JPH1152645A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convey transfer material separated from a toner image receiving body, stably to a fixing means by arranging a conveying part on the back face side of the transfer material on the extended face of a transfer material conveying face of a second image holding means which is the toner image receiving body, and setting the radius of a fixing means side roller member for tightly streching the second image holding means, to specific length. SOLUTION: A conveying part 160 with spurs 162 for conveying transfer material separated from a toner image receiving body 14a, to a fixing device 17 is provided between the toner image receiving body 14a which is a second image holding means, and the fixing device 17 which is a fixing means. The conveying part 160 is provided on the back face side of the transfer material on the extended face of a transfer material conveying face PL1 of the toner image receiving body 14a. The radius R1 of a driving roller 14d of the fixing device 17 side for tightly streching the toner image receiving body 14a is to be 5-20 mm, and distance L1 between the center position of the driving roller 14a and the center position of the spur 162 closest to the driving roller 14a is to be 10-40 mm. The transfer material with unfixed images on both faces can therefore be conveyed stably to the fixing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image writing 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. The present invention relates to an electrophotographic image forming apparatus such as a printer, a printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in forming a double-sided image, an image on one side formed on an image carrier is transferred and fixed onto a transfer material, which is temporarily stored in a double-sided reversing sheet feeding device, and is again subjected to image bearing. 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 image forming 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, causing jams and wrinkles of the transfer material. .

On the other hand, JP-B-49-37538, JP-B-54-28740, and JP-A-1-444.
Japanese Patent Application Laid-Open No. Hei 4-144576 and Japanese Patent Application Laid-Open No. Hei 4-214576 propose a method in which a toner image is formed on both surfaces of a transfer material and then fixed once after forming the toner image. Publications include an image carrier, charging means,
There has been proposed a method of forming a two-sided color image by arranging image forming means including image writing means, developing means and the like in parallel on a plurality of sets of toner image receivers.

Further, the present inventors have arranged a plurality of sets of toner image forming means including a charging means, an image writing means, a developing means and the like around a first image bearing means (photosensitive drum), Once the superimposed color toner image formed on the drum is once transferred to the second image carrying means (toner image receiver) by the first transfer means, the superimposed color toner image is again transferred onto the photosensitive drum. The transfer material, which is formed and supplied in time with the toner image on the photosensitive drum and the toner image on the toner image receiver, is charged by the transfer material charging means and is attracted to the toner image receiver, so that the toner image receiver is The toner images on the photosensitive drums are respectively transferred as surface images by a first transfer unit to both surfaces of the transfer material conveyed above,
In addition, the toner image on the toner image receiver
After the transfer by the transfer means, the transfer material is separated from the toner image receiver by the curvature separation of the roller member provided on the fixing means side and stretching the toner image receiver, or by removing the charge of the transfer material separation means provided as necessary. An image forming apparatus for forming a two-sided color image by separating and fixing the toner image on the transfer material by a fixing unit is manufactured, and using this apparatus, a two-sided image formation (image formation on both sides of the transfer material) and a front surface A single-sided image formation of only an image (image formation only on the front surface of the transfer material), a single-sided image formation of only back surface image (image formation on only the back surface of the transfer material), and the like are being studied.

[0006]

In the above study,
If the transfer material separated from the toner image receiver is directly conveyed to the fixing unit after transferring the double-sided image to the transfer material, problems such as deformation and deterioration of the toner image receiver due to the heat of the fixing unit may occur. Occur. Therefore, a transport unit having a spur is provided between the toner image receiver and the fixing unit, and the transfer material separated from the toner image receiver is transported to the fixing unit via the spur of the transport unit. If the spur is far from the toner image receiver or too high with respect to the transfer material transport surface of the toner image receiver, the transfer material will fall before the spur due to its own weight, and conversely, will be too close to the toner image receiver, If the transfer material is too low with respect to the transfer material conveying surface of the toner image receiver, the transfer material having an unfixed toner image on both surfaces separated from the toner image receiver without contacting the spur is stably transferred to the fixing unit. There is a problem that the toner image is not conveyed and the toner image is disturbed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide an image forming apparatus in which a transfer material separated from a toner image receiving body is stably conveyed to a fixing unit.

[0008]

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 second image carrying means for carrying the transferred toner image, and a first image carrying means for transferring the toner image carried on the first image carrying means to the surface of the second image carrying means and the transfer material. Transfer means, second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material, and fixing means for fixing the toner images transferred to both surfaces of the transfer material. An image forming apparatus which transports the transfer material by the second image bearing means, separates the transfer material from the second image bearing means, and fixes the transfer material by the fixing means. The second image bearing member is provided between the carrying unit and the fixing unit. A transfer unit having a spur for transferring the transfer material separated from the unit to the fixing unit; and providing the transfer unit on a back surface side of the transfer material of an extension surface of a transfer material transfer surface of the second image bearing unit. The radius R1 of the roller member on the fixing unit side that is disposed and stretches the second image bearing unit
(Mm) is set to 5 to 20 mm, and the distance between the center position of the spur closest to the roller member and the center position of the roller member is set to 10 to 40 mm.

[0009]

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 back side of the transfer material is called a back side 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 conveying unit having a spur 162; 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 a transparent member such as optical glass or transparent acrylic resin. And rotated clockwise as indicated by the arrow in FIG. 1 with the conductive layer grounded.

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.

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 image forming processes, and four sets are provided.
With respect to the 0 rotation direction, 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 Y, M, and C toners. For this reason, a shorter wavelength of 400 to 780 nm which does not have sufficient transparency to the color toner may be used. In FIG. 2, WA is a lead wire from a light emitting element (LED) of the image exposure means.

A 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 the forward direction with respect to the rotating 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 2.0 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, a guide roller 14f, and a tension roller 14i, which are roller members, and is rotated in a counterclockwise direction indicated by an arrow in FIG. Toner image receiver 1
Driven roller 14e, driving roller 1
4d, a tension roller 14i, and a guide roller 14f are provided in this order. The driven roller 14e, the drive roller 14d, and the guide roller 14f are fixedly rotated, and the tension roller 14i is resilient by a spring or the like (not shown) of the toner image receiver 14a. The toner image receiver 14a is rotated while being stretched. The drive roller 14d is rotated by the drive from the drive motor M1 (see FIG. 4), and the toner image receiver 14a is driven and rotated. The driven roller 14e, the guide roller 14f, and the tension roller 14i are driven to rotate by the rotation of the toner image receiver 14a. Rotating toner image receiver 1
The slack of the belt 4a is tensioned by the tension roller 14i.

A transfer unit 14c, which is preferably a first transfer unit constituted by a corona discharger, is provided opposite to the photosensitive drum 10 with the toner image receiver 14a interposed therebetween.
A transfer area 14b is formed between the toner image receiver 14a and the photosensitive drum 10. By applying a DC voltage of the opposite polarity (positive polarity in the present embodiment) to the transfer device 14c and forming a transfer electric field in the transfer area 14b,
The toner image on the photosensitive drum 10 is transferred to the toner image receiving member 14a.
The image is transferred onto the upper surface or the surface of the recording paper P as a transfer material.

A back transfer unit 14g, which is preferably a second transfer unit constituted by a corona discharger, includes a conductive drive roller 14 grounded with a toner image receiver 14a interposed therebetween.
d, a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to transfer the toner image on the toner image receiver 14 a to the back surface of the recording paper P.

A paper charger 150, which is preferably a transfer material charging means constituted by a corona discharger, is provided to face the driven roller 14e, which is grounded across the toner image receiver 14a, and charges the recording paper P. And the toner image receiver 14a
To be absorbed.

A paper separating AC neutralizer 14h, which is preferably a transfer material separating means constituted by a corona discharger, interposes the toner image receiver 14a at the end of the toner image receiver 14a on the fixing device 17 side as required. A recording is carried by the toner image receiving body 14a, which is provided opposite to the conductive driving roller 14d which is grounded at the above, and is applied with an AC voltage on which a DC voltage having the same polarity or opposite polarity to the toner is superimposed if necessary. The paper P is neutralized to separate the recording paper P from the toner image receiver 14a.

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 scoops up the recording paper P that is to be bent and conveyed in the direction of the toner image receiving body 14a when the recording paper P is separated from the toner image receiving body 14a, and the recording paper P having the toner image on the back surface.
Is transported to the fixing device 17 while preventing the rear 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 and a pressure roller 17b.
The toner image on the recording paper P is fixed by applying heat and pressure at a nip T between the a and the pressure roller 17b.

Next, the image forming process will be described.

The start of image recording causes the photosensitive drum drive motor (not shown) to start, thereby rotating the photosensitive drum 10 in the clockwise direction indicated by the arrow in FIG. 1 and simultaneously exposing the photosensitive drum 10 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 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 the Y toner image by a charging action of a magenta (M) scorotron charger 11, and a second color signal, that is, an M color signal is applied by an 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 side 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 transferring 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 may be performed by the simultaneous transfer exposure device 12d provided inside the photoconductor drum 10 so that good transfer is performed.

After the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16, the toner is transferred to a cleaning device 19, which is a first image carrier cleaning means, or is exposed to light. The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the body drum 10, and is 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 as the back surface image is formed on the toner image receiving member 14a as described above, the superimposed color toner image as the front surface image is continuously formed in the same manner as in the above 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, the recording paper P is provided with a DC voltage of the same polarity as the toner (in the present embodiment, a negative polarity) provided on the surface side of the fed recording paper P, and the recording paper P is made to have the same polarity as the toner. , And is adsorbed on the toner image receiving body 14a and 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. Unless the paper charger 150 described later is used as the second image carrier charging means, the voltage is normally applied to the paper charger 150 as the transfer material charging means.
The voltage applied to the paper charger 150 is cut off simultaneously with the passage of the recording paper P.
As the paper charger 150, a paper charging brush, a paper charging roller, or the like can be used in addition to the corona discharger.

In the transfer area 14b, a first voltage to which a voltage having a polarity opposite to that of the toner (positive polarity in the present 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 surface image on the peripheral surface of the toner image receiver 14a is collectively transferred to the back surface of the recording paper P by the back surface transfer device 14g (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is driven by a driving roller 14 for driving a toner image receiver 14a.
The spur 162 is separated from the toner image receiver 14a by the curvature of d and the static electricity removing action of the paper separating AC static electricity eliminator 14h as a transfer material separating means provided as needed at the end of the toner image receptor 14a. The toner image is conveyed to a fixing device 17 as a fixing unit through a conveying unit 160 provided, and is applied with heat and pressure at a nip portion T between the fixing roller 17a and the pressure roller 17b, so that the toner image on the recording paper P is formed. Is established. The recording paper P on which double-sided image recording has been performed is sent upside down, and is discharged by a discharge roller 18 to a tray outside the apparatus. Further, as shown by a dashed line in FIG. 1, a switching member (not shown) may be provided at an outlet of the fixing device 17 so as to be discharged to a tray outside the device.

The toner remaining on the peripheral surface of the toner image receiving member 14a after the transfer is provided to face the guide roller 14f with the toner image receiving member 14a interposed therebetween, and the toner image receiving member 14 is rotated around the support shaft 142 as a fulcrum. The toner image receiving member is cleaned by a toner image receiving member cleaning device 140 which is a second image carrying means cleaning means having a toner image receiving member cleaning blade 141 capable of contacting and releasing contact with 14a.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by the photoreceptor 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 unit 12e,
The next image forming cycle is started.

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 hardly undergoes color misregistration, toner scattering or rubbing, and image deterioration is reduced. A double-sided color image is formed.

Although the embodiment of the double-sided image forming apparatus has been described with reference to the 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, the 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.

The spur and the transporting unit having the spur according to the present invention will be described with reference to FIGS. 4 to 6 and FIG. FIG. 4 is a diagram showing a transport unit, FIG. 5 is a perspective view of a spur provided in the transport unit, and FIG. 6 is an enlarged view of the spur.

The recording paper P on which the toner image of the front surface image and the toner image of the back surface image are formed by the toner image receiving member 14a moved by the driving roller 14d which is a roller member driven and rotated by the driving motor M1 is conveyed. However, the transfer material conveying surface of the toner image receiving body 14a or its extension surface PL
1 (hereinafter referred to as a transfer material transport surface PL1; see FIG. 7), a transport unit 16 provided with a spur 162 on the back side of the recording paper P.
0 is disposed between the toner image receiving member 14a and the fixing device 17, and the recording paper P separated from the toner image receiving member 14a passes through the transport unit 160 and has a fixing roller 17a and a pressure roller 17b provided vertically. It is transported to the device 17.

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.

A plurality of spurs 162 are provided as a set of spurs H1, H2 in a direction orthogonal to the direction in which the recording paper P is conveyed. At least one set of spurs is provided.

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.
Outer diameter 5 to 25 mm (when the radius of the drive roller 14 d is R1 mm as described later, preferably (0.2 to 1.
0) × R1), a thickness of 0.5 to 2.0 mm, and an outer diameter of 5 to 25 mm (when the radius of the driving roller 14d is R1 mm as described later, it is preferably (0.2 to 1.0) )
× R1) made of an insulating resin member, and is made of a polygonal, for example, hexagonal, plate-shaped member having a sharp projection 162b at the tip. When the spur 162 is a metal plate, it is preferable that the spur 162 be grounded via a resistor of 10 ⁸ to 10 ¹⁴ Ω. The spur 152 passes through a metal plate and is grounded via a high-resistance body or using a high-resistance member because the toner and the transfer material have a charge, and the spur 152 accumulates electric charge and adheres to the toner due to a mirror image force. Is prevented by static elimination to prevent the toner image from being disturbed. It is also possible to prevent the toner from adhering and prevent the toner image from being disturbed by floating the metal plate in an insulating state. It is also possible to apply a voltage of the same polarity as the toner (minus polarity in the present embodiment) to the metal plate to prevent the toner from adhering and prevent the toner image from being disturbed. By using an insulating member such as an insulating resin member for the spur 162, it is possible to prevent charge accumulation of the spur 152 and toner adhesion due to mirror image force by static elimination and to prevent the toner image from being disturbed in the same manner as the above-mentioned floating. Become.

The positional relationship between the spurs will be described with reference to FIGS. FIG. 7 is a diagram illustrating a positional relationship between the spur and the drive roller.

Toner image receiver 1 as second image bearing means
Roller 14 which is a roller member for stretching and driving 4a
Generally, the radius of the driving roller 14d is R1
(Mm), a radius of 5 to 20 mm (outer diameter of 10 to 40)
mm) is used to transport the toner image receiving body 14a, but the spur 162 of the set closest to the drive roller 14d is
L1 between the center position of the driving roller 14d and the center position of the driving roller 14d
Is preferably 10 to 40 mm. Distance L1 is 4
If the distance exceeds 0 mm and the spur 14d is far from the toner image receiver 14a, the recording paper P falls before the spur due to its own weight.
If the distance is too close to a, the recording paper P does not contact the spur 162 and the transportability is not good.

Further, the distance L2 (mm) between the protrusion 162b of the pair of spurs 162 closest to the drive roller 14d and the transfer material transporting surface PL1 of the toner image receiver 14a is (0.1 to 0.1 mm).
0.5) × R1. If the distance L2 is 0.
If the spur 162 is less than 1 × R1 and the spur 162 is too high with respect to the transfer material transport plane PL1, the recording paper P falls before the spur due to its own weight, and conversely, the distance L2 exceeds 0.5 × R1 and the spur 162 Is too low with respect to the transfer material transport surface PL1, the recording paper P does not contact the spur 162, and the transportability is not good. As the roller diameter of the drive roller 14d is larger, the separability becomes worse, so that the spur 162 needs to be installed below.

If the radius of the circle formed by the projection 162b of the spur 162 is R2 (mm), the radius R2 is preferably (0.2 to 1.0) × R1. If the radius R2 exceeds 1.0 × R1 and is too large, the driving roller 1
If the radius R2 is less than 0.2 × R1 and too small, it is not possible to cope with a slight change in the conveyance path of the recording paper P.

FIG. 8 shows a separation claw for separating the transfer material by the second image bearing means. FIG. 8 is a diagram illustrating a configuration in which a spur and a separation claw are integrally provided.

As shown in FIG. 8, the separation claw 21 for separating the recording paper P from the toner image receiving member 14a integrally with the spur 162 of the set closest to the drive roller 14d with the spur 162 described above.
0 is provided. As the separation claw 210, a resin molded member using a resin having good releasability and abrasion resistance, such as Teflon or polyimide, or a polycarbonate resin is used. Spur 16
When the recording paper P is provided integrally with the separation claw 210, the recording paper P is separated from the separation claw 210 immediately after being separated by the separation claw 210 and guided by the spur 162.
Disorder of the toner image on the back side image on the recording paper P and separation claw 210
Stains are less likely to occur. Also, space can be saved.

[0056]

According to the first to fourth aspects of the present invention, a transfer material having an unfixed toner image on both surfaces separated from the second image bearing means is stably fixed without disturbing the toner image. Transported to

According to the fifth to seventh aspects, the contamination of the spur due to the adhesion of the back surface toner is prevented.

[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 an enlarged view of a spur.

FIG. 7 is a diagram showing a positional relationship between a spur and a driving roller.

FIG. 8 is a diagram showing a structure in which a spur and a separation claw are provided integrally.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14 a toner image receiver 14 c transfer device 14 d drive roller 14 g backside transfer device 17 fixing device 160 transport unit 162 spur 162 b projecting portion 210 separation claw P recording paper PL1 transfer material Transfer surface

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Haneda Konica Corporation 2970 Ishikawacho, Hachioji-shi, Tokyo

Claims (7)

[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 second image carrying unit for carrying the toner image, and a toner image carried on the first image carrying unit.
A first transfer unit that transfers the toner image held by the second image holding unit to a back surface of the transfer material; and a transfer unit that transfers the toner image held by the second image holding unit to the back surface of the transfer material. Fixing means for fixing the toner images transferred to both surfaces of the material, wherein the transfer material is transported by the second image bearing means, and the transfer material is separated from the second image bearing means. In the image forming apparatus for fixing by a fixing unit, a spur that conveys the transfer material separated from the second image holding unit to the fixing unit is provided between the second image holding unit and the fixing unit. A transport unit, and the transport unit is disposed on the back side of the transfer material on the extension surface of the transfer material transport surface of the second image bearing unit; and the fixing unit side on which the second image bearing unit is stretched. The radius R1 (mm) of the roller member is 5 to 20 mm Together, the image forming apparatus, characterized in that the distance between the center position of the closest spur to the roller member and the center position of the roller member with the 10 to 40 mm. 2. An upper end of the spur closest to the roller member is positioned on the back side of the extension surface of the transfer material conveying surface (from 0.1 to 0.1).
0.5) × R1 apart.
An image forming apparatus according to claim 1. 3. The radius R of the spur closest to said roller member.
3. The image forming apparatus according to claim 1, wherein 2 is (0.2 to 1.0) × R1. 4. The image forming apparatus according to claim 1, further comprising: a separation claw for separating the transfer material from the second image bearing means integrally with a spur closest to the roller member. Image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the spur is electrically floating with respect to the image forming apparatus main body or is charged with the same polarity as toner.
Item 10. The image forming apparatus according to item 1. 6. The image forming apparatus according to claim 1, wherein the spur is formed of an insulating member. 7. The image forming apparatus according to claim 1, wherein the spur is grounded via a high-resistance member.