JPH11224009A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the difference of gloss between images on both sides of a body to be transferred and to form the images on both sides similarly by actuating a backup roller cooling device so that a backup roller may be cooled in the case of forming the image on the 2nd side of the body to be transferred whose 1st side the image is formed on. SOLUTION: This device is provided with the backup roller cooling device 16 cooling the backup roller 9 and a control part COHT1 for the device 16. The device 16 includes a cooling fan 161, a supporting member 162 for the fan 161 and a sensor 163. The fan 161 is provided to face to the roller 9 so as to cool the roller 9. The sensor 163 is arranged in contact with the roller 9 so as to detect the surface temperature of the roller 9. The fan 161 is turned on/off according to an instruction signal from the control part CONT1 based on the detected value from the sensor 163. The fan 161 is turned on the control part CONT1 and cools the roller 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copier, a printer, and the like, in which an electrostatic latent image is developed using a developer, and the obtained visible toner image is temporarily transferred to an intermediate transfer member, and then transferred to an intermediate transfer member. An image forming apparatus for performing secondary transfer onto a transfer target, and more particularly, after forming an image on a first surface (one surface) of a transfer target, the transfer target is turned over and the second surface (opposite surface) is turned over. The present invention relates to an image forming apparatus capable of forming a double-sided image in which an image can be formed in the same manner as one surface.

[0002]

2. Description of the Related Art In an image forming apparatus, generally, a surface of an electrostatic latent image carrier such as a photoreceptor is charged, and an electrostatic latent image is formed in the charged area by image exposure or the like based on image information. ,
The latent image is developed with a developer to form a visible toner image,
This toner image is firstly transferred onto an intermediate transfer member such as an intermediate transfer drum, and then secondarily transferred from the intermediate transfer member to one surface of a transfer member such as paper and fixed. Further, when performing double-sided image formation, the transfer-receiving member on which the image has been formed on the first surface by the secondary transfer is turned upside down, and the visible toner image on the intermediate transfer member which is primarily transferred from the electrostatic latent image carrier is transferred. On the second surface of the transfer object.
Next, transfer and fix.

As such an image forming apparatus, for example, an image forming apparatus using a so-called thermal transfer system in which transfer is performed using heat for secondary transfer has been proposed. In addition, as a method for forming a double-sided image on a transfer medium, the following method is generally employed. That is, first, normal single-sided image formation is performed on the first surface of the transfer target sent from the transfer target supply unit to the secondary transfer unit. The transfer object on which the single-sided image has been formed is guided again to the original transfer object supply unit or another second transfer object supply unit. Next, the transferred object is transferred from the original transferred object supply unit or another second transferred object supply unit to the secondary transfer unit again so that an image is formed on the second surface of the transferred object. Send in. Then, an image is formed on the back surface of the transfer object in the same manner as the front surface.

On the other hand, the conditions necessary for the thermal transfer in the secondary transfer include that the toner image on the intermediate transfer member is in a molten state and that the releasability of the intermediate transfer member is higher than the releasability of the object to be transferred. Can be In addition to these conditions, a backup roller is provided in the secondary transfer section in order to increase the adhesion between the transfer target body and the toner image on the intermediate transfer body during thermal secondary transfer.
A method is employed in which the transfer target is pressed against the intermediate transfer member by the backup roller.

[0005]

However, in an image forming apparatus employing such a thermal secondary transfer system using a backup roller, at the time of image formation, image formation and subsequent image formation are performed in a secondary transfer section. Between the backup roller and the intermediate transfer member in the area where there is no transfer object between
During image formation, the two parts partially contact each other outside the paper passing area, and as the operation time of the image forming apparatus elapses, the temperature of the backup roller surface and the temperature of the intermediate transfer body surface become higher.
It will be almost the same temperature.

When double-sided image formation is performed in such a state,
When an image is formed on the first surface of the transfer object and then the transfer object is again passed through the thermal secondary transfer section so as to form an image on the second surface, the image on the first surface comes into contact with the heated backup roller. Will be heated again. For this reason, the first-side image heated twice is applied with a larger amount of heat to the toner than the second-side image heated only once, and in an extreme case, the first-side toner image is re-melted. There is a problem that the gloss of the image is different between the first surface and the second surface.

Therefore, the present invention develops an electrostatic latent image formed on an electrostatic latent image carrier into a visible toner image, and temporarily transfers the visible toner image to an intermediate transfer member once. An image forming section for performing a thermal secondary transfer to a transfer member pressed against the intermediate transfer member by a backup roller; and a first surface of the transfer member (one side of the transfer member in the single-sided image forming mode, and a transfer member in the double-sided image forming mode). A transfer object supply unit for supplying the transfer object to the thermal secondary transfer unit for forming an image on the transfer body first surface (including both the first surface and the transfer unit first surface); An image forming apparatus comprising: a transfer object re-supply unit for re-supplying the transfer object to the thermal secondary transfer unit in order to form an image on the second surface of the transfer object; When forming an image on the second surface of the image-receiving body, the gloss of the two-sided image of the And to provide an image forming apparatus capable of similarly forming images on both sides to suppress different.

[0008]

An image forming apparatus according to the present invention for solving the above-mentioned problems develops an electrostatic latent image formed on an electrostatic latent image carrier into a visible toner image, and forms the visible toner image. An image forming section for temporarily transferring the first image onto the intermediate transfer member, and then thermally secondary-transferring the image onto the transfer member pressed against the intermediate transfer member by a backup roller; A transfer medium supply unit for supplying the transfer medium to the thermal secondary transfer unit to form an image on the transfer object single side in the mode and the transfer object first surface in the double-sided image forming mode). A transfer object re-supply unit for re-supplying the transfer object to the heat secondary transfer unit in order to form an image on the second surface of the transfer object having an image formed on the first surface by the thermal secondary transfer; Have.

In one aspect of the image forming apparatus according to the present invention, an apparatus for cooling the backup roller,
A control unit for operating the backup roller cooling device so as to cool the backup roller when forming an image on the second surface of the transfer-receiving body having the image formed on the first surface. According to still another aspect, a pressing force adjusting device for adjusting a pressing force of the transfer target against the intermediate transfer member by the backup roller, and an image forming device on the second surface of the transfer target having an image formed on the first surface. In doing so, the pressure applied by the backup roller to the intermediate transfer member against the intermediate transfer member is increased by the first roller.
And a control unit for controlling the pressure-contact force adjusting device so as to make the pressure lower than at the time of the thermal secondary transfer of the toner image to the surface.

According to still another aspect, a first surface roller for forming an image on the first surface of the transfer object as the backup up roller and a second roller for forming an image on the second surface of the transfer object are provided. A two-sided roller provided between the intermediate transfer body and the intermediate transfer body formed by pressing the intermediate transfer body against the intermediate transfer body. The nip width is smaller than the nip width between the transferred body and the intermediate transfer body formed by pressing the transferred body against the intermediate transfer body by the first surface roller, Further, when forming an image on the first surface of the transfer target, the roller for the first surface is at the pressure contact position of the transfer target, and when forming an image on the second surface of the transfer target, the roller for the second surface is connected to the transfer target. A roller switching device is provided for each of the pressing positions. .

In any one of the image forming apparatuses according to the present invention, the visible toner image formed on the electrostatic latent image carrier is primarily transferred to the intermediate transfer member, and is moved along with the surface of the intermediate transfer member. The process proceeds to the thermal secondary transfer section. Further, the heat is applied before the heat reaches the secondary transfer portion, and the toner is melted at least in the secondary transfer portion. Heating of the toner image on the intermediate transfer body is performed by, for example, a heat source built in the intermediate transfer body as in the related art, a heat source disposed outside the intermediate transfer body, or a heat source for heating the toner image on the intermediate transfer body such as both. I can do it.

On the other hand, an object to be transferred is supplied to the thermal secondary transfer portion in synchronization with the visible toner image on the intermediate transfer member. The transfer medium is supplied from the transfer medium supply unit when the image is formed on the first surface in the single-sided image forming mode or the double-sided image forming mode, and when the image is formed on the second surface in the double-sided image forming mode. The transfer is performed from the transfer object re-supply unit.

The transfer object sent to the secondary transfer portion is pressed against the intermediate transfer member by the backup roller with a predetermined pressing force. Thus, the toner image on the intermediate transfer member is pressed against the transfer object, melts and adheres to the transfer object, and is separated from the intermediate transfer member. In this way, the toner image is thermally secondary-transferred from the intermediate transfer member to the transfer-receiving member and fixed. In the image forming apparatus including the backup roller cooling device and the control unit, when the thermal secondary transfer is a toner image transfer in the one-sided image forming mode or a toner image transfer to the first surface in the two-sided image forming mode, The control unit does not operate the backup roller cooling device. However, when the toner image is transferred to the second surface of the transfer object in the double-sided image forming mode, the control unit operates the cooling device to cool the backup roller.

In this way, the amount of heat applied from the backup roller to the first surface image (toner image) during the thermal secondary transfer of the toner image to the second surface of the transfer member having the image formed on the first surface is suppressed. As a result, the gloss of the first surface image is easily maintained as it is, and the difference in gloss between the two-sided image of the transfer-receiving body is suppressed, so that the image can be formed on both surfaces in the same manner. The backup roller cooling device may be a blower device, but is not limited thereto.

Also, in the image forming apparatus provided with the pressure contact force adjusting device for the backup roller and its control unit, the heat
When the next transfer is a toner image transfer in a one-sided image forming mode or a toner image transfer to a first surface in a two-sided image forming mode, the pressing force adjusting device and its control unit use a backup roller to transfer the intermediate transfer member of the transferred object. The toner image on the intermediate transfer member is thermally secondary-transferred to one surface of the transfer-receiving member, and is fixed.

However, when the toner image is transferred to the second surface of the transfer medium in the double-sided image forming mode, the pressing force adjusting device and its control unit receive the pressing force of the transfer medium against the intermediate transfer member by the backup roller. It is weaker than when the toner image is transferred to the first surface of the transfer member. Thereby, the mutual contact nip width between the transfer object and the intermediate transfer member and the mutual contact nip width between the transfer member and the backup roller are reduced accordingly, and therefore, the first surface image (toner image) from the intermediate transfer member to the transfer member is reduced. And the heat is hardly transmitted to the image of the first surface of the transfer-receiving body even if the temperature of the backup roller is increased. As a result, the gloss of the first-side image is easily maintained as it is, and the difference in gloss between the two-sided image of the transfer-receiving body is suppressed, so that images can be formed on both sides in the same manner.

When the toner image is transferred to the second surface of the transfer object in the double-sided image forming mode, the mutual contact nip width between the transfer object and the intermediate transfer member is slightly reduced. Is sufficiently heated on the side of the intermediate transfer member, so that the toner image is thermally secondary-transferred to the second surface of the transfer-receiving member without any problem.
Be established. In addition, the toner image on the intermediate transfer member to be transferred to the transfer target second surface can receive heat from the backup roller via the transfer target member. In this case, the toner image is transferred to the transfer target second surface without any trouble. Thermal secondary transfer is performed and fixed.

The press-contact force adjusting device includes a support member for reciprocatingly supporting the backup roller toward or away from the intermediate transfer member, and a support member position for obtaining a target press-contact force. And a drive device for moving the support member. in this case,
The support member may be any of a swingable member, a rotatable member, a member capable of reciprocating linear movement, and a combination thereof. Examples of the driving device include a motor (a rotary motor, a solenoid, etc.) for moving the support member, a motor and a transmission mechanism for transmitting the driving force of the motor to the support member, and a cam device capable of driving the support member.
However, it is not limited to these.

Further, the first roller is used as a backup roller.
In an image forming apparatus including a surface roller and a second surface roller and a roller switching device, thermal secondary transfer is performed by transferring a toner image in a one-sided image forming mode or transferring a toner image to a first surface in a two-sided image forming mode. When
The roller for the first surface is caused to face the intermediate transfer member by the roller switching device, and is disposed at a position where the transfer target member is pressed against the intermediate transfer member.
When the toner image is transferred to the second surface of the transfer medium in the double-sided image forming mode, the roller for the second surface is arranged at the pressure contact position of the transfer medium by the roller switching device.

The mutual contact nip width between the transfer member pressed against the intermediate transfer member by the second surface roller and the intermediate transfer member is determined by the difference between the transfer member nip width and the transfer member pressed against the intermediate transfer member by the first surface roller. Since the nip width is set smaller than the mutual contact nip width with the intermediate transfer member, when the toner image on the intermediate transfer member is thermally secondary-transferred to the second surface of the transfer member in the double-sided image forming mode, the transfer from the intermediate transfer member is performed. Heat is hardly transmitted to the image on the first surface of the body (toner image), and the roller for the second surface is disposed at the pressure-contact position of the transferred body only when transferring the toner image to the second surface of the transferred body. If not, or if it has already been used and the temperature has risen, the temperature is low. Therefore, much heat is not applied from the second surface roller to the image of the first surface of the transferred body. As a result, the gloss of the first-side image is easily maintained as it is, and the difference in gloss between the two-sided image of the transfer-receiving body is suppressed, so that images can be formed on both sides in the same manner.

Incidentally, the roller switching device includes:
A support member that supports the first surface roller and the second surface roller, and that can be moved so that one of the two rollers can be selectively disposed at the transfer object pressure contact position; An apparatus including a device for driving the support member such that the first surface roller or the second surface roller is disposed at the transfer member pressure contact position can be exemplified.

In this case, the supporting member may be any of a swingable member, a rotatable member, a member capable of reciprocating linear movement, and a combination thereof. Further, as the driving device, a motor (a rotary motor, a solenoid, etc.) for moving the support member, a motor and a transmission mechanism for transmitting the driving force of the motor to the support member, and a first surface roller or a second surface roller are pressed against the transfer object. A cam device capable of driving the support member so as to be arranged at a position can be used. However, it is not limited to these.

As described above, the first roller is used as a backup roller.
When a surface roller and a second surface roller are provided and a roller switching device is further provided, the surface hardness of the second surface roller may be larger than the surface hardness of the first surface roller, or A state in which the roller for one surface is pressed toward the intermediate transfer member by the first pressing device in a state where the roller for one surface is disposed at the pressure contact position of the transfer object, and the roller for the second surface is disposed at the pressure contact position of the transfer object. The second pressing device may be pressed toward the intermediate transfer body, and the pressing force of the second pressing device may be weaker than the pressing force of the first pressing device. Also, both of them may be used. Examples of the first and second pressing devices include a device that applies a pressing force to a roller by an elastic body such as a spring.

In order to make the surface hardness of the roller for the second surface larger than the surface hardness of the roller for the first surface, for example, but not limited to, the materials of at least the surfaces of both rollers have different hardnesses. You just have to use something. By making the surface hardness of the roller for the second surface larger than the surface hardness of the roller for the first surface, it is possible to reduce the pressing force of the object to be transferred to the intermediate transfer member between the roller for the first surface and the roller for the second surface. Even if it is set to be the same, the mutual contact nip width between the intermediate transfer body and the intermediate transfer body pressed against the intermediate transfer body by the second surface roller is set to the intermediate transfer body pressed against the intermediate transfer body by the first surface roller. Nip width between the sheet and the intermediate transfer member.

Further, when the first surface roller is disposed at the transfer member pressing position, the first pressing device is pressed toward the intermediate transfer member, and the second surface roller is pressed against the transfer member. When placed at the position, when pressed by the second pressing device toward the intermediate transfer body, and when the pressing force by the second pressing device is weaker than the pressing force by the first pressing device,
Even if the surface hardness of the roller for the first surface and the surface hardness of the roller for the second surface are the same, the mutual contact nip width between the transfer object and the intermediate transfer member pressed against the intermediate transfer member by the roller for the second surface is set to The mutual contact nip width between the intermediate transfer body and the transfer-receiving body pressed against the intermediate transfer body by the one-surface roller can be made smaller.

As described above, when the backup roller is cooled, when the pressure applied to the intermediate transfer member by the backup roller is adjusted, and when two rollers having different transfer conditions are switched, the intermediate transfer member and the intermediate transfer member are switched. The case where the size of the nip width between the two is changed has been described, but two or more of them may be used in combination.

When the toner image is transferred to the second surface of the transfer object in the double-sided image forming mode, the toner image already formed on the first surface of the transfer object is glossy even if it is reheated. It is desirable that the toner be heated only at or below the glass transition temperature Tg of the toner in order to maintain the same as possible, and the backup roller is cooled and the nip width is set so as to achieve this. Is desirable.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electrophotographic image forming apparatus according to an embodiment of the present invention. FIG.
The image forming apparatus shown in FIG. 1 can form an image in the following two image forming modes. That is, one is a single-sided image forming mode in which an image is formed only on one side of the recording sheet S described later, and the other is both sides of the first side (front side) and the second side (back side) of the recording sheet S. This is a double-sided image forming mode in which an image is formed on the second side.

This image forming apparatus includes an image forming section 100,
It includes a sheet feeding unit 200 (an example of a transferred object supply unit) and a sheet re-feeding unit 300 (an example of a transferred object resupply unit). In the single-sided image forming mode, the recording paper S is supplied from the paper supply unit 200 to the image forming unit 100, and after an image is formed on one side of the recording paper S, the recording paper S is discharged to a paper discharge tray 15 described later.

In the double-sided image forming mode, the recording paper S is supplied from the paper supply unit 200 to the image forming unit 100, and after the image is formed on the first surface of the recording paper S, it is sent to the re-feeding unit 300. . The recording paper S is turned upside down in the re-feeding unit 300, supplied again to the image forming unit 100, formed on the second surface of the recording paper S, and then discharged to the discharge tray 15. FIG.
9 shows a state of an image forming operation on the first side of the recording sheet S in the double-sided image forming mode.

The image forming section 100 includes a drum-shaped photosensitive member 1 (an example of an electrostatic latent image carrier). Around the photoreceptor 1, a corona charging device 2, an exposure device 3, a liquid developing device 4, a squeeze roller 5, an intermediate transfer drum 6 (an example of an intermediate transfer member), a cleaning blade 7, and an eraser lamp 8 are arranged in this order. Have been. The photoconductor 1 is driven to rotate in a counterclockwise direction A in the figure. Here, the photoconductor 1 is a drum-shaped photoconductor drum, but may be a belt-shaped photoconductor belt or the like.

The intermediate transfer drum 6 faces the photoreceptor 1 and forms a primary transfer portion P1 in the figure. A backup roller 9 and a cleaning blade 10 are arranged around the intermediate transfer drum 6. The backup roller 9 faces the intermediate transfer drum 6 and forms a thermal secondary transfer portion P2 in the figure. A guide plate 11 and a timing roller pair 12 are provided on the right side of the secondary transfer portion P2 in the drawing. A guide plate 13 is provided on the left side, and a discharge roller pair 14 is further provided.
And a paper discharge tray 15.

The charging device 2 can apply a high voltage from the power supply PW1, and can charge the photosensitive member 1 by this.
The exposure device 3 can irradiate the photoconductor 1 with the laser beam L based on image information sent from an image reading device or the like (not shown), and thereby form an electrostatic latent image on the photoconductor 1.

The liquid developing device 4 includes a developing roller 41 and a developer tank 42 and stores the liquid developer D. The liquid developer D contains a toner. The developing roller 41 is driven to rotate clockwise B in the figure, and can apply a developing bias voltage from the power supply PW2. Thereby, the electrostatic latent image on the photoconductor 1 can be developed. The squeeze roller 5 is provided on the photoconductor 1 and is driven to rotate. As a result, excess carrier liquid adhering to the photoreceptor 1 can be removed. Although the squeeze roller 5 is provided separately from the liquid developing device 4 in FIG. 1, the squeeze roller 5 may be provided integrally at the same position as the liquid developing device 4.

The cleaning blade 7 is arranged in contact with the photosensitive member 1. As a result, the transfer residual toner remaining on the photoreceptor 1 without being primarily transferred to the intermediate transfer drum 6 can be removed.
The eraser lamp 8 can irradiate the photoreceptor 1 with light, so that the charges on the photoreceptor 1 can be removed by light. The intermediate transfer drum 6 includes a heat source 61 and is driven to rotate in the direction B in the drawing.
The heat source 61 is built in the drum 6 and generates heat by the power supply PW4. The heat generated by the heat source 61 heats the surface of the drum 6 to a predetermined temperature, so that the toner image T2 primarily transferred onto the drum 6 can be heated as described later. The intermediate transfer drum 6 is a drum-shaped transfer drum, but may be a belt-shaped transfer belt. Although the heat source 61 here is incorporated in the intermediate transfer drum 6, a heat source provided outside the drum 6 and facing the drum 6 may be provided to directly heat the toner T2 on the drum 6.

Between the intermediate transfer drum 6 and the photosensitive member 1,
The transfer voltage can be applied by the power supply PW3. As a result, the toner image T1 on the photosensitive member 1 can be primary-transferred electrostatically onto the drum 6. The backup roller 9 includes the intermediate transfer drum 6,
It can rotate following the movement of the recording paper S passed between the roller 9 and the drum 6. The backup roller 90 presses the intermediate transfer drum 6 with a predetermined force. That is, the backup roller 9 has its shaft 9
The bearing member 9b of a is supported by the bearing member support frame 92 so as to be able to move up and down, so that the bearing member 9b is movably supported in the direction of coming and going with respect to the drum 6. A pressure contact spring 91 is mounted on the support frame 92, and the pressure contact spring 91 is in contact with the roller bearing member 9 b on one side, and is supported by a lower portion of the support frame 92 on the other side. The press-contact spring 91 connects the backup roller 9 to the drum 6
Is pressed with a predetermined force. As a result, a recording sheet S (transfer object), which will be described later, is pressed against the drum 6, and the toner image T2 on the drum 6 can be thermally secondary-transferred and fixed on the recording sheet S.

Further, this image forming apparatus is provided with a backup roller cooling device 16 for cooling the backup roller 9 and a control unit CONT1 thereof. Cooling device 1
6 includes a cooling fan 161, a support member 162 thereof, and a sensor 163. The cooling fan 161 is provided on the backup roller 9 and can cool the roller 9. The sensor 163 is disposed in contact with the roller 9,
The surface temperature of the object. The detected value is in the control unit CONT1.
(See FIG. 7A). The cooling fan 161 is turned on and off by an instruction signal from the control unit CONT1 based on the detection value from the sensor 163 (see FIG. 7A).
The roller 9 is cooled by the cooling fan 161 being turned on by the control unit CONT1. Thus, even when the surface of the backup roller 9 is heated, the temperature can be lowered to the glass transition temperature Tg of the toner or lower or lower.

The cleaning blade 10 is disposed in contact with the intermediate transfer drum 6. Thereby, the secondary transfer residual toner remaining on the intermediate transfer drum 6 without being secondary-transferred to the recording paper S can be removed. The control unit CONT1 is mainly composed of a computer. The control unit CONT1 is shown in FIGS.
As shown in (A), the cooling fan 161 and the sensor 16
3 is connected. The control unit CONT1 controls the toner image 2 on the second surface (back surface) of the recording paper S in the duplex image forming mode.
In the next transfer, the cooling device 16 is operated based on an instruction signal from a main control unit (see FIG. 7A) for controlling the operation of the entire image forming apparatus, and thereby the surface of the backup roller 9 is brought to a predetermined temperature. Can be maintained. Although the control unit CONT1 is provided separately from the main control unit, it may be included in the main control unit.

The paper feeding section 200 has transport paths 201 and 20
2. A sheet feed roller group 203 and a sheet tray 204 are provided. The sheet tray 204 can store the recording paper S. The paper feed roller group 203 can send the recording paper S in the sheet tray 204 to the transport path 201. The transport path 201 transports the recording paper S sent from the sheet tray 204 to the transport path 20.
2 can be transported. The transport path 202 can guide the recording paper S transported from the transport path 201 to the timing roller pair 12. Thereby, the paper supply unit 200 can supply the recording paper S in the sheet tray 204 to the image forming unit 100.

The re-feeding section 300 includes transport paths 301 and 30
2, a switching claw 303, an intermediate tray 304, and a roller group 305 are provided. The switching claw 303 can switch the recording paper S discharged from the image forming unit 100 so as to guide the recording paper S toward the discharge tray 15 or the transport path 301. Thus, the recording sheet S is directed toward the discharge tray 15 when forming an image on the second side in the single-sided image forming mode or the double-sided image forming mode, and is formed when forming an image on the first side in the double-sided image forming mode. S can be guided toward the transport path 301. The transport path 301 can transport the recording paper S discharged from the discharge roller pair 14 to the intermediate tray 304. The recording paper S is stored in the intermediate tray 304 such that the image surface (first surface) faces downward. The roller group 305 includes the intermediate tray 3
The recording paper S accommodated in the printer 04 can be sent to the transport path 302. Here, the front and back of the recording paper S are reversed. Conveyance path 302
Transfer the recording paper S sent from the intermediate tray 304 to the transport path 2
02 can be transported. As a result, the re-feeding unit 300 can turn the recording paper S discharged from the image forming unit 100 upside down and supply the recording paper S to the image forming unit 100 again.

Next, the operation of forming an image on the first and second surfaces of the recording sheet S in the double-sided image forming mode will be described. According to this image forming apparatus, the photoconductor 1 is driven to rotate, and is uniformly charged by the charging device 2. The laser beam L emitted from the exposure device 3 exposes the charged area to form an electrostatic latent image. This electrostatic latent image is transferred to the liquid developing device 4 as the photosensitive member 1 rotates.

In the liquid developing device 4, a part of the developing roller 41 is immersed in the liquid developer D, and the developer D is pumped up with the rotation of the developing roller 41 to be used for an electrostatic latent image on the photosensitive member 1. This is developed under application of a developing bias voltage to obtain a visible toner image. The visible toner image moves to the squeeze roller 5 as the photoconductor 1 rotates, and the excess carrier liquid on the photoconductor 1 is removed by the squeeze roller 5. Thereafter, the visible toner image T1 moves to the primary transfer portion P1.

In the primary transfer section P1, a transfer voltage is applied, and the toner image T1 on the photosensitive member 1 is electrostatically primary-transferred onto the intermediate transfer drum 6. The transferred toner image T2 is conveyed to the secondary transfer portion P2 while being heated on the intermediate transfer drum 6 by the heat source 61. Since the toner image T2 is thermally secondary-transferred onto the recording paper S, the present invention is not limited to this. For example, if a toner having a melting point temperature of 90 ° C. is adopted and the system speed (the peripheral speed of the intermediate transfer drum 6) is 300 mm / sec, , To about 150 ° C.

The toner image T2 conveyed to the transfer section P2
Is secondarily transferred onto the recording paper S and fixed. The recording sheet S is sent out of the sheet tray 204 by the sheet feeding roller group 203, and is sent to the timing roller pair 12 through the conveyance paths 201 and 202. The timing roller pair 12 sends out the recording paper S in synchronization with the toner image T2 on the drum 6. The recording paper S is supported by the guide plate 11 and
Move to 2.

The toner image T2 on the drum 6 transferred to the secondary transfer portion P2 is sent to the secondary transfer portion P2 in synchronization with the toner image T2, and is pressed against the drum 6 by the backup roller 9. The recording paper S comes into contact with the recording paper S in a molten state, adheres to the recording paper S due to a difference in releasability between the drum 6 and the recording paper S, is separated from the drum 6, and is transferred from the drum 6 to the first surface of the recording paper S. Thermal secondary transfer is performed and fixed. In this thermal secondary transfer, the control unit CONT1 does not operate the cooling device 16.

The intermediate transfer drum 6 retains transfer residual toner remaining on the recording paper S without being secondary-transferred. The transfer residual toner is collected by the cleaning blade 10. Although the cleaning blade 10 having a blade shape is employed here, a cleaning roller having a roller shape may be employed. The photoreceptor 1 has an intermediate transfer drum 6
The remaining transfer toner remaining without being primary-transferred is retained by the cleaning blade 7. Then, the photoreceptor 1 from the eraser lamp 8
Is irradiated with light, and the charges on the photoreceptor 1 are removed by light.

After the toner image T2 is transferred and fixed on the recording paper S, the recording paper S is supported by the guide plate 13 and is transferred to the switching claw 303 by the paper discharge roller pair 14. The recording paper S is guided by the switching claw 303, passes through the conveyance path 301, and is stored in the intermediate tray 304. The recording paper S in the intermediate tray 304 is re-fed by a group of rollers 305 and sent to the timing roller pair 12 through the conveyance paths 302 and 202. At about this time, the toner image T1 for the second surface has been formed in the same manner as described above, and has been primarily transferred onto the intermediate transfer drum 6. The timing roller pair 12 sends out the recording paper S in synchronization with the toner image T2 for the second surface on the drum 6. The recording paper S is supported by the guide plate 11 and moves again to the transfer portion P2.

FIG. 2 shows a state of an image forming operation on the second surface of the recording sheet S on which the image is formed on the first surface in the image forming apparatus shown in FIG. As shown in FIG. 2, the toner image T2 on the intermediate transfer drum 6 transferred to the secondary transfer portion P2
Is now in a molten state. The recording paper S sent to the secondary transfer portion P2 is pressed against the drum 6 by the rollers 9. The toner image in the molten state pressed against the recording sheet S is formed by the difference in the releasability between the drum 6 and the recording sheet S.
The recording medium S is separated from the drum 6, is thermally secondary-transferred from the drum 6 to the second surface of the recording paper S, and is fixed. In this thermal secondary transfer, the cooling device 16 is operated by the control unit CONT1, and the surface of the roller 9 is cooled by the cooling device 16, so that the toner image on the first surface is not melted again. The temperature is maintained at or below Tg. Therefore, the amount of heat applied to the first side image (toner image) from the backup roller 9 is suppressed, whereby the gloss of the first side image is easily maintained as it is, and the difference in gloss between the two sides of the recording paper S is suppressed. The image is similarly formed on both sides.

Although the backup fan 9 is cooled by using the cooling fan 161 here, other cooling means may be used. The recording sheet S is supported by the guide plate 13 after the toner image T2 is transferred and fixed to the second surface, and is discharged to the discharge tray 15 by the discharge roller pair 14. At this time, the switching claw 3
Numeral 03 denotes a posture for guiding the recording paper S to the discharge tray.

The intermediate transfer drum 6 retains the transfer residual toner remaining on the recording paper S without being secondary-transferred. The transfer residual toner is collected by the cleaning blade 10. The photoreceptor 1 retains transfer residual toner remaining on the intermediate transfer drum 6 without being primarily transferred. The transfer residual toner is collected by the cleaning blade 7. After that, light is irradiated from the eraser lamp 8 to the photoconductor 1,
The charge on the photoreceptor 1 is removed by light. Then, the photoconductor 1 is prepared for the next image formation.

FIG. 3 is a side view of a main part of a modified example of the image forming apparatus shown in FIG. 1, and FIG. 4 is a view showing the recording paper on which the image is formed on the first side of the image forming apparatus shown in FIG. FIG. 3 is a diagram illustrating a state when an image is formed. The image forming apparatus shown in FIG. 3 and FIG. 4 is different from the image forming apparatus shown in FIG. 1 in that a cooling device 16 and a control unit CONT1 thereof and a pressing force adjusting device 17 and a control unit CONT2 thereof are provided in place of the pressing device 90. is there. The other parts are the same as those of the apparatus shown in FIG. 1, and the same parts are denoted by the same reference numerals.

Hereinafter, the image forming apparatus shown in FIGS. 3 and 4 will be described focusing on the differences from the image forming apparatus shown in FIG. The pressing force adjusting device 17 of the image forming apparatus supports the backup roller 9 so as to reciprocate toward the intermediate transfer drum 6 or away from the drum 6.
b, and a driving device for moving the support member 9b to a support member position for obtaining a target backup roller pressing force.

Here, the support member 9b is a member which also serves as a bearing member for rotatably supporting the shaft 9a of the backup roller 9, and is fitted to a guide member (frame member here) 172 arranged at a fixed position and can be moved up and down. is there. Support member 9b
Is a cam device here. The cam device is
A spring 173 incorporated in the frame 172 and abutting on the support member 9b;
An elevating piston 174 supporting the lower end of the piston 3 and a piston rod 175 connected to the piston and extending outside the frame;
And an eccentric disk cam 171 that contacts the lower end 175a of the rod 175.

The cam 171 is connected and fixed to a cam shaft 171a driven by a motor m1, and a disk-shaped shutter plate 171b is also connected and fixed to the shaft 171a. Therefore, the cam 171 and the shutter plate 171b are
1 is rotationally driven. A light transmitting portion 171c is formed at a part of the peripheral portion of the shutter 171b, and a photo interrupter type photo switch S
W1a and SW1b are facing. These switches are arranged on the diameter line of the shutter plate 171b at a center angle interval of 180 ° C.

The switches SW1a and SW1b and the motor m1 are connected to a control unit CONT2 (see FIG. 7B).
It is connected to the. When a rotation instruction signal is sent from the control unit CONT2 to the motor m1, the motor rotates, and the cam 171 is rotated accordingly. At this time, the shutter plate 171
b is also turned at the same time, whereby the switch is turned on when the switch SW1a reaches the light transmitting portion 171c (see FIG. 3), and the switch is turned on when the switch SW1b reaches the light transmitting portion 171c (see FIG. 4). And its output signal is sent to the control unit CONT2. Based on this signal, the control unit CONT2 sends a stop instruction signal to the motor m1 to stop the rotation of the motor m1. As a result, the cam 171 switches the light transmitting portion 171c of the shutter plate 171b to the switch SW.
1a or one of two positions facing SW2a. In addition, when the rotation instruction signal is output again from the control unit CONT2 in the state of being arranged as described above, the rotation can be started.

Therefore, in this image forming apparatus, when forming an image on one side of the recording sheet S in the single-sided image forming mode, or when forming an image on the first side of the recording sheet S in the double-sided image forming mode, the control unit CONT2 is mainly used. Control unit (Fig. 7
The operation of the motor m1 is controlled based on the instruction signal from (B), and the position of the cam 171 is set at a position where the switch SW1a faces the light transmitting portion 171c of the shutter plate 171b. Thus, as shown in FIG. 3, a state is set in which the amount of pushing up of the piston rod 175 by the cam 171 is increased, so that the backup roller 9 is relatively strongly pressed toward the intermediate transfer drum 6.

In this setting state, the intermediate transfer drum 6
The recording sheet S is fed to the thermal secondary transfer section P2 in synchronization with the primary transfer toner image T2 formed thereon, and the toner image T2 on the intermediate transfer drum 6 is formed on one side or both sides of the recording sheet S. In the mode, the image is thermally secondary-transferred onto the first surface of the recording sheet S and fixed. Thus, the toner image T3 on one side or the first side of the recording paper S is formed.

In the double-sided image forming mode, the second sheet of the recording paper S on which an image has been formed on the first side by thermal secondary transfer has already been formed.
When forming an image on the surface, the control unit CONT2 controls the operation of the motor m1 so that the switch SW1b switches the shutter plate 1
The position of the cam 171 is set at a position facing the light transmitting portion 171c of the cam 71b. Thus, as shown in FIG.
A state is set in which the push-up amount of the piston rod 175 by 71 is reduced, so that the backup roller 9 is relatively weakly pressed toward the intermediate transfer drum 6.

In this setting state, the intermediate transfer drum 6
The recording paper S is re-supplied to the thermal secondary transfer portion P2 in synchronization with the primary transfer toner image T2 for the second surface formed thereon, and the toner image T2 on the intermediate transfer drum 6 is The heat is secondarily transferred to the second surface and fixed. Thus, the second of the recording paper S
The toner image T4 is also formed on the surface. In this image forming apparatus, when the image T4 is formed on the second surface of the recording sheet S in the double-sided image forming mode, the pressing force of the backup roller 9 against the intermediate transfer drum 6 of the recording sheet S is changed to the image T3 on the first surface. Therefore, the nip width between the recording paper S and the intermediate transfer drum 6 and the nip width between the recording paper S and the backup roller 9 are smaller than when the image is formed on the first surface of the recording paper. Therefore, heat is less likely to be transmitted from the intermediate transfer drum 6 to the first surface image (toner image) T3 of the recording paper S, and even if the backup roller 9 is heated, the heat is transferred to the first surface image of the recording paper S. It becomes difficult to participate in T3. As a result, the first surface image T3 is maintained at a temperature equal to or lower than the glass transition temperature Tg of the toner so as not to remelt. Therefore the first
The gloss of the surface image is easily maintained as it is, and the difference in gloss between the two-sided images T3 and T4 of the recording paper S is suppressed, so that the image can be formed on both sides in the same manner.

When the toner image is thermally secondary-transferred onto the second surface of the recording paper in the double-sided image forming mode, the mutual contact nip width between the recording paper S and the intermediate transfer drum 6 is slightly reduced.
Since the primary transfer toner image T2 for the second surface is sufficiently heated on the drum 6 side, it is thermally secondary-transferred to the second surface of the recording paper without any trouble.
Be established. In addition, the toner image T2 on the intermediate drum to be transferred to the second surface of the recording sheet can still receive heat via the recording sheet S when the backup roller 9 has already been heated. Is thermally secondary-transferred to the second surface of the recording paper without any trouble and is fixed.

The pressing force adjusting device 17 described above may be used together with the cooling device 16 shown in FIG. FIG. 5 is FIG.
It is a side view of a main part of another modification of the image forming apparatus shown in FIG.
FIG. 6 is a diagram illustrating a state in which an image is formed on the second surface of the recording paper having the image formed on the first surface in the image forming apparatus illustrated in FIG.

The image forming apparatus shown in FIG. 5 and FIG.
In the image forming apparatus shown in FIG. 1, two backup rollers 181 and 182 are employed in place of the backup roller 9, and a roller switching device 18 and a control unit CONT3 are provided in place of the cooling device 16 and its control unit CONT1 and the pressing device 90. It is a thing. The other parts are the same as those of the apparatus shown in FIG. 1, and the same parts are denoted by the same reference numerals.

Hereinafter, the image forming apparatus shown in FIGS. 5 and 6 will be described focusing on the differences from the image forming apparatus shown in FIG. One of the backup rollers 181 and 182 is used for forming an image on one side of a recording sheet in the one-sided image forming mode and for forming an image on the first side of the recording sheet in the two-sided image forming mode, so-called a first roller.
This is a surface roller. The roller 182 is a second surface roller used when forming an image on the second surface of the recording paper in the double-sided image forming mode. The surface of the backup roller 182 is formed harder than the surface of the backup roller 181.

The roller switching device 18 includes a V-shaped support member 185 for supporting the first surface roller 181 and the second surface roller 182, and a driving device therefor. The lower end of the V-shaped support member 185 is swingably supported by a fulcrum shaft 185a, and the roller 181 is supported on one of the two upper ends and the roller 182 on the other.
The roller 181 has its shaft 181a rotatably supported by a bearing member 181b.
The spring 181s fitted in the guide hole 181c provided in the guide hole 185 so as to be able to move up and down, and further fitted in the guide hole 181c.
Applies a predetermined pushing force to the bearing member 181b. The roller 182 has a shaft 182a rotatably supported by a bearing member 182b. The bearing member is fitted in a guide hole 182c provided in a support member 185 so as to be able to move up and down. The fitted spring 182s applies a predetermined pushing force to the bearing member 182b. The pushing forces of the springs 181s and 182s are set to be the same.

The driving device of the support member 185 is a cam device here. The cam device includes an eccentric disk cam 183. The cam 183 is supported by a camshaft 183a at a fixed position, and can be driven to rotate by a motor m2, for example, in the direction A in the figure. A spring 184 is connected on one side to a spring locking member 185b on the support member 185, and on the other side is connected to a spring locking member 183b on the cam side. The spring locking member 183b is provided at a position where the camshaft 183a and the center axis coincide. The support member 1 is
85 is always drawn to the cam 183 side in the X direction in the figure,
It is always in contact with the cam 183.

The support member 185 is driven by the rotation of the cam 183 driven by the motor m2 so that the backup roller 181 having a relatively low surface hardness is brought into contact with the transfer member, as shown in FIG. As shown in FIG. 6, the position where S is pressed against the intermediate transfer drum 6, or the backup roller 182 having relatively high surface hardness is the transfer member pressing position as shown in FIG. The position at which the transfer drum 6 is pressed against the transfer drum 6 can be selectively set.

A limit switch SW2a which is turned on when the support member 185 assumes the position shown in FIG. 6 and a limit switch SW2b which is turned on when the support member 185 assumes the position shown in FIG. The switches SW2a and SW2b and the motor m2 are connected to the control unit CONT3 (see FIG. 7C).

That is, according to the roller switching device 18, a rotation instruction signal is sent from the control unit CONT3 to the motor m2 in response to an instruction from the main control unit (see FIG. 7C), so that the motor m2 rotates. Accordingly, the cam 183 is rotated, and the roller 181 is disposed at the recording paper pressing position or the roller 182 is disposed at the recording paper pressing position. At this time, the switch SW2b is turned on (in the case shown in FIG. 5) or the switch SW2a is turned on (in the case shown in FIG. 6), and the output signal is sent to the control unit CONT3. Based on this signal, the control unit CONT3 sends a stop instruction signal to the motor m2,
The rotation of the motor m2 is stopped. Thus, the switching device 18 can arrange the roller 181 or the roller 182 at the recording paper pressure contact position.

In this image forming apparatus, when forming an image on one side of the recording sheet S in the single-sided image forming mode, or when forming an image on the first side of the recording sheet S in the double-sided image forming mode, the control unit CONT3 controls the main control unit. The operation of the motor m2 is controlled based on the instruction signal from the section (see FIG. 7C), and the position of the cam 183 at which the switch SW2b is turned on by the support member 185 is set. Thus Figure 5
As shown in FIG. 5, the state in which the amount of pushing of the supporting member 185 by the cam 183 is large, in other words, the surface stiffness is relatively low. The backup roller 181 which can make the size relatively large is disposed at the recording paper pressure contact position.

In this setting state, the intermediate transfer drum 6
The recording sheet S is fed to the thermal secondary transfer section P2 in synchronization with the primary transfer toner image T2 formed thereon, and the toner image T2 on the intermediate transfer drum 6 is formed on one side or both sides of the recording sheet S. In the mode, the image is thermally secondary-transferred onto the first surface of the recording sheet S and fixed. Thus, the toner image T3 on one side or the first side of the recording paper S is formed.

In the double-sided image forming mode, the second sheet of the recording paper S on which an image has been formed on the first side by thermal secondary transfer has already been formed.
When an image is formed on the surface, the control unit CONT3 controls the operation of the motor m2 so that the switch SW2a
The position of the cam 183 to be turned on in step 5 is set. Thus, as shown in FIG. 6, a state in which the amount of pushing of the support member 185 by the cam 183 is reduced, in other words,
A backup roller 182 is disposed at a recording paper pressing position for relatively reducing the mutual nip width between the recording paper S and the intermediate transfer drum under a pressing force of a spring 182s having a relatively high surface hardness and thus the same force as the spring 181s. Is done.

In this setting state, the intermediate transfer drum 6
The recording paper S is re-supplied to the thermal secondary transfer portion P2 in synchronization with the primary transfer toner image T2 for the second surface formed thereon, and the toner image T2 on the intermediate transfer drum 6 is The heat is secondarily transferred to the second surface and fixed. Thus, the second of the recording paper S
The toner image T4 is also formed on the surface. In this image forming apparatus, when the image T4 is formed on the second surface of the recording sheet S in the double-sided image forming mode, the recording sheet S and the drum 6 are mutually pressed by the backup roller 182 pressing the recording sheet S against the intermediate transfer drum 6. Since the contact nip width is smaller than when the first surface image T3 is formed, heat is less likely to be transmitted from the intermediate transfer drum 6 to the first surface image (toner image) T3 of the recording paper S. Further, since the roller 182 is disposed at the recording paper pressure contact position only when the toner image is transferred to the second surface of the recording paper, even if the temperature has not been raised, or even if the temperature has already been used and the temperature has been raised. Temperature is low. Therefore, much heat is not applied from the roller 182 to the recording paper first surface image T3. As a result, the toner image T3 on the first surface is not re-melted,
The temperature is maintained at or below the glass transition temperature Tg of the toner. As a result, the gloss of the first surface image T3 is easily maintained as it is, and the difference in gloss between the two-sided images T3 and T4 of the recording paper S is suppressed, so that the image can be formed on both sides in the same manner.

When the toner image is transferred to the second side of the recording paper in the double-sided image forming mode, the mutual contact nip width between the recording paper S and the intermediate transfer drum 6 is slightly reduced.
Since the primary transfer toner image T2 for the second surface is sufficiently heated on the drum 6 side, it is thermally secondary-transferred to the second surface of the recording paper without any trouble.
Be established. 5 and 6, in the image forming apparatus, springs 181s and 1s added to the backup rollers 181 and 182 are used.
By changing the surface hardness of both rollers while keeping the pressing force of 82 s the same, the nip width of the mutual contact between the recording paper S and the intermediate transfer drum 6 was changed. The contact nip width may be similarly changed by making the pressing force of the spring 182s smaller than the pressing force. Alternatively, the same nip width change may be achieved by a combination of both adjustment of the surface hardness and adjustment of the spring force.

The image forming apparatuses shown in FIGS. 1 to 6 employ a liquid developing method as a developing method, but the present invention can be applied to an image forming apparatus of a dry developing method.

[0075]

According to the present invention, the electrostatic latent image formed on the electrostatic latent image carrier is developed into a visible toner image, and the visible toner image is temporarily transferred onto an intermediate transfer member once. Thereafter, an image forming unit that thermally secondary-transfers the image onto the transfer member pressed against the intermediate transfer member by the backup roller, and a first surface of the transfer member (one side of the transfer member in the single-sided image forming mode, A transfer object supply unit for supplying the transfer object to the thermal secondary transfer unit to form an image on the transfer target first surface (including both the first surface of the transfer object); and image formation by thermal secondary transfer on the first surface An image forming apparatus comprising: a transfer object re-supply unit for re-supplying the transfer object to the thermal secondary transfer unit in order to form an image on the second surface of the transferred transfer object; When an image is formed on the second surface of the transfer object on which the image has been formed, It is possible to provide an image forming apparatus capable of similarly forming images on both sides to suppress different.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an operation state when an image is formed on a second surface of a recording sheet having an image formed on a first surface in the image forming apparatus illustrated in FIG. 1;

FIG. 3 is a partial side view of a modification of the image forming apparatus shown in FIG.

4 is a diagram illustrating an operation state when an image is formed on a second surface of a recording sheet on which an image has been formed on the first surface in the image forming apparatus illustrated in FIG. 3;

FIG. 5 is a side view of a part of another modification of the image forming apparatus shown in FIG. 1;

6 is a diagram illustrating an operation state when an image is formed on a second surface of a recording sheet having an image formed on the first surface in the image forming apparatus illustrated in FIG. 5;

FIG. 7A is a schematic block diagram of a control circuit for operating the cooling device of the image forming apparatus shown in FIG. 1, and FIG. 7B controls the pressing force adjusting device of the image forming apparatus shown in FIG. FIG. 5C is a schematic block diagram of a control circuit for controlling the roller switching device of the image forming apparatus shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Image forming unit 1 Photoconductor (one example of electrostatic latent image carrier) 2 Corona charging device 3 Exposure device 4 Liquid developing device 41 Developing roller 42 Developer tank 5 Squeeze roller 6 Intermediate transfer drum (One example of intermediate transfer member) ) 61 heat source 7 cleaning blade 8 eraser lamp 9 backup roller 9a backup roller shaft 9b bearing member 90 backup roller pressure contact device 91 pressure contact spring 92 bearing member support frame 10 cleaning blade 11 guide plate 12 timing roller pair 13 guide plate 14 discharge roller pair 15 Discharge tray 16 Backup roller cooling device 161 Cooling fan 162 Support member 163 Sensor CONT1 Control unit 17 Pressure contact force adjusting device 171 Eccentric disk cam 171a Cam shaft 171b Shutter plate 171c Light transmitting unit 172 Guide member 1 73 Pressure contact spring 174 Piston 175 Piston rod 175a Rod lower end SW1a, SW1b Photo switch m1 Motor CONT2 Control unit 18 Roller switching device 181 First surface roller 182 Second surface roller 181a, 182a Roller shaft 181b, 182b Bearing member 181c 182c Guide hole 181s, 182s Spring 183 Eccentric disk cam 183a Cam shaft 183b, 185b Spring locking member 184 Spring 185 Support member 185a Support shaft SW2a, SW2b Limit switch m2 Motor CONT3 Control unit 200 Feeding unit (transferring unit supply unit) 201, 202 Transport path 203 Paper feed roller group 204 Sheet tray 300 Refeed section (one example of transfer medium resupply section) 301, 302 Transport path 303 Switching claw 304 Intermediate Tray 305 Roller group P1 Primary transfer section P2 Thermal secondary transfer section (recording paper pressure contact position) PW1, PW2, PW3, PW4 Power supply L Laser light D Liquid developer T1, T2, T3, T4 Toner image S Recording paper (receiving Transcript)

Claims (5)

[Claims] An electrostatic latent image formed on an electrostatic latent image carrier is developed into a visible toner image, and the visible toner image is firstly transferred onto an intermediate transfer member, and then is transferred to a backup roller. An image forming unit for performing a thermal secondary transfer to a transfer-receiving body pressed against the intermediate transfer body; and an image forming unit for supplying the transfer-receiving body to the thermal secondary transfer unit for forming an image on the first surface of the transfer receiving body. A transfer body supply unit, and the heat transfer unit for forming an image on the second surface of the transfer target image formed on the first surface by the thermal secondary transfer;
In an image forming apparatus including a transfer medium re-supplying unit for re-supplying a transfer object to a next transfer unit, an apparatus for cooling the backup roller and forming an image on a second surface of the transfer object on which an image is formed on the first surface. A control unit that operates the backup roller cooling device so as to cool the backup roller. 2. An electrostatic latent image formed on an electrostatic latent image carrier is developed into a visible toner image, and the visible toner image is temporarily transferred onto an intermediate transfer member by a primary transfer method. An image forming unit for performing a thermal secondary transfer to a transfer-receiving body pressed against the intermediate transfer body; and an image forming unit for supplying the transfer-receiving body to the thermal secondary transfer unit for forming an image on the first surface of the transfer receiving body. A transfer body supply unit, and the heat transfer unit for forming an image on the second surface of the transfer target image formed on the first surface by the thermal secondary transfer;
An image forming apparatus provided with a transfer medium re-supply section for re-supplying the transfer medium to the next transfer section, a pressing force adjusting apparatus for adjusting a pressing force of the transfer medium to the intermediate transfer body by the backup roller; When an image is formed on the second surface of the image-transferred object, the pressure of the backup roller against the intermediate transfer member by the backup roller is lower than that during the thermal secondary transfer of the toner image to the first surface. And a control unit for controlling the press-contact force adjusting device. 3. An electrostatic latent image formed on an electrostatic latent image carrier is developed into a visible toner image, and the visible toner image is once primarily transferred onto an intermediate transfer member, and then is backed up by a backup roller. An image forming unit for performing a thermal secondary transfer to a transfer-receiving body pressed against the intermediate transfer body; and an image forming unit for supplying the transfer-receiving body to the thermal secondary transfer unit for forming an image on the first surface of the transfer receiving body. A transfer body supply unit, and the heat transfer unit for forming an image on the second surface of the transfer target image formed on the first surface by the thermal secondary transfer;
An image forming apparatus including a transfer medium re-supplying unit for re-supplying the transfer medium to the next transfer unit; a first surface roller for forming an image on a first surface of the transfer medium as the backup up roller; A second surface roller for forming an image on the second surface of the body, wherein the second surface roller is formed by pressing a transferred body against the intermediate transfer body. The nip width between the transfer object and the intermediate transfer member is adjusted by pressing the transfer member against the intermediate transfer member by the first surface roller. In addition, when the image is formed on the first surface of the transfer object, the roller for the first surface is placed at the pressure contact position of the transfer object, and the image on the second surface of the transfer object is formed. In order to arrange the rollers for the second surface at the pressure contact positions of the transfer object at the time of formation, Image forming apparatus characterized by over La switching device is provided. 4. The surface hardness of the second surface roller is equal to the first surface hardness.
The image forming apparatus according to claim 3, wherein the surface hardness of the surface roller is larger than that of the surface roller. 5. The first surface roller is pressed toward the intermediate transfer member by a first pressing device in a state where the first surface roller is disposed at the transfer member pressing position, and the second surface roller is fixed to the transfer member. 5. A pressing force by the second pressing device toward the intermediate transfer member in a state where the pressing member is disposed at the pressing position, wherein a pressing force by the second pressing device is weaker than a pressing force by the first pressing device.
The image forming apparatus as described in the above.