JP2005314020A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of detecting paper feed delay caused by the wear of a conveying roller or the like, the increase in load or the like of a paper feed drive motor or the like, and stabilizing the time before a paper sheet reaches a resist roller. <P>SOLUTION: The image forming device comprises a paper feed means 18, a first paper sheet detection sensor 36 provided on the downstream side of the paper feed means 18, a loop forming roller to form a loop on a paper sheet 2, a resist roller, a second paper sheet detection sensor 42 provided in a vicinity of the resist roller, and an image forming unit, and further comprises a control means 35 to control whether or not the paper sheet is temporarily stopped based on the determination whether or not the paper sheet 2 reaches the first paper sheet detection sensor 36 in a predetermined time after starting the paper feed. The control means 35 counts the reaching time before the paper sheet 2 reaches the second paper sheet detection sensor 42 from the start of paper feed when the paper sheet is temporarily stopped, and the time for the temporary stop is corrected based on the reaching time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that detects a conveyance delay due to wear or the like of a conveyance roller, corrects a temporary stop time, and ensures stable conveyance.

  In a general image forming apparatus, a sheet fed from a sheet feeding tray by a sheet feeding unit is conveyed to a registration roller by a plurality of conveying rollers provided in a conveying path. On the other hand, in the image forming section on the downstream side of the registration roller, the charging device uniformly charges the surface of the photosensitive member, the image writing device forms an electrostatic latent image on the photosensitive member, and the developing device forms a toner image. To do. The registration roller is driven to rotate in order to convey the sheet to the image forming unit in synchronization with the toner image formed on the photosensitive member. A toner image is transferred to the surface of the paper transported to the image forming unit by a transfer device, and the paper on which the toner image has been transferred is transported to a fixing device to fix the toner image.

  Among such image forming apparatuses, there are models in which the number of image forming sheets per unit time is increased. Increasing the number of images formed per unit time is realized by increasing the sheet conveyance speed and by narrowing the interval between the sheets conveyed and discharged.

  The paper feed means consists of a feed roller, paper feed roller, and paper roller. The feed roller feeds the top sheet from the paper stacked in the paper feed tray to the paper feed roller, which feeds the paper feed roller. Transport paper to the path. At this time, the second and subsequent sheets may be sent out together with the first sheet, and a double feed is not generated in which the second and subsequent sheets are sent out to the conveyance path together with the first sheet by the roller. Card the paper. As described above, in the paper feeding unit that feeds the paper by the feed roller, the position of the paper during feeding varies. Variation in this position leads to variation in sheet feeding timing, which is the time from the start of sheet feeding to the conveyance path. Also, the feeding roller may idle on the surface of the paper during paper feeding, which also causes variations in paper feeding timing. Such variations in the sheet feeding timing are variations in the sheet interval and variations in the time until the sheet reaches the registration roller.

  If the sheet interval becomes too narrow due to variations in the sheet feeding timing, the succeeding sheet as well as the preceding sheet will be conveyed to the image forming unit. If the paper interval is too wide, the toner image formed on the photoreceptor cannot be synchronized and it is determined that the paper is jammed.

In order to solve such problems due to variations in paper feed timing, an intermediate sensor is provided in the transport path, and the intermediate sensor classifies whether the paper transport state at the check timing is early or late. Some perform control of temporarily stopping or not (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2001-213537 (paragraph 0024, FIG. 3)

  In Patent Document 1, the temporary stop time and check timing of the transport roller are fixed to predetermined values. However, in the image forming apparatus, when the total number of image forming sheets increases, the time required for paper feeding is delayed due to a decrease in the conveyance speed due to wear of each conveyance roller, a change in the starting characteristics of the drive motor, and the like. In spite of the state in which the transport speed is reduced in this way, if the check timing and the pause time are fixed to predetermined values, the frequency of occurrence of paper jams increases.

  SUMMARY OF THE INVENTION Accordingly, the present invention is an image forming apparatus capable of detecting a paper feed delay due to wear of a transport roller or the like and a load increase of a paper feed drive motor or the like, and to stabilize the time until the paper reaches the registration roller. The purpose is to provide.

  In order to achieve the above object, an image forming apparatus according to claim 1, a sheet feeding unit that feeds a sheet, a first sheet detection sensor provided on a downstream side of the sheet feeding unit, and a sheet fed A loop forming roller that forms a loop on the sheet, a registration roller that re-feeds the fed paper after it has been abutted and stopped, and a second paper detection sensor provided in the vicinity of the registration roller; And an image forming unit that forms an image on the paper, and the paper is based on a determination as to whether or not the first paper detection sensor has been reached after a predetermined time from the start of paper feeding by the paper feeding means. Control means for controlling whether or not to temporarily stop the paper, and the control means measures an arrival time from the start of paper feeding when the paper is temporarily stopped until the paper reaches the second paper detection sensor. And said It is characterized by correcting the time of the pause on the basis of time.

  The image forming apparatus according to claim 2, wherein a sheet feeding unit that feeds a sheet, a first sheet detection sensor provided on a downstream side of the sheet feeding unit, and a loop forming roller that forms a loop on the fed sheet. And a registration roller that re-feeds the fed paper to the image forming unit after stopping and a second paper detection sensor provided in the vicinity of the registration roller, and forms an image on the paper Whether or not to temporarily stop the sheet based on the determination as to whether or not the first sheet detection sensor has been reached after a predetermined time from the start of sheet feeding by the sheet feeding unit, in an image forming apparatus having an image forming unit The control means controls the time required for the paper to reach the second paper detection sensor from the start of paper feed when the paper is temporarily stopped, and the second paper detection sensor. Paper The measured sheet time from after detecting until detecting the next sheet, the arrival time and the time the pause on the basis of the inter-paper time and is characterized by correcting the predetermined time.

  The image forming apparatus according to claim 3, wherein a paper feeding unit that feeds paper, a first paper detection sensor provided downstream of the paper feeding unit, and a loop forming roller that forms a loop on the fed paper. And a registration roller that re-feeds the fed paper to the image forming unit after stopping and a second paper detection sensor provided in the vicinity of the registration roller, and forms an image on the paper Whether or not to temporarily stop the sheet based on the determination as to whether or not the first sheet detection sensor has been reached after a predetermined time from the start of sheet feeding by the sheet feeding unit, in an image forming apparatus having an image forming unit Control means for performing the control of the above, the control means, the arrival time from the start of paper feed when the paper is temporarily stopped and when the paper is not temporarily stopped until the paper reaches the second paper detection sensor, and 2 The paper detection sensor measures the inter-paper time from the detection of the passage of the previous paper to the detection of the next paper. Based on the arrival time and the inter-paper time, the pause time and the predetermined time are calculated. It is characterized by correction.

  The image forming apparatus according to claim 4, wherein the control unit measures the arrival time for a predetermined number of image forming sheets, and corrects the pause time based on an average value of the measured arrival times.

  6. The image forming apparatus according to claim 5, wherein the control unit measures the arrival time and the inter-paper time for a predetermined number of image forming sheets, and the average value of the measured arrival time and the average value of the measured inter-paper time. Based on the above, the pause time and the predetermined time are corrected.

  The image forming apparatus according to claim 6, wherein the control unit measures the arrival time when the total number of formed images reaches a predetermined value.

  The image forming apparatus according to claim 7, wherein the control unit measures the arrival time and the inter-paper time when the total number of formed images reaches a predetermined value.

  The image forming apparatus includes a paper feeding unit, a first paper detection sensor, a loop forming roller, a registration roller, a second paper detection sensor, an image forming unit, and a control unit. The first paper detection sensor is provided on the downstream side of the paper feeding means, and the second paper detection sensor is disposed in the vicinity of the registration roller. The control unit controls whether or not to temporarily stop the sheet depending on whether or not the second sheet detection sensor detects the sheet after a predetermined time from the start of sheet feeding by the sheet feeding unit. The control means measures the time from the start of paper feeding until the second paper detection sensor detects the paper when the paper is paused, and corrects the pause time based on the measured time. As a result, the time until the sheet reaches the registration roller is constant, and stable conveyance can be ensured.

  According to a second aspect of the present invention, the image forming apparatus includes a paper feeding unit, a first paper detection sensor, a loop forming roller, a registration roller, a second paper detection sensor, an image forming unit, and a control unit. The first paper detection sensor is provided on the downstream side of the paper feeding means, and the second paper detection sensor is disposed in the vicinity of the registration roller. The control unit controls whether or not to temporarily stop the sheet depending on whether or not the second sheet detection sensor detects the sheet after a predetermined time from the start of sheet feeding by the sheet feeding unit. Further, the control means measures the time from the start of paper feeding until the second paper detection sensor detects the paper and the paper interval when the paper is paused, and based on the result, the pause time, Correct the predetermined time. Thereby, the time until the paper reaches the registration roller and the paper interval are kept constant.

  According to a third aspect of the present invention, the image forming apparatus includes a paper feeding unit, a first paper detection sensor, a loop forming roller, a registration roller, a second paper detection sensor, an image forming unit, and a control unit. The first paper detection sensor is provided on the downstream side of the paper feeding means, and the second paper detection sensor is disposed in the vicinity of the registration roller. The control unit controls whether or not to temporarily stop the sheet depending on whether or not the second sheet detection sensor detects the sheet after a predetermined time from the start of sheet feeding by the sheet feeding unit. Further, the control means measures the time from the start of paper feeding until the second paper detection sensor detects the paper and the paper interval for each of when the paper is paused and when the paper is not paused, Based on the result, the pause time and the predetermined time are corrected. Thereby, the time until the paper reaches the registration roller and the paper interval are kept constant.

  According to a fourth aspect of the present invention, the control unit measures the time from the start of paper feeding until the second paper detection sensor detects the paper for a predetermined number of image forming sheets, and temporarily determines the average value based on the average value. Correct the stop time. Thereby, more accurate correction becomes possible.

  6. The image forming apparatus according to claim 5, wherein the control unit measures the time from the start of paper feeding until the second paper detection sensor detects the paper and the paper interval for a predetermined number of image forming sheets, and averages the time. The pause time and the predetermined time are corrected by the value. As a result, the time from when the paper starts to reach the registration roller is constant, and paper jams can be prevented.

  The image forming apparatus according to claim 6 performs the correction process of the pause time when the total number of image forming sheets reaches a predetermined value. As a result, the number of corrections can be reduced, and the load on the control means can be reduced.

  The image forming apparatus according to claim 7 performs the correction processing for the pause time and the predetermined time when the total number of formed images reaches a predetermined value. As a result, the number of corrections can be reduced, and the load on the control means can be reduced.

  Next, the image forming apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus of the present invention. The image forming apparatus 1 has an image forming apparatus main body 3 that forms an image on a sheet 2, and an image reading apparatus 4 that reads an image to be formed on the sheet 2 from an original is provided on the upper part of the image forming apparatus main body 3. Yes. In addition, an automatic document feeder 5 that automatically conveys a document to the image reading device 4 is provided at the top.

  The automatic document feeder 5 has a document placement table 6 on which a document is placed. A document feed roller 7 that feeds the documents one by one is provided at one end of the document placement table 6. A document support roller 8 that rotates while supporting a document is provided below the document table 6. A document discharge table that discharges a document that has been read by the image reading device 4 is disposed below the document table 6. 9 is provided. In the automatic document feeder 5, the document sent from the document table 6 is conveyed to the upper part of the peripheral surface of the document support roller 8, and is conveyed along the peripheral surface of the document feed roller 7. A document conveying roller 10 for discharging to the discharge table 9 is provided.

  The image reading apparatus 4 further includes a first mirror unit 13 in which a light source 11 that irradiates light on a document and a mirror 12 that reflects light reflected from the document are integrally formed, and light from the first mirror unit 13. The first and second mirror units 13 and 14 are movable in the left-right direction in FIG. Further, the image reading device 4 includes an image sensor 15 that photoelectrically converts light, such as a CCD, and images the light from the second mirror unit 14 on the image sensor 15 on the front surface of the image sensor 15. A lens 16 is provided.

  A slit for irradiating light to the document conveyed along the document support roller 8 is provided below the document support roller 8. The image reading device 4 positions the first mirror unit 13 below the slit. The image is read. The automatic document feeder 5 is openable and closable with respect to the image reading device 4, and the upper surface of the image reading device 4 is formed of a platen glass on which a document is placed. The image reading device 4 can also scan the original placed on the platen glass by scanning the first and second mirror units 13 and 14 to read the image.

  Below the inside of the image forming apparatus main body 3, a plurality of paper feed trays 17 that stack and store a plurality of paper sheets 2 are provided in three upper and lower stages. A sheet feeding means 18 for feeding sheets 2 to be formed from the sheet feeding tray 17 one by one is provided.

  An image forming unit 19 for forming an image is disposed above the paper feed tray 17. The image forming unit 19 includes a cylindrical photosensitive drum 20, and the photosensitive drum 20 is driven to rotate clockwise in FIG. 1 by a drum driving mechanism (not shown).

  A charging device 21 is provided in the vicinity of the upper peripheral surface of the photosensitive drum 20. The charging device 21 performs corona discharge on the surface of the photosensitive drum 20 to uniformly charge the surface of the photosensitive drum 20.

  An exposure device 22 using a laser diode or the like as an exposure light source is disposed around the photosensitive drum 20 and downstream of the charging device 21 in the rotation direction of the photosensitive drum 20. The exposure device 22 performs image exposure on the surface of the photosensitive drum 20 based on the image signal, thereby attenuating and extinguishing the electric charge on the surface of the photosensitive drum 20 in the exposed portion, thereby generating an electrostatic latent image. It is supposed to form.

  A developing device 23 is provided downstream of the exposure device 22 in the rotation direction of the photosensitive drum 20. The developing device 23 develops the electrostatic latent image formed on the surface of the photosensitive drum 20 with toner charged to the same polarity as that of the photosensitive drum 20 by a reversal developing method.

  A transfer separation device 24 is disposed downstream of the developing device 23 in the rotation direction of the photosensitive drum 20. A conveyance path for conveying the sheet 2 is formed between the transfer separation device 24 and the photosensitive drum 20. The transfer separation device 24 transfers the toner image to the paper 2 by discharging corona discharge from the back surface of the paper 2 in a state where the paper 2 is pressed against the photosensitive drum 20, and discharges the charged paper 2. As a result, the sheet 2 is separated from the photosensitive drum 20.

  A fixing device 25 is provided on the downstream side of the conveyance path of the transfer separation device 24. The sheet 2 is conveyed to the fixing device 25 so that the toner on the surface is melted by heat and fixed on the sheet 2.

  A cleaning device 26 that removes and cleans toner remaining on the surface of the photosensitive drum 20 is provided around the photosensitive drum 20 and downstream of the transfer separation device 24 in the rotation direction of the photosensitive drum 20.

  A discharge tray 27 for discharging the sheet 2 on which an image is formed is provided on the side of the image forming apparatus 1. Further, an input operation unit (not shown) for inputting an instruction from the user is provided on the upper surface of the image forming apparatus main body 3.

  FIG. 2 is a diagram schematically showing the conveyance path of the image forming apparatus of the present invention. The sheet feeding means 18 includes a feeding roller 28, a sheet feeding roller 29, a separating roller 30, a first feeding clutch 31 and a sheet feeding solenoid 32. The feed roller 28 takes out the top sheet from the paper 2 stacked on the paper feed tray 17 and feeds it to the paper feed roller 29. The feed roller 28 can swing in the vertical direction in the figure, and swinging is controlled by the paper feed solenoid 32. The paper feed roller 29 feeds the paper 2 sent out by the feed roller 28 to the transport path 33. The whirling roller 30 contacts the lower surface of the paper 2 and is driven when the torque exceeds a predetermined torque, and rotates in the conveyance direction of the paper 2. When the delivery roller 28 picks up a plurality of sheets 2, it is in a stopped state because it does not reach a predetermined torque or more in the rolling roller 30, and is stopped so that the second and subsequent sheets 2 are not conveyed. Only the uppermost sheet 2 is sent in the transport direction.

  The first paper feed clutch 31 is provided in each paper feed roller 29 of the plurality of paper feed means 18, and switches transmission of power from the paper feed motor 34 that is a drive source to the paper feed roller 29. Switching of the first paper feed clutch 31 is performed by the control means 35.

  A first paper detection sensor 36 is provided on the downstream side in the transport direction from the paper supply unit 18. For example, this is configured by a photosensor in which a light emitting element and a light receiving element are arranged on the same surface, and the paper 2 is detected by the intensity of reflected light.

  In the conveyance path 33, a conveyance roller 37, a loop forming roller 38, and a registration roller 39 are provided. The conveying roller 37 conveys the sheet 2 fed by the sheet feeding unit 18 to the registration roller 39, and the loop forming roller 38 continues to convey the sheet 2 that has hit the registration roller 39, and the loop forming roller 38 A deflection called a loop is formed with the registration roller 39. The transport roller 37 and the loop forming roller 38 are provided with a second paper feed clutch 40, and the transmission of power from the paper feed motor 34 is switched by the second paper feed clutch 40.

  The registration roller 39 is disposed in the vicinity of the photosensitive drum 20, and corrects the bending of the sheet 2 conveyed through the conveyance path 33 and conveys it to the image forming unit 19. The registration roller 39 starts rotating when a predetermined time has elapsed after the paper feeding unit 18 starts feeding paper, and conveys the paper 2 to the image forming unit 19. The registration roller 39 is provided with a third paper feed clutch 41, and the transmission of the driving force from the paper feed motor 34 is switched. A second paper detection sensor 42 is disposed in the vicinity of the registration roller 39 and upstream of the conveyance path 33. This is constituted by a photo sensor or the like similar to the first paper detection sensor 36.

  The control means 35 includes a CPU and a storage device such as a ROM / RAM (not shown), and controls the drive of the paper feed solenoid 32, the first to third paper feed clutches 31, 40, 41, and the paper feed motor 34. Is. The control means 35 receives signals from the first and second paper detection means 36 and 42 as to whether or not the paper 2 has been detected.

  FIG. 3 is a timing chart showing the drive timing of each unit during paper conveyance. When the user gives an instruction to start image formation by pressing a start button arranged on the input operation unit, the control means 35 starts driving the paper feed motor 34, and then the paper feed solenoid 32 and the first and first feeds. 2 The paper feed clutches 31 and 40 are driven. The paper feed motor 34 continues to be driven while a series of image forming processes called jobs are being performed.

  The control means 35 measures the predetermined time t1 simultaneously with the driving of the paper feed solenoid 32. After the elapse of t1, the control unit 35 acquires the detection result of the first paper detection sensor 36. In the timing chart shown in FIG. 3, when the first sheet detection sensor 36 does not detect the sheet 2 at the elapse of t1 as in the case where the first sheet 2 is being conveyed, the sheet is left as it is. Continue to carry 2

  The control means 35 turns off the first and second paper feed clutches 31 and 40 after a predetermined time from the detection of the paper 2 by the second paper detection sensor 42. Between the time when the second paper detection sensor 42 detects the paper 2 and before the first and second paper feed clutches 31 and 40 are turned off, the paper 2 reaches the registration roller 39 to form a loop. . Thereafter, the third sheet feeding clutch 41 and the first and second sheet feeding clutches 31 and 40 are turned on, and the sheet 2 is conveyed to the image forming unit 19. Thus, the conveyance of the first sheet 2 to the image forming unit 19 is completed.

  While the third paper feed clutch 41 is on and the paper 2 is being conveyed to the image forming unit 19, the paper feed solenoid 32 is driven to feed the next paper 2. The control means 35 measures t1 simultaneously with the driving of the paper feed solenoid 32. If the first paper detection sensor 36 detects the paper 2 when t1 has elapsed, the first and second paper feed clutches 31 and 40 are turned off for a temporary stop time t2 after the time t1 has elapsed to temporarily transport the paper 2. Stop. After the elapse of t2, the first and second paper feeding clutches 31 and 40 are turned off after a predetermined time since the second paper detection sensor 42 detects the paper 2 in the same manner as the conveyance of the first paper 2. Simultaneously with the third paper feed clutch 41 being turned on, the first and second paper feed clutches 31 and 40 are also turned on, and the paper 2 is conveyed to the image forming unit 19. In this way, since it is determined whether or not the paper 2 to be transported is temporarily stopped, variation in the arrival time of the paper 2 to the registration roller 39 is reduced.

  Further, the control unit 35 activates a paper feed JAM detection timer at the start of driving of the paper feed solenoid 32 separately from the measurement of t1. The paper feed JAM detection timer is set in advance, and the second paper detection sensor 42 does not detect the paper 2 from the start of paper feed until the time specified by the paper feed JAM detection timer elapses. Further, the control unit 35 determines that a paper jam has occurred and interrupts the image forming process.

  Also, T3 in FIG. 3 is the time from when the sheet feeding solenoid 32 is started to feed one sheet 2 until the second sheet detection sensor 42 detects the sheet 2, that is, the sheet 2 T4 indicates the time from when the second paper detection sensor 42 detects the trailing edge of the preceding paper 2 until the leading edge of the next paper 2 is detected, that is, the time between papers. Yes.

  FIG. 4 is a diagram of paper conveyance. The vertical axis of the diagram represents the position on the transport path 33 from the paper feed tray 17, and the horizontal axis represents the elapsed time. Further, “a” in the figure represents the transport state of the leading edge of the sheet 2 immediately after the image forming apparatus 1 is installed, and “b” represents the transport state of the trailing edge of the sheet 2. Among these, the first sheet is an example in which the first sheet detection sensor 36 does not detect the sheet 2 immediately after the predetermined time t1 has elapsed, and the sheet 2 is conveyed to the registration roller 39 without being temporarily stopped. The second sheet is an example in which the first sheet detection sensor 36 detects the sheet 2 when t1 has elapsed, and the conveyance of the sheet 2 is temporarily stopped after t1.

  By the way, the rollers used for transporting the paper 2, that is, the feed roller 28, the paper feed roller 29, the transport roller 37, and the loop forming roller 38 are worn by repeating the transport of the paper 2. As wear progresses, the roller diameter decreases and the conveying speed decreases. FIG. 4c shows the transport state of the leading edge of the paper 2 when the roller is worn. When the conveyance speed becomes slow, the value of T3, which is the arrival time, becomes larger than the initial value. Also, T4, which is the time between sheets, varies depending on the wear of the rollers. When the wear progresses and the arrival time T3 becomes larger than the value of the paper feed JAM detection timer, the occurrence frequency of the paper jam increases.

  In order to prevent such a paper jam due to a decrease in the conveyance speed, the control unit 35 measures T3 and T4 when the sheet 2 is conveyed, and corrects the predetermined time t1 and the pause time t2 based on the measurement result.

  FIG. 5 is a flowchart showing a first embodiment of the correction procedure for t1 and t2. This flowchart is executed when the user designates the number of images to be formed from the input operation unit and presses the start button. When executed, it is first determined whether or not the total number of images formed so far has reached a predetermined value (S01). The delay in the conveyance of the paper 2 due to the wear of each roller does not become significant unless the number of image formations reaches a certain level. The predetermined number varies depending on the model of the image forming apparatus 1, but for example, t1 and t2 are corrected every 20,000 sheets.

  When the number of formed images is a predetermined number (S01Y), a flag indicating whether sampling is necessary is turned on (S02). The arrival time T3 and the inter-paper time T4 are more accurate if the t1 and t2 are not corrected by only one measurement value, but are measured for a predetermined number of times and the average value is used for correction. This is because correction is possible. If the number of formed images is not a predetermined number in S01, the process of S02 is skipped. Here, the initial value of the flag is OFF.

  Next, when the flag indicating the necessity of sampling is OFF (S03N), sampling is not performed, and the sheet 2 is conveyed according to the timing chart of FIG. 3 (S04). If the flag is on (S03Y), it is determined whether sampling has been performed for a predetermined number of sheets (S05). The number of samples varies depending on the model of the image forming apparatus 1, but is set to 100, for example.

  If the sampling number is less than the predetermined number (S05Y), the paper feed motor 34 and the paper feed solenoid 32 are driven to turn on the first and second paper feed clutches 31 and 40 (S06). Measurement of arrival time T3 is started (S07). Thereafter, the sheet 2 is conveyed according to the timing chart shown in FIG. 3 (S08). When the second paper detection sensor 42 detects the paper 2 (S09Y), it is determined whether or not the paper 2 is temporarily stopped during the conveyance (S10). If the paper is temporarily stopped (S10Y), T4 and T3 are determined. Are obtained (S12, S13). Since T4 is the time between sheets, it cannot be measured for the first sheet 2 of the job. Therefore, it is determined whether or not the sheet 2 currently being conveyed is the first sheet (S11), and if it is not the first sheet, the value of T4 is acquired. After obtaining T3 and T4, the sampling number is incremented by 1 (S14). When the temporary stop is not performed (S10N), the processing from S11 to S14 is skipped.

  At this point, since the sheet 2 hits the registration roller 39 and forms a loop, the control unit 35 turns on the third sheet feeding clutch 41 at a predetermined timing and conveys the sheet 2 to the image forming unit 19 (S15). ). When the second paper detection sensor 42 detects the trailing edge of the paper 2 (S16Y), the measurement of the paper interval time T4 is started (S17), and the total copy number counter is incremented by 1 (S18). Thereafter, if there is an image to be formed (S19Y), the process returns to S01. If there is no image to be formed (S19N), measurement of T4 is stopped (S20) and the image forming process is ended.

  Returning to S05, if the number of samples reaches the predetermined number (S05N), the average value of the acquired T3 and T4 is obtained, and t1 and t2 are corrected based on the average value (S21). Then, the flag indicating the necessity of sampling is turned off (S22), and the number of samples is initialized to 0 (S23). Next, image formation is performed according to the timing chart shown in FIG. 3 (S24).

  FIG. 6 is a flowchart showing a second embodiment of the correction procedure for t1 and t2. The same steps as those in FIG. 5 are denoted by the same reference numerals, and differences will be described. In the second example of FIG. 6, the values of T3 and T4 are acquired even when the paper 2 is not temporarily stopped by determining whether or not the paper 2 is temporarily stopped during the conveyance in S10 (S10N). (S25 to S28). This is the same processing as S11 to S14 when paused (S10Y), but the acquired T3 and T4 are stored in another storage area when not temporarily paused. In the correction processing of t1 and t2 by S21, averages of T3 and T4 when paused and T3 and T4 when not paused are obtained, and correction is performed using the obtained average.

  FIG. 7 is a flowchart showing a third embodiment of the correction procedure for t1 and t2. In the third embodiment, the measurement results of T3 and T4 are stored in a storage device such as a RAM for the previous sampling number (for example, 100 sheets), and when the predetermined number (for example, 20,000) is reached, Correction of t1 and t2 is performed.

  When image formation is started, it is determined whether or not the total number of formed images has reached a predetermined number (S30), and if it has reached, the average of arrival time T3 and inter-paper time T4 stored in the storage device is obtained. Based on the value, the predetermined time t1 and the temporary stop time t2 are corrected (S31). Thereafter, measurement of T3 is started simultaneously with the start of feeding (S32) (S33), and the sheet 2 is fed according to the timing chart of FIG. 3 (S34). When the second paper detection sensor 42 detects the leading edge of the paper 2 (S35Y), it is determined whether or not the paper 2 is paused (S36). If the paper is paused, the measurement results of T4 and T3 are stored in the storage device. Store (S38, S39). At this time, if the stored value exceeds the sampling number, the oldest T3 and T4 are discarded. The inter-paper time T4 cannot be measured when the currently conveyed paper 2 is the first sheet, and is not measured when the first sheet is present (S37N).

  After performing the measurement, the control unit 35 conveys the sheet 2 to the image forming unit 19 (S40). When the second paper detection sensor 42 detects the trailing edge of the paper 2 (S41Y), the measurement of the paper interval time T4 is started (S42), and the total number of formed images is incremented by 1 (S43). If there is still an image forming process (S44Y), the process returns to S30. If there is no more image forming process (S44N), the measurement of T4 is interrupted (S45) and the process is terminated.

  Note that it is also possible to measure T3 and T4 even when the temporary stop is not performed in S36. At this time, T3 and T4 use different storage areas depending on whether they are stopped or not.

1 is a configuration diagram of an image forming apparatus of the present invention. FIG. 3 is a diagram schematically illustrating a conveyance path of the image forming apparatus of the present invention. 6 is a timing chart showing drive timing of each unit during paper conveyance. It is a diagram of paper conveyance. It is a flowchart which shows 1st Example of the correction procedure of t1 and t2. It is a flowchart which shows 2nd Example of the correction procedure of t1 and t2. It is a flowchart which shows the 3rd Example of the correction procedure of t1 and t2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper 18 Paper supply means 19 Image formation part 35 Control means 36 1st paper detection sensor 38 Loop formation roller 39 Registration roller 42 2nd paper detection sensor

Claims (7)

Paper feeding means for feeding paper, a first paper detection sensor provided on the downstream side of the paper feeding means, a loop forming roller for forming a loop on the fed paper, and the fed paper abut An image forming apparatus having a registration roller that re-feeds to an image forming unit after being stopped, a second sheet detection sensor provided in the vicinity of the registration roller, and an image forming unit that forms an image on the sheet ,
Control means for controlling whether or not to temporarily stop the paper based on whether or not the first paper detection sensor has been reached after a predetermined time from the start of paper feeding by the paper feeding means; The control means measures an arrival time from the start of paper feed when the paper is temporarily stopped until the paper reaches the second paper detection sensor, and corrects the pause time based on the arrival time. Image forming apparatus. Paper feeding means for feeding paper, a first paper detection sensor provided on the downstream side of the paper feeding means, a loop forming roller for forming a loop on the fed paper, and the fed paper abut An image forming apparatus having a registration roller that re-feeds to an image forming unit after being stopped, a second sheet detection sensor provided in the vicinity of the registration roller, and an image forming unit that forms an image on the sheet ,
Control means for controlling whether or not to temporarily stop the paper based on whether or not the first paper detection sensor has been reached after a predetermined time from the start of paper feeding by the paper feeding means; The control means performs the next time from the time when the paper reaches the second paper detection sensor to the time when the paper reaches the second paper detection sensor in the case of the temporary stop, and after the second paper detection sensor detects the passage of the previous paper. An image forming apparatus comprising: measuring an interval between sheets until a sheet is detected, and correcting the pause time and the predetermined time based on the arrival time and the interval between sheets. Paper feeding means for feeding paper, a first paper detection sensor provided on the downstream side of the paper feeding means, a loop forming roller for forming a loop on the fed paper, and the fed paper abut An image forming apparatus having a registration roller that re-feeds to an image forming unit after being stopped, a second sheet detection sensor provided in the vicinity of the registration roller, and an image forming unit that forms an image on the sheet ,
Control means for controlling whether or not to temporarily stop the paper based on whether or not the first paper detection sensor has been reached after a predetermined time from the start of paper feeding by the paper feeding means; And a control unit configured to control the arrival time until the paper reaches the second paper detection sensor from the start of paper feeding when the paper is temporarily stopped and when the paper is not temporarily stopped, and the passage of the previous paper through the second paper detection sensor. An image forming apparatus that measures a paper interval time from the detection to the detection of the next paper, and corrects the pause time and the predetermined time based on the arrival time and the paper interval time. .   The image forming apparatus according to claim 1, wherein the control unit measures the arrival time for a predetermined number of image forming sheets and corrects the pause time based on an average value of the measured arrival times.   The control means measures the arrival time and the paper interval time for a predetermined number of image forming sheets, and based on the measured average value of the arrival time and the measured average value of the paper interval time, the pause time and the predetermined time The image forming apparatus according to claim 2, wherein the time is corrected.   The image forming apparatus according to claim 1, wherein the control unit measures the arrival time when the total number of image formed sheets reaches a predetermined value.   7. The image formation according to claim 2, wherein the control unit measures the arrival time and the inter-paper time when the total number of image formation sheets reaches a predetermined value. apparatus.

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