JPH01276179A - Transfer process device for multiple transfer type image forming device - Google Patents

Abstract

PURPOSE:To prevent a toner image at the head end part of a sheet from being transferred to a toner carrier by making an electrostatic field which operates between an image carrying sheet and an image carrier weaker in 2nd and successive transfer cycles than in a 1st cycle when an image is edited by transferring a toner image on the toner carrier plural times electrostatically. CONSTITUTION:In the 2nd transfer cycle, a copying form 8 is charged electrostatically by a transfer corotron 15, the toner image on the side of a latent image carrier 2 is transferred to the form 8 by the electrostatic force, and the form is separated from the carrier 2 through the operation of a destaticizing corotron 16 for separation. In this case, the value of a destaticizing bias applied to the form 8 is made higher than in the 1st cycle with the switch 53 of a bias switching means 50. Consequently, the electrostatic field between the carrier 2 and form 8 becomes weaker than in the 1st cycle and even if the head end curl part 8a of the form 8 approaches the carrier 2 to a distance (d), the electrostatic field between them does not increase extremely and there is not such a transfer phenomenon that the toner image of the curl 8a is retransferred to the carrier 2.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a transfer process device used in an image forming apparatus such as a copying machine or a printer, and in particular, a toner image bearing member is provided on both sides or one side of an image bearing sheet. The present invention relates to an improvement in a transfer process device used in a multi-transfer type image forming apparatus that electrostatically transfers toner images multiple times.

[Prior Art] To explain a conventional multiple transfer type image forming apparatus using a double-sided copying machine as an example, as shown in FIG. , front charger 3
, an optical system 6 that guides an optical image based on the document 5 on the platen 4 to the latent image carrier 2, a developer 7 that develops the latent image formed on the latent image carrier 2 by the optical system 6 with toner, and a latent image carrier. A transfer process device 9 transfers the toner image formed on the body 2 onto a copy paper 8 as an image bearing sheet and separates the copy paper 8 from the latent image carrier 2, and removes residual toner on the latent image carrier 2. The first toner image on the latent image carrier 2 is transferred onto one side of the copy paper 8 using a cleaner 10 that is equipped with a cleaner 10 to remove the residual charge on the latent image carrier 2 and a discharge lamp 11 that removes the residual charge on the latent image carrier 2. As shown by the dotted chain line, this copy paper 8 is transferred to the fixing device 1.
2 to fix the transferred toner image, the copy paper 8 is once conveyed to an intermediate tray (not shown), the copy paper 8 is reversed, and then the copy paper 8 is transferred to the transfer site as shown by the two-dot chain line. The copy paper 8 is conveyed again, the second toner image on the latent image carrier 2 is transferred to the other side of the copy paper 8, and the fixing device 1
It is known that after the second toner image is also fixed on the copy paper 8 in Step 2, the copy paper 8 on which both sides have been copied is sent to a discharge tray (not shown).

The transfer process device 9 in such a double-sided copying machine is
It is similar to that used in ordinary copying machines, and for example, as shown in FIG. It consists of a separation static elimination corotron 16 that removes charges.

[Problems to be Solved by the Invention] Incidentally, in such a double-sided copying machine, since the copy paper 18 that has been copied on one side passes through the fixing device 12 once, especially when the copy paper 8 has a high moisture content, This results in a situation where the edges of the copy paper 8 are curled.

At this time, since the second transfer cycle of the transfer process device 9 is under the same conditions as the first, the distance wId between the curled end portion 8a of the copying [8] and the latent image carrier 2 becomes closer. However, the strength of the electrostatic field S between the copy paper 8 and the latent image carrier 2 is higher than that in the first transfer cycle, and the toner image T transferred to the curled end portion 8a of the copy paper 8 is again There is a risk that the so-called redundancy phenomenon 7, in which the latent image is transferred to the side of the latent image carrier 2, may occur, and there is a problem that white areas in the image will lead to deterioration of the image quality. In particular, such a problem becomes more pronounced as the radius of curvature of the curled end portion 8a of the copy paper 8 becomes smaller.

Incidentally, such a problem similarly occurs when multiple toner images are transferred to one side of the copy paper 8.

The present invention has been made based on the above-mentioned viewpoint, and is a multiple transfer method that effectively prevents the transferred toner image paste transfer phenomenon caused by the edge curl of the image-bearing silt during the second and subsequent transfer cycles. A transfer process device for a mold image forming device is provided.

[Means for Solving the Problems] That is, the present invention provides a multi-layer image forming apparatus that electrostatically multiple-transfers toner images on a toner image carrier onto both sides or one side of an image-bearing sheet to form an edited image. The image forming apparatus is based on a transfer type image forming apparatus, and includes a transfer means that applies an electric charge for attracting a toner image to an image bearing sheet that is arranged opposite to a toner image carrier and enters a transfer site, and a transfer means that is disposed after the transfer means to apply a charge for attracting a toner image. A separation charge eliminating means removes the electric charge of the image bearing sheet that has passed through the area and separates the image bearing sheet from the toner image bearing member. The transfer image holding means is provided for weakening the electrostatic field acting between the image bearing sheet and the toner image bearing member after passing therethrough, compared to that during the first transfer cycle.

In such technical means, target multiple transfer type image forming apparatuses include a type in which the toner image on a toner image carrier is transferred onto one side of an image bearing sheet in an overlapping manner, and a type in which the toner image is transferred onto both sides of the image bearing sheet, respectively. It is possible to select an appropriate type as long as it is possible to form various edited images.

In addition, as a toner image carrier, as long as it can carry a latent image that is a prerequisite for carrying a toner image, it is provided with a photoreceptor layer and a dielectric layer depending on the type of latent image forming means. etc. may be selected as appropriate, and the specific configuration may be either drum-shaped or belt-shaped.

Furthermore, the transfer means of the transfer process device applies a charge necessary to attract the toner image on the toner image carrier side to the image carrier sheet, and electrostatically transfers the toner image on the toner image carrier side to the image carrier sheet. As long as there is a device capable of metastasizing, a corotron, a sufrotron, etc. may be used as appropriate. Further, the usage conditions of the transfer means do not necessarily have to be the same for each transfer cycle of the multiple transfer image forming cycle, and the optimum usage conditions without waste may be set for each transfer cycle.

As for the separation static eliminating means, if it is capable of removing the charge on the image bearing sheet by the amount necessary to separate the image bearing sheet after passing through the transfer site, a corotron or a sufrotron using AC corona discharge may be used. First, a type using a pointed electrode, a type using a brush-like electrode, etc. can be selected as appropriate.

In addition, as a transfer image holding means, even if the curled end portion of the image carrying sheet is placed close to the toner image carrying member in the second and subsequent transfer cycles of the multiple transfer image forming cycle, the electrostatic field that acts between the two If the transfer cycle is weaker than the first transfer cycle without transferring the toner image on the image bearing sheet side to the toner image bearing member side again, the static eliminating bias of the separation static eliminating means may be changed appropriately, or the toner image bearing member side The design may be changed as appropriate, such as lowering the potential or combining the two.

[Operation] According to the technical means described above, the transferred image holding means reduces the electrostatic field that acts between the image bearing sheet and the toner image bearing member after passing through the transfer site in the second and subsequent transfer cycles. It is weaker than during the first transfer cycle, so even if the leading edge curled part of the image bearing sheet is placed close to the toner image bearing member in the second and subsequent transfer cycles, the transfer that is on the leading edge curled part of the image bearing sheet This does not result in sufficient attractive force to transfer the toner image to the toner image carrier.

[Embodiments] Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

Embodiment 1 FIG. 2 is an explanatory diagram schematically showing a copying machine with double-sided multiple copying function to which the present invention is applied.

In the figure, an image forming unit 1 irradiates light onto a latent image carrier 2 such as a photosensitive drum, a front charger 3 that charges the surface of the latent image carrier 2 in advance, and a document 5 on a platen 4. It is composed of an exposure lamp 6a, a plurality of mirrors 6b forming an optical path for guiding reflected light from the original 5 to the latent image carrier 2, and an imaging lens 6C for forming a light image from the original 5 onto the position of the latent image carrier 2. an optical system 6, a developing device 7 that develops the latent image formed on the latent image carrier 2 by the optical system 6 with toner, and a toner image formed on the latent image carrier 2 as an image carrier sheet. A transfer process device 9 transfers the toner onto a copy paper 8 and separates the copy paper 8 from the latent image carrier 2; a cleaner 10 removes residual toner on the latent image carrier 2; and a cleaner 10 removes residual toner on the latent image carrier 2; The transferred toner image on the copy paper 8 after the transfer cycle is transferred to the heating roll 12.
The image is heated and fixed by a fixing device 12 consisting of a roller a and a pressure roller 12b.

Further, in this embodiment, an automatic document feeder (hereinafter referred to as ADF) 20 is provided at the top of the copying machine. A document feed roll 22 that supplies the original 1i5 set in the document set tray 21 to the platen 4 side according to each copy cycle timing, and a document feed roll 22 that is incorporated in the platen cover 23 and supplies the document set tray 21 to the platen 4 side according to each copy cycle timing.
a conveyor belt 24 that conveys the original 5 sent from the original 1 to the platen 4 side to the registration position of the platen 4, and discharges and conveys the original 5 from the registration position of the platen 4 after the copying cycle for one original 5 is completed; A document storage tray 25 is formed integrally with the platen cover 23 and stores the document 5 discharged by the conveyor belt 24.
It is made up of.

Furthermore, in this embodiment, the paper transport system 30 that transports the copy paper 8 is configured to be capable of double-sided copying and multiple copying operations. In other words, the paper conveyance system 30 includes, for example, paper feed cassettes 3 each accommodating copy paper 8 of a plurality of sizes.
1.32, an intermediate tray 33 that temporarily stores the copy paper 8 that has completed the first copy cycle during double-sided copying and multiple copying, and feeds out the copy paper 8 from the paper feed cassette 31, 32 and the intermediate tray 33. Feed rolls 34 to 36 and a supply transport path 3 for guiding the copy sheets 8 from the paper feed cassettes 31, 32 and the intermediate tray 33 to the transfer site.
7, and a registration roll 3 disposed near the transfer site in this supply side conveyance path 37, which once positions the supplied copy paper 8 and then sends it out to the transfer site at a predetermined timing.
8, a discharge tray 39 for discharging and storing the copy paper 8 on which a series of copying operations has been completed, and a copy paper 8 that has passed through the transfer site.
a discharge side conveyance path 40 for guiding copy paper 8 to the output tray 39 side after passing through the fixing device 12; and a U-turn conveyance path 41 for guiding copy paper 8 that has passed through the fixing device 12 to the intermediate tray 33 side.
a first switching gate 42 disposed at the intersection of the discharge side conveyance path 40 and the U-turn conveyance path 41 to select either of the conveyance paths; and a first switching gate 42 provided in the middle of the U-turn conveyance path 41. A curl correction device 43 that corrects the curl of copy paper 8 after passing through the fixing device 12 between a heating roll 43a and a pressure roll 43b, and an intermediate tray 3 of the U-turn conveyance path 41.
3. A reversing conveyance path 44 provided near the copy paper 8 and used when reversing the copy paper 8; and a second switching gate 45 for selection. In the figure, reference numeral 46 denotes a conveyance roll that conveys the copy paper 8 within each conveyance path, and 47 denotes a conveyance belt for conveying the copy paper 8.

In this embodiment, as particularly shown in FIG. 2, the transfer process device 9 is provided with a discharge wire 15b disposed within a shield 15a having an opening-shaped cross section.
A transfer corotron 15 to which a DC high voltage Vt is applied to b, and a discharge wire 16b disposed within a shield 16a having a square cross section, and a DC bias vb as a static elimination bias and an AC high voltage Vc applied to the discharge wire 16b during transfer. bias switching means 50 for setting the DC bias vb of the separation static elimination corotron 16 to which is applied, and the DC bias vb of the separation static elimination corotron 16 in the second and subsequent transfer cycles to a level v2 higher than the level 1 in the first transfer cycle. It is made up of. The bias switching means 50 is configured to automatically select, for example, DC power sources 51 and 52 corresponding to the two DC biases Vl and V2 using a changeover switch 53.

Next, the operation of the transfer process device will be explained by taking as an example a case where the copying machine according to this embodiment performs a single-sided multiple copying operation.

That is, to perform a single-sided multiple copying operation, a single-sided multiple copying mode (not shown) may be selected, and then a copying switch (not shown) may be turned on.

Then, first, the ADF 20 works and the original 5 is placed on the platen 4.
After the latent image carrier 2 is charged positively, for example, a latent image and a toner image (negative polarity in this embodiment) of the document 5 are formed on the latent image carrier 1. On the other hand, in the paper transport system 30, the copy paper 8 is fed out from a predetermined paper feed cassette 31 or 32, and is supplied to the transfer site at the timing when the toner image on the latent image carrier 2 reaches the transfer site. Ru.

In this state, the transfer corotron 15 operates under normal conditions, and the bias switching means 50 of the transfer process device 9 is switched to one of the DC power supplies 51 (DC bias V1
) is selected, the separation static eliminator corotron 16 operates as shown in FIG. Then, as shown in FIG. 4(a), the copy paper 8 is appropriately charged by the charge e from the transfer corotron 15, and the copy paper 8 is electrostatically charged based on the electrostatic field between the copy paper 8 and the latent image carrier 2. The toner IglT on the image carrier 2 is transferred to the copy paper 8 side, and after that, the copy paper 8 after passing through the transfer site is neutralized by the separation static elimination corotron 16 to the neutralization bias v1, and the latent image carrier 2 separated from

At this time, since the leading edge of the copying paper 8 is not particularly curled, the distance between the copying paper 8 and the latent image carrier 2 does not approach the edge, and as shown in FIGS. ), the electrostatic field S(
Specifically, there are almost no situations where Sl) becomes extremely large. Therefore, the redundancy phenomenon 7 in which the toner image T on the copy paper 8 side is transferred again to the latent image carrier 2 side does not occur.

Next, the copy sheet 8 on which the image has been transferred passes through the fixing device 12 , is conveyed toward the U-turn conveyance path 41 , passes through the curl correction device 43 , and is then conveyed to the intermediate tray 33 .

At this time, even if the leading edge of the copy paper 8 is largely curled in the fixing device 12, the copy paper 8 is stored in the intermediate tray 33 after being effectively corrected by the curl correction device 43.

In parallel with this, the ADF 20 sets the second original 8j5 at a registration position on the platen 4, and a latent image and toner image corresponding to the original 5 are formed on the latent image carrier 2. Then, at the timing when the toner' image on the latent image carrier 2 reaches the transfer site, the copy paper 8 is again supplied from the intermediate tray 33 to the transfer site.

At this time, the copy paper 8 entering the transfer site is basically straight with no curls, but the curl correction device 4
3, or when the copy paper 8 with a low moisture content passes through the curl correction device 43 after passing through the fixing device 12, the amount of curl caused by passing through the fixing device 12 may be small. If the curl correction is performed more than necessary, in the second transfer cycle, the copy paper 8 will have a curled end portion 8a as shown in FIG. 4(b).
It is then transported to the transcription site.

In this state, the bias switching means 50 of the transfer process device 9 switches the other DC power supply 52 (DC bias V2
'), the transfer corotron 15 operates under the same conditions as in the first transfer cycle, but as shown in FIG. 3, the separation static elimination corotron 16 operates under conditions different from those in the first transfer cycle.

That is, in the second transfer cycle, the copy paper 8 is charged with the charge e from the transfer corotron 15, and the toner image T on the latent image carrier 2 side is transferred to the copy paper 8 based on the attractive force of the electrostatic field. . Then, the copy paper 8 is separated from the latent image carrier 2 by the action of the separating static eliminating corotron 16.

At this time, as shown in FIGS. 3 and 4(b), since the neutralization bias v2 of the copy paper 8 is set higher than that during the first transfer cycle, the latent image carrier 2 and the copy paper 8 The electrostatic field S2 between them becomes weaker than during the first transfer cycle, and the leading edge curled portion 8a of the copy paper 8 becomes closer to the latent image carrier 2.
Even if the distal end curl portion 8a is placed close to the
The electrostatic field S (specifically, 82) between the and the latent image carrier 1 does not become extremely large, and the toner image T on the curled end portion 8a of the copy paper 8 is transferred to the latent image carrier 2 side again. The Ridransufu 7 phenomenon of metastasis is avoided.

As shown in FIG. 5, the electrostatic field S between the static eliminating bias vb and the latent image carrier 2 and the copying paper 8 can be reduced as the static eliminating bias vb is set higher. There is an inversely proportional relationship.

During this process, the copy paper 8 on which the second transfer cycle has been completed is discharged and stored in the discharge tray 39 via the fixing device 2.

In this embodiment, it has been confirmed that the transfer process device 9 functions effectively even in a type that does not use the curl correction device 43.

Embodiment 2 FIG. 6 shows a transfer process device used in a copying machine similar to that of Embodiment 1. This transfer process device 9 includes a transfer corotron 15 similar to that of Embodiment 1, and a constant neutralizing bias vb. Separation static elimination corotron 16 and transfer corotron 1
5, and a discharge lamp 60 that is turned on in the second and subsequent transfer cycles of a multiple transfer image forming cycle (single-sided multiple copying cycle, double-sided copying cycle, etc.).

According to this type, as shown in FIGS. 6 and 7,
In the second and subsequent transfer cycles, the static elimination lamp 60
When lit, the surface of the latent image carrier 2 is completely neutralized in areas where there is no toner image, and the toner 1! ! Even where T is attached, the surface of the latent image carrier 2 is neutralized to some extent because light penetrates through the gaps between the toner particles, and the surface potential of the latent image carrier 2 is substantially eliminated. Therefore, even if the separation static eliminating corotron 16 operates under the same conditions as in the first transfer cycle, the electrostatic field S between the latent image carrier 2 and the copy paper 8 is weakened, which is different from the first embodiment. It has a similar effect.

Embodiment 3 FIG. 8 shows a transfer process device used in a copying machine similar to that of Embodiment 1. This transfer process device 9 includes a transfer corotron 15 similar to that of Embodiment 1, a static elimination corotron for separation 16, and a bias switching device. It consists of a means 50 and a static elimination lamp 60 used in the second embodiment.

According to this type, in the second and subsequent transfer cycles, the charge removal level of the copy paper 8 is suppressed to the charge removal bias vb by the action of the bias switching means 50, and the charge removal level of the copy paper 8 is suppressed to the charge removal bias vb by the action of the charge removal lamp 600. The surface of No. 2 is neutralized.

Therefore, the electrostatic field S between the latent image carrier 2 and the copy paper 8
is weakened more efficiently than in each of the above embodiments.

In this embodiment, since the static elimination lamp 60 operates to lower the potential of the latent image carrier 2, the static elimination bias vb in the second and subsequent transfer cycles is reduced as shown by the imaginary line in FIG. Even if S is not set as high as in the first embodiment, it is possible to set the electrostatic field S between the latent image carrier 2 and the copy paper 8 to be sufficiently small.

[Effects of the Invention] As described above, according to the transfer process device of the multiple transfer type image forming apparatus according to claims 1 to 4, the second and subsequent transfer cycles are devised to reduce the curling of the leading edge of the image bearing sheet. The transfer toner image on the surface is transferred again to the toner image carrier side. Since this phenomenon is effectively avoided, there are no white spots or the like in the image transferred to the image bearing sheet, and the image quality of the multiple transfer image can be maintained at a good level.

Further, according to the transfer process device of the multi-transfer type image forming apparatus according to claim 4, in the second and subsequent transfer cycles, the level of charge removal of the image bearing sheet is suppressed and the potential of the toner image bearing member is lowered. , the electrostatic field between the image-bearing sheet and the toner image-bearing member can be effectively weakened, and the retransfer phenomenon described above can be avoided more reliably.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing Embodiment 1 in which the present invention is applied to a copying machine with double-sided multiple copying function, FIG. A timing chart showing the operation of the transfer process device of Example 1, FIGS. 4(a) and 4(b) are explanatory diagrams showing the operating state of the multiple transfer cycle, and FIG. 5 shows the static elimination bias, latent image carrier, and copy paper. A graph diagram showing the relationship between the electrostatic field and the 6th
The figure is an explanatory view of the main parts of a second embodiment of the transfer process device of the multiple transfer type image forming apparatus according to the present invention, FIG. 7 is a timing chart showing the operation of the transfer process device of the second embodiment, and FIG. FIG. 9 is an explanatory diagram showing an example of a conventional double-sided copying machine; FIG. 10 is an explanatory diagram showing an example of a conventional double-sided copying machine. FIG. 2 is an explanatory diagram showing an example of a transfer process device used. [Description of symbols 2...Latent image carrier (toner image carrier) 8...Copy paper (image carrier sheet) 9...Transfer wrestling device 15...Transfer corotron (transfer means) 16... - Static elimination corotron for separation (static elimination means for separation) 50...bias switching means (transferred image holding means) 60.
... Static elimination lamp (static elimination means, transferred image holding means) Patent applicant Fuji Xerox Co., Ltd. Agent
Patent attorney Tomohiro Nakamura (3 others) Figure 3 Figure 4 (b) Figure 5 Static elimination bias V. Figure 6 °°″″″′″″′ ± 2 Figure 7 Transfer cycle 1 Figure 8 7a 7aT

Claims (1)

[Claims] 1) A multi-transfer type in which an edited image is formed by electrostatically multiple-transferring toner images on a toner image carrier (2) onto both sides or one side of an image-bearing sheet (8). In the image forming apparatus, a transfer means (15) applies an electric charge for attracting a toner image to an image carrying sheet (8) which is disposed opposite to a toner image carrier (2) and enters a transfer site; and this transfer means (15). a separation charge eliminator (16) that is disposed at a subsequent stage and removes the electric charge of the image bearing sheet (8) that has passed through the transfer site to separate the image bearing sheet (8) from the toner image bearing member (2); In the second and subsequent transfer cycles of one multiple transfer image forming cycle, the image bearing sheet (8) after passing through the transfer site
Transfer image holding means (50,
60) A transfer process device for a multiple transfer type image forming apparatus. 2) In the device according to claim 1, the transferred image holding means:
Multi-transfer type image formation characterized by comprising a bias switching means (50) that sets the static elimination bias of the separation static elimination means (16) higher in the second and subsequent transfer cycles than in the first transfer cycle. Equipment transfer process equipment. 3) In the device according to claim 1, the transferred image holding means:
A static eliminating means (60) for removing electric charges on the toner image bearing member 2)
) A transfer process device for a multiple transfer type image forming device. 4) In the device according to claim 1, the transferred image holding means:
Bias switching means (50) that sets the static elimination bias of the separation static elimination means (16) higher in the second and subsequent transfer cycles than in the first transfer cycle;
) A transfer process device for a multiple transfer type image forming apparatus, characterized in that the transfer process device is comprised of a static eliminating means (60) for removing charges on the image forming apparatus.