JP2015164873A - Paper feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder which can reduce noise.SOLUTION: A paper feeder includes: a resist roller 14 which conveys paper PA to a printing part 3; a paper feed roller 12 which conveys the paper PA on a paper feeding table 11 to the resist roller 14; and a control part which starts the resist roller 14 after the paper feed roller 12 is stopped when the paper PA conveyed by the paper feed roller 12 abuts on the resist roller 14 and a predetermined amount of slack is formed on the paper PA, and then starts the paper feed roller 12 and controls so as to maintain constant speed difference between conveyance speed by the resist roller 14 and conveyance speed by the paper feed roller 12 until the slack of the paper PA is eliminated. The control part controls the resist roller 14 and the paper feed roller 12 in response to a paper feed mode selected from a standard mode and a highly-silent mode in which the speed differences between the conveyance speed by the resist roller 14 and the conveyance speed by the paper feed roller 12 at a time point when the slack is eliminated are different from each other.

Description

  The present invention relates to a paper feeding device that feeds a printing medium.

  2. Description of the Related Art Conventionally, a paper feeding device that is provided in a printing device and transports a sheet taken out from a paper feeding table to a printing unit by a registration roller is known. In such a paper feeding device, the paper is abutted against the registration roller and temporarily stopped to form a slack in the paper, thereby correcting the skew of the paper. Thereafter, the registration roller is driven to feed the paper to the printing unit.

  In such a paper feeding device, when the paper slack is eliminated when the registration roller sends out the paper, noise (due to back tension) between the registration roller and the upstream roller is generated. (Paper sound) may occur.

  On the other hand, Patent Document 1 discloses a paper feed mechanism that performs an assist operation for driving a roller on the upstream side of a registration roller while the registration roller is being driven.

  In the paper feed mechanism disclosed in Patent Document 1, when feeding from the side paper feed tray, the primary paper feed roller picks up the paper from the side paper feed tray, and abuts the paper against the registration roller to form a slack in the paper. Then, the primary paper feed roller starts an assist operation with the activation of the registration roller.

  Specifically, the primary paper feed roller is activated simultaneously with the registration roller. After startup, the primary paper feed roller is accelerated at a smaller acceleration than the registration rollers. Thereby, the speed difference between the conveyance speed by the registration rollers and the conveyance speed by the primary paper feed roller gradually increases. As a result, the sag of the paper is gradually reduced and eliminated. When the slack of the paper is eliminated, the primary paper feed roller stops and the assist operation ends. Since the primary paper feed roller picks up and conveys the paper, an assist operation is performed before the trailing edge of the paper to be fed reaches the primary paper feed roller so that the next paper is not mistakenly conveyed. finish.

  With the assist operation as described above, the paper feed mechanism disclosed in Patent Document 1 is configured such that the back tension of the sheet when the sag is eliminated is smaller than when the assist operation is not performed. Thereby, noise due to the back tension of the paper is reduced.

JP 2010-215389 A

  As described above, in the assist operation of Patent Document 1, the primary paper feed roller is activated simultaneously with the registration roller. Therefore, at the start of the assist operation, the speed difference between the two rollers is zero. In order to eliminate the slack of the sheet from this state to the timing when the assist operation is finished, it is necessary to increase the difference in acceleration between both rollers to some extent. This is because the greater the difference in acceleration between the two rollers, the faster the speed difference increases between the two rollers and the faster the slack reduction.

  The smaller the speed difference between the rollers at the time of eliminating the sagging of the paper, the smaller the back tension of the paper. However, in the assist operation of Patent Document 1 as described above, the difference in acceleration between the two rollers is large, and thus the speed difference between the two rollers at the time of eliminating the sagging of the sheet cannot be sufficiently reduced. For this reason, the paper feed mechanism disclosed in Patent Document 1 is not sufficient in reducing the noise caused by the back tension of the paper.

  The present invention has been made in view of the above, and an object thereof is to provide a paper feeding device capable of reducing noise.

  In order to achieve the above object, the paper feeding device according to the present invention is characterized by a registration roller that conveys a print medium to a printing unit of the printing device, and a registration roller that picks up the printing medium loaded on the paper feed table and When a predetermined amount of slack is formed on the printing medium when the printing roller conveyed to the printing medium and the printing medium conveyed by the feeding roller abut against the registration roller, the feeding roller is stopped, and then the registration A control unit that activates the roller, then activates the paper feed roller, and controls the conveyance speed by the registration roller to be higher than the conveyance speed by the paper feed roller until slack in the print medium is eliminated, A plurality of different difference in speed between the transport speed by the registration roller and the transport speed by the paper feed roller at the time of eliminating the sagging of the print medium. Depending on the paper feeding mode selected from a paper mode is to control the registration roller and the paper feed roller.

  According to the feature of the sheet feeding device according to the present invention, the control unit activates the sheet feeding roller after the registration roller is activated, and the conveyance speed by the registration roller is the conveyance speed by the sheet feeding roller until the slack of the printing medium is eliminated. Control to be faster than speed. As a result, the speed difference between the registration roller and the paper feed roller at the time of eliminating the slack in the print medium can be suppressed, and noise due to the back tension of the print medium can be reduced. In addition, the control unit can suppress the noise caused by the back tension of the print medium by selecting a paper feed mode in which the speed difference between the registration roller and the paper feed roller is small when the slack of the print medium is eliminated. It becomes possible. Thus, according to the 1st characteristic of the paper feeder concerning the present invention, noise can be reduced.

1 is a block diagram illustrating a configuration of a printing apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of a paper feeding unit and a printing unit of the printing apparatus shown in FIG. 1. 6 is a timing chart showing changes in the conveyance speed of a paper feed roller and a registration roller in a standard mode. It is a figure for demonstrating the speed difference between the registration roller and paper feed roller in standard mode. It is explanatory drawing of the amount of sagging. 6 is a timing chart showing transitions of conveyance speeds of a paper feed roller and a registration roller in a high silent mode. It is a figure for demonstrating the method of determining the maximum speed of the registration roller in a high silent mode. 6 is a timing chart showing a transition of a conveyance speed of a sheet feeding roller and a registration roller and a transition of a slack amount of a sheet in a comparative example. 6 is a timing chart illustrating a specific example of a transition of a conveyance speed of a sheet feeding roller and a registration roller and a transition of a slack amount of a sheet in an assist operation in a standard mode. 6 is a timing chart showing a specific example of a change in conveyance speed of a paper feed roller and a registration roller and a change in the amount of slack in a sheet in an assist operation in a high-silence mode.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a block diagram illustrating a configuration of a printing apparatus including a paper feeding device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a paper feeding unit and a printing unit of the printing apparatus shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. In addition, the top, bottom, left, and right of the paper surface in FIG. In FIG. 2, the direction from left to right is the conveyance direction of the paper PA. In the following description, upstream and downstream mean upstream and downstream in the conveyance direction of the paper PA.

  As shown in FIG. 1, the printing apparatus 1 according to the present embodiment includes a paper feeding unit 2, a printing unit 3, an image reading unit 4, an operation panel unit 5, and a control unit 6. The paper feeding device includes a paper feeding unit 2 and a control unit 6.

  The paper feeding unit 2 feeds paper PA, which is a printing medium, to the printing unit 3. As shown in FIGS. 1 and 2, the paper feed unit 2 includes a paper feed table 11, a pair of paper feed rollers 12, a paper feed motor 13, a pair of registration rollers 14, and a registration motor 15.

  The paper feed table 11 is used for loading paper PA used for printing.

  The paper feed roller 12 picks up the paper PA stacked on the paper feed tray 11 one by one and conveys it to the registration roller 14. The paper feed roller 12 performs an assist operation for assisting the conveyance of the paper PA by the registration roller 14. The paper feed roller 12 is disposed above the downstream end of the paper feed table 11.

  The paper feed motor 13 rotates the paper feed roller 12.

  The registration roller 14 temporarily stops the paper PA conveyed by the paper supply roller 12, and after the slack is formed on the paper PA, conveys the paper PA toward the printing unit 3 while nipping the paper PA. The registration roller 14 is disposed on the downstream side of the paper feed roller 12. When a predetermined amount of slack is formed on the paper PA abutted against the registration roller 14, the registration roller 14 does not reach the upstream (left side) paper supply roller 12 at the rear end of the paper PA ( It is arranged at such a position that the upstream paper feed roller 12 is not removed.

  The registration motor 15 rotates the registration roller 14.

  The printing unit 3 performs printing on the paper PA while conveying the fed paper PA. As shown in FIGS. 1 and 2, the printing unit 3 includes a belt conveyance unit 21 and an inkjet head unit 22.

  The belt transport unit 21 transports the paper PA fed by the paper feed unit 2. The belt conveyance unit 21 is disposed on the downstream side of the registration roller 14. The belt conveyance unit 21 includes a conveyance belt 31, a driving roller 32, driven rollers 33, 34, and 35, and a belt motor 36.

  The conveyor belt 31 sucks and holds the paper PA and conveys it. The conveyor belt 31 is an annular belt that is stretched around the driving roller 32 and the driven rollers 33 to 35. A number of through holes are formed in the transport belt 31. The conveyance belt 31 adsorbs and holds the paper PA on the upper surface (conveyance surface) by the adsorption force generated in the through hole by driving a fan (not shown). The conveyance belt 31 rotates in the clockwise direction in FIG. 2 and conveys the sheet PA held by suction from the left to the right.

  The driving roller 32 supports the conveyor belt 31 together with the driven rollers 33 to 35 and rotates the conveyor belt 31.

  The driven rollers 33 to 35 support the conveying belt 31 together with the driving roller 32. The driven rollers 33 to 35 are driven by the driving roller 32 via the conveyance belt 31. The driven roller 33 has the same height as the drive roller 32 and is disposed on the left side of the drive roller 32. The driven rollers 34 and 35 are spaced apart from each other in the left-right direction below the driving roller 32 and the driven roller 33 and are disposed at the same height.

  The belt motor 36 drives the drive roller 32 to rotate.

  The inkjet head unit 22 has a plurality of inkjet heads each having a plurality of nozzles arranged in the front-rear direction. The inkjet head unit 22 is disposed above the belt conveyance unit 21. The ink jet head unit 22 prints an image by ejecting ink from the ink jet head onto the paper PA transported by the belt transport unit 21.

  The image reading unit 4 optically reads an image of a document and generates image data.

  The operation panel unit 5 accepts an input operation by a user and displays various types of information. The operation panel unit 5 includes an input unit having operation buttons and a touch panel, and a display unit (none of which is shown) including a liquid crystal display panel or the like.

  The control unit 6 controls the operation of each unit of the printing apparatus 1. The control unit 6 includes a CPU, RAM, ROM, hard disk, and the like.

  Specifically, the control unit 6 feeds the paper PA to the printing unit 3 by the paper feeding unit 2 and discharges the ink by the ink jet head unit 22 while transporting the paper PA by the belt transport unit 21. Control to print to

  In the paper feeding operation by the paper feeding unit 2, the control unit 6 drives the paper feeding roller 12 so that the paper PA conveyed by the paper feeding roller 12 hits the registration roller 14 and a predetermined amount of slack is formed on the paper PA. Then, the paper feed roller 12 is stopped. After stopping the paper feed roller 12, the control unit 6 activates the registration roller 14. When the registration roller 14 is driven, the control unit 6 executes an assist operation in which the paper feed roller 12 assists the registration roller 14. In the assist operation, the control unit 6 activates the paper feed roller 12 after the registration roller 14 is activated, and the speed difference between the conveyance speed by the registration roller 14 and the conveyance speed by the paper supply roller 12 until the slack of the paper PA is eliminated. Is controlled to be constant.

  The control unit 6 can select a standard mode or a high-silence mode as a paper feed mode when performing a paper feed operation. The standard mode is a mode for printing with standard productivity in the printing apparatus 1. In the high-silence mode, noise due to the back tension of the paper PA is standardized so that the speed difference between the conveyance speed by the registration roller 14 and the conveyance speed by the paper feed roller 12 at the time of eliminating the slack of the paper PA is smaller than that in the standard mode. This mode reduces the mode. In the high silent mode, the productivity of printed matter is lower than in the standard mode. In the paper feeding operation, the control unit 6 controls the paper feeding roller 12 and the registration roller 14 according to the selected paper feeding mode.

  Next, an operation during printing of the printing apparatus 1 will be described.

  When the start of printing is instructed, the control unit 6 causes the belt motor 36 to start driving the belt conveyance unit 21. Here, when the document read by the image reading unit 4 is printed, the control unit 6 determines that the start of printing is instructed when an operation for starting printing is performed on the operation panel unit 5. In this case, the control unit 6 causes the image reading unit 4 to read an image of the document. On the other hand, when printing is performed based on the print data received from the external terminal, when receiving the print data, the control unit 6 determines that the start of printing has been instructed.

  When the start of printing is instructed, the control unit 6 selects the standard mode or the high-silence mode as the paper feed mode. When printing a document read by the image reading unit 4, the control unit 6 selects a standard mode or a high-silence mode based on a user operation on the operation panel unit 5. On the other hand, when printing is performed based on print data received from an external terminal, the control unit 6 selects a standard mode or a high-silence mode based on setting information included in the print data.

  After starting the driving of the belt conveyance unit 21, the control unit 6 controls the paper feeding unit 2 according to the selected paper feeding mode to feed the paper PA to the printing unit 3. When printing a plurality of sheets, the control unit 6 sequentially feeds the paper PA from the paper feeding unit 2.

  The fed paper PA is transported by the belt transport unit 21 in the printing unit 3. The belt transport unit 21 transports the paper PA at the print transport speed Vg. The control unit 6 controls the inkjet head unit 22 based on the image data of the document read by the image reading unit 4 or the print data received from the external terminal, and causes the image to be printed on the conveyed paper PA. The printed paper PA is discharged by a paper discharge unit (not shown).

  Next, a standard mode paper feeding operation in the paper feeding unit 2 will be described.

  FIG. 3 is a timing chart showing changes in the conveyance speed of the paper feed roller 12 and the registration roller 14 in the standard mode. In FIG. 3, the upper row shows the change in the conveyance speed of the registration roller 14, and the lower row shows the change in the conveyance speed of the paper feed roller 12.

  At time t <b> 1 in FIG. 3, which is the activation timing of the paper feed roller 12 for normal conveyance, the control unit 6 activates the paper feed roller 12 by the paper feed motor 13. As a result, the uppermost paper PA on the paper feed tray 11 is picked up by the paper feed roller 12 and begins to be conveyed toward the registration roller 14.

  When the conveyance speed of the paper feed roller 12 reaches the maximum speed Vs, the control unit 6 maintains the paper feed roller 12 at the maximum speed Vs for a predetermined time and then stops it. Between the time t1 when the paper feed roller 12 is activated and the time t2 when it is stopped, the leading edge of the paper PA hits the registration roller 14, and a slack of a predetermined amount of slack Lt is formed on the paper PA. The operation from time t1 to time t2 is the normal conveyance operation in the paper feed roller 12.

  The control unit 6 activates the registration roller 14 by the registration motor 15 at time t <b> 3, which is the activation timing of the registration roller 14, after the normally transported paper feed roller 12 is stopped. The activation timing of the registration roller 14 is set a predetermined time after the stop of the paper feed roller 12 in the normal conveyance. After the registration roller 14 is activated, the control unit 6 accelerates at a predetermined acceleration α1.

  After activation of the registration roller 14, at time t4, which is the start timing of the assist operation, the control unit 6 activates the paper feed roller 12 by the paper feed motor 13 for the assist operation. The controller 6 accelerates the paper feed roller 12 at the same acceleration α1 as the registration roller 14 after the paper feed roller 12 is activated. During acceleration of the registration roller 14 and the paper feed roller 12, the sag of the paper PA is gradually reduced due to the difference in speed between the registration roller 14 and the paper feed roller 12, and eliminated.

  When the paper feed roller 12 reaches the maximum speed Vs, the control unit 6 drives the paper feed roller 12 at the maximum speed Vs at a constant speed from the time t5 for a predetermined time. Then, the control unit 6 starts the deceleration of the paper feed roller 12 at time t6 and stops the paper feed roller 12 at time t7. Thereby, the assist operation of the paper feed roller 12 is completed. The assist operation ends before the trailing edge of the paper PA reaches the upstream (left side) paper feed roller 12 (before passing through the upstream paper feed roller 12). This is to prevent the paper feed roller 12 from erroneously transporting the next paper PA.

  The registration roller 14 is accelerated at an acceleration α1 until it reaches the maximum speed Vt after starting at time t3. When the registration roller 14 reaches the maximum speed Vt, the controller 6 drives the registration roller 14 at the maximum speed Vt at a constant speed from the time t8 for a predetermined time. Then, the control unit 6 starts decelerating at a predetermined deceleration acceleration α2 of the registration roller 14 at time t9.

  When the conveyance speed by the registration rollers 14 is reduced to the printing conveyance speed Vg, the control unit 6 drives the registration rollers 14 at a constant speed at the printing conveyance speed Vg for a predetermined time from the time t10. The print conveyance speed Vg is a conveyance speed of the paper PA by the belt conveyance unit 21. When the leading edge of the sheet PA reaches the upstream end (left end) of the upper surface (conveying surface) of the conveying belt 31, the conveying speed by the registration roller 14 is reduced to the printing conveying speed Vg.

  Then, the control unit 6 starts decelerating the registration roller 14 at the deceleration acceleration α2 from the print conveyance speed Vg at time t11, and stops the registration roller 14 at time t12. Thereby, the conveying operation of the registration roller 14 is completed. The timing (time t11) is set so that when the trailing edge of the paper PA passes through the registration roller 14, deceleration for stopping the registration roller 14 is started.

  In the case where a plurality of sheets of paper PA are continuously fed, the control unit 6 performs the above-described feeding operation for each paper PA at a time interval of feeding at a predetermined paper interval time Ts. The inter-paper time Ts is a time corresponding to the transport time corresponding to the distance between the trailing edge of the preceding paper PA and the leading edge of the succeeding paper PA at the print transport speed Vg.

  Next, the speed difference between the registration roller 14 and the paper feed roller 12 in the above-described standard mode paper feed operation will be described.

  As shown in FIG. 4, when the time from the activation timing (time t3) of the registration roller 14 to the activation timing (time t4) of the paper feed roller 12 in the assist operation is T1, the registration roller at the time when the paper feed roller 12 is activated. The conveyance speed of 14 is α1 × T1. Accordingly, the speed difference ΔV between the registration roller 14 and the paper feed roller 12 is α1 × T1 when the paper feed roller 12 is activated in the assist operation.

  Since both the registration roller 14 and the paper feed roller 12 are accelerated at the acceleration α1, the speed difference ΔV = α1 × T1 is maintained until the paper feed roller 12 reaches the maximum speed Vs. Due to this speed difference ΔV, the sag of the paper PA gradually decreases.

  Here, the smaller the back tension of the paper PA at the time of eliminating the sag, the smaller the noise caused by the back tension. The back tension of the paper PA at the time of eliminating the sag becomes smaller as the speed difference between the registration roller 14 and the paper feed roller 12 at that time becomes smaller.

  Since the acceleration α1 is a fixed value, the speed difference ΔV is smaller as the time T1 is shorter. For this reason, in order to reduce the back tension of the paper PA at the time of eliminating the sag, it is better that the time T1 is short.

  However, the smaller the speed difference ΔV, the slower the rate of decrease in the slack of the paper PA. For this reason, if the time T1 is too short, the sag cannot be eliminated until the paper feed roller 12 reaches the maximum speed Vs. After the paper feed roller 12 reaches the maximum speed Vs, the speed difference between the registration roller 14 and the paper feed roller 12 widens, leading to an increase in the back tension of the paper PA when the sag is eliminated.

  For this reason, the time T1 is set such that the speed difference ΔV is minimized within a range in which the sag of the sheet PA of the sag amount Lt can be eliminated before the paper feed roller 12 reaches the maximum speed Vs. As a result, the speed difference between the registration roller 14 and the paper feed roller 12 when the slack is eliminated becomes equal to the speed difference ΔV when the paper feed roller 12 is activated.

  Here, as shown in FIG. 4, it is assumed that the time from time t3 to time t5 is T2, and the sagging of the paper PA is eliminated at time t5. In this case, the difference ΔL between the conveyance amount by the registration rollers 14 from time t3 to t5 and the conveyance amount by the paper feed roller 12 from time t4 to t5 is equal to the sag amount Lt. ΔL corresponds to the area of a region indicated by hatching in FIG. Therefore, the following formula (1) is established.

Lt = (α1 × T2 ² ) / 2− (α1 × (T2−T1) ² ) / 2 (1)
Further, from the above equation (1), the following equation (2) representing the time T2 during which the sag is eliminated is derived.

T2 = T1 / 2 + Lt / (α1 × T1) (2)
Here, as shown in FIG. 5, the amount of sag Lt is obtained when the paper PA is slacked by an appropriate amount to correct the skew of the paper PA when the paper PA is abutted against the registration roller 14. This is a reduction for the original length Lp of the paper PA. The slack amount Lt is set according to the paper type of the paper PA.

  Next, the sheet feeding operation in the high silent mode will be described.

  FIG. 6 is a timing chart showing changes in the conveyance speed of the paper feed roller 12 and the registration roller 14 in the high-silence mode. In FIG. 6, the upper row shows the change in the conveyance speed of the registration roller 14, and the lower row shows the change in the conveyance speed of the paper feed roller 12. The normal conveyance operation of the paper feed roller 12 is the same as that in the standard mode shown in FIG. 3, and is not shown in FIG. For comparison, the transition of the conveyance speeds of the paper feed roller 12 and the registration roller 14 in the standard mode described above is also shown in FIG.

  At time t <b> 3 in FIG. 6, which is the activation timing of the registration roller 14, the control unit 6 activates the registration roller 14 with the registration motor 15. After the registration roller 14 is activated, the control unit 6 accelerates at the acceleration α3. The acceleration α3 is smaller than the acceleration α1 in the standard mode described above.

  After activation of the registration roller 14, at time t21, which is the start timing of the assist operation, the control unit 6 activates the paper feed roller 12 by the paper feed motor 13 for the assist operation. The controller 6 accelerates the paper feed roller 12 at the same acceleration α3 as the registration roller 14 after the paper feed roller 12 is activated. During acceleration of the registration roller 14 and the paper feed roller 12, the sag of the paper PA is gradually reduced due to the difference in speed between the registration roller 14 and the paper feed roller 12, and eliminated.

  When the paper feed roller 12 reaches the maximum speed Vs, the control unit 6 drives the paper feed roller 12 at the maximum speed Vs at a constant speed from the time t22 for a predetermined time. Then, the control unit 6 starts deceleration of the paper feed roller 12 at time t23 and stops the paper feed roller 12 at time t24. Thereby, the assist operation of the paper feed roller 12 is completed.

  The registration roller 14 is accelerated at an acceleration α3 until it reaches the maximum speed Vu after being activated at time t3. When the registration roller 14 reaches the maximum speed Vu, the control unit 6 drives the registration roller 14 at the maximum speed Vu at a constant speed from the time t25 for a predetermined time. Then, the control unit 6 starts decelerating at a predetermined deceleration acceleration α2 of the registration roller 14 at time t26. The maximum speed Vu of the registration roller 14 in the high silent mode is smaller than the maximum speed Vt of the registration roller 14 in the standard mode described above.

  When the conveyance speed by the registration rollers 14 is reduced to the printing conveyance speed Vg, the controller 6 drives the registration rollers 14 at a constant speed at the printing conveyance speed Vg for a predetermined time from the time t27. Then, the control unit 6 starts decelerating the registration roller 14 at the deceleration acceleration α2 from the print conveyance speed Vg at time t28, and stops the registration roller 14 at time t29. Thereby, the conveying operation of the registration roller 14 is completed.

  When the time from the activation timing (time t3) of the registration roller 14 in the high-silence mode to the activation timing (time t21) of the paper feed roller 12 in the assist operation is T3, the conveyance of the registration roller 14 at the time of activation of the paper feed roller 12 is performed. The speed is α3 × T3. Accordingly, the speed difference ΔV between the registration roller 14 and the paper feed roller 12 is α3 × T3 when the paper feed roller 12 is activated in the assist operation.

  As the acceleration α3, an arbitrary value smaller than the acceleration α1 in the standard mode is set. Then, at the acceleration α3, the time T3 is set so that the speed difference ΔV is minimized within a range in which the sagging of the sheet PA of the sagging amount Lt before the paper feeding roller 12 reaches the maximum speed Vs can be eliminated.

  Since the acceleration α3 is smaller than the acceleration α1 in the standard mode, the time during which the speed difference ΔV at the start time of the paper feed roller 12 in the assist operation is maintained is longer in the high-silence mode than in the standard mode. For this reason, in the high-silence mode, it is possible to eliminate the sag during the period in which the speed difference ΔV is maintained with a smaller speed difference ΔV than in the standard mode. Therefore, a value is set as the time T3 such that the speed difference ΔV is smaller than that in the standard mode.

  As a result, in the high-silence mode, the speed difference between the registration roller 14 and the paper feed roller 12 at the time of eliminating the sag is smaller than in the standard mode. For this reason, in the high-silence mode, noise due to the back tension of the paper PA when the sag is eliminated can be reduced as compared with the standard mode.

  As the acceleration α3 is smaller, the speed difference ΔV can be reduced, and noise due to the back tension of the paper PA when the sag is eliminated can be further reduced.

  Further, in the high-silence mode, the acceleration of the paper feed roller 12 and the registration roller 14 is smaller than that in the standard mode, so that the maximum power consumption of the paper feed motor 13 and the registration motor 15 is reduced.

  Since the acceleration α3 is smaller than the acceleration α1 in the standard mode, the maximum speed Vu of the registration roller 14 in the high silent mode is set to a speed slower than the maximum speed Vt in the standard mode. A method for determining the maximum speed Vu will be described.

  The conveyance speed by the registration rollers 14 needs to be the print conveyance speed Vg when the leading edge of the paper PA reaches the upstream end (left end) of the upper surface (conveyance surface) of the conveyance belt 31. The maximum speed Vu is determined so as to satisfy this condition.

  Specifically, the maximum speed Vu is determined so that the conveyance distance corresponding to the area of the quadrangle shown in FIG. 7 is equal to the distance obtained by subtracting the predetermined margin Lm from the distance Ls shown in FIG. The distance Ls is a distance from the nip point of the registration roller 14 to the upstream end (left end) of the upper surface (conveying surface) of the conveying belt 31.

  The square area in FIG. 7 indicates the conveyance distance by the registration roller 14 until the printing conveyance speed Vg is decelerated when the deceleration starts when the registration roller 14 reaches the maximum speed Vu. It is. If this transport distance is equal to the distance obtained by subtracting the margin Lm from the distance Ls, the following expression (3) is established.

Ls−Lm = Vu ² / (2 × α3)
+ (Vu + Vg) × (Vu−Vg) / (2 × | α2 |) (3)
From the above equation (3), the following equation (4) is derived.

The maximum speed Vu of the registration roller 14 in the high silent mode is determined by the above equation (4).

  In this way, the maximum speed Vu is determined, and the distance corresponding to the margin Lm is controlled so as to be conveyed in the constant speed driving period (time t25 to t26 in FIG. 6) at the maximum speed Vu of the registration roller 14. This makes it possible to absorb variations in the operation of the registration rollers 14 by adjusting the length of the constant speed driving period at the maximum speed Vu.

  Next, the interval between sheets in the high-silence mode paper feeding operation will be described.

  As can be seen from FIG. 6, in the high-silence mode, the operation time, which is the time from the start to the stop of the registration roller 14, is longer than that in the standard mode. For this reason, in the high-silence mode, the paper interval (inter-paper time) during continuous paper feeding is made longer than that in the standard mode by the length of the operation time of the registration roller 14.

  Accordingly, when the operation time of the registration roller 14 in the standard mode is Tra, the operation time of the registration roller 14 in the high-silence mode is Trb, and the paper interval time Ts in the standard mode, the paper interval time Tu in the high-silence mode is It is represented by (5).

Tu = Ts + (Trb−Tra) (5)
Here, the operation time Trb of the registration roller 14 in the high-silence mode is the sum of the times Ta, Tb, Tc, Td, and Te shown in FIG. Time Ta is time t3 to t25, time Tb is time t25 to t26, time Tc is time t26 to t27, time Td is time t27 to t28, and time Te is time t28 to t29.

  The times Ta to Te are represented by the following formulas (6) to (10).

Ta = Vu / α3 (6)
Tb = Lm / Vu (7)
Tc = (Vu−Vg) / | α2 | (8)
Td = (Lp−Ls) / Vg (9)
Te = Vg / | α2 | (10)
Therefore, the operation time Trb of the registration roller 14 in the high-silence mode is expressed by the following formula (11).

Trb = Vu / α3 + Lm / Vu + (Vu−Vg) / | α2 |
+ (Lp−Ls) / Vg + Vg / | α2 | (11)
The operation time Tra of the registration roller 14 in the standard mode can be calculated by an equation in which Trb in the above equation (11) is replaced with Tra, α3 with α1, and Vu with Vt.

  Next, a specific example of the transition of the conveyance speed of the paper feed roller 12 and the registration roller 14 during the assist operation and the transition of the slack amount of the paper PA, including a comparative example, will be described.

  FIG. 8 is a timing chart showing the transition of the conveyance speed of the paper feed roller 12 and the registration roller 14 and the transition of the amount of sagging of the paper PA in the comparative example. The assist operation of this comparative example is an example of a conventional assist operation different from the present embodiment. In this comparative example, the paper feed roller 12 is activated simultaneously with the registration roller 14. The paper feed roller 12 is accelerated at a smaller acceleration than that of the registration roller 14 after being activated. As a result, the speed difference between the registration roller 14 and the paper feed roller 12 is gradually increased, and the slack of the paper PA is gradually reduced accordingly.

In the example of FIG. 8, the acceleration α5 of the sheet feeding roller 12 is 12500 mm / s ² while the acceleration α4 of the registration roller 14 is 25000 mm / s ² . Further, the slack amount Lt of the paper PA when the registration roller 14 is activated is 6 mm.

  In FIG. 8, when the time from the start of the paper feed roller 12 and the registration roller 14 to the elimination of the slack of the paper PA is T11, the following equation (12) is established.

Lt = (α4 × T11 ² ) / 2− (α5 × T11 ² ) / 2 (12)
Further, the speed difference ΔVa between the registration roller 14 and the paper feed roller 12 at the time of eliminating the slack of the paper PA is obtained by the following equation (13).

ΔVa = α4 × T11−α5 × T11 (13)
From Expressions (12) and (13), when α4 = 25000 mm / s ² , α5 = 12,500 mm / s ² , and Lt = 6 mm as described above, T11 = 0.031 s and ΔVa = 387 mm / s.

  FIG. 9 is a timing chart showing a specific example of changes in the conveyance speeds of the paper feed roller 12 and the registration roller 14 and changes in the amount of sagging of the paper PA in the assist operation in the standard mode according to this embodiment.

In the example of FIG. 9, the acceleration α1 of the registration roller 14 and the paper feed roller 12 = 25000 mm / s ² . This is the same value as the acceleration α4 of the registration roller 14 in the example of FIG. In the example of FIG. 9 as well, as in the example of FIG. 8, the amount of sag Lt of the paper PA when the registration roller 14 is started is Lt = 6 mm. Further, in the example of FIG. 9, the time T1 from the activation timing of the registration roller 14 to the activation timing of the paper feed roller 12 in the assist operation is 0.009 s.

In the example of FIG. 9, the maximum speed Vt of the registration roller 14 is 1289 mm / s, the deceleration acceleration α2 of the registration roller 14 is −40000 mm / s ² , and the print conveyance speed Vg is 632 mm / s. Further, in the example of FIG. 9, the length Lp in the conveyance direction of the paper PA is 210 mm, the distance from the nip point of the registration roller 14 to the upstream end (left end) of the upper surface (conveyance surface) of the conveyance belt 31 is Ls = 55 mm, the distance The margin Lm with respect to Ls = 6 mm, and the paper interval time Ts = 0.0592 s.

From the above equation (2), when α1 = 25000 mm / s ² , Lt = 6 mm, and T1 = 0.000 s as in the example of FIG. 9, from the start of the registration roller 14 to the point when the slack of the paper PA is eliminated. Time T2 = 0.0315 s.

Further, as described above, in the present embodiment, the speed difference ΔV between the registration roller 14 and the paper feed roller 12 when the paper feed roller 12 is started is maintained until the paper PA sag is eliminated. Accordingly, in the example of FIG. 9, the speed difference ΔVb between the registration roller 14 and the paper feed roller 12 at the time point when the slack of the paper PA is eliminated is ΔVb = α1 × T1. When α1 = 25000 mm / s ² and T1 = 0.09 s as in the example of FIG. 9, ΔVb = 225 mm / s.

  Thus, the speed difference ΔVb in the example of FIG. 9 is smaller than the speed difference ΔVa in the example of FIG. Accordingly, in the example of FIG. 9, noise due to the back tension of the paper PA is smaller than in the example of FIG.

  Here, for comparison with the example of FIG. 10 described later, the productivity of the printed matter in the example of FIG. 9 is calculated. The productivity of printed matter is the number of printed sheets per minute (60 s).

  The productivity P1 [ppm] in the example of FIG. 9 is calculated by the following equation (14).

P1 = 60 / (Lp / Vg + Ts) (14)
Therefore, when Lp = 210 mm, Vg = 632 mm / s, and Ts = 0.0592 s as in the example of FIG. 9, P1 = 153 ppm.

  FIG. 10 is a timing chart showing a specific example of the transition of the conveyance speed of the paper feed roller 12 and the registration roller 14 and the transition of the amount of sag of the paper PA in the assist operation in the high-silence mode according to the present embodiment.

In the example of FIG. 10, the acceleration α3 = 12,500 mm / s ² of the registration roller 14 and the paper feed roller 12. Further, the time from the activation timing of the registration roller 14 to the activation timing of the paper feed roller 12 in the assist operation is T3 = 0.111 s. The values of the deceleration acceleration α2, the print conveyance speed Vg, the sag amount Lt, the paper length Lp, the distance Ls, and the margin Lm are the same as in the example of FIG.

From the above equation (4), when α2 = −40000 mm / s ² , α3 = 12,500 mm / s ² , Vg = 632 mm / s, Ls = 55 mm, Lm = 6 mm as in the example of FIG. The maximum speed Vu is 1014 mm / s.

The time T4 from the start of the registration roller 14 in the high-silence mode to the time point when the slack of the paper PA is eliminated is calculated by an equation in which T2 is replaced with T4, T1 is replaced with T3, and α1 is replaced with α3. Is done. Therefore, when α3 = 12,500 mm / s ² , Lt = 6 mm, and T3 = 0.011 s as in the example of FIG. 10, T4 = 0.049 s.

In the example of FIG. 10, the speed difference ΔV between the registration roller 14 and the paper feed roller 12 when the paper feed roller 12 is activated is α3 × T3. Therefore, the speed difference ΔVc = α3 × T3 between the registration roller 14 and the paper feed roller 12 at the time when the slack of the paper PA is eliminated. When α3 = 12,500 mm / s ² and T3 = 0.011 s as in the example of FIG. 10, ΔVc = 137.5 mm / s.

  Thus, the speed difference ΔVc at the time of eliminating the sag in the example of FIG. 10 is smaller than the speed difference ΔVb in the example of FIG. Therefore, in the example of the high-silence mode in FIG. 10, the noise due to the back tension when the sagging of the paper PA is eliminated is smaller than in the example of the standard mode in FIG.

From the above equation (11), α2 = −40000 mm / s ² , α3 = 12,500 mm / s ² , Vu = 1014 mm / s, Vg = 632 mm / s, Lp = 210 mm, Ls = 55 mm, as in the example of FIG. When Lm = 6 mm, the operation time Trb = 0.358 s of the registration roller 14 is obtained.

  On the other hand, as described above, the operation time Tra of the registration roller 14 in the standard mode can be calculated by an expression in which Trb in Expression (11) is replaced with Tra, α3 is replaced with α1, and Vu is replaced with Vt. Therefore, in the example of FIG. 9 described above, the operation time Tra of the registration roller 14 is 0.334 s.

  Further, as described above, the inter-paper time Ts in the example of the standard mode in FIG. 9 is 0.0592 s. Therefore, from the above equation (5), the inter-paper time Tu = 0.083 s in the example of FIG.

  The productivity P2 [ppm] in the example of FIG. 10 can be calculated by an equation in which P1 in Equation (15) is replaced with P2 and Ts is replaced with Tu. When Lp = 210 mm, Vg = 632 mm / s, and Tu = 0.083 s as in the example of FIG. 10, P2 = 144 ppm. This is smaller than the productivity P1 = 153 ppm in the example of FIG.

  As described above, in the high-silence mode, productivity is lower than that in the standard mode, but noise due to back tension when the sag of the paper PA is eliminated is suppressed to a small level. The high-silence mode is suitable when quietness is more important than productivity.

  As described above, in the printing apparatus 1 according to the present embodiment, the control unit 6 activates the paper feed roller 12 after the registration roller 14 is activated in the assist operation by the paper feed roller 12, so Provide speed difference. Then, the control unit 6 controls the speed difference between the two rollers to be constant until the slack of the paper PA is eliminated. As a result, the speed difference between the two rollers at the time of eliminating the slack of the paper PA can be kept small, and noise due to the back tension of the paper PA can be reduced. In the printing apparatus 1, the standard mode or the high-silence mode can be selected as the paper feed mode. By selecting the high-silence mode, the speed difference between the registration roller 14 and the paper feed roller 12 can be further reduced, and noise due to the back tension of the paper PA can be further reduced. As described above, according to the printing apparatus 1, it is possible to reduce noise in the paper feeding operation by the paper feeding unit 2.

  Here, the acceleration of the paper feed roller 12 in the conventional assist operation as shown in the comparative example of FIG. 8 and the start timing of the paper feed roller 12 in the assist operation of the present embodiment are various conditions such as a slack amount Lt. It depends on. Under the conditions such as the standard sag amount Lt, according to the assist operation of the present embodiment, the sag between the registration roller 14 and the paper feed roller 12 at the time of eliminating the sag of the paper PA is compared with the conventional assist operation. Speed difference can be reduced.

  Further, in the printing apparatus 1, after the time point at which the slack of the paper PA is eliminated, the conveyance speed by the paper feed roller 12 is temporarily set to a constant speed as shown at times t5 to t6 in FIG. After that, start deceleration. By providing the constant speed section in this way, it is possible to reduce the backlash elimination sound of the gear in the driving force transmission system that transmits the driving force from the sheet feeding motor 13 to the sheet feeding roller 12 at the start of deceleration.

  In the above embodiment, after the feed roller 12 is activated in the assist operation, the speed difference between the registration roller 14 and the feed roller 12 is controlled to be constant until the slack of the paper PA is eliminated. However, the control is not limited to making the speed difference constant. Control may be performed so that the conveyance speed by the registration roller 14 is faster than the conveyance speed by the paper feed roller 12 until the slack of the paper PA is eliminated. By starting the paper feed roller 12 after the registration roller 14 is started, a speed difference is provided between both rollers. Thereafter, the conveyance speed by the registration roller 14 is higher than the conveyance speed by the paper feed roller 12 until the slack of the paper PA is eliminated. By controlling the speed to be fast, the speed difference between the two rollers at the time of eliminating the slack of the paper PA can be kept small, and noise due to the back tension of the paper PA can be reduced.

  Further, in the high-silence mode, the amount of sag formed by abutting the paper PA against the registration roller 14 may be made smaller than in the standard mode. If the amount of slack is reduced, the normal conveyance time of the paper feed roller 12 can be shortened. As a result, a decrease in productivity in the high silent mode can be reduced.

  In the above embodiment, two modes, the standard mode and the high-silence mode, are provided as the paper feed mode, but the number of paper feed modes is not limited to two. One of three or more paper feed modes in which the speed difference between the registration roller 14 and the paper feed roller 12 at the time of eliminating the slack of the paper PA may be selectable. In this case, the amount of sag formed on the paper PA may be reduced as the paper feed mode has a smaller speed difference between the registration roller 14 and the paper feed roller 12 when the paper PA sag is eliminated.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 2 Paper feed part 3 Printing part 4 Image reading part 5 Operation panel part 6 Control part 11 Paper feed stand 12 Paper feed roller 13 Paper feed motor 14 Registration roller 15 Registration motor 21 Belt conveyance part 22 Inkjet head part PA Paper

Claims (1)

A registration roller that conveys the print medium to the printing unit of the printing apparatus;
A paper feed roller that picks up a print medium loaded on a paper feed stand and conveys it to the registration roller;
When a predetermined amount of sag is formed on the print medium when the print medium conveyed by the paper feed roller hits the registration roller, the paper feed roller is stopped and then the registration roller is started. A controller that activates the paper roller and controls the conveyance speed by the registration roller to be higher than the conveyance speed by the paper feed roller until slack in the print medium is eliminated,
The control unit is configured to control the printing medium according to a paper feeding mode selected from a plurality of paper feeding modes in which a speed difference between the conveyance speed by the registration roller and the conveyance speed by the paper feeding roller at the time of eliminating the sagging of the printing medium is different. A sheet feeding device that controls a registration roller and the sheet feeding roller.