JPH0990769A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a peeling failure or image defect by arranging a peeling corotron apart from a transfer drum in a position where a transfer material peeled from the transfer drum is never interfered before a peeling force is acted, and collecting the electrostatic eliminating action to the peeling area. SOLUTION: The surface charge of a transfer sheet 24 having a toner image transferred thereon from a photoreceptor drum 20 is eliminated by a peeling corotron 34, and a peeling finger 50 makes contact with it. The peeling corotron 34 is separated from a transfer drum to a position where the transfer sheet 24 peeled from the transfer drum is never interfered, and arranged on a straight line passing the peeling part on the transfer drum surface to collect the peeling discharge to the tip part of the peeling finger 50. Further, a thin electrode plate 60 is fixed and arranged in a position opposed to the peeling corotron 34 within the transfer drum to collect the electrostatic eliminating action by the peeling corotron 34 to the peeling part of the transfer drum. Thus, the peeling failure of a transfer material or an image defect accompanying peeling discharge can be prevented with a simple structure at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a plurality of toner images of different colors in sequence on a photosensitive drum and transfers the plurality of toner images formed on the photosensitive drum to a transfer drum, a transfer belt or the like. The present invention relates to an image forming apparatus suitable for an electrophotographic copying machine, a printer, or the like that forms a color image by sequentially transferring the images on a transfer material carried on a material carrier in a state of being superposed, and particularly, the transfer material is a transfer material. The present invention relates to an image forming apparatus capable of preventing the unfixed image transferred on the transfer material from being disturbed when it is peeled from a carrier, due to occurrence of discharge or the like.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using a transfer drum of this type, black,
A plurality of toner images of different colors such as yellow, magenta, and cyan are formed, and the plurality of toner images formed on the photosensitive drum are sequentially superposed on a transfer material such as transfer paper carried on the transfer drum. There is one configured to form a color image by transferring in a combined state. Then, in this image forming apparatus, after a predetermined number of toner images are transferred in multiple layers onto the transfer material attracted to the transfer drum, the transfer material is peeled off from the surface of the transfer drum, and is fixed onto the transfer material by a fixing device. It is designed to fix the toner image. At that time, in the image forming apparatus, generally, a peeling device including a sharp peeling finger at a tip portion is used in order to reliably peel the transfer material from the surface of the transfer drum.

In such an image forming apparatus, the toner image of the final color formed on the photosensitive drum is electrostatically transferred onto a transfer material on the transfer drum by a transfer corotron, and then the transfer material is removed by a peeling device. It is configured to be peeled off from the transfer drum and to be conveyed to a fixing device by a sheet conveying means. At that time, when the transfer material is peeled from the transfer drum, an AC voltage in which an AC voltage or a DC voltage is superimposed is applied to the static elimination corotron arranged in the peeling portion, and an AC discharge or a discharge obtained by adding a DC discharge to the AC discharge. Then, the transfer material charged by the transfer corotron is removed to remove the transfer material from the transfer drum.

As the peeling device, for example, FIGS.
As shown in FIG. 18, a peeling finger 100 having a sharp tip made of a narrow plate-shaped member made of metal is brought into contact with the transfer film 101 forming the surface of the transfer drum 105 at a predetermined timing, and the peeling finger 100 is formed. After the transfer material 102 is separated from the transfer film 101 by the sharp tip of the transfer material 102, the transfer material 102 is lifted by the upper surface of the separation finger 100 to separate the transfer material 102 from the surface of the transfer drum 105. (Japanese Patent Laid-Open No. 1-254986). Further, in the above peeling device, in order to assist the peeling action of the peeling finger 100, the peeling finger 100 is used to transfer the transfer drum 10.
5, the plurality of peeling guide members 103 that lift up the transfer material 102 peeled from the surface of the peeling finger 5
Are arranged on both sides of. The plurality of peeling guide members 103 are fixed to the support body 104 integrally with the peeling finger 100. By rotating the support body 104 at a predetermined timing, the tip portion of the peeling finger 100 is moved. It is configured to be in contact with the surface of the transfer film 101.

In FIG. 17, 106 and 107 are transfer materials 102.
2 shows a static elimination corotron for enabling the separation of the.

[0006]

However, the prior art described above has the following problems. That is, in the case of the above-described conventional image forming apparatus, if the leading end of the transfer paper 102 separated from the transfer drum 105 is curled, or the transfer paper 102 is a strong paper such as a thick paper such as a postcard, Due to the elastic restoring force of the transfer sheet 102, the front end of the transfer sheet 102 is separated from the transfer drum 105 before being conveyed to the peeling section, and is arranged above the peeling section of the transfer drum 105 as shown by a phantom line in FIG. Phenomena called "smudge" that interferes with the static elimination corotron 106 or the like and causes a conveyance failure such as a jam, or the unfixed toner image on the transfer paper 102 is scraped by contact with a member such as the static elimination corotron 106. However, there is a problem that the image quality is deteriorated.

As means for solving such a problem, the output of a transfer corotron for transferring a toner image from a photosensitive drum onto a transfer sheet is increased to increase the electrostatic attraction force of the transfer sheet to the transfer drum. Transfer paper 102
It may be possible to prevent the tip of the toner from jumping up from the transfer drum 105, but in this case, the electrostatic attraction force at the time of electrostatically transferring the toner image of each color onto the transfer paper 102 becomes too strong. As a result, a new problem arises in that transfer defects such as white spots occur. That is, the transfer current flowing through the transfer corotron and the transfer efficiency ρ have a relationship as shown in FIG. 20, and if the output of the transfer corotron is increased too much, the transfer efficiency ρ rather decreases.

Therefore, as a means for solving such a problem, the one disclosed in JP-A-1-209328 has already been proposed. This Japanese Patent Laid-Open No. 1-2093
In the transfer device according to Japanese Patent No. 28, the transfer sheet is electrostatically adsorbed on a transfer drum having an electrostatic screen on the front side, and the toner image formed on the photosensitive drum is electrostatically transferred onto the transfer sheet. In a transfer device configured to separate the transfer sheet from the transfer drum after the sheet separation and transfer the transfer sheet to the sheet unloading means, a subcharger having the same polarity as the transfer charger for electrostatic transfer, the transfer charger and the sheet separation unit It is arranged so as to be located on the inner surface side of the transfer drum at an intermediate position with respect to the electrostatic charger arranged in (1), and the subcharger is configured to output only at the time of sheet separation.

However, in the case of the transfer device according to this proposal, a subcharger having the same polarity as the transfer charger for electrostatic transfer is transferred at an intermediate position between the transfer charger and the electrostatic charger arranged in the sheet separating section. Since it is arranged so as to be located on the inner surface side of the drum, and the subcharger is configured to output only when the sheets are separated, the subcharger having the same polarity as that of the electrostatic transfer transfer charger should face the transfer drum. However, not only the number of parts is increased, but also the cost is increased.

Therefore, without causing such a problem,
The leading edge of the transfer paper 102 described above is the static elimination corotron 106.
In order to solve the problem that the conveyance failure such as jam occurs due to the interference with the transfer drum 1
However, in such a case, when the transfer sheet 102 is separated from the transfer drum 105, the transfer sheet 102 by the static elimination corotron 106 is removed.
It is impossible to sufficiently carry out the static elimination action, and peeling failure occurs. Further, in order to sufficiently charge the transfer paper 102 by the charge eliminating corotron 106, the output of the charge eliminating corotron 106 must be increased, and the power supply capacity of the charge eliminating corotron 106 must be increased and peeling can be performed. There is a problem that an image defect such that the toner image transferred on the transfer paper 102 is disturbed by the accompanying discharge occurs.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art. The purpose of the present invention is to make the tip of the transfer material interfere with the charge eliminating means with a simple structure and low cost. It is an object of the present invention to provide an image forming apparatus capable of preventing the peeling defect of the transfer material and the image defect caused by the peeling discharge while surely preventing the above.

[0012]

An image forming apparatus according to a first aspect of the present invention forms a plurality of toner images of different colors on an image carrier, and the toner images are formed on the image carrier. An image is formed by sequentially transferring a plurality of toner images in a state of being superposed on the transfer material electrostatically adsorbed on the transfer material carrier, and the transfer material is removed from the transfer material carrier by the charge removing means. In an image forming apparatus that performs debonding by combining charge removal and a mechanical force generated by a peeling unit, the charge eliminating unit is moved to a position where the transfer material peeled from the transfer material carrier does not interfere with the mechanical force applied by the peeling unit. It is arranged so as to be separated from the transfer material carrying member, and is provided with a charge removing effect concentrating means for concentrating the charge removing effect of this charge removing means in the peeling area of the transfer material carrying body.

The distance between the charge eliminating means and the transfer material carrier is at least 20 at the peeling portion of the transfer material.
It is set to mm or more.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect of the present invention, in which static elimination by the static eliminating means is concentrated in a peeling area of the transfer material carrier. The action concentrating means is composed of an electrode provided inside the transfer material carrier facing the charge eliminating means.

Further, the image forming apparatus according to claim 3 of the present invention is the image forming apparatus according to claim 1 or 2, wherein the charge eliminating means is responsive to a change in electric resistance of the transfer material. Output is controlled, and when the electric resistance of the transfer material is small, the output of the DC discharge of the static eliminator is set to be small.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, in which the DC bias voltage applied to the charge eliminating means is applied. , 2.0 kV or more.

As the above-mentioned electrode, for example, a conductive flat plate is used, which has a curvature so that it is arranged in parallel with the transfer material carrier, and the range of the surface where the electrode faces the transfer material carrier. Is set to a size that covers, for example, the charge removing unit to the peeling unit. Further, for example, a predetermined voltage is applied to the electrodes or grounded.

The output of the charge eliminating means is controlled, for example, according to the type of the transfer material, and in the case of an OHP film, the output of the AC voltage is increased.

Further, as the charge eliminating means, for example,
A static elimination corotron is used.An alternating voltage is applied between the shield of the static elimination corotron and the discharge wire, and a DC bias voltage is applied between the electrodes provided inside the transfer material carrier. Is composed of.

[0020]

In the image forming apparatus according to the first aspect of the present invention, the charge removing means is arranged apart from the transfer material carrier up to a position where the transfer material separated from the transfer material carrier does not interfere. Since the static elimination effect concentration means for concentrating the static elimination effect by the static elimination means on the peeling area of the transfer material carrier is provided, the static elimination means is disposed at a position where the transfer material peeled from the transfer material carrier does not interfere. By arranging the transfer material carrier apart from the transfer material carrier, it is possible to reliably prevent the tip of the transfer material from interfering with the charge eliminating means. Further, since the static elimination effect concentration means for concentrating the static elimination effect by the static elimination means on the peeling area of the transfer material carrier is provided, even when the static elimination means is arranged apart from the transfer material carrier, the static elimination effect concentration means It is possible to concentrate the charge removal action of the charge removal unit on the peeling area of the transfer material carrier, and it is not necessary to increase the output of the charge removal unit more than necessary, and it is possible to prevent the peeling of the transfer material or the image defect due to the peeling discharge. Can be prevented. Further, since it is only necessary to provide the static eliminating action concentrating means, the above effect can be achieved with a simple configuration and low cost.

Further, in the image forming apparatus according to claim 2 of the present invention, in the image forming apparatus according to claim 1, the charge removing action by the charge removing means is concentrated on the peeling area of the transfer material carrier. Since the static elimination action concentrating means is composed of the electrodes provided inside the transfer material carrier facing the static elimination means, the tip of the transfer material serves as the static elimination means with a simple structure of adding electrodes and at low cost. It is possible to provide an image forming apparatus capable of reliably preventing interference and preventing image defects due to defective peeling of a transfer material or peeling discharge.

Further, in the image forming apparatus according to claim 3 of the present invention, in the image forming apparatus according to claim 1 or 2, the charge eliminating means is responsive to the electric resistance of the transfer material. When the output is controlled and the electric resistance of the transfer material is small, the output of the DC discharge of the static eliminator is set to be small, so when the electric resistance of the transfer material is small such as in a high temperature and high humidity environment. Even if the DC discharge output of the static eliminator is set small, it is possible to reliably prevent the tip of the transfer material from interfering with the static eliminator, and prevent peeling defects of the transfer material and image defects caused by the peel discharge. can do.

Further, in the image forming apparatus according to claim 4 of the present invention, in the image forming apparatus according to claim 1 or 2, the DC bias voltage applied to the charge eliminating means is 2. Since it is configured to be set to 0 kV or more, it is possible to reliably prevent the toner from scattering due to the peeling discharge, as is clear from the experiments by the present inventors.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows a multiple transfer type digital color image forming apparatus as an embodiment of the image forming apparatus according to the present invention.

In FIG. 2, reference numeral 1 denotes a main body of the digital color image forming apparatus. At the upper end portion of the main body 1 of the digital color image forming apparatus, an image reading device 3 (Image Input) for reading an image of a document 2 is read. Ter
minal) is arranged. This image reading device 3
Illuminates the image of the document 2 placed on the platen glass 4 while being pressed by the platen cover 5 by the light source 6, and reflects the reflected light image of the document 2 on the first and second scanning mirrors 7, 8 and The CCD sensor 10 is scanned and exposed through the imaging lens 9, and the CCD sensor 10 scans the original 2
The color material reflected light image of is read at a predetermined dot density (for example, 16 dots / mm).

The color material reflected light image of the document 2 read by the image reading device 3 is, for example, document reflectance data of three colors of red (R), green (G), blue (B) (each 8 bits). As the image processing apparatus 12 (Image Proce
The image processing apparatus 12 transmits the reflectance data of the document 2 to the shading correction, the position shift correction, the lightness / color space conversion, the gamma correction, the frame erasure, the color / movement editing, and the like. Predetermined image processing is performed.

The image data subjected to the predetermined image processing by the image processing device 12 as described above is black (K), yellow (Y), magenta (M), cyan (C) (each 8 bi).
t) is converted into the original color material gradation data of the three colors ROS1
5 (Raster Output Scanner), and the ROS 15 performs image exposure with the laser beam LB according to the original color material gradation data.

As shown in FIG. 2, the ROS 15 modulates the semiconductor laser 16 according to the original color material gradation data 14, and emits the laser beam LB from the semiconductor laser 16 according to the gradation data 14. . The laser beam LB emitted from the semiconductor laser 16 is rotated by the rotating polygon mirror 17.
The image is deflected and scanned by the scanning unit, and scanning exposure is performed on the photoconductor drum 20 via the reflection mirror 18.

The photosensitive drum 20, which is scanned and exposed with the laser beam LB by the ROS 15, is rotationally driven at a predetermined speed in the direction of the arrow by a driving means (not shown). The surface of this photosensitive drum 20 is
After being charged to a predetermined potential by the charging corotron 21 in advance, an electrostatic latent image is formed by scanning and exposing a laser beam LB in accordance with document color material gradation data. The electrostatic latent images formed on the photoreceptor drum 20 include four color developing units 22K, 22Y, 22M, 22C of black (K), yellow (Y), magenta (M), and cyan (C).
Are sequentially developed by a rotary type developing device 22 provided with a toner image having a predetermined color.

The toner image formed on the photosensitive drum 20 is transferred onto a transfer drum 23 arranged adjacent to the photosensitive drum 20, and a transfer sheet 2 as a transfer material is held.
4 is sequentially transferred by the charging of the transfer corotron 25. As shown in FIG. 2, the transfer material 24 includes a plurality of paper feed cassettes 2 arranged in the lower portion of the image forming apparatus main body 1.
It is possible to feed paper from the paper feed roll 31 from 8, 29, 30 and also from the manual feed tray 38 arranged on the side surface outside the image forming apparatus main body 1. , Conveying roller 32 and registration roller 3
It is conveyed to the surface of the transfer drum 23 by 2a and 32b. Then, the transfer material 24 is held on the surface of the transfer drum 23 in a state of being electrostatically adsorbed on the surface of the transfer drum 23 by the charging of the transfer corotron 25 which also functions as a suction corotron. In addition to the non-standard size transfer paper, a transparent OHP sheet for an overhead projector or a thick paper such as a special postcard can be fed from the manual feed tray 38, and an image can be formed on the OHP sheet or the like. You can do it.
Further, from the manual feed tray 38, the transfer material 24 having an image formed on one side is turned upside down and fed,
Double-sided copying is possible.

The transfer material 24 on which the toner images of a predetermined number of colors have been transferred from the photosensitive drum 20 is peeled from the surface of the transfer drum 23 by the charging of the peeling corotron 34, and then conveyed to the fixing device 35. Then, the toner image is fixed on the transfer material 24 by heat and pressure by the fixing device 35, and is discharged onto the paper discharge tray 36 to complete the color image forming process.

In FIG. 2, reference numeral 37 denotes a static elimination corotron pair for static elimination on both front and back surfaces of the transfer drum 23.

FIG. 3 is a block diagram showing the image forming portion of the digital color image forming apparatus of the multiple transfer system.

In FIG. 3, reference numeral 20 denotes the above-mentioned photosensitive drum, which is rotatably driven at a predetermined speed in the arrow direction by a driving means (not shown). As the photoconductor drum 20, for example, one having a photoconductor layer made of an organic photoconductor (OPC) or the like formed on the surface is used. At the transfer position of the photosensitive drum 20, the transfer drum 23 as a transfer material carrier is in non-contact with the surface of the photosensitive drum 20 and a transfer material 24 having a thickness (90 to 100 μm). Are arranged close to each other. The transfer drum 23 is rotationally driven in the arrow direction at the same speed as the peripheral speed of the photosensitive drum 20 by a driving mechanism (not shown). As shown in FIG. 4, the transfer drum 23 includes a pair of ring members 40 and 40 as annular members arranged at both ends in the axial direction, and the ring members 40 and 40.
Tie plate 4 as a connecting member for connecting the parts to each other
1 and a drum-shaped frame body having a thickness of 150 .mu.m, the transfer member 42 made of a dielectric film such as polyvinylidene fluoride (PVdF) having a thickness of 150 .mu.m.
0 and 40 are fixed to the frame body around the outer peripheral surface of the transfer film 42 by gluing or the like with a double-sided tape, as shown in FIG. By adhering with a double-sided tape 43 in a state where they are overlapped with each other, they are formed into a hollow cylindrical shape. At this time, the adhesive portion of the transfer film 42 cannot transfer the toner image formed on the photoconductor drum 20 well, so that the adhesive portion of the transfer film 42 is
Non-image area of the transfer drum 23, that is, the tie bar plate 4
1 is set to be located on the tie bar plate 41 with a gap therebetween.

As described above, the transfer paper 24 as a transfer material is supplied to the transfer drum 23 from any one of the plurality of paper feed cassettes 28, 29, 30. Rolls 32a, 32
b is conveyed to the transfer position of the transfer drum 23 at a predetermined timing by b, and is charged from the back side of the transfer drum 23 by the transfer corotron 25 which also functions as a suction, and the transfer film 42 of the transfer drum 23 is charged. It is electrostatically adsorbed on top. On the transfer paper 24 attracted onto the transfer drum 23, black (K), yellow (Y), magenta (M) and cyan which are sequentially formed on the photoconductor drum 20 at the same time when the transfer paper 23 is attracted to the transfer drum 23. Of the toner images of (C), the black (K) toner image of the first color is transferred by the charging of the transfer corotron 25. After that, on the transfer paper 24 that is continuously attracted onto the transfer drum 23, yellow (Y), magenta (M), and cyan (C) toner images sequentially formed on the photoconductor drum 20 are transferred.
The transfer corotron 25 is sequentially transferred by charging.

Then, the transfer paper 24 on which the toner images of the predetermined number of colors have been transferred from the photosensitive drum 20 is conveyed as the transfer drum 23 rotates and is guided to the peeling section. The transfer paper 24 guided to the peeling section is the peeling corotron 3
Surface charges are removed by 4. At the same time, as shown in FIG.
As shown in FIG. 5, the finger 50 of the peeling device 44, which is on standby at a predetermined distance from the transfer drum 23 during the transfer process, is adjusted to the transfer timing of the transfer paper 24 based on a signal from a reference signal generator 55 described later. The drive mechanism (not shown) makes contact with the surface of the transfer drum 23. The internal pressing roll 51 of the peeling device 44 is also retracted at a predetermined distance from the transfer drum 23 during the transfer process, like the peeling finger 50, and based on a signal from a reference signal generating device 55 described later, the transfer paper is transferred. A drive mechanism (not shown) contacts the peeling finger 50 and the inner surface of the transfer drum 23 at the same time as the conveyance timing of 24. The position where the tip of the inner pressing roll 51 abuts the transfer drum 23 is located upstream of the tip position of the peeling finger 50 that also abuts the surface of the transfer drum 23. The transfer film 42 of the transfer drum 23 is partially deformed due to the pressing force of 51 and the position close thereto. And this transfer film 4
Due to the deformation of No. 2, the tip of the peeling finger 50 can be embedded between the transfer paper 24 and the transfer film 42. At that time, transfer paper 2
4 is conveyed to the downstream side as the transfer drum 23 rotates, the transfer paper 24 is separated by the peeling fingers 50.
It is peeled off from the transfer drum 23. In this way,
The transfer sheet 4 is peeled from the surface of the transfer drum 23 and then conveyed to the fixing device 35 via the conveyance guide 45.
The fixing roller 35a and the pressure roller 35 of the fixing device 35
The toner image is fixed on the transfer material 24 by heat and pressure by b, and is discharged onto the paper discharge tray 36 outside the apparatus by the fuser outlet roll 46. The peeling finger 5
0 and the inner pressing roll 51 may be configured to be electrically conductive and grounded to prevent charging.

In the digital color image forming apparatus according to this embodiment, a relatively thick transfer material 24 such as a postcard is used.
So that an image can be formed on the resist roll 32a.
As shown in FIG. 3, on the downstream side of the
4 is provided with a curl roll 52 that facilitates winding around the transfer film 42. The curl roll 52 includes an elastic roll 52 a having a large diameter located on the front surface side of the transfer material 24 and a metal roll 52 b having a small diameter located on the back surface side of the transfer material 24. Further, since the curl roll 52 does not need to be curled for ordinary transfer paper, the elastic roll 52a
Can be retracted to a position separated from the metal roll 52b.

Further, in this embodiment, the fuser outlet roll 4 is used to correct the curl of the transfer material 24 which has passed through the fixing device 35 and which has been subjected to the fixing process so as to return it to a flat state.
A decurling roll is used as 6. The decurling roll 46 is composed of a roll 46 a having a small diameter located on the front surface side of the transfer material 24 and a roll 46 b having a large diameter located on the back surface side of the transfer material 24.

Further, in the digital color image forming apparatus constructed as described above, as shown in FIG.
A reference signal generator 55 for generating a reference signal for dividing the surface of the transfer drum 23 in the circumferential direction into two regions is provided inside the unit 3. The reference signal generator 55 is integrally attached to the transfer drum 23,
It is composed of a slit plate 57 having a half-moon shaped slit 56 that rotates together with the transfer drum 23, and an optical sensor 58 for optically detecting the slit 56 of the slit plate 57 and generating a reference signal. And
From the reference signal generator 55, as shown in FIG.
A reference signal (TR0 signal) consisting of a pulse signal is output every time the transfer drum 23 rotates half a turn (180 degrees).

In FIG. 3, reference numeral 47 denotes a cleaning brush for cleaning the surface of the transfer drum 23. The cleaning brush 47 is usually separated from the surface of the transfer drum 23 and transferred at a predetermined timing. The surface of the transfer drum 23 is cleaned by rotating in contact with the surface of the drum 23.

By the way, in the digital color image forming apparatus according to this embodiment, the charge removing means for removing the charge when peeling the transfer material from the transfer material carrier is used up to the position where the transfer material peeled from the transfer material carrier does not interfere. It is arranged so as to be separated from the transfer material carrying member, and is provided with a charge removing effect concentrating means for concentrating the charge removing effect of this charge removing means in the peeling area of the transfer material carrying body.

That is, in this embodiment, FIG. 1 and FIG.
As shown in FIG. 7, the peeling corotron 34 is arranged not in the vicinity of the peeling portion of the transfer drum 23 but apart from the transfer drum 23 to a position where the transfer paper 24 peeled from the transfer drum 23 does not interfere. The peeling corotron 34 needs to concentrate the peeling discharge on the peeling portion of the surface of the transfer drum 23, that is, the tip of the peeling finger 50 where the transfer paper 24 is peeled from the surface of the transfer drum 23. 34 is the transfer drum 2
It is arranged on a straight line passing through the peeling portion on the surface 3. Moreover, the angle θ formed by the straight line L passing through the center of the peeling corotron 34 and the peeling portion on the surface of the transfer drum 3 with the tangent to the transfer drum 23 and the distance M from the peeling portion are the transfer paper 24 peeled from the transfer drum 23. Is set to a value that does not interfere.
The angle θ formed by these straight lines with the tangent line of the transfer drum 23 and the distance M from the peeling section determines the distance G between the end of the peeling corotron 34 and the surface of the transfer drum 23, as shown in FIG. 7. Therefore, the distance G between the end of the peeling corotron 34 and the surface of the transfer drum 23 is appropriately set to a predetermined value. Note that, in FIG. 7, for convenience, the inner pressing roll 51 is shown in a state of pressing the transfer film 42.

Further, in this embodiment, the static elimination effect concentration means for concentrating the static elimination effect by the static elimination means in the peeling area of the transfer material carrier is provided inside the transfer material carrier facing the static elimination means. It is composed of an electrode plate.

That is, in this embodiment, FIG. 1 and FIG.
As shown in, the peeling corotron 34 is provided at a position facing the peeling corotron 34 inside the transfer drum 23.
A thin plate-shaped electrode plate 60 is arranged in a fixed state as a static elimination effect concentration means for concentrating the static elimination effect due to the static electricity removal action on the peeling portion of the transfer drum 23. The electrode plate 60 arranged at a position facing the peeling corotron 34 via the transfer drum 23 is made of a conductive flat plate made of metal.
3 has a curvature so as to form a constant interval.
Further, the range in which the electrode plate 60 is provided is set from the upstream end portion of the transfer drum 23 where the discharge of the peeling corotron 34 reaches to the peeling finger 50 and the peeling guide. Furthermore, as shown in FIG.
A notch 61 is partially provided so as to avoid interference with the inner pressing roll 51.

FIG. 9 is a layout view of a counter electrode plate and an internal pressing roll for explaining this. The electrode plate 60 is grounded. By doing so, the directivity of the electric field formed between the peeling corotron 34 and the electrode plate 60 can be enhanced, and the electric field for peeling can be concentrated in the peeling portion, particularly in the vicinity of the tip position of the peeling finger 50. it can. A bias voltage having a reverse polarity to the discharge polarity of the peeling corotron 34 may be applied to the electrode plate 60, if necessary.

Further, the peeling corotron 34 has a structure shown in FIG.
As shown in, the AC power supply 62 applies an effective voltage of 5.0 kV between the shield and the discharge wire, and the DC power supply 63 applies a DC voltage of 3.0 kV to the shield. Thus, by applying a DC voltage of 3.0 kV to the shield of the peeling corotron 34 and biasing the shield, an electric field for concentrating the peeling discharge of the peeling corotron 34 with the opposing electrode plate 60 is formed. It is supposed to do.

Further, the voltage applied to the peeling corotron 34 is controlled according to the type of the transfer paper 24, and
In the case of P film, the output of AC voltage is 5.5 effective value.
It is set to increase to kV. By doing so, it is possible to prevent toner scattering due to peeling discharge even in the case where the surface resistance is high and the amount of residual charges is large as in the case of an OHP film.

With the above structure, the digital color image forming apparatus according to this embodiment surely prevents the leading end of the transfer material from interfering with the charge eliminating means with a simple structure and low cost as follows. At the same time, it is possible to prevent defective peeling of the transfer material and image defects caused by peeling discharge.

That is, in the digital color image forming apparatus according to this embodiment, as shown in FIGS. 2 and 3, black (K), yellow (Y), and magenta (M) are sequentially formed on the photosensitive drum 20. ), A cyan (C) toner image,
After the transfer drum 23 is attracted onto the transfer drum 23, the transfer drum 23 is sequentially transferred in multiples as the transfer drum 23 rotates.
The transfer paper 24 on which the toner images of the predetermined number of colors have been transferred
Is conveyed with the rotation of the transfer drum 23 and guided to the peeling section. The transfer paper 24 guided to the peeling section has its surface charge removed by a peeling corotron 34, and a peeling device 44 that comes into contact with both front and back surfaces of the transfer drum 23.
The fingers 50 and the inner pressing roll 51 separate the transfer film 23 from the transfer film 42. In this way, the transfer paper 24 is separated from the surface of the transfer drum 23, and then the fixing device 35 is inserted through the conveyance guide 45.
The sheet is conveyed to the fixing unit 35 and fixed by the fixing unit 35, and is ejected by the fuser outlet roll 46 to the outside of the apparatus.
6 is discharged.

By the way, in this embodiment, as shown in FIGS.
As shown in FIG. 7, the peeling corotron 34 is not located near the peeling portion of the transfer drum 23 but before the peeling force of the peeling fingers 50 or the like acts, to a position where the transfer paper 24 peeled from the transfer drum 23 does not interfere. It is arranged apart from the transfer drum 23. Therefore, when the tip of the transfer paper 24 separated from the transfer drum 23 is curled or when the transfer paper 24 is a strong paper such as a thick paper such as a postcard, the transfer paper 24 is elastically restored by the elastic restoring force. Even if the leading edge of the transfer sheet 24 is separated from the transfer drum 23 before being conveyed to the peeling section, the leading edge of the transfer sheet 24 does not interfere with the peeling corotron 34, so that a jam of the transfer sheet 24 or a so-called unfixed toner image. It is possible to prevent an image defect called "smudge" from occurring.
Further, even when the peeling corotron 34 is arranged so as to be separated from the transfer drum 23 to a position where the transfer paper 24 peeled off does not interfere, as shown in FIG. 1, FIG. 8 and FIG. Since the electrode plate 60 is provided as the static electricity removing action concentrating means for concentrating on the peeling portion of the drum 23, the static eliminating action by the peeling corotron 34 can be sufficiently exerted, and the peeling failure and the toner scattering are surely generated. Can be prevented.

As described above, in the above embodiment, the transfer corotron 34 is separated from the transfer drum 23 before the separation force by the separation fingers 50 or the like acts on the transfer paper 24.
Is arranged so as to be separated from the transfer drum 23 to a position where the peeling corotron 34 does not interfere with each other, and an electrode plate 60 for concentrating the charge removal action of the peeling corotron 34 in the peeling region of the transfer drum 23 is provided. The transfer paper 24 separated from the transfer drum 23
Is separated from the transfer drum 23 up to a position where the peeling corotron 34 does not interfere, the interference of the leading end of the transfer paper 24 with the peeling corotron 34 can be surely prevented, and the charge removing action by the peeling corotron 34 is achieved. Since the electrode plate 60 for concentrating the peeling corotron on the peeling portion of the transfer drum 23 is provided, the charge removing action of the peeling corotron 34 can be concentrated on the peeling region of the transfer drum 23 by the electrode plate 60. Even when they are arranged apart from each other, it is not necessary to increase the output of the peeling corotron 34 more than necessary, and it is possible to prevent defective peeling of the transfer paper 24 and image defects due to peeling discharge. Further, in the present invention, since the electrode plate 60 only has to be provided, the above effect can be achieved with a simple configuration and low cost.

In order to clarify the relationship between the scattering of toner and the occurrence of jams / smudges and the distance between the peeling corotron 34 and the transfer drum 23, the present inventors prototyped a device as shown in FIG. An experiment was conducted to check the occurrence of toner scattering. That is, the inventors of the present invention prototyped a device as shown in FIG. 3, and when the gap between the end of the peeling corotron 34 and the surface of the transfer drum 23 was changed, the peeling corotron 34 was formed on the surface of the transfer drum 23. The presence or absence of a jam or so-called "smudge" of the transfer paper 24 due to the proximity thereof and the presence or absence of toner scattering due to poor charge removal due to the separation corotron 34 moving away from the separation portion of the transfer drum 23 are determined. An experiment was carried out to confirm by changing the basis weight (weight per unit area) of 24.

FIG. 10 shows the result of the above experiment.

As is clear from this figure, the transfer paper 24
It was found that it is necessary to set the gap between the end of the peeling corotron 34 and the surface of the transfer drum 23 to 20 mm or more and 40 mm or less in order to simultaneously prevent the occurrence of jamming and so-called "smudge" and toner scattering. .

Next, the present inventors conducted an experiment to examine the relationship between the toner scattering and the voltage applied to the peeling corotron 34. The measurement environment was a low temperature and low humidity environment, and the transfer paper 24 having a basis weight of 64 gsm was used.

FIG. 11 shows the result of the above experiment.

As is apparent from this figure, in order to prevent the toner from scattering, the AC voltage and the DC voltage applied to the peeling corotron 34, and the AC voltage has an effective value of 5.0 k.
It is desirable to set the DC voltage to V or more and the DC voltage to 2.0 kV or more and 4.0 kV or less. In addition, the above peeling corotron 3
The upper limit of the DC voltage applied to 4 is 4.0 kV, which is a value required for reasons of the dielectric strength of the peeling corotron 34.

Second Embodiment FIG. 12 shows a second embodiment of the image forming apparatus according to the present invention. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals. , Is configured to control the voltage applied to the charge eliminating unit in accordance with the change in the environment.

That is, in the second embodiment, as shown in FIG. 12, a temperature sensor 70 for detecting the temperature inside the machine and a humidity sensor 7 for detecting the relative humidity inside the machine are provided.
1 and 1 are arranged to control the voltage applied to the peeling corotron 34 as a charge eliminating means depending on the temperature and humidity inside the machine.

FIG. 13 shows the control state of the voltage applied to the peeling corotron 34, and this control table is stored in advance in a ROM or the like connected to the CPU.

In the figure, in the case of high humidity environments 1 to 3 where the absolute humidity AH is 16 or more, only the AC voltage is applied to the peeling corotron 34 without applying the DC voltage.

As described above, under high humidity conditions in which peeling discharge is unlikely to occur, even if the DC output of the peeling corotron 34 is turned off, the unfixed toner image is not disturbed, and transfer defects due to excessive static elimination are caused. It can be avoided.

When only the humidity sensor 71 for detecting the relative humidity inside the machine is arranged to simplify the structure, when the relative humidity RH becomes 70% or more according to the output value of the humidity sensor 71. Alternatively, the peeling corotron 34 may be configured so that a DC voltage is not applied.

The other structure and operation are the same as those of the first embodiment, and therefore the description thereof is omitted.

Third Embodiment FIG. 14 shows an image forming apparatus according to a third embodiment of the present invention. The same parts as those in the above embodiment are designated by the same reference numerals. , The static elimination action concentrating means does not consist of the electrode plates arranged in parallel along the transfer drum, but the tip disposed along the axial direction in the peeling portion of the transfer drum is orthogonal to the transfer drum. It is composed of a plate-shaped electrode plate.

That is, in this embodiment, the electrode plate 60 as the static eliminating action concentrating means is not arranged along the surface of the transfer drum 23, but at the peeling portion of the transfer drum 23, the electrode plate 60 of the transfer drum 23 is removed. It is arranged so as to be orthogonal to the surface. Further, as shown in FIG. 15, the electrode plate 60 has a saw-toothed end portion on the transfer drum 23 side, which facilitates concentration of an electric field formed by the peeling corotron 34.

The other structure and operation are the same as those in the first embodiment, and therefore their explanations are omitted.

[0069]

As described above, according to the present invention, in the image forming apparatus according to the first aspect of the present invention, the charge removing means is used to transfer the transfer material separated from the transfer material carrier to a position where the transfer material does not interfere with the transfer material. The charge removing means is arranged apart from the material carrying member, and the charge removing means is arranged so as to concentrate the charge removing effect by the charge removing means in the peeling area of the transfer material carrying member. By arranging the transfer material separated from the transfer material carrier so as not to interfere with the transfer material, it is possible to reliably prevent the tip of the transfer material from interfering with the charge eliminating means. Also,
Since the static elimination effect concentration means for concentrating the static elimination effect by the static elimination means on the peeling area of the transfer material carrier is provided, even if the static elimination means is arranged apart from the transfer material carrier, the static elimination effect concentrated means is used. It is possible to concentrate the charge removal effect of the transfer material on the peeling area of the transfer material carrier, and it is not necessary to increase the output of the charge removing means more than necessary, and it is possible to prevent image defects due to defective peeling of the transfer material or peeling discharge. be able to. Further, since it is only necessary to provide the static eliminating action concentrating means, the above effect can be achieved with a simple configuration and low cost.

Further, in the image forming apparatus according to claim 2 of the present invention, in the image forming apparatus according to claim 1, the charge removing action by the charge removing means is concentrated on the peeling area of the transfer material carrier. Since the static elimination action concentrating means is composed of the electrodes provided inside the transfer material carrier facing the static elimination means, the tip of the transfer material serves as the static elimination means with a simple structure of adding electrodes and at low cost. It is possible to provide an image forming apparatus capable of reliably preventing interference and preventing image defects due to defective peeling of a transfer material or peeling discharge.

Further, in the image forming apparatus according to claim 3 of the present invention, in the image forming apparatus according to claim 1 or 2, the charge eliminating means corresponds to the electric resistance of the transfer material. When the output is controlled and the electric resistance of the transfer material is small, the output of the DC discharge of the static eliminator is set to be small, so when the electric resistance of the transfer material is small such as in a high temperature and high humidity environment. Even if the DC discharge output of the static eliminator is set small, it is possible to reliably prevent the tip of the transfer material from interfering with the static eliminator, and prevent peeling defects of the transfer material and image defects caused by the peel discharge. can do.

Further, in the image forming apparatus according to claim 4 of the present invention, in the image forming apparatus according to claim 1 or 2, the DC bias voltage applied to the discharging unit is 2. Since it is configured to be set to 0 kV or more, it is possible to reliably prevent the toner from scattering due to the peeling discharge, as is clear from the experiments by the present inventors.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts showing a digital color image forming apparatus as an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram showing a digital color image forming apparatus as an embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a main part configuration diagram showing a digital color image forming apparatus as an embodiment of the image forming apparatus according to the present invention.

FIG. 4 is an external perspective view showing a transfer drum.

FIG. 5 is a sectional configuration diagram showing a main part of a transfer drum.

FIG. 6 is a timing chart showing the timing of the peeling operation.

FIG. 7 is a cross-sectional configuration diagram showing a peeling portion of the transfer drum.

FIG. 8 is a configuration diagram showing an electrode plate provided inside a transfer drum.

FIG. 9 is a perspective configuration diagram showing an electrode plate and an internal pressing roll.

FIG. 10 is a graph showing the relationship between the distance between the peeling corotron and the transfer drum and the state of occurrence of toner scattering and the like.

FIG. 11 is a chart showing the relationship between the AC and DC applied voltages of the peeling corotron and the occurrence of toner scattering.

FIG. 12 is a main part configuration diagram showing a digital color image forming apparatus as another embodiment of the image forming apparatus according to the present invention.

FIG. 13 is a chart showing a method of setting conditions in environmental changes of a digital color image forming apparatus according to another embodiment of the present invention.

FIG. 14 is a cross-sectional configuration diagram showing a peeling portion of a transfer drum according to another embodiment of the present invention.

15 is a partially omitted front view showing an electrode plate in the embodiment of FIG.

FIG. 16 is a perspective view showing a peeling device for a transfer drum in a conventional image forming apparatus.

17 (a) and 17 (b) are cross-sectional explanatory views showing the operation of the peeling section in the apparatus shown in FIG. 16, respectively.

18 (a) and (b) are X- of FIG. 17 (b).
It is an X-ray sectional view and a YY line sectional view.

FIG. 19 is an explanatory diagram showing a peeling unit in a conventional image forming apparatus.

FIG. 20 is a graph showing the relationship between transfer current and transfer efficiency.

[Explanation of symbols]

20 photoconductor drum, 23 transfer drum, 24 transfer paper, 25 transfer corotron, 20 photoconductor drum, 25
Transfer corotron, 34 peeling corotron, 50 peeling finger, 51 internal pressing roll, 60 electrode plate, 62
AC power supply, 63 DC power supply.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Yamamoto 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor Fumio Furusawa 2274, Hongo Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor Masaaki Tokunaga 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A plurality of toner images of different colors are sequentially formed on an image carrier, and the plurality of toner images formed on the image carrier are electrostatically adsorbed on the transfer material carrier. In an image forming apparatus for forming an image by transferring the transfer material in a state of being sequentially superposed on the transfer material, and for separating the transfer material from the transfer material carrier by a combination of charge removal by the charge removing means and mechanical force by the peeling means, The static elimination means is arranged apart from the transfer material carrier until the position where the transfer material separated from the transfer material carrier does not interfere with the mechanical force applied by the peeling means, and the static elimination effect by the static elimination means is achieved. An image forming apparatus comprising: a static eliminating effect concentrating means for concentrating the charge in a peeling area of a transfer material carrier. 2. The image forming apparatus according to claim 1, wherein the static elimination effect concentration means for concentrating the static elimination effect of the static elimination means on the peeling area of the transfer material carrier is opposed to the static elimination means. An image forming apparatus comprising an electrode provided on the inside of the image forming apparatus. 3. The image forming apparatus according to claim 1 or 2, wherein the discharging unit controls the output according to a change in the electric resistance of the transfer material, and when the electric resistance of the transfer material is small. An image forming apparatus characterized in that the output of the DC discharge of the charge eliminating means is set to be small. 4. The image forming apparatus according to claim 1, wherein the DC bias voltage applied to the charge eliminating unit is set to 2.0 kV or more. apparatus.