Image forming apparatus, control method of image forming apparatus, and control program of image forming apparatus

Abstract

To provide an image forming apparatus that can prevent color shift even when a sudden load variation of a photoreceptor occurs.SOLUTION: An image forming apparatus of the present disclosure comprises: a motor; an image carrier that is rotated by a motor through a gear; a first detection unit that detects rotation information on the motor; a second detection unit that detects rotation information on the image carrier; and a control unit that controls the rotation of the motor based on results of detection performed by the first detection unit and the second detection unit. The control unit has a first mode of performing feedback control at a first ratio in which a gain ratio becomes larger in the detection result from the first detection unit than the detection result from the second detection unit, and a second mode of performing feedback control at a second ratio in which a gain ratio becomes larger in the detection result from the second detection unit than the detection result from the first detection unit.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus.

Background Art

[0002] As one aspect for evaluating the image quality in an image forming apparatus such as a printer or a copier, color misregistration due to positional variation of each color image is cited, and since it is important in full-color image formation such as a photograph, etc., highly accurate and stable driving control of a photosensitive drum (photoconductor) is required.

[0003] The misregistration of the image formation positions of the four-color toner images transferred from the intermediate transfer belt to the recording material appears as color misregistration or a change in hue. To prevent this "misregistration", for example, measures such as matching the rotational speeds of the photosensitive drums of each image forming unit and keeping the moving speed of the intermediate transfer belt constant are necessary, and various methods have been proposed (see Patent Documents 1-3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when uneven rotation of the photoconductor (image carrier) occurred according to sudden load fluctuations, color misregistration of the output image could not be sufficiently suppressed.

[0006] The present disclosure has been made in view of the above background, and an object thereof is to provide an image forming apparatus, a control method for the image forming apparatus, and a control program for the image forming apparatus that can suppress color misregistration even when a sudden load fluctuation of an image carrier occurs.

Means for Solving the Problems

[0007] The image forming apparatus of the present disclosure includes a motor, an image carrier rotated by the motor via a gear, a first detection unit that detects rotation information of the motor, a second detection unit that detects rotation information of the image carrier, and a control unit that controls the rotation of the motor based on detection results of the first detection unit and the second detection unit. The control unit has a first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the first detection unit is larger than the detection result of the second detection unit, and a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the second detection unit is larger than the detection result of the first detection unit.

[0008] Preferably, the control unit determines whether or not a phase difference between the rotation information of the motor and the rotation information of the image carrier exceeds a predetermined threshold based on the detection results of the first detection unit and the second detection unit, and when it is determined that the predetermined threshold is exceeded, switches from the first mode to the second mode.

[0009] Preferably, the control unit determines whether or not a phase difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold based on the detection results of the first detection unit and the second detection unit, and when it is determined that the phase difference is within the predetermined threshold, switches from the second mode to the first mode.

[0010] Preferably, the control unit determines whether or not a phase difference between the rotation information of the motor and the rotation information of the image carrier exceeds the predetermined threshold a predetermined number of times based on the detection results of the first detection unit and the second detection unit, and when it is determined that the phase difference exceeds the predetermined threshold a predetermined number of times, switches from the first mode to the second mode.

[0011] Preferably, the control unit determines whether a speed difference between the rotation information of the motor and the rotation information of the image carrier exceeds a predetermined threshold based on the detection results of the first detection unit and the second detection unit, and switches from the first mode to the second mode when it is determined that the predetermined threshold is exceeded.

[0012] Preferably, the control unit determines whether a speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold based on the detection results of the first detection unit and the second detection unit, and switches from the second mode to the first mode when it is determined that the speed difference is within the predetermined threshold.

[0013] Preferably, the control unit determines whether a speed difference between the rotation information of the motor and the rotation information of the image carrier exceeds the predetermined threshold a predetermined number of times based on the detection results of the first detection unit and the second detection unit, and switches from the first mode to the second mode when it is determined that the speed difference exceeds the predetermined threshold a predetermined number of times.

[0014] Preferably, in the second mode, the second ratio sets the gain value of the detection result of the first detection unit to 0 and sets the gain value of the detection result of the second detection unit to 1 or more.

[0015] The control method of the image forming apparatus according to the present disclosure is a control method of an image forming apparatus including a motor and an image carrier rotated by the motor via a gear, and includes a step of detecting rotation information of the motor, a step of detecting rotation information of the image carrier, and a step of controlling rotation of the motor based on detection results of a first detection unit and a second detection unit. The step of controlling the rotation of the motor includes a step of setting a first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the first detection unit is larger than the gain ratio of the detection result of the second detection unit, and a step of setting a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the second detection unit is larger than the gain ratio of the detection result of the first detection unit.

[0016] The control program of the image forming apparatus according to the present disclosure is a control program for an image forming apparatus including a motor and an image carrier rotated by the motor via a gear. The computer of the image forming apparatus executes the control program to perform steps of detecting rotation information of the motor, detecting rotation information of the image carrier, and controlling the rotation of the motor based on the detection results of the first detection unit and the second detection unit. The step of controlling the rotation of the motor includes steps of setting to a first mode of performing feedback control at a first ratio in which the gain ratio of the detection result of the first detection unit is larger than that of the detection result of the second detection unit, and setting to a second mode of performing feedback control at a second ratio in which the gain ratio of the detection result of the second detection unit is larger than that of the detection result of the first detection unit, and executes the processing.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0018] Hereinafter, each embodiment will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Note that each of the embodiments and each modification described below may be selectively combined as appropriate.

[0019] In the following embodiments, examples of the image forming apparatus include an MFP, a printer, a copier, or a facsimile machine.

[0020] FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to an embodiment. FIG. 2 is a diagram for explaining the main part of the control system of the image forming apparatus 1 according to an embodiment.

[0021] The image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. That is, the image forming apparatus 1 transfers (primary transfer) the Y (yellow), M (magenta), C (cyan), and K (black) color toner images formed on the photoreceptor 413 to the intermediate transfer belt 421, overlaps the four color toner images on the intermediate transfer belt 421, and then transfers (secondary transfer) them to the paper S to form an image.

[0022] In addition, the image forming apparatus 1 employs a tandem system in which photoreceptors 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and each color toner image is sequentially transferred to the intermediate transfer belt 421 in one procedure.

[0023] As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveyance unit 50, a fixing unit 60, a communication unit 70, and a control unit 100.

[0024] The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, etc. The CPU 101 reads out a program corresponding to the processing content from the ROM 102 and expands it in the RAM 103, and centrally controls the operations of the respective blocks of the image forming apparatus 1 in cooperation with the expanded program.

[0025] The ROM 102 and the RAM 103 are constituted by, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0026] The ROM 102 and the RAM 103 store a program executed by the CPU 101 and various data used for the execution of the program. At least one of the above program and data may be stored in a storage device other than the control unit 100 (such as an external server) as long as it is a storage device accessible by the CPU 101.

[0027] The processing in the control unit 100 is realized by each piece of hardware and the software executed by the control unit 100. Such software may be pre-stored in the ROM 102 and the RAM 103. Also, the software may be stored in a CD-ROM or other recording medium and distributed as a computer program. Alternatively, the software may be provided as an application program that can be downloaded by an information provider connected to the so-called Internet. Such software is read from the recording medium by an optical disk drive or other reading device, or downloaded via the communication unit 70, and then temporarily stored in the RAM 103. The software is read out from the RAM 103 by the CPU 101 and stored in the RAM 103 in a form of an executable program. The control unit 100 executes the program.

[0028] The control unit 100 performs transmission and reception of various data with an external device (such as a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 70. For example, the control unit 100 receives image data transmitted from an external device and causes an image to be formed on the paper S based on this image data (input image data). The communication unit 70 is composed of a communication control card such as a LAN card, for example.

[0029] The image reading unit 10 is configured to include an automatic document feeder 11 called an ADF (Auto Document Feeder) and a document image scanning device 12 (scanner), etc.

[0030] The automatic document feeder 11 conveys the document S placed on the document tray by a conveying mechanism and sends it to the document image scanning device 12. The automatic document feeder 11 can continuously read the images (including both sides) of a large number of documents D placed on the document tray all at once.

[0031] The original document image scanning device 12 optically scans a document conveyed onto the contact glass from the automatic document feeder 11 or a document placed on the contact glass, forms an image of the reflected light from the document on the light-receiving surface of a CCD (Charge Coupled Device) sensor 12a, and reads the document image. The image reading unit 10 generates input image data based on the reading result by the original document image scanning device 12. Predetermined image processing is performed on this input image data in the image processing unit 30.

[0032] The operation display unit 20 is composed of, for example, a liquid crystal display (LCD) with a touch panel and functions as a display unit 21 and an operation unit 22. The display unit 21 performs displays such as various operation screens, image status displays, and operation statuses of each function according to the display control signal input from the control unit 100. The operation unit 22 is provided with various operation keys such as numeric keys and a start key, accepts various input operations by the user, and outputs an operation signal to the control unit 100.

[0033] The image processing unit 30 includes a circuit or the like that performs digital image processing on the input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table) under the control of the control unit 100. In addition to gradation correction, the image processing unit 30 also performs various correction processes such as color correction and shading correction, and compression processing on the input image data. The image forming unit 40 is controlled based on the image data subjected to these processes.

[0034] The image forming unit 40 includes image forming units 41Y, 41M, 41C, 41K for forming images with respective colored toners of Y component, M component, C component, and K component, an intermediate transfer unit 42, etc. based on the input image data.

[0035] The image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have the same configuration. For the sake of convenience in illustration and description, common components are denoted by the same reference numerals, and when distinguishing each of them, Y, M, C, or K is appended to the reference numeral. In FIG. 1, only the components of the image forming unit 41Y for the Y component are labeled with reference numerals, and the components of the other image forming units 41M, 41C, and 41K are omitted.

[0036] The image forming unit 41 includes an exposure device 411, a developing device 412, a photoreceptor 413, a charging device 414, a drum cleaning device 415, and the like.

[0037] The photoreceptor 413 is a negatively chargeable organic photoreceptor (OPC) in which an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) are sequentially laminated on the peripheral surface of an aluminum conductive cylindrical body (aluminum base tube) having a drum diameter of 80 [mm], for example. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure with the exposure device 411. The charge transport layer is made of a material in which a hole transporting material (electron-donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports the positive charges generated in the charge generation layer to the surface of the charge transport layer.

[0038] By controlling the drive current supplied to a drive motor (not shown) that rotates the photoreceptor 413 by the control unit 100, the photoreceptor 413 rotates at a constant peripheral speed.

[0039] The charging device 414 uniformly charges the surface of the photoconductive photoreceptor 413 to a negative polarity. As an example, a charging roller or the like can be used.

[0040] The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive member 413 with laser light corresponding to the images of respective color components. Positive charges are generated in the charge generation layer of the photosensitive member 413 and are transported to the surface of the charge transport layer, whereby the surface charges (negative charges) of the photosensitive member 413 are neutralized. Electrostatic latent images of respective color components are formed on the surface of the photosensitive member 413 due to the potential difference from the surroundings.

[0041] The developing device 412 is, for example, a developing device using a two-component developing method, and visualizes the electrostatic latent image by attaching toner (oil-less toner containing wax in toner particles) of respective color components to the surface of the photosensitive member 413 to form a toner image.

[0042] The drum cleaning device 415 has a drum cleaning blade or the like that is in sliding contact with the surface of the photosensitive member 413, and removes transfer residual toner remaining on the surface of the photosensitive member 413 after primary transfer.

[0043] The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

[0044] The intermediate transfer belt 421 is formed of an endless belt and is looped around a plurality of support rollers 423. At least one of the plurality of support rollers 423 is a driving roller, and the others are driven rollers. For example, it is preferable that the driving roller 423A disposed on the downstream side in the belt running direction from the primary transfer roller 422 for the K component is the driving roller. This makes it easier to keep the running speed of the belt constant in the primary transfer section. When the driving roller 423A rotates, the intermediate transfer belt 421 runs at a constant speed in the direction of arrow A.

[0045] The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 facing the photoreceptor 413 of each color component. By pressing the primary transfer roller 422 against the photoreceptor 413 with the intermediate transfer belt 421 interposed therebetween, a primary transfer nip for transferring the toner image from the photoreceptor 413 to the intermediate transfer belt 421 is formed.

[0046] The secondary transfer rollers 424A and 424B are disposed on the outer peripheral surface side of the intermediate transfer belt 421 facing the drive rollers 423A and 423B disposed on the downstream side in the belt running direction. By pressing the secondary transfer rollers 424A and 424B against the drive rollers 423A and 424B with the intermediate transfer belt 421 interposed therebetween, a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S is formed.

[0047] When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoreceptor 413 are sequentially superimposed and primarily transferred onto the intermediate transfer belt 421. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and charges of the opposite polarity to the toner are applied to the back surface side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422), whereby the toner images are electrostatically transferred onto the intermediate transfer belt 421.

[0048] Thereafter, when the sheet S passes through the secondary transfer nip, the toner images on the intermediate transfer belt 421 are secondarily transferred onto the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer rollers 424A and 424B, and charges of the opposite polarity to the toner are applied to the back surface side of the sheet S (the side in contact with the secondary transfer roller 424), whereby the toner images are electrostatically transferred onto the sheet S. The sheet S onto which the toner images have been transferred is conveyed toward the fixing unit 60.

[0049] The belt cleaning unit 426 has a belt cleaning blade or the like that slidably contacts the surface of the intermediate transfer belt 421, and removes the residual transfer toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer.

[0050] The fixing unit 60 includes a fixing member 60A having a fixing surface side member disposed on the fixing surface (the surface on which the toner image is formed) side of the sheet S, a pressing member 60B having a back surface side support member disposed on the back surface (the surface opposite to the fixing surface) side of the sheet S, a heating source 60C, and the like. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for sandwiching and conveying the sheet S is formed.

[0051] The fixing unit 60 fixes the toner image on the sheet S by heating and pressing the sheet S, on which the toner image has been secondarily transferred and conveyed, with the fixing nip. The fixing unit 60 is disposed as a unit in the fixing device F. Further, an air separation unit for separating the sheet S from the fixing surface side member or the back surface side support member by blowing air may be disposed in the fixing device F. Details of the fixing unit 60 will be described later.

[0052] The sheet conveyance unit 50 is controlled according to an instruction from the control unit 100. The sheet conveyance unit 50 includes a paper feeding unit 51, a paper discharging unit 52, a refeeding unit 57, a conveyance path unit 53, and the like. In the three paper feeding tray units 51a to 51c constituting the paper feeding unit 51, sheets S (standard sheets, special sheets) identified based on basis weight, size, etc. are accommodated for each preset type. The conveyance path unit 53 has a plurality of conveyance roller pairs such as a registration roller pair 53a.

[0053] The sheets S accommodated in the paper feeding tray units 51a to 51c are sent out one by one from the top and conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the inclination of the fed sheet S is corrected and the conveyance timing is adjusted by the registration roller unit provided with the registration roller pair 53a. Then, in the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred to one surface of the sheet S all at once, and a fixing process is performed in the fixing unit 60. The sheet S on which the image is formed is discharged outside the machine by the paper discharging unit 52 including a paper discharging roller 52a.

[0054] When performing image formation on the back surface of the sheet S, the sheet S on which the image fixing on the front surface has been completed is conveyed by the sheet guide member 56 to the refeeding unit 57 below.

[0055] The refeeding unit 57 has a refeeding reversing roller 71. After sandwiching the trailing edge of the sheet S, the refeeding reversing roller 71 reversely feeds the sheet S to invert it and sends it out to the refeeding conveyance path 72. From the refeeding conveyance path 72, it is sent out to the conveyance path unit 53 again. Then, it is conveyed to the image forming unit 40 by the conveyance path unit 53. And in the image forming unit 40, a toner image is secondarily transferred onto the back surface of the sheet S, and a fixing process is performed in the fixing unit 60. The sheet S on which images are formed on both sides is discharged outside the machine by the discharging unit 52 including a discharging roller 52a.

[0056] FIG. 3 is a diagram for explaining the outline of the motor control system according to the embodiment. Referring to FIG. 3, the control unit 100 controls the rotation of a motor 300 that drives the photoreceptor 413. The motor 300 and the photoreceptor 413 are connected by a gear (not shown). An encoder 302 for detecting the rotation of the photoreceptor 413 is provided on the photoreceptor 413, and the encoder 302 outputs encoder pulses that are the rotation information of the photoreceptor 413. An FG pattern is provided on the motor 300, and an FG pulse signal corresponding to the rotation of the rotor of the motor 300 is generated based on the FG pattern.

[0057] The control unit 100 includes a first detection unit 310 that detects an FG pulse signal (rotation information of the motor 300) from the motor 300, a second detection unit 312 that detects an encoder pulse signal (rotation information of the photoreceptor 413) from the encoder 302, and a motor control unit 314 that controls the drive of the motor 300. The motor control unit 314 controls the rotation of the motor 300 based on the rotation information of the photoreceptor 413 and the rotation information of the motor 300.

[0058] The motor control unit 314 controls the motor 300 to achieve a constant rotation by feedback control based on general PID control.

[0059] FIG. 4 is a diagram for explaining the concept of control of the motor control unit 314 according to the embodiment. As shown in FIG. 4, the drive is transmitted from the motor 300 to the photoreceptor 413 via a gear. Due to gear accuracy, drum eccentricity, etc., the rotational fluctuations at the motor 300 and the fluctuations at the shaft portion of the photoreceptor 413 may be different.

[0060] As shown in FIG. 4, a case is shown where different speed unevenness occurs in the motor 300 and the encoder 302, respectively. In this case, for the component that varies in the motor 300 itself, it is possible to detect the speed unevenness of the motor 300 based on the FG pulse signal.

[0061] The deviation between the target rotational speed and the target detection result of the FG pulse signal is calculated, and feedback control for suppressing the speed unevenness of the motor 300 is executed.

[0062] The encoder 302 directly connected to the rotation shaft of the photoreceptor 413 detects the rotational speed unevenness of the rotation shaft of the photoreceptor 413 and executes feedback control.

[0063] Specifically, the deviation between the target rotational speed and the detection result of the encoder 302 is calculated, and feedback control is executed.

[0064] The motor control unit 314 outputs a PWM signal to the motor 300 as a result of the feedback control.

[0065] In the conventional method, when speed unevenness occurs due to sudden load fluctuations by the encoder 302, feedback control sufficient to sufficiently converge the speed unevenness of the encoder 302 is not applied, and color misregistration due to the speed unevenness has occurred.

[0066] As a factor causing sudden load fluctuations, fluctuations in the restraining force between the photoreceptor and the intermediate transfer belt can be cited. That is, the restraining force fluctuates greatly depending on the presence or absence of toner (image) on the contact surface between the photoreceptor and the intermediate transfer belt. The printed image is selected by the user and has irregular and various patterns, and sudden load fluctuations may always occur.

[0067] In the conventional method, since a fixed control coefficient was set, it was impossible to cope with sudden load fluctuations in the print job. That is, it was impossible to cope with load fluctuations due to changes in the toner image, and there was a possibility of impairing the rotation performance and causing color misregistration in the output image.

[0068] In the embodiment, a method of detecting sudden load fluctuations and switching to control corresponding to the load fluctuations will be described.

[0069] FIG. 5 is a block diagram for explaining the functional configuration within the motor control unit 314. Referring to FIG. 5, the motor control unit 314 includes a subtractor 320 that calculates the deviation between the target speed and the encoder speed, a feedback compensator 330 that outputs a first control amount based on the deviation, a subtractor 322 that calculates the deviation between the target speed and the motor FG speed, a feedback compensator 340 that outputs a second control amount based on the deviation, an adder 350 that adds the first and second control amounts, an output converter 360 that outputs a PWM signal based on the control amount added by the adder 350, and a gain switching determination unit 370.

[0070] The gain switching determination unit 370 adjusts the gain values used in the feedback compensators 330 and 340 based on the detection results of the first detection unit 310 and the second detection unit 312.

[0071] Specifically, the gain switching determination unit 370 adjusts the gain value in the first and second modes. In the first mode, the gain ratio is set such that the gain value (first and second gain values) prioritizes the motor FG speed over the encoder speed. In the second mode, the gain ratio is set such that the gain value (third and fourth gain values) prioritizes the encoder speed over the motor FG speed.

[0072] The gain switching determination unit 370 according to the embodiment sets to the first mode or the second mode based on the detection results of the first detection unit 310 and the second detection unit 312.

[0073] The gain switching determination unit 370 determines whether the phase difference between the rotation information of the motor 300 and the rotation information of the photoreceptor 413 exceeds a predetermined threshold based on the detection results of the first detection unit 310 and the second detection unit 312. If it is determined that the predetermined threshold is exceeded, it switches from the first mode to the second mode. In this example, it is assumed that the initial state is set to the first mode. The gain switching determination unit 370 determines whether the phase difference between the rotation information of the motor 300 and the rotation information of the photoreceptor 413 is within a predetermined threshold based on the detection results of the first detection unit 310 and the second detection unit 312. If it is determined that it is within the predetermined threshold, it switches from the second mode to the first mode. That is, it returns to the initial first mode.

[0074] FIG. 6 is a diagram for explaining the gain switching flow of the gain switching determination unit 370 according to the embodiment. Referring to FIG. 6, the gain switching determination unit 370 acquires the FG pulse signal (step S2). Next, the gain switching determination unit 370 acquires the encoder pulse signal U (step S4). Next, the gain switching determination unit 370 calculates the phase difference (step S6).

[0075] The gain switching determination unit 370 determines whether the phase difference is within a predetermined threshold (step S8). In step S8, when the gain switching determination unit 370 determines that the phase difference is within the predetermined threshold (YES in step S8), it sets to the first mode (step S16). Then, the gain switching determination unit 370 sets the first and second gain values G1 and G2 to the feedback compensators 330 and 340, respectively (step S18).

[0076] Then, the gain switching determination unit 370 determines whether the process has ended (step S14). When the gain switching determination unit 370 determines that the process has not ended (NO in step S14), it returns to step S2 and repeats the above process.

[0077] On the other hand, when the gain switching determination unit 370 determines that the process has ended (YES in step S14), it ends the process (END).

[0078] In step S8, when the gain switching determination unit 370 determines that the phase difference is not within the predetermined threshold (NO in step S8), it sets to the second mode (step S10). Then, the gain switching determination unit 370 sets the third and fourth gain values G3 and G4 to the feedback compensators 330 and 340, respectively (step S12).

[0079] Then, the gain switching determination unit 370 determines whether the process has ended (step S14). When the gain switching determination unit 370 determines that the process has not ended (NO in step S14), it returns to step S2 and repeats the above process.

[0080] FIG. 7 is a diagram for explaining a specific example when the gain switching determination unit 370 according to the embodiment determines that the phase difference is greater than or equal to the threshold value.

[0081] FIG. 8 is a diagram showing the actual measurement values of the motor according to the embodiment. As shown in FIG. 7, when the gain switching determination unit 370 determines that the phase difference is within the threshold value, it sets the first gain value G1:1 and the second gain value G2:3 as the first mode.

[0082] When the gain switching determination unit 370 determines that the phase difference is equal to or greater than the threshold value, it sets the first gain value G1:1 and the second gain value G2:0 as the second mode.

[0083] Then, again, when the gain switching determination unit 370 determines that the phase difference is within the threshold value, it sets the first gain value G1:1 and the second gain value G2:3 as the first mode.

[0084] FIG. 8 shows the measured values when the threshold value is set to 0.5 as the phase difference. The case where the setting is changed from the first mode to the second mode and the first gain value G1:1 and the second gain value G2:0 are set when the phase difference becomes 0.5 or more is shown. Also, the case where the setting is changed from the second mode to the first mode when the phase becomes less than 0.5 is shown.

[0085] Even when a sudden load fluctuation occurs due to the above processing and speed unevenness occurs, it is possible to suppress color misregistration at an early stage.

[0086] (Modification example) In the above embodiment, the case where the gain switching determination unit 370 sets the first mode or the second mode based on whether the phase difference is within the threshold value as the detection results of the first detection unit 310 and the second detection unit 312 has been described.

[0087] In a modification example of the embodiment, the gain switching determination unit 370 sets the first mode or the second mode based on whether the speed difference is within the threshold value as the detection results of the first detection unit 310 and the second detection unit 312.

[0088] The gain switching determination unit 370 determines whether the speed difference between the rotation information of the motor 300 and the rotation information of the photoreceptor 413 exceeds a predetermined threshold based on the detection results of the first detection unit 310 and the second detection unit 312. If it is determined that the predetermined threshold is exceeded, the mode is switched from the first mode to the second mode. In this example, it is assumed that the initial state is set to the first mode. The gain switching determination unit 370 determines whether the speed difference between the rotation information of the motor 300 and the rotation information of the photoreceptor 413 is within a predetermined threshold based on the detection results of the first detection unit 310 and the second detection unit 312. If it is determined that the speed difference is within the predetermined threshold, the mode is switched from the second mode to the first mode. That is, it returns to the initial first mode.

[0089] FIG. 9 is a diagram for explaining the gain switching flow of the gain switching determination unit 370 according to a modification of the embodiment. The flowchart of FIG. 9 is different from the flowchart of FIG. 6 in that step S6 is replaced with step S7. The gain switching determination unit 370 acquires the FG pulse signal (step S2). Next, the gain switching determination unit 370 acquires the encoder pulse signal U (step S4). Next, the gain switching determination unit 370 calculates the speed difference (step S6).

[0090] The gain switching determination unit 370 determines whether the speed difference is within a predetermined threshold (step S8). In step S8, when the gain switching determination unit 370 determines that the speed difference is within the predetermined threshold (YES in step S8), it sets the first mode (step S16). Then, the gain switching determination unit 370 sets the first and second gain values G1 and G2 to the feedback compensators 330 and 340, respectively (step S18).

[0091] Then, the gain switching determination unit 370 determines whether the process has ended (step S14). If the gain switching determination unit 370 determines that the process has not ended (NO in step S14), it returns to step S2 and repeats the above process.

[0092] On the other hand, when the gain switching determination unit 370 determines that the process has ended (YES in step S14), it ends the process (END).

[0093] In step S8, when the gain switching determination unit 370 determines that the speed difference is not within the predetermined threshold (NO in step S8), it sets it to the second mode (step S10). Then, the gain switching determination unit 370 sets the third and fourth gain values G3 and G4 to the feedback compensators 330 and 340, respectively (step S12).

[0094] Then, the gain switching determination unit 370 determines whether the process has ended (step S14). When the gain switching determination unit 370 determines that the process has not ended (NO in step S14), it returns to step S2 and repeats the above process.

[0095] FIG. 10 is a diagram for explaining a specific example when the gain switching determination unit 370 according to a modification of the embodiment determines that the speed difference is equal to or greater than the threshold.

[0096] FIG. 11 is a diagram showing the measured values of the motor according to a modification of the embodiment. As shown in FIG. 10, when the gain switching determination unit 370 determines that the speed difference is within the threshold, it sets the first gain value G1: 1 and the second gain value G2: 3 as the first mode.

[0097] When the gain switching determination unit 370 determines that the speed difference is equal to or greater than the threshold, it sets the first gain value G1: 1 and the second gain value G2: 0 as the second mode.

[0098] Then, again, when the gain switching determination unit 370 determines that the speed difference is within the threshold, it sets the first gain value G1: 1 and the second gain value G2: 3 as the first mode.

[0099] In FIG. 11, the measured values when the threshold is set to 0.5 as the speed difference are shown. When the speed difference becomes 0.5 or more, it is set from the first mode to the second mode, and the case where the first gain value G1 is set to 1 and the second gain value G2 is set to 0 is shown. Also shown is the case where it is set from the second mode to the first mode when the speed difference becomes less than 0.5.

[0100] Even when a sudden load fluctuation occurs due to the process and speed unevenness occurs, it is possible to suppress color misregistration at an early stage.

[0101] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0102] 1 Image forming apparatus, 10 Image reading unit, 11 Automatic document feeder, 12 Document image scanning device, 20 Operation display unit, 21 Display unit, 22 Operation unit, 30 Image processing unit, 40 Image forming unit, 50 Paper conveyance unit, 60 Fixing unit, 70 Communication unit, 100 Control unit, 101 CPU, 102 ROM, 103 RAM, 300 Motor, 302 Encoder, 310 First detection unit, 312 Second detection unit, 314 Motor control unit, 320, 322 Subtractor, 330, 340 Feedback compensator, 350 Adder, 360 Output converter, 370 Gain switching determination unit.

Claims

1. A motor, An image carrier rotated by the motor via a gear, A first detection unit that detects rotation information of the motor, A second detection unit that detects rotation information of the image carrier, And a control unit that controls the rotation of the motor based on detection results of the first detection unit and the second detection unit, The control unit, A first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the first detection unit is larger than that of the detection result of the second detection unit, And a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the second detection unit is larger than that of the detection result of the first detection unit, The control unit, Determines whether a phase difference or a speed difference between the rotation information of the motor and the rotation information of the image carrier based on detection results of the first detection unit and the second detection unit exceeds a predetermined threshold value, When it is determined that the predetermined threshold value is exceeded, switches from the first mode to the second mode, an image forming apparatus.

2. A motor, An image carrier rotated by the motor via a gear, A first detection unit that detects rotation information of the motor, A second detection unit that detects rotation information of the image carrier, And a control unit that controls the rotation of the motor based on detection results of the first detection unit and the second detection unit, The control unit, A first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the first detection unit is larger than that of the detection result of the second detection unit, And a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the second detection unit is larger than that of the detection result of the first detection unit, The control unit, Based on the detection results of the first detection unit and the second detection unit, determine whether the phase difference or speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold. When it is determined that the difference is within the predetermined threshold, switch from the second mode to the first mode, an image forming apparatus.

3. A control method for an image forming apparatus including a motor and an image carrier rotated by the motor via a gear, a step of detecting rotation information of the motor; a step of detecting rotation information of the image carrier; and a step of controlling the rotation of the motor based on the detection results of the rotation information of the motor and the image carrier, The step of controlling the rotation of the motor includes: setting to a first mode in which feedback control is performed at a first ratio at which the gain ratio of the detection result of the rotation information of the motor is larger than the detection result of the rotation information of the image carrier; setting to a second mode in which feedback control is performed at a second ratio at which the gain ratio of the detection result of the rotation information of the image carrier is larger than the detection result of the rotation information of the motor; a step of determining whether a phase difference or speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold; and when it is determined that the difference exceeds the predetermined threshold, switching from the first mode to the second mode, a control method for an image forming apparatus.

4. A control method for an image forming apparatus including a motor and an image carrier rotated by the motor via a gear, a step of detecting rotation information of the motor; a step of detecting rotation information of the image carrier; and a step of controlling the rotation of the motor based on the detection results of the rotation information of the motor and the image carrier, The step of controlling the rotation of the motor includes: A step of setting to a first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the rotation information of the motor is larger than the detection result of the rotation information of the image carrier; A step of setting to a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the rotation information of the image carrier is larger than the detection result of the rotation information of the motor; A step of determining whether a phase difference or a speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold; When it is determined that the difference is within the predetermined threshold, a step of switching from the second mode to the first mode, a control method of an image forming apparatus.

5. A control program for an image forming apparatus including a motor and an image carrier rotated by the motor via a gear, The computer of the image forming apparatus, by executing the control program, A step of detecting the rotation information of the motor; A step of detecting the rotation information of the image carrier; Based on the detection results of the rotation information of the motor and the image carrier, a step of controlling the rotation of the motor, The step of controlling the rotation of the motor is A step of setting to a first mode in which feedback control is performed at a first ratio in which the gain ratio of the detection result of the rotation information of the motor is larger than the detection result of the rotation information of the image carrier; A step of setting to a second mode in which feedback control is performed at a second ratio in which the gain ratio of the detection result of the rotation information of the image carrier is larger than the detection result of the rotation information of the motor; A step of determining whether a phase difference or a speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold; When it is determined that the difference exceeds the predetermined threshold, a step of switching from the first mode to the second mode, a control program of an image forming apparatus that executes processing. A control program for an image forming apparatus including a motor and an image carrier rotated by the motor via a gear, wherein a computer of the image forming apparatus executes the control program to detect rotation information of the motor, detect rotation information of the image carrier, and control rotation of the motor based on detection results of the rotation information of the motor and the image carrier, wherein the step of controlling rotation of the motor includes setting to a first mode in which feedback control is performed at a first ratio where a gain ratio of the detection result of the rotation information of the motor is larger than that of the detection result of the rotation information of the image carrier, setting to a second mode in which feedback control is performed at a second ratio where a gain ratio of the detection result of the rotation information of the image carrier is larger than that of the detection result of the rotation information of the motor, determining whether a phase difference or a speed difference between the rotation information of the motor and the rotation information of the image carrier is within a predetermined threshold, and when it is determined that the difference is within the predetermined threshold, switching from the second mode to the first mode, the control program for the image forming apparatus that executes the process.

Images