JPH06118809A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device preventing a toner image after being transferred from being made irregular by peeling a form after a transfer is performed, having electric resistance sufficiently higher than that of a plain form from a photosensitive body without discharging a spark. CONSTITUTION:This image forming device is constituted so as to apply a bias voltage having the polarity reverse to the electrifying polarity of the toner image and a prescribed level on the front surface 15A of the form having the electric resistance sufficiently higher than that of the plain form carried via an electrifying voltage applying means 6 provided opposite to a form guiding means 5, moreover, apply a prescribed bias voltage having the polarity reverse to the electrifying polarity of the toner image on the side edge part of the front surface 15A of the form 15 via a form feeding auxiliary means 9 provided so as to opposite to a form carrying means 8 and pressed with contact with both side edge parts of the form 15 to carry it, and peel the form 15 after the transfer is performed from the photosensitive body 1 without generating the discharge of the spark.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transfers a toner image of a photoconductor onto a paper having an electric resistance sufficiently higher than that of plain paper, and then peels off the paper from the sensitizer without generating spark discharge. The present invention relates to a possible image forming apparatus.

[0002]

2. Description of the Related Art A toner image on a photoconductor is transferred by a transfer charger to a sheet which is in sliding contact with the photoconductor, and the toner image is separated from the photoconductor by a peeling charger and fixed by a fixing device. In order to charge the opposite polarity of the charge at the time of transfer, the paper conveyed toward the fixing device has the charge charged at the time of transfer neutralized after peeling, or the charge of the polarity received at the time of peeling. Therefore, the electrostatic force acting between the toner image and the paper is reduced, and a part of the toner is pulled onto the fixing roller during fixing, which causes so-called electrostatic fixing offset. There is.

In order to solve this, as shown in FIG. 5 (Japanese Patent Laid-Open No. 3-67282), a sheet conveyed in the direction of arrow M is introduced between the photoconductor 21 and the transfer charger 22. Then, the toner image formed on the photoconductor 21 is transferred from the back surface of the paper by charging with an electric charge having a polarity opposite to the polarity of the toner image, and after the transfer, the peeling charger 23 has a polarity opposite to the polarity of the transfer voltage. A sheet is peeled from the photoconductor 21 by applying an electric charge, and the sheet is conveyed by a belt type sheet conveying device 24 to which a voltage of a predetermined magnitude is applied from a grounded voltage source 26 such as a varistor.
To send to. Since the leakage current from the shield member of the transfer charger 22 is applied to the belt of the sheet conveying device 24, the conveying device 24 is charged with a charge having a polarity opposite to that of the toner image. Therefore, the toner is attracted from the back surface of the paper to the front surface of the paper, and electrostatic offset that occurs during fixing is prevented.

According to the structure shown in FIG. 5, since the transfer current is greatly attenuated, the shield current that can be supplied to the transport device 24 is affected, and a stable voltage cannot be supplied. Therefore, as shown in FIG.
No. 67282), the photoconductor 2 not transferred to the paper
Cleaning roller 2 that removes residual toner on the peripheral surface
7 is applied to the belt surface of the transport device 24, so that the toner is attracted from the back surface of the paper to the paper surface, and the defect of the toner image suction power supply device shown in FIG. 5 is eliminated. I have to.

[0005]

Although not clearly shown in any one of FIG. 5 and FIG. 6, in the electrophotographic image forming apparatus of this type, as shown in FIG. A conductive paper guide plate 30 to which a constant voltage is applied by a grounded voltage source 31 and a conductive tube 33 are arranged between the container 22 and a paper cassette (not shown). Then, when the plain paper 32 having an electric resistance, that is, a surface resistance of, for example, 10 ^{12 to} 10 ¹³ Ωcm taken out from the paper cassette is fed to the transfer charger 22 while being sucked by the paper guide plate 30. A negative transfer voltage is applied from the transfer charger 22 from the back surface of the paper, but since the surface resistance is low, the excess charge is generated by the conductive tube 3.
The toner is discharged to the ground side via 3, so that a transfer voltage of a constant level sufficient to attract the toner image to the paper 32 is uniformly charged, and a good charged state appears on the paper surface.
Therefore, an electric potential of an appropriate level lower than the discharge start voltage is held between the photoconductor 21 and the paper 32, and when the paper 32 after transfer is separated from the photoconductor, the photoconductor and the paper 32 are separated from each other. It is peeled off without generating spark discharge in the meantime.

However, the surface resistance of the paper is 10 ^{14 to} 10 ¹⁶ Ωcm rather than the electric resistance of the above-mentioned plain paper.
Volume resistance in the thickness direction is 10 ^{15 to} 10 ¹⁶ Ωcm
The volume resistance is high even if a negative charge is applied from the back of a transfer charger having a certain level of characteristics, such as OHP (over head projector) paper, which is much higher. Therefore, the charging voltage appearing on the front side of the paper may be weak, and the high surface resistance makes it difficult for the charged charges on the back side of the paper to flow to the ground side, and the electrostatic charge from the photoconductor causes the charging voltage on the paper surface to be abnormal. The charge potential on the paper surface is not maintained at a constant potential.

When an abnormally high charging voltage is generated, the potential difference between the photoconductor and the paper becomes large, and when the potential difference becomes equal to or higher than the discharge start, spark discharge is generated at the time of peeling, and toner on the paper after transfer is generated. If the image is scattered or, on the contrary, if it is not sufficiently charged, the adsorbing force for the toner image is reduced, and a white blank image is locally formed. Therefore, the transfer method in which the bias voltage is applied from the back surface of the paper has a problem that the electric potential on the paper surface, which has an electric resistance sufficiently higher than that of plain paper, cannot be well controlled.

Therefore, also in the case shown in FIGS. 5 and 6, even if the transfer charger is used to charge from the back surface of the paper having an electric resistance sufficiently higher than that of plain paper, for the same reason.
There are problems such as spark discharge when peeling,
In addition, the leading edge of the separated sheet of paper after transfer is the transport roller 24.
When it reaches the upper side, the shield current of the transfer charger 22 or the friction voltage of the cleaning roller 27 is changed to the conveying roller 2
Even if the voltage is applied to the back side of the sheet from No. 4, the charged state of the front side of the sheet can be controlled only from the back side of the sheet, and the above-mentioned problems cannot be solved.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to transfer a toner image of a photoconductor onto a sheet having an electric resistance sufficiently higher than that of ordinary paper, An object of the present invention is to provide an image forming apparatus in which the toner is peeled off from a photoconductor without generating spark discharge and the toner image after transfer is not disturbed.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a transfer charger for transferring a toner image formed on the peripheral surface of a photoconductor to a paper on the outer periphery of a photoconductor, and a peeling charge for peeling a transfer paper from the photoconductor. While the units are sequentially arranged, a peeling charger, a transfer charger, a sheet guiding unit that guides the sheet between the photoconductor, and a sheet conveying unit that conveys the separated sheet toward the fixing device. In the electrophotographic image forming apparatus for applying a voltage of a predetermined magnitude with a polarity opposite to the charging polarity of the toner image to the paper guiding means and the paper transporting means. Through the opposite charging voltage applying means, the surface of the sheet having the electric resistance sufficiently higher than the electric resistance of the plain paper conveyed to the paper guiding means is provided with a predetermined polarity opposite to the charging polarity of the toner image. Sized grounded via The side of the sheet that is conveyed toward the fixing device through the sheet feed assisting means that is applied with a voltage and is opposed to the sheet conveying means, and presses the both side edges of the surface of the sheet facing the top to convey the sheet. A grounded bias voltage having the same polarity and magnitude as the above bias voltage is applied to the edge-facing surface of the paper, and the charging potential of the paper-facing surface of the paper is changed from the photoconductor to the top. It is configured so as to be held at the potential for peeling without causing spark discharge.

Further, the charging voltage applying means of the present invention is characterized by being a conductive brush or a conductive roller.

[0012]

By the charging voltage applying means, a predetermined polarity opposite to the charging polarity of the toner image is applied to the surface of the paper having a sufficiently higher electric resistance than the plain paper conveyed from the paper guiding means toward the transfer charger. A bias voltage of a magnitude is applied to charge the surface of the paper to a constant potential, and the front end of the paper after transfer is separated from the photoconductor without generating spark discharge. Then, even when the leading edge of the sheet reaches the sheet transporting means and the trailing edge of the sheet is separated from the photoconductor, the above-mentioned bias voltage Since the bias voltage having the same polarity and the same magnitude is applied to the surface of the paper, the surface of the paper is charged to the same potential, and spark discharge does not occur even when the trailing edge is separated from the photoconductor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on the embodiments shown in the accompanying drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a view showing a state in which a sheet is being fed to a transfer charger in the above embodiment, and FIG. 3 is a sheet guide plate to be conveyed and a sheet feed assist. It is a figure which shows the state which is straddling the apparatus. The functions of the paper guide plate 5, the conductive tube 4, and the paper transport belt 8 of this embodiment have the same functions as those of the conventional example described above, and thus detailed description thereof will be omitted.

In FIG. 1, a corona transfer charger 2 for generating a negative charge and a corona type for generating a positive charge are provided on the peripheral surface of the photoreceptor 1 from the upper side to the lower side in the rotation direction of the photoreceptor 1. The peeling charger 3 is sequentially arranged in parallel. To this transfer charger 2, a sufficiently large electric resistance, that is, a surface resistance of about 10 ^{14 to} 10 ¹⁶ Ωcm and a volume resistance of 10 ¹⁵ is higher than that of plain paper having a surface resistance of about 10 ^{12 to} 10 ¹³ Ωcm. A conductive paper guide plate 5 so that a paper of about 10 ¹⁶ Ωcm can be guided toward the transfer charger 2 and the peeling charger 3 while slidingly contacting the photoreceptor 1, And a conductive tube 4 that is driven to rotate are sequentially arranged.

A conductive paper transport belt 8 for attracting a toner image from the back surface of the paper toward the pressure roll 13 and the heating roll 14 which form the fixing device from the peeling charger 3, and a conductive paper guide plate. 11 are sequentially arranged. Each of the paper guide plate 5, the conductive tube 4, the conveyor belt 8 and the paper guide plate 11 has a negative polarity opposite to the charge polarity of the toner image on the photoconductor 1; To apply a voltage, a grounded DC voltage source, a varistor, a Zener diode, or a bias power source 12 having a high resistance of about 100 MΩ is connected.

A conductive brush 6 is provided opposite to the paper guide plate 5 on the paper supply side, and the brush 6 has a surface 15A (FIG. 2) of the paper 15 conveyed to the paper guide plate 5, that is, the ceiling. A grounded DC power supply 7 is connected so that a constant voltage of, for example, 1000V, which has a negative polarity opposite to the voltage polarity of the toner image, is applied to the surface facing toward. Further, the peeling charger 3
The paper transport belt 8 that discharges the paper from the pressure roll 13 and the heating roll 14 to the pressure roll 13 and the heating roll 14 has a peripheral edge portion on both side edges of the surface 15A (FIG. 3) of the peeled paper 15 that is transported by the belt 8. A sheet-feeding assisting device 9 composed of a pair of rotating bodies that are driven to rotate as the sheet is conveyed is provided opposite to the sheet-feeding assisting device 9. Is a bias power supply 10 composed of a DC power supply, a varistor, a Zener diode, or a high resistance grounded so as to apply a negative constant voltage of 1000 V opposite to the voltage polarity of the toner image.
Are connected. The conductive brush 6 and the sheet feeding auxiliary device 9 are arranged at intervals shorter than the length from the leading end to the trailing end of the sheet.

The operation of the thus constructed apparatus will be described. In FIG. 2, a sheet having an electric resistance sufficiently higher than that of the plain sheet is now conveyed from a sheet cassette (not shown) toward the sheet guide plate 5 as shown by an arrow A. From the front end portion to the rear end portion of the surface 15A of the paper 15 conveyed to the paper guide plate 5, the conductive brush 6 is sequentially brought into contact with the conveyance, whereby the polarity opposite to the charge polarity of the toner image. The entire surface 15A of the paper 15 is uniformly charged by the negative voltage of 1000V.

Then, the paper 15 is introduced from the leading end of the paper 15 into the transfer charger 2 while slidingly contacting the photoconductor 1 through the conductive roll 4, and the transfer charger 2 applies a negative transfer voltage to the back surface of the paper 15. Is applied. However, since a charging voltage having a polarity opposite to the charging polarity of the toner image on the photoconductor 1 and having a predetermined magnitude is applied to the paper surface 15A through the conductive brush 6, the paper applied by the transfer charger 2 is charged. Surface 15
When the charging potential of A is too high, the surplus charge is discharged to the ground side through the conductive brush 6 and the power source 7, so that the potential difference between the photoconductor 1 and the paper slidingly contacting it is uniform. In addition, when the charging potential of the paper surface 15A is low, electric charges are supplied from the power source 7 to the paper surface 15A via the conductive brush 6, and the surface 15A of the paper 15 is uniformly charged.

Therefore, the toner image formed on the peripheral surface of the photosensitive member 1 is transferred onto the surface 15A of the paper 15 without white spots, and further, from the front end of the paper 15 after the transfer.
After reaching the peeling charger 3, a positive voltage is applied by the peeling charger 3, and spark 15 is not generated, that is, the toner image after transfer is not disturbed, and the paper 15 is fed from the photoreceptor 1. Are sequentially peeled off from the tip. And paper 1
Even when the front end of the sheet 5 reaches the sheet feeding assisting device 9 on the sheet conveying belt 8, the surface 15A of the sheet 15 is charged to the same potential via the conductive brush 6, so that the spark voltage is not generated. It will be peeled off.

Further, as shown in FIG. 3, as the photosensitive member 1 rotates, the sheet 15 is continuously conveyed toward the conveying roller 8, and the leading end of the sheet 15 reaches the sheet conveying belt 8,
The sheet feeding assisting device 9 presses both side edges of the surface 15A of the sheet 15 to convey the sheet 15. The paper feed assisting device 9 has a power source 10 which has a negative polarity of 1000.
Since the voltage of V is applied, the surface 15A of the paper 15
Even if the rear end is released from contact with the conductive brush 6, the charging voltage of the same polarity and the same magnitude as that of the power supply 7 is applied to and retained on the surface 15A of the paper 15, so that the rear end of the photoreceptor 1
Even when the toner image is peeled off, the spark discharge is not generated and the toner image is not disturbed. Then, it is conveyed toward the rollers 13 and 14 of the fixing device.

FIG. 4 shows another embodiment of the present invention. Instead of the conductive brush 6, a conductive roll 17 can be used to apply a negative charging voltage to the paper 15.
Further, instead of the DC voltage source 7, it is possible to use a varistor, a Zener diode, or a resistor having a high resistance, which is grounded.

In this embodiment, the power source 12 for the paper guide plate 5 and the like and the Baice power source 7 for the conductive brush 6 are provided separately, but they may be commonly connected to a single power source for use. Often,
Further, the three bias power sources 10 of the sheet feeding auxiliary device 9 may be commonly connected to a single power source and used.

[0023]

As described above, according to the present invention, the transfer voltage is applied from the back side of the paper by the transfer charger, and the paper is conveyed through the charging voltage applying means opposite to the paper guiding means. A sheet feeding auxiliary that applies a bias voltage of a predetermined magnitude and has a polarity opposite to the charging polarity of the toner image on the surface that faces the top of the sheet, and that is placed opposite to the sheet conveying unit and conveys the sheet toward the fixing device. The bias voltage having the same polarity and the same magnitude as the above bias voltage is applied to the side of the side of the sheet facing the top through the means, so that the electric resistance is sufficiently higher than that of the ordinary sheet. Apply a transfer voltage to the back surface of the papers you have, and apply the charging voltage from the surface facing the top of the paper even if the charging voltage applied to the surface of the papers by this voltage is insufficient due to its electric resistance. Control this constant Since Rukoto can, a paper such post-transcriptional having electrical characteristics described above, the photosensitive member can be peeled off without generating spark discharge between the paper. For this reason, the toner image can be conveyed toward the fixing device without causing any disturbance, and white spots and the like in the image that occur during the transfer process when the magnitude of the charging voltage is insufficient. It can be removed and the image quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an apparatus of the present invention.

FIG. 2 is a diagram showing a state in which a sheet is conveyed onto a transfer charger in the above embodiment.

FIG. 3 is a diagram showing a state in which a sheet is conveyed across a sheet guide plate and a sheet feeding auxiliary device in the above embodiment.

FIG. 4 is a configuration diagram of another embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional image forming apparatus.

FIG. 6 is a configuration diagram of a conventional apparatus which is an improvement of the image forming apparatus shown in FIG.

FIG. 7 is a configuration diagram of a conventional image forming apparatus including a paper guide plate.

[Explanation of symbols]

1 Photoconductor, 2 Transfer Charger, 3 Peeling Charger, 4 Conductive Tube, 5 Paper Guide Plate, 6 Conductive Brush, 7
DC power supply for bias, 8 paper feeding belt, 9 paper feeding auxiliary device, 10 bias power supply, 11 paper guide plate, 12 power supply, 13 fixing pressure roll, 14 fixing heating roller, 15 sufficiently higher electric resistance than plain paper Paper to have.

Claims (2)

[Claims] 1. A transfer charger for transferring a toner image formed on the peripheral surface of the photoreceptor to a sheet and a peeling charger for peeling the transfer sheet from the photoreceptor are sequentially arranged on the outer periphery of the photoreceptor. On the other hand, the peeling charging device, the transfer charging device, a paper guiding unit for guiding the paper between the photoconductor, and a paper conveying unit for conveying the peeled paper toward the fixing device, In an electrophotographic image forming apparatus that applies a voltage of a predetermined magnitude to each of the paper guide means and the paper transport means, the polarity being opposite to the charging polarity of the toner image, the paper guide means is provided opposite to the paper guide means. Via the charging voltage applying means, the surface of the paper having an electric resistance sufficiently higher than the electric resistance of the plain paper conveyed to the paper guiding means has a predetermined polarity opposite to the charging polarity of the toner image. Bulk grounded vias Voltage is applied to the sheet conveying means, and the sheet is conveyed toward the fixing device through the sheet feeding assisting means that is pressed against both side edges of the surface of the sheet facing the top and conveys the sheet. A grounded bias voltage having the same polarity and the same magnitude of the bias voltage is applied to the surface of the side edge portion of the paper which faces the top,
An image forming apparatus, characterized in that the charging potential of the surface of the sheet facing the top is held at a potential at which the sheet is separated from the photoconductor without generating spark discharge. 2. The image forming apparatus according to claim 1, wherein the charging voltage applying unit is a conductive brush or a conductive roller.