JPH1115287A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner soil on a transfer material, which is caused by soiled spurs, by carrying a fixing means with the transfer material separated from the spurs. SOLUTION: When one end of recording paper P as the transfer material is held in the circular-arc-shaped nip T of a fixing device 17, force is exerted for lifting the recording paper P in the direction of a tangent of a fixing roller 17a at a point P1 on the side where the recording paper P enters the nip T, with the back of the recording paper P separated from the spurs 162 the recording paper P is carried over a carrying part 160, and fixing on the recording paper P is carried out by the fixing device 17. In the case, it is preferable that a plane extended from the transfer-material carrying face PL1 of a toner- image receiving body 14a abut on the vicinity of the nip T of the fixing roller 17a as the upper roller-member of the fixing device 17, for example the part of it which is 1-3 mm higher than the nip T from the point P1 on the entrance side for the recording paper P. Thus, the recording paper P is caused to enter the nip T smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine in which a charging means, an image exposing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. More particularly, the present invention relates to an electrophotographic image forming apparatus such as a printer, a facsimile, and the like, and more particularly, to a method of conveying a transfer material to a transfer unit.

[0002]

2. Description of the Related Art Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a two-sided reversing paper feeder, and the image bearing is again performed. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeder in synchronization with an image formed on the body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided copying apparatus, as described above, the transfer of the transfer material, such as feeding to the two-sided reversing paper feeder and passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low. And so on. In contrast, JP-B-49-37538 and JP-B-54-28740.
And JP-A-1-44457 and JP-A-4-21
Japanese Patent Application Laid-Open No. 4576/1994 proposes a method in which a toner image is formed on both surfaces of a transfer material and then fixed once.
JP-A-44457 and JP-A-4-214576 disclose that a plurality of sets of image forming means including an image carrier, a charging means, an image exposing means, a developing means and the like are arranged in parallel on a toner image receiving body. Has been proposed.

[0004]

On the other hand, the inventors of the present invention have proposed a method in which a toner image formed on an image carrier (first image carrier) is temporarily transferred to a belt-shaped toner image receiver (second image carrier). ), And a toner image is formed again on the image carrier, and the toner image on the toner image receiver and the toner image formed on the image carrier again are recorded on both sides of a recording paper (transfer material). The transfer of the transfer material separated from the belt-shaped toner image receiver is not uniform, but is transferred unevenly depending on the type of transfer material. There is a problem that the toner image is disturbed, and the transfer material is wrinkled when the transfer material is nipped by the fixing unit, and good fixing is not performed.

For this reason, a transfer section having a spur is provided between the toner image receiving member and the fixing means to attempt to convey the transfer material to the fixing means. There is a problem that spur marks occur on the image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems and prevents generation of spur marks on a toner image on a transfer material.

When the transfer material is conveyed by spurs,
The toner on the transfer material adheres to the spur, causing the spur to become dirty, causing a problem that the transfer material conveyed by the spur becomes soiled with toner.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which solves the above problems and prevents transfer material from being soiled by spurs.

[0009]

An object of the present invention is to provide a first image carrying means for carrying a toner image formed by a toner image forming means, and a transfer of the toner image carried by the first image carrying means. A belt-shaped second image carrying means for carrying the transferred toner image on the surface, and a first image carrying means for transferring the toner image carried on the first image carrying means to the surface of the transfer material.
Transfer means, a second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material, and the transfer material sandwiched by a pair of fixing members which rotate. A fixing unit for conveying and fixing the toner images transferred to both surfaces of the transfer material. The fixing unit conveys the transfer material by the second image holding unit, and transfers the transfer material from the second image holding unit. In the image forming apparatus which is fixed by the fixing unit after the separation, in the image forming apparatus, between the second image bearing unit and the fixing unit, the transfer material is extended from an extension surface of the transfer material transport surface of the second image bearing unit. A transfer unit having a spur for transferring the transfer material is provided on the back side of the transfer unit, and the transfer material is sent to the fixing unit through the transfer unit. The transfer unit is provided at an end of the second image bearing unit on the fixing unit side. From the belt-shaped second image bearing means. When the material is separated and moved to the fixing unit along the spur of the transport unit, and when the leading end of the transfer material is clamped in a nip formed by the pair of fixing members of the fixing unit, According to a first aspect of the present invention, there is provided an image forming apparatus, wherein the transfer material is separated from the spur, and the transfer material is transported through the fixing unit in a state of being separated from the spur.

The above object is also achieved by a first image carrying means for carrying a toner image formed by a toner image forming means,
A belt-shaped second image carrying means for transferring the toner image carried on the first image carrying means and carrying the transferred toner image on the surface; and a belt-like second image carrying means carried on the first image carrying means. A first transfer unit for transferring a toner image to a front surface of a transfer material, and a second transfer unit for transferring the toner image carried by the second image carrying unit to a back surface of the transfer material. Transporting the transfer material by the second image bearing means,
An image forming apparatus for fixing a toner image transferred to both surfaces of the transfer material by a fixing unit after separating the transfer material from the second image holding unit, wherein the second image holding unit and the fixing unit In between, a transport unit is provided, which feeds the transfer material to the fixing unit through the transport unit, and a spur rotatable by the transfer material on the transport unit, and a spur that comes into contact with a tip end of the spur. This is achieved by an image forming apparatus including a cleaning member for cleaning (second invention).

[0011]

Embodiments of the present invention will be described below. The description in this section does not limit the technical scope of the claims and the meaning of the terms. The assertive description below shows the best mode, and limits the meaning of the terms and the technical scope of the present invention. It does not do. In the following description of the embodiment, in the transfer area, the surface of the transfer material on the side facing the first image bearing means is the front surface, and the surface on the other side of the transfer material, that is, the side on the side facing the second image bearing means. The surface of the transfer material is called the back surface, and the image transferred to the front surface of the transfer material is the front image,
The image transferred to the other 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 sectional view of a color image forming apparatus showing an embodiment of the image forming apparatus according to the present invention. FIG. 2 is a side sectional view of the first image bearing means of FIG. FIG. 3A is a diagram illustrating a state where toner images are formed on both surfaces of the image forming apparatus according to the present invention, and FIG.
FIG. 3B is a diagram in which the toner image formed on the first image bearing unit is transferred onto the second image bearing unit to form a back image, and FIG.
FIG. 3C is a diagram in which a front image is formed on the first image carrier in synchronization with a back image on the second image carrier, and FIG.
FIG. 4 is a diagram showing double-sided image formation on a transfer material.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as first image bearing means, 11 a scorotron charger as charging means for each color, 12 an exposure optical system as image writing means for each color, 13 Denotes a developing device which is a developing means for each color;
a is a toner image receiving body as a second image carrying means, 14c is a transfer unit as a first transfer unit, 14g is a back side transfer unit as a second transfer unit, and 150 is a paper charging unit as a transfer material charging unit. Reference numeral 14h denotes a paper separation AC static eliminator serving as a transfer material separating unit; 160, a transport unit; and 17, a fixing device as a fixing unit.

Photosensitive drum 10 as first image bearing means
Is formed by forming a photosensitive layer such as a transparent conductive layer, an a-Si layer, or an organic photosensitive layer (OPC) on the outer periphery of a cylindrical substrate formed of, for example, a transparent member made of optical glass or transparent acrylic resin. With the conductive layer grounded,
It is rotated clockwise as indicated by the arrow.

The photosensitive drum 10, as shown in FIG.
Flange members 10a and 1 at both ends for engaging and fixing it
A gear G integrated with the flange member 10b is rotatably supported by bearings B1 and B2 fitted into the drum body 30 and supported by a drum shaft 30 erected and fixed to the apparatus main body. The gear is driven in mesh with the gear to rotate at a constant speed in a predetermined direction. WA is a lead wire from a light emitting element (LED) of an image exposure unit described later.

In the present embodiment, a scorotron charger 11 as a charging unit for each color, an exposure optical system 12 as an image writing unit for each color, and a developing unit 13 as a developing unit for each color have one unit. Four sets are provided for image forming processes of each color of yellow (Y), magenta (M), cyan (C) and black (K), and are arranged in the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG. On the other hand, Y, M,
C and K are arranged in this order.

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. As shown in FIG. 2, each exposure optical system 12 has a line in which a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light arranged in the main scanning direction in parallel with the drum shaft 30 are arranged. An exposure unit composed of an exposure element 12a in the shape of a circle, a light-converging light transmitter (trade name: Selfoc lens array) 12b as an imaging element, and a lens holder 12c, 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. Exposure optical system 1 for each color
2 exposes the photosensitive layer of the photosensitive drum 10 from the rear surface in accordance with image data of each color read by a separate image reading device and stored in a memory to form an electrostatic latent image on the photosensitive drum 10. As the exposure element 12a, an element in which a plurality of light-emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array can be used. The emission wavelength of the image exposure light emitting element is usually in the range of 780 to 900 nm, which is highly transparent to the Y, M, and C toners. In this embodiment, the image exposure is performed from the back. Since it is a system, the wavelength may be shorter than 400 to 780 nm, which does not have sufficient transparency to the color toner.

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 rotation direction of the photosensitive drum 10, for example, 0.5 to 1 mm in thickness. A cylindrical developing sleeve 131 made of non-magnetic stainless steel or aluminum having an outer diameter of 15 to 25 mm, and a developing casing 138. Yellow (Y), magenta (M), cyan (C), It contains a black (K) one-component or two-component developer. Each of the developing devices 13 is provided with a predetermined gap, for example, 100 to 500 μm, from the photosensitive drum 10 by an abutting roller (not shown).
Is applied, and a non-contact reversal development is performed by applying a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 131, and a toner image is formed on the photosensitive drum 10. Form.

Toner image receiver 1 as second image bearing means
Reference numeral 4a denotes an endless belt having a volume resistivity of 10 ¹² to 10 ¹⁵ Ω · cm. For example, a conductive material is dispersed in engineering plastics such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy. 0.1-1.0mm thick
Is a seamless belt having a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is preferably formed on the outside of the semiconductive film substrate as a toner filming preventing layer. In addition to the above, as a base of the belt, a conductive material dispersed in silicon rubber or urethane rubber or the like is used in a thickness of 0.1 to 0.1.
A 1.0 mm semiconductive rubber belt can also be used. The toner image receiver 14a is stretched in contact with a driving roller 14d, a driven roller 14e, and a tension roller 14i, and is rotated in a counterclockwise direction indicated by an arrow in FIG. The driven roller 14 according to the rotation direction of the toner image receiver 14a
e, a drive roller 14d, and a tension roller 14i are provided in this order, the driven roller 14e and the drive roller 14d are fixedly rotated, and the tension roller 14i is movable during rotation by the elastic force of the toner image receiver 14a. The drive roller 14d is rotated by the drive of the drive motor, and the toner image receiver 14a is driven and rotated. The driven roller 14e and the tension roller 14i are driven and rotated by the rotation of the toner image receiver 14a. Belt slack of the rotating toner image receiving body 14a is caused by the tension roller 1
Tensioned by 4i.

A transfer device 14c, which is a first transfer means, is provided opposite to the photosensitive drum 10 with the toner image receiver 14a interposed therebetween.
The transfer area 14b is formed between the steps. 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 a transfer electric field is formed in the transfer area 14b, so that the toner image on the photosensitive drum 10 is transferred to the toner image receiving member. Transfer onto 14a or onto the surface of the transfer material.

A backside transfer unit 14g, which is a second transfer unit, is provided to face a conductive drive roller 14d that is grounded with a toner image receiver 14a interposed therebetween, and has a polarity opposite to that of the toner (positive in this embodiment). (Polarity) DC voltage is applied to transfer the toner image on the toner image receiver 14a to the back surface of the transfer material.

A paper charger 150 as a transfer material charging means is driven by a driven roller 14 grounded with a toner image receiving member 14a interposed therebetween.
The transfer member is provided so as to face the toner image receiving member 14a with the support shaft 152 as a rotation fulcrum, and the transfer material is charged and attracted to the toner image receiving member 14a.

Paper separation AC static eliminator 1 as transfer material separating means
4h, the toner image receiving member 14a is arranged on the fixing device 17 side end of the toner image receiving member 14a along with the back side transfer device 14g if necessary.
a, which is provided opposite to a conductive drive roller 14d which is grounded with an a.
The charge of the transfer material conveyed by is removed.

The transport section 160 is provided between the toner image receiver 14a and the fixing device 17, and a spur 162 is provided on the upper surface of the transport section 160. The spur 162 is used when the transfer material is separated from the toner image receiver 14a.
The transfer material that bends in the direction 4a and is conveyed is scooped, and the transfer material having a toner image on the back surface is conveyed to the fixing device 17 while preventing the rear surface toner image from being disturbed.

The fixing device 17 as a fixing means is composed of two roller-shaped fixing members, a fixing roller 17a having a heater inside both rollers and a pressure roller 17b.
By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner image on the transfer material is fixed.

Next, the image forming process will be described.

When the image recording starts, the photosensitive drum driving motor (not shown) is started to rotate the photosensitive drum 10 clockwise as shown by the arrow in FIG. 1 and at the same time, the photosensitive drum is charged by the charging action of the 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 by 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 to form a yellow (Y) toner image in accordance with the rotation of 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.

The superimposed color toner image, which is the back image formed on the photosensitive drum 10 as the first image carrying means by the above image forming process, is transferred in the transfer area 14b as the first transfer means. By the vessel 14c
The toner image is transferred onto the toner image receiving member 14a, which is a second image bearing member, at a time (FIG. 3A). At this time, uniform exposure is performed by the simultaneous transfer exposure device 12d provided inside the photosensitive 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 a photoconductive drum 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). The history of the photosensitive drum 10 in the previous image formation on the peripheral surface of the photosensitive drum 10 is eliminated by, for example, exposure by the uniform exposure device 12e before charging using a light emitting diode.

After the superimposed color toner image serving as the back side image is formed on the toner image receiver 14a as described above, the superimposed color toner image serving as the front side image is continuously formed in the same manner as in the above-described color image forming process. To form on the photosensitive drum 10 (FIG. 3B). At this time, the image data is changed so that the front surface image formed on the photosensitive drum 10 is a mirror image of the rear surface 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 to synchronize the color toner image of the front surface image carried on the photosensitive drum 10 with the color toner image of the rear surface image carried on the toner image receiver 14a. Transfer area 14
b. At this time, a brush-shaped paper charger 150 is applied to the recording paper P, and is applied with a DC voltage having the same polarity as the toner (minus polarity in the present embodiment).
As a result, the recording paper P is charged to the same polarity as the toner, is attracted to the toner image receiving body 14a, and is fed to the transfer area 14b. By charging the paper with the same polarity as the toner, the toner is prevented from being attracted to the toner image on the toner image receiving member 14a or the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed. Simultaneously with the passage of the recording paper P, the paper charger 150 is separated from the toner image receiving body 14a, and the contact is released.

The paper charger 150 is released from the toner image receiving body 14a immediately before or simultaneously with the passage of the rear end of the recording paper P, and is separated from the recording paper P. Also, the paper charger 150
The voltage is applied only when the recording paper P is being fed, and the voltage applied to the paper charger 150 is cut off simultaneously with the separation from the recording paper P.

As a transfer material charging means, a conductive roller, a semiconductive film member or a blade member capable of contacting and releasing contact with the toner image receiving member 14a and applying a DC voltage having the same polarity as the toner. Can also be used.

In the transfer area 14b, the first voltage to which a voltage having a polarity opposite to that of the toner (positive in this embodiment) is applied.
The surface image on the photosensitive drum 10 is collectively transferred onto the surface of the recording paper P by the transfer device 14c as a transfer means. At this time, the back surface image on the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. At the time of transfer by the transfer device 14c, the photosensitive drum 10 is opposed to the transfer area 14b so that good transfer is performed.
A uniform exposure may be performed by a simultaneous transfer exposure device 12d using, for example, a light emitting diode provided inside the device.

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 second 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 toner image receiving body 14a is collectively transferred to the back side of the recording paper P by the back side transfer unit 14g (FIG. 3C).

The recording paper P is used as a transfer material separating means provided to face the drive roller 14d at the end of the toner image receiver 14a, if necessary, with the curvature of the drive roller 14d for driving the toner image receiver 14a. Paper removal AC neutralizer 14h
Is electrostatically separated from the toner image receiving body 14a by the static elimination action of the transfer section 160 provided with a spur 162 to be described later.
Is conveyed to a fixing device 17 as fixing means. At this time, the paper separating AC static eliminator 14h to which the voltage is applied is connected to the grounded driving roller 1 so that good separation is performed.
4d.

The recording paper P on which the color toner images are formed on both sides is conveyed to a fixing device 17 as fixing means composed of two roller-shaped fixing members having heaters inside both rollers. A fixing roller 17a which is a fixing member disposed on the upper side for fixing the toner image of the front side image (image on the upper side) and a lower side for fixing the toner image of the rear side image (image on the lower side). By applying heat and pressure at a nip portion T formed by the pressure roller 17b, which is a fixing member to be fixed, the adhered toner images on the front and back sides of the recording paper P are fixed, and the recording paper P on which double-sided image recording has been performed. The recording paper P is conveyed through the fixing paper discharge roller 17e, the conveyance rollers 18a and 18b, and the paper discharge roller 18 while being inverted, and is discharged to the upper part of the apparatus with the toner image of the surface image as a lower surface.
Further, as shown by the dashed line in FIG. 1, a switching member (not shown) is provided at the outlet of the fixing device 17 at the rear of the fixing discharge roller 17e, and the toner image of the front image is straightly discharged to a tray outside the device with the upper surface being discharged. You may make it.

The toner remaining on the peripheral surface of the toner image receiver 14a after transfer is provided to face the driven roller 14e with the toner image receiver 14a interposed therebetween, and the toner image receiver is supported on a support shaft 142 as a rotation fulcrum. The toner image receiving member cleaning device 140 having a toner image receiving member cleaning blade 141 capable of making contact with and releasing contact with 14a is cleaned.

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 the residual toner is removed by the cleaning device 19. The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure device 12e, and the process proceeds to the next image formation cycle.

Since the superimposed color toner images are collectively transferred by using the above-described method, the color image on the toner image receiving member 14a is hardly discolored, the toner is scattered or rubbed, and the image deterioration is small. A double-sided color image is formed.

A transport unit having a spur according to the present invention will be described with reference to FIGS. 4, 5 and 1. FIG. 4 is a diagram showing a transport unit, and FIG. 5 is a perspective view of a spur provided in the transport unit.

A conveying section 160 provided with a spur 162 below the transfer material conveying surface of the toner image receiving member 14a is disposed between the toner image receiving member 14a and the fixing device 17, and is provided between the toner image receiving member 14a and the fixing device 17. The separated recording paper P is transported to the transport unit 160.
Is conveyed to a fixing device 17 provided with a fixing roller 17a and a pressure roller 17b above and below.

Center shaft 1 provided integrally with spur 162
62a is inserted into the hole of the semicircular stop 163b on the opposite side of the guide surface 163a of the transport guide member 163, and the front end of the center shaft 162a is stopped by the E-ring E.
2 is rotatably attached to the transport guide member 163.
A plurality of conveyance guide members 163 to which spurs 162 are attached
Are attached to the transport section housing 161 to form the transport section 160.

Guide surface 163a of transport guide member 163
Is provided on the transfer material transport surface side of the rotation center of the spur 162. Accordingly, even when the leading end of the recording paper P separated from the toner image receiver 14a contacts the guide surface 163a, the recording paper P is scooped up by the guide surface 163a and sent to the spur 162, and the protrusion 162b of the spur 162 is attached to the recording paper P. The spur 162 is driven and rotated in a state of contact or piercing, and the recording paper P is conveyed to the fixing device 17 without rubbing the toner image.

The spur 162 has a thickness of 0.05 to 0.5 mm obtained by etching a metal plate such as a stainless steel plate or a copper plate.
With an outer diameter of 5 to 25 mm, a thickness of 0.5 to 2.0 mm,
A member made of a resin member having an outer diameter of 5 to 25 mm is used, and is made of a polygonal, for example, hexagonal, plate-shaped member provided with a sharp projection 162b at the tip.

The configuration of the rollers used for the fixing means and the method of transporting the transfer material by using the rollers will be described with reference to FIGS. FIG. 6 is a diagram illustrating a first example of a roller configuration used for a fixing unit, and FIG. 7 is a diagram illustrating a first example of a method of conveying a transfer material by the roller configuration of FIG. FIG. 8 is a diagram showing a second example of a method of transporting the transfer material by the roller configuration of FIG. 6, and FIG. 9 is a second example of a roller configuration used for the fixing unit and the transfer material transport using the same. FIG. 10 is a diagram illustrating a third example of the roller configuration used for the fixing unit and a transfer material conveying method using the third example.

According to FIGS. 6 and 7, the recording paper P is intermittently formed at the time of double-sided image formation requiring heat capacity at the time of fixing.
Is passed through the fixing device 17, and the recording paper P is continuously passed when the photosensitive drum 10 forms a single-sided surface image. In any case, the fixing roller 17 a for fixing the surface image has a thermal conductivity. As shown in FIG. 6, it is preferable that the fixing roller 17a as an upper roller member is made of, for example, steel or aluminum having a surface coated with Teflon, as shown in FIG. A hard roller using a metal roller member 171a such as a material is used, and a pressure roller 17b as a lower roller member is a metal pipe 17 using, for example, an aluminum material.
A soft roller having a rubber roller 172b made of, for example, a silicon material is formed on 2a, and the surface thereof is coated with, for example, Teflon. An arc-shaped nip portion T is formed by the pressure roller 17b using a soft roller by pressing both rollers. Halogen heaters 171c and 172c for fixing heat are provided inside each roller member.

As shown in FIG. 7, the recording paper P on which the color toner images are formed on both sides is rotated by the curvature of the drive roller 14d for driving the toner image receiver 14a and, if necessary, the end of the toner image receiver 14a. Paper removing AC neutralizer 14h as a transfer material separating means provided to face the drive roller 14d in the section
Is separated from the toner image receiver 14a.

The recording paper P separated from the toner image receiving member 14a as the second image bearing means is used as the toner image receiving member 14a.
Spur 162 provided below the transfer material transport surface PL1
And is fed to the nip portion T of the fixing device 17 as a fixing unit using upper and lower rollers having a configuration using a hard roller as the fixing roller 17a and a soft roller as the pressure roller 17b.

When the leading end of the recording paper P as the transfer material is sandwiched between the arc-shaped nip portions T of the fixing device 17, the nip portions T
The force that lifts the recording paper P in the tangential direction of the fixing roller 17a at the point P1 on the entry side of the recording paper P acts, and the back surface of the recording paper P is separated from the spur 162 as shown by the thick arrow in FIG. The recording paper P is transported above the transport unit 160 in a state where the recording paper P is separated from the spur 162, and the fixing of the recording paper P by the fixing device 17 is performed. At this time, the extension surface of the transfer material transport surface PL1 of the toner image receiver 14a is located near the nip portion T of the fixing roller 17a as a roller member on the upper side of the fixing device 17, for example, on the entry side of the recording paper P in the nip portion T. It is preferable to abut on a point 1 to 3 mm above the point P1. Thereby, the recording paper P smoothly enters the nip portion T.

As described above, when the surface image fixing roller is a hard roller, even if recording paper or OHT used as a transfer material collides with the surface image fixing roller, the surface image fixing roller is damaged. Nothing. Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion is increased, and satisfactory fixing is performed.

Further, as shown by a dashed line in FIG. 7, a plate-shaped entry guide member 1 is provided between the transport section 160 and the fixing device 17.
65 may be provided so that the leading end of the recording paper P is brought into contact with the fixing roller 17a as an upper roller member through the entry guide member 165. At this time, it is preferable that the leading end of the entrance guide member 165 be disposed below the point P1 of the nip portion T without causing the toner image of the back surface image of the recording paper P to be rubbed by the leading end of the entrance guide member 165.

As described above, the occurrence of spur marks on the toner image on the transfer material is prevented.

According to FIG. 8, in this embodiment, the conveying section 160 described with reference to FIG. 7 is arranged above the arrangement of FIG. 7, and the roller configuration of the fixing means is explained with reference to FIG. The same configuration as described above is used.

A recording paper P having a color toner image formed on both sides is driven by a driving roller 14 for driving a toner image receiver 14a.
The toner image receiving member is formed by the curvature of the toner image receiving member 14h as a transfer material separating means provided as a transfer material separating means provided at the end of the toner image receiving member 14a facing the driving roller 14d as necessary. 14a.

The recording paper P separated from the toner image receiving member 14a as the second image bearing means is used as the toner image receiving member 14a.
Spur 162 provided below the transfer material transport surface PL1
And is fed to an arc-shaped nip portion T of the fixing device 17 as a fixing unit using upper and lower rollers having a configuration using a hard roller as the fixing roller 17a and a soft roller as the pressure roller 17b.

When the leading end of the recording paper P as a transfer material is sandwiched between the arc-shaped nip portions T of the fixing device 17, the nip portions T
A force that lifts the recording paper P in the tangential direction of the fixing roller 17a at the point P1 on the entry side of the recording paper P acts, and the back surface of the recording paper P is separated from the spur 162 as shown by the thick arrow in FIG. The recording paper P is transported above the transport unit 160 in a state where the recording paper P is separated from the spur 162, and the fixing of the recording paper P by the fixing device 17 is performed.

The extension surface PL2 of the conveying surface of the recording paper P along the spur 162 enters the vicinity of the nip T of the fixing roller 17a as a roller member at the upper part of the fixing device 17, for example, the recording paper P at the nip T enters. 0.5-2.5m from side point P1
m so that it comes into contact with the upper part.
The recording paper P smoothly enters the nip portion T.

As described above, when the surface image fixing roller is a hard roller, even if recording paper or OHT used as a transfer material collides with the surface image fixing roller, the surface image fixing roller is damaged. Nothing. Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion is increased, and satisfactory fixing is performed.

As described above, the generation of spur marks on the toner image on the transfer material is prevented, and the transfer material is pulled when the transfer material is sandwiched by the fixing means. Image rubbing and transfer deviation in the second transfer unit are prevented.

According to FIG. 9, as the roller member of the fixing device 17 of this embodiment, a fixing roller 17c using a soft roller instead of the upper fixing roller 17a using a hard roller described in FIGS. 6 and 7 is used. Is used as the upper roller.

As the respective roller members of the fixing device 17, as the fixing roller 17c as an upper roller member, for example, a soft roller in which a metal pipe 173a using an aluminum material and a rubber roller 173b using a silicon material are used, for example, is used. Crimping roller 1 as lower roller member
Similarly to the upper roller member 7b, a soft roller having a metal pipe 172a made of, for example, aluminum and a rubber roller 172b made of, for example, silicon is used, and the surface thereof is coated with, for example, Teflon. Nip part T by upper and lower rollers using a soft roller by pressing both rollers
Is formed. Since the upper and lower rollers are composed of soft rollers, the nip portion T is provided in a straight line substantially perpendicular to a plane PL3 passing through the central axis of the fixing roller 17c and the central axis of the pressure roller 17b. Halogen heaters 173c and 172c for fixing heat are provided inside each roller member.

Since the nip portion T is formed in a straight line, the upper roller is inclined toward the discharge side of the recording paper P with respect to the transfer material transport surface PL1 of the toner image receiving member 14a as the second image carrying means. The surface PL3 is disposed on the fixing roller 17c.
And the pressure roller 17b are disposed obliquely, and the entrance of the nip portion T is disposed obliquely above the exit.

The recording paper P having the color toner images formed on both sides is driven by a driving roller 14 for driving the toner image receiving member 14a.
d, and the static electricity elimination action of the paper separating AC static eliminator 14h as a transfer material separating means provided at the end of the toner image receptor 14a opposite to the drive roller 14d, thereby causing the electrostatic charge from the toner image receptor 14a. Separated.

The recording paper P separated from the toner image receiving member 14a serving as the second image bearing means is placed on the toner image receiving member 14a.
Spur 162 provided below the transfer material transport surface PL1
And is fed to a nip portion T of a fixing device 17 as a fixing unit using upper and lower rollers configured using soft rollers as the fixing roller 17c and the pressure roller 17b.

When the leading end of the recording paper P as the transfer material is sandwiched between the nip portions T of the fixing device 17, the force for lifting the recording paper P in the extending direction of the linear nip portion T provided at an angle is provided. In operation, the back surface of the recording paper P is separated from the spur 162 as shown by the thick arrow in FIG.
It is transported above the transport unit 160 in a more separated state,
The fixing of the recording paper P by the fixing device 17 is performed. At this time, the extension surface of the transfer material transport surface PL1 of the toner image receiving member 14a is
It is preferable to abut on the vicinity of the nip T of 7c, for example, 1 to 3 mm above the point P1 on the entry side of the recording paper P in the nip T. Thereby, the recording paper P smoothly enters the nip portion T.

As described above, the generation of spur marks on the toner image on the transfer material is prevented, and the transfer material is pulled when the transfer material is nipped by the fixing means. Image rubbing and transfer deviation in the second transfer unit are prevented.

According to FIG. 10, the heat fixing film 17d acting as a hard roller described below is used instead of the upper fixing roller 17a described with reference to FIGS. 6 and 7 as the roller member of the fixing device 17 of this embodiment. Is used as the upper roller member.

The heat fixing film 17d as the upper roller member is composed of a thin film fixing film 174a having a thickness of, for example, 40 to 100 μm and a plate-like heating element (ceramic heater) 1.
74b and a heater holder 174c for holding the ceramic heater 174b. The seamless fixing film 174a includes an internal base material, an intermediate conductive layer, and a surface release layer. The pressure roller 17b serving as a lower roller member is, for example, a metal pipe 1 made of aluminum, as described with reference to FIG.
A rubber roller 172b using, for example, a silicon material is used for 72a.
Is used, and a halogen heater 172c for fixing heat is provided inside the roller member. Crimping roller 1 using a soft roller by pressing both rollers
7b forms an arc-shaped nip portion T.

The base material of the fixing film 174a withstands a high temperature, and is rotationally driven while sliding with the ceramic heater 174b at the high temperature. In order to maintain a high elastic modulus with little dimensional change even in such an environment, it is preferable to use a polyimide resin.
Carbon having a thickness of 5 to 15 μm is dispersed on the surface of a polyimide resin having a thickness of 0 μm, and the total thickness is 40 to 10 μm.
The thickness is preferably as thick as about 0 μm. 40 μm thickness
By increasing the thickness of the fixing film 174a, the strength and rigidity are increased, and the deviation of the fixing film 174a during rotation can be regulated at the end without buckling. On the other hand, if the thickness is more than 100 μm, 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. Further, in order to prevent offset, it is preferable to use a two-layer structure in which a release resin layer such as a fluororesin (PFA or PTFE) is provided, and further, the inner surface of the base material of the fixing film 174a and the surface of the ceramic heater 174b are further provided. A conductive layer is provided and grounded in order to eliminate the influence of the triboelectric charge generated by the sliding between and.

Further, a conductive filler is provided in the release layer to lower the resistance so as to release the charged charges separated 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 a resistance value of 2 × 10 ^{10 to} 5 × 10 ¹¹ Ω / cm ² is preferable.

A recording paper P having a color toner image formed on both sides is driven by a driving roller 14 for driving a toner image receiver 14a.
d, and the static electricity elimination action of the paper separating AC static eliminator 14h as a transfer material separating means provided at the end of the toner image receptor 14a opposite to the drive roller 14d, thereby causing the electrostatic charge from the toner image receptor 14a. Separated.

The recording paper P separated from the toner image receiving member 14a serving as the second image bearing means is placed on the toner image receiving member 14a.
Spur 162 provided below the transfer material transport surface PL1
And is fed to a nip portion T of a fixing device 17 as a fixing unit using upper and lower rollers having a configuration in which a soft roller is used as a heat fixing film 17d acting as a hard roller and a pressure roller 17b.

When the leading edge of the recording paper P as the transfer material is nipped by the arc-shaped nip T of the fixing device 17, the nip T
The force for lifting the recording paper P in the tangential direction of the heat fixing film 17d at the point P1 on the entry side of the recording paper P acts, and the back surface of the recording paper P is separated from the spur 162 as shown by the thick arrow in FIG. The recording paper P is conveyed above the conveyance section 160 in a state where the recording paper P is separated from the spur 162, and the fixing of the recording paper P by the fixing device 17 is performed. At this time, the toner image receiver 14
The extension surface of the transfer material transporting surface PL1 of FIG. 1A is located near the nip portion T of the heat fixing film 17d as a roller member at the upper portion of the fixing device 17, for example, from the point P1 of the nip portion T on the entry side of the recording paper P by 1 to It is preferable to contact the upper part of 3 mm. Thereby, the recording paper P smoothly enters the nip portion T.

As described above, when the surface image fixing roller is a hard roller, even if recording paper or OHT used as a transfer material collides with the surface image fixing roller, the surface image fixing roller is damaged. Nothing. Further, by using a soft roller as the back surface image fixing roller, the width of the nip portion is increased, and satisfactory fixing is performed.

As described above, the generation of spur marks on the toner image on the transfer material is prevented, and the transfer material is pulled when the transfer material is sandwiched by the fixing means. Image rubbing and transfer deviation in the second transfer unit are prevented.

FIG. 11 shows the spur cleaning member and its arrangement.
14 to FIG. 14, FIG. 4, FIG. 5, and FIG.
FIG. 11 is a diagram showing a first example of a method of attaching the cleaning member to the spur, FIG. 12 is a perspective view showing the cleaning member, and FIG. 13 is a second example of the method of attaching the cleaning member to the spur. FIG. 14 is a diagram illustrating an example, and FIG. 14 is a diagram illustrating a third example of a method of attaching the cleaning member to the spur.

As described with reference to FIGS. 4, 5 and 1, the transport section 160 having a spur 162 between the toner image receiving member 14a as the second image carrying means and the fixing device 17 as the fixing means. Is provided.

A recording paper P having a color toner image formed on both sides is driven by a driving roller 14 for driving a toner image receiving member 14a.
The toner image receiving member 14a is formed by the curvature of the toner image receiving member 14a as a transfer material separating means provided as a transfer material separating means provided at the end of the toner image receiving member 14a facing the driving roller 14d as necessary. Separated from

The recording paper P separated from the toner image receiving member 14a as the second image carrying means is conveyed by a spur 162 provided in the conveying section 160, and is fixed by a fixing roller 17c and a pressure roller 17b as a fixing means. Device 17
Is supplied to the nip portion T, and the toner images on both sides are fixed.

As shown in FIGS. 11 and 12, a central shaft 162 integrated with a spur 162 is
a is attached, and the spur 162 is
Can be rotated. The recording paper P on which the toner image is formed is conveyed on the spur 162, and the protrusion 162b of the spur 162 driven and rotated by the recording paper P is stained by the toner image of the back surface image, and the toner attached to the protrusion 162b. The recording paper P conveyed by the above causes image stains. For this reason, a cleaning member 210 for cleaning the toner attached to the protruding portion 162b is provided. Further, a guide surface 163a of the conveyance guide member 163 is provided on the side of the recording paper P that passes through the center of the spur 162 so that the leading end of the recording paper P after separation from the toner image receiver 14a described with reference to FIG. Have them pick up. This prevents the toner image from being rubbed due to the drooping of the leading end when the transfer material enters the transporting unit or the drooping of the rear end when the transfer material exits the transporting unit.

As shown in FIG. 12, the cleaning member 210 includes a cleaning brush 211 and a brush holder 212 for holding the cleaning brush 211. In FIG. 12, the cleaning brush 211 is provided at a position corresponding to the spur 162, but the brush portion may be provided continuously.

By using a brush member as a cleaning member, the rotation of the spur can be kept good and the spur can be cleaned well.

Further, as shown in FIG. 11, the cleaning brush 211 is attached to the protruding portion 162b with the downstream end in the rotational direction of the spur 162 on the side opposite to the recording paper P passing side as the tip of the cleaning brush 211.
The cleaning member 210 is disposed with the front end of the cleaning member 210 abutting.
By arranging the brush eyes of the cleaning brush 211 in parallel, the rotation of the spur 162 is not hindered, and the toner attached to the protrusion 162b is cleaned. A brush with an open eye is preferable for satisfactorily cleaning the adhered toner. Further, if the protrusion 162b comes into deep contact with the brush of the cleaning brush 211, the spur 162 will rotate poorly. Therefore, it is preferable that the spur 162 be shallow, for example, contact the brush with a tip of about 0.5 to 1.5 mm.

The cleaning member is provided without hindering the transfer of the transfer material.

As shown in FIG. 13, the cleaning member 2 is provided below the rotating portion of the spur 162 on the side opposite to the side on which the recording paper P passes.
10 is set substantially vertically, and the cleaning brush 21 is
It is also possible to dispose the cleaning member 210 with the front end of the cleaning member 210 in contact therewith, and clean the toner attached to the protrusion 162b. This makes it possible to make a deeper contact with the brush than the horizontal arrangement. However, if the protrusion 162b comes into deep contact with the brush of the cleaning brush 211, the spur 162 will rotate poorly. It is preferable that the contact be made at about 0.0 mm.

The cleaning member is provided without hindering the transfer of the transfer material.

As shown in FIG. 14, the cleaning member 210 is disposed on the guide surface 163a of the conveyance guide member 163 on the side of the recording paper P, and the cleaning brush 2 of the cleaning member 210 is disposed.
It is also possible to clean the toner adhered to the protrusion 162b by bringing the tip of 11 into contact with the protrusion 162b of the spur 162. The brush surface of the cleaning brush 211 is changed to the guide surface 163.
It may be arranged on the same plane as a. In FIG. 14, the cleaning member 210 is arranged on the downstream side in the rotation direction of the spur 162 with respect to the contact position with the recording paper P, but on the upstream side, on the guide surface 163a of the conveyance guide member 163, or on the same surface as the guide surface 163a. The cleaning member 210 may be provided so that the brush tip of the cleaning brush 211 is in contact with the protrusion 162b.

As described above with reference to FIGS. 11 to 14, the spur is well cleaned and the spur is prevented from being stained.

Although the embodiment of the double-sided image forming apparatus has been described in the case of a color image forming apparatus, the present invention is not necessarily limited to this, and the present invention is not limited to this. The present invention is also applied to a double-sided image forming apparatus.

Further, in the image forming apparatus of the present invention, in addition to the double-sided image formation for forming an image on both sides of the transfer material as described in the above embodiment, an image is formed on one side of only the front surface or the back surface of the transfer material. It goes without saying that one-sided image formation can also be performed.

[0098]

According to the first to fifth aspects, generation of spur marks on the toner image on the transfer material is prevented, and image rubbing when the transfer material is sandwiched by the fixing means is prevented.

According to the sixth aspect, the spur is cleaned well and the spur is prevented from being stained.

According to the seventh aspect, the rotation of the spur is kept good and the spur is well cleaned.

According to the eighth aspect, it is possible to prevent the toner image from being rubbed by the drooping of the leading end portion when the transfer material enters the transporting portion or by the trailing edge portion falling out of the transporting portion.

According to the ninth aspect, the cleaning member is provided without hindering the transfer of the transfer material.

[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 according to the present invention.

FIG. 2 is a side sectional view of a first image bearing unit of FIG. 1;

FIG. 3 is a diagram illustrating a state where toner images are formed on both surfaces of the image forming apparatus according to the present invention.

FIG. 4 is a diagram illustrating a transport unit.

FIG. 5 is a perspective view of a spur provided in a transport unit.

FIG. 6 is a diagram illustrating a first example of a roller configuration used for a fixing unit.

FIG. 7 is a diagram illustrating a first example of a method of conveying a transfer material by the roller configuration of FIG. 6;

FIG. 8 is a diagram illustrating a second example of a method of conveying a transfer material by the roller configuration of FIG. 6;

FIG. 9 is a diagram illustrating a second example of a roller configuration used for a fixing unit and a transfer material conveying method using the same.

FIG. 10 is a diagram illustrating a third example of a roller configuration used for a fixing unit and a transfer material conveying method using the same.

FIG. 11 is a diagram showing a first example of a method of attaching a cleaning member to a spur.

FIG. 12 is a perspective view showing a cleaning member.

FIG. 13 is a diagram illustrating a second example of a method of attaching the cleaning member to the spur.

FIG. 14 is a diagram showing a third example of a method of attaching the cleaning member to the spur.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a toner image receiver 14c transfer device 14d drive roller 14g back surface transfer device 14h paper separation AC neutralizer 17 fixing device 17a, 17c fixing roller 17b pressure roller 17d heat fixing Film 160 transport section 162 spur 163 transport guide member 165 entry guide member 211 cleaning brush P recording paper T nip

Claims (9)

[Claims] A first image carrying means for carrying the toner image formed by the toner image forming means; and a toner image carried by the first image carrying means is transferred. A belt-shaped second image carrying means carried on the surface, a first transfer means for transferring the toner image carried on the first image carrying means to the surface of the transfer material, and the second image carrying means A second transfer unit for transferring the toner image carried by the unit to the back surface of the transfer material; and a transfer member which nips and conveys the transfer material by a fixing member that rotates in pairs and is transferred to both surfaces of the transfer material. An image fixed by the fixing unit after the transfer material is conveyed by the second image holding unit, and the transfer material is separated from the second image holding unit. In the forming apparatus, the second image bearing means and the front A transfer unit having a spur for transferring the transfer material from an extension surface of the transfer material transfer surface of the second image bearing unit to a back surface side of the transfer material is provided between the transfer unit and the fixing unit, and the transfer is performed through the transfer unit. The transfer material is fed to a fixing unit. At the end of the second image bearing unit on the fixing unit side, the transfer material is separated from the belt-shaped second image bearing unit. The transfer material is moved from the spur to the fixing unit along the spur, and the transfer material is separated from the spur when the leading end of the transfer material is sandwiched by a nip formed by the pair of fixing members of the fixing unit. An image forming apparatus, wherein the transfer material is conveyed through the fixing unit while being separated from a spur. 2. The nip portion when the fixing member is brought into a deformed pressure contact state is formed in a convex shape on the back surface side of the transfer material, or the inclination between an inlet and an outlet is changed with respect to the transfer direction of the transfer material. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to either one of: 3. An image forming apparatus according to claim 2, wherein an extension surface of a transfer surface of said transfer material of said second image bearing means is in contact with a vicinity of said nip portion of a fixing member on a surface side of said transfer material of said fixing means. Item 2. The image forming apparatus according to Item 1. 4. An image forming apparatus according to claim 1, wherein an extension surface of a transfer surface of the transfer material along the spur abuts near a nip portion of a fixing member on a surface side of the transfer material of the fixing unit. 4. The image forming apparatus according to 3. 5. An image forming apparatus according to claim 1, wherein an entrance guide member is provided between said conveyance section and said fixing unit, and a leading end of said transfer material is brought into contact with a roller member above said fixing unit via said entrance guide member. The image forming apparatus according to claim 1, wherein: 6. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred, and the transferred toner image is A belt-shaped second image carrying means carried on the surface, a first transfer means for transferring the toner image carried on the first image carrying means to the surface of the transfer material, and the second image carrying means And a second transfer means for transferring the toner image carried by the means to the back surface of the transfer material, wherein the transfer material is transported by the second image bearing means, and After separating the transfer material, in an image forming apparatus that fixes the toner images transferred to both surfaces of the transfer material by a fixing unit, a transport unit is provided between the second image bearing unit and the fixing unit, Sending the transfer material to the fixing unit through the transport unit An image forming apparatus, comprising: a spur rotatable by the transfer material; and a cleaning member that abuts on a tip of the spur and cleans the spur. 7. The image forming apparatus according to claim 6, wherein the cleaning member is a brush-like member. 8. The image forming apparatus according to claim 6, wherein the transfer section includes a transfer guide member for transferring the transfer material on a side of the transfer material passing from a center of the spur. 9. The image forming apparatus according to claim 6, wherein the cleaning member is provided on the same surface as the conveyance guide member or on a side opposite to the transfer material passage side.