (magenta in FIG. 3).

On the other hand, the so-called untransferred toner remaining on the surface of the photosensitive drum 20 without being transferred onto the transfer material P is removed by the cleaning means 22 and cleaned. Thereafter, the surface of the photosensitive drum 20 is charged by the primary charger 21, and an electrostatic latent image is formed by the image exposure means 24 in accordance with a magenta image signal.

The rotating body 3 of the developing section III rotates while the above-described electrostatic latent image is formed, arranges the magenta developing device 3M at the developing position, performs a predetermined magenta developing, and performs the above-described yellow developing. The transfer of the magenta toner image onto the transfer material P is performed in the same manner as in the case of the toner image.

Subsequently, the above-described process is performed for cyan and black, whereby toner images of four colors are formed on the transfer material P carried on the transfer drum 110 so as to overlap. When the transfer of the toner images of four colors to the surface is completed, the transfer material P is transferred to the separation chargers 113 and 11.
4, the gripping by the gripper 111 is released, and the transfer drum 110 is
From the transport belt means 116 and the arrow R11
The sheet is conveyed to the fixing device 50 in six directions. The transfer material P is heated and pressurized by the fixing device 50 to be mixed and fixed in color. Then, the transfer material P is discharged onto the paper discharge tray 52 by the carry-out roller 51, thereby completing the four-color full-color image formation.

In the above-described image forming apparatus, laser exposure was performed as a latent image forming means. However, the present invention is not limited to this. For example, an LED array, a liquid crystal array, and a digital latent image forming apparatus such as an ionograph. It is also effective in an apparatus using a so-called analog latent image forming means for directly forming an image signal as light on the photosensitive drum 20 without using an image reading means such as the reader 2 and the like. .

Next, the fixing device 50 will be described in more detail.

As described above, FIG. 4 is a schematic sectional view of a layer structure showing an embodiment of the intermediate transfer belt 501 used in the fixing device 50 according to the present invention.

The fixing belt 501 is a 1 mm thick endless belt in which carbon black is dispersed as conductive material C in silicone rubber as rubber elastic material G and volume resistance is 5 Ω · cm and Asker C hardness is 40 °. It is.

The fixing belt 501 was mounted on the fixing device 50 shown in FIG. 1, and the fixing device 50 was provided in the image forming apparatus shown in FIG. 3 to perform a fixing experiment. As a result, the temperature at which the toner can be fixed to the transfer material P in a short time of about 5 seconds (1
50 ° C.), and a quick start was realized. In addition, there was no need for standby temperature control in which the heating element was previously energized and heated, so that energy saving could be realized and image formation could be performed at high speed. In addition to the above advantages of the film heating type fixing device,
It was also possible to prevent a decrease in image quality, which was a disadvantage of the film heating method. This is because, as described with reference to FIGS. 12A and 12B, the fixing belt 501
This is because, unlike the case of the fixing film 401 shown in (a) and (b), it has excellent elasticity and follows the unevenness of the transfer material P well.

As described above, with this configuration, a fixing device having high speed and high fixed image quality can be obtained.

<Second Embodiment> FIG. 5 is a schematic sectional view of a layer structure showing a second embodiment of a fixing belt 501 used in the present invention.

In the second embodiment, in order to improve the surface release performance of the fixing belt 501, an 8 μm-thick PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) is applied to the surface of the rubber elastic body D having a thickness of 1 mm. A multilayer structure having a high release layer F made of

Further, the high release layer F is
Carbon black, which is the same conductive substance as in Example 1, is dispersed, and the volume resistance of the high release layer F alone is 10 ⁵ to 10 ⁷
It is adjusted to be Ω · cm.

The fixing belt 501 is connected to the fixing device 5 shown in FIG.
0, and further attached to the image forming apparatus shown in FIG. 3 to perform a fixing experiment. As a result, the temperature reached a temperature at which the toner can be fixed to the transfer material (150 ° C.) in a short time of about 7 seconds, and a quick start was realized. In addition, there is no need for standby temperature control in which the heating element is energized and heated in advance, and energy can be saved.
High-speed image formation was also possible. In addition to the above advantages of the film heating type fixing device, it was also possible to prevent the deterioration of image quality which was a disadvantage of the film heating type. This is for the same reason as in the first embodiment.

In the second embodiment, in addition to the advantages of the first embodiment, it is possible to favorably prevent the fixing offset of the toner to the fixing belt 501.

<Embodiment 3> FIG. 6 is a schematic sectional view of a layer structure showing Embodiment 3 of a fixing belt 501 used in the present invention.

In Embodiment 3, in order to increase the strength of the fixing belt 501, a polyimide film having a thickness of 50 μm is provided as a base layer (base film) B as shown in FIG. The same low resistance rubber elastic material D was laminated in a thickness of 300 μm.

The fixing belt 501 was mounted on the fixing device 50 shown in FIG. 1, and a fixing experiment was conducted with the image forming apparatus shown in FIG. As a result, the temperature at which the toner can be fixed to the transfer material P (150 ° C.) was reached in a short time of about 7 seconds, and a quick start was realized. In addition, there was no need for standby temperature control in which the heating element was previously energized and heated, so that energy saving could be realized and image formation could be performed at high speed. In addition to the above advantages of the film heating type fixing device, it was also possible to prevent the deterioration of image quality which was a disadvantage of the film heating type. This is for the same reason as in the first embodiment.

In addition, in the third embodiment, by providing the base layer B, the total belt strength of the fixing belt 501 is improved, so that the durability of the fixing belt 501 can be remarkably improved.

<Fourth Embodiment> FIG. 7 is a perspective view showing the configuration of a fourth embodiment of a fixing belt 501 used in the present invention. This is a system in which a perforation drive is further added to a method based on the friction drive of the inner peripheral surface of the belt.

The fixing device 50 shown in FIG.
01, a large number of perforations 510 are continuously formed along the circumferential direction at both ends in the width direction, and at least one of the driving roller 505 and the driven roller 506 is provided with a gear 511 integrally or separately, While the gear 511 is engaged with the perforation 510, the fixing belt 50
Run 1 FIG. 7 shows an example in which a gear 511 is provided on the outer peripheral surface of the driving roller 505.

According to this configuration, it is possible to assist the conveyance of the fixing belt 501 and to prevent the fixing belt 501 from shifting in the width direction. In this case, the transportability of the fixing belt 501 is almost determined by the friction drive between the inner surface of the fixing belt 501 and the driving roller 505, and the perforations 510 are
This is mainly for controlling the approach of 1.

<Fifth Embodiment> Fixing device 50 shown in FIG.
In contrast to the fourth embodiment shown in FIG. 7, a perforation (not shown) is provided at at least one end in the axial direction of the outer peripheral surface of each of the driving roller 505 and the driven roller 506, and engages with this. The gear (teeth portion) 512 is provided to protrude from the inner peripheral surface of the fixing belt 501.

In this configuration, unlike the conventional fixing film, the mechanical strength of the fixing belt 501 can be remarkably improved, so that a perforation mechanism (perforations 510, gears 511, 512) can be further added. . As a result, the transportability of the fixing belt 501 is stabilized, and the width of the fixing belt 501 can be prevented, and the occurrence of wrinkling of the fixing belt can be prevented, and the life of the fixing device 50 as a whole can be extended.

[0091]

As described above, according to the present invention,
Since the fixing belt itself can be heated by the energizing means, heat can be efficiently supplied to the transfer material and the toner image.

When the fixing belt is made of an elastic material, the width of the fixing nip can be easily changed, so that the fixing efficiency can be increased.
The fixing speed can be further increased.

Further, since the fixing belt is an elastic body,
Even if the transfer material surface has irregularities, the fixing belt follows the irregularities well and the contact with the toner image becomes dense,
It is possible to form a uniform fixed image surface and to provide visually uniform image quality.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of a fixing device according to a first embodiment.

FIG. 2 is a perspective view illustrating a schematic configuration of a fixing device according to the first embodiment.

FIG. 3 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus (laser beam printer) equipped with a fixing device according to the present invention.

FIG. 4 is a longitudinal sectional view showing a part of the fixing belt according to the first embodiment.

FIG. 5 is a longitudinal sectional view showing a part of a fixing belt according to a second embodiment.

FIG. 6 is a longitudinal sectional view showing a part of a fixing belt according to a third embodiment.

FIG. 7 is a perspective view illustrating a schematic configuration of a fixing device according to a fourth embodiment.

FIG. 8 is a longitudinal sectional view illustrating a schematic configuration of a fixing device according to a fifth embodiment.

FIG. 9 is a longitudinal sectional view showing a schematic configuration of a conventional fixing device.

FIG. 10 is a longitudinal sectional view showing a schematic configuration of another conventional fixing device.

FIGS. 11A and 11B are diagrams showing how a toner image is fixed by a fixing film of a conventional fixing device.

FIGS. 12A and 12B are diagrams showing how a toner image is fixed by a fixing belt of the fixing device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer part 2 Leader part 20 Photosensitive drum 50 Fixing device 110 Transfer drum 501 Fixing belt 502 Pressing member (Pressing roller) 503, 504 electrode (Electrified electrode) 505 Driving roller 506 Driving roller 507 Temperature detecting element 508 Power supply 509 Cleaning and oil Supply member 510 Perforation 511, 512 Tooth (gear) B Reinforcement layer (base layer) D Elastic body (rubber elastic layer) F Surface layer (high release layer) N1 Fixing nip P Transfer material Ta Toner image before fixing Tb Softening Fused toner image Tc Toner image after fixing I Transfer material transport system II Image forming unit III Developing unit V Fixing unit

Claims (6)

[Claims] A movable fixing belt in which a conductive member that generates heat by energization is formed in a belt shape; and a pressing member that is in contact with the fixing belt and forms a fixing nip portion between the fixing belt and the fixing belt. Energizing means for generating heat in a portion corresponding to the fixing nip portion of the fixing belt, wherein the transfer material having an unfixed toner image on its surface is pinched and conveyed by the fixing nip portion, and the unfixed toner is conveyed. An image fixing device for fixing an image on the surface of the transfer material. 2. The fixing device according to claim 1, wherein the fixing belt is formed of a conductive elastic material having heat resistance. 3. The fixing device according to claim 1, wherein the fixing belt has a highly releasable surface layer on a surface side in contact with the unfixed toner image. 4. The fixing belt according to claim 1, wherein the fixing belt has a reinforcing layer on a back surface side.
The fixing device according to the item. 5. The fixing device according to claim 1, further comprising: an electrode contacting the fixing belt on an upstream side and a downstream side of the fixing nip portion in a running direction of the fixing belt; and a power supply for energizing the electrodes. 5. The method according to claim 1, wherein:
The fixing device according to the item. 6. The fixing belt is formed in an endless shape, and has a roller member around which the fixing belt is wound. One of the fixing belt and the roller member is provided with a perforation, and the other is provided with a perforation. The tooth part which engages is provided, The claim 1 characterized by the above-mentioned.
The fixing device according to the item.