Image forming device

Abstract

To maintain cleaning performance in a configuration that has a cleaning member in contact with a surface of an intermediate transfer body.SOLUTION: An image forming apparatus 100 has: an image carrier 1; an intermediate transfer body 8 that has ion conductivity and has a rotatable endless belt shape; a primary transfer member 6; a secondary transfer member 11; a cleaning member 21; an environment detection unit 70; and a control unit 150 that, on the basis of a result of detection performed by the environment detection unit 70, controls to change the current balance based on an integrated value of a current flowing from the inside toward the outside of the intermediate transfer body 8 and a current flowing from the outside toward the inside of the intermediate transfer body 8.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a printer, a copying machine, or a facsimile machine that uses an electrophotographic system or an electrostatic recording system. [Background technology]

[0002] Conventionally, image forming apparatuses using an electrophotographic method or the like include intermediate transfer image forming apparatuses using an intermediate transfer member. In an intermediate transfer image forming apparatus, for example, a toner image formed on a photosensitive member as an image carrier is primarily transferred onto the intermediate transfer member, and then the toner image on the intermediate transfer member is secondarily transferred onto a recording material. An intermediate transfer belt formed of an endless belt is widely used as the intermediate transfer member. Below, an electrophotographic image forming apparatus using an intermediate transfer type having an intermediate transfer belt as the intermediate transfer member will be described as an example.

[0003] In intermediate transfer image forming devices, toner (secondary transfer residual toner) remains on the intermediate transfer belt after the secondary transfer process. Therefore, a cleaning process is required to remove the secondary transfer residual toner from the intermediate transfer belt before transferring the next toner image to the intermediate transfer belt. Blade cleaning is widely used for this cleaning process. In blade cleaning, a cleaning blade is positioned downstream of the secondary transfer unit and upstream of the primary transfer unit in the direction of movement of the intermediate transfer belt surface. This cleaning blade physically scrapes the secondary transfer residual toner off the moving intermediate transfer belt and collects the toner. Cleaning blades typically made of an elastic material such as urethane rubber are used. This cleaning blade is positioned counter-direction to the direction of movement of the intermediate transfer belt surface, i.e., with its free end facing upstream in the direction of movement of the intermediate transfer belt surface, and the edge of the free end is often pressed against the surface of the intermediate transfer belt.

[0004] In blade cleaning systems, the scraping performance (cleaning performance) of the cleaning blade is known to decrease in low-temperature, low-humidity environments. This is because the cleaning blade's elastic performance decreases in low-temperature environments, reducing the contact area, and because the moisture content on the surface of the intermediate transfer belt decreases in low-humidity environments, reducing the frictional force between the cleaning blade and the intermediate transfer belt. One method for increasing the frictional force between the cleaning blade and the intermediate transfer belt is to increase the contact pressure of the cleaning blade. However, this method increases the frictional force between the cleaning blade and the intermediate transfer belt in high-temperature, high-humidity environments, which can lead to abnormal noise (squeaks) caused by cleaning blade vibration and, in more severe cases, the risk of the cleaning blade curling up.

[0005] To address this issue, Patent Document 1 attempts to maintain a constant frictional force between the cleaning blade and the intermediate transfer belt by changing the area and amount of lubricant applied depending on the humidity inside the image forming apparatus. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-275022 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional technology requires a special lubricant application means, and therefore, from the viewpoint of simplifying the device configuration and reducing costs, it is desirable to be able to maintain a stable frictional force between the cleaning blade and the intermediate transfer belt with a simple configuration without requiring such a special lubricant application means.

[0008] Furthermore, in recent years, there has been a demand for further improvements in durability in image forming apparatuses, and image forming apparatuses using a blade cleaning system are also required to have improved durability against repeated use. While reducing the contact pressure of the cleaning blade can improve durability, it becomes difficult to ensure stable cleaning performance. Thus, there is a demand for ensuring stable cleaning performance while also extending the life of the apparatus.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to maintain cleaning performance in a configuration having a cleaning member that contacts the surface of an intermediate transfer member. [Means for solving the problem]

[0010] The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus including an image carrier that carries a toner image, a rotatable, endless belt-like intermediate transfer body that has ion conductivity, a primary transfer member that performs primary transfer of the toner image from the image carrier to the intermediate transfer body at a primary transfer section, a secondary transfer member that performs secondary transfer of the toner image from the intermediate transfer body to a recording material at a secondary transfer section, a cleaning member that contacts the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body, an environment detection unit that detects at least one of the temperature and humidity of the environment, and a control unit that controls to change the current balance based on the integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body based on the detection result of the environment detection unit. and when at least one of the temperature and humidity indicated by the detection result of the environment detection unit is lower than that of a predetermined environment, the control unit controls to increase the absolute value of the current balance based on the current balance over a predetermined period in the past. The image forming apparatus is characterized by the above. According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries a toner image; a rotatable, endless belt-like intermediate transfer member that has ion conductivity; a primary transfer member that performs primary transfer of the toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that performs secondary transfer of the toner image from the intermediate transfer member to a recording material at a secondary transfer section; a cleaning member that contacts the outer surface of the intermediate transfer member to remove deposits from the outer surface of the intermediate transfer member; an environment detection unit that detects at least one of environmental temperature and humidity; and a control unit that controls, based on the detection result of the environment detection unit, to change the current balance based on the integrated value of the current flowing from the inside to the outside of the intermediate transfer member and the current flowing from the outside to the inside of the intermediate transfer member, wherein the control unit controls to increase the absolute value of the current balance based on whether the mode is full color or monochrome when at least one of the temperature and humidity indicated by the detection result of the environment detection unit is lower than that of a predetermined environment. According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries a toner image; a rotatable, endless belt-like intermediate transfer member that has ion conductivity; a primary transfer member that performs primary transfer of the toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that performs secondary transfer of the toner image from the intermediate transfer member to a recording material at a secondary transfer section; a cleaning member that contacts the outer surface of the intermediate transfer member to remove deposits on the outer surface of the intermediate transfer member; an environment detection unit that detects at least one of the temperature and humidity of the environment; and a control unit that controls, based on the detection results of the environment detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer member and a current flowing from the outside to the inside of the intermediate transfer member, wherein, when at least one of the temperature and humidity indicated by the detection results of the environment detection unit is higher than that of a predetermined environment, the control unit controls to reduce the absolute value of the current balance based on the current balance over a predetermined past period. According to another aspect of the present invention, an image forming apparatus includes an image carrier that carries a toner image, a rotatable, endless belt-like intermediate transfer body that is ionically conductive, a primary transfer member that performs a primary transfer of the toner image from the image carrier to the intermediate transfer body at a primary transfer section, a secondary transfer member that performs a secondary transfer of the toner image from the intermediate transfer body to a recording material at a secondary transfer section, a cleaning member that contacts the outer surface of the intermediate transfer body to remove any deposits on the outer surface of the intermediate transfer body, an environment detection unit that detects at least one of the temperature and humidity of the environment, and a control unit that controls to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body based on the detection result of the environment detection unit, wherein the control unit controls to reduce the absolute value of the current balance based on whether the mode is full color or monochrome when at least one of the temperature and humidity indicated by the detection result of the environment detection unit is higher than that of a predetermined environment.

[0011] According to another aspect of the present invention, a recording medium includes an image carrier that carries a toner image, a rotatable endless belt-like intermediate transfer member that has ion conductivity, a primary transfer member that performs primary transfer of the toner image from the image carrier to the intermediate transfer member at a primary transfer section, a secondary transfer member that performs secondary transfer of the toner image from the intermediate transfer member to a recording material at a secondary transfer section, a cleaning member that contacts the outer surface of the intermediate transfer member to remove deposits on the outer surface of the intermediate transfer member, a torque detection unit that detects the rotational torque of a motor that drives the intermediate transfer member, and a control unit that controls to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer member and a current flowing from the outside to the inside of the intermediate transfer member based on a detection result from the torque detection unit. The control unit controls the current balance to increase an absolute value when the rotational torque of the motor indicated by the detection result of the torque detection unit is smaller than a predetermined value. An image forming apparatus characterized by the above features is provided. According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries a toner image; a rotatable, endless belt-like intermediate transfer member that has ion conductivity; a primary transfer member that performs primary transfer of the toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that performs secondary transfer of the toner image from the intermediate transfer member to a recording material at a secondary transfer section; a cleaning member that contacts the outer surface of the intermediate transfer member to remove deposits on the outer surface of the intermediate transfer member; a torque detection unit that detects the rotational torque of a motor that drives the intermediate transfer member; and a control unit that controls, based on the detection result of the torque detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer member and a current flowing from the outside to the inside of the intermediate transfer member, wherein the control unit controls to reduce the absolute value of the current balance when the rotational torque of the motor indicated by the detection result of the torque detection unit is greater than a predetermined value. [Effects of the Invention]

[0012] According to the present invention, cleaning performance can be maintained in a configuration having a cleaning member that contacts the surface of the intermediate transfer member. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is a schematic diagram of a primary transfer unit and a secondary transfer unit. [Figure 3] FIG. 10 is a sequence chart of a primary transfer current and a secondary transfer current in a monochrome mode. [Figure 4] FIG. 10 is a sequence chart of a primary transfer current and a secondary transfer current in a full-color mode. [Figure 5] FIG. 2 is a flowchart of control in the first embodiment. [Figure 6] FIG. 10 is a flowchart of the control in the second embodiment. [Figure 7] FIG. 10 is a flowchart of the control of the third embodiment. [Figure 8] FIG. 2 is a schematic block diagram for explaining a control mode of the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0014] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0015] [Example 1] 1. Configuration and operation of image forming apparatus 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem laser printer that employs an intermediate transfer system and is capable of forming full-color images using an electrophotographic system.

[0016] The image forming apparatus 100 includes an image forming unit 30 capable of forming superimposed multicolor toner images of four colors—yellow (Y), magenta (M), cyan (C), and black (K)—on a rotating intermediate transfer belt 8. The image forming unit 30 includes image forming units (stations) PY, PM, PC, and PK, which form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Elements of the image forming units PY, PM, PC, and PK that have the same or corresponding functions or configurations will be generally described by omitting the Y, M, C, or K suffixes to designate elements for a specific color. In this embodiment, the image forming unit P includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 6, a drum cleaning device 5, and other components, which will be described later.

[0017] The photosensitive drum 1, a rotatable drum-type photosensitive member (electrophotographic photosensitive member) serving as an image carrier, is driven to rotate at a predetermined peripheral speed in the direction of arrow R1 (clockwise direction) in FIG. 1 by a drum drive motor 91 (FIG. 8) serving as a driving means (drive source). In this embodiment, the photosensitive drum 1 is driven to rotate at a peripheral speed of 300 mm / s (corresponding to the process speed) when the recording material S is plain paper. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative in this embodiment) by a charging roller 2, a roller-type charging member serving as a charging means. During the charging process, a predetermined negative charging voltage (charging bias) is applied to the charging roller 2 by a charging power source (not shown) serving as a charging voltage application means (charging voltage application unit). The charged surface of the photosensitive drum 1 is scanned and exposed by an exposure device (laser unit) 3 serving as an exposure means, forming an electrostatic latent image (electrostatic image) on the photosensitive drum 1. The exposure device 3 irradiates the photosensitive drum 1 with laser light based on an image signal.

[0018] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by the developing device 4, which serves as a developing means, by supplying toner as a developer, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. The developing device 4 includes a toner container 23 as a developer container and a developing roller 41 as a developer carrier (developing member) that carries the toner and transports it toward the photosensitive drum 1. During the development process, a predetermined negative developing voltage (developing bias) is applied to the developing roller 41 by a developing power supply (not shown) serving as a developing voltage application means (developing voltage application unit). In this embodiment, toner charged with the same polarity as the charge polarity of the photosensitive drum 1 (negative in this embodiment) adheres to the exposed area (image area) on the photosensitive drum 1, where the absolute value of the potential has been reduced by exposure after being uniformly charged (reverse development method). In this embodiment, the normal charging polarity of the toner, which is the main charging polarity of the toner during the development process, is negative.

[0019] An intermediate transfer belt 8, which is a flexible, endless belt serving as an intermediate transfer body, is disposed facing the four photosensitive drums 1Y, 1M, and 1C. The intermediate transfer belt 8 is stretched around a drive roller 9 and a tension roller 10, which serve as multiple support rollers, and is tensioned with a predetermined tension. Primary transfer rollers 6, which are roller-type primary transfer members serving as primary transfer means, are disposed on the inner circumferential surface of the intermediate transfer belt 8, corresponding to each of the photosensitive drums 1Y, 1M, 1C, and 1K. In this embodiment, each primary transfer roller 6 is disposed so as to be able to contact the corresponding photosensitive drum 1 via the intermediate transfer belt 8. This forms a primary transfer portion (primary transfer nip portion) N1, which is the contact portion between each photosensitive drum 1 and the intermediate transfer belt 8.

[0020] In this embodiment, polyethylene naphthalate is used as the material constituting the base material of the intermediate transfer belt 8, but this is not limited to this. Examples of materials constituting the base material of the intermediate transfer belt 8 include thermoplastic resins such as polyethylene naphthalate, polycarbonate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polysulfone, polyarylate, polybutylene terephthalate, polyimide, polybutylene naphthalate, polyphenylene sulfide, polyethersulfone, polyethernitrile, thermoplastic polyimide, polyetheretherketone, thermotropic liquid crystal polymer, and polyamic acid. Two or more of these materials can also be mixed and used.

[0021] The intermediate transfer belt 8 is constructed by incorporating an ion-conductive material that exhibits ion conductivity into these thermoplastic resins. In this example, an alkali metal salt was used as the ion-conductive material. Specifically, in this example, potassium perfluorobutanesulfonate (potassium nonafluorobutanesulfonate; CFSOK) was used as the ion-conductive material. This is a material commercially available as "KFBS" (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.).

[0022] Furthermore, the intermediate transfer belt 8 may have a surface layer made of a thermosetting material or a curable material that is cured by irradiation with energy rays such as ultraviolet rays or electron beams, in order to increase its surface hardness and durability (wear resistance). In this embodiment, the intermediate transfer belt 8 has a surface layer. In this embodiment, acrylic resin is used as the curable material constituting the surface layer of the intermediate transfer belt 8, but this is not limited to this. Examples of curable materials constituting the surface layer of the intermediate transfer belt 8 include organic materials such as acrylic resin, melamine resin, urethane resin, alkyd resin, and fluorine-based curable resin. Examples of inorganic materials include alkoxysilane-alkoxyzirconium-based materials and silicate-based materials. Examples of organic-inorganic hybrid materials include inorganic particle-dispersed organic polymer-based materials, inorganic particle-dispersed organoalkoxysilane-based materials, acrylic silicon-based materials, and organoalkoxysilane-based materials. From the viewpoint of the wear resistance and crack resistance of the surface layer of the intermediate transfer belt 8, resin materials are preferred among curable materials, and acrylic resin obtained by curing an unsaturated double bond-containing acrylic copolymer is preferred among curable resins. The unsaturated double bond-containing acrylic copolymer is available, for example, as Lucifural (trade name, manufactured by Nippon Paint Co., Ltd.), an acrylic ultraviolet-curable hard coat material.

[0023] In this embodiment, the intermediate transfer belt 8 has a thickness of 70 μm, a circumferential length of 790 mm, a width (length in a direction substantially perpendicular to the moving direction of the surface) of 250 mm, and a volume resistivity of 1.0×10 9 Ω cm, surface resistivity is 1.0×10 10 The electrical properties of the intermediate transfer belt 8 were measured using a Hiresta·UP MCP-HT450 (manufactured by Mitsubishi Chemical Corporation) at a temperature of 23°C, a relative humidity of 50%, and an applied voltage of 250V. The surface resistivity was measured from the back side (inner peripheral surface) of the intermediate transfer belt 8.

[0024] The intermediate transfer belt 8 rotates (circulates or moves) in the direction of arrow R2 in FIG. 1 (counterclockwise) when the drive roller 9 is driven by a belt drive motor 92 (FIG. 8) serving as a drive means (drive source). The intermediate transfer belt 8 rotates at a peripheral speed corresponding to the peripheral speed of the photosensitive drum 1 (300 mm / s when the recording material S is plain paper). The tension roller 10 and each primary transfer roller 6 are driven to rotate in accordance with the rotation of the intermediate transfer belt 8. The toner image formed on the photosensitive drum 1 is primarily transferred onto the rotating intermediate transfer belt 8 at the primary transfer section N1 by the action of the primary transfer roller 6. During the primary transfer process, a predetermined primary transfer voltage (primary transfer bias), which is a DC voltage of the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, is applied to the primary transfer roller 6 by a primary transfer power supply 60 serving as a primary transfer voltage application means (primary transfer voltage application section). In this embodiment, a primary transfer voltage is applied to each primary transfer roller 6 from an independent primary transfer power supply 60. Furthermore, the primary transfer current flowing through each primary transfer roller 6 (primary transfer unit N1, primary transfer power supply 60) can be detected by a primary transfer current detection circuit 61 serving as a primary transfer current detection means (primary transfer current detection unit) connected to each primary transfer power supply 60. For example, when a full-color image is formed, toner images of four colors, yellow, magenta, cyan, and black, are sequentially primarily transferred onto the intermediate transfer belt 8 so as to be superimposed on top of each other.

[0025] On the outer peripheral surface of the intermediate transfer belt 8, a secondary transfer roller (secondary transfer outer roller) 11, which is a roller-type secondary transfer member serving as a secondary transfer means, is disposed at a position facing the drive roller 9, which also serves as a secondary transfer opposing roller (secondary transfer inner roller). The secondary transfer roller 11 contacts the drive roller 9 via the intermediate transfer belt 8. This forms a secondary transfer portion (secondary transfer nip portion) N2, which is the contact portion between the intermediate transfer belt 8 and the secondary transfer roller 11. The secondary transfer roller 11 may be rotationally driven, or may be rotated in accordance with the rotation of the intermediate transfer belt 8. At the secondary transfer portion N2, the toner image formed on the intermediate transfer belt 8 is secondarily transferred by the action of the secondary transfer roller 11 onto the recording material S, which is being conveyed while being sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 11. During the secondary transfer process, a predetermined secondary transfer voltage (secondary transfer bias), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, is applied to the secondary transfer roller 11 by a secondary transfer power supply 62 serving as a secondary transfer voltage application means (secondary transfer voltage application unit). The secondary transfer current flowing through the secondary transfer roller 11 (secondary transfer unit N2, secondary transfer power supply 62) can be detected by a secondary transfer current detection circuit 63 serving as a secondary transfer current detection means (secondary transfer current detection unit) connected to the secondary transfer power supply 62. In this embodiment, the drive roller 9 is electrically grounded.

[0026] The feeding and conveying device 12 has a recording material cassette 13 that stores a stack of sheet-like recording material S such as paper, a feeding roller 14 that feeds the recording material S from the cassette 13, and a conveying roller pair 15 that conveys the recording material S fed by the feeding roller 14. The recording material S is conveyed from the feeding and conveying device 12 at a speed of 300 mm / s that corresponds to the rotation speed of the intermediate transfer belt 8, and is introduced into the secondary transfer section N2 at a predetermined control timing by a registration roller pair 16, where it is sandwiched and conveyed between the secondary transfer roller 11 and the intermediate transfer belt 8. As a result, the toner image on the intermediate transfer belt 8 is secondarily transferred onto the recording material S that is sandwiched and conveyed between the secondary transfer roller 11 and the intermediate transfer belt 8 as described above.

[0027] The recording material S onto which the toner image has been transferred is introduced into a fixing device 17 as a fixing means. The fixing device 17 heats and pressurizes the recording material S bearing the unfixed toner image, thereby fixing (melting and solidifying) the toner image onto the recording material S. The recording material S onto which the toner image has been fixed is discharged (output) by a pair of discharge rollers 18 onto a discharge tray 50 provided outside the apparatus main body 110 of the image forming apparatus 100.

[0028] Meanwhile, the toner remaining on the surface of the photosensitive drum 1 after the primary transfer step (primary transfer residual toner) is removed from the surface of the photosensitive drum 1 and collected by a drum cleaning device 5 serving as a photosensitive body cleaning means. The drum cleaning device 5 has a drum collected toner container 24 that stores the collected toner, and a drum cleaning blade 51 serving as a cleaning member. The drum cleaning device 5 uses the drum cleaning blade 51, which is arranged in contact with the surface of the photosensitive drum 1, to scrape and remove the primary transfer residual toner from the surface of the rotating photosensitive drum 1, and collects it in the drum collected toner container 24.

[0029] Furthermore, toner remaining on the surface of the intermediate transfer belt 8 after the secondary transfer process (secondary transfer residual toner) is removed and collected from the surface of the intermediate transfer belt 8 by a belt cleaning device 20 serving as an intermediate transfer member cleaning means. The belt cleaning device 20 includes a collected toner container 22 for storing collected toner and a cleaning blade 21 serving as a cleaning member. The belt cleaning device 20 uses the cleaning blade 21, which is disposed in contact with the surface of the intermediate transfer belt 8, to scrape and remove the secondary transfer residual toner from the surface of the rotating intermediate transfer belt 8 and store it in the collected toner container 22. In this embodiment, the cleaning blade 21 is formed by attaching a blade (rubber blade portion) made of rubber as an elastic body to a support member. In this embodiment, the support member for the cleaning blade 21 is formed of a galvanized steel plate that is 240 mm long and 3 mm thick and is disposed along the width direction of the intermediate transfer belt 8. In this embodiment, the rubber blade portion of the cleaning blade 21 is formed of a urethane rubber blade that is 230 mm long in the longitudinal direction, 2 mm thick, and has a hardness of 77 degrees according to JIS K 6253, and is disposed along the width direction of the intermediate transfer belt 8. In this embodiment, the cleaning blade 21 is pressed against the tension roller 10 via the intermediate transfer belt 8 with a linear pressure of approximately 0.49 N / cm. The cleaning blade 21 is disposed in the counter direction to the moving direction of the surface of the intermediate transfer belt 8, i.e., with its free end facing upstream in the moving direction of the surface of the intermediate transfer belt 8, and the edge of the free end is pressed against the outer surface (outer circumferential surface) of the intermediate transfer belt 8.

[0030] In this embodiment, in each image forming unit P, the photosensitive drum 1, the charging roller 2 acting as process means, the developing device 4, and the drum cleaning device 5 are integrally configured as a process cartridge 7 that is detachable from the apparatus main body 110. The four process cartridges 7Y, 7M, 7C, and 7K have substantially the same structure, but each contains different colors of toner.

[0031] In this embodiment, the intermediate transfer belt 8, its tension rollers 9 and 10, and each primary transfer roller 6, etc., integrally constitute an intermediate transfer belt unit 40 that is detachable from the apparatus main body 110.

[0032] In this embodiment, the image forming apparatus 100 can perform printing operations in two print modes: a full-color mode and a monochrome mode. The full-color mode is a print mode in which all four image forming units PY, PM, PC, and PK form toner images to form a full-color image. The monochrome mode is a print mode in which only the black image forming unit PK among the four image forming units forms a toner image to form a black monochrome image. In the monochrome mode, a toner image is formed only on the black photosensitive drum 1K. In the monochrome mode, only the black primary transfer roller 6K is brought into contact with the photosensitive drum 1K via the intermediate transfer belt 8, and a primary transfer voltage is applied, causing a primary transfer current to flow, thereby primarily transferring the toner image onto the intermediate transfer belt 8. In the monochrome mode, in the image forming units PY, PM, and PC for colors other than black, the primary transfer roller 6 is separated from the photosensitive drum 1, thereby separating the intermediate transfer belt 8 from the photosensitive drum 1. In addition, in the monochrome mode, in the image forming units PY, PM, and PC for colors other than black, the developing roller 41 is separated from the photosensitive drum 1, the rotation of the photosensitive drum 1 and the developing roller 41 is stopped, and the charging voltage, developing voltage, and primary transfer voltage are not applied. The image forming apparatus 100 is provided with a transfer separation mechanism 93 (FIG. 8) that enables the movement of the primary transfer roller 6 as described above, and a development separation mechanism 94 (FIG. 8) that enables the movement of the developing roller 41 as described above.

[0033] The image forming apparatus 100 is also provided with an environment sensor 70 as an environment detection means (environment detection unit). The environment detection means (environment detection unit) may be any device that can acquire information about at least one of the temperature and humidity inside or outside the image forming apparatus 100. In this embodiment, the environment sensor 70 is configured as a temperature and humidity sensor that can continuously detect the temperature and humidity (relative humidity) inside the apparatus main body 110 as the usage environment of the image forming apparatus 100.

[0034] 2. Control mode 8 is a schematic block diagram for explaining the control mode of image forming apparatus 100 of this embodiment. Image forming apparatus 100 is provided with a control unit 150. Control unit 150 has a CPU 151 as an arithmetic control means which is a central element for performing arithmetic processing, a memory (storage element) 152 such as a ROM or RAM as a storage means, an input / output unit (not shown) that controls the exchange of signals with elements connected to control unit 150, and the like. The RAM stores the detection results of sensors, arithmetic results, and the like, and the ROM stores a control program, a pre-determined data table, and the like.

[0035] The control unit 150 is a control unit capable of comprehensively controlling the operation of the image forming apparatus 100. The control unit 150 is connected to various components of the image forming apparatus 100. In this embodiment, the control unit 150 is connected to various power supplies, such as a primary transfer power supply 60 and a secondary transfer power supply 62. The control unit 150 is also connected to various detection units, such as a primary transfer current detection circuit 61, a secondary transfer current detection circuit 63, and an environment sensor 70. The control unit 150 is also connected to various drive units, such as a drum drive motor 91 and a belt drive motor 92. The control unit 150 is also connected to the aforementioned transfer separation mechanism 93 and development separation mechanism 94. The control unit 150 controls the operation (ON / OFF and output value) of the various power supplies, the operation of the various drive units and the exposure device 4, and the timing of these operations, thereby executing image formation operations and the like.

[0036] The image forming apparatus 100 can execute a job (print job, print operation), which is a series of operations for forming an image on one or more recording materials S, initiated by a single start command. In this embodiment, the start command is input to the image forming apparatus 100 from an external device such as a personal computer. A job generally includes an image formation process (printing process), a pre-rotation process, a sheet-to-sheet process (when forming images on multiple recording materials S), and a post-rotation process. The image formation process is a period during which electrostatic latent image formation on the photosensitive drum 1, development of the electrostatic latent image (toner image formation), primary transfer of the toner image, secondary transfer of the toner image, and fixing of the toner image are actually performed. The image formation process refers to this period. More specifically, the timing of the electrostatic latent image formation, toner image formation, primary transfer of the toner image, secondary transfer of the toner image, and fixing of the toner image vary depending on the location where the electrostatic latent image formation, toner image formation, primary transfer of the toner image, secondary transfer of the toner image, and fixing of the toner image are performed. The pre-rotation process is a period during which preparatory operations are performed prior to the image formation process. The inter-sheet process (inter-image process) is the period corresponding to the interval between recording materials S when the image forming process is performed continuously on a plurality of recording materials S (during continuous image formation). The post-rotation process is a period during which an organizing operation (preparatory operation) is performed after the image forming process. The non-image formation time is a period other than when image formation is being performed, and includes the pre-rotation process, inter-sheet process, post-rotation process, and also the pre-multiple rotation process which is a preparatory operation when the image forming apparatus 100 is turned on or when it returns from a sleep state.

[0037] For convenience, a torque detector 80, which will be described in the third embodiment, is shown in FIGS. 1 and 8, but this does not have to be provided in this embodiment.

[0038] 3. Current balance control When electricity is applied to the ionically conductive intermediate transfer belt 8, ionic substances are precipitated on its surface. This occurs when the electric field generated within the intermediate transfer belt 8 applies a force to the cations and anions responsible for ionic conductivity, causing the cations to move in the direction of the electric field and the anions to move in the opposite direction to the electric field. Figure 2 is a schematic diagram of the primary transfer portion N1 and the secondary transfer portion N2, and explains the movement of the ionically conductive substances.

[0039] 2(a), at the primary transfer portion N1, a positive voltage is applied from the primary transfer roller 6 that contacts the inside (inner peripheral surface side) of the intermediate transfer belt 8, and an electric field is generated in a direction from the inside to the outside (outer peripheral surface side) of the intermediate transfer belt 8. The generated electric field causes positive ions in the intermediate transfer belt 8 to move to the outside of the intermediate transfer belt 8, and negative ions to move to the inside.

[0040] 2(b), at the secondary transfer portion N2, a positive voltage is applied from the secondary transfer roller 11 that contacts the outside of the intermediate transfer belt 8, generating an electric field in the direction from the outside to the inside of the intermediate transfer belt 8. The generated electric field causes positive ions in the intermediate transfer belt 8 to move toward the inside of the intermediate transfer belt 8, and negative ions to move toward the outside.

[0041] The primary transfer roller 8 and the photosensitive drum 1, and the secondary transfer roller 11 and the drive roller 9 do not have to be directly opposite each other. Even if the primary transfer roller 8 and the photosensitive drum 1, and the secondary transfer roller 11 and the drive roller 9 are arranged in offset positions (positions where the center positions are shifted in the direction of movement of the intermediate transfer belt 8), they are considered to be in opposing positions as long as an electric field is formed between them. For example, Figure 2(c) shows the primary transfer unit N1 in an offset system. The movement of ions is the same as in Figure 2(a).

[0042] When the balance of the current flowing through the intermediate transfer belt 8 is significantly disrupted, ionic substances are deposited on the surface of the intermediate transfer belt 8. These deposited substances increase the frictional force between the intermediate transfer belt 8 and the cleaning blade 21. The current flowing through the intermediate transfer belt 8 is controlled (adjusted) in this embodiment by utilizing the characteristics of the ionically conductive intermediate transfer belt 8 to control the frictional force between the intermediate transfer belt 8 and the cleaning blade 21.

[0043] In this embodiment, the ionic substances contained in the intermediate transfer belt 8 have potassium ions as cations and perfluorobutanesulfonate ions as anions. Whether cations or anions are deposited on the outer surface of the intermediate transfer belt 8, the frictional force between the intermediate transfer belt 8 and the cleaning blade 21 can be increased. In this embodiment, a method of depositing cations on the outer surface of the intermediate transfer belt 8 was selected. This is because cations have a smaller molecular weight than anions and are therefore more likely to deposit on the outer surface of the intermediate transfer belt 8, resulting in a greater effect in increasing the frictional force between the intermediate transfer belt 8 and the cleaning blade 21.

[0044] In this embodiment, the current balance is defined as follows. First, the direction of current flowing from the inside to the outside of the intermediate transfer belt 8 is defined as positive, and the direction of current flowing from the outside to the inside is defined as negative. In this embodiment, as described above, current flows between the inside and outside of the intermediate transfer belt 8 at the primary transfer portion N1 and the secondary transfer portion N2. Therefore, in this embodiment, the total value of the current flowing through the intermediate transfer belt 8 by the primary transfer roller 6 and the secondary transfer roller 11 per 100 prints using letter-size recording material S (the same applies below) is calculated as follows. That is, the positive integrated value obtained by multiplying the current flowing from the inside to the outside of the intermediate transfer belt 8 by the time during which this current flowed is added together with the negative integrated value obtained by multiplying the current flowing from the outside to the inside of the intermediate transfer belt 8 by the time during which this current flowed. The total value is then divided by the area of ​​the intermediate transfer belt 8, and the value converted to a value per unit area is defined as the current balance.

[0045] FIG. 3(a) shows a sequence chart of the primary transfer current and secondary transfer current when printing one sheet in monochrome mode in normal mode, which will be described later. Here, a specific method for calculating the current balance will be explained using the case of printing in monochrome mode and normal mode shown in FIG. 3(a) as an example. The primary transfer current is 15 μA for 3 seconds, so 45 μC flows per print. The secondary transfer current is 30 μA for 2 seconds, so -60 μC flows per print. Therefore, the integrated current value per print is -15 μC. The integrated current value per 100 prints is -1500 μC. This integrated current value per 100 prints is multiplied by 0.1975 m, which is the surface area of ​​the intermediate transfer belt 8. 2 ] is -7594[μC / m 2 As described above, the current balance per 100 prints is defined as the current balance in this embodiment.

[0046] Next, the current balance increasing mode and current balance decreasing mode, which are print modes for controlling the current balance, will be described. In this embodiment, the image forming apparatus 100 is capable of performing print operations in a normal mode, which does not control the current balance, and the current balance increasing mode and current balance decreasing mode, which control the current balance. In particular, in this embodiment, the image forming apparatus 100 is capable of performing print operations in either the monochrome mode or the full-color mode in either the normal mode, the current balance increasing mode, or the current balance decreasing mode, through control described below.

[0047] 3 shows a sequence chart of the primary transfer current and secondary transfer current when printing one sheet in monochrome mode in the normal mode, the current balance increase mode, and the current balance decrease mode. Note that FIG. 3 also shows the current flowing through the primary transfer roller 6 (the current flowing from the primary transfer roller 6 to the intermediate transfer belt 8 is positive) and the current flowing through the secondary transfer roller 11 (the current flowing from the secondary transfer roller 11 to the intermediate transfer belt 8 is positive).

[0048] As mentioned above, FIG. 3(a) shows the case where printing is performed in monochrome mode and normal mode.

[0049] Figure 3(b) shows printing in monochrome mode and current balance increased mode. In addition to flowing a primary transfer current of 15 μA and a secondary transfer current of 30 μA, the current balance is increased by flowing -35 μA from the secondary transfer roller 11 for 1.5 seconds during post-rotation after the secondary transfer of the toner image.

[0050] Figure 3(c) shows printing in monochrome mode and current balance reduction mode. In addition to flowing a primary transfer current of 15 μA and a secondary transfer current of 30 μA, the current balance is reduced by flowing 42 μA from the secondary transfer roller 11 for 1.5 seconds during post-rotation after the secondary transfer of the toner image.

[0051] 4 shows a sequence chart of the primary transfer current and secondary transfer current when printing one sheet in full-color mode in the normal mode, the current balance increase mode, and the current balance decrease mode. Note that FIG. 4 also shows the current flowing through the primary transfer roller 6 (the current flowing from the primary transfer roller 6 to the intermediate transfer belt 8 is positive) and the current flowing through the secondary transfer roller 11 (the current flowing from the secondary transfer roller 11 to the intermediate transfer belt 8 is positive).

[0052] 4(a) shows printing in full color mode and normal mode, with a primary transfer current of 15 μA and a secondary transfer current of 30 μA flowing at the primary transfer section N1 for each color.

[0053] Figure 4(b) shows printing in full-color mode and current balance increased mode. In the primary transfer unit N1 for each color, a primary transfer current of 15 μA flows, a secondary transfer current of 30 μA flows, and in addition, a current of -35 μA flows from the secondary transfer roller 11 for 1.5 seconds during post-rotation after the secondary transfer of the toner image, thereby increasing the current balance.

[0054] Figure 4(c) shows printing in full-color mode and current balance reduction mode. In the primary transfer unit N1 for each color, a primary transfer current of 15 μA flows, a secondary transfer current of 30 μA flows, and in addition, 42 μA flows from the secondary transfer roller 11 for 1.5 seconds during post-rotation after secondary transfer of the toner image, thereby reducing the current balance.

[0055] Table 1 shows the occurrence of "cleaning failure" after printing 200,000 sheets in monochrome mode (intermittent printing) in three modes with different current balances in an environment with a temperature of 15°C and humidity of 10% (low temperature, low humidity environment). The current balance was adjusted to 12,000 [μC / m 2 ], 15000[μC / m 2 ], 16000[μC / m 2 The current balance was set to 12000 [μC / m 2 When the current balance was 15000 [μC / m 2 When the current balance was 16000 [μC / m 2 ], it was possible to suppress the occurrence of cleaning failures.

[0056] [Table 1]

[0057] Table 2 shows the occurrence of "squeaks (abnormal noise)" after printing 200,000 sheets in full color mode (intermittent printing) in three modes with different current balances in an environment with a temperature of 30°C and humidity of 80% (high temperature and high humidity environment). The current balance was adjusted to 32,000 [μC / m 2 ], 34000[μC / m 2 ], 36000[μC / m 2 The current balance was set to 36000 [μC / m 2 When the current balance was 34000 [μC / m 2When the current balance was 32000 [μC / m 2 By keeping it to ], we were able to suppress the occurrence of squealing.

[0058] [Table 2]

[0059] From the above results, in the configuration of this embodiment, the optimum current balance that can suppress both cleaning defects and squealing is 16000 to 32000 [μC / m 2 Therefore, in this embodiment, the following control is executed so that the current balance falls within the above range.

[0060] FIG. 5 is a flowchart of the control of this embodiment. First, when a print operation is started, the control unit 150 refers to the current balance of the most recent 100 prints stored in the memory 152 as a storage means (S101). If the number of most recent prints is less than 100, the control unit 150 refers to a value converted to a current balance equivalent to 100 prints. Next, the control unit 150 determines that the current balance of the most recent 100 prints is 16,000 [μC / m 2 ] or less than 16000 [μC / m 2 ] or more, 32000[μC / m 2 ] or less or 32000 [μC / m 2 ] is larger than 16000 [μC / m 2 If it is determined that the current balance is less than 32000 [μC / m], the control unit 150 determines whether the temperature is 19°C or lower and the humidity is 30% or lower based on the information (temperature and humidity detection results) from the environment sensor 70 (S103). 2 If it is determined that the temperature is greater than 27° C., it is determined whether the temperature is 27° C. or higher and the humidity is 65% or higher based on the information (temperature and humidity detection results) from the environment sensor 70 (S104).

[0061] Then, the control unit 150 determines that the current balance is 16000 [μC / m 2 If the temperature is 19°C or less and the humidity is 30% or less (S103), the control unit 150 controls the printing to be performed in a current balance increase mode that includes an operation to increase the current balance (S105). 2 ] (S102), and the temperature is not 19°C or less and the humidity is not 30% or less (S103), the control unit 150 controls the printing to be performed in the normal mode (S106). 2 ] or more, 32000[μC / m 2 ] or less (S102), the control unit 150 controls the printing to be performed in the normal mode (S106). 2 ] (S102), and the temperature is 27°C or higher and the humidity is 65% or higher (S104), the control unit 150 controls the printing to be performed in a current balance reduction mode that includes an operation to reduce the current balance (S107). 2 ] (S102), and the temperature is not above 27° C. and the humidity is not above 65% (S104), control is performed to print in the normal mode (S106).

[0062] In this embodiment, since the current balance is adjusted by post-rotation, the effect may be reduced during continuous printing. However, jobs involving large-volume continuous printing are relatively rare, and most jobs on the market involve intermittent printing. Therefore, in many cases, adjusting the current balance by post-rotation can sufficiently control the frictional force between the cleaning blade 21 and the intermediate transfer belt 8. Furthermore, for example, when continuous printing jobs are repeated, the current balance may be adjusted by increasing the current balance in the current balance increasing mode or decreasing the current balance in the current balance decreasing mode at a predetermined timing during continuous printing (e.g., every predetermined number of prints or every predetermined time).

[0063] As described above, the cleaning performance of the cleaning blade 21 may be correlated with either the temperature or the humidity. Therefore, although the control of the increase or decrease in the current balance is determined based on the temperature and the humidity in this embodiment, the control of the increase or decrease in the current balance can also be determined based on at least one of the temperature and the humidity.

[0064] 4. Effect of current balance control Next, the effects of the control of this embodiment will be explained using Tables 3 and 4.

[0065] Example 1-1 is an example for explaining the effect of the control of this embodiment in monochrome mode in an environment with a temperature of 15°C and humidity of 10%, and Comparative Example 1-1 is an example of printing in normal mode without the control of this embodiment. Example 1-2 is an example for explaining the effect of the control of this embodiment in full color mode in an environment with a temperature of 30°C and humidity of 80%, and Comparative Example 1-2 is an example of printing in normal mode without the control of this embodiment. In this example, after switching the print mode based on the current balance and the environment, printing continued in that print mode.

[0066] Table 3 shows the current balance of Comparative Example 1-1 and Example 1-1 and the occurrence of "cleaning failure" when printing 200,000 sheets (intermittent printing). In Comparative Example 1-1, the current balance was -7594 [μC / m 2 In Example 1-1, the current balance was 18987 [μC / m 2 By biasing the cleaning amount to [ ], it was possible to suppress the occurrence of cleaning defects.

[0067] Table 4 shows the current balance of Comparative Example 1-2 and Example 1-2 and the results of the occurrence of "squeak" when printing 200,000 sheets (intermittent printing). In Comparative Example 1-2, the current balance was 60759 [μC / m 2 In Example 1-2, the current balance was 28861 [μC / m 2By keeping the value within the appropriate range, we were able to suppress the occurrence of squealing.

[0068] [Table 3]

[0069] [Table 4]

[0070] In this embodiment, a specific range of the current balance is described as being preferable for the configuration of this embodiment, but the present invention does not limit the range of the current balance to the range in this embodiment. For example, it may be adjusted to an appropriate range depending on the material of the intermediate transfer belt used, the ion conductive material, the surface layer material, the thickness and physical properties of the substrate and surface layer, etc. However, when a general ion conductive intermediate transfer belt is used, the current balance should be 16,000 to 32,000 μC / m 2 ] range is preferable, and it is even more preferable to aim for the center of that range.

[0071] As described above, in this embodiment, image forming apparatus 100 includes image carrier 1 that carries a toner image, intermediate transfer member 8 that is a rotatable, endless belt-like ion-conductive belt, primary transfer member 6 that performs primary transfer of the toner image from image carrier 1 to intermediate transfer member 8 at primary transfer portion N1, secondary transfer member 11 that performs secondary transfer of the toner image from intermediate transfer member 8 to recording material S at secondary transfer portion N2, cleaning member 21 that contacts the outer surface of intermediate transfer member 8 to remove deposits from the outer surface of intermediate transfer member 8, environment detection unit 70 that detects at least one of the temperature and humidity of the environment, and control unit 150 that controls, based on the detection result of environment detection unit 70, to change the current balance based on the integrated value of the current flowing from the inside to the outside of intermediate transfer member 8 and the current flowing from the outside to the inside of intermediate transfer member 8. Control unit 150 can perform at least one of an adjustment operation to increase the absolute value of the current balance or an adjustment operation to decrease the absolute value of the current balance.

[0072] In this embodiment, the control unit 150 controls the current balance so as to increase the absolute value when at least one of the temperature and humidity detected by the environment detection unit 70 is lower than that of the predetermined environment. Furthermore, in this embodiment, the control unit 150 controls the current balance so as to increase the absolute value based on the current balance over a predetermined period in the past. In particular, in this embodiment, the control unit 150 controls the current balance so as to increase the absolute value when at least one of the temperature and humidity detected by the environment detection unit 70 is lower than that of the predetermined environment and the absolute value of the current balance over a predetermined period in the past is smaller than a predetermined value. In this embodiment, the control unit 150 controls the current balance so as to decrease the absolute value when at least one of the temperature and humidity detected by the environment detection unit 70 is higher than that of the predetermined environment. Furthermore, in this embodiment, the control unit 150 controls the current balance so as to decrease the absolute value based on the current balance over a predetermined period in the past. In particular, in this embodiment, the control unit 150 controls the absolute value of the current balance to decrease when at least one of the temperature and humidity detected by the environment detection unit 70 is higher than that of a specified environment and the absolute value of the current balance during a specified period in the past is greater than a specified value.

[0073] In this embodiment, the control unit 150 controls the secondary transfer voltage application unit 62, which applies voltage to the secondary transfer member 11, to change the current balance during the period when the toner image is not being transferred from the intermediate transfer member 8 to the recording material S at the secondary transfer unit N2. In this case, the secondary transfer member 11, the secondary transfer voltage application unit 62, and other components constitute an adjustment unit that adjusts the current balance. As will be described later, the control unit 150 may also control the primary transfer voltage application unit 60, which applies voltage to the primary transfer member 6, to change the current balance during the period when the toner image is not being transferred from the image carrier 1 to the intermediate transfer member 8 at the primary transfer unit N1. In this case, the primary transfer member 6, the primary transfer voltage application unit 60, and other components constitute an adjustment unit that adjusts the current balance. In this embodiment, the intermediate transfer member contains an alkali metal salt as an ion-conductive material that exhibits ion conductivity. In this embodiment, the cleaning member is a cleaning blade that contacts the outer surface of the intermediate transfer member 8 in a direction counter to the rotational direction of the intermediate transfer member 8.

[0074] As described above, according to this embodiment, with a simple configuration, it is possible to maintain a stable frictional force between the cleaning blade 21 and the intermediate transfer belt 8, and to maintain stable cleaning performance of the cleaning blade 21. Furthermore, according to this embodiment, it is possible to ensure stable cleaning performance without increasing the contact pressure of the cleaning blade 21, thereby extending the life of the device.

[0075] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted.

[0076] 1. Overview of this Example In monochrome mode, the primary transfer current flows for 6 times the amount of one primary transfer roller, whereas in full-color mode, the primary transfer current flows for 6 times the amount of four primary transfer rollers. Therefore, the current balance differs significantly between monochrome mode and full-color mode. That is, the current balance in full-color mode is significantly more positive than the current balance in monochrome mode. Therefore, in this embodiment, instead of the step of determining whether to control the increase or decrease in the current balance based on the current balance of the most recent 100 prints in Example 1 (S102 in FIG. 5), the current balance is determined based on whether the mode is monochrome or full-color.

[0077] 2. Current balance control 6 is a flowchart of the control of this embodiment. First, when a print operation is started, the control unit 150 determines whether the mode is monochrome or full-color (S201). If the control unit 150 determines that the mode is monochrome in S201, it determines whether the temperature is 19°C or lower and the humidity is 30% or lower based on information from the environmental sensor 70 (temperature and humidity detection results) (S202). On the other hand, if the control unit 150 determines that the mode is full-color in S201, it determines whether the temperature is 27°C or higher and the humidity is 65% or higher based on information from the environmental sensor 70 (temperature and humidity detection results) (S203).

[0078] Then, when the printer is in monochrome mode (S201) and the temperature is 19°C or lower and the humidity is 30% or lower (S202), the control unit 150 controls the printer to print in a current balance increasing mode that includes an operation to increase the current balance (S204). When the printer is in monochrome mode (S201) and the temperature is not 19°C or lower and the humidity is not 30% or lower (S202), the control unit 150 controls the printer to print in a normal mode (S205). When the printer is in full-color mode (S201) and the temperature is 27°C or higher and the humidity is 65% or higher (S203), the control unit 150 controls the printer to print in a current balance decreasing mode that includes an operation to decrease the current balance (S206). When the printer is in full-color mode (S201) and the temperature is not 27°C or higher and the humidity is not 65% or higher (S203), the control unit 150 controls the printer to print in the normal mode (S205).

[0079] 3. Effect of current balance control According to this embodiment, the same effects as those of Example 1 shown in Tables 3 and 4 were obtained. In other words, when printing was performed in normal mode without performing the control of this embodiment in monochrome mode, cleaning defects occurred when 200,000 sheets were printed (intermittent printing). In contrast, when the control of this embodiment was performed in monochrome mode, the current balance was biased, thereby suppressing cleaning defects. Furthermore, when printing was performed in normal mode without performing the control of this embodiment in full color mode, squealing occurred when 200,000 sheets were printed (intermittent printing). In contrast, when the control of this embodiment was performed in full color mode, squealing was suppressed by keeping the current balance within an appropriate range.

[0080] In this embodiment, a specific range of the current balance that is preferable in the configuration of this embodiment has been described, but as explained in embodiment 1, the present invention does not limit the range of the current balance to the range in this embodiment.

[0081] As described above, in this embodiment, the control unit 150 controls the current flowing through the intermediate transfer body 8 to increase the absolute value of the current balance based on the detection result of the environment detection unit 70 and also based on whether the mode is full-color or monochrome. In particular, in this embodiment, the control unit 150 controls the current balance to increase the absolute value when at least one of the temperature and humidity detected by the environment detection unit 70 is lower than that of the predetermined environment and the monochrome mode is selected. Furthermore, in this embodiment, the control unit 150 controls the current balance to decrease the absolute value based on the detection result of the environment detection unit 70 and also based on whether the mode is full-color or monochrome. In particular, in this embodiment, the control unit 150 controls the current balance to decrease the absolute value when at least one of the temperature and humidity detected by the environment detection unit 70 is higher than that of the predetermined environment and the full-color mode is selected.

[0082] [Example 3] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted.

[0083] 1. Overview of this Example In the image forming apparatus 100 of this embodiment, the rotational torque of the belt drive motor 92 that rotates the drive roller 9, which is highly correlated with the frictional force between the cleaning blade 21 and the intermediate transfer belt 8, is detected by a torque detection unit 80 (FIGS. 1 and 8) as a torque detection means. The torque detection circuit unit 80 inputs a signal indicating the detection result of the rotational torque of the belt drive motor 92 to the control unit 150. When the torque falls below a reference value, the current balance is increased to increase the frictional force between the cleaning blade 21 and the intermediate transfer belt 8, thereby suppressing cleaning defects. When the torque exceeds the reference value, the current balance is decreased to decrease the frictional force between the cleaning blade 21 and the intermediate transfer belt 8, thereby suppressing squealing.

[0084] Note that any known torque detection means may be used. For example, the torque detection unit 80 can detect a torque current component that generates torque in a stepping motor constituting the belt drive motor 92. This allows the torque detection unit 80 to detect the motor torque generated in the belt drive motor 92, which correlates with the drive torque of the drive roller 9 (intermediate transfer belt 8). Furthermore, without being limited to this, in the case of a stepping motor, motor torque can be detected based on the torque current component in vector control, and in the case of a DC brushless motor, motor torque can be detected by detecting the current value, voltage PWM value, or the like.

[0085] 2. Current balance control Table 5 shows the relationship between the drive torque of the belt drive motor 92 during printing (while the intermediate transfer belt 8 is rotating) in an environment with a temperature of 15°C and humidity of 10% (low temperature, low humidity environment) and the occurrence of cleaning defects. The drive torque is the average value per second (same below). When the drive torque was 0.049 [N·m], cleaning defects occurred. On the other hand, when the drive torque was 0.059 [N·m], no cleaning defects occurred.

[0086] [Table 5]

[0087] Table 6 shows the relationship between the drive torque of the belt drive motor 92 during printing in an environment with a temperature of 30°C and humidity of 80% (high temperature and humidity environment) and the occurrence of squealing. When the drive torque was 0.098 [N m], squealing occurred. On the other hand, when the drive torque was 0.088 [N m], no squealing occurred.

[0088] [Table 6]

[0089] From the above results, it can be seen that the optimum drive torque for suppressing both cleaning defects and squealing is 0.059 to 0.088 [N·m] in the configuration of this embodiment. Therefore, in this embodiment, the following control is performed to keep the drive torque within the above range.

[0090] 7 is a flowchart of the control of this embodiment. The control unit 150 references the average drive torque per second (herein simply referred to as "drive torque") of the belt drive motor 92 detected by the torque detection unit 80 during printing (S301). Next, the control unit 150 determines whether the drive torque is less than 0.059 [N·m], is equal to or greater than 0.059 [N·m] and is equal to or less than 0.088 [N·m], or is greater than 0.088 [N·m] (S302).

[0091] If the drive torque is less than 0.059 [N·m] (S302), the control unit 150 controls printing to occur in a current balance increasing mode that incorporates an operation to increase the current balance (S303). If the drive torque is between 0.059 [N·m] and 0.088 [N·m] (S302), the control unit 150 controls printing to occur in a normal mode (S304). If the drive torque is greater than 0.088 [N·m] (S302), the control unit 150 controls printing to occur in a current balance decreasing mode that incorporates an operation to decrease the current balance (S305).

[0092] Furthermore, in this embodiment, the control unit 150 repeats the above flow chart every time a predetermined number of sheets are printed or every predetermined time during the printing operation, and performs control to periodically switch the print mode.

[0093] In addition, the rotational torque of the belt drive motor 92 during printing operation may be a representative value, such as the rotational torque when the final image of a job is being formed on the intermediate transfer belt 8, to determine the control of the increase or decrease in the current balance during post-rotation.

[0094] 3. Effect of current balance control Next, the effects of the control of this embodiment will be explained using Tables 7 and 8.

[0095] Example 3-1 is an example for explaining the effect of the control of this embodiment in monochrome mode in an environment of temperature 15°C and humidity 10%, and Comparative Example 3-1 is an example of printing in normal mode without the control of this embodiment. Also, Example 3-2 is an example for explaining the effect of the control of this embodiment in full color mode in an environment of temperature 30°C and humidity 80%, and Comparative Example 3-2 is an example of printing in normal mode without the control of this embodiment.

[0096] Table 7 shows the drive torque and the occurrence of "cleaning failure" when printing 200,000 sheets (intermittent printing) for Comparative Example 3-1 and Example 3-1. In Comparative Example 3-1, the drive torque was 0.046 [N m], and cleaning failure occurred. In Example 3-1, when the drive torque fell below the threshold, the current balance was increased to raise the drive torque to 0.059 [N m], which is above the threshold, thereby preventing cleaning failure.

[0097] Table 8 shows the results of the drive torque and the occurrence of "squeak" when printing 200,000 sheets (intermittent printing) for Comparative Example 3-2 and Example 3-2. In Comparative Example 3-2, the drive torque reached 0.100 [N m], causing squeal. In Example 3-2, squealing was suppressed by reducing the current balance when the drive torque exceeded the threshold value, lowering the drive torque to 0.088 [N m], which was below the threshold value.

[0098] [Table 7]

[0099] [Table 8]

[0100] In this embodiment, by monitoring the drive torque of the belt drive motor 92, which is highly correlated with the frictional force between the cleaning blade 21 and the intermediate transfer belt 8, it is possible to more accurately suppress cleaning defects and noise.

[0101] Although the present embodiment describes a specific range of the driving torque that is preferable for the configuration of the present embodiment, the present invention does not limit the range of the driving torque to the range described in the present embodiment. For example, the driving torque may be adjusted to an appropriate range depending on the material of the intermediate transfer belt, the ion conductive material, the surface layer material, the thickness and physical properties of the substrate and surface layer, etc. However, when using a general ion conductive intermediate transfer belt and cleaning blade, the driving torque is preferably in the range of 0.059 to 0.088 [N·m], and it is more preferable to aim for the center of this range.

[0102] As described above, in this embodiment, the image forming apparatus 100 includes a torque detection unit 80 that detects the rotational torque of the motor 92 that drives the intermediate transfer body 8, and a control unit 150 that controls the current balance based on the integrated value of the current flowing from the inside to the outside of the intermediate transfer body 8 and the current flowing from the outside to the inside of the intermediate transfer body 8, based on the detection result of the torque detection unit 80. The control unit 150 can perform at least one of an adjustment operation to increase the absolute value of the current balance or an adjustment operation to decrease the absolute value of the current balance. Furthermore, in this embodiment, the control unit 150 controls the current balance to increase the absolute value when the rotational torque of the motor 92 indicated by the detection result of the torque detection unit 80 is smaller than a predetermined value. Furthermore, in this embodiment, the control unit 150 controls the current balance to decrease the absolute value when the rotational torque of the motor 92 indicated by the detection result of the torque detection unit 80 is greater than a predetermined value.

[0103] As described above, according to this embodiment, the same effects as those of the first embodiment can be obtained, and it is possible to more accurately suppress cleaning defects and squealing.

[0104] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0105] In the above-described embodiment, the current balance of the intermediate transfer belt 8 is adjusted using the secondary transfer roller 11. However, the current balance of the intermediate transfer belt 8 may also be adjusted using the primary transfer roller 6. Specifically, for example, in Example 1-1, a positive primary transfer current flows during post-rotation, and in Example 1-2, a negative primary transfer current flows during post-rotation. In other embodiments, the primary transfer current may be controlled in a similar manner. Furthermore, the current supplying member that supplies current to the intermediate transfer body and constitutes the adjusting unit for adjusting the current balance is not limited to the secondary transfer member or the primary transfer member. For example, opposing members such as a pair of rollers arranged to sandwich the intermediate transfer body and a current supplying member, and a voltage applying unit that applies a voltage to the current supplying member, may be separately provided. This can then be used to increase or decrease the current balance, as in the above-described embodiment. These may also be used in combination.

[0106] In the above-described embodiment, the current balance of the intermediate transfer belt 8 is adjusted during post-rotation, but the current balance of the intermediate transfer belt 8 can also be adjusted when no image is being formed. For example, the current balance of the intermediate transfer belt 8 may be adjusted during pre-rotation or downtime (a period when no image is being formed due to other adjustment controls such as image density control), or these may be used in combination.

[0107] In addition, in the above-described embodiment, in order to increase the frictional force, the current balance is biased to the positive side, causing cations to deposit on the outer surface of the intermediate transfer belt 8, but it may also be biased to the negative side, causing anions to deposit on the outer surface of the intermediate transfer belt 8.

[0108] In the above-described embodiment, a voltage is applied to the secondary transfer roller (outer secondary transfer roller) as the secondary transfer member, and the driving roller (inner secondary transfer roller) as the opposing member is electrically grounded. However, this is not limited to this. The inner secondary transfer roller can be used as the secondary transfer member and a voltage can be applied to it, and the outer secondary transfer roller can be used as the opposing member and electrically grounded. In this case, during the secondary transfer process, a secondary transfer voltage of the same polarity as the normal charging polarity of the toner can be applied to the inner secondary transfer roller. Even in this configuration, the voltage applied to the inner secondary transfer roller can be controlled to increase or decrease the current balance.

[0109] In the above embodiment, the current balance adjustment is performed by selecting one of three modes: a normal mode, a current balance increasing mode, and a current balance decreasing mode. However, the present invention is not limited to this. For example, multiple thresholds for the current balance, environment, or torque may be set, and at least one of the current balance increasing mode and the current balance decreasing mode may be a multiple-stage mode with different amounts of current balance adjustment.

[0110] Furthermore, when the cleaning member is a cleaning blade, the cleaning performance is likely to be reduced and abnormal noise is likely to be generated due to changes in the frictional force between the cleaning member and the intermediate transfer member, and the effects of the present invention are particularly pronounced. However, the present invention is not limited to cases where the cleaning member is a blade-shaped member, but can be applied to any form of cleaning member in which the above-mentioned problems may occur due to changes in the frictional force between the cleaning member and the intermediate transfer member due to changes in the environment, etc. Examples of such cleaning members in other forms include pad-shaped, sheet-shaped, and brush-shaped members. [Explanation of symbols]

[0111] 1 Photosensitive drum 6 Primary transfer roller 8 Intermediate transfer belt 11 Secondary transfer roller 21 Cleaning blade 60 Primary transfer power supply 61 Primary transfer current detection circuit 62 Secondary transfer power supply 63 Secondary transfer current detection circuit 100 Image forming device 150 control section

Claims

1. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; an environment detection unit that detects at least one of the temperature and humidity of the environment; a control unit that controls, based on the detection result of the environment detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and When at least one of the temperature and humidity indicated by the detection result of the environment detection unit is lower than that of a predetermined environment, the control unit controls to increase the absolute value of the current balance based on the current balance over a predetermined period in the past. The image forming apparatus is characterized by the above.

2. The image forming apparatus according to claim 1, characterized in that the control unit controls the absolute value of the current balance to increase when at least one of the temperature or humidity detected by the environmental detection unit is lower than that of a predetermined environment and the absolute value of the current balance during a predetermined period in the past is smaller than a predetermined value.

3. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; an environment detection unit that detects at least one of the temperature and humidity of the environment; a control unit that controls, based on the detection result of the environment detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and the control unit controls the current balance so as to increase an absolute value thereof based on whether the mode is a full-color mode or a monochrome mode when at least one of the temperature and humidity indicated by the detection result of the environment detection unit is lower than that of a predetermined environment. The image forming apparatus is characterized by the above.

4. The image forming apparatus according to claim 3, wherein the control unit controls the current balance to increase its absolute value when at least one of the temperature and humidity detected by the environment detection unit is lower than that of a predetermined environment and the image forming apparatus is in monochrome mode.

5. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; an environment detection unit that detects at least one of the temperature and humidity of the environment; a control unit that controls, based on the detection result of the environment detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and When at least one of the temperature and humidity indicated by the detection result of the environment detection unit is higher than that of a predetermined environment, the control unit controls to reduce the absolute value of the current balance based on the current balance over a predetermined period in the past. The image forming apparatus is characterized by the above.

6. The image forming apparatus according to claim 5, wherein the control unit controls the absolute value of the current balance to decrease when at least one of the temperature or humidity detected by the environmental detection unit is higher than that of a predetermined environment and the absolute value of the current balance during a predetermined period in the past is greater than a predetermined value.

7. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; an environment detection unit that detects at least one of the temperature and humidity of the environment; a control unit that controls, based on the detection result of the environment detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and When at least one of the temperature and humidity detected by the environment detection unit is higher than that of a predetermined environment, the control unit controls the absolute value of the current balance to be reduced based on whether the mode is a full-color mode or a monochrome mode. The image forming apparatus is characterized by the above.

8. The image forming apparatus according to claim 7, wherein the control unit controls the current balance to reduce its absolute value when at least one of the temperature and humidity detected by the environmental detection unit is higher than that of a predetermined environment and when in full-color mode.

9. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; a torque detection unit that detects the rotation torque of a motor that drives the intermediate transfer body; a control unit that controls, based on a detection result of the torque detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and the control unit controls the current balance to increase an absolute value when the rotational torque of the motor indicated by the detection result of the torque detection unit is smaller than a predetermined value. An image forming apparatus characterized by:

10. An image carrier that carries a toner image; an ionically conductive rotatable endless belt-like intermediate transfer member; a primary transfer member that primarily transfers a toner image from the image carrier to the intermediate transfer member at a primary transfer section; a secondary transfer member that transfers the toner image from the intermediate transfer body to a recording material at a secondary transfer portion; a cleaning member that comes into contact with the outer surface of the intermediate transfer body to remove deposits from the outer surface of the intermediate transfer body; a torque detection unit that detects the rotation torque of a motor that drives the intermediate transfer body; a control unit that controls, based on a detection result of the torque detection unit, to change a current balance based on an integrated value of a current flowing from the inside to the outside of the intermediate transfer body and a current flowing from the outside to the inside of the intermediate transfer body; and the control unit controls the current balance to decrease an absolute value when the rotational torque of the motor indicated by the detection result of the torque detection unit is greater than a predetermined value. An image forming apparatus characterized by:

11. 11. The image forming apparatus according to claim 1, wherein the control unit controls a secondary transfer voltage application unit that applies voltage to the secondary transfer member during a period when the secondary transfer unit is not transferring a toner image from the intermediate transfer body to the recording material, thereby changing the current balance.

12. 11. The image forming apparatus according to claim 1, wherein the control unit controls a primary transfer voltage application unit that applies voltage to the primary transfer member during a period when the primary transfer unit is not transferring a toner image from the image carrier to the intermediate transfer member, thereby changing the current balance.

13. 13. The image forming apparatus according to claim 1, wherein the intermediate transfer member contains an alkali metal salt as an ion-conductive material that exhibits the ion conductivity.

14. 14. The image forming apparatus according to claim 1, wherein the cleaning member is a cleaning blade that faces in a counter direction to a rotation direction of the intermediate transfer body and abuts against the outer surface of the intermediate transfer body.

Images