Image forming apparatus

Abstract

To allow a user to easily check dirt on a surface of an image carrier.SOLUTION: An image forming apparatus comprises: a rotating image carrier; a unit that can take a first state for allowing a part of a surface of the image carrier to be exposed to the outside of the image forming apparatus, and a second state in which the surface of the image carrier is not exposed to the outside of the image forming apparatus; a driving source that drives the image carrier; and control means that controls the driving source. The control means can execute a mode for causing the driving source to rotate the image carrier when the unit is in the first state.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that forms an image on a recording material. [Background technology]

[0002] In an electrophotographic image forming apparatus, when an opening / closing member on the exterior of the apparatus is opened to replace a cartridge or clear a jam, the surface of the photosensitive drum may be left with the user's finger, and dirt or dust from the surrounding area may adhere to the surface of the photosensitive drum. If dirt adheres to the surface of the photosensitive drum, toner may accumulate in the dirt-adhered area, resulting in poor image quality.

[0003] Patent Document 1 describes a method in which a photosensitive drum and an intermediate transfer belt are rotated idly with their peripheral speeds different from each other, and are polished against each other to remove foreign matter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-155447 Summary of the Invention [Problem to be solved by the invention]

[0005] It has been desired that users be able to visually check for dirt on the photosensitive drum or intermediate transfer belt, which are image carriers, but even if the image carrier is exposed by opening an opening / closing member or removing a process cartridge, the user can only see a part of the entire surface of the image carrier.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that allows easy confirmation of stains on the surface of an image carrier. [Means for solving the problem]

[0007] One aspect of the present invention is an image forming apparatus comprising: a rotating image carrier; a unit that can take a first state in which a portion of the surface of the image carrier is allowed to be exposed outside the image forming apparatus; and a second state in which the surface of the image carrier is not exposed outside the image forming apparatus; a drive source that drives the image carrier; and a control means that controls the drive source, wherein the control means is capable of executing a mode in which the image carrier is rotated by the drive source when the unit is in the first state. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an image forming apparatus in which it is possible to easily check for dirt on the surface of the image carrier. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of an image forming apparatus according to a first embodiment. [Figure 2] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Figure 3] FIG. 2 is a block diagram relating to a circuit board according to the first embodiment. [Figure 4] 3A to 3C are explanatory views of a rear cover and a transfer unit according to the first embodiment. [Figure 5] 3A to 3D are explanatory views of a rear cover and a transfer unit according to the first embodiment. [Figure 6] 5A to 5D are explanatory views relating to attachment and detachment of a process unit according to the first embodiment. [Figure 7] 5A to 5D are explanatory views relating to attachment and detachment of a process unit according to the first embodiment. [Figure 8] 1A to 1C are explanatory diagrams of stains and toner clumps on a photosensitive drum. [Figure 9] Illustration of white spots and missing letters (a, b). [Figure 10] FIG. 4 is a sequence diagram of a manual drive mode according to the first embodiment. [Figure 11] FIG. 10 is a sequence diagram of a manual drive mode according to the second embodiment. [Figure 12] 11A and 11B are diagrams showing the relationship between the surface potential of a photosensitive drum and the potential of a process member according to the third embodiment. [Figure 13] FIG. 10 is a schematic view of an image forming apparatus according to a fourth embodiment. [Figure 14] 10A and 10B are diagrams showing the relationship between the surface potential of a photosensitive drum and the potential of a process member according to the fourth embodiment. [Figure 15] FIG. 10 is a schematic diagram of an image forming apparatus according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] First Embodiment Fig. 1 is a perspective view showing an image forming apparatus 1 according to a first embodiment. Fig. 2 is a cross-sectional view of the image forming apparatus 1. The image forming apparatus 1 is a monochrome printer that forms an image on a recording material based on image information input from an external device. The recording material includes a variety of sheet materials made of different materials, such as paper such as plain paper and cardboard, plastic film such as sheets for overhead projectors, sheets of special shapes such as envelopes and index paper, and cloth.

[0012] As shown in Figures 1 and 2, the image forming apparatus 1 has an image forming section 20 that forms a toner image on a recording material, a feeding section 30 that feeds the recording material P, a fixing section 9 that fixes the toner image formed by the image forming section 20 to the recording material, and a pair of discharge rollers 10.

[0013] The image forming section 20 has a scanner unit 50, an electrophotographic process unit 40, and a transfer unit 7 including a transfer roller 7a as a transfer member. The process unit 40 includes a photosensitive drum 11 and one or more process means arranged around the photosensitive drum 11. In this embodiment, the process means arranged in the process unit 40 include a cleaning unit 13, a charging roller 17, and a developing device including a developing roller 12 and a toner storage unit 18.

[0014] The image forming apparatus 1 excluding the process unit 40 is called an apparatus main body 1A (image forming apparatus main body). The process unit 40 is detachable from the apparatus main body 1A.

[0015] The photosensitive drum 11 functions as an image carrier in this embodiment that carries a toner image. The photosensitive drum 11 is a drum-shaped substrate made of aluminum with a diameter of 24 mm, on which a negatively chargeable photosensitive layer made of a photosensitive material such as OPC (organic photoconductor), amorphous selenium, or amorphous silicon is formed.

[0016] During image formation, the photosensitive drum 11 is driven to rotate in a predetermined rotation direction R at a predetermined process speed by a drive motor 311 (FIG. 3) serving as a drive source. The process speed during image formation can be set in multiple stages depending on the type and size of the recording material P, the environment of use, etc. In the image forming apparatus 1 of this embodiment, the basis weight of the recording material P is, for example, 50 to 100 g / m 2 The first mode corresponds to so-called plain paper, and the speed is 140 mm / sec, 100 to 300 g / m 2 The speed is 93 mm / sec in the second mode, which corresponds to thick paper.

[0017] The charging roller 17 contacts the photosensitive drum 11 with a predetermined pressure to form a charging portion. A desired charging voltage is applied by a charging high-voltage power supply, thereby uniformly charging the surface of the photosensitive drum 11 to a predetermined potential. In this embodiment, the photosensitive drum 11 is negatively charged by the charging roller 17.

[0018] The scanner unit 50 uses a polygon mirror to irradiate the photosensitive drum 11 with laser light corresponding to image information input from an external device, thereby scanning and exposing the surface of the photosensitive drum 11. This exposure forms an electrostatic latent image corresponding to the image information on the surface of the photosensitive drum 11. Note that the scanner unit 50 is not limited to a laser scanner device, and may, for example, be an LED exposure device having an LED array in which a plurality of LEDs are arranged along the longitudinal direction of the photosensitive drum 11.

[0019] The developing device of this embodiment employs a magnetic single-component jumping development method. The developing device includes a developing roller 12 as a toner carrier (developer carrier) that can rotate facing the photosensitive drum 11. The developing roller 12 rotates while carrying toner contained in a toner container 18 as a developer. The developing device includes a metal blade that contacts the developing roller 12, and as the developing roller 12 rotates, the metal blade regulates the thickness of the toner layer and frictionally charges the toner. The toner is magnetic and is held on the developing roller 12 by a magnet inside the developing roller 12. The developing roller 12 of this embodiment is a cylindrical member with a magnet disposed inside, and is also called a developing sleeve.

[0020] A gap is provided between the surface of the photosensitive drum 11 and the developing roller 12. The portion where the photosensitive drum 11 and the developing roller 12 face each other across the gap is called the developing section. A developing voltage consisting of a DC voltage superimposed on a square-wave AC voltage is applied to the developing roller 12. The toner on the developing roller 12 flies in a cloud-like manner toward the surface of the photosensitive drum 11 and is transferred to the surface of the photosensitive drum 11 according to the potential distribution on the photosensitive drum 11 (jumping development). As a result, the electrostatic latent image on the surface of the photosensitive drum 11 is developed into a toner image.

[0021] The cleaning unit 13 includes a cleaning blade 13a and a cleaning container 13b that contains toner collected by the cleaning blade 13a. The cleaning blade 13a has a stainless steel plate (SUS sheet metal) and an elastic rubber tip that is pressed onto the tip (free end) of the sheet metal. The tip of the rubber tip of the cleaning blade 13a abuts against the photosensitive drum 11 at a predetermined angle and penetration amount (distance). The cleaning unit 13 removes residual toner from the surface of the photosensitive drum 11 using the tip of the rubber tip. The cleaning blade 13a is an example of a cleaning member that cleans the surface of the photosensitive drum 11; for example, a brush that rubs against the surface of the photosensitive drum 11 may also be used as the cleaning member.

[0022] The transfer roller 7a is urged by an urging member (not shown) toward the photosensitive drum 11. A transfer nip N1 is formed between the transfer roller 7a and the photosensitive drum 11 as a transfer portion where a toner image is transferred onto a recording material P, which is a transfer target.

[0023] The fixing unit 9 uses a film heating system that can shorten the warm-up time by using a film with a small heat capacity as the fixing member. The fixing unit 9 includes a fixing film 9a with a built-in fixing heater 9c and a pressure roller 9b that presses against the fixing film 9a. Grease is applied to the inner surface of the fixing film 9a that contacts the fixing heater 9c, stabilizing the movement of the fixing film 9a. A fixing nip N2 is formed between the fixing film 9a and the pressure roller 9b.

[0024] The pressure roller 9b is driven to rotate by a drive motor 311 (FIG. 3) serving as a drive source, and the fixing film 9a rotates following the pressure roller 9b by receiving frictional force from the pressure roller 9b at the fixing nip N2. The fixing unit 9 fixes the image by heating and pressurizing the toner on the recording material P while nipping and transporting the recording material P at the fixing nip N2.

[0025] The feeding section 30 has a cassette 4 as a sheet supporting section on which the recording material P is stacked, a pickup roller 3 as a feeding member, a feeding roller 5a, and a separation roller 5b. A front cover 70 is provided on the end surface on the front side of the image forming apparatus 1. The front cover 70 covers the circuit board 100.

[0026] The image forming apparatus 1 also has a housing 72. The housing 72 includes a front cover 70, a discharge tray 14, a rear cover 73, and an exterior cover 71. The exterior cover 71 constitutes the exterior of the image forming apparatus 1 other than the front cover 70, the discharge tray 14, and the rear cover 73. The housing 72 is formed with a discharge port 15 through which sheets pass before being discharged onto the discharge tray 14. The discharge tray 14 is provided on the top surface of the image forming apparatus 1.

[0027] The image forming apparatus 1 also has a conveying roller pair 5c, a discharge roller pair 10, a double-sided conveying roller pair 5d, a main conveying path 19, and a double-sided conveying path 16. The conveying roller pair 5c is disposed between the feed roller 5a and the transfer nip N1 in the conveying direction of the recording material P. The discharge roller pair 10 is a discharge member that discharges the recording material P to the outside of the apparatus, and is disposed at a discharge port 15. The double-sided conveying roller pair 5d is disposed in the double-sided conveying path 16.

[0028] The main transport path 19 is a transport path that runs from the feed roller 5a through the transport roller pair 5c, transfer nip N1, and fixing nip N2 to the discharge roller pair 10. A portion of the main transport path 19 is formed by a transport guide portion 7e of the transfer unit 7, which will be described later. The double-sided transport path 16 is a transport path that branches off from the main transport path 19 downstream of the fixing portion 9 and merges with the main transport path 19 upstream of the transport roller pair 5c. A portion of the double-sided transport path 16 is formed by a rear cover 73, which will be described later, and transport guide portions 73g and 7d of the transfer unit 7. Each of the transport guide portions 73g, 7d, and 7e is, for example, composed of a plurality of transport ribs that extend along the recording material transport direction and are aligned in the width direction (X-axis direction) perpendicular to the recording material transport direction.

[0029] As shown in FIG. 2, the image forming apparatus 1 has a circuit board 100. The circuit board 100 includes a wiring board 101 made of an insulator and electronic components 111 and 121 soldered to the wiring board 101. The electronic components 111 and 121 are components of a low-voltage power supply unit 110 or a high-voltage power supply unit 120, which will be described later. Conductive wiring is provided on and inside the wiring board 101, so that the electronic components 111 and 121 are electrically connected. The circuit board 100 has the function of converting AC current supplied from outside the image forming apparatus 1 into DC current and converting input voltage to obtain a predetermined voltage value required for the image formation process.

[0030] In the following description and in each drawing, the vertical direction (direction of gravity) when the image forming apparatus 1 is placed on a horizontal surface is referred to as the Z-axis direction. The direction of the rotation axis of the photosensitive drum 11 provided in the image forming apparatus 1 is referred to as the X-axis direction. The direction intersecting both the Z-axis direction and the X-axis direction is referred to as the Y-axis direction. The X-axis, Y-axis, and Z-axis directions are preferably perpendicular to each other. Furthermore, when distinguishing between one side and the other side of each of the X, Y, and Z axes, a + (plus) or - (minus) sign is used to indicate the direction. For example, the positive direction of the X-axis (the direction indicated by the arrow X in the drawing) is referred to as the +X side, and the negative direction of the X-axis (the opposite side of the arrow X) is referred to as the -X side.

[0031] In the Y-axis direction, the downstream side (+Y side) of the discharge direction of the recording material by the discharge roller pair 10 is referred to as the "front" or "front side," and the opposite side (-Y side) is referred to as the "rear" or "back side." Furthermore, the right-hand side (+X side) when viewing the image forming apparatus 1 from the front side (+Y side) is referred to as the "right direction" or "right side," and the opposite side (-X side) is referred to as the "left direction" or "left side."

[0032] [Image formation operation] Next, we will explain the image forming operation of the image forming apparatus 1. When an image formation command is input to the image forming apparatus 1, the image forming unit 20 starts to create a toner image based on image information input from an external computer connected to the image forming apparatus 1.

[0033] The charging roller 17, which is a charging member, contacts the photosensitive drum 11 with a predetermined pressure, forming a charging section. A negative charging voltage is applied to the charging roller 17 by a high-voltage power supply unit 120 (see FIG. 3). As a result, the surface of the photosensitive drum 11 is uniformly charged to a dark potential Vd1. During image formation, a charging voltage Vpri1 is applied to the charging roller 17, which is a DC component of -800 V superimposed with an AC component with a duty of 50%, a frequency of 1500 Hz, and a peak-to-peak voltage of 2000 V, thereby forming a dark potential Vd1 of -800 V (see FIG. 12).

[0034] The scanner unit 50, which is an exposure unit, outputs laser light corresponding to image information input from an external device such as a host computer, and scans and exposes the surface of the photosensitive drum 11. By this exposure, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of the photosensitive drum 11. In this embodiment, the absolute value of the surface potential of the photosensitive drum 11, which has been uniformly charged and formed, decreases from a dark area potential Vd1 to a light area potential Vl1 by exposure by the scanner unit 50. In this embodiment, the light area potential Vl1 is -100V (see FIG. 12).

[0035] In this embodiment, the developing roller 12 is disposed in a non-contact manner with respect to the photosensitive drum 11 (jumping development method). For this reason, a developing voltage including an AC component is applied to the developing roller 12. In this embodiment, a developing voltage in which an AC component with a duty of 50%, a frequency of 3 kHz, and 1750 V (peak-to-peak voltage) is superimposed on a DC component of −300 V is applied, thereby forming a developing potential Vdc1=−300 V (see FIG. 12).

[0036] During image formation, the toner carried on the developing roller 12 is transferred to the image area on the photosensitive drum 11 by electrostatic force generated by the potential difference between the development potential Vdc1 (=-300V) and the light area potential Vl1 (=-100V), which is the potential of the image area on the photosensitive drum 11. As a result, the electrostatic latent image on the surface of the photosensitive drum 11 is developed.

[0037] In parallel with the above-described toner image creation process, the pickup roller 3 of the feeding unit 30 feeds the recording material P supported by the cassette 4. The recording material P fed by the pickup roller 3 is further conveyed by the feeding roller 5a toward the conveying roller pair 5c. When multiple sheets of the recording material P enter the separation nip between the feeding roller 5a and the separation roller 5b, the recording materials P are separated one by one by the separation roller 5b. The recording material P is then conveyed toward the transfer nip N1 by the conveying roller pair 5c serving as a conveying unit.

[0038] A transfer voltage is applied to the transfer roller 7a from a high-voltage power supply unit 120 (FIG. 3). As a result, the toner image carried on the photosensitive drum 11 is transferred to the recording material P being conveyed by the conveying roller pair 5c. The recording material P with the transferred toner image is conveyed to the fixing unit 9, and the toner image is heated and pressurized as it passes through the fixing nip N2. This melts the toner particles and then solidifies them, thereby fixing the toner image to the recording material P. After passing through the fixing unit 9, the recording material P is discharged from the discharge port 15 by the discharge roller pair 10 to the outside of the image forming apparatus 1 (outside the machine) and is stacked on the discharge tray 14.

[0039] When forming images on both sides of the recording material P, the pair of discharge rollers 10 switches back the recording material P with the image formed on its first side, thereby conveying the recording material P to the double-sided conveying path 16. The recording material P conveyed to the double-sided conveying path 16 is conveyed again toward the transfer nip N1 by the pair of double-sided conveying rollers 5d. After the recording material P passes through the transfer nip N1 and the fixing nip N2, an image is formed on its second side, and the recording material P is then discharged to the outside of the apparatus by the pair of discharge rollers 10. Note that any toner remaining on the photosensitive drum 11 even after the toner image has been transferred to the recording material P (transfer residual toner) is cleaned by a cleaning unit 13.

[0040] [Control Block] FIG. 3 is a block diagram illustrating the function of the circuit board 100 of this embodiment. The circuit board 100 includes a low-voltage power supply unit 110 and a high-voltage power supply unit 120. The low-voltage power supply unit 110 receives power from an external power supply (commercial power supply) via a power supply input unit (not shown) mounted on the edge of the board and converts the AC voltage into a stable DC voltage using a rectifying and smoothing circuit including an electrolytic capacitor. The low-voltage power supply unit 110 then converts the DC voltage into a high-frequency AC voltage using switching elements such as transistors and inputs the high-frequency AC voltage to a low-voltage power supply transformer. The low-voltage power supply transformer converts the high-frequency AC voltage (the input voltage) into an AC voltage (output voltage) having a desired voltage value. The low-voltage power supply unit 110 then converts the AC voltage back into a DC voltage and outputs the resulting DC voltage to the high-voltage power supply unit 120. Because the loss of each circuit component in the low-voltage power supply unit 110 manifests itself as heat, a heat sink (not shown) made of aluminum or iron is provided in the low-voltage power supply unit 110 to dissipate the heat.

[0041] The high-voltage power supply unit 120 converts the voltage (for example, 24 V) supplied from the low-voltage power supply unit 110 into a high voltage required for the image formation process, such as charging, developing, and transferring. The voltage supplied from the low-voltage power supply unit 110 is supplied to the charging roller 17, the developing roller 12, and the transfer roller 7a.

[0042] The low-voltage power supply unit 110 supplies voltage (e.g., 3.3 V or 5 V) not only to the high-voltage power supply unit 120 but also to the scanner unit 50, the drive motor 311, the engine controller 130, and the video controller 140. The engine controller 130, which serves as a control means, plays a role in overall control of various units (including the drive motor 311) within the image forming apparatus 1. The engine controller 130 includes a CPU, RAM used for calculations and temporary storage of data necessary for controlling the image forming apparatus 1, and ROM for storing programs and various data for controlling the image forming apparatus 1. The video controller 140 plays a role in communicating with an external device such as a personal computer to receive print data and informing the engine controller 130 of the results of analyzing the print data. The engine controller 130 and the video controller 140 may be provided on a board separate from the circuit board 100, or may be provided on the same board.

[0043] The AC power received by the power input unit from the external power source is supplied not only to the low-voltage power supply unit 110 but also to the fixing heater 9c. The various rotating members in the fixing unit 9, such as the pressure roller 9b, are driven by a drive motor 311.

[0044] [Rear cover and transfer unit] Next, the rear cover 73 and the transfer unit 7 will be described with reference to Fig. 4(a) to Fig. 5(d). Fig. 4(a) to Fig. 4(c) are perspective views mainly showing the configuration of the rear side of the image forming apparatus 1. Fig. 5(a) to Fig. 5(d) are views showing cross sections of the image forming apparatus 1 cut along a plane perpendicular to the left-right direction (YZ plane).

[0045] 4(a) to 5(d), an opening 91 (first opening, outer opening) formed in an exterior cover 71 and a rear cover 73 covering the opening 91 are provided on the rear surface of the image forming apparatus 1. The transfer unit 7 is disposed inside the rear cover 73.

[0046] The rear cover 73, which serves as an opening / closing member, is provided so as to be able to open and close between an open position and a closed position. In the closed position, the rear cover 73 covers the opening 91 (FIGS. 4(a) and 5(a)). In the open position, the rear cover 73 is retracted from the opening 91 so that the opening 91 is exposed to the outside of the image forming apparatus 1 (FIGS. 4(b) and 4(c) and 5(b) and 5(c)).

[0047] When the rear cover 73 is in the closed position (FIGS. 4(a) and 5(a)), the transfer unit 7 and the process unit 40 are covered by the rear cover 73. When the rear cover 73 is in the open position (FIGS. 4(b) and 5(b)), the transfer unit 7 can be exposed to the outside of the image forming apparatus 1 through the opening 91.

[0048] The rear cover 73 is an example of an opening / closing member that can move between an open position that opens the opening 91 of the housing 72 and a closed position that closes the opening 91. The rear cover 73 is also an example of a unit that can be in a first state that allows a portion of the surface of the photosensitive drum 11 to be exposed to the outside of the image forming apparatus 1, and a second state that does not expose the surface of the photosensitive drum 11 to the outside of the image forming apparatus 1. In this embodiment, the state in which the rear cover 73 is in the open position corresponds to the first state, and the state in which the rear cover 73 is in the closed position corresponds to the second state.

[0049] The image forming apparatus 1 includes a cover open / close sensor S1 (FIG. 2) as a detector (open / close detector) capable of detecting whether the rear cover 73 is open or closed. The cover open / close sensor S1 is configured to output a detection signal corresponding to whether the rear cover 73 is in the closed position. The cover open / close sensor S1 is, for example, a contact switch arranged to detect a part of the rear cover 73 in the closed position (for example, an engagement claw 73a, described below), but the detection method is not limited to the contact type. The engine controller 130 can detect whether the rear cover 73 is open or closed based on the detection signal from the cover open / close sensor S1.

[0050] The rear cover 73 has an engaging claw 73a, an outer surface 73b, a gripping portion 73c, a rotation shaft 73d, a pressing rib 73e, and a conveyance guide portion 73g. The pressing rib 73e will be described later.

[0051] The outer surface 73b, together with the exterior cover 71, constitutes the exterior surface of the housing 72 when the rear cover 73 is in the closed position (FIG. 4(a)). The gripping portion 73c is provided on the outer surface 73b. The engaging claws 73a, the pressing rib 73e, and the conveying guide portion 73g are disposed on the inner surface of the rear cover 73 opposite to the outer surface 73b (FIG. 4(b)).

[0052] The engaging claw 73a is configured to engage with an engaged portion provided on the exterior cover 71. The engagement between the engaging claw 73a (engaging portion) and the engaged portion holds the rear cover 73 in the closed position (FIGS. 4(a) and 5(a)). The grip portion 73c is a portion that is gripped by the user to operate the rear cover 73. When the rear cover 73 is in the closed position, the user can grasp the grip portion 73c and pull it toward the rear side (-Y side) to disengage the engaging claw 73a from the engaged portion of the exterior cover 71 and move the rear cover 73 from the closed position to the open position.

[0053] The portion of the housing 72 other than the rear cover 73 is referred to as the housing main body 72A. The rear cover 73 is supported by the housing main body 72A so as to rotate about a rotation shaft 73d (FIGS. 5(a) and 5(b)). When the rear cover 73 is in the closed position, the conveying guide portion 73g forms the duplex conveying path 16 (FIG. 5(a)) together with the conveying guide portion 7d of the transfer unit 7.

[0054] The fixing unit 9 (FIG. 2) described above is connected to the opening and closing of the rear cover 73 via a link mechanism. In this embodiment, the pressure roller 9b is configured to move between a contact position where it contacts the fixing film 9a and a spaced position where it is spaced from the fixing film 9a in conjunction with the opening and closing of the rear cover 73. The pressure roller 9b is configured to be held in the contact position during image formation.

[0055] The transfer unit 7 includes a transfer roller 7a, a gripper 7b, a rotating shaft 7c, and conveyance guides 7d and 7e. The transfer unit 7 is supported by the housing main body 72A so as to be openable and closable (rotatable) about the rotating shaft 7c.

[0056] The transfer unit 7 is provided so as to be able to open and close between a closed position (first position) and an open position (second position). In the closed position, a transfer nip N1 is formed between the transfer roller 7a and the photosensitive drum 11 (FIGS. 5(a) and 5(b)). In the closed position, the transfer unit 7 covers an opening 92 (second opening, inner opening) of the housing main body 72A (FIGS. 4(b) and 5(b)). In the open position, the transfer roller 7a is separated from the photosensitive drum 11 (FIGS. 4(c) and 5(c)). In addition, when the rear cover 73 is in the open position and the transfer unit 7 is in the open position, the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1 through the openings 91 and 92.

[0057] The opening 92 is formed closer to the inside (+Y side) of the housing main body 72A than the opening 91 (FIG. 4(b)) of the exterior cover 71. In this embodiment, the opening 92 is formed between an upper guide 93 located above the transfer unit 7 (closed position) and a lower guide 94 located below the transfer unit 7 (closed position). The upper guide 93 and the lower guide 94 each have a transport guide portion that forms part of the main transport path 19 and a transport guide portion that forms part of the double-sided transport path 16. In addition, the upper guide 93 and the lower guide 94 are fixed to the housing main body 72A.

[0058] With the posture of the transfer unit 7 in the closed position as a reference, the surface on the rear side (-Y side) of the transfer unit 7 is the outer surface, and the surface on the front side (+Y side) of the transfer unit 7 is the inner surface. The transport guide portion 7d and the gripping portion 7b are arranged on the outer surface of the transfer unit 7, and the transport guide portion 7e and the transfer roller 7a are arranged on the inner surface of the transfer unit 7.

[0059] (When the rear cover and transfer unit are closed) 4(a) and 5(a) show a state in which the rear cover 73 is in the closed position and the transfer unit 7 is also in the closed position. In this case, a part of the duplex conveying path 16 is formed between the conveying guide portion 73g of the rear cover 73 and the conveying guide portion 7d of the transfer unit 7.

[0060] Furthermore, when the rear cover 73 is in the closed position and the transfer unit 7 is in the closed position, the recording material P can be transported through the transfer nip N1 and the toner image can be transferred at the transfer nip N1. In other words, the image forming apparatus 1 is allowed to perform the image forming operation.

[0061] When the rear cover 73 is in the closed position, the pressure roller 9b of the fixing unit 9 abuts against the fixing film 9a. In this embodiment, when the rear cover 73 is in the closed position, the transfer unit 7 is drawn into the image forming apparatus 1 by a link member (not shown) and is held in the closed position.

[0062] (When only the back cover is opened) 4(b) and 5(b) show a state in which the rear cover 73 is in the open position and the transfer unit 7 is in the closed position. When the rear cover 73 is moved from the closed position to the open position, the duplex conveying path 16 (FIG. 4(a)) is opened.

[0063] As described above, in this embodiment, the cover open / close sensor S1 is disposed on the exterior cover 71, and the engine controller 130 detects that the rear cover 73 has been opened based on a detection signal from the cover open / close sensor S1.

[0064] Furthermore, the pressure roller 9b of the fixing unit 9 moves from a contact position to a separated position relative to the fixing film 9a in conjunction with the movement of the rear cover 73 from the closed position to the open position. Therefore, when the rear cover 73 is in the open position and the duplex conveying path 16 is open, the pressure roller 9b is also separated from the fixing film 9a. In other words, the manual drive mode, which will be described later, is performed with the rear cover 73 and the transfer unit 7 open, and the pressure roller 9b and the fixing film 9a are separated during execution of the manual drive mode.

[0065] The pressure roller 9b and the fixing film 9a are separated in the manual drive mode to prevent the fixing film 9a from rotating due to the driving force of the drive motor 311, which is the common driving source for the photosensitive drum 11 and the fixing unit 9. Let's assume that the pressure roller 9b is driven to rotate and the fixing film 9a rotates while the fixing heater 9c is not energized. In this case, the viscosity of the grease applied between the fixing film 9a and the fixing heater 9c may be too high, causing the fixing film 9a to run unstably. Meanwhile, in the manual drive mode, the drive motor 311 drives the photosensitive drum 11 to rotate for a short period of time. Therefore, if the fixing heater 9c is energized in the manual drive mode, heat may build up in the fixing nip N2 while the drive motor 311 is stopped, causing problems such as overheating of the fixing heater 9c, which may cause the fixing film 9a or the pressure roller 9b to melt.

[0066] In this embodiment, since the pressure roller 9b and the fixing film 9a are separated from each other during the manual drive mode, the fixing film 9a is kept stopped even if the drive motor 311 drives and rotates the photosensitive drum 11 for only a short time. Therefore, there is no need to energize the fixing heater 9c, and overheating of the fixing heater 9c can be prevented.

[0067] Instead of separating the pressure roller 9b from the fixing film 9a, a mechanism for interrupting the drive transmission may be interposed between the drive motor 311 and the pressure roller 9b to interrupt the drive transmission during the manual drive mode. The drive transmission interruption mechanism may be a mechanism in which the gear that drives the pressure roller 9b moves sideways in conjunction with the rear cover 73 being opened, thereby disengaging from the drive train from the drive motor 311, or a mechanism that uses an electromagnetic clutch. Alternatively, a drive source for rotating the fixing unit 9 may be added in addition to the drive motor 311 that rotates the photosensitive drum 11, so that the fixing unit 9 is not rotated during the manual drive mode.

[0068] (When the rear cover and transfer unit are open) 4(c) and 5(c) show a state in which the rear cover 73 is in the open position and the transfer unit 7 is in the open position. With the rear cover 73 in the open position, the user can move the transfer unit 7 from the closed position to the open position by gripping the grip portion 7b and pulling it toward the rear side (-Y side).

[0069] When the transfer unit 7 is moved to the open position, the main transport path 19 is opened. Furthermore, when the transfer unit 7 is moved to the open position, the surface of the photosensitive drum 11 becomes visible through the opening 92. That is, when the image forming apparatus 1 is viewed in the Y direction from the rear side with the rear cover 73 and the transfer unit 7 in the open position, a portion of the surface of the photosensitive drum 11 is exposed inside the opening 92.

[0070] In this embodiment, the area of ​​the part of the surface of the photosensitive drum 11 that is exposed when the rear cover 73 and the transfer unit 7 are in the open position (the exposed area, the area that is visible in the state of FIG. 8(a)) is approximately one-third of the area of ​​the entire surface of the photosensitive drum 11. The width of the exposed area of ​​the photosensitive drum 11 when measured along the outer circumferential surface of the photosensitive drum 11 in the rotation direction of the photosensitive drum 11 is approximately 25 mm.

[0071] (When the rear cover is closed) 5(d), when the rear cover 73 and the transfer unit 7 are in the open position and the rear cover 73 is moved toward the closed position, the pressing rib 73e comes into contact with the transfer unit 7. While the rear cover 73 is moving from the open position to the closed position, the pressing rib 73e presses the transfer unit 7 to move it to the closed position.

[0072] The user may manually move the transfer unit 7 from the open position to the closed position, and then move the rear cover 73 from the open position to the closed position. Also, the pressing rib 73e may not be provided, and the transfer unit 7 may not be interlocked with the rear cover 73.

[0073] [Jam Clearance] Next, a jam clearance method will be described when a jam occurs in the double-sided conveying path 16 or the main conveying path 19. When a jam of recording material P occurs during an image forming operation, the image forming apparatus 1 suspends the image forming operation and notifies the user of the occurrence of the jam. To clear the jam, the user opens the rear cover 73 (FIGS. 4(b) and 5(b)). This opens the double-sided conveying path 16, allowing the user to remove the recording material P that has become stuck in the double-sided conveying path 16 due to the jam.

[0074] On the other hand, if a jam occurs near the transfer nip N1, as shown in Figures 4(c) and 5(c), the user opens the rear cover 73 and then opens the transfer unit 7. This opens the main transport path 19, allowing the user to remove the recording material P that has accumulated near the transfer nip N1.

[0075] In this embodiment, the user is configured to remove the recording material P stuck in the transfer nip N1 by opening the rear cover 73 and the transfer unit 7 on the rear side of the image forming apparatus 1, but the configuration for jam clearance is not limited to this. For example, the photosensitive drum 11 of the process unit 40 may be exposed by opening the discharge tray 14 arranged at the top of the image forming apparatus 1. In this case, the user can open the discharge tray, remove the process unit 40 upward from the housing 72, and then access the vicinity of the transfer nip N1 to remove the recording material P.

[0076] [Attaching and detaching the process unit] Next, with reference to Figures 6(a) to 7(d), a method for attaching and detaching the process unit 40, for example, when replacing the process unit 40 or performing maintenance on the apparatus main body 1A, will be described. Figures 6(a) to 6(d) are perspective views of the image forming apparatus 1, with the exterior cover 71, discharge tray 14, front cover 70, etc. seen through. Figures 7(a) to 7(d) are cross-sectional views of the image forming apparatus 1 in the state shown in Figures 6(a) to 6(d), taken along a plane perpendicular to the X-axis direction (YZ plane).

[0077] When removing the process unit 40 from the image forming apparatus 1, the user moves the rear cover 73 and the transfer unit 7 to the open position, as shown in Figures 6(a)(b) and 7(a)(b). This exposes the process unit 40 to the outside of the image forming apparatus 1. However, in this state, the process unit 40 is fixed to the left side plate 74 and the right side plate 75 by fixing members 79L and 79R.

[0078] The left side plate 74 and the right side plate 75 are frame members that form the frame of the image forming apparatus 1. The left side plate 74 and the right side plate 75 are part of the housing 72 (housing main body 72A). The left side plate 74 is a sheet metal member that is provided on one side (left side) of the housing 72 in the X-axis direction (left-right direction) and extends approximately perpendicular to the X-axis direction. The right side plate 75 is a sheet metal member that is provided on the other side (right side) of the housing 72 in the X-axis direction (left-right direction) and extends approximately perpendicular to the X-axis direction. Inside the housing main body 72A, an installation space in which the process unit 40 is installed is formed between the left side plate 74 and the right side plate 75 in the X-axis direction.

[0079] The fixing member 79L is fixed to the left side plate 74 with a screw. The fixing member 79R is fixed to the right side plate 75 with a screw. The fixing members 79L and 79R attached to the left side plate 74 and the right side plate 75 restrict the process unit 40 from moving toward the rear side (-Y side).

[0080] Furthermore, a positioning portion 81L and a rotation restricting portion 82L are provided on the left side plate 74. Meanwhile, a positioning boss 41L and a rotation restricting boss 42L are disposed on the left end surface of the process unit 40. When the process unit 40 is attached to the apparatus main body 1A (FIGS. 6(a) and 7(a)), the positioning boss 41L engages with the positioning portion 81L, and the rotation restricting boss 42L engages with the rotation restricting portion 82L. The engagement between the positioning boss 41L and the positioning portion 81L determines the position of the process unit 40 in the attachment direction AD of the process unit 40. The engagement between the rotation restricting boss 42L and the rotation restricting portion 82L also restricts the rotation of the process unit 40 around the positioning boss 41L and the positioning portion 81L, thereby determining the orientation of the process unit 40.

[0081] Note that a positioning portion and a rotation restricting portion corresponding to the positioning portion 81L and the rotation restricting portion 82L are also provided on the right side plate 75. A positioning boss that engages with the positioning portion of the right side plate 75 and a rotation restricting boss that engages with the rotation restricting portion 82L of the right side plate 75 are arranged on the right end surface of the process unit 40.

[0082] In this embodiment, the process unit 40 is fixed to the left side plate 74 and the right side plate 75 using fixing members 79L, 79R and screws, but the method of fixing the process unit 40 is not limited to this. For example, the process unit 40 may be held in a predetermined position within the apparatus main body 1A by a biasing member such as a spring. Also, the process unit 40 may be held in a predetermined position within the apparatus main body 1A by using the force of the transfer roller 7a of the transfer unit 7 pressing against the photosensitive drum 11.

[0083] After moving the rear cover 73 and the transfer unit 7 to the open position, the user removes the fixing members 79L, 79R from the left side plate 74 and the right side plate 75. As shown in Figures 6(c) and 7(c), the user moves the process unit 40 in a removal direction DD, which is opposite to the attachment direction AD with respect to the housing main body 72A. In addition, as the process unit 40 moves in the removal direction DD, the coupling portion (drive transmission portion) for transmitting the driving force of the drive motor 311 (Figure 7(c)) to the process unit 40 is released.

[0084] As the process unit 40 moves in the removal direction DD, the positioning boss 41L and rotation restriction boss 42L on the left side of the process unit 40 disengage from the positioning portion 81L and rotation restriction portion 82L, respectively, of the left side plate 74. The positioning boss and rotation restriction boss on the right side of the process unit 40 also disengage from the positioning portion and rotation restriction portion, respectively, of the right side plate 75. The user then removes the process unit 40 from the apparatus main body 1A (FIGS. 6(d) and 7(d)) ​​through the openings 91 and 92 (FIG. 4(c)) of the housing main body 72A.

[0085] The procedure for installing the process unit 40 in the apparatus main body 1A is the reverse of the removal procedure. That is, with the rear cover 73 in the open position and the transfer unit 7 in the open position, the user inserts the process unit 40 into the apparatus main body 1A through the openings 91 and 92 in the installation direction AD. The user then engages the positioning boss 41L and the rotation restricting boss 42L of the process unit 40 with the positioning portion 81L and the rotation restricting portion 82L, and then attaches the fixing members 79L and 79R to the left side plate 74 and the right side plate 75. This installs the process unit 40 in the predetermined position within the apparatus main body 1A.

[0086] In this way, the process unit 40 is detachable from the apparatus main body 1A in a state where the rear cover 73 is in the open position and the transfer unit 7 is in the open position.

[0087] In this embodiment, the process unit 40 is removed from the apparatus main body 1A through the openings 91 and 92 on the rear side, but the process unit 40 may be removed in a direction other than the rear side. For example, the process unit 40 may be exposed by opening the discharge tray 14 as described above, and the process unit 40 may be removed upward from the apparatus main body 1A.

[0088] [Dirt adhesion to the photosensitive drum surface] Next, we will explain the process by which dirt adheres to the surface of the photosensitive drum 11. As described above, when clearing a jam or replacing the process unit 40, part of the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1. Therefore, dust, sand, etc. from around the image forming apparatus 1 may directly adhere to the surface of the photosensitive drum 11, or a user may accidentally touch the surface of the photosensitive drum 11 and get sebum on it.

[0089] If image formation is performed while leaving dirt adhering to the surface of the photosensitive drum 11, image defects due to the dirt may occur. In addition to oily dirt such as sebum, other dirt that is likely to cause image defects include food dirt such as fruit juice and starch, cosmetics such as hand cream and sunscreen, and stationery products such as glue and tape. In other words, various substances used in daily life can cause image defects when they adhere to the surface of the photosensitive drum 11.

[0090] [Bad image] The process by which image defects occur due to dirt adhering to the surface of the photosensitive drum 11 will be described with reference to Figures 8(a) to 8(c). Figures 8(a) to 8(c) are schematic diagrams showing the process unit 40 viewed from the rear side with the rear cover 73 and transfer unit 7 in the open position. As described above, with the rear cover 73 and transfer unit 7 in the open position, an area equivalent to one-third of the entire surface of the photosensitive drum 11 (circumferential width 25 mm) can be seen.

[0091] Fig. 8(a) shows the state where stains Ka1 and Ka2 have adhered to the surface of the photosensitive drum 11. Fig. 8(b) shows the state after stains Ka1 and Ka2 have adhered, a print job (a command to execute an image forming operation) is sent to the image forming apparatus 1, and the photosensitive drum 11 has rotated several times as a result of the image forming operation being executed.

[0092] The stains Ka1 and Ka2 adhering to the photosensitive drum 11 may be scraped off by passing through the cleaning unit 13, but if the stain droplets are large or highly viscous, they may not be completely scraped off in one pass. When the stains pass through the cleaning unit 13, they are stretched and may turn into tear-shaped stains Kb1 and Kb2 as shown in FIG. 8(b).

[0093] Figure 8(c) shows the state after the image forming operation has been repeated multiple times while maintaining the state of Figure 8(b). If the portion where the stain remains overlaps the area on the surface of the photosensitive drum 11 where the toner image is developed (image area), toner that is electrically attracted from the developing roller 12 during the image forming operation adheres to the stain on the photosensitive drum 11. The toner that has adhered to the stain is repeatedly rubbed by the charging roller 17 and cleaning unit 13 that are in contact with the photosensitive drum 11. As a result, although the size of the stain becomes smaller, the toner on the stain may be crushed and form toner clumps K1 and K2.

[0094] If the toner clumps are soft, such as when the dirt has just adhered to the photosensitive drum 11 and contains moisture, they can be easily removed by lightly pressing a clean cloth against the toner clump and wiping it off. Also, if the toner clumps are still soft, they may gradually become smaller and disappear as the photosensitive drum 11 rotates with repeated print jobs and the toner clumps K1 and K2 on the photosensitive drum 11 repeatedly pass through the cleaning unit 13.

[0095] However, after the toner adheres to the stains and forms toner clumps K1 and K2, if time passes before the next print job starts, the moisture in the stains evaporates and the toner clumps dry out. When they dry out, the toner clumps K1 and K2 harden and become more firmly attached to the surface of the photosensitive drum 11.

[0096] 8(a) to 8(c) are toner clumps that have been left for a long period of time and have adhered to the surface of the photosensitive drum 11. Such toner clumps K3 may remain on the photosensitive drum 11 without being scraped off even when the cleaning unit 13 passes repeatedly.

[0097] The toner clumps K1, K2, and K3 adhering to the surface of the photosensitive drum 11 do not allow light from the scanner unit 50 to reach the photosensitive layer, even in the image area, and the surface potential of the photosensitive drum 11 does not reach the light area potential Vl1. Then, the potential of the areas on the surface of the photosensitive drum 11 where the toner clumps K1, K2, and K3 are located becomes higher than the development potential Vdc1 (the surface of the photosensitive drum 11 has a more negative polarity than the developing roller 12), so the toner image is not developed in the areas where the toner clumps K1, K2, and K3 are located. As a result, an image defect (hereinafter referred to as a white spot) occurs in the areas on the recording material P corresponding to the areas where the toner clumps K1, K2, and K3 are located.

[0098] 9(a) and 9(b) are examples of images in which white spots occur. Fig. 9(a) shows a case where a full-page halftone image is printed on A4 paper in a state where there are toner clumps adhered to the photosensitive drum 11, and Fig. 9(b) shows a case where a character image is printed on A4 paper in a similar state.

[0099] In the example of FIG. 9(a), white dots Kg1, Kg2, and Kg3 correspond to the toner clumps K1, K2, and K3 in FIG. 8(c), respectively. As shown in FIG. 9(a), white dots occur periodically in the paper transport direction, which is the sub-scanning direction during image formation, at intervals corresponding to the outer circumferential length of the photosensitive drum 11. In this embodiment, a photosensitive drum 11 with a diameter of 24 mm (outer circumferential length of approximately 75 mm) is used. For this reason, in the case of A4 paper, three white dots may occur per toner clump on one sheet of paper.

[0100] As shown in Figure 9(b), even when a character image is formed on a recording material P, if the adhered portion of the toner mass on the photosensitive drum 11 overlaps with the image area, an image defect (the area indicated by the arrow Kh in the figure) may occur in which part of the character is missing.

[0101] Here, the white dot Kg4 in Fig. 9(a) and the missing characters indicated by the arrow Ki in Fig. 9(b) are caused by toner clumps that have adhered to areas of the surface of the photosensitive drum 11 that cannot be seen in Fig. 8(c). As such, because the user can only visually check a portion of the entire surface of the photosensitive drum 11 at a time, if a toner clump has adhered to an area that cannot be seen, it may not be possible to remove the toner clumps even if an attempt is made to clean the toner clumps as described below, and the image defect may not be resolved.

[0102] [Cleaning toner clumps] A method for cleaning stains and toner clumps adhering to the surface of the photosensitive drum 11 will now be described. First, the user opens the rear cover 73 and the transfer unit 7 to expose the photosensitive drum 11 and observe the surface of the photosensitive drum 11. If a toner clump that is causing white spots is found through observation, the toner clump can be removed by repeatedly rubbing it with a clean cloth, or by wiping it with a cloth moistened with clean water to soften the toner clump, while being careful not to damage the photosensitive drum 11.

[0103] It is preferable to use a cloth that does not easily produce lint. This is because if a cloth that produces lint easily is used, lint may adhere to the photosensitive drum 11 during wiping, and the dirty lint may cause white spots to form again. It is also recommended that the user wear new gloves when cleaning to prevent the user from touching the photosensitive drum 11 again during cleaning and transferring oils and other contaminants to the gloves. Disposable gloves made of latex or nitrile are preferred. Drinking water, distilled water, deionized water, etc. are preferred as water to use for cleaning.

[0104] However, as mentioned above, the user can only visually check a portion of the entire surface of the photosensitive drum 11 at one time, so if toner clumps are attached to areas that cannot be seen with the naked eye, some of the toner clumps may remain even after cleaning.

[0105] In order to check for the presence or absence of stains or toner clumps over the entire surface of the photosensitive drum 11, it is necessary to change the rotation angle (rotation phase) of the photosensitive drum 11. Here, for example, suppose that a user removes the process unit 40 from the image forming apparatus 1 and tries to manually change the rotation angle of the photosensitive drum 11. However, if the load torque required to rotate the photosensitive drum 11 is large, it is difficult to manually change the rotation angle. Furthermore, even if it were possible to manually change the rotation angle of the photosensitive drum 11, it would be difficult to distinguish between areas on the surface of the photosensitive drum 11 that have been visually checked and areas that have not been checked, which could result in stains or toner clumps being overlooked.

[0106] [Manual drive mode] The image forming apparatus 1 of this embodiment has a manual drive mode as a function to assist in checking the surface of the photosensitive drum 11. The manual drive mode is a mode in which the photosensitive drum 11 is rotationally driven based on instructions from a user in a state in which part of the surface of the photosensitive drum 11 is visible from outside the image forming apparatus 1. In other words, the manual drive mode is a mode in which the drive motor 311 is caused to rotationally drive the photosensitive drum 11 in a state in which the rear cover 73 as a unit of this embodiment is in the open position (first state).

[0107] Since the photosensitive drum 11 is driven to rotate with part of its surface exposed to the outside, the user can easily check whether dirt or toner clumps are attached to the surface of the photosensitive drum 11. Furthermore, by controlling the amount of rotation of the photosensitive drum 11, the possibility of overlooking dirt or toner clumps can be reduced. Details of the manual drive mode are described below.

[0108] 10 is an example of a sequence diagram of the manual drive mode. In this embodiment, the manual drive mode is implemented as a function of the engine controller 130.

[0109] At the start of this sequence, it is assumed that the engine controller 130 is in a ready state (SE1), which is a state (standby state) in which an image forming operation can be started when a print job is input.

[0110] The user selects to transition to the manual drive mode on the driver screen (SY1). The driver screen may be an operation screen displayed on the display of an external computer connected to and communicating with the image forming apparatus 1, or an operation screen displayed on a display unit (operation panel) provided in the image forming apparatus 1. Upon receiving the user's selection, the video controller 140 transmits a command to the engine controller 130 to transition to the manual drive mode (SV1). Upon receiving the command, the engine controller 130 enters a mode transition waiting state (SE2).

[0111] In the mode transition waiting state (SE2), the user moves the rear cover 73 from the closed position to the open position (SY2). When the engine controller 130 detects that the rear cover 73 has been opened based on the detection signal from the cover open / close sensor S1, it determines that the rotational driving of the photosensitive drum 11 can be started in response to an instruction from the user, and enters the manual drive mode (SE3). During the execution of the manual drive mode, the engine controller 130 can rotate the photosensitive drum 11 in response to an instruction from the user.

[0112] The user exposes the surface of the photosensitive drum 11 by moving the transfer unit 7 to the open position after the rear cover 73, and checks whether there is any dirt or toner clumps on the surface of the photosensitive drum 11 (SY3). If there is any dirt or toner clumps, they may be cleaned with a cloth or the like at this stage.

[0113] When the user presses the power button 80 (FIG. 1) while the manual drive mode is being executed (SY4), the engine controller 130 operates the drive motor 311 to rotate the photosensitive drum 11 (SE4). The drive speed of the photosensitive drum 11 (circumferential speed of the photosensitive drum 11) during the operation of SE4 is set to 93 mm / sec. This drive speed is the same as the process speed in the mode for a print job using thick paper (second mode), and is slower than the process speed when using plain paper (first mode). The drive speed of the photosensitive drum 11 during the operation of SE4 may be set to a speed different from the process speed in the second mode.

[0114] After starting the rotation of the photosensitive drum 11 in SE4, the engine controller 130 stops the rotation of the photosensitive drum 11 in a state where an area of ​​the surface of the photosensitive drum 11 that is different from the area that was exposed to the outside of the image forming apparatus 1 before the rotation was started is exposed. That is, in the manual drive mode, the engine controller 130 causes the drive motor 311 to start the rotation of the photosensitive drum 11 in a state where a first area of ​​the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1, and then stops the rotation of the photosensitive drum 11 in a state where a second area of ​​the surface that is different from the first area is exposed to the outside of the image forming apparatus 1. This allows the user to check the area that would not be exposed if the photosensitive drum 11 were stationary.

[0115] In this embodiment, each time the user presses the power button 80 as an operation unit, the engine controller 130 executes a unit operation of rotating the photosensitive drum 11 a predetermined amount and then stopping the rotation of the photosensitive drum 11. Therefore, the user only needs to repeat the series of operations of checking and cleaning the currently exposed area of ​​the photosensitive drum 11 and then pressing the power button 80.

[0116] The rotation amount (predetermined amount) by which the photosensitive drum 11 is rotationally driven in one unit operation is set so that the surface of the photosensitive drum 11 moves approximately 19 mm. This movement distance of approximately 19 mm corresponds to approximately one-fourth of the outer circumferential length of the photosensitive drum 11. In other words, the movement distance of the surface of the photosensitive drum 11 in one unit operation is narrower than the width (approximately 25 mm) of the exposed area of ​​the surface of the photosensitive drum 11 that is exposed when the rear cover 73 and transfer unit 7 are in the open position.

[0117] For this reason, a part of the exposed area before and after the unit operation overlaps. In other words, a part of the exposed area (first area) on the surface of the photosensitive drum 11 before the unit operation is performed overlaps a part of the exposed area (second area) after the unit operation is performed. For this reason, it is less likely that an area will be invisible to the user, and it is possible to reduce the possibility of overlooking a stain or toner clump.

[0118] After pressing the power button 80 at SY4, the user checks the surface of the photosensitive drum 11, which has been newly exposed by the rotation of the photosensitive drum 11, for dirt and toner clumps (SY5). The user repeats the steps SY4 and SY5 until the entire surface of the photosensitive drum 11 has been checked (SY6). In this embodiment, the entire surface of the photosensitive drum 11 has been checked when the power button 80 is pressed three times. The engine controller 130 may notify the user that the photosensitive drum 11 has been rotated one revolution (the entire surface of the photosensitive drum 11 has been checked) by, for example, displaying a message on the driver screen.

[0119] Note that the user may repeat steps SY4 and SY5 until he or she feels that he or she has sufficiently checked for dirt or toner clumps even after the photosensitive drum 11 has been rotated one revolution. In other words, if the user feels that there are still dirt or toner clumps on the surface of the photosensitive drum 11 or if he or she wants to check more carefully, he or she may return to step SY4 at the discretion of SY6 and continue the work.

[0120] When the user has sufficiently confirmed that the entire surface of the photosensitive drum 11 is free of dirt and toner clumps (SY6Y), the user ends the manual drive mode. To end the manual drive mode, the user closes the rear cover 73 (SY7). When the engine controller 130 detects that the rear cover 73 has been closed based on the detection signal from the cover open / close sensor S1, it ends the manual drive mode and reboots (restarts) (SE5). After rebooting, the engine controller 130 performs an initialization operation to prepare for the submission of a print job, enters a ready state, and ends this flow (SE6).

[0121] In this way, the image forming apparatus 1 of this embodiment can execute a manual drive mode in which the photosensitive drum 11 is driven to rotate with part of the surface of the photosensitive drum 11 exposed to the outside of the image forming apparatus 1. This allows the user to easily check for dirt on the surface of the photosensitive drum 11.

[0122] In this embodiment, no sensor is provided for detecting the opening and closing of the transfer unit 7. In the manual drive mode, the photosensitive drum 11 can be driven to rotate with the transfer unit 7 in the closed position. In other words, in the manual drive mode, the engine controller 130 can cause the drive motor 311 to rotate the photosensitive drum 11 with the rear cover 73 (opening / closing member) in the open position and the transfer unit 7 in the closed position (first position). In order to drive the photosensitive drum 11 to rotate with the transfer unit 7 in the closed position, for example, the user may press the power button 80 with a cloth sandwiched in the transfer nip N1 to perform the rotation operation (SE4) of the photosensitive drum 11. This allows the surface of the photosensitive drum 11 to be cleaned without manually moving the cloth.

[0123] It goes without saying that in the manual drive mode, the photosensitive drum 11 can be rotated with the transfer unit 7 in the open position. In other words, in the manual drive mode, the engine controller 130 can cause the drive motor 311 to rotate the photosensitive drum 11 with the rear cover 73 (opening / closing member) in the open position and the transfer unit 7 in the open position (second position).

[0124] Furthermore, the manual drive mode in this embodiment is a dedicated mode for the user to visually check for dirt and toner clumps adhering to the surface of the photosensitive drum 11. Therefore, print job instructions are not accepted while the manual drive mode is being executed. Furthermore, in this embodiment, while the manual drive mode is being executed, the power button 80 is used as a means for instructing the rotation operation of the photosensitive drum 11. Therefore, while the manual drive mode is being executed, the operation (such as power OFF) that would occur if the power button 80 were pressed in the ready state is not performed.

[0125] Furthermore, in this embodiment, the engine controller 130 receives a mode transition command from the video controller 140 triggered by an operation on the driver screen, and then enters the manual drive mode when the rear cover 73 is opened. As a comparative example, if the engine controller 130 were configured to enter the manual drive mode only in response to a mode transition command, the user could open and close the rear cover 73 while the manual drive mode was in progress. If the rear cover 73 were repeatedly opened and closed while the manual drive mode was in progress, the vibrations could cause foreign matter, such as dust or fluff, adhering to the top surface of the image forming apparatus 1 or the transport path within the apparatus to fall onto the photosensitive drum 11. Foreign matter that falls onto the photosensitive drum 11 could damage the photosensitive drum 11 or other components, resulting in image defects. Therefore, it is preferable to keep the rear cover 73 open at all times while the manual drive mode is in progress. In this embodiment, the manual drive mode is initiated only when the rear cover 73 is moved from the closed position to the open position, thereby reducing the possibility of image defects due to the adhesion of foreign matter.

[0126] Furthermore, the procedure of instructing the driver to switch to manual drive mode through an operation on the driver screen and then opening the rear cover 73 is different from the procedure for sending a general print job, which reduces the possibility that the user will mistakenly switch the engine to manual drive mode.

[0127] However, the means for setting engine controller 130 to the manual drive mode is not limited to the above. For example, engine controller 130 may be set to the manual drive mode by a user operating a button or switch provided on image forming apparatus 1 (which may be a button or switch on a screen displayed on an operation panel). In this case, a mode transition command may be sent to engine controller 130 triggered by the user operation, without going through video controller 140, and engine controller 130 may be set to the manual drive mode.

[0128] Furthermore, in the present embodiment, an example has been described in which the power button 80 is used as a means for instructing the rotational drive of the photosensitive drum 11 in the manual drive mode, but other means may be used so that the user instructs the rotational drive of the photosensitive drum 11. For example, in the manual drive mode, a dedicated button for instructing the rotational drive of the photosensitive drum 11 may be arranged on the operation panel of the image forming apparatus 1. Also, a button for instructing the execution of the rotational drive of the photosensitive drum 11 may be displayed on the driver screen.

[0129] Second Embodiment Next, a second embodiment will be described. The second embodiment differs from the first embodiment in that the photosensitive drum 11 continues to be slowly rotated in manual drive mode. This allows the user to visually check how the cleaning unit 13 cleans the dirt on the photosensitive drum 11. This embodiment can reduce the effort required for the user to clean the dirt on the photosensitive drum 11.

[0130] Hereinafter, unless otherwise specified, elements with the same reference numerals as those in the first embodiment have basically the same configurations and functions as those described in the first embodiment, and differences from the first embodiment will be mainly described.

[0131] After the user selects the manual drive mode on the driver screen, the procedure from when the rear cover 73 is opened until the engine controller 130 enters the manual drive mode (SE3) is the same as in the first embodiment (FIG. 10). After the engine controller 130 enters the manual drive mode, when the user presses the power button 80 (SY4), the drive motor 311 starts to rotate the photosensitive drum 11 (SE4A).

[0132] Here, in this embodiment, the engine controller 130 causes the drive motor 311 to continuously rotate the photosensitive drum 11 at a low speed (SE4A). After the rotational driving of the photosensitive drum 11 has started, if the user presses the power button 80 again (SY5B), the engine controller 130 stops the drive motor 311 and stops the rotational driving of the photosensitive drum 11 (SE4B). That is, in the manual drive mode, the engine controller 130 continuously rotates the photosensitive drum 11 until it is instructed to stop the rotation of the photosensitive drum 11.

[0133] In this way, as the photosensitive drum 11 continues to rotate, the dirt and toner clumps on the photosensitive drum 11 are gradually cleaned as they repeatedly pass through the cleaning unit 13, and eventually disappear. In particular, if the dirt adhering to the photosensitive drum 11 has just been deposited and is easy to remove, it is removed relatively quickly. The user visually observes the surface of the rotating photosensitive drum 11 and confirms that the dirt and toner clumps have disappeared (SY5A). This embodiment reduces the burden on the user compared to when the user cleans the photosensitive drum 11 themselves.

[0134] It is desirable that the peripheral speed of the photosensitive drum 11 in the manual drive mode be slower than the process speed during image formation (the peripheral speed of the photosensitive drum 11 when an image forming operation is performed). This makes it easier for the user to visually check for the presence or absence of dirt on the photosensitive drum 11. However, if it is too slow, it will take a long time for the cleaning unit 13 to clean the dirt adhering to the photosensitive drum 11. In this embodiment, the rotational speed (peripheral speed) of the photosensitive drum 11 in the manual drive mode is 15 mm / sec, which is slower than the process speed (93 mm / sec) when a print job is executed in the second mode corresponding to thick paper or the like.

[0135] Here, if time has passed since the dirt adhered to the photosensitive drum 11 and the dirt has hardened, there may be dirt or toner clumps that cannot be removed by simply rotating the photosensitive drum 11 (SY6N). In this case, while the photosensitive drum 11 is stopped, the user softens the dirt by wetting a cloth or the like with water, and then presses the power button 80 again (SY4A). This starts the rotation of the photosensitive drum 11 again (SE4A), allowing the cleaning unit 13 to clean the softened dirt or toner clumps. Alternatively, while the photosensitive drum 11 is stopped, the user may clean the dirt or toner clumps by rubbing the surface of the photosensitive drum 11 with a cloth or the like.

[0136] In SY6, if it is confirmed that there is no dirt or toner clumps on the entire surface of the photosensitive drum 11 (SY6Y), the user moves the rear cover 73 to the closed position (SY7), which causes the engine controller 130 to end the manual drive mode in the same manner as in the first embodiment (SE5, SE6).

[0137] In this way, the image forming apparatus 1 of this embodiment can execute a manual drive mode in which the photosensitive drum 11 is driven to rotate in a state in which a part of the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1. This allows the user to easily check for dirt on the surface of the photosensitive drum 11.

[0138] Furthermore, according to this embodiment, the photosensitive drum 11 is continuously rotated in the manual drive mode, so the user can see how the cleaning unit 13 cleans the dirt off the photosensitive drum 11. This reduces the effort required for the user to perform the cleaning themselves.

[0139] In this embodiment, the photosensitive drum 11 is configured to switch between rotational driving and stop every time the power button 80 is pressed in the manual drive mode. However, the present invention is not limited to this. For example, the photosensitive drum 11 may continue to be rotated while the user is pressing the power button 80 in the manual drive mode, and the rotational driving of the photosensitive drum 11 may stop when the user releases the power button 80. Alternatively, when the power button 80 is pressed once briefly, the photosensitive drum 11 may be stopped after being rotated a predetermined amount as in the first embodiment, and the rotational driving of the photosensitive drum 11 may continue while the power button 80 is pressed and held.

[0140] Third Embodiment Next, a third embodiment will be described. In the third embodiment, when the manual drive mode is executed, a voltage is applied to the developing roller 12. This causes a small amount of toner to adhere to the surface of the photosensitive drum 11, making it easier for the user to visually recognize stains.

[0141] Hereinafter, unless otherwise specified, elements having the same reference symbols as those in the first embodiment will be considered to have basically the same configurations and functions as those described in the first embodiment, and the following description will focus on the differences from the first embodiment. Note that the sequence of the manual drive mode in the third embodiment is the same as the sequence described in the second embodiment (FIG. 11) except for the point that a voltage is applied to the developing roller 12 when the photosensitive drum 11 is driven to rotate (SE4A in FIG. 11), and therefore a description thereof will be omitted.

[0142] The voltages applied to the developing roller 12 in the manual drive mode will be described. Figure 12(a) shows the relationship between the charging voltage Vpri1, dark area potential Vd1, developing potential Vdc1, and light area potential Vl1 during execution of a normal print job (image formation). Figure 12(b) shows the relationship between the surface potential Vext of the photosensitive drum 11 and the potential Vdc2 of the developing roller 12 during execution of the manual drive mode.

[0143] In the manual drive mode, the voltage is applied to the developing roller 12 over a period from when the drive motor 311 starts to drive the photosensitive drum 11 to rotate until the photosensitive drum 11 completes one rotation.

[0144] As shown in FIG. 12(a), during image formation, a charging voltage Vpri1 with a DC component of −800 V is applied to the charging roller 17 from the high-voltage power supply unit 120 (FIG. 3). As a result, the surface of the photosensitive drum 11 is charged to a dark potential Vd1 (=−500 V), for example. The charged surface of the photosensitive drum 11 is exposed to laser light irradiation from the scanner unit 50. As a result, the surface potential of the image area on the surface of the photosensitive drum 11 is reduced to a light potential Vl1 (=−100 V).

[0145] A development voltage is applied to the development roller 12. In this embodiment, a jumping development method is adopted in which the development roller 12 is disposed in non-contact with the photosensitive drum 11, and a development voltage including an AC component is applied to the development roller 12. In this embodiment, a development voltage in which an AC component with a duty of 50%, a frequency of 3 kHz, and 1750 V (peak-to-peak voltage) is superimposed on a DC component of −300 V is applied, thereby forming a development potential Vdc1=−300 V.

[0146] In the development section where the developing roller 12 and photosensitive drum 11 face each other, a bias electric field is formed by a potential difference Vcont1 (development contrast) between the development potential Vdc1 and the light-area potential Vl1 of the photosensitive drum 11. This bias electric field causes the toner carried on the developing roller 12 to transfer to the image area on the photosensitive drum 11 that has the light-area potential Vl1, and the electrostatic latent image is developed into a toner image. Therefore, the DC component (Vdc1) of the voltage applied to the developing roller 12 during image formation is a voltage of the same polarity as the normal polarity of the toner, with the light-area potential Vl1 of the photosensitive drum 11 as the reference.

[0147] Next, the setting of the voltage applied to the developing roller 12 in the manual drive mode will be described. In the manual drive mode, the rear cover 73 and the transfer unit 7 are in the open position, and the photosensitive drum 11 is driven to rotate with part of its surface exposed to the outside of the image forming apparatus 1. Also, in the manual drive mode, no voltage is applied to the charging roller 62. Therefore, the surface of the photosensitive drum 11 is exposed to external light (for example, light from room lighting). Therefore, the surface potential Vext of the photosensitive drum 11 during execution of the manual drive mode is approximately 0 V.

[0148] In this embodiment, the surface of the photosensitive drum 11, which is driven to rotate in the manual drive mode, is exposed to external light, so that the surface potential Vext of the entire surface of the photosensitive drum 11, including the dirty portion, is set to approximately 0 V. For example, when light is irradiated from the scanner unit 50, the time that any one point on the photosensitive drum 11 receives light from the scanner unit 50 is extremely short, so the potential of the dirty portion may not drop sufficiently. In contrast, in the manual drive mode, the time that any one point on the photosensitive drum 11 receives external light is long, so the integrated value of the light amount increases and the potential of the dirty portion also drops to approximately 0 V.

[0149] To transfer the toner on the developing roller 12 to the photosensitive drum 11, a voltage including a DC component of the same polarity as the normal polarity of the toner is applied to the developing roller 12 in the manual drive mode. The potential difference Vcont2 between the potential Vdc2 of the developing roller 12 and the surface potential Vext of the photosensitive drum 11 is set to a voltage of the same polarity as the potential difference Vcont1 between the development potential Vdc1 and the light area potential Vl1 during image formation. In other words, when the manual drive mode is executed, a voltage is applied to the developing roller 12 such that the potential of the developing roller 12 has a predetermined potential difference Vcont2 with respect to the surface potential Vext of the photosensitive drum 11, which is approximately 0 V. It is preferable that the absolute value of the predetermined potential difference Vcont2 be smaller than the potential difference Vcont1 during image formation. In other words, it is preferable that the density of the toner transferred from the developing roller 12 to the surface of the photosensitive drum 11 due to the potential difference Vcont2 be lower than the density of the toner in the image area during image formation.

[0150] In this embodiment, a voltage in which an AC component of 1750 V (peak-to-peak voltage) with a duty of 50% and a frequency of 3 kHz is superimposed on a DC component of −100 V is applied to the developing roller 12. This forms a potential Vdc2 of −100 V for the developing roller 12. The waveform of the AC component may be the same as the waveform of the AC component of the developing voltage during image formation (for example, a square wave).

[0151] In this way, in the manual drive mode, a voltage including a DC component of -100 V is applied to the developing roller 12, thereby generating a potential difference Vcont2 of -100 V with respect to the surface potential Vext of the photosensitive drum 11. In other words, the surface potential of the photosensitive drum 11 when rotating in the manual drive mode is set to Vm1, and the potential of the developing roller 12 when rotating in the manual drive mode is set to Vm2. In this case, in the manual drive mode, a voltage is applied to the developing roller 12 that is set so that the potential difference Vcont2 (=Vm2-Vm1) matches the normal polarity of the toner.

[0152] In manual drive mode, this potential difference Vcont2 allows the toner on the developing roller 12 to be transferred to the photosensitive drum 11. At this time, because the entire surface of the photosensitive drum 11 is lowered to the surface potential Vext (=0 V) for the reasons described above, a thin toner layer (halftone) is formed on the entire surface. The toner layer formed in areas other than the contaminated areas on the photosensitive drum 11 is removed when the cleaning blade 13a (FIG. 2) passes over the photosensitive drum. However, due to the adhesiveness of the contaminants, not all of the toner in the toner layer formed in the contaminated areas on the photosensitive drum 11 is removed even when the cleaning blade 13a passes over the photosensitive drum. Some toner remains on the surface of the photosensitive drum 11. As a result, even if the contaminants on the photosensitive drum 11 are transparent and difficult to see, toner can be attached from the developing roller 12 to the contaminants on the photosensitive drum 11, improving the visibility of the contaminants.

[0153] A user who visually recognizes dirt on the photosensitive drum 11 can, for example, press the power button 80 to stop the rotation of the photosensitive drum 11 (SY5B, SE4B in FIG. 11 ), and then wipe off the dirt with a cloth or the like. In this embodiment, the visibility of dirt in the manual drive mode can be improved, so the user can stop the rotation of the photosensitive drum 11 at an appropriate timing when the dirty portion on the photosensitive drum 11 becomes exposed.

[0154] However, if voltage is continuously applied to the developing roller 12 during the manual drive mode, too much toner may adhere to the dirt, resulting in large toner clumps. In this embodiment, the high-voltage power supply unit 120 applies voltage to the developing roller 12 only during the period from when the photosensitive drum 11 starts to rotate in the manual drive mode until one rotation of the photosensitive drum 11 is completed (until the surface of the photosensitive drum 11 moves 75 mm). After the photosensitive drum 11 has completed one rotation, the application of voltage to the developing roller 12 is stopped.

[0155] In this embodiment, since voltage is applied to the developing roller 12 with the rear cover 73 and transfer unit 7 open, it is desirable to configure the developing roller 12 so that the user cannot directly touch it while the voltage is being applied. In particular, since a voltage including an AC component is applied to the developing roller 12, it is desirable to configure the developing roller 12 so that the user cannot directly touch it. For example, when the image forming apparatus 1 is viewed from the rear side in the state shown in FIG. 4(c), it is desirable that the developing roller 12 and the terminals for applying voltage to the developing roller 12, which are provided on the outer surface of the process unit 40, are not exposed. Alternatively, the voltage applied to the developing roller 12 in the manual drive mode may be set to a voltage value and energy level that will not cause any problems even if the user accidentally touches it.

[0156] As described above, the image forming apparatus 1 of this embodiment can execute a manual drive mode in which the photosensitive drum 11 is driven to rotate in a state in which a portion of the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1. This allows the user to easily check for dirt on the surface of the photosensitive drum 11.

[0157] Furthermore, according to this embodiment, in the manual drive mode, toner is caused to adhere to the stains by applying a voltage to the developing roller 12. This makes it easier to check whether or not there is any stain on the photosensitive drum 11 that could cause white spots.

[0158] Fourth Embodiment Next, a fourth embodiment will be described with reference to Figures 13 and 14. In the fourth embodiment, a cleaner-less image forming apparatus 500 that does not have a cleaning unit for cleaning the surface of the photosensitive drum 11 will be described as an example. This image forming apparatus 500 employs a separation-less contact development method in which the photosensitive drum 11 and the developing roller 512 are always in contact with each other in the developing section. In the contact development method, the toner carried by the developing roller 512 comes into contact with the surface of the photosensitive drum 11 in the developing section. In the contact development method, a separation mechanism that brings the developing roller 512 into and out of contact with the photosensitive drum 11 may be provided, but in this embodiment, a separation-less contact development method in which the two are always in contact with each other is used.

[0159] Hereinafter, unless otherwise specified, elements with the same reference symbols as those in the first embodiment will be assumed to have basically the same configuration and function as those described in the first embodiment, and the following will mainly describe the parts that differ from the first embodiment.

[0160] In the cleaner-less image forming apparatus 500, stains adhering to the photosensitive drum 11 are difficult to remove simply by rotating the photosensitive drum 11 in the manual drive mode.

[0161] Furthermore, in the jumping development method shown in the first to third embodiments, there is a gap between the developing roller 512 and the photosensitive drum 11. Therefore, toner adheres to a dirty portion on the photosensitive drum 11 and forms a toner clump when the dirty portion becomes an image area (exposure area) during image formation. On the other hand, in the contact development method, when the photosensitive drum 11 becomes dirty, the dirty portion comes into contact with toner on the developing roller 512 as it passes through the development unit, regardless of whether the dirty portion is an image area or a non-image area. Therefore, in the contact development method, toner may adhere to a dirty portion on the photosensitive drum 11 and form a toner clump more easily than in the jumping development method.

[0162] That is, in the image forming apparatus 500 of the cleaner-less system and the separation-less developing contact system, white spots as shown in FIG. 8 may easily occur.

[0163] Furthermore, in the separation-less contact development method, when the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 500 and the surface potential becomes approximately 0 V, the photosensitive drum 11 and the developing roller 512 come into contact with each other with the same potential. As a result, part of the toner on the developing roller 512 transfers to the photosensitive drum 11, causing so-called fogging (a thin layer of toner adhering to the entire surface of the photosensitive drum 11).

[0164] Therefore, in a cleaner-less and separation-less contact-development image forming apparatus, even when the manual drive mode is executed, fogging is likely to occur, and the visibility of toner masses on the photosensitive drum 11 may be low. Note that fogging may also occur when part of the toner is transferred to the photosensitive drum 11 from a process member (e.g., charging roller 17) that acts on the photosensitive drum 11 during the image formation process.

[0165] Therefore, in this embodiment, a configuration is proposed that allows the entire surface of the photosensitive drum 11 to be more easily visually inspected while improving the visibility of stains and toner clumps adhering to the photosensitive drum 11.

[0166] 13 is a schematic diagram showing a cross section of an image forming apparatus 500 according to this embodiment. Image forming apparatus 500 differs from image forming apparatus 1 shown in the first embodiment in that it has a pre-exposure device 523 instead of cleaning unit 13, and in the configuration of the developing unit. Other configurations are the same as those of image forming apparatus 1.

[0167] [Cleanerless system] The process unit 540 of this embodiment has a pre-exposure device 523. The pre-exposure device 523 is disposed downstream of the transfer nip N1 and upstream of the charging portion in the rotation direction R of the photosensitive drum 11. The pre-exposure device 523 irradiates light onto the surface area of ​​the photosensitive drum 11 after it has passed through the transfer nip N1 and before it reaches the charging portion to remove static electricity, thereby enabling stable discharge to occur in the charging portion.

[0168] In this embodiment, a contact development method is adopted as the development method. The toner layer carried on the development roller 512 comes into contact with the photosensitive drum 11 in a development section where the photosensitive drum 11 and the development roller 512 face each other. The toner storage section 18 may be provided with a supply roller that applies the stored toner as a developer to the surface of the development roller 12.

[0169] A developing voltage is applied to the developing roller 512 by a high-voltage power supply unit 120. Under the developing voltage, the toner carried on the developing roller 512 is transferred from the developing roller 512 to the drum surface in accordance with the potential distribution on the surface of the photosensitive drum 11. As a result, the electrostatic latent image on the photosensitive drum 11 is developed into a toner image.

[0170] The toner used in this embodiment is a polymerized toner produced by a polymerization method. The normal charging polarity (normal polarity) of this toner is negative. This toner does not contain a magnetic component and is a so-called non-magnetic one-component developer that is supported on the developing roller 12 mainly by intermolecular forces and electrostatic forces (image forces). However, one-component developers containing magnetic components may also be used. In addition to toner particles, the one-component developer may contain additives (e.g., wax or silica fine particles) to adjust the fluidity and charging performance of the toner.

[0171] The image forming apparatus 500 in this embodiment is a cleanerless system. Toner (transfer residual toner) remaining on the photosensitive drum 11 without being transferred to the recording material at the transfer nip N1 is negatively charged by the charging roller 17 and reaches the development unit. In the development unit, the transfer residual toner is collected into the toner storage unit 18 by the development roller 12 due to the potential difference between the photosensitive drum 11 and the development roller 12. More specifically, the transfer residual toner in the non-image area not irradiated with light from the scanner unit 50 is transferred from the photosensitive drum 11 to the development roller 12 due to the potential difference between the dark area potential Vd1 and the development potential Vdc1 during image formation. On the other hand, the transfer residual toner in the image area irradiated with light from the scanner unit 50 remains on the surface of the photosensitive drum 11 due to the potential difference between the light area potential Vl1 and the development potential Vdc1 during image formation, and becomes part of the toner image.

[0172] In the cleaner-less system, a container for collecting waste toner is not required, and therefore the image forming apparatus 500 can be made smaller.

[0173] [Potential setting in manual drive mode] In this embodiment as well, the rear cover 73 and the transfer unit 7 can be opened to expose the surface of the photosensitive drum 11 to the outside of the image forming apparatus 500, and a manual drive mode can be executed in which the photosensitive drum 11 is driven to rotate. This allows the user to easily check for dirt on the surface of the photosensitive drum 11.

[0174] However, in this embodiment, as described above, there is a possibility that fogging may occur when the photosensitive drum 11 is rotated while the rear cover 73 and the transfer unit 7 are open. Therefore, in this embodiment, in the manual drive mode, a voltage is applied to the process members in contact with the photosensitive drum 11 to reduce the occurrence of fogging. In this embodiment, the "process members in contact with the photosensitive drum 11" are the charging roller 17 and the developing roller 512.

[0175] 14(a) shows the potential relationship in the non-image area during image formation, and FIG. 14(b) shows the potential relationship in the non-image area during execution of the manual drive mode.

[0176] 14(a), during image formation, a DC voltage of −1350 V is applied from the high-voltage power supply unit 120 to the charging roller 17 as a charging voltage Vpri51. As a result, for example, the surface potential of the photosensitive drum 11 is charged to Vd51=−800 V. In addition, in this embodiment, a DC voltage of Vdc51=−380 V is applied to the developing roller 512. Furthermore, the surface potential after exposure by the scanner unit 50 (light area potential Vl51) is −80 V.

[0177] The surface potential of the non-image area not exposed by the scanner unit 50 remains at the dark potential Vd51. Therefore, in the development section, a potential difference Vback51 (=Vd51-Vdc51) is formed between the development roller 12 and the non-image area of ​​the photosensitive drum 11. This potential difference Vback51 has the effect of preventing the toner carried on the development roller 12 from migrating to the photosensitive drum 11, and is therefore also called the fog removal contrast.

[0178] Furthermore, the charging roller 17 may retain residual toner that has been transferred from the photosensitive drum 11 to the charging roller 17. The residual toner includes toner particles (reverse toner) that have been charged to an irregular polarity (positive polarity) due to discharge at the transfer nip N1, and toner particles (low charge toner) with a charge amount close to zero. The reverse toner and low charge toner are easily attracted to and retained by the charging roller 17 to which a charging voltage Vpri51 of -1350V is applied.

[0179] In addition, since the present embodiment employs a cleanerless system, residual toner generated at the transfer nip N1 reaches the charging section without being removed by a cleaning unit, which may result in a larger amount of residual toner being retained on the charging roller 17 than in an image forming apparatus equipped with a cleaning unit.

[0180] The charging voltage Vpri51 applied to the charging roller 17 during image formation is set to a voltage value with a more negative polarity than the dark potential Vd51 of the photosensitive drum 11. Due to the existence of a potential difference Vpd51 between the charging voltage Vpri51 and the dark potential Vd51, the transfer residual toner (reverse toner and low charge toner) held on the charging roller 17 is kept in a state where it is difficult for it to migrate from the charging roller 17 to the photosensitive drum 11.

[0181] 14(b), during execution of the manual drive mode, the photosensitive drum 11 is exposed to light outside the device, and therefore the surface potential Vext of the photosensitive drum 11 becomes approximately 0 V. In the following description, it is assumed that Vext = 0 V, but it does not have to be strictly 0 V.

[0182] To prevent the toner on the developing roller 512 from transferring to the photosensitive drum 11 in the manual drive mode, a potential difference Vback52 similar to the potential difference Vback51 during image formation is formed between the developing roller 512 and the photosensitive drum 11. It is preferable to apply a voltage Vdc52 containing a DC component of polarity opposite to the normal polarity of the toner to the developing roller 512. In other words, the voltage applied to the developing roller 512 when the manual drive mode is executed is set so that a predetermined potential difference Vcont2 is achieved between the potential (Vdc52) of the developing roller 512 and the surface potential Vext=0V of the photosensitive drum 11.

[0183] In this embodiment, a DC voltage of +150 V is applied to the developing roller 512 as the voltage Vdc52 during execution of the manual drive mode.

[0184] Furthermore, in order to prevent the transfer residual toner on the charging roller 17 from transferring to the photosensitive drum 11 in the manual drive mode, a potential difference Vpd52 similar to the potential difference Vpd51 during image formation is formed between the charging roller 17 and the photosensitive drum 11. It is preferable to apply a voltage Vpri52 containing a DC component of the same polarity as the normal polarity of the toner to the charging roller 17. In other words, the voltage Vpri52 applied to the charging roller 17 in the manual drive mode is set so that the potential of the charging roller 17 and the surface potential Vext=0V of the photosensitive drum 11 become a predetermined potential difference Vpd52.

[0185] In this embodiment, during execution of the manual drive mode, a DC voltage of −340 V, which is a potential difference with respect to the surface potential Vext of the photosensitive drum 11 so as not to cause discharge, is applied as the voltage Vpri52 to the charging roller 17.

[0186] In other words, the surface potential of the non-image area of ​​the photosensitive drum 11 during image formation is Vg1, and the potential of the process member during image formation is Vg2. Furthermore, the surface potential of the photosensitive drum 11 when rotating the photosensitive drum 11 in the manual drive mode is Vm1, and the potential of the process member when rotating the photosensitive drum 11 in the manual drive mode is Vm2. In this case, in the manual drive mode, a voltage is applied to the process member such that the sign of the potential difference (Vg2-Vg1) matches the sign of the potential difference (Vm2-Vm1). This makes it possible to prevent toner held on the process member from transferring to the photosensitive drum 11 during execution of the manual drive mode, thereby improving the visibility of stains and toner clumps on the photosensitive drum 11.

[0187] Specifically, a voltage is applied to the developing roller 512 during execution of the manual drive mode so that the polarity of the potential of the developing roller 512, based on the surface potential of the non-image area of ​​the photosensitive drum 11 during image formation, is the same as the polarity of the potential of the developing roller 512, based on the surface potential of the photosensitive drum 11 during execution of the manual drive mode. This makes it possible to suppress the transfer of toner from the developing roller 512 to the photosensitive drum 11, thereby improving the visibility of stains and toner clumps adhering to the photosensitive drum 11. In particular, in this embodiment, although a separation-less contact development system is used in which the toner on the developing roller 512 is always in contact with the photosensitive drum 11, it is possible to suppress the transfer of toner from the developing roller 512 to the photosensitive drum 11 during execution of the manual drive mode.

[0188] Furthermore, a voltage is applied to the charging roller 17 during the manual drive mode so that the polarity of the potential of the charging roller 17, based on the surface potential of the non-image area of ​​the photosensitive drum 11 during image formation, is the same as the polarity of the potential of the charging roller 17, based on the surface potential of the photosensitive drum 11 during the manual drive mode. This makes it possible to suppress the transfer of toner from the charging roller 17 to the photosensitive drum 11 during the manual drive mode, thereby improving the visibility of stains and toner clumps adhering to the photosensitive drum 11. In particular, in this embodiment, although a cleaner-less system is used in which transfer residual toner easily reaches the charging roller 17, it is possible to suppress the transfer of toner from the charging roller 17 to the photosensitive drum 11 during the manual drive mode.

[0189] In this embodiment, the developing roller 512 and the charging roller 17 are given as examples of process members that come into contact with the photosensitive drum 11, but a voltage may also be applied to other process members that come into contact with the photosensitive drum 11 while the manual drive mode is being executed.

[0190] In this embodiment, it is preferable that the period during which voltage is applied to the developing roller 512 and the charging roller 17 during the manual drive mode is only while the photosensitive drum 11 is being rotated.

[0191] Furthermore, in this embodiment, because voltage is applied to the developing roller 512 and the charging roller 17 with the rear cover 73 and the transfer unit 7 open, it is desirable that the user not directly touch the developing roller 512 or the charging roller 17 while voltage is being applied. For example, when the image forming apparatus 1 is viewed from the rear side in the state shown in FIG. 4(c), it is preferable that the developing roller 512, the charging roller 17, and the terminals for applying voltage to the developing roller 512 or the charging roller 17, which are provided on the outer surface of the process unit 40, are not exposed. Alternatively, the voltage applied to the developing roller 512 and the charging roller 17 in the manual drive mode may be set to a voltage value and energy level that will not cause any problems even if the user accidentally touches them.

[0192] Furthermore, in this embodiment, the settings of the voltages applied to the charging roller 17 and the developing roller 512 have been described on the assumption that the surface potential Vext of the photosensitive drum 11 is approximately 0 V when the rear cover 73 and the transfer unit 7 are open. However, the present invention is not limited to this. For example, consider a configuration in which the photosensitive drum 11 is shielded from light at least in the range from the charging unit to the developing unit when the rear cover 73 and the transfer unit 7 are open. In this case, the same voltage settings as those used during image formation may be applied to the charging roller 17 and the developing roller 512 in the manual drive mode.

[0193] Thus, according to this embodiment, in a cleanerless image forming apparatus 500 in which white spots are likely to occur, fogging in manual drive mode is suppressed, while the rotation of the photosensitive drum 11 makes it easy to check for the presence or absence of dirt on the photosensitive drum 11.

[0194] Other Forms In the above-described embodiments, the image carrier is a photosensitive drum, but the image carrier may be an intermediate transfer member in an intermediate transfer type image forming apparatus. The intermediate transfer member is, for example, an intermediate transfer belt used in a tandem type color image forming apparatus. In this case, the toner images formed on the photosensitive drums of the plurality of process units are primarily transferred to the intermediate transfer belt, and then secondarily transferred from the intermediate transfer belt to a recording material at a secondary transfer section.

[0195] Furthermore, in the above-described embodiments, a configuration has been exemplified in which, when both the rear cover 73 and the transfer unit 7 are open, a portion of the surface of the photosensitive drum 11 is exposed to the outside of the image forming apparatus 1. However, the image forming apparatus 1 may have, for example, a unit including an outer surface that forms the exterior surface of the image forming apparatus 1 and a transfer roller 7a as a transfer member (for example, a configuration in which the rear cover 73 and the transfer unit 7 are integrated). In this case, by moving the unit from a closed position that covers the opening 91 of the housing 72 to an open position that opens the opening 91, a portion of the surface of the photosensitive drum 11 can be exposed to the outside of the image forming apparatus 1.

[0196] In addition, in each of the above-described embodiments, an image forming apparatus with a so-called C-path configuration has been exemplified, in which the conveyance path of the recording material P inside the image forming apparatus is approximately C-shaped. The approximately C-shaped conveyance path is a path in which the recording material P is fed to one side (-Y side) in the horizontal direction, an image is formed on the recording material P while it is conveyed upward inside the apparatus, and the recording material is discharged to the other side (+Y side) in the horizontal direction. In an image forming apparatus with a C-path configuration, the image carrier is often exposed to the outside of the image forming apparatus by opening the rear cover 73 and / or the transfer unit 7.

[0197] However, the advantages of this technology are not limited to the C-path configuration. For example, as shown in Fig. 15, this technology may be applied to an image forming apparatus with a so-called S-path configuration, in which the conveying path of the recording material P inside the image forming apparatus is approximately S-shaped. The approximately S-shaped conveying path is a path in which the recording material P is fed to one side in the horizontal direction (-Y side), an image is formed while the recording material P is conveyed inside the apparatus toward the other side in the horizontal direction (+Y side), and the recording material P is discharged toward one side in the horizontal direction (-Y side).

[0198] 15, for example, the fixing unit 9 may be removed from the housing of the image forming apparatus, thereby exposing the photosensitive drum 11 as an image carrier to the outside of the image forming apparatus. The detachable fixing unit 9 is an example of a unit that is detachably attached to the housing. The state in which the fixing unit 9 is attached corresponds to the first state, and the state in which the fixing unit 9 is removed corresponds to the second state. Even in this case, by configuring the image forming apparatus to be able to execute a manual drive mode in which the photosensitive drum 11 is rotated while a portion of the surface of the photosensitive drum 11 is exposed to the outside of the apparatus, the same advantages as those of the above-described embodiments can be obtained.

[0199] The operation timing of rotation and stopping of the image carrier (photosensitive drum), the amount of rotation, the rotation speed, the potential settings of each component, etc. in the manual drive mode described in each of the above-mentioned embodiments are merely examples, and can be changed as appropriate depending on the specific configuration and operating conditions of the image forming apparatus.

[0200] In the above-described embodiments, a fixing film 9a and a pressure roller 9b are used as a pair of rotating bodies in the fixing unit 9, and the fixing film 9a is not driven to rotate in the manual drive mode. The configuration of the fixing unit 9 is not limited to this, and for example, a pair of rollers consisting of two cylindrical rollers may be used as the pair of rotating bodies. Furthermore, the fixing unit 9 is not limited to a configuration in which the pressure roller 9b is separated from the fixing film 9a in the manual drive mode, so that the fixing film 9a is not driven to rotate, and any configuration may be used as long as the driving force of the drive source is not transmitted to at least one of the pair of rotating bodies.

[0201] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0202] Summary of the Disclosure The present disclosure includes at least the following: (Configuration 1) An image forming apparatus, a rotating image carrier; a unit that can be in a first state in which a part of a surface of the image carrier is allowed to be exposed to the outside of the image forming apparatus, and a second state in which the surface of the image carrier is not exposed to the outside of the image forming apparatus; a drive source that drives the image carrier; a control means for controlling the driving source; Equipped with the control means is capable of executing a mode in which the image carrier is rotated by the drive source when the unit is in the first state; An image forming apparatus characterized by: (Configuration 2) in the mode, the control means causes the drive source to start rotation of the image carrier in a state where a first region of the surface of the image carrier is exposed to the outside of the image forming apparatus, and then stops rotation of the image carrier in a state where a second region of the surface of the image carrier, which is different from the first region, is exposed to the outside of the image forming apparatus; 2. The image forming apparatus according to claim 1, (Configuration 3) A portion of the first region overlaps with the second region. 3. The image forming apparatus according to configuration 2. (Configuration 4) further comprising an operation unit that accepts user operations; the control unit executes a unit operation of rotating the image carrier a predetermined amount and then stopping the rotation of the image carrier every time the operation unit is operated in the mode. 4. The image forming apparatus according to configuration 2 or 3. (Configuration 5) Further, a cleaning unit for cleaning the surface of the image carrier is provided. the control means, in the mode, continuously rotates the image carrier until an instruction to stop the rotation of the image carrier is received. 2. The image forming apparatus according to claim 1, (Configuration 6) a peripheral speed of the image carrier in the mode is slower than a peripheral speed of the image carrier when the image forming apparatus performs an image forming operation using the image carrier; 6. The image forming apparatus according to configuration 5. (Configuration 7) the image carrier is a photosensitive drum, The image forming apparatus further includes a developing roller that supplies toner to the photosensitive drum to develop the latent image into a toner image, When the surface potential of the photosensitive drum when rotating the photosensitive drum in the mode is Vm1, and the potential of the developing roller when rotating the photosensitive drum in the mode is Vm2, In the mode, a voltage is applied to the developing roller so that the potential difference (Vm2-Vm1) coincides with the normal polarity of the toner. 7. The image forming apparatus according to any one of configurations 1 to 6. (Configuration 8) a process member that acts on the image carrier in an image forming process; When the surface potential of the non-image area of ​​the image carrier during image formation is Vg1, the potential of the process member during image formation is Vg2, the surface potential of the image carrier when rotating the image carrier in the mode is Vm1, and the potential of the process member when rotating the image carrier in the mode is Vm2, In the mode, a voltage is applied to the process member so that the sign of the potential difference (Vg2-Vg1) and the sign of the potential difference (Vm2-Vm1) match. 7. The image forming apparatus according to any one of configurations 1 to 6. (Configuration 9) the image carrier is a photosensitive drum, the process member is a charging roller that is in contact with the photosensitive drum and charges the surface of the photosensitive drum; 9. The image forming apparatus according to configuration 8, (Configuration 10) the image forming apparatus does not have a cleaning unit for removing toner that has not been transferred from the photosensitive drum to a transfer target, from the photosensitive drum; 10. The image forming apparatus according to configuration 9, (Configuration 11) the image carrier is a photosensitive drum, the process member is a developing roller that supplies toner to the photosensitive drum to develop the latent image into a toner image, and is configured so that the toner carried on the outer peripheral surface of the developing roller is always in contact with the surface of the photosensitive drum; 11. The image forming apparatus according to any one of configurations 8 to 10. (Configuration 12) a housing having an opening; the unit is an opening / closing member that is movable between an open position that opens the opening and a closed position that closes the opening, the first state is a state in which the unit is in the open position, and the second state is a state in which the unit is in the closed position; When the opening / closing member is in the open position, the part of the surface of the image carrier is allowed to be exposed to the outside of the image forming apparatus through the opening. 12. The image forming apparatus according to any one of configurations 1 to 11. (Configuration 13) Further comprising a transfer unit having a transfer member, the transfer unit is movable between a first position where a transfer portion where a toner image is transferred from the image carrier to a transferee is formed between the transfer member and the image carrier, and a second position where the transfer member is separated from the image carrier; When the opening / closing member is in the open position and the transfer unit is in the second position, the part of the surface of the image carrier is exposed to the outside of the image forming apparatus through the opening. 13. The image forming apparatus according to configuration 12. (Configuration 14) the control unit causes the drive source to rotate the image carrier when the opening / closing member is in the open position and the transfer unit is in the first position in the mode. 14. The image forming apparatus according to claim 13, (Configuration 15) the control unit causes the drive source to rotate the image carrier when the opening / closing member is in the open position and the transfer unit is in the second position in the mode. 15. The image forming apparatus according to claim 13 or 14. (Configuration 16) a detection unit that outputs a detection signal according to whether the opening / closing member is in the closed position, the control means starts the mode when, after a user instructs the control means to transition to the mode, it detects that the opening / closing member has been moved from the closed position to the open position based on a detection signal from the detection unit. 16. The image forming apparatus according to any one of configurations 13 to 15. (Configuration 17) The unit has an outer surface that forms an exterior surface of the image forming apparatus, and a transfer member that forms a transfer portion between the unit and the image carrier. 12. The image forming apparatus according to any one of configurations 1 to 11. (Configuration 18) The unit further includes a housing to which the unit is removably attached, the first state is a state in which the unit is attached to the housing, The second state is a state in which the unit is detached from the housing. 12. The image forming apparatus according to any one of configurations 1 to 11. (Configuration 19) The recording medium conveying device further includes a fixing device having a pair of rotating rotors, and fixing a toner image on the recording medium while sandwiching and conveying the recording medium at a nip portion of the pair of rotors, the drive source drives the pair of rotors to rotate; During execution of the mode, at least one of the pair of rotating bodies is not rotationally driven by the drive source. 19. The image forming apparatus according to any one of configurations 1 to 18. (Configuration 20) the image carrier is a photosensitive drum, 20. The image forming apparatus according to any one of configurations 1 to 19. (Configuration 21) the image carrier is an intermediate transfer member, the image forming apparatus transfers a toner image from the photosensitive drum to the intermediate transfer body, and then transfers the toner image from the intermediate transfer body to a recording material; 20. The image forming apparatus according to any one of configurations 1 to 19. [Explanation of symbols]

[0203] 7...Transfer unit / 11...Image carrier (photosensitive drum) / 12, 512...Process member, developing roller / 13...Cleaning unit / 17...Process member, charging roller / 73...Unit, opening / closing member (rear cover) / 80...Operation unit (power button) / 130...Control means (engine controller) / 311...Drive source (drive motor)

Claims

1. An image forming apparatus, a rotating image carrier; a unit that can be in a first state in which a part of a surface of the image carrier is allowed to be exposed to the outside of the image forming apparatus, and a second state in which the surface of the image carrier is not exposed to the outside of the image forming apparatus; a drive source that drives the image carrier; a control means for controlling the driving source; Equipped with the control unit is capable of executing a mode in which the image carrier is rotated by the drive source when the unit is in the first state; An image forming apparatus characterized by:

2. In the mode, the control unit causes the drive source to start rotation of the image carrier in a state where a first region of the surface of the image carrier is exposed to the outside of the image forming apparatus, and then stops the rotation of the image carrier in a state where a second region of the surface of the image carrier, which is different from the first region, is exposed to the outside of the image forming apparatus.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. A portion of the first region overlaps with the second region.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. further comprising an operation unit that accepts user operations; the control unit executes a unit operation of rotating the image carrier a predetermined amount and then stopping the rotation of the image carrier every time the operation unit is operated in the mode.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

5. Further, a cleaning unit for cleaning the surface of the image carrier is provided. the control means, in the mode, continuously rotates the image carrier until an instruction to stop the rotation of the image carrier is received.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. a peripheral speed of the image carrier in the mode is slower than a peripheral speed of the image carrier when the image forming apparatus performs an image forming operation using the image carrier; 6. The image forming apparatus according to claim 5,

7. the image carrier is a photosensitive drum, The image forming apparatus further includes a developing roller that supplies toner to the photosensitive drum to develop the latent image into a toner image, When the surface potential of the photosensitive drum when rotating the photosensitive drum in the mode is Vm1, and the potential of the developing roller when rotating the photosensitive drum in the mode is Vm2, In the mode, a voltage is applied to the developing roller so that a potential difference (Vm2-Vm1) coincides with the normal polarity of the toner.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. a process member that acts on the image carrier in an image forming process; When the surface potential of the non-image area of ​​the image carrier during image formation is Vg1, the potential of the process member during image formation is Vg2, the surface potential of the image carrier when rotating the image carrier in the mode is Vm1, and the potential of the process member when rotating the image carrier in the mode is Vm2, In the mode, a voltage is applied to the process element such that the sign of the potential difference (Vg2-Vg1) and the sign of the potential difference (Vm2-Vm1) match.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. the image carrier is a photosensitive drum, the process member is a charging roller that is in contact with the photosensitive drum and charges the surface of the photosensitive drum; 9. The image forming apparatus according to claim 8,

10. the image forming apparatus does not have a cleaning unit for removing toner that has not been transferred from the photosensitive drum to a transfer target, from the photosensitive drum; 10. The image forming apparatus according to claim 9,

11. the image carrier is a photosensitive drum, the process member is a developing roller that supplies toner to the photosensitive drum to develop the latent image into a toner image, and is configured so that the toner carried on the outer peripheral surface of the developing roller is always in contact with the surface of the photosensitive drum; 9. The image forming apparatus according to claim 8,

12. a housing having an opening; the unit is an opening / closing member that is movable between an open position that opens the opening and a closed position that closes the opening, the first state is a state in which the unit is in the open position, and the second state is a state in which the unit is in the closed position; When the opening / closing member is in the open position, the part of the surface of the image carrier is allowed to be exposed to the outside of the image forming apparatus through the opening.

12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

13. Further comprising a transfer unit having a transfer member, the transfer unit is movable between a first position where a transfer portion where a toner image is transferred from the image carrier to a transferee is formed between the transfer member and the image carrier, and a second position where the transfer member is separated from the image carrier; When the opening / closing member is in the open position and the transfer unit is in the second position, the part of the surface of the image carrier is exposed to the outside of the image forming apparatus through the opening.

13. The image forming apparatus according to claim 12.

14. the control unit causes the drive source to rotate the image carrier when the opening / closing member is in the open position and the transfer unit is in the first position in the mode.

14. The image forming apparatus according to claim 13.

15. the control unit causes the drive source to rotate the image carrier when the opening / closing member is in the open position and the transfer unit is in the second position in the mode.

14. The image forming apparatus according to claim 13.

16. a detection unit that outputs a detection signal according to whether the opening / closing member is in the closed position, the control means starts the mode when, after a user instructs the control means to transition to the mode, it detects that the opening / closing member has been moved from the closed position to the open position based on a detection signal from the detection unit.

14. The image forming apparatus according to claim 13.

17. The unit has an outer surface that forms an exterior surface of the image forming apparatus, and a transfer member that forms a transfer portion between the unit and the image carrier.

12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

18. The unit further includes a housing to which the unit is removably attached, the first state is a state in which the unit is attached to the housing, the second state is a state in which the unit is detached from the housing; 12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

19. The recording medium conveying device further includes a fixing device having a pair of rotating rotors, and fixing a toner image on the recording medium while sandwiching and conveying the recording medium at a nip portion of the pair of rotors, the drive source drives the pair of rotors to rotate; During execution of the mode, at least one of the pair of rotating bodies is not rotationally driven by the drive source.

12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

20. the image carrier is a photosensitive drum, 12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

21. the image carrier is an intermediate transfer member, the image forming apparatus transfers a toner image from the photosensitive drum to the intermediate transfer body, and then transfers the toner image from the intermediate transfer body to a recording material; 12. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

Images