JPH10221894A - Both-side image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the rush-in posture of a recording material with respect to a fixing unit and to surely obtain an excellent both-side image without image irregularities and paper wrinkling by simple constitution. SOLUTION: This device is provided with a first image carrying and feeding body 1 carrying and feeding a first image T1 , a second image carrying and feeding body 2 carrying and feeding a second image T2 and a bending transfer means 3 transferring the respective images T1 and T2 of the carrying and feeding bodies 1 and 2 on both sides of the recording material 4 in an area where the bodies 1 and 2 are brought into contact with each other or made to approach each other and imparting bending force to the material 4 in this transfer area and before and behind the area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as a printer, and more particularly to an improvement in a double-sided image forming apparatus capable of forming a double-sided image.

[0002]

2. Description of the Related Art As a conventional double-sided image forming apparatus capable of forming a double-sided image, a first image formed on a latent image carrier such as a photoreceptor is transferred and fixed to a first surface of a sheet. Is reversed, and the sheet is fed again, and subsequently, the second image formed on the latent image carrier is transferred and fixed to the second surface of the sheet. However, in this method, since the image forming unit is caused to pass the paper twice, the productivity per sheet is reduced by one in one-side recording.
/ 2 or less, paper curls at the first fixing, transfer failure at the second transfer and fixing, paper wrinkles,
There are various problems, such as the occurrence of jams in the conveyance path and the noise when reversing the paper by reversing the paper.

As a double-sided image forming apparatus which solves such a problem, two photoconductors are arranged to face each other, and a first toner image (first image) and a second toner image (second image) are formed on each photoconductor.
Are formed, and the first toner image and the second toner image on each photoreceptor are simultaneously transferred onto both sides of a sheet (for example, JP-A-63-63057 and JP-A-2-63057). 259670).

[0004]

However, this type of double-sided image forming apparatus has the following technical problems. First, since transfer is performed using a potential difference between photoconductors, transfer efficiency is lower than when a transfer device is used. Second, it is difficult to adjust the gap between the photoconductors between the hard photoconductors. If the gap is small, an impact occurs when the paper enters, and the image is disturbed. If the gap is wide, transfer failure occurs. Or adjust the gap for each sheet thickness. Third, since the photosensitive member and the fixing device cannot be arranged close to each other because of the influence of heat, and unless a special conveying means is provided, the sheet for conveying the unfixed double-sided image sheet from the transfer position to the fixing device is used. Posture control becomes difficult, the posture of the sheet entering the fixing device is not stable, and toner image disturbance and paper wrinkles are likely to occur.

In order to solve such a technical problem,
As shown in FIG. 7, the present applicant primarily transfers the first image T1 on the first photoconductor 201 to the first intermediate transfer belt 202 via the primary transfer device 203, and on the other hand, on the second photoconductor 211. Is primarily transferred to the second intermediate transfer belt 212 via the primary transfer device 213, and the transfer roll pair 220 sandwiching the intermediate transfer belts 202 and 212
A technique for simultaneously transferring the images T1 and T2 on the respective intermediate transfer belts 202 and 212 to both sides of the sheet 230 has already been proposed (for example, Japanese Patent Application No. 8-108449).
According to this type, the use of an intermediate transfer member such as the intermediate transfer belts 202 and 212 causes the final transfer position on the sheet 230 to be arranged close to the fixing device 240.
The degree of freedom in the layout of the apparatus can be increased, and the thickness of the sheet can be absorbed by giving the transfer roll pair some elasticity. For this reason, it is possible to obtain a double-sided image with little image disturbance at the same recording speed as that for one side per sheet.

However, in the above-described prior art, if the paper has a relatively high stiffness (surface rigidity), the discharging posture of the paper passing through the transfer roll pair 220 is relatively stable, but the paper having a weak stiffness can be obtained. In this case, the discharging posture of the sheet passing through the transfer roll pair 220 is still unstable, and a request for further stabilizing the entering position of the sheet into the fixing device 240 has been found. In order to solve such a technical problem, the intermediate transfer belt 212 is routed to the vicinity of the fixing device as shown by a virtual line in FIG.
30 while being held by the intermediate transfer belt 212.
0, the discharge posture of the sheet 230 while moving from the end of the intermediate transfer belt 212 to the fixing device 240 is still unstable.
Since the area of the sheet that is in contact with the surface of the intermediate transfer belt 212 from the transfer portion 20 is wide, if a speed mismatch occurs between the sheet 230 that has entered the fixing device 240 and the intermediate transfer belt 212, the image disturbance will rather occur. There is also a technical problem that is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problem, and has a simple structure to stabilize the posture of a recording material entering a fixing device and to prevent image disturbance and paper wrinkles from occurring. An object of the present invention is to provide a double-sided image forming apparatus capable of reliably obtaining a good double-sided image.

[0008]

That is, as shown in FIG. 1A, a double-sided image forming apparatus according to the present invention comprises: a first image carrying / transporting body 1 carrying a first image T ₁ ; In a region where the second image carrier _{2 on} which the second image T ₂ is carried and conveyed, and the first image carrier 1 and the second image carrier 2 are in contact with or close to each other, both surfaces of the recording material 4 And bending transfer means 3 for transferring the images T ₁ , T ₂ on the image carrying members ₁ , ₂ , and applying a bending force to the recording material 4 before and after the transfer area. It is a feature.

In such technical means, the first image carrier 1 and the second image carrier ₂ are appropriately selected as long as they carry the images T ₁ and T ₂ , respectively. No problem. For example, only the image forming carrier 5 on which the images T ₁ and T ₂ are formed and supported, or the image forming carrier 5 and the image forming carrier 5 which are disposed to face the image forming carrier 5 and are supported. A mode in which each of the images T ₁ and T ₂ on the body 5 is temporarily transferred by the primary transfer means 7, or one is only the image forming carrier 5 and the other is the image A combination mode of the forming carrier 5 and the intermediate transfer body 6 is exemplified. From various viewpoints of this type, from the viewpoint of effectively eliminating the image quality difference between the two-sided images, the first image T ₁ and the second image T ₂ are each formed of only the image forming carrier 5. Alternatively, it is preferable that each of them is a combination of the image forming carrier 5 and the intermediate transfer body 6.

Here, an embodiment in which both the first image carrier 1 and the second image carrier 2 are provided with the image forming carrier 5 and the intermediate transfer member 6 will be described. The carrier 5 may be in any form (drum-shaped, belt-shaped, or a combination thereof) as long as it can carry a monochrome image or a color image. Also, various methods such as an electrophotographic method, an electrostatic transfer method, and an ink jet method can be adopted. In addition, each image carrier 1 and 2
As for the intermediate transfer member 6, if the image T ₁ and T ₂ from each image forming carrier 5 can be temporarily held,
Any form such as a belt shape or a drum shape is acceptable.

At this time, from the viewpoint of securing the degree of freedom in layout, each of the intermediate transfer members 6 is preferably in the form of a belt, but one may be in the form of a drum and the other may be in the form of a belt. The two intermediate transfer members 6 may have a drum shape as long as they have a certain degree of elasticity in the radial direction.

In an embodiment in which each of the image carrying carriers 1 and 2 is only the image forming carrier 5, from the viewpoint of securing the degree of freedom in layout, each of the image forming carriers 5 is required. Is preferably a belt-like member, but one may be a drum-like member and the other may be a belt-like member, and if both members have a certain degree of elasticity in the radial direction, both image-forming carriers 5 may be used. May be made into a drum shape. Incidentally, even in an embodiment in which one of the image carrying carriers 1 and 2 is only the image forming carrier 5, the same may be selected between the other intermediate transferring body 6.

As an embodiment in which the transfer of the recording material 4 to both sides is performed at the same time, for example, in a type in which the first image T ₁ and the second image T ₂ are formed by an electrophotographic method, the first image carrier 1 The first and second images T ₁ and T ₂ carried on the second image carrying / transporting body 2 need to have polarities opposite to each other in a transfer area to the recording material 4. At this time, the first and second
The images T ₁ and T ₂ may be originally made of the opposite polarity material, or the same polarity material may be used, and a polarity inversion means may be provided at an appropriate place to invert the polarity of one of the images.

Further, the bending transfer means 3 only needs to be provided at a portion where the images T ₁ and T ₂ on the image carriers ₁ and ₂ are transferred substantially simultaneously to both surfaces of the recording material 4. In an embodiment in which both the carrying carriers 1 and 2 include the image forming carrier 5 and the intermediate transfer body 6, the bending transfer means 3 is provided in a region where the two intermediate transfer bodies 6 are in contact with or close to each other. do it.

The bending transfer means 3 includes images T ₁ , T 2 on the image carrying members 1, 2 on both sides of the recording material 4.
A function of transferring the T _2, no problem this transfer area and appropriately if it has a function of imparting bending force to the recording material 4 selected in the front and rear. For example, as the bending transfer unit 3, the first image carrying / transporting body 1 and the second image carrying / transporting body 2
And a linear direction connecting the central axes of the transfer roll pairs 3a and 3b may be arranged non-orthogonally with respect to the direction in which the recording material 4 enters. Two transfer rolls 3b (one is omitted) may be arranged so as to face one transfer roll 3a sandwiching the first image carrying transport 1 and the second image carrying transport 2, or A mode in which the transfer rollers 3a and 3b sandwich the first image carrying and transporting body 1 and the second image carrying and transporting body 2 and the hardness of each of the transfer rolls 3a and 3b may be changed.

Next, the operation of the above technical means will be described. Now, as an example, a type in which both the first image carrier 1 and the second image carrier 2 are provided with the image forming carrier 5 and the intermediate transfer body 6 is shown in FIG. In each of the image carrying carriers 1 and 2, the first images T ₁ and T ₂ on the image forming carrier 5 are transferred to each intermediate transfer body 6 by the primary transfer means 7.
Is primarily transferred. Thereafter, as shown in FIG. 1B, the bending transfer unit 3 applies a bending force to the recording material 4 in a region where the intermediate transfer body 6 of each of the image carrying transporters 1 and 2 comes in contact with or approaches. Then, the primary transfer images T ₁ and T ₂ on each intermediate transfer body 6 are secondarily transferred to both surfaces of the recording material 4 on both surfaces of the recording material 4. At this time, when a bending force is applied to the recording material 4, the tip 4 a of the recording material 4 bends and deforms, and the waist (surface rigidity) increases, so that the behavior of the tip of the recording material 4 in the running direction decreases. The attitude of entering the fixing device 8 is stabilized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a schematic configuration of a two-sided image forming apparatus according to a first embodiment of the present invention. In FIG. 1, the two-sided image forming apparatus includes a first image forming unit 20a that forms a first image on a first surface of a sheet P, and a second image forming unit that forms a second image on a second surface of the sheet P. 20b, and both image forming units 20a, 20
and a fixing device 50 for fixing the image on the sheet P that has passed through b.

In this embodiment, each image forming unit 20
Reference numerals a and 20b denote photosensitive drums 21a and 21b and a charging roll 22 for charging the surfaces of the photosensitive drums 21a and 21b.
a, 22b and an exposure device 23 for writing electrostatic latent images for the first and second images on the charged photosensitive drums 21a, 21b.
a, 23b and developing units 24a, 2 for visualizing the electrostatic latent images written on the photosensitive drums 21a, 21b with toner.
4b, intermediate transfer belts 25a and 25b arranged in contact with photosensitive drums 21a and 21b, and photosensitive drums 21a and 2b.
Primary transfer rolls 26a, 26b for primarily transferring toner images T ₁ , T ₂ (for example, normal images in this embodiment) on the intermediate transfer belts 25a, 25b, and photosensitive drums 21a, 2
Cleaners 27a and 27b for removing the residual toner on
And A pair of polarity-reversing corotrons 28 and 29 are disposed on the downstream side of the primary transfer position of the intermediate transfer belt 25b of the second image forming unit 20b so as to face each other with the intermediate transfer belt 25b interposed therebetween. In the present embodiment, each of the intermediate transfer belts 25a and 25b is wound around an appropriate number of holding rolls (one is a driving roll and the other is a driven roll), and is synchronized with the photosensitive drums 21a and 21b. To rotate. Reference numerals 30a, 30b
Is a belt cleaner for removing residual toner on the intermediate transfer belts 25a and 25b. Then, the intermediate transfer belt 2
5a and 25b are polyimide, acrylic, vinyl chloride,
A resin such as polyester, polycarbonate, polyethylene terephthalate (PET) or various rubbers containing an appropriate amount of an antistatic agent such as carbon black to form a volume resistivity of 10 ⁹ to 10 ¹⁴ Ω · cm; The thickness is set to, for example, 0.08 mm.

Further, holding rolls arranged corresponding to areas where the intermediate transfer belts 25a and 25b are in contact with or close to each other are configured as secondary transfer rolls 40a and 40b. Although the transfer can be performed by using a conductive material for both the secondary transfer rolls 40a and 40b, the secondary transfer rolls 40a and 40b can be transferred to a small-sized sheet when the first and second intermediate transfer belts 25a and 25b are in direct contact with each other. Since an excessive current flows between the transfer rolls 40a and 40b and a sufficient transfer electric field cannot be formed, transfer failure occurs, and the intermediate transfer belts 25a and 25b are easily damaged. It is preferable to use a conductive roll coated with a semiconductive or insulating material.

In the present embodiment, the secondary transfer roll 40
For both a and b, a metal shaft coated with EPDM rubber dispersed with carbon black and having a volume resistivity of 10 ⁶ Ω · cm is used.
The transfer bias 41 was applied to the shaft a, and the shaft of the secondary transfer roll 40b was grounded. In addition, as the coating material, a material in which conductive particles (such as carbon black or aluminum) or an ionic conductive agent (such as LiClO ₄ ) are dispersed in polyurethane rubber or silicon rubber can be used. It is preferably set to 10 ⁵ to 10 ⁹ Ω · cm.

In particular, in the present embodiment, as shown in FIG. 3, the secondary transfer rolls 40a and 40b are arranged such that a straight line L connecting their center axes O is non-orthogonal to the direction in which the paper P enters (this embodiment). In the embodiment, the straight line L connecting the central axes O is inclined obliquely to the lower right with respect to the direction in which the sheet P enters, for example, θ = 80 °
(Approximately 50 degrees). The inclination angle θ may be variable according to the thickness of the sheet P.

Furthermore, in this embodiment, the toners T ₁ and T ₂ use negatively charged toner, and the primary transfer roll 26
DC current +10 μA to a and 26b, and AC voltage 8 kV _PP / 60 to polarity inversion corotrons 28 and 29, respectively.
DC voltages of +1 kV and -1 kV were superimposed on 0 Hz, respectively, and a DC voltage of -2 kV was applied to the secondary transfer roll 40a. Also, the first and second photosensitive drums 21a and 21b
And the peripheral lengths of the first and second intermediate transfer belts 25a and 25b were the same. Further, the distance from the secondary transfer position to the fixing device 50 was shorter than the minimum sheet length, and the rotation speed of the fixing roll was equal to or slightly lower than the speed of the intermediate transfer belts 25a and 25b. Further, the fixing device 50 has the same shape of the upper and lower fixing rolls so that the fixing nip is linear, and the heaters are arranged inside thereof. FIG.
Reference numeral 31 denotes a paper tray, and reference numeral 32 denotes a transport roll that transports the paper P.

Next, an image forming process of the double-sided image forming apparatus according to the present embodiment will be described. First photosensitive drum 2
The first toner image T ₁ formed on 1a is transferred onto the first intermediate transfer belt 25a which moves the primary transfer roll 26a at approximately the same speed as the first photosensitive drum 21a. Similarly transferred onto the second intermediate transfer belt 25b by the first second toner image T ₂ the first transfer roller 26b which at the same time as the photosensitive drum 21a is formed on the second photosensitive drum 21b, a second intermediate transfer belt 25b inverts the second polarity of the toner image T ₂ by applying interposed therebetween voltage to the pair of polarity reversal corotron 28 and 29 provided with. Then, the secondary transfer rolls 40a which shift the paper P from the paper tray 31 back and forth with respect to the paper advancing direction at the same time,
After the toner images T ₁ and T ₂ on the intermediate transfer belts 25 a and 25 _b are simultaneously transferred onto the sheet P while being conveyed between the sheets 40 _b and applying a bending force to the sheet P, both sides are simultaneously fixed by the fixing device 50.

Here, the principle of the secondary transfer will be described in detail mainly with reference to FIG. The negative toner image T1 on the _first intermediate transfer belt 25a cancels the positive charge 42 on the back surface of the intermediate transfer belt 25a and applies the same polarity repulsion by applying a negative bias voltage 41 to the secondary transfer roll 40a. The force is transferred onto the sheet P from the intermediate transfer belt 25a by the force. On the other hand, by the toner image T ₂ of the on the second intermediate transfer belt 25b by inverting the polarity to the positive polarity by the polarity reversal corotron 28 and 29 to ground the secondary transfer roll 40b, the negative charges 43 on the rear intermediate transfer belt 25b is The sheet is canceled and is transferred onto the sheet P by the suction force of the secondary transfer roll 40a. In this way, transfer can be performed on both sides simultaneously.

Further, the secondary transfer rolls 40a and 40b
Since the straight line L connecting the central axes O is inclined by θ (θ ≠ 90 °) with respect to the direction of entry of the paper P, the leading end Pa of the paper P passing between the secondary transfer rolls 40a and 40b is L (in this embodiment, the fixing device 5
The nip position of the sheet P toward the fixing device 50 is stabilized by the strength of its stiffness (bending rigidity).

In the case of single-sided recording, for example, by applying a bias having a polarity opposite to that of a normal transfer bias to the primary transfer roll 26a or 26b on which no recording is performed, it is possible to prevent back surface contamination. In addition, a method of switching the developing bias or a method of separating the photosensitive drums 21a and 21b from the intermediate transfer belts 25a and 25b may be used.

As described above, the photosensitive drums 21a, 21b
From the toner image T ₁ on the intermediate transfer belts 25a and 25b.
T ₂ were respectively transferred, a secondary transfer roll 40a which is shifted back and forth relative to the sheet travel direction to each other, paper between 40b P
And simultaneously transferring images on the intermediate transfer belts 25a and 25b to both sides of the sheet P while applying a bending force to the sheet P,
By transporting the sheet to the fixing device 50 as it is, and fixing both sides simultaneously, it was possible to obtain a double-sided image without image disturbance at the same recording speed as one side per sheet.

Second Embodiment FIG. 4 shows a schematic configuration of a two-sided image forming apparatus according to a second embodiment of the present invention. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but the configuration of the secondary transfer device is different from that of the first embodiment. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted here. That is, in the present embodiment, the secondary transfer device is:
Secondary transfer rolls 40a and 40b similar to those in the first embodiment.
In addition to the first transfer roller 40a, the straight line L connecting the central axes O of the secondary transfer rolls 40a and 40b is inclined at an angle of θ (θ に 対 し 90 °) in the upper left diagonal direction with respect to the direction in which the sheet P enters.
Secondary transfer roll 4 provided on intermediate transfer belt 25a side
Auxiliary transfer roll 40a 'is opposed to secondary transfer roll 40b before 0a (in this embodiment, a straight line connecting both central axes is inclined obliquely to the lower left with respect to the direction in which paper P enters). It was done.

According to the present embodiment, the leading end of the sheet P
First, the auxiliary transfer roll 40a 'and the secondary transfer roll 40b
After being deformed obliquely upward and between the secondary transfer rolls 40a and 40b, the paper P can be bent obliquely downward, so that the force for bending the paper P can be further increased. Secondary transfer rolls 40a, 40b
The stiffness (surface rigidity) of the leading edge of the paper P at the time of passage becomes stronger,
The posture in which the paper P enters the fixing device 50 is more stable.

In this embodiment, the auxiliary transfer roll 40a 'functions only for bending and deforming the sheet P. For example, the auxiliary transfer roll 40a' is similar to the secondary transfer roll 40a. Needless to say, a transfer bias 41 may be applied to perform a substantial transfer operation.

Third Embodiment FIG. 5 shows a schematic structure of a double-sided image forming apparatus according to a third embodiment of the present invention. In the figure, the basic configuration of the double-sided image forming apparatus is substantially the same as that of the first embodiment, but the secondary transfer device is different from that of the first embodiment. That is, in the present embodiment, the secondary transfer device reduces the hardness of the secondary transfer roll 40a provided on the first intermediate transfer belt 25a side and reduces the hardness of the secondary transfer roll provided on the second intermediate transfer belt 25b side. The contact portion is deformed by the pressure of the roll 40b so that a bending force is applied to the sheet P.

According to the present embodiment, the secondary transfer roll 4
The bending force of the paper P can be controlled by changing the hardness of 0a or 40b. Further, since the secondary transfer roll 40a is appropriately deformed due to the stiffness of the paper P itself, it is possible to set the deformation amount to be small for thick paper and large for thin paper.

Fourth Embodiment FIG. 6 shows a schematic configuration of a four-sided image forming apparatus according to a fourth embodiment of the present invention. In the figure, the basic configuration of the double-sided image forming apparatus includes a first image forming unit 20a that forms a first image on the first surface of a sheet P, as in the first to third embodiments.
Second image forming unit 2 that forms a second image on the second surface of sheet P
0b and the sheet P passing through both image forming units 20a and 20b.
And a fixing device 50 for fixing the upper image.
The image forming unit 20a and the second image forming unit 20b are different from the first to third embodiments in that the intermediate transfer belts 25a and 25b are not used.

That is, in the present embodiment, each of the image forming units 20a and 20b wraps around an appropriate number of rolls and circulates and rotates, and charges the surfaces of the photosensitive belts 61a and 61b. Charging roll 22
a, 22b and an exposure device 23 for writing electrostatic latent images for the first and second images on the charged photosensitive belts 61a, 61b.
a, 23b and developing units 24a, 24 for visualizing the electrostatic latent images written on the photosensitive belts 61a, 61b with toner.
4b, the toner images T ₁ , on the photosensitive belts 61a, 61b.
Transfer rolls 62a and 62b for transferring T ₂ (for example, a normal image in the present embodiment) onto the sheet P, and photosensitive belts 61a and 61
Cleaners 27a and 27b for removing the residual toner on
And A pair of polarity-reversing corotrons 28 and 29 are provided on the photosensitive belt 6 downstream of the developing position of the photosensitive belt 61b of the second image forming unit 20b and upstream of the transfer position.
1b.

In particular, in the present embodiment, the transfer rolls 62a and 62b also serve as rolls for hanging the photosensitive belts 61a and 61b, and have substantially the same configuration as the secondary transfer device of the first embodiment. As shown in FIG. 6, a straight line connecting the central axes is non-orthogonal to the intrusion direction of the paper P (in the present embodiment, the straight line connecting the central axes is a diagonally lower right direction to the intruding direction of the paper P) At a predetermined angle).

Next, an image forming process of the double-sided image forming apparatus according to the present embodiment will be described. First photosensitive belt 6
The first toner image T ₁ formed on the first photosensitive belt 61 b moves to the transfer position as it is, while the second toner image T ₂ formed on the second photosensitive belt 61 b is formed by a pair of polarity-reversing corotrons. After the polarity is inverted by the operations of 28 and 29, the image moves to the transfer position. Then, the paper P is conveyed from the paper tray 31 to the transfer rolls 62a and 62b shifted from the paper tray 31 back and forth with respect to the paper traveling direction at the same time.
While applying a bending force to the sheet P, the photosensitive belts 61a, 61
After the toner images T ₁ and T ₂ on b are simultaneously transferred onto the paper P, both sides are fixed simultaneously by the fixing device 50.

At this time, the transfer rolls 62a and 62b
Since the straight line connecting the central axes is inclined obliquely to the lower right with respect to the direction in which the paper P enters, the transfer rolls 62a, 62
The leading end of the sheet P that has passed between the points b and b is deformed (changed in direction) in a predetermined direction (corresponding to the direction toward the nip position of the fixing device 50 in the present embodiment), and the stiffness (bending rigidity) of the paper P depends on its strength. The entering posture of the sheet P toward the fixing device 50 is stabilized. As a result of examining the quality of the double-sided image after the above-described image forming process, it was possible to obtain a double-sided image without image disturbance at the same recording speed as that for one side per sheet.

[0038]

As described above, according to the present invention,
While carrying and transporting the first image on the first image bearing and transporting body,
The second image is carried and conveyed on the second image carrier, and in a region where the first image carrier and the second image carrier are in contact with or in proximity to each other, each of the recording material is transferred to both sides of the recording material by bending transfer means. Since each image on the image carrier is transferred and a bending force is applied to the recording material in and around the transfer area, the recording material is bent and deformed toward the fixing device side. By effectively using the waist (surface rigidity) of the leading end of the recording material, the conveyance direction of the recording material after the transfer can be stabilized. This makes it possible to stabilize the position of the recording material entering the fixing device and effectively avoid the disturbance of unfixed images on both sides of the recording material due to the variation of the recording material entering the fixing device. can do.

Particularly, in the present invention, an image forming carrier and an intermediate transfer member for temporarily transferring each image on the image forming carrier are used as the image carrying members, and the intermediate transfer members are in contact with each other. Alternatively, if a bending transfer unit is provided in an adjacent area, the degree of freedom in the layout of the apparatus can be increased with the use of the intermediate transfer body, and there is no image disturbance and the front and back positions are eliminated. It is possible to obtain a double-sided image of the same quality with no deviation at the same recording speed as that for one side per recording material.

Further, in the present invention, the bending transfer means can be easily realized by simply changing the arrangement relationship of existing transfer rolls, increasing the number of transfer rolls, or changing the hardness of the transfer rolls. Therefore, there is no concern that the device configuration is unnecessarily complicated.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing an outline of a double-sided image forming apparatus according to the present invention, and FIG. 1B is a schematic view showing an operation of a bending transfer unit according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a double-sided image forming apparatus according to the first embodiment;

FIG. 3 is an explanatory diagram showing details of a secondary transfer device used in the first embodiment.

FIG. 4 is a schematic configuration diagram showing a two-sided image forming apparatus according to a second embodiment.

FIG. 5 is a schematic configuration diagram illustrating a double-sided image forming apparatus according to a third embodiment.

FIG. 6 is a schematic configuration diagram illustrating a double-sided image forming apparatus according to a fourth embodiment.

FIG. 7 is an explanatory diagram illustrating a prior example of a double-sided image forming apparatus.

DESCRIPTION OF SYMBOLS 1 ... first image carrier, 2 ... second image carrier, 3 ... bending transfer means, 4 ... recording material, 5 ... image forming carrier, 6 ... intermediate transfer body, 7 ... Primary transfer means, T ₁ ... First image (first toner image), T ₂ ... Second image (second toner image), 20
a: first image forming unit, 20b: second image forming unit, 21a
... First photosensitive drum, 21b ... Second photosensitive drum, 25a ...
First intermediate transfer belt, 25b... Second intermediate transfer belt, 2
6a: first primary transfer roll, 26b: second primary transfer roll, 28, 29 ... polarity reversal corotron, 40a, 4
0b: secondary transfer roll, 40a ': auxiliary transfer roll, 5
0: fixing device, 61a: first photosensitive belt, 61b: second photosensitive belt, 62a, 62b: transfer roll, P: paper

Claims (5)

[Claims] 1. A first image carrying and transporting a first image (T ₁ ).
An image carrier (1), a second image carrier ( ₂ ) on which the second image (T ₂ ) is carried, and a first image carrier (1) and a second image carrier (2). ), Each image (T ₁ , T ₂ ) on each image carrier ( ₁ , ₂ ) is transferred onto both surfaces of the recording material (4) in the area where the recording material (4) is in contact with or close to the recording material (4). A double-sided image forming apparatus, comprising: a bending transfer unit (3) for applying a bending force to a recording material (4) before and after that. 2. The double-sided image forming apparatus according to claim 1, wherein each of the first and second image carriers (1) and (2) has an image (T ₁ , T ₂ ) formed thereon. Image forming carrier (5), and each image (T ₁ , T ₂ ) on the image forming carrier (5) which is disposed opposite to the image forming carrier (5).
T ₂ ) is temporarily transferred, and the intermediate transfer members (6) of the first image-carrying and conveying member (1) and the second image-carrying and conveying member (2) are in contact with each other. A double-sided image forming apparatus, wherein a bending transfer unit (3) is provided in an adjacent area. 3. The double-sided image forming apparatus according to claim 1, wherein the bending transfer unit (3) comprises a pair of transfer rolls sandwiching the first image carrying and transporting body (1) and the second image carrying and carrying body (2).
A double-sided image forming apparatus, wherein a linear direction connecting the central axes of the transfer roll pair is arranged non-orthogonally with respect to a direction in which the recording material (4) enters. 4. The double-sided image forming apparatus according to claim 1, wherein the bending transfer means (3) is provided for one of the transfer rolls sandwiching the first image carrier and the second image carrier (2). A two-sided image forming apparatus, wherein two transfer rolls are arranged to face each other. 5. The double-sided image forming apparatus according to claim 1, wherein the bending transfer means (3) comprises a pair of transfer rolls sandwiching the first image carrying and conveying member (1) and the second image carrying and conveying member (2).
A double-sided image forming apparatus wherein the hardness of each transfer roll is changed.