JP2021117240A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent an increase in surface friction coefficient of an image carrier on the outside in a width direction of a recording medium.SOLUTION: An image forming apparatus comprises: an image forming unit including an image carrier, an electrifying device, an exposure device, a developing device, a cleaning member, and a static eliminating device; an input unit that receives input of information on the size of a recording medium; and a control unit. The static eliminating device has a first static eliminating lamp that irradiates, with static eliminating light, a first area including an area on the inside in a width direction of a recording medium with a predetermined size, and a second static eliminating lamp that irradiates, with static eliminating light, second areas that are on the outside in the width direction of the first area and on the inside in a width direction of a recording medium with the maximum size. When the size of the recording medium is equal to or less than the predetermined size, the control unit turns on only the first static eliminating lamp, and when the size of the recording medium is larger than the predetermined size, turns on the first static eliminating lamp and the second static eliminating lamp.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus including a static elimination device that emits static elimination light to a photoconductor to eliminate residual charges.

In an image forming apparatus using an electrophotographic process, when image formation is performed, the surface of the photoconductor drum is uniformly charged by the charging device, and then the surface of the photoconductor drum is exposed by the exposure apparatus to perform electrostatic latency on the surface of the photoconductor drum. An image is formed, and an electrostatic latent image is further developed by a developing device. The developed toner image is transferred onto the recording medium by the transfer member, and the recording medium is conveyed to the fixing device to be fixed, and then discharged to the outside of the image forming apparatus. After the transfer, the static eliminator removes the residual charge on the photoconductor drum, and the photoconductor drum is charged again by the charging device. Light elimination or the like is used to eliminate residual charges.

In recent years, an image forming apparatus using an electrophotographic process is required to be compatible with various recording media in addition to high speed and high image quality. Therefore, it is also necessary to support SRA3 size paper (width 320 mm) and 13-inch paper (width 330 mm) required in the printing industry in terms of the corresponding paper size. As a result, the photoconductor drum becomes long, and the developing device, the charging device, and the cleaning blade also become long.

However, in general, A4 size horizontal placement or A3 size (width 297 mm), or 8.5 inch horizontal placement or 11 inch paper (width 279 mm) is mostly used, and larger paper is used. The frequency is low.

When A4 size or 11 inch paper is used, the photoconductor drum is charged but the toner is not developed from the developing device in the non-passing area outside the width direction of the paper size. Therefore, the discharge product adheres to the non-paper-passing region of the photoconductor drum and the surface friction coefficient increases, while the toner does not adhere to the cleaning blade and the rubbing roller of the cleaning device. Friction force increases. As a result, problems such as blade squeal, blade curling, and poor cleaning occur.

Therefore, a method of suppressing an increase in the frictional force between the image carrier and the cleaning member has been proposed. For example, in Patent Document 1, a region on the surface of the image carrier that avoids a region where a toner image is formed is used. Disclosed is an apparatus for forming a toner band extending in the width direction of an image carrier so that a portion where a toner image is not formed does not occur when the image carrier is viewed in the width direction.

In Patent Document 2, a toner reservoir member forming a reservoir for temporarily storing toner particles scraped from the photoconductor drum is attached to both ends of the cleaning blade, and uneven wear of the photoconductor drum and damage to the cleaning blade are provided. Drum assemblies that prevent

Japanese Unexamined Patent Publication No. 2001-175090 Japanese Unexamined Patent Publication No. 2011-75712

The methods of Patent Documents 1 and 2 reduce damage to the cleaning blade by the toner developed from the developing apparatus, and the range in which the damage to the cleaning blade can be reduced is the developable range. Therefore, even if the methods of Patent Documents 1 and 2 are used, the photoconductor drum is hit in a region outside the paper-passing region, that is, in a region where the surface of the photoconductor drum is charged but the toner is not developed. No toner is supplied to the cleaning blades or rubbing rollers that come into contact with it. As a result, the surface of the photoconductor drum cannot be sufficiently rubbed in this region, the surface friction coefficient of the photoconductor drum increases, the cleaning blade is damaged, and problems such as poor cleaning occur.

Further, in order to prevent an increase in the surface friction coefficient in the outer region of the paper, it is conceivable to make the charged region and the developable region substantially the same width. In this case, since the non-charged region on the photoconductor drum and the developable region are very close to each other, the toner scattered from the developing device is developed in the non-charged region, causing problems such as contamination inside the device. Generally, the charged region needs to be widened by 3 mm on one side from the developed region.

In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of suppressing an increase in the surface friction coefficient of an image carrier on the outer side in the width direction of a recording medium.

In order to achieve the above object, the first configuration of the present invention is an image forming apparatus including an image forming unit, an input unit, and a control unit. The image forming unit forms an electrostatic latent image by exposing an image carrier on which a photosensitive layer is formed, a charging device for charging the surface of the image carrier, and an image carrier charged by the charging device. An exposure device for forming a toner image by adhering toner to an electrostatic latent image formed on an image carrier, a cleaning member that contacts the surface of the image carrier to remove residual toner, and an image. Includes a static eliminator that irradiates the surface of the carrier with static eliminating light to remove residual charges. The size information of the recording medium on which the toner image formed by the image forming unit is transferred is input to the input unit. The control unit controls the image forming unit. The static elimination device includes a first static elimination lamp that irradiates a first region including an area inside the width direction of a recording medium of a predetermined size with static elimination light, and a static elimination lamp that is outside the width direction of the first region and is the width direction of the maximum size recording medium. It has a second static elimination lamp that irradiates the inner second region with static elimination light. When the size of the recording medium input to the input unit is smaller than or equal to the predetermined size, the control unit turns on only the first static elimination lamp to remove the residual charge of the image carrier, and the size of the recording medium is larger than the predetermined size. If it is large, the first static elimination lamp and the second static elimination lamp are turned on to remove the residual charge of the image carrier.

According to the first configuration of the present invention, when the recording medium is smaller than a predetermined size, only the first static elimination lamp is turned on. Therefore, the first region is charged by the charging step and statically eliminated by the static elimination step to form a regular surface. It becomes an electric potential. As a result, a stable image can be obtained in the first region. Further, the second region is charged after being charged in the first round of the image carrier, and is hardly charged after the second round. Therefore, in the second region, the proximity discharge occurs only in the first round of the image carrier, so that the generation of discharge products is small and the increase in the surface friction coefficient of the image carrier is suppressed. On the other hand, when the recording medium is larger than the predetermined size, the second static elimination lamp is turned on in addition to the first static elimination lamp, so that the residual charge in the second region is sufficiently statically eliminated and the surface potential in the next printing is stabilized.

Side sectional view showing the structure of the image forming apparatus 100 according to the embodiment of the present invention. Partially enlarged view around the image forming portion Pa in FIG. Schematic diagram showing the configuration of the static elimination device 20 mounted on the image forming apparatus 100 of the present embodiment and the static elimination regions of the photoconductor drums 1a to 1d. A block diagram showing an example of a control path of the image forming apparatus 100 A flowchart showing an example of static elimination control of the photoconductor drums 1a to 1d in the image forming apparatus 100 of the present embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an internal structure of an image forming apparatus 100 according to an embodiment of the present invention. In the main body of the image forming apparatus 100 (here, a color printer), four image forming portions Pa, Pb, Pc and Pd are arranged in order from the upstream side in the transport direction (right side in FIG. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (yellow, cyan, magenta, and black), and are respectively charged, exposed, developed, and transferred to yellow, cyan, and magenta. And black images are formed sequentially.

Photoreceptor drums (image carriers) 1a, 1b, 1c, and 1d that support visible images (toner images) of each color are arranged on these image forming portions Pa to Pd, respectively. The photoconductor drums 1a to 1d are, for example, organic photoconductors in which an organic photosensitive layer (OPC) is laminated on the outer peripheral surface of an aluminum drum tube, and a coat layer is further laminated on the surface of the organic photosensitive layer, and is a main motor. It is rotationally driven by (not shown). Instead of the organic photoconductor drum, an amorphous silicon photoconductor drum in which an amorphous silicon photosensitive layer is formed on the outer peripheral surface of the drum tube can also be used.

Further, an intermediate transfer belt 8 rotated in the clockwise direction in FIG. 1 by a belt drive motor (not shown) is provided adjacent to each image forming portion Pa to Pd. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a seamless (seamless) belt is mainly used. Further, a blade-shaped belt cleaner 19 for removing toner and the like remaining on the surface of the intermediate transfer belt 8 is arranged on the downstream side of the secondary transfer roller 9.

The transfer paper P on which the toner image is secondarily transferred is housed in a paper cassette 16 arranged in the lower part of the main body of the image forming apparatus 100, and is housed in a paper cassette 16 and is interposed via a paper feed roller 12a and a resist roller pair 12b. It is conveyed to the nip portion between 9 and the drive roller 11 of the intermediate transfer belt 8.

Next, the image forming units Pa to Pd will be described. FIG. 2 is an enlarged view of the vicinity of the image forming portion Pa in FIG. Since the image forming portions Pb to Pd have basically the same configuration, the description thereof will be omitted. As shown in FIG. 2, a charging device 2a for charging the photoconductor drum 1a and an exposure device 5 for exposing image information to the photoconductor drum 1a are located around and below the photoconductor drum 1a rotatably arranged. (See FIG. 1), a developing device 3a that forms a toner image on the photoconductor drum 1a, a cleaning device 7a that removes a developer (toner) and the like remaining on the photoconductor drum 1a, and a static elimination device 20. Is arranged, and the primary transfer roller 6a is arranged with the intermediate transfer belt 8 interposed therebetween.

The charging device 2a includes a charging roller 21 that contacts the photoconductor drum 1a to charge the surface of the photoconductor drum 1a, and a charging cleaning roller 22 that cleans the charging roller 21. A DC voltage or a charging voltage obtained by superimposing an AC voltage on the DC voltage is applied to the charging roller 21.

The developing device 3a includes a developing roller 31 facing the photoconductor drum 1a. A two-component developer composed of a magnetic carrier and a toner is housed in the developing apparatus 3a. A brush is formed. A developing voltage obtained by superimposing an AC voltage on a DC voltage is applied to the developing roller 31.

The cleaning device 7a includes a cleaning blade 32 for removing residual toner on the surface of the photoconductor drum 1a, and a rubbing roller for removing residual toner on the surface of the photoconductor drum 1a and rubbing and polishing the surface of the photoconductor drum 1a. 33 includes a transport spiral 35 that discharges residual toner removed from the photoconductor drum 1a by the cleaning blade 32 and the rubbing roller 33 to the outside of the cleaning device 7a.

The static eliminator 20 is arranged on the downstream side of the primary transfer roller 6a and on the upstream side of the cleaning device 7a with respect to the rotation direction of the photoconductor drum 1a. The static elimination device 20 irradiates the photoconductor drums 1a to 1d with static elimination light to remove the residual charge on the surface of the photoconductor drum 1a to a predetermined potential or less. The detailed configuration of the static elimination device 20 will be described later.

Further, the photoconductor drum 1a, the charging device 2a, the cleaning device 7a, and the static elimination device 20 are unitized. In each image forming unit Pa to Pd, the unit including the photoconductor drums 1a to 1d, the charging devices 2a to 2d, the cleaning devices 7a to 7d, and the static elimination device 20 is referred to as a drum unit 40a to 40d.

When image data is input from a higher-level device such as a personal computer, first, the surfaces of the photoconductor drums 1a to 1d are uniformly charged by the charging devices 2a to 2d. Next, the exposure apparatus 5 irradiates light according to the image data to form an electrostatic latent image according to the image data on each of the photoconductor drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer containing toners of yellow, cyan, magenta, and black, respectively. When the ratio of toner in the two-component developer filled in the developing devices 3a to 3d falls below the specified value due to the formation of the toner image described later, the toner containers 4a to 4d to the developing devices 3a to 3d are used. Toner is replenished. The toner in this developer is supplied onto the photoconductor drums 1a to 1d by the developing devices 3a to 3d, and is electrostatically adhered to the toners according to the electrostatic latent image formed by the exposure from the exposure device 5. A toner image is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photoconductor drums 1a to 1d by the primary transfer rollers 6a to 6d at a predetermined transfer voltage, and yellow, cyan, magenta and yellow, cyan, magenta and magenta on the photoconductor drums 1a to 1d are applied. The black toner image is primarily transferred onto the intermediate transfer belt 8. These four-color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. After that, in preparation for the subsequent formation of a new electrostatic latent image, the toner and the like remaining on the surfaces of the photoconductor drums 1a to 1d after the primary transfer are removed by the cleaning devices 7a to 7d. Further, the residual charge on the surface of the photoconductor drums 1a to 1d is removed by the static elimination device 20.

When the intermediate transfer belt 8 starts rotating in the clockwise direction, the transfer paper P is conveyed from the resist roller pair 12b to the nip portion (secondary transfer nip portion) between the drive roller 11 and the secondary transfer roller 9 at a predetermined timing. , The full-color image on the intermediate transfer belt 8 is secondarily transferred onto the transfer paper P. The transfer paper P on which the toner image is secondarily transferred is conveyed to the fixing portion 13.

The transfer paper P conveyed to the fixing portion 13 is heated and pressurized by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is distributed in the transport direction by the branching portions 14 branched in a plurality of directions, and is sent to the double-sided transport path 18 as it is (or after being sent to the double-sided transport path 18 to form an image on both sides), and the discharge roller is used. It is discharged to the discharge tray 17 by pair 15.

FIG. 3 is a schematic view showing the configuration of the static elimination device 20 mounted on the image forming apparatus 100 of the present embodiment and the static elimination regions of the photoconductor drums 1a to 1d. The static elimination device 20 includes a first static elimination lamp 51 and a second static elimination lamp 52 that emit static elimination light, a rod-shaped light guide 53 extending along the axial direction of the photoconductor drums 1a to 1d, and a first light guide 53. 1 It is composed of a reflecting member 55 arranged to face the end surface (opposing surface 53b described later) opposite to the static elimination lamp 51.

The first static elimination lamp 51 and the second static elimination lamp 52 are composed of a light emitting diode (LED) or the like that emits static elimination light. The first static elimination lamp 51 and the second static elimination lamp 52 are mounted on a light source substrate (not shown). The first static elimination lamp 51 is arranged to face the light incident surface 53a on one end side of the light guide body 53. A pair of the second static elimination lamps 52 are arranged so as to face the back surface 53d in the vicinity of both ends in the longitudinal direction of the light guide body 53.

The light guide body 53 is formed in an elongated shape having a substantially semicircular cross section by using a translucent acrylic resin or the like. The light guide body 53 directs the light from the first static elimination lamp 51 toward the photoconductor drums 1a to 1d while guiding the light from the light guide body 53 along the extending direction of the light guide body 53 (the axial direction of the photoconductor drums 1a to 1d). And emit.

The light guide 53 has a light incident surface 53a that is arranged to face the first static elimination lamp 51 and is incident with light from the first static elimination lamp 51, and a facing surface 53b that is arranged on the opposite side of the first static elimination lamp 51. A light emitting surface 53c having an arcuate cross section facing the photoconductor drums 1a to 1d and a flat back surface 53d facing the light emitting surface 53c, which are arranged between the light incident surface 53a and the facing surface 53b. ..

In the region excluding both ends of the back surface 53d, the reflecting portion 53e that reflects the light incident on the light guide body 53 to the photoconductor drums 1a to 1d side (light emitting surface 53c side) is along the longitudinal direction of the light guide body 53. Is formed. The reflecting portion 53e is formed with a large number of prisms (not shown) formed of V-grooves or the like extending in a direction intersecting the axial direction of the photoconductor drums 1a to 1d (direction perpendicular to the paper surface in FIG. 5).

The light emitted from the first static elimination lamp 51 and incident on the light incident surface 53a of the light guide body 53 travels in the light guide body 53 while diffusing, and is reflected by the reflecting portion 53e toward the light emitting surface 53c side, and the light is emitted. The light is emitted from the exit surface 53c toward the photoconductor drums 1a to 1d.

The reflecting member 55 is made of a material having a high light reflectance such as an aluminum plate, reflects the light leaked from the facing surface 53b, and is made to enter the inside of the light guide 53 again from the facing surface 53b. As a result, the utilization efficiency of the light emitted from the first static elimination lamp 51 is improved.

The second static elimination lamp 52 is arranged adjacent to both ends in the longitudinal direction of the reflecting portion 53e on the back surface 53d. The light emitted from the second static elimination lamp 52 and incident on the back surface 53d of the light guide body 53 passes through the light guide body 53 and is emitted from the light emitting surface 53c toward the photoconductor drums 1a to 1d.

Further, the outer peripheral surfaces of the photoconductor drums 1a to 1d are divided into three axial regions A, B, and C. The area A is an area inside the paper width w1 (297 mm) of a predetermined size (here, A4 horizontal size). The area B is an area outside the A4 horizontal size paper width w1 and inside the forming width w2 (310 mm) of the reflecting portion 53e of the light guide body 53. The regions A and B are regions in which the static elimination light of the first static elimination lamp 51 is irradiated to the photoconductor drums 1a to 1d by the reflecting portion 53e of the light guide body 53. That is, the width of the region (first region) in which the regions A and B are combined is the same width as the formation width w2 of the reflection portion 53e.

The area C (second area) is outside the forming width w2 (310 mm) of the reflecting portion 53e of the light guide body 53 and has a paper width w3 (330 mm) of the maximum size (13 inch size in this case) that can be passed through. The inner area. The region C is a region in which the static elimination light of the first static elimination lamp 51 is not irradiated, and the static elimination light of the second static elimination lamp 52 passes through the light guide 53 and is irradiated.

The developing region width w4 (332 mm) of the developing devices 3a to 3d is substantially the same as the 13-inch size paper width w3. The charging region width w5 (340 mm) of the charging devices 2a to 2d, the blade width of the cleaning blade 32, and the roller width w6 (350 mm) of the rubbing roller 33 are all larger than the 13-inch size paper width w3 and are photosensitive. It is smaller than the axial length (360 mm) of the body drums 1a to 1d.

FIG. 4 is a block diagram showing an example of a control path used in the image forming apparatus 100. Since various controls are performed for each part of the image forming apparatus 100 in using the image forming apparatus 100, the control path of the entire image forming apparatus 100 becomes complicated. Therefore, here, the part of the control path required for the implementation of the present invention will be mainly described.

The control unit 90 includes a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only storage unit, a RAM (Random Access Memory) 93 as a readable and writable storage unit, and a temporary storage unit. A plurality of (here, two) that transmit a control signal or receive an input signal from the operation unit 80 to each device in the temporary storage unit 94, the counter 95, and the image forming device 100 that specifically stores image data and the like. It has at least the I / F (interface) 96 of. Further, the control unit 90 can be arranged at an arbitrary place inside the main body of the image forming apparatus 100.

The ROM 92 contains data such as a control program for the image forming apparatus 100, numerical values necessary for control, and the like that are not changed during use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100, data temporarily required for controlling the image forming apparatus 100, and the like. The counter 95 integrates and counts the number of printed sheets.

Further, the control unit 90 transmits a control signal from the CPU 91 to each part and the device in the image forming apparatus 100 through the I / F 96. Further, a signal indicating the state and an input signal from each part and the device are transmitted to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include image forming units Pa to Pd, fixing unit 13, voltage control circuit 61, image input unit 70, and operation unit 80.

The voltage control circuit 61 is connected to a charging voltage power supply 62, a developing voltage power supply 63, and a transfer voltage power supply 64, and operates each of these power supplies by an output signal from the control unit 90. In each of these power supplies, the charging voltage power supply 62 is connected to the charging rollers 21 in the charging devices 2a to 2d, and the developing voltage power supply 63 is connected to the developing rollers 31 in the developing devices 3a to 3d by the control signal from the voltage control circuit 61. The transfer voltage power supply 64 applies a predetermined voltage to each of the primary transfer rollers 6a to 6d and the secondary transfer roller 9.

The image input unit 70 is a receiving unit that receives image data transmitted from a personal computer or the like to the image forming apparatus 100. The image signal input from the image input unit 70 is converted into a digital signal and then sent to the temporary storage unit 94.

The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 indicating various states. The user operates the stop / clear button of the operation unit 80 to stop image formation, and operates the reset button to operate the image. The various settings of the forming device 100 are set to the default state. The liquid crystal display unit 81 is designed to show the state of the image forming apparatus 100, and to display the image forming status and the number of printed copies. Various settings of the image forming apparatus 100 are performed from the printer driver of the personal computer.

As described above, in the image forming apparatus 100, a charging voltage (DC voltage) is applied to the charging rollers 21 of the charging devices 2a to 2d to charge the photoconductor drums 1a to 1d. Then, after each step of exposure, development, transfer and cleaning is performed, static elimination light is irradiated from the static elimination device 20 in order to eliminate the residual charge of the photoconductor drums 1a to 1d. Here, if the exposure and static elimination of the photoconductor drums 1a to 1d are not executed, the electric charge is still retained in the photosensitive layer of the photoconductor drums 1a to 1d. Therefore, in the next charging step, the charging roller 21 and the photoconductor drum The potential difference from 1a to 1d becomes very small. Therefore, close discharge hardly occurs between the charging roller 21 and the photoconductor drums 1a to 1d, and the surface of the photoconductor drums 1a to 1d is hardly charged.

On the other hand, the increase in the surface friction coefficient of the photoconductor drums 1a to 1d is generated when a discharge product such as NOx generated by the proximity discharge by the charging roller 21 adheres to the surface of the photoconductor drums 1a to 1d. That is, when the proximity discharge does not occur, there is almost no adhesion of the discharge product, and the increase in the surface friction coefficient of the photoconductor drums 1a to 1d is small.

Therefore, the image forming apparatus 100 of the present embodiment pays attention to the relationship between charging and static elimination outside the above-mentioned image region, and prints on paper of a predetermined size (generally used here, A4 horizontal size) or less. Occasionally, by not irradiating the outside of the image region (region C in FIG. 3) with static elimination light, proximity discharge by the charging roller 21 in the next printing is prevented, and an increase in the surface friction coefficient of the photoconductor drums 1a to 1d is suppressed. It is supposed to be.

FIG. 5 is a flowchart showing an example of static elimination control of the photoconductor drums 1a to 1d in the image forming apparatus 100 of the present embodiment. The static elimination control procedure of the photoconductor drums 1a to 1d will be described in detail along the steps of FIG. 5 with reference to FIGS. 1 to 4 as necessary.

First, the control unit 90 determines whether or not a print command has been received (step S1). If the print command is not received (No in step S1), the print standby state is continued. When the print command is received (Yes in step S1), the control unit 90 detects the paper size used for printing (step S2). The paper size is determined by the paper size detection sensor (not shown) arranged in the paper feed cassette 2a or the manual paper feed tray 2b, or the image data transmitted from an external device such as a personal computer to the image input unit 70. After that, printing is executed by a normal image forming operation (step S3).

Next, the control unit 90 determines whether or not the paper size detected in step S2 is A4 horizontal size or less (step S4). When the paper size is A4 horizontal size or less (Yes in step S4), only the first static elimination lamp 51 is turned on when the residual charges of the photoconductor drums 1a to 1d are removed (step S5). On the other hand, when the paper size is larger than the A4 horizontal size (No in step S4), both the first static elimination lamp 51 and the second static elimination lamp 52 are turned on (step S6).

After that, it is determined whether or not printing is completed (step S7), and if printing is continued (No in step S7), the process returns to step S2 to detect the paper size and continue the printing operation (steps S2 to S6). ). If printing is completed (Yes in step S7), the process ends.

According to the configuration of the present embodiment, when the paper size is A4 horizontal size or less, only the first static elimination lamp 51 is turned on. Therefore, the regions A and B in FIG. 3 are charged by the charging step and statically eliminated by the static elimination step. It becomes a normal surface potential. As a result, stable images can be obtained in the regions A and B. Further, since the second static elimination lamp 52 is not turned on, in the region C of FIG. 3, the electric charge is retained after being charged in the first lap of the photoconductor drums 1a to 1d, and is hardly charged in the second and subsequent laps. .. Therefore, in the region C, the proximity discharge occurs only in the first lap of the photoconductor drums 1a to 1d, so that the generation of discharge products is small and the increase in the surface friction coefficient of the photoconductor drums 1a to 1d is suppressed.

On the other hand, when the paper size is larger than the A4 horizontal size (for example, in the case of 13-inch paper), the second static elimination lamp 52 is lit in addition to the first static elimination lamp 51. Since the light guide body 53 does not have the reflecting portion 53e formed in the portion through which the light emitted from the second static elimination lamp 52 passes, the static elimination light of the second static elimination lamp 52 is the static elimination light of the first static elimination lamp 51. The region C of the photoconductor drums 1a to 1d is irradiated without being hindered. Therefore, the residual charge in the region C is sufficiently eliminated, and the surface potential in the next printing is stabilized.

Therefore, since the increase in the surface friction coefficient of the portion of the photoconductor drums 1a to 1d facing both ends of the cleaning blade 32 is suppressed, the blade squealing, curling, and cleaning failure of the cleaning blade 32 can be effectively suppressed. Can be done. Further, the residual charge of the photoconductor drums 1a to 1d can be sufficiently eliminated regardless of the paper size, and the surface potential is also stabilized.

Others The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the lighting patterns of the first static elimination lamp 51 and the second static elimination lamp 52 are switched between the case where the paper size is A4 horizontal size or less and the case where the paper size is larger than the A4 horizontal size. The paper size can be set arbitrarily. However, it is preferable that the size most frequently used in the image forming apparatus 100 is set as the size that triggers the switching.

Further, the wavelength of the static elimination light of the first static elimination lamp 51 and the second static elimination lamp 52, the dimensions and the shape of the light guide body 53, and the like should be appropriately changed according to the specifications of the photoconductor drums 1a to 1d and the static elimination device 20. Can be done.

Further, in the above embodiment, the position of the static eliminator 20 is the upstream side of the cleaning devices 7a to 7d and the downstream side of the primary transfer rollers 6a to 6d with respect to the rotation direction of the photoconductor drums 1a to 1d. 20 may be arranged on the upstream side of the charging devices 2a to 2d and on the downstream side of the cleaning devices 7a to 7d with respect to the rotation direction of the photoconductor drums 1a to 1d.

Further, in the above embodiment, as the image forming apparatus 100, a color printer as shown in FIG. 1 is taken as an example, but the present invention includes a monochrome printer, a monochrome copier, a digital multifunction device, a facsimile, and the like. It may be an image forming apparatus of. Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

A verification test was conducted on the effect of suppressing an increase in the surface friction coefficient of the photoconductor drums 1a to 1d in the image forming apparatus 100 of the present invention. As a testing machine, an intermediate transfer type image forming apparatus 100 as shown in FIG. 1 is equipped with a static elimination device 20 having a first static elimination lamp 51 and a second static elimination lamp 52 as shown in FIG. When the lighting control of the first static elimination lamp 51 and the second static elimination lamp 52 is performed according to the paper size as shown in 5 (the present invention), the first static elimination lamp 51 and the second static elimination lamp 51 and the second static elimination lamp are always irrespective of the paper size. The surface friction coefficient of the photoconductor drums 1a to 1d was compared with that of the case where the lamp 52 was turned on (comparative example).

As a test method, 1000 sheets of test images with a printing rate of 5% are continuously printed on A4 horizontal size plain paper (paper width 297 mm) at a process linear speed of 152 mm / sec, and after printing is completed, a friction coefficient measuring jig is used. The surface friction coefficient of the photoconductor drums 1a to 1d outside the width direction (region C in FIG. 3) of the paper passing region was measured.

The image formation conditions were the surface potential (bright potential) V0 = 350V and the post-exposure potential (dark potential) VL = 150V of the photoconductor drums 1a to 1d. A developing voltage was applied by superimposing a square wave AC voltage having a frequency of 5 kHz, Vpp = 1100 V, and Duty = 50% on a DC voltage of 350 V. Further, a two-component developer composed of a positively charged toner having an average particle diameter of 6.8 μm and a ferrite / resin coat carrier having an average particle diameter of 35 μm was used, and the toner concentration was set to 6%. The results are shown in Table 1.

As shown in Table 1, in the present invention in which the second static elimination lamp 52 was turned off, the surface friction coefficient of the region C was suppressed to 0.3. The reason for this is that by turning off the second static elimination lamp 52, the electric charge is retained in the area C at the time of printing the first sheet, and the charging roller 21 and the photoconductor drum are held in the charging process in the printing of the second and subsequent sheets. It is considered that this is because the proximity discharge hardly occurs between 1a and 1d, and the discharge product is unlikely to be generated.

On the other hand, in the comparative example in which the first static elimination lamp 51 and the second static elimination lamp 52 were turned on, the surface friction coefficient of the region C increased to 0.6. The reason for this is that since the second static elimination lamp 52 is turned on, charging and static elimination of the region C are repeated for each printed sheet, and proximity discharge between the charging roller 21 and the photoconductor drums 1a to 1d is repeatedly generated. It is considered that this is because the discharge product was generated.

From the above results, the present invention that turns off the second static elimination lamp 52 when the paper size is smaller than a predetermined size (here, A4 horizontal size) effectively suppresses an increase in the surface friction coefficient of the photoconductor drums 1a to 1d. It was confirmed that it would be done.

The present invention can be used in an image forming apparatus including a static elimination device that emits static elimination light to a photoconductor to eliminate residual charges. By utilizing the present invention, it is possible to provide an image forming apparatus capable of suppressing an increase in the surface friction coefficient of the image carrier on the outer side in the width direction of the recording medium.

Pa to Pd Image forming parts 1a to 1d Photoreceptor drum (image carrier)
2a to 2d Charging device 3a to 3d Developing device 5 Exposure device 7a to 7d Cleaning device 20 Static elimination device 32 Cleaning blade (cleaning member)
33 Rubbing roller (cleaning member)
51 1st static elimination lamp 52 2nd static elimination lamp 53 Light guide 53a Light incident surface 53b Opposing surface 53c Light emitting surface 53d Rear 52e Reflecting part 55 Reflecting member 70 Image input part (input part)
90 Control unit 100 Image forming device

Claims (4)

An image carrier on which a photosensitive layer is formed and
A charging device that charges the surface of the image carrier,
An exposure device that forms an electrostatic latent image by exposing the image carrier charged by the charging device, and an exposure device.
A developing device that forms a toner image by adhering toner to the electrostatic latent image formed on the image carrier.
A cleaning member that comes into contact with the surface of the image carrier to remove residual toner, and
A static eliminator that irradiates the surface of the image carrier with static eliminating light to remove residual charges.
Image forming part including
An input unit into which size information of a recording medium on which the toner image formed by the image forming unit is transferred is input, and an input unit.
A control unit that controls the image forming unit and
In an image forming apparatus equipped with
The static elimination device includes a first static elimination lamp that irradiates a first region including a region inside the width direction of the recording medium having a predetermined size with the static elimination light, and the static elimination lamp having the maximum size outside the width direction of the first region. It has a second static elimination lamp that irradiates the static elimination light to the second region inside in the width direction of the recording medium.
When the size of the recording medium input to the input unit is smaller than or equal to the predetermined size, the control unit turns on only the first static elimination lamp to remove the residual charge of the image carrier, and the recording An image forming apparatus characterized in that when the size of the medium is larger than the predetermined size, the first static elimination lamp and the second static elimination lamp are turned on to remove the residual charge of the image carrier. The static eliminator is
With the first static elimination lamp
A rod-shaped light guide body that emits light incident from the first static elimination lamp while guiding the light along the axial direction, and a rod-shaped light guide body.
The second static elimination lamp arranged on the opposite side of the image carrier with the light guide body in between,
With
The light guide body is formed at one end in the axial direction, extends along a light incident surface on which light from the first static elimination lamp is incident, and along the longitudinal direction of the light guide body, and extends from the light incident surface. It has a light emitting surface that emits incident light to the image carrier, and a back surface that faces the light emitting surface.
The image forming apparatus according to claim 1, wherein a reflecting portion having the same width as that of the first region is formed on the back surface to reflect the light incident on the light guide body toward the light emitting surface side. The second static elimination lamp is arranged adjacent to both ends in the longitudinal direction of the reflecting portion, and the light emitted from the second static elimination lamp and incident on the back surface passes through the light guide body. The image forming apparatus according to claim 2, wherein the light is emitted from the light emitting surface to the second region of the image carrier. The image forming apparatus according to any one of claims 1 to 3, wherein the predetermined size is the size most frequently used among the sizes of the plurality of usable recording media.

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