Image forming apparatus

Abstract

To provide an image forming apparatus that controls a state of electrification of toner and developing voltage in a developing device so that a toner image with a proper density is formed.SOLUTION: An image density detection unit 6 detects a density of a test toner image formed on a surface of a photoreceptor 41 or a surface of an intermediate transfer body 441. A control unit 8 causes an exposure device 40 and a developing device 43 to execute processing of forming the test toner image. The control unit 8 adjusts developing voltage according to the level of the developing voltage when the test toner image is formed, the density of the test toner image detected by the image density detection unit 6, and a target density of the test toner image. When the level of the adjusted developing voltage falls outside a reference range, the control unit 8 corrects an amount of the toner supplied by a toner supply device 5 to the developing device 43.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that controls the charge state of toner in a developing device and the developing voltage. [Background technology]

[0002] In an electrophotographic image forming apparatus, the charged state of toner in a developing device affects image quality.

[0003] It is known that the image forming device calculates the charge amount of the toner based on the detection result of the magnetic permeability of the developer in the developing device, and controls the amount of the toner supplied to the developing device based on the calculation result of the charge amount (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-18212 Summary of the Invention [Problem to be solved by the invention]

[0005] In the image forming apparatus, the charge amount of the toner in the developing device and the developing voltage in the developing device affect the density of the toner image.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of controlling the charge state of the toner in the developing device and the developing voltage so that a toner image of appropriate density is formed. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus includes a photoconductor, an exposure device, a development device, a transfer device, a toner supply device, an image density detection unit, and a control unit. The exposure device forms an electrostatic latent image on the surface of the photoconductor. The development device develops the electrostatic latent image into a toner image using a toner carrier to which a development voltage is applied. The transfer device transfers the toner image on the surface of the photoconductor to a sheet directly or via an intermediate transfer body. The toner supply device supplies toner to the development device. The image density detection unit detects the density of a test toner image formed on the surface of the photoconductor or the intermediate transfer body. The control unit causes the exposure device and the development device to execute a process for forming the test toner image, and executes a development voltage adjustment process for adjusting the development voltage in accordance with the level of the development voltage when the test toner image is formed, the density of the test toner image detected by the image density detection unit, and the target density of the test toner image. The control unit corrects the amount of toner supplied to the development device by the toner supply device if the adjusted development voltage level falls outside a reference range. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an image forming apparatus that can control the charge state of the toner in the developing device and the developing voltage so that a toner image of appropriate density is formed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram of a developing device in the image forming apparatus according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a procedure for density adjustment processing in the image forming apparatus according to the embodiment. [Figure 5]FIG. 5 is a diagram illustrating a process of estimating the toner charge amount based on the development voltage and the detected density of the test toner image. [Figure 6] FIG. 6 is a diagram illustrating a process for adjusting the development voltage based on the estimated result of the toner charge amount and the target density of the test toner image. [Figure 7] FIG. 7 is a flowchart showing the procedure of a modified example of the density adjustment process in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0011] [Configuration of image forming apparatus 10] The image forming apparatus 10 according to the embodiment is capable of performing a print process by electrophotography. The print process is a process of forming an image on a sheet 9. The sheet 9 is an image forming medium such as paper or a resin sheet.

[0012] 1 is a printer. However, the image forming apparatus 10 may also be a copying machine, a facsimile machine, a multifunction machine, or the like.

[0013] As shown in FIG. 1, the image forming apparatus 10 includes a main housing 1, a sheet storage unit 2, a conveying device 3, a printing device 4, a toner supplying device 5, a control device 8, an operating device 801, and a display device 802.

[0014] The main housing 1 is a housing that houses the transport device 3, the printing device 4, the toner supply device 5, and the control device 8. Inside the main housing 1, a transport path 300 that is a passage for the sheet 9 is provided.

[0015] The conveying device 3 includes a sheet feeding mechanism 30 and a plurality of pairs of conveying rollers 31. The sheet feeding mechanism 30 sends out the sheets 9 stored in the sheet storage unit 2 to a conveying path 300 one by one.

[0016] The plurality of pairs of transport rollers 31 transport the sheet 9 along the transport path 300. One of the plurality of pairs of transport rollers 31 discharges the sheet 9, on which an image has been formed by the printing device 4, from the transport path 300 onto the discharge tray 1x.

[0017] The printing device 4 performs the printing process on the sheet 9 conveyed along the conveying path 300. In the example shown in Fig. 1, the printing device 4 performs the printing process by electrophotography.

[0018] The printing apparatus 4 includes an exposure device 40, one or more image forming units 4x, a transfer device 44, and a fixing device 46. The printing apparatus 4 shown in Fig. 1 is a tandem color printing apparatus. In this case, the printing apparatus 4 includes multiple image forming units 4x corresponding to multiple developing colors.

[0019] In the example shown in FIG. 1, the printing device 4 includes four image forming units 4x corresponding to the developing colors of yellow, magenta, cyan, and black.

[0020] Each image forming unit 4x includes a photoconductor 41, a charging device 42, a developing device 43, and a drum cleaning device 45. The photoconductor 41 rotates, and the charging device 42 charges the surface of the photoconductor 41.

[0021] The exposure device 40 scans the charged surface of the photoreceptor 41 with laser light to form an electrostatic latent image on the surface of the photoreceptor 41. The development device 43 supplies toner to the surface of the photoreceptor 41 to develop the electrostatic latent image into a toner image.

[0022] The transfer device 44 transfers the toner image on the surface of the photoreceptor 41 onto the sheet 9 being transported along the transport path 300 .

[0023] In the tandem printing apparatus 4, the transfer device 44 includes an intermediate transfer belt 441, a plurality of primary transfer devices 442, a secondary transfer device 443, and a belt cleaning device 444. The plurality of primary transfer devices 442 are provided corresponding to the plurality of image forming units 4x.

[0024] The intermediate transfer belt 441 rotates with a portion thereof aligned with the plurality of image forming units 4x. The plurality of primary transfer devices 442 transfer the toner images on the surfaces of the photoconductors 41 of the plurality of image forming units 4x onto the surface of the intermediate transfer belt 441. As a result, a color toner image, which is a composite of the toner images of the plurality of colors, is formed on the surface of the intermediate transfer belt 441.

[0025] The secondary transfer device 443 transfers the color toner image on the surface of the intermediate transfer belt 441 to the sheet 9. That is, the transfer device 44 transfers the toner image on the surface of the photosensitive member 41 to the sheet 9 via the intermediate transfer belt 441. The intermediate transfer belt 441 is an example of an intermediate transfer body.

[0026] When the printing device 4 is a device dedicated to monochrome printing, the transfer device 44 transfers the toner image on the surface of the photosensitive member 41 directly onto the sheet 9 .

[0027] The fixing device 46 applies heat and pressure to the color toner image on the sheet 9 to fix the color toner image to the sheet 9 .

[0028] The toner supply device 5 supplies toner to the developing device 43 of each image forming unit 4x. The toner supply device 5 includes a plurality of toner containers 51 and a toner sending mechanism 52.

[0029] The plurality of toner containers 51 each contain toner of a different color. A toner delivery mechanism 52 delivers the toner contained in each toner container 51 to the developing device 43 of each image forming unit 4x. Each toner container 51 is removably attached inside the main housing 1.

[0030] 2, the developing device 43 includes a developer container 430, a developing roller 431, and a developing voltage output circuit 432. The developer container 430 contains a two-component developer. The two-component developer contains a magnetic carrier and the toner supplied from the toner supply device 5.

[0031] The developing voltage output circuit 432 outputs a developing voltage to the developing roller 431. The developing voltage is a bias voltage applied to the developing roller 431 with the potential of the photosensitive member 41 as a reference.

[0032] The developing roller 431 is a toner carrier that receives the developing voltage and carries the toner. The developing device 43 develops the electrostatic latent image into the toner image by supplying the toner to the surface of the photoreceptor 41 with the developing roller 431.

[0033] Furthermore, the developing device 43 includes a developer transport member 433 and a remaining amount detection unit 434. The developer transport member 433 rotates in the developer accommodating unit 430. The developer transport member 433 transports the two-component developer in the developer accommodating unit 430 while stirring it.

[0034] The remaining amount detection unit 434 detects the remaining amount of toner in the developer accommodating unit 430. In this embodiment, the remaining amount detection unit 434 is a magnetic permeability sensor that detects the magnetic permeability in the developer accommodating unit 430. A high magnetic permeability in the developer accommodating unit 430 indicates that the remaining amount of toner in the developer accommodating unit 430 is low.

[0035] The operation device 801 is a device that accepts operations by a person, and includes, for example, one or both of a touch panel and operation buttons.

[0036] The display device 802 is capable of displaying various types of information. For example, the display device 802 is a panel display device such as a liquid crystal display device. The control device 8 controls various electrical devices included in the image forming apparatus 10.

[0037] As shown in FIG. 3, the control device 8 includes a central processing unit (CPU) 80, a random access memory (RAM) 81, a secondary storage device 82, a signal interface 83, a communication device 84, and the like.

[0038] The CPU 80 is an example of a processor that executes computer programs to perform various control and data processing operations. The RAM 81 temporarily stores the computer programs executed by the CPU 80 and various data.

[0039] The secondary storage device 82 is a computer-readable non-volatile storage device. The secondary storage device 82 stores the computer programs executed by the CPU 80 and various data. For example, one or both of a flash memory and a hard disk drive may be used as the secondary storage device 82.

[0040] The signal interface 83 converts the detection signals of the various sensors into digital detection data, which is then transmitted to the CPU 80.

[0041] The communication device 84 communicates with a plurality of external devices, including one or more host devices, via a network. The CPU 80 communicates with each of the external devices through the communication device 84. The host device is an information processing device that requests the image forming apparatus 10 to perform the print processing.

[0042] The CPU 80 includes a plurality of processing modules that are realized by executing the computer programs, including a main control unit 8a, a supply control unit 8b, and a print control unit 8c (see FIG. 2).

[0043] The main control unit 8a receives various requests and controls other modules to execute processes according to the requests. For example, the main control unit 8a receives a print request through the operation device 801 or the communication device 84. The main control unit 8a then causes the print control unit 8c to execute processes according to the print request.

[0044] The supply control unit 8 b controls the toner supply device 5 to thereby control the supply of toner from the toner supply device 5 to the printing device 4 .

[0045] In this embodiment, the supply control unit 8b controls the amount of toner supplied by the toner supply device 5 to the developing device 43 in accordance with the difference between the remaining amount detected by the remaining amount detection unit 434 and a preset target remaining amount.

[0046] The print control unit 8c controls the conveying device 3 and the printing device 4. The print control unit 8c causes the conveying device 3 to convey the sheet 9, while causing the printing device 4 to execute the printing process.

[0047] In the image forming apparatus 10, the charge amount of the toner in the developer container 430 of the developing device 43 and the developing voltage affect the density of the toner image.

[0048] Therefore, it is important to control the charge state of the toner in the developing device 43 and the developing voltage so that the toner image has an appropriate density. The CPU 80 executes a density adjustment process (described later) so that the toner image has an appropriate density (see FIG. 4).

[0049] The plurality of processing modules of the CPU 80 include an adjustment unit 8d that executes the density adjustment process (see FIG. 3). The image forming apparatus 10 further includes an image density detection unit 6 that is used in the density adjustment process (see FIG. 1).

[0050] In this embodiment, the image density detection unit 6 detects the density of a test toner image formed on the surface of the intermediate transfer belt 441. The test toner image is a uniform solid image, a shaded image, or an image with a uniform pattern.

[0051] For example, the image density detection unit 6 is a reflective photosensor. In this case, the image density detection unit 6 irradiates the surface of the intermediate transfer belt 441 with light and detects the amount of diffused reflected light reflected by the surface of the intermediate transfer belt 441.

[0052] When the printing device 4 is a device dedicated to monochrome printing, the image density detection unit 6 detects the density of the test toner image formed on the surface of the photosensitive member 41 .

[0053] [Density adjustment processing] An example of the procedure for the density adjustment process will be described below with reference to the flowchart shown in FIG.

[0054] The adjusting unit 8d executes the density adjustment process each time the adjustment condition is met. The CPU 80 including the adjusting unit 8d is an example of a processor that executes the density adjustment process. The control device 8 including the supply control unit 8b, the print control unit 8c, and the adjusting unit 8d is an example of a control unit that controls the image forming apparatus 10.

[0055] For example, the adjustment condition may be that the number of prints reaches a predetermined number. Alternatively, the adjustment condition may be that the cumulative number of pixels drawn for each development color in the print process reaches a predetermined number.

[0056] In the following description, S1, S2, ... represent identification codes of a plurality of steps in the density adjustment process. In the density adjustment process, step S1 is executed first.

[0057] <Process S1> In step S1, the adjustment unit 8d executes a test output process, which is a process of causing the exposure device 40 and the image forming unit 4x to form the test toner image.

[0058] After performing the process of step S1, the adjustment unit 8d performs the process of step S2.

[0059] <Process S2> In step S2, the adjusting unit 8d acquires the density of the test toner image detected by the image density detecting unit 6.

[0060] After performing the process of step S2, the adjustment unit 8d performs the process of step S3.

[0061] <Process S3> In step S3, the adjusting unit 8d estimates the toner charge amount according to the level of the developing voltage when the test toner image is formed and the detected density of the test toner image by the image density detecting unit 6.

[0062] The toner charge amount is the charge amount of the toner in the developing device 43 of each image forming section 4x.

[0063] For example, development characteristic data is set in advance for the developing device 43 of each image forming unit 4x. As shown in Fig. 5, the development characteristic data represents the correspondence relationship between the development voltage for each charge amount of the toner and the density of the test toner image (see Fig. 5).

[0064] 5, Q1 to Q3 represent different toner charge amounts. Toner charge amount Q2 is smaller than toner charge amount Q1, and toner charge amount Q3 is smaller than toner charge amount Q2.

[0065] The development characteristic data is data of a mathematical formula or data of a lookup table. The adjustment unit 8d derives an estimated toner charge amount QX1 by applying a combination of a test development voltage V1 and a test detection density D1 to the development characteristic data (see FIG. 5). The estimated toner charge amount QX1 is an estimation result of the toner charge amount.

[0066] The test developing voltage V1 is the developing voltage when the test toner image is formed. The test detected density D1 is the density of the test toner image detected by the image density detection unit 6.

[0067] For example, the adjusting unit 8d identifies a first charge amount having characteristics closest to the combination of the test developing voltage V1 and the test detection density D1 and a second charge amount having characteristics second closest to the combination of the test developing voltage V1 and the test detection density D1 based on the development characteristic data.

[0068] In the example shown in FIG. 5, the toner charge amount Q3 and the toner charge amount Q2 are the first charge amount and the second charge amount, respectively.

[0069] Furthermore, the adjustment unit 8d derives an estimated toner charge amount QX1 by interpolation calculation based on the data corresponding to the first charge amount and the data corresponding to the second charge amount in the development characteristic data and the test detection density D1 (see FIG. 5).

[0070] The adjusting unit 8d may derive the first charge amount as the estimated toner charge amount QX1.

[0071] After performing the process of step S3, the adjustment unit 8d performs the process of step S4.

[0072] <Process S4> In step S4, the adjusting unit 8d adjusts the developing voltage in accordance with the estimated toner charge amount QX1 and the target density DT1 of the test toner image (see FIG. 6).

[0073] In this embodiment, the adjusting section 8d derives a set developing voltage VS1, which is the developing voltage corresponding to the estimated toner charge amount QX1 and the target density DT1, based on the developing characteristic data (see FIG. 6).

[0074] The processes of steps S1 to S4 performed by the adjustment unit 8d are an example of a development voltage adjustment process. The development voltage adjustment process includes a process of causing the exposure device 40 and the development device 43 to perform a process of forming the test toner image (step S1).

[0075] Furthermore, the developing voltage adjustment process includes a process of adjusting the developing voltage in accordance with the level of the test developing voltage V1, the test detected density D1, and the target density DT1 (S2 to S4).

[0076] The print control unit 8c controls the developing voltage output circuit 432 so that the set developing voltage VS1 is applied to the developing roller 431 in the print process.

[0077] After performing the process of step S4, the adjustment unit 8d performs the process of step S5.

[0078] <Process S5> In step S5, the adjusting section 8d determines whether the set developing voltage VS1, which is the adjusted developing voltage, is within a preset reference range or is outside the reference range.

[0079] The reference range of the developing voltage is a part of the control range of the developing voltage by the print control unit 8c. Specifically, the lower limit voltage of the reference range is higher than the lower limit voltage of the control range, and the upper limit voltage of the reference range is lower than the upper limit voltage of the control range.

[0080] The adjusting unit 8d ends the density adjustment process when the set developing voltage VS1 is within the reference range. On the other hand, the adjusting unit 8d executes the process of step S6 when the set developing voltage VS1 is out of the reference range.

[0081] <Process S6> In step S6, the adjustment unit 8d corrects the amount of toner supplied to the developing device 43. The adjustment unit 8d corrects the amount of toner supplied of the developing color corresponding to the set developing voltage VS1 outside the reference range.

[0082] Specifically, when the set developing voltage VS1 is below the reference range, the adjustment unit 8d corrects the amount of toner supplied to the developing device 43 to decrease. On the other hand, when the set developing voltage VS1 is above the reference range, the adjustment unit 8d corrects the amount of toner supplied to the developing device 43 to increase.

[0083] When the set development voltage VS1 is below the reference range, the charge amount of the toner is too low. In this case, the charge amount of the toner in the developing device 43 increases due to a decrease in the amount of the toner supplied.

[0084] On the other hand, when the set development voltage VS1 exceeds the reference range, the toner charge amount is excessive. In this case, the toner supply amount increases, and the toner charge amount in the developing device 43 decreases.

[0085] In this embodiment, the adjusting unit 8d corrects the amount of toner supplied to the developing device 43 by correcting the target remaining amount of toner.

[0086] That is, when the set developing voltage VS1 is below the reference range, the adjusting unit 8d corrects the target remaining amount in a decreasing direction, whereas when the set developing voltage VS1 is above the reference range, the adjusting unit 8d corrects the target remaining amount in an increasing direction.

[0087] For example, the adjustment unit 8d sets a correction range for the target remaining amount in accordance with the difference between the set development voltage VS1 and the reference range.

[0088] The supply control unit 8b controls the amount of toner supplied to the developing device 43 by the toner supply device 5 in accordance with the difference between the remaining amount detected by the remaining amount detection unit 434 and the corrected target remaining amount.

[0089] After performing the process of step S6, the adjustment unit 8d performs the process of step S7.

[0090] <Process S7> In step S7, the adjustment unit 8d corrects the adjustment conditions so that the frequency of the density adjustment process increases.

[0091] Therefore, when the level of the developing voltage is outside the reference range, the adjusting unit 8d executes the density adjustment process more frequently than when the level of the developing voltage is within the reference range. Note that the density adjustment process includes the developing voltage adjustment process of steps S1 to S4.

[0092] After executing the process of step S7, the adjusting section 8d ends the density adjusting process.

[0093] As described above, the density of the toner image is affected by the charge amount of the toner in the developing device 43 and the developing voltage. The adjustment of the developing voltage in step S4 has an immediate effect on the density of the toner image.

[0094] However, if the charge amount of the toner is too high or too low, it is difficult to adjust the toner image to an appropriate density by adjusting only the development voltage.

[0095] On the other hand, the correction of the amount of toner supplied to the developing device 43 in step S6 takes time to contribute to the charge amount of the toner and the density of the toner image.

[0096] By executing the density adjustment process, a situation in which the charge amount of the toner becomes too high or too low is avoided, and the toner image is maintained at an appropriate density by adjusting the developing voltage.

[0097] Furthermore, the development voltage needs to be readjusted at the timing when the excess or deficiency in the charge amount of the toner is eliminated by correcting the amount of the toner supplied to the development device 43. By executing the process of step S7, delay in the timing of readjustment of the development voltage is avoided.

[0098] As described above, by executing the density adjustment process, the charge state of the toner in the developing device 43 and the developing voltage are controlled so that the toner image of appropriate density is formed.

[0099] [Modification of density adjustment process] Next, the procedure of a modified example of the density adjustment process will be described with reference to the flowchart shown in FIG.

[0100] The modified density adjustment process is performed by adding step S8 to the density adjustment process shown in Fig. 4. The following describes the differences between this modified density adjustment process and the density adjustment process shown in Fig. 4.

[0101] In this modified example, the adjustment section 8d executes the process of step S8 when the set development voltage VS1 is within the reference range.

[0102] If the set development voltage VS1 is outside the reference range, the adjustment unit 8d executes the processes of steps S6 and S7, which is the same as the density adjustment process shown in FIG.

[0103] <Process S8> In step S8, if the amount of toner supplied to the developing device 43 has been corrected by the process in step S6, the adjusting unit 8d cancels the correction of the amount of toner supplied.

[0104] For example, each time the process of step S8 is executed, the adjustment unit 8d gradually cancels the correction of the amount of toner supplied to the developing device 43. Alternatively, the adjustment unit 8d may gradually cancel the correction of the amount of toner supplied to the developing device 43 by a predetermined amount at predetermined time intervals.

[0105] Furthermore, the adjusting unit 8d may immediately cancel the correction of the amount of toner supplied to the developing device 43.

[0106] After executing the process of step S8, the adjusting section 8d ends the density adjusting process.

[0107] By adopting this modified example, it is possible to prevent the exceptional state in which the amount of toner supplied to the developing device 43 is corrected from continuing for a long period of time.

[0108] [First Modification of Image Forming Apparatus 10] Next, a first modification of the image forming apparatus 10 will be described.

[0109] In this modification, a level meter that detects the accumulation level of the two-component developer in the developer container 430 is employed as the remaining amount detection unit 434. For example, the level meter is a plurality of photosensors.

[0110] When this modified example is adopted, the same effects as when the image forming apparatus 10 is adopted can be obtained.

[0111] [Second Modification of Image Forming Apparatus 10] Next, a description will be given of a second modified example of the image forming apparatus 10. This modified example differs from the image forming apparatus 10 in the method of correcting the amount of toner supply in step S6 of the density adjustment process.

[0112] The adjusting unit 8d in this modification corrects the toner supply speed or supply operation time of the toner supply device 5, thereby correcting the amount of toner supplied to the developing device 43 (step S6 in FIG. 4).

[0113] When this modified example is adopted, the same effects as when the image forming apparatus 10 is adopted can be obtained.

[0114] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0115] <Appendix 1> A photoreceptor; an exposure device for forming an electrostatic latent image on the surface of the photoreceptor; a developing device that develops the electrostatic latent image into a toner image using a toner carrier to which a developing voltage is applied; a transfer device that transfers the toner image on the surface of the photoreceptor directly or via an intermediate transfer body to a sheet; a toner supplying device for supplying toner to the developing device; an image density detection unit that detects the density of a test toner image formed on the surface of the photosensitive member or the surface of the intermediate transfer member; a control unit that causes the exposure device and the developing device to execute a process for forming the test toner image, and executes a developing voltage adjustment process that adjusts the developing voltage in accordance with a level of the developing voltage when the test toner image is formed, a density of the test toner image detected by the image density detection unit, and a target density of the test toner image, The control unit corrects the amount of toner supplied to the developing device by the toner supply device when the adjusted level of the developing voltage falls outside a reference range.

[0116] <Appendix 2> a remaining amount detection unit that detects the remaining amount of toner in the developing device, the control unit controls the amount of toner supplied to the developing device by the toner supply device in accordance with a difference between the remaining amount detected by the remaining amount detection unit and a target remaining amount; Further, the control unit corrects the amount of toner supplied to the developing device by correcting the target remaining amount when the adjusted level of the developing voltage falls outside the standard range.

[0117] <Appendix 3> the developing device includes a developer container that contains a two-component developer containing the toner and a magnetic carrier; 3. The image forming apparatus according to claim 2, wherein the remaining amount detection unit includes a sensor that detects magnetic permeability within the developer container.

[0118] <Appendix 4> The image forming apparatus according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the control unit estimates the charge amount of the toner based on the level of the developing voltage when the test toner image is formed and the detected density of the test toner image by the image density detection unit, and adjusts the developing voltage based on the estimated charge amount and the target density of the test toner image.

[0119] <Appendix 5> 5. The image forming apparatus according to claim 1, wherein the reference range of the development voltage is a part of a control range of the development voltage controlled by the control unit.

[0120] <Appendix 6> The image forming apparatus of any one of Appendix 1 to Appendix 5, wherein the control unit executes the development voltage adjustment process more frequently when the level of the development voltage is outside the reference range than when the level of the development voltage is within the reference range. [Explanation of symbols]

[0121] 5: Toner supply device 6: Image density detection unit 8: Control device (control unit) 10: Image forming device 40: Exposure equipment 41: Photoreceptor 42: Charging device 43: Developing device 44: Transcription device 430: Developer storage section 431: Developing roller (toner carrier) 432: Development voltage output circuit 433: Developer transport member 434: Remaining amount detection unit 441: Intermediate transfer belt (intermediate transfer body)

Claims

1. A photoreceptor; an exposure device for forming an electrostatic latent image on the surface of the photoreceptor; a developing device that develops the electrostatic latent image into a toner image using a toner carrier to which a developing voltage is applied; a transfer device that transfers the toner image on the surface of the photoreceptor directly or via an intermediate transfer body to a sheet; a toner supplying device for supplying toner to the developing device; an image density detection unit that detects the density of a test toner image formed on the surface of the photosensitive member or the surface of the intermediate transfer member; a control unit that causes the exposure device and the developing device to execute a process for forming the test toner image, and executes a developing voltage adjustment process that adjusts the developing voltage in accordance with a level of the developing voltage when the test toner image is formed, a density of the test toner image detected by the image density detection unit, and a target density of the test toner image, The control unit corrects the amount of toner supplied to the developing device by the toner supply device when the adjusted level of the developing voltage falls outside a reference range.

2. a remaining amount detection unit that detects the remaining amount of toner in the developing device, the control unit controls the amount of toner supplied to the developing device by the toner supply device in accordance with a difference between the remaining amount detected by the remaining amount detection unit and a target remaining amount; 2. The image forming apparatus according to claim 1, wherein the control unit further corrects the amount of toner supplied to the developing device by correcting the target remaining amount when the adjusted level of the developing voltage falls outside the reference range.

3. the developing device includes a developer container that contains a two-component developer containing the toner and a magnetic carrier; 3. The image forming apparatus according to claim 2, wherein the remaining amount detection unit includes a sensor that detects magnetic permeability within the developer container.

4. 4. The image forming apparatus according to claim 1, wherein the control unit estimates the charge amount of the toner based on the level of the developing voltage when the test toner image is formed and the detected density of the test toner image by the image density detection unit, and adjusts the developing voltage based on the estimated charge amount and the target density of the test toner image.

5. 4. The image forming apparatus according to claim 1, wherein the reference range of the development voltage is a part of a control range of the development voltage controlled by the control unit.

6. 4. The image forming apparatus according to claim 1, wherein the control unit executes the development voltage adjustment process more frequently when the level of the development voltage falls outside the reference range than when the level of the development voltage is within the reference range.

Images