JPH11119617A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely remove electric charges remaining on an image carrier in reduced occupacy space even if the image carrier is electrified to a positive potential by providing a contact charging member coming into contact with the image carrier so as to apply the charge and a photodestaticization means for irradiating the image carrier with light, in such a manner that the contact charging member transmits the light in a destaticization means. SOLUTION: The surface of a photoreceptor drum 41 after a transfer operation is electrified to the positive potential, because the positive potential is applied by a transfer charger 46, at the time of transferring a toner image. Thereafter, the charge remaining on the drum 41 can not be removed only by a discharge lamp 50, so that the application of the charge at a negative potential is attained by a conductive member 52. Simultaneously with this, almost the same position as a charge-applied position on the drum 41 is irradiated with irradiating light from the discharge lamp 50, in such a manner that the irradiating light passes through a light transmissive member 53. Therefore, in a state where the drum 41 is electrified to the negative potential, photodestaticization is executed to effectively eliminate the potential remaining on the drum 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for obtaining an output image by transferring a toner image on an image carrier to a recording medium, and more particularly, to a transfer on an image carrier. The present invention relates to an image forming apparatus that reliably removes residual charges later using both charge application and light removal.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, first, the surface of an image carrier is charged, and the charged surface of the image carrier is exposed to laser light or the like to form an electrostatic latent image. . Subsequently, the electrostatic latent image is developed with toner to form a toner image, and the toner image is transferred to a recording medium. After the transfer of the toner image, the residual toner is removed from the surface of the image carrier by a cleaner. At this time, since the surface of the image carrier is charged by the residual charge, it is necessary to remove the residual charge to uniformly charge the surface of the image carrier at a desired potential for the next image formation.

Therefore, as a method of removing the residual charges on the image carrier, a method of performing an optical erase by irradiating light after transfer is generally performed. As an image forming apparatus using such a method, for example, an image forming apparatus described in Japanese Patent Publication No. 6-25897 can be mentioned. As shown in FIG. 8, the configuration is as follows: around a photosensitive drum 141 on which an electrostatic latent image is formed, a charging charger 144 for charging the surface of the photosensitive drum 141 to a desired potential;
Exposure scanning section 1 for performing exposure scanning to form an electrostatic latent image
05 and a developing device 145 for developing the electrostatic latent image with toner
A transfer charger 146 for transferring a toner image formed by development onto a recording medium; a cleaner 142 for cleaning residual toner on the photosensitive drum 141 when one image forming process is completed; An eraser 147 for removing charges is disposed.

[0004] The erasing device 147, as shown in FIG.
It has a static elimination lamp 178 and an optical fiber 170, and is configured so that light irradiation on the photosensitive drum 141 can be made uniform. The cross section of the optical fiber 170 has a rectangular cross section, and its axial length is slightly longer than the image forming width of the photosensitive drum 141. The optical fiber 170 is covered with a cover other than the incident surface 177 and the irradiation surface 174 of the light from the neutralization lamp 178. Therefore, the static elimination lamp 178
Is irradiated from the wall surface 174 of the optical fiber 170 toward the photosensitive drum 141.

Here, the light transmission rate of the optical fiber 170 decreases as the distance from the discharge lamp 178 increases. Therefore, the wall surface 1 gradually expanded from the entrance surface 177
The surface indicated by reference numeral 182 in the surface of the surface 74 is appropriately roughened, and light from the neutralization lamp 178 passes through the optical fiber in the area 182. Since the area 182 gradually increases as the distance from the charge removing lamp 178 increases, the light from the charge removing lamp 178 can be irradiated to the photosensitive drum 141 with uniform intensity. I have. Therefore, the residual charges remaining on the photosensitive drum 141 can be eliminated.

In the case where charges having a polarity opposite to the normal charge polarity, that is, a positive potential, remain on the photosensitive drum 141 due to the operation of the transfer charger 146, the charge erasing is completely performed by the above-described optical erase method. Can not. Therefore, a technique for effectively removing static electricity in such a case is described in Japanese Patent Laid-Open No. Hei 5-173460. In this configuration, as shown in FIG. 10, a contact electrode 112 that is in contact with a photosensitive drum 141 is provided between a transfer charger 146 and a charging charger 144 to directly remove residual charges.

Further, as disclosed in Japanese Patent Application Laid-Open No. 5-80680, an auxiliary charger 121 for charging between the transfer charger 146 and the charger 144 to have the same polarity as that of the charger 144, and a back of the auxiliary charger 121 In some cases, static elimination light sources 122 are arranged to eliminate static electricity (see FIG. 11). In this case, in order to effectively use the charge removal effect by light charge removal, the photoreceptor drum 141 is first charged to a negative potential by the auxiliary charger 121, and then the optical erase is performed.

[0008]

However, the conventional image forming apparatus has the following problems. That is,
In an apparatus for performing optical erasing as disclosed in Japanese Patent Publication No. Hei 6-25897, an effective neutralizing effect can be obtained when the photosensitive drum 141 is charged to a negative potential.
When the photosensitive drum 141 is charged to a positive potential, there is a problem that a sufficient charge removing effect cannot be obtained. Further, an apparatus for performing a charge removal method as disclosed in Japanese Patent Application Laid-Open No. 5-173460 has a charge removal effect even when the photosensitive drum 141 is charged to a positive potential, but has a complete effect, as compared with a device for performing optical erase. It was difficult to remove static electricity. Further, in an apparatus for performing a static elimination method as disclosed in Japanese Patent Application Laid-Open No. 5-80680, although a large static elimination effect is required, a large space is required due to the configuration of the static elimination apparatus. It was a big barrier. In particular, this is a major problem when applied to a tandem-type copying machine in which image forming systems (photosensitive drums, developing devices, transfer devices, etc.) provided independently for each developing color are arranged in parallel along a paper path. Becomes

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problem, and even when the image carrier is charged to a positive potential, the residual charge on the image carrier is completely eliminated in a space-saving manner. It is an object of the present invention to provide an image forming apparatus capable of performing the following.

[0010]

According to a first aspect of the present invention, there is provided an image carrier for carrying a toner image, and a recording medium for carrying the toner image on the image carrier. Transfer means for transferring the toner image to the recording medium, and a charge removing means for removing charge from the surface of the image carrier after transferring the toner image to the recording medium, wherein the charge removing means contacts the image carrier. A light-transmissive contact charging member that applies electric charges to the image carrier, and a light discharging unit that irradiates the image carrier with light through the contact charging member.

According to the first aspect of the invention, first, a negative charge is applied to the image carrier by the contact charging member in contact with the image carrier. As a result, the image carrier is charged to a negative potential. Further, since the contact charging member is in contact with the image carrier, it is less susceptible to the surroundings than a charge applying means such as a corona type, and charges are reliably applied to the image carrier. In addition, since the voltage applied to the contact charging member can be reduced, the degree of freedom regarding the configuration of the device is increased. Further, it is possible to prevent the charge from being excessively applied to the image carrier.

[0012] Then, light from the light discharging means is transmitted through the contact charging member and irradiated on the image carrier to remove the residual charges on the image carrier. In addition, since the charge application and the light elimination are performed at substantially the same position on the image carrier, the charge mobility on the image carrier is higher than when the charge application and the light elimination are performed separately. . Therefore, even when the image carrier is charged to a positive potential, the residual charges can be efficiently removed.

As described above, according to the first aspect of the present invention, a light-transmissive contact charging member for applying a charge by contacting the image carrier is provided.
By providing a charge eliminator having a light eliminator for irradiating the image carrier with light through the contact charging member, it is possible to perform charge application and light elimination at almost the same position on the image carrier, The residual charges on the image carrier can be completely eliminated in a small space.

As the contact charging member, for example, a member obtained by bonding soft PA (polyamide) and PET (polyethylene terephthalate), a soft PA resin mixed with an ion conductive resin, or the like can be used.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the image forming apparatus according to the first aspect, the contact charging member is provided with a light of a wavelength component which deteriorates the image carrier. On the other hand, it is characterized in that it has low transmittance and high selective transmittance with respect to light having a wavelength component that does not deteriorate the image carrier.

Here, the charge transport layer of the image carrier absorbs light having a wavelength component around 450 to 600 nm as shown in FIG. The charge transport layer of the image carrier deteriorates when absorbing light. For this reason, at the time of performing the light removal, by cutting off the light of the wavelength component in the vicinity thereof, it is possible to prevent the deterioration of the charge transport layer of the image carrier.

According to the second aspect of the present invention, a negative charge is reliably applied to the image carrier by the contact charging member in contact with the image carrier. As a result, the image carrier is charged to a negative potential. Then, the light from the light discharging unit is transmitted through the contact charging member and is irradiated on the image carrier, and the residual charges on the image carrier are discharged. Therefore, even when the image carrier is charged to a positive potential, the residual charges can be reliably removed. Further, the contact charging member is shown in FIG.
As shown in (1), the transmissivity is low for light having a wavelength component of about 600 nm or less and high for light having a wavelength component of about 700 nm or more. That is,
As for the light from the light removing unit, only light having a wavelength component (other than 450 to 600 nm) that does not adversely affect the image carrier is transmitted and irradiated to the image carrier. Accordingly, the charge transport layer of the image carrier does not absorb light, so that deterioration can be prevented.

According to a third aspect of the present invention, in order to solve the above problem, the image forming apparatus according to the first or second aspect is characterized in that the image forming apparatus has two or more sets of the contact charging members. .

According to the third aspect of the present invention, similarly to the first aspect of the present invention, static elimination of residual charges on the image carrier is performed. In addition, since two or more sets of contact charging members are provided for performing charge elimination, charge application and light elimination are repeated a plurality of times in a short cycle. Therefore, it is possible to more reliably obtain the static elimination effect.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as an embodiment of the image forming apparatus of the present invention, a tandem type digital color copying machine (hereinafter simply referred to as "copying machine") provided with the image forming apparatus of the present invention. ) Will be described with reference to the accompanying drawings. In a tandem-type copying machine, each image forming system simultaneously forms toner images of each development color, and these toner images can be transferred onto a sheet one after another during a series of sheet passing operations. it can. Therefore, the speed of the image forming process can be increased as compared with a conventional type color copying machine in which toner images of respective development colors are sequentially formed on one photoconductor.

First, the configuration of the copying machine according to the first embodiment is shown in FIG. 1, and the overall configuration will be described. The copying machine includes an image reader section IR for reading a document image and a print section PR for printing the read image on a recording sheet S and reproducing it.

The image reader section IR separates an original image into three colors of red (R), green (G), and blue (B) with an image sensor such as a CCD and reads the image. Since the configuration of the image reader section IR is well known, detailed illustration and description thereof are omitted. The printer unit PR includes a transport unit 2 that transports the recording paper S along the transport path 20 and a recording paper S.
Image forming units 3 for forming images of four colors on the
C, 3M, 3Y, and 3K (hereinafter, C, M, Y, and K are added as color symbols to the numbers of the parts related to the respective colors of cyan, magenta, yellow, and black. There is no difference.). The image forming units 3C, 3M, 3Y, and 3K include image forming process units 4C, 4M, 4Y, and 4K arranged in parallel along the transport path 20, and exposure scanning units (including an optical system) 5C. 5M, 5Y, and 5K. further,
A control unit 100 that performs overall control of the copying machine 1 is provided.

The transport section 2 is formed around an endless transport belt 27 stretched through a driving roller 24, a driven roller 25, and a tension roller 26, and the recording sheet S on the transport belt 27 is fixed. It is designed to be transported at a speed. On the upstream side (paper feed side) of the transport belt 27, a paper feed cassette 21 for stacking and storing recording paper S of a predetermined size,
A paper feed roller 22 for feeding out the recording paper S one by one from the paper feed cassette 21, and a transport belt 27 for feeding the fed out recording paper S.
Timing roller 23 which sends it out at a predetermined timing
And are arranged. On the other hand, on the downstream side of the transport belt 27, a fixing device 28 for fixing the toner transferred to the recording paper S, and a paper discharge tray 29 for stacking and storing the recording paper S after completion of copying are provided. I have. Also, the conveyor belt 2
Sensors SE1 and SE2 are provided on the upstream side and the downstream side of 7, respectively, so as to detect the timing of paper feeding, paper jam, and the like.

The image processing units 4C, 4M, 4Y, and 4K of the image forming units 3C, 3M, 3Y, and 3K form images by an electrostatic copying method.
Photoconductor drums 41 arranged in parallel along the transport direction of
C, 41M, 41Y, and 41K are centered. Then, the photosensitive drums 41C, 41M, 41Y, 4
Around 1K, cleaners 42C, 42M, 42Y, 4
2K, charging chargers 44C, 44M, 44Y, 44
K, developing devices 45C, 45M, 45Y, 45K, and erasing devices 47C, 47M, 47Y, 47K, and the like. Further, each of the photosensitive drums 41C, 41M, 41
Transfer chargers 46C, 46M, 46Y, and 46K are disposed immediately below Y and 41K via a transport belt 27.

Next, the operation of the copying machine configured as described above will be described. First, the image data for each of the red (R), green (G), and blue (B) color components obtained by the image reader IR is subjected to shading correction, density conversion, edge enhancement, and the like in the control unit 100. Perform necessary data processing. Further, the image data is converted into image data of each reproduced color of cyan (C), magenta (M), yellow (Y), and black (K), and these image data are converted into cyan (C), magenta (M), yellow (Y), and black. The image data of (K) is temporarily stored in an image memory (not shown) of the control unit 100.

Thereafter, based on the image data stored in the image memory, the exposure scanning units 5C, 5M, 5Y, 5K
, Laser light corresponding to image data of each reproduced color is modulated and emitted. Photoconductor drums 41C, 41
M, 41Y and 41K rotate in the direction of the arrow in the figure,
The surfaces are uniformly charged to a negative potential by the charging chargers 44C, 44M, 44Y, and 44K. afterwards,
Exposure scanning is performed by the laser light. The portions exposed by the positive potential charges generated by the exposure are electrically neutralized, and the respective photosensitive drums 41C, 41M, 41Y,
An electrostatic latent image corresponding to each reproduction color is formed on 41K.
The electrically neutralized portion of the electrostatic latent image is developed by the toner of each color charged to a negative potential by the developing units 45C, 45M, 45Y, and 45K to form a toner image for each color. . These toner images are transferred to the transfer chargers 46C, 46C at the opposing portions of the photosensitive drums 41C, 41M, 41Y, 41K and the conveyor belt 27.
46M, 46Y, and 46K successively superimpose and transfer the recording paper S fed from the paper feed cassette 21. Then 4
The recording paper S on which the color toner image has been overlaid is transferred to the fixing device 28.
, Whereby each toner image is melted to form a full-color image, and is fixed on the recording paper S. After the image is fixed, the recording paper S is discharged to the discharge tray 29. By the above operation, one sheet is copied.

Subsequently, the erasing units 47C, 47M, 47Y,
47K will be described. Since these have the same structure and perform the same operation, only one of them will be described as a representative. Therefore, in the following description, C, M,
The color symbols of Y and K are omitted, and they are referred to as “erase device 47”, “photoconductor drum 41”, and the like.

As shown in FIG. 2, the erasing device 47 has a charge elimination lamp 50 as a charge elimination light source, and a contact charging member 51 for applying a negative potential charge to the photosensitive drum 41. Further, the contact charging member 51 includes a conductive member 52 and a light transmitting member 53, has a width substantially equal to the image forming width of the photosensitive drum 41, and has one end in contact with the photosensitive drum 41. Have been. The conductive member 52 has a thickness of 100 to 200 μm made of soft PA (polyamide).
m of the conductive film. And the volume resistance is 1
0 a ^{6 Ω} · cm, the voltage applied to the conductive member 52 -
It is 800V. The light transmitting member 53 is made of P
It is a 200 μm thick light transmissive film made of ET (polyethylene terephthalate).

On the other hand, the static elimination lamp 50 includes a contact charging member 51.
Is disposed near the light transmitting member 53 so that the irradiation light can be incident on the light transmitting member 53. The light from the neutralization lamp 50 is incident on the light transmitting member 53, and effectively irradiates the surface of the photosensitive drum 41 from the end. That is, the light from the neutralization lamp 50 is applied to almost the same position as the position where the conductive member 52 applies a charge to the photosensitive drum 41.

The eraser 47 having the above configuration operates as follows. The surface of the photosensitive drum 41 after the transfer operation is partially charged to a positive potential. This is because a positive voltage is applied by the transfer charger 46 when transferring the toner image. For this reason, the residual charge on the photosensitive drum 41 cannot be effectively removed only by the charge removing lamp 50, so that the conductive member 52 first applies a charge at a negative potential. At almost the same time, the irradiation light from the charge removing lamp 50 is transmitted through the light transmitting member 53 and is irradiated on the photosensitive drum 41 at substantially the same position as the charge application position. Therefore, the photosensitive drum 41
The light charge is removed while the surface of the photosensitive drum 41 is charged to a negative potential, so that the residual charge on the photosensitive drum 41 can be effectively removed.

The change in the surface potential of the photosensitive drum 41 in the present embodiment will now be described with reference to FIG. FIG. 3A shows a change in the surface potential of the photosensitive drum in the conventional image forming apparatus using the optical erase.
FIG. 3B illustrates a change in the photosensitive drum surface potential in the image forming apparatus according to the present embodiment.

First, the change up to the transfer operation will be described. In the operation up to this point, as shown in FIG. 3, the surface potential of the photoconductor is the same as that of the conventional photoconductor and that of the present embodiment, so that they will be described together. Photoconductor drum 41
(Or 141) is the surface potential of the charged charger 42
(Or 142), the potential becomes negative. next,
Since the portion exposed by the exposure scanning unit 5 (or 105) is electrically neutralized, the photosensitive drum 41 (or 1)
The surface potential of 41) decreases. Since a positive voltage is applied to the photosensitive drum 41 (or 141) by the transfer operation by the transfer charger 46 (or 146), the photosensitive drum 41 (or 141) is applied.
Has a positive potential.

Next, the static elimination operation will be described. In the related art, the residual charge on the photosensitive drum 141 cannot be completely eliminated, and has a positive potential as shown in FIG. On the other hand, in the case of the present embodiment, charge is applied at a negative potential by the conductive member 52,
At substantially the same time, the light from the neutralization lamp 50 is transmitted through the light-transmitting portion 53 and applied to the photosensitive drum 41 at substantially the same position as the charge application position. Accordingly, since light is removed while the surface of the photosensitive drum 41 is charged to a negative potential, residual charges on the photosensitive drum 41 can be effectively removed. Therefore, the photoconductor surface potential is
It becomes "0" as shown in (B). Further, since the light is neutralized immediately after the charge is applied by the conductive member 52, the surface potential of the photosensitive drum 41 does not become extremely high.

Finally, the charging and exposing operations in the next image formation will be described. In the related art, since the surface potential of the photoconductor drum 141 is not completely eliminated, even if the surface of the photoconductor drum 141 is charged by the transfer charger 142, the surface potential does not become the same as the previous time. That is, the surface of the photosensitive drum 41 cannot be set to a desired potential. For this reason, the electrostatic latent image formed on the photosensitive drum 141 by exposure by the exposure scanning unit 105 thereafter does not become faithful to the original document, but contains image noise. Therefore, a high quality output image cannot be obtained. On the other hand, in the image forming apparatus according to the present embodiment, since the charging is performed by the charging charger 44 in a state where the charge is completely removed, the surface of the photosensitive drum 41 has the same potential as the previous time, that is, a desired potential. After that, the photosensitive drum 4
An electrostatic latent image faithful to the original is formed on the surface of the document 1. Therefore, a high-quality output image free from image noise can be obtained.

As described in detail above, according to the image forming apparatus of the first embodiment, first, the photosensitive drum 4
The photosensitive drum 4 by the conductive member 52 that is in contact with
A charge of a negative potential is applied to 1, and the surface of the photosensitive drum 41 has a negative potential. In addition, since the conductive member 52 is in contact with the photosensitive drum 41, the conductive member 52 is less affected by the surroundings than a charge applying means such as a corona method,
The charge is reliably applied to the photosensitive drum 41. Further, since the voltage applied to the conductive member 52 can be reduced, the degree of freedom regarding the configuration of the device is increased. Further, it is possible to prevent the charge from being excessively applied to the photosensitive drum 41.

The light from the charge removing lamp 50 passes through the light transmitting member 53 and irradiates almost the same position as the charge application position on the photosensitive drum 41, and the residual charge on the photosensitive drum 41 is removed. You. That is, since the charge application and the light elimination are performed at substantially the same position on the photoconductor drum 41, the charge mobility on the photoconductor drum 41 is lower than when the charge application and the light elimination are performed separately. Get higher. Therefore, even when the surface of the photosensitive drum 41 has a positive potential, the residual charges can be completely eliminated.

As described above, by the contact charging member 51 having the simple structure including the conductive member 52 and the light transmitting member 53, it is possible to perform the charge application and the light elimination at almost the same position on the photosensitive drum 41. Because the photosensitive drum 4
1 can be completely eliminated in a space-saving manner.

Next, a copying machine according to a second embodiment will be described. In this embodiment, the configuration and operation of the entire copying machine are the same as those of the first embodiment, and the difference lies in the details of the eraser. Specifically, instead of using the contact charging member 51 including the conductive member 52 and the light transmitting member 53, a conductive light transmitting member 60 as shown in FIG. 4 is used. Further, the light from the static elimination lamp 50 is incident on the end of the conductive light transmitting member 60 which is not in contact with the photosensitive drum 41. The conductive light transmitting member 60 is a 100-200 μm thick film made of soft PA (polyamide) mixed with an ion conductive resin. The volume resistance is 10 ⁶ Ω · cm, and the conductive light-transmitting member 60
The applied voltage to is -800V. The conductive light transmitting member 60 has a spectral transmittance of 600 as shown in FIG.
It has a low selective transmittance at a wavelength of not more than nm and a high selective transmittance at a wavelength of not less than 700 nm. That is, the conductive translucent member 60 hardly transmits a wavelength component of 600 nm or less. On the other hand, as shown in FIG. 5, the charge transport layer of the photosensitive drum 41 mainly absorbs wavelength components of 450 to 600 nm.

In this embodiment, the conductive light transmitting member 60
The charge application to the photosensitive drum 41 and the light removal by the
Therefore, the residual charges on the photosensitive drum 41 can be completely eliminated in a space-saving manner. Further, the light applied to the photoconductor drum 41 is transmitted through the conductive light transmitting member 60 so that 60
The wavelength component of 0 nm or less is almost cut off. Therefore, the charge transport layer of the photosensitive drum 41 does not absorb the light from the charge removing lamp 50, so that its deterioration is prevented.

That is, according to the second embodiment, the photosensitive drum 41 is provided with the conductive light transmitting member 60 which hardly transmits the light of the wavelength component absorbed by the charge transport layer. The application of the electric charge at the potential and the light elimination can be performed at substantially the same position. For this reason, even when the surface of the photosensitive drum 41 is charged to a positive potential, the residual charges can be reliably removed. Further, deterioration of the photosensitive drum 41 due to irradiation of the charge removing lamp 50 can be prevented.

Next, a copying machine according to a third embodiment will be described. In this embodiment, the configuration and operation of the entire copying machine are the same as those of the first embodiment, and the difference lies in the details of the eraser. Specifically, instead of providing only one contact charging member 51, for example, as shown in FIG. 6, a plurality of contact charging members 51a are arranged in parallel. This contact charging member 5
1a includes a conductive member 52a and a light-transmitting member 53a as in the first embodiment. That is,
The contact charging member 51a has a configuration in which a conductive member 52a is bonded to the light transmitting member 53a so as to transmit light around the light transmitting member 53a.

In this embodiment, the electric charge is applied to the photosensitive drum 41 by the conductive member 52a.
Light elimination to 1 is performed by the light transmitting member 53a in the same manner as in the first embodiment. Then, the conductive member 52
contact charging member 51a including a and a light transmitting member 53a
Are provided side by side, the charge application to the photoconductor drum 41 and the light removal are repeated within a short period of time. Therefore, the residual charge on the photosensitive drum 41 can be completely eliminated by the stable static elimination performance.

That is, according to the third embodiment, by providing a plurality of sets of the contact charging members 51a in parallel, it is possible to provide the photosensitive drum 41 with a plurality of electric charges at a negative potential and a light elimination within a short period of time. You can do it many times.
Therefore, the effect of eliminating the residual charges on the photosensitive drum 41 can be enhanced.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications can be made without departing from the gist of the present invention. For example, in each of the above embodiments, a tandem-type color copying machine has been described as a specific example. However, the present invention is not limited to a monochromatic electrophotographic copying machine, and a toner image of each development color may be sequentially developed on one photoconductor. Needless to say, the present invention can also be applied to a color copying machine, a printer, a facsimile machine, and the like of the type of superimposed transfer. Further, in the above-described embodiment, the sheet applying unit is exemplified as the charge applying unit. However, the present invention is not limited to such a unit. For example, a brush 65 as shown in FIG. 7 can be used.

[0045]

As described above, according to the image forming apparatus of the present invention, even when the image carrier is charged at a positive potential, the residual charge on the image carrier can be completely eliminated in a space-saving manner. . Further, by cutting a part of the wavelength component of the light from the light removing unit by the contact charging member, it is possible to prevent the deterioration of the image carrier due to the light irradiation. Further, since the contact charging member is compact, a plurality of sets of contact charging members can be provided. By providing a plurality of sets of the contact charging members in this manner, the effect of removing residual charges on the image carrier can be enhanced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a copying machine to which the present invention is applied.

FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the first embodiment.

FIGS. 3A and 3B are diagrams showing changes in the surface potential of the photosensitive drum, wherein FIG. 3A shows a conventional case, and FIG. 3B shows a case where the present invention is applied.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 5 is a diagram showing a light absorption rate of a charge transport layer of a photosensitive drum and a spectral transmittance of a conductive light transmitting member.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

FIG. 7 is a view showing a case where a brush-shaped contact charging member is used.

FIG. 8 is a schematic configuration diagram of an image forming apparatus using an optical erase.

FIG. 9 is a schematic configuration diagram of the eraser shown in FIG. 8;

FIG. 10 is a schematic configuration diagram of an image forming apparatus provided with contact electrodes.

FIG. 11 is a schematic configuration diagram of an image forming apparatus including an auxiliary charger and a light source for static elimination.

[Explanation of symbols]

 41 Photoconductor drum 42 Cleaner 44 Charger 45 Developing device 46 Transfer charger 47 Erase device 50 Static elimination lamp 51 Contact charging member 52 Conductive member 53 Light transmissive member

Claims (3)

[Claims] An image carrier for carrying a toner image; a transfer unit for transferring the toner image on the image carrier to a recording medium; and the image after the toner image is transferred to the recording medium. In the image forming apparatus having a charge elimination unit that eliminates a charge on a surface of the carrier, the charge elimination unit includes a light-transmissive contact charging member that contacts the image carrier and imparts a charge, and the contact charging member is transparent. And a light erasing unit for irradiating the image carrier with light. 2. The image forming apparatus according to claim 1, wherein the contact charging member has a low transmittance for light of a wavelength component that deteriorates the image carrier, and a wavelength component that does not deteriorate the image carrier. An image forming apparatus having a selective transmittance having a high transmittance with respect to light. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus includes two or more sets of the contact charging members.