JP2000066536A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the tailing of transfer material in a high humidity environment. SOLUTION: This image forming device is provided with a transfer roller 14 transferring a toner image on a photoreceptor drum 1 to the transfer material 19, a discharging member 8 discharging the transfer material in order to separate the transfer material from the drum 1; and the member 8 is provided with plural levels of applied potential, and also provided with a switching means 15 switching the level of potential applied to the member 18 according to detected voltage at the time of applying constant current bias to the roller 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer or ion conductive transfer roller for transferring a toner image on an image carrier to a transfer material, and a charge eliminator for separating the transfer material from the image carrier. And an image forming apparatus having a plurality of levels of potentials applied when the charge eliminating member removes electricity from the transfer material.

[0002]

2. Description of the Related Art In an image forming apparatus for transferring a toner image formed on a photosensitive drum, which is an image carrier, to a transfer material by a transfer roller to which a voltage is applied, the transferred transfer material is electrostatically attracted to the photosensitive drum. Therefore, when the transfer material is separated from the photosensitive drum, the rear end of the transfer material is charged to the same polarity as the transfer voltage by peeling charging, and the separation of the rear end of the transfer material from the photosensitive drum may be delayed.

If the separation of the rear end of the transfer material from the drum is delayed,
The trailing edge of the transfer material is pulled in the direction in which the drum rotates, and the trailing edge of the transfer material is moved closer to the drum. Image formation is disturbed due to disturbed image formation, and toner adhered by scattering at the bottom of the cleaning container is transferred to the transfer material, thereby causing a wood end stain on the rear end of the transfer material.

In the case of performing double-sided printing, a transfer material that is curled in the same direction as the curvature of the drum after printing on the first side is passed during printing on the second side, and the effect of curvature separation is small. This makes it impossible to separate the leading end of the transfer material from the drum, thereby causing a problem that a paper jam occurs.

[0005] Therefore, a predetermined potential is applied to the charge removing needle to remove charge from the transfer material to promote separation from the photosensitive drum. FIG. 6 shows the sequence at this time.

By applying a voltage of -2.5 kV to the vicinity of the rear end of the transfer material and eliminating the charge, image defects such as image rubbing and dirt due to the rear end of the transfer material can be prevented. By applying -2.5 kV to the tip and eliminating the charge,
The transfer material having a curl in the same direction as the photosensitive drum can be separated from the photosensitive drum at the end of the second surface of the transfer material.

A transfer needle bias of -1.5 kV is also applied to the center of the transfer material to prevent a transfer failure due to electrostatic attraction to the transfer guide.

[0008]

However, in the above conventional example, the following problems occur depending on the use environment of the apparatus.

In a high-humidity environment, the current to be transferred as transfer charge cannot be held on the transfer material because the resistance of the transfer material is reduced, and the electrostatic force for retaining the toner on the transfer material is weakened. In such a state, the water contained in the transfer material evaporates violently at the time of fixing, and the unfixed toner on the transfer material may be scattered in the direction opposite to the paper transport direction and fixed. This is called tailing, and an image as shown in FIG. 10 is formed.

When a hygroscopic paper is used in a high-humidity environment, if a bias having a polarity opposite to that of the transfer bias is applied to the discharging needle at the rear end of the transfer material, the resistance of the transfer material is low. In some cases, the electric charges in the portion are eliminated, and a wide area tailing may occur at the rear end of the first surface as shown in FIG. The range in which tailing occurs is the distance between static elimination and fixing.
When the transfer material is thin and weak in a low-humidity environment, or when the outer diameter of the photosensitive drum is so large that separation of the transfer material from the drum (curvature separation) cannot be expected, the leading edge of the first surface may also cause damage from the drum. There has been a problem that the paper cannot be separated and a paper jam occurs. For example, when thin paper having a basis weight of 60 g / m ² or less such as a badger bond is used as a transfer material, or when the outer diameter of the photosensitive drum is 40 mm or more, paper jam is likely to occur.

[0011]

In order to achieve the above object, a first aspect of the present invention provides a polymer or ion conductive transfer roller for transferring a toner image on an image carrier to a transfer material, An electricity removing member for removing the transfer material from the image carrier to remove the transfer material, wherein the charge removing member has a plurality of levels of potentials applied when removing the transfer material. When the detection voltage at the time of applying a constant current bias to the roller is equal to or lower than a predetermined voltage, the apparatus further comprises a switching unit that switches a potential level to be applied when the charge removing member removes the charge from the transfer material.

In the above configuration, the switching means acts to apply an appropriate charge eliminating bias in a high-humidity environment to suppress the occurrence of tailing when the transfer material absorbs moisture.

To achieve the above object, a second invention according to the present application is directed to a polymer or ion conductive transfer roller for transferring a toner image on an image carrier to a transfer material, and a transfer roller for transferring the toner image from the image carrier. An image forming apparatus having a plurality of levels of potentials applied when the charge removing member removes charges from the transfer material, wherein the constant charge bias is applied to the transfer roller. Means for switching a potential level applied when the charge removing member removes the charge of the transfer material when the detection voltage at the time is equal to or higher than a predetermined voltage. In addition, there is provided switching means for switching a potential level applied when the charge removing member removes the charge of the transfer material with respect to the setting of the thin paper.

In the above configuration, the switching means acts to apply an appropriate charge-eliminating bias in a low-humidity environment to suppress paper jams that occur when the transfer material is thin in a low-humidity environment.

According to a third aspect of the present invention, there is provided a polymer or ion conductive transfer roller for transferring a toner image on an image carrier to a transfer material, and a transfer roller for transferring the toner image from the image carrier. A charge removing member for removing a transfer material to separate the material, and an image forming apparatus having a plurality of levels of potentials applied when the charge removing member removes the charge from the transfer material; It is characterized in that the charge removing member has means for switching a potential level to be applied when the charge of the transfer material is removed.

In the above configuration, the switching means applies an appropriate static elimination bias in accordance with the type of the transfer material, and acts to reduce the power supply and driving load of the high-speed image forming apparatus when thick paper is set.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below. FIG. 2 is an example of an image forming apparatus that performs double-sided printing on a transfer material. When performing double-sided printing, first, the paper 19 on the paper cassette 36 is fed to the paper feed roller 2.
5, the paper is fed one by one, and is conveyed to a conveying roller pair 33 along a guide. The paper 19 is further transported by the rotation of the transport roller pair 33 and is transported along the guide 32 to the registration roller pair 31.

The registration roller pair 31 rotates in accordance with the toner image formed on the drum 1 and conveys the paper to the transfer nip. The image formation on the photosensitive drum 1 is performed first by the charger 2
9, the photosensitive drum 1 is uniformly charged,
To form an electrostatic latent image. The latent image is developed by the developing device 30 to obtain a toner image.

Paper 19 on which a toner image has been transferred at the transfer section
Is fixed by the fixing device 13 to obtain a fixed image. The paper discharged from the fixing device 13 is discharged downward by a flapper 37 rotatably attached, and is conveyed to a reversing roller 40 along a guide 39. While the paper 19 is supported by the guide 41, the forward and reverse rotation of the reversing roller 40 causes
The sheet is transported to the transport roller pair 43 along the guide 42 while being reversed in the traveling direction. The transport roller 43 transports the paper 19 to the transport roller pair 33, and the paper 19 is again subjected to the image transfer fixing process. The paper 19 on which the second surface has been fixed on the transfer material is discharged upward by the flapper 37 and is guided by the guide 38.
The paper is transported along the paper
Is discharged on top. Incidentally, reference numeral 47 shown in FIG. 2 is a housing of the image forming apparatus.

FIG. 1 shows a main part of the present embodiment, and shows a side view of a transfer section of an image forming apparatus. 1, the same members as those in FIG. 2 are denoted by the same reference numerals.

In FIG. 1, reference numeral 1 denotes a photosensitive drum provided with an organic photosensitive member (OPC) layer on the surface of an aluminum cylinder. The outer diameter of the photosensitive drum 1 is 30 mm. The photosensitive drum 1 is negatively and uniformly charged by a charging device (not shown), is image-exposed to form a latent image, and is subjected to reversal development by a developing device (not shown) to form a toner image on its surface.

The toner image is transferred onto paper 19 which is a transfer material conveyed along transfer guide 14. Transcription is
An outer diameter of 2 having a conductive elastic layer 2 on a metal core 3
A transfer nip N formed by the photosensitive drum 1 and the transfer roller 4 as a transfer charger is performed by applying a positive voltage having a polarity opposite to the charge polarity of the toner image from the transfer high voltage power supply 5 to the transfer roller 4 of 0 mm. .

The volume resistivity of the elastic layer 2 of the transfer roller 4 is
It is about 2 × 10 ⁸ Ωcm under the environment of 20 ° C. and 60% Rh, and the transfer voltage applied to the core 3 of the transfer roller is about 0 V to +6 kV.

The magnitude of the voltage applied to the transfer roller is changed depending on the resistance value of the transfer roller, and the magnitude of the voltage is controlled during transfer, during non-transfer, or during stoppage. The control is performed by a control system including a CPU 15, an I / O port 16, a bus line 18, and a memory 17.

The paper 19 after the transfer is electrostatically attracted to the photosensitive drum, and the electricity removing needle 6 separates the paper. The static elimination needle 6 is a SUS plate having a thickness of 0.1 mm, and has a pointed tip (saw shape) as shown in FIG. The pitch a at the tip of the static elimination needle 6 is 1 mm, and the height b of the peak is 2 mm. The static elimination needle 6 is sandwiched between insulating members 7 to form a static elimination needle unit 8.

The paper 19 after the separation is conveyed on the conveyance guide 10 made of insulating resin and conveyed to the fixing device 13. The fixing device 13 has a cylindrical cored bar made of aluminum
Fixing roller 20 coated with FA (perfluoroalkoxy) and halogen heater 2 for warming it from inside
1. A pressure roller 22 for pressing the paper 19 against the fixing roller 20 and a fixing entrance guide 23 for guiding the paper 19 to the nip between the fixing roller 20 and the pressure roller 22.

The paper 19 on which the transfer has been completed passes through the fixing nip to fix the toner image on the paper surface.
The toner remaining on the photosensitive drum 1 without being transferred to the paper 19 in the transfer step is collected by the cleaning device 12. The cleaning device includes a cleaning blade 24 for scraping off residual toner from the drum, and a cleaning container 25 for storing waste toner.

Here, the control of the transfer bias will be specifically described. Voltage value V _t is applied to the transfer roller, a constant current bias is applied to the transfer current when the drum potential dark potential at the non-sheet passing, to determine the voltage V _t0 generated at this time based.

That is, in order to obtain a good image, the transfer voltage is controlled so as to apply an appropriate transfer voltage in accordance with variations in the resistance value of the transfer roller during manufacturing, environmental fluctuations, and durability fluctuations. When the resistance value of the transfer roller is small, the detected voltage _Vt0 also becomes small, and when the resistance value is large, the detected voltage _Vt0 also becomes large.

In particular, when a polymer conductive transfer roller containing NBR or epichlorohydrin rubber as a main component or an ion conductive transfer roller whose resistance is adjusted by an ionic conductive agent is used, the environmental fluctuation of the resistance value is large. .

For example, in the case of a transfer roller having a resistance value of 2 × 10 ⁸ Ω in an environment of 20 ° C. and 60% Rh, 32.5 ° C. and 8%
In a high-temperature and high-humidity environment of 5% Rh, the resistance value is 1 × 10 ⁸
In a low-temperature and low-humidity environment of Ω, 15 ° C. and 10% Rh, the resistance value is 5 × 10 ⁸ Ω.

FIG. 5 shows the resistance value of the transfer roller and the detection voltage _Vt0.
Shows the relationship. From this figure, it can be seen that as the resistance of the transfer roller increases, the value of the detection voltage _Vt0 also increases. In the case of the transfer roller of the present embodiment, the width is 30
When the measurement is performed at 0 mm, the process speed is 150 mm / sec, and the constant current value is 10 μA, the value of the detection voltage V _t0 is 1.4 kV under an environment of 20 ° C. and 60% Rh, 32.5 kV.
0.7kV under 15 ℃, 85% Rh environment, 15 ℃, 10% R
Under the environment of h, the output value becomes 3 kV.

In the present embodiment, it is the same as the conventional example that a bias is applied to the charge eliminating needle to prevent separation of the front end of the second side of the transfer material, splashing of the rear end, and sticking to the transport guide. In addition, the static electricity removal needle bias control is switched by the value of the detection voltage _Vt0 .

FIG. 7 shows a sequence when the value of the detection voltage _Vt0 is small. If the value of the detection voltage _Vt0 of the transfer roller is 0.
When the voltage is 8 kV or less, the environment is determined to be a high humidity environment, and a large bias is not applied to the static elimination needle at the rear end of the first surface where the paper absorbs moisture.

As a result, it is possible to prevent the electric charge between the fixing and static elimination needles from being neutralized, and to prevent the occurrence of an extremely poor level of tailing at the rear end of several hundreds of mm.

In a high-humidity environment, since the resistance of the paper is reduced, the charge is small and the separation from the photosensitive drum is not delayed, and the rear end is unlikely to splash. Therefore, even if a large bias is not applied, problems such as image rubbing and wood-stain stains do not occur.

Further, by applying -2.5 kV to the leading end of the second surface of the paper, the paper can be separated from the photosensitive drum satisfactorily, and by applying -1.5 kV to the center, the paper can be applied to the transport guide. Prevents sticking, and -2.
By applying 5 kV, the rear end splash is prevented,
The paper-passing performance of the second side is also secured.

(Second Embodiment) In this embodiment,
A case in which printing is performed on weakly stiff paper such as thin paper in a low humidity environment will be described. FIG. 4 is a side view of the transfer unit of the image forming apparatus. In FIG. 4, the same members as those in FIG. 2 are denoted by the same reference numerals, and the description of the same parts as those in the first embodiment will be omitted. Further, the transfer guide after the transfer is composed of insulating resinous ribs 27 in which the portions in contact with the paper are arranged in a comb-like shape. By placing the grounded sheet metal 11 on
This prevents paper transport from becoming unstable due to paper curl and lift due to resistance to air.

The image forming apparatus shown in FIG. 4 has a special paper mode. A switch for setting special paper is provided on an operator operation panel 45 of the apparatus. Depending on this, it is possible to partially change the process conditions such as the transfer speed of the transfer material and the fixing temperature.

For example, for paper having a basis weight of 65 g / m ² or less,
We recommend users to set to thin paper mode.
In an apparatus having such a special paper mode, the bias control of the static elimination needle is switched in combination with the special paper setting.

When the value of the detection voltage V _t0 of the transfer roller is large,
FIG. 8 shows a sequence when thin paper is set.

The value of the detected voltage V _t0 is determined that the low-humidity environment when not less than 2 kV, in the case of further passed thin paper also apply a large potential level of -2.5kV to the static charge eliminator in the first side tip . Thereby, the effect of electrostatic separation at the front end of the first surface by the static elimination needle can be increased, so that paper jam of thin paper in a low humidity environment can be prevented.

Further, by applying -2.5 kV to the tip of the second surface, the paper can be separated from the photosensitive drum satisfactorily. -1.2k from the leading edge of the paper to just before the trailing edge
V is applied to prevent electrostatic attraction to the transport guide to prevent paper jam due to sticking.
By applying 5 kV, the rear end splash can be prevented.

Note that this embodiment may be applied independently when the value of the detection voltage _Vt0 of the transfer roller is large or when the thin paper setting is set.

(Third Embodiment) In the present embodiment,
The case of printing on thick paper regardless of the environment will be described.
In the apparatus having the special paper setting shown in FIG. 4, for example, for paper having a basis weight of 115 g / m ² or more, it is recommended to the user to set the thick paper mode. FIG. 9 shows a sequence when thick paper is set. In the case of thick paper, since the paper has stiffness, paper jam or rear end splash due to deterioration of the curvature separation performance does not occur. Therefore, the static elimination needle bias prevents the paper from sticking to the conveyance guide. Only a low level voltage of 2 kV is used.

As a result, the ON / OFF of the bias for applying the static elimination needle is performed.
The number of times of turning off can be reduced, and the power supply and driving load in the case of a higher-speed image forming apparatus can be reduced.

In the first to third embodiments described above, the case where the potential level applied to the static elimination needle is switched has been described, but the application timing may be changed. The same can be applied to the case of single-sided printing.

[0048]

As described above, according to the present invention,
When the detection voltage at the time of applying the constant current bias of the polymer or ion conductive transfer roller is equal to or lower than a predetermined voltage, it is determined that the environment is a high-humidity environment, and by switching the neutralization needle bias, the transfer material in the high-humidity environment is The occurrence of tailing can be prevented.

When the detection voltage when the constant current bias of the transfer roller is applied is equal to or lower than a predetermined voltage, it is determined that the environment is a low humidity environment. Can prevent the thin paper from jamming.

Further, by switching the static elimination needle bias in accordance with the mode setting, for example, in the case of thick paper setting, the static elimination needle bias is reduced to only a low-level voltage to reduce the power supply and driving load of the high-speed image forming apparatus. Can be.

[Brief description of the drawings]

FIG. 1 is a side view of a transfer unit of an image forming apparatus according to a first embodiment.

FIG. 2 is a configuration diagram of an image forming apparatus that performs double-sided printing on a transfer material.

FIG. 3 is an enlarged front view of a static elimination needle.

FIG. 4 is a side view of a transfer unit of the image forming apparatus according to the second embodiment.

FIG. 5 is a diagram illustrating a relationship between a resistance value of a transfer roller and _Vt0 .

FIG. 6 is a diagram showing a sequence of a voltage applied to a conventional static elimination needle.

FIG. 7 is a diagram illustrating a sequence of a voltage applied to the static elimination needle according to the first embodiment;

FIG. 8 is a diagram illustrating a sequence of a voltage applied to a static elimination needle according to a second embodiment.

FIG. 9 is a diagram showing a sequence of a voltage applied to a static elimination needle according to a third embodiment.

FIG. 10 is an explanatory diagram showing a tailing phenomenon.

FIG. 11 is an explanatory diagram showing a tailing occurrence range.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Transfer roller 6 Static elimination needle 9 Power supply of static elimination needle 10 Transport guide 13 Fixer 19 Paper 25 Cleaning container

Continued on the front page F term (reference) 2H027 DA01 EA10 EC06 ED26 EE07 EF09 2H032 AA05 BA01 DA02 DA23 DA24 DA28

Claims (10)

[Claims] A transfer roller configured to transfer a toner image on an image carrier onto a transfer material; and a charge removing member configured to remove a transfer material from the image carrier to separate the transfer material from the image carrier. An image forming apparatus having a plurality of levels of potentials applied by the image forming apparatus, comprising: a switching unit that switches a potential level applied to the charge removing member according to a detection voltage when a constant current bias is applied to the transfer roller. 2. The image forming apparatus according to claim 1, further comprising a switching unit that switches a timing of applying a voltage to the charge removing member according to a detection voltage when a constant current bias is applied to the transfer roller. 3. The transfer roller according to claim 1, wherein the transfer roller contains NBR or hydrin rubber as a component.
An image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the transfer roller includes an ionic conductive agent. 5. The image forming apparatus according to claim 1, wherein a potential having a polarity opposite to a charging polarity of the transfer roller is applied to the charge removing member. 6. A method according to claim 1, further comprising: means for transferring an image to the second surface of the transfer material after transferring the image to the first surface of the transfer material, wherein a detection voltage of the transfer roller when a constant current bias is applied is equal to or lower than a predetermined voltage. 6. The method according to claim 1, wherein a potential level applied to the charge removing member near a rear end of the first surface of the transfer material in the transfer material transport direction is set to be small. Image forming device. 7. A method according to claim 1, further comprising means for transferring an image to the second surface of the transfer material after transferring the image to the first surface of the transfer material, and wherein a detection voltage of the transfer roller when a constant current bias is applied is equal to or higher than a predetermined voltage. 6. The image forming apparatus according to claim 1, wherein a potential level applied to the charge removing member near the front end of the first surface of the transfer material in the transfer material transport direction is set high. apparatus. 8. A printer has a plurality of modes in which process conditions for image formation, transfer, and fixing can be changed, and when at least one of the modes is set, the second mode of the transfer material in the transfer material transport direction is set. The image forming apparatus according to any one of claims 1 to 5, wherein a potential level applied to the charge removing member near one end of one surface is set to be large. 9. A printer has a plurality of modes in which process conditions of image forming, transferring, and fixing can be changed. When at least one of the modes is set, the first surface and the second surface of the transfer material are set. The image forming apparatus according to any one of claims 1 to 5, wherein a potential level applied to the charge removing member on the surface is set low. 10. The image forming apparatus according to claim 1, wherein the diameter of the image carrier is 40 mm or less.