JPH11327335A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make energy appropriately consumed, to shorten the warming-up time and to make a stably excellent fixation performable by providing a heater holder with a solid heating element and an elastic member inscribed in a film member in parallel and oppositely arranging both of them. SOLUTION: An upper ceramic heater 172a and a lower elastic rubber 173b and an upper elastic rubber 173a and a lower ceramic heater 172b are oppositely arranged while putting respective fixing films 171a and 171b fixing respective toner images being a front surface image and a back surface image in between. Excellent instant fixation is performed by a sure and wide nip part T formed by the upper and the lower ceramic heater 172a and 172b pressed by the elastic rubbers 173b and 173a acting as a soft member. By arranging them zigzag, the toner image is fixed on the back surface continuously to fixing the toner image on the front surface, and deviation between the toner images on both sides of recording paper P is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for transferring and fixing a toner image formed on an image forming body onto a transfer material to form an image in a copying machine, a printer, a facsimile or the like. In particular, the toner image on the image forming body is transferred to the front surface of the transfer material or temporarily transferred onto the intermediate transfer member, and then transferred to the back surface of the transfer material and fixed, so that the image is formed on both the front and back surfaces of the transfer material. The present invention relates to an image forming apparatus capable of forming an image.

[0002]

2. Description of the Related Art Conventionally, in double-sided image formation, an image on one side formed on an image forming body is transferred and fixed on a transfer material, and this is temporarily stored in a double-sided reversal feeding device and formed again. A method has been adopted in which a transfer material is inverted and fed by a double-sided inversion feeding device in synchronization with an image formed on a body, and an image on the other surface is transferred and fixed on the transfer material.

In this double-sided image forming apparatus, as described above,
By inverting and feeding the transfer material by the two-sided inversion feeding device, or by passing the fixing device twice, the reliability of transfer of the transfer material is low, which causes a jam or wrinkles of the transfer material. Was.

On the other hand, JP-B-49-37538 and JP-B-54-28740, and JP-A-1-44457.
Japanese Patent Application Laid-Open Publication No. 4-214576 and the like propose a method in which a toner image is formed on both surfaces of a transfer material using an image forming body and an intermediate transfer body, and then fixed once.

Further, the inventors of the present invention arranged a plurality of toner image forming means for forming a toner image on a photosensitive drum (image forming body), and temporarily superimposed the color toner image formed on the photosensitive drum. After collective transfer (primary transfer) to a belt-shaped intermediate transfer member by the first transfer means, a superimposed color toner image is formed on the photosensitive drum again, and the color toner image and the intermediate The transfer material fed at the same time as the color toner image on the transfer body is charged by the transfer material charging means and adsorbed on the intermediate transfer body, and the photosensitive material is provided on both surfaces of the transfer material transported by the intermediate transfer body. The color toner image on the drum is transferred (secondary transfer) by a second transfer unit (using the same one as the first transfer unit), and the color toner image on the intermediate transfer body is transferred by a third transfer unit. Transcript ( After the next transfer, the transfer material is transferred from the intermediate transfer body by the curvature of the roller member provided on the fixing device (fixing means) side and stretching the intermediate transfer body, and by the charge removal by the transfer material separating means provided as necessary. JP-A-9-258492 and JP-A-9-258516 disclose an image forming apparatus and an image forming method for forming a double-sided color image by separating a color toner image on a transfer material with a fixing device and fixing the color toner image on the transfer material. did.

On the other hand, a track-shaped elliptical fixing film is vertically arranged in a fixing device for fixing the front and back toner images, and a fixed heating element and an elastic roller are provided at both ends in each fixing film. Japanese Patent Application Laid-Open No. 5-55555 proposes an apparatus in which a roller and an elastic roller are arranged to face each other to perform double-side fixing.

[0007]

However, in the above image forming apparatus, a heat fixing roller having a heating element is used for both upper and lower rollers of a fixing device for fixing a toner image of a front surface image and a toner image of a rear surface image. However, since the upper and lower heat fixing rollers with large heat capacity are heated, the warm-up time becomes longer,
Since both heating elements are always in a heating state, heat is also supplied to unnecessary heat fixing rollers or intermittent fixing of the transfer material is performed at the time of single-sided image formation of only the upper surface (front surface), which is used more frequently. However, there arises a problem that extra energy is consumed for the required energy at the time of double-sided image formation or at the time of single-sided image formation of only the lower surface (back surface). In addition, there is a problem that a long warm-up time is required when performing single-sided image formation or double-sided image formation. Further, in the double-sided fixing device proposed in the above-mentioned Japanese Patent Application Laid-Open No. 5-55555, the distance between the pair of the fixed heating element and the elastic roller disposed opposite to each other is long, and the fixing interval of the unfixed toner image on the front and back sides is increased. Is vacant, causing a problem that the toner images on the front and back are shifted.

The present invention solves the above-mentioned problems, so that proper energy consumption is performed corresponding to single-sided or double-sided image formation only on the front side or back side, and single-sided or double-sided image formation. It is an object of the present invention to provide an image forming apparatus in which the warming-up time in the case of performing the fixing is shortened, and stable and satisfactory fixing is performed without causing a shift between the front and back toner images.

[0009]

An object of the present invention is to provide an image forming body, means for forming a toner image on the image forming body, a toner image on the image forming body transferred, and the transferred toner image. And an endless belt-shaped intermediate transfer body that conveys a transfer material, a first transfer unit that transfers a toner image on the image forming body to the intermediate transfer body, A second transfer unit that transfers the toner image to the front surface of the transfer material, a third transfer unit that transfers the toner image on the intermediate transfer body to the back surface of the transfer material, and a film-shaped rotating member as a pair, In an image forming apparatus for fixing an unfixed toner image on the front surface and the back surface of a transfer material by fixing means arranged to face each other, the inside of each of the film members provided on the film-shaped rotating members arranged in a pair A heater holder An image forming apparatus, wherein a fixed heating element and an elastic member which are respectively inscribed in the film member are provided side by side on the heater holder, and the fixed heating element and the elastic member are arranged to face each other. (First invention).

The above object is also achieved by a first image forming body and a second image forming body.
Image forming body, first toner image forming means for forming a toner image on the first image forming body, and second toner image forming means for forming a toner image on the second image forming body And an endless belt-shaped intermediate transfer body that transfers the toner image on the second image forming body, carries the transferred toner image on the surface, and conveys a transfer material. First transfer means for transferring a toner image on a body to the intermediate transfer body, second transfer means for transferring the toner image on the first image forming body to a surface of the transfer material, and the intermediate transfer An unfixed toner image on the front and back surfaces of the transfer material is provided by third transfer means for transferring the toner image on the body to the back surface of the transfer material, and fixing means arranged opposite to each other with the film-shaped rotating member as a pair. In the image forming apparatus for fixing the toner, A heater holder is provided inside each of the film members provided on the rotating member, and a fixed heating element and an elastic member that are respectively inscribed in the film member are provided side by side on the heater holder, and the fixed heating element and the elastic member are provided in parallel. Are arranged so as to face each other (second invention).

[0011]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description of the embodiment, the surface of the transfer material on the side facing the image forming body in the transfer area is called the front surface, and the other surface of the transfer material, that is, the surface of the transfer material on the side facing the intermediate transfer body is called the back surface. The image transferred to the front surface of the transfer material is called a front image, and the image transferred to the back surface of the transfer material is called a back image.

An image forming process and each mechanism of an embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the image forming apparatus,
FIG. 2 is a diagram illustrating a toner image forming state in the image forming apparatus in FIG. 1, and FIG. 2A is a toner image forming state when a back side image formed on the image forming body is transferred onto an intermediate transfer body. FIG. 2B is a diagram showing a toner image forming state when a front surface image is formed on an image forming body in synchronization with a back side image on the intermediate transfer body, and FIG. FIG. 3 is a diagram illustrating double-sided image formation on a transfer material, FIG. 3 is a diagram illustrating an example of a document image reading unit, FIG. 4 is a control circuit block diagram of an image forming apparatus, and FIG. FIG. 6 is an enlarged view of a first configuration of a fixing unit on which a toner image on a front surface side is fixed first, and a diagram illustrating conveyance of a transfer material to the fixing unit.
It is a temperature control timing chart at the time of double-sided image formation,
FIG. 7 is a temperature control timing chart when forming a single-sided image on the front side, and FIG. 8 is a temperature control timing chart when forming a single-sided image on the back side.

As shown in FIGS. 3 and 4, a document image reading device 500 as a document image reading means includes a reading device main body 501, a document storage plate 505 for storing a document PS, a document sending roller 502, a transparent plate 503. , Document feed roller 504, document discharge tray 506, and transparent plate 503
And a line-shaped document image reading sensor PS1 and PS2 for reading the document image of the document PS from above and below. The control unit is controlled by a signal line incorporated in an external device or a color image forming apparatus described below. Connected.

When the original PS sent by the original sending roller 502 passes through the transparent plate 503, the original PS is converted to a one-sided original by original image reading sensors PS1 and PS2 provided above and below the transparent plate 503. Determination of whether the document is a double-sided document (single-sided or double-sided) and reading of image data of the document PS are performed.

In this embodiment, one-sided / two-sided discrimination and image data reading are performed by one set of upper and lower sensors. However, a plurality of sensors respectively corresponding to image data reading and one-sided / two-sided discrimination may be provided. For example, image data may be read after a single-sided or double-sided discrimination has been performed using a plurality of sensors respectively corresponding to each other. Original image reading sensor PS1
Alternatively, the image data of one bundle of originals PS is read by PS2 and stored in the RAM through the control unit.

When the image is determined to be a double-sided image,
The image data of the document PS is read by the document image reading means shown in FIG. 3, and the double-sided image forming program P1 stored in the ROM shown in FIG. P1 is executed, and the image forming process is performed.

1 and 2, reference numeral 10 denotes a photosensitive drum as an image forming body, 11 denotes a scorotron charger as a charging unit for each color, and 12 denotes an exposure optical system as an image writing unit for each color. , 13 are developing devices as developing means for each color, 14
a is an intermediate transfer belt that is an intermediate transfer member, 14c is a transfer device that is a first and a second transfer unit, 14g is a back surface transfer device that is a third transfer unit, 14m is a charge remover that is a charge removing unit,
Reference numeral 150 denotes a paper charger serving as a transfer material charging unit, 14 h denotes a paper separation AC static eliminator serving as a transfer material separating unit, 160 denotes a transport unit having a separation claw 210 serving as a claw member and a spur 162 serving as a spur member, and 169 denotes a spur member. An entry guide plate 17 serving as an entry guide member is a fixing device serving as fixing means.

The photosensitive drum 10, which is an image forming body, has a transparent conductive layer, a, on the outer periphery of a cylindrical substrate formed of a transparent member such as optical glass or transparent acrylic resin.
A photosensitive layer (also referred to as a photoconductive layer) such as an Si layer or an organic photosensitive layer (OPC), which is rotated clockwise as indicated by an arrow in FIG. 1 with the conductive layer grounded.

A scorotron charger 11, which is a charging unit for each color, an exposure optical system 12, which is an image writing unit for each color, and a developing unit 13, which is a developing unit for each color, form a set of yellow (Y) ), Magenta (M), cyan (C), and black (K) are provided for the image forming process, and four sets are provided.
With respect to the 0 rotation direction, they are arranged in the order of Y, M, C, and K.

The scorotron charger 11, which is a charging means for each color, has a control grid maintained at a predetermined potential and a discharge electrode 11a composed of, for example, a sawtooth electrode, and faces the photosensitive layer of the photosensitive drum 10. And installed
The charging operation (in the present embodiment, negative charging) is performed by corona discharge having the same polarity as that of the toner.
A uniform potential is given to 0. As the discharge electrode 11a, a wire electrode or a needle electrode may be used.

Exposure optical system 1 as image writing means for each color
2 indicates that the exposure position on the photosensitive drum 10 is the photosensitive drum 1 with respect to the scorotron charger 11 for each color described above.
It is arranged inside the photoconductor drum 10 so as to be located on the downstream side in the rotation direction of 0. Each exposure optical system 12
Is a linear exposure element 12a in which a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light arranged in the main scanning direction are arranged in parallel with the drum axis, and a light focusing element as an imaging element. Exposure unit composed of an optical transmission body (trade name: Selfoc lens array) 12b and a lens holder (not shown), which is attached to the holding member 20. In addition to the exposure optical system 12 for each color, a transfer simultaneous exposure unit 12d and a uniform exposure unit 12e are attached to the holding member 20, and are housed integrally within the light-transmitting substrate of the photosensitive drum 10. The exposure optical system 12 for each color performs image exposure of the photosensitive layer of the photosensitive drum 10 from the back side in accordance with image data of each color read by a separate image reading device and stored in the memory, and electrostatically exposes the photosensitive layer on the photosensitive drum 10. Form a latent image. As the exposure element 12a, besides LED, FL (phosphor emission), EL (electroluminescence), PL
It is also possible to use a plurality of light-emitting elements such as (plasma discharge) arranged in an array. The emission wavelength of the image exposure light emitting element usually ranges from 780 to 900 nm, which is highly transparent to the Y, M, and C toners.
In the present embodiment, since the image exposure is performed from the back surface, a shorter wavelength of 400 to 780 nm, which does not have sufficient transparency to the color toner, may be used.

The developing device 13 as a developing means for each color keeps a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 and rotates in a forward direction with respect to the rotating direction of the photosensitive drum 10, for example, 0.5 to 1 mm in thickness. And a developing casing 131 formed of a cylindrical nonmagnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm, and a developing casing 138. Inside the developing casing 138, yellow (Y) and magenta ( M), cyan (C) and black (K) one-component or two-component developers. Each developing unit 13
Is maintained in a non-contact state with the photosensitive drum 10 with a predetermined gap, for example, 100 to 500 μm, by an abutting roller (not shown), and applies a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 131. By doing
Non-contact reversal development is performed to form a toner image on the photosensitive drum 10.

The intermediate transfer belt 14a is an intermediate transfer member is an endless belt having a volume resistivity of 10 ¹² ~10 ¹⁵ Ω · cm, for example modified polyimide, thermal curing polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride A 0.1 to 1.0 mm thick semiconductive film substrate in which a conductive material is dispersed in an engineering plastic such as nylon alloy is coated with a fluorine coating preferably having a thickness of 5 to 50 μm as a toner filming preventing layer. This is a seamless belt having a two-layer structure. In addition to the above, as the base of the belt, a conductive material dispersed in silicon rubber or urethane rubber or the like having a thickness of 0.5 to 2.0
mm semi-conductive rubber belts can also be used. The intermediate transfer belt 14a includes a driving roller 14d, a ground roller 14j, and a driven roller 14e, which are roller members.
1 and tension roller 14i.
Is rotated counterclockwise as indicated by the arrow. Following roller 14e, ground roller 14j, drive roller 14d, tension roller 14i according to the rotation direction of intermediate transfer belt 14a.
, A driven roller 14e, an earth roller 14
j and the drive roller 14d are fixedly rotated, the tension roller 14i is movably supported by an elastic force such as a spring (not shown), and the tension roller 14i is rotated by stretching the intermediate transfer belt 14a. The drive roller 14d is rotated by a drive from a drive motor (not shown), and drives and rotates the intermediate transfer belt 14a. The rotation of the intermediate transfer belt 14a causes the earth roller 14j and the driven roller 1 to rotate.
4e and the tension roller 14i are driven to rotate. Belt slack of the rotating intermediate transfer belt 14a is tensioned by the tension roller 14i. Drive roller 14
The recording paper P is separated from the intermediate transfer belt 14a at a curvature portion KT at the end of the intermediate transfer belt 14a stretched around d on the fixing device 17 side.

Transfer device 14 as first and second transfer means
c denotes the photosensitive drum 10 with the intermediate transfer belt 14a interposed therebetween.
A transfer area 14b is formed between the intermediate transfer belt 14a and the photosensitive drum 10. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the transfer device 14c, and the toner image on the photosensitive drum 10 is transferred onto the intermediate transfer belt 14a or onto the surface of the recording paper P as a transfer material. Transcribe.

The back transfer unit 14g, which is a third transfer means, is preferably constituted by a corona discharger, and is a conductive ground roller 14 grounded with the intermediate transfer belt 14a interposed therebetween.
j, a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied, and the toner image on the intermediate transfer belt 14a is transferred to the back surface of the recording paper P.

The static eliminator 14m, which is a static eliminator, is preferably constituted by a corona discharger, and is disposed downstream of the transfer unit 14c, which is the first and second transfer unit, in the moving direction of the intermediate transfer belt 14a. 14c is provided in parallel with
An AC voltage on which a DC voltage having the same polarity or opposite polarity to the toner is superimposed is applied, and the charge of the intermediate transfer belt 14a charged by the voltage application of the transfer device 14c is eliminated.

The paper charger 150, which is a transfer material charging means, is preferably constituted by a corona discharger, and is provided to face the driven roller 14e with the intermediate transfer belt 14a interposed therebetween.
Same polarity as toner (minus polarity in this embodiment)
Is applied, and the recording paper P is charged and attracted to the intermediate transfer belt 14a. In addition to the corona discharger, a paper charging brush or a paper charging roller that can abut and release the intermediate transfer belt 14a can be used as the paper charger 150.

Paper separation AC neutralizer 1 as transfer material separating means
4h is preferably formed of a corona discharger, and is provided at an end of the intermediate transfer belt 14a on the side of the fixing device 17 as needed, facing the conductive drive roller 14d grounded with the intermediate transfer belt 14a interposed therebetween. If necessary, an AC voltage in which a DC voltage having the same polarity or opposite polarity to the toner is superimposed is applied, and the recording paper P conveyed by the intermediate transfer belt 14a is discharged and separated from the intermediate transfer belt 14a.

The transport section 160 includes a separation claw 210 as a claw member.
And a spur member 162 serving as a spur member. The spur member 162 is provided between the fixing device 17 and the curvature portion KT at the end of the intermediate transfer belt 14a on the fixing device 17 side. The transport unit 160 includes the fixing device 1
7, the intermediate transfer belt 14a is deformed, the toner image carried on the intermediate transfer belt 14a tends to be fused, and the transfer is difficult.
4a is prevented from sticking to the toner.

The separation claw 210, which is a claw member, approaches the curvature portion KT of the intermediate transfer belt 14a, and
The recording paper P is fixed to the support shaft 221 with a predetermined interval, preferably 0.1 to 2.0 mm, provided when the recording paper P is separated from the intermediate transfer belt 14a.
The leading end of the recording paper P that is to be conveyed while being bent in the direction a is brought into contact with the recording paper P to assist the separation of the recording paper P.

The spur 162, which is a spur member, has a plurality of protrusions 162a on its peripheral surface, and is provided rotatably about a rotation support shaft 165. The spur 162 guides the back side of the recording sheet P to convey the recording sheet P, prevents the back side toner image of the recording sheet P having the toner image on both sides from being disturbed, and transfers the recording sheet P to the fixing device 17. The recording paper P is stably conveyed to the fixing device 17 while keeping the entering direction constant.

The separation claw 210 and the spur 162 are connected to the curvature portion KT of the intermediate transfer belt 14a and the nip portion T of the fixing device 17.
A surface PL1 (hereinafter referred to as a transfer material transport surface PL1; see FIG. 5) connecting an entrance portion (entry portion) of the transfer material to the transfer material transport surface PL1 on the opposite side of the photosensitive drum 10 from or close to the surface. Is arranged. It is also possible to provide spurs 162 as spur members on both sides of the transfer material transport surface PL1.

An entry guide plate 169 serving as an entry guide member
Is disposed in contact with or close to the transfer material transport surface PL1 on the opposite side of the photosensitive drum 10, and the leading end guides the recording paper P so that the leading end of the recording paper P is prevented from wrinkling during fixing. The fixing device 17 is caused to enter the nip portion T. Entry guide plate 1
69 is provided on the transport unit 160 or the fixing device 17, but is preferably attached to the fixing device 17 as shown in FIG.

A fixing device 17 serving as a fixing means is formed in a trapezoidal shape as an upper (front side) film-shaped rotating member for fixing a toner image of a front side image (upper side side image) (front side). And a lower (rear side) heat formed in a trapezoidal shape as a lower (rear side) film-shaped rotating member for fixing the toner image of the rear side image (lower side image). The recording paper P is sandwiched by a nip T formed between the upper and lower heat fixing films 17a and 17b, and the toner image on the recording paper P is applied by applying heat and pressure. Establish. Upper heat fixing film 17a and lower heat fixing film 17
The trapezoid with b is arranged in a mirror image relationship.

Next, the image forming process will be described.

The photosensitive drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by starting a photosensitive member driving motor (not shown) at the start of image recording, and is simultaneously exposed to light by the charging action of a yellow (Y) scorotron charger 11. Body drum 1
Application of a potential to 0 starts.

After the photosensitive drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing with a first color signal, that is, an electric signal corresponding to the Y image data. An electrostatic latent image corresponding to the Y image of the original image is formed on the front surface.

The latent image is reversal-developed in a non-contact state by the Y developing unit 13, and a yellow (Y) toner image is formed on the photosensitive drum 10.

Next, a potential is applied to the photosensitive drum 10 from above the Y toner image by the charging action of the magenta (M) scorotron charger 11, and the second color signal, that is, the M color signal, is applied by the M exposure optical system 12. Image writing is performed by an electric signal corresponding to the image data, and the magenta (M) toner image is superimposed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13. It is formed.

By the same process, the cyan (C) toner image corresponding to the third color signal is further superimposed by the cyan (C) scorotron charger 11, the exposure optical system 12 of C and the developing device 13 of C. The black (K) toner image corresponding to the fourth color signal is sequentially superimposed thereon by a black (K) scorotron charger 11, a K exposure optical system 12, and a K developing device 13. A superposed color toner image of four colors of yellow (Y), magenta (M), cyan (C) and black (K) is formed on the peripheral surface within one rotation of the photosensitive drum 10. (Toner image forming means).

These Y, M, C and K exposure optical systems 12
Image writing on the photosensitive layer of the photosensitive drum 10 is performed from the inside of the drum through the above-described translucent substrate. Therefore, the writing of the images corresponding to the second, third and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. Can be formed.

In the transfer area 14b, the superimposed color toner image serving as the back surface image formed on the photosensitive drum 10 as the image forming body by the above-described image forming process is formed.
By the transfer device 14c as a first transfer unit, the transfer (1) is collectively performed on the intermediate transfer belt 14a as the intermediate transfer body.
The next transfer is performed (FIG. 2A). At this time, uniform exposure may be performed by the simultaneous transfer exposure device 12d provided inside the photoconductor drum 10 so that good transfer is performed.

The toner remaining on the peripheral surface of the photoconductive drum 10 after the transfer is subjected to static elimination by the photoconductive drum AC static eliminator 16, and then enters a cleaning device 19 as image forming body cleaning means. The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the toner, and collected by a screw 19b in a toner discharge container (not shown). Further, the peripheral surface of the photosensitive drum 10
For example, a uniform exposure device 12 before charging using a light emitting diode
The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure by e.

The charge on the intermediate transfer belt 14a charged by the transfer unit 14c is removed by a charge removal unit 14m which is a charge removal unit provided in parallel with the transfer unit 14c.

After the superimposed color toner image (second toner image) serving as the back surface image is formed on the intermediate transfer belt 14a as described above, the above-described color image forming process is performed on the photosensitive drum 10. Similarly, a superimposed color toner image (first toner image) to be a surface image continuously
Is formed (FIG. 2B). At this time, the photosensitive drum 1
The image data is changed so that the front side image formed on 0 is a mirror image of the back side image formed on the photosensitive drum 10.

With the formation of a surface image on the photosensitive drum 10, recording paper P as a transfer material is sent out from a paper feed cassette 15 as a transfer material storage means by a feed roller 15a, and is used as a transfer material feeding means. Timing roller 1
5b, and driven by the timing roller 15b, the first toner image formed on the photosensitive drum 10 is a surface toner color toner image and the intermediate transfer belt 14
The sheet is fed to the transfer area 14b in synchronization with the color toner image of the back side image, which is the second toner image carried on the transfer area 14b. At this time, the fed recording paper P is charged to the same polarity as the toner by a paper charger 150 which is a transfer material charging means provided on the surface side of the recording paper P, and the intermediate transfer belt 14a
And is fed to the transfer area 14b. By charging the paper with the same polarity as that of the toner, the toner is prevented from being attracted to the toner image on the intermediate transfer belt 14a and the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed.

In the transfer area 14b, a second voltage to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied.
The surface image on the photosensitive drum 10 is collectively transferred to the surface of the recording paper P by the transfer device 14c as the transfer means (2).
Next transfer). At this time, the back side image on the intermediate transfer belt 14a is not transferred to the recording paper P, and the intermediate transfer belt 1
4a. Transfer device 14 as second transfer means
In the case of secondary transfer by c, so that good transfer is performed,
The uniform exposure may be performed by a simultaneous transfer exposure device 12d using, for example, a light emitting diode, provided inside the photosensitive drum 10 so as to face the transfer area 14b. Further, the intermediate transfer belt 14a charged by the transfer device 14c
Is removed by the charge remover 14m.

The recording paper P on which the color toner image has been transferred to the front surface is conveyed to a back transfer device 14g as a third transfer means to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Then, the back side image on the peripheral surface of the intermediate transfer belt 14a is collectively transferred (tertiary transfer) to the back side of the recording paper P by the back side transfer unit 14g (FIG. 2C).

The recording paper P on which the color toner images are formed on both sides is formed by the curvature of the curvature portion KT of the intermediate transfer belt 14a and the paper as transfer material separating means provided at the end of the intermediate transfer belt 14a as necessary. The spur 162 provided on the transport unit 160 is separated from the intermediate transfer belt 14a by the static elimination action of the separation AC neutralizer 14h and the separation claw 210 provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a. The fixing device 17 is stably conveyed to the fixing device 17 as a fixing unit, and the leading end portion is sent to the nip portion T of the fixing device 17 by the entry guide plate 169 to fix the toner image of the front surface image (upper image). And a heat fixing film 17b disposed on the lower side for fixing the toner image of the back side image (lower image). The toner image on the recording sheet P is fixed by the nip portion T by applied heat and pressure. The recording paper P on which the double-sided image has been recorded is fixed to the fixing separation claw 17.
After being separated by 9a, the sheet is discharged from the fixing device 17 through the fixing sheet discharging guide 179b and the fixing sheet discharging roller 179c, is sent upside down, and is discharged by the sheet discharging roller 18 to a tray outside the apparatus.

The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is provided opposite to the driven roller 14e with the intermediate transfer belt 14a interposed therebetween, and is applied to the intermediate transfer belt 14a with the support shaft 142 as a rotation fulcrum. The intermediate transfer member is cleaned by an intermediate transfer member cleaning device 140 which is an intermediate transfer member cleaning unit having an intermediate transfer member cleaning blade 141 capable of contacting and releasing contact.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is removed by a photoreceptor drum AC static eliminator 16 and then cleaned by a cleaning device 19. By 12e, the history of the photosensitive drum 10 in the previous image formation is eliminated, and the next image formation cycle is started.

Since the superimposed color toner images are collectively transferred by using the above-described method, color shift of the color image on the intermediate transfer belt 14a, scattering or rubbing of the toner, and the like are less likely to occur, and the image deterioration is small. Double-sided color image formation is performed.

In the original image reading apparatus 500,
When the image data of the document PS read by the document image reading unit shown in FIG. 3 is copied as a single-sided image of only the surface of the photosensitive drum 10 when the image is determined to be a single-sided image or a double-sided image The RO shown in FIG.
A single-sided image forming program P2 of the front surface by the photosensitive drum 10 as an image forming body stored in M is read into the RAM through the control unit, and the single-sided image forming program P2 of the front surface is executed by the control unit. The described image forming process of only the surface by the photosensitive drum 10 is continuously performed.

When the image data is determined to be a single-sided image or a double-sided image, the image data of the original PS read by the original image reading means shown in FIG. In the case of copying as an image, a single-sided image forming program P3 on the back surface of the intermediate transfer belt 14a as an intermediate transfer member stored in the ROM shown in FIG. The image forming program P3 is executed, and the image forming process for only the back surface by the intermediate transfer belt 14a described in FIG. 1 is continuously performed.

Although the embodiment of the double-sided image forming apparatus has been described in the case of forming a color image, the present invention is not necessarily limited to this, and the same process as described with reference to FIGS. The present invention is also applied to monochrome one-sided or two-sided image formation.

According to FIG. 5, as described above with reference to FIG.
The recording paper P having a color toner image formed on the surface thereof has a curvature of a driving roller 14d for driving the intermediate transfer belt 14a,
The intermediate transfer belt 14a is separated from the intermediate transfer belt 14a by the static elimination action of a paper separation AC static eliminator 14h serving as a transfer material separating means provided opposite to the drive roller 14d at the end of the intermediate transfer belt 14a and the separation claw 210.

Intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1 and fed to a nip portion T of a fixing device 17 as a fixing unit.

The fixing device 17 has a trapezoidal upper heat-fixing film 17a as a film-shaped rotating member for fixing the toner image of the front image, and a film-shaped rotating member for fixing the toner image of the back image. A lower heat-fixing film 17b formed in a trapezoidal shape as a member, and heat and pressure are applied at a nip T formed by the upper and lower heat-fixing films 17a and 17b, so that the nip T Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 17a formed in an upper trapezoidal shape for fixing the toner image of the front surface image has, for example, a thickness of 2 mm.
A fixing film 171a which is a film member on the upper side of a thin film having a thickness of 0 to 100 μm, preferably 25 to 60 μm, and a fixing film 17 provided inside the fixing film 171a.
1a, a film drive roller 176a and a film tension roller 177a, and a fixing film 171a.
Holds a ceramic heater 172a as a fixed heating element provided in the inside, an elastic rubber 173a as an elastic member also provided in the vicinity of and in parallel with the ceramic heater 172a, and a ceramic heater 172a and the elastic rubber 173a. Heater holder 174a for performing
It is composed of Film drive roller 176a, film tension roller 177a, and heater holder 174
a, the fixing film 171a is stretched in a trapezoidal shape. An aluminum roller 178a is provided opposite to the film driving roller 176a with the fixing film 171a interposed therebetween.
The aluminum roller 178a is used to make the temperature of the fixing film 171a uniform and to prevent the temperature of the non-sheet passing portion from rising.
TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172a for performing temperature control.

The heat-fixing film 17b formed in the lower trapezoidal shape for fixing the toner image of the back image is thicker than the fixing film 171a of the upper heat-fixing film 17a, for example, 30 to 130 μm, preferably. Is 40-8
A fixing film 171b which is a lower film member of a 0 μm thin film, and a film driving roller 1 provided inside the fixing film 171b and extending the fixing film 171b.
76b, a film tension roller 177b, a ceramic heater 172b as a fixed heating element provided inside the fixing film 171b, and an elastic rubber 173b as an elastic member also provided inside and adjacent to and parallel to the ceramic heater 172b. And a heater holder 174b for holding the ceramic heater 172b and the elastic rubber 173b. The fixing film 171b is stretched in a trapezoidal shape by the film driving roller 176b, the film tension roller 177b, and the heater holder 174b. An aluminum roller 178 is opposed to the film drive roller 176b with the fixing film 171b interposed therebetween.
b is provided, and the aluminum roller 178b is used to make the temperature of the fixing film 171b uniform and to prevent the temperature of the non-sheet passing portion from rising. TS2 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172b for performing temperature control.

The fixing films 171a, 171b are driven by driving one of the film driving rollers 176a, 176b.
One of b is driven and rotated, and the other is driven and rotated.

The heat-fixing film 17a as the upper film-shaped rotating member has an upper fixed portion upstream in the fixing area (nip portion T) with respect to the rotating direction of the upper fixing film 171a (conveying direction of the recording paper P). A ceramic heater 172a as a heating element and an elastic rubber 173a are arranged on the downstream side, and a heat fixing film 17b as a lower film-shaped rotating member is rotated in a direction of rotation of the lower fixing film 171b in a fixing area. An elastic rubber 173b is disposed on the upstream side with respect to the conveying direction of the recording paper P), and a ceramic heater 172b as a fixed heating element on the downstream side is disposed on the downstream side.

The upper ceramic fixing film 171a for fixing the toner image of the front surface image and the fixing film 171b of the lower heat fixing film 17b for fixing the toner image of the rear surface image are sandwiched between the upper ceramic fixing film 171a and the upper ceramic fixing film 171b. The heater 172a and the lower elastic rubber 173b face each other, and the upper elastic rubber 173a and the lower ceramic heater 172b face each other. Lower elastic rubber 173
b is pressed against the upper ceramic heater 172a, and the upper elastic rubber 173a is pressed against the lower ceramic heater 172b by pressing members (not shown) with the fixing films 171a and 171b interposed therebetween.
A fixing area (nip portion T) is formed by 1a and 171b.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the upper and lower ceramic heaters 172a, 172b pressed by the elastic rubbers 173b, 173a acting as soft members. Further, the upper ceramic heater 172a and the upper elastic rubber 173a, and the lower elastic rubber 173b and the lower ceramic heater 172b are arranged close to each other as a dimension width described later. The heater 172a and the lower elastic rubber 173b, and the upper elastic rubber 173a and the lower ceramic heater 1
By arranging the front and rear surfaces 72b and 72b in a staggered manner, the backside toner image is fixed following the fixing of the frontside toner image, thereby preventing the toner image on the recording paper P from being shifted. You. Further, a ceramic heater 172a for fixing the surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which a single-sided image is formed on a surface frequently.

The upper heat-fixing film 17a is formed in a trapezoidal shape and has a thickness of, for example, 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 171a of 5 to 60 μm, and the lower heat fixing film 17b has a trapezoidal shape, for example, a thickness of 30 to 130 μm, preferably 40 to 80 μm.
.mu.m thin film fixing film 171b, and the thickness of the lower fixing film 171b is larger than that of the upper fixing film 171a.
And the heat capacity of the lower fixing film 171b is larger than the heat capacity of the upper fixing film 171a. By reducing the heat capacity of the upper fixing film 171a, it is possible to perform a quick quick start, in which warming up at the time of forming a single-sided image on the front surface, which is generally frequently performed, is substantially zero. Also, by increasing the heat capacity of the lower fixing film 171b, it is possible to reliably perform double-sided fixing. In any case, the heat capacity of the fixing films 171a and 171b is about 1/100 of that of a conventionally used fixing heat fixing roller, and a quick start with almost zero warm-up is possible.

Ceramic heater 17 as fixed heating element
For 2a and 172b, an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm, in which a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer are sequentially provided by thick film printing, is used. Ceramic heater 172
The thermal resistance between the fixing films 171a and 171b is lower than that of the fixing films 171a and 171b. The surface protective layer functions to protect the resistance heating layer and prevent the fixing films 171a and 171b from being worn.

Elastic rubbers 173b and 17 as elastic members
3a is formed of heat-resistant rubber such as silicon rubber, for example.
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 172a, 172b pressed by elastic rubbers 173b, 173a.
To form At least the fixing films 171a, 171
A smooth surface such as a fluorine coat is provided on the contact surface with the fixing film b to facilitate rotation of the fixing films 171a and 171b.

The heater holders 174a and 174b are formed of a metal member having good heat conductivity using, for example, aluminum or iron, have a width of about 20 mm, and have upper and lower ceramic heaters 172a and 172b and upper and lower elastic rubbers 173a and 173a.
73b are arranged close to each other. At least a smooth surface such as a fluorine coat is provided on the contact surface with the fixing films 171a and 171b to facilitate the rotation of the fixing films 171a and 171b.

Further, the upper and lower fixing films 171a,
171b has the same configuration, and as shown in the enlarged view of FIG. 5, the base material 171A, the conductive layer 171B, and the release layer 17.
1C.

The base material 171A is preferably a polyimide resin having excellent strength and dimensional stability at high temperatures, and the upper fixing film 171a has a thickness of 20 to 100.
μm, preferably 25 to 60 μm, and the lower fixing film 171b is 30 to 130 μm, preferably 40 to 8 μm.
Preferably, the thickness is about 0 μm, and the thickness of the lower fixing film 171b is larger than the thickness of the upper fixing film 171a. Preferably, by setting the thickness to about 20 to 30 μm or more, the strength and rigidity are increased, and the fixing film 1
The deviation during rotation of the 71 can be regulated at the end without buckling. On the other hand, if the thickness is more than 100 to 130 [mu] m, the heat conduction becomes poor, and the heat conduction becomes large, so that it becomes difficult to heat up instantaneously and the electric power used increases.

As described above, the upper fixing film 171a
Is made thinner than the lower fixing film 171b, the generation of wrinkles in both the fixing films 171a and 171b is prevented, and the upper part which is more frequently performed by the heat from the ceramic heater 172a as the upper fixed heating element is formed. Fixing means that can favorably print only on the (front) surface is possible. Further, heat from the upper ceramic heater 172a is efficiently transmitted to the lower elastic rubber 173b, so that the toner image is not disturbed when the leading end of the transfer material is added to the nip portion, and the lower side of the lower rubber rubber 173b is not disturbed. Ceramic heater 1
The heat from 72b is also efficiently transmitted to the upper elastic rubber 173a, so that the toner image of the single-sided image or the double-sided image on the front surface or the back surface (upper surface or lower surface) is fixed well.

The lower fixing film 171b is inferior in thermal conductivity from below due to its thickness, but forms a nip at the upstream part, and has thermal conductivity by the upper ceramic heater 172a. Since T is large, sufficient overheating can be performed on the toner image.

To prevent offset, the release layer 1
71C, for example, a layer of fluororesin (PFA or PTFE) is preferably provided.
A conductive layer 171B is provided and grounded to eliminate the influence of the triboelectric charge generated by the sliding between the inner surface of the base material 171A of the a and 171b and the surfaces of the ceramic heaters 172a and 172b.

Further, a conductive filler is inserted in the release layer 171C to reduce the resistance so as to release the charged charge peeled off from the rear end of the recording paper P in a low humidity environment, thereby preventing the offset.
However, if the resistance value is too low, the transfer charge leaks and an offset occurs, so that 2 × 10 ^{10 to} 5 × 10 ¹¹ Ω / cm.
A resistance value of ² is preferred.

According to the above-described structure, an image forming apparatus is provided which has a wide nip width in the fixing area, high fixing performance, and a fixing means capable of performing double-side fixing with a low heat capacity and a substantially zero warm-up time. You.

As shown in FIGS. 6 and 4, when forming a double-sided image, the conveyance timing of the recording paper P passing through the fixing device 17 in accordance with the formation of the front and back images by the photosensitive drum 10 is determined based on the one-sided image on the front side. Unlike the continuous printing by forming, the printing is performed intermittently every other sheet. However, the upper heat fixing film 17a for fixing the toner image of the front surface image is formed on the recording paper P.
The ceramic heater 172a as an upper fixed heating element is heated in an on state in accordance with the passage timing of
The temperature control of the heat fixing film 17a is performed at an alternate level between the fixing temperature set value T during the image forming suspension and the appropriate fixing temperature set value T2 during the image forming.

Similarly, the heat fixing film 17b for fixing the toner image of the back side image is heated with the ceramic heater 172b as a fixed heating element turned on in synchronization with the passage timing of the recording paper P to form an image. The temperature control of the heat fixing film 17b is performed at an alternate level of the fixing temperature set value T during the pause and the appropriate fixing temperature set value T2 during the image formation. At this time, since the double-sided image formation is intermittently performed every other sheet, the non-passing time of the recording paper P is long, so that the temperature can be controlled and the temperature can be made uniform, and the heat fixing films 17a and 17b having a small heat capacity can be obtained. Can fix a double-sided image.

The temperature control is performed by fixing temperature setting values T, T1, T2 stored in advance in the ROM and temperature sensors TS1, T2.
This is performed through the control unit via the comparison circuit by the detection in S2.

In FIG. 6, the heat fixing films 17a, 17a
The temperature control of 7b is performed in an area sandwiching the front and rear ends of the recording paper P. However, when the linear velocity is high, it is necessary to set the temperature control timing earlier.

As shown in FIGS. 7 and 4, when forming a single-sided image on the front side, the conveyance timing of the recording paper P passing through the fixing device 17 for forming an image on the front side by the photoreceptor drum 10 is determined based on the double-sided image formation. Unlike the continuous printing in forming the image on the back surface of only one side, the image is continuously formed in response to the continuous image formation on the front surface by the photosensitive drum 10, but the heat fixing film 17a for fixing the toner image of the front surface image is used.
The upper portion of the ceramic heater 172a as a fixed heating element is heated in the ON state in synchronization with the passage timing of the recording paper P, and the fixing temperature set value T during image formation pause and the proper fixing temperature set value T2 during image formation are set. The temperature control of the heat fixing film 17a is performed at the level alternate with the above. During copying by forming a single-sided image on the front surface, the ceramic heater 172a is turned on before the recording paper P passes and heated.
In order to maintain an appropriate fixing temperature set value T1 during image formation,
The heating temperature of the heat fixing roller 17a is controlled.

On the other hand, the heat fixing film 17b is
During copying by forming a single-sided image on the front surface, the heating control is not performed, or the temperature of the heat fixing film 17b is controlled so as to maintain the fixing temperature set value T during the suspension of image formation.

The temperature control is performed through a control unit via a comparison circuit based on fixing temperature set values T and T1 stored in the ROM in advance and detection by the temperature sensors TS1 and TS2.

In FIG. 7, the temperature of the heat fixing film 17a is controlled in a region sandwiching the front and rear ends of the recording paper P. However, if the linear velocity is high, the temperature control timing must be set earlier.

As shown in FIGS. 8 and 4, when forming a single-sided image on the back side, the conveyance timing of the recording paper P passing through the fixing device 17 in response to the image formation on the back side by the intermediate transfer belt 14a is as follows. Unlike the continuous printing by forming the single-sided image on the front side, the printing is performed intermittently every other sheet. However, the lower heat fixing film 17 for fixing the toner image of the back side image is used.
b, the ceramic heater 172b as a fixed heating element on the lower side is heated to an on state in synchronization with the passage timing of the recording paper P, and the fixing temperature set value T during image formation pause and the proper fixing temperature setting during image formation. The temperature control of the heat fixing film 17b is performed at an alternate level with the value T2. During the copying by the one-sided image formation on the back side, the heating temperature of the heat fixing film 17b is controlled so that the ceramic heater 172b is turned on before the recording paper P passes and the fixing temperature setting value T2 during the image formation is maintained at an appropriate value. Is performed.

On the other hand, the heat fixing film 17a
During copying by forming a single-sided image on the back surface, the heating control is not performed, or the temperature of the heat-fixing film 17a is controlled so as to maintain the fixing temperature set value T during the pause of image formation.

As shown by the dashed line in FIG. 8, the heat fixing film 17a
The ceramic heater 172a is turned on before the recording paper P passes.
More preferably, heating is performed so as to maintain an appropriate fixing temperature set value T1 during image formation, and the nip portion T is formed by heating the heat fixing film 17a to an on state.
Is heated so that the toner image is not disturbed when the leading edge of the recording paper P is added to the nip portion, and the fixing of the toner image of the single-sided image only on the back surface is performed satisfactorily.

The temperature control is performed by setting the fixing temperature set values T, T2, (T1) stored in advance in the ROM and the temperature sensor TS.
1, through the control unit through the comparison circuit by the detection by TS2.

In FIG. 8, the temperature control of the heat fixing film 17b and the heat fixing film 17a is performed in a region sandwiching the front and rear ends of the recording paper P. However, if the linear velocity is high, the temperature control timing should be set earlier. Is required.

According to FIGS. 6 to 8 described above, at the time of forming a single-sided image on the front surface, forming a single-sided image on the back surface, or forming a double-sided image, the fixing of the toner image has a small heat capacity and the heat fixing film 17a which can be quick-started. 17b, good fixing is performed without providing a warm-up time.

In particular, since the double-sided image formation and the image formation on the back side of only one side are performed intermittently every other sheet, the toner image on the back side is fixed by the heat fixing film 17b having a smaller heat capacity than the conventional heat fixing roller. Also, the heat capacity is sufficient, and the fixing of the back surface image by the heat fixing film 17b becomes possible.

Note that the image forming apparatus is set so that temperature control is automatically performed in the double-sided image forming state at the time of the initial operation when the power switch is turned on, or when the mode is changed from the pause mode to the print operation mode. When the unused time elapses a predetermined time, the heat fixing films 17a and 17
b can be controlled so that the heating control is turned off.

With the configuration of the embodiment described above,
Different energy consumption is performed when forming a single-sided image on the front side only, when forming a single-sided image only on the backside, and when forming a double-sided image. In both-sided image formation, appropriate energy consumption is performed, both sides consume less energy, a wide nip width in the fixing area, high fixing performance can be obtained, and low heat capacity and almost zero warm-up time are required for both sides. An image forming apparatus capable of fixing is provided.

Another example of the fixing means will be described with reference to FIGS. FIG. 9 is an enlarged view of a second configuration of the fixing unit on which the toner image on the front side is fixed first, and a diagram illustrating conveyance of the transfer material to the fixing unit. FIG. FIG. 8 is an enlarged view of a third configuration of a fixing unit on which an image is fixed first and a diagram illustrating conveyance of a transfer material to the fixing unit;
FIG. 11 is an enlarged view of a first configuration of the fixing unit on which the toner image on the back side is fixed first, and a diagram illustrating conveyance of the transfer material to the fixing unit. FIG. FIG. 13 is an enlarged view of a second configuration of a fixing unit to which an image is fixed first and a diagram illustrating conveyance of a transfer material to the fixing unit. FIG. 13 is a fixing diagram in which a toner image on a back side is fixed first. FIG. 8 is an enlarged view of a third configuration of the unit and a diagram illustrating conveyance of a transfer material to the fixing unit.

According to FIG. 9, as described above with reference to FIG.
The recording paper P having a color toner image formed on the surface thereof has a curvature of a driving roller 14d for driving the intermediate transfer belt 14a,
The intermediate transfer belt 14a is separated from the intermediate transfer belt 14a by the static elimination action of a paper separation AC static eliminator 14h serving as a transfer material separating means provided opposite to the drive roller 14d at the end of the intermediate transfer belt 14a and the separation claw 210.

Intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1, and is fed to a nip portion T of a fixing device 17A as a fixing unit.

The fixing device 17A includes an upper heat fixing film 47a formed in a circular shape as a film-shaped rotating member for fixing the toner image of the front surface image, and a film-shaped rotating member for fixing the toner image of the rear surface image. The lower heat-fixing film 17b formed in a trapezoidal shape as a member, and heat and pressure are applied to the nip T formed by the upper and lower heat-fixing films 47a and 17b, so that the nip T Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 47a formed in an upper circular shape for fixing the toner image of the front surface image has a thickness of, for example, 2 mm.
A fixing film 471a formed in a circular shape, which is a film member on the upper side of a thin film of 0 to 100 μm, preferably 25 to 60 μm, a holder 475a provided inside the fixing film 471a, and also provided inside the fixing film 471a. A ceramic heater 472a as a fixed heating element, an elastic rubber 473a as an elastic member disposed in parallel with and adjacent to the ceramic heater 472a, and a heater holder 474a for holding the ceramic heater 472a and the elastic rubber 473a. You. The fixing film 471a is stretched in a circular shape by the holder 475a and the heater holder 474a. TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 472a for performing temperature control.

The heat fixing film 17b formed in the lower trapezoidal shape for fixing the toner image of the back side image is a member having the same configuration as that described with reference to FIG. 5, and is formed in the upper circular shape. Fixing film 471a of heat fixing film 47a
A fixing film 171b, which is a film member formed in a trapezoidal shape on the lower side of a thin film having a larger thickness, for example, a thickness of 30 to 130 μm, and preferably 40 to 80 μm, and a fixing film provided inside the fixing film 171b. 171b
Drive roller 176b and film tension roller 177b for stretching the film, and ceramic heater 1 as a fixed heating element provided inside fixing film 171b.
72b and the ceramic heater 17 also provided inside.
It comprises an elastic rubber 173b as an elastic member disposed in parallel with and in close proximity to 2b, and a ceramic heater 172b and a heater holder 174b for holding the elastic rubber 173b. The fixing film 171b is stretched in a trapezoidal shape by the film driving roller 176b, the film tension roller 177b, and the heater holder 174b. The film drive roller 176 sandwiches the fixing film 171b.
An aluminum roller 178b is provided so as to face the surface of the fixing film 171b. The aluminum roller 178b is used to make the temperature of the fixing film 171b uniform and to prevent the temperature of the non-sheet passing portion from rising. TS2
Is a thermistor mounted on the back surface of the ceramic heater 172b as a temperature sensor for performing temperature control.

The fixing film 171b is driven and rotated by the driving of the film driving roller 176b.
71a is driven and rotated.

The heat-fixing film 47a as a film-shaped rotating member formed in an upper circular shape is located in a fixing area (nip portion T) with respect to the rotation direction of the upper fixing film 471a (the conveying direction of the recording paper P). A ceramic heater 472a as an upper fixed heating element is disposed on the upstream side, an elastic rubber 473a is disposed on the downstream side, and the heat fixing film 17 as a film-shaped rotating member formed in a lower trapezoidal shape.
b, in the fixing area, an elastic rubber 173b is disposed on the upstream side with respect to the rotation direction of the lower fixing film 171b (the conveying direction of the recording paper P), and a ceramic heater 172b as a lower fixed heating element is disposed on the downstream side. Is done.

The upper ceramic fixing film 471a for fixing the toner image of the front surface image and the fixing film 171b of the lower heat fixing film 17b for fixing the toner image of the rear image are sandwiched between the upper ceramic fixing film 471a and the upper ceramic fixing film 471b. The heater 472a and the lower elastic rubber 173b face each other, and the upper elastic rubber 473a and the lower ceramic heater 172b face each other. Lower elastic rubber 173
b is pressed against the upper ceramic heater 472a, and the upper elastic rubber 473a is pressed against the lower ceramic heater 172b by pressing members (not shown) with the fixing films 471a and 171b interposed therebetween.
A fixing area (nip portion T) is formed by 1a and 171b.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the upper and lower ceramic heaters 472a and 172b pressed by the elastic rubbers 173b and 473a acting as soft members. Further, the upper ceramic heater 472a and the upper elastic rubber 473a, and the lower elastic rubber 173b and the lower ceramic heater 172b are arranged close to each other as a dimensional width to be described later. The heater 472a and the lower elastic rubber 173b, and the upper elastic rubber 473a and the lower ceramic heater 1
By arranging the front and rear surfaces 72b and 72b in a staggered manner, the backside toner image is fixed following the fixing of the frontside toner image, thereby preventing the toner image on the recording paper P from being shifted. You. Further, a ceramic heater 472a for fixing the surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which a single-sided image is formed on a surface frequently.

The upper heat fixing film 47a is formed in a circular shape and has a thickness of, for example, 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 471a of 5 to 60 μm, and the lower heat fixing film 17b is formed in a trapezoidal shape, for example, a thickness of 30 to 130 μm, preferably 40 to 80 μm.
A fixing film 171b having a thin film having a thickness of μm, and a lower fixing film 171b having a thickness of the upper fixing film 471a.
And the heat capacity of the lower fixing film 171b is larger than the heat capacity of the upper fixing film 471a. By reducing the heat capacity of the upper fixing film 471a, it is possible to perform a quick quick start, in which the warming up at the time of forming a single-sided image on the surface, which is frequently performed, is almost zero. Also, by increasing the heat capacity of the lower fixing film 171b, it is possible to reliably perform double-sided fixing. In any case, the heat capacity of the fixing films 471a and 171b is about 1/100 of that of a conventionally used fixing heat fixing roller, and a quick start with almost zero warm-up is possible.

Ceramic heater 47 as fixed heating element
For 2a and 172b, an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm, in which a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer are sequentially provided by thick film printing, is used. Ceramic heater 472
The thermal resistance between the fixing films 471a and 171b is lower than that of the fixing films 471a and 171b. The surface protective layer functions to protect the resistance heating layer and prevent the fixing films 471a and 171b from being worn.

Elastic rubbers 173b, 47 as elastic members
3a is formed of heat-resistant rubber such as silicon rubber, for example.
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 472a and 172b pressed by elastic rubbers 173b and 473a.
To form At least the fixing films 471a and 171
A smooth surface such as a fluorine coat is provided on the contact surface with b to facilitate the rotation of the fixing films 471a and 171b.

The heater holders 474a and 174b are formed of a metal member having good thermal conductivity using, for example, aluminum or iron, have a width of about 20 mm, and have upper and lower ceramic heaters 472a and 172b and upper and lower elastic rubbers 473a and 473a.
73b are arranged close to each other. At least a smooth surface such as a fluorine coat is provided on a contact surface with the fixing films 471a and 171b to facilitate rotation of the fixing films 471a and 171b.

The holder 475a is formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
1a, and a smooth surface such as a fluorine coat is provided on at least a contact surface with the fixing film 471a.
1a is facilitated to rotate.

Further, the upper and lower fixing films 471a,
171b has a configuration similar to that described above with reference to FIG. 5, and includes a base material 171A, a conductive layer 171B, and a release layer 171C, each having the same material, structure, characteristics, effects, and the like as described above.

The fixing of the toner image on the recording paper P by the fixing device 17A using the upper heat-fixing film 47a and the lower heat-fixing film 17b is performed as shown in FIG. In FIG. 7, the same control as described with reference to FIG. 8 is performed when forming a single-sided image on the back surface.

According to the above configuration, there is provided an image forming apparatus provided with a fixing means capable of performing a double-side fixing with a wide nip width in the fixing region and a high fixing performance, a low heat capacity and a substantially zero warm-up time. You. In addition, different energy consumptions are performed when forming a single-sided image only on the front surface, when forming a single-sided image only on the back surface, and when forming a double-sided image, and compared with a conventional fixing unit using a heating element for upper and lower rollers. During formation, both sides consume proper energy during both-sided image formation, which requires less energy consumption, provides a wide nip width in the fixing area, high fixing performance, and has a low heat capacity and almost no warm-up time. An image forming apparatus capable of performing both-side fixing is provided.

According to FIG. 10, as described above with reference to FIG. 1, the recording paper P having the color toner image formed on the surface thereof is driven by the curvature of the drive roller 14d for driving the intermediate transfer belt 14a and the intermediate transfer belt 14a. Paper separation AC as transfer material separating means provided at the end of
The charge is removed from the intermediate transfer belt 14a by the charge removing operation of the charge remover 14h and the separation claw 210.

An intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1, and is fed to a nip portion T of a fixing device 17B as a fixing unit.

The fixing device 17B has an upper heat fixing film 17a formed in a trapezoidal shape as a film-shaped rotating member for fixing the toner image of the front image, and a film-shaped rotating member for fixing the toner image of the back image. A lower heat-fixing film 47b formed in a circular shape as a member, and heat and pressure are applied at a nip T formed by the upper and lower heat-fixing films 17a and 47b, so that the nip T Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 17a formed in an upper trapezoidal shape for fixing the toner image of the front surface image has, for example, a thickness of 2 mm.
A fixing film 171a which is a film member on the upper side of a thin film having a thickness of 0 to 100 μm, preferably 25 to 60 μm, and a fixing film 17 provided inside the fixing film 171a.
1a, a film drive roller 176a and a film tension roller 177a, and a fixing film 171a.
Holds a ceramic heater 172a as a fixed heating element provided in the inside, an elastic rubber 173a as an elastic member also provided in the vicinity of and in parallel with the ceramic heater 172a, and a ceramic heater 172a and the elastic rubber 173a. Heater holder 174a for performing
It is composed of Film drive roller 176a, film tension roller 177a, and heater holder 174
a, the fixing film 171a is stretched in a trapezoidal shape. An aluminum roller 178a is provided opposite to the film driving roller 176a with the fixing film 171a interposed therebetween.
The aluminum roller 178a is used to make the temperature of the fixing film 171a uniform and to prevent the temperature of the non-sheet passing portion from rising.
TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172a for performing temperature control.

The lower heat-fixing film 47b for fixing the toner image of the back side image has a thickness of, for example, 2 mm.
A fixing film 471b formed in a circular shape, which is a film member on the upper side of a thin film of 0 to 100 μm, preferably 25 to 60 μm, a holder 475b provided inside the fixing film 471b, and also provided inside the fixing film 471b. A ceramic heater 472a as a fixed heating element, an elastic rubber 473b as an elastic member disposed in parallel with and adjacent to the ceramic heater 472b, and a heater holder 474b for holding the ceramic heater 472b and the elastic rubber 473b. You. The fixing film 471b is stretched in a circular shape by the holder 475b and the heater holder 474b. TS2 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 472b for performing temperature control.

The driving of the film drive roller 176a drives and rotates the fixing film 171a.
71b is driven and rotated.

The heat fixing film 17a formed in a trapezoidal shape as the upper film-shaped rotating member is moved in the fixing area (nip portion T) with respect to the rotation direction of the upper fixing film 171a (the conveying direction of the recording paper P). An upper ceramic heater 172a as an upper fixed heating element is disposed on the upstream side, an elastic rubber 173a is disposed on a downstream side, and a circular heat-fixing film 47 is formed as a lower film-shaped rotating member.
b, in the fixing area, an elastic rubber 473b is arranged on the upstream side with respect to the rotation direction of the lower fixing film 471b (conveying direction of the recording paper P), and a ceramic heater 472b as a lower fixed heating element is arranged on the downstream side. Is done.

Fixing film 1 of heat fixing film 17a formed in an upper trapezoidal shape for fixing the toner image of the surface image
71a and a fixing film 47 of a heat fixing film 47b formed in a lower circular shape for fixing the toner image of the back surface image
1b, the upper ceramic heater 172a and the lower elastic rubber 473b face each other, and the upper elastic rubber 173a and the lower ceramic heater 472b face each other. The lower elastic rubber 473b is connected to the upper ceramic heater 172a and the upper elastic rubber 173a.
Is pressed against a lower ceramic heater 472b by a pressing member (not shown) with the fixing films 171a and 471b interposed therebetween, so that a fixing area (nip portion T) formed by the upper and lower fixing films 171a and 471b is formed.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the upper and lower ceramic heaters 172a and 472b pressed by the elastic rubbers 473b and 173a acting as soft members. Further, the upper ceramic heater 172a and the upper elastic rubber 173a, and the lower elastic rubber 473b and the lower ceramic heater 472b are arranged close to each other as a dimension width to be described later. The heater 172a and the lower elastic rubber 473b, and the upper elastic rubber 173a and the lower ceramic heater 4
By arranging the front and rear surfaces 72b and 72b in a staggered manner, the backside toner image is fixed following the fixing of the frontside toner image, thereby preventing the toner image on the recording paper P from being shifted. You. Further, a ceramic heater 172a for fixing the surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which a single-sided image is formed on a surface frequently.

The upper heat-fixing film 17a has a trapezoidal shape, for example, a thickness of 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 171a of 5 to 60 μm, and the lower heat fixing film 47b is formed in a circular shape and has a thickness of, for example, 30 to 130 μm, preferably 40 to 80 μm.
μm thin film fixing film 471b, and the thickness of the lower fixing film 471b is set to the upper fixing film 171a.
And the heat capacity of the lower fixing film 471b is larger than the heat capacity of the upper fixing film 171a. By reducing the heat capacity of the upper fixing film 171a, a quick quick start is possible, in which warming up at the time of forming a single-sided image on the surface, which is frequently performed, is almost zero. In addition, by increasing the heat capacity of the lower fixing film 471b, it is possible to reliably perform double-sided fixing. In any case, the heat capacity of the fixing films 171a and 471b is about 1/100 of that of a conventionally used fixing heat fixing roller, so that quick start with almost zero warm-up is possible.

Ceramic heater 17 as fixed heating element
For 2a and 472b, an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm is provided with a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer sequentially by thick film printing. Ceramic heater 172
The thermal resistance between the fixing films 171a and 471b is lower than that of the fixing films 171a and 471b. The surface protective layer functions to protect the resistance heating layer and prevent the fixing films 171a and 471b from being worn.

Elastic rubbers 473b and 17 as elastic members
3a is formed of heat-resistant rubber such as silicon rubber, for example.
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 172a and 472b pressed by elastic rubbers 473b and 173a.
To form At least the fixing films 171a, 471
A smooth surface such as a fluorine coat is provided on a contact surface with the fixing film b to facilitate rotation of the fixing films 171a and 471b.

The heater holders 174a, 474b are formed of a metal member having good thermal conductivity using, for example, aluminum or iron, have a width of about 20 mm, and have upper and lower ceramic heaters 172a, 472b and upper and lower elastic rubbers 173a, 173b.
73b are arranged close to each other. At least a smooth surface such as a fluorine coat is provided on a contact surface with the fixing films 171a and 471b to facilitate rotation of the fixing films 171a and 471b.

The holder 475b is formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
1b, and a smooth surface such as a fluorine coat is provided on at least a contact surface with the fixing film 471b.
1b is facilitated to rotate.

Further, the upper and lower fixing films 171a,
471b has the same configuration as that described above with reference to FIG. 5 and includes a base material 171A, a conductive layer 171B, and a release layer 171C, each having the same material, structure, characteristics, effects, and the like as described above.

The fixing of the toner image on the recording paper P by the fixing device 17B using the upper heat-fixing film 17a and the lower heat-fixing film 47b is performed as shown in FIG. In FIG. 7, the same control as described with reference to FIG. 8 is performed when forming a single-sided image on the back surface.

According to the above configuration, there is provided an image forming apparatus provided with a fixing means capable of providing a wide nip width in the fixing region, high fixing performance, and low-heat capacity and capable of performing double-side fixing with substantially no warm-up time. You. In addition, different energy consumptions are performed when forming a single-sided image only on the front surface, when forming a single-sided image only on the back surface, and when forming a double-sided image, and compared with a conventional fixing unit using a heating element for upper and lower rollers. During formation, both sides consume proper energy during both-sided image formation, which requires less energy consumption, provides a wide nip width in the fixing area, high fixing performance, and has a low heat capacity and almost no warm-up time. An image forming apparatus capable of performing both-side fixing is provided.

According to FIG. 11, as described above with reference to FIG. 1, the recording paper P having the color toner image formed on the surface is rotated by the curvature of the driving roller 14d for driving the intermediate transfer belt 14a and the intermediate transfer belt 14a. Paper separation AC as transfer material separating means provided at the end of
The charge is removed from the intermediate transfer belt 14a by the charge removing operation of the charge remover 14h and the separation claw 210.

An intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1, and is fed to a nip portion T of a fixing device 17C as a fixing unit.

The fixing device 17C has a trapezoidal upper heat-fixing film 17c as a film-shaped rotating member for fixing the toner image of the front image, and a film-shaped rotating member for fixing the toner image of the back image. A lower heat-fixing film 17d formed in a trapezoidal shape as a member, and heat and pressure are applied at a nip T formed by the upper and lower heat-fixing films 17c and 17d, thereby forming the nip T Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 17c formed in an upper trapezoidal shape for fixing the toner image of the front surface image is a member having the same configuration as the heat fixing film 17a described with reference to FIG. 100 μm, preferably 25-6
A fixing film 171c, which is a film member on the upper side of a thin film of 0 μm, and a film driving roller 1 provided inside the fixing film 171c and stretching the fixing film 171c.
76c and a film tension roller 177c, a ceramic heater 172c as a fixed heating element provided inside the fixing film 171c, and an elastic rubber 173c as an elastic member also provided inside and adjacent to and parallel to the ceramic heater 172c. And a heater holder 174c for holding the ceramic heater 172c and the elastic rubber 173c. The fixing film 171c is stretched in a trapezoidal shape by the film driving roller 176c, the film tension roller 177c, and the heater holder 174c. An aluminum roller 178 is opposed to the film drive roller 176c with the fixing film 171c interposed therebetween.
The temperature of the fixing film 171c is made uniform by the aluminum roller 178c and the temperature of the non-sheet passing portion is increased. TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172c for performing temperature control.

The heat fixing film 17d formed in a trapezoidal shape on the lower side for fixing the toner image of the back side image is a member having the same configuration as the heat fixing film 17b described in FIG. Fixing film 171 of film 17c
c, a fixing film 171d which is a lower film member of a thin film having a thickness of, for example, 30 to 130 μm, preferably 40 to 80 μm, and a fixing film 171d provided inside the fixing film 171d and stretched. Film drive roller 176d and film tension roller 1
77d, a ceramic heater 172d as a fixed heating element provided inside the fixing film 171d, and an elastic rubber 173d as an elastic member similarly provided inside and disposed in parallel with the ceramic heater 172d.
It comprises a ceramic heater 172d and a heater holder 174d for holding the elastic rubber 173d.
The fixing film 171d is stretched in a trapezoid by the film driving roller 176d, the film tension roller 177d, and the heater holder 174d. Fixing film 171
An aluminum roller 178d is provided opposite to the film drive roller 176d with d interposed therebetween, and the aluminum roller 178d is used to make the temperature of the fixing film 171d uniform and to prevent the temperature of the non-sheet passing portion from rising. TS2 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172d for performing temperature control.

The fixing films 171c, 171d are driven by driving one of the film driving rollers 176c, 176d.
One of d is driven and rotated, and the other is driven and rotated.

The heat-fixing film 17c as the upper film-shaped rotating member has an upper elasticity in the fixing area (nip portion T) on the upstream side with respect to the rotation direction of the upper fixing film 171c (conveying direction of the recording paper P). A rubber heater 173c is provided on the downstream side as a ceramic heater 172 as an upper fixed heating element.
c is disposed, and the heat-fixing film 17d as the lower film-shaped rotating member has a rotation direction of the lower fixing film 171d in the fixing area (conveying direction of the recording paper P).
On the other hand, a ceramic heater 172d as a lower fixed heating element is arranged on the upstream side, and a lower elastic rubber 173d is arranged on the downstream side.

The upper elastic fixing film 171c for fixing the toner image of the front image and the lower elastic fixing film 171d of the lower heat fixing film 17d for fixing the toner image of the rear image sandwich the upper elastic film. Rubber 173
c and the lower ceramic heater 172d face each other, and the upper ceramic heater 172c and the lower elastic rubber 173d face each other. Upper elastic rubber 173
c is pressed against the lower ceramic heater 172d, and the lower elastic rubber 173d is pressed against the upper ceramic heater 172c by pressing members (not shown) with the fixing films 171c and 171d interposed therebetween.
A fixing area (nip portion T) is formed by 1c and 171d.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the ceramic heaters 172d and 172c pressed by the upper and lower elastic rubbers 173c and 173d acting as soft members. Further, the upper elastic rubber 173c and the upper ceramic heater 172c are connected to each other, and the lower ceramic heater 1
The upper elastic rubber 173c and the lower ceramic heater 172d, and the upper ceramic heater 172c and the lower Elastic rubber 1
By arranging the 73d and 73d in a staggered manner, the front toner image is fixed continuously to the fixing of the back toner image, and the toner image on the recording paper P is prevented from shifting. You. Furthermore, a ceramic heater 172d for fixing the back surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which double-sided image formation or single-sided image formation on the back surface is performed.

The upper heat-fixing film 17c has a trapezoidal shape, for example, a thickness of 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 171c of 5 to 60 μm, and the lower heat fixing film 17d has a trapezoidal shape, for example, a thickness of 30 to 130 μm, preferably 40 to 80 μm.
μm, and the thickness of the lower fixing film 171d is smaller than that of the upper fixing film 171c.
And the heat capacity of the lower fixing film 171d is larger than the heat capacity of the upper fixing film 171c. By reducing the heat capacity of the upper fixing film 171c, it is possible to perform a quick quick start in which the warming-up at the time of forming a single-sided image on the surface, which is frequently performed, is almost zero. In addition, by increasing the heat capacity of the lower fixing film 171d, it is possible to reliably perform both-side fixing. In any case, the heat capacity of the fixing films 171c and 171d is about 1/100 of that of a conventionally used fixing heat fixing roller, and a quick start with almost zero warm-up is possible.

Ceramic heater 17 as fixed heating element
For 2c and 172d, an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm, in which a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer are sequentially provided by thick film printing, is used. Ceramic heater 172
The thermal resistance between the fixing films 171c and 171d is lower than that of the fixing films 171c and 172d. The surface protective layer functions to protect the resistance heating layer and prevent the fixing films 171c and 171d from being worn.

Elastic rubbers 173d and 173 as elastic members
3c is formed of heat-resistant rubber such as silicon rubber,
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 172c, 172d pressed by elastic rubbers 173d, 173c.
To form At least the fixing films 171c and 171
A smooth surface such as a fluorine coat is provided on the contact surface with d to facilitate rotation of the fixing films 171c and 171d.

The heater holders 174c and 174d are formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
The width is about 20 mm, and the upper and lower ceramic heaters 172 are provided.
c, 172d and the upper and lower elastic rubbers 173c, 173d are arranged close to each other. At least fixing film 1
A smooth surface such as a fluorine coat is provided on the contact surface with the fixing films 71c and 171d to facilitate the rotation of the fixing films 171c and 171d.

Further, the upper and lower fixing films 171c, 171c,
171d has the same configuration as that described above with reference to FIG. 5 and includes a base material 171A, a conductive layer 171B, and a release layer 171C, and has the same materials, structures, characteristics, effects, and the like as described above.

The fixing of the toner image on the recording paper P by the fixing device 17C using the upper heat-fixing film 17c and the lower heat-fixing film 17d will be described with reference to FIG. In FIG. 7, the same control as described with reference to FIG. 8 is performed when forming a single-sided image on the back surface.

According to the above configuration, there is provided an image forming apparatus provided with a fixing means capable of providing a wide nip width in the fixing area, a high fixing performance, a low heat capacity, and a double-side fixing with a substantially zero warm-up time. You. In addition, different energy consumptions are performed when forming a single-sided image only on the front surface, when forming a single-sided image only on the back surface, and when forming a double-sided image, and compared with a conventional fixing unit using a heating element for upper and lower rollers. During formation, both sides consume proper energy during both-sided image formation, which requires less energy consumption, provides a wide nip width in the fixing area, high fixing performance, and has a low heat capacity and almost no warm-up time. An image forming apparatus capable of performing both-side fixing is provided.

According to FIG. 12, as described above with reference to FIG. 1, the recording paper P on the surface of which the color toner image has been formed is moved by the curvature of the driving roller 14d for driving the intermediate transfer belt 14a and the intermediate transfer belt 14a. Paper separation AC as transfer material separating means provided at the end of
The charge is removed from the intermediate transfer belt 14a by the charge removing operation of the charge remover 14h and the separation claw 210.

An intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1, and is fed to a nip portion T of a fixing device 17D as a fixing unit.

The fixing device 17D has an upper heat fixing film 47c formed in a circular shape as a film-shaped rotating member for fixing the toner image of the front surface image, and a film-shaped rotating member for fixing the toner image of the rear surface image. The lower heat-fixing film 17d formed in a trapezoidal shape as a member, and heat and pressure are applied to the nip T formed by the upper and lower heat-fixing films 47c and 17d. Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 47c formed in an upper circular shape for fixing the toner image of the front surface image has a thickness of, for example, 2 mm.
A fixing film 471c formed in a circular shape, which is a film member on the upper side of a thin film of 0 to 100 μm, preferably 25 to 60 μm, a holder 475c provided inside the fixing film 471c, and also provided inside the fixing film 471c. A ceramic heater 472c as a fixed heating element, an elastic rubber 473c as an elastic member disposed in parallel with and adjacent to the ceramic heater 472c, and a heater holder 474c for holding the ceramic heater 472c and the elastic rubber 473c. You. The fixing film 471c is stretched in a circular shape by the holder 475c and the heater holder 474c. TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 472c for performing temperature control.

The heat fixing film 17d formed in the lower trapezoidal shape for fixing the toner image of the back side image is a member having the same configuration as that described with reference to FIG. 5, and is formed in the upper circular shape. Fixing film 471c of heat fixing film 47c
A fixing film 171d, which is a film member formed in a trapezoidal shape on the lower side of a thin film having a greater thickness, for example, a thickness of 30 to 130 μm, preferably 40 to 80 μm, and a fixing film provided inside the fixing film 171d. 171d
Drive roller 176d and film tension roller 177d for stretching the film, and ceramic heater 1 as a fixed heating element provided inside fixing film 171d.
72d and a ceramic heater 17 also provided inside.
It comprises an elastic rubber 173d as an elastic member disposed in parallel with 2d and a heater 174d for holding the ceramic heater 172d and the elastic rubber 173d. The fixing film 171d is stretched in a trapezoid by the film driving roller 176d, the film tension roller 177d, and the heater holder 174d. The film drive roller 176 sandwiches the fixing film 171d.
An aluminum roller 178d is provided so as to oppose d, and the aluminum roller 178d is used to make the temperature of the fixing film 171d uniform and to prevent the temperature of the non-sheet passing portion from rising. TS2
Is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172d for controlling temperature.

By driving the film drive roller 176d, the fixing film 171d is driven and rotated.
71c is driven and rotated.

The heat-fixing film 47c as a film-shaped rotating member formed in an upper circular shape is located in a fixing area (nip portion T) with respect to the rotation direction of the upper fixing film 471c (the conveying direction of the recording paper P). An upper elastic rubber 473c is arranged on the upstream side, a ceramic heater 472c as a fixed heating element is arranged on the downstream side, and the heat fixing film 17 as a film-shaped rotating member formed in a lower trapezoidal shape.
In the fixing area, a ceramic heater 172d as a lower fixed heating element is disposed on the upstream side with respect to the rotation direction of the lower fixing film 171d (conveying direction of the recording paper P) in the fixing area, and an elastic rubber 173d is disposed on the downstream side. Is done.

The upper elastic fixing film 471c of the upper thermal fixing film 47c for fixing the toner image of the front image and the lower elastic fixing film 171d of the lower heat fixing film 17d for fixing the toner image of the back image sandwich the upper elastic film. Rubber 473
c and the lower ceramic heater 172d face each other, and the upper ceramic heater 472c and the lower elastic rubber 173d face each other. Upper elastic rubber 473
c is pressed against the lower ceramic heater 172d, and the lower elastic rubber 173d is pressed against the upper ceramic heater 472c by pressing members (not shown) with the fixing films 471c and 171d interposed therebetween.
A fixing area (nip portion T) is formed by 1c and 171d.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the upper and lower ceramic heaters 472c and 172d pressed by the elastic rubbers 173d and 473c acting as soft members. Further, the upper elastic rubber 473c and the upper ceramic heater 472c are connected to each other, and the lower ceramic heater 1
The upper elastic rubber 473c and the lower ceramic heater 172d, and the upper ceramic heater 472c and the lower ceramic heater 472c are disposed adjacently to each other with respect to the lower elastic rubber 173d and the lower elastic rubber 173d. Elastic rubber 1
By arranging the 73d and 73d in a staggered manner, the front toner image is fixed continuously to the fixing of the back toner image, and the toner image on the recording paper P is prevented from shifting. You. Furthermore, a ceramic heater 172d for fixing the back surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which double-sided image formation or single-sided image formation on the back surface is performed.

The upper heat fixing film 47c is formed in a circular shape and has a thickness of, for example, 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 471c of 5 to 60 μm, and the lower heat fixing film 17d has a trapezoidal shape, for example, a thickness of 30 to 130 μm, preferably 40 to 80 μm.
μm thin film fixing film 171d, and the lower fixing film 171d has an upper fixing film 471c.
And the heat capacity of the lower fixing film 171d is larger than the heat capacity of the upper fixing film 471c. By reducing the heat capacity of the upper fixing film 471c, it is possible to perform a quick quick start, in which the warming-up at the time of forming a single-sided image on the surface, which is frequently performed, is almost zero. In addition, by increasing the heat capacity of the lower fixing film 171d, it is possible to reliably perform both-side fixing. In any case, the heat capacity of the fixing films 471c and 171d is about 1/100 of that of a conventionally used fixing heat fixing roller, so that a quick start with almost zero warm-up is possible.

Ceramic heater 47 as fixed heating element
For 2c and 172d, an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm, in which a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer are sequentially provided by thick film printing, is used. Ceramic heater 472
The thermal resistance between the fixing films 471c and 171d is lower than that of the fixing films 471c and 172d. The surface protective layer functions to protect the resistance heating layer and to prevent wear of the fixing films 471c and 171d.

Elastic rubbers 173d and 47 as elastic members
3c is formed of heat-resistant rubber such as silicon rubber,
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 472c and 172d pressed by elastic rubbers 173d and 473c.
To form At least the fixing films 471c and 171
A smooth surface such as a fluorine coat is provided on the contact surface with d to facilitate rotation of the fixing films 471c and 171d.

The heater holders 474c and 174d are formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
The upper and lower ceramic heaters 472 are about 20 mm wide.
c, 172d and the upper and lower elastic rubbers 473c, 173d are arranged close to each other. At least the fixing film 4
A smooth surface such as a fluorine coat is provided on the contact surface with the fixing films 71c and 171d to facilitate the rotation of the fixing films 471c and 171d.

The holder 475c is made of, for example, a heat-resistant resin using a liquid crystal polyester resin.
1c, and a smooth surface such as a fluorine coat is provided on at least the contact surface with the fixing film 471c.
1c can be easily rotated.

Further, the upper and lower fixing films 471c, 471c,
171d has the same configuration as that described above with reference to FIG. 5 and includes a base material 171A, a conductive layer 171B, and a release layer 171C, and has the same materials, structures, characteristics, effects, and the like as described above.

The fixing of the toner image on the recording paper P by the fixing device 17D using the upper heat-fixing film 47c and the lower heat-fixing film 17d is performed as shown in FIG. In FIG. 7, the same control as described with reference to FIG. 8 is performed when forming a single-sided image on the back surface.

According to the above configuration, there is provided an image forming apparatus having a wide nip width in the fixing area, high fixing performance, and a fixing means capable of performing double-side fixing with a low heat capacity and a substantially zero warm-up time. You. In addition, different energy consumptions are performed when forming a single-sided image only on the front surface, when forming a single-sided image only on the back surface, and when forming a double-sided image, and compared with a conventional fixing unit using a heating element for upper and lower rollers. During formation, both sides consume proper energy during both-sided image formation, which requires less energy consumption, provides a wide nip width in the fixing area, high fixing performance, and has a low heat capacity and almost no warm-up time. An image forming apparatus capable of performing both-side fixing is provided.

According to FIG. 13, as described above with reference to FIG. 1, the recording paper P on the surface of which the color toner image has been formed is moved by the curvature of the driving roller 14d for driving the intermediate transfer belt 14a and the intermediate transfer belt 14a. Paper separation AC as transfer material separating means provided at the end of
The charge is removed from the intermediate transfer belt 14a by the charge removing operation of the charge remover 14h and the separation claw 210.

Intermediate transfer belt 14a as an intermediate transfer member
The recording paper P separated from the recording medium P is conveyed by a spur 162 provided below the transfer material conveying surface PL1, and is fed to a nip portion T of a fixing device 17E as a fixing unit.

The fixing device 17E includes an upper heat fixing film 17c formed in a trapezoidal shape as a film-shaped rotating member for fixing the toner image of the front surface image, and a film-shaped rotating member for fixing the toner image of the rear surface image. A lower heat-fixing film 47d formed in a circular shape as a member, and heat and pressure are applied at a nip T formed by the upper and lower heat-fixing films 17c and 47d, so that the nip T Is fixed on the recording paper P fed to the recording paper P.

The heat fixing film 17c formed in an upper trapezoidal shape for fixing the toner image of the surface image has a thickness of, for example, 2 mm.
A fixing film 171c which is an upper film member of a thin film having a thickness of 0 to 100 μm, preferably 25 to 60 μm, and a fixing film 17 provided inside the fixing film 171c.
1c, a film drive roller 176c and a film tension roller 177c, and a fixing film 171c.
Holds a ceramic heater 172c as a fixed heating element provided in the inside, an elastic rubber 173c as an elastic member provided in the vicinity of and in parallel with the ceramic heater 172c, and a ceramic heater 172c and the elastic rubber 173c. Heater holder 174c for performing
It is composed of Film drive roller 176c, film tension roller 177c, and heater holder 174
and c, the fixing film 171c is stretched in a trapezoidal shape. An aluminum roller 178c is provided to face the film drive roller 176c with the fixing film 171c interposed therebetween.
The aluminum roller 178c is used to make the temperature of the fixing film 171c uniform and to prevent the temperature of the non-sheet passing portion from rising.
TS1 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 172c for performing temperature control.

The heat fixing film 47d formed in a lower circular shape for fixing the toner image of the back side image has, for example, a thickness of 2 mm.
A fixing film 471d formed in a circular shape, which is a film member on the upper side of a thin film of 0 to 100 μm, preferably 25 to 60 μm, a holder 475d provided inside the fixing film 471d, and also provided inside the fixing film 471d. A ceramic heater 472c as a fixed heating element, an elastic rubber 473d as an elastic member disposed in parallel with and adjacent to the ceramic heater 472d, and a heater holder 474d for holding the ceramic heater 472d and the elastic rubber 473d. You. The fixing film 471d is stretched in a circular shape by the holder 475d and the heater holder 474d. TS2 is a thermistor as a temperature sensor mounted on the back surface of the ceramic heater 472d for performing temperature control.

By driving the film drive roller 176c, the fixing film 171c is driven and rotated.
71d is driven and rotated.

The heat fixing film 17c formed in a trapezoidal shape as the upper film-shaped rotating member is moved in the fixing area (nip portion T) with respect to the rotation direction of the upper fixing film 171c (conveying direction of the recording paper P). An upper elastic rubber 173c is arranged on the upstream side, a ceramic heater 172c as a fixed heating element is arranged on the downstream side, and a heat fixing film 47 formed in a circular shape as a lower film-shaped rotating member.
In the fixing area, a ceramic heater 472d serving as a lower fixed heating element is disposed on the upstream side with respect to the rotation direction of the lower fixing film 471d (the conveying direction of the recording paper P) in the fixing area, and an elastic rubber 473d is disposed on the downstream side. Is done.

Fixing film 1 of heat fixing film 17c formed in an upper trapezoidal shape for fixing the toner image of the front surface image
71c and a fixing film 47 of a heat fixing film 47d formed in a lower circular shape for fixing the toner image of the back side image
The upper elastic rubber 173c and the lower ceramic heater 472d face each other, and the upper ceramic heater 172c and the lower elastic rubber 473d face each other with 1d therebetween. The upper elastic rubber 173c is connected to the lower ceramic heater 472d and the lower elastic rubber 473d.
Is pressed against the upper ceramic heater 172c by a pressing member (not shown) with the fixing films 171c and 471d interposed therebetween, thereby forming a fixing area (nip portion T) by the upper and lower fixing films 171c and 471d.

As described above, good instant fixing is performed by the reliable and wide nip portion T formed by the upper and lower ceramic heaters 172c and 472d pressed by the elastic rubbers 473d and 173c acting as soft members. Further, the upper ceramic heater 172c and the upper elastic rubber 173c, and the lower elastic rubber 473d and the lower ceramic heater 472d are arranged close to each other as a dimensional width described later. The rubber 173c and the lower ceramic heater 472d, and the upper ceramic heater 172c and the lower elastic rubber 4
By arranging the 73d and 73d in a staggered manner, the front toner image is fixed continuously to the fixing of the back toner image, and the toner image on the recording paper P is prevented from shifting. You. Further, a ceramic heater 472d for fixing the back surface toner image on the upstream side in the transport direction of the recording paper P
Is effective as a fixing unit for an image forming apparatus in which double-sided image formation or single-sided image formation on the back surface is performed.

The upper heat-fixing film 17c has a trapezoidal shape, for example, a thickness of 20 to 100 μm, preferably 2 to 100 μm.
It has a thin fixing film 171c of 5 to 60 μm, and the lower heat fixing film 47d is formed in a circular shape and has a thickness of, for example, 30 to 130 μm, preferably 40 to 80 μm.
A fixing film 471d having a thin film having a thickness of μm, and the thickness of the lower fixing film 471d is larger than that of the upper fixing film 171c.
And the heat capacity of the lower fixing film 471d is larger than the heat capacity of the upper fixing film 171c. By reducing the heat capacity of the upper fixing film 171c, it is possible to perform a quick quick start in which the warming-up at the time of forming a single-sided image on the surface, which is frequently performed, is almost zero. In addition, by increasing the heat capacity of the lower fixing film 471d, reliable double-sided fixing is enabled. In any case, the heat capacity of the fixing films 171c and 471d is about 1/100 of that of a conventionally used fixing heat fixing roller, and a quick start with almost zero warm-up is possible.

Ceramic heater 17 as fixed heating element
For 2c and 472d, use is made of an alumina substrate having a thickness of 1 mm and a width of 2 to 8 mm, and preferably a width of 4 mm, on which a resistance heating layer and a 10 μm-thick overcoat glass as a surface protection layer are sequentially provided by thick film printing. Ceramic heater 172
The thermal resistance between the fixing films 171c and 471d is lower than that of the fixing films 471c and 472d. The surface protective layer functions to protect the resistance heating layer and to prevent the fixing films 171c and 471d from being worn.

Elastic rubbers 473d and 173d as elastic members
3c is formed of heat-resistant rubber such as silicon rubber,
It has a width of about 10 mm, acts as a soft member, and has a reliable nip T between upper and lower ceramic heaters 172c and 472d pressed by elastic rubbers 473d and 173c.
To form At least the fixing films 171c and 471
A smooth surface such as a fluorine coat is provided on the contact surface with d to facilitate rotation of the fixing films 171c and 471d.

The heater holders 174c and 474d are formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
The width is about 20 mm, and the upper and lower ceramic heaters 172 are provided.
c, 472d and upper and lower elastic rubbers 173c, 473d are arranged close to each other. At least fixing film 1
A smooth surface such as a fluorine coat is provided on the contact surface with the fixing films 71c and 471d to facilitate the rotation of the fixing films 171c and 471d.

The holder 475d is formed of, for example, a heat-resistant resin using a liquid crystal polyester resin.
1d, and a smooth surface such as a fluorine coat is provided on at least the contact surface with the fixing film 471d.
The rotation of 1d is facilitated.

The upper and lower fixing films 171c, 171c,
471d has a configuration similar to that described above with reference to FIG. 5, and includes a base material 171A, a conductive layer 171B, and a release layer 171C, and has the same materials, structures, characteristics, effects, and the like as described above.

The fixing of the toner image on the recording paper P by the fixing device 17E using the upper heat-fixing film 17c and the lower heat-fixing film 47d will be described with reference to FIG. In FIG. 7, the same control as described with reference to FIG. 8 is performed when forming a single-sided image on the back surface.

According to the above configuration, there is provided an image forming apparatus provided with a fixing means capable of performing wide-area fixing with a wide nip width in a fixing area, high fixing performance, a low heat capacity, and a substantially zero warm-up time. You. In addition, different energy consumptions are performed when forming a single-sided image only on the front surface, when forming a single-sided image only on the back surface, and when forming a double-sided image, and compared with a conventional fixing unit using a heating element for upper and lower rollers. During formation, both sides consume proper energy during both-sided image formation, which requires less energy consumption, provides a wide nip width in the fixing area, high fixing performance, and has a low heat capacity and almost no warm-up time. An image forming apparatus capable of performing both-side fixing is provided.

FIGS. 14 and 15 show the structure of the upper and lower film-shaped rotating members at the transfer material separating portion of the film member.
This will be described with reference to FIG. FIG. 14 is a view for explaining the angle formed by the upper and lower film members in the separation section of the fixing means.
FIG. 4 is a diagram illustrating a positional relationship between upper and lower film members in a separation unit of a fixing unit. As the film members of the upper and lower film-shaped rotating members, the fixing film 171a used for the upper heat fixing film 17a and the fixing film 171a used for the lower heat fixing film 17b described in FIG. 5 are used as representative examples. Will be explained.

According to FIG. 14, an extension plane PL2 (hereinafter referred to as extension plane PL2) of the nip portion T and an upper fixing film 171a at an exit portion (separation portion) of the nip portion T of the recording paper P of the fixing means. (Opening angle) α and the extension plane P
The relationship between L2 and the angle (opening angle) β formed by the lower fixing film 171b is such that when the recording paper P is separated at the separation section, the recording paper P is adsorbed to the smaller opening angle. 14 (a), the opening angle β is made larger than the opening angle α as shown in FIG. 14 (a).
It is preferable to make the opening angle α larger than the opening angle β, as shown in FIG. FIG.
If the opening angle α and the opening angle β are substantially the same as shown in (b), the leading end of the recording paper P is
a and the lower fixing film 171b,
Since the separation is performed in a non-stick state, good separation is not performed, which is not preferable.

According to FIG. 15, the upper and lower film members at the exit (separation portion) of the nip portion T of the recording paper P of the fixing means are connected to the lower fixing film 171b as shown in FIG. Of the upper fixing film 171a is shifted from the end of the upper fixing film 171a in the discharge direction of the recording paper P, and the recording paper P is shifted to the lower fixing film 171b.
It is preferable that the upper fixing film 171a is separated before the upper fixing film 171a in a state where it is adsorbed because good separation is performed. Similarly, as shown in FIG. The lower fixing film 171b is shifted from the end of the lower fixing film 171b so as to be located on the downstream side in the discharge direction of the recording paper P, and the recording paper P is adsorbed on the upper fixing film 171a. Separation first is preferable because good separation is performed. As shown in FIG. 15B, the upper fixing film 17
1a and the end of the lower fixing film 171b are disposed at substantially the same position, the leading end of the recording paper P is attached to both the upper fixing film 171a and the lower fixing film 171b. Since it is adsorbed and separated in a non-stick state, good separation is not performed, which is not so preferable.

The structure of the upper and lower film-shaped rotating members at the portion where the transfer material enters the transfer material and the formation of a loop of the transfer material will be described with reference to FIGS. FIG.
FIG. 17 is a view for explaining a positional relationship between upper and lower film members in a separation portion of a fixing unit. FIG. 17 is a view showing a loop formation of a transfer material according to FIG. 16, and FIG. It is a figure showing other examples of. As the film members of the upper and lower film-shaped rotating members, the fixing film 171a used for the upper heat fixing film 17a and the fixing film 17 used for the lower heat fixing film 17b described with reference to FIG.
1a will be described as a representative example.

According to FIG. 16, the upper and lower film members at the entrance (entrance) of the nip portion T of the recording paper P of the fixing means are connected to the lower fixing film 1 as shown in FIG.
The end of the upper fixing film 171a is shifted from the end of the upper fixing film 171a so as to be located on the upstream side in the entering direction of the recording paper P, and the recording paper P slides on the lower fixing film 171b. It is preferable to enter the nip portion T with the fixing film 171a because good addition without wrinkles is performed. As shown in FIG. 16C, the end of the upper fixing film 171a is
When the recording paper P enters the upper fixing film 171a or the lower fixing film 171b so as to be abutted with the recording paper P, the recording is performed. In a state where the paper P is added to the nip portion T, a loop of the recording paper P described later with reference to FIG. 17 is not formed, and the toner image on the back surface of the recording paper P is disturbed by the entrance guide plate 169 and the spur 162. Not preferred. FIG.
As shown in (b), when the end of the upper fixing film 171a and the end of the lower fixing film 171b are disposed at substantially the same position, the leading end of the recording paper P is moved to the upper fixing film 171a. And the fixing film 171b on the lower side are not entered, so that it is not preferable that good addition is not performed.

According to FIG. 17, the upper and lower film members at the entrance (entrance) of the nip portion T of the recording paper P of the fixing means are, as described with reference to FIG. The end of the upper fixing film 171a
Of the recording paper P is preferably shifted upstream from the end of the recording paper P in the direction of entry of the recording paper P, and the nip portion with the upper fixing film 171a in a state where the recording paper P slides on the lower fixing film 171b. T enters the recording paper P
Is applied to the nip portion T, a force for lifting the recording paper P in the upward direction of the recording paper P in the nip portion T on the entry side acts, and as shown by the thick dotted line, the spur 162 and the entrance guide plate 169 The recording paper P has a convex loop formed on the front side (upper side in this embodiment) so as to be separated from the recording paper P, and is conveyed in a state where the back surface of the recording paper P is separated from the spur 162 or pressed slightly. It is preferable that the back side toner image of the paper P is not disturbed by the spur 162. Thus, the recording paper P
When the recording paper P is added to the nip portion T, a loop is formed, and the recording paper P is conveyed in many cases apart from the spur 162 even if the recording paper P is occasionally lightly contacted except for the front and rear ends of the recording paper P.

Further, as shown in FIG. 18, the upper and lower film members at the entrance (entrance) of the nip portion T of the recording paper P of the fixing means are fixed to the upper fixing film 171a on the side for fixing the toner image on the front side. Is a hard member, a lower fixing film 171b on the side on which the toner image on the back side is fixed is formed as a soft member, and a nip portion T having a convex surface on the back side is formed. The recording paper P is caused to enter the nip portion T so that the leading end of the recording paper P comes into contact with the upper fixing film 171a surface made of a hard member. In a state where the recording paper P is applied to the nip portion T formed as a convex on the back surface side, a force for lifting the recording paper P in the upper direction of the nip portion T on the entry side of the recording paper P acts, and the thick dotted line represents As shown, the recording paper P is formed with a convex loop on the front side (upper side in the present embodiment) so as to be further away from the spur 162 and the approach guide plate 169,
It is more preferable that the back side of the recording sheet P is conveyed in a state where the back side is separated from the spur 162 or is slightly pressed, and the back side toner image of the recording sheet P is not disturbed by the spur 162. In this manner, when the recording paper P is applied to the nip portion T, a larger loop is formed. Even if the recording paper P occasionally makes light contact except for the front and rear ends of the recording paper P, most of the recording paper P is separated from the spur 162 and the recording paper P is separated. Conveyed.

FIG. 20 shows a modification of the image forming apparatus described with reference to FIG.

In this example, four image forming bodies are arranged in parallel,
This is an example of color image formation by a tandem color image forming apparatus in which Y, M, C, and K toner images are formed and sequentially transferred.

According to FIG. 20, the photosensitive drum 10 (image forming body), scorotron charger 11 (charging means), exposure optical system 12 (image writing means), developing device 13 (developing means), and cleaning device 19 (Image forming body cleaning means)
Y, M, C and K toner image forming units 20
0, Y, M, C and K toner image forming units 2
00 is sequentially transferred (primary transfer) by a transfer unit 14c as a first transfer unit to form a superimposed color toner image serving as a back surface image on an intermediate transfer belt 14a as an intermediate transfer body. After that, the transfer belt 14a
The recording paper P, which is a transfer material, is supplied thereon, and the Y, M, C, and K toner image forming units 200 sequentially form toner images that become the front surface images again in synchronization with the recording paper P and the back surface image. After the image is sequentially transferred (secondarily transferred) to the surface of the recording paper P by a transfer device 14c as a second transfer device, the back toner image on the intermediate transfer belt 14a is transferred by a back transfer device 14g as a third transfer device. Transfer to the back side of recording paper P (3
Next transfer), a front and back color toner image is formed on the recording paper P to obtain a double-sided image.

The recording paper P on which the color toner images are formed on both sides is formed by the curvature of the curvature portion KT of the intermediate transfer belt 14a and the paper as transfer material separating means provided at the end of the intermediate transfer belt 14a as necessary. The charge removing operation by the separation AC charge remover 14h and the separation claw 210, which is a separation member provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a.
As a result, the spur member 162, which is a spur member provided in the conveyance section 160, is separated from the intermediate transfer belt 14a, and is stably fixed by the transfer material conveyance surface (the curvature portion KT of the intermediate transfer belt 14a and the fixing guide 169). Surface P connecting transfer material entrance to nip T of device 17 (entrance)
L1 is conveyed to a fixing device 17 as a fixing unit, and heat is transferred to a nip portion T between a heat fixing film 17a as an upper film-shaped rotating member and a heat fixing film 17b as a lower film-shaped rotating member. After the toner images on the front and back sides of the recording paper P are fixed by applying pressure and pressure, the recording paper P is discharged outside the apparatus.

As the fixing means, a fixing device 17 having the same structure, function and performance as that described with reference to FIG. 5 is used. The temperature of the fixing device 17 is controlled at the time of formation, at the time of forming a single-sided image of only the front surface, or at the time of forming a single-sided image of only the back surface. Further, also in the image forming apparatus of this example, a fixing unit having the same structure, function, and performance as described with reference to FIGS. 9 to 13 is used. Further, the preferable shape and arrangement of the separation portion of the nip portion T of the film member of the film-shaped rotating member above and below each fixing unit in the image forming apparatus of the present example are the same as those described with reference to FIGS. The preferred arrangement of the upper and lower film-shaped rotating members in the entry portion of the nip portion T of the film member is the same as that described with reference to FIG. 16, and the same loop formation as that described with reference to FIGS. Is taken.

Another example of the image forming apparatus will be described with reference to FIG. FIG. 19 is a schematic explanatory view of a color image forming apparatus showing another example of the image forming apparatus according to the present invention.
Although the image forming apparatus of this embodiment is also described with a color image forming apparatus, the present invention is not necessarily limited to this, and is also applicable to a monochrome double-sided image forming apparatus by a process similar to that of this embodiment. is there. Further, as described above with reference to FIGS. 3 and 4, in addition to the double-sided image formation in which images are formed on both surfaces of the transfer material, a single-sided image formation in which an image is formed only on one side of the front surface or the back surface of the transfer material is also performed. You.

In the image forming apparatus described above with reference to FIG. 1, first, four sets of yellow (Y), magenta (M), cyan (C) and black (K) are developed on the photosensitive drum 10 (image forming body). A toner image forming means, which is a second toner image, is formed by a toner image forming means including a device 13 (developing means), a scorotron charger 11 (charging means), and an exposure optical system 12 (image writing means). And temporarily transfer the intermediate transfer belt 14a
(Intermediate transfer member), and subsequently, a toner image serving as a surface image as a first toner image is formed on the same photosensitive drum 10, and the toner image on the photosensitive drum 10 is recorded on a recording paper P. The two-sided image is obtained by transferring the toner image on the intermediate transfer belt 14a to the front surface of the (transfer material) onto the back surface of the recording paper P, respectively. In the image forming apparatus of this embodiment, as shown in FIG. A photosensitive drum 10b serving as a second image forming member for forming a toner image serving as a back image (back toner image) serving as a second toner image, and a toner image serving as a front image serving as a first toner image ( A photosensitive drum 10a, which is a first image forming member for forming a front toner image), is separately provided, and the back toner image formed on the photosensitive drum 10b has a polarity opposite to that of the toner (positive polarity in the present embodiment). ) Voltage is applied A transfer means primary transfer device 11
After the transfer (primary transfer) onto the intermediate transfer belt 114a as an intermediate transfer member by 4b, the recording paper P as a transfer material is supplied onto the intermediate transfer belt 114a between the photosensitive drums 10b and 10a. And the intermediate transfer belt 114a
The recording paper P is attracted to and conveyed to the intermediate transfer belt 114a by the charging of the paper charger 150 provided opposite the grounding roller 14k, which is grounded across the surface, and the surface toner image formed on the photosensitive drum 10a Is transferred (secondary transfer) to the surface of the recording paper P by a secondary transfer unit 114c, which is a second transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. The back side toner image on the transfer belt 114a is transferred to a recording paper P by a tertiary transfer unit 114g which is a third transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied.
(Tertiary transfer) on the back surface of the recording paper P to form a front and back toner image on the recording paper P to obtain a double-sided image.

The recording paper P on which toner images are formed on both sides is
The curvature of the curvature portion KT of the intermediate transfer belt 114a, the charge removal operation by the paper separation AC charge remover 14h as a transfer material separating means provided as necessary at the end of the intermediate transfer belt 114a, and the intermediate transfer belt 114a and a predetermined Separating claw 210 which is a separating member provided on the transporting unit 160 at intervals.
As a result, the spur 162, which is a spur member provided on the conveyance section 160, is separated from the intermediate transfer belt 114a, and further stably fixed by the transfer material conveyance surface (the curvature portion KT of the intermediate transfer belt 14a and the fixing portion KT). The transfer material is conveyed to a fixing device 17 as a fixing means through a surface (a surface connecting an entrance portion (entry portion) of the transfer material to a nip portion T of the device 17) PL1 and a heat fixing film 17a which is an upper film-shaped rotating member. Heat and pressure are applied in a nip portion T between the heat-fixing film 17b, which is a lower film-shaped rotating member, so that the front and back toner images on the recording paper P are fixed and then discharged outside the machine. You.

As the fixing means, a fixing device 17 having the same structure, function and performance as that described with reference to FIG. 5 is used. The temperature of the fixing device 17 is controlled at the time of formation, at the time of forming a single-sided image of only the front surface, or at the time of forming a single-sided image of only the back surface. Further, also in the image forming apparatus of this example, a fixing unit having the same structure, function, and performance as described with reference to FIGS. 9 to 13 is used. Further, the preferable shape and arrangement of the separation portion of the nip portion T of the film member of the film-shaped rotating member above and below each fixing unit in the image forming apparatus of the present example are the same as those described with reference to FIGS. The preferred arrangement of the upper and lower film-shaped rotating members in the entry portion of the nip portion T of the film member is the same as that described with reference to FIG. 16, and the same loop formation as that described with reference to FIGS. Is taken.

The photosensitive drums 10a and 10b and the intermediate transfer belt 114a in the image forming apparatus of this embodiment have the same function and structure as those of the photosensitive drum 10 and the intermediate transfer belt 14a described in the image forming apparatus. Is used. The intermediate transfer belt 114a is stretched in contact with a driving roller 14d, a ground roller 14j, a facing ground roller 14k, a driven roller 14e, and a tension roller 14i, which are roller members. Each of the charge eliminators 114m and 114n, which is a charge eliminator, is preferably constituted by a corona discharger, and the primary transfer device 114b and the secondary transfer device 114 are arranged in the moving direction of the intermediate transfer belt 114a.
c, the primary transfer unit 114b and the secondary transfer unit 114c
Is applied in parallel, and an AC voltage on which a DC voltage having the same polarity or opposite polarity to the toner is superimposed is applied.
4b and the charge of the intermediate transfer belt 114a charged by the voltage application of the secondary transfer device 114c is removed.

Toner image forming means (second toner image forming means) for forming a toner image serving as a back image serving as a second toner image on a photosensitive drum 10b serving as a second image forming body, and a first toner The toner image forming means (first toner image forming means) for forming a toner image as a surface image as an image on a photosensitive drum 10a as a first image forming body is used in the above-described image forming apparatus. Yellow (Y), similar to
Magenta (M), cyan (C) and black (K) four sets of developing units 13 (developing means), scorotron charger 11
(Charging unit) and the exposure optical system 12 (image writing unit) are used for each of the photosensitive drums 10a and 10b, and a toner image of a front surface image and a toner image of a back surface image are formed.

Therefore, similarly to the above-described effects of the image forming apparatus, different energy consumptions are performed during the single-sided image formation and the double-sided image formation, respectively. In comparison, proper energy consumption is performed during single-sided image formation and double-sided image formation, respectively, energy consumption is reduced for both sides, low heat capacity, almost zero warm-up time is possible for both-side fixing, and toner on the front and back Stable and good fixing is performed without causing a shift in the image. Similarly, the separation of the transfer material from the film member by the fixing means is performed well, and the transfer material enters the film-shaped rotating member by the fixing means reliably. Is prevented.

FIG. 21 shows a modification of the image forming apparatus described with reference to FIG.

In this example, eight image forming bodies are arranged in parallel,
This is an example of color image formation by a tandem color image forming apparatus in which Y, M, C, and K toner images are formed and sequentially transferred.

According to FIG. 21, the photosensitive drum 10b (first image forming body), scorotron charger 11 (charging means), exposure optical system 12 (image writing means), developing device 13
(Developing means) and a Y, M, C, and K first toner image forming unit 200b including a cleaning device 19 (image forming body cleaning means), a photosensitive drum 10a (second image forming body), and scorotron charging. Unit 11 (charging unit), exposure optical system 12 (image writing unit), developing unit 13
(Developing means) and a Y, M, C and K second toner image forming unit 200a comprising a cleaning device 19 (image forming body cleaning means).
The first toner image forming unit 200b sequentially forms a toner image to be a back image, and sequentially transfers the primary toner image onto an intermediate transfer belt 114a as an intermediate transfer member by a primary transfer device 114b as a first transfer means (primary transfer device). (Transfer) to form a superimposed color toner image serving as a back side image, and then a transfer material on the intermediate transfer belt 114a between the first toner image forming unit 200b group and the second toner image forming unit 200a group. A certain recording paper P is supplied, and the Y, M, C, and K second toner image forming units 200a sequentially form toner images of the front surface image in synchronization with the recording paper P and the rear surface image, thereby forming the front surface of the recording paper P. A secondary transfer unit 11 serving as a second transfer unit;
4c sequentially (secondary transfer), and the intermediate transfer belt 1
The color toner image of the back side image on 14a is transferred (tertiary transfer) to the back side of the recording sheet P by a tertiary transfer unit 114g as a third transfer unit, and is transferred onto the recording sheet P conveyed by the intermediate transfer belt 114a. This is to form a front and back color toner image to obtain a double-sided image.

The recording paper P on which the color toner images are formed on both sides has the curvature of the curvature portion KT of the intermediate transfer belt 114a,
An electricity removing operation by a paper separation AC electricity remover 14h as a transfer material separating means provided as necessary at an end of the intermediate transfer belt 114a, and a separating member provided in the transport unit 160 at a predetermined interval from the intermediate transfer belt 114a. Is separated from the intermediate transfer belt 114 a by the separation claw 210, and the spur 16 which is a spur member provided in the conveyance unit 160.
2. Further, the transfer material transport surface (the surface connecting the curvature portion KT of the intermediate transfer belt 14a and the entrance portion (entry portion) of the transfer material to the nip portion T of the fixing device 17) PL1 stably by the entry guide plate 169 and the like. Fixing device 1 as fixing means through above
The recording is performed by applying heat and pressure at a nip portion T between a heat fixing film 17a as an upper film-shaped rotating member and a heat fixing film 17b as a lower film-shaped rotating member. After the front and back toner images on the paper P are fixed, the paper P is discharged outside the apparatus.

As the fixing means, a fixing device 17 having the same structure, function and performance as that described with reference to FIG. 5 is used. The temperature of the fixing device 17 is controlled at the time of formation, at the time of forming a single-sided image of only the front surface, or at the time of forming a single-sided image of only the back surface. Further, also in the image forming apparatus of this example, a fixing unit having the same structure, function, and performance as described with reference to FIGS. 9 to 13 is used. Further, the preferable shape and arrangement of the separation portion of the nip portion T of the film member of the film-shaped rotating member above and below each fixing unit in the image forming apparatus of the present example are the same as those described with reference to FIGS. The preferred arrangement of the upper and lower film-shaped rotating members in the entry portion of the nip portion T of the film member is the same as that described with reference to FIG. 16, and the same loop formation as that described with reference to FIGS. Is taken.

[0202]

According to the first to fourth aspects of the present invention, different energy consumptions are performed during single-sided image formation and double-sided image formation, respectively. During image formation, proper energy consumption is performed at the time of both-side image formation, energy consumption is low for both, both-side fixing with low heat capacity and almost zero warm-up time is possible, and the toner image on the front and back is shifted , And good fixing is stably performed.

According to the fifth or sixth aspect, the separation of the transfer material from the film member by the fixing means is performed favorably.

According to the seventh or eighth aspect, the transfer material can reliably enter the film-shaped rotary member by the fixing means, and the rear surface toner image is prevented from being disturbed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus.

FIG. 2 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 1;

FIG. 3 is a diagram illustrating an example of a document image reading unit.

FIG. 4 is a block diagram of a control circuit of the image forming apparatus.

FIG. 5 is an enlarged view of a first configuration of a fixing unit on which a toner image on a front surface side is fixed first, and a diagram illustrating conveyance of a transfer material to the fixing unit.

FIG. 6 is a temperature control timing chart during double-sided image formation.

FIG. 7 is a temperature control timing chart when forming a single-sided image on the front side.

FIG. 8 is a temperature control timing chart when forming a single-sided image on the back surface.

FIG. 9 is an enlarged view of a second configuration of the fixing unit to which the toner image on the front surface is fixed first, and a diagram illustrating conveyance of the transfer material to the fixing unit.

FIG. 10 is an enlarged view of a third configuration of a fixing unit to which a toner image on a front surface is fixed first, and a diagram illustrating conveyance of a transfer material to the fixing unit.

FIG. 11 is an enlarged view of a first configuration of a fixing unit to which a toner image on a back side is fixed first, and a diagram illustrating conveyance of a transfer material to the fixing unit.

FIG. 12 is an enlarged view of a second configuration of the fixing unit on which the toner image on the back side is fixed first, and a diagram illustrating conveyance of the transfer material to the fixing unit.

FIG. 13 is an enlarged view of a third configuration of the fixing unit on which the toner image on the back side is fixed first, and a diagram illustrating conveyance of a transfer material to the fixing unit.

FIG. 14 is a diagram illustrating angles formed by upper and lower film members in a separation unit of a fixing unit.

FIG. 15 is a diagram illustrating a positional relationship between upper and lower film members in a separation unit of a fixing unit.

FIG. 16 is a diagram illustrating a positional relationship between upper and lower film members in a separation unit of a fixing unit.

FIG. 17 is a diagram showing a loop formation of the transfer material according to FIG. 16;

FIG. 18 is a diagram illustrating another example of forming a loop of a transfer material.

FIG. 19 is a schematic explanatory view of a color image forming apparatus showing another example of the image forming apparatus according to the present invention.

FIG. 20 is a diagram illustrating a modification of the image forming apparatus described with reference to FIG.

FIG. 21 is a diagram illustrating a modification of the image forming apparatus described with reference to FIG.

[Explanation of symbols]

10, 10a, 10b Photoreceptor drum 11 Scorotron charger 12 Exposure optical system 13 Developing device 14a, 114a Intermediate transfer belt 14c Transfer device 14g Back transfer device 17, 17A, 17B, 17C, 17D, 17E Fixing devices 17a, 17b, 17c , 17d, 47a, 47b, 4
7c, 47d Thermal fixing film 114b Primary transfer unit 114c Secondary transfer unit 114g Tertiary transfer unit 171a, 171b, 171c, 171d, 471a,
471b, 471c, 471d Fixing film 172a, 172b, 172c, 172d, 472a,
472b, 472c, 472d Ceramic heaters 173a, 173b, 173c, 173d, 473a,
473b, 473c, 473d Elastic rubber 174a, 174b, 174c, 174d, 474a,
474b, 474c, 474d Heater holder 475a, 475b, 475c, 475d Holder 176a, 176b, 176c, 176d Film drive roller P Recording paper PL1 Transfer material transport surface PL2 Extension surface T Nip portion

Claims (8)

[Claims] 1. An image forming body, means for forming a toner image on the image forming body, a toner image on the image forming body is transferred, and the transferred toner image is carried on the surface and transferred. An endless belt-shaped intermediate transfer member that conveys a material, a first transfer unit that transfers the toner image on the image forming member to the intermediate transfer member, and a surface of the transfer material that transfers the toner image on the image forming member. Second transfer means for transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and fixing means arranged opposite to each other with a film-shaped rotating member as a pair. And an image forming apparatus for fixing unfixed toner images on the front and back surfaces of the transfer material, wherein a heater holder is provided inside each of the film members provided on the film-shaped rotating member arranged in pairs, and the heater is provided. Folder to provided respectively to parallel the fixed heating element and the elastic member is inscribed in the film member, the image forming apparatus characterized by disposing the fixed heating element and said the elastic member are opposed to each other. 2. A first image forming body, a second image forming body, a first toner image forming means for forming a toner image on the first image forming body, and the second image forming. A second toner image forming means for forming a toner image on a body, a toner image on the second image forming body being transferred, carrying the transferred toner image on the surface, and conveying a transfer material An endless belt-shaped intermediate transfer member, first transfer means for transferring the toner image on the second image forming member to the intermediate transfer member, and a transfer material for transferring the toner image on the first image forming member. A second transfer unit for transferring the toner image on the intermediate transfer body to the back surface of the transfer material; and a film-shaped rotating member as a pair and arranged to face each other. Image forming apparatus for fixing an unfixed toner image on the front and back surfaces of a transfer material by a fixing unit In the above, a heater holder is provided inside each of the film members provided on the film-shaped rotating member arranged in a pair, and a fixed heating element and an elastic member inscribed in the film member are arranged in parallel with the heater holder. An image forming apparatus, wherein the fixed heating element and the elastic member are arranged to face each other. 3. The image forming apparatus according to claim 1, wherein a film driving roller for rotating the film member is disposed inside one of the film members, and the other film member is driven to rotate. apparatus. 4. The heat capacity of the film member provided on the film-shaped rotating member on the side for fixing the back surface toner image of the transfer material is equal to the heat capacity of the film member provided on the film-shaped rotating member on the side fixing the surface toner image on the transfer material. The image forming apparatus according to claim 1, wherein the heat capacity is larger than a heat capacity. 5. An angle formed between an extension surface of a nip portion of one side of the film-shaped rotating member and a separation portion of the transfer material of the film-shaped rotating member arranged in a pair is increased. The method according to any one of claims 1 to 4, wherein
Item 10. The image forming apparatus according to item 1. 6. The transfer material separating portion of the film-shaped rotating member arranged in a pair, wherein the transfer material is separated from the film member on one side of the film-shaped rotating member first. The image forming apparatus according to claim 1. 7. An end portion of the film member on the front surface side of the film-shaped rotating member on which the toner image is fixed, at the entrance of the transfer material of the film-shaped rotating member arranged in the pair, The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged so as to be shifted downstream of an end of the film member on which the toner image is fixed, in a direction in which the transfer material enters. 8. A film member for fixing a toner image on a front surface side of the film-shaped rotating member at a portion where the transfer material of the film-shaped rotating member enters a transfer material, and a toner member on a back surface side. The film member on the side on which the image is fixed is a soft member, and a nip portion is formed as a convex on the back side, so that the leading end of the transfer material abuts on the film member surface of the hard member at the entrance to the nip portion. 8. The printing medium according to claim 1, wherein
The image forming apparatus according to claim 1.