JP2012246128A - Printer - Google Patents

Abstract

An object of the present invention is to improve the alignment of print media discharged to a paper discharge tray while maintaining productivity.
A printing apparatus includes a conveyance printing unit that performs printing on a sheet P while conveying sheets P that are fed one after another, and conveys the printed sheet P to a sheet discharge tray 53 to be discharged. A paper discharge unit 5, an intermediate conveyance unit 4 that conveys the paper P from the conveyance printing unit 3 to the paper discharge unit 5, and the conveyance printing unit 3 conveys the paper P at a conveyance speed and an interval according to a predetermined printing speed, A control unit 7 that controls the intermediate transport unit 4 to transport the paper P at a transport speed higher than the transport printing unit 3 and the paper discharge unit 5 to discharge the paper P to the paper discharge tray at a transport speed lower than the intermediate transport unit 4. With.
[Selection] Figure 1

Description

  The present invention relates to a printing apparatus that performs printing on a printing medium such as paper.

  Along with the improvement in productivity in printing apparatuses, there is a need to transport paper at high speed. If the conveyance speed of the paper is increased, the paper discharged to the paper discharge tray may become slanted or jump out of the paper discharge tray, and the paper may become uneven on the paper discharge tray.

  In view of this, a technique has been proposed in which the sheet alignment on the sheet discharge table is improved by reducing the transport speed and discharging the sheet (see, for example, Patent Document 1).

JP 2009-173367 A

  However, when the conveyance speed is decelerated during conveyance, there may be a problem such as a paper collision. In order to prevent this, if a measure such as increasing the interval between sheets conveyed is performed, the productivity of the printing apparatus is consequently reduced.

  The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus capable of improving the alignment of print media discharged to a paper discharge tray while maintaining productivity.

  In order to achieve the above object, the first feature of the printing apparatus according to the present invention is that a printing unit that conveys printing media fed one after another and prints on the printing medium, and a printed printing medium are excluded. A paper discharge unit that conveys the paper to the paper table and discharges it, an intermediate conveyance unit that conveys the print medium from the conveyance printing unit to the paper discharge unit, and a conveyance speed and an interval according to a predetermined printing speed by the conveyance printing unit The intermediate conveyance unit conveys the print medium at a conveyance speed larger than the conveyance printing unit, and the discharge unit discharges the print medium to the discharge table at a conveyance speed smaller than the intermediate conveyance unit. And a control unit that controls to paper.

  A second feature of the printing apparatus according to the present invention is that the control unit sets a conveyance speed of the intermediate conveyance unit according to the length of the print medium in the conveyance direction.

  According to a third aspect of the printing apparatus of the present invention, the printing apparatus further includes an offset drive unit that offsets the discharge tray in a direction different from the conveyance direction, and the control unit includes the offset among a plurality of print media in the middle of conveyance. The conveyance speed by the intermediate conveyance unit of the print medium conveyed to the paper discharge unit immediately before the offset movement of the paper discharge table by the drive unit is higher than the conveyance speed of the print medium adjacent to the print medium and the downstream side in the conveyance direction. To be fast.

  According to the first feature of the printing apparatus according to the present invention, the intermediate transport unit transports a print medium transported at a transport speed and an interval according to the print speed by the transport printing unit at a transport speed larger than the transport printing unit. To do. As a result, the interval between the print media is larger in the intermediate conveyance unit than in the conveyance printing unit. As a result, it is possible to secure the time necessary for the print media to be aligned in the paper discharge unit without changing the conveyance speed and the interval according to the printing speed in the conveyance printing unit. Further, the paper discharge unit discharges the print medium to the paper discharge table at a lower conveyance speed than the intermediate conveyance unit. As a result, it is possible to prevent the print medium from being disturbed on the paper discharge table. Therefore, the printing apparatus can improve the alignment of the print medium discharged to the paper discharge tray while maintaining productivity.

  According to the second feature of the printing apparatus according to the present invention, the printing medium is conveyed at a higher speed than necessary by setting the conveying speed of the intermediate conveying unit according to the length of the printing medium in the conveying direction. Can be avoided and an increase in noise can be suppressed.

  According to the third feature of the printing apparatus of the present invention, the conveyance speed by the intermediate conveyance unit of the print medium conveyed to the paper discharge unit immediately before the offset movement of the paper discharge table is set to the downstream side in the conveyance direction with respect to the print medium. By making it faster than the conveyance speed of the printing medium adjacent to the sheet, it is possible to secure time for performing the offset operation without disturbing the discharged printing medium. As a result, the printing apparatus can maintain the alignment of the print medium discharged to the discharge table even when the offset function is used.

1 is a schematic configuration diagram of a printing apparatus according to an embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the printing apparatus illustrated in FIG. 1. It is a flowchart for demonstrating the operation | movement of single sided printing. It is a flowchart for demonstrating the operation | movement of single sided printing. It is a timing chart for demonstrating the operation | movement of single-sided printing. It is a figure for demonstrating the method of determining the conveyance speed of an intermediate conveyance part. It is a figure for demonstrating the method of determining the conveyance speed of an intermediate conveyance part.

  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.

  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 is to arrange the components and the like as follows. It is not something specific. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a control system of the printing apparatus shown in FIG. In the following description, the paper surface direction of FIG. Moreover, as shown in FIG. 1, when viewed from the user, the vertical and horizontal directions are the vertical and horizontal directions.

  In FIG. 1, a path indicated by a thick line is a transport path through which the print medium is transported. Among the transport routes, a route indicated by a solid line is a normal route RC, a route indicated by a one-dot chain line is a reverse route RR, a route indicated by a broken line is a paper discharge route RD, and a route indicated by a two-dot chain line is a paper feed route RS. In the following description, upstream and downstream mean upstream and downstream in the transport path.

  As shown in FIGS. 1 and 2, the printing apparatus 1 according to the present embodiment includes a paper feeding unit 2, a transport printing unit 3, an intermediate transport unit 4, a paper discharge unit 5, a reversing unit 6, The control part 7 and the housing | casing 8 which accommodates each part are provided.

  The paper feeding unit 2 supplies the paper P, which is a printing medium, to the transport printing unit 3. The paper feed unit 2 is provided on the most upstream side of the transport path. The paper feed unit 2 includes an external paper feed stand 21, an external paper feed roller 22, a plurality of internal paper feed stands 23, a plurality of internal paper feed rollers 24, a plurality of pairs of internal paper feed transport rollers 25, and a vertical A transport roller 26, a vertical transport motor 27, and an internal paper feed motor 28 are provided.

The external paper feed tray 21 is for loading paper P. The external paper feed tray 21 is partly exposed outside the casing 8 of the printing apparatus 1.

  The external paper feed roller 22 takes out the paper P one by one from the external paper feed tray 21 and conveys the paper P toward a later-described registration roller 31 along the paper feed path RS. The external paper feed roller 22 is provided on the upper side of the external paper feed table 21.

  The internal paper feed tray 23 is for loading paper P. The internal paper feed table 23 is provided inside the housing 8.

  The internal paper feed roller 25 transports the paper P taken out from the internal paper feed stand 23 toward a registration roller 31 described later. The internal paper feeding / conveying roller 25 is arranged along the paper feeding path RS.

  The vertical transport roller 26 transports the paper P transported from any of the plurality of internal paper feed stands 23 toward a registration roller 31 described later.

  The vertical transport motor 27 rotates the external paper feed roller 22 and the vertical transport roller 26. The vertical conveyance motor 27 can be connected / released to / from the external paper feed roller 22 and the vertical conveyance roller 26 via a clutch (not shown). The driving of the external paper feed roller 22 and the vertical conveyance roller 26 is switched by the clutch.

  The internal paper feed motor 28 drives the internal paper feed roller 24 and the internal paper feed transport roller 25 to rotate. The internal paper feeding motor 28 can be connected / released to / from the internal paper feeding roller 24 and the internal paper feeding / conveying roller 25 via a clutch (not shown). The internal paper feeding roller 24 and the internal paper feeding / conveying roller 25 that are rotationally driven are switched by the clutch.

  The transport printing unit 3 prints an image on the paper P while transporting the paper P. The transport printing unit 3 is disposed on the downstream side of the paper feeding unit 2. The conveyance printing unit 3 includes a registration roller 31, a belt conveyance unit 32, a plurality of pairs of ascending conveyance rollers 33, an inkjet head unit 34, a registration motor 35, a belt motor 36, and an ascending conveyance motor 37.

  The registration roller 31 temporarily stops the paper P conveyed from the paper feeding unit 2 or the reversing unit 6 and then sends the paper P to the belt conveyance unit 32 at a predetermined timing. The registration roller 31 is disposed on the normal route RC upstream of the transport printing unit 3. In other words, the registration roller 31 is disposed in the vicinity of the junction point between the sheet feeding path RS and the reversing path RR.

  The belt conveyance unit 32 conveys the sheet P conveyed from the registration roller 31 to the ascending conveyance roller 33. The belt conveyance unit 32 is provided on the downstream side of the registration roller 31. The belt conveyance unit 32 includes an annular conveyance belt 321 provided facing the lower side of the inkjet head unit 34, a belt driving roller 322 that drives the conveyance belt 321 to rotate, and a driven roller 323 that is driven by the belt driving roller 322. 325. The conveyance belt 321 is an endless belt having a large number of holes, and conveys the sheet P by suction and holding with a negative pressure generated when air is sucked from the holes by a suction fan (not shown).

  The ascending conveyance roller 33 conveys the paper P conveyed by the belt conveyance unit 32 to the upper intermediate conveyance unit 4. The plurality of pairs of ascending conveyance rollers 33 are arranged at a predetermined interval along the normal path RC between the belt conveyance unit 32 and the intermediate conveyance unit 4. The normal route RC in the region where the ascending conveyance roller 33 is disposed is formed in a semicircular shape with an opening on the left side. The ascending conveyance roller 33 has a one-way clutch structure in the conveyance direction.

  The inkjet head unit 34 includes a plurality of line-type inkjet heads arranged above the belt conveyance unit 32 and having a plurality of nozzles arranged in a direction (front-rear direction) substantially orthogonal to the conveyance direction of the paper P. The inkjet head unit 34 prints an image by ejecting ink from the inkjet head onto the paper P conveyed by the belt conveyance unit 32.

  The registration motor 35, the belt motor 36, and the ascending conveyance motor 37 rotate the registration roller 31, the belt driving roller 322, and the ascending conveyance roller 33, respectively.

  The intermediate transport unit 4 transports the paper P transported by the ascending transport roller 33 to the paper discharge unit 5 or the reversing unit 6. The intermediate conveyance unit 4 includes a plurality of pairs of intermediate conveyance rollers 41 </ b> A to 41 </ b> D and an intermediate conveyance motor 42.

  The intermediate transport rollers 41A to 41D nip and transport the paper P. Intermediate transport rollers 41 </ b> A to 41 </ b> C are arranged in order from the upstream side along a normal path RC between the transport printing unit 3 and the paper discharge unit 5. The pair of intermediate conveyance rollers 41D on the most downstream side is disposed in the upstream portion of the reversing path RR.

  The intermediate conveyance motor 42 rotates the intermediate conveyance rollers 41A to 41D.

  The paper discharge unit 5 discharges and stacks the printed paper P. The paper discharge unit 5 includes a switching unit 51, two pairs of paper discharge rollers 52A and 52B, a paper discharge table 53, a paper return roller 54, a solenoid 55, a paper discharge motor 56, a paper return motor 57, An offset motor 58 and a paper discharge sensor 59 are provided.

  The switching unit 51 is disposed at a branch point between the paper discharge path RD and the reversal path RR, and switches the transport path of the paper P between the paper discharge path RD and the reversal path RR. The paper discharge route RD is a route that extends from the downstream end of the normal route RC toward the paper discharge tray 53.

  The paper discharge rollers 52 </ b> A and 52 </ b> B transport the paper P conveyed by the intermediate transport unit 4 along the paper discharge path RD and discharge the paper P onto the paper discharge tray 53. Discharge rollers 52A and 52B are arranged between the switching unit 51 and the discharge table 53 in order from the upstream side. The downstream paper discharge roller 52B is disposed at the downstream end of the paper discharge path RD.

  The paper discharge tray 53 is for stacking printed paper P conveyed by the paper discharge rollers 52A and 52B. The paper discharge table 53 is disposed on the downstream side of the paper discharge roller 52B. A part of the paper discharge tray 53 protrudes from the housing 8. The paper discharge table 53 is inclined downwardly to the right, and a wall 531 is erected at a position below the inclination. The wall 531 serves as a regulation standard for orderly stacking the sheets P.

  The paper return roller 54 returns the printed paper P discharged onto the paper discharge tray 53 in a downward direction opposite to the paper discharge direction, and aligns the paper P based on the wall 531. The paper return roller 54 is provided in the vicinity of the paper discharge roller 52 </ b> B and the paper discharge table 53.

  The solenoid 55 drives the switching unit 51. The paper discharge motor 56 and the paper return motor 57 drive the paper discharge rollers 52A and 52B and the paper return roller 54, respectively.

  The offset motor 58 offsets the paper discharge table 53 in a direction different from the conveyance direction of the paper P, thereby realizing an offset function. The offset function is a function for shifting the paper discharge position in order to sort the printed paper P in units of copies. More specifically, the offset motor 58 offsets the discharge table 53 in a direction (front-rear direction) that is substantially orthogonal to the transport direction of the paper P. The offset motor 58 corresponds to the offset drive unit in the claims.

  The paper discharge sensor 59 detects the paper P conveyed to the paper discharge tray 53 between the paper discharge rollers 52A and the paper discharge rollers 52B along the paper discharge path RD. The paper discharge sensor 59 outputs an ON signal when the paper P exists within the detection range, and outputs an OFF signal when the paper P does not exist. Accordingly, when the paper P is discharged, the output of the paper discharge sensor 59 is switched to an ON signal when the leading edge of the paper P passes the detection range, and is switched to an OFF signal when the trailing edge of the paper P passes the detection range.

  The reversing unit 6 reverses the single-side printed paper P and supplies it again to the transport printing unit 3 during duplex printing. The reversing unit 6 includes a reversing roller 61, a switchback unit 62, a refeed roller 63, a switching gate 64, a reversing motor 65, and a refeeding motor 66.

  The reverse roller 61 temporarily transports the paper P transported by the intermediate transport unit 4 to the switchback unit 62 and then transports it to the refeed roller 63. The reverse roller 61 is disposed between the intermediate transport roller 41 </ b> D and the carry-in port of the switchback unit 62 on the reverse path RR.

  The switchback unit 62 is a space for the reversing roller 61 to temporarily carry in the paper P. The switchback unit 62 is formed of a space formed in the lower part of the paper discharge tray 53. The switchback unit 62 is opened in the vicinity of the reversing roller 61 for carrying the paper P therein.

  The refeed roller 63 transports the paper P transported by the reverse roller 61 to the registration roller 31. The refeed roller 63 is disposed on the reverse path RR between the reverse roller 61 and the registration roller 31.

  The switching gate 64 guides the paper P conveyed by the intermediate conveyance unit 4 to the reverse roller 61. Further, the switching gate 64 guides the paper P carried out from the switchback unit 62 by the reversing roller 61 to the refeed roller 63. The switching gate 64 is disposed in the vicinity of the center of gravity at the three locations of the most downstream intermediate conveyance roller 41 </ b> D, the reverse roller 61, and the refeed roller 63.

  The reversing motor 65 and the refeeding motor 66 drive the reversing roller 61 and the refeeding roller 63, respectively.

  The control unit 7 controls each unit of the printing apparatus 1. The control unit 7 includes a CPU, a RAM, a ROM, and the like.

  In single-sided printing, the control unit 7 controls the intermediate conveyance speed Vb, which is the conveyance speed of the paper P in the intermediate conveyance unit 4, to be greater than the print conveyance speed Va in the conveyance printing unit 3. Here, the printing conveyance speed Va is set according to the printing speed. The printing speed is the number of printed sheets per minute. The interval between sheets P (inter-sheet distance, inter-sheet time) in the transport printing unit 3 is also set according to the printing speed. The inter-paper distance is a distance between the trailing edge of the preceding paper P and the leading edge of the succeeding paper P. The inter-paper time is a time from when the trailing edge of the preceding paper P passes a certain point until the leading edge of the succeeding paper P passes the same point. Further, in single-sided printing, the controller 7 causes the paper discharge transport speed Vc, which is the transport speed of the paper P in the paper discharge section 5 when discharging the paper P to the paper discharge tray 53, to be smaller than the intermediate transport speed Vb. Control.

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

  The printing apparatus 1 feeds a certain sheet P, waits for the sheet P to be printed and discharged, and does not feed the next sheet P, but before the preceding sheet P is discharged. In addition, the subsequent paper P can be fed and continuously printed at a predetermined interval. Thereby, high productivity is realized.

  In the printing apparatus 1, double-sided printing is performed as follows. The paper P whose surface is printed by the transport printing unit 3 is guided from the intermediate transport unit 4 to the reversing unit 6, turned upside down by the reversing unit 6, and re-fed to the transport printing unit 3. During the printing operation of a large number of sheets in duplex printing, feeding and refeeding of another sheet P is performed between feeding and refeeding a certain sheet P, and unprinted sheet P and single-sided printing are performed. The completed paper P is alternately sent to the belt conveyance unit 32. In other words, the double-side printed paper P guided to the paper discharge path RD and the single-side printed paper P guided to the reversing path RR arrive at the switching unit 51 alternately. Therefore, every other sheet P conveyed by the intermediate conveyance unit 4 is guided to the sheet discharge unit 5 and discharged. Therefore, in such double-sided printing, the time for preparing the paper P by the paper return roller 54 in the paper discharge unit 5 and the time for the offset operation by the offset motor 58 are secured, and the paper P is not aligned on the paper discharge table 53. There is little risk of it occurring.

  On the other hand, in the case of single-sided printing, the paper P sequentially fed by the paper feed unit 2 is printed by the transport printing unit 3 and then transported from the intermediate transport unit 4 to the paper discharge unit 5 and continuously discharged. The For this reason, when the sequentially fed paper P is sent to the paper discharge unit 5 at the transport speed and interval in the transport printing unit 3, the time for paper alignment by the paper return roller 54 and the time for the offset operation by the offset motor 58. May not be secured, and the paper P may become uneven on the paper discharge tray 53.

  On the other hand, in the printing apparatus 1 according to the present embodiment, when performing single-sided printing, the intermediate transport speed Vb by the intermediate transport unit 4 is set to be larger than the print transport speed Va of the transport printing unit 3, so The distance between sheets and the time between sheets are increased, and a time for paper alignment in the paper discharge unit 5 is secured. Such single-sided printing operation will be described.

  3 and 4 are flowcharts for explaining the single-sided printing operation of the printing apparatus 1, and FIG. 5 is a timing chart for explaining the single-sided printing operation. Here, it is assumed that an offset function is used in which a plurality of copies and a plurality of copies are printed, and the paper discharge position is shifted by the division of copies.

  The processing of the flowcharts of FIGS. 3 and 4 is started, for example, when print data is input to the printing apparatus 1 from an external PC or the like. First, in step S <b> 10, the control unit 7 starts driving the belt motor 36 and the ascending transport motor 37 of the transport printing unit 3, the intermediate transport motor 42 of the intermediate transport unit 4, and the paper discharge motor 56 of the paper discharge unit 5. Accordingly, driving of the belt conveyance unit 32, the ascending conveyance roller 33, the intermediate conveyance rollers 41A to 41D, and the paper discharge rollers 52A and 52B is started. The control unit 7 also starts driving the paper return motor 57. Here, as shown in FIG. 5, the control unit 7 performs printing conveyance speed Va = v1 by the belt conveyance unit 32 and the ascending conveyance roller 33 of the conveyance printing unit 3 and intermediate by the intermediate conveyance rollers 41 </ b> A to 41 </ b> D of the intermediate conveyance unit 4. Control is performed so that the conveyance speed Vb = v2 and the discharge conveyance speed Vc = v2 by the discharge rollers 52A and 52B. v2> v1. The value of v1 is set according to the printing speed. A method for determining v2 will be described later.

  In step S <b> 20, the control unit 7 causes the paper feeding unit 2 to start feeding paper. The control unit 7 determines the paper size based on the print data, and feeds the paper P from the paper feed tray on which the paper of the corresponding size is stacked among the external paper feed tray 21 and the plurality of internal paper feed trays 23. . When the paper P from the paper feeding unit 2 hits the registration roller 31, the control unit 7 drives the registration motor 35 and causes the registration roller 31 to convey the paper P to the belt conveyance unit 32. When the leading edge of the paper P reaches the belt conveyance unit 32, the control unit 7 controls the conveyance speed by the registration rollers 31 to be substantially equal to the print conveyance speed Va = v1. Paper feeding is repeated for the required number of printed sheets. As a result, the sheets P are fed one after another to the transport printing unit 3. The control unit 7 controls the paper feeding unit 2 and the registration rollers so that the interval between the sheets P (paper distance, paper time) continuously conveyed in the conveyance printing unit 3 becomes a set value according to the printing speed. The drive of 31 is controlled.

  In step S30, the control unit 7 sets “1” to the variable m indicating the number of copies to be printed.

  In step S <b> 40, the control unit 7 sets “0” to a variable n indicating the number of printed sheets (number of discharged sheets) in the set.

  The paper P sent out to the belt conveyance unit 32 by the registration roller 31 is printed by the inkjet head unit 34 while being conveyed at the print conveyance speed Va = v1. Thereafter, the printed paper P is conveyed by the ascending conveyance roller 33. When the leading edge of the sheet P reaches the uppermost intermediate conveyance roller 41A of the intermediate conveyance unit 4, the conveyance is shifted to the intermediate conveyance speed Vb = v2. Since the ascending transport roller 33 has a one-way clutch structure as described above, the intermediate transport unit 4 can pull out the paper P from the ascending transport roller 33 at a transport speed v2 that is faster than the transport speed v1. Then, the paper P is transported at the transport speed v2 by the intermediate transport rollers 41A to 41C. Thus, since the paper P is transported at the transport speed v2 in the intermediate transport unit 4, while the subsequent paper P is transported at the transport speed v1 in the transport printing unit 3, an interval between the subsequent paper P and the subsequent paper P. (Paper distance, paper time) increases.

  Thereafter, the paper P is guided to the paper discharge path RD by the switching unit 51 of the paper discharge unit 5 and is conveyed toward the paper discharge table 53 by the paper discharge rollers 52A and 52B. At this time, the paper P is detected by the paper discharge sensor 59.

  In step S50, the control unit 7 determines whether or not the output of the paper discharge sensor 59 is an ON signal. When determining that the signal is not an ON signal (step S50: NO), the control unit 7 repeats the process of step S50.

  When it is determined that the output of the paper discharge sensor 59 is an ON signal (step S50: YES), in step S60, the control unit 7 adds “1” to the variable n.

  Next, in step S70, the control unit 7 determines whether or not the trailing edge of the sheet P has passed through the intermediate conveyance roller 41C adjacent to the upstream side with respect to the upstream discharge roller 52A. Specifically, the control unit 7 determines whether the time required for transporting the distance La at the transport speed v2 after the output of the paper discharge sensor 59 has been turned on has elapsed after the sheet P. It is determined whether or not the end has passed through the intermediate conveyance roller 41C. Here, the distance La corresponds to a transport distance required from the time when the leading edge of the paper P reaches the detection range of the paper discharge sensor 59 until the trailing edge of the paper P passes through the intermediate transport roller 41C. The distance La differs depending on the size of the paper P (length in the transport direction). In addition, it may be configured to detect that the rear end of the sheet P has passed through the intermediate conveyance roller 41C using a sensor or the like. If it is determined that the trailing edge of the paper P has not passed through the intermediate transport roller 41C (step S70: NO), the control unit 7 repeats the process of step S70.

  When it is determined that the trailing edge of the sheet P has passed through the intermediate conveyance roller 41C (step S70: YES), in step S80, the control unit 7 causes the trailing edge of the sheet P to move the intermediate conveyance roller 41C as shown in FIG. At time t1 when the sheet passes through, deceleration of the conveyance speed by the sheet discharge rollers 52A and 52B from v2 to v3 is started. As a result, the discharge conveyance speed Vc = v3. v3 <v2. When the paper discharge unit 5 receives the paper P from the intermediate transport unit 4, it is necessary to match the transport speeds of the two, so the paper discharge transport speed Vc = v2. When the trailing edge of the paper P passes through the intermediate transport roller 41C, the paper transport speed is reduced to Vc = v3, and the paper P is discharged onto the paper discharge tray 53 at this transport speed v3. v3 is set as an appropriate value in order to prevent the sheet P from being inclined on the sheet discharge table 53 or from jumping out from the sheet discharge table 53. v3 is, for example, a value obtained experimentally.

  Next, in step S90, the control unit 7 determines whether or not the output of the paper discharge sensor 59 is an OFF signal. If it is determined that the signal is not an OFF signal (step S90: NO), the control unit 7 repeats the process of step S90.

  When it is determined that the output of the paper discharge sensor 59 is an OFF signal (step S90: YES), in step S100, the control unit 7 determines whether or not the rear end of the paper P has passed through the downstream paper discharge roller 52B. to decide. Specifically, the control unit 7 determines whether the time required for transporting the distance Lb at the transport speed v3 after the output of the paper discharge sensor 59 has been turned off has elapsed after the sheet P. It is determined whether or not the end has passed through the paper discharge roller 52B. Here, the distance Lb corresponds to the distance on the conveyance path between the paper discharge sensor 59 and the paper discharge roller 52B. Note that a configuration in which the rear end of the paper P passes through the paper discharge roller 52B using a sensor or the like may be used. If it is determined that the trailing edge of the paper P has not passed through the paper discharge roller 52B (step S100: NO), the control unit 7 repeats the process of step S100.

  When it is determined that the trailing edge of the paper P has passed through the paper discharge roller 52B (step S100: YES), in step S110, the control unit 7 determines whether or not the variable n = N−1. N is the number of printed sheets per copy. For example, the control unit 7 acquires information indicating the number N of copies to be printed from the print data.

  When it is determined that n = N−1 is not satisfied (step S110: NO), in step S120, the control unit 7 at time t2 when the trailing edge of the sheet P passes through the sheet discharge roller 52B as shown in FIG. The acceleration of the conveyance speed by the paper discharge rollers 52A and 52B from v3 to v2 is started. As a result, the discharge conveyance speed Vc = v2. As described above, when one sheet is discharged, the control unit 7 returns the discharge conveyance speed Vc to v2 in order for the discharge unit 5 to receive the next sheet P. Then, the control part 7 returns to step S50, and repeats subsequent processes.

  When it is determined that n = N−1 (step S110: YES), in step S130, the control unit 7 at time t2 when the trailing edge of the paper P passes through the paper discharge roller 52B as shown in FIG. Then, acceleration of the conveyance speed by the intermediate conveyance rollers 41A to 41C from v2 to v4 is started. Further, the control unit 7 starts to accelerate the conveyance speed from the v3 to the v4 by the paper discharge rollers 52A and 52B at time t2. As a result, the intermediate transport speed Vb = v4 and the paper discharge transport speed Vc = v4. A method for determining v4 will be described later.

  By setting the intermediate transport speed Vb = v4, the Nth sheet P is transported through the intermediate transport unit 4 at a transport speed v4 that is faster than the other sheets P up to the (N-1) th sheet. As a result, in the intermediate transport unit 4, the interval between the Nth sheet P and the subsequent first sheet P (the distance between sheets, the time between sheets) is the distance between other sheets P. Bigger than. When the paper discharge unit 5 receives the paper P from the intermediate transport unit 4, it is necessary to match the transport speeds of the two, so the paper discharge transport speed Vc is also set to v4.

  Next, in step S140, the control unit 7 determines whether or not the output of the paper discharge sensor 59 is an ON signal. When determining that the signal is not an ON signal (step S140: NO), the control unit 7 repeats the process of step S140.

  When it is determined that the output of the paper discharge sensor 59 is an ON signal (step S140: YES), in step S150, the control unit 7 determines whether the output of the paper discharge sensor 59 is an OFF signal. When determining that the signal is not an OFF signal (step S150: NO), the control unit 7 repeats the process of step S150.

  When it is determined that the output of the paper discharge sensor 59 is an OFF signal (step S150: YES), in step S160, the control unit 7 determines that the output of the paper discharge sensor 59 is an OFF signal as shown in FIG. At time t3, deceleration of the conveyance speed from the intermediate conveyance rollers 41A to 41C from v4 to v3 is started. Further, the control unit 7 starts decelerating the conveyance speed from v4 to v3 by the paper discharge rollers 52A and 52B at time t3. As a result, the intermediate transport speed Vb = v2 and the paper discharge transport speed Vc = v3.

  Next, in step S170, the control unit 7 determines whether or not the variable m = M. M is the designated number of print copies. For example, the control unit 7 acquires information indicating the number of copies M from the print data. If it is determined that m = M (step S170: YES), the control unit 7 ends the printing operation.

  If it is determined that m = M is not satisfied (step S170: NO), in step S180, the control unit 7 determines whether or not the trailing edge of the sheet P has passed through the downstream discharge roller 52B. Specifically, the control unit 7 decelerates at a predetermined deceleration acceleration from the conveyance speed v4 to v3 after the output of the paper discharge sensor 59 becomes an OFF signal, and then maintains v3 only for the distance Lb. It is determined whether or not the trailing edge of the paper P has passed through the paper discharge roller 52B depending on whether or not the time required for conveyance has passed. If it is determined that the trailing edge of the paper P has not passed through the paper discharge roller 52B (step S180: NO), the control unit 7 repeats the process of step S180.

  If it is determined that the trailing edge of the paper P has passed through the paper discharge roller 52B (step S180: YES), in step S190, the control unit 7 causes the trailing edge of the paper P to pass the paper discharge roller 52B as shown in FIG. The offset operation by the offset motor 58 is started at the passing time t4. By the offset operation, the paper discharge tray 53 is offset by a predetermined amount in the front-rear direction. As a result, the printed paper P of the next copy is stacked with a predetermined amount shifted in the front-rear direction with respect to the current copy of the paper P stacked on the paper discharge tray 53.

  In step S200, the control unit 7 starts to accelerate the conveyance speed from v3 to v2 by the paper discharge rollers 52A and 52B at time t4. As a result, the discharge conveyance speed Vc = v2.

  Next, in step S210, the control unit 7 adds “1” to the variable m. Then, the control part 7 returns to step S40, and repeats subsequent processes.

  Next, a method for determining the conveyance speeds v2 and v4 will be described.

  As shown in FIG. 6, it is assumed that the preceding paper P1 and the succeeding paper P2 are transported at the transport speed v1. The paper length of the paper P1, P2 (length in the transport direction) is Lp, and the distance between the papers P1, P2 is Lg1. When the time from when the leading edge of the paper P1 passes a certain point K until the leading edge of the paper P2 reaches the point K as shown in FIG. 6 is T, the following equation (1) is established.

T × v1 = Lp + Lg1 (1)
Next, as illustrated in FIG. 7, at the point K, the conveyance speed is switched to v2. In this case, if the distance between the sheets P1 and P2 when the leading edge of the sheet P2 reaches the point K is Lg2, the sheet P1 is conveyed at the conveyance speed v2 during the time T, and the distance between the sheets is Lg2. Therefore, the following equation (2) is established.

T × v2 = Lp + Lg2 (2)
From the equations (1) and (2), the following equation (3) is obtained.

Tg2 = (1 / v1-1 / v2) × Lp + Tg1 (3)
Here, Tg1 and Tg2 are inter-paper times, and Tg1 = Lg1 / v1 and Tg2 = Lg2 / v2. Since v2> v1, Tg2> Tg1 is obtained from Equation (3).

  The inter-paper time Tg2 is the inter-paper time in the intermediate transport unit 4. In Expression (3), the conveyance speed v1 and the paper interval time Tg1 are set according to the printing speed. The paper length Lp is determined by the paper size to be used. Therefore, if the sheet interval time Tg2 is set according to the time required for aligning the sheets P in the sheet discharge unit 5, the sheet alignment time in the sheet discharge unit 5 in the steady state is secured from the equation (3). It is possible to calculate the conveyance speed v2 necessary for the operation. The steady state is a state in which sheets from the first sheet to the (N-1) th sheet are sequentially discharged at equal intervals.

  The inter-paper time Tg3 when the conveyance speed is switched from v1 to v4 is obtained by an expression in which v2 on the right side of Expression (3) is replaced with v4. Therefore, if the sheet interval time Tg3 is set according to the time required for the offset operation in the paper discharge unit 5, the conveyance speed v4 necessary for securing the time for the offset operation can be calculated.

  Here, as described above, the transport speed v4 in the intermediate transport unit 4 of the Nth (last) sheet P in the section is faster than the transport speed v2 of the other sheets P. As a result, the time from when the Nth sheet in the section is ejected to the sheet ejection tray 53 until the first sheet in the next section is ejected becomes longer than in the steady state, and the offset is increased along with the sheet alignment time. Time for operation is secured. On the other hand, the time from the discharge of the (N-1) th sheet to the discharge of the Nth sheet in the section is shorter than in the steady state.

  For this reason, even when the Nth sheet is discharged with the discharge interval being shorter than the steady state, the Nth sheet P remains until the immediately preceding (N−1) th sheet is adjusted by the sheet return roller 54 and stopped. It is necessary to determine the conveyance speeds v2 and v4 so as not to be discharged to the discharge tray 53. That is, in the present embodiment, the sheet alignment time and the offset operation time in the sheet discharge unit 5 in the steady state are ensured, and the sheet alignment time is also ensured when the Nth sheet is discharged. The conveyance speeds v2 and v4 are determined. Such conveyance speeds v2 and v4 may be obtained by calculation in consideration of various conditions such as the conveyance speed v3 at the time of paper discharge to the paper discharge tray 53, the rotation speed of the paper return roller 54, and the distances La and Lb. However, it may be obtained experimentally.

  Further, as can be seen from the equation (3), when the paper length Lp is larger, the desired inter-paper time Tg2 can be obtained even if the conveyance speed v2 is smaller. Therefore, the control unit 7 can set appropriate transport speeds v2 and v4 according to the size of the paper P used for printing.

  As described above, the printing apparatus 1 uses the conveyance speed v1 corresponding to the printing speed by the conveyance printing unit 3 and the sheet P conveyed at intervals in the single-sided printing at the intermediate conveyance unit 4, which is larger than the conveyance speed v1. Transport at a transport speed v2. Thereby, in the intermediate conveyance unit 4, the interval between the sheets P is larger than that in the conveyance printing unit 3. As a result, it is possible to secure the time required for paper alignment in the paper discharge unit 5 without changing the transport speed v1 and the interval corresponding to the printing speed in the transport printing unit 3. Further, the paper discharge unit 5 discharges the paper P to the paper discharge tray 53 at a transport speed v3 that is lower than the transport speed v2 in the intermediate transport unit 4. Thereby, it is possible to prevent the paper P from being distorted by being inclined on the paper discharge tray 53 or jumping out of the paper discharge tray 53. As described above, in the printing apparatus 1, it is possible to improve the alignment of the paper ejected to the paper ejection tray 53 while maintaining productivity.

  Further, in the printing apparatus 1, among the plurality of sheets P in the middle of conveyance, intermediate conveyance of the sheet P (the Nth sheet P in the unit) conveyed to the sheet discharge unit 5 immediately before the offset movement of the sheet discharge table 53. The conveyance speed by the unit 4 is set to v4 that is faster than the other paper P. For this reason, the conveyance speed of the Nth sheet P in the section by the intermediate conveyance section 4 is the conveyance speed of the next sheet of the first sheet P adjacent to the downstream side in the conveyance direction by the intermediate conveyance section 4. Greater than speed. Thereby, a time for performing the offset operation without disturbing the discharged paper P is secured. As a result, the printing apparatus 1 can maintain the alignment of the paper ejected to the paper ejection tray 53 even when the offset function is used.

  Further, in the printing apparatus 1, the conveyance speeds v2 and v4 of the intermediate conveyance unit 4 are set according to the sheet length. Thereby, the printing apparatus 1 can avoid conveying the paper P at an unnecessarily high speed while ensuring the time required for paper alignment in the paper discharge unit 5, and can suppress an increase in noise.

  When the offset function is not used, steps S30, S110, and S130 to S210 in the flowcharts of FIGS. 3 and 4 may be omitted. The present invention can also be applied to a printing apparatus having no paper return roller 54. Further, the present invention may be applied to double-sided printing.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 2 Paper feed part 3 Conveyance printing part 4 Intermediate | middle conveyance part 5 Paper discharge part 6 Inversion part 7 Control part 32 Belt conveyance part 33 Ascending conveyance roller 36 Belt motor 37 Ascending conveyance motor 41A-41D Intermediate conveyance roller 42 Intermediate conveyance motor 52A, 52B Discharge roller 53 Discharge stand 56 Discharge motor 58 Offset motor 59 Discharge sensor

Claims (3)

A transport printing unit that performs printing on the print medium while transporting the fed print media one after another,
A paper discharge unit that conveys the printed print medium to a paper discharge tray and discharges it;
An intermediate transport unit that transports a print medium from the transport printing unit to the paper discharge unit;
The transport printing unit transports the print medium at a transport speed and an interval according to a predetermined printing speed, the intermediate transport unit transports the print medium at a transport speed greater than the transport printing unit, and the paper discharge unit is the intermediate And a control unit that controls to discharge the print medium to the discharge table at a conveyance speed smaller than the conveyance unit.   The printing apparatus according to claim 1, wherein the control unit sets a conveyance speed of the intermediate conveyance unit according to a length of a print medium in a conveyance direction. An offset drive unit that offset-moves the discharge table in a direction different from the transport direction;
The control unit is configured to determine a conveyance speed by the intermediate conveyance unit of the print medium conveyed to the paper discharge unit immediately before the offset movement of the paper discharge table by the offset driving unit among the plurality of print media in the middle of the conveyance. The printing apparatus according to claim 1, wherein the printing apparatus is faster than a conveyance speed of a print medium adjacent to the medium on the downstream side in the conveyance direction.