Image forming device

Abstract

To provide an image forming apparatus that can reduce the inconvenience where toner scattering easily occurs regardless of the state of a user's use of the image forming apparatus.SOLUTION: An image forming apparatus 100 comprises: a developing device 2 that stores developer; a toner density detection unit 210 that detects a toner density that is the density of toner in developer D stored in the developing device; a toner density adjustment unit 220 that adjusts a toner density correction amount for correcting the toner density; and a control unit 110 that performs toner density correction control of correcting the toner density with the toner density correction amount adjusted by the toner density adjustment unit 220 based on the toner density detected by the toner density detection unit 210. The toner density adjustment unit 220 performs adjustment of the toner density correction amount within a predetermined toner density adjustment range. The control unit 110 changes the toner density adjustment range according to the state of a user's user of the image forming apparatus 100.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a multifunction machine, a printer, or a facsimile machine. [Background technology]

[0002] Conventional image forming devices have a toner concentration correction control as one of the image density adjustment means, which detects the toner concentration, which is the concentration of toner in a developer contained in a developing device, and corrects the toner concentration using a toner concentration correction amount based on the detected toner concentration.

[0003] Meanwhile, users use image forming apparatuses in various usage situations (for example, usage situations such as high and low printing frequency and / or high and low image ratio).

[0004] In such image forming devices, depending on how the user uses the image forming device, the amount of charge on the toner can easily become unstable due to insufficient stirring of the developer in the developing device, etc., which can cause the toner to easily scatter, which can lead to the inconvenience of components of the transport system (for example, transport guide members and detection units) becoming contaminated with toner.

[0005] In this regard, Patent Document 1 describes an image forming device that calculates an index value using detection values ​​obtained by detecting a gradation pattern consisting of multiple toner images formed under different image-forming conditions, and adjusts the toner concentration based on the difference between the calculated index value and a target index value, thereby changing the target index value depending on how the device is actually used. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-56094 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the image forming apparatus described in Patent Document 1 does not reduce the inconvenience of toner scattering easily occurring depending on the usage conditions of the image forming apparatus by the user.

[0008] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an image forming apparatus capable of reducing the inconvenience of toner scattering occurring easily regardless of how the image forming apparatus is used by a user. [Means for solving the problem]

[0009] In order to solve the above problem, an image forming apparatus according to the present invention includes a developing device that contains a developer, and a toner concentration detection unit that detects a toner concentration in the developer contained in the developing device. ,before The toner concentration detected by the toner concentration detection unit and the reference toner concentration Based on Teto a toner concentration adjustment unit that adjusts a toner concentration correction amount; ,before and a control unit that performs toner concentration correction control to correct the toner concentration using the toner concentration correction amount adjusted by the toner concentration adjustment unit, wherein the toner concentration adjustment unit adjusts the toner concentration correction amount within a predetermined toner concentration adjustment range, and the control unit changes the toner concentration adjustment range depending on how the image forming device is used by a user. Effect of the Invention

[0010] According to the present invention, it is possible to reduce the inconvenience of toner scattering occurring easily regardless of how the user uses the image forming apparatus. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view showing an image forming unit in the image forming apparatus shown in FIG. [Diagram 3]FIG. 2 is a system block diagram for controlling image density in the image forming apparatus. [Figure 4] 11 is a chart showing a relationship between a toner concentration correction amount corrected by a toner concentration correction control and a development bias correction amount corrected by a development bias correction control in existing image forming apparatuses on the market, expressed as a histogram of the number of units. [Figure 5A] 11 is a diagram showing an adjustment threshold table of an example of adjustment thresholds used as a usage status of an image forming apparatus. [Figure 5B] 5B is a graph showing the adjustment thresholds shown in FIG. 5A. [Figure 6] 11 is a chart showing a toner concentration adjustment range table as an example of a toner concentration adjustment range according to a usage status of an image forming apparatus. [Figure 7A] 10 is a chart showing another example of a toner concentration adjustment range table according to the usage status of the image forming apparatus; [Figure 7B] 13 is a chart showing a toner concentration adjustment range table of still another example of toner concentration adjustment according to the usage status of the image forming apparatus. [Figure 8] 11 is a chart showing an example of a development bias adjustment range table showing an example of a development bias adjustment range according to a usage status of an image forming apparatus. [Figure 9A] 5B is a graph showing a division between a development bias correction control priority mode and a toner concentration correction control priority mode with the adjustment threshold shown in FIG. 5A as a boundary. [Figure 9B] 5B is a table showing a division between a development bias correction control priority mode and a toner concentration correction control priority mode with respect to the adjustment threshold value shown in FIG. 5A. [Figure 10A] 10 is a chart showing an example of an adjustment threshold table of adjustment thresholds for each ambient temperature and ambient humidity of an image forming apparatus. [Figure 10B] 10B is a graph showing the adjustment thresholds shown in FIG. 10A. [Figure 11A] 11 is a chart showing a toner concentration adjustment range table in an ambient environment of normal temperature and normal humidity. [Figure 11B] 11 is a chart showing a toner concentration adjustment range table in a high temperature and high humidity ambient environment. [Figure 11C]11 is a chart showing a toner concentration adjustment range table in a low temperature and low humidity ambient environment. [Figure 12] 11 is a diagram showing a first correction coefficient table as an example of first correction coefficients. [Figure 13] 10 is a diagram showing a second correction coefficient table as an example of second correction coefficients. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0013] [Explanation of the Image Forming Apparatus as a Whole] FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to the present embodiment.

[0014] The image forming apparatus 100 is a multifunction machine having a copy function, a scanner function, a facsimile function, and a printer function, and transmits to the outside an image of an original G read by an image reading device 102. The image forming apparatus 100 also forms an image of the original G read by the image reading device 102 or an image received from the outside on a sheet P such as paper in color or monochrome.

[0015] An original feeder 160 (automatic document feeder (ADF)) is provided above the image reading unit 130 and is supported so as to be freely opened and closed relative to the image reading unit 130. The image reading device 102 includes the original feeder 160. The original feeder 160 sequentially transports one or more originals G one by one. The image reading device 102 reads the originals G transported one by one of the one or more originals by the original feeder 160. The image reading device 102 includes an original placement table 130a on which the originals G are placed, and a placed original reading function that reads the originals G placed on the original placement table 130a. When the original feeder 160 is opened, the image forming device 100 opens the original placement table 130a above the image reading unit 130, allowing the originals G to be placed manually. Further, the document feeder 160 includes a document placement tray 161 on which the document G is placed, and a document discharge tray 162 on which the document G discharged to the outside is stacked. The image reading device 102 includes a transported document reading function for reading the document G transported by the document feeder 160. The document feeder 160 transports the document G placed on the document placement tray 161 onto the document reading section 130b in the image reading section 130. The image reading section 130 scans the scanning optical system 130c to read the document placed on the document placement table 130a or reads the document G transported by the document feeder 160 to generate image data.

[0016] The image forming apparatus main body 101 includes an optical scanning device 1, developing devices 2-2, photosensitive drums 3-3 acting as image carriers, drum cleaning devices 4-4, chargers 5-5, a primary transfer device 70 (in this example, a transfer belt device), a secondary transfer device 11, a fixing device 12, a sheet transport path S, a paper feed cassette 18, and a sheet discharge tray 141.

[0017] The image forming apparatus 100 primarily transfers a toner image formed using toners of multiple colors onto an endless primary transfer belt 71 that acts as a transfer body, and then secondarily transfers the toner image primarily transferred onto the primary transfer belt 71 onto a sheet P.

[0018] In this embodiment, image data corresponding to a color image using each of the colors yellow (Y), magenta (M), and cyan (C), or a monochrome image using a single color, such as black (K), is handled. In the following description, yellow, magenta, cyan, and black are simply referred to as Y, M, C, and K, respectively.

[0019] The image forming section 50 of the image forming apparatus 100 is provided with four developing devices 2, four photoconductor drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, which correspond to Y, M, C, and K, respectively, to form four image stations Pa, Pb, Pc, and Pd. The image forming apparatus main body 101 is further provided with detachable toner storage devices 8-8 (specifically, toner cartridges) for storing toner. In the image stations Pa-Pd, toner is supplied to the developing devices 2-2 from the toner storage devices 8-8, which store toner of each color, yellow (Y), magenta (M), cyan (C), and black (K), respectively.

[0020] The optical scanning device 1 exposes the surfaces of the photoconductor drums 3-3 to light to form electrostatic latent images. The developing devices 2-2 develop the electrostatic latent images on the surfaces of the photoconductor drums 3-3 to form toner images on the surfaces of the photoconductor drums 3-3. The drum cleaning devices 4-4 remove and collect residual toner on the surfaces of the photoconductor drums 3-3. The chargers 5-5 uniformly charge the surfaces of the photoconductor drums 3-3 to a predetermined potential. Through the series of operations described above, a toner image of each color is formed on the surface of each photoconductor drum 3-3.

[0021] The primary transfer device 70 includes primary transfer rollers 6-6, a primary transfer belt 71, a transfer driving roller 72, a transfer driven roller 73, and a belt cleaning device 9. The primary transfer belt 71 is stretched around the transfer driving roller 72 and the transfer driven roller 73. Four primary transfer rollers 6 are provided inside the primary transfer belt 71 so as to form four types of toner images corresponding to the respective colors. The primary transfer rollers 6-6 primarily transfer the toner images of the respective colors formed on the surfaces of the photosensitive drums 3-3 onto the primary transfer belt 71 which moves in a circumferential direction W.

[0022] The secondary transfer device 11 forms a transfer nip portion TN (transfer nip area) between the secondary transfer roller 11a and the primary transfer belt 71, and conveys a sheet P conveyed through a sheet conveying path S by pinching it in the transfer nip portion TN. When the sheet P passes through the transfer nip portion TN, the toner image on the surface of the primary transfer belt 71 is secondarily transferred onto the sheet P, and the sheet P is conveyed to the fixing device 12. The belt cleaning device 9 removes and collects waste toner remaining on the surface of the primary transfer belt 71 without being transferred to the sheet P.

[0023] The fixing device 12 includes a fixing roller 31 and a pressure roller 32 that rotate while sandwiching the sheet P. The fixing device 12 sandwiches the sheet P, on which the toner image has been transferred, between the fixing roller 31 and the pressure roller 32, and applies heat and pressure to fix the toner image to the sheet P.

[0024] The paper feed cassette 18 is provided below the optical scanning device 1 to store sheets P used for image formation. The sheet P is pulled out from the paper feed cassette 18 by a pickup roller 16 and conveyed to a sheet conveying path S. The sheet P conveyed to the sheet conveying path S passes through a secondary transfer device 11 and a fixing device 12, is conveyed to a discharge roller 17, and is discharged to a sheet discharge tray 141 in a discharge section 140. A conveying roller 13, a registration roller 14, and a discharge roller 17 are arranged on the sheet conveying path S. The conveying roller 13 promotes the conveyance of the sheet P. The registration roller 14 stops the sheet P once and aligns the leading edge of the sheet P. The registration roller 14 conveys the stopped sheet P in accordance with the timing of the toner image on the primary transfer belt 71. The toner image on the primary transfer belt 71 is secondarily transferred to the sheet P at a transfer nip portion TN between the primary transfer belt 71 and the secondary transfer roller 11a.

[0025] In FIG. 1, one sheet feed cassette 18 is shown, but the present invention is not limited to this. A configuration may be provided in which a plurality of sheet feed cassettes 18 are provided to stack the same or different types of sheets P.

[0026] Furthermore, when forming an image on the back side of the sheet P in addition to the front side, the image forming apparatus 100 conveys the sheet P in the reverse direction from the discharge rollers 17 to a sheet inversion path Sr. The image forming apparatus 100 inverts the sheet P conveyed in the reverse direction and guides it again to the registration rollers 14. The image forming apparatus 100 also forms an image on the back side of the sheet P guided to the registration rollers 14 in the same manner as on the front side, and conveys the sheet P to the sheet discharge tray 141.

[0027] [Image density control] Fig. 2 is a cross-sectional view showing the image forming section 50 in the image forming apparatus 100 shown in Fig. 1. Fig. 3 is a system block diagram for performing image density control in the image forming apparatus 100.

[0028] 2, the transfer drive roller 72 and the transfer driven roller 73 are wound around the primary transfer belt 71 to tension the primary transfer belt 71. A rotational drive force from a rotation drive unit (drive motor) (not shown) is transmitted to the transfer drive roller 72 via a drive transmission mechanism (not shown). This allows the primary transfer belt 71 to move in a circumferential direction W from the image stations Pa, Pb, Pc, and Pd toward the secondary transfer device 11. Although each of the image stations Pa, Pb, Pc, and Pd is provided with components, these components have substantially the same configuration, so in the following description, one of these components will be used as a representative.

[0029] The developing device 2 includes a developing tank 21. The developing tank 21 contains a developer D. The developer D is a two-component developer having a toner T and a carrier C as main components.

[0030] As shown in FIG. 3, the image forming apparatus 100 further includes a control unit 110, a toner concentration detection unit 210, a toner concentration adjustment unit 220, an image concentration detection unit 230, and a development bias adjustment unit 240.

[0031] The control unit 110 has a processing unit 111 and a storage unit 112. The processing unit 111 is composed of a microcomputer such as a CPU. The storage unit 112 includes a non-volatile memory such as a ROM and a volatile memory such as a RAM. The control unit 110 controls the operation of various components by the processing unit 111 loading a control program stored in advance in the ROM of the storage unit 112 onto the RAM of the storage unit 112 and executing it.

[0032] <Toner concentration correction control> Toner concentration detection unit 210 detects the toner concentration, which is the concentration of toner T in developer D contained in developing tank 21. In this example, the toner concentration is the weight ratio of toner T to developer D. A representative example of toner concentration detection unit 210 is a toner concentration sensor that detects the toner concentration based on a change in magnetic permeability. Toner concentration detection unit 210 has the same configuration as a conventional one, and detailed description thereof will be omitted here. Toner concentration detection unit 210 is electrically connected to an input system of control unit 110. This allows control unit 110 to detect a detection signal corresponding to the toner concentration.

[0033] Toner concentration adjustment unit 220 adjusts a toner concentration correction amount for correcting the toner concentration. In detail, toner concentration adjustment unit 220 constitutes a toner supply device that supplies toner T contained in toner storage device 8 to developer tank 21.

[0034] The control unit 110 includes a toner concentration correction control unit Q1. The toner concentration correction control unit Q1 performs toner concentration correction control to correct the toner concentration by the toner concentration correction amount adjusted by the toner concentration adjustment unit 220 based on the toner concentration detected by the toner concentration detection unit 210. In detail, the control unit 110 adjusts the toner concentration correction amount (toner supply amount) of the toner T to the developing tank 21 so that the detection signal corresponding to the toner concentration detected by the toner concentration detection unit 210 becomes a reference signal corresponding to a predetermined reference toner concentration. Here, the value of the detection signal of the toner concentration detection unit 210 can be typically exemplified by a value corresponding to the ratio of the weight of the toner T to the weight of the developer D. The reference toner concentration can be, for example, the toner concentration of a new developer D (for example, 6%). The value of the reference signal of the toner concentration detection unit 210 corresponding to the reference toner concentration is stored in the storage unit 112 when the new developer D is set up for the first time.

[0035] In this embodiment, toner concentration adjustment unit 220 adjusts the toner concentration correction amount within a predetermined toner concentration adjustment range.

[0036] That is, in the toner concentration correction control, if the toner concentration detected by toner concentration detection unit 210 deviates from the reference toner concentration (e.g., 6%), toner concentration adjustment unit 220 adjusts the toner concentration correction amount so that the toner concentration becomes the reference toner concentration within the toner concentration adjustment range.

[0037] <Development bias correction control> The image density detection unit 230 detects the image density (shade), which is the density of a toner image. More specifically, the image density detection unit 230 detects the image density of a toner pattern PT (so-called patch) (see FIG. 2) formed on the primary transfer belt 71. In this example, the image density is a value corresponding to a value obtained by measuring the image density (ID) of a solid portion using a reflection densitometer. A representative example of the image density detection unit 230 is one that detects the image density based on the amount of reflected light.

[0038] As shown in FIG. 2, the image density detection unit 230 detects the image density of the toner pattern PT primarily transferred onto the primary transfer belt 71 by the primary transfer roller 6 in the image forming unit 50. In this example, the image density detection unit 230 is a process control sensor (so-called pro-con sensor). The image density detection unit 230 includes a light-emitting unit 231 including a light-emitting element (specifically, a light-emitting diode) and a light-receiving unit 232 including a light-receiving element (specifically, a photodiode). The light-emitting unit 231 irradiates the toner pattern PT on the primary transfer belt 71 with emitted light L1. The light-receiving unit 232 receives reflected light L2 reflected from the toner pattern PT on the primary transfer belt 71.

[0039] The image density detection section 230 is electrically connected to an input system of the control section 110. This enables the control section 110 to detect a detection signal corresponding to the image density of the toner patterns PT to PT.

[0040] The developing bias adjustment unit 240 adjusts a developing bias correction amount for correcting the developing bias to the developing device 2. In detail, the developing bias adjustment unit 240 constitutes a developing bias power supply that applies a developing bias to the developing roller 22 of the developing device 2 in an adjustable manner.

[0041] The control unit 110 includes a development bias correction control means Q2. The development bias correction control means Q2 performs development bias correction control to correct the development bias by the development bias correction amount adjusted by the development bias adjustment unit 240 based on the image density detected by the image density detection unit 230. In detail, the control unit 110 adjusts the development bias correction amount to the developing device 2 so that the detection signal corresponding to the image density detected by the image density detection unit 230 becomes a reference signal corresponding to a predetermined reference image density. Here, the value of the detection signal of the image density detection unit 230 can be representatively exemplified as a value corresponding to the image density (ID) measured in a solid portion using a reflection densitometer. For example, the reference image density can be a rated image density (e.g. ID1.3). The value of the reference signal of the image density detection unit 230 corresponding to the reference image density is stored in the storage unit 112 in advance.

[0042] In this embodiment, the developing bias adjustment unit 240 adjusts the developing bias correction amount within a predetermined developing bias adjustment range.

[0043] That is, in the development bias correction control, if the image density detected by the image density detection unit 230 deviates from the reference image density (e.g., ID1.3), the development bias adjustment unit 240 adjusts the development bias correction amount so that the image density becomes the reference image density within the development bias adjustment range.

[0044] Fig. 4 is a chart showing the relationship between the toner concentration correction amount corrected by the toner concentration correction control and the development bias correction amount corrected by the development bias correction control in existing image forming devices on the market, expressed as a histogram of the number of units. In Fig. 4, the horizontal axis represents the toner concentration correction amount, and the vertical axis represents the development bias correction amount (development bias voltage). The toner concentration correction amount is a predetermined toner supply amount, which is a value that changes the toner concentration by a predetermined concentration (for example, about 1%).

[0045] Here, the α portion in FIG. 4 represents dependence on the toner concentration correction control, and the β portion in FIG. 4 represents dependence on the development bias correction control.

[0046] Users use image forming apparatuses in various usage situations (eg, usage situations such as high and low printing frequency and / or high and low image ratio).

[0047] Here, the printing frequency can be exemplified by the number of printed sheets (number of printed sheets) per unit period (for example, one month or one day). Users whose printing frequency is equal to or lower than a predetermined standard printing frequency are so-called low copy volume users (low CV users), and users whose printing frequency is higher than the standard printing frequency are so-called high copy volume users (high CV users). Here, the standard printing frequency can be exemplified by, for example, the average printing frequency or a predetermined image ratio.

[0048] Examples of the image ratio include the area ratio (area ratio calculated from pixel count, for example) of the image (toner image) per total area of ​​the sheet on which the image is formed (e.g., A4-sized sheet), and the consumption amount of toner T per number of sheets consumed for sheets of a predetermined size (e.g., A4-sized sheets). Users whose image ratio is equal to or less than a predetermined reference image ratio are so-called low-printing rate users, and users whose image ratio is higher than the reference image ratio are so-called high-printing rate users. Examples of the reference image ratio include an average image ratio and a predetermined image ratio.

[0049] As shown in FIG. 2, the image forming apparatus 100 further includes a count measurement unit 250, a calendar measurement unit 260, and a pixel measurement unit 270.

[0050] The count measurement unit 250 measures the number of printed sheets. The count measurement unit 250 is electrically connected to an input system of the control unit 110. This enables the control unit 110 to detect the number of printed sheets.

[0051] The calendar measurement unit 260 measures the time and the number of days. The calendar measurement unit 260 is electrically connected to an input system of the control unit 110. This allows the control unit 110 to detect the printing frequency from the number of printed sheets and the time or the number of days.

[0052] The pixel measurement unit 270 counts the number of pixels of an image from the image data read by the image reading device 102. The pixel measurement unit 270 is electrically connected to an input system of the control unit 110. This allows the control unit 110 to detect the image ratio from the area ratio calculated from the pixel count.

[0053] However, in conventional image forming devices, depending on how the user uses the image forming device, the amount of charge on the toner can easily become unstable due to insufficient stirring of the developer in the developing device, etc., which can cause the toner to easily scatter. This can then lead to the inconvenience of components of the transport system (for example, transport guide members and detection units) becoming soiled with toner.

[0054] First Embodiment In this regard, the control unit 110 changes the toner concentration adjustment range in accordance with the usage status of the image forming apparatus 100 by the user (in this example, the adjustment threshold value TH).

[0055] Fig. 5A is a diagram showing an adjustment threshold table TB1 (TB11) of an example of an adjustment threshold [TH (TH1)] used as a usage status of the image forming apparatus 100. Fig. 5B is a graph showing the adjustment threshold TH (TH1) shown in Fig. 5A. The adjustment threshold table TB1 is stored in advance in the storage unit 112.

[0056] As shown in Figures 5A and 5B, the usage of the image forming device 100 can be divided into users with a low printing frequency and low image ratio and users with a high printing frequency and high image ratio by the adjustment threshold value TH (TH1).

[0057] FIG. 6 is a chart showing a toner concentration adjustment range table TB2 (TB21) which is an example of a toner concentration adjustment range according to the usage status of the image forming apparatus 100. The toner concentration adjustment range table TB2 is stored in advance in the storage unit 112. The values ​​of the toner concentration adjustment range table TB21 shown in FIG. 6 indicate the ratio of the actual adjustment range to the maximum adjustment range of the toner concentration. For example, if the maximum actual adjustment range of the toner concentration (the maximum range of the actual control value actually output from the control unit 110) is ±30, the toner concentration adjustment range for users of the low print frequency layer and low image ratio layer is ±16.7% or ±5 (actual control range), and the toner concentration adjustment range for users of the high print frequency layer and high image ratio layer is ±100% or ±30 (actual control range). This also applies to the toner concentration adjustment range tables TB22 to TB26 shown in FIGS. 7A, 7B, and 11A to 11C described later.

[0058] As shown in FIG. 6, the control unit 110 executes the toner concentration correction control by dividing the toner concentration adjustment range into large and small ranges at a usage state adjustment threshold value TH (TH1) (see the double line in FIG. 6).

[0059] This allows the toner concentration adjustment range to be set according to the usage conditions of the image forming apparatus 100 by the user.

[0060] Moreover, the image density can be stabilized by the toner density correction amount within the toner density adjustment range changed by the adjustment threshold value TH according to the usage status of the image forming apparatus 100 by the user.

[0061] Therefore, the toner concentration correction control can be performed with high accuracy according to the usage status of the image forming apparatus 100.

[0062] Since the usage status of the image forming apparatus 100 is inaccurate in the initial stage of installation of the image forming apparatus 100, the toner concentration correction control according to the present embodiment can be performed a predetermined period (e.g., one month) after the start of installation of the image forming apparatus 100. This allows the toner concentration adjustment range to be changed with high accuracy.

[0063] In this embodiment, control unit 110 changes the toner concentration adjustment range stepwise depending on the usage status of image forming apparatus 100.

[0064] Fig. 7A is a chart showing another example of toner concentration adjustment range table TB2 (TB22) of the toner concentration adjustment range according to the usage status of image forming apparatus 100. The upper side of the double line in Fig. 7A is users in the low print frequency layer and low image ratio layer, and the lower side of the double line in Fig. 7A is users in the high print frequency layer and high image ratio layer.

[0065] As shown in Fig. 7A, the toner concentration adjustment range can be narrowed as the printing frequency increases. Also, the toner concentration adjustment range can be widened as the image ratio increases. In this way, the toner concentration can be kept low, which can prevent toner scattering.

[0066] Therefore, regardless of how the user uses the image forming apparatus 100, the inconvenience of toner scattering easily occurring can be reduced.

[0067] The toner concentration adjustment width shown in FIG. 7A has the same absolute value on the positive side and the negative side, but may be different.

[0068] FIG. 7B is a chart showing a toner concentration adjustment range table TB2 (TB23) of still another example of toner concentration adjustment according to the usage status of image forming apparatus 100. In FIG.

[0069] The toner concentration adjustment range shown in Fig. 7B is shifted by a predetermined amount (0.3% in this example) to the negative side with respect to the toner concentration adjustment range in which the positive and negative values ​​are equal in absolute value as shown in Fig. 7A. Also, without being limited thereto, it is also possible to shift by a predetermined amount to the positive side with respect to the toner concentration adjustment range in which the positive and negative values ​​are equal in absolute value as shown in Fig. 7A.

[0070] <Second embodiment> Conventionally, image quality is often stabilized by two types of image density correction control: development bias correction control and toner concentration correction control. More specifically, after development bias correction control is performed to suppress process electric field fluctuations, toner concentration correction control is performed to supply toner to the developing device as necessary. In this configuration, image quality performance can be ensured when used by users of high print frequency layers and high image ratio layers, but when used by users of low print frequency layers and low image ratio layers, the charge amount of the toner is likely to become unstable due to insufficient stirring of the developer in the developing device. This causes the inconvenience of toner scattering, which in turn causes the inconvenience of toner staining of the transport system components (e.g., transport guide members and detection units) with toner.

[0071] In this regard, the control unit 110 changes the development bias adjustment width in accordance with the usage status of the image forming apparatus 100 by the user (in this example, the adjustment threshold value TH).

[0072] FIG. 8 is a chart showing an example of a development bias adjustment range table (TB3) of an example of a development bias adjustment range according to the usage status of the image forming apparatus 100. The development bias adjustment range table TB3 is stored in advance in the storage unit 112. The values ​​of the development bias adjustment range table TB3 shown in FIG. 8 indicate the ratio of the actual adjustment range to the maximum adjustment range (actual voltage range) of the development bias. For example, if the maximum actual adjustment range of the development bias (the maximum range of the actual voltage value actually output from the control unit 110) is ±100V, the development bias adjustment range for users of the low print frequency layer and low image ratio layer is ±100% or ±100V (actual voltage range), and the development bias adjustment range for users of the high print frequency layer and high image ratio layer is ±40% or ±40V (actual voltage range).

[0073] As shown in FIG. 8, the control unit 110 executes the developing bias correction control by dividing the developing bias adjustment range into large and small ranges at an adjustment threshold value TH (see the double line in FIG. 8) of the usage state.

[0074] This allows the developing bias adjustment range to be set according to how the image forming apparatus 100 is used by the user.

[0075] Furthermore, the image density can be stabilized by the developing bias correction amount within the developing bias adjustment range changed by the adjustment threshold value TH according to the usage status of the image forming apparatus by the user.

[0076] Therefore, the development bias correction control can be performed with high accuracy in accordance with the usage conditions of the image forming apparatus.

[0077] Since the usage status of the image forming apparatus 100 is inaccurate at the beginning of installation of the image forming apparatus 100, the development bias correction control according to the present embodiment can be performed a predetermined period (e.g., one month) after the start of installation of the image forming apparatus 100. This allows the development bias adjustment range to be changed with high accuracy.

[0078] In the present embodiment, control unit 110 gradually changes the development bias adjustment range in accordance with the usage status of image forming apparatus 100. The upper side of the double line in Fig. 8 is for users in the low print frequency and low image ratio layers, and the lower side of the double line in Fig. 8 is for users in the high print frequency and high image ratio layers.

[0079] As shown in Fig. 8, the development bias adjustment range can be increased as the printing frequency increases. Also, the development bias adjustment range can be decreased as the image ratio increases. In this way, the image density can be stabilized by the development bias correction amount within the development bias adjustment range that is changed in stages according to the usage status of the image forming apparatus 100.

[0080] In this embodiment, when one of the toner concentration adjustment range and the developing bias adjustment range is changed to be larger or smaller depending on the usage situation, the other adjustment range is changed in the opposite direction to the change in the one adjustment range depending on the usage situation. In other words, when one of the toner concentration adjustment range and the developing bias adjustment range is changed to be larger depending on the usage situation, the other adjustment range is changed to be smaller depending on the usage situation, and when one adjustment range is changed to be smaller depending on the usage situation, the other adjustment range is changed to be larger depending on the usage situation.

[0081] In this way, the toner concentration can be kept low, which in turn makes it possible to prevent toner scattering and stabilize the image concentration.

[0082] <Third embodiment> In this embodiment, the control unit 110 performs a development bias correction control priority mode and a toner concentration correction control priority mode. In the development bias correction control priority mode, the toner concentration correction control is performed after the development bias correction control. Also, in the toner concentration correction control priority mode, the development bias correction control is performed after the toner concentration correction control.

[0083] 9A and 9B are a graph and a chart, respectively, showing the division between the development bias correction control priority mode and the toner concentration correction control priority mode with the adjustment threshold value TH shown in FIG. 5A as the boundary.

[0084] In the development bias correction control priority mode, the development bias correction control is performed first, but if the development bias correction control is not sufficient, the toner concentration correction control is performed. Also, in the toner concentration correction control priority mode, the toner concentration correction control is performed first, but if the toner concentration correction control is not sufficient, the development bias correction control is performed.

[0085] In this way, it is possible to give priority to the development bias correction control and the toner concentration correction control, thereby making it clear which of the development bias correction control and the toner concentration correction control is to be given priority.

[0086] In the development bias correction control priority mode, the toner concentration correction control can be performed after the development bias correction control, so that the priority of the development bias correction control can be increased. For example, by making the development bias adjustment range larger than a predetermined reference development bias adjustment range, the priority of the development bias correction control can be further increased, and the development bias correction control can be mainly performed. Also, in the toner concentration correction control priority mode, the development bias correction control can be performed after the toner concentration correction control, so that the priority of the toner concentration correction control can be increased. For example, by making the toner concentration adjustment range larger than the reference toner concentration adjustment range, the priority of the toner concentration correction control can be further increased, and the toner concentration correction control can be mainly performed.

[0087] When performing the development bias correction control priority mode and the toner concentration correction control priority mode of this embodiment, for example, the toner concentration adjustment ranges shown in Figures 6, 7A, and 7B and the development bias adjustment ranges shown in Figure 8 can be used.

[0088] As shown in FIGS. 9A and 9B, the control unit 110 executes a development bias correction control priority mode and a toner concentration correction control priority mode by dividing the mode into two modes using an adjustment threshold value TH (TH1 in this example) of the usage state as a boundary.

[0089] This allows the mode to be switched to the development bias correction control priority mode when the user's usage of image forming apparatus 100 requires that development bias correction control be given priority. Also, when the user's usage of image forming apparatus 100 requires that toner concentration correction control be given priority, the mode can be switched to the toner concentration correction control priority mode.

[0090] Therefore, the development bias correction control priority mode and the toner concentration correction control priority mode can be switched by the adjustment threshold TH of the user's usage of the image forming apparatus 100. In more detail, when used by a user in a low print frequency layer and a low image ratio layer (see the area above the double line in FIG. 9B), the development bias correction control is prioritized, so that the image density can be stabilized mainly by the development bias correction amount within the development bias adjustment range. On the other hand, when used by a user in a high print frequency layer and a high image ratio layer (see the area below the double line in FIG. 9B), the toner concentration correction control is prioritized, so that the image density can be stabilized mainly by the toner concentration correction amount within the toner concentration adjustment range.

[0091] In this manner, in this embodiment, selective control operation can be performed to prioritize either development bias correction control or toner density correction control depending on the user's usage conditions (printing frequency and image ratio).

[0092] In this embodiment, the usage status includes the printing frequency, which is the number of sheets printed per unit period by image forming apparatus 100, and the image ratio, which is the area ratio of the image to the total area of ​​the sheet on which the image is formed by image forming apparatus 100.

[0093] The adjustment thresholds include a first predetermined adjustment threshold for the printing frequency and a second predetermined adjustment threshold for the image ratio.

[0094] The control unit 110 switches to the development bias correction control priority mode when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold, and switches to the toner concentration correction control priority mode when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold.

[0095] In this way, when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold, for example, when used by a user of a low printing frequency layer and a low image ratio layer, the development bias correction control priority mode can be performed. Also, when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold, for example, when used by a user of a high printing frequency layer and a high image ratio layer, the toner concentration correction control priority mode can be performed.

[0096] In detail, when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold, the image density can be stabilized mainly by the developing bias correction amount within the developing bias adjustment range by giving priority to the developing bias correction control. Also, when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold, the image density can be stabilized mainly by the toner concentration correction amount within the toner concentration adjustment range by giving priority to the toner concentration correction control.

[0097] In this embodiment, the toner concentration adjustment range when the printing frequency of image forming device 100 is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold is smaller than the toner concentration adjustment range when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold (see Figures 6, 7A and 7B when the development bias correction control priority mode and the toner concentration correction control priority mode are performed).

[0098] In this way, the toner concentration correction amount can be adjusted according to the usage status of the image forming apparatus 100.

[0099] In this embodiment, the development bias adjustment range when the printing frequency of image forming device 100 is equal to or less than the first adjustment threshold and the image ratio of image forming device 100 is equal to or less than the second adjustment threshold is larger than the development bias adjustment range when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold (see Figure 8 when the development bias correction control priority mode and the toner concentration correction control priority mode are performed).

[0100] In this way, the development bias correction amount can be adjusted according to the usage status of the image forming apparatus 100.

[0101] <Fourth embodiment> However, changes in the development characteristics such as the toner charge amount also occur due to changes in the surrounding environment of the image forming apparatus 100, resulting in unstable image density. Specifically, in a low-temperature and low-humidity surrounding environment, the toner charge amount is likely to increase, and the image density is likely to decrease. On the other hand, in a high-temperature and high-humidity surrounding environment, the toner charge amount is likely to decrease, and the image density is likely to increase.

[0102] Here, the low temperature range is, but is not limited to, 5° C. or more and less than 15° C., the normal temperature range is, but is not limited to, 15° C. or more and less than 25° C., and the high temperature range is, but is not limited to, 25° C. or more and less than 35° C. The low humidity range is, but is not limited to, 10% or more and less than 35%, the normal humidity range is, but is not limited to, 35% or more and less than 60%, and the high humidity range is, but is not limited to, 60° C. or more and less than 85° C.

[0103] In this regard, in the present embodiment, the adjustment threshold value TH increases as the ambient temperature and humidity around the image forming apparatus 100 increase.

[0104] Fig. 10A is a chart showing an adjustment threshold table TB1 (TB12) of an example of adjustment thresholds [TH (TH1, TH2, TH3)] for each ambient temperature and ambient humidity of the image forming apparatus 100. Fig. 10B is a graph showing the adjustment thresholds TH (TH1, TH2, TH3) shown in Fig. 10A.

[0105] The temperature detection unit 280 and the humidity detection unit 290 respectively detect the temperature and humidity around the image forming apparatus 100. The temperature detection unit 280 and the humidity detection unit 290 are electrically connected to an input system of the control unit 110. This allows the control unit 110 to detect the temperature and humidity around the image forming apparatus 100.

[0106] As shown in Figures 10A and 10B, the usage status of the image forming device 100 can be categorized into users with a low printing frequency and low image ratio, and users with a high printing frequency and high image ratio, depending on the adjustment threshold value TH (TH1) for each ambient temperature and ambient humidity of the image forming device 100.

[0107] 11A to 11C are charts showing toner concentration adjustment range tables TB2 (TB24, TB25, TB26) for ambient environments of normal temperature and normal humidity, high temperature and high humidity, and low temperature and low humidity, respectively.

[0108] As shown in FIGS. 11A to 11C, control unit 110 divides the toner concentration adjustment range into sections based on usage status adjustment thresholds TH (TH1, TH2, TH3) (see double lines in FIGS. 11A to 11C) and executes toner concentration correction control.

[0109] In this way, even if the development characteristics such as the toner charge amount change due to the change in the surrounding environment of the image forming apparatus 100, the adjustment threshold TH can be changed according to the surrounding environment of the image forming apparatus 100, and the image density can be stabilized. In detail, the adjustment threshold TH (TH1, TH2, TH3) can be changed according to the surrounding temperature and humidity of the image forming apparatus 100. For example, in a high temperature and high humidity surrounding environment (see FIG. 11B), the adjustment threshold TH2 is shifted to the larger side than the adjustment threshold TH1 of the normal temperature and normal humidity surrounding environment (see FIG. 10B), and the region of the development bias correction control priority mode is enlarged. On the other hand, in a low temperature and low humidity surrounding environment (see FIG. 11C), the adjustment threshold TH3 is shifted to the smaller side than the adjustment threshold TH1 of the normal temperature and normal humidity surrounding environment (see FIG. 10B), and the region of the toner concentration correction control priority mode is enlarged. In this way, the development bias correction control priority mode and the toner concentration correction control priority mode can be set to the priority mode according to the surrounding environment of the image forming apparatus 100.

[0110] <Fifth embodiment> In the present embodiment, control unit 110 varies the toner concentration correction amount to be corrected in the toner concentration correction control by using a first correction coefficient K1 according to the surrounding environment of image forming apparatus 100.

[0111] 12 is a diagram showing a first correction coefficient table TB4 of an example of the first correction coefficient (K1). Note that the first correction coefficient table TB4 is stored in the storage unit 112 in advance.

[0112] As shown in FIG. 12, the toner concentration adjustment range can be multiplied by a first correction coefficient K1 (in this example, "0.9", "1", and "1.1") determined according to the temperature and humidity.

[0113] In this way, the toner concentration adjustment range can be changed by the first correction coefficient K1 according to the ambient temperature and humidity of the image forming apparatus 100. In this example, the toner concentration adjustment range is reduced as the ambient environment becomes hotter and more humid. In other words, the toner concentration adjustment range is increased as the ambient environment becomes colder and less humid. This makes it possible to stabilize the image density by the toner concentration correction amount within the toner concentration adjustment range that is varied by the first correction coefficient K1.

[0114] Sixth Embodiment In this embodiment, control unit 110 varies the toner concentration correction amount used in toner concentration correction control using a second correction coefficient K2 according to the usage status (printing frequency and / or image ratio (printing frequency in this example)).

[0115] 13 is a diagram showing a second correction coefficient table TB5 as an example of the second correction coefficient (K2). Note that the second correction coefficient table TB5 is stored in the storage unit 112 in advance.

[0116] As shown in FIG. 12, the toner concentration adjustment range can be multiplied by a second correction coefficient K2 (in this example, "0.9", "0.95", "1", "1.05", "1.1") determined according to the printing frequency.

[0117] In this way, the toner concentration adjustment range can be changed by the second correction coefficient K2 according to the usage status of the image forming apparatus 100 (in this example, the printing frequency). In this example, the toner concentration adjustment range is reduced as the printing frequency decreases. In other words, the toner concentration adjustment range is increased as the printing frequency increases. This makes it possible to stabilize the image density by the toner concentration correction amount within the toner concentration adjustment range that is varied by the second correction coefficient K2.

[0118] The present invention is not limited to the above-described embodiment, but can be embodied in various other forms. Therefore, the embodiment is merely illustrative in all respects and should not be interpreted as being restrictive. The scope of the present invention is defined by the claims, and is not limited in any way by the text of the specification. Furthermore, all modifications and changes within the scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0119] 100 Image forming device 102 Image reading device 110 Control section 111 Processing section 112 Storage section 2. Developing device 21 Developer tank 22 Developing roller 210 Toner concentration detection unit 220 Toner density adjustment unit 230 Image density detection unit 240 Development bias adjustment unit 250 Counting Unit 260 Calendar Measurement Unit 270 Pixel measurement section 280 Temperature detection unit 290 Humidity detector 50 Image forming section 8 Toner storage device C Career D Developer K1 First correction factor K2 Second correction factor P-sheet PT Toner Pattern Q1 Toner concentration correction control means Q2 Development bias correction control means T Toner TB1 Adjustment threshold table TB2 Toner density adjustment width table TB21 Toner density adjustment width table TB22 Toner density adjustment width table TB3 Development bias adjustment range table TB4 First correction factor table TB5 Second correction factor table TH Adjustment Threshold TH1 Surrounding environment TH2 Adjustment Threshold TH3 Adjustment Threshold

Claims

1. an image forming apparatus including: a developing device that contains a developer; a toner concentration detection unit that detects a toner concentration, which is a concentration of toner in the developer contained in the developing device; a toner concentration adjustment unit that adjusts a toner concentration correction amount based on the toner concentration detected by the toner concentration detection unit and a reference toner concentration; and a control unit that performs toner concentration correction control to correct the toner concentration using the toner concentration correction amount adjusted by the toner concentration adjustment unit, the toner concentration adjustment unit adjusts the toner concentration correction amount within a predetermined toner concentration adjustment range, The control unit changes the toner concentration adjustment range in response to a usage state of the image forming apparatus by a user.

2. 2. The image forming apparatus according to claim 1, The control unit changes the toner concentration adjustment range in stages according to the usage status.

3. 2. The image forming apparatus according to claim 1, the control unit performs a developing bias correction control for correcting the developing bias by the developing bias correction amount adjusted by the developing bias adjustment unit based on the image density detected by the image density detection unit; the developing bias adjustment unit adjusts the developing bias correction amount within a predetermined developing bias adjustment range, The image forming apparatus according to claim 1, wherein the control unit changes the developing bias adjustment range in accordance with the usage status.

4. 4. The image forming apparatus according to claim 3, The control unit changes the developing bias adjustment range in stages in accordance with the usage status.

5. 5. The image forming apparatus according to claim 3, an image forming apparatus characterized in that, when one of the toner concentration adjustment range and the developing bias adjustment range is changed to be larger or smaller depending on the usage conditions, the other adjustment range is changed in the opposite direction to the change in the one adjustment range depending on the usage conditions.

6. 6. The image forming apparatus according to claim 3, An image forming apparatus characterized by performing a toner concentration correction control priority mode in which the developing bias correction control is performed after the toner concentration correction control, and a developing bias correction control priority mode in which the toner concentration correction control is performed after the developing bias correction control.

7. 7. The image forming apparatus according to claim 6, The image forming apparatus according to the present invention, wherein the control unit executes the toner concentration correction control priority mode and the development bias correction control priority mode by dividing the mode into two modes by an adjustment threshold value of the usage state.

8. 8. The image forming apparatus according to claim 7, The usage status includes a printing frequency and an image ratio of the image forming apparatus, the adjustment threshold includes a first adjustment threshold for the print frequency and a second adjustment threshold for the image ratio; an image forming apparatus which switches to the development bias correction control priority mode when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold, and switches to the toner concentration correction control priority mode when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold.

9. 9. The image forming apparatus according to claim 8, The usage status includes a printing frequency and an image ratio of the image forming apparatus, the adjustment threshold includes a predetermined first adjustment threshold for the printing frequency and a predetermined second adjustment threshold for the image ratio; An image forming apparatus characterized in that the toner concentration adjustment range when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold is smaller than the toner concentration adjustment range when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold.

10. 10. The image forming apparatus according to claim 8, The usage status includes a printing frequency and an image ratio of the image forming apparatus, the adjustment threshold includes a predetermined first adjustment threshold for the printing frequency and a predetermined second adjustment threshold for the image ratio; an image forming apparatus characterized in that the development bias adjustment range when the printing frequency is equal to or less than the first adjustment threshold and the image ratio is equal to or less than the second adjustment threshold is larger than the development bias adjustment range when the printing frequency is greater than the first adjustment threshold and the image ratio is greater than the second adjustment threshold.

11. 11. The image forming apparatus according to claim 7, The adjustment threshold value increases as the ambient temperature and the ambient humidity of the image forming apparatus increase.

12. 12. The image forming apparatus according to claim 1, 11. An image forming apparatus, comprising: an image forming device which varies an amount of toner concentration correction performed in said toner concentration correction control by using a first correction coefficient according to an ambient environment of said image forming apparatus.

13. 13. The image forming apparatus according to claim 1, the toner concentration correction amount corrected in the toner concentration correction control is varied using a second correction coefficient according to the usage state.

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