JP2009132504A - Paper conveying device and image forming device with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by shortening a paper sheet interval without causing inconvenience such as damage to synchronization between an image on an image carrier and the paper sheets, a limitation on sizes, and difficulty in lowering costs. <P>SOLUTION: When the front end of a succeeding paper sheet is not detected by an intermediate roller sensor until the expiration of the prescribed minimum paper sheet interval equivalent time t1 from detection of the rear end of a prior paper sheet by the intermediate roller sensor, which is being conveyed at a first speed V1 by an intermediate roller, the speed is changed into a second one V2, thereby starting high-speed conveyance of the succeeding paper sheet. Furthermore, when the rear end of the prior paper sheet which is being conveyed at the first speed is detected by the intermediate roller sensor, measurement of an actual paper sheet interval equivalent time t2 is started, and a high-speed conveyance remaining time t3 is obtained corresponding to the actual paper sheet interval equivalent time obtained when the front end of the succeeding paper sheet is detected by the intermediate roller sensor. When this high-speed conveyance remaining time is expired, the speed is returned to the first one, thereby conveying the succeeding paper sheet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet as an image forming medium by an electrophotographic process or the like to an image forming unit, and an image forming apparatus including the sheet conveying apparatus.

  In image forming apparatuses (printers, facsimile machines, copiers, and multifunction machines) that form images on recording paper using electrophotographic processes, etc., in recent years, there has been an increasing demand for higher productivity through faster processing. In order to achieve this, there is a method of increasing the process speed. However, in this case, a high-output motor is required, and it is not desirable in terms of durable parts such as bearings and the life of the developer. In view of this, it has been attempted to increase productivity by increasing the number of printed sheets per unit time by narrowing the sheet interval during continuous printing to shorten the idle time.

  However, there is a concern that a paper jam (paper jam) may occur simply by shortening the paper feed interval of the paper fed from the paper feed cassette. That is, in order to feed the sheets in the sheet feeding cassette one by one, a separation roller pair is provided, and a process of separating the overlapping sheets one by one by the frictional force of the rubber roller is performed. Since the stopping position of the paper stopped by the frictional force of the rubber roller varies, the paper feeding interval is not constant. If the paper feeding is controlled so that the paper is sent out at a short interval, the paper is fed in a state where it overlaps the previous paper. Double feed occurs, and a paper collision occurs due to a difference in transport speed due to various factors such as slip on the transport roller, causing a paper jam.

In order to solve such a problem, conventionally, a sheet sensor is provided on a conveyance path that guides the sheet fed from the sheet feeding cassette to the transfer position of the image forming unit, and based on the timing at which the sheet sensor detects the sheet being conveyed. In addition, a technique is known in which the paper interval is shortened by controlling the paper conveyance speed while preventing paper jam (see Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 9-249333 JP 2001-206583 A

  However, in the technique disclosed in Patent Document 1, after changing the paper feed speed for feeding paper from the paper cassette and controlling the paper to arrive at a predetermined position immediately before image transfer at an appropriate timing, To control the same speed as the image carrier, the paper transport speed is changed after synchronizing with the image position on the image carrier, and the synchronization between the image and the paper is likely to be shifted. There is a problem that it is impossible to cope with the case where the interval is longer than the paper length.

  Further, in the technique disclosed in Patent Document 2, since the paper conveyance speed is controlled steplessly based on the detection result of the paper sensor, a drive mechanism capable of changing the speed steplessly like a stepping motor is required. This requires an expensive motor and a dedicated drive circuit for driving the motor, and there is a problem that it is difficult to reduce the cost.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is the inconvenience of losing the synchronization between the image on the image carrier and the paper and the size. There is provided a sheet conveying apparatus configured to shorten a sheet interval and improve productivity without incurring inconveniences that cause restrictions and inconvenience that cost reduction is difficult, and an image forming apparatus including the sheet conveying apparatus. It is to provide.

  The paper transport device and the image forming apparatus including the paper transport device according to the present invention include a paper feed unit that sequentially feeds paper from a paper storage unit, a registration unit that feeds paper in synchronization with an image on an image carrier, and the paper feed An intermediate conveyance unit that conveys a sheet on a sheet conveyance path between the unit and the registration unit, and the intermediate conveyance unit is driven to be switchable between two stages of a first speed and a second speed higher than the first speed. A drive unit; an intermediate detection unit that detects passage of a sheet in the vicinity of the intermediate conveyance unit; and a control unit that controls the intermediate conveyance unit based on a detection result of the intermediate detection unit. The leading edge of the succeeding sheet is detected by the intermediate detection means until a predetermined minimum interval between the sheets has elapsed after the trailing edge of the preceding sheet being transported at the first speed by the intermediate transporting means. Means not detected If the intermediate detection means detects the trailing edge of the preceding paper that is being conveyed at the first speed, the time corresponding to the actual paper is measured. And the remaining high-speed conveyance time is determined according to the actual sheet-interval equivalent time obtained when the intermediate detection means detects the leading edge of the subsequent sheet, and when the remaining high-speed conveyance time has elapsed, the first speed is reached. The configuration is such that the subsequent sheet is conveyed by returning it.

  According to the present invention, high-speed conveyance is started at a timing at which a predetermined minimum sheet interval can be secured based on the trailing edge position of the preceding sheet, regardless of the position of the succeeding sheet, and then detected by detecting the leading edge position of the succeeding sheet. The remaining high-speed conveyance time for continuing high-speed conveyance is set based on the actual paper interval, and control is performed to return to standard conveyance when this high-speed conveyance remaining time ends, so avoid collision between the preceding paper and the following paper. However, it is possible to increase the distance at which the succeeding sheet is conveyed at high speed, thereby reducing the gap between the preceding sheet and the succeeding sheet without causing a paper jam and improving the productivity of the image forming apparatus. A great effect can be obtained. If control is performed so that the high-speed conveyance is returned to the standard conveyance before synchronization with the image position on the image carrier, the synchronization between the image on the image carrier and the paper is not impaired, and the paper container It is possible to cope with the case where the distance between the transfer positions is longer than the paper length, there is no dimensional limitation, and the driving means that can switch the conveying speed of the intermediate conveying means in two stages is sufficient, so that the cost can be reduced. Becomes easier.

  In order to solve the above problems, a first invention includes a paper feeding unit that sequentially feeds paper from a paper storage unit, a registration unit that feeds paper in synchronization with an image on an image carrier, and the paper feeding unit. An intermediate transport unit that transports a sheet on a sheet transport path between the first and second registration units, and a drive that drives the intermediate transport unit so that the intermediate transport unit can be switched between a first speed and a second speed higher than the first speed. Means, intermediate detection means for detecting the passage of paper in the vicinity of the intermediate conveyance means, and control means for controlling the intermediate conveyance means based on the detection result of the intermediate detection means, the control means, The intermediate detection means detects the leading edge of the succeeding sheet until a predetermined minimum interval between sheets has elapsed after the intermediate detection means detects the trailing edge of the preceding sheet being conveyed at the first speed by the intermediate conveyance means. If does not detect Then, switching to the second speed starts high-speed conveyance of the succeeding paper, and when the intermediate detection means detects the trailing edge of the preceding paper being conveyed at the first speed, measurement of the time corresponding to the actual paper is started. Then, the remaining high-speed conveyance time is obtained according to the equivalent time between actual sheets obtained when the intermediate detection means detects the leading edge of the subsequent sheet, and when the remaining high-speed conveyance time has elapsed, the first speed is returned to the subsequent speed. The sheet is transported.

  According to this, the preceding sheet is conveyed at the standard speed at the first speed while the succeeding sheet is conveyed at the second speed at a high speed, so that a speed difference is generated between the preceding sheet and the succeeding sheet, and the preceding sheet and the succeeding sheet are conveyed. It is possible to shorten the gap between the sheets. Then, regardless of the position of the succeeding sheet, since the high speed conveyance is started with the position of the trailing edge of the preceding sheet as a reference, the distance for conveying the succeeding sheet at a high speed can be increased, and the gap between the preceding sheet and the succeeding sheet can be increased. The number of prints per unit time can be increased by narrowing. Since high-speed conveyance is started after a time corresponding to the minimum paper interval, a minimum required paper space is ensured between the preceding paper and the succeeding paper, so that collision between the preceding paper and the succeeding paper can be avoided. .

  In this case, the minimum paper interval time is from the detection of the trailing edge of the preceding paper by the intermediate detection unit to the time when the intermediate detection unit reaches the paper interval reference position set on the downstream side by a predetermined minimum paper interval. It is the time required for this, and is set in advance based on the configuration of the actual machine. The remaining high-speed conveyance time is the remaining time for which high-speed conveyance is continued after the intermediate detection means detects the leading edge of the succeeding paper, and the difference between the actual paper and the target paper, as well as the first speed and the second speed. It is calculated based on the speed difference. In addition, a first subtracting timing unit that performs subtraction timing for a preset minimum paper interval time, a second integration timing unit that performs integration timing for the actual paper interval time, and a preset high-speed conveyance remaining time It is preferable to provide third subtracting time measuring means for performing subtractive time counting.

  According to a second aspect of the present invention for solving the above-mentioned problem, the control means obtains the high-speed conveyance remaining time from the time corresponding to the actual sheet based on a preset table.

  According to this, the burden of the control means can be reduced, and further appropriate control based on the actual machine can be realized.

  According to a third aspect of the present invention for solving the above-described problem, the control unit detects the trailing edge of the succeeding sheet before the time corresponding to the minimum sheet interval elapses after the intermediate detecting unit detects the trailing edge of the preceding sheet. When the leading edge is detected by the intermediate detection unit, the intermediate conveyance unit is stopped, and when the predetermined reference position arrival expected time has elapsed since the registration unit resumed the conveyance of the preceding sheet by the registration process, The intermediate conveying means is resumed.

  According to this, if the intermediate detection means detects the leading edge of the succeeding sheet before the time corresponding to the minimum sheet interval has elapsed, the minimum sheet interval is not secured between the preceding sheet and the succeeding sheet. By stopping the transport of the succeeding paper, the succeeding paper is stopped, but the preceding paper is transported by the registration means. By restarting the conveyance with the elapse of the estimated position arrival time, it is possible to secure a minimum sheet interval between the preceding sheet and the succeeding sheet.

  In this case, the estimated reference position arrival time is the time required for the trailing edge of the preceding sheet to reach the reference position after the registration unit resumes the conveyance of the preceding sheet by the registration process, and is obtained based on the size of the sheet. It is done. In addition, it is preferable to provide a fourth subtraction time measuring means for performing subtraction time measurement of a preset reference position arrival expected time.

  According to a fourth aspect of the present invention, there is provided a sheet feeding detection unit that detects passage of a sheet in the vicinity of the sheet feeding unit, and the sheet feeding detection unit detects a leading edge of a subsequent sheet. If the intermediate detection means does not detect the trailing edge of the preceding paper even after a predetermined intermediate detection position arrival estimated time has elapsed, the intermediate conveyance means is stopped, and the registration means performs the registration process to advance the preceding paper. The intermediate transport means is restarted when a predetermined reference position arrival time has elapsed since the restart of the transport.

  According to this, if the intermediate detection unit cannot detect the trailing edge of the preceding sheet even after the estimated intermediate detection position arrival time has elapsed, it can be determined that the preceding sheet and the succeeding sheet overlap. In this case, by stopping the conveyance of the succeeding sheet by the intermediate conveying unit, the succeeding sheet is stopped. On the other hand, the preceding sheet is conveyed by the registration unit, so that the superposition of the preceding sheet and the succeeding sheet is eliminated. By restarting the conveyance with the elapse of the reference position arrival expected time, it is possible to secure the minimum sheet interval between the preceding sheet and the succeeding sheet.

  In this case, the estimated arrival time of the intermediate detection position is the time required for the leading edge of the subsequent sheet to move from the detection position by the paper feed detection means to the detection position by the intermediate detection means, and is set in advance based on the configuration of the actual machine. deep. In addition, it is preferable to provide a fifth subtracting timing unit that performs subtraction timing of a preset intermediate detection position arrival expected time.

  According to a fifth aspect of the present invention, there is provided a registration detection unit configured to detect a position of a sheet in the vicinity of the upstream side of the registration unit, and the control unit detects the leading end of the sheet as the registration detection unit. The registration unit is controlled on the basis of the detected timing so that the high-speed conveyance at the second speed is terminated and the standard conveyance at the first speed is returned to before the leading edge of the sheet reaches the registration detection unit. The high-speed conveyance remaining time is set.

  According to this, it is possible to avoid that the registration process becomes inaccurate due to the change in the sheet conveyance speed after the registration detection unit detects the leading edge of the sheet.

  In a sixth aspect of the present invention made to solve the above problem, the control means controls the intermediate conveying means and the paper feeding means in synchronization with each other.

  According to this, it is possible to avoid a delay in the conveyance of the sheet due to the difference in the conveyance speed between the intermediate conveyance unit and the sheet feeding unit.

  According to a seventh aspect of the present invention for solving the above-described problems, the paper feeding unit is provided for each of a plurality of paper storage units, and the individual transport paths for each of the plurality of paper storage units are sequentially joined to a common transport path. The sheet is guided to the image transfer unit, and the control unit is configured to detect the detection result of the intermediate detection unit provided on the downstream side of the junction point between the individual conveyance path and the common conveyance path on the most downstream side. On the basis of this, a plurality of the intermediate conveyance means provided at each junction of the individual conveyance path and the common conveyance path are controlled.

  According to this, since the control is based on the detection result of the single intermediate detection means, the control procedure can be simplified.

  In this case, it may be configured to control the speed switching and transport stop operations of a plurality of intermediate transport means provided at each merging point between the individual transport path and the common transport path in synchronization with each other. It is possible to avoid the non-uniformity between the papers depending on the position of the original paper storage unit.

  In an eighth aspect of the invention made to solve the above-mentioned problem, the intermediate conveying means on the downstream side and the upstream side are respectively driven by different first and second driving means, and the intermediate conveying means on the upstream side is The time required for the second driving means to be driven to start driving the intermediate conveying means at a speed after the speed switching is shorter than that of the first driving means for driving the intermediate conveying means on the downstream side. The structure has characteristics.

  According to this, since the upstream intermediate conveying means is switched to high-speed conveyance earlier than the downstream side, the duration of high-speed conveyance in the paper sent from the upstream paper storage unit becomes longer. It is possible to compensate for the distance loss due to the conveyance loss that becomes conspicuous by being conveyed for a long distance, and to prevent the paper interval sent from the upstream paper storage unit from being delayed and the space between the papers from being enlarged.

  According to a ninth aspect of the invention made to solve the above-mentioned problem, when the control means switches from high-speed conveyance at the second speed to standard conveyance at the first speed, the speed switching of the intermediate conveyance means on the upstream side is performed. The timing is set so as to be delayed from the intermediate conveying means on the downstream side.

  According to this, since the upstream intermediate conveyance means is switched to the standard conveyance later than the downstream side, the duration of the high-speed conveyance in the sheet sent from the upstream paper storage unit becomes longer. It is possible to compensate for the distance loss due to the conveyance loss that becomes conspicuous by being conveyed for a long distance, and to prevent the paper interval sent from the upstream paper storage unit from being delayed and the space between the papers from being enlarged.

  According to a tenth aspect of the invention for solving the above-described problems, the control means sets the stop timing of the upstream intermediate conveyance means to the downstream intermediate conveyance means when the intermediate conveyance means is stopped. The configuration is to delay.

  According to this, since the intermediate conveying means on the upstream side stops late as compared with the downstream side, the conveyance time for the paper sent out from the upstream paper storage unit becomes longer, so that the paper is conveyed for a long distance from the upstream side. This makes it possible to compensate for the distance loss due to the transport loss that becomes conspicuous, and to avoid an increase in the gap between the papers due to the delay in transport of the paper fed from the upstream paper storage unit.

  In an eleventh aspect of the invention made to solve the above-mentioned problem, the time measuring means for measuring the time serving as a reference for the control of the intermediate conveying means has a unit corresponding to the speed ratio between the first speed and the second speed. The count amount per hour is increased or decreased.

  According to this, when the transport distance is processed in time conversion and the paper position is estimated, it is possible to avoid the estimation of the paper position being inaccurate due to a change in speed in the middle. Furthermore, since accurate time measurement is possible without changing the accuracy of the time measurement means for controlling the paper feed pitch and the like, the burden on the control means can be reduced.

  In a twelfth aspect of the invention made to solve the above-described problem, when there is no preceding sheet on the conveyance path from the sheet feeding unit to the registration unit, the sheet from the time of sheet feeding until the sheet reaches the registration unit. The high-speed conveyance is performed at a speed of 2.

  According to this, since the sheet is conveyed at a high speed from the time of sheet feeding, productivity can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an image forming apparatus to which the present invention is applied. The image forming apparatus includes an image forming unit 1 that forms an image on a sheet through processes of charging, exposure, development, transfer, and fixing. The image forming unit 1 includes a paper feed cassette (paper storage unit) 4a. Sheets S accommodated in 4 to 4d are sequentially fed through a sheet conveying section (sheet conveying apparatus) 2, and the sheet S on which a required image is formed in the image forming section 1 is discharged to the sheet discharging section 5.

  The image forming unit 1 includes a plurality of process units 11 to 14 that form toner images for respective colors of yellow, magenta, cyan, and black, and photosensitive drums (image carriers) in the process units 11 to 14. A laser scanning unit (hereinafter referred to as LSU) 16 that scans a light beam for exposure on the image forming surfaces 11a to 14a and images on the photosensitive drums 11a to 14a in the process units 11 to 14 are formed. In addition, an intermediate transfer belt (image carrier) 17 to which toner images for each color are sequentially transferred and combined is provided, and photosensitive drums 11 a to 14 a for each color are arranged side by side along the intermediate transfer belt 17. It has a tandem structure.

  In each of the process units 11 to 14, the electrostatic latent image is obtained by scanning the light beam for exposure from the LSU 16 on the image forming surfaces of the photosensitive drums 11a to 14a uniformly charged by the chargers 11b to 14b. An image is formed, and the electrostatic latent images on the respective photoconductive drums 11a to 14a are developed with the respective color toners supplied from the respective developing units 11c to 14c, and single color toner images for the respective colors are formed on the respective photoconductive drums 11a to 11a. 14a is formed on the image forming surface.

  The intermediate transfer belt 17 is supported by being wound around a driving roller 21 and a driven roller 22. Inside the intermediate transfer belt 17, the intermediate transfer belt 17 is pressed to form a toner image on each of the photosensitive drums 11 a to 14 a. Are provided with primary transfer rollers 24 to 27 for each color for transferring the toner image to the intermediate transfer belt 17. Further, a secondary transfer roller 28 for transferring the toner image on the intermediate transfer belt 17 onto the paper S is disposed on the side of the end of the intermediate transfer belt 17.

  The sheet S on which the toner image is transferred by the secondary transfer roller 28 is conveyed to the fixing device 19 and is subjected to a process of fixing the toner image to the sheet S by heat and pressure.

  FIG. 2 is a schematic diagram illustrating a configuration of a sheet conveyance unit in the image forming apparatus illustrated in FIG. 1. In the paper transport unit 2, the first to fourth pickup rollers 31a to 31d for picking up the paper in the first to fourth paper feed cassettes 4a to 4d, and the first to fourth for feeding the paper taken out thereby. Paper feed rollers (paper feed means) 32a to 32d and paper feed sensors (paper feed detection means) 33a to 33d for detecting passage of paper in the vicinity of the downstream side are provided.

  The individual transport paths 34a to 34d provided for the first to fourth paper feed cassettes 4a to 4d are sequentially joined to the common transport path 35, and the sheets in the paper feed cassettes 4a to 4d correspond to the individual transport paths. The toner is guided to the secondary transfer roller (image transfer unit) 28 of the image forming unit 1 through the transport paths 34 a to 34 d and the common transport path 35.

  On the downstream side of the merging point between each of the individual conveyance paths 34 a to 34 d and the common conveyance path 35, first to fourth intermediates that convey the paper fed from the individual conveyance paths 34 a to 34 d on the common conveyance path 35. Rollers (intermediate transport means) 36a to 36d are provided. Further, intermediate roller sensors (intermediate detection means) 37a to 37c for detecting the passage of paper are provided in the vicinity of the downstream side of the intermediate rollers 36a to 36d.

  At the most downstream side of the sheet conveying section 2, a registration roller (registration means) 38 that feeds the sheet in synchronism with the image on the intermediate transfer belt 17 (image carrier), and the position of the sheet near the upstream side of the registration roller 38. A registration sensor (registration detection means) 39 is provided for controlling the operation of the registration roller 38 based on the timing when the registration sensor 39 detects the leading edge of the paper.

  The first and second paper feed cassettes 4 a and 4 b are provided in the main body 7, and the third and fourth paper feed cassettes 4 c and 4 d are provided in the optional paper feed stand (extension unit) 8. The registration roller 38 and the first and second intermediate rollers 36a and 36b provided in the main body 7 are driven by a first drive mechanism (first drive means) 42 and provided in an optional paper feed stand. The third and fourth intermediate rollers 36 c and 36 d are driven by a second drive mechanism (second drive means) 43.

  As shown below, the first drive mechanism 42 on the main body 7 side and the second drive mechanism 43 on the optional paper feed stand 8 side have a standard transport at a first speed and a high speed at a second speed higher than this. Switching to conveyance is possible.

  FIG. 3 is a perspective view showing the first drive mechanism 42 on the main body 7 side shown in FIG. 4 and 5 are schematic perspective views for explaining the operating state of the first drive mechanism 42 shown in FIG. FIG. 6 is a diagram for explaining the control procedure of the first drive mechanism 42 shown in FIG.

  The first drive mechanism 42 provided in the main body 7 includes a motor 51 and first and second intermediate roller clutches for intermittently transmitting power from the motor 51 to the first and second intermediate rollers 36a and 36b. 52, 53, an interlocking mechanism 54 that transmits power at a constant speed between the driven shafts 61, 62 of the first and second intermediate roller clutches 52, 53, and the first and second intermediate roller clutches 52. A speed increasing mechanism 55 that increases the speed of power transmission between the rotors 63 and 64 on the drive side of 53.

  The first and second intermediate roller clutches 52 and 53 are electromagnetic clutches, and the shafts 61 and 62 and the rotors 63 and 64 cannot be rotated relative to each other by applying a voltage to the exciting coil. The power transmission between the rotors 63 and 64 is possible, and the power transmission is intermittently performed according to the on / off instruction from the controller 41.

  The first and second intermediate roller clutches 52 and 53 are provided coaxially with the first and second intermediate rollers 36a and 36b. That is, the shafts 61 and 62 that serve as the rotation shafts of the first and second intermediate rollers 36a and 36b are provided so as to pass through the center portions of the intermediate roller clutches 52 and 53.

  The power of the motor 51 is transmitted to the rotor 63 of the first intermediate roller clutch 52 via the speed reduction mechanism 56. The speed reduction mechanism 56 includes a first gear 71 connected to the output shaft of the motor 51, and the first gear 71. A second gear 72 that meshes with the first gear 71; a third gear 73 that is coaxially coupled to the second gear 72; and a fourth gear 74 that meshes with the third gear 73. The fourth gear 74 meshes with a gear portion provided on the rotor 63 of the first intermediate roller clutch 52.

  The interlocking mechanism 54 includes a pair of pulleys 67 and 68 and a belt 69 wound around the pair of pulleys 67 and 68. The pulleys 67 and 68 include first and second intermediate rollers 36a and 36a. It is coaxially connected to the end opposite to the intermediate rollers 36a and 36b in the shafts 61 and 62 that serve as the rotation shaft 36b and penetrate the central portions of the first and second intermediate roller clutches 52 and 53. .

  The speed increasing mechanism 55 includes a fifth gear 75 that meshes with a gear portion provided on the rotor 63 of the first intermediate roller clutch 52, a sixth gear 76 that meshes with the fifth gear 75, and a sixth gear 76. A seventh gear 77 coaxially connected to the gear 76, an eighth gear 78 meshing with the seventh gear 77, and a ninth gear 79 coaxially connected to the eighth gear 78; The ninth gear 79 meshes with a gear portion provided on the rotor 64 of the second intermediate roller clutch 53.

  In the first drive mechanism 42, as shown in FIG. 4, when the first intermediate roller clutch 52 is turned on and the second intermediate roller clutch 53 is turned off, the rotational force of the motor 51 passes through the speed reduction mechanism 56. Then, the first intermediate roller 36a is transmitted to the rotor 63 of the first intermediate roller clutch 52 and further transmitted to the shaft 61, so that the first intermediate roller 36a rotates at the first speed. The rotation of the shaft 61 is transmitted to the shaft 62 via the interlocking mechanism 54, and the second intermediate roller 36b rotates at the first speed.

  At this time, the rotational force of the motor 51 is transmitted from the rotor 63 side of the first intermediate roller clutch 52 to the rotor 64 of the second intermediate roller clutch 53 via the speed increasing mechanism 55. Since 53 is OFF, the rotor 64 of the second intermediate roller clutch 53 is idled with respect to the shaft 62.

  Further, as shown in FIG. 5, when the first intermediate roller clutch 52 is turned off and the second intermediate roller clutch 53 is turned on, the rotational force of the motor 51 is transmitted through the speed reduction mechanism 56 to the first intermediate roller clutch. 52, is further transmitted to the speed increasing mechanism 55, the rotational force increased by the speed increasing mechanism 55 is transmitted to the second intermediate roller clutch 53, and the second intermediate roller 36b is Rotate at a speed of. Further, the rotation of the shaft 62 of the second intermediate roller clutch 53 is transmitted to the shaft 61 via the interlocking mechanism 54, and the first intermediate roller 36a rotates at the second speed.

  At this time, the rotation of the motor 51 is transmitted to the rotor 63 of the first intermediate roller clutch 52, while the increased rotational force is transmitted to the shaft 61, but the first intermediate roller clutch 52 is turned off. Therefore, the rotor 63 of the first intermediate roller clutch 52 is idled with respect to the shaft 61.

  As described above, in the first drive mechanism 42 on the main body 7 side, the speed is switched by turning on one of the first and second intermediate roller clutches 52 and 53 and turning off the other. If both the first and second intermediate roller clutches 52 and 53 are turned on at the same time, the components will be damaged. Therefore, both the first and second intermediate roller clutches 52 and 53 are temporarily turned off when the speed is switched. Then, control is performed to turn on one of them.

  Further, as shown in FIG. 6, there are four patterns for the signals for the first and second intermediate roller clutches 52 and 53, but both the first and second intermediate roller clutches 52 and 53 are simultaneously turned on. In the pattern 1, when the signals for the first and second intermediate roller clutches 52 and 53 are both on, the operation of the first intermediate roller clutch 52 is off and the second intermediate roller The operation of the clutch 53 is set to be on.

  As shown in FIG. 2, the registration roller 38 is also driven by the motor 51, and a registration clutch 59 that interrupts transmission of power from the motor 51 to the registration roller 38 according to an instruction from the controller 41 is provided. Yes.

  FIG. 7 is a perspective view showing the second drive mechanism 43 on the option paper supply stand 8 side shown in FIG. 8 and 9 are schematic perspective views for explaining the operation state of the second drive mechanism 43 shown in FIG.

  The second drive mechanism 43 provided in the optional paper supply stand 8 includes a motor 81 and a third intermediate roller clutch 82 that intermittently transmits power from the motor 81 to the third and fourth intermediate rollers 36c and 36d. And a one-way clutch 83 provided between the third intermediate roller clutch 82 and the intermediate rollers 36c and 36d, and the power from the shaft 96 on the driving side of the one-way clutch 83 to the intermediate rollers 36c and 36d. A fourth intermediate roller clutch 84 for intermittent transmission and a transmission mechanism 85 for shifting and transmitting power from the rotor 99 on the driven side of the one-way clutch to the intermediate rollers 36c and 36d.

  The third and fourth intermediate roller clutches 82 and 84 are electromagnetic clutches, and the shafts 95 and 96 and the rotors 97 and 98 are prevented from rotating relative to each other by applying a voltage to the exciting coil. In this configuration, the power transmission is intermittently performed in response to an on / off instruction from the controller 41. The one-way clutch 83 is configured to transmit power to the rotor 99 when the shaft 96 rotates in the locking direction.

  The power from the motor 81 is transmitted to the third intermediate roller clutch 82 via the first transmission mechanism 87, and the first transmission mechanism 87 is connected to the output shaft of the motor 81. And a second gear 102 that meshes with the first gear 101, and a third gear 103 that is coaxially connected to the second gear 102. The third gear 103 is a third clutch. It meshes with a gear portion provided on 82 rotors 97.

  Power from the third intermediate roller clutch 82 is transmitted to the one-way clutch 83 and the fourth intermediate roller clutch 84 via the second transmission mechanism 88, and the second transmission mechanism 88 includes a pair of pulleys. 111 and 112, and a belt 113 wound around the pair of pulleys 111 and 112. One pulley 111 is connected to a shaft 95 penetrating the center of the third intermediate roller clutch 82. The other pulley 112 is connected to a shaft 96 that passes through the central portions of the one-way clutch 83 and the fourth intermediate roller clutch 84.

  The interlocking mechanism 86 includes a pair of pulleys 115 and 116 and a belt 117 wound around the pair of pulleys 115 and 116. The pulleys 115 and 116 are respectively provided with third and fourth intermediate rollers 36c. Gears 123 and 124 that mesh with gears 121 and 122 that are coaxially connected to the rotating shafts 91 and 92 of 36d are connected to shafts 93 and 94 that are connected to one end.

  The speed reduction mechanism 85 includes a small-diameter fourth gear 104 that is coaxially connected to the rotor 99 of the one-way clutch 83, and a large-diameter fifth gear 105 that meshes with the fourth gear 104. The fifth gear 105 is connected to a shaft 94 that transmits rotation to the fourth intermediate roller 36d. Further, a sixth gear 106 that meshes with the gear portion of the rotor 98 of the fourth clutch 84 is coaxially connected to the shaft 94.

  In the second drive mechanism 43, as shown in FIG. 8, when the third intermediate roller clutch 82 is turned on and the fourth intermediate roller clutch 84 is turned off, the rotational force of the motor 81 is transmitted to the transmission mechanisms 87 and 88. The rotational force of the shaft 96 acts on the one-way clutch 83 in the locking direction and is transmitted to the rotor 99, and is further decelerated via the gears 104 and 105 constituting the speed reduction mechanism 85. The rotating force thus transmitted is transmitted to the shaft 94, and the third and fourth intermediate rollers 36c and 36d rotate at the first speed.

  At this time, the rotational force of the shaft 94 is input to the rotor 98 of the fourth intermediate roller clutch 84 via the sixth gear 106. Since the fourth intermediate roller clutch 84 is off, The rotor 98 of the intermediate roller clutch 84 is idle with respect to the shaft 96.

  As shown in FIG. 9, when both the third and fourth intermediate roller clutches 82 and 84 are turned on, the rotational force of the motor 81 is transmitted to the shaft 96 via the transmission mechanisms 87 and 88. Is transmitted from the rotor 98 of the fourth intermediate roller clutch 84 to the shaft 94 via the sixth gear 106, and the third and fourth intermediate rollers 36c and 36d rotate at the second speed.

  At this time, the rotational force of the shaft 94 is input to the rotor 99 of the one-way clutch 83 via the fifth gear 105 and the fourth gear 104, but the rotation of the rotor 99 is faster than the shaft 96, Since the rotor 99 rotates relative to the free direction, the one-way clutch 83 is idle.

  As shown in FIG. 2, on the main body 7 side, the first and second pickup rollers 31 a and 31 b and the first and second paper feed rollers 32 a and 32 b are driven by the first drive mechanism 42. , The paper feed clutches 131a and 131b for intermittently transmitting the power from the first drive mechanism 42 to the paper feed rollers 32a and 32b and the pickup rollers 31a and 31b, and the paper feed for feeding the paper in the paper feed cassettes 4a and 4b. Paper feed solenoids 132a and 132b for raising and lowering the pickup rollers 31a and 31b are provided between the position and the retracted position.

  Here, when the rotational forces from the first and second intermediate roller clutches 52 and 53 are input to the paper feed clutches 131a and 131b, respectively, and the paper feed clutches 131a and 131b are turned on, the speed of the intermediate rollers 36a and 36b is switched. When the sheet feeding rollers 32a and 32b and the pickup rollers 31a and 31b are operated in conjunction with the stop / restart operation and the sheet feeding solenoids 132a and 132b are turned on, the pickup rollers 31a and 31b are lowered to feed the sheet. To start.

  On the other hand, on the optional paper supply stand 8 side, the third and fourth pickup rollers 31c and 31d and the third and fourth paper supply rollers 32c and 32d are driven by the second drive mechanism 43, and the second Feed clutches 131c and 131d for intermittently transmitting power from the drive mechanism 43 to the feed rollers 32c and 32d and the pickup rollers 31c and 31d, and a feed position and a retract position for feeding sheets in the sheet cassettes 4c and 4d Are provided with sheet feeding solenoids 132c and 132d for raising and lowering the pickup rollers 31c and 31d.

  Here, the rotational force from the second drive mechanism 43 is input to the paper feed clutches 131c and 131d, and the rotational force from the paper feed clutches 131c and 131d is input to the paper feed solenoids 132c and 132d. When 131d is turned on, the feed rollers 32c and 32d operate in conjunction with the speed switching and stop / restart operations of the intermediate rollers 36c and 36d, and when the feed solenoids 132c and 132d are turned on, the pickup rollers 31c and 31d descends to start the paper feeding operation.

  The control controller 41 receives output signals of the registration sensor 39, the first to third intermediate roller sensors 37a to 37c, and the first to fourth paper feed sensors 33a to 33d, and the motor 51 is based on these signals. 81, the registration clutch 59, the first to fourth intermediate roller clutches 52, 53, 82, and 84, the sheet feeding clutches 131a to 131d, and the sheet feeding solenoids 132a to 132d are controlled.

  Further, as will be described in detail later, the controller 41 includes a subtraction timer (first subtraction timing means) T1 that performs subtraction timing of the minimum paper interval equivalent time t1 that defines the start timing of high-speed conveyance, and the actual paper interval. An integration timer (second integration timing means) T2 that counts the time corresponding to the time t2, and a subtraction timer (third subtraction timing means) T3 that counts the remaining high-speed conveyance time t3 that defines the end timing of the high-speed conveyance. A subtraction timer (fourth subtraction timing means) T4 that performs subtraction timing of the reference position arrival expected time t4 that defines the release timing of the conveyance stop, and a subtraction timer (first counter) that performs subtraction timing of the intermediate detection position arrival expected time t5. 5 subtracting time measuring means) T5.

  FIG. 10 is a timing chart showing the operation status of the paper transport unit shown in FIG. FIG. 11 is a schematic diagram showing the operation status of the paper transport unit shown in FIG. 10 in stages.

  Here, the leading edge of the succeeding sheet S2 until the predetermined minimum sheet interval time t1 elapses after the intermediate roller sensor 37a detects the trailing edge of the preceding sheet S1 being conveyed at the first speed by the intermediate roller 36a. Is not detected by the intermediate roller sensor 37a, the high speed conveyance of the succeeding paper S2 is started by switching to the second speed, and the intermediate roller sensor 37a detects the trailing edge of the preceding paper S1 being conveyed at the first speed. At the time of detection, measurement of the actual paper equivalent time (t4) is started, and the high-speed conveyance remaining time t3 is obtained according to the actual paper equivalent time obtained when the intermediate roller sensor 37a detects the leading edge of the succeeding paper S2. When the remaining high-speed conveyance time (t5) has elapsed, the subsequent sheet S2 is conveyed by returning to the first speed.

  That is, as shown in FIG. 11A, when the trailing edge of the preceding paper S1 passes through the intermediate roller sensor 37a, the subtraction timer T1 starts subtraction counting for subtracting the minimum paper equivalent time t1. In addition, the measurement between the trailing edge of the preceding sheet S1 and the leading edge of the succeeding sheet S2 is started, that is, the integration count of the integration timer T2 for measuring the interval between sheets is started.

  Then, when the subtraction timer T1 times out due to the elapse of the minimum paper interval time t1, as shown in FIG. 11B, the intermediate roller sensor 37a is set downstream by a predetermined minimum paper interval (for example, 10 mm) Lmin. When the trailing edge of the preceding sheet S1 reaches the reference position between the sheets, and at this time, the intermediate roller sensor 37a does not have paper, that is, the leading edge of the succeeding sheet S2 is positioned upstream of the intermediate roller 36a sensor 37a. It can be determined that a space between the trailing edge of the preceding paper S1 and the leading edge of the succeeding paper S2 is secured at least, and the intermediate roller 36a is switched to the second speed to increase the speed. Start conveyance.

  Here, during the minimum paper interval equivalent time t1, the rear end of the preceding sheet S1 reaches the reference position between the sheets from the state of FIG. 11A in which the intermediate roller sensor 37a detects the passage of the rear end of the preceding sheet S1. This is the time required until the state shown in FIG. 11B, and is set in advance based on the configuration of the actual machine.

  Further, the second speed V2 is preferably 1.5 to 2.5 times the first speed V1, thereby enabling the paper interval shortening control without adding special control such as motor gain switching. It becomes. Further, if the speed increasing ratio of the second speed V2 to the first speed V1 is smaller than 1.5, the speed increasing effect is small, and 1.5 is required to obtain a sufficient paper space shortening effect in consideration of the switching loss. It is better to do this. On the other hand, if the speed increasing ratio is larger than 2.5, the paper transportability becomes unstable.

  Next, as shown in FIG. 11C, when the intermediate roller sensor 37a detects the leading edge of the succeeding sheet S2, the sheet interval measurement is terminated, and based on the actual sheet interval corresponding time t2 indicated by the integration timer T2 at this time, The remaining high-speed conveyance time t3, that is, the remaining time for continuing the high-speed conveyance from the time when the intermediate roller sensor 37a detects the leading edge of the succeeding paper S2 shown in FIG. Is done.

The actual sheet interval L1 at the time of detecting the leading edge of the succeeding sheet in FIG. 11C is obtained by multiplying the actual sheet interval equivalent time t2 by the first speed V1, which is the conveyance speed of the preceding sheet S1. Further, the remaining high-speed conveyance time t3 is a reduction amount (L1-Lt) between the first speed V1 and the second speed V2, which is a difference between the actual paper distance L1 and the target paper distance (for example, 15 mm) Lt. It is obtained by dividing by the speed difference (V2-V1). This can be expressed as an expression:
t3 = (L1-Lt) / (V2-V1)
= (T2 × V1-Lt) / (V2-V1)
It becomes. Here, since the time other than the actual paper equivalent time t2 is given as a constant, the formula for calculating the high-speed conveyance remaining time t3 is a linear function of t2.

  When the high-speed conveyance remaining time t3 is determined from the actual sheet equivalent time t2, the subtraction timer T3 starts counting to subtract the high-speed conveyance remaining time t3, and when the high-speed conveyance remaining time t3 elapses. When the subtraction timer T3 expires, as shown in FIG. 11D, the high-speed conveyance of the subsequent sheet S2 is finished, and the subsequent sheet S2 is conveyed at the first speed.

  In this way, while the preceding sheet S1 is standard conveyed at the first speed, the subsequent sheet S2 is conveyed at a high speed at the second speed, so that a speed difference is generated between the preceding sheet S1 and the succeeding sheet S2. It is possible to shorten the space between the sheet S1 and the succeeding sheet S2. Then, regardless of the position of the succeeding sheet S2, high speed conveyance is started with the position of the trailing edge of the preceding sheet S1 as a reference, so that the distance for conveying the succeeding sheet S2 at a high speed can be increased. The space between the paper and the paper can be narrowed to increase productivity. Then, since high-speed conveyance is started after the minimum sheet interval time t1, a minimum necessary sheet interval is ensured between the preceding sheet S1 and the succeeding sheet S2, and the collision between the preceding sheet S1 and the succeeding sheet S2 is ensured. Can be avoided.

  FIG. 12 shows a table for obtaining the high-speed conveyance remaining time t3 shown in FIG. FIG. 13 shows a control result based on the table shown in FIG.

  The high-speed conveyance remaining time t3 is obtained from the actual paper equivalent time t2 based on a preset table. In this table, the remaining high-speed conveyance time t3 is set stepwise in accordance with the length of the actual paper equivalent time t2. Thereby, the burden of control can be reduced, and further appropriate control based on the actual machine can be realized.For example, an error component such as a time loss for speed switching in the drive mechanism is appropriately added. An appropriate setting can be made based on the actual measurement, and the change can be easily performed.

  In this table, as shown in FIG. 10, before the leading edge of the subsequent sheet S2 reaches the detection position of the registration sensor 39, the high-speed conveyance at the second speed is terminated and the standard conveyance at the first speed is returned. As described above, the high-speed conveyance remaining time t3 is set. Accordingly, it is possible to prevent the registration process from becoming inaccurate due to a change in the sheet conveyance speed after the registration sensor 39 detects the leading edge of the sheet.

  FIG. 14 is a diagram showing an operation state of a timer in the control controller shown in FIG. Timers (time measuring means) T1 to T4 for measuring the time serving as a reference for controlling the intermediate roller 36a increase or decrease the count amount per unit time according to the speed ratio between the first speed and the second speed. It has become.

  For example, as shown in FIG. 10, the speed changes halfway during the real paper equivalent time t2, but during high-speed conveyance, the count amount per unit time is increased from that during standard conveyance, that is, the count time interval (count By making the (interval) shorter than during standard conveyance, the measurement distance per count can be made to coincide between high-speed conveyance and standard conveyance. When estimating, it can be avoided that the estimation of the paper position becomes inaccurate due to a change in speed in the middle.

  If there is no preceding paper on the conveyance path from the paper feed rollers 32a to 32d to the registration roller 38 after a lapse of time from the immediately preceding printing process, the paper is fed until the paper reaches the registration roller 38 from the time of paper feeding. High speed conveyance is performed at the second speed. In the case of the first sheet of a print job in which a series of printing operations, for example, printing of a plurality of pages is specified, there is usually no preceding sheet, so there is no problem even if the sheet is fed at high speed at the second speed from the time of feeding. Productivity can be improved.

  FIG. 15 is a timing chart showing the operation status of the paper transport unit shown in FIG. FIG. 16 is a schematic diagram showing the operation status of the paper transport unit shown in FIG. 15 in stages.

  Here, when the intermediate roller sensor 37a detects the leading edge of the succeeding sheet S2 before the minimum sheet interval time t1 elapses after the intermediate roller sensor 37a detects passage of the trailing edge of the preceding sheet S1, The intermediate roller 36a is stopped, and when a predetermined reference position arrival time t4 elapses after the registration roller 38 resumes transport of the preceding paper S1 by registration processing, the intermediate roller 36a is resumed.

  That is, as shown in FIG. 16A, when the registration roller 38 resumes transport of the preceding paper S1 by the registration process, the subtraction count of the subtraction timer T4 that starts subtraction of the reference position arrival expected time t4 is started. . Next, as shown in FIG. 16B, when the intermediate roller sensor 37a detects the trailing edge of the preceding sheet S1, a subtraction count of a subtraction timer T1 that starts subtraction for the minimum paper interval time t1 is started. In addition, the measurement between the trailing edge of the preceding sheet S1 and the leading edge of the succeeding sheet S2 is started, that is, the integration count of the integration timer T2 for measuring the interval between sheets is started.

  Here, the reference position arrival expected time t4 is the time required for the trailing edge of the preceding sheet S1 to reach the sheet gap reference position after the registration roller 38 resumes transport of the preceding sheet S1 by the registration process, that is, the preceding sheet. This is the time from when the leading edge of S1 is at the registration position until the trailing edge of the preceding paper S1 reaches the inter-paper reference position, and is determined based on the paper size.

  Then, before the subtraction timer T1 expires due to the elapse of the minimum sheet-equivalent time t1, that is, as shown in FIG. 16C, the trailing edge of the preceding sheet S1 is at a sheet-to-sheet reference position where the minimum sheet interval can be secured. When the intermediate roller sensor 37a detects the leading edge of the succeeding sheet S2 before reaching, the inter-sheet measurement is stopped, the conveyance of the succeeding sheet S2 by the intermediate roller 36a is stopped, and the succeeding sheet S2 is kept waiting at the current position. . As a result, while the succeeding sheet S2 is stopped, the preceding sheet S1 is continuously conveyed at the first speed (process speed) by the registration roller 38, so that the preceding sheet S1 and the succeeding sheet S2 The space between the papers expands

  The intermediate roller 36a is stopped until the subtraction timer T4 expires due to the elapse of the reference position arrival expected time t4, that is, until the trailing edge of the preceding paper S1 reaches the inter-paper reference position as shown in FIG. As a result, a minimum sheet gap (for example, 10 mm) is ensured between the preceding sheet S1 and the succeeding sheet S2, and the conveyance of the succeeding sheet S2 by the intermediate roller 36a is resumed from this point, and the succeeding sheet S2 is the first sheet S2. Standard transport at speed.

  FIG. 17 is a timing chart showing an operation state of the paper transport unit shown in FIG. FIG. 18 is a schematic diagram showing the operation status of the paper transport unit shown in FIG. 17 in stages.

  Here, when the intermediate roller sensor 37a does not detect the trailing edge of the preceding sheet S1 even after a predetermined intermediate detection position arrival time t5 has elapsed after the sheet feeding sensor 33a detects the leading edge of the succeeding sheet S2. The intermediate roller 36a is stopped, and the intermediate roller 36a is restarted when a predetermined reference position arrival time t4 has elapsed after the registration roller 38 resumes transport of the preceding sheet S1 by the registration process.

  That is, as shown in FIG. 18A, when the paper feed sensor 33a detects the leading edge of the succeeding paper S2, the subtraction timer T5 starts subtraction counting to subtract the intermediate detection position arrival expected time t5. Then, as shown in FIG. 18B, when the registration roller 38 resumes the conveyance of the preceding sheet S1 by the registration process, a subtraction count of a subtraction timer T4 that starts subtraction of the reference position arrival expected time t4 is started.

  Here, the estimated intermediate detection position arrival time t5 is the time required for the leading edge of the succeeding paper S2 to move from the detection position by the paper feed sensor 33a to the detection position by the intermediate roller sensor 37a. Set it.

  As shown in FIG. 18C, even if the subtraction timer T5 times out due to the elapse of the intermediate detection position arrival time t5, the intermediate roller sensor 37a detects the trailing edge of the preceding sheet S1 and the leading edge of the succeeding sheet S2. If this is not possible, it is determined that the preceding sheet S1 and the succeeding sheet S2 overlap each other, and the conveyance of the succeeding sheet S2 by the intermediate roller 36a is stopped. Thus, while the succeeding sheet S2 is stopped, the preceding sheet S1 is continuously conveyed at the first speed (process speed) by the registration roller 38, so that the superposition of the preceding sheet S1 and the succeeding sheet S2 is eliminated. Further, the space between the preceding sheet S1 and the succeeding sheet S2 increases as time elapses.

  The intermediate roller 36a is stopped until the subtraction timer T4 expires as the reference position arrival expected time t4 elapses, that is, as shown in FIG. 18D, until the trailing edge of the preceding sheet S1 reaches the inter-paper reference position. As a result, a minimum sheet gap (for example, 10 mm) is ensured between the preceding sheet S1 and the succeeding sheet S2, and the conveyance of the succeeding sheet S2 by the intermediate roller 36a is resumed from this point, and the succeeding sheet S2 is the first sheet S2. Standard transport at speed.

  Here, the estimated reference position arrival time t4 is required until the trailing edge of the preceding sheet S1 reaches the inter-paper reference position after the registration roller 38 resumes transport of the preceding sheet S1 by the registration process as described above. Even if the intermediate roller sensor 37a cannot detect the trailing edge of the preceding sheet S1 by setting the state where the leading edge of the preceding sheet S1 is at the registration position as the starting point of time measurement, the time after the preceding sheet S1 is reached. It is possible to accurately predict the time for the end to reach the inter-paper reference position.

  Here, an example is shown in which the succeeding sheet S2 is sent out from the first sheet feeding cassette 4a and the leading edge of the succeeding sheet S2 is detected by the first sheet feeding sensor 33a. When the paper is fed from the fourth paper feed cassettes 4b to 4d, the timing at which the second to fourth paper feed sensors 33b to 33d detect the leading edge of the succeeding paper S2 becomes the start point of the intermediate detection position arrival expected time t5.

  FIG. 19 is a timing chart showing an operation state of the paper transport unit shown in FIG. FIG. 19A shows the situation when the speed of the intermediate roller 36a is switched between the first speed and the second speed, as in the example of FIG. 10, and FIG. 19B shows the state of FIG. Similarly to the example, the situation when the intermediate roller 36a is stopped and restarted is shown.

  Here, the speeds of the first and second intermediate rollers 36a and 36b on the downstream side provided in the main body 7 and the third and fourth intermediate rollers 36c and 36d on the upstream side provided in the optional paper supply stand 8 are illustrated. The switching, stopping and restarting operations are performed in synchronization with each other, and the speed switching and stopping / restarting operations of the first to fourth intermediate rollers 36a to 36d are performed on the first intermediate roller sensor 37a on the most downstream side. It is controlled based on the detection result. As a result, the control procedure can be simplified, and it is possible to avoid the non-uniform spacing between the sheets depending on the positions of the first to fourth sheet feeding cassettes 4a to 4d serving as sheet feeding sources.

  Here, as shown in FIGS. 2 to 9, the second drive mechanism 43 that drives the third and fourth intermediate rollers 36 c and 36 d on the upstream side provided in the optional paper feed stand 8 is provided on the main body 7. Compared to the first drive mechanism 42 for driving the first and second intermediate rollers 36a and 36b on the downstream side provided in the first and second intermediate rollers 36a and 36b, the time required to start driving at the speed after the speed switching is short. Have.

  That is, in the first drive mechanism 42 on the main body 7 side, as described above, at the time of speed switching, both the first and second intermediate roller clutches 52 and 53 are once turned off and then one of them is turned on. Since it becomes control, a time loss occurs in speed switching. On the other hand, in the second drive mechanism 43 on the option paper supply stand 8 side, the speed is switched by turning the fourth intermediate roller clutch 84 on and off, so the speed is switched in a short time. For this reason, if the 1st drive mechanism 42 and the 2nd drive mechanism 43 are controlled at the same timing, the 2nd drive mechanism 43 will become high speed conveyance time longer.

  On the other hand, the paper fed from the third and fourth paper feed cassettes 4c and 4d of the optional paper feed stand 8 is transported for a long distance, so that a transport loss due to slippage at the intermediate rollers 36a to 36d becomes remarkable. (Generally 5% to 10%), the third and fourth intermediate rollers 36c and 36d on the upstream side are faster for high-speed conveyance than the first and second intermediate rollers 36a and 36b on the downstream side. Since the high-speed transport time of the paper sent out from the upstream paper feed cassettes 4c and 4d becomes longer, the distance loss due to the transport loss is compensated and sent out from the paper feed cassettes 4c and 4d of the optional paper feed stand 8 It is possible to avoid an increase in the gap between the sheets due to a delay in the conveyance of the printed paper.

  FIG. 20 is a timing chart showing the operation status of the paper transport unit shown in FIG. In the example shown in FIG. 20A, the high-speed conveyance at the second speed is switched to the standard conveyance at the first speed after the remaining high-speed conveyance time t3, as in the example of FIG. The switching timing of the upstream third and fourth intermediate rollers 36c and 36d provided in the paper stand 8 is delayed from the downstream first and second intermediate rollers 36a and 36b provided in the main body 7. Therefore, the duration of the high-speed conveyance of the third and fourth intermediate rollers 36c and 36d becomes longer by the delay time (delay).

  In the example shown in FIG. 20B, as in the example of FIG. 15, when the intermediate roller sensor 37a detects the leading edge of the succeeding paper S2 before the minimum paper interval time t1 elapses, the intermediate rollers 36a to 36d are moved. Here, the stop start timings of the upstream third and fourth intermediate rollers 36 c and 36 d provided in the optional paper supply stand 8 are set as the downstream first and second downstreams provided in the main body 7. The stop time of the third and fourth intermediate rollers 36c and 36d is shortened by the delay time (delay).

  As described above, the third and fourth intermediate rollers 36c and 36d are increased in duration of high-speed conveyance, and the stop time is shortened as described above. The distance loss due to the transport loss of the paper sent out from the paper feed cassettes 4c and 4d is compensated, and the transport of the paper sent out from the paper feed cassettes 4c and 4d of the optional paper feed stand 8 is delayed to increase the space between the papers. Can be avoided.

  In the example of FIG. 17 as well, as in the example shown in FIG. 20B, the stop start timing of the upstream third and fourth intermediate rollers 36c and 36d provided in the optional paper feed stand 8 is set as the main body. 7 can be controlled so as to be delayed from the downstream first and second intermediate rollers 36a and 36b.

  21 and 22 are flowcharts showing the control procedure of the paper transport unit shown in FIG. Here, first, feeding of the preceding sheet S1 is started (step 101), and then feeding of the succeeding sheet S2 is started (step 102). Then, when the paper feed sensors 33a to 33d detect the leading edge of the succeeding paper S2, a subtraction timer T5 whose initial value is set to the intermediate detection position arrival expected time t5 is started (step 103). Further, the conveyance of the preceding sheet S1 is resumed by the registration process (step 104). At this time, a subtraction timer T4 whose initial value is set to the reference position arrival expected time t4 is started, and after the preceding sheet S1 by the intermediate roller sensor 37a. Wait for edge detection. In some cases, the front and rear detection (step 103) of the succeeding sheet by the sheet feed sensor and the registration process (step 104) of the preceding sheet are reversed.

  Then, as shown in FIGS. 17 and 18, before the intermediate roller sensor 37a detects the trailing edge of the preceding sheet S1 (No in step 105), the subtraction timer T5 times out due to the elapsed intermediate detection position arrival time t5. If the subtraction timer T4 is up due to the elapse of the estimated reference position arrival time t4 (Yes in Step 107), it is determined that the paper jam has occurred, and the process is terminated. On the other hand, if the subtraction timer T4 is not up (No in step 107), the conveyance by the intermediate roller 36a is stopped (step 108), and when the subtraction timer T4 ends (Yes in step 109), the intermediate roller 36a is stopped. The transfer by the above is resumed (step 110), and the process proceeds to the registration operation.

  On the other hand, after the conveyance of the preceding sheet S1 is resumed by the registration process (step 104), when the intermediate roller sensor 37a detects the trailing edge of the succeeding sheet S2 (Yes in step 105), the initial value is set to the minimum sheet interval time t1. The set subtraction timer T1 is started (step 111). At the same time, the integration timer T2 for measuring the interval between sheets is started, and the detection of the leading edge of the succeeding sheet S2 by the intermediate roller sensor 37a is awaited. Further, the subtraction timer T5 is terminated without processing.

  Then, as shown in FIGS. 15 and 16, when the intermediate roller sensor 37a detects the leading edge of the succeeding sheet S2 before the subtraction timer T1 expires due to the elapse of the minimum sheet interval time t1, (Yes in step 112). Then, the integration timer T2 for measuring the interval between papers and the subtraction timer T1 for measuring the subtraction of the minimum interval between papers t1 are ended without processing (step 113). If the subtraction timer T4 is timed up due to the elapse of the reference position arrival expected time t4 (Yes in step 114), the process proceeds to a registration operation, and if the subtraction timer T4 is not timed up (in step 115). No), the conveyance by the intermediate roller 36a or the like is stopped (step 108), and when the subtraction timer T4 is up (Yes in step 109), the conveyance by the intermediate roller 36a or the like is resumed (step 110), and the process proceeds to the registration operation. To do.

  Further, as shown in FIGS. 10 and 11, the intermediate roller sensor 37a does not detect the leading edge of the succeeding paper S2, and the subtraction timer T1 expires due to the elapse of the minimum paper interval time t1 (No in step 112). ), The intermediate roller 36a and the like are increased to the second speed and high-speed conveyance is started. Further, the subtraction timer T4 for counting the subtraction of the reference position arrival expected time t4 is terminated without processing (step 116). When the intermediate roller sensor 37a detects the leading edge of the succeeding paper S2 (Yes in Step 117), the inter-sheet-measuring integration timer T2 is stopped, and the high-speed corresponding to the actual inter-paper equivalent time t2 indicated by the integration timer T2 is stopped. The remaining conveyance time t3 is determined, and a subtraction timer T3 for counting the remaining high-speed conveyance time t3 is started. Further, the integration timer T2 is reset (step 118). When the subtraction timer T3 reaches time-up due to the elapse of the high-speed conveyance remaining time t3 (Yes in step 119), the high-speed conveyance is finished, and the subsequent sheet S2 is conveyed by returning to the first speed (step 120). Migrate to

  The paper transport device and the image forming apparatus including the paper transport device according to the present invention are disadvantageous in that the synchronization between the image on the image carrier and the paper is impaired, inconvenient in terms of size, and difficult in cost reduction. And a sheet conveying apparatus for conveying a sheet as an image forming medium by an electrophotographic process or the like to an image forming unit, which has the effect of reducing the sheet interval and improving productivity without incurring It is useful as an image forming apparatus provided.

1 is a schematic configuration diagram showing an image forming apparatus to which the present invention is applied. Schematic diagram showing the configuration of the paper transport unit shown in FIG. The perspective view which shows the 1st drive mechanism of the main body side shown in FIG. FIG. 3 is a schematic perspective view for explaining an operation state of the first drive mechanism shown in FIG. 3. FIG. 3 is a schematic perspective view for explaining an operation state of the first drive mechanism shown in FIG. 3. The figure explaining the control point of the 1st drive mechanism shown in FIG. The perspective view which shows the 2nd drive mechanism by the side of the optional paper supply stand shown in FIG. FIG. 7 is a schematic perspective view for explaining an operation state of the second drive mechanism shown in FIG. FIG. 7 is a schematic perspective view for explaining an operation state of the second drive mechanism shown in FIG. FIG. 2 is a timing chart showing the operation status of the paper transport unit shown in FIG. Schematic diagram showing the operational status of the paper transport unit shown in FIG. 10 in stages. The figure which shows the table which calculates | requires the high-speed conveyance remaining time shown in FIG. The figure which shows the control result based on the table shown in FIG. The figure which shows the operation | movement condition of the timer in the control controller shown in FIG. FIG. 2 is a timing chart showing the operation status of the paper transport unit shown in FIG. Schematic diagram showing the operational status of the paper transport unit shown in FIG. FIG. 2 is a timing chart showing the operation status of the paper transport unit shown in FIG. FIG. 17 is a schematic diagram showing the operation status of the paper transport unit shown in FIG. 17 in stages. FIG. 2 is a timing chart showing the operation status of the paper transport unit shown in FIG. FIG. 2 is a timing chart showing the operation status of the paper transport unit shown in FIG. FIG. 3 is a flowchart showing a control procedure of the paper transport unit shown in FIG. FIG. 21 is a flowchart showing the control procedure of the paper transport unit following FIG.

Explanation of symbols

2 Paper transport unit (paper transport device)
4a to 4d Paper feed cassette (paper storage unit)
7 Main body 8 Optional paper supply stands 11a to 14a Photosensitive drum (image carrier)
17 Intermediate transfer belt (image carrier)
28 Secondary transfer roller (image transfer means)
31a to 31d Pickup rollers 32a to 32d Paper feed roller (paper feed means)
33a to 33d Paper feed sensor (paper feed detection means)
34a to 34d Individual conveyance path 35 Common conveyance path 36a to 36d Intermediate roller (intermediate conveyance means)
37a to 37c Intermediate roller sensor (intermediate detection means)
38 Registration Roller 39 Registration Sensor 41 Control Controller (Control Unit)
42 1st drive mechanism (1st drive means)
43 Second drive mechanism (second drive means)
S1 preceding paper, S2 subsequent paper T1 to T5 Timer t1 Minimum paper equivalent time, t2 Real paper equivalent time, t3 High-speed conveyance remaining time, t4 Reference position arrival expected time, t5 Intermediate detection position arrival time V1 First speed , V2 second speed

Claims (13)

Paper feeding means for sequentially feeding paper out of the paper storage unit;
Registration means for sending out paper in synchronization with the image on the image carrier;
Intermediate transport means for transporting paper on a paper transport path between the paper feed means and the registration means;
A driving means for driving the intermediate conveying means so as to be switchable between a first speed and a second speed higher than the first speed;
Intermediate detection means for detecting passage of paper in the vicinity of the intermediate conveyance means;
Control means for controlling the intermediate conveying means based on the detection result of the intermediate detecting means,
The control means detects the leading edge of the succeeding sheet from the time when the intermediate detecting means detects the trailing edge of the preceding sheet being conveyed at the first speed by the intermediate conveying means until the predetermined minimum interval between sheets has elapsed. Is not detected by the intermediate detection means, the high-speed conveyance of the succeeding paper is started by switching to the second speed, and the intermediate detection means detects the trailing edge of the preceding paper being conveyed at the first speed. By the way, measurement of the equivalent time between actual sheets is started, and the remaining high-speed conveyance time is obtained according to the equivalent time between actual sheets obtained when the intermediate detection means detects the leading edge of the succeeding sheet, and this remaining high-speed conveyance time has elapsed. Then, the sheet conveying apparatus characterized in that the subsequent sheet is conveyed by returning to the first speed.   2. The sheet conveying apparatus according to claim 1, wherein the control unit obtains the high-speed conveyance remaining time from the actual sheet-corresponding time based on a preset table.   When the intermediate detection unit detects the leading edge of the succeeding sheet before the time corresponding to the minimum sheet interval elapses after the intermediate detection unit detects the trailing end of the preceding sheet, the control unit 2. The intermediate transport unit is restarted when a predetermined reference position arrival expected time has elapsed after the transport unit is stopped and the registration unit resumes transport of the preceding sheet by registration processing. The sheet conveying apparatus according to claim 2. A paper feed detecting means for detecting passage of paper in the vicinity of the paper feed means;
If the intermediate detection means does not detect the trailing edge of the preceding paper even if a predetermined intermediate detection position arrival expected time has elapsed after the paper feed detection means detects the leading edge of the subsequent paper, the intermediate conveyance means 2. The intermediate transport unit is restarted when a predetermined reference position arrival time has elapsed after the registration unit resumes transport of the preceding paper by the registration process. 4. The paper conveying device according to any one of 3. A resist detection means for detecting the position of the paper in the vicinity of the upstream side of the registration means;
The control means controls the registration means based on the timing when the registration detection means detects the leading edge of the paper;
The remaining high-speed conveyance time is set so that the high-speed conveyance at the second speed is terminated and the high-speed conveyance at the first speed is returned to the standard conveyance before the leading edge of the sheet reaches the registration detection unit. The sheet conveying device according to any one of claims 1 to 4.   6. The sheet conveying apparatus according to claim 1, wherein the control unit controls the intermediate conveying unit and the sheet feeding unit in synchronization with each other. The paper feeding unit is provided for each of the plurality of paper storage units, and is configured to sequentially join the individual transport paths for the plurality of paper storage units to the common transport path to guide the paper to the image transfer unit,
The control means is based on the detection result of the intermediate detection means provided on the downstream side of the merging point between the individual conveying path and the common conveying path at the most downstream, and the merging point between the individual conveying path and the common conveying path. 7. The sheet conveying apparatus according to claim 1, wherein the plurality of intermediate conveying units provided for each of the plurality of intermediate conveying units are controlled.   The intermediate conveying means on the downstream side and the upstream side are respectively driven by different first and second driving means, and the second driving means for driving the intermediate conveying means on the upstream side is the intermediate conveying means on the downstream side. 8. The sheet according to claim 7, wherein the sheet has a characteristic that a time required to start driving of the intermediate conveying unit at a speed after speed switching is shorter than that of the first driving unit that drives the unit. Conveying device.   The control means delays the speed switching timing of the intermediate transport means on the upstream side from the intermediate transport means on the downstream side when switching from high speed transport at the second speed to standard transport at the first speed. The sheet conveying apparatus according to claim 7 or 8.   10. The control unit according to claim 7, wherein when the intermediate transport unit is stopped, the control unit delays the stop start timing of the upstream intermediate transport unit from the downstream intermediate transport unit. 11. The paper conveying device according to claim 1.   The time counting means for measuring a time serving as a reference for controlling the intermediate conveying means increases or decreases a count amount per unit time according to a speed ratio between the first speed and the second speed. The paper transport device according to claim 1.   The high-speed conveyance is performed at the second speed from the time of sheet feeding until the sheet reaches the registration unit when there is no preceding sheet on the conveyance path from the sheet feeding unit to the registration unit. The paper transport device according to claim 1.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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