Image forming apparatus

Abstract

To efficiently remove a toner aggregate.SOLUTION: A developing device of an image forming apparatus has a developer carrier that carries developer and is rotatable, a layer regulation member that regulates the layer thickness of the developer carried by the developer carrier, a storage unit that stores the developer, a developer tank to which the developer carrier and the layer regulation member are attached, and a side part that is provided with a first inclined surface. The first inclined surface is adjacent to the layer regulation member and faces the developer carrier, and is inclined with respect to a horizontal plane so that the distance from the developer carrier is increased as approaching the storage unit from the layer regulation member side. The distance between the layer regulation member and the developer carrier is smaller than the shortest distance between the first inclined surface and the developer carrier. When a predetermined condition is satisfied, the image forming apparatus executes, after the completion of image formation, a loosening mode for rotating the developer carrier in a direction opposite to the normal direction by a length in a circumferential direction facing the first inclined surface or longer and then rotating in the normal direction.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus. Background Art

[0002] Patent Document 1 discloses a developing device for a printer. In the developing device of Patent Document 1, a developer composed of a magnetic carrier and toner is supplied to a supply chamber. The developer supplied to the supply chamber is attracted by magnetic force to the surface of a developing sleeve rotating in the forward direction, and is regulated to a predetermined amount by a doctor blade. Then, the toner in the predetermined amount of developer attracted to the surface of the developing sleeve rotating in the forward direction is supplied to a photosensitive drum by magnetic force, thereby performing a developing process.

[0003] Further, in Patent Document 1, toner aggregates grow inside the angle formed by the doctor base body and the doctor auxiliary member on the doctor blade through the developing process, it is described that after the developing process, by repeating rotation in the forward direction and rotation in the reverse direction a plurality of times while changing the rotation speed of the developing sleeve, the toner aggregates at the angle formed by the doctor base body and the doctor auxiliary member can be removed. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2013-20092 Summary of the Invention Problem to be Solved by the Invention

[0005] In the developing apparatus described in Patent Document 1, toner aggregates that have grown deep in the corner between the doctor auxiliary member and the doctor substrate are removed by moving them along the surface of the doctor auxiliary member and dropping them into the supply chamber. However, because the doctor auxiliary member is positioned horizontally, the efficiency of moving the toner aggregates along the surface of the doctor auxiliary member is poor. In addition, the distance for rotating the developing sleeve in the forward and reverse directions to remove the toner aggregates is not considered, resulting in poor efficiency in removing the toner aggregates. The object of this disclosure is to provide an image forming apparatus that efficiently removes toner aggregates. [Means for solving the problem]

[0006] An image forming apparatus according to one aspect of the present disclosure is an image forming apparatus comprising: a developer carrier having a developer on its surface and being rotatable in a forward or reverse direction; a layer restricting member that restricts the thickness of the layer of developer carried by the developer carrier; and a developing tank having a storage section for containing the developer to be carried on the developer carrier, wherein the developer carrier and the layer restricting member are attached to the developing tank, wherein the developing tank has a position adjacent to the layer restricting member, facing the developer carrier, and as it approaches the storage section from the layer restricting member side, the developer carrier The layer restricting member has a side portion provided with a first inclined surface that is inclined with respect to the horizontal plane so as to increase the distance between the layers, and is attached to the side portion such that the distance between the layer restricting member and the developer carrier is smaller than the shortest distance between the first inclined surface and the developer carrier, and the image forming apparatus rotates the developer carrier in the positive direction during image formation, and if predetermined conditions are met, after image formation is completed, it performs a loosening mode in which it rotates the developer carrier in the opposite direction to the positive direction for a distance greater than or equal to the length in the circumferential direction opposite to the first inclined surface, and then rotates it in the positive direction. [Effects of the Invention]

[0007] According to an image forming apparatus in one aspect of this disclosure, toner aggregates can be removed efficiently. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment. [Figure 2] Figure 2 is a perspective view showing the schematic configuration of a developing apparatus according to this embodiment. [Figure 3] Figure 3 is a functional block diagram showing the schematic configuration of the image forming apparatus according to this embodiment. [Figure 4] Figure 4 shows the developing apparatus according to the embodiment performing the developing process. [Figure 5] Figure 5 shows how toner aggregates are formed in the developing apparatus according to this embodiment. [Figure 6] Figure 6 is a diagram showing predetermined conditions for the control unit according to the embodiment to execute the loosening mode. [Figure 7] Figure 7 is a diagram illustrating the detailed configuration of each part in the developing apparatus according to this embodiment. [Figure 8] Figure 8 shows the control unit according to the embodiment rotating the developing roller in the reverse direction during the loosening mode. [Figure 9] Figure 9 shows the control unit according to the embodiment rotating the developing roller in the forward direction during the loosening mode. [Figure 10] Figure 10 is a diagram illustrating an example of the magnetic force generated around the surface of a developing roller according to an embodiment. [Figure 11] Figure 11 is a diagram showing the processing flow of the image forming apparatus according to the embodiment. [Figure 12] Figure 12 is a diagram showing the processing flow of an image forming apparatus according to a modified embodiment. [Modes for carrying out the invention]

[0009] [Embodiment] The embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted. The embodiments described below are not intended to unduly limit the scope of the claims. Furthermore, not all of the configurations described in these embodiments are essential components of this disclosure.

[0010] Figure 1 is a cross-sectional view showing the configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 is an example of an electronic device to which a developing apparatus 10, described later, is provided. For example, the image forming apparatus 100 is a device having an image forming function for forming a color image or a monochrome image, and a printing function for printing the formed image. The image forming apparatus 100 may be a printer, a printer with a scanner function, or a multifunction device (MFP: Multifunction Peripheral) having various functions including an image forming function and a printing function. In this embodiment, as an example, the image forming apparatus 100 will be described as a multifunction device. For example, the image forming apparatus 100 has a printing function for forming a color image or a monochrome image and printing the formed color image or monochrome image on paper. The types of colors used by the image forming apparatus 100 when printing a color image are not limited, but examples include black (Bk), cyan (Cy), magenta (Mg), and yellow (Ye). The image forming apparatus 100 may also print a monochrome image on paper using a single color (for example, black).

[0011] For example, the image forming apparatus 100 includes an apparatus body 101 and an apparatus lid 102 that is openably attached to the apparatus body 101. For example, the apparatus lid 102 includes a transport section 102a for transporting original documents. For example, the apparatus body 101 includes an image reading device 110, a feeding tray 120 that holds paper on which an image is formed (printed), a plurality of transport rollers, image forming stations Pa, Pb, Pc, Pd, an intermediate transfer belt 150, a belt cleaning device 152, a transfer device 153, a fixing device 160, an output tray 170, an optical scanning device 180, etc. The plurality of transport rollers are a paper transport mechanism for transporting paper on which an image is formed, and include, for example, a pickup roller 131, a transport roller 132, a registration roller 133, and an output roller 134. The optical scanning device 180 and the image forming stations Pa, Pb, Pc, and Pd are image forming mechanisms that form toner images (printing images) to be transferred to paper. The intermediate transfer belt 150, the belt cleaning device 152, the transfer device 153, and the fixing device 160 are printing mechanisms that print by transferring the toner images (printing images) formed by the image forming mechanisms to paper.

[0012] Although not shown in the diagram, the main body of the device 101 also has an operation unit, which is an input interface that receives input operations from the user. The operation unit can be configured, for example, as a touch panel.

[0013] The image reading device 110 reads the image on the document placed on the image reading device 110 and stores the image data representing the read image in, for example, the storage unit 70 (Figure 3). The document to be read by the image reading device 110 may be transported by the transport unit 102a and read by the image reading device 110, or the user may place it directly on the image reading device 110 for reading. The feed tray 120 stores paper before printing. The feed tray 120 is, for example, provided on the main body 101 so that it can be pulled out.

[0014] The image forming stations Pa, Pb, Pc, Pd are configured to intermediately transfer toner images (images) onto the surface of the intermediate transfer belt 150, and each of the image forming stations Pa, Pb, Pc, Pd is provided for each type of color used when the image forming apparatus 100 prints an image. For example, the image forming station Pa intermediately transfers a yellow toner image onto the intermediate transfer belt 150, the image forming station Pb intermediately transfers a magenta toner image onto the intermediate transfer belt 150, the image forming station Pc intermediately transfers a cyan toner image onto the intermediate transfer belt 150, and the image forming station Pd intermediately transfers a black toner image onto the intermediate transfer belt 150. In the case where the image forming apparatus 100 prints only monochrome images instead of color images, only any one of the image forming stations Pa, Pb, Pc, Pd may be provided.

[0015] Each of the image forming stations Pa, Pb, Pc, Pd includes a developing device 10, a photosensitive drum 142, a drum cleaning device 143, a charger 144, and the like. In any of the image forming stations Pa, Pb, Pc, Pd, a toner image is formed in the following manner. The drum cleaning device 143 removes and collects residual toner on the surface of the photosensitive drum 142. Thereafter, the surface of the photosensitive drum 142 is uniformly charged to a predetermined potential by the charger 144. Then, the surface of the charged photosensitive drum 142 is exposed to light from an optical scanning device 180, so that an electrostatic latent image is formed on the surface of the photosensitive drum 142. Thereafter, toner is supplied by the developing device 10 to the electrostatic latent image formed on the surface of the rotating photosensitive drum 142, and development processing for visualization (development) is performed. Accordingly, a toner image of each color is formed on each photosensitive drum 142 included in each of the image forming stations Pa, Pb, Pc, Pd. That is, image formation is performed on each photosensitive drum 142. A detailed description of the developing device 10 will be given later.

[0016] The intermediate transfer belt 150 is provided so as to be in contact with the surfaces of the respective photosensitive drums 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd. The intermediate transfer belt 150 circulates in the arrow direction A1 as the plurality of intermediate transfer rollers 151 rotate. Accordingly, the toner images of respective colors formed on the surfaces of the respective photosensitive drums 142 provided in each of the image forming stations Pa, Pb, Pc, and Pd are sequentially intermediately transferred onto the surface of the intermediate transfer belt 150. In this way, a color toner image is formed on the surface of the intermediate transfer belt 150. Then, the toner image formed on the surface of the intermediate transfer belt 150 is transferred onto the surface of sheets fed one by one from the feeding tray 120 at a position corresponding to the transfer device 153.

[0017] The belt cleaning device 152 cleans the surface of the intermediate transfer belt 150. The belt cleaning device 152 is disposed at a position downstream, in the arrow direction A1 in which the intermediate transfer belt 150 circulates, of the position where the toner image on the intermediate transfer belt 150 is transferred onto a sheet, so as to be in contact with the surface of the intermediate transfer belt 150. Accordingly, the belt cleaning device 152 removes and collects residual toner on the surface of the intermediate transfer belt 150.

[0018] The transfer device 153 includes a transfer roller 153a. The transfer roller 153a is provided opposite to the surface of the intermediate transfer belt 150 such that a nip area is formed between the transfer roller 153a and the intermediate transfer belt 150. A sheet before printing, which has been conveyed to the nip area via the substantially S-shaped sheet conveyance path B1 that is the conveyance path for sheets from being fed from the feeding tray 120 to reaching the discharge tray 170, is conveyed while being sandwiched in the nip area between the transfer roller 153a and the intermediate transfer belt 150, and the toner image formed on the surface of the intermediate transfer belt 150 is transferred onto the sheet. Thereafter, the sheet that has passed through the nip area between the transfer roller 153a and the intermediate transfer belt 150, onto which the toner image has been transferred, is conveyed to the fixing device 160.

[0019] The fixing device 160 has a heating roller 161 and a pressure roller 162. Paper on which the toner image has been transferred in the nip area is sandwiched between the heating roller 161 and the pressure roller 162 and heated and pressurized. This fixes the toner image transferred to the paper. In other words, the printing of the image onto the surface of the paper is completed.

[0020] The paper transport path B1 is equipped with multiple rollers in the following order: a pickup roller 131, a transport roller 132, a register roller 133, the aforementioned intermediate transfer belt 150 and transfer roller 153a, the aforementioned heating roller 161 and pressure roller 162, and a discharge roller 134.

[0021] Multiple sheets of paper stored in the feed tray 120 are pulled out one by one by the pickup roller 131 and transported along the paper transport path B1 by the transport roller 132 and the registration roller 133. The paper discharged from the registration roller 133 is then transported between the intermediate transfer belt 150 and the transfer roller 153a, and between the heating roller 161 and the pressure roller 162, and discharged to the discharge tray 170 via the discharge roller 134.

[0022] The registration roller 133 is located upstream of the intermediate transfer belt 150 and transfer roller 153a, where the toner image is transferred to the paper, in the paper transport path B1. The registration roller 133 stops the paper before it is transported to the intermediate transfer belt 150 and transfer roller 153a to align the leading edge of the paper. After stopping the paper, the registration roller 133 transports the paper in accordance with the timing of the toner image transfer in the nip area between the intermediate transfer belt 150 and the transfer roller 153a. The transport roller 132 facilitates the transport of the paper from the pickup roller 131 to the registration roller 133.

[0023] Next, the schematic configuration of the developing apparatus 10 provided in each of the image forming stations Pa, Pb, Pc, and Pd will be described using Figure 2. Figure 2 is a perspective view showing the schematic configuration of the developing apparatus 10 according to the embodiment. In Figure 2, the upper housing is omitted from the illustration in order to explain the inside of the developing apparatus 10. Note that the developing apparatus 10 provided in each of the image forming stations Pa, Pb, Pc, and Pd have the same configuration except for the color of the toner used. The developing apparatus 10 is installed inside the image forming apparatus 100 such that the direction of extension of the developing apparatus 10, indicated by the arrow pointing to the lower left in Figure 2, is the direction toward the rear side of the image forming apparatus 100, and the direction indicated by the arrow pointing to the upper right in Figure 2 is the direction toward the front side of the image forming apparatus 100.

[0024] The developing apparatus 10 includes a developing roller (developer carrier) 11, a first transport screw (agitation transport member) 12, a second transport screw 13, and a housing 14, etc. The housing 14 forms a developing tank 19 in which the developer, the first transport screw 12, and the second transport screw 13 are housed. The inside of the developing tank 19 is divided by a partition wall 15 into a supply tank (housing section) 19A and an agitation tank 19B, and the developer is housed in each. In other words, the developing tank 19 of the developing apparatus 10 has a supply tank 19A that houses the developer to be carried on the developing roller 11, which will be described later, and an agitation tank 19B.

[0025] The developing roller 11, as will be described in more detail later, has developer on its surface and is mounted on the developing tank 19 so as to be rotatable in the forward or reverse direction. The developing roller 11 rotates in the forward direction during the developing process (image formation). The supply tank 19A is located below the developing roller 11 and has a first transport screw 12 rotatably positioned inside. The first transport screw 12 rotates to transport the developer in the supply tank 19A while agitating it. The agitation tank 19B is adjacent to the supply tank 19A and has a second transport screw 13 rotatably positioned inside. The second transport screw 13 rotates to transport the developer in the agitation tank 19B while agitating it.

[0026] As the developer contained in the developing tank 19, for example, a two-component developer containing a non-magnetic toner and a magnetic carrier can be used. The developer contained in the agitation tank 19B is agitated by the rotation of the second transport screw 13 and transported along the longitudinal direction of the agitation tank 19B in the direction indicated by arrow E1. This agitation creates friction between the non-magnetic toner and the magnetic carrier contained in the developer, and this friction charges the non-magnetic toner. The developer transported in the agitation tank 19B in the direction indicated by arrow E1 is transported from the agitation tank 19B to the supply tank 19A through the opening 15h1 formed at one end of the partition wall 15, as shown by arrow E2. The developer transported to the supply tank 19A is agitated by the rotation of the first transport screw 12 and transported along the longitudinal direction of the supply tank 19A in the direction indicated by arrow E3, which is the opposite direction to arrow E1. Furthermore, as will be described in more detail later, the developer being transported within the supply tank 19A is partially drawn up onto the surface of the developing roller 11 by the magnetic force from the developing roller 11, and is transported within the supply tank 19A in the direction indicated by arrow E3. The developer transported within the supply tank 19A in the direction indicated by arrow E3 is then transported from the supply tank 19A to the agitation tank 19B through the opening 15h2 formed at the other end of the partition wall 15, as shown by arrow E4. In this way, the developer is transported in a circulating manner within the developing tank 19. In addition, the amount of toner consumed by development is supplied into the developing tank 19 from the toner supply port 18 located above the developing tank 19.

[0027] Figure 3 is a functional block diagram showing the schematic configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 includes a control unit 60, a storage unit 70, a communication unit 80, and a temperature and humidity sensor 190. Each of the image forming stations Pa to Pd is also equipped with a counter 145 that counts the rotation speed of the photoreceptor drum 142. Note that the counter 145 only needs to be able to count the rotation speed of the photoreceptor drum 142 in each of the image forming stations Pa to Pd, and may be provided outside the image forming stations Pa to Pd.

[0028] The temperature and humidity sensor 190 measures the temperature and humidity and outputs information representing the measured temperature and humidity to the control unit 60. The temperature and humidity sensor 190 may be mounted inside the main body 101 of the device or on the outside of the main body 101 of the device.

[0029] The control unit 60 controls the driving of each part of the image forming apparatus 100. The control unit 60 has a processor such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), or ASIC (application specific integrated circuit). For example, the control unit 60 controls the driving of the image reading device 110, multiple transport rollers, optical scanning device 180, intermediate transfer roller 151, belt cleaning device 152, transfer device 153, fixing device 160, storage unit 70, communication unit 80, photoreceptor drum 142, drum cleaning device 143, charger 144, counter 145, temperature and humidity sensor 190, developing roller 11, first transport screw 12, and second transport screw 13 by reading and executing a computer-readable control program stored in the storage unit 70. Furthermore, the control unit 60 acquires information representing the number of rotations of the photoreceptor drum 142 counted by the counter 145 and calculates the distance traveled by the rotation of the photoreceptor drum 142. The control unit 60 also acquires information representing the temperature and humidity from the temperature and humidity sensor 190. As will be described in detail later, the control unit 60 executes a loosening mode to loosen toner aggregates formed by the aggregation of toner in the developer within the developing device 10, based on the distance traveled (in other words, the number of rotations) of the photoreceptor drum 142.

[0030] The storage unit 70 is a computer-readable recording medium. The storage unit 70 may be a semiconductor memory such as SRAM (Static Random Access Memory), DRAM (Dynamic Random Access Memory), ROM (Read Only Memory), or flash memory; it may be a register; it may be a magnetic storage device such as a hard disk drive (HDD); or it may be an optical storage device such as an optical disk drive. The storage unit 70 stores a control program (not shown) on a non-temporary basis. The control program stored in the storage unit 70 may be pre-stored in the storage unit 70; or it may be supplied to the storage unit 70 via a wide-area communication network, including the Internet.

[0031] The communication unit 80 is an interface for communicating with external devices. The communication unit 80 may, for example, be equipped with a fax modem, or it may be an interface for communication in accordance with the USB standard, or it may be an interface for communication in accordance with the IEEE 802.11 method, or it may be an interface for communication in accordance with another method.

[0032] Figure 4 shows the developing apparatus 10 according to the embodiment in the process of developing. In Figure 4, the developing apparatus 10 is shown as a cross-section cut in a direction perpendicular to the longitudinal direction. As shown in Figure 4, an upper housing 14A covering the developing roller 11, the first transport screw 12, and the second transport screw 13 is attached to the housing 14, and the housing 14 and the upper housing 14A form the developing tank 19. The developing apparatus 10 also includes a doctor blade (layer restricting member) 20 and an inclined member 30. Developer 5 is stored in the developing tank 19.

[0033] The developing roller 11 is located above the supply tank 19A in the developing tank 19 and to the side of the photoreceptor drum 142. The developing roller 11 is positioned opposite the photoreceptor drum 142. Inside the developing roller 11, there is a magnet roller that forms multiple magnetic poles in the circumferential direction, and a non-magnetic sleeve is provided to cover the outer circumference of the magnet roller. The developing roller 11 includes the magnet roller and the non-magnetic sleeve as described above, and is mounted in the developing tank 19 such that the magnet roller does not rotate, and only the non-magnetic sleeve rotates. Hereafter, for convenience, it may be explained that "the developing roller 11 rotates," but more accurately, it means that "the non-magnetic sleeve of the developing roller 11 rotates." The magnet roller generates a magnetic force around the surface of the non-magnetic sleeve, that is, around the surface of the developing roller 11. The developing roller 11 uses this magnetic force to draw up the developer 5 from the supply tank 19A in the developing tank 19 and load it onto its surface, and by rotating, it transfers the developer 5 loaded onto its surface to a position opposite the photoreceptor drum 142.

[0034] The developing tank 19 has a side portion 16 (a side portion facing the partition wall 15 via the first transport screw 12) that forms the outer wall portion of the supply tank 19A (opposite the partition wall 15). The side portion 16 is positioned below the developing roller 11. The side portion 16 also has a top surface facing the developing roller 11, and a first inclined surface F1 is formed on the top surface that is inclined with respect to the horizontal plane. The first inclined surface F1 is positioned so as to create a gap between it and the surface of the developing roller 11.

[0035] The doctor blade 20 regulates the thickness of the developer 5 layer supported on the surface of the developing roller 11. The doctor blade 20 is mounted facing the outer side surface 16e of the side portion 16 that forms the wall portion of the supply tank 19A opposite to the partition wall 15 (the side portion 16 opposite to the inner side surface inside the supply tank 19A). Furthermore, the doctor blade 20 is positioned such that the gap between it and the developing roller 11 (non-magnetic sleeve) is smaller than the gap between the top of the side portion 16 and the developing roller 11 (non-magnetic sleeve). In other words, the doctor blade 20 protrudes from the first inclined surface F1 toward the developing roller 11 and is positioned with a gap between it and the developing roller 11. As described above, the developing tank 19, to which the developing roller 11 and doctor blade 20 are attached, has a side portion 16 adjacent to the doctor blade 20, facing the developing roller 11, and having a first inclined surface F1 that is inclined with respect to the horizontal plane such that the distance from the developing roller 11 increases as the doctor blade 20 approaches the supply tank 19A. The doctor blade 20 is attached to the side portion 16 (the side opposite to the supply tank 19A) such that the distance from the developing roller 11 (distance DG described later) is smaller than the shortest distance between the first inclined surface F1 and the developing roller 11 (distance D0 described later).

[0036] The inclined member 30, as will be described in detail later, is a guide member for smoothly returning the developer 5 between the developing roller 11 and the first inclined surface F1 to the supply tank 19A when the loosening mode is performed to eliminate the aggregation of toner in the developer 5. For example, the inclined member 30 is located between the side portion 16 and the first transport screw 12, and is provided on the inner side surface of the side portion 16. Of the inclined member 30, the top surface facing the developing roller 11 is a second inclined surface F2 that is inclined with respect to the horizontal plane. The second inclined surface F2 is adjacent to the first inclined surface F1 and is provided with a gap between it and the surface of the developing roller 11. The inclination angle of the second inclined surface F2 is steeper than the inclination angle of the first inclined surface F1.

[0037] During the developing process, the control unit 60 rotates the first transport screw 12 counterclockwise around the rotation center C12 as shown by arrow G1, rotates the developing roller 11 counterclockwise around the rotation center C11 as shown by arrow J1, and rotates the photoreceptor drum 142 clockwise around the rotation center C142 as shown by arrow K1. The direction of rotation in which the control unit 60 rotates the first transport screw 12, the developing roller 11, and the photoreceptor drum 142 during the developing process is referred to as the positive direction.

[0038] As the first transport screw 12 rotates in the direction of arrow G1 (forward direction), the developer 5 between the first transport screw 12 and the inclined member 30 in the supply tank 19A is pushed up from below the second inclined surface F2 toward the second inclined surface F2 along the surface of the inclined member 30 facing the first transport screw 12. Due to the magnetic force moving from the first transport screw 12 toward the developing roller 11, the developer 5 is drawn up from the surface of the first transport screw 12 along the second inclined surface F2 toward the surface of the developing roller 11, as shown by arrow E5. The drawn-up developer 5 is carried on the surface of the developing roller 11. As the developing roller 11 rotates in the direction of arrow J1 (forward direction), the developer 5 carried by the developing roller 11 passes through the gap between the developing roller 11 and the side 16 along the first inclined surface F1, and then passes through the gap between the developing roller 11 and the doctor blade. The gap between the developing roller 11 and the doctor blade is smaller than the gap between the developing roller 11 and the side 16 located upstream of the developing roller 11's rotation in the forward direction. Therefore, as shown by arrow E6, the developer 5 carried on the surface of the developing roller 11 that passes through the gap between the developing roller 11 and the doctor blade 20 is restricted to a predetermined layer thickness corresponding to the distance between the developing roller 11 and the doctor blade 20. As the developing roller 11 rotates in the direction of arrow J1 (forward direction), the developer 5 carried on the surface of the developing roller 11, restricted to a predetermined layer thickness, approaches the photoreceptor drum 142. This is caused by a magnetic force moving from the developing roller 11 towards the photoreceptor drum 142, causing it to rise and supply toner to the electrostatic latent image formed on the surface of the photoreceptor drum 142. In this way, the developing process is performed. Subsequently, the toner supplied to the surface of the photoreceptor drum 142 is intermediately transferred to the surface of the intermediate transfer belt 150, which moves in a circular motion in the direction of arrow A1 by the intermediate transfer roller 151 as the photoreceptor drum 142 rotates in the direction of arrow K1 (forward direction).

[0039] Figure 5 shows how toner aggregates 5a are formed in the developing apparatus 10 according to the embodiment. As described above, as the developing apparatus 10 performs the developing process, toner aggregates 5a, which are aggregates of toner contained in the developer 5, may form at the corner between the first inclined surface F1 and the doctor blade 20. If the developing apparatus 10 continues the developing process with toner-like aggregates 5a formed, the toner aggregates 5a will gradually grow over time, and the thickness of the developer 5 layer that passes through the gap between the developing roller 11 and the toner aggregates 5a will become thinner than a predetermined thickness. When the thickness of the developer 5 layer carried on the surface of the developing roller 11 becomes thinner than a predetermined thickness, a predetermined amount of toner will no longer be supplied to the surface of the photoreceptor drum 142, causing image defects such as the image (toner image) formed on the surface of the photoreceptor drum 142 being lighter in density or having white areas.

[0040] Therefore, the image forming apparatus 100 according to this embodiment performs a loosening mode to loosen the aggregates of the formed toner aggregates 5a when predetermined conditions are met, and also has a structure that makes it easy to remove the loosened toner aggregates 5a from the gap between the first inclined surface F1 and the developing roller 11.

[0041] Next, using Figure 6, an example of predetermined conditions that serve as the criteria for determining whether or not the control unit 60 will execute the loosening mode will be explained. Figure 6 is a diagram showing the predetermined conditions for the control unit 60 to execute the loosening mode according to the embodiment. For example, the control unit 60 determines whether or not the predetermined conditions that serve as the criteria for determining whether or not to execute the loosening mode are met, based on environmental conditions including temperature and humidity measured by the temperature and humidity sensor 190, and the cumulative number of rotations (i.e., the cumulative distance traveled by the rotation of the photoreceptor drum 142) counted by the counter 145 for a fixed period (e.g., the most recent 4 hours) of the photoreceptor drum 142 that rotates during the developing process.

[0042] In the table shown in Figure 6, "0" represents the temperature and humidity range in which the control unit 60 determines not to execute the loosening mode, and "V1" represents the temperature and humidity range in which the control unit 60 determines to execute the loosening mode if the rotation speed of the photoreceptor drum 142 over the immediate vicinity (for example, the last 4 hours) is 2000 rpm or more.

[0043] For example, when the temperature is relatively low and the humidity is low, toner aggregation is less likely to occur, so the control unit 60 determines that it is not necessary to execute the loosening mode. On the other hand, when the temperature and humidity are relatively high, toner aggregation is more likely to occur, and if the cumulative number of rotations of the photoreceptor drum 142 is relatively high, the control unit 60 determines that the developer 5 is in a state where toner aggregation is likely to occur, so it executes the loosening mode.

[0044] Specifically, in the example shown in Figure 6, if the temperature is 15°C or lower, the humidity is greater than 50% but less than or equal to 100%, and the rotation speed of the photoreceptor drum 142 satisfies condition "V1", the control unit 60 determines that the predetermined conditions are met and executes the loosening mode after the development process. Also, for example, if the temperature is greater than 15°C but less than or equal to 20°C, the humidity is greater than 40% but less than or equal to 100%, and the rotation speed of the photoreceptor drum 142 satisfies condition "V1", the control unit 60 determines that the predetermined conditions are met and executes the loosening mode after the development process. Also, for example, if the temperature is greater than 20°C but less than or equal to 25°C, the humidity is greater than 20% but less than or equal to 100%, and the rotation speed of the photoreceptor drum 142 satisfies condition "V1", the control unit 60 determines that the predetermined conditions are met and executes the loosening mode after the development process. Furthermore, for example, if the temperature is above 25°C and below 30°C, the humidity is above 10% and below 100%, and the rotation speed of the photoreceptor drum 142 satisfies condition "V1", the control unit 60 determines that the predetermined conditions are met and executes the loosening mode after the development process. Also, for example, if the temperature is above 30.1°C, the humidity is above 0% and below 100%, and the rotation speed of the photoreceptor drum 142 satisfies condition "V1", the control unit 60 determines that the predetermined conditions are met and executes the loosening mode after the development process.

[0045] In this way, the control unit 60 determines whether predetermined conditions are met, which serve as criteria for deciding whether or not to execute the loosening mode, based on the travel distance of the photoreceptor drum 142 and environmental conditions. Thus, when there is a high probability that toner aggregation has occurred, the control unit 60 executes the loosening mode, and when it is estimated that there is a high probability that toner aggregation has not occurred, the control unit 60 does not execute the loosening mode. As a result, the control unit 60 can efficiently remove toner aggregation.

[0046] The rotational speed of the photoreceptor drum 142 (2000 rpm), which is the criterion for determining whether or not the above-mentioned condition "V1" is met, is just an example and may be any other rotational speed, and may also be changed depending on whether the rotational speed of the photoreceptor drum 142 is low, medium, or high.

[0047] Next, using Figures 7 to 9, we will explain the loosening mode performed by the image forming apparatus 100 and the structure for quickly removing the loosened toner aggregates 5a from the gap between the first inclined surface F1 and the developing roller 11.

[0048] First, the configuration of each part of the developing apparatus 10 will be described in detail using Figure 7. Figure 7 is a diagram for explaining the detailed configuration of each part of the developing apparatus 10 according to this embodiment. In Figure 7, the developing apparatus 10 is viewed from the front to the back, and the cross-section is shown cut in a direction perpendicular to the longitudinal direction of the developing apparatus 10.

[0049] The boundary between the adjacent first inclined surface F1 and second inclined surface F2 is called end R. End R is the end of the first inclined surface F1 that contacts the second inclined surface F2, and also the end of the second inclined surface F2 that contacts the first inclined surface F1. Of the first inclined surface F1, the end that contacts the doctor blade 20 is called end Q. Of the two ends of the first inclined surface F1, end Q is the end closer to the doctor blade 20, and end R is the end further away from the doctor blade 20. Of the second inclined surface F2, the end opposite to the first inclined surface F1 is called end S. Of the two ends of the second inclined surface F2, end R is the end closer to the first inclined surface F1, and end S is the end further away from the first inclined surface F1.

[0050] The first inclined surface F1 is inclined from one end Q to the other end R such that end R is located below the horizontal plane H1 passing through end Q. The first inclined surface F1 is inclined by an angle α with respect to the horizontal plane H1.

[0051] The second inclined surface F2 is inclined from one end R to the other end S such that end S is positioned below the horizontal plane H2 passing through end R. The second inclined surface F2 is inclined downward from the horizontal plane H2 by an angle β (angle β > angle α) that is larger than that of the first inclined surface F1. The second inclined surface F2 extends from the first inclined surface F1 such that the end S opposite to the first inclined surface F1 is positioned above the first conveying screw 12.

[0052] On the surface 11f of the developing roller 11, point P0 is defined as the intersection of a hypothetical straight line from the rotation center C11 to end Q with the surface 11f, point P1 is defined as the intersection of a hypothetical straight line from the rotation center C11 to end R with the surface 11f, and point P2 is defined as the intersection of a hypothetical straight line from the rotation center C11 to end S with the surface 11f. The angle formed by point P0, the rotation center C11, and point P1 is called angle θ, and the circumferential length from point P0 to point P1 (the length from point P0 to point P1 along the surface 11f) is called length L. The length between the two ends (end Q and end R) of the first inclined surface F1 is called length DF1.

[0053] As described above, the gap between the doctor blade 20 and the developing roller 11 is smaller than the gap between the first inclined surface F1 and the developing roller 11. That is, the distance DG from the top surface 20f of the doctor blade 20 facing the developing roller 11 to point P0 is smaller than the distance D0 from point P0 to end Q.

[0054] Furthermore, the first inclined surface F1 is inclined with respect to the horizontal plane H1 such that the distance from the developing roller 11 increases as it approaches the end R from the end Q, or in other words, as it approaches the inside of the feed tank 19A from the doctor blade 20. That is, the distance D1 from point P1 to end R is greater than the distance D0 from point P0 to end Q.

[0055] Furthermore, the second inclined surface F2 is inclined with respect to the horizontal plane H2 such that the distance from the developing roller 11 increases as it approaches the end S from the end R, or in other words, as it approaches the opposite end S from the end R closer to the first inclined surface F1. That is, the distance D2 from point P2 to end S is greater than the distance D1 from point P1 to end R.

[0056] For example, the diameter of the developing roller 11 can be 18 mm, the angle θ = 15°, the length L = 2.3 mm, the length DF = 2.9 mm, and the distance D0 = 1.8 mm, but these values ​​are not the only ones that can be used.

[0057] Next, using Figures 7 to 9, we will explain the loosening mode performed by the image forming apparatus 100 and the structure for quickly removing the loosened toner aggregates 5a from the gap between the first inclined surface F1 and the developing roller 11.

[0058] Figure 8 shows the control unit according to the embodiment rotating the developing roller 11 in the reverse direction during the loosening mode. As described above, when the control unit 60 determines that predetermined conditions are met, it can determine that there is a high possibility that toner aggregates 5a are formed at the corner between the first inclined surface F1 and the doctor blade 20, and therefore executes the loosening mode after the development process is completed.

[0059] When the loosening mode is started, the control unit 60 rotates the developing roller 11, which has finished developing and stopped rotating, in the direction of arrow J2, which is opposite to the forward direction (direction of arrow J1 shown in Figure 4). The direction of arrow J2 is clockwise around the rotation center C11. The control unit 60 also rotates the first transport screw 12 in the direction of arrow G2, which is opposite to the forward direction (direction of arrow G1 shown in Figure 4). The direction of arrow G2 is clockwise around the rotation center C12.

[0060] As the developing roller 11 rotates in the opposite direction (arrow J2 direction), the toner aggregates 5a that were formed at the corner between the first inclined surface F1 and the doctor blade 20 are loosened. In addition, the developer 5 between the developing roller 11 and the first inclined surface F1, which is supported on the surface 11f of the developing roller 11, is transferred in the direction from the first inclined surface F1 towards the supply tank 19A, as shown by arrow E7. Therefore, the loosened toner aggregates 5a are carried by the flow of developer 5 in the direction of arrow E7 and transferred towards the supply tank 19A. This allows the toner aggregates 5a that were agglomerated at the corner between the first inclined surface F1 and the doctor blade 20 to be transferred into the supply tank 19A.

[0061] In particular, the control unit 60 rotates the developing roller 11 in the opposite direction (direction of arrow J2) by a circumferential length L or more opposite the first inclined surface F1. In other words, the control unit 60 rotates the developing roller 11 in the opposite direction (direction of arrow J2) by an angle θ or more. This allows for more effective loosening of the toner aggregates 5a compared to the case where the developing roller 11 is rotated in the opposite direction for less than a circumferential length L, and as a result, the toner aggregates 5a can be more effectively removed from the corner formed by the first inclined surface F1 and the doctor blade 20.

[0062] Furthermore, the first inclined surface F1 facing the developing roller 11 is inclined with respect to the horizontal plane H1 (Figure 7) such that the distance from the developing roller 11 increases as it approaches the supply tank 19A from the doctor blade 20. That is, as explained using Figure 7, the first inclined surface F1 is inclined with respect to the horizontal plane H1 such that the distance D1 from point P1 to end R is greater than the distance D0 from point P0 to end Q. This allows the toner aggregates 5a that had accumulated at the corner formed by the first inclined surface F1 and the doctor blade 20 to be more effectively transferred along the first inclined surface F1 to the supply tank 19A located below the first inclined surface F1. This also allows for more effective removal of the toner aggregates 5a that had accumulated at the corner formed by the first inclined surface F1 and the doctor blade 20.

[0063] Furthermore, the developing apparatus 10 according to this embodiment includes a second inclined surface F2 in the supply tank 19A that faces the developing roller 11 and is adjacent to the first inclined surface F1. The second inclined surface F2 is inclined downward from the horizontal plane H2 (Figure 7) at a larger angle β than the first inclined surface F1, and the end S opposite to the first inclined surface F1 is located above the first transport screw 12. As a result, when the developing roller 11 rotates in the opposite direction (direction of arrow J2 in Figure 8), the developer 5 transferred from the first inclined surface F1 to the second inclined surface F2 can be more effectively guided and transferred along the second inclined surface F2 to the first transport screw 12, i.e., into the supply tank 19A. This makes it possible to more effectively reduce the density of the developer 5 on the first inclined surface F1, and as a result, the aggregation of toner aggregates 5a that had aggregated at the corner between the first inclined surface F1 and the doctor blade 20 can be more effectively loosened.

[0064] Furthermore, when the developing roller 11 rotates in the reverse direction (arrow J2 direction), the first transport screw 12 rotates in the reverse direction (arrow G2 direction), which is the direction in which the developer 5 is sent from the second inclined surface F2 downwards. This means that the first transport screw 12 rotates in a direction that lowers the liquid level of the developer 5 that flows from the first transport screw 12 to the developing roller 11, so that the developer 5 on the second inclined surface F2 slides down along the second inclined surface F2 into the supply tank 19A. When the developer 5 on the second inclined surface F2 slides down into the supply tank 19A, the density of the developer 5 on the first inclined surface F1 can be reduced more effectively. This makes it possible to more effectively loosen the toner aggregates 5a that were agglomerated at the corner formed by the first inclined surface F1 and the doctor blade 20.

[0065] Figure 9 shows the control unit in the embodiment rotating the developing roller 11 in the forward direction during the loosening mode. As described above, the control unit 60 starts the loosening mode and rotates the developing roller 11 in the reverse direction for a length of L or more in the circumferential direction opposite to the first inclined surface F1, and then, as shown in Figure 9, rotates the developing roller 11 in the forward direction (direction of arrow J1). This loosens the toner aggregates 5a remaining between the first inclined surface F1 and the developing roller 11 and allows them to be removed through the gap between the developing roller 11 and the top surface 20f of the doctor blade 20. This allows the toner aggregates 5a between the first inclined surface F1 and the developing roller 11 to be removed more effectively from between the developing roller 11 and the first inclined surface F1.

[0066] Furthermore, when the developing roller 11 rotates in the forward direction (direction of arrow J1), the control unit 60 rotates the first transport screw 12 in a direction that pushes the developer 5 in the supply tank 19A upward from below the second inclined surface F2 toward the second inclined surface F2 (forward direction as shown by arrow G1). As a result, the developer 5 is supplied from the supply tank 19A along the second inclined surface F2 onto the first inclined surface F1. The developer 5 supplied onto the first inclined surface F1 is then carried on the surface 11f of the developing roller 11 rotating in the forward direction and is removed from between the first inclined surface F1 and the developing roller 11 by passing through the gap between the developing roller 11 and the doctor blade 20. This also allows for more effective removal of toner aggregates 5a between the first inclined surface F1 and the developing roller 11.

[0067] Thus, in the developing apparatus 10 according to this embodiment, the first inclined surface F1 facing the developing roller 11 is inclined with respect to the horizontal plane H1 (Figure 7) such that the distance from the developing roller (developer carrier) 11 increases as it approaches the supply tank (housing section) 19A from the doctor blade (layer restricting member) 20. In addition, the image forming apparatus 100 (or its control unit 60) rotates the developing roller 11 in the forward direction during image formation, and if predetermined conditions (Figure 6) are met, after image formation is completed, it performs a loosening mode in which it rotates the developing roller 11 in the opposite direction to the forward direction (direction of arrow J2 in Figure 8) for a circumferential length L (Figures 7 and 8) or more facing the first inclined surface F1, and then rotates it in the forward direction (direction of arrow J1 in Figure 9).

[0068] As a result, when it is determined that there is a high probability that toner aggregates 5a are formed at the corner between the first inclined surface F1 and the doctor blade 20, the control unit 60 rotates the developing roller 11 in the opposite direction for a length of L (Figures 7 and 8) or more in the circumferential direction opposite to the first inclined surface F1, thereby thoroughly loosening the toner aggregates 5a. Furthermore, by tilting the first inclined surface F1 with respect to the horizontal plane H1 (Figure 7), the thoroughly loosened toner aggregates 5a can be efficiently dropped along the first inclined surface F1 into the supply tank 19A. In addition, the control unit 60 rotates the developing roller 11 in the opposite direction for a length L (Figures 7 and 8) or more in the circumferential direction opposite to the first inclined surface F1 to sufficiently loosen the toner aggregates 5a, and then rotates it in the forward direction (direction of arrow J1 in Figure 9). As a result, the toner aggregates 5a remaining between the developing roller 11 and the first inclined surface F1 can be efficiently removed from between the developing roller 11 and the first inclined surface F1 through the gap between the developing roller 11 and the top surface 20f of the doctor blade 20.

[0069] Thus, according to the image forming apparatus 100 of this embodiment, toner aggregates 5a can be removed efficiently.

[0070] Furthermore, it is preferable that the distance between the first inclined surface F1 and the developing roller 11 (distance D0 shown in Figure 7) is four times or less the distance between the doctor blade 20 and the developing roller 11 (distance DG shown in Figure 7). This makes it easier for the developer 5 carried on the surface 11f of the developing roller 11 to be transported in the direction of rotation of the developing roller 11, both when the developing roller 11 is rotated in the forward direction and when the developing roller 11 is rotated in the reverse direction. As a result, compared to the case where the distance between the first inclined surface F1 and the developing roller 11 (distance D0 shown in Figure 7) exceeds four times the distance between the doctor blade 20 and the developing roller 11 (distance DG shown in Figure 7), the toner aggregates 5a formed between the first inclined surface F1 and the developing roller 11 can be loosened and removed from between the first inclined surface F1 and the developing roller 11 more effectively.

[0071] When the control unit 60 executes the loosening mode, it is preferable that the speed at which the developing roller 11 rotates in the reverse direction is slower than the speed at which the developing roller 11 rotates in the forward direction during the developing process. This allows for more effective loosening of the toner aggregates 5a between the developing roller 11 and the first inclined surface F1.

[0072] For example, the speed at which the developing roller 11 rotates in the forward direction during the developing process can be set to 280 mm / s, the speed at which the developing roller 11 rotates in the reverse direction during the loosening mode can be set to 140 mm / s, and the speed at which the developing roller 11 rotates in the forward direction after rotating in the reverse direction during the loosening mode can be set to 140 mm / s. Note that the above-mentioned speeds of the developing roller 11 are just examples and are not limited to those speeds.

[0073] Figure 10 is a diagram showing an example of the magnetic force generated around the surface 11f of the developing roller 11 according to the embodiment. As described above, a magnet provided inside the developing roller 11 generates a magnetic force around the surface 11f of the developing roller 11. Figure 10 shows the magnetic flux (density) generated in a direction perpendicular to the circumferential surface of the developing roller 11, and the longer the arrow in the figure, the higher the magnetic flux (density) generated. For example, the developing roller 11 generates a magnetic flux that is drawn up in the direction toward the developing roller 11 between the first transport screw 12 and the developing roller 11, as shown by the magnetic fluxes indicated by arrows M1a and M1b. As a result, when the first transport screw 12 rotates in the positive direction (direction of arrow G1 shown in Figure 9) during the developing process, the developer 5 in the supply tank 19A can be drawn up to the surface of the developing roller 11 along the magnetic force indicated by arrows M1a and M1b.

[0074] Furthermore, it is preferable that the developing roller 11 generates a magnetic force such that the magnetic flux (density) decreases as it moves from the doctor blade 20 toward the end S on the second inclined surface F2 opposite to the first inclined surface F1, as shown by arrows M2a, M2b, and M2c. As a result, the magnetic flux (density) in the direction perpendicular to the surface 11f of the developing roller 11 decreases as it moves from the doctor blade 20 toward the end S on the second inclined surface F2 opposite to the first inclined surface F1. Therefore, when the loosening mode is executed, the developer 5 carried on the surface 11f of the developing roller 11, which rotates in the opposite direction (direction of arrow J2), becomes more likely to separate from the surface 11f as it approaches the end S from the doctor blade 20, and is more likely to fall into the supply tank 19A along the first inclined surface F1 and the second inclined surface F2. This makes it possible to loosen the toner aggregates 5a between the developing roller 11 and the first inclined surface F1 more efficiently.

[0075] Figure 11 is a diagram showing the processing flow of the image forming apparatus 100 according to the embodiment. In step S11, the control unit 60 waits until it receives an instruction to form an image (if NO in step S11), and when it receives an instruction to form an image (if YES in step S11), in step S12, the control unit 60 starts forming an image by rotating various rollers in the forward direction. Specifically, the control unit 60 performs the development process by rotating, for example, the first transport screw 12, the developing roller 11, and the photoreceptor drum 142 in the forward direction. At this time, the counter 145 counts the number of rotations of the rotating photoreceptor drum 142.

[0076] Next, in step S13, the control unit 60 determines whether all the instructed image formation has been completed. In other words, the control unit 60 determines whether the development process for forming all the instructed images has been completed.

[0077] In step S13, if the control unit 60 determines that image formation (i.e., development process) is not yet complete (in the case of NO in step S13), it repeats the process in step S12 until image formation (i.e., development process) is completed. In step S13, if the control unit 60 determines that image formation (i.e., development process) is complete (in the case of YES in step S13), in step S14, the control unit 60 stops the rotation of the various rollers that were rotating in the forward direction, such as the first transport screw 12, the developing roller 11, and the photosensitive drum 142.

[0078] Next, in step S15, the control unit 60 determines whether or not to execute the loosening mode, based on the rotation speed of the photoreceptor drum 142 counted by the counter 145 and the temperature and humidity measured by the temperature and humidity sensor 190, whether or not to meet the predetermined conditions (Figure 6). Note that the control unit 60 may perform the processing in step S15 before completely stopping the rotation of the various rollers in step S14.

[0079] In step S15, if the control unit 60 determines that a predetermined condition is met (if the result of step S15 is YES), it can determine that there is a high probability that toner aggregates 5a have been formed, and therefore executes the loosening mode. That is, as shown in Figure 8, the control unit 60 rotates the developing roller 11 and the first transport screw 12 in opposite directions, and then, as shown in Figure 9, rotates the developing roller 11 and the first transport screw 12 in the forward direction. Next, in step S17, the counter 145 resets the count of the number of rotations of the photoreceptor drum 142. Then, the image forming apparatus 100 ends its operation.

[0080] In step S15, if the control unit 60 determines that the predetermined conditions are not met (in the case of NO in step S15), it can determine that the possibility of toner aggregates 5a being formed is low, and therefore does not execute the loosening mode, and the image forming apparatus 100 terminates its operation.

[0081] Thus, the control unit 60 executes the loosening mode only when predetermined conditions are met, and does not execute the loosening mode when the predetermined conditions are not met. As a result, the loosening mode is not executed unnecessarily even when the predetermined conditions are met and the possibility of toner aggregates 5a being formed is low, and from this point of view as well, the toner aggregates 5a can be removed efficiently.

[0082] Figure 12 is a diagram showing the processing flow of an image forming apparatus 100 according to a modified embodiment. The image forming apparatus 100 may not only execute the loosening mode after image formation is completed (development processing is completed), but may also temporarily suspend image formation (development processing) and execute the loosening mode during the image formation process (development processing) if predetermined conditions are met.

[0083] As shown in Figure 12, the image forming apparatus 100 performs the processes in steps S11 and S12. Next, in step S12A, the control unit 60 determines whether or not to satisfy the predetermined conditions (Figure 6), which are the criteria for deciding whether or not to execute the loosening mode, based on the rotation speed of the photoreceptor drum 142 counted by the counter 145 and the temperature and humidity measured by the temperature and humidity sensor 190. The control unit 60 may perform the process in step S12A before the process in step S12 (before operating each part to form an image).

[0084] In step S12A, if the control unit 60 determines that a predetermined condition is met (if the result of step S12A is YES), it can determine that there is a high probability that toner aggregates 5a have already been formed. Therefore, in step S12B, it stops the forward rotation of the first transport screw 12, the developing roller 11, and the photoreceptor drum 142, resets the counter 145's count of rotations of the photoreceptor drum 142, and then in step S12C, executes the loosening mode. That is, as shown in Figure 8, the control unit 60 rotates the developing roller 11 and the first transport screw 12 in opposite directions, and then, as shown in Figure 9, rotates the developing roller 11 and the first transport screw 12 in the forward direction. After the execution of the loosening mode in step S12C is completed, the process returns to step S12A.

[0085] Furthermore, in step S12A, if the control unit 60 determines that the predetermined conditions are not met (in the case of NO in step S12A), it can determine that the possibility of toner aggregates 5a being formed is low and that it is not necessary to perform the loosening mode, and proceeds to perform the processes of steps S13 to S17 as explained with reference to Figure 11.

[0086] Thus, the image forming apparatus 100 may temporarily suspend image forming (development) and execute a loosening mode not only after the image forming process, but also during the image forming process (development process), if predetermined conditions are met. This allows for more reliable loosening of the toner aggregates 5a between the developing roller 11 and the first inclined surface F1, and removal from between the developing roller 11 and the first inclined surface F1.

[0087] Furthermore, the elements that appeared in the embodiments and modifications described above may be combined as appropriate, to the extent that no contradictions arise. [Explanation of Symbols]

[0088] 5: Developer, 5a: Toner aggregate, 10: Developing device, 11: Developing roller (developer carrier), 12: First transport screw (agitation transport member), 13: Second transport screw, 14: Housing, 16: Side, 19: Developing tank, 19A: Supply tank (housing section), 19B: Agitation tank, 20: Doctor blade (layer regulating member), 20f: Top surface, 30: Inclined member, 60: Control unit, 100: Image forming apparatus, 142: Photoreceptor drum, 145: Counter, 150: Intermediate transfer belt, 151: Intermediate transfer roller, 190: Temperature and humidity sensor, F1: First inclined surface, F2: Second inclined surface, H1·H2: Horizontal surface, Pa~Pd: Image forming station

Claims

1. An image forming apparatus comprising a developing device having a developer carrier that carries a developer on its surface and is rotatable in the forward or reverse direction, a layer restricting member that restricts the thickness of the developer layer carried by the developer carrier, and a developing tank to which the developer carrier and the layer restricting member are attached, wherein the developing device has a storage section for containing the developer to be carried on the developer carrier, The developing tank has a side portion adjacent to the layer restricting member, facing the developer carrier, and having a first inclined surface that slopes with respect to the horizontal plane such that the distance from the developer carrier increases as it approaches the housing portion from the layer restricting member side. The layer restricting member is attached to the side such that the distance from the developer carrier is less than the shortest distance between the first inclined surface and the developer carrier. The image forming apparatus rotates the developer carrier in the forward direction during image formation, and if predetermined conditions are met, after image formation is completed, it performs a loosening mode in which it rotates the developer carrier in the opposite direction to the forward direction for a length equal to or greater than the circumferential length opposite to the first inclined surface, and then rotates it in the forward direction. The developing tank further comprises an agitation and conveying member for conveying the developer while agitating it, and a second inclined surface that faces the developer carrier and is adjacent to the first inclined surface, The second inclined surface is inclined downward from the horizontal plane at a larger angle than the first inclined surface, and the end opposite to the first inclined surface is located above the stirring and conveying member. An image forming apparatus in which, when the developer carrier rotates in the reverse direction, the developer transferred to the second inclined surface is transferred along the second inclined surface toward the stirring and conveying member.

2. When the developer carrier rotates in the forward direction, the agitation and conveying member rotates in a direction that pushes the developer in the developing tank upward from below the second inclined surface toward the second inclined surface. The image forming apparatus according to claim 1, wherein when the developer carrier rotates in the opposite direction, the agitation conveying member rotates in a direction that sends the developer from the second inclined surface downwards from the second inclined surface.

3. The image forming apparatus according to claim 1, wherein the distance between the first inclined surface and the developer carrier is four times or less the distance between the layer restricting member and the developer carrier.

4. The image forming apparatus according to claim 1, wherein the speed at which the developer carrier rotates in the reverse direction during the execution of the loosening mode is slower than the speed at which the developer carrier rotates in the forward direction during the developing process.

5. The developer contains toner, The image forming apparatus includes a photoreceptor drum to which the toner contained in the developer carried by the developer carrier is supplied while rotating during the developing process. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises a control unit, and the control unit determines whether or not the predetermined conditions are met based on the distance traveled by the rotation of the photoreceptor drum and environmental conditions.

6. The image forming apparatus according to claim 1, wherein the magnetic flux formed around the surface of the developer carrier decreases from the layer restricting member toward the end of the second inclined surface opposite to the first inclined surface.

Images