Image-forming device, image-forming method, and program

Abstract

To realize a more stable adjustment of image density by excluding an influence of diverse variation factors causing the image density to be unstable.SOLUTION: An image-forming device comprises: image-forming means for forming a toner image on an image carrier; first transfer means for transferring the toner image formed on the image carrier to a first image-carrying belt; second transfer means for transferring the toner image transferred onto the first image-carrying belt onto a second image-carrying belt; adhesion amount detection means for detecting the amount of adhesion of toner of the toner image transferred onto the second image-carrying belt; and control means. The control means comprises: a pattern-forming section for forming a pattern image between pieces of paper; a setting section for setting a representative value of a variation value of a detection adhesion amount on the basis of the detection adhesion amount that is the amount of adhesion of toner detected by the adhesion amount detection means; a calculation section for calculating a variation value of a detection adhesion amount of a pattern image by using a representative value and the detection adhesion amount of a pattern image detected by the adhesion amount detection means; a correction section for correcting the detection adhesion amount of the pattern image by using the variation value; and an adjustment section for adjusting an image-forming condition of the toner image.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an image forming apparatus that includes an imaging unit equipped with a photosensitive member, a developing unit, etc., and a control unit that performs a target value correction process to correct the control target value of a control parameter that affects the development capability of the imaging unit with a correction amount determined by a predetermined algorithm.The image forming apparatus is provided with an image density sensor that detects the image density of an image formed by the imaging unit, and the control unit is configured to perform a correction process to correct the algorithm based on the detection result of the image density by the image density detection sensor. Summary of the Invention [Problem to be solved by the invention]

[0003] However, with the configuration described in Patent Document 1, when the transfer pressure at the secondary transfer nip is changed depending on the type of recording medium used, it is difficult to optimize the image creation conditions during image formation in accordance with the change in transfer pressure, resulting in unstable image density. Also, while there are various factors (variation factors) that cause unstable image density, conventional technologies do not take these factors into consideration, resulting in insufficient optimization.

[0004] The present invention has been made in consideration of the above, and aims to enable more stable adjustment of image density by eliminating the influence of various variable factors that cause unstable image density. [Means for solving the problem]

[0005] The present invention is an image forming apparatus comprising: an image carrier that forms an electrostatic latent image; an image creating unit that develops the electrostatic latent image formed on the image carrier to form a toner image; a first image carrier belt; a first transfer unit that transfers the toner image formed on the image carrier to the first image carrier belt; a second image carrier belt; a second transfer unit that transfers the toner image transferred onto the first image carrier belt to the second image carrier belt; an adhesion amount detection unit that detects the toner adhesion amount of the toner image transferred onto the second image carrier belt; and a control unit, wherein the control unit comprises: a pattern forming unit that forms a predetermined pattern image between sheets; a setting unit that sets a representative value of the fluctuation value of the detected adhesion amount based on the detected adhesion amount, which is the toner adhesion amount detected by the adhesion amount detection unit; a calculation unit that calculates the fluctuation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection unit; a correction unit that corrects the detected adhesion amount of the pattern image using the fluctuation value; and an adjustment unit that adjusts the image creating conditions of the toner image. [Effects of the Invention]

[0006] According to the present invention, the effects of various variable factors that cause unstable image density can be eliminated, thereby enabling more stable image density adjustment. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram showing an example of the peripheral configuration of the secondary transfer unit. [Figure 3] FIG. 3 is an explanatory diagram showing an example of a concentration sensor. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between the fluctuation factors and the detected adhesion amount. [Figure 5] FIG. 5 is a diagram showing an example of the calculation results of fluctuation values ​​for fluctuation factors stored in the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of a hardware configuration of the controller. [Figure 7] FIG. 7 is a diagram illustrating an example of a functional configuration of the controller according to the first embodiment. [Figure 8] FIG. 8 is a flowchart showing the procedure for setting the representative value. [Figure 9] FIG. 9 is a flowchart showing the procedure for adjusting the image forming conditions using the pattern image between sheets. [Figure 10] FIG. 10 is a diagram illustrating an example of a functional configuration of a controller according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of an image forming apparatus, an image forming method, and a program will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0009] (First embodiment) 1 is a schematic diagram showing an example of an image forming apparatus 500 according to the first embodiment. The illustrated image forming apparatus 500 is a printing apparatus that finally transfers and fixes a toner image formed using an electrophotographic method onto a recording medium such as paper, and outputs the image as a printed matter.

[0010] The image forming apparatus 500 includes a toner image forming section 1, a primary transfer unit 2, a sheet supply unit 3, a secondary transfer unit 4, a conveyor belt unit 5, a fixing unit 6, a double-sided conveying unit 7, a sheet discharge unit 8, an exposure unit 9, a toner bottle mounting section 10, and a controller 400. Of these, the toner image forming section 1, which is an example of an image creating section, includes multiple photosensitive developing units 10a, 10b, 10c, and 10d. The controller 400, which is an example of a control section, controls the image forming apparatus 500 in an overall manner using a hardware configuration described below.

[0011] The photosensitive developing units 10a to 10d are arranged along the direction of movement of the primary transfer belt 20 described below, and for example, the photosensitive developing unit 10a forms a yellow (Y) toner image, the photosensitive developing unit 10b forms a magenta (M) toner image, the photosensitive developing unit 10c forms a cyan (C) toner image, and the photosensitive developing unit 10d forms a black (K) toner image.

[0012] Each photosensitive developing unit 10a to 10d includes a drum-shaped photosensitive member 11a, 11b, 11c, 11d which is an example of an image carrier, a charging device 12a, 12b, 12c, 12d which charges the surface of the photosensitive member 11a to 11d, a developing device 13a, 13b, 13c, 13d which develops the electrostatic latent image formed on the photosensitive member 11a to 11d, and a cleaning device 14a, 14b, 14c, 14d which cleans the surface of the photosensitive member 11a to 11d.

[0013] The primary transfer unit 2, which is an example of a first transfer means, is arranged below the toner image forming section 1, and includes a primary transfer belt 20, which is an example of a first image carrying belt, primary transfer rollers 21a, 21b, 21c, and 21d, a secondary transfer opposing roller 22, and a primary transfer belt cleaning device 23.

[0014] The primary transfer belt 20 is an endless belt made of a single layer or multiple layers of PVDF (vinyldiene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc. The primary transfer belt 20 moves in the clockwise direction (direction of arrow A) in the figure while being stretched over primary transfer rollers 21a to 21d, a secondary transfer opposing roller 22, and multiple support rollers.

[0015] The primary transfer belt 20 is sandwiched between the primary transfer rollers 21a-21d and the opposing photoconductors 11a-11d. This brings the primary transfer belt 20 into contact with the photoconductors 11a-11d, forming a primary transfer portion (primary transfer nip portion). The primary transfer portion forms a primary transfer electric field between the primary transfer rollers 21a-21d and the photoconductors 11a-11d so that the toner images formed on the surfaces of the photoconductors 11a-11d are electrostatically transferred to the primary transfer belt 20. When the primary transfer belt 20 receives the toner images from the photoconductors 11a-11d at a position where it contacts the photoconductors 11a-11d, it transports the toner images toward the secondary transfer opposing roller 22 by moving the primary transfer belt 20 in the direction of arrow A.

[0016] The secondary transfer opposing roller 22 forms a secondary transfer portion (secondary transfer nip portion) together with a secondary transfer roller 41, which will be described later.

[0017] The primary transfer belt cleaning device 23 is disposed downstream of the secondary transfer opposing roller 22 in the movement direction of the primary transfer belt 20 , and cleans the surface of the primary transfer belt 20 that has passed the secondary transfer opposing roller 22 .

[0018] The sheet supply unit 3 is disposed below the primary transfer unit 2, and includes conveyance rollers 30 and 31 for conveying recording media, which are separated and sent out one by one from the sheet storage section, to the secondary transfer unit 4. The sheet storage section is connected to the main body of the image forming apparatus 500 so as to communicate with the sheet conveyance paths 3a, 3b, and 3c of the sheet supply unit 3, but is not shown here.

[0019] The secondary transfer unit 4, which is an example of a second transfer means, is arranged below the primary transfer unit 2, and includes a secondary transfer belt 40, which is an example of a second image bearing belt, and a secondary transfer roller 41.

[0020] The secondary transfer belt 40 is an endless belt made of a single layer or multiple layers of PVDF (vinyldiene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), or the like. The secondary transfer belt 40 moves counterclockwise in the drawing while being stretched over a secondary transfer roller 41 and multiple support rollers. The secondary transfer belt 40 transports the recording medium sent by the transport roller 30, and transfers the toner image on the primary transfer belt 20 to the recording medium at a position (secondary transfer portion) where the secondary transfer roller 41 faces a secondary transfer opposing roller 22. Details of the secondary transfer unit 4 will be described later.

[0021] The conveyor belt unit 5 is disposed below the primary transfer unit 2 and guides the recording medium that has passed through the secondary transfer unit 4 to the fixing unit 6 .

[0022] The fixing unit 6 is disposed below the primary transfer unit 2, and fixes the toner image transferred to the recording medium by the secondary transfer unit 4, for example, by applying heat and pressure to the toner image.

[0023] The double-sided conveying unit 7 is located below the secondary transfer unit 4, conveying belt unit 5, and fixing unit 6, and when double-sided printing is performed, the recording medium after fixing passes through the double-sided conveying unit 7 and is returned to the conveying roller 31 side.

[0024] The sheet discharge unit 8 is located after the fixing unit 6 (downstream in the recording medium transport direction), and transports the recording medium sent out from the fixing unit 6 outside the image forming device 500 or toward the double-sided transport unit 7.

[0025] The exposure unit 9 is disposed above the toner image forming section 1, and the laser light emitted from the light source is guided to the photosensitive members 11a to 11d via optical members such as lenses and mirrors, and the laser light forms an electrostatic latent image on the surface of the photosensitive members 11a to 11d.

[0026] The toner bottle mounting section 10 is disposed above the exposure unit 9, and toner bottles 100a, 100b, 100c, and 100d containing toner to be supplied to the developing devices 13a to 13d are detachably provided in the toner bottle mounting section 10.

[0027] In the above configuration, when image forming apparatus 500 receives image data from an external computer or the like, it starts a print job and begins driving toner image forming unit 1, primary transfer unit 2, exposure unit 9, and the like. In toner image forming unit 1, charging devices 12a-12d uniformly charge the surfaces of rotationally driven photoconductors 11a-11d to a predetermined charging potential. After charging, electrostatic latent images are formed on the surfaces of photoconductors 11a-11d by exposure unit 9 based on image data. The electrostatic latent images formed on photoconductors 11a-11d are developed into toner images by developing devices 13a-13d, and then sequentially transferred onto primary transfer belt 20. After the toner images are transferred, the surfaces of photoconductors 11a-11d are cleaned by cleaning devices 14a-14d.

[0028] In parallel with the formation of the toner image, the sheet supply unit 3 conveys the recording medium toward the conveying roller 30. The conveying roller 30 also functions as a registration roller, and when the recording medium strikes the conveying roller 30, the conveyance of the recording medium is temporarily stopped. The conveying roller 30 then resumes conveying the recording medium in time with the toner image transferred to the primary transfer belt 20 reaching the secondary transfer nip. Once the conveyance of the recording medium has resumed, the toner image is transferred to the surface of the recording medium in synchronization with the toner image on the primary transfer belt 20 within the secondary transfer nip. After the toner image has been transferred, the recording medium is conveyed by the conveying belt unit 5 to the fixing unit 6. Heat and pressure are applied to the recording medium with the toner image thereon in the fixing unit 6, and the toner image is fixed to the recording medium.

[0029] After fixing, the recording medium moves to sheet discharge unit 8, where, for example, a direction switching claw is operated to switch the path of the recording medium to either the outside of image forming apparatus 500 or duplex conveying unit 7. If the recording medium is sent from sheet discharge unit 8 to duplex conveying unit 7, it is sent again to the secondary transfer nip, where a toner image is formed on the back side of the recording medium, and then discharged from sheet discharge unit 8. In addition, after passing through the secondary transfer nip, the surface of primary transfer belt 20 is cleaned by primary transfer belt cleaning device 23, and toner remaining on the surface of primary transfer belt 20 is removed. Note that image forming apparatus 500 is equipped with temperature and humidity sensor 200 that detects the temperature and humidity inside the main body, and temperature and humidity information detected by temperature and humidity sensor 200 is used when adjusting image formation conditions, which will be described later.

[0030] The number of photosensitive developing units 10a to 10d and toner bottles 100a to 100d mounted in the image forming apparatus 500 may be increased or decreased as appropriate depending on the number and types of toner colors used in the image forming apparatus 500.

[0031] Furthermore, the recording medium used for printing is not limited to paper, and can be applied to various materials other than paper, such as fiber, fabric, leather, metal, plastic, glass, wood, and ceramics.

[0032] Next, the configuration of the secondary transfer unit 4 and its surroundings will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram showing an example of the configuration of the secondary transfer unit 4 and its surroundings.

[0033] 1, the secondary transfer unit 4 includes a plurality of support rollers 42a, 42b, 42c, and 42d, a density sensor 43 which is an example of adhesion amount detection means, a secondary transfer belt cleaning device 44, and a frame 45 which holds the secondary transfer belt 40, the secondary transfer roller 41, the support rollers 42a to 42d, the density sensor 43, and the secondary transfer belt cleaning device 44. The secondary transfer unit 4 also includes a pressure device 46 which is an example of transfer pressure changing means.

[0034] The secondary transfer belt 40 moves counterclockwise in the figure (in the direction of arrow B) while being stretched over a secondary transfer roller 41 and multiple support rollers 42a to 42d. The secondary transfer roller 41 sandwiches the secondary transfer belt 40 between itself and the opposing primary transfer belt 20, forming a secondary transfer region (secondary transfer nip region) P where the primary transfer belt 20 and secondary transfer belt 40 face each other. The secondary transfer nip region P forms a secondary transfer electric field for electrostatically transferring the toner image T transferred onto the surface of the primary transfer belt 20 to the recording medium S being conveyed. The secondary transfer region P also forms a secondary transfer electric field for electrostatically transferring the toner image T' transferred onto the surface of the primary transfer belt 20 to the secondary transfer belt 40.

[0035] The density sensor 43 is disposed opposite the surface of the secondary transfer belt 40, and detects the amount of toner (toner adhesion amount) adhered to the secondary transfer belt 40 when the toner image T' is transferred from the primary transfer belt 20 to the secondary transfer belt 40. The density sensor 43 includes a light-emitting element such as an infrared LED (Light Emitting Diode), and a light-receiving element such as a phototransistor that receives reflected light and outputs an electrical signal according to the intensity of the received light. Note that the density sensor 43 is not limited to this, and may be any sensor that can detect the toner adhesion amount.

[0036] The secondary transfer belt cleaning device 44 is disposed downstream of the density sensor 43 in the direction of movement of the secondary transfer belt 40 , and cleans the surface of the secondary transfer belt 40 that has passed the density sensor 43 .

[0037] The pressure device 46 includes a cam member 47 and an arm member 48 that is supported so as to be swingable in the direction of arrow C in response to rotation of the cam member 47. The pressure device 46 is provided at a position where the arm member 48 can come into contact with a part of the frame body 45, and the frame body 45 is also provided so as to be displaceable in the direction of arrow C according to the position of the arm member 48. In other words, the pressure (transfer pressure) generated in the secondary transfer nip portion P can be changed by the pressure device 46.

[0038] At the secondary transfer nip P, the recording medium S onto which the toner image T has been transferred from the primary transfer belt 20 is then transported in the direction of arrow D, where the above-mentioned toner image fixing and other processes are carried out. On the other hand, the toner image T' is not transferred to the recording medium S at the secondary transfer nip P, but is transferred to the secondary transfer belt 40 in a no-recording-medium section (paper gap) set between the preceding and succeeding recording media. Here, the toner image T' is, for example, a predetermined pattern image, and is formed on the secondary transfer belt 40 each time a predetermined number of toner images T are transferred to the recording media S, and is detected by the density sensor 43.

[0039] Here, the reason why the density sensor 43 is provided in the secondary transfer unit 4 will be explained with reference to Fig. 3. Fig. 3 is an explanatory diagram showing an example of the density sensor 43.

[0040] The density sensor 43 includes a light-emitting element 43a such as an infrared LED, a specular reflection light receiving element 43b that receives so-called specularly reflected light that is reflected at a reflection angle equal to the angle of incidence of the incident light on the reflecting surface Rs, and a diffuse reflection light receiving element 43c that receives light that is diffusely reflected by the reflecting surface Rs. Consider a case where this density sensor 43 is used as a specular reflection light detection method in which specular reflection light is detected by the specular reflection light receiving element 43b, and the reflecting surface Rs is made of an elastic material.

[0041] In this case, since there is no toner image on the reflecting surface Rs in the state shown in Figure 3(a), the light from the light emitting element 43a is reflected in proportion to the specular gloss of the elastic body surface, and the reflected light is detected by the specular reflection light receiving element 43b.

[0042] However, when a toner image t is attached to the reflective surface Rs as shown in Figure 3(b), the toner image t scatters light, and the amount of specularly reflected light decreases as the amount of attached toner increases. In particular, when the toner image t is black toner, the light from the light emitting element 43a is scattered or absorbed by the toner surface, resulting in a significant decrease in specularly reflected light.

[0043] Furthermore, when determining the amount of toner adhesion based on the specularly reflected light detected by the specularly reflected light receiving element 43b, the amount can be determined using the ratio between the smoothness of the reflecting surface Rs and the roughness of the toner image t, i.e., the specular gloss ratio. However, if the reflecting surface Rs is an elastic body, its surface is relatively rough, making it difficult for the density sensor 43 to obtain specularly reflected light from the reflecting surface Rs, and thus making it difficult to accurately determine the amount of toner adhesion.

[0044] In the image forming apparatus 500 of this embodiment, the primary transfer belt 20 is an elastic belt having an elastic layer on at least its surface. Therefore, when attempting to detect the amount of toner adhesion on the primary transfer belt 20, a problem arises in that the amount of toner adhesion cannot be detected accurately. In contrast, the secondary transfer belt 40 is made of a resin film with high gloss, such as a PI (polyimide) film. This makes it easier for the density sensor 43 to obtain specularly reflected light from the reflective surface Rs and to determine the ratio of the specular gloss of the reflective surface Rs to that of the toner image t. For these reasons, in this embodiment, the density sensor 43 is provided in the secondary transfer unit 4.

[0045] 2, the secondary transfer unit 4 is equipped with a pressure device 46 to enable printing on various types of recording media (for example, paper of various thicknesses and surface roughnesses). The secondary transfer unit 4 sets the pressure (transfer pressure) of the secondary transfer nip P to an appropriate value using the pressure device 46 depending on the type of recording medium, and transfers the toner image T onto the recording medium S.

[0046] On the other hand, since the toner image T' (pattern image) formed between the sheets is to be transferred to the secondary transfer belt 40, it should be transferred to the secondary transfer belt 40 under a constant transfer pressure regardless of the type of recording medium S used for printing.

[0047] However, in the conventional image forming apparatus 500, when the pattern image T' is transferred to the secondary transfer belt 40, the same transfer pressure is used as when the toner image T is transferred to the recording medium S. In other words, when attempting to switch the transfer pressure between sheets of paper, the transfer pressure switching operation cannot keep up with the printing speed, which reduces the productivity of printed matter. For this reason, the transfer of the toner image T to the recording medium S and the transfer of the pattern image T' to the secondary transfer belt 40 are carried out using the same transfer pressure.

[0048] As a result, the transfer rate of the pattern image T' to the secondary transfer belt 40 decreases, and the toner adhesion amount (detected adhesion amount) calculated based on the detection value of the density sensor 43 also becomes lower than the actual toner adhesion amount (target detected adhesion amount). In other words, the detected adhesion amount fluctuates due to fluctuations in transfer pressure. Hereinafter, the value by which the detected adhesion amount fluctuates from the target detected adhesion amount (deviation amount of the detected adhesion amount) will be referred to as the fluctuation value.

[0049] The relationship between the transfer pressure and the adhesion amount detection value may differ depending on the combination of materials of the primary transfer belt 20 and the secondary transfer belt 40. In this embodiment, the primary transfer belt 20 is an elastic belt, and the secondary transfer belt 40 is a PI film. In this case, the influence of minute gap discharges that occur between the elastic belt and the toner image, and between the PI film and the toner image, tends to increase as the transfer pressure increases, and it is thought that the higher the transfer pressure, the lower the adhesion amount detection value. Note that the opposite configuration may also be adopted, in which the higher the transfer pressure, the higher the adhesion amount detection value.

[0050] The detected adhesion amount fluctuates due to factors other than transfer pressure. In other words, the fluctuation value is also caused by factors other than transfer pressure. For example, if the difference in the moving speed between the primary transfer belt 20 and the secondary transfer belt 40 (the speed difference between the two transfer belts) fluctuates, the detected adhesion amount fluctuates. In addition, if the temperature or humidity inside the main body fluctuates, the detected adhesion amount may also fluctuate. Furthermore, there are differences between image forming apparatuses, and even if the same model is used, there are variations due to individual differences in components and aging, so the detected adhesion amount also fluctuates due to differences between machines. In this way, the factors that cause fluctuations in the detected adhesion amount are the same factors that cause fluctuations in density.

[0051] As a result, when adjusting image creation conditions such as the density of a toner image using the detected adhesion amount, a new problem arises in that optimal adjustment (optimization) cannot be achieved because the detected adhesion amount fluctuates. In other words, the inability to optimize image creation conditions results in unstable (fluctuating) toner image density during continuous printing, resulting in a problem of reduced image quality.

[0052] In this embodiment, the fluctuations in the density of the toner image caused by the various fluctuation factors described above are measured in advance, the measurement results are stored, and the value used to correct the detected adhesion amount is calculated based on the stored measurement results, thereby eliminating the effects of these various factors.

[0053] The relationship between the variation factors and the detected adhesion amount and the correction process will be described below with reference to FIG. 4. FIG. 4 is an explanatory diagram showing the relationship between the variation factors and the detected adhesion amount. In FIG. 4, the horizontal axis represents the variation factors and the vertical axis represents the detected adhesion amount. The dashed-dotted line represents the detected adhesion amount calculated based on the detection value of the concentration sensor 43 (the detected adhesion amount before correction), and the solid line represents the detected adhesion amount corrected by the correction process described below (the detected adhesion amount after correction). Note that variation factors such as transfer pressure, the speed difference between the two transfer belts, temperature and humidity fluctuations, and machine differences are collectively represented by the variable Px (x is t, a, b, c, etc.). Here, Mt is the target detected adhesion amount, and this value is obtained from the concentration sensor 43 without correction when the variation factor is Pt. Furthermore, when the variation factor is values ​​Pa, Pb, and Pc other than Pt, the detected adhesion amounts obtained from the concentration sensor 43 are Ma, Mb, and Mc, respectively.

[0054] In this example, the fluctuation values ​​Vta, Vtb, and Vtc corresponding to the fluctuation factors Pa, Pb, and Pc are calculated by the following equations (1) to (3).

[0055] Vta = Mt - Ma (1) Vtb = Mt - Mb (2) Vtc = Mt - Mc (3)

[0056] FIG. 5 is a diagram showing an example of the calculation results (table) of the fluctuation values ​​for the fluctuation factors stored in this embodiment. Here, the fluctuation values ​​obtained by prior measurement are referred to as representative values. By storing the values ​​of multiple fluctuation factors and their corresponding representative values ​​in a table, the values ​​can be used when adjusting the image formation conditions using the sheet-to-sheet pattern image T'. Specifically, if the fluctuation factor Px is found when the detected adhesion amount Mx is calculated using the sheet-to-sheet pattern image T', the corresponding fluctuation value Vtx is calculated with reference to the representative value. For example, if Px is close to a stored fluctuation factor, the fluctuation value corresponding to that fluctuation factor is read from the table. If Px is different from the fluctuation factor stored in the table, the representative value in the table is interpolated to find the fluctuation value. When finding the fluctuation value by interpolation, linear interpolation using a linear function or curve interpolation using a quadratic function or the like can be used.

[0057] When the fluctuation value is calculated by subtraction as in equations (1) to (3), the corrected value Mx' of the detected adhesion amount Mx is calculated by the following equation (4) using the fluctuation value Vtx.

[0058] Mx´=Mx+Vtx (4)

[0059] The fluctuation values ​​Vta, Vtb, and Vtc corresponding to the fluctuation factors Pa, Pb, and Pc may be calculated by division as shown in the following equations (5) to (7). In this case, the correction value Mx' of the detected adhesion amount Mx is calculated by the following equation (8) using the fluctuation value Vtx.

[0060] Vta = Mt / Ma (5) Vtb=Mt / Mb (6) Vtc=Mt / Mc (7) Mx´ = Mx × Vtx (8)

[0061] 6 is a diagram showing an example of the hardware configuration of the controller 400. The controller 400 is constructed by a computer, and includes a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, a RAM (Random Access Memory) 403, a non-volatile element 404, and a bus line 405.

[0062] The CPU 401 controls the overall operation of the image forming apparatus 500. The ROM 402 stores programs used to drive the CPU 401, such as an IPL (Initial Program Loader). The RAM 403 is used as a work area for the CPU 401. The non-volatile element 404 is a hard disk drive (HDD), a solid-state drive (SSD), a non-volatile RAM (NVRAM), an electrically erasable programmable ROM (EEPROM), or the like, and is a storage unit that reads and writes various information such as programs and data. The bus line 405 is an address bus, a data bus, or the like for electrically connecting the components such as the CPU 401 shown in FIG. 6.

[0063] 7 is a diagram showing an example of the functional configuration of the controller 400 according to this embodiment. The controller 400 includes a pattern forming unit 4001, a setting unit 4011, a calculation unit 4020, a correction unit 4021, and an adjustment unit 4022. Each of these functional units is configured by cooperation between the hardware constituting the controller 400 as shown in FIG. 6 and software (programs, etc.). Furthermore, at least one of the functional units may be configured by dedicated hardware (circuits, etc.). Note that the functional configuration of the controller 400 is not limited to this.

[0064] The pattern forming unit 4001 forms a pattern image T' formed between sheets of paper. Note that the pattern forming unit 4001 also forms a pattern image T' when a setting unit 4011, which will be described later, sets a representative value.

[0065] The setting unit 4011 sets the representative value at a predetermined timing. The predetermined timing may be when the image forming apparatus 500 is shipped from the factory, when the power is turned on on an operation day after installation, or every time a certain number of sheets are printed after operation. Alternatively, the representative value may be set at any timing by the user. If the influence of the temperature and humidity of the installation location of the image forming apparatus 500 and the influence of aging of the used parts are small, the frequency of the predetermined timing may be reduced.

[0066] 8 is a flowchart showing the procedure for setting the representative value. First, the pattern forming unit 4001 forms a pattern image T' (step S10), and the secondary transfer unit 4 transfers the toner image to the secondary transfer belt 40 with the fluctuation factor Pn (step S11). Here, n is a natural number and its initial value is set to 1. Next, the density sensor 43 obtains the toner adhesion amount (detected adhesion amount Mn corresponding to the fluctuation factor Pn) (step S12).

[0067] Next, the setting unit 4011 calculates a representative value Vtn from the acquired detected adhesion amount Mn and the target detected adhesion amount Mt (step S13), and sets (adds) the calculated representative value Vtn to the table (step S14).

[0068] If n is equal to the maximum value N (N is a natural number), the setting unit 4011 proceeds to step S17, and if n has not reached the maximum value N, the setting unit 4011 increments the value of n by 1 (step S16) and returns to step S10 (step S15). The setting unit 4011 stores a set (table) of the values ​​of the N variation factors P1 to PN and their corresponding representative values ​​Vt1 to VtN in the non-volatile element 404 (step S17).

[0069] In the above example, a toner image was transferred onto the secondary transfer belt 40 for each of the N variation factors and N representative values ​​were set, but when setting (updating) representative values ​​at a timing after installation, a toner image may be transferred onto the secondary transfer belt 40 for fewer than N variation factors. For example, a toner image may be transferred onto the secondary transfer belt 40 at Pb in FIG. 5 to update Vtb, and representative values ​​other than Vtb may be updated by reflecting the amount of change in Vtb (the difference between the previously set Vtb and the currently set Vtb). Note that it is also possible to transfer a toner image onto the secondary transfer belt 40 for each of all variation factors and update the representative values ​​at a timing after installation.

[0070] The calculation unit 4020, correction unit 4021, and adjustment unit 4022 are functional units used when adjusting image formation conditions using the inter-sheet pattern image T' after installation of the image forming apparatus 500. The calculation unit 4020 uses a table stored in the non-volatile element 404 to calculate a fluctuation value corresponding to a fluctuation factor during transfer to the secondary transfer belt 40. The correction unit 4021 corrects the detected adhesion amount obtained from the density sensor 43 using the fluctuation value calculated by the calculation unit 4020. As described above, addition or multiplication can be used for the correction. The adjustment unit 4022 adjusts the image formation conditions using the detected adhesion amount corrected by the correction unit 4021. Specifically, the corrected adhesion amount detection value is notified to the toner image forming unit 1, etc., and the toner image forming unit 1, etc. forms a toner image by regarding the notified adhesion amount detection value as a correct value.

[0071] 9 is a flowchart showing the procedure for adjusting the image forming conditions using the pattern image T' between sheets. First, the pattern forming unit 4001 forms the pattern image T' between sheets (step S20), and the secondary transfer unit 4 transfers the toner image onto the secondary transfer belt 40 (step S21). Here, the fluctuation factor during transfer is assumed to be Px. Next, the density sensor 43 obtains the toner adhesion amount (detected adhesion amount Mx corresponding to the fluctuation factor Px) (step S22).

[0072] Next, the calculation unit 4020 calculates a fluctuation value Vtx corresponding to the fluctuation factor Px using the detected adhesion amount Mx and the table (step S23), and the correction unit 4021 corrects the detected adhesion amount Mx using the fluctuation value Vtx (step S24).Then, the adjustment unit 4022 adjusts the image formation conditions using the corrected detected adhesion amount (step S25).

[0073] In this way, according to this embodiment, the fluctuations in density of a toner image caused by various fluctuation factors are measured in advance, representative values ​​are stored, the detected adhesion amount is corrected using a fluctuation value calculated based on the stored representative values, and the image creation conditions are adjusted using the corrected detected adhesion amount, thereby eliminating the effects of various fluctuation factors and enabling more stable image density adjustment.

[0074] (Second embodiment) If the representative value described above differs for each density of the pattern image T', a representative value may be set for each density. In this embodiment, the pattern image T' is formed with a plurality of densities, and a representative value is set and a variation value is calculated for each density, thereby improving the accuracy of correction and adjustment of the image-forming conditions.

[0075] 10 is a diagram showing an example of the functional configuration of a controller 400 according to this embodiment. The difference from the first embodiment is that a density setting unit 4002 is newly provided. In the following description of this embodiment, the same parts as those in the first embodiment will be omitted, and only the parts that differ from the first embodiment will be described.

[0076] The density setting unit 4002 sets the density of the pattern image T'. For example, the density of the pattern image T' can be set to 20 gradations, 40 gradations, 60 gradations, 80 gradations, 100 gradations, 120 gradations, 140 gradations, 160 gradations, 180 gradations, 200 gradations, or 220 gradations. For example, the smaller the gradation value, the higher the density. The gradation value may be set appropriately depending on the model and usage state of the image forming apparatus 500. Furthermore, the number of densities and the gradation value of each density can be changed appropriately.

[0077] A pattern forming unit 4001 forms a pattern image at a density set by a density setting unit 4002. A setting unit 4011 sets a representative value for each density of the formed pattern image, and a table including the set representative values ​​is stored for each density in a non-volatile element 404. A calculation unit 4020 calculates a variation value by referring to the representative value stored for each density of the formed pattern image.

[0078] The process of setting a representative value for each density can be realized by executing steps S10 to S17 in the flowchart shown in Fig. 8 for each density of the pattern image T'. Also, the process of calculating a fluctuation value for each density and adjusting the image-forming conditions can be realized by executing steps S20 to S25 in the flowchart shown in Fig. 9 for each density of the pattern image T'.

[0079] In this way, according to this embodiment, it is possible to calculate a fluctuation value for each density of the pattern image, correct the detected adhesion amount, and adjust the image creation conditions, thereby improving the accuracy of the correction and enabling more stable adjustment of the image density.

[0080] Although various embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These novel embodiments and modifications thereof are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, components from different embodiments and modifications may be combined as appropriate.

[0081] For example, aspects of the present invention are as follows. <1> an image forming apparatus comprising: an image carrier for forming an electrostatic latent image; an image forming unit for developing the electrostatic latent image formed on the image carrier to form a toner image; a first image carrier belt; a first transfer unit for transferring the toner image formed on the image carrier to the first image carrier belt; a second image carrier belt; a second transfer unit for transferring the toner image transferred onto the first image carrier belt to the second image carrier belt; an adhesion amount detection unit for detecting the amount of toner adhesion of the toner image transferred onto the second image carrier belt; and a control unit, wherein the control unit controls a pattern forming unit for forming a predetermined pattern image between sheets. a setting unit that sets a representative value of the fluctuation value of the detected adhesion amount based on the detected adhesion amount, which is the amount of toner adhesion detected by the adhesion amount detection means; a calculation unit that calculates the fluctuation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction unit that corrects the detected adhesion amount of the pattern image using the fluctuation value; and an adjustment unit that adjusts the image creation conditions of the toner image, wherein the control unit adjusts the image creation conditions of the toner image using the detected adhesion amount of the pattern image corrected by the correction unit. <2> The fluctuation value is caused by an instrument difference. <1> 2. The image forming apparatus according to claim 1, wherein: <3> the fluctuation value is generated by a difference in transfer pressure in the second transfer means; <1> 2. The image forming apparatus according to claim 1, wherein: <4> the fluctuation value is caused by a difference in speed between the first image bearing belt and the second image bearing belt; <1> 2. The image forming apparatus according to claim 1, wherein: <5> the control means further comprises a density setting unit that sets a density of the pattern image to a predetermined value, the density setting unit sets a plurality of densities of the pattern image, the pattern forming unit forms the pattern image at the plurality of densities set by the density setting unit, the setting unit sets the representative value for each density of the pattern image, and the calculation unit calculates the variation value for each density of the pattern image; <1> ~ <4> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <6> an image forming method for use in an image forming apparatus including an image carrier that forms an electrostatic latent image, an image forming unit that develops the electrostatic latent image formed on the image carrier to form a toner image, a first image carrier belt, a first transfer unit that transfers the toner image formed on the image carrier to the first image carrier belt, a second image carrier belt, a second transfer unit that transfers the toner image transferred onto the first image carrier belt to the second image carrier belt, and an adhesion amount detection unit that detects the amount of toner adhesion of the toner image transferred onto the second image carrier belt, the image forming method comprising: a pattern forming step that forms a predetermined pattern image between sheets; The image forming method includes a setting step of setting a representative value of the fluctuation value of the detected adhesion amount based on the detected adhesion amount, which is the toner adhesion amount detected by the amount detection means; a calculation step of calculating a fluctuation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction step of correcting the detected adhesion amount of the pattern image using the fluctuation value; and an adjustment step of adjusting the image formation conditions of the toner image, wherein the adjustment step adjusts the image formation conditions of the toner image using the detected adhesion amount of the pattern image corrected in the correction step. <7> In an image forming apparatus comprising an image carrier that forms an electrostatic latent image, an image forming means that forms a toner image by developing the electrostatic latent image formed on the image carrier, a first image carrier belt, a first transfer means that transfers the toner image formed on the image carrier to the first image carrier belt, a second image carrier belt, a second transfer means that transfers the toner image transferred onto the first image carrier belt to the second image carrier belt, and an adhesion amount detection means that detects the amount of toner adhesion of the toner image transferred onto the second image carrier belt, the image forming apparatus further comprising: a computer; a pattern forming function that forms a predetermined pattern image between sheets; The toner image forming apparatus operates as a setting function that sets a representative value of the fluctuation value of the detected adhesion amount based on the detected adhesion amount, which is the toner adhesion amount detected in the first stage; a calculation function that calculates a fluctuation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction function that corrects the detected adhesion amount of the pattern image using the fluctuation value; and an adjustment function that adjusts the image forming conditions of the toner image, wherein the adjustment function is a program that adjusts the image forming conditions of the toner image using the detected adhesion amount of the pattern image corrected by the correction function. [Explanation of symbols]

[0082] 1 Toner image forming unit 2 Primary Transfer Unit 4 Secondary transfer unit 20 Primary transfer belt 40 Secondary transfer belt 43 Concentration sensor 46 Pressure device 400 Controller 500 Image forming device [Prior art documents] [Patent documents]

[0083] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-056124

Claims

1. an image carrier on which an electrostatic latent image is formed; an image forming means for developing the electrostatic latent image formed on the image carrier to form a toner image; a first image bearing belt; a first transfer means for transferring the toner image formed on the image carrier onto the first image carrier belt; a second image bearing belt; a second transfer means for transferring the toner image transferred onto the first image bearing belt onto the second image bearing belt; an adhesion amount detecting means for detecting the amount of toner adhesion of the toner image transferred onto the second image carrying belt; a control means; An image forming apparatus comprising: The control means a pattern forming unit that forms a predetermined pattern image between sheets of paper; a setting unit that sets a representative value of fluctuations in the detected adhesion amount based on the detected adhesion amount, which is the amount of toner adhesion detected by the adhesion amount detection unit; a calculation unit that calculates a variation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction unit that corrects the detected adhesion amount of the pattern image using the fluctuation value; an adjusting unit that adjusts the image forming conditions of the toner image, The control unit adjusts the image forming conditions for the toner image using the detected adhesion amount of the pattern image corrected by the correction unit.

2. The image forming apparatus according to claim 1 , wherein the fluctuation value is caused by machine differences.

3. 2. The image forming apparatus according to claim 1, wherein the fluctuation value is caused by a difference in transfer pressure in the second transfer means.

4. 2. The image forming apparatus according to claim 1, wherein the fluctuation value is caused by a difference in speed between the first image bearing belt and the second image bearing belt.

5. the control means further includes a density setting unit that sets the density of the pattern image to a predetermined value; the density setting unit sets a plurality of densities of the pattern image; the pattern forming unit forms the pattern image at a plurality of densities set by the density setting unit, the setting unit sets the representative value for each density of the pattern image; The image forming apparatus according to claim 1 , wherein the calculation unit calculates the fluctuation value for each density of the pattern image.

6. an image carrier on which an electrostatic latent image is formed; an image forming means for developing the electrostatic latent image formed on the image carrier to form a toner image; a first image bearing belt; a first transfer means for transferring the toner image formed on the image carrier onto the first image carrier belt; a second image bearing belt; a second transfer means for transferring the toner image transferred onto the first image bearing belt onto the second image bearing belt; an adhesion amount detecting means for detecting the amount of toner adhesion of the toner image transferred onto the second image carrying belt; An image forming method used in an image forming apparatus comprising: a pattern forming step of forming a predetermined pattern image between sheets of paper; a setting step of setting a representative value of fluctuations in the detected adhesion amount based on the detected adhesion amount, which is the amount of toner adhesion detected by the adhesion amount detection means; a calculation step of calculating a variation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction step of correcting the detected adhesion amount of the pattern image using the fluctuation value; an adjusting step of adjusting the image forming conditions of the toner image, The adjusting step adjusts the image forming conditions of the toner image using the detected adhesion amount of the pattern image corrected in the correcting step.

7. an image carrier on which an electrostatic latent image is formed; an image forming means for developing the electrostatic latent image formed on the image carrier to form a toner image; a first image bearing belt; a first transfer means for transferring the toner image formed on the image carrier onto the first image carrier belt; a second image bearing belt; a second transfer means for transferring the toner image transferred onto the first image bearing belt onto the second image bearing belt; an adhesion amount detecting means for detecting the amount of toner adhesion of the toner image transferred onto the second image carrying belt; In an image forming apparatus comprising: Computer, a pattern forming function for forming a predetermined pattern image between sheets of paper; a setting function for setting a representative value of fluctuations in the detected adhesion amount based on the detected adhesion amount, which is the amount of toner adhesion detected by the adhesion amount detection means; a calculation function for calculating a variation value of the detected adhesion amount of the pattern image using the representative value and the detected adhesion amount of the pattern image detected by the adhesion amount detection means; a correction function of correcting the detected adhesion amount of the pattern image using the fluctuation value; and an adjusting function for adjusting the image forming conditions of the toner image, The adjustment function is a program that adjusts the image forming conditions of the toner image using the detected adhesion amount of the pattern image corrected by the correction function.

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