JPH06186803A - Image forming device - Google Patents

Abstract

PURPOSE:To make a power source low in cost, preventative in interference unevenness due to AC voltages, suppressible in electrifying sound, and small in fog. CONSTITUTION:An image forming device is provided with an electrifying member 102 for electrifying a photosensitive body 101, an electrifying-member power source 121 for applying an electric field to the electrifying member 102, a development means 104 for developing a latent image formed on the photosensitive body 101, and a development power source 122 for applying an electric field to the developing means 104. The electrifying-member power source 121 and the developing means power source 122 consist of a DC power source, and an AC photosensitive body bias power source 120 is connected to the photosensitive body 101.

Description

Detailed Description of the Invention

[0001]

[Industrial applications]

(Industrial field of use of the first invention) The first invention relates to an image forming apparatus using an electrophotographic method such as a copying machine or a printer. (Industrial field of application of the second invention) The second invention relates to an image forming apparatus using an electrophotographic method such as a copying machine or a printer. (Industrial field of use of the third invention) The third invention relates to an image forming apparatus using an electrophotographic method such as a copying machine or a printer.

[0002]

[Prior art]

(First Conventional Example) FIG. 5 shows an example of a conventional image forming apparatus using a charging roller which is an elastic charging member and a transfer roller.

Reference numeral 1101 shown in the figure is a photosensitive drum in which a photosensitive layer 1101a is provided on a metal conductive base material 1101b, and the conductive base material 1101b is grounded. 1102 is a charging roller for charging the photosensitive drum 1101 uniformly and uniformly.
An elastic layer 1102b is provided on the surface layer of the. 1113
Is a bias power source for applying a voltage to the core metal 1102a of the charging roller.
A bias in which a direct current bias (DC) and an alternating current bias (AC) are superimposed is applied to the photosensitive drum 13 in order to uniformly and uniformly charge the photoconductor.

Reference numeral 1103 is exposure light for forming an electrostatic latent image on a charged photosensitive drum, 1104 is a developing device for visualizing the latent image on the photosensitive drum, and 1104a is photosensitive for toner in the developing device. A developing sleeve for developing on the drum 1, in which a magnet is arranged inside a hollow conductive base material. The developing bias power source 1 is attached to the developing sleeve 1104a.
Direct current bias (DC) and alternating current bias (A
Bias in which C) is superimposed is applied. Reference numeral 1105 denotes a transfer roller for transferring the toner image visualized on the photosensitive drum 1101 to a transfer material (not shown). The transfer roller 1105 is a medium resistance foam EPD for the surface layer 1105b.
An elastic layer made of M and a core metal 1105a.

Reference numeral 1114 denotes a DC bias power source for applying a voltage to the transfer roller core metal 1105a, 1106 a transfer guide for guiding a transfer material between the transfer roller and the photosensitive drum, 1107 a toner remaining on the photosensitive drum, It is a cleaner for removing paper dust. The transfer material that has been transferred is sent to the fixing device 1109 by the transport guide 1108 and heated under pressure, so that the toner image is fixed on the transfer material. The fixing device 1109 includes the fixing roller 111.
0 and the pressure roller 1111.

Here, in the above apparatus, the charging roller 110 for charging the photosensitive drum 1101.
By using a contact charging / transferring member such as 2 or a transfer roller, it is possible to lower the power supply voltage compared to the one using a corona charger, and the generation of uncomfortable corona products such as ozone is small. There are advantages. (Second Conventional Example) FIG. 11 shows an example of a conventional image forming apparatus using a charging roller which is an elastic charging member and a transfer roller.

Reference numeral 1201 shown in the figure is a photosensitive drum in which a photosensitive layer 1201a is provided on a metal conductive base material 1201b, and the conductive base material 1201b is grounded. Reference numeral 1202 is a charging roller for uniformly charging the photosensitive drum 1201.
An elastic layer 1202b is provided on the surface layer of the. 1213
Is a bias power source for applying a voltage to the core metal 1202a of the charging roller.
A bias in which a direct current bias (DC) and an alternating current bias (AC) are superimposed is applied to the photosensitive drum 13 in order to uniformly and uniformly charge the photoconductor 1201. Reference numeral 1203 denotes exposure light for forming an electrostatic latent image on the charged photosensitive drum 1201,
Reference numeral 1204 denotes a developing device for visualizing the latent image on the photosensitive drum, and 1204 a denotes toner in the developing device for the photosensitive drum 1.
A developing sleeve for developing on 201, and a magnet is arranged inside a hollow conductive base material. Development sleeve 1
A bias obtained by superimposing a DC bias (DC) and an AC bias (AC) is applied to the developing unit 204a from the developing bias power source 1215. Reference numeral 1205 is a transfer roller for transferring the toner image visualized on the photosensitive drum 1201 to a transfer material (not shown). The transfer roller 1205 is an elastic layer made of a medium resistance foamed EPDM and a core metal 1205a. It is composed of Reference numeral 1223 is a DC bias power source for applying a voltage to the transfer roller core metal 1205a, 1206 is a transfer guide for guiding the transfer material between the transfer roller and the photosensitive drum, and 1207 is the photosensitive drum 120.
It is a cleaner for removing the toner and paper dust remaining on 1. The transfer material after transfer is sent to the fixing device 1209 by the transport guide 1208 and heated under pressure, whereby the toner image is fixed on the transfer material. Fixing device 120
Reference numeral 9 includes a fixing roller 1210 and a pressure roller 1211.

Here, in the apparatus as described above, the charging roller 120 for charging the photosensitive drum 1201.
By using a contact charging / transferring member such as the transfer roller 1205 and the transfer roller 1205, it is possible to lower the power supply voltage as compared with the one using a corona charger, and the generation of unpleasant corona products such as ozone is small. And so on. (Third Conventional Example) FIG. 20 shows an example of a conventional reversal development image forming apparatus in a system in which a charging roller and a transfer roller which are contact charging members are used and an alternating electric field is applied to a conductive base material of a photosensitive drum.

Reference numeral 1301 shown in the figure is a photosensitive drum in which a photoconductor layer 1301a is provided on a metal conductive base material 1301b, and an alternating electric field is applied to the conductive base material 1301b by an AC bias power source 1320. Has been done.

Reference numeral 1302 denotes a charging roller for uniformly charging the photosensitive drum 1301.
An elastic layer 1302b is provided on the surface layer of 2a. Thirteen
Reference numeral 11 denotes a bias power source for applying a DC bias to the charging roller core metal 1302a.
The surface is uniformly and uniformly charged to the bias potential applied to the charging roller 1302 by the alternating electric field applied to the conductive base material. In the case of this conventional example, the photosensitive drum 130
The surface potential of 1 is charged to about -700V.

Reference numeral 1303 denotes a charged photosensitive drum 1301.
The exposure light is for forming an electrostatic latent image on the upper surface. In the case of the conventional example, the surface potential of the exposed portion is about -150V.

Reference numeral 1304 denotes a developing device for developing a latent image on the photosensitive drum 1301. Reference numeral 1304a denotes a developing sleeve for developing the toner in the developing device on the photosensitive drum 1301, which is a hollow conductive base material. A magnet is arranged inside the. A DC bias is applied from the developing bias power source 1312 to the developing sleeve 1304a, and in the case of the conventional example, a voltage of about -500V is applied.

Reference numeral 1305 denotes a transfer roller for transferring the toner image visualized on the photosensitive drum 1301 to a transfer material (not shown). The transfer roller 1305 has an elastic layer 1305b made of medium resistance foam EPDM and a core metal. It is composed of 1305a.

Reference numeral 1313 is a DC bias power source for applying a voltage to the transfer roller core metal 1305a, and in the case of this conventional example, a voltage of about +3 KV is applied.

Reference numeral 1306 denotes a transfer roller and the photosensitive drum 13.
01 is a transfer guide for guiding the transfer material, and 1307 is a cleaner for removing the toner and paper dust remaining on the photosensitive drum 1301. In this conventional example, the elastic blade 1307a abuts on the photosensitive drum 1301. Then, the residual toner is cleaned.

The transfer material which has been transferred is conveyed by the guide 130.
The toner image is fixed to the transfer material by being sent to the fixing device 1309 and heated under pressure. Fixing device 1
309 is a fixing roller 1309 a and a pressure roller 13.
09b.

Here, in the above apparatus, the charging roller 130 for charging the photosensitive drum 1301.
By using the contact charging / transferring member such as the transfer roller 1305 and the transfer roller 1305, it is possible to lower the power supply voltage as compared with the one using the corona charger, and the generation of uncomfortable corona products such as ozone is less. And so on.

Further, by applying an alternating electric field to the conductive base material 1301b of the photosensitive drum 1301, conventionally,
Since the alternating electric field applied to both the charging roller 1302 and the developing sleeve 1304a need only be applied to one of the photosensitive drums 1301, the AC bias power source can be reduced and the cost can be reduced.

[0019]

[Problems to be Solved by the Invention]

(First Problem) (1) However, it is necessary to apply an alternating electric field to the charging roller 1102 in order to uniformly charge the photosensitive drum 1101, and a charging method in which only a DC bias by a conventional corona charger is applied. Compared with, an AC bias power supply is additionally required, and the power supply becomes expensive. (2) Further, there is a problem that the alternating electric field applied to the charging roller 1102 and the alternating electric field applied to the developing sleeve 1104a interfere with each other to cause uneven interference called "moire" in a halftone image or the like. Interference unevenness occurs depending on the frequency of each alternating electric field. (3) Further, the elastic body 11 such as the charging roller 1102.
When an alternating electric field is applied to 02b, a charging sound is generated in the rotation cycle of the photosensitive drum 1101. If the frequency of the alternating electric field applied to the charging roller 1102 is high, the charging noise is also high. (4) For example, in the case of reversal development, the toner is negatively charged in the developing device 1104, but some reversal toner that is positively charged is also generated. In particular, like particulate toner,
This tendency becomes more remarkable as the toner particle size becomes smaller, and the amount of the positively charged reversal toner tends to increase. In such a case, there arises a problem of "fogging" in which toner adheres to the white part other than the character part of the transfer material. (Second Problem) By the way, in order to stabilize the charging by the charging roller 1202, it is effective to apply the AC bias in superposition with the DC bias. At this time, an AC bias power source is additionally required, resulting in high cost, and application of an AC bias to the charging roller 1202 causes drawbacks such as generation of charging noise.

Therefore, in the configuration shown in FIG. 12, an AC bias is applied to the photosensitive drum 1201 from the power source 1220, and DC bias power sources 1221 and 1222 are applied to the charging roller 1202 and the developing sleeve 1204a, respectively.
Therefore, the first image forming apparatus applying only the DC bias is
It was invented as the invention of. By applying an AC bias to the photosensitive drum 1201, the AC bias power supply is set to 1
It is possible to use only one piece, and it is possible to realize cost reduction, and furthermore, it is possible to suppress the charging noise to a low level.

However, the surface potential of the photosensitive drum 1201 is measured, and the DC bias value applied to the charging roller 1202 and the developing sleeve 1204a, the amount of exposure light, and the AC bias applied to the photosensitive drum 1201 are measured according to the measured values. In an image forming apparatus equipped with a mechanism for adjusting the Vpp and the frequency, etc. to optimum values, in a system that applies an AC bias to the photosensitive drum 1201, the surface potential on the photosensitive drum 1201 is measured by the AC bias. Things turned out to be difficult. (Third Problem) (1) In the reversal development type image forming apparatus of the third conventional example, when the transfer voltage applied to the transfer roller 1305 is larger than the roller resistance, the transfer current is transferred. A memory is formed in the photosensitive drum 1301 by penetrating through the material, and in the memory portion, the photosensitive drum 1301 cannot be charged to a predetermined charging potential by the charging process, and a charging failure occurs, so that the photosensitive drum 1301.
1. A problem occurs that black sesame-like dots called "sand" appear on the image after one round. (2) In the reversal development type image forming apparatus of the third conventional example, when the resistance value of the transfer roller 1305 is low, the transfer roller 1305 and the photosensitive drum are not interposed in the non-sheet passing portion without the transfer material. Since 1301 is in contact, the transfer current is transferred between the transfer roller 1305 and the photosensitive drum 1.
A portion of the photosensitive drum 1301 having a low resistance value flows into the non-sheet passing portion of the photosensitive drum 130, and electric charges remain in the non-sheet passing portion of the photosensitive drum 1301 to form a transfer memory. Since the charging cannot be performed up to the charging potential and charging failure occurs, the photosensitive drum 130
1. After one round, a defective image called "paper trace", for example, in reverse development, when printing a paper interval or a small size paper, a black image in the width between the paper and an edge portion of the paper becomes black and edge stains. Paper mark "
Occurs.

Both (1) and (2) are phenomenologically caused by poor charging, which is the difference between the paper passing portion and the non-paper passing portion. Which is more likely to occur is determined by the resistance value of the transfer roller and the resistance value of the transfer material. (3) Furthermore, there is a problem called "photo memory" in which the potential of the exposed portion is not charged to a required potential in the charging process regardless of whether the development is normal development or reversal development, and the problem is more likely to occur in a high-sensitivity drum. This is because the exposure light is the photosensitive drum 130.
A memory is created in No. 1, and the image of the drum 1301 and one round before appears in the image, which is called a ghost. (Aim of the first invention) The first invention is made to solve the first problem, and the object thereof is to reduce the cost of a power supply, prevent interference unevenness due to AC voltage, and prevent charging noise. An object of the present invention is to provide an image forming apparatus capable of suppressing and reducing fogging. (Object of the Second Invention) The second invention is made to solve the second problem. The object of the second invention is to provide a photoconductor even if the system applies an AC bias to the photoconductor. An object of the present invention is to provide an image forming apparatus capable of easily measuring the surface potential of the. (Aim of the third invention) The third invention is made to solve the third problem. The purpose of the third invention is to improve the function of removing the residual charge on the image carrier and to assist the charging. An object of the present invention is to provide an image forming apparatus capable of performing the above.

[0023]

[Means for Solving the Problems]

(First Invention) In order to achieve the first object, in the first invention, a contact charging member for charging an image carrier having a photosensitive layer on a conductive base material, and a charging member An image forming apparatus comprising: a power source for a charging member that applies an electric field; a developing unit that visualizes a latent image formed on the photoconductor; and a power source for a developing unit that applies an electric field to the developing unit. The member power source and the developing unit power source are DC power sources, and an AC bias power source is connected to the conductive base material of the image carrier. (Second invention) Further, a contact charging member for charging an image carrier having a photosensitive layer on a conductive base material, a charging member power source for applying an electric field to the charging member, and a contact charging member formed on the photosensitive member. A developing means for visualizing the latent image; and a developing means power source for applying an electric field to the developing means, wherein the charging member power source and the developing means power source are direct current power sources, and An image forming apparatus in which an AC bias power source is connected to the conductive base material has a measuring unit that measures the surface potential of the photoconductor and a measurement bias power source that applies an AC bias to the measuring unit. Control means for turning off the AC bias power supply when the surface potential is measured by the means.

Further, a contact charging member for charging an image carrier having a photosensitive layer on a conductive base material, a charging member power source for applying an electric field to the charging member, and a latent image formed on the photosensitive member. A developing means for making the image visible; and a developing means power source for applying an electric field to the developing means. The charging member power source and the developing means power source are direct current power sources, and the conductivity of the image carrier is also provided. In an image forming apparatus in which an AC bias power source is connected to a base material, a measuring unit that measures the surface potential of the photoconductor, and an AC bias applied to the photosensitive unit and the measuring unit when measuring the surface potential by the measuring unit. Is characterized by canceling each other. (Third invention) Further, a charging means for charging an image carrier having a photoreceptor layer on a conductive substrate, and a toner image formed on the image carrier by exposing and developing after charging. An image in which an AC bias power source is connected to the conductive base material of the image carrier, which includes a transfer unit for transferring to a material and a contact type cleaning unit for cleaning residual toner on the image carrier after transfer. In the forming apparatus, the cleaning means is electrically conductive and is connected to the ground.

Further, a charging means for charging an image carrier having a photoconductor layer on a conductive base material, and a toner image formed on the image carrier by exposing and developing after charging are transferred to a transfer material. An image forming apparatus in which an AC bias power supply is connected to the conductive base material of the image carrier, and a contact type cleaning unit that cleans residual toner on the image carrier after transfer. , Making the cleaning means conductive and connecting it to ground,
It is characterized by interposing a DC bias power supply.

[0026]

[Action]

(Operation of the first invention) In the first invention, the power source for the charging member and the power source for the developing means are DC power sources, and
Since an AC bias power supply is connected to the photoconductor, there is no need to provide an AC power supply for each of the charging member power supply and the developing device power supply as in the conventional case, and only one AC power supply is required, resulting in low power supply cost Is realized.

Further, since the charging member power source and the developing means power source are composed of only a DC power source, no alternating voltage is applied as in the first conventional example, so that there is no interference of AC voltage between the charging member and the developing means. No moiré occurs in the halftone image.

Further, as compared with the charging means, the charging noise can be reduced by applying the AC bias to a rigid body having a large mass such as a photoconductor.

Further, since only the DC bias is applied to the developing means, the toner on the developing means is likely to be uniformly charged, the reversal toner is reduced, and the fog can be reduced. (Operation of the Second Invention) In the second invention, when the surface potential of the photoconductor is measured by the measuring means, the AC bias applied to the photoconductor is turned OFF, and the DC bias or the ground is applied to the photoconductor. By connecting to, it becomes possible to measure the accurate surface potential of the photoconductor even in an image forming apparatus in which an AC bias is applied to the photoconductor.

Further, by applying an alternating voltage that cancels the alternating voltage applied to the photosensitive member to the measuring means for measuring the surface potential on the photosensitive member, the surface potential on the photosensitive member to be measured becomes an alternating electric field. It is possible to measure without being affected. (Operation of the third invention) In the third invention, the cleaning means in contact is made conductive and grounded, or a bias having the same polarity as the voltage applied to the charging means is applied to the transfer step. By eliminating the residual charge (memory) on the image carrier and assisting in charging, defective images such as "paper marks" and "sand" are prevented, and the latitude of the resistance value that can be used by the transfer means is reduced. The present invention can be enlarged, and the present invention can prevent ghosts due to a "photo memory" caused by an exposure process when a high-sensitivity image bearing member is used.

Furthermore, by applying a voltage to the cleaning means, it is possible to perform the cleaning step and the charging step at the same time, and the conventional charging means can be eliminated to reduce the cost and simplify the image forming step. can do.

[0032]

【Example】

[Embodiment of the First Invention] (First Embodiment) FIG. 1 is an explanatory diagram of a first embodiment of the first invention.

The photosensitive drum 101 as a photosensitive member has a photosensitive layer 101a provided on a conductive aluminum drum 101b. This aluminum drum 101b is a photosensitive drum bias power source 120 as an AC bias power source as shown in FIG.
More AC bias is applied.

By applying an AC bias to the aluminum drum 101b, the charging roller 10 as a charging member is
Even if only a DC bias is applied from the power source 121 as a power source for the charging member to the photosensitive drum 101, the photosensitive drum 101 is similar to the conventional example.
Since an alternating electric field acts between the charging roller 102 and the charging roller 102, the photosensitive drum 101 can be uniformly charged.

Further, in the developing sleeve 104a of the developing device 104 which is the developing means, an alternating electric field works between the developing sleeve 104a and the photosensitive drum 101 even if only a DC bias is applied from the power source 122 as the power source for the developing means. The toner is transferred from the developing sleeve 104a to the photosensitive drum 10.
1 and the latent image on the photosensitive drum 101 can be developed and visualized.
Further, it is possible to remove the AC bias power supply from the bias power supply applied to the developing sleeve 104a and use it as a DC bias power supply such as the power supplies 121 and 122, and the cost of the bias power supply can be reduced.

Actually, in the non-contact reversal developing system, the process speed is 90 mm / sec, the developing sleeve 104a.
When the distance between the photosensitive drum 101 and the photosensitive drum 101 is 300 μm and the carbon sleeve is used as the developing sleeve 104a, and the fine particle toner has an average particle diameter of 6 μm,
Vpp = 1 from the power supply 120 to the aluminum drum 101b of
An AC bias of 600 V and a frequency of 1000 Hz is applied. When a DC bias of -700V is applied to the charging roller 102 from the power supply 121 and a DC bias of -500V is applied to the developing sleeve 104a from the power supply 122, the photosensitive drum 101 is uniformly and uniformly charged (dark portion potential =-). 700 V), a latent image (bright portion potential = −150 V) is formed on the photosensitive drum 101 by the laser light 103, the latent image on the photosensitive drum 101 is visualized by the developing sleeve 104a, and the core of the transfer roller 105 is formed. A DC bias of about +3 KV is applied to the gold 105a to form a toner image on the transfer material, and the transfer residual toner on the drum 101 is collected by the cleaning device 107. The transfer material onto which the toner image was transferred was conveyed to the fixing device 109 by the conveyance guide 108, and an image could be formed.

As described above, compared with the first conventional example shown in FIG. 6, the AC bias power source can be reduced from two to one, and only the DC bias is applied to the developing sleeve 104a. Is more likely to be uniformly charged, the reversal toner is reduced, and the occurrence of fog is also reduced.

Further, since an alternating current is applied to the photosensitive drum 101 at the time of transfer, the adhesive force between the toner and the photosensitive drum 101 is reduced, so that the transfer efficiency is improved and the transfer material and the photosensitive drum 101 are electrostatically attached. Since the adhesion force is also reduced, the separation of the transfer material after transfer is also good. Similarly, the untransferred toner is collected by the cleaning device 107, and the alternating current is applied to the photosensitive drum 101 at this time as well, so that the adhesive force between the toner and the photosensitive drum 101 is reduced, so that the cleaning performance is good. Has the advantage of being.

Furthermore, since the AC bias applied to the charging roller 102 and the AC bias applied to the developing sleeve 104a are in phase, a good halftone image can be obtained without mutual interference of the biases. Further, conventionally, a sound generated when an AC bias is applied to an elastic body such as the charging roller 102, that is, a charging sound may be a problem, but an AC bias is applied to a rigid body having a large mass such as the photosensitive drum 101. By applying, it becomes possible to reduce the charging noise. (Second Embodiment) In the first embodiment, an AC bias is applied in all of the image forming processes of charging, latent image, development, transfer and cleaning, but in this method, the average toner particle size is 10 μm or more. In the particle toner of No. 3, there is a problem that the toner image is scattered and disturbed in the transfer process.

Therefore, in this embodiment, as shown in FIG. 2, a CPU 130 is added as a control device for changing the frequency of the AC bias power source 120 to ON, OFF or Vpp.

On the circumference of the photosensitive drum 101, the nip portion A between the photosensitive drum 101 and the developing sleeve 104a.
By setting the distance between the photosensitive drum 101 and the nip portion B between the transfer roller 105 and the length of the arc AB longer than that of the transfer material, the photosensitive drum 10 can be used in the charging, latent image, and developing processes.
1 is turned on, and in the transfer step, the AC bias applied to the photosensitive drum 101 is turned off, and the toner image on the photosensitive drum 101 is transferred onto the transfer material. It is possible to obtain a clear image. After the transfer process is completed, the photosensitive drum 1 is again used.
An AC bias is applied to 01 to charge the photosensitive drum 101, and the image forming process is started.

Further, on the photosensitive drum 101, the distance between the photosensitive drum 101, the transfer roller 105 nip portion B and the cleaning portion C, and the length of the arc BC are made longer than that of the transfer material. OF in the transfer process
By turning on the AC bias applied to the photosensitive drum 101, which has been F, after the transfer step is turned on again, it is possible to obtain a clean image without scattering without impairing the cleaning performance.

Further, on the photosensitive drum 101, the distance between the charging section D and the developing section A and the length of the arc DA are made longer than that of the transfer material, so that the photosensitive drum 10 can be used during the charging step.
It is possible to change the AC bias applied to No. 1 and the Vpp and the frequency of the AC bias applied to the photosensitive drum 101 during the developing process, and it is possible to apply the AC bias more suitable for each of charging and development. The range of design can be expanded, and clearer images can be obtained.

Actually, in the image forming apparatus of the first embodiment, the distance between the charging, developing, transferring and cleaning sections is made longer than that of the transfer material, and the AC bias applied to the photosensitive drum 101 is set in the charging step. Vpp = 2000V, frequency = 650 Hz, Vpp = 1640V in development process, frequency = 2000 Hz, AC bias OFF in transfer process,
In the cleaning process, Vpp = 1000V, frequency = 3
By setting the frequency to 00 Hz, it is possible to obtain a clean image without scattering, the cleaning performance is good, and the fog on which the toner adheres to the non-image area can be suppressed.

As described above, the performance of each process is further improved by switching the AC bias applied to the photosensitive drum 101 to ON, OFF, Vpp, or frequency in each process of charging, developing, transferring, and cleaning. be able to. (Third Embodiment) In the second embodiment, the photosensitive drum 101
In the above, by making the distances between the charging, developing, transferring, and cleaning process portions longer than the transfer material, and applying an AC bias suitable for each process to the photosensitive drum 101, clear and non-scattering I was able to get a good image.

However, in the second embodiment, the photosensitive drum 1
Since the circumference of No. 01 cannot be made smaller than the length of the transfer material, there is a drawback that the image forming apparatus itself becomes large.

Therefore, in the present embodiment, as shown in FIG. 3, the AC bias 120 applied to the photosensitive drum 101 is also applied to the DC bias 114 of the transfer roller 105 so that the AC bias 120 is superimposed and applied. In the above, it is possible to transfer the toner image on the photosensitive drum 101 onto the transfer material by using only the DC bias without being affected by the AC bias, and it is possible to obtain a clear image without scattering, and at the same time, perform the exposure Since the diameter of the drum 101 can be reduced, the image forming apparatus can be downsized. (Fourth Embodiment) In the above embodiment, the case of a single color was described, but it is obvious that the present invention can be applied to a color image forming apparatus of four colors as shown in FIG.

In the case of color image formation, the photosensitive drum 1
101 rotates in the direction of the arrow, is uniformly charged by the charging roller 1102, and an electrostatic latent image is formed by the exposure light 1103. Then, the first developing device 1151 causes the toner of the first color (magenta) to be electrostatically latent. It is applied to the photosensitive drum 1101 according to the image. At this time, the second to fourth developing units 1152 to 115
No. 4 is in the OFF state, and the visible image of the first color is the second to fourth images.
The toner image of the first color is transferred onto the transfer material by the charging device 1157 on the transfer material wound around the transfer drum 1155 by the charging device 1158 without being affected by the developing devices 1152 to 1154. The surface of the photosensitive drum 1101 on which the transfer of the first color toner image is completed is cleaned by the cleaning device 1107, and then the second color (cyan) image forming process is started. In the process of the second color, only the second developing device 1152 is operated, the developing device for hitting is turned off, and the transfer material is sequentially transferred onto the transfer material wound around the transfer drum 1155 by the procedure described above. A four-color superimposed color image is formed on top. Then, the transfer material carrying the four color toner images is separated from the transfer drum 1155, conveyed to the fixing device 1109, heated under pressure and fixed on the transfer material.

In the case of the color image forming apparatus as described above,
Similar to the above-described embodiment, the charging roller 1102 is applied by applying an AC bias to the photosensitive drum 1101.
Since it is only necessary to apply the DC bias to the four developing sleeves 1151a to 1154a of the developing units 1151 to 1154, the AC bias power supply can be reduced.

Further, as shown in FIG. 4, the bias control device 1
By making it possible to vary the DC bias value of the bias power supply 162 that applies the AC bias superimposed on the DC bias to the photosensitive drum 101, the Vpp of the AC bias, and the frequency by 63, the color is transferred onto the transfer material wound around the transfer drum 155. When the toner images are sequentially transferred, if an AC bias superimposed on the DC bias of the opposite polarity to the toner is applied to the photosensitive drum 101 so that the color toner image on the transfer material is not retransferred to the photosensitive drum 101, the retransfer is performed. Can be eliminated.

In fact, in the case of reversal development, the toner is negatively charged, so that when the process speed is 90 mm / sec, the aluminum drum 101b of the photosensitive drum 101 is
V superposed on DC bias of -300V from power supply 162
An AC bias of pp = 1600V and frequency = 1000 Hz is applied. For the charging roller 102, a DC bias of −700 V from the power source 161 and a developing sleeve 151a to
154a has a DC bias of −500 from the power supply 160.
By applying V, the toner transferred to the transfer material was not retransferred to the photosensitive drum 101, and a good color image could be obtained.

Further, since the toner has a different charge amount depending on the color, the CPU 163 as a control device uses the AC bias Vp applied to the photosensitive drum 101 depending on the color of the toner.
By changing the p or the frequency, an AC bias suitable for the toner of that color is applied to obtain a color image without image density and fog. Since the higher the frequency is, the smaller the fog is and the lower the image density is. Therefore, it is possible to make the adjustment such that the frequency of the toner of the color with large fog is increased and the frequency of the toner of the color with low image density is decreased. .

Further, since the color image is obtained by mixing the toners of four colors, the photosensitive drum 1 is also transferred during transfer.
By applying an AC bias to 01, the superposed toner on the transfer material wound on the transfer drum 102 is
It mixes well and a beautiful color image can be obtained. [Embodiment of the Second Invention] (Fifth Embodiment) FIG. 7 is an explanatory view of a fifth embodiment of the second invention.

When measuring the charging potential (dark potential) of the photosensitive drum 201 as a photosensitive member that has been charged by the charging roller 202 as a charging member, first of all, during pre-rotation, etc. (when warming up the fixing roller, etc.). During non-image formation, an alternating voltage is applied to the photosensitive drum 201 from an AC bias power source 220 as a photoconductor bias power source, a DC bias voltage is applied to the charging roller 202, and the relative potential difference between them is used. Then the photosensitive drum 20
A predetermined charge is applied to the surface of 1. At this time, a surface potential meter 230 as a measuring means is arranged on the downstream side of the charging roller 202 in the rotation direction of the photosensitive drum 201, and when the charged portion on the photosensitive drum 201 rotates in the measuring portion, the photosensitive drum 201 is rotated. AC bias applied to
The FF is performed, the conductive base material 201b of the photosensitive drum 201 is connected to the ground 232, and the grounded state is established.

As a result, a potential substantially equal to the DC bias value of the charging roller 202 appears on the surface of the photosensitive drum 201, and the dark potential on the photosensitive drum 201 can be measured.

Then, the measured value of the dark potential on the photosensitive drum 201 is compared with a predetermined value by the CPU 231 as the control means, and the DC bias value applied to the charging roller 202 or the measured value of the dark potential is applied to the photosensitive drum 201. The Vpp value of the AC bias to be adjusted is adjusted to change the charging potential depending on the environment of the photoconductor layer 201a of the photoconductor drum 201 or the photoconductor layer of the photoconductor drum 201 is scraped due to durability.
It is possible to prevent a decrease in the charging potential, keep the charging potential of the photosensitive drum 201 constant, and obtain a stable and clear image.

At this time, the dark potential darkly decays with the passage of time, but if the potential is measured at a predetermined timing immediately after the AC bias is turned off, there is no practical problem.

Actually, in the non-contact reversal developing system, the developing speed of the developing sleeve 204a is 90 mm / sec.
The distance between the photosensitive drum 201 and the photosensitive drum 201 is 300 μm, and the developing means 20
When a carbon coated sleeve is used as the developing sleeve 204a of No. 4 and fine particle toner having an average particle diameter of 6 μm is used, the aluminum drum 201b of the photosensitive drum 201 is supplied with Vpp = 1600V from the power source 220 and frequency = 1000 Hz.
AC bias is applied. The charging roller 202 includes
DC bias from the power source 221 as the charging member power source =
A voltage of -700V is applied to the developing sleeve 204a from a power source 222 serving as a developing unit power source, and a DC bias of -500V is applied. When the dark potential is set to -700V, the dark potential measured by the surface electrometer 30 is measured. The value of the electric potential is
For example, when the voltage is −680V, the controller 231 sets the DC bias value applied to the charging roller 202 to −720.
By changing it to V, the charging potential of the photosensitive drum 201 is −
The dark potential of the photosensitive drum 201 can be maintained at 700 V by changing the DC bias value applied to the charging roller 202 even when the photoconductor layer 201a is scraped due to durability and the dark potential is lowered. I was able to keep it constant. (Sixth Embodiment) FIG. 8 is an explanatory view of a sixth embodiment of the second invention.

The photosensitive drum 201 is charged by the charging roller 202, and the exposure potential (bright potential) exposed by the exposure light 203 is measured at the time of non-image formation at the time of pre-rotation (at the time of warming up the fixing roller). An alternating voltage is applied to the photosensitive drum 201 from the power source 220 and an alternating voltage is applied to the charging roller 202 to charge the photosensitive drum 201 to a charging potential (dark potential), and the exposure light 203 such as laser light is used. Photosensitive drum 20
1 is exposed to obtain an exposure potential (bright potential) on the downstream side of the exposure unit in the rotation direction of the photosensitive drum 201, and the surface potential meter 23
0 is provided, and when the exposure unit reaches the measurement unit of the surface electrometer 203, the AC bias applied to the photosensitive drum 201 is turned off and connected to the ground 232.
By setting the conductive base material 201b of No. 01 to the grounded state, the bright potential on the photosensitive drum 201 can be accurately measured.

Then, the measured value of the bright potential of the photosensitive drum 201 is compared with a predetermined value by the control device 231, and the light quantity of the exposure light 203, that is, the laser power or the DC bias applied to the developing sleeve 204a is compared. By adjusting the values and the like, fluctuations in the bright potential due to the environment of the photosensitive drum 201 and the photosensitive layer 2 of the photosensitive drum 201 due to durability
Since the reduction of the bright potential due to the scraping of 01a can be prevented and the bright potential of the photosensitive drum 201 can be kept constant, the image density, the line width, etc. can be kept constant.

Actually, in the non-contact reversal developing system, the developing speed of the developing sleeve 204a is 90 mm / sec.
When the distance between the photosensitive drum 201 and the photosensitive drum 201 is 300 μm and the carbon sleeve is used as the developing sleeve 204, and the fine particle toner has an average particle diameter of 6 μm, the photosensitive drum 201
Vpp = 1 from the power supply 220 to the aluminum drum 201b of
An AC bias of 600 V and a frequency of 1000 Hz is applied. When the charging roller 202 is configured to apply a DC bias of −700V from the power source 221 and the developing sleeve 204a is applied to a DC bias of −500V from the power source 222, and the bright potential is set to −150V, a surface potential meter is used. When the measured value of the bright potential measured by 203 is −170 V, for example, the control device 231 causes the exposure light 2
03, the light quantity of the laser beam is increased to adjust the bright potential of the photosensitive drum 201 to −150 V. Further, for example, when the measured value of the bright potential is −130 V, the laser light amount is decreased to the contrary. It is possible to adjust the bright potential to −150. Further, a decrease in bright potential due to durability can be similarly corrected, and a constant bright potential can be obtained through durability.

Further, in order to form a latent image, the photosensitive drum 2
When exposing 01, instead of exposing the entire surface as described above, 1
If a halftone image such as dot2space is formed, the halftone potential at that time is measured with a surface electrometer, and the amount of laser light or the bias value applied to the developing sleeve is changed according to the measured value, the halftone reproducibility is improved. It can be kept constant. (Seventh Embodiment) FIG. 9 is an explanatory view of a seventh embodiment of the second invention.

In the fifth and sixth embodiments, the photosensitive drum 20
When the surface potential of No. 1 was measured, the conductive base material 201b of the photosensitive drum 201 was grounded. However, the conductive base material 201b of the photosensitive drum 201 as shown in FIG. In an image forming apparatus or the like that forms an image by applying an AC bias on which a DC bias is superimposed for the purpose of adjusting the bright portion potential, the DC bias is superimposed on the surface potential of the photosensitive drum 201. It is possible to accurately measure the latent image potential (dark portion potential and bright portion potential) by turning off the alternating voltage and applying only the DC bias. (Eighth Embodiment) FIG. 10 is an explanatory diagram of an eighth embodiment of the second invention.

In the embodiments of FIGS. 5 to 7, it is possible to measure the surface potential of the photosensitive drum 201 by turning off the AC bias applied to the photosensitive drum 201 at the potential measuring portion of the surface electrometer and at the time of measuring the potential. However, in the present embodiment, as shown in FIG.
With the AC bias applied from 0, the surface electrometer 20
The AC voltage applied to the photosensitive drum 201 from the power source 220 is also applied to the third circuit 3, so that the alternating voltage applied to the photosensitive drum 201 is canceled, and the photosensitive drum 201 is not affected by the alternating voltage. The upper surface potential can be measured.

In practice, an alternating voltage having the same phase, frequency and Vpp as the alternating voltage applied to the photosensitive drum 201 may be applied to the surface electrometer.

As shown in FIG. 10, an AC bias power source 220
By connecting the photosensitive drum 201 and the surface electrometer 203 to each other, only one AC bias power source is required, and
By measuring the dark potential and the bright potential on the photosensitive drum 201 and adjusting the charging roller bias, the developing bias, the laser light amount, and the like, it is possible to secure the surface potential of the photosensitive drum that is free from changes in environment and durability.

Further, the surface electrometer 203 and the photosensitive drum 20
An AC bias power source for applying an AC bias to 1 may be separately prepared. [Embodiment of the Third Invention] (Ninth Embodiment) FIG. 13 is an explanatory diagram of a ninth embodiment of the third invention.

Reference numeral 301 shown in FIG. 13 denotes a photosensitive drum as an image carrier having a photosensitive layer 301a provided on a metal conductive base material 301b. An AC bias power source 1320 is provided on the conductive base material 301b. Due to this, an alternating electric field is applied.

Reference numeral 302 denotes a charging roller as a charging means for uniformly and uniformly charging the photosensitive drum 301, and an elastic layer 302b is provided on the surface layer of the cored bar 302a. Reference numeral 311 is a bias power source for applying a DC bias to the charging roller core metal 302a.
01 surface, due to the alternating electric field applied to the conductive substrate,
The bias potential applied to the charging roller 302 is uniformly and uniformly charged. In the case of this conventional example, the photosensitive drum 30
The surface potential of 1 is charged to about -700V.

Reference numeral 303 denotes exposure light for forming an electrostatic latent image on the charged photosensitive drum 301, and in the case of this conventional example, the surface potential of the exposed portion is about -150V.

Reference numeral 304 denotes a developing device for developing the latent image on the photosensitive drum 301, and 304a is a developing sleeve for developing the toner in the developing device on the photosensitive drum 301, which is a hollow conductive base material. A magnet is arranged inside the.
A DC bias is applied to the developing sleeve 304a from a developing bias power source 312, and in the case of the conventional example, it is about -5.
A voltage of 00V is applied.

Reference numeral 305 denotes a transfer roller as a transfer means for transferring the toner image visualized on the photosensitive drum 301 to a transfer material (not shown), and the transfer roller 305 is an elastic layer made of medium resistance foam EPDM. 305b and core metal 30
5a.

Reference numeral 313 is a DC bias power source for applying a voltage to the transfer roller core metal 305a, and in the case of the conventional example, a voltage of about +3 KV is applied.

Reference numeral 306 is a transfer roller and a photosensitive drum 301.
A transfer guide for guiding the transfer material between them, and a cleaner 307 as a cleaning unit for removing toner and paper dust remaining on the photosensitive drum 301. In the conventional example, the elastic blade 330 is used as the photosensitive drum 301. To remove residual toner.

After the transfer, the transfer material is transferred to the transfer guide 308.
The toner image is fixed to the transfer material by being sent to the fixing device 309 and heated under pressure. Fixer 309
Is composed of a fixing roller 309a and a pressure roller 309b.

The cleaning blade has a resistance of 10 ⁸ Ω.
The elastic blade 330 whose resistance is adjusted to cm or less, and the elastic blade 330 is connected to the ground 331.

For example, in the case of a reversal developing system, an AC bias is applied to the photosensitive drum 301 from the power source 320 when the positive charge applied from the transfer roller 305 remains on the photosensitive drum 301 after the transfer process. By the interaction of the AC bias between the cleaning blade 330 connected to the ground 331 and the photosensitive drum 301, the surface potential of the photosensitive drum 301 is uniformly converged to 0V, and the residual positive charge on the photosensitive drum 301 is removed. Of course, this is an effect that cannot be obtained by the conventional method in which the core metal of the photosensitive drum 301 is used in a grounded state.

Actually, the process speed is 94 mm / se
c, charging roller bias: -700 V, charging portion surface potential: -670 V, exposure amount: 20 μJ / cm ² , exposed portion surface potential: -150 V, developing bias: -500 V, photosensitive drum bias: DC; 0 V, AC; Vpp = 1600
FIG. 21 shows the relationship between the occurrence of defective images (explosion, paper marks, punch-through) in the applied voltage-resistance graph of the conventional transfer roller in the image forming apparatus applying V and frequency = 1000 Hz. “Explosion” is a state in which an image is scattered when the transfer roller does not supply enough charge to hold the toner on the transfer material. And "explosion",
The shaded area surrounded by the “paper trace” and the “penetration” line is the usable range of the transfer roller 305.

However, the addition of the static elimination step by the conductive cleaning blade 330 of the present invention alleviates the influence of the bias of the transfer roller 305 on the photosensitive drum 301, and as shown in FIG. Is enlarged, the transfer roller 3
05 The usable range has also been expanded to the shaded area in Figure 14,
A transfer roller having a lower resistance can be used.

Further, the latitude of the applied voltage could be widened even in the transfer roller having a higher resistance. (The transfer roller resistance here is that the transfer roller as shown in FIG. 19 is brought into pressure contact with an aluminum drum and driven to rotate,
When the voltage V is applied to the transfer roller core metal, the voltage value V ₁ of the resistor R is measured, and the current value I (= V ₁₎ flowing through the resistor R is measured.
/ R) is a value calculated by calculation of the transfer roller resistance R _r (= V / I). ) Moreover, even if a high-sensitivity drum is used here, a "photo memory" is created by the exposure light.
The grounded conductive blade removed the charge from the memory and prevented the generation of ghosts. (Tenth Embodiment) FIG. 15 is an explanatory diagram of the tenth embodiment.

In the ninth embodiment, the conductive cleaning member is grounded, but in this embodiment, the conductive cleaning blade 33 is connected from the DC bias power source 350 as shown in FIG.
Even if a bias having the same polarity as the charging polarity is applied to 0, the same charge removal effect of the transfer memory can be obtained, and at the same time, the photosensitive drum 301 can be charged in two stages of the cleaning process and the charging process. As compared with the case of grounding in the ninth embodiment, the charging ability is improved, and the latitude of "paper mark" and "sandy land" can be further expanded.

Actually, in the image forming apparatus used in the ninth embodiment, when a −300 V is applied to the conductive cleaning blade 330 from the DC bias power source 350, a “paper mark” is generated.
I was able to expand the latitude of "sand".

Further, since the photosensitive drum 301 is pre-charged to −300 V before the charging step, the photosensitive drum 301 is charged in the charging step by the charging roller 302.
The charging ability of uniformly charging the toner is improved, the surface potential of the charging portion becomes −680V, and the charging surface potential increases by 10V as compared with the ninth embodiment. That is, since the charging ability is improved, the value of the voltage applied to the charging roller 302 and the surface potential of the charging portion of the photosensitive drum 301 are equalized, and the charging efficiency can be improved.

Further, even when the high-sensitivity drum was used, the "photo memory" by the exposure light was able to prevent the generation of ghost by eliminating the charge by the conductive blade to which the bias was applied. (Eleventh Embodiment) FIG. 16 is an explanatory diagram of an eleventh embodiment of the third invention.

In the ninth embodiment, the blade is used for cleaning, but the same effect can be obtained by using the electrically conductive fur brush 340 as in the present embodiment.

With the blade of the ninth embodiment, it was difficult to design the blade due to problems such as slipping through of the blade in the case of ultrafine particle toner having a small toner particle diameter. However, by using a fur brush, it is easy to use the photosensitive drum. The residual toner on 301 can be cleaned, and the photosensitive drum 301 is less likely to be scratched.
At this time, the fur brush 340 is made conductive and the earth 33
As in the case of the above-mentioned conductive blade, the residual charge on the photosensitive drum 301 is eliminated by connecting to No. 1 to assist the charging ability by the charging process, and the generation of "paper marks" and "sand" and the photo memory. It is possible to prevent "ghost" due to.

As in the tenth embodiment, the conductive fur brush 340 is connected to the DC bias power source 35 as shown in FIG.
When a bias having the same polarity as the charging polarity of 0 is applied, the charging ability is further improved, and at the same time, the toner has a negative polarity. Therefore, the toner does not adhere to the conductive fur brush 340, and the fur brush is always in a clean state to provide a photosensitive drum. Since 301 can be cleaned, cleaning performance can also be improved. (Twelfth Embodiment) FIG. 18 is an explanatory diagram of a twelfth embodiment of the third invention.

In the ninth to eleventh embodiments, the cleaning process has a role as a charge eliminating process as a pre-stage of the charging process using a charging roller or the like and further as a charging assisting means. By applying a charging bias to the conductive cleaning member as shown in FIG. 18, it is possible to perform the cleaning process and the charging process at the same time, and by removing the charging roller,
Cost reduction can be realized.

That is, the conductive cleaning blade 33
When 0, the toner remaining on the photosensitive drum 301 can be cleaned and the photosensitive drum 301 can be charged at the same time.

In practice, the cleaning blade 330
Applying 700V, the surface potential of the photosensitive drum 301-
It was possible to charge it to 670 V, and it was possible to obtain an image similar to the conventional one.

Further, the same effect can be obtained in the fur brush cleaning system, and at the same time as the cleaning with the conductive fur brush, the charging step is performed, the charging roller is eliminated, and the cost can be reduced and the simple image forming process can be realized. Become.

[0092]

【The invention's effect】

(Effect of the first invention) In the first invention, the power source for the charging member and the power source for the developing means are DC power sources, and
Since an AC bias power supply is connected to the photoconductor, there is no need to provide an AC power supply for each of the charging member power supply and the developing device power supply as in the conventional case, and only one AC power supply is required, resulting in low cost Is realized.

Further, since the charging member power source and the developing means power source are composed of only a DC power source, an alternating voltage is not applied as in the first conventional example, so that there is no unevenness in the interference between the charging member and the developing means. No moiré occurs in the halftone image.

Further, as compared with the charging means, the charging noise can be reduced by applying the AC bias to a rigid body having a large mass such as a photoconductor.

Further, since only the DC bias is applied to the developing means, the toner on the developing means is likely to be uniformly charged, the reversal toner is reduced, and the fog can be reduced. (Effect of the Second Invention) In the second invention, when the surface potential is measured by the measuring means for measuring the surface potential on the photoreceptor in the image forming apparatus for applying the AC bias to the photoreceptor. By turning off the AC bias applied to the photoconductor, the surface potential on the photoconductor can be accurately measured.

Further, the surface potential on the photoconductor can be accurately measured by applying to the measuring means an alternating voltage that cancels the AC bias applied to the photoconductor.

As described above, in a system in which an AC bias is applied to the photosensitive member, the surface potential is accurately measured, and the DC bias value applied to the charging means and the developing means, the light amount of the exposure light, By varying the Vpp and frequency of the AC bias applied to the photoconductor, the surface potential on the photoconductor can be kept constant, and the image density and line width can be kept constant at appropriate values. As a result, you can always obtain a clear image regardless of the environment and durability. (Effect of the third invention) According to the third invention, the cleaning means in contact is made conductive and is grounded, or a bias having the same polarity as the voltage applied to the charging means is applied to the transfer step. By eliminating the residual charge (memory) on the image carrier and assisting in charging, defective images such as "paper marks" and "sand" are prevented, and the latitude of the resistance value that can be used by the transfer means is reduced. The present invention can be enlarged, and the present invention can prevent ghosts due to a "photo memory" caused by an exposure process when a high-sensitivity image bearing member is used.

Further, by applying a voltage to the cleaning means, the cleaning step and the charging step can be performed at the same time, and the conventional charging means can be eliminated to realize the cost reduction and the simplification of the image forming step. can do.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to a first embodiment of the first invention.

FIG. 2 is a schematic configuration diagram of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a main part of an image forming apparatus according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a main part of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a main part of an image forming apparatus according to a first conventional example.

FIG. 6 is a schematic configuration diagram of a main part of another image forming apparatus of a first conventional example.

FIG. 7 is a schematic configuration diagram of a main part of an image forming apparatus according to a fifth embodiment of the second invention.

FIG. 8 is a schematic configuration diagram of a main part of an image forming apparatus according to a sixth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of main parts of an image forming apparatus according to a seventh embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a main part of an image forming apparatus according to an eighth embodiment of the present invention.

FIG. 11 is a schematic configuration diagram of a main part of an image forming apparatus according to a second conventional example.

FIG. 12 is a schematic configuration diagram of main parts of another image forming apparatus according to a twelfth conventional example.

FIG. 13 is a schematic view of a main part of an image forming apparatus of a ninth embodiment according to the third invention.

FIG. 14 is a graph showing a resistance usable range of a transfer roller of the apparatus.

FIG. 15 is a schematic configuration diagram of a main part of an image forming apparatus according to a tenth embodiment of the present invention.

FIG. 16 is a schematic diagram showing the main parts of an image forming apparatus according to an eleventh embodiment of the present invention.

FIG. 17 is a schematic configuration diagram of main parts of an image forming apparatus according to a twelfth embodiment of the present invention.

FIG. 18 is a schematic configuration diagram of a main part of an image forming apparatus according to a thirteenth embodiment of the present invention.

FIG. 19 is an explanatory diagram of a resistance measuring method of a transfer roller of the image forming apparatus according to the present invention.

FIG. 20 is a schematic perspective view of a main part of an image forming apparatus according to a third conventional example.

FIG. 21 is a graph showing a resistance usable range of a transfer roller of the apparatus.

[Explanation of symbols]

 101 Photosensitive Drum (Photosensitive Member) 102 Charging Roller (Charging Member) 120 Photosensitive Drum Bias Power Supply (AC Bias Power Supply) 121 Power Supply (Charging Member Power Supply) 104 Developing Device (Developing Means) 122 Power Supply (Developing Means Power Supply) 202 Charging Roller (Charging member) 201 Photosensitive drum (photoreceptor) 231 CPU (control means) 230 Surface potential meter (measurement means) 220 AC bias power supply 221 Power supply (power supply for charging member) 204 Developing means 222 Power supply (power supply for developing means) 301 Photosensitive Drum (image carrier) 302 Charging roller (charging means) 305 Transfer roller (transfer means) 307 Cleaner (cleaning means) 331 Ground 350 DC bias power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Matsukuma 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Tanigawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (72) Inventor Akihiko Takeuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takayasu Yunomo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A contact charging member for charging an image carrier having a photosensitive layer on a conductive base material, a charging member power source for applying an electric field to the charging member, and a latent image formed on the photosensitive member. An image forming apparatus comprising: a developing unit that visualizes the image; and a developing unit power source that applies an electric field to the developing unit, wherein the charging member power source and the developing unit power source are DC power sources, and An image forming apparatus, wherein an AC bias power source is connected to the conductive base material of the body. 2. A contact charging member for charging an image carrier having a photoreceptor layer on a conductive base material, a charging member power source for applying an electric field to the charging member, and a latent image formed on the photoreceptor. A developing means for visualizing and a power source for developing means for applying an electric field to the developing means, wherein the power source for the charging member and the power source for the developing means are DC power sources, and the conductivity of the image carrier is provided. In an image forming apparatus in which an AC bias power source is connected to a base material, a measuring unit that measures the surface potential of the photoconductor, and the AC bias power source is turned on when the surface potential is measured by the measuring unit.
An image forming apparatus comprising: a control unit that performs FF. 3. A contact charging member for charging an image carrier having a photoreceptor layer on a conductive base material, a charging member power source for applying an electric field to the charging member, and a latent image formed on the photoreceptor. A developing means for visualizing and a power source for developing means for applying an electric field to the developing means, wherein the power source for the charging member and the power source for the developing means are DC power sources, and the conductivity of the image carrier is provided. In an image forming apparatus in which an AC bias power source is connected to a substrate, a measuring means for measuring the surface potential of the photoconductor and a measuring bias power source for applying an AC bias to the measuring means are provided. An image forming apparatus, wherein an AC bias applied to the photoconductor and the measuring means cancels each other when measuring a potential. 4. A charging means for charging an image carrier having a photoconductor layer on a conductive substrate, and a toner image formed on the image carrier by exposing and developing after charging is transferred to a transfer material. An image forming apparatus in which an AC bias power supply is connected to the conductive base material of the image carrier, and a contact type cleaning unit that cleans residual toner on the image carrier after transfer. An image forming apparatus, wherein the cleaning means is electrically conductive and is connected to a ground. 5. A charging means for charging an image carrier having a photoconductor layer on a conductive base material, and exposure and development after charging to transfer a toner image formed on the image carrier to a transfer material. An image forming apparatus in which an AC bias power supply is connected to the conductive base material of the image carrier, and a contact type cleaning unit that cleans residual toner on the image carrier after transfer. An image forming apparatus, characterized in that the cleaning means is made electrically conductive and is connected to ground, and a DC bias power source is interposed.