Image forming apparatus

Abstract

This invention provides a technology for efficiently refreshing toner remaining in the developing unit of an image forming apparatus. [Solution] The image forming apparatus comprises an image carrier, a developing unit including a developing container, a stirring member, a developer carrier and a supply member, a replenishment unit positioned above the developing unit, a replenishment control member for controlling the replenishment of developer, and a control unit, wherein the control unit executes a refresh mode including a discharge operation for discharging developer from the developing container onto the image carrier and a replenishment operation for replenishing developer from the replenishment container, the replenishment operation is started before the discharge operation is completed, and the rotation speed of the stirring member is slowed down or the stirring member is stopped for at least a portion of the refresh mode.

Description

TECHNICAL FIELD

[0001] The present invention relates to an image forming apparatus.

BACKGROUND ART

[0002] An image forming apparatus is provided with a developing device that accommodates toner. In recent years, with growing awareness of environmental protection, the need to achieve a long service life for developing devices, which were conventionally disposable, by additionally replenishing toner has been increasing. When additionally replenishing toner, the remaining amount of toner in the developing device is detected by a remaining amount detection sensor, and when the remaining amount becomes low, a method of performing an additional toner replenishing operation from a replaceable toner cartridge connected to the developing device is common.

[0003] Incidentally, the toner used in image forming apparatuses is formed of a powder having a certain degree of particle size distribution. For this reason, the toner in the developing device may include toner that is easily developed and toner that is less easily developed. Furthermore, in a toner recycling system (cleanerless configuration) or the like that returns waste toner to the developing device to reuse the toner, toner that is less likely to be consumed returns to the developing device again without being cleaned, so the phenomenon described above tends to occur more easily.

[0004] Patent Document 1 discloses a configuration for addressing the problem caused by changes in toner physical properties accompanying such toner consumption. In Patent Document 1, in order to refresh the toner in the developing device when the toner cartridge is replaced, a configuration is disclosed in which the toner in the developing device is discharged to a waste toner container or the like via a photosensitive drum in a state where the amount of toner in the developing device is small. When the amount of toner in the developing device is small, the ratio of toner that is difficult to develop (large particle diameter toner, or durable toner that can no longer maintain charge) increases, so the toner that is difficult to develop can be efficiently discharged to a waste toner container or the like.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0005] [Patent Document 1] Patent No. 5118881 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the configuration in which toner is ejected via a photosensitive drum, as described in Patent Document 1, had the following problems. First, because the configuration ejects toner using a solid image when the amount of toner in the developing unit is low, it was possible that the toner could not be ejected efficiently and it would take a long time. Also, during the toner refresh operation, it was necessary to refill with new toner after the toner ejection operation in the developing unit, which could result in a long downtime.

[0007] The present invention has been made in view of the above problems. The object of the present invention is to provide a technology for efficiently refreshing toner remaining in the developing apparatus of an image forming apparatus. [Means for solving the problem]

[0008] This invention employs the following configuration: In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit that controls the rotation of the stirring member, Equipped with, The control unit, (i) Control to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) In at least a portion of the interval from when the refresh mode is started until the refresh mode is terminated, the rotation speed of the stirring member is slowed down compared to the time of the image forming operation, or the stirring member is stopped. This is an image forming apparatus characterized by the following features.

[0009] The present invention also employs the following configuration: In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit for controlling the stirring member, Equipped with, The control unit, (i) Control to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) Controlling the discharge of the developer such that the stirring member in the developing container does not come into contact with the developer in at least a part of the period from the start of the refresh mode to the control period for ending the refresh mode An image forming apparatus characterized by the above features. Effects of the Invention

[0010] As described above, according to the present invention, it is possible to provide a technique for efficiently refreshing the toner remaining in the developing device of the image forming apparatus. Brief Description of the Drawings

[0011] [Figure 1] Schematic cross-sectional view of the image forming apparatus in the embodiment [Figure 2] Detailed cross-sectional view of the process and the toner cartridge in the embodiment [Figure 3A] Top view illustrating the remaining toner amount detection unit in the embodiment [Figure 3B] Illustrative view of remaining toner amount detection in the embodiment [Figure 3C] Illustrative view of remaining toner amount and light quantity in the embodiment [Figure 4] Control block diagram in Embodiment 1 [Figure 5] Flowchart diagram in Embodiment 1 [Figure 6] Transition of remaining toner amount and timing chart diagram in Embodiment 1 and Comparative Example 1 [Figure 7] Schematic diagram of toner circulation in Embodiment 1 [Figure 8] Schematic diagram of toner circulation in Comparative Example 1 [Figure 9] Schematic diagram of toner circulation in Comparative Example 2 [Figure 10] Schematic diagram of toner circulation in Embodiment 2 [Figure 11] Flowchart diagram in Embodiment 1 [Figure 12] Transition of remaining toner amount and timing chart diagram in Embodiment 2 [Figure 13] Diagram illustrating the toner supply port and toner discharge position in Example 3 [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately modified depending on the configuration and various conditions of the apparatus to which the present invention is applied. Therefore, unless otherwise specifically stated, this is not intended to limit the scope of the present invention. Although multiple features are described in the embodiments, not all of these features are necessarily essential to the invention, and the features may be combined in any way.

[0013] [Example 1] The following describes Example 1 with reference to Figure 1. In Example 1, an image forming apparatus having four process cartridges 3 (3Y, 3M, 3C, 3K) and a toner supply unit 20 is shown as an example. However, the number of process cartridges 3 installed in the image forming apparatus is not limited to this. It can be set as appropriate as needed.

[0014] Furthermore, in the embodiments described below, a laser beam printer is given as an example of an image forming apparatus.

[0015] [Outline configuration of an image forming apparatus] Figure 1 is a schematic cross-sectional view of the image forming apparatus 1, process cartridge 3, and toner supply unit 20 (toner cartridge) in Example 1. Figure 2 is an enlarged cross-sectional view of the process cartridge 3 and toner supply unit 20. In this invention, the upward direction in the drawings is the direction of gravity.

[0016] Image forming apparatus 1 is a four-color full-color laser printer that forms a color image on a recording medium S using an electrophotographic process. Image forming apparatus 1 uses a process cartridge system, and the process cartridge 3 is removablely mounted in image forming apparatus 1 via the front door 2.

[0017] The image forming apparatus 1 has first to fourth process cartridges 3 (3Y, 3M, 3C, 3K) arranged in a substantially horizontal direction. The 3C and 3K cartridges each have similar electrophotographic process mechanisms, but differ in the color of the developer (hereinafter referred to as toner). The first to fourth process cartridges 3 (3Y, 3M, 3C, 3K) are supplied by the drive output unit of the image forming apparatus 1 (such as the drive motor 116 in Figure 4). Rotational driving force is transmitted. Hereafter, unless otherwise necessary, the subscript indicating the color type (Y, M, C, K) will be omitted, and it will simply be referred to as process cartridge 3. Similarly, for components other than process cartridge 3, subscripts will be omitted unless otherwise necessary.

[0018] Furthermore, the process cartridge 3 is supplied with voltage from various power supply units of the image forming apparatus 1. As shown in Figure 4, the voltages include the charging voltage supplied from the charging power supply 111 to the charging roller 61, the developing voltage supplied from the developing power supply 112 to the developing roller 41, and the regulating voltage supplied from the regulating power supply 113 to the developing blade 42. The transfer power supply 114 of the image forming apparatus 1 supplies the transfer voltage to the primary transfer roller 5c and the secondary transfer roller 10.

[0019] As shown in Figure 2, the process cartridge 3 of this embodiment has a photosensitive drum 63 which is an image carrier, and a drum unit 60 which is equipped with a charging means as a process means that acts on the photosensitive drum 63. Here, the drum unit 60 may have a cleaning means in addition to a charging means as a process means.

[0020] Furthermore, the process cartridge 3 has a developing unit 40 equipped with developing means for developing the electrostatic latent image on the photosensitive drum 63.

[0021] Furthermore, each of the first to fourth process cartridges 3 (3Y, 3M, 3C, 3K) is connected to the first to fourth toner supply units 20 (20Y, 20M, 20C, 20K). The drum unit 60, the developer unit 40, and the toner supply units 20 are all interconnected. A more detailed description of the process cartridge 3 will be provided later.

[0022] The first toner supply unit 20Y contains yellow (Y) toner T. The developing container 44 of the first process cartridge 3Y also contains yellow (Y) toner T. The first process cartridge 3Y forms a yellow toner image on the surface of the photosensitive drum 63. Similarly, the second process cartridges 3M to the fourth process cartridges 3K and the second toner supply units 20M to the fourth toner supply units 20K also contain toner T for forming images of the corresponding colors.

[0023] A toner level detection unit 6 (6Y~6K), which has a toner level detection board 6a, is located near the developing container 44. The toner level detection unit 6 reads the remaining toner in the developing container 44 by estimating the height of the toner surface. The detailed operation will be described later.

[0024] Above the first to fourth process cartridges 3 (3Y, 3M, 3C, 3K), a laser scanner unit 11 is provided as an exposure means. The laser scanner unit 11 outputs laser light U corresponding to image information. The laser light U scans and exposes the surface of the photosensitive drum 63. The image information may be received from an external host device, or if the image forming apparatus 1 has an image reading unit, it may use image information read by the device.

[0025] Below the first to fourth process cartridges 3 (3Y, 3M, 3C, 3K), an intermediate transfer unit 5 is provided as a transfer member. The intermediate transfer unit 5 has a drive roller 5d and a tension roller 5b, and a flexible intermediate transfer belt 5a is stretched across it.

[0026] The photosensitive drum 63 of each of the first to fourth process cartridges 3 (3Y, 3M, 3C, 3K) has its lower surface in contact with the upper surface of the intermediate transfer belt 5a. This contact area is the primary transfer area. Inside the intermediate transfer belt 5a, primary transfer rollers 5c (5cY, 5cM, 5cC, 5cK) are provided, facing the photosensitive drum 63.

[0027] The secondary transfer roller 10 is in contact with the drive roller 5d via the intermediate transfer belt 5a. The contact area between the intermediate transfer belt 5a and the secondary transfer roller 10 is the secondary transfer area. After secondary transfer, any remaining transfer material is cleaned from the belt surface by the belt cleaning member 5e, and the waste toner is collected.

[0028] Below the intermediate transfer unit 5, a feeding unit 4 is provided. The feeding unit 4 has a paper feed tray 4a that holds and stores the recording medium S (recording material), and a paper feed roller 4b.

[0029] In Figure 1, the image forming apparatus 1 has a fuser 7 and a paper output device 8 located in the upper left of the main body. The top surface of the image forming apparatus 1 is the paper output tray 9. The recording medium S onto which the toner images of each color have been transferred is fixed with toner by the fixing means provided in the fuser 7 and then discharged into the paper output tray 9.

[0030] The control unit 100 transmits and receives information to and from each component of the image forming apparatus 1 and controls its operation. The drive motor 116 acts as a drive source, transmitting power to movable parts such as rotating elements via a drive path such as a belt or gears.

[0031] [Image Formation Process] The operation for forming a full-color image is as follows: The photosensitive drums 63 of each of the first to fourth process cartridges 3 (3Y, 3M, 3C, 3K) are rotated at a predetermined speed (in the direction of arrow A1 in Figure 2). In the image forming apparatus 1 of this embodiment, the printing speed when A4 size paper is fed continuously is 36 sheets per minute, and the circumferential surface of the photosensitive drum 63 rotates at 180 mm / second.

[0032] The intermediate transfer belt 5a is also driven to rotate in the forward direction of the rotation of the photosensitive drum 63 (in the direction of arrow B in Figures 1 and 2) at a speed corresponding to the speed of the photosensitive drum 63.

[0033] The charging roller 61 contacts the photosensitive drum 63 with a predetermined pressure, and a desired charging voltage is applied, thereby uniformly charging the surface of the photosensitive drum 63 to a predetermined potential.

[0034] The laser scanner unit 11 is also driven. Synchronized with the driving of the laser scanner unit 11, the charging roller 61 in each process cartridge 3 uniformly charges the surface of the photosensitive drum 63 to a predetermined polarity and potential. The laser scanner unit 11 scans and exposes the surface of each photosensitive drum 63 with laser light U according to the image signal of each color. As a result, an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the surface of each photosensitive drum 63. The formed electrostatic latent image is developed by the developing roller 41, which is driven to rotate at a predetermined speed.

[0035] [Detailed operation of process cartridges] Next, the process cartridge 3 will be described in detail. The process cartridge 3, shown in detail in Figure 2, has a developing unit 40. The developing unit 40 includes a developing roller 41 which is a developing roller that holds the developing agent, a developing container 44 which is the container for the developing unit 40, and a supply roller 43 which is a supply member that can supply the developing roller 41 with the developing agent. The developing roller 41 and the supply roller 43 are rotatably supported by the developing container 44.

[0036] Furthermore, the developing roller 41 is rotatably positioned in the opening of the developing container 44 in the direction of arrow A2, facing the photosensitive drum 63. The supply roller 43 is rotatably supported in the direction of A3 so as to contact the developing roller 41. The toner T, which is the developer contained in the developing container 44, is applied to the surface of the developing roller 41 by the supply roller 43.

[0037] The toner replenishment unit 20 is attachable to the process cartridge 3 and has a toner container 21 that contains toner T. The toner replenishment unit 20 is positioned above the developing container 44 in the direction of gravity. The toner replenishment unit 20 is located at the developing opening 2 of the developing container 44. It has a replenishment opening 28 connected to 5. The replenishment opening 28 has a toner replenishment shutter 24. A supply roller 43 is located vertically below the developing opening 25. The toner replenishment unit 20 is replaceable by the user.

[0038] The toner supply shutter 24, located at the connection point between the toner supply unit 20 and the developing container 44, is opened and closed at any desired timing by drive control from the control unit 100, thereby connecting or disconnecting the toner supply unit 20 and the developing container 44.

[0039] The toner supply unit 20 contains a toner supply agitation shaft 22 and a toner supply agitation sheet 23. The toner supply agitation sheet 23 rotates counterclockwise in the diagram (arrow F). The rotation of the toner supply agitation sheet 23 circulates the toner T inside the toner supply unit 20 and also transports the toner T from the toner supply unit 20 to the developing container 44.

[0040] In this embodiment, the toner replenishment stirring shaft 22 is configured to rotate continuously when the process cartridge 3 is being driven, and the toner T replenishment operation is controlled by opening and closing the toner replenishment shutter 24. However, the rotation of the toner replenishment stirring shaft 22 can be set according to the control of the control unit 100.

[0041] As shown in Figure 4, the control unit 100 of the image forming apparatus 1 receives a signal from the toner level detection board 6a and performs toner replenishment to maintain a constant toner level in the developing container 44. Specifically, the control unit 100 performs toner replenishment by controlling the opening and closing of the toner replenishment shutter 24 and the rotation of the toner replenishment agitation sheet 23. In this configuration, the toner replenishment agitation sheet 23 is configured to adjust its rotation speed according to the control unit 100, and the replenishment speed can be changed by adjusting the rotation speed of the toner replenishment agitation sheet 23.

[0042] In this embodiment, the supply speed can be changed by the rotation speed of the toner supply agitation sheet 23. However, the method of changing the supply speed is not limited to this configuration; it may also be done by changing the opening and closing size of the toner supply shutter 24, or by changing the airflow rate in a system where toner T is supplied from the toner supply container along with air by a pump. The configuration of the supply control member that controls the supply of toner T from the toner supply unit 20 to the developing container 44 can be any configuration as long as it can control the start and stop of supply and control the supply speed. For example, the toner supply unit 20 may be considered as the supply control member, or the functions of the toner supply unit 20 and the control unit 100 that controls the start, stop and supply speed of toner supply may be considered together as the supply control member.

[0043] Figure 3A is a perspective view showing a schematic of the toner level detection unit 6. Figure 3B is a schematic diagram showing the positional relationship of the toner level detection substrate 6a, light reflective member 6d, developing container 44, and light L of the toner level detection unit 6, as viewed from above in the direction of gravity of the developing unit 40. Note that the lower part of Figure 3B is the front side of the schematic diagram of the process cartridge 3 in Figure 2.

[0044] The toner level detection board 6a is positioned near the developing container 44. The toner level detection board 6a is equipped with an LED light-emitting element 6b, whose emission is controlled at any timing by the control unit 100, and a light intensity detection sensor 6c. A light-reflecting member 6d is fixedly positioned near the toner level detection board 6a, opposite it via the developing container 44.

[0045] The LED light-emitting element 6b of the toner level detection substrate 6a emits light L that is directional towards the light-reflecting member 6d. Of the wall surface of the developing container 44, the area facing the toner level detection substrate 6a is formed by a transparent window 44a1, and the area facing the light-reflecting member 6d is formed by a transparent window 44a2. As a result, the light L emitted from the LED light-emitting element 6b is directional towards the light-reflecting member 6d. It suppresses reflection and absorption.

[0046] The emitted light L crosses the inside of the developing container 44, is reflected by the light reflecting member 6d, and enters the light intensity detection sensor 6c of the toner remaining amount detection substrate 6a. The light intensity detection sensor 6c reads the amount of light L that has been reflected. The amount of light detected at this time changes greatly depending on the height of the toner surface in the developing container 44. If the proportion of the light path that is blocked by the toner surface is high, the amount of light detected will be small, and if the proportion of the light path that is blocked by the toner surface height is small, the amount of light detected will be large. By reading the intensity of the light, the control unit 100 can estimate the toner surface height, that is, the amount of toner remaining in the developing container 44.

[0047] Figure 3C is a graph showing the relationship between the toner level (toner surface height) in the developing container 44 on the horizontal axis and the light intensity detected by the light intensity detection sensor 6c on the vertical axis. When the light intensity Lf is detected by the toner level detection substrate 6a and the light reflecting member 6d, the toner level in the developing container 44 is assumed to be the target level Tf.

[0048] In this embodiment, the control unit 100 reads the signal from the toner level detection board 6a and drives the toner replenishment shutter 24 to control the amount of toner T remaining in the developing container 44 to an average of approximately 40g. To this end, the control unit 100 starts the replenishment operation when the amount of toner in the developing container 44 reaches 37g (D-LOW) based on the signal from the toner level detection board 6a, and continues the replenishment operation until the amount of toner in the developing container 44 is detected to be 43g (D-FULL). As a result, the amount of toner in the developing container 44 is maintained at an average of 40g.

[0049] In this embodiment, a light-based toner level detection method was used as an example for estimating the remaining toner level in the developing container 44. However, the means for estimating the remaining toner level are not limited to this. For example, the amount of toner used could be estimated from the printed image information, and the current remaining toner level could be calculated by subtracting the estimated amount of toner used from the amount of toner initially contained.

[0050] When the amount of toner in the toner supply unit 20 becomes low and it is time to replace the toner supply unit 20, the image forming apparatus 1 notifies the user of Toner LOW (T-LOW). User notification is performed, for example, by a notification unit 121 equipped with a display device and an audio output device. Furthermore, when the amount of toner in the toner supply unit 20 becomes so low that toner replenishment is no longer possible, the image forming apparatus 1 notifies the user of Toner OUT (T-OUT) and requests that the toner supply unit 20 be replaced.

[0051] In this embodiment, the control unit 100 estimates the remaining toner amount in the toner supply unit 20 based on the relationship between toner supply by opening and closing the toner supply shutter 24 and rotating the toner supply stirring shaft 22, and the increase in the amount of toner in the developing container 44, and notifies the user of toner LOW or toner OUT. Specifically, the control unit 100 determines toner LOW (T-LOW) when the increase in the amount of toner in the developing container 44 relative to the number of rotations of the toner supply stirring shaft 22 falls below a predetermined threshold. Furthermore, the control unit 100 determines toner OUT when the amount of toner in the developing container 44 no longer increases even after toner supply operations are performed.

[0052] Furthermore, if it is desired to detect a wide range of toner levels in the developing container 44, the above configuration may be arranged in a vertical direction in the direction of gravity, such as by placing two of them together, so that the amount of light L changes in response to a wider range of toner surface changes.

[0053] The method for detecting the remaining toner level in the toner supply unit 20 is not limited to this; the remaining toner level may also be estimated from image information printed by the user. Furthermore, a toner level detection means may be installed in the toner supply unit 20.

[0054] The developing unit 40 in this embodiment uses a contact developing method. That is, the toner layer supported on the developing roller 41 comes into contact with the photosensitive drum 63 in the developing section (developing area) where the photosensitive drum 63 and the developing roller 41 face each other. A developing voltage is also applied to the developing roller 41 from the developing power supply 112. Under the condition that the developing voltage is applied, the toner T supported on the developing roller 41 is transferred to the surface of the photosensitive drum 63 according to the electrostatic latent image on the surface of the photosensitive drum 63, thereby developing the toner image.

[0055] In this embodiment, the development voltage was set to -300V. This embodiment employs a reverse development method. Specifically, the surface of the photosensitive drum 63 is charged during the charging process, and then the surface of the photosensitive drum 63 is exposed during the exposure process. This creates an exposed region on the surface of the photosensitive drum where the charge is attenuated. Toner T from the developing roller 41 adheres to this exposed region, forming a toner image.

[0056] Toner images are transferred from each color's photosensitive drum 63 to the intermediate transfer belt 5a. After the toner images are transferred from the photosensitive drum 63 to the intermediate transfer belt 5a, the potential of the surface of the photosensitive drum 63 is neutralized and made uniform by the pre-exposure unit 62 (see Figure 2). Then, the surface of the photosensitive drum is recharged by the charging roller 61.

[0057] In this example, toner T with a particle size of 7.0 μm and a normal charge polarity of negative polarity is used. As an example, polymerized toner produced by polymerization is used as the toner T. Toner T does not contain any magnetic components and is supported on the developing roller 41 mainly by intermolecular forces and electrostatic forces (mirror image forces), making it a so-called non-magnetic, one-component developer.

[0058] The toner particles contain multiple waxes to adjust the melting properties of the toner T during the fixing process and its adhesion to the printing medium and fixing roller. The surface of the toner particles is coated with fine silica particles of submicron size to adjust the fluidity and electrostatic properties of the toner T. In this embodiment, the toner T with the added fine particles is defined as the developer.

[0059] In this embodiment, a non-magnetic one-component developer is given as an example, but a one-component developer containing a magnetic component may also be used. Alternatively, a two-component developer consisting of a non-magnetic toner T and a magnetic carrier may be used as the developer. When a magnetic developer is used, for example, a cylindrical developer sleeve with a magnet placed inside may be used as the developer carrier.

[0060] The developing container 44 is equipped with a stirring member 45 as a means of agitation. The stirring member 45 is driven and rotates (arrow G) to agitate the toner T inside the developing container 44 and to feed the toner T towards the developing roller 41 and the supply roller 43. The stirring member 45 also plays a role in circulating the toner T that is not used for developing and is stripped from the developing roller 41 within the developing container, thereby homogenizing the toner T inside the developing container. In this embodiment, the stirring member 45 is configured to operate independently of the developing roller 41.

[0061] Furthermore, a developing blade 42 made of stainless steel is positioned at the opening of the developing container 44 where the developing roller 41 is located, to regulate the amount of toner T carried on the developing roller 41. A voltage 200V greater in absolute value than that on the negative polarity side of the developing roller 41 is applied to the developing blade 42 from the regulating power supply 113. In other words, a voltage 200V greater than that on the normal polarity side of the toner T is applied to the developing blade 42.

[0062] The developer supplied to the surface of the developing roller 41 is uniformly thinned as it passes through the area opposite the developing blade 42 as the developing roller 41 rotates. At the same time, the developer is also processed by the developing blade The toner T is charged to its normal polarity, negative polarity, by frictional charging with the blade 42 and direct injection charging based on the potential difference between the developing blade 42 and the developing roller 41.

[0063] This embodiment employs a so-called cleanerless configuration in which the transfer residue toner that remains on the photosensitive drum 63 without being transferred to the recording medium S is collected in the developing unit 40 and reused. The transfer residue toner is reused in the following steps.

[0064] The remaining toner after transfer contains a mixture of toner T that is positively charged, which is the opposite polarity to the normal polarity in this embodiment, and toner T that is negatively charged but does not have sufficient charge. During the charging process of the photosensitive drum 63 by the charging roller 61, these toners T are uniformly charged to the negative polarity by the discharge of the negative polarity bias of the charging roller 61.

[0065] The negatively charged transfer residue toner reaches the developing section as the photosensitive drum 63 rotates. Here, the behavior of the transfer residue toner that reaches the developing section will be explained separately for the exposed and unexposed parts of the photosensitive drum 63. In the unexposed part of the photosensitive drum 63, i.e., the dark potential part, the surface potential of the photosensitive drum 63 is greater on the negative side than the developing voltage applied to the developing roller 41. Therefore, the transfer residue toner, which has a sufficient negative charge, moves to the developing roller 41 by the Coulomb force due to the electric field and is collected in the developing container 44. Here, the dark potential part of the photosensitive drum 63 is not limited to the unexposed part; weak exposure is also possible as long as the surface potential of the photosensitive drum 63 is greater on the negative side than the developing voltage applied to the developing roller 41.

[0066] The toner T collected in the developing container 44 is mixed and dispersed with the toner T inside the developing container 44 by the agitator 45, and is then carried on the developing roller 41 for use in the developing process again.

[0067] On the other hand, in the exposure area of ​​the photosensitive drum 63, the surface potential of the photosensitive drum 63 is less negative than the development voltage applied to the development roller 41. Therefore, the residual toner remains on the surface of the photosensitive drum 63 without transferring from the photosensitive drum 63 to the development roller 41 in the development area. The residual toner remaining on the surface of the photosensitive drum 63, along with other toner T transferred from the development roller 41 to the exposure area, is carried on the photosensitive drum 63 and moves to the transfer area, where it is transferred to the recording medium S.

[0068] In this embodiment, the dark area potential was set to -500V and the exposure potential was set to -50V. As described above, since the development voltage is -300V, the back contrast, which is the potential difference between the dark area potential of the photosensitive drum 63 after it has passed the contact area with the charging roller 61 and the development voltage (surface potential of the development roller 41), is Δ200V. Also, the development contrast, which is the potential difference between the exposure area of ​​the photosensitive drum 63 and the development voltage (surface potential of the development roller 41), is Δ250V.

[0069] Through the electrophotographic image formation process described above, a yellow toner image corresponding to the yellow component of the full-color image is formed on the photosensitive drum 63 of the first process cartridge 3Y. This toner image is then primary transferred onto the intermediate transfer belt 5a.

[0070] Similarly, a magenta toner image corresponding to the magenta component of the full-color image is formed on the photosensitive drum 63 of the second process cartridge 3M. This toner image is then superimposed on the yellow toner image already transferred onto the intermediate transfer belt 5a for primary transfer.

[0071] Similarly, a cyan toner image corresponding to the cyan component of the full-color image is formed on the photosensitive drum 63 of the third process cartridge 3C. Then, this toner image is superimposed on the yellow and magenta toner images already transferred on the intermediate transfer belt 5a to form a primary It will be transcribed.

[0072] Similarly, a black toner image corresponding to the black component of the full-color image is formed on the photosensitive drum 63 of the fourth process cartridge 3K. This toner image is then superimposed on the yellow, magenta, and cyan toner images already transferred onto the intermediate transfer belt 5a for primary transfer. In this way, unfixed toner images of the four full-color colors—yellow, magenta, cyan, and black—are formed on the intermediate transfer belt 5a.

[0073] Meanwhile, the recording media S are separated and fed one by one at predetermined control timings. The recording media S are then introduced to the secondary transfer section, which is the contact point between the secondary transfer roller 10 and the intermediate transfer belt 5a, at predetermined control timings. As a result, during the process of transporting the recording media S to the secondary transfer section, the four-color superimposed toner image on the intermediate transfer belt 5a is sequentially and simultaneously transferred to the surface of the recording media S.

[0074] [Control Mode] Figure 4 is a schematic block diagram showing the control configuration of the main parts of the image forming apparatus 1. The control unit 100 includes a CPU 101 as a calculation control means, which is the central element for performing calculation processing; memory elements such as ROM 102, RAM 103, and non-volatile memory 104 as storage means; and an input / output unit (not shown) that controls the exchange of signals between the control unit 100 and various elements connected to it. The RAM 103 stores sensor detection results, calculation results, etc., and the ROM 102 stores control programs, pre-determined data tables, etc.

[0075] The control unit 100 is a control means that comprehensively controls the operation of the image forming apparatus 1. The control unit 100 controls the exchange of various electrical information signals and the timing of drives to execute a predetermined image forming sequence. Various parts of the image forming apparatus 1 are connected to the control unit 100. For example, in this embodiment, the control unit 100 is connected to a charging power supply 111, a developing power supply 112, a regulating power supply 113, a transfer power supply 114, a laser scanner unit 11, a toner supply shutter 24, a toner stirring control 26, a drive motor 116, an LED light-emitting element 6b, a toner remaining amount detection board 6a, a toner cartridge switch 118, a notification unit 121, and the like.

[0076] [Unit and cartridge replacement] In this embodiment, the toner replenishment unit 20 notifies the user to replace the toner when the amount of toner remaining inside is low. Furthermore, the developing unit 40 and the drum unit 60 are integrated as a process cartridge 3, which is detachable from the image forming apparatus 1.

[0077] The developing roller 41, developing blade 42, supply roller 43, photosensitive drum 63, charging roller 61, toner T, etc. deteriorate with use by the user, and it becomes difficult to provide sufficient image quality beyond a certain amount of use. In the image forming apparatus 1 of this embodiment, the deterioration of each component and toner T is predicted based on the rotation speed of the developing roller 41 and photosensitive drum 63, and when it exceeds a certain threshold, the process cartridge 3 has reached the end of its lifespan and the user is notified to replace it with a new one.

[0078] In this embodiment, for example, if the user performs continuous printing at an average rate of two pages per day, the system will notify the user that the process cartridge 3 has reached the end of its lifespan when it has printed a total of 50,000 pages, and will also provide information regarding replacement with a new cartridge.

[0079] [Toner Refresh Mode] Toner refresh mode is a process that, after replacing the toner supply unit 20 (toner cartridge) with a new one, ejects any deteriorated toner T remaining in the process cartridge 3. This mode performs a series of operations to replenish with new toner T. The ejected toner T is transferred from the photosensitive drum 63 to the intermediate transfer belt 5a, cleaned by the belt cleaning member 5e, and stored in a waste toner container (not shown). Detailed control is described in the toner refresh operation below.

[0080] [Confirmation of the effects of the examples] In this example, the evaluation was performed using the image forming apparatus 1 described above. Table 1 shows the toner refresh mode configurations for Examples 1-3 and Comparative Examples 1-3.

[0081] (Durability evaluation method) • Test environment: Temperature 23.5℃, humidity 50% The toner level in the developing container 44 of process cartridge 3 was controlled to range from 43g (D-FULL) to 37g (D-LOW), and durability was evaluated using vitality paper with 2% print coverage in a 2-second intermittent operation.

[0082] An unused toner supply unit 20 contains 60g of toner T. When the toner supply unit 20 runs out of toner, the user who receives the notification replaces it. After that, the control unit 100 performs a toner refresh mode and then continues the durability test.

[0083] In the case of Comparative Example 3, the toner refresh mode was not performed. After the toner cartridge ran out, the toner cartridge was replaced with a new one, and the durability was continued until the number of pages printed reached 18,000. [Table 1]

[0084] Table 2 shows the results and effects of durability evaluations for each configuration in Table 1. For performance comparison, it shows downtime, failure risk, and image quality at 18,000 pages. It also shows the time taken for toner refresh mode. Furthermore, at the end of durability testing, density, toner fogging, halftone image quality, and average toner particle size within the developing container were checked. [Table 2]

[0085] The effectiveness was verified as follows: • Cover measurement: Using a REFLECTMETER MODEL TC-6DS (manufactured by Tokyo Denshoku Co., Ltd.), the whiteness T1 of the area of ​​the printed recording medium S where no Post-it note is attached and the whiteness T2 of the area of ​​the recording medium S where a Post-it note is attached are measured. From these results, (T2-T1) is calculated as the toner cover density (%). • Concentration measurement: Measurement is performed using an X-rite exact advance (manufactured by X-rite). • Measurement of average toner particle size: The average particle size of toner T was measured using the Coulter Counter Multisizer 3 (registered trademark, manufactured by Beckman Coulter), a precision particle size distribution analyzer using the pore electrical resistance method with a 100 μm aperture tube.

[0086] [Toner refresh mode operation] Using Example 1, we will explain the toner refresh mode, which is a feature of this embodiment.

[0087] Figure 5 is a flowchart showing the procedure for the toner refresh mode executed by the control unit 100. The procedure for Example 1 will be described below.

[0088] Figure 6 also shows timing charts related to the flow. Specifically, Figure 6(a) shows the change in the remaining amount of toner in the toner supply unit during execution. Figure 6(b) shows the change in the remaining amount of toner in the developing container. For example, between timings T1 and T2, toner supply is performed, and the toner T in the toner supply unit moves into the developing device. As a result, at T2, the toner supply unit 20 shows toner OUT, and the developing container 44 shows D-FULL. Figure 6(c) also shows timing charts for various operations. In each chart, the horizontal axis T represents an arbitrary time.

[0089] In Figures 6(a) to 6(c), the solid lines show the toner level change and control timing for Example 1. The dashed lines show the case for Comparative Example 1.

[0090] Step S1: The control unit 100 performs toner LOW / OUT processing. Thereafter, the control unit 100 detects the detection signal in the developing container 44 sent from the toner level detection board 6a. The timing of this process is arbitrary and can be performed periodically, at the user's instruction, or when replacing various cartridges.

[0091] Step S2: Based on the toner level detection signal in the developing container sent from the toner level detection board 6a, the control unit 100 determines whether the toner cartridge level is low (T-LOW) or the toner level is low. The system detects whether or not there is no toner remaining (T-OUT). If the toner level is not low or empty, the control unit 100 controls the system to terminate the toner refresh mode (S2:N).

[0092] Step S3: If low toner level or no toner level is detected (S2:Y), the control unit 100 detects whether the toner supply unit 20 has been replaced based on the detection signal from the toner cartridge switch 118. If the toner supply unit 20 has not been replaced (S3:N), the control unit 100 controls the system to terminate the toner refresh mode.

[0093] Step S4: Upon confirming that the toner supply unit 20 has been replaced (S3:Y), the control unit 100 clears the detection result for the replaced toner supply unit 20, indicating either low toner level (T-LOW) or no toner level (T-OUT). In Figure 6(a), as a result of the cartridge replacement, the timing T2 shows T-FULL.

[0094] Step S5: The control unit 100 sets the developing unit 40 to "no replenishment mode". When this "no replenishment mode" is set, the control unit 100 stops the replenishment operation using the full-container detection method with the toner remaining amount detection board 6a, and does not replenish toner from the toner replenishment unit 20. As a result, subsequent image forming operations (printing operations) are performed using only the toner T remaining in the developing container of the developing unit 40. In Figure 6(b), during the R0 section (timing T2~T3), from D-FULL to D-LOW, the toner T in the developing container is consumed and decreases.

[0095] Step S6: The control unit 100 sets a predetermined threshold value, the "no-replenishment dot count". The threshold value here is the first threshold value. The "no-replenishment dot count" is the dot count (number of print data outputs in the image) that can be output during image formation after the control unit 100 has set the "no-replenishment mode". Since the dot count is approximately proportional to the size of the print area (the area to which toner T is transferred) on the paper during image formation, the development density (development bias), etc., it is easy for the control unit 100 to calculate the dot count.

[0096] Step S7: The control unit 100 checks whether the dot count output in "no-replenishment mode" exceeds the "no-replenishment dot count". In this embodiment, the dot count was set so that the threshold is 37g when the toner T in the developing container becomes D-LOW.

[0097] Step S8: When the control unit 100 confirms that the output dot count exceeds the "dot count without replenishment" (Step S7:Y), it stops the agitator 45 of the developing unit 40.

[0098] Step S9: Next, the control unit 100 sets the "ejection mode" and the "refill mode". In this embodiment, the toner refresh mode is a simultaneous operation of the ejection mode and the refill mode. In the "ejection mode", the unit instructs the formation of a solid image, and in the "refill mode", it instructs the opening and closing of the toner supply shutter 24 and determines the rotation speed of the toner supply stirring sheet 23. In this embodiment, the relationship between the toner ejection speed and the development setting has been confirmed in advance through experiments, and the control unit 100 appropriately adjusts the development contrast to eject ink for a solid image so that the toner ejection speed is 0.16 g / s. The control unit 100 also sets the refill speed to 0. The rotation speed of the toner replenishment stirring sheet 23 is set to 216 g / s. The system is also set to continue dispensing toner T until the amount dispensed reaches 20 g.

[0099] Step S10: The control unit 100 simultaneously executes the ejection mode (toner ejection operation) and the refilling mode (toner T refilling). Specifically, the control unit 100 instructs the formation of a solid image and concentrates on consuming (ejecting) the deteriorated toner Td and toner T with large particle size remaining in the developing unit 40. The ejected toner T is transferred from the photosensitive drum 63 to the intermediate transfer belt 5a and collected in the waste toner container by the belt cleaning member 5e.

[0100] Here, we will explain the reason for consuming the toner with larger particle size T. For example, in a single-component contact developing system, small particle size T is generally easier to develop, while large particle size T is more difficult to develop. As a result, large particle size toner tends to remain in the developing device. In addition, within the developing device, there is toner T whose shape and the adhesion of external additives to the toner surface have changed due to durability, and which can no longer maintain the proper charge. These toner T also tend to remain in the developing device. Therefore, in developing devices whose lifespan has been extended by repeatedly replenishing toner, the proportion of large particle size T and toner T that cannot maintain the proper charge increases. As a result, this can cause various image defects such as reduced density and fogging.

[0101] Figures 7(a) to 7(c) schematically show the circulation within the developing container. At the start of S10, the remaining toner amount is LOW 37g, which corresponds to state D11 in Figure 7(a). In each figure, black circles represent degraded toner Td, and white circles represent newly supplied toner Tn. At this time, the agitator 45 in the developing unit 40 is stopped, so even if toner Tn is supplied as shown in D12 in Figure 7(b), the newly supplied toner Tn and the originally remaining toner Td do not mix easily, and there is almost no vertical circulation. Therefore, when ejecting, mainly the originally remaining toner Td is ejected. Also, from above in the direction of gravity, more new toner Tn is filled than toner T that has been ejected, so the overall surface height of toner T does not decrease. Therefore, in this embodiment, refilling is possible while the ejection mode is being performed (D13 in Figure 6(b) and D13 in Figure 7(c)).

[0102] Therefore, in Example 1, the toner refresh mode time can be shortened compared to when ejection and replenishment are performed separately. Specifically, as shown in Table 2, it becomes 120 seconds. This corresponds to section R1 (timing T3~T4) in Figure 6(a). In addition, the risk of failure of the developing blade 42 and other components, which can occur when the toner level is low, can be reduced. Specifically, while the toner T in the developing unit is ejected by the solid image, the toner T may not be properly loaded onto the developing roller 41, and the developing blade 42 and the developing roller 41 in the developing unit may come into direct contact, potentially causing a failure. Furthermore, since it is possible to eject deteriorated toner T without reducing the toner level in the developing unit 40, the ejection mode can be executed efficiently without reducing the ejection volume.

[0103] Step S11: The control unit 100 determines whether the amount of toner T ejected has exceeded a threshold. If it has not exceeded the threshold, it determines that ejection is not complete (S11:N) and continues the toner ejection operation from step S10. The threshold dot count used as the criterion for determining whether toner T ejection is complete should be set in advance based on the amount of toner ejected predicted from the relationship between the number of dots and the amount consumed.

[0104] Step S12: On the other hand, if the discharge volume exceeds the threshold (S11:Y), the discharge mode is stopped and the process moves to the next step.

[0105] Step S13: Next, the control unit 100 drives the stirring member 45 inside the developing container.

[0106] Step S14: The control unit 100 determines whether the toner T in the developing container is full based on the detection signal from the toner level detection board 6a. When the amount of toner in the developing device reaches 43g, it is detected as full and refilling is completed (Step S15). The control unit 100 clears all mode settings (Step S16) and exits the toner refresh mode.

[0107] In the refresh mode of this embodiment, the dispensing and replenishment operations are set to start and end simultaneously. In this case, "simultaneous" means that the control by the control unit 100 is substantially simultaneous. However, the present invention is not limited to this configuration. For example, although the effect of suppressing downtime is reduced, if the stirring member 45 is stopped when the refilling mode is started, the dispensing mode may be started first.

[0108] Furthermore, in this embodiment, the stirring member 45 is set to stop for the entire duration of the refresh mode (in this flow, the duration from the start of refilling to the end of the discharge mode), but this is not limited to this. For example, the stirring member 45 may be stopped only for a portion of the period from the start of refilling to the end of the discharge mode. Also, for example, the stirring speed by the stirring member 45 may be slower than normal only for a portion of the period from the start of refilling to the end of the discharge mode.

[0109] When stirring is stopped or slowed down in certain sections, it is preferable to stop or slow down the stirring member 45 from the start to the end of refilling. That is, by stopping the stirring member 45 while the replenishment operation is being performed, the active mixing of new toner Tn and degraded toner Td is suppressed, and the degraded toner Td can be preferentially ejected. These configurations also provide the effect of reducing downtime compared to conventional methods. However, as in Example 1, if the stirring member 45 is stopped for the entire period from the start of refilling to the end of the ejection mode, the effect of the refresh mode is greater because new refilled toner is almost never ejected during ejection.

[0110] The evaluation results after 18,000 prints in Example 1 are shown in Table 1, demonstrating that it is possible to maintain images with good density and reduced fogging, and to shorten the toner refresh mode time.

[0111] [Comparative Example 1] Next, Comparative Example 1 will be described. Unless otherwise specified, the configuration is the same as in Example 1. In Comparative Example 1, the toner refresh mode ejection mode and the refill mode are performed independently. As shown in Table 1, in Comparative Example 1, the stirring member 45 remains rotating during the toner refresh mode. Therefore, in order to prevent the new toner Tn and deteriorated toner Td from mixing and the new toner Tn from being ejected, it is necessary to perform the ejection mode first to eject the deteriorated toner Td completely before performing refilling.

[0112] In Comparative Example 1, the change in the remaining toner amount in the developing container 44 during the toner refresh mode follows the change shown by the dashed line in Figure 6(b). Schematically, this is shown as D21 in Figure 8(a) → D22 in Figure 8(b) → D23 in Figure 8(c), and the remaining toner amount decreases from 37g to 17g. As the amount of toner decreases, the ejection rate decreases. There is also a risk of failure of the developing blade 42 due to toner depletion on the developing roller 41. This is because the surface of the developing roller 41 and the developing blade 42 come into direct contact, causing scratches and other damage to the developing blade 42. Subsequently, the refilling mode is executed and the toner is refilled to 43g (D24 in Figure 8(d)).

[0113] The durability test results, as shown in Table 2, show that the time in toner refresh mode was R4 = 205 seconds in Figure 6(a), which is significantly longer than in Example 1. Furthermore, the image evaluation results showed that... Streaks appeared in the halftone image. Furthermore, because the toner level decreases as in D23, there is a risk of malfunction of components such as the developing blade 42.

[0114] [Example 2] In Example 1, the rotation of the agitator 45 in the developing unit 40 was stopped before executing the toner refresh mode. In Example 2, the toner refresh mode in the developing container is executed in a simpler way without controlling the agitator 45 in the developing container. The configuration and control common to Example 1 will not be explained.

[0115] Figure 11 is a flowchart showing the procedure for the toner refresh mode processing performed by the control unit 100 in Example 2. The procedure for Example 2 will be described below. Since steps S1 to S6 are the same as in Example 1, only steps 17 onwards will be explained. Figure 12 is a timing chart for Example 2.

[0116] Step S17: The control unit 100 checks whether the dot count output in "no-replenishment mode" exceeds the "no-replenishment dot count". The no-replenishment dot count here is set as the second threshold. The second threshold is set to a value such that the surface of the degraded toner Td remaining in the developing unit 40 is below the rotating agitator 45 and does not come into contact with the agitator 45. In Example 2, the dot count was set so that the threshold was reached when the toner remaining amount was 33g.

[0117] Step S18: When it is confirmed that the output dot count exceeds the no-replenishment dot count threshold, which is a second threshold (Step S17:Y), the control unit 100 sets the "discharge mode" and the "refill mode".

[0118] In this embodiment, the control unit 100 sets the rotation speed of the toner replenishment stirring sheet 23 so that the toner ejection speed (0.16 g / s) and the refilling speed are the same. In Embodiment 2, the toner ejection speed and the refilling speed (replenishment speed) were set to be the same, but this is not limited to this, and either speed may be faster as long as the stirring member 45 and the toner surface do not come into contact.

[0119] Step S19: The control unit 100 simultaneously starts the ejection mode and the refilling mode. Figure 12(b) shows the change in the amount of toner remaining in the developing container, and Figures 10(a) to 10(c) show schematic diagrams of the circulation in the developing container. This is the state of D41 in Figure 10(a) at the start of S19. At this time, the stirring member 45 in the developing container is not in contact with the surface of the deteriorated toner Td.

[0120] Even if a replenishment operation is performed in this state, there is almost no vertical circulation between the newly replenished toner Tn and the degraded toner Td (D42 in Figure 10(b)). Therefore, the toner T used during ejection is mainly the degraded toner Td that was originally remaining in the developing unit. Also, similar to Example 1, the overall surface height of the toner T does not decrease. As a result, as shown in Figure 12(b), the surface height does not drop to a level where a failure risk occurs (timing T8-T9, section R21). Therefore, in this embodiment, refilling is possible while the ejection mode is being performed.

[0121] Step S20: The control unit 100 determines whether the amount of toner T ejected exceeds a threshold. If it does not exceed the threshold, it determines that ejection is not complete (S20:N) and continues the toner ejection operation. Similar to Example 1, the threshold dot count, which is the criterion for determining whether or not toner T ejection is complete, should be set in advance based on the ejection amount predicted from the relationship between the number of dots and the amount consumed. Here, an ejection amount of 15g is set as the threshold dot count.

[0122] Steps S21-S22: When the discharge amount exceeds the threshold, the discharge mode is stopped and the refill mode is reset. At this point, since discharge is complete, there is no longer a need to control the mixture so that the stirring member 45 and the surface of the toner T do not come into contact. Therefore, the control unit 100 can be set to increase the replenishment speed (0.5 g / s in this embodiment). Refilling is performed over 20 seconds, at timings T9-T10 (section R22) in Figure 12.

[0123] Step S14: From this point onward, the process is carried out in the same manner as in Example 1. The control unit 100 determines whether the toner T in the developing container is full based on the detection signal from the toner remaining amount detection board 6a. If it is full, the process proceeds to step S15, and when the amount of toner in the developing device reaches 43g, refilling is completed (D43 in Figure 10(c)). The control unit 100 clears all mode settings (step S16) and exits the toner refresh mode.

[0124] In this embodiment, the settings are configured to start the ejection and refilling of toner T simultaneously. However, the configuration is not limited to this. For example, although the effect of suppressing downtime will be reduced, the ejection mode may be started first, as long as the stirring member 45 and the toner surface do not come into contact when the refilling mode is started.

[0125] Furthermore, in this embodiment, the stirring member 45 is set not to contact the surface of the toner T over the entire period from the start of refilling to the end of the ejection mode, but this is not limited to this. For example, the stirring member 45 may come into contact with the toner surface only in a portion of the period from the start of refilling to the end of the ejection mode. However, as in Embodiment 2, if the stirring member 45 does not come into contact with the toner surface over the entire period from the start of refilling to the end of the ejection mode, the effect of the refresh mode is enhanced because it becomes more difficult for new refilled toner to be ejected during ejection.

[0126] As shown in Table 1, the durability results in Example 2 demonstrate that it is possible to maintain images with good density and minimal fogging, and to shorten the toner refresh mode time. Furthermore, since it can be implemented regardless of the control of the stirring member 45, it has a simpler configuration than Example 1. In addition, when the toner particle size in the developing container after durability was measured, it was found to be 8.0 μm, confirming that the change in durability was small.

[0127] As shown in Table 2, the toner refresh mode time (Figure 12(a) R2 = 110 seconds) in Example 2 is shorter than in Example 1. Furthermore, it is possible to eject deteriorated toner T without reducing the remaining toner amount. Therefore, the ejection mode can be executed efficiently without reducing the ejection volume.

[0128] [Comparative Example 2] In Comparative Example 2, the ejection mode and the refilling mode are executed simultaneously, similar to Example 1, resulting in a configuration that shortens the toner refresh mode. However, unlike Examples 1 and 2, the agitator 45 rotates as it penetrates the toner surface in the developing container. As a result, the deteriorated toner T and new toner T in the developing device are mixed and circulated.

[0129] As shown in Table 1, in Comparative Example 2, the stirring member 45 continues to rotate even in refresh mode (D31 in Figure 9(a)). Therefore, new toner Tn and degraded toner Td are mixed together during ejection. As a result, not only degraded toner Td but also new toner Tn is ejected (D32 in Figure 9(b)).

[0130] In Comparative Example 2, the change in the remaining toner amount in the developing container 44 during refresh mode was the same as in Example 1. The transition follows a similar pattern as the solid lines in Figure 6(b) D11→D12→D13. Schematically, this is represented as D31 in Figure 9(a)→D32 in Figure 9(b)→D33 in Figure 9(c). In Comparative Example 2, since ejection and refilling are performed simultaneously, the toner refresh mode time can be shortened to R11=120 seconds, the same as in Example 1, but new toner Tn is included in the ejected toner T. Furthermore, new toner Tn tends to have a larger charge than deteriorated toner Td, and is preferentially supplied to the developing roller 41 and ejected due to mirroring force, etc. Therefore, in Comparative Example 2, a large amount of new toner Tn is ejected, resulting in insufficient toner refreshment in the developing container.

[0131] Therefore, as shown in Table 2, the durability evaluation revealed deterioration in fogging and a decrease in density. In addition, the average toner particle size in the developing container also changed significantly to 9.0 μm.

[0132] [Example 3] In Example 3, the configuration is the same as in Example 2, but the configuration is characterized by the way toner T is ejected in ejection mode. As a result, even with the same configuration as in Example 2, it is possible to efficiently eject a large amount of degraded toner Td.

[0133] Figure 13(a) is a view of the developing container 44 from the direction of arrow 70 in Figure 2, looking downward in the direction of gravity. The figure shows the developing roller 41 and supply roller 43 as seen through other components, and also shows the position of the toner supply shutter 24 projected downward in the direction of gravity.

[0134] In Example 3, the ejection mode is characterized by increasing the amount of toner T ejected at a position far from the position of the replenishment opening (position of the toner replenishment shutter 24) in the longitudinal direction of the supply roller 43. In this example, since the replenishment opening is located in the center of the developing unit 40, the ejection amount is increased at both ends in the longitudinal direction of the supply roller 43.

[0135] Figures 13(b) and 13(c) illustrate the toner ejection process in this embodiment. When the control unit 100 starts toner ejection in step S19 of the flow in Figure 11, it prints solid black on the front surface of the intermediate transfer belt 5a as shown in Figure 13(b) to eject the toner T.

[0136] When the control unit 100 determines, based on dot count measurement, that the toner discharge amount exceeds 15g, it prints a solid black image only on both ends of the supply roller 43, which are farther from the toner supply shutter 24, as shown in Figure 13(c), thereby increasing the toner discharge amount at both ends. This is because new toner Tn is supplied to the toner surface from the center of the top of the supply port, and the new toner Tn reaches the supply roller 43 more quickly in the center. When 15g of toner T has been consumed, the new toner Tn reaches the center of the supply roller, but degraded toner Td still remains around the supply roller at both ends. Therefore, by discharging only at both ends, it becomes possible to discharge more degraded toner Td while minimizing the consumption of new toner T when discharging and supplying toner T simultaneously. The toner remaining amount changes as in Example 2 until the end of section R2 in Figure 12(a), after which the 20-second end-discharging operation is performed.

[0137] As shown in Table 2, in Example 3, the toner refresh mode time was shortened while maintaining good image quality, including density and fogging. The toner particle size in the developing container was 7.7 μm, which was smaller than the change in particle size in Examples 1 and 2.

[0138] [Comparative Example 3] Comparative Example 3 involved endurance testing without performing any toner refresh mode. As shown in Table 2, significant image quality deterioration, including density reduction and fogging, was observed. Furthermore, the average particle size of toner T became significantly larger compared to the initial toner state. This result indicates that toner refresh mode significantly contributes to image quality stabilization.

[0139] As described above, according to each embodiment of the present invention, the toner T in the developing container can be efficiently refreshed, and good image quality can be provided throughout durability while reducing the risk of malfunctions that occur when toner is ejected.

[0140] [Configuration 1] In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit that controls the rotation of the stirring member, Equipped with, The control unit, (i) Control to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) In at least a portion of the interval from when the refresh mode is started until the refresh mode is terminated, the rotation speed of the stirring member is slowed down compared to the time of the image forming operation, or the stirring member is stopped. An image forming apparatus characterized by the following features. [Configuration 2] The control unit controls the rotation speed of the stirring member to be slower than during image formation, or to stop the stirring member, at least during the period after the replenishment operation has started. The image forming apparatus according to configuration 1, characterized in that it is a picture forming apparatus. [Configuration 3] The control unit controls the rotation speed of the stirring member to be slower than during image formation, or to stop the stirring member, at least during the period until the discharge operation is completed. The image forming apparatus according to configuration 1, characterized in that it is a picture forming apparatus. [Structure 4] In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit for controlling the stirring member, Equipped with, The control unit, (i) Control to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) Control the dispensing of the developer so that the stirring member in the developing container does not come into contact with the developer during at least a portion of the interval from when the refresh mode is started until the refresh mode is terminated. An image forming apparatus characterized by the following features. [Composition 5] The control unit controls the discharge speed during the discharge operation and the replenishment speed during the replenishment operation so that the stirring member does not come into contact with the surface of the developer during the refresh mode. The image forming apparatus according to configuration 4, characterized in that... [Composition 6] The control unit controls the replenishment speed in the replenishment operation to be faster after the discharge operation is completed. The image forming apparatus according to configuration 5, characterized by the features described herein. [Composition 7] The system further comprises a supply control member that controls the supply of the developer from the supply container to the developing container, The control unit controls the replenishment control member so that the discharge operation and the replenishment operation start and end simultaneously. An image forming apparatus according to any one of configurations 1 to 6, characterized by the above. [Structure 8] The replenishment control member changes the developer replenishment rate by changing the rotation speed of the stirring member. The image forming apparatus according to configuration 7, characterized by the features described above. [Composition 9] The developing unit further includes a supply member that supplies the developer to the developer carrier, The supply member has a longitudinal direction, and the supply port connecting the supply container and the developing container is positioned above the supply member in the direction of gravity. The control unit controls the dispensing operation such that the amount of developer dispensed increases as the distance from the supply member to the position where the supply port is projected in the direction of gravity increases. An image forming apparatus according to any one of configurations 1 to 6, characterized by the above. [Configuration 10] The replenishment unit is a cartridge that can be attached to the developing unit. An image forming apparatus according to any one of configurations 1 to 9, characterized by the features described above. [Explanation of symbols]

[0141] 1: Image forming apparatus, 3: Process cartridge, 20: Toner supply unit, 21: Toner supply container, 24: Toner supply shutter, 25: Developing opening, 40: Developing unit, 41: Developing roller, 43: Supply roller, 44: Developing container, 45: Agitation member, 63: Photosensitive drum, 100: Control unit

Claims

1. In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit that controls the rotation of the stirring member, Equipped with, The control unit, (i) Control the system to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) In at least a portion of the interval from when the refresh mode is started until the refresh mode is terminated, the rotation speed of the stirring member is slowed down compared to the time of the image forming operation, or the stirring member is stopped. An image forming apparatus characterized by the following features.

2. The control unit controls the rotation speed of the stirring member to be slower than during image formation, or to stop the stirring member, at least during the period after the replenishment operation has started. The image forming apparatus according to feature 1.

3. The control unit controls the rotation speed of the stirring member to be slower than during image formation, or to stop the stirring member, at least during the period until the discharge operation is completed. The image forming apparatus according to feature 1.

4. In an image forming apparatus capable of performing an image forming operation to form an image on a recording material, An image carrier on which an electrostatic latent image is formed on its surface, A developing unit comprising a developing container for containing a developer, a rotatable stirring member disposed in the developing container for stirring the developer, and a developer carrier for supplying the developer in the developing container to the electrostatic latent image to form an image, A supply unit is located above the developing unit in the direction of gravity and includes a supply container for containing the developer, the supply container being in communication with the developing unit via a supply port, A control unit for controlling the stirring member, Equipped with, The control unit, (i) Control the system to perform a refresh mode which includes an ejection operation that ejects the developer from the developing container onto the image carrier and a replenishment operation that replenishes the developer from the replenishment container to the developing container, (ii) When the refresh mode is executed, the replenishment operation is controlled to start before the end of the discharge operation, (iii) After the refresh mode is started, In the section controlled to complete the process, the dispensing of the developer is controlled so that the stirring member in the developing container does not come into contact with the developer in at least a portion of the section. An image forming apparatus characterized by the following features.

5. The control unit controls the discharge speed during the discharge operation and the replenishment speed during the replenishment operation so that the stirring member does not come into contact with the surface of the developer during the refresh mode. The image forming apparatus according to feature 4.

6. The control unit controls the replenishment speed in the replenishment operation to be faster after the discharge operation is completed. The image forming apparatus according to feature 5.

7. The system further comprises a supply control member that controls the supply of the developer from the supply container to the developing container, The control unit controls the replenishment control member so that the discharge operation and the replenishment operation start and end simultaneously. The image forming apparatus according to feature 1 or 4.

8. The replenishment control member changes the developer replenishment rate by changing the rotation speed of the stirring member. The image forming apparatus according to feature 7.

9. The developing unit further includes a supply member that supplies the developer to the developer carrier, The supply member has a longitudinal direction, and the supply port connecting the supply container and the developing container is positioned above the supply member in the direction of gravity. The control unit controls the dispensing operation such that the amount of developer dispensed increases as the distance from the supply member to the position where the supply port is projected in the direction of gravity increases. The image forming apparatus according to feature 1 or 4.

10. The replenishment unit is a cartridge that can be attached to the developing unit. The image forming apparatus according to feature 1 or 4.

Images