Image forming apparatus

Abstract

An image forming apparatus includes: a plurality of developing devices accommodating different types of developer; a first replenishing member that replenishes the developer to at least one of the plurality of developing devices when the concentration of the developer in the at least one developing device is a predetermined value; a second replenishing member that replenishes the developer to the remaining developing devices when the concentration of the developer in the remaining developing devices among the plurality of developing devices is a predetermined value; and a control means for performing control for operating the first replenishment means at the same time as the operating time of the second replenishment means.

Description

Technical Field

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

[0002] Patent Document 1 listed below describes an image forming apparatus including first and second developing devices, an image density detecting member, a first replenishing member, a ratio detecting member, and a second replenishing member.

[0003] The first and second developing units contain two-component developers. The image density detecting unit detects the density of a reference toner image developed by the first developing unit. The first replenishing unit replenishes toner to the first developing unit based on the image density. The ratio detecting unit detects the ratio of toner to carrier in the second developing unit. The second replenishing unit replenishes toner to the second developing unit based on the ratio.

[0004] Furthermore, Patent Document 1 describes that the volume resistivity of the carrier of the first developing device is set lower than the volume resistivity of the carrier of the second developing device.

[0005] Patent Document 2 listed below describes an electrophotographic apparatus including a plurality of developers arranged around a single photoreceptor.

[0006] Furthermore, Patent Document 2 describes that the toner concentration of each of the developing devices is controlled by different toner concentration control means according to the color and volume of the toner accommodated in each of the developing devices.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 09-22156 (Claim 1, Figure 1 、 Figure 2 )

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 09-190069 (Claim 1, Figure 1 、 Figure 3 ) Summary of the Invention

[0009] In an image forming apparatus including a first replenishing member for replenishing developer to at least one of a plurality of developing devices and a second replenishing member for replenishing developer to the remaining developing devices, an ongoing image forming operation is interrupted by the developer replenishing operation.

[0010] The present invention provides an image forming apparatus capable of reducing the number of times that an image forming operation is interrupted due to a developer replenishment operation, compared to a case where a first replenishment member and a second replenishment member are operated independently without adjusting their respective operation timings.

[0011] A first aspect of the present invention is an image forming apparatus comprising:

[0012] a plurality of developing devices containing different types of developers;

[0013] a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when the concentration of the developer in the at least one developing device reaches a predetermined value;

[0014] a second replenishing means for replenishing the developer to the remaining developing devices among the plurality of developing devices when the concentration of the developer in the remaining developing devices reaches a predetermined value; and

[0015] The control means performs control so as to cause the first replenishing means to operate at the same timing as the operation timing of the second replenishing means.

[0016] A second aspect of the present invention is an image forming apparatus comprising:

[0017] a plurality of developing devices containing different types of developers;

[0018] a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when a result of measuring the concentration of the developer in at least one of the plurality of developing devices at a first measurement period is a predetermined value;

[0019] a second replenishing means for replenishing the developer to the remaining developing devices when a result of measuring the developer concentration in the remaining developing devices among the plurality of developing devices at a second measurement time different from the first measurement time is a predetermined value; and

[0020] The control means performs control to put the operation of the first replenishing means on standby until the second measurement period is reached.

[0021] A third aspect of the present invention is the image forming apparatus according to the first aspect,

[0022] The control means activates the first replenishing means when measuring the concentration of the developer remaining in the developing device.

[0023] A fourth aspect of the present invention is the image forming apparatus according to the second aspect,

[0024] The control means activates the first replenishing means on standby when the second measurement time comes.

[0025] A fifth aspect of the present invention is the image forming apparatus according to the third aspect,

[0026] The control means activates the second supplementary means during operation of the first supplementary means.

[0027] A sixth aspect of the present invention is the image forming apparatus according to the fourth aspect,

[0028] The control means activates the second supplementary means during operation of the first supplementary means.

[0029] According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects,

[0030] The predetermined value in the first replenishing member is a value equal to or greater than a first threshold value that is a lower limit value of a first allowable concentration value of the developer in the at least one developing device.

[0031] The predetermined value in the second replenishing member is a value equal to or greater than a second threshold value that is a lower limit value of a second allowable concentration value of the developer in the remaining developing device.

[0032] The control means uses, as the first threshold value, a value consisting of a deviation amount smaller than a deviation amount of the second threshold value from the second allowable concentration value.

[0033] According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects,

[0034] When the concentration of the developer returns to the allowable concentration value at a stage where the number of replenishments of the first replenishing component does not exceed the upper limit value, the control component will maintain the result of the exhaustion detection that determines that the developer in at least one developing device is exhausted as the determination result that the developer is not exhausted until the concentration of the remaining developer in the developing device is measured.

[0035] Effects of the Invention

[0036] The image forming apparatus according to the first and second aspects can reduce the interruption of the image forming operation due to the developer replenishment operation, compared to the case where the first and second replenishment members are operated independently without adjusting their operation timings.

[0037] According to the image forming apparatus of the third aspect, the image forming operation is not interrupted by activating the first replenishing means before measuring the concentration of the developer remaining in the developing device.

[0038] According to the image forming apparatus of the fourth aspect, the image forming operation is not interrupted by activating the first replenishing means before the second measurement time period.

[0039] According to the image forming apparatus of the fifth aspect, the operating period of the first replenishing means and the operating period of the second replenishing means overlap at least partially, thereby shortening the time during which the image forming operation is interrupted.

[0040] According to the image forming apparatus of the sixth aspect, the operating period of the first replenishing means and the operating period of the second replenishing means overlap at least partially, thereby shortening the time during which the image forming operation is interrupted.

[0041] According to the image forming apparatus of the seventh aspect, it is possible to suppress a decrease in the developing characteristics of at least a part of the developing device due to a delay in replenishment of the developer from the first replenishing member to the at least part of the developing device.

[0042] According to the image forming apparatus of the eighth aspect, it is also possible to reduce the number of times that the image forming operation is interrupted due to the replacement work of the developer container containing the developer to be replenished. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0044] Figure 1 This is a schematic diagram of an image forming apparatus according to Embodiment 1;

[0045] Figure 2 Yes Figure 1 A schematic diagram of a portion of an image forming apparatus related to developer replenishment;

[0046] Figure 3 Yes Figure 1 a block diagram of a control-related portion of an image forming apparatus;

[0047] Figure 4 This is a flowchart showing the flow of control operations related to adjustment of the operating period of the replenishment device;

[0048] Figure 5 is a flow chart showing the flow of control actions related to ATC;

[0049] Figure 6 These are explanatory diagrams showing the states of the replenishing operation of the replenishing device and the state of the interruption of the image forming operation in the comparative example and the embodiment, respectively.

[0050] Explanation of symbols

[0051] 1-image forming device, 6A-supplementing device (an example of the first supplementing component), 6B, 6C, 6D-supplementing device (an example of the second supplementing component), 25A-developing device (an example of at least one developing device among a plurality of developing devices), 25B, 25C, 25D-developing device (an example of the remaining developing devices among a plurality of developing devices), 185-developability control unit (an example of a control component). DETAILED DESCRIPTION

[0052] Hereinafter, the mode for carrying out the present invention will be described.

[0053] Implementation method 1.

[0054] Figure 1 This is a schematic diagram of an image forming apparatus according to Embodiment 1 of the present invention.

[0055] In this specification and the drawings, substantially identical components are denoted by identical reference numerals, and repeated description of the identical components will be omitted in this specification.

[0056] The image forming apparatus 1 is configured as, for example, a printer.

[0057] And, as Figure 1 As shown, the image forming apparatus 1 includes an image generating section 20 , an intermediate transfer section 30 , a paper feeding section 40 , a fixing section 50 , and the like arranged inside a housing 10 .

[0058] The housing 10 has a paper discharge container 12 on its upper portion and an operation display panel 47 on its upper surface. The operation display panel 47 includes a display portion for displaying information required for operation and an operation portion for performing operation.

[0059] The image generating section 20 is a portion that forms a developed image by developing a latent image with a developer.

[0060] like Figure 1 or Figure 2 As shown, the image generating unit 20 in the first embodiment is composed of four image generating units 21A, 21B, 21C, and 21D.

[0061] The image generating units 21A, 21B, 21C, and 21D each include a photosensitive drum 22. The image generating units 21A, 21B, 21C, and 21D each generate a developed image on the photosensitive drum 22 using a developer of a predetermined color (A, B, C, and D) by electrophotography.

[0062] Examples of the predetermined colors (A, B, C, D) include black, cyan, magenta, and yellow.

[0063] In the image generating section 20 , the photosensitive drums 22 in the image generating units 21A, 21B, 21C, and 21D rotate in the directions indicated by arrows.

[0064] Then, the outer peripheral surface of each photosensitive drum 22 is charged to a predetermined surface potential by each charging device 23 .

[0065] Each latent image forming device 24 then exposes the charged outer peripheral surface of each photosensitive drum 22 to an image of each color component formed according to the image information. Thus, an electrostatic latent image of a predetermined color component (A, B, C, D) is distributed and formed on the outer peripheral surface of each photosensitive drum 22.

[0066] Image information is input from an external device 300 such as an information terminal or a storage medium connected to the image forming apparatus 1 .

[0067] Next, in each photosensitive drum 22 , the electrostatic latent image formed on the outer peripheral surface thereof is developed by the developer of the corresponding color supplied from the developing devices 25A, 25B, 25C, and 25D.

[0068] For example, a two-component developer containing a toner and a carrier is used as the developer. When the developer is a two-component developer, a toner image composed of toners of predetermined colors (A, B, C, D) can be obtained as a developed image.

[0069] The developing devices 25 differ in that they contain developers containing toners of different colors (A, B, C, D), and are therefore shown as developing devices 25A, 25B, 25C, and 25D.

[0070] Each of the developing devices 25A, 25B, 25C, and 25D has a developing roller, a stirring and conveying member, a layer thickness regulating member, and the like (not shown) arranged inside a container for storing developer.

[0071] By the developing operations of the developing devices 25A, 25B, 25C, and 25D, toner images of predetermined colors (A, B, C, and D) are formed on the outer peripheral surfaces of the photosensitive drums 22 .

[0072] In the image forming section 20 , the toner images of the respective colors formed on the respective photosensitive drums 22 are transferred to the intermediate transfer section 30 .

[0073] Then, in the image forming section 20 , the surfaces of the photosensitive drums 22 after the transfer are cleaned by the drum cleaning device 26 to prepare for the next image forming process.

[0074] The intermediate transfer section 30 temporarily holds the toner images of predetermined colors generated by the image generating units 21A, 21B, 21C, and 21D of the image generating section 20 on the intermediate transfer belt 31 by primary transfer and then performs secondary transfer on the paper 9 .

[0075] In the intermediate transfer section 30 , the intermediate transfer belt 31 is wound around a plurality of rollers 32 a , 32 b , 32 c , and 32 d , and rotates in the direction indicated by the arrow.

[0076] Then, in the intermediate transfer section 30 , the toner images of the respective colors on the respective photosensitive drums 22 are sequentially and primarily transferred onto the outer peripheral surface of the rotating intermediate transfer belt 31 by the primary transfer devices 33 .

[0077] The rotating intermediate transfer belt 31 then conveys the toner image primarily transferred to its outer peripheral surface to a secondary transfer position facing the secondary transfer device 34 .

[0078] In the intermediate transfer section 30 , the toner image primarily transferred to the outer peripheral surface of the intermediate transfer belt 31 is secondarily transferred by the secondary transfer device 34 onto the paper 9 supplied from the paper supply section 40 .

[0079] Then, in the intermediate transfer section 30 , the outer peripheral surface of the intermediate transfer belt 31 after the secondary transfer is cleaned by the belt cleaning device 36 in preparation for the next transfer process.

[0080] The paper feed section 40 accommodates the paper 9 on which an image is to be formed and feeds the paper 9 to the secondary transfer position of the intermediate transfer section 30 .

[0081] In the paper feed section 40 , the paper sheets 9 are fed out one by one by a feeding device 42 from a container 41 that contains the paper sheets 9 toward a secondary transfer position of the intermediate transfer section 30 .

[0082] A plurality of container bodies 41 and delivery devices 42 may be assembled.

[0083] Furthermore, the paper feed unit 40 is connected to a paper conveyance path Tr indicated by a dashed line.

[0084] The paper transport path Tr is provided so as to connect from the paper feed section 40 to the paper discharge accommodating section 12 via the secondary transfer position of the intermediate transfer section 30 and the fixing section 50. The paper transport path Tr is constituted by a predetermined number of transport roller pairs 46a, 46b, 46c, and 46d, or a paper guide member (not shown).

[0085] In the paper feed unit 40, the delivery device 42 delivers the paper 9 in the container 41 one by one to the paper transport path Tr. Then, on the paper transport path Tr, the transport roller pair 46b delivers the paper 9 to the secondary transfer position of the intermediate transfer unit 30 in synchronization with the secondary transfer timing.

[0086] Then, in the intermediate transfer section 30 , the secondary transfer device 34 secondarily transfers the toner image from the intermediate transfer belt 31 to one surface of the paper 9 at the secondary transfer position.

[0087] The fixing section 50 is a portion that applies pressure and heat to the toner image transferred onto the paper 9 to fix the toner image onto the paper 9 .

[0088] The fixing unit 50 includes a heating rotator 52 and a pressurizing rotator 53 that rotate in a pressurized state within a housing 51. A fixing processing section (nip section) is formed between the heating rotator 52 and the pressurizing rotator 53, which guides the paper 9 and applies pressure and heat to the paper.

[0089] In the fixing section 50 , the paper 9 fed from the secondary transfer position of the intermediate transfer section 30 is introduced into the fixing process section and passes through the fixing process section.

[0090] At this time, in the fixing section 50, the unfixed toner image on the paper 9 is heated under pressure while passing through the fixing process section. As a result, the toner image is fixed to the paper 9 in the form of an image.

[0091] Finally, in the image forming apparatus 1 , the paper 9 discharged from the fixing unit 50 is transported along the paper transport path Tr toward the paper discharge accommodating portion 12 . Thus, the paper 9 on which the image is formed is accommodated in the paper discharge accommodating portion 12 .

[0092] As described above, an operation of forming an image (printing operation) is performed in the image forming apparatus 1 . Thus, the image forming apparatus 1 forms an image made of developer (toner) on one side of the paper 9 .

[0093] (Structure related to developer replenishment)

[0094] like Figure 2 As shown, the image forming apparatus 1 includes replenishing devices 6A, 6B, 6C, and 6D.

[0095] The replenishing devices 6A, 6B, 6C, and 6D are devices that individually replenish developers of the colors (A, B, C, and D) corresponding to the developing devices 25A, 25B, 25C, and 25D.

[0096] The replenishing devices 6A, 6B, 6C, and 6D include replenishing operating portions 61A, 61B, 61C, and 61D, developer containers 15A, 15B, 15C, and 15D, developer conveying paths 17A, 17B, 17C, and 17D, and the like.

[0097] The replenishing operation sections 61A, 61B, 61C, and 61D are composed of a container driving section, a developer receiving section, a developer feeding member, and the like (not shown).

[0098] The container driving portion drives the driving portion of the developer container 15 to discharge the developer. The developer receiving portion receives the developer discharged from the developer container 15. The developer delivery member delivers the developer in the receiving portion.

[0099] The developer containers 15A, 15B, 15C, and 15D are containers specifically for storing developers of replenishment colors (A, B, C, and D), respectively. In the first embodiment, toner is stored as the developer.

[0100] The developer containers 15A, 15B, 15C, and 15D are detachably mounted on mounting portions 16A, 16B, 16C, and 16D provided at predetermined portions of the housing 10. The developer containers 15A, 15B, 15C, and 15D are containers that rotate to deliver the developer or containers that have a member inside that rotates to deliver the developer.

[0101] The developer conveying paths 17A, 17B, 17C, and 17D are conveying paths for conveying developer individually from the replenishing working portions 61A, 61B, 61C, and 61D to the developing devices 25A, 25B, 25C, and 25D.

[0102] When the replenishment period arrives, the replenishment devices 6A, 6B, 6C, and 6D operate the replenishment operation sections 61A, 61B, 61C, and 61D that require replenishment.

[0103] At this time, the replenishing devices 6A, 6B, 6C, and 6D that have been operated deliver a predetermined amount of developer to the developer conveying paths 17A, 17B, 17C, and 17D, respectively. Furthermore, the replenishing operating portions 61A, 61B, 61C, and 61D receive developer in advance from the developer containers 15A, 15B, 15C, and 15D.

[0104] Thus, the replenishing devices 6A, 6B, 6C, and 6D respectively convey predetermined amounts of developer to the developing devices 25A, 25B, 25C, and 25D for replenishment.

[0105] The replenishing device 6A, which is one of the replenishing devices 6A, 6B, 6C, and 6D, operates based on the measurement information of the toner density measuring section 65 .

[0106] The toner concentration measuring section 65 measures the toner concentration of the developer stored in the developing device 25A to be measured. The toner concentration measuring section 65 is a first concentration detecting member as an example of a concentration detecting member.

[0107] If the two-component developer contains non-magnetic toner and magnetic carrier, the toner concentration measuring section 65 is constituted by, for example, a permeability-type TC sensor or the like.

[0108] The permeability type TC sensor measures the permeability of the developer contained in the developing device 25A. As will be described later, the toner concentration measuring section 65 determines the toner concentration based on the permeability of the developer.

[0109] On the other hand, the remaining replenishing devices 6B, 6C, and 6D among the replenishing devices 6A, 6B, 6C, and 6D operate based on the measurement information of the toner image density measuring section 67 .

[0110] The toner image density measuring section 67 measures the density of the reference toner image. The density of the reference toner image is also the density of the toner amount after development. The toner image density measuring section 67 is a second density detecting section, which is another example of a density detecting section.

[0111] The reference toner image is a toner image for density measurement obtained by developing a specific electrostatic latent image by a developing device to be measured. The reference toner image is formed on the photosensitive drum 22 or is transferred from the photosensitive drum 22 to the intermediate transfer belt 31 .

[0112] When measuring the density of a reference toner image composed of a color toner other than black, the toner image density measuring section 67 is composed of, for example, a diffuse reflection type developing density sensor.

[0113] The toner image density measuring section 67 measures the density of the reference toner images of each color developed by the developing devices 25B, 25C, and 25D. Furthermore, the toner image density measuring section 67 measures the density of the reference toner images primarily transferred from the photosensitive drums 22 to the intermediate transfer belt 31 at a position immediately before the secondary transfer position.

[0114] Furthermore, the image forming apparatus 1 uses two developing control methods, ATC and ADC, to control the developer replenishment operation. ATC is an abbreviation for Auto Toner Concentration Control, and ADC is an abbreviation for Auto Density Control.

[0115] ATC measures the toner concentration in the developing device by the toner concentration measuring section 65. ATC is a method of controlling toner replenishment based on the toner concentration measurement information so that the toner concentration in the developing device to be replenished remains constant.

[0116] In the first embodiment, the replenishing device 6A is operated when the measurement result of the toner density measuring unit 65 is equal to or greater than a first threshold value. The first threshold value is the lower limit of the deviation from the first allowable density value of the toner density in the ATC target developing device 25A.

[0117] Therefore, the replenishing device 6A in the first embodiment operates when the concentration of the developer accommodated in the developing device 25A reaches a predetermined value.

[0118] Furthermore, in the first embodiment, the developability control unit 185, described later, estimates the amount of carrier per unit volume of developer based on permeability information measured by a permeability-type TC sensor. Furthermore, the developer replenishment operation control unit 186 calculates the weight ratio of toner to carrier based on this carrier amount, thereby obtaining information representing the toner concentration.

[0119] Furthermore, in the first embodiment, the developability control section 185 collects measurement information of the toner density measuring section 65. In the first embodiment, the developability control section 185 determines whether the measurement result of the toner density measuring section 65 is equal to or greater than the first threshold.

[0120] ADC is a system in which the toner image density measuring section 67 measures the density of a reference toner image and controls toner replenishment so that the development characteristics are constant.

[0121] In the first embodiment, when the measurement result of the toner image density measuring unit 67 is a density value equal to or greater than a second threshold value, the replenishing devices 6B, 6C, and 6D are each activated. The second threshold value is a permissible lower limit value of the amount of deviation from a second permissible density value, which is the image density of each reference toner image developed by the ADC target developing devices 25B, 25C, and 25D, respectively.

[0122] Therefore, the replenishing devices 6B, 6C, and 6D operate when the density of each reference toner image reaches a predetermined value. The density of each reference toner image substantially corresponds to the density of each developer stored in the developing devices 25B, 25C, and 25D.

[0123] In the first embodiment, the developability control section 185 collects measurement information from the toner image density measuring section 67. In the first embodiment, the developability control section 185 determines whether the measurement result from the toner image density measuring section 67 is a density value equal to or greater than the second threshold value.

[0124] The toner density measuring section 65 measures the toner density at a density measurement timing (first measurement timing) corresponding to the ATC.

[0125] Specifically, the toner density measuring unit 65 measures the toner density while the developing device 25A is in operation. In this case, the density measurement period corresponding to the ATC of the toner density measuring unit 65 is during the operation of the developing device 25A.

[0126] Then, the toner image density measuring section 67 measures the toner image density at a density measurement timing (second measurement timing) corresponding to the ADC. The second measurement timing in this case may be different from the first measurement timing.

[0127] Specifically, the toner image density measuring unit 67 measures the toner image density when the amount of image forming operation (print volume: PV) reaches a predetermined threshold. In this case, the density measurement period corresponding to the ADC of the toner image density measuring unit 67 is the period when the amount of image forming operation reaches the predetermined threshold.

[0128] The amount of image forming operations includes, for example, the number of sheets 9 used for image formation or the number of pixels in the formed image. Furthermore, the amount of image forming operations is the cumulative amount of various control operations related to the processing conditions during image formation executed by the image forming apparatus 1 since the end of the immediately preceding control operation.

[0129] Furthermore, in the image forming apparatus 1 , when an image forming operation is in progress, if the replenishment devices 6A, 6B, 6C, and 6D reach their operating periods, the image forming operation being executed is interrupted.

[0130] Furthermore, in the image forming apparatus 1, when the toner image density measuring unit 67 reaches the density measurement time corresponding to the ADC while image forming is in progress, the image forming operation is prematurely interrupted. This is to prematurely start the operation of forming the reference toner image to be measured by the toner image density measuring unit 67.

[0131] Therefore, in the image forming apparatus 1 , the operation timing of the replenishment device 6A operating according to the ATC developability control method and the operation timing of the replenishment devices 6B, 6C, and 6D operating according to the ADC developability control method are often performed independently at different times.

[0132] In other words, the timing when the image forming operation being executed is interrupted by the replenishment operation of the replenishment device 6A and the timing when the image forming operation being executed is interrupted by the replenishment operation of the replenishment devices 6B, 6C, and 6D are always different from each other.

[0133] Therefore, the image forming apparatus 1 is provided with a control unit 18 having a function of performing control to adjust the operation timing of the replenishment device 6A and the operation timing of the replenishment devices 6B, 6C, and 6D.

[0134] like Figure 3 As shown, the control member 18 is composed of a central control unit including a developability control unit 185 and the like.

[0135] The central control unit of the control means 18 is a unit that centrally controls the overall operation of the image forming apparatus 1. The control means 18 is composed of a processing unit (not shown), a storage unit, an input / output unit, etc. Other control units described below are also configured in a similar manner.

[0136] The control means 18 obtains information required for control from the processing device and performs necessary processing according to the control program and control data stored in the storage unit. Then, the control means 18 receives a signal from the processing device or the like to control the operation of the control object to be controlled.

[0137] Information required for control includes, for example, detection information and input information.

[0138] like Figure 3 As shown, the control unit 18 is connected to a toner density measuring section 65 , a toner image density measuring section 67 , a surface potential measuring section 68 , a communication / input / output section 192 , and the like.

[0139] Thereby, the control means 18 can obtain necessary detection information, input information, etc.

[0140] The surface potential measuring unit 68 measures the surface potential of each photosensitive drum 22 in the image generating units 21A, 21B, 21C, and 21D. The surface potential measuring unit 68 is comprised of a known potential sensor, etc. The communication / input / output unit 192 communicates with external devices 300, such as information terminals and storage media, and performs information input and output.

[0141] The control unit 18 is connected to the image processing unit 191, the image forming operation control unit 181, the paper conveying operation control unit 182, the developer replenishing operation control unit 186, the display operation control unit 187, etc. Thus, the control unit 18 can output control signals to the desired control targets.

[0142] The image processing unit 191 performs predetermined processing on image information input to the image forming apparatus 1 to generate an image signal to be formed. The image processing unit 191 obtains information such as the number of sheets 9 on which an image is to be formed and the number of pixels.

[0143] The image forming operation control unit 181 controls the operations related to the image forming unit 20, the intermediate transfer unit 30, and the fixing unit 50. The paper conveying operation control unit 182 controls the operations related to the paper feeding unit 40 including the paper conveying path Tr.

[0144] The developer replenishment operation control unit 186 controls the operation of (the replenishment operation units 61 of) the replenishment devices 6A, 6B, 6C, and 6D. The display operation control unit 187 controls the operation related to the operation display panel unit 47.

[0145] Furthermore, the central control section of the control member 18 includes a developability control section 185 and an end-of-life detection section 188 as part of its functions.

[0146] The developability control section 185 is a portion that controls operations related to the aforementioned ATC and ADC control methods.

[0147] The developability control unit 185 also performs the following control operation as an operation related to the ATC control method: Specifically, the developability control unit 185 collects measurement information from the toner density measurement unit 65 and determines whether the measurement result is equal to or greater than a first threshold value.

[0148] Furthermore, the developability control section 185 performs the following control operation as an operation related to the ADC control method: Specifically, the developability control section 185 collects measurement information from the toner image density measurement section 67 and determines whether the measurement result is a density value equal to or greater than a second threshold value.

[0149] The end detection unit 188 monitors the remaining amount of the toner to be replenished in the developer containers 15A, 15B, 15C, and 15D and detects when the remaining toner amount reaches almost zero and the container is empty.

[0150] The end-of-life detection section 188 obtains necessary information from the developability control section 185 and the like to perform end-of-life detection.

[0151] (Control Action Related to Adjustment of the Operating Period of the Replenishing Device)

[0152] Next, a control operation for adjusting the operation timing of the replenishment device 6A and the operation timing of the replenishment devices 6B, 6C, and 6D during the image forming operation will be described.

[0153] In the image forming apparatus 1, as Figure 4 As shown, when the image forming operation (printing operation) is started (S100), the control means 18 determines whether the density measurement time corresponding to the ADC has arrived (S101).

[0154] S100 and S101 are abbreviations of step S100 and step S101, respectively. The same abbreviations apply to other steps thereafter.

[0155] The ADC density measurement period is set when the image formation volume (print volume: PV) reaches a predetermined threshold. The PV is the cumulative value of the number of images formed or the number of pixels. The cumulative value is the value accumulated from the time the immediately preceding control operation, related to the image formation processing conditions, ended.

[0156] If it is determined in step S101 that the density measurement time corresponding to the ADC has arrived, the printing operation in progress is interrupted (S102), and then the operation related to the ADC and the operation related to the ATC are performed independently (S103).

[0157] ADC-related operations

[0158] like Figure 4 As shown, the operation related to ADC first performs concentration measurement corresponding to ADC (S104).

[0159] The density measurement corresponding to the ADC forms a reference toner image to be measured and measures the density of the reference toner image.

[0160] Specifically, after the image forming units 21A, 21B, 21C, and 21D operate and the developing devices 25B, 25C, and 25D form reference toner images of respective colors on the respective photosensitive drums 22, the reference toner images of respective colors are primarily transferred onto the intermediate transfer belt 31. Subsequently, the densities of the reference toner images of respective colors on the intermediate transfer belt 31 are measured as they pass through the toner image density measuring unit 67.

[0161] At this time, the developability control section 185 collects information measured by the toner image density measuring section 67. At this time, the developability control section 185 calculates the deviation amount Db from the second permissible density value, which is the image density of the reference toner image of each color, based on the measured information.

[0162] Incidentally, at this time, the reference toner image of each color is removed by the belt cleaning device 36 after passing through the secondary transfer position without being secondarily transferred onto the paper 9 .

[0163] Next, the developability control section 185 determines whether the density deviation amount Db obtained from the measurement result of the toner image density measurement section 67 is equal to or greater than a second threshold value ( S105 ).

[0164] As described above, the second threshold value is the permissible lower limit value of the amount deviating from the second permissible concentration value.

[0165] When it is determined in step S105 that the divergence amount Db is equal to or greater than the second threshold value, the corresponding replenishing device among the replenishing devices 6B, 6C, and 6D corresponding to the ADC is activated ( S106 ).

[0166] The replenishing devices 6B, 6C, and 6D are activated when the deviation amount Db of any one of them is equal to or greater than the second threshold value. As a result, the replenishing devices 6B, 6C, and 6D replenish predetermined amounts of developer of a predetermined color (B, C, and D) to the developing devices 25B, 25C, and 25D, respectively.

[0167] If the corresponding replenishing device in step S105 is operated and the replenishing operation is performed, the concentration measurement corresponding to the ADC is performed again (S107).

[0168] In this ADC corresponding density re-measurement, the formation of the reference toner image to be measured and the measurement of the density of the reference toner image in the first ADC corresponding density measurement are performed again in the same manner.

[0169] In this case, the developability control section 185 determines whether the density deviation amount Db obtained from the measurement result of the toner image density measurement section 67 is smaller than the second threshold value ( S108 ).

[0170] When it is determined in step S108 that the divergence amount Db is smaller than the second threshold value, the next potential adjustment control operation is performed ( S109 ).

[0171] When the divergence amount Db is smaller than the second threshold value, it is considered that the concentration of the developer in any one of the corresponding developing devices 25B, 25C, and 25D has been restored by returning to the second allowable concentration value through the above-mentioned replenishment operation.

[0172] During the potential adjustment control operation, the surface potential of the photosensitive drum 22 measured by the surface potential measuring section 68 is checked.

[0173] The potential adjustment control operation is an operation for performing necessary adjustments related to potential setting in response to fluctuations in toner charge due to developer replenishment, etc. Specifically, it is an operation for performing necessary adjustments to the developing bias voltage, the charging potential, the latent image potential, etc.

[0174] After the potential adjustment control operation is performed, the printing operation that was interrupted due to the density measurement corresponding to the ADC or the replenishment operation performed as needed is resumed ( S110 ).

[0175] Finally, it is determined whether the restarted printing operation has been completed (S111). At this time, if it is determined to be completed, then the printing operation is completely completed.

[0176] In the case of the above-described operation flow, the printing operation being executed may be interrupted by the density measurement operation corresponding to the ADC or the operation of the replenishment device corresponding to the ADC.

[0177] On the other hand, if it is determined in step S101 that it is not the density measurement period corresponding to the ADC, the printing operation is continued without interruption. Furthermore, if it is determined in step S105 that the density deviation Db is less than the second threshold value, the printing operation is continued without interruption.

[0178] In the case of such an action flow, it is determined whether the printing action being executed has been completed (S111). If it is determined to be completed at this time, the printing action is completely completed.

[0179] In the case of the latter operation flow, the printing operation being executed is not interrupted by the density measurement operation corresponding to the ADC or the operation of the replenishment device corresponding to the ADC, but continues.

[0180] Incidentally, when it is determined in step S108 that the divergence amount Db is not less than the second threshold but is equal to or greater than the second threshold, the developer concentration in the corresponding developing device does not return to the second allowable concentration value during the replenishment operation.

[0181] In this case, the developability control section 185 determines whether the number of replenishment operations performed by the corresponding replenishment device among the replenishment devices 6B, 6C, and 6D is equal to or greater than a threshold value ( S112 ).

[0182] The threshold value at this time is the upper limit of the number of times the replenishment operation can be repeated without the toner in the developer container 15 running out.

[0183] If it is determined in step S112 that the number of replenishment times is less than the threshold value, the process returns to step S106 and the corresponding replenishment device 6B, 6C, or 6D corresponding to the ADC operates.

[0184] In this case, starting from the supplementation operation of step S106, the operations of steps S107 and S108 are repeated in the same manner.

[0185] On the contrary, when it is determined in step S112 that the number of replenishment times is equal to or greater than the threshold value, the process proceeds to the potential adjustment control operation in step S109.

[0186] In this case, further supplementary operation cannot be performed and is prohibited.

[0187] In this case, the end detection portion 188 determines that any one of the developer containers 15B, 15C, and 15D containing the toner of the corresponding color is nearly empty.

[0188] <ATC-related actions>

[0189] In ATC-related actions, such as Figure 4 As shown, first, the ATC supplementary determination Flag is checked (S120).

[0190] The ATC supplementary determination flag is set in the developability control section 185 when performing density measurement corresponding to the ATC, which will be described later.

[0191] (ATC Supplementary Judgment Flag Setting)

[0192] Here, the setting of the ATC supplementary determination Flag is first described.

[0193] In this case, Figure 4 The printing action shown is started at the same time, as shown in Figure 5 As shown, an ATC corresponding color image generation action (S200) is executed.

[0194] In the first embodiment, the ATC-compatible color is “A color” which is the color of the developer of the developing device 25A that performs the developability control of the ATC.

[0195] When an image generation operation for forming a toner image of a color corresponding to the ATC is executed, density measurement corresponding to the ATC is performed ( S201 ).

[0196] In the ATC-compliant density measurement, the toner density measuring section 65 measures the density of the developer accommodated in the developing device 25A to be measured.

[0197] At this time, the developability control section 185 collects information measured by the toner density measuring section 65. At this time, the developability control section 185 calculates a deviation Da from a first permissible density value, which is the image density of the developer in the developing device 25A, based on the measured information.

[0198] Next, the developability control section 185 determines whether the density deviation amount Da obtained from the measurement result of the toner density measuring section 65 is equal to or greater than a first threshold value ( S202 ).

[0199] As described above, the first threshold value is the permissible lower limit value of the amount deviating from the first permissible concentration value.

[0200] If it is determined in step S202 that the divergence amount Da is smaller than the first threshold, since the developer does not need to be replenished to the developing device 25A, the ATC replenishment determination Flag is set to "Flag=0" indicating that replenishment is not necessary (S203).

[0201] In this case, the replenishing device 6A does not need to replenish the developer and therefore does not operate.

[0202] On the other hand, if it is determined in step S202 that the divergence amount Da is equal to or greater than the first threshold, the developing device 25A needs to be replenished with developer, and therefore the ATC replenishment determination Flag is set to "Flag=1" indicating replenishment is necessary (S204).

[0203] However, in this case, the ATC replenishment determination Flag is simply set to "Flag=1" and the ATC-compatible replenishment device 6A is not operated.

[0204] That is, in this case, the operation of the replenishing device 6A is put on standby.

[0205] Next, after the ATC replenishment determination Flag is set to "Flag=1", the developability control section 185 checks the end-of-life detection state transition Flag set in the end-of-life detection section 188 (S205).

[0206] The setting of the exhaustion detection state transition flag will be described later.

[0207] In step S205 , when the end-of-life detection state transition Flag is “Flag=0” indicating a prompt to transition to the end-of-life detection state, a storage process is performed to prevent the end-of-life detection state from being transitioned ( S206 ).

[0208] In this case, the developer in the developing device 25A corresponding to the ATC is reduced, and the developer container 15A containing the developer to be replenished to the developing device 25A is nearly empty. However, even in this state, the step of determining that the developer container 15A is empty is put on standby in the empty detection unit 188 through the above-mentioned storage process.

[0209] Therefore, in this case, the state where the developer container 15A is not replaced with a new one is maintained. As a result, the printing operation is not interrupted by the replacement of the developer container 15A.

[0210] On the other hand, in step S205, if the empty detection state transition Flag is "Flag = 1" indicating that the empty detection state is transitioned, a storage process of transitioning the empty detection state to "Near Empty" is performed (S207).

[0211] “Nearly Ended” is a determination item indicating that the developer container 15A is in a nearly ended state.

[0212] In this case as well, the step of determining that the developer container 15A has been detected as empty is put on standby in the empty detection section 188 by the above-mentioned storage process.

[0213] However, in this case, a warning message or the like notifying that the developer container 15A is in a “nearly empty” state is displayed on the operation display panel portion 47 .

[0214] This can inform the user that the developer container 15A is nearing the replacement time and call their attention.

[0215] <Follow-up on ATC-related actions>

[0216] Here, return to Figure 4 Description of ATC-related actions shown.

[0217] When it is determined in step S120 that the ATC supplementary determination Flag is "Flag=0", the process proceeds to step S111.

[0218] In this case, since the replenishment operation by the ATC-compatible replenishment device 6A is unnecessary, the replenishment device 6A does not operate.

[0219] In this case, there are the following two cases regarding the interruption of the printing operation.

[0220] One is to perform the density measurement corresponding to the ADC and the replenishment operation of at least one of the replenishment devices 6B, 6C, and 6D as needed, thereby interrupting the ongoing printing operation. The other is to not perform the density measurement or replenishment operation corresponding to the ADC, and not interrupt the ongoing printing operation.

[0221] On the other hand, when it is determined in step S120 that the ATC replenishment determination Flag is "Flag=1", the ATC-compatible replenishment device 6A operates (S121).

[0222] In this case, the replenishing device 6A is operated to replenish a predetermined amount of the color A developer to the developing device 25A.

[0223] The supplementary device 6A corresponding to the ATC at this time is Figure 5 In step S204 shown, the device is set to be in standby mode. However, the replenishing device 6A is controlled so as to be activated when the concentration measurement corresponding to the ADC is performed.

[0224] Furthermore, the replenishing device 6A at this time can be said to be controlled so as to cancel the above-mentioned standby process and start up when the concentration measurement time corresponding to the ADC shown in step S101 arrives.

[0225] When the replenishing device 6A corresponding to the ATC is operated and the replenishing operation is performed, the concentration measurement corresponding to the ATC is performed again (S122).

[0226] The concentration corresponding to this ATC will be re-measured Figure 5 The concentration of the developer in the developing device 25A corresponding to the ATC is measured during the first concentration measurement corresponding to the ATC shown.

[0227] When the density re-measurement corresponding to the ATC is performed, the developability control section 185 determines whether the density deviation amount Da obtained from the measurement result of the toner density measuring section 65 is smaller than the first threshold value ( S123 ).

[0228] If it is determined in step S123 that the divergence amount Da is smaller than the first threshold value, the concentration of the developer in the developing device 25A is restored to the first allowable concentration value by the replenishing operation of the replenishing device 6A.

[0229] In this case, the ATC replenishment determination Flag is changed to "Flag=0" (S124) in the developability control section 185. That is, at this time, the process is such that the replenishment operation of the ATC-compatible replenishment device 6A is not required.

[0230] Furthermore, in this case, since the replenishing operation of the replenishing device 6A is performed, the end-of-life detection state transition Flag is set to “Flag=0” in the developability control section 185 ( S125 ).

[0231] That is, at this time, the developer container 15A that is handled so as to accommodate the developer replenished to the replenishing device 6A does not have the risk of being exhausted.

[0232] Next, after the processing of steps S124 and S125 is performed, the process proceeds to step S109 to perform the potential adjustment control operation.

[0233] In this case, the developer is replenished to the developing device 25A by the operation of the replenishing device 6A, and therefore the above-mentioned potential adjustment control operation is performed in the same manner.

[0234] Furthermore, the potential adjustment control operation at this time is performed once when both the supplementary operation corresponding to ADC and the supplementary operation corresponding to ATC are performed.

[0235] Compared with the situation where the supplementary action corresponding to ADC and the supplementary action corresponding to ATC are performed separately at different times, and the potential adjustment control action is performed separately after each supplementary action is completed, the unified potential adjustment control action can shorten the time of interruption of the printing action.

[0236] After the potential adjustment control operation is performed at this time, the interrupted printing operation is resumed with the density measurement corresponding to the ADC or the supplementation operation performed as needed ( S110 ).

[0237] Finally, it is determined whether the restarted printing operation has been completed (S111). If it is determined to be completed, then the printing operation is completely completed.

[0238] In the case of the above-described operation flow, the printing operation being executed may be interrupted by performing a density measurement operation corresponding to the ADC or a replenishment operation by the replenishment device corresponding to the ADC.

[0239] However, in this case, the replenishing operation of the replenishing device 6A corresponding to the ATC is performed during the interruption period.

[0240] Incidentally, when it is determined in step S123 that the divergence amount Da is equal to or greater than the first threshold value, it is determined whether the number of replenishment times by the replenishment device 6A is equal to or greater than the threshold value ( S126 ).

[0241] In this case, if it is determined that the replenishment count is less than the threshold, the developer concentration in the developing device 25A will not be restored to the first allowable concentration value. Therefore, in this case, the process proceeds to step S121, and the replenishment operation of the replenishing device 6A and the subsequent operations of steps S122 and S123 are repeated in the same manner.

[0242] If it is determined in step S126 that the replenishment count is equal to or greater than the threshold, the replenishment operation of the replenishment device 6A is performed. Therefore, in this case, the development performance control unit 185 sets the end detection state transition Flag to "Flag=1" (S127).

[0243] That is, at this time, there is a risk that the developer container 15A, which is handled to accommodate the developer replenished to the replenishing device 6A, will become empty.

[0244] After the operation of step S127 is completed, the process proceeds to step S109 in the same manner as when the operation of step S125 is completed, and the operation of potential adjustment control is performed.

[0245] As described above, in the image forming apparatus 1 , the operation timing of the replenishment device 6A and the operation timing of the replenishment devices 6B, 6C, and 6D during the image forming operation are adjusted.

[0246] Specifically, in the image forming apparatus 1, as in Figure 6 As conceptually illustrated in the lower part of , the replenishing device 6A corresponding to the ATC is controlled so as to operate at the same time as the operation time of any one of the replenishing devices 6B, 6C, and 6D corresponding to the ADC.

[0247] This can also be understood as controlling the image forming apparatus 1 to put the operation of the replenishing device 6A corresponding to the ATC on standby until the operation timing of any one of the replenishing devices 6B, 6C, and 6D corresponding to the ADC.

[0248] The phrase "same period" indicates that the operating period of replenishing device 6A only needs to coincide with the operating period of any one of replenishing devices 6B, 6C, and 6D. Therefore, the phrase "same period" is not limited to the case where the operating period of replenishing device 6A coincides with the operating period of any one of replenishing devices 6B, 6C, and 6D, but is used in a manner that includes cases where the operating period of replenishing device 6A coincides with the operating period of any one of replenishing devices 6B, 6C, and 6D.

[0249] exist Figure 6 , the following two states of image generation action and supplementary action are shown.

[0250] Specifically, one is the state of the image generation and supplementation operation in the image generation unit 21A for color A, which performs developability control of ATC, and the other is the state of the image generation and supplementation operation in the image generation units 21B, 21C, and 21D for colors B, C, and D, which perform developability control of ADC.

[0251] Figure 6 The symbol St in exemplifies the start time of the cumulative count of the print volume PV corresponding to the density measurement period of the ADC. Figure 6 Symbols t1 to t3 in exemplify the arrival time points of the ADC concentration measurement period, that is, the respective time points arriving from the respective start time points St.

[0252] And, in Figure 6 , the operation of the supplementary device 6B among the supplementary devices 6B, 6C, and 6D corresponding to the ADC is illustrated.

[0253] Figure 6 The interruption A shown is the interruption time when the developer of color A corresponding to the ATC is interrupted by the replenishment operation. Figure 6 The interruption B shown is the interruption time when the process is interrupted due to the replenishment operation of the developer of the color B corresponding to the ADC.

[0254] The reason why the interruption B is longer than the interruption A is that the development control of the ADC requires time for not only the replenishment operation but also the time required for the operation of forming the reference toner image and the operation of measuring the density of the reference toner image.

[0255] Figure 6 The comparative example shown in the upper part of FIG is an example of a case where the replenishing device 6A corresponding to the ATC and one replenishing device 6B corresponding to the ADC operate independently without adjusting their operation timings.

[0256] In the comparative example, the replenishing device 6A and the replenishing device 6B sometimes operate completely separately at different times.

[0257] In this case, the printing operation is interrupted for the sum of the time of interruption A and interruption B. In this case, the printing operation is also interrupted twice, interruption A and interruption B, at different times.

[0258] Therefore, according to the image forming apparatus 1, compared with a case where the replenishing device 6A and the replenishing devices 6B, 6C, and 6D are operated independently without adjusting the operating periods of each other during the image forming operation, the interruption of the image forming operation due to the developer replenishing operation is reduced. Figure 6 The case is similar to the comparative example shown in the upper part of .

[0259] More specifically, according to the image forming apparatus 1, as in Figure 6 As in the embodiment illustrated in the lower part of FIG, the replenishing device 6A is operated in the same period as the operation period of the replenishing device 6B, partially overlapping the operation period.

[0260] Therefore, as in Figure 6 As shown in the embodiment illustrated in the lower part of FIG, the duration of the interruption C of the printing operation in this case is shorter than the duration obtained by adding the duration of the interruptions A and B at different times in the comparative example.

[0261] Furthermore, in the image forming apparatus 1 , as shown in the comparative example, the replenishment timing of the replenishment device 6A corresponding to the ATC arrives before t1 , which is the density measurement timing corresponding to the ADC.

[0262] However, in the image forming apparatus 1 , despite this, when the ADC corresponding density measurement period t2 arrives and the ADC corresponding density is measured, the ATC corresponding replenishing device 6A is activated.

[0263] Thus, in the image forming apparatus 1 , by activating the replenishing device 6A corresponding to the ATC before measuring the density corresponding to the ADC, the printing operation is not interrupted.

[0264] That is, in the image forming apparatus 1 , if the printing operation is interrupted due to the developer replenishment operation, the time during which the printing operation is prevented from being interrupted is reduced.

[0265] Furthermore, in the image forming apparatus 1, when the ADC density measurement period arrives, the ATC-compliant replenishing device 6A can be immediately activated. This is because the replenishing device 6A does not have to perform the operations of forming a reference toner image and measuring the density of the reference toner image required for the ADC density measurement.

[0266] Therefore, in the image forming apparatus 1 , when a replenishing operation by the replenishing device 6B corresponding to the ADC or the like is required, the replenishing device 6B corresponding to the ADC or the like is activated while the replenishing device 6A corresponding to the ATC is operating for the replenishing operation.

[0267] Thus, according to the image forming apparatus 1, as Figure 6 As shown in the embodiment below, the operation period of the replenishment device 6A corresponding to the ATC overlaps at least partially with the operation period of the replenishment device 6B corresponding to the ADC. As a result, the time during which the printing operation is interrupted in the image forming apparatus 1 is shortened by the overlapping time.

[0268] Furthermore, when performing the ATC developability control in the developability control section 185 of the image forming apparatus 1 , a value consisting of a deviation smaller than a deviation of the second threshold value from the second allowable density value is used as the first threshold.

[0269] The small divergence amount serving as the first threshold at this time is, for example, the following value.

[0270] That is, the value is adjusted to satisfy the condition that the density of the reference toner image developed by the ATC-compatible developing device 25A after the replenishment operation of the ATC-compatible replenishing device 6A on standby reaches the allowable density.

[0271] Thus, in the image forming apparatus 1 , even when the replenishment of the developer from the ATC-compatible replenishing device 6A to the ATC-compatible developing device 25A is delayed due to standby, degradation of the developing characteristics of the developing device 25A can be suppressed.

[0272] That is, in this case, degradation of the developing characteristic of the developing device 25A can be suppressed compared to the case where a threshold value consisting of a deviation amount smaller than the deviation amount of the second threshold value from the second allowable density value is not applied as the first threshold value.

[0273] Variation example.

[0274] The present invention is not limited to the configuration exemplified in the above-mentioned embodiment 1. That is, the present invention can be variously modified or altered within the scope of the gist of each invention described in the claims.

[0275] Therefore, the present invention also includes, for example, the following modified examples.

[0276] In the first embodiment, an image forming apparatus 1 is illustrated as including four developing devices as developing devices 25. However, the image forming apparatus 1 may include multiple developing devices containing developers of different types (colors, etc.) as developing devices 25. Therefore, the number of multiple developing devices is not limited to four.

[0277] Furthermore, in Embodiment 1, a case where the ATC-compatible replenishing device (an example of the first replenishing means) is a single replenishing device 6A is exemplified. However, the ATC-compatible replenishing device may be a plurality of replenishing devices.

[0278] Furthermore, in Embodiment 1, the replenishing device corresponding to the ADC (an example of the second replenishing member) is illustrated as the replenishing device 6B to 6D other than the replenishing device 6A. However, the replenishing device corresponding to the ADC may be a plurality of other replenishing devices or a single replenishing device.

[0279] As long as the image forming apparatus of the present invention includes a plurality of developing devices, it may also be an image forming apparatus that adopts a direct transfer method instead of the intermediate transfer unit 30. In this case, the direct transfer method is a method of directly transferring a toner image from the photosensitive drum 22 to the paper 9.

[0280] The image forming apparatus using the direct transfer method is configured such that, for example, a sheet 9 is conveyed by a conveyor belt or the like so as to sequentially pass through transfer positions of the respective photosensitive drums 22 of a plurality of image forming units 21 .

[0281] (Note)

[0282] (1) An image forming apparatus comprising:

[0283] a plurality of developing devices containing different types of developers;

[0284] a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when the concentration of the developer in the at least one developing device reaches a predetermined value;

[0285] a second replenishing means for replenishing the developer to the remaining developing devices among the plurality of developing devices when the concentration of the developer in the remaining developing devices reaches a predetermined value; and

[0286] The control means performs control so as to cause the first replenishing means to operate at the same timing as the operation timing of the second replenishing means.

[0287] (2) An image forming apparatus comprising:

[0288] a plurality of developing devices containing different types of developers;

[0289] a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when a result of measuring the concentration of the developer in at least one of the plurality of developing devices at a first measurement period is a predetermined value;

[0290] a second replenishing means for replenishing the developer to the remaining developing devices when a result of measuring the developer concentration in the remaining developing devices among the plurality of developing devices at a second measurement time different from the first measurement time is a predetermined value; and

[0291] The control means performs control to put the operation of the first replenishing means on standby until the second measurement period is reached.

[0292] (3) The image forming apparatus according to (1), wherein

[0293] The control means activates the first replenishing means when measuring the concentration of the developer remaining in the developing device.

[0294] (4) The image forming apparatus according to (2), wherein

[0295] The control means activates the first replenishing means on standby when the second measurement time comes.

[0296] (5) The image forming apparatus according to (3), wherein

[0297] The control means activates the second supplementary means during operation of the first supplementary means.

[0298] (6) The image forming apparatus according to (4), wherein

[0299] The control means activates the second supplementary means during operation of the first supplementary means.

[0300] (7) The image forming apparatus according to any one of (1) to (6), wherein

[0301] The predetermined value in the first replenishing member is a value equal to or greater than a first threshold value that is a lower limit value of a first allowable concentration value of the developer in the at least one developing device.

[0302] The predetermined value in the second replenishing member is a value equal to or greater than a second threshold value that is a lower limit value of a second allowable concentration value of the developer in the remaining developing device.

[0303] The control means uses, as the first threshold value, a value consisting of a deviation amount smaller than a deviation amount of the second threshold value from the second allowable concentration value.

[0304] (8) The image forming apparatus according to any one of (1) to (7), wherein

[0305] When the concentration of the developer returns to the allowable concentration value at a stage where the number of replenishments of the first replenishing component does not exceed the upper limit value, the control component will maintain the result of the exhaustion detection that determines that the developer in at least one developing device is exhausted as the determination result that the developer is not exhausted until the concentration of the remaining developer in the developing device is measured.

[0306] According to the image forming apparatuses of (1) and (2), compared with the case where the first replenishing member and the second replenishing member are operated independently without adjusting their respective operation timings, interruptions of the image forming operation due to the developer replenishing operation can be reduced.

[0307] According to the image forming apparatus of (3), the image forming operation is not interrupted by activating the first replenishing means before measuring the concentration of the developer remaining in the developing device.

[0308] According to the image forming apparatus of (4), the image forming operation is not interrupted by activating the first replenishing means before the second measurement time period is reached.

[0309] According to the image forming apparatus of (5), the operating period of the first replenishing means and the operating period of the second replenishing means overlap at least partially, thereby shortening the time during which the image forming operation is interrupted.

[0310] According to the image forming apparatus of (6), the operating period of the first replenishing means and the operating period of the second replenishing means overlap at least partially, thereby shortening the time during which the image forming operation is interrupted.

[0311] According to the image forming apparatus of (7), it is possible to suppress a decrease in the developing characteristics of the developing device due to a delay in replenishment of the developer from the first replenishing member to at least a part of the developing device.

[0312] According to the image forming apparatus of (8), it is also possible to reduce the number of times that the image forming operation is interrupted due to the replacement operation of the developer container containing the developer to be replenished.

[0313] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other technical personnel in this field can understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. An image forming apparatus comprising: a plurality of developing devices containing different types of developers; a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when the concentration of the developer in the at least one developing device reaches a predetermined value; a second replenishing means for replenishing the developer to the remaining developing devices among the plurality of developing devices when the concentration of the developer in the remaining developing devices reaches a predetermined value; and The control means performs control so as to cause the first replenishing means to operate at the same timing as the operation timing of the second replenishing means.

2. An image forming apparatus comprising: a plurality of developing devices containing different types of developers; a first replenishing means for replenishing the developer to at least one of the plurality of developing devices when a result of measuring the concentration of the developer in at least one of the plurality of developing devices at a first measurement period is a predetermined value; a second replenishing means for replenishing the developer to the remaining developing devices when a result of measuring the developer concentration in the remaining developing devices among the plurality of developing devices at a second measurement time different from the first measurement time is a predetermined value; and The control means performs control to put the operation of the first replenishing means on standby until the second measurement period is reached.

3. The image forming apparatus according to claim 1, wherein The control means activates the first replenishing means when measuring the concentration of the developer remaining in the developing device.

4. The image forming apparatus according to claim 2, wherein: The control means activates the first replenishing means on standby when the second measurement time comes.

5. The image forming apparatus according to claim 3, wherein The control means activates the second supplementary means during operation of the first supplementary means.

6. The image forming apparatus according to claim 4, wherein The control means activates the second supplementary means during operation of the first supplementary means.

7. The image forming apparatus according to any one of claims 1 to 6, wherein: The predetermined value in the first replenishing member is a value equal to or greater than a first threshold value that is a lower limit value of a first allowable concentration value of the developer in the at least one developing device. The predetermined value in the second replenishing member is a value equal to or greater than a second threshold value that is a lower limit value of a second allowable concentration value of the developer in the remaining developing device. The control means uses, as the first threshold value, a value consisting of a deviation amount smaller than a deviation amount of the second threshold value from the second allowable concentration value.

8. The image forming apparatus according to any one of claims 1 to 7, wherein When the concentration of the developer returns to the allowable concentration value at a stage where the number of replenishments of the first replenishing component does not exceed the upper limit value, the control component will maintain the result of the exhaustion detection that determines that the developer in at least one developing device is exhausted as the determination result that the developer is not exhausted until the concentration of the remaining developer in the developing device is measured.

Images