JP2000293065A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of transfer defect owing to the environmental change, at the time of collectively performing transfer on both side of recording material, in the case of forming images on both side by the once time transportation of recording material. SOLUTION: This image forming device is, let arranging the fixing device 9 provided with a fixing roller 51 and the pressure roller 52 holding a transporting belt 130 there between, in between the image forming part Pd on the supreme downstream side and the driving roller 45 driving the transporting belt 130. The image forming device is, let transferring the toner image by directly laying the same on the transporting belt 130, further transferring it on the B side (rear side), transferring the toner image on the A side in overlapping at the same time, and letting the recording material separated from the transporting belt 130, after fixing both sides by the fixing device 9. In the processing stage simultaneously performing transfer on the A side and the B side, bias of the optimum condition is applied on the A side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a laser beam printer, and more particularly, to a multicolor image forming method on both sides of a recording material. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus, a toner image of each color of yellow, magenta, cyan and black is formed on a photosensitive drum as an image carrier, and the toner image of each color is charged by a corona transfer charger. 2. Description of the Related Art There is known a transfer drum which is a recording material carrier or a transfer drum which is superimposed on a recording material carried on a transport belt. The recording material onto which the four color toner images have been transferred is sent to a fixing device, where the four color toner images are fused and mixed and fixed to the recording material by fixing to obtain a full-color print image.

In recent years, as colorization has progressed, the demand for forming images on both sides of a recording material has increased.
In view of this, for example, an electrophotographic color image forming apparatus as shown in FIG. 8 has been proposed and generally used.

As shown in FIG. 8, in a color image forming apparatus of this embodiment, first, second, third, and fourth image forming sections Pa, Pb, Pc, and Pd are arranged in a main body of the apparatus. Toner images of different colors are formed through the processes of latent image, development, and transfer.

[0005] Each image forming unit Pa, Pb, Pc, Pd
An image carrier for exclusive use, an electrophotographic photosensitive drum (hereinafter, simply referred to as “photosensitive drum”) 3a, 3b, 3
c, 3d, and a toner image of each color is formed on each of the photosensitive drums 3a to 3d. A transport belt 130, which is a recording material carrier, is installed adjacent to each of the photosensitive drums 3a to 3d, and toner images of respective colors formed on the photosensitive drums 3a to 3d are transported while being carried on the transport belt 130. The image is transferred onto the recording material S. Further, the recording material S to which the toner images of each color have been transferred is heated and pressed to fix the toner images by a fixing device 9 as a fixing unit, and then discharged as a recording image to a discharge tray 63 outside the device.

More specifically, exposure lamps 111a, 111b, 111c,
111d, drum chargers 2a, 2b, 2c, 2d, potential sensors 113a, 113b, 113c, 113d, developing devices 1a, 1b, 1c, 1d, brush transfer chargers 24a, 2d
4b, 24c, 24d and cleaners 4a, 4b, 4
c and 4d are provided, and a light source device (not shown) and a polygon mirror 117 are further installed on the upper part of the device.

The polygon mirror 117 scans the laser light emitted from the light source device by rotating the polygon mirror 117, deflects the light beam of the scanning light by the reflection mirror, and places the latent image on the photosensitive drums 3a to 3d according to the image signal by the fθ lens. An image is formed.

The developing devices 1a to 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners, respectively, as a developer by a supply device (not shown). The developing devices 1a to 1d are respectively provided with the photosensitive drums 3a to 3d.
The latent image on d is developed and visualized as a cyan toner image, a magenta toner image, a yellow toner image, and a black toner image.

The recording material S is accommodated in a recording material cassette 10, and is supplied onto a conveyor belt 130 through a plurality of conveyor rollers 11 and registration rollers 12, and the transfer belt 130 faces the photosensitive drums 3a to 3d by the conveyor belt 130. Are sent in sequence.

The conveyor belt 130 is made of a dielectric resin sheet such as a polyethylene terephthalate resin sheet (PET sheet), a polyvinylidene fluoride resin sheet, or a polyurethane resin sheet. Either endless or seamless (seamless) belts are used.

In the case of a belt having no seams, it is difficult not only to manufacture the belt so as to have uniform physical properties, but also because of the stability of the circumference of the belt and the manufacturing time, cost is low for mass production. Unsuitable in terms of, for example.

On the other hand, in a belt having a seam, changes in physical properties such as unevenness and resistance value of the seam portion cannot be avoided.
Performing image formation on the seam disturbs the image. Therefore, in order to obtain a high-quality image, the peripheral length of the conveyance belt 130 is determined by the length of the recording material and the length of the gap between the recording material and the next recording material, that is, the total length of the length between the sheets. It is common to provide an integral multiple and provide a seam position detecting means so that image formation is not performed on the seam.

As the seam position detecting means, when the transport belt 130 is opaque, a reflection type optical sensor is used, and a seam portion is provided with a detection mark having a different light reflection characteristic to detect the seam position. When the transport belt 130 is transparent, the position of the seam is directly detected by using a transmission type optical sensor, or the position of the seam is mechanically detected by using a notch or a protrusion provided at the seam using a displacement sensor.

When the conveyor belt 130 rotates and is confirmed to be at a predetermined position, the registration roller 1
2, the recording material S is sent out to the transport belt 130, and the recording material S is transported toward the transfer unit of the first image forming unit Pa. At the same time, the image writing signal is turned ON, and an image is formed on the photosensitive drum 3a of the first image forming unit Pa at a certain timing based on the signal. Then, the first color toner image formed on the photosensitive drum 3a is transferred onto the recording material S by the brush transfer charger 24a applying an electric field or charge at the lower transfer portion of the photosensitive drum 3a. . By this transfer, the recording material S is securely held on the conveyor belt 130 by electrostatic attraction, and is conveyed to the second image forming portion Pb and thereafter.

Hereinafter, similarly, the second image forming units Pb to Pb
Image formation and transfer are performed in the fourth image forming unit Pd. Next, the recording material S to which the four color toner images have been transferred is neutralized by the separation charger 32 at the downstream portion of the transport belt 130 in the transport direction to attenuate the electrostatic attraction force, so that the transport belt 1
Leave from the end of 30. The detached recording material S is conveyed to the fixing device 9.

The fixing device 9 includes a fixing roller 51 as a fixing rotating body, a pressure roller 52 as a pressing rotating body, heat-resistant cleaning members 54 and 55 for cleaning these rollers 51, 52, and each roller 51. , 52, the application rollers 50 for applying a release agent oil such as dimethyl silicone oil to the fixing roller 51, the oil reservoir 53 thereof, and the temperature of the surface of the pressure roller 52 are detected. Thermistor 58 for controlling fixing temperature
It is composed of

In the fixing device 9, the recording material S to which the four color toner images have been transferred is mixed with the toner images and fixed to the recording material S to form a full-color copy image.

The photosensitive drums 3a to 3d after the transfer are completed.
The toner remaining after transfer is cleaned and removed by each of the cleaners 4a to 4d, and is prepared for the formation of the next latent image. The toner adhering to the surface of the conveyor belt 130 removes the surface of the conveyor belt 130 from the charge removing device 33.
After the charge is removed by the counter electrode 34 on the back side of the belt, the cleaning web (nonwoven fabric) 35 in contact with the surface of the conveyor belt 130 and the backup member 36 on the back side of the belt are wiped off. As another cleaning means, a blade or a fur brush is used alone or in combination.

When a double-sided image is formed on the recording material S, the transfer of the first surface (A side) is completed, and after passing through the fixing device 9, the recording material S is not conveyed to the paper discharge tray 63, 6
The recording material S is turned upside down by 1 or the like, and the recording material S is temporarily stored in the intermediate tray 65 in the inverted state. afterwards,
The recording material S is re-sent to the transport belt 130, and an image is formed again on the second surface (B surface) opposite to the first surface (A surface) on which image formation has been completed. Then, after the fixing device 9 fixes the toner image on the surface B of the recording material S, the discharge tray 63
Paper. The general method for forming a double-sided image is as described above.

In order to unify the following description, the upper surface of the recording material on which the toner image newly supplied to the transport belt 130 is not transferred is referred to as A surface, and the opposite rear surface is referred to as B. The first surface A and the second surface B meet this definition.

As an image forming apparatus for forming an image on both sides of a recording material by one conveyance of the recording material, for example, Japanese Patent Application Laid-Open No. 08-082970 proposes the following image forming apparatus. Here, the operation of the portion relating to the present invention will be described. Further, since the configuration of the image forming apparatus is substantially the same as that of the above-described image forming apparatus of FIG. 8, in the following description, the overlapping parts will not be described.

In the image forming apparatus shown in FIG. 8, before the recording material S is supplied to the transport belt 130 and carried thereon, first, the second
Of the first to fourth image forming units Pa to
On the photosensitive drums 3a to 3d of Pd, a toner image of each color for the surface B (back surface) of the recording material S is formed, and the toner image of each color is rotated at the transfer unit of each image forming unit by the rotating conveyor belt 130. The images are superimposed on each other and transferred directly. Next, the recording material S is supplied to the transport belt 130 at the time when the superimposed toner images of the respective colors on the transport belt 130 are brought forward of the first image forming unit Pa with the rotation of the transport belt 130. Then, the recording material S is superimposed on the superimposed toner image.

Next, the first photosensitive drums 3a to 3d
In the image forming mode, a toner image of each color for the surface A of the recording material S is formed, and the toner image of each color is sequentially superimposed and transferred onto the recording material S at a transfer unit of each image forming unit. At this time, the toner images of the respective colors on the conveying belt 130 on the side B of the recording material S are transferred when the first color toner image is transferred onto the side A of the recording material S by the brush charger 3a of the first image forming unit Pa. By adjusting the transfer electric field, collective transfer is performed simultaneously with transfer to the A surface. However, it is also possible to transfer the toner images of the other colors at the same time as the transfer. Further, by providing a dedicated transfer charging unit, the toner images of each color on the transport belt 130 can be collectively transferred to the surface B of the recording material S prior to the transfer of the toner image to the surface A of the recording material S. .

Further, in order to enhance the efficiency of the transfer of the B-side toner image to the recording material (second transfer), an electric field opposite to that at the time of transfer is applied prior to the second transfer. It is effective to charge the conveyor belt 130. As for the charging, in FIG. 8, a separation charger 32 for separating the recording material S from the transport belt 130 or a charge removing charger 33 for removing the charge of the transport belt 130 after the recording material is separated.
Can be used.

It is desirable that the cleaning device 35 of the transport belt 130 be separated when the toner image for the side B arrives, and should be in contact with the cleaning device 35 in other cases. Further, the transfer charging means includes brush transfer charging devices 24a to 24a.
It is desirable to use a contact-type charger which can easily control the transfer current as shown by d.

[0026]

However, in the above-described image forming apparatus, the area where the optimum transfer conditions of the A-side and the B-side coincide with each other is narrow. In some cases, an image defect occurs due to a change or the like, and a suitable transfer cannot be obtained.

Further, when the recording material is separated from the conveyor belt, the toner image formed on the conveyor belt remains, and the reproducibility of the color of the image is reduced.
In addition, there has been a problem that the toner image on the surface in contact with the recording material carrier is disturbed by the separation discharge at the time of separation.

Accordingly, a main object of the present invention is to provide an image forming apparatus which does not cause a transfer failure due to a change in environment even when collective transfer is performed on both sides of a recording material.

Another object of the present invention is to prevent the toner image formed on the recording material carrier from remaining when the recording material is separated from the recording material carrier, and therefore, the reproducibility of the image tint. Another object of the present invention is to provide a good image forming apparatus.

It is another object of the present invention to provide an image forming apparatus in which a toner image on a surface in contact with a recording material carrier is not disturbed by peeling discharge at the time of recording material separation.

[0031]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A plurality of image carriers for forming toner images of different colors, a recording material carrier for carrying a recording material and moving it sequentially to each transfer section facing the image carrier, and The image forming apparatus further includes a transfer charging unit provided, and a fixing unit for fixing the toner image transferred to the recording material to the recording material, and the toner images of each color formed on each of the image carriers are formed on one side of the recording material. A first image forming mode in which the toner images of the respective colors formed on the respective image carriers are sequentially superimposed on the recording material carrier and transferred. A second image forming mode for collectively transferring toner images of each color to the other surface of the recording material, wherein the recording material carrier conveys the recording material so as to pass through the fixing unit, The recording material after fixing the image is located after the exit of the fixing unit. An image forming apparatus, characterized in that it is released from said recording material bearing member.

According to one embodiment of the present invention, the fixing unit includes a fixing rotator and a pressing rotator pressed by the fixing rotator, or the fixing unit includes a fixing rotator. And an endless belt for heating, a heating body, and a rotating body for pressurization pressed toward the heating body with the endless belt for fixing interposed therebetween.

It is preferable that the recording material carrier is wound around at least two supporting rotators, and the supporting rotator also serves as the pressing rotator of the fixing unit.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. Note that the configuration and operation of the image forming apparatus in the following embodiment are substantially the same as those of the image forming apparatus having the first and second image forming modes described with reference to FIG. Are denoted by the same reference numerals, description of the same configuration and operation is omitted, and different portions, that is,
The process of transferring the toner image on the side B, the separation of the recording material from the recording material carrier, and the fixing will be described in detail.

Embodiment 1 First, a first embodiment of the present invention will be described with reference to FIGS.

In the image forming apparatus of this embodiment, image forming units Pa, Pb, Pc, and Pd are arranged in the main body 10 of the apparatus, and a driving roller 45 as a supporting rotating body is provided below the image forming units Pa to Pd. Recording material carrier having a seam wound around driven support roller 44, that is, endless transport belt 13
0 is provided so as to be rotated in the direction of the arrow.

The transport belt 130 is made of a dielectric resin sheet such as a polyethylene terephthalate resin sheet or a polyvinylidene fluoride resin sheet.

The conditions of the transfer bias in this embodiment are as follows.
The transfer efficiency is always set to be optimal from the photosensitive drums 3a, 3b, 3c, 3d to the transport belt 130. That is, in the step of performing the batch transfer of the surface A and the surface B, the transfer is performed by the bias of the optimal condition for transferring the toner image of the surface A to the recording material S, and the transfer belt 130
The toner image on the upper side B is completely transferred to the recording material in a fixing step described below.

The distance between the drive roller 45 and the image forming portion Pd on the most downstream side is set larger in the transport belt 130 of this embodiment than in the conventional transport belt 130 shown in FIG. . In a region where the distance is set to be large, a fixing unit 51 having a fixing roller 51 as a fixing rotating body and a pressing roller 52 as a pressing rotating body on the opposite side of the conveyance belt 130 is provided.

The fixing roller 51 has a structure in which a surface of a metal core is coated with a predetermined thickness of silicone rubber and fluorine rubber. The fixing roller 51 includes a heater 56 such as a halogen lamp as a heating means, and is provided in a direction indicated by an arrow. It is rotatably supported.

On the other hand, the fixing roller 51 and the conveying belt 130
The pressing roller 52 opposed to the fixing roller 51 sandwiches the fixing roller 51.
It is arranged so as to be pressed against. The pressure roller 52 is formed by providing silicone rubber on the surface of a metal cored bar and applying fluorocarbon resin to the surface thereof, and is not provided in this embodiment. A heater such as a halogen lamp may be provided. The pressure roller 52 is rotatably supported in the direction of the arrow, and is configured to rotate following the fixing roller 51.

The fixing roller 51 is provided with a thermistor 58 as a temperature detecting element so as to be in contact with the fixing roller 51. By controlling the voltage to the heater 56 through a temperature adjusting circuit, the surface temperature of the fixing roller 51 is always 150 °. The temperature is adjusted so as to be maintained at ~ 180 ° C.

Further, as shown in FIG.
Mechanism 1 that allows the belt to contact and separate from the conveyor belt 130
9a and 19b are provided. Pressing mechanisms 19a, 19
Each of b has a pressure spring, a solenoid, and a pressure rod (not shown) inside, each of which is applied to the solenoid based on a signal from a processing unit (not shown) provided in the image forming apparatus. By controlling the voltage to be applied, the pressing force of the pressing spring can be applied to the fixing roller 51.

At the time of B-side image formation, the fixing roller 51 operates so as to be separated from the transport belt 130, and immediately after the batch transfer of the A and B surfaces of the recording material S, the fixing roller 51 Pressurized to touch. A for recording material
When the image forming process for transferring the toner images on the surfaces B and B is completed, the recording material S is transported to the transport belt 130 by the electrostatic attraction force generated each time the transfer process is performed.
The sheet is conveyed to the fixing unit 9 while being suction-held.

In the fixing section 9, the color of the toner image on the recording material S is mixed by the heat of the fixing roller 51 and the pressure generated between the fixing roller 51 and the pressure roller 52, and is fixed on the recording material. At the same time, the toner image formed on the transport belt is completely transferred to the surface B at this point. When the fixing of the toner to the recording material S is completed, the recording material S is transferred from the transport belt 130 to the driving roller 45.
The paper is then separated into curvatures and discharged to a paper discharge tray 63 outside the apparatus.

By adopting such a configuration, the surface A,
The recording material S can be separated from the conveyor belt 130 after the toner image on each of the B surfaces is heat-fixed on the recording material S, and the conventional problem, that is, optimal transfer of each of the A surface and the B surface The area where the conditions match is narrow,
When performing the batch transfer of the B surface, an image defect may occur due to a change in environment, and a suitable transfer may not be obtained. In addition, when the recording material S is separated from the transport belt 130, The problem is that the toner image formed on the transfer belt 1 remains, and the reproducibility of the tint of the image deteriorates.
This solves the problem that the toner image on the surface in contact with 30 is disturbed.

In the present embodiment, the configuration in which the curvature separation is applied to separate the recording material S from the transport belt 130 is adopted. However, as shown in FIG. Further, the separation property is stable and preferable.

Further, as shown in FIG. 4, by providing a cooling unit 18 such as a fan for cooling the transport belt 130 after fixing, heat accumulation in the transport belt 130 can be prevented. In particular, when the conveying belt 130 is moved at a high speed with a short image forming interval, the time from when the conveying belt 130 passes through the fixing unit 9 to when the conveying belt 130 returns to the fixing unit 9 is short. Needless to say, a heat pipe may be used in addition to the fan as the cooling means.

In this embodiment, in addition to the above-described effects, after the toner is fixed on the recording material S, the conveyance belt 13
Since the recording material S is configured to be separated from zero, the recording material S can be mechanically and forcibly separated from the transport belt 130 without worrying about image disturbance at the time of separation. Since there is no such device, the device configuration can be simplified.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the driving roller 45 has a configuration substantially similar to that of the first embodiment,
It is characterized in that it is configured to also serve as.

In the present embodiment, the conventional problem can be solved without any problem similarly to the first embodiment.

Further, by adopting the configuration of this embodiment,
The fixing unit 9 can be simplified, and the apparatus can be designed to be more compact.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIGS.

In this embodiment, as shown in FIG. 6, an endless belt for fixing, that is, a fixing device 90 having an endless belt-like fixing film is used in place of the heating roller type fixing device 9 in the second embodiment. Things. The operation of the apparatus according to the present embodiment has been described in each of the above embodiments, and a description thereof will be omitted.

Here, the fixing device 90 of this embodiment will be described with reference to FIG.

In FIG. 7, an endless belt-shaped fixing film 57 includes a driving roller 54 as a fixing rotating body on the left side and a driven roller 55 as a fixing rotating body on the right side.
And a low-heat-capacity linear heating element 56 disposed below between the rollers 54 and 55.

The driven roller 55 also serves as a tension roller for an endless belt-shaped fixing film 57. The fixing film 57 is rotated at a predetermined peripheral speed in the clockwise direction, that is, when the driving roller 54 is rotated clockwise in FIG. It is rotated at the same peripheral speed as the conveying speed of the recording material S carrying the unfixed toner image conveyed from the forming unit side on the upper surface without wrinkles, meandering, and speed delay.

The heating member 56 is in contact with the driving roller 45 of the conveyor belt 130 with the fixing film 57 interposed therebetween. The drive roller 45 also serves as a pressure roller 52 as a pressure rotating body, has a rubber elastic layer with good releasability such as silicon rubber, and has a lowering side of the fixing film 57 as in the second embodiment. The lower surface of the heating body 56 is pressed against the lower surface of the heating member 56 with a contact pressure of, for example, a total pressure of 4 to 7 kg across the film portion, and is counterclockwise in the forward direction in the transport direction of the recording material S. To rotate.

In the present embodiment, the low heat capacity linear heating element 56 is arranged in the transverse direction of the fixing film 57 (fixing film 5).
7) The rigidity of the lateral hand whose length is perpendicular to the running direction
A heater support 84 having high heat resistance and heat insulating properties, and a heater element 85 and a temperature measuring element 86 as heating elements integrally attached and held along the longitudinal direction on the lower surface side of the heater support 84 are provided. And a heater substrate 87.

The heater support 84 supports the heating body 56 in a heat-insulating manner with respect to the fixing device 90 and the entire image forming apparatus, for example, PPS (polyphenylene sulfide),
PAI (polyamide imide), PI (polyimide), P
High heat resistant resins such as EEK (polyetheretherketone) and liquid crystal polymer, and these resins and ceramics,
It can be composed of a composite material with metal, glass, or the like.

In this embodiment, the heater substrate 87 is an alumina substrate having a thickness of 1.0 mm, a width of 10 mm, and a length of 150 mm. The heater element 85 is, for example, Ag / P at a substantially central portion of the lower surface of the heater substrate 87 along the longitudinal direction.
d (silver palladium) or other electric resistance material
m, a width of 1 to 3 mm, which is applied by screen printing or the like, and a heat-resistant glass 87a is coated thereon as a surface protective layer by about 10 μm.

In the present embodiment, the temperature detecting element 86 is a Pt film formed by applying a screen printing or the like to a substantially central portion of the upper surface of the heater substrate 87 (the surface opposite to the surface on which the heater element 85 is provided). Is a low heat capacity resistor. Temperature sensing element 8
As 6, a thermistor having a low heat capacity or the like may be arranged so as to be in contact with the heater substrate 87.

In the case of the heating element 56 of this embodiment, electricity is supplied to the linear or band-shaped heater element 85 from both ends in the longitudinal direction so that the heater element 85 generates heat over substantially the entire length. The energization is 100 V AC, and the energization power is controlled by controlling the phase angle to be energized by an energization control circuit (not shown) including a triac according to the temperature detected by the temperature detecting element 86.

The fixing film 47 is generally 100 μm or less, preferably 4 μm, having heat resistance, releasability and durability.
A single-layer or multi-layer film of 0 μm or less can be used.

The fixing film 57 in FIG. 7 is the above-described composite layer film, and includes a heat-resistant layer 57a as a base layer (base film) of the fixing film 57 and an outer surface (a surface facing the toner image) of the heat-resistant layer 57a. Release layer 57 laminated on
b.

The heat-resistant layer 57a is made of a high heat-resistant resin film such as polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (PEI), polyparabanic acid (PPA), Ni, SUS , Al and other metals having excellent strength and heat resistance can be used.

The release layer 57b is made of, for example, a fluororesin such as PTFE (polytetrafluoroethylene), PFA, or FEP. Release layer 5 for heat-resistant layer 57a
7b is formed by adhesive lamination of a release layer film, electrostatic coating (coating) of a release layer material, lamination by a film forming technique such as vapor deposition and CVD, and two layers by co-extrusion of a heat-resistant layer material and a release layer material. It can be performed by film formation or the like.

When the image forming process described in each of the above-described embodiments is completed, the recording material S is attracted and held on the conveyor belt 130 by the static electricity generated each time the transfer process is performed, and the fixing unit is stopped. 90. In the fixing unit 90, the recording material S enters between the fixing film 57 and the pressure roller 52 at the pressure contact portion N between the heating body 56 and the pressure roller 52, and the unfixed toner image surface is moved at the conveying speed of the recording material S. Fixing film 57 rotated in the same direction at the same speed as
The heating member 56 and the pressurizing roller 52 pass while receiving a pressing force in an overlapping state together with the fixing film 57 without causing surface deviation or wrinkling due to close contact with the lower surface of the heating member 56. The heating element 56 is heated by the image formation start signal immediately before the recording material S enters the press contact portion N.

The heat generated by the heating element 56 is
Since the heat capacity of the fixing film 57 is very small, it is quickly transmitted to the surface of the fixing film 57, and the surface of the fixing film 57 immediately reaches a fixing-possible temperature. Also, the recording material S is
Is completed, the power supply is stopped, and the surface of the fixing film 57 is immediately cooled.

When the fixing of the toner image onto the recording material S is completed as described above, the recording material S is separated from the conveyor belt 130 by the curvature on the drive roller 45 and is discharged out of the apparatus.
On the other hand, each of the photosensitive drums 3a, 3b, 3c,
The cleaning unit 5a removes the residual toner by the cleaning units 5a, 5b, 5c, and 5d, and prepares for the subsequent latent image formation.

In this embodiment, the conventional problems can be solved without any adverse effects, as in the first embodiment.

Further, according to such a configuration, unnecessary heat storage in the transport belt 130 is prevented, and the fogging toner and the scattered toner attached to the transport belt portion on which the recording material S is not placed are directly transferred to the transport belt 130. Fixing can also be prevented.

[0074]

As is clear from the above description, according to the image forming apparatus of the present invention, the recording material is conveyed so that the recording material carrier passes through the fixing section, and the recording material after fixing the toner image is removed. Since the recording material is released from the recording material carrier at a position after the exit of the fixing unit, even when performing batch transfer to both surfaces of the recording material, transfer failure does not occur due to a change in the environment. When the recording material is separated from the recording material support, the toner image formed on the recording material support does not remain, and therefore, the reproducibility of the color of the image is good. The toner image on the surface in contact with the recording material carrier is not disturbed by the peeling discharge,
High quality images can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram illustrating a fixing unit pressing mechanism according to the first embodiment.

FIG. 3 is a main part configuration diagram in which a separation claw is applied to the image forming apparatus of the first embodiment.

FIG. 4 is a schematic configuration diagram in which a cooling unit is applied to the image forming apparatus of the first embodiment.

FIG. 5 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment.

FIG. 6 is a schematic configuration diagram illustrating an image forming apparatus according to a third embodiment.

FIG. 7 is an enlarged view showing a fixing unit of the image forming apparatus of FIG.

FIG. 8 is a configuration diagram illustrating an example of a conventional image forming apparatus.

[Explanation of symbols]

3a, 3b, 3c, 3d Photosensitive Drum (Image Carrier) 9, 90 Fixing Device (Fixing Unit) 24a, 24b, 24c, 24d Transfer Charging Means 44 Follower Roller (Support Rotor) 45 Drive Roller (Support Rotor) 51 Fixing roller (rotating member for fixing) 52 Pressure roller (rotating member for pressing) 56 Heating member 57 Fixing film (endless belt-shaped member for fixing) 130 Conveying roller (recording material carrier)

Claims (4)

[Claims] 1. A plurality of image carriers for forming toner images of different colors, a recording material carrier for carrying a recording material and moving so as to be sequentially conveyed to respective transfer units facing the image carrier. A transfer charging unit installed in each transfer unit, and a fixing unit for fixing the toner image transferred to the recording material to the recording material, wherein each color toner image formed on each image carrier is A first image forming mode in which the toner images of respective colors formed on the respective image carriers are successively superimposed on the recording material carrier in a first image forming mode in which the toner images of respective colors are sequentially superimposed on one surface of the recording material and directly transferred. A second image forming mode in which the toner images of the respective colors are collectively transferred to the other surface of the recording material after the transfer, wherein the recording material carrier is configured to pass through the fixing unit. And the recording material after fixing the toner image is An image forming apparatus characterized in that it is released from said recording material bearing member at a position of the mouth after. 2. The image forming apparatus according to claim 1, wherein the fixing unit includes a fixing rotator and a pressing rotator pressed by the fixing rotator. 3. The fixing unit according to claim 1, wherein the fixing unit includes a fixing endless band, a heating body, and a pressing rotary body pressed toward the heating body with the fixing endless band interposed therebetween. Image forming device. 4. The image forming apparatus according to claim 2, wherein the recording material carrier is wound around at least two supporting rotating members, and the supporting rotating member also functions as the pressing rotating member of the fixing unit.