JPH0926688A - Image forming device and electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device made compact by remarkably simplifying constitution, having excellent electrification uniformity without a white dot, a black dot, a white stripe and a black stripe in the case of electrification, always obtaining good image quality regardless of the thickness of a medium to be transferred in the case of transfer, and being excellent in antistaining against the adhesion of developer and paper powder. SOLUTION: A photoreceptor 8 on which an electrostatic latent image corresponding to the image of an original is formed is formed like an endless belt and rotated by a driving roller 13. An electrifying and transferring roller 10 formed of a conductive foaming roller is provided in a state where it comes in contact with the surface of the photoreceptor 8. An AC power source 42 and DC power sources 43, 45 and 46 are connected to the roller 10 through change-over switches 41 and 44. By changing over the switches 41 and 44, voltage for electrification, voltage for transferring and voltage for cleaning are selectively impressed as necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device which exhibits both charging and transfer functions by a single conductive roller, and an analog or digital electronic copying machine using the charging device. The present invention relates to an image forming apparatus such as a machine.

[0002]

2. Description of the Related Art Conventionally, an electronic copying machine for two-rotation, one-copy (one copy is performed by two rotations of the photoconductor drum) using a photoconductor drum having a perimeter longer than the length of paper has been put into practical use. ing. Such a two-revolution, one-copy electronic copying machine is
As a dual-purpose device for transfer, charging by corona discharge
Since it is a transfer / combined device, a large amount of harmful ozone gas is generated. Therefore, a filter or the like has been installed at the exhaust port of the electronic copying machine to reduce the discharge of ozone.

Further, in recent years, due to the growing interest in the environment,
From the viewpoint of ozone-less, a contact charging device using a solid rubber roller, a brush or the like and a contact transfer device using a flexible foam rubber roller have been put into practical use.

As a contact charging device, for example, the "contact charging method (Shunji Nakamura)" disclosed in Journal of Electrophotography, Vol. 30, No. 3, (1991) is well known. From this, (1) Brush charging: A fibrous conductive brush is brought into contact with a photoconductor to be charged, and there is a stationary fixed type or a roller type which is contact-rotated. In this case, it is necessary to make mechanical consideration so that the photoconductor can be evenly and softly contacted.
The length of the bristle foot does not decrease (durability), and hair fall is less likely to occur, so it is necessary to prevent the brush tip from becoming dirty.

(2) Roller charging: A conductive elastic layer, a medium resistance thin layer, and a protective layer are formed from the bottom around a roller core. In this case, for example, US Pat. No. 5,008,70
As described in No. 6, if the surface roughness of the charging member exceeds 5.0 μm, the charging uniformity becomes poor. Therefore, 0.05
It is necessary to have a relatively small surface roughness of about μm to 5.0 μm.

On the other hand, as the contact transfer device, for example,
68th Electrophotographic Society Research Symposium P. 27-P. The method of roller transfer using a medium resistance elastic body (Junji Araya et al.) Disclosed in No. 30 is well known, and as described therein, 1. Since the medium to be transferred (paper) is surely brought into close contact with the photoconductor and conveyed, an image without blur can be obtained.

[0007] 2. The transfer current is very small, and the amount of ozone generated by discharge is extremely small. There is an advantage. The transfer roller uses a flexible foam rubber roller.
That is, an EPD having a cell diameter of about 100 μm to 200 μm
Conductive powder is dispersed in M foam and the resistance value is 10 ⁸ Ω to 10
^This is a single-layer roller adjusted to a medium resistance region around ⁹ Ω, with an outer diameter of approximately φ17 mm and hardness of approximately 30 degrees (Asker
C).

[0008]

As described above,
A contact charging roller having a small surface roughness of about 0.05 μm to 5.0 μm and a transfer roller having a cell diameter of about 100 μm to 200 μm are used as a charging / transferring roller.
The following problems occur when one-rotation copying is performed.

A charging roller having a small surface roughness, that is,
When the transfer is performed using a solid type charging roller, (1) it is difficult to reduce the hardness to obtain the flexibility required for the transfer roller because it is a solid type.
At the transfer nip, the pressure on the photoconductor via the medium to be transferred becomes high, and particularly in thick paper, OHP film, etc., the toner image is missing (for example, there is no toner in the central portion of the character etc. There is toner only in the image), and good transfer cannot be performed.

(2) Further, since the surface roughness is small, it is difficult to obtain friction for sufficiently holding and carrying the transfer medium,
Due to slippage at the transfer portion, transfer blurring may occur and jitter may occur in the image.

(3) On the transfer roller, contamination by toner or paper powder cannot be ignored, and these foreign substances adhere to the roller surface, resulting in non-uniform charging during charging. For example, black stripes, black dots, White lines, white dots, etc. appear on the image.

Next, about 100 μm according to the transfer roller.
A case where a foaming roller having a cell diameter of up to 200 μm is used as a charging roller will be described. (1) For example, when a DC voltage is applied to the foaming roller to carry out charging, black spots are generated on the image corresponding to the pore diameters, resulting in a non-uniform charging image. In order to take measures against this black spot, for example, Japanese Patent Publication No. 3-5205, which has been conventionally proposed.
When the superimposed voltage, which is formed by superimposing the AC voltage on the DC voltage, is applied, which is disclosed in Japanese Patent Publication No. 8, the black spot area gradually decreases corresponding to the peak-to-peak voltage of the AC voltage.

However, the applied voltage is about 1.2 KVp.
If it is more than p, halftone part (reflectance is about 50%)
On the contrary, at the applied voltage (about 1.8 KVpp) at which white spots start to occur and black spots disappear, the white spots remarkably occur at all halftone portions.

That is, since the pore diameter is large, the uneven charging potential cannot be corrected even if the charging is performed by a superposed voltage obtained by superposing an AC voltage on a DC voltage. Further, even when the peripheral speed difference was given to the photoconductor, black streaks and white streaks occurred, and sufficient charging uniformity could not be obtained.

Therefore, according to the present invention, both the charging and transfer functions can be exhibited by a single conductive roller.
Therefore, it is an object of the present invention to provide an image forming apparatus and a charging device which can be remarkably simplified in structure, can be made compact, and can be reduced in cost.

Further, according to the present invention, in charging and transferring by a single conductive roller, excellent charging uniformity without white spots, black spots, white stripes, black stripes, etc. is obtained at the time of charging, and a medium to be transferred is transferred at the time of transferring. An object of the present invention is to provide an image forming apparatus and a charging device that can always obtain good image quality regardless of the thickness.

Further, according to the present invention, when charging and transferring with a single conductive roller, the stain resistance is excellent against adhesion of developer, paper powder, etc., and reliable and stable charging is possible. An object of the present invention is to provide an image forming apparatus and a charging device that can obtain good images.

Further, according to the present invention, in charging and transferring by a single conductive roller, the functions of the charging and transferring do not affect each other, and the amount of ozone generated is extremely small. The purpose is to provide.

[0019]

An image forming apparatus of the present invention is provided in contact with the surface of a photoconductor, charges the surface of the photoconductor, and coats a developer image formed on the surface of the photoconductor. A conductive roller for transferring to a transfer medium, a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as necessary, and a charging voltage by the voltage applying means. Of latent image forming means for forming a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller to which is applied, and the surface of the photoconductor formed by the latent image forming means. A developing means for forming a developer image by developing the latent image with a developer; and for transferring the developer image on the surface of the photoreceptor formed by the developing means to a transfer medium. Roll over the conductive roller And a control means for controlling said voltage applying means to apply a voltage when.

Further, the image forming apparatus of the present invention is provided in contact with the surface of the photoconductor, charges the surface of the photoconductor, and transfers the developer image formed on the surface of the photoconductor to the transfer medium. Average pore size of 10μm for transfer
A conductive roller formed of a conductive foam member having a thickness of ˜100 μm, a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as needed, and charging by the voltage applying means. A latent image forming means for forming a latent image corresponding to an image of a document on the surface of the photoconductor charged by the conductive roller to which a voltage is applied, and the photoconductor formed by the latent image forming means. Developing means for forming a developer image by developing the latent image on the surface with a developer, and the developer image on the surface of the photoreceptor formed by the development by the developing means is transferred onto a transfer medium. To this end, a control means is provided for controlling the voltage application means so as to apply a transfer voltage to the conductive roller.

Further, the image forming apparatus of the present invention is provided in contact with the surface of the photosensitive member having a peripheral length of not less than the maximum length of the transfer medium, and charges the surface of the photosensitive member and the surface of the photosensitive member. A conductive roller for transferring the developer image formed on the transfer medium to the transfer medium, and a voltage at the time of charging, a voltage at the time of transfer or the developer on the conductive roller to the conductive roller of the photosensitive member. A voltage applying means for selectively applying a cleaning voltage for returning to the surface as needed, and an original document on the surface of the photoconductor charged by the conductive roller to which the charging voltage is applied by the voltage applying means. Image forming means for forming a latent image corresponding to the above image, and development for forming a developer image by developing the latent image on the surface of the photoreceptor formed by the latent image forming means with a developer. Means and
A first means for controlling the voltage applying means so as to apply a transfer voltage to the conductive roller in order to transfer the developer image on the surface of the photoconductor formed by the development of the developing means onto the transfer medium. Second control means for controlling the voltage applying means to apply a cleaning voltage to the conductive roller to return the developer on the conductive roller to the surface of the photoconductor after the transfer is completed. And a cleaning means for collecting the developer remaining on the surface of the photoconductor after the transfer is completed.

Further, the image forming apparatus of the present invention is provided in contact with the surface of the photoconductor to charge the surface of the photoconductor and to transfer the developer image formed on the surface of the photoconductor to the transfer medium. A conductive roller for transferring, a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as necessary, and a charging voltage is applied by the voltage applying means. Latent image forming means for forming a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller, and developing the latent image on the surface of the photoconductor formed by the latent image forming means. A reversal developing means for forming a developer image by reversal development using a developing agent, and for transferring the developer image on the surface of the photoreceptor formed by the reversal development of the reversal developing means onto a transfer medium. For the conductive roller And a control means for controlling said voltage applying means so as to apply a transfer time of voltage.

Further, the image forming apparatus of the present invention is provided in contact with the surface of the photoconductor, charges the surface of the photoconductor, and transfers the developer image formed on the surface of the photoconductor to the transfer medium. A conductive roller for transferring, a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as necessary, and a charging voltage is applied by the voltage applying means. Latent image forming means for forming a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller, and developing the latent image on the surface of the photoconductor formed by the latent image forming means. A reversal developing means for forming a developer image by reversal development using a developing agent, and for transferring the developer image on the surface of the photoreceptor formed by the reversal development of the reversal developing means onto a transfer medium. For the conductive roller First control means for controlling the voltage applying means so as to apply a voltage during transfer, and developer diffusing means for diffusing and evenly dispersing the developer remaining on the surface of the photoconductor after the completion of the transfer. And second control means for controlling the reversal developing means so as to recover the developer remaining on the surface of the photoconductor dispersed by the developer diffusing means.

Further, the image forming apparatus of the present invention is provided in contact with the surface of the photoconductor, charges the surface of the photoconductor, and transfers the developer image formed on the surface of the photoconductor to the transfer medium. A conductive roller for transferring, a first voltage applying means for applying a first voltage of a first polarity to the conductive roller to charge the surface of the photoreceptor, and the first voltage application. Latent image forming means for forming a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller to which the first voltage is applied by the means, and the latent image forming means. And a developing means for forming a developer image by developing a latent image on the surface of the photoconductor with a developer, and applying a second voltage of the first polarity to the conductive roller, Of the photoconductor developed by the developing means. Second voltage applying means for transferring the developer image on the surface onto the transfer medium, and transfer of the developer image by the conductive roller by applying the second voltage from the second voltage applying means. Then, by applying a third voltage having a second polarity different from the first polarity to the conductive roller, the developer on the conductive roller is moved onto the photosensitive member. 3 voltage applying means.

Further, in the charging device of the present invention, a conductive roller provided in contact with the surface of the photosensitive member, and a first voltage having a first polarity and a first magnitude are applied to the conductive roller. Voltage applying means, and second voltage applying means for applying a second magnitude voltage of the first polarity to the conductive roller,
A third voltage applying unit that applies a third magnitude voltage having a second polarity different from the first polarity to the conductive roller is provided.

According to the above construction, since a single conductive roller exhibits both charging and transferring functions, the construction is remarkably simplified as compared with the conventional one, and an extremely compact image forming apparatus and charging apparatus can be realized. Further, by forming the conductive roller with a conductive foam member having an average pore diameter of 10 μm to 100 μm, excellent charging uniformity without white spots, black spots, white streaks, black streaks during charging, and a medium to be transferred during transfer are obtained. Image quality is always obtained regardless of the thickness of the sheet, and it has excellent stain resistance against the adhesion of developer, paper dust, etc., and enables stable and reliable charging. The function is not affected, the amount of ozone generated is extremely small, and further simplification can lead to compactness and cost reduction.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment will be described. FIG. 1 schematically shows a configuration of an analog type electronic copying machine which performs two rotations and one copy as an example of the image forming apparatus according to the first embodiment. In FIG. 1, reference numeral 1 is a main body of a copying machine, and an original table 2 made of transparent glass is provided on the upper surface thereof, and an original cover 3 is provided on the original table 2 so as to be openable and closable.

A small-capacity paper feed cassette 4 and a large-capacity paper feed cassette 5 each containing a sheet of paper P as a transfer medium are detachably provided on the right side of the drawing of the main body 1. A discharge tray 6 for discharging the copied paper P is provided on the left side of the body 1 in the drawing.

In the main body 1, charging, exposure, development, transfer,
Image forming means 7 is provided for forming an image by an image forming process such as fixing and cleaning. Image forming means 7
Has an endless belt-shaped photoconductor 8 in a substantially central portion of the main body 1, and a magnetic field for performing normal development using a two-component developer composed of a toner and a carrier around the photoconductor 8. Brush-type developing device (developing means) 9, contact-type charging / transferring roller 10, cleaning device 11, and static elimination lamp 1
2 are arranged in order.

The photosensitive member 8 is wound around, for example, three driving rollers 13, and is rotationally driven in the clockwise direction at a predetermined peripheral speed (process speed) by these driving rollers 13 and a main motor (not shown). The charging / transferring roller 10 is installed in contact with the surface of the charging / transferring roller 10, and is uniformly charged by the charging / transferring roller 10.

An exposure device 14 as an exposure means is arranged below the document table 2. The exposure device 14 includes an exposure lamp 1 whose back is surrounded by a reflector 15.
6, a first reflecting mirror 17, a first carriage 18 fixed to the first reflecting mirror 17, and a second carriage reciprocating in the direction of the arrow at a speed half that of the first carriage 18 19, second and third reflection mirrors 20 and 21 fixed to the second carriage 19, lens 2
2 and fixed optical systems such as the fourth, fifth, and sixth reflection mirrors 23, 24, and 25.

That is, an image of a document (not shown) placed on the document table 2 is optically scanned by the exposure device 14 and exposed on the photoconductor 8 of the image forming means 7 to expose it. An electrostatic latent image is formed on the body 8. The electrostatic latent image formed on the photoconductor 8 is the developer in the magnetic brush of the developer supplied by the developing device 9. As a toner image.

A pickup roller 2 is selectively selected from paper feed cassettes 4 and 5 which are detachably provided on the right side of the main body 1.
The sheets P are taken out one by one through the sheets 6, 27 and the sheet feeding rollers 28, 29.

The paper P taken out from the paper feed cassette 4 or 5 is guided to a pair of registration rollers 30 and guided by the pair of registration rollers 30 to a charging / transferring roller 10 arranged opposite to the photoconductor 8. While being conveyed, the toner image on the photoconductor 8 is transferred onto the sheet P by the charging / transferring roller 10 to which the voltage at the time of transfer is applied.

The sheet P after transfer is sent to the fixing device 32 by the conveyor belt 31, and the fixing device 32 melts and fixes the toner image on the sheet P. Paper P after fixing
Is an eject roller pair 3 provided on the downstream side of the fixing device 32.
3 and the gate 34 provided on the downstream side of the take-out roller pair 33 is switched so that the discharge roller pair 35 is discharged.
It is configured to be discharged onto a paper discharge tray 6 provided outside the main body 1 via the sheet or to be conveyed again to the reversing means 36 formed at the bottom of the main body 1.

The sheet P conveyed to the reversing means 36 is switched back and guided again between the photoconductor 8 and the charging / transferring roller 10 via the pair of registration rollers 37 and 30, whereby both sides are conveyed. Copying is possible.

Unnecessary substances such as residual toner and paper dust remaining on the photoconductor 8 after the toner image is transferred onto the paper P are collected by the cleaning device 11, and the surface of the cleaned photoconductor 8 is cleaned. The static elimination lamp 12 eliminates the potential below a certain level to enable the next copying operation.

A copying process is performed by repeating the above steps. These steps will be described in detail with reference to the schematic diagram around the photoconductor shown in FIG. 2 and the timing chart of the main part shown in FIG.

As shown in FIG. 2, the charging / transferring roller 10 is adapted to selectively apply a charging voltage, a transfer voltage or a cleaning voltage as required. That is, the charging / transferring roller 10 is connected to the movable contact of the changeover switch 41 for changing the charging / transferring. An alternating-current power supply 42 and a direct-current power supply 43 for applying a charging voltage (superimposed voltage obtained by superimposing alternating current voltage on direct current voltage) between the fixed contact on one side (charging side) of the changeover switch 41 and the ground point.
Are connected in series, and the movable contact of the transfer / cleaning changeover switch 44 is connected to the other fixed contact (transfer side) of the changeover switch 41. A DC power supply 45 for applying a transfer voltage is connected between one of the fixed contacts (transfer side) of the changeover switch 44 and the ground point, and is connected to the fixed contact of the other side (cleaning side) of the changeover switch 44. A DC power supply 46 for applying a cleaning voltage (reverse bias voltage during transfer) is connected between the point and the point.

At the same time when the main motor (not shown) is turned on, the changeover switch 41 is set to the transfer side and the changeover switch 44 is set to the cleaning side, whereby the charging / transferring roller 10 from the DC power source 46 is set. A voltage having the same polarity as the toner in the developing device 9 is applied to. As a result, the toner adsorbed on the charging / transferring roller 10 is returned to the photoconductor 8. Unwanted substances such as toner and paper dust on the photoconductor 8 are scraped off and cleaned from the photoconductor 8 by the cleaning blade of the cleaning device 11 at the phase difference φ1 shown in the timing chart of FIG. In this case, the cleaning operation on the charging / transferring roller 10 needs to be performed at least once around the charging / transferring roller 10.

Next, the charging / transferring roller 10 is set to the charging side by the changeover switch 41, so that the charging voltage from the AC power source 42 and the DC power source 43 (DC 810V, AC 600Vpp 416Hz in this embodiment). Is applied, and the surface of the photoconductor 8 is uniformly charged to about −600V. Then, according to the phase of each process arrangement, the cleaning blade of the cleaning device 11 is turned off to separate from the photoconductor 8 at the phase difference φ1 from the charging portion, and the static elimination lamp 12 is turned off at the phase difference φ2. About −
The photoconductor 8 having a surface potential of 600 V has a phase difference of φ3.
Then, the process proceeds to the exposure process. Here, the electrostatic latent image formed by irradiating the photoconductor 8 with the reflected light from the above-mentioned document is visualized by the normal development of the developing device 9 to which a bias of about -200 V is applied after the phase difference φ4. (Toner image).

The toner image thus formed on the photosensitive member 8 is transferred from the DC power supply 45 by setting the changeover switches 41 and 44 to the transfer side after the phase difference φ5 between the developing and charging / transferring roller 10. A voltage (DC-1.2 KV) at the time of transfer is applied to the charging / transferring roller 10, and the charging / transferring roller 10 to which the voltage at the time of transfer is applied transfers it onto the conveyed paper P.

In the second cycle of the photoconductor 8,
After the phase difference φ1 ′, the cleaning blade of the cleaning device 11 is brought into pressure contact with the photoconductor 8 to clean the residual toner on the photoconductor 8.

Further, after the phase difference φ2 ′, the static elimination lamp 12
Is turned on, the surface potential on the photoconductor 8 is photo-electrified and initialized. Further, after the phase difference φ3 ', the process proceeds to the developing device 9 with the exposure being turned off.

Here, as in the first cycle, the latent image is not formed on the surface of the photoconductor 8 and the surface potential of the photoconductor 8 is almost uniformly below -100 V, so that it is not developed. After the phase difference .phi.5 'between the developing device 9 and the charging / transferring roller 10, the process proceeds to the charging / transferring roller 10.

The charging / transferring roller 10 is applied with the charging voltage after the transfer of the toner image onto the paper P is started and then the length of the paper P + α, and the undeveloped portion is charged. -By the charging function of the transfer / combined roller 10,
The charging process of the first cycle is repeated to perform continuous copying operation.

Finally, regarding the copy end sequence,
After the transfer of the toner image onto the sheet P is completed, a voltage (+1.5 KV) for cleaning is applied to the charging / transferring roller 10 so that the toner attached to the surface of the charging / transferring roller 10 has the same polarity. The voltage is applied to the photosensitive member 8 and cleaning is performed by returning the photosensitive member 8 onto the photosensitive member 8. In this case, the cleaning operation on the charging / transferring roller 10 is performed at least at the charging / transferring roller 1 as in the copy start sequence.
After one or more rounds of 0, the transfer voltage is set to -1.2 KV again, and the photosensitive drum 8 is turned off after one or more rounds.

In the broken line portion shown in FIG. 2, instead of the AC power source 42 and the DC power source 43, the DC constant voltage power source 4 is used.
By connecting No. 7, a case where a DC constant voltage is applied as the charging voltage is shown, and charging can be performed with a DC constant voltage of about -1.1 KV.

Next, the details of the photosensitive member 8 will be described.
The photoreceptor 8 has, for example, a CGL layer (carrier generation layer) made of a disazo pigment and a resin having a thickness of 0.1 μm on an annular aluminum belt having a circumference of 299 mm and a thickness of 50 μm. A CTL layer (carrier transport layer) in which a hydrazone derivative and a resin are mixed is applied and formed thereon to a thickness of 25 μm.

The belt-shaped photosensitive member 8 requires a peripheral length of not less than the maximum length of the paper P to be used, and if the lateral direction of the letter size is the maximum length, a peripheral length of 8.5 inches or more is required. , A4 size in the vertical direction, a peripheral length of 297 mm or more is required.

Next, details of the charging / transferring roller 10 will be described. As the charging / transferring roller 10,
For example, a conductive roller is used in which a SUS shaft having a diameter of 8 mm is uniformly kneaded with a thermoplastic ester urethane as a main component and carbon black or the like and then foamed to have a thickness of 5 mm. In this example, a trade name Ruby cell (manufacturer, Toyo Polymer Co., Ltd.) has a volume resistance of about 10 ⁷ Ω · cm, a hardness of 32 degrees (Asker C), and an average pore diameter of 20 μm to 60 μm.
What was controlled in the range of m was used. The peripheral speed (process speed) of the photoconductor 8 is 120 mm / s.
ec.

Here, the average pore diameter will be described. The foamed conductive urethane used in this example is one in which the pores in the urethane are connected to the adjacent pores, so the bubble point method is used as one of the measurement methods. In this method, air pressure is gradually applied to one side of the foam material, and the pore diameter is obtained from the pressure when the foam material first comes out. The calculation formula is determined based on a model of the material structure in which capillaries are lined up, and the fact that the pore diameter and the air pressure are in an inversely proportional relationship as shown in the following formula is used.

K = 2.18 × 10 ³ / p where K is the pore diameter (μm) and p is the air pressure (mmHg)
Means In addition, this measuring method is in agreement with a measuring method of a scanning electron microscope (SEM) photograph. Also, in the case of a foam member having an independent pore shape, the measurement was made from this SEM photograph.

Next, a method of installing the charging / transferring roller 10 will be described. For example, as shown in FIG. 4, a gear 51 is fixed to one end of the driving roller 13 of the photoconductor 8, and a gear 52 meshing with the gear 51 is fixed to one end of the charging / transferring roller 10. There is. As a result, the rotational force of the driving roller 13 is transmitted to the charging / transferring roller 10 via the gears 51 and 52, and the charging / transferring roller 10 is rotated. The load of the charging / transferring roller 10 on the photoconductor 8 is pressed by the spring pressure (total load pressure of 9.8 N) of the coil spring 53 whose one end is fixed to the main body 1.

Here, the basic performance of the charging / transferring roller 10 at the time of charging and at the time of transferring will be described. First, the charging performance will be described. FIG. 5 shows charging characteristics when a superposed voltage obtained by superposing an AC voltage on a DC voltage is applied as the charging voltage. The charging potential VO (-V) with respect to the AC peak-to-peak voltage increases almost linearly up to about 1.2 KV. Furthermore, if the AC peak-to-peak voltage is increased,
It converges and saturates in the vicinity of almost overlapping DC voltage, and becomes constant regardless of the AC peak-to-peak voltage.

On the other hand, when a DC voltage is applied as the charging voltage, as shown in FIG. 6, it rises from a DC voltage of about 400 V, and thereafter, a linear charging characteristic corresponding to the DC voltage is obtained.

In the former charging by superposed voltage, when a peak-to-peak voltage having an inflection point of 1.2 KV or more is applied in the graph, the surface potential of the photoconductor 8 can be made uniform and stable.
The following problems occur. First, due to the effect of Joule heat associated with the magnitude of the alternating current, toner filming on the photoconductor 8 becomes noticeable, and white streaks tend to occur on the image. These occur even when the normal charging device and the transfer device are separately installed, and when the charging / transferring is used in the present embodiment, the interposition of the toner cannot be ignored and a higher heat is generated. Adhesion of the toner to the photoconductor 8 due to the melting occurs with high probability.

Secondly, there is a problem of AC sound. The AC sound appears as vibrations on the photoconductor 8 in addition to the toner filming due to the AC current. These vibrating sounds depend on the applied frequency and can be improved a little if the frequency is low (about 300 to 800 Hz), but it is necessary to take measures against vibration of the photoconductor 8 as a countermeasure.

In view of the above problems, in this example, the AC peak-to-peak voltage was 600 Vpp, the frequency was 416 Hz, and the DC voltage was -800 V, and the charging performance was relatively similar to that of DC charging.

Next, the transfer performance will be described. FIG. 7 shows the relationship between the transfer voltage applied and the transfer efficiency.
The transfer efficiency is, for example, Toshiba Recycle Paper PR
Using S, the residual toner image on the photoconductor 8 after transfer and the transferred toner image on the paper P are sampled with a mending tape (Sumitomo 3M) and measured with a Macbeth densitometer (RD-918). Then, it was calculated by the following formula.

Transfer efficiency η (%) = toner image on photoconductor after transfer / (toner density on paper) + (toner image on photoconductor after transfer) The applied transfer voltage is about −1. It can be seen that the maximum transfer efficiency is exhibited at 2 KV, and the transfer efficiency of about 90% is obtained.

Next, the charging performance and the transfer performance viewed from the average pore diameter will be described. FIG. 8 shows the results obtained by testing the relationship between the average pore diameter and the charging / transferring performance. The average pore diameter is 0 μm, that is, 10 μm, 40 μ using a solid roller (a roller formed by applying a conductive polyurethane coating on the surface of an elastic layer made of conductive urethane rubber, further drying and then heat treating).
m and 80 μm, the above-mentioned trade name Rubycell (manufacturer, Toyo Polymer Co., Ltd.) is used, and 100 μm to
For 500 μm, trade name LL rubber ”(manufacturer,
Kyowa Giken Co., Ltd. with a different expansion ratio was used.

In the test, the photosensitive member 8 was rotated at a peripheral speed of 120 mm / se.
Then, the charging / transferring roller 10 is moved at c, and a superposed voltage obtained by superposing an alternating voltage of 600 Vpp and 416 Hz on a direct current voltage of −800 V is applied to the surface of the photoconductor 8 according to the process timing described above. -20 in a developing device 9 using a two-component developer that is charged, exposed by reflected light from an original, and mixed with a toner containing polyester resin as a main component and a ferrite carrier.
Applying a bias voltage of 0V to visualize the image
Toshiba Recycle Paper P is used under the voltage condition in which the voltage applied to the transfer / roller 10 is switched to a DC voltage of -1.2 KV.
-Transfer to RS to obtain image output.

From the results shown in FIG. 8, the solid roller had no problem in the charging performance at the initial stage, but after copying about 1000 sheets, the charging and
Contamination of the transfer / transfer roller 10 caused a problem in charging performance, resulting in an image in which charging such as white streaks and black streaks was non-uniform.

On the other hand, in terms of transfer performance, the hardness peculiar to the solid roller (about 50 degrees Asker C) is set to OHP.
It was not possible to obtain a good image due to hollow characters such as characters on the film.

The hardness of the solid roller can be lowered in order to solve such a hollow phenomenon. However, for example, when silicone rubber is used for softening, a plasticizer or the like is used. When mixed in a large amount, the photoreceptor 8 is contaminated and cannot be used. Even if the layered structure is a structure in which the inner rubber is made flexible and the surface is covered with a tube or the like, it does not actually provide sufficient countermeasures against the hollow phenomenon, but it has a drawback that the structure becomes complicated.

Next, among the foam types, the pore size is 10
From the point of exceeding 0 μm, uneven charging occurs from the initial stage with respect to the charging performance, and black spots and white spots occur at a practically insufficient level.

Further, looking at the results in the range of 10 μm to 100 μm, it was possible to obtain an image in which the charging uniformity was maintained at the initial stage and after 1000 sheets. As for transfer performance, the hardness is about 32 degrees (Ask
Since rC) is low, there is no high load portion in the transfer nip, so that a good image without a hollow defect can be obtained even in an OHP film.

Therefore, in summarizing the above results, the charge uniformity is in the range of 10 μm to 100 μm in average pore diameter,
A sufficiently good image can be obtained in terms of transferability. Here, when the charging property is devised, as in this embodiment,
In the charging / transferring roller 10 to which toner and paper powder are constantly exposed, these contaminants enter the pores of the foam. This is because the surface of the foam body is constantly in contact with the photoconductor 8 and the paper P, so that the foam body hardly stays and enters the pores with a small load.

However, if the pore diameter is large, the contact surface with the photoconductor 8 is reduced, and charging due to Paschen discharge in the pores is no longer expected, resulting in black spots and white spots, which affect the charging performance. I think that.

In the above description, the case where the photoconductor 8 is formed in the shape of an endless belt has been described, but the same can be done even if the photoconductor 8 is formed in the shape of a drum, as shown in FIG. . The photoreceptor 8 shown in FIG. 9 is, for example, a CGL layer made of a disazo pigment and a resin having a thickness of 0.1 μm on an aluminum tube having an outer diameter of 99.96 mm and a thickness of 2.5 mm. (Carrier generation layer) is formed by coating, and then a CTL layer (carrier transport layer) in which a hydrazone derivative and a resin are mixed is formed by coating to have a thickness of 25 μm to have a film thickness of 25.1 μm. Diameter is about 1
Negative charge type OPC (Or
ganic Photoconductor).

The drum-shaped photosensitive member 8 also requires a peripheral length of not less than the maximum length of the paper P to be used, and if the lateral direction of the letter size is the maximum length, a peripheral length of 8.5 inches or more is required.
In the vertical direction of the size, a circumference of 297 mm or more is required. That is, in the case of using a drum-shaped photoconductor, the maximum length of the paper P in the vertical direction of A4 size is 94.5.
mm or more is required.

Next, a second embodiment will be described. The second embodiment is a case where the invention is applied to, for example, a digital electronic copying machine using a reversal development method, and unlike the first embodiment, the residual toner on the photoconductor after the transfer process is applied to the developing device. It collects the toner, and does not require any special cleaning device for collecting the residual toner.

FIG. 10 schematically shows the configuration of a digital electronic copying machine which performs two-rotation one-copy as an example of the image forming apparatus according to the second embodiment. The digital electronic copying machine is roughly classified into a scanner section (reading means) 61 for optically reading image information of an original, and
The printer unit 62 is configured as an image forming unit that forms an image on a sheet by electrophotography according to an image signal read by the scanner unit 61 or supplied from an external device (not shown). .

The scanner section 61 is provided on a document table 63 on which a document to be copied is placed, and is provided on the document table 63 so as to be freely openable and closable. The scanner section 61 also functions as a document cover for pressing the document placed on the document table 63. Document feeder 64, fluorescent lamp 65 as a light source for illuminating a document placed on document table 63, fluorescent lamp 6
It has a CCD type line sensor 66 as a photoelectric conversion means for photoelectrically converting the reflected light from the original by the light irradiation from 5. Between the fluorescent lamp 65 and the line sensor 66, a plurality of reflection mirrors 67, 68, 69 for bending an optical path through which the light traveling from the document to the line sensor 66, that is, the reflected light from the document passes, and A lens unit 70 for focusing the reflected light on the light receiving surface of the line sensor 66 is provided.

With respect to the document placed on the document table 63, the scanning system including the fluorescent lamp 65 and the reflection mirrors 67 to 69 reciprocates along the lower surface of the document table 63 in the direction of arrow a. As a result, exposure scanning is performed during the reciprocation. In this case, the reflection mirrors 68 and 69 move at a speed half that of the reflection mirror 67 so as to maintain the optical path length.

The reflected light from the original by the scanning of the scanning system, that is, the reflected light from the original by the light irradiation of the fluorescent lamp 65 is reflected by the reflection mirrors 67 to 69, and then passes through the lens unit 70 to pass through the line. Guided by the sensor 66,
The image of the document is formed on the light receiving surface of the line sensor 66.

The fluorescent lamp 65, the line sensor 66, the reflecting mirrors 67 to 69, and the lens unit 70 constitute a scanning unit 71. The fluorescent lamp 65 and the reflection mirror 67 are arranged on the first carriage 72.
And the reflection mirrors 68 and 69 are fixed to the second carriage 7.
The carriages 72 and 73 are fixed to the carriage 3, and are moved by motors (not shown).

The printer unit 62 is configured to be rotatable in a predetermined direction by a motor or the like (not shown) in a substantially central portion of the main body 80, is charged to a predetermined potential, and is a laser beam light modulated according to print data. The photosensitive member 81 is in the form of an endless belt on which an electrostatic latent image is formed by being irradiated with the photosensitive member 81.
A laser unit 82 that outputs laser beam light modulated according to print data (image information to be copied or output) on the surface of No. 1 is formed on the photoconductor 81 by the laser beam light from the laser unit 82. A reversal development device (reversal development means) 83 which also functions as a cleaning device for reversal development of the electrostatic latent image using a one-component developer (toner), a contact type charging / transferring roller 84, and a development Memory removal brushes 85 as the agent diffusion means are arranged in order.

The photosensitive member 81 is, for example, wound around three driving rollers 86, and is rotationally driven in the clockwise direction at a predetermined peripheral speed (process speed) by these driving rollers 86 and a main motor (not shown). The charging / transferring roller 84 is placed in contact with the surface of the charging / transferring roller 84, and is uniformly charged by the charging / transferring roller 84.

The memory removing brush 85 is used to diffuse and evenly disperse the toner remaining on the surface of the photosensitive member 81. The memory removing brush 85 is composed of, for example, a conductive rayon brush, and may be connected to a solenoid (not shown) as needed. And is separated from the surface of the photoconductor 81, and a predetermined bias voltage is applied from a DC power source (not shown).

A small-capacity paper feed cassette 87 and a large-capacity paper feed cassette 88 are detachably provided on the right side of the main body 80 with respect to the drawing, and one of these paper feed cassettes 87, 88 can be selected. Pickup rollers 89, 9
The paper P is taken out one by one through the paper feed rollers 91 and 92.

The paper P taken out from the paper feed cassette 87 or 88 is guided to the registration roller pair 93, and is guided by the registration roller pair 93 to the charging / transferring roller 84 arranged opposite to the photoconductor 81. While being transported,
At this time, the toner image on the photoconductor 81 is transferred onto the paper P by the charging / transferring roller 84 to which the voltage during transfer is applied.

The sheet P after transfer is sent to the fixing device 95 by the conveyor belt 94, and the toner image is fused and fixed on the sheet P by the fixing device 95. Paper P after fixing
Is a take-out roller pair 9 provided on the downstream side of the fixing device 95.
6 and the gate 97 provided on the downstream side of the take-out roller pair 96 is switched, so that the discharge roller pair 98 is discharged.
The sheet is discharged onto a sheet discharge tray 99 provided outside the main body 80 via the paper or is conveyed again to the reversing means 100 formed at the bottom of the main body 80.

The sheet P conveyed to the reversing means 100 is switched back and is guided and conveyed again between the photoconductor 81 and the charging / transferring roller 84 via the pair of registration rollers 101 and 93. Copying is possible.

Photosensitive member 81 after transfer of toner image onto paper P
Unnecessary substances such as residual toner and paper dust remaining on the upper surface are diffused and dispersed by the memory removing brush 85, and then collected by the reversal developing device 83 to enable the next copying operation.

A copying process is performed by repeating the above steps. These steps will be described in detail with reference to the schematic diagram around the photoconductor shown in FIG. 11 and the timing chart of the main part shown in FIG.

As shown in FIG. 11, the charging / transferring roller 84 is adapted to selectively apply a charging voltage, a transfer voltage or a cleaning voltage as required.
That is, the charging / transferring roller 84 is connected to the movable contact of the changeover switch 111 for switching the charging / transferring.
An AC power supply 112 and a DC power supply 113 for applying a charging voltage (superimposed voltage obtained by superimposing AC voltage on DC voltage) between a fixed contact on one side (charging side) of the changeover switch 111 and the ground point. The movable contact of the transfer / cleaning changeover switch 114 is connected to the other fixed contact (transfer side) of the changeover switch 111 connected in series. A DC power supply 115 for applying a transfer voltage is connected between one of the fixed contacts (transfer side) of the changeover switch 114 and the ground point, and is connected to the fixed contact of the other side (cleaning side) of the changeover switch 114. A DC power supply 116 for applying a cleaning voltage (reverse bias voltage during transfer) is connected to the point.

A DC power source 118 for applying a bias voltage is connected to the memory removing brush 85. Further, a DC power supply 119 for applying a bias voltage is connected to the developing roller of the developing device 83.

The broken line portion shown in FIG. 11 shows the case where a constant DC voltage is applied as the charging voltage by connecting a constant DC voltage power supply 117 instead of the alternating current power supply 112 and the direct current power supply 113. Charging is possible with a constant DC voltage of about 1.1 KV.

At the same time that the main motor (not shown) is turned on, the changeover switch 111 is set to the transfer side, and the changeover switch 114 is set to the cleaning side, so that the DC power supply 116 and the charging / transferring roller 84 are set.
A voltage having the same polarity as the toner in the developing device 83 is applied to. As a result, the toner adsorbed on the charging / transferring roller 84 is returned to the photoconductor 81. Unwanted substances such as toner and paper powder on the photoconductor 81 are removed by the memory removal brush 8 at the phase difference φ10 shown in the timing chart of FIG.
5 (at this time, separated from the surface of the photoconductor 81 by the solenoid), and proceeds to the reversal developing device 83.

The reversal developing device 83 collects the residual toner on the photosensitive member 81 by applying a direct current of −200 V as a bias voltage in the contact one-component development mainly containing polyester resin. In this case, the cleaning property is further improved by setting the bias voltage to -200 V or less or a positive polarity. The cleaning process of the charging / transferring roller 84 needs to be equal to or longer than the circumference of the charging / transferring roller 84.

After the cleaning process of the charging / transferring roller 84 is completed, the changeover switch 111 is set to the charging side so that the charging voltage (AC 810V, AC 600Vp in this embodiment) is supplied from the AC power supply 112 and the DC power supply 113.
(p 416 Hz) is applied, and the photosensitive member 81 is uniformly charged to a surface potential of about −600V. Then, through the phase difference φ10 and φ11 from the charging / transferring roller 84,
Exposure by laser beam light is performed to form an electrostatic latent image on the photoconductor 84, and after the phase difference φ12, the reversal developing device 83 visualizes it. In this embodiment, the bias voltage of the reversal developing device 83 was set to -200V.

Further, after the phase difference φ13, the process proceeds to the charging / transferring roller 84 again.
Is set in synchronization with the conveyed paper P by setting the changeover switches 111 and 114 to the transfer side, respectively, so that the transfer voltage (DC-1.2K
V) is applied. Charging with voltage applied during this transfer
The toner image on the photoconductor 84 is transferred onto the conveyed paper P by the transfer / transfer roller 84.

Next, after the phase difference φ10 from the charging / transferring roller 84, the memory removing brush 85 biased to a DC voltage of about +400 V from the DC power source 118 is attached to the photoconductor 8.
By touching the surface of No. 4, the memory removal brush 8
Therefore, the residual toner on the photoconductor 84 after the transfer is diffused and dispersed. Then, the reversal developing device 83 collects (cleans) the residual toner diffused on the photoconductor 84.

At this time, as described above, cleaning can be performed even with a bias voltage of -200V, but in order to further improve the cleaning performance, the cleaning can be efficiently performed by setting it to -200V or less or with a positive bias.

On the other hand, the charging / transferring roller 84 is connected to the paper P.
After passing through, the transfer voltage is switched to the charging voltage, so that continuous copying is possible as in the case of the first copying.

In the above description, the case where the photoconductor 81 is formed in the shape of an endless belt has been described.
As shown in FIG. 13, even if the photoconductor 81 is formed in a drum shape, the same operation can be performed. Photoreceptor 81 shown in FIG.
Has, for example, an outer diameter of 99.96 mm and a thickness of 2.5.
A CGL layer (carrier generation layer) made of a disazo pigment and a resin having a thickness of 0.1 μm is formed by coating on an aluminum tube of mm, and further, a CTL layer obtained by mixing a hydrazone derivative and a resin on the CGL layer. (Carrier Transport Layer) 25
This is a negatively charged OPC (Organic Photoconductor) having a diameter of about 100 mm and a length of about 246 mm, which is formed by coating to a thickness of 25.1 μm.

The drum-shaped photosensitive member 81 also requires a peripheral length of not less than the maximum length of the paper P to be used, and if the lateral direction of the letter size is the maximum length, a peripheral length of 8.5 inches or more is required.
In the case of four sizes in the vertical direction, a peripheral length of 297 mm or more is required. That is, in the case of using a drum-shaped photoconductor, the maximum length of the paper P in the vertical direction of A4 size is 94.
5 mm or more is required.

As described above, according to the above-described embodiment, the conductive foam roller having the average pore diameter of 10 μm to 100 μm is used as the charging / transferring roller, and two rotations and one copy are performed. Benefits are obtained.

1. Since it is a fine foam pore, there is no image noise such as black spots, white spots, white streaks, and black streaks associated with non-uniform charging corresponding to this pore size at the time of charging, and uniform charging is possible. A good quality image can be obtained regardless of the thickness of the.

2. Since contact charging uses a foam, it has excellent stain resistance of toner, paper powder, etc. that adheres to the charging / transferring roller, and reliable and stable charging is possible. 3. Without impairing the function of paper transportability and transferability,
It is possible to sufficiently satisfy the basic performance of the transfer roller, and the functions of the transfer roller and the transfer roller do not affect each other, and the amount of ozone generated is extremely small.

4. Since it is a charging / transferring roller, it is simplified as compared with the conventional one, so that an extremely compact image forming apparatus becomes possible. 5. In the digital type electronic copying machine or printer using the optical writing means such as laser, LED, LCD using the reversal developing method, the cleanerless process excluding the cleaning device and the discharging lamp can be applied, and the regular developing method was used. It can be further simplified compared to the one.

In the first and second embodiments,
The case where the present invention is applied to an electronic copying machine which performs two rotations and one copy has been described, but two rotations and one copy or more, for example, three rotations and one copy.
The same effect can be obtained by copying.

Further, in the second embodiment, two-rotation one-copy by the cleanerless process using the memory removing brush is shown, but the memory removing brush may be made of a fiber material such as nylon other than conductive rayon. The same effect can be obtained even if it is made of another material such as a conductive urethane sheet or a resin film, or has a fixed or rotatable roll shape as long as it has a function of diffusing the residual toner. can get.

Further, even if the memory removing brush is not installed, the image is slightly generated due to the two-rotation one-copy, but since it is at a practical level, there is no problem even if the memory removing brush is removed.

[0107]

As described in detail above, according to the present invention, since a single conductive roller exhibits both charging and transferring functions, the structure is remarkably simplified as compared with the conventional one, and an extremely compact image is formed. A device and a charging device can be realized. In addition, the conductive roller has an average pore diameter of 10 μm to 10 μm.
By forming it with a conductive foam member of 0 μm, it is excellent in charging uniformity without white spots, black spots, white streaks, black streaks, etc. at the time of charging, and at the time of transfer, always gives good image quality regardless of the thickness of the transfer medium In addition to being obtained, it has excellent stain resistance against the adhesion of developer, paper powder, etc., which enables stable charging with high reliability. Furthermore, the functions of charging and transferring do not affect each other. Is extremely small, and moreover, it is possible to achieve compactness and cost reduction by simplification.

[Brief description of drawings]

FIG. 1 is a side view schematically showing the configuration of an analog type electronic copying machine according to a first embodiment of the present invention.

FIG. 2 is a schematic view around a photoconductor.

FIG. 3 is a timing chart of main parts for explaining the operation.

FIG. 4 is a perspective view showing an installation example of a charging / transferring roller.

FIG. 5 is a diagram showing charging characteristics of a charging / transferring roller when a superimposed voltage obtained by superimposing an AC voltage on a DC voltage is applied as a charging voltage.

FIG. 6 is a diagram showing charging characteristics of a charging / transferring roller when a DC voltage is applied as a charging voltage.

FIG. 7 is a diagram showing a relationship between a transfer voltage applied to a charging / transferring roller and a transfer efficiency.

FIG. 8 is a diagram showing a result of a test conducted on a relationship between an average pore diameter of a charging / transferring roller and charging / transferring performance.

FIG. 9 is a schematic view around a photoconductor for explaining a modified example of the photoconductor.

FIG. 10 is a side view schematically showing the configuration of a digital electronic copying machine according to a second embodiment of the present invention.

FIG. 11 is a schematic view around a photoconductor.

FIG. 12 is a timing chart of the main part for explaining the operation.

FIG. 13 is a schematic view around a photoconductor for explaining a modified example of the photoconductor.

[Explanation of symbols]

P: Paper (transferred medium), 1 ... Copier body, 2 ...
Document table, 4, 5 ... Paper feed cassette, 7 ... Image forming means, 8 ... Photoconductor, 9 ... Developing device (developing means), 10
...... Charging / transfer roller (conductive roller), 11 ……
Cleaning device, 14 ... Exposure device, 32 ... Fixing device, 4
1, 44 ... Changeover switch, 42 ... AC power supply, 43,
45, 46 ... DC power supply, 61 ... Scanner section, 62 ...
... printer section, 63 ... manuscript table, 65 ... fluorescent lamp, 66
... line sensor (photoelectric conversion means), 71 ... scanning unit, 81 ... photoconductor, 82 ... laser unit, 83
...... Reversal developing device (reversal developing means), 84 …… Charging / transfer roller (conductive roller), 85 …… Memory removal brush (developer diffusion means), 87,88 …… Sheet feed cassette, 95 …… Fixing device, 111, 114 ... Changeover switch, 112 ... AC power supply, 113, 115, 116 ...
DC power supply.

Claims (7)

[Claims] 1. A conductive roller which is provided in contact with the surface of a photoconductor and charges the surface of the photoconductor and transfers a developer image formed on the surface of the photoconductor to a transfer medium. And a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as needed, and the conductive roller to which the charging voltage is applied by the voltage applying means. A latent image forming means for forming a latent image corresponding to an image of an original on the surface of the photoreceptor, and a latent image formed on the surface of the photoreceptor formed by the latent image forming means is developed with a developer. Developing means for forming a developer image, and a transfer voltage is applied to the conductive roller in order to transfer the developer image on the surface of the photoreceptor formed by the development of the developing means onto a transfer medium. So that the voltage applying hand An image forming apparatus characterized by including a control means for controlling the. 2. An average gas for contacting the surface of the photoconductor and charging the surface of the photoconductor and transferring the developer image formed on the surface of the photoconductor to a transfer medium. A conductive roller formed of a conductive foam member having a pore diameter of 10 μm to 100 μm, a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as necessary, and this voltage application Latent image forming means for forming a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller to which the voltage at the time of charging is applied by the means, and the latent image forming means for forming the latent image. Developing means for forming a developer image by developing the latent image on the surface of the photoreceptor with a developer, and the developer image on the surface of the photoreceptor formed by the development of the developing means on the transfer medium. To transfer to An image forming apparatus and control means for controlling said voltage applying means to apply a transfer time of voltage to Kishirube conductive roller, characterized by comprising a. 3. The charging of the surface of the photoconductor, which is provided in contact with the surface of the photoconductor having a peripheral length of not less than the maximum length of the medium to be transferred, and the developer image formed on the surface of the photoconductor. A conductive roller for transferring to a transfer medium, and a voltage for charging, a voltage for transfer, or a cleaning voltage for returning the developer on the conductive roller to the surface of the photoconductor for the conductive roller. And a latent image corresponding to the image of the original on the surface of the photoconductor charged by the conductive roller to which the voltage at the time of charging is applied by the voltage applying unit. A latent image forming means for forming, a developing means for forming a developer image by developing the latent image on the surface of the photoreceptor formed by the latent image forming means with a developer, and a developing means for the developing means. Of the photoconductor formed by First control means for controlling the voltage application means so as to apply a transfer voltage to the conductive roller in order to transfer the developer image on the surface onto the transfer medium, and the conductive material after the transfer is completed. Second control means for controlling the voltage application means to apply a cleaning voltage to the conductive roller to return the developer on the roller to the surface of the photoreceptor, and the photoreceptor after the transfer is completed. An image forming apparatus comprising: a cleaning unit that recovers the developer remaining on the surface of the image forming apparatus. 4. A conductive roller which is provided in contact with the surface of a photoconductor, and which charges the surface of the photoconductor and transfers a developer image formed on the surface of the photoconductor to a transfer medium. And a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as needed, and the conductive roller to which the charging voltage is applied by the voltage applying means. Latent image forming means for forming a latent image corresponding to an image of an original on the surface of the photoconductor, and reversal development of the latent image on the surface of the photoconductor formed by the latent image forming means using a developer. And a reversal developing means for forming a developer image by means of the reversal development means, and a developer image on the surface of the photoreceptor formed by the reversal development of the reversal development means is transferred to the conductive roller in order to transfer it onto the transfer medium. I will apply a voltage An image forming apparatus characterized by including a control unit which controls the voltage applying means. 5. A conductive roller which is provided in contact with the surface of the photoconductor and which charges the surface of the photoconductor and transfers the developer image formed on the surface of the photoconductor to a transfer medium. And a voltage applying means for selectively applying a charging voltage or a transfer voltage to the conductive roller as needed, and the conductive roller to which the charging voltage is applied by the voltage applying means. Latent image forming means for forming a latent image corresponding to an image of an original on the surface of the photoconductor, and reversal development of the latent image on the surface of the photoconductor formed by the latent image forming means using a developer. And a reversal developing means for forming a developer image by means of the reversal development means, and a developer image on the surface of the photoreceptor formed by the reversal development of the reversal development means is transferred to the conductive roller in order to transfer it onto the transfer medium. I will apply a voltage First control means for controlling the voltage application means, a developer diffusing means for diffusing and evenly dispersing the developer remaining on the surface of the photoconductor after the transfer is completed, and a developer diffusing means for diffusing the developer. An image forming apparatus comprising: a second control unit that controls the reversal developing unit so as to recover the developer remaining on the surface of the photosensitive member. 6. A conductive roller which is provided in contact with the surface of the photoconductor and which charges the surface of the photoconductor and transfers the developer image formed on the surface of the photoconductor to a transfer medium. And a first voltage applying unit that applies a first voltage of a first polarity to the conductive roller to charge the surface of the photosensitive member, and the first voltage applying unit applies the first voltage to the first voltage. Latent image forming means for forming a latent image corresponding to an image of an original on the surface of the photoconductor charged by the applied conductive roller, and a latent image on the surface of the photoconductor formed by the latent image forming means. A developing unit that forms a developer image by developing the image with a developer; and the photosensitive member developed by the developing unit by applying a second voltage having the first polarity to the conductive roller. Transferring the developer image on the body surface to the transfer medium Second voltage applying means for transferring the developer image onto the conductive roller after the transfer of the developer image by the conductive roller by applying the second voltage from the second voltage applying means. A third voltage applying unit that moves the developer on the conductive roller onto the photoconductor by applying a third voltage having a second polarity different from the first polarity. An image forming apparatus characterized by the above. 7. A conductive roller provided in contact with the surface of the photosensitive member, a first voltage applying means for applying a first magnitude voltage having a first polarity to the conductive roller, and Second voltage applying means for applying a voltage of a second magnitude having the first polarity to the conductive roller; and a third magnitude of a second polarity different from the first polarity for the conductive roller. And a third voltage applying means for applying a voltage of 10 mm, and a charging device comprising: