Image forming apparatus and setting method

Abstract

To provide an image forming apparatus capable of suppressing a decrease in fluidity of toner, and a setting method.SOLUTION: An image forming apparatus includes a developing roller 44 that conveys a one component developer containing a toner and fluorocarbon resin particles to an opposing region R1 and supplies the toner conveyed to the opposing region R1 to a photosensitive drum 31 in response to application of a developing bias voltage containing an alternating-current voltage, a layer thickness regulating blade 45 that comes into contact with a developer layer formed on an outer circumferential surface of the developing roller 44 and regulates a layer thickness of the developer layer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a setting method. [Background technology]

[0002] Image forming devices that form an image on a sheet using a single-component developer are known. This type of image forming device includes an image carrier, a developing member, and a regulating member. An electrostatic latent image is formed on the image carrier. The developing member is rotatably disposed in a position facing the image carrier, transports the single-component developer to a facing region facing the image carrier, and supplies the toner contained in the single-component developer transported to the facing region to an exposed region included in the electrostatic latent image formed on the image carrier in response to application of a development bias voltage. The regulating member contacts a developer layer formed on the outer peripheral surface of the developing member by the single-component developer to regulate the thickness of the developer layer.

[0003] Also, there is known a one-component developer containing an external additive to improve the fluidity of the toner, such as polytetrafluoroethylene fine particles, which are charged with a polarity opposite to that of the toner, as the external additive (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-180910 Summary of the Invention [Problem to be solved by the invention]

[0005] In the developer layer, the fluororesin particles may separate from the toner, and the separated fluororesin particles may move to non-exposed areas of the electrostatic latent image. When a large number of the fluororesin particles move to the non-exposed areas, the proportion of the toner from which the fluororesin particles have separated increases in the developer layer, and the fluidity of the toner in the developer layer decreases. When the fluidity of the toner in the developer layer decreases, the load on the toner at the contact point between the developer layer and the regulating member increases, and the toner becomes more susceptible to deterioration.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a setting method that can suppress a decrease in the fluidity of toner. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus includes an image carrier, a developing member, a regulating member, a drive unit, an acquisition processing unit, and a setting processing unit. An electrostatic latent image is formed on the image carrier. The developing member is rotatably disposed opposite the image carrier and transports a single-component developer containing toner and fluororesin particles charged with an opposite polarity to the toner to a facing region facing the image carrier. The toner transported to the facing region is supplied to an exposure region included in the electrostatic latent image formed on the image carrier in response to application of a development bias voltage containing an AC component. The regulating member contacts a developer layer formed on the outer peripheral surface of the developing member by the single-component developer to regulate the thickness of the developer layer. The drive unit rotates the developing member. The acquisition processing unit acquires a related value related to the torque applied to the rotation shaft of the developing member while the drive unit is operating. The setting processing unit sets the frequency of the AC component based on the related value acquired by the acquisition processing unit.

[0008] According to another aspect of the present invention, a setting method is implemented in an image forming apparatus including an image carrier on which an electrostatic latent image is formed, a developing member rotatably disposed opposite the image carrier, transporting a single-component developer containing toner and fluororesin particles charged to the opposite polarity to the toner to a facing region facing the image carrier, and supplying the toner transported to the facing region to an exposure region included in the electrostatic latent image formed on the image carrier in response to application of a developing bias voltage containing an AC component, a regulating member contacting a developer layer formed on the outer peripheral surface of the developing member by the single-component developer to regulate the thickness of the developer layer, and a drive unit rotating the developing member. The setting method includes an acquiring step and a setting step. In the acquiring step, a related value related to the torque applied to a rotation shaft of the developing member while the drive unit is operating is acquired. In the setting step, the frequency of the AC component is set based on the related value acquired in the acquiring step. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress a decrease in the fluidity of the toner. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the system configuration of the image forming apparatus according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing the configuration of an image forming unit of the image forming apparatus according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing an example of the related value acquisition process executed in the image forming apparatus according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of the first frequency setting process executed in the image forming apparatus according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a block diagram showing the system configuration of an image forming apparatus according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart showing an example of a second frequency setting process executed in the image forming apparatus according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0012] [First embodiment] First, the configuration of an image forming apparatus 100A according to a first embodiment of the present invention will be described with reference to FIGS.

[0013] For ease of explanation, the vertical direction in the installation state where image forming apparatus 100A is usable (the state shown in FIG. 1) is defined as up-down direction D1. Also, the front-rear direction D2 is defined with the left side of image forming apparatus 100A in the plane of the drawing shown in FIG. 1 as the front (front face). Also, the left-right direction D3 is defined with the front face of image forming apparatus 100A in the installation state as the reference point.

[0014] Image forming apparatus 100A has a printing function that forms an image on a sheet by electrophotography. Specifically, image forming apparatus 100A is a printer that has the printing function. Note that the present invention may also be applied to image forming apparatuses such as fax machines, copy machines, and multifunction peripherals that are capable of forming an image on a sheet by electrophotography.

[0015] The image forming apparatus 100A can perform an image forming process to form an image on a sheet at any one of a plurality of predetermined image forming speeds. For example, the image forming apparatus 100A can perform the image forming process at any one of the fastest first image forming speed, the second image forming speed, and the slowest third image forming speed.

[0016] As shown in FIGS. 1 and 2, the image forming apparatus 100A includes an image forming unit 1, a sheet conveying unit 2, an operation display unit 3, a storage unit 4, and a control unit 5.

[0017] The image forming unit 1 realizes the printing function. Specifically, the image forming unit 1 forms a color or monochrome image on a sheet fed from the sheet conveying unit 2 in accordance with an electrophotographic method.

[0018] The sheet transport unit 2 transports the sheet along a sheet transport path passing through an image formation position by the image forming unit 1. The sheet transport unit 2 includes a paper feed cassette, a manual feed tray, and a plurality of transport rollers.

[0019] The operation display unit 3 is a user interface of the image forming apparatus 100A. The operation display unit 3 has a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 5. Specifically, the display unit is a display device such as a liquid crystal display. The operation unit inputs various information to the control unit 5 in response to user operations. Specifically, the operation unit is an operation device such as an operation key or a touch panel.

[0020] The storage unit 4 is a non-volatile storage device, such as a flash memory.

[0021] The control unit 5 performs overall control of the image forming apparatus 100A. As shown in FIG. 2, the control unit 5 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 11 to execute various types of processing. The RAM 13 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11. The CPU 11 performs overall control of the image forming apparatus 100A by executing the various control programs that are stored in advance in the ROM 12.

[0022] The control unit 5 may be a control unit provided separately from a main control unit that performs overall control of the image forming apparatus 100A. The control unit 5 may also be configured with an electronic circuit such as an integrated circuit (ASIC).

[0023] [Configuration of image forming unit 1] Next, the configuration of the image forming section 1 will be described with reference to Figures 1 to 3. Here, Figure 3 is a cross-sectional view showing the configuration of the image forming unit 24.

[0024] As shown in FIG. 1, the image forming section 1 includes a plurality of image forming units 21 to 24, an optical scanning device 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29.

[0025] Image forming unit 21 forms a Y (yellow) toner image. Image forming unit 22 forms a C (cyan) toner image. Image forming unit 23 forms an M (magenta) toner image. Image forming unit 24 forms a K (black) toner image. As shown in FIG. 1, image forming units 21 to 24 are arranged side by side in the order of yellow, cyan, magenta, and black from the front side of image forming apparatus 100A along the front-rear direction D2 of image forming apparatus 100A.

[0026] 3, the image forming unit 24 includes a photosensitive drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, and a drum cleaning unit 35. Each of the image forming units 21 to 23 has the same configuration as the image forming unit 24.

[0027] An electrostatic latent image is formed on the surface of the photosensitive drum 31. For example, the photosensitive drum 31 has a photosensitive layer made of amorphous silicon. The photosensitive drum 31 receives a rotational driving force supplied from a motor (not shown) and rotates in a rotation direction D4 shown in FIG. 3. This causes the photosensitive drum 31 to transport the electrostatic latent image formed on its surface. The photosensitive drum 31 is an example of an image carrier of the present invention. The photosensitive layer may be formed of other photosensitive materials, such as an organic photosensitive material.

[0028] A preset charging voltage is applied to the charging roller 32, which charges the surface of the photosensitive drum 31. For example, the charging roller 32 charges the surface of the photosensitive drum 31 to a positive polarity. The surface of the photosensitive drum 31 charged by the charging roller 32 is irradiated with light based on image data emitted from the optical scanning device 25. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

[0029] The developing device 33 uses a one-component developer containing toner to develop the electrostatic latent image formed on the surface of the photosensitive drum 31. As a result, a toner image is formed on the surface of the photosensitive drum 31.

[0030] The primary transfer roller 34 transfers the toner image formed on the surface of the photosensitive drum 31 by the developing device 33 onto the intermediate transfer belt 26 .

[0031] The drum cleaning unit 35 removes the toner remaining on the surface of the photosensitive drum 31 after the toner image has been transferred by the primary transfer roller 34 .

[0032] The image forming section 1 includes a developer container 36 (see FIG. 1) corresponding to each of the image forming units 21 to 24. The image forming section 1 also includes a motor 37 (see FIG. 2) and a voltage application section 38 (see FIG. 2) corresponding to each of the image forming units 21 to 24.

[0033] Here, a description will be given of the developer container 36, the motor 37, and the voltage application section 38 corresponding to the image forming unit 24. Note that the motor 37 and the voltage application section 38 corresponding to the image forming unit 24 are shown in FIG.

[0034] The developer container 36 accommodates the one-component developer of K (black). The developer container 36 also supplies the one-component developer of K (black) to the developing device 33. Specifically, a conveying screw is provided inside the developer container 36 to convey the one-component developer to a discharge port that leads to the outside of the developer container 36. The conveying screw rotates upon receiving a rotational driving force supplied from a motor (not shown), and conveys the one-component developer accommodated inside the developer container 36 to the discharge port. The one-component developer discharged from the discharge port is supplied to the developing device 33 via a supply path (not shown).

[0035] The motor 37 rotates the developing roller 44 (see FIG. 3) of the developing device 33. The motor 37 is an example of the driving unit of the present invention.

[0036] The voltage application unit 38 is a power source that applies a predetermined development bias voltage to the development roller 44 (see FIG. 3) of the development device 33. Specifically, the development bias voltage is a voltage including a DC component and an AC component. For example, the DC component is a DC voltage having a positive polarity. The AC component is an AC voltage that is a square wave and has a preset amplitude, duty ratio, and frequency.

[0037] The optical scanning device 25 emits light based on image data toward the surface of the photosensitive drum 31 of each of the image forming units 21-24.

[0038] The intermediate transfer belt 26 is an endless belt member onto which the toner images formed on the surfaces of the photosensitive drums 31 of the image forming units 21 to 24 are transferred. The intermediate transfer belt 26 is stretched with a predetermined tension by a drive roller and a tension roller. The intermediate transfer belt 26 rotates in a rotation direction D5 shown in FIGS. 1 and 3 as the drive roller rotates upon receiving a rotational driving force supplied from a motor (not shown).

[0039] The secondary transfer roller 27 transfers the toner image transferred onto the surface of the intermediate transfer belt 26 onto a sheet fed from the sheet conveying unit 2 .

[0040] The fixing device 28 fixes the toner image transferred onto the sheet by the secondary transfer roller 27 onto the sheet.

[0041] The sheet on which the toner image has been fixed by the fixing device 28 is discharged onto the paper discharge tray 29.

[0042] [Configuration of developing device 33] Next, the configuration of the developing device 33 of the image forming unit 24 will be described with reference to Fig. 3. The developing device 33 of each of the image forming units 21 to 23 also has the same configuration as the developing device 33 described below.

[0043] As shown in FIG. 3, the developing device 33 includes a housing 41, an agitating member 42, a supply roller 43, a developing roller 44, and a layer thickness regulating blade 45.

[0044] 3, the housing 41 accommodates an agitating member 42, a supply roller 43, a developing roller 44, and a layer thickness regulating blade 45. The housing 41 also accommodates the one-component developer.

[0045] Here, the one-component developer used for forming an image in the image forming apparatus 100A will be described.

[0046] The one-component developer contains the non-magnetic toner and an external additive. The external additive contains silica particles and fluororesin particles. The fluororesin particles are charged with a polarity opposite to that of the toner. Specifically, the toner is charged with a positive polarity. The fluororesin particles are charged with a negative polarity.

[0047] The silica particles are added to improve the fluidity of the toner. The silica particles are preferably surface-treated to impart positive charging properties. The number-average primary particle diameter of the silica particles is preferably 10 nm (nanometers) or more and 40 nm (nanometers) or less. When the number-average primary particle diameter of the silica particles is 10 nm (nanometers) or more, embedding of the silica particles in the toner base particles is suppressed. When the number-average primary particle diameter of the silica particles is 40 nm (nanometers) or less, detachment of the silica particles from the toner base particles is suppressed.

[0048] The fluororesin particles are, for example, polytetrafluoroethylene (hereinafter referred to as "PTFE"), perfluoroalkoxy fluororesin, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, or tetrafluoroethylene-perfluoroalkoxyethylene copolymer. The fluororesin particles are preferably PTFE.

[0049] The number average particle size of the fluororesin particles is preferably 100 to 300 nm (nanometers), where the number average particle size of the fluororesin particles is calculated by averaging the particle sizes of primary particles measured from a scanning electron microscope photograph.

[0050] When the fluororesin particles are PTFE, the PTFE is preferably particles having a nearly spherical shape produced by emulsion polymerization. Examples of such commercially available products include "KTL-500F" (Kitamura Co., Ltd., number average particle size 300 nm (nanometers)), "Lubron L2" (Daikin Industries, Ltd., number average particle size 300 nm (nanometers)), "Lubron L5" (Daikin Industries, Ltd., number average particle size 200 nm (nanometers)), "Fluon Lubricant L170J" (Asahi ICI Fluoropolymers Co., Ltd., number average particle size 100 nm (nanometers)), and "Fluon Lubricant L1 Examples of such fluoropolymers include "72J" (manufactured by Asahi ICI Fluoropolymers Co., Ltd., number average particle size 0.1 μm (micrometers)), "MP-1100" (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd., number average particle size 200 nm (nanometers)), "MP-1200" (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd., number average particle size 300 nm (nanometers)), and "TLP-10F-1" (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd., number average particle size 200 nm (nanometers)).

[0051] The amount of the silica particles added is preferably 0.5 to 2.5 parts by weight, and more preferably 1.0 to 2.0 parts by weight, per 100 parts by weight of toner. The amount of the fluororesin particles added is preferably 0.05 to 1.00 parts by weight, and more preferably 0.1 to 0.8 parts by weight, per 100 parts by weight of toner. The amounts of the silica particles and the fluororesin particles added may be adjusted as appropriate to adjust the chargeability and fluidity of the toner.

[0052] The stirring member 42 stirs the one-component developer contained in the housing 41 and transports the one-component developer to the supply roller 43 side.

[0053] Supply roller 43 supplies the single-component developer to development roller 44. Supply roller 43 is rotatably provided at a position where it contacts development roller 44. Supply roller 43 receives a rotational driving force supplied from motor 37 and rotates in a rotation direction D6 shown in FIG.

[0054] The developing roller 44 is rotatably disposed in a position facing the photosensitive drum 31. Specifically, the developing roller 44 is disposed so as not to come into contact with the photosensitive drum 31. For example, the developing roller 44 includes a roller main body made of silicone rubber and a surface layer formed on the outer periphery of the roller main body by urethane. The developing roller 44 receives a rotational driving force supplied from the motor 37 and rotates in a rotation direction D7 shown in FIG. 3.

[0055] Developing roller 44 transports the one-component developer supplied from supply roller 43 to a facing region R1 (see FIG. 3) facing photosensitive drum 31. In response to application of the developing bias voltage, developing roller 44 supplies the toner transported to facing region R1 to an exposed region (region irradiated with light emitted from optical scanning device 25) included in the electrostatic latent image formed on photosensitive drum 31. Developing roller 44 is an example of a developing member of the present invention.

[0056] When the image formation process is performed at the first image formation speed, the developing roller 44 is rotated at a first speed corresponding to the first image formation speed. When the image formation process is performed at the second image formation speed, the developing roller 44 is rotated at a second speed corresponding to the second image formation speed. When the image formation process is performed at the third image formation speed, the developing roller 44 is rotated at a third speed corresponding to the third image formation speed.

[0057] The layer thickness regulating blade 45 comes into contact with the developer layer formed on the outer peripheral surface of the developing roller 44 by the one-component developer to regulate the thickness of the developer layer. For example, the layer thickness regulating blade 45 is a leaf spring made of SUS. The regulating pressure of the layer thickness regulating blade 45 is preferably 15 to 40 N / m (Newtons per meter). If the regulating pressure of the layer thickness regulating blade 45 is less than 15 N / m (Newtons per meter), the toner cannot be regulated. If the regulating pressure of the layer thickness regulating blade 45 exceeds 40 N / m (Newtons per meter), the frictional force generated between the toner and the layer thickness regulating blade 45 becomes strong, resulting in a thinner layer thickness of the developer layer. The layer thickness regulating blade 45 is an example of a regulating member of the present invention.

[0058] In the developer layer, the fluororesin particles may separate from the toner, and the separated fluororesin particles may move to non-exposed regions (regions not irradiated with light emitted from the optical scanning device 25) included in the electrostatic latent image. When a large number of the fluororesin particles move to the non-exposed regions, the proportion of the toner from which the fluororesin particles have separated increases in the developer layer, and the fluidity of the toner in the developer layer decreases. When the fluidity of the toner in the developer layer decreases, the load on the toner at the contact point between the developer layer and the layer thickness regulating blade 45 increases, and the toner becomes more susceptible to deterioration.

[0059] In contrast to this, in the image forming apparatus 100A according to the first embodiment of the present invention, it is possible to suppress the decrease in the fluidity of the toner, as will be described below.

[0060] [Configuration of control unit 5] Next, the configuration of the control unit 5 will be described with reference to FIG.

[0061] As shown in FIG. 2, the control unit 5 includes a rotation processing unit 51, an acquisition processing unit 52, and a setting processing unit 53A.

[0062] Specifically, an operation control program for causing the CPU 11 to function as each of the above-mentioned processing units is stored in advance in the ROM 12 of the control unit 5. The CPU 11 functions as each of the above-mentioned processing units by executing the operation control program stored in the ROM 12. Note that some or all of the processing units included in the control unit 5 may be configured with electronic circuits. The operation control program may also be a program for causing multiple processors to function as each of the processing units included in the control unit 5.

[0063] In the following, of the image forming units 21 to 24, the description will be given taking as an example the various parts included in the image forming unit 24 and the various parts provided corresponding to the image forming unit 24. The following description also applies to each of the image forming units 21 to 23.

[0064] After the image forming process is completed, the rotation processing unit 51 executes a rotation process in which the motor 37 is used to rotate the developing roller 44 at a predetermined specific speed.

[0065] For example, the specific speed is different from any of the first speed, the second speed, and the third speed. For example, the specific speed is faster than the first speed. Note that the specific speed may be the same as any of the first speed, the second speed, and the third speed.

[0066] The acquisition processing unit 52 acquires a related value relating to the torque applied to the rotation shaft of the developing roller 44 while the motor 37 is being driven.

[0067] For example, the acquisition processing unit 52 acquires the associated value during the execution of the rotation process.

[0068] For example, the acquisition processing unit 52 acquires, as the related value, the current value of the current flowing through the motor 37. The current value of the current flowing through the motor 37 may be acquired using an ammeter or the like.

[0069] The image forming apparatus 100A may be provided with a torque meter capable of measuring the torque applied to the rotation shaft of the developing roller 44. In this case, the acquisition processing unit 52 may acquire the measurement value measured by the torque meter as the related value.

[0070] The acquisition processing unit 52 may acquire the associated value during the execution of the image formation process. In this case, the acquisition processing unit 52 may correct the acquired associated value using a correction coefficient determined for each image formation speed.

[0071] The setting processing unit 53A sets the frequency of the AC component included in the developing bias voltage based on the associated value acquired by the acquisition processing unit 52.

[0072] For example, when the related value is equal to or less than a predetermined first threshold, the setting processing unit 53A sets the frequency of the AC component to a predetermined reference value, and when the related value exceeds the first threshold, the setting processing unit 53A sets the frequency of the AC component to within a specific range equal to or greater than the reference value.

[0073] Here, the first threshold value is a value for determining whether the fluidity of the toner contained in the developer layer has decreased below a predetermined level. The first threshold value may be a value determined at the time of manufacturing the image forming apparatus 100A, or may be set based on the related value obtained during the first execution of the rotation process after the image forming apparatus 100A is shipped from the factory.

[0074] The reference value may be set arbitrarily so that the image quality of the image formed on the sheet using the image forming unit 1 reaches a desired level.

[0075] For example, when the related value exceeds the first threshold value, the setting processing unit 53A sets the frequency of the AC component within the specific range based on the printing rate of the image to be formed.

[0076] For example, in the image forming apparatus 100A, table data indicating the correspondence relationship between the printing rate and frequency is stored in advance in the storage unit 4. For example, in the table data, frequencies corresponding to printing rates of 50 to 100% (percent) are defined as the reference values. In addition, in the table data, frequencies corresponding to printing rates of 0 to 50% (percent) are defined as predetermined specific values. The specific values ​​are higher than the reference values ​​and are values ​​that prevent (or sufficiently suppress) the migration of the fluororesin particles separated from the toner to the non-exposed region. By increasing the frequency of the AC component only when the printing rate is low, at which the outflow of the fluororesin particles from the developer layer is likely to occur, it is possible to suppress the outflow of the fluororesin particles from the developer layer while suppressing the effect of frequency change on image quality.

[0077] For example, when the image forming process is executed and the related value last acquired by the acquisition processing unit 52 is less than or equal to the first threshold value, the setting processing unit 53A sets the frequency of the AC component to the reference value.

[0078] Furthermore, when the image forming process is executed and the related value last acquired by the acquisition processing unit 52 exceeds the first threshold, the setting processing unit 53A acquires the printing rate based on the image data used to form the image. For example, when multiple images are formed in the image forming process, the setting processing unit 53A acquires the average value of the printing rate for each image.

[0079] Furthermore, the setting processing unit 53A uses the table data to identify the value of the frequency corresponding to the acquired printing rate.

[0080] Then, the setting processing unit 53A sets the frequency of the AC component to a value specified using the table data.

[0081] It should be noted that the setting processing unit 53A may set the frequency of the AC component within the specific range based on the printing rate of the image each time an image is formed in the image forming process.

[0082] Furthermore, in the table data, the correspondence relationship between the printing rate and the frequency may be defined such that the frequency increases from the specific value as the printing rate decreases from 100% (percent).

[0083] Furthermore, the setting processing unit 53A may use a predetermined calculation formula instead of the table data to obtain the value of the frequency corresponding to the printing rate.

[0084] In addition, when the image formation process is executed and the related value last acquired by the acquisition processing unit 52 exceeds the first threshold value, the setting processing unit 53A may set the frequency of the AC component to the specific value.

[0085] Below, an example of the procedure of each process executed by the control unit 5 and the setting method of the present invention will be described.

[0086] [Related value acquisition process] First, an example of the procedure of the related value acquisition process executed by the control unit 5 in the image forming apparatus 100A will be described with reference to Fig. 4. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 5. The related value acquisition process is executed when the image forming process is completed.

[0087] <Step S11> First, in step S11, the control unit 5 executes the rotation process. The process of step S11 is executed by the rotation processing unit 51 of the control unit 5.

[0088] <Step S12> In step S12, the control unit 5 acquires the associated value related to the torque applied to the rotation shaft of the developing roller 44. The processing of step S12 is an example of an acquisition step of the present invention, and is executed by the acquisition processing unit 52 of the control unit 5.

[0089] Specifically, the control unit 5 acquires the current value of the current flowing through the motor 37 as the related value.

[0090] <Step S13> In step S13, the control unit 5 stores the associated value acquired in the process of step S12 in the storage unit 4.

[0091] Specifically, the control unit 5 adds date and time information indicating the current date and time to the association value acquired in the process of step S12, and stores the association value with the added date and time information in the storage unit 4.

[0092] [First frequency setting process] Next, an example of the procedure of the first frequency setting process executed by the control unit 5 in the image forming apparatus 100A will be described with reference to Fig. 5. Note that the first frequency setting process is executed before the start of the image forming process when the image forming process is to be started.

[0093] <Step S21> First, in step S21, the control unit 5 determines whether the last acquired association value is equal to or less than the first threshold value.

[0094] If the control unit 5 determines that the last acquired association value is equal to or less than the first threshold value (Yes in S21), the control unit 5 shifts the process to step S22. If the last acquired association value is not equal to or less than the first threshold value (No in S21), the control unit 5 shifts the process to step S23.

[0095] <Step S22> In step S22, the control unit 5 sets the frequency of the AC component to the reference value.

[0096] Specifically, the control unit 5 sends a control signal to the voltage application unit 38 to set the frequency of the AC component to the reference value.

[0097] <Step S23> In step S23, the control unit 5 obtains the printing rate based on the image data used to form the image.

[0098] <Step S24> In step S24, the control unit 5 uses the table data to identify the value of the frequency corresponding to the printing rate acquired in the process of step S23.

[0099] <Step S25> In step S25, the control unit 5 sets the frequency of the AC component to the value identified by the process of step S24. The processes from step S21 to step S25 are an example of a setting step of the present invention, and are executed by the setting processing unit 53A of the control unit 5.

[0100] Specifically, the control unit 5 transmits a control signal to the voltage application unit 38 to set the frequency of the AC component to the value specified by the process in step S24.

[0101] In this way, the image forming apparatus 100A acquires the related value related to the torque applied to the rotation shaft of the developing roller 44 while the motor 37 is running. When the fluidity of the toner decreases, the frictional force acting between the developer layer and the layer thickness regulating blade 45 increases, thereby increasing the torque applied to the rotation shaft of the developing roller 44. Therefore, the related value can be said to reflect the fluidity of the toner. The image forming apparatus 100A then sets the frequency of the AC component included in the developing bias voltage based on the acquired related value. This allows the frequency of the AC component to be increased when the fluidity of the toner is low, thereby suppressing the outflow of the fluororesin particles from the developer layer and thereby increasing the fluidity of the toner. Therefore, the image forming apparatus 100A can suppress a decrease in the fluidity of the toner.

[0102] Furthermore, in image forming apparatus 100A, when the related value is equal to or less than the first threshold, the frequency of the AC component is set to the reference value, and when the related value exceeds the first threshold, the frequency of the AC component is set to within the specific range equal to or greater than the reference value, thereby making it possible to prevent the fluidity of the toner from decreasing beyond a level corresponding to the first threshold.

[0103] Furthermore, in the image forming apparatus 100A, when the related value exceeds the first threshold, the frequency of the AC component is set within the specific range based on the printing rate of the image to be formed. This makes it possible to increase the frequency of the AC component only when the printing rate is low, at which the fluororesin particles are likely to flow out of the developer layer. Therefore, it is possible to suppress the influence of frequency change on image quality while suppressing a decrease in the fluidity of the toner.

[0104] Furthermore, in image forming apparatus 100A, the related value is acquired during the execution of the rotation process, which is executed after the end of the image formation process. This eliminates the need to correct the related value depending on the image formation speed, compared to a configuration in which the related value is acquired during the execution of the image formation process, and therefore simplifies the process of acquiring the related value.

[0105] [Second embodiment] Hereinafter, an image forming apparatus 100B according to a second embodiment of the present invention will be described with reference to FIG.

[0106] 2 and 6, image forming apparatus 100B differs from image forming apparatus 100A in that it includes setting processing unit 53B instead of setting processing unit 53A. Note that other points are common to image forming apparatus 100A and image forming apparatus 100B. Below, only the points of the configuration of image forming apparatus 100B that are different from image forming apparatus 100A will be described.

[0107] The setting processing unit 53B sets the frequency of the AC component to the reference value until a first timing arrives at which the related value decreases beyond a predetermined second threshold and then increases beyond the second threshold, and after the first timing arrives, the setting processing unit 53B sets the frequency of the AC component within the specific range until a predetermined second timing arrives.

[0108] In the developing device 33, before the fluidity of the toner decreases due to the outflow of the fluororesin particles from the developer layer, the fluidity of the toner temporarily increases due to separation of the toner and the fluororesin particles contained in the developer layer. In other words, before the related value increases due to the outflow of the fluororesin particles from the developer layer, the related value temporarily decreases due to separation of the toner and the fluororesin particles contained in the developer layer.

[0109] The second threshold value is a value for determining whether a temporary decrease in the associated value has occurred due to separation of the toner contained in the developer layer from the fluororesin particles before the associated value increases due to the outflow of the fluororesin particles from the developer layer. Specifically, the second threshold value is a value lower than the first threshold value. The second threshold value is also a value lower than the associated value when the fluidity of the toner contained in the developer layer is at a desirable level. In other words, when the associated value is lower than the second threshold value, the fluidity of the toner is higher than normal.

[0110] For example, the second timing may be a timing when the number of printed sheets since the first timing arrives reaches a predetermined number, or may be a timing when the driving time of the developing device 33 since the first timing arrives reaches a predetermined time.

[0111] For example, after the first timing arrives, the setting processing unit 53B sets the frequency of the AC component within the specific range based on the printing rate of the image to be formed until the second timing arrives.

[0112] For example, after the first timing arrives, the setting processing unit 53B sets the frequency of the AC component within the specific range using the table data until the second timing arrives.

[0113] [Second frequency setting process] An example of the procedure of the second frequency setting process executed by the control unit 5 in the image forming apparatus 100B will be described below with reference to Fig. 7. Note that the second frequency setting process is executed before the start of the image forming process when the image forming process is to be started.

[0114] <Step S31> First, in step S31, the control unit 5 determines whether or not the first timing has arrived after the setting of the last reference timing, which is set in the process of step S33, which will be described later.

[0115] Specifically, the control unit 5 determines whether the first timing has arrived after the last reference timing was set based on the multiple associated values ​​to which the date and time information stored in the memory unit 4 has been added.

[0116] Here, if the control unit 5 determines that the first timing has arrived after the last reference timing was set (Yes in S31), the control unit 5 shifts the process to step S32. On the other hand, if the first timing has not arrived after the last reference timing was set (No in S31), the control unit 5 shifts the process to step S34.

[0117] <Step S32> In step S32, the control unit 5 determines whether the second timing has arrived.

[0118] Specifically, the control unit 5 determines that the second timing has arrived when the number of printed sheets since the last arrival of the first timing has reached a predetermined number.

[0119] Here, if the control unit 5 determines that the second timing has arrived (Yes in S32), it shifts the process to step S33. On the other hand, if the second timing has not arrived (No in S32), it shifts the process to step S35.

[0120] <Step S33> In step S33, the control unit 5 sets the current date and time as the reference timing.

[0121] <Step S34> In step S34, the control unit 5 sets the frequency of the AC component to the reference value.

[0122] <Step S35> In step S35, the control unit 5 acquires the printing rate based on the image data used to form the image.

[0123] <Step S36> In step S36, the control unit 5 uses the table data to identify the value of the frequency corresponding to the printing rate acquired in the process of step S35.

[0124] <Step S37> In step S37, the control unit 5 sets the frequency of the AC component to the value identified by the process of step S36. The processes from step S31 to step S37 are another example of the setting step of the present invention, and are executed by the setting processing unit 53B of the control unit 5.

[0125] In this way, in the image forming apparatus 100B, the frequency of the AC component is set within the specific range after the first timing arrives until the second timing arrives. This makes it possible to suppress the outflow of the fluororesin particles from the developer layer at a stage where the associated value temporarily decreases due to separation of the toner and the fluororesin particles contained in the developer layer before the outflow of the fluororesin particles from the developer layer occurs. In other words, it is possible to prevent the outflow of the fluororesin particles from the developer layer.

[0126] [Notes on the Invention] The following will provide an outline of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0127] <Appendix 1> an image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed; a developing member rotatably disposed at a position opposite to the image carrier, the developing member transporting a one-component developer containing toner and fluororesin particles charged with a polarity opposite to that of the toner to an opposing region facing the image carrier, and supplying the toner transported to the opposing region to an exposure region included in the electrostatic latent image formed on the image carrier in response to application of a developing bias voltage including an AC component; a regulating member contacting a developer layer formed on an outer peripheral surface of the developing member by the one-component developer to regulate the layer thickness of the developer layer; a driving unit rotating the developing member; an acquisition processing unit acquiring a related value related to the torque applied to a rotation shaft of the developing member while the driving unit is operating; and a setting processing unit setting the frequency of the AC component based on the related value acquired by the acquisition processing unit.

[0128] <Appendix 2> The image forming apparatus of claim 1, wherein the setting processing unit sets the frequency of the AC component to a predetermined reference value when the related value is equal to or less than a predetermined threshold, and sets the frequency of the AC component to within a specific range equal to or greater than the reference value when the related value exceeds the threshold.

[0129] <Appendix 3> 3. The image forming apparatus according to claim 2, wherein the setting processing unit sets the frequency of the AC component within the specific range based on the printing rate of the image to be formed when the related value exceeds the threshold value.

[0130] <Appendix 4> The image forming apparatus of claim 1, wherein the setting processing unit sets the frequency of the AC component to a predetermined reference value until a first timing arrives at which the related value decreases beyond a predetermined threshold and then increases beyond the threshold, and after the first timing arrives, sets the frequency of the AC component within a specific range equal to or greater than the reference value until a predetermined second timing arrives.

[0131] <Appendix 5> The image forming apparatus of claim 4, wherein the setting processing unit sets the frequency of the AC component within the specific range based on the printing rate of the image to be formed after the first timing arrives until the second timing arrives.

[0132] <Appendix 6> The image forming apparatus is capable of executing an image forming process to form an image on a sheet at any one of a plurality of predetermined image forming speeds, and the image forming apparatus includes a rotation processing unit that executes a rotation process to rotate the developing member at a predetermined specific speed using the drive unit after the image forming process is completed, and the acquisition processing unit acquires the related value during the execution of the rotation process.

[0133] <Appendix 7> a developing member that is rotatably disposed opposite the image carrier and transports a one-component developer containing toner and fluororesin particles charged with a polarity opposite to that of the toner to an opposing region facing the image carrier, and supplies the toner transported to the opposing region to an exposure region included in the electrostatic latent image formed on the image carrier in response to application of a developing bias voltage containing an AC component; a regulating member that contacts a developer layer formed on the outer surface of the developing member by the one-component developer to regulate the layer thickness of the developer layer; and a driving unit that rotates the developing member, the setting method comprising: an acquisition step of acquiring a related value related to the torque applied to a rotation shaft of the developing member while the driving unit is operating; and a setting step of setting the frequency of the AC component based on the related value acquired by the acquisition step. [Explanation of symbols]

[0134] 1 Image forming unit 2 Sheet transport section 3 Operation display section 4 Storage section 5. Control section 24 Image forming unit 25 Optical scanning device 26 Intermediate transfer belt 27 Secondary transfer roller 28 Fixing device 29 Paper output tray 31 Photosensitive drum 32 Charging roller 33 Developing device 34 Primary transfer roller 35 Drum Cleaning Department 36 Developer container 37 Motor 38 Voltage application section 41 Case 42 stirring member 43 Supply roller 44 Developing roller 45 Layer thickness regulation blade 51 Rotation processing section 52 Acquisition processing unit 53A Setting processing section 100A Image forming device

Claims

1. an image carrier on which an electrostatic latent image is formed; a developing member that is rotatably provided at a position facing the image carrier, that transports a one-component developer containing toner and fluororesin particles that are charged to a polarity opposite to that of the toner to an opposing region facing the image carrier, and that supplies the toner transported to the opposing region to an exposed region included in the electrostatic latent image formed on the image carrier in response to application of a developing bias voltage containing an AC component; a regulating member that comes into contact with a developer layer formed on the outer peripheral surface of the developing member by the one-component developer and regulates the thickness of the developer layer; a drive unit that rotates the developing member; an acquisition processing unit that acquires a related value related to a torque applied to a rotation shaft of the developing member while the drive unit is driving; a setting processing unit that sets a frequency of the AC component based on the associated value acquired by the acquisition processing unit; An image forming apparatus comprising:

2. the setting processing unit sets the frequency of the AC component to a predetermined reference value when the related value is equal to or less than a predetermined threshold, and sets the frequency of the AC component to within a specific range equal to or greater than the reference value when the related value exceeds the threshold. The image forming apparatus according to claim 1 .

3. the setting processing unit sets the frequency of the AC component within the specific range based on the printing rate of the image to be formed when the related value exceeds the threshold value; The image forming apparatus according to claim 2 .

4. the setting processing unit sets the frequency of the AC component to a predetermined reference value until a first timing arrives at which the related value decreases beyond a predetermined threshold and then increases beyond the threshold, and after the first timing arrives, sets the frequency of the AC component within a specific range equal to or greater than the reference value until a predetermined second timing arrives. The image forming apparatus according to claim 1 .

5. the setting processing unit sets the frequency of the AC component within the specific range based on a printing rate of an image to be formed after the first timing arrives until the second timing arrives; The image forming apparatus according to claim 4 .

6. the image forming apparatus is capable of executing an image forming process of forming an image on a sheet at any one of a plurality of predetermined image forming speeds, the image forming apparatus includes a rotation processing unit that executes a rotation process of rotating the developing member at a predetermined specific speed using the driving unit after the image forming process is completed, the acquisition processing unit acquires the associated value during execution of the rotation process.

6. The image forming apparatus according to claim 1.

7. a developing member that is rotatably disposed at a position facing the image carrier on which an electrostatic latent image is formed, and that transports a one-component developer containing toner and fluororesin particles charged to a polarity opposite to that of the toner to an opposing region facing the image carrier, and supplies the toner transported to the opposing region to an exposed region included in the electrostatic latent image formed on the image carrier in response to application of a developing bias voltage containing an AC component; a regulating member that contacts a developer layer formed on an outer peripheral surface of the developing member by the one-component developer to regulate a layer thickness of the developer layer; and a driving unit that rotates the developing member, an acquiring step of acquiring a related value related to a torque applied to a rotation shaft of the developing member while the driving unit is driving; a setting step of setting a frequency of the AC component based on the associated value acquired by the acquiring step; Including how to set it up.

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