Image forming apparatus and method for adjusting the same

Abstract

To properly adjust an amount of toner attached to an image carrier surface.SOLUTION: An image forming apparatus of an embodiment comprises a forming unit, a sensor, an adjustment unit, a storage unit, and a determination unit. The forming unit attaches toner to an image carrier surface to form an image. The sensor faces the image carrier surface and detects a quantity of reflected light from the image carrier surface. The adjustment unit adjusts an amount of toner attached to the image carrier surface along with image formation performed by the forming unit, so as to bring, closer to a target value, a detection value from the sensor related to reflected light from an area of the image carrier surface where an image with a predetermined density value is formed by the forming unit. The storage unit stores a reference value according to a detection value from the sensor related to reflected light from a reference surface exhibiting a reference reflectance according to a reflectance of an area of the image carrier surface to which a reference attachment amount of toner is attached. The determination unit determines the target value on the basis of a detection value from the sensor related to reflected light from an area of the image carrier surface where an amount of attached toner is zero, and the reference value stored in the storage unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an image forming apparatus and an adjustment method thereof. [Background technology]

[0002] 2. Description of the Related Art Image forming apparatuses are known as one type of equipment used in workplaces to create office environments or remote work environments. In an image forming apparatus that forms an image by adhering toner to the image bearing surface of an image carrier, the amount of toner adhering to the image bearing surface during an operation to form an image of a certain density value varies depending on the operating conditions and environmental conditions of the apparatus.

[0003] Therefore, the amount of toner adhering to the image bearing surface when an image of a predetermined density value is formed is detected by a reflective optical sensor placed opposite the image bearing surface, and the operating conditions of the device are adjusted so that the detected value of the sensor approaches a predetermined target value. However, if there is an error in the amount of toner adhesion detected by the reflective optical sensor, there is a risk that the amount of toner adhesion cannot be adjusted properly. In view of these circumstances, it has been desired to be able to appropriately adjust the amount of toner adhered to the image bearing surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-93972 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide an image forming apparatus capable of properly adjusting the amount of toner adhered to the image bearing surface, and a method for adjusting the same. [Means for solving the problem]

[0006] An image forming apparatus according to an embodiment includes a forming unit, a sensor, an adjusting unit, a storage unit, and a determining unit. The forming unit forms an image by depositing toner on an image bearing surface provided on an image carrier. The sensor is disposed opposite the image bearing surface and detects the amount of light reflected from the image bearing surface. The adjusting unit adjusts the amount of toner deposited on the image bearing surface during image formation by the forming unit so that the sensor's detection value of light reflected from an area of ​​the image bearing surface on which an image of a predetermined density value has been formed by the forming unit approaches a target value. The storage unit stores a reference value corresponding to the sensor's detection value of light reflected from a reference surface exhibiting a reference reflectance corresponding to the reflectance of an area of ​​the image bearing surface on which a predetermined reference amount of toner has been deposited. The determining unit determines the target value based on the image bearing surface detection value, which is the sensor's detection value of light reflected from an area of ​​the image bearing surface on which no toner has been deposited, and the reference value stored in the storage unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating a mechanical configuration of a multifunction peripheral according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating a configuration related to control of the multifunction peripheral shown in FIG. [Figure 3] FIG. 3 is a block diagram showing the main circuit configuration of the printer controller in FIG. 2. [Figure 4] FIG. 10 is a diagram showing the acquisition status of the reference value. [Figure 5] 10 is a flowchart of an adjustment process. [Figure 6] FIG. 10 is a diagram showing a specific example of determining a target value. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment will be described with reference to the drawings. In the following embodiment, a multifunction peripheral (MFP) is used as an example, which includes an image forming apparatus as a printer. A multifunction peripheral is also called an MFP (multi-function peripheral). First, the configuration of the multifunction peripheral according to this embodiment will be described. FIG. 1 is a diagram illustrating a schematic mechanical configuration of a multifunction peripheral 100 according to an embodiment.

[0009] As shown in FIG. 1, the multifunction peripheral 100 includes a scanner 101 and a printer 102 . The scanner 101 reads an image of an original document and generates corresponding image data. The scanner 101 uses an image sensor, such as a CCD (charge-coupled device) line sensor, to generate image data according to a reflected light image from the surface of the original document to be read. The scanner 101 scans an original document placed on a platen with an image sensor that moves along the original document. Alternatively, the scanner 101 scans an original document transported by an ADF (auto document feeder) with a fixed image sensor. The scanner 101 is an example of a reading unit.

[0010] The printer 102 forms an image on a medium by electrophotography. The medium is typically print paper such as cut paper. Therefore, the following description will be given assuming that print paper is used as the medium. However, the medium may be a paper sheet other than cut paper, or a sheet made of a material other than paper, such as resin. The printer 102 has a color printing function for printing color images on print paper and a monochrome printing function for printing monochrome images on print paper. The printer 102 forms color images by overlaying element images using toner of three colors, for example, yellow, magenta, and cyan, or four colors, including these, plus black. The printer 102 also forms monochrome images using, for example, black toner.

[0011] In the configuration example shown in FIG. 1, the printer 102 includes a paper feed unit 1, a print engine 2, a fixing unit 3, an ADU (automatic double-sided unit) 4, and a paper discharge tray 5. The paper feed unit 1 includes paper feed cassettes 10-1, 10-2, and 10-3, pickup rollers 11-1, 11-2, and 11-3, conveyance rollers 12-1, 12-2, and 12-3, a conveyance roller 13, and a registration roller 14.

[0012] The paper feed cassettes 10-1, 10-2, and 10-3 store stacks of printing paper. The printing paper stored in the paper feed cassettes 10-1, 10-2, and 10-3 may be of different sizes and materials, or may be of the same type. The paper feed unit 1 may also include a manual feed tray.

[0013] Pickup rollers 11-1, 11-2, and 11-3 pick up print sheets one by one from paper feed cassettes 10-1, 10-2, and 10-3, respectively, and feed the picked-up print sheets to transport rollers 12-1, 12-2, and 12-3. Conveying rollers 12-1, 12-2, and 12-3 feed the print paper fed from pickup rollers 11-1, 11-2, and 11-3 to conveying roller 13 via a conveying path formed by a guide member or the like (not shown).

[0014] The conveying roller 13 further conveys the print paper fed from any one of the conveying rollers 12-1, 12-2, and 12-3, and feeds it to the registration rollers 14. The registration rollers 14 correct the skew of the print paper and adjust the timing at which the print paper is fed into the print engine 2.

[0015] The number of sets of paper feed cassettes, pickup rollers, and transport rollers is not limited to three, and any number of sets may be provided. Also, if a manual feed tray is provided, it is not necessary to provide a single set of paper feed cassettes and their corresponding pickup rollers and transport rollers.

[0016] The print engine 2 includes an image carrier 20, support rollers 21, 22, and 23, image forming units 24-1, 24-2, 24-3, and 24-4, an exposure unit 25, a transfer roller 26, and a belt cleaner 27. The image carrier 20 is belt-like and endless, and is supported by support rollers 21, 22, and 23 so as to maintain the state shown in FIG. 1. The image carrier 20 rotates counterclockwise in FIG. 1 as the support roller 21 rotates. The image carrier 20 temporarily carries a toner image to be formed on print paper on its outer surface (hereinafter referred to as the image carrying surface). For example, semiconductive polyimide is used for the image carrier 20 because of its heat resistance and abrasion resistance. The movement of the image carrying surface as the image carrier 20 rotates achieves so-called sub-scanning, and the movement direction of the image carrying surface is also called the sub-scanning direction.

[0017] Each of the image forming units 24-1 to 24-4 includes a photosensitive element, a charging roller, a developing device, a transfer roller, and a cleaner, and forms an image by electrophotography in cooperation with the exposure unit 25. The image forming units 24-1 to 24-4 are arranged along the image carrier 20 with the axial directions of their photosensitive elements parallel to each other. The image forming units 24-1 to 24-4 use different colors of toner, but are basically similar in structure and operation. The image forming unit 24-1 forms element images using, for example, black toner. The image forming unit 24-2 forms element images using, for example, cyan toner. The image forming unit 24-3 forms element images using, for example, magenta toner. The image forming unit 24-4 forms element images using, for example, yellow toner. Thus, each of the image forming units 24-1 to 24-4 is an example of a forming section. The image forming units 24-1 to 24-4 form elemental images of each color superimposed on one another on the image bearing surface of the image carrier 20. As a result, the image forming units 24-1 to 24-4 form a color image in which the elemental images of each color are superimposed on the image bearing surface of the image carrier 20 at the time when the image forming units 24-1 have passed the image forming unit 24-1. Although not shown, developer containers containing developers containing toners of each color are disposed, for example, in the space above the image carrier 20. The developer may be a one-component developer consisting only of toner, or a multi-component developer containing other substances such as a carrier in addition to the toner.

[0018] The exposure unit 25 exposes the photoconductors of the image forming units 24-1 to 24-4 to light in accordance with image data representing element images of each color. The exposure unit 25 includes a laser scanner. Specifically, the exposure unit 25 includes, for example, a semiconductor laser element, a polygon mirror, an imaging lens system, and a mirror. In this case, the exposure unit 25 selectively applies a laser beam emitted from the semiconductor laser element in accordance with the image data to the photoconductors of the image forming units 24-1 to 24-4 by switching the emission direction using a mirror. The exposure unit 25 also scans the laser beam in the axial direction of the photoconductor (the depth direction in FIG. 1) using a polygon mirror. This laser beam scanning is known as main scanning, and its direction is called the main scanning direction. The exposure unit 25 may include another exposure device, such as an LED (light emitting diode) head, instead of the laser scanner.

[0019] The transfer roller 26 is disposed parallel to the support roller 23, and sandwiches the image carrier 20 between it and the support roller 23. The transfer roller 26 sandwiches the print paper sent out from the registration roller 14 between it and the image bearing surface of the image carrier 20. The transfer roller 26 then transfers the toner image formed on the image bearing surface of the image carrier 20 onto the print paper using electrostatic force. In other words, the support roller 23 and the transfer roller 26 form a transfer section.

[0020] The belt cleaner 27 removes toner that was not completely transferred to the print paper and remains on the image carrying surface of the image carrier 20. However, the belt cleaner 27 may not be able to completely remove the toner that remains on the image carrying surface, and a small amount of toner may remain on the image carrying surface after the image has passed through the belt cleaner 27. In other words, the belt cleaner 27 is an example of a cleaner unit that attempts to remove toner from the image carrying surface. Thus, the print engine 2 forms an image on the print paper fed by the registration rollers 14 by electrophotography.

[0021] The fixing unit 3 includes a fixing roller 30 and a pressure roller 31 . The fixing roller 30 is a hollow roller made of, for example, heat-resistant resin, and houses a heater inside. The heater is, for example, an induction heater (IH) heater, but any other type of heater can be used as appropriate. The fixing roller 30 melts the toner adhering to the print paper sent out from the print engine 2, thereby fixing the toner to the print paper. The pressure roller 31 is provided parallel to the fixing roller 30 and is pressed against the fixing roller 30. The pressure roller 31 sandwiches the print paper sent out from the print engine 2 between itself and the fixing roller 30 and presses it against the fixing roller 30.

[0022] The ADU 4 includes multiple rollers and selectively performs the following two operations. In the first operation, the print paper that has passed through the fixing unit 3 is sent directly toward the paper output tray 5. This first operation is performed when single-sided or double-sided printing is completed. In the second operation, the print paper that has passed through the fixing unit 3 is transported toward the paper output tray 5, and then switched back and sent to the print engine 2. This second operation is performed when image formation on only one side of double-sided printing is completed. The paper discharge tray 5 receives the print paper on which an image has been formed and discharged.

[0023] Fig. 2 is a block diagram that shows a schematic configuration related to the control of the multifunction peripheral 100. In Fig. 2, the same elements as those shown in Fig. 1 are given the same reference numerals, and detailed description thereof will be omitted. The multifunction peripheral 100 includes a scanner 101 and a printer 102 as well as a communication unit 103 , a system controller 104 and an operation panel 105 .

[0024] The communication unit 103 performs processing for communicating with information terminals such as computers and image terminals such as facsimile machines via communication networks such as LANs (local area networks) and public communication networks. The system controller 104 comprehensively controls each component of the multifunction device 100 in order to realize the desired operation of the multifunction device 100. The desired operation of the multifunction device 100 is an operation for realizing various functions realized by existing multifunction devices, such as a print function, a scan function, a facsimile function, or an image file management function.

[0025] The operation panel 105 includes an input device and a display device. An operator inputs instructions into the operation panel 105 using the input device. The operation panel 105 displays various information to be notified to the operator using the display device. The operation panel 105 may be, for example, a touch panel, various switches, various lamps, etc., used alone or in appropriate combination.

[0026] The above-mentioned fixing unit 3, ADU 4, image forming units 24-1 to 24-4, exposure unit 25, and transfer roller 26 provided in printer 102 are elements to be controlled. In addition to these, printer 102 also includes a motor group 6 as an element to be controlled. Motor group 6 includes a plurality of motors for rotating pickup rollers 11-1, 11-2, and 11-3, conveyance rollers 12-1, 12-2, and 12-3, conveyance roller 13, registration roller 14, support roller 21, transfer roller 26, fixing roller 30, and various rotating bodies included in image forming units 24-1 to 24-4, as well as rollers included in ADU 4.

[0027] The printer 102 further includes a sensor group 7 , a printer controller 81 , a formation controller 82 , an exposure controller 83 , a transfer controller 84 , a fuser controller 85 , an inversion controller 86 , and a motor controller 87 . The sensor group 7 includes various sensors for monitoring the operating status of the device. One of the sensors included in the sensor group 7 is a toner sensor 71. As shown in FIG. 1, the toner sensor 71 is disposed facing the image bearing surface of the image carrier 20 at a position between the image forming unit 24-1 and the transfer roller 26. The toner sensor 71 is a reflective optical sensor. That is, the toner sensor 71 outputs a voltage value corresponding to the amount of reflected light of light irradiated onto the image bearing surface of the image carrier 20 as a digital value. The reflectance of light on the image bearing surface of the image carrier 20 changes depending on the amount of toner adhered to it. Thus, the digital value output by the toner sensor 71 is a detection value corresponding to the amount of toner adhered to the image bearing surface.

[0028] The printer controller 81, under the control of the system controller 104, comprehensively controls each component of the printer 102 in order to realize the desired operation of the printer 102. The formation controller 82, exposure controller 83, transfer controller 84, fixing controller 85, reversal controller 86 and motor controller 87 all operate under the control of the printer controller 81, and control the operation of the image forming units 24-1 to 24-4, exposure unit 25, transfer roller 26, ADU 4 and motor group 6, respectively.

[0029] FIG. 3 is a block diagram showing the main circuit configuration of the printer controller 81. The printer controller 81 includes a processor 811 , a main memory unit 812 , an auxiliary memory unit 813 , a communication unit 814 , and a transmission path 815 . The processor 811, main storage unit 812, and auxiliary storage unit 813 are connected via a transmission line 815 to form a computer that performs information processing for overall control of each component of the printer 102. The processor 811 corresponds to the central part of the computer. The processor 811 executes information processing, which will be described later, in accordance with information processing programs such as an operating system, middleware, and application programs.

[0030] The main memory unit 812 corresponds to the main memory portion of the computer. The main memory unit 812 includes a read-only memory area and a rewritable memory area. The main memory unit 812 stores information processing programs in the read-only memory area. The main memory unit 812 may also store data necessary for the processor 811 to execute processes for controlling each component in the read-only or rewritable memory area. The main memory unit 812 uses the rewritable memory area as a work area where data is rewritten by the processor 811 as needed.

[0031] The auxiliary storage unit 813 corresponds to the auxiliary storage portion of the computer. The auxiliary storage unit 813 may be, for example, a single or a combination of well-known storage devices such as an EEPROM (electrical erasable programmable read-only memory), an HDD (hard disk drive), or an SSD (solid state drive). The auxiliary storage unit 813 stores data used by the processor 811 when performing various processes and data generated by the processes performed by the processor 811. The auxiliary storage unit 813 stores an information processing program. In this embodiment, the auxiliary storage unit 813 stores a control program PRA. The control program PRA is an information processing program that describes information processing procedures for comprehensively controlling the components of the printer 102. In this embodiment, the auxiliary storage unit 813 stores a reference value VR as data used by the processor 811 when performing various processes. The reference value VR will be described later.

[0032] The communication unit 814 performs communication processing for communication with the system controller 104 , the sensor group 7 , the printer controller 81 , the formation controller 82 , the exposure controller 83 , the transfer controller 84 , the fixing controller 85 , the reversal controller 86 , and the motor controller 87 . The transmission path 815 includes an address bus, a data bus, and control signal lines, and transmits data and control signals exchanged between the connected components.

[0033] The multifunction peripheral 100 is generally transferred with the control program PRA stored in the auxiliary storage unit 813. However, the control program PRA may be transferred separately from the hardware without the control program PRA stored in the auxiliary storage unit 813, or with a different version of the same application program stored in the auxiliary storage unit 813. The multifunction peripheral 100 may then be configured by writing the control program PRA to the auxiliary storage unit 813 in response to an operation by any operator. The control program PRA may be transferred by recording it on a removable recording medium such as a magnetic disk, magneto-optical disk, optical disk, or semiconductor memory, or by communication via a network. The reference value VR is acquired using the toner sensor 71 selected to be mounted in the multifunction device 100 during the manufacturing process of the multifunction device 100, and is stored in the auxiliary storage unit 813. Thus, the auxiliary storage unit 813 is an example of a storage section.

[0034] FIG. 4 is a diagram showing the acquisition status of the reference value VR. Before arranging the toner sensor 71 opposite the image carrier 20 as shown on the left side of Fig. 4, a jig 200 is placed opposite the toner sensor 71 as shown on the right side of Fig. 4. A reference surface 201 is formed on the surface of the jig 200 that faces the toner sensor 71. As shown in the figure, the distance between the toner sensor 71 and the reference surface 201 is set to match the distance between the image carrier 20 and the toner sensor 71 in the specifications. The light reflectance of the reference surface 201 will be described later.

[0035] Next, a description will be given of the operation of the multifunction device 100 configured as described above. The various operations and processes described below are merely examples, and it is possible to change the order of some of the operations and processes, omit some of the operations and processes, or add other operations and processes as appropriate. In the following, the operation of the multifunction peripheral 100 according to the present embodiment is characterized by the operation of the printer controller 81.

[0036] When an image is to be printed by printer 102, processor 811 provides image data to be printed to exposure controller 83. If the provided image data represents a color image, exposure controller 83 generates element image data representing element images of each color of black, cyan, magenta, and yellow from the image data. Then, exposure unit 25 exposes the element images represented by these element image data so that they are formed on the image bearing surface of image carrier 20 by image forming units 24-1 to 24-4 at predetermined time intervals. As a result, the element images of each color of black, cyan, magenta, and yellow are superimposed on the image bearing surface of image carrier 20 to form a color image. This color image is then transferred to printing paper by transfer roller 26, and then heated, melted, and fixed by fixing unit 3, forming a color image on the printing paper.

[0037] As such printing operations are repeated, the amount of toner adhered to the image bearing surface may change when forming an element image of a certain density value due to changes in the operating conditions of the image forming units 24-1 to 24-4 and environmental changes. Therefore, when a predetermined adjustment timing is reached, the processor 811 in the printer controller 81 starts an adjustment process for adjusting the amount of toner adhered to the image bearing surface during information processing based on the control program PRA. The adjustment timing may be determined as appropriate, for example, by the person who determines the specifications of the multifunction peripheral 100 or an administrator. The adjustment timing may be, for example, each time the cumulative number of printed sheets reaches a predetermined number, each time the cumulative execution time of the printing operation reaches a predetermined time, or each time a predetermined time has elapsed regardless of whether a printing operation is being performed. The adjustment timing is set to a time when no printing operation is being performed.

[0038] FIG. 5 is a flowchart of the adjustment process. As ACT1, processor 811 acquires a first detection value. The first detection value is a detection value by toner sensor 71 regarding the amount of light reflected from the image bearing surface when the amount of toner adhesion is zero, and corresponds to an image bearing surface detection value. For example, processor 811 controls motor controller 87 to rotate image carrier 20 at a predetermined speed. Furthermore, processor 811 acquires, as the first detection value, a detection value by toner sensor 71 after an area of ​​the image bearing surface that has been cleaned by belt cleaner 27 reaches a detection position by toner sensor 71 in a state in which image forming units 24-1 to 24-4 are not performing image formation. Note that, as described above, even if a very small amount of toner remains on the image bearing surface after passing through belt cleaner 27, this can be considered a state in which the amount of toner adhesion is zero. Thus, the first detection value is a value corresponding to the light reflectance of the image bearing surface itself of image carrier 20.

[0039] In ACT2, processor 811 analyzes the relationship between the first detection value and the reference value VR stored in auxiliary storage unit 813. For example, processor 811 finds a linear function including a point related to the first detection value and a point related to the reference value VR in a coordinate system in which the X axis represents the amount of toner adhesion and the Y axis represents the detection value of toner sensor 71.

[0040] In ACT3, the processor 811 determines a target value. For example, based on the analysis results in ACT2, the processor 811 determines target values ​​for the first detection value and the reference value VR as detection values ​​having a relationship similar to that between the first detection value and the reference value VR. More specifically, the processor 811 determines a point related to a toner adhesion amount (hereinafter referred to as a target adhesion amount) appropriate for forming an image with a predetermined adjustment density value using the linear function obtained in ACT2, and determines the target value as a detection value related to that point. The adjustment density value may be determined as appropriate, for example, by someone who determines the specifications of the multifunction peripheral 100. In this embodiment, the adjustment density value is set to the maximum density value within the density value range of the image data. Thus, the processor 811 executes information processing based on the control program PRA, and the computer, with the processor 811 as its central part, functions as a determination means.

[0041] FIG. 6 is a diagram showing a specific example of determining the target value. In FIG. 6, AT and AR represent the target adhesion amount and the reference adhesion amount, respectively. The optical reflectance of the reference surface 201 of the jig 200 is determined in advance so that the reference adhesion amount AR is different from the target adhesion amount AT. The optical reflectance of the reference surface 201 of the jig 200, i.e., the reference adhesion amount AR, may be determined as appropriate, for example, by the person who determines the specifications of the multifunction printer 100. In this embodiment, the optical reflectance of the reference surface 201 of the jig 200 is determined so that the reference adhesion amount AR is greater than the target adhesion amount AT. Thus, point PR shown in FIG. 6 is a point related to the reference value VR. However, the reference adhesion amount AR may also be determined to be smaller than the target adhesion amount AT.

[0042] The first detection value may vary depending on variations in the light reflectance of the image bearing surface itself. In Figure 6, the first detection value for an image bearing surface exhibiting a light reflectance consistent with the specifications is designated as VDA. VDB shown in Figure 6 is an example of the first detection value for an image bearing surface exhibiting a light reflectance higher than the specifications. VDC shown in Figure 6 is an example of the first detection value for an image bearing surface exhibiting a light reflectance lower than the specifications.

[0043] When processor 811 acquires first detection value VDA as ACT1, it determines linear function LFA as ACT2. In this case, processor 811 determines the detection value represented as VTA in FIG. 6 as the target value as ACT3. When the processor 811 acquires the first detected value VDB as ACT1, it obtains the linear function LFB as ACT2. In this case, the processor 811 determines the detected value represented as VTB in FIG. 6 as the target value as ACT3. When the processor 811 acquires the first detected value VDC as ACT1, it determines the linear function LFC as ACT2. In this case, the processor 811 determines the detected value represented as VTC in FIG. 6 as the target value as ACT3.

[0044] Thus, when determining the target value here, differences in the light reflectance of the image bearing surface itself are taken into consideration. Also, since individual toner sensors 71 may have sensitivity errors, and these differences in sensitivity cause the coordinates of point PR to change, differences in the sensitivity of toner sensors 71 are also taken into consideration when determining the target value here.

[0045] In ACT4, the processor 811 starts forming a test pattern. The processor 811 controls the formation controller 82, for example, to bring all of the image forming units 24-1 to 24-4 into an operating state in which they form element images. The processor 811 then provides the exposure controller 83 with predetermined image data for forming element images of adjustment density values ​​so that they do not overlap each other, for example. As a result, element images of the adjustment density values ​​for each color are formed on the image carrying surface of the image carrier so as to sequentially reach the detection position of the toner sensor 71.

[0046] In ACT5, the processor 811 acquires a second detection value related to the amount of toner adhesion involved in actual image formation. The processor 811 acquires the detection value of the toner sensor 71 when the element image of the adjustment density value for each color passes through the detection position of the toner sensor 71 as the second detection value related to each color. In ACT6, the processor 811 calculates the error between the target value determined in ACT3 and the second detection value of each color acquired in ACT5.

[0047] In ACT 7, the processor 811 checks whether any of the errors for each color calculated in ACT 6 are outside a predetermined allowable range. The allowable range may be determined as appropriate by, for example, the person who decided the specifications for the multifunction peripheral 100. If there is even one error that is outside the allowable range, the processor 811 determines YES and proceeds to ACT 8.

[0048] As ACT8, processor 811 changes the density control conditions. For example, processor 811 changes the density control conditions for the color related to the error outside the allowable range so as to reduce the error. Then, processor 811 ends the adjustment process. When the density control conditions are changed, the amount of toner to be deposited on the image bearing surface when an image of a certain density value is formed by image forming units 24-1 to 24-4 is changed. In this way, processor 811 executes information processing based on control program PRA, and the computer with processor 811 as its central part functions as an adjustment unit. Then, when the processor 811 has finished changing the density control conditions, it repeats ACT4 and subsequent steps, i.e., it forms a test pattern applying the changed density control conditions, and checks the state of formation of the test pattern. If none of the errors for each color calculated in ACT6 are outside the allowable range, the processor 811 determines NO in ACT7 and ends this adjustment process.

[0049] As described above, the multifunction peripheral 100 uses the target value determined based on the reference value VR and the first detection value for density control. Here, the reference value VR is the detection value of the toner sensor 71 for light reflected from the reference surface 201, which exhibits a reference reflectance corresponding to the reflectance of an area on the image bearing surface to which a predetermined reference amount of toner is attached. In other words, the reference value VR may vary depending on the sensitivity of the toner sensor 71. Thus, the target value determined based on the reference value VR is adjusted depending on the sensitivity of the toner sensor 71. Furthermore, the first detection value is the detection value of the toner sensor 71 for light reflected from an area on the image bearing surface where the toner adhesion amount is zero. In other words, the first detection value may vary depending on the light reflectance of the image bearing surface itself. Thus, the target value determined based on the first detection value is adjusted depending on the light reflectance of the image bearing surface itself. Then, by adjusting the density control conditions so that the second detection value, which is the detection value by the toner sensor 71 for the test pattern, approaches the target value determined as described above, the amount of toner adhesion to the image bearing surface can be appropriately adjusted, taking into account the influence of the sensitivity of the toner sensor 71 and the light reflectance of the image bearing surface itself.

[0050] In recent years, toner has become more highly color-developable, and the amount of toner adhesion required to achieve a certain density tends to decrease. As the amount of toner adhesion decreases, the detection value of the toner sensor 71 for the toner-adhered area on the image bearing surface also becomes more affected by the light reflectance of the image bearing surface itself. Therefore, when using toner with high color development, it is even more important to take into account the effect of the light reflectance of the image bearing surface itself, as described above.

[0051] In this embodiment, the reference value VR is obtained using a toner sensor 71 selected to be mounted in the multifunction device 100 during the manufacturing process of the multifunction device 100, with the reference surface 201 facing the toner sensor 71. This makes it possible to apply, to each of a plurality of multifunction devices 100, a reference value VR that accurately represents the difference in sensitivity of the toner sensors 71 used in each multifunction device 100.

[0052] This embodiment can be modified in various ways as follows. The target value determined by ACT3 in Figure 5 may be stored, for example, in the auxiliary memory unit 813, and in subsequent adjustment processing, ACT1 to ACT3 may be omitted, and processing from ACT4 onwards may be performed using the target value stored above.

[0053] The reference value VR stored in the auxiliary storage unit 813 may be a value different from the detection value of the toner sensor 71 regarding the light reflected from the reference surface 201, as long as the detection value can be determined.

[0054] The distance between toner sensor 71 and reference surface 201 when acquiring reference value VR may be a predetermined distance different from the specified distance between image carrier 20 and toner sensor 71. The detection value of toner sensor 71 in this state and a value corrected based on the difference between the distance between toner sensor 71 and reference surface 201 and the specified distance between image carrier 20 and toner sensor 71 may be used as reference value VR.

[0055] The number of image forming units may be any number other than four.

[0056] An image formed on a photosensitive member provided in the image forming unit may be transferred onto a printing sheet.

[0057] The amount of toner attached to the photosensitive member provided in the image forming unit may be detected by a toner sensor.

[0058] It may be realized as a device that omits any of the various functions realized by existing multifunction devices other than the print function, i.e., it may be realized not as a multifunction device but as a printer, copier, facsimile machine, or the like.

[0059] Some or all of the functions realized by the processor 811 through information processing can be realized by hardware that executes information processing not based on a program, such as a logic circuit, etc. Each of the above functions can also be realized by combining hardware such as the above logic circuit with software control.

[0060] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0061] [Appendix 1] The image forming apparatus includes a plurality of forming units so as to form a plurality of element images by attaching toner to the image bearing surface, and the element images are superimposed to form a single image, One of the sensors is provided at a position through which all of the element images formed by the plurality of forming units pass. 2. The image forming apparatus according to claim 1.

[0062] [Appendix 2] the adjusting unit adjusts the amount of toner adhered to the image bearing surface in association with the formation of element images of predetermined density values ​​by each of the plurality of forming units, so as to approach the target value determined by the determining unit; 2. The image forming apparatus according to claim 1.

[0063] [Appendix 3] a cleaner unit that attempts to remove toner from the image bearing surface; the determination unit determines the detection value of the sensor regarding the light reflected from an area of ​​the image bearing surface from which toner has been removed by the cleaner unit and to which no toner has been deposited by the forming unit as the detection value of the sensor regarding the light reflected from an area where the amount of toner deposition is zero. 2. The image forming apparatus according to claim 1.

[0064] [Appendix 4] the adjustment density value is the maximum density value in the range of density values ​​represented by the image data; 5. The image forming apparatus according to claim 4. [Explanation of symbols]

[0065] 100...multifunction device, 101...scanner, 102...printer, 103...communication unit, 104...system controller, 105...operation panel, 200...jig, 201...reference surface, 1...paper feed unit, 2...print engine, 20...image carrier, 21 to 23...support roller, 24-1 to 24-4...image forming unit, 25...exposure unit, 26...transfer roller, 27...belt cleaner, 3...fixing unit, 30...fixing roller, 31...pressure roller, 5...paper output tray, 6...motor group, 7...sensor group, 71... Toner sensor, 10-1 to 10-3...paper feed cassettes, 11-1 to 11-3...pickup rollers, 12-1 to 12-3...conveyor rollers, 13...conveyor roller, 14...registration roller, 81...printer controller, 811...processor, 812...main memory unit, 813...auxiliary memory unit, 814...communication unit, 815...transmission path, 82...forming controller, 83...exposure controller, 84...transfer controller, 85...fixing controller, 86...reversal controller, 87...motor controller.

Claims

1. a forming unit that forms an image by depositing toner on an image bearing surface of an image bearing member; a sensor disposed opposite to the image bearing surface and detecting an amount of reflected light from the image bearing surface; an adjustment unit that adjusts the amount of toner adhered to the image bearing surface in association with image formation by the forming unit, so as to bring the detection value of the sensor relating to reflected light from an area of ​​the image bearing surface on which an image of a predetermined density value has been formed by the forming unit closer to a target value; a storage unit that stores a reference value corresponding to a detection value of the sensor regarding light reflected from a reference surface that exhibits a reference reflectance corresponding to the reflectance of an area of ​​the image bearing surface to which a predetermined reference amount of toner is attached; a determination unit that determines the target value based on an image bearing surface detection value, which is a detection value of the sensor relating to reflected light from an area of ​​the image bearing surface where the amount of toner adhesion is zero, and a reference value stored in the storage unit; An image forming apparatus comprising:

2. and a reference value corresponding to a detection value obtained by the sensor in a state where the reference surface faces the sensor before the sensor is disposed opposite the image bearing surface during manufacturing of the image forming apparatus is stored in the storage unit. The image forming apparatus according to claim 1 .

3. The determination unit In a coordinate system in which the amount of toner adhesion to the image bearing surface and the detection value of the sensor are perpendicular to each other, a linear function is found that passes through a point relating to the detection value corresponding to the reference value stored in the storage unit and the reference adhesion amount, and a point relating to the image bearing surface detection value and an adhesion amount of zero; determining, as the target value, a detected value corresponding to a point included in the linear function with respect to a target adhesion amount different from zero adhesion amount and the reference adhesion amount; The image forming apparatus according to claim 1 .

4. the adjustment unit adjusts the amount of toner adhered to the image bearing surface in association with image formation by the formation unit so that the detection value of the sensor regarding reflected light from an area where an image having a predetermined adjustment density value is formed by the formation unit approaches a target value. The image forming apparatus according to claim 1 .

5. the reference reflectance is smaller than the reflectance on the image bearing surface in a toner adhesion state where the detection value of the sensor becomes a target value; The image forming apparatus according to claim 1 .

6. a forming unit that forms an image by depositing toner on an image bearing surface of an image bearing member; a sensor disposed opposite the image bearing surface and configured to detect reflected light from the image bearing surface; a storage unit that stores a reference value corresponding to a detection value of the sensor regarding light reflected from a reference surface that exhibits a reference reflectance corresponding to the reflectance of an area of ​​the image bearing surface to which a predetermined reference amount of toner is attached; An image forming apparatus comprising: determining a target value based on an image bearing surface detection value, which is a detection value of the sensor relating to reflected light from an area of ​​the image bearing surface where the amount of toner adhesion is zero, and a reference value stored in the storage unit; adjusting the amount of toner adhered to the image bearing surface in association with image formation by the forming unit so that the detection value of the sensor relating to reflected light from an area on the image bearing surface where an image of a predetermined density value is formed by the forming unit approaches the determined target value; Adjustment method.

Images