Image forming apparatus

Abstract

The present disclosure relates to an image forming apparatus including an image bearing member, a charging member to charge a surface of the image bearing member, an exposure unit, a developing member to form a toner image, a transfer member, an irradiation unit, and a blocking member. The irradiation unit includes a light source disposed at one end of the irradiation unit in a rotational axis direction of the image bearing member and a guide configured to guide light emitted from the light source in the rotational axis direction, the irradiation unit irradiating the surface of the image bearing member with light after the transfer member transfers the toner image to a transfer receiving member, and the blocking member blocks the light irradiated from the irradiation unit in the rotational axis direction so that an amount of the light irradiated from the irradiation unit is different in the rotational axis direction.

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus. Background Technology

[0002] An image forming apparatus uniformly charges a photosensitive drum, which serves as an image carrier, to a predetermined potential by discharging from a charging unit, and then exposes it according to an image pattern, thereby forming an electrostatic latent image on the photosensitive drum. Subsequently, the image forming apparatus develops the electrostatic latent image on the photosensitive drum with toner to form a toner image, and transfers the toner image onto a recording material such as paper. When charging the surface of the photosensitive drum, if residual charge exists on the surface, the surface potential of the photosensitive drum may become uneven. Therefore, due to the potential difference formed on the photosensitive drum between the image forming area where the toner image is formed and the non-image forming area where the toner image is not formed, an image defect called drum ghosting may occur. Therefore, to eliminate the potential difference formed on the surface of the photosensitive drum, a known effective method is to provide a so-called charge elimination unit, which eliminates the surface potential of the photosensitive drum to a predetermined potential by irradiating the surface of the photosensitive drum with light before the charging step. The charge elimination unit is called a pre-exposure unit. The pre-exposure unit can be an LED (light-emitting diode) or a combination of an LED circuit board and a light guide unit such as a light guide. These technologies are useful as systems for eliminating charge along the entire length of the photosensitive drum. However, in recent years, due to cost considerations, instead of arranging LEDs along the entire longitudinal direction of the photosensitive drum, light guides with LEDs arranged at the ends of the longitudinal direction of the photosensitive drum are commonly used (Japanese Patent Application Laid-Open No. 2018-132743 and Japanese Patent Application Laid-Open No. 2009-053603).

[0003] However, when using a photoconductor as a pre-exposure unit, the following problems exist. When using a photoconductor, charge is removed from the photosensitive drum by irradiating light from the end in the longitudinal direction. Therefore, the amount of light on the surface of the photosensitive drum increases on the light-incident side, and the amount of charge removal on the photosensitive drum becomes uneven in the longitudinal direction. To eliminate this unevenness in charge removal in the longitudinal direction, one known method is to measure the amount of charge removal on the photosensitive drum after pre-exposure and adjust the amount of charge removal so that the amount of charge removal in the longitudinal direction becomes uniform when the image is exposed through the exposure unit. Another known method is to adjust the sensitivity of the photosensitive drum in the longitudinal direction by changing the layer thickness of the photosensitive drum, thereby balancing the unevenness in charge removal.

[0004] However, conventional techniques require a detector configured to detect the amount of charge removal on the photosensitive drum and manage the layers of the drum in the longitudinal direction, which necessitates significant manpower and cost. Furthermore, conventional techniques cannot reduce the amount of light irradiating the incident side of the photosensitive drum itself, thus failing to address concerns about the lifespan caused by the effects of light irradiation on the photosensitive drum (hereinafter also referred to as light degradation). Summary of the Invention

[0005] This disclosure discloses an image forming apparatus designed to suppress charge elimination unevenness in the longitudinal direction of a photosensitive drum, the photosensitive drum being configured to have a photoguide disposed in a pre-exposure unit.

[0006] According to one aspect of this disclosure, the image forming apparatus includes: a rotatable image carrier member; a charging member configured to charge a surface of the image carrier member; an exposure unit configured to form an electrostatic latent image on the surface of the image carrier member charged by the charging member; a developing member configured to develop the electrostatic latent image formed by the exposure unit with a developing agent to form a toner image; and a transfer member configured to transfer the toner image formed by the developing member on the surface of the image carrier member to a transfer receiving member. The irradiation unit has a light source disposed at one end of the irradiation unit in the direction of rotation of the image carrier and a guide configured to guide light emitted from the light source in the direction of rotation, wherein the irradiation unit is configured to irradiate the surface of the image carrier with light after the transfer member transfers the toner image to the transfer receiving member; and a blocking member configured to block light irradiated from the irradiation unit in the direction of rotation, wherein the blocking member is configured such that the amount of light blocked from the irradiation unit in the direction of rotation is different.

[0007] Other features of this disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1A This is an external perspective view of the image forming apparatus of the first embodiment.

[0009] Figure 1B This is a cross-sectional view of the image forming apparatus of the first embodiment.

[0010] Figure 2A and Figure 2B This is a perspective view of the housing of the image forming apparatus according to the first embodiment.

[0011] Figure 3This is a control block diagram of the image forming apparatus of the first embodiment.

[0012] Figure 4A This is a view showing solid black blocks.

[0013] Figure 4B This is a view illustrating the mechanism of drum ghosting.

[0014] Figure 4C It is a view showing the relationship between the surface potential of the photosensitive drum and its position in the longitudinal direction.

[0015] Figure 5A This is a perspective view taken from the upper right side of the box tray.

[0016] Figure 5B This is a perspective view taken from the lower left side of the box tray.

[0017] Figure 6 This is a perspective view of the light guide component of the first embodiment.

[0018] Figure 7A and Figure 7B This is an enlarged view of the blocking component of the first embodiment.

[0019] Figure 8 This is a diagram showing the light distribution of the first embodiment and the comparative example in the longitudinal direction.

[0020] Figure 9A , Figure 9B and Figure 9C This is a view showing the variation in the longitudinal extension of the blocking member of the first embodiment.

[0021] Figure 10A This is a perspective view of the processing box equipped with a light guide.

[0022] Figure 10B and Figure 10C These are views showing light guides with other shapes.

[0023] Figure 11A and Figure 11B This is an enlarged view showing a variation of the blocking member of the first embodiment.

[0024] Figure 12 This is an enlarged view of the blocking component of the second embodiment, which is configured to attenuate light intensity.

[0025] Figure 13A and Figure 13B This is a view showing another shape of the blocking member of the second embodiment, configured to attenuate light. Detailed Implementation

[0026] The embodiments of this disclosure relating to the image forming apparatus will be described in detail below with reference to the accompanying drawings. The image forming apparatus forms an image on a recording material (recording medium) using an electrophotographic image forming method. Examples of image forming apparatuses include, for example, copiers, printers (laser beam printers, LED printers, etc.), fax machines, word processors, and multifunction peripherals (multifunction printers).

[0027] 1. Image forming apparatus

[0028] Reference Figure 1A and Figure 1B A schematic configuration of the image forming apparatus 100 according to the first embodiment is described. Figure 1A This is an external perspective view of the image forming apparatus 100. Figure 1B This is a cross-sectional view of the image forming apparatus 100. The image forming apparatus 100 includes a front door 31. (As shown...) Figure 1B As shown, the image forming apparatus 100 is a four-color full-color printer (electrophotographic image forming apparatus) using an electrophotographic process. The four-color full-color printer has four processing boxes as multiple boxes, namely, a first processing box PPY, a second processing box PPM, a third processing box PPC, and a fourth processing box PPK.

[0029] The image forming apparatus 100 forms a panchromatic or monochrome image on a sheet S, which is a sheet recording material, based on electrical image signals output from a controller 400 (which is an external host device) via an interface 300 and input to a control unit 200. The controller 400 can be a personal computer, image reader, fax machine, smartphone, etc. The control unit 200 controls the electrophotographic image forming process of the image forming apparatus 100. The control unit 200 exchanges various electrical information with the controller 400. The control unit 200 processes electrical information input from various processing devices and sensors, processes command signals from various processing devices, performs predetermined initial sequence control, and performs predetermined sequence control of the electrophotographic image forming process.

[0030] In the following description, such as Figure 1AAs shown, relative to the image forming apparatus 100, the front side is the side on which the front door 31 is disposed. The rear side (back side) is the side opposite to the front side. The front-back direction is the direction from the rear side to the front side of the image forming apparatus 100 (forward direction) and the opposite direction (rearward direction). Left and right refer to left and right when viewed from the front side of the image forming apparatus 100. The left-right direction is the direction from right to left (leftward direction) and the opposite direction (rightward direction). Up and down refer to up and down along the direction of gravity. The upward direction is the direction from bottom to top, and the downward direction is the direction from top to bottom. The longitudinal direction is the direction parallel to the rotation axis of the electrophotographic photosensitive drum 1 (hereinafter referred to as photosensitive drum 1), on which an image carrier member forms an electrostatic latent image. The short direction is the direction orthogonal to the longitudinal direction (orthogonal direction). One end of the longitudinal direction is the driving side, and the other end is the non-driving side.

[0031] In the first embodiment, the right end in the longitudinal direction is the driving side, while the left end is the non-driving side. Inside the image forming apparatus 100, the first to fourth processing cartridges PPY, PPM, PPC, and PPK are held in a cartridge tray 40 from the rear to the front of the image forming apparatus 100. The cartridge tray 40 (in-line configuration, tandem) holding the processing cartridges PPY, PPM, PPC, and PPK is installed in a predetermined position (installation position). The cartridge tray 40 will be described in detail later.

[0032] Figure 1B Four color image forming stations are shown in the image. Figure 1B The image forming stations, arranged in order from left to right, are configured to form yellow, magenta, cyan, and black images. Figure 1B The suffix letters Y, M, C, and K appended to the reference numbers or symbols denote components of stations that form yellow, magenta, cyan, and black toner images on the surface of the photosensitive drum 1, respectively. Since the construction of stations for forming yellow, magenta, cyan, and black images is common, one such station will be described below. In the following description, the suffix letters Y, M, C, and K will be omitted except when describing components related to specific colors.

[0033] A cylindrical photosensitive drum 1 rotates about its own axis (hereinafter referred to as the rotation axis). The surface of the photosensitive drum 1 is uniformly charged by a contact charging device (e.g., charging roller 2) serving as a charging component, and then an electrostatic latent image is formed by the exposure unit 11. The charging roller 2 has a core metal and a conductive elastomer layer concentrically and integrally formed around the core metal, and is charged by a charging voltage application unit 71 (…). Figure 3 The charging voltage is applied to the core metal. The developing unit DP (which serves as the developing component) Figure 2BThe developing roller 3 contains toner as a single-component developer. Toner with a predetermined charge polarity is supplied to the electrostatic latent image on the photosensitive drum 1 via the developing roller 3, and the toner is visualized (developed) into a toner image. The developing roller 3 is both a toner carrying component and a developing component. The developing roller 3 has a core metal and a conductive elastomer layer concentrically and integrally formed around the core metal, and is connected via a developing voltage application unit 72. Figure 3 The developing voltage is applied to the core metal. The toner image on the photosensitive drum 1 is electrostatically transferred to the intermediate transfer unit 12 via the primary transfer roller 17, which is connected by the primary transfer voltage application unit 73. Figure 3 The transfer unit applies a transfer voltage. The primary transfer roller 17 is formed in a roller shape, with a conductive elastic layer disposed on its shaft, and a voltage is applied to the shaft. Toner images of each color are sequentially transferred (primary transfer) onto an intermediate transfer member (e.g., intermediate transfer belt 13), which serves as a transfer receiving member, thereby forming a full-color toner image. Subsequently, the full-color toner image is transferred onto the sheet S via the secondary transfer roller 27, which acts as a secondary transfer unit (secondary transfer). The sheet S carrying unfixed toner is conveyed to the fixing unit 23, where the unfixed toner is thermally melted and mixed, fixing it onto the sheet S as a permanent image, and the sheet S is discharged as an image-formed product. The image-formation operation will be described in detail later.

[0034] (Processing box)

[0035] Reference Figure 2A and Figure 2B The processing cartridge PP is described. The processing cartridge PP is mounted in a position where image forming operations can be performed. The processing cartridge PP facilitates the image forming process of forming an image on the sheet S. The processing cartridge PP is detachably mounted and used in the image forming apparatus 100. Figure 2A and Figure 2B As shown, each processing cartridge PP in the first embodiment includes a drum unit OP and a developing unit DP. The drum unit OP has a photosensitive drum 1 on which an electrostatic latent image is formed, and the developing unit DP acts as an electrophotographic image forming processing unit on the photosensitive drum 1. The drum unit OP has a photosensitive drum 1 and a charging roller 2 configured to charge the surface of the photosensitive drum 1. Figure 1A and Figure 1BA drum coupling 1b is provided on the drive side of the photosensitive drum 1 along its rotation axis. The drum unit OP has drum flanges 1a and recesses 1d at both ends. The developing unit DP has a developing device 4. The developing device 4 has a developing roller 3 as a toner carrying component and a toner container 3b. The developing roller 3 is configured to develop an electrostatic latent image into a toner image by supplying toner to the photosensitive drum 1, while the toner container 3b is configured to hold the toner. A developing coupling 3a is provided on the drive side of the developing roller 3.

[0036] Each processing cartridge PP contains a different color of toner. Specifically, in the first processing cartridge PPY, yellow (Y) toner is contained in the toner container 3b, and a yellow toner image is formed on the surface of the photosensitive drum 1. Subsequently, magenta (M) toner is contained in the second processing cartridge PPM, cyan (C) toner is contained in the third processing cartridge PPC, and black (K) toner is contained in the fourth processing cartridge PPK, forming a toner image for each color.

[0037] Description Return to Figure 1B Below the processing cartridge PP, the primary transfer roller 17, serving as a transfer component, is arranged opposite to the photosensitive drum 1 of each drum unit OP. A transfer voltage is applied from the primary transfer voltage application unit 73 to the primary transfer roller 17, and the toner image formed on the surface of the photosensitive drum 1 is transferred in one pass to the surface of the intermediate transfer belt 13 of the intermediate transfer unit 12. Figure 1B As shown, the intermediate transfer unit 12 includes an intermediate transfer belt 13 as a flexible annular belt, a drive roller 14 for tensioning the intermediate transfer belt 13 and for circulating and moving the intermediate transfer belt 13, an auxiliary roller 15, and a tension roller 16. The drive roller 14 and the auxiliary roller 15 are disposed on the rear side of the image forming apparatus 100. The tension roller 16 is disposed on the front side of the image forming apparatus 100.

[0038] With each processing cartridge PP installed in its predetermined position, the lower surface of the photosensitive drum 1 contacts the intermediate transfer belt 13. A primary transfer roller 17 is disposed inside the intermediate transfer belt 13 facing the photosensitive drum 1. The clamping portion that serves as the contact point between the photosensitive drum 1 and the intermediate transfer belt 13 is called the primary transfer clamping portion T1. The secondary transfer roller 27 contacts the drive roller 14 via the intermediate transfer belt 13. The clamping portion between the secondary transfer roller 27 and the intermediate transfer belt 13 is called the secondary transfer clamping portion T2. ​​A light guide 57 is arranged at the lower part of the cartridge tray 40. A cleaning unit 26 is arranged on the intermediate transfer belt 13 and cleans the intermediate transfer belt 13.

[0039] Below the intermediate transfer unit 12, a feeding unit 18 is arranged. The feeding unit 18 is configured to hold sheets S on which toner images are transferred and to feed the sheets S one by one to the intermediate transfer unit 12. The feeding unit 18 has a sheet feed tray 19 stacked and holding the sheets S, a sheet feed roller 20, an inner plate 21, and an alignment roller pair 22. The sheet feed tray 19 can be freely pushed in and pulled out (inserted and removed) (front loading) from the front side of the image forming apparatus 100.

[0040] A fixing unit 23 and an ejector roller pair 24 are arranged on the upper rear side of the image forming apparatus 100. The fixing unit 23 is configured to heat and pressurize a sheet S on which a toner image has been transferred to fix the image onto the sheet S. The fixing unit 23 includes a fixing film assembly 23a and a pressure roller 23b. The clamping portion between the fixing film assembly 23a and the pressure roller 23b is called the fixing clamping portion Q. The ejector roller pair 24 has an ejector roller 24a and a roller 24b. An ejector tray 25 is formed on the upper surface of the main body of the image forming apparatus 100.

[0041] A front door 31 is disposed on the front side of the image forming apparatus 100 and is rotatably attached to the image forming apparatus 100. By opening the front door 31, a user can receive the cartridge tray 40, and by pulling the cartridge tray 40 toward the user, the processing cartridge PP can be replaced. That is, each processing cartridge PP can be inserted into and removed from the image forming apparatus 100. The image forming apparatus using this disclosure is not limited to... Figure 1B The image forming apparatus 100 shown may be, for example, an image forming apparatus having a conveyor belt configured to transport sheet S or an image forming apparatus having a processing box.

[0042] [2. Control Modes of the Image Forming Apparatus]

[0043] Figure 3This is a block diagram illustrating the schematic control mode of the main parts of the image forming apparatus 100 in the first embodiment. The control unit 200 controls the operation of the image forming apparatus 100. The control unit 200 transmits and receives various electrical information signals. The control unit 200 also processes electrical information signals input from various processing devices and sensors, as well as command signals to various processing devices. The controller 400 sends and receives various types of electrical information from the host device, and the control unit 200 controls the image forming operation of the image forming apparatus 100 as a whole according to a predetermined control program and reference table via the interface unit 300. The control unit 200 includes a CPU 155 as a central element configured to perform various arithmetic operations, RAM as a storage element, and a memory 30 such as ROM. The RAM stores sensor detection results, counter counting results, calculation results, etc., while the ROM stores control programs, data tables obtained through prior experiments, etc.

[0044] The control unit 200 is connected to the object to be controlled, sensors, counters, etc. in the image forming apparatus 100. The control unit 200 controls the transmission and reception of various electrical information signals and the driving timing of each part to control a predetermined image forming sequence. For example, in order to form a toner image on the surface of the photosensitive drum 1, the control unit 200 controls the high-voltage power supply and equipment described below. The control unit 200 controls the charging voltage application unit 71 as a charging power supply, the developing voltage application unit 72 as a developing power supply, and the exposure unit 11. Furthermore, the control unit 200 controls the primary transfer voltage application unit 73 as a primary transfer power supply and the secondary transfer voltage application unit 74 as a secondary transfer power supply to form a toner image on the sheet S. Furthermore, the control unit 200 controls the drive unit 70, the pre-exposure unit 55 (which serves as a charge elimination unit), the developing and separating mechanism 50, and the fixing unit 23. The drive unit 70 is configured to rotate various rollers, the pre-exposure unit 55 is configured to eliminate the charge on the surface of the photosensitive drum 1, and the developing and separating mechanism 50 is configured to control the contact / separation between the photosensitive drum 1 and the developing roller 3. The specific construction of the pre-exposure unit 55 will be described in detail later.

[0045] 【3. Image Formation Operations】

[0046] Next, we will refer to Figure 1B , Figure 2A and Figure 3 The operation for forming a panchromatic image is described. First, when the control unit 200 receives a work signal from the interface unit 300, the control unit 200 moves the developing and separating mechanism 50 in the front-rear direction of the image forming apparatus 100. (As follows...) Figure 2AAs shown, in the processing cartridge PP, a developing coupling 3a is disposed on the drive side of the developing roller 3, and the developing unit DP is rotatably supported around the developing coupling 3a. When the developing and separating mechanism 50 rotates the developing unit DP, the developing roller 3 and the photosensitive drum 1 abut against each other. Furthermore, the monochrome image forming operation and the panchromatic image forming operation are different in operation, and in the monochrome image forming operation, the developing and separating mechanism 50 operates such that only the fourth developing roller 3K and the fourth photosensitive drum 1K abut against each other.

[0047] The first processing box PPY's photosensitive drum 1Y, the second processing box PPM's photosensitive drum 1M, the third processing box PPC's photosensitive drum 1C, and the fourth processing box PPK's photosensitive drum 1K are... Figure 1B The intermediate transfer belt 13 is driven to rotate clockwise at a predetermined speed in a counter-clockwise direction. Synchronously with this drive, in each processing cartridge PP, the charging roller 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential of a predetermined polarity at predetermined intervals. In the first embodiment, the predetermined polarity (normal polarity) is defined as the negative electrode. Therefore, the normal polarity of the toner is the negative electrode.

[0048] Next, the exposure unit 11 exposes the surface of the photosensitive drum 1 to light from a light source according to the image signals of each color. Thus, an electrostatic latent image corresponding to the corresponding color image signal is formed on the surface of the photosensitive drum 1. The developing roller 3 develops the electrostatic latent image into a toner image. Through an image forming operation, a yellow toner image corresponding to the Y color component of the panchromatic image is formed on the photosensitive drum 1Y at the first station. At the primary transfer clamping section T1, the toner image is transferred once onto the intermediate transfer belt 13. Thereafter, in the same manner as the first station, the magenta, cyan, and black toner images from the second, third, and fourth stations are sequentially transferred once onto the intermediate transfer belt 13 at the primary transfer clamping section T1. In this way, four colors of toner images are superimposed and transferred on the surface of the intermediate transfer belt 13 to form an unfixed panchromatic toner image.

[0049] Toner residue remaining on the surface of the photosensitive drum 1 that was not transferred to the intermediate transfer belt 13 during the primary transfer clamping section T1 is collected by a cleaning device (not shown), which is a cleaning unit that rests against the photosensitive drum 1. Meanwhile, the sheet feed roller 20 is driven at a predetermined time. Therefore, the sheet feed roller 20 cooperates with the inner plate 21 to separate and feed a sheet S stacked on the sheet feed tray 19, and the alignment roller pair 22 introduces the sheet S into the secondary transfer clamping section T2 at a predetermined time. At this time, while the secondary transfer clamping section T2 is clamping and conveying the sheet S, the toner images of the four colors superimposed on the intermediate transfer belt 13 are collectively transferred to the surface of the sheet S. The sheet S is then separated from the surface of the intermediate transfer belt 13, conveyed along the conveying path, and introduced into the fixing unit 23. The unfixed toner image transferred onto the sheet S is heated and pressurized by the fixing unit 23 at the fixing clamping part Q, and then fixed onto the sheet S.

[0050] The sheet S passes through the fixing unit 23 and is discharged onto the discharge tray 25 by the discharge roller pair 24 as a pancolor image forming product. The toner remaining on the surface of the intermediate transfer belt 13 after the sheet S is separated (secondary transfer residual toner) is removed by the cleaning unit 26 arranged on the intermediate transfer belt 13. When the image forming operation (job) is completed, the developing and separating mechanism 50 operates to separate the photosensitive drum 1 of the drum unit OP from the developing roller 3 of the developing unit DP, and stops the driving of each voltage application unit, thereby completing image forming.

[0051] 4. Drum Shadow

[0052] The surface potential formed on the surface of the photosensitive drum 1 is changed by the image forming process. Specifically, the surface potential of the photosensitive drum 1 is changed by the latent image process, the charging process, and the transfer process. The surface potential formed on the photosensitive drum 1 is affected by the discharge magnitude in the aforementioned discharge processes, such as the charging process and the transfer process, as well as the surface potential formed on the photosensitive drum 1 before receiving the discharge. More specifically, in order to form an image on the sheet S, when an image forming area (bright area potential: Vl area) in which a toner image is formed and a non-image forming area (dark area potential: Vd area) in which a toner image is not formed are formed on the surface of the photosensitive drum 1, the surface states of the two areas differ after transfer. If discharge occurs by the charging roller 2 in this state, the surface potential after charging may differ. Since the transfer voltage applied to the primary transfer roller 17 during image forming has a positive polarity opposite to the polarity of the surface potential formed on the photosensitive drum 1, a positive residual charge is generated on the surface of the photosensitive drum 1. The amount of positive residual charge varies depending on the surface potential of the photosensitive drum 1. Therefore, even if the same surface potential can be formed in the area that is the image forming area and the area that is not the image forming area through discharge caused by charging, the absolute value of the surface potential may still decrease due to the influence of residual charge when latent image processing or development is performed after a period of time.

[0053] Once a toner image is formed on the outer peripheral surface of the photosensitive drum 1, the potential of the toner image remains on the outer peripheral surface of the photosensitive drum 1 after the toner image is transferred. Therefore, a ghost image (afterimage) of the previously formed toner image is generated as a historical image in the next image formed on the outer peripheral surface of the photosensitive drum 1. This phenomenon is called drum ghosting. Specifically, the potential difference between the image-forming area and the non-image-forming area of ​​the historical image remaining on the outer peripheral surface of the photosensitive drum 1 after the image is formed in the first revolution of the photosensitive drum still exists even during the image formation process of the second revolution, and the density of the historical image appears in the second revolution image output on the sheet S.

[0054] The process of generating drum ghosting is considered as follows. Each process of charging, latent image formation, development, and transfer of the photosensitive drum 1 in one rotation is defined as one cycle of image formation. In this case, after the image formation process of the first cycle is completed, a potential difference remains on the surface of the photosensitive drum 1. Even if the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 in the second cycle, the potential difference in the first cycle will not completely disappear. Therefore, the surface of the photosensitive drum 1 is not uniformly charged, and the residual potential difference after charging will not disappear even after exposure. Therefore, because the effect of the potential difference in the first cycle still exists, the potential of the electrostatic latent image after exposure of the photosensitive drum 1 in the second cycle is not uniform. When developing the electrostatic latent image on the outer peripheral surface of the photosensitive drum 1 in the second cycle, the amount of toner adhering to the non-image formation area varies depending on the residual potential difference in the first cycle. That is, in the toner image of the second cycle, which should be uniform, portions with a large amount of toner and portions with a small amount of toner are generated due to the effect of the potential difference of the electrostatic latent image in the first cycle. Therefore, the toner image transferred onto the intermediate transfer belt 13 will also gradually change depending on the amount of toner, and the final image formed on the sheet S will also gradually change into dark and light areas. The mechanism of ghosting will be described in detail later.

[0055] (Pre-exposure unit)

[0056] Therefore, in the first embodiment, a pre-exposure unit 55 is arranged to cancel the potential difference generated in the photosensitive drum 1 and suppress the generation of drum ghosting. The pre-exposure unit 55 is an illumination unit that will be described later. The pre-exposure unit 55 is used to expose the surface of the photosensitive drum 1 before the photosensitive drum 1 passes through the primary transfer clamp T1 and reaches the contact portion with the charging roller 2. Even if the charge state on the surface of the image forming area and the non-image forming area of ​​the photosensitive drum 1 is different, the pre-exposure unit 55 resets the charge and uniformly eliminates the charge from the surface of the photosensitive drum 1. Since the charge is uniformly eliminated from the surface of the photosensitive drum 1, the potential of the photosensitive drum 1 is uniformly formed by the charging roller 2. Therefore, the occurrence of drum ghosting generated in the photosensitive drum 1 can be suppressed.

[0057] (Drum Shadow and the Mechanism of Drum Shadow Appearance)

[0058] The image formed under the actual condition of drum ghosting will be described. Here, the length of the outer perimeter of the photosensitive drum 1 is defined as L. Figure 4A This is a view showing the image to be formed on the sheet S (the image to be output if there is no ghosting). Figure 4B This is a view showing an image formed on sheet S when ghosting occurs. When the photosensitive drum 1 is installed in the image forming apparatus 100 and the surface potential of the photosensitive drum 1 is adjusted, the output is as follows: Figure 4A When the image shown is displayed, the following may occur: Figure 4BThe image defect shown. (As shown) Figure 4A As shown, multiple solid black blocks 500 are formed on the leading edge LE side of sheet S. In this case, as... Figure 4B As shown, multiple ghosting images 500g are formed at a distance L from the leading edge of multiple solid black blocks 500 on the trailing edge TE side facing the sheet S, resulting in image defects. The distance L corresponds to the circumference of the photosensitive drum 1. Multiple ghosting images 500g are formed after the photosensitive drum 1 rotates once. Image defects such as ghosting images 500g become particularly noticeable in high-temperature and humid environments. More specifically, when the portion of the solid black block 500 printed in the image forming area again facilitates image formation, a change in density occurs, and a predetermined surface potential is not formed on the photosensitive drum 1.

[0059] The mechanism of drum ghosting in the image will be described in detail below. As mentioned above, when the exposed and unexposed portions of the photosensitive drum 1 are charged in the next charging step, drum ghosting may occur due to the potential difference. In the exposed portion of the previous step, a potential difference is generated in the next charging step due to the influence of residual charge, etc. This situation is as follows: Figure 4C As shown. Figure 4C The relationship between the surface potential of the photosensitive drum 1 and its position in the longitudinal direction is shown. Figure 4C The surface potential of the photosensitive drum 1 is shown when the exposed portion (previously exposed portion (previously image portion)) and the unexposed portion (previously unexposed portion (previously non-image portion)) are recharged and reexposed in the direction of rotation axis of the photosensitive drum 1. Figure 4C In the diagram, the horizontal axis represents the position of the photosensitive drum 1 in the longitudinal direction (rotation axis direction), while the vertical axis represents the surface potential (-V) of the photosensitive drum 1. The dashed line represents the potential after charging, while the solid line represents the potential after exposure.

[0060] like Figure 4C As shown, when exposure is performed again in the exposure step, after the exposure, there is a potential difference between the exposed portion (previous image portion "y") and the unexposed portion (previous non-image portion "x") in the previous step. Figure 4C The potential difference between the previously exposed image portion "y" before the photosensitive drum 1 rotates one revolution and the previously unexposed non-image portion "x" before the photosensitive drum 1 rotates one revolution remains on the photosensitive drum 1 even when the next image is formed. When the potential difference (the "z" portion) increases, drum ghosting occurs in the final image, which is a density difference.

[0061] 5. Handling the relationship between boxes and box trays

[0062] Next, we will refer to Figure 2A , Figure 2B , Figure 5A and Figure 5B This describes the state of the box tray 40 and the processing box PP installed onto the box tray 40. Figure 5A In this context, the suffix "R" indicates a component on the right side (drive side). Figure 5B In the diagram, the suffix letter L indicates a component on the left side (non-driving side). The cartridge tray 40 is a movable component configured to move between an internal and external position within the image forming apparatus 100 while holding the processing cartridge PP, and the cartridge tray 40 facilitates the replacement of the processing cartridge PP. The cartridge tray 40 is configured to allow the processing cartridge PP to be detachably mounted to the cartridge tray 40.

[0063] Figure 5A This is a perspective view taken from the upper right side of the tray 40 on which the processing box PP is mounted. Figure 5B This is a perspective view taken from the lower left side of the tray 40 on which the processing box PP is mounted. Since the processing boxes PP are mounted in the same state according to their respective colors, one processing box PP will be described here. With the processing box PP mounted on the tray 40, the drum flange 1a contacts the box engagement portion 41Ra of the tray 40. A force generated in the direction of gravity, either by its own weight or downward pressure, is applied to the processing box PP to position it relative to the tray 40. The box engagement portion 41Ra of the tray 40 is formed, for example, in a V-shape and is designed with an optimal angle to prevent the processing box PP from moving during image formation. Specifically, the slope on the front side is 65° and the slope on the rear side is 45° relative to the pull-out direction of the tray 40. Furthermore, the recessed portion 1d of the processing box PP fits onto the engagement bosses 42a (43a, 44a, 45a) of the tray 40 and serves to prevent the processing box PP from rotating. Specifically, the recessed portion 1d of the processing cartridge PPK is fitted onto the engaging boss 42a of the cartridge tray 40. The recessed portion 1d of the processing cartridge PPC is fitted onto the engaging boss 43a of the cartridge tray 40. The recessed portion 1d of the processing cartridge PPM is fitted onto the engaging boss 44a of the cartridge tray 40. The recessed portion 1d of the processing cartridge PPY is fitted onto the engaging boss 45a of the cartridge tray 40. Although this is a description of the driving side of the cartridge tray 40, the processing cartridge PP is also brought into contact with the cartridge tray 40 on the non-driving side to maintain the posture of the processing cartridge PP. The cartridge tray 40 is positioned in the image forming apparatus 100 while holding the processing cartridge PP.

[0064] The tray 40 has a pair of metal tray side plates 41R and 41L, each having a box engagement portion 41Ra and 41La (not shown) corresponding to a processing box PP. The tray 40 includes five resin connecting members disposed between the tray side plates 41L and 41R. Each connecting member includes a first connecting member 42 having an engagement boss 42a configured to engage with a processing box PPK at a fourth station. Hereinafter, the connecting members, from front to back, include: a second connecting member 43 having an engagement boss 43a at a third station; a third connecting member 44 having an engagement boss 44a at a second station; a fourth connecting member 45 having an engagement boss 45a at a first station; and a fifth connecting member 46. The second connecting member 43, the third connecting member 44, and the fourth connecting member 45 have the same shape. The tray side plates 41 (41L, 41R) have a shape that extends outward from the upper part compared to the lower part. Between the tray side plates 41L and 41R, the upper part is wide, the middle part is sloped, and the lower part is narrow. The lower part of the tray side plates 41L and 41R is provided with a positioning part between the box joint 41Ra of the box tray 40 and the connecting member. The upper part of the tray side plates 41L and 41R is used to stop the rotation of the first connecting member 42 to the fourth connecting member 45 near the engaging bosses 42a to 45a. With this configuration, the width of the box tray 40 in the left-right direction can be reduced without compromising the insertion and removal of the processing box PP, thereby contributing to the miniaturization of the image forming apparatus 100. The lower side of the tray side plates 41L and 41R is L-shaped to ensure strength. The tray side plates 41L and 41R are fastened to their respective connecting members by screws. However, this embodiment is not limited to screws. This embodiment can use heat riveting, etc. The first connecting part 42 and the fifth connecting part 46 can be fastened to the tray side plates 41L and 41R, and the second connecting part 43, the third connecting part 44 and the fourth connecting part 45 can be unfastened to each other.

[0065] 6. Pre-exposure unit

[0066] Next, the pre-exposure unit 55, which is the charge elimination unit in the first embodiment, will be described. Figure 5B As shown, four light guides 57 are disposed on the lower part of the tray 40 and are arranged in the first connecting member 42, the second connecting member 43, the third connecting member 44, and the fourth connecting member 45, to pass through the tray guide member 47L. The tray guide member 47R is disposed on the drive side. In the first embodiment, cylindrical light guides 57 with a diameter of 4 mm are used.

[0067] Figure 6This is a view showing the construction of the pre-exposure unit 55. The pre-exposure unit 55 has a light-emitting portion 58 serving as a light source and a light guide 57, wherein the light guide 57 is provided with the light-emitting portion 58 at one end (non-driving side) and guides the light emitted from the light-emitting portion 58 in the direction of rotation of the photosensitive drum 1. After the toner image is transferred to the intermediate transfer belt 13 by the primary transfer roller 17, the pre-exposure unit 55 illuminates the photosensitive drum 1 with light. The light guide 57 has a plurality of tabs 57a for colliding with ejector pins during molding. The plurality of tabs 57a also serve to position the light guide relative to the cartridge tray 40 and prevent the light guide 57 from being attached in the opposite direction. The light guide 57 has ribs 57b, which include inclined surfaces such that the phase in the rotational direction can be determined when the light guide 57 is attached to the cartridge tray 40. Light emitted from the light-emitting unit 58 enters the light guide 57 through a sub-light guide 56 disposed on the main body side. The light-emitting unit 58 is a light-emitting unit such as an LED disposed on the non-driving side of the image forming apparatus 100. The light is uniformly scattered by Fresnel portions 57d having a Fresnel shape formed inside the light guide 57. By irradiating the surface of the photosensitive drum 1 with the light scattered by the Fresnel portions 57d, the surface potential formed on the surface of the photosensitive drum 1 before charging by the charging roller 2 is discharged to a predetermined surface potential and stabilized.

[0068] The Fresnel portion 57d is shaped as follows: a shallow hill-shaped section with an apex angle of approximately 114 degrees continues at a pitch of approximately 0.7 mm while being inclined at 80 degrees relative to the rotation axis of the photosensitive drum 1, and is arranged on a surface opposite to the position facing the photosensitive drum 1. With the processing cartridge PP located in the cartridge tray 40, the gap between the surface of the light guide 57 and the surface of the photosensitive drum 1 is approximately 5.6 mm. The light guide 57 is formed of a transparent material such as acrylic resin, but any transparent material can also be used. Although the light input side is the non-driving side in the first embodiment, it can also be the driving side. In the case of insufficient light, light-emitting portions 58 can be provided at both ends. The light-emitting portions 58 are not limited to LEDs and can also be elements such as laser diodes.

[0069] The amount of light in the light guide 57 is strongest on the light input side. As light is scattered by the Fresnel portion 57d towards the other end (the non-input side) opposite to the light input side and irradiates the photosensitive drum 1, the light becomes weaker closer to the other end. Therefore, in order to uniformly irradiate light in the longitudinal direction, the width of the Fresnel portion 57d differs between the light input side and the opposite side of the light guide 57. In the first embodiment, the width of the Fresnel portion 57d changes from approximately 0.8 mm on the light input side to approximately 1.7 mm on the opposite side.

[0070] However, the thick light guide 57 makes it difficult to completely prevent bubbles generated during molding. If light in the light guide 57 hits a bubble, diffuse reflection occurs. Specifically, on the light input side with high light intensity, light is easily affected by diffuse reflection caused by bubbles, and the amount of light to be irradiated increases locally, causing uneven charge elimination. To solve this problem, the first embodiment has the following structure. That is, each of the first connecting member 42, the second connecting member 43, the third connecting member 44, and the fourth connecting member 45, which are configured to hold the light guide 57, is provided with a blocking member 48 configured to reduce the light emitted from the light guide 57. Figure 7A The blocking member 48 reduces the amount of irradiated light at the portion where the charge elimination amount locally increases. That is, the blocking member 48 serves as a shielding member, which is configured to shield the irradiated light from the photosensitive drum 1 to reduce the amount of irradiated light at the portion where the charge elimination amount locally increases. The blocking member 48 is disposed on the cartridge tray 40. In a first embodiment, the blocking member 48 is integrated with each of the first connecting member 42, the second connecting member 43, the third connecting member 44, and the fourth connecting member 45. However, the blocking member 48 may also be a separate component from each of them.

[0071] (Blocking component)

[0072] Figure 7A and Figure 7B This is a view showing the blocking member 48 disposed on the first connecting member 42 of the fourth station. Figure 7A and Figure 7B The diagram shows the construction of the fourth station, but the other stations, from the first to the third, have the same construction. The blocking member 48 is formed of an opaque material and is configured to irradiate the photosensitive drum 1 with light from the portion where the blocking member 48 is not located. That is, by changing the shape of the blocking member 48, the amount of light blocked from irradiating the photosensitive drum 1 can be adjusted. In other words, depending on the shape of the blocking member 48, the amount of light blocked from irradiating from the pre-exposure unit 55 can be changed in the direction of rotation of the photosensitive drum 1. In the first embodiment, the blocking member 48 is in the vertical direction (e.g., Figure 7A The blocking member 48 extends along the orthogonal direction indicated by the double-headed arrow (hereinafter referred to as line Lfd), thereby adjusting the amount of irradiated light. This vertical direction is the first direction perpendicular to the dashed line Lfd (hereinafter referred to as line Lfd) connecting the center of the Fresnel portion 57d and the center of the photosensitive drum 1. That is, in the vertical direction orthogonal to line Lfd connecting the light guide 57 and the photosensitive drum 1, the length of the blocking member 48 extending towards line Lfd increases with increasing proximity to the light-emitting portion 58. Furthermore, as... Figure 7B As shown, the blocking component 48 can be adjusted in the horizontal direction (e.g.) Figure 7BThe amount of light blocked is adjusted by the length (thickness) in the direction indicated by the double-headed arrow (the horizontal direction is a second direction parallel to the line Lfd). That is, in the horizontal direction parallel to the line Lfd, the length of the blocking member 48 can be made longer as it gets closer to the light-emitting unit 58. Furthermore, the amount of light irradiated can be adjusted by changing its length in the vertical direction and its length in the horizontal direction relative to the line Lfd. As described above, the blocking member 48 is arranged such that the amount of light reduction is different between the light input side and the other end opposite the light input side at the center of the photosensitive drum 1 in the rotation axis direction. Specifically, the closer the blocking member 48 is to the light-emitting unit 58 in the rotation axis direction of the photosensitive drum 1, the greater the amount of light blocked from the pre-exposure unit 55.

[0073] (First Embodiment and Comparative Example)

[0074] Figure 8 This is a graph showing the amount of light incident on the photosensitive drum 1, as measured using a light intensity measurement tool. Figure 8 In the diagram, the horizontal axis represents the position of the light guide 57 in the longitudinal direction, where "0" represents the non-driving side (light source side, one end), and the position increases towards the driving side (non-light source side and the other end) as it moves to the right. The vertical axis represents the amount of light [V] illuminating the photosensitive drum 1. The amount of light illuminating the photosensitive drum 1 from the light-emitting part 58 through the light guide 57 is measured using a light quantity measurement tool, and the changes in light quantity in the longitudinal direction are compared. The light quantity measurement tool uses a Si photodiode S6775 (manufactured by Hamamatsu Photonics Co., Ltd.) in the light receiving part to convert light into voltage and evaluate the voltage. The comparative example shows the amount of irradiated light without the first embodiment (without the blocking member 48), while the first embodiment shows the amount of irradiated light with the blocking member 48. In the comparative example (dashed line), the amount of irradiated light is higher in about 1 / 3 of the area on the light source side, while at some locations, the amount of irradiated light is about twice as high as the amount of irradiated light at the other end (non-light source side). On the other hand, in the first embodiment (solid line), the amount of light is substantially constant in the longitudinal direction of the light guide 57.

[0075] Here, the specific construction of the blocking member 48 of the first embodiment will be described. Figure 9A , Figure 9B Figure 9C This is a view showing the light guide 57 and the blocking member 48 when viewed from the side of the photosensitive drum 1. Figure 9A It is shown Figure 8 A view showing the construction of the light guide 57 according to the first embodiment. In the first embodiment, as... Figure 9AAs shown, the blocking member 48 extends such that the distance α1 in the direction perpendicular to the line Lfd is 1 mm on the light input side where the light-emitting part 58 is disposed, thereby reducing the amount of irradiated light. On the other hand, in the blocking member 48, the distance α2 is set to 1.3 mm for other areas where the blocking effect is reduced. For example, when the blocking member 48 is divided into three regions (divided into three parts) along the rotation axis direction of the photosensitive drum 1, the blocking member 48 is configured such that the reduction in the amount of light in at least one region is different from the reduction in other regions. As described above, by disposing of the blocking member 48 in the first connecting member 42 and making the extension degree of the blocking member 48 different in the longitudinal direction, the amount of irradiated light in the longitudinal direction can be made uniform. However, this disclosure is not limited to this. When the amount of irradiated light on the non-light source side increases instead of the amount of irradiated light on the light source side, the distance between the line Lfd and the blocking member 48 on the non-light source side can be reduced.

[0076] Furthermore, in the comparative example, the amount of illumination is higher in approximately one-third of the area on the light input side, while the amount of illumination is more uniform in the other parts. Therefore, although the shape of the blocking member 48 has been based on... Figure 9A The shape may be changed, but this disclosure is not limited thereto. Based on the distribution of the amount of irradiated light in the longitudinal direction in the absence of the blocking member 48, the shape of the blocking member 48 may, for example, be based on... Figure 9B or Figure 9C The shape change shown is to make the light intensity uniform. Here, Figure 9B and Figure 9C This is a view illustrating another embodiment of the blocking member 48. More specifically, as Figure 9B and Figure 9C As shown, the blocking member 48 can be configured such that the distance between the line Lfd and the blocking member 48 gradually increases from the light input side (light source side) to a predetermined position, while maintaining a constant distance from the predetermined position to the non-light source side. Furthermore, as... Figure 9B As shown, the distance between line Lfd and blocking component 48 can increase linearly, or as... Figure 9C As shown, the distance can be curved.

[0077] In the first embodiment, the light guide 57 is disposed in the housing tray 40. However, this disclosure is not limited thereto. Figure 10A This is a view showing another embodiment of the location where the light guide 57 is disposed. For example, as... Figure 10A As shown, the light guide 57 can be disposed in the processing box PP. Therefore, the blocking member 48 can also be disposed in the processing box PP.

[0078] In the first embodiment, the light guide 57 has a cylindrical shape. However, this disclosure is not limited thereto. Figure 10B and Figure 10CThis is a view showing another embodiment of the shape of the light guide 57. For example, as... Figure 10B As shown, the light guide 57 can have a rectangular shape or a quadrangular prism shape in a cross-section perpendicular to the rotation axis of the photosensitive drum 1. For example... Figure 10C As shown, the light guide 57 can have a polygonal shape and a polygonal prism shape in a cross-section perpendicular to the rotation axis of the photosensitive drum 1. Thus, the light guide 57 can have, for example, a circular, rectangular, or polygonal shape in a cross-section perpendicular to the rotation axis of the photosensitive drum 1.

[0079] In the first embodiment, the light guide 57 has a flat end shape at both ends. However, this disclosure is not limited to this. Although the light input side is preferably a flat surface, a triangular pyramid or cone can also be used on the non-light input side to make light more easily reflected, thereby increasing the reflectivity of the light input. A cap-shaped blocking material configured to block light can be disposed at the end of the light guide 57 on the non-incident light side.

[0080] The following will describe a modified example of the blocking component of the first embodiment. Figure 11A and Figure 11B This is a view showing a modification of the blocking member 48. In the first embodiment, the blocking member 48 is arranged only on the upper part of the light guide 57. However, this disclosure is not limited to this. For example, as Figure 11A As shown, the blocking member 48a can be disposed at the lower part of the light guide 57. (As indicated...) Figure 11B As shown, the first blocking member 48b and the second blocking member 48c can be respectively disposed on the upper and lower parts of the light guide 57. That is, the second blocking member 48c can be disposed on the side opposite to the first blocking member 48b relative to the line Lfd. In either case, by changing the length of the blocking member 48a, the blocking member 48b, or the blocking member 48c in the direction orthogonal to the line Lfd or in the horizontal direction, the amount of light incident from the light-emitting part 58 onto the photosensitive drum 1 can be adjusted.

[0081] Furthermore, in the first embodiment, the light guide 57 is defined as the first light guide, and a sub-light guide 56, which serves as the second light guide, is disposed between the light-emitting portion 58, which serves as the light source, and the light guide 57 along the axial direction. The sub-light guide 56 is configured to introduce light into the first light guide. However, light from the light-emitting portion 58 can be directly incident on the light guide 57 without the need for the sub-light guide 56.

[0082] As described above, according to the first embodiment, in the configuration where the photoconductor is disposed in the pre-exposure unit, uneven charge in the longitudinal direction of the photosensitive drum can be suppressed and eliminated.

[0083] [Blocking Component]

[0084] In the configuration of the image forming apparatus 100 used in the second embodiment, components and their descriptions that are identical to those in the first embodiment, indicated by the same reference numerals, are omitted. In the first embodiment, the blocking member 48 is made of a light-nontransmitting component. In the first embodiment, the blocking member 48 is configured such that the amount of charge removal on the photosensitive drum 1 is uniform in the longitudinal direction by changing the shape of the blocking member 48.

[0085] Figure 12 This is a view used to illustrate the blocking member of the second embodiment. In the second embodiment, as... Figure 12 As shown, a filter 49, configured to transmit and attenuate light, is used as a blocking component. The filter 49 is configured such that light irradiated from the light guide 57 passes through the filter 49 and reaches the photosensitive drum 1. By placing the filter 49 in a region where the amount of irradiated light from the light-emitting section 58 is high, the amount of irradiated light can be reduced regardless of the positional accuracy of the blocking component.

[0086] Figure 13A and 13B This is a view illustrating an example of the construction of the filter 49 according to the second embodiment. Figure 13A As shown, in the longitudinal direction of the light guide 57, filters 49 with different transmittances (49a, 49b, 49c) can be arranged by dividing the filters 49 according to the amount of light emitted from the light-emitting part 58 to the photosensitive drum 1. More specifically, as Figure 13A As shown, filters 49a (transmittance τ1), 49b (transmittance τ2), and 49c (transmittance τ3) are arranged in order from the light source side (τ3>τ2>τ1). Here, filters 49a, 49b, and 49c are arranged such that the transmittance increases with increasing distance from the light source side. As described above, Figure 13A The blocking component shown is a filter 49 that transmits light irradiated from the pre-exposure unit 55, and has multiple filters 49a, 49b and 49c, which are arranged along the rotation axis of the photosensitive drum 1 and have different transmittances.

[0087] In addition, such as Figure 13B As shown, a filter 49d with different transmittance distribution characteristics depending on the amount of light irradiated from the light-emitting part 58 to the photosensitive drum 1 can be used. Specifically, the filter 49d is arranged along the longitudinal direction of the light guide 57. The filter 49d has the characteristic that the transmittance increases with distance from the light source. As described above, Figure 13B The blocking component shown has a transmittance that varies along the rotation axis of the photosensitive drum 1, and has a filter 49d that transmits light incident from the pre-exposure unit 55. Note that it can be positioned corresponding to the location where the light guide 57 is disposed (cassette 40 or processing cassette PP). Figure 13AFilters 49a, 49b and 49c and Figure 13B The filter 49d.

[0088] As described above, according to the second embodiment, in the configuration where the photoconductor 57 is disposed in the pre-exposure unit 55, the unevenness of charge elimination in the longitudinal direction of the photosensitive drum 1 can be suppressed.

[0089] According to this disclosure, in the configuration where the photoconductor 57 is disposed in the pre-exposure unit 55, uneven charge in the longitudinal direction of the photosensitive drum 1 can be suppressed and eliminated.

[0090] Although this disclosure has been described with reference to exemplary embodiments, it should be understood that this disclosure is not limited to the disclosed exemplary embodiments. The appended claims should be interpreted in the broadest possible sense to cover all such variations and equivalent structures and functions.

Claims

1. An image forming apparatus, the image forming apparatus comprising: An image carrier component, wherein the image carrier component is configured to be rotatable; A charging component configured to charge the surface of the image-bearing component; An exposure unit configured to form an electrostatic latent image on the surface of the image-bearing member charged by the charging member; A developing unit configured to develop the electrostatic latent image formed by the exposure unit with a toner to form a toner image; A transfer component configured to transfer the toner image formed by the developing component on the surface of the image carrying component to a transfer receiving component; An illumination unit having a light source disposed at one end of the illumination unit in the direction of rotation axis of the image carrier and a light guide configured to guide light emitted from the light source along the direction of rotation axis, wherein the illumination unit is configured to illuminate the surface of the image carrier with the light after the transfer member transfers the toner image to the transfer receiving member; and A blocking component, configured to block light incident from the irradiation unit along the direction of the rotation axis. The blocking member is configured such that it blocks different amounts of light incident from the irradiation unit in the direction of the rotation axis. The light guide includes a first part close to the light source, a second part away from the light source in the rotation axis direction of the image carrier, and a Fresnel part for dispersing light for illuminating the image carrier. In the direction of rotation axis, the amount of light blocked by the blocking member from the irradiation unit is greater in the first part than in the second part, and The width of the second part, in the longitudinal direction of the light guide perpendicular to the Fresnel portion, is wider than the width of the first part, in the longitudinal direction of the light guide perpendicular to the Fresnel portion.

2. The image forming apparatus according to claim 1, further comprising: A cartridge having the image carrying component, the charging component, and the developing component; as well as A tray that holds the box and can be inserted and removed relative to the image forming apparatus while holding the box. The blocking component is disposed on the tray.

3. The image forming apparatus according to claim 1, wherein, In the direction of the rotation axis, the amount of light blocked by the blocking member at one end of the irradiation unit is greater than the amount of light blocked by the blocking member at the center of the irradiation unit.

4. The image forming apparatus according to claim 3, wherein, In the direction of the rotation axis, the amount of light blocked by the blocking member from the irradiation unit increases with the proximity to the light source.

5. The image forming apparatus according to claim 3, wherein, The blocking member is configured such that its length in a second direction parallel to the dashed line connecting the light guide and the image carrier increases with increasing proximity to the light source.

6. The image forming apparatus according to claim 3, wherein, The blocking component includes multiple filters that transmit light irradiated from the irradiation unit and are arranged along the rotation axis and have different transmittance.

7. The image forming apparatus according to claim 6, wherein, The blocking component is configured such that the light transmittance increases with distance from the light source in the direction of the rotation axis.

8. The image forming apparatus according to claim 1, wherein, In the direction of the rotation axis, the amount of light blocked by the blocking member from the irradiation unit increases with the proximity to the light source.

9. The image forming apparatus according to claim 1, wherein, The blocking member is configured such that its length in a second direction parallel to the dashed line connecting the light guide and the image carrier increases with increasing proximity to the light source.

10. The image forming apparatus of claim 1, further comprising a cartridge having the image carrying member, the charging member, and the developing member, and capable of being inserted into and removed relative to the image forming apparatus. in, The blocking component is mounted on the box.

11. The image forming apparatus according to claim 1, wherein, The blocking member is configured such that its length in a first direction orthogonal to the dashed line connecting the light guide and the image carrier increases with increasing proximity to the light source.

12. The image forming apparatus according to claim 11, wherein, The blocking component is a first blocking component, and the image forming apparatus further includes a second blocking component, which is disposed on the side opposite to the first blocking component relative to the dotted line.

13. The image forming apparatus according to claim 1, wherein, The light guide has a circular, rectangular, or polygonal shape on a cross section orthogonal to the direction of the rotation axis.

14. An image forming apparatus, the image forming apparatus comprising: An image carrier component, wherein the image carrier component is configured to be rotatable; A charging component configured to charge the surface of the image-bearing component; An exposure unit configured to form an electrostatic latent image on the surface of the image-bearing member charged by the charging member; A developing unit configured to develop the electrostatic latent image formed by the exposure unit with a toner to form a toner image; A transfer component configured to transfer the toner image formed by the developing component on the surface of the image carrying component to a transfer receiving component; An illumination unit having a light source disposed at one end of the illumination unit in the direction of rotation axis of the image carrier and a light guide configured to guide light emitted from the light source along the direction of rotation axis, wherein the illumination unit is configured to illuminate the surface of the image carrier with light after the transfer member transfers the toner image to the transfer receiving member; and A blocking component, configured to block light incident from the irradiation unit. In a first direction orthogonal to the dashed line connecting the light guide and the image-carrying component, the length of the blocking component at one end of the irradiation unit towards the dashed line is longer than the length of the blocking component at the center of the irradiation unit towards the dashed line along the rotation axis. The light guide includes a first part close to the light source, a second part away from the light source in the rotation axis direction of the image carrier, and a Fresnel part for dispersing light for illuminating the image carrier. In the direction of rotation axis, the amount of light blocked by the blocking member from the irradiation unit is greater in the first part than in the second part, and The width of the second part, in the longitudinal direction of the light guide perpendicular to the Fresnel portion, is wider than the width of the first part, in the longitudinal direction of the light guide perpendicular to the Fresnel portion.

Images