JP6036319B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, electrophotographic image forming apparatuses are known as printers, copiers, and the like. In this image forming apparatus, a series of processes of transferring an image onto a sheet with a transfer member and then fixing the image onto the sheet with a fixing member is performed on the conveyed sheet. When attention is paid to the paper in the conveyance process, the paper may be in a state of straddling both the transfer nip formed by the transfer member and the fixing nip formed by the fixing member. By the way, since the fluctuating component is included in the paper conveyance speed of the fixing member, it is assumed that the paper is pulled by the fixing member and causes a transfer deviation when the speed fluctuation occurs. As factors of the fluctuation component, various causes such as the state of the fixing nip, the temperature, the mechanical accuracy of the fixing member, and the operation unevenness of the driving means for driving the fixing member are considered. Therefore, the sheet is bent in a loop between the fixing nip and the transfer nip by appropriately controlling the sheet conveyance speed of the fixing member in order to suppress the tension of the sheet. That is, the fluctuation of the sheet conveying speed of the fixing member is absorbed by the bending generated in the sheet.

  For controlling the sheet conveyance speed, the following techniques are known. For example, Patent Document 1 discloses an image forming apparatus capable of transporting paper without causing image defects. This image formation is provided with a paper transport belt that can change the paper transport speed for transporting the paper onto which the toner image has been transferred to the fixing unit. The paper transport belt is a paper of the paper transport belt according to the rigidity of the paper. The conveyance speed is controlled to increase or decrease so as to satisfy a predetermined relationship.

  For example, in Patent Document 2, a speed detection film that is sandwiched between nip portions where a fixing film and a pressure roller are pressed against each other and moves together with a sheet, and a reading unit that reads a signal pattern formed on the speed detection film; There is disclosed an image forming apparatus having speed control means for controlling the driving speed of the fixing drive unit based on a reading signal from the reading means.

  For example, Patent Document 3 discloses an image forming apparatus that can detect the movement state of a sheet. The image forming apparatus includes a sheet conveying unit, a plurality of imaging units that continuously shoot different areas on the surface of a moving sheet, and outputs images, and a plurality of sheets in a plurality of areas based on the plurality of output images. A moving state detecting unit that detects a moving speed, a moving amount of the sheet, or a moving direction of the sheet, and a sheet conveying control unit that controls the sheet conveying unit based on the detection result.

JP 2008-40263 A JP 2002-258658 A JP 2012-96852 A

  By the way, the use demand for the image forming apparatus is increasing, and the use of highly rigid paper is increasing. When a bend is formed on a sheet having high rigidity, the sheet scraper acts as a force for pushing the sheet back to the transfer nip side. For this reason, there is a problem that transfer performance such as transfer deviation of the paper is deteriorated and image quality is lowered.

  The present invention has been made in view of such circumstances, and an object thereof is to ensure image quality without forming a loop by appropriately controlling the sheet conveyance speed of the fixing member.

In order to solve such a problem, the present invention includes a transfer member that conveys a sheet and transfers an image to the sheet, and is disposed downstream of the transfer member in the sheet conveyance direction. a fixing member for fixing an image on a sheet, and driving means for rotating the fixing member, and outputs a speed command to the drive means, and a control unit for controlling the sheet conveying speed of the fixing member, corresponding to the rotation period of the fixing member changes and sheet conveying speed of, is created on the basis of the sheet conveying speed of the transfer member, a storage unit for storing a profile of the speed command corresponding to the rotation period of the fixing member, a predetermined detection formed on the sheet Provided is an image forming apparatus having a sheet detection unit for detecting a pattern and a phase detection unit for detecting a phase of a fixing member . In this case, the control unit (1) outputs a speed command to the drive unit based on the profile of the speed command stored in the storage unit , (2) outputs a predetermined speed command to the drive unit, and A measurement process for measuring the transition of the paper conveyance speed corresponding to the rotation period is performed, and based on the result of the measurement process, the fluctuation component included in the paper conveyance speed is canceled and the paper conveyance speed of the fixing member is changed to the paper of the transfer member. A speed command profile is created so that the target speed specified from the transport speed is obtained, and (3) a plurality of detection patterns arranged along the paper transport direction are formed on the paper. Specifying the sheet conveyance speed based on the passage time of the obtained detection pattern and storing the sheet conveyance speed in association with the phase of the fixing member detected by the phase detection unit; This is done as a measurement process. Here, the plurality of detection patterns are formed in an area to be cut of the paper .

Here, in the present invention, it is preferable that the control unit performs the measurement process according to the sheet conveyance accompanying the execution of the print job .

  According to the present invention, the sheet conveyance speed of the fixing member can be appropriately controlled by the profile of the speed command. Thereby, the sheet conveyance speed of the fixing member and the sheet conveyance speed of the transfer member can be harmonized. As a result, a decrease in image transfer performance can be suppressed, and a decrease in image quality can be suppressed.

Configuration diagram schematically showing an image forming apparatus Configuration diagram schematically showing an enlarged main part of an image forming apparatus Block diagram showing configuration of control system of image forming apparatus Flow chart showing control procedure of image forming apparatus Explanatory drawing which shows the measurement concept of transition of the paper conveyance speed corresponding to 1 rotation period of a fixing roller. Explanatory drawing of speed command profile Explanation of parameters Explanatory drawing of detection pattern formed on paper Explanatory drawing which shows the measurement concept of transition of the paper conveyance speed corresponding to 1 rotation period of a fixing roller.

  FIG. 1 is a configuration diagram schematically illustrating an image forming apparatus according to the present embodiment. FIG. 2 is a configuration diagram schematically showing an enlarged main part of the image forming apparatus. This image forming apparatus is an electrophotographic image forming apparatus such as a copying machine, and forms a full-color image by arranging a plurality of photoconductors facing one intermediate transfer belt in a vertical direction. A tandem type color image forming apparatus.

  The image forming apparatus mainly includes a document reading device SC, image forming units 10Y, 10M, 10C, and 10K, a fixing device 50, and a control unit 70, which are housed in a single casing.

  The document reader SC scans and exposes an image of the document with the optical system of the scanning exposure device, reads the reflected light with a line image sensor, and obtains an image signal. This image signal is subjected to processing such as A / D conversion, shading correction, and compression, and then input to the control unit 70 as image data. Note that the image data input to the control unit 70 is not limited to the data read by the document reading device SC. For example, the image data received from a personal computer connected to the image forming device or another image forming device, or the USB It may be stored in a portable recording medium such as a memory.

  The image forming units 10Y, 10M, 10C, and 10K are an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image that forms a cyan (C) image. The image forming unit 10C corresponds to the image forming unit 10K that forms a black (K) image.

  The image forming unit 10Y includes a photosensitive drum 1Y and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y arranged around the photosensitive drum 1Y. Similarly, the image forming units 10M, 10C, and 10K include photoconductor drums 1M, 1C, and 1K and charging units 2M, 2C, and 2K, optical writing units 3M, 3C, and 3K, and developing devices 4M, 4C, 4K and drum cleaners 5M, 5C, 5K.

  The surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged by the charging units 2Y, 2M, 2C, and 2K, and by scanning exposure by the optical writing units 3Y, 3M, 3C, and 3K, Latent images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K. Further, the developing devices 4Y, 4M, 4C, and 4K develop the latent images on the photosensitive drums 1Y, 1M, 1C, and 1K by developing with toner. As a result, an image (toner image) of a predetermined color corresponding to any of yellow, magenta, cyan, and black is formed on the photosensitive drums 1Y, 1M, 1C, and 1K. Images formed on the photoconductive drums 1Y, 1M, 1C, and 1K are sequentially transferred to predetermined positions on the intermediate transfer belt 6 that is a belt-like intermediate transfer member by primary transfer rollers 7Y, 7M, 7C, and 7K. Transcribed.

  The image composed of each color transferred onto the intermediate transfer belt 6 is transferred by a secondary transfer roller 9 as a transfer member to a sheet P conveyed at a predetermined timing by a sheet conveying unit 20 described later. The secondary transfer roller 9 is a roller-like rotating member, and is arranged in pressure contact with the intermediate transfer belt 6 to form a nip (transfer nip). An image is transferred to the paper P while the paper P is being conveyed. Transcript.

  The paper transport unit 20 transports the paper P along the transport path. The paper P is stored in the paper feed tray 21, and the paper P stored in the paper feed tray 21 is taken in by the paper feed unit 22 and sent out to the transport path. In the transport path, a plurality of transport means for transporting the paper P is provided upstream of the transfer nip portion. Each of the conveying means is composed of a pair of rollers that are in pressure contact with each other, and at least one of the rollers is rotationally driven through an electric motor that is a driving means. The conveying means conveys the paper P by sandwiching and rotating the paper P. In addition to the configuration of the pair of rollers, the conveyance unit can widely employ a configuration including a pair of rotating members such as a combination of belts or a combination of a belt and a roller.

  The fixing device 50 is a device that performs a fixing process for fixing an image on the paper P conveyed from the transfer nip. The fixing device 50 is disposed in pressure contact with each other to form a pair of fixing members that form a nip (fixing nip), for example, fixing rollers 51 and 52, and a heater that heats one or both of the fixing rollers 51 and 52. It consists of Each of the fixing rollers 51 and 52 is configured to be rotatable, and at least one of the rollers (for example, the fixing roller 52) is rotationally driven through a fixing roller driving motor 53 (see FIG. 3) that is a driving unit. The pair of fixing rollers 51 and 52 convey the paper P and fix the image on the paper P through the action of the pressure applied by the pair of fixing rollers 51 and 52 and the heat of the fixing rollers 51 and 52.

  The paper P subjected to the fixing process by the fixing device 50 is discharged by a paper discharge roller 28 to a paper discharge tray 29 attached to the outer side surface of the housing. When image formation is also performed on the back surface of the paper P, the paper P on which image formation on the paper surface has been completed is conveyed by the switching gate 30 to the reverse roller 31 below. The reversing roller 31 pinches the rear end of the conveyed paper P, reverses the paper P by reverse feeding, and sends it out to the refeed conveyance path. The paper P sent out to the re-feed transport path is transported by a plurality of transport means for re-feeding, and the paper P is returned to the transfer position.

  The operation unit 60 outputs various information set by the user to the control unit 70. As the operation unit 60, for example, a touch panel capable of performing an input operation according to information displayed on the display can be used. Through the operation unit 60, the user can set the printing conditions, that is, the type (for example, thickness (basis weight) and size) of the paper P, the density and magnification of the image, and the like. The control unit 70 can display various messages to the user via the operation unit 60 by controlling the operation unit 60.

  FIG. 3 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the present embodiment. The control unit 70 has a function of controlling the image forming apparatus in an integrated manner, and a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used.

  The control unit 70 forms an image on the paper P by controlling the image forming unit 10 (elements that are necessary for image formation such as the image forming units 10Y, 10M, 10C, and 10K). In relation to this embodiment, the control unit 70 outputs a speed command to the fixing roller driving motor 53 that rotationally drives the fixing roller 52, and controls the sheet conveyance speed of the fixing roller 52. In this case, the control unit 70 outputs a speed command to the fixing roller drive motor 53 based on the speed command profile stored in the storage unit 75. This speed command profile is created based on the transition of the sheet conveyance speed corresponding to one rotation period of the fixing roller 52 and the sheet conveyance speed of the secondary transfer roller 9. As the storage unit 75, various storage devices such as a hard disk device and a semiconductor memory can be used, and the control unit 70 can be read or written.

  In order to perform such control, sensor signals from the first paper detection sensor 71, the second paper detection sensor 72, and the phase detection sensor 73 are input to the control unit 70.

  The first paper detection sensor 71 detects that the transported paper P (for example, the front end of the paper P) has reached the first detection position on the transport path (paper detection unit). The second paper detection sensor 72 detects that the paper P to be transported (for example, the front end of the paper P) has reached the second detection position on the transport path (paper detection unit). As the individual paper detection sensors 71 and 72, a photo sensor or the like can be used. The individual paper detection sensors 71 and 72 normally output an off signal, but when the leading edge of the paper reaches the detection position, the paper detection sensor 71 and 72 are switched to an on signal, and the paper P passes through the detection position for a period of time. And continue to output the ON signal. The first detection position related to the first paper detection sensor 71 is set downstream of the fixing device 50 in the paper conveyance direction, and the second detection position related to the second paper detection sensor 72 is the first detection position. The offset is set by a predetermined distance downstream of the detection position in the paper transport direction.

  The phase detection sensor 73 is a sensor that detects one rotation cycle of the fixing roller 52 that is rotationally driven. For example, the phase detection sensor 73 can detect one rotation period of the fixing roller 52 by reading a reference mark formed on the surface of the fixing roller 52, and can detect from the timing at which the reference mark is detected. Based on the elapsed time, the position in the rotation direction of the fixing roller 52 (hereinafter referred to as “phase”) can be detected.

  FIG. 4 is a flowchart showing a control procedure of the image forming apparatus according to the present embodiment. The process shown in this flowchart is called with the execution of the adjustment mode as a trigger, and is executed by the control unit 70. This adjustment mode is used for non-image formation, such as when the factory is shipped, when an adjustment mode execution signal is input from the operation unit 60 due to a user operation, or when a predetermined maintenance cycle determined by the control unit 70 is provided. Sometimes executed. Here, FIG. 5 is an explanatory diagram showing a measurement concept of the transition of the sheet conveyance speed corresponding to one rotation cycle of the fixing roller 52. In the figure, Rd represents a detection signal of the phase detection sensor 73, D1 represents a detection signal of the first paper detection sensor 71, and D2 represents a detection signal of the second paper detection sensor 72. In the lower part of the figure, the horizontal axis indicates the phase Rd, and the vertical axis indicates the velocity V (hereinafter the same in the corresponding drawings).

  First, in step 10 (S10), the control unit 70 starts conveying the paper P. In this case, the control unit 70 also outputs a predetermined speed command to the fixing roller drive motor 53. Since the adjustment mode is executed when non-image formation is performed, the control unit 70 forcibly conveys the paper P when executing the adjustment mode, and even if the paper P is conveyed, the paper P No image formation is performed.

  In step 11 (S11), the control unit 70 determines whether or not the leading edge of the paper P has passed through the first detection position based on the detection signal D1 of the first paper detection sensor 71. If an affirmative determination is made in step 11, that is, if the leading edge of the paper P has passed the first detection position, the process proceeds to step 12 (S12). On the other hand, if a negative determination is made in step 11, that is, if the leading edge of the paper P has not passed the first detection position, the processing in step 11 is performed again.

  In step 12, the control unit 70 determines whether the leading edge of the paper P has passed the second detection position based on the detection signal D <b> 2 of the second paper detection sensor 72. If an affirmative determination is made in step 12, that is, if the leading edge of the paper P has passed the second detection position, the process proceeds to step 13 (S13). On the other hand, if a negative determination is made in step 12, that is, if the leading edge of the paper P has not passed the second detection position, the process of step 12 is performed again.

  In step 13, the control unit 70 detects the phase Rd (Rd 1, Rd 2, Rd 3, Rd 4, Rd 5...) Of the fixing roller 52 based on the detection signal Rd of the phase detection sensor 73. The phase detection timing of the fixing roller 52 corresponds to the timing at which the leading edge of the paper P is detected by the second paper detection sensor 72.

  In step 14 (S14), the control unit 70 determines the first difference from the timing when the leading edge of the sheet P passes the first detection position and the timing when the leading edge of the sheet P passes the second detection position. The passage time Tf (Tf1, Tf2, Tf3, Tf4, Tf5...) Of the leading end of the sheet from the detection position to the second detection position is calculated. Then, the control unit 14 divides the distance from the first detection position to the second detection position by the passage time Tf, so that the sheet conveyance speed Vf (Vf1, Vf1, V1) of the fixing roller 52 at the phase detected in Step 13 is obtained. Vf2, Vf3, Vf4, Vf5...) Are calculated.

  In step 15 (S15), the control unit 70 associates the phase Rd of the fixing roller 52 detected in step 13 with the paper conveyance speed Vf of the fixing roller 52 calculated in step 14, and then stores this data. The data is stored in the storage unit 75.

  In step 16 (S16), the control unit 70 determines whether or not the number of data necessary for creating the speed command profile has been collected. The prescribed number of data is set in advance through experiments and simulations in consideration of whether the transition of the sheet conveyance speed Vf corresponding to one rotation cycle is sufficiently reproduced. If an affirmative determination is made in step 16, that is, if the necessary number of data is collected and the transition of the sheet conveyance speed Vf corresponding to one rotation period of the fixing roller 52 is measured, the process proceeds to step 17 (S 17). . On the other hand, if a negative determination is made in step 16, that is, if the necessary number of data is not collected, the process returns to step 10 and the above-described processing is repeated.

  In step 17, the control unit 70 creates a speed command profile. Here, FIG. 6 is an explanatory diagram of the transition of the sheet conveyance speed Vf and the profile of the speed command. In the drawing, Vft indicates the speed command of the fixing roller driving motor 53, Vt2 indicates the paper transport speed of the secondary transfer roller 9, and Vf indicates the paper transport speed of the fixing roller 52.

  First, the control unit 70 refers to each data stored in the storage unit 75, that is, the sheet conveyance speed Vf of the fixing roller 52 at a predetermined phase, and the sheet conveyance speed corresponding to one rotation cycle of the fixing roller 52. Create a transition of Vf. As shown in FIG. 6A, as can be seen from the transition of the paper conveyance speed Vf, the paper conveyance speed Vf includes the pressing state of the fixing nip, the temperature, the accuracy of the fixing member, and the operation unevenness of the fixing member driving mechanism. Because of this, a fluctuation component is included.

  Therefore, as shown in FIG. 5B, the control unit 70 creates a profile of the speed command Vfta based on the measurement result of the transition of the paper transport speed Vf. The profile of the speed command Vfta cancels the fluctuation component included in the paper transport speed Vf, and the target speed (for example, the paper transport speed Vf of the fixing roller 52 is specified from the paper transport speed Vt2 of the secondary transfer roller 9). The value is slightly lower than the sheet conveyance speed Vt2 of the secondary transfer roller 9. For example, the control unit 70 sets the profile of the speed command Vfta based on the reverse phase relationship obtained by inverting the profile of the paper transport speed Vf.

  In step 18 (S18), the control unit 70 stores the profile of the speed command in the storage unit 75. If the speed command profile already exists, the control unit 70 updates the previous profile with the newly created speed command profile, and if it does not already exist, the control unit 70 newly stores the speed command profile. .

  When the speed command profile is created according to the procedure described above, the control unit 70 outputs the speed command to the fixing roller drive motor 53 based on the speed command profile stored in the storage unit 75 when the job is executed. To do. Specifically, the control unit 70 refers to the detection signal Rd of the phase detection sensor 73 and outputs a speed command corresponding to the phase of the fixing roller 52 to the fixing roller driving motor 53.

  As described above, the image forming apparatus according to this embodiment includes the secondary transfer roller 9, the fixing roller 52, the fixing roller driving motor 53 that rotationally drives the fixing roller 52, and the speed command to the motor 53. 52, and a storage unit 75 for storing a speed command profile corresponding to one rotation cycle of the fixing roller. Here, the profile of the speed command is created based on the transition of the sheet conveyance speed corresponding to one rotation cycle of the fixing roller 52 and the sheet conveyance speed of the secondary transfer roller 9. A speed command is output to the fixing roller drive motor 53 based on the command profile.

  According to such a configuration, the profile of the speed command is created based on the transition of the sheet conveyance speed corresponding to one rotation cycle of the fixing roller 52 and the sheet conveyance speed of the secondary transfer roller 9. Therefore, by outputting a speed command based on the profile of the speed command, the paper conveyance speed of the fixing roller 52 can be appropriately controlled. The paper conveyance speed of the fixing roller 52 and the paper conveyance speed of the secondary transfer roller 9 can be controlled. Can be harmonized with. As a result, it is possible to realize a form of paper conveyance that does not require loop formation. As a result, even in the case of transporting thick paper, and not limited to such paper P, it is possible to suppress a decrease in image transfer performance, thereby suppressing a decrease in image quality. it can.

  In this embodiment, the control unit 70 outputs a predetermined speed command to the fixing roller driving motor 53 and measures the transition of the sheet conveyance speed corresponding to one rotation cycle of the fixing roller 52 (measurement process). Then, the control unit 70 cancels the fluctuation component included in the sheet conveyance speed based on the result of the measurement process, and the target in which the sheet conveyance speed of the fixing roller 52 is specified from the sheet conveyance speed of the secondary transfer roller 9. A speed command profile is created to achieve speed.

  According to such a configuration, the paper conveyance speed by the fixing roller 52 can be held at a constant speed by creating a speed command profile so as to cancel the fluctuation component included in the paper conveyance speed. Further, by creating a speed command profile so that the paper conveyance speed of the fixing roller 52 becomes a target speed specified from the paper conveyance speed of the secondary transfer roller 9, the paper conveyance speed of the fixing roller 52 is secondary-transferred. Since the speed according to the paper conveyance speed of the roller 9 can be controlled, the situation where the paper P is pulled between them can be appropriately suppressed.

  In the present embodiment, the control unit 70 performs a measurement process for creating a sheet conveyance speed profile by forcibly conveying the sheet P in an adjustment mode executed during non-image formation. However, the control unit 70 may perform the measurement process according to the sheet conveyance accompanying the execution of the print job. According to the former method, necessary data can be reliably collected without intermediate data collection, and a desired profile can be appropriately created. On the other hand, according to the latter method, since a desired profile can be obtained in the course of executing a print job, productivity is not lowered.

  The former method and the latter method may be combined. For example, the adjustment mode is preferentially executed, a desired profile is newly created and stored in the storage unit 75, and thereafter, the profile is created along with the execution of the print job. Is updated. According to this configuration, it is possible to start a print job in a state where an appropriate profile is held, and by updating the profile, the speed caused by subsequent factors such as deterioration over time and temperature change in the machine The fluctuation component can be reflected in the profile.

(Second Embodiment)
The image forming apparatus according to the second embodiment will be described below. The image forming apparatus according to the second embodiment is different from that of the first embodiment in that the time required for the measurement process is minimized. In addition, suppose that description about the point which overlaps with 1st Embodiment is abbreviate | omitted, and demonstrates below centering on difference.

In creating the profile, the paper conveyance speed is measured according to the timing when the paper P reaches the detection position of the sensor and the phase of the fixing roller 52 at that time. The phase of the fixing roller 52 on which the paper conveyance speed is measured needs to exist discretely within the range of one rotation, but depending on the conveyance mode of the paper P, the time required to collect necessary data is long. May range. Therefore, in the present embodiment, the control unit 70 conveys the paper P based on the relationship shown below.
[Formula 1]
Tid = TL + Td− (Tp + Ti0)

  FIG. 7 is an explanatory diagram of the parameters shown in Equation 1. In the equation, Tid is a correction value of the paper feed interval of the paper P, and Ti0 is a paper feed interval of the paper P that is initially set. Here, the paper feed interval of the paper P is a time indicating the interval between the preceding paper P and the succeeding paper P following the paper P. Further, as shown in FIG. 7, TL is one rotation period of the fixing roller 52 in the measurement process, and Td is a phase division period of the fixing roller 52, that is, a plot period necessary for creating a speed command profile. Yes, it is calculated by dividing one rotation period TL of the fixing roller 52 by the number of phase divisions. Tp is the paper feed time per sheet P.

  That is, in the measurement process, the controller 70 corrects the paper feed interval of the paper P by adding the correction value Tid to the initial value Ti0, and transports the paper P at the corrected paper feed interval. In other words, the control unit 70 determines the rotation period of the fixing roller 52, the sheet feeding time per sheet, the sheet feeding interval, and the phase division period of the fixing member necessary for creating the speed command profile. Based on the above, the paper feeding interval is corrected. According to such a configuration, the paper P can be transported so that data corresponding to a predetermined number of phase divisions can be collected in the shortest period. As a result, the processing period required to create the speed command profile can be shortened, so that downtime can be prevented from being prolonged.

(Third embodiment)
The image forming apparatus according to the third embodiment will be described below. The image forming apparatus according to the third embodiment is different from that of the first embodiment in that the time required for the measurement process is minimized. In addition, suppose that description about the point which overlaps with 1st Embodiment is abbreviate | omitted, and demonstrates below centering on difference.

  FIG. 8 is an explanatory diagram of the detection pattern Pa formed on the paper P. In the present embodiment, a predetermined pattern is formed on the paper P when the adjustment mode is executed. This pattern is composed of a plurality of detection patterns Pa arranged in a line along the paper transport direction. And the control part 70 conveys the paper P in which each detection pattern Pa was formed in a measurement process. The control unit 70 specifies the sheet conveyance speed for each detection pattern Pa according to the passage time of the detection pattern Pa obtained from the detection results of the first sheet detection sensor 71 and the second sheet detection sensor 72. As a result, as shown in FIG. 9, a plurality of pieces of data A1 and A2 corresponding to individual patterns Pa can be collected by conveying one sheet of paper P.

  As described above, according to the present embodiment, the processing period required for creating the speed command profile can be shortened, so that the downtime can be prevented from being prolonged. Moreover, the measurement process can be efficiently executed by setting the layout of the detection pattern Pa corresponding to the phase division period.

  Note that the embodiment of the measurement process using such a detection pattern Pa may be performed not only when the adjustment mode is executed, but also according to the sheet conveyance accompanying the execution of the print job. For example, when there is a region to be cut by post-processing after image formation, it is preferable to form the detection pattern Pa in the cut region. Thereby, the measurement process can be performed without affecting the final finished form.

  In each of the above-described embodiments, the first paper detection sensor 71 and the second paper detection sensor 72 are arranged on the downstream side of the fixing roller 52 and detect the leading edge of the paper P. However, since the first paper detection sensor 71 and the second paper detection sensor 72 are for detecting the paper conveyance speed of the fixing rollers 51 and 52, the paper P is sandwiched at least by the fixing rollers 51 and 52. It suffices if it is set within a range in which the sheet P in the existing state can be detected. For example, the first paper detection sensor 71 and the second paper detection sensor 72 may be disposed upstream of the fixing roller 52 in the paper transport direction and detect the trailing edge of the paper P. In addition, the first paper detection sensor 71 and the second paper detection sensor 72 are not limited to this, and need only be arranged offset in the paper transport direction within a range that satisfies the above-described conditions. Further, the detection position of the paper is not limited to the end portion, and a detection mark may be formed at an arbitrary position of the paper P, and the paper P may be detected by the presence of the detection mark.

  The image forming apparatus according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. .

SC Document reader 10Y to 10K Image forming unit 20 Paper transport unit 21 Paper feed tray 22 Paper feed unit 23 Loop roller 24 Registration roller 35 Loop sensor 36 Environmental sensor 50 Fixing device 51 Fixing roller 52 Fixing roller 60 Operation unit 70 Control unit 71 First paper detection sensor 72 Second paper detection sensor 73 Phase detection sensor 75 Storage unit

Claims (2)

A transfer member for conveying the paper and transferring the image onto the paper;
A fixing member that is disposed downstream of the transfer member in the sheet conveying direction, conveys the sheet, and fixes an image on the sheet;
Driving means for rotationally driving the fixing member;
A control unit that outputs a speed command to the driving unit and controls a paper conveyance speed of the fixing member;
Storing the changes of the sheet conveying speed corresponding to the rotation period of the fixing member, wherein is created based on the sheet conveying speed of the transfer member, the profile of the speed command corresponding to the rotation period of the fixing member A storage unit;
A paper detection unit for detecting a predetermined detection pattern formed on the paper;
A phase detector for detecting the phase of the fixing member ,
The control unit outputs a speed command to the driving unit based on the profile of the speed command stored in the storage unit ,
The control unit outputs a predetermined speed command to the driving unit, performs a measurement process of measuring a transition of a sheet conveyance speed corresponding to a rotation cycle of the fixing member, and based on a result of the measurement process, the sheet Create a profile of the speed command so that the fluctuation component included in the transport speed is canceled and the paper transport speed of the fixing member becomes a target speed specified from the paper transport speed of the transfer member,
The control unit forms a plurality of detection patterns arranged along the sheet conveyance direction on the sheet, specifies the sheet conveyance speed based on the passage time of the detection pattern obtained from the detection result of the sheet detection unit. Storing the sheet conveyance speed in association with the phase of the fixing member detected by the phase detection unit as the measurement process;
The image forming apparatus, wherein the plurality of detection patterns are formed in an area to be cut of a sheet . The image forming apparatus according to claim 1 , wherein the control unit performs the measurement process in accordance with sheet conveyance accompanying execution of a print job.

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