Image forming apparatus

Abstract

To reduce toner usage while stabilizing the removal performance of the belt's cleaning blade. [Solution] An image forming apparatus in which, when the first total toner usage at the first image forming station is greater than the second total toner usage at the second image forming station, the first toner is supplied from the first image forming station to the cleaning blade via an intermediate transfer belt when not forming an image.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus using electrophotography, such as a laser printer, a copying machine, and a facsimile machine.

Background Art

[0002] In an electrophotographic color image forming apparatus, toner images are sequentially transferred from the image forming units for respective colors to an intermediate transfer member, and then the toner images are collectively transferred from the intermediate transfer member to a transfer material. Configurations using such a so-called intermediate transfer method have been conventionally known.

[0003] In such an image forming apparatus, each image forming unit for each color has a drum-shaped photoconductor as an image bearing member (hereinafter referred to as a photosensitive drum). Further, an intermediate transfer belt formed of an endless belt is widely used as the intermediate transfer member.

[0004] A primary transfer member is provided opposite to the photosensitive drum via the intermediate transfer belt. Voltage is applied to these primary transfer members from a primary transfer power source. Accordingly, the toner image formed on the photosensitive drum of each image forming unit is primarily transferred onto the intermediate transfer belt. Then, in a secondary transfer section, voltage is applied from a secondary transfer power source to a secondary transfer member. Accordingly, the toner images of respective colors that have been primarily transferred from the image forming units for respective colors onto the intermediate transfer belt are secondarily transferred collectively from the intermediate transfer belt to a transfer material such as paper or an OHP sheet. The toner images of respective colors transferred onto the transfer material are then fixed onto the transfer material by a fixing unit.

[0005] In an intermediate transfer type image forming apparatus, toner (residual transfer toner) remains on the intermediate transfer belt after the toner image is secondarily transferred from the intermediate transfer belt to the transfer material. Therefore, it is necessary to remove the residual transfer toner remaining on the intermediate transfer belt before the toner image corresponding to the next image is primarily transferred onto the intermediate transfer belt.

[0006] The blade cleaning method is widely used as a cleaning method to remove residual toner from the transfer. In this blade cleaning method, the cleaning blade is positioned downstream of the secondary transfer section in the direction of movement of the intermediate transfer belt and contacts the intermediate transfer belt. The cleaning blade, acting as the contact member, scrapes off the residual toner and allows it to be collected in a cleaning container. In addition to toner, the cleaning blade removes not only toner but also paper dust and other particles that have fallen off the printing paper.

[0007] The removal performance of the cleaning blade needs to be maintained over a long period of time. Therefore, a technology in which toner is supplied to the cleaning blade when not forming an image has been disclosed in prior art literature. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-173310 [Overview of the project] [Problems that the invention aims to solve]

[0009] Patent Document 1 discloses a configuration in which toner is supplied to a cleaning blade when not forming an image, and an external additive contained in the toner is held at the contact point between the cleaning blade and the intermediate transfer belt. In Patent Document 1, a station among several image forming stations that contains a large amount of the external additive in the toner is identified, and toner is supplied from that station. As a result, toner filming on the intermediate transfer belt is removed by the external additive. Patent Document 1 also discloses that the behavior of the cleaning blade is stabilized as a result.

[0010] On the other hand, if toner is supplied to the cleaning blade based solely on the amount of external additive contained in the toner, then the toner may not be retained by the cleaning blade properly, and the toner may slip off the cleaning blade before the external additive is sufficiently retained at the contact point. This could then result in that toner being unintentionally printed on the paper in the next printing process. As a result, it may become necessary to supply a large amount of toner to compensate for the shortage. Consequently, there were concerns that the supply of toner to the cleaning blade would increase, leading to increased toner consumption and the need for a larger collection container around the cleaning blade.

[0011] Therefore, in this invention, toner that is easily retained by the cleaning blade is preferentially supplied, thereby enabling efficient supply of external additives and other materials from the supplied toner to the blade. This suppresses the use of toner supplied throughout the lifespan of the image forming apparatus. Consequently, the removal performance of the cleaning blade is stabilized. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides an image forming apparatus comprising: a first image forming station; a second image forming station; an intermediate transfer belt; a contact member; a secondary transfer roller; and a toner supply means, wherein the first image forming station comprises: a first photosensitive drum for carrying an image; a first developing container for containing a first toner; a first developing roller for carrying the first toner and developing the image on the first photosensitive drum; and a first primary transfer roller, wherein the second image forming station comprises: a second photosensitive drum for carrying an image; a second developing container for containing a second toner; a second developing roller for carrying the second toner and developing the image on the second photosensitive drum; and a second primary transfer roller, wherein the first toner image developed on the first photosensitive drum is transferred by the first primary transfer roller, and the second toner image developed on the second photosensitive drum is transferred by the second primary Each of the first toner images is first transferred to the intermediate transfer belt by a transfer roller, and the first toner image and the second toner image that have been first transferred to the intermediate transfer belt are secondarily transferred to the transfer material by a secondary transfer roller. The contact member is in contact with the intermediate transfer belt and is configured to recover residual toner remaining on the intermediate transfer belt after the first toner image and the second toner image have been transferred to the transfer material. When the cumulative amount of first toner used at the first image forming station is defined as the first total toner usage, and the cumulative amount of second toner used at the second image forming station is defined as the second total toner usage, if the first total toner usage is greater than the second total toner usage, the first toner is supplied from the first image forming station to the contact member via the intermediate transfer belt when not forming an image. [Effects of the Invention]

[0013] According to the present invention, the toner removal performance of the cleaning blade can be stabilized with an appropriate amount of toner, and the amount of toner used for stabilization can also be prevented from becoming excessive. [Brief explanation of the drawing]

[0014] [Figure 1]1 is a schematic cross-sectional view illustrating the configuration of an image forming apparatus according to a first embodiment. [Figure 2] 1 is a block diagram for explaining operation control of the image forming apparatus according to the first embodiment. [Figure 3] 1 is a block diagram showing the operation of a normal print sequence according to the first embodiment. [Figure 4] 1 is a diagram illustrating a contact state between a cleaning blade and an intermediate transfer belt. [Figure 5] 1 is a schematic diagram illustrating the overall configuration of an intermediate transfer belt. [Figure 6] 1 is a diagram illustrating a cross-sectional configuration of an intermediate transfer belt. [Figure 7] 1 is a conceptual diagram showing how an external additive and an organosilicon polymer form a stationary layer at the tip of a cleaning blade. [Figure 8] 1 is a conceptual diagram showing the ease of forming a stationary layer at the tip of a cleaning blade depending on toner particle diameter. [Figure 9] 1 is a schematic diagram illustrating a change in particle diameter of toner in a developing device accompanying use of the image forming apparatus. [Figure 10] 1 is a flowchart for executing a supply sequence. [Figure 11] 1 is a block diagram illustrating an operation of a supply sequence. [Figure 12] 1 is a diagram showing divided regions for value calculation of a divided integration counter according to a second embodiment. DESCRIPTION OF EMBODIMENTS

[0015] Modes for carrying out the present invention are described below with reference to the drawings. However, dimensions, materials, shapes, relative arrangements, and the like of components described in the embodiments should be appropriately changed depending on the configuration of an apparatus to which the invention is applied and various conditions. Therefore, these are not intended to necessarily limit the scope of the present invention to the range disclosed in the embodiments.

[0016] <First Embodiment> (Image forming apparatus) Figure 1 is a schematic cross-sectional view illustrating the configuration of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is provided with multiple image forming units a to d. The image forming apparatus 100 of this embodiment is a so-called tandem-type image forming apparatus. Each of the image forming units a to d (first image forming station, second image forming station, third image forming station, and fourth image forming station) forms an image using toner of a specific color. These toners may also be referred to as the first toner, second toner, third toner, and fourth toner. The first image forming unit a forms a yellow (Y) image, the second image forming unit b forms a magenta (M) image, the third image forming unit c forms a cyan (C) image, and the fourth image forming unit d forms a black (Bk) image. These four image forming units are arranged in a line at regular intervals. The configuration of each image forming unit is substantially similar in many ways, except for the color of the toner contained within. Therefore, the image forming apparatus 100 of this embodiment will be described below using the first image forming unit a.

[0017] The first image forming unit a includes a photosensitive drum 1a, which is a drum-shaped photoreceptor; a charging roller 2a, which is a charging member; and a developing device 4a. Each photosensitive drum in each image forming unit may be referred to as the first photosensitive drum, second photosensitive drum, third photosensitive drum, and fourth photosensitive drum.

[0018] The photosensitive drum 1a is an image carrier that holds the toner image. The photosensitive drum 1a is rotated at a predetermined process speed (200 mm / sec in this embodiment) in the direction of the arrow R1 shown in the figure. The developing device 4a has a developing container 41a, a developing roller 42a, and a developing blade 43a. Each developing container for each image forming unit may be called the first developing container, second developing container, third developing container, and fourth developing container. Similarly, each developing roller for each image forming unit may be called the first developing roller, second developing roller, third developing roller, and fourth developing roller. The developing container 41a contains yellow toner. The developing roller 42a is a developing member that holds the yellow toner contained in the developing container 41a and develops a yellow toner image on the photosensitive drum 1a. The developing blade 43a is a regulating member that contacts the developing roller 42a and thins the toner on the developing roller 42a. A toner supply container 7a is connected to the developing device 4a. The toner supply container 7a contains yellow toner to be supplied to the developing unit 4a. Each toner supply container for each image forming unit may be called the first toner supply container, the second toner supply container, the third toner supply container, and the fourth toner supply container.

[0019] An unillustrated receiving means receives an image signal from outside the image forming apparatus 100. The received image signal is sent to an unillustrated control means. This starts the image forming operation in the image forming apparatus 100. The photosensitive drum 1a is rotated, and as the photosensitive drum 1a rotates, it is uniformly charged by the charging roller 2a to a predetermined potential (charging potential) with a predetermined polarity (negative polarity in this embodiment). Subsequently, the photosensitive drum 1a is exposed by the exposure means 3a according to the image signal. This forms an electrostatic latent image corresponding to the image of the yellow component of the target color image. Next, at the development position, the electrostatic latent image is developed by the developing means 4a. The electrostatic latent image is visualized as a yellow toner image (hereinafter simply referred to as a toner image). Here, the normal charging polarity of the toner contained in the developing means 4a is negative polarity. In this embodiment, the electrostatic latent image is inverted and developed by toner charged with the same polarity as the charging polarity of the photosensitive drum by the charging member. However, the present invention can also be applied to an image forming apparatus in which an electrostatic latent image is developed by toner charged with the opposite polarity to the charging polarity of the photosensitive drum.

[0020] The intermediate transfer belt 10, which is an endless and movable intermediate transfer body, is positioned to contact each of the photosensitive drums 1a to 1d in each of the image forming sections a to d. The intermediate transfer belt 10 is stretched by three axes: a support roller 11, a tension roller 12, and an opposing roller 13, which are tensioning members. The intermediate transfer belt 10 is stretched by the tension roller 12 with a total tension of 60 N. The intermediate transfer belt 10 moves in the direction of arrow R2 shown in the figure by the rotation of the opposing roller 13, which rotates under the driving force. As will be described in detail later, the intermediate transfer belt 10 in this embodiment is composed of multiple layers.

[0021] The toner image formed on the photosensitive drum 1a passes through the primary transfer section N1a, where the photosensitive drum 1a and the intermediate transfer belt 10 are in contact. During this process, a positive voltage is applied from the primary transfer power supply 23 to the primary transfer roller 6a, and the toner image is primary transferred to the intermediate transfer belt 10 by this voltage. Each primary transfer roller in each image forming section may be called the first primary transfer roller, second primary transfer roller, third primary transfer roller, and fourth primary transfer roller. Each toner image in each image forming section may be called the first toner image, second toner image, third toner image, and fourth toner image.

[0022] Here, the primary transfer roller 6a is provided at a position corresponding to the photosensitive drum 1a via the intermediate transfer belt 10. The primary transfer roller 6a is a primary transfer member (contact member) that contacts the inner circumferential surface of the intermediate transfer belt 10. The primary transfer power supply 23 is a power source. The primary transfer power supply 23 can apply a positive or negative voltage to the primary transfer rollers 6a to 6d. In this embodiment, a voltage is applied to multiple primary transfer members from a common primary transfer power supply 23. However, the present invention is not limited to this configuration, and can also be applied to a configuration in which multiple primary transfer power supplies corresponding to each primary transfer member are provided.

[0023] Subsequently, the second color magenta toner image, the third color cyan toner image, and the fourth color black toner image are formed in the same manner as the first color yellow toner image. These toner images are sequentially transferred onto the intermediate transfer belt 10. This forms four toner images on the intermediate transfer belt 10 corresponding to the desired color image. After that, the four toner images formed and supported on the intermediate transfer belt 10 pass through the secondary transfer section formed by the contact between the secondary transfer roller 20 and the intermediate transfer belt 10. In this process, these toner images are collectively transferred to the surface of the transfer material P, such as paper or an OHP sheet, fed by the paper feeding means 50.

[0024] The secondary transfer roller 20 uses a nickel-plated steel rod with an outer diameter of 8 mm covered with a foamed sponge, resulting in an outer diameter of 18 mm. The foamed sponge has a volume resistivity of 10 8The foamed sponge is primarily composed of NBR and epichlorohydrin rubber, adjusted to Ω·cm and 5mm thick. The rubber hardness of the foamed sponge was measured using an Asker hardness tester type C, and it was found to be 30° under a 500g load. The secondary transfer roller 20 is in contact with the outer surface of the intermediate transfer belt 10. The opposing roller 13 is positioned opposite the secondary transfer roller 20 via the intermediate transfer belt 10. The secondary transfer roller 20 is pressed against the opposing roller 13 with a pressure of 50N. This forms the secondary transfer section N2.

[0025] The secondary transfer roller 20 rotates in a driven manner relative to the intermediate transfer belt 10. A voltage is applied from the secondary transfer power supply 21, causing current to flow from the secondary transfer roller 20 towards the opposing roller 13. This transfers the toner image carried on the intermediate transfer belt 10 to the transfer material P in the secondary transfer section. When the toner image on the intermediate transfer belt 10 is transferred to the transfer material P, the current flowing from the secondary transfer roller 20 towards the opposing roller 13 via the intermediate transfer belt 10 is controlled to remain constant. This control is achieved by controlling the voltage applied to the secondary transfer roller 20 from the secondary transfer power supply 21. Furthermore, the magnitude of the current required for secondary transfer is predetermined based on the surrounding environment in which the image forming apparatus 100 is installed and the type of transfer material P. The secondary transfer power supply 21 is connected to the secondary transfer roller 20. The secondary transfer power supply 21 applies a transfer voltage to the secondary transfer roller 20. The secondary transfer power supply 21 is capable of outputting voltages in the range of 100[V] to 4000[V].

[0026] The transfer material P onto which the four-color toner images have been transferred by secondary transfer is then heated and pressurized in the fixing means 30. This melts and mixes the four colors of toner, fixing them to the transfer material P. Toner remaining on the intermediate transfer belt 10 after secondary transfer is cleaned and removed by the belt cleaning means 16 (recovery means). The belt cleaning means 16 (recovery means) is provided to recover toner downstream of the secondary transfer section N2 with respect to the direction of movement of the intermediate transfer belt 10. The belt cleaning means 16 has a cleaning blade 16a and a waste toner container 16b. The cleaning blade 16a is a contact member that contacts the outer circumferential surface of the intermediate transfer belt 10 at a position opposite to the opposing roller 13. The waste toner container 16b contains the toner recovered by the cleaning blade 16a. In the following description, the cleaning blade 16a will be simply referred to as blade 16a.

[0027] In the image forming apparatus 100 of this embodiment, a full-color print image is formed by the above operations.

[0028] (Explanation of the control block diagram) Next, the control block will be described. Figure 2 is a control block diagram for controlling the operation of the image forming apparatus. The host computer, PC271, transmits a print command and image data of the print image to the formatter 273 located inside the image forming apparatus 100. The formatter 273 converts the image data from PC271 into exposure data. The formatter 273 then transfers this exposure data to the exposure control unit 277 located in the DC controller 274. The exposure control unit 277 controls the exposure means by controlling the on / off state of the exposure data according to instructions from the CPU 276. In the image forming apparatus 100 in Figure 2, halftone control is controlled by adjusting the exposure data. This adjustment involves adjusting the on area, which is the area to be exposed, and the off area, which is the area not to be exposed, in the exposure data. When the CPU 276 receives a print command from the formatter 273, it starts the image forming sequence. The DC controller 274 is equipped with the CPU 276, memory 275, etc. The formatter is also equipped with a CPU, memory, and buses connecting them. The DC controller 274 performs pre-programmed operations. The CPU 276 controls the charging high voltage, developing high voltage, and transfer high voltage. Through these controls, the CPU 276 performs image formation, including the formation of the electrostatic latent image and the transfer of the developed toner image.

[0029] The CPU 276 also has the function of calculating the print density of each color based on the image data. Various high-voltage settings and operating sequences can be adjusted according to these print density values. These print density values ​​for each color may also be referred to as the first print density, second print density, third print density, and fourth print density.

[0030] Figure 3 shows a typical timing chart of operations for a normal printing sequence. The example illustrates printing one A4 sheet of paper.

[0031] First, in the pre-processing operation, the developing roller 42 comes into contact with the photoreceptor drum 1 after the high-voltage charge has been built up. The pre-processing operation takes 1 second. Next, in the image forming operation, development and primary transfer are performed. The image forming operation takes 1.5 seconds. Next, in the post-processing operation, secondary transfer and fixing are performed, and the developing roller 42 is separated from the photoreceptor drum 1. Furthermore, residual toner on the intermediate transfer belt 10 is cleaned. Once cleaning is complete, the rotation of the intermediate transfer belt 10 is stopped immediately. The post-processing operation takes 3 seconds.

[0032] When the toner level in the developing unit falls below a threshold, toner is transported from the toner replenishment container 7 to the developing unit 4, and toner is replenished. Toner replenishment is performed during post-processing. The remaining toner level can be calculated from the print rate calculated by the CPU 276. The CPU 276 can also calculate the amount of toner to replenishment, and the amount of toner in the developing unit after replenishment can also be calculated based on these calculations.

[0033] (Belt cleaning method 16) Next, the belt cleaning means will be described. Figure 4(a) is a schematic diagram illustrating the contact state between the blade 16a and the intermediate transfer belt 10. Figure 4(b) is a schematic diagram showing an enlarged view of the contact point between the blade 16a and the intermediate transfer belt 10. In this embodiment, the blade 16a is a long plate-shaped member in the width direction of the intermediate transfer belt 10 (hereinafter referred to as the belt width direction). The belt width direction is the direction that intersects with the movement direction of the intermediate transfer belt 10 (hereinafter referred to as the belt conveying direction).

[0034] The blade 16a in this embodiment has an elastic portion 53 that contacts the intermediate transfer belt 10 and scrapes off toner, and a sheet metal portion 52 that supports the elastic portion 53. The elastic portion 53 is a blade member formed from polyurethane. The blade 16a has a blade shape in which the width of the elastic portion 53 that contacts the intermediate transfer belt 10 is 230 mm in length. The elastic portion 53 and the sheet metal portion 52 of the blade 16a are bonded together. The elastic portion 53 of the blade 16a has a longitudinal width of 230 mm in the belt width direction and a thickness of 2 mm. The free length of the elastic portion 53, which is the length from the bonding point with the sheet metal portion 52, is 13 mm. The hardness of the blade 16a is 77 degrees according to the JIS K 6253 standard.

[0035] On the inner circumference of the intermediate transfer belt 10, a counter roller 13 is positioned opposite the blade 16a. The blade 16a is positioned in a counter-direction relative to the belt transport direction and contacts the surface of the intermediate transfer belt 10. That is, the blade 16a contacts the surface of the intermediate transfer belt 10 with its free end facing upstream in the belt transport direction. As a result, a blade nip portion Nb is formed between the blade 16a and the intermediate transfer belt 10, as shown in Figure 4(a). At the blade nip portion Nb, the blade 16a scrapes toner from the surface of the moving intermediate transfer belt 10 and collects the toner as waste toner in the waste toner container 16b. In this embodiment, the width of the blade nip Nb where the blade 16a and the intermediate transfer belt 10 contact is 75 μm in the belt transport direction.

[0036] As shown in Figure 4(b), in this embodiment, the blade 16a is positioned in a counter-direction with respect to the belt conveying direction. Therefore, the tip of the blade 16a that contacts the intermediate transfer belt 10 is subjected to a frictional force in the direction of belt conveying. The frictional force received by the tip of the blade 16a is a force that causes the tip of the blade 16a to bend in the direction of belt conveying, following the belt. As a result, the contact portion of the blade 16a is curved due to the frictional force at the contact portion, as shown in Figure 4(b), and the blade 16a becomes wrapped around the intermediate transfer belt 10. The region in which the blade 16a is wrapped when viewed as shown in Figure 4(b) is defined as the wrapped portion M, and the distance (length) of the wrapped portion M in the direction of belt conveying is defined as the amount of wrapped portion m. Furthermore, as shown in Figure 4(c), let's assume that there was virtually no intermediate transfer belt at the position where the blade 16a contacts and is pushed against the intermediate transfer belt. A virtual line is drawn along the shape of the blade 16a if it were to extend without curving after contacting the intermediate transfer belt. In the shape of the virtual blade 16a along this imaginary line, the maximum depth to which the blade penetrates the opposing roller 13 in the thickness direction of the blade along the blade tip surface is defined as the penetration amount δ.

[0037] The pressure applied from the blade 16a to the intermediate transfer belt 10 is concentrated in the winding section M. This prevents the toner that has reached the blade 16a from passing through it, thereby preventing cleaning failures.

[0038] In this embodiment, the blade 16a is positioned relative to the intermediate transfer belt 10 such that the set angle θ is 22°, the penetration amount δ is 1.5 mm, and the contact pressure is 20 N. Here, the set angle θ is defined at the intersection point where the intermediate transfer belt 10 and the blade 16a are assumed to be virtually in contact and not curved, and is the angle between the tangent to the opposing roller 13 at that intersection point and the blade 16a. More specifically, that intersection point is the intersection point with the end face on the free end side of the blade 16a. Furthermore, the set angle θ is more specifically the angle between one surface of the blade 16a that is approximately perpendicular to the thickness direction and the tangent to the aforementioned opposing roller 13.

[0039] Furthermore, the penetration depth δ is the length in the thickness direction over which the blade 16a virtually overlaps with the opposing roller 13. The contact pressure is defined as the pressing force (linear pressure in the longitudinal direction) from the blade 16a at the blade nip portion Nb. The contact pressure is measured using a film-type pressure measurement system (product name: PINCH, manufactured by Nitta Corporation).

[0040] Furthermore, the winding portion M of the blade 16a, which is wound up by the frictional force between it and the intermediate transfer belt 10, applies pressure to the intermediate transfer belt 10. As a result, the toner remaining on the intermediate transfer belt 10 is blocked by the blade 16a. The toner blocked by the blade 16a is then collected in the waste toner container 16b. Therefore, toner recovery is ensured by applying a predetermined pressure to the intermediate transfer belt 10 so that the blade 16a makes contact and prevents toner from slipping through.

[0041] (Intermediate transfer belt) Next, the configuration of the intermediate transfer belt 10 in this embodiment will be described. Figure 5 is a schematic diagram illustrating the overall configuration of the intermediate transfer belt 10. Figure 6 is a diagram showing the cross-sectional configuration of the intermediate transfer belt 10, and is a schematic enlarged view of the cross-section. Figure 6 is a diagram showing the intermediate transfer belt 10 cut in a direction perpendicular to the belt conveying direction (viewed along the belt conveying direction).

[0042] The intermediate transfer belt 10 is an endless belt member (or film-like member) consisting of two layers: a base layer 61 and a surface layer 60. The circumference of the intermediate transfer belt 10 is 700 mm, and the longitudinal width in the belt width direction is 250 mm. Here, the base layer is defined as the thickest layer among the layers constituting the intermediate transfer belt 10 in the thickness direction. In this embodiment, the base layer 61 is a layer in which a quaternary ammonium salt, which is an ionic conductive agent, is dispersed in polyethylene naphthalate resin as an electrical resistance modifier, and is a layer with a thickness of 70 μm.

[0043] The material of the base layer 61 is not limited to those listed above. For example, in addition to polyethylene naphthalate resin, other thermoplastic resins that can be used for the base layer 61 include polycarbonate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyethersulfone, polyethernitrile, thermoplastic polyimide, polyetheretherketone, thermotropic liquid crystal polymer, and polyamic acid. Two or more of these can also be used in mixture form. Furthermore, ionic liquids, conductive oligomers, and quaternary ammonium salts can also be used as ionic conductive agents added to the base layer 61. One or more of these conductive materials may be appropriately selected, or a mixture of electronically conductive materials and ionic conductive materials may be used.

[0044] The surface layer 60 is a layer formed on the outer circumferential surface side of the intermediate transfer belt 10. In this embodiment, the surface layer 60 is a layer in which zinc oxide antimond dope, which is used as an electrical resistance modifier 63, is dispersed in an acrylic resin, which is used as a base material 62. Polytetrafluoroethylene (PTFE) particles, which are fluorine-containing particles, are added to the surface layer 60 as a solid lubricant 64. The thickness of the surface layer 60 is 3 μm. In this embodiment, 20 parts by weight of polytetrafluoroethylene (PTFE) particles are added.

[0045] Regarding the substrate 62 of the surface layer 60, curable resins such as melamine resin, urethane resin, alkyd resin, and fluorine-based curable resin (fluorine-containing curable resin) can be listed as organic materials other than acrylic resin. Inorganic materials include alkoxysilane / alkoxyzirconium-based materials and silicate-based materials. Organic-inorganic hybrid materials include inorganic fine particle dispersed organic polymer-based materials, inorganic fine particle dispersed organoalkoxysilane-based materials, acrylic silicon-based materials, and organoalkoxysilane-based materials.

[0046] In addition to the above, conductive materials to be added to the surface layer 60 include particulate, fibrous, or flake-shaped carbon-based conductive fillers such as carbon black, PAN-based carbon fibers, and expanded graphite pulverized products. Particulate, fibrous, or flake-shaped metal-based conductive fillers such as silver, nickel, copper, zinc, aluminum, stainless steel, and iron are also included. Furthermore, particulate metal oxide-based conductive fillers such as zinc antimonate, antimond-doped tin oxide, antimond-doped zinc oxide, tin-doped indium oxide, and aluminum-doped zinc oxide are also included.

[0047] From the viewpoint of strength, such as abrasion resistance and crack resistance, the surface layer 60 is preferably made of a resin material (curable resin) among curable materials. Among curable resins, an acrylic resin obtained by curing an unsaturated double bond-containing acrylic copolymer is preferred as the surface layer 60. The surface layer 60 in this embodiment is obtained by applying a liquid containing ultraviolet-curable monomers and / or oligomer components to the surface of the base layer 61 and curing it by irradiating it with energy rays such as ultraviolet light.

[0048] The volume resistivity of the intermediate transfer belt 10 in this embodiment is 1 × 10⁻⁶ 10 The volume resistivity is Ω·cm. The volume resistivity was measured using a Hiresta-UP (MCP-HT450) from Mitsubishi Chemical Corporation, with a UR probe (model MCP-HTP12) connected to the intermediate transfer belt 10, at an applied voltage of 100V and a measurement time of 10 seconds. The environment of the measurement room for measuring volume resistivity was set to a temperature of 23°C and a humidity of 50%, and the volume resistivity of the intermediate transfer belt 10 was measured after being left in the measurement room for 4 hours.

[0049] (Toner description) The toner used in the image forming apparatus of this embodiment will be described below. The toner manufacturing method will be described below, but the manufacturing method is not limited to the method described below.

[0050] Methods for producing toner matrix particles include suspension polymerization, dissolution-suspension, and emulsification-coagulation methods, which involve producing resin particles in an aqueous medium. Among these, suspension polymerization is preferred as a method for producing toner matrix particles. Toner produced by suspension polymerization has high circularity and excellent shape uniformity, resulting in superior fluidity and good image quality.

[0051] The suspension polymerization method is a method for obtaining toner mother particles by polymerizing polymerizable monomers contained in a polymerizable monomer composition. The polymerizable monomer composition contains polymerizable monomers capable of forming a resin, a release agent, and other additives as needed, and is granulated in an aqueous medium.

[0052] Furthermore, after the polymerization process is complete, the generated particles can be recovered by known methods such as washing and filtration, and these particles can be dried to obtain toner matrix particles.

[0053] Furthermore, the polymerization process may be heated to increase the temperature during the latter half of the process. Additionally, it is possible to remove some of the dispersion medium from the reaction system by distillation during the latter half of the polymerization process or after the completion of the polymerization process to remove unreacted polymerizable monomers or by-products.

[0054] It is even preferable to manufacture the toner matrix particles in an aqueous medium and to form protrusions containing the organosilicon polymer described later on the surface of the toner matrix particles.

[0055] This embodiment describes a toner having protrusions containing an organosilicon polymer, which is suitable as a toner. This toner contains an organosilicon polymer represented by the following formula (1) on the surface of the toner particles. R-SiO 3 / 2 ...Equation (1) (R is an alkyl group having 1 to 6 carbon atoms, or a phenyl group.)

[0056] In the substructure shown in Equation 1, the Si atom has four valencies, one bonded to the organic group represented by R and the remaining three to the O atom. The O atom forms a siloxane bond (Si-O-Si) where both of its valencies are bonded to Si. In the substructure shown in Equation 1, in the relationship between Si atoms and O atoms as an organosilicon polymer, there are 2 Si atoms for every 3 O atoms. Therefore, -SiO 3 / 2 It is expressed as follows: In other words, it has a structure like the structural formula (1) below.

[0057] [ka]

[0058] This organosilicon polymer -SiO 3 / 2 This structure is thought to have properties similar to silica (SiO2), which is composed of numerous siloxane structures. Having such a structure on the surface improves environmental stability, suppression of charge reversal components, and durability. Furthermore, when the toner reaches the blade 16a, the surface layer containing the organosilicon polymer moves to the vicinity of the cleaning nip Nb. The surface layer containing the organosilicon polymer then prevents the toner from being directly sandwiched between the blade 16a and the intermediate transfer belt 10, thereby stabilizing the behavior of the blade 16a.

[0059] Furthermore, it is preferable to manufacture the toner by adding and mixing external additives to the toner particles using a known method (for example, using a Henschel mixer or the FM10C model manufactured by Nippon Coke Industries, Ltd.). This allows for adjustment of the toner's electrostatic properties and fluidity. The external additives also migrate to the vicinity of the cleaning nip Nb when the toner reaches the blade 16a, thus stabilizing the behavior of the blade 16a.

[0060] (Adhesion of external additives and organosilicon polymers to the blade) In this embodiment, the external additive added to the toner and the protrusions containing the organosilicon polymer formed on the toner matrix particles have the property of migrating from the toner matrix particles to the blade 16a after the toner is recovered by the blade 16a. As shown in Figure 7(a), the recovered toner matrix particles become densely packed near the cleaning member and rub against each other, causing migration to occur. The migration progresses gradually with the number of times the toner matrix particles rub against each other. Therefore, by being densely packed and rubbed near the cleaning member for a certain period of time or longer, the external additive and the organosilicon polymer particles that have detached from the toner matrix particles can be more preferably migrated to the vicinity of the contact portion of the blade 16a.

[0061] The migrated external additives and organosilicon polymer particles are pressed against the elastic portion 53 of the blade 16a, forming a stable, stationary layer 54. This stationary layer 54 prevents the toner matrix particles from being directly caught in the nip portion, thereby suppressing toner leakage. Furthermore, this stationary layer 54 adheres to the winding portion M along the longitudinal direction of the blade 16a and acts as a lubricant. This prevents wear and tearing of the elastic portion 53 of the blade 16a.

[0062] On the other hand, if the amount of external additive and organosilicon polymer adhering to the blade 16a is too small, there is a risk that the nip portion Nb and the intermediate transfer belt 10 will come into direct contact. This may accelerate wear of the blade 16a in the winding portion M. Furthermore, if the nip portion Nb and the intermediate transfer belt 10 come into direct contact as described above, the frictional force on the tip of the blade 16a will increase. As a result, the amount of winding m in the winding portion M of the blade 16a, which is the amount explained in Figure 4(b), will also increase. If the amount of winding m becomes too large, there is a risk that the blade 16a, which is in contact with the intermediate transfer belt 10 in the counter direction, may peel off towards the downstream side in the belt conveying direction.

[0063] As mentioned above, for the external additive to migrate to the vicinity of the cleaning nip Nb as the toner supplied to the blade 16a circulates, the toner needs to remain near the cleaning nip Nb for a certain period of time. On the other hand, the suspension polymerization toner preferably used in this embodiment has high circularity. Therefore, the suspension polymerization toner, which is a spherical, small-particle toner, easily gets trapped in the contact area between the blade 16a and the intermediate transfer belt and slips through. As shown in Figure 8(a), the suspension polymerization toner easily reaches the vicinity of the blade winding section M. A portion of the suspension polymerization toner gets caught between the blade 16a and the intermediate transfer belt. Then, due to the frictional force at that time, the suspension polymerization toner slips through to the downstream side of the nip Nb. When it slips through, the suspension polymerization toner removes the external additive and the layer 54 of organosilicon polymer interposed near the nip Nb from the blade. Therefore, in this part where the suspension polymerization toner slips through to the downstream side of the nip Nb, there is a risk of a chain reaction of toner slippage. On the other hand, as shown in Figure 8(b), even spherical toner particles tend to stay on the blade 16a without slipping through if their particle size is large. As the toner circulates while staying on the blade, the external additive and organosilicon polymer migrate to the vicinity of the cleaning nip Nb and form a stationary layer 54. This stabilizes the behavior of the blade 16a against peeling and other issues. Therefore, it is preferable that large-particle toner is selectively supplied in the application sequence, which is the sequence in which the external additive and organosilicon polymer are applied to the vicinity of the cleaning nip Nb. Once the stationary layer 54 is properly formed, toner slippage is suppressed.

[0064] Even when toner containing small particle sizes reaches the blade 16a as shown in Figure 8(c), the stationary layer prevents the toner from being directly jammed between the blade 16a and the intermediate transfer belt 10.

[0065] (Adjusting the amount of material adhering to the blade) Next, we will describe the supply operation in which the external additive is supplied to the blade 16a. Figure 10 is a flowchart of the adhesion amount adjustment sequence. The calculations in these sequences are performed by the formatter 273, as explained in the control block diagram in Figure 2.

[0066] In STEP 1, the print coverage ratios for yellow, magenta, cyan, and black are calculated based on the print job information sent from PC271.

[0067] In STEP 2, the cumulative counter value for each station is calculated using the following formula (2) based on the printing rate calculated in STEP 1. Cumulative counter value = Σ(coefficient × printing rate) ... Equation (2)

[0068] The coefficient in equation (2) is the amount of toner used per 1% of print density and per printed page. Information such as continuous / intermittent printing, image pattern, printing environment, and differences between image forming stations may be included in the coefficient. For example, for continuous yellow printing at a room temperature of 20°C to 27°C, the coefficient may be set to 3 [mg / % / page]. The coefficient multiplied by the print density represents the amount of toner used per printed page.

[0069] In STEP 3, the number of pages printed since the previous supply sequence is accumulated based on the print job information sent from PC271.

[0070] In STEP 4, it is determined whether the number of printed pages since the previous supply sequence is 1000 or more. If the calculation result in STEP 4 is less than 1000 pages, the process moves to STEP 8 and the sequence ends. The image forming apparatus 100 waits until the next print job information is sent from PC 271 and the next print job is started.

[0071] If the calculation result in STEP 4 is 1000 or more, the process moves to STEP 5.

[0072] In STEP 5, the image forming stations to be used in the supply sequence are selected. When the cumulative counter values ​​of each image forming station are compared, the image forming station with the highest cumulative counter value is selected as supply station L. If the cumulative counter values ​​of multiple stations are equivalent, those multiple stations may be selected as supply station L.

[0073] In STEP 6, the supply sequence is executed.

[0074] Figure 11 shows a typical timing chart of the print sequence when the supply sequence is executed. The supply sequence is executed when a print job that has printed 1000 or more pages since the previous sequence is completed.

[0075] Figure 11 shows, with solid lines, the case where the development operation for the supply toner is performed at a single image forming station. In the configuration shown in Figure 1, the exposure means 3 of station L exposes the photoreceptor 1 at the timing when the toner of the print job, which has been primary transferred onto the intermediate transfer belt 10, passes through the secondary transfer section. Subsequently, the developing device 4a performs an operation equivalent to a 32 mm wide full-black print in the belt transport direction.

[0076] Let's assume that the toner for supply is developed at two image forming stations during a single supply sequence. In this case, the "exposure / development" operation is performed at the second image forming station at the timing indicated by the dashed block in Figure 11.

[0077] If multiple stations are selected as supply station L in STEP 5 of Figure 10, the 32mm length, which was previously printed entirely in black, is divided by color according to the number of stations. For example, suppose magenta M and cyan C are selected as supply station L. In this case, 16mm is printed for each color, and their toners are supplied to the blade 16a. At this time, the image formation timing on the intermediate transfer belt 10 is shifted to different timings between stations. This prevents multiple colors from overlapping on the belt. When the development operation of the supplied toner is completed, the developing roller 42 moves away from the photosensitive drum 1.

[0078] It is necessary to prevent the supply toner, which has been primarily transferred onto the intermediate transfer belt 10, from adhering to the secondary transfer roller 20, which receives the second transfer. Therefore, a voltage is applied to the secondary transfer roller 20 in accordance with the timing at which the supply toner reaches the secondary transfer roller. The voltage is applied so that the toner, which is charged with the correct polarity, receives a Coulomb force directed toward the intermediate transfer belt 10.

[0079] The supply operation ends when the supplied toner reaches the blade 16a. The intermediate transfer drive and the application of various high-voltage power supplies are stopped accordingly. In this embodiment, as described above, the sequence ends when the supplied toner reaches the blade 16a, so the transfer of external additives and organosilicon polymers to the blade 16a may not be completely completed. However, when the intermediate transfer belt 10 is driven again in the next print job, the transfer will be performed again and the transfer will be completed.

[0080] In STEP 7, the print count counter, which manages the interval between supply operations, is reset.

[0081] This explains why toner supply stations are selected based on these criteria.

[0082] In a developing apparatus included in an image forming apparatus as shown in this embodiment, the particle size of the toner developed on the photosensitive drum is small initially and gradually increases with use. That is, the toner developed on the photosensitive drum is smaller than the average particle size of the toner initially filled into the developing apparatus during the initial period of use. Subsequently, the amount of toner developed on the photosensitive drum gradually increases with use. The degree of particle size change depends on the amount of toner used in the developing apparatus, and the effect of the print density on the degree of particle size change is small. A conceptual diagram of this phenomenon is shown in Figure 9.

[0083] As shown in Figure 9(a), the average toner particle size in the developer increases with the number of printed pages, but it is larger at high print levels than at low print levels. The print coverage is higher at high print levels, and in this case, the total toner usage is also higher at high print levels. As shown in Figure 9(b), if the horizontal axis is total toner usage instead of the number of printed pages, the average toner particle size in the developer increases along with the total toner usage, but there is no difference between low and high print levels.

[0084] Therefore, instead of using the print density directly as the standard, the total toner usage and the corresponding cumulative counter value are used. This provides an amount that reflects the average particle size of the toner contained in the developing unit. As a result, as shown in Figure 8, toner from stations where blade behavior stabilization is efficiently achieved is preferentially used. This method of toner supply allows for both saving toner and stabilizing blade behavior. The total toner usage for each image forming unit may be referred to as the first total toner usage, second total toner usage, third total toner usage, and fourth total toner usage.

[0085] This section describes the case where toner is replenished in the developing unit. Immediately before replenishment, the average particle size of the toner remaining in the developing unit is larger than that of new toner. When new toner is replenished in this state, the average particle size of the toner in the developing unit after replenishment becomes somewhere between the size of the remaining toner and the new toner. Therefore, during the replenishment operation, the cumulative counter value is corrected according to the following equation (3).

[0086] If x is the cumulative counter value immediately before replenishment, w_before is the amount of toner in the developing container immediately before replenishment, and w_after is the amount of toner in the developing container after replenishment, then the cumulative counter value y after replenishment is calculated by the following equation (3).

[0087] The cumulative counter value y after replenishment is the result of multiplying the cumulative counter value immediately before replenishment by the amount of toner in the developing container before replenishment / the amount of toner in the developing container after replenishment. y = w_before ÷ w_after × x ... (Equation 3)

[0088] Assume the toner amount in the developing container immediately before replenishment is 30g, the toner amount after replenishment is 100g, and the cumulative counter value immediately before replenishment is 100. In this case, the cumulative counter value immediately after replenishment will be 30. For print jobs after replenishment, the cumulative counter value is updated in the following way until toner is replenished again: A value corresponding to the print density is added to y according to equation (4), and the cumulative counter value is updated. Cumulative counter value = y + Σ(coefficient × printing rate) ... Equation (4)

[0089] The cumulative counter value is updated according to equation (4), thereby obtaining a cumulative count value that reflects the change in toner particle size within the developing container.

[0090] This concerns cases where the interval between supply sequences is widened in order to reduce the number of times the supply sequence is performed. In this case, it may be desirable to maximize the transfer of the external additive and organosilicon polymer to the blade 16a during the post-processing sequence. In such cases, the post-processing sequence may be extended, taking into account the transfer time of the external additive and organosilicon polymer, and the idle distance of the intermediate transfer belt 10 may be extended.

[0091] (Effects and Benefits) Next, the effects of executing the sequence in this embodiment will be explained. Table 1 shows the results of the print durability test of the image forming apparatus under intermittent two-sheet durability conditions, both when the sequence of this embodiment was executed and when it was not. Table 1 also shows the print density of each image forming station used in the experiment. Toner was replenished in each developing unit when it was detected that the toner level had reached a certain value, and a total of 50,000 sheets were printed. During this process, the developing units were not replaced; only the toner was replenished.

[0092] [Table 1]

[0093] The 50,000-page usage in Table 1 represents the amount of toner used by the image forming apparatus to print 50,000 pages. Specifically, it represents the amount of toner developed for supply to the blade in the supply sequence, expressed as the total length corresponding to printing in the belt transport direction. In the blade width direction, a toner image is formed across the entire printable area.

[0094] In Example 1-1 in Table 1, the supply sequence was performed using the method of this embodiment. In Example 1-1, the print coverage of the yellow, magenta, and cyan stations was 1%, and the print coverage of the black station was 10%. The toner usage for the supply sequence up to 50,000 prints was 1600 mm. The supply sequence was performed almost entirely at the black image forming station.

[0095] During toner supply, no toner leakage from the blade occurred, and good cleaning behavior was observed up to 50,000 images during normal image formation.

[0096] In Example 1-2 of Table 1, the supply sequence of this embodiment was executed. In Example 1-2, the print coverage for magenta and cyan was 5%, while the print coverage for yellow and black was 1%. In this case, toner was mainly supplied to the blade from the magenta station and the cyan station. In Example 1-2, as in Example 1-1, the toner usage for the supply sequence up to 50,000 prints was 1600 mm. No toner leakage occurred during either the supply sequence or normal image formation.

[0097] In Examples 1-3 of Table 1, the supply sequence of this embodiment was executed. Similarly, 50,000 sheets were printed in Examples 1-3, but the print density of the black station during printing was halved compared to Example 1. In Examples 1-3, the supply sequence was primarily performed from the black station. However, compared to Example 1-1, the proportion of toner used in the supply sequence from the yellow, magenta, and cyan image forming stations increased. No toner leakage occurred during either the supply sequence or normal image forming.

[0098] The results from Examples 1-1 to 1-3 demonstrated that it is possible to print 50,000 sheets without any paper slippage, even when different image forming stations are used in the supply sequence. By selecting an image forming station that reflects the amount of toner used, it was possible to print 50,000 sheets with the same sequence usage.

[0099] As a comparative example, the print rate of each image forming station was the same as in Example 1-1, but the case where the supply sequence was not performed was conducted as Comparative Example 1. The toner used in the supply sequence was depleted. However, during normal image forming after 30,000 prints, toner sometimes slipped through the intermediate transfer belt 10, and this leaked toner was printed on the white areas.

[0100] Next, Comparative Example 2 was conducted. The print density was the same as in Example 1-1. In Comparative Example 2, the supply toner was developed in 8mm widths from each station regardless of the cumulative counter value during the supply sequence. In this case, the amount of toner used in the supply sequence up to 50,000 prints was the same as in Examples 1-1 and 1-2. In Comparative Example 2, no toner seepage onto white areas occurred during normal image formation. However, toner seepage sometimes occurred during the supply sequence. This is thought to be because the amount of external additives and organosilicon polymers present on the blade decreases at the timing when toner is supplied every 1,000 sheets. It is presumed that this is because toner seepage occurs when toner is supplied at this time from an image forming station with a small cumulative counter value, which contains a large amount of small particle size toner.

[0101] Furthermore, as Comparative Example 3, an experiment was conducted in which the same amount of toner was supplied from each station in the supply sequence, but the print length of each was 16 mm. This was based on the assumption that a larger amount of toner would form a stable stationary layer 54, as toner leakage from the blade 16a is possible. As a result, no toner leakage was observed, but the amount of toner required in the supply sequence was greater compared to Examples 1-1 to 1-3.

[0102] As shown in Examples 1-1 to 1-3 and Comparative Examples 1 to 3, by selecting the station to be used in the supply sequence using the cumulative counter value, it can be expected that large-particle toner will be preferentially supplied to the blade 16a. It is thought that the amount of external additives and organosilicon polymers adhering to the blade 16a is reduced immediately before the supply sequence. By supplying large-particle toner at this time, the risk of slippage is suppressed. In addition, the external additives and organosilicon polymers migrated from the large-particle toner stabilize the blade behavior. As a result, it is thought that the amount of toner supplied required for stabilization will not increase.

[0103] As described above, in this embodiment, a supply sequence is implemented according to the total amount of toner used by the process station. This makes it possible to stabilize the blade behavior throughout the lifespan of the image forming apparatus while suppressing the amount of toner supplied that is necessary for stabilization from becoming excessive.

[0104] In this embodiment, the same exposure and development conditions used for printing a solid monochrome image during normal image formation were used for toner development during the supply sequence. However, halftones and horizontal line patterns can also be used if they are more suitable for stabilizing the behavior of the blade 16a.

[0105] In this embodiment, the supply sequence was performed as a post-processing sequence at a time when image formation was not occurring. However, the timing of the sequence is not limited to a post-processing sequence. It may also be performed at a predetermined timing during the print job, such as when the page spacing is widened. Alternatively, it may be performed as a pre-processing sequence at a time when image formation is not occurring, when the next print job is ordered.

[0106] In this embodiment, the station with the maximum counter cumulative value was selected. However, when station L, which has the maximum value, is designated as the first station, any station other than L may be selected as the second station. In this case, it is preferable to configure the system so that the toner supplied from the first station L reaches the blade first. By doing so, the toner, which is estimated to have large particle sizes, is supplied from the toner that reaches the blade, and the stabilization of the blade behavior begins. Then, even if toner that does not necessarily have large particle sizes subsequently reaches the vicinity of the blade, it is prevented from penetrating very close to the tip of the blade. However, toner from stations other than L is also circulated near the blade after reaching the vicinity of the blade. As a result, the toner and organosilicon polymer are further transferred, and these toners also contribute to the stabilization of the blade behavior. This helps to equalize the toner colors used in the supply sequence.

[0107] Furthermore, as shown in Example 1-2, if there are multiple stations L with the highest cumulative counter value, a preferred station may be selected by referring to the average print rate. In this case, it is preferable to select a station with a high average print rate. Even if the cumulative counter value is the same, the fewer the number of printed pages (i.e., the higher the average print rate), the less the external additives and organosilicon polymers on the surface of the toner matrix particles are embedded in the toner matrix particles. Therefore, these are more easily transferred by the blade 16a, and it is expected that they can contribute to stabilizing the behavior of the blade 16a. In this way, in the supply sequence, the toner for supply can be developed first from stations with a high average print rate, and then from stations with a low average print rate.

[0108] <Second Embodiment> In the first embodiment, an integrated counter value was calculated from the print density calculated from the entire image area, and the image forming station to be used in the supply sequence was determined. However, the area in which the toner image is formed may be biased depending on the printed image.

[0109] In this case, depending on the longitudinal position where the blade 16a contacts the intermediate transfer belt 10, there is a possibility that areas with a large average toner particle size and areas with a small average toner particle size may coexist within the developing device 4a.

[0110] In light of these circumstances, in the second embodiment, the print density is counted by dividing the blade 16a in the longitudinal direction.

[0111] Figure 12 shows the state in which the region is divided in the longitudinal direction from one end to the other in this embodiment. The longitudinal direction is the longitudinal direction of the blade 16a. This longitudinal direction is also the rotation axis direction of the rotating bodies such as the photosensitive drum 1, developing roller 42, primary transfer roller 6, and secondary transfer roller 20.

[0112] The divided regions indicate the calculation regions for the cumulative counter value. As an example, in this embodiment, it is divided into three regions. As shown in Figure 12, regions A, B, and C are set with respect to the rotation direction of the intermediate transfer belt 10. Regions A, B, and C may also be called the first region, second region, and third region. To distinguish them from the cumulative counter value in the first embodiment, the cumulative counter value for each region is called the divided cumulative counter value. In this embodiment, divided cumulative counter value A, divided cumulative counter value B, and divided cumulative counter value C are calculated for each of the three divided regions.

[0113] In this embodiment, each divided cumulative counter value is calculated in the same manner as in the first embodiment and is accumulated according to the printing density of each divided area.

[0114] In this embodiment, a 5mm margin is provided on each side of the LTR paper. The area excluding these margins is defined as follows: Area A is 68.7mm from the left edge, Area B is 68.7mm in the center, and Area C is 68.7mm from the right edge excluding the margins.

[0115] (Effects and Benefits) Table 2 shows the print coverage for each color, the amount supplied per supply sequence, the amount of toner used in the supply sequence up to 50,000 pages printed, and the cleaning results in this embodiment.

[0116] [Table 2]

[0117] Similar to the first embodiment, 50,000 sheets were printed in a 2-sheet intermittent manner. In the toner supply sequence of this embodiment, the following printing is performed as an example: In area A, printing occurs 30 mm from station M; in area B, printing occurs 30 mm from station C; and in area C, printing occurs 30 mm from station Y, and there are timings when toner is supplied to the blade 16a.

[0118] The total toner usage during the supply sequence for printing up to 50,000 pages was 1,500 mm in the transport direction, and no toner leakage occurred during either the supply sequence or normal printing.

[0119] In each region of the blade's longitudinal direction, the segmented cumulative counter value of each image forming station is referenced. By selecting the station with the highest segmented cumulative counter value and performing the supply sequence accordingly, the blade behavior can be stabilized more effectively.

[0120] <Third Embodiment> When low-print density printing is performed continuously in an image forming apparatus, the possibility of not only toner leaking from the blade 16a but also blade peeling increases. To address this, toner is supplied to the blade 16a, and the external additive and organosilicon polymer are transferred from the toner that reaches the blade to the blade. This reduces friction between the blade 16a and the intermediate transfer belt 10, preventing peeling. Since blade peeling tends to occur from the longitudinal ends, supplying toner to the ends can stabilize the blade behavior.

[0121] Assume that low print density printing continues for an extended period, and prior to this, there is a difference in the cumulative counter value between areas A and B, and C. In this case, it is preferable to supply toner from the station where the cumulative counter value is larger in areas A and C. Area division and cumulative counter values ​​are determined in the same way as in Examples 1 and 2. However, the division width at the edges may be set to be narrower, with more emphasis placed on edge peeling. If the print density remains low, the amount of the stationary layer 54 at the tip of the blade 16a will also decrease. This makes the blade 16a more prone to peeling and also increases the likelihood of toner leakage. Therefore, prioritizing the supply of large-particle toner from stations with large division cumulative counter values ​​is an effective countermeasure. For peeling, the supply sequence interval is not limited to 1000 sheets, and the sequence may be performed as appropriate, such as when the torque of the intermediate transfer belt begins to increase. In this case, toner may not be supplied to the central area where the possibility of peeling is low. This reduces the amount of toner used to prevent peeling. [Explanation of symbols]

[0122] 1 Photosensitive drum 2 Charging rollers 3. Exposure apparatus 4. Developing device 6. Primary transfer roller 7. Toner container 10 Intermediate transfer belt 11 Support rollers 12 tension rollers 13 Opposing roller 16 Belt Cleaning Blades 20 Secondary transfer roller 21 Secondary Transfer Power Supply 23 Primary Transfer Power Supply 30 Fixing means 41 Developing container 42 Developing roller 43 Developing Blade 50 Paper feeding means 52 Cleaning blade sheet metal section 53 Cleaning blade elastic part 54. The stationary layer formed on the cleaning blade. 60 Intermediate transfer belt surface 61 Intermediate Transfer Belt Base Layer 62 Intermediate transfer belt surface substrate 63 Intermediate transfer belt surface electrical resistance modifier 64 Intermediate transfer belt surface solid lubricant 100 Image forming apparatus M Cleaning blade winding section P Transfer Material

Claims

1. An image forming apparatus comprising a first image forming station, a second image forming station, an intermediate transfer belt, a contact member, a secondary transfer roller, and a toner supply means, The first image forming station is, The first photosensitive drum that holds the image, A first developing container for containing the first toner, A first developing roller that carries the first toner and develops the image on the first photosensitive drum, First primary transfer roller, It has, The second image forming station is, A second photosensitive drum that holds the image, A second developing container for containing the second toner, A second developing roller that carries a second toner and develops the image on the second photosensitive drum, Second primary transfer roller, It has, The first toner image developed on the first photosensitive drum is primary transferred to the intermediate transfer belt by the first primary transfer roller, and the second toner image developed on the second photosensitive drum is primary transferred to the intermediate transfer belt by the second primary transfer roller. The first toner image and the second toner image, which have been primary transferred to the intermediate transfer belt, are then secondary transferred to the transfer material by the secondary transfer roller. The contact member is configured to contact the intermediate transfer belt and to recover residual toner remaining on the intermediate transfer belt after the first toner image and the second toner image have been transferred to the transfer material. The cumulative value of the amount of toner used in the first image forming station is defined as the first total toner usage. When the cumulative value of the amount of second toner used in the second image forming station is defined as the second total toner usage, When the first total toner usage is greater than the second total toner usage, the first toner is supplied from the first image forming station to the contact member via the intermediate transfer belt during non-image forming. An image forming apparatus characterized by the following:

2. When the region of the intermediate transfer belt on which the first toner image and the second toner image are primary transferred is defined as the first region on one end in the direction of the rotation axis of the secondary transfer roller, and the other end excluding the first region is defined as the second region, In the first region, the first total toner usage is greater than the second total toner usage. In the second region, when the first total toner usage is less than the second total toner usage, In the first region, the first toner is supplied from the first image forming station to the intermediate transfer belt when not forming an image. In the second region, the second toner is supplied from the second image forming station to the intermediate transfer belt when not forming an image. The image forming apparatus according to feature 1.

3. When the other end of the second region in the direction of the rotation axis is defined as the third region, When the first total toner usage in the third region is greater than the second total toner usage, Regardless of the first total toner usage and the second total toner usage in the first and second regions, in the third region, the first toner is supplied from the first image forming station to the intermediate transfer belt when not forming an image. The image forming apparatus according to feature 2.

4. Even when the first printing rate per transfer material in the first image forming station is smaller than the second printing rate per transfer material in the second image forming station, When the first total toner usage is greater than the second total toner usage, the first toner is supplied from the first image forming station to the contact member via the intermediate transfer belt during non-image forming. The image forming apparatus according to feature 1.

5. Even when the first printing rate per transfer material in the first image forming station is smaller than the second printing rate per transfer material in the second image forming station in the first region, When the first total toner usage in the first region is greater than the second total toner usage, In the first region, the first toner is supplied from the first image forming station to the intermediate transfer belt when not forming an image. The image forming apparatus according to feature 2.

6. The first image forming station further includes a first toner supply container for supplying the first toner to the first developing container, The second image forming station further includes a second toner supply container for supplying the second toner to the second developing container, Before the first toner is supplied to the first developing container, the first total toner usage is greater than the second total toner usage. After the first toner has been replenished to the first developing container, if the result of multiplying the amount of toner in the first developing container before replenishment / the amount of toner in the first developing container after replenishment by the first total toner usage is less than the second total toner usage, The second toner is supplied from the second image forming station to the contact member via the intermediate transfer belt when not forming an image. The image forming apparatus according to claim 1, characterized in that

7. The first image forming station further includes a first toner supply container for supplying the first toner to the first developing container, The second image forming station further includes a second toner supply container for supplying the second toner to the second developing container, When the region of the intermediate transfer belt on which the first toner image and the second toner image are primary transferred is defined as the first region on one end in the direction of the rotation axis of the secondary transfer roller, and the other end excluding the first region is defined as the second region, In the first region, Before the first toner is supplied to the first developing container, the first total toner usage is greater than the second total toner usage. After the first toner has been replenished to the first developing container, if the result of multiplying the amount of toner in the first developing container before replenishment / the amount of toner in the first developing container after replenishment by the first total toner usage is less than the second total toner usage, In the second region, Before the first toner is supplied to the first developing container, the first total toner usage is greater than the second total toner usage. Even after the first toner has been replenished to the first developing container, if the result of multiplying the amount of toner in the first developing container before replenishment / the amount of toner in the first developing container after replenishment by the first total toner usage is greater than the second total toner usage, For the first region, the second toner is supplied from the second image forming station to the intermediate transfer belt when not forming an image. The image forming apparatus according to claim 2, characterized in that

8. When the first total toner usage is greater than the second total toner usage, the first toner is supplied to the first photosensitive drum from the first developing roller, and the second toner is not supplied to the second photosensitive drum from the second developing roller, thereby supplying the first toner from the first image forming station to the contact member via the intermediate transfer belt when not forming an image. The image forming apparatus according to feature 1.

9. In the first region, the first total toner usage is greater than the second total toner usage. In the second region, when the first total toner usage is less than the second total toner usage, In the first region, the first toner is supplied to the first photosensitive drum from the first developing roller, and the second toner is not supplied to the second photosensitive drum from the second developing roller, so that the first toner is supplied to the intermediate transfer belt from the first image forming station when no image is being formed. In the second region, the first toner is not supplied to the first photosensitive drum from the first developing roller, and the second toner is supplied to the second photosensitive drum from the second developing roller, so that the second toner is supplied to the intermediate transfer belt from the second image forming station when not forming an image. The image forming apparatus according to feature 2.

Images