JP2010271602A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of improving stability in image density and image quality, and capable of achieving high productivity. <P>SOLUTION: The image forming apparatus has: a transfer charging device 5 transferring a toner image on a photoreceptor 2 to an image receiving member; and an optical static charge eliminator means 13 eliminating the static charge on the photoreceptor 2 with light irradiation. The image forming apparatus includes a control means that controls the optical static charge eliminator means 13 so that quantity of light, which is radiated when an area of the photoreceptor 2 charged by the transfer charging device 5 passes, is smaller than quantity of light, radiated when an area of the photoreceptor 2 not charged by the transfer charging device 5 passes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser printer, a facsimile machine, and a printing apparatus, and more particularly to an image forming apparatus having an optical charge eliminating device.

  Conventionally, in this type of image forming apparatus, a photosensitive member is used, and while rotating the photosensitive member, the polarity and potential are uniformly charged and then exposed to form an electrostatic image. Then, the electrostatic image is developed with toner of each color, and the toner images of different colors formed in the respective image forming units are superimposed on the intermediate transfer belt for primary transfer.

  Thereafter, the toner image is secondarily transferred to a sheet of transfer material or the like, and the toner and other deposits remaining on the surface of the photoreceptor and the intermediate transfer belt are removed by a cleaning unit. Thereafter, the toner image on the sheet is fixed to obtain a desired image.

  In such image formation, the distribution of the charged potential on the surface of the photoconductor greatly affects the image quality to be formed. That is, when the charging potential is not uniform on the photoconductor, a ground blurring occurs in a part of the formed image and the image density is lowered. Therefore, in order to stabilize the charging potential uniformly, a method of irradiating light on the surface of the photoreceptor before the charging means is used (see Patent Document 1).

JP 2001-142365 A

  However, in Patent Document 1, by repeatedly charging and exposing the photoconductor in a short time and over a long period of time, the photoconductor is not sufficiently neutralized, and the photoconductor deteriorates and the desired potential is increased. There is a risk that it will not be obtained.

  In addition, if the amount of light for light neutralization is strong, deterioration of the photoreceptor is promoted, and if the light neutralization device is used for a long time in a state where the amount of light is strong, the life of the light source of the light neutralization device will be short-lived. Static elimination cannot be obtained.

  Therefore, there is a means for stopping the charging until the charge on the photosensitive member is attenuated to some extent without performing the static elimination, but this does not provide sufficient neutralization. If the desired photoreceptor potential cannot be obtained due to these factors, there are circumstances in which image defects such as ground force blur and image density decrease occur, and high productivity cannot be realized.

  The technical problem of the present invention has been made in view of the circumstances as described above, and an object thereof is an image forming apparatus capable of improving image density and image stability and realizing high productivity. Is to provide.

  In order to achieve the above object, a typical configuration according to the present invention includes a photoconductor on which a toner image is formed, a transfer charger for transferring the toner image on the photoconductor to an image receiving member, In an image forming apparatus having a light neutralizing means for neutralizing by irradiation, the amount of light irradiated when passing through the area of the photosensitive member charged by the transfer charger is not charged by the transfer charger. And a control means for controlling the light neutralizing means so as to be weaker than the amount of light irradiated when the region of the photoconductor passes.

  According to the present invention, it is possible to suppress the occurrence of image defects such as ground blur and image density decrease due to potential deterioration of the photoconductor and potential unevenness that occurs after image formation, thereby enabling high productivity.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the photosensitive drum electric potential transition when a ghost electric potential is measured. It is an image when the ghost potential is measured, (a) is an explanatory diagram of an image with a white image tip, and (b) is an explanatory diagram of an image with a black image tip. It is a characteristic view of the ghost potential by the presence or absence of a transfer bias and the input voltage of the photostatic device. FIG. 6 is a diagram illustrating a photosensitive drum potential transition during post-rotation after image formation. (A) is a timing chart at the time of conventional image formation. (B) is a timing chart at the time of image formation of the present embodiment. (C) is a timing chart at the time of image formation of the present embodiment. (A) is the timing chart at the time of the conventional continuous paper passing. (B) is a timing chart at the time of continuous paper feeding of this embodiment. 1 is a block diagram of a main part of an image forming apparatus. It is a characteristic view of the ghost potential by the rotation speed difference of a photosensitive drum, and the input voltage of a light static elimination apparatus. 2A and 2B show a method for removing static electricity from a photosensitive drum, in which FIG. 1A is a diagram showing a configuration in which the photosensitive drum is neutralized only by a light static eliminating device, and FIG. It is a figure which shows a structure. 3 is a flowchart for explaining the operation of the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention.

[Entire configuration of image forming apparatus]
In FIG. 1, the image forming apparatus includes a printer unit and a reader unit. The printer unit includes an image forming unit that forms a yellow image, an image forming unit that forms a magenta image, an image forming unit that forms a cyan image, and an image forming unit that forms a black image. Yes. These four image forming units are arranged in a line.

  In each image forming unit, a photosensitive drum 2 (2Y, 2M, 2C, 2Bk), which is a drum-type electrophotographic photosensitive member on which a toner image is formed, is disposed. Around each photosensitive drum 2, a charging roller 3 (3Y, 3M, 3C, 3Bk) as a charging device for charging the surface of the photosensitive drum 2 is disposed. Further, an exposure apparatus that is an image exposure device that performs exposure to form an electrostatic image by irradiating the photosensitive drum 2 with light according to an image signal downstream of the charging roller 3 in the rotation direction of the photosensitive drum 2. 7 (7Y, 7M, 7C, 7Bk) are arranged. Further, on the downstream side of the exposure device 7, a developing device 4 (4Y, 4M, 4C, 4Bk) for developing the electrostatic image with toner is disposed. Further, around the photosensitive drum 2, a transfer roller 5 (5Y, 5M) as a transfer charger for applying a transfer bias for transferring the toner image developed by the developing device 4 to an intermediate transfer member 8 as an image receiving member. , 5C, 5Bk). Further, a photoreceptor cleaning device 6 (6Y, 6M, 6C, 6Bk) for cleaning toner remaining on the photosensitive drum 2 after the toner image is transferred to the intermediate transfer body 8 is disposed.

  The photosensitive drum 2 of the present embodiment is driven to rotate counterclockwise in FIG. 1 with an outer diameter of 40 mm and a process speed (circumferential speed) of 260 mm / sec centered on the central support shaft. When the image is formed, the outer peripheral surface of the rotating photosensitive drum 2 is uniformly charged by the charging roller 3.

  When an image signal is input from the reader unit or an external device to the image signal processing unit, the image signal processing unit creates a digital image signal obtained by color-converting the image signal into yellow, cyan, magenta, and black. Based on this signal, the exposure device 7 selectively exposes the photosensitive drum 2 to form an electrostatic image, and the developing device 4 develops the toner.

  The developed toner image is transferred from the photosensitive drum 2 to the intermediate transfer member 8. This intermediate transfer member 8 is an endless belt-like member supported by support rollers 13 a, 13 b, 14 and the like, and rotates in synchronization with the photosensitive drum 2. The yellow, magenta, cyan, and black toner images formed on the respective photosensitive drums 2 by the charging process by bias application to the transfer roller 5 are sequentially primary-transferred to the intermediate transfer body 8 in order to form a color image.

  In addition, a secondary transfer counter roller 9 and a secondary transfer roller 10 are disposed on the downstream side of the primary transfer portion in the rotational direction of the intermediate transfer member 8 so as to sandwich the intermediate transfer member 8, thereby forming a secondary transfer portion. Has been. In the secondary transfer portion, the toner image on the intermediate transfer member 8 is transferred to the conveyed sheet. The sheet is conveyed to the fixing device 11, heated and pressed at a fixing nip portion between the fixing roller 11 a and the pressure roller 11 b to fix the toner image on the sheet, and then discharged onto a discharge tray.

  In addition, the electric potential of the outer peripheral surface of the photosensitive drum 2 after the primary transfer process is neutralized by an optical neutralization device 13 (13Y, 13M, 13C, 13Bk) that is an optical neutralization unit. The light neutralizing device 13 is downstream of the primary transfer portion in the rotational direction of the photosensitive drum 2 (downstream in the movement direction of the photosensitive drum circumferential surface) and upstream of the cleaning device 6 (upstream in the movement direction of the photosensitive drum circumferential surface). ). By irradiating the photosensitive drum 2 with light by the light neutralizing device 13, charges remaining on the peripheral surface of the photosensitive drum 2 are neutralized.

  As described above, the cleaning device 6 cleans residues such as the primary transfer residual toner of the photosensitive drum 2. The cleaning device 6 according to this embodiment includes a cleaning blade 6 a (see FIG. 10) that is in contact with the photosensitive drum 2, and scrapes residual toner and the like from the peripheral surface of the rotating photosensitive drum 2.

  Further, a belt cleaning device 12 is provided for removing residues such as secondary transfer residual toner remaining on the intermediate transfer member 8.

  The sheet is selectively fed by a feeding roller 42 from a cassette 41 that is detachably disposed below the intermediate transfer body 8, and then a resist disposed downstream from the feeding roller 42 in the sheet conveying direction. It is conveyed to the roller 43.

  The sheet conveyed to the registration roller 43 is conveyed to the secondary transfer unit in accordance with the timing at which the color image on the intermediate transfer body 8 is conveyed to the secondary transfer unit, and is subjected to transfer processing and fixing processing.

  The light neutralizing device 13 includes an LED chip array type and a light guide type. The LED chip array is conventionally used, and a plurality of LED chips are arranged in the longitudinal direction, and light emitted from the LEDs is directly irradiated onto the photosensitive drum.

  The light guide type has LED lamps as light sources mounted on the front side and the back side of the main body of the image forming apparatus, and a light incident portion is formed and guided to both the LED lamps. There is a light guide type that irradiates the surface of the photosensitive drum in the longitudinal direction.

  In any type of light neutralizing device 13, the amount of light emitted can be adjusted in accordance with the input power. In this embodiment, an LED chip array type is used.

  Since the photosensitive drum 2 uses a high light (electron beam) curable resin having good abrasion resistance and scratch resistance, the deterioration proceeds by repeated charging and exposure over a long period of time. Furthermore, since a desired photoreceptor potential cannot be obtained due to charging or exposure, image defects such as ground force blur and image density reduction are likely to occur.

[Relationship between the potential of the photosensitive drum and the amount of light static elimination and the level of image failure]
Next, the relationship between the potential of the photosensitive drum 2 and the light removal amount and the image defect level will be described. FIG. 2 shows the transition of the photosensitive drum potential when the image as shown in FIG. 3A and the image as shown in FIG. 3B are continuously passed in A3 size in the image forming apparatus of this embodiment. It is.

  In the image shown in FIG. 3A, the photosensitive drum 2 is charged to a charging potential VD = −600 V, and one turn of the photosensitive drum is white from the leading edge of the image, and the remaining one turn or more of the photosensitive drum is a halftone. . Further, in the image shown in FIG. 3B, the entire circumference of the photosensitive drum is solid from the leading edge of the image, and the remaining one or more rounds of the photosensitive drum is halftone.

  For the photosensitive drum potential, a value obtained by continuously measuring the surface potential of the photosensitive drum 2 with a measuring probe connected to an electrometer by arranging a photosensitive drum potential measuring jig in the developing device portion of the image forming unit. This is a graph read by a recorder. In addition, the trek Japan company make and Model-344 were used for the electrometer, and the measurement probe used the Trek Japan company make and Model-6000B-8.

  As a method for evaluating the level of a ghost that is an image defect, a ghost potential was measured so as not to be affected by other devices such as a developing device, and the evaluation was performed based on the magnitude of the value. The ghost potential is a potential in a state in which the remaining electricity due to charging or exposure cannot be completely eliminated by the light neutralization device 13 and the remaining potential appears on the photosensitive drum surface potential of the halftone portion for one turn of the photosensitive drum 2. . The image defect level of ghost was judged by the magnitude of this potential.

  The ghost potential is obtained by adding the difference A between the ghost potential generated on the first sheet and the potential of the halftone part to the difference B between the potential of the second halftone part and the ghost potential generated on the area. To do.

  FIG. 4 is a diagram showing the relationship between the light amount (input voltage) of the photostatic discharge device 13 and the ghost potential by measuring the photosensitive drum potential shown in FIG. 2 while varying the voltage input to the photostatic discharge device 13. is there. In addition, a relationship diagram between the light amount (input voltage) of the light neutralizer 13 and the ghost potential depending on the presence or absence of the transfer bias is also shown. The transfer bias is set so that the transfer current is 40 μA.

  When the voltage input to the light neutralizing device 13 is reduced, the amount of light applied to the photosensitive drum 2 is reduced. For this reason, the charge on the photosensitive drum 2 due to charging or exposure cannot be completely erased, and the remaining charge appears as a potential because the charge and exposure are performed again with the charge remaining. In particular, when the entire circumference of the photosensitive drum 2 from the leading edge of the image is white or solid and the remaining image is a halftone image, the residual charge appears as a ghost potential.

  Regarding the presence or absence of the transfer bias, the drum area to which the transfer bias is applied (the area subjected to the charging process) can obtain a neutralizing effect, and therefore, compared to the drum area to which the transfer bias is not applied (the area not subjected to the charging process), A small amount of light is required to eliminate the ghost potential.

  However, when the voltage input to the light neutralizing device 13 is reduced and image formation is performed, as shown in FIG. 2 remains charged. In FIG. 5, the transition of the photosensitive drum potential was measured with a measuring probe connected to an electrometer with a photosensitive drum potential measuring jig disposed in the developing portion of the image forming unit. The photosensitive drum potential is a potential at the time of post-rotation with the charging potential set to −800 V and the bias application to the charging roller 3 being turned off after the image formation is completed.

  This residual charge causes uneven charging potential at the time of the next image formation, resulting in image defects such as background fog and density unevenness. Further, waiting until the photosensitive drum potential is attenuated to such an extent that no image defect occurs will affect high productivity and rise time of image formation. These are prominent at the time of post-rotation after the end of image formation where there is a presence or absence of transfer bias and at the time of paper interval.

  For example, if a transfer bias is not applied during post-rotation, an image defect such as a ghost occurs at the next image formation with the normal light amount. Similarly, when image-formed toner such as a toner band is supplied to the cleaning device 6 at the time of post-rotation, image defects such as ghosts occur at the next image formation.

  Further, if the transfer bias is continuously applied during the sheet interval, the photosensitive drum is damaged. Therefore, even when the transfer bias is not applied during the sheet interval, an image defect such as a ghost occurs during the next image formation.

  Therefore, in this embodiment, the area of the photosensitive drum 2 where the transfer bias is not applied during pre-processing for starting toner image formation on the photosensitive drum 2 or during post-processing accompanying completion of toner image formation on the photosensitive drum 2 is the light neutralization device. The amount of light to be irradiated when passing through 13 is made stronger than in normal image formation.

  Similarly, the amount of neutralizing light to be emitted is also normal when the region between the plurality of images on the photosensitive drum 2 when the plurality of images to which the transfer bias is not applied is continuously formed passes through the light neutralizing device 13. Make it stronger than when creating an image.

  Similarly, as a region of the photosensitive drum to which no transfer bias is applied, a predetermined toner image formed on the photosensitive drum 2 is transferred to the cleaning blade without being transferred to the intermediate transfer body 8, and a predetermined toner image is applied to the photosensitive drum. Even when the region where the toner image is formed passes through the light neutralizing device 13, the amount of neutralizing light to be irradiated is made stronger than during normal image formation.

  The amount of charge to be discharged when the drum area that has not been subjected to the charging process without applying the transfer bias passes through the light discharging device 13 is made stronger than that during normal image formation. At this time, at least one of the pre-processing area, the post-processing area, the area between the plurality of images, and the area where the cleaning image is formed is the area that has not been subjected to the charging process. You may make it make static elimination light intensity | strength stronger than the time of normal image formation at the time of passing.

  6 and 7 are timing charts of drum driving and charging bias, pre-exposure and transfer bias during image formation. The control relating to the image formation is performed based on a timer.

  In FIG. 8, a timer 15 is connected to a controller (control means) 14 and performs overall control of an image forming sequence based on a control program stored in the controller 14 and the timer 15. The operation unit 16 is a key for setting a copy mode (single-sided, double-sided, multiple, etc.) and a copy mode (magnification, sheet size, etc.), and its command signal is input to the controller 14. This command signal determines the rotational speed of the photosensitive drum 2.

  The motor control unit 17 controls the photosensitive drum driving motor 20, and the photosensitive drum driving motor 20 drives the photosensitive drum 2 at the rotation speed determined by the controller 14. The DC voltage control unit 18 controls the input voltage to the light source of the optical static elimination device 13 and changes the input voltage to the light source of the optical static elimination device 13 in accordance with a signal from the controller 14.

  The high voltage unit 19 applies a predetermined voltage to devices that require various high voltages, such as the charging roller 3, the transfer roller 5, and the developing device 4. The high voltage unit 19 is controlled based on signals from the timer 15 and the controller 14. In this embodiment, the timer 15 is described. However, the method is not limited as long as the position of the photosensitive drum 2 is known.

  As shown in FIG. 6A, in the prior art, the drum drive has been turned on for a long time, and the charging bias is turned on in a shorter time. The static elimination light of the optical static elimination device was lit for the same or extra time as the charging bias was ON, and the amount of light at that time was constant.

  However, in this case, the photosensitive drum 2 is excessively irradiated with light although the effect of removing the transfer bias is obtained. For this reason, deterioration of the photosensitive drum 2 due to light progresses, and a desired photosensitive drum potential cannot be obtained by charging or exposure, and image defects such as ground force blur and image density reduction tend to occur.

  Further, if the light amount of the light neutralizing device 13 is weakened, although the photosensitive drum 2 is irradiated with light, the charge remains at the time of the subsequent rotation, and the charged potential unevenness is generated at the next image formation, Image defects such as background fog and density unevenness occur.

(Transfer bias and charge removal)
Therefore, in the present embodiment, the controller 14 as the control means controls the input voltage for adjusting the light amount by the light neutralizing device 13 as shown in FIG.

  That is, with the drum drive turned on, the light neutralizing device 13 is turned on with a weak light amount simultaneously with the charging bias or first. During the image formation, the light quantity of the light static elimination device 13 is set to be weak, and when the photosensitive drum surface with the transfer bias turned off passes through the position of the light static elimination device 13 during the post-rotation after completion of the image formation. Strengthen. Then, the surface of the photosensitive drum whose charging bias has been turned off reaches the light static elimination device 13, and after at least one round of the photosensitive drum, the light static elimination device 13 is turned off.

  By adjusting the light neutralizing device 13 at such a timing, it is possible to suppress the occurrence of image defects such as background fogging and a decrease in image density due to light deterioration of the photosensitive drum 2 and residual charge at the time of post-rotation. .

  FIG. 6C shows the case where the control for applying the transfer bias is performed at the time of post-rotation after the image formation is completed. In this case, since the transfer bias is applied for a moment, In addition, it is difficult to adjust the light amount of the light neutralizing device 13. Further, in this case, considering that the influence of light deterioration on the photosensitive drum 2 is small even when the light quantity of the light static elimination device 13 is increased, the light quantity of the light static elimination device 13 is increased at any time during post-rotation. Also good.

  In addition, by irradiating the photosensitive drum 2 with a strong light amount either before or after image formation, the residual charge at the time of post-rotation is erased before the next image formation, resulting in a reduction in geoblits and image density. It is possible to suppress the occurrence of image defects such as.

  FIG. 7A shows a conventional timing chart in continuous operation. In order to improve productivity, there are cases where the gap between the sheets is reduced as much as possible. Conventionally, the amount of static electricity removed by the photostatic device is constant regardless of the presence or absence of a transfer bias. For this reason, density unevenness due to the presence or absence of a transfer bias may occur on the images obtained on the second and subsequent sheets.

  Therefore, as shown in FIG. 7B, the light quantity of the light static elimination device 13 is weakened when there is a transfer bias, and the light quantity of the light static elimination device 13 is increased when there is no transfer bias. By adjusting the light neutralizing device 13 at such a timing, it is possible to suppress the occurrence of image defects such as background fogging and a decrease in image density due to light deterioration of the photosensitive drum 2 and residual charge at the time of post-rotation. .

(Process speed and static electricity removal)
An image forming apparatus having a configuration in which the speed of the photosensitive drum 2 at the time of image formation is variable by inputting information on the desired product to the image forming apparatus by the user depending on the thickness of the sheet, the glossiness of the product, the image quality, and the like. is there.

  In this case, the amount of light applied to the surface of the photosensitive drum during the preprocessing for starting the toner image formation is adjusted according to the speed. The usefulness of reducing the amount of light applied to the photosensitive drum surface during image formation when the amount of light at that time becomes slower than the normal speed will be described.

  FIG. 9 is a characteristic diagram of the light quantity (input voltage) of the photostatic discharge device 13 and the ghost potential measured by varying the voltage input to the photostatic discharge device 13 with respect to the photosensitive drum potential. In addition, a characteristic diagram of the light amount (input voltage) of the light static elimination device 13 and the ghost potential due to the difference in speed during image formation is also shown. In the present embodiment, the normal speed is set to 260 mm / s, and 130 mm / s, which is reduced to 1/2 speed.

  In the case of 130 mm / s, since the speed is lower than usual, the ghost potential is attenuated to the position of the developing device of the image forming unit where the photosensitive drum potential measurement jig is arranged, and the light is faster than the normal speed. Even if the amount of light of the static eliminator 13 is small, the occurrence of ghost is suppressed.

  Further, if the amount of light from the light neutralizing device 13 is not reduced as much as the normal speed, the light deterioration on the photosensitive drum 2 is promoted, and image defects such as ground burr and image density decrease occur. There is a risk of doing.

  For this reason, when the light quantity of the light neutralizing device 13 is decreased by the amount that the rotational speed of the photosensitive drum 2 is reduced, a ghost image is not generated, but the residual charge during the subsequent rotation cannot be completely erased, and the ground force blur and the image density decrease. May cause image defects.

  According to this embodiment, the influence of the light neutralizing device 13 due to the decrease in the speed of the photosensitive drum 2 is suppressed by increasing the amount of light by the light neutralizing device 13 during the post-rotation, and the photodegradation of the photosensitive drum 2 and the completion of toner image formation are suppressed. It is possible to suppress the occurrence of image defects such as ground blur and image density reduction due to residual charges at the time of subsequent post-rotation.

(Static neutralization by the light static eliminating device 13 and the exposure device 7)
In this embodiment, as shown in FIG. 10A, the amount of light applied to the photosensitive drum 2 is adjusted only by the light neutralizing device 13 as the light neutralizing means. However, as shown in FIG. 10B, the amount of charge removal may be adjusted by using an exposure device (image exposure device) 7 and a light charge removal device (light charge removal device) 13 together as the light charge removal means.

  In this case, the control means performs the charge removal process by irradiating light only to the area of the photosensitive drum 2 that has received the transfer bias by only the light neutralization device 13, and applies to the area of the photosensitive drum 2 that has not received the transfer bias. Irradiates light with the light static elimination device 13 and the exposure device 7 to execute the static elimination processing.

  The light neutralizing device 13 is disposed on the upstream side of the cleaning device 6 with respect to the rotation direction of the photosensitive drum 2, but may be disposed on the downstream side of the cleaning device 6.

  Further, the light amount of at least one of the exposure device 7 and the light neutralizing device 13 is lowered or increased. Thus, the amount of light applied to the surface of the photosensitive drum when there is a transfer bias may be adjusted to be larger than the amount of light applied to the surface of the photosensitive drum when there is no transfer bias.

  With the above configuration, when forming an image at a lower speed than usual, it is possible to suppress the amount of light irradiated per unit time on the surface of the photosensitive drum, to suppress deterioration of light durability, and to reduce ground strength and image density. Reduce the occurrence of image defects.

(Image forming operation)
Next, the operation of the image forming apparatus of this embodiment will be described with reference to the flowchart of FIG. In addition, on the outer periphery of the photosensitive drum 2, when the position of the charging roller 3 is set to 0 °, the photostatic device 13 is disposed at the position of the transfer roller 5 and the position of 225 ° counterclockwise.

  First, information on a desired product is input, and the rotation speed of the photosensitive drum 2 is changed based on the information. At that time, the rotational speed of the photosensitive drum 2 on which an image is formed is determined (step S1).

  When the normal speed is 260 mm / s, the light amount (voltage) of the light neutralizing device 13 is selected to be 13 V (weak) when there is a transfer bias, and to 15 V (strong) when there is no transfer bias (step) S2). When the speed is 130 mm / s, which is slower than the normal speed, the light amount (voltage) of the light static elimination device 13 is 0 V (weak) because the ghost potential is small when there is a transfer bias, and the post-rotation when there is no transfer bias. In order to erase the remaining charges, 15 V (strong) is selected (step S3).

  Next, the photosensitive drum drive and the timer 15 are simultaneously turned on (step S4). Thereby, the timing described below is performed based on the timer 15. When the photosensitive drum drive and the timer 15 are turned on and the timer 15 reaches a certain time, the photostatic device 13 is turned on simultaneously with the charging bias (step S5). However, the photostatic device 13 is turned on simultaneously with the charging bias, but the photostatic device 13 may be turned on first.

  During image formation, the voltage input to the light neutralizing device 13 is set to 13V (weak), and the transfer bias is turned off (step S6). When the turned-off photosensitive drum surface passes through the position of the light neutralization device 13, the voltage input to the light neutralization device 13 is increased to 15 V (strong) about 60 ms after the transfer bias OFF of the timer 15 ( Step S7).

  Thereafter, the charging bias is turned off at a certain time (step S8), and the turned-off photosensitive drum surface passes through the position of the light neutralizing device 13, and further makes at least one round of the photosensitive drum 2. Thereafter, about 785 ms after the timer 15 is turned on, the photostatic device 13 is turned off (step S9), and the drum drive and the timer 15 are turned off after a certain time (step S10).

  Here, the timing of image formation may be the timing shown in FIGS. 6C and 7B. That is, in FIG. 6C, even if the control to turn on the transfer bias is performed after step S6, the voltage input to the light neutralizing device 13 is not changed and the voltage is kept at 15V (strong). . FIG. 7B is a timing chart at the time of continuous paper passing, in which the voltage input to the light neutralizing device 13 is changed during the paper interval. 15V (strong). When the rotational speed of the photosensitive drum 2 is slow, the voltage input to the light neutralizing device 13 is 0 V (weak).

  According to the present embodiment as described above, it is possible to suppress the occurrence of image defects such as ground blur and image density reduction due to the photodegradation of the photosensitive drum 2 and the residual charge during post-rotation, and high productivity can be executed.

DESCRIPTION OF SYMBOLS 2 ... Photosensitive drum 3 ... Charging roller 4 ... Developing device 5 ... Transfer roller 6 ... Cleaning device 6a ... Cleaning blade 7 ... Exposure device 8 ... Intermediate transfer body 10 ... Secondary transfer roller 12 ... Belt cleaning device 13 ... Photostatic device 14 …controller

Claims (5)

In an image forming apparatus, comprising: a photoconductor on which a toner image is formed; a transfer charger that transfers the toner image on the photoconductor to an image receiving member; and a light discharger that discharges the photoconductor by light irradiation.
The amount of light emitted when the region of the photoconductor subjected to the charging process by the transfer charger passes through the amount of light emitted when the region of the photoconductor not subjected to the charging process by the transfer charger passes. An image forming apparatus comprising: a control unit that controls the light neutralizing unit so as to be weakened.   The area of the photoconductor that has not been subjected to the charging process by the transfer charger is the area of the photoconductor that passes through the light neutralizing means during pre-processing for starting toner image formation on the photoconductor, and the photosensitive area. A region of the photosensitive member that passes through the light neutralizing unit during post-processing upon completion of toner image formation on the body, and a region between the plurality of images on the photosensitive member when a plurality of images are continuously formed. The image forming apparatus according to claim 1, wherein the number is at least one.   The area of the photoconductor that has a blade for cleaning the photoconductor and has not been subjected to the charging process by the transfer charger is the area where the predetermined toner image formed on the photoconductor is not transferred to the image receiving member. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is an area in which a predetermined toner image is formed on the photoconductor for supplying to a blade. 4. The light neutralizing means includes an image exposure device that performs exposure to form an electrostatic image on the photosensitive member, and a downstream side in the moving direction of the photosensitive member with respect to the transfer charger, and is moved with respect to the image exposing device. An optical static eliminator provided on the upstream side in the direction,
The control means causes the photocharger to perform a neutralization process on the area of the photoconductor that has been subjected to the charging process by the transfer charger, and causes the photoconductor that has not been charged by the transfer charger. The image forming apparatus according to claim 1, wherein a neutralization process is performed on the area by the light neutralizer and the image exposure unit.   The image forming apparatus according to claim 1, further comprising: a transfer charger that transfers the toner image transferred from the photoconductor to the image receiving member onto a sheet.