Image forming apparatus, cleaning method, and cleaning program

Abstract

To clean a duct in which surplus toner is accumulated while maintaining exhausting performance.SOLUTION: An image forming apparatus 1 comprises: a developing unit 21Y that has a developing roller 25Y holding toner; a dust collection duct 60 that has a suction port 62Y connected with a first space SP1 in contact with a portion of the developing roller 25Y exposed from the developing unit 21Y, and an exhaust port 64Y connected with the outside; a fan 79 that is connected with the exhaust port 64Y, and exhausts air in a second space SP2 inside the dust collection duct 60Y to the outside; an opening 65 that is formed between the suction port 62Y and the exhaust port 64Y, and opens the second space SP2 in the dust collection duct 60Y to the outside; a first shield member 67Y configured to be able to open and close the suction port 62Y; and a second shield member 69Y configured to be able to open and close the opening 65 according to the difference in atmospheric pressure between the inside and outside of the dust collection duct 60Y.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, a cleaning method, and a cleaning program, and more particularly to an image forming apparatus that forms an image on a recording medium using toner, a cleaning method executed by the image forming apparatus, and a cleaning program that causes a computer to execute the cleaning method.

Background Art

[0002] Image forming apparatuses that form a toner image composed of toner on paper are known. In such an image forming apparatus, an electrostatic latent image formed on a photosensitive drum is developed with toner by a developing device. The image forming apparatus has a function of generating an air flow to collect the toner scattered from the developing device so that the toner scattered from the developing device does not adhere to other components such as the photosensitive drum during the developing process.

[0003] For example, in Japanese Patent Application Laid-Open No. 2013-125148, an exhaust fan is operated with the air inlet of a duct closed and the air inflow path of a developing container open to generate an air flow with a first flow rate in the duct and the collective duct, so that the toner floating in the developing container is sucked into the duct. During non-image formation, the exhaust fan is operated with the air inlet open and the air inflow path closed to generate an air flow with a second flow rate faster than the first flow rate in the duct and the collective duct, so that a forced discharge mode for forcibly discharging the toner deposited in the duct and the collective duct can be executed. In the image forming apparatus described in this document, an air flow with a second flow rate faster than the first flow rate can be generated in the duct and the collective duct, but the flow rate is limited by the capacity of the exhaust fan. Therefore, in order to discharge larger toner deposited in the duct and the collective duct, a higher-performance exhaust fan must be used, resulting in a problem of increased product cost.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-125148 [Overview of the project] [Problems that the invention aims to solve]

[0005] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide an image forming apparatus that can clean a duct where excess toner has accumulated while maintaining exhaust performance.

[0006] Another object of this invention is to provide a cleaning method that can clean a duct in which excess toner has accumulated while maintaining exhaust performance.

[0007] Another object of this invention is to provide a cleaning program that can clean a duct where excess toner has accumulated while maintaining exhaust performance. [Means for solving the problem]

[0008] To achieve the above-mentioned objective, according to one aspect of this invention, an image forming apparatus includes a developer having a developing roller that holds toner, a duct having an intake port connected to a space in contact with the portion of the developing roller exposed from the developer and an exhaust port connected to the outside, a blowing means connected to the exhaust port for discharging gas from inside the duct to the outside, an opening formed between the intake port and the exhaust port for opening the internal space of the duct to the outside, and a first shielding member configured to open and close the intake port. This occurs when the first shielding member closes the intake port and the blowing means discharges the gas inside the duct. The system includes a second shielding member configured to open and close its opening in accordance with the pressure difference between the inside and outside of the duct.

[0009] In this scenario, the air blower expels the gas inside the duct to the outside, thus expelling excess toner floating in the space in contact with the part of the developing roller exposed to the developing unit. Furthermore, when the air blower expels the gas inside the duct from the outlet while the opening formed between the duct's intake and exhaust is closed by the second shielding member and the intake is closed by the first shielding member, the air pressure inside the duct decreases. When the second shielding member opens its opening while the air pressure inside the duct is lower than the outside air pressure, outside air is sent into the duct's interior through the opening, creating an airflow in the duct's interior with a faster wind speed than the airflow generated by the air blower. As a result, foreign matter such as clumps of excess toner accumulated on the inner wall of the duct's interior is blown away by the airflow. Consequently, an image forming apparatus can be provided that can clean a duct where excess toner has accumulated while maintaining exhaust performance.

[0010] Preferably, each duct extends from an intake to an exhaust, and at least a portion of it has opposing upper and lower surfaces, with the opening formed in the portion of the upper surface that faces the lower surface.

[0011] Following this procedure allows for the discharge of excess toner accumulated on the underside of the duct.

[0012] Preferably, the opening is formed on the outlet side of the first shielding member.

[0013] Following this procedure, outside air can be introduced into the duct's internal space, where the air pressure is lower than the outside.

[0014] Preferably, multiple openings are formed in a row along the axial direction of the developing roller.

[0015] Following this procedure, excess toner that accumulates in a dispersed manner along the axial direction of the developing roller in the duct can be discharged.

[0016] Preferably, in the axial direction of the developing roller, the distance between two adjacent openings at each end is narrower than the distance between two adjacent openings at the center.

[0017] In this configuration, the spacing between the multiple openings in the axial direction of the developing roller is narrower at both ends than at the center, so more air flows to both ends of the duct than to the center. Therefore, when excess toner tends to accumulate more at both ends of the duct than in the center, the excess toner accumulated in the duct can be discharged.

[0018] Preferably, in the axial direction of the developing roller, the inner diameters of the openings at both ends are larger than the inner diameter of the central opening.

[0019] In this configuration, the inner diameters of the multiple openings are larger at both ends than at the center, so more air flows to both ends of the duct than to the center. Therefore, when excess toner tends to accumulate more at both ends of the duct than in the center, the excess toner accumulated in the duct can be discharged.

[0020] Preferably, the second shielding member is in the state with the opening open. open Position and with the opening closed Blockage It includes a shielding plate that is movable to a position, and an elastic member that biases the shielding plate in the direction from the open position to the closed position.

[0021] In this scenario, the shielding plate is biased by the elastic member in the direction from the open position to the closed position. Therefore, when the force acting on the shielding plate from the opening due to the difference in air pressure inside and outside the duct becomes greater than the elastic force of the elastic member, the shielding plate moves to the open position. As a result, if the first shielding member maintains the state of closing the intake port, the shielding plate repeatedly opens and closes the opening, allowing the second shielding member to be opened and closed automatically.

[0022] Preferably, the elastic force of the elastic member is determined based on the force with which the elastic member biases the shielding plate and the force that the shielding plate receives from the opening due to the pressure difference between the inside and outside of the duct.

[0023] According to this aspect, by adjusting the elastic force of the elastic member, the velocity of the airflow generated in the internal space of the duct can be adjusted.

[0024] Preferably, it further includes switching control means for switching the first shielding member to a state of closing the suction port while the developing device stops the developing roller.

[0025] According to this aspect, since the first shielding member is switched to a state of closing the suction port while the developing device stops the developing roller, the internal space of the duct is cleaned while there is no excess toner floating in the space contacting the exposed portion of the developing roller from the developing device. Therefore, it can be ensured that the developing operation by the developing device is not adversely affected.

[0026] Preferably, the switching control means switches the first shielding member to a closed state based on the driving history of the developing device.

[0027] According to this aspect, since the first shielding member is switched to a closed state based on the driving history of the developing device, the internal space of the duct can be cleaned at an appropriate timing when the amount of toner accumulated in the internal space of the duct reaches an appropriate level.

[0028] Preferably, after the switching control means switches the first shielding member to a state of closing the suction port, the first shielding member maintains the state of closing the suction port until the second shielding member opens and closes the opening a predetermined number of times continuously.

[0029] According to this aspect, since the second shielding member opens and closes the opening a predetermined number of times continuously, the internal space of the duct can be efficiently cleaned.

[0030] Preferably, the system comprises a plurality of developing units, each of which is provided with a duct, an opening, a first shielding member, and a second shielding member, and further comprises a blocking means corresponding to each of the plurality of ducts that blocks the space between the outlet and the blowing means, and a blocking control means that controls the blocking means corresponding to non-target developing units other than the target developing unit to block the space between the outlet and the blowing means corresponding to the non-target developing unit, and controls the blocking means corresponding to the target developing unit to prevent the space between the outlet and the blowing means corresponding to the target developing unit from being blocked.

[0031] In this configuration, the connection between the duct outlets corresponding to non-target developers (among the multiple developers) and the blowing means is blocked, and the connection between the duct outlet corresponding to the target developer and the blowing means is blocked. As a result, the airflow generated by the blowing means does not flow into multiple ducts, and all the airflow generated by the supply means flows into the duct corresponding to the target developer. Therefore, multiple ducts corresponding to multiple developers can be cleaned.

[0032] According to another aspect of this invention, the cleaning method is a cleaning method for controlling an image forming apparatus, the image forming apparatus comprising: a developer having a developing roller that holds toner; a duct having an intake port connected to a space in contact with the portion of the developing roller exposed from the developer and an exhaust port connected to the outside; a blowing means connected to the exhaust port for discharging gas from inside the duct to the outside; an opening formed between the intake port and the exhaust port for opening the internal space of the duct to the outside; and a first shielding member configured to open and close the intake port. This occurs when the first shielding member closes the intake port and the blowing means discharges the gas inside the duct. The device comprises a second shielding member configured to open and close an opening in accordance with the pressure difference between the inside and outside of the duct, and includes a switching control step of switching the first shielding member to a state where the intake port is closed while the developing unit has stopped the developing rollers.

[0033] Following this approach, it is possible to provide a cleaning method that allows for the cleaning of ducts where excess toner has accumulated while maintaining exhaust performance.

[0034] According to yet another aspect of this invention, the cleaning program is a cleaning program executed by a computer that controls an image forming apparatus, the image forming apparatus comprising a developer having a developing roller that holds toner, and an intake port connected to a space in contact with the portion of the developing roller exposed from the developer Connecting to the outside world A duct having an outlet, a blowing means connected to the outlet for discharging gas from inside the duct to the outside, an opening formed between the intake and outlet for opening the internal space of the duct to the outside, and a first shielding member configured to open and close the intake. This occurs when the first shielding member closes the intake port and the blowing means discharges the gas inside the duct. The system includes a second shielding member configured to open and close its opening in accordance with the pressure difference between the inside and outside of the duct, and causes a computer to perform a switching control step in which the first shielding member switches to a state where the intake port is closed while the developing unit has stopped the developing rollers.

[0035] Following this approach, it is possible to provide a cleaning program that can clean ducts where excess toner has accumulated while maintaining exhaust performance. [Brief explanation of the drawing]

[0036] [Figure 1] This figure shows a schematic example of the internal configuration of an image forming apparatus in one embodiment of the present invention. [Figure 2] This figure shows an example of a cross-sectional view of the area around a developing unit. [Figure 3] This is a perspective view of the lower part of the duct. [Figure 4] This is a side view of the top of the duct. [Figure 5] This is a plan view showing an example of a second shielding member. [Figure 6] This is the first diagram illustrating the state of the first shielding member and the second shielding member. [Figure 7] This is a second diagram illustrating the state of the first and second shielding members. [Figure 8] This is a perspective view showing an example of an exhaust duct. [Figure 9] This is a block diagram showing an example of the detailed configuration of the control unit. [Figure 10] This is a block diagram showing an example of the functions provided by the control unit. [Figure 11] This is a flowchart illustrating an example of the cleaning process. [Figure 12] This is a side view of the upper part of the duct in the first modified example. [Figure 13] This is a bottom view showing an example of the second shielding member in the second modified example. [Figure 14] This is a bottom view showing the second shielding member along with the surrounding members in the third modified example. [Figure 15] This is a cross-sectional view showing the second shielding member together with the surrounding members in the third modified example. [Figure 16] This is a cross-sectional view showing the second shielding member together with the surrounding members in the fourth modified example. [Modes for carrying out the invention]

[0037] The image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0038] Figure 1 is a diagram illustrating a schematic example of the internal configuration of an image forming apparatus in one embodiment of the present invention. Here, the X, Y, and Z directions are defined as intersecting each other perpendicularly. The X and Y directions are parallel to the horizontal plane, and the Z direction is perpendicular to the horizontal plane. Figure 1 shows the components necessary for describing the present invention, and the image forming apparatus of the present invention is not limited to the example shown in Figure 1. Referring to Figure 1, the image forming apparatus 1 comprises a main body 11, a paper feeder 13, and a winding device 15. The paper feeder 13 is located in front of the main body 11, and the winding device 15 is located behind the main body 11. The paper feeder 13 feeds roll paper R to the main body 11 in the transport direction indicated by the arrow in Figure 1. The transport direction is parallel to the X direction. The winding device 15 winds up the roll paper R on which the image has been formed by the main body 11. The roll paper R wound up by the winding device 15 is processed by a post-processing machine (not shown). The post-processing machine, for example, cuts out labels, package images, etc., that have been formed on roll paper R.

[0039] The main unit 11 comprises an image forming unit IM and a control unit 100. The control unit 100 controls the image forming unit IM. The control unit 100 includes a central processing unit (CPU) and memory, and controls the image forming unit IM by executing a program stored in the memory. The image forming unit IM includes image forming units 20Y, 20M, 20C, and 20K corresponding to yellow, magenta, cyan, black, and white, respectively. Here, "Y", "M", "C", and "K" represent yellow, magenta, cyan, and black, respectively. The image forming units 20Y, 20M, 20C, and 20K are arranged in this order from top to bottom in the Z direction. Printing data for yellow, magenta, cyan, and black are input to the image forming units 20Y, 20M, 20C, and 20K, respectively. An image is formed when at least one of the image forming units 20Y, 20M, 20C, and 20K is driven. When all image forming units 20Y, 20M, 20C, and 20K are driven, a full-color image is formed. Since the only difference between image forming units 20Y, 20M, 20C, and 20K is the color of the toner they handle, this explanation will focus on image forming unit 20Y, which is used to form a yellow image.

[0040] The image forming unit 20Y includes a developer unit 21Y, a photoreceptor drum 22Y which is an image carrier, a bottle storage section 40Y on which a toner bottle 30Y can be attached and detached, and a toner hopper 45Y. The developer unit 21Y includes a cylindrical developing roller 25Y that extends in the main scanning direction. The main scanning direction is parallel to the Y direction. The developing roller 25Y has a built-in magnetic roller that holds the charged toner stored in the developer unit 21Y by magnetic force. The photoreceptor drum 22Y has a cylindrical shape that extends in the main scanning direction. The developing roller 25Y is fixed to the frame so that its axis of rotation and the axis of rotation of the photoreceptor drum 22Y are parallel. Around the photoreceptor drum 22Y, a charging roller 23Y, an exposure device 24Y, a developing roller 25Y, and a primary transfer roller 26Y are arranged in order along the rotation direction of the photoreceptor drum 22Y.

[0041] After the surface of the photoreceptor drum 22Y is charged by the charging roller 23Y, it is irradiated with laser light emitted by the exposure device 24Y. The exposure device 24Y exposes the image-corresponding portion of the surface of the photoreceptor drum 22Y to form an electrostatic latent image. As a result, an electrostatic latent image is formed on the photoreceptor drum 22Y. Subsequently, the developer 21Y develops the electrostatic latent image formed on the photoreceptor drum 22Y with toner. Specifically, the toner held by the developing roller 25Y is placed on the electrostatic latent image formed on the photoreceptor drum 22Y by the action of an electric field, thereby forming a toner image on the photoreceptor drum 22Y. The toner image formed on the photoreceptor drum 22Y is transferred onto the intermediate transfer belt 29, which is an image carrier, by the action of an electric field by the primary transfer roller 26Y.

[0042] The intermediate transfer belt 29 is suspended by a drive roller R1 and a driven roller R2 to prevent slack. When the drive roller R1 rotates clockwise in Figure 1, the intermediate transfer belt 29 rotates clockwise in the figure at a predetermined speed. As the intermediate transfer belt 29 rotates, the driven roller R2 rotates clockwise.

[0043] As a result, the image forming units 20Y, 20M, 20C, and 20K transfer toner images onto the intermediate transfer belt 29 in this order. The timing at which each of the image forming units 20Y, 20M, 20C, and 20K transfers toner images onto the intermediate transfer belt 29 is adjusted by detecting reference marks attached to the intermediate transfer belt 29. As a result, yellow, magenta, cyan, black, and white toner images are superimposed on the intermediate transfer belt 29.

[0044] The toner image formed on the intermediate transfer belt 29 is transferred to the roll paper R by the action of an electric field force by the secondary transfer roller R3. The roll paper R on which the toner image has been transferred is transported to the fixing roller pair R4, where it is heated and pressurized. This melts the toner and fixes it to the roll paper R.

[0045] When forming a full-color image, the image forming apparatus 1 drives all of the image forming units 20Y, 20M, 20C, and 20K. However, when forming a monochrome image, it drives only one of the image forming units 20Y, 20M, 20C, and 20K. It is also possible to form an image by combining two or more of the image forming units 20Y, 20M, 20C, and 20K.

[0046] The control unit 100 is connected to a terminal device, such as a personal computer operated by a user, via a network (not shown). The control unit 100 executes jobs submitted from the terminal device and controls the image forming units 20Y, 20M, 20C, and 20K to form images on the roll paper R. A job includes image data indicating the image to be formed by the image forming units 20Y, 20M, 20C, and 20K, and includes image formation conditions for forming the image data. The image formation conditions include the position where the image data is placed on the roll paper R, the number of image data images to be formed on the roll paper R, etc. When the control unit 100 executes a job, the control unit 100 controls the image forming units 20Y, 20M, 20C, and 20K so that the image data is formed according to the image formation conditions defined in the job.

[0047] Figure 2 shows an example of a cross-sectional view of the area around the developing unit. Referring to Figure 2, the developing unit 21Y uses a developer consisting of a carrier and toner to form a toner image on the photoreceptor drum 22Y. The developing unit 21Y comprises a housing 50Y, a first screw 51Y, a second screw 53Y, a developing roller 25Y, and a regulating blade 57Y.

[0048] The housing 50Y is a casing that houses the developer, the first screw 51Y, the second screw 53Y, the developing roller 25Y, and the regulating blade 57Y. The housing 50Y is equipped with a sensor that detects the amount of developer inside the housing 50Y. If the amount of developer detected by the sensor is less than a predetermined value, developer is supplied from the toner hopper 45Y to the housing 50Y.

[0049] Within the housing 50Y, the developing roller 25Y, the first screw 51Y, and the second screw 53Y are arranged side by side and are rotatably supported by the housing 50Y. The direction in which the developing roller 25Y, the first screw 51Y, and the second screw 53Y extend is the Y direction.

[0050] The housing 50Y is a container extending in the Y direction and has two spaces, a first circulation tank Tk1 and a second circulation tank Tk2, separated by a partition wall 55Y extending in the Y direction. The first circulation tank Tk1 is provided with a first screw 51Y, and the second circulation tank Tk2 is provided with a second screw 53Y. Each of the first screw 51Y and the second screw 53Y has a shape in which spiral blades are provided on the outer surface of a cylindrical rotating shaft extending in the Y direction, and conveys the developer by rotating. The first circulation tank Tk1 and the second circulation tank Tk2 are storage spaces for containing the developer.

[0051] Openings are provided at both ends of the partition wall 55Y in the Y direction, connecting the first circulation tank Tk1 and the second circulation tank Tk2. As the first screw 51Y rotates, the developer in the first circulation tank Tk1 is transported from the negative side to the positive side in the Y direction, and the developer transported to the end of the partition wall 55Y enters the second circulation tank Tk2 through the opening. As the second screw 53Y rotates, the developer in the second circulation tank Tk2 is transported from the positive side to the negative side in the Y direction, and the developer transported to the end of the partition wall 55Y enters the first circulation tank Tk1 through the opening. In this way, the developer is circulated between the first circulation tank Tk1 and the second circulation tank Tk2 by the first screw 51Y and the second screw 53Y.

[0052] The developing roller 25Y is located in the second circulation tank Tk2, facing the second screw 53Y. Furthermore, the developing roller 25Y is exposed from the housing 50Y. The developing roller 25Y faces the photoreceptor drum 22Y at the portion that is exposed from the housing 50Y. Specifically, the developing roller 25Y's axis of rotation is rotatably supported in the housing 50Y such that a small gap is maintained between it and the photoreceptor drum 22Y. The developer contains a magnetic carrier and a non-magnetic toner. The developing roller 25Y and the photoreceptor drum 22Y face each other at the position where the distance between them is shortest.

[0053] The developing roller 25Y uses the magnetic force of magnets placed inside it to attract magnetic carriers together with non-magnetic toner, thereby carrying the developer that has been transported by the first screw 51Y. Hereinafter, the collection of developer carried by the developing roller 25Y will be referred to as the developing brush.

[0054] The developing roller 25Y rotates in the direction indicated by arrow a1, and the photoreceptor drum 22Y rotates in the direction indicated by arrow a2. A regulating blade 57Y is positioned above the developing roller 25Y, at a predetermined distance from it. The regulating blade 57Y is a flat plate shape with its longitudinal direction extending in the main scanning direction (Y direction), and is supported at both ends by a housing 50Y. The end of the regulating blade 57Y facing the developing roller 25Y is located upstream in the circumferential direction from the part of the surface of the developing roller 25Y that is closest to the photoreceptor drum 22Y.

[0055] Therefore, the amount of developer carried by the developing roller 25Y is limited by the regulating blade 57Y. Specifically, as the developing roller 25Y rotates, the amount of developer carried by the developing roller 25Y that comes into contact with the regulating blade 57Y is no longer carried by the developing roller 25Y. The developer passing through the gap between the regulating blade 57Y and the developing roller 25Y reaches the developing region where the distance between the developing roller 25Y and the photosensitive drum 22Y is minimized.

[0056] The developing roller 25Y develops the electrostatic latent image by applying toner to the photoreceptor drum 22Y. Specifically, a developing bias is applied to the developing roller 25Y. As a result, the potential of the surface of the developing roller 25Y is lower than the potential of the area on the surface of the photoreceptor drum 22Y where the electrostatic latent image is formed (approximately 0V), and higher than the potential of the area on the photoreceptor drum 22Y where the electrostatic latent image is not formed. The toner in the developer carried by the developing roller 25Y is negatively charged, so it adheres to the area on the surface of the photoreceptor drum 22Y where the electrostatic latent image is formed. As a result, a toner image is formed on the area on the surface of the photoreceptor drum 22Y where the electrostatic latent image is formed by the negatively charged toner.

[0057] Of the surface of the photoreceptor drum 22Y, the area from the position of the photoreceptor drum 22Y facing the developing roller 25Y to the position facing the positive X-side end of the upper duct 63Y constitutes a part of the first space SP1. In addition, of the portion of the developing roller 25Y exposed from the housing 50Y, the area from the position facing the positive X-side end of the lower duct 61Y to the portion facing the photoreceptor drum 22Y constitutes a part of the first space SP1.

[0058] A dust collection duct 60Y is positioned above the housing 50Y (on the positive Z-direction side). The dust collection duct 60Y includes an upper duct 63Y and a lower duct 61Y. The lower duct 61Y is fixed to the housing 50Y so as to cover the second circulation tank Tk2, the developing roller 25Y, and the regulating blade 57Y from above. The lower duct 61Y has a shape formed by joining two flat plates extending in the Y direction. One end of the lower duct 61Y on the positive X-direction side is positioned between the position where the developing roller 25Y faces the regulating blade 57Y and the position where the developing roller 25Y faces the photosensitive drum 22Y in the rotational direction of the developing roller 25Y. The lower part of the duct 61Y has a first lower inclined portion having an inclined surface that slopes upward toward the negative side in the X direction from the end on the positive side in the X direction, and a second lower inclined portion having an inclined surface that slopes downward toward the negative side in the X direction from the portion that contacts the first lower inclined portion.

[0059] The upper duct section 63Y is positioned above the lower duct section 61Y so as to cover the entire lower duct section 61Y from above. The upper duct section 63Y has a shape formed by joining two flat plates that extend in the Y direction. The upper duct section 63Y has a first upper inclined section having an inclined surface that slopes upward toward the negative X direction from the end on the positive X direction, and a second upper inclined section having an inclined surface that slopes upward toward the negative X direction at a smaller angle than the first upper inclined section, from the portion in contact with the first upper inclined section toward the negative X direction.

[0060] The first lower inclined portion of the lower duct 61Y and the first upper inclined portion of the upper duct 63Y are opposite each other, and are arranged so that the upper surface of the first lower inclined portion and the lower surface of the first upper inclined portion are parallel. The second lower inclined portion of the lower duct 61Y and the second upper inclined portion of the upper duct 63Y are opposite each other, and are arranged so that the distance between the upper surface of the first lower inclined portion and the lower surface of the first upper inclined portion gradually increases toward the negative side in the X direction.

[0061] The upper part of the duct 63Y is fixed to the housing 50Y such that its positive end in the X direction is positioned at a predetermined distance from the photoreceptor drum 22Y. The positive end in the X direction of the upper part of the duct 63Y faces the photoreceptor drum 22Y downstream in the rotational direction from the position where the photoreceptor drum 22Y faces the developing roller 25Y.

[0062] Figure 3 is a perspective view of the lower part of the duct. Referring to Figures 2 and 3, the lower part of the duct 61Y and the upper part of the duct 63Y are connected by a plurality of partition plates 83Y that intersect perpendicularly with each other. The upper surface of the lower part of the duct 61Y, the lower surface of the upper part of the duct 63Y, and the plurality of partition plates 83Y divide the second space SP2, which is the internal space of the dust collection duct 60Y, into multiple sections. The dust collection duct 60Y has an intake port 62Y at its positive X-direction end that opens the second space SP2 to the first space SP1. The intake port 62Y connects the second space SP2 to the first space SP1.

[0063] The dust collection duct 60Y has an outlet 81Y at its negative X-direction end and a positive Y-direction end that opens a second space SP2 to the exhaust duct 71Y. The outlet 81Y communicates the second space SP2 with the internal space of the exhaust duct 71Y. The length of the intake port 62Y in the Y-direction is the same as or longer than the length of the developing roller 25Y in the Y-direction. The length of the outlet 81Y in the Y-direction is shorter than the length of the intake port 62Y in the Y-direction. Multiple partition plates 83Y adjust the difference between the length of the outlet 81Y in the Y-direction and the length of the intake port 62Y in the Y-direction.

[0064] The exhaust duct 71Y is cylindrical in shape, with one end connected to the outlet 64Y and the other end open to the outside via a dust collection filter 77 and a fan 79.

[0065] As the fan 79 rotates, an airflow is generated from the first space SP1 towards the second space SP2. Some of the toner from the developer supported by the developing roller 25Y may detach from the developing roller 25Y and scatter into the first space SP1. The toner scattered in the first space SP1 is excess toner. This excess toner is carried by the airflow from the first space SP1 towards the second space SP2 through the intake port 62Y of the dust collection duct 60Y, through the second space SP2, and from the outlet port 81Y to the exhaust duct 71Y. Furthermore, the toner that enters the exhaust duct 71Y from the outlet port 81Y is collected by the dust collection filter 77 of the exhaust duct 71Y. This prevents the toner scattered from the developing roller 25Y into the first space SP1 from adhering to the photoreceptor drum 22Y. On the other hand, because toner passes through the second space SP2 of the dust collection duct 60Y, depending on the airflow path, clumps of toner TD may adhere to the inner wall of the dust collection duct 60Y. The developer unit 21Y in this embodiment has a configuration to remove the clumps of toner TD that have adhered to the inside of the dust collection duct 60Y.

[0066] Figure 4 is a side view of the upper part of the duct. Figure 4 is a view from the direction from the positive side to the negative side in the X direction. Referring to Figures 2 and 4, a plurality of openings 65 are formed in the upper part 63Y of the dust collection duct 60Y, opening the second space SP2 to the outside. The plurality of openings 65 are formed in the upper part 63Y of the duct between the intake port 62Y and the exhaust port 81Y. The position where the plurality of openings 65 are formed in the upper part 63Y of the duct is the part of the upper part 63Y of the duct facing the lower part 61Y of the duct. The inner diameter of the plurality of openings 65 is larger as the position where the plurality of openings 65 are located in the Y direction of the upper part 63Y of the duct is further away from the center.

[0067] Referring to Figure 2, the dust collection duct 60Y has a first shielding member 67Y and a second shielding member 69Y. The first shielding member 67Y is configured to open and close the intake port 62Y. Specifically, a rotating shaft extending in the Y direction is fixed to the end of the lower part of the duct 61Y on the intake port 62Y side, and the first shielding member 67Y is attached so as to be rotatable around the axis of that rotating shaft. A motor (not shown) rotates the first shielding member 67Y around the rotating shaft. By rotating, the first shielding member 67Y switches between a state in which the intake port 62Y is closed and a state in which the intake port 62Y is open.

[0068] The second shielding member 69Y is configured to be deformable between a closed state with the opening 65 closed and an open state with the opening 65 open, depending on the pressure difference between the inside and outside of the dust collection duct 60Y. The second shielding member 69Y is a flat plate extending in the Y direction.

[0069] Figure 5 is a plan view showing an example of a second shielding member. Referring to Figure 5, the second shielding member 69Y has a sealing portion 91Y, a deformable portion 92Y, and a fixed portion 93Y. The sealing portion 91Y, the deformable portion 92Y, and the fixed portion 93Y are each flat plate shapes extending in the Y direction and are arranged in this order. The deformable portion 92Y is positioned between the sealing portion 91Y and the fixed portion 93Y and is made of an elastic material.

[0070] The fixing portion 93Y is fixed to the joint surface of the upper part 63Y of the duct with an adhesive or the like. The joint surface is the lower surface of the upper part 63Y of the duct, in an area a predetermined distance away from the positive side in the X direction of the opening 65, and extending in the Y direction. The sealing portion 91Y is configured to have greater elasticity than the deformable portion 92Y. Furthermore, the sealing portion 91Y is configured to have a predetermined rigidity in the torsional direction so as to suppress torsional deformation. For example, the sealing portion 91Y may be thicker than the deformable portion 92Y.

[0071] Figures 6 and 7 illustrate the states of the first and second shielding members. As shown in Figure 6, when the second shielding member 69Y is closed and the first shielding member 67Y closes the intake port 62Y, the fan 79 discharges the air from the second space SP2 to the outside, so the air pressure in the second space SP2 becomes lower than the outside air pressure. If the fan 79 continues to operate, the air pressure difference between the second space SP2 and the outside gradually increases.

[0072] The pressure difference between the second space SP2 and the outside is proportional to the force exerted on the second shielding member 69Y by the outside air through the opening 65. Therefore, as shown in Figure 7, when the pressure difference between the second space SP2 and the outside overcomes the elastic force of the deformable portion 92Y of the second shielding member 69Y, the deformable portion 92Y of the second shielding member 69Y elastically deforms, causing the sealing portion 91Y to move downward and become open. When the second shielding member 69Y moves from a closed state to an open state, the opening 65 is opened. As a result, outside air enters the second space SP2 through the opening 65, and a high-velocity airflow is generated, as shown by the thick arrows in Figure 7. This airflow blows away the toner clumps TD adhering to the inside of the dust collection duct 60Y towards the discharge port 81Y.

[0073] Figure 8 is a perspective view showing an example of an exhaust duct. Referring to Figure 8, the developing units 21Y, 21M, 21C, and 21K are arranged from top to bottom in this order. A common duct 75 is located near the positive Y-side ends of the developing units 21Y, 21M, 21C, and 21K. The common duct 75 is a rectangular prism shape with its longitudinal direction extending vertically, and its top and bottom surfaces are sealed with plates. Exhaust ducts 71Y, 71M, 71C, and 71K extend from the developing units 21Y, 21M, 21C, and 21K, respectively. One end of exhaust duct 71Y is connected to developing unit 21Y, and the other end is connected to the common duct 75. Exhaust duct 71Y is connected to the dust collection duct 60Y of developing unit 21Y. One end of exhaust duct 71M is connected to developing unit 21M, and the other end is connected to the common duct 75. Exhaust duct 71C is connected at one end to the developing unit 21C and at the other end to the common duct 75. Exhaust duct 71K is connected at one end to the developing unit 21K and at the other end to the common duct 75. The common duct 75 has communication ports that connect to exhaust ducts 71Y, 71M, 71C, and 71K, respectively.

[0074] The exhaust ducts 71Y, 71M, 71C, and 71K each have shutters 73Y, 73M, 73C, and 73K that can open and close a communication opening that connects to the common duct 75. The common duct 75 has an opening 76 at its lower end that connects to a fan 79. A dust collection filter 77 is positioned between the opening 76 and the fan 79.

[0075] When all shutters 73Y, 73M, 73C, and 73K have their communication ports open, the airflow generated by fan 79 flows through exhaust ducts 71Y, 71M, 71C, and 71K to the developing units 21Y, 21M, 21C, and 21K.

[0076] Shutters 73Y, 73M, 73C, and 73K can be opened and closed independently. For example, shutter 73Y can be opened while all other shutters 73M, 73C, and 73K are closed. In this case, the airflow generated by fan 79 flows through exhaust duct 71Y to the developing unit 21Y, but not through developing units 21M, 21C, and 21K. When shutter 73Y is open and all other shutters 73M, 73C, and 73K are closed, even if the rotation speed of fan 79 is the same, the speed of the airflow flowing through the developing unit 21Y is greater compared to when all shutters 73Y, 73M, 73C, and 73K have their communication ports open.

[0077] Figure 9 is a block diagram showing an example of the detailed configuration of the control unit. Referring to Figure 9, the control unit 100 includes a central processing unit (CPU) 101 for controlling the entire control unit 100, a ROM (Read Only Memory) 102 for storing programs to be executed by the CPU 101, a RAM (Random Access Memory) 103 used as a workspace for the CPU 101, a hard disk drive (HDD) 104 for non-volatile data storage, a communication unit 105 for connecting the CPU 101 to a network, a display unit 106 for displaying information, an operation unit 107 for receiving user input, and an external storage device 108 into which a CD-ROM 108A is mounted.

[0078] The external storage device 108 can accommodate a CD-ROM 108A containing a cleaning program. The CPU 101 can access the CD-ROM 108A via the external storage device 108. The CPU 101 can load the cleaning program recorded on the CD-ROM 108A inserted in the external storage device 108 into the RAM 103 and execute it.

[0079] Furthermore, the medium used to store the program executed by the CPU 101 is not limited to the CD-ROM 108A, but may also be semiconductor memory such as optical discs (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), IC cards, optical cards, mask ROMs, or EPROMs (Erasable Programmable ROMs).

[0080] Furthermore, the programs executed by the CPU 101 are not limited to those recorded on the CD-ROM 108A; programs stored on the HDD 104 may be loaded into the RAM 103 and executed. In this case, other computers connected to the network may overwrite programs stored on the HDD 104 of the control unit 100, or add and write new programs. In addition, the control unit 100 may download programs from other computers connected to the network and store those programs on the HDD 104. The term "program" here includes not only programs that the CPU 101 can directly execute, but also source programs, compressed programs, encrypted programs, and the like.

[0081] Figure 10 is a block diagram showing an example of the functions of the control unit. The functions of the control unit 100 are realized by the CPU 101 of the control unit 100 executing a cleaning program stored in the ROM 102, HDD 104, or CD-ROM 108A. Referring to Figure 10, the control unit 100 includes a switching control unit 151, an image forming control unit 153, a fan control unit 155, and a shielding member control unit 157.

[0082] The image forming control unit 153 controls the image forming unit IM. The switching control unit 151 obtains the image forming status from the image forming control unit 153. The image forming status includes at least information indicating whether or not the developing units 21Y, 21M, 21C, and 21K are operating.

[0083] The switching control unit 151 switches the operating mode of the image forming apparatus 1 to either cleaning mode or non-cleaning mode. The switching control unit 151 switches the operating mode to cleaning mode when the image forming status indicates that the developer units 21Y, 21M, 21C, and 21K are not being driven. When the developer units 21Y, 21M, 21C, and 21K are not being driven, the respective developing rollers of each unit are stopped. In addition, the switching control unit 151 switches the operating mode to cleaning mode when the image forming status indicates that the developer units 21Y, 21M, 21C, and 21K are not being driven, based on the drive history of the developer units 21Y, 21M, 21C, and 21K. For example, the switching control unit 151 switches the operating mode to cleaning mode when the drive history of the developer units 21Y, 21M, 21C, and 21K meets predetermined conditions. The specified conditions include, for example, cases where the operating time of the developing units 21Y, 21M, 21C, and 21K is equal to or greater than a predetermined period. Furthermore, the specified conditions also include cases where the number of times the developing units 21Y, 21M, 21C, and 21K are operated is equal to or greater than a predetermined number.

[0084] Furthermore, the switching control unit 151 may switch the operating mode from non-cleaning mode to cleaning mode at predetermined time intervals. For example, the switching control unit 151 switches the operating mode to cleaning mode when the elapsed time since switching to non-cleaning mode exceeds a predetermined period.

[0085] Furthermore, the switching control unit 151 switches the operating mode to cleaning mode at predetermined timings. These predetermined timings include, for example, the time when power is turned on or off to the image forming apparatus 1. They also include the time when the developing units 21Y, 21M, 21C, and 21K stop operating, and the time registered by the user in the image forming apparatus 1.

[0086] When the switching control unit 151 switches the operating mode to cleaning mode, it outputs a drive command to the fan control unit 155 and a shielding command to the shielding member control unit 157.

[0087] The switching control unit 151 switches the operating mode to cleaning mode, and then switches the operating mode back to non-cleaning mode when a predetermined termination condition is met. The predetermined termination condition includes when the shielding member control unit 157 receives a second shielding member open signal a predetermined number of times or more, or when the cleaning mode continues for a predetermined time.

[0088] The switching control unit 151 controls the opening and closing of shutters 73Y, 73M, 73C, and 73K in accordance with the switching of the operating mode to cleaning mode. The switching control unit 151 opens one of the shutters 73Y, 73M, 73C, and 73K and closes all the others. Specifically, the switching control unit 151 sequentially selects the developing units 21Y, 21M, 21C, and 21K as the cleaning targets. Here, we will explain using the case where developing unit 21Y is selected as the cleaning target as an example. The switching control unit 151 opens the shutter 73Y corresponding to the developing unit 21Y selected as the cleaning target and closes all the other shutters 73M, 73C, and 73K. Then, when the shielding member control unit 157 inputs a second shielding member open signal to the developer unit 21Y selected as the cleaning target a predetermined number of times, the switching control unit 151 switches the cleaning target from among the developers 21Y, 21M, 21C, and 21K. When the switching control unit 151 has selected all of the developers 21Y, 21M, 21C, and 21K as cleaning targets, and the second shielding member open signal to the developer unit 21K, which was last selected as the cleaning target, inputs a second shielding member open signal a predetermined number of times, it switches the operation mode to non-cleaning mode. When the switching control unit 151 switches the operation mode from cleaning mode to non-control mode, it outputs a stop command to the fan control unit 155.

[0089] The fan control unit 155 controls the drive motor of the fan 79. When a drive command is input from the switching control unit 151, the fan control unit 155 drives the drive motor to rotate the fan 79. This generates airflow in the common duct 75.

[0090] The shielding member control unit 157 controls the opening and closing of the first shielding member 67Y provided in each of the developing units 21Y, 21M, 21C, and 21K. In response to a shut-off instruction input from the switching control unit 151, the shielding member control unit 157 closes the first shielding member 67Y provided in each of the developing units 21Y, 21M, 21C, and 21K. As a result, the air pressure in the second space SP2 decreases in the developing unit 21Y, 21M, 21C, and 21K that has been selected for cleaning, becoming lower than the external air pressure. For example, if developing unit 21Y is selected for cleaning, when the difference between the air pressure in the second space SP2 and the external air pressure exceeds a predetermined value, the second shielding member 69Y opens its opening 65 from a closed state. At this time, due to the pressure difference between the second space SP2 and the outside, air flows in from the outside, and this airflow blows away the clumps of toner TD that have adhered to the inner wall of the dust collection duct 60Y.

[0091] When the difference between the air pressure in the second space SP2 and the external air pressure falls below a predetermined value, the second shielding member 69Y closes its opening 65 from an open state. Subsequently, as time passes, the air pressure in the second space SP2 of the dust collection duct 60Y decreases, and the difference with the external air pressure becomes greater than or equal to the predetermined value. As a result, the opening and closing of the second shielding member 69Y is repeated. Therefore, the opening and closing operation of the second shielding member 69Y is repeated as long as the first shielding member 67Y is closing the intake port 62Y. The shielding member control unit 157 outputs a second shielding member open signal to the switching control unit 151 in response to the opening of the second shielding member 69Y. The other developers 21M, 21C, and 21K operate in the same manner as developer 21Y.

[0092] Figure 11 is a flowchart showing an example of the cleaning process flow. The cleaning process is performed by the CPU 101 of the control unit 100, which executes a cleaning program stored in the ROM 102, HDD 104, or CD-ROM 108A. Referring to Figure 11, the CPU 101 determines whether it is the start timing or not (step S01). The CPU 101 remains in a waiting state until it is the start timing (NO in step S01), and if it determines that it is the start timing (YES in step S01), it switches the operation mode to cleaning mode and proceeds to step S02. The CPU 101 determines that it is the start timing when the drive history of the developer units 21Y, 21M, 21C, and 21K satisfies predetermined conditions. The predetermined conditions include, for example, when the drive time of the developer units 21Y, 21M, 21C, and 21K is longer than a predetermined period, and when the number of times the developer units 21Y, 21M, 21C, and 21K are driven is longer than a predetermined number. Furthermore, the start timing includes when the elapsed time since switching the operating mode to non-cleaning mode exceeds a predetermined period. The start timing may also be predetermined. A predetermined start timing includes, for example, when power is turned on or off to the image forming apparatus 1, when the developing units 21Y, 21M, 21C, and 21K stop operating, and the date and time registered by the user to the image forming apparatus 1.

[0093] In step S02, it is determined whether the image forming unit IM is stopped or not. The system enters a waiting state until the image forming unit IM stops (NO in step S02), and if the image forming unit IM is stopped, the process proceeds to step S03. While the image forming unit IM is stopped, the developing rollers 25Y, 22M, 22C, and 22K are stopped.

[0094] In step S03, the drive motor that rotates the fan 79 is activated, and the process proceeds to step S04. As a result, the airflow generated by the rotation of the fan 79 flows through the common duct 75.

[0095] In step S04, one of the developing units 21Y, 21M, 21C, or 21K is selected for cleaning, and the process proceeds to step S04. Here, we will explain using the case where developing unit 21Y is selected as an example. In step S05, among the shutters 73Y, 73M, 73C, and 73K, shutters 73M, 73C, and 73K other than the shutter 73Y corresponding to the developing unit 21Y to be cleaned are closed, and the process proceeds to step S08. Only the shutter 73Y corresponding to the developing unit 21Y selected for cleaning is left open. As a result, the airflow generated by the rotation of the fan 79 flows through the common duct 75 and the exhaust duct 71Y to the dust collection duct 60Y of the developing unit 21Y.

[0096] In step S06, the first shielding member 67Y closes the intake port 62Y, and the process proceeds to step S07. As a result, the air pressure in the second space SP2 gradually decreases. In step S07, it is determined whether or not the second shielding member 69Y is open. The process remains in a waiting state until the second shielding member 69Y is opened (NO in step S07), and if the second shielding member 69Y is open (YES in step S07), the process proceeds to step S08.

[0097] In step S08, it is determined whether the number of times the second shielding member 69Y has opened is the predetermined number. The number of times the second shielding member 69Y has opened consecutively since the first shielding member 67Y closed the intake port 62Y is compared with the predetermined number. If the number of times the second shielding member 69Y has opened is the predetermined number, the process proceeds to step S09; otherwise, the process returns to step S06.

[0098] In step S09, it is determined whether there are any developers among the developers 21Y, 21M, 21C, and 21K that were not selected as targets for cleaning in step S04. If there are unselected developers, the process returns to step S04; otherwise, the process proceeds to step S10.

[0099] In step S10, all shutters 73Y, 73M, 73C, and 73K are opened, and the process proceeds to step S11. In step S11, the drive motor that rotates the fan 79 is stopped, and the process ends. As a result, the developing units 21Y, 21M, 21C, and 21K are selected in order, and the processes from steps S05 to S08 are executed for each of the developing units 21Y, 21M, 21C, and 21K.

[0100] <First variation> Figure 12 is a side view of the upper part of the duct in the first modified example. Referring to Figure 12, the multiple openings 65 have the same inner diameter, and the distance between two adjacent openings 65 decreases as the position where the multiple openings 65 are located in the Y direction of the upper part of the duct 63Y moves away from the center.

[0101] <Second variation> Figure 13 is a bottom view showing an example of the second shielding member in the second modified example. Referring to Figure 13, the second shielding member 69Y in the second modified example has a plurality of reinforcing members 99Y that extend vertically from the lower surface of the sealing portion 91Y and along the lower surface. The plurality of reinforcing members 99Y are arranged along the lower surface so as to intersect. Note that if the thickness of the sealing portion 91Y is greater than that of the deformed portion 92Y, it is not necessarily required to provide the plurality of reinforcing members 99Y.

[0102] <Third variation> Figure 14 is a bottom view showing the second shielding member together with its surrounding members in the third modified example. Figure 15 is a cross-sectional view showing the second shielding member together with its surrounding members in the third modified example. Referring to Figures 14 and 15, a sealing wall 94Y is provided on the lower surface of the upper part 63Y of the duct, extending downward from the upper part 63Y of the duct along the periphery of the second shielding member 69Y. The sealing wall 94Y extends vertically from the lower surface of the upper part 63Y of the duct. An elastic member such as rubber is provided to fill the gap between the sealing wall 94Y and the second shielding member 69Y without any gaps. This prevents air from entering between the sealing wall 94Y and the second shielding member 69Y. This improves the accuracy of the second shielding member 69Y in closing the opening 65.

[0103] Furthermore, as long as the deformation portion 92Y of the second shielding member 69Y undergoes elastic deformation, and the amount of elastic deformation in the thickness direction of the sealing portion 91Y is less than the height h of the sealing wall 94Y, the second shielding member 69Y can maintain a state in which it closes the opening 65.

[0104] <Fourth variation> Figure 16 is a cross-sectional view showing the second shielding member together with its surrounding members in the fourth modified example. Referring to Figure 16, the second shielding member 69Y in the fourth modified example is mounted on the lower surface of the upper part 63Y of the duct so as to be rotatable around an axis in the axial direction (parallel to the Y direction) of the developing roller 25Y, and moves between an open position and a closed position by rotating around the axis. Specifically, the second shielding member 69Y in the fourth modified example is a flat plate that does not have elasticity and extends in the Y direction. In the second shielding member 69Y in the fourth modified example, a sealing wall 94Y is provided along the periphery of the second shielding member 69Y, similar to the third modified example, and an elastic member is provided between the sealing wall 94Y and the second shielding member 69Y.

[0105] In the fourth modification, the second shielding member 69Y is mounted so as to be rotatable around a rotation axis 95Y. The rotation axis 95Y is fixed to the upper part of the duct 63Y so as to extend in the Y direction, on the positive X-direction side of the opening 65 of the upper part of the duct 63Y, and in a position that does not overlap with the opening 65. In the fourth modification, the second shielding member 69Y is biased clockwise by a torsion coil spring 96Y, as indicated by arrow a3.

[0106] The torsion coil spring 96Y undergoes elastic deformation, allowing the second shielding member 69Y to maintain a closed state of the opening 65 as long as the amount of movement of the end of the second shielding member 69Y when the second shielding member 69Y rotates in the fourth modified example is less than the height h of the sealing wall 94Y.

[0107] As described above, the image forming apparatus 1 in this embodiment includes a developer 21Y having a developing roller 25Y that holds toner, a dust collection duct 60 having an intake port 62Y connected to a first space SP1 in contact with the portion of the developing roller 25Y exposed from the developer 21Y and an exhaust port 64Y connected to the outside, a fan 79 connected to the exhaust port 64Y that discharges air from the second space SP2 inside the dust collection duct 60Y to the outside, an opening 65 formed between the intake port 62Y and the exhaust port 64Y that opens the second space SP2 of the dust collection duct 60Y to the outside, a first shielding member 67Y configured to open and close the intake port 62Y, and a second shielding member 69Y configured to open and close the opening 65 according to the pressure difference between the inside and outside of the dust collection duct 60Y.

[0108] As the fan 79 discharges the gas inside the dust collection duct 60Y to the outside, excess toner floating in the first space SP1 is discharged from the dust collection duct 60Y to the outside. Furthermore, when the fan 79 discharges the gas inside the dust collection duct 60Y to the outside from the outlet 64Y while the opening 65 formed between the intake port 62Y and the outlet port 64Y of the dust collection duct 60Y is closed by the second shielding member 69Y and the intake port 62Y is closed by the first shielding member 67Y, the air pressure in the second space SP2 of the dust collection duct 60Y decreases. When the air pressure in the second space SP2 is lower than the outside air pressure, and the second shielding member 69Y opens the opening 65, outside air is sent into the second space SP2 from the opening 65, and an airflow with a faster wind speed than the airflow generated by the fan 79 is generated in the second space SP2. Therefore, the airflow blows away foreign matter such as clumps of excess toner TD accumulated on the inner wall of the duct in the second space SP2. Consequently, the second space SP2 of the dust collection duct 60Y, where clumps of excess toner TD have accumulated, can be cleaned.

[0109] Furthermore, in the image forming apparatus 1, the dust collection duct 60Y has an upper duct 63Y and a lower duct 61Y, each extending from the intake port 62Y to the discharge port 64Y. The upper duct 63Y and the lower duct 61Y face each other in at least part, and the opening 65 is formed in the portion of the upper duct 63Y that faces the lower duct 61Y. As a result, excess toner clumps TD accumulated in the lower duct 61Y can be discharged.

[0110] Furthermore, the opening 65 is formed on the exhaust port 64Y side of the first shielding member 67Y. This allows outside air to be supplied to the second space SP2, where the air pressure is lower than that of the outside.

[0111] Furthermore, multiple openings 65 are formed in a row along the axial direction of the developing roller 25Y. This allows for the discharge of excess toner that is dispersed and accumulated along the axial direction of the developing roller 25Y in the dust collection duct 60Y.

[0112] Furthermore, in the axial direction of the developing roller 25Y, the inner diameters of the multiple openings 65 formed in the upper part 63Y of the duct are larger the further away from the center. The inner diameters of the multiple openings 65 formed in the upper part 63Y of the duct are larger at both ends than at the central opening 65. As a result, more air flows to both ends of the dust collection duct 60Y than to the center. Therefore, when excess toner tends to accumulate more at both ends of the dust collection duct 60Y than in the center, the clumps of excess toner TD accumulated in the dust collection duct 60Y can be discharged.

[0113] Furthermore, the second shielding member 69Y includes a sealing portion 91Y that is movable between a closed position with the opening 65 open and an open position with the opening 65 closed, and a deformation portion 92Y that biases the sealing portion 91Y in the direction from the open position toward the closed position. Since the sealing portion 91Y is biased by the deformation portion 92Y in the direction from the open position toward the closed position, when the force that the sealing portion 91Y receives from the opening 65 due to the difference in air pressure inside and outside the dust collection duct 60Y becomes greater than the elastic force of the deformation portion 92Y, the sealing portion 91Y moves to the open position. For this reason, when the first shielding member 67Y maintains a closed state of the intake port 62Y, the sealing portion 91Y repeatedly opens and closes the opening 65, so the second shielding member 69Y can be opened and closed automatically.

[0114] Furthermore, the elastic force of the deformable portion 92Y is determined based on the force with which the deformable portion 92Y biases the sealing portion 91Y and the force that the sealing portion 91Y receives from the opening 65 due to the pressure difference between the inside and outside of the dust collection duct 60Y. Therefore, by adjusting the elastic force of the deformable portion 92Y, the velocity of the airflow generated in the second space SP2 of the dust collection duct 60Y can be adjusted.

[0115] Furthermore, the control unit 100 of the image forming apparatus 1 switches the first shielding member 67Y to a state where the intake port 62Y is closed while the developing roller 25Y of the developing unit 21Y is stopped. As a result, the second space SP2 of the dust collection duct 60 is cleaned while there is no excess toner floating in the first space SP1. Therefore, the developing operation by the developing unit 21Y is not adversely affected.

[0116] Furthermore, the control unit 100 of the image forming apparatus 1 switches the first shielding member 67Y to a closed state based on the drive history of the developer unit 21Y. This allows the dust collection duct 60Y to be cleaned at the appropriate time when the amount of excess toner accumulated in the second space SP2 of the dust collection duct 60Y is appropriate.

[0117] Furthermore, the control unit 100 of the image forming apparatus 1 switches the first shielding member 67Y to a state where it closes the intake port 62Y, and maintains the state where the first shielding member 67Y closes the intake port 62Y until the second shielding member 69Y opens and closes the opening 65 a predetermined number of times in a row. As a result, in a single cleaning cycle, the second space SP2 of the dust collection duct 60Y can be cleaned efficiently because the second shielding member 69Y opens and closes the opening 65 a predetermined number of times in a row.

[0118] Furthermore, the image forming apparatus 1 is equipped with a plurality of developing units 21Y, 21M, 21C, and 21K, and each of the plurality of developing units 21Y, 21M, 21C, and 21K is equipped with a dust collection duct 60Y, an opening 65, a first shielding member 67Y, and a second shielding member 69Y, and each of the plurality of dust collection ducts 60Y is equipped with shutters 72C, 72M, 73Y, and 73K that block the space between the discharge port 64Y and the fan 79. The control unit 100 of the image forming apparatus 1 controls the shutters 72M, 73C, and 73K corresponding to one of the multiple developing units 21Y, 21M, 21C, and 21K, for example, the non-target developing units 21M, 21C, and 21K other than the target developing unit 21Y, to block the connection between them and the fan 79. It also controls the shutter 72Y corresponding to the target developing unit 21Y to prevent the connection between the exhaust port 64Y corresponding to the target developing unit 21Y and the fan 79. As a result, the airflow generated by the fan 79 does not flow into the multiple dust collection ducts 60Y, and all of the airflow generated by the fan 79 flows into the dust collection duct 60Y corresponding to the target developing unit 21Y. Therefore, the multiple dust collection ducts 60Y corresponding to each of the multiple developing units 21Y, 21M, 21C, and 21K can be cleaned.

[0119] In particular, since the distances between each of the shutters 72C, 72M, 73Y, and 73K and the fan 79 are different, there are differences in the pressure applied to the developing units 21Y, 21M, 21C, and 21K. The pressure decreases the further away from the fan 79. For this reason, if two or more of the shutters 72C, 72M, 73Y, and 73K are not shut off, the cleaning operation will be performed on the developing unit closer to the fan, but the pressure in the second space SP2 of the developing unit further from the fan may not drop to the predetermined pressure. For this reason, it is preferable to shut off all of the shutters 72C, 72M, 73Y, and 73K, leaving only one open.

[0120] Furthermore, in the first modified example, in the axial direction of the developing roller 25Y, the spacing between the multiple openings 65 formed in the upper part 63Y of the duct narrows as you move away from the center. The spacing between the two openings 65 at both ends of the multiple openings 65 formed in the upper part 63Y of the duct is smaller than the spacing between the two openings 65 in the center. As a result, more air flows to both ends of the dust collection duct 60Y than to the center. Therefore, when excess toner tends to accumulate more at both ends of the dust collection duct 60Y than in the center, the clumps of excess toner TD accumulated in the dust collection duct 60Y can be discharged.

[0121] Furthermore, the fourth modification includes a second shielding member 69Y that is rotatable around a rotation axis 95Y so as to be movable between a closed position and an open position with the opening 65 closed, and a torsion coil spring 96Y that biases the second shielding member 69Y in the direction from the open position toward the closed position. Since the second shielding member 69Y is biased by the torsion coil spring 96Y in the direction from the open position toward the closed position, when the force that the second shielding member 69Y receives from the opening 65 due to the difference in air pressure inside and outside the dust collection duct 60Y becomes greater than the elastic force of the torsion coil spring 96Y, the second shielding member 69Y moves to the open position. For this reason, if the state in which the first shielding member 67Y closes the intake port 62Y is maintained, the second shielding member 69Y repeatedly opens and closes the opening 65, so the second shielding member 69Y can be opened and closed automatically.

[0122] Furthermore, the elastic force of the torsion coil spring 96Y is determined based on the force with which the torsion coil spring 96Y biases the second shielding member 69Y and the force that the second shielding member 69Y receives from the opening 65 due to the pressure difference between the inside and outside of the dust collection duct 60Y. Therefore, by adjusting the elastic force of the torsion coil spring 96Y, the velocity of the airflow generated in the second space SP2 of the dust collection duct 60Y can be adjusted.

[0123] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0124] 1 Image forming apparatus, 11 Main body, 13 Paper feeder, 15 Winding device, 20Y, 20M, 20C, 20K Image forming unit, 21Y, 21M, 21C, 21K Developer, 22Y Photoreceptor drum, 23Y Charging roller, 24Y Exposure apparatus, 25Y Developer roller, 26Y Primary transfer roller, 29 Intermediate transfer belt, 30Y Toner bottle, 40Y Bottle storage section, 45Y Toner hopper, 50Y Housing, 51Y First screw, 53Y Second screw, 55Y Partition, 57Y Regulating blade, 60Y Dust collection duct, 61Y Lower part of duct, 62 Inlet, 62Y Inlet, 63Y Upper part of duct, 63Y Upper part of duct, 64Y Outlet, 65 Opening, 67Y First shielding member, 69Y Second shielding member, 71Y, 71M, 71C, 71K Exhaust duct, 73Y, 73M, 73C, 73K Shutter, 75 Common duct, 76 Opening, 77 Dust collection filter, 79 Fan, 81Y Outlet, 83Y Partition plate, 91Y Sealing part, 92Y Deformable part, 93Y Fixing part, 94Y Sealing wall, 95Y Rotating shaft, 96Y Torsion coil spring, 99Y Reinforcement member, 100 Control unit, 101 CPU, 102 ROM, 103 RAM, 151 Switching control unit, 153 Image forming control unit, 155 Fan control unit, 157 Shielding member control unit, IM Image forming unit, SP1 First space, SP2 Second space, TD Toner clump.

Claims

1. A developing unit having a developing roller that holds toner, A duct having an intake port connected to the space in contact with the part of the developing roller exposed from the developing unit and an exhaust port connected to the outside, A blowing means connected to the aforementioned outlet for discharging the gas inside the duct to the outside, An opening is formed between the intake port and the exhaust port, which opens the internal space of the duct to the outside, A first shielding member configured to open and close the aforementioned intake port, An image forming apparatus comprising: a second shielding member configured to open and close the opening in accordance with the pressure difference between the inside and outside of the duct, which is generated when the blowing means discharges gas from inside the duct while the first shielding member is closing the intake port.

2. Each of the ducts extends from the intake port to the exhaust port and has at least a portion of opposing upper and lower surfaces. The image forming apparatus according to claim 1, wherein the opening is formed in the portion of the upper surface facing the lower surface.

3. The image forming apparatus according to claim 2, wherein the opening is formed on the side of the discharge port that is closer to the first shielding member.

4. The image forming apparatus according to claim 2 or 3, wherein a plurality of the openings are formed in a line in the axial direction of the developing roller.

5. The image forming apparatus according to claim 4, wherein, in the axial direction of the developing roller, the distance between two adjacent openings at both ends is narrower than the distance between two adjacent openings at the center.

6. The image forming apparatus according to claim 4, wherein, in the axial direction of the developing roller, the inner diameter of the openings at both ends is larger than the inner diameter of the opening at the center.

7. The image forming apparatus according to any one of claims 1 to 3, wherein the second shielding member includes a shielding plate that is movable between an open position with the opening open and a closed position with the opening closed, and an elastic member that biases the shielding plate in the direction from the open position toward the closed position.

8. The image forming apparatus according to claim 7, wherein the elastic force of the elastic member is determined based on the force with which the elastic member biases the shielding plate and the force with which the shielding plate receives from the opening due to the pressure difference between the inside and outside of the duct.

9. The image forming apparatus according to claim 1, further comprising a switching control means for switching the first shielding member to a state in which the intake port is closed while the developing unit has stopped the developing roller.

10. The image forming apparatus according to claim 9, wherein the switching control means switches the first shielding member to a closed state based on the drive history of the developing unit.

11. The image forming apparatus according to claim 9, wherein the switching control means maintains the state in which the first shielding member closes the intake port from the time the first shielding member switches to a state in which the intake port is closed until the second shielding member opens and closes the opening a predetermined number of times in a row.

12. The system comprises a plurality of the aforementioned developing units, Each of the multiple developing units is provided with the duct, the opening, the first shielding member, and the second shielding member. A blocking means corresponding to each of the multiple ducts, which blocks the space between the exhaust port and the blowing means, An image forming apparatus according to any one of claims 1, 9 to 11, further comprising: a blocking control means for controlling the blocking means corresponding to non-target developers other than the target developer among a plurality of developers, to block the space between the outlet corresponding to the non-target developer and the blowing means; and a blocking control means for controlling the blocking means corresponding to the target developer, to prevent the space between the outlet corresponding to the target developer and the blowing means from being blocked.

13. A cleaning method for controlling an image forming apparatus, The image forming apparatus includes a developing unit having a developing roller that holds toner, A duct having an intake port connected to the space in contact with the part of the developing roller exposed from the developing unit and an exhaust port connected to the outside, A blowing means connected to the aforementioned outlet for discharging the gas inside the duct to the outside, An opening is formed between the intake port and the exhaust port, which opens the internal space of the duct to the outside, A first shielding member configured to open and close the aforementioned intake port, The system comprises a second shielding member configured to open and close the opening in accordance with the pressure difference between the inside and outside of the duct, which is generated when the air blowing means discharges gas from inside the duct while the first shielding member is closing the intake port, A cleaning method comprising a switching control step of switching the first shielding member to a state in which the intake port is closed while the developing unit has stopped the developing roller.

14. A cleaning program executed by a computer that controls an image forming apparatus, The image forming apparatus includes a developing unit having a developing roller that holds toner, A duct having an intake port connected to the space in contact with the part of the developing roller exposed from the developing unit and an exhaust port connected to the outside, A blowing means connected to the aforementioned outlet for discharging the gas inside the duct to the outside, An opening is formed between the intake port and the exhaust port, which opens the internal space of the duct to the outside, A first shielding member configured to open and close the aforementioned intake port, The system comprises a second shielding member configured to open and close the opening in accordance with the pressure difference between the inside and outside of the duct, which is generated when the air blowing means discharges gas from inside the duct while the first shielding member is closing the intake port, A cleaning program that causes the computer to execute a switching control step in which the first shielding member switches to a state in which the intake port is closed while the developing roller is stopped in the developing unit.

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