JPH11133824A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device constituted so that the memory ghost of an image carrier can be effectively eliminated by an exposure means and the cleaning property of the image carrier is enhanced while suppressing a problem concerning the space of a cleaning device or the increase of a cost. SOLUTION: This image forming device is constituted so that a photoreceptor drum 5 is primarily electrified by a voltage obtained by superimposing an AC voltage and a DC voltage by a contact type electrifying roller 1. Then, a discharge lamp 20 is arranged on the downstream side of the transfer part of a toner image from the drum 5 and on the upstream side of the cleaning device 6 of the drum 5 in the rotating direction of the drum 5 so as to expose and discharge the whole surface of the drum 5 after transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an image forming apparatus such as an electrophotographic type or an electrostatic recording type, and is not particularly limited, but is a color copying machine provided with a plurality of developing units. And a multicolor image forming apparatus that can be embodied in a color printer or the like.

[0002]

2. Description of the Related Art As shown in FIG. 8, a multicolor electrophotographic apparatus has an image carrier rotatably supported in the direction of an arrow, in this example, a photosensitive drum 5, and forms an image on an outer peripheral portion thereof. Means are arranged.

In this embodiment, a primary charger 1 for charging the surface of the photosensitive drum 5, a light image obtained by color-separating a color image or a light image 2 corresponding thereto is used in this embodiment. Through a polygon mirror 17 and the like, and an exposure means such as a laser beam exposure device for forming an electrostatic latent image of an image on the photosensitive drum 5, and developing the electrostatic latent image on the photosensitive drum 5 as a toner image It is composed of a developing device 3 for visualizing.

[0004] The developing device 3 is of a rotary type, and a yellow (Y), cyan (C), magenta (M), and black ( Developing devices 3a, 3b, 3 containing the developer of K)
c and 3d are held. By rotating the housing 3 ′ of the rotary developing device 3, the developing device containing the developer of the color corresponding to the electrostatic latent image formed on the surface of the photosensitive drum 5 is developed by the developing device facing the photosensitive drum 5. The electrostatic latent image on the photosensitive drum 5 is developed with the developer and visualized as a toner image. The developing device 3 converts this into another 3
It is configured such that full-color development for four colors can be performed repeatedly for colors.

[0005] The toner image formed on the photosensitive drum 5 is
The image is transferred onto the transfer material by the transfer device 7. Transfer device 7
Is a drum type provided with a transfer drum 8 which is rotatably supported in the present embodiment.
, A pair of cylinders 8a arranged at both ends,
A transfer material carrying sheet 8c of a transfer material carrying member is stretched in a cylindrical shape in an empty space of the frame body in which the transfer material 8a is connected by the connecting member 8b, and the leading end of the transfer material is gripped near the connecting member 8b. A gripper 8d is provided.

A brief description of full-color image formation by the multicolor electrophotographic apparatus having the above-described configuration will be given below. First, the surface of the photosensitive drum 5 is primarily charged to a predetermined potential by the primary charger 1. In this example, the primary charger 1 is a contact charging type charging roller, and a rubber or sponge whose electric resistance is adjusted to a desired value is provided on a conductive shaft in a roller shape. In this example, in order to improve the uniformity of charging of the photosensitive drum 5, the electric resistance value of the charging roller 1 is set to 10 ⁶ Ω, and
A high voltage in which an AC constant current of 1 mA is superimposed on a DC constant voltage of 0 V is applied.

Next, the exposure means is actuated on the uniformly charged photosensitive drum 5 to first expose the blue color separation light image 2 of the image to form an electrostatic latent image of the yellow component of the image. Then, the electrostatic latent image is developed by the yellow developing device 3a of the rotary developing device 3 and is visualized as a yellow toner image.

On the other hand, a transfer material fed from a paper feed cassette (not shown) is supplied to the transfer device 7 by a registration roller 13 in synchronization with image formation on the photosensitive drum 5, and the transfer material is transferred to the transfer drum 8. The tip is gripped by the gripper 8d and is adsorbed on the transfer material carrying sheet 8c,
As the transfer drum 8 rotates, it is conveyed to the transfer section facing the photosensitive drum 5 and is brought into contact with the photosensitive drum 5. The yellow toner image on the photosensitive drum 5 is transferred onto a transfer material as a final image receiving member by the operation of the transfer charger 4 disposed inside the transfer drum 8.

By repeating the above-described latent image formation, development and transfer for each of the colors magenta, cyan and black, toner images of four colors of yellow, magenta, cyan and black are transferred onto the transfer material in a superimposed manner. A multicolor image is obtained.

The transfer material on which the toner images of the four colors have been transferred is neutralized by operating a separation charger (not shown), then separated from the transfer drum 8 by separation claws 9, and transferred to a fixing device (not shown) by conveyance rollers 10. The toner is melted and mixed by a heat fixing roller and fixed to a transfer material to complete the fixing, and then discharged outside the electrophotographic apparatus. On the other hand, the transfer residual toner remaining on the photosensitive drum 5 is removed by the cleaner 6 and is again used for image formation. The toner remaining on the transfer drum 8 is also removed by the cleaner 1
1 removed.

[0011]

However, although the above-mentioned conventional multicolor electrophotographic apparatus operates extremely well, a phenomenon called ghost occurs in an image obtained on a transfer material depending on the conditions of a transfer process. Was found.

FIG. 10 is a potential diagram schematically showing a ghost on an image. ON / O of image exposure for simplicity
A description will be given of a binary image forming condition of only the FF. Further, the exposed portion on the surface of the photosensitive drum 5 which was primary charged negatively was developed with the negatively charged toner by a reversal developing method. In the reference numerals shown in FIG. 10, reference numerals a to a4 indicate the same location on the surface of the photosensitive drum 5. Similarly, b
To b4 and c to c4 also indicate different and identical portions of the photosensitive drum 5.

In FIG. 10, reference numerals a and c denote unexposed portions (dark portions) of the photosensitive drum 5 after image exposure, and its surface potential (dark portion potential) A is the surface potential (primary charge) of the photosensitive drum 5 after primary charging. Minus). b denotes an exposed portion (bright portion) of the photosensitive drum 5 after image exposure, and its surface potential (bright portion potential)
B moves to the plus side from the dark part due to the exposure, and has a potential difference between the dark part and D.

Applying a developing bias potential Vdc (specific bias value is determined by developing conditions) located between a dark portion potential A and a bright portion potential B to a developing sleeve which carries a developer of a developing device to a photosensitive drum. Accordingly, the condition is set such that the toner does not adhere to the dark portion (unexposed portion), but adheres to the bright portion (exposed portion), and the bright portion, that is, the latent image is developed.

Although the potentials of the dark portions a1 and c1 of the photosensitive drum 5 after development are not different from the potentials of the dark portions before development, the potential of the bright portion b1 after development shifts to the minus side by the amount of the attached minus toner charge. Then, the potential difference between the dark area and the light area after development is D1.

The photosensitive drum 5 proceeds to the transfer process in a state where the toner is not present in the dark area on the surface and the toner is present in the light area. In the transfer step, a positive transfer bias is applied to transfer the negative toner on the photosensitive drum 5. As a result, a positive charge is applied to the photosensitive drum 5, and the bright portion and the dark portion are shifted to the positive side as a whole. However, the difference between the bright portion where the toner is interposed and the dark portion where the positive charge is applied is not. As a result, the potential difference decreases, and the potential difference between the dark portions a2 and c2 after transfer and the dark portion b2 becomes D2. This potential difference D2 is about 15 to 20V.

That is, in the dark areas a2 and c2 on the surface of the photosensitive drum 5 where no toner is present, the bright areas b where toner is present
It is considered that more positive charges are injected into the photosensitive drum 5 as compared with 2. After performing the next cleaning process in this state, when primary charging and image exposure are performed again, the portions a2 to c2 become unexposed portions and become dark portions, and in the dark portions a3 to c3, Although there is almost no potential difference as shown by the solid line, when the portions a2 to c2 become exposed portions and become bright portions, a potential difference occurs between the bright portions a4 to c4 as shown by dotted lines, and the bright portion potential, That is, a positive charge pattern (so-called memory ghost) remains in the electrostatic latent image.

This phenomenon is considered to be because positive charges are accumulated in the photosensitive layer of the photosensitive drum 5, and apparently the light attenuation characteristics in that portion are accelerated. The potential difference in the bright areas a4 to c4 after such primary charging and image exposure is about 5 to 15 V, but when this becomes a sharp step, it becomes such that it can be visually confirmed on the image. ,
The image becomes defective.

In order to solve the above problem, the photosensitive drum 5
Conventionally, in general, the entire surface of the photosensitive drum 5 is exposed after cleaning and before primary charging in consideration of the influence of the toner remaining after transfer in many cases.

However, in order to effectively perform the cleaning, the efficiency is increased by introducing an auxiliary means such as a charging device, etc., so that the space for disposing the cleaning device and the high pressure to the cleaning auxiliary charging device are reduced. There is a problem that a rise in cost is unavoidable, such as adding a system for applying the voltage.

It is an object of the present invention to remove the memory ghost of the image carrier by the exposure means effectively, and to improve the cleaning performance of the image carrier while suppressing the space and cost increase of the cleaning device. An object of the present invention is to provide an image forming apparatus that can be improved.

[0022]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
Primary charging means for charging the image carrier by applying a voltage obtained by superimposing an AC voltage and a DC voltage on the image carrier in contact with the rotating image carrier; Image exposure means for forming an electrostatic latent image, developing means for developing the latent image to visualize it as a toner image, transfer means for transferring the obtained toner image to an image receiving member, and transfer residue remaining on the image carrier In an image forming apparatus in which cleaning means for cleaning toner is installed in this order along the rotation direction of the image carrier, an image carrier is provided between the transfer means and the cleaning means along the rotation direction of the image carrier. An image forming apparatus, comprising: an exposing unit for exposing the entire surface to remove electricity.

According to the present invention, the charge removal of the image carrier by the exposure means can be performed based on the timing of forming the next electrostatic latent image by the image exposure means. Further, the charge removal of the image carrier by the exposure means can be performed based on the transfer conditions by the transfer means. Further, two kinds of static elimination of the image carrier by the exposing means, namely, static elimination based on the formation timing of the next electrostatic latent image by the image exposing means and static elimination based on the transfer conditions by the transfer means can be performed.

According to the invention, the image receiving member is a transfer material carried on a transfer material carrier. Alternatively, the image receiving member is an intermediate transfer body that also serves as a transfer unit, to which the toner image is temporarily transferred before transferring the toner image to the transfer material.
The developing means is provided so as to be switchable between developing devices containing yellow, magenta, cyan, and black developers, respectively.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of the image forming apparatus of the present invention.

In this embodiment, in the conventional image forming apparatus shown in FIG. 8, as shown in FIG. 1, the photosensitive drum 5 is discharged between the transfer section facing the transfer drum 8 and the cleaning device 6. The difference is that the lamp 20 is installed, and after the transfer of the toner image, before the cleaning of the photosensitive drum 5 by the cleaning device 6, the entire surface of the photosensitive drum 5 is exposed and the charge is removed. Other configurations of the image forming apparatus according to the present embodiment are basically the same as those of the conventional image forming apparatus. In FIG. 1, the same reference numerals as those shown in FIG. 8 denote the same members.

The above-described static elimination lamp 20 is provided to extend over the entire length of the photosensitive drum 5 in the longitudinal direction so that the entire surface of the photosensitive drum 5 can be exposed. In this embodiment, the LED lamp array 65 having a peak wavelength of 700 nm as shown in FIG. In the present embodiment, basically, the static elimination lamp 20 is controlled so as to be always lit during image formation, to be turned on when the photosensitive drum 5 rotates, and to be turned off when the rotation is stopped.

The image forming process in this embodiment is the same as the conventional one, except that the photosensitive drum 5 is neutralized by the neutralization lamp 20 after the transfer and before the photosensitive drum 5 is cleaned. FIG. 2 is a diagram schematically showing a transition of the surface potential of the photosensitive drum 5 when the static elimination by the exposure of the static elimination lamp 20 is performed. The use of reference numerals a to a4, b to b4, and c to c4 is the same as that in FIG.

As shown in FIG. 2, the surface potential (dark potential) of the unexposed portions (dark portions) a and c of the photosensitive drum 5 after image exposure.
A is the same as the surface potential (minus) of the photosensitive drum 5 after primary charging, and the surface potential (bright portion potential) B of the exposed portion (bright portion) b of the photosensitive drum 5 after image exposure is changed by exposure. It moves to the plus side from the dark part, and has a potential difference between the dark part and D.

By applying a developing bias potential Vdc located between the dark portion potential A and the bright portion potential B to the developing sleeve of the developing device, toner adheres only to the bright portion (exposed portion), That is, the latent image is developed.

Although the potentials of the dark portions a1 and c1 of the photosensitive drum 5 after development are not different from the potentials of the dark portions before development, the potential of the bright portion b1 after development shifts to the minus side by the amount of the attached minus toner charge. Then, the potential difference between the dark area and the light area after development is D1.

After development, a positive transfer bias is applied to transfer the negative toner on the light portion of the photosensitive drum 5. As a result, a positive charge is given to the photosensitive drum 5, and the bright portion and the dark portion are shifted to the positive side as a whole,
In addition, the potential difference is reduced by the difference in the way positive charges are applied between the light portion and the dark portion where the toner is interposed, and the potential difference D2 between the potentials of the dark portions a2 and c2 and the dark portion b2 after transfer is about 15 to 20 V About.

In this embodiment, as described above, after the transfer of the toner image and before the cleaning of the photosensitive drum 5, the entire surface of the photosensitive drum 5 is exposed by the charge removing lamp 20 to remove the charge. As a result, the portions a2 to c2 of the photosensitive drum 5 become a2 'to c2' portions having substantially no potential difference of about 2 to 3 V.

As a result, the primary charging and image exposure are performed again, and when the portions a2 'to c2' of the photosensitive drum 5 become bright portions by the exposure, the bright portions a4 to c4 are indicated by dotted lines. No potential difference is generated. That is, conventionally,
When primary charging and image exposure were performed again, the potential difference in the bright portion was about 5 to 15 V, and the history after transfer appeared as a memory ghost after the next image exposure. The potential history after transfer does not appear as a memory ghost after the next image exposure.

When the portions a2 'to c2' of the photosensitive drum 5 become unexposed dark portions due to primary charging and image exposure after static elimination, the dark portions a3 to c3 are as shown by solid lines.
There is no potential difference, and the potential is about 20 V lower than the potential of the dark portions a and c at the beginning.

It can be considered from these facts that the exposure of the charge removing lamp 20 removes and sufficiently attenuates the potential after transfer by exposing the carrier in the photosensitive drum 5 to the charge decay. It is considered that by providing sufficient light to the drum, the uneven light attenuation characteristics of the photosensitive drum are eliminated by generating carriers on the entire surface of the photosensitive drum, so to speak, as a ghost.

Conventionally, a method of improving the uniformity of the potential after static elimination has been adopted by performing static elimination of the photosensitive drum by the static elimination lamp upstream of the primary band roller 1 and downstream of the cleaning device 6. . This means that if static elimination by exposure is performed before cleaning, the amount of static elimination exposure on the carrier generation layer in the photosensitive drum varies depending on the toner remaining after transfer on the photosensitive drum, and the potential after static elimination tends to fluctuate. It was due to.

However, according to the primary charging of the photosensitive drum 5 using the voltage obtained by superimposing the AC voltage on the DC voltage using the contact type primary charger 1 (charging roller), the DC voltage is superimposed on the AC voltage. Very high voltage convergence,
Memory ghosts, uneven charging, and the like do not occur due to variations in the amount of light from the charge removing lamp 20 to the carrier generation layer of the photosensitive drum 5. Therefore, in the present embodiment, there is no problem even if the static elimination by the static elimination lamp 20 is performed on the upstream side of the cleaning device 6.

Also in this embodiment, as in the prior art, the contact type primary charger 1 has a conductive shaft on which rubber or sponge whose electric resistance is adjusted to a desired value, for example, 10 ⁵ Ω, is rolled. The charging roller is provided in the shape of a circle, and a DC voltage of 600 V
A high voltage in which an AC constant current of 1 mA was superimposed on the constant voltage was applied.

With respect to the cleaning property of the transfer residual toner on the photosensitive drum 5 in this embodiment, the potential of the photosensitive drum 5 after the transfer is negative, and the transfer residual toner receives the positive transfer electric field and moves to the positive side. Because of the shift, the toner hardly separates from the photosensitive drum, and the cleaning performance is reduced. However, in this embodiment, since the exposure by the exposure lamp 20 is performed after the transfer to remove the residual potential on the surface of the photosensitive drum 5, the cleaning performance is improved.

As described above, the present embodiment is an image forming apparatus in which the photosensitive drum 5 is primarily charged by applying a voltage in which an AC voltage and a DC voltage are superimposed by the contact type primary charging roller 1. Since a static elimination lamp 20 is provided upstream of the cleaning device 6 for cleaning the surface of the photosensitive drum 5 after the transfer and the entire surface of the photosensitive drum 5 after the transfer is subjected to the static elimination, an image defect due to a memory ghost can be prevented. Thus, the cleaning performance by the cleaning device 6 can be improved, and problems such as a space for improving the cleaning performance and an increase in cost can be suppressed.

Incidentally, according to the present embodiment, the memory ghost is not generated at all, and the cleaning performance is remarkably improved as well. Conventionally, the cleaning failure due to the toner slipping through the cleaning device 6 is about 1%. In contrast to the case where the image was formed on 10,000 sheets,
It did not occur even when forming 15,000 images.

In the above description, the LED lamp array 65 shown in FIG. 6 is used as the static elimination lamp 20, but a fuse lamp array 66 as shown in FIG. 7 can be used.

Embodiment 2 FIG. 3 is a schematic structural view showing another embodiment of the image forming apparatus of the present invention.

The image forming apparatus according to the present embodiment employs an intermediate transfer member 22.
The intermediate transfer member 22 and the photosensitive drum 5 are in contact with each other to form a primary transfer portion, and on a substantially opposite side of the primary transfer portion,
The intermediate transfer member 22 and the transfer belt 24 are in contact with each other to form a secondary transfer portion. The transfer belt 22 is installed on the intermediate transfer body 22 so as to be able to freely contact and separate.

In the first embodiment shown in FIGS. 1 and 2, a full-color image is obtained on the transfer material by directly transferring and superimposing the toner image of each color from the photosensitive drum 5 onto the transfer material. In this embodiment, before each color toner image from the photosensitive drum 5 is transferred to a final image receiving member, the toner image is temporarily superimposed and transferred onto an intermediate transfer body 22 which is an intermediate image receiving member, and thereafter, the intermediate transfer is performed. A secondary transfer belt 24 is brought into contact with the body 22, and the toner images of each color superimposed and transferred on the intermediate transfer body 22 in the secondary transfer unit are collectively transferred to a transfer material conveyed by the transfer belt 24 It is.

In the present embodiment, one of the photosensitive drums 5
The processes of the next charging, image exposure, development, charge elimination, and cleaning are the same as those in the first embodiment, and will not be described. In FIG. 3, reference numeral 26 denotes a fixing device.

Also in the present embodiment, similarly, a static elimination lamp 20 is provided between the primary transfer section and the cleaning device 6, and after the primary transfer of the toner image and before the cleaning of the photosensitive drum 5 by the cleaning device 6. Next, the entire surface of the photosensitive drum 5 is exposed by the charge removing lamp 20 to remove the charge. The primary charging of the photosensitive drum 5 is performed by applying a voltage obtained by superimposing an AC voltage and a DC voltage by the contact-type charging roller 1.

Therefore, also in this embodiment, it is possible to prevent the occurrence of an image defect due to a memory ghost, to improve the cleaning performance by the cleaning device 6, and to suppress problems such as an increase in space and cost for improving the cleaning performance. I was able to.

Embodiment 3 This embodiment is different from the image forming apparatus of Embodiment 2 in that the ON / OFF of the neutralizing lamp 20 is performed based on the timing of image exposure.
A feature is that F is controlled.

Normally, ON / OFF of the static elimination lamp 20 is as follows.
In many cases, the control is performed based on the timing of rotation of the photosensitive drum 5, but this method is mainly used in a system using a non-contact corona charger as the primary charger 1. This is because the surface potential after charging greatly differs depending on the surface potential state of the photosensitive drum 5 before charging, and therefore, it is necessary to always operate the static elimination plan 20 during the operation of the primary charger. .

However, the photosensitive layer of the photosensitive drum 5 is generally apt to be fatigued by continuously receiving light.
When viewed in the span of the day, it causes instability of the charged potential and changes in sensitivity. Therefore, in order to stably maintain the photosensitive characteristics of the photosensitive drum 5, it is effective to shorten the irradiation time of the light applied to the photosensitive drum 5.

In the image forming apparatus of the present invention, the photosensitive drum 5
On the other hand, by using contact charging in which AC and DC voltages are superimposed by the charging roller 1, the potential convergence of the surface of the photosensitive drum 5 to the DC voltage due to the superimposition of the AC voltage is enhanced. It is possible to remove static electricity only at the position. Thereby, the photosensitive drum 5
The irradiation time of the discharge lamp 20 to the lamp can be shortened.

FIG. 4 is an explanatory diagram showing the image exposure and the operation timing of the charge removing lamp 20 in this embodiment. The image forming apparatus in the present embodiment has a process speed of 11
7 mm / sec, the outer diameter of the photosensitive drum 5 is 62 mm, and the angle between the static elimination exposure position and the image exposure position as viewed from the center of the photosensitive drum 5 is 120 ° (65 m in the circumferential direction of the photosensitive drum).
m).

Accordingly, the surface of the photosensitive drum 5 reaches the image exposure position in 0.55 seconds from the position where the charge is removed by the charge removing lamp 20. Therefore, assuming that the rise and fall times of the neutralizing lamp 20 are 0.15 seconds each, the lamp 20 is turned on 0.70 seconds before the start of image exposure, and the lamp 20 is turned off 0.40 seconds before the end of image exposure. doing. By such lighting control of the neutralization lamp 20, depending on the image forming conditions, in the case of one image output, about 1/1 of the image forming process.
It has become possible to set the lighting time of the static elimination lamp to be only the time of No. 4.

In this embodiment, as described above, the static elimination lamp 2
Since the lighting control of 0 was performed, the photosensitive characteristics such as the surface potential fluctuation of the photosensitive drum 5 became unstable when about 500 sheets were continuously used in the second embodiment.
It can be used stably even with continuous use of sheets.

Embodiment 4 In the present embodiment, in addition to the lighting control of the discharging lamp 20 based on the image exposure condition in the embodiment 3, the lighting control of the discharging lamp 20 based on the transfer condition was also performed.

In the transfer step in full-color image formation, a toner image is transferred from the photosensitive drum 5 to the intermediate transfer member 22 in the order of yellow, magenta, cyan, and black to form a full-color image. A transfer bias is applied for transferring the toner image. However, if the transfer is repeated normally, the impedance of the transfer portion of the intermediate transfer body 22 increases for each transfer, so that the transfer bias is made different for each color. I have. On the other hand, the memory ghost becomes more conspicuous as the transfer bias is higher, and cannot be visually discriminated below a certain bias. Therefore, by controlling ON / OFF of the charge removing lamp 20 based on the transfer bias, light fatigue of the photosensitive drum 5 can be reduced.

FIG. 5 is a graph showing the transfer bias value on the horizontal axis and the color difference between the memory ghost part and the non-memory ghost part on the vertical axis. In human visual characteristics, the color difference, which is said to be able to determine the difference between adjacent colors, is 1.2 or more. Considering this, the transfer bias value is 200V
As described above, the memory ghost can be determined, and the static elimination by the static elimination lamp is required.

In this embodiment, the transfer bias values for yellow are 150 V, magenta is 250 V, and cyan is 300 V.
V and black are 300V. Therefore, at the time of yellow image formation, even if static elimination is not performed, the occurrence of memory ghost has no visual problem, and the static elimination lamp 20 is turned off in a portion corresponding to yellow image formation.

According to the present embodiment, the light irradiation time on the photosensitive drum 5 can be reduced to about ／ of that in the third embodiment, and the instability of the photosensitive drum 5 due to light fatigue can be further improved. It has become possible.

[0063]

As described above, according to the present invention,
The contact-type primary charger applies AC voltage and D to the image carrier.
In an image forming apparatus that performs primary charging with a voltage obtained by superimposing a C voltage, the image forming apparatus is arranged such that, with respect to the rotation direction of the image carrier, downstream of a transfer portion of a toner image from the image carrier and upstream of a cleaning device for the image carrier. By providing a static elimination lamp and exposing the entire surface of the image carrier after transfer to eliminate electricity, it is possible to prevent the occurrence of image defects due to memory ghosts, and to improve the cleaning performance of the image carrier by the cleaning device in terms of space and cost. It is possible to improve while suppressing problems such as up.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a transition of a surface potential of a photosensitive drum of the image forming apparatus of FIG.

FIG. 3 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention.

FIG. 4 is an explanatory diagram showing the timing of image exposure and ON / OFF of a static elimination lamp in still another embodiment of the image forming apparatus of the present invention.

FIG. 5 is a diagram illustrating a relationship between a transfer bias value and a color difference of a memory ghost portion, which are the basis of lighting control by a transfer condition of a static elimination lamp performed in still another embodiment of the image forming apparatus of the present invention.

FIG. 6 is a diagram showing an LED lamp array that can be used as a static elimination lamp in the present invention.

FIG. 7 is a diagram showing a fuse lamp array that can be used as a static elimination lamp in the present invention.

FIG. 8 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus.

FIG. 9 is a perspective view illustrating a transfer drum of a transfer device used in the image forming apparatus of FIG. 8;

FIG. 10 is an explanatory diagram showing transition of the surface potential of the photosensitive drum of the image forming apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary charger (charge roller) 2 Image exposure 5 Photosensitive drum 6 Cleaning device 8 Transfer drum 20 Static elimination lamp 22 Intermediate transfer body 24 Transfer belt

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/14 G03G 21/00 372

Claims (7)

[Claims] And a primary charging means for charging the image carrier by applying a voltage obtained by superimposing an AC voltage and a DC voltage on the image carrier in contact with the rotating image carrier, and a charged image carrier. Image exposure means for forming an electrostatic latent image of an image by exposure to light, developing means for developing the latent image to visualize it as a toner image, transfer means for transferring the obtained toner image to an image receiving member, and on an image carrier In an image forming apparatus in which a cleaning unit for cleaning the remaining transfer residual toner is installed in this order along the rotation direction of the image carrier, the cleaning unit is disposed between the transfer unit and the cleaning unit along the rotation direction of the image carrier. An image forming apparatus, further comprising: an exposing means for exposing the entire surface of the image carrier to remove electricity. 2. The method according to claim 1, further comprising:
2. The image forming apparatus according to claim 1, wherein the image forming is performed based on the timing of forming the next electrostatic latent image by the image exposure unit. 3. The method according to claim 2, further comprising:
The image forming apparatus according to claim 1, wherein the transfer is performed based on a transfer condition by a transfer unit. 4. The method according to claim 1, further comprising:
2. The image forming apparatus according to claim 1, wherein charge elimination based on the timing of forming the next electrostatic latent image by the image exposure means and charge elimination based on transfer conditions by the transfer means are performed. 5. The image forming apparatus according to claim 1, wherein said image receiving member is a transfer material carried on a transfer material carrier. 6. The image receiving member according to claim 1, wherein the image receiving member is an intermediate transfer body that also serves as a transfer unit, to which a toner image is temporarily transferred before transferring the toner image to a transfer material. The image forming apparatus as described in the above. 7. The image forming apparatus according to claim 1, wherein said developing means is switchably provided with a developing device containing a developer of yellow, magenta, cyan, and black, respectively.