Image forming apparatus and method for controlling the same

Abstract

To adjust a proper formation condition based on a formation state of test patterns.SOLUTION: An image forming apparatus of an embodiment comprises a control unit, a first sensor, a determination unit, a detection unit, and a decision unit. The control unit controls a plurality of forming units to form test patterns comprising a plurality of patches by forming patches in a predetermined shape while preventing them from overlapping each other. The first sensor is arranged facing an image carrier surface and detects toner attached to the image carrier surface. The determination unit determines the formation state of the test patterns formed by the plurality of forming units on the basis of a result of detection performed by the first sensor. The detection unit detects fluttering of an image carrier surface at a position facing the first sensor. The decision unit decides a formation condition for element images in the plurality of forming units on the basis of the formation state determined by the determination unit without detection of fluttering by the detection unit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an image forming apparatus and a control 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. 2. Description of the Related Art Image forming apparatuses are already known that form a single image, such as a color image, by forming, for example, elemental images of different colors in layers using a plurality of forming units. In this type of image forming apparatus, it is important to overlap multiple element images with high accuracy in order to improve image quality. To achieve this, a process called alignment control is carried out in which a predetermined test pattern is formed to determine the deviation in the formation status of each of the multiple element images, and the formation conditions of each element image are adjusted so that the multiple element images overlap with high accuracy.

[0003] This alignment control requires accurate detection of the test pattern formation status. However, if the test pattern formation status is detected by detecting the toner adhesion status on the image bearing surface of the image carrier using a sensor positioned opposite the image bearing surface, flapping of the image bearing surface due to deformation of the belt-like image carrier will cause fluctuations in the distance between the image bearing surface and the sensor, which will also cause fluctuations in the status detected by the sensor. Therefore, adjusting the formation conditions based on the formation status detected under such conditions may not be appropriate. In view of these circumstances, there has been a demand for an image forming apparatus and a control method thereof that can adjust the formation conditions appropriately based on the formation status of the test pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-20970 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 and a control method thereof that can adjust the formation conditions appropriately based on the formation status of the test pattern. [Means for solving the problem]

[0006] An image forming apparatus according to an embodiment includes a plurality of forming units that individually form element images by depositing toner on the image bearing surface of a belt-shaped image carrier, and the plurality of forming units form an image by overlapping the element images on the image bearing surface. The image forming apparatus also includes a control unit, a first sensor, a determination unit, a detection unit, and a determination unit. The control unit controls the plurality of forming units to form a test pattern consisting of the plurality of patches by forming patches of a predetermined shape so that they do not overlap each other. The first sensor is disposed opposite the image bearing surface and detects toner deposited on the image bearing surface. The determination unit determines the formation status of the test patterns formed by the plurality of forming units based on the detection result by the first sensor. The detection unit detects fluttering of the image bearing surface at a position opposite the first sensor. The determination unit determines the formation conditions of the element images for each of the plurality of forming units based on the formation status determined by the determination unit without fluttering being detected by the detection 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. [Figure 3] FIG. 2 is a block diagram showing the main circuit configuration of a printer controller. [Figure 4] 10 is a flowchart of information processing for alignment control. [Figure 5]FIG. 10 is a diagram illustrating an example of a test pattern. 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. As shown in FIG. 1, the multifunction peripheral 100 includes a scanner 101 and a printer 102 .

[0009] 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.

[0014] 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). 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. The belt cleaner 27 removes toner that has not been completely transferred to the print paper and remains on the image bearing surface of the image bearing member 20. Thus, the print engine 2 forms an image on the print paper fed by the registration rollers 14 by electrophotography.

[0020] 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.

[0021] 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.

[0022] 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 .

[0023] 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, for example, an operation for realizing various functions realized by existing multifunction devices.

[0024] 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.

[0025] 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. 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 .

[0026] The sensor group 7 includes various sensors for monitoring the operating status of the device. The sensor group 7 includes toner sensors 71, 72, and 73. As shown in FIG. 1, the toner sensors 71, 72, and 73 are arranged facing the image bearing surface of the image carrier 20 between the image forming unit 24-1 and the transfer roller 26. The toner sensors 71, 72, and 73 are arranged side by side in the depth direction in FIG. 1. That is, the toner sensors 71, 72, and 73 are arranged in a direction perpendicular to the direction of movement of the image carrier 20. As a result, the toner sensors 71, 72, and 73 face the image bearing surface at a front position (hereinafter referred to as the “front position”), a central position (hereinafter referred to as the “center position”), and a rear position (hereinafter referred to as the “rear position”) in the depth direction in FIG. 1. Therefore, when it is necessary to distinguish between the toner sensors 71, 72, and 73, they will be referred to as the front sensor 71, the center sensor 72, and the rear sensor 73, respectively.

[0027] The toner sensors 71, 72, and 73 each detect toner adhering to the image bearing surface of the image carrier 20. For example, a reflective optical sensor can be used as the toner sensors 71, 72, and 73. In this case, the toner sensors 71, 72, and 73 output a voltage value as a digital value corresponding to the amount of reflected light of light irradiated onto the image bearing surface of the image carrier 20. In this way, the toner sensors 71, 72, and 73 detect toner adhering to the image bearing surface of the image carrier 20 based on the difference in light reflectance between the image bearing surface of the image carrier 20 and the toner.

[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 each component of the printer 102. In this embodiment, the auxiliary storage unit 813 stores test pattern data DAA as data used by the processor 811 when performing various processes. The test pattern data DAA is image data for causing the image forming units 24-1 to 24-4 to form test patterns, which 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 type of 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.

[0034] 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.

[0035] 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.

[0036] As such printing operations are repeated, the formation position and inclination of each element image may change, resulting in a situation where the element images cannot be properly superimposed. Therefore, when a predetermined alignment timing occurs, the processor 811 of the printer controller 81 starts processing for alignment control within information processing based on the control program PRA. The alignment timing may be appropriately determined, for example, by the person who determines the specifications of the multifunction peripheral 100 or an administrator. The alignment 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 the elapsed time reaches a predetermined time regardless of whether the printing operation is being performed. The alignment timing is also determined to be a timing when no printing operation is being performed.

[0037] FIG. 4 is a flowchart of information processing for alignment control. In ACT11, the processor 811 starts forming a test pattern. That is, the processor 811 controls the motor controller 87 to rotate the image carrier 20 at a predetermined speed, for example. The processor 811 also controls the formation controller 82 to bring all of the image forming units 24-1 to 24-4 into an operating state to form element images. The processor 811 then provides the test pattern data DAA to the exposure controller 83, for example.

[0038] FIG. 5 is a diagram showing an example of a test pattern. The horizontal direction in FIG. 5 is the main scanning direction, and the vertical direction is the sub-scanning direction. Points PF, RC, and PR in FIG. 5 represent detection points by the front sensor 71, center sensor 72, and rear sensor 73, respectively. That is, the front sensor 71 outputs a voltage value according to the amount of light reflected from detection point PF. The center sensor 72 outputs a voltage value according to the amount of light reflected from detection point PC. The rear sensor 73 outputs a voltage value according to the amount of light reflected from detection point PR. Thus, the front sensor 71 and rear sensor 73 correspond to a first sensor. The separation distance between detection points PF and PR is, for example, 4000 dots.

[0039] The test pattern includes eight patches. Two patches aligned in the main scanning direction form a pair, and these two patches are formed by the same image forming unit. For example, the two patches shown at the top in FIG. 5 are black patches formed by image forming unit 24-1. For example, the two patches shown second from the top in FIG. 5 are cyan patches formed by image forming unit 24-2. For example, the two patches shown third from the top in FIG. 5 are magenta patches formed by image forming unit 24-3. For example, the two patches shown at the bottom in FIG. 5 are yellow patches formed by image forming unit 24-4.

[0040] Each patch is wedge-shaped and includes a straight line along the main scanning direction (hereinafter referred to as a horizontal portion) and a straight line inclined at 45 degrees to the main scanning direction (hereinafter referred to as a diagonal portion). The width of the horizontal portion and the diagonal portion in the main scanning direction is, for example, 300 dots. The maximum distance between the horizontal portion and the diagonal portion in the sub-scanning direction is, for example, 300 dots. The width of the horizontal portion and the diagonal portion in the sub-scanning direction is WA dots. WA is an appropriate integer, and is expected to be, for example, approximately 60 to 100. Each patch is formed by filling in the hatched area in Figure 5 with the appropriate color.

[0041] The formation position of each patch on the left side in Fig. 5 is a position where the approximate center in the main scanning direction passes through the detection point PR. The formation position of each patch on the right side in Fig. 5 is a position where the approximate center in the main scanning direction passes through the detection point PF. In the above example, the minimum interval in the main scanning direction between a pair of patches is 3700 dots, and the interval between the detection point PF and the detection point PC and the interval between the detection point PR and the detection point PC are each approximately 2000 dots, so each patch does not pass through the detection point PC.

[0042] When the exposure controller 83 receives the test pattern data DAA, it drives the exposure unit 25 to form patches of each color by the image forming units 24-1 to 24-4 corresponding to that color. Thus, the processor 811 executes information processing based on the control program, and the computer with the processor 811 as its central part functions as a control unit.

[0043] When the image forming conditions of each of the image forming units 24-1 to 24-4 are ideal, the test pattern will be formed as set in Fig. 5. However, if there is a discrepancy in the image forming conditions of each of the image forming units 24-1 to 24-4, the test pattern will be formed in a state that differs for each patch, such as a change in the positional relationship between horizontal portions or a change in the inclination of the diagonal portions.

[0044] In ACT12, the processor 811 waits for the start of the detection period. The detection period is a period during which the front sensor 71 and the rear sensor 73 detect the test pattern. The detection period may be appropriately determined by, for example, a person who determines the specifications of the multifunction peripheral 100, as a period during which at least the test pattern can pass the detection points PF and PR. As described above, the position at which the test pattern is formed may deviate from the normal state shown in FIG. 5, and therefore the time required for the test pattern to actually pass the detection points PF and PR may also vary. Therefore, it is preferable to determine the start timing of the detection period as a time that is shorter than the time required for the leading edge of a properly formed test pattern in the sub-scanning direction to reach the detection points PF and PR from the time when test pattern formation is started. It is also preferable to determine the end timing of the detection period as a time that is longer than the time required for the trailing edge of a properly formed test pattern in the sub-scanning direction to reach the detection points PF and PR from the time when test pattern formation is started.

[0045] When the start timing of the detection period determined as above arrives, the processor 811 determines YES in ACT12 as the start of the detection period, and proceeds to ACT13. In ACT 13, the processor 811 starts recording situation data that indicates the formation status of the test pattern. That is, the processor 811 starts a process of, for example, acquiring voltage values ​​output by the front sensor 71 and the rear sensor 73 at a predetermined sampling period and sequentially updating situation data in which the acquired voltage values ​​are arranged in chronological order.

[0046] In ACT 14, the processor 811 checks whether the detection period has ended. If the processor 811 cannot confirm the event, it determines NO and proceeds to ACT 15. In ACT15, the processor 811 checks whether fluttering of the image carrier 20 near the detection points PF and PR has been detected. If the processor 811 cannot confirm this event, it determines NO and returns to ACT14. Thus, in ACT14 and ACT15, the processor 811 waits for the detection period to end or for flapping to be detected.

[0047] When the end timing of the detection period arrives, the processor 811 determines YES in ACT14 and proceeds to ACT16. In ACT 16, the processor 811 stores the status data updated up to this point in, for example, the auxiliary storage unit 813 as data representing the formation status of one test pattern.

[0048] In ACT17, the processor 811 checks whether collection of situation data has been completed. For example, the processor 811 checks whether situation data related to a predetermined required number of test patterns has been saved. The required number may be determined as appropriate by, for example, the person who determines the specifications of the multifunction peripheral 100. As an example, the required number is assumed to be "10." If the required number of situation data has not yet been collected by saving in the previous ACT16, the processor 811 determines NO in ACT17, returns to ACT11, and repeats the subsequent processes. Thus, processor 811 attempts to collect status data for each of a number of test patterns.

[0049] The image carrier 20 is supported under tension by support rollers 21, 22, and 23, maintaining the state shown in FIG. 1, and rotates during image formation. This can result in roller-shaped irregularities. Furthermore, deterioration over time due to continued use can cause the image carrier 20 to stretch, resulting in differences in its circumferential length at different positions in the main scanning direction. Such deformation of the image carrier 20 can cause changes in the test pattern formation.

[0050] When the deformed portion of the image carrier 20 passes near the detection points PF and PR, fluttering of the image carrier 20 occurs near the detection points PF and PR. When fluttering of the image carrier 20 occurs near the detection points PF and PR, fluttering of the image carrier 20 often also occurs at the detection point PC. When fluttering of the image carrier 20 occurs at the detection point PC, the distance between the center sensor 72 and the image bearing surface of the image carrier 20 fluctuates. However, in the multifunction peripheral 100 of this embodiment, because the support roller 22 is located behind the detection point PC, the effect of fluttering appears as a shortening of the distance between the center sensor 72 and the image bearing surface. During the detection period, no element image is formed in the area of ​​the image bearing surface that passes through the detection point PC, so the center sensor 72 outputs a voltage value corresponding to the amount of light reflected from the image bearing surface. However, when the distance between the center sensor 72 and the image bearing surface shortens, this voltage value increases. Thus, the center sensor 72 is an example of a second sensor.

[0051] Therefore, for example, if the voltage value output from the center sensor 72 is in a predetermined increasing state, the processor 811 determines YES in ACT 15 as flutter detection and proceeds to ACT 18. A threshold value is predefined as a value greater than the voltage value that should be output from the center sensor 72 when the distance between the center sensor 72 and the image bearing surface is normal. The specific value of this threshold value may be determined appropriately, for example, by the person who determines the specifications of the multifunction peripheral 100. The processor 811 then determines the increasing state, for example, if the voltage value output from the center sensor 72 is equal to or greater than the threshold value. Alternatively, the processor 811 may determine the increasing state, for example, if the voltage value output from the center sensor 72 is greater than the threshold value. Thus, by the processor 811 executing information processing based on the control program PRA, the computer, with the processor 811 as its central part, functions as a detection unit.

[0052] In ACT18, the processor 811 discards all the situation data that has been saved in ACT16 up to this point. In ACT19, the processor 811 checks whether an error has occurred in the collection of status data. For example, the processor 811 checks whether a predetermined error condition is met. The error condition is assumed to be defined as, for example, "the number of times that the process proceeded to ACT19 is three," but may be defined as appropriate by, for example, the person who decides the specifications for the multifunction peripheral 100 or an administrator. If the processor 811 cannot confirm that the error condition has been met, it cannot confirm that an error has occurred, so it determines NO and returns to ACT11.

[0053] In this way, the processor 811 repeats the process of continuously collecting the required amount of situation data without detecting fluttering. Then, when the processor 811 has finished collecting the required amount of situation data, it judges YES in ACT17 and proceeds to ACT20. When the processor 811 judges YES in ACT17, it means that it has collected the specified number of judgment results of the test pattern formation status through the processing up to that point. In this way, 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 collection unit.

[0054] If there is a discrepancy in the formation status of each patch, the processor 811, as the ACT20, performs an adjustment process to adjust the image formation conditions of each of the image forming units 24-1 to 24-4 to compensate for the discrepancy. This adjustment process is, for example, a process to compensate for discrepancies in the formation position or inclination between each color, and may be similar to the process already performed in existing multifunction peripherals. The processor 811 determines the occurrence of discrepancies in the formation position or inclination between each color based on the formation status of the test pattern represented by the status data. The processor 811 then determines the image formation conditions for each of the image forming units 24-1 to 24-4 after adjustment. Thus, by the processor 811 executing information processing based on the control program PRA, the computer, with the processor 811 as its core, functions as a determination unit and a decision unit. Then, when the adjustment process is completed, the processor 811 ends the current alignment control.

[0055] Now, for example, in a situation where the image carrier 20 is significantly deformed and flapping occurs frequently, the probability that the detection period can end without detecting flapping decreases, and therefore the possibility of having to discard the status data in ACT 18 and start collecting the status data again increases. If the processor 811 reaches a situation where an error condition is met without being able to confirm that collection has been completed in ACT 17, it determines YES in ACT 19 and proceeds to ACT 21.

[0056] As ACT21, the processor 811 performs a predetermined error process. The error process is, for example, a process for notifying the user that maintenance by a maintenance worker is necessary because alignment control could not be completed normally. The type of error process to be performed may be determined as appropriate by, for example, the person who decides the specifications or the administrator of the multifunction peripheral 100. Then, the processor 811 ends the information processing for this alignment control.

[0057] As described above, the multifunction peripheral 100 detects fluttering of the image carrier 20 during the period in which status data on the test pattern formation status is acquired, discards the status data acquired during the detection period in which fluttering is detected, and determines the test pattern formation status based on the status data continuously collected without fluttering being detected.Then, based on the test pattern formation status determined in this manner, the image formation conditions for each of the image forming units 24-1 to 24-4 after adjustment are determined.In this way, it is possible to adjust the formation conditions appropriately based on the test pattern formation status without referring to status data that does not appropriately represent the test pattern formation status due to the influence of fluttering of the image carrier 20.

[0058] Furthermore, if the MFP 100 is able to collect the required number of status data consecutively without detecting fluttering, it executes adjustment processing based on the required number of status data. This allows for more appropriate adjustment based on the test pattern formation status in a situation that is almost unaffected by fluttering of the image carrier 20.

[0059] This embodiment can be modified in various ways as follows. In ACT18, the processor 811 may discard only the situation data acquired during the current detection period and retain the situation data previously acquired for a single test pattern without detecting flapping. In other words, instead of continuously collecting the required number of situation data without detecting flapping, if no flapping is detected during the detection period for a single test pattern, the situation data acquired during that detection period may be considered valid and the required number of such valid situation data may be collected. This reduces the time required to collect the required number of situation data compared to the previous embodiment. In this case, the error condition used for the determination in ACT19 may be, for example, a condition that is met when attempting to acquire situation data based on a predetermined number of test patterns (a value greater than the required number) but is unable to complete collection of the required number of situation data. For example, it may be assumed that the error condition is when ACT11 and subsequent steps are executed a predetermined number of times (a value greater than the required number). Alternatively, it may be assumed that the error condition used for the determination in ACT19 is, for example, when the number of times proceeding to ACT19 reaches a predetermined limit. Since the test pattern formed on the image carrier 20 is not transferred to print paper, the toner used to form the test pattern is removed by the belt cleaner 27. In other words, all of the toner used to form the test pattern becomes waste toner. For this reason, reducing the number of times the test pattern is formed is beneficial for reducing waste toner.

[0060] Different types of devices may be used as the toner sensors 71, 72, and 73. For example, imaging devices may be used as the toner sensors 71, 72, and 73. Furthermore, a vibration sensor provided in contact with the image carrier 20 may be used instead of the center sensor 72. If a vibration sensor is used, the vibration sensor may be disposed opposite the patch formation area.

[0061] A plurality of sensors may be provided to detect fluttering at different positions of the image carrier 20, respectively.

[0062] The shape of the patch is not limited to the wedge shape shown in Fig. 5, and may be any other shape. For example, if an LED head is used for the exposure unit 25, the tilt of the element image is unlikely to change, so a patch with only a horizontal portion may be used.

[0063] 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.

[0064] 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.

[0065] [Appendix 1] the first sensor is disposed opposite to an area of ​​the image bearing surface where the test pattern is formed, and detects the toner adhering to the image bearing surface based on the difference between the amount of light reflected from the toner-adhered area on the image bearing surface and the amount of light reflected from the toner-free area on the image bearing surface. 2. The image forming apparatus according to claim 1.

[0066] [Appendix 2] a processing unit that stops collection by the collection unit and executes a predetermined error process when a predetermined error condition is met before collection by the collection unit is completed; The image forming apparatus according to claim 2, further comprising:

[0067] [Appendix 3] The processing unit determines that the error condition is established when the number of times that the determination unit does not determine the formation state without the detection unit detecting fluttering reaches a predetermined number of times. 3. The image forming apparatus according to claim 2.

[0068] [Appendix 4] the second sensor is disposed opposite to an area of ​​the image bearing surface where the test pattern is not formed, and detects an amount of reflected light from the non-adhered area of ​​the image bearing surface; The detection unit detects fluttering based on the amount of reflected light detected by the second sensor. 6. The image forming apparatus according to claim 5. [Explanation of symbols]

[0069] 1...paper feed unit, 2...print engine, 3...fixing unit, 5...paper output tray, 6...motor group, 7...sensor group, 10-1, 10-2, 10-3...paper feed cassette, 11-1, 11-2, 11-3...pickup roller, 12-1, 12-2, 12-3, 13...conveyor roller, 14...registration roller, 20...image carrier, 21, 22, 23...support roller, 24-1 to 24-4...image forming unit, 25...exposure unit, 26...transfer roller, 30...fixing roller, 31...pressure roller, 71...toner sensor (front sensor 71), 72...toner sensor (center sensor 72), 73...toner sensor (rear sensor 73), 81...printer controller, 82...forming controller, 83...exposure controller, 84...transfer controller, 85...fixing controller, 86...reversal controller, 87...motor controller, 100...multifunction device, 101...scanner, 102...printer, 103...communication unit, 104...system controller, 105...operation panel, 811...processor, 812...main memory unit, 813...auxiliary memory unit, 814...communication unit, 815...transmission path.

Claims

1. An image forming apparatus including a plurality of forming units that form element images individually by depositing toner on an image bearing surface of a belt-shaped image carrier, and that forms an image by forming the plurality of element images on the image bearing surface in a superimposed manner by the plurality of forming units, a control unit that controls a plurality of forming units to form patches of a predetermined shape so as not to overlap each other, thereby forming a test pattern consisting of a plurality of patches; a first sensor disposed opposite the image bearing surface and configured to detect toner adhering to the image bearing surface; a determination unit that determines the formation status of the test patterns formed by each of the plurality of formation units based on the detection result by the first sensor; a detection unit that detects flapping of the image bearing surface at a position facing the first sensor; a determination unit that determines element image formation conditions for each of the plurality of formation units based on the formation status determined by the determination unit without fluttering being detected by the detection unit; An image forming apparatus comprising:

2. the control unit controls the forming unit to sequentially form a plurality of test patterns; the determining unit determines a formation status for each of a plurality of test patterns; A collection unit is further provided which collects a predetermined number of formation states determined by the determination unit without flapping being detected by the detection unit, the determination unit determines element image formation conditions for each of the plurality of formation units based on the specified number of formation states collected by the collection unit. The image forming apparatus according to claim 1 .

3. The collection unit collects a predetermined number of formation states determined by the determination unit consecutively without fluttering being detected by the detection unit. The image forming apparatus according to claim 2 .

4. The collection unit does not collect formation situations in which fluttering is detected by the detection unit when the determination unit makes a judgment, but collects formation situations in which fluttering is not detected by the detection unit when the determination unit makes a judgment up to a specified number. The image forming apparatus according to claim 3 .

5. a second sensor disposed opposite the image bearing surface and configured to measure a distance to the image bearing surface; Furthermore, The detection unit detects fluttering based on the distance measured by the second sensor. The image forming apparatus according to claim 1 .

6. an image forming apparatus comprising: a plurality of forming units that form element images individually by adhering toner to an image carrying surface of a belt-shaped image carrier; and a first sensor that is disposed opposite the image carrying surface and detects the toner adhering to the image carrying surface, and that forms an image by forming a plurality of element images on the image carrying surface by overlapping them with the plurality of forming units; controlling the plurality of forming units to form a test pattern consisting of a plurality of patches by forming patches of a predetermined shape so as not to overlap each other; determining a formation status of the test patterns formed by the plurality of forming units based on a detection result by the first sensor; detecting fluttering of the image bearing surface at a position facing the first sensor; determining a formation condition for the element image in each of the plurality of forming units based on the formation state determined without detecting fluttering; Control method.

Images